Mitochondrial alteration in type 2 diabetes and obesity: an epigenetic link

Targeting the 'DNA methylation mark': Analysis of early epigenetic-alterations in children chronically exposed to arsenic

Chronic exposure to arsenic causes adverse health effects in children. Aberrant epigenetic modifications including altered DNA methylation pattern are one of the major steps towards malignant transformation of cells. Our group has previously identified significant alteration in DNA methylation mark in arsenic exposed adults, affecting major biological pathways. Till date, no information is available exploring the altered DNA methylation mark in telomere regulation and altered mitochondrial functionality in association with DNA damage in arsenic-exposed children. Our study aims in identifying signature epigenetic pattern associated with telomere lengthening, mitochondrial functionality and DNA damage repair in children with special emphasis on DNA methylation. Biological samples (blood and urine) and drinking water were collected from the children aged between 5 and 16 years of arsenic exposed areas (N = 52) of Murshidabad district and unexposed areas (N = 50) of East Midnapur districts, West Bengal, India. Methylation-specific PCR was performed to analyse subtelomeric methylation status and promoter methylation status of target genes. Results revealed altered DNA methylation profile in the exposed children compared to unexposed. Promoter hypermethylation was observed in MLH1 and MSH2 (p < 0.05 and p < 0.001) indicating inefficiency in DNA damage repair. Hypomethylation in mitochondrial D-loop (p < 0.05) and TFAM promoter region (p < 0.05) along with increased mitochondrial DNA copy number among exposed children was also observed. Significant increase in telomere length and region specific subtelomeric hypermethylation (XpYp, p < 0.05) was found. Analysis of S-Adenosyl Methionine (SAM) and 8-oxoDG level revealed significant depletion of SAM (p < 0.001) and elevated oxidative DNA damage (p < 0.001) respectively in arsenic toxicity. Our study identified key methylation patterns in arsenic-exposed children which may act as an early predictive biomarker in the near future. Further in-depth studies involving large sample size and transcriptomic analysis are required for understanding the mechanistic details.

Mitochondrial dysfunction and epigenetics underlying the link between early-life nutrition and non-alcoholic fatty liver disease

Early-life malnutrition plays a critical role in foetal development and predisposes to metabolic diseases later in life, according to the concept of 'developmental programming'. Different types of early nutritional imbalance, including undernutrition, overnutrition and micronutrient deficiency, have been related to long-term metabolic disorders. Accumulating evidence has demonstrated that disturbances in nutrition during the period of preconception, pregnancy and primary infancy can affect mitochondrial function and epigenetic mechanisms. Moreover, even though multiple mechanisms underlying non-alcoholic fatty liver disease (NAFLD) have been described, in the past years, special attention has been given to mitochondrial dysfunction and epigenetic alterations. Mitochondria play a key role in cellular metabolic functions. Dysfunctional mitochondria contribute to oxidative stress, insulin resistance and inflammation. Epigenetic mechanisms have been related to alterations in genes involved in lipid metabolism, fibrogenesis, inflammation and tumorigenesis. In accordance, studies have reported that mitochondrial dysfunction and epigenetics linked to early-life nutrition can be important contributing factors in the pathogenesis of NAFLD. In this review, we summarise the current understanding of the interplay between mitochondrial dysfunction, epigenetics and nutrition during early life, which is relevant to developmental programming of NAFLD.

The role of mitochondria in myocardial damage caused by energy metabolism disorders: From mechanisms to therapeutics

Myocardial damage is the most serious pathological consequence of cardiovascular diseases and an important reason for their high mortality. In recent years, because of the high prevalence of systemic energy metabolism disorders (e.g., obesity, diabetes mellitus, and metabolic syndrome), complications of myocardial damage caused by these disorders have attracted widespread attention. Energy metabolism disorders are independent of traditional injury-related risk factors, such as ischemia, hypoxia, trauma, and infection. An imbalance of myocardial metabolic flexibility and myocardial energy depletion are usually the initial changes of myocardial injury caused by energy metabolism disorders, and abnormal morphology and functional destruction of the mitochondria are their important features. Specifically, mitochondria are the centers of energy metabolism, and recent evidence has shown that decreased mitochondrial function, caused by an imbalance in mitochondrial quality control, may play a key role in myocardial injury caused by energy metabolism disorders. Under chronic energy stress, mitochondria undergo pathological fission, while mitophagy, mitochondrial fusion, and biogenesis are inhibited, and mitochondrial protein balance and transfer are disturbed, resulting in the accumulation of nonfunctional and damaged mitochondria. Consequently, damaged mitochondria lead to myocardial energy depletion and the accumulation of large amounts of reactive oxygen species, further aggravating the imbalance in mitochondrial quality control and forming a vicious cycle. In addition, impaired mitochondria coordinate calcium homeostasis imbalance, and epigenetic alterations participate in the pathogenesis of myocardial damage. These pathological changes induce rapid progression of myocardial damage, eventually leading to heart failure or sudden cardiac death. To intervene more specifically in the myocardial damage caused by metabolic disorders, we need to understand the specific role of mitochondria in this context in detail. Accordingly, promising therapeutic strategies have been proposed. We also summarize the existing therapeutic strategies to provide a reference for clinical treatment and developing new therapies.

Role of Oxidative Stress and Inflammation in Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is one of the most common pregnancy complications. It is related to several gestational and fetal adverse outcomes. Moreover, women with GDM and their infants have a high risk of developing type 2 diabetes in the future. The pathogenesis of GDM is not completely understood; nevertheless, two factors that contribute to its development are oxidative stress and inflammation. Oxidative stress and inflammation are related; reactive oxygen species (ROS) production can activate inflammatory cells and enhance the production of inflammatory mediators. Inflammation, in turn, leads to an increased ROS release, causing a vicious circle to ensue. Inflammatory responses can be achieved via the activation of the NF-κB signaling pathway. Herein, we review the English literature regarding oxidative stress and inflammation evaluated simultaneously in the same population, attempting to identify mechanisms through which these factors contribute to the development of GDM. Furthermore, the modulation of oxidative stress and inflammation by different therapies used in women with GDM and in cell models of GDM is included in the review. Probiotics and nutrient supplementations have been shown to reduce biomarkers of inflammation and oxidative stress in vitro and in women with GDM.

Inhibition of the Proteasome Regulator PA28 Aggravates Oxidized Protein Overload in the Diabetic Rat Brain

Oxidized protein overloading caused by diabetes is one accelerating pathological pathway in diabetic encephalopathy development. To determine whether the PA28-regulated function of the proteasome plays a role in diabetes-induced oxidative damaged protein degradation, brain PA28α and PA28β interference experiments were performed in a high-fat diet (HFD) and streptozotocin (STZ)-induced rat model. The present results showed that proteasome activity was changed in the brains of diabetic rats, but the constitutive subunits were not. In vivo PA28α and PA28β inhibition via adeno-associated virus (AAV) shRNA infection successfully decreased PA28 protein levels and further exacerbated oxidized proteins load by regulating proteasome catalytic activity. These findings suggest that the proteasome plays a role in the elimination of oxidized proteins and that PA28 is functionally involved in the regulation of proteasome activity in vivo. This study suggests that abnormal protein turbulence occurring in the diabetic brain could be explained by the proteasome-mediated degradation pathway. Changes in proteasome activity regulator PA28 could be a reason to induce oxidative aggregation in diabetic brain. Proteasome regulator PA28 inhibition in vivo by AAV vector injection could aggravate oxidized proteins abundance in brain of HFD-STZ diabetic rat model.

Salvianolic acid A promotes mitochondrial biogenesis and mitochondrial function in 3T3-L1 adipocytes through regulation of the AMPK-PGC1α signalling pathway

Mitochondrial dysfunction is associated with insulin resistance and type 2 diabetes (T2DM). Decreased mitochondrial abundance and function were found in white adipose tissue (WAT) of T2DM patients. Therefore, promoting WAT mitochondrial biogenesis and improving adipocyte metabolism may be strategies to prevent and reverse T2DM. Salvianolic acid A (SAA) has been found to exert anti-diabetic and lipid disorder-improving effects. However whether SAA benefits mitochondrial biogenesis and function in adipose tissue is unclear. Here, we evaluated SAA's effect on mitochondrial biogenesis and function in 3T3-L1 adipocytes and investigated its potential regulatory mechanism. Results showed that SAA treatment significantly promoted the transcription and expression of peroxisome proliferator-activated receptor γ coactivator- 1α (PGC-1α), nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM). Meanwhile, SAA treatment significantly promoted mitochondrial biogenesis by increasing mitochondrial DNA (mtDNA) quantity, mitochondrial mass, and expression of mitochondrial respiratory chain enzyme complexes III and complex IV. These enhancements were accompanied by enhanced phosphorylation of AMPK and ACC and were suppressed by Compound C, a specific AMPK inhibitor. Furthermore, SAA treatment improved adipocytes mitochondrial respiration and stimulated ATP generation. These findings indicate that SAA exerts a potential therapeutic capacity against adipocytes mitochondrial dysfunction in diabetes by activating the AMPK-PGC-1α pathway.

Bioinformatics analysis of candidate genes and potential therapeutic drugs targeting adipose tissue in obesity

Obesity is a complex medical condition that affects multiple organs in the body. However, the underlying mechanisms of obesity, as well as its treatment, are largely unexplored. The focus of this research was to use bioinformatics to discover possible treatment targets for obesity. To begin, the GSE133099 database was used to identify 364 differentially expressed genes (DEGs). Then, DEGs were subjected to tissue-specific analyses and enrichment analyses, followed by the creation of a protein-protein interaction (PPI) network and generation of a drug-gene interaction database to screen key genes and potential future drugs targeting obesity. Findings have illustrated that the tissue-specific expression of neurologic markers varied significantly (34.7%, 52/150). Among these genes, Lep, ApoE, Fyn, and FN1 were the key genes observed in the adipocyte samples from obese patients relative to the controls. Furthermore, nine potential therapeutic drugs (dasatinib, ocriplasmin, risperidone, gemfibrozil, ritonavir, fluvastatin, pravastatin, warfarin, atorvastatin) that target the key genes were also screened and selected. To conclude the key genes discovered (Lep, ApoE, Fyn, and FN1), as well as 9 candidate drugs, could be used as therapeutic targets in treating obesity.

DEMETHYLATION REGULATOR 1 regulates DNA demethylation of the nuclear and mitochondrial genomes

Active DNA demethylation effectively modulates gene expression during plant development and in response to stress. However, little is known about the upstream regulatory factors that regulate DNA demethylation. We determined that the demethylation regulator 1 (demr1) mutant exhibits a distinct DNA methylation profile at selected loci queried by methylation-sensitive polymerase chain reaction and globally based on whole-genome bisulfite sequencing. Notably, the transcript levels of the DNA demethylase gene REPRESSOR OF SILENCING 1 (ROS1) were lower in the demr1 mutant. We established that DEMR1 directly binds to the ROS1 promoter in vivo and in vitro, and the methylation level in the DNA methylation monitoring sequence of ROS1 promoter decreased by 60% in the demr1 mutant. About 40% of the hyper-differentially methylated regions (DMRs) in the demr1 mutant were shared with the ros1-4 mutant. Genetic analysis indicated that DEMR1 acts upstream of ROS1 to positively regulate abscisic acid (ABA) signaling during seed germination and seedling establishment stages. Surprisingly, the loss of DEMR1 function also caused a rise in methylation levels of the mitochondrial genome, impaired mitochondrial structure and an early flowering phenotype. Together, our results show that DEMR1 is a novel regulator of DNA demethylation of both the nuclear and mitochondrial genomes in response to ABA and plant development in Arabidopsis.

Antidiabetic-activity sulfated polysaccharide from Chaetomorpha linum: Characteristics of its structure and effects on oxidative stress and mitochondrial function

A water-soluble polysaccharide from the green alga Chaetomorpha linum, designated CHS2, was obtained by water extraction, preparative anion-exchange and size-exclusion chromatography. Results of chemical and spectroscopic analyses showed that CHS2 was a sulfated rhamnogalactoarabinan, and its backbone was mainly constituted by 4-linked and 3,4-linked β-l-arabinopyranose with sulfate groups at C-2/C-3 of 4-linked β-l-arabinopyranose. The branching contained 4-linked, 6-linked β-d-galactopyranose and terminal rhamnose residues. Based on the inhibition of human islet amyloid polypeptide (hIAPP) aggregation and morphology change of hIAPP aggregates in in vitro tests, it was proved that CHS2 effectively inhibited the hIAPP aggregation and possessed strong antidiabetic activity. CHS2 was nearly no toxicity in NIT-1 cells and could attenuate hIAPP-induced cytotoxicity. CHS2 may significantly reduce the generation of intracellular reactive oxygen species and hIAPP aggregation-induced oxidative stress in NIT-1 cells. CHS2 was co-localized with mitochondria, and largely protected mitochondria function from hIAPP aggregation-induced damage through stabilizing mitochondrial membrane potential and enhancing the mitochondrial complex I, II or III activity and ATP level. The data demonstrated that CHS2 could have potential prospect to become an antidiabetic drug for type 2 diabetes mellitus treatment.

Clinical Characteristics and Management Strategies for Adult Obese Asthma Patients

The rates of asthma and obesity are increasing concurrently in the United States. Epidemiologic studies demonstrate that the incidence of asthma increases with obesity. Furthermore, obese individuals have asthma that is more severe, harder to control, and resistant to standard medications. In fact, specific asthma-obesity phenotypes have been identified. Various pathophysiologic mechanisms, including mechanical, inflammatory, metabolic and microbiome-associated, are at play in promulgating the obese-asthma phenotypes. While standard asthma medications, such as inhaled corticosteroids and biologics, are currently used to treat obese asthmatics, they may have limited effectiveness. Targeting the underlying aberrant processes, such as addressing steroid resistance, microbiome, metabolic and weight loss approaches, may be helpful.

Humanin and diabetes mellitus: A review of in vitro and in vivo studies

Humanin (HN) is a 24-amino acid mitochondrial-derived polypeptide with cyto-protective and anti-apoptotic effects that regulates the mitochondrial functions under stress conditions. Accumulating evidence suggests the role of HN against age-related diseases, such as Alzheimer’s disease. The decline in insulin action is a metabolic feature of aging and thus, type 2 diabetes mellitus is considered an age-related disease, as well. It has been suggested that HN increases insulin sensitivity, improves the survival of pancreatic beta cells, and delays the onset of diabetes, actions that could be deployed in the treatment of diabetes. The aim of this review is to present the in vitro and in vivo studies that examined the role of HN in insulin resistance and diabetes and to discuss its newly emerging role as a therapeutic option against those conditions.

FoxO transcription factors in mitochondrial homeostasis

Mitochondria play essential roles in cellular energetics, biosynthesis, and signaling transduction. Dysfunctional mitochondria have been implicated in different diseases such as obesity, diabetes, cardiovascular disease, nonalcoholic fatty liver disease, neurodegenerative disease, and cancer. Mitochondrial homeostasis is controlled by a triad of mitochondrial biogenesis, dynamics (fusion and fission), and autophagy (mitophagy). Studies have underscored FoxO transcription factors as key mitochondrial regulators. Specifically, FoxOs regulate mitochondrial biogenesis by dampening NRF1-Tfam and c-Myc-Tfam cascades directly, and inhibiting NAD-Sirt1-Pgc1α cascade indirectly by inducing Hmox1 or repressing Fxn and Urod. In addition, FoxOs mediate mitochondrial fusion (via Mfn1 and Mfn2) and fission (via Drp1, Fis1, and MIEF2), during which FoxOs elicit regulatory mechanisms at transcriptional, posttranscriptional (e.g. via miR-484/Fis1), and posttranslational (e.g. via Bnip3-calcineurin mediated Drp1 dephosphorylation) levels. Furthermore, FoxOs control mitochondrial autophagy in the stages of autophagosome formation and maturation (e.g. initiation, nucleation, and elongation), mitochondria connected to and engulfed by autophagosome (e.g. via PINK1 and Bnip3 pathways), and autophagosome-lysosome fusion to form autolysosome for cargo degradation (e.g. via Tfeb and cathepsin proteins). This article provides an up-to-date view of FoxOs regulating mitochondrial homeostasis and discusses the potential of targeting FoxOs for therapeutics.

Metformin improves epigenetic modification involved in oocyte growth and embryo development in polycystic ovary syndrome mice model

The possible relationship between dehydroepiandrosterone (DHEA)-induced polycystic ovary syndrome (PCOS) and epigenetic changes (ECs) leading to the impaired oocyte quality, has not been investigated yet. So, this study aimed to provide an insight into the relationship of the impaired oocyte quality with ECs in a mice DHEA-induced PCOS model and to further reveal the effect of metformin treatment. For this purpose, 80 female BALB/C mice were randomly divided into four equal groups, named as the control, sham, (DHEA) and DHEA + Metformin groups. The alterations in acetylation of H4K5 and H4K16, and in methylation of DNA (5MeC) and H3K9 were evaluated using immunocytochemical. Moreover, the expression of Hdac1, Hdac2, Dnmt1, and Dnmt3a genes involved in ECs were analyzed using reverse-transcription polymerase chain reaction. As well, the levels of mitochondrial membrane potential (MMP), oxidative stress (OS), embryo development, ovarian morphology, sexual hormone, ovulatory function, and AMPKα phosphorylation activity were compared in all the studied groups. Metformin attenuated the damages induced by DHEA as indicated by the normalized the estrous cycle, the improved ovarian morphology, the decreased sexual hormone and OS levels, and the increased MMP and AMPKα phosphorylation levels. In the metformin group, the Dnmt1, Dnmt3a, and Hdac2 genes have significantly upregulated compared to the DHEA group. However, metformin was found to have no effect on the expression level of Hdac1. In this regard, significant decrease and increase were observed in both the acetylated H4K16 and methylated H3K9 within MII oocytes in the DHEA + Metformin group compared with the DHEA group. Our results show that metformin could enhance the developmental competence of PCOS oocytes via reducing OS and ECs.

Diet normalization or caloric restriction as a preconception care strategy to improve metabolic health and oocyte quality in obese outbred mice

BACKGROUND

Maternal metabolic disorders are linked to reduced metabolic health and oocyte quality. Obese women are advised to lose weight before conception to increase pregnancy chances. However, as human studies show no univocal guidelines, more research is necessary to provide fundamental insights in the consequences of dietary weight loss on oocyte quality. Therefore, we investigated the impact of diet normalization or calorie restricted diet for two, four or six weeks, as preconception care intervention (PCCI), in obese mice on metabolic health and oocyte quality.

METHODS

Outbred female mice were fed a control (CTRL) or high-fat (HF) diet for 7 weeks (7w). Afterwards, HF-mice were put on different PCCIs, resulting in four treatment groups: 1) control diet up to 13w, 2) HF diet up to 13w (HF_HF), switch from a HF (7w) to 3) an ad libitum control diet (HF_CTRL) or 4) 30% calorie restricted control diet (HF_CR) for two, four or six weeks. Body weight, metabolic health, oocyte quality and overall fertility results were assessed.

RESULTS

Negative effects of HF diet on metabolic health, oocyte quality and pregnancy rates were confirmed. HF_CTRL mice progressively improved insulin sensitivity, glucose tolerance, serum insulin and cholesterol from PCCI w2 to w4. No further improvements in metabolic health were present at PCCI w6. However, PCCI w6 showed best oocyte quality improvements. Mature oocytes still showed elevated lipid droplet volume and mitochondrial activity but a significant reduction in ROS levels and ROS: active mitochondria ratio compared with HF_HF mice. HF_CR mice restored overall insulin sensitivity and glucose tolerance by PCCI w4. However, serum insulin, cholesterol and ALT remained abnormal. At PCCI w6, glucose tolerance was again reduced. However, only at PCCI w6, oocytes displayed reduced ROS levels and restored mitochondrial activity compared with HF_HF mice. In addition, at PCCI w6, both PCCI groups showed decreased mitochondrial ultrastructural abnormalities compared with the HF_HF group and restored pregnancy rates.

CONCLUSIONS

Diet normalization for 4 weeks showed to be the shortest, most promising intervention to improve metabolic health. Most promising improvements in oocyte quality were seen after 6 weeks of intervention in both PCCI groups. This research provides fundamental insights to be considered in developing substantiated preconception guidelines for obese women planning for pregnancy.

Mitochondrial-induced Epigenetic Modifications: From Biology to Clinical Translation

Mitochondria are maternally inherited semi-autonomous organelles that play a central role in redox balance, energy metabolism, control of integrated stress responses, and cellular homeostasis. The molecular communication between mitochondria and the nucleus is intricate and bidirectional in nature. Though mitochondrial genome encodes for several key proteins involved in oxidative phosphorylation, several regulatory factors encoded by nuclear DNA are prominent contributors to mitochondrial biogenesis and function. The loss of synergy between this reciprocal control of anterograde (nuclear to mitochondrial) and retrograde (mitochondrial to nuclear) signaling, triggers epigenomic imbalance and affects mitochondrial function and global gene expressions. Recent expansions of our knowledge on mitochondrial epigenomics have offered novel perspectives for the study of several non-communicable diseases including cancer. As mitochondria are considered beacons for pharmacological interventions, new frontiers in targeted delivery approaches could provide opportunities for effective disease management and cure through reversible epigenetic reprogramming. This review focuses on recent progress in the area of mitochondrial-nuclear cross-talk and epigenetic regulation of mitochondrial DNA methylation, mitochondrial micro RNAs, and post-translational modification of mitochondrial nucleoid-associated proteins that hold major opportunities for targeted drug delivery and clinical translation.

The effects of two iso-volume endurance training protocols on mitochondrial dysfunction in type 2 diabetic male mice

Purpose

Type 2diabetes(T2D) is one of the more common diseases in the world and has been widely spread. One of the suggested mechanisms in development of T2D, is mitochondrial dysfunction. The purpose of this study is to compare the effects of two endurance training protocols with low and moderate intensity on biogenesis and mitochondrial function, in Diabetic mice induced by high fat diet and Streptozotocin(STZ).

Methods

40 five week old mice divided to four groups including: health control (HC, n = 7), diabetic control (DC, n = 7), low endurance training (DLT, n = 7) and moderate endurance training (DMT, n = 7). DMT group ran at 5 m/min for an hour, 3 days a week on a treadmill, and DLT group ran at 3 m/min for an hour, 5 days a week on a treadmill for 8 weeks.

Results

The cytosolic content of PGC1α, Tfam and mitochondrial content of citrate synthase(Cs) and cytochrome c oxidase(Cox) in DC was significantly reduced compared to HC(P˂0.05). All of the parameters except for Cs in both DLT and DMT were increased compared to DC (P˂0.05), but there was no difference between them and the HC (P˃0.05). There was no difference in Cs enzyme between the DC and the DLT(P˃0.05), but it was significantly increased in the DMT(P˂0.05). There was a significantly difference between Cs enzyme in HC and DLT(P˂0.05), but there wasn't any significant difference between HC and DMT(P˃0.05).

Conclusions

The results showed that in same volume condition, both endurance training protocols improved the proteins involved in biogenesis and mitochondrial function in T2D mice and there was no significant difference between them.

The NLRP3 inflammasome as a bridge between neuro-inflammation in metabolic and neurodegenerative diseases

Evidence increasingly suggests that type 2 diabetes mellitus (T2DM) is a risk factor for neurodegenerative diseases (NDDs), such as Alzheimer's disease (AD) and Parkinson's disease (PD). These diseases share many pathological processes, including oxidative stress, local inflammation/neuroinflammation and chronic, low-grade (systemic) inflammation, which are exacerbated by aging, a common risk factor for T2DM and NDDs. Here, we focus on the link between chronic inflammation driven by peripheral metabolic disease and how this may impact neurodegeneration in AD and PD. We review the relationship between these common pathological processes in AD and PD from the perspective of the "pro-inflammatory" signaling of the nucleotide-binding oligomerization domain (NOD)-, leucine-rich repeat- (LRR)-, and pyrin domain-containing protein 3 (NLRP3) inflammasome complex. Since the need for effective disease-modifying therapies in T2DM, AD and PD is significant, the relationship between these diseases is important as a positive clinical impact on one may benefit the others. We briefly consider how novel strategies may target neuro-inflammation and provide potential therapies for AD and PD.

Changes in Body Weight, Physical Activity, and Lifestyle During the Semi-lockdown Period After the Outbreak of COVID-19 in China: An Online Survey

Objectives:

The outbreak of novel coronavirus (COVID-19) provided an opportunity to undertake an online survey to study the relationships between body weight changes with changes in physical activity and lifestyle during an unusual event of forced isolation, or quarantine.

Methods:

We distributed an electronic questionnaire using the popular social application WeChat to adults from any province of China except Hubei Province, the epicenter of the outbreak. The questionnaire asked for demographic information, body weight, physical activity, and lifestyle factors before and during the quarantine.

Results:

Of 376 questionnaires returned, 339 were valid (90.2%). During the period of semi-lockdown, both females and males with BMI <24 gained weight, males with BMI ≥24 lost weight, and females with BMI ≥24 gained weight. The average steps per day and the average moderate or vigorous-intensity exercise declined significantly for both males and females during the semi-lockdown. Changes in body weight inversely correlated with changes in steps per day and moderate or vigorous-intensity exercise during the quarantine.

Conclusions:

Normal weight individuals, who are not normally troubled by overweight or obesity, had less awareness of weight gain than people with a BMI ≥ 24. Under the conditions of the semi-lockdown, they tended to gain weight.

Exercise, redox homeostasis and the epigenetic landscape

Physical exercise represents one of the strongest physiological stimuli capable to induce functional and structural modifications in all biological systems. Indeed, beside the traditional genetic mechanisms, physical exercise can modulate gene expression through epigenetic modifications, namely DNA methylation, post-translational histone modification and non-coding RNA transcripts.

Initially considered as merely damaging molecules, it is now well recognized that both reactive oxygen (ROS) and nitrogen species (RNS) produced under voluntary exercise play an important role as regulatory mediators in signaling processes. While robust scientific evidences highlight the role of exercise-associated redox modifications in modulating gene expression through the genetic machinery, the understanding of their specific impact on epigenomic profile is still at an early stage. This review will provide an overview of the role of ROS and RNS in modulating the epigenetic landscape in the context of exercise-related adaptations.

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Physical exercise can modulate gene expression through epigenetic modifications.

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Epigenetic regulation of ROS/RNS generating, sensing and neutralizing enzymes can impact the cellular levels of ROS and RNS.

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ROS might act as modulators of epigenetic machinery, interfering with DNA methylation, hPTMs and ncRNAs expression.

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Redox homeostasis might hold a relevant role in the epigenetic landscape modulating exercise-related adaptations.

Sirtuin 1 regulates mitochondrial function and immune homeostasis in respiratory syncytial virus infected dendritic cells

Respiratory syncytial virus (RSV) is the major cause of lower respiratory tract infection in children worldwide. Sirtuin 1 (SIRT1), a NAD+ dependent deacetylase, has been associated with induction of autophagy, reprogramming cellular metabolism, and regulating immune mediators. In this study, we investigated the role of SIRT1 in bone marrow dendritic cell (BMDC) function during RSV infection. SIRT1 deficient (SIRT1 -/-) BMDC showed a defect in mitochondrial membrane potential (Δ⍦m) that worsens during RSV infection. This defect in Δ⍦m caused the generation of elevated levels of reactive oxygen species (ROS). Furthermore, the oxygen consumption rate (OCR) was reduced as assessed in Seahorse assays, coupled with lower levels of ATP in SIRT1-/- DC. These altered responses corresponded to altered innate cytokine responses in the SIRT1-/- DC in response to RSV infection. Reverse Phase Protein Array (RPPA) functional proteomics analyses of SIRT1-/- and WT BMDC during RSV infection identified a range of differentially regulated proteins involved in pathways that play a critical role in mitochondrial metabolism, autophagy, oxidative and ER stress, and DNA damage. We identified an essential enzyme, acetyl CoA carboxylase (ACC1), which plays a central role in fatty acid synthesis and had significantly increased expression in SIRT1-/- DC. Blockade of ACC1 resulted in metabolic reprogramming of BMDC that ameliorated mitochondrial dysfunction and reduced pathologic innate immune cytokines in DC. The altered DC responses attenuated Th2 and Th17 immunity allowing the appropriate generation of anti-viral Th1 responses both in vitro and in vivo during RSV infection thus reducing the enhanced pathogenic responses. Together, these studies identify pathways critical for appropriate DC function and innate immunity that depend on SIRT1-mediated regulation of metabolic processes.

Biological and Clinical Relevance of microRNAs in Mitochondrial Diseases/Dysfunctions

Mitochondrial dysfunction arises from an inadequate number of mitochondria, an inability to provide necessary substrates to mitochondria, or a dysfunction in their electron transport and a denosine triphosphate synthesis machinery. Occurrences of mitochondrial dysfunction are due to genetic or environmental changes in the mitochondria or in the nuclear DNA that codes mitochondrial components. Currently, drug options are available, yet no treatment exists in sight of this disease and needs a new insight into molecular and signaling pathways for this disease. microRNAs (miRNAs) are small, endogenous, and noncoding RNAs function as a master regulator of gene expression. The evolution of miRNAs in the past two decades emerged as a key regulator of gene expression that controls physiological pathological cellular differentiation processes, and metabolic homeostasis such as development and cancer. It has been known that miRNAs are a potential biomarker in both communicable and noncommunicable diseases. But, in the case of mitochondrial dysfunction in miRNAs, the number of studies and investigations are comparatively less than those on other diseases and dysfunctions. In this review, we have elaborated the roles of miRNAs in the mitochondrial diseases and dysfunctions.

Dietary Supplementation of Methyl Donor l-Methionine Alters Epigenetic Modification in Type 2 Diabetes

SCOPE

The aim of the current study is to evaluate whether l-methionine supplementation (l-Met-S) improves type 2 diabetes-induced alterations in glucose and lipid metabolism by modulating one-carbon metabolism and methylation status.

METHODS AND RESULTS

Diabetes is induced in male Sprague-Dawley rats using high-fat diet and low dose streptozotocin. At the end of study, various biochemical parameters, immunoblotting, qRT-PCR and ChIP-qPCR are performed. The first evidence that l-Met-S activates p-AMPK and SIRT1, very similar to "metformin," is provided. l-Met-S improves the altered key one-carbon metabolites in diabetic rats by modulating methionine adenosyl transferase 1A and cystathione β synthase expression. qRT-PCR shows that l-Met-S alleviates diabetes-induced increase in Forkhead transcription factor 1 expression and thereby regulating genes involved in glucose (G6pc, Pdk4, Pklr) and lipid metabolism (Fasn). Interestingly, l-Met-S inhibits the increased expression of DNMT1 and also prevents methylation of histone H3K36me2 under diabetic condition. ChIP assay shows that persistent increase in abundance of histone H3K36me2 on the promoter region of FOXO1 in diabetic rats and it is recovered by l-Met-S.

CONCLUSION

The first evidence that dietary supplementation of l-Met prevents diabetes-induced epigenetic alterations and regulating methionine levels can be therapeutically exploited for the treatment of metabolic diseases is provided.

The FoxO-Autophagy Axis in Health and Disease

Autophagy controls cellular remodeling and quality control. Dysregulated autophagy has been implicated in several human diseases including obesity, diabetes, cardiovascular disease, neurodegenerative diseases, and cancer. Current evidence has revealed that FoxO (forkhead box class O) transcription factors have a multifaceted role in autophagy regulation and dysregulation. Nuclear FoxOs transactivate genes that control the formation of autophagosomes and their fusion with lysosomes. Independently of transactivation, cytosolic FoxO proteins induce autophagy by directly interacting with autophagy proteins. Autophagy is also controlled by FoxOs through epigenetic mechanisms. Moreover, FoxO proteins can be degraded directly or indirectly by autophagy. Cutting-edge evidence is reviewed that the FoxO-autophagy axis plays a crucial role in health and disease.

Effects of obesity and weight loss on mitochondrial structure and function and implications for colorectal cancer risk

Colorectal cancer (CRC) is the third most common cancer globally. CRC risk is increased by obesity, and by its lifestyle determinants notably physical inactivity and poor nutrition. Obesity results in increased inflammation and oxidative stress which cause genomic damage and contribute to mitochondrial dysregulation and CRC risk. The mitochondrial dysfunction associated with obesity includes abnormal mitochondrial size, morphology and reduced autophagy, mitochondrial biogenesis and expression of key mitochondrial regulators. Although there is strong evidence that increased adiposity increases CRC risk, evidence for the effects of intentional weight loss on CRC risk is much more limited. In model systems, energy depletion leads to enhanced mitochondrial integrity, capacity, function and biogenesis but the effects of obesity and weight loss on mitochondria in the human colon are not known. We are using weight loss following bariatric surgery to investigate the effects of altered adiposity on mitochondrial structure and function in human colonocytes. In summary, there is strong and consistent evidence in model systems and more limited evidence in human subjects that over-feeding and/or obesity result in mitochondrial dysfunction and that weight loss might mitigate or reverse some of these effects.

Nutritional Factors, DNA Methylation, and Risk of Type 2 Diabetes and Obesity: Perspectives and Challenges

A healthy diet improves life expectancy and helps to prevent common chronic diseases such as type 2 diabetes (T2D) and obesity. The mechanisms driving these effects are not fully understood, but are likely to involve epigenetics. Epigenetic mechanisms control gene expression, maintaining the DNA sequence, and therefore the full genomic information inherited from our parents, unchanged. An interesting feature of epigenetic changes lies in their dynamic nature and reversibility. Accordingly, they are susceptible to correction through targeted interventions. Here we will review the evidence supporting a role for nutritional factors in mediating metabolic disease risk through DNA methylation changes. Special emphasis will be placed on the potential of using DNA methylation traits as biomarkers to predict risk of obesity and T2D as well as on their response to dietary and pharmacological (epi-drug) interventions.

Biomarkers of Oxidative Stress in Metabolic Syndrome and Associated Diseases

Metabolic syndrome (MS) represents worldwide public health issue characterized by a set of cardiovascular risk factors including obesity, diabetes, dyslipidemia, hypertension, and impaired glucose tolerance. The link between the MS and the associated diseases is represented by oxidative stress (OS) and by the intracellular redox imbalance, both caused by the persistence of chronic inflammatory conditions that characterize MS. The increase in oxidizing species formation in MS has been accepted as a major underlying mechanism for mitochondrial dysfunction, accumulation of protein and lipid oxidation products, and impairment of the antioxidant systems. These oxidative modifications are recognized as relevant OS biomarkers potentially able to (i) clarify the role of reactive oxygen and nitrogen species in the etiology of the MS, (ii) contribute to the diagnosis/evaluation of the disease's severity, and (iii) evaluate the utility of possible therapeutic strategies based on natural antioxidants. The antioxidant therapies indeed could be able to (i) counteract systemic as well as mitochondrial-derived OS, (ii) enhance the endogenous antioxidant defenses, (iii) alleviate MS symptoms, and (iv) prevent the complications linked to MS-derived cardiovascular diseases. The focus of this review is to summarize the current knowledge about the role of OS in the development of metabolic alterations characterizing MS, with particular regard to the occurrence of OS-correlated biomarkers, as well as to the use of therapeutic strategies based on natural antioxidants.

The impact of a short-term high-fat diet on mitochondrial respiration, reactive oxygen species production, and dynamics in oxidative and glycolytic skeletal muscles of young rats

Multiple aspects of mitochondrial function and dynamics remain poorly studied in the skeletal muscle of pediatric models in response to a short-term high-fat diet (HFD). This study investigated the impact of a short-term HFD on mitochondrial function and dynamics in the oxidative soleus (SOL) and glycolytic extensor digitorum longus (EDL) muscles in young rats. Young male Wistar rats were submitted to either HFD or normal chow (NCD) diets for 14 days. Permeabilized myofibers from SOL and EDL were prepared to assess mitochondrial respiration and reactive oxygen species (ROS) production. The expression and content of protein involved in mitochondrial metabolism and dynamics (fusion/fission) were also quantified. While no effects of HFD was observed on mitochondrial respiration when classical complex I and II substrates were used, both SOL and EDL of rats submitted to a HFD displayed higher basal and ADP-stimulated respiration rates when Malate + Palmitoyl-L-carnitine were used as substrates. HFD did not alter ROS production and markers of mitochondrial content. The expression of CPT1b was significantly increased in SOL and EDL of HFD rats. Although the expression of UCP3 was increased in SOL and EDL muscles from HFD rats, mitochondrial coupling efficiency was not altered. In SOL of HFD rats, the transcript levels of Mfn2 and Fis1 were significantly upregulated. The expression and content of proteins regulating mitochondrial dynamics was not modulated by HFD in the EDL. Finally, DRP1 protein content was increased by over fourfold in the SOL of HFD rats. Taken altogether, our findings show that exposing young animals to short-term HFD results in an increased capacity of skeletal muscle mitochondria to oxidize fatty acids, without altering ROS production, coupling efficiency, and mitochondrial content. Our results also highlight that the impact of HFD on mitochondrial dynamics appears to be muscle specific.

MiR-21 protected against diabetic cardiomyopathy induced diastolic dysfunction by targeting gelsolin

Background

Diabetes is a leading cause of mortality and morbidity across the world. Over 50% of deaths among diabetic patients are caused by cardiovascular diseases. Cardiac diastolic dysfunction is one of the key early signs of diabetic cardiomyopathy, which often occurs before systolic dysfunction. However, no drug is currently licensed for its treatment.

Methods

Type 9 adeno-associated virus combined with cardiac Troponin T promoter were employed to manipulate miR-21 expression in the leptin receptor-deficient (db/db) mice. Cardiac structure and functions were measured by echocardiography and hemodynamic examinations. Primary cardiomyocytes and cardiomyocyte cell lines were used to perform gain/loss-of-function assays in vitro.

Results

We observed a significant reduction of miR-21 in the diastolic dysfunctional heart of db/db mice. Remarkably, delivery of miR-21 efficiently protected against the early impairment in cardiac diastolic dysfunction, represented by decreased ROS production, increased bioavailable NO and relieved diabetes-induced cardiomyocyte hypertrophy in db/db mice. Through bioinformatic analysis and Ago2 co-immunoprecipitation, we identified that miR-21 directly targeted gelsolin, a member of the actin-binding proteins, which acted as a transcriptional cofactor in signal transduction. Moreover, down-regulation of gelsolin by siRNA also attenuated the early phase of diabetic cardiomyopathy.

Conclusion

Our findings reveal a new role of miR-21 in attenuating diabetic cardiomyopathy by targeting gelsolin, and provide a molecular basis for developing a miRNA-based therapy against diabetic cardiomyopathy.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0767-z) contains supplementary material, which is available to authorized users.

Mitochondrial Dysfunction Linking Obesity and Asthma

The bidirectional epidemiological association between asthma and obesity is well known. Recent evidence suggests that there is an intersection of the pathophysiological molecular pathways leading to either obesity or asthma, at the level of mitochondria. This is not surprising, because mitochondria, beyond their roles as the metabolic powerhouses of the cell, serve as sensors of threats, regulators of stress signaling, and effectors of cytotoxicity. Reduced mitochondrial function and low metabolic activity are well-recognized features of obesity. Three distinct lines of experimental evidences connect mitochondrial dysfunction with asthma. First, asthma is associated with aberrant mitochondrial metabolism. Second, mitochondrial dysfunction may either induce asthma-like features or increase asthma severity. Third, mitochondria-targeted therapies appear effective in preventing or reversing asthma features. Importantly, mitochondrial dysfunction in airway epithelial cells appears to be a powerful trigger for airway remodeling that is independent of cellular inflammation. This is clinically relevant to the obese-asthma phenotype, with exaggerated symptoms despite apparently low levels of inflammation, and poor response to antiinflammatory treatment. In summary, mitochondrial dysfunction is a common thread tying together the twin epidemics of obesity and asthma. Environmental and lifestyle factors leading to primary mitochondrial dysfunction may be increasing the risk for either disease. Further, secondary mitochondrial dysfunction emerging from the pathogenesis of either obesity or asthma may increase the risk of the other. Mitochondrial health-centric strategies may be relevant to prevention and treatment of both obesity and asthma, and should be actively considered.

Prenatal Lipopolysaccharide Exposure Promotes Dyslipidemia in the Male Offspring Rats

Inflammation is critical to the pathogenesis of cardiovascular diseases (CVDs). We have uncovered intrauterine inflammation induced by lipopolysaccharide (LPS) increases CVDs in adult offspring rats. The present study aimed to explore the role of prenatal exposure to LPS on the lipid profiles in male offspring rats and to further assess their susceptibility to high fat diet (HFD). Maternal LPS (0.79 mg/kg) exposure produced a significant increase in serum and hepatic levels of total cholesterol, triglycerides, low-density lipoprotein cholesterol, aspartate amino transferase as well as liver morphological abnormalities in 8-week-old offspring rats. Meanwhile, disturbed gene expressions involved in hepatic lipid metabolism and related signaling pathways were found, especially the up-regulated very-low density lipoprotein receptor (VLDLR) and down-regulated transmembrane 7 superfamily member 2 (TM7SF2). Following HFD treatment, however, the lipid profile shifts and liver dysfunction were exacerbated compared to the offsprings treated with prenatal LPS exposure alone. Compared with that in control offsprings, the hepatic mitochondria (Mt) in offspring rats solely treated with HFD exhibited remarkably higher ATP level, enforced Complex IV expression and a sharp reduction of its activity, whereas the offsprings from LPS-treated dams showed the loss of ATP content, diminished membrane potential, decline in protein expression and activity of mitochondrial respiratory complex IV, increased level of MtDNA deletion as well. Furthermore, treatment with HFD deteriorated these mitochondrial disorders in the prenatally LPS-exposed offspring rats. Taken together, maternal LPS exposure reinforces dyslipidemia in response to a HFD in adult offsprings, which should be associated with mitochondrial abnormalities and disturbed gene expressions of cholesterol metabolism.

Epigenetics of Subcellular Structure Functioning in the Origin of Risk or Resilience to Comorbidity of Neuropsychiatric and Cardiometabolic Disorders

Mechanisms controlling mitochondrial function, protein folding in the endoplasmic reticulum (ER) and nuclear processes such as telomere length and DNA repair may be subject to epigenetic cues that relate the genomic expression and environmental exposures in early stages of life. They may also be involved in the comorbid appearance of cardiometabolic (CMD) and neuropsychiatric disorders (NPD) during adulthood. Mitochondrial function and protein folding in the endoplasmic reticulum are associated with oxidative stress and elevated intracellular calcium levels and may also underlie the vulnerability for comorbid CMD and NPD. Mitochondria provide key metabolites such as nicotinamide adenine dinucleotide (NAD+), ATP, α-ketoglutarate and acetyl coenzyme A that are required for many transcriptional and epigenetic processes. They are also a source of free radicals. On the other hand, epigenetic markers in nuclear DNA determine mitochondrial biogenesis. The ER is the subcellular organelle in which secretory proteins are folded. Many environmental factors stop the ability of cells to properly fold proteins and modify post-translationally secretory and transmembrane proteins leading to endoplasmic reticulum stress and oxidative stress. ER functioning may be epigenetically determined. Chronic ER stress is emerging as a key contributor to a growing list of human diseases, including CMD and NPD. Telomere loss causes chromosomal fusion, activation of the control of DNA damage-responses, unstable genome and altered stem cell function, which may underlie the comorbidity of CMD and NPD. The length of telomeres is related to oxidative stress and may be epigenetically programmed. Pathways involved in DNA repair may be epigenetically programmed and may contribute to diseases. In this paper, we describe subcellular mechanisms that are determined by epigenetic markers and their possible relation to the development of increased susceptibility to develop CMD and NPD.

GLP-1 receptor agonist ameliorates obesity-induced chronic kidney injury via restoring renal metabolism homeostasis

Increasing evidence indicates that obesity is highly associated with chronic kidney disease (CKD). GLP-1 receptor (GLP-1R) agonist has shown benefits on kidney diseases, but its direct role on kidney metabolism in obesity is still not clear. This study aims to investigate the protection and metabolic modulation role of liraglutide (Lira) on kidney of obesity. Rats were induced obese by high-fat diet (HFD), and renal function and metabolism changes were evaluated by metabolomic, biological and histological methods. HFD rats exhibited systemic metabolic disorders such as obesity, hyperlipidemia and impaired glucose tolerance, as well as renal histological and function damages, while Lira significantly ameliorated these adverse effects in HFD rats. Metabolomic data showed that Lira directly reduced renal lipids including fatty acid residues, cholesterol, phospholipids and triglycerides, and improved mitochondria metabolites such as succinate, citrate, taurine, fumarate and nicotinamide adenine dinucleotide (NAD+) in the kidney of HFD rats. Furthermore, we revealed that Lira inhibited renal lipid accumulation by coordinating lipogenic and lipolytic signals, and partly rescued renal mitochondria function via Sirt1/AMPK/PGC1α pathways in HFD rats. This study suggested that Lira alleviated HFD-induced kidney injury at least partly via directly restoring renal metabolism, thus GLP-1R agonist is a promising therapy for obesity-associated CKD.

Humanin promotes mitochondrial biogenesis in pancreatic MIN6 β-cells

Mitochondrial dysfunction is associated with β-cell failure and insulin resistance in diabetes. Humanin is an endogenous cytoprotective peptide. In the current study, we aimed to define the effects of Humanin on mitochondrial biogenesis in pancreatic β-cells. Our findings demonstrated that Humanin treatment significantly increased the expression of PGC-1α and its downstream target genes NRF1 and TFAM in MIN6 β-cells. Notably, Humanin treatment significantly promoted mitochondrial biogenesis by increasing mitochondrial mass, elevating mtDNA/nDNA ratio, and stimulating the expression of cytochrome B, which were suppressed by the specific AMPK inhibitor compound C. Indeed, Humanin treatment caused the phosphorylation of AMPK, which was involved in the induction of PGC-1α, NRF1, and TFAM by Humanin. Importantly, our findings indicate that Humanin treatment led to a possible functional gain of the mitochondria by increasing ATP levels and respiratory rate. Our findings provided a new insight into the molecular mechanisms of action by which Humanin improves pancreatic β-cell function via enhanced mitochondrial mass and performance.

Structure, function, and regulation of mitofusin-2 in health and disease

Mitochondria are highly dynamic organelles that constantly migrate, fuse, and divide to regulate their shape, size, number, and bioenergetic function. Mitofusins (Mfn1/2), optic atrophy 1 (OPA1), and dynamin-related protein 1 (Drp1), are key regulators of mitochondrial fusion and fission. Mutations in these molecules are associated with severe neurodegenerative and non-neurological diseases pointing to the importance of functional mitochondrial dynamics in normal cell physiology. In recent years, significant progress has been made in our understanding of mitochondrial dynamics, which has raised interest in defining the physiological roles of key regulators of fusion and fission and led to the identification of additional functions of Mfn2 in mitochondrial metabolism, cell signalling, and apoptosis. In this review, we summarize the current knowledge of the structural and functional properties of Mfn2 as well as its regulation in different tissues, and also discuss the consequences of aberrant Mfn2 expression.

Epigenetic reprogramming in metabolic disorders: nutritional factors and beyond

Environmental factors (e.g., malnutrition and physical inactivity) contribute largely to metabolic disorders including obesity, type 2 diabetes, cardiometabolic disease and nonalcoholic fatty liver diseases. The abnormalities in metabolic activity and pathways have been increasingly associated with altered DNA methylation, histone modification and noncoding RNAs, whereas lifestyle interventions targeting diet and physical activity can reverse the epigenetic and metabolic changes. Here we review recent evidence primarily from human studies that links DNA methylation reprogramming to metabolic derangements or improvements, with a focus on cross-tissue (e.g., the liver, skeletal muscle, pancreas, adipose tissue and blood samples) epigenetic markers, mechanistic mediators of the epigenetic reprogramming, and the potential of using epigenetic traits to predict disease risk and intervention response. The challenges in epigenetic studies addressing the mechanisms of metabolic diseases and future directions are also discussed and prospected.

High Glucose Induces Mitochondrial Dysfunction in Retinal Müller Cells: Implications for Diabetic Retinopathy

Purpose

To investigate whether high glucose (HG) induces mitochondrial dysfunction and promotes apoptosis in retinal Müller cells.

Methods

Rat retinal Müller cells (rMC-1) grown in normal (N) or HG (30 mM glucose) medium for 7 days were subjected to MitoTracker Red staining to identify the mitochondrial network. Digital images of mitochondria were captured in live cells under confocal microscopy and analyzed for mitochondrial morphology changes based on form factor (FF) and aspect ratio (AR) values. Mitochondrial metabolic function was assessed by measuring oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) using a bioenergetic analyzer. Cells undergoing apoptosis were identified by differential dye staining and TUNEL assay, and cytochrome c levels were assessed by Western blot analysis.

Results

Cells grown in HG exhibited significantly increased mitochondrial fragmentation compared to those grown in N medium (FF = 1.7 ± 0.1 vs. 2.3 ± 0.1; AR = 2.1 ± 0.1 vs. 2.5 ± 0.2; P < 0.01). OCR and ECAR were significantly reduced in cells grown in HG medium compared to those grown in N medium (steady state: 75% ± 20% of control, P < 0.02; 64% ± 22% of control, P < 0.02, respectively). These cells also exhibited a significant increase (∼2-fold) in the number of apoptotic cells compared to those grown in N medium (P < 0.01), with a concomitant increase in cytochrome c levels (247% ± 94% of control, P < 0.05).

Conclusions

Findings indicate that HG-induced mitochondrial morphology changes and subsequent mitochondrial dysfunction may contribute to retinal Müller cell loss associated with diabetic retinopathy.

Uncoupling protein 2 and metabolic diseases

Mitochondria are fascinating organelles involved in various cellular-metabolic activities that are integral for mammalian development. Although they perform diverse, yet interconnected functions, mitochondria are remarkably regulated by complex signaling networks. Therefore, it is not surprising that mitochondrial dysfunction is involved in plethora of diseases, including neurodegenerative and metabolic disorders. One of the many factors that lead to mitochondrial-associated metabolic diseases is the uncoupling protein-2, a family of mitochondrial anion proteins present in the inner mitochondrial membrane. Since their discovery, uncoupling proteins have attracted considerable attention due to their involvement in mitochondrial-mediated oxidative stress and energy metabolism. This review attempts to provide a summary of recent developments in the field of uncoupling protein 2 relating to mitochondrial associated metabolic diseases.

Isolation of Mouse Stromal Vascular Cells for Monolayer Culture

Positive energy balance contributes to adipose tissue expansion and dysfunction, which accounts largely for obesity and related metabolic disorders. Thermogenic fat can dissipate energy, activation or induction of which may promote energy balance and address the pressing health issues. Recent studies have shown that stromal vascular fraction (SVF) from white adipose tissue (WAT) can develop both white and brown-like adipocyte phenotypes, thus serving as a unique model to study adipogenesis and thermogenesis. Here, we describe a protocol for effective isolation of mouse SVF from WAT, induction of differentiation, and detection of adipogenesis. Success tips for isolation and culture of SVF are also discussed.

Abl2 kinase phosphorylates Bi-organellar regulator MNRR1 in mitochondria, stimulating respiration

We previously showed that MNRR1 (Mitochondrial Nuclear Retrograde Regulator 1, also CHCHD2) functions in two subcellular compartments, displaying a different function in each. In the mitochondria it is a stress regulator of respiration that binds to cytochrome c oxidase (COX) whereas in the nucleus it is a transactivator of COX4I2 and other hypoxia-stimulated genes. We now show that binding of MNRR1 to COX is promoted by phosphorylation at tyrosine-99 and that this interaction stimulates respiration. We show that phosphorylation of MNRR1 takes place in mitochondria and is mediated by Abl2 kinase (ARG). A family with Charcot-Marie-Tooth disease type 1A with an exaggerated phenotype harbors a Q112H mutation in MNRR1, located in a domain that is necessary for transcriptional activation by MNRR1. Furthermore, the mutation causes the protein to function suboptimally in the mitochondria in response to cellular stress. The Q112H mutation hinders the ability of the protein to interact with Abl kinase, leading to defective tyrosine phosphorylation and a resultant defect in respiration.

FoxO1 interacts with transcription factor EB and differentially regulates mitochondrial uncoupling proteins via autophagy in adipocytes

Mitochondrial uncoupling proteins (UCPs) are inducible and play an important role in metabolic and redox homeostasis. Recent studies have suggested that FoxO1 controls mitochondrial biogenesis and morphology, but it remains largely unknown how FoxO1 may regulate mitochondrial UCPs. Here we show that FoxO1 interacted with transcription factor EB (Tfeb), a key regulator of autophagosome and lysosome, and mediated the expression of UCP1, UCP2 and UCP3 differentially via autophagy in adipocytes. UCP1 was down-regulated but UCP2 and UCP3 were upregulated during adipocyte differentiation, which was associated with increased Tfeb and autophagy activity. However, inhibition of FoxO1 suppressed Tfeb and autophagy, attenuating UCP2 and UCP3 but increasing UCP1 expression. Pharmacological blockade of autophagy recapitulated the effects of FoxO1 inhibition on UCPs. Chromatin immunoprecipitation assay demonstrated that FoxO1 interacted with Tfeb by directly binding to its promoter, and silencing FoxO1 led to drastic decrease in Tfeb transcript and protein levels. These data provide the first line of evidence that FoxO1 interacts with Tfeb to regulate autophagy and UCP expression in adipocytes. Dysregulation of FoxO1→autophagy→UCP pathway may account for metabolic changes in obesity.

Coordinated Upregulation of Mitochondrial Biogenesis and Autophagy in Breast Cancer Cells: The Role of Dynamin Related Protein-1 and Implication for Breast Cancer Treatment

Overactive mitochondrial fission was shown to promote cell transformation and tumor growth. It remains elusive how mitochondrial quality is regulated in such conditions. Here, we show that upregulation of mitochondrial fission protein, dynamin related protein-1 (Drp1), was accompanied with increased mitochondrial biogenesis markers (PGC1α, NRF1, and Tfam) in breast cancer cells. However, mitochondrial number was reduced, which was associated with lower mitochondrial oxidative capacity in breast cancer cells. This contrast might be owing to enhanced mitochondrial turnover through autophagy, because an increased population of autophagic vacuoles engulfing mitochondria was observed in the cancer cells. Consistently, BNIP3 (a mitochondrial autophagy marker) and autophagic flux were significantly upregulated, indicative of augmented mitochondrial autophagy (mitophagy). The upregulation of Drp1 and BNIP3 was also observed in vivo (human breast carcinomas). Importantly, inhibition of Drp1 significantly suppressed mitochondrial autophagy, metabolic reprogramming, and cancer cell viability. Together, this study reveals coordinated increase of mitochondrial biogenesis and mitophagy in which Drp1 plays a central role regulating breast cancer cell metabolism and survival. Given the emerging evidence of PGC1α contributing to tumor growth, it will be of critical importance to target both mitochondrial biogenesis and mitophagy for effective cancer therapeutics.

Epigenetics and nutrition-related epidemics of metabolic diseases: Current perspectives and challenges

We live in a world fascinated by the relationship between disease and nutritional disequilibrium. The subtle and slow effects of chronic nutrient toxicity are a major public health concern. Since food is potentially important for the development of "metabolic memory", there is a need for more information on the type of nutrients causing adverse or toxic effects. We now know that metabolic alterations produced by excessive intake of some nutrients, drugs and chemicals directly impact epigenetic regulation. We envision that understanding how metabolic pathways are coordinated by environmental and genetic factors will provide novel insights for the treatment of metabolic diseases. New methods will enable the assembly and analysis of large sets of complex molecular and clinical data for understanding how inflammation and mitochondria affect bioenergetics, epigenetics and health. Collectively, the observations we highlight indicate that energy utilization and disease are intimately connected by epigenetics. The challenge is to incorporate metabolo-epigenetic data in better interpretations of disease, to expedite therapeutic targeting of key pathways linking nutritional toxicity and metabolism. An additional concern is that changes in the parental phenotype are detectable in the methylome of subsequent offspring. The effect might create a menace to future generations and preconceptional considerations.

The Role of Mitochondria in Diabetic Kidney Disease

Despite major improvements in the treatment of patients with diabetes mellitus, many patients still suffer from progressive diabetic kidney disease. More research is needed to improve treatment and to understand why some patients develop complications while others do not. Mitochondrial dysfunction has turned out to be central to the pathogenesis of diabetes, and we will review some new aspects in this field and the potential for treatment. The conventional theory has been that the intracellular surplus of glucose leads to mitochondrial overproduction of superoxide that contributes to general cell damage and activation of deleterious pathways specific for diabetes complications. However, recent data suggests that reduced mitochondrial activity could be the basis for disease progression and complications through increased inflammation and pro-fibrotic factors. Physical exercise is a very strong stimulus to mitochondrial biogenesis, and we now understand many of the underlying signaling pathways. Clinical trials have also shown that training, especially high-intensity training, can delay the onset of diabetes and improve insulin resistance. Furthermore, intermittent fasting and various pharmacological agents are other potential options for stimulating mitochondrial function and reducing the risk of development and progression of diabetic kidney disease.

Mitochondrial Epigenetic Changes Link to Increased Diabetes Risk and Early-Stage Prediabetes Indicator

Type 2 diabetes (T2D) is characterized by mitochondrial derangement and oxidative stress. With no known cure for T2D, it is critical to identify mitochondrial biomarkers for early diagnosis of prediabetes and disease prevention. Here we examined 87 participants on the diagnosis power of fasting glucose (FG) and hemoglobin A1c levels and investigated their interactions with mitochondrial DNA methylation. FG and A1c led to discordant diagnostic results irrespective of increased body mass index (BMI), underscoring the need of new biomarkers for prediabetes diagnosis. Mitochondrial DNA methylation levels were not correlated with late-stage (impaired FG or A1c) but significantly with early-stage (impaired insulin sensitivity) events. Quartiles of BMI suggested that mitochondrial DNA methylation increased drastically from Q1 (20 < BMI < 24.9, lean) to Q2 (30 < BMI < 34.9, obese), but marginally from Q2 to Q3 (35 < BMI < 39.9, severely obese) and from Q3 to Q4 (BMI > 40, morbidly obese). A significant change was also observed from Q1 to Q2 in HOMA insulin sensitivity but not in A1c or FG. Thus, mitochondrial epigenetic changes link to increased diabetes risk and the indicator of early-stage prediabetes. Further larger-scale studies to examine the potential of mitochondrial epigenetic marker in prediabetes diagnosis will be of critical importance for T2D prevention.

Both diet and gene mutation induced obesity affect oocyte quality in mice

Obesity was shown to cause reproductive dysfunctions such as reduced conception, infertility and early pregnancy loss. However, the possible effects of obesity on oocyte quality are still not fully understood. In this study we investigated the effects of both diet and gene mutation induced obesity on impairments in mouse oocyte polarization, oxidative stress, and epigenetic modifications. Our results showed that high-fat diet induced obesity (HFD) and gene mutation induced obesity (ob/ob) could both impair oocyte meiotic maturation, disrupt spindle morphology, and reduce oocyte polarity. Oocytes from obese mice underwent oxidative stress, as shown by high DHE and ROS levels. Abnormal mitochondrial distributions and structures were observed in oocytes from obese groups of mice and early apoptosis signals were detected, which suggesting that oxidative stress had impaired mitochondrial function and resulted in oocyte apoptosis. Our results also showed that 5 mC levels and H3K9 and H3K27 methylation levels were altered in oocytes from obese mice, which indicated that DNA methylation and histone methylation had been affected. Our results showed that both HFD and ob/ob induced obesity affected oocyte maturation and that oxidative stress-induced early apoptosis and altered epigenetic modifications may be the reasons for reduced oocyte quality in obese mice.