Aims: Sleeve gastrectomy (SG) leads to substantial weight loss and improvement in type 2 diabetes, but the underlying mechanisms remain incompletely understood. Given that circulating ghrelin concentrations are reduced after SG; we hypothesized that lower ghrelin may contribute to enhanced insulin sensitivity and beta-cell function after SG. Methods: Human, placebo-controlled, randomized, crossover study. We investigated the effect of elevating ghrelin by an intravenous ghrelin infusion on beta-cell function and insulin sensitivity using the “Botnia-clamp” (intravenous glucose tolerance test combined with hyperinsulinemic-euglycemic clamp), compared with saline co-infusion. Twelve SG operated (age 51±10.9 years, BMI 32.1±4.6 kg/m 2 (mean±SD)), and 10 sex-, age-, and BMI -matched unoperated controls without diabetes were included. Outcomes were peripheral insulin sensitivity (M/I) and beta-cell function, assessed as the disposition index (DI), calculated as first phase insulin secretion x M/I. Results: Ghrelin infusion significantly reduced peripheral insulin sensitivity (M/I) by 25% following SG and 29% in controls compared with saline infusion. Beta-cell function was significantly impaired with a 37% and 29% reduced first phase insulin secretion, and a 49% and 48% reduction in DI, respectively. No groups differences were observed. Main conclusions: Ghrelin infusion impairs insulin sensitivity and beta-cell function in individuals, who have undergone SG as well as in matched control. However, the present findings do not provide evidence that the lower circulating ghrelin concentrations following SG are directly responsible for improvements, as it remains unclear whether this relationship reflects a simple and reversible mechanism.
Dichman et al. (Mon,) studied this question.