Insulin-resistant HepG2 Cells Research Articles

Preparation and Characterization of Auricularia cornea Ehrenb Polysaccharide-Zn Complex and Its Hypoglycemic Activity through Regulating Insulin Resistance in HepG2 Cells

With Auricularia cornea Ehrenb polysaccharide (ACEP) as raw material, the purpose of the study was to prepare Auricularia cornea Ehrenb polysaccharide-zinc (ACEP-Zn) complex. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and other means are used to analyze the physical-chemical properties and structure of ACEP and ACEP-Zn, to investigate the inhibition of α-glycosidase and α-amylase enzymes, and to explore its effects on the glucose metabolism of insulin-resistant HepG2 cells. Nuclear magnetic resonance (NMR) results show that a group of COO-, -CH3, and -OH in the sugar chain binds to Zn2+. Compared with the original polysaccharides, the surface morphology of ACEP-Zn changed obviously, and the molecular weight (Mn) of ACEP-Zn decreased, but the molecular agglomeration of ACEP-Zn increased. Moreover, the inhibitory effect of ACEP-Zn on α-glucosidase and α-amylase was stronger than that of the original polysaccharide. The results indicated that the structure of Auricularia cornea Ehrenb polysaccharide was changed obviously after the zinc complex, and its hypoglycemic activity was enhanced in vitro. In the cell experiment, the glucose consumption of IR-HepG2 cells was significantly increased at a concentration of 50–200 μg/mL ( P < 0.05 ). The activity of SOD and NOS significantly increased ( P < 0.01 ), and the activity of intracellular PK increased ( P < 0.05 ). Therefore, it was speculated that the hypoglycemic effect of Auricularia cornea Ehrenb polysaccharide combined with zinc was related to the alleviation of liver cell damage caused by oxidative stress and the improvement of glucose metabolism of IR-HepG2 cells. The study provides a theoretical basis for the application of the polysaccharide-zinc complex in the hypoglycemic functional food field.

Simultaneous Tests of Theaflavin-3,3'-digallate as an Anti-Diabetic Drug in Human Hepatoma G2 Cells and Zebrafish (Danio rerio).

Theaflavin-3,3′-digallate (TF3) is the most important theaflavin monomer in black tea. TF3 was proved to reduce blood glucose level in mice and rats. However, the elaborate anti-diabetic mechanism was not well elucidated. In this work, human hepatoma G2 (HepG2) cells and zebrafish (Danio rerio) were used simultaneously to reveal anti-diabetic effect of TF3. The results showed that TF3 could effectively rise glucose absorption capacity in insulin-resistant HepG2 cells and regulate glucose level in diabetic zebrafish. The hypoglycemic effect was mediated through down-regulating phosphoenolpyruvate carboxykinase and up-regulating glucokinase. More importantly, TF3 could significantly improve β cells regeneration in diabetic zebrafish at low concentrations (5 μg/mL and 10 μg/mL), which meant TF3 had a strong anti-diabetic effect. Obviously, this work provided the potential benefit of TF3 on hypoglycemic effect, regulating glucose metabolism enzymes, and protecting β cells. TF3 might be a promising agent for combating diabetes.

Sea buckthorn leaf L-quebrachitol extract for improved glucose and lipid metabolism in insulin resistant hepG2 cells

L-quebrachitol is a natural monomethyl ether derivative of inositol, and it is abundant in sea buckthorn leaves. In this study, the potential efficacy on hepatic glucose, lipid metabolism disorder, and damaged pathway in vitro of sea buckthorn leaf L-quebrachitol extract (SQE) and L-quebrachitol standard (QS) was evaluated. The SQE and QS exhibited good inhibitory activity on α-amylase, and the kinetic study revealed that their type of enzyme inhibition was competitive inhibition in each case. Both QS and SQE increased the glucose consumption and decreased the contents of total triglyceride (TG) and non-esterified fatty acid (NEFA) in HepG2 cells displaying insulin resistance (IR). In addition, QS and SQE attenuated the expression levels of G6Pase and enhanced the expression of PPARα. These findings suggested that QS and SQE contributed to the modulation of glucose and lipid metabolism, and they might be a promising functional food additives and pharmaceuticals against Type 2 diabetes mellitus (T2DM).

Monitoring the fluctuation of H2S in insulin-resistant HepG2 cells and diabetic mice with a dual-locked NIR fluorescent probe

Diabetes has emerged as a global health challenge and hydrogen sulfide (H2S) is thought to be related to diabetes. We herein reported a dual-locked near-infrared fluorescent probe (DLSP) to monitor the fluctuation of H2S in vitro and in vivo. DLSP displayed excellent selectivity and high sensitivity to H2S comparing with single-locked probes (SLSP-1/2). Using probe DLSP, the visualization of the biosynthesis of endogenous H2S production in insulin-resistant HepG2 cells (IR-HepG2 cells) and the fluctuation of H2S in diabetic mice was realized for the first time.

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.

Interaction and Inhibition of a Ganoderma lucidum Proteoglycan on PTP1B Activity for Anti-diabetes.

Protein tyrosine phosphatase 1B (PTP1B) is a key negative regulator of insulin and an effective target for the treatment of type 2 diabetes (T2D). A natural hyperbranched proteoglycan extracted from Ganoderma lucidum, namely, Fudan-Yueyang G. Lucidum (FYGL), was demonstrated capable of inhibiting the activity of PTP1B. Here, to identify the effective active components of FYGL, three different components, the polysaccharide FYGL-1, proteoglycans FYGL-2, and FYGL-3, were isolated from FYGL, and then, the protein moiety of FYGL-3 was further separated, namely, FYGL-3-P. Their abilities to enhance the glucose uptake in cells and inhibit the activity of PTP1B were compared. The inhibitory mechanisms were systematically explored by spectroscopic methods and MD simulations. The results showed that FYGL-3 and FYGL-3-P significantly enhanced the insulin-provoked glucose uptake in insulin-resistant HepG2 cells, detected by the glucose oxidase method. Also, the FYGL-3-P protein moiety in FYGL played an essential role in inhibiting the activity of PTP1B. A strong, enthalpy-driven, and multitargeted interaction by electrostatic forces between PTP1B and FYGL-3-P dramatically inhibited the catalytic activity of PTP1B. These results provided deep insights into the molecular mechanisms of FYGL inhibiting the activity of PTP1B and structurally helped researchers seek natural PTP1B inhibitors.

ANGPTL8/Betatrophin Improves Glucose Tolerance in Older Mice and Metabolomic Analysis Reveals Its Role in Insulin Resistance in HepG2 Cells.

BackgroundInsulin resistance is a determining factor in the pathophysiology of type 2 diabetes mellitus (T2DM). Angiopoietin-like protein 8 (ANGPTL8, also known as betatrophin), associated with glucose homeostasis and lipid metabolism, has attracted attention. But its mechanism in glucose metabolism remains unclear. This study aimed to explore the effect of ANGPTL8/betatrophin on glucose tolerance in Kunming (KM) mice of different ages and metabolic profiles in insulin-resistant HepG2 cells. Our study may provide a new perspective of ANGPTL8/betatrophin in insulin resistance from the metabolic changes.MethodsOral glucose tolerance test was performed in KM mice of different ages. Insulin concentration was measured by using a quantitative enzyme-linked immunosorbent assay (ELISA). ANGPTL8/betatrophin knockouts in HepG2 cells were established with clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) protein 9 (CRISPR/Cas9) system. Cell counting kit-8 (CCK-8) assay was used to determine cell viability after gene knockout. The effect of ANGPTL8/betatrophin on the metabolomic changes was evaluated in high insulin-induced insulin-resistant HepG2 cells by an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method.ResultsANGPTL8/betatrophin improved glucose tolerance in older mice not by altering the concentration of insulin. Cell growth was affected in ANGPTL8/betatrophin knockout HepG2. Based on UPLC-MS/MS, compared with wild type insulin-resistant HepG2 cells, we identified 83 differential metabolites in ANGPTL8/betatrophin knockout HepG2 cells after high insulin induction. Among the 14 differential up-regulated metabolites, D-mannose had the highest fold change. In insulin-resistant HepG2 cells, ANGPTL8/betatrophin knockout exerted an effect on the amino acid metabolism, carbohydrate metabolism, metabolism of cofactors and vitamins, lipid metabolism, nucleotide metabolism, and genetic information processing pathway.ConclusionThis study identified the effect of ANGPTL8/betatrophin on glucose tolerance in mice of different ages and metabolic profiles in insulin-resistant HepG2 cells. These findings may contribute to a new understanding of its role in glucose metabolism in the context of insulin resistance.

Taurine ameliorates oxidative stress by regulating PI3K/Akt/GLUT4 pathway in HepG2 cells and diabetic rats

The study evaluated the capacity of taurine on insulin resistance amelioration in HepG2 cells induced by BSA and palmitic acid (PA) and diabetes-related metabolic changes in type 2 diabetic rats. In vitro, taurine alleviated insulin resistance in HepG2 cells, increased glucose consumption and improved oxidative stress. Further, taurine could up-regulate the expression of PI3K, Akt and GLUT4, which could improve insulin resistance. In vivo, taurine supplementation markedly regulated blood glucose and improved the oxidative stress in T2DM rats. The improvement of related metabolic parameters and oxidative stress was in part associated with the impact of taurine on activating PI3K, Akt and GLUT4 in liver. In summary, the finding suggested that taurine have potential benefits on improving dysfunction in diabetes rats and mitigating insulin resistance in HepG2 cells via activation of PI3K/Akt/GLUT4 pathways.

Effects of phloridzin on blood glucose and key enzyme G-6-Pase of gluconeogenesis in mice.

The effects of phloridzin (PHL), main component of Malus hupehensis (MH) tea leaves, on blood glucose (BG) and glucose-6-phosphatase (G-6-Pase) were investigated to provide a basis for finding a scheme of stabilizing BG. Glucose uptake of insulin resistant HepG2 cells was measured by glucose oxidase method. Glucose tolerance, fasting BG (FBG) and postprandial BG (PBG) were determined by BG test strips. The expression of G-6-Pase was detected by Western blot. The results showed that glucose uptake was enhanced and the expression of G-6-Pase was inhibited by PHL in insulin resistant HepG2 cells. Glucose tolerance was enhanced, FBG level was increased and PBG level was decreased by PHL in mice. The expression of G-6-Pase in the liver was enhanced under fasting state, and was inhibited by the low and medium dose under postprandial state. It indicated that PHL has a positive effect on stabilizing BG in mice, which is related to bidirectional regulation of G-6-Pase activity. PRACTICAL APPLICATIONS: Malus hupehensis, edible and medicinal plant, which has been proved by long-term application and experiments that it has a good effect on stabilizing blood glucose, preventing diabetes and adjuvant treatment. Its effect is closely related to its main component PHL. Thus, MH can be used as a dietary regulating drink for daily life to maintain blood glucose. Its main ingredient is PHL, which can be developed as a candidate drug for diabetes treatment.

Anti-diabetic effect of aloin via JNK-IRS1/PI3K pathways and regulation of gut microbiota

This research aimed to investigate the antidiabetic activity, underlying mechanisms, and gut microbiota regulation of aloin. The insulin-resistant HepG2 (IR-HepG2) cell model and the type 2 diabetic (T2D) mouse model were successfully established using dexamethasone and a high-fat high-sucrose diet with low-dose streptozotocin, respectively. Aloin intervention increased glucose consumption and stimulated the activity of hexokinase and pyruvate dehydrogenase in IR-HepG2 cells. Additionally, it diminished the weight loss, reduced fasting blood glucose levels and hemoglobin A1c activity, and promoted glucose tolerance and fasting serum insulin activity in T2D mice. Histopathological analysis of the liver indicated hepatic protection by aloin. Additionally, aloin treatment inhibited the protein expression of c-Jun N-terminal kinases and activated that of IRS1/PI3K/Akt in the liver. Moreover, aloin modulated the bacterial community in the gut by raising the abundance of Bacteroidota and reducing the richness of Firmicutes, Proteobacteria, and Actinobacteriota. Thus, aloin ameliorated IR via activating IRS1/PI3K/Akt signaling pathway and regulating the gut microbiota, and it may be promising candidate as functional food for diabetic therapy.

Loureirin B attenuates insulin resistance in HepG2 cells by regulating gluconeogenesis signaling pathway

Insulin resistance (IR) is the main cause of type 2 diabetes. The liver is the organ where insulin is secreted from the pancreas, and it regulates the storage and release of glucose according to the body's demand. Althouth Loureirin B (LB) has been reported to promote insulin secretion and decrease blood glucose, the effects of LB on glucose metabolism in the liver and the mechanism is still unclear. Different concentrations of LB were applied to treat on insulin resistance model (IR-HepG2) cells. The research results showed that LB inhibited the production of ROS (Reactive oxygen species) in IR-HepG2 cells, promoted the phosphorylation of AKT, down-regulated the expression of FoxO1, and up-regulated the expression of IRS1 and GLUT4. In addition, LB also down regulated the glucose metabolism related genes PEPCK and GSK3β. The glucose uptake, consumption and glycogen content were increased. Moreover, LB-treated diabetic mice also showed hypoglycaemic effects. In summary, LB may ameliorate type 2 diabetes by preventing the inactivation of IRS1/AKT pathway in IR-HepG2 cells, increasing insulin sensitivity, and regulating glucose uptake and production.

Evaluation of phytochemicals, antioxidants, and antidiabetic efficacy of various solvent fractions of Gynura procumbens (Lour.) Merr

This work aimed to evaluate the phytochemicals, antioxidants, antidiabetic, and biocompatibility of methanolic extract and its various solvent fractions (hexane, ethyl acetate, methanol, methanol/water) of Gynura procumbens (GP). Among the extract/fractions, ethyl acetate fraction (EA-F) exhibited the higher total phenol content (88.52 ± 1.21 GAE μg/g) and total flavonoid content (51.69 ± 1.16 QE μg/g) with higher DPPH, ABTS radical scavenging, and enzyme inhibition activities. The IC50 of GP-EA-F were 144 ± 12.1 μg/mL for DPPH scavenging, 72 ± 2 μg/mL for ABTS+ scavenging, 90.7 ± 2.5 μg/mL for α-glucosidase inhibition and 136 ± 4 μg/mL for α-amylase inhibition. Also, GP-EA-F augmented the glucose uptake in insulin-resistant (IR) HepG2 cells. Besides, the ultra-high-performance liquid chromatography quadrupole time of flight mass spectrometer (UPLC/QTOF-MS/MS) analysis revealed the presence of phytochemicals including kaempferol, quercetin, caffeoyl-O-hexoside, caffeoylquinic acid, coumaroyl-O-hexoside, and coumaroylquinic acid in GP-EA-F. Further, the molecular docking analysis demonstrated the strong molecular interaction between the digestive enzymes (α-glucosidase and α-amylase) and selected molecules. Hence, this work concluded that GP-EA-F contains potent antidiabetic molecules which deserved further isolation, purification, and pharmacological studies.

Sesquiterpenes and polyphenols with glucose-uptake stimulatory and antioxidant activities from the medicinal mushroom Sanghuangporus sanghuang.

A chemical investigation on the fermentation products of Sanghuangporus sanghuang led to the isolation and identification of fourteen secondary metabolites (1-14) including eight sesquiterpenoids (1-8) and six polyphenols (9-14). Compounds 1-3 were sesquiterpenes with new structures which were elucidated based on NMR spectroscopy, high resolution mass spectrometry (HRMS) and electronic circular dichroism (ECD) data. All the isolates were tested for their stimulation effects on glucose uptake in insulin-resistant HepG2 cells, and cellular antioxidant activity. Compounds 9-12 were subjected to molecular docking experiment to primarily evaluate their anti-coronavirus (SARS-CoV-2) activity. As a result, compounds 9-12 were found to increase the glucose uptake of insulin-resistant HepG2 cells by 18.1%, 62.7%, 33.7% and 21.4% at the dose of 50 μmol·L-1, respectively. Compounds 9-12 also showed good cellular antioxidant activities with CAA50 values of 12.23, 23.11, 5.31 and 16.04 μmol·L-1, respectively. Molecular docking between COVID-19 Mpro and compounds 9-12 indicated potential SARS-CoV-2 inhibitory activity of these four compounds. This work provides new insights for the potential role of the medicinal mushroom S. sanghuang as drugs and functional foods.

Hypoglycemic effect of astragaloside IV via modulating gut microbiota and regulating AMPK/SIRT1 and PI3K/AKT pathway

Ethnopharmacological relevanceRadix Astragali, the dried root of Astragalus mongholicus Bunge, has long been used in traditional Chinese Medicine to treat diabetes. Astragaloside IV (AS-IV), one of the most active ingredients in the root, has been shown to have anti-diabetes ability; however, its underlying mechanism is still unclear. Materials and methodsIn this study, we evaluated the hypoglycemic effect and possible mechanisms of AS-IV in diabetic mice and insulin resistance-HepG2 cells. The components of the intestinal microflora in mice with type 2 diabetes mellitus (T2DM) were determined using high-throughput 16S rRNA gene sequencing. Moreover, the molecular mechanisms of specific members of insulin signaling pathways were analyzed. ResultsAS-IV significantly reversed the abnormalities in blood lipids, glucose, insulin resistance, as well as oxidative stress levels in T2DM mice. Histological finding showed that AS-IV could protect the cellular architecture of the liver and pancreas. AS-IV also regulated the abundance and diversity of intestinal flora of T2DM mice in a positive direction and increased butyric acid levels. The active role of AS-IV as an anti-diabetic compound by regulating the AMPK/SIRT1 and PI3K/AKT signaling pathways was revealed using a T2DM model and verified through the intervention of inhibitors using insulin-resistance HepG2 cells. ConclusionOur results suggested that AS-IV may be used as an anti-diabetic drug candidate owing to its effects of regulating gut microbiota and AMPK/SIRT1 and PI3K/AKT signaling pathways.

Flavonoids from Hypericum patulum enhance glucose consumption and attenuate lipid accumulation in HepG2 cells.

Hypericum patulum has been used as a folk medicine for its varied therapeutic effects including antifungal, wound-healing, spasmolytic, stimulant, hypotensive activities. The water decoction is drank as tea could treat cold, infantile malnutrition. The present study aims to isolate the constituents of the plant and investigate their effects on the glucose consumption in insulin-resistant HepG2 cells,furthermore, lipid metabolism in oleic acid (OA)-treated HepG2 cells was also studied. The phytochemical investigation of the plant led to the isolation of eleven compounds, and their structures were identified by spectroscopic analysis as n-dotriacontanol (1), shikimic acid (2), 1-O-caffeoylquinic acid methyl ester (3), 5-O-caffeoylquinic acid methyl ester (4), 5-O-coumaroylquinic acid methyl ester (5), 5-O-caffeoylquinic acid butyl ester (6), quercetin-3-O-α-L-rhamnoside (7), quercetin (8), quercetin-3-O-(4״-methoxy)-α-L-rahmnopyranosyl (9), hyperoside (10), and rutin (11). The results revealed that compounds 7, 9, and 10 could enhance glucose consumption significantly in hyperglycemia induced HepG2 cells and insulin-resistant HepG2 cells. In addition, the western blotting analysis result exhibited that compounds 7, 9, and 10 in high concentration (5μM, H) group could dramatically upregulate the expression of PPARγ protein, and even the effect of them had no significant difference compared with that of rosiglitazone. Furthermore, compounds 9 and 10 in middle concentration (2.5μM, M) group and H group could dramatically promote triglyceride metabolism and decrease TG content in OA-treated HepG2 cells, and even in H group, reactive oxygen species (ROS) level were significantly decreased compared with model group. PRACTICAL APPLICATIONS: Hypericum patulum is a well-known plant of the genera Hypericum for its varied preventive and therapeutic potential activities. To study the chemical constituents and their effects on glucose and lipid metabolism in vitro, we detected glucose consumption in insulin-resistant HepG2 cells, triglyceride content and reactive oxygen species level in OA-treated HepG2 cells. In addition, PPARγ protein was also detected by western blotting analysis in the study. Compounds 1, 2, 3, 5, 6, 9, 10, and 11 were isolated from the plant for the first time. Quercetin-3-O-(4"-methoxy)-α-L-rahmnopyranosyl (9) and hyperoside (10) had potential therapeutic benefit against glucose and lipid metabolic disease. Therefore, this study might have certain guiding significance for further research and development of H. patulum.

Fruits of Rosa laevigata and its bio-active principal sitostenone facilitate glucose uptake and insulin sensitivity in hepatic cells via AMPK/PPAR-γ activation

BackgroundFruits of Rosa laevigata Michx is commonly used in traditional Chinese medicine for treating of spleen deficiency, chronic diarrhea, and chronic urinary tract infection. Recently, fruits of R. laevigate have been shown to have renal protective effects in diabetic rats. However, up to now, no studies have been reported on the anti-hyperglycemic or anti-diabetic effect of R. laevigata or its derived compounds. PurposeTherefore, this study investigated the anti-diabetic effect of ethanol extract of R. laevigata (EtRL) fruits, its derivate sub-fractions, and pure compounds in terms of glucose-lowering effect on hyperglycemia-induced hepatic cells in vitro. MethodsWe investigated the anti-hyperglycemic effect of EtRL and its derivate sub-fractions (water, n-butanol, ethyl acetate, and n-hexane), and its major bioactive compound, sitostenone, in normal and high glucose-induced insulin-resistant hepatic HepG2 cells using in vitro DNS glucose uptake and Western blotting assays. ResultsTreatment with EtRL and its derivate sub-fractions significantly increased glucose uptake by hepatic cells. Besides, co-treatment with insulin further improved glucose uptake in insulin-resistant cells. Notably, compared with all soluble fractions, the n-hexane sub-fraction displayed the strongest activity in the context of glucose consumption. Furthermore, sitostenone, a primary bioactive compound was isolated from n-hexane sub-fraction by bioactivity-guided fractionation procedure. Sitostenone treatment significantly increased glucose uptake, whereas there was no further increase when co-treatment with insulin. Indeed, sitostenone significantly increased glucose uptake and promote insulin sensitivity in insulin-resistant cells. Further analysis revealed that sitostenone activates proteins involved in the insulin signal transduction pathway, including insulin receptor substrate-1 (IRS-1), AKT, and glycogen synthase kinase 3 β (GSK3β). It was also found that sitostenone provoked glucose uptake in insulin-resistant cells via peroxisome proliferator-activated receptor-γ (PPAR-γ) and AMP-activated protein kinase (AMPK) activation, which facilitates up-regulation of glucose transporters, GLUT2 and GLUT4 in the cell membrane and down-regulation of Forkhead box protein O1 (FOXO1) in the nucleus. ConclusionThis study demonstrating that sitostenone, a steroid-like compound from fruits of R. laevigata has a promising ability to promote glucose uptake and repairs insulin resistance in hepatic cells.

Ginsenoside Rg5 Improves Insulin Resistance and Mitochondrial Biogenesis of Liver via Regulation of the Sirt1/PGC-1α Signaling Pathway in db/db Mice.

Type 2 diabetes mellitus (T2DM) is a common metabolic syndrome that decreases insulin sensitivity and mitochondrial biogenesis in the liver. Our previous study demonstrated that ginsenoside Rg5 (Rg5) could attenuate renal injury in diabetic mice but its underlying mechanism in mitochondrial biogenesis and insulin sensitivity remains poorly understood. In this study, we found that Rg5 intervention significantly inhibited blood glucose increases in db/db mice, improved liver function damage and hepatocyte apoptosis, and activated the IRS-1/phosphatidylinositol 3-kinase/AKT insulin metabolism signaling pathway. Rg5 treatment also increased the level of glycogen synthesis and activated sirtuin1 (Sirt1) to increase glucose uptake and insulin sensitivity in insulin-resistant HepG2 (IR-HepG2) cells. Rg5 intervention also effectively improved liver oxidative stress and inflammation in db/db mice and increased mitochondrial biogenesis caused by T2DM. Additionally, the Rg5 treatment increased the mitochondrial mass in IR-HepG2 cells and activated Sirt1 to regulate the Sirt1/PGC-1α/mitofusin-2 mitochondrial biosynthesis pathway. Our findings demonstrated that Rg5 enhanced liver mitochondrial biogenesis and insulin sensitivity in db/db mice by activating the Sirt1/PGC-1α signaling pathway, suggesting the potential of Rg5 as a natural product for T2DM interventions.

Resveratrol Ameliorates High-Fat-Diet-Induced Abnormalities in Hepatic Glucose Metabolism in Mice via the AMP-Activated Protein Kinase Pathway.

Diabetes mellitus is highly prevalent worldwide. High-fat-diet (HFD) consumption can lead to liver fat accumulation, impair hepatic glycometabolism, and cause insulin resistance and the development of diabetes. Resveratrol has been shown to improve the blood glucose concentration of diabetic mice, but its effect on the abnormal hepatic glycometabolism induced by HFD-feeding and the mechanism involved are unknown. In this study, we determined the effects of resveratrol on the insulin resistance of high-fat-diet-fed mice and a hepatocyte model by measuring serum biochemical indexes, key indicators of glycometabolism, glucose uptake, and glycogen synthesis in hepatocytes. We found that resveratrol treatment significantly ameliorated the HFD-induced abnormalities in glucose metabolism in mice, increased glucose absorption and glycogen synthesis, downregulated protein phosphatase 2A (PP2A) and activated Ca2+/CaM-dependent protein kinase kinase β (CaMKKβ), and increased the phosphorylation of AMP-activated protein kinase (AMPK). In insulin-resistant HepG2 cells, the administration of a PP2A activator or CaMKKβ inhibitor attenuated the effects of resveratrol, but the administration of an AMPK inhibitor abolished the effects of resveratrol. Resveratrol significantly ameliorates abnormalities in glycometabolism induced by HFD-feeding and increases glucose uptake and glycogen synthesis in hepatocytes. These effects are mediated through the activation of AMPK by PP2A and CaMKKβ.

Antidiabetic Function of Lactobacillus fermentum MF423-Fermented Rice Bran and Its Effect on Gut Microbiota Structure in Type 2 Diabetic Mice.

Rice bran is an industrial byproduct that exerts several bioactivities despite its limited bioavailability. In this study, rice bran fermented with Lactobacillus fermentum MF423 (FLRB) had enhanced antidiabetic effects both in vitro and in vivo. FLRB could increase glucose consumption and decrease lipid accumulation in insulin resistant HepG2 cells. Eight weeks of FLRB treatment significantly reduced the levels of blood glucose and lipids and elevated antioxidant activity in type 2 diabetic mellitus (T2DM) mice. H&E staining revealed alleviation of overt lesions in the livers of FLRB-treated mice. Moreover, high-throughput sequencing showed notable variation in the composition of gut microbiota in FLRB-treated mice, especially for short-chain fatty acids (SCFAs)-producing bacteria such as Dubosiella and Lactobacillus. In conclusion, our results suggested that rice bran fermentation products can modulate the intestinal microbiota and improve T2DM-related biochemical abnormalities, so they can be applied as potential probiotics or dietary supplements.

Effect of trivalent chromium on erythropoietin production and the prevention of insulin resistance in HepG2 cells

In erythropoietin (EPO)-producing HepG2 cells, we investigated the effect of trivalent chromium (Cr) on the promotion of EPO production and the induction of insulin resistance. Cr increased hypoxia-inducible factor (HIF)-1α protein, EPO mRNA expression and EPO protein levels in HepG2 cells. The effect of Cr on EPO production was inhibited by inhibition of proliferator-activated receptor γ (PPARγ). Insulin resistance was induced by culturing with insulin resistance induction medium supplemented with palmitic acid for 24 h. When Cr was added to the medium, the increase in glucose-6-phosphatase and phosphoenolpyruvate carboxykinase 1 mRNA expression levels and the decrease in the ratio of phosphorylated Akt to Akt protein were suppressed, and the induction of insulin resistance prevented. When a PPARγ inhibitor or siPPARγ was added together with Cr, the inhibitory effect of Cr on the induction of insulin resistance disappeared. In addition, pretreatment with siEPO suppressed the increase in EPO mRNA expression, and the inhibitory effect on the induction of insulin resistance due to the addition of Cr was significantly reduced. These results suggest that the inhibition of insulin resistance induction by Cr in HepG2 cells involves the promotion of EPO production mediated by PPARγ, in addition to other PPARγ-mediated activities.