Adipose glucocorticoid action influences whole-body metabolism via modulation of hepatic insulin action

Metabolic and microbial mechanisms related to the effects of dietary wheat levels on intramuscular fat content in finishing pigs

The current study aimed to investigate the metabolic and microbial mechanisms behind the effects of dietary wheat levels on intramuscular fat (IMF) content in the psoas major muscle (PM) of finishing pigs. Thirty-six barrows were arbitrarily assigned to two groups and fed with diets containing 25% or 55% wheat. Enhancing dietary wheat levels led to low energy states, resulting in reduced IMF content. This coincided with reduced serum glucose and low-density lipoprotein cholesterol levels. The AMP-activated protein kinase α2/sirtuin 1/peroxisome proliferator-activated receptor-γ coactivator 1α pathway may be activated by high-wheat diets, causing downregulation of adipogenesis and lipogenesis genes, and upregulation of lipolysis and gluconeogenesis genes. High-wheat diets decreased relative abundance of Lactobacillus and Coprococcus, whereas increased SMB53 proportion, subsequently decreasing colonic propionate content. Microbial glycolysis/gluconeogenesis, d-glutamine and D-glutamate metabolism, flagellar assembly, and caprolactam degradation were linked to IMF content. Metabolomic analysis indicated that enhancing dietary wheat levels promoted the protein digestion and absorption and affected amino acids and lipid metabolism. Enhancing dietary wheat levels reduced serum glucose and colonic propionate content, coupled with strengthened amino acid metabolism, contributing to the low energy states. Furthermore, alterations in microbial composition and propionate resulted from high-wheat diets were associated with primary bile acid biosynthesis, arachidonic acid metabolism, steroid hormone biosynthesis, and biosynthesis of unsaturated fatty acids, as well as IMF content. Colonic microbiota played a role in reducing IMF content through modulating the propionate-mediated peroxisome proliferators-activated receptor signaling pathway. In conclusion, body energy and gut microbiota balance collectively influenced lipid metabolism.

The Metabolic Syndrome, a Human Disease

This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.

Adipocyte Glucocorticoid Receptor Activation With High Glucocorticoid Doses Impairs Healthy Adipose Tissue Expansion by Repressing Angiogenesis

In humans, glucocorticoids (GCs) are commonly prescribed because of their anti-inflammatory and immunosuppressive properties. However, high doses of GCs often lead to side effects, including diabetes and lipodystrophy. We recently reported that adipocyte glucocorticoid receptor (GR)-deficient (AdipoGR-KO) mice under corticosterone (CORT) treatment exhibited a massive adipose tissue (AT) expansion associated with a paradoxical improvement of metabolic health compared with control mice. However, whether GR may control adipose development remains unclear. Here, we show a specific induction of hypoxia-inducible factor 1α (HIF-1α) and proangiogenic vascular endothelial growth factor A (VEGFA) expression in GR-deficient adipocytes of AdipoGR-KO mice compared with control mice, together with an increased adipose vascular network, as assessed by three-dimensional imaging. GR activation reduced HIF-1α recruitment to the Vegfa promoter resulting from Hif-1α downregulation at the transcriptional and posttranslational levels. Importantly, in CORT-treated AdipoGR-KO mice, the blockade of VEGFA by a soluble decoy receptor prevented AT expansion and the healthy metabolic phenotype. Finally, in subcutaneous AT from patients with Cushing syndrome, higher VEGFA expression was associated with a better metabolic profile. Collectively, these results highlight that adipocyte GR negatively controls AT expansion and metabolic health through the downregulation of the major angiogenic effector VEGFA and inhibition of vascular network development.

ARTICLE HIGHLIGHTS

A Mechanistic Review on Therapeutic Potential of Medicinal Plants and their Pharmacologically Active Molecules for Targeting Metabolic Syndrome

Metabolic syndrome (MetS) therapy with phytochemicals is an emerging field of study with therapeutic potential. Obesity, insulin resistance, high blood pressure, and abnormal lipid profiles are all components of metabolic syndrome, which is a major public health concern across the world. New research highlights the promise of phytochemicals found in foods, including fruits, vegetables, herbs, and spices, as a sustainable and innovative method of treating this illness. Anti-inflammatory, antioxidant, and insulin-sensitizing qualities are just a few of the many positive impacts shown by bioactive substances. Collectively, they alleviate the hallmark symptoms of metabolic syndrome by modulating critical metabolic pathways, boosting insulin sensitivity, decreasing oxidative stress, and calming chronic low-grade inflammation. In addition, phytochemicals provide a multimodal strategy by targeting not only adipose tissue but also the liver, skeletal muscle, and vascular endothelium, all of which have a role in the pathogenesis of MetS. Increasing evidence suggests that these natural chemicals may be useful in controlling metabolic syndrome as a complementary treatment to standard medication or lifestyle changes. This review article emphasizes the therapeutic potential of phytochemicals, illuminating their varied modes of action and their ability to alleviate the interconnected causes of metabolic syndrome. Phytochemical-based interventions show promise as a novel and sustainable approach to combating the rising global burden of metabolic syndrome, with the ultimate goal of bettering public health and quality of life.

Positive association of nap duration with risk of non-alcoholic fatty liver disease in an occupational population in Guangdong Province, China: a cross-sectional study

BACKGROUND

A lack of sleep or disorder in sleep-wake cycles has been associated with metabolic impairments. However, few studies have investigated the association between daytime napping duration and the risk of non-alcoholic fatty liver disease. This study aimed to investigate the association of daytime napping duration with the risk of non-alcoholic fatty liver disease in a Chinese population.

METHODS

This cross-sectional study analyzed data from the Health Management Center of Nanfang Hospital, Guangdong Province. A total of 3363 participants aged 20-79 years were recruited and admitted from January 20, 2018, to October 16, 2020. Non-alcoholic fatty liver disease was diagnosed using abdominal ultrasonography. The outcome was the association between daytime sleep duration and the risk of non-alcoholic fatty liver disease.

RESULTS

Compared with non-nappers, long daytime nappers (≥ 60 min) were associated with a higher risk of non-alcoholic fatty liver disease in the crude model (odds ratio 2.138; 95% confidence interval 1.88-2.61, P < 0.05) and in the multivariable adjustment model (odds ratio 2.211; 95% confidence interval 1.042-4.690, P < 0.05) after adjusting for demographic, educational, and metabolic risk factors. The association was moderately enhanced with additional adjustments for night sleep duration and socioeconomic or other factors (odds ratio 2.253; 95% confidence interval 1.061-4.786, P = 0.035).

CONCLUSION

In this cross-sectional study, daytime napping duration of ≥ 60 min was positively associated with the risk of non-alcoholic fatty liver disease in an occupational population of Guangdong Province after multivariable adjustment.

Thyroid-Stimulating Hormone Inhibits Insulin Receptor Substrate-1 Expression and Tyrosyl Phosphorylation in 3T3-L1 Adipocytes by Increasing NF-κB DNA-Binding Activity

Background. Abundant evidence indicates that thyroid-stimulating hormone (TSH) levels are associated with insulin resistance in adipocytes. However, the potential mechanism of the association remains uncertain. The objective of this study was to determine the potential role of TSH in the suppression of insulin receptor substrate-1 (IRS-1) expression and IRS-1 tyrosyl phosphorylation, which might contribute to insulin resistance. Methods. Mouse 3T3-L1 preadipocytes were differentiated into adipocytes. After treatment with 0.01, 0.1, and 1.0 mIU/ml bovine TSH, the TNF-α concentration in the medium was determined by enzyme-linked immunosorbent assay (ELISA). Nuclear factor-kappa B (NF-κB) DNA-binding activity was quantified by electrophoretic mobility shift assay (EMSA). IRS-1 levels in adipocytes were quantified by Western blotting, and tyrosine phosphorylation was measured by immunoprecipitation. Results. TSH induced TNF-α secretion in a dose-dependent manner. There was a significant positive correlation between NF-κB DNA-binding activity and TNF-α secretion. This effect and correlation were weakened by BAY 11-7082 (a nuclear NF-κB inhibitor) and H89 (an inhibitor of cyclic adenosine monophosphate- (cAMP-) dependent protein kinase A (PKA)). Treatment of cultured adipocytes with TSH inhibited insulin-stimulated IRS-1 tyrosyl phosphorylation but promoted TSH-dependent secretion of TNF-α and activation of NF-κB DNA-binding activity. The effects of TSH were significantly inhibited by BAY 11-7082 and H89 and were completely blocked by the TNF-α antagonist WP9QY. Conclusion. TSH inhibited IRS-1 protein expression and tyrosyl phosphorylation in 3T3-L1 adipocytes by stimulating TNF-α production via promotion of NF-κB DNA-binding activity. TSH might play a pivotal role in the development of insulin resistance.

The long winding road to the safer glucocorticoid receptor (GR) targeting therapies

Glucocorticoids (Gcs) are widely used to treat inflammatory diseases and hematological malignancies, and despite the introduction of novel anti-inflammatory and anti-cancer biologics, the use of inexpensive and effective Gcs is expected to grow. Unfortunately, chronic treatment with Gcs results in multiple atrophic and metabolic side effects. Thus, the search for safer glucocorticoid receptor (GR)-targeted therapies that preserve therapeutic potential of Gcs but result in fewer adverse effects remains highly relevant. Development of selective GR agonists/modulators (SEGRAM) with reduced side effects, based on the concept of dissociation of GR transactivation and transrepression functions, resulted in limited success, and currently focus has shifted towards partial GR agonists. Additional approach is the identification and inhibition of genes associated with Gcs specific side effects. Others and we recently identified GR target genes REDD1 and FKBP51 as key mediators of Gcs-induced atrophy, and selected and validated candidate molecules for REDD1 blockage including PI3K/Akt/mTOR inhibitors. In this review, we summarized classic and contemporary approaches to safer GR-mediated therapies including unique concept of Gcs combination with REDD1 inhibitors. We discussed protective effects of REDD1 inhibitors against Gcs–induced atrophy in skin and bone and underlined the translational potential of this combination for further development of safer and effective Gcs-based therapies.

The Role and Mechanism of Oxidative Stress and Nuclear Receptors in the Development of NAFLD

The overproduction of reactive oxygen species (ROS) and consequent oxidative stress contribute to the pathogenesis of acute and chronic liver diseases. It is now acknowledged that nonalcoholic fatty liver disease (NAFLD) is characterized as a redox-centered disease due to the role of ROS in hepatic metabolism. However, the underlying mechanisms accounting for these alternations are not completely understood. Several nuclear receptors (NRs) are dysregulated in NAFLD, and have a direct influence on the expression of a set of genes relating to the progress of hepatic lipid homeostasis and ROS generation. Meanwhile, the NRs act as redox sensors in response to metabolic stress. Therefore, targeting NRs may represent a promising strategy for improving oxidation damage and treating NAFLD. This review summarizes the link between impaired lipid metabolism and oxidative stress and highlights some NRs involved in regulating oxidant/antioxidant turnover in the context of NAFLD, shedding light on potential therapies based on NR-mediated modulation of ROS generation and lipid accumulation.

Comparative Analysis of Metabolite Profiling of Momordica charantia Leaf and the Anti-Obesity Effect through Regulating Lipid Metabolism

This study investigated the effects of Momordica charantia (M. charantia) extract in obesity and abnormal lipid metabolism in mice fed high fat diet (HFD). Fruit, root, stem, and leaf extracts of M. charantia were obtained using distilled water, 70% ethanol and 95% hexane. M. charantia leaf distilled water extract (MCLW) showed the highest antioxidant activity in both 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity tests and reducing power. Metabolite profiles of M. charantia leaf extracts were analyzed for identification of bioactive compounds. HFD-fed mice were treated with MCLW (oral dose of 200 mg/kg/d) for 4 weeks. MCLW reduced lipid accumulation, body weight, organ weight, and adipose tissue volume and significantly improved glucose tolerance and insulin resistance in HFD mice. Furthermore, MCLW administration reduced serum total cholesterol and low-density lipoprotein cholesterol, and increased serum high-density lipoprotein cholesterol compared with HFD mice. Moreover, MCLW significantly reduced the levels of serum urea nitrogen, alanine aminotransferase, alkaline phosphatase, and aspartate aminotransferase; alleviated liver and kidney injury. MCLW decreases expression of genes that fatty acid synthesis; increase the expression of catabolic-related genes. These results indicate that MCLW has an inhibitory effect on obese induced by high fat diet intake, and the mechanism may be related to the regulation of abnormal lipid metabolism in liver and adipose tissue, suggesting that MCLW may be a suitable candidate for the treatment of obesity.

Nuclear receptors and transcriptional regulation in non-alcoholic fatty liver disease

BACKGROUND

As a result of a sedentary lifestyle and excess food consumption in modern society, non-alcoholic fatty liver disease (NAFLD) characterized by fat accumulation in the liver is becoming a major disease burden. Non-alcoholic steatohepatitis (NASH) is an advanced form of NAFLD characterized by inflammation and fibrosis that can lead to hepatocellular carcinoma and liver failure. Nuclear receptors (NRs) are a family of ligand-regulated transcription factors that closely control multiple aspects of metabolism. Their transcriptional activity is modulated by various ligands, including hormones and lipids. NRs serve as potential pharmacological targets for NAFLD/NASH and other metabolic diseases.

SCOPE OF REVIEW

In this review, we provide a comprehensive overview of NRs that have been studied in the context of NAFLD/NASH with a focus on their transcriptional regulation, function in preclinical models, and studies of their clinical utility.

MAJOR CONCLUSIONS

The transcriptional regulation of NRs is context-dependent. During the dynamic progression of NAFLD/NASH, NRs play diverse roles in multiple organs and different cell types in the liver, which highlights the necessity of targeting NRs in a stage-specific and cell-type-specific manner to enhance the efficacy and safety of treatment methods.

Hepatic miR-192-3p reactivation alleviates steatosis by targeting glucocorticoid receptor

Background & Aims

The paradox of hepatic insulin resistance describes the inability for liver to respond to bioenergetics hormones in suppressing gluconeogenesis whilst maintaining lipid synthesis. Here, we report the deficiency of miR-192-3p in the livers of mice with diabetes and its role in alleviating hepatic steatosis.

Methods

As conventional pre-microRNA (miRNA) stem-loop overexpression only boosts guiding strand (i.e. miR-192-5p) expression, we adopted an artificial AAV(DJ)-directed, RNA Pol III promoter-driven miRNA hairpin construct for star-strand-specific overexpression in the liver. Liver steatosis and insulin resistance markers were evaluated in primary hepatocytes, mice with diabetes, and mice with excessive carbohydrate consumption.

Results

Functional loss of miR-192-3p in liver exacerbated hepatic micro-vesicular steatosis and insulin resistance in either mice with diabetes or wild-type mice with excessive fructose consumption. Liver-specific overexpression of miR-192-3p effectively halted hepatic steatosis and ameliorated insulin resistance in these mice models. Likewise, hepatocytes overexpressing miR-192-3p exhibited improved lipid accumulation, accompanied with decreases in lipogenesis and lipid-accumulation-related transcripts. Mechanistically, glucocorticoid receptor (GCR, also known as nuclear receptor subfamily 3, group C, member 1 [NR3C1]) was demonstrated to be negatively regulated by miR-192-3p. The effect of miR-192-3p on mitigating micro-vesicular steatosis was ablated by the reactivation of NR3C1.

Conclusions

The star strand miR-192-3p was an undermined glycerolipid regulator involved in controlling fat accumulation and insulin sensitivity in liver through blockade of hepatic GCR signalling; this miRNA may serve as a potential therapeutic option for the common co-mobility of diabetic mellitus and fatty liver disease.

Lay summary

The potential regulatory activity of star strand microRNA (miRNA) species has been substantially underestimated. In this study, we investigate the role and mechanism of an overlooked star strand miRNA (miR-192-3p) in regulating hepatic steatosis and insulin signalling in the livers of mice with diabetes and mice under excessive carbohydrate consumption.

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Liver-specific knockdown of miR-192-3p recapitulated functional loss of the miRNA as in mice with diabetes.

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This knockdown was characterised by pronounced hepatic micro-vesicular steatosis coupled to insulin resistance.

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In vivo overexpression of miR-192-3p alleviated hepatic steatosis in mice with diabetes and wild-type mice with excessive fructose consumption.

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Glucocorticoid receptor (also known as NR3C1) was discovered as the immediate target of miR-192-3p in regulating hepatic lipid turnover and storage.

The glucocorticoid receptor in brown adipocytes is dispensable for control of energy homeostasis

Aberrant activity of the glucocorticoid (GC)/glucocorticoid receptor (GR) endocrine system has been linked to obesity-related metabolic dysfunction. Traditionally, the GC/GR axis has been believed to play a crucial role in adipose tissue formation and function in both, white (WAT) and brown adipose tissue (BAT). While recent studies have challenged this notion for WAT, the contribution of GC/GR signaling to BAT-dependent energy homeostasis remained unknown. Here, we have generated and characterized a BAT-specific GR-knockout mouse (GR^BATKO ), for the first time allowing to genetically interrogate the metabolic impact of BAT-GR. The HPA axis in GR^BATKO mice was intact, as was the ability of mice to adapt to cold. BAT-GR was dispensable for the adaptation to fasting-feeding cycles and the development of diet-induced obesity. In obesity, glucose and lipid metabolism, insulin sensitivity, and food intake remained unchanged, aligning with the absence of changes in thermogenic gene expression. Together, we demonstrate that the GR in UCP1-positive BAT adipocytes plays a negligible role in systemic metabolism and BAT function, thereby opposing a long-standing paradigm in the field.