Insulin is not mandatory for postprandial decrease of human plasma ghrelin

Ghrelin is the most powerful peripheral orexigenic hormone in mammalian physiology. Ghrelin plasma concentrations increase prior to meal onset, but decrease postprandially. We and others reported previously that insulin reduces circulating ghrelin levels and might therefore be a driving force for postprandial suppression of ghrelin. To test the influence of insulin on postprandial ghrelin regulation, a patient with type 1 diabetes with complete insulin deficiency received a low glycemic index meal and subsequently an additional high glycemic index meal in the absence of insulin substitution. Subsequently, a subcutaneous injection of 0,08 IU Lispro Insulin per kg bodyweight was given. Results were compared to those of a healthy control subject matched for sex, age and BMI, who was undergoing the same test series (without Lispro bolus) in the presence of endogenous postprandial insulin secretion. A substantial decrease of plasma ghrelin levels was observed in the insulin deficient patient following low glycemic index carbohydrate load (27% plasma ghrelin decrease). The subsequent exposure to a high glycemic index meal resulted in a slight additional reduction of ghrelin levels (32% from baseline), while Lispro bolus did not induce further changes of circulating ghrelin (27% of baseline at termination). This postprandial response was comparable to that of the healthy control subject (33% reduction after the first meal, 40% after the second meal).

These data tentatively suggest that postprandial secretion of ghrelin is not exclusively regulated by plasma insulin or plasma glucose but may depend on other metabolic factors yet to be identified.