Circadian metabolic rhythms in obese children.

Obese children display constant hyperinsulinism and, frequently, hyperphagia. In animals, lesions of the hypothalamic system affect simultaneously the circadian rhythm of insulin secretion and of food intake. In this study, circadian metabolic rhythm was examined in obese and non-obese children, by two different protocols. (1) Oral glucose tolerance tests (OGTT) were carried out at 9 a.m. and 3 p.m. on 2 consecutive days. (2) Circadian variations of plasma glucose and insulin were determined. After OGTT, in the control children there was a significant drop in the insulin/glucose ratio in the afternoon, whereas in the obese group this ratio remained high, with no significant change during the day. Differences were also observed in free fatty acid, growth hormone, and cortisol responses. The control children showed a circadian rhythm for blood glucose levels which was not present in obesity. These preliminary data suggest impairment of metabolic rhythms in obese children; they should stimulate further studies on the hypothalamic system in obesity.

[Plasma insulin, C-peptide and glucose concentrations in type I diabetic children after a morning injection of insulin (author's transl)]. / Taux plasmatiques d'insuline, de C peptide et de glucose chez l'enfant diabétique après injection matinale d'un mélange d'insulin.

Plasma levels of insulin, C-peptide and glucose were monitored for 24 hours after a single injection of a mixture of regular and protamine zinc insulin in 22 diabetic children. Results were compared with those in 7 control children. They indicate that plasma insulin in diabetic children is similar or higher than that in controls over the entire time of survey. Plasma insulin is usually high in the first part of the day. However, important variations were observed from one patient to another and, in the same patient, from one day to another. These results stress the necessity of a daily individual adaptation of the doses in diabetic children and adolescents treated with one or several daily injections of insulin.