PGC-1alpha: a potent transcriptional cofactor involved in the pathogenesis of type 2 diabetes

RNA-sequencing revisited data shed new light on wooden breast myopathy

Wooden Breast (WB) abnormality represents one of the major challenges that the poultry industry has faced in the last 10 years. Despite the enormous progress in understanding the mechanisms underlying WB, the precise initial causes remain to be clarified. In this scenario, the present research is intended to characterize the gene expression profiles of broiler Pectoralis major muscles affected by WB, comparing them to the unaffected counterpart, to provide new insights into the biological mechanisms underlying this defect and potentially identifying novel genes likely involved in its occurrence. To this purpose, data obtained in a previous study through the RNA-sequencing technology have been used to identify differentially expressed genes (DEGs) between 6 affected and 5 unaffected broilers' breast muscles, by using the newest reference genome assembly for Gallus gallus (GRCg7b). Also, to deeply investigate molecular and biological pathways involved in the WB progression, pathways analyses have been performed. The results achieved through the differential gene expression analysis mainly evidenced the downregulation of glycogen metabolic processes, gluconeogenesis, and tricarboxylic acid cycle in WB muscles, thus corroborating the evidence of a dysregulated energy metabolism characterizing breasts affected by this abnormality. Also, genes related to hypertrophic muscle growth have been identified as differentially expressed (e.g., WFIKKN1). Together with that, a downregulation of genes involved in mitochondrial biogenesis and functionality has been detected. Among them, PPARGC1A and PPARGC1B chicken genes are particularly noteworthy. These genes not only have essential roles in regulating mitochondrial biogenesis but also play pivotal roles in maintaining glucose and energy homeostasis. In view of that, their downregulation in WB-affected muscle may be considered as potentially related to both the mitochondrial dysfunction and altered glucose metabolism in WB muscles, and their key involvement in the molecular alterations characterizing this muscular abnormality might be hypothesized.

DNA methylation in human diseases

Aberrant epigenetic modifications, particularly DNA methylation, play a critical role in the pathogenesis and progression of human diseases. The current review aims to reveal the role of aberrant DNA methylation in the pathogenesis and progression of diseases and to discuss the original data obtained from international research laboratories on this topic. In the review, we mainly summarize the studies exploring the role of aberrant DNA methylation as diagnostic and prognostic biomarkers in a broad range of human diseases, including monogenic epigenetics, autoimmunity, metabolic disorders, hematologic neoplasms, and solid tumors. The last section provides a general overview of the possibility of the DNA methylation machinery from the perspective of pharmaceutic approaches. In conclusion, the study of DNA methylation machinery is a phenomenal intersection that each of its ways can reveal the mysteries of various diseases, introduce new diagnostic and prognostic biomarkers, and propose a new patient-tailored therapeutic approach for diseases.

SIRT6's function in controlling the metabolism of lipids and glucose in diabetic nephropathy

Diabetic nephropathy (DN) is a complication of diabetes mellitus (DM) and the main cause of excess mortality in patients with type 2 DM. The pathogenesis and progression of DN are closely associated with disorders of glucose and lipid metabolism. As a member of the sirtuin family, SIRT6 has deacetylation, defatty-acylation, and adenosine diphosphate-ribosylation enzyme activities as well as anti-aging and anticancer activities. SIRT6 plays an important role in glucose and lipid metabolism and signaling, especially in DN. SIRT6 improves glucose and lipid metabolism by controlling glycolysis and gluconeogenesis, affecting insulin secretion and transmission and regulating lipid decomposition, transport, and synthesis. Targeting SIRT6 may provide a new therapeutic strategy for DN by improving glucose and lipid metabolism. This review elaborates on the important role of SIRT6 in glucose and lipid metabolism, discusses the potential of SIRT6 as a therapeutic target to improve glucose and lipid metabolism and alleviate DN occurrence and progression of DN, and describes the prospects for future research.

Interactive Associations between PPARγ and PPARGC1A and Bisphosphonate-Related Osteonecrosis of the Jaw in Patients with Osteoporosis

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is a rare but severe adverse effect that can occur as a result of bisphosphonate treatment. This study aimed to examine the relationship between PPARγ and PPARGC1A polymorphisms and the BRONJ development in female osteoporosis patients undergoing bisphosphonate treatment. We prospectively conducted this nested case-control study at the Ewha Womans University Mokdong Hospital between 2014 and 2018. We assessed five single-nucleotide polymorphisms (SNPs) of PPARγ and six SNPs of PPARGC1A and performed a multivariable logistic regression analysis to determine the independent risk factors for developing BRONJ. There were a total of 123 patients included in this study and 56 patients (45.5%) developed BRONJ. In the univariate analysis, PPARGC1A rs2946385 and rs10020457 polymorphisms were significantly associated with BRONJ (p = 0.034, p = 0.020, respectively), although the results were not statistically significant in the multivariable analysis. Patients with the combined genotypes of GG in both PPARγ rs1151999 and PPARGC1A rs2946385 showed a 3.03-fold higher risk of BRONJ compared to individuals with other genotype combinations after adjusting for confounders (95% confidence interval (CI): 1.01-9.11). Old age (≥70 years) and duration of bisphosphonate use (≥60 months) increased the risk of BRONJ. The area under the receiver operating characteristic curve for the predicted probability was 0.78 (95% CI: 0.69-0.87, p < 0.001), demonstrating a satisfactory level of discriminatory power. Our study elucidated that PPARγ and PPARGC1A polymorphisms were interactively associated with BRONJ development. These results have potential implications for tailoring personalized treatments for females undergoing bisphosphonate therapy for osteoporosis.

The Src1-PGC1α-AP1 complex-dependent secretion of substance P induces inflammation and apoptosis in encephalomyocarditis virus-infected mice

Substance P (SP), a neuropeptide consisting of 11 amino acid residues, is involved in the pathogenesis of encephalomyocarditis virus (EMCV)-induced myocarditis by stimulating the production of proinflammatory cytokines. However, the underlying mechanism that regulates SP production is still unknown. In this study, we report the transcriptional regulation of the Tachykinin Precursor 1 (TAC1) gene that encodes SP by a transcriptional complex composed of Steroid Receptor Coactivator 1 (Src1), Peroxisome proliferator-activated receptor-gamma coactivator 1 (PGC1α), and Activator Protein 1 (AP1) transcription factor. Infection of mice with EMCV induced the accumulation of PGC1α and increased TAC1 expression, thereby promoting the secretion of SP, initiating apoptosis, and elevating proinflammatory cytokine levels. In vitro overexpression of the Src1-PGC1α-AP1 members also induced TAC1 expression, increased the SP concentration, initiated apoptosis, and elevated proinflammatory cytokine concentrations. Depletion or inhibition of the Src1-PGC1α-AP1 complex reversed these effects. The administration of gossypol, an Src1 inhibitor, or SR1892, a PGC1α inhibitor, to EMCV-infected mice attenuated myocarditis. Taken together, our results reveal that the upregulation of TAC1 and the secretion of SP in EMCV-induced myocarditis are dependent on the Src1-PGC1α-AP1 complex. Targeting the Src1-PGC1α-AP1 complex may represent a new therapeutic strategy for myocarditis.

Pleiotropic and multi-systemic actions of physical exercise on PGC-1α signaling during the aging process

Physical training is a potent therapeutic approach for improving mitochondrial health through peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) signaling pathways. However, comprehensive information regarding the physical training impact on PGC-1α in the different physiological systems with advancing age is not fully understood. This review sheds light on the frontier-of-knowledge data regarding the chronic effects of exercise on the PGC-1α signaling pathways in rodents and humans. We address the molecular mechanisms involved in the different tissues, clarifying the precise biological action of PGC-1α, restricted to the aged cell type. Distinct exercise protocols (short and long-term) and modalities (aerobic and resistance exercise) increase the transcriptional and translational PGC-1α levels in adipose tissue, brain, heart, liver, and skeletal muscle in animal models, suggesting that this versatile molecule induces pleiotropic responses. However, PGC-1α function in some human tissues (adipose tissue, heart, and brain) remains challenging for further investigations. PGC-1α is not a simple transcriptional coactivator but supports a biochemical environment of mitochondrial dynamics, controlling physiological processes (primary metabolism, tissue remodeling, autophagy, inflammation, and redox balance). Acting as an adaptive mechanism, the long-term effects of PGC-1α following exercise may reflect the energy demand to coordinate multiple organs and contribute to cellular longevity.

Emerging Role of SMILE in Liver Metabolism

Small heterodimer partner-interacting leucine zipper (SMILE) is a member of the CREB/ATF family of basic leucine zipper (bZIP) transcription factors. SMILE has two isoforms, a small and long isoform, resulting from alternative usage of the initiation codon. Interestingly, although SMILE can homodimerize similar to other bZIP proteins, it cannot bind to DNA. As a result, SMILE acts as a co-repressor in nuclear receptor signaling and other transcription factors through its DNA binding inhibition, coactivator competition, and direct repression, thereby regulating the expression of target genes. Therefore, the knockdown of SMILE increases the transactivation of transcription factors. Recent findings suggest that SMILE is an important regulator of metabolic signals and pathways by causing changes in glucose, lipid, and iron metabolism in the liver. The regulation of SMILE plays an important role in pathological conditions such as hepatitis, diabetes, fatty liver disease, and controlling the energy metabolism in the liver. This review focuses on the role of SMILE and its repressive actions on the transcriptional activity of nuclear receptors and bZIP transcription factors and its effects on liver metabolism. Understanding the importance of SMILE in liver metabolism and signaling pathways paves the way to utilize SMILE as a target in treating liver diseases.

Emerging Role of SMILE in Liver Metabolism

Small heterodimer partner-interacting leucine zipper (SMILE) is a member of the CREB/ATF family of basic leucine zipper (bZIP) transcription factors. SMILE has two isoforms, a small and long isoform, resulting from alternative usage of the initiation codon. Interestingly, although SMILE can homodimerize similar to other bZIP proteins, it cannot bind to DNA. As a result, SMILE acts as a co-repressor in nuclear receptor signaling and other transcription factors through its DNA binding inhibition, coactivator competition, and direct repression, thereby regulating the expression of target genes. Therefore, the knockdown of SMILE increases the transactivation of transcription factors. Recent findings suggest that SMILE is an important regulator of metabolic signals and pathways by causing changes in glucose, lipid, and iron metabolism in the liver. The regulation of SMILE plays an important role in pathological conditions such as hepatitis, diabetes, fatty liver disease, and controlling the energy metabolism in the liver. This review focuses on the role of SMILE and its repressive actions on the transcriptional activity of nuclear receptors and bZIP transcription factors and its effects on liver metabolism. Understanding the importance of SMILE in liver metabolism and signaling pathways paves the way to utilize SMILE as a target in treating liver diseases.

The regulating pathway of creatine on muscular protein metabolism depends on the energy state

Creatine (Cr) is beneficial for increasing muscle mass and preventing muscle atrophy via involving in energy metabolism through the Cr and phosphocreatine (PCr) system. This study aimed to evaluate the supplemental effect of Cr on protein metabolism under normal and starvation conditions. The primary myoblasts were obtained from the breast muscle of chicks. The mammalian target of rapamycin (mTOR)/P70S6 kinase (P70S6K), ubiquitin proteasome (UP) pathways, and mitochondrial function of myotubes were evaluated at normal or starvation state and with or without glucose supplementation. Under normal condition, Cr supplementation enhanced protein synthesis rate as well as upregulated the total and phosphorylated P70S6K expressions. Cr had little influence on protein catabolism, and mitochondrial function. In a starvation state, however, Cr alleviated myotube atrophy and enhanced protein accretion by inhibiting Atrogin1 and myostatin (MSTN) expression. Furthermore, Cr treatment upregulated the transcriptional coactivators peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) expression, and decreased reactive oxygen species (ROS) accumulation under starvation condition. In the presence of glucose, however, the favorable effect of Cr on protein content and myotube diameter did not occur under starvation condition. The present result indicates that at normal state, Cr stimulated protein synthesis via the mTOR/P70S6K pathway. In a starvation state, Cr mainly take a favorable effect on protein accumulation via suppression of UP pathway and mediated mitochondrial function mainly by serving as an energy supplier. The result highlights the potential clinical application for the modulation of muscle mass under different nutritional conditions.

Oxidative Stress in Non-Alcoholic Fatty Liver Disease

Non-alcoholic fatty liver disease (NAFLD) is a challenging disease caused by multiple factors, which may partly explain why it still remains an orphan of adequate therapies. This review highlights the interaction between oxidative stress (OS) and disturbed lipid metabolism. Several reactive oxygen species generators, including those produced in the gastrointestinal tract, contribute to the lipotoxic hepatic (and extrahepatic) damage by fatty acids and a great variety of their biologically active metabolites in a “multiple parallel-hit model”. This leads to inflammation and fibrogenesis and contributes to NAFLD progression. The alterations of the oxidant/antioxidant balance affect also metabolism-related organelles, leading to lipid peroxidation, mitochondrial dysfunction, and endoplasmic reticulum stress. This OS-induced damage is at least partially counteracted by the physiological antioxidant response. Therefore, modulation of this defense system emerges as an interesting target to prevent NAFLD development and progression. For instance, probiotics, prebiotics, diet, and fecal microbiota transplantation represent new therapeutic approaches targeting the gut microbiota dysbiosis. The OS and its counter-regulation are under the influence of individual genetic and epigenetic factors as well. In the near future, precision medicine taking into consideration genetic or environmental epigenetic risk factors, coupled with new OS biomarkers, will likely assist in noninvasive diagnosis and monitoring of NAFLD progression and in further personalizing treatments.

Epigenetics and Beyond: Targeting Histone Methylation to Treat Type 2 Diabetes Mellitus

Diabetes mellitus is a global public health challenge with high morbidity. Type 2 diabetes mellitus (T2DM) accounts for 90% of the global prevalence of diabetes. T2DM is featured by a combination of defective insulin secretion by pancreatic β-cells and the inability of insulin-sensitive tissues to respond appropriately to insulin. However, the pathogenesis of this disease is complicated by genetic and environmental factors, which needs further study. Numerous studies have demonstrated an epigenetic influence on the course of this disease via altering the expression of downstream diabetes-related proteins. Further studies in the field of epigenetics can help to elucidate the mechanisms and identify appropriate treatments. Histone methylation is defined as a common histone mark by adding a methyl group (-CH3) onto a lysine or arginine residue, which can alter the expression of downstream proteins and affect cellular processes. Thus, in tthis study will discuss types and functions of histone methylation and its role in T2DM wilsed. We will review the involvement of histone methyltransferases and histone demethylases in the progression of T2DM and analyze epigenetic-based therapies. We will also discuss the potential application of histone methylation modification as targets for the treatment of T2DM.

Astaxanthin Exerts Anabolic Effects via Pleiotropic Modulation of the Excitable Tissue

Astaxanthin is a lipid-soluble carotenoid influencing lipid metabolism, body weight, and insulin sensitivity. We provide a systematic analysis of acute and chronic effects of astaxanthin on different organs. Changes by chronic astaxanthin feeding were analyzed on general metabolism, expression of regulatory proteins in the skeletal muscle, as well as changes of excitation and synaptic activity in the hypothalamic arcuate nucleus of mice. Acute responses were also tested on canine cardiac muscle and different neuronal populations of the hypothalamic arcuate nucleus in mice. Dietary astaxanthin significantly increased food intake. It also increased protein levels affecting glucose metabolism and fatty acid biosynthesis in skeletal muscle. Inhibitory inputs innervating neurons of the arcuate nucleus regulating metabolism and food intake were strengthened by both acute and chronic astaxanthin treatment. Astaxanthin moderately shortened cardiac action potentials, depressed their plateau potential, and reduced the maximal rate of depolarization. Based on its complex actions on metabolism and food intake, our data support the previous findings that astaxanthin is suitable for supplementing the diet of patients with disturbances in energy homeostasis.

Epigenetics of Mitochondria-Associated Genes in Striated Muscle

Striated muscle has especially large energy demands. We identified 97 genes preferentially expressed in skeletal muscle and heart, but not in aorta, and found significant enrichment for mitochondrial associations among them. We compared the epigenomic and transcriptomic profiles of the 27 genes associated with striated muscle and mitochondria. Many showed strong correlations between their tissue-specific transcription levels, and their tissue-specific promoter, enhancer, or open chromatin as well as their DNA hypomethylation. Their striated muscle-specific enhancer chromatin was inside, upstream, or downstream of the gene, throughout much of the gene as a super-enhancer (CKMT2, SLC25A4, and ACO2), or even overlapping a neighboring gene (COX6A2, COX7A1, and COQ10A). Surprisingly, the 3' end of the 1.38 Mb PRKN (PARK2) gene (involved in mitophagy and linked to juvenile Parkinson's disease) displayed skeletal muscle/myoblast-specific enhancer chromatin, a myoblast-specific antisense RNA, as well as brain-specific enhancer chromatin. We also found novel tissue-specific RNAs in brain and embryonic stem cells within PPARGC1A (PGC-1α), which encodes a master transcriptional coregulator for mitochondrial formation and metabolism. The tissue specificity of this gene's four alternative promoters, including a muscle-associated promoter, correlated with nearby enhancer chromatin and open chromatin. Our in-depth epigenetic examination of these genes revealed previously undescribed tissue-specific enhancer chromatin, intragenic promoters, regions of DNA hypomethylation, and intragenic noncoding RNAs that give new insights into transcription control for this medically important set of genes.

Preventing Oxidative Stress in the Liver: An Opportunity for GLP-1 and/or PASK

The liver’s high metabolic activity and detoxification functions generate reactive oxygen species, mainly through oxidative phosphorylation in the mitochondria of hepatocytes. In contrast, it also has a potent antioxidant mechanism for counterbalancing the oxidant’s effect and relieving oxidative stress. PAS kinase (PASK) is a serine/threonine kinase containing an N-terminal Per-Arnt-Sim (PAS) domain, able to detect redox state. During fasting/feeding changes, PASK regulates the expression and activation of critical liver proteins involved in carbohydrate and lipid metabolism and mitochondrial biogenesis. Interestingly, the functional inactivation of PASK prevents the development of a high-fat diet (HFD)-induced obesity and diabetes. In addition, PASK deficiency alters the activity of other nutrient sensors, such as the AMP-activated protein kinase (AMPK) and the mammalian target of rapamycin (mTOR). In addition to the expression and subcellular localization of nicotinamide-dependent histone deacetylases (SIRTs). This review focuses on the relationship between oxidative stress, PASK, and other nutrient sensors, updating the limited knowledge on the role of PASK in the antioxidant response. We also comment on glucagon-like peptide 1 (GLP-1) and its collaboration with PASK in preventing the damage associated with hepatic oxidative stress. The current knowledge would suggest that PASK inhibition and/or exendin-4 treatment, especially under fasting conditions, could ameliorate disorders associated with excess oxidative stress.

The effect of gestational diabetes on the expression of mitochondrial fusion proteins in placental tissue

INTRODUCTION

Gestational diabetes mellitus (GDM) poses a risk factor for fetal mortality and morbidity by directly affecting the placenta and fetus. Mitochondria are dynamic organelles that play a key role in energy production and conversion in placental tissue. Mitochondrial fusion and fission proteins are important in terms of providing mitochondrial dynamics, the adaptation of the cell to different conditions, and maintaining the metabolic stability of the cells. Although GDM shares many features with Type 2 diabetes mellitus (T2DM), different effects of these conditions on the mother and the child suggest that GDM may have specific pathological effects on placental cells. The aim of this study is to investigate the expression of mitochondrial dynamics, and mitochondrial protein folding markers in placentas from GDM patients and women with pre-existing diabetes mellitus.

METHODS

Placentas were properly collected from women, who had pre-existing diabetes (Pre-DM), from women with gestational diabetes mellitus (GDM) and from healthy (non-diabetic) pregnant women. Levels of mitochondrial fusion markers were determined in these placentas by real time quantitative PCR and Western blot experiments.

RESULTS

mRNA expressions and protein levels of mitochondrial fusion markers, mitofusin 1, mitofusin 2 (MFN1 and MFN2) and optical atrophy 1 (OPA1) proteins were found to be significantly lower in both Pre-DM placentas and those with GDM compared to healthy (non-diabetic) control group. Likewise, proteins involved in mitochondrial protein folding were also found to be significantly reduced compared to control group.

DISCUSSION

Diabetes during pregnancy leads to processes that correlate with mitochondria dysfunction in placenta. Our results showed that mitochondrial fusion markers significantly decrease in placental tissue of women with GDM, compared to the healthy non-diabetic women. The decrease in mitochondrial fusion markers was more severe during GDM compared to the Pre-DM. Our results suggest that there may be differences in the pathophysiology of these conditions.

Ubiquilin 1 suppresses the cancer stem cell-like traits of non-small cell lung cancer cells by regulating reactive oxygen species homeostasis

Cancer stem cell (CSC) has been confirmed to trigger tumor occurrence and progression and CSC can develop strategies to maintain a lower reactive oxygen species (ROS) level compared to cancer cells. However, the mechanisms contributing to ROS homeostasis in CSC are still lacking key elements. In the current study, we found that reductive redox states and ROS levels were suppressed in non-adherent spheres formed by non-small cell lung cancer (NSCLC) cells, which were confirmed to hold CSC-like traits. However, mitochondria DNA content and cellular oxygen consumption rate analyses revealed fewer numbers of mitochondria in NSCLC spheres. Further exploration attributed this result to decreased mitochondrial biogenesis, likely resulted from the accelerated degradation of peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α). Mechanistic studies indicated that Ubiquilin 1 (UBQLN1) increased PGC1α protein stability via reducing the ubiquitination of PGC1α protein. Moreover, UBQLN1 was lowly expressed in NSCLC spheres compared to that in parental NSCLC cells and UBQLN1 overexpression suppressed the CSC-like traits of NSCLC cells, which was characterized as the decrease of ALDH1 activity, sphere-formation ability, and CSC marker expression. Finally, clinical investigations further demonstrated that UBQLN1 level was positively correlated with patient’s survival of lung adenocarcinoma, but not squamous cell carcinoma of lung. Taken together, our results revealed a novel mechanism involving ROS homeostasis and mitochondrial biogenesis in non-small cell lung CSCs, which may provide novel potential targets and methods for NSCLC patients.

[Myokines and adipomyokines: inflammatory mediators or unique molecules of targeted therapy for obesity?]

Skeletal muscles make up about 25% of the total mass in children and more than 40% in adults. Studies of the last twenty years have shown that along with the main functions, muscle tissue has hormonal activity. It was found that myocytes are able to release signaling molecules-myokines. They act auto-and paracrine within the muscle, and at a high level-through the systemic circulation, carrying out interactions between skeletal muscles and various organs and tissues, such as the liver, bone and adipose tissue, the brain. It is proved that the key factor in the expression of myokines is physical activity, and their level largely depends on physical fitness, the amount of skeletal muscle mass and its composition (the ratio of fast and slow fibers), on the intensity and duration of physical activity. Myokines have a wide range of physiological effects: myostatin suppresses the growth and differentiation of muscle tissue, and decorin, acting as its antagonist, promotes muscle hypertrophy. Interleukin 6 provides an energy substrate for contracting muscle fibers, fibroblast growth factor 21 activates the mechanisms of energy production during fasting and improves tissue sensitivity to insulin; irisin stimulates thermogenesis, glucose uptake by myocytes, and also contributes to an increase in bone mineral density. The study of myokines is one of the key links in understanding the mechanisms underlying obesity and metabolic complications, the consequences of a sedentary lifestyle, as well as the implementation of the action of physical activity. Taking into account the physiological effects of myokines in the body, in the future they can become therapeutic targets for the treatment of these conditions.

The m6A methyltransferase METTL3 modifies PGC-1α mRNA promoting mitochondrial dysfunction and oxLDL-induced inflammation in monocytes

Mitochondrial biogenesis and energy metabolism are essential for regulating the inflammatory state of monocytes. This state is partially controlled by peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), a coactivator that regulates mitochondrial biogenesis and energy metabolism. Disruption of these processes can also contribute to the initiation of chronic inflammatory diseases, such as pulmonary fibrosis, atherosclerosis, and rheumatoid arthritis. Methyltransferase-like 3 (METTL3)-dependent N⁶-methyladenosine (m⁶A) methylation has recently been shown to regulate a variety of inflammatory processes. However, the role of m⁶A mRNA methylation in affecting mitochondrial metabolism in monocytes under inflammation is unclear, nor is there an established relationship between m⁶A methylation and PGC-1α. In this study, we identified a novel mechanism by which METTL3 acts during oxidized low-density lipoprotein (oxLDL)-induced monocyte inflammation, where METTL3 and YTH N⁶-methyladenosine RNA binding protein 2 (YTHDF2) cooperatively modify PGC-1α mRNA, mediating its degradation, decreasing PGC-1α protein levels, and thereby enhancing the inflammatory response. METTL3 coordinated with YTHDF2 to suppress the expression of PGC-1α, as well as that of cytochrome c (CYCS) and NADH:ubiquinone oxidoreductase subunit C2 (NDUFC2) and reduced ATP production and oxygen consumption rate (OCR). This subsequently increased the accumulation of cellular and mitochondrial reactive oxygen species (ROS) and the levels of proinflammatory cytokines in inflammatory monocytes. These data may provide new insights into the role of METTL3-dependent m⁶A modification of PGC-1α mRNA in the monocyte inflammation response. These data also contribute to a more comprehensive understanding of the pathogenesis of monocyte-macrophage inflammation-associated diseases, such as pulmonary fibrosis, atherosclerosis, and rheumatoid arthritis.

Anti-inflammatory and immunoregulatory effects of pinolenic acid in rheumatoid arthritis

Objectives

In pre-clinical studies, pinolenic acid (PNLA), an omega-6-polyunsaturated fatty acid from pine nuts, has shown anti-inflammatory effects. We aimed to investigate the effect of PNLA in human cell lines and peripheral blood mononuclear cells (PBMCs) from RA patients and healthy controls (HCs).

Methods

A modified Boyden chamber was used to assess chemokine-induced migration of THP-1 monocytes. Macropinocytosis was assessed using Lucifer yellow and oxidized low-density lipoprotein (oxLDL) uptake using DiI-labelled oxLDL in THP-1 macrophages and human monocyte-derived macrophages (HMDMs). IL-6, TNF-α and prostaglandin E₂ (PGE2) release by lipopolysaccharide (LPS)-stimulated PBMCs from RA patients and HCs was measured by ELISA. The transcriptomic profile of PNLA-treated, LPS-activated PBMCs was investigated by RNA-sequencing.

Results

PNLA reduced THP-1 cell migration by 55% (P < 0.001). Macropinocytosis and DiI-oxLDL uptake were reduced by 50% (P < 0.001) and 40% (P < 0.01), respectively, in THP-1 macrophages and 40% (P < 0.01) and 25% (P < 0.05), respectively, in HMDMs. PNLA reduced IL-6 and TNF-α release from LPS-stimulated PBMCs from RA patients by 60% (P < 0.001) and from HCs by 50% and 35%, respectively (P < 0.01). PNLA also reduced PGE2 levels in such PBMCs from RA patients and HCs (P < 0.0001). Differentially expressed genes whose expression was upregulated included pyruvate dehydrogenase kinase-4, plasminogen activator inhibitor-1, fructose bisphosphatase1 and N-Myc downstream-regulated gene-2, which have potential roles in regulating immune and metabolic pathways. Pathway analysis predicted upstream activation of the nuclear receptors peroxisome proliferator-activated receptors involved in anti-inflammatory processes, and inhibition of nuclear factor-κB and signal transducer and activator of transcription 1.

Conclusions

PNLA has immune-metabolic effects on monocytes and PBMCs that are pathogenic in RA and atherosclerosis. Dietary PNLA supplementation may be beneficial in RA.

Selective Activation of CNS and Reference PPARGC1A Promoters Is Associated with Distinct Gene Programs Relevant for Neurodegenerative Diseases

The transcriptional regulator peroxisome proliferator activated receptor gamma coactivator 1A (PGC-1α), encoded by PPARGC1A, has been linked to neurodegenerative diseases. Recently discovered CNS-specific PPARGC1A transcripts are initiated far upstream of the reference promoter, spliced to exon 2 of the reference gene, and are more abundant than reference gene transcripts in post-mortem human brain samples. The proteins translated from the CNS and reference transcripts differ only at their N-terminal regions. To dissect functional differences between CNS-specific isoforms and reference proteins, we used clustered regularly interspaced short palindromic repeats transcriptional activation (CRISPRa) for selective endogenous activation of the CNS or the reference promoters in SH-SY5Y cells. Expression and/or exon usage of the targets was ascertained by RNA sequencing. Compared to controls, more differentially expressed genes were observed after activation of the CNS than the reference gene promoter, while the magnitude of alternative exon usage was comparable between activation of the two promoters. Promoter-selective associations were observed with canonical signaling pathways, mitochondrial and nervous system functions and neurological diseases. The distinct N-terminal as well as the shared downstream regions of PGC-1α isoforms affect the exon usage of numerous genes. Furthermore, associations of risk genes of amyotrophic lateral sclerosis and Parkinson's disease were noted with differentially expressed genes resulting from the activation of the CNS and reference gene promoter, respectively. Thus, CNS-specific isoforms markedly amplify the biological functions of PPARGC1A and CNS-specific isoforms and reference proteins have common, complementary and selective functions relevant for neurodegenerative diseases.

FX5 as a non-steroidal GR antagonist improved glucose homeostasis in type 2 diabetic mice via GR/HNF4α/miR-122-5p pathway

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease characterized by glucose metabolic disorders, and gluconeogenesis inhibiting is a promisingly therapeutic strategy for T2DM. Glucocorticoid receptor (GR) is tightly implicated in the regulation of gluconeogenesis, although the underlying mechanism remains obscure. Here, we discovered that small molecule, 5-chloro-N-[4-chloro-3-(trifluoromethyl)phenyl]thiophene-2-sulfonamide (FX5) as a new non-steroidal GR antagonist efficiently ameliorated glucose homeostasis in db/db and HFD/STZ-induced T2DM mice. The mechanism underlying the suppression of FX5 against gluconeogenesis was highly investigated. FX5 suppressed gluconeogenetic genes G6Pase and PEPCK in mouse primary hepatocytes and liver tissues of T2DM mice. Results of mammalian one-hybrid and transactivation as well as nuclear translocation assays totally evaluated the antagonistic features of FX5 against GR. Moreover, siRNA and overexpression related assays verified that FX5 alleviated gluconeogenesis either directly by antagonizing GR or indirectly through GR/HNF4α/miR122-5p signaling pathway. Our work has presented a new mode for GR antagonist in the regulation of gluconeogenesis, which is expected to highlight the potential of FX5 in the treatment of T2DM.

Novel metabolic system for lactic acid via LRPGC1/ERRγ signaling pathway

Lactic acid (LA) is a byproduct of glycolysis resulting from intense exercise or a metabolic defect in aerobic processes. LA metabolism is essential to prevent lactic acidosis, but the mechanism through which LA regulates its own metabolism is largely unknown. Here, we identified a LA-responsive protein, named LRPGC1, which has a distinct role from PGC1α, a key metabolic regulator, and report that LRPGC1 particularly mediates LA response to activate liver LA metabolism. Following LA stimulation, LRPGC1, but not PGC1α, translocates from the cytoplasm to the nucleus through deactivation of nuclear export signals, interacts with the nuclear receptor ERRγ, and upregulates TFAM, which ensures mitochondrial biogenesis. Knockout of PGC1 gene in HepG2 hepatocarcinoma cells decreased the LA consumption and TFAM expression, which were rescued by LRPGC1 expression, but not by PGC1α. These LRPGC1-induced effects were mediated by ERRγ, concomitantly with mitochondrial activation. The response element for LRPGC1/ERRγ signaling pathway was identified in TFAM promoter. Notably, the survival rate of a mouse model of lactic acidosis was reduced by the liver-targeted silencing of Lrpgc1, while it was significantly ameliorated by the pharmacological activation of ERRγ. These findings demonstrate LA-responsive transactivation via LRPGC1 that highlight an intrinsic molecular mechanism for LA homeostasis.

Natural products, PGC-1 , and Duchenne muscular dystrophy

Peroxisome proliferator-activated receptor γ (PPARγ) is a transcriptional coactivator that binds to a diverse range of transcription factors. PPARγ coactivator 1 (PGC-1) coactivators possess an extensive range of biological effects in different tissues, and play a key part in the regulation of the oxidative metabolism, consequently modulating the production of reactive oxygen species, autophagy, and mitochondrial biogenesis. Owing to these findings, a large body of studies, aiming to establish the role of PGC-1 in the neuromuscular system, has shown that PGC-1 could be a promising target for therapies targeting neuromuscular diseases. Among these, some evidence has shown that various signaling pathways linked to PGC-1α are deregulated in muscular dystrophy, leading to a reduced capacity for mitochondrial oxidative phosphorylation and increased reactive oxygen species (ROS) production. In the light of these results, any intervention aimed at activating PGC-1 could contribute towards ameliorating the progression of muscular dystrophies. PGC-1α is influenced by different patho-physiological/pharmacological stimuli. Natural products have been reported to display modulatory effects on PPARγ activation with fewer side effects in comparison to synthetic drugs. Taken together, this review summarizes the current knowledge on Duchenne muscular dystrophy, focusing on the potential effects of natural compounds, acting as regulators of PGC-1α.

Changes in Serum Levels and Gene Expression of PGC-1α in The Cardiac Muscle of Diabetic Rats: The Effect of Dichloroacetate and Endurance Training

Objective

Physical activity leads to changes in the level of gene expression in different kinds of cells, including changes in mitochondrial biogenesis in the myocardium in diabetic patients. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is a gene that plays an important role in regulating mitochondrial biogenesis. The purpose of this study was to investigate changes in serum levels and cardiac muscle expression of PGC-1α in diabetic rats in response to the administration of dichloroacetate (DCA) and endurance training.

Materials and Methods

In this experimental study, 64 male Wistar rats were selected and randomly divided into eight groups after induction of diabetes with streptozotocin (STZ). The endurance training protocol was performed on a treadmill for 6 weeks. Intraperitoneal injection of DCA of 50 mg/ kg body weight was used for the inhibition of Pyruvate Dehydrogenase Kinase 4 (PDK4) in the myocardium. Gene expression were measured using real-time polymerase chain reaction (PCR). One-way ANOVA and Tukey’s test were used to statistically analyze the data.

Results

The results of the study showed that PDK4 gene expression in the endurance training group, diabetes+endurance training group, diabetes+endurance training+DCA group and endurance training+DCA group was higher compared to the control group. Expression of PGC-1α was higher in the endurance training group compared to the control group but was lower compared to the control group in diabetes+endurance training+DCA group and diabetes+DCA group (P<0.05).

Conclusion

Considering that PGC-1α plays an important role in mitochondrial biogenesis, it is likely that by inhibiting PDK4 and subsequently controlling oxidation of fatty acid (FA) in the heart tissue, oxidative stress in the heart tissue of diabetic patients will be reduced and cardiac efficiency will be increased.

Effect of Peroxisome Proliferator-Activated Receptor-γ Coactivator-1 Alpha Variants on Spontaneous Clearance and Fibrosis Progression during Hepatitis C Virus Infection in Moroccan Patients

Hepatitis C virus (HCV) is still one of the main causes of liver disease worldwide. Metabolic disorders, including non-alcoholic fatty liver disease (NAFLD), induced by HCV have been shown to accelerate the progression of fibrosis to cirrhosis and to increase the risk of hepatocellular carcinoma. An optimal peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PPARGC1A) activity is crucial to prevent NAFLD installation. The present study aims to investigate the associations between two common PPARGC1A polymorphisms (rs8192678 and rs12640088) and the outcomes of HCV infection in a North African context. A series of 592 consecutive Moroccan subjects, including 292 patients with chronic hepatitis C (CHC), 100 resolvers and 200 healthy controls were genotyped using a TaqMan allelic discrimination assay. PPARGC1A variations at rs8192678 and rs12640088 were not associated with spontaneous clearance of HCV infection (adjusted ORs = 0.76 and 0.79 respectively, P > 0.05, for both). Furthermore, multivariable logistic regression analysis showed that both SNPs were not associated with fibrosis progression (OR = 0.71; 95% CI 0.20-2.49; P = 0.739; OR = 1.28; 95% CI 0.25-6.54; P = 0.512, respectively). We conclude that, in the genetic context of South Mediterranean patients, rs8192678 and rs12640088 polymorphisms of PPARGC1A are neither associated with spontaneous clearance nor with disease progression in individuals infected with HCV.

The Expression of CNS-Specific PPARGC1A Transcripts Is Regulated by Hypoxia and a Variable GT Repeat Polymorphism

PPARGC1A encodes a transcriptional co-activator also termed peroxisome proliferator-activated receptor (PPAR) gamma coactivator 1-alpha (PGC-1α) which orchestrates multiple transcriptional programs. We have recently identified CNS-specific transcripts that are initiated far upstream of the reference gene (RG) promoter. The regulation of these isoforms may be relevant, as experimental and genetic studies implicated the PPARGC1A locus in neurodegenerative diseases. We therefore studied cis- and trans-regulatory elements activating the CNS promoter in comparison to the RG promoter in human neuronal cell lines. A naturally occurring variable guanidine thymidine (GT) repeat polymorphism within a microsatellite region in the proximal CNS promoter increases promoter activity in neuronal cell lines. Both the RG and the CNS promoters are activated by ESRRA, and the PGC-1α isoforms co-activate ESRRA on their own promoters suggesting an autoregulatory feedback loop. The proximal CNS, but not the RG, promoter is induced by FOXA2 and co-activated by PGC-1α resulting in robust activation. Furthermore, the CNS, but not the RG, promoter is targeted by the canonical hypoxia response involving HIF1A. Importantly, the transactivation by HIF1A is modulated by the size of the GT polymorphism. Increased expression of CNS-specific transcripts in response to hypoxia was observed in an established rat model, while RG transcripts encoding the full-length reference protein were not increased. These results suggest a role of the CNS region of the PPARGC1A locus in ischemia and warrant further studies in humans as the activity of the CNS promoter as well as its induction by hypoxia is subject to inter-individual variability due to the GT polymorphism.

Multiorgan Systems Study Reveals Igfbp7 as a Suppressor of Gluconeogenesis after Gastric Bypass Surgery

Roux-en-Y gastric bypass (RYGB) surgery reduces weight in obese patients. A marked decrease in blood glucose levels occurs before weight loss; however, key molecules that improve the glycemic profile remain largely unknown. Using a murine RYGB surgery model, we performed multiorgan proteomics and bioinformatics to monitor the proteins and molecular pathways that change in this early glycemic response. Multiplexed proteomic kinetics data analysis revealed that the Roux limb, biliopancreatic limb, liver, and pancreas each exhibited unique temporal and molecular responses to the RYGB surgery. In addition, protein-protein network analysis indicated that the changes to the microbial environment in the intestine may play a crucial role in the beneficial effects of RYGB surgery. Furthermore, insulin-like growth factor binding protein 7 (Igfbp7) was identified as an early induced protein in the Roux limb. Known secretory properties of Igfbp7 prompted us to further investigate its role as a remote organ regulator of glucose metabolism. Igfbp7 overexpression decreased blood glucose levels in diet-induced obese mice and attenuated gluconeogenic gene expression in the liver. Secreted Igfbp7 appeared to mediate these beneficial effects. These results demonstrate that organs responded differentially to RYGB surgery and indicate that Igfbp7 may play an important role in improving blood glucose levels.

New Perspectives on Genetic Prediction for Pediatric Metabolic Associated Fatty Liver Disease

Non-alcoholic or recently re-defined metabolic associated fatty liver disease (MAFLD), a spectrum of progressive hepatic disease, has become a public health issue in obese children and adolescents. MAFLD is a complex metabolic disease strongly associated with obesity and insulin resistance. It is not known why not every obese subject will develop MAFLD. Different ethnic/racial groups display differences in MAFLD prevalence, indicating genetic factor plays a role. In the past two decades, sequence variations in genetic loci, including PNPLA3, TM6SF2, GCKR, MBOAT7, HSD17B13, etc. have been shown to confer susceptibility to MAFLD in children and adults. This review article provides an updated viewpoint of genetic predictors related to pediatric MAFLD. We discuss whether these susceptible genes can be clinically used for risk stratification and personalized care. Understanding human genetics and molecular mechanisms can give important information not only for prediction of risk but also on how to design drugs. In view of current epidemic of MAFLD worldwide, it is necessary to identify which children with MAFLD progress rapidly and need earlier intervention. In the future, a comprehensive analysis of individualized genetic and environmental factors may help assess the risk of children with MAFLD and personalize their treatment.

Role of cytochrome P450-derived, polyunsaturated fatty acid mediators in diabetes and the metabolic syndrome

Over the last decade, cases of metabolic syndrome and type II diabetes have increased exponentially. Exercise and ω-3 polyunsaturated fatty acid (PUFA)-enriched diets are usually prescribed but no therapy is effectively able to restore the impaired glucose metabolism, hypertension, and atherogenic dyslipidemia encountered by diabetic patients. PUFAs are metabolized by different enzymes into bioactive metabolites with anti- or pro-inflammatory activity. One important class of PUFA metabolizing enzymes are the cytochrome P450 (CYP) enzymes that can generate a series of bioactive products, many of which have been attributed protective/anti-inflammatory and insulin-sensitizing effects in animal models. PUFA epoxides are, however, further metabolized by the soluble epoxide hydrolase (sEH) to fatty acid diols. The biological actions of the latter are less well understood but while low concentrations may be biologically important, higher concentrations of diols derived from linoleic acid and docosahexaenoic acid have been linked with inflammation. One potential application for sEH inhibitors is in the treatment of diabetic retinopathy where sEH expression and activity is elevated as are levels of a diol of docosahexaenoic acid that can induce the destabilization of the retina vasculature.

The association of circulating irisin with metabolic risk factors in Chinese adults: a cross-sectional community-based study

BACKGROUND

Irisin is a myokine that leads to increased energy expenditure by stimulating the browning of white adipose tissue. We aimed to investigate the association of serum irisin levels with metabolic parameters in middle aged Chinese population.

METHODS

The study was based on a cross-sectional analysis of data from 524 nondiabetic subjects aged 40~65. All participants were recruited from a screening survey for Metabolic Syndrome in a community in Southwest China, including 294 subjects categorized as overweight (defined as BMI≧25 kg/m²) and 230 subjects as normal control (defined as 18.5≦BMI < 25 kg/m²). Serum irisin concentration was quantified by enzyme linked immunosorbent assay (ELISA). The relationship of irisin with metabolic factors was determined by Pearson correlation. Multivariate linear regression was used to analyze the association of irisin with insulin resistance. Logistic regression was performed to assess the association of irisin with odds of overweight.

RESULTS

Serum irisin levels were significantly lower in nondiabetic overweight subjects compared with control (11.46 ± 4.11vs14.78 ± 7.03 μg/mL, p = 0.02). Circulating irisin was positively correlated with quantitative insulin sensitivity check index (QUICKI, r = 0.178, p = 0.045) and triglycerides (r = 0.149, p = 0.022); while irisin was negatively correlated with waist circumference (WC, r = - 0.185, p = 0.037), waist-to-hip ratio (WHR, r = - 0.176, p = 0.047), fasting insulin (r = - 0.2, p = 0.024), serum creatinine (r = - 0.243, p = 0.006), homeostasis model assessment for insulin resistance (HOMA-IR, r = - 0.189, p = 0.033). Multiple linear regression showed that irisin was inversely associated with HOMA-IR (β = - 0.342 ± 0.154, p = 0.029). Higher irisin was associated with decreased odds of being overweight (OR = 0.281, β = - 1.271, p = 0.024).

CONCLUSIONS

We found that serum irisin levels were lower in overweight subjects. Moreover, serum irisin levels were inversely correlated with adverse metabolic parameters including WC, WHR, creatinine, HOMA-IR and fasting insulin, suggesting that irisin may play a role in obesity related insulin resistance.

Astaxanthin: A Potential Mitochondrial-Targeted Antioxidant Treatment in Diseases and with Aging

Oxidative stress is characterized by an imbalance between prooxidant and antioxidant species, leading to macromolecular damage and disruption of redox signaling and cellular control. It is a hallmark of various diseases including metabolic syndrome, chronic fatigue syndrome, neurodegenerative, cardiovascular, inflammatory, and age-related diseases. Several mitochondrial defects have been considered to contribute to the development of oxidative stress and known as the major mediators of the aging process and subsequent age-associated diseases. Thus, mitochondrial-targeted antioxidants should prevent or slow down these processes and prolong longevity. This is the reason why antioxidant treatments are extensively studied and newer and newer compounds with such an effect appear. Astaxanthin, a xanthophyll carotenoid, is the most abundant carotenoid in marine organisms and is one of the most powerful natural compounds with remarkable antioxidant activity. Here, we summarize its antioxidant targets, effects, and benefits in diseases and with aging.

Fine-Tuning of PGC1α Expression Regulates Cardiac Function and Longevity

RATIONALE

PGC1α (peroxisome proliferator-activated receptor gamma coactivator 1α) represents an attractive target interfering bioenergetics and mitochondrial homeostasis, yet multiple attempts have failed to upregulate PGC1α expression as a therapy, for instance, causing cardiomyopathy.

OBJECTIVE

To determine whether a fine-tuning of PGC1α expression is essential for cardiac homeostasis in a context-dependent manner.

METHODS AND RESULTS

Moderate cardiac-specific PGC1α overexpression through a ROSA26 locus knock-in strategy was utilized in WT (wild type) mice and in G3Terc^-/- (third generation of telomerase deficient; hereafter as G3) mouse model, respectively. Ultrastructure, mitochondrial stress, echocardiographic, and a variety of biological approaches were applied to assess mitochondrial physiology and cardiac function. While WT mice showed a relatively consistent PGC1α expression from 3 to 12 months old, age-matched G3 mice exhibited declined PGC1α expression and compromised mitochondrial function. Cardiac-specific overexpression of PGC1α (PGC1α^OE) promoted mitochondrial and cardiac function in 3-month-old WT mice but accelerated cardiac aging and significantly shortened life span in 12-month-old WT mice because of increased mitochondrial damage and reactive oxygen species insult. In contrast, cardiac-specific PGC1α knock in in G3 (G3 PGC1α^OE) mice restored mitochondrial homeostasis and attenuated senescence-associated secretory phenotypes, thereby preserving cardiac performance with age and extending health span. Mechanistically, age-dependent defect in mitophagy is associated with accumulation of damaged mitochondria that leads to cardiac impairment and premature death in 12-month-old WT PGC1α^OE mice. In the context of telomere dysfunction, PGC1α induction replenished energy supply through restoring the compromised mitochondrial biogenesis and thus is beneficial to old G3 heart.

CONCLUSIONS

Fine-tuning the expression of PGC1α is crucial for the cardiac homeostasis because the balance between mitochondrial biogenesis and clearance is vital for regulating mitochondrial function and homeostasis. These results reinforce the importance of carefully evaluating the PGC1α-boosting strategies in a context-dependent manner to facilitate clinical translation of novel cardioprotective therapies.

Fenofibrate attenuates cardiac and renal alterations in young salt-loaded spontaneously hypertensive stroke-prone rats through mitochondrial protection

OBJECTIVES

The simultaneous presence of cardiac and renal diseases is a pathological condition that leads to increased morbidity and mortality. Several lines of evidence have suggested that lipid dysmetabolism and mitochondrial dysfunction are pathways involved in the pathological processes affecting the heart and kidney. In the salt-loaded spontaneously hypertensive stroke-prone rat (SHRSP), a model of cardiac hypertrophy and nephropathy that shows mitochondrial alterations in the myocardium, we evaluated the cardiorenal effects of fenofibrate, a peroxisome proliferator-activated receptor alpha (PPARα) agonist that acts by modulating mitochondrial and peroxisomal fatty acid oxidation.

METHODS

Male SHRSPs aged 6-7 weeks were divided in three groups: standard diet (n = 6), Japanese diet with vehicle (n = 6), and Japanese diet with fenofibrate 150 mg/kg/day (n = 6) for 5 weeks. Cardiac and renal functions were assessed in vivo by MRI, ultrasonography, and biochemical assays. Mitochondria were investigated by transmission electron microscopy, succinate dehydrogenase (SDH) activity, and gene expression analysis.

RESULTS

Fenofibrate attenuated cardiac hypertrophy, as evidenced by histological and MRI analyses, and protected the kidneys, preventing morphological alterations, changes in arterial blood flow velocity, and increases in 24-h proteinuria. Cardiorenal inflammation, oxidative stress, and cellular senescence were also inhibited by fenofibrate. In salt-loaded SHRSPs, we observed severe morphological mitochondrial alterations, reduced SDH activity, and down-regulation of genes regulating mitochondrial fatty-acid oxidation (i.e. PPARα, SIRT3, and Acadm). These changes were counteracted by fenofibrate. In vitro, a direct protective effect of fenofibrate on mitochondrial membrane potential was observed in albumin-stimulated NRK-52E renal tubular epithelial cells.

CONCLUSION

The results suggest that the cardiorenal protective effects of fenofibrate in young male salt-loaded SHRSPs are explained by its capacity to preserve mitochondrial function.

Comparison of gene expression in cynomolgus monkeys with preclinical type II diabetes induced by different high energy diets

BACKGROUND

Cynomolgus disease models that are similar to the preclinical stage of human type 2 diabetes mellitus (T2DM) were established by feeding middle-aged cynomolgus monkeys different high energy diets to study the differential expression of diabetes-related genes.

METHODS

A total of 36 male monkeys were randomly divided into four groups and fed human diets with high sugar, high fat, double high sugar and fat, and a normal diet. The preclinical diabetes phase was determined by monitoring the metabolic characteristic indices and the results of oral glucose tolerance tests (OGTT). The mRNA expression of 45 diabetes-related genes in peripheral blood leukocytes was analyzed using real-time PCR.

RESULTS

A total of 22, 25, and 21 genes were significantly up-regulated (P < 0.05) and 5, 7, and 5 genes were significantly down-regulated (P < 0.05) in the above three induced groups, respectively, compared with the control group. Of the 45 tested genes, the expression profiles of 21 genes were consistent. Most of the expression levels in the double high sugar-and-fat individuals were slightly lower than those in the high glucose and high fat groups, although the expression patterns of the three groups were essentially similar.

CONCLUSION

The different high energy diets all induced diabetes and shared some phenotypic properties with human T2DM. Most of the expression patterns of the related genes were identical. The gene expression profiles could be used as references for the study of early diagnostic indicators and T2DM pathogenesis.

Beneficial effects of metformin on muscle atrophy induced by obesity in rats

AIM

A growing interest to understand the signaling pathways mediating obesity-induced muscle atrophy is given. Metformin (Met) was reported to possess positive effects on preventing muscle damage and promoting muscle mass maintenance. The aim of the present study to investigate pathways involved in Met effect on obesity induced muscle atrophy.

METHODS

Thirty adult male albino rats were assigned into two groups: normal chew diet fed group as control group (C; n = 10) and high-fat-diet (HFD) fed group ( n = 20). After 16 weeks, the HFD-fed animals were subdivided into two groups; HFD group ( n = 10) and HFD fed treated with oral Met (320 mg/day) treatment (Met, n = 10) for 4 weeks. At the end of the experiment; final body weight, visceral fat weight, fasting blood glucose, insulin, lactate, total cholesterol, triglycerides were measured and calculated homeostatic model assessment insulin resistant (HOMA-IR) for all groups. Soleus muscle weight, histopathlogical examination and expression of peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), forkhead box O3 (FoxO3), atrogin-1/MAFbx, and muscle RING finger 1 (MuRF-1) were performed.

RESULTS

HFD-fed animals showed significant increase in final body weight, visceral fat mass, fasting blood glucose, insulin, calculated HOMA-IR, lactate, total cholesterol and triglycerides with significant decrease in soleus muscle weight, PGC-1α and significant increase in FoxO3, atrogin-1/MAFbx, and MuRF-1 expression. Also, there was significant decrease in fiber diameter, myosin heavy chain (MHC) I content while collagen content and myosin heavy chain IIa were increased compared with control group. Met-treated group showed a significant decrease in the measured parameters compared with the HFD group. It also restored the gene expression, morphometric measures and MHC composition toward normal.

CONCLUSION

The current study is the first to provide evidence that Met could ameliorate muscle atrophy in high-fat diet induced obesity and this effect may be in part due to regulation of PGC-1α-FoxO3 pathway.

Pas Kinase Deficiency Triggers Antioxidant Mechanisms in the Liver

Metabolic dysfunction in the liver is the cause of numerous pathologies, which are associated with an altered redox state. PASK (PAS Domain Kinase) is a nutrient and bioenergetic sensor. We contend that PASK could act as an oxidative stress sensor in liver and/or control the metabolic balance, playing a role in the mitochondrial homeostasis. Using PASK-deficient mice, we observed that PASK deficiency promotes antioxidant response mechanisms: a lower production of ROS/RNS under non-fasting conditions, overexpression of genes coding to ROS-detoxifying enzymes and mitochondrial fusion proteins (MnSod Gpx, Mfn1 and Opa1), coactivator Ppargc1a, transcription factors (Pparg and FoxO3a) and deacetylase Sirt1. Also, under fasting conditions, PASK deficiency induced the overexpression of Ppargc1a, Ppara, Pparg, FoxO3a and Nrf2 leading to the overexpression of genes coding to antioxidant enzymes such as MnSOD, Cu/ZnSOD, GPx, HO1 and GCLm. Additionally, inducing PINK1 involved in cell survival and mitophagy. These changes kept ROS steady levels and improved the regenerative state. We suggest a new role for PASK as a controller of oxidative stress and mitochondrial dynamics in the liver. In fact, antioxidant response is PASK dependent. PASK-targeting could therefore be a good way of reducing the oxidative stress in order to prevent or treat liver diseases.

Prognostic value of plasma levels of HIF-1a and PGC-1a in breast cancer

Cellular adaptive mechanisms are crucial for tumorigenesis and a common feature in solid tumor progression. Hypoxia-inducible factor-1α (HIF-1α) facilitates the biological response to hypoxia, advancing angiogenesis and metastatic potential of the tumor. The peroxisome proliferator–activated receptor γ coactivators 1α (PGC-1α) enhances mitochondrial biogenesis, favored by migratory/invasive cancer cells. We conducted a prospective, long-term follow up study to determine whether HIF-1α and PGC-1α can be implemented as predictive biomarker in breast cancer. HIF-1α and PGC-1α plasma concentrations were measured in patients and in healthy controls by enzyme linked immune sorbent assay. Breast cancer patients had significantly higher HIF-1α and PGC-1α levels, which correlated with clinicopathological features, overall with more aggressive cancer characteristics. Disease free and overall survival of breast cancer patients with high HIF-1α and PGC-1α were significantly poorer than in patients with low plasma levels. In multivariate analysis, high amount of PGC-1α showed independent prognostic value. Our data suggests that HIF-1α and PGC-1α may be promising, noninvasive, biomarkers with a high potential for future clinical implication to identify subgroups of patients with poorer prognosis and to indicate early, subclinical metastasis.

Linking Metabolic Disease With the PGC-1α Gly482Ser Polymorphism

Peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) is a highly conserved transcriptional coactivator enriched in metabolically active tissues including liver, adipose, pancreas, and muscle. It plays a role in regulating whole body energy metabolism and its deregulation has been implicated in type 2 diabetes (T2D). A single nucleotide variant of the PPARGC1A gene (rs8192678) is associated with T2D susceptibility, relative risk of obesity and insulin resistance, and lower indices of β cell function. This common polymorphism is within a highly conserved region of the bioactive protein and leads to a single amino acid substitution (glycine 482 to serine). Its prevalence and effects on metabolic parameters appear to vary depending on factors including ethnicity and sex, suggesting important interactions between genetics and cultural/environmental factors and associated disease risk. Interestingly, carriers of the serine allele respond better to some T2D interventions, illustrating the importance of understanding functional impacts of genetic variance on PGC-1α when targeting this pathway for personalized medicine. This review summarizes a growing body of literature surrounding possible links between the PGC-1α Gly482Ser single nucleotide polymorphism and diabetes, with focus on key clinical findings, affected metabolic systems, potential molecular mechanisms, and the influence of geographical or ethnic background on associated risk.

Thermoregulatory disorders in Huntington disease

Huntington disease (HD) is a paradigmatic autosomal-dominant adult-onset neurodegenerative disease. Since the identification of an abnormal expansion of a trinucleotide repeat tract in the huntingtin gene as the underlying genetic defect, a broad range of transgenic animal models of the disease has become available and these have helped to unravel the relevant molecular pathways in unprecedented detail. Of note, some of the most informative of these models develop thermoregulatory defects such as hypothermia, problems with adaptive thermogenesis, and an altered circadian temperature rhythm. Both central, e.g., in the hypothalamus and peripheral, i.e., the brown adipose tissue and skeletal muscle, problems contribute to the phenotype. Importantly, these structures and pathways are also affected in human HD. Yet, currently the evidence for bona fide thermodysregulation in human HD patients remains anecdotal. This may be due to a lack of reliable tools for monitoring body temperature in an outpatient setting. Regardless, study of the temperature phenotype has contributed to the identification of unexpected molecular targets, such as the PGC-1α pathway.

Association between long sleep duration and increased risk of obesity and type 2 diabetes: A review of possible mechanisms

For the last two decades research has revealed an alarming association between short sleep duration and metabolic disorders. In tandem, the hormonal, behavioral, and genetic mechanisms underlying this relationship have been extensively investigated and reviewed. However, emerging evidence is revealing that excessive sleep duration has remarkably similar deleterious effects. Unfortunately, to date there has been little attention to what drives this connection. This narrative review therefore aims to summarize existing epidemiological findings, experimental work, and most importantly putative molecular and behavioral mechanisms connecting excessive sleep duration with both obesity and type 2 diabetes mellitus. It will also address recent findings suggesting a worrisome bidirectional effect such that metabolic disorders create a positive feedback loop which further perpetuates excessive sleep.

Association of PGC-1α gene with type 2 diabetes in three unrelated endogamous groups of North-West India (Punjab): a case-control and meta-analysis study

PGC-1α (Peroxisome proliferator-activated receptor gamma, coactivator 1 alpha) plays a key role in glucose homeostasis inside liver and muscle. The impact of six polymorphisms of PGC-1α with Type 2 Diabetes (T2D) susceptibility was evaluated on 1125 samples comprising of 554 T2D cases and 571 controls among three endogamous groups (Bania, Brahmin and Jat Sikh) of North-West India (Punjab). Single-locus analysis showed a significant differential pattern of genetic association of PGC-1α among studied groups emphasizing the role of ethnicity towards disease susceptibility. Haplotypes G-A-G-G-C-C in Bania group; G-G-G-G-C-A in Brahmin; G-A-A-G-T-C, G-G-G-G-T-C in Jat Sikh groups conferred ~ two to fivefold increased T2D risk. Intriguingly, the haplotype combination G-A-G-G-C-C provided T2D risk in Banias whereas it played a protective role in Brahmins reflecting the role of ethnic heterogeneity. In the secondary structure prediction of mRNA, slight free energy change along with structural changes was observed between the wild and variant allele of rs3736265, rs8192678 and rs2970847 loci. Meta-analyses conducted on rs8192678 and rs2970847 variants illustrated the overall effect of minor alleles providing a higher risk for the T2D development. Divergence in genetic variants and haplotype combinations associated with T2D risk among studied groups is inferred from the present dataset, which strongly highlights the combinatorial effect of diverse ethnic background of the population under study with genetics towards susceptibility to complex diseases like T2D.

Gene Expression and DNA Methylation of PPARGC1A in Muscle and Adipose Tissue From Adult Offspring of Women With Diabetes in Pregnancy

Prenatal exposure to maternal hyperglycemia is associated with an increased risk of later adverse metabolic health. Changes in the regulation of peroxisome proliferator-activated receptor-γ coactivator-1α (PPARGC1A) in skeletal muscle and subcutaneous adipose tissue (SAT) is suggested to play a role in the developmental programming of dysmetabolism based on studies of human subjects exposed to an abnormal intrauterine environment (e.g., individuals with a low birth weight). We studied 206 adult offspring of women with gestational diabetes mellitus (O-GDM) or type 1 diabetes (O-T1D) and of women from the background population (O-BP) using a clinical examination, oral glucose tolerance test, and gene expression and DNA methylation of PPARGC1A in skeletal muscle and SAT. Plasma glucose was significantly higher for both O-GDM and O-T1D compared with O-BP (P < 0.05). PPARGC1A gene expression in muscle was lower in O-GDM compared with O-BP (P = 0.0003), whereas no differences were found between O-T1D and O-BP in either tissue. PPARGC1A DNA methylation percentages in muscle and SAT were similar among all groups. Decreased PPARGC1A gene expression in muscle has previously been associated with abnormal insulin function and may thus contribute to the increased risk of metabolic disease in O-GDM. The unaltered PPARGC1A gene expression in muscle of O-T1D suggests that factors other than intrauterine hyperglycemia may contribute to the decreased PPARGC1A expression in O-GDM.

Serum irisin concentrations were increased after transient continuous subcutaneous insulin infusion in type 2 diabetes mellitus patients

Irisin, identified as a novel myokine, plays an important role in improving metabolic disorders, including type 2 diabetes mellitus (T2DM). In this interventional study, we investigated the alteration of serum irisin levels in T2DM subjects after transient continuous subcutaneous insulin infusion (CSII) treatment.