Fermentation, Isolation, Structure, and antidiabetic activity of NFAT-133 produced by Streptomyces strain PM0324667

Type-2 diabetes is mediated by defects in either insulin secretion or insulin action. In an effort to identify extracts that may stimulate glucose uptake, similar to insulin, a high throughput-screening assay for measuring glucose uptake in skeletal muscle cells was established. During the screening studies to discover novel antidiabetic compounds from microbial resources a Streptomyces strain PM0324667 (MTCC 5543, the Strain accession number at Institute of Microbial Technology, Chandigarh, India), an isolate from arid soil was identified which expressed a secondary metabolite that induced glucose uptake in L6 skeletal muscle cells. By employing bioactivity guided fractionation techniques, a tri-substituted simple aromatic compound with anti-diabetic potential was isolated. It was characterized based on MS and 2D NMR spectral data and identified as NFAT-133 which is a known immunosuppressive agent that inhibits NFAT-dependent transcription in vitro. Our investigations revealed the antidiabetic potential of NFAT-133. The compound induced glucose uptake in differentiated L6 myotubes with an EC50 of 6.3 ± 1.8 μM without activating the peroxisome proliferator-activated receptor-γ. Further, NFAT-133 was also efficacious in vivo in diabetic animals and reduced systemic glucose levels. Thus it is a potential lead compound which can be considered for development as a therapeutic for the treatment of type-2 diabetes. We have reported herewith the isolation of the producer microbe, fermentation, purification, in vitro, and in vivo antidiabetic activity of the compound

My Sweetheart Is Broken: Role of Glucose in Diabetic Cardiomyopathy

Despite overall reductions in heart disease prevalence, the risk of developing heart failure has remained 2-fold greater among people with diabetes. Growing evidence has supported that fluctuations in glucose level and uptake contribute to cardiovascular disease (CVD) by modifying proteins, DNA, and gene expression. In the case of glucose, clinical studies have shown that increased dietary sugars for healthy individuals or poor glycemic control in diabetic patients further increased CVD risk. Furthermore, even after decades of maintaining tight glycemic control, susceptibility to disease progression can persist following a period of poor glycemic control through a process termed "glycemic memory." In response to chronically elevated glucose levels, a number of studies have identified molecular targets of the glucose-mediated protein posttranslational modification by the addition of an O-linked N-acetylglucosamine to impair contractility, calcium sensitivity, and mitochondrial protein function. Additionally, elevated glucose contributes to dysfunction in coupling glycolysis to glucose oxidation, pentose phosphate pathway, and polyol pathway. Therefore, in the "sweetened" environment associated with hyperglycemia, there are a number of pathways contributing to increased susceptibly to "breaking" the heart of diabetics. In this review we will discuss the unique contribution of glucose to heart disease and recent advances in defining mechanisms of action

Metabolic Origins of Heart Failure

Summary: For more than half a century, metabolic perturbations have been explored in the failing myocardium, highlighting a reversion to a more fetal-like metabolic profile (characterized by depressed fatty acid oxidation and concomitant increased reliance on use of glucose). More recently, alterations in ketone body and amino acid/protein metabolism have been described during heart failure, as well as mitochondrial dysfunction and perturbed metabolic signaling (e.g., acetylation, O-GlcNAcylation). Although numerous mechanisms are likely involved, the current review provides recent advances regarding the metabolic origins of heart failure, and their potential contribution toward contractile dysfunction of the heart. Key Words: amino acids, fatty acids, glucose, heart failure, ketone bodie

The Nova1-Bim axis in pancreatic beta-cells does not impact glucose homeostasis in obesity and multiple low-dose streptozotocin-induced diabetes

info:eu-repo/semantics/publishe

Nova1 or Bim Deficiency in Pancreatic β-Cells Does Not Alter Multiple Low-Dose Streptozotocin-Induced Diabetes and Diet-Induced Obesity in Mice.

The loss of functional pancreatic β-cell mass is an important hallmark of both type 1 and type 2 diabetes. The RNA-binding protein NOVA1 is expressed in human and rodent pancreatic β-cells. Previous in vitro studies indicated that NOVA1 is necessary for glucose-stimulated insulin secretion and its deficiency-enhanced cytokine-induced apoptosis. Moreover, Bim, a proapoptotic protein, is differentially spliced and potentiates apoptosis in NOVA1-deficient β-cells in culture. We generated two novel mouse models by Cre-Lox technology lacking Nova1 (βNova1-/-) or Bim (βBim-/-) in β-cells. To test the impact of Nova1 or Bim deletion on β-cell function, mice were subjected to multiple low-dose streptozotocin (MLD-STZ)-induced diabetes or high-fat diet-induced insulin resistance. β-cell-specific Nova1 or Bim deficiency failed to affect diabetes development in response to MLD-STZ-induced β-cell dysfunction and death evidenced by unaltered blood glucose levels and pancreatic insulin content. In addition, body composition, glucose and insulin tolerance test, and pancreatic insulin content were indistinguishable between control and βNova1-/- or βBim-/- mice on a high fat diet. Thus, Nova1 or Bim deletion in β-cells does not impact on glucose homeostasis or diabetes development in mice. Together, these data argue against an in vivo role for the Nova1-Bim axis in β-cells.info:eu-repo/semantics/publishe

Single-cell sequencing reveals preserved pancreatic islet cell identity by administration of metabolite-based diet in autoimmune diabetes

Background and aims: An altered gut bacterial composition is associatedwith the pathogenesis of type 1 diabetes (T1D) and short-chain fatty acids(SCFA) are known play a pivotal role in maintaining gut homeostasis. Aspecial diet based on high-amylose maize-resistant starch modified withacetate and butyrate metabolites (HAMSAB) provided protection fromautoimmune diabetes in the NOD mouse model. We recently tested theHAMSAB diet in patients with established T1D showing improvement inglucose control. Based on these findings, we studied the molecular mechanisms and effects of SCFA in pre-diabetic pancreatic islets.Materials and methods: EndoC-βH1 and INS-1E β-cell lines weretreated with acetate (250μM), butyrate (10μM) and/or IFN-γ (1,000U/mL) + IL-1β (50U/mL). The cell viability was analyzed using SYTOX™Green Nucleic Acid Stain assay. five-week-old female NOD mice werefed with HAMSAB or HAMS control diet for five consecutive weeks.The pancreata were harvested, islets isolated using collagenase, anddispersed into single cells by trypsin. Single-cell RNA (scRNA)-sequencing was performed with 10x Chromium. The raw counts were analyzedusing RStudio with the Seurat package. The cells were filtered based onRNA features, counts, and mitochondrial percentage and annotated bytheir principal component analysis using UMAP.Results: Physiological concentrations of acetate and/or butyrate showedminimal effects on pro-inflammatory cytokine-induced cell death inEndoC-βH1 and INS-1E β-cell lines, suggesting that improved β-cellfunction is not due to SCFA-induced β-cell survival. To study the effectof the gut metabolites in the endocrine cells, we performed scRNA-seq inpancreatic islets isolated from pre-diabetic NOD mice fed HAMSAB orHAMS diets for five weeks. scRNA-seq analysis mapped the geneexpression profiles of 4,301 and 4,113 individual islet cells fromHAMSAB or HAMS fed mice, respectively. Cells were annotated into12 clusters: 5 immune and 7 pancreatic endocrine cell types. The scRNAseq dataset indicated that T-cells, B-cells, macrophages, and dendritic cellsubsets infiltrated the islets of Langerhans from both HAMSAB andHAMS-fed mice. Interestingly, HAMSAB reduced the number ofCD8+ cytotoxic cells, in line with previously described tolerogeniceffects. Moreover, subclustering and differential gene expression analysisindicated that HAMSAB enhances β-cell function and decreases theirstress response. In addition, the HAMSAB preserved the identity of endocrine cells evaluated by decreased dedifferentiated poly-hormonal (Ins+Gluc, Ins+Sst) cells expressing endocrine progenitor genes (MafA, Nfix)in mice fed this diet.Conclusion: The HAMSAB diet prevents diabetes development in NODmice, at least in part, by enhancing β-cell function and preserving cellidentity of endocrine cells under inflammatory-mediated autoimmunestress.info:eu-repo/semantics/publishe

Antiretroviral therapy potentiates high-fat diet induced obesity and glucose intolerance

Objective: Breakthroughs in HIV treatment, especially combination antiretroviral therapy (ART), have massively reduced AIDS-associated mortality. However, ART administration amplifies the risk of non-AIDS defining illnesses including obesity, diabetes, and cardiovascular disease, collectively known as metabolic syndrome. Initial reports suggest that ART-associated risk of metabolic syndrome correlates with socioeconomic status, a multifaceted finding that encompasses income, race, education, and diet. Therefore, determination of causal relationships is extremely challenging due to the complex interplay between viral infection, ART, and the many environmental factors. Methods: In the current study, we employed a mouse model to specifically examine interactions between ART and diet that impacts energy balance and glucose metabolism. Previous studies have shown that high-fat feeding induces persistent low-grade systemic and adipose tissue inflammation contributing to insulin resistance and metabolic dysregulation via adipose-infiltrating macrophages. Studies herein test the hypothesis that ART potentiates the inflammatory effects of a high-fat diet (HFD). C57Bl/6J mice on a HFD or standard chow containing ART or vehicle, were subjected to functional metabolic testing, RNA-sequencing of epididymal white adipose tissue (eWAT), and array-based kinomic analysis of eWAT-infiltrating macrophages. Results: ART-treated mice on a HFD displayed increased fat mass accumulation, impaired glucose tolerance, and potentiated insulin resistance. Gene set enrichment and kinomic array analyses revealed a pro-inflammatory transcriptional signature depicting granulocyte migration and activation. Conclusion: The current study reveals a HFD-ART interaction that increases inflammatory transcriptional pathways and impairs glucose metabolism, energy balance, and metabolic dysfunction. Keywords: Antiretroviral therapy, Obesity, Glucose intolerance, Adipose tissue inflammation, Insulin resistance, Macrophage activatio

HAMSAB diet ameliorates dysfunctional signaling in pancreatic islets in autoimmune diabetes

Summary: An altered gut microbiota is associated with type 1 diabetes (T1D), affecting the production of short-chain fatty acids (SCFA) and glucose homeostasis. We previously demonstrated that enhancing serum acetate and butyrate using a dietary supplement (HAMSAB) improved glycemia in non-obese diabetic (NOD) mice and patients with established T1D. The effects of SCFA on immune-infiltrated islet cells remain to be clarified. Here, we performed single-cell RNA sequencing on islet cells from NOD mice fed an HAMSAB or control diet. HAMSAB induced a regulatory gene expression profile in pancreas-infiltrated immune cells. Moreover, HAMSAB maintained the expression of β-cell functional genes and decreased cellular stress. HAMSAB-fed mice showed preserved pancreatic endocrine cell identity, evaluated by decreased numbers of poly-hormonal cells. Finally, SCFA increased insulin levels in human β-like cells and improved transplantation outcome in NOD/SCID mice. Our findings support the use of metabolite-based diet as attractive approach to improve glucose control in T1D

Fibroblast growth factor 21 is induced upon cardiac stress and alters cardiac lipid homeostasis

Fibroblast growth factor 21 (FGF21) is a PPARα-regulated gene elucidated in the liver of PPARα-deficient mice or PPARα agonist-treated mice. Mice globally lacking adipose triglyceride lipase (ATGL) exhibit a marked defect in TG catabolism associated with impaired PPARα-activated gene expression in the heart and liver, including a drastic reduction in hepatic FGF21 mRNA expression. Here we show that FGF21 mRNA expression is markedly increased in the heart of ATGL-deficient mice accompanied by elevated expression of endoplasmic reticulum (ER) stress markers, which can be reversed by reconstitution of ATGL expression in cardiac muscle. In line with this assumption, the induction of ER stress increases FGF21 mRNA expression in H9C2 cardiomyotubes. Cardiac FGF21 expression was also induced upon fasting of healthy mice, implicating a role of FGF21 in cardiac energy metabolism. To address this question, we generated and characterized mice with cardiac-specific overexpression of FGF21 (CM-Fgf21). FGF21 was efficiently secreted from cardiomyocytes of CM-Fgf21 mice, which moderately affected cardiac TG homeostasis, indicating a role for FGF21 in cardiac energy metabolism. Together, our results show that FGF21 expression is activated upon cardiac ER stress linked to defective lipolysis and that a persistent increase in circulating FGF21 levels interferes with cardiac and whole body energy homeostasis

Glucose Transporter 4-Deficient Hearts Develop Maladaptive Hypertrophy in Response to Physiological or Pathological Stresses

Pathological cardiac hypertrophy may be associated with reduced expression of glucose transporter 4 (GLUT4) in contrast to exercise-induced cardiac hypertrophy, where GLUT4 levels are increased. However, mice with cardiac-specific deletion of GLUT4 (G4H-/-) have normal cardiac function in the unstressed state. This study tested the hypothesis that cardiac GLUT4 is required for myocardial adaptations to hemodynamic demands. G4H-/- and control littermates were subjected to either a pathological model of left ventricular pressure overload [transverse aortic constriction (TAC)] or a physiological model of endurance exercise (swim training). As predicted after TAC, G4H-/- mice developed significantly greater hypertrophy and more severe contractile dysfunction. Somewhat surprisingly, after exercise training, G4H-/- mice developed increased fibrosis and apoptosis that was associated with dephosphorylation of the prosurvival kinase Akt in concert with an increase in protein levels of the upstream phosphatase protein phosphatase 2A (PP2A). Exercise has been shown to decrease levels of ceramide; G4H-/- hearts failed to decrease myocardial ceramide in response to exercise. Furthermore, G4H-/- hearts have reduced levels of the transcriptional coactivator peroxisome proliferator-activated receptor- γ coactivator-1, lower carnitine palmitoyl-transferase activity, and reduced hydroxyacyl-CoA dehydrogenase activity. These basal changes may also contribute to the impaired ability of G4H-/- hearts to adapt to hemodynamic stresses. In conclusion, GLUT4 is required for the maintenance of cardiac structure and function in response to physiological or pathological processes that increase energy demands, in part through secondary changes in mitochondrial metabolism and cellular stress survival pathways such as Akt. NEW & NOTEWORTHY Glucose transporter 4 (GLUT4) is required for myocardial adaptations to exercise, and its absence accelerates heart dysfunction after pressure overload. The requirement for GLUT4 may extend beyond glucose uptake to include defects in mitochondrial metabolism and survival signaling pathways that develop in its absence. Therefore, GLUT4 is critical for responses to hemodynamic stresses