Deletion of skeletal muscle SOCS3 prevents insulin resistance in obesity

Interleukin-4 inhibits the hypothalamic appetite control by modulating the insulin-AKT and JAK-STAT signaling in leptin mutant mice

Our previous research identified interleukin-4 (IL-4) as a key regulator of glucose/lipid metabolism, circulatory leptin levels, and insulin action, suggesting its potential as a therapeutic target for obesity and related complications. This study aimed to further elucidate the role of IL-4 in regulating hypothalamic appetite-controlling neuropeptides using leptin dysfunctional Leptin145E/145E mice as the experimental model. IL-4 significantly reduces body weight, food intake, and serum glucose levels. Our data demonstrated that IL-4 exhibits multiple functions in regulating hypothalamic appetite control, including downregulating orexigenic agouti-related peptide and neuropeptide Y levels, promoting expression of anorexigenic proopiomelanocortin, alleviating microenvironmental hypothalamic inflammation, enhancing leptin and insulin pathway, and attenuating insulin resistance. Furthermore, IL-4 promotes uncoupling protein 1 expression of white adipose tissue (WAT), suggesting its role in triggering WAT-beige switch. In summary, this study uncovers novel function of IL-4 in mediating food-intake behaviors and metabolic efficiency by regulating hypothalamic appetite-control and WAT browning activities. These findings support the therapeutic potential of targeting hypothalamic inflammation and reducing adiposity through IL-4 intervention for tackling the pandemic increasing prevalence of obesity and associated metabolic disorders.

Gene expression analyses reveal potential mechanism of inorganic arsenic-induced apoptosis in zebrafish

Our previous study showed that sodium arsenite (200 mg/L) affected the nervous system and induced motor neuron development via the Sonic hedgehog pathway in zebrafish larvae. To gain more insight into the effects of arsenite on other signaling pathways, including apoptosis, we have performed quantitative polymerase chain reaction array-based gene expression analyses. The 96-well array plates contained primers for 84 genes representing 10 signaling pathways that regulate several biological functions, including apoptosis. We exposed eggs at 5 h postfertilization until the 72 h postfertilization larval stage to 200 mg/L sodium arsenite. In the Janus kinase/signal transducers and activators of transcription, nuclear factor κ-light-chain-enhancer of activated B cells, and Wingless/Int-1 signaling pathways, the expression of only one gene in each pathway was significantly altered. The expression of multiple genes was altered in the p53 and oxidative stress pathways. Sodium arsenite induced excessive apoptosis in the larvae. This compelled us to analyze specific genes in the p53 pathway, including cdkn1a, gadd45aa, and gadd45ba. Our data suggest that the p53 pathway is likely responsible for sodium arsenite-induced apoptosis. In addition, sodium arsenite significantly reduced global DNA methylation in the zebrafish larvae, which may indicate that epigenetic factors could be dysregulated after arsenic exposure. Together, these data elucidate potential mechanisms of arsenic toxicity that could improve understanding of arsenic's effects on human health.

Differential Roles of Interleukin-6 in Severe Acute Respiratory Syndrome-Coronavirus-2 Infection and Cardiometabolic Diseases

Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection can lead to a cytokine storm, unleashed in part by pyroptosis of virus-infected macrophages and monocytes. Interleukin-6 (IL-6) has emerged as a key participant in this ominous complication of COVID-19. IL-6 antagonists have improved outcomes in patients with COVID-19 in some, but not all, studies. IL-6 signaling involves at least 3 distinct pathways, including classic-signaling, trans-signaling, and trans-presentation depending on the localization of IL-6 receptor and its binding partner glycoprotein gp130. IL-6 has become a therapeutic target in COVID-19, cardiovascular diseases, and other inflammatory conditions. However, the efficacy of inhibition of IL-6 signaling in metabolic diseases, such as obesity and diabetes, may depend in part on cell type-dependent actions of IL-6 in controlling lipid metabolism, glucose uptake, and insulin sensitivity owing to complexities that remain to be elucidated. The present review sought to summarize and discuss the current understanding of how and whether targeting IL-6 signaling ameliorates outcomes following SARS-CoV-2 infection and associated clinical complications, focusing predominantly on metabolic and cardiovascular diseases.

Higher pNRF2, SOCS3, IRF3, and RIG1 Tissue Protein Expression in NASH Patients versus NAFL Patients: pNRF2 Expression Is Concomitantly Associated with Elevated Fasting Glucose Levels

Non-alcoholic fatty liver disease (NAFLD) embraces simple steatosis in non-alcoholic fatty liver (NAFL) to advanced non-alcoholic steatohepatitis (NASH) associated with inflammation, fibrosis, and cirrhosis. NAFLD patients often have metabolic syndrome and high risks of cardiovascular and liver-related mortality. Our aim was to clarify which proteins play a role in the progression of NAFL to NASH. The study investigates paraffin-embedded samples of 22 NAFL and 33 NASH patients. To detect potential candidates, samples were analyzed by immunohistochemistry for the proteins involved in innate immune regulation, autophagy, apoptosis, and antioxidant defense: IRF3, RIG-1, SOCS3, pSTAT3, STX17, SGLT2, Ki67, M30, Caspase 3, and pNRF2. The expression of pNRF2 immunopositive nuclei and SOCS3 cytoplasmic staining were higher in NASH than in NAFL (p = 0.001); pNRF2 was associated with elevated fasting glucose levels. SOCS3 immunopositivity correlated positively with RIG1 (r = 0.765; p = 0.001). Further, in NASH bile ducts showed stronger IRF3 immunostaining than in NAFL (p = 0.002); immunopositive RIG1 tissue was higher in NASH than in NAFL (p = 0.01). Our results indicate that pNRF2, SOCS3, IRF3, and RIG1 are involved in hepatic lipid metabolism. We suggest that they may be suitable for further studies to assess their potential as therapeutics.

Serotonin transporter-deficient mice display enhanced adipose tissue inflammation after chronic high-fat diet feeding

Introduction

Serotonin is involved in leukocyte recruitment during inflammation. Deficiency of the serotonin transporter (SERT) is associated with metabolic changes in humans and mice. A possible link and interaction between the inflammatory effects of serotonin and metabolic derangements in SERT-deficient mice has not been investigated so far.

Methods

SERT-deficient (Sert -/-) and wild type (WT) mice were fed a high-fat diet, starting at 8 weeks of age. Metabolic phenotyping (metabolic caging, glucose and insulin tolerance testing, body and organ weight measurements, qPCR, histology) and assessment of adipose tissue inflammation (flow cytometry, histology, qPCR) were carried out at the end of the 19-week high-fat diet feeding period. In parallel, Sert -/- and WT mice received a control diet and were analyzed either at the time point equivalent to high-fat diet feeding or as early as 8-11 weeks of age for baseline characterization.

Results

After 19 weeks of high-fat diet, Sert -/- and WT mice displayed similar whole-body and fat pad weights despite increased relative weight gain due to lower starting body weight in Sert -/-. In obese Sert -/- animals insulin resistance and liver steatosis were enhanced as compared to WT animals. Leukocyte accumulation and mRNA expression of cytokine signaling mediators were increased in epididymal adipose tissue of obese Sert -/- mice. These effects were associated with higher adipose tissue mRNA expression of the chemokine monocyte chemoattractant protein 1 and presence of monocytosis in blood with an increased proportion of pro-inflammatory Ly6C+ monocytes. By contrast, Sert -/- mice fed a control diet did not display adipose tissue inflammation.

Discussion

Our observations suggest that SERT deficiency in mice is associated with inflammatory processes that manifest as increased adipose tissue inflammation upon chronic high-fat diet feeding due to enhanced leukocyte recruitment.

Molecular Mechanisms for the Vicious Cycle between Insulin Resistance and the Inflammatory Response in Obesity

The comprehensive anabolic effects of insulin throughout the body, in addition to the control of glycemia, include ensuring lipid homeostasis and anti-inflammatory modulation, especially in adipose tissue (AT). The prevalence of obesity, defined as a body mass index (BMI) ≥ 30 kg/m², has been increasing worldwide on a pandemic scale with accompanying syndemic health problems, including glucose intolerance, insulin resistance (IR), and diabetes. Impaired tissue sensitivity to insulin or IR paradoxically leads to diseases with an inflammatory component despite hyperinsulinemia. Therefore, an excess of visceral AT in obesity initiates chronic low-grade inflammatory conditions that interfere with insulin signaling via insulin receptors (INSRs). Moreover, in response to IR, hyperglycemia itself stimulates a primarily defensive inflammatory response associated with the subsequent release of numerous inflammatory cytokines and a real threat of organ function deterioration. In this review, all components of this vicious cycle are characterized with particular emphasis on the interplay between insulin signaling and both the innate and adaptive immune responses related to obesity. Increased visceral AT accumulation in obesity should be considered the main environmental factor responsible for the disruption in the epigenetic regulatory mechanisms in the immune system, resulting in autoimmunity and inflammation.

Bioinformatics and network biology approach to identifying type 2 diabetes genes and pathways that influence the progression of breast cancer

Breast cancer is the second most prevalent malignancy affecting women. Postmenopausal women breast tumor is one of the top causes of death in women, accounting for 23% of cancer cases. Type 2 diabetes, a worldwide pandemic, has been connected to a heightened risk of several malignancies, although its association with breast cancer is still uncertain. In comparison to non-diabetic women, women with T2DM had a 23% elevated likelihood of developing breast cancer. It is difficult to determine causative or genetic susceptibility that connect T2DM and breast cancer. We created a large-scale network-based quantitative approach employing unbiased methods to discover abnormally amplified genes in both T2DM and breast cancer, to solve these issues. We performed transcriptome analysis to uncover identical genetic biomarkers and pathways to clarify the connection between T2DM and breast cancer patients. In this study, two RNA-seq datasets (GSE103001 and GSE86468) from the Gene Expression Omnibus (GEO) are used to identify mutually differentially expressed genes (DEGs) for breast cancer and T2DM, as well as common pathways and prospective medicines. Firstly, 45 shared genes (30 upregulated and 15 downregulated) between T2D and breast cancer were detected. We employed gene ontology and pathway enrichment to characterize prevalent DEGs' molecular processes and signal transduction pathways and observed that T2DM has certain connections to the progression of breast cancer. Using several computational and statistical approaches, we created a protein-protein interactions (PPI) network and revealed hub genes. These hub genes can be potential biomarkers, which may also lead to new therapeutic strategies for investigated diseases. We conducted TF-gene interactions, gene-microRNA interactions, protein-drug interactions, and gene-disease associations to find potential connections between T2DM and breast cancer pathologies. We assume that the potential drugs that emerged from this study could be useful therapeutic values. Researchers, doctors, biotechnologists, and many others may benefit from this research.

Paternal phthalate exposure-elicited offspring metabolic disorders are associated with altered sperm small RNAs in mice

Exposure to ubiquitous plastic-associated endocrine disrupting chemicals (EDCs) is associated with the increased risk of many chronic diseases. For example, phthalate exposure is associated with cardiometabolic mortality in humans, with societal costs ∼ $39 billion/year or more. We recently demonstrated that several widely used plastic-associated EDCs increase cardiometabolic disease in appropriate mouse models. In addition to affecting adult health, parental exposure to EDCs has also been shown to cause metabolic disorders, including obesity and diabetes, in the offspring. While most studies have focused on the impact of maternal EDC exposure on the offspring's health, little is known about the effects of paternal EDC exposure. In the current study, we investigated the adverse impact of paternal exposure to a ubiquitous but understudied phthalate, dicyclohexyl phthalate (DCHP) on the metabolic health of F1 and F2 offspring in mice. Paternal DCHP exposure led to exacerbated insulin resistance and impaired insulin signaling in F1 offspring without affecting diet-induced obesity. We previously showed that sperm small non-coding RNAs including tRNA-derived small RNAs (tsRNAs) and rRNA-derived small RNAs (rsRNAs) contribute to the intergenerational transmission of paternally acquired metabolic disorders. Using a novel PANDORA-seq, we revealed that DCHP exposure can lead to sperm tsRNA/rsRNA landscape changes that were undetected by traditional RNA-seq, which may contribute to DCHP-elicited adverse effects. Lastly, we found that paternal DCHP can also cause sex-specific transgenerational adverse effects in F2 offspring and elicited glucose intolerance in female F2 descendants. Our results suggest that exposure to endocrine disrupting phthalates may have intergenerational and transgenerational adverse effects on the metabolic health of their offspring. These findings increase our understanding of the etiology of chronic human diseases originating from chemical-elicited intergenerational and transgenerational effects.

Hepatic cytokine-inducible SH2-containing protein (CISH) regulates gluconeogenesis via cAMP-responsive element binding protein (CREB)

Impairment of gluconeogenesis is a key factor responsible for hyperglycemia in patients with type 2 diabetes. As an important member of the suppressors of cytokine signaling (SOCS) protein family, many physiological functions of cytokine-inducible SH2-containing protein (CISH) have been described; however, the role of hepatic CISH in gluconeogenesis is poorly understood. In the present study, we observed that hepatic CISH expression was reduced in fasted wild-type (WT) mice. Overexpression of CISH decreased glucose production in mouse primary hepatocytes, while silencing of CISH had the opposite effects. In addition, adenovirus-mediated hepatic CISH overexpression resulted in improved glucose tolerance and decreased gluconeogenesis in WT and leptin receptor-deficient diabetic (db/db) mice. In contrast, adenovirus-mediated hepatic CISH knockdown impaired glucose tolerance and increased gluconeogenesis in WT mice. We also generated liver-specific CISH knockout (LV-CISH KO) mice and discovered that these mice had a similar phenotype in glucose tolerance and gluconeogenesis as mice injected with adenoviruses that knockdown CISH expression. Mechanistically, we found that CISH overexpression decreased and CISH knockdown increased the mRNA and protein levels of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase 1 (PEPCK), two key enzymes involved in gluconeogenesis, in vitro, and in vivo. Moreover, we discovered that the phosphorylation of cAMP-responsive element binding protein 1 (CREB), a transcription factor of G6pase and Pepck, was required for regulating gluconeogenesis by CISH. Taken together, this study identifies hepatic CISH as an important regulator of gluconeogenesis. Our results also provide important insights into the metabolic functions of the SOCS protein family and the potential targets for the treatment of diabetes.

Retinoic acid and RARγ maintain satellite cell quiescence through regulation of translation initiation

In adult skeletal muscle, satellite cells are in a quiescent state, which is essential for the future activation of muscle homeostasis and regeneration. Multiple studies have investigated satellite cell proliferation and differentiation, but the molecular mechanisms that safeguard the quiescence of satellite cells remain largely unknown. In this study, we purposely activated dormant satellite cells by using various stimuli and captured the in vivo-preserved features from quiescence to activation transitions. We found that retinoic acid signaling was required for quiescence maintenance. Mechanistically, retinoic acid receptor gamma (RARγ) binds to and stimulates genes responsible for Akt dephosphorylation and subsequently inhibits overall protein translation initiation in satellite cells. Furthermore, the alleviation of retinoic acid signaling released the satellite cells from quiescence, but this restraint was lost in aged cells. Retinoic acid also preserves the quiescent state during satellite cell isolation, overcoming the cellular stress caused by the isolation process. We conclude that active retinoic acid signaling contributes to the maintenance of the quiescent state of satellite cells through regulation of the protein translation initiation process.

Chloroquine modulates the sulforaphane anti-obesity mechanisms in a high-fat diet model: Role of JAK-2/ STAT-3/ SOCS-3 pathway

The phytochemical sulforaphane (SFN) has been studied for its potential anti-obesity effect, but neither its molecular targets nor its interaction with the antimalarial drug chloroquine (CQ) has been fully delineated. Therefore, high-fat diet (HFD) obese rats were randomly allocated into one of five groups and were left untreated or gavaged orally with SFN (0.5 or 1 mg/kg), CQ (5 mg/kg), or their combination (0.5/5 mg/kg) for six successive weeks to assess their potential interaction and the enrolled mechanisms. SFN effectively reduced the HFD-induced weight gain, blood glucose, and serum leptin levels, and improved lipid profile. On the molecular level, SFN inhibited the lipogenesis-related enzymes, namely sterol regulatory element-binding protein (SREBP)-1c, fatty acid synthase (FAS), and acetyl-CoA carboxylase (ACC) in both liver and visceral white adipose tissue (vWAT) of HFD obese rats. SFN also turned off the inflammatory pathway conserved Janus kinase/signaling transducers and activators of transcription/suppressor of cytokine signaling (JAK-2/STAT-3/SOCS-3) in these tissues, as well as the inflammatory markers nuclear factor-kappa (NF-κ) B and interleukin (IL)-22 in serum. In contrast, SFN downregulated the gene expression of microRNA (miR-200a), while significantly increasing the autophagic parameters; viz., beclin-1, autophagy-related protein (ATG)-7, and microtubule-associated protein 2 light chain 3 (LC3-II) in both liver and vWAT. On most of the parameters mentioned above, treatment with CQ solely produced a satisfactory effect and intensified the low dose of SFN in the combination regimen. These findings demonstrated the beneficial effects of using CQ as an add-on anti-obesity medicine to SFN.

Inflammation and Wasting of Skeletal Muscles in Kras-p53-Mutant Mice with Intraepithelial Neoplasia and Pancreatic Cancer-When Does Cachexia Start?

Skeletal muscle wasting critically impairs the survival and quality of life in patients with pancreatic ductal adenocarcinoma (PDAC). To identify the local factors initiating muscle wasting, we studied inflammation, fiber cross-sectional area (CSA), composition, amino acid metabolism and capillarization, as well as the integrity of neuromuscular junctions (NMJ, pre-/postsynaptic co-staining) and mitochondria (electron microscopy) in the hindlimb muscle of LSL-KrasG12D/+; LSL-TrP53R172H/+; Pdx1-Cre mice with intraepithelial-neoplasia (PanIN) 1-3 and PDAC, compared to wild-type mice (WT). Significant decreases in fiber CSA occurred with PDAC but not with PanIN 1-3, compared to WT: These were found in the gastrocnemius (type 2x: −20.0%) and soleus (type 2a: −21.0%, type 1: −14.2%) muscle with accentuation in the male soleus (type 2a: −24.8%, type 1: −17.4%) and female gastrocnemius muscle (−29.6%). Significantly higher densities of endomysial CD68+ and cyclooxygenase-2+ (COX2+) cells were detected in mice with PDAC, compared to WT mice. Surprisingly, CD68+ and COX2+ cell densities were also higher in mice with PanIN 1-3 in both muscles. Significant positive correlations existed between muscular and hepatic CD68+ or COX2+ cell densities. Moreover, in the gastrocnemius muscle, suppressor-of-cytokine-3 (SOCS3) expressions was upregulated >2.7-fold with PanIN 1A-3 and PDAC. The intracellular pools of proteinogenic amino acids and glutathione significantly increased with PanIN 1A-3 compared to WT. Capillarization, NMJ, and mitochondrial ultrastructure remained unchanged with PanIN or PDAC. In conclusion, the onset of fiber atrophy coincides with the manifestation of PDAC and high-grade local (and hepatic) inflammatory infiltration without compromised microcirculation, innervation or mitochondria. Surprisingly, muscular and hepatic inflammation, SOCS3 upregulation and (proteolytic) increases in free amino acids and glutathione were already detectable in mice with precancerous PanINs. Studies of initial local triggers and defense mechanisms regarding cachexia are warranted for targeted anti-inflammatory prevention.

Cytokine-inducible SH2 domain containing protein contributes to regulation of adiposity, food intake, and glucose metabolism

The cytokine-inducible SH2 domain containing protein (CISH) is the founding member of the suppressor of cytokine signaling (SOCS) family of negative feedback regulators and has been shown to be a physiological regulator of signaling in immune cells. This study sought to investigate novel functions for CISH outside of the immune system. Mice deficient in CISH were generated and analyzed using a range of metabolic and other parameters, including in response to a high fat diet and leptin administration. CISH knockout mice possessed decreased body fat and showed resistance to diet-induced obesity. This was associated with reduced food intake, but unaltered energy expenditure and microbiota composition. CISH ablation resulted in reduced basal expression of the orexigenic Agrp gene in the arcuate nucleus (ARC) region of the brain. Cish was basally expressed in the ARC, with evidence of co-expression with the leptin receptor (Lepr) gene in Agrp-positive neurons. CISH-deficient mice also showed enhanced leptin responsiveness, although Cish expression was not itself modulated by leptin. CISH-deficient mice additionally exhibited improved insulin sensitivity on a high-fat diet, but not glucose tolerance despite reduced body weight. These data identify CISH as an important regulator of homeostasis through impacts on appetite control, mediated at least in part by negative regulation of the anorexigenic effects of leptin, and impacts on glucose metabolism.

The Role of IL-6 Released During Exercise to Insulin Sensitivity and Muscle Hypertrophy

Interleukin-6 (IL-6) influences both inflammatory response and anti-inflammatory processes. This cytokine can be released by the exercising skeletal muscle, which characterizes it as a myokine. Unlike what is observed in inflammation, IL-6 produced by skeletal muscle is not preceded by the release of other pro-inflammatory cytokines, but is seems to be dependent on the lactate produced during exercise, thus causing different effects from those of seen in inflammatory state. After binding to its receptor, myokine IL-6 activates the PI3K-Akt pathway. One consequence of this upregulation is the potentiation of insulin signaling, which enhances insulin sensitivity. IL-6 increases GLUT-4 vesicle mobilization to muscle cell periphery, increasing the glucose transport into the cell, and also glycogen synthesis. Muscle glycogen provides energy for the ATP resynthesis, and regulates Ca2+ release by the sarcoplasmic reticulum, influencing muscle contraction, and, hence, muscle function by multiple pathways. Another implication for the upregulation of PI3K-Akt pathway is the activation of mTORC1, which regulates mRNA translational efficiency by regulating translation machinery, and translational capacity by inducing ribosomal biogenesis. Thus, IL-6 may contribute for skeletal muscle hypertrophy and function by increasing contractile protein synthesis.

Interleukins in adipose tissue: Keeping the balance

The role of the immune system is to defend the host and preserve the functionality in response to stress. This function is not limited to infection or injury as it also plays a role in the response to overnutrition. Indeed, low-grade chronic activation of the immune system associated with overnutrition may be deleterious, contributing importantly to diabetes and long-term complications, such as cardiovascular disorders. Increasing evidence shows that adipose tissue participates in the obesity-related inflammatory response and that interleukins are one of the key players, either as a pro-inflammatory response to the metabolic dysregulation or to restore homeostasis. The crosstalk between adipocytes and immune cells through some important interleukins and their role in metabolic disruption is the topic of this review.

Effect of chronic intermittent hypoxia (CIH) on neuromuscular junctions and mitochondria in slow- and fast-twitch skeletal muscles of mice—the role of iNOS

Background

Obstructive sleep apnea (OSA) imposes vascular and metabolic risks through chronic intermittent hypoxia (CIH) and impairs skeletal muscle performance. As studies addressing limb muscles are rare, the reasons for the lower exercise capacity are unknown. We hypothesize that CIH-related morphological alterations in neuromuscular junctions (NMJ) and mitochondrial integrity might be the cause of functional disorders in skeletal muscles.

Methods

Mice were kept under 6 weeks of CIH (alternating 7% and 21% O₂ fractions every 30 s, 8 h/day, 5 days/week) compared to normoxia (NOX). Analyses included neuromuscular junctions (NMJ) postsynaptic morphology and integrity, fiber cross-sectional area (CSA) and composition (ATPase), mitochondrial ultrastructure (transmission-electron-microscopy), and relevant transcripts (RT-qPCR). Besides wildtype (WT), we included inducible nitric oxide synthase knockout mice (iNOS^−/−) to evaluate whether iNOS is protective or risk-mediating.

Results

In WT soleus muscle, CIH vs. NOX reduced NMJ size (− 37.0%, p < 0.001) and length (− 25.0%, p < 0.05) together with fiber CSA of type IIa fibers (− 14%, p < 0.05) and increased centronucleated fiber fraction (p < 0.001). Moreover, CIH vs. NOX increased the fraction of damaged mitochondria (1.8-fold, p < 0.001). Compared to WT, iNOS^−/− similarly decreased NMJ area and length with NOX (− 55%, p < 0.001 and − 33%, p < 0.05, respectively) or with CIH (− 37%, p < 0.05 and − 29%, p < 0.05), however, prompted no fiber atrophy. Moreover, increased fractions of damaged (2.1-fold, p < 0.001) or swollen (> 6-fold, p < 0.001) mitochondria were observed with iNOS^−/− vs. WT under NOX and similarly under CIH. Both, CIH- and iNOS^−/− massively upregulated suppressor-of-cytokine-signaling-3 (SOCS3) > 10-fold without changes in IL6 mRNA expression. Furthermore, inflammatory markers like CD68 (macrophages) and IL1β were significantly lower in CIH vs. NOX. None of these morphological alterations with CIH- or iNOS^−/− were detected in the gastrocnemius muscle. Notably, iNOS expression was undetectable in WT muscle, unlike the liver, where it was massively decreased with CIH.

Conclusion

CIH leads to NMJ and mitochondrial damage associated with fiber atrophy/centronucleation selectively in slow-twitch muscle of WT. This effect is largely mimicked by iNOS^−/− at NOX (except for atrophy). Both conditions involve massive SOCS3 upregulation likely through denervation without Il6 upregulation but accompanied by a decrease of macrophage density especially next to denervated endplates. In the absence of muscular iNOS expression in WT, this damage may arise from extramuscular, e.g., motoneuronal iNOS deficiency (through CIH or knockout) awaiting functional evaluation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13395-022-00288-7.

Altered microbiota by a high-fat diet accelerates lethal myeloid hematopoiesis associated with systemic SOCS3 deficiency

The suppressors of cytokine signaling (SOCS) proteins are negative regulators of cytokine signaling required to prevent excessive cellular responses. In particular, SOCS3 is involved in the regulation of metabolic syndromes, such as obesity and diabetes, by suppressing leptin and insulin signals. SOCS3 also suppresses the inflammatory response associated with metabolic stress, but this specific role remains undefined. Wild-type mice on a high-fat diet (HFD) exhibited only fatty liver, whereas systemic deletion of SOCS3 resulted in excessive myeloid hematopoiesis and hepatic inflammation. In addition, depletion of the gut microbiota resulted in considerable improvement in excess granulopoiesis and splenomegaly, halting the progression of systemic inflammation in SOCS3KO mice on the HFD. This result suggests that intestinal dysbiosis is involved in inflammation associated with SOCS3KO. Although contributing to diet-induced obesity and fatty liver, SOCS3 is nevertheless critical to suppress excess myeloid hematopoiesis and severe systemic inflammation associated with intestinal dysbiosis on HFD.

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SOCS3 suppresses severe systemic inflammation associated with high-fat diet

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SOCS3 deficiency on high-fat diet accelerates excess myeloid hematopoiesis

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SOCS3 controls gut dysbiosis on high-fat diet

Maternal Socs3 knockdown attenuates postnatal obesity caused by an early life environment of maternal obesity and intrauterine overnutrition in progeny mice

Pathological states in the early life environment of mammalian offspring, including maternal obesity and intrauterine overnutrition, can induce obesity and metabolic disorder later in life. Leptin resistance caused by upregulation of Socs3 in the hypothalamus of offspring was believed to be the main mechanism of this effect. In this study, obese mother (OM) and lean mother (LM) models were generated by feeding C57BL/6N female mice a high-fat diet or standard lean diet, respectively. Additionally, an obese mother with intervention (OMI) model was generated by injecting the high-fat diet group with Socs3-shRNA lentivirus during early pregnancy. The offspring of the groups was correspondingly named OM-F1 , LM-F1 , and OMI-F1 , representing progeny mouse models of different early life environments. The offspring were fed a high-fat diet to test their propensity for obesity. The body weight, food intake and fat accumulation were higher, while glucose intolerance and insulin resistance were worse in the OM-F1 group than LM-F1 group. By contrast, the obesity phenotype, hyperphagia and metabolic disorder were alleviated in the OMI-F1 group compared with the OM-F1 group. The mechanism was identified that downregulation of hypothalamic SOCS3 resulted in an increased level of p-STAT3 and p-JAK2, which ameliorated the leptin resistance and restored the lean expression of appetite regulatory genes (Pomc and Agrp) in hypothalamus of OMI-F1 group. Taken together, these results indicate that reducing maternal Socs3 expression during pregnancy can attenuate obesity caused by the early life environment in mice, which may inspire therapies that enable obese mothers to bear metabolically healthy children.

Combined effects of progesterone and SOCS3 DNA methylation on T2DM: a case-control study

BACKGROUND

This study aims to investigate the independent and combined effects of progesterone and suppressor of cytokine signaling (SOCS)-3 DNA methylation on type 2 diabetes mellitus (T2DM) among men and postmenopausal women in rural China.

METHODS

A case-control study with 914 participants (329 T2DM, 585 controls) was conducted. Serum progesterone was detected with liquid chromatography-tandem mass spectrometry. DNA methylation of SOCS3 was determined by MethylTarget™. Linear regression was applied to evaluate the associations of progesterone and SOCS3 methylation with marks of glucose metabolism. Logistic regression was employed to investigate the independent and combined effects of progesterone and SOCS3 methylation with T2DM in men and postmenopausal women.

RESULTS

After multiple adjustment, progesterone was positively associated with T2DM in both men (odds ratio (OR) (95% confidence interval (CI)): 2.77 (1.79, 4.29)) and postmenopausal women (OR (95% CI): 1.85 (1.26, 2.72)). Methylation level of Chr17:76,356,190 or Chr17:76,356,199 (SOCS3) was negatively associated with T2DM in both men (OR (95% CI): 0.58 (0.39, 0.86) or 0.27 (0.14, 0.51)) and postmenopausal women (OR (95% CI): 0.43 (0.29, 0.65) or 0.53 (0.28, 0.99)). Subjects with high progesterone and low Chr17:76,356,190 or Chr17:76,356,199 methylation were more susceptible to have a higher prevalence of T2DM (men: OR (95% CI): 5.20 (2.49, 10.85) or 5.62 (2.74, 11.54); postmenopausal women: OR (95% CI): 3.66 (1.85, 7.26) or 3.27 (1.66, 6.45)).

CONCLUSIONS

The independent and combined effects of progesterone and SOCS3 methylation on T2DM were found among men and postmenopausal women, suggesting that ensuring low levels of progesterone and high methylation of SOCS3 could reduce the prevalence of T2DM. Trial registration The Chinese Clinical Trial registration: The Henan Rural Cohort Study, ChiCTR-OOC-15006699. Registered 06 July 2015, http://www.chictr.org.cn/showproj.aspx?proj=11375.

Exercise tolls the bell for key mediators of low-grade inflammation in dysmetabolic conditions

Metabolic conditions share a common low-grade inflammatory milieu, which represents a key-factor for their ignition and maintenance. Exercise is instrumental for warranting systemic cardio-metabolic balance, owing to its regulatory effect on inflammation. This review explores the effect of physical activity in the modulation of sub-inflammatory framework characterizing dysmetabolic conditions. Regular exercise suppresses plasma levels of TNFα, IL-1β, FFAs and MCP-1, in dysmetabolic subjects. In addition, a single session of training increases the anti-inflammatory IL-10, IL-1 receptor antagonist (IL-1ra), and muscle-derived IL-6, mitigating low-grade inflammation. Resting IL-6 levels are decreased in trained-dysmetabolic subjects, compared to sedentary. On the other hand, the acute release of muscle-IL-6, after exercise, seems to exert a regulatory effect on the metabolic and inflammatory balance. In fact, muscle-released IL-6 is presumably implicated in fat loss and boosts plasma levels of IL-10 and IL-1ra. The improvement of adipose tissue functionality, following regular exercise, is also critical for the mitigation of sub-inflammation. This effect is likely mediated by muscle-released IL-15 and IL-6 and partly relies on the brown-shifting of white adipocytes, induced by exercise. In obese-dysmetabolic subjects, moderate training is shown to restore gut-microbiota health, and this mitigates the translocation of bacterial-LPS into bloodstream. Finally, regular exercise can lower plasma advanced glycated endproducts. The articulated physiology of circulating mediators and the modulating effect of the pathophysiological background, render the comprehension of the exercise-regulatory effect on sub-inflammation a key issue, in dysmetabolism.

The mediation role of SOCS3 methylation in the effect of serum testosterone on type 2 diabetes

BACKGROUND

Previous studies reported that testosterone and DNA methylation of suppressor of cytokine signaling-3 (SOCS3) were associated with type 2 diabetes (T2D). Testosterone affects SOCS3 gene expression. Therefore, we aimed to investigate how the SOCS3 methylation mediates the relationship between testosterone and T2D among Chinese rural adults.

METHODS

A case-control study comprised 365 T2D patients and 651 controls was conducted. Liquid chromatography-tandem mass spectrometry and MethylTarget were used to determine the levels of serum testosterone and DNA methylation of SOCS3 gene, respectively. The odds ratio (OR) of testosterone or SOCS3 methylation for T2D was calculated using logistic regression models, and β value of testosterone for SOCS3 methylation was evaluated by linear regression models. Furthermore, through mediation analysis the mediating effect of SOCS3 methylation on the association of testosterone with T2D was estimated.

RESULTS

After adjusting for multiple variables, the protective effect of testosterone on T2D was found in men (OR = 0.61, 95% confidence interval [CI]: 0.47-0.80), and the methylation of Chr17:76356190 or Chr17:76356199 was negatively related to T2D in both men and women. Moreover, testosterone was positively associated with Chr17:76356190 methylation in men and Chr17:76356199 methylation in women (both P < .05). The mediation analysis showed that the Chr17:76356190 methylation partly mediated effect of testosterone on T2D in men was approximately 8.2%.

CONCLUSIONS

High levels of serum testosterone in men and Chr17:76356190 and Chr17:76356199 (SOCS3) methylation were related to a lower prevalent T2D. In addition, Chr17:76356190 methylation partially mediated the effect of testosterone on T2D in Chinese rural men.

Coordination of tumor growth and host wasting by tumor-derived Upd3

yki-induced gut tumors in Drosophila are associated with host wasting, including muscle dysfunction, lipid loss, and hyperglycemia, a condition reminiscent of human cancer cachexia. We previously used this model to identify tumor-derived ligands that contribute to host wasting. To identify additional molecular networks involved in host-tumor interactions, we develop PathON, a web-based tool analyzing the major signaling pathways in Drosophila, and uncover the Upd3/Jak/Stat axis as an important modulator. We find that yki-gut tumors secrete Upd3 to promote self-overproliferation and enhance Jak/Stat signaling in host organs to cause wasting, including muscle dysfunction, lipid loss, and hyperglycemia. We further reveal that Upd3/Jak/Stat signaling in the host organs directly triggers the expression of ImpL2, an antagonistic binding protein for insulin-like peptides, to impair insulin signaling and energy balance. Altogether, our results demonstrate that yki-gut tumors produce a Jak/Stat pathway ligand, Upd3, that regulates both self-growth and host wasting.

Ding et al. show that yki^3SA-gut tumors produce Upd3 as a cachectic ligand to simultaneously promote self-growth and host organ wasting via systemic activation of Jak/Stat signaling in Drosophila. The Upd3/Jak/Stat axis induces host ImpL2 production and perturbs insulin response, leading to muscle mitochondrial dysfunction, lipid loss, and carbohydrate elevation.

Increased PARylation impacts the DNA methylation process in type 2 diabetes mellitus

Background

Epigenetic modifications, such as DNA methylation, can influence the genetic susceptibility to type 2 diabetes mellitus (T2DM) and the progression of the disease. Our previous studies demonstrated that the regulation of the DNA methylation pattern involves the poly(ADP-ribosyl)ation (PARylation) process, a post-translational modification of proteins catalysed by the poly(ADP-ribose) polymerase (PARP) enzymes. Experimental data showed that the hyperactivation of PARylation is associated with impaired glucose metabolism and the development of T2DM. Aims of this case–control study were to investigate the association between PARylation and global and site-specific DNA methylation in T2DM and to evaluate metabolic correlates.

Results

Data were collected from 61 subjects affected by T2DM and 48 healthy individuals, recruited as controls. Global levels of poly(ADP-ribose) (PAR, a surrogate of PARP activity), cytosine methylation (5-methylcytosine, 5mC) and de-methylation intermediates 5-hydroxymethylcytosine (5hmC) and 5-formylcytosine (5fC) were determined in peripheral blood cells by ELISA-based methodologies. Site-specific DNA methylation profiling of SOCS3, SREBF1 and TXNIP candidate genes was performed by mass spectrometry-based bisulfite sequencing, methyl-sensitive endonucleases digestion and by DNA immuno-precipitation. T2DM subjects presented higher PAR levels than controls. In T2DM individuals, increased PAR levels were significantly associated with higher HbA1c levels and the accumulation of the de-methylation intermediates 5hmC and 5fC in the genome. In addition, T2DM patients with higher PAR levels showed reduced methylation with increased 5hmC and 5fC levels in specific SOCS3 sites, up-regulated SOCS3 expression compared to both T2DM subjects with low PAR levels and controls.

Conclusions

This study demonstrates the activation of PARylation processes in patients with T2DM, particularly in those with poor glycaemic control. PARylation is linked to dysregulation of DNA methylation pattern via activation of the DNA de-methylation cascade and may be at the basis of the differential gene expression observed in presence of diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13148-021-01099-1.

Pro-inflammatory interleukin-6 signaling links cognitive impairments and peripheral metabolic alterations in Alzheimer's disease

Alzheimer's disease (AD) is associated with memory impairment and altered peripheral metabolism. Mounting evidence indicates that abnormal signaling in a brain-periphery metabolic axis plays a role in AD pathophysiology. The activation of pro-inflammatory pathways in the brain, including the interleukin-6 (IL-6) pathway, comprises a potential point of convergence between memory dysfunction and metabolic alterations in AD that remains to be better explored. Using T2-weighted magnetic resonance imaging (MRI), we observed signs of probable inflammation in the hypothalamus and in the hippocampus of AD patients when compared to cognitively healthy control subjects. Pathological examination of post-mortem AD hypothalamus revealed the presence of hyperphosphorylated tau and tangle-like structures, as well as parenchymal and vascular amyloid deposits surrounded by astrocytes. T2 hyperintensities on MRI positively correlated with plasma IL-6, and both correlated inversely with cognitive performance and hypothalamic/hippocampal volumes in AD patients. Increased IL-6 and suppressor of cytokine signaling 3 (SOCS3) were observed in post-mortem AD brains. Moreover, activation of the IL-6 pathway was observed in the hypothalamus and hippocampus of AD mice. Neutralization of IL-6 and inhibition of the signal transducer and activator of transcription 3 (STAT3) signaling in the brains of AD mouse models alleviated memory impairment and peripheral glucose intolerance, and normalized plasma IL-6 levels. Collectively, these results point to IL-6 as a link between cognitive impairment and peripheral metabolic alterations in AD. Targeting pro-inflammatory IL-6 signaling may be a strategy to alleviate memory impairment and metabolic alterations in the disease.

Diet-Induced Obesity Promotes the Upregulation of Fas Expression on T-cells

This study was conducted to assess the expression of Fas (CD95) and programmed cell death-1 (PD-1) on circulating T-cells in obesity using a diet-induced obesity mouse model. Furthermore, we aimed to determine if there are any associations between metabolic disorders and the expression of T-cell regulatory markers. A total of 12 male C57BL/6 mice were randomized into either a high-fat diet (HFD) or low-fat diet (LFD) group for 8 weeks (n = 6/group). Changes in body weights were monitored on a weekly basis. The lipid, glucose, and hematological profiles, as well as Fas and PD1 expression on the T-cell immunophenotype, were measured after 8 weeks of feeding. The HFD-fed group had a higher percentage weight gain (29.17%) in comparison with the LFD-fed group (21.74%) after the 8-week period. In addition, the HFD group had increased fasting glucose and glucose excursion following a 2-h postprandial period. The levels of total cholesterol were elevated in the HFD group when compared with the LFD group (p < 0.05). Notably, the absolute white cell count (p = 0.0096), neutrophil count (p = 0.0022, lymphocytes (p = 0.0155), and monocyte count (p = 0.0015) were elevated in the HFD group when compared with the LFD-fed group. However, the platelets (0.0680), red cell counts (0.3575), and their indices (p > 0.05) were comparable between the two groups. Interestingly, HFD feeding was associated with elevated expression of Fas on T-cells (p < 0.0001), which positively correlated with body weights (r = 0.93, p = 0.0333). No associations were found between Fas expression and dyslipidemia or fasting blood glucose levels (p > 0.05). The multivariant regression analysis showed that the association between the levels of Fas on T-cells and body weights (coefficient: -1.00, t-value: 19.27, p = 0.0330) was independent of fasting blood glucose, total cholesterol, and lymphocyte count. Lastly, the expression of PD-1 on T-cells was comparable between the two diet groups (p = 0.1822). In all, immune activation, dyslipidemia, and poor glucose control in the early stages of obesity may drive the pathogenesis of metabolic T-cell disorders. Importantly, T-cell dysfunction in obesity is partially mediated by an upregulation of Fas which is independent of dyslipidemia and hyperglycemia.

Ghrelin and adipokines: An overview of their physiological role, antimicrobial activity and impact on cardiovascular conditions

The human body has many different hormones that interact with each other and with other factors such as proteins, cell receptors and metabolites. There is still a limited understanding of some of the underlying biological mechanisms of some hormones. In the past decades, science and technology have made major advancements in regard to innovation and knowledge in fields such as medicine. However, some conditions are complex and have many variables that their full picture is still unclear, even though some of these conditions have an alarming rate of incidence and serious health consequences. Conditions such as type 2 diabetes, obesity, nonalcoholic liver disease (NAFLD), cancer in its different forms and even mental conditions, such as Alzheimer's disease, are some of the most common diseases in the 21st century. These conditions are relevant not only because of their high incidence on the general population, but also because of their severity. In this chapter, we present an overview of cardiovascular (CV) diseases. According to the World Health Organization (WHO), cardiovascular diseases, such as coronary artery disease (CAD), heart attack, cardiomyopathy and heart failure (among others), are the number one cause of death worldwide. In 2016, it was estimated that 17.9 million people died from CV diseases, representing more than 30% of all global deaths. Approximately 95% of people who died from CV diseases were so-called "premature deaths" because were referenced to individuals under the age of 70 years old. In this chapter we described some of the hormones that may have an impact on CV diseases, including ghrelin, a peptide that is mostly produced in the stomach, known to induce hunger. Ghrelin is linked to an increase in body fat, i.e., adipose tissue in animals. For this reason, we also included the adipokines leptin, adiponectin and resistin. The main objectives of this chapter are to present the state of the art knowledge concerning the mechanisms of each hormone relevant to CV diseases; to compile data and results that further elucidate the relevance of these peptides for several physiological events, conditions and diseases; and to discuss the metabolic impact of each hormone. We established connections between multiple peptides and the underlying condition/disease with tools such as STRING, referring to research using databases, such as UniProt, DisGeNET and Proteomics DB. Fig. 1 shows a network that summarizes the information presented in this chapter, which serves as a visual representation.

Gut Microbiota as a Trigger for Metabolic Inflammation in Obesity and Type 2 Diabetes

The gut microbiota has been linked to the development of obesity and type 2 diabetes (T2D). The underlying mechanisms as to how intestinal microbiota may contribute to T2D are only partly understood. It becomes progressively clear that T2D is characterized by a chronic state of low-grade inflammation, which has been linked to the development of insulin resistance. Here, we review the current evidence that intestinal microbiota, and the metabolites they produce, could drive the development of insulin resistance in obesity and T2D, possibly by initiating an inflammatory response. First, we will summarize major findings about immunological and gut microbial changes in these metabolic diseases. Next, we will give a detailed view on how gut microbial changes have been implicated in low-grade inflammation. Lastly, we will critically discuss clinical studies that focus on the interaction between gut microbiota and the immune system in metabolic disease. Overall, there is strong evidence that the tripartite interaction between gut microbiota, host immune system and metabolism is a critical partaker in the pathophysiology of obesity and T2D.

Targeting Janus Kinases and Signal Transducer and Activator of Transcription 3 to Treat Inflammation, Fibrosis, and Cancer: Rationale, Progress, and Caution

Before it was molecularly cloned in 1994, acute-phase response factor or signal transducer and activator of transcription (STAT)3 was the focus of intense research into understanding the mammalian response to injury, particularly the acute-phase response. Although known to be essential for liver production of acute-phase reactant proteins, many of which augment innate immune responses, molecular cloning of acute-phase response factor or STAT3 and the research this enabled helped establish the central function of Janus kinase (JAK) family members in cytokine signaling and identified a multitude of cytokines and peptide hormones, beyond interleukin-6 and its family members, that activate JAKs and STAT3, as well as numerous new programs that their activation drives. Many, like the acute-phase response, are adaptive, whereas several are maladaptive and lead to chronic inflammation and adverse consequences, such as cachexia, fibrosis, organ dysfunction, and cancer. Molecular cloning of STAT3 also enabled the identification of other noncanonical roles for STAT3 in normal physiology, including its contribution to the function of the electron transport chain and oxidative phosphorylation, its basal and stress-related adaptive functions in mitochondria, its function as a scaffold in inflammation-enhanced platelet activation, and its contributions to endothelial permeability and calcium efflux from endoplasmic reticulum. In this review, we will summarize the molecular and cellular biology of JAK/STAT3 signaling and its functions under basal and stress conditions, which are adaptive, and then review maladaptive JAK/STAT3 signaling in animals and humans that lead to disease, as well as recent attempts to modulate them to treat these diseases. In addition, we will discuss how consideration of the noncanonical and stress-related functions of STAT3 cannot be ignored in efforts to target the canonical functions of STAT3, if the goal is to develop drugs that are not only effective but safe. SIGNIFICANCE STATEMENT: Key biological functions of Janus kinase (JAK)/signal transducer and activator of transcription (STAT)3 signaling can be delineated into two broad categories: those essential for normal cell and organ development and those activated in response to stress that are adaptive. Persistent or dysregulated JAK/STAT3 signaling, however, is maladaptive and contributes to many diseases, including diseases characterized by chronic inflammation and fibrosis, and cancer. A comprehensive understanding of JAK/STAT3 signaling in normal development, and in adaptive and maladaptive responses to stress, is essential for the continued development of safe and effective therapies that target this signaling pathway.

SOCS2 Inhibits Mitochondrial Fatty Acid Oxidation via Suppressing LepR/JAK2/AMPK Signaling Pathway in Mouse Adipocytes

Suppressor of cytokine signaling 2 (SOCS2) plays an important role in fat deposition, skeletal muscle, central nervous system development, and mitochondria biogenesis. Nevertheless, the regulatory mechanisms of SOCS2 on mitochondrial fatty acid oxidation (FAO) remain unclear. Leptin could inhibit food intake and increase thermogenesis through leptin receptor (LepR), which was present in the hypothalamus and certain peripheral organs, including adipose tissue. With strong interest, we focused on the connection between leptin and SOCS2 and their effect on FAO in adipocytes. In our study, we found that the mRNA level of SOCS2 and the protein levels of PGC-1α, CPT-1b, FAT, and p-ACC were elevated by leptin in the inguinal adipose tissue of mice. On the contrary, the protein levels of FABP4, FATP1, and FAS were declined. The genes related to fatty acid oxidation such as PGC-1α, NRF-1, TFAM, CPT-1b, AOX1, COX2, and UCP2 were attenuated by SOCS2, but elevated by leptin. Moreover, fatty acid oxidation enzyme MCAD, LCAD, and Cyt C levels were reduced in response to SOCS2. These reductions correspond well with the reduced release of free fatty acid and the reduction of mitochondrial complexes I and III by SOCS2. Furthermore, JAK2/AMPK pathway-specific inhibitors could block the mitochondrial FAO; hence, this pathway was implied to have a potential impact on FAO. Together, these studies suggested that SOCS2 had a negative effect on mitochondrial fatty acid oxidation, and the LepR/JAK2/AMPK pathway played a crucial role in this process.

Precision Nutrition and Childhood Obesity: A Scoping Review

Environmental exposures such as nutrition during life stages with high developmental plasticity—in particular, the in utero period, infancy, childhood, and puberty—may have long-lasting influences on risk of chronic diseases, including obesity-related conditions that manifest as early as childhood. Yet, specific mechanisms underlying these relationships remain unclear. Here, we consider the study of ‘omics mechanisms, including nutrigenomics, epigenetics/epigenomics, and metabolomics, within a life course epidemiological framework to accomplish three objectives. First, we carried out a scoping review of population-based literature with a focus on studies that include ‘omics analyses during three sensitive periods during early life: in utero, infancy, and childhood. We elected to conduct a scoping review because the application of multi-‘omics and/or precision nutrition in childhood obesity prevention and treatment is relatively recent, and identifying knowledge gaps can expedite future research. Second, concomitant with the literature review, we discuss the relevance and plausibility of biological mechanisms that may underlie early origins of childhood obesity identified by studies to date. Finally, we identify current research limitations and future opportunities for application of multi-‘omics in precision nutrition/health practice.

Multifactorial effects of hyperglycaemia, hyperinsulinemia and inflammation on bone remodelling in type 2 diabetes mellitus

Bones undergo continuous cycles of bone remodelling that rely on the balance between bone formation and resorption. This balance allows the bone to adapt to changes in mechanical loads and repair microdamages. However, this balance is susceptible to upset in various conditions, leading to impaired bone remodelling and abnormal bones. This is usually indicated by abnormal bone mineral density (BMD), an indicator of bone strength. Despite this, patients with type 2 diabetes mellitus (T2DM) exhibit normal to high BMD, yet still suffer from an increased risk of fractures. The activity of the bone cells is also altered as indicated by the reduced levels of bone turnover markers in T2DM observed in the circulation. The underlying mechanisms behind these skeletal outcomes in patients with T2DM remain unclear. This review summarises recent findings regarding inflammatory cytokine factors associated with T2DM to understand the mechanisms involved and considers potential therapeutic interventions.

DNA Methylation Markers of Type 2 Diabetes Mellitus Among Male Veterans With or Without Human Immunodeficiency Virus Infection

Epigenetic modifications such as DNA methylation are associated with both human immunodeficiency virus (HIV) infection and type 2 diabetes mellitus (T2DM). We investigated epigenetic associations with T2DM according to HIV infection status and assessed interaction effects among 681 male participants of the Veterans Aging Cohort Study. Methylation at previously reported sites, cg1963031 (TXNIP), cg18181703 (SOCS3), and cg09152259 (PROC), was significantly associated with T2DM in HIV-infected individuals. We identified 3 novel associations with suggestive statistical significance: cg1231141 (ADAMTS2), cg19534769 (HGFAC), and cg13163919 (TLE3). Suggestive interaction with HIV infection status was found at cg17862404 (TSC22D1). The implicated genes are involved in inflammation, pancreatic β-cell function, and T2DM pathogenesis.

Fetal ovine skeletal and cardiac muscle transcriptomics are differentially altered by increased maternal cortisol during gestation

We have previously found that in utero exposure to excess maternal cortisol (1 mg/kg/day) in late gestation increases the incidence of stillbirth during labor and produces fetal bradycardia at birth. In the interventricular septum, mitochondrial DNA (mt-DNA) was decreased, and transcriptomics and metabolomics were consistent with altered mitochondrial metabolism. The present study uses transcriptomics to model effects of increased maternal cortisol on fetal biceps femoris. Transcriptomic modeling revealed that pathways related to mitochondrial metabolism were downregulated, whereas pathways for regulation of reactive oxygen species and activation of the apoptotic cascade were upregulated. Mt-DNA and the protein levels of cytochrome C were significantly decreased in the biceps femoris. RT-PCR validation of the pathways confirmed a significant decrease in SLC2A4 mRNA levels and a significant increase in PDK4, TXNIP, ANGPTL4 mRNA levels, suggesting that insulin sensitivity of the biceps femoris muscle may be reduced in cortisol offspring. We also tested for changes in gene expression in diaphragm by rt-PCR. PDK4, TXNIP, and ANGPTL4 mRNA were also increased in the diaphragm, but SLC2A4, cytochrome C protein, and mt-DNA were unchanged. Comparison of the change in gene expression in biceps femoris to that in cardiac interventricular septum and left ventricle showed few common genes and little overlap in specific metabolic or signaling pathways, despite reduction in mt-DNA in both heart and biceps femoris. Our results suggest that glucocorticoid exposure alters expression of nuclear genes important to mitochondrial activity and oxidative stress in both cardiac and skeletal muscle tissues, but that these effects are tissue-specific.

C1q/TNF-related Protein 4 Induces Signal Transducer and Activator of Transcription 3 Pathway and Modulates Food Intake

C1q/TNF-related protein 4 (CTRP4) has been reported to decrease food intake and regulate energy homeostasis. However, its underlying mechanism and signaling pathway remain unknown. Using an adenovirus-mediated hypothalamic CTRP4 overexpression model, we investigated the impact of CTRP4 on food intake and signal transducer and activator of transcription 3 (STAT3) signaling pathway in normal chow-fed mice. Expressions of neuropeptides including proopiomelanocortin (POMC) and neuropeptide Y (NPY) were studied in hypothalamus by Western blot and immunochemistry. STAT3 and suppressor of cytokine signaling 3 (SOCS3) were determined by Western blot. STAT3 signaling pathway was also investigated in Neuro 2A (N2a) cells after CTRP4 overexpression intervention. We found that food intake decreased significantly in mice under normal chow condition after CTRP4 overexpression. Both immunohistochemistry and Western blot demonstrated that POMC expression was significantly increased while NPY expression was significantly decreased. The changes of neuropeptides were accompanied by significant increased STAT3 phosphorylation and decreased SOCS3 levels. The same changes of neuropeptides and STAT3 signaling were also found in N2a cells after CTRP4 overexpression intervention. Collectively, our data reveals that CTRP4 induces the activation of STAT3 signaling and decreases food intake.

Pro-Inflammatory Markers Negatively Regulate IRS1 in Endometrial Cells and Endometrium from Women with Obesity and PCOS

A pro-inflammatory environment is characteristic of obesity and polycystic ovary syndrome (PCOS). This environment through cytokines secretion negatively affects insulin action. Endometria from women with both conditions (obesity and PCOS) present high TNF-α level and altered insulin signaling. In addition, these patients present reproductive failures that could be associated to an abnormal endometrial function. Here, TNF-α and IL-6 effects on insulin signaling pathway were evaluated. Serum and endometrial IL-6, phospho-IRS1-S270 (inactive form) and phospho-IRS1-Y612 (active form) levels were evaluated in women with: Normal-Weight, Obesity and Obesity-PCOS. In endometrial cells under hyperandrogenic/hyperinsulinic conditions resembling PCOS, it was evaluated IL-6/TNF-α effects on phospho-IRS1-S270, phospho-IRS1-Y612, phospho-AKT-S473 levels, and S6K and JNK activation (IRS1-inactivating molecules). In obesity groups, diminution of IRS1-active form was observed, being more significantly in Obesity-PCOS; whereas, IRS1-inactive form increased in Obesity-PCOS. Serum and endometrial IL-6 were higher in Obesity-groups compared to Normal-Weight. In endometrial cells, TNF-α increases phospho-IRS1-S270, while IL-6 decreases phospho-IRS1-Y612. Importantly, TNF-α and IL-6 promote S6K and JNK activation; TNF-α increases and IL-6 decreases phospho-AKT-S473 levels. Thus, pro-inflammatory cytokines in endometrium could negatively influence insulin signaling by different mechanisms: TNF-α promotes activation of IRS1-inactivating kinases, whereas, IL-6 decreases IRS1 and AKT activation. Moreover, when obesity and PCOS are present the disruption of insulin signaling is aggravated. These effects could explain endometrial abnormal function and reproductive failures observed in women with obesity and PCOS.

PM2.5 aggravates diabetes via the systemically activated IL-6-mediated STAT3/SOCS3 pathway in rats' liver

PM_2.5 exposure aggravates type 2 diabetes, in which inflammatory factors play an important role. In this study, we aimed to explore the mechanisms responsible for aggravating diabetes after PM_2.5 exposure, and study the roles of inflammatory factors in insulin-resistant type 2 diabetes. Our study indicated that short-time PM_2.5 exposure enhances insulin resistance in type 2 diabetic rats and significantly raises inflammatory factors, including IL-6, TNF-α, and MCP-1, in lungs. However, we found that of these inflammatory factors only IL-6 levels are elevated in blood, liver, adipose tissue, and macrophages, but not in skeletal muscle. IL-6 induced activation of the STAT3/SOCS3 pathway in liver, but not other downstream pathways including STAT1, ERK1/2, and PI3K. Both STAT3 inhibition and IL-6 neutralization effectively alleviated the disorders of glucose metabolism after PM_2.5 exposure. Taken together, this suggests that the systemic increase in IL-6 may play an important role in the deterioration of the type 2 diabetes via IL-6/STAT3/SOCS3 pathway in liver after short-time exposure to PM_2.5. Besides, we unexpectedly found a stronger resistance to the PM_2.5 exposure-induced increase in IL-6 in skeleton muscle than those of many other tissues.

Edematous severe acute malnutrition is characterized by hypomethylation of DNA

Edematous severe acute childhood malnutrition (edematous SAM or ESAM), which includes kwashiorkor, presents with more overt multi-organ dysfunction than non-edematous SAM (NESAM). Reduced concentrations and methyl-flux of methionine in 1-carbon metabolism have been reported in acute, but not recovered, ESAM, suggesting downstream DNA methylation changes could be relevant to differences in SAM pathogenesis. Here, we assess genome-wide DNA methylation in buccal cells of 309 SAM children using the 450 K microarray. Relative to NESAM, ESAM is characterized by multiple significantly hypomethylated loci, which is not observed among SAM-recovered adults. Gene expression and methylation show both positive and negative correlation, suggesting a complex transcriptional response to SAM. Hypomethylated loci link to disorders of nutrition and metabolism, including fatty liver and diabetes, and appear to be influenced by genetic variation. Our epigenetic findings provide a potential molecular link to reported aberrant 1-carbon metabolism in ESAM and support consideration of methyl-group supplementation in ESAM.

Epigenetic disturbances in obesity and diabetes: Epidemiological and functional insights

BACKGROUND

Obesity and type 2 diabetes (T2D) are major public health issues worldwide, and put a significant burden on the healthcare system. Genetic variants, along with traditional risk factors such as diet and physical activity, could account for up to approximately a quarter of disease risk. Epigenetic factors have demonstrated potential in accounting for additional phenotypic variation, along with providing insights into the causal relationship linking genetic variants to phenotypes.

SCOPE OF REVIEW

In this review article, we discuss the epidemiological and functional insights into epigenetic disturbances in obesity and diabetes, along with future research directions and approaches, with a focus on DNA methylation.

MAJOR CONCLUSIONS

Epigenetic mechanisms have been shown to contribute to obesity and T2D disease development, as well as potential differences in disease risks between ethnic populations. Technology to investigate epigenetic profiles in diseased individuals and tissues has advanced significantly in the last years, and suggests potential in application of epigenetic factors in clinical monitoring and as therapeutic options.

miRNA-Gene Regulatory Network in Gnotobiotic Mice Stimulated by Dysbiotic Gut Microbiota Transplanted From a Genetically Obese Child

Gut microbiota (GM) dysbiosis has been considered a pathogenic origin of many chronic diseases. In our previous trial, a shift in GM structure caused by a complex fiber-rich diet was associated with the health improvement of obese Prader-Willi syndrome (PWS) children. The pre- and post-intervention GMs (pre- and post-group, respectively) from one child were then transplanted into gnotobiotic mice, which resulted in significantly different physiological phenotypes, each of which was similar to the phenotype of the corresponding GM donor. This study was designed to investigate the miRNA-gene regulatory networks involved in causing these phenotypic differences. Using the post-group as a reference, we systematically identified and annotated the differentially expressed (DE) miRNAs and genes in the colon and liver of the pre-group in the second and fourth weeks after GM inoculation. Most of the significantly enriched GO terms and KEGG pathways were observed in the liver and were in the second week after GM transplantation. We screened 23 key genes along with their 73 miRNA regulators relevant to the host phenotype changes and constructed a network. The network contained 92 miRNA-gene regulation relationships, 51 of which were positive, and 41 of which were negative. Both the colon and liver had upregulated pro-inflammatory genes, and genes involved in fatty acid oxidation, lipolysis, and plasma cholesterol clearance were downregulated in only the liver. These changes were consistent with lipid and cholesterol accumulation in the host and with a high inflammation level. In addition, the colon showed an impacted glucagon-like peptide 1 (GLP-1) signaling pathway, while the liver displayed decreased insulin receptor signaling pathway activity. These molecular changes were mainly found in the second week, 2 weeks before changes in body fat occurred. This time lag indicated that GM dysbiosis might initially induce cholesterol and lipid metabolism-related miRNA and gene expression disorder and then lead to lipid accumulation and obesity development, which implicates a causative role of GM dysbiosis in obesity development rather than a result of obesity. This study provides fundamental molecular information that elucidates how dysbiotic GM increases host inflammation and disturbs host lipid and glucose metabolism.

MiR-17 and miR-19 cooperatively promote skeletal muscle cell differentiation

Skeletal myogenesis is a highly coordinated process that involves cell proliferation, differentiation and fusion controlled by a complex gene regulatory network. The microRNA gene cluster miR-17–92 has been shown to be related to this process; however, the exact role of each cluster member remains unclear. Here, we show that miR-17 and miR-20a could effectively promote the differentiation of both C2C12 myoblasts and primary bovine satellite cells. In contrast, miR-18a might play a negative role in C2C12 cell differentiation, while miR-19 and miR-92a had little influence. Transcriptome and target analyses revealed that miR-17 could act on Ccnd2, Jak1 and Rhoc genes that are critical for cell proliferation and/or fusion. Notably, the addition of miR-19 could reverse the lethal effect of miR-17 and could thus facilitate the maturation of myotubes. Furthermore, by co-injecting the lentiviral shRNAs of miR-17 and miR-19 into mouse tibialis anterior muscles, we demonstrated the wound healing abilities of the two miRNAs. Our findings indicate that in combination with miR-19, miR-17 is a potent inducer of skeletal muscle differentiation.

SOCS3 as a future target to treat metabolic disorders

The suppressors of cytokine signaling (SOCS) are a group of eight proteins responsible for preventing excessive cytokine signaling. Among this protein family, SOCS3 has received special attention. SOCS3 expression is important to control certain allergy autoimmune diseases. Furthermore, SOCS3 expression is elevated in obesity and it is involved in the inhibition of leptin and insulin signaling, two important hormones involved in the control of energy metabolism. Therefore, increased SOCS3 expression in obese individuals is associated with several metabolic disorders, including reduced energy expenditure, increased food intake and adiposity, and insulin and leptin resistance. In addition, recent studies found that SOCS3 expression regulates energy and glucose homeostasis in several metabolic conditions, such as pregnancy, caloric restriction, and refeeding. Importantly, attenuation of SOCS3 expression in most cases improves leptin and insulin sensitivity, leading to beneficial metabolic effects. This review aims to discuss the role of SOCS3 in the control of blood glucose levels as well as in energy homeostasis. The development of pharmacological compounds to inhibit SOCS3 activity and/or expression may represent a promising therapeutic approach to treat type 2 diabetes mellitus, obesity, and other metabolic imbalances.

Nonalcoholic fatty liver disease and nonalcoholic steatohepatitis in HIV infection: a metabolic approach of an infectious disease

With the successes of antiretroviral therapy, patients infected with human immunodeficiency virus (HIV) living longer. Regarding this, the common diseases of HIV population (i.e., opportunistic infections) are now losing ground in front of metabolic alterations. This phenomenon is related to the delay in progression to acquired immune deficiency syndrome (AIDS), making it so that patients live in a chronic inflammatory state which, combined with other mechanisms such infectious ones, cause metabolic diseases. Areas covered: Considering a high prevalence of metabolic alterations, the relationship between metabolic syndrome (MetS) with nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH), and liver diseases as a major cause of death in the HIV-infected population, this paper aims to overview the mechanisms and prevalence of NAFLD and NASH as they relate to the developed metabolic diseases of HIV patients. Expert opinion: The pathways underlying MetS include the effects of HIV and ART on the liver, adipose tissue, and muscle. These mechanisms result in liver damage, consequently leading to NAFLD and its more severe form NASH. These conditions have increased in HIV-infected population in recent years and since their life expectancy is improving it is important to be ready to attend their new emerging diseases.

Silencing of SAA1 inhibits palmitate- or high-fat diet induced insulin resistance through suppression of the NF-κB pathway

Background

Obesity is one of the leading causes of insulin resistance. Accumulating reports have highlighted that serum amyloid A-1 (SAA1) is a potential candidate that is capable of attenuating insulin resistance. Hence, we conducted the current study with aims of investigating our proposed hypothesis that silencing SAA1 could inhibit the progression of obesity-induced insulin resistance through the NF-κB pathway.

Methods

Gene expression microarray analysis was initially performed to screen differentially expressed genes (DEGs) associated with obesity. Palmitate (PA)-induced insulin resistance Huh7 cell models and high-fat diet (HFD)-induced mouse models were established to elucidate the effect of SAA1/Saa1 on insulin resistance. The NF-κB pathway-related expression was subsequently determined through the application of reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis.

Results

Saa1 was identified as an obesity-related gene based on the microarray data of GSE39549. Saa1 was determined to be highly expressed in HFD-induced insulin resistance mouse models. PA-induced Huh7 cells, treated with silenced SAA1 or NF-κB pathway inhibition using BAY 11–7082, displayed a marked decrease in both Saa1 and SOCS3 as well as an elevation in 2DG, IRS1 and the extent of IRS1 phosphorylation. HFD mice treated with silenced Saa1 or inhibited NF-κB pathway exhibited improved fasting blood glucose (FBG) levels as well as fasting plasma insulin (FPI) levels, glucose tolerance and systemic insulin sensitivity. Saa1/SAA1 was determined to show a stimulatory effect on the transport of the NF-κBp65 protein from the cytoplasm to the nucleus both in vivo and in vitro, suggesting that Saa1/SAA1 could activate the NF-κB pathway.

Conclusion

Taken together, our key findings highlight a novel mechanism by which silencing of SAA1 hinders PA or HFD-induced insulin resistance through inhibition of the NF-κB pathway.

Electronic supplementary material

The online version of this article (10.1186/s10020-019-0075-4) contains supplementary material, which is available to authorized users.

Ceramide and sphingosine 1-phosphate in adipose dysfunction

The increased adipose tissue mass of obese individuals enhances the risk of metabolic syndrome, type 2 diabetes and cardiovascular diseases. During pathological expansion of adipose tissue, multiple molecular controls of lipid storage, adipocyte turn-over and endocrine secretion are perturbed and abnormal lipid metabolism results in a distinct lipid profile. There is a role for ceramides and sphingosine 1-phosphate (S1P) in inducing adipose dysfunction. For instance, the alteration of ceramide biosynthesis, through the de-regulation of key enzymes, results in aberrant formation of ceramides (e.g. C_16:0 and C_18:0) which block insulin signaling and promote adipose inflammation. Furthermore, S1P can induce defective adipose tissue phenotypes by promoting chronic inflammation and inhibiting adipogenesis. These abnormal changes are discussed in the context of possible therapeutic approaches to re-establish normal adipose function and to, thereby, increase insulin sensitivity in type 2 diabetes. Such novel approaches include blockade of ceramide biosynthesis using inhibitors of sphingomyelinase or dihydroceramide desaturase and by antagonism of S1P receptors, such as S1P₂.

Anxa2 gene silencing attenuates obesity-induced insulin resistance by suppressing the NF-κB signaling pathway

Insulin resistance (IR) continues to pose a major threat to public health due to its role in the pathogenesis of metabolic syndrome and its ever-increasing prevalence on a global scale. The aim of the current study was to investigate the efficacy of Anxa2 in obesity-induced IR through the mediation of the NF-κB signaling pathway. Microarray analysis was performed to screen differentially expressed genes associated with obesity. To verify whether Anxa2 was differentially expressed in IR triggered by obesity, IR mouse models were established in connection with a high-fat diet (HFD). In the mouse IR model, the role of differentially expressed Anxa2 in glycometabolism and IR was subsequently detected. To investigate the effect of Anxa2 on IR and its correlation with inflammation, a palmitic acid (PA)-induced IR cell model was established, with the relationship between Anxa2 and the NF-κB signaling pathway investigated accordingly. Anxa2 was determined to be highly expressed in IR. Silencing Anxa2 was shown to inhibit IR triggered by obesity. When Anxa2 was knocked down, elevated expression of phosphorylated insulin receptor substrate 1 (IRS1), IRS1 and peroxisome proliferator-activated receptor coactivator-1a, and glucose tolerance and insulin sensitivity along with 2-deoxy-d-glucose uptake was detected, whereas decreased expression of suppressor of cytokine signaling 3, IL-6, IL-1β, TNF-α, and p50 was observed. Taken together, the current study ultimately demonstrated that Anxa2 may be a novel drug strategy for IR disruption, indicating that Anxa2 gene silencing is capable of alleviating PA or HFD-induced IR and inflammation through its negative regulatory role in the process of p50 nuclear translocation of the NF-κB signaling pathway.

Purple sweet potato color improves hippocampal insulin resistance via down-regulating SOCS3 and galectin-3 in high-fat diet mice

Hippocampal insulin resistance is the key factor in cognitive deficits. The obesity induces chronic inflammation and the inflammation molecules suppressors of cytokine signaling3 (SOCS3) and galectin-3 directly impair the insulin signaling. The anti-inflammation properties of purple sweet potato color (PSPC) prompted us to investigate the effect of PSPC on cognitive impairment associated with obesity. 60 C57BL/6 mice were randomly divided into four groups: normal, high fat diets (HFD), HFD+PSPC and PSPC. The mice were fed with the HFD or normal diet for 32 weeks. The PSPC (500 mg/kg/day) was administered via oral gavage from 21 to 32 weeks. The results showed the PSPC rectified the abnormal metabolism indexes induced by HFD, including ameliorated obesity, decreased the concentration of fasting blood glucose and improved the glucose tolerance. The Morris water maze test showed the PSPC alleviated the cognitive impairment in HFD mice. The PSPC decreased the expression of Iba1, tumor necrosis factor-α, interleukin-1β, SOCS3 and galectin-3 in hippocampus of HFD mice. The insulin signaling molecules including the p-IRS1 (Tyr608), PI3K p110α and p-AKT (Ser473) were detected and the PSPC treatment improved the insulin resistance in hippocampus of HFD mice. Furthermore, the PSPC increased Bcl-2, diminished the Bak and the cleaved-caspase3 in HFD mice hippocampus. These findings indicated that PSPC could be a potential treatment to improve the cognitive impairment associated with obesity.

miR-125a-5p ameliorates hepatic glycolipid metabolism disorder in type 2 diabetes mellitus through targeting of STAT3

Glycolipid metabolic disorder is an important cause for the development of type 2 diabetes mellitus (T2DM). Clarification of the molecular mechanism of metabolic disorder and exploration of drug targets are crucial for the treatment of T2DM.

Methods: We examined miR-125a-5p levels in palmitic acid-induced AML12 cells and the livers of type 2 diabetic rats and mice, and then validated its target gene. Through gain- and loss-of-function studies, the effects of miR-125a-5p via targeting of STAT3 on regulating glycolipid metabolism were further illustrated in vitro and in vivo.

Results: We found that miR-125a-5p was significantly decreased in the livers of diabetic mice and rats, and STAT3 was identified as the target gene of miR-125a-5p. Overexpression of miR-125a-5p in C57BL/6 mice decreased STAT3 level and downregulated the expression levels of p-STAT3 and SOCS3. Consequently, SREBP-1c-mediated lipogenesis pathway was inhibited, and PI3K/AKT pathway was activated. Moreover, silencing of miR-125a-5p significantly increased the expression levels of STAT3, p-STAT3 and SOCS3, thus activating SREBP-1c pathway and suppressing PI3K/AKT pathway. Therefore, hyperglycemia, hyperlipidemia and decreased liver glycogen appeared in C57BL/6 mice. In palmitic acid-induced AML12 cells, miR-125a-5p mimic markedly increased glucose consumption and uptake and decreased the accumulation of lipid droplets by regulating STAT3 signaling pathway. Consistently, miR-125a-5p overexpression obviously inhibited STAT3 expression in diabetic KK-Ay mice, thereby decreasing blood glucose and lipid levels, increasing hepatic glycogen content, and decreasing accumulation of hepatic lipid droplets in diabetic mice. Furthermore, inhibition of miR-125a-5p in KK-Ay mice aggravated glycolipid metabolism dysfunction through regulating STAT3.

Conclusions: Our results confirmed that miR-125a-5p should be considered as a regulator of glycolipid metabolism in T2DM, which can inhibit hepatic lipogenesis and gluconeogenesis and elevate glycogen synthesis by targeting STAT3.