Acute effect of glipizide on glucose tolerance in obesity and diabetes mellitus (NIDDM)

Insulin secretagogues for prevention or delay of type 2 diabetes mellitus and its associated complications in persons at increased risk for the development of type 2 diabetes mellitus

BACKGROUND

The projected rise in the incidence of type 2 diabetes mellitus (T2DM) could develop into a substantial health problem worldwide. Whether insulin secretagogues (sulphonylureas and meglitinide analogues) are able to prevent or delay T2DM and its associated complications in people at risk for the development of T2DM is unknown.

OBJECTIVES

To assess the effects of insulin secretagogues on the prevention or delay of T2DM and its associated complications in people with impaired glucose tolerance, impaired fasting blood glucose, moderately elevated glycosylated haemoglobin A1c (HbA1c) or any combination of these.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials, MEDLINE, PubMed, Embase, ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform, and the reference lists of systematic reviews, articles and health technology assessment reports. We asked investigators of the included trials for information about additional trials. The date of the last search of all databases was April 2016.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) with a duration of 12 weeks or more comparing insulin secretagogues with any pharmacological glucose-lowering intervention, behaviour-changing intervention, placebo or no intervention in people with impaired fasting glucose, impaired glucose tolerance, moderately elevated HbA1c or combinations of these.

DATA COLLECTION AND ANALYSIS

Two review authors read all abstracts and full-text articles/records, assessed quality and extracted outcome data independently. One review author extracted data which were checked by a second review author. We resolved discrepancies by consensus or the involvement of a third review author. For meta-analyses we used a random-effects model with investigation of risk ratios (RRs) for dichotomous outcomes and mean differences (MDs) for continuous outcomes, using 95% confidence intervals (CIs) for effect estimates. We carried out trial sequential analyses (TSAs) for all outcomes that could be meta-analysed. We assessed the overall quality of the evidence by using the GRADE instrument.

MAIN RESULTS

We included six RCTs with 10,018 participants; 4791 participants with data on allocation to intervention groups were randomised to a second- or third-generation sulphonylurea or a meglitinide analogue as monotherapy and 29 participants were randomised to a second-generation sulphonylurea plus metformin. Three trials investigated a second-generation sulphonylurea, two trials investigated a third-generation sulphonylurea and one trial a meglitinide analogue. A total of 4873 participants with data on allocation to control groups were randomised to a comparator group; 4820 participants were randomised to placebo, 23 to diet and exercise, and 30 participants to metformin monotherapy. One RCT of nateglinide contributed 95% of all participants. The duration of the intervention varied from six months to five years. We judged none of the included trials as at low risk of bias for all 'Risk of bias' domains.All-cause and cardiovascular mortality following sulphonylurea (glimepiride) treatment were rarely observed (very low-quality evidence). The RR for incidence of T2DM comparing glimepiride monotherapy with placebo was 0.75; 95% CI 0.54 to 1.04; P = 0.08; 2 trials; 307 participants; very low-quality evidence. One of the trials reporting on the incidence of T2DM did not define the diagnostic criteria used. The other trial diagnosed T2DM as two consecutive fasting blood glucose values ≥ 6.1 mmol/L. TSA showed that only 4.5% of the diversity-adjusted required information size was accrued so far. No trial reported data on serious adverse events, non-fatal myocardial infarction (MI), non-fatal stroke, congestive heart failure (HF), health-related quality of life or socioeconomic effects.One trial with a follow-up of five years compared a meglitinide analogue (nateglinide) with placebo. A total of 310/4645 (6.7%) participants allocated to nateglinide died compared with 312/4661 (6.7%) participants allocated to placebo (hazard ratio (HR) 1.00; 95% CI 0.85 to 1.17; P = 0.98; moderate-quality evidence). The two main criteria for diagnosing T2DM were a fasting plasma glucose level ≥ 7.0 mmol/L or a 2-hour post challenge glucose ≥ 11.1 mmol/L. T2DM developed in 1674/4645 (36.0%) participants in the nateglinide group and in 1580/4661 (33.9%) in the placebo group (HR 1.07; 95% CI 1.00 to 1.15; P = 0.05; moderate-quality evidence). One or more serious adverse event was reported in 2066/4602 (44.9%) participants allocated to nateglinide compared with 2089/4599 (45.6%) participants allocated to placebo. A total of 126/4645 (2.7%) participants allocated to nateglinide died because of cardiovascular disease compared with 118/4661 (2.5%) participants allocated to placebo (HR 1.07; 95% CI 0.83 to 1.38; P = 0.60; moderate-quality evidence). Comparing participants receiving nateglinide with those receiving placebo for the outcomes MI, non-fatal stroke and HF gave the following event rates: MI 116/4645 (2.5%) versus 122/4661 (2.6%), stroke 100/4645 (2.2%) versus 110/4661 (2.4%) and numbers hospitalised for HF 85/4645 (1.8%) versus 100/4661 (2.1%) - (HR 0.85; 95% CI 0.64 to 1.14; P = 0.27). The quality of the evidence was moderate for all these outcomes. Health-related quality of life or socioeconomic effects were not reported.

AUTHORS' CONCLUSIONS

There is insufficient evidence to demonstrate whether insulin secretagogues compared mainly with placebo reduce the risk of developing T2DM and its associated complications in people at increased risk for the development of T2DM. Most trials did not investigate patient-important outcomes.

Lifestyle intervention, glucose tolerance, and risk of developing type 2 diabetes mellitus

Diabetes mellitus is rapidly becoming one of the main health issues in the 21st century. Environmental factors such as lifestyle habits (i.e., physical inactivity and dietary intake) and obesity may act as initiating factors or progression factors for type 2 diabetes. Therefore, changes in lifestyle (i.e., diet and physical activity) should have the potential to postpone or prevent the development of type 2 diabetes mellitus in subjects at high risk (for example, those with impaired glucose tolerance [IGT]). Several independent and well-controlled randomized studies have shown the beneficial impact of a lifestyle intervention program on glucose tolerance, insulin resistance, and diabetes risk in populations at risk for developing type 2 diabetes mellitus. After 2 years of a combined diet and physical activity intervention program, according to general public health guidelines, the Study on Lifestyle-intervention and IGT Maastricht (SLIM) revealed an improved glucose tolerance in the intervention group compared to a further deterioration in the control group. The Finnish Diabetes Prevention Study (DPS) and the US Diabetes Prevention Program (DPP) both observed a 58% reduction in diabetes risk after 3 years of intervention in a high-risk population. Although other intervention strategies can reduce the incidence of diabetes, lifestyle changes are the most effective mean of delaying or preventing the development of type 2 diabetes mellitus. For a successful implementation of a diabetes prevention program in a primary healthcare setting, both patients and healthcare professionals should be aware of the (clinical) significance of impaired glucose tolerance and the effectiveness of lifestyle interventions to prevent or postpone type 2 diabetes mellitus and its complications.

A novel mechanism of glipizide sulfonylurea action: decreased metabolic clearance rate of insulin

To examine whether sulfonylureas inhibit the metabolic clearance rate (MCR) of insulin, 19 healthy young subjects participated in two experiments. In the first protocol (n = 10), a 3-h oral glucose load was performed with and without 2 mg of glipizide given 30 min before glucose ingestion. The total insulin response was 60% greater with than without glipizide (5.9 +/- 0.6 vs 3.7 +/- 0.5 microU/ml; P < 0.001). However, the total C-peptide responses were virtually identical (4.7 +/- 0.5 vs 4.8 +/- 0.4 nmol/l) in both studies. In the second protocol (n = 9), the MCR of insulin was measured during 4-h euglycemic insulin clamps performed with and without glipizide. In the study with glipizide, the subjects ingested 5 mg of glipizide at 120 min. The steady-state plasma insulin concentration during the 4th h, i.e., 1-2 h after glipizide ingestion, was significantly higher than during the 2nd h, i.e., before glipizide ingestion (99 +/- 22 vs 78 +/- 17 microU/ml; P < 0.01). In addition, glucose uptake during the 4th h was greater (8.0 +/- 1.6 vs 6.4 +/- 1.5 mg/kg.min) and the MCR of insulin was reduced (503 +/- 126 vs 621 +/- 176 ml/m2.min; P < 0.01). We conclude that glipizide augments plasma insulin levels both by enhancing its secretion and by decreasing the MCR of insulin.