Trans-ethnic gut microbial signatures of prediabetic subjects from India and Denmark.

BACKGROUND: Recent studies have indicated an association of gut microbiota and microbial metabolites with type 2 diabetes mellitus (T2D). However, large-scale investigation of the gut microbiota of "prediabetic" (PD) subjects has not been reported. Identifying robust gut microbiome signatures of prediabetes and characterizing early prediabetic stages is important for the understanding of disease development and could be crucial in early diagnosis and prevention. METHODS: The current study performed amplification and sequencing on the variable regions (V1-V5) of the 16S rRNA genes to profile and compare gut microbiota of prediabetic individuals (N = 262) with normoglycemic individuals (N = 275) from two cohorts in India and Denmark. Similarly, fasting serum inflammatory biomarkers were profiled from the study participants. RESULTS: After correcting for strong country-specific cohort effect, 16 operational taxonomic units (OTUs) including members from the genera Prevotella9, Phascolarctobacterium, Barnesiella, Flavonifractor, Tyzzerella_4, Bacteroides, Faecalibacterium, and Agathobacter were identified as enriched in normoglycaemic subjects with respect to the subjects with prediabetes using a negative binomial Wald test. We also identified 144 OTUs enriched in the prediabetic subjects, which included members from the genera Megasphaera, Streptococcus, Prevotella9, Alistipes, Mitsuokella, Escherichia/Shigella, Prevotella2, Vibrio, Lactobacillus, Alloprevotella, Rhodococcus, and Klebsiella. Comparative analyses of relative abundance of bacterial taxa revealed that the Streptococcus, Escherichia/Shigella, Prevotella2, Vibrio, and Alloprevotella OTUs exhibited more than fourfold enrichment in the gut microbiota of prediabetic subjects. When considering subjects from the two geographies separately, we were able to identify additional gut microbiome signatures of prediabetes. The study reports a probable association of Megasphaera OTU(s) with impaired glucose tolerance, which is significantly pronounced in Indian subjects. While the overall results confirm a state of proinflammation as early as in prediabetes, the Indian cohort exhibited a characteristic pattern of abundance of inflammatory markers indicating low-grade intestinal inflammation at an overall population level, irrespective of glycemic status. CONCLUSIONS: The results present trans-ethnic gut microbiome and inflammation signatures associated with prediabetes, in Indian and Danish populations. The identified associations may be explored further as potential early indicators for individuals at risk of dysglycemia.

A comparative study on the cellular stressors in mesenchymal stem cells (MSCs) and pancreatic ß-cells under hyperglycemic milieu.

ß-cell dysfunction is a critical determinant for both type 1 diabetes and type 2 diabetes and ß-cells are shown to be highly susceptible to cellular stressors. Mesenchymal stem cells (MSCs) on the other hand are known to have immunomodulatory potential and preferred in clinical applications. However, there is paucity of a comparative study on these cells in relation to several cellular stressors in response to hyperglycemia and this forms the rationale for the present study. INS1 ß-cells and MSCs were subjected to high-glucose treatment without and with Metformin, Lactoferrin, or TUDCA and assessed for stress signaling alterations using gene expression, protein expression, as well as functional read-outs. Compared to the untreated control cells, INS1 ß-cells or MSCs treated with high glucose showed significant increase in mRNA expressions of ER stress, senescence, and proinflammation. This was accompanied by increased miR146a target genes and decreased levels of SIRT1, NRF2, and miR146a in both the cell types. Consistent with the mRNA results, protein expression levels do reflect the same alterations. Notably, the alterations are relatively less extent in MSCs compared to INS1 ß-cells. Interestingly, three different agents, viz., Metformin, Lactoferrin, or TUDCA, were found to overcome the high glucose-induced cellular stresses in a concerted and inter-linked way and restored the proliferation and migration capacity in MSCs as well as normalized the glucose-stimulated insulin secretion in INS1 ß-cells. While our study gives a directionality for potential supplementation of metformin/lactoferrin/TUDCA in optimization protocols of MSCs, we suggest that in vitro preconditioning of MSCs with such factors should be further explored with in-depth investigations to harness and enhance the therapeutic capacity/potential of MSCs.

High molecular weight adiponectin reduces glucolipotoxicity-induced inflammation and improves lipid metabolism and insulin sensitivity via APPL1-AMPK-GLUT4 regulation in 3T3-L1 adipocytes.

BACKGROUND AND AIMS: Although the importance of adipokines in modulating the disease process of type 2 diabetes is well recognized, there is dearth of data on the specific role of high molecular weight adiponectin (HMW Ad) on insulin resistance and obesity. Therefore, we tested the effects of HMW Ad on glucolipotoxcity-induced inflammation and insulin resistance in 3T3-L1 adipocytes. METHODS: 3T3-L1 adipocytes were subject to glucolipotoxicity with and without HMW Ad treatment. Real-time PCR and Western-blot experiments were performed to analyse gene and protein expressions, respectively. Lipolysis, adipored staining, and glucose uptake assay were performed to evaluate alterations in lipid and glucose metabolism. RESULTS: Adipocytes subject to glucolipotoxicity showed significantly (p < 0.05) decreased mRNA expression of adiponectin, AdipoR2, GLUT4, and increased inflammation, lipid accumulation as well as lipolysis. Treatment with HMW Ad beneficially modulated lipid metabolism, reduced inflammation and improved glucose uptake in adipocytes. HMW Ad also beneficially regulated APPL1 and AMPK signaling in adipocytes. Silencing of APPL1 gene in adipocytes significantly reduced the effects of HMW Ad on pAMPK protein expression, indicating that HMW Ad plays an important role in regulating AMPK phosphorylation via APPL1 in 3T3-L1 adipocytes. CONCLUSIONS: HMW Ad treatment improved glucose homeostasis and resulted in reduced lipolysis, inflammation and insulin resistance in adipocytes subject to glucolipotoxicity. The beneficial modulation and regulation of APPL1 and AMPK signals by HMW Ad observed in this study represent a novel mechanism. Raising endogenous HMW Ad levels either by pharmacological or lifestyle modification could have a therapeutic value.

Bisphenol A exposure under metabolic stress induces accelerated cellular senescence in vivo in a p53 independent manner.

Senescence is an irreversible process that is a characteristic of age-associated disease like Type 2 diabetes (T2D). Bisphenol-A (BPA), one of the most common endocrine disruptor chemicals, received special attention in the development of insulin resistance and T2D. To understand the role played by BPA in cellular senescence under metabolic stress, zebrafish embryos were exposed to BPA in the absence and presence of hyperglycaemia. Transcriptional levels of the senescence markers p15, p53, Rb1 and ß-galactosidase were increased when BPA was combined with metabolic stress. In addition, zebrafish embryos that were exposed to combination of hyperglycaemia and BPA exhibited increased levels of apoptosis. However, cellular senescence remained induced by a combination of hyperglycaemia and BPA exposure even in the absence of a translated p53 protein suggesting that senescence is primarily independent of it but dependent on the p15-Rb1 pathway under our experimental conditions. To confirm that our results hold true in adult mammalian tissues, we validated our embryonic experiments in an adult mammalian metabolic model of skeletal muscle cells. Our work reveals a novel and unique converging role of senescence and apoptosis axis contributing to glucose dyshomeostasis. Thus, we conclude that BPA exposure can exacerbate existing metabolic stress to increase cellular senescence that leads to aggravation of disease phenotype in age-associated diseases like type 2 diabetes.

Improvement in glucose tolerance and insulin sensitivity by probiotic strains of Indian gut origin in high-fat diet-fed C57BL/6J mice.

PURPOSE: Diabetes and obesity are characterized by glucose intolerance, fat deposition, inflammation, and dyslipidemia. Recent reports postulated that distinct gut microbiota alterations were observed in obese/diabetic subjects and modulating gut microbiota beneficially through specific probiotics could be a potential therapeutic option for type 2 diabetes/obesity. Therefore, we attempted to study the efficacy of probiotics of Indian gut origin (Lactobacillus plantarum MTCC5690 and Lactobacillus fermentum MTCC5689) along with a positive control, Lactobacillus rhamnosus (LGG) on glucose/lipid homeostasis in high-fat-diet-induced diabetic animal model. METHODS: C57BL/6J male mice were divided into seven groups (n = 6 per group) comprising feeding on: (1) Normal Pellet Diet (NPD), (2) High-Fat Diet (HFD), (3) HFD with LGG, (4) HFD with MTCC5690, (5) HFD with MTCC5689, (6) HFD with metformin, and 7) HFD with vildagliptin for a period of 6 months. Biochemical markers, glucose tolerance, insulin resistance, and GLP-1 and LPS levels were assessed by standard protocols. Gut integrity was measured by intestinal permeability test. Transcriptional levels of tight junction proteins (TJPs) were probed in small intestinal tissues while inflammatory signals and other pathway specific genes were profiled in liver, visceral adipose tissue, and skeletal muscle. RESULTS: Mice fed with HFD became insulin resistant, glucose intolerant, hyperglycemic, and dyslipidemic. Diabetic mice were characterized to exhibit decreased levels of GLP-1, increased gut permeability, increased circulatory levels of LPS, decrease in the gene expression patterns of intestinal tight junction markers (occludin and ZO-1), and increased proinflammatory gene markers (TNFα and IL6) in visceral fat along with decreased mRNA expression of FIAF and adiponectin. Diabetic mice also exhibited increased mRNA expression of ER stress markers in skeletal muscle. In addition, liver from HFD-fed diabetic mice showed increased gene expressions of proinflammation, lipogenesis, and gluconeogenesis. Probiotic interventions (most prominently the MTCC5689) resisted insulin resistance and development of diabetes in mice under HFD feeding and beneficially modulated all the biochemical and molecular alterations in a mechanistic way in several tissues. The metabolic benefits offered by the probiotics were also more or less similar to that of standard drugs such as metformin and vildagliptin. CONCLUSION: Native probiotic strains MTCC 5690 and MTCC 5689 appear to have potential against insulin resistance and type 2 diabetes with mechanistic, multiple tissue-specific mode of actions.

Picroside II attenuates fatty acid accumulation in HepG2 cells via modulation of fatty acid uptake and synthesis.

BACKGROUND/AIMS: Hepatic steatosis is caused by an imbalance between free fatty acids (FFAs) uptake, utilization, storage, and disposal. Understanding the molecular mechanisms involved in FFAs accumulation and its modulation could drive the development of potential therapies for Nonalcoholic fatty liver disease. The aim of the current study was to explore the effects of picroside II, a phytoactive found in Picrorhiza kurroa, on fatty acid accumulation vis-à-vis silibinin, a known hepatoprotective phytoactive from Silybum marianum. METHODS: HepG2 cells were loaded with FFAs (oleic acid:palmitic acid/2:1) for 20 hours to mimic hepatic steatosis. The FFAs concentration achieving maximum fat accumulation and minimal cytotoxicity (500 µM) was standardized. HepG2 cells were exposed to the standardized FFAs concentration with and without picroside II pretreatment. RESULTS: Picroside II pretreatment inhibited FFAs-induced lipid accumulation by attenuating the expression of fatty acid transport protein 5, sterol regulatory element binding protein 1 and stearoyl CoA desaturase. Preatreatment with picroside II was also found to decrease the expression of forkhead box protein O1 and phosphoenolpyruvate carboxykinase. CONCLUSIONS: These findings suggest that picroside II effectively attenuated fatty acid accumulation by decreasing FFAs uptake and lipogenesis. Picroside II also decreased the expression of gluconeogenic genes.