👤 Joao Pedroso

The central melanocortin system, composed of peptides derived from pro-opiomelanocortin (POMC) such as the melanocyte-stimulating hormones (α-, β-, γ-MSH) and melanocortin 4 receptors (MC4R), along with the agouti-related protein (AgRP), plays a pivotal role in controlling energy balance. To elucidate the dynamic role of α-MSH release in regulating appetite, specific, sensitive, and spatiotemporally resolved genetic sensors are required. The melanocortin 1 receptor (MC1R) scaffold was leveraged for its robust plasma membrane expression, high affinity for melanocortins and low affinity for AgRP to design a α-MSH selective sensor for in vivo use. This was achieved by integrating circularly permuted green fluorescent protein (cpGFP) into the receptor, which we named Fluorescence Amplified Receptor sensor for Melanocortin (FLARE The FLARE FLARE Show less

We aim to characterize patients with Gomez-López-Hernández syndrome (GLHS) clinically and to investigate them molecularly. A clinical protocol, including a morphological and neuropsychological assessment, was applied to 13 patients with GLHS. Single-nucleotide polymorphism (SNP) array and whole-exome sequencing were undertaken; magnetic resonance imaging was performed in 12 patients, including high-resolution, heavily T2-weighted sequences (HRT2) in 6 patients to analyze the trigeminal nerves. All patients presented alopecia; two did not present rhombencephalosynapsis (RES); trigeminal anesthesia was present in 5 of the 11 patients (45.4%); brachycephaly/brachyturricephaly and mid-face retrusion were found in 84.6 and 92.3% of the patients, respectively. One patient had intellectual disability. HRT2 sequences showed trigeminal nerve hypoplasia in four of the six patients; all four had clinical signs of trigeminal anesthesia. No common candidate gene was found to explain GLHS phenotype. RES does not seem to be an obligatory finding in respect of GLHS diagnosis. We propose that a diagnosis of GLHS should be considered in patients with at least two of the following criteria: focal non-scarring alopecia, rhombencephalosynapsis, craniofacial anomalies (brachyturrycephaly, brachycephaly or mid-face retrusion), trigeminal anesthesia or anatomic abnormalities of the trigeminal nerve. Studies focusing on germline whole genome sequencing or DNA and/or RNA sequencing of the alopecia tissue may be the next step for the better understanding of GLHS etiology. Show less

The central melanocortin system is composed of neurons that express either the proopiomelanocortin (POMC) or the agouti-related protein (AgRP). POMC is cleaved in bioactive peptides, including the α-melanocyte-stimulating hormone (α-MSH). α-MSH activates the melanocortin-4 receptor (MC4R) inducing satiety, whereas AgRP acts as an inverse agonist of MC4R. However, only limited information is available regarding possible area-specific differences in the interaction between α-MSH and AgRP terminals on MC4R-expressing cells. Therefore, the objective of the present study was to compare the distribution pattern of α-MSH and AgRP terminals on the perikarya of MC4R-expressing neurons. We performed a triple-label immunofluorescence reaction in brain series of MC4R-reporter mice to visualize MC4R-expressing neurons together with AgRP and α-MSH terminals. POMC and AgRP neurons project to areas that contain MC4R-expressing cells, although several brain nuclei exhibit AgRP and α-MSH terminals, but they do no express MC4R, while other brain areas contain MC4R-expressing cells and receive no apparent innervation of AgRP and POMC neurons. AgRP terminals make more presumptive appositions than α-MSH on the soma of MC4R-expressing neurons of the medial preoptic area and paraventricular nucleus of the hypothalamus (Pa). Additionally, a higher percentage of MC4R cells receive at least one presumptive apposition from AgRP terminals in the median preoptic nucleus and Pa, compared to α-MSH appositions. Thus, our study revealed area-specific differences in the interaction between α-MSH and AgRP terminals and the soma of MC4R-expressing neurons. These findings provide new insights about the relationship between first- and second-order neurons of the central melanocortin system. Show less

Leucine activates the intracellular mammalian target of the rapamycin (mTOR) pathway, and hypothalamic mTOR signaling regulates food intake. Although central infusion of leucine reduces food intake, it is still uncertain whether oral leucine supplementation is able to affect the hypothalamic circuits that control energy balance. We observed increased phosphorylation of p70s6k in the mouse hypothalamus after an acute oral gavage of leucine. We then assessed whether acute oral gavage of leucine induces the activation of neurons in several hypothalamic nuclei and in the brainstem. Leucine did not induce the expression of Fos in hypothalamic nuclei, but it increased the number of Fos-immunoreactive neurons in the area postrema. In addition, oral gavage of leucine acutely increased the 24 h food intake of mice. Nonetheless, chronic leucine supplementation in the drinking water did not change the food intake and the weight gain of ob/ob mice and of wild-type mice consuming a low- or a high-fat diet. We assessed the hypothalamic gene expression and observed that leucine supplementation increased the expression of enzymes (BCAT1, BCAT2 and BCKDK) that metabolize branched-chain amino acids. Despite these effects, leucine supplementation did not induce an anorectic pattern of gene expression in the hypothalamus. In conclusion, our data show that the brain is able to sense oral leucine intake. However, the food intake is not modified by chronic oral leucine supplementation. These results question the possible efficacy of leucine supplementation as an appetite suppressant to treat obesity. Show less