Mitochondrial dysfunction in diabetes: from molecular mechanisms to functional significance and therapeutic opportunities

Impairment of Mitochondrial Respiration in Metabolic Diseases: An Overview

Mitochondrial dysfunction has emerged as a central pathomechanism in the setting of obesity and diabetes mellitus, linking these intertwined pathologies that share insulin resistance as a common denominator. High-resolution respirometry (HRR) is a state-of-the-art research method currently used to study mitochondrial respiration and its impairment in health and disease. Tissue samples, cells or isolated mitochondria are exposed to various substrate-uncoupler-inhibitor-titration protocols, which allows the measurement and calculation of several parameters of mitochondrial respiration. In this review, we discuss the alterations of mitochondrial bioenergetics in the main dysfunctional organs that contribute to the development of the obese and diabetic phenotypes in both animal models and human subjects. Herein we review data regarding the impairment of oxidative phosphorylation as integrated mitochondrial function assessed by means of HRR. We acknowledge the critical role of this method in determining the alterations in oxidative phosphorylation occurring in the early stages of metabolic pathologies. We conclude that there is a mutual two-way relationship between mitochondrial dysfunction and insulin insensitivity that characterizes these diseases.

Immune Modulation of Adipocyte Mitochondrial Metabolism

Immune cells infiltrate adipose tissue as a function of age, sex, and diet, leading to a variety of regulatory processes linked to metabolic disease and dysfunction. Cytokines and chemokines produced by resident macrophages, B cells, T cells and eosinophils play major role(s) in fat cell mitochondrial functions modulating pyruvate oxidation, electron transport and oxidative stress, branched chain amino acid metabolism, fatty acid oxidation, and apoptosis. Indeed, cytokine-dependent downregulation of numerous genes affecting mitochondrial metabolism is strongly linked to the development of the metabolic syndrome, whereas the potentiation of mitochondrial metabolism represents a counterregulatory process improving metabolic outcomes. In contrast, inflammatory cytokines activate mitochondrially linked cell death pathways such as apoptosis, pyroptosis, necroptosis, and ferroptosis. As such, the adipocyte mitochondrion represents a major intersection point for immunometabolic regulation of central metabolism.

Lipotoxicity in a Vicious Cycle of Pancreatic Beta Cell Exhaustion

Hyperlipidemia is a common metabolic disorder in modern society and may precede hyperglycemia and diabetes by several years. Exactly how disorders of lipid and glucose metabolism are related is still a mystery in many respects. We analyze the effects of hyperlipidemia, particularly free fatty acids, on pancreatic beta cells and insulin secretion. We have developed a computational model to quantitatively estimate the effects of specific metabolic pathways on insulin secretion and to assess the effects of short- and long-term exposure of beta cells to elevated concentrations of free fatty acids. We show that the major trigger for insulin secretion is the anaplerotic pathway via the phosphoenolpyruvate cycle, which is affected by free fatty acids via uncoupling protein 2 and proton leak and is particularly destructive in long-term chronic exposure to free fatty acids, leading to increased insulin secretion at low blood glucose and inadequate insulin secretion at high blood glucose. This results in beta cells remaining highly active in the “resting” state at low glucose and being unable to respond to anaplerotic signals at high pyruvate levels, as is the case with high blood glucose. The observed fatty-acid-induced disruption of anaplerotic pathways makes sense in the context of the physiological role of insulin as one of the major anabolic hormones.

Characterization of ampicillin-resistant genes in Vibrio parahaemolyticus

Vibrio parahaemolyticus is strongly resistant to ampicillin (AMP). In this study, AMP-resistant genes in V. parahaemolyticus ATCC33846 were characterized. Transcriptomic analysis of V. parahaemolyticus exposed to AMP revealed 4608 differentially transcribed genes, including 670 significantly up-regulated genes and 655 significantly down-regulated genes. Based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses, significantly modulated genes in ATCC33846 under AMP stimulation were observed in the following categories: microbial metabolism in diverse environments, metabolic pathways, bacterial secretion system, citrate cycle, biofilm formation, oxidative phosphorylation, ribosome, citrate cycle, pyruvate metabolism, carbon metabolism, nitrogen metabolism, fatty acid metabolism and tryptophan metabolism. The genes VPA0510, VPA0252, VPA0699, VPA0768, VPA0320, VP0636, VPA1096, VPA0947 and VP1775 were significantly up-regulated at the similar level to blaA in V. parahaemolyticus under AMP stimulation, and their overexpression in V. parahaemolyticus could increase its resistance to AMP. These results indicate that AMP has a global influence on V. parahaemolyticus cells. The findings would provide new insights into the resistant mechanism of V. parahaemolyticus to AMP, which would be helpful for developing novel drugs for treating V. parahaemolyticus infection.

Emerging role of mitochondrial DAMPs, aberrant mitochondrial dynamics and anomalous mitophagy in gut mucosal pathogenesis

Gastroduodenal inflammation and ulcerative injuries are increasing due to expanding socio-economic stress, unhealthy food habits-lifestyle, smoking, alcoholism and usage of medicines like non-steroidal anti-inflammatory drugs. In fact, gastrointestinal (GI) complications, associated with the prevailing COVID-19 pandemic, further, poses a challenge to global healthcare towards safeguarding the GI tract. Emerging evidences have discretely identified mitochondrial dysfunctions as common etiological denominators in diseases. However, it is worth realizing that mitochondrial dysfunctions are not just consequences of diseases. Rather, damaged mitochondria severely aggravate the pathogenesis thereby qualifying as perpetrable factors worth of prophylactic and therapeutic targeting. Oxidative and nitrosative stress due to endogenous and exogenous stimuli triggers mitochondrial injury causing production of mitochondrial damage associated molecular patterns (mtDAMPs), which, in a feed-forward loop, inflicts inflammatory tissue damage. Mitochondrial structural dynamics and mitophagy are crucial quality control parameters determining the extent of mitopathology and disease outcomes. Interestingly, apart from endogenous factors, mitochondria also crosstalk and in turn get detrimentally affected by gut pathobionts colonized during luminal dysbiosis. Although mitopathology is documented in various pre-clinical/clinical studies, a comprehensive account appreciating the mitochondrial basis of GI mucosal pathologies is largely lacking. Here we critically discuss the molecular events impinging on mitochondria along with the interplay of mitochondria-derived factors in fueling mucosal pathogenesis. We specifically emphasize on the potential role of aberrant mitochondrial dynamics, anomalous mitophagy, mitochondrial lipoxidation and ferroptosis as emerging regulators of GI mucosal pathogenesis. We finally discuss about the prospect of mitochondrial targeting for next-generation drug discovery against GI disorders.

Cross-Talk between Obesity and Diabetes: Introducing Polyphenols as an Effective Phytomedicine to Combat the Dual Sword Diabesity

: Obesity-associated diabetes mellitus, a chronic metabolic affliction accounting for 90% of all diabetic patients, has been affecting humanity extremely badly and escalating the risk of developing other serious disorders. It is observed that 0.4 billion people globally have diabetes, whose major cause is obesity. Currently, innumerable synthetic drugs like alogliptin and rosiglitazone are being used to get through diabetes, but they have certain complications, restrictions with severe side effects, and toxicity issues. Recently, the frequency of plant-derived phytochemicals as advantageous substitutes against diabesity is increasing progressively due to their unparalleled benefit of producing less side effects and toxicity. Of these phytochemicals, dietary polyphenols have been accepted as potent agents against the dual sword "diabesity". These polyphenols target certain genes and molecular pathways through dual mechanisms such as adiponectin upregulation, cannabinoid receptor antagonism, free fatty acid oxidation, ghrelin antagonism, glucocorticoid inhibition, sodium-glucose cotransporter inhibition, oxidative stress and inflammation inhibition etc. which sequentially help to combat both diabetes and obesity. In this review, we have summarized the most beneficial natural polyphenols along with their complex molecular pathways during diabesity.

Paricalcitol Attenuates Metabolic Syndrome-Associated Heart Failure through Enhanced Mitochondrial Fusion

Objectives

Transition from cardiac hypertrophy to failure involves adverse metabolic reprogramming involving mitochondrial dysfunction. We have earlier shown that vitamin D deficiency induces heart failure, at least in part, through insulin resistance. However, whether activation of vitamin D receptor (VDR) can attenuate heart failure and underlying metabolic phenotype requires investigation. Thus, we aimed to assess the cardioprotective potential of paricalcitol, a vitamin D receptor-activator, against cardiac hypertrophy and failure in high-fat high-fructose-fed rats.

Methods

Male Sprague Dawley rats were fed control (Con) or high-fat high-fructose (HFHFrD) diet for 20 weeks. After 12 weeks, rats from HFHFrD group were divided into the following: HFHFrD, HFHFrD+P (paricalcitol i.p. 0.08 μg/kg/day) and HFHFrD+E (enalapril maleate i.p. 10 mg/kg/day). Intraperitoneal glucose tolerance test, blood pressure measurement, and 2D echocardiography were performed. Cardiac fibrosis was assessed by Masson's trichrome staining of paraffin-embedded heart sections. Mitochondrial DNA and proteins, and citrate synthase activity were measured in rat hearts. VDR was silenced in H9c2 cardiomyoblasts, and immunoblotting was performed.

Results

Paricalcitol improved glucose tolerance, serum lipid profile, and blood pressure in high-fat high-fructose-fed rats. Paricalcitol reduced cardiac wall thickness and increased ejection fraction in high-fat high-fructose-fed rats but had no effect on perivascular fibrosis. PGC1-α was upregulated in the HFHFrD+P group compared to the HFHFrD group, but there was no significant difference in mitochondrial content. Citrate synthase activity was significantly higher in the HFHFrD+P group compared to the HFHFrD group. Rat hearts of the HFHFrD+P group had significantly higher expression of mitofusins. H9c2 cells with VDR knockdown showed significantly lower expression of Mfn2. Improvement in the HFHFrD+P group was comparable with that in the HFHFrD+E group.

Conclusions

Paricalcitol reverses cardiac dysfunction in rats with metabolic syndrome by enhancing mitochondrial fusion. We demonstrate repurposing potential of the drug currently used in end-stage kidney disease.

High glucose-induced inhibition of osteoblast like MC3T3-E1 differentiation promotes mitochondrial perturbations

Diabetes mellitus is a metabolic disorder that causes health concerns worldwide. Patients with diabetes exhibit multisystemic symptoms, including loss of bone quality over time. The progressive deterioration of bone promotes failure to withstand damage and increases the risk of fractures. Much of the molecular and metabolic mechanism(s) in diabetic bone remains unclear. In vitro studies suggest that hyperglycemia inhibits mineralization, affecting bone formation and function. In this study, inhibition of osteoblast differentiation was induced using hyperglycemia to assess whether high glucose promotes mitochondrial impairment along with altered bone matrix formation. It was hypothesized that bone energy metabolism would be altered in these cells as calcium deposition, a key phase for bone function, is suppressed. Early passages of osteoblast like MC3T3-E1 cells were differentiated under normal and high glucose conditions. To investigate osteoblast differentiation, we quantified calcium accumulation by alizarin red staining and analyzed immunoblots of key proteins. To assess mitochondrial function, we quantified mitochondrial DNA (mtDNA), detected expression and function of key proteins from the Tricarboxylic (TCA) cycle, measured mitochondrial respiration, and fuel oxidation of alternative nutrients. Results confirmed previous work showing that mineralization was inhibited and AKT expression was reduced in high glucose-treated bone cells. Unexpectedly, high glucose-treated osteoblast cells utilize both mitochondrial respiration and glycolysis to maintain energy demands with partial help of fatty acid for reliance of baseline bioenergetics. These metabolic shifts suggest that hyperglycemia maintain bone metabolic needs in an early differentiated state concurrent to the inhibition in bone matrix formation.

Molecular Basis of Irisin Regulating the Effects of Exercise on Insulin Resistance

Insulin resistance is recognized as one major feature of metabolic syndrome, and frequently emerges as a difficult problem encountered during long-term pharmacological treatment of diabetes. Insulin resistance often causes organs or tissues, such as skeletal muscle, adipose, and liver, to become less responsive or resistant to insulin. Exercise can promote the physiological function of those organs and tissues and benefits insulin action via increasing insulin receptor sensitivity, glucose uptake, and mitochondrial function. This is done by decreasing adipose tissue deposition, inflammatory cytokines, and oxidative stress. However, understanding the mechanism that regulates the interaction between exercise and insulin function becomes a challenging task. As a novel myokine, irisin is activated by exercise, released from the muscle, and affects multi-organ functions. Recent evidence indicates that it can promote glucose uptake, improve mitochondrial function, alleviate obesity, and decrease inflammation, as a result leading to the improvement of insulin action. We here will review the current evidence concerning the signaling pathways by which irisin regulates the effect of exercise on the up-regulation of insulin action in humans and animals.

Mitochondrial ATP6 and ND3 genes are associated with type 2 diabetic peripheral neuropathy

BACKGROUND AND AIMS

The association of mitochondrial NADH dehydrogenase gene mutations with type 2 diabetes in the Karaikudi population was previously reported. This is a case report that demonstrated rare mutations are responsible for maternally inherited peripheral neuropathy of diabetes.

METHODS

We describe a 70-year-old male and his family (n = 25) with type 2 diabetic peripheral neuropathy having four rare mutations, 8597T > C, 8699T > C, 8966T > C, 10188A > G, and 9 bp deletion in various regions of the mitochondrial genes. Mutations were identified through direct sequencing of DNA isolated from the blood of the selected individuals. Blood samples were also analyzed for glucose, hemoglobin A1c, triglyceride, total cholesterol, oxidative stress markers, antioxidant status, cytochrome-C-oxidase and mitochondrial DNA content using appropriate methods.

RESULTS

Oxidative stress markers were found elevated while the antioxidant status, mitochondrial DNA content and the activity of cytochrome C-oxidase was reduced significantly. Analysis of mtDNA showed the presence of several mutations in various regions of mitochondrial genome. However, 8597T > C, 8699T > C, 8966T > C, 10188A > G, and 9 bp deletion were observed in the patient's family including his siblings.

CONCLUSION

This study shows that the mutations observed in the patient and his family is maternally inherited and suspected to be pathogenic in developing T2D associated peripheral neuropathy.

An anti-diabetic drug targets NEET (CISD) proteins through destabilization of their [2Fe-2S] clusters

Elevated levels of mitochondrial iron and reactive oxygen species (ROS) accompany the progression of diabetes, negatively impacting insulin production and secretion from pancreatic cells. In search for a tool to reduce mitochondrial iron and ROS levels, we arrived at a molecule that destabilizes the [2Fe-2S] clusters of NEET proteins (M1). Treatment of db/db diabetic mice with M1 improved hyperglycemia, without the weight gain observed with alternative treatments such as rosiglitazone. The molecular interactions of M1 with the NEET proteins mNT and NAF-1 were determined by X-crystallography. The possibility of controlling diabetes by molecules that destabilize the [2Fe-2S] clusters of NEET proteins, thereby reducing iron-mediated oxidative stress, opens a new route for managing metabolic aberration such as in diabetes.

Sestrin2 overexpression attenuates osteoarthritis pain via induction of AMPK/PGC-1α-mediated mitochondrial biogenesis and suppression of neuroinflammation

BACKGROUND

Our previous study indicated that reactive oxygen species (ROS) are critically involved in chronic pain. Sestrin2 (Sesn2), a novel stress-inducible protein, is evidenced to reduce the generation of ROS. The study examined the role of Sesn2 in osteoarthritis (OA) pain and delineated the underlying molecular mechanisms.

METHODS

In the present study, we investigated the impact of Sesn2 on mitochondrial biogenesis in a rat model of OA pain. After adeno-associated viral (AAV)-Sesn2EGFP was injected for 14 days, OA was induced by intra-articular injection of monosodium iodoacetate (MIA). We assessed pain behaviors (weight-bearing asymmetry and paw withdrawal threshold) and explored possible mechanisms in the L4-6 spinal cord.

RESULTS

Our results showed that overexpression of Sesn2 in the spinal cord alleviated pain behaviors in OA rats. Moreover, overexpression of Sesn2 increased the activity of AMP-activated protein kinase (AMPK) signaling and significantly restored mitochondrial biogenesis. Besides, Sesn2 overexpression inhibited the activation of astrocytes and microglia, and decreased the production of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the spinal cord of the OA pain rats. These effects were significantly reversed by an AMPK inhibitor.

CONCLUSIONS

Collectively, these results suggest that Sesn2 overexpression ameliorates mechanical allodynia and weight-bearing asymmetry in OA rats via activation of AMPK/PGC-1α-mediated mitochondrial biogenesis in the spinal cord. Moreover, Sesn2 overexpression attenuates OA-induced neuroinflammation at least partly by activating AMPK signaling. Sesn2 may become an encouraging therapeutic strategy for OA pain relief and other disorders.

Nitric oxide-releasing biomaterials for promoting wound healing in impaired diabetic wounds: State of the art and recent trends

Impaired diabetic wounds are serious pathophysiological complications associated with persistent microbial infections including failure in the closure of wounds, and the cause of a high frequency of lower limb amputations. The healing of diabetic wounds is attenuated due to the lack of secretion of growth factors, prolonged inflammation, and/or inhibition of angiogenic activity. Diabetic wound healing can be enhanced by supplying nitric oxide (NO) endogenously or exogenously. NO produced inside the cells by endothelial nitric oxide synthase (eNOS) naturally aids wound healing through its beneficial vasculogenic effects. However, during hyperglycemia, the activity of eNOS is affected, and thus there becomes an utmost need for the topical supply of NO from exogenous sources. Thus, NO-donors that can release NO are loaded into wound healing patches or wound coverage matrices to treat diabetic wounds. The burst release of NO from its donors is prevented by encapsulating them in polymeric hydrogels or nanoparticles for supplying NO for an extended duration of time to the diabetic wounds. In this article, we review the etiology of diabetic wounds, wound healing strategies, and the role of NO in the wound healing process. We further discuss the challenges faced in translating NO-donors as a clinically viable nanomedicine strategy for the treatment of diabetic wounds with a focus on the use of biomaterials for the encapsulation and in vivo controlled delivery of NO-donors.

The Mighty Mitochondria Are Unifying Organelles and Metabolic Hubs in Multiple Organs of Obesity, Insulin Resistance, Metabolic Syndrome, and Type 2 Diabetes: An Observational Ultrastructure Study

Mitochondria (Mt) are essential cellular organelles for the production of energy and thermogenesis. Mt also serve a host of functions in addition to energy production, which include cell signaling, metabolism, cell death, and aging. Due to the central role of Mt in metabolism as metabolic hubs, there has been renewed interest in how Mt impact metabolic pathways and multiple pathologies. This review shares multiple observational ultrastructural findings in multiple cells and organs to depict aberrant mitochondrial (aMt) remodeling in pre-clinical rodent models. Further, it is intended to show how remodeling of Mt are associated with obesity, insulin resistance, metabolic syndrome (MetS), and type 2 diabetes mellitus (T2DM). Specifically, Mt remodeling in hypertensive and insulin-resistant lean models (Ren2 rat models), lean mice with streptozotocin-induced diabetes, obesity models including diet-induced obesity, genetic leptin-deficient ob/ob, and leptin receptor-deficient db/db diabetic mice are examined. Indeed, aMt dysfunction and damage have been implicated in multiple pathogenic diseases. Manipulation of Mt such as the induction of Mt biogenesis coupled with improvement of mitophagy machinery may be helpful to remove leaky damaged aMt in order to prevent the complications associated with the generation of superoxide-derived reactive oxygen species and the subsequent reactive species interactome. A better understanding of Mt remodeling may help to unlock many of the mysteries in obesity, insulin resistance, MetS, T2DM, and the associated complications of diabetic end-organ disease.

Reactive oxygen species in cardiovascular diseases: an update

Cardiovascular diseases are among the leading causes of death worldwide, imposing major health threats. Reactive oxygen species (ROS) are one of the most important products from the process of redox reactions. In the onset and progression of cardiovascular diseases, ROS are believed to heavily influence homeostasis of lipids, proteins, DNA, mitochondria, and energy metabolism. As ROS production increases, the heart is damaged, leading to further production of ROS. The vicious cycle continues on as additional ROS are generated. For example, recent evidence indicated that connexin 43 (Cx43) deficiency and pyruvate kinase M2 (PKM2) activation led to a loss of protection in cardiomyocytes. In this context, a better understanding of the mechanisms behind ROS production is vital in determining effective treatment and management strategies for cardiovascular diseases.

Liraglutide preserves CD34+ stem cells from dysfunction Induced by high glucose exposure

Background

Glucagon like peptide-1 receptor agonists (GLP-1RAs) have shown to reduce mortality and cardiovascular events in patients with type 2 diabetes mellitus (T2DM). Since the impairment in number and function of vasculotrophic circulating CD34⁺ hematopoietic stem progenitor cells (HSPCs) in T2D has been reported to increase cardiovascular (CV) risk, we hypothesized that one of the mechanisms whereby GLP-1 RAs exert CV protective effects may be related to the ability to improve CD34⁺ HSPC function.

Methods

In cord blood (CB)-derived CD34⁺ HSPC, the expression of GLP-1 receptor (GLP-1R) mRNA, receptor protein and intracellular signaling was evaluated by RT-qPCR and Western Blot respectively. CD34⁺ HSPCs were exposed to high glucose (HG) condition and GLP-1RA liraglutide (LIRA) was added before as well as after functional impairment. Proliferation, CXCR4/SDF-1α axis activity and intracellular ROS production of CD34⁺ HSPC were evaluated.

Results

CD34⁺ HSPCs express GLP-1R at transcriptional and protein level. LIRA treatment prevented and rescued HSPC proliferation, CXCR4/SDF-1α axis activity and metabolic imbalance from HG-induced impairment. LIRA stimulation promoted intracellular cAMP accumulation as well as ERK1/2 and AKT signaling activation. The selective GLP-1R antagonist exendin (9–39) abrogated LIRA-dependent ERK1/2 and AKT phosphorylation along with the related protective effects.

Conclusion

We provided the first evidence that CD34⁺ HSPC express GLP-1R and that LIRA can favorably impact on cell dysfunction due to HG exposure. These findings open new perspectives on the favorable CV effects of GLP-1 RAs in T2DM patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01486-9.

Prenatal Low-Protein Diet Affects Mitochondrial Structure and Function in the Skeletal Muscle of Adult Female Offspring

Gestational low-protein (LP) diet leads to glucose intolerance and insulin resistance in adult offspring. We had earlier demonstrated that LP programming affects glucose disposal in females. Mitochondrial health is crucial for normal glucose metabolism in skeletal muscle. In this study, we sought to analyze mitochondrial structure, function, and associated genes in skeletal muscles to explore the molecular mechanism of insulin resistance LP-programmed female offspring. On day four of pregnancy, rats were assigned to a control diet containing 20% protein or an isocaloric 6% protein-containing diet. Standard laboratory diet was given to the dams after delivery until the end of weaning and to pups after weaning. Gestational LP diet led to changes in mitochondrial ultrastructure in the gastrocnemius muscles, including a nine-fold increase in the presence of giant mitochondria along with unevenly formed cristae. Further, functional analysis showed that LP programming caused impaired mitochondrial functions. Although the mitochondrial copy number did not show significant changes, key genes involved in mitochondrial structure and function such as Fis1, Opa1, Mfn2, Nrf1, Nrf2, Pgc1b, Cox4b, Esrra, and Vdac were dysregulated. Our study shows that prenatal LP programming induced disruption in mitochondrial ultrastructure and function in the skeletal muscle of female offspring.

Chronic Lactate Exposure Decreases Mitochondrial Function by Inhibition of Fatty Acid Uptake and Cardiolipin Alterations in Neonatal Rat Cardiomyocytes

Introduction

Lactate is an important signaling molecule with autocrine, paracrine and endocrine properties involved in multiple biological processes including regulation of gene expression and metabolism. Levels of lactate are increased chronically in diseases associated with cardiometabolic disease such as heart failure, type 2 diabetes, and cancer. Using neonatal ventricular myocytes, we tested the hypothesis that chronic lactate exposure could decrease the activity of cardiac mitochondria that could lead to metabolic inflexibility in the heart and other tissues.

Methods

Neonatal rat ventricular myocytes (NRVMs) were treated for 48 h with 5, 10, or 20 mM lactate and CPT I and II activities were tested using radiolabelled assays. The molecular species profile of the major mitochondrial phospholipid, cardiolipin, was determined using electrospray ionization mass spectrometry along with reactive oxygen species (ROS) levels measured by Amplex Red and mitochondrial oxygen consumption using the Seahorse analyzer.

Results

CPT I activity trended downward (p = 0.07) and CPT II activity significantly decreased with lactate exposure (p < 0.001). Cardiolipin molecular species containing four 18 carbon chains (72 carbons total) increased with lactate exposure, but species of other sizes decreased significantly. Furthermore, ROS production was strongly enhanced with lactate (p < 0.001) and mitochondrial ATP production and maximal respiration were both significantly down regulated with lactate exposure (p < 0.05 and p < 0.01 respectively).

Conclusions

Chronic lactate exposure in cardiomyocytes leads to a decrease in fatty acid transport, alterations of cardiolipin remodeling, increases in ROS production and decreases in mitochondrial oxygen consumption that could have implications for both metabolic health and flexibility. The possibility that both intra-, or extracellular lactate levels play roles in cardiometabolic disease, heart failure, and other forms of metabolic inflexibility needs to be assessed in vivo.

Glucose and oleic acid mediate cellular alterations in GLP-1-induced insulin-positive differentiating UCBMSCs

Coordinated effects of glucose and oleic acid on glucagon-like peptide-1 (GLP-1) mediated differentiation of insulin-positive differentiating umbilical cord mesenchymal stromal cells (dUCBMSCs) was studied using a co-culture of NCI-H716 (GLP-1+) and UCBMSCs (insulin+). The addition of 2.5 mM glucose increased the proliferation of NCI-H716 cells by 30% and induced transformation of UCBMSCs into insulin-secreting cells in 18 days as compared to 22 days in control cells. Oleic acid (25 μM) showed decrease in cell proliferation, autophagy, and apoptosis in NCI-H716 cells while no effect was observed in dUCBMSCs. Prolonged glucose and oleic acid resulted in apoptosis and cell cycle changes in dUCBMSCs after day 18 while higher concentrations resulted in cell death. Additionally, the expression of FAS and ACC mRNA was observed in NCI-H716 and dUCBMSCs post 24-hr addition of glucose and/or oleic acid. Absorption of oleic acid was high in NCI-H716 compared to dUCBMSCs. Taken together, optimal concentrations of glucose and oleic acid could be a key factor in stimulating intrinsic GLP-1, which in turn stimulates differentiating MSCs in a glucose-dependent manner. PRACTICAL APPLICATIONS: The aim of this article was to study whether differentiating or differentiated MSCs after mobilization or post-transplant would require optimal glucose and oleic acid to naturally stimulate intrinsic GLP-1, or otherwise, the high or long-term overload of glucose or oleic acid could result in inhibition of differentiated cells resulting in failure of insulin secretion.

Combination of Aerobic Training and Cocoa Flavanols as Effective Therapies to Reduce Metabolic and Inflammatory Disruptions in Insulin-Resistant Rats: The Exercise, Cocoa, and Diabetes Study

We aimed to investigate the combined effects of aerobic exercise (EXE) and cocoa flavanol (COCOA) supplementation on performance, metabolic parameters, and inflammatory and lipid profiles in obese insulin-resistant rats. Therefore, 32 male Wistar rats (230-250 g) were fed a high-fat diet and a fructose-rich beverage for 30 days to induce insulin resistance. Next, the rats were randomized into four groups, orally administered placebo solution or COCOA supplementation (45 mg·kg-1), and either remained sedentary or were subjected to EXE on a treadmill at 60% peak velocity for 30 min, for 8 weeks. Blood samples and peripheral tissues were collected and processed to analyze metabolic and inflammatory parameters, lipid profiles, and morphological parameters. Supplementation with COCOA and EXE improved physical performance and attenuated body mass gain, adipose index, and adipocyte area. When analyzed as individual interventions, supplementation with COCOA and EXE improved glucose intolerance and the lipid profile reduced the concentrations of leptin, glucose, and insulin, and reduced homeostasis assessment index (all effects were p < .001 for both interventions), while ameliorated some inflammatory mediators in examined tissues. In skeletal muscles, both COCOA supplementation and EXE increased the expression of glucose transporter (p < .001 and p < .001), and combined intervention showed additive effects (p < .001 vs. COCOA alone or EXE alone). Thus, combining COCOA with EXE represents an effective nonpharmacological strategy to treat insulin resistance; it could prevent Type 2 diabetes mellitus by improving physical performance, glucose metabolism, neuroendocrine control, and lipid and inflammatory mediators in the liver, pancreas, adipose tissue, and skeletal muscle in obese male insulin-resistant rats.

Peripheral and cognitive benefits of physical exercise in a mouse model of midlife metabolic syndrome

Despite national and international efforts for the prevention of metabolic syndrome and its underlying diseases/disorders, its prevalence is still rising, especially in the middle-aged population. In this study, we explore the effect of high fat diet on the development of metabolic syndrome in middle-aged mice and to evaluate the potential benefits of voluntary physical exercise on the periphery as well as brain cognitive function, and to explore the potential mechanisms. We found that metabolic syndrome developed at middle age significantly impairs cognitive function and the impairment is associated with gene dysregulation in metabolic pathways that are largely affecting astrocytes in the brain. Eight-week voluntary wheel running at a frequency of three times a week, not only improves peripheral glucose control but also significantly improves learning and memory. The improvement of cognitive function is associated with restoration of gene expression involved in energy metabolism in the brain. Our study suggests that voluntary physical exercise is beneficial for metabolic syndrome-induced peripheral as well as cognitive dysfunction and can be recommended as therapeutic intervention for metabolic syndrome and associated diseases.

The Role of Mitochondrial miRNAs in the Development of Radon-Induced Lung Cancer

MicroRNAs are short, non-coding RNA molecules regulating gene expression by inhibiting the translation of messenger RNA (mRNA) or leading to degradation. The miRNAs are encoded in the nuclear genome and exported to the cytosol. However, miRNAs have been found in mitochondria and are probably derived from mitochondrial DNA. These miRNAs are able to directly regulate mitochondrial genes and mitochondrial activity. Mitochondrial dysfunction is the cause of many diseases, including cancer. In this review, we consider the role of mitochondrial miRNAs in the pathogenesis of lung cancer with particular reference to radon exposure.

Physical activity and COVID-19. The basis for an efficient intervention in times of COVID-19 pandemic

The Coronavirus Disease 2019 (COVID-19) pandemic has shocked world health authorities generating a global health crisis. The present study aimed to analyze the different factors associated with physical activity that could have an impact in the COVID-19, providing a practical recommendation based on actual scientific knowledge. We conducted a consensus critical review using primary sources, scientific articles, and secondary bibliographic indexes, databases, and web pages. The method was a narrative literature review of the available literature regarding physical activity and physical activity related factors during the COVID-19 pandemic. The main online database used in the present research were PubMed, SciELO, and Google Scholar. COVID-19 has negatively influenced motor behavior, levels of regular exercise practice, eating and nutritional patterns, and the psychological status of citizens. These factors feed into each other, worsening COVID-19 symptoms, the risk of death from SARS-CoV-2, and the symptoms and effectiveness of the vaccine. The characteristics and symptoms related with the actual COVID-19 pandemic made the physical activity interventions a valuable prevention and treatment factor. Physical activity improves body composition, the cardiorespiratory, metabolic, and mental health of patients and enhancing antibody responses in vaccination.

Cardioprotective Role of BGP-15 in Ageing Zucker Diabetic Fatty Rat (ZDF) Model: Extended Mitochondrial Longevity

Impaired mitochondrial function is associated with several metabolic diseases and health conditions, including insulin resistance and type 2 diabetes (T2DM), as well as ageing. The close relationship between the above-mentioned diseases and cardiovascular disease (CVD) (diabetic cardiomyopathy and age-related cardiovascular diseases) has long been known. Mitochondria have a crucial role: they are a primary source of energy produced in the form of ATP via fatty acid oxidation, tricarboxylic acid (TCA) cycle, and electron transport chain (ETC), and ATP synthase acts as a key regulator of cardiomyocyte survival. Mitochondrial medicine has been increasingly discussed as a promising therapeutic approach in the treatment of CVD. It is well known that vitamin B3 as an NAD+ precursor exists in several forms, e.g., nicotinic acid (niacin) and nicotinamide (NAM). These cofactors are central to cellular homeostasis, mitochondrial respiration, ATP production, and reactive oxygen species generation and inhibition. Increasing evidence suggests that the nicotinic acid derivative BGP-15 ((3-piperidine-2-hydroxy-1-propyl)-nicotinic amidoxime) improves cardiac function by reducing the incidence of arrhythmias and improves diastolic function in different animal models. Our team has valid reasons to assume that these cardioprotective effects of BGP-15 are based on its NAD+ precursor property. Our hypothesis was supported by an animal experiment where ageing ZDF rats were treated with BGP-15 for one year. Haemodynamic variables were measured with echocardiography to detect diabetic cardiomyopathy (DbCM) and age-related CVD as well. In the ZDF group, advanced HF was diagnosed, whereas the BGP-15-treated ZDF group showed diastolic dysfunction only. The significant difference between the two groups was supported by post-mortem Haematoxylin and eosin (HE) and Masson’s trichrome staining of cardiac tissues. Moreover, our hypothesis was further confirmed by the significantly elevated Cytochrome c oxidase (MTCO) and ATP synthase activity and expression detected with ELISA and Western blot analysis. To the best of our knowledge, this is the first study to demonstrate the protective effect of BGP-15 on cardiac mitochondrial respiration in an ageing ZDF model.

Trends in Antidiabetic Drug Discovery: FDA Approved Drugs, New Drugs in Clinical Trials and Global Sales

Type 2 diabetes mellitus (T2DM) continues to be a substantial medical problem due to its increasing global prevalence and because chronic hyperglycemic states are closely linked with obesity, liver disease and several cardiovascular diseases. Since the early discovery of insulin, numerous antihyperglycemic drug therapies to treat diabetes have been approved, and also discontinued, by the United States Food and Drug Administration (FDA). To provide an up-to-date account of the current trends of antidiabetic pharmaceuticals, this review offers a comprehensive analysis of the main classes of antihyperglycemic compounds and their mechanisms: insulin types, biguanides, sulfonylureas, meglitinides (glinides), alpha-glucosidase inhibitors (AGIs), thiazolidinediones (TZD), incretin-dependent therapies, sodium-glucose cotransporter type 2 (SGLT2) inhibitors and combinations thereof. The number of therapeutic alternatives to treat T2DM are increasing and now there are nearly 60 drugs approved by the FDA. Beyond this there are nearly 100 additional antidiabetic agents being evaluated in clinical trials. In addition to the standard treatments of insulin therapy and metformin, there are new drug combinations, e.g., containing metformin, SGLT2 inhibitors and dipeptidyl peptidase-4 (DPP4) inhibitors, that have gained substantial use during the last decade. Furthermore, there are several interesting alternatives, such as lobeglitazone, efpeglenatide and tirzepatide, in ongoing clinical trials. Modern drugs, such as glucagon-like peptide-1 (GLP-1) receptor agonists, DPP4 inhibitors and SGLT2 inhibitors have gained popularity on the pharmaceutical market, while less expensive over the counter alternatives are increasing in developing economies. The large heterogeneity of T2DM is also creating a push towards more personalized and accessible treatments. We describe several interesting alternatives in ongoing clinical trials, which may help to achieve this in the near future.

Time-restricted feeding during the inactive phase abolishes the daily rhythm in mitochondrial respiration in rat skeletal muscle

Shift-workers show an increased incidence of type 2 diabetes mellitus (T2DM). A possible mechanism is the disruption of the circadian timing of glucose homeostasis. Skeletal muscle mitochondrial function is modulated by the molecular clock. We used time-restricted feeding (TRF) during the inactive phase to investigate how mistimed feeding affects muscle mitochondrial metabolism. Rats on an ad libitum (AL) diet were compared to those that could eat only during the light (inactive) or dark (active) phase. Mitochondrial respiration, metabolic gene expressions, and metabolite concentrations were determined in the soleus muscle. Rats on AL feeding or dark-fed TRF showed a clear daily rhythm in muscle mitochondrial respiration. This rhythm in mitochondrial oxidative phosphorylation capacity was abolished in light-fed TRF animals and overall 24h respiration was lower. The expression of several genes involved in mitochondrial biogenesis and the fission/fusion machinery was altered in light-fed animals. Metabolomics analysis indicated that light-fed animals had lost rhythmic levels of α-ketoglutarate and citric acid. Contrastingly, lipidomics showed that light-fed animals abundantly gained rhythmicity in levels of triglycerides. Furthermore, while the RER shifted entirely with the food intake in the light-fed animals, many measured metabolic parameters (e.g., activity and mitochondrial respiration) did not strictly align with the shifted timing of food intake, resulting in a mismatch between expected metabolic supply/demand (as dictated by the circadian timing system and light/dark-cycle) and the actual metabolic supply/demand (as dictated by the timing of food intake). These data suggest that shift-work impairs mitochondrial metabolism and causes metabolic inflexibility, which can predispose to T2DM.

Altered muscle mitochondrial, inflammatory and trophic markers and reduced exercise training adaptations in type 1 diabetes

KEY POINTS

Type 1 diabetes negatively affects skeletal muscle health; however, the effect of structured exercise training on markers of mitochondrial function, inflammation and regeneration is not known. Even though participants with type 1 diabetes and healthy control were comparable for cardiorespiratory fitness (VO₂ max) and muscle strength at baseline, molecular markers related to muscle health were decreased in type 1 diabetes. After training, both groups increased the VO₂ max and muscle strength, however, a larger improvement was achieved by the control group. The training intervention decreased glucose fluctuations and occurrence of hypoglycaemic events in type 1 diabetes, while signs of mild myopathy found in the muscle of participants with type 1 diabetes only partially improved after training Improving muscle health by specific exercise protocols is of considerable clinical interest in therapeutic strategies for improving type 1 diabetes management and prevent or delay long-term complications.

ABSTRACT

Growing evidence of impaired skeletal muscle health in people with type 1 diabetes points toward the presence of a mild myopathy in this population. However, this myopathic condition is not jet well characterised and often overlooked, even though it might affect the whole-body glucose homeostasis and the development of comorbidities. This study aims to compare skeletal muscle adaptations and changes in glycaemic control after 12 weeks of combined resistance and aerobic (COMB) training between people with type 1 diabetes and healthy controls, and whether the impaired muscle health in type 1 diabetes can affect the exercise-induced adaptations. The COMB training intervention increased aerobic capacity and muscle strength in both healthy and type 1 diabetes sedentary participants, although these improvements were higher in the control group. Better glucose control, reduced glycaemic fluctuations and fewer hypoglycaemic events were recorded at Post- compared to Pre-intervention in type 1 diabetes. Analysis of muscle biopsies showed an alteration of muscle markers of mitochondrial functions, inflammation, aging and growth/atrophy compared to the control group. These muscular molecular differences were only partially modified by the COMB training and might explain the reduced exercise adaptation observed in type 1 diabetes. In brief, type 1 diabetes impairs many aspects of skeletal muscle health and might affect the exercise-induced adaptations. Defining the magnitude of diabetic myopathy and the effect of exercise, including longer duration of the intervention, will drive the development of strategies to maximize muscle health in the type 1 diabetes population. This article is protected by copyright. All rights reserved.

Higher fasting blood glucose worsens knee symptoms in patients with radiographic knee osteoarthritis and comorbid central sensitization: an Iwaki cohort study

BACKGROUND

Although cross-sectional and cohort data suggest that higher serum blood glucose levels in patients with knee osteoarthritis (KOA) are associated with more severe knee symptoms, little is known about the longitudinal relationship between serum blood glucose and knee symptoms, particularly considering central sensitization (CS) comorbidity, which also worsens knee symptoms.

METHODS

We evaluated the longitudinal relationship between serum blood glucose and knee symptoms by dividing the cohort of patients with KOA into those with and without CS. We hypothesized that higher serum blood glucose levels would worsen knee symptoms. A total of 297 participants (mean age: 59.6 years; females: 211; average BMI: 23.7 kg/m²) were enrolled in this study. At baseline, plain radiographs of the bilateral knee joints were evaluated according to the Kellgren-Lawrence grade (KLG). All participants exhibited at least a KLG ≥ 2 in each knee. At baseline, fasting blood glucose (FBG) and Central Sensitization Inventory-9 (CSI-9) were evaluated; ≥ 10 points on the CSI-9 was defined as CS+. Knee injury and Osteoarthritis Outcome Score (KOOS) was evaluated at baseline and at 1-year follow-up; the change in KOOS (ΔKOOS) was calculated by subtracting the KOOS at baseline from that at the 1-year follow-up. Multiple linear regression analysis was conducted with ΔKOOS as the dependent variable and FBG at baseline as the independent variable, adjusted for age, sex, BMI, and CSI-9 at baseline.

RESULTS

Of the 297 subjects, 48 (16.2 %) were defined as CS+. In the CS - group, there was no association between FBG levels at baseline and ΔKOOS. In contrast, FBG at baseline was negatively associated with ΔKOOS pain (B = - 0.448; p = 0.003), ADL (B = - 0.438; p = 0.003), and sports (B = - 0.706; p = 0.007).

CONCLUSIONS

In patients with radiographic KOA and CS, higher blood glucose levels were associated with deteriorated knee symptoms during the 1-year follow-up. Healthcare providers should pay attention to controlling blood glucose, particularly in patients with KOA and concurrent CS, to mitigate their knee symptoms.

STUDY DESIGN

Retrospective cohort study (evidence level: III).

GDF15: a potential therapeutic target for type 1 diabetes

INTRODUCTION

Current treatment for type 1 diabetes (T1D) is centered around insulin supplementation to manage the effects of pancreatic β cell loss. GDF15 is a potential preventative therapy against T1D progression that could work to curb increasing disease incidence.

AREAS COVERED

This paper discusses the known actions of GDF15, a pleiotropic protein with metabolic, feeding, and immunomodulatory effects, connecting them to highlight the open opportunities for future research. The role of GDF15 in the prevention of insulitis and protection of pancreatic β cells against pro-inflammatory cytokine-mediated cellular stress are examined and the pharmacological promise of GDF15 and critical areas of future research are discussed.

EXPERT OPINION

GDF15 shows promise as a potential intervention but requires further development. Preclinical studies have shown poor efficacy, but this result may be confounded by the measurement of gross GDF15 instead of the active form. Additionally, the effect of GDF15 in the induction of anorexia and nausea-like behavior and short-half-life present significant challenges to its deployment, but a systems pharmacology approach paired with chronotherapy may provide a possible solution to therapy for this currently unpreventable disease.

Low-intensity ultrasound (LIUS) differentially modulates mitochondrial reactive oxygen species (mtROS) generation by three different chemicals in PC12 cells

We have previously shown that low-intensity ultrasound (LIUS) can modulate mitochondrial complex I activity and the generation of mitochondrial reactive oxygen species (mtROS) in PC12 cells. This study investigated the mechanism of LIUS by comparing its effect on mitochondrial dysfunction by three different pathways. LIUS was shown to reverse the effects of rotenone, a Q-site blocker, on the complex I inhibition, mtROS generation, and drop of mitochondrial membrane potential (Δψm). In contrast, common antioxidants, N-acetyl cysteine (NAC), and uric acid (UA) blocked rotenone-induced mtROS generation and Δψm drop without recovering the complex I activity, which suggested that Δψm drop is correlated with mtROS generation rather than complex I inhibition itself. Ionomycin, an ionophore for Ca²⁺, and L-buthionine-S,R-sulfoximine (BSO), an inhibitor of glutathione (GSH) biosynthesis, induced mtROS generation and Δψm drop without inhibiting complex I activity via different mechanisms. LIUS showed no effect on ionomycin-induced Δψm drop but showed partial inhibition on the other effects of ionomycin and BSO. These results suggest that LIUS might have redundant mechanisms but acted mainly on the complex I activity thereby modulating mtROS and Δψm levels. LIUS appeared to act on the Q-module of complex I because it showed no inhibitory effect on Zn²⁺, an inhibitor of the proton transporting P-module of complex I. Interestingly, pretreatment of LIUS for up to an hour in advance blocked the rotenone effect as efficiently as the co-treatment. Further studies are needed to reveal the exact mechanism of LIUS to inhibit complex I activity.

Heart failure in diabetes

Heart failure and cardiovascular disorders represent the leading cause of death in diabetic patients. Here we present a systematic review of the main mechanisms underlying the development of diabetic cardiomyopathy. We also provide an excursus on the relative contribution of cardiomyocytes, fibroblasts, endothelial and smooth muscle cells to the pathophysiology of heart failure in diabetes. After having described the preclinical tools currently available to dissect the mechanisms of this complex disease, we conclude with a section on the most recent updates of the literature on clinical management.

p66Shc-mediated oxidative stress is involved in gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is associated with a heightened level of oxidative stress, which is characterized by the overproduction of reactive oxygen species (ROS) from mitochondria. Previous studies showed that mitochondrial dysfunction is regulated by dynamin-related protein 1 (Drp1) and p66Shc in GDM.

AIM

The aim was to investigate the expression of Drp1 and p66Shc and their possible mechanisms in the pathogenesis of GDM.

METHODS

A total of 30 pregnant women, 15 with GDM and 15 without GDM, were enrolled. Peripheral blood mononuclear cells and placental tissue were collected. The human JEG3 trophoblast cell line was cultivated in 5.5 mmol/L or 30 mmol/L glucose and transfected with wild-type (wt)-p66Shc and p66Shc siRNA. P66Shc and Drp1 mRNA levels were detected by quantitative real-time polymerase chain reaction. The expression of p66Shc and Drp1 was assayed by immunohistochemistry and western blotting. ROS was assayed by dihydroethidium staining.

RESULTS

The p66Shc mRNA level was increased in the serum (P < 0.01) and placentas (P < 0.01) of women with GDM, and the expression of Drp1 mRNA and protein were also increased in placentas (P < 0.05). In JEG3 cells treated with 30 mmol/L glucose, the mRNA and protein expression of p66Shc and Drp1 were increased at 24 h (both P < 0.05), 48 h (both P < 0.01) and 72 h (both P < 0.001). ROS expression was also increased. High levels of Drp1 and ROS expression were detected in JEG3 cells transfected with wt-p66Shc (P < 0.01), and low levels were detected in JEG3 cells transfected with p66Shc siRNA (P < 0.05).

CONCLUSION

The upregulated expression of Drp1 and p66shc may contribute to the occurrence and development of GDM. Regulation of the mitochondrial fusion-fission balance could be a novel strategy for GDM treatment.

The ameliorative effect of bromelain on STZ-induced type 1 diabetes in rats through Oxi-LDL/LPA/LPAR1 pathway

AIMS

Diabetes, a serious worldwide problem, is modulated via inflammation and oxidative stress. Bromelain, a natural compound, recently attracts interest due to its anti-inflammatory effects, while its mode of action remains not properly understood. Thus, investigating the antidiabetic effect of bromelain is promising.

MATERIALS AND METHODS

Rats were randomized into normal group, STZ group (were administrated single intraperitoneal (i.p) injection of 55 mg/kg streptozotocin (STZ)) and STZ + Bro group (were administrated single i.p injection of STZ, 72 h later were i.p administrated 10 mg/kg/day bromelain for 15 days). Wound healing ability was investigated for different groups. Spectrophotometry, ELISA, histopathological and immunohistochemical techniques were applied.

KEY FINDINGS

Bromelain significantly decreased fasting blood glucose, serum triglycerides and cholesterol and hepatic malondialdehyde levels compared with STZ group. Moreover, Bromelain significantly increased serum albumin and total protein levels and percentage of wound healing compared with STZ group. These results were confirmed through the histopathological examination of liver, pancreas, and skin tissues. Investigating the molecular mechanism underlying these effects, STZ injection caused significant increase in hepatic oxidized-LDL (Oxi-LDL) and lysophosphatidic acid (LPA) levels and hepatic lysophosphatidic acid receptor 1 (LPAR1), and beta secretase (BACE1) protein tissue expressions, while bromelain significantly aborted these effects. Thus, STZ caused upregulation of Oxi-LDL/LPA/LPAR1/BACE1 pathway, while bromelain significantly ameliorated these effects.

SIGNIFICANCE

To our best knowledge, this study represents the 1^st study investigating Oxi-LDL/LPA/LPAR1/BACE1 pathway in STZ-induced diabetes in rats, in addition to the promising ameliorative effect of bromelain in STZ-induced diabetes in rats.

3-hydroxymorphinan enhances mitochondrial biogenesis and adipocyte browning through AMPK-dependent pathway

3-hydroxymorphinan (3-HM), a metabolite of dextromethorphan, has previously been reported to have anti-inflammatory, anti-oxidative stress, and neuroprotective effects. However, its effect on energy metabolism in adipocytes remains unclear. Herein, we investigated 3-hydroxymorphinan (3-HM) effects on mitochondrial biogenesis, oxidative stress, and lipid accumulation in 3T3-L1 adipocytes. Further, we explored 3-HM-associated molecular mechanisms. Mouse adipocyte 3T3-L1 cells were treated with 3-HM, and various protein expression levels were determined by western blotting analysis. Mitochondria accumulation and lipid accumulation were measured by staining methods. Cell toxicity was assessed by cell viability assay. We found that treatment of 3T3-L1 adipocytes with 3-HM increased expression of brown adipocyte markers, such as uncoupling protein-1 (UCP-1) and peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α). 3-HM promotes mitochondrial biogenesis and its-mediated gene expression. Additionally, 3-HM treatment suppressed mitochondrial ROS generation and superoxide along with improved mitochondrial complex I activity. We found that treatment of 3-HM enhanced AMPK phosphorylation. siRNA-mediated suppression of AMPK reversed all these changes in 3T3-L1 adipocytes. In sum, 3-HM promotes mitochondrial biogenesis and browning and attenuates oxidative stress and lipid accumulation in 3T3-L1 adipocytes via AMPK signaling. Thus, 3-HM-mediated AMPK activation can be considered a therapeutic approach for treating obesity and related diseases.

Therapeutic Approach of Flavonoid in Ameliorating Diabetic Cardiomyopathy by Targeting Mitochondrial-Induced Oxidative Stress

Diabetes cardiomyopathy is one of the key factors of mortality among diabetic patients around the globe. One of the prior contributors to the progression of diabetic cardiomyopathy is cardiac mitochondrial dysfunction. The cardiac mitochondrial dysfunction can induce oxidative stress in cardiomyocytes and was found to be the cause of majority of the heart morphological and dynamical changes in diabetic cardiomyopathy. To slow down the occurrence of diabetic cardiomyopathy, it is crucial to discover therapeutic agents that target mitochondrial-induced oxidative stress. Flavonoid is a plentiful phytochemical in plants that shows a wide range of biological actions against human diseases. Flavonoids have been extensively documented for their ability to protect the heart from diabetic cardiomyopathy. Flavonoids' ability to alleviate diabetic cardiomyopathy is primarily attributed to their antioxidant properties. In this review, we present the mechanisms involved in flavonoid therapies in ameliorating mitochondrial-induced oxidative stress in diabetic cardiomyopathy.

Reduced expression of OXPHOS and DNA damage genes is linked to protection from microvascular complications in long-term type 1 diabetes: the PROLONG study

Type 1 diabetes is a chronic autoimmune disease requiring insulin treatment for survival. Prolonged duration of type 1 diabetes is associated with increased risk of microvascular complications. Although chronic hyperglycemia and diabetes duration have been considered as the major risk factors for vascular complications, this is not universally seen among all patients. Persons with long-term type 1 diabetes who have remained largely free from vascular complications constitute an ideal group for investigation of natural defense mechanisms against prolonged exposure of diabetes. Transcriptomic signatures obtained from RNA sequencing of the peripheral blood cells were analyzed in non-progressors with more than 30 years of diabetes duration and compared to the patients who progressed to microvascular complications within a shorter duration of diabetes. Analyses revealed that non-progressors demonstrated a reduction in expression of the oxidative phosphorylation (OXPHOS) genes, which were positively correlated with the expression of DNA repair enzymes, namely genes involved in base excision repair (BER) machinery. Reduced expression of OXPHOS and BER genes was linked to decrease in expression of inflammation-related genes, higher glucose disposal rate and reduced measures of hepatic fatty liver. Results from the present study indicate that at transcriptomic level reduction in OXPHOS, DNA repair and inflammation-related genes is linked to better insulin sensitivity and protection against microvascular complications in persons with long-term type 1 diabetes.

Simulating Metabolic Flexibility in Low Energy Expenditure Conditions Using Genome-Scale Metabolic Models

Metabolic flexibility is the ability of an organism to adapt its energy source based on nutrient availability and energy requirements. In humans, this ability has been linked to cardio-metabolic health and healthy aging. Genome-scale metabolic models have been employed to simulate metabolic flexibility by computing the Respiratory Quotient (RQ), which is defined as the ratio of carbon dioxide produced to oxygen consumed, and varies between values of 0.7 for pure fat metabolism and 1.0 for pure carbohydrate metabolism. While the nutritional determinants of metabolic flexibility are known, the role of low energy expenditure and sedentary behavior in the development of metabolic inflexibility is less studied. In this study, we present a new description of metabolic flexibility in genome-scale metabolic models which accounts for energy expenditure, and we study the interactions between physical activity and nutrition in a set of patient-derived models of skeletal muscle metabolism in older adults. The simulations show that fuel choice is sensitive to ATP consumption rate in all models tested. The ability to adapt fuel utilization to energy demands is an intrinsic property of the metabolic network.

Adverse Effects of Metformin From Diabetes to COVID-19, Cancer, Neurodegenerative Diseases, and Aging: Is VDAC1 a Common Target?

Metformin has been used for treating diabetes mellitus since the late 1950s. In addition to its antihyperglycemic activity, it was shown to be a potential drug candidate for treating a range of other diseases that include various cancers, cardiovascular diseases, diabetic kidney disease, neurodegenerative diseases, renal diseases, obesity, inflammation, COVID-19 in diabetic patients, and aging. In this review, we focus on the important aspects of mitochondrial dysfunction in energy metabolism and cell death with their gatekeeper VDAC1 (voltage-dependent anion channel 1) as a possible metformin target, and summarize metformin's effects in several diseases and gut microbiota. We question how the same drug can act on diseases with opposite characteristics, such as increasing apoptotic cell death in cancer, while inhibiting it in neurodegenerative diseases. Interestingly, metformin's adverse effects in many diseases all show VDAC1 involvement, suggesting that it is a common factor in metformin-affecting diseases. The findings that metformin has an opposite effect on various diseases are consistent with the fact that VDAC1 controls cell life and death, supporting the idea that it is a target for metformin.

Effects of early-life stress on peripheral and central mitochondria in male mice across ages

Exposure to early-life stress (ES) increases the vulnerability to develop metabolic diseases as well as cognitive dysfunction, but the specific biological underpinning of the ES-induced programming is unknown. Metabolic and cognitive disorders are often comorbid, suggesting possible converging underlying pathways. Mitochondrial dysfunction is implicated in both metabolic diseases and cognitive dysfunction and chronic stress impairs mitochondrial functioning. However, if and how mitochondria are impacted by ES and whether they are implicated in the ES-induced programming remains to be determined. ES was applied by providing mice with limited nesting and bedding material from postnatal day (P)2-P9, and metabolic parameters, cognitive functions and multiple aspects of mitochondria biology (i.e. mitochondrial electron transport chain (ETC) complex activity, mitochondrial DNA copy number, expression of genes relevant for mitochondrial function, and the antioxidant capacity) were studied in muscle, hypothalamus and hippocampus at P9 and late adulthood (10-12 months of age). We show that ES altered bodyweight (gain), adiposity and glucose levels at P9, but not in late adulthood. At this age, however, ES exposure led to cognitive impairments. ES affected peripheral and central mitochondria in an age-dependent manner. At P9, both muscle and hypothalamic ETC activity were affected by ES, while in hippocampus, ES altered the expression of genes involved in fission and antioxidant defence. In adulthood, alterations in ETC complex activity were observed in the hypothalamus specifically, whereas in muscle and hippocampus ES affected the expression of genes involved in mitophagy and fission, respectively. Our study demonstrates that ES affects peripheral and central mitochondria biology throughout life, thereby uncovering a converging mechanism that might contribute to the ES-induced vulnerability for both metabolic diseases and cognitive dysfunction, which could serve as a novel target for intervention.

Case Report: Homozygous DNAJC3 Mutation Causes Monogenic Diabetes Mellitus Associated With Pancreatic Atrophy

Introduction

DNAJC3, abundant in the pancreatic cells, attenuates endoplasmic reticulum stress. Homozygous DNAJC3 mutations have been reported to cause non-immune juvenile-onset diabetes, neurodegeneration, hearing loss, short stature, and hypothyroidism.

Case Description

We report a case of homozygous DNAJC3 mutation in two siblings of a consanguineous family. A 3-year-old boy presented with short stature and a thyroid nodule. Laboratory findings confirmed hypothyroidism. Subsequently, levothyroxine was administered. Growth hormone (GH) stimulation test results were within the normal limits. His stature was exceedingly short (80.5 cm) (-3.79 SDS). The patient developed sensorineural hearing loss at age 6 years; his intellectual functioning was impaired. Recombinant Human Growth Hormine (rhGH) treatment was postponed until the age of 6.9 years due to a strong family history of diabetes. At age 9 years, he developed an ataxic gait. Brain magnetic resonance imaging (MRI) revealed neurodegeneration. The patient developed diabetes at the age of 11 years-5 years after the initiation of rhGH treatment. Tests for markers of autoimmune diabetes were negative. Lifestyle modification was introduced, but insulin therapy was eventually required. Whole-exome-sequencing (WES) revealed a homozygous DNAJC3 mutation, which explained his clinical presentation. MRI revealed a small, atrophic pancreas. At the age of 17, his final adult height was 143 cm (-4.7 SDS). His elder brother, who had the same mutation, had a similar history, except that he had milder ataxia and normal brain MRI finding at the age of 28 years.

Conclusion

We propose that DNAJC3 mutation can be considered as a cause of maturity onset diabetes of the young. Patients with DNAJC3 mutations may possess a small atrophic pancreas.

Tumor Necrosis Receptor Superfamily Interact with Fusion and Fission of Mitochondria of Adipose Tissue in Obese Patients without Type 2 Diabetes

Interactions between receptors and ligands of the tumor necrosis factor superfamily (TNFSF) provide costimulatory signals that control the survival, proliferation, differentiation, and effector function of immune cells. All components of the TNF superfamily are associated with NF-kB functions that are not limited to cell death and may promote survival in the face of adipose tissue inflammation in obesity. Inflammation dysfunction of mitochondria is a key factor associated with insulin resistance in obesity. The aim of the study was to analyze the relationship of soluble forms of receptors and ligands of the TNF superfamily in blood plasma with mitochondrial dynamics in adipose tissue (greater omentum (GO) and subcutaneous adipose tissue (Sat)) of obese patients with and without type 2 diabetes mellitus (T2DM). Increased plasma sTNF-R1, sTNF-R2, sTNFRSF8 receptors, and ligands TNFSF12, TNFSF13, TNFSF13B are characteristic of obese patients without T2DM. The TNF-a levels in blood plasma were associated with a decrease in MFN2 gene expression in GO and IL-10 in blood plasma. The TNFSF12 levels contributed to a decrease in glucose levels, a decrease in BMI, and an increase in IL-10 levels by influencing the MFN2 gene expression in GO, which supports mitochondrial fusion.

The Role of miR-181c in Mechanisms of Diabetes-Impaired Angiogenesis: An Emerging Therapeutic Target for Diabetic Vascular Complications

Diabetes mellitus is estimated to affect up to 700 million people by the year 2045, contributing to an immense health and economic burden. People living with diabetes have a higher risk of developing numerous debilitating vascular complications, leading to an increased need for medical care, a reduced quality of life and increased risk of early death. Current treatments are not satisfactory for many patients who suffer from impaired angiogenesis in response to ischaemia, increasing their risk of ischaemic cardiovascular conditions. These vascular pathologies are characterised by endothelial dysfunction and abnormal angiogenesis, amongst a host of impaired signaling pathways. Therapeutic stimulation of angiogenesis holds promise for the treatment of diabetic vascular complications that stem from impaired ischaemic responses. However, despite significant effort and research, there are no established therapies that directly stimulate angiogenesis to improve ischaemic complications such as ischaemic heart disease and peripheral artery disease, highlighting the immense unmet need. However, despite significant effort and research, there are no established therapies that directly stimulate angiogenesis in a clinical setting, highlighting the immense unmet need. MicroRNAs (miRNAs) are emerging as powerful targets for multifaceted diseases including diabetes and cardiovascular disease. This review highlights the potential role of microRNAs as therapeutic targets for rescuing diabetes-impaired angiogenesis, with a specific focus on miR-181c, which we have previously identified as an important angiogenic regulator. Here we summarise the pathways currently known to be regulated by miR-181c, which include the classical angiogenesis pathways that are dysregulated in diabetes, mitochondrial function and axonal guidance, and describe how these relate both directly and indirectly to angiogenesis. The pleiotropic actions of miR-181c across multiple key angiogenic signaling pathways and critical cellular processes highlight its therapeutic potential as a novel target for treating diabetic vascular complications.

Fibrometabolism-An emerging therapeutic frontier in pulmonary fibrosis

Fibrosis is the final pathological outcome and major cause of morbidity and mortality in many common and chronic inflammatory, immune-mediated, and metabolic diseases. Despite the growing incidence of fibrotic diseases and extensive research efforts, there remains a lack of effective therapies that improve survival. The application of omics technologies has revolutionized our approach to identifying previously unknown therapeutic targets and potential disease biomarkers. The application of metabolomics, in particular, has improved our understanding of disease pathomechanisms and garnered a wave of scientific interest in the role of metabolism in the biology of myofibroblasts, the key effector cells of the fibrogenic response. Emerging evidence suggests that alterations in metabolism not only are a feature of but also may play an influential role in the pathogenesis of fibrosis, most notably in idiopathic pulmonary fibrosis (IPF), the most rapidly progressive and fatal of all fibrotic conditions. This review will detail the role of key metabolic pathways, their alterations in myofibroblasts, and the potential this new knowledge offers for the development of antifibrotic therapeutic strategies.

Does Metformin Modulate Mitochondrial Dynamics and Function in Type 2 Diabetic Patients?

Metformin is an effective drug against type 2 diabetes (T2D), a pathogenesis in which mitochondrial dysfunction is one of the main players. Thus, our first aim was to describe the effect of metformin on mitochondrial function in an outpatient population with T2D. For analyzing this hypothesis, we performed a preliminary cross-sectional study complying with the STROBE requirements. We studied leukocytes from 139 healthy controls, 39 T2D patients without metformin treatment, and 81 T2D patients who had been on said treatment for at least 1 year. Leukocytes from T2D patients displayed higher total and mitochondrial reactive oxygen species levels, lower mitochondrial membrane potential, and lower oxygen consumption. Moreover, their mitochondria expressed lower mRNA and protein levels of fusion proteins mitofusin-1 (MFN1), mitofusin-2 (MFN2), and optic atrophy 1 (OPA1), and higher protein and gene expression levels of mitochondrial fission protein 1 (FIS1) and dynamin-related protein 1 (DRP-1). In addition, we observed enhanced leukocyte/endothelial interactions in T2D patients. Metformin reversed most of these effects, ameliorating mitochondrial function and dynamics, and reducing the leukocyte/endothelial interactions observed in T2D patients. These results raise the question of whether metformin tackles T2D by improving mitochondrial dysfunction and regulating mitochondrial dynamics. Furthermore, it would seem that metformin modulates the alteration of interactions between leukocytes and the endothelium, a subclinical marker of early atherosclerosis. Antioxid. Redox Signal. 35, 377-385.

Ginsenoside Rg5 Improves Insulin Resistance and Mitochondrial Biogenesis of Liver via Regulation of the Sirt1/PGC-1α Signaling Pathway in db/db Mice

Type 2 diabetes mellitus (T2DM) is a common metabolic syndrome that decreases insulin sensitivity and mitochondrial biogenesis in the liver. Our previous study demonstrated that ginsenoside Rg5 (Rg5) could attenuate renal injury in diabetic mice but its underlying mechanism in mitochondrial biogenesis and insulin sensitivity remains poorly understood. In this study, we found that Rg5 intervention significantly inhibited blood glucose increases in db/db mice, improved liver function damage and hepatocyte apoptosis, and activated the IRS-1/phosphatidylinositol 3-kinase/AKT insulin metabolism signaling pathway. Rg5 treatment also increased the level of glycogen synthesis and activated sirtuin1 (Sirt1) to increase glucose uptake and insulin sensitivity in insulin-resistant HepG2 (IR-HepG2) cells. Rg5 intervention also effectively improved liver oxidative stress and inflammation in db/db mice and increased mitochondrial biogenesis caused by T2DM. Additionally, the Rg5 treatment increased the mitochondrial mass in IR-HepG2 cells and activated Sirt1 to regulate the Sirt1/PGC-1α/mitofusin-2 mitochondrial biosynthesis pathway. Our findings demonstrated that Rg5 enhanced liver mitochondrial biogenesis and insulin sensitivity in db/db mice by activating the Sirt1/PGC-1α signaling pathway, suggesting the potential of Rg5 as a natural product for T2DM interventions.