Objective: To explore the impact of genetic background on pancreatic beta-cell first-phase secretion function with L-arginine (L-ARG) stimulation test.
Methods: Plasma insulin level was detected in 201 cases before and after L-ARG stimulation test. Among them, 61 cases were newly diagnosed type 2 diabetic patients with family history of diabetes (FH+DM), 55 newly diagnosed type 2 diabetic patients without family history of diabetes (FH-DM), 31 with normal glucose tolerance and family history of diabetes (FH+) 54 with normal glucose tolerance but without family history of diabetes (FH-). Homeostasis model assessment (HOMA) was used to estimate insulin resistance (HOMA-IR).
Results: It was premised that gender, age and BMI were similar among the 4 groups. (1) TC, TG, fasting plasma glucose, 2h plasma glucose, fasting insulin and HOMA-IR in the two groups of newly diagnosed type 2 diabetic patients with or without family history of diabetes were significantly higher than those in the two groups of normal glucose tolerance with or without family history of diabetes. The multiples of the peak level and the base level of insulin secretion in the groups of newly diagnosed diabetes were significantly lower than those in the groups of normal glucose tolerance with and without family history (P < 0.05). (2) Insulin secretion reached a peak in 2 minutes and started to decline in 4 minutes in all the four groups. (3) The multiples of the peak level and the base level of insulin secretion in normal glucose tolerance group with family history of diabetes were 20.8% lower than those in the group without family history, being 7.27 and 9.18 respectively (P < 0.05). (4) Two-minute peak insulin secretion, HOMA-IR and age in the newly diagnosed type 2 diabetic group with family history of diabetes was significantly lower than these in the group without family history (P < 0.05). The multiples of the peak level and the base level of insulin secretion in the newly diagnosed type 2 diabetic group with family history of diabetes and that group without family history were 5.18 and 5.31 respectively and there was no significant difference between the two groups (P > 0.05). (5) When the normal glucose tolerance subjects with family history of diabetes progressed to suffer from diabetes, the multiples of the peak level and the base level of insulin secretion declined 43.6% (P < 0.05) more than those in the subjects still with normal glucose tolerance without family history.
Conclusion: In the early course of diabetes, insulin resistance dose not function significantly, but genetic background make the first-phase secretory function of the beta-cell to decline gradually and type 2 diabetes occurs easily. In the absence of genetic background, insulin resistance makes first-phase the secretion of insulin to decline relatively slow.