Normal Body Weight Homeostasis Research Articles

Hsa-miR-34a mediated repression of corticotrophin releasing hormone receptor 1 regulates pro-opiomelanocortin expression in patients with complex regional pain syndrome.

BackgroundKetamine provides relief for a subset of patients with complex regional pain syndrome (CRPS). The poor responders had a lower body mass index (BMI) relative to responders. Regulation of proopiomelanocortin (POMC) expression is crucial in normal body weight homeostasis. The main objectives of this study were to investigate the mechanisms underlying lower BMI characterizing CRPS patients responding poorly to intravenous ketamine therapy and identify potential biomarkers for predicting response.MethodsWe investigated POMC transcript levels in blood from CRPS patients grouped as responders and poor responders to ketamine therapy. Plasma levels of β-endorphin, ACTH and α-MSH were measured by ELISA. We previously identified differential expression of small noncoding microRNA hsa-miR-34a in blood between responders and poor responders. We investigated whether a 11-fold downregulation of hsa-miR-34a in poor responders relative to responders is contributing to the differences in POMC levels by targeting POMC regulator CRHR1. Binding of miR-34a to CRHR1 was assessed using reporter assay; changes in mRNA and protein levels of CRHR1 were used to determine the regulation of CRHR1 by miR-34a. RNA from blood of CRPS and control subjects were used for quantitative PCR for CRHR1.ResultsThough ketamine treatment did not alter POMC expression, poor responders had higher levels of POMC mRNA than responders, both before and after treatment. Corticotropin-releasing hormone (CRH) is a key regulator of POMC expression and the biological effects are mediated through its receptor corticotrophin releasing hormone receptor 1 (CRHR1). We show that hsa-miR-34a is a negative regulator of CRHR1; overexpression of hsa-miR-34a in Jurkat cells resulted in reduction of CRH-mediated POMC expression. Poor responders had higher expression of CRHR1 transcripts than responders, indicating a regulatory role for miR-34a. In addition, we found positive correlations between the pretreatment levels of miR-34a to BMI and response to ketamine therapy.ConclusionsOur findings indicate a mechanism by which hsa-miR-34a can regulate the CRH/CRHR1/POMC axis and may influence BMI. Studies in larger patient cohorts are required to confirm the biomarker utility of circulating hsa-miR-34a levels in predicting treatment response to ketamine therapy.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-0820-1) contains supplementary material, which is available to authorized users.

Essential role of STAT3 in body weight and glucose homeostasis.

STAT3 is a ubiquitous transcription factor that is indispensable during early embryogenesis. To study the functions of STAT3 postnatally, we generated conditional STAT3-deficient mice. To that end, STAT3(lox/lox) mice were crossed with mice expressing Cre under the control of rat insulin II gene promoter (RIP-Cre mice). Immunohistochemical and Western blot analyses showed that STAT3 is deleted from beta cells in the islets of Langerhans. Genomic DNA PCR revealed that STAT3 deletion also occurred in the hypothalamus. Hypothalamic Cre expression was further confirmed by crossing RIP-Cre/STAT3(lox/lox) mice with the ROSA26 Cre reporter strain and staining for lacZ activity. Double immunohistochemical staining confirmed that deletion of STAT3 occurred in leptin receptor (OB-Rb isoform)-positive neurons. RIP-Cre/STAT3(lox/lox) mice are mildly hyperglycemic and hyperinsulinemic at the time of weaning, become hyperphagic immediately after weaning, and exhibit impaired glucose tolerance. Body weight, body fat, and mRNA and protein levels of leptin are all significantly increased in RIP-Cre/STAT3(lox/lox) mice. Administration of recombinant leptin by intracerebroventricular infusion failed to cause complete loss of body fat in RIP-Cre/STAT3(lox/lox) mice. Transplantation of wild-type islets into RIP-Cre/STAT3(lox/lox) mice also failed to decrease adiposity or to correct other abnormalities in these mice. These data thus suggest that loss of STAT3 in the hypothalamus caused by RIP-Cre action likely interferes with normal body weight homeostasis and glucose metabolism.