Since hypothalamic obesity (HyOb) was first described over 120 years ago by Joseph Babinski and Alfred Fröhlich, advances in molecular genetic laboratory techniques have allowed us to elucidate various components of the intricate neurocircuitry governing appetite and weight regulation connecting the hypothalamus, pituitary gland, brainstem, adipose tissue, pancreas, and gastrointestinal tract. On a background of an increasing prevalence of population-level common obesity, the number of survivors of congenital (eg, septo-optic dysplasia, Prader-Willi syndrome) and acquired (eg, central nervous system tumors) hypothalamic disorders is increasing, thanks to earlier diagnosis and management as well as better oncological therapies. Although to date the discovery of several appetite-regulating peptides has led to the development of a range of targeted molecular therapies for monogenic obesity syndromes, outside of these disorders these discoveries have not translated into the development of efficacious treatments for other forms of HyOb. This review aims to summarize our current understanding of the neuroendocrine physiology of appetite and weight regulation, and explore our current understanding of the pathophysiology of HyOb.

Obesity is a global epidemic with steadily increasing prevalence in most countries. Weight loss is generally challenging for patients to tackle in the face of the temptation to overeat and avoid physical activity. Hence, clinicians and patients alike are likely to steer toward the use of anorexigens. We report the case of a 33-year-old female with no significant cardiac history who presented with dyspnea, productive cough, and chest pressure for one month and was diagnosed with new-onset heart failure with a reduced ejection fraction secondary to prolonged phentermine use. The authors aim to highlight phentermine\'s potential for precipitating heart failure, even in a young, relatively healthy person, especially with a growing obese population. Ultimately, healthy weight loss can be achieved by implementing dietary changes and encouraging adequate physical activity, as the World Health Organization (WHO) recommended. Anorectic drugs may be employed for short-term use. Further research concerning the long-term side effects of phentermine may avert the prescriber and patient from abusing this drug.

The function of the gonadotropin-releasing hormone (GnRH) neuron is critical to maintain reproductive function and a significant decrease in GnRH can lead to disorders affecting fertility, including hypogonadotropic hypogonadism. Spexin (SPX) is a novel hypothalamic neuropeptide that exerts inhibitory effects on reproduction and feeding by acting through galanin receptor 2 (GALR2) and galanin receptor 3 (GALR3). Fatty acids can act as nutritional signals that regulate the hypothalamic-pituitary-gonadal (HPG) axis, and elevated levels of circulating saturated fatty acids associated with high fat diet (HFD)-feeding have been shown to induce neuroinflammation, endoplasmic reticulum stress and hormonal resistance in the hypothalamus, as well as alter neuropeptide expression. We previously demonstrated that palmitate, the most common saturated fatty acid in a HFD, elevates the expression of Spx, Galr2 and Galr3 mRNA in a model of appetite-regulating neuropeptide Y hypothalamic neurons. Here, we found that Spx, Galr2 and Galr3 mRNA were also significantly induced by palmitate in a model of reproductive GnRH neurons, mHypoA-GnRH/GFP. As a follow-up to our previous report, we examined the molecular pathways by which Spx and galanin receptor mRNA was regulated in this cell line. Furthermore, we performed inhibitor studies, which revealed that the effect of palmitate on Spx and Galr3 mRNA involved activation of the innate immune receptor TLR4, and we detected differential regulation of the three genes by the protein kinases PKC, JNK, ERK, and p38. However, the intracellular metabolism of palmitate to ceramide did not appear to be involved in the palmitate-mediated gene regulation. Overall, this suggests that SPX may play a role in reproduction at the level of the hypothalamus and the pathways by which Spx, Galr2 and Galr3 are altered by fatty acids could provide insight into the mechanisms underlying reproductive dysfunction in obesity.

Spexin (SPX) is a novel satiety factor that putatively binds the galanin receptors R2 and R3 (GalR2/R3). SPX reduces body weight, and circulating SPX is decreased in obesity. It is unknown how SPX and its receptors are regulated in the hypothalamus, critical for energy homeostasis. We therefore examined the regulation of hypothalamic Spx, GalR2 and GalR3 gene expression in mouse primary and immortalized hypothalamic neurons. We report that Spx, GalR2 and GalR3 mRNA levels were regulated by acute treatments of palmitate, a dietary saturated fatty acid, as well as the nitric oxide (NO) donor sodium nitroprusside (SNP), but through a pathway independent of cyclic GMP and protein kinase G. Additionally, the palmitate- and NO-mediated induction of Spx and galanin receptors was blocked with the PKC inhibitor k252c. Furthermore, palmitate induced mRNA levels of endoplasmic reticulum (ER) stress markers, including Chop, Grp78 and Bax/Bcl2, as well as C/ebp-β, whereas SNP induced Bax/Bcl2 and C/ebp-β. Transcriptional changes in Spx, GalR2, GalR3, C/ebp-β and ER stress marker mRNAs were blocked by pre-treatment with at least one of the chemical chaperones PBA or TUDCA. We also describe the presence of OCT-1 and C/EBP-β response elements in the 5\' regulatory region of Spx and demonstrate that SNP increases binding of C/EBP-β to this region, but not Oct-1 mRNA nor OCT-1 binding. Our findings suggest an acute modulation of anorexigenic SPX signaling by palmitate and NO. Furthermore, ER stress and C/EBP-β appear to mediate the changes in Spx, GalR2 and GalR3 in hypothalamic neurons.

Fenfluramine is prescribed either alone or in combination with phentermine as part of Fen-Phen, an anti-obesity medication. Fenfluramine was withdrawn from the US market in 1997 due to reports of heart valvular disease, pulmonary arterial hypertension, and cardiac fibrosis. Particularly, idiopathic pulmonary arterial hypertension (IPAH), previously referred to as primary pulmonary hypertension (PPH), was found to be associated with the use of Fen-Phen, fenfluramine, and fenfluramine derivatives. The underlying mechanism of fenfluramine-associated pulmonary hypertension is still largely unknown. We reasoned that investigating drug-induced gene dysregulation would enhance our understanding of the fenfluramine-associated pathogenic mechanism of IPAH. Whole-genome gene expression profiles in fenfluramine-treated human pulmonary artery smooth muscle (PASMC) and endothelial (PAEC) cells (isolated from normal subjects) were compared with baseline expression in untreated cells. Fenfluramine treatment caused dysregulation in a substantial number of genes involved in a variety of pathways and biological processes. In addition to several common pathways and biological processes such as \"MAPK signaling pathway,\" \"inflammation response,\" and \"calcium signaling pathway\" shared between both cell types, pathways and biological processes such as \"blood circulation,\" \"muscle system process,\" and \"immune response\" were enriched among the dysregulated genes in PASMC. Pathways and biological processes such as those related to cell cycle, however, were enriched among the dysregulated genes in PAEC, indicating that fenfluramine could affect unique pathways (or differentially) in different types of pulmonary artery cells. While awaiting validation in a larger cohort, these results strongly suggested that fenfluramine could induce significant dysregulation of genes in multiple biological processes and pathways critical for normal pulmonary vascular functions and structure. The transcriptional and posttranscriptional changes in these genes may, therefore, contribute to the pathogenesis of fenfluramine-associated IPAH.