PGBR extract ameliorates TNF-α induced insulin resistance in hepatocytes

The role of TNF in metabolic disorders and liver diseases

Tumor necrosis factor (TNF) is identified as a pro-inflammatory cytokine critical to the pathology of liver disease. In the carbohydrate metabolism, TNF has been demonstrated to impede the insulin signaling pathway, thereby precipitating glucose intolerance and insulin resistance. In lipid metabolism, TNF upregulates genes implicated in fatty acid synthesis, resulting in increased lipid accumulation within the liver. In amino acid metabolism, TNF has shown to promote the gene expression for amino acid catabolism, leading to decreased protein synthesis. Additionally, TNF stimulates the production of other chemokines and inflammatory cytokines that can further exacerbate liver injury. Overall, TNF is crucial in developing liver diseases by disrupting various metabolic pathways in the liver, causing insulin resistance, lipid accumulation, and decreased protein synthesis. This review summarizes the present understanding of TNF's role in the regulation of carbohydrate, lipid and amino acid metabolism in liver disease together with its potential therapeutic implications.

A Network Pharmacology Study and In Vitro Evaluation of the Bioactive Compounds of Kadsura coccinea Leaf Extract for the Treatment of Type 2 Diabetes Mellitus

Kadsura coccinea is a traditional Chinese medicine whose roots have long been used to treat various ailments, but little is known about the efficacy of its leaves. In this study, the antidiabetic activity of K. coccinea leaf extract (KCLE) was determined, the main components of KCLE were identified using UPLC-TOF-MS, and network pharmacology and molecular docking were integrated to elucidate the antidiabetic mechanism of KCLE. The results showed that KCLE effectively increased the glucose consumption of IR-HepG2 cells through pyruvate kinase (PK) and hexokinase (HK), promoted glycogen synthesis, and inhibited α-glucosidase and α-amylase activities. KCLE also improves diabetes by regulating AKT1, TNF, EGFR, and GSK3β. These targets (especially AKT1 and TNF) have a high binding affinity with the main active ingredients of KCLE (rutin, luteolin, demethylwedelolactone, maritimetin, and polydatin). Pathway enrichment analysis showed that the antidiabetic effect of KCLE was closely related to the PI3K-Akt signaling pathway, MAPK signaling pathway, AGE-RAGE signaling pathway, and FoxO signaling pathway. These findings provide a theoretical basis for promoting the pharmacodynamic development of K. coccinea and its application in treating diabetes.

Research progress on the association of insulin resistance with type 2 diabetes mellitus and Alzheimer's disease

Type 2 diabetes mellitus (T2DM) is a metabolic disorder that is characterized by insulin resistance and hyperglycemia. It is also known to be a risk factor for Alzheimer's disease (AD). Insulin plays a crucial role in regulating the body's metabolism and is responsible for activating the Phosphoinotide-3-Kinase (PI3K)/Protein Kinase B (Akt) signaling pathway. This pathway is activated when insulin binds to the insulin receptor on nerve cells, and it helps regulate the metabolism of glucose and lipids. Dysfunction in the insulin signaling pathway can lead to a decrease in brain insulin levels and insulin sensitivity, thereby inducing disruptions in insulin signal transduction and leading to disorders in brain energy metabolism. Moreover, these dysfunctions also contribute to the accumulation of β-amyloid (Aβ) deposition and the hyperphosphorylation of Tau protein, both of which are characteristic features of AD. Therefore, this article focuses on insulin resistance to reveal the complex mechanism between brain insulin resistance and AD occurrence in T2DM. On this basis, this article further summarizes the biological effects and mechanisms of antidiabetic drugs on the two diseases, aiming to provide new ideas for the discovery of drugs for the treatment of T2DM combined with AD.

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.

Ten-Week Sucralose Consumption Induces Gut Dysbiosis and Altered Glucose and Insulin Levels in Healthy Young Adults

Sucralose consumption alters microbiome and carbohydrate metabolism in mouse models. However, there are no conclusive studies in humans. Our goals were to examine the effect of sucralose consumption on the intestinal abundance of bacterial species belonging to Actinobacteria, Bacteroidetes, and Firmicutes and explore potential associations between microbiome profiles and glucose and insulin blood levels in healthy young adults. In this open-label clinical trial, volunteers randomly drank water, as a control (n = 20), or 48 mg sucralose (n = 20), every day for ten weeks. At the beginning and the end of the study, participants were subjected to an oral glucose tolerance test (OGTT) to measure serum glucose and insulin every 15 min for 3 h and provided fecal samples to assess gut microbiota using a quantitative polymerase chain reaction. Sucralose intake altered the abundance of Firmicutes without affecting Actinobacteria or Bacteroidetes. Two-way ANOVA revealed that volunteers drinking sucralose for ten weeks showed a 3-fold increase in Blautia coccoides and a 0.66-fold decrease in Lactobacillus acidophilus compared to the controls. Sucralose consumption increased serum insulin and the area under the glucose curve compared to water. Long-term sucralose ingestion induces gut dysbiosis associated with altered insulin and glucose levels during an OGTT.

A Novel STAT3-Mediated GATA6 Pathway Contributes to tert-Butylhydroquinone- (tBHQ-) Protected TNFα-Activated Vascular Cell Adhesion Molecule 1 (VCAM-1) in Vascular Endothelium

The activation of vascular cell adhesion molecule 1 (VCAM-1) in vascular endothelial cells has been well considered implicating in the initiation and processing of atherosclerosis. Oxidative stress is mechanistically involved in proatherosclerotic cytokine-induced VCAM-1 activation. tert-Butylhydroquinone (tBHQ), a synthetic phenolic antioxidant used for preventing lipid peroxidation of food, possesses strongly antioxidant capacity against oxidative stress-induced dysfunction in various pathological process. Here, we investigated the protective role of tBHQ on tumor necrosis factor alpha- (TNFα-) induced VCAM-1 activation in both aortic endothelium of mice and cultured human vascular endothelial cells and uncovered its potential mechanisms. Our data showed that tBHQ treatment significantly reversed TNFα-induced activation of VCAM-1 at both transcriptional and protein levels. The mechanistic study revealed that inhibiting neither nuclear factor (erythroid-derived 2)-like 2 (Nrf2) nor autophagy blocked the beneficial role of tBHQ. Alternatively, tBHQ intervention markedly alleviated TNFα-increased GATA-binding protein 6 (GATA6) mRNA and protein expressions and its translocation into nucleus. Further investigation indicated that tBHQ-inhibited signal transducer and activator of transcription 3 (STAT3) but not mitogen-activated protein kinase (MAPK) pathway contributed to its protective role against VCAM-1 activation via regulating GATA6. Collectively, our data demonstrated that tBHQ prevented TNFα-activated VCAM-1 via a novel STAT3/GATA6-involved pathway. tBHQ could be a potential candidate for the prevention of proatherosclerotic cytokine-caused inflammatory response and further dysfunctions in vascular endothelium.

Towards an Insulin Resistant Adipose Model on a Chip

Introduction

Adipose tissue and adipocytes are primary regulators of insulin sensitivity and energy homeostasis. Defects in insulin sensitivity of the adipocytes predispose the body to insulin resistance (IR) that could lead to diabetes. However, the mechanisms mediating adipocyte IR remain elusive, which emphasizes the need to develop experimental models that can validate the insulin signaling pathways and discover new mechanisms in the search for novel therapeutics. Currently in vitro adipose organ-chip devices show superior cell function over conventional cell culture. However, none of these models represent disease states. Only when these in vitro models can represent both healthy and disease states, they can be useful for developing therapeutics. Here, we establish an organ-on-chip model of insulin-resistant adipocytes, as well as characterization in terms of insulin signaling pathway and lipid metabolism.

Methods

We differentiated, maintained, and induced insulin resistance into primary adipocytes in a microfluidic organ-on-chip. We then characterized IR by looking at the insulin signaling pathway and lipid metabolism, and validated by studying a diabetic drug, rosiglitazone.

Results

We confirmed the presence of insulin resistance through reduction of Akt phosphorylation, Glut4 expression, Glut4 translocation and glucose uptake. We also confirmed defects of disrupted insulin signaling through reduction of lipid accumulation from fatty acid uptake and elevation of glycerol secretion. Testing with rosiglitazone showed a significant improvement in insulin sensitivity and fatty acid metabolism as suggested by previous reports.

Conclusions

The adipose-chip exhibited key characteristics of IR and can serve as model to study diabetes and facilitate discovery of novel therapeutics.

Efficiency comparison of PGBR extract and γ-oryzanol in antioxidative stress and anti-inflammatory properties against metabolic syndrome

This research aims to delineate the anti-inflammatory effect of pregerminated brown rice extract (PE) and γ-oryzanol on improving metabolic features of high-fat diet (HFD)-induced metabolic syndrome (MetS) mouse model. C57BL/6 mice were randomly divided into eight groups: regular diet (RD), HFD, HFD-combined treatment of 0.5, 5, or 10 mg kg^-1  day^-1 oral gavage γ-oryzanol, and 30, 300, or 600 mg kg^-1  day^-1 PE for 18 weeks. HFD-fed mice showed overweight, hyperglycemia, hyperlipidemia signs of metabolic disorder, and elevation of inflammatory cytokines such as IL-6, TNF-α, IFN-γ, NO, PGE2 in serum and MAPKs, transcription factor p65, iNOS, and MDA in the liver. In contrast, HFD-fed mice showed lower levels of adiponectin in serum and antiperoxidation enzymes GPx, SOD, and catalase in the liver. While HFD-fed mice cotreated with PE or γ-oryzanol, HFD-induced metabolic disorders, ROS, and inflammation were improved. The anti-MetS, antioxidative stress and anti-inflammation properties of PE were more potent than γ-oryzanol. PRACTICAL APPLICATIONS: Our study showed that PE or γ-oryzanol supplement could help control metabolic disorders, oxidative stress, chronic inflammation, and related complications.

Flavonoids from Camellia sinensis (L.) O. Kuntze seed ameliorates TNF-α induced insulin resistance in HepG2 cells

The aim of this study is to discuss the non-catechin flavonoids (NCF) from Camellia sinensis (L.) O. Kuntze seed improving TNF-α impaired insulin stimulated glucose uptake and insulin signaling. Flavonoids had anti-metabolic syndrome and anti-inflammatory properties. It had widely been known for biological activity of catechins in tea, but very few research reports discussed the biological activity of non-catechin flavonoids in tea seed. We used HepG2 cell to treat with 5 μM insulin or with 5 μM insulin + 30 ng/ml TNF-α. Detecting the glucose concentration of medium, insulin decreased the glucose levels of medium meant that insulin promoted glucose uptake into cells, but TNF-α inhibited the glucose uptake effect of insulin. Furthermore, insulin increased the protein expressions of IR, IRS-1, IRS-2, PI3K-α, Akt/PKB, GLUT-2, AMPK, GCK, pyruvate kinase, and PPAR-γ. TNF-α activated p65 and MAPKs (p38, JNK1/2 and ERK1/2), iNOS and COX-2 which worsened the insulin signaling expressions of IR, IRS-1, IRS-2, PI3K-α, Akt/PKB, GLUT-2, AMPK, GCK, pyruvate kinase, and PPAR-γ. We added NCF (500, 1000, 2000 ppm) to cell with insulin and TNF-α. Not only glucose levels of medium were lowered, and the protein expressions of insulin signaling were increased, but p38, JNK1/2, iNOS and COX-2 were also reduced. NCF could ameliorate TNF-α induced insulin resistance through inhibiting p38, JNK1/2, iNOS and COX-2, and suggested that it might be used in the future to help control insulin resistance. This finding is the first report to present the discovery.

Pre-germinated brown rice extract ameliorates high-fat diet-induced metabolic syndrome

This study examined the effect of pre-germinated brown rice extract (PGBRE), containing no dietary fibers, but γ-oryzanol, γ-aminobutyric acid (GABA), flavonoids, and anthocyanidin, on high-fat-diet (HFD)-induced metabolic syndrome. C57BL/6 mice were divided into five groups: regular diet, HFD, HFD with oral PGBRE 30, 300, or 600 mg/kg per day for 18 weeks. In the HFD group, higher body and liver weight gain, hyperglycemia, HbA1c, and insulin; higher TG, TC, LDL-C, non-HDL, atherosclerosis index, lower HDL, adiponectin in blood; higher TG in the liver; higher TG, bile acid in feces; and lower protein levels of AMP-activated protein kinase, insulin receptor, insulin receptor substrate-1, insulin receptor substrate-2, peroxisome proliferator-activated receptor-γ, phosphatidylinositol-3-kinase, Akt/PKB, glucose transporter-1, glucose transporter-4, glucokinase in the skeletal muscle; lower glucagon-like peptide 1 (GLP-1) in the intestine; higher sterol regulatory element-binding protein-1 (SREBP-1), stearoyl-CoA desaturase 1 (SCD-1), fatty acid synthase (FAS), 3-hydroxy-3-methylglutaryl-CoA reductase, proprotein convertase subtilisin/kexin type 9 (PCSK9), and lower PPAR-α, low-density lipoprotein receptor, cholesterol-7α-hydroxylase in the liver; higher SREBP-1, SCD-1, FAS, and lower PPAR-α, adiponectin in the adipose tissue were found. In HFD + PGBRE groups, the above biochemical parameters were improved. PRACTICAL APPLICATIONS: According to the results, we suggested that dietary fibers played a minor role in this study. Extract of PGBR, excluding dietary fiber, showed beneficial activity to ameliorate metabolic syndrome. γ-oryzanol, GABA, flavonoids, and anthocyanidin in PGBRE can inhibit HFD-induced metabolic syndrome and we demonstrated clearly its action mechanisms. This is the first report to examine the relation between PGBRE, GLP-1, and PCSK9. Taken together, PGBRE can potentially be used to develop a good supplement to control metabolic syndrome.

Panax ginseng improves glucose metabolism in streptozotocin-induced diabetic rats through 5' adenosine monophosphate kinase up-regulation

5′ AMP-activated protein kinase (AMPK), insulin receptors and transporters are distorted in diabetes mellitus. In this study, the effect of Panax ginseng was assessed on glucose manipulating enzymes activities and gene expression of AMPK, IRA and GLUT2 in streptozotocin-induced diabetic male rats. Forty male albino rats were randomly divided to four groups 10 rats of each, group I, normal control group (received saline orally); group II, normal rats received 200 mg/kg of Panax ginseng orally; group III, Streptozotocin (STZ) –induced diabetic rats and group IV, STZ-induced diabetic rats received 200 mg/kg of Panax ginseng orally. The duration of experiment was 30 days. Results showed the ability of Panax ginseng to induce a significant decrease in the blood glucose and increase in the serum insulin levels, hepatic glucokinase (GK), and glycogen synthase (GS) activities with a modulation of lipid profile besides high expression levels of AMPK, insulin receptor A (IRA), glucose transporting protein-2 (GLUT-2) in liver of diabetic rats. In conclusion, the obtained results point to the ability of Panax ginseng to improve the glucose metabolism in diabetic models.