Key points are not available for this paper at this time.
The relative roles of insulin sensitivity, insulin secretion, and glucose effectiveness to the diurnal rhythm of glucose tolerance were examined in normal-weight (n = 12) and obese (n = 11) subjects. Two frequently sampled intravenous glucose tolerance tests were performed in each subject at 0800 on one occasion and 1800 on a separate day. Tests were preceded by identical fasts of 10-12 h. In nonobese subjects, glucose tolerance, expressed as the 10- to 16-min KG value (KGs), was much reduced in the evening (AM 2.98 +/- 0.45, PM 1.86 +/- 0.33 min-1, P less than 0.002). In the obese subjects, tolerance was lower in the morning than normal-weight subjects (2.19 +/- 0.31 min-1), but unlike in nonobese subjects, tolerance was not significantly reduced during the day (1.90 +/- 0.18 min-1, P greater than 0.40). The reduction in glucose tolerance in the normal-weight subjects was caused by diminished insulin sensitivity (parameter S1, AM 15.4 +/- 2.9, PM 10.2 +/- 1.9 x 10(-5) min-1/pM, P less than 0.01) and reduced beta-cell responsivity to glucose. The evening decrease in the latter was reflected both in first-phase plasma insulin (AM 2466 +/- 441, PM 1825 +/- 381 pM/10 min, P less than 0.05) and the potentiation slope (AM 462 +/- 68, PM 267 +/- 35 pM/mM, P less than 0.01). In contrast, consistent with no diurnal variation in glucose tolerance, obese subjects exhibited no decline in insulin sensitivity in the evening (AM 3.6 +/- 0.7, PM 4.9 +/- 1.0 x 10(-5) min-1/pM).(ABSTRACT TRUNCATED AT 250 WORDS)
Lee et al. (Mon,) studied this question.