Circadian variations of blood sugar and plasma insulin levels in man

Abstract

Blood sugar, plasma insulin, non-esterified fatty acids (NEFA), plasma cortisol, and urinary catecholamines were measured for 24 h in seven normal subjects receiving a standard diet. During the night, blood sugar and plasma insulin remained low, NEFA decreased progressively, and the excretion of catecholamines diminished. During the day, the insulin response appeared particularly important after the morning meal. This last observation was also made when normal subjects were given three identical meals at intervals of four and a half hours. Under these conditions, the postprandial elevations of blood sugar were not statistically different, but the plasma insulin rose significantly higher after the morning meal. These observations may be explained by the existence of a periodicity which would regulate the insulin secretion. It is also possible that the insulin liberated postprandially conserves a certain activity at the moment of the next meal, and still intervenes in the maintaining of blood sugar homeostasis. Later in the day, however, blood sugar homeostasis would necessitate a new synthesis of insulin, which would explain the delayed plasma insulin response to the evening meal. © 1969 Springer-Verlag.