Prolactin anterior pituitary expression and circulating levels are reduced in obese and diabetic rats: role of TGF-β and TNF-α

The levels of the hormone prolactin (PRL) are reduced in the circulation of patients with Type 2 diabetes and in obese children, and lower systemic PRL levels correlate with an increased prevalence of diabetes and a higher risk of metabolic syndrome. The secretion of anterior pituitary (AP) PRL in metabolic diseases may be influenced by the interplay between transforming growth factor β (TGF-β) and tumor necrosis factor α (TNF-α), which inhibit and can stimulate AP PRL synthesis, respectively, and are known contributors to insulin resistance and metabolic complications. Here, we show that TGF-β and TNF-α antagonize the effect of each other on the expression and release of PRL by the GH4C1 lactotrope cell line. The levels of AP mRNA and circulating PRL decrease in high-fat diet-induced obese rats in parallel with increased and reduced AP levels of TGF-β and TNF-α mRNA, respectively. Likewise, AP expression and circulating levels of PRL are reduced in streptozotocin-induced diabetic rats and are associated ...