GLP1T-36HK Sigma-AldrichGlucagon Like Peptide-1 (Total) RIA

Glucagon-like peptide-1 (GLP-1) is an incretin hormone that performs a wide array of well-characterized antidiabetic actions, including stimulation of glucose-dependent insulin secretion, upregulation of insulin gene expression and improvements in beta-cell survival. GLP-1-receptor agonists have been developed for treatment of diabetes; however, the short biological half-lives of these peptide-based therapeutics requires that frequent injections be administered to maintain sufficient circulating levels. Thus, novel methods of delivering GLP-1 remain an important avenue of active research. It has recently been demonstrated that self-complimentary, double-stranded, adeno-associated virus serotype-8 (DsAAV8) can efficiently transduce pancreatic beta-cells in vivo, resulting in long-term transgene expression. In this study, we engineered a DsAAV8 vector containing a GLP-1 transgene driven by the mouse insulin-II promoter (MIP). Biological activity of the GLP-1 produced from this transgene was assessed using a luciferase-based bioassay. DsAAV8-MIP-GLP-1 was delivered via intraperitoneal injection and beta-cell damage induced by multiple low dose streptozotocin (STZ) administration. Glucose tolerance was assessed following intraperitoneal glucose injections and beta-cell proliferation measured by PCNA expression. Expression of GLP-1 in Min6 beta-cells resulted in glucose-dependent secretion of biologically active GLP-1. Intraperitoneal delivery of DsAAV8-MIP-GLP-1 to mice led to localized GLP-1 expression in beta-cells and protection against development of diabetes induced by multiple low-dose STZ administration. This protection was associated with significant increase in beta-cell proliferation. Results from this study indicate that expression and secretion of GLP-1 from beta-cells in vivo via DsAAV8 represents a novel therapeutic strategy for treatment of diabetes.

BACKGROUND: Epidemiologic and clinical data indicate that nuts can be incorporated into the diet without compromising body weight. This has been attributed to strong satiety properties, increased resting energy expenditure, and limited lipid bioaccessibility. OBJECTIVE: The role of mastication was explored because of evidence that the availability of nut lipids is largely dependent on the mechanical fracture of their cell walls. DESIGN: In a randomized, 3-arm, crossover study, 13 healthy adults (body mass index, in kg/m(2): 23.1 +/- 0.4) chewed 55 g almonds 10, 25, or 40 times. Blood was collected and appetite was monitored during the following 3 h. Over the next 4 d, all foods were provided, including 55 g almonds, which were consumed under the same chewing conditions. Complete fecal samples were collected. RESULTS: Hunger was acutely suppressed below baseline (P 0.05), and fullness was elevated above baseline longer (P 0.05) after 40 chews than after 25 chews. Two hours after consumption, fullness levels were significantly lower and hunger levels were significantly higher after 25 chews than after 10 and 40 chews (P 0.05). Initial postingestive glucagon-like peptide-1 concentrations were significantly lower after 25 chews than after 40 chews (P 0.05), and insulin concentrations declined more rapidly after 25 and 40 chews than after 10 chews (both P 0.05). Fecal fat excretion was significantly higher after 10 chews than after 25 and 40 chews (both P 0.05). All participants had higher fecal energy losses after 10 and 25 chews than after 40 chews (P 0.005). CONCLUSION: The results indicate important differences in appetitive and physiologic responses to masticating nuts and likely other foods and nutrients. This trial was registered at clinicaltrials.gov as NCT00768417.

Glucagon-like peptide (GLP)-1 is an incretin hormone with well-characterized antidiabetic properties, including glucose-dependent stimulation of insulin secretion and enhancement of beta-cell mass. GLP-1 agonists have recently been developed and are now in clinical use for the treatment of type 2 diabetes. Rapid degradation of GLP-1 by enzymes including dipeptidyl-peptidase (DPP)-IV and neutral endopeptidase (NEP) 24.11, along with renal clearance, contribute to a short biological half-life, necessitating frequent injections to maintain therapeutic efficacy. Gene therapy may represent a promising alternative approach for achieving long-term increases in endogenous release of GLP-1. We have developed a novel strategy for glucose-regulated production of GLP-1 in hepatocytes by expressing a DPP-IV-resistant GLP-1 peptide in hepatocytes under control of the liver-type pyruvate kinase promoter. Adenoviral delivery of this construct to hepatocytes in vitro resulted in production and secretion of bioactive GLP-1 as measured by a luciferase-based bioassay developed to detect the NH(2)-terminally modified GLP-1 peptide engineered for this study. Transplantation of encapsulated hepatocytes into CD-1 mice resulted in an increase in plasma GLP-1 levels that was accompanied by a significant reduction in fasting plasma glucose levels. The results from this study demonstrate that a gene therapy approach designed to induce GLP-1 production in hepatocytes may represent a novel strategy for long-term secretion of bioactive GLP-1 for the treatment of type 2 diabetes.

OBJECTIVE: Compared with Caucasians, obese African-American adolescents have a higher risk for type 2 diabetes. Subclinical inflammation and reduced glucagon-like peptide 1 (GLP-1) concentration are linked to the pathogenesis of the disease. We determined the relationship between insulin resistance, beta-cell activity, and subclinical inflammation with GLP-1 concentrations and whether racial disparities in GLP-1 response were present in 49 obese adolescents (14 +/- 3 years; 76% African American; 71% female). RESEARCH DESIGN AND METHODS: Subjects underwent physical examination and an oral glucose tolerance test. We measured levels of high-sensitivity CRP (CRP(hs)), fibrinogen, glucose, GLP-1(total), GLP-1(active), and insulin. Insulin and glucose area under the curve (AUC), insulinogenic index (DeltaI30/DeltaG30), and composite insulin sensitivity index (CISI) were computed. Subjects were categorized by race and as inflammation positive (INF+) if CRP(hs) or fibrinogen were elevated. RESULTS: No racial differences were seen in mean or relative BMI. Thirty-five percent of subjects had altered fasting or 2-h glucose levels (African American vs. Caucasian, NS), and 75% were INF+ (African American vs. Caucasian, P = 0.046). Glucose and insulin, CISI, and DeltaI30/DeltaG30 values were similar; African Americans had lower GLP-1(total) AUC (P = 0.01), GLP-1(active) at 15 min (P = 0.03), and GLP-1(active) AUC (P = 0.06) and higher fibrinogen (P = 0.01) and CRP(hs) (NS) compared with Caucasians. CONCLUSIONS: African Americans exhibited lower GLP-1 concentrations and increased inflammatory response. Both mechanisms may act synergistically to enhance the predisposition of obese African Americans to type 2 diabetes. Our findings might be relevant to effective deployment of emerging GLP-1-based treatments across ethnicities.

Glucagonlike peptide (GLP) 1, a peptide of 30 amino acids with 50% sequence homology to glucagon, results from expression of the glucagon gene in the L cells of the distal intestinal mucosa. It is secreted early in response to mixed meals by mechanisms involving the presence of unabsorbed nutrients in the gut lumen or the absorptive process itself, but other mechanisms may also be involved. GLP-1 has two important actions. First, it stimulates insulin secretion and inhibits glucagon secretion and thereby inhibits hepatic glucose production and lowers blood glucose levels. It may have effects on glucose clearance independent of its pancreatic effects. It acts on recently cloned G protein-coupled specific receptors and seems to increase insulin secretion via cyclic adenosine monophosphate-dependent increases in intracellular calcium. It has been suggested that activation of the beta cells by GLP-1 is a prerequisite for glucose-induced insulin secretion. Second, it also potently inhibits gastrointestinal secretion and motility and is likely to act as an ileal brake, possibly after activation of cerebral receptors. Therefore, GLP-1 physiologically seems to signal nutritional abundancy and enhance deposition of nutrients. Because of these effects, however, the peptide can completely normalize blood glucose levels in type 2 diabetics and is therefore of considerable pharmaceutical interest.