Lean (underweight) NIDDM - peculiarities and differences in metabolic and hormonal status - a pilot study

In the present series of 204 patients with NIDDM, 37 were lean and 35 obese. Mean FBG and HbA1C were significantly higher (P<0.02 and <0.01) in the former. Serum lipids such as total cholesterol (Tc) and triglycerides (Tg) were lower (P<0.05) in the lean while HDLc values were similar. Eight lean patients and 6 obese (Mean BMI : 15.7 vs.27.4) having similar age (48.0 vs 47.7 years) and mean duration of diabetes (4.6 vs 4.2 years) were subjected to the study of insulin and C-peptide status as well as beta cell reserve. The mean basal serum insulin (IRI) level was lower in the lean (15.3 vs. 28.9 mu u/ml ; P<0.05) while there was no statistical difference in the basal C-peptide values. Serum samples analysed 2 hours after 75 G of oral glucose and 1 mg I.V. glucagon (Novo) on two consecutive occasions for IRI and C-peptide responses revealed remarkable differences. The rise in IRI was significantly lower (p<0.01) in the lean after oral glucose and glucagon as compared to the obese. But the C-peptide values did not reveal significant difference suggesting similar reserve in beta cell function in both these groups of patients with NIDDM. The disparity between IRI and C-peptide levels observed was most likely due to excess extraction of insulin by the liver in lean-NIDDM, leading to lower peripheral levels. This phenomenon accounts for the occurrence of severe hyperglycemia inspite of good beta cell function in lean NIDDM.