Mitochondrial dysfunction and complications associated with diabetes

Mitochondrial ATP synthase regulates corpus cavernosum smooth muscle cell function in vivo and in vitro

Adenosine triphosphate (ATP) levels are closely associated with diabetes-related erectile dysfunction (DMED). Mitochondrial ATP synthase serves a key role in ATP production. The present study aimed to investigate the relationship between F₁-ATP synthase and DMED in vivo and in vitro. The F₁-ATP synthase expression levels in corpus cavernosum tissues from rats with DMED were examined. F₁-ATP synthase expression was found to be lower in corpus cavernosum tissues from rats with DMED compared with healthy controls, suggesting a role for ATP synthase under high glucose conditions. In addition, the present study also demonstrated that hyperglycemia could downregulate F₁-ATP synthase expression in rat corpus cavernosum smooth muscle cells (CCSMCs) in vitro. The overexpression of F₁-ATP synthase in CCSMCs influenced the phenotypic CCSMC transformation, upregulated eNOS expression, increased cGMP levels and reduced CCSMC apoptosis under high glucose in vitro. In conclusion, the present study indicates that the upregulation of mitochondrial ATP synthase expression may improve CCSMC function, suggesting that mitochondrial ATP synthase could serve as a potential therapeutic target for the treatment of DMED.

The beneficial effects of Agaricus blazei Murrill on hepatic antioxidant enzymes and the pancreatic tissue recovery in streptozotocin-induced diabetic rats

Agaricus blazei Murrill (ABM), is a medicinal mushroom, has beneficial effects on diabetes mellitus. In this study, ABM extracts (ethanol extract, EE and ethyl acetate extract, EA) were evaluated to explore the beneficial effect on hepatic antioxidant activity and recovery of the pancreatic tissue in streptozotocin-induced diabetic rats. The hepatic antioxidant activities of ABM extracts were analyzed by superoxide dismutase, catalase activity, glutathione, aspartate transaminase, and alanine transaminase. Moreover, the effects of ABM extracts on pancreatic tissue restoration were investigated by histopathological analysis. The results revealed that the EA showed a better protective effect on hepatic antioxidant activity and recovery of the impaired pancreatic tissues, compared to EE. The results suggested that ABM treatment could effectively reduce oxidative stress and contribute to pancreatic tissue recovery. Therefore, ABM could be used as a functional food to control diabetes. PRACTICAL APPLICATIONS: The research may contribute to the development of ABM as functional foods or dietary supplements for diabetes in the future.

Sex differences in redox homeostasis in renal disease

Sex differences in redox signaling in the kidney present new challenges and opportunities for understanding the physiology and pathophysiology of the kidney. This review will focus on reactive oxygen species, immune-related signaling pathways and endothelin-1 as potential mediators of sex-differences in redox homeostasis in the kidney. Additionally, this review will highlight male-female differences in redox signaling in several major cardiovascular and renal disorders namely acute kidney injury, diabetic nephropathy, kidney stone disease and salt-sensitive hypertension. Furthermore, we will discuss the contribution of redox signaling in the pathogenesis of postmenopausal hypertension and preeclampsia.

The impact of mitochondrial quality control by Sirtuins on the treatment of type 2 diabetes and diabetic kidney disease

The incidence of type 2 diabetes mellitus (T2DM) and diabetic kidney disease (DKD) has significantly increased worldwide in recent decades, and improved treatments for T2DM and DKD are urgently needed. The pathogenesis of aging-related disorders, such as T2DM and DKD, involves multiple mechanisms, including inflammation, autophagy impairment, and oxidative stress, which are closely associated with mitochondrial dysfunction. Therefore, mitochondrial quality control may be a novel therapeutic target for T2DM and DKD. Previous reports have shown that members of the mammalian Sirtuin family, SIRT 1-7, which are recognized as antiaging molecules, play a crucial role in the regulation of mitochondrial function and quality control through the modulation of oxidative stress, inflammation and autophagy. In this review, we summarized the research published in recent years to highlight the role of Sirtuins in mitochondrial quality control as a therapeutic target for T2DM and DKD.

Grape seed proanthocyanidins prevent H2 O2 -induced mitochondrial dysfunction and apoptosis via SIRT 1 activation in embryonic kidney cells

Grape proanthocyanidins are compounds widely ingested in the diet. This study evaluated their effects on mitochondrial function, apoptosis, and sirtuin 1 and 3 expressions in HEK-293 cells exposed to H₂ O₂ . High-resolution mass spectrometry and high-performance liquid chromatography characterized the proanthocyanidins extract and the presence of procyanidins B and C was detected. The extract prevented H₂ O₂ -induced oxidative damage to proteins and lipids and depletion in superoxide dismutase activity. Moreover, it was able to regulate the expression of NADH: Ubiquinone oxidoreductase core subunit S7 and prevent mitochondrial electron transport chain dysfunction, ATP depletion, and apoptosis induced by H₂ O₂ . Finally, the extract was able to regulate sirtuin 1 and 3 expressions, thus maintaining cell viability. These data show that the grape seed proanthocyanidins can target mitochondrial proteins, which may represent an important approach for the management of numerous chronic illnesses associated with mitochondrial dysfunction. PRACTICAL APPLICATIONS: Proanthocyanidins are phenolic compounds abundant in regular diet, commonly found in grapes and derivatives, pomegranates, apples, and red fruits, all foods known for their beneficial effects on health. The current study highlights the role of proanthocyanidins as mitochondrial modulators that may explain the biological activity attributed to these compounds. This study brings evidence that proanthocyanidins might be considered as a value-added agent for the development of new nutraceutical and or pharmaceutical approaches.

High-Intensity Interval Training Restores Glycolipid Metabolism and Mitochondrial Function in Skeletal Muscle of Mice With Type 2 Diabetes

High-intensity interval training has been reported to lower fasting blood glucose and improve insulin resistance of type 2 diabetes without clear underlying mechanisms. The purpose of this study was to investigate the effect of high-intensity interval training on the glycolipid metabolism and mitochondrial dynamics in skeletal muscle of high-fat diet (HFD) and one-time 100 mg/kg streptozocin intraperitoneal injection-induced type 2 diabetes mellitus (T2DM) mice. Our results confirmed that high-intensity interval training reduced the body weight, fat mass, fasting blood glucose, and serum insulin of the T2DM mice. High-intensity interval training also improved glucose tolerance and insulin tolerance of the T2DM mice. Moreover, we found that high-intensity interval training also decreased lipid accumulation and increased glycogen synthesis in skeletal muscle of the T2DM mice. Ultrastructural analysis of the mitochondria showed that mitochondrial morphology and quantity were improved after 8 weeks of high-intensity interval training. Western blot analysis showed that the expression of mitochondrial biosynthesis related proteins and mitochondrial dynamics related proteins in high-intensity interval trained mice in skeletal muscle were enhanced. Taken together, these data suggest high-intensity interval training improved fasting blood glucose and glucose homeostasis possibly by ameliorating glycolipid metabolism and mitochondrial dynamics in skeletal muscle of the T2DM mice.

Chronic Stress and Diabetes Mellitus: Interwoven Pathologies

Stress threatens the homeostasis and mobilizes a plethora of adaptive physiological and behavioral changes via the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system. The HPA axis influences the pituitary gland, hypothalamus and adrenal gland via a complex set of positive and negative feedback system. The feedback system operates in a well regulated neuroendocrine manner to reestablish the threatened body equilibrium. The HPA axis secreted major product is a glucocorticoid (cortisol) which is kept within a physiologically optimal range and serves to accomplish the various physiological functions crucial for survival. In chronically stressed individuals dishabituation of HPA axis is followed by increased release of glucocorticoids and catecholamines. Higher secretion of glucocorticoids influences glucose metabolism by promoting gluconeogenesis in the liver, suppressing glucose uptake (adipocytes and skeletal muscles), promoting lipolysis in adipocytes, suppressing insulin secretion, inflicting insulin resistance and inflammation. These biological changes alter neuroendocrine mechanisms and lead to maladaptive congregation of events that form the underlying cause of development of Type 2 diabetes (T2D). The currently reviewed evidences advocate that targeting stress mediated hypersecretion of glucocorticoids may be a viable approach for the treatment of T2D and to reinstate glucose homeostasis.

The Cellular Localization of the p42 and p46 Oligoadenylate Synthetase 1 Isoforms and Their Impact on Mitochondrial Respiration

The importance of the IFN-induced oligoadenylate synthetase (OAS) proteins and the OAS/RNase L pathway in the innate response against viral pathogens is well-established, however the observed differences in anti-viral activity between the human OAS1 p46 and p42 isoforms are not fully understood. The protein expression of these isoforms is determined by the SNP rs10774671, either being an A or a G allele resulting in expression of either the p42 or the p46 isoform. Using fluorescence microscopy and immunoblot analysis of fractionated cell samples, we show here that the CaaX motif is of key importance to the cellular localization. The OAS1 p42 isoform is mainly located in the cytosol, whereas the p46 isoform with a C-terminal CaaX motif is translocated to membranous organelles, like the mitochondria. We furthermore observed differences between p42 and p46 in their effect on mitochondrial physiology using high resolution respirometry and fluorometry. Overexpression of OAS1 p42 and IFN-β treatment of HeLa cells (AA genotype) resulted in significantly increased respiration, which was not seen with p46 overexpression. The difference in subcellular localization and mitochondrial effect of these two OAS1 isoforms might help to explain the anti-viral mechanisms that differentiate these proteins.

The Role of Adipose Tissue Mitochondria: Regulation of Mitochondrial Function for the Treatment of Metabolic Diseases

: Mitochondria play a key role in maintaining energy homeostasis in metabolic tissues, including adipose tissues. The two main types of adipose tissues are the white adipose tissue (WAT) and the brown adipose tissue (BAT). WAT primarily stores excess energy, whereas BAT is predominantly responsible for energy expenditure by non-shivering thermogenesis through the mitochondria. WAT in response to appropriate stimuli such as cold exposure and β-adrenergic agonist undergoes browning wherein it acts as BAT, which is characterized by the presence of a higher number of mitochondria. Mitochondrial dysfunction in adipocytes has been reported to have strong correlation with metabolic diseases, including obesity and type 2 diabetes. Dysfunction of mitochondria results in detrimental effects on adipocyte differentiation, lipid metabolism, insulin sensitivity, oxidative capacity, and thermogenesis, which consequently lead to metabolic diseases. Recent studies have shown that mitochondrial function can be improved by using thiazolidinedione, mitochondria-targeted antioxidants, and dietary natural compounds; by performing exercise; and by controlling caloric restriction, thereby maintaining the metabolic homeostasis by inducing adaptive thermogenesis of BAT and browning of WAT. In this review, we focus on and summarize the molecular regulation involved in the improvement of mitochondrial function in adipose tissues so that strategies can be developed to treat metabolic diseases.

Genes associated with Type 2 Diabetes and vascular complications

Type 2 Diabetes (T2D) is a chronic disease associated with a number of micro- and macrovascular complications that increase the morbidity and mortality of patients. The risk of diabetic complications has a strong genetic component. To this end, we sought to evaluate the association of 40 single nucleotide polymorphisms (SNPs) in 21 candidate genes with T2D and its vascular complications in 503 T2D patients and 580 healthy controls. The genes were chosen because previously reported to be associated with T2D complications and/or with the aging process. We replicated the association of T2D risk with IGF2BP rs4402960 and detected novel associations with TERT rs2735940 and rs2736098. The addition of these SNPs to a model including traditional risk factors slightly improved risk prediction. After stratification of patients according to the presence/absence of vascular complications, we found significant associations of variants in the CAT, FTO, and UCP1 genes with diabetic retinopathy and nephropathy. Additionally, a variant in the ADIPOQ gene was found associated with macrovascular complications. Notably, these genes are involved in some way in mitochondrial biology and reactive oxygen species regulation. Hence, our findings strongly suggest a potential link between mitochondrial oxidative homeostasis and individual predisposition to diabetic vascular complications.

Healthy Nordic Diet Modulates the Expression of Genes Related to Mitochondrial Function and Immune Response in Peripheral Blood Mononuclear Cells from Subjects with Metabolic Syndrome-A SYSDIET Sub-Study

SCOPE

To explore the effect of a healthy Nordic diet on the global transcriptome profile in peripheral blood mononuclear cells (PBMCs) of subjects with metabolic syndrome.

METHODS AND RESULTS

Subjects with metabolic syndrome undergo a 18/24 week randomized intervention study comparing an isocaloric healthy Nordic diet with an average habitual Nordic diet served as control (SYSDIET study). Altogether, 68 participants are included. PBMCs are obtained before and after intervention and total RNA is subjected to global transcriptome analysis. 1302 probe sets are differentially expressed between the diet groups (p-value < 0.05). Twenty-five of these are significantly regulated (FDR q-value < 0.25) and are mainly involved in mitochondrial function, cell growth, and cell adhesion. The list of 1302 regulated probe sets is subjected to functional analyses. Pathways and processes involved in the mitochondrial electron transport chain, immune response, and cell cycle are downregulated in the healthy Nordic diet group. In addition, gene transcripts with common motifs for 42 transcription factors, including NFR1, NFR2, and NF-κB, are downregulated in the healthy Nordic diet group.

CONCLUSION

These results suggest that benefits of a healthy diet may be mediated by improved mitochondrial function and reduced inflammation.

Type 2 diabetes-induced hyposalivation of the submandibular gland through PINK1/Parkin-mediated mitophagy

Diabetes is often accompanied by dysfunction of salivary glands. However, the molecular mechanism remains unclear. The mechanisms that underlie diabetic hyposalivation were studied by db/db mice and SMG‐C6 cells. We found morphological changes and decreased stimulated salivary flow rates of the submandibular gland (SMG) in diabetic mice. We observed structural changes and dysfunction of mitochondria. More mitophagosomes and higher expression of autophagy‐related proteins were detected. Increased levels of proteins PINK1 and Parkin indicate that PINK1/Parkin‐mediated mitophagy was activated in diabetic SMG. Consistently, high glucose (HG) induced mitochondrial dysfunction and PINK1/Parkin‐mediated mitophagy in cultivated SMG‐C6 cells. HG also increased reactive oxygen species (ROS) and lessened activation of antioxidants in SMG‐C6 cells. In addition, HG lowered ERK1/2 phosphorylation and HG‐induced mitophagy was decreased after ERK1/2 was activated by LM22B‐10. Altogether, these data suggest that ROS played a crucial role in diabetes‐induced mitochondrial dysfunction and PINK1/Parkin‐mediated mitophagy and ERK1/2 was required in HG‐induced mitophagy in SMG.

Mitochondrial dysfunction in diabetes and the regulatory roles of antidiabetic agents on the mitochondrial function

The prevalence of type 2 diabetes mellitus (T2DM) is increasing rapidly with its associated morbidity and mortality. Many pathophysiological pathways such as oxidative stress, inflammatory responses, adipokines, obesity‐induced insulin resistance, improper insulin signaling, and beta cell apoptosis are associated with the development of T2DM. There is increasing evidence of the role of mitochondrial dysfunction in the onset of T2DM, particularly in relation to the development of diabetic complications. Here, the role of mitochondrial dysfunction in T2DM is reviewed together with its modulation by antidiabetic therapeutic agents, an effect that may be independent of their hypoglycemic effect.

Targeting mitochondrial dynamics by regulating Mfn2 for therapeutic intervention in diabetic cardiomyopathy

Increasing evidence has implicated the important role of mitochondrial pathology in diabetic cardiomyopathy (DCM), while the underlying mechanism remains largely unclear. The aim of this study was to investigate the role of mitochondrial dynamics in the pathogenesis of DCM and its underlying mechanisms.

Methods: Obese diabetic (db/db) and lean control (db/+) mice were used in this study. Mitochondrial dynamics were analyzed by transmission electron microscopy in vivo and by confocal microscopy in vitro.

Results: Diabetic hearts from 12-week-old db/db mice showed excessive mitochondrial fission and significant reduced expression of Mfn2, while there was no significant alteration or slight change in the expression of other dynamic-related proteins. Reconstitution of Mfn2 in diabetic hearts inhibited mitochondrial fission and prevented the progression of DCM. In an in-vitro study, cardiomyocytes cultured in high-glucose and high-fat (HG/HF) medium showed excessive mitochondrial fission and decreased Mfn2 expression. Reconstitution of Mfn2 restored mitochondrial membrane potential, suppressed mitochondrial oxidative stress and improved mitochondrial function in HG/HF-treated cardiomyocytes through promoting mitochondrial fusion. In addition, the down-regulation of Mfn2 expression in HG/HF-treated cardiomyocytes was induced by reduced expression of PPARα, which positively regulated the expression of Mfn2 by directly binding to its promoter.

Conclusion: Our study provides the first evidence that imbalanced mitochondrial dynamics induced by down-regulated Mfn2 contributes to the development of DCM. Targeting mitochondrial dynamics by regulating Mfn2 might be a potential therapeutic strategy for DCM.

Drug-Induced Mitochondrial Toxicity in the Geriatric Population: Challenges and Future Directions

Mitochondrial function declines with age, leading to a variety of age-related diseases (metabolic, central nervous system-related, cancer, etc.) and medication usage increases with age due to the increase in diseases. Drug-induced mitochondrial toxicity has been described for many different drug classes and can lead to liver, muscle, kidney and central nervous system injury and, in rare cases, to death. Many of the most prescribed medications in the geriatric population carry mitochondrial liabilities. We have demonstrated that, over the past decade, each class of drugs that demonstrated mitochondrial toxicity contained drugs with both more and less adverse effects on mitochondria. As patient treatment is often essential, we suggest using medication(s) with the best safety profile and the avoidance of concurrent usage of multiple medications that carry mitochondrial liabilities. In addition, we also recommend lifestyle changes to further improve one’s mitochondrial function, such as weight loss, exercise and nutrition.

Urinary mitochondrial DNA: A potential early biomarker of diabetic nephropathy

BACKGROUND

Mitochondrial dysfunction and chronic sterile inflammation are common features of type 2 diabetes. Therefore, we aimed to investigate whether mitochondrial DNA (mtDNA) could be a biomarker implicated in the progression of type 2 diabetes and diabetic nephropathy and explore the underlying mechanism.

MATERIAL AND METHODS

We developed a method for relative quantification of mtDNA content in clinical practice. qRT-PCR was used to measure the mtDNA content both in vivo in CD-1 mice with diabetes induction by streptozotocin and in vitro in murine endothelial cells and conditionally immortalized mouse podocytes. By pumping mtDNA into the mouse circulation, the effect of mtDNA on the kidney was assessed in mice. In patients with type 2 diabetes (n = 42; 24 males; mean age 57.9 ± 12.00 years), plasma mtDNA was evaluated.

RESULTS

Plasma mtDNA content was significantly decreased in patients with type 2 diabetes, particularly those with significant proteinuria. In vitro, high glucose treatment suppressed intracellular mtDNA content and facilitated the extracellular release of mtDNA, so excessive circulatory mtDNA induced by high glucose might be filtered through the kidney and then into urine. Indeed, urinary mtDNA content was significantly increased in both diabetic patients and mice. Moreover, by pumping excess mtDNA into circulation in mice, filtered mtDNA could trigger inflammation and induce kidney injury.

CONCLUSION

Excessive mtDNA filtered through the kidney under diabetic conditions may be involved in chronic renal inflammation. Reduced plasma mtDNA content and increased urinary mtDNA/creatinine ratio might play a potential role as an early biomarker of diabetic nephropathy.

Mitochondria in precision medicine; linking bioenergetics and metabolomics in platelets

Mitochondria possess reserve bioenergetic capacity, supporting protection and resilience in the face of disease. Approaches are limited to understand factors that impact mitochondrial functional reserve in humans. We applied the mitochondrial stress test (MST) to platelets from healthy subjects and found correlations between energetic parameters and mitochondrial function. These parameters were not correlated with mitochondrial complex I-IV activities, however, suggesting that other factors affect mitochondrial bioenergetics and metabolism. Platelets from African American patients with sickle cell disease also differed from controls, further showing that other factors impact mitochondrial bioenergetics and metabolism. To test for correlations of platelet metabolites with energetic parameters, we performed an integrated analysis of metabolomics and MST parameters. Subsets of metabolites, including fatty acids and xenobiotics correlated with mitochondrial parameters. The results establish platelets as a platform to integrate bioenergetics and metabolism for analysis of mitochondrial function in precision medicine.

Candida sp. Infections in Patients with Diabetes Mellitus

Candidiasis has increased substantially worldwide over recent decades and is a significant cause of morbidity and mortality, especially among critically ill patients. Diabetes mellitus (DM) is a metabolic disorder that predisposes individuals to fungal infections, including those related to Candida sp., due to a immunosuppressive effect on the patient. This review aims to discuss the latest studies regarding the occurrence of candidiasis on DM patients and the pathophysiology and etiology associated with these co-morbidities. A comprehensive review of the literature was undertaken. PubMed, Scopus, Elsevier’s ScienceDirect, and Springer’s SpringerLink databases were searched using well-defined search terms. Predefined inclusion and exclusion criteria were applied to classify relevant manuscripts. Results of the review show that DM patients have an increased susceptibility to Candida sp. infections which aggravates in the cases of uncontrolled hyperglycemia. The conclusion is that, for these patients, the hospitalization periods have increased and are commonly associated with the prolonged use of indwelling medical devices, which also increase the costs associated with disease management.

Mitochondrial-Derived Peptides Are Down Regulated in Diabetes Subjects

Background: Mitochondrial dysfunction is implicated in the pathogenesis of Type 2 diabetes (T2D) and the development of diabetes related complications such as cardiovascular disease and stroke. Mitochondria produce several small polypeptides that may influence mitochondrial function and may impact on insulin sensitivity, such as humanin (HN) and the mitochondrial open reading frame of the 12S rRNA type-c (MOTS-c) that are mitochondrial derived proteins (MDP). The aim of this study was to determine MDP in normal, prediabetes and diabetes subjects. Subjects and Measurements: In this cross-sectional study, we analyzed the serum concentrations of MDP and adiponectin (ADP) in 225 subjects: normal (n = 68), pre-diabetes (n = 33), T2D less than (good control; n = 31), and greater than HbA1c 7% (poor control; n = 93) subjects. The relationship of serum MDP and ADP concentrations with biochemical and anthropometric measurements were performed and assessed by multilinear regression. Results: Serum HN concentrations were lower in T2D (p < 0.0001) and negatively correlated with age (p < 0.0001), HbA1c (p < 0.0001), glucose (p < 0.0001), triglycerides (p < 0.003), ALT (p < 0.004), and TG/HDL ratio (p < 0.001). Circulating HN levels were positively correlated to cholesterol (p < 0.017), LDL (p < 0.001), and HDL (p < 0.001). Linear regression analysis showed that HbA1c and ALT were two independent predictors of circulating HN. Similarly, serum MOTS-c was significantly lower in T2D subjects compared to controls (p < 0.007). Circulating MOTS-c positively correlated with BMI (p < 0.035), total cholesterol (p < 0.0001), and LDL (p < 0.001) and negatively correlated with age (p < 0.002), HbA1c (p < 0.001), and glucose (p < 0.002). Serum ADP concentrations were lower in T2D (p < 0.002) and negatively correlated with HbA1c (p < 0.001), weight (p < 0.032) TG (p < 0.0001), and ALT (p < 0.0001); and positively correlated with HDL (p < 0.0001) and HN (p < 0.003). Linear regression analysis showed that HbA1c and weight were two independent predictors of circulating ADP. Multilinear regression showed that HN and MOT-c correlated with each other, and only HN correlated with HbA1c. Conclusion: The MDPs HN and MOT-c, similar to ADP, are decreased in T2D and correlate with HbA1c. The data provide an additional evidence that mitochondrial dysfunction contributes to glycemic dysregulation and metabolic defects in T2D.

Impact of Metabolic Syndrome on Neuroinflammation and the Blood-Brain Barrier

Metabolic syndrome, which includes diabetes and obesity, is one of the most widespread medical conditions. It induces systemic inflammation, causing far reaching effects on the body that are still being uncovered. Neuropathologies triggered by metabolic syndrome often result from increased permeability of the blood-brain-barrier (BBB). The BBB, a system designed to restrict entry of toxins, immune cells, and pathogens to the brain, is vital for proper neuronal function. Local and systemic inflammation induced by obesity or type 2 diabetes mellitus can cause BBB breakdown, decreased removal of waste, and increased infiltration of immune cells. This leads to disruption of glial and neuronal cells, causing hormonal dysregulation, increased immune sensitivity, or cognitive impairment depending on the affected brain region. Inflammatory effects of metabolic syndrome have been linked to neurodegenerative diseases. In this review, we discuss the effects of obesity and diabetes-induced inflammation on the BBB, the roles played by leptin and insulin resistance, as well as BBB changes occurring at the molecular level. We explore signaling pathways including VEGF, HIFs, PKC, Rho/ROCK, eNOS, and miRNAs. Finally, we discuss the broader implications of neural inflammation, including its connection to Alzheimer's disease, multiple sclerosis, and the gut microbiome.

Mitochondria as a therapeutic target for common pathologies

Although the development of mitochondrial therapies has largely focused on diseases caused by mutations in mitochondrial DNA or in nuclear genes encoding mitochondrial proteins, it has been found that mitochondrial dysfunction also contributes to the pathology of many common disorders, including neurodegeneration, metabolic disease, heart failure, ischaemia-reperfusion injury and protozoal infections. Mitochondria therefore represent an important drug target for these highly prevalent diseases. Several strategies aimed at therapeutically restoring mitochondrial function are emerging, and a small number of agents have entered clinical trials. This Review discusses the opportunities and challenges faced for the further development of mitochondrial pharmacology for common pathologies.

Quercetin preserves redox status and stimulates mitochondrial function in metabolically-stressed HepG2 cells

Hyperglycemia augments formation of intracellular reactive oxygen species (ROS) with associated mitochondrial damage and increased risk of insulin resistance in type 2 diabetes. We examined whether quercetin could reverse chronic high glucose-induced oxidative stress and mitochondrial dysfunction. Following long-term high glucose treatment, complex I activity was significantly decreased in isolated mitochondria from HepG2 cells. Quercetin dose-dependently recovered complex I activity and lowered cellular ROS generation under both high and normal glucose conditions. Respirometry studies showed that quercetin could counteract the detrimental increase in inner mitochondrial membrane proton leakage resulting from high glucose while it increased oxidative respiration, despite a decrease in electron transfer system (ETS) capacity, and lower non-ETS oxygen consumption. A quercetin-stimulated increase in cellular NAD⁺/NADH was evident within 2 h and a two-fold increase in PGC-1α mRNA within 6 h, in both normal and high glucose conditions. A similar pattern was also found for the mRNA expression of the repulsive guidance molecule b (RGMB) and its long non-coding RNA (lncRNA) RGMB-AS1 with quercetin, indicating a potential change of the glycolytic phenotype and suppression of aberrant cellular growth which is characteristic of the HepG2 cells. Direct effects of quercetin on PGC-1α activity were minimal, as quercetin only weakly enhanced PGC-1α binding to PPARα in vitro at higher concentrations. Our results suggest that quercetin may protect mitochondrial function from high glucose-induced stress by increasing cellular NAD⁺/NADH and activation of PGC-1α-mediated pathways. Lower ROS in combination with improved complex I activity and ETS coupling efficiency under conditions of amplified oxidative stress could reinforce mitochondrial integrity and improve redox status, beneficial in certain metabolic diseases.

Bioactive food and exercise in chronic kidney disease: Targeting the mitochondria

Chronic kidney disease (CKD), which affects 10%-15% of the population, associates with a range of complications-such as cardiovascular disease, frailty, infections, muscle and bone disorders and premature ageing-that could be related to alterations of mitochondrial number, distribution, structure and function. As mitochondrial biogenesis, bioenergetics and the dynamic mitochondrial networks directly or indirectly regulate numerous intra- and extracellular functions, the mitochondria have emerged as an important target for interventions aiming at preventing or improving the treatment of complications in CKD. In this review, we discuss the possible role of bioactive food compounds and exercise in the modulation of the disturbed mitochondrial function in a uraemic milieu.

Protocatechuic Acid Ameliorated Palmitic-Acid-Induced Oxidative Damage in Endothelial Cells through Activating Endogenous Antioxidant Enzymes via an Adenosine-Monophosphate-Activated-Protein-Kinase-Dependent Pathway

Protocatechuic acid (PCA, 3,4-dihydroxybenzoic acid), the main metabolite of anthocyanins, is widely distributed in fruits and vegetables and has been reported to possess a strong antioxidant activity. Herein, we aimed to investigate the protective effect of PCA against high palmitic-acid (PA)-induced oxidative damage and the underling molecular mechanisms in human umbilical vein endothelial cells (HUVECs). PCA reduced the levels of intracellular reactive oxygen species and malondialdehyde and increased the activities of endogenous antioxidant enzymes, including superoxide dismutase, glutathione peroxidase 1, and heme oxygenase 1 (HO-1). Metabolomic analysis showed that PCA affected numerous metabolites, especially some of which were related with energy metabolism. PCA also upregulated the phosphorylation of adenosine-monophosphate-activated protein kinase (AMPK) at Thr¹⁷² through activating liver kinase B1 and then promoted the expression of p-Nrf2 and HO-1. Moreover, PCA reversed the decreased expression of peroxisome proliferator-activated receptor γ coactivator 1α and significantly increased the mitochondrial density. Collectively, these results demonstrated that PCA attenuated PA-induced oxidative damage in HUVECs via an AMPK-dependent pathway.

Dicarbonyl Stress and Glyoxalase-1 in Skeletal Muscle: Implications for Insulin Resistance and Type 2 Diabetes

Glyoxalase-1 (GLO1) is a ubiquitously expressed cytosolic protein which plays a role in the natural maintenance of cellular health and is abundantly expressed in human skeletal muscle. A consequence of reduced GLO1 protein expression is cellular dicarbonyl stress, which is elevated in obesity, insulin resistance and type 2 diabetes (T2DM). Both in vitro and pre-clinical models suggest dicarbonyl stress per se induces insulin resistance and is prevented by GLO1 overexpression, implicating a potential role for GLO1 therapy in insulin resistance and type 2 diabetes (T2DM). Recent work has identified the therapeutic potential of novel natural agents as a GLO1 inducer, which resulted in improved whole-body metabolism in obese adults. Given skeletal muscle is a major contributor to whole-body glucose, lipid, and protein metabolism, such GLO1 inducers may act, in part, through mechanisms in skeletal muscle. Currently, investigations examining the specificity of dicarbonyl stress and GLO1 biology in human skeletal muscle are lacking. Recent work from our lab indicates that dysregulation of GLO1 in skeletal muscle may underlie human insulin resistance and that exercise training may impart therapeutic benefits. This minireview will summarize the existing human literature examining skeletal muscle GLO1 and highlight the emerging therapeutic concepts for GLO1 gain-of-function in conditions such as insulin resistance and cardiometabolic disease.

Altered mitochondrial function in insulin-deficient and insulin-resistant states

Diabetes profoundly alters fuel metabolism; both insulin deficiency and insulin resistance are characterized by inefficient mitochondrial coupling and excessive production of reactive oxygen species (ROS) despite their association with normal to high oxygen consumption. Altered mitochondrial function in diabetes can be traced to insulin's pivotal role in maintaining mitochondrial proteome abundance and quality by enhancing mitochondrial biogenesis and preventing proteome damage and degradation, respectively. Although insulin enhances gene transcription, it also induces decreases in amino acids. Thus, if amino acid depletion is not corrected, increased transcription will not result in enhanced translation of transcripts to proteins. Mitochondrial biology varies among tissues, and although most studies in humans are performed in skeletal muscle, abnormalities have been reported in multiple organs in preclinical models of diabetes. Nutrient excess, especially fat excess, alters mitochondrial physiology by driving excess ROS emission that impairs insulin action. Excessive ROS irreversibly damages DNA and proteome with adverse effects on cellular functions. In insulin-resistant people, aerobic exercise stimulates both mitochondrial biogenesis and efficiency concurrent with enhancement of insulin action. This Review discusses the association between both insulin-deficient and insulin-resistant diabetes and alterations in mitochondrial proteome homeostasis and function that adversely affect cellular functions, likely contributing to many diabetic complications.

Is autophagy associated with diabetes mellitus and its complications? A review

Diabetes mellitus (DM) is an endocrine disorder. In coming decades it will be one of the leading causes of death globally. The key factors in the pathogenesis of diabetes are cellular injuries and disorders of energy metabolism leading to severe diabetic complications. Recent studies have confirmed that autophagy plays a pivotal role in diabetes and its complications. It has been observed that autophagy regulates the normal function of pancreatic β cells and insulin-target tissues, such as skeletal muscle, liver, and adipose tissue. This review will summarize the regulation of autophagy in diabetes and its complications, and explore how this process would emerge as a potential therapeutic target for diabetes treatment.

Effect of the antioxidant idebenone on maternal diabetes-induced embryo alterations during early organogenesis

RESEARCH QUESTION

Can maternal treatments with idebenone, a structural analogue of coenzyme Q10, prevent alterations on markers of proinflammatory-prooxidant processes, on the expression of genes involved in mitochondrial biogenesis and function, and on the apoptotic rate in embryos from mild diabetic rats?

DESIGN

A mild diabetic rat model was induced by neonatal-streptozotocin administration (90 mg/kg subcutaneously). Female diabetic rats and controls were mated with healthy males. From day 1 of pregnancy, control and diabetic rats were orally treated with idebenone (100 mg/kg daily). On day 10.5 of gestation, the embryos were explanted and prepared for immunohistochemical studies, for the evaluation of gene expression by reverse transcription polymerase chain reaction and for TdT (terminal deoxynucleotidyl transferase)-mediated dUDP nick-end-labelling assay analysis.

RESULTS

Embryos from mild diabetic rats showed increased levels of nitrated proteins, 4-hydroxynonenal and matrix metalloproteinase 9, which were prevented by idebenone administration. We also found a decreased embryonic expression of cytochrome c oxidase and reduced mRNA levels of peroxisome proliferator activated receptor-γ coactivator-1-α and nuclear respiratory factor-1, both of which were prevented by idebenone administration to the diabetic pregnant rats. Embryos from mild diabetic rats also showed an increased apoptotic rate, which was diminished by idebenone treatment.

CONCLUSION

Maternal idebenone treatment ameliorates altered parameters related to the prooxidant-proinflammatory environment found in embryos from mild diabetic rats, suggesting a putative treatment to prevent diabetes-induced embryo alterations.

Longitudinal associations of lifetime adiposity with leukocyte telomere length and mitochondrial DNA copy number

Adiposity may cause adverse health outcomes by increasing oxidative stress and systemic inflammation, which can be reflected by altered telomere length (TL) and mitochondrial DNA copy number (mtCN) in peripheral blood leukocytes. However, little is known about the influence of lifetime adiposity on TL and mtCN in later life. This study was performed to investigate the associations of lifetime adiposity with leukocyte TL and mtCN in 9613 participants from the Nurses' Health Study. A group-based trajectory modelling approach was used to create trajectories of body shape from age 5 through 60 years, and a genetic risk score (GRS) was created based on 97 known adiposity susceptibility variants. Associations of body shape trajectories and GRS with dichotomized TL and mtCN were assessed by logistic regression models. After adjustment for lifestyle and dietary factors, compared with the lean-stable group, the lean-marked increase group had higher odds of having below-median TL (OR = 1.18, 95% CI 1.04, 1.35; P = 0.01), and the medium-marked increase group had higher odds of having below-median mtCN (OR = 1.28, 95% CI 1.00, 1.64; P = 0.047). There was a suggestive trend toward lower mtCN across the GRS quartiles (P for trend = 0.07). In conclusion, telomere attrition may be accelerated by marked weight gain in middle life, whereas mtCN is likely to be reduced persistently by adiposity over the life course. The findings indicate the importance of lifetime weight management to preserve functional telomeres and mitochondria.

Antidiabetic effects and erythrocyte stabilization by red cabbage extract in streptozotocin-treated rats

The protective effect of red cabbage extract (RCE) was evaluated in rats with streptozotocin-induced diabetes, assessing a probable role of this extract in the prevention of erythrocyte impairments associated with a high risk of vascular complications in diabetes. RCE was analyzed by ultrahigh performance liquid chromatography and mass spectrometry, and 11 anthocyanins, 3 hydroxybenzoic acids and 9 hydroxycinnamic acids were identified. Type 1 diabetes was induced by streptozotocin (60 mg kg^-1) in Wistar male rats (n = 8 per group). After 7 days of acclimatization, streptozotocin-treated rats were given RCE (800 mg kg^-1) or vehicle by intragastric administration for 4 weeks. The RCE treatment lowered blood glucose, and glycated and fetal hemoglobin concentrations and improved glucose tolerance as well as considerably raised serum insulin, proinsulin and C-peptide levels in streptozotocin-treated rats. Simultaneously, RCE improved pancreatic islet morphology, increasing the amount of pancreatic β-cells in diabetic animals. The RCE administration prevented anemia in rats with streptozotocin-induced diabetes, enhanced erythrocyte resistance to acid hemolysis, and normalized reticulocyte production as well as sialic acid content in erythrocyte membranes. The enhanced lectin-induced erythrocyte aggregation in diabetic rats was significantly lowered after the RCE treatment. RCE demonstrated a significant antioxidant effect, decreasing MDA and protein carbonyl contents and increasing catalase and glutathione peroxidase activities in erythrocytes. These results indicate that RCE can be considered as a promising candidate for use as a drug or a food supplement to alleviate diabetes and its vascular complications.

Recovery of Corneal Sensitivity and Increase in Nerve Density and Wound Healing in Diabetic Mice After PEDF Plus DHA Treatment

Diabetic keratopathy decreases corneal sensation and tear secretion and delays wound healing after injury. In the current study, we tested the effect of treatment with pigment epithelium-derived factor (PEDF) in combination with docosahexaenoic acid (DHA) on corneal nerve regeneration in a mouse model of diabetes with or without corneal injury. The study was performed in streptozotocin-induced diabetic mice (C57BL/6). Ten weeks after streptozotocin injection, diabetic mice showed significant decreases of corneal sensitivity, tear production, and epithelial subbasal nerve density when compared with age-matched normal mice. After diabetic mice were wounded in the right eye and treated in both eyes with PEDF+DHA for 2 weeks, there was a significant increase in corneal epithelial nerve regeneration and substance P-positive nerve density in both wounded and unwounded eyes compared with vehicle-treated corneas. There also was elevated corneal sensitivity and tear production in the treated corneas compared with vehicle. In addition, PEDF+DHA accelerated corneal wound healing, selectively recruited type 2 macrophages, and prevented neutrophil infiltration in diabetic wounded corneas. These results suggest that topical treatment with PEDF+DHA promotes corneal nerve regeneration and wound healing in diabetic mice and could potentially be exploited as a therapeutic option for the treatment of diabetic keratopathy.

The Impact of Environmental Factors in Influencing Epigenetics Related to Oxidative States in the Cardiovascular System

Oxidative states exert a significant influence on a wide range of biological and molecular processes and functions. When their balance is shifted towards enhanced amounts of free radicals, pathological phenomena can occur, as the generation of reactive oxygen species (ROS) in tissue microenvironment or in the systemic circulation can be detrimental. Epidemic chronic diseases of western societies, such as cardiovascular disease, obesity, and diabetes correlate with the imbalance of redox homeostasis. Current advances in our understanding of epigenetics have revealed a parallel scenario showing the influence of oxidative stress as a major regulator of epigenetic gene regulation via modification of DNA methylation, histones, and microRNAs. This has provided both the biological link and a potential molecular explanation between oxidative stress and cardiovascular/metabolic phenomena. Accordingly, in this review, we will provide current insights on the physiological and pathological impact of changes in oxidative states on cardiovascular disorders, by specifically focusing on the influence of epigenetic regulation. A special emphasis will highlight the effect on epigenetic regulation of human's current life habits, external and environmental factors, including food intake, tobacco, air pollution, and antioxidant-based approaches. Additionally, the strategy to quantify oxidative states in humans in order to determine which biological marker could best match a subject's profile will be discussed.

Mitochondrial dysfunction and oxidative stress in metabolic disorders - A step towards mitochondria based therapeutic strategies

Mitochondria are the powerhouses of the cell and are involved in essential functions of the cell, including ATP production, intracellular Ca2+ regulation, reactive oxygen species production & scavenging, regulation of apoptotic cell death and activation of the caspase family of proteases. Mitochondrial dysfunction and oxidative stress are largely involved in aging, cancer, age-related neurodegenerative and metabolic syndrome. In the last decade, tremendous progress has been made in understanding mitochondrial structure, function and their physiology in metabolic syndromes such as diabetes, obesity, stroke and hypertension, and heart disease. Further, progress has also been made in developing therapeutic strategies, including lifestyle interventions (healthy diet and regular exercise), pharmacological strategies and mitochondria-targeted approaches. These strategies were mainly focused to reduce mitochondrial dysfunction and oxidative stress and to maintain mitochondrial quality in metabolic syndromes. The purpose of our article is to highlight the recent progress on the mitochondrial role in metabolic syndromes and also summarize the progress of mitochondria-targeted molecules as therapeutic targets to treat metabolic syndromes. This article is part of a Special Issue entitled: Oxidative Stress and Mitochondrial Quality in Diabetes/Obesity and Critical Illness Spectrum of Diseases - edited by P. Hemachandra Reddy.

A fast method for high resolution oxymetry study of skeletal muscle mitochondrial respiratory chain complexes

High resolution oxymetry study (HROS) of skeletal muscle usually requires 90-120 min preparative phase (dissection, permeabilization and washing). This work reports on the suitability of a rapid muscle preparation which by-passes this long preparation. For a few seconds only, muscle biopsy from pigs is submitted to gentle homogenization at 8000 rotations per minute using an ultra-dispersor apparatus. Subsequent HROS is performed using FCCP instead of ADP, compounds crossing and not plasma membrane, respectively. This simplified procedure compares favorably with classical (permeabilized fibers) HROS in terms of respiratory chain complex activities. Mitochondria from cells undergoing ultradispersion were functionally preserved as attested by relative inefficacy of added cytochrome C (not crossing intact mitochondrial outer membrane) to stimulate mitochondrial respiration. Responsiveness of respiration to ADP (in the absence of FCCP) suggested that these intact mitochondria were outside cells disrupted by ultradispersion or within cells permeated by this procedure.

Therapeutic Strategies for Mitochondrial Dysfunction and Oxidative Stress in Age-Related Metabolic Disorders

Mitochondria are complex, intercellular organelles present in the cells and are involved in multiple roles including ATP formation, free radicals generation and scavenging, calcium homeostasis, cellular differentiation, and cell death. Many studies depicted the involvement of mitochondrial dysfunction and oxidative damage in aging and pathogenesis of age-related metabolic disorders and neurodegenerative diseases. Remarkable advancements have been made in understanding the structure, function, and physiology of mitochondria in metabolic disorders such as diabetes, obesity, cardiovascular diseases, and stroke. Further, much progress has been done in the improvement of therapeutic strategies, including lifestyle interventions, pharmacological, and mitochondria-targeted therapeutic approaches. These strategies were mainly focused to reduce the mitochondrial dysfunction caused by oxidative stress and to retain the mitochondrial health in various diseases. In this chapter, we have highlighted the involvement of mitochondrial dysfunction in the pathophysiology of various disorders and recent progress in the development of mitochondria-targeted molecules as therapeutic measures for metabolic disorders.

Potential Biochemical Mechanisms of Lung Injury in Diabetes

Accumulating evidence has shown that the lung is one of the target organs for microangiopathy in patients with either type 1 or type 2 diabetes mellitus (DM). Diabetes is associated with physiological and structural abnormalities in the diabetic lung concurrent with attenuated lung function. Despite intensive investigations in recent years, the pathogenic mechanisms of diabetic lung injury remain largely elusive. In this review, we summarize currently postulated mechanisms of diabetic lung injury. We mainly focus on the pathogenesis of diabetic lung injury that implicates key pathways, including oxidative stress, non-enzymatic protein glycosylation, polyol pathway, NF-κB pathway, and protein kinase c pathway. We also highlight that while numerous studies have mainly focused on tissue or cell damage in the lung, studies focusing on mitochondrial dysfunction in the diabetic lung have remained sketchy. Hence, further understanding of mitochondrial mechanisms of diabetic lung injury should provide invaluable insights into future therapeutic approaches for diabetic lung injury.

Modulation of VEGF signaling in a mouse model of diabetes by xanthohumol and 8-prenylnaringenin: Unveiling the angiogenic paradox and metabolism interplay

SCOPE

Imbalance in kidney and heart neovascularization is common in type2 diabetes (T2DM) patients. Nevertheless, the mechanisms governing this angiogenic paradox have not been elucidated. Xanthohumol (XN) and 8-prenylnaringenin (8PN) beer polyphenols modulate angiogenesis, being thus targets for T2DM-related complications. Our work examined whether polyphenols consumption affects angiogenic paradox and metabolism in a T2DM mouse model.

METHODS AND RESULTS

An increase in kidney and a reduction in left ventricle (LV) microvessels of diabetic C57Bl/6 mice were observed. XN consumption reduced angiogenesis, VEGFR-2 expression/activity, VEGF-A and phosphofructokinase-2/fructose-2,6-bisphosphatase-3 enzyme expression, a metabolic marker present in endothelial tip cells in T2DM mice kidney. 8PN had opposite effects in T2DM mice LV. These XN and 8PN effects were dependent on VEGF levels as revealed by in vitro assays. These findings were accompanied by tissue and plasma reduced expression levels of VEGF-B and its receptors, VEGFR1 and neuropilin-1, by both polyphenols.

CONCLUSION

Beer polyphenols modulate T2DM angiogenic paradox in a tissue-dependent manner. We also show for the first time that both polyphenols decreased VEGF-B pathway, which is implicated in endothelial-to-tissue lipid metabolism. Altogether, the effects of these polyphenols in the crosstalk between angiogenesis and metabolism render them potent agents for novel diabetic therapeutic interventions.

Phosphorus-31 Magnetic Resonance Spectroscopy: A Tool for Measuring In Vivo Mitochondrial Oxidative Phosphorylation Capacity in Human Skeletal Muscle

Skeletal muscle mitochondrial oxidative phosphorylation (OXPHOS) capacity, which is critically important in health and disease, can be measured in vivo and noninvasively in humans via phosphorus-31 magnetic resonance spectroscopy (³¹PMRS). However, the approach has not been widely adopted in translational and clinical research, with variations in methodology and limited guidance from the literature. Increased optimization, standardization, and dissemination of methods for in vivo ³¹PMRS would facilitate the development of targeted therapies to improve OXPHOS capacity and could ultimately favorably impact cardiovascular health. ³¹PMRS produces a noninvasive, in vivo measure of OXPHOS capacity in human skeletal muscle, as opposed to alternative measures obtained from explanted and potentially altered mitochondria via muscle biopsy. It relies upon only modest additional instrumentation beyond what is already in place on magnetic resonance scanners available for clinical and translational research at most institutions. In this work, we outline a method to measure in vivo skeletal muscle OXPHOS. The technique is demonstrated using a 1.5 Tesla whole-body MR scanner equipped with the suitable hardware and software for ³¹PMRS, and we explain a simple and robust protocol for in-magnet resistive exercise to rapidly fatigue the quadriceps muscle. Reproducibility and feasibility are demonstrated in volunteers as well as subjects over a wide range of functional capacities.

Mitochondria Damage and Kidney Disease

The kidney is a vital organ that demands an extraordinary amount of energy to actively maintain the body's metabolism, plasma hemodynamics, electrolytes and water homeostasis, nutrients reabsorption, and hormone secretion. Kidney is only second to the heart in mitochondrial count and oxygen consumption. As such, the health and status of the energy power house, the mitochondria, is pivotal to the health and proper function of the kidney. Mitochondria are heterogeneous and highly dynamic organelles and their functions are subject to complex regulations through modulation of its biogenesis, bioenergetics, dynamics and clearance within cell. Kidney diseases, either acute kidney injury (AKI) or chronic kidney disease (CKD), are important clinical issues and global public health concerns with high mortality rate and socioeconomic burden due to lack of effective therapeutic strategies to cure or retard the progression of the diseases. Mitochondria-targeted therapeutics has become a major focus for modern research with the belief that maintaining mitochondria homeostasis can prevent kidney pathogenesis and disease progression. A better understanding of the cellular and molecular events that govern mitochondria functions in health and disease will potentially lead to improved therapeutics development.

The Role of Reactive Oxygen Species in β-Adrenergic Signaling in Cardiomyocytes from Mice with the Metabolic Syndrome

The metabolic syndrome is associated with prolonged stress and hyperactivity of the sympathetic nervous system and afflicted subjects are prone to develop cardiovascular disease. Under normal conditions, the cardiomyocyte response to acute β-adrenergic stimulation partly depends on increased production of reactive oxygen species (ROS). Here we investigated the interplay between beta-adrenergic signaling, ROS and cardiac contractility using freshly isolated cardiomyocytes and whole hearts from two mouse models with the metabolic syndrome (high-fat diet and ob/ob mice). We hypothesized that cardiomyocytes of mice with the metabolic syndrome would experience excessive ROS levels that trigger cellular dysfunctions. Fluorescent dyes and confocal microscopy were used to assess mitochondrial ROS production, cellular Ca2+ handling and contractile function in freshly isolated adult cardiomyocytes. Immunofluorescence, western blot and enzyme assay were used to study protein biochemistry. Unexpectedly, our results point towards decreased cardiac ROS signaling in a stable, chronic phase of the metabolic syndrome because: β-adrenergic-induced increases in the amplitude of intracellular Ca2+ signals were insensitive to antioxidant treatment; mitochondrial ROS production showed decreased basal rate and smaller response to β-adrenergic stimulation. Moreover, control hearts and hearts with the metabolic syndrome showed similar basal levels of ROS-mediated protein modification, but only control hearts showed increases after β-adrenergic stimulation. In conclusion, in contrast to the situation in control hearts, the cardiomyocyte response to acute β-adrenergic stimulation does not involve increased mitochondrial ROS production in a stable, chronic phase of the metabolic syndrome. This can be seen as a beneficial adaptation to prevent excessive ROS levels.

Stem Cell-Derived, microRNA-Carrying Extracellular Vesicles: A Novel Approach to Interfering with Mesangial Cell Collagen Production in a Hyperglycaemic Setting

Extracellular vesicles (EVs) that are derived from stem cells are proving to be promising therapeutic options. We herein investigate the therapeutic potential of EVs that have been derived from different stem cell sources, bone-marrow (MSC) and human liver (HLSC), on mesangial cells (MCs) exposed to hyperglycaemia. By expressing a dominant negative STAT5 construct (ΔNSTAT5) in HG-cultured MCs, we have demonstrated that miR-21 expression is under the control of STAT5, which translates into Transforming Growth Factor beta (TGFβ) expression and collagen production. A number of approaches have been used to show that both MSC- and HLSC-derived EVs protect MCs from HG-induced damage via the transfer of miR-222. This resulted in STAT5 down-regulation and a decrease in miR-21 content, TGFβ expression and matrix protein synthesis within MCs. Moreover, we demonstrate that changes in the balance between miR-21 and miR-100 in the recipient cell, which are caused by the transfer of EV cargo, further contribute to providing beneficial effects. Interestingly, these effects were only detected in HG-cultured cells. Finally, it was found that HG reduced the expression of the nuclear encoded mitochondrial electron transport chain (ETC) components, CoxIV. It is worth noting that EV administration can rescue CoxIV expression in HG-cultured MCs. These results thus demonstrate that both MSC- and HLSC-derived EVs transfer the machinery needed to preserve MCs from HG-mediated damage. This occurs via the horizontal transfer of functional miR-222 which directly interferes with damaging cues. Moreover, our data indicate that the release of EV cargo into recipient cells provides additional therapeutic advantages against harmful mitochondrial signals.

Mitochondrial dysfunction and diabetic retinopathy

Mitochondrial dysfunction may predispose to the development of diabetes mellitus with the accompanying risk for developing diabetic retinopathy or may contribute directly to the diabetic metabolic dysregulation and thereby increase the risk of diabetic late complications including retinopathy. Diabetes mellitus in mitochondrial disease can lead to the development of vision threatening retinopathy, but visual acuity is often reduced secondary to neurological deficits resulting from the mitochondrial dysfunction. The relation between mitochondrial disease and diabetic retinopathy can be influenced by epigenetics where factors in the environment modify the expression of regulatory proteins coding for the elimination of reactive oxygen species.

Thyroid hormone induction of mitochondrial activity is coupled to mitophagy via ROS-AMPK-ULK1 signaling

Currently, there is limited understanding about hormonal regulation of mitochondrial turnover. Thyroid hormone (T3) increases oxidative phosphorylation (OXPHOS), which generates reactive oxygen species (ROS) that damage mitochondria. However, the mechanism for maintenance of mitochondrial activity and quality control by this hormone is not known. Here, we used both in vitro and in vivo hepatic cell models to demonstrate that induction of mitophagy by T3 is coupled to oxidative phosphorylation and ROS production. We show that T3 induction of ROS activates CAMKK2 (calcium/calmodulin-dependent protein kinase kinase 2, β) mediated phosphorylation of PRKAA1/AMPK (5' AMP-activated protein kinase), which in turn phosphorylates ULK1 (unc-51 like autophagy activating kinase 1) leading to its mitochondrial recruitment and initiation of mitophagy. Furthermore, loss of ULK1 in T3-treated cells impairs both mitophagy as well as OXPHOS without affecting T3 induced general autophagy/lipophagy. These findings demonstrate a novel ROS-AMPK-ULK1 mechanism that couples T3-induced mitochondrial turnover with activity, wherein mitophagy is necessary not only for removing damaged mitochondria but also for sustaining efficient OXPHOS.

Increased Hydration Can Be Associated with Weight Loss

This mini-review develops the hypothesis that increased hydration leads to body weight loss, mainly through a decrease in feeding, and a loss of fat, through increased lipolysis. The publications cited come from animal, mainly rodent, studies where manipulations of the central and/or the peripheral renin–angiotensin system lead to an increased drinking response and a decrease in body weight. This hypothesis derives from a broader association between chronic hypohydration (extracellular dehydration) and raised levels of the hormone angiotensin II (AngII) associated with many chronic diseases, such as obesity, diabetes, cancer, and cardiovascular disease. Proposed mechanisms to explain these effects involve an increase in metabolism due to hydration expanding cell volume. The results of these animal studies often can be applied to the humans. Human studies are consistent with this hypothesis for weight loss and for reducing the risk factors in the development of obesity and type 2 diabetes.