Meal-feeding promotes skeletal growth by ghrelin-dependent enhancement of growth hormone rhythmicity

The physiological impact of ultradian temporal feeding patterns remains a major unanswered question in nutritional science. We have employed automated and nasogastric feeding to address this question in male rodents and human volunteers. While grazing and meal-feeding reduced food intake in parallel (compared to ad libitum-fed rodents), body length and tibial epiphysial plate width were maintained in meal-fed rodents via the action of ghrelin and its receptor, GHS-R. Grazing and meal-feeding initially suppressed elevated pre-prandial ghrelin levels in rats, followed by either a sustained elevation in ghrelin in grazing rats or pre-prandial ghrelin surges in meal-fed rats. Episodic growth hormone (GH) secretion was largely unaffected in grazing rats, but meal-feeding tripled GH secretion, with burst height augmented and two additional bursts of GH per day. Continuous nasogastric infusion of enteral feed in humans failed to suppress circulating ghrelin, producing continuously elevated circulating GH with minimal rhythmicity. In contrast, bolus enteral infusion elicited post-prandial ghrelin troughs accompanied by reduced circulating GH, with enhanced ultradian rhythmicity. Taken together, our data imply that the contemporary shift from regular meals to snacking behaviour may be detrimental to optimal skeletal growth outcomes by sustaining circulating GH at levels associated with undernourishment and diminishing GH pulsatility.