Daily glucose and insulin rhythms in diabetic dogs on the artificial beta cell

The circadian periods of plasma glucose, insulin and alpha-amino nitrogen (alpha-AN) were studied in fed and fasting normal and diabetic dogs which were fed either beef or beef supplemented with carbohydrates (CH). The diabetics were either withdrawn from insulin supply or treated with an artificial beta cell (ABC) or infused a constant insulin dose (CI).--There was a significant daily glucose rhythm in normal fasting animals and in fasting diabetics on CI or on insulin withdrawal. In the fed controls, the phase of the rhythms depends on carbohydrate content of food. In CH-free fed controls the insulin maxima were related to alpha-AN but in CH-fed controls they were related to glycemia. Due to the mechanism of ABC-provided insulin dosage, the phases of glucose and of insulin oscillations were correlated in all diabetics on ABC. Thus even if the mean glucose level is normalized by ABC the intrinsic phase relations remain altered.--It is concluded that the daily glucose periodicity is based on endogenous rhythms in glucose production and utilization and is essentially independent of current insulin provision. But it is governed by the meals as main "Zeitgebers" and modified by the actual insulin supply.