Type 2 diabetes (T2D) is a complex metabolic syndrome characterized by insulin dysfunction and abnormalities in glucose and lipid metabolism. The gut microbiome has been recently identified as an important factor for development of T2D. In this study, a total of 102 subjects were recruited, and we have looked at the gut microbiota of prediabetics (PreDMs) (n = 17), newly diagnosed diabetics (NewDMs) (n = 11), and diabetics on antidiabetic treatment (KnownDMs) (n = 39) and compared them with healthy nondiabetics (ND) (n = 35). Twenty-five different serum biomarkers were measured to assess the status of diabetes and their association with gut microbiota. Our analysis revealed nine different genera as differentially abundant in four study groups. Among them, Akkermansia, Blautia, and Ruminococcus were found to be significantly (P < 0.05) decreased, while Lactobacillus was increased in NewDMs compared to ND and recovered in KnownDMs. Akkermansia was inversely correlated with HbA1c and positively correlated with total antioxidants. Compared to ND, there was increased abundance of Megasphaera, Escherichia, and Acidaminococcus and decreased abundance of Sutterella in KnownDMs. Among many taxa known to act as community drivers during disease progression, we observed genus Sutterella as a common driver taxon among all diabetic groups. On the basis of the results of random forest analysis, we found that the genera Akkermansia and Sutterella and that the serum metabolites fasting glucose, HbA1c, methionine, and total antioxidants were highly discriminative factors among studied groups. Taken together, our data revealed that gut microbial diversity of NewDMs but not of PreDMs is significantly different from that of ND. Interestingly, after antidiabetic treatment, the microbial diversity of KnownDMs tends to recover toward that of ND. IMPORTANCE Gut microbiota is considered to play a role in disease progression, and previous studies have reported an association of microbiome dysbiosis with T2D. In this study, we have attempted to investigate gut microbiota of ND, PreDMs, NewDMs, and KnownDMs. We found that the genera Akkermansia and Blautia decreased significantly (P < 0.05) in treatment-naive diabetics and were restored in KnownDMs on antidiabetic treatment. To the best of our knowledge, comparative studies on shifts in the microbial community in individuals of different diabetic states are lacking. Understanding the transition of microbiota and its association with serum biomarkers in diabetics with different disease states may pave the way for new therapeutic approaches for T2D.

Pancreatic β-cells secrete insulin in response to changes in extracellular glucose concentration. Persistent hyperglycemia during diabetes exerts toxic effects on islets by creating redox imbalance arising from overproduction of reactive oxygen species (ROS). ROS accumulation disturbs the integrity and physiological function of cellular biomolecules impairing viability and functionality of cells. Susceptibility of an organ to oxidative stress (OS) is determined by its defense mechanism and ability to repair DNA damage caused by ROS. Weak defense status of islets along with its inefficiency to repair oxidative DNA damage as compared to other tissues renders it extraordinarily sensitive to OS. Realizing the vulnerability of islet cells to oxidative damage, several efforts to boost their defense mechanism in the form of oral administration of antioxidants and overexpression of genes responsible for antioxidant enzymes have proven successful. Recently accountability for this low antioxidant defense of islets have been given by correlating it with its metabolic evolution.

BackgroundPterostilbene, a methoxylated analog of Resveratrol, is gradually gaining more importance as a therapeutic drug owing to its higher lipophilicity, bioavailability and biological activity than Resveratrol. This study was undertaken to characterize its ability to scavenge free radicals such as superoxide, hydroxyl and hydrogen peroxide and to protect bio-molecules within a cell against oxidative insult.MethodsAnti-oxidant activity of Pterostilbene was evaluated extensively by employing several in vitro radical scavenging/inhibiting assays and pulse radiolysis study. In addition, its ability to protect rat liver mitochondria against tertiary-butyl hydroperoxide (TBHP) and hydroxyl radical generated oxidative damage was determined by measuring the damage markers such as protein carbonyls, protein sulphydryls, lipid hydroperoxides, lipid peroxides and 8-hydroxy-2'-deoxyguanosine. Pterostilbene was also evaluated for its ability to inhibit •OH radical induced single strand breaks in pBR322 DNA.ResultPterostilbene exhibited strong anti-oxidant activity against various free radicals such as DPPH, ABTS, hydroxyl, superoxide and hydrogen peroxide in a concentration dependent manner. Pterostilbene conferred protection to proteins, lipids and DNA in isolated mitochondrial fractions against TBHP and hydroxyl radical induced oxidative damage. It also protected pBR322 DNA against oxidative assault.ConclusionsThus, present study provides an evidence for the strong anti-oxidant property of Pterostilbene, methoxylated analog of Resveratrol, thereby potentiating its role as an anti-oxidant.

Insulin resistance (IR) is known to precede onset of type 2 diabetes and increased oxidative stress appears to be a deleterious factor leading to IR. In this study, we evaluated ability of Pterostilbene (PTS), a methoxylated analog of Resveratrol and a known antioxidant, to reverse palmitic acid (PA)-mediated IR in HepG2 cells. PTS prevented ROS formation and subsequent oxidative lipid damage by reducing the expression of NADPH Oxidase 3 (NOX3) in PA treated HepG2 cells. Hepatic glucose production was used as a measure of IR and PTS reversed PA-mediated increase in hepatic glucose production by reducing expression of genes coding for gluconeogenic enzymes namely glucose-6-phosphatase (G6Pase), phosphoenolpyruvate carboxykinase (PEPCK) and pyruvate carboxylase (PC); and their transcription factors cAMP response element binding protein (CREB) and fork head class box O (FOXO1) along with its co-activator peroxisome proliferator-activated receptor gamma co-activator-1 α (PGC1α). PTS reversed PA-mediated activation of c-jun N-terminal kinase (JNK), which in turn altered insulin signaling pathway by phosphorylating IRS-1 at Ser 307, leading to inhibition of phosphorylation of Akt and GSK3β. PTS also reduced PA-mediated lipid accumulation by reducing expression of transcription factors SREBP1c and PPARα. SREBP1c activates genes involved in fatty acid and triglyceride synthesis while PPARα activates CPT1, a rate limiting enzyme for controlling entry and oxidation of fatty acids into mitochondria. PTS, however, did not influence PA uptake confirmed by using BODIPY-labeled fluorescent C16 fatty acid analog. Thus, our data provides a possible mechanistic explanation for reversal of PA-mediated IR in HepG2 cells.

The human islet amyloid polypeptide (hIAPP) or amylin is the major constituent of amyloidogenic aggregates found in pancreatic islets of type 2 diabetic patients that have been associated with β-cell dysfunction and/or death associated with type 2 diabetes mellitus (T2DM). Therefore, developing and/or identifying inhibitors of hIAPP aggregation pathway and/or compound that can mediate disaggregation of preformed aggregates holds promise as a medical intervention for T2DM management. In the current study, the anti-amyloidogenic potential of Azadirachtin (AZD)—a secondary metabolite isolated from traditional medicinal plant Neem (Azadirachta indica)—was investigated by using a combination of biophysical and cellular assays. Our results indicate that AZD supplementation not only inhibits hIAPP aggregation but also disaggregates pre-existing hIAPP fibrils by forming amorphous aggregates that are non-toxic to pancreatic β-cells. Furthermore, AZD supplementation in pancreatic β-cells (INS-1E) resulted in inhibition of oxidative stress; along with restoration of the DNA damage, lipid peroxidation and the associated membrane damage, endoplasmic reticulum stress and mitochondrial membrane potential. AZD treatment also restored glucose-stimulated insulin secretion from pancreatic islets exposed to hIAPP. All-atom molecular dynamics simulation studies on full-length hIAPP pentamer with AZD suggested that AZD interacted with four possible binding sites in the amyloidogenic region of hIAPP. In summary, our results suggest AZD to be a promising candidate for combating T2DM and related amyloidogenic disorders.