Relationship between insulin sensitivity and insulin secretion rate: not necessarily hyperbolic

Pregnancy glucagon-like peptide 1 predicts insulin but not glucose concentrations

AIMS

Incretin hormones glucagon-like peptide 1 (GLP-1) and gastric inhibitory peptide (GIP) cause increased insulin secretion in non-pregnant adults, but their role in pregnancy, where there are additional metabolically-active hormones from the placenta, is less clear. The aim of the present study was to assess if fasting and post-load incretin concentrations were predictive of pregnancy insulin and glucose concentrations.

METHODS

Pregnant women (n = 394) with one or more risk factors for gestational diabetes were recruited at 28 weeks for a 75 g oral glucose tolerance test (OGTT). Glucose, insulin, GLP-1 and GIP were measured in the fasting state and 120 min after glucose ingestion.

RESULTS

Fasting plasma GLP-1 concentrations were associated with plasma insulin (standardised β' 0.393 (0.289-0.498), p = 1.3 × 10-12; n = 306), but not with glucose concentrations (p = 0.3). The association with insulin was still evident when adjusting for BMI (β' 0.271 (0.180-0.362), p = 1.1 × 10-8; n = 297). Likewise, at 120 min the OGTT GLP-1 concentrations were associated with plasma insulin concentrations (β' 0.216 (0.100-0.331), p  = 2.7 × 10-4; n = 306) even after adjusting for BMI (β' 0.178 (0.061-0.294), p = 2.9 × 10-3; n = 296), but not with glucose (p  = 0.9). GIP concentrations were not associated with insulin or glucose concentrations at either time point (all p  > 0.2). In pregnancy plasma GLP-1, but not GIP, concentrations appear to be predictive of circulating insulin concentrations, independently of associations with BMIs.

CONCLUSIONS

These results suggest that the relationship between insulin and incretins is preserved in pregnancy, but that other factors, such as placental hormones or counter-regulatory hormones, may be more important determinants of glycaemia and gestational diabetes aetiology.

Follow-Up of Patients After Total Pancreatectomy and Islet Cell Autotransplantation at Off-Site Islet Isolation Facility

CONTEXT

Total pancreatectomy with islet autotransplantation (TPIAT) is a definitive management for intractable pain in patients with chronic pancreatitis (CP). Islet autotransplantation (IAT) allows for the preservation of beta cells to prevent complications of long-term diabetes.

OBJECTIVE

Our study follows TPIAT recipients for up to 12 years to determine the efficacy of the procedure completed with an off-site islet isolation facility.

METHODS

Patient demographics, mixed meal tolerance test measures, glycosylated hemoglobin, insulin requirements, and homeostatic model assessment for insulin resistance values were collected prior to surgery and at the most recent follow-up assessment.

RESULTS

Forty-four patients (median age, 46.0 years; range, 20-78 years) underwent TPIAT for CP. At an overall median follow-up time of 845.5 days (range, 195-4470 days) 8 patients were insulin independent and 36 patients were insulin dependent. At the most recent follow-up time point, islet yield per kilogram was the strongest indicator of insulin independence. Homeostatic model assessment for insulin resistance values were comparable between insulin independent and dependent cohorts.

CONCLUSIONS

Our long-term follow-up data suggest that IAT can effectively reduce insulin requirements and improve postoperative glycemic control.

Prediction of subclinical atherosclerosis in low Framingham risk score individuals by using the metabolic syndrome criteria and insulin sensitivity index

Background

Subclinical atherosclerosis can be present in individuals with an optimal cardiovascular risk factor profile. Traditional risk scores such as the Framingham risk score do not adequately capture risk stratification in low-risk individuals. The aim of this study was to determine if markers of metabolic syndrome and insulin resistance can better stratify low-risk individuals.

Methods

A cross-sectional study of 101 healthy participants with a low Framingham risk score and no prior morbidities was performed to assess prevalence of subclinical atherosclerosis using computed tomography (CT) and ultrasound. Participants were compared between groups based on Metabolic Syndrome (MetS) and Insulin-Sensitivity Index (ISI-cal) scores.

Results

Twenty three individuals (23%) had subclinical atherosclerosis with elevated CT Agatston score ≥1. Presence of both insulin resistance (ISI-cal <9.23) and fulfillment of at least one metabolic syndrome criterion denoted high risk, resulting in significantly improved AUC (0.706 95%CI 0.588–0.822) over the Framingham risk score in predicting elevated CT Agatston score ≥1, with net reclassification index of 50.9 ± 23.7%. High-risk patients by the new classification also exhibited significantly increased carotid intima thickness.

Conclusions

The overlap of insulin resistance and presence of ≥1 criterion for metabolic syndrome may play an instrumental role in identifying traditionally low-risk individuals predisposed to future risk of atherosclerosis and its sequelae.

Relationship Between Insulin Secretion and Insulin Sensitivity and its Role in Development of Type 2 Diabetes Mellitus: Beyond the Disposition Index

We assessed whether the relationship between insulin secretion and sensitivity predicted development of type 2 diabetes in American Indians participating in a longitudinal epidemiologic study. At baseline, when all subjects did not have diabetes, 1566 participants underwent oral tests and 420 had intravenous measures of glucose regulation with estimates of insulin secretion and sensitivity. Standardized major axis regression was used to study the relationship of secretion and sensitivity. Distances away from and along the regression line estimated compensatory insulin secretion and secretory demand, respectively. This relationship differed according to glucose tolerance and BMI categories. The distance away from the line is similar to the disposition index (DI) defined as the product of estimated secretion and sensitivity, but the regression line may differ from a line with constant DI (i.e., it is not necessarily hyperbolic). Subjects with the same DI but different levels of insulin secretion and sensitivity had different incidence rates of diabetes; lower sensitivity with higher secretory demand was associated with greater diabetes risk. Insulin secretion and insulin sensitivity, analyzed together, predict diabetes better than DI alone. Physiologically, this may reflect long-term risk associated with increased allostatic load resulting from the stimulation of insulin hypersecretion by increased glycemia.

Patterns of Insulin Secretion During First-Phase Insulin Secretion in Normal Chinese Adults

BACKGROUND

The increase in diabetes worldwide is alarming. Decreased acute insulin response to intravenous glucose tolerance test (IVGTT) during first-phase insulin secretion (FPIS) is a characteristic of diabetes. However, knowledge of the insulin secretion characteristics identified by different time to glucose peak in subjects with different metabolic state is sparse.

AIMS

This study aimed to find different patterns of FPIS in subjects with normal glucose tolerance (NGT) and analyzed the relationship between insulin secretion patterns and the risk for development of type 2 diabetes mellitus (T2DM).

METHODS

A total of 126 subjects were divided into three groups during a 10-min IVGTT, including NGT with time to glucose peak after 3 min (G1, n = 21), NGT with time to glucose peak at 3 min (G2, n = 95), and prediabetes or diabetes with time to glucose peak at 3 min (G3, n = 10). Glucose, insulin, and C-peptide concentrations at 0, 3, 5, 7, and 10 min during the IVGTT were tested. IVGTT-based indices were calculated to evaluate the insulin secretion and insulin sensitivity.

RESULTS

Age, body mass index (BMI), waist-to-hip ratio, triglyceride (TG), and hemoglobin A1c (HbA1c) of subjects were gradually higher, while high-density lipoprotein cholesterol (HDL-C) was gradually lower from G1 to G3 (p for linear trend <0.05), and the differences between G1 and G2 were also statistically significant (p < 0.05). Glucose peak of most participants in G1 converged at 5 min, and the curves shape of insulin and C-peptide in G2 were the sharpest among three groups. There was no significant difference in all IVGTT-based indices between G1 and G2, but AUC_Ins, AUC_Ins/AUC_Glu, and △Ins₃/△Glu₃ in G2 were the highest, and the p-value for linear trend of those indices among three groups were statistically significant (p < 0.05).

CONCLUSIONS

Two patterns of FPIS were in subjects with NGT, while subjects with later time to glucose peak during FPIS might be less likely to develop T2DM in the future.