Selective insulin resistance with differential expressions of IRS-1 and IRS-2 in human NAFLD livers

A metabolic-dysfunction associated steatotic liver acinus biomimetic induces pancreatic islet dysfunction in a coupled microphysiology system

Preclinical and clinical studies suggest that lipid-induced hepatic insulin resistance is a primary defect that predisposes to dysfunction in pancreatic islets, implicating a perturbed liver-pancreas axis underlying the comorbidity of T2DM and MASLD. To investigate this hypothesis, we developed a human biomimetic microphysiological system (MPS) coupling our vascularized liver acinus MPS (vLAMPS) with primary islets on a chip (PANIS) enabling MASLD progression and islet dysfunction to be quantitatively assessed. The modular design of this system (vLAMPS-PANIS) allows intra-organ and inter-organ dysregulation to be deconvoluted. When compared to normal fasting (NF) conditions, under early metabolic syndrome (EMS) conditions, the standalone vLAMPS exhibited characteristics of early stage MASLD, while no significant differences were observed in the standalone PANIS. In contrast, with EMS, the coupled vLAMPS-PANIS exhibited a perturbed islet-specific secretome and a significantly dysregulated glucose stimulated insulin secretion (GSIS) response implicating direct signaling from the dysregulated liver acinus to the islets. Correlations between several pairs of a vLAMPS-derived and a PANIS-derived secreted factors were significantly altered under EMS, as compared to NF conditions, mechanistically connecting MASLD and T2DM associated hepatic factors with islet-derived GLP-1 synthesis and regulation. Since vLAMPS-PANIS is compatible with patient-specific iPSCs, this platform represents an important step towards addressing patient heterogeneity, identifying complex disease mechanisms, and advancing precision medicine.

Afriplex GRTTM extract attenuates hepatic steatosis in an in vitro model of NAFLD

BACKGROUND

Currently, it is acknowledged that vitamin E, insulin sensitizers and anti-diabetic drugs are used to manage non-alcoholic fatty liver disease (NAFLD), however, these therapeutic interventions harbour adverse side effects. Pioglitazone, an anti-diabetic drug, is currently the most effective therapy to manage NAFLD. The use of natural medicines is widely embraced due to the lack of evidence of their negative side effects. Rooibos has been previously shown to decrease inflammation and oxidative stress in experimental models of diabetes, however, this is yet to be explored in a setting of NAFLD. This study was aimed at investigating the effects of an aspalathin-rich green rooibos extract (Afriplex GRTTM) against markers of hepatic oxidative stress, inflammation and apoptosis in an in vitro model of NAFLD.

METHODS

Oleic acid [1 mM] was used to induce hepatic steatosis in C3A liver cells. Thereafter, the therapeutic effect of Afriplex GRTTM, with or without pioglitazone, was determined by assessing its impact on cell viability, changes in mitochondrial membrane potential, intracellular lipid accumulation and the expression of genes and proteins (ChREBP, SREBF1, FASN, IRS1, SOD2, Caspase-3, GSTZ1, IRS1 and TNF-α) that are associated with the development of NAFLD.

RESULTS

Key findings showed that Afriplex GRTTM added to the medium alone or combined with pioglitazone, could effectively block hepatic lipid accumulation without inducing cytotoxicity in C3A liver cells exposed oleic acid. This positive outcome was consistent with effective regulation of genes involved in insulin signaling, as well as carbohydrate and lipid metabolism (IRS1, SREBF1 and ChREBP). Interestingly, in addition to reducing protein levels of an inflammatory marker (TNF-α), the Afriplex GRTTM could ameliorate oleic acid-induced hepatic steatotic damage by decreasing the protein expression of oxidative stress and apoptosis related markers such as GSTZ1 and caspase-3.

CONCLUSION

Afriplex GRTTM reduced hepatic steatosis in oleic acid induced C3A liver cells by modulating SREBF1, ChREBP and IRS-1 gene expression. The extract may also play a role in alleviating inflammation by reducing TNF-α expression, suggesting that additional experiments are required for its development as a suitable therapeutic option against NAFLD. Importantly, further research is needed to explore its antioxidant role in this model.

The Effect and Mechanism of Oleanolic Acid in the Treatment of Metabolic Syndrome and Related Cardiovascular Diseases

Metabolic syndromes (MetS) and related cardiovascular diseases (CVDs) pose a serious threat to human health. MetS are metabolic disorders characterized by obesity, dyslipidemia, and hypertension, which increase the risk of CVDs' initiation and development. Although there are many availabile drugs for treating MetS and related CVDs, some side effects also occur. Considering the low-level side effects, many natural products have been tried to treat MetS and CVDs. A five-cyclic triterpenoid natural product, oleanolic acid (OA), has been reported to have many pharmacologic actions such as anti-hypertension, anti-hyperlipidemia, and liver protection. OA has specific advantages in the treatment of MetS and CVDs. OA achieves therapeutic effects through a variety of pathways, attracting great interest and playing a vital role in the treatment of MetS and CVDs. Consequently, in this article, we aim to review the pharmacological actions and potential mechanisms of OA in treating MetS and related CVDs.

A prognostic molecular signature of hepatic steatosis is spatially heterogeneous and dynamic in human liver

Metabolic dysfunction-associated steatotic liver disease (MASLD) prevalence is increasing in parallel with an obesity pandemic, calling for novel strategies for prevention and treatment. We defined a circulating proteome of human MASLD across ≈7000 proteins in ≈5000 individuals from diverse, at-risk populations across the metabolic health spectrum, demonstrating reproducible diagnostic performance and specifying both known and novel metabolic pathways relevant to MASLD (central carbon and amino acid metabolism, hepatocyte regeneration, inflammation, fibrosis, insulin sensitivity). A parsimonious proteomic signature of MASLD was associated with a protection from MASLD and its related multi-system metabolic consequences in >26000 free-living individuals, with an additive effect to polygenic risk. The MASLD proteome was encoded by genes that demonstrated transcriptional enrichment in liver, with spatial transcriptional activity in areas of steatosis in human liver biopsy and dynamicity for select targets in human liver across stages of steatosis. We replicated several top relations from proteomics and spatial tissue transcriptomics in a humanized "liver-on-a-chip" model of MASLD, highlighting the power of a full translational approach to discovery in MASLD. Collectively, these results underscore utility of blood-based proteomics as a dynamic "liquid biopsy" of human liver relevant to clinical biomarker and mechanistic applications.

Supplementation with the Probiotic Strains Bifidobacterium longum and Lactiplantibacillus rhamnosus Alleviates Glucose Intolerance by Restoring the IL-22 Response and Pancreatic Beta Cell Dysfunction in Type 2 Diabetic Mice

Type 2 diabetes (T2D) is known as adult-onset diabetes, but recently, T2D has increased in the number of younger people, becoming a major clinical burden in human society. The objective of this study was to determine the effects of Bifidobacterium and Lactiplantibacillus strains derived from the feces of 20 healthy humans on T2D development and to understand the mechanism underlying any positive effects of probiotics. We found that Bifidobacterium longum NBM7-1 (Chong Kun Dang strain 1; CKD1) and Lactiplantibacillus rhamnosus NBM17-4 (Chong Kun Dang strain 2; CKD2) isolated from the feces of healthy Korean adults (n = 20) have anti-diabetic effects based on the insulin sensitivity. During the oral gavage for 8 weeks, T2D mice were supplemented with anti-diabetic drugs (1.0-10 mg/kg body weight) to four positive and negative control groups or four probiotics (200 uL; 1 × 109 CFU/mL) to groups separately or combined to the four treatment groups (n = 6 per group). While acknowledging the relatively small sample size, this study provides valuable insights into the potential benefits of B. longum NBM7-1 and L. rhamnosus NBM17-4 in mitigating T2D development. The animal gene expression was assessed using a qRT-PCR, and metabolic parameters were assessed using an ELISA assay. We demonstrated that B. longum NBM7-1 in the CKD1 group and L. rhamnosus NBM17-4 in the CKD2 group alleviate T2D development through the upregulation of IL-22, which enhances insulin sensitivity and pancreatic functions while reducing liver steatosis. These findings suggest that B. longum NBM7-1 and L. rhamnosus NBM17-4 could be the candidate probiotics for the therapeutic treatments of T2D patients as well as the prevention of type 2 diabetes.

The effect of heat-killed Lactobacillus brevis SBL88 on improving selective hepatic insulin resistance in non-alcoholic fatty liver disease mice without altering the gut microbiota

BACKGROUND AND AIM

There have been several reports that some probiotics improve non-alcoholic fatty liver disease (NAFLD); however, many studies have involved cocktail therapies. We evaluated whether heat-killed Lactobacillus brevis SBL88 (L. brevis SBL88) monotherapy improves the clinical features of NAFLD.

METHODS

The NAFLD model was induced in mice fed a high-fat diet (HFD) (HFD mice) or HFD + 1% heat-killed L. brevis SBL88 (SBL mice) for 16 weeks. Histopathological liver findings were analyzed. To evaluate the gut microbiota, a modified terminal restriction fragment length polymorphism analysis of the feces was performed. RNA sequencing in the liver was performed with Ion Proton™. To investigate the direct effects of heat-killed L. brevis SBL88, an in vitro study was performed.

RESULTS

Histopathological findings revealed that fat droplets in the liver were significantly reduced in SBL mice; however, terminal restriction fragment length polymorphism did not show alterations in the gut microbiota between HFD mice and SBL mice. RNA sequencing and pathway analysis revealed that the regulation of lipid and insulin metabolism was affected. The mRNA expression of insulin receptor substrate 2 (IRS-2) was significantly higher in SBL mice, whereas the expression of IRS-1 was not significantly different. Phospho-IRS-2 expression was also significantly increased in SBL mice. In addition, an in vitro study revealed significant alterations in IRS-2 and forkhead box protein O1 expression levels.

CONCLUSION

SBL mice exhibited partially improved selective hepatic insulin resistance. Our data suggest that heat-killed L. brevis SBL88 could attenuate the clinical features of NAFLD that are not mediated by alterations in the gut microbiota.

Liver insulinization as a driver of triglyceride dysmetabolism

Metabolic dysfunction-associated fatty liver disease (MAFLD) is an increasingly prevalent fellow traveller with the insulin resistance that underlies type 2 diabetes mellitus. However, the mechanistic connection between MAFLD and impaired insulin action remains unclear. In this Perspective, we review data from humans to elucidate insulin's aetiological role in MAFLD. We focus particularly on the relative preservation of insulin's stimulation of triglyceride (TG) biosynthesis despite its waning ability to curb hepatic glucose production (HGP). To explain this apparent 'selective insulin resistance', we propose that hepatocellular processes that lead to TG accumulation require less insulin signal transduction, or 'insulinization,' than do those that regulate HGP. As such, mounting hyperinsulinaemia that barely compensates for aberrant HGP in insulin-resistant states more than suffices to maintain hepatic TG biosynthesis. Thus, even modestly elevated or context-inappropriate insulin levels, when sustained day and night within a heavily pro-lipogenic metabolic milieu, may translate into substantial cumulative TG biosynthesis in the insulin-resistant state.

Uncoupling hepatic insulin resistance - hepatic inflammation to improve insulin sensitivity and to prevent impaired metabolism-associated fatty liver disease in type 2 diabetes

Diabetes mellitus is a metabolic disease clinically-characterized as acute and chronic hyperglycemia. It is emerging as one of the common conditions associated with incident liver disease in the US. The mechanism by which diabetes drives liver disease has become an intense topic of discussion and a highly sought-after therapeutic target. Insulin resistance (IR) appears early in the progression of type 2 diabetes (T2D), particularly in obese individuals. One of the co-morbid conditions of obesity-associated diabetes that is on the rise globally is referred to as non-alcoholic fatty liver disease (NAFLD). IR is one of a number of known and suspected mechanism that underlie the progression of NAFLD which concurrently exhibits hepatic inflammation, particularly enriched in cells of the innate arm of the immune system. In this review we focus on the known mechanisms that are suspected to play a role in the cause-effect relationship between hepatic IR and hepatic inflammation and its role in the progression of T2D-associated NAFLD. Uncoupling hepatic IR/hepatic inflammation may break an intra-hepatic vicious cycle, facilitating the attenuation or prevention of NAFLD with a concurrent restoration of physiologic glycemic control. As part of this review, we therefore also assess the potential of a number of existing and emerging therapeutic interventions that can target both conditions simultaneously as treatment options to break this cycle.

Ameliorative effects of gallic acid on GLUT-4 expression and insulin resistance in high fat diet-induced obesity animal model mice, Mus musculus

Reduced activity of glucose transporter type 4 isoform (GLUT-4), an insulin-sensitive glucose transporter distributed on the adipocytes, is associated with impaired insulin signaling. Insulin resistance resulting from alteration in glucose transport is responsible for exacerbating the emergence of metabolic abnormalities. The present study aimed to investigate the effects of the antidote gallic acid (GA) on expression-related changes in GLUT-4 and insulin receptor substrate-1 (IRS-1) in the visceral adipose tissue and on the subsequent development of insulin resistance in a high-fat diet (HFD)-induced obesity animal model. Methods: Twenty-four female Swiss albino mice were used and separated into the following four groups (six animals in each group): control group (standard pellet diet), HFD group, (60% HFD), HFD + GA group (60% HFD and GA 50 mg/kg body weight for 60 days), and GA group (GA 50 mg/kg body weight for 60 days). The effect of HFD on serum glucose, total cholesterol, triglycerides, high-density lipoprotein cholesterol (HDL), low-density lipoprotein (LDL) cholesterol, and insulin was evaluated. Additionally, homeostasis model assessment for insulin resistance (HOMA-IR) and glucose tolerance test (GTT) was performed. The serum antioxidative profile, which comprises oxidative parameters (superoxide dismutase [SOD], catalase [CAT], and glutathione peroxidase [GPx]) was measured. The effectiveness of GA against HFD-induced alteration in GLUT-4 and IRS-1 expression was also evaluated. Results: The experimental group that fed on GA + HFD had improved levels of serum triglycerides (p˂0.001), cholesterol (p˂0.05), and LDL cholesterol. GA administration also significantly improved hyperinsulinemia and HOMA-IR index (p˂0.001) in HFD mice. GA improved GTT results (p˂0.05); activity of SOD, CAT, and GPx (p˂0.05); and upregulated mRNA expression of GLUT-4 and IRS-1(p˂0.05) in the visceral adipose tissue in the HFD + GA experimental group. Conclusion: A link exists between insulin resistance, GLUT-4, and IRS-1 expression in the adipose tissue, and the initiation of metabolic syndrome, a condition characterized by obesity. GA may promote insulin signaling, glucose uptake, and lipid metabolism in the adipose tissues by mitigating oxidative stress. GA can also be used to manage obesity-related comorbidities including type 2 diabetes and dyslipidemia.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01194-5.

Dysregulation of Lipid and Glucose Metabolism in Nonalcoholic Fatty Liver Disease

Non-Alcoholic Fatty Liver Disease (NAFLD) is a highly prevalent condition affecting approximately a quarter of the global population. It is associated with increased morbidity, mortality, economic burden, and healthcare costs. The disease is characterized by the accumulation of lipids in the liver, known as steatosis, which can progress to more severe stages such as steatohepatitis, fibrosis, cirrhosis, and even hepatocellular carcinoma (HCC). This review focuses on the mechanisms that contribute to the development of diet-induced steatosis in an insulin-resistant liver. Specifically, it discusses the existing literature on carbon flux through glycolysis, ketogenesis, TCA (Tricarboxylic Acid Cycle), and fatty acid synthesis pathways in NAFLD, as well as the altered canonical insulin signaling and genetic predispositions that lead to the accumulation of diet-induced hepatic fat. Finally, the review discusses the current therapeutic efforts that aim to ameliorate various pathologies associated with NAFLD.

Transcriptome Sequencing Reveals Autophagy Networks in Rat Livers during the Development of NAFLD and Identifies Autophagy Hub Genes

(1) Autophagy is an important biological process in cells and is closely associated with the development and progression of non-alcoholic fatty liver disease (NAFLD). Therefore, this study aims to investigate the biological function of the autophagy hub genes, which could be used as a potential therapeutic target and diagnostic markers for NAFLD. (2) Male C57BL/6J mice were sacrificed after 16 and 38 weeks of a high-fat diet, serum biochemical indexes were detected, and liver lobules were collected for pathological observation and transcriptome sequencing. The R software was used to identify differentially expressed autophagy genes (DEGs) from the transcriptome sequencing data of mice fed with a normal diet for 38 weeks (ND38) and a high-fat diet for 38 weeks (HFD38). Gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed on the DEGs, a protein-protein interaction (PPI) network of the DEGs was established using the STRING data website, and the results were visualized through Cytoscape. (3) After 16 weeks and 38 weeks of a high-fat diet, there was a significant increase in body weight, serum total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C) and triglycerides (TG) in mice, along with lipid accumulation in the liver, which was more severe at 38 weeks than at 16 weeks. The transcriptome data showed significant changes in the expression profile of autophagy genes in the livers of NAFLD mice following a long-term high-fat diet. Among the 31 differentially expressed autophagy-related genes, 13 were upregulated and 18 were downregulated. GO and KEGG pathway analysis revealed that these DEGs were primarily involved in autophagy, cholesterol transport, triglyceride metabolism, apoptosis, the FoxO signaling pathway, the p53 signaling pathway and the IL-17 signaling pathway. Four hub genes were identified by the PPI network analysis, of which Irs2, Pnpla2 and Plin2 were significantly downregulated, while Srebf2 was significantly upregulated by the 38-week high-fat diet. (4) The hub genes Irs2, Pnpla2, Srebf2 and Plin2 may serve as key therapeutic targets and early diagnostic markers in the progression of NAFLD.

RNA-binding proteins in metabolic-associated fatty liver disease (MAFLD): From mechanism to therapy

Metabolic-associated fatty liver disease (MAFLD) is the most common chronic liver disease globally and seriously increases the public health burden, affecting approximately one quarter of the world population. Recently, RNA binding proteins (RBPs)-related pathogenesis of MAFLD has received increasing attention. RBPs, vividly called the gate keepers of MAFLD, play an important role in the development of MAFLD through transcription regulation, alternative splicing, alternative polyadenylation, stability and subcellular localization. In this review, we describe the mechanisms of different RBPs in the occurrence and development of MAFLD, as well as list some drugs that can improve MAFLD by targeting RBPs. Considering the important role of RBPs in the development of MAFLD, elucidating the RNA regulatory networks involved in RBPs will facilitate the design of new drugs and biomarkers discovery.

Excessive gluconeogenesis causes the hepatic insulin resistance paradox and its sequelae

Background

Hepatic insulin signaling suppresses gluconeogenesis but promotes de novo lipid synthesis. Paradoxically, hepatic insulin resistance (HIR) enhances both gluconeogenesis and de novo lipid synthesis. Elucidation of the etiology of this paradox, which participates in the pathogenesis of non-alcoholic fatty liver disease (NAFLD), cardiovascular disease, the metabolic syndrome and hepatocellular carcinoma, has not been fully achieved.

Scope of review

This article briefly outlines the previously proposed hypotheses on the etiology of the HIR paradox. It then discusses literature consistent with an alternative hypothesis that excessive gluconeogenesis, the direct effect of HIR, is responsible for the aberrant lipogenesis. The mechanisms involved therein are explained, involving de novo synthesis of fructose and uric acid, promotion of glutamine anaplerosis, and induction of glucagon resistance. Thus, gluconeogenesis via lipogenesis promotes hepatic steatosis, a component of NAFLD, and dyslipidemia. Gluconeogenesis-centred mechanisms for the progression of NAFLD from simple steatosis to non-alcoholic steatohepatitis (NASH) and fibrosis are suggested. That NAFLD often precedes and predicts type 2 diabetes is explained by the ability of lipogenesis to cushion against blood glucose dysregulation in the earlier stages of NAFLD.

Major conclusions

HIR-induced excessive gluconeogenesis is a major cause of the HIR paradox and its sequelae. Such involvement of gluconeogenesis in lipid synthesis rationalizes the fact that several types of antidiabetic drugs ameliorate NAFLD. Thus, dietary, lifestyle and pharmacological targeting of HIR and hepatic gluconeogenesis may be a most viable approach for the prevention and management of the HIR-associated network of diseases.

Dietary iron overload enhances Western diet induced hepatic inflammation and alters lipid metabolism in rats sharing similarity with human DIOS

Hepatic iron overload is often concurrent with nonalcoholic fatty liver disease (NAFLD). Dysmetabolic iron overload syndrome (DIOS) is characterized by an increase in the liver and body iron stores and metabolic syndrome components. Increasing evidences suggest an overlap between NAFLD with iron overload and DIOS; however, the mechanism how iron is involved in their pathogenesis remains unclear. Here we investigated the role of iron in the pathology of a rat model of NAFLD with iron overload. Rats fed a Western (high-fat and high-fructose) diet for 26 weeks represented hepatic steatosis with an increased body weight and dyslipidemia. Addition of dietary iron overload to the Western diet feeding further increased serum triglyceride and cholesterol, and enhanced hepatic inflammation; the affected liver had intense iron deposition in the sinusoidal macrophages/Kupffer cells, associated with nuclear translocation of NFκB and upregulation of Th1/M1-related cytokines. The present model would be useful to investigate the mechanism underlying the development and progression of NAFLD as well as DIOS, and to elucidate an important role of iron as one of the "multiple hits" factors.

Co-Adjuvancy of Solasodine & CoQ10 Against High Fat Diet-Induced Insulin Resistance Rats Via Modulating IRS-I and PPAR-γ Proteins Expression

Insulin resistance (IR) is a condition in which target cells become insensitive to normal insulin concentrations in order to deliver glucose. The goal of this study was to see if solasodine combined with coenzyme Q10 could help rats with insulin resistance caused by a high-fat diet (HFD) by regulating the expression of IRS-I and PPAR-γ proteins.One of the six groups (n=6) got a conventional diet for 16 weeks as a control (normal), the HFD was given to the other five groups for 16 weeks, which further classified as-one group as HFD control while others treated with pioglitazone (10 mg/kg), coenzyme Q10 (50 mg/kg), solasodine (50 mg/kg) and combination of solasodine and coenzyme Q10i.e. SDQ10 (total 50 mg/kg) for the last 4 weeks orally once daily. Blood and tissue samples were collected by the end of study period for the biochemical and histological studies. As a result, HFD fed rats exhibited a significant increase in food and energy intake, body mass index, kidney and pancreas weight, fasting glucose, glycosylated haemoglobin, insulin level, liver enzyme ALT and AST and decrease antioxidant activity of superoxide dismutase and catalase. HFD received animals also produced a lower level of p-IRS1 and PPAR-y protein expression in western blot analysis. SDQ10 in combination successfully restored the above-mentioned complexity of insulin resistance caused by aHFD. Besides, increasesthe antioxidant activity of superoxide dismutase and catalase and normalized the architecture of kidney, pancreas and adipose tissue as well astreatment with SDQ10 raised the level of p-IRS1 and PPAR-y protein in liver tissue. As a result, supplementing with solasodine and coenzyme Q10 reversed the effect of the HFD on p-IRS1 and PPAR-y protein in liver tissue while also alleviating insulin resistance symptoms.

Dengue virus is involved in insulin resistance via the downregulation of IRS-1 by inducing TNF-α secretion

During the epidemic, the individuals with underlying diseases usually have a higher rate of mortality. Diabetes is highly prevalent worldwide, making it a frequent comorbidity in dengue fever patients. Therefore, understanding the relationship between dengue virus (DENV) infection and diabetes is important. We first demonstrated that DENV-3 infection down-regulated the expression of IRS-1. In vitro, treatment of HepG2 cells with TNF-α inhibitors and siRNA proved that after DENV-3 infection in HepG2 cells, cellular TNF-α secretion was increased, which negatively regulated IRS-1, thereby leading to an insulin-resistant state. In vivo, DENV-3 induced insulin resistance (IR) in hepatocytes by promoting the secretion of TNF-α and inhibiting the expression of IRS-1 was proved. In vivo approaches also showed that after DENV-3 infection, TNF-α levels in the serum of C57BL/6 mice with insulin resistance increased, and upon TNF-α antagonist III treatment, IRS-1 expression in the liver, reduced by infection, was upregulated. In addition, transcriptomic analysis revealed more negative regulatory events in the insulin receptor signaling pathway after DENV-3 infection. This is the first report of a link between DENV-3 infection and insulin resistance, and it lays a foundation for further research.

Dysregulation of hepatic metabolism with obesity: factors influencing glucose and lipid metabolism

The liver is a key metabolic organ that undertakes a multitude of physiological processes over the course of a day, including intrahepatic lipid and glucose metabolism which plays a key role in the regulation of systemic lipid and glucose concentrations. It serves as an intermediary organ between exogenous (dietary) and endogenous energy supply to extrahepatic organs. Thus, perturbations in hepatic metabolism can impact widely on metabolic disease risk. For example, the accumulation of intra-hepatocellular TAG (IHTG), for which adiposity is almost invariably a causative factor may result in dysregulation of metabolic pathways. Accumulation of IHTG is likely due to an imbalance between fatty acid delivery, synthesis and removal (via oxidation or export as TAG) from the liver; insulin plays a key role in all of these processes.

Potential role of microRNAs in selective hepatic insulin resistance: From paradox to the paradigm

The paradoxical action of insulin on hepatic glucose metabolism and lipid metabolism in the insulin-resistant state has been of much research interest in recent years. Generally, insulin resistance would promote hepatic gluconeogenesis and demote hepatic de novo lipogenesis. The underlying major drivers of these mechanisms were insulin-dependent, via FOXO-1-mediated gluconeogenesis and SREBP1c-mediated lipogenesis. However, insulin-resistant mouse models have shown high glucose levels as well as excess lipid accumulation. As suggested, the inert insulin resistance causes the activation of the FOXO-1 pathway promoting gluconeogenesis. However, it does not affect the SREBP1c pathway; therefore, cells continue de novo lipogenesis. Many hypotheses were suggested for this paradoxical action occurring in insulin-resistant rodent models. A "downstream branch point" in the insulin-mediated pathway was suggested to act differentially on the FOXO-1 and SREBP1c pathways. MicroRNAs have been widely studied for their action of pathway mediation via suppressing the intermediate protein expressions. Many in vitro studies have postulated the roles of hepato-specific expressions of miRNAs on insulin cascade. Thus, miRNA would play a pivotal role in selective hepatic insulin resistance. As observed, there were confirmations and contradictions between the outcomes of gene knockout studies conducted on selective hepatic insulin resistance and hepato-specific miRNA expression studies. Furthermore, these studies had evaluated only the effect of miRNAs on glucose metabolism and few on hepatic de novo lipogenesis, limiting the ability to conclude their role in selective hepatic insulin resistance. Future studies conducted on the role of miRNAs on selective hepatic insulin resistance warrant the understanding of this paradoxical action of insulin.

A Novel PTP1B Inhibitor-Phosphate of Polymannuronic Acid Ameliorates Insulin Resistance by Regulating IRS-1/Akt Signaling

Protein tyrosine phosphatase 1B (PTP1B) is a critical negative modulator of insulin signaling and has attracted considerable attention in treating type 2 diabetes mellitus (T2DM). Low-molecular-weight polymannuronic acid phosphate (LPMP) was found to be a selective PTP1B inhibitor with an IC₅₀ of 1.02 ± 0.17 μM. Cellular glucose consumption was significantly elevated in insulin-resistant HepG2 cells after LPMP treatment. LPMP could alleviate oxidative stress and endoplasmic reticulum stress, which are associated with the development of insulin resistance. Western blot and polymerase chain reaction (PCR) analysis demonstrated that LPMP could enhance insulin sensitivity through the PTP1B/IRS/Akt transduction pathway. Furthermore, animal study confirmed that LPMP could decrease blood glucose, alleviate insulin resistance, and exert hepatoprotective effects in diabetic mice. Taken together, LPMP can effectively inhibit insulin resistance and has high potential as an anti-diabetic drug candidate to be further developed.

Circular RNAs; powerful microRNA sponges to overcome diabetic nephropathy

Diabetic nephropathy (DN), also known as diabetic kidney disease (DKD), is a drastic renal complication of type 1 and type 2 diabetes mellitus (DM). Poorly controlled DM over the years, may disrupt kidneys' blood vessels, leading to the hypertension (HTN) and DN onset. During DN, kidneys' waste filtering ability becomes disturbed. Being on a healthy lifestyle and controlling both DM and HTN are now the best proceedings to prevent or at least delay DN occurrence. Unfortunately, about one-fourth of diabetic individuals eventually experience the corresponding renal failure, and thus it is critical to discover effective diagnostic biomarkers and therapeutic strategies to combat DN. In the past few years, circular RNAs (circRNAs), as covalently closed endogenous non-coding RNAs (ncRNAs), are believed to affect DN pathogenesis in a positive manner. CircRNAs are able to impact different cellular processes and signaling pathways by targeting biological molecules or various molecular mechanisms. Still, as a key regulatory axis, circRNAs can select miRNAs as their molecular targets, in which they are considered as miRNA sponges. In this way, circRNA-induced suppression of particular miRNAs may prevent from DN progression or promotes the DN elimination. Since the expression of circRNAs has also been reported to be increased in DN-associated cells and tissues, they can be employed as either diagnostic biomarkers or therapeutic targets.

Circular RNAs in metabolism and metabolic disorders

Metabolic syndrome (MetS) is a serious health condition triggered by hyperglycemia, dyslipidemia, and abnormal adipose deposition. Recently, circular RNAs (circRNAs) have been proposed as key molecular players in metabolic homeostasis due to their regulatory effects on genes linked to the modulation of multiple aspects of metabolism, including glucose and lipid homeostasis. Dysregulation of circRNAs can lead to metabolic disorders, indicating that circRNAs represent plausible potential targets to alleviate metabolic abnormalities. More recently, a series of circulating circRNAs have been identified to act as both essential regulatory molecules and biomarkers for the progression of metabolism-related disorders, including type 2 diabetes mellitus (T2DM or T2D) and cardiovascular disease (CVD). The findings of this study highlight the function of circRNAs in signaling pathways implicated in metabolic diseases and their potential as future therapeutics and disease biomarkers.

HepaRG Maturation in Silk Fibroin Scaffolds: Toward Developing a 3D In Vitro Liver Model

In vitro liver models are necessary tools for the development of new therapeutics. HepaRG cells are a commonly used cell line to produce hepatic progenitor cells and hepatocytes. This study demonstrates for the first time the suitability of 3% silk scaffolds to support HepaRG growth and differentiation. The modulus and pore size of 3% silk scaffolds were shown to be within the desired range for liver cell growth. The optimal seeding density for HepaRG cells on silk scaffolds was determined. The growth and maturation of scaffolded HepaRG cells was evaluated for 28 days, where the first 14 days of culture were a proliferation period and the last 14 days of culture were a differentiation period using dimethyl sulfoxide (DMSO) treatment. After the first 14 days of culture, the scaffolded HepaRG cells exhibited increased metabolic activity and albumin secretion compared to monolayer cultured controls and preserved these attributes through the duration of culture. Additionally, after the first 14 days of culture, the scaffolded HepaRG cells displayed a significantly reduced expression of genes associated with hepatocyte maturation. This difference in expression was no longer apparent after 28 days of culture, suggesting that the cells underwent rapid differentiation within the scaffold. The functionalization of silk scaffolds with extracellular matrix (ECM) components (type I collagen and/or an arginylglycylaspartic acid (RGD)-containing peptide) was investigated to determine the impact on HepaRG cell attachment and maturation. The inclusion of ECM components had no noticeable impact on cell attachment but did significantly influence CYP3A4 expression and albumin secretion. Finally, the matrix support provided by the 3% silk scaffolds could prime the HepaRG cells for steatosis liver model applications, as evidenced by lipid droplet accumulation and expression of steatosis-related genes after 24 h of exposure to oleic acid. Overall, our work demonstrates the utility of silk scaffolds in providing a modifiable platform for liver cell growth.

The Immunomodulating Effect of Baicalin on Inflammation and Insulin Resistance in High-Fat-Diet-Induced Obese Mice

Background

Obesity is a chronic low-grade systemic inflammation state, which causes insulin resistance, diabetes, and other metabolic diseases. Baicalin is known to have anti-inflammatory and antiobesity effects. In this study, we investigated the cellular and molecular immunological effects of baicalin on obesity-induced inflammation.

Methods

Male C57BL/6 mice were assigned to four groups: the normal chow, high-fat diet (HFD), BC2 (HFD + baicalin 200 mg/kg), and BC4 (HFD + baicalin 400 mg/kg) group; the three groups except normal chow were fed with a high-fat diet for 8 weeks to induce obesity followed by baicalin treatment with two doses for 8 weeks. The body weight, epididymal fat weight, liver weight, food intake, oral glucose tolerance test (OGTT), oral fat tolerance test (OFTT), and serum lipids were measured. We evaluated insulin resistance by measuring the serum insulin level and homeostatic model assessment of insulin resistance (HOMA-IR). Also, the major obesity-associated immune cells including monocytes, macrophages, T lymphocytes, and dendritic cells in the blood, fat, and liver and the inflammatory and insulin signaling-related gene expressions in the fat and liver were evaluated.

Results

Baicalin significantly reduced the body weight and liver weight and improved serum fasting glucose, insulin, HOMA-IR, free fatty acid, HDL cholesterol, and the levels of glucose and triglyceride at each time point in the OGTT and OFTT. In the analysis of immune cells, baicalin significantly decreased inflammatory Ly6C^hi monocytes, M1 adipose tissue macrophages (ATMs), and M1 Kupffer cells. On the contrary, baicalin increased anti-inflammatory M2 ATMs and liver CD4+ T cells and CD4/CD8 ratio. In the analysis of inflammatory and insulin signaling molecules, baicalin significantly downregulated the gene expression of tumor necrosis factor-α, F4/80, and C-C motif chemokine 2 while upregulated the insulin receptor mRNA expression.

Conclusion

From these results, baicalin can be a promising treatment option for obesity and its related metabolic diseases based on its anti-inflammatory property.

Evaluating causality of cellular senescence in non-alcoholic fatty liver disease

Cellular senescence is a state of irreversible cell cycle arrest that has important physiological functions. However, cellular senescence is also a hallmark of ageing and has been associated with several pathological conditions. A wide range of factors including genotoxic stress, mitogens and inflammatory cytokines can induce senescence. Phenotypically, senescent cells are characterised by short telomeres, an enlarged nuclear area and damaged genomic and mitochondrial DNA. Secretion of proinflammatory proteins, also known as the senescence-associated secretory phenotype, is a characteristic of senescent cells that is thought to be the main contributor to their disease-inducing properties. In the past decade, the role of cellular senescence in the development of non-alcoholic fatty liver disease (NAFLD) and its progression towards non-alcoholic steatohepatitis (NASH) has garnered significant interest. Until recently, it was suggested that hepatocyte cellular senescence is a mere consequence of the metabolic dysregulation and inflammatory phenomena in fatty liver disease. However, recent work in rodents has suggested that senescence may be a causal factor in NAFLD development. Although causality is yet to be established in humans, current evidence suggests that targeting senescent cells has therapeutic potential for NAFLD. We aim to provide insights into the quality of the evidence supporting a causal role of cellular senescence in the development of NAFLD in rodents and humans. We will elaborate on key cellular and molecular features of senescence and discuss the efficacy and safety of novel senolytic drugs for the treatment or prevention of NAFLD.

Role of Insulin Resistance in MAFLD

Many studies have reported that metabolic dysfunction is closely involved in the complex mechanism underlying the development of non-alcoholic fatty liver disease (NAFLD), which has prompted a movement to consider renaming NAFLD as metabolic dysfunction-associated fatty liver disease (MAFLD). Metabolic dysfunction in this context encompasses obesity, type 2 diabetes mellitus, hypertension, dyslipidemia, and metabolic syndrome, with insulin resistance as the common underlying pathophysiology. Imbalance between energy intake and expenditure results in insulin resistance in various tissues and alteration of the gut microbiota, resulting in fat accumulation in the liver. The role of genetics has also been revealed in hepatic fat accumulation and fibrosis. In the process of fat accumulation in the liver, intracellular damage as well as hepatic insulin resistance further potentiates inflammation, fibrosis, and carcinogenesis. Increased lipogenic substrate supply from other tissues, hepatic zonation of Irs1, and other factors, including ER stress, play crucial roles in increased hepatic de novo lipogenesis in MAFLD with hepatic insulin resistance. Herein, we provide an overview of the factors contributing to and the role of systemic and local insulin resistance in the development and progression of MAFLD.

Purple grumixama anthocyanins (Eugenia brasiliensis Lam.) attenuate obesity and insulin resistance in high-fat diet mice

Some polyphenols have been reported to modulate the expression of several genes related to lipid metabolism and insulin signaling, ameliorating metabolic disorders. We investigated the potential for the polyphenols of two varieties of grumixama, the purple fruit rich in anthocyanins and the yellow fruit, both also rich in ellagitannins, to attenuate obesity-associated metabolic disorders. Mice were fed a high fat and high sucrose diet, supplemented daily with yellow and purple extracts (200 mg per kg of body weight) for eight weeks. Purple grumixama supplementation was found to decrease body weight gain, improve insulin sensitivity and glucose-induced hyperinsulinemia, and reduce hepatic triglyceride accumulation. A decrease in intrahepatic lipids in mice treated with the purple grumixama extract was associated with lipid metabolism modulation by the PPAR signaling pathway. LPL, ApoE, and LDLr were found to be down-regulated, while Acox1 and ApoB were found to be upregulated. Some of these genes were also modulated by the yellow extract. In addition, both extracts decreased oGTT and plasma LPS. The results were associated with the presence of phenolic acids and urolithins. In conclusion, most likely the anthocyanins from the purple grumixama phenolic extract is responsible for reducing obesity and insulin resistance.

Fortifying Butterfat with Soybean Oil Attenuates the Onset of Diet-Induced Non-Alcoholic Steatohepatitis and Glucose Intolerance

The addition of plant oils such as soybean oil (S) to a diet rich in saturated fatty acids is discussed as a possible route to prevent or diminish the development of metabolic disease. Here, we assessed whether a butterfat-rich diet fortified with S affects the development of early non-alcoholic steatohepatitis (NASH) and glucose intolerance. Female C57BL/6J mice were fed a standard-control diet (C); a fat-, fructose-, and cholesterol-rich diet (FFC, 25E% butterfat, 50% (wt./wt.) fructose, 0.16% (wt./wt.) cholesterol); or FFC supplemented with S (FFC + S, 21E% butterfat + 4E% S) for 13 weeks. Indicators of liver damage, inflammation, intestinal barrier function, and glucose metabolism were measured. Lipopolysaccharide (LPS)-challenged J774A.1 cells were incubated with linolenic and linoleic acids (ratio 1:7.1, equivalent to S). The development of early NASH and glucose intolerance was significantly attenuated in FFC + S–fed mice compared to FFC-fed mice associated with lower hepatic toll-like receptor-4 mRNA expression, while markers of intestinal barrier function were significantly higher than in C-fed mice. Linolenic and linoleic acid significantly attenuated LPS-induced formation of reactive nitrogen species and interleukin-1 beta mRNA expression in J774A.1 cells. Our results indicate that fortifying butterfat with S may attenuate the development of NASH and glucose intolerance in mice.

High Prevalence of Insulin Resistance in Asymptomatic Patients with Acute Intermittent Porphyria and Liver-Targeted Insulin as a Novel Therapeutic Approach

Acute porphyria attacks are associated with the strong up-regulation of hepatic heme synthesis and over-production of neurotoxic heme precursors. First-line therapy is based on carbohydrate loading. However, altered glucose homeostasis could affect its efficacy. Our first aim was to investigate the prevalence of insulin resistance (IR) in an observational case-control study including 44 Spanish patients with acute intermittent porphyria (AIP) and 55 age-, gender- and BMI-matched control volunteers. Eight patients (18.2%) and one control (2.3%, p = 0.01) showed a high HOMA-IR index (cut-off ≥ 3.4). Patients with IR and hyperinsulinemia showed clinically stable disease. Thus, the second aim was to evaluate the effect of the co-administration of glucose and a fast-acting or new liver-targeted insulin (the fusion protein of insulin and apolipoprotein A-I, Ins-ApoAI) in AIP mice. The combination of glucose and the Ins-ApoAI promoted partial but sustained protection against hepatic heme synthesis up-regulation compared with glucose alone or co-injected with fast-acting insulin. In a prevention study, Ins-ApoAI improved symptoms associated with a phenobarbital-induced attack but maintained high porphyrin precursor excretion, probably due to the induction of hepatic mitochondrial biogenesis mediated by apolipoprotein A-I. In conclusion, a high prevalence of IR and hyperinsulinemia was observed in patients with AIP. The experimental data provide proof-of-concept for liver-targeted insulin as a way of enhancing glucose therapy for AIP.

RELATIONSHIP BETWEEN LIVING HABITS AND METABOLIC DISEASES IN COMMUNITY POPULATIONS BASED ON ULTRASOUND DIAGNOSIS OF NAFLD

ABSTRACT As a common metabolic disease, non-alcoholic fatty liver disease (NAFLD) is the most common type of liver disease in western developed countries and an important liver disease in the Asia Pacific region. At present, NAFLD lacks targeted conventional therapy and its basic treatment is the correction of bad living habits. In order to verify the effectiveness of the basic treatment of NAFLD, and explore the prevention methods of NAFLD, this study used ultrasound diagnosis, baseline survey and follow-up survey, and conducted a cross-sectional study on the correlation between nighttime and midday sleep duration and NAFLD, and carried out a prospective study on the correlation between sleep duration and NAFLD. The results showed that there was a negative correlation between the length of sleep at night and the prevalence of NAFLD, while the length of midday sleep was positively correlated with the prevalence of NAFLD. The time of night sleep was an independent factor of NAFLD, and the relationship between midday sleep time and NAFLD was not statistically significant. NAFLD-susceptible people can prevent NAFLD by ensuring adequate sleep at night and reducing midday sleep. This study is expected to provide theoretical reference and data support for the prevention and treatment of NAFLD.

Palbociclib negatively regulates fatty acid synthesis due to upregulation of AMPKα and miR-33a levels to increase apoptosis in Panc-1 and MiaPaCa-2 cells

Fatty acids (FAs) synthesis mechanism has various regulators such as fatty acid synthase (FASN), AMP-regulated protein kinase (AMPK), or mammalian target of rapamycin (mTOR), which are aberrantly dysregulated in various pancreatic cancer cells. In this study, we aim to understand the regulatory role of palbociclib, a CDK4/6 inhibitor, on the cellular energy metabolism through regulation of AMPK/mTOR signaling by modulation of intracellular miR-33a levels in Panc-1 and MiaPaCa-2 cells. Palbociclib downregulated FAs metabolism more effectively in MiaPaCa-2 cells than Panc-1 cells. Moreover, palbociclib treatment increased the levels of miR-33a in each cell line albeit a higher increase was evident in MiaPaCa-2 cells. Stress-mediated activation of mTOR signaling axis was found associated with palbociclib-mediated AMPKα activation and miR33a upregulation. These findings provided that a deeper understanding about possible interactions of cell cycle activity and reduction of FAs synthesis may facilitate the enhancement of cell death mechanisms in pancreatic cancer cells.

The Role of Hepatic Fat Accumulation in Glucose and Insulin Homeostasis-Dysregulation by the Liver

Accumulation of hepatic triacylglycerol (TG) is associated with obesity and metabolic syndrome, which are important pathogenic factors in the development of type 2 diabetes. In this narrative review, we summarize the effects of hepatic TG accumulation on hepatic glucose and insulin metabolism and the underlying molecular regulation in order to highlight the importance of hepatic TG accumulation for whole-body glucose metabolism. We find that liver fat accumulation is closely linked to impaired insulin-mediated suppression of hepatic glucose production and reduced hepatic insulin clearance. The resulting systemic hyperinsulinemia has a major impact on whole-body glucose metabolism and may be an important pathogenic step in the development of type 2 diabetes.

Epigenetics of Hepatic Insulin Resistance

Insulin resistance (IR) is largely recognized as a unifying feature that underlies metabolic dysfunction. Both lifestyle and genetic factors contribute to IR. Work from recent years has demonstrated that the epigenome may constitute an interface where different signals may converge to promote IR gene expression programs. Here, we review the current knowledge of the role of epigenetics in hepatic IR, focusing on the roles of DNA methylation and histone post-translational modifications. We discuss the broad epigenetic changes observed in the insulin resistant liver and its associated pathophysiological states and leverage on the wealth of 'omics' studies performed to discuss efforts in pinpointing specific loci that are disrupted by these changes. We envision that future studies, with increased genomic resolution and larger cohorts, will further the identification of biomarkers of early onset hepatic IR and assist the development of targeted interventions. Furthermore, there is growing evidence to suggest that persistent epigenetic marks may be acquired over prolonged exposure to disease or deleterious exposures, highlighting the need for preventative medicine and long-term lifestyle adjustments to avoid irreversible or long-term alterations in gene expression.

An Integrated Analysis of miRNA and Gene Expression Changes in Response to an Obesogenic Diet to Explore the Impact of Transgenerational Supplementation with Omega 3 Fatty Acids

Insulin resistance decreases the ability of insulin to inhibit hepatic gluconeogenesis, a key step in the development of metabolic syndrome. Metabolic alterations, fat accumulation, and fibrosis in the liver are closely related and contribute to the progression of comorbidities, such as hypertension, type 2 diabetes, or cancer. Omega 3 (n-3) polyunsaturated fatty acids, such as eicosapentaenoic acid (EPA), were identified as potent positive regulators of insulin sensitivity in vitro and in animal models. In the current study, we explored the effects of a transgenerational supplementation with EPA in mice exposed to an obesogenic diet on the regulation of microRNAs (miRNAs) and gene expression in the liver using high-throughput techniques. We implemented a comprehensive molecular systems biology approach, combining statistical tools, such as MicroRNA Master Regulator Analysis pipeline and Boolean modeling to integrate these biochemical processes. We demonstrated that EPA mediated molecular adaptations, leading to the inhibition of miR-34a-5p, a negative regulator of Irs2 as a master regulatory event leading to the inhibition of gluconeogenesis by insulin during the fasting-feeding transition. Omics data integration provided greater biological insight and a better understanding of the relationships between biological variables. Such an approach may be useful for deriving innovative data-driven hypotheses and for the discovery of molecular-biochemical mechanistic links.

The 2039 A/G FSH receptor gene polymorphism influences glucose metabolism in healthy men

OBJECTIVE

To assess the role of c. 2039 A/G (p. Asp680Ser) (rs6166) and c. -29 G/A (rs1394205) follicle-stimulating hormone receptor (FSHR) gene single nucleotide polymorphisms (SNPs) in a cohort of healthy men.

METHODS

One-hundred twenty-seven healthy men underwent evaluation of the anthropometric parameters, assessment of metabolic and lipid profile, measurement FSH serum levels, and genotyping of both the aforementioned FSHR SNPs. Data grouped according to the FSHR rs6166 or rs1394205 genotypes underwent to statistical analysis.

MAIN RESULTS

The three groups of men for each FSHR SNP did not differ statistically significantly for body mass index and serum FSH levels. As for FSHR rs6166 SNP, glucose levels were significantly lower in men with the GG genotype compared with those with the AA genotype. Men with AG had lower insulin levels and HOMA index values compared with those carrying the genotype AA (p < 0.05). The GG group showed a negative correlation between serum FSH levels and insulin and between serum FSH levels and HOMA index (p < 0.05). In contrast, men grouped according to the FSHR rs1394205 genotype showed no significant difference in blood glucose, serum insulin levels, and HOMA index. The AG group showed a negative correlation between FSH insulin and between serum FSH levels and HOMA index (p < 0.05).

CONCLUSIONS

Men with the genotype GG of the FSHR rs6166 SNP have lower blood glucose levels than those with the AA genotype. Their FSH levels inversely correlated with insulin and HOMA index. In contrast, the genotype FSHR rs6166 A/G did not reveal any role of FSH on glucose metabolism in healthy men. The inverse relationship between FSH and insulin or HOMA index in the group with the genotype GG of the FSHR rs6166 SNP suggests a possible cross-talk between FSH and insulin.

Combination of Pancreastatin inhibitor PSTi8 with metformin inhibits Fetuin-A in type 2 diabetic mice

In the preceding study, we delineated that high-fat diet (HFD) consumption in mice increases the circulatory level of pancreastatin (PST), which additionally enhances the free fatty acid (FFA) concentration in circulation. Consequently, the aggravated FFA activates Fetuin-A, which facilitates hepatic lipid accumulation, insulin resistance (IR), and culminates in type 2 diabetes (T2D). Metformin (Met) is a widely known first-line drug for the treatment of T2D. We previously unveiled PSTi8, an inhibitor of PST, comprising antidiabetic property. Hence, we hypothesized that combination therapy of Met and PSTi8, at reduced therapeutic doses, would mitigate HFD-induced IR by inhibiting hepatic Fetuin-A in mice model of T2D. C57BL/6 mice were fed HFD for 12 weeks, followed by treatment with Met, PSTi8, and its combination for 10 days. Glucose and insulin tolerance tests were conducted. Circulatory levels of PST, Fetuin-A, and lipid markers were determined. Also, the mRNA and protein expression of Fetuin-A was assessed by qPCR, western blotting, and immunofluorescence. Moreover, the energy expenditure was measured by comprehensive laboratory animal monitoring system (CLAMS). Combination therapy displayed improved PST, Fetuin-A, and lipid profile in plasma. We also found reduced hepatic Fetuin-A, which reduced inhibitory phosphorylation of IRS and increased phosphorylation of AKT. Consequently, ameliorated hepatic lipogenesis, gluconeogenesis, and inflammation. Also, combination treatment attenuated Fetuin-A expression, lipid accumulation, and glucose production in palmitate-induced HepG2 cells. Altogether current study promulgates the beneficial effect of combination therapy of Met and PSTi8 (comparable to alone higher therapeutic doses) to ameliorate Fetuin-A activation, hepatic lipid accumulation, insulin resistance, and associated progressive pathophysiological alterations in T2D.

Multi-layered epigenetic regulation of IRS2 expression in the liver of obese individuals with type 2 diabetes

AIMS/HYPOTHESIS

IRS2 is an important molecular switch that mediates insulin signalling in the liver. IRS2 dysregulation is responsible for the phenomenon of selective insulin resistance that is observed in type 2 diabetes. We hypothesise that epigenetic mechanisms are involved in the regulation of IRS2 in the liver of obese and type 2 diabetic individuals.

METHODS

DNA methylation of seven CpG sites was studied by bisulphite pyrosequencing and mRNA and microRNA (miRNA) expression was assessed by quantitative real-time PCR in liver biopsies of 50 obese non-diabetic and 31 obese type 2 diabetic participants, in a cross-sectional setting. Methylation-sensitive luciferase assays and electrophoretic mobility shift assays were performed. Furthermore, HepG2 cells were treated with insulin and high glucose concentrations to induce miRNA expression and IRS2 downregulation.

RESULTS

We found a significant downregulation of IRS2 expression in the liver of obese individuals with type 2 diabetes (0.84 ± 0.08-fold change; p = 0.0833; adjusted p value [p_a] = 0.0417; n = 31) in comparison with non-diabetic obese participants (n = 50). This downregulation correlated with hepatic IRS2 DNA methylation at CpG5. Additionally, CpG6, which is located in intron 1 of IRS2, was hypomethylated in type 2 diabetes; this site spans the sterol regulatory element binding transcription factor 1 (SREBF1) recognition motif, which likely acts as transcriptional repressor. The adjacent polymorphism rs4547213 (G>A) was significantly associated with DNA methylation at a specificity-protein-1 (SP1) binding site (CpG3). Moreover, DNA methylation of cg25924746, a CpG site located in the shore region of the IRS2 promoter-associated CpG island, was increased in the liver of individuals with type 2 diabetes, as compared with those without diabetes. A second epigenetic mechanism, upregulation of hepatic miRNA hsa-let-7e-5p (let-7e-5p) in obese individuals with type 2 diabetes (n = 29) vs non-diabetic obese individuals (n = 49) (1.2 ± 0.08-fold change; p = 0.0332; p_a = 0.0450), is likely to act synergistically with altered IRS2 DNA methylation to decrease IRS2 expression. Mechanistic in vitro experiments demonstrated an acute upregulation of let-7e-5p expression and simultaneous IRS2 downregulation in a liver (HepG2) cell line upon hyperinsulinaemic and hyperglycaemic conditions.

CONCLUSIONS/INTERPRETATION

Our study highlights a new multi-layered epigenetic network that could be involved in subtle dysregulation of IRS2 in the liver of individuals with type 2 diabetes. This might lead to fine-tuning of IRS2 expression and is likely to be supplementary to the already known factors regulating IRS2 expression. Thereby, our findings could support the discovery of new diagnostic and therapeutic strategies for type 2 diabetes. Graphical abstract.

Regulatory roles of circRNAs in adipogenesis and lipid metabolism: emerging insights into lipid-related diseases

Disorder of lipid metabolism has become an urgent health problem that brings about a variety of metabolic syndromes, including hepatic steatosis, adipose tissue dysfunction, diabetes and obesity. Circular RNAs (circRNAs), a class of emerging RNA molecules with unique structure and extensive effects, have been verified to participate in various biological programs through distinct mechanisms, especially in lipid-related processes. In this review, the biogenesis, characteristics, and functional mechanisms of circRNAs are discussed. Furthermore, the methods for circRNA identification and expression profiles of circRNAs associated with adipogenesis and lipid metabolism are described. Additionally, we emphasize the regulatory roles of circRNAs in adipogenesis, lipid metabolism, and lipid-related diseases. Finally, the diagnostic and therapeutic potential of circRNAs is highlighted, showing potential for the clinical application of circRNAs in the treatment of lipid-related diseases in the near future.

MiR-542-5p Inhibits Hyperglycemia and Hyperlipoidemia by Targeting FOXO1 in the Liver

PURPOSE

This research was designed to investigate how miR-542-5p regulates the progression of hyperglycemia and hyperlipoidemia.

MATERIALS AND METHODS

An in vivo model with diabetic db/db mice and an in vitro model with forskolin/dexamethasone (FSK/DEX)-induced primary hepatocytes and HepG2 cells were employed in the study. Bioinformatics analysis was conducted to identify the expression of candidate miRNAs in the liver tissues of diabetic and control mice. H&E staining revealed liver morphology in diabetic and control mice. Pyruvate tolerance tests, insulin tolerance tests, and intraperitoneal glucose tolerance test were utilized to assess insulin resistance. ELISA was conducted to evaluate blood glucose and insulin levels. Red oil O staining showed lipid deposition in liver tissues. Luciferase reporter assay was used to depict binding between miR-542-5p and forkhead box O1 (FOXO1).

RESULTS

MiR-542-5p expression was under-expressed in the livers of db/db mice. Further in vitro experiments revealed that FSK/DEX, which mimics the effects of glucagon and glucocorticoids, induced cellular glucose production in HepG2 cells and in primary hepatocytes cells. Notably, these changes were reversed by miR-542-5p. We found that transcription factor FOXO1 is a target of miR-542-5p. Further in vivo study indicated that miR-542-5p overexpression decreases FOXO1 expression, thereby reversing increases in blood glucose, blood lipids, and glucose-related enzymes in diabetic db/db mice. In contrast, anti-miR-542-5p exerted an adverse influence on blood glucose and blood lipid metabolism, and its stimulatory effects were significantly inhibited by sh-FOXO1 in normal control mice.

CONCLUSION

Collectively, our results indicated that miR-542-5p inhibits hyperglycemia and hyperlipoidemia by targeting FOXO1.

Integrated analysis of differentially expressed long noncoding RNAs and mRNAs associated with high-fat diet-induced hepatic insulin resistance in mice

Background

Hepatic insulin resistance (IR) is an early pathological characteristic of many metabolic diseases, such as type 2 diabetes. Long noncoding RNAs (lncRNAs) have been identified as mediators of IR and related diseases. However, the roles of lncRNAs in hepatic IR remain largely unknown.

Method

High-throughput sequencing was performed on ten liver tissue samples from five normal diet (ND)-fed mice and five high-fat diet (HFD)-induced hepatic IR mice, respectively. lncRNAs and mRNAs that were differentially expressed (DE) between the two groups were identified by bioinformatic analyses. Seven DE lncRNAs were validated by quantitative real-time PCR (q-PCR). The potential functions of the DE lncRNAs were predicted by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses of target genes. In addition, integrated analysis was performed for the DE lncRNAs and mRNAs to predict their interaction relationships.

Results

A total of 232 DE lncRNAs were identified in the HFD-induced hepatic IR mice compared with the ND-fed mice. These DE lncRNAs included 108 upregulated and 124 downregulated lncRNAs, and 7 of the DE lncRNAs were validated by q-PCR. In addition, 291 DE mRNAs including 166 upregulated and 125 downregulated mRNAs were identified in the HFD group. Furthermore, target genes of the DE lncRNAs were predicted, and functional enrichment results showed that the enriched genes were involved in IR- and glycolipid metabolism-related processes. Additionally, the coexpression network was also constructed to further reflect the potential functions of the DE lncRNAs.

Conclusion

The study describes the expression profiles of lncRNAs and mRNAs and the functional networks involved in HFD-induced hepatic IR. These findings may provide a new perspective for the study of lncRNAs in hepatic IR- and glycolipid metabolism-related diseases.

The Role of Insulin Resistance and Diabetes in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) consists of the entire spectrum of fatty liver disease in patients without significant alcohol consumption, ranging from nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH) to cirrhosis, with NASH recently shown as an important cause of hepatocellular carcinoma (HCC). There is a close relationship between insulin resistance (IR) and NAFLD, with a five-fold higher prevalence of NAFLD in patients with type 2 diabetes (T2DM) compared to that in patients without T2DM. IR is involved in the progression of disease conditions such as steatosis and NASH, as well as hepatic fibrosis progression. The mechanisms underlying these processes involve genetic factors, hepatic fat accumulation, alterations in energy metabolism, and inflammatory signals derived from various cell types including immune cells. In NASH-associated fibrosis, the principal cell type responsible for extracellular matrix production is the hepatic stellate cell (HSC). HSC activation by IR involves “direct” and “indirect” pathways. This review will describe the molecular mechanisms of inflammation and hepatic fibrosis in IR, the relationship between T2DM and hepatic fibrosis, and the relationship between T2DM and HCC in patients with NAFLD.

Hepatic lipid droplet homeostasis and fatty liver disease

In cells, lipids are stored in lipid droplets, dynamic organelles that adapt their size, abundance, lipid and protein composition and organelle interactions to metabolic changes. Lipid droplet accumulation in the liver is the hallmark of non-alcoholic fatty liver disease (NAFLD). Due to the prevalence of obesity, the strongest risk factor for steatosis, NAFLD and its associated complications are currently affecting more than 1 billion people worldwide. Here, we review how triglyceride and phospholipid homeostasis are regulated in hepatocytes and how imbalances between lipid storage, degradation and lipoprotein secretion lead to NAFLD. We discuss how organelle interactions are altered in NAFLD and provide insights how NAFLD progression is associated with changes in hepatocellular signaling and organ-crosstalk. Finally, we highlight unsolved questions in hepatic LD and lipoprotein biology and give an outlook on therapeutic options counteracting hepatic lipid accumulation.

Circular RNA HIPK3 contributes to hyperglycemia and insulin homeostasis by sponging miR-192-5p and upregulating transcription factor forkhead box O1

It has been shown that circular RNAs, a class of non-coding RNA molecules, play an important role in the regulation of glucose and lipid homeostasis. In the present study, we sought to investigate the function of circular RNA HIPK3 (circHIPK3) in diabetes-associated metabolic disorders, including hyperglycemia and insulin resistance. Results show that oleate stimulated circHIPK3 increase, and that circHIPK3 enhanced the stimulatory effect of oleate on adipose deposition, triglyceride (TG) content, and cellular glucose content in HepG2 cells. MiR-192-5p was the potential target of circHIPK3, since circHIPK3 significantly decreased miR-192-5p mRNA level, whereas anti-circHIPK3 significantly increased miR-192-5p mRNA level. Further study shows that transcription factor forkhead box O1 (FOXO1) was a downstream regulator of miR-192-5p, since miR-192-5p significantly decreased FOXO1 expression, whereas circHIPK3 significantly increased FOXO1 expression. Notably, the inhibitory effect of miR-192-5p was significantly reversed by circHIPK3. In vivo study shows that anti-miR-192-5p significantly increased blood glucose content, which was significantly inhibited by FOXO1 shRNA. MiR-192-5p significantly decreased adipose deposition and TG content in HepG2 cells, which was significantly reversed by the co-treatment with circHIPK3. Forskolin/dexamethasone (FSK/DEX) significantly increased cellular glucose, mRNA level of phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6-phosphatase (G6Pase), and this stimulatory effect of FSK/DEX was significantly inhibited by miR-192-5p. In the presence of circHIPK3, however, the inhibitory effect of miR-192-5p was totally lost. In summary, the present study demonstrated that circHIPK3 contributes to hyperglycemia and insulin resistance by sponging miR-192-5p and up-regulating FOXO1.

Hepatocellular carcinoma in the context of non-alcoholic steatohepatitis (NASH): recent advances in the pathogenic mechanisms

Hepatocellular carcinoma (HCC) is the most common type of liver cancer. HCC is particularly aggressive and is one of the leading causes of cancer mortality. In recent decades, the epidemiological landscape of HCC has undergone significant changes. While chronic viral hepatitis and excessive alcohol consumption have long been identified as the main risk factors for HCC, non-alcoholic steatohepatitis (NASH), paralleling the worldwide epidemic of obesity and type 2 diabetes, has become a growing cause of HCC in the US and Europe. Here, we review the recent advances in epidemiological, genetic, epigenetic and pathogenic mechanisms as well as experimental mouse models that have improved the understanding of NASH progression toward HCC. We also discuss the clinical management of patients with NASH-related HCC and possible therapeutic approaches.

Liver gene regulatory networks: Contributing factors to nonalcoholic fatty liver disease

Metabolic diseases such as nonalcoholic fatty liver disease (NAFLD) result from complex interactions between intrinsic and extrinsic factors, including genetics and exposure to obesogenic environments. These risk factors converge in aberrant gene expression patterns in the liver, which are underlined by altered cis-regulatory networks. In homeostasis and in disease states, liver cis-regulatory networks are established by coordinated action of liver-enriched transcription factors (TFs), which define enhancer landscapes, activating broad gene programs with spatiotemporal resolution. Recent advances in DNA sequencing have dramatically expanded our ability to map active transcripts, enhancers and TF cistromes, and to define the 3D chromatin topology that contains these elements. Deployment of these technologies has allowed investigation of the molecular processes that regulate liver development and metabolic homeostasis. Moreover, genomic studies of NAFLD patients and NAFLD models have demonstrated that the liver undergoes pervasive regulatory rewiring in NAFLD, which is reflected by aberrant gene expression profiles. We have therefore achieved an unprecedented level of detail in the understanding of liver cis-regulatory networks, particularly in physiological conditions. Future studies should aim to map active regulatory elements with added levels of resolution, addressing how the chromatin landscapes of different cell lineages contribute to and are altered in NAFLD and NAFLD-associated metabolic states. Such efforts would provide additional clues into the molecular factors that trigger this disease. This article is categorized under: Biological Mechanisms > Metabolism Biological Mechanisms > Regulatory Biology Laboratory Methods and Technologies > Genetic/Genomic Methods.

Acetyl-CoA carboxylase 1 and 2 inhibition ameliorates steatosis and hepatic fibrosis in a MC4R knockout murine model of nonalcoholic steatohepatitis

Acetyl-CoA carboxylase (ACC) catalyzes the rate-limiting step in de novo lipogenesis, which is increased in the livers of patients with nonalcoholic steatohepatitis. GS-0976 (firsocostat), an inhibitor of isoforms ACC1 and ACC2, reduced hepatic steatosis and serum fibrosis biomarkers such as tissue inhibitor of metalloproteinase 1 in patients with nonalcoholic steatohepatitis in a randomized controlled trial, although the impact of this improvement on fibrosis has not fully been evaluated in preclinical models. Here, we used Western diet-fed melanocortin 4 receptor-deficient mice that have similar phenotypes to nonalcoholic steatohepatitis patients including progressively developed hepatic steatosis as well as fibrosis. We evaluated the effects of ACC1/2 inhibition on hepatic fibrosis. After the confirmation of significant hepatic fibrosis with a 13-week pre-feeding, GS-0976 (4 and 16 mg/kg/day) treatment for 9 weeks lowered malonyl-CoA and triglyceride content in the liver and improved steatosis, histologically. Furthermore, GS-0976 reduced the histological area of hepatic fibrosis, hydroxyproline content, mRNA expression level of type I collagen in the liver, and plasma tissue metalloproteinase inhibitor 1, suggesting an improvement of hepatic fibrosis. The treatment with GS-0976 was also accompanied by reductions of plasma ALT and AST levels. These data demonstrate that improvement of hepatic lipid metabolism by ACC1/2 inhibition could be a new option to suppress fibrosis progression as well as to improve hepatic steatosis in nonalcoholic steatohepatitis.

Fructose and hepatic insulin resistance

Excessive caloric intake in a form of high-fat diet (HFD) was long thought to be the major risk factor for development of obesity and its complications, such as fatty liver disease and insulin resistance. Recently, there has been a paradigm shift and more attention is attributed to the effects of sugar-sweetened beverages (SSBs) as one of the culprits of the obesity epidemic. In this review, we present the data invoking fructose intake with development of hepatic insulin resistance in human studies and discuss the pathways by which fructose impairs hepatic insulin action in experimental animal models. First, we described well-characterized pathways by which fructose metabolism indirectly leads to hepatic insulin resistance. These include unequivocal effects of fructose to promote de novo lipogenesis (DNL), impair fatty acid oxidation (FAO), induce endoplasmic reticulum (ER) stress and trigger hepatic inflammation. Additionally, we entertained the hypothesis that fructose can directly impede insulin signaling in the liver. This appears to be mediated by reduced insulin receptor and insulin receptor substrate 2 (IRS2) expression, increased protein-tyrosine phosphatase 1B (PTP1b) activity, whereas knockdown of ketohexokinase (KHK), the rate-limiting enzyme of fructose metabolism, increased insulin sensitivity. In summary, dietary fructose intake strongly promotes hepatic insulin resistance via complex interplay of several metabolic pathways, at least some of which are independent of increased weight gain and caloric intake. The current evidence shows that the fructose, but not glucose, component of dietary sugar drives metabolic complications and contradicts the notion that fructose is merely a source of palatable calories that leads to increased weight gain and insulin resistance.

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

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

Sinapine reduces non-alcoholic fatty liver disease in mice by modulating the composition of the gut microbiota

Non-alcoholic fatty liver disease (NAFLD) is associated with low-grade chronic inflammation and intestinal dysbiosis. In this study, we investigated the potential benefits of sinapine, a rapeseed polyphenol known to exert anti-inflammatory and anti-oxidant effects, on high-fat diet (HFD)-induced NAFLD in C57BL/6 J mice and the underlying mechanisms. Four week-old mice were randomly divided into four groups and fed a low-fat diet (LFD), a HFD, a HFD with common rapeseed oil (HFD + CRO) and a HFD with sinapine in rapeseed oil (HFD + SRO) for 12 weeks. Supplementation with sinapine reduced the body weight of HFD mice by 10.99%, and decreased the levels of TG and LDL-C by 15.67% and 73.62%, respectively. In addition, sinapine also suppressed the intestinal NF-κB and TNF-α expressions and enhanced the adipose tissue IRS-1 expression in the HFD mice (P < 0.05). In terms of effects on the gut microbiota, sinapine induced a decrease in the ratio of Firmicutes to Bacteroidetes and increased the abundance of probiotics, such as Lactobacillaceae, Akkermansiaceae and Blautia, along with metabolite short-chain fatty acid (SCFA)-mediated upregulation of G protein-coupled receptor 43 (GPR43) to inhibit expression of inflammatory factors. Our collective results strongly supported the fact that the utility of sinapine as a prebiotic agent could prevent gut dysbiosis and obesity-related chronic diseases, such as insulin resistance (IR) and NAFLD.