Monitoring beta cell responses in obese and normal weight subjects--a pilot study.

Six obese and six normal subjects were given a test meal after an overnight fast. Blood glucose, plasma immunoreactive C peptide, immunoreactive insulin and proinsulin plus its circulating fragment des Lys64, Arg65 proinsulin were measured. Responses to the test meal were not significantly different for immunoreactive C peptide and insulin concentrations. Plasma insulin responses were similar in the two groups. Plasma C-peptide values showed wide variations in the obese subjects. Plasma proinsulin and proinsulin fragment levels rose slightly in the normal subjects reaching a peak level of 28.9 +/- 6.4 pmol/l whereas in the obese subjects these same levels rose to a maximum of 88 +/- 45 pmol/l. However because of the large intra group variation, differences were not significant.