Search

G protein‐coupled receptors (GPCRs) comprise the largest group of membrane receptors in eukaryotic genomes and collectively they regulate nearly all cellular processes. Despite the widely recognized importance of this class of proteins, many GPCRs remain understudied. G protein‐coupled receptor 27 (Gpr27) is an orphan GPCR that displays high conservation during vertebrate evolution. Although, GPR27 is known to be expressed in tissues that regulate metabolism including the pancreas, skeletal muscle, and adipose tissue, its functions are poorly characterized. Therefore, to investigate the potential roles of Gpr27 in energy metabolism, we generated a whole body gpr27 knockout zebrafish line. Loss of gpr27 potentiated the elevation in glucose levels induced by pharmacological or nutritional perturbations. We next leveraged a mass spectrometry metabolite profiling platform to identify other potential metabolic functions of Gpr27. Notably, genetic deletion of gpr27 elevated medium‐chain acylcarnitines, in particular C6‐hexanoylcarnitine, C8‐octanoylcarnitine, C9‐nonanoylcarnitine, and C10‐decanoylcarnitine, lipid species known to be associated with insulin resistance in humans. Concordantly, gpr27 deletion in zebrafish abrogated insulin‐dependent Akt phosphorylation and glucose utilization. Finally, loss of gpr27 increased the expression of key enzymes in carnitine shuttle complex, in particular the homolog to the brain‐specific isoform of CPT1C which functions as a hypothalamic energy senor. In summary, our findings shed light on the biochemical functions of Gpr27 by illuminating its role in lipid metabolism, insulin signaling, and glucose homeostasis. [ABSTRACT FROM AUTHOR]

Exposure to cyanide causes a spectrum of cardiac, neurological, and metabolic dysfunctions that can be fatal. Improved cyanide antidotes are needed, but the ideal biological pathways to target are not known. To understand better the metabolic effects of cyanide and to discover novel cyanide antidotes, we developed a zebrafish model of cyanide exposure and scaled it for high-throughput chemical screening. In a screen of 3120 small molecules, we discovered 4 novel antidotes that block cyanide toxicity. The most potent antidote was riboflavin. Metabolomic profiling of cyanide-treated zebrafish revealed changes in bile acid and purine metabolism, most notably by an increase in inosine levels. Riboflavin normalizes many of the cyanide-induced neurological and metabolic perturbations in zebrafish. The metabolic effects of cyanide observed in zebrafish were conserved in a rabbit model of cyanide toxicity. Further, humans treated with nitroprusside, a drug that releases nitric oxide and cyanide ions, display increased circulating bile acids and inosine. In summary, riboflavin may be a novel treatment for cyanide toxicity and prophylactic measure during nitroprusside treatment, inosine may serve as a biomarker of cyanide exposure, and metabolites in the bile acid and purine metabolism pathways may shed light on the pathways critical to reversing cyanide toxicity. [ABSTRACT FROM AUTHOR]

This study was performed to investigate the role of leptin in wound healing. The specific aims were to determine whether leptin is present at the wound site and whether this might reflect up-regulation of leptin expression as a consequence of active synthesis in response to the tissue insult. Leptin is a hypoxia-inducible cytokine functionally related to the IL-6 cytokine family. As a well-documented angiogenic molecule, leptin may mediate wound neovascularization and have additional effects in cells involved in the healing process, including fibroblasts, macrophages, and keratinocytes. Wound resident cells actively engage in acute synthesis of leptin within the first 4 h after injury, which is maintained throughout the various phases of the healing process. Treatment of wounds with neutralizing anti-leptin antibodies severely disrupts a variety of morphological parameters of wound healing such as wound contraction, re-epithelialization, and matrix density. The increase observed in leptin synthesis within the wound results in a transient elevation in circulating leptin, arising directly from the wound bed. This report demonstrates for the first time that leptin synthesis occurs rapidly in wound ischemic tissue and that the presence of leptin is necessary for normal healing progression to occur. [ABSTRACT FROM AUTHOR]