Early-onset obesity, especially in girls, is frequently associated with advanced puberty; a phenomenon bound to increased risk of long-term complications. Hypothalamic endoplasmic reticulum (ER) stress has been implicated in the pathophysiology of obesity and its comorbidities. However, its contribution to pubertal disorders associated with obesity remains unexplored. We report herein that central ER stress drives obesity-induced precocious female puberty. Hypothalamic expression of key ER stress markers was blunted during normal pubertal transition and altered in female rats with early-onset obesity and advanced puberty, which displayed increased levels of p-PERK and p-eIF2α, and reduced ATF6α content. Central stimulation of hypothalamic ER stress with Thapsigargin in prepuberal lean female rats mimicked advanced puberty onset caused by obesity, without changes in body weight. This phenomenon seemingly involves a circuit including the hypothalamic arcuate nucleus (ARC), since obesity-induced precocious puberty was largely prevented by alleviation of ER stress via virogenetic overexpression of the ER chaperone, GRP78, in the ARC, but not in the paraventricular nucleus, in female rats. In addition, expression analyses of ER stress markers in mouse Kiss1 neurons isolated from juvenile and pubertal female mice revealed increased expression of Perk and Ire1α mRNAs in Kiss1 ^ARC neurons in early-overfed mice at the juvenile stage, while Xbp1s/u expression ratio was significantly increased during juvenile–pubertal transition in overweighed mice. Collectively, our data uncover a relevant role of hypothalamic ER stress in the control of female puberty and the pathogenesis of obesity-induced pubertal alterations.

Proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC) play a critical role in energy homeostasis. 5’-adenosine monophosphate-activated protein kinase (AMPK) is a serine/threonine kinase, which acts as the main energy sensor in the cell. The heterotrimeric AMPK results from the combination of a catalytic α subunit (α1, α2) with two regulatory subunits, β (β1, β2) and γ (γ1, γ2 and γ3). Hypothalamic AMPK plays a key role in the control of energy balance, but current evidence shows that the precise combination of its heterotrimeric components determines its physiological action. Our findings show that AMPKα1 ablation in POMC neurons has a sex-dependent protective effect against diet-induced obesity because of increased thermogenesis in brown adipose tissue (BAT) in males, but not in females. At the molecular level, deletion of AMPKα1 in POMC neurons disrupts the ARC phosphoproteome and is associated with ameliorated endoplasmic reticulum (ER) stress and reduced ceramide content. These findings highlight the complex function of the different AMPK subunits in the hypothalamic regulation of energy balance.

Endoplasmic reticulum (ER) stress has been proposed as a link between insulin resistance, oxidative stress, and endothelial dysfunction in metabolic disorders. Penile erectile dysfunction shares risk factors with cardiovascular disease (CVD) including insulin resistance, diabetes, and obesity. In the present study, involvement of ER stress in penile endothelial and vascular dysfunction was investigated in an in vivo model of ER stress induced by tunicamycin. Endothelial function was assessed by using wire myography, mitochondrial reactive oxygen species (mtROS) by mitoSOX and Amplex Red fluorometry, mitochondrial bioenergetics by Seahorse XF Analyzer, and expression of ER-stress markers by Western blot. Tunicamycin increased expression of BiP, pPERK, ATF6α, and pIRE1α in penile erectile tissue. Endothelium-dependent relaxations to acetylcholine were impaired, while α₁-adrenergic vasoconstriction was blunted in penile arteries from ER-stress rats. Selective NADPH oxidase 1 (Nox1) inhibition restored endothelial relaxations, while blockade of Nox2 and Nox4 revealed H₂O₂-mediated endothelial relaxations in control but not in tunicamycin-treated rats. ER stress reduced basal mtROS levels and mitoTEMPO- sensitive relaxant responses. On the other hand, enhanced mitochondrial respiration and glycolytic activity were found in penile arteries from tunicamycin-treated rats. These findings indicate that ER stress blunts adrenergic vasoconstriction, and induces endothelial dysfunction by enhancing Nox1-derived ROS and reducing mitochondrial vasodilator H₂O₂. Attenuation of ER stress emerges as a potential therapeutic target in the management of metabolic disease-associated erectile dysfunction.