Time-of-Day Adrenal Modulation of Corticosterone Synthesis is Affected by Sex and Diet but Not by Proanthocyanidins in Rat.

Scope: The aim of this study is to investigate the effect of time-of-day on serum hormones and gene expression in adrenal glands, studying the impact of sex, obesogenic diet, and timing of proanthocyanidins administration, with a focus on glucocorticoids synthesis by this gland.
Methods and Results: Female and male rats, assigned to a standard chow or a cafeteria diet-fed group, receive a daily oral dose of a grape seed proanthocyanidin extract (GSPE), or a vehicle (when light is turned on, or when light is turned off). Corticosterone, estradiol, and testosterone serum levels, and the expression analysis of clock genes and genes related to corticosterone synthesis pathway, are assessed. Serum hormone levels exhibited a marked time-of-day effect also see in the expression of scavenger receptor class B member 1 (Scarb1) and cyp11b genes. The correlation between these two genes and period circadian regulator 2 (Per2) is also extended to other clock genes, although to a lesser extent: cryptochrome (Cry) and nuclear receptor subfamily 1 group D member 1 (Rev-erba).
Conclusion: The strong correlations found suggest an important role of local Per2 (but also of Cry and Rev-erbA) in regulating the expression of the enzymes involved in the corticosterone synthesis pathway. The expression of clock genes in adrenals is influenced by sex and diet but not by GSPE.
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