A unifying hypothesis for control of body weight and reproduction in seasonally breeding mammals

YesAnimals have evolved diverse seasonal variations in physiology and reproduction to accommodate yearly changes in environmental and climatic conditions. These changes in physiology are initiated by changes in photoperiod (daylength) and are mediated through melatonin, which relays photoperiodic information to the pars tuberalis of the pituitary gland. Melatonin drives thyroid‐stimulating hormone transcription and synthesis in the pars tuberalis, which, in turn, regulates thyroid hormone and retinoic acid synthesis in the tanycytes lining the third ventricle of the hypothalamus. Seasonal variation in central thyroid hormone signalling is conserved among photoperiodic animals. Despite this, different species adopt divergent phenotypes to cope with the same seasonal changes. A common response amongst different species is increased hypothalamic cell proliferation/neurogenesis in short photoperiod. That cell proliferation/neurogenesis may be important for seasonal timing is based on (i) the neurogenic potential of tanycytes; (ii) the fact that they are the locus of striking seasonal morphological changes; and (iii) the similarities to mechanisms involved in de novo neurogenesis of energy balance neurones. We propose that a decrease in hypothalamic thyroid hormone and retinoic acid signalling initiates localised neurodegeneration and apoptosis, which leads to a reduction in appetite and body weight. Neurodegeneration induces compensatory cell proliferation from the neurogenic niche in tanycytes and new cells are born under short photoperiod. Because these cells have the potential to differentiate into a number of different neuronal phenotypes, this could provide a mechanistic basis to explain the seasonal regulation of energy balance, as well as reproduction. This cycle can be achieved without changes in thyroid hormone/retinoic acid and explains recent data obtained from seasonal animals held in natural conditions. However, thyroid/retinoic acid signalling is required to synchronise the cycles of apoptosis, proliferation and differentiation. Thus, hypothalamic neurogenesis provides a framework to explain diverse photoperiodic responses.MRC. Grant Number: MR/P012205/1 - Scottish Government - BBSRC. Grant Number: BB/K001043/1 - Physiological Societ

Melatonin receptors (version 2019.4) in the IUPHAR/BPS Guide to Pharmacology Database

Melatonin receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Melatonin Receptors [36]) are activated by the endogenous ligands melatonin and clinically used drugs like ramelteon, agomelatine and tasimelteon

Melatonin receptors in GtoPdb v.2023.1

Melatonin receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Melatonin Receptors [40]) are activated by the endogenous ligands melatonin and clinically used drugs like ramelteon, agomelatine and tasimelteon

Melatonin receptors in GtoPdb v.2021.3

Melatonin receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Melatonin Receptors [40]) are activated by the endogenous ligands melatonin and clinically used drugs like ramelteon, agomelatine and tasimelteon

C-type lectins in immunity : recent developments

Acknowledgements We thank the Wellcome Trust (Grant No. 102705) and Wellcome Trust Strategic Award in Medical Mycology and Fungal Immunology (Grant No. 97377) for funding. We apologise to our many colleagues whose recent work we were unable to cite due to space constraints.Peer reviewedPublisher PD

Determining the Relationship Among Cattle Genotype, Hair Coat Score, and Productivity Through the Investigation of Single Nucleotide Polymorphisms within Prolactin, Dopamine Receptor D2, and Melatonin Receptor 1A

Prolactin (PRL), melatonin (MTN), and dopamine (DA) are all hormones that are believed to play a role in the regulation and growth of hair in beef cattle. There are also single nucleotide polymorphisms associated with each of these hormones or their receptors, indicating that the investigation of these polymorphisms could allow them to serve as genetic markers for the future productivity of an animal. The objective of this study was to determine the relationships among cattle genotype, hair coat score, and productivity through the investigation of single nucleotide polymorphisms within prolactin, dopamine receptor D2, and melatonin receptor 1A. Body weights, hair coat scores, and blood samples were collected in May, June, and July from each non-lactating crossbred beef cow (n=71). The cows were grazing mixed grass pastures that included native endophyte infected tall fescue. Serum PRL, MTN, and DA concentrations were established by validated RIA. Based on the measurements recorded from the May samples, cows were categorized as high (n = 11; 159 ± 29 ng/mL PRL), medium (n = 48; 51 ± 4 ng/mL PRL), or low (n = 12; 21 ± 4 ng/mL PRL). Data were analyzed with Pearson correlations and repeated measures ANOVA with year, month, prolactin category (PRLCAT) and genotype as the main effects. Concentrations of PRL were correlated (r \u3e 0.53; P \u3c 0.0001) over the three months, and May PRL concentrations were correlated (r \u3e 0.29; P \u3c 0.02) with cow body weights in May, June, and July. Cows in the low PRLCAT had lower (

Polymorphism of the MTNR1A Melatonin Receptor Gene in Goat Breeds of Northern Italy

Melatonin receptor MT1, encoded by the MTNR1A gene, is the main one involved in the seasonal regulation of reproductive activity. A correlation between this gene polymorphism and reproductive performance has been demonstrated in sheep. To date, no data about MTNR1A gene polymorphism are available regarding Italian goat breeds other than the Sarda goat. This study aimed to detect any PCR-RFLP polymorphic sites of MTNR1A using MnlI and RsaI enzymes in Northern Italian goat breeds, which are characterized by a pronounced reproductive seasonality. One-hundred-eight adult female goats belonging to four different breeds were included in the study (i.e., Frisa Valtellinese, n = 29; Orobica, n = 23; Lariana, n = 29; Camosciata delle Alpi, n = 27). Blood was sampled from each goat. Genomic DNA was extracted from each sample and the main part of exon II of MTNR1A gene was amplified by PCR and digested with MnlI and RsaI enzymes. Unexpectedly, none of the fragments were found to be polymorphic. The absence of polymorphism may be linked to the macro group of goat breeds that evolved during human migrations. Breeds of the Alpine-European strain would appear to show no polymorphism, as confirmed by our study, whereas breeds belonging to the Mediterranean-African or Asian-Middle Eastern strains do

A neuroendocrine role for chemerin in hypothalamic remodelling and photoperiodic control of energy balance

YesLong-term and reversible changes in body weight are typical of seasonal animals. Thyroid hormone (TH) and retinoic acid (RA) within the tanycytes and ependymal cells of the hypothalamus have been implicated in the photoperiodic response. We investigated signalling downstream of RA and how this links to the control of body weight and food intake in photoperiodic F344 rats. Chemerin, an inflammatory chemokine, with a known role in energy metabolism, was identified as a target of RA. Gene expression of chemerin (Rarres2) and its receptors were localised within the tanycytes and ependymal cells, with higher expression under long (LD) versus short (SD) photoperiod, pointing to a physiological role. The SD to LD transition (increased food intake) was mimicked by 2 weeks of ICV infusion of chemerin into rats. Chemerin also increased expression of the cytoskeletal protein vimentin, implicating hypothalamic remodelling in this response. By contrast, acute ICV bolus injection of chemerin on a 12h:12h photoperiod inhibited food intake and decreased body weight with associated changes in hypothalamic neuropeptides involved in growth and feeding after 24hr. We describe the hypothalamic ventricular zone as a key site of neuroendocrine regulation, where the inflammatory signal, chemerin, links TH and RA signaling to hypothalamic remodeling.BBSRC (grant number BB/K001043/1) and the Scottish Government