Testosterone Deficiency Caused by Castration Modulates Mitochondrial Biogenesis Through the AR/PGC1α/TFAM Pathway

Is castration leading to biological aging in dogs? Assessment of lipid peroxidation, inflammation, telomere length, mitochondrial DNA copy number, and expression of telomerase and age-related genes

BACKGROUND

Biological aging is a complex process influenced by various factors, including reproductive status and castration. This study aimed to evaluate the impact of castration on biological aging in dogs.

METHOD

Fifteen male crossbred dogs were randomly divided into a sham-operation control group (n = 5) and a castrated group (n = 10). Blood samples were collected at weeks 0, 4, 8, 12, 16, and 18 post-surgery. Malondialdehyde (MDA as indicator of Lipid peroxidation), C-reactive protein (as an indicator of inflammation), telomere length, mitochondrial DNA (mtDNA) copy number, and the expression of age-related (P16, P21, TBX2) and telomerase-related (TERT) genes were assessed in blood samples.

RESULTS

Plasma MDA levels were higher in the control group at weeks 16 and 18, while CRP levels were higher only at week 18. Telomere length and mtDNA copy number were lower in the control group at week 18. Gene expression analysis showed that P16 was lower in the control group at weeks 8 and 12, P21 and TERT were lower at weeks 16 and 18, and TBX2 was lower at weeks 16 and 18. The TBX2/P16 ratio was lower in the control group at weeks 16 and 18 but higher at week 12, while the TBX2/P21 ratio did not differ between groups.

CONCLUSION

Castration appears to have a protective effect against biological aging in dogs, as evidenced by lower lipid peroxidation, inflammation, and age-related changes in telomere length, mtDNA copy number, and gene expression.

Sex-Related Differences in the Pathophysiology, Cardiac Imaging, and Clinical Outcomes of Aortic Stenosis: A Narrative Review

Aortic stenosis (AS) is the most common valvular heart disease in developed countries, and its prevalence is higher in older patients. Clinical studies have shown gender disparity in the pathogenesis and the progression of aortic stenosis. This disparity has led to several overwhelming questions regarding its impact on the clinical outcomes and treatment of the disease and the requirement of personalized sex-specific approaches for its management. Indeed, aortic stenosis differs in the pathophysiological response to pressure overload created by the stenosis in women compared to men, which would translate into differences in cardiac remodeling and clinical outcomes. Several studies have focused on understanding the differences regarding disease progression according to biological gender and have found that sex hormones play a crucial role. Sex hormones affect many metabolic processes, thus activating crucial cell signaling and energy metabolism through mitochondrial activity. Yet, there is still a significant gap in knowledge on how biological sex influences the pathophysiology of AS. In this review, we have discussed studies that point to the role of sex-related physiological differences in the molecular pathways and the clinical presentation of the disease and outcome in women and men. We used the format of narrative review to review and summarize the body of literature without being systematic but with taking great care of considering the most impactful data available to date on the topic, especially randomized trials, metanalyses, and prospective studies and registries when available, as well as experimental studies with rigorous methodological approaches regarding the basic mechanisms and pathophysiology of the disease in women compared to men. The opinion of the authors on a particular issue or finding was expressed when appropriate for clarification.

Testosterone Inhibits Lipid Accumulation in Porcine Preadipocytes by Regulating ELOVL3

Castration is commonly used to reduce stink during boar production. In porcine adipose tissue, castration reduces androgen levels resulting in metabolic disorders and excessive fat deposition. However, the underlying detailed mechanism remains unclear. In this study, we constructed porcine preadipocyte models with and without androgen by adding testosterone exogenously. The fluorescence intensity of lipid droplet (LD) staining and the fatty acid synthetase (FASN) mRNA levels were lower in the testosterone-treated cells than in the untreated control cells. In contrast, the mRNA levels of adipose triglycerides lipase (ATGL) and androgen receptor (AR) were higher than in the testosterone-treated cells than in the control cells. Subsequently, transcriptomic sequencing of porcine preadipocytes incubated with and without testosterone showed that the mRNA expression levels of very long-chain fatty acid elongase 3 (ELOVL3), a key enzyme involved in fatty acids synthesis and metabolism, were high in control cells. The siRNA-mediated knockdown of ELOVL3 reduced LD accumulation and the mRNA levels of FASN and increased the mRNA levels of ATGL. Next, we conducted dual-luciferase reporter assays using wild-type and mutant ELOVL3 promoter reporters, which showed that the ELOVL3 promoter contained an androgen response element (ARE); furthermore, its transcription was negatively regulated by AR overexpression. In conclusion, our study reveals that testosterone inhibits fat deposition in porcine preadipocytes by suppressing ELOVL3 expression. Moreover, our study provides a theoretical basis for further studies on the mechanisms of fat deposition caused by castration.

Mitochondrial Elongation and ROS-Mediated Apoptosis in Prostate Cancer Cells under Therapy with Apalutamide and Complex I Inhibitor

Metabolic reprogramming and mitochondrial dynamics are pivotal in prostate cancer (PCa) progression and treatment resistance, making them essential targets for therapeutic intervention. In this study, we investigated the effects of the androgen receptor antagonist apalutamide (ARN) and the mitochondrial electron transport chain complex I inhibitor IACS-010759 (IACS) on the mitochondrial network architecture and dynamics in PCa cells. Treatment with ARN and/or IACS induced significant changes in mitochondrial morphology, particularly elongation, in androgen-sensitive PCa cells. Additionally, ARN and IACS modulated the mitochondrial fission and fusion processes, indicating a convergence of metabolic and androgen-signaling pathways in shaping mitochondrial function. Notably, the combination treatment with ARN and IACS resulted in increased apoptotic cell death and mitochondrial oxidative stress selectively in the androgen-sensitive PCa cells. Our findings highlight the therapeutic potential of targeting mitochondrial metabolism in prostate cancer and emphasize the need for further mechanistic understanding to optimize treatment strategies and improve patient outcomes.

Testosterone deficiency worsens mitochondrial dysfunction in APP/PS1 mice

Background

Recent studies show testosterone (T) deficiency worsens cognitive impairment in Alzheimer's disease (AD) patients. Mitochondrial dysfunction, as an early event of AD, is becoming critical hallmark of AD pathogenesis. However, currently, whether T deficiency exacerbates mitochondrial dysfunction of men with AD remains unclear.

Objective

The purpose of this study is to explore the effects of T deficiency on mitochondrial dysfunction of male AD mouse models and its potential mechanisms.

Methods

Alzheimer's disease animal model with T deficiency was performed by castration to 3-month-old male APP/PS1 mice. Hippocampal mitochondrial function of mice was analyzed by spectrophotometry and flow cytometry. The gene expression levels related to mitochondrial biogenesis and mitochondrial dynamics were determined through quantitative real-time PCR (qPCR) and western blot analysis. SH-SY5Y cells treated with flutamide, T and/or H2O2 were processed for analyzing the potential mechanisms of T on mitochondrial dysfunction.

Results

Testosterone deficiency significantly aggravated the cognitive deficits and hippocampal pathologic damage of male APP/PS1 mice. These effects were consistent with exacerbated mitochondrial dysfunction by gonadectomy to male APP/PS1 mice, reflected by further increase in oxidative damage and decrease in mitochondrial membrane potential, complex IV activity and ATP levels. More importantly, T deficiency induced the exacerbation of compromised mitochondrial homeostasis in male APP/PS1 mice by exerting detrimental effects on mitochondrial biogenesis and mitochondrial dynamics at mRNA and protein level, leading to more defective mitochondria accumulated in the hippocampus. In vitro studies using SH-SY5Y cells validated T's protective effects on the H2O2-induced mitochondrial dysfunction, mitochondrial biogenesis impairment, and mitochondrial dynamics imbalance. Administering androgen receptor (AR) antagonist flutamide weakened the beneficial effects of T pretreatment on H2O2-treated SH-SY5Y cells, demonstrating a critical role of classical AR pathway in maintaining mitochondrial function.

Conclusion

Testosterone deficiency exacerbates hippocampal mitochondrial dysfunction of male APP/PS1 mice by accumulating more defective mitochondria. Thus, appropriate T levels in the early stage of AD might be beneficial in delaying AD pathology by improving mitochondrial biogenesis and mitochondrial dynamics.

Investigation of Mitochondrial Homeostasis Changes in Lens Epithelium of High-Myopic Cataract

PURPOSE

High myopia is demonstrated as a pathogenic factor for nuclear cataract. The main mechanism of high-myopia cataracts (HMC) is oxidative damage, which causes mitochondrial homeostasis imbalance. This study aimed to explore the mitochondrial homeostasis alterations in lens epithelial cells (LECs) of HMC.

METHODS

The lens epithelium tissues of 20 patients with HMC and 20 control subjects with age-related cataracts (ARC) were collected. The real-time quantitative PCR and western blot assays were performed for gene expressions. Immunofluorescence (IF) assays were performed for mitochondrial marker TOM20, DNA damage marker 15A3, and autophagosome marker LC3. Transmission electron microscopy (TEM) was used to observe the changes in mitochondria morphology. Mitochondrial ROS, and mitochondrial membrane potential were detected by MitoSOX fluorescence, and JC-1 MitoMP staining, respectively. Rat lenses cultured in vitro were pretreated with CCCP and H2O2 (10 and 400 µM) for 24 h.

RESULTS

The copy number of mtDNA was decreased in HMC patients compared to the ARC patients. Increased mitochondrial-oriented oxidative stress response was detected in LECs of HMC compared to that of ARC. Altered expressions of mitochondrial homeostasis and mitophagy markers, including TFAM, PGC1α, MFN1, MFN2, Drp1, PINK1, Parkin and LC3, were found in HMC patients. Reciprocally, no significant differences in the expression of BNIP3 and FUNDC1 were found between HMC and ARC patients. Importantly, TEM revealed that the obvious mitochondrial fission and mitophagy phenomena occur in the LECs of HMC patients compared to the ARC patients. Moreover, CCCP aggreated the mitoROS production and depolarized mitochondrial membrane potential in the H2O2-treated human lens epithelial cells line (SRA01/04); Most important, rat lens organ culture experiments indicated a significant increase in H2O2-induced lens opacity following mitochondrial uncoupling CCCP treatment.

CONCLUSION

This study has identified for the first time the abnormal mitochondrial homeostasis in HMC, and provide a new perspective on the potential mechanisms of HMC, which occurs earlier and at a higher incidence rate than ARC.

Tetramethylpyrazine protects mitochondrial function by up-regulation of TFAM and inhibition of neuronal apoptosis in a rat model of surgical brain injury

Objectives

Mitochondrial dysfunction caused by mitochondrial DNA (mtDNA) damage and mutation is widely accepted as one of the pathological processes of neurodegenerative diseases. As an mtDNA binding protein, mitochondrial transcription factor A (TFAM) maintains the integrity of mtDNA through transcription, replication, nucleoid formation, damage perception, and DNA repair. In recent works, the overexpression of TFAM increased the mtDNA copy count, promoted mitochondrial function, and improved the neurological dysfunction of neurodegenerative diseases. The role of TFAM in neurodegenerative diseases has been well explained. However, the role of TFAM after surgical brain injury (SBI) has not been studied. In this work, we aimed to study the role of TFAM in the brain after SBI and its mechanism of action.

Materials and Methods

One hour after the occurrence of SBI, tetramethylpyrazine (TMP) was injected into the abdominal cavity of rats, and the brain was collected 48 hr later for testing. The evaluation included neurobehavioral function test, brain water content measurement, immunofluorescence, western blot, TUNEL staining, FJC staining, ROS test, and ATP test.

Results

After SBI, the content of TFAM on the ipsilateral side increased and reached a peak at about 48 hr. After intraperitoneal injection of TMP in rats, 48 hr after SBI, the concentration of TFAM, Bcl-2, and adenosine triphosphate (ATP) increased; the content of caspase-3, reactive oxygen species (ROS), and cerebral edema decreased; and the nerve function significantly improved.

Conclusion

TMP inhibited cell apoptosis after SBI in rats by up-regulating TFAM and protecting brain tissues.

Advances in mitochondria-centered mechanism behind the roles of androgens and androgen receptor in the regulation of glucose and lipid metabolism

An increasing number of studies have reported that androgens and androgen receptors (AR) play important roles in the regulation of glucose and lipid metabolism. Impaired glucose and lipid metabolism and the development of obesity-related diseases have been found in either hypogonadal men or male rodents with androgen deficiency. Exogenous androgens supplementation can effectively improve these disorders, but the mechanism by which androgens regulate glucose and lipid metabolism has not been fully elucidated. Mitochondria, as powerhouses within cells, are key organelles influencing glucose and lipid metabolism. Evidence from both pre-clinical and clinical studies has reported that the regulation of glucose and lipid metabolism by androgens/AR is strongly associated with the impact on the content and function of mitochondria, but few studies have systematically reported the regulatory effect and the molecular mechanism. In this paper, we review the effect of androgens/AR on mitochondrial content, morphology, quality control system, and function, with emphases on molecular mechanisms. Additionally, we discuss the sex-dimorphic effect of androgens on mitochondria. This paper provides a theoretical basis for shedding light on the influence and mechanism of androgens on glucose and lipid metabolism and highlights the mitochondria-based explanation for the sex-dimorphic effect of androgens on glucose and lipid metabolism.

Characterization of trophoblast mitochondrial function and responses to testosterone treatment in ACH-3P cells

INTRODUCTION

Trophoblast mitochondria play important roles in placental energy metabolism, physiology and pathophysiology. Hyperandrogenism has been associated with mitochondrial abnormalities in pregnancy disorders such as pre-eclampsia, gestational diabetes, and intrauterine growth restriction, but the direct impacts of androgen exposure on placental mitochondrial function are unknown. Given the inherent limitations of studying the human placenta during pregnancy, trophoblast cell lines are routinely used to model placental biology in vitro. The aim of this study was to characterize mitochondrial respiratory function in four commonly used trophoblast cell lines to provide a basis for selecting one well-suited to investigating the impact of androgens on trophoblast mitochondrial function.

METHODS

Androgen receptor expression, mitochondrial respiration (JO₂) and reactive oxygen species (ROS) release rates were evaluated in three human trophoblast cell lines (ACH-3P, BeWo and Swan-71) and one immortalized ovine trophoblast line (iOTR) under basal and substrate-stimulated conditions using high-resolution fluorespirometry.

RESULTS

ACH-3P cells exhibited the greatest mitochondrial respiratory capacity and coupling efficiency of the four trophoblast lines tested, along with robust expression of androgen receptor protein that was found to co-localize with mitochondria by immunoblot and immunofluorescence. Acute testosterone administration (10 nM) tended to decrease ACH-3P mitochondrial JO₂ and increase ROS release, while chronic (7 days) testosterone exposure increased expression of mitochondrial proteins, JO₂, and ROS release.

DISCUSSION

These studies establish ACH-3P as a suitable cell line for investigating trophoblast mitochondrial function, and provide foundational evidence supporting links between hyperandrogenism and placental mitochondrial ROS production with potential relevance to several common pregnancy disorders.

NRF-2α and mitophagy underlie enhanced mitochondrial functions and biogenesis induced by T-2 toxin in GH3 cells

T-2 toxin is a natural contaminant in grain cereals produced by species of Fusarium. Studies indicate that T-2 toxin can positively affect mitochondrial function, but the underlying mechanism is unclear. In this study, we examined the role of nuclear respiratory factor 2α (NRF-2α) in T-2 toxin-activated mitochondrial biogenesis and the direct target genes of NRF-2α. Furthermore, we investigated T-2 toxin-induced autophagy and mitophagy, and the role of mitophagy in changes in mitochondrial function and apoptosis. It was found that T-2 toxin significantly increased NRF-2α levels and nuclear localization of NRF-2α was induced. NRF-2α deletion significantly increased the production of reactive oxygen species (ROS), abrogated T-2 toxin-induced increases in ATP and mitochondrial complex I activity, and inhibited the mitochondrial DNA copy number. Meanwhile, With chromatin immunoprecipitation sequencing (ChIP-Seq), various novel NRF-2α target genes were identified, such as mitochondrial iron-sulphur subunits (Ndufs 3,7) and mitochondrial transcription factors (Tfam, Tfb1m, and Tfb2m). Some target genes were also involved in mitochondrial fusion and fission (Drp1), mitochondrial translation (Yars2) and splicing (Ddx55), and mitophagy. Further studies showed that T-2 toxin induced Atg5 dependent autophagy and Atg5/PINK1-dependent mitophagy. In addition, mitophagy defects increase ROS production, inhibit ATP levels and the expression of genes related to mitochondrial dynamics, and promote apoptosis in the presence of T-2 toxins. Altogether, these results suggest that NRF-2α plays a critical role in promoting mitochondrial function and biogenesis through regulation of mitochondrial genes, and, interestingly, mitophagy caused by T-2 toxin positively affected mitochondrial function and protected cell survival against T-2 toxin.

Developmental programming of mitochondrial substrate metabolism in skeletal muscle of adult sheep by cortisol exposure before birth

Prenatal glucocorticoid overexposure causes adult metabolic dysfunction in several species but its effects on adult mitochondrial function remain largely unknown. Using respirometry, this study examined mitochondrial substrate metabolism of fetal and adult ovine biceps femoris (BF) and semitendinosus (ST) muscles after cortisol infusion before birth. Physiological increases in fetal cortisol concentrations pre-term induced muscle- and substrate-specific changes in mitochondrial oxidative phosphorylation capacity in adulthood. These changes were accompanied by muscle-specific alterations in protein content, fibre composition and abundance of the mitochondrial electron transfer system (ETS) complexes. In adult ST, respiration using palmitoyl-carnitine and malate was increased after fetal cortisol treatment but not with other substrate combinations. There were also significant increases in protein content and reductions in the abundance of all four ETS complexes, but not ATP synthase, in the ST of adults receiving cortisol prenatally. In adult BF, intrauterine cortisol treatment had no effect on protein content, respiratory rates, ETS complex abundances or ATP synthase. Activity of citrate synthase, a marker of mitochondrial content, was unaffected by intrauterine treatment in both adult muscles. In the ST but not BF, respiratory rates using all substrate combinations were significantly lower in the adults than fetuses, predominantly in the saline-infused controls. The ontogenic and cortisol-induced changes in mitochondrial function were, therefore, more pronounced in the ST than BF muscle. Collectively, the results show that fetal cortisol overexposure programmes mitochondrial substrate metabolism in specific adult muscles with potential consequences for adult metabolism and energetics.

From mitochondria to sarcopenia: role of 17β-estradiol and testosterone

Sarcopenia, characterized by a loss of muscle mass and strength with aging, is prevalent in older adults. Although the exact mechanisms underlying sarcopenia are not fully understood, evidence suggests that the loss of mitochondrial integrity in skeletal myocytes has emerged as a pivotal contributor to the complex etiology of sarcopenia. Mitochondria are the primary source of ATP production and are also involved in generating reactive oxygen species (ROS), regulating ion signals, and initiating apoptosis signals in muscle cells. The accumulation of damaged mitochondria due to age-related impairments in any of the mitochondrial quality control (MQC) processes, such as proteostasis, biogenesis, dynamics, and mitophagy, can contribute to the decline in muscle mass and strength associated with aging. Interestingly, a decrease in sex hormones (e.g., 17β-estradiol and testosterone), which occurs with aging, has also been linked to sarcopenia. Indeed, 17β-estradiol and testosterone targeted mitochondria and exhibited activities in regulating mitochondrial functions. Here, we overview the current literature on the key mechanisms by which mitochondrial dysfunction contribute to the development and progression of sarcopenia and the potential modulatory effects of 17β-estradiol and testosterone on mitochondrial function in this context. The advance in its understanding will facilitate the development of potential therapeutic agents to mitigate and manage sarcopenia.

Androgen and androgen receptor control of mitochondrial function

The effects of androgens have been extensively studied in a variety of organs and cell types with increasing focus on the sexually dimorphic role androgens play not only with respect to cellular functions but also in metabolism. Although the classical mechanism of androgen action is via ligand-dependent binding with the nuclear transcription factor, androgen receptor (AR), cytosolic AR can also activate second messenger signaling pathways. Given that cytosolic AR can signal in this manner, there has been increased interest in the mechanisms by which androgens may control cellular organelle function. This review highlights the effects that androgens have on mitochondrial structure and function with emphasis on biogenesis, fusion/fission, mitophagy, bioenergetics (oxidative phosphorylation), and reactive oxygen species production. There are a number of publications on the effects of androgens in these general areas of mitochondrial function. However, the precise mechanisms by which androgens cause these effects are not known. Additionally, given that the nucleus and mitochondria work in tandem to control mitochondrial function and the mitochondria has its own DNA, future research efforts should focus on the direct, mechanistic effects of androgens on mitochondrial function.

Sesamol Reverses Myofiber-Type Conversion in Obese States via Activating the SIRT1/AMPK Signal Pathway

Obesity can evoke changes of skeletal muscle structure and function, which are characterized by the conversion of myofiber from type I to type II, leading to a vicious cycle of metabolic disorders. Reversing the muscle fiber-type conversion in obese states is a novel strategy for treating those with obesity. Sesamol, a food ingredient compound isolated from sesame seeds, exerted potential antiobesity effects. The present research aimed to explore the therapeutic effects of sesamol on obesity-related skeletal muscle-fiber-type conversion and elucidate the underlying molecular mechanisms through utilizing a high-fat-diet-induced obese C57BL/6J mice model and palmitic acid-exposed C2C12 myotubes. The results showed that sesamol attenuated obesity-related metabolic disturbances, elevated exercise endurance of obese mice, and decreased lipid accumulation and insulin resistance in skeletal muscle. After the treatment with sesamol, the muscular mitochondrial content and biogenesis were increased, accompanied by the enzyme activities and myosin heavy-chain isoform changed from type II fiber to type I fiber. Mechanistic studies revealed that the effects of sesamol on reversing skeletal muscle-fiber-type conversion in obese states were associated with the stimulation of the muscular sirtuin 1 (SIRT1)/AMP-activated protein kinase (AMPK) signal pathway, and these effects could be inhibited by a specific inhibitor of SIRT1, EX-527. In conclusion, our research provided novel evidence that sesamol could regulate myofiber-type conversion to treat obesity and obesity-related metabolic disorders by stimulating the muscular SIRT1/AMPK signal pathway.

Polycystic ovarian syndrome: signs and feedback effects of hyperandrogenism and insulin resistance

Polycystic ovary syndrome (PCOS) is a disease whose diagnosis is based on the detection of hyperandrogenism (HA) and ovulatory dysfunction. Women with PCOS frequently develop insulin resistance (IR), which generates a metabolic condition that involves a decrease in the action of insulin at the cellular level and is linked to compensatory hyperinsulinemia (HI). In PCOS, the ovary remains sensitive to the action of insulin. Additionally, it has been observed that the main effect of insulin in the ovary is the stimulation of androgen synthesis, resulting in HA, one of the fundamental characteristics of the PCOS. In this sense, the excess of androgens favors the development of IR, thus perpetuating the cycle of IR-HI-HA, and therefore PCOS. Moreover, mitochondrial dysfunction is present in PCOS patients and is a common feature in both IR and HA. This review places electron transfer as a key element in HA and IR development, with emphasis on the relationship between androgen biosynthesis and mitochondrial function. Indeed, metformin has been involved in repair mitochondrial dysfunction, decrease of oxidative stress, reduction of androgens levels and the enhancing of insulin sensitivity. Therefore, we propose that treatment with metformin could decrease HI and consequently HA, restoring, at least in part, the metabolic and hormonal disorders of PCOS.

DNA Methylation of PGC-1α Is Associated With Elevated mtDNA Copy Number and Altered Urinary Metabolites in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complex disorder that is underpinned by numerous dysregulated biological pathways, including pathways that affect mitochondrial function. Epigenetic mechanisms contribute to this dysregulation and DNA methylation is an important factor in the etiology of ASD. We measured DNA methylation of peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1α), as well as five genes involved in regulating mitochondrial homeostasis to examine mitochondrial dysfunction in an ASD cohort of South African children. Using targeted Next Generation bisulfite sequencing, we found differential methylation (p < 0.05) at six key genes converging on mitochondrial biogenesis, fission and fusion in ASD, namely PGC-1α, STOML2, MFN2, FIS1, OPA1, and GABPA. PGC-1α, the transcriptional regulator of biogenesis, was significantly hypermethylated at eight CpG sites in the gene promoter, one of which contained a putative binding site for CAMP response binding element 1 (CREB1) (p = 1 × 10^–6). Mitochondrial DNA (mtDNA) copy number, a marker of mitochondrial function, was elevated (p = 0.002) in ASD compared to controls and correlated significantly with DNA methylation at the PGC-1α promoter and there was a positive correlation between methylation at PGC-1α CpG#1 and mtDNA copy number (Spearman’s r = 0.2, n = 49, p = 0.04) in ASD. Furthermore, DNA methylation at PGC-1α CpG#1 and mtDNA copy number correlated significantly (p < 0.05) with levels of urinary organic acids associated with mitochondrial dysfunction, oxidative stress, and neuroendocrinology. Our data show differential methylation in ASD at six key genes converging on PGC-1α-dependent regulation of mitochondrial biogenesis and function. We demonstrate that methylation at the PGC-1α promoter is associated with elevated mtDNA copy number and metabolomic evidence of mitochondrial dysfunction in ASD. This highlights an unexplored role for DNA methylation in regulating specific pathways involved in mitochondrial biogenesis, fission and fusion contributing to mitochondrial dysfunction in ASD.

Testosterone treatment is associated with reduced adipose tissue dysfunction and nonalcoholic fatty liver disease in obese hypogonadal men

PURPOSE

In both preclinical and clinical settings, testosterone treatment (TTh) of hypogonadism has shown beneficial effects on insulin sensitivity and visceral and liver fat accumulation. This prospective, observational study was aimed at assessing the change in markers of fat and liver functioning in obese men scheduled for bariatric surgery.

METHODS

Hypogonadal patients with consistent symptoms (n = 15) undergoing 27.63 ± 3.64 weeks of TTh were compared to untreated eugonadal (n = 17) or asymptomatic hypogonadal (n = 46) men. A cross-sectional analysis among the different groups was also performed, especially for data derived from liver and fat biopsies. Preadipocytes isolated from adipose tissue biopsies were used to evaluate insulin sensitivity, adipogenic potential and mitochondrial function. NAFLD was evaluated by triglyceride assay and by calculating NAFLD activity score in liver biopsies.

RESULTS

In TTh-hypogonadal men, histopathological NAFLD activity and steatosis scores, as well as liver triglyceride content were lower than in untreated-hypogonadal men and comparable to eugonadal ones. TTh was also associated with a favorable hepatic expression of lipid handling-related genes. In visceral adipose tissue and preadipocytes, TTh was associated with an increased expression of lipid catabolism and mitochondrial bio-functionality markers. Preadipocytes from TTh men also exhibited a healthier morpho-functional phenotype of mitochondria and higher insulin-sensitivity compared to untreated-hypogonadal ones.

CONCLUSIONS

The present data suggest that TTh in severely obese, hypogonadal individuals induces metabolically healthier preadipocytes, improving insulin sensitivity, mitochondrial functioning and lipid handling. A potentially protective role for testosterone on the progression of NAFLD, improving hepatic steatosis and reducing intrahepatic triglyceride content, was also envisaged.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02248467, September 25th 2014.

Mechanistic insights into AMPK-SIRT3 positive feedback loop-mediated chondrocyte mitochondrial quality control in osteoarthritis pathogenesis

Osteoarthritis (OA) is a major cause of disability in the elderly population and represents a significant public health problem and socioeconomic burden worldwide. However, no disease-modifying therapeutics are currently available for OA due to an insufficient understanding of the pathogenesis of this disability. As a unique cell type in cartilage, chondrocytes are essential for cartilage homeostasis and play a critical role in OA pathogenesis. Mitochondria are important metabolic centers in chondrocytes and contribute to cell survival, and mitochondrial quality control (MQC) is an emerging mechanism for maintaining cell homeostasis. An increasing number of recent studies have demonstrated that dysregulation of the key processes of chondrocyte MQC, which involve mitochondrial redox, biogenesis, dynamics, and mitophagy, is associated with OA pathogenesis and can be regulated by the chondroprotective molecules 5' adenosine monophosphate-activated protein kinase (AMPK) and sirtuin 3 (SIRT3). Moreover, AMPK and SIRT3 regulate each other, and their expression and activity are always consistent in chondrocytes, which suggests the existence of an AMPK-SIRT3 positive feedback loop (PFL). Although the precise mechanisms are not fully elucidated and need further validation, the current literature indicates that this AMPK-SIRT3 PFL regulates OA development and progression, at least partially by mediating chondrocyte MQC. Therefore, understanding the mechanisms of AMPK-SIRT3 PFL-mediated chondrocyte MQC in OA pathogenesis might yield new ideas and potential targets for subsequent research on the OA pathomechanism and therapeutics.

Mitochondria in Sex Hormone-Induced Disorder of Energy Metabolism in Males and Females

Androgens have a complex role in the regulation of insulin sensitivity in the pathogenesis of type 2 diabetes. In male subjects, a reduction in androgens increases the risk for insulin resistance, which is improved by androgen injections. However, in female subjects with polycystic ovary syndrome (PCOS), androgen excess becomes a risk factor for insulin resistance. The exact mechanism underlying the complex activities of androgens remains unknown. In this review, a hormone synergy-based view is proposed for understanding this complexity. Mitochondrial overactivation by substrate influx is a mechanism of insulin resistance in obesity. This concept may apply to the androgen-induced insulin resistance in PCOS. Androgens and estrogens both exhibit activities in the induction of mitochondrial oxidative phosphorylation. The two hormones may synergize in mitochondria to induce overproduction of ATP. ATP surplus in the pancreatic β-cells and α-cells causes excess secretion of insulin and glucagon, respectively, leading to peripheral insulin resistance in the early phase of type 2 diabetes. In the skeletal muscle and liver, the ATP surplus contributes to insulin resistance through suppression of AMPK and activation of mTOR. Consistent ATP surplus leads to mitochondrial dysfunction as a consequence of mitophagy inhibition, which provides a potential mechanism for mitochondrial dysfunction in β-cells and brown adipocytes in PCOS. The hormone synergy-based view provides a basis for the overactivation and dysfunction of mitochondria in PCOS-associated type 2 diabetes. The molecular mechanism for the synergy is discussed in this review with a focus on transcriptional regulation. This view suggests a unifying mechanism for the distinct metabolic roles of androgens in the control of insulin action in men with hypogonadism and women with PCOS.

Changes in peripheral mitochondrial DNA copy number in metformin-treated women with polycystic ovary syndrome: a longitudinal study

BACKGROUND

Patients with polycystic ovarian syndrome (PCOS) are associated with known alterations in mitochondria DNA copy number (mtDNA-CN). The aim of this study is to study the change in mtDNA-CN in patients with PCOS who were treated with metformin.

METHODS

This is a prospective cohort of patients with PCOS, who received metformin for one year. From 2009 to 2015, 88 women diagnosed with PCOS, based on the Rotterdam criteria, were enrolled. Serial measurements of mtDNA-CN, 8-hydroxydeoxyguanosine (8-OHdG), anthropometric, metabolic, endocrine, and inflammatory markers were obtained before and after 3, 6, and 12 months of treatment.

RESULTS

A significant decrease in mtDNA-CN was seen over the course of one year. Other markers, including 8-OHdG, testosterone, free androgen index, blood pressure and liver enzymes, also decreased in the same interval. On regression analysis, there was a significant association between the change in mtDNA-CN and serum total testosterone, and no association between mtDNA-CN and metabolic factors.

CONCLUSIONS

Treatment with metformin is associated with a time-dependent decrease in mtDNA-CN in patients with PCOS who are treated over the course of one year. This may signify a reduction in mitochondria dysfunction. The change in mtDNA-CN corresponds to a similar change in serum total testosterone, and suggests a possible relationship between mtDNA-CN and testosterone.

TRIAL REGISTRATION

ClinicalTrials.gov , NCT00172523 . Registered September 15, 2005.

CD8 T-cell Recruitment Into the Central Nervous System of Cuprizone-Fed Mice: Relevance to Modeling the Etiology of Multiple Sclerosis

Cuprizone (CPZ)-feeding in mice induces atrophy of peripheral immune organs (thymus and spleen) and suppresses T-cell levels, thereby limiting its use as a model for studying the effects of the immune system in demyelinating diseases such as Multiple Sclerosis (MS). To investigate whether castration (Cx) can protect the peripheral immune organs from CPZ-induced atrophy and enable T-cell recruitment into the central nervous system (CNS) following a breach of the blood-brain barrier (BBB), three related studies were carried out. In Study 1, Cx prevented the dose-dependent reductions (0.1% < 0.2% CPZ) in thymic and splenic weight, size of the thymic medulla and splenic white pulp, and CD4 and CD8 (CD4/8) levels remained comparable to gonadally intact (Gi) control males. Importantly, 0.1% and 0.2% CPZ were equipotent at inducing central demyelination and glial activation. In Study 2, combining Cx with 0.1% CPZ-feeding and BBB disruption with pertussis toxin (PT) enhanced CD8⁺ T-cell recruitment into the CNS. The increased CD8⁺ T-cell level observed in the parenchyma of the cerebrum, cerebellum, brainstem and spinal cord were confirmed by flow cytometry and western blot analyses of CNS tissue. In Study 3, PT+0.1% CPZ-feeding to Gi female mice resulted in similar effects on the peripheral immune organs, CNS demyelination, and gliosis comparable to Gi males, indicating that testosterone levels alone were not responsible for the immune response seen in Study 2. The combination of Cx+0.1% CPZ-feeding+PT indicates that CPZ-induced demyelination can trigger an “inside-out” immune response when the peripheral immune system is spared and may provide a better model to study the initiating events in demyelinating conditions such as MS.