Hyperinsulinemia decreases second-phase but not first-phase arginine-induced insulin release in humans

Autologous Pancreatic Islet Cell Transplantation Following Pancreatectomy for Pancreas Diseases Other Than Chronic Pancreatitis: A 15-Y Study of the Milan Protocol

BACKGROUND

Pancreatogenic diabetes, a consequence of pancreatic tissue loss following pancreatectomy, poses a significant challenge for patients undergoing pancreatic surgery. Islet autotransplantation (IAT) offers a promising approach to prevent or alleviate pancreatogenic diabetes, but its application has been limited to individuals with painful chronic pancreatitis.

METHODS

This study presents a 15-y clinical experience with the Milan Protocol, which expands IAT after pancreatectomy to a broader spectrum of patients with malignant and nonmalignant pancreatic diseases. The analysis evaluates feasibility, efficacy, and safety of IAT. Modified Igls criteria validated through the arginine test and mixed meal tolerance tests were used to assess long-term metabolic outcomes.

RESULTS

Between November 2008 and June 2023, IAT procedures were performed on 114 of 147 candidates. IAT-related complications occurred in 19 of 114 patients (16.7%), with 5 being potentially serious. Patients exhibited sustained C-peptide secretion over the 10-y follow-up period, demonstrating a prevalence of optimal and good beta-cell function. Individuals who underwent partial pancreatectomy demonstrated superior metabolic outcomes, including sustained C-peptide secretion and a reduced risk of developing diabetes or insulin dependence compared with those who underwent total pancreatectomy. For patients who had total pancreatectomy, the quantity of infused islets and tissue volume were identified as critical factors influencing metabolic outcomes. An increased risk of recurrence or progression of baseline diseases was not observed in subjects with neoplasms.

CONCLUSIONS

These findings provide valuable insights into the benefits and applications of IAT as a therapeutic option for pancreatogenic diabetes after pancreatic surgery, expanding its potential beyond painful chronic pancreatitis.

Experimental BPA Exposure and Glucose-Stimulated Insulin Response in Adult Men and Women

Context

Human cross-sectional and animal studies have shown an association of the chemical bisphenol A (BPA) with insulin resistance, type 2 diabetes, and other metabolic diseases, but no human experimental study has investigated whether BPA alters insulin/C-peptide secretion.

Design

Men and postmenopausal women (without diabetes) were orally administered either the vehicle or a BPA dose of 50 µg/kg body weight, which has been predicted by US regulators (Food and Drug Administration, Environmental Protection Agency) to be the maximum, safe daily oral BPA dose over the lifetime. Insulin response was assessed in two cross-over experiments using an oral glucose tolerance test (OGTT; experiment 1) and a hyperglycemic (HG) clamp (experiment 2). Main outcomes were the percentage change of BPA session measures relative to those of the control session.

Results

Serum bioactive BPA after experimental exposure was at levels detected in human biomonitoring studies. In the OGTT, a strong positive correlation was found between hemoglobin A1c(HbA1c) and the percentage change in the insulinogenic index (Spearman = 0.92), an indicator of early-phase insulin response, and the equivalent C-peptide index (Pearson = 0.97). In the HG clamp study, focusing on the later-phase insulin response to a stable level of glucose, several measures of insulin and C-peptide appeared suppressed during the BPA session relative to the control session; the change in insulin maximum concentration (Cmax) was negatively correlated with HbA1c and the Cmax of bioactive serum BPA.

Conclusions

This exploratory study suggests that BPA exposure to a dose considered safe by US regulators may alter glucose-stimulated insulin response in humans.

Autologous pancreatic islet transplantation in human bone marrow

The liver is the current site of choice for pancreatic islet transplantation, even though it is far from being ideal. We recently have shown in mice that the bone marrow (BM) may be a valid alternative to the liver, and here we report a pilot study to test feasibility and safety of BM as a site for islet transplantation in humans. Four patients who developed diabetes after total pancreatectomy were candidates for the autologous transplantation of pancreatic islet. Because the patients had contraindications for intraportal infusion, islets were infused in the BM. In all recipients, islets engrafted successfully as shown by measurable posttransplantation C-peptide levels and histopathological evidence of insulin-producing cells or molecular markers of endocrine tissue in BM biopsy samples analyzed during follow-up. Thus far, we have recorded no adverse events related to the infusion procedure or the presence of islets in the BM. Islet function was sustained for the maximum follow-up of 944 days. The encouraging results of this pilot study provide new perspectives in identifying alternative sites for islet infusion in patients with type 1 diabetes. Moreover, this is the first unequivocal example of successful engraftment of endocrine tissue in the BM in humans.

Regulation of glucose tolerance in patients after liver transplantation: impact of cyclosporin versus tacrolimus therapy

BACKGROUND

We investigated the factors regulating glucose homeostasis in 10 healthy (control) subjects, as well as in stable, long-term, liver-grafted patients receiving monotherapy in the form of either cyclosporin A (n=10) or tacrolimus (n=10).

METHODS

We measured insulin sensitivity, first- and second-phase insulin secretion, with a minimal modeling technique based on the analysis of glucose, insulin, and C-peptide profiles during frequently sampled intravenous glucose tolerance tests (FSIGTT). Proinsulin levels, as a marker of beta-cell dysfunction, were measured in the fasting state and during FSIGTT.

RESULTS

Glucose and insulin concentrations before and after glucose loading did not differ in liver transplant patients and in control subjects. Fasting C-peptide levels in both liver-grafted groups were higher than in healthy subjects and remained elevated during FSIGTT (P<0.05). Intravenous glucose tolerance [(K(G)), i.e. the slope of the regression of logarithm of the blood glucose concentrations vs. time], insulin sensitivity, and first-phase insulin secretion did not differ in liver-grafted groups and healthy subjects. Second-phase insulin secretion was about 56% higher in liver-grafted patients than in controls (P<0.05). Body mass index was the overall determinant of insulin sensitivity in all groups.

CONCLUSIONS

Long-term monotherapy with cyclosporin A or tacrolimus has no deleterious effects on insulin sensitivity, first-phase insulin secretion, and insulin synthesis in liver transplant patients. Normal insulin sensitivity (posthepatic insulin effect) and enhanced second-phase insulin secretion (prehepatic insulin) point to an accelerated hepatic insulin clearance rate in liver transplant patients. Increased hepatic insulin clearance is compensated by enhanced insulin secretion, indicating that insulin clearance is the major determinant of pancreatic function in liver-grafted patients.

Interaction of insulin, glucagon-like peptide 1, gastric inhibitory polypeptide, and appetite in response to intraduodenal carbohydrate

The relation between gastrointestinal incretin hormones in the control of insulin release and short-term satiety by intestinal carbohydrate was investigated in 8 fasted, healthy male volunteers. Insulin, gastric inhibitory polypeptide (GIP), glucagon-like peptide 1 (GLP-1), and appetite ratings were measured during, and food intake was measured after, intraduodenal infusions of glucose or saline. Studies were conducted under hyperinsulinemic and euglycemic conditions. Raising plasma insulin with intravenous insulin infusion to concentrations slightly above usual postprandial concentrations (356.4 +/- 4.8 pmol/L) had no effect on GIP, GLP-1, or appetite ratings before the intraduodenal infusions began. Intraduodenal glucose infusion resulted in a further increase in plasma insulin to a peak of 779.4 +/- 114.0 pmol/L, caused an early increase in plasma GIP and a later increase in GLP-1 concentrations (P < 0.01), suppressed appetite (P < 0.05), and reduced energy intake (P < 0.01) compared with intraduodenal infusion of saline. There was a close association between the increase in GLP-1 and decrease in appetite. Infusion of octreotide to suppress the release of gastrointestinal hormones prevented the rise in insulin, GIP, and GLP-1 induced by intraduodenal glucose infusion and reversed the suppression of appetite and reduction in energy intake. These results suggest that 1) when infused to result in plasma concentrations slightly above usual postprandial concentrations, insulin does not inhibit its own release and 2) the effects of intraduodenal glucose on appetite may be mediated through the release of GLP-1 and not insulin.