Comment on: Gögebakan et al. Glucose-Dependent Insulinotropic Polypeptide Reduces Fat-Specific Expression and Activity of 11β-Hydroxysteroid Dehydrogenase Type 1 and Inhibits Release of Free Fatty Acids. Diabetes 2012;61:292–300

Gogebakan et al. (1) suggest that glucose-dependent insulinotropic polypeptide (GIP) inhibits free fatty acid (FFA) release via direct insulin-independent effects. Their in vitro data are accompanied by a clinical study in which 11 obese male subjects were studied during two (blinded?) 240-min intravenous infusions with GIP (2 pmol/kg/min) and saline, respectively. Because insulin is a well-known suppressor of circulating FFAs, one of the challenges that Gogebakan et al. encounter is to differentiate between the effect of GIP per se and any indirect effects of GIP (in particular via insulin) as outlined by Asmar et al. (2,3). Gogebakan et al. state that the trial was performed under euglycemic and …