Diabetes Care, Vol 17, Issue 8 805-809, Copyright © 1994 by American Diabetes Association

ARTICLES

Comparison of acute daytime and nocturnal insulinization on diurnal glucose homeostasis in NIDDM

I Puhakainen, MR Taskinen and H Yki-Jarvinen
Second Department of Medicine, University of Helsinki, Finland.

OBJECTIVE--The question of whether to use insulin in the evening or in the morning during combination therapy in patients with non-insulin-dependent diabetes mellitus (NIDDM) is controversial. We compared the acute effects of 12-h nocturnal or daytime insulin infusions on the 24-h glucose profile in 20 patients with NIDDM. RESEARCH DESIGN AND METHODS--NIDDM patients were 56 +/- 2 (mean +/- SE) years of age and had a body mass index of 29.6 +/- 1.1 kg/m2; fasting plasma glucose concentration of 12.2 +/- 0.5 mM; and fasting C-peptide concentration of 0.9 +/- 0.2 nM. Each patient was studied twice. On one occasion, the patient received a 12-h intravenous infusion of insulin (mean 1.5 +/- 0.1 IU/h) during the day, and on the other occasion an identical dose of insulin was infused during the night. Blood glucose, insulin, c-peptide, and free fatty acid concentrations were determined for 24 h. RESULTS--The mean 24-h free insulin concentrations were similar in both studies (150 +/- 12 vs. 162 +/- 12 pM, daytime versus nocturnal insulin infusion). The mean 24-h free fatty acid concentration was 18% lower in the nocturnal than in the daytime (309 +/- 30 vs. 376 +/- 30 microM, P < 0.001) insulin infusion study. The mean 24-h C-peptide concentration was less suppressed if insulin was infused overnight than during the day (1.3 +/- 0.2 vs. 1.1 +/- 0.2 nM, P < 0.01). The mean 24-h plasma glucose concentrations were identical in both studies (11.1 +/- 0.6 vs. 11.4 +/- 0.7 mM, daytime versus nocturnal insulin infusion). We also searched for factors predicting the decrease in the blood glucose concentration during the nocturnal insulin infusion. The best predictors were a high initial blood glucose concentration at 2200 and a low fasting C-peptide concentration. These factors explained, independent of each other, 50% of the rate of decrease in the plasma glucose concentration. CONCLUSIONS--Despite better suppression of lipolysis and less suppression of endogenous insulin secretion by nocturnal than daytime insulinization, the hypoglycemic effect of these two treatments is similar.
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