Understanding the role of hypothalamic neuropeptides and hormones in energy balance is paramount in the search for approaches to mitigate the obese state. Increased hypothalamicpituitary-adrenal axis activity leads to increased levels of glucocorticoids (GC) that are known to regulate body weight. The axis initiates the production and release of corticotropin-releasing hormone (CRH) from the paraventricular nucleus (PVN) of the hypothalamus. Levels of active CRH peptide are dependent on the processing of its precursor pro-CRH by the action of two members of the family of prohormone convertases 1 and 2 (PC1 and PC2). Here, we propose that the nutrient sensor sirtuin 1 (Sirt1) regulates the production of CRH post-translationally by affecting PC2. Data suggest that Sirt1 may alter the preproPC2 gene directly or via deacetylation of the transcription factor Forkhead box protein O1 (FoxO1). Data also suggest that Sirt1 may alter PC2 via a post-translational mechanism. Our results show that Sirt1 levels in the PVN increase in rats fed a high fat diet for 12 weeks. Furthermore, elevated Sirt1 increased PC2 levels, which in turn increased the production of active CRH and GC. Collectively, this study provides the first evidence supporting the hypothesis that PVN Sirt1 activates the hypothalamicpituitary-adrenal axis and basal GC levels by enhancing the production of CRH through an increase in the biosynthesis of PC2, which is essential in the maturation of CRH from its prohormone, pro-CRH.Since its discovery in 1981 (1), corticotropin-releasing hormone (CRH) 2 has been demonstrated to be involved in mediating various physiological processes, including those involved in organismal homeostasis. Renowned for its critical role in mediating the stress response (2), CRH functions to regulate metabolic, immunologic, and homeostatic changes both basally and under various pathologic conditions (3-5). CRH heterogeneously expresses in the periphery and the brain with high expression in the hypothalamic paraventricular nucleus (PVN) (6 -8). Arginine vasopressin (AVP) is also produced in the PVN and acts to synergize CRH actions. It is the CRH that is produced in the medial parvocellular division of the PVN that functions as the central regulator of the HPA axis (9). Levels of bioactive CRH are dependent on the post-translational processing of its precursor pro-CRH. Prohormone posttranslational processing is the mechanism by which all peptide hormones become biologically active (10, 11). In rodents and humans, aberrations in prohormone processing results in deleterious health consequences, including metabolic dysfunctions (12-17). CRH is initially produced as a large inactive precursor, preproCRH, that is made of 196 amino acids (18,19). After cleavage of the signal sequence, the prohormone (pro-CRH) enters the lumen of the rough endoplasmic reticulum and is routed to the trans-Golgi network where it undergoes enzymatic post-translational modifications to generate several intermediate forms as well as the bioactive CRH(1-41) peptid...