Incretin Effect in People With Impaired Fasting Glucose

Exploring the Incretin Effect in People With IFG

Regulation of endogenous glucose production (EGP) and insulin secretion are major actions of glucagon-like peptide-1 (GLP-1). Determining whether alterations in GLP-1 may contribute to abnormal EGP and insulin secretion in people with impaired fasting glucose (IFG) was the objective of the current study. The investigators hypothesized that defects in GLP-1 may explain the inappropriate basal EGP and diminished insulin secretion in IFG, and, furthermore, that by increasing circulating GLP-1 levels (using a new medicine called "sitagliptin") the investigators could reverse these defects.

Inclusion Criteria:

• Healthy, sedentary, non-smokers, men and women 45-70 years old Subjects were placed into 1 of the 2 groups based on two 2-hour 75g oral glucose tolerance tests (2h OGTT), separated by one week: a control group with normal glucose tolerance (NGT; n=14; fasting glucose <5.6 mmol/l and 2h OGTT <7.8 mmol/l), or IFG (n=10; fasting glucose 5.6-6.9 mmol/l, and 2h OGTT <7.8 mmol/l).

Exclusion Criteria:

• Subjects were excluded for: thyroid stimulating hormone <50 or >500 milliunits/L, fasting triglycerides >10.3 mmol/l, creatinine >130 μmol/l, elevated liver function tests (>2 times normal), hematocrit < 38%, or white blood cell count <3.0 x 103. Use of medications for lipid and/or glucose lowering also excluded enrollees. Women may not have used hormone replacement therapy in the past 1 year. Smokers. BMI <25 or >40 kg/m2. Diabetes or impaired glucose tolerance.