Elevated Plasma Insulin Levels Research Articles

Investigation of the effects of maternal separation on the pancreatic oxidative and inflammatory damages along with metabolic impairment in response to chronic social defeat stress in young adult male rats.

Chronic glucocorticoid release during the stress response has been proposed to initiate certain damages, which in turn produce metabolic disorders. The present study is the first work to test whether maternal separation (MS) would impact the metabolic alterations associated with pancreatic oxidative and inflammatory damages under chronic exposure to social defeat stress (CSDS) in adulthood. During the first 2weeks of life, male Wistar rats were exposed to MS or left undisturbed with their mothers (Std). Starting on postnatal day 50, the animals of each group were either left undisturbed in the standard group housing (Con) or underwent CSDS for 3weeks. Thus, there were 4 groups (n = 7/group): Std-Con, Ms-Con, Std-CSDS, MS-CSDS. Each animal was weighed and then decapitated so that we could collect trunk blood for assessment of fasting plasma corticosterone, insulin, glucose, lipid profile, and insulin resistance. Plasma and pancreatic catalase activity, reduced glutathione (GSH), malondialdehyde levels and pancreatic interleukin-1 beta (IL-1β) content were also measured. MS-CSDS animals showed elevated plasma corticosterone and insulin levels (P < 0.01) along with insulin resistance (P < 0.05). According to one-way ANOVA results, chronic exposure to early or adult life adversity decreased body weight (P < 0.0001), Catalase activity and GSH levels (P < 0.0001) and increased malondialdehyde level (P = 0.0006) in plasma. Pancreatic MDA and IL-1β contents elevated just in MS-CSDS rats (P < 0.05). Maternal separation shapes vulnerability to develop corticosterone hypersecretion, insulin resistance, pancreatic oxidative, and inflammatory damages associated with chronic exposure to later social challenges, which could potentially trigger metabolic disorders. The online version contains supplementary material available at 10.1007/s40200-021-00902-3.

115-LB: Liver-Derived FGF21 Mediates the Promoting Effect of Glucagon Receptor Antagonism on Beta-Cell Regeneration in Type 2 Diabetic Mice

Objective: Based on the clear role for glucagon in the pathogenesis of diabetes, glucagon-blocking therapies have been pursued as a therapeutic strategy for this disease. Here, we used REMD 2.59, a human antagonistic glucagon receptor (GCGR) monoclonal antibody (mAb), to clarify the effects of GCGR mAb in promoting pancreatic β cell regeneration in type 2 diabetes (T2D), and its potential mechanism. Methods: GCGR mAb was administrated weekly for 4 weeks in db/db mice and HFD/STZ-induced T2D mice, including different lineage-tracing mice. The plasma insulin and glucagon were determined by using ELISA. The evaluation of islet morphology was performed with immunofluorescent analysis. GCGR mAb was also treated in the systemic Fgf21 gene knockout (Fgf21-/-) and hepatocyte-specific Fgf21 gene knockout (Fgf21Hep-/-) T2D mice. Results: Treatment with GCGR mAb lowered blood glucose, improved glucose tolerance, and elevated plasma glucagon and insulin levels in both db/db mice and HFD/STZ-induced T2D mice. The β cell dedifferentiation as indicated by β cell lineage-tracing was blocked by GCGR mAb. The β cell proliferation as indicated by insulin+ and BrdU+ cells was boosted by GCGR mAb. The α-to-β cell conversion, as evaluated by glucagon+ insulin+ cells and confirmed by α cell lineage-tracing, was facilitated by GCGR mAb. After GCGR mAb treatment, some insulin+ cells were located in the duct region or even colocalized with duct cell markers, suggestive of duct-derived β cell neogenesis that was also verified by Ngn3+ cell lineage-tracing. Notably, GCGR mAb could still improve glucose tolerance and increase β cell mass, but these effects were attenuated in Fgf21-/- and Fgf21Hep-/- T2D mice compared with WT T2D mice. Conclusions: GCGR mAb promotes β cell regeneration via inhibiting β cell dedifferentiation and promoting β cell self-replication, α-to-β cell conversion and duct-derived β cell neogenesis in T2D mice, which is partly mediated by liver-derived FGF21. Disclosure X. Cui: None. T. Wei: None. J. Feng: None. J. Yang: None. H. Yan: Board Member; Self; REMD Biotherapeutics, Other Relationship; Spouse/Partner; REMD Biotherapeutics. R. Wei: None. T. Hong: Speaker’s Bureau; Self; AstraZeneca, Boehringer Ingelheim International GmbH, Merck Sharp &amp; Dohme Corp., Novo Nordisk, Sanofi. Funding National Natural Science Foundation of China (81830022)

The Expression of Genes Encoding ABCA1 and ABCG1 Transporters and PPARγ, LXRβ, and RORα Transcriptional Factors in Subcutaneous and Visceral Adipose Tissue in Women with Metabolic Syndrome

The study aimed to investigate tissue-specific gene expression of ABCA1 and ABCG1, encoding cholesterol transporters, as well as PPARG, LXRβ (NR1H2), and RORA, encoding the most important transcriptional regulators of lipid metabolism, in subcutaneous and visceral adipose tissue (SAT and VAT) in women with metabolic syndrome. It was shown that the ABCG1 mRNA SAT/VAT ratio decreases with age and correlates with the development of metabolic syndrome. After age adjustment, women have reduced chances of metabolic syndrome development when ABCG1 gene expression in SAT is higher relative to VAT than women with VAT ABCG1 gene expression higher or comparable to SAT: OR = 0.15 (95% CI 0.03-0.76), p = 0.023. The ABCA1 mRNA SAT/VAT ratio positively correlated with HDL cholesterol levels (after age adjustment β = 0.350, p = 0.046), therefore individuals with higher ABCA1 mRNA level in SAT relative to VAT had elevated HDL levels. The ABCA1 mRNA level in SAT was decreased in smokers (p = 0.001). There was a negative correlation between the PPARG mRNA level in SAT with body mass index and waist circumference in the general sample (β = -0.602, p = 0.003 and β = -0.642, p = 0.001, respectively, after age adjustment). A decrease of the PPARG mRNA SAT/VAT ratio was associated with elevated plasma insulin level and the insulin resistance index HOMA-IR β = -0.819, p = 0.004 and β = -1.053, p = 0.008, respectively, after age adjustment). Thus, the study has shown that the ratio of ABCA1, ABCG1, and PPARG genes expression in different types of adipose tissue (SAT/VAT) could be a significant factor that predicts the development of atherogenic dyslipidemia, metabolic syndrome, and insulin resistance in obesity.

The role of impaired glucose and lipid metabolism and liver enzyme abnormalities in the formation of multiple acrochordons: a case-control study

Background Acrochordons, one of skin tumors, are protrusions of the loose fibrous tissue. In various studies, they have found to be associated with abnormal lipid profile, diabetes, cardiovascular disease, obesity, abnormal liver enzymes and genetic factors. In our case-control study, we aimed to determine possible associations of multiple acrochordons with obesity, impaired glucose and lipid metabolism, thyroid disorders, anemia and liver enzymes abnormalities.Methods Sixty-five patients (32 male, 33 female) with at least 8 skin tags and age- and gender-matched 60 controls without skin tags (30 male, 30 female) were enrolled to the study. We noted patients’ and controls’ age, height, weight, body mass index (BMI) and detailed medical history. Locations of acrochordons were recorded for the patient group. We recorded values of fasting plasma glucose, insulin, homeostatic model assessment insulin resistance (HOMA-IR), total cholesterol, triglyceride, high-density lipoprotein (HDL), low-density lipoprotein (LDL), free T3 (fT3), free T4 (fT4), thyroid-stimulating hormone (TSH), hemoglobin, ferritin, vitamin B12, aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), alkaline phosphatase (ALP).Results Our study has shown a genetic predisposition to the development of multiple skin tags (P=0.0001). The mean BMI was statistically significant between the patients and controls (P&amp;lt;0.0001). In addition, we have found that when fasting plasma glucose, AST and GGT levels increase, the possibility of the forming of multiple acrochordons also increases (P=0.048, P=0.003, P=0.013). We determined that increasing of BMI is a risk factor for both genders (P=0.003, P&amp;lt;0.0001, respectively). We found that elevated fasting plasma glucose, insulin, HOMA-IR, total cholesterol, triglyceride, AST, ALT and GGT levels increase possibility of the forming of multiple acrochordons in females (P=0.037, P=0.022, P=0.013, P=0.03, P=0.007, P&amp;lt;0.0001, P=0.015, P=0.005, respectively).Conclusion Our results show that multiple acrochordons may be the cutaneous signs of abnormal glucose and lipid metabolism and liver enzyme abnormalities. Thus, we suggest that clinicians should see appropriate bloodtests for patients with multiple skin tags and manage them accordingly.

Beta‐cell Prohormone Convertase 1/3 Plays a Larger Role in Glucose Homeostasis Than Beta‐cell Prohormone Convertase 2 in Mice

Insulin is synthesized in pancreatic beta cells from its precursor proinsulin, which is cleaved by the prohormone convertases 1/3 (PCSK1) and 2 (PCSK2) to generate mature insulin. In patients with type 1 or type 2 diabetes, proinsulin processing to mature insulin is impaired and elevated circulating proinsulin:insulin ratios are found in both conditions. It is unknown whether the beta‐cell prohormone processing impairments observed in diabetes contribute to or are secondary consequences of beta‐cell failure. Given the key role of PCSK1 and PCSK2 in insulin synthesis and beta‐cell function, we hypothesized that beta‐cell PCSK1 or PCSK2 deficiency would result in beta‐cell dysfunction and glucose intolerance.Beta‐cell specific knockout mouse models of Pcsk1 (Pcsk1betaKO) and Pcsk2 (Pcsk2betaKO) were generated using cre‐lox recombination and monitored for changes in glycemia on chow and high‐fat (HF) diets. Neither Pcsk1betaKO or Pcsk2betaKO chow‐fed animals displayed hyperglycemia or impaired glucose tolerance in the first 14 weeks of life. By 26 weeks of age Pcsk1betaKO, but not Pcsk2betaKO, chow‐fed male mice displayed fasting hyperglycemia and impaired glucose tolerance. After 19 weeks of HF diet, 3 of 5 Pcsk1betaKO male mice developed diabetes (fasting glycemia &gt; 16mM), while no hyperglycemia was observed in Pcsk2betaKO mice up to 30 weeks of diet duration. Pcsk1betaKO mice displayed elevated islet and plasma (pro)insulin levels, decreased islet mature insulin levels, translucent insulin granules, and trended toward increased beta‐cell area in the pancreas. Despite altered insulin biosynthesis and immature granules, Pcsk1betaKO islets displayed similar insulin secretion kinetics to Pcsk1 wild‐type islets ex vivo.Our data suggest that Pcsk1 plays a larger role in proinsulin processing and beta‐cell function in mice than Pcsk2. However, despite severe impairments in insulin biosynthesis, Pcsk1‐deficient beta cells compensate remarkably well at early ages and hyperglycemia is only observed in states of increased beta‐cell secretory demand (mild insulin resistance associated with aging or HF diet in mice). Thus, impaired Pcsk1‐mediated prohormone processing, but not Pcsk2‐mediated processing, in beta cells increases diabetes susceptibility in mice.Support or Funding InformationFunding was provided by the Canadian Institutes of Health Research and Canucks for Kids Fund Childhood Diabetes Laboratories

1797-P: ß-arrestin-1 in AgRP Neurons Plays Crucial Role in Maintaining Whole Body Glucose Homeostasis

Hunger and satiety are regulated, to a major extent, by the agouti-related protein (AgRP)/neuropeptide Y (NPY) and proopiomelanocortin (POMC) neurons residing in the arcuate nucleus of the hypothalamus. During starvation, AgRP neurons are strongly activated to promote hunger. Peripheral hormones and nutrients regulate the function of AgRP neurons, thus ensuring proper glucose and energy homeostasis. Recent studies from various labs, including our group, have shown the importance of G-protein coupled receptors (GPCRs) in regulating the activity of AgRP neurons. GPCR function is modulated by a pair of proteins known as beta-arrestin-1 and -2 (barr1 and barr2, respectively), which can terminate GPCR signaling and/or mediate GPCR-independent signaling. It is well established that barr1 and barr2 are involved in many important physiological functions. However, the potential roles of barr1 and barr2 in regulating the activity of AgRP neurons remain unexplored. To address this issue, we generated mice that lacked barr1 or barr2 selectively in AgRP neurons using Cre/loxP-flex-switch technology. Interestingly, AgRP-barr1-KO mice consuming a high fat diet showed significantly impaired glucose tolerance, decreased insulin sensitivity, and elevated plasma glucose and insulin levels. AgRP-barr1-KO mice did not differ from their control littermates in body weight and food intake. More detailed studies into the mechanisms through which barr1 regulates the activity of AgRP neurons may lead to new strategies to alter the activity of AgRP neurons for therapeutic purposes. Disclosure S. Pydi: None. Z. Cui: None. L.F. Barella: None. Y. Cui: None. W. Chen: None. O. Gavrilova: None. J. Wess: None.

Metabolic dysfunction in Emirati subjects in Abu Dhabi: Relationship to levels of soluble RAGEs

BackgroundThe United Arab Emirates is experiencing increasing rates of type 2 diabetes (T2D) and its complications. As soluble levels of the receptor for advanced glycation end products, (sRAGE), and endogenous secretory RAGE (esRAGE), the latter an alternatively spliced form of AGER (the gene encoding RAGE), have been reported to be associated with T2D and its complications, we tested for potential relationships between these factors and T2D status in Emirati subjects. MethodsIn a case-control study, we recruited Emirati subjects with T2D and controls from the Sheikh Khalifa Medical City in Abu Dhabi. Anthropomorphic characteristics, levels of plasma sRAGE and esRAGE, and routine chemistry variables were measured. ResultsTwo hundred and sixteen T2D subjects and 215 control subjects (mean age, 57.4 ± 12.1 vs. 50.7 ± 15.4 years; P < 0.0001, respectively) were enrolled. Univariate analyses showed that levels of sRAGE were significantly lower in the T2D vs. control subjects (1033.9 ± 545.3 vs. 1169.2 ± 664.1 pg/ml, respectively; P = 0.02). Multivariate analyses adjusting for age, sex, systolic blood pressure, pulse, body mass index, Waist/Hip circumference ratio, fasting blood glucose, HDL, LDL, insulin, triglycerides, Vitamin D and urea levels revealed that the difference in sRAGE levels between T2D and control subjects remained statistically-significant, P = 0.03, but not after including estimated glomerular filtration rate in the model, P = 0.14. There were no significant differences in levels of esRAGE. Levels of plasma insulin were significantly higher in the control vs. the T2D subjects (133.6 ± 149.9 vs. 107.6 ± 93.3 pg/L. respectively; P = 0.01, after adjustment for age and sex). Conclusion/discussionLevels of sRAGE, but not esRAGE, were associated with T2D status in Abu Dhabi, but not after correction for eGFR. Elevated levels of plasma insulin in both control and T2D subjects suggests the presence of metabolic dysfunction, even in subjects without diabetes.

SUN-125 Role of Various Insulin Assays in the Diagnosis of Factitious Hypoglycemia

Introduction Factitious hypoglycemia, caused by the surreptitious use of insulin, is an uncommon cause of hypoglycemia, but is similar in presentation to insulinoma and is often a major diagnostic challenge to the physicians. We present the case of a 48-year-old woman who presented with recurrent episodes of hypoglycemia, associated with an elevated plasma insulin level on one assay, but low on another. Factitious illness was denied by the patient until it was definitively proven by mass spectroscopy that the insulin circulating at the time of hypoglycemia was a synthetic insulin analog. Case Report A 48-year-old woman with no significant past medical history presented with recurrent episodes of light headedness, shakiness and sweating of 2 weeks duration that resolved with eating. Her blood pressure was 106/70, pulse 60/min, rest of the physical examination was unremarkable. Her fasting blood glucose was 40 mg/dL with insulin of 81.4 µIU/mL and C peptide 0.71 ng/mL, yet she denied exposure to insulin. Shortly after initiating a 72-hour fast she developed symptomatic hypoglycemia to 45 mg/dL. After 1 mg glucagon, glucose rose to 96 and 83 mg/dL at 10 and 20 minutes, respectively. Her insulin level by chemiluminescent assay was 5 uU/mL (<15 uU/mL fasting, Yale Labs), but 40.2 uU/mL by immunoassay (Quest). C peptide and proinsulin were <0.1 ng/mL, and < 5 pM, respectively. Because of discordant results we further measured free insulin and the beta chain of insulin which were 43 uU/mL (1.5-14.9 uU/mL) by radioimmunoassay, and 53.8 uU/mL (<13.7 uU/mL) by mass spectroscopy. An oral glucose tolerance test was performed when she presented with fasting hypoglycemia with measurement of C peptide, insulin and proinsulin along with mass spectroscopy to identify if an analog insulin was present vs. another substance accounting for discordant results between the two insulin assays. Mass spectroscopy identified the substance as insulin lispro which declined during the glucose tolerance test, while endogenous insulin, C peptide and proinsulin increased, confirming the diagnosis of surreptitious insulin use. Conclusion A high index of clinical suspicion is key to the diagnosis of factitious hypoglycemia as assays specific for human insulin may report low insulin levels when an analog is used. We were able to make a diagnosis of factitious hypoglycemia by measuring insulin using two assays, one specific for human insulin, and the other nonspecific, resulting in discordant findings suspicious for surreptitious use of insulin, which we then confirmed by mass spectroscopy to be insulin lispro. Therefore, in evaluating hypoglycemia, it is important to be aware of variability in the detection of insulin analogues by different assays and the opportunity for definitive identification by mass spectroscopy.

Role of the heterotrimeric inhibitory G‐protein, Gαz, and its unique G‐protein coupled receptor, EP3, in the progression and pathophysiology of Type 2 Diabetes

The hyperglycemia of Type 2 Diabetes (T2D) results from a combination of factors, including insulin resistance, impaired and inefficient insulin secretion, and destruction of pancreatic beta‐cells. Pathways that inhibit beta‐cell cyclic AMP (cAMP) production are pathologically upregulated in T2D. Prostaglandin E2 (PGE2) receptor 3 (EP3), a G protein‐coupled receptor whose expression is up‐regulated in islets of T2D mice and humans, acts through a unique inhibitory G protein, Gz to reduce islet cAMP production. In contrast to expectations, genetic deletion of EP3 greatly accelerates hyperglycemia in the BTBRLeptinOb/Ob(BTBR‐Ob) model of T2D, likely through unregulated adipose tissue lipolysis and severe glucolipotoxicity. In contrast to the ubiquitously‐expressed EP3, the catalytic α‐subunit of Gz (Gαz) is quite tissue‐limited. We back‐crossed the Gαz‐null mutation into the BTBR‐Ob strain for more than 10 generations. Gαz‐null BTBR‐Ob mice maintained normal fasting blood glucose levels, even though they were as obese and insulin resistant as T2D wild‐type controls. Euglycemia correlated directly with elevated plasma insulin levels, islet insulin content and insulin secretion, the latter stimulated by glucose or the glucagon‐like peptide 1 (GLP‐1) agonist, exendin‐4. With the known paracrine effect(s) of GLP‐1 and other islet hormones on beta‐cell function and mass, we quantified the percentage of GLP‐1‐postive alpha‐cells by immunofluorescence of pancreas sections, revealing a strong effect of the Gαz‐null mutation independent of the Ob mutation. To confirm effects on GLP‐1 secretion, isolated islets were cultured overnight and the medium assayed for active GLP‐1. Somatostatin, expressed in delta‐cells and a negative regulator of beta‐cell cAMP production, was also analyzed. Islets from Ob mice secreted significantly more active GLP‐1 into culture medium than lean controls, with no further impact of the Gαz‐null mutation: a result at odds with active GLP‐1 immunofluorescence data. Islets from lean Gαz‐null mice and wild‐type BTBR‐Ob mice secreted significantly more somatostatin into culture medium than wild‐type lean controls, with the Gαz‐null mutation reversing this effect in the BTBR‐Ob background. These somewhat paradoxical results may be due to multiple factors, including islet isolation selecting for healthier, intact islets and/or maintenance of glucolipotoxic conditions being necessary in culturing islets isolated from BTBR‐Ob mice. We are currently exploring the effects of glucolipotoxicity on our hormone secretion assays. To summarize, we have identified a central role for Gαz in the islet pathophysiology of T2D, potentially through both beta‐cell autonomous and intra‐islet cell‐cell communication mechanisms, confirming loss of Gαz permits a more efficient beta‐cell response to glucose and GLP‐1, a physiologic regulator of beta‐cell function and mass.Support or Funding InformationVA Merit Review Award: I01 BX003700‐01A1, VA BLR&amp;DR01 DK102598, NIH/NIDDKAmerican Diabetes Association Innovative Basic Science Award: 1‐14‐BS‐115This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Tissue-dependent effects of cis-9,trans-11- and trans-10,cis-12-CLA isomers on glucose and lipid metabolism in adult male mice

Mixtures of the two major conjugated linoleic acid (CLA) isomers trans-10,cis-12-CLA and cis-9,trans-11-CLA are used as over the counter supplements for weight loss. Because of the reported adverse effects of CLA on insulin sensitivity in some mouse studies, we sought to compare the impact of dietary t10c12-CLA and c9t11-CLA on liver, adipose tissue, and systemic metabolism of adult lean mice. We fed 8 week-old C57Bl/6J male mice with low fat diets (10.5% Kcal from fat) containing 0.8% t10c12-CLA or c9t11-CLA for 9 or 38 days. Diets containing c9t11-CLA had minimal impact on the endpoints studied. However, 7 days after starting the t10c12-CLA diet, we observed a dramatic reduction in fat mass measured by NMR spectroscopy, which interestingly rebounded by 38 days. This rebound was apparently due to a massive accumulation of lipids in the liver, because adipose tissue depots were visually undetectable. Hepatic steatosis and the disappearance of adipose tissue after t10c12-CLA feeding was associated with elevated plasma insulin levels and insulin resistance, compared to mice fed a control diet or c9t11-CLA diet. Unexpectedly, despite being insulin resistant, mice fed t10c12-CLA had normal levels of blood glucose, without signs of impaired glucose clearance. Hepatic gene expression and fatty acid composition suggested enhanced hepatic de novo lipogenesis without an increase in expression of gluconeogenic genes. These data indicate that dietary t10c12-CLA may alter hepatic glucose and lipid metabolism indirectly, in response to the loss of adipose tissue in mice fed a low fat diet.

Oral Ang-(1-7) treatment improves white adipose tissue remodeling and hypertension in rats with metabolic syndrome

ObjectiveAngiotensin (Ang)-(1-7) has preventive effects on metabolic syndrome (MetS). The aim of this study was to evaluate the therapeutic effect of oral Ang-(1-7) on mean arterial pressure (MAP), insulin resistance (IR), inflammatory process, and remodeling of white adipose tissue (WAT) in rats with established MetS. MethodsRats were subjected to control (CT; AIN-93M) or high-fat (HF) diets for 13 wk to induce MetS and treated with Ang-(1-7) or vehicle (V) for the last 6 wk. At the end of 13 wk, MAP, biochemical and histological parameters, and uncoupling protein (UCP) and inflammatory gene expression were determined by quantitative reverse transcription polymerase chain reaction. ResultsHF-V rats showed increased visceral fat deposition, inflammatory cytokine expression, hyperplasia, and hypertrophy in retroperitoneal (WAT) and brown adipose tissue (BAT). Additionally, the gastrocnemius muscle reduced UCP-3 and increased the UCP-1 expression in BAT. HF-V also elevated levels of plasma insulin, glucose, homeostatic model assessment (HOMA) of IR and HOMA-β, and increased body mass, adiposity, and MAP. Ang-(1-7) treatment in rats with MetS [HF-Ang-(1-7)] reduced WAT area, number of adipocytes, and expression of proinflammatory adipokines in WAT and BAT and increased UCP-3 in gastrocnemius muscle and UCP-1 expression in BAT compared with the HF-V group. These events prevented body mass gain, reduced adiposity, and normalized fasting plasma glucose, insulin levels, HOMA-IR, HOMA-β, and MAP. ConclusionData from the present study demonstrated that oral Ang-(1-7) treatment is effective in restoring biochemical parameters and hypertension in established MetS by improving hypertrophy and hyperplasia in WAT and inflammation in adipose tissue, and regulating metabolic processes in the gastrocnemius muscle and BAT.

A novel role of bone morphogenetic protein 6 (BMP6) in glucose homeostasis

AimsBone morphogenetic proteins (BMPs) are involved in the development and homeostasis of multiple organs and tissues. There has been a significant focus on understanding the role of BMPs in pancreatic β-cell dysfunction associated with type 2 diabetes (T2D). Our objective was to investigate the relationship between BMP6 and glucose homeostasis.MethodsOb/ob mice were treated with BMP6 for 6 days and analyzed for insulin release, body weight, lipid parameters and glucose tolerance. Quantitative real-time PCR, chromatin immunoprecipitation and glucose output assays were used to assess BMP6 effect on gluconeogenesis in rat hepatoma H4IIE cells. Specificity of BMP6 receptors was characterized by the utilization of various receptor Fc fusion proteins in luciferase reporter gene and glucose output assays in INS1 and H4IIE cells.ResultsTreatment of ob/ob mice with BMP6 for 6 days resulted in a reduction of circulating glucose and lipid levels, followed by a significantly elevated plasma insulin level in a dose-dependent manner. In addition, BMP6 improved the glucose excursion during an oral glucose tolerance test, lowering the total glycemic response by 21%. In rat H4IIE hepatoma cells, BMP6 inhibited gluconeogenesis and glucose output via downregulation the PepCK expression. Moreover, BMP6 inhibited glucose production regardless of the presence of cAMP, antagonizing its glycogenolytic effect. BMP6 acted on pancreatic and liver cells utilizing Alk3, Alk6 and ActRIIA serine/threonine kinase receptors.ConclusionsCollectively, we demonstrate that BMP6 improves glycaemia in T2D mice and regulates glucose metabolism in hepatocytes representing an exciting prospect for future treatments of diabetes.

The methanolic extract of Thymus praecox subsp. skorpilii var. skorpilii restores glucose homeostasis, ameliorates insulin resistance and improves pancreatic β-cell function on streptozotocin/nicotinamide-induced type 2 diabetic rats

Ethnopharmacological relevanceThymus praecox subsp. skorpilii var. skorpilii (syn. Thymus praecox subsp. jankae (Celak.) Jalas) is consumed as a Turkish folk medicine for the treatment of spasm, sore throat and shortness of breath, also having strong antioxidant activity and the leaves of the plant have been utilized for the treatment of diabetes as the decoction in Turkey. Aim of the studyIn the present study, we aimed to investigate the potential mechanism of antidiabetic action of Thymus praecox subsp. skorpilii var. skorpilii methanolic extract (TPSE) on streptozotocin (STZ)/nicotinamide (NA)-induced type 2 diabetic rats. Materials and methodsSprague Dawley rats were randomly divided into four groups; control, diabetes, TPSE (100 mg/kg b.w, p.o.) and metformin group (400 mg/kg b.w, p.o.). Diabetes was established in all groups except control group by 55 mg/kg STZ (i.p.) for once 15 min after 100 mg/kg NA injection. 3 days after STZ/NA injection, treatments were administered for three weeks and then rats were decapitated; tissue and blood samples were obtained for measuring the level of glucose transporters (both GLUTs and sodium glucose co-transporters (SGLTs)), enzymes related to glucose (Hexokinase (HK), phosphoenolpyruvate carboxykinase (PEPCK), α-glucosidase) and lipid metabolism (Acetyl-coenzyme carboxylase (ACC)), AST, ALT, creatinine, insulin, anti-inflammatory (IL-10) and inflammatory (TNF-α, IL-1β, IL-6) cytokines, AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor gamma (PPAR-γ) and glucagon like peptide-1 (GLP-1). Histopathological alterations of the pancreas were examined. ResultsAfter three weeks of treatment, TPSE has exhibited a significant reduction of plasma levels of the proinflammatory cytokines. Besides, TPSE treatment elevated plasma insulin levels and normalized blood glucose levels. Moreover, it improved the values of AMPK in liver and GLP-1 in pancreas. Increased α-glucosidase, PEPCK, GLUT-2 and SGLTs levels with the induction of diabetes considerably lowered with TPSE treatment. Especially on SGLT-2, TPSE achieved a more prominent decrease. After the atrophy in Langerhans islets due to diabetes induction, treatment was found to prevent the damage of islets. ConclusionsBased on the findings presented here, it has been concluded that TPSE has marked antidiabetic effects through various pathways on STZ/NA-induced diabetic rats and it may potentially be used as an effective treatment for type 2 diabetes mellitus (T2DM). Further research on isolation of the bioactive components is underway.

Polymorphic Role of P2Y6 Receptor in Insulin Sensitive Organs—Adipose Tissue and Skeletal Muscle

Adipose tissue and skeletal muscle are the two largest insulin-sensitive organs in the body. They play a major role in maintaining whole body glucose and energy homeostasis. Insulin action results in glucose disposal principally in skeletal muscle and to a lesser extent in adipose tissue. Dysregulation of this function promotes the development of obesity, insulin resistance and type 2 diabetes. Many G protein-coupled receptors (GPCRs) are expressed in insulin sensitive organs and thus have emerged as potential targets for novel antidiabetic drugs. P2Y purinergic receptors are a class of GPCRs activated by nucleotides and nucleotide sugars. The purinergic P2Y6 receptor (P2Y6R) is activated by uridine 5’-diphosphate. The potential role of P2Y6R in adipose tissue and skeletal muscle with respect to maintaining whole body glucose homeostasis remains unexplored. To address this issue, we used Cre/loxP technology to generate mice that lack P2Y6R selectively in adipose tissue (AT-Y6-KO) or skeletal muscle (SK-Y6-KO). Interestingly, AT-Y6-KO mice consuming a high fat diet gained less weight, while SK-Y6-KO mice gained more weight than the corresponding control mice. Body composition revealed that the difference in body weight was due to loss or gain in fat mass in AT-Y6-KO and SK-Y6-KO mice, respectively. Improved vs. impaired glucose tolerance and insulin sensitivity was observed in AT-Y6-KO and SK-Y6-KO mice, respectively. Moreover, fasting blood glucose and fed plasma insulin levels were decreased in AT-Y6-KO mice. SK-Y6-KO mice showed elevated blood glucose and plasma insulin levels under both fasting and fed conditions. Detailed mechanistic studies are required for understanding the role of P2Y6R in metabolic tissues and to alter its function for therapeutic purposes. Disclosure S. Jain: None. J. Wess: None. K.A. Jacobson: None.

Neuroendocrine and immune disequilibrium as a probable link between metabolic syndrome and carcinogenesis

Numerous investigations prove a higher incidence of carcinogenesis in metabolic syndrome (MetS). They indicate the important role of obesity, elevated inflammatory biomarkers, hyperinsulinemia, hyperglycemia, and dyslipidemia as well. Elevated plasma insulin and free insulin-like growth factor-1 (IGF-1) levels stimulate cell proliferation. The present publication considers the role of neuroendocrine and immune disequilibrium in MetS as a reason for transition to carcinogenesis. It emphasizes the role of hormonal disbalance, i.e. hyperleptinemia, hyperinsulinemia, hypercortisolemia, hypercatecholaminemia, hyperestrogenemia and hyperandrogenemia in MetS. It is presumed that these important components modify cellular microenvironment towards carcinogenesis. The interactions between neurotrophins, leptin, and mast cells and the alterations in the hypothalamo-hypophyseal-adrenal axis in MetS are discussed. It is assumed that they are the consequence of inflammatory distress followed by hormonal and immune disbalance at a central level as well as of enlarged adipose tissue and changed adipocyte microenvironment leading, finally, to carcinogenesis.

Sirtuin 4 controls leucine metabolism and insulin secretion by reversing effects of reactive metabolites

Sirtuins are a family of conserved NAD+‐dependent enzymes that remove a variety of post‐translational acyl lysine modifications. By performing this deacylation function, sirtuins can regulate several aspects of metabolism and aging. Recently, we discovered new post‐translational modifications (PTMs) that can be removed by sirtuin 4 (SIRT4). Interestingly, these PTMs can be generated by reactive metabolites produced during leucine oxidation and in the absence of SIRT4, these PTMs accumulate on and inhibit enzymes in the leucine oxidation pathway. These observations suggest that SIRT4 is a key regulator of leucine metabolism through a novel mechanism that responds to levels of reactive metabolites. Accordingly, we found that SIRT4KO mice have dysregulated leucine metabolism. As a consequence of this, SIRT4KO mice have elevated leucine‐stimulated insulin secretion. Long‐term stimulation of insulin secretion by leucine over time in SIRT4KO mice led to elevated plasma insulin levels even in the basal state. This chronic elevation of insulin was associated with an acceleration of aging‐induced insulin resistance in SIRT4KO mice. Interestingly, when leucine was administered as a bolus with glucose, insulin secretion was synergistically increased more than 3‐fold over glucose or leucine alone in aged SIRT4KO mice. Importantly, this elevated insulin secretion resulted in total normalization of glucose tolerance to resemble that of a young mouse and despite extremely high insulin levels, there was no sign of dangerous hypoglycemia. Thus, our data reveal that short‐term inhibition of SIRT4 potentially has therapeutically relevant effects on leucine metabolism and insulin secretion, but a long‐term loss of SIRT4 can drive inappropriate hyperinsulinemia and lead to insulin resistance. Taken together, our data reveal a novel mechanism of metabolic control involving reactive metabolites and position SIRT4 as a key regulator of leucine metabolism and insulin secretion.Support or Funding InformationWe would like to acknowledge funding support from the American Heart Association grants 12SDG8840004 and 12IRG9010008, The Ellison Medical Foundation, the National Institutes of Health and the NIA grant R01AG045351, and the Duke Pepper Older Americans Independence Center (OAIC) Program in Aging Research supported by the National Institute of Aging (P30AG028716‐01). FKH was supported by an American Diabetes Association/Canadian Diabetes Association Post‐doctoral Fellowship (PF‐3‐13‐4342‐FH).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Cutting the brakes to prevent Type 2 Diabetes onset: augmenting insulin secretion and conserving pancreatic beta‐cell mass by deleting Gαz

The hyperglycemia of Type 2 Diabetes (T2D) results from a combination of factors, including insulin resistance, impaired and inefficient insulin secretion, and destruction of pancreatic beta‐cells. The second messenger molecule, cyclic AMP (cAMP), amplifies glucose‐stimulated insulin secretion and has been suggested to preserve beta‐cell mass. Pathways that inhibit beta‐cell cAMP production are pathologically upregulated in T2D. One such pathway is mediated by Prostaglandin E2 (PGE2) receptor 3 (EP3), a G protein‐coupled receptor whose expression, as well as that of its natural ligand, PGE2, are both up‐regulated in islets collected from T2D mice and humans. While EP3 is ubiquitously expressed, in the beta‐cell it couples to a unique and non‐ubiquitously expressed G protein, Gz. We hypothesized the genetic elimination of the catalytic a‐subunit of Gz (Gαz) would augment beta‐cell function and mass, preventing or delaying the onset of hyperglycemia in the BTBR ob/ob mouse model of T2D. As expected, Gαz‐null ob/ob mice were as obese and as insulin resistant as wild‐type ob/ob mice, consistent with little to no liver, adipose, or muscle Gaz expression, but displayed near‐normal fasting blood glucose levels. Fasting euglycemia in Gaz‐null ob/ob mice correlated directly with elevated plasma insulin levels, suggesting that Gαz‐null ob/ob beta‐cells were able to better compensate for the increased insulin demand of obesity and insulin resistance. To test this directly, we isolated islets from Gaz‐null and wild‐type ob/ob mice, and found higher insulin content and insulin secretion from Gaz‐null ob/ob islets. To further elucidate the molecular mechanisms augmenting beta cell function in Gaz‐null ob/ob islets, we considered the influence of Gaz on glucagon‐like peptide‐1 (GLP‐1), which is a cAMP‐stimulatory gut/islet hormone. We postulated that, in the beta‐cell, Gaz signaling competes with GLP‐1 receptor signling to block the full effects of GLP‐1 on beta‐cell function and/or mass. To test this hypothesis, we subjected wild‐type and Gaz‐null ob/ob mice to intraperitoneal and oral glucose challenge, and found the Gaz‐null mutation partially restored glucose tolerance after an oral glucose challenge but not an intraperitoneal glucose challenge. Plasma levels of the GLP‐1 were not different between the genotypes, but intra‐islet GLP‐1 produced and secreted by alpha cells was altered in Gaz‐null ob/ob islets. Increased GLP‐1 responsiveness of Gaz‐null ob/ob islets was tested directly ex‐vivo by treatment with the stable GLP‐1 analog, exendin‐4. In sum, we identified a key role for Gαz in the islet pathophysiology of T2D and confirmed that deleting Gaz allowed for a more efficient response of the beta‐cell to a physiologic potentiator of insulin secretion and beta‐cell mass, GLP‐1.Support or Funding InformationMolecular and Applied Nutrition Training Program T32

Betaine Down Regulates Apelin Gene Expression in Cardiac and Adipose Tissues of Insulin Resistant Diabetic Rats Fed by High-Calorie Diet

Apelin is a newly discovered peptide that its serum level increases in diabetic patients with cardiovascular dysfunction. Recent studies indicate the beneficial actions of betaine in reducing the cardiovascular and metabolic complications, however data related to its effect on adipocytokine expression is limited. The aim of this study was to evaluate the effect of betaine supplementation on Apelin gene expression in cardiac muscle and adipose tissue of insulin resistance, diabetic rats fed by a high calorie diet. To induce insulin resistance rats were fed with high fat/high carbohydrate diet for five weeks and then 30 mg/kg STZ was injected intraperitoneally. After confirming of diabetes incidence (serum glucose above 7.5 mmol/l) the animals were treated with 1 % betaine in drinking water for 28 days. At days 14 and 28 after treatment, animals were euthanized and Apelin gene expression was evaluated by real time PCR and western blot in heart and adipose tissues. Serum levels of insulin, Apelin and glucose and HOMA–IR were also measured. Our results showed that feeding of rats by a high calorie diets caused insulin resistance, which was manifested by elevated plasma insulin, glucose and Apelin levels and also HOMA–IR. Apelin gene expression in heart and adipose tissues were significantly increased simultaneously with the progression of diabetes. Betaine supplementation decreased serum Apelin and down regulated Apelin expression in adipose tissue and cardiac muscle, particularly at day 28 of treatment. We concluded that betaine might improve metabolic and cardiovascular complications in diabetic patients by regulation of Apelin expression and secretion.

A common variation of the PTEN gene is associated with peripheral insulin resistance

AimPhosphatase and tensin homologue (PTEN) reduces insulin sensitivity by inhibiting the phosphatidylinositol 3-kinase (PI3K)/v-akt murine thymoma viral oncogene homologue (Akt) pathway. This study investigated how a common single nucleotide polymorphism near PTEN, previously associated with fasting levels of plasma insulin and glucose, influences in vivo glucose metabolism and insulin signalling. The primary outcome measure was the gene variant's association with peripheral glucose disposal rate and, secondarily, whether this association was explained by altered activities of PTEN targets PI3K and Akt. MethodsA total of 183 normoglycaemic Danes, including 158 twins and 25 singletons, were genotyped for PTEN rs11202614, which is in complete linkage disequilibrium with rs2142136 and rs10788575, which have also been reported in association with glycaemic traits and type 2 diabetes (T2D). Hepatic and peripheral insulin sensitivity was measured using tracer and euglycaemic–hyperinsulinaemic clamp techniques; insulin secretion was assessed by intravenous glucose tolerance test; and muscle biopsies were taken during insulin infusion from 150 twins for measurement of PI3K and Akt activities. ResultsThe minor G allele of PTEN rs11202614 was associated with elevated fasting plasma insulin levels and a decreased peripheral glucose disposal rate, but not with the hepatic insulin resistance index or insulin secretion measured as the first-phase insulin response and disposition index. The single nucleotide polymorphism was not associated with either PI3K or Akt activities. ConclusionA common PTEN variation is associated with peripheral insulin resistance and subsequent risk of developing T2D. However, the association with insulin resistance is not explained by decreased proximal insulin signalling in skeletal muscle.

Beta Cells Deletion of the Angiotensin‐II Type 1a Receptor Differentially Influences Insulin Levels in Male and Female Mice

Renin‐angiotensin system (RAS) blockade with either Angiotensin Converting Enzyme (ACE) inhibitors or Angiotensin‐II type 1 receptor blockers improves type 2 diabetic (T2D) symptoms. We have shown that up‐regulation of islet AT1a receptors (AT1aR) may be associated with T2D in male mice. However, the role of islet AT1aR on the glucose regulating hormone “insulin”, is yet to be elucidated in a gender specific manner. Therefore, we hypothesized that β‐cell specific AT1aR loss of function positively regulates insulin in male and female C57BL/6 mice. To address this hypothesis, we used male and female 2 months old wildtype (WT) and transgenic β‐AT1a KO (β‐cell specific AT1aR knock out) mice. This new strain was generated by breeding AT1aR flox/flox mice with animals expressing Cre recombinase under the control of a mouse insulin 2 promoter. Basal non‐fasted plasma insulin levels were assessed using an ELISA kit. Plasma insulin levels were significantly increased in β‐AT1a KO male mice compared to gender‐matched WT mice (β‐AT1a KO: 1.24±0.17 vs. WT: 0.9±0.07 ng/mL, P&lt;0.05). However, plasma insulin levels did not differ among β‐AT1a KO and WT females. In addition, β‐AT1a KO males displayed significantly higher plasma insulin levels compared to β‐AT1aKO females (β‐AT1a KO: 1.24±0.17 vs. WT: 0.73±0.09 ng/mL, P&lt;0.05). Further, basal islet ACE2 activity levels were significantly (p&lt;0.05) higher in females compared to males. In addition, we previously showed that, after 16 weeks of high fat diet (HFD) feeding, WT males had significantly increased body weight compared to animals on regular diet (RD) (HFD: 41±0.9 vs. RD: 30.3±0.6 g). Additional features included elevated plasma insulin levels (HFD: 7±0.1 vs. RD: 2.6±0.8 ng/mL) that were associated with hyperglycemia (HFD: 137.2±0.48 vs. RD: 90±3.2 mg/dL) and glucose intolerance (HFD: 44898±2297 vs. RD: 37928±1273 arbitrary units). These changes in glucose homeostasis were associated with an upregulation in islet AT1aR gene (−1.5 fold vs. RD) expression levels but not ACE2 gene expression and activity. Altogether, our results demonstrate that despite having higher basal islet ACE2 activity, islet AT1aR loss of function positively impacts plasma insulin levels in male but not female mice. Therefore, islet AT1aR plays an important role in the regulation of basal insulin levels. Although islet AT1aR levels are positively correlated to impaired glucose homeostasis as well as hyperinsulinemia in a diet induced obese mouse model, further studies are required to better our understanding about the role of islet AT1aR loss of function on blood glucose levels and glucose regulating hormone “insulin” in a diabetic milieu.Support or Funding InformationAmerican Heart Association: 12EIA8030004 and 14PRE18830012COBRE: P30GM106392