Notes on "roux en y gastric bypass increases ethanol intake in the rat" by Davis et al

Fasting-induced increase in plasma ghrelin is blunted by intravenous alcohol administration: a within-subject placebo-controlled study

Ghrelin is a 28-amino acid peptide produced mainly by mucosal neuroendocrine cells lining the fundus of the stomach. Preclinical and clinical studies suggest that ghrelin plays a role in alcoholism. Furthermore, human laboratory studies indicate that acute oral administration of alcohol results in reduced circulating ghrelin. As ghrelin is primarily produced in the stomach, one question never previously explored is whether alcohol administered intravenously (IV) results in similar decrease in ghrelin levels. Thus, this study analyzed the potential effects of IV alcohol administration on plasma ghrelin levels in healthy nonsmoking social drinkers (n=44) who received either a 180-min IV infusion of 6% (v/v) alcohol or 0.9% normal saline in two separate counterbalanced sessions. At each session, participants arrived having fasted for ~7 h and received a light breakfast 60 min before the infusion. The percent change (%Δ) in ghrelin levels was 4.5-fold less in the alcohol condition than the saline condition. In fact, there was only a modest change in ghrelin levels from baseline in the IV alcohol condition (9.6%Δghrelin) while in the IV saline condition there was a robust change (43.4%Δghrelin). There was a trend toward significance in %Δghrelin in the alcohol condition compared to the placebo condition (F[1,33]=3.3, p=0.07). While the exact mechanisms by which alcohol influences ghrelin levels are unclear, alcohol may act directly in the stomach by inhibiting ghrelin secretion and/or release, and may also attenuate ghrelin levels systemically. Although IV alcohol did not reduce circulating ghrelin levels, as seen in previous studies with oral alcohol administration, the present findings suggest that, despite bypassing the stomach, alcohol still attenuated circulating ghrelin levels, i.e. the fasting-induced increase in circulating ghrelin was blunted by IV alcohol administration. These findings lead us to hypothesize that alcohol might affect ghrelin signaling not only via a local effect on the stomach mucosa, but also via a systemic effect.