Prader-Willi syndrome (PWS) is caused by a loss of paternally expressed genes in an imprinted region of chromosome 15q. Among the canonical PWS phenotypes are hyperphagic obesity, central hypogonadism, and low growth hormone (GH). Rare microdeletions in PWS patients define a 91-kb minimum critical deletion region encompassing 3 genes, including the noncoding RNA gene SNORD116. Here, we found that protein and transcript levels of nescient helix loop helix 2 (NHLH2) and the prohormone convertase PC1 (encoded by PCSK1) were reduced in PWS patient induced pluripotent stem cell-derived (iPSC-derived) neurons. Moreover, Nhlh2 and Pcsk1 expression were reduced in hypothalami of fasted Snord116 paternal knockout (Snord116p-/m+) mice. Hypothalamic Agrp and Npy remained elevated following refeeding in association with relative hyperphagia in Snord116p-/m+ mice. Nhlh2-deficient mice display growth deficiencies as adolescents and hypogonadism, hyperphagia, and obesity as adults. Nhlh2 has also been shown to promote Pcsk1 expression. Humans and mice deficient in PC1 display hyperphagic obesity, hypogonadism, decreased GH, and hypoinsulinemic diabetes due to impaired prohormone processing. Here, we found that Snord116p-/m+ mice displayed in vivo functional defects in prohormone processing of proinsulin, pro-GH-releasing hormone, and proghrelin in association with reductions in islet, hypothalamic, and stomach PC1 content. Our findings suggest that the major neuroendocrine features of PWS are due to PC1 deficiency.

Streamside measurements of critical thermal maxima (T crit ), swimming performance (U crit ), and routine (R r ) and maximum (R max ) metabolic rates were performed on three populations of genetically distinct redband trout Oncorhynchus mykiss in the high-desert region of south-eastern Oregon. The T crit values (29Á4 AE 0Á1 C) for small (40-140 g) redband trout from the three streams, and large (400-1400 g) redband trout at Bridge Creek were not different, and were comparable to published values for other salmonids. At high water temperatures (24-28 C), large fish incurred higher metabolic costs and were more thermally sensitive than small fish. U crit (3Á6 AE 0Á1 L F s À1 ), R r (200 AE 13 mg O 2 kg À0Á830 h À1 ) and metabolic power (533 AE 22 mg O 2 kg À0Á882 h À1 ) were not significantly different between populations of small redband trout at 24 C. R max and metabolic power, however, were higher than previous measurements for rainbow trout at these temperatures. Fish from Bridge Creek had a 30% lower minimum total cost of transport (C min ), exhibited a lower refusal rate, and had smaller hearts than fish at 12-mile or Rock Creeks. In contrast, no differences in U crit or metabolism were observed between the two size classes of redband trout, although C min was significantly lower for large fish at all swimming speeds. Biochemical analyses revealed that fish from 12-mile Creek, which had the highest refusal rate (36%), were moderately hyperkalemic and had substantially lower circulating levels of free fatty acids, triglycerides and albumin. Aerobic and anaerobic enzyme activities in axial white muscle, however, were not different between populations, and morphological features were similar. Results of this study: 1) suggest that the physiological mechanisms that determine T crit in salmonids are highly conserved; 2) show that adult (large) redband trout are more susceptible to the negative affects of elevated temperatures than small redband trout; 3) demonstrate that swimming efficiency can vary considerably between redband trout populations; 4) suggest that metabolic energy stores correlate positively with swimming behaviour of redband trout at high water temperatures; 5) question the use of T crit for assessing physiological function and defining thermal habitat requirements of stream-dwelling salmonids like the redband trout.

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Retinoic acid signaling is required for maintaining a range of cellular processes, including cell differentiation, proliferation, and apoptosis. We investigated the actions of all-trans-retinoic acid (atRA) signaling in pancreatic b-cells of adult mice. atRA signaling was ablated in b-cells by overexpressing a dominant-negative retinoic acid receptor (RAR)-a mutant (RARdn) using an inducible Cre-Lox system under the control of the pancreas duodenal homeobox gene promoter. Our studies establish that hypomorphism for RAR in b-cells leads to an age-dependent decrease in plasma insulin in the fed state and in response to a glucose challenge. Glucose-stimulated insulin secretion was also impaired in islets isolated from mice expressing RARdn. Among genes that are atRA responsive, Glut2 and Gck mRNA levels were decreased in isolated islets from RARdn-expressing mice. Histologic analyses of RARdn-expressing pancreata revealed a decrease in b-cell mass and insulin per b-cell 1 mo after induction of the RARdn. Our results indicate that atRA signaling mediated by RARs is required in the adult pancreas for maintaining both b-cell function and mass, and provide insights into molecular mechanisms underlying these actions.-Brun, P.-J., Grijalva, A., Rausch, R., Watson, E., Yuen, J. J., Das, B. C., Shudo, K., Kagechika, H., Leibel, R. L., Blaner, W. S. Retinoic acid receptor signaling is required to maintain glucose-stimulated insulin secretion and b-cell mass. FASEB J. 29, 671-683 (2015). www.fasebj.orgHUMANS AND OTHER VERTEBRATES must acquire retinoids (vitamin A and its metabolites) from the diet in order to maintain normal health (1). Retinoids regulate many cellular processes including cellular proliferation, differentiation, and apoptosis, and hence, they have roles in many essential physiologic processes including the maintenance of immunity, reproduction, and embryonic development (2, 3). These essential actions are thought to be mediated primarily by the all-trans-retinoic acid (atRA) and 9-cis-retinoic acid (9cRA), which regulate transcription by serving as ligands for nuclear hormone receptors (4, 5). atRA serves as the natural ligand for the 3 retinoic acid receptors (RARs; a, b, and g); whereas 9cRA is proposed to be a natural ligand for the 3 retinoid X receptors (RXRs; a, b, and g) (6). Over 500 genes are reported to be responsive to either atRA or 9cRA (7).An extensive literature supports a role for retinoids in the maintenance of pancreatic endocrine functions (8-18). Pancreatic islets express genes encoding retinoland retinoic acid-binding proteins, as well as RARs and RXRs (14,19,20). Isolated pancreatic islets from rats fed a vitamin A-deficient diet display a markedly diminished capacity to secrete insulin in response to a glucose challenge (10). This phenotype was reversed by administering either retinyl ester or atRA to the rats prior to islet isolation. Two recent reports have identified a function for 9cRA and RXR signaling in the regulation of insulin secretion. Using an inducible dominant-ne...

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Perturbations in the functional integrity of the leptin axis are obvious candidates for mediation of altered adiposity. In a large number of genetic association studies in humans, the nonconservative LEPR Q223R allele has been inconsistently associated with adiposity. Subtle, long‐term effects of such genetic variants can be obscured by effects of the environment and other confounders that render definitive inferences difficult to reach. We directly assessed the biological effects of this variant in 129P3/J mice segregating for the humanized Lepr allele at codon 223. No effects of this allele were detected on body weight, composition, or energy expenditure in animals fed diets of varying fat content over periods as long as 235 days. In vitro, Q223R did not affect leptin signaling as reflected by activation of STAT3. We conclude that Q223R is unlikely to play a significant role in regulation of human adiposity. This approach to vetting of human allelic variation might be more widely used.

Background The adipokine hormone, leptin, is a major component of body weight homeostasis. Numerous studies have been performed administering recombinant mouse leptin as an experimental reagent; however, the half life of circulating leptin following exogenous administration of recombinant mouse leptin has not been carefully evaluated. Methods Exogenous leptin was administered (3 mg leptin/kg body weight) to ten week old fasted non-obese male mice and plasma was serially collected at seven time points; plasma leptin concentration was measured by ELISA at each time point to estimate the circulating half life of mouse leptin. Results Under the physiological circumstances tested, the half life of mouse leptin was 40.2 (+/− 2.2) minutes. Circulating leptin concentrations up to one hour following exogenous leptin administration were 170-fold higher than endogenous levels at fasting. Conclusions The half life of mouse leptin was determined to be 40.2 minutes. These results should be useful in planning and interpreting experiments employing exogenous leptin. The unphysiological elevations in circulating leptin resulting from widely used dosing regimens for exogenous leptin are likely to confound inferences regarding some aspects of the hormone’s clinical biology.

Effects of hypoxia, anoxia, and endogenous ethanol (EtOH) on selected temperature (T(sel)) and activity in goldfish were evaluated. Blood and brain EtOH concentrations ([EtOH]) and brain oxygen partial pressure (PO(2)) were quantified at crucial ambient oxygen pressures. Below a threshold value near 31 Torr, T(sel) decreased as a function of environmental PO(2). T(sel) of 15 degrees C-acclimated fish was approximately 10 degrees C at the onset of anoxia and changed little over 2 h. Activity showed a similar response pattern. Brain [EtOH] was significantly elevated above control levels after 1 h anoxia. In normoxic water, T(sel) remained different in previously anoxic and normoxic control fish for approximately 20 min. Blood [EtOH] of previously anoxic fish remained significantly elevated ([EtOH] >4.0 micromol/g blood), and activity was significantly depressed at 20 min. Brain PO(2) reached normal levels in <3 min. We conclude that [EtOH] (brain or blood) and brain PO(2) are not proximal causes of either behavioral anapyrexia (hypothermia) or inactivity in goldfish exposed to oxygen-depleted environments.