Endogenous insulin secretion in newly diagnosed diabetic patients in Saudi Arabia

Diabetes mellitus is a major health problem in Saudi Arabia. The evaluation of endogenous insulin secretion at diagnosis has not yet been studied in this population. We have therefore studied fasting and post-glucagon stimulation levels of glucose, insulin and C-peptide in 216 newly diagnosed untreated diabetic patients. The mean ± SD fasting insulin and C-peptide levels were 14.0 ± 1.8 μU/ml and 1.8 ± 0.4 ng/ml, while post-glucagon stimulation levels were 21.1 ± 3 μU/ml and 2.4 ± 0.4 ng/ml. There were significant post-stimulatory increment levels for insulin, from 4.9 to 13.7 μU/ml, and C-peptide from 0.2 to 1.3 ng/ml ( P < 0.001). Such increments did not affect specified age distribution. We found a significant correlation between the fasting levels and post-stimulation levels of C-peptide and insulin. Obesity correlated with higher basal and post-stimulation levels of both hormones ( r = 0.67, P < 0.001). The mean ± SD fasting insulin and C-peptide levels were 18.5 ± 9.1 μU/ml and 2.4 ± 0.8 ng/ml for obese patients and 11.5 ± 5.1 μU/ml and 1.9 ± 1.1 ng/ml for non-obese patients. The type of diabetes among the Saudi adult diabetic patients studied is characterized by high basal C-peptide and insulin levels which increase significantly with stimulation, suggesting diminished but present endogenous B-cell function.