Endocrine Abstracts

Ultradian rhythms of metabolic hormone secretion govern biological activity and are themselves regulated by temporal patterns of feeding behaviour. Despite these well-established phenomena, the broader metabolic impact of temporal feeding patterns remains a major unanswered question in nutritional science. Using an automated CLAMS-based feeding system, we have shown that nocturnal grazing (GR) had no impact on cumulative food intake (cF/I) or body weight gain (ΔBW) in male and female C57BL6/J (WT) mice (vs ad libitum-fed (AL) animals). In contrast, while cF/I in nocturnal meal-fed (MF) male WT mice was only 88% of that in AL males (P=0.1036), this was exaggerated in GHSR-null males (reduced by 15%; P=0.0082). ΔBW was also reduced by 62% in MF GHSR-null females (vs AL GHSR-null females; P=0.0099). Although GR did not affect skeletal growth rate (tibial epiphyseal plate width (tEPW)) in males, MF accelerated skeletal growth by 13% (P=0.0166). However, in females GR and MF reduced tEPW by 13% and 15% (P=0.0158; 0.0029). These effects were absent in GHSR-null mice. GR increased retroperitoneal white adipose tissue (WAT) mass in male and female mice (by 84% and 41%; P=0.0146, 0.0219), with no significant effect on gonadal WAT mass. Inguinal WAT mass was elevated only in males (by 37%; P=0.032). These effects were abolished in GHSR-null mice. Neither GR nor MF significantly affected interscapular brown AT (BAT) mass. Thus, GR elevates fat mass in ghrelin-sensitive depots in both sexes, while ghrelin maintains orexigenic drive in MF males, promoting skeletal growth. In contrast, interruption of AL feeding in females inhibits skeletal growth, but MF only leads to weight loss in the absence of GHSR activation. Our data imply that the contemporary shift from regular meals to less structured feeding may impair male growth outcomes and elevate fat mass.