Insulin and amylin release are both diminished in first-degree relatives of subjects with type 2 diabetes

Abstract

OBJECTIVE - To determine whether first-degree relatives of individuals with type 2 diabetes, who are at high risk of subsequently developing hyperglycemia, manifest alterations in β-cell function including an alteration in the co-release of insulin and amylin. RESEARCH DESIGN AND METHODS - In 30 first-degree relatives and 24 matched subjects with no family history of diabetes, β-cell function was measured as the intravenous glucose-induced acute insulin response (AIRg) and acute amylin response (AAR g). The insulin sensitivity index (S1) was quantified and used to account for the role of insulin sensitivity to modulate β-cell function (S1 x β-cell function). RESULTS - Fasting plasma glucose (5.3 ± 0.1 vs. 5.1 ± 0.1 mmol/l; means ± SEM), immunoreactive insulin (IRI) (68 ± 7 vs. 57 ± 6 pmol/l) and amylin-like immunoreactivity (ALI) (5.5 ± 0.6 vs. 4.7 ± 0.7 pmol/l) were similar in relatives and control subjects, respectively. Relatives were insulin resistant compared with control subjects (S1: 4.86 ± 0.63 vs. 7.20 ± 0.78 × 10-5 min -1·pmol-1·l-1, P = 0.01), but their AIRg (392 ± 59 vs. 386 ± 50 pmol/l) and AAR g (5.9 ± 0.9 vs. 6.1 ± 0.8 pmol/l) did not differ. When β-cell function was determined relative to insulin sensitivity, in the first-degree relatives, both AIRg (S1 x AIRg: 1.60 ± 0.23 vs. 2.44 ± 0.31 × 10-2 min -1, P < 0.05) and AARg (S1 x AAR g: 2.39 ± 0.35 vs. 4.06 ± 0.56 x 10-4 min-1, P < 0.05) were reduced. The molar proportion of ALI to IRI was not altered in high-risk subjects (1.75 ± 0.16 vs. 1.71 ± 0.15%). CONCLUSIONS - First-degree relatives of subjects with type 2 diabetes have diminished β-cell function at a time when they are not hyperglycemic, and this reduction affects insulin and amylin responses proportionally. Thus, an altered amylin-to-insulin ratio is not likely to identify individuals at high risk of developing type 2 diabetes.