Insulin Resistance In Mice Research Articles

Antidiabetic activity of Tartary buckwheat protein-derived peptide AFYRW and its effects on protein glycosylation of pancreas in mice.

Diabetes Mellitus (DM) is one of the most important public health problems, and new antidiabetic drugs with fewer side effects are urgently needed. Here, we measured the antidiabetic effects of an antioxidant peptide (Ala-Phe-Tyr-Arg-Trp, AFYRW) from Tartary Buckwheat Albumin (TBA) in a high-fat diet/streptozotocin (HFD/STZ)-induced diabetic mouse model. The data showed that AFYRW suppressed hepatocyte steatosis and triglycerides while ameliorating insulin resistance in mice. Successively, the influence of AFYRW on aberrant protein glycosylation in diabetic mice was further investigated by lectin microarrays. The results suggested AFYRW could restore the expression of GalNAc, GalNAcα1-3Gal and GalNAcα1-3Galβ1-3/4Glc recognized by PTL-I, Siaα2-3Galβ1-4Glc(NAc)/Glc, Siaα2-3Gal, Siaα2-3 and Siaα2-3GalNAc recognized by MAL-II, terminating in GalNAcα/β1-3/6Gal recognized by WFA and αGalNAc, αGal, anti-A and B recognized by GSI-I to normal levels in the pancreas of HFD-STZ-induced diabetic mice. This work may provide new targets for the future discovery of potential biomarkers to evaluate the efficacy of food-derived antidiabetic drugs based on precise alterations of glycopatterns in DM.

Reciprocal Regulation of Hepatic TGF-β1 and Foxo1 Controls Gluconeogenesis and Energy Expenditure.

Hepatic TGF-β1 levels are increased in obese humans and mice. Hepatic TGF-β1 maintains glucose homeostasis in lean mice and causes glucose and energy dysregulations in obese and diabetic mice. Hepatic TGF-β1 exerts an autocrine effect to promote hepatic gluconeogenesis via cAMP-dependent protein kinase-mediated Foxo1 phosphorylation at serine 273, endocrine effects on brown adipose tissue action, and inguinal white adipose tissue browning (beige fat), causing energy imbalance in obese and insulin-resistant mice. TGF-β1→Foxo1→TGF-β1 looping in hepatocytes plays a critical role in controlling glucose and energy metabolism in health and disease.

1561-P: Dietary Proteins Impact Glucose Tolerance and Hepatic Insulin Resistance in Mice through Modulation of the Urea Cycle

We recently reported that dietary proteins (DP) modulate diet-induced obesity and insulin resistance in mice (Nat Commun 12: 3377, 2021). We posit that these metabolic alterations are caused by differential activation of the hepatic urea cycle in response to different amino acid (AA) compositions and total nitrogen load. Objective: To test whether DP sources alter hepatic metabolism and insulin resistance through the urea cycle. Methods: Metabolic phenotypes, hepatic urea cycle and insulin resistance were measured in mice fed low-fat, low-sucrose (LFLS) or high-fat, high-sucrose (HFHS) diets containing either pork (PP), soy (SP) or casein (CP) protein for 12 weeks. Based on their AA composition, PP had the highest nitrogen load, followed by SP and CP. Results: When compared to SP and CP, feeding PP to HFHS mice induced more glucose intolerance which was correlated with higher post-prandial AA-derived nitrogen load in the portal vein. PP feeding in HFHS mice induced hepatic insulin resistance, revealed by impaired insulin-induced Akt phosphorylation on Ser473. Mice fed the LFLS diet were, however, protected from PP-induced glucose intolerance and insulin resistance, and this was associated with robust increase in the protein levels of urea cycle enzymes (CPS1, OTC) in the liver. In starked contrast, induction of urea cycle enzymes was blunted in the liver of PP-fed HFHS mice. PP feeding also increased the expression of inducible nitric oxide synthase (iNOS) and reactive oxygen species (ROS) as showed by DHE staining of liver sections. Conclusion: Dietary PP increases total nitrogen load activating the urea cycle, which may protect against metabolic dysfunction and hepatic insulin resistance in LFLS mice. This protective mechanism is lost in PP-fed HFHS mice, likely by downregulation of urea cycle activity, when the liver is overloaded with dietary fat. iNOS induction could be acting as an alternative nitrogen handling pathway, causing a build-up of mitochondrial ROS. Disclosure F.Bégin: None. A.Caron: None. A.Marette: Advisory Panel; Valbiotis, Amancia, Plexus, Acasti.

Long-Term Consumption of Sucralose Induces Hepatic Insulin Resistance through an Extracellular Signal-Regulated Kinase 1/2-Dependent Pathway.

Sugar substitutes have been recommended to be used for weight and glycemic control. However, numerous studies indicate that consumption of artificial sweeteners exerts adverse effects on glycemic homeostasis. Although sucralose is among the most extensively utilized sweeteners in food products, the effects and detailed mechanisms of sucralose on insulin sensitivity remain ambiguous. In this study, we found that bolus administration of sucralose by oral gavage enhanced insulin secretion to decrease plasma glucose levels in mice. In addition, mice were randomly allocated into three groups, chow diet, high-fat diet (HFD), and HFD supplemented with sucralose (HFSUC), to investigate the effects of long-term consumption of sucralose on glucose homeostasis. In contrast to the effects of sucralose with bolus administration, the supplement of sucralose augmented HFD-induced insulin resistance and glucose intolerance, determined by glucose and insulin tolerance tests. In addition, we found that administration of extracellular signal-regulated kinase (ERK)-1/2 inhibitor reversed the effects of sucralose on glucose intolerance and insulin resistance in mice. Moreover, blockade of taste receptor type 1 member 3 (T1R3) by lactisole or pretreatment of endoplasmic reticulum stress inhibitors diminished sucralose-induced insulin resistance in HepG2 cells. Taken together, sucralose augmented HFD-induced insulin resistance in mice, and interrupted insulin signals through a T1R3-ERK1/2-dependent pathway in the liver.

1603-P: Differential Effects of Cocoa Butter, Sunflower, Soybean, and Fish Oil Based Sucrose-Free HFDs on Hepatic Steatosis, Lipogenesis, Inflammation, and Insulin Resistance in Mice

Nonalcoholic fatty liver disease (NAFLD) is a risk factor of type-2 diabetes and cardiovascular disease. Obesity induced by various high-fat diets from different sources results in different types of meta-inflammatory derangements, including NAFLD. Fats are a central part of healthy diets, however, the impact of various dietary fats, lacking in sucrose, on liver fat accumulation and expression of lipogenic and inflammatory markers remains unclear. To study this, C57BL/6J mice were fed sucrose-free HFDs comprising fat from diverse sources, including cocoa butter (c-HFD), sunflower oil (s-HFD), soybean oil (so-HFD), and fish oil (f-HFD). Mice fed c-HFD or so-HFD developed more severe liver steatosis, compared with those fed s-HFD or f-HFD. Liver histopathology displayed high levels of lobular inflammation in mice fed c-HFD, so-HFD, and s-HFD. Kupffer cell counts were higher in mice fed c-HFD and s-HFD. Hepatic fibrosis was seen in mice fed s-HFD or so-HFD. Of note, there was no hepatic fibrosis in mice fed f-HFD. None of the diet had a significant impact on total body weight. However, liver weight was slightly increased in mice fed c-HFD or s-HFD. Mice fed c-HFD, s-HFD, and so-HFD displayed insulin resistance. Expression of the key genes of glycolysis (Pklr), de novo lipogenesis (Acaca, Fasn, Scd1), fatty acid oxidation (Cpt1a, Ppar-α), inflammation (Tnf-α) was upregulated in mice fed c-HFD or s-HFD. No significant difference was seen regarding genes of fatty acid uptake (Cd36, Fabp2), and chemokine-associated inflammation (Ccl2). Interestingly, hepatic IL-1β and IL-6 were elevated only in mice fed c-HFD. Taken together, these findings indicate that mice fed the sucrose-free HFDs comprising lipids from various dietary sources may have differential effects on hepatic steatosis at levels of de novo lipogenesis, hepatic inflammation, and whole-body insulin resistance. Disclosure R. Ahmad: None. T.K. Jacob: None. S.P. Kochumon: None. R.S. Thomas: None. S. Shenouda: None. N. Akhter: None. A. Wilson: None. F. Bahman: None. A. Hasan: None. F. Alrashed: None. H. Arefanian: None. A. Al Madhoun: None. F. Almulla: None. S.T.K. Sindhu: None. Funding Kuwait Foundation for the Advancement of Sciences (RAAM-2016-007)

363-OR: Brown Adipose Tissue m6A mRNA Methylation Regulates Systemic Insulin Sensitivity via a Prostaglandin Interorgan Axis

Brown adipose tissue (BAT) has the capacity to regulate peripheral insulin sensitivity via the secretion of signaling lipids. N6-methyladenosine (m6A) is among the most prevalent and abundant post-transcriptional RNA modifications in eukaryotes. Recently, m6A has been shown to regulate islet and hepatic metabolism as well as BAT adipogenesis and energy expenditure. Here, we demonstrate that deficiency of m6A methyltransferase-like 14 (M14) in BAT positively regulates BAT-secretory function to improve systemic insulin sensitivity through inter-organ communication. Using lipidomic approaches, we identified prostaglandin E2 (PGE2) and prostaglandin F2a (PGF2a) as M14KOBAT-secreted insulin sensitizers. Notably, circulatory PGE2 and PGF2a showed significant inverse correlation with HOMA-IR in humans. Furthermore, in vivo administration of PGE2 and PGF2a in HFD-induced insulin resistant obese mice recapitulated the phenotypes of M14KO mice. Exogenous PGE2 or PGF2a significantly improved insulin stimulated-pAKT by suppressing expression of specific phosphatases in human hepatocyte cell line. Mechanistically, M14-mediated m6A installation destabilizes transcripts encoding PGE2 and PGF2a synthases in brown adipocytes in an YTHDF2/3-dependent manner. Collectively, these results unveil a new mechanism by which m6A-facilitated BAT-secretory function enables the regulation of whole body insulin sensitivity. Disclosure L.Xiao: None. J.Pihlajamaki: None. Y.Tseng: Consultant; Cellarity, LyGenesis. R.Kulkarni: Advisory Panel; Novo Nordisk, Inversago, Biomea Fusion, Inc., REDD Pharma, Research Support; Inversago. D.F.De jesus: None. C.Ju: None. J.Wei: None. J.Hu: None. T.Tsuji: None. C.Cero: None. D.Kaminska: None. A.M.Cypess: None.

838-P: Reversion of Nonalcoholic Steatohepatitis by Skeletal-Muscle Directed FGF21 Gene Therapy

Nonalcoholic steatohepatitis (NASH) is a severe form of nonalcoholic fatty liver disease, which is driven by the global obesity and type 2 diabetes epidemic. NASH is characterized by liver inflammation and fibrosis that can progress to cirrhosis, liver failure, cancer and death. Currently, NASH is an unmet medical need. Recent studies revealed the therapeutic potential of fibroblast growth factor 21 (FGF21) analogues/mimetics against NASH in pre-clinical models and in human patients, although periodic administrations are required and immunological responses may raise due to the use of engineered, non-native, proteins. Here, we demonstrated that adeno-associated viral (AAV) vector-mediated-FGF21 genetic engineering of skeletal muscle of high-fat diet-fed obese and insulin-resistant mice resulted in increased circulating levels of native FGF21. AAV-FGF21-treatment normalized liver fat content, liver inflammatory and fibrotic markers and counteracted hepatocyte damage, consistent with NASH resolution. It also precluded progression from NASH to cirrhosis and hepato-cellular carcinoma. Moreover, circulating FGF21 reversed adipose tissue hypertrophy and inflammation, increased energy expenditure, normalized glycemia and insulinemia, and increased insulin sensitivity. Scale-up of muscular FGF21 gene transfer to large animals also successfully resulted in long-term secretion of biologically active FGF21 and therapeutic effects in key target tissues, in the absence of adverse events. All these results point out the potential of the AAV-FGF21-mediated gene therapy to treat NASH and support the clinical translation of the approach. Disclosure V. Jimenez: None. V. Sacristán: None. C. Jambrina: None. M. Jaén: None. S.A. Munoz: None. E. Casana: None. M. Garcia: None. I. Grass: None. X. Leon: None. I. Elias: None. A. Ribera: None. G. Elias: None. V. Sanchez: None. A. Casellas: None. T. Ferré: None. M. Molas: None. F. Bosch: None.

Excess pancreatic elastase alters acinar-β cell communication by impairing the mechano-signaling and the PAR2 pathways

Type 1 (T1D) or type 2 diabetes (T2D) are caused by a deficit of functional insulin-producing β cells. Thus, the identification of β cell trophic agents could allow the development of therapeutic strategies to counteract diabetes. The discovery of SerpinB1, an elastase inhibitor that promotes human β cell growth, prompted us to hypothesize that pancreatic elastase (PE) regulates β cell viability. Here, we report that PE is up-regulated in acinar cells and in islets from T2D patients, and negatively impacts β cell viability. Using high-throughput screening assays, we identified telaprevir as a potent PE inhibitor that can increase human and rodent β cell viability invitro and invivo and improve glucose tolerance in insulin-resistant mice. Phospho-antibody microarrays and single-cell RNA sequencing analysis identified PAR2 and mechano-signaling pathways as potential mediators of PE. Taken together, our work highlights PE as a potential regulator of acinar-β cell crosstalk that acts to limit β cell viability, leading to T2D.

Effects of the pesticide deltamethrin on high fat diet-induced obesity and insulin resistance in male mice.

Worldwide, rates of metabolic diseases are rapidly increasing and environmental exposure to pesticides, pollutants and/or other chemicals may play a role. Reductions in Brown Adipose Tissue (BAT) thermogenesis, mediated in part by uncoupling protein 1 (Ucp1), are associated with metabolic diseases. In the current study, we investigated whether the pesticide deltamethrin (0.01-1mg/kg bw/day) incorporated into a high-fat diet and fed to mice housed at either room temperature (21°C) or thermoneutrality (29°C) would suppress BAT activity and accelerate the development of metabolic disease. Importantly, thermoneutrality allows for more accurate modeling of human metabolic disease. We found that, 0.01mg/kg bw/day of deltamethrin induced weight loss, improved insulin sensitivity and increased energy expenditure, effects that were associated with increases in physical activity. In contrast, exposure to 0.1 and 1mg/kg bw/day deltamethrin had no effect on any of the parameters examined. Deltamethrin treatment in mice did not alter molecular markers of BAT thermogenesis, despite observing suppression of UCP1 expression in cultured brown adipocytes. These data indicate that while deltamethrin inhibits UCP1 expression in vitro, 16wks exposure does not alter BAT thermogenesis markers nor exacerbates the development of obesity and insulin resistance in mice.

Hachimijiogan, a traditional herbal medicine, modulates adipose cell function and ameliorates diet-induced obesity and insulin resistance in mice.

Hachimijiogan (HJG) has originally been used to ameliorate a variety of symptoms associated with low ambient temperatures. However, its pharmacological action in metabolic organs remains unclear. We hypothesized that HJG may modulate metabolic function and have a potential therapeutic application to metabolic diseases. To test this hypothesis, we investigated metabolic action of HJG in mice. Male C57BL/6J mice chronically administered with HJG showed a reduction in adipocyte size with increased transcription of beige adipocyte-related genes in subcutaneous white adipose tissue. HJG-mixed high-fat diet (HFD)-fed mice showed alleviation of HFD-induced weight gain, adipocyte hypertrophy, liver steatosis with a significant reduction in circulating leptin and Fibroblast growth factor 21 despite no changes in food intake or oxygen consumption. Feeding an HJG-mixed HFD following 4-weeks of HFD feeding, while a limited effect on body weight, improved insulin sensitivity with a reversal of decreased circulating adiponectin. In addition, HJG improved insulin sensitivity in the leptin-deficient mice without significant effects on body weight. Treatment with n-butanol soluble extracts of HJG potentiated transcription of Uncoupling protein 1 mediated by β3-adrenergic agonism in 3T3L1 adipocytes. These findings provide evidence that HJG modulates adipocyte function and may exert preventive or therapeutic effects against obesity and insulin resistance.

Supplementation with a New Standardized Extract of Green and Black Tea Exerts Antiadipogenic Effects and Prevents Insulin Resistance in Mice with Metabolic Syndrome.

Insulin resistance is one of the main characteristics of metabolic syndrome (MetS) and the main cause of the development of type II diabetes. The high prevalence of this syndrome in recent decades has made it necessary to search for preventive and therapeutic agents, ideally of natural origin, with fewer side effects than conventional pharmacological treatments. Tea is widely known for its medicinal properties, including beneficial effects on weight management and insulin resistance. The aim of this study was to analyze whether a standardized extract of green and black tea (ADM® Complex Tea Extract (CTE)) prevents the development of insulin resistance in mice with MetS. For this purpose, C57BL6/J mice were fed for 20 weeks with a standard diet (Chow), a diet with 56% kcal from fat and sugar (HFHS) or an HFHS diet supplemented with 1.6% CTE. CTE supplementation reduced body weight gain, adiposity and circulating leptin levels. Likewise, CTE also exerted lipolytic and antiadipogenic effects in 3T3-L1 adipocyte cultures and in the C. elegans model. Regarding insulin resistance, CTE supplementation significantly increased plasma adiponectin concentrations and reduced the circulating levels of insulin and the HOMA-IR. Incubation of liver, gastrocnemius muscle and retroperitoneal adipose tissue explants with insulin increased the pAkt/Akt ratio in mice fed with Chow and HFHS + CTE but not in those fed only with HFHS. The greater activation of the PI3K/Akt pathway in response to insulin in mice supplemented with CTE was associated with a decrease in the expression of the proinflammatory markers Mcp-1, IL-6, IL-1β or Tnf-α and with an overexpression of the antioxidant enzymes Sod-1, Gpx-3, Ho-1 and Gsr in these tissues. Moreover, in skeletal muscle, mice treated with CTE showed increased mRNA levels of the aryl hydrocarbon receptor (Ahr), Arnt and Nrf2, suggesting that the CTE's insulin-sensitizing effects could be the result of the activation of this pathway. In conclusion, supplementation with the standardized extract of green and black tea CTE reduces body weight gain, exerts lipolytic and antiadipogenic effects and reduces insulin resistance in mice with MetS through its anti-inflammatory and antioxidant effects.

Cellular cholesterol homeostasis supports visceral adipose tissue (VAT) regulatory T cell (Treg) accumulation and promotes metabolic health

Abstract A unique population of regulatory T cells (Tregs), characterized by a clonally expanded TCR repertoire and distinct transcriptional profile, is highly enriched in the visceral adipose tissue (VAT) at steady state but is lost during obesity, which exacerbates VAT inflammation and promotes metabolic disease. Therefore, understanding the factors that control the accumulation of VAT Tregs, which might be dysregulated during obesity, is important for developing novel therapies for obesity-associated metabolic diseases. Here we show that cellular cholesterol homeostasis is particularly important for VAT Treg accumulation and function. First, bulk RNA sequencing analysis of VAT Tregs from mice fed long-term high fat diet (HFD) showed a reduction in gene expression involved in cholesterol homeostasis (CH), corresponding to loss of VAT Tregs in vivo. Second, we found that VAT Tregs showed increased cholesterol-associated gene expression, cholesterol levels, and cholesterol uptake compared to lymphoid Tregs at steady state, suggesting this pathway is particularly important for VAT Tregs. Third, CRISPR-Cas9-mediated ablation of Srebf2, the master regulator of cholesterol homeostasis, followed by adoptive Treg transfer or Treg-specific germline deletion of Srebf2(Foxp3cre Srebf2-flox) reduced Tregs in the VAT, but not those in other tissues. Deletion of Srebf2in Tregs also increased VAT inflammatory cytokine expression, inflammatory cell infiltration, and insulin resistance in mice following short-term HFD feeding. These data highlight an importance of cellular CH for VAT Treg accumulation and function and implicate this pathway as a potential therapeutic target for treatment of obesity-associated metabolic diseases. NIH R01 (5R01DK128061-02)

Evaluation of the effect of interleukin-1 receptor associated kinase (IRAK) inhibitor on PPAR.γ and GLUT.4 genes expression in muscle tissueof insulin resistant mice

Evaluation of the effect of interleukin-1 receptor associated kinase (IRAK) inhibitor on PPAR.γ and GLUT.4 genes expression in muscle tissueof insulin resistant mice

Heptadecanoic Acid Is Not a Key Mediator in the Prevention of Diet-Induced Hepatic Steatosis and Insulin Resistance in Mice.

Epidemiological studies found that the intake of dairy products is associated with an increased amount of circulating odd-chain fatty acids (OCFA, C15:0 and C17:0) in humans and further indicate that especially C17:0 is associated with a lower incidence of type 2 diabetes. However, causal relationships are not elucidated. To provide a mechanistic link, mice were fed high-fat (HF) diets supplemented with either milk fat or C17:0 for 20 weeks. Cultured primary mouse hepatocytes were used to distinguish differential effects mediated by C15:0 or C17:0. Despite an induction of OCFA after both dietary interventions, neither long-term milk fat intake nor C17:0 supplementation improved diet-induced hepatic lipid accumulation and insulin resistance in mice. HF feeding with milk fat actually deteriorates liver inflammation. Treatment of primary hepatocytes with C15:0 and C17:0 suppressed JAK2/STAT3 signaling, but only C15:0 enhanced insulin-stimulated phosphorylation of AKT. Overall, the data indicate that the intake of milk fat and C17:0 do not mediate health benefits, whereas C15:0 might be promising in further studies.

Distinct Metabolomic Profiling of Serum Samples from High-Fat-Diet-Induced Insulin-Resistant Mice.

High-fat-diet (HFD)-induced obesity is associated with an elevated risk of insulin resistance (IR), which may precede the onset of type 2 diabetes mellitus and associated metabolic complications. Being a heterogeneous metabolic condition, it is pertinent to understand the metabolites and metabolic pathways that are altered during the development and progression of IR toward T2DM. Serum samples were collected from C57BL/6J mice fed with HFD or chow diet (CD) for 16 weeks. Collected samples were analyzed by gas chromatography-tandem mass spectrometry (GC-MS/MS). Data on the identified raw metabolites were evaluated using a combination of univariate and multivariate statistical methods. Mice fed with HFD had glucose and insulin intolerance associated with impairment of insulin signaling in key metabolic tissues. From the GC-MS/MS analysis of serum samples, a total of 75 common annotated metabolites were identified between HFD- and CD-fed mice. In the t-test, 22 significantly altered metabolites were identified. Out of these, 16 metabolites were up-accumulated, whereas 6 metabolites were down-accumulated. Pathway analysis identified 4 significantly altered metabolic pathways. In particular, primary bile acid biosynthesis and linoleic acid metabolism were upregulated, whereas the TCA cycle and pentose and glucuronate interconversion were downregulated in HFD-fed mice in comparison to CD-fed mice. These results show the distinct metabolic profiles associated with the onset of IR that could provide promising metabolic biomarkers for diagnostic and clinical applications.

Carboxylesterase 2a deletion provokes hepatic steatosis and insulin resistance in mice involving impaired diacylglycerol and lysophosphatidylcholine catabolism

ObjectiveHepatic triacylglycerol accumulation and insulin resistance are key features of NAFLD. However, NAFLD development and progression are rather triggered by the aberrant generation of lipid metabolites and signaling molecules including diacylglycerol (DAG) and lysophosphatidylcholine (lysoPC). Recent studies showed decreased expression of carboxylesterase 2 (CES2) in the liver of NASH patients and hepatic DAG accumulation was linked to low CES2 activity in obese individuals. The mouse genome encodes several Ces2 genes with Ces2a showing highest expression in the liver. Herein we investigated the role of mouse Ces2a and human CES2 in lipid metabolism in vivo and in vitro. MethodsLipid metabolism and insulin signaling were investigated in mice lacking Ces2a and in a human liver cell line upon pharmacological CES2 inhibition. Lipid hydrolytic activities were determined in vivo and from recombinant proteins. ResultsCes2a deficient mice (Ces2a-ko) are obese and feeding a high-fat diet (HFD) provokes severe hepatic steatosis and insulin resistance together with elevated inflammatory and fibrotic gene expression. Lipidomic analysis revealed a marked rise in DAG and lysoPC levels in the liver of Ces2a-ko mice fed HFD. Hepatic lipid accumulation in Ces2a deficiency is linked to lower DAG and lysoPC hydrolytic activities in liver microsomal preparations. Moreover, Ces2a deficiency significantly increases hepatic expression and activity of MGAT1, a PPAR gamma target gene, suggesting aberrant lipid signaling upon Ces2a deficiency. Mechanistically, we found that recombinant Ces2a and CES2 show significant hydrolytic activity towards lysoPC (and DAG) and pharmacological inhibition of CES2 in human HepG2 cells largely phenocopies the lipid metabolic changes present in Ces2a-ko mice including reduced lysoPC and DAG hydrolysis, DAG accumulation and impaired insulin signaling. ConclusionsCes2a and CES2 are critical players in hepatic lipid signaling likely via the hydrolysis of DAG and lysoPC at the ER.

Tripeptide IRW Improves AMPK/eNOS Signaling Pathway via Activating ACE2 in the Aorta of High-Fat-Diet-Fed C57BL/6 Mice.

This study aims to investigate the effect of tripeptide IRW on the local renin-angiotensin system (RAS), particularly angiotensin-converting enzyme 2 (ACE2), and their association with signaling pathways in the aorta of a high-fat-diet (HFD)-induced insulin-resistant mouse model. C57BL/6 mice were fed HFD (45% of the total calories) for six weeks, and then IRW was added to the diet (45 mg/kg body weight (BW)) for another eight weeks. ACE2 mRNA expression and protein level(s) were increased (p < 0.05), while angiotensin II receptor (AT1R) and angiotensin-converting enzyme (ACE) protein abundance was significantly reduced (p < 0.05) in the aorta of HFD mice treated by IRW. IRW supplementation also improved glucose transporter 4 (GLUT4) abundance (p < 0.05) alongside AMP-activated protein kinase (AMPK) (p < 0.05), Sirtuin 1 (SIRT1) (p < 0.05), and endothelial nitric oxide synthase (eNOS) (p < 0.05) expression. IRW downregulated the levels of endothelin 1 (ET-1) and p38 mitogen-activated protein kinases (p38 MAPK, p < 0.05). Furthermore, the levels of AMPK and eNOS in vascular smooth muscle cells (VSMCs) were significantly reduced in ACE2 knockdown cells treated with or without IRW (p < 0.01). In conclusion, this study provided new evidence of the regulatory role of IRW on the aortic ACE2 against metabolic syndrome (MetS) in an HFD-induced insulin-resistant model.

TXLNG improves insulin resistance in obese subjects in vitro and in vivo by inhibiting ATF4 transcriptional activity

Lipotoxicity contributes to insulin resistance and dysfunction of pancreatic β-cells. Insulin promotes 3T3-L1 preadipocyte differentiation and facilitates glucose entry into muscle, adipose, and other tissues. In this study, differential gene expression was analyzed using four datasets, and taxilin gamma (TXLNG) was the only shared downregulated gene in all four datasets. TXLNG expression was significantly reduced in obese subjects according to online datasets and in high-fat diet (HFD)-induced insulin-resistant (IR) mice according to experimental investigations. TXLNG overexpression significantly improved IR induced by HFD in mouse models by reducing body weight and epididymal adipose weight, decreasing mRNA expression of pro-inflammatory factors interleukin 6 (IL-6) and tumor necrosis factor alpha (TNF-α), and reducing adipocyte size. High-glucose/high-insulin-stimulated adipocytes exhibited decreased TXLNG and increased signal transducer and activator of transcription 3 (STAT3) and activating transcription factor 4 (ATF4). IR significantly decreased glucose uptake, cell surface glucose transporter type 4 (GLUT4) levels, and Akt phosphorylation, while increasing the mRNA expression levels of IL-6 and TNF-α in adipocytes. However, these changes were significantly reversed by TXLNG overexpression, while they were exacerbated by TXLNG knockdown. TXLNG overexpression had no effect on ATF4 protein levels, while ATF4 overexpression increased ATF4 protein levels. Furthermore, ATF4 overexpression notably abolished the improvements in IR adipocyte dysfunction caused by TXLNG overexpression. In conclusion, TXLNG improves IR in obese subjects in vitro and in vivo by inhibiting ATF4 transcriptional activity.

Douchi Peptides Vy and Sfllr Improve Glucose Homeostasis and Gut Dysbacteriosis In High-Fat Diet-Induced Insulin Resistant Mice.

Two peptides VY (Val-Tyr) and SFLLR (Ser-Phe-Leu-Leu-Arg) were recently identified from soy-fermented douchi with hypoglycemic activity in cells. The study aimed to understand their potential effects on glucose metabolism and insulin sensitivity as well as their mechanisms of action in a high-fat diet (HFD) induced insulin resistant model. C57BL/6 mice were fed HFD for 8 weeks, followed by peptide supplementation (doses: 10 and 50 mg/kg body weight) for 8 weeks. Peptides supplementation, especially SFLLR, reduced body weight gain, insulin resistance, hyperglycemia, inflammation, liver injury, and lipid accumulation. In both muscle and liver, both peptides activated glycogen synthase (GS), the key enzyme for glycogen synthesis, and also inhibited phosphoenolpyruvate carboxykinase (PEPCK) and glucose 6-phosphatase (G6PC), two rate-limiting enzymes for gluconeogenesis, via insulin and AMPK (5' adenosine monophosphate-activated protein kinase) signalling pathways. Furthermore, VY and SFLLR supplementation reversed HFD-induced gut dysbacteriosis by decreasing the abundance of Enterococcus, Oscillibacter, and Deferribacter, and also increased the abundances of Alistipes, Lactobacillus, Faecalibaculum, Akkermansia, and Bifidobacterium (usually beneficial in the intestine). Our study revealed the potential applications of peptides VY and SFLLR as a diet-based strategy for the prevention of type 2 diabetes. This article is protected by copyright. All rights reserved.

The effect of G0S2 on insulin sensitivity: A proteomic analysis in a G0S2-overexpressed high-fat diet mouse model.

Previous research has shown a tight relationship between the G0/G1 switch gene 2 (G0S2) and metabolic diseases such as non-alcoholic fatty liver disease (NAFLD) and obesity and diabetes, and insulin resistance has been shown as the major risk factor for both NAFLD and T2DM. However, the mechanisms underlying the relationship between G0S2 and insulin resistance remain incompletely understood. Our study aimed to confirm the effect of G0S2 on insulin resistance, and determine whether the insulin resistance in mice fed a high-fat diet (HFD) results from G0S2 elevation. In this study, we extracted livers from mice that consumed HFD and received tail vein injections of AD-G0S2/Ad-LacZ, and performed a proteomics analysis. Proteomic analysis revealed that there was a total of 125 differentially expressed proteins (DEPs) (56 increased and 69 decreased proteins) among the identified 3583 proteins. Functional enrichment analysis revealed that four insulin signaling pathway-associated proteins were significantly upregulated and five insulin signaling pathway -associated proteins were significantly downregulated. These findings show that the DEPs, which were associated with insulin resistance, are generally consistent with enhanced insulin resistance in G0S2 overexpression mice. Collectively, this study demonstrates that G0S2 may be a potential target gene for the treatment of obesity, NAFLD, and diabetes.