Mini-review: Mitochondrial DNA methylation in type 2 diabetes and obesity

Mechanisms of endurance and resistance exercise in type 2 diabetes mellitus: A Narrative review

In the treatment and management of type 2 diabetes mellitus (T2DM), exercise therapy has received increasing attention due to its accessibility and cost-effectiveness. Regular physical exercise improves glycemic control by ameliorating insulin resistance (IR) and reducing the risk of complications. However, the distinct mechanisms underlying the efficacy of endurance training (ET) and resistance training (RT) in T2DM remain incompletely understood. This review systematically compares the molecular pathways through which ET and RT improve IR, focusing on epigenetic regulation, metabolic reprogramming, and anti-inflammatory effects. We highlight that RT enhances protein synthesis via the IGF-1/PI3K/AKT/mTOR pathway, while ET predominantly improves mitochondrial biogenesis and lipid oxidation through AMPK/SIRT1/PGC-1α signaling. Additionally, ET exerts immunomodulatory effects by suppressing pro-inflammatory cytokines (e.g., TNF-α) and elevating anti-inflammatory myokines (e.g., IL-6). These findings provide a mechanistic basis for personalized exercise prescriptions in T2DM management.

Molecular Effects of Physical Activity and Body Composition: A Systematic Review and Meta-Analysis

Physical activity (PA) and body composition are important lifestyle factors that influence public health. Research suggests that DNA regions (CpG site locations) are differentially methylated in a physically active population. This meta-analysis aimed to identify CpG sites associated with various levels of PA and associated metabolic pathways. The meta-analysis followed PRISMA guidelines using PubMed, SportDISCUS, Embase, Scopus, Cochrane and Web of Science. Epigenomic analyses performed on DNA of participants with no underlying health conditions were included. Articles were screened using Rayyan AI and extracted CpG sites, and their location were confirmed using the EWAS catalogue. Six studies comprising 770 subjects were included in this meta-analysis. The meta-analysis was performed on clinical metrics extracted from the six studies and showed that BMI, blood pressure, insulin and glucose testing are significantly improved upon PA intervention. Amongst the included studies, a total of 257 CpG sites were differentially methylated in physically active participants, with 134 CpGs located in 92 genes associated with obesity-related pathways. The identified differentially methylated genes either belonged to the lipid metabolism or insulin signalling pathway. The genes which were differentially regulated in multiple tissue types and studies are JAZF1 (insulin signalling, and lipid and carbohydrate metabolism pathways) and NAV1 (mTOR signalling pathway). In conclusion, the current epigenomic meta-analysis showed that PA levels induce differential DNA methylation signatures on genes that affect metabolism. To understand the positive molecular effects of PA, further research on the above candidate genes needs to be conducted amongst various levels of a physically active population.

Mitochondrial mt12361A>G increased risk of metabolic dysfunction-associated steatotic liver disease among non-diabetes

BACKGROUND

Insulin resistance, lipotoxicity, and mitochondrial dysfunction contribute to the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD). Mitochondrial dysfunction impairs oxidative phosphorylation and increases reactive oxygen species production, leading to steatohepatitis and hepatic fibrosis. Artificial intelligence (AI) is a potent tool for disease diagnosis and risk stratification.

AIM

To investigate mitochondrial DNA polymorphisms in susceptibility to MASLD and establish an AI model for MASLD screening.

METHODS

Multiplex polymerase chain reaction was performed to comprehensively genotype 82 mitochondrial DNA variants in the screening dataset (n = 264). The significant mitochondrial single nucleotide polymorphism was validated in an independent cohort (n = 1046) using the Taqman® allelic discrimination assay. Random forest, eXtreme gradient boosting, Naive Bayes, and logistic regression algorithms were employed to construct an AI model for MASLD.

RESULTS

In the screening dataset, only mt12361A>G was significantly associated with MASLD. mt12361A>G showed borderline significance in MASLD patients with 2-3 cardiometabolic traits compared with controls in the validation dataset (P = 0.055). Multivariate regression analysis confirmed that mt12361A>G was an independent risk factor of MASLD [odds ratio (OR) = 2.54, 95% confidence interval (CI): 1.19-5.43, P = 0.016]. The genetic effect of mt12361A>G was significant in the non-diabetic group but not in the diabetic group. mt12361G carriers had a 2.8-fold higher risk than A carriers in the non-diabetic group (OR = 2.80, 95%CI: 1.22-6.41, P = 0.015). By integrating clinical features and mt12361A>G, random forest outperformed other algorithms in detecting MASLD [training area under the receiver operating characteristic curve (AUROC) = 1.000, validation AUROC = 0.876].

CONCLUSION

The mt12361A>G variant increased the severity of MASLD in non-diabetic patients. AI supports the screening and management of MASLD in primary care settings.

Trimethylamine N-oxide induces pyroptosis in HTR8-S/Vneo cells through the ten-eleven translocation 2-cytochrome b-reactive oxygen species pathway

AIM

Pyroptosis is a type of programmed cell death characterized by pro-inflammatory activity and is an important factor in pre-eclampsia (PE). Trimethylamine N-oxide (TMAO) is a gut microbial metabolite closely associated with pyroptosis and PE. This study aims to investigate the role of TMAO in trophoblast cell pyroptosis and explore possible mechanisms.

METHODS

Western blot and qRT-polymerase chain reaction (PCR) were used to detect the expression levels of ten-eleven translocation 2 (TET2), cytochrome b (CYTB), pyroptosis-related molecules, and mitochondrial proteins. The level of mitochondrial reactive oxygen species (mtROS) was detected by fluorescent probe DCFH-DA. Immunofluorescence was used to measure the level of 5-hydroxymethylcytosine (5hmC). TET2 overexpression/silencing and CYTB overexpression/silencing lentiviruses were transfected into HTR8/SVneo cells, respectively. MitoTEMPO was used to reduce mtROS. TMAO levels in placental tissues were quantified by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and representative extracted ion chromatograms were analyzed for retention times and peak areas. ELISA was used to further validate TMAO concentrations in placental tissues.

RESULTS

TMAO is capable of enhancing the expression of proteins related to pyroptosis (including NLRP3, GSDMD, GSDMD-N, Caspase-1) as well as inflammatory factors (such as IL-1β, IL-18) in HTR8-S/Vneo cells. Meanwhile, the positive rate of propidium iodide (PI), mtROS levels, and intracellular Ca2+ levels all increased. Electron microscopy results showed an increase in mitochondrial membrane pore numbers, abnormal mitochondrial morphology, and downregulation of the expression levels of mitochondrial proteins nuclear respiratory factor 1 (NRF1), NRF2, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), and NADH dehydrogenase subunit 2 (ND2). LC-MS/MS and ELISA analyses revealed significantly elevated TMAO levels in PE placental tissues compared to normal tissues, further supporting the role of TMAO accumulation in placental dysfunction associated with PE. Overexpression of CYTB inhibited TMAO-induced pyroptosis and mitochondrial dysfunction (MDF) in HTR8-S/Vneo cells, while silencing of CYTB promoted pyroptosis and MDF in HTR8-S/Vneo cells, but this condition could be partially reversed by MitoTEMPO. TMAO inhibited the expression of TET2 and CYTB and downregulated the level of 5hmc. The results of TET2 overexpression/knockout indicated that the expression of CYTB was regulated by TET2, and overexpression of TET2 alleviated TMAO-induced pyroptosis and MDF as well as the decrease in 5hmc levels in HTR8-S/Vneo cells, but this condition could be partially reversed by silencing CYTB.

CONCLUSION

In summary, these findings suggest that TMAO induces pyroptosis in HTR8/SVneo cells through the TET2-CYTB-mtROS pathway, contributing to mitochondrial dysfunction and inflammation. The significant elevation of TMAO levels in PE placental tissues further supports its role in the pathophysiology of PE. Targeting the TET2-CYTB-mtROS pathway may provide a novel therapeutic strategy for the treatment of PE.

Mitochondrial Health Markers and Obesity-Related Health in Human Population Studies: A Narrative Review of Recent Literature

PURPOSE OF REVIEW

This narrative review summarizes current literature on the relationship of mitochondrial biomarkers with obesity-related characteristics, including body mass index and body composition.

RECENT FINDINGS

Mitochondria, as cellular powerhouses, play a pivotal role in energy production and the regulation of metabolic process. Altered mitochondrial functions contribute to obesity, yet evidence of the intricate relationship between mitochondrial dynamics and obesity-related outcomes in human population studies is scarce and warrants further attention. We discuss emerging evidence linking obesity and related health outcomes to impaired oxidative phosphorylation pathways, oxidative stress and mtDNA variants, copy number and methylation, all hallmark of suboptimal mitochondrial function. We also explore the influence of dietary interventions and metabolic and bariatric surgery procedures on restoring mitochondrial attributes of individuals with obesity. Finally, we report on the potential knowledge gaps in the mitochondrial dynamics for human health for future study.

The Role of Insulin Within the Socio-Psycho-Biological Framework in Type 2 Diabetes-A Perspective from Psychoneuroimmunology

The interplay between socio-psychological factors and biological systems is pivotal in defining human health and disease, particularly in chronic non-communicable diseases. Recent advancements in psychoneuroimmunology and mitochondrial psychobiology have emphasized the significance of psychological factors as critical determinants of disease onset, progression, recurrence, and severity. These insights align with evolutionary biology, psychology, and psychiatry, highlighting the inherent social nature of humans. This study proposes a theory that expands insulin's role beyond traditional metabolic functions, incorporating it into the Mitochondrial Information Processing System (MIPS) and exploring it from an evolutionary medicine perspective to explore its function in processing psychological and social factors into biological responses. This narrative review comprises data from preclinical animal studies, longitudinal cohort studies, cross-sectional studies, machine learning analyses, and randomized controlled trials, and investigates the role of insulin in health and disease. The result is a proposal for a theoretical framework of insulin as a social substance within the socio-psycho-biological framework, emphasizing its extensive roles in health and disease. Type 2 Diabetes Mellitus (T2DM) with musculoskeletal disorders and neurodegeneration exemplifies this narrative. We suggest further research towards a comprehensive treatment protocol meeting evolutionary expectations, where incorporating psychosocial interventions plays an essential role. By supporting the concept of 'insulin resilience' and suggesting the use of heart rate variability to assess insulin resilience, we aim to provide an integrative approach to managing insulin levels and monitoring the effectiveness of interventions. This integrative strategy addresses broader socio-psychological factors, ultimately improving health outcomes for individuals with T2DM and musculoskeletal complications and neurodegeneration while providing new insights into the interplay between socio-psychological factors and biological systems in chronic diseases.

Mitochondrial DNA content and methylation in sperm of patients with asthenozoospermia

PURPOSE

The aim of the current study was to investigate the mtDNA methylation levels and mtDNA copy numbers in the sperm of patients with asthenozoospermia and compare them to those observed in controls with normozoospermia.

METHODS

Pyrosequencing analysis of the methylation levels of the mitochondrial D-loop and MT-CO1/chr1:631,907-632083/chrX:26,471,887-126,472,063 (hereinafter referred to as "MT-CO1-AVG") region and quantitative PCR analysis of the mtDNA copy number were performed on sperm from 30 patients with asthenozoospermia and 30 controls with normozoospermia.

RESULTS

Compared with those of controls with normozoospermia, the methylation levels of D-loop and MT-CO1-AVG regions and mtDNA copy number were significantly higher in patients with asthenozoospermia. The methylation level of the D-loop region in patients with asthenozoospermia and controls with normozoospermia and that of MT-CO1-AVG region in patients with asthenozoospermia showed a decreasing tendency with increasing total sperm motility. A significant inverse correlation between the mtDNA copy number and total sperm motility was observed in patients with asthenozoospermia but not in controls with normozoospermia. In patients with asthenozoospermia, but not in controls with normozoospermia, we observed a significant inverse correlation between D-loop methylation levels and mtDNA copy number, while no significant correlation was observed between MT-CO1-AVG methylation levels and mtDNA copy number.

CONCLUSION

These results reveal the occurrence of mtDNA methylation in human sperm and altered D-loop and MT-CO1-AVG methylation levels in patients with asthenozoospermia. Additional research is needed to determine the function of these features in the etiology and course of asthenozoospermia.

Effects of PM2.5 and high-fat diet on glucose and lipid metabolisms and role of MT-COX3 methylation in male rats

Both fine particulate matter (PM2.5) and high-fat diet (HFD) can cause changes in glucose and lipid metabolisms; however, the mechanism of their combined effects on glucose and lipid metabolisms is still unclear. This study aimed to investigate the effects of PM2.5 and HFD co-exposure on glucose and lipid metabolisms and mitochondrial DNA methylation in Wistar rats. PM2.5 and HFD co-treatment led to an increase in fasting blood glucose levels, an alteration in glucose tolerance, and a decrease in high density lipoprotein cholesterol (HDL-C) levels in Wistar rats. In the homeostasis model assessment (HOMA), HOMA-insulin resistance (HOMA-IR) increased and HOMA-insulin sensitivity (HOMA-IS) and HOMA-β cell function (HOMA-β) decreased in rats co-exposed to PM2.5 and HFD. Additionally, superoxide dismutase (SOD) and malondialdehyde (MDA) levels were increased, and interleukin-6 (IL-6) and interleukin-10 (IL-10) mRNA expressions were upregulated in the brown adipose tissue following PM2.5 and HFD co-exposure. Bisulfite pyrosequencing was used to detect the methylation levels of mitochondrially-encoded genes (MT-COX1, MT-COX2 and MT-COX3), and MT-COX3 was hypermethylated in the PM2.5 and HFD co-exposure group. Moreover, MT-COX3-Pos.2 mediated 36.41 % (95 % CI: -27.42, -0.75) of the total effect of PM2.5 and HFD exposure on HOMA-β. Our study suggests that PM2.5 and HFD co-exposure led to changes in glucose and lipid metabolisms in rats, which may be related to oxidative stress and inflammatory responses, followed by mitochondrial stress leading to MT-COX3 hypermethylation. Moreover, MT-COX3-Pos.2 was found for the first time as a mediator in the impact of co-exposure to PM2.5 and HFD on β-cell function. It could serve as a potential biomarker, offering fresh insights into the prevention and treatment of metabolic diseases.

Epigenetic modifications in obesity-associated diseases

The global prevalence of obesity has reached epidemic levels, significantly elevating the susceptibility to various cardiometabolic conditions and certain types of cancer. In addition to causing metabolic abnormalities such as insulin resistance (IR), elevated blood glucose and lipids, and ectopic fat deposition, obesity can also damage pancreatic islet cells, endothelial cells, and cardiomyocytes through chronic inflammation, and even promote the development of a microenvironment conducive to cancer initiation. Improper dietary habits and lack of physical exercise are important behavioral factors that increase the risk of obesity, which can affect gene expression through epigenetic modifications. Epigenetic alterations can occur in early stage of obesity, some of which are reversible, while others persist over time and lead to obesity-related complications. Therefore, the dynamic adjustability of epigenetic modifications can be leveraged to reverse the development of obesity-associated diseases through behavioral interventions, drugs, and bariatric surgery. This review provides a comprehensive summary of the impact of epigenetic regulation on the initiation and development of obesity-associated cancers, type 2 diabetes, and cardiovascular diseases, establishing a theoretical basis for prevention, diagnosis, and treatment of these conditions.

Molecular mechanisms of noncoding RNA and epigenetic regulation in obesity with consequent diabetes mellitus development

Diabetes mellitus (DM) and obesity have become two of the most prevalent and challenging diseases worldwide, with increasing incidence and serious complications. Recent studies have shown that noncoding RNA (ncRNA) and epigenetic regulation play crucial roles in the pathogenesis of DM complicated by obesity. Identification of the involvement of ncRNA and epigenetic regulation in the pathogenesis of diabetes with obesity has opened new avenues of investigation. Targeting these mechanisms with small molecules or RNA-based therapies may provide a more precise and effective approach to diabetes treatment than traditional therapies. In this review, we discuss the molecular mechanisms of ncRNA and epigenetic regulation and their potential therapeutic targets, and the research prospects for DM complicated with obesity.

Understanding the Consequences of Fatty Bone and Fatty Muscle: How the Osteosarcopenic Adiposity Phenotype Uncovers the Deterioration of Body Composition

Adiposity is central to aging and several chronic diseases. Adiposity encompasses not just the excess adipose tissue but also body fat redistribution, fat infiltration, hypertrophy of adipocytes, and the shifting of mesenchymal stem cell commitment to adipogenesis. Bone marrow adipose tissue expansion, inflammatory adipokines, and adipocyte-derived extracellular vesicles are central to the development of osteopenic adiposity. Adipose tissue infiltration and local adipogenesis within the muscle are critical in developing sarcopenic adiposity and subsequent poorer functional outcomes. Ultimately, osteosarcopenic adiposity syndrome is the result of all the processes noted above: fat infiltration and adipocyte expansion and redistribution within the bone, muscle, and adipose tissues, resulting in bone loss, muscle mass/strength loss, deteriorated adipose tissue, and subsequent functional decline. Increased fat tissue, typically referred to as obesity and expressed by body mass index (the latter often used inadequately), is now occurring in younger age groups, suggesting people will live longer with the negative effects of adiposity. This review discusses the role of adiposity in the deterioration of bone and muscle, as well as adipose tissue itself. It reveals how considering and including adiposity in the definition and diagnosis of osteopenic adiposity, sarcopenic adiposity, and osteosarcopenic adiposity will help in better understanding the pathophysiology of each and accelerate possible therapies and prevention approaches for both relatively healthy individuals or those with chronic disease.

TET protein inhibitors: Potential and limitations

TET proteins (methylcytosine dioxygenases) play an important role in the regulation of gene expression. Dysregulation of their activity is associated with many serious pathogenic states such as oncological diseases. Regulation of their activity by specific inhibitors could represent a promising therapeutic strategy. Therefore, this review describes various types of TET protein inhibitors in terms of their inhibitory mechanism and possible applicability. The potential and possible limitations of this approach are thoroughly discussed in the context of TET protein functionality in living systems. Furthermore, possible therapeutic strategies based on the inhibition of TET proteins are presented and evaluated, especially in the field of oncological diseases.

Lower Circulating Cell-Free Mitochondrial DNA Is Associated with Heart Failure in Type 2 Diabetes Mellitus Patients

Cell-free nuclear (cf-nDNA) and mitochondrial (cf-mDNA) DNA are released from damaged cells in type 2 diabetes mellitus (T2DM) patients, contributing to adverse cardiac remodeling, vascular dysfunction, and inflammation. The purpose of this study was to correlate the presence and type of cf-DNAs with HF in T2DM patients. A total of 612 T2DM patients were prescreened by using a local database, and 240 patients (120 non-HF and 120 HF individuals) were ultimately selected. The collection of medical information, including both echocardiography and Doppler imagery, as well as the assessment of biochemistry parameters and the circulating biomarkers, were performed at baseline. The N-terminal brain natriuretic pro-peptide (NT-proBNP) and cf-nDNA/cf-mtDNA levels were measured via an ELISA kit and real-time quantitative PCR tests, respectively. We found that HF patients possessed significantly higher levels of cf-nDNA (9.9 ± 2.5 μmol/L vs. 5.4 ± 2.7 μmol/L; p = 0.04) and lower cf-mtDNA (15.7 ± 3.3 μmol/L vs. 30.4 ± 4.8 μmol/L; p = 0.001) than those without HF. The multivariate log regression showed that the discriminative potency of cf-nDNA >7.6 μmol/L (OR = 1.07; 95% CI = 1.03–1.12; p = 0.01) was higher that the NT-proBNP (odds ratio [OR] = 1.10; 95% confidence interval [CI] = 1.04–1.19; p = 0.001) for HF. In conclusion, we independently established that elevated levels of cf-nDNA, originating from NT-proBNP, were associated with HF in T2DM patients.