Effects of cafeteria diet and caloric restriction on pituitary hormones and metabolic phenotype in male Wistar rats

Obesity is associated with neuroendocrine and metabolic dysregulation, yet the underlying mechanisms remain incompletely understood. This study aimed to investigate how pituitary hormonal axes and peripheral hormones respond to a cafeteria diet or a calorie-restricted diet in rats. Ten-week-old male Wistar rats (n = 36) were randomized (1:1:1) to one of three diets for 12 weeks: an ad libitum standard rat chow diet (control group); an ad libitum cafeteria diet, containing cheese doodles, chocolate balls and salted peanuts, in addition to standard chow (diet-induced obesity group, DIO); or calorie-restriction (aiming at 85% body weight of controls; restricted group). We assessed endocrine gland weights, plasma levels of pituitary hormones and related peripheral signals, and explored their associations with metabolic and behavioral outcomes. While the DIO group exhibited increased body weight, insulin resistance, and altered metabolic markers, only modest changes in pituitary hormones were observed, with a reduction in luteinizing hormone (p < 0.05). Correlation analysis showed that when combining the control and DIO groups, prolactin inversely correlated with exploratory-activity (rho = -0.458, p < 0.05) from the behavioral test. In contrast, the restricted group showed more pronounced hormonal changes, including reduced levels of adrenocorticotropic hormone (p < 0.01), prolactin, and thyroid-stimulating hormone (both p < 0.05) as well as insulin-like growth factor-1 (p < 0.01). Multivariate data analysis showed a clear separation of the DIO group from the other groups, mainly driven by metabolic variables. Despite notable metabolic perturbations in the DIO group, the absence of endocrine changes suggests a partly different phenotype than what is typically observed in humans with obesity.