bims-kimdis 2023-11-19 papers

bims-kimdis

Biomed News

on Ketones, inflammation and mitochondria in disease

Issue of 2023‒11‒19
28 papers selected by
Matías Javier Monsalves Álvarez

Ketone body β-hydroxybutyrate (BHB) preserves mitochondrial bioenergetics.
Ketogenic Diet Improves Motor Function and Motor Unit Connectivity in Aged C57BL/6 Mice.
Does a Ketogenic Diet Have a Place Within Diabetes Clinical Practice? Review of Current Evidence and Controversies.
A diet-dependent host metabolite shapes the gut microbiota to protect from autoimmunity.
Nutritional Intervention in Cushing's Disease: The Ketogenic Diet's Effects on Metabolic Comorbidities and Adrenal Steroids.
Ketogenic Diet Has Moderate Effects on the Fecal Microbiota of Wild-Type Mice.
Higher beta-hydroxybutyrate ketone levels associated with a slower kidney function decline in ADPKD.
Habitual carbohydrate intake is not correlated with circulating β-hydroxybutyrate levels in pregnant women with overweight and obesity at 28 weeks' gestation.
Classic ketogenic diet versus further antiseizure medicine in infants with drug-resistant epilepsy (KIWE): a UK, multicentre, open-label, randomised clinical trial.
Combined changes in temperature and pH mimicking exercise results in decreased efficiency in muscle mitochondria.
Rationale and protocol for a safety, tolerability and feasibility randomized, parallel group, double-blind, placebo-controlled, pilot study of a novel ketone ester targeting frailty via immunometabolic geroscience mechanisms.
Changes in Plasma Pyruvate and TCA Cycle Metabolites upon Increased Hepatic Fatty Acid Oxidation and Ketogenesis in Male Wistar Rats.
Associations of Skeletal Muscle Mass, Muscle Fat Infiltration, Mitochondrial Energetics, and Cardiorespiratory Fitness with Liver Fat Among Older Adults.
Interactions of mitochondrial and skeletal muscle biology in mitochondrial myopathy.
Mitochondrial entry gate as regulatory hub.
Ketosis Suppression and Ageing (KetoSAge): The Effects of Suppressing Ketosis in Long Term Keto-Adapted Non-Athletic Females.
MCUb is an inducible regulator of calcium-dependent mitochondrial metabolism and substrate utilization in muscle.
Stuart has got the PoWeR! Skeletal muscle adaptations to a novel heavy progressive weighted wheel running exercise model in C57BL/6 mice.
Sodium-glucose cotransporter-2 inhibition for heart failure with preserved ejection fraction and chronic kidney disease with or without type 2 diabetes mellitus: a narrative review.
Xanthohumol alleviates palmitate-induced inflammation and prevents osteoarthritis progression by attenuating mitochondria dysfunction/NLRP3 inflammasome axis.
People with obesity exhibit losses in muscle proteostasis that are partly improved by exercise training.
3D reconstruction of murine mitochondria reveals changes in structure during aging linked to the MICOS complex.
The E3 ubiquitin ligase RNF31 mediates the development of ulcerative colitis by regulating NLRP3 inflammasome activation.
Mitochondria-targeted SkQ1 nanoparticles for dry eye disease: Inhibiting NLRP3 inflammasome activation by preventing mitochondrial DNA oxidation.
The mechanisms of action of mitochondrial targeting agents in cancer: inhibiting oxidative phosphorylation and inducing apoptosis.
Critical Velocity, Maximal Lactate Steady State, and Muscle MCT1 and MCT4 after Exhaustive Running in Mice.
Real-time OXPHOS capacity analysis in wounded skin from diabetic mice: A pilot study.
Effects of acute exercise and training status on glucocorticoid-induced leucine zipper (GILZ) expression in human skeletal muscle.

Sci Rep. 2023 11 11. 13(1): 19664

Ketone body β-hydroxybutyrate (BHB) preserves mitochondrial bioenergetics.

I Llorente-Folch, H Düssmann, O Watters, N M C Connolly, Jochen H M Prehn.

The ketogenic diet is an emerging therapeutic approach for refractory epilepsy, as well as certain rare and neurodegenerative disorders. The main ketone body, β-hydroxybutyrate (BHB), is the primary energy substrate endogenously produced in a ketogenic diet, however, mechanisms of its therapeutic actions remain unknown. Here, we studied the effects of BHB on mitochondrial energetics, both in non-stimulated conditions and during glutamate-mediated hyperexcitation. We found that glutamate-induced hyperexcitation stimulated mitochondrial respiration in cultured cortical neurons, and that this response was greater in cultures supplemented with BHB than with glucose. BHB enabled a stronger and more sustained maximal uncoupled respiration, indicating that BHB enables neurons to respond more efficiently to increased energy demands such as induced during hyperexcitation. We found that cytosolic Ca2+ was required for BHB-mediated enhancement of mitochondrial function, and that this enhancement was independent of the mitochondrial glutamate-aspartate carrier, Aralar/AGC1. Our results suggest that BHB exerts its protective effects against hyperexcitation by enhancing mitochondrial function through a Ca2+-dependent, but Aralar/AGC1-independent stimulation of mitochondrial respiration.

DOI: https://doi.org/10.1038/s41598-023-46776-8
Res Sq. 2023 Oct 27. pii: rs.3.rs-3335211. [Epub ahead of print]

Ketogenic Diet Improves Motor Function and Motor Unit Connectivity in Aged C57BL/6 Mice.

Carlos J Padilla, Hallie Harris, Jeff S Volek, Brian C Clark, W David Arnold.

Objective Pathological, age-related loss of muscle function, commonly referred to as sarcopenia, contributes to loss of mobility, impaired independence, as well as increased risk of adverse health events. Sarcopenia has been attributed to changes in both neural and muscular integrity during aging. Current treatment options are primarily limited to exercise and dietary protein fortification, but the therapeutic impact of these approaches are often inadequate. Prior work has suggested that a ketogenic diet (KD) might improve healthspan and lifespan in aging mice. Thus, we sought to investigate the effects of a KD on neuromuscular indices of sarcopenia in aged C57BL/6 mice.DESIGN: A randomized, controlled pre-clinical experiment consisting of longitudinal assessments performed starting at 22-months of age (baseline) as well as 2, 6 and 10 weeks after the start of a KD vs. regular chow intervention.
SETTING: Preclinical laboratory study.
SAMPLE SIZE: Thirty-six 22-month-old mice were randomized into 2 dietary groups: KD [n = 22 (13 female and 9 male)], and regular chow [n = 15 (7 female and 8 male)].
MEASUREMENTS: Measures included body mass, hindlimb and all limb grip strength, rotarod for motor performance, plantarflexion muscle contractility, motor unit number estimations (MUNE), and repetitive nerve stimulation (RNS) as an index of neuromuscular junction transmission efficacy recorded from the gastrocnemius muscle. At end point, blood samples were collected to assess blood beta-hydroxybutyrate levels.
STATISTICAL ANALYSIS: Two-way ANOVA mixed-effects analysis (time x diet) were performed to analyze grip, rotarod, MUNE, and muscle contractility data. Results Beta-hydroxybutyrate (BHB) was significantly higher at 10 weeks in mice on a KD vs control group (0.83 ± 0.44 mmol/l versus 0.42 ± 0.21 mmol/l, η 2 = 0.265, unpaired t-test, p = 0.0060). Mice on the KD intervention demonstrated significantly increased hindlimb grip strength (time x diet, p = 0.0030), all limb grip strength (time x diet, p = 0.0523), and rotarod latency to fall (time x diet, p = 0.0021). Mice treated with the KD intervention also demonstrated significantly greater MUNE (time x diet, p = 0.0064), but no difference in muscle contractility (time x diet, p = 0.5836) or RNS (time x diet, p = 0.9871). Conclusion KD intervention improved neuromuscular and motor function in aged mice. This pre-clinical work suggests that further research is needed to assess the efficacy and physiological effects of a KD on indices of sarcopenia.

DOI: https://doi.org/10.21203/rs.3.rs-3335211/v1
Diabetes Ther. 2023 Nov 15.

Does a Ketogenic Diet Have a Place Within Diabetes Clinical Practice? Review of Current Evidence and Controversies.

Chloe H Firman, Duane D Mellor, David Unwin, Adrian Brown.

  Carbohydrate restriction has gained increasing popularity as an adjunctive nutritional therapy for diabetes management. However, controversy remains regarding the long-term suitability, safety, efficacy and potential superiority of a very low carbohydrate, ketogenic diet compared to current recommended nutritional approaches for diabetes management. Recommendations with respect to a ketogenic diet in clinical practice are often hindered by the lack of established definition, which prevents its capacity to be most appropriately prescribed as a therapeutic option for diabetes. Furthermore, with conflicted evidence, this has led to uncertainty amongst clinicians on how best to support and advise their patients. This review will explore whether a ketogenic diet has a place within clinical practice by reviewing current evidence and controversies.

Keywords:  Ketogenic diets; Low carbohydrate diets; Obesity; Type 1 diabetes; Type 2 diabetes

DOI:  https://doi.org/10.1007/s13300-023-01492-4
bioRxiv. 2023 Nov 03. pii: 2023.11.02.565382. [Epub ahead of print]

A diet-dependent host metabolite shapes the gut microbiota to protect from autoimmunity.

Margaret Alexander, Vaibhav Upadhyay, Rachel Rock, Lorenzo Ramirez, Patrycja Puchalska, Diego Orellana, Qi Yan Ang, Jessie A Turnbaugh, Yuan Tian, Darren Dumlao, Renuka Nayak, Andrew Patterson, John C Newman, Peter A Crawford, Peter J Turnbaugh.

Diet can protect from autoimmune disease; however, whether diet acts via the host and/or microbiome remains unclear. Here, we use a ketogenic diet (KD) as a model to dissect these complex interactions. A KD rescued the experimental autoimmune encephalomyelitis (EAE) mouse model of multiple sclerosis in a microbiota-dependent fashion. Dietary supplementation with a single KD-dependent host metabolite (β-hydroxybutyrate, βHB) rescued EAE whereas transgenic mice unable to produce βHB in the intestine developed more severe disease. Transplantation of the βHB-shaped gut microbiota was protective. Lactobacillus sequence variants were associated with decreased T helper 17 (Th17) cell activation in vitro . Finally, we isolated a L. murinus strain that protected from EAE, which was phenocopied by the Lactobacillus metabolite indole lactic acid. Thus, diet alters the immunomodulatory potential of the gut microbiota by shifting host metabolism, emphasizing the utility of taking a more integrative approach to study diet-host-microbiome interactions.

DOI: https://doi.org/10.1101/2023.11.02.565382
Nutrients. 2023 Nov 02. pii: 4647. [Epub ahead of print]15(21):

Nutritional Intervention in Cushing's Disease: The Ketogenic Diet's Effects on Metabolic Comorbidities and Adrenal Steroids.

Valentina Guarnotta, Roberta Amodei, Francesca Di Gaudio, Carla Giordano.

  BACKGROUND: a very low-calorie ketogenic diet (VLCKD) is associated with improvement of metabolic and cardiovascular disorders. We aimed to evaluate the effects of a VLCKD in patients with Cushing's disease (CD) as adjunctive therapy to treatment for the primary disease.METHODS: we evaluated clinical, hormonal and metabolic parameters in 15 patients with CD and 15 controls at baseline after 1 week and 3 weeks of VLCKD and, further, after 2 weeks of a low-carbohydrate ketogenic diet (LCKD).
RESULTS: after 5 weeks of diet, a significant decrease in BMI (p = 0.002), waist circumference (WC) (p = 0.024), systolic blood pressure (p = 0.015), diastolic blood pressure (p = 0.005), ACTH (p = 0.026), cortisone (p = 0.025), total cholesterol (p = 0.006), LDL cholesterol (p = 0.017), triglycerides (p = 0.016) and alkaline phosphatase (p = 0.008) and a significant increase in HDL cholesterol (p = 0.017), vitamin D (p = 0.015) and oral disposition index (oDI) (p = 0.004) was observed in the CD patients. A significant decrease in BMI (p = 0.003), WC (p = 0.002), systolic blood pressure (p = 0.025), diastolic (p = 0.007) blood pressure and total cholesterol (p = 0.026) and an increase in HDL cholesterol (p = 0.001) and oDI (p < 0.001) was observed in controls.
CONCLUSIONS: the current study confirms that a ketogenic diet is effective in improving metabolic disorders in CD and shows that a nutritional approach may be combined with conventional CD therapy in order to improve metabolic and cardiovascular comorbidities.

Keywords:  cortisone; diabetes mellitus; obesity; very low-calorie ketogenic diet

DOI:  https://doi.org/10.3390/nu15214647
Nutrients. 2023 Oct 31. pii: 4629. [Epub ahead of print]15(21):

Ketogenic Diet Has Moderate Effects on the Fecal Microbiota of Wild-Type Mice.

Nadine Rohwer, Racha El Hage, Christopher Smyl, Soeren Ocvirk, Tobias Goris, Tilman Grune, Alexander Swidsinski, Karsten-H Weylandt.

  The ketogenic diet (KD) is a high-fat, low-carbohydrate diet that has been reported to have neuroprotective effects. The health effects of KD might be linked to an altered gut microbiome, which plays a major role in host health, leading to neuroprotective effects via the gut-brain axis. However, results from different studies, most often based on the 16S rRNA gene and metagenome sequencing, have been inconsistent. In this study, we assessed the effect of a 4-week KD compared to a western diet (WD) on the colonic microbiome of female C57Bl/6J mice by analyzing fecal samples using fluorescence in situ hybridization. Our results showed distinct changes in the total number of gut bacteria following the 4-week KD, in addition to changes in the composition of the microbiome. KD-fed mice showed higher absolute numbers of Actinobacteria (especially Bifidobacteria spp.) and lower absolute levels of Proteobacteria, often linked to gut inflammation, in comparison with WD-fed mice. Furthermore, an increased abundance of the typically rare genus Atopobium was observed. These changes may indicate the possible anti-inflammatory effects of the KD. However, since the overall changes in the microbiota seem low, the KD effects might be linked to the differential abundance of only a few key genera in mice.

Keywords:  gut; ketogenic diet; ketosis; microbiome

DOI:  https://doi.org/10.3390/nu15214629
Nephrol Dial Transplant. 2023 Nov 16. pii: gfad239. [Epub ahead of print]

Higher beta-hydroxybutyrate ketone levels associated with a slower kidney function decline in ADPKD.

Martine G E Knol, Thomas Bais, Paul Geertsema, Margery A Connelly, Stephan J L Bakker, Ron T Gansevoort, Maatje D A van Gastel, R T Gansevoort, J P H Drenth, D J M Peters, M Salih, J W de Fijter, T Nijenhuis, E J Hoorn, E Meijer.

  BACKGROUND AND HYPOTHESIS: Dysregulated energy metabolism is a recently discovered key feature of Autosomal Dominant Polycystic Kidney Disease (ADPKD). Cystic cells depend on glucose and are poorly able to use other energy sources such as ketone bodies. Raising ketone body concentration reduced disease progression in animal models of polycystic kidney diseases. Therefore, we hypothesized that higher endogenous plasma beta-hydroxybutyrate concentrations are associated with reduced disease progression in patients with ADPKD.METHODS: We analyzed data from 670 patients with ADPKD participating in the DIPAK cohort, a multi-center prospective observational cohort study. Beta-hydroxybutyrate was measured at baseline using nuclear magnetic resonance spectroscopy. Participants were excluded if they had type 2 diabetes, were using disease-modifying drugs (e.g. tolvaptan, somatostatin analogs), were not fasting, or had missing beta-hydroxybutyrate levels, leaving 521 participants for the analyses. Linear regression analyses were used to study cross-sectional associations and linear mixed-effect modeling for longitudinal associations.
RESULTS: Of the participants, 61% were female, with an age of 47.3 ± 11.8 years, a height-adjusted total kidney volume (htTKV) of 834 (IQR 495-1327) ml/m, and an estimated glomerular filtration rate (eGFR) of 63.3 ± 28.9 mL/min/1.73m2. The median concentration of beta-hydroxybutyrate was 94 (IQR 68-147) µmol/L. Cross-sectionally, beta-hydroxybutyrate was neither associated with eGFR nor with htTKV. Longitudinally, beta-hydroxybutyrate was positively associated with eGFR slope (B = 0.35 ml/min/1.73m2 (95% CI 0.09 to 0.61), p = 0.007), but not with kidney growth. After adjustment for potential confounders, every doubling in beta-hydroxybutyrate concentration was associated with an improvement in the annual rate of eGFR by 0.33 ml/min/1.73m2 (95% CI 0.09 to 0.57, p = 0.008).
CONCLUSION: These observational analyses support the hypothesis that interventions that raise beta-hydroxybutyrate concentration could reduce the rate of kidney function decline in patients with ADPKD.

Keywords:  ADPKD; beta-hydroxybutyrate; biomarker; ketone bodies; kidney function; total kidney volume

DOI:  https://doi.org/10.1093/ndt/gfad239
Diabetologia. 2023 Nov 16.

Habitual carbohydrate intake is not correlated with circulating β-hydroxybutyrate levels in pregnant women with overweight and obesity at 28 weeks' gestation.

Helen L Tanner, Hui Ting Ng, Grace Murphy, Helen L Barrett, Leonie K Callaway, H David McIntyre, Marloes Dekker Nitert.

  AIMS/HYPOTHESIS: Pregnant women are advised to consume a minimum of 175 g per day of carbohydrate to meet maternal and fetal brain glucose requirements. This recommendation comes from a theoretical calculation of carbohydrate requirements in pregnancy, rather than from clinical data. This study aimed to determine whether fasting maternal ketone levels are associated with habitual carbohydrate intake in a subset of participants of the Study of PRobiotics IN Gestational diabetes (SPRING) randomised controlled trial.METHODS: Food frequency questionnaires on dietary intake during pregnancy were completed by pregnant women with overweight or obesity at 28 weeks' gestation (considering their intake from the beginning of pregnancy). Dietary intake from early pregnancy through to 28 weeks was analysed for macronutrient intake. At the same time, overnight fasting serum samples were obtained and analysed for metabolic parameters including serum β-hydroxybutyrate, OGTTs, insulin and C-peptide.
RESULTS: Fasting serum β-hydroxybutyrate levels amongst 108 women (mean BMI 34.7 ± 6.3 kg/m2) ranged from 22.2 to 296.5 μmol/l. Median fasting β-hydroxybutyrate levels were not different between women with high (median [IQR] 68.4 [49.1-109.2 μmol/l]) and low (65.4 [43.6-138.0 μmol/l]) carbohydrate intake in pregnancy. Fasting β-hydroxybutyrate levels were not correlated with habitual carbohydrate intake (median 155 [126-189] g/day). The only metabolic parameter with which fasting β-hydroxybutyrate levels were correlated was 1 h venous plasma glucose (ρ=0.23, p=0.03) during a 75 g OGTT.
CONCLUSIONS/INTERPRETATION: Fasting serum β-hydroxybutyrate levels are not associated with habitual carbohydrate intake at 28 weeks' gestation in pregnant women with overweight and obesity.

Keywords:  Carbohydrate intake; Gestational diabetes mellitus; Glucose; Insulin; Ketones; Pregnancy

DOI:  https://doi.org/10.1007/s00125-023-06044-w
Lancet Neurol. 2023 Dec;pii: S1474-4422(23)00370-8. [Epub ahead of print]22(12): 1113-1124

Classic ketogenic diet versus further antiseizure medicine in infants with drug-resistant epilepsy (KIWE): a UK, multicentre, open-label, randomised clinical trial.

KIWE study group

BACKGROUND: Many infancy-onset epilepsies have poor prognosis for seizure control and neurodevelopmental outcome. Ketogenic diets can improve seizures in children older than 2 years and adults who are unresponsive to antiseizure medicines. We aimed to establish the efficacy of a classic ketogenic diet at reducing seizure frequency compared with further antiseizure medicine in infants with drug-resistant epilepsy.METHODS: In this phase 4, open-label, multicentre, randomised clinical trial, infants aged 1-24 months with drug-resistant epilepsy (defined as four or more seizures per week and two or more previous antiseizure medications) were recruited from 19 hospitals in the UK. Following a 1-week or 2-week observation period, participants were randomly assigned using a computer-generated schedule, without stratification, to either a classic ketogenic diet or a further antiseizure medication for 8 weeks. Treatment allocation was masked from research nurses involved in patient care, but not from participants. The primary outcome was the median number of seizures per day, recorded during weeks 6-8. All analyses were by modified intention to treat, which included all participants with available data. Participants were followed for up to 12 months. All serious adverse events were recorded. The trial is registered with the European Union Drug Regulating Authorities Clinical Trials Database (2013-002195-40). The trial was terminated early before all participants had reached 12 months of follow-up because of slow recruitment and end of funding.
FINDINGS: Between Jan 1, 2015, and Sept 30, 2021, 155 infants were assessed for eligibility, of whom 136 met inclusion criteria and were randomly assigned; 75 (55%) were male and 61 (45%) were female. 78 infants were assigned to a ketogenic diet and 58 to antiseizure medication, of whom 61 and 47, respectively, had available data and were included in the modifified intention-to-treat analysis at week 8. The median number of seizures per day during weeks 6-8, accounting for baseline rate and randomised group, was similar between the ketogenic diet group (5 [IQR 1-16]) and antiseizure medication group (3 [IQR 2-11]; IRR 1·33, 95% CI 0·84-2·11). A similar number of infants with at least one serious adverse event was reported in both groups (40 [51%] of 78 participants in the ketogenic diet group and 26 [45%] of 58 participants in the antiseizure medication group). The most common serious adverse events were seizures in both groups. Three infants died during the trial, all of whom were randomly assigned a ketogenic diet: one child (who also had dystonic cerebral palsy) was found not breathing at home; one child died suddenly and unexpectedly at home; and one child went into cardiac arrest during routine surgery under anaesthetic. The deaths were judged unrelated to treatment by local principal investigators and confirmed by the data safety monitoring committee.
INTERPRETATION: In this phase 4 trial, a ketogenic diet did not differ in efficacy and tolerability to a further antiseizure medication, and it appears to be safe to use in infants with drug-resistant epilepsy. A ketogenic diet could be a treatment option in infants whose seizures continue despite previously trying two antiseizure medications.
FUNDING: National Institute for Health and Care Research.

DOI: https://doi.org/10.1016/S1474-4422(23)00370-8
J Appl Physiol (1985). 2023 Nov 16.

Combined changes in temperature and pH mimicking exercise results in decreased efficiency in muscle mitochondria.

Mathias Flensted-Jensen, Ann-Sofie Kleis-Olsen, Rasmus Kinimond Hassø, Søren Lindtofte, Juan Corral-Pérez, Sonia Ortega-Gómez, Steen Larsen.

  It is well known that exercise efficiency declines at intensities above the lactate threshold, yet the underlying mechanisms are poorly understood. Some have suggested it is due to a decline in mitochondrial efficiency, but this is difficult to examine in vivo. Therefore, the aim of the current study was to examine how changes in temperature and pH, mimicking those that occur during exercise, affect mitochondrial efficiency in skeletal muscle mitochondria. The study was performed on quadriceps muscle of 20 wild type mice. Muscle tissue was dissected and either permeabilized (n = 10) or homogenized for isolation of mitochondria (n = 10), and oxidative phosphorylation capacity and P/O ratio was assessed using high-resolution respirometry. Samples from each muscle was analyzed in both normal physiological conditions (37℃, pH 7.4), decreased pH (6.8), increased temperature (40℃) and a combination of both. The combination of increased temperature and decreased pH resulted in a significantly lower P/O ratio, mirrored by an increase in leak respiration and a decrease in respiratory control ratio (RCR), in isolated mitochondria. In permeabilized fibers, RCR and leak was relatively unaffected, though a main effect of temperature was observed. Oxidative phosphorylation capacity was unaffected by changes in pH and temperature in both isolated mitochondria and permeabilized fibers. These results indicate that exercise-like changes in temperature and pH leads to impaired mitochondrial efficiency. These findings offer some degree of support to the concept of decreased mitochondrial efficiency during exercise, and may have implications for the assessment of mitochondrial function related to exercise.

Keywords:  Exercise; Mitochondria; Mitochondrial efficiency; Temperature; pH

DOI:  https://doi.org/10.1152/japplphysiol.00293.2023
medRxiv. 2023 Oct 26. pii: 2023.10.25.23297571. [Epub ahead of print]

Rationale and protocol for a safety, tolerability and feasibility randomized, parallel group, double-blind, placebo-controlled, pilot study of a novel ketone ester targeting frailty via immunometabolic geroscience mechanisms.

Brianna J Stubbs, Gabriela Alvarez-Azanedo, Sawyer Peralta, Stephanie Roa-Diaz, Wyatt Gray, Laura Alexander, Wendie Silverman-Martin, Thelma Garcia, Traci M Blonquist, Vaibhav Upadhyay, Peter J Turnbaugh, James B Johnson, John C Newman.

Background: Frailty is a geriatric syndrome characterized by chronic inflammation and metabolic insufficiency that creates vulnerability to poor outcomes with aging. We hypothesize that geroscience interventions, which target mechanisms of aging, could ameliorate frailty. Metabolites such as ketone bodies are candidate geroscience interventions, having pleiotropic effects on inflammo-metabolic aging mechanisms. Ketone esters (KEs) induce ketosis without dietary changes, but KEs have not been studied in an older adult population. Our long-term goal is to examine if KEs modulate geroscience mechanisms and clinical outcomes relevant to frailty in older adults.Objectives: The primary objective of this randomized, placebo-controlled, double-blinded, parallel-group, pilot trial is to determine tolerability of 12-weeks of KE ingestion in a generalizable population of older adults (≥ 65 years). Secondary outcomes include safety and acute blood ketone kinetics. Exploratory outcomes include physical function, cognitive function, quality of life, aging biomarkers and inflammatory measures.
Methods: Community-dwelling adults who are independent in activities of daily living, with no unstable acute medical conditions (n=30) will be recruited. The study intervention is a KE or a taste, appearance, and calorie matched placebo beverage. Initially, acute 4-hour ketone kinetics after 12.5g or 25g of KE consumption will be assessed. After collection of baseline safety, functional, and biological measurements, subjects will randomly be allocated to consume KE 25g or placebo once daily for 12-weeks. Questionnaires will assess tolerability daily for 2-weeks, and then via phone interview at bi-monthly intervals. Safety assessments will be repeated at week 4. All measures will be repeated at week 12.
Conclusion: This study will evaluate feasibility, tolerability, and safety of KE consumption in older adults and provide exploratory data across a range of geroscience-related endpoints. This data will inform design of larger trials to rigorously test KE effects on geroscience mechanisms and clinical outcomes relevant to frailty.

DOI: https://doi.org/10.1101/2023.10.25.23297571
Int J Mol Sci. 2023 Oct 24. pii: 15536. [Epub ahead of print]24(21):

Changes in Plasma Pyruvate and TCA Cycle Metabolites upon Increased Hepatic Fatty Acid Oxidation and Ketogenesis in Male Wistar Rats.

Simon Nitter Dankel, Tine-Lise Kalleklev, Siri Lunde Tungland, Marit Hallvardsdotter Stafsnes, Per Bruheim, Thomas Aquinas Aloysius, Carine Lindquist, Jon Skorve, Ottar Kjell Nygård, Lise Madsen, Bodil Bjørndal, Magne Olav Sydnes, Rolf Kristian Berge.

  Altered hepatic mitochondrial fatty acid β-oxidation and associated tricarboxylic acid (TCA) cycle activity contributes to lifestyle-related diseases, and circulating biomarkers reflecting these changes could have disease prognostic value. This study aimed to determine hepatic and systemic changes in TCA-cycle-related metabolites upon the selective pharmacologic enhancement of mitochondrial fatty acid β-oxidation in the liver, and to elucidate the mechanisms and potential markers of hepatic mitochondrial activity. Male Wistar rats were treated with 3-thia fatty acids (e.g., tetradecylthioacetic acid (TTA)), which target mitochondrial biogenesis, mitochondrial fatty acid β-oxidation, and ketogenesis predominantly in the liver. Hepatic and plasma concentrations of TCA cycle intermediates and anaplerotic substrates (LC-MS/MS), plasma ketones (colorimetric assay), and acylcarnitines (HPLC-MS/MS), along with associated TCA-cycle-related gene expression (qPCR) and enzyme activities, were determined. TTA-induced hepatic fatty acid β-oxidation resulted in an increased ratio of plasma ketone bodies/nonesterified fatty acid (NEFA), lower plasma malonyl-CoA levels, and a higher ratio of plasma acetylcarnitine/palmitoylcarnitine (C2/C16). These changes were associated with decreased hepatic and increased plasma pyruvate concentrations, and increased plasma concentrations of succinate, malate, and 2-hydroxyglutarate. Expression of several genes encoding TCA cycle enzymes and the malate-oxoglutarate carrier (Slc25a11), glutamate dehydrogenase (Gdh), and malic enzyme (Mdh1 and Mdh2) were significantly increased. In conclusion, the induction of hepatic mitochondrial fatty acid β-oxidation by 3-thia fatty acids lowered hepatic pyruvate while increasing plasma pyruvate, as well as succinate, malate, and 2-hydroxyglutarate.

Keywords:  biomarkers; fatty acid oxidation; ketogenesis; liver; mitochondria

DOI:  https://doi.org/10.3390/ijms242115536
medRxiv. 2023 Oct 25. pii: 2023.10.24.23297480. [Epub ahead of print]

Associations of Skeletal Muscle Mass, Muscle Fat Infiltration, Mitochondrial Energetics, and Cardiorespiratory Fitness with Liver Fat Among Older Adults.

Daria Igudesman, Justine Mucinski, Stephanie Harrison, Peggy M Cawthon, Jennifer Linge, Bret H Goodpaster, Steven R Cummings, Russell T Hepple, Michael J Jurczak, Stephen B Kritchevsky, David Marcinek, Paul M Coen, Karen D Corbin.

Background: Muscle mass loss may be associated with liver fat accumulation, yet scientific consensus is lacking and evidence in older adults is scant. It is unclear which muscle characteristics might contribute to this association in older adults.Methods: We associated comprehensive muscle-related phenotypes including muscle mass normalized to body weight (D 3 -creatine dilution), muscle fat infiltration (MRI), carbohydrate-supported muscle mitochondrial maximal oxidative phosphorylation (respirometry), and cardiorespiratory fitness (VO 2 peak) with liver fat among older adults. Linear regression models adjusted for age, gender, technician (respirometry only), daily minutes of moderate to vigorous physical activity, and prediabetes/diabetes status tested main effects and interactions of each independent variable with waist circumference (high: women-≥88 cm, men-≥102 cm) and gender.
Results: Among older adults aged 75 (IQR 73, 79 years; 59.8% women), muscle mass and liver fat were not associated overall but were positively associated among participants with a high waist circumference (β: 25.2; 95%CI 11.7, 40.4; p =.0002; N=362). Muscle fat infiltration and liver fat were positively associated (β: 15.2; 95%CI 6.8, 24.3; p =.0003; N=378). Carbohydrate-supported maximum oxidative phosphorylation and VO 2 peak (adjusted β: -12.9; 95%CI -20.3, -4.8; p =0.003; N=361) were inversely associated with liver fat; adjustment attenuated the estimate for maximum oxidative phosphorylation although the point estimate remained negative (β: -4.0; 95%CI -11.6, 4.2; p =0.32; N=321).
Conclusions: Skeletal muscle-related characteristics are metabolically relevant factors linked to liver fat in older adults. Future research should confirm our results to determine whether trials targeting mechanisms common to liver and muscle fat accumulation are warranted.

DOI: https://doi.org/10.1101/2023.10.24.23297480
Biochem J. 2023 Nov 15. 480(21): 1767-1789

Interactions of mitochondrial and skeletal muscle biology in mitochondrial myopathy.

Valeria Di Leo, Tiago M Bernardino Gomes, Amy E Vincent.

  Mitochondrial dysfunction in skeletal muscle fibres occurs with both healthy aging and a range of neuromuscular diseases. The impact of mitochondrial dysfunction in skeletal muscle and the way muscle fibres adapt to this dysfunction is important to understand disease mechanisms and to develop therapeutic interventions. Furthermore, interactions between mitochondrial dysfunction and skeletal muscle biology, in mitochondrial myopathy, likely have important implications for normal muscle function and physiology. In this review, we will try to give an overview of what is known to date about these interactions including metabolic remodelling, mitochondrial morphology, mitochondrial turnover, cellular processes and muscle cell structure and function. Each of these topics is at a different stage of understanding, with some being well researched and understood, and others in their infancy. Furthermore, some of what we know comes from disease models. Whilst some findings are confirmed in humans, where this is not yet the case, we must be cautious in interpreting findings in the context of human muscle and disease. Here, our goal is to discuss what is known, highlight what is unknown and give a perspective on the future direction of research in this area.

Keywords:  function; metabolism; mitochondria; mitochondrial dysfunction; structure

DOI:  https://doi.org/10.1042/BCJ20220233
Biochim Biophys Acta Mol Cell Res. 2023 Jul 04. pii: S0167-4889(23)00101-5. [Epub ahead of print] 119529

Mitochondrial entry gate as regulatory hub.

Fabian den Brave, Nikolaus Pfanner, Thomas Becker.

  Mitochondria import 1000-1300 different precursor proteins from the cytosol. The main mitochondrial entry gate is formed by the translocase of the outer membrane (TOM complex). Molecular coupling and modification of TOM subunits control and modulate protein import in response to cellular signaling. The TOM complex functions as regulatory hub to integrate mitochondrial protein biogenesis and quality control into the cellular proteostasis network.

Keywords:  Mitochondria; Protein sorting; Proteostasis; Quality control; Stress response; TOM complex

DOI:  https://doi.org/10.1016/j.bbamcr.2023.119529
Int J Mol Sci. 2023 Oct 26. pii: 15621. [Epub ahead of print]24(21):

Ketosis Suppression and Ageing (KetoSAge): The Effects of Suppressing Ketosis in Long Term Keto-Adapted Non-Athletic Females.

Isabella D Cooper, Yvoni Kyriakidou, Kurtis Edwards, Lucy Petagine, Thomas N Seyfried, Tomas Duraj, Adrian Soto-Mota, Andrew Scarborough, Sandra L Jacome, Kenneth Brookler, Valentina Borgognoni, Vanusa Novaes, Rima Al-Faour, Bradley T Elliott.

  Most studies on ketosis have focused on short-term effects, male athletes, or weight loss. Hereby, we studied the effects of short-term ketosis suppression in healthy women on long-standing ketosis. Ten lean (BMI 20.5 ± 1.4), metabolically healthy, pre-menopausal women (age 32.3 ± 8.9) maintaining nutritional ketosis (NK) for > 1 year (3.9 years ± 2.3) underwent three 21-day phases: nutritional ketosis (NK; P1), suppressed ketosis (SuK; P2), and returned to NK (P3). Adherence to each phase was confirmed with daily capillary D-beta-hydroxybutyrate (BHB) tests (P1 = 1.9 ± 0.7; P2 = 0.1 ± 0.1; and P3 = 1.9 ± 0.6 pmol/L). Ageing biomarkers and anthropometrics were evaluated at the end of each phase. Ketosis suppression significantly increased: insulin, 1.78-fold from 33.60 (± 8.63) to 59.80 (± 14.69) pmol/L (p = 0.0002); IGF1, 1.83-fold from 149.30 (± 32.96) to 273.40 (± 85.66) µg/L (p = 0.0045); glucose, 1.17-fold from 78.6 (± 9.5) to 92.2 (± 10.6) mg/dL (p = 0.0088); respiratory quotient (RQ), 1.09-fold 0.66 (± 0.05) to 0.72 (± 0.06; p = 0.0427); and PAI-1, 13.34 (± 6.85) to 16.69 (± 6.26) ng/mL (p = 0.0428). VEGF, EGF, and monocyte chemotactic protein also significantly increased, indicating a pro-inflammatory shift. Sustained ketosis showed no adverse health effects, and may mitigate hyperinsulinemia without impairing metabolic flexibility in metabolically healthy women.

Keywords:  ageing; beta-hydroxybutyrate; cancer; hyperinsulinaemia; insulin resistance; ketosis; type 2 diabetes mellitus

DOI:  https://doi.org/10.3390/ijms242115621
Cell Rep. 2023 Nov 16. pii: S2211-1247(23)01477-8. [Epub ahead of print]42(11): 113465

MCUb is an inducible regulator of calcium-dependent mitochondrial metabolism and substrate utilization in muscle.

Jiuzhou Huo, Vikram Prasad, Kelly M Grimes, Davy Vanhoutte, N Scott Blair, Suh-Chin Lin, Michael J Bround, Donald M Bers, Jeffery D Molkentin.

  Mitochondria use the electron transport chain to generate high-energy phosphate from oxidative phosphorylation, a process also regulated by the mitochondrial Ca2+ uniporter (MCU) and Ca2+ levels. Here, we show that MCUb, an inhibitor of MCU-mediated Ca2+ influx, is induced by caloric restriction, where it increases mitochondrial fatty acid utilization. To mimic the fasted state with reduced mitochondrial Ca2+ influx, we generated genetically altered mice with skeletal muscle-specific MCUb expression that showed greater fatty acid usage, less fat accumulation, and lower body weight. In contrast, mice lacking Mcub in skeletal muscle showed increased pyruvate dehydrogenase activity, increased muscle malonyl coenzyme A (CoA), reduced fatty acid utilization, glucose intolerance, and increased adiposity. Mechanistically, pyruvate dehydrogenase kinase 4 (PDK4) overexpression in muscle of Mcub-deleted mice abolished altered substrate preference. Thus, MCUb is an inducible control point in regulating skeletal muscle mitochondrial Ca2+ levels and substrate utilization that impacts total metabolic balance.

Keywords:  CP: Metabolism; metabolism; mitochondria; obesity; skeletal muscle; substrate utilization

DOI:  https://doi.org/10.1016/j.celrep.2023.113465
Exp Physiol. 2023 Nov 16.

Stuart has got the PoWeR! Skeletal muscle adaptations to a novel heavy progressive weighted wheel running exercise model in C57BL/6 mice.

Pieter J Koopmans, Therin D Williams-Frey, Kevin A Zwetsloot.

  Murine exercise models are developed to study the molecular and cellular mechanisms regulating muscle mass. A progressive weighted wheel running model, named 'PoWeR', was previously developed to serve as a more translatable alternative to involuntary resistance-type exercise models in rodents, such as synergist ablation. However, mice still run great distances despite the added resistance as evidenced by a large glycolytic-to-oxidative shift in muscle fibre type. Thus, PoWeR reflects a blended resistance/endurance model. In an attempt to bias PoWeR further towards resistance-type exercise, we developed a novel heavy PoWeR model (hPoWeR) utilizing higher wheel loads (max of 12.5 g vs 6 g). Adult male C57BL/6 mice voluntarily performed an 8-week progressive loading protocol (PoWeR or hPoWeR). Running distance peaked at ∼5-6 km day-1 in both treatments and was maintained by PoWeR mice, but declined in the hPoWeR mice as load increased beyond 7.5 g. Peak isometric force of the gastrocnemius-soleus-plantaris complex tended to increase in wheel running treatments. Soleus mass increased by 19% and 24% in PoWeR and hPoWeR treatments, respectively, and plantaris fibre cross-sectional area was greater in hPoWeR, compared to PoWeR. There were fewer glycolytic and more oxidative fibres in the soleus and plantaris muscles in the PoWeR treatment, but not hPoWeR. Collectively, these data suggest hPoWeR may modestly alter skeletal muscle supporting the aim of better reflecting typical resistance training adaptations, in line with decreased running volume and exposure to higher resistance. Regardless, PoWeR remains an effective hypertrophic concurrent training model in mice. NEW FINDINGS: What is the central question of this study? Can utilizing a heavier loading protocol, compared to the previously developed progressive weighted wheel running (PoWeR) exercise model, bias skeletal muscle adaptations further towards resistance-type exercise in mice? What is the main finding and its importance? Utilizing a significantly heavier wheel loading protocol, which may better reflect traditional resistance-type exercise training, only modestly alters skeletal muscle adaptations. These results intuitively demonstrate decreased running distance with exposure to higher resistance, compared to PoWeR; however, murine wheel running models may always inherently possess a strong endurance training component.

Keywords:  murine exercise models; muscle hypertrophy; resistance exercise

DOI:  https://doi.org/10.1113/EP091494
Cardiovasc Diabetol. 2023 Nov 16. 22(1): 316

Sodium-glucose cotransporter-2 inhibition for heart failure with preserved ejection fraction and chronic kidney disease with or without type 2 diabetes mellitus: a narrative review.

Robert J Mentz, Stephen A Brunton, Janani Rangaswami.

  BACKGROUND: Heart failure (HF), chronic kidney disease (CKD), and type 2 diabetes mellitus (T2DM) are common and interrelated conditions, each with a significant burden of disease. HF and kidney disease progress through pathophysiologic pathways that culminate in end-stage disease, for which T2DM is a major risk factor. Intervention within these pathways can disrupt disease processes and improve patient outcomes. Sodium-glucose cotransporter-2 inhibitors (SGLT2is) have been investigated in patient populations with combinations of T2DM, CKD, and/or HF. However, until recently, the effect of these agents in patients with HF with preserved ejection fraction (HFpEF) was not well studied.MAIN BODY: The aim of this review is to summarize key information regarding the interaction between HFpEF, CKD, and T2DM and discuss the role of SGLT2 inhibition in the management of patients with comorbid HFpEF and CKD, with or without T2DM. Literature was retrieved using Boolean searches for English-language articles in PubMed and Google Scholar and included terms related to SGLT2is, HFpEF, T2DM, and CKD. The reference lists from retrieved articles were also considered.
CONCLUSION: SGLT2is are efficacious and safe in treating HFpEF in patients with comorbid CKD with and without T2DM. The totality of evidence from clinical trials data suggests there are benefits in using SGLT2is across the spectrum of left ventricular ejection fractions, but there may be a potential for different renal effects in the different ejection fraction groups. Further analysis of these clinical trials has highlighted the need to obtain more accurate phenotypes for patients with HF and CKD to better determine which patients might respond to guideline-directed medical therapies, including SGLT2is. CI confidence interval, EF ejection fraction, eGFR estimated glomerular filtration rate, HF heart failure, HHF hospitalization for HF, HR hazard ratio, LVEF left ventricular ejection fraction, SGLT2i sodium-glucose cotransporter-2 inhibitor, UACR urine albumin-creatinine ratio. a Mean value, unless otherwise stated, b SGLT2i vs. placebo, c Data reanalyzed using more conventional endpoints (≥ 50% sustained decrease in eGFR, and including renal death) (UACR at baseline not stated in trial reports).

Keywords:  Cardio-kidney metabolic; Cardiorenal syndrome; Cardiovascular disease; Chronic kidney disease; Diabetic kidney disease; Heart failure with preserved ejection fraction; Sodium-glucose cotransporter-2 inhibitors; Type 2 diabetes mellitus

DOI:  https://doi.org/10.1186/s12933-023-02023-y
Heliyon. 2023 Nov;9(11): e21282

Xanthohumol alleviates palmitate-induced inflammation and prevents osteoarthritis progression by attenuating mitochondria dysfunction/NLRP3 inflammasome axis.

Weichao Sun, Jiaji Yue, Tianhao Xu, Yinxing Cui, Dixi Huang, Houyin Shi, Jianyi Xiong, Wei Sun, Qian Yi.

  Osteoarthritis (OA) is a prevalent chronic degenerative joint disease worldwide. Obesity has been linked to OA, and increased free fatty acid levels (e.g., palmitate) contribute to inflammatory responses and cartilage degradation. Xanthohumol (Xn), a bioactive prenylated chalcone, was shown to exhibit antioxidative, anti-inflammatory, and anti-obesity capacities in multiple diseases. However, a clear description of the preventive effects of Xn on obesity-associated OA is unavailable. This study aimed to assess the chondroprotective function of Xn on obesity-related OA. The in vitro levels of inflammatory and ECM matrix markers in human chondrocytes were assessed after the chondrocytes were treated with PA and Xn. Additionally, in vivo cartilage degeneration was assessed following oral administration of HFD and Xn. This study found that Xn treatment completely reduces the inflammation and extracellular matrix degradation caused by PA. The proposed mechanism involves AMPK signaling pathway activation by Xn, which increases mitochondrial biogenesis, attenuates mitochondrial dysfunction, and inhibits NLRP3 inflammasome and the NF-κB signaling pathway induced by PA. In summary, this study highlights that Xn could decrease inflammation reactions and the degradation of the cartilage matrix induced by PA by inhibiting the NLRP3 inflammasome and attenuating mitochondria dysfunction in human chondrocytes.

Keywords:  AMPK/NF-κB signaling pathway; Mitochondria dysfunction; NLRP3 inflammasome; Osteoarthritis; Palmitate; Xanthohumol

DOI:  https://doi.org/10.1016/j.heliyon.2023.e21282
Proteomics. 2023 Nov 14. e2300395

People with obesity exhibit losses in muscle proteostasis that are partly improved by exercise training.

Kanchana Srisawat, Connor A Stead, Katie Hesketh, Mark Pogson, Juliette A Strauss, Matt Cocks, Ivo Siekmann, Stuart M Phillips, Paulo J Lisboa, Sam Shepherd, Jatin G Burniston.

  This pilot experiment examines if a loss in muscle proteostasis occurs in people with obesity and whether endurance exercise positively influences either the abundance profile or turnover rate of proteins in this population. Men with (n = 3) or without (n = 4) obesity were recruited and underwent a 14-d measurement protocol of daily deuterium oxide (D2 O) consumption and serial biopsies of vastus lateralis muscle. Men with obesity then completed 10-weeks of high-intensity interval training (HIIT), encompassing 3 sessions per week of cycle ergometer exercise with 1 min intervals at 100% maximum aerobic power interspersed by 1 min recovery periods. The number of intervals per session progressed from 4 to 8, and during weeks 8-10 the 14-d measurement protocol was repeated. Proteomic analysis detected 352 differences (p < 0.05, false discovery rate < 5%) in protein abundance and 19 (p < 0.05) differences in protein turnover, including components of the ubiquitin-proteasome system. HIIT altered the abundance of 53 proteins and increased the turnover rate of 22 proteins (p < 0.05) and tended to benefit proteostasis by increasing muscle protein turnover rates. Obesity and insulin resistance are associated with compromised muscle proteostasis, which may be partially restored by endurance exercise.

Keywords:  biosynthetic labelling; deuterium oxide; fractional synthesis rate; heat shock proteins; heavy water; muscle protein synthesis; protein turnover; proteomics; skeletal muscle; ubiquitin proteasome system

DOI:  https://doi.org/10.1002/pmic.202300395
Aging Cell. 2023 Nov 13. e14009

3D reconstruction of murine mitochondria reveals changes in structure during aging linked to the MICOS complex.

Zer Vue, Edgar Garza-Lopez, Kit Neikirk, Prasanna Katti, Larry Vang, Heather Beasley, Jianqiang Shao, Andrea G Marshall, Amber Crabtree, Alexandria C Murphy, Brenita C Jenkins, Praveena Prasad, Chantell Evans, Brittany Taylor, Margaret Mungai, Mason Killion, Dominique Stephens, Trace A Christensen, Jacob Lam, Benjamin Rodriguez, Mark A Phillips, Nastaran Daneshgar, Ho-Jin Koh, Alice Koh, Jamaine Davis, Nina Devine, Saleem Muhammod, Estevão Scudese, Kenneth Ryan Arnold, Valeria Vanessa Chavarin, Ryan Daniel Robinson, Moumita Chakraborty, Jennifer A Gaddy, Mariya T Sweetwyne, Genesis Wilson, Elma Zaganjor, James Kezos, Cristiana Dondi, Anilkumar K Reddy, Brian Glancy, Annet Kirabo, Anita M Quintana, Dao-Fu Dai, Karen Ocorr, Sandra A Murray, Steven M Damo, Vernat Exil, Blake Riggs, Bret C Mobley, Jose A Gomez, Melanie R McReynolds, Antentor Hinton.

  During aging, muscle gradually undergoes sarcopenia, the loss of function associated with loss of mass, strength, endurance, and oxidative capacity. However, the 3D structural alterations of mitochondria associated with aging in skeletal muscle and cardiac tissues are not well described. Although mitochondrial aging is associated with decreased mitochondrial capacity, the genes responsible for the morphological changes in mitochondria during aging are poorly characterized. We measured changes in mitochondrial morphology in aged murine gastrocnemius, soleus, and cardiac tissues using serial block-face scanning electron microscopy and 3D reconstructions. We also used reverse transcriptase-quantitative PCR, transmission electron microscopy quantification, Seahorse analysis, and metabolomics and lipidomics to measure changes in mitochondrial morphology and function after loss of mitochondria contact site and cristae organizing system (MICOS) complex genes, Chchd3, Chchd6, and Mitofilin. We identified significant changes in mitochondrial size in aged murine gastrocnemius, soleus, and cardiac tissues. We found that both age-related loss of the MICOS complex and knockouts of MICOS genes in mice altered mitochondrial morphology. Given the critical role of mitochondria in maintaining cellular metabolism, we characterized the metabolomes and lipidomes of young and aged mouse tissues, which showed profound alterations consistent with changes in membrane integrity, supporting our observations of age-related changes in muscle tissues. We found a relationship between changes in the MICOS complex and aging. Thus, it is important to understand the mechanisms that underlie the tissue-dependent 3D mitochondrial phenotypic changes that occur in aging and the evolutionary conservation of these mechanisms between Drosophila and mammals.

Keywords:   Drosophila ; 3D morphometry; MICOS; aging; mitochondria; mitochondrial disease; mitochondrion; reconstruction; reticulum; serial block-face SEM; skeletal muscle

DOI:  https://doi.org/10.1111/acel.14009
Int Immunopharmacol. 2023 Nov 09. pii: S1567-5769(23)01521-7. [Epub ahead of print]125(Pt B): 111194

The E3 ubiquitin ligase RNF31 mediates the development of ulcerative colitis by regulating NLRP3 inflammasome activation.

Peng Wang, Chao-Tao Tang, Jun Li, Xia Huang, Ruiri Jin, Fang Yin, Zide Liu, Youxiang Chen, Chunyan Zeng.

  Ulcerative colitis (UC) is characterized by dysregulated inflammation and disruption of the intestinal barrier. The NLRP3 inflammasome, which is composed of NLRP3, ASC, and caspase-1, plays a crucial role in UC pathogenesis by triggering the production of proinflammatory cytokines. In this study, we investigated the regulatory role of RNF31 in NLRP3 inflammasome activation during UC development. Through comprehensive analysis of ulcerative colitis tissues using the GEO database and immunohistochemistry, we found that RNF31 expression was elevated in UC tissues, which prompted further investigation into its function. We constructed an RNF31 knockdown cell model and observed a significant reduction in NLRP3 inflammasome activation, indicating the involvement of RNF31 in regulating NLRP3. Mechanistically, RNF31 could interact with NLRP3 through the RBR structural domain, leading to increased K63-linked ubiquitination of NLRP3 and consequent stabilization. Coimmunoprecipitation experiments revealed a mutual interaction between RNF31 and NLRP3, substantiating their functional association. Finally, an in vivo mouse model with RNF31 knockdown showed a notable reduction in NLRP3 expression, which was accompanied by a decrease in the proinflammatory cytokines IL-18 and IL-1β. The successful attenuation of DSS-induced tissue inflammation by this treatment confirmed the physiological relevance of RNF31-mediated regulation of NLRP3. This study unveils a novel regulatory pathway by which RNF31 affects NLRP3 inflammasome activation, providing new insights into UC pathogenesis and potential therapeutic targets for UC treatment.

Keywords:  E3 ubiquitin ligase; NLRP3 inflammasome; RNF31; Ulcerative colitis

DOI:  https://doi.org/10.1016/j.intimp.2023.111194
J Control Release. 2023 Nov 14. pii: S0168-3659(23)00738-1. [Epub ahead of print]

Mitochondria-targeted SkQ1 nanoparticles for dry eye disease: Inhibiting NLRP3 inflammasome activation by preventing mitochondrial DNA oxidation.

Baoshan Huang, Na Zhang, Xinying Qiu, Rui Zeng, Shuimiao Wang, Mengxia Hua, Qing Li, Kaihui Nan, Sen Lin.

  Dry eye disease (DED) is a multifactorial ocular surface disorder mutually promoted by reactive oxygen species (ROS) and ocular surface inflammation. NLRP3 is the key regulator for inducing ocular surface inflammation in DED. However, the mechanism by which ROS influences the bio-effects of NLRP3, and the consequent development of DED, largely remains elusive. In the present study, we uncovered that robust ROS can oxidate mitochondrial DNA (ox-mtDNA) along with loss of mitochondria compaction causing the cytosolic release of ox-mtDNA and subsequent co-localization with cytosolic NLRP3, which can promote the activation of NLRP3 inflammasome and stimulate NLRP3-mediated inflammation. Visomitin (also known as SkQ1), a mitochondria-targeted anti-oxidant, could reverse such a process by in situ scavenging of mitochondrial ROS. To effectively deliver SkQ1, we further developed a novel mitochondria-targeted SkQ1 nanoparticle (SkQ1 NP) using a charge-driven self-assembly strategy. Compared with free SkQ1, SkQ1 NPs exhibited significantly higher cytosolic- and mitochondrial-ROS scavenging activity (1.7 and 1.9 times compared to levels of the free SkQ1 group), thus exerting a better in vitro protective effect against H2O2-induced cell death in human corneal epithelial cells (HCECs). After topical administration, SkQ1 NPs significantly reduced in vivo mtDNA oxidation, while suppressing the expressions of NLRP3, Caspase-1, and IL-1β, which consequently resulted in better therapeutic effects against DED. Results suggested that by efficiently scavenging mitochondrial ROS, SkQ1 NPs could in situ inhibit DED-induced mtDNA oxidation, thus blocking the interaction of ox-mtDNA and NLRP3; this, in turn, suppressed NLRP3 inflammasome activation and NLRP3-mediated inflammatory signaling. Results suggested that SkQ1 NPs have great potential as a new treatment for DED.

Keywords:  Dry eye disease; Mitochondria-specific antioxidants; Mitochondrial DNA; NLRP3 inflammasome; SkQ1 nanoparticle

DOI:  https://doi.org/10.1016/j.jconrel.2023.11.021
Front Pharmacol. 2023 ;14 1243613

The mechanisms of action of mitochondrial targeting agents in cancer: inhibiting oxidative phosphorylation and inducing apoptosis.

Yi Yang, Yahui An, Mingli Ren, Haijiao Wang, Jing Bai, Wenli Du, Dezhi Kong.

  The tumor microenvironment affects the structure and metabolic function of mitochondria in tumor cells. This process involves changes in metabolic activity, an increase in the amount of reactive oxygen species (ROS) in tumor cells compared to normal cells, the production of more intracellular free radicals, and the activation of oxidative pathways. From a practical perspective, it is advantageous to develop drugs that target mitochondria for the treatment of malignant tumors. Such drugs can enhance the selectivity of treatments for specific cell groups, minimize toxic effects on normal tissues, and improve combinational treatments. Mitochondrial targeting agents typically rely on small molecule medications (such as synthetic small molecules agents, active ingredients of plants, mitochondrial inhibitors or autophagy inhibitors, and others), modified mitochondrial delivery system agents (such as lipophilic cation modification or combining other molecules to form targeted mitochondrial agents), and a few mitochondrial complex inhibitors. This article will review these compounds in three main areas: oxidative phosphorylation (OXPHOS), changes in ROS levels, and endogenous oxidative and apoptotic processes.

Keywords:  electron transport chain (ETC); mechanism; mitocans; mitochondria targeting drug; oxidative phoshorylation; reactive oxygen species

DOI:  https://doi.org/10.3389/fphar.2023.1243613
Int J Mol Sci. 2023 Oct 30. pii: 15753. [Epub ahead of print]24(21):

Critical Velocity, Maximal Lactate Steady State, and Muscle MCT1 and MCT4 after Exhaustive Running in Mice.

Juan B Orsi, Lara S Araujo, Pedro P M Scariot, Emanuel E C Polisel, Luisa O Cardoso, Claudio A Gobatto, Fúlvia B Manchado-Gobatto.

  Although the critical velocity (CV) protocol has been used to determine the aerobic capacity in rodents, there is a lack of studies that compare CV with maximal lactate steady state intensity (iMLSS) in mice. As a consequence, their physiological and molecular responses after exercise until exhaustion at CV intensity remain unclear. Thus, we aimed to compare and correlate CV with iMLSS in running mice, following different mathematical models for CV estimation. We also evaluated their physiological responses and muscle MCT1 and MCT4 after running until exhaustion at CV. Thirty C57BL/6J mice were divided into two groups (exercised-E and control-C). Group E was submitted to a CV protocol (4 days), using linear (lin1 and lin2) and hyperbolic (hyp) mathematical models to determine the distance, velocity, and time to exhaustion (tlim) of each predictive CV trial, followed by an MLSS protocol. After a running effort until exhaustion at CV intensity, the mice were immediately euthanized, while group C was euthanized at rest. No differences were observed between iMLSS (21.1 ± 1.1 m.min-1) and CV estimated by lin1 (21.0 ± 0.9 m.min-1, p = 0.415), lin2 (21.3 ± 0.9 m.min-1, p = 0.209), and hyp (20.6 ± 0.9 m.min-1, p = 0.914). According to the results, CV was significantly correlated with iMLSS. After running until exhaustion at CV (tlim = 28.4 ± 8,29 min), group E showed lower concentrations of hepatic and gluteal glycogen than group C, but no difference in the content of MCT1 (p = 0.933) and MCT4 (p = 0.123) in soleus muscle. Significant correlations were not found between MCT1 and MCT4 and tlim at CV intensity. Our results reinforce that CV is a valid and non-invasive protocol to estimate the maximal aerobic capacity in mice and that the content of MCT1 and MCT4 was not decisive in determining the tlim at CV, at least when measured immediately after the running effort.

Keywords:  aerobic capacity; blood lactate; mathematical models; monocarboxylate transporters; physiological parameters; running mice

DOI:  https://doi.org/10.3390/ijms242115753
Eur J Clin Invest. 2023 Nov 17. e14128

Real-time OXPHOS capacity analysis in wounded skin from diabetic mice: A pilot study.

Aryane Cruz Oliveira Pinho, Diana Santos, Paulo J Oliveira, Ermelindo Carreira Leal, Eugenia Carvalho.

  INTRODUCTION: Diabetes mellitus (DM) impairs wound healing. The aim was to determine whether DM influences mitochondrial respiration in wounded skin (WS) and non-wounded skin (NWS), in a pre-clinical wound healing model of streptozotocin (STZ)-induced diabetes.METHODS: Six weeks after diabetes induction, two wounds were created in the back of C57BL/J6 mice. Using high-resolution respirometry (HRR), oxygen flux was measured, in WS and NWS, using two substrate-uncoupler-inhibitor titration protocols, at baseline (day 0), day 3 and 10 post-wounding, in STZ-DM and non-diabetic (NDM) mice. Flux control ratios for the oxidative phosphorylation (OXPHOS) capacity were calculated.
RESULTS: A significant increase in mitochondrial respiration was observed in STZ-DM skin compared to control skin at baseline. The OXPHOS capacity was decreased in WS under diabetes at day 3 post-wounding (inflammation phase). However, at day 10 post-wounding (remodeling phase), the OXPHOS capacity was higher in WS from STZ-DM compared to NDM mice, and compared to NWS from STZ-DM mice. A significant relative contribution of pyruvate, malate and glutamate (PMG) oxidation to the OXPHOS capacity was observed in WS compared to NWS from STZ-DM mice, at day 10, while the relative contribution of fatty acid oxidation to the OXPHOS capacity was higher in NWS. The OXPHOS capacity is altered in WS from STZ-DM compared to NDM mice across the healing process, and so is the substrate contribution in WS and NWS from STZ-DM mice, at each time point.
CONCLUSION: HRR may be a sensitive tool to evaluate the underlying mechanisms of tissue repair during wound healing.

Keywords:  OXPHOS capacity; diabetes; diabetic wound; high-resolution respirometry; mitochondrial respiration; skin

DOI:  https://doi.org/10.1111/eci.14128
J Sci Med Sport. 2023 Oct 21. pii: S1440-2440(23)00428-0. [Epub ahead of print]

Effects of acute exercise and training status on glucocorticoid-induced leucine zipper (GILZ) expression in human skeletal muscle.

A Hecksteden, J Hoppstädter, D A Bizjak, A Jerg, J Kirsten, K Krüger, A Niess, J Steinacker, A K Kiemer.

  Interactions between statin therapy and physical exercise complicate effective cardiovascular prevention. Emerging evidence suggests that muscle strain related changes in the expression of the glucocorticoid-induced leucine zipper (GILZ) may be involved. Therefore, we measured GILZ mRNA expression levels in M. vastus lateralis samples of 32 healthy individuals before and after a standardized bout of strength or endurance exercise. Overall, we found a highly significant downregulation of GILZ after exercise training (p < 0.001). Within-subgroup changes were statistically significant only after strength training, supporting the role of muscle (as opposed to cardiocirculatory) strain. If confirmed, this may help fitting training recommendations and medication.

Keywords:  Exercise training; Glucocorticoid; Myopathy; Strength training

DOI:  https://doi.org/10.1016/j.jsams.2023.10.007