bims-kimdis 2023-04-23 papers

bims-kimdis

Biomed News

on Ketones, inflammation and mitochondria in disease

Issue of 2023–04–23
24 papers selected by
Matías Javier Monsalves Álvarez, Universidad de O’Higgins

Ketone body oxidation: Glycogen-sparing yet glucose-dependent?
A ketogenic diet alters mTOR activity, systemic metabolism and potentially prevents collagen degradation associated with chronic alcohol consumption in mice.
Efficacy of low carbohydrate and ketogenic diets in treating mood and anxiety disorders: systematic review and implications for clinical practice.
Role of EEG as a Monitoring Tool in Patients with Glucose Transporter Type I Deficiency Syndrome (GLUT1 -DS) on Ketogenic Diet.
Twenty-four hour rhythmicity in mitochondrial network connectivity and mitochondrial respiration; a study in human skeletal muscle biopsies of young lean and older individuals with obesity.
The ketogenic diet for Dravet syndrome: A multicenter retrospective study.
The Ketogenic Diet but not Hydroxycitric Acid Keeps Brain Mitochondria Quality Control and mtDNA Integrity Under Focal Stroke.
Skeletal muscle insulin resistance.
A ketogenic diet improves vascular hyperpermeability in type 2 diabetic mice by downregulating vascular pescadillo1 expression.
Age-associated inflammation and implications for skeletal muscle responses to exercise.
Exogenous ketosis elevates circulating erythropoietin and stimulates muscular angiogenesis during endurance training overload.
Impact of School-supervised Ultra-long-acting Basal Insulin Injections on Ketosis in Youth with T1D and Elevated Hemoglobin A1c: A Pilot Study.
High fat diet improves metabolic flexibility during progressive exercise to exhaustion (VO2max testing) and during 5 km running time trials.
Metabolic switch in the aging astrocyte supported via integrative approach comprising network and transcriptome analyses.
Assessment of NLRP3 Inflammasome Activation and NLRP3-NEK7 Complex Assembly.
A chronic high-fat diet does not exacerbate muscle atrophy in fast-twitch skeletal muscle of aged mice.
Pyruvate-supported flux through medium-chain ketothiolase promotes mitochondrial lipid tolerance in cardiac and skeletal muscles.
Identifying Inflammasome Activation in Human Tissues.
Does this person have obesity?
AMPK is mitochondrial medicine for neuromuscular disorders.
Metabolic role of the hepatic valine/3-hydroxyisobutyrate (3-HIB) pathway in fatty liver disease.
Watching the human retina breath in real time and the slowing of mitochondrial respiration with age.
Can Lactate Clearance Predict Mortality in Critically Ill Children?
Measuring Mitochondrial Uncoupling in Mouse Primary Brown Adipocytes Differentiated Ex Vivo.

J Physiol. 2023 Apr 17.

Ketone body oxidation: Glycogen-sparing yet glucose-dependent?

Heather L Petrick, Philippe J M Pinckaers, Henver S Brunetta.



Keywords:  beta-hydroxybutyrate; glucose; glycogen; heart; ketone bodies; muscle

DOI:  https://doi.org/10.1113/JP284561
Metabolomics. 2023 Apr 19. 19(5): 43

A ketogenic diet alters mTOR activity, systemic metabolism and potentially prevents collagen degradation associated with chronic alcohol consumption in mice.

Luciano Willemse, Karin Terburgh, Roan Louw.

   INTRODUCTION: A ketogenic diet (KD), which is a high fat, low carbohydrate diet has been shown to inhibit the mammalian target of rapamycin (mTOR) pathway and alter the redox state. Inhibition of the mTOR complex has been associated with the attenuation and alleviation of various metabolic and- inflammatory diseases such as neurodegeneration, diabetes, and metabolic syndrome. Various metabolic pathways and signalling mechanisms have been explored to assess the therapeutic potential of mTOR inhibition. However, chronic alcohol consumption has also been reported to alter mTOR activity, the cellular redox- and inflammatory state. Thus, a relevant question that remains is what effect chronic alcohol consumption would have on mTOR activity and overall metabolism during a KD-based intervention.
OBJECTIVES: The aim of this study was to evaluate the effect of alcohol and a KD on the phosphorylation of the mTORC1 target p70S6K, systemic metabolism as well as the redox- and inflammatory state in a mouse model.
METHODS: Mice were fed either a control diet with/without alcohol or a KD with/without alcohol for three weeks. After the dietary intervention, samples were collected and subjected towards western blot analysis, multi-platform metabolomics analysis and flow cytometry.
RESULTS: Mice fed a KD exhibited significant mTOR inhibition and reduction in growth rate. Alcohol consumption alone did not markedly alter mTOR activity or growth rate but moderately increased mTOR inhibition in mice fed a KD. In addition, metabolic profiling showed alteration of several metabolic pathways as well as the redox state following consumption of a KD and alcohol. A KD was also observed to potentially prevent bone loss and collagen degradation associated with chronic alcohol consumption, as indicated by hydroxyproline metabolism.
CONCLUSION: This study sheds light on the influence that a KD alongside alcohol intake can exert on not just mTOR, but also their effect on metabolic reprogramming and the redox state.

Keywords:  Ketogenic diet; Metabolic reprogramming; Metabolomics; Mtor; Redox; Western blot

DOI:  https://doi.org/10.1007/s11306-023-02006-w
BJPsych Open. 2023 Apr 17. 9(3): e70

Efficacy of low carbohydrate and ketogenic diets in treating mood and anxiety disorders: systematic review and implications for clinical practice.

Daniel M Dietch, Jess Kerr-Gaffney, Meghan Hockey, Wolfgang Marx, Anu Ruusunen, Allan H Young, Michael Berk, Valeria Mondelli.

   BACKGROUND: There is mounting interest in the potential efficacy of low carbohydrate and very low carbohydrate ketogenic diets in various neurological and psychiatric disorders.
AIMS: To conduct a systematic review and narrative synthesis of low carbohydrate and ketogenic diets (LC/KD) in adults with mood and anxiety disorders.
METHOD: MEDLINE, Embase, PsycINFO and Cochrane databases were systematically searched for articles from inception to 6 September 2022. Studies that included adults with any mood or anxiety disorder treated with a low carbohydrate or ketogenic intervention, reporting effects on mood or anxiety symptoms were eligible for inclusion. PROSPERO registration CRD42019116367.
RESULTS: The search yielded 1377 articles, of which 48 were assessed for full-text eligibility. Twelve heterogeneous studies (stated as ketogenic interventions, albeit with incomplete carbohydrate reporting and measurements of ketosis; diet duration: 2 weeks to 3 years; n = 389; age range 19 to 75 years) were included in the final analysis. This included nine case reports, two cohort studies and one observational study. Data quality was variable, with no high-quality evidence identified. Efficacy, adverse effects and discontinuation rates were not systematically reported. There was some evidence for efficacy of ketogenic diets in those with bipolar disorder, schizoaffective disorder and possibly unipolar depression/anxiety. Relapse after discontinuation of the diet was reported in some individuals.
CONCLUSIONS: Although there is no high-quality evidence of LC/KD efficacy in mood or anxiety disorders, several uncontrolled studies suggest possible beneficial effects. Robust studies are now needed to demonstrate efficacy, to identify clinical groups who may benefit and whether a ketogenic diet (beyond low carbohydrate) is required and to characterise adverse effects and the risk of relapse after diet discontinuation.

Keywords:  Ketogenic diet; anxiety disorders; low carbohydrate diet; mood disorders; nutritional psychiatry

DOI:  https://doi.org/10.1192/bjo.2023.36
Epileptic Disord. 2023 Apr 18.

Role of EEG as a Monitoring Tool in Patients with Glucose Transporter Type I Deficiency Syndrome (GLUT1 -DS) on Ketogenic Diet.

Juan Toro-Perez, Sarah Healy, Erick Sell, Srinivas Bulusu, Sharon Whiting.

   RATIONALE: Glucose transporter type I deficiency syndrome (GLUT1-DS) is the fourth most frequent single-gene epilepsy refractory to standard antiepileptic drugs. Multiple seizures types and variable electrographic findings are reported. Ketogenic diet is expected to result in the complete resolution of the epileptiform activity.
METHODS: A retrospective chart review of patients with GLUT1-DS on ketogenic diet between December 2012 and February 2022 was done. Analysis of the EEGs prior to and during the ketogenic diet was done.
RESULTS: 34 patients on ketogenic diet were reviewed. Ten had clinical diagnosis of GLUT1-DS, seven of them had genetic confirmation. 71% were female. Average age at seizure onset was 13.85 m.o. (range: 3-60, SD±20.52), at diagnosis was 44.57 m.o (range: 19-79), and at the onset of Ketogenic Diet was 46.43 m.o. (range: 20-83). 29 months (range: 13-38) delay between symptoms onset until diagnosis was noticed. At the diagnosis 100% reported seizures: 71% myoclonic, 57% generalized motor, 57% absence, 28% atonic, and 14% focal motor. Also, 71% abnormal eyes movements, 57% ataxia and 28% intolerance to fasting. 86% had normal brain MRI. 71% had abnormal EEG. All were on ketogenic diet, four on classical (1.75:1 - 2.25:1 ratio). Six were clinically seizure-free after ketogenic diet. EEG features included notch delta, focal spike and wave, and generalized spike/polyspike and wave. One patient had bilateral independent centrotemporal spikes. Spikes showed high and very high amplitude in all of them (>200 μV). The variation of the spike index decreased in three patients but increased in two.
CONCLUSION: Ketogenic diet is the choice treatment for patients with GLUT1-DS. Electrographic features could show worsening after initiation of the ketogenic diet even with seizure control. EEG did not prove to be reliable tool for adjusting KD in our cohort. Centrotemporal spikes have not been reported in patients with GLUT-1 DS.

Keywords:  EEG; GLUT1-DS; epilepsy; ketogenic diet; seizure

DOI:  https://doi.org/10.1002/epd2.20063
Mol Metab. 2023 Apr 14. pii: S2212-8778(23)00061-3. [Epub ahead of print] 101727

Twenty-four hour rhythmicity in mitochondrial network connectivity and mitochondrial respiration; a study in human skeletal muscle biopsies of young lean and older individuals with obesity.

Anne Gemmink, Sabine Daemen, Jakob Wefers, Jan Hansen, Dirk van Moorsel, Puji Astuti, Johanna A Jorgensen, Esther Kornips, Gert Schaart, Joris Hoeks, Patrick Schrauwen, Matthijs K C Hesselink.

   OBJECTIVE: Mitochondrial network dynamics may play role in metabolic homeostasis. Whether mitochondrial network dynamics are involved in adaptations to day-night fluctuations in energy supply and demand is unclear. Here we visualized and quantified the mitochondrial network morphology in human skeletal muscle of young healthy lean and older individuals with obesity over the course of 24 h METHODS: Muscle biopsies taken at 5 timepoints over a 24-hour period obtained from young healthy lean and older metabolically impaired obese males were analyzed for mitochondrial network integrity with confocal laser scanning microscopy. Variation of level of fragmentation over the course of the day were aligned with variation of mitochondrial respiration over the day RESULTS: Young healthy lean individuals displayed a day-night rhythmicity in mitochondrial network morphology, which aligned with the day-night rhythmicity of mitochondrial respiratory capacity, with a more fused network coinciding with higher mitochondrial respiratory capacity. In the older individuals with obesity, the mitochondrial network was more fragmented overall compared to young healthy lean individuals and completely lacked 24 h rhythmicity, which was also true for the mitochondrial respiratory capacity CONCLUSIONS: Our data shows a paralleled rhythmicity between mitochondrial network morphology and mitochondrial oxidative capacity, which oscillates over the course of a mimicked real-life day in human skeletal muscle of young, healthy lean individuals. In older individuals with obesity, the lack of a 24-hour rhythmicity in mitochondrial network connectivity was also aligned with a lack in respiratory capacity. This suggests that 24-hour rhythmicity in mitochondrial network connectivity is a determinant of rhythmicity in mitochondrial respiratory capacity. Thus, restoring mitochondrial network integrity may promote mitochondrial respiratory capacity and hence contribute to blunting the metabolic aberrations in individuals with a disturbed 24-hour rhythmicity in metabolism, like older individuals with obesity.

Keywords:  Day-night rhythm; Mitochondrial function; Mitochondrial network integrity; Skeletal muscle

DOI:  https://doi.org/10.1016/j.molmet.2023.101727
Nutrition. 2023 Feb 12. pii: S0899-9007(23)00006-0. [Epub ahead of print]110 111976

The ketogenic diet for Dravet syndrome: A multicenter retrospective study.

China Association Against Epilepsy Ketogenic Diet Group

   OBJECTIVE: The ketogenic diet (KD) is one of the main treatments for drug-resistant epilepsy. However, there have been few multicenter reports on the use of the KD for the treatment of Dravet syndrome (DS). The aim of this study was to analyze the efficacy and safety of this approach based on a large number of multicenter cases.
METHODS: This was a retrospective, multicenter cohort study from 14 centers in China. All patients were treated with the KD. We compared the effects of KD intervention time, age, and other factors.
RESULTS: From March 2014 to March 2020, we treated 114 patients with DS with the KD. The male-to-female ratio was 67:47. The KD median initiation age was 3 y and 4 mo, and the median number of antiseizure medications (ASMs) was 2.4. KD therapy was the first choice for three patients. Exactly 10.5% of the patients started KD therapy after failure of the first ASM therapy, with 35.1% after failure of the second, 44.7% after the third, and 7% after the fourth or more. After KD therapy for 1, 3, 6, and 12 mo, the seizure-free rates were 14%, 32.5%, 30.7%, and 19.3%, respectively; KD efficacy (≥50% reduction in seizure frequency) were 57.9%, 76.3%, 59.6%, and 43%, respectively; the retention rates were 97.4%, 93%, 71.9%, and 46.5%, respectively; and the rates of adverse events were 25.2%, 19.9%, 11%, and 5.7%, respectively.
CONCLUSIONS: Real-world, multicenter data analysis showed that the KD is effective for patients with DS and has a low incidence of side effects.

Keywords:  Adverse events; Dravet syndrome; Effective rate; Epilepsy; Ketogenic diet

DOI:  https://doi.org/10.1016/j.nut.2023.111976
Mol Neurobiol. 2023 Apr 19.

The Ketogenic Diet but not Hydroxycitric Acid Keeps Brain Mitochondria Quality Control and mtDNA Integrity Under Focal Stroke.

Artem P Gureev, Denis N Silachev, Irina S Sadovnikova, Ekaterina P Krutskikh, Ekaterina V Chernyshova, Daria E Volodina, Natalia A Samoylova, Daria V Potanina, Inna Yu Burakova, Yuliya D Smirnova, Vasily N Popov, Egor Y Plotnikov.

  Mitochondrial dysfunction in the ischemic brain is one of the hallmarks of stroke. Dietary interventions such as the ketogenic diet and hydroxycitric acid supplementation (a caloric restriction mimetic) may potentially protect neurons from mitochondrial damage induced by focal stroke in mice. We showed that in control mice, the ketogenic diet and the hydroxycitric acid did not impact significantly on the mtDNA integrity and expression of genes involved in the maintenance of mitochondrial quality control in the brain, liver, and kidney. The ketogenic diet changed the bacterial composition of the gut microbiome, which via the gut-brain axis may affect the increase in anxiety behavior and reduce mice mobility. The hydroxycitric acid causes mortality and suppresses mitochondrial biogenesis in the liver. Focal stroke modelling caused a significant decrease in the mtDNA copy number in both ipsilateral and contralateral brain cortex and increased the levels of mtDNA damage in the ipsilateral hemisphere. These alterations were accompanied by a decrease in the expression of some of the genes involved in maintaining mitochondrial quality control. The ketogenic diet consumption before stroke protects mtDNA in the ipsilateral cortex, probably via activation of the Nrf2 signaling. The hydroxycitric acid, on the contrary, increased stroke-induced injury. Thus, the ketogenic diet is the most preferred variant of dietetic intervention for stroke protection compared with the hydroxycitric acid supplementation. Our data confirm some reports about hydroxycitric acid toxicity, not only for the liver but also for the brain under stroke condition.

Keywords:  Focal stroke; Gut microbiome; Hydroxycitric acid; Ketogenic diet; Mitochondrial DNA; Nrf2/ARE signal pathway

DOI:  https://doi.org/10.1007/s12035-023-03325-8
J Physiol. 2023 Apr 18.

Skeletal muscle insulin resistance.

James Smorenburg, Patrick McTavish, Giulia Kobylnik.



Keywords:  DAGs; PKC; ceramides; inflammation; insulin resistance; muscle fibers; skeletal muscle

DOI:  https://doi.org/10.1113/JP284721
J Cell Mol Med. 2023 Apr 15.

A ketogenic diet improves vascular hyperpermeability in type 2 diabetic mice by downregulating vascular pescadillo1 expression.

Song Wang, Jielin Zhou, Jing Lu, Yan Lin, Shuaishuai Liu, Keyang Chen.

  The role of pescadillo1 (PES1) in regulating vascular permeability has been unknown. This study probes the role of PES1 and its mediated molecular mechanism in modulating vascular hyperpermeability in diabetic mice. Male C57BL/6J and db/db mice were fed a standard diet and a ketogenic diet (KD). Meanwhile, mouse vascular endothelial cells (MVECs) were treated with β-hydroxybutyric acid (β-HB), Pes1 siRNA or a Pes1 overexpression plasmid. Additionally, knockout (KO) of Pes1 in mice was applied. After 12 weeks of feedings, enhanced vascular PES1 expression in diabetic mice was inhibited by the KD. The suppression of PES1 was also observed in β-HB-treated MVECs. In mice with Pes1 KO, the levels of vascular VEGF and PES1 were attenuated, while the levels of vascular VE-cadherin, Ang-1 and Occludin were upregulated. Similar outcomes also occurred after the knockdown of Pes1 in cultured MVECs, which were opposite to the effects induced by PES1 overexpression in MVECs. In vitro and in vivo experiments showed that high glucose concentration-induced increases in vascular paracellular permeability declined after MVECs were treated by β-HB or by knockdown of Pes1. In contrast, increases in vascular permeability were induced by overexpression of Pes1, which were suppressed by coadministration of β-HB in cultured endothelial cells. Similarly declines in vascular permeability were found by Pes1 knockdown in diabetic mice. Mechanistically, β-HB decreased PES1-facilitated ubiquitination of VE-cadherin. The KD suppressed the diabetes-induced increase in PES1, which may result in vascular hyperpermeability through ubiquitination of VE-cadherin in type 2 diabetic mice.

Keywords:  KD; PES1; diabetes; vascular permeability; β-HB

DOI:  https://doi.org/10.1111/jcmm.17744
Exp Gerontol. 2023 Apr 19. pii: S0531-5565(23)00098-0. [Epub ahead of print] 112177

Age-associated inflammation and implications for skeletal muscle responses to exercise.

Hawley E Kunz, Ian R Lanza.

  Aging is associated with profound alterations in skeletal muscle, including loss of muscle mass and function, local inflammation, altered mitochondrial physiology, and attenuated anabolic responses to exercise termed anabolic resistance. "Inflammaging," the chronic, low-grade inflammation associated with aging, may contribute to many of the age-related derangements in skeletal muscle, including its ability to respond to exercise and nutritional stimuli. Inflammation and exercise are closely intertwined in numerous ways. A single bout of muscle-damaging exercise stimulates an acute inflammatory response in the skeletal muscle that is essential for muscle repair and regeneration; however, the chronic systemic and local inflammation associated with aging may impair acute inflammatory and anabolic responses to exercise. In contrast, exercise training is anti-inflammatory, targeting many of the potential root causes of inflammaging. In this review, we discuss the interplay between inflammation and exercise in aging and highlight potential therapeutic targets for improving adaptive responses to exercise in older adults.

Keywords:  Aging; Exercise; Inflammation; Skeletal muscle

DOI:  https://doi.org/10.1016/j.exger.2023.112177
J Physiol. 2023 Apr 16.

Exogenous ketosis elevates circulating erythropoietin and stimulates muscular angiogenesis during endurance training overload.

Chiel Poffé, Ruben Robberechts, Ruud Van Thienen, Peter Hespel.

  De novo capillarization is a primary muscular adaptation to endurance exercise training and is crucial to improve performance. Excess training load, however, impedes such beneficial adaptations, yet we recently demonstrated that such downregulation may be counteracted by ketone ester ingestion (KE) post-exercise. Therefore, we investigated whether KE could increase pro-angiogenic factors and thereby stimulate muscular angiogenesis during a three-week endurance training-overload period involving 10 training sessions/week in healthy, male volunteers. Subjects received either 25g of a ketone ester (KE, n = 9) or a control drink (CON, n = 9) immediately after each training session and before sleep. In KE, but not in CON, the training intervention increased number of capillary contacts and capillary-to-fiber perimeter exchange index by 44% and 42%, respectively. Furthermore, KE also substantially increased VEGF and eNOS expression both at the protein and mRNA level. Serum erythropoietin concentration was concomitantly increased by 26%. Conversely, in CON the training intervention increased only the protein content of eNOS. These data indicate that intermittent exogenous ketosis during endurance overload training stimulates muscular angiogenesis. This likely resulted from a direct stimulation of muscle angiogenesis, which may be at least partly due to stimulation of erythropoietin secretion and elevated VEGF activity, and/or an inhibition of the suppressive effect of overload training on the normal angiogenic response to training. This study provides novel evidence to support the potential of exogenous ketosis to benefit endurance training-induced muscular adaptation. KEY POINTS SUMMARY: Increased capillarization is a primary muscular adaptation to endurance exercise training. However, excess training load may impede such response. We previously observed that intermittent exogenous ketosis by postexercise and pre-sleep ketone ester ingestion (KE) counteracted physiological dysregulations induced by endurance overload training. Therefore, we investigated whether KE could increase pro-angiogenic factors thereby stimulating muscular angiogenesis during a three-week endurance training-overload period. We show that the overload training period in the presence, but not in the absence of KE, markedly increased muscle capillarization (+40%). This increase was accompanied by higher circulating erythropoietin concentration and stimulation of the pro-angiogenic factors VEGF and eNOS in skeletal muscle. Collectively, our data indicate that intermittent exogenous ketosis may evolve as a potent nutritional strategy to facilitate recovery from strenuous endurance exercise, thereby stimulating beneficial muscular adaptations. Abstract figure legend: Eighteen healthy, fit male volunteers were subjected to a 3 week endurance training-overload program. Subjects received either 25g of a ketone ester drink or an isocaloric placebo immediately after each training session and before sleep. The training intervention increased skeletal muscle capillarization in the ketone ester group, but not in the placebo group. The angiogenic response in the ketone ester group was accompanied by an increase in circulating erythropoietin (EPO) concentrations, and stimulation of pro-angiogenic factors in skeletal muscle. These findings indicate that intermittent ketone ester supplementation stimulates beneficial muscular adaptations during strenuous endurance exercise training. This article is protected by copyright. All rights reserved.

Keywords:  EPO; VEGF; angiogenesis; exercise training; ketone

DOI:  https://doi.org/10.1113/JP284346
Diabet Med. 2023 Apr 20. e15123

Impact of School-supervised Ultra-long-acting Basal Insulin Injections on Ketosis in Youth with T1D and Elevated Hemoglobin A1c: A Pilot Study.

Laura M Nally, Jennifer L Sherr, Eileen Tichy, Kate Weyman, Andrea Urban, Veronika Shabanova, Sarah McCollum, Amy Steffen, William V Tamborlane, Michelle Van Name.

  In youth with type 1 diabetes (T1D), high hemoglobin A1c (HbA1c) levels are associated with increased risk for diabetic ketoacidosis (DKA). This study examined whether daily school supervised basal insulin injections were feasible and if they reduced the risk of morning ketosis in children and adolescents with high HbA1c levels. We hypothesized that supervised glargine and degludec would reduce the risk of ketosis and that the prolonged action of degludec would protect from ketosis after consecutive days of unsupervised injections. After a 2-4-week run-in, youth (10-18y, HbA1c ≥8.5%) managing T1D with injections were randomized to school supervised administration of degludec or glargine for 4 months. School nurses observed daily blood β-hydroxybutyrate (BHB) and glucose checks. During COVID closures, the research team supervised procedures remotely. Data from 28 youth (age 14.3 ± 2.3 years, HbA1c 11.4 ± 1.9%, 64% F) were analyzed. School supervised injections of both basal insulins for 1-4 days progressively lowered the percent of participants with elevated BHB. The percent of participants with elevated BHB (≥0.6 mmol/L) after 2 days of unsupervised basal insulin doses at home was greater in the glargine than degludec group but had a high p-value (17.2% vs 9.0%, p=0.3). HbA1c was unchanged in both groups. In youth with T1D at high risk for DKA, daily supervised insulin administration decreased the probability of elevated ketone levels on subsequent school days, regardless of basal insulin type. A larger sample size may have demonstrated that the longer action profile of degludec would offer additional protection from ketosis during days not attending school.

Keywords:  Diabetic ketoacidosis; degludec; glargine; school; type 1 diabetes

DOI:  https://doi.org/10.1111/dme.15123
Biol Sport. 2023 Apr;40(2): 465-475

High fat diet improves metabolic flexibility during progressive exercise to exhaustion (VO2max testing) and during 5 km running time trials.

Philip J Prins, Timothy D Noakes, Jeffrey D Buxton, Gary L Welton, Amy S Raabe, Katie E Scott, Adam D Atwell, Sarah J Haley, Noah J Esbenshade, Jacqueline Abraham.

  Recently we reported similar performances in both progressive tests to exhaustion (VO2max) and 5km running time trials (5KTT) after consuming low-carbohydrate, high-fat (LCHF) or high-carbohydrate, low-fat (HCLF) diets. Accordingly, we tested the null hypothesis that the metabolic responses during both tests would be similar across diets. In a randomized, counterbalanced, cross-over design, seven male athletes (VO2max: 61.9 ± 6.1 mL/kg/min; age: 35.6 ± 8.4 years; height: 178.7 ± 4.1 cm; mass: 68.6 ± 1.6 kg; body fat: 5.0 ± 1.3%) completed six weeks of LCHF (6/69/25% energy carbohydrate/fat/protein) and HCLF (57/28/15% energy carbohydrate/fat/protein) diets, separated by a two-week washout. Substrate utilization and energy expenditure were measured during VO2max tests and 5KTTs. The LCHF diet markedly increased fat oxidation and reduced carbohydrate oxidation, with no associated impairment in either the VO2max tests or the 5KTTs. Following the LCHF diet, athletes generated 50% or more of their energy requirements from fat at exercise intensities up to 90% VO2max and reached the crossover point for substrate utilization at ~85% VO2max. In contrast, following the HCLF diet, carbohydrate provided more than 50% of the total energy consumption at all exercise intensities. During the 5KTT, ~56% of energy was derived from fat following the LCHF diet whereas more than 93% of the energy came from carbohydrate following the HCLF diet. This study provides evidence of greater metabolic flexibility following LCHF eating and challenges the popular doctrines of "carbohydrate dependence" for high intensity exercise and the role dietary macronutrients play in human performance.

Keywords:  Carbohydrate oxidation; Crossover point; Fat oxidation; High fat diet; High-carbohydrate; Low-carbohydrate

DOI:  https://doi.org/10.5114/biolsport.2023.116452
Aging (Albany NY). 2023 Apr 18. 15

Metabolic switch in the aging astrocyte supported via integrative approach comprising network and transcriptome analyses.

Alejandro Acevedo, Felipe Torres, Miguel Kiwi, Felipe Baeza-Lehnert, L Felipe Barros, Dasfne Lee-Liu, Christian González-Billault.

  Dysregulated central-energy metabolism is a hallmark of brain aging. Supplying enough energy for neurotransmission relies on the neuron-astrocyte metabolic network. To identify genes contributing to age-associated brain functional decline, we formulated an approach to analyze the metabolic network by integrating flux, network structure and transcriptomic databases of neurotransmission and aging. Our findings support that during brain aging: (1) The astrocyte undergoes a metabolic switch from aerobic glycolysis to oxidative phosphorylation, decreasing lactate supply to the neuron, while the neuron suffers intrinsic energetic deficit by downregulation of Krebs cycle genes, including mdh1 and mdh2 (Malate-Aspartate Shuttle); (2) Branched-chain amino acid degradation genes were downregulated, identifying dld as a central regulator; (3) Ketone body synthesis increases in the neuron, while the astrocyte increases their utilization, in line with neuronal energy deficit in favor of astrocytes. We identified candidates for preclinical studies targeting energy metabolism to prevent age-associated cognitive decline.

Keywords:  astrocyte; brain aging; flux balance analysis; network centrality; neuron

DOI:  https://doi.org/10.18632/aging.204663
Methods Mol Biol. 2023 ;2641 17-26

Assessment of NLRP3 Inflammasome Activation and NLRP3-NEK7 Complex Assembly.

Nathan Kelley, Yuan He.

  The NLRP3 inflammasome is a critical component of innate immunity that activates caspase-1 to induce inflammation in response to a wide spectrum of endogenous and exogenous stimuli. NLRP3 inflammasome activation has been shown by assays for the cleavage of caspase-1 and gasdermin D, the maturation of IL-1β and IL-18, and ASC speck formation in innate immune cells such as macrophages and monocytes. Recently, NEK7 has been revealed as an essential regulator for NLRP3 inflammasome activation by forming high-molecular-weight complexes with NLRP3. Blue native polyacrylamide gel electrophoresis (BN-PAGE) has been used to study multi-protein complexes in many experimental systems. Here, we provide a detailed protocol to detect NLRP3 inflammasome activation and NLRP3-NEK7 complex assembly in mouse macrophages by Western blot and BN-PAGE.

Keywords:  BMDM; BN-PAGE; Caspase-1; Complex assembly; Inflammasome; NEK7; NLRP3; Western blot

DOI:  https://doi.org/10.1007/978-1-0716-3040-2_2
Exp Physiol. 2023 Apr 19.

A chronic high-fat diet does not exacerbate muscle atrophy in fast-twitch skeletal muscle of aged mice.

Tsutomu Tagawa, Hiroaki Eshima, Saori Kakehi, Ryuzo Kawamori, Hirotaka Watada, Yoshifumi Tamura.

   NEW FINDINGS: What is the central question of this study? Ageing leads to a loss of mass in skeletal muscle, but the effect of obesity on ageing-related muscle wasting is unclear. In this study, we aimed to demonstrate the specific effect of obesity on fast-twitch skeletal muscle in ageing. What is the main finding and its importance? Our findings show that the obesity induced by long-term ingestion of a high-fat diet does not aggravate muscle wasting in fast-twitch skeletal muscle of aged mice, indicating that the present study provides morphological characteristics for skeletal muscle of sarcopenic obesity.
ABSTRACT: Obesity and ageing reduce muscle mass and lead to deficits in muscle maintenance, but it is not known whether obesity accelerates muscle wasting additively in the setting of ageing. We investigated morphological characteristics in fast-twitch extensor digitorum longus (EDL) muscle of mice fed a low-fat diet (LFD) or a high-fat diet (HFD) for 4 or 20 months. The fast-twitch EDL muscle was harvested, and the muscle fibre-type composition, individual muscle cross-sectional area and myotube diameter were measured. We found an increase in the percentage of type IIa and IIx myosin heavy chain fibres in the whole EDL muscle, but a decrease in type IIB myosin heavy chain in both HFD protocols. The cross-sectional area and myofibre diameter were lower in both groups of aged mice (after 20 months of LFD or HFD) compared with young mice (after 4 months of the diets), but there were no differences between mice fed LFD or HFD for 20 months. These data suggest that long-term feeding of HFD does not aggravate muscle wasting in fast-twitch EDL muscle of male mice.

Keywords:  ageing; cross-sectional area; fast-twitch muscle; high-fat diet; myofibre diameter; skeletal muscle

DOI:  https://doi.org/10.1113/EP091106
Cell Metab. 2023 Apr 11. pii: S1550-4131(23)00094-3. [Epub ahead of print]

Pyruvate-supported flux through medium-chain ketothiolase promotes mitochondrial lipid tolerance in cardiac and skeletal muscles.

Timothy R Koves, Guo-Fang Zhang, Michael T Davidson, Alec B Chaves, Scott B Crown, Jordan M Johnson, Dorothy H Slentz, Paul A Grimsrud, Deborah M Muoio.

  Even-chain acylcarnitine (AC) metabolites, most of which are generated as byproducts of incomplete fatty acid oxidation (FAO), are viewed as biomarkers of mitochondrial lipid stress attributable to one or more metabolic bottlenecks in the β-oxidation pathway. The origins and functional implications of FAO bottlenecks remain poorly understood. Here, we combined a sophisticated mitochondrial phenotyping platform with state-of-the-art molecular profiling tools and multiple two-state mouse models of respiratory function to uncover a mechanism that connects AC accumulation to lipid intolerance, metabolic inflexibility, and respiratory inefficiency in skeletal muscle mitochondria. These studies also identified a short-chain carbon circuit at the C4 node of FAO wherein reverse flux of glucose-derived acetyl CoA through medium-chain ketothiolase enhances lipid tolerance and redox stability in heart mitochondria by regenerating free CoA and NAD+. The findings help to explain why diminished FAO capacity, AC accumulation, and metabolic inflexibility are tightly linked to poor health outcomes.

Keywords:  acylcarnitines; bioenergetics; exercise; fatty acid oxidation; heart; ketothiolase; metabolic flexibility; mitochondria; pyruvate; skeletal muscle

DOI:  https://doi.org/10.1016/j.cmet.2023.03.016
Methods Mol Biol. 2023 ;2641 101-113

Identifying Inflammasome Activation in Human Tissues.

Eleonora Mezzaroma, Adolfo Mauro, Stefano Toldo.

  The NACHT, LRR, and PYD domain-containing protein-3 (NLRP3) inflammasome activation is part of a stereotyped cellular response to injury or infection. The NLRP3 inflammasome activation promotes cellular dysfunction and death, leading to local and systemic inflammation, organ dysfunction, and adverse outcome. Immunohistochemistry and immunofluorescence can be used to determine whether the NLRP3 inflammasome components are present in human biopsy or autopsy tissue samples.

Keywords:  ASC; Caspase-1; Heart; Human tissues; Immunofluorescence; Immunohistochemistry; Inflammasome; Lung; NLRP3

DOI:  https://doi.org/10.1007/978-1-0716-3040-2_8
EClinicalMedicine. 2023 Apr;58 101935

Does this person have obesity?

Arya M Sharma.

DOI: https://doi.org/10.1016/j.eclinm.2023.101935
Trends Mol Med. 2023 Apr 19. pii: S1471-4914(23)00070-9. [Epub ahead of print]

AMPK is mitochondrial medicine for neuromuscular disorders.

Andrew I Mikhail, Sean Y Ng, Stephanie R Mattina, Vladimir Ljubicic.

  Duchenne muscular dystrophy (DMD), myotonic dystrophy type 1 (DM1), and spinal muscular atrophy (SMA) are the most prevalent neuromuscular disorders (NMDs) in children and adults. Central to a healthy neuromuscular system are the processes that govern mitochondrial turnover and dynamics, which are regulated by AMP-activated protein kinase (AMPK). Here, we survey mitochondrial stresses that are common between, as well as unique to, DMD, DM1, and SMA, and which may serve as potential therapeutic targets to mitigate neuromuscular disease. We also highlight recent advances that leverage a mutation-agnostic strategy featuring physiological or pharmacological AMPK activation to enhance mitochondrial health in these conditions, as well as identify outstanding questions and opportunities for future pursuit.

Keywords:  Duchenne muscular dystrophy; mitophagy; myotonic dystrophy type 1; skeletal muscle; spinal muscular atrophy

DOI:  https://doi.org/10.1016/j.molmed.2023.03.008
EBioMedicine. 2023 Apr 19. pii: S2352-3964(23)00134-2. [Epub ahead of print]91 104569

Metabolic role of the hepatic valine/3-hydroxyisobutyrate (3-HIB) pathway in fatty liver disease.

Mona Synnøve Bjune, Laurence Lawrence-Archer, Johnny Laupsa-Borge, Cathrine Horn Sommersten, Adrian McCann, Robert Clay Glastad, Iain George Johnston, Matthias Kern, Matthias Blüher, Gunnar Mellgren, Simon N Dankel.

   BACKGROUND: The valine (branched-chain amino acid) metabolite 3-hydroxyisobutyrate (3-HIB), produced by 3-Hydroxyisobutyryl-CoA Hydrolase (HIBCH), is associated with insulin resistance and type 2 diabetes, but implicated tissues and cellular mechanisms are poorly understood. We hypothesized that HIBCH and 3-HIB regulate hepatic lipid accumulation.
METHODS: HIBCH mRNA in human liver biopsies ("Liver cohort") and plasma 3-HIB ("CARBFUNC" cohort) were correlated with fatty liver and metabolic markers. Human Huh7 hepatocytes were supplemented with fatty acids (FAs) to induce lipid accumulation. Following HIBCH overexpression, siRNA knockdown, inhibition of PDK4 (a marker of FA β-oxidation) or 3-HIB supplementation, we performed RNA-seq, Western blotting, targeted metabolite analyses and functional assays.
FINDINGS: We identify a regulatory feedback loop between the valine/3-HIB pathway and PDK4 that shapes hepatic FA metabolism and metabolic health and responds to 3-HIB treatment of hepatocytes. HIBCH overexpression increased 3-HIB release and FA uptake, while knockdown increased cellular respiration and decreased reactive oxygen species (ROS) associated with metabolic shifts via PDK4 upregulation. Treatment with PDK4 inhibitor lowered 3-HIB release and increased FA uptake, while increasing HIBCH mRNA. Implicating this regulatory loop in fatty liver, human cohorts show positive correlations of liver fat with hepatic HIBCH and PDK4 expression (Liver cohort) and plasma 3-HIB (CARBFUNC cohort). Hepatocyte 3-HIB supplementation lowered HIBCH expression and FA uptake and increased cellular respiration and ROS.
INTERPRETATION: These data implicate the hepatic valine/3-HIB pathway in mechanisms of fatty liver, reflected in increased plasma 3-HIB concentrations, and present possible targets for therapeutic intervention.
FUNDING: Funding was provided by the Research Council of Norway (263124/F20), the University of Bergen, the Western Norway Health Authorities, Novo Nordisk Scandinavia AS, the Trond Mohn Foundation and the Norwegian Diabetes Association.

Keywords:  Branched-chain amino acids (BCAA); Insulin resistance; Lipid metabolism; NAFLD; NASH

DOI:  https://doi.org/10.1016/j.ebiom.2023.104569
Sci Rep. 2023 Apr 20. 13(1): 6445

Watching the human retina breath in real time and the slowing of mitochondrial respiration with age.

Pardis Kaynezhad, Ilias Tachtsidis, Sobha Sivaprasad, Glen Jeffery.

The retina has the greatest metabolic demand in the body particularly in dark adaptation when its sensitivity is enhanced. This requires elevated level of perfusion to sustain mitochondrial activity. However, mitochondrial performance declines with age leading to reduced adaptive ability. We assessed human retina metabolism in vivo using broad band near-infrared spectroscopy (bNIRS), which records colour changes in mitochondria and blood as retinal metabolism shifts in response to changes in environmental luminance. We demonstrate a significant sustained rise in mitochondrial oxidative metabolism in the first 3 min of darkness in subjects under 50 years old. This was not seen in those over 50 years. Choroidal oxygenation declines in < 50 s as mitochondrial metabolism increases, but gradually rises in the > 50 s. Significant group differences in blood oxygenation are apparent in the first 6 min, consistent with mitochondrial demand leading hemodynamic changes. A greater coupling between mitochondrial oxidative metabolism with hemodynamics is revealed in subjects older than 50, possibly due to reduced capacity in the older retina. Rapid in vivo assessment of retinal metabolism with bNIRS provides a route to understanding fundamental physiology and early identification of retinal disease before pathology is established.

DOI: https://doi.org/10.1038/s41598-023-32897-7
J Pediatr Intensive Care. 2023 Jun;12(2): 112-117

Can Lactate Clearance Predict Mortality in Critically Ill Children?

Azza A Moustafa, Abeer S Elhadidi, Mona A El-Nagar, Hadir M Hassouna.

  Serial evaluation of blood lactate, including lactate clearance, may have greater value over single measurement at the time of presentation. The rationale of the current study was to evaluate the use of lactate clearance after 6 hours of admission to pediatric intensive care unit (PICU) as a predictor of mortality in critically ill children. A prospective observational study was conducted in a nine-bed PICU of a tertiary care teaching hospital over a period of 6 months. Lactate levels were measured in arterial blood samples of 76 patients at the time of admission and 6 hours later. According to calculated lactate clearance, patients were divided into group A (lactate clearance more than 0) which included 71% of patients and group B (lactate clearance ≤0) which included 29% of patients. Lactate level at admission was a poor predictor of mortality (area under receiver operating characteristic curve [AUC] = 0.519, p = 0.789). Lactate clearance after 6 hours of admission was a significant predictor of mortality (AUC = 0.766, p < 0.001). Using Kaplan-Meier survival curve, overall survival was significantly better among group A ( p < 0.001). Using multivariate logistic regression model, lactate clearance after 6 hours (odds ratio = 0.98, 95% confidence interval [CI]: 0.96-0.99) and The Pediatric Index of Mortality 2 (PIM2) score (odds ratio = 4.7, 95% CI: 1.85-12.28) had independent prognostic significance with regard to mortality ( p = 0.030, 0.001 respectively). We conclude that lactate clearance after 6 hours of admission can predict mortality in critically ill children.

Keywords:  critical illness; intensive care units; kinetics; lactic acid; pediatric

DOI:  https://doi.org/10.1055/s-0041-1730930
Methods Mol Biol. 2023 ;2662 53-65

Measuring Mitochondrial Uncoupling in Mouse Primary Brown Adipocytes Differentiated Ex Vivo.

Michaela Veliova, Marcus J Tol, Peter Tontonoz, Orian S Shirihai, Marc Liesa.

  Measuring the mitochondrial respiratory capacity of brown adipocytes ex vivo is an essential approach to understand the cell-autonomous regulators of mitochondrial uncoupling in brown adipose tissue. Here, we describe two protocols to isolate brown preadipocytes from mice, their ex vivo differentiation to mature brown adipocytes and the quantification of their mitochondrial uncoupling capacity by respirometry.

Keywords:  Brown adipocytes; Mitochondria; Respirometry; Thermogenesis; Uncoupling

DOI:  https://doi.org/10.1007/978-1-0716-3167-6_5