Increased Plasma Insulin Levels Research Articles

In vivo functional profiling and structural characterisation of the human Glp1r A316T variant.

Glucagon-like peptide-1 receptor (GLP-1R) agonists (GLP-1RAs) are a highly effective therapy class for type 2 diabetes (T2D) and obesity, yet there are variable patient responses. Variation in the human Glp1r gene leading to altered receptor structure, signal transduction, and function might be directly linked to variable therapeutic responses in patients. A naturally occurring, low-frequency, gain-of-function missense variant, rs10305492 G>A (A316T), protects against T2D and cardiovascular disease. Here we employ CRISPR/Cas9 technology to generate a humanised knock-in mouse model bearing the homozygous Glp1r A316T substitution. Human Glp1r A316T/A316T mice displayed lower fasting blood glucose levels and improved glucose tolerance, as well as increased plasma insulin levels and improved insulin secretion compared to human Glp1r +/+ littermates, even under metabolic stress. They also exhibited alterations in islet cytoarchitecture and β-cell identity under a high-fat, high-sucrose (HFHS) diet. This was however associated with blunted responses to pharmacological GLP-1RAs in vivo . Further investigations in several rodent and human β-cell models demonstrated that the human Glp1r A316T variant exhibits characteristics of constitutive activation but dampened GLP-1RA responses. Our results are further supported by the cryo-EM analysis and molecular dynamics (MD) simulations of the GLP-1R A316T structure, collectively demonstrating that the A316T Glp1r variant governs basal receptor activity and pharmacological responses to GLP-1R-targeting anti-diabetic therapies, highlighting the importance of the molecular characterisation of human Glp1r variants to predict individual therapy responses.

Pro-inflammatory cytokines increase temporarily after adjuvant treatment for breast cancer in postmenopausal women: a longitudinal study

BackgroundBreast cancer patients have an increased risk of cardiometabolic disease and for many patients, adjuvant therapy causes an altered lipid profile, insulin resistance and inflammation. Previous follow-up studies are inconclusive regarding the duration of therapy-induced inflammation. We examined the acute and persistent changes of adjuvant chemotherapy on inflammatory and metabolic health markers in breast cancer patients.MethodsPlasma levels of IL-6, IL-8, IL-10, IFN-γ, TNF-α, high-sensitivity C-reactive protein (hsCRP) and metabolic health parameters were analyzed before, shortly after and every six months up to two years after adjuvant chemotherapy treatment in 51 postmenopausal early breast cancer (EBC) patients, as well as in 41 healthy age- and BMI-matched controls. A target-specific multiplex assay was applied for cytokine measurements.ResultsBefore initiation of adjuvant therapy, plasma IL-8 levels were higher in EBC patients (31%, p = 0.0001). Also, a larger proportion of the patients had a hsCRP level above 2 mg/L (41%) compared to the controls (17%, Χ2 = 5.15, p = 0.023). Plasma levels of all five cytokines, but not hsCRP, were significantly increased after compared to before adjuvant chemotherapy (15–48% increase; all p ≤ 0.05). Already six months after ending chemotherapy treatment, all plasma cytokine levels were significantly reduced and close to pre-chemotherapy levels. Adjuvant chemotherapy caused a worsened lipid profile (increased triglycerides, lower HDL levels), insulin resistance and increased plasma insulin levels that remained high during the first year after chemotherapy.ConclusionPostmenopausal women with EBC have temporarily increased plasma levels of pro-inflammatory cytokines after adjuvant chemotherapy. Although transient, the therapy-induced increase in plasma cytokine levels, together with dyslipidemia and insulin resistance, may contribute to cardiometabolic risk in breast cancer patients treated with adjuvant chemotherapy.Trial registration The clinical trial (registration number NCT03784651) was registered on www.clinicaltrials.gov on 24 December 2018.

Phenolic enriched fraction of Clerodendrum glandulosum Lindl. leaf extract ameliorates hyperglycemia and oxidative stress in streptozotocin-nicotinamide induced diabetic rats

BackgroundClerodendrum glandulosum Lindl. is an important ethnomedicinal shrub of Northeast India, used by traditional healers to control various ailments like diabetes, hypertension, arthritis, etc. ObjectivesThe present study was conducted to explore the anti-hyperglycemic and antioxidative effects of the polyphenol-rich fraction (PRF) of C. glandulosum leaf extract and identification of its major bioactive compounds. Further, an in-silico molecular docking study was also performed to understand the molecular interactions of the identified major compounds with some target proteins associated with diabetic complications. Materials and methodsPRF was purified from the hydromethanolic (80% MeOH) extract of leaves and subjected to assessment of in-vitro antioxidant and anti-diabetic properties. It was also subjected to evaluate the ameliorative effect during streptozotocin-nicotinamide-induced hyperglycemia in Wistar albino rats. An in-silico molecular docking study was also performed to complement the in-vitro/in-vivo studies. ResultsChemical analysis of PRF showed the presence of phenolics like caffeic acid, verbascoside, isoverbascoside, and apigenin, of which verbascoside (598.14 ± 1.24 mg/g) was found to be the principal compound. In-vitro studies showed potent antioxidant (IC50 of DPPH:32.45 ± 2.16 μg/mL; ABTS:39.08 ± 0.53 μg/mL) properties and excellent aldose reductase inhibition potential (IC50 2.18 ± 0.10 μg/mL). Treatment with PRF showed reduced blood glucose levels and increased plasma insulin levels. The results also indicate an improvement of endogenous antioxidants and suppression of inflammatory cytokines (IL-6 and TNF-α) comparable to the standard. Molecular docking studies predicted promising interactions between the identified molecules and the crucial amino acid residues of the enzymes involved in the development of hyperglycemia. ConclusionThis study revealed the antihyperglycemic and antioxidant potential of partially purified fraction PRF of C. glandulosum leaves.

Impact of the timing of metformin administration on glycaemic and glucagon-like peptide-1 responses to intraduodenal glucose infusion in type 2 diabetes: a double-blind, randomised, placebo-controlled, crossover study

Aims/hypothesisMetformin lowers postprandial glycaemic excursions in individuals with type 2 diabetes by modulating gastrointestinal function, including the stimulation of glucagon-like peptide-1 (GLP-1). The impact of varying the timing of metformin administration on postprandial glucose metabolism is poorly defined. We evaluated the effects of metformin, administered at different intervals before an intraduodenal glucose infusion, on the subsequent glycaemic, insulinaemic and GLP-1 responses in metformin-treated type 2 diabetes.MethodsSixteen participants with type 2 diabetes that was relatively well-controlled by metformin monotherapy were studied on four separate days in a crossover design. On each day, participants were randomised to receive a bolus infusion of metformin (1000 mg in 50 ml 0.9% saline) via a nasoduodenal catheter at t = −60, −30 or 0 min (and saline at the other timepoints) or saline at all timepoints (control), followed by an intraduodenal glucose infusion of 12.56 kJ/min (3 kcal/min) at t = 0–60 min. The treatments were blinded to both participants and investigators involved in the study procedures. Plasma glucose, insulin and total GLP-1 levels were measured every 30 min between t = −60 min and t = 120 min.ResultsThere was a treatment-by-time interaction for metformin in reducing plasma glucose levels and increasing plasma GLP-1 and insulin levels (p<0.05 for each). The reduction in plasma glucose levels was greater when metformin was administered at t = −60 or −30 min vs t = 0 min (p<0.05 for each), and the increases in plasma GLP-1 levels were evident only when metformin was administered at t = −60 or −30 min (p<0.05 for each). Although metformin did not influence insulin sensitivity, it enhanced glucose-induced insulin secretion (p<0.05), and the increases in plasma insulin levels were comparable on the 3 days when metformin was given.Conclusions/interpretationIn well-controlled metformin-treated type 2 diabetes, glucose-lowering by metformin is greater when it is given before, rather than with, enteral glucose, and this is associated with a greater GLP-1 response. These observations suggest that administration of metformin before meals may optimise its effect in improving postprandial glycaemic control.Trial registrationwww.anzctr.org.au ACTRN12621000878875FundingThe study was not funded by a specific research grant.Graphical

Changes in Cells Associated with Insulin Resistance.

Insulin is a polypeptide hormone synthesized and secreted by pancreatic β-cells. It plays an important role as a metabolic hormone. Insulin influences the metabolism of glucose, regulating plasma glucose levels and stimulating glucose storage in organs such as the liver, muscles and adipose tissue. It is involved in fat metabolism, increasing the storage of triglycerides and decreasing lipolysis. Ketone body metabolism also depends on insulin action, as insulin reduces ketone body concentrations and influences protein metabolism. It increases nitrogen retention, facilitates the transport of amino acids into cells and increases the synthesis of proteins. Insulin also inhibits protein breakdown and is involved in cellular growth and proliferation. On the other hand, defects in the intracellular signaling pathways of insulin may cause several disturbances in human metabolism, resulting in several chronic diseases. Insulin resistance, also known as impaired insulin sensitivity, is due to the decreased reaction of insulin signaling for glucose levels, seen when glucose use in response to an adequate concentration of insulin is impaired. Insulin resistance may cause, for example, increased plasma insulin levels. That state, called hyperinsulinemia, impairs metabolic processes and is observed in patients with type 2 diabetes mellitus and obesity. Hyperinsulinemia may increase the risk of initiation, progression and metastasis of several cancers and may cause poor cancer outcomes. Insulin resistance is a health problem worldwide; therefore, mechanisms of insulin resistance, causes and types of insulin resistance and strategies against insulin resistance are described in this review. Attention is also paid to factors that are associated with the development of insulin resistance, the main and characteristic symptoms of particular syndromes, plus other aspects of severe insulin resistance. This review mainly focuses on the description and analysis of changes in cells due to insulin resistance.

Polymorphisms in insulin pathway genes and cancer risk

Background: Insulin is a big hormone (5808 Da) generally produced with the aid of the pancreas. Insulin receptors (IR) are found in neurons and glial cells. Insulin resistance has been related to increased plasma insulin levels, glucose intolerance, elevated insulin-like growth factor-1 (IGF-I), glucose and free fatty acids, body mass index, and an elevated risk for colorectal cancers. Proinflammatory cytokines, boom components, and hormones secreted by adipocytes play a key role in colorectal cancer etiology. Acetyl-CoA acetyltransferase (ACAT1) mediates insulin-precipitated cell proliferation and metastatic outcomes in colorectal cancer cells. Therefore, miRNAs might serve as a biological connection between metabolic changes linked to obesity and the beginning and progression of Colorectal Cancer Cancer (CRC). Furthermore, these findings shed new light on weight problems as a CRC danger component in which miRNA dysregulation may be involved. The function of IGFs in CRC is investigated by examining the association of two genetic polymorphisms in IGFBP-3 (a G → C single nucleotide polymorphism) and IGF-1 (a cytosine-adenosine dinucleotide repeat) with CRC risk in addition to the possibility of the other interventions, including physical activity, body mass index (BMI), and the use of postmenopausal hormones. These factors can exert their effects by modifying IGF-1 and the related binding proteins (IGFBP). Furthermore, the IGFBP-3 genotype can lead to a substantial effect modifier in the association between CRC and risk factors. It has been found that functional polymorphisms in the pathway of insulin genes, including IGFBPI, INSR, INS, and insulin receptor substrates 1 and 2 (IRS1 and IRS2), can be related to CRC.

Effects of creatine supplementation on strength exercise and its optimization through carbohydrates: A review

Nutritional supplements integrated with any physical or sports activity are substances aimed at increasing physical performance, improving physical effort efficiency, enhancing physical recovery processes after intense exertion, enhancing training quality, and facilitating physiological adaptations. Among the most commonly used supplements is creatine (CR), a non-essential nitrogenous compound formed by three amino acids: glycine, arginine, and methionine, whose main benefit lies in improving performance in high-intensity activities. The consumption of CR along with carbohydrate (CHO) sources promotes supplement absorption compared to isolated consumption due to increased plasma insulin levels. The human body can absorb approximately 25% more CR when ingested with a CHO source. This review aimed to provide an expanded outlook on the consumption of CR combined with CHO sources and its relationship with increased CR transport into muscle cells in individuals engaging in strength exercises. Studies have shown that the increase or improvement in CR absorption by muscle cells may be related to increased blood glucose levels and consequent insulin release, which acts in a co-dependent and direct manner on the membrane transporter that regulates the entry of CR together with sodium into the intracellular environment, demonstrating that CHO supplementation is not necessary every time CR is consumed, but instead that this improvement consists of increased serum glucose and insulin release.

Gαi -coupled GPR41 activation increases Ca2+ influx in C2C12 cells and shows a therapeutic effect in diabetic animals.

This study aimed to investigate the possible mechanisms by which orphan G protein-coupled receptor GPR41 activation enhances glucose uptake into C2C12 myotubes using a GPR41-selective agonist, AR420626, and to examine the ability of this agent to improve insulin sensitivity and glucose homeostasis in vivo. Basal and insulin-stimulated glucose uptake and glucose transporter 4 translocations were measured in C2C12 myotubes. Ca2+ influx into cells was measured and GPR41-mediated signaling by AR420626 was examined. An oral glucose tolerance test was performed, and plasma insulin levels were measured in streptozotocin-treated or high-fat diet-fed diabetic mice. The glycogen content was measured in skeletal muscle tissue. AR420626 increased basal and insulin-stimulated glucose uptake, which was reduced by pertussis toxin, an inhibitor of Gαi -mediated signaling, and treatment with small interfering RNA for GPR41 (siGPR41). AR420626 increased intracellular Ca2+ influx and phosphorylated Ca2+ /calmodulin-dependent protein kinase type II, cyclic AMP-responsive element-binding protein, and mitogen-activated protein kinase (p38) in C2C12 myotubes, which were inhibited by treating with pertussis toxin, amlodipine (Ca2+ channel blocker), and siGPR41. AR420626 increased plasma insulin levels and skeletal muscle glycogen content and improved glucose tolerance in streptozotocin- and high-fat diet-induced diabetic mouse models. GPR41 activation with AR420626 increased glucose uptake mediated by Ca2+ signaling via GPR41, improving diabetes mellitus.

Gymnema Sylvestre Supplementation Restores Normoglycemia, Corrects Dyslipidemia, and Transcriptionally Modulates Pancreatic and Hepatic Gene Expression in Alloxan-Induced Hyperglycemic Rats.

Gymnema sylvestre is traditionally used as an herbal remedy for diabetes. The effect of Gymnema sylvestre supplementation on beta cell and hepatic activity was explored in an alloxan-induced hyperglycemic adult rat. Animals were made hyperglycemic via a single inj. (i.p) of Alloxan. Gymnema sylvestre was supplemented in diet @250 mg/kg and 500 mg/kg b.w. Animals were sacrificed, and blood and tissues (pancreas and liver) were collected for biochemical, expression, and histological analysis. Gymnema sylvestre significantly reduced blood glucose levels with a subsequent increase in plasma insulin levels in a dosage-dependent manner. Total oxidant status (TOS), malondialdehyde, LDL, VLDL, ALT, AST, triglyceride, total cholesterol, and total protein levels were reduced significantly. Significantly raised paraoxonase, arylesterase, albumin, and HDL levels were also observed in Gymnema sylvestre treated hyperglycemic rats. Increased mRNA expression of Ins-1, Ins-2, Gck, Pdx1, Mafa, and Pax6 was observed, while decreased expression of Cat, Sod1, Nrf2, and NF-kB was observed in the pancreas. However, increased mRNA expression of Gck, Irs1, SREBP1c, and Foxk1 and decreased expression of Irs2, ChREBP, Foxo1, and FoxA2 were observed in the liver. The current study indicates the potent effect of Gymnema sylvestre on the transcription modulation of the insulin gene in the alloxan-induced hyperglycemic rat model. Enhanced plasma insulin levels further help to improve hyperglycemia-induced dyslipidemia through transcriptional modulation of hepatocytes.

Stimulatory effect of imeglimin on incretin secretion.

Imeglimin is a new antidiabetic drug structurally related to metformin. Despite this structural similarity, only imeglimin augments glucose-stimulated insulin secretion (GSIS), with the mechanism underlying this effect remaining unclear. Given that glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) also enhance GSIS, we examined whether these incretin hormones might contribute to the pharmacological actions of imeglimin. Blood glucose and plasma insulin, GIP, and GLP-1 concentrations were measured during an oral glucose tolerance test (OGTT) performed in C57BL/6JJcl (C57BL/6) or KK-Ay/TaJcl (KK-Ay) mice after administration of a single dose of imeglimin with or without the dipeptidyl peptidase-4 inhibitor sitagliptin or the GLP-1 receptor antagonist exendin-9. The effects of imeglimin, with or without GIP or GLP-1, on GSIS were examined in C57BL/6 mouse islets. Imeglimin lowered blood glucose and increased plasma insulin levels during an OGTT in both C57BL/6 and KK-Ay mice, whereas it also increased the plasma levels of GIP and GLP-1 in KK-Ay mice and the GLP-1 levels in C57BL/6 mice. The combination of imeglimin and sitagliptin increased plasma insulin and GLP-1 levels during the OGTT in KK-Ay mice to a markedly greater extent than did either drug alone. Imeglimin enhanced GSIS in an additive manner with GLP-1, but not with GIP, in mouse islets. Exendin-9 had only a minor inhibitory effect on the glucose-lowering action of imeglimin during the OGTT in KK-Ay mice. Our data suggest that the imeglimin-induced increase in plasma GLP-1 levels likely contributes at least in part to its stimulatory effect on insulin secretion.

Chemical induction of gut β-like-cells by combined FoxO1/Notch inhibition as a glucose-lowering treatment for diabetes

ObjectiveLifelong insulin replacement remains the mainstay of type 1 diabetes treatment. Genetic FoxO1 ablation promotes enteroendocrine cell (EECs) conversion into glucose-responsive β-like cells. Here, we tested whether chemical FoxO1 inhibitors can generate β-like gut cells. MethodsWe used Ngn3-or Villin-driven FoxO1 ablation to capture the distinctive developmental effects of FoxO1 on EEC pool. We combined FoxO1 ablation with Notch inhibition to enhance the expansion of EEC pool. We tested the ability of an orally available small molecule of FoxO1 inhibitor, Cpd10, to phenocopy genetic ablation of FoxO1. We evaluated the therapeutic impact of genetic ablation or chemical inhibition of FoxO1 on insulin-deficient diabetes in Ins2Akita/+ mice. ResultsPan-intestinal epithelial FoxO1 ablation expanded the EEC pool, induced β-like cells, and improved glucose tolerance in Ins2Akita/+ mice. This genetic effect was phenocopied by Cpd10. Cpd10 induced β-like cells that released insulin in response to glucose in gut organoids, and this effect was enhanced by the Notch inhibitor, DBZ. In Ins2Akita/+ mice, a five-day course of either Cpd10 or DBZ induced intestinal insulin-immunoreactive β-like cells, lowered glycemia, and increased plasma insulin levels without apparent adverse effects. ConclusionThese results provide proof of principle of gut cell conversion into β-like cells by a small molecule FoxO1 inhibitor, paving the way for clinical applications.

Glucose-mediated insulin secretion is improved in FHL2-deficient mice and elevated FHL2 expression in humans is associated with type 2 diabetes

Aims/hypothesisThe general population is ageing, involving an enhanced incidence of chronic diseases such as type 2 diabetes. With ageing, DNA methylation of FHL2 increases, as well as expression of the four and a half LIM domains 2 (FHL2) protein in human pancreatic islets. We hypothesised that FHL2 is actively involved in glucose metabolism.MethodsPublicly available microarray datasets from human pancreatic islets were analysed for FHL2 expression. In FHL2-deficient mice, we studied glucose clearance and insulin secretion. Gene expression analysis and glucose-stimulated insulin secretion (GSIS) were determined in isolated murine FHL2-deficient islets to evaluate insulin-secretory capacity. Moreover, knockdown and overexpression of FHL2 were accomplished in MIN6 cells to delineate the underlying mechanism of FHL2 function.ResultsTranscriptomics of human pancreatic islets revealed that individuals with elevated levels of HbA1c displayed increased FHL2 expression, which correlated negatively with insulin secretion pathways. In line with this observation, FHL2-deficient mice cleared glucose more efficiently than wild-type littermates through increased plasma insulin levels. Insulin sensitivity was comparable between these genotypes. Interestingly, pancreatic islets isolated from FHL2-deficient mice secreted more insulin in GSIS assays than wild-type mouse islets even though insulin content and islet size was similar. To support this observation, we demonstrated increased expression of the transcription factor crucial in insulin secretion, MAF BZIP transcription factor A (MafA), higher expression of GLUT2 and reduced expression of the adverse factor c-Jun in FHL2-deficient islets. The underlying mechanism of FHL2 was further delineated in MIN6 cells. FHL2-knockdown led to enhanced activation of forkhead box protein O1 (FOXO1) and its downstream genes such as Mafa and Pdx1 (encoding pancreatic and duodenal homeobox 1), as well as increased glucose uptake. On the other hand, FHL2 overexpression in MIN6 cells blocked GSIS, increased the formation of reactive oxygen species and increased c-Jun activity.Conclusions/interpretationOur data demonstrate that FHL2 deficiency improves insulin secretion from beta cells and improves glucose tolerance in mice. Given that FHL2 expression in humans increases with age and that high expression levels of FHL2 are associated with beta cell dysfunction, we propose that enhanced FHL2 expression in elderly individuals contributes to glucose intolerance and the development of type 2 diabetes.Data availabilityThe human islet microarray datasets used are publicly available and can be found on https://www.ncbi.nlm.nih.gov/geo/.Graphical abstract

Effect of dual inhibition of DPP4 and SGLT2 on tacrolimus-induced diabetes mellitus and nephrotoxicity in a rat model

Sodium/glucose co-transporter-2 inhibitor (SGLT2i) or dipeptidyl peptidase IV inhibitor (DPP4i) is a newer anti-diabetic drug in type II diabetes mellitus (DM), but their use in tacrolimus (TAC)-induced DM is still undetermined. We performed this study to evaluate the effect of these two drugs in TAC-induced DM and nephrotoxicity in ex vivo and in vivo. In the experimental Sprague Dawley rat model of TAC-induced DM and nephrotoxicity, dual inhibition of DPP4 and SGLT2significantly decreased blood glucose level, HbA1C and increased plasma insulin levels and pancreatic islet size compared with each drug. In the kidney, dual inhibition improved renal function decreased interstitial fibrosis and profibrotic cytokines compared with DPP4i and SGLT2i alone. Increased oxidative stress by TAC was remarkably decreased with DPP4i or SGLT2i in serum, pancreatic and renal tissues and this decrease was much more significant in the combination group. In in vitro study, TAC decreased the cell viability of human kidney-2(HK-2) cells and insulin-secreting beta-cell-derived line(INS-1) cells. SGLT2i protected TAC-induced cell death in HK-2 cells, but not in INS-1 cells. The addition of DPP4i to SGLT2i compensated for a lack of protective effect of SGLT2i on INS-1 cells. This finding provides the rationale for the combined treatment of SGLG2i and DPP4i in TAC-induced DM and nephrotoxicity.

314-OR: Synaptotagmin-9 Regulates Early Phase Insulin Secretion by Regulating Tomosyn-1

Insulin secretion from pancreatic β-cells occurs in a biphasic manner. The loss of insulin secretion, entailing the inability of insulin granules to fuse with the plasma membrane (PM) via the formation of the SNARE complex, is a key determinant in impaired glucose tolerance and development of type 2 diabetes (T2D) . Synaptotagmins (Syt) are calcium sensors that regulate insulin-containing granule fusion to the PM for insulin secretion. Syt9 is highly expressed in β-cells; however, its role in insulin secretion is not well-characterized. Our goal is to determine how Syt9 affects insulin secretion from pancreatic β-cells. Mice lacking Syt9 (Syt9-/-) have improved glucose clearance with no change in insulin action than wild-type control mice. Interestingly, Syt9-/- mice showed increased plasma insulin levels at 5 min and 15 min post-glucose challenge. Similarly, islets isolated from Syt9-/- mice demonstrate increased stimulation of insulin secretion in response to the early phase insulin secretagogues (KCl and tolbutamide) compared to WT control islets. Similarly, siRNA-mediated knockdown of Syt9 in INS1 cells increased KCL-stimulated insulin secretion at 5 min and min. Altogether, these data suggest that Syt9 regulates the early phase of insulin secretion from β-cells. Strikingly, Syt9-/- mouse islets have reduced Tomosyn-1 levels (∼50%) without altering the levels of other key SNARE proteins (Stx1A, Stx4A, SNAP25) . Tomosyn-1, an inhibitor of insulin secretion whose increased protein abundance is associated with reduced insulin secretion, binds, cofractionates, and colocalizes with Syt9 and Stx1A. The knockdown of Tomosyn-1 in INS1 β-cells treated with KCL prevents the localization of Syt9 with Stx1A. Further, the knockdown of Syt9 or Tomosyn-1 increases the SNARE complex formation. In sum, these data demonstrate the identification of a novel Stx1A-Tomosyn-1-Syt9 molecular complex that regulates the fusion of insulin granules in the early phase. Disclosure M.Rahman: None. H.Alsharif: n/a. S.Bhatnagar: None. Funding R01DK120684-01

Glucagon-receptor-antagonism-mediated β-cell regeneration as an effective anti-diabetic therapy.

Type 1 diabetes mellitus (T1D) is a chronic disease with potentially severe complications, and β-cell deficiency underlies this disease. Despite active research, no therapy to date has been able to induce β-cell regeneration in humans. Here, we discover the β-cell regenerative effects of glucagon receptor antibody (anti-GcgR). Treatment with anti-GcgR in mouse models of β-cell deficiency leads to reversal of hyperglycemia, increase in plasma insulin levels, and restoration of β-cell mass. We demonstrate that both β-cell proliferation and α- to β-cell transdifferentiation contribute to anti-GcgR-induced β-cell regeneration. Interestingly, anti-GcgR-induced α-cell hyperplasia can be uncoupled from β-cell regeneration after antibody clearance from the body. Importantly, we are able to show that anti-GcgR-induced β-cell regeneration is also observed in non-human primates. Furthermore, anti-GcgR and anti-CD3 combination therapy reverses diabetes and increases β-cell mass in a mouse model of autoimmune diabetes.

A fixed single meal in the subjective day prevents free-running of the human sleep-wake cycle but not of the circadian pacemaker under temporal isolation.

Effects of a fixed single meal per day were examined on the circadian pacemaker and sleep-wake cycle in subjects under temporal isolation. When the time of single meal was allowed to take at any time of day (ad-lib meal), the sleep-wake cycle as well as the circadian rhythms in plasma melatonin, cortisol, and core body temperature were significantly phase-delayed in 8 days. On the other hand, when the time of meal was fixed at 1800 h in local time (RF meal), the phase-shift of sleep-wake cycle was not significant while those of the circadian rhythms were significant. The differential effects of a fixed single meal schedule were confirmed in most individual subjects. There was no evidence for the prefeeding increase in plasma cortisol and leptin levels under the fixed single meal schedule. The plasma ghrelin level was apparently high before meal in both ad-lib and RF meal groups, which was, however, likely sculptured by a nonspecific prandial drop and gradual increase after meal intake. Single meal augmented the prandial increase of plasma insulin levels by four to five times. These findings indicate that a single meal at a fixed time of the day during the subjective day failed to prevent the human circadian pacemaker but prevented the sleep-wake cycle from free running for at least 8 days under temporal isolation, suggesting that mealtime was a potent nonphotic time cue for the human sleep-wake cycle.

Norlignans as potent GLP-1 secretagogues from the fruits of Amomum villosum

The dried fruit of Amomum villosum (Amomi Fructus) is an important spices and traditional Chinese medicine. In this study, the EtOH extract of Amomi Fructus was revealed with hypoglycemic effects on db/db mice by increasing plasma insulin levels. After extracted with EtOAc, the EtOAc fraction showed increased activity in stimulating glucagon-like peptide-1 (GLP-1) secretion compared with the EtOH extract. In order to clarify the antidiabetic constituents, four undescribed norlignans, amovillosumins A‒D, were isolated from the EtOAc fraction, and the subsequent chiral resolution yielded three pairs of enantiomers. Their structures were determined by extensive spectroscopic data (1D and 2D NMR, HRESIMS, IR, UV and [α]D) and ECD calculations. Amovillosumins A and B significantly stimulated GLP-1 secretion by 375.1% and 222.7% at 25.0 μM, and 166.9% and 62.7% at 12.5 μM, representing a new type of GLP-1 secretagogues.

A novel therapeutic combination of sitagliptin and melatonin regenerates pancreatic β-cells in mouse and human islets

Autoimmune-led challenge resulting in β-cell loss is responsible for the development of type 1 diabetes (T1D). Melatonin, a pineal hormone or sitagliptin, a dipeptidyl peptidase IV (DPP-IV) inhibitor, has increased β-cell mass in various diabetic models and has immunoregulatory property. Both β-cell regenerative capacity and melatonin secretion decrease with ageing. Thus, we aimed to investigate the therapeutic potential of melatonin combined with sitagliptin on β-cell regeneration under glucotoxic stress, in the streptozotocin-induced young and old diabetic mouse models, and euglycemic humanized islet transplant mouse model. Our results suggest that combination therapy of sitagliptin and melatonin show an additive effect in inducing mouse β-cell regeneration under glucotoxic stress, and in the human islet transplant mouse model. Further, in the young diabetic mouse model, the monotherapies induce β-cell transdifferentiation and reduce β-cell apoptosis whereas, in the old diabetic mouse model, melatonin and sitagliptin induce β-cell proliferation and β-cell transdifferentiation, and it also reduces β-cell apoptosis. Further, in both the models, combination therapy reduces fasting blood glucose levels, increases plasma insulin levels and glucose tolerance and promotes β-cell proliferation, β-cell transdifferentiation, and reduces β-cell apoptosis. It can be concluded that combination therapy is superior to monotherapies in ameliorating diabetic manifestations, and it can be used as a future therapy for β-cell regeneration in diabetes patients.

Loss of Microglial Insulin Receptor Leads to Sex-Dependent Metabolic Disorders in Obese Mice.

Obesity and type 2 diabetes mellitus (T2DM) are highly prevalent disorders, associated with insulin resistance and chronic inflammation. The brain is key for energy homeostasis and contains many insulin receptors. Microglia, the resident brain immune cells, are known to express insulin receptors (InsR) and to be activated by a hypercaloric environment. The aim of this study was to evaluate whether microglial insulin signaling is involved in the control of systemic energy homeostasis and whether this function is sex-dependent. We generated a microglia-specific knockout of the InsR gene in male and female mice and exposed them to control or obesogenic dietary conditions. Following 10 weeks of diet exposure, we evaluated insulin tolerance, energy metabolism, microglial morphology and phagocytic function, and neuronal populations. Lack of microglial InsR resulted in increased plasma insulin levels and insulin resistance in obese female mice. In the brain, loss of microglial InsR led to a decrease in microglial primary projections in both male and female mice, irrespective of the diet. In addition, in obese male mice lacking microglial InsR the number of proopiomelanocortin neurons was decreased, compared to control diet, while no differences were observed in female mice. Our results demonstrate a sex-dependent effect of microglial InsR-signaling in physiology and obesity, and stress the importance of a heterogeneous approach in the study of diseases such as obesity and T2DM.

The Effect of SGLT2 Inhibition on Diabetic Kidney Disease in a Model of Diabetic Retinopathy.

Diabetic kidney disease (DKD) is a chronic disorder characterized by elevated urine albumin excretion, reduced glomerular filtration rate, or both. At present, angiotensin-converting enzyme inhibitors or angiotensin receptor blockers are the standard care for the treatment of DKD, resulting in improved outcomes. However, alternative treatments may be required because although the standard treatments have been found to slow the progression of DKD, they have not been found to halt the disease. In the past decade, sodium glucose co-transporter 2 (SGLT2) inhibitors have been widely researched in the area of cardiovascular disease and diabetes and have been shown to improve cardiovascular outcomes. SGLT2 inhibitors including canagliflozin and dapagliflozin have been shown to slow the progression of kidney disease. There is currently an omission of literature where three SGLT2 inhibitors have been simultaneously compared in a rodent diabetic model. After diabetic Akimba mice were treated with SGLT2 inhibitors for 8 weeks, there was not only a beneficial impact on the pancreas, signified by an increase in the islet mass and increased plasma insulin levels, but also on the kidneys, signified by a reduction in average kidney to body weight ratio and improvement in renal histology. These findings suggest that SGLT2 inhibition promotes improvement in both pancreatic and kidney health.