bims-celmim 2023-08-06 papers

bims-celmim

Biomed News

on Cellular and mitochondrial metabolism

Issue of 2023–08–06
twenty-two papers selected by
Marc Segarra Mondejar, University of Cologne

Decreased MFN2 activates the cGAS-STING pathway in diabetic myocardial ischaemia-reperfusion by triggering the release of mitochondrial DNA.
O-GlcNAcylation of Raptor transduces glucose signals to mTORC1.
Phosphorylation of the N-terminus of Syntaxin-16 controls interaction with mVps45 and GLUT4 trafficking in adipocytes.
Negative regulation of pro-apoptotic AMPK/JNK pathway by itaconate in mice with fulminant liver injury.
Metformin Induces Lipogenesis and Apoptosis in H4IIE Hepatocellular Carcinoma Cells.
A Metabolomics-Based Study on NMDAR-Mediated Mitochondrial Damage through Calcium Overload and ROS Accumulation in Myocardial Infarction.
The role of dynamin-related protein 1 in cerebral ischemia/hypoxia injury.
2,8-Dihydroxyadenine-induced nephropathy causes hexosylceramide accumulation with increased mTOR signaling, reduced levels of protective SirT3 expression and impaired renal mitochondrial function.
Aging, oxidative stress and degenerative diseases: mechanisms, complications and emerging therapeutic strategies.
Membrane estrogen receptor-α contributes to female protection against high-fat diet-induced metabolic disorders.
Alterations of SIRT1/SIRT3 subcellular distribution in aging undermine cardiometabolic homeostasis during ischemia and reperfusion.
Sugar, salt, immunity and the cause of primary hypertension.
Increased cardiac PFK-2 protects against high-fat diet-induced cardiomyopathy and mediates beneficial systemic metabolic effects.
CPT2-mediated fatty acid oxidation inhibits tumorigenesis and enhances sorafenib sensitivity via the ROS/PPARγ/NF-κB pathway in clear cell renal cell carcinoma.
UCP1 alleviates renal interstitial fibrosis progression through oxidative stress pathway mediated by SIRT3 protein stability.
The effects of extracellular vesicles and their cargo on metabolism and its adaptation to physical exercise in insulin resistance and type 2 diabetes.
High-fat diet causes mitochondrial damage and downregulation of mitofusin-2 and optic atrophy-1 in multiple organs.
Role of sestrins in metabolic and aging-related diseases.
Endoplasmic reticulum stress in Alzheimer's disease: Molecular mechanisms and therapeutic prospects.
Phosphoinositides and intracellular calcium signaling: novel insights into phosphoinositides and calcium coupling as negative regulators of cellular signaling.
Dapagliflozin protects heart function against type-4 cardiorenal syndrome through activation of PKM2/PP1/FUNDC1-dependent mitophagy.
Effects of a high-fat low-carbohydrate diet under different energy conditions on glucose homeostasis and fatty liver development in rats and on gluconeogenesis in the isolated perfused liver.

Cell Commun Signal. 2023 Aug 03. 21(1): 192

Decreased MFN2 activates the cGAS-STING pathway in diabetic myocardial ischaemia-reperfusion by triggering the release of mitochondrial DNA.

Yonghong Xiong, Yan Leng, Hao Tian, Xinqi Deng, Wenyuan Li, Wei Li, Zhongyuan Xia.

   BACKGROUND: The cause of aggravation of diabetic myocardial damage is yet to be elucidated; damage to mitochondrial function has been a longstanding focus of research. During diabetic myocardial ischaemia-reperfusion (MI/R), it remains unclear whether reduced mitochondrial fusion exacerbates myocardial injury by generating free damaged mitochondrial DNA (mitoDNA) and activating the cGAS-STING pathway.
METHODS: In this study, a mouse model of diabetes was established (by feeding mice a high-fat diet (HFD) plus a low dose of streptozotocin (STZ)), a MI/R model was established by cardiac ischaemia for 2 h and reperfusion for 30 min, and a cellular model of glycolipid toxicity induced by high glucose (HG) and palmitic acid (PA) was established in H9C2 cells.
RESULTS: We observed that altered mitochondrial dynamics during diabetic MI/R led to increased mitoDNA in the cytosol, activation of the cGAS-STING pathway, and phosphorylation of the downstream targets TBK1 and IRF3. In the cellular model we found that cytosolic mitoDNA was the result of reduced mitochondrial fusion induced by HG and PA, which also resulted in cGAS-STING signalling and activation of downstream targets. Moreover, inhibition of STING by H-151 significantly ameliorated myocardial injury induced by MFN2 knockdown in both the cell and mouse models. The use of a fat-soluble antioxidant CoQ10 improved cardiac function in the mouse models.
CONCLUSIONS: Our study elucidated the critical role of cGAS-STING activation, triggered by increased cytosolic mitoDNA due to decreased mitochondrial fusion, in the pathogenesis of diabetic MI/R injury. This provides preclinical insights for the treatment of diabetic MI/R injury. Video Abstract.

Keywords:  Diabetes; Mitochondrial DNA; Myocardial ischaemia–reperfusion; cGAS-STING

DOI:  https://doi.org/10.1186/s12964-023-01216-y
Mol Cell. 2023 Jul 28. pii: S1097-2765(23)00526-9. [Epub ahead of print]

O-GlcNAcylation of Raptor transduces glucose signals to mTORC1.

Chenchen Xu, Xiaoqing Pan, Dong Wang, Yuanyuan Guan, Wenyu Yang, Xing Chen, Ying Liu.

  The mechanistic target of rapamycin complex 1 (mTORC1) regulates metabolism and cell growth in response to nutrient levels. Dysregulation of mTORC1 results in a broad spectrum of diseases. Glucose is the primary energy supply of cells, and therefore, glucose levels must be accurately conveyed to mTORC1 through highly responsive signaling mechanisms to control mTORC1 activity. Here, we report that glucose-induced mTORC1 activation is regulated by O-GlcNAcylation of Raptor, a core component of mTORC1, in HEK293T cells. Mechanistically, O-GlcNAcylation of Raptor at threonine 700 facilitates the interactions between Raptor and Rag GTPases and promotes the translocation of mTOR to the lysosomal surface, consequently activating mTORC1. In addition, we show that AMPK-mediated phosphorylation of Raptor suppresses Raptor O-GlcNAcylation and inhibits Raptor-Rags interactions. Our findings reveal an exquisitely controlled mechanism, which suggests how glucose coordinately regulates cellular anabolism and catabolism.

Keywords:  O-GlcNAcylation; Raptor; glucose sensing; mTOR

DOI:  https://doi.org/10.1016/j.molcel.2023.07.011
PeerJ. 2023 ;11 e15630

Phosphorylation of the N-terminus of Syntaxin-16 controls interaction with mVps45 and GLUT4 trafficking in adipocytes.

Shaun K Bremner, Rebecca Berends, Alexandra Kaupisch, Jennifer Roccisana, Calum Sutherland, Nia J Bryant, Gwyn W Gould.

  The ability of insulin to stimulate glucose transport in muscle and fat cells is mediated by the regulated delivery of intracellular vesicles containing glucose transporter-4 (GLUT4) to the plasma membrane, a process known to be defective in disease such as Type 2 diabetes. In the absence of insulin, GLUT4 is sequestered in tubules and vesicles within the cytosol, collectively known as the GLUT4 storage compartment. A subset of these vesicles, known as the 'insulin responsive vesicles' are selectively delivered to the cell surface in response to insulin. We have previously identified Syntaxin16 (Sx16) and its cognate Sec1/Munc18 protein family member mVps45 as key regulatory proteins involved in the delivery of GLUT4 into insulin responsive vesicles. Here we show that mutation of a key residue within the Sx16 N-terminus involved in mVps45 binding, and the mutation of the Sx16 binding site in mVps45 both perturb GLUT4 sorting, consistent with an important role of the interaction of these two proteins in GLUT4 trafficking. We identify Threonine-7 (T7) as a site of phosphorylation of Sx16 in vitro. Mutation of T7 to D impairs Sx16 binding to mVps45 in vitro and overexpression of T7D significantly impaired insulin-stimulated glucose transport in adipocytes. We show that both AMP-activated protein kinase (AMPK) and its relative SIK2 phosphorylate this site. Our data suggest that Sx16 T7 is a potentially important regulatory site for GLUT4 trafficking in adipocytes.

Keywords:  GLUT4; Glucose transport; Insulin; Membrane traffic; Syntaxin; sec1/munc protein

DOI:  https://doi.org/10.7717/peerj.15630
Cell Death Dis. 2023 07 31. 14(7): 486

Negative regulation of pro-apoptotic AMPK/JNK pathway by itaconate in mice with fulminant liver injury.

Kerui Fan, Kun Chen, Xinyan Zan, Ying Zhi, Xue Zhang, Xinyue Zhang, Jinghuan Qiu, Gang Liu, Longjiang Li, Li Tang, Kai Hu, Jingyuan Wan, Xianqiong Gong, Yongqiang Yang, Li Zhang.

Accumulating evidence indicates that metabolic responses are deeply integrated into signal transduction, which provides novel opportunities for the metabolic control of various disorders. Recent studies suggest that itaconate, a highly concerned bioactive metabolite catalyzed by immune responsive gene 1 (IRG1), is profoundly involved in the regulation of apoptosis, but the underlying mechanisms have not been fully understood. In the present study, the molecular mechanisms responsible for the apoptosis-modulatory activities of IRG1/itaconate have been investigated in mice with lipopolysaccharide (LPS)/D-galactosamine (D-Gal)-induced apoptotic liver injury. The results indicated that LPS/D-Gal exposure upregulated the level of IRG1 and itaconate. Deletion of IRG1 resulted in exacerbated hepatocytes apoptosis and liver injury. The phospho-antibody microarray analysis and immunoblot analysis indicated that IRG1 deletion enhanced the activation of AMP-activated protein kinase (AMPK)/c-jun-N-terminal kinase (JNK) pathway in LPS/D-Gal exposed mice. Mechanistically, IRG1 deficiency impaired the anti-oxidative nuclear factor erythroid-2 related factor 2 (Nrf2) signaling and then enhanced the activation of the redox-sensitive AMPK/JNK pathway that promotes hepatocytes apoptosis. Importantly, post-insult supplementation with 4-octyl itaconate (4-OI), a cell-permeable derivate of itaconate, resulted in beneficial outcomes in fulminant liver injury. Therefore, IRG1/itaconate might function as a negative regulator that controls AMPK-induced hepatocyte apoptosis in LPS/D-Gal-induced fulminant liver injury.

DOI: https://doi.org/10.1038/s41419-023-06001-w
Dev Reprod. 2023 Jun;27(2): 77-89

Metformin Induces Lipogenesis and Apoptosis in H4IIE Hepatocellular Carcinoma Cells.

Deokbae Park, Sookyoung Lee, Hyejin Boo.

  Metformin is the most widely used anti-diabetic drug that helps maintain normal blood glucose levels primarily by suppressing hepatic gluconeogenesis in type II diabetic patients. We previously found that metformin induces apoptotic death in H4IIE rat hepatocellular carcinoma cells. Despite its anti-diabetic roles, the effect of metformin on hepatic de novo lipogenesis (DNL) remains unclear. We investigated the effect of metformin on hepatic DNL and apoptotic cell death in H4IIE cells. Metformin treatment stimulated glucose consumption, lactate production, intracellular fat accumulation, and the expressions of lipogenic proteins. It also stimulated apoptosis but reduced autophagic responses. These metformin-induced changes were clearly reversed by compound C, an inhibitor of AMP-activated protein kinase (AMPK). Interestingly, metformin massively increased the production of reactive oxygen species (ROS), which was completely blocked by compound C. Metformin also stimulated the phosphorylation of p38 mitogen-activated protein kinase (p38MAPK). Finally, inhibition of p38MAPK mimicked the effects of compound C, and suppressed the metformin-induced fat accumulation and apoptosis. Taken together, metformin stimulates dysregulated glucose metabolism, intracellular fat accumulation, and apoptosis. Our findings suggest that metformin induces excessive glucose-induced DNL, oxidative stress by ROS generation, activation of AMPK and p38MAPK, suppression of autophagy, and ultimately apoptosis.

Keywords:  Apoptosis; Hepatocellular carcinoma (HCC); Lipogenesis; Metformin; Reactive oxygen species (ROS)

DOI:  https://doi.org/10.12717/DR.2023.27.2.77
Front Biosci (Landmark Ed). 2023 Jul 19. 28(7): 140

A Metabolomics-Based Study on NMDAR-Mediated Mitochondrial Damage through Calcium Overload and ROS Accumulation in Myocardial Infarction.

Yuanyuan Wang, Li He, Dan Du, Zeyi Cheng, Chaoyi Qin.

   BACKGROUND: Coronary artery disease is a leading public health problem. However, the mechanisms underlying mitochondrial damage remain unclear. The present study verified and explored the novel mechanisms underlying ischemic injury based on a metabolomic analysis.
METHODS: Mouse models of acute myocardial infarction were established, and serum samples were collected for targeted liquid chromatography with tandem mass spectrometry analysis. Based on metabolomic analyses, the N-methyl-d-aspartic acid receptor (NMDAR)-related calcium transporting signaling pathway was selected. Primary cardiomyocyte cultures were used, and N-methyl-d-aspartic acid (NMDA) was used as an agonist to confirm the role of NMDAR in ischemic injury. In addition, Bax, Bcl-2, mitochondrial calcium, potential, and mitochondrial reactive oxygen species accumulation were used to explore the role of NMDAR in mitochondrial damage-induced apoptosis.
RESULTS: Glutamate-related metabolism was significantly altered following in acute myocardial infarction. NMDA induces apoptosis under hypoxic conditions NMDAR was translocated to the mitochondrial-related membrane after activation, and its mitochondrial expression was significantly increased (p < 0.05). Mitochondrial damage-induced apoptosis was significantly inhibited by a selective NDMAR antagonist (p < 0.05), while Bax expression was remarkably decreased and Bcl-2 expression was increased (p < 0.05). To further explore the mechanism of NMDAR, mitochondrial calcium, membrane potential, and reactive oxygen species were detected. With NMDAR inhibition under hypoxic conditions, mitochondrial morphology and function were preserved (p < 0.05).
CONCLUSIONS: Our metabolomic study identified NMDAR as a promising target. In conclusion, our study provides solid data for further studies of the role of NMDAR in cardiovascular diseases and a promising target to interfere with apoptosis in acute myocardial infarction.

Keywords:  NMDAR; calcium overload; metabolomics; mitochondrial damage; myocardial infarction

DOI:  https://doi.org/10.31083/j.fbl2807140
Biomed Pharmacother. 2023 Jul 27. pii: S0753-3322(23)01038-7. [Epub ahead of print]165 115247

The role of dynamin-related protein 1 in cerebral ischemia/hypoxia injury.

Yu Huan, Guangzhi Hao, Zuolin Shi, Yong Liang, Yushu Dong, Huilin Quan.

  Mitochondrial dysfunction, especially in terms of mitochondrial dynamics, has been reported to be closely associated with neuronal outcomes and neurological impairment in cerebral ischemia/hypoxia injury. Dynamin-related protein 1 (Drp1) is a cytoplasmic GTPase that mediates mitochondrial fission and participates in neuronal cell death, calcium signaling, and oxidative stress. The neuroprotective role of Drp1 inhibition has been confirmed in several central nervous system disease models, demonstrating that targeting Drp1 may shed light on novel approaches for the treatment of cerebral ischemia/hypoxia injury. In this review, we aimed to highlight the roles of Drp1 in programmed cell death, oxidative stress, mitophagy, and mitochondrial function to provide a better understanding of mitochondrial disturbances in cerebral ischemia/hypoxia injury, and we also summarize the advances in novel chemical compounds targeting Drp1 to provide new insights into potential therapies for cerebral ischemia/hypoxia injury.

Keywords:  Cerebral ischemia-hypoxia injury; Drp1; Mitochondrial fission; Post-translational modification

DOI:  https://doi.org/10.1016/j.biopha.2023.115247
Biochim Biophys Acta Mol Basis Dis. 2023 Aug 01. pii: S0925-4439(23)00191-6. [Epub ahead of print] 166825

2,8-Dihydroxyadenine-induced nephropathy causes hexosylceramide accumulation with increased mTOR signaling, reduced levels of protective SirT3 expression and impaired renal mitochondrial function.

Julia Moellmann, Katja Krueger, Dickson W L Wong, Barbara M Klinkhammer, Eva M Buhl, Jonas Dehairs, Johan V Swinnen, Heidi Noels, Joachim Jankowski, Corinna Lebherz, Peter Boor, Nikolaus Marx, Michael Lehrke.

   AIM: Chronic kidney disease (CKD) is accompanied by increased cardiovascular risk and heart failure. In rodents, 2,8-dihydroxyadenine (DHA)-induced nephropathy is a frequently used CKD model. Cardiac and kidney tubular cells share high energy demand to guarantee constant contractive force of the heart or reabsorption/secretion of primary filtrated molecules and waste products by the kidney. Here we analyze time-dependent mechanisms of kidney damage and cardiac consequences under consideration of energetic pathways with the focus on mitochondrial function and lipid metabolism in mice.
METHODS AND RESULTS: CKD was induced by alternating dietary adenine supplementation (0.2 % or 0.05 % of adenine) in C57BL/6J mice for 9 weeks. Progressive kidney damage led to reduced creatinine clearance, kidney fibrosis and renal inflammation after 3, 6, and 9 weeks. No difference in cardiac function, mitochondrial respiration nor left ventricular fibrosis was observed at any time point. Investigating mechanisms of renal damage, protective SirT3 was decreased in CKD, which contrasted an increase in protein kinase B (AKT) expression, mechanistic target of rapamycin (mTOR) downstream signaling, induction of oxidative and endoplasmic reticulum (ER) stress. This occurred together with impaired renal mitochondrial function and accumulation of hexosylceramides (HexCer) as an established mediator of inflammation and mitochondrial dysfunction in the kidney.
CONCLUSIONS: 2,8-DHA-induced CKD results in renal activation of the mTOR downstream signaling, endoplasmic reticulum stress, tubular injury, fibrosis, inflammation, oxidative stress and impaired kidney mitochondrial function in conjunction with renal hexosylceramide accumulation in C57BL/6J mice.

Keywords:  2,8-Dihydroxyadenine nephropathy; Chronic kidney disease; Endoplasmic reticulum stress; Hexosylceramides; Mitochondrial function; mTOR

DOI:  https://doi.org/10.1016/j.bbadis.2023.166825
Biogerontology. 2023 Jul 30.

Aging, oxidative stress and degenerative diseases: mechanisms, complications and emerging therapeutic strategies.

Mani Raj Chaudhary, Sakshi Chaudhary, Yogita Sharma, Thokchom Arjun Singh, Alok Kumar Mishra, Shweta Sharma, Mohammad Murtaza Mehdi.

  Aging accompanied by several age-related complications, is a multifaceted inevitable biological progression involving various genetic, environmental, and lifestyle factors. The major factor in this process is oxidative stress, caused by an abundance of reactive oxygen species (ROS) generated in the mitochondria and endoplasmic reticulum (ER). ROS and RNS pose a threat by disrupting signaling mechanisms and causing oxidative damage to cellular components. This oxidative stress affects both the ER and mitochondria, causing proteopathies (abnormal protein aggregation), initiation of unfolded protein response, mitochondrial dysfunction, abnormal cellular senescence, ultimately leading to inflammaging (chronic inflammation associated with aging) and, in rare cases, metastasis. RONS during oxidative stress dysregulate multiple metabolic pathways like NF-κB, MAPK, Nrf-2/Keap-1/ARE and PI3K/Akt which may lead to inappropriate cell death through apoptosis and necrosis. Inflammaging contributes to the development of inflammatory and degenerative diseases such as neurodegenerative diseases, diabetes, cardiovascular disease, chronic kidney disease, and retinopathy. The body's antioxidant systems, sirtuins, autophagy, apoptosis, and biogenesis play a role in maintaining homeostasis, but they have limitations and cannot achieve an ideal state of balance. Certain interventions, such as calorie restriction, intermittent fasting, dietary habits, and regular exercise, have shown beneficial effects in counteracting the aging process. In addition, interventions like senotherapy (targeting senescent cells) and sirtuin-activating compounds (STACs) enhance autophagy and apoptosis for efficient removal of damaged oxidative products and organelles. Further, STACs enhance biogenesis for the regeneration of required organelles to maintain homeostasis. This review article explores the various aspects of oxidative damage, the associated complications, and potential strategies to mitigate these effects.

Keywords:  Aging; Antioxidant; Autophagy; Degenerative diseases; Inflammation; Oxidative stress

DOI:  https://doi.org/10.1007/s10522-023-10050-1
Front Endocrinol (Lausanne). 2023 ;14 1215947

Membrane estrogen receptor-α contributes to female protection against high-fat diet-induced metabolic disorders.

Aurélie Fabre, Blandine Tramunt, Alexandra Montagner, Céline Mouly, Elodie Riant, Marie-Lou Calmy, Marine Adlanmerini, Coralie Fontaine, Rémy Burcelin, Françoise Lenfant, Jean-François Arnal, Pierre Gourdy.

   Background: Estrogen Receptor α (ERα) is a significant modulator of energy balance and lipid/glucose metabolisms. Beyond the classical nuclear actions of the receptor, rapid activation of intracellular signaling pathways is mediated by a sub-fraction of ERα localized to the plasma membrane, known as Membrane Initiated Steroid Signaling (MISS). However, whether membrane ERα is involved in the protective metabolic actions of endogenous estrogens in conditions of nutritional challenge, and thus contributes to sex differences in the susceptibility to metabolic diseases, remains to be clarified.
Methods: Male and female C451A-ERα mice, harboring a point mutation which results in the abolition of membrane localization and MISS-related effects of the receptor, and their wild-type littermates (WT-ERα) were maintained on a normal chow diet (NCD) or fed a high-fat diet (HFD). Body weight gain, body composition and glucose tolerance were monitored. Insulin sensitivity and energy balance regulation were further investigated in HFD-fed female mice.
Results: C451A-ERα genotype had no influence on body weight gain, adipose tissue accumulation and glucose tolerance in NCD-fed mice of both sexes followed up to 7 months of age, nor male mice fed a HFD for 12 weeks. In contrast, compared to WT-ERα littermates, HFD-fed C451A-ERα female mice exhibited: 1) accelerated fat mass accumulation, liver steatosis and impaired glucose tolerance; 2) whole-body insulin resistance, assessed by hyperinsulinemic-euglycemic clamps, and altered insulin-induced signaling in skeletal muscle and liver; 3) significant decrease in energy expenditure associated with histological and functional abnormalities of brown adipose tissue and a defect in thermogenesis regulation in response to cold exposure.
Conclusion: Besides the well-characterized role of ERα nuclear actions, membrane-initiated ERα extra-nuclear signaling contributes to female, but not to male, protection against HFD-induced obesity and associated metabolic disorders in mouse.

Keywords:  estrogen receptor alpha (ERα); insulin resistance; membrane-initiated steroid signaling; obesity; sex differences; thermogenesis

DOI:  https://doi.org/10.3389/fendo.2023.1215947
Aging Cell. 2023 Aug 03. e13930

Alterations of SIRT1/SIRT3 subcellular distribution in aging undermine cardiometabolic homeostasis during ischemia and reperfusion.

Jingwen Zhang, Hao Wang, Lily Slotabec, Feng Cheng, Yi Tan, Ji Li.

  Age-related sensors Sirtuin1 (SIRT1) and Sirtuin3 (SIRT3) play an essential role in the protective response upon myocardial ischemia and/or reperfusion (I/R). However, the subcellular localization and co-regulatory network between cardiac SIRT1 and SIRT3 remain unknown, especially their effects on age-related metabolic regulation during acute ischemia and I/R. Here, we found that defects of cardiac SIRT1 or SIRT3 with aging result in an exacerbated cardiac physiological structural and functional deterioration after acute ischemic stress and failed recovery through reperfusion operation. In aged hearts, SIRT1 translocated into mitochondria and recruited more mitochondria SIRT3 to enhance their interaction during acute ischemia, acting as adaptive protection for the aging hearts from further mitochondria dysfunction. Subsequently, SIRT3-targeted proteomics revealed that SIRT1 plays a crucial role in maintaining mitochondrial integrity through SIRT3-mediated substrate metabolism during acute ischemic and I/R stress. Although the loss of SIRT1/SIRT3 led to a compromised PGC-1α/PPARα-mediated transcriptional control of fatty acid oxidation in response to acute ischemia and I/R, their crosstalk in mitochondria plays a more important role in the aging heart during acute ischemia. However, the increased mitochondria SIRT1-SIRT3 interaction promoted adaptive protection to aging-related fatty acid metabolic disorder via deacetylation of long-chain acyl CoA dehydrogenase (LCAD) during ischemic insults. Therefore, the dynamic network of SIRT1/SIRT3 acts as a mediator that regulates adaptive metabolic response to improve the tolerance of aged hearts to ischemic insults, which will facilitate investigation into the role of SIRT1/SIRT3 in age-related ischemic heart disease.

Keywords:  SIRT1; SIRT3; aging; fatty acid oxidation; ischemia/reperfusion

DOI:  https://doi.org/10.1111/acel.13930
Clin Kidney J. 2023 Aug;16(8): 1239-1248

Sugar, salt, immunity and the cause of primary hypertension.

Laura G Sánchez-Lozada, Magdalena Madero, Marilda Mazzali, Daniel I Feig, Takahiko Nakagawa, Miguel A Lanaspa, Mehmet Kanbay, Masanari Kuwabara, Bernardo Rodriguez-Iturbe, Richard J Johnson.

  Despite its discovery more than 150 years ago, the cause of primary hypertension remains unknown. Most studies suggest that hypertension involves genetic, congenital or acquired risk factors that result in a relative inability of the kidney to excrete salt (sodium chloride) in the kidneys. Here we review recent studies that suggest there may be two phases, with an initial phase driven by renal vasoconstriction that causes low-grade ischemia to the kidney, followed by the infiltration of immune cells that leads to a local autoimmune reaction that maintains the renal vasoconstriction. Evidence suggests that multiple mechanisms could trigger the initial renal vasoconstriction, but one way may involve fructose that is provided in the diet (such as from table sugar or high fructose corn syrup) or produced endogenously. The fructose metabolism increases intracellular uric acid, which recruits NADPH oxidase to the mitochondria while inhibiting AMP-activated protein kinase. A drop in intracellular ATP level occurs, triggering a survival response. Leptin levels rise, triggering activation of the sympathetic central nervous system, while vasopressin levels rise, causing vasoconstriction in its own right and stimulating aldosterone production via the vasopressin 1b receptor. Low-grade renal injury and autoimmune-mediated inflammation occur. High-salt diets can amplify this process by raising osmolality and triggering more fructose production. Thus, primary hypertension may result from the overactivation of a survival response triggered by fructose metabolism. Restricting salt and sugar and hydrating with ample water may be helpful in the prevention of primary hypertension.

Keywords:  autoimmune; fructose; hypertension; leptin; uric acid; vasopressin

DOI:  https://doi.org/10.1093/ckj/sfad058
iScience. 2023 Jul 21. 26(7): 107131

Increased cardiac PFK-2 protects against high-fat diet-induced cardiomyopathy and mediates beneficial systemic metabolic effects.

Maria F Mendez Garcia, Satoshi Matsuzaki, Albert Batushansky, Ryan Newhardt, Caroline Kinter, Yan Jin, Shivani N Mann, Michael B Stout, Haiwei Gu, Ying Ann Chiao, Michael Kinter, Kenneth M Humphries.

  A healthy heart adapts to changes in nutrient availability and energy demands. In metabolic diseases like type 2 diabetes (T2D), increased reliance on fatty acids for energy production contributes to mitochondrial dysfunction and cardiomyopathy. A principal regulator of cardiac metabolism is 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2), which is a central driver of glycolysis. We hypothesized that increasing PFK-2 activity could mitigate cardiac dysfunction induced by high-fat diet (HFD). Wild type (WT) and cardiac-specific transgenic mice expressing PFK-2 (GlycoHi) were fed a low fat or HFD for 16 weeks to induce metabolic dysfunction. Metabolic phenotypes were determined by measuring mitochondrial bioenergetics and performing targeted quantitative proteomic and metabolomic analysis. Increasing cardiac PFK-2 had beneficial effects on cardiac and mitochondrial function. Unexpectedly, GlycoHi mice also exhibited sex-dependent systemic protection from HFD, including increased glucose homeostasis. These findings support improving glycolysis via PFK-2 activity can mitigate mitochondrial and functional changes that occur with metabolic syndrome.

Keywords:  Metabolomics; Molecular biology; Physiology; Proteomics

DOI:  https://doi.org/10.1016/j.isci.2023.107131
Cell Signal. 2023 Aug 02. pii: S0898-6568(23)00252-8. [Epub ahead of print] 110838

CPT2-mediated fatty acid oxidation inhibits tumorigenesis and enhances sorafenib sensitivity via the ROS/PPARγ/NF-κB pathway in clear cell renal cell carcinoma.

Kai Zeng, Qinyu Li, Guoda Song, Bingliang Chen, Min Luo, Jianping Miao, Bo Liu.

  Kidney cancer is a common kind of tumor with approximately 400,000 new diagnoses each year. Clear cell renal cell carcinoma (ccRCC) accounts for 70-80% of all renal cell carcinomas. Lipid metabolism disorder is a hallmark of ccRCC. With a better knowledge of the importance of fatty acid oxidation (FAO) in cancer, carnitine palmitoyltransferase 2 (CPT2) has gained prominence as a major mediator in the cancer metabolic pathway. However, the biological functions and mechanism of CPT2 in the progression of ccRCC are still unclear. Herein, we performed assays in vitro and in vivo to explore CPT2 functions in ccRCC. Moreover, we discovered that CPT2 induced FAO, which inhibited the generation of reactive oxygen species (ROS) by increasing nicotinamide adenine dinucleotide phosphate (NADPH) production. Additionally, we demonstrated that CPT2 suppresses tumor proliferation, invasion, and migration by inhibiting the ROS/ PPARγ /NF-κB pathway. Gene set enrichment analysis (GSEA) and drug sensitivity analysis showed that high expression of CPT2 in ccRCC was associated with higher sorafenib sensitivity, which was also validated in vitro and in vivo. In summary, our results suggest that CPT2 acts as a tumor suppressor in the development of ccRCC through the ROS/PPARγ/NF-κB pathway. Moreover, CPT2 is a potential therapeutic target for increasing sorafenib sensitivity in ccRCC.

Keywords:  CPT2; Clear cell renal cell carcinoma; Fatty acid oxidation; ROS; Sorafenib

DOI:  https://doi.org/10.1016/j.cellsig.2023.110838
J Transl Med. 2023 08 02. 21(1): 521

UCP1 alleviates renal interstitial fibrosis progression through oxidative stress pathway mediated by SIRT3 protein stability.

Wei Xiong, Zhiyong Xiong, Anni Song, Chuntao Lei, Chen Ye, Hua Su, Chun Zhang.

   BACKGROUND: Renal interstitial fibrosis is a common pathway for the progressive development of chronic renal diseases (CKD) with different etiology, and is the main pathological basis leading to end-stage renal disease. Although the current research on renal interstitial fibrosis is gradually deepening, the diagnosis and treatment methods are still very lacking. Uncoupling protein 1 (UCP1) is a nuclear encoded protein in mitochondria inner membrane and plays an important role in regulating energy metabolism and mitochondrial homeostasis. However, the biological significance of UCP1 and potential regulatory mechanisms in the development of CKD remain unclear.
METHODS: Unilateral ureteral obstruction (UUO) model was used to construct the animal model of renal fibrosis, and TGF-β1 stimulation of HK2 cells was used to construct the vitro model of renal fibrosis. UCP1 expression was detected by Western blot, immunoblot analysis and immunohistochemistry. UCP1 was upregulated by UCP1 overexpressing lentivirus and UCP1 agonist CL316243. Western blot and immunofluorescence were used to detect epithelial mesenchymal transition (EMT)-related markers, such as collagen I, fibronectin, antioxidant enzyme SOD2 and CAT. Reactive oxygen species (ROS) production was detected by ROS detection kit. SIRT3 knockdown was performed by siRNA.
RESULTS: This study presents that UCP1 is significantly downregulated in patients with renal fibrosis and UUO model. Further studies discover that UCP1 overexpression and CL316243 treatments (UCP1 agonists) reversed EMT and extracellular matrix (ECM) accumulation in renal fibrosis models in vivo and in vitro. Simultaneously, UCP1 reduced the ROS production by increasing the stability of SIRT3. When SIRT3 was knocked down, the production of ROS decreased.
CONCLUSIONS: Elevating the expression of UCP1 can inhibit the occurrence of oxidative stress by stabilizing SIRT3, thereby reducing EMT and ECM accumulation, and ultimately alleviating renal interstitial fibrosis. It will provide new instructions and targets for the treatment of CKD.

Keywords:  Chronic kidney disease (CKD); Reactive oxygen species (ROS); Renal interstitial fibrosis; SIRT3; UCP1

DOI:  https://doi.org/10.1186/s12967-023-04376-0
Proteomics. 2023 Jul 31. e2300078

The effects of extracellular vesicles and their cargo on metabolism and its adaptation to physical exercise in insulin resistance and type 2 diabetes.

Lucia Mastrototaro, Michael Roden.

  Lifestyle modification represents the first-line strategy for the prevention and treatment of type 2 diabetes mellitus (T2DM), which is frequently associated with obesity and characterized by defective pancreatic insulin secretion and/or insulin resistance. Exercise training is an essential component of lifestyle modification and has been shown to ameliorate insulin resistance by reducing body fat mass and by enhancing skeletal muscle mitochondrial biogenesis and insulin-independent glucose uptake. Additionally, exercising stimulates the release of exerkines such as metabolites or cytokines, but also long non-coding RNA, microRNAs, cell-free DNA (cf-DNA), and extracellular vesicles (EVs), which contribute to inter-tissue communication. There is emerging evidence that EV number and content are altered in obesity and T2DM and may be involved in several metabolic processes, specifically either worsening or improving insulin resistance. This review summarizes the current knowledge on the metabolic effects of exercise training and on the potential role of humoral factors and EV as new biomarkers for early diagnosis and tailored treatment of T2DM.

Keywords:  diabetes mellitus; exercise; exerkines; extracellular vesicles; organ crosstalk

DOI:  https://doi.org/10.1002/pmic.202300078
J Clin Biochem Nutr. 2023 Jul;73(1): 61-76

High-fat diet causes mitochondrial damage and downregulation of mitofusin-2 and optic atrophy-1 in multiple organs.

Peng Zheng, Wenjing Ma, Yilu Gu, Hengfang Wu, Zhiping Bian, Nannan Liu, Di Yang, Xiangjian Chen.

  High-fat consumption promotes the development of obesity, which is associated with various chronic illnesses. Mitochondria are the energy factories of eukaryotic cells, maintaining self-stability through a fine-tuned quality-control network. In the present study, we evaluated high-fat diet (HFD)-induced changes in mitochondrial ultrastructure and dynamics protein expression in multiple organs. C57BL/6J male mice were fed HFD or normal diet (ND) for 24 weeks. Compared with ND-fed mice, HFD-fed mice exhibited increased body weight, cardiomyocyte enlargement, pulmonary fibrosis, hepatic steatosis, renal and splenic structural abnormalities. The cellular apoptosis of the heart, liver, and kidney increased. Cellular lipid droplet deposition and mitochondrial deformations were observed. The proteins related to mitochondrial biogenesis (TFAM), fission (DRP1), autophagy (LC3 and LC3-II: LC3-I ratio), and mitophagy (PINK1) presented different changes in different organs. The mitochondrial fusion regulators mitofusin-2 (MFN2) and optic atrophy-1 (OPA1) were consistently downregulated in multiple organs, even the spleen. TOMM20 and ATP5A protein were enhanced in the heart, skeletal muscle, and spleen, and attenuated in the kidney. These results indicated that high-fat feeding caused pathological changes in multiple organs, accompanied by mitochondrial ultrastructural damage, and MFN2 and OPA1 downregulation. The mitochondrial fusion proteins may become promising targets and/or markers for treating metabolic disease.

Keywords:  high-fat diet; hyperlipidemia; mitochondria; mitofusin-2; optic atrophy-1

DOI:  https://doi.org/10.3164/jcbn.22-73
Biogerontology. 2023 Jul 30.

Role of sestrins in metabolic and aging-related diseases.

Huan Fang, Xiaomin Shi, Juyi Wan, Xiaolin Zhong.

  Sestrins are a type of highly conserved stress-inducing protein that has antioxidant and mTORC1 inhibitory functions. Metabolic dysfunction and aging are the main risk factors for development of human diseases, such as diabetes, neurodegenerative diseases, and cancer. Sestrins have important roles in regulating glucose and lipid metabolism, anti-tumor functions, and aging by inhibiting the reactive oxygen species and mechanistic target of rapamycin complex 1 pathways. In this review, the structure and biological functions of sestrins are summarized, and how sestrins are activated and contribute to regulation of the downstream signal pathways of metabolic and aging-related diseases are discussed in detail with the goal of providing new ideas and therapeutic targets for the treatment of related diseases.

Keywords:  Aging; Metabolism; ROS; Sestrins; mTORC1

DOI:  https://doi.org/10.1007/s10522-023-10053-y
Life Sci. 2023 Jul 29. pii: S0024-3205(23)00618-5. [Epub ahead of print] 121983

Endoplasmic reticulum stress in Alzheimer's disease: Molecular mechanisms and therapeutic prospects.

Pushank Nagar, Prajjwal Sharma, Rishika Dhapola, Sneha Kumari, Bikash Medhi, Dibbanti HariKrishnaReddy.

  Alzheimer's disease (AD) is a progressive neurodegenerative condition that leads to memory loss and cognitive impairment over time. It is characterized by protein misfolding as well as prolonged cellular stress, such as perturbing calcium homeostasis and redox management. Numerous investigations have proven that endoplasmic reticulum failure may exhibit exacerbation of AD pathogenesis in AD patients, in-vivo and in-vitro models. The endoplasmic reticulum (ER) participates in a variety of biological functions including folding of protein, quality control, cholesterol production, and maintenance of calcium balance. A diverse range of physiological, pathological and pharmacological substances can interfere with ER activity and thus lead to exaggeration of ER stress. The unfolded protein response (UPR), an intracellular signaling network is stimulated due to ER stress. Three stress sensors found in the endoplasmic reticulum, the PERK, ATF6, and IRE1 transducers detect protein misfolding in the ER and trigger UPR, a complex system to maintain homeostasis. ER stress is linked to many of the major pathological processes that are seen in AD, including presenilin1 and 2 (PS1 and PS2) gene mutation, tau phosphorylation and β-amyloid formation. The role of ER stress and UPR in the pathophysiology of AD implies that they can be employed as potent therapeutic target. This study shows the relationship between ER and AD and how the pathogenesis of AD is influenced by the impact of ER stress. An effective method for the prevention or treatment of AD may involve therapeutic strategies that modify ER stress pathways.

Keywords:  ATF6; Alzheimer's disease; Endoplasmic reticulum stress; IRE1; PERK; Unfolded protein response

DOI:  https://doi.org/10.1016/j.lfs.2023.121983
Exp Mol Med. 2023 Aug 01.

Phosphoinositides and intracellular calcium signaling: novel insights into phosphoinositides and calcium coupling as negative regulators of cellular signaling.

Byung-Chul Oh.

Intracellular calcium (Ca2+) and phosphoinositides (PIPs) are crucial for regulating cellular activities such as metabolism and cell survival. Cells maintain precise intracellular Ca2+ and PIP levels via the actions of a complex system of Ca2+ channels, transporters, Ca2+ ATPases, and signaling effectors, including specific lipid kinases, phosphatases, and phospholipases. Recent research has shed light on the complex interplay between Ca2+ and PIP signaling, suggesting that elevated intracellular Ca2+ levels negatively regulate PIP signaling by inhibiting the membrane localization of PIP-binding proteins carrying specific domains, such as the pleckstrin homology (PH) and Ca2+-independent C2 domains. This dysregulation is often associated with cancer and metabolic diseases. PIPs recruit various proteins with PH domains to the plasma membrane in response to growth hormones, which activate signaling pathways regulating metabolism, cell survival, and growth. However, abnormal PIP signaling in cancer cells triggers consistent membrane localization and activation of PIP-binding proteins. In the context of obesity, an excessive intracellular Ca2+ level prevents the membrane localization of the PIP-binding proteins AKT, IRS1, and PLCδ via Ca2+-PIPs, contributing to insulin resistance and other metabolic diseases. Furthermore, an excessive intracellular Ca2+ level can cause functional defects in subcellular organelles such as the endoplasmic reticulum (ER), lysosomes, and mitochondria, causing metabolic diseases. This review explores how intracellular Ca2+ overload negatively regulates the membrane localization of PIP-binding proteins.

DOI: https://doi.org/10.1038/s12276-023-01067-0
Int J Biol Macromol. 2023 Aug 02. pii: S0141-8130(23)03012-X. [Epub ahead of print] 126116

Dapagliflozin protects heart function against type-4 cardiorenal syndrome through activation of PKM2/PP1/FUNDC1-dependent mitophagy.

Yang Shen, Xiaojie Peng, Haizhe Ji, Wei Gong, Hang Zhu, Jin Wang.

  Dapagliflozin (DAPA) confers significant protection against heart and kidney diseases. However, whether DAPA can alleviate type 4 cardiorenal syndrome (CRS-4)-related cardiomyopathy remains unclear. We tested the hypothesis that DAPA attenuates CRS-4-related myocardial damage through pyruvate kinase isozyme M2 (PKM2) induction and FUN14 domain containing 1 (FUNDC1)-related mitophagy. Cardiomyocyte-specific PKM2 knockout (PKM2CKO) and FUNDC1 knockout (FUNDC1CKO) mice were subjected to subtotal (5/6) nephrectomy to establish a CRS-4 model in vivo. DAPA enhanced PKM2 expression and improved myocardial function and structure in vivo, and this effect was abrogated by PKM2 knockdown. A significant improvement in mitochondrial function was observed in HL-1 cells exposed to sera from DAPA-treated mice, as featured by increased ATP production, decreased mtROS production, improved mitochondrial membrane potential, preserved mitochondrial complex activity, and reduced mitochondrial apoptosis. DAPA restored FUNDC1-dependent mitophagy through post-transcriptional dephosphorylation in a manner dependent on PKM2 whereas ablation of FUNDC1 abolished the defensive actions of DAPA on myocardium and mitochondria under CRS-4. Co-IP and molecular docking assays indicated that PKM2 directly interacted with protein phosphatase 1 (PP1) and FUNDC1, leading to PP1-mediated FUNDC1 dephosphorylation. These results suggest that DAPA attenuates CRS-4-related cardiomyopathy through activating the PKM2/PP1/FUNDC1-mitophagy pathway.

Keywords:  CRS-4; Dapagliflozin; FUNDC1; Mitochondria; PKM2; PP1

DOI:  https://doi.org/10.1016/j.ijbiomac.2023.126116
Can J Physiol Pharmacol. 2023 Jul 31.

Effects of a high-fat low-carbohydrate diet under different energy conditions on glucose homeostasis and fatty liver development in rats and on gluconeogenesis in the isolated perfused liver.

Mateus José de Oliveira, Evelyn Silva Moreira, Naiara Cristina Lucredi, Carla Indianara Bonetti, Anacharis Babeto de Sá-Nakanishi, Jurandir Fernando Comar, Adelar Bracht, Lívia Bracht.

The beneficial effects of high-fat, low-carbohydrate diets (HFLC) on glucose metabolism have been questioned and its effects on liver metabolism are not totally clear. The aim of this work was to investigate the effects of a HFLC diet under different energy conditions on glucose homeostasis, fatty liver development and hepatic gluconeogenesis using the isolated perfused rat liver. HFLC diet (79% fat, 19% protein, and 2% carbohydrates in Kcal%) was administered to rats for four weeks under three conditions: ad libitum (hypercaloric); isocaloric and hypocaloric (energy reduction of 20%). Fasting blood glucose levels and total fat in the liver were higher in all HFLC diet rats. Oral glucose tolerance was impaired in isocaloric and hypercaloric groups, although insulin sensitivity wasn´t altered. HFLC diet also caused marked liver metabolic alterations: higher gluconeogenesis rate from lactate and a reduced capacity to metabolize alanine, the latter effect being more intense in the hypocaloric condition. Thus, even when HFLC diets are used for weight loss, our data imply that they can potentially cause harmful consequences for the liver.

DOI: https://doi.org/10.1139/cjpp-2023-0071