Food Restriction Differentially Affects Pituitary Hormone mRNAs throughout the Adult Life Span of Male F344 Rats

Abstract

Because neuroendocrine mechanisms may contribute to the antiaging effects of food restriction (FR), we measured the effect of FR on mRNAs encoding anterior pituitary (AP) tropic hormones. Slot blots or RNase protection assays were done on AP RNA from 3-, 6-, 12-, 18- and 24-mo-old male F344 rats consuming food ad libitum (AL) or food restricted (FR; to 60% of AL food intake) from 6 wk. Both AL and FR rats gained body weight during the study (P < 0.05), but FR rats weighed ∼40% less (P < 0.0001). Messenger RNA levels were expressed in two ways, i.e., per total AP and per microgram total AP RNA. Proopiomelanocortin (POMC) mRNA/μg RNA was higher (P < 0.0005) in FR than in AL rats at all ages. Thyroid-stimulating hormone (TSH) β mRNA declined with age (P < 0.05) in AL but not FR rats and was reduced by FR up to 12 mo (P < 0.01). Growth hormone (GH) mRNA/μg RNA declined with age (P < 0.05) in AL but not FR rats, and total GH mRNA in the AP was reduced by FR at early ages (P < 0.05). FR reduced prolactin (PRL) mRNA and its age-related increase (P < 0.0005). Levels of luteinizing hormone (LH) β and follicle-stimulating hormone (FSH) β mRNAs did not differ between AL and FR rats until 12 mo, but thereafter rose in FR (LH β mRNA; P < 0.01, FSH β mRNA; P < 0.05). Many of these changes in gene expression corroborate previously reported hormonal changes in FR rodents and mutant mice with extended life spans, and thus provide further support for the hypothesis that an altered hormonal milieu contributes to the antiaging effects of food restriction.