Meals inhibited secretion of both ghrelin and des-acyl ghrelin, yet long-term fasting inhibited acylation but not total secretion. Acylation may be regulated independently of secretion by nutrient availability in the gut or by esterases that cleave the acyl group. These studies highlight the importance of stringent conditions for sample collection and evaluation of full-length ghrelin and des-acyl ghrelin using specific two-site assays.

These findings suggest possible mechanisms contributing to the effects of high-protein/low-carbohydrate diets to promote weight loss, and high-fat diets to promote weight gain.

Our data support the hypothesis that under normal conditions in subjects given regular meals endogenous acyl-ghrelin acts to increase the amplitude of GH pulses.

Background: Vacuolar ATPase (V-ATPase) proton pumps maintain pH homeostasis. Results: We discovered new V-ATPase inhibitors that uncouple the proton transport and ATPase activity of the pump. Conclusion: Residues at the tether connecting V 0 subunit a to the membrane give uncoupling potential to V-ATPases. Significance: The tether may offer new mechanisms to regulate V-ATPase and cellular pH in vivo by uncoupling the pump.

The lower levels and greater relative changes in ghrelin values reported by the sandwich assays are consistent with greater assay specificity. When applied to the nutrient study, the sandwich assays were better able to distinguish the different responses to different nutrients than were the RIAs.