Topmouth culter melanocortin-3 receptor: regulation by two isoforms of melanocortin-2 receptor accessory protein 2.

Melanocortin-3 receptor (MC3R) is a regulator of energy homeostasis, and interaction of MC3R and melanocortin-2 receptor accessory protein 2 (MRAP2) plays a critical role in MC3R signaling of mammals. However, the physiological roles of MC3R in teleosts are not well understood. In this study, qRT-PCR was used to measure gene expression. Radioligand binding assay was used to study the binding properties of topmouth culter MC3R (caMC3R). Intracellular cAMP generation was determined by RIA, and caMC3R expression was quantified with flow cytometry. We showed that culter mc3r had higher expression in the CNS. All agonists could bind and stimulate caMC3R to increase dose dependently intracellular cAMP accumulation. Compared to human MC3R, culter MC3R showed higher constitutive activity, higher efficacies, and Rmax to alpha-melanocyte-stimulating hormone (α-MSH), des-α-MSH, and adrenocorticotrophic hormone. Both caMRAP2a and caMRAP2b markedly decreased caMC3R basal cAMP production. However, only caMRAP2a significantly decreased cell surface expression, Bmax, and Rmax of caMC3R. Expression analysis suggested that MRAP2a and MRAP2b might be more important in regulating MC3R/MC4R signaling during larval period, and reduced mc3r, mc4r, and pomc expression might be primarily involved in modulation of MC3R/MC4R in adults. These data indicated that the cloned caMC3R was a functional receptor. MRAP2a and MRAP2b had different effects on expression and signaling of caMC3R. In addition, expression analysis suggested that MRAP2s, receptors, and hormones might play different roles in regulating culter development and growth.

Regulation of Melanocortin-4 Receptor Pharmacology by Two Isoforms of Melanocortin Receptor Accessory Protein 2 in Topmouth Culter (Culter alburnus).

Melanocortin-4 receptor (MC4R) plays important roles in regulation of multiple physiological processes, and interaction of MC4R and melanocortin receptor accessory protein 2 (MRAP2) is suggested to play pivotal role in energy balance of vertebrates. Topmouth culter (Culter alburnus) is an economically important freshwater fish in China. Herein we cloned culter mc4r, mrap2a, and mrap2b. Culter mc4r consisted of a 981 bp open reading frame encoding a protein of 326 amino acids. qRT-PCR revealed that mc4r, mrap2a, and mrap2b were primarily expressed in the central nervous system. In the periphery, mc4r and mrap2b were expressed more widely in the male, while mrap2a was expressed more widely in the female. Culter MC4R could bind to four peptide agonists and increase intracellular cAMP production dose dependently. Culter MC4R was constitutively active in both cAMP and ERK1/2 pathways, which was differentially regulated by culter MRAP2a and MRAP2b. Culter MRAP2a significantly increased Bmax and decreased agonist-stimulated cAMP, while MRAP2b increased cell surface and total expression but did not affect Bmax and agonist-stimulated cAMP. These results will aid the investigation of the potential physiological processes that MC4R might be involved in topmouth culter.

Mediation analysis for the relationship between dyslipidemia and coronary artery disease via hypersensitive C-reactive protein in a case-control study.

BACKGROUND: The pathological basis of coronary artery disease (CAD) is atherosclerosis which is associated with inflammation and dyslipidemia. However, the involvement of hypersensitive C-reactive protein (hs-CRP) in lipid metabolism and how it affects the pathogenesis of CAD is uncertain. OBJECTIVE: To explore whether the relationship between dyslipidemia and CAD is partly mediated by hs-CRP levels. METHODS: Three hundred fifteen pairs of randomly sexand age-matched CAD and non-CAD subjects collected from Zhongda Hospital Affiliated to Southeast University were involved in the final analysis. We gathered information about each subjects clinical history as well as their results of detected hs-CRP and lipid levels. Linear regression analysis was used to determine the association between dyslipidemia and hs-CRP levels in which univariate and multivariate logistic regression analyzes were performed to determine the relationship between hs-CRP levels and CAD as well as dyslipidemia and CAD. Mediation analysis was used to evaluate whether hs-CRP levels act as a mediator of the relationship between dyslipidemia and CAD. RESULTS: Dyslipidemia and hs-CRP levels were significantly associated with an increased risk of CAD, with ß = 0.594 (P = 0.001) and ß = 0.016 (P = 0.024), respectively, and there was a correlation between dyslipidemia and hs-CRP levels (ß = 3.273, P = 0.004). Mediation analysis results revealed that the correlation between dyslipidemia and CAD was 8.27% mediated by hs-CRP levels with a direct effect of 0.621 and an indirect effect of 0.056. CONCLUSION: Hs-CRP levels played a partial mediation role in the association between dyslipidemia and CAD.