Circannual rhythm of insulin release and hypoglycemic effect of tolbutamide stimulus in healthy man.
Four healthy non obese young volunteers were observed for a 24-hr period, every other month, over the course of one year. Tolbutamide was injected i.v. each day of the experiment every four hours. Tolbutamide-induced insulin secretion (T.I.I.S.) was evaluated by planimetrically measuring insulin areas above basal levels. Tolbutamide-induced hypoglycemic effect was evaluated by measuring the blood glucose difference between the 5th and 25th minute after the drug injection (delta G5'-25'). The macroscopic evaluation of T.I.I.S. and delta G5'-25' (mean chronograms) permitted the detection of the existence of a circannual variation of both variables. In particular the maximum level of the blood glucose drop (delta G5'-25') was registered in February. Subsequently the quantification of the rhythm of T.I.I.S. was obtained by fitting a sine curve, according to the Cosinor method. The highest insulin release was confirmed in winter. As previously documented, the existence of a statistically significant circadian rhythm of T.I.I.S. was confirmed in the morning, i.e. the same period of the day in which insulin-induced hypoglycemia occurs.
D000328:Adult; D001786:Blood Glucose / Q000032:analysis*; D006801:Humans; D007003:Hypoglycemia / Q000139:chemically induced / Q000503:physiopathology; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D010507:Periodicity; D012621:Seasons; D012636:Secretory Rate / Q000187:drug effects; D014044:Tolbutamide / Q000494:pharmacology
D001786:Blood Glucose; D007328:Insulin; D014044:Tolbutamide