Obesity causes mitochondrial fragmentation and dysfunction in white adipocytes due to RalA activation

Insulin resistance in type 2 diabetes mellitus

Insulin resistance is an integral pathophysiological feature of type 2 diabetes mellitus. Here, we review established and emerging cellular mechanisms of insulin resistance, their complex integrative features and their relevance to disease progression. While recognizing the heterogeneity of the elusive fundamental disruptions that cause insulin resistance, we endorse the view that effector mechanisms impinge on insulin receptor signalling and its relationship with plasma levels of insulin. We focus on hyperinsulinaemia and its consequences: acutely impaired but persistent insulin action, with reduced ability to lower glucose levels but preserved lipid synthesis and lipoprotein secretion. We emphasize the role of insulin sensitization as a therapeutic goal in type 2 diabetes mellitus.

Obesity accelerates cardiovascular ageing

A global obesity pandemic, coupled with an increasingly ageing population, is exacerbating the burden of cardiovascular disease. Indeed, clinical and experimental evidence underscores a potential connection between obesity and ageing in the pathogenesis of various cardiovascular disorders. This is further supported by the notion that weight reduction not only effectively reduces major cardiovascular events in elderly individuals but is also considered the gold standard for lifespan extension, in obese and non-obese model organisms. This review evaluates the intricate interplay between obesity and ageing from molecular mechanisms to whole organ function within the cardiovascular system. By comparatively analysing their characteristic features, shared molecular and cell biological signatures between obesity and ageing are unveiled, with the intent to shed light on how obesity accelerates cardiovascular ageing. This review also elaborates on how emerging metabolic interventions targeting obesity might protect from cardiovascular diseases largely through antagonizing key molecular mechanisms of the ageing process itself. In sum, this review aims to provide valuable insight into how understanding these interconnected processes could guide the development of novel and effective cardiovascular therapeutics for a growing aged population with a concerning obesity problem.

Large adipocytes in a biomimetic adipose tissue model promote breast cancer malignancy

Obesity worsens breast cancer survival but how increased adipocyte size, which typifies obese adipose tissue and correlates with poor prognosis, impacts cancer progression remains unclear. Understanding these connections is challenging as adipocyte size is highly heterogeneous and not tunable with traditional experimental approaches. Here, we develop a biomimetic, engineered adipose tissue model to culture size-sorted adipocytes isolated from the same donor and assess their impact on tumor cell behavior. We find that large adipocytes are transcriptionally distinct from small adipocytes and upregulate genes related to adipose tissue dysfunction, including altered lipid processing. In coculture, large adipocytes promote lipid accumulation in cancer cells, increasing their migration and proliferation via enhanced fatty acid oxidation. These changes align with greater extracellular vesicle release by large adipocytes, which transfer lipid to recipient tumor cells. Our findings posit adipocyte size as an independent prognostic biomarker for breast cancer patients and demonstrate the value of biomimetic tissue models for mechanistic studies.

Implications of obesity-mediated cellular dysfunction and adipocytokine signaling pathways in the pathogenesis of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage degradation, bone sclerosis, and chronic low-grade inflammation. Aging and injury play key roles in OA pathogenesis by triggering the release of proinflammatory factors from adipose tissue and other sources. Obesity and aging impair the function of endoplasmic reticulum (ER) chaperones, leading to ER stress, protein misfolding, and cellular apoptosis. Obesity also induces mitochondrial dysfunction in OA through oxidative stress and disrupts mitochondrial dynamics, exacerbating chondrocyte damage. These factors contribute to inflammation, matrix imbalance, and chondrocyte apoptosis. Adipocytes, the primary source of adipokines, release inflammatory mediators that affect joint cells. Several adipocytokines have a central role in the regulation of many aspects of inflammation. Adiponectin and leptin are the two most abundant adipocytokines that are strongly associated with OA progression. This literature review suggests that adipokines activate many signaling pathways to exert downstream effects and play significant roles in obesity-induced OA. Understanding this rapidly growing family of mainly adipocyte-derived mediators and obesity-mediated cellular dysfunction may be important in the development of new therapies for obesity-associated OA management.

Ginsenoside Rg1 attenuates T2DM-induced renal damage and fibrosis by inhibiting TRPC6-ChREBP-TXNIP signaling

ETHNOPHARMACOLOGICAL RELEVANCE

As a traditional Chinese medicine, ginseng has many benefits, including regulating blood sugar, blood pressure and so on. Ginsenoside Rg1 is the main active component of ginseng and has been found to significantly improve renal pathological injury in type 2 diabetes mellitus (T2DM) mice. However, the effects and mechanisms of Rg1 in attenuating T2DM are not fully understood.

AIM OF THE STUDY

This study aims to investigate the role of Rg1 in the treatment of renal damage and fibrosis induced by T2DM and its molecular mechanism.

MATERIALS AND METHODS

T2DM models were constructed on mice and cells respectively and were administered with corresponding drugs. SA-β-Gal and Oil Red O were used to observe cell senescence and lipid droplet deposition; H&E and PAS were used to observe pathological changes in the kidney; masson and sirius red were used to evaluate the level of renal fibrosis. Immunohistochemistry, immunofluorescence and Western blotting were performed to analyze the relevant indexes which resulted in the detection of ROS levels in vitro and in vivo. Calcium imaging was used to test the level of [Ca2+]i.

RESULTS

Rg1 and Trpc6 knockout could significantly improve kidney dysfunction, attenuate renal injury and fibrosis and also decrease the expression levels of TRPC6, CaN, TXNIP, ChREBP, p-ASK1 and NLRP3 inflammasome. Meanwhile, Rg1 and Trpc6 knockout significantly inhibited mitochondrial damage and apoptosis protein release. Additionally, Rg1 treatment has been shown to markedly reduce lipid deposition and ROS accumulation in T2DM, while Trpc6 knockout exhibited no effect on these parameters.

CONCLUSION

Rg1 treatment can inhibit the TRPC6-ChREBP-TXNIP pathway, thereby improving chronic T2DM-induced renal injury and fibrosis.

Mitochondrial GCN5L1 coordinates with YME1L and MICOS to remodel mitochondrial cristae in white adipocytes and modulate obesity

The relationship between mitochondrial architecture and energy homeostasis in adipose tissues is not well understood. In this study, we utilized GCN5L1-knockout mice in white (AKO) and brown (BKO) adipose tissues to examine mitochondrial homeostasis in adipose tissues. GCN5L1, a regulator of mitochondrial metabolism and dynamics, influences resistance to high-fat-diet-induced obesity in AKO but not BKO mice. This resistance is mediated by an increase in mitochondrial cristae that stabilizes oxidative phosphorylation (OXPHOS) complexes and enhances energy expenditure. Our protein-interactome analysis reveals that GCN5L1 is associated with the mitochondrial crista complex MICOS (MIC13) and the protease YME1L, facilitating the degradation of MICOS and disassembly of cristae during obesity. This interaction results in decreased OXPHOS levels and subsequent adipocyte expansion. Accumulation of GCN5L1 in the mitochondrial intermembrane space is triggered by a high-fat diet. Our findings highlight a regulatory pathway involving YME1L/GCN5L1/MIC13 that remodels mitochondrial cristae in WAT in response to overnutrition-induced obesity.

Uncoupling protein 1-mediated protective effects of β3-adrenergic receptor agonist on kidney fibrosis via promoting adipose tissue browning in diabetic mice

BACKGROUND

Diabetes mellitus (DM) is a global health concern. Diabetic kidney disease (DKD) is a prevalent severe complication of DM and therapy is urgently needed. Adipose tissue (AT) plays a crucial role in the energy mediation through glucolipid metabolism. Mirabegron is a specific β3-adrenergic receptor agonist, which can activate thermogenesis in adipocytes, improve energy consumption, and increase insulin sensitivity and glucose tolerance. Therefore, mirabegron may play a role in DKD pathogenesis. However, its effects and precise mechanisms remain unclear.

METHODS

A DKD mouse model based on type 2 DM (T2DM) was constructed and treated with mirabegron. Mice with AT surgically removed and mice with uncoupling protein 1 (Ucp1) knockout were used to confirm whether thermogenesis induced by mirabegron was the key process.

RESULTS

Mirabegron promoted AT browning in DKD mice. Mirabegron increased insulin sensitivity, promoted glucolipid metabolism, reduced inflammatory factor levels in kidney tissue, and improved renal function and fibrosis in DKD mice. Notably, all of these benefits disappeared in AT-removed DKD mice or in Ucp1 knockout DKD mice.

CONCLUSIONS

Mirabegron protects against kidney fibrosis in DM mice by activating AT thermogenesis via the UCP1 pathway. Thus, mirabegron may provide a promising potential option for DKD therapy.

Diet-induced obesity dampens the temporal oscillation of hepatic mitochondrial lipids

Mitochondria play a pivotal role in energy homeostasis and regulate several metabolic pathways. The inner and outer membrane of mitochondria comprises unique lipid composition and proteins that are essential to form electron transport chain complexes, orchestrate oxidative phosphorylation, β-oxidation, ATP synthesis, etc. As known, diet-induced obesity affects mitochondrial function, dynamics, and mitophagy, which are governed by circadian clock machinery. Though DIO impairs the interplay between circadian oscillation and lipid metabolism, the impact of DIO on mitochondrial membrane lipid composition and their temporal oscillation is unknown. Thus, we investigated the diurnal oscillation of liver mitochondrial lipidome at various Zeitgeber times using quantitative lipidomics. Our data suggested that obesity disrupted lipid accumulation profiles and diminished the oscillating lipid species in the hepatic mitochondria. Strikingly, HFD manifested a more homogenous temporal oscillation pattern in phospholipids regardless of possessing different fatty acyl-chain lengths and degrees of unsaturation. In particular, DIO impaired the circadian rhythmicity of phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl serine, and ether-linked phosphatidyl ethanolamine. Also, DIO altered the rhythmic profile of PE/PC, ePE/PC, PS/PC ratio, and key proteins related to mitochondrial function, dynamics, and quality control. Since HFD dampened lipid oscillation, we examined whether the diurnal oscillation of mitochondrial lipids synchronized with mitochondrial function. Also, our data emphasized that acrophase of mitochondrial lipids synchronized with increased oxygen consumption rate and Parkin levels at ZT16 in chow-fed mice. Our study revealed that obesity altered the mitochondrial lipid composition and hampered the rhythmicity of mitochondrial lipids, oxygen consumption rate, and Parkin levels in the liver.

Obesity- and High-Fat-Diet-Induced Neuroinflammation: Implications for Autonomic Nervous System Dysfunction and Endothelial Disorders

Obesity is a multifactorial condition linked to severe health complications, including cardiovascular diseases and endothelial dysfunction. Both obesity and high-fat diets (HFDs) are strongly associated with neuroinflammation, particularly in the hypothalamus. The autonomic nervous system (ANS), which controls involuntary physiological processes, is critical for maintaining cardiovascular health, and its dysfunction is implicated in endothelial disorders. With its homeostatic control centers located in the hypothalamus and brainstem, a crucial question arises: could obesity- and HFD-induced neuroinflammation disrupt central ANS structures, leading to ANS dysfunction and subsequent endothelial disorders? This review examined whether neuroinflammation caused by obesity and HFD contributes to endothelial dysfunction through the dysregulation of the ANS. Our analysis revealed that hypothalamic inflammation linked to obesity and an HFD is associated with sympathetic hyperactivity and endothelial disorders. Identified molecular mechanisms include the influence of inflammatory cytokines, activation of the NF-κB/IKK-β pathway, microglial activation mediated by angiotensin II, circulating mitochondria triggering cGAS activation, and the stimulation of the TLR4 pathway. Our findings suggest that hypothalamic inflammation may play a central role in the interplay between obesity/an HFD, ANS dysfunction, and endothelial disorders.

Gut microbiota-mitochondrial crosstalk in obesity: novel mechanistic insights and therapeutic strategies with traditional Chinese medicine

Obesity rates are rising globally and have become a major public health issue. Recent research emphasizes the bidirectional communication between gut microbiota and mitochondrial function in obesity development. Gut microbiota regulates energy metabolism through metabolites that impact mitochondrial processes, such as oxidative phosphorylation, biogenesis, and autophagy. In turn, alterations in mitochondrial function impact microbiota homeostasis. Traditional Chinese medicine (TCM), which encompasses TCM formulas and the metabolites of botanical drugs, employs a holistic and integrative approach that shows promise in regulating gut microbiota-mitochondrial crosstalk. This review systematically explores the intricate interactions between gut microbiota and mitochondrial function, underscoring their crosstalk as a critical mechanistic axis in obesity pathogenesis. Furthermore, it highlights the potential of TCM in developing innovative, targeted interventions, paving the way for personalized approaches in obesity treatment through the precise modulation of gut microbiota-mitochondrial interactions, offering more effective and individualized therapeutic options.

Sympathetic activation of white adipose tissue recruits neutrophils to limit energy expenditure

Adipose tissue maintains energy homeostasis by storing lipids during nutrient surplus and releasing them through lipolysis in times of energy demand. While lipolysis is essential for short term metabolic adaptation, prolonged metabolic stress requires adaptive changes that preserve energy reserves. Here, we report that β-adrenergic activation of adipocytes induces a transient and depot-specific infiltration of neutrophils into white adipose tissue (WAT), particularly in lipid-rich visceral WAT. Neutrophil recruitment requires the stimulation of both lipolysis and p38 MAPK activation in adipocytes. Recruited neutrophils locally secrete IL-1β, which suppresses lipolysis and limits excessive energy expenditure. Neutrophil depletion or blockade of IL-1β production increased lipolysis, leading to reduced WAT mass upon repeated β3-adrenergic stimulation. Together, these findings reveal an unexpected role of neutrophil-derived IL-1β in preserving lipid stores during metabolic stress, highlighting a physiological function of innate immune cells in maintaining energy homeostasis.

Exercise-induced anti-obesity effects in male mice generated by a FOXO1-KLF10 reinforcing loop promoting adipose lipolysis

Exercise combats obesity and metabolic disorders, but the underlying mechanism is incompletely understood. KLF10, a transcription factor involved in various biological processes, has an undefined role in adipose tissue and obesity. Here, we show that exercise facilitates adipocyte-derived KLF10 expression via SIRT1/FOXO1 pathway. Adipocyte-specific knockout of KLF10 blunts exercise-promoted white adipose browning, energy expenditure, fat loss, glucose tolerance in diet-induced obese male mice. Conversely, adipocyte-specific transgenic expression of KLF10 in male mice enhanced the above metabolic profits induced by exercise. Mechanistically, KLF10 interacts with FOXO1 and facilitates the recruitment of KDM4A to form a ternary complex on the promoter regions of Pnpla2 and Lipe genes to promote these key lipolytic genes expression by demethylating H3K9me3 on their promoters, which facilitates lipolysis to defend against obesity in male mice. As a downstream effector responding to exercise, adipose KLF10 could act as a potential target in the fight against obesity.

Subcutaneous adipose tissue and skeletal muscle mitochondria following weight loss

Obesity is a major global health issue with various metabolic complications. Both bariatric surgery and dieting achieve weight loss and improve whole-body metabolism, but vary in their ability to maintain these improvements over time. Adipose tissue and skeletal muscle metabolism are crucial in weight regulation, and obesity is linked to mitochondrial dysfunction in both tissues. The impact of bariatric surgery versus dieting on adipose tissue and skeletal muscle mitochondrial metabolism remains to be elucidated. Understanding the molecular pathways that modulate tissue metabolism following weight loss holds potential for identifying novel therapeutic targets in obesity management. This narrative review summarizes current knowledge on mitochondrial metabolism following bariatric surgery and diet-induced weight loss in adipose tissue and skeletal muscle, and sheds light on their respective effects.

Hydroxytyrosol as a Mitochondrial Homeostasis Regulator: Implications in Metabolic Syndrome and Related Diseases

Hydroxytyrosol (HT), a principal bioactive phytochemical abundant in Mediterranean dietary sources, has emerged as a molecule of significant scientific interest owing to its multifaceted health-promoting properties. Accumulating evidence suggests that HT's therapeutic potential in metabolic disorders extends beyond conventional antioxidant capacity to encompass mitochondrial regulatory networks. This review synthesizes contemporary evidence from our systematic investigations and the existing literature to delineate HT's comprehensive modulatory effects on mitochondrial homeostasis. We systematically summarized the impact of HT on mitochondrial dynamics (fusion/fission equilibrium), biogenesis and energy metabolism, mitophagy, inter-organellar communication with the endoplasmic reticulum, and microbiota-mitochondria crosstalk. Through this multidimensional analysis, we established HT as a mitochondrial homeostasis modulator with potential therapeutic applications in metabolic syndrome (MetS) and its related pathologies including type 2 diabetes mellitus, obesity-related metabolic dysfunction, dyslipidemia, non-alcoholic steatohepatitis, and hypertension-related complications. Moreover, we further discussed translational challenges in HT research, emphasizing the imperative for direct target identification, mitochondrial-targeted delivery system development, and combinatorial therapeutic strategies. Collectively, this review provides a mechanistic framework for advancing HT research and accelerating its clinical implementation in MetS and its related diseases.

Unraveling the Mystery of Insulin Resistance: From Principle Mechanistic Insights and Consequences to Therapeutic Interventions

Insulin resistance (IR) is a significant factor in the development and progression of metabolic-related diseases like dyslipidemia, T2DM, hypertension, nonalcoholic fatty liver disease, cardiovascular and cerebrovascular disorders, and cancer. The pathogenesis of IR depends on multiple factors, including age, genetic predisposition, obesity, oxidative stress, among others. Abnormalities in the insulin-signaling cascade lead to IR in the host, including insulin receptor abnormalities, internal environment disturbances, and metabolic alterations in the muscle, liver, and cellular organelles. The complex and multifaceted characteristics of insulin signaling and insulin resistance envisage their thorough and comprehensive understanding at the cellular and molecular level. Therapeutic strategies for IR include exercise, dietary interventions, and pharmacotherapy. However, there are still gaps to be addressed, and more precise biomarkers for associated chronic diseases and lifestyle interventions are needed. Understanding these pathways is essential for developing effective treatments for IR, reducing healthcare costs, and improving quality of patient life.

Mitochondrial regulation of obesity by POMC neurons

Pro-opiomelanocortin (POMC) neurons, nestled in the hypothalamus, play a pivotal role in the intricate coordination of energy homeostasis and metabolic pathways. These neurons' mitochondria, often hailed as the cell's powerhouses, are crucial for maintaining cellular energy equilibrium and metabolic functionality. Recent research has illuminated the complex interplay between mitochondrial dynamics and POMC neuronal activity, underscoring their critical involvement in the pathogenesis of a spectrum of metabolic disorders, notably obesity and diabetes. This comprehensive review delves into the molecular mechanisms that underlie how mitochondrial function within POMC neurons modulates metabolic regulation. We dissect the impact of mitochondrial dynamics, encompassing fusion, fission, mitophagy, and biogenesis, on the regulation of POMC neuronal activity. Furthermore, we scrutinize the role of mitochondrial dysfunction in POMC neurons in the etiology of obesity, identifying key therapeutic targets within these pathways. We offer an in-depth perspective on the indispensable role of POMC neuronal mitochondria in metabolic regulation and chart future research directions to bridge the existing knowledge gaps in this field.

A Novel Polysaccharide From Tremella fuciformis Alleviated High-Fat Diet-Induced Obesity by Promoting AMPK/PINK1/PRKN-Mediated Mitophagy in Mice

SCOPE

Polysaccharides from Tremella fuciformis have gained significant interest due to their diverse biological activities. This study focuses on characterizing a purified polysaccharide, TPSP2, extracted from T. fuciformis and evaluating its antiobesity effect and underlying mechanisms in vivo.

METHODS AND RESULTS

Structural analysis revealed that TPSP2, with a molecular weight of 1.51 × 103 kDa, is composed of mannose, rhamnose, glucuronic acid, galactose, xylose, arabinose, and fucose in specific molar ratios. The primary linkages identified include t-Fuc(p), 1,2-Xyl(p), t-GlcA(p), 1,3-Man(p), and 1,2,3-Man(p), with their corresponding ratios being 12.987%, 11.404%, 16.050%, 16.527%, and 26.624%, respectively. In vivo experiments demonstrated that TPSP2 significantly alleviated high-fat diet-induced weight gain, hyperlipidemia, hepatic steatosis, hyperglycemia, and insulin resistance in mice. Mechanistically, TPSP2 was found to enhance AMPK/PINK1-PRKN-dependent mitophagy by upregulating the p-AMPK/AMPK ratio, LC3-II/I ratio, and expression of PINK1, PRKN, prohibitin 2 (PHB2), and LAMP2, while downregulating p62 and TOM20 expression.

CONCLUSION

This study suggested that TPSP2 could be a promising candidate for addressing obesity-related metabolic disorders by targeting mitochondrial quality control mechanisms.

A novel PDE4 inhibitor ZX21011 alleviates neuronal apoptosis by decreasing GSK3β-mediated Drp1 Ser616 phosphorylation in cerebral ischemia reperfusion

Dynamin-related protein 1 (Drp1) regulates mitochondrial fission and participates in neuronal apoptosis during the pathology of cerebral ischemia. We have previously shown that inhibition of phosphodiesterase-4 (PDE4) protects against neuronal apoptosis in models of ischemic stroke. However, it remains unclear whether PDE4 inhibition affects Drp1-mediated mitochondrial dysfunction and apoptosis under cerebral ischemia conditions. This study aimed to determine whether ZX21011, a novel PDE4 inhibitor synthesized in our laboratory, can act on Drp1 to counteract ischemic brain injury and to elucidate its mechanism of action. We demonstrated that ZX21011 effectively reduced neuronal apoptosis caused by oxygen-glucose deprivation/reoxygenation (OGD/R) in HT22 cells and ameliorated neurological deficits caused by middle cerebral artery occlusion/reperfusion (MCAO/R) in rats. ZX21011 enhanced glycogen synthase kinase-3β (GSK3β) phosphorylation (Ser9), GSK3β(S9A) mutation blocked the protective effects of ZX21011. Simultaneously, ZX21011 reduced the levels of reactive oxygen species (ROS), restored the morphology of mitochondria, and inhibited the phosphorylation of Drp1(Ser616). The Drp1(S616E) mutation blocked the protective effects of ZX21011 on ROS production and mitochondrial morphology function after cerebral ischemia. What's more, co-immunoprecipitation analysis revealed that ZX21011 decreased the binding of GSK3β to Drp1, and GSK3β(S9A) mutation reversed the effects of ZX21011 on Drp1 phosphorylation and cell viability. Moreover, ZX21011 decreased Drp1(Ser616) phosphorylation within the ischemic penumbra of rats following cerebral ischemia/reperfusion. In summary, ZX21011 counteracts ischemic stroke-induced oxidative stress and neuronal death, and its action is related to decreased Drp1 phosphorylation at Ser616. Thus, ZX21011 is a potential compound for the intervention of stroke.

Protective role of sulforaphane in lipid metabolism-related diseases

Sulforaphane (SFN) is a phytochemical bioactive substance commonly found in cruciferous plants, such as broccoli and mustard. It has been reported to possess antibacterial, anti-inflammatory, anti-oxidant, anti-cancer and autophagy regulating properties. Recent studies have revealed that SFN regulates fat metabolism both in vivo and in vitro through various mechanisms, including alleviating endoplasmic reticulum stress, inhibiting inflammatory response and improving mitochondrial dysfunction, involving Nrf2/ARE, NF-κB, NLRP3 inflammasome, HDAC8-PGC1α axis and other signaling pathways. By curbing complications associated with abnormal fat metabolic diseases, SFN exhibits therapeutic effects on conditions like obesity, fatty liver disease, atherosclerosis, type 2 diabetes, etc., with minimal side effects. Therefore, it holds promise as a potential alternative treatment for lipid metabolism-related diseases. Although its extraction method has been matured, the thermal instability and preservation difficulties of SFN limit its clinical promotion. More effective and low-cost methods to improve the stability and production of SFN remain to be further studied. This paper reviews the physiological and biological activities of SFN, and summarizes the protective effects and molecular mechanisms of SFN in diseases related to abnormal lipid metabolism. Additionally, it proposes potential challenges, possible solutions and future research directions in the clinical application of SFN.

Therapeutic targeting of obesity-induced neuroinflammation and neurodegeneration

Obesity is a major modifiable risk factor leading to neuroinflammation and neurodegeneration. Excessive fat storage in obesity promotes the progressive infiltration of immune cells into adipose tissue, resulting in the release of pro-inflammatory factors such as cytokines and adipokines. These inflammatory mediators circulate through the bloodstream, propagating inflammation both in the periphery and in the central nervous system. Gut dysbiosis, which results in a leaky intestinal barrier, exacerbates inflammation and plays a significant role in linking obesity to the pathogenesis of neuroinflammation and neurodegeneration through the gut-brain/gut-brain-liver axis. Inflammatory states within the brain can lead to insulin resistance, mitochondrial dysfunction, autolysosomal dysfunction, and increased oxidative stress. These disruptions impair normal neuronal function and subsequently lead to cognitive decline and motor deficits, similar to the pathologies observed in major neurodegenerative diseases, including Alzheimer's disease, multiple sclerosis, and Parkinson's disease. Understanding the underlying disease mechanisms is crucial for developing therapeutic strategies to address defects in these inflammatory and metabolic pathways. In this review, we summarize and provide insights into different therapeutic strategies, including methods to alter gut dysbiosis, lifestyle changes, dietary supplementation, as well as pharmacological agents derived from natural sources, that target obesity-induced neuroinflammation and neurodegeneration.

Downregulated DKK2 may serve as a molecular mechanism of high-fat diet-induced myocardial injury via Wnt/β-catenin pathway

OBJECTIVE

High-fat diet could induce structural and functional disorders of the heart, but the underlying mechanism remains elusive. This study aimed to explore related mechanism of obesity cardiomyopathy.

METHODS

Obesity model was established by feeding rats with a high-fat diet, and H9c2 cells were stimulated with palmitic acid to mimic high-fat stimulation. Whole transcriptome analysis results showed that the expression of Dickkopf-2 (DKK2) in obesity cardiomyopathy group was significantly lower than that in control group and simple obesity group. Overexpression and knockdown of DKK2 was achieved by infection with lentivirus. Weight, blood glucose, lipids, blood pressure, and insulin, HE staining, Sirius red staining and echocardiography results were analyzed in rats at 8 and 16 weeks after various interventions. qRT-PCR and western blots were used to detect the expression of RNAs and proteins.

RESULTS

High-fat diet-induced obese rats presented with changes in serum lipid, insulin, and increases in myocardial inflammation and fibrosis. Protein and mRNA expression levels of DKK2 were significantly decreased in the obesity cardiomyopathy group compared with the obesity and control group. In vitro, knockdown of DKK2 activated β-catenin/Wnt3a pathway, while overexpress of DKK2 inhibited β-catenin/Wnt3a expression.

CONCLUSION

Activating DKK2 may serve as a novel therapeutic intervention option for obesity cardiomyopathy and obesity-related metabolic disorders, and future studies are needed to validate this hypothesis.

Outer mitochondrial membrane E3 Ub ligase MARCH5 controls de novo peroxisome biogenesis

We report that the outer mitochondrial membrane (OMM)-associated E3 Ub ligase MARCH5 is vital for generating mitochondria-derived pre-peroxisomes. In human immortalized cells, MARCH5 knockout leads to the accumulation of immature peroxisomes, reduced fatty-acid-induced peroxisomal biogenesis, and abnormal peroxisome biogenesis in MARCH5/Pex14 and MARCH5/Pex3 dko cells. Upon fatty-acid-induced peroxisomal biogenesis, MARCH5 redistributes to peroxisomes, and ubiquitination activity-deficient mutants of MARCH5 accumulate on peroxisomes containing high levels of the OMM protein Tom20 (mitochondria-derived pre-peroxisomes). Similarly, depletion of peroxisome biogenesis factor Pex14 leads to the accumulation of MARCH5- and Tom20-positive pre-peroxisomes, whereas no peroxisomes are detected in MARCH5/Pex14 dko cells. Inconsistent with MARCH5 merely acting as a quality factor, mitochondrial decline is not evident in tested models. Furthermore, reduced expression of peroxisomal proteins is detected in MARCH5-/- cells, whereas some of these proteins are stabilized in peroxisome biogenesis deficiency models lacking MARCH5 expression. Thus, MARCH5 is central for mitochondria-dependent peroxisome biogenesis.

Obesity modifies the association between abnormal glucose metabolism and atrial fibrillation in older adults: a community-based longitudinal and prospective cohort study

OBJECTIVE

To investigate the modifying role of obesity in the association between abnormal glucose metabolism and atrial fibrillation (AF) risk in older individuals.

METHODS

From April 2007 to November 2011, 11,663 participants aged ≥60 years were enrolled in the Shandong area. Glucose metabolic status was determined using fasting plasma glucose and hemoglobin A1c levels, and obesity was determined using body mass index (BMI), waist-to-hip ratio (WHR), and visceral fat area (VFA). Obesity-associated metabolic activities were assessed using the adiponectin-to-leptin ratio (ALR), galectin-3, and triglyceride-glucose index (TyG). New-onset AF was diagnosed by ICD-10.

RESULTS

During an average of 11.1 years of follow-up, 1343 participants developed AF. AF risks were higher in those with prediabetes, uncontrolled diabetes, and well-controlled diabetes than with normoglycemia. The hazard ratios were decreased by 14.79%, 40.29%, and 25.23% in those with prediabetes; 31.44%, 53.56%, and 41.90% in those with uncontrolled diabetes; and 21.16%, 42.38%, and 27.59% in those with well-controlled diabetes after adjusting for BMI, WHR, and VFA, respectively. The population-attributable risk percentages of general obesity, central obesity, and high VFA for new-onset AF were 10.43%, 34.78%, and 31.30%, respectively. ALR, galectin-3, and TyG significantly mediated the association of BMI, WHR, and VFA with AF risk (all Padj. < 0.001).

CONCLUSION

Obesity mediates the association between abnormal glucose metabolism and AF risk in older individuals. WHR is a more effective modifier than BMI and VFA for moderating the association. ALR, TyG, and galectin-3 mediate the moderating effect of obesity on the association between abnormal glucose metabolism and AF risk.

Mitochondria and the Repurposing of Diabetes Drugs for Off-Label Health Benefits

This review describes our current understanding of the role of the mitochondria in the repurposing of the anti-diabetes drugs metformin, gliclazide, GLP-1 receptor agonists, and SGLT2 inhibitors for additional clinical benefits regarding unhealthy aging, long COVID, mental neurogenerative disorders, and obesity. Metformin, the most prominent of these diabetes drugs, has been called the "Drug of Miracles and Wonders," as clinical trials have found it to be beneficial for human patients suffering from these maladies. To promote viral replication in all infected human cells, SARS-CoV-2 stimulates the infected liver cells to produce glucose and to export it into the blood stream, which can cause diabetes in long COVID patients, and metformin, which reduces the levels of glucose in the blood, was shown to cut the incidence rate of long COVID in half for all patients recovering from SARS-CoV-2. Metformin leads to the phosphorylation of the AMP-activated protein kinase AMPK, which accelerates the import of glucose into cells via the glucose transporter GLUT4 and switches the cells to the starvation mode, counteracting the virus. Diabetes drugs also stimulate the unfolded protein response and thus mitophagy, which is beneficial for healthy aging and mental health. Diabetes drugs were also found to mimic exercise and help to reduce body weight.

Resveratrol stimulates brown of white adipose via regulating ERK/DRP1-mediated mitochondrial fission and improves systemic glucose homeostasis

PURPOSE

Diabetes mellitus and metabolic homeostasis disorders may benefit from white adipose tissue (WAT) browning, which is associated with mitochondrial fission. Resveratrol, a dietary polyphenol, exhibits beneficial effects against abnormalities related to metabolic diseases. However, it remains unknown whether resveratrol contributes to WAT browning by regulating mitochondrial fission.

METHODS

We administered resveratrol (0.4% mixed with control) to db/db mice for 12 weeks, measuring body weight, oral glucose tolerance, insulin tolerance, and histological changes. The uncoupling protein 1 (UCP1) and dynamin-related protein 1 (DRP1) expressions in the epididymal WAT were assessed via immunoblotting.

RESULTS

We found that resveratrol improved systemic glucose homeostasis and insulin resistance in db/db mice, which was associated with increased UCP1 in epididymal WAT. Resveratrol-treated mice exhibited more fragmented mitochondria and increased phosphorylation of DRP1 in the epididymal WAT of the db/db mice. These results were further confirmed in vitro, where resveratrol induced extracellular signal-regulated kinase (ERK) signaling activation, leading to phosphorylation of DRP1 at the S616 site (p-DRP1S616) and mitochondrial fission, which was reversed by an ERK inhibitor in 3T3-L1 adipocytes.

CONCLUSION

Resveratrol plays a role in regulating the phosphorylation of ERK and DRP1, resulting in the promotion of beige cells with epididymal WAT and the improvement of glucose homeostasis. Our present study provides novel insights into the potential mechanism of resveratrol-mediated effects on WAT browning, suggesting that it is, at least in part, mediated through ERK/DRP1-mediated mitochondrial fission.

Subcutaneous adipose tissue: Implications in dermatological diseases and beyond

Subcutaneous adipose tissue (SAT) is the deepest component of the three-layered cutaneous integument. While mesenteric adipose tissue-based immune processes have gained recognition in the context of the metabolic syndrome, SAT has been traditionally considered primarily for energy storage, with less attention to its immune functions. SAT harbors a reservoir of immune and stromal cells that significantly impact metabolic and immunologic processes not only in the skin, but even on a systemic level. These processes include wound healing, cutaneous and systemic infections, immunometabolic, and autoimmune diseases, inflammatory skin diseases, as well as neoplastic conditions. A better understanding of SAT immune functions in different processes, could open avenues for novel therapeutic interventions. Targeting SAT may not only address SAT-specific diseases but also offer potential treatments for cutaneous or even systemic conditions. This review aims to provide a comprehensive overview on SAT's structure and functions, highlight recent advancements in understanding its role in both homeostatic and pathological conditions within and beyond the skin, and discuss the main questions for future research in the field.

Mitochondria in skeletal system-related diseases

Skeletal system-related diseases, such as osteoporosis, arthritis, osteosarcoma and sarcopenia, are becoming major public health concerns. These diseases are characterized by insidious progression, which seriously threatens patients' health and quality of life. Early diagnosis and prevention in high-risk populations can effectively prevent the deterioration of these patients. Mitochondria are essential organelles for maintaining the physiological activity of the skeletal system. Mitochondrial functions include contributing to the energy supply, modulating the Ca2+ concentration, maintaining redox balance and resisting the inflammatory response. They participate in the regulation of cellular behaviors and the responses of osteoblasts, osteoclasts, chondrocytes and myocytes to external stimuli. In this review, we describe the pathogenesis of skeletal system diseases, focusing on mitochondrial function. In addition to osteosarcoma, a characteristic of which is active mitochondrial metabolism, mitochondrial damage occurs during the development of other diseases. Impairment of mitochondria leads to an imbalance in osteogenesis and osteoclastogenesis in osteoporosis, cartilage degeneration and inflammatory infiltration in arthritis, and muscle atrophy and excitationcontraction coupling blockade in sarcopenia. Overactive mitochondrial metabolism promotes the proliferation and migration of osteosarcoma cells. The copy number of mitochondrial DNA and mitochondria-derived peptides can be potential biomarkers for the diagnosis of these disorders. High-risk factor detection combined with mitochondrial component detection contributes to the early detection of these diseases. Targeted mitochondrial intervention is an effective method for treating these patients. We analyzed skeletal system-related diseases from the perspective of mitochondria and provided new insights for their diagnosis, prevention and treatment by demonstrating the relationship between mitochondria and the skeletal system.

Transcriptional analysis of cancer cachexia: conserved and unique features across preclinical models and biological sex

Studies suggest heterogeneity in cancer cachexia (CC) among models and biological sexes, yet examinations comparing models and sexes are scarce. We compared the transcriptional landscape of skeletal muscle across murine CC models and biological sexes during early and late CC. Global gene expression analyses were performed on gastrocnemius [Lewis lung carcinoma (LLC)], quadriceps (KPC-pancreatic), and tibialis anterior [Colon-26 (C26)-colorectal and ApcMin/+] muscles across biological sexes. Differentially expressed genes (DEGs) were identified using an adj-P value of <0.05, followed by pathway and computational cistrome analyses. Integrating all controls, early and late stages of all models and sexes revealed up to 68% of DEGs and pathways were enriched at early and late CC, indicating a conserved transcriptional profile during CC development. Comparing DEGs and pathways within sexes and across models, in early CC, the transcriptional response was highly heterogeneous. At late stage, 11.5% of upregulated and 10% of downregulated genes were shared between models in males, whereas 18.9% of upregulated and 7% of downregulated DEGs were shared in females. Shared DEGs were enriched in proteasome and mitophagy/autophagy pathways (upregulated), and downregulation of energy metabolism pathways in males only. Between sexes, though the proportion of shared DEGs was low (<16%), similar pathway enrichment was observed, including proteasome and mitophagy at late-stage CC. In early CC, oncostatin M receptor (Osmr) upregulation was the only commonality across all models and sexes, whereas CLOCK and ARNTL/BMAL1 were predicted transcriptional factors associated with dysregulations in all three male models. This study highlights sex and model differences in CC progression and suggests conserved transcriptional changes as potential therapeutic targets.NEW & NOTEWORTHY This study is among the first to integrate and compare the skeletal muscle transcriptional landscape across multiple preclinical models and biological sexes. We highlight that 1) early CC transcriptional changes are two-thirds conserved at late stages, 2) DEGs are largely model and sex specific, and 3) transcriptional factors including CLOCK and ARNTL/BMAL1, which influence early CC gene expression, might represent a global therapeutic target with a chance of efficacy across various cancer types.

Exercise-regulated lipolysis: Its role and mechanism in health and diseases

Exercise has received considerable attention because of its importance not just in regulating physiological function, but also in ameliorating multiple pathological processes. Among these processes, lipolysis may play an important role in exercise-induced benefits. It is generally accepted that active lipolysis contributes to breakdown of fats, leading to the release of free fatty acids (FFAs) that serve as an energy source for muscles and other tissues during exercise. However, the significance of lipolysis in the context of exercise has not been fully understood. This review comprehensively outlines the potential regulatory mechanisms by which exercise stimulates lipolysis. The potential roles of exercise-mediated lipolysis in various physiological and pathological processes are also summarized. Additionally, we also discussed the potential non-classical effects of key lipolytic effectors induced by exercise. This will enhance our understanding of how exercise improves lipolytic function to bring about beneficial effects, offering new insights into potential therapeutic avenues for promoting health and alleviating diseases.

Calorie restriction modulates mitochondrial dynamics and autophagy in leukocytes of patients with obesity

BACKGROUND

Although it is established that caloric restriction offers metabolic and clinical benefits, the molecular mechanisms underlying these effects remain unclear. Thus, this study aimed to investigate whether caloric restriction can modulate mitochondrial function and remodeling and stimulate autophagic flux in the PBMCs of patients with obesity.

METHODS

This was an interventional study of 38 obese subjects (BMI >35 kg/m2) who underwent 6 months of dietary therapy, including a 6-week very-low-calorie diet (VLCD) followed by an 18-week low-calorie diet (LCD). We determined clinical variables, mitochondrial function parameters (by fluorescence imaging of mitochondrial ROS and membrane potential), and protein expression of markers of mitochondrial dynamics (MNF1, MFN2, OPA, DRP1 and FIS1) and autophagy (LC3, Beclin, BCL2 and NBR1) by Western blot.

RESULTS

Caloric restriction induced an improvement in metabolic outcomes that was accompanied by an increase in AMPK expression, a decrease of mitochondrial ROS and mitochondrial membrane potential, which was associated with increased markers of mitochondrial dynamics (MFN2, DRP1 and FIS1) and activation of autophagy as evidenced by augmented LC3 II/I, Beclin1 and NBR1, and a decrease in BCL2.

CONCLUSION

These findings shed light on the specific molecular mechanisms by which caloric restriction facilitates metabolic improvements, highlighting the relevance of pathways involving energy homeostasis and cell recovery, including mitochondrial function and dynamics and autophagy.

The role of macrophage and adipocyte mitochondrial dysfunction in the pathogenesis of obesity

Obesity has emerged as a prominent global public health concern, leading to the development of numerous metabolic disorders such as cardiovascular diseases, type-2 diabetes mellitus (T2DM), sleep apnea and several system diseases. It is widely recognized that obesity is characterized by a state of inflammation, with immune cells-particularly macrophages-playing a significant role in its pathogenesis through the production of inflammatory cytokines and activation of corresponding pathways. In addition to their immune functions, macrophages have also been implicated in lipogenesis. Additionally, the mitochondrial disorders existed in macrophages commonly, leading to decreased heat production. Meantime, adipocytes have mitochondrial dysfunction and damage which affect thermogenesis and insulin resistance. Therefore, enhancing our comprehension of the role of macrophages and mitochondrial dysfunction in both macrophages and adipose tissue will facilitate the identification of potential therapeutic targets for addressing this condition.

Mitochondrial Dysfunction and Risk Factors for Noncommunicable Diseases: From Basic Concepts to Future Prospective

BACKGROUND/OBJECTIVES

Noncommunicable diseases (NCDs) are a very important medical problem. The key role of mitochondrial dysfunction (MD) in the occurrence and progression of NCDs has been proven. However, the etiology and pathogenesis of MD itself in many NCDs has not yet been clarified, which makes it one of the most serious medical problems in the modern world, according to many scientists.

METHODS

An extensive research in the literature was implemented in order to elucidate the role of MD and NCDs' risk factors in the pathogenesis of NCDs.

RESULTS

The authors propose to take a broader look at the problem of the pathogenesis of NCDs. It is important to understand exactly how NCD risk factors lead to MD. The review is structured in such a way as to answer this question. Based on a systematic analysis of scientific data, a theoretical concept of modern views on the occurrence of MD under the influence of risk factors for the occurrence of NCDs is presented. This was done in order to update MD issues in clinical medicine. MD and NCDs progress throughout a patient's life. Based on this, the review raised the question of the existence of an NCDs continuum.

CONCLUSIONS

MD is a universal mechanism that causes organ dysfunction and comorbidity of NCDs. Prevention of MD involves diagnosing and eliminating the factors that cause it. Mitochondria are an important therapeutic target.

Differential mitochondrial adaptation and FNDC5 production in brown and white adipose tissue in response to cold and obesity

OBJECTIVE

Fibronectin type III domain-containing protein 5 (FNDC5) modulates adipocyte metabolism by increasing white and brown adipose tissue (WAT and BAT) browning and activity, respectively. We investigated whether FNDC5 can regulate visceral WAT and BAT adaptive thermogenesis by improving mitochondrial homeostasis in response to cold and obesity.

METHODS

Adipose tissue expression of FNDC5 and factors involved in mitochondrial homeostasis were determined in patients with normal weight and obesity (n = 159) and in rats with diet-induced obesity after 1 week of cold exposure (n = 61). The effect of different FNDC5 concentrations on mitochondrial biogenesis, dynamics, and mitophagy was evaluated in vitro in human adipocytes.

RESULTS

In human visceral adipocytes, FNDC5/irisin triggered mitochondrial biogenesis (TFAM) and fusion (MFN1, MFN2, and OPA1) while inhibiting peripheral fission (DNM1L and FIS1) and mitophagy (PINK1 and PRKN). Circulating and visceral WAT expression of FNDC5 was decreased in patients and experimental animals with obesity, whereas its receptor, integrin αV, was upregulated. Obesity increased mitochondrial fusion while decreasing mitophagy in visceral WAT from patients and rats. By contrast, in rat BAT, an upregulation of Fndc5 and genes involved in mitochondrial biogenesis and fission was observed. Cold exposure promoted mitochondrial biogenesis and healthy peripheral fission while repressing Fndc5 expression and mitophagy in BAT from rats.

CONCLUSIONS

Depot differences in FNDC5 production and mitochondrial adaptations in response to obesity and cold might indicate a self-regulatory mechanism to control thermogenesis in response to energy needs.

Aging mitochondria in the context of SARS-CoV-2: exploring interactions and implications

The coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has presented global challenges with a diverse clinical spectrum, including severe respiratory complications and systemic effects. This review explores the intricate relationship between mitochondrial dysfunction, aging, and obesity in COVID-19. Mitochondria are vital for cellular energy provision and resilience against age-related macromolecule damage accumulation. They manage energy allocation in cells, activating adaptive responses and stress signals such as redox imbalance and innate immunity activation. As organisms age, mitochondrial function diminishes. Aging and obesity, linked to mitochondrial dysfunction, compromise the antiviral response, affecting the release of interferons, and worsening COVID-19 severity. Furthermore, the development of post-acute sequelae of SARS-CoV-2 infection (PASC), also known as long COVID has been associated with altered energy metabolism, and chronic immune dysregulation derived from mitochondrial dysfunction. Understanding the interplay between mitochondria, aging, obesity, and viral infections provides insights into COVID-19 pathogenesis. Targeting mitochondrial health may offer potential therapeutic strategies to mitigate severe outcomes and address long-term consequences in infected individuals.

New Insights into Mitochondria in Health and Diseases

Mitochondria are a unique type of semi-autonomous organelle within the cell that carry out essential functions crucial for the cell's survival and well-being. They are the location where eukaryotic cells carry out energy metabolism. Aside from producing the majority of ATP through oxidative phosphorylation, which provides essential energy for cellular functions, mitochondria also participate in other metabolic processes within the cell, such as the electron transport chain, citric acid cycle, and β-oxidation of fatty acids. Furthermore, mitochondria regulate the production and elimination of ROS, the synthesis of nucleotides and amino acids, the balance of calcium ions, and the process of cell death. Therefore, it is widely accepted that mitochondrial dysfunction is a factor that causes or contributes to the development and advancement of various diseases. These include common systemic diseases, such as aging, diabetes, Parkinson's disease, and cancer, as well as rare metabolic disorders, like Kearns-Sayre syndrome, Leigh disease, and mitochondrial myopathy. This overview outlines the various mechanisms by which mitochondria are involved in numerous illnesses and cellular physiological activities. Additionally, it provides new discoveries regarding the involvement of mitochondria in both disorders and the maintenance of good health.

A new perspective on liver diseases: Focusing on the mitochondria-associated endoplasmic reticulum membranes

The pathogenesis of liver diseases is multifaceted and intricate, posing a persistent global public health challenge with limited therapeutic options. Therefore, further research into liver diseases is imperative for better comprehension and advancement in treatment strategies. Numerous studies have confirmed the endoplasmic reticulum (ER) and mitochondria as key organelles driving liver diseases. Notably, the mitochondrial-associated ER membranes (MAMs) establish a physical and functional connection between the ER and mitochondria, highlighting the importance of inter-organelle communication in maintaining their functional homeostasis. This review delves into the intricate architecture and regulative mechanism of the integrated MAM that facilitate the physiological transfer of signals and substances between organelles. Additionally, we also provide a detailed overview regarding the varied pathogenic roles of malfunctioning MAM in liver diseases, focusing on its involvement in the progression of ER stress and mitochondrial dysfunction, the regulation of mitochondrial dynamics and Ca2+ transfer, as well as the disruption of lipid and glucose homeostasis. Furthermore, the current challenges and prospects associated with MAM in liver disease research are thoroughly discussed. In conclusion, elucidating the specific structure and function of MAM in different liver diseases may pave the way for novel therapeutic strategies.

Mechanistic insights into metabolic function of dynamin-related protein 1

Dynamin-related protein 1 (DRP1) plays crucial roles in mitochondrial and peroxisome fission. However, the mechanisms underlying the functional regulation of DRP1 in adipose tissue during obesity remain unclear. To elucidate the metabolic and pathological significance of diminished DRP1 in obese adipose tissue, we utilized adipose tissue-specific DRP1 KO mice challenged with a high-fat diet. We observed significant metabolic dysregulations in the KO mice. Mechanistically, DRP1 exerts multifaceted functions in mitochondrial dynamics and endoplasmic reticulum (ER)-lipid droplet crosstalk in normal mice. Loss of function of DRP1 resulted in abnormally giant mitochondrial shapes, distorted mitochondrial membrane structure, and disrupted cristae architecture. Meanwhile, DRP1 deficiency induced the retention of nascent lipid droplets in ER, leading to perturbed overall lipid dynamics in the KO mice. Collectively, dysregulation of the dynamics of mitochondria, ER, and lipid droplets contributes to whole-body metabolic disorders, as evidenced by perturbations in energy metabolites. Our findings demonstrate that DRP1 plays diverse and critical roles in regulating energy metabolism within adipose tissue during the progression of obesity.

Targeting Mitochondria: Influence of Metabolites on Mitochondrial Heterogeneity

Mitochondria are vital organelles that provide energy for the metabolic processes of cells. These include regulating cellular metabolism, autophagy, apoptosis, calcium ions, and signaling processes. Despite their varying functions, mitochondria are considered semi-independent organelles that possess their own genome, known as mtDNA, which encodes 13 proteins crucial for oxidative phosphorylation. However, their diversity reflects an organism's adaptation to physiological conditions and plays a complex function in cellular metabolism. Mitochondrial heterogeneity exists at the single-cell and tissue levels, impacting cell shape, size, membrane potential, and function. This heterogeneity can contribute to the progression of diseases such as neurodegenerative diseases, metabolic diseases, and cancer. Mitochondrial dynamics enhance the stability of cells and sufficient energy requirement, but these activities are not universal and can lead to uneven mitochondria, resulting in heterogeneity. Factors such as genetics, environmental compounds, and signaling pathways are found to affect these cellular processes and heterogeneity. Additionally, the varying roles of metabolites such as NADH and ATP affect glycolysis's speed and efficiency. An imbalance in metabolites can impair ATP production and redox potential in the mitochondria. Therefore, this review will explore the influence of metabolites in shaping mitochondrial morphology, how these changes contribute to age-related diseases and the therapeutic targets for regulating mitochondrial heterogeneity.

Ferulic acid restores mitochondrial dynamics and autophagy via AMPK signaling pathway in a palmitate-induced hepatocyte model of metabolic syndrome

Mitochondrial dysfunction, characterized by elevated oxidative stress, impaired energy balance, and dysregulated mitochondrial dynamics, is a hallmark of metabolic syndrome (MetS) and its comorbidities. Ferulic acid (FA), a principal phenolic compound found in whole grains, has demonstrated potential in ameliorating oxidative stress and preserving energy homeostasis. However, the influence of FA on mitochondrial health within the context of MetS remains unexplored. Moreover, the impact of FA on autophagy, which is essential for maintaining energy homeostasis and mitochondrial integrity, is not fully understood. Here, we aimed to study the mechanisms of action of FA in regulating mitochondrial health and autophagy using palmitate-treated HepG2 hepatocytes as a MetS cell model. We found that FA improved mitochondrial health by restoring redox balance and optimizing mitochondrial dynamics, including biogenesis and the fusion/fission ratio. Additionally, FA was shown to recover autophagy and activate AMPK-related cell signaling. Our results provide new insights into the therapeutic potential of FA as a mitochondria-targeting agent for the prevention and treatment of MetS.

Extracellular flux assay (Seahorse assay): Diverse applications in metabolic research across biological disciplines

Metabolic networks are fundamental to cellular processes, driving energy production, biosynthesis, redox regulation, and cellular signaling. Recent advancements in metabolic research tools have provided unprecedented insights into cellular metabolism. Among these tools, the extracellular flux analyzer stands out for its real-time measurement of key metabolic parameters: glycolysis, mitochondrial respiration, and fatty acid oxidation, leading to its widespread use. This review provides a comprehensive summary of the basic principles and workflow of the extracellular flux assay (the Seahorse assay) and its diverse applications. We highlight the assay's versatility across various biological models, including cancer cells, immunocytes, Caenorhabditis elegans, tissues, isolated mitochondria, and three-dimensional structures such as organoids, and summarize key considerations for using extracellular flux assay in these models. Additionally, we discuss the limitations of the Seahorse assay and propose future directions for its development. This review aims to enhance the understanding of extracellular flux assay and its significance in biological studies.

Altered Mitochondrial Function in MASLD: Key Features and Promising Therapeutic Approaches

Metabolic dysfunction-associated steatotic liver disease (MASLD), formerly known as nonalcoholic fatty liver disease (NAFLD), encompasses a range of liver conditions from steatosis to nonalcoholic steatohepatitis (NASH). Its prevalence, especially among patients with metabolic syndrome, highlights its growing global impact. The pathogenesis of MASLD involves metabolic dysregulation, inflammation, oxidative stress, genetic factors and, notably, mitochondrial dysfunction. Recent studies underscore the critical role of mitochondrial dysfunction in MASLD's progression. Therapeutically, enhancing mitochondrial function has gained interest, along with lifestyle changes and pharmacological interventions targeting mitochondrial processes. The FDA's approval of resmetirom for metabolic-associated steatohepatitis (MASH) with fibrosis marks a significant step. While resmetirom represents progress, further research is essential to understand MASLD-related mitochondrial dysfunction fully. Innovative strategies like gene editing and small-molecule modulators, alongside lifestyle interventions, can potentially improve MASLD treatment. Drug repurposing and new targets will advance MASLD therapy, addressing its increasing global burden. Therefore, this review aims to provide a better understanding of the role of mitochondrial dysfunction in MASLD and identify more effective preventive and treatment strategies.

Bacteria-organelle communication in physiology and disease

Bacteria, omnipresent in our environment and coexisting within our body, exert dual beneficial and pathogenic influences. These microorganisms engage in intricate interactions with the human body, impacting both human health and disease. Simultaneously, certain organelles within our cells share an evolutionary relationship with bacteria, particularly mitochondria, best known for their energy production role and their dynamic interaction with each other and other organelles. In recent years, communication between bacteria and mitochondria has emerged as a new mechanism for regulating the host's physiology and pathology. In this review, we delve into the dynamic communications between bacteria and host mitochondria, shedding light on their collaborative regulation of host immune response, metabolism, aging, and longevity. Additionally, we discuss bacterial interactions with other organelles, including chloroplasts, lysosomes, and the endoplasmic reticulum (ER).

Adipocyte Mitochondria: Deciphering Energetic Functions across Fat Depots in Obesity and Type 2 Diabetes

Adipose tissue, a central player in energy balance, exhibits significant metabolic flexibility that is often compromised in obesity and type 2 diabetes (T2D). Mitochondrial dysfunction within adipocytes leads to inefficient lipid handling and increased oxidative stress, which together promote systemic metabolic disruptions central to obesity and its complications. This review explores the pivotal role that mitochondria play in altering the metabolic functions of the primary adipocyte types, white, brown, and beige, within the context of obesity and T2D. Specifically, in white adipocytes, these dysfunctions contribute to impaired lipid processing and an increased burden of oxidative stress, worsening metabolic disturbances. Conversely, compromised mitochondrial function undermines their thermogenic capabilities, reducing the capacity for optimal energy expenditure in brown adipocytes. Beige adipocytes uniquely combine the functional properties of white and brown adipocytes, maintaining morphological similarities to white adipocytes while possessing the capability to transform into mitochondria-rich, energy-burning cells under appropriate stimuli. Each type of adipocyte displays unique metabolic characteristics, governed by the mitochondrial dynamics specific to each cell type. These distinct mitochondrial metabolic phenotypes are regulated by specialized networks comprising transcription factors, co-activators, and enzymes, which together ensure the precise control of cellular energy processes. Strong evidence has shown impaired adipocyte mitochondrial metabolism and faulty upstream regulators in a causal relationship with obesity-induced T2D. Targeted interventions aimed at improving mitochondrial function in adipocytes offer a promising therapeutic avenue for enhancing systemic macronutrient oxidation, thereby potentially mitigating obesity. Advances in understanding mitochondrial function within adipocytes underscore a pivotal shift in approach to combating obesity and associated comorbidities. Reigniting the burning of calories in adipose tissues, and other important metabolic organs such as the muscle and liver, is crucial given the extensive role of adipose tissue in energy storage and release.