Metabolic and hormonal studies of Type 1 (insulin-dependent) diabetic patients after successful pancreas and kidney transplantation

Long-term normalization of glucose metabolism is necessary to prevent or ameliorate diabetic complications. Although pancreatic grafting is able to restore normal blood glucose and glycated haemoglobin, the degree of normalization of the deranged diabetic metabolism after pancreas transplantation is still questionable. Consequently glucose, insulin, C-peptide, glucagon, and pancreatic polypeptide responses to oral glucose and i.v. arginine were measured in 36 Type 1 (insulin-dependent) diabetic recipients of pancreas and kidney allografts and compared to ten healthy control subjects. Despite normal HbA1 (7.2±0.2%; normal <8%) glucose disposal was normal only in 44% and impaired in 56% of the graft recipients. Normalization of glucose tolerance was achieved at the expense of hyperinsulinaemia in 52% of the subjects. C-peptide and glucagon were normal, while pancreatic polypeptide was significantly higher in the graft recipients. Intravenous glucose tolerance (n=21) was normal in 67% and borderline in 23%. Biphasic insulin release was seen in patients with normal glucose tolerance. Glucose tolerance did not deteriorate up to 7 years post-transplant. In addition, stress hormone release (cortisol, growth hormone, prolactin, glucagon, catecholamines) to insulin-induced hypoglycaemia was examined in 20 graft recipients and compared to eight healthy subjects. Reduced blood glucose decline indicates insulin resistance, but glucose recovery was normal, despite markedly reduced catecholamine and glucagon release. These data demonstrate the effectiveness of pancreatic grafting in normalizing glucose metabolism, although hyperinsulinaemia and deranged counterregulatory hormone response are observed frequently

Hyperinsulinaemia as long-term predictor of death and ischaemic heart disease in nondiabetic men: The Malmö Preventive Project.

Objectives. Prospective studies have indicated that hyperinsulinaemia/insulin resistance is a risk factor for ischaemic heart disease (IHD), the risk decreasing with time of follow-up. Few studies have so far investigated the role of hyperinsulinaemia in the prediction of long-term total mortality. Setting. Section of Preventive Medicine, Department of Medicine, University Hospital, Malmö, Sweden. Subjects. A total of 6074 nondiabetic, middle-aged, healthy Swedish males. Screening examination. We determined IHD risk factors including blood glucose and plasma insulin before and 2 h after an oral glucose tolerance test (OGTT). Total follow-up time was 19 years. Hyperinsulinaemia was defined as values above the 10th decentile of fasting or 2 h insulin concentration. Main outcome measures. Total mortality and cardiac event (CE) rate for IHD. Results. Unadjusted relative risks (RRs) for both death and CE were J-shaped with the highest relative risk (RR: 1.4-1.6) in the hyperinsulinaemic group compared with all other men. The RRs for death and CE were significant for fasting insulin but became nonsignificant after adjustment for other risk factors and also with a longer follow-up. The risk of death in hyperinsulinaemic men, defined on the basis of 2-h insulin level, increased with time of follow-up and was still significantly increased after 19 years [RR: 1.32 (95% CI: 1.05-1.65], even after adjustment for other risk factors. Conclusions. Fasting hyperinsulinaemia was a predictor of total mortality and IHD in nondiabetic men, although not more significantly after adjustment for other risk factors and with lengthening of follow-up time. The 2-h postglucose hyperinsulinaemia appeared to be a stronger and independent predictor of mortality over long-term follow-up. These findings support the view that insulin resistance with associated cluster of risk factors predicts increased long-term risk of mortality and IHD

Palmitate-Induced β-Cell Dysfunction Is Associated with Excessive NO Production and Is Reversed by Thiazolidinedione-Mediated Inhibition of GPR40 Transduction Mechanisms

BACKGROUND: Type 2 diabetes often displays hyperlipidemia. We examined palmitate effects on pancreatic islet function in relation to FFA receptor GPR40, NO generation, insulin release, and the PPARgamma agonistic thiazolidinedione, rosiglitazone. PRINCIPAL FINDINGS: Rosiglitazone suppressed acute palmitate-stimulated GPR40-transduced PI hydrolysis in HEK293 cells and insulin release from MIN6c cells and mouse islets. Culturing islets 24 h with palmitate at 5 mmol/l glucose induced beta-cell iNOS expression as revealed by confocal microscopy and increased the activities of ncNOS and iNOS associated with suppression of glucose-stimulated insulin response. Rosiglitazone reversed these effects. The expression of iNOS after high-glucose culturing was unaffected by rosiglitazone. Downregulation of GPR40 by antisense treatment abrogated GPR40 expression and suppressed palmitate-induced iNOS activity and insulin release. CONCLUSION: We conclude that, in addition to mediating acute FFA-stimulated insulin release, GPR40 is an important regulator of iNOS expression and dysfunctional insulin release during long-term exposure to FFA. The adverse effects of palmitate were counteracted by rosiglitazone at GPR40, suggesting that thiazolidinediones are beneficial for beta-cell function in hyperlipidemic type 2 diabetes

Excessive Islet NO Generation in Type 2 Diabetic GK Rats Coincides with Abnormal Hormone Secretion and Is Counteracted by GLP-1

BACKGROUND: A distinctive feature of type 2 diabetes is inability of insulin-secreting beta-cells to properly respond to elevated glucose eventually leading to beta-cell failure. We have hypothesized that an abnormally increased NO production in the pancreatic islets might be an important factor in the pathogenesis of beta-cell dysfunction. PRINCIPAL FINDINGS: We show now that islets of type 2 spontaneous diabetes in GK rats display excessive NO generation associated with abnormal iNOS expression in insulin and glucagon cells, increased ncNOS activity, impaired glucose-stimulated insulin release, glucagon hypersecretion, and impaired glucose-induced glucagon suppression. Pharmacological blockade of islet NO production by the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) greatly improved hormone secretion from GK islets suggesting islet NOS activity being an important target to inactivate for amelioration of islet cell function. The incretin hormone GLP-1, which is used in clinical practice suppressed iNOS and ncNOS expression and activity with almost full restoration of insulin release and partial restoration of glucagon release. GLP-1 suppression of iNOS expression was reversed by PKA inhibition but unaffected by the proteasome inhibitor MG132. Injection of glucose plus GLP-1 in the diabetic rats showed that GLP-1 amplified the insulin response but induced a transient increase and then a poor depression of glucagon. CONCLUSION: The results suggest that abnormally increased NO production within islet cells is a significant player in the pathogenesis of type 2 diabetes being counteracted by GLP-1 through PKA-dependent, nonproteasomal mechanisms

The effects of hyperinsulinemia on arterial wall and peripheral muscle metabolism in dogs

Peripheral hyperinsulinemia may be associated with metabolic consequences that could contribute to the high incidence of macrovascular disease in patients with diabetes mellitus. Arterial wall and striated muscle cells were studied in dogs to examine the effect of hyperinsulinemia on the lipid content and on lipogenic and glycolytic enzyme activity. Eight pancreatectomized dogs received segmental pancreatic autografts with venous drainage into the iliac vein. Glucose disappearance rates (K values) were normal four years after transplantation, but both fasting serum insulin levels (48.9 ± 4.8 v 11.8 ± 1.9 μU/mL) and the total area under the glucose-insulin response curve (1797 ± 196 v 1110 ± 158 μU · min/mL) were significantly greater than in control animals ( P < 0.05). The hyperinsulinemic dogs had a marked triglyceride elevation in arterial smooth muscle (20.6 ± 8.0 v 0.5 ± 0.4 μmol/g) and striated muscle (171.4 ± 46.6 v 41.2 ± 7.7 μmol/g) ( P < 0.001). Moreover, key enzymes in lipid synthesis (glucose-6-phosphate dehydrogenase, malic enzyme, and 3-hydroxyacyl-CoA DH) were significantly increased ( P < 0.01) in the hyperinsulinemic animals, while the glycolytic enzymes, (phosphofructokinase, hexokinase, pyruvate kinase, and α-glycerophosphate DH) were not significantly different. These data demonstrate substantial enhancement of lipid synthesis in arterial wall and striated muscle in hyperinsulinemic dogs. Altered substrate metabolism in arterial walls, in association with hyperinsulinemia, may have important implications with regard to macrovascular disease in diabetes, particularly in insulin-treated patients. In addition, these studies may serve to stimulate longer term assessments of macroangiopathy in the increasing number of patients with functioning pancreatic allografts draining into the systemic circulation