Research Paper Volume 12, Issue 10 pp 9761—9780

Physiological and metabolic features of mice with CRISPR/Cas9-mediated loss-of-function in growth hormone-releasing hormone

Mert Icyuz1, *, , Michael Fitch1, *, , Fang Zhang1, , Anil Challa1, , Liou Y. Sun1, ,

  • 1 Department of Biology, University of Alabama at Birmingham, Birmingham, AL 35233, USA
* Equal contribution

Received: February 8, 2020       Accepted: April 20, 2020       Published: May 18, 2020
How to Cite

Copyright © 2020 Icyuz et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Our previous study demonstrated that the loss of growth hormone releasing hormone (GHRH) results in increased lifespan and improved metabolic homeostasis in the mouse model generated by classical embryonic stem cell-based gene-targeting method. In this study, we targeted the GHRH gene using the CRISPR/Cas9 technology to avoid passenger alleles/mutations and performed in-depth physiological and metabolic characterization. In agreement with our previous observations, male and female GHRH-/- mice have significantly reduced body weight and enhanced insulin sensitivity when compared to wild type littermates. Dual-energy X-ray absorptiometry showed that there were significant decreases in lean mass, bone mineral content and density, and a dramatic increase in fat mass of GHRH-/- mice when compared to wild type littermates. Indirect calorimetry measurements showed dramatic reductions in oxygen consumption, carbon dioxide production and energy expenditure in GHRH-/- mice compared to wild type mice in both light and dark cycles. Respiratory exchange ratio was significantly lower in GHRH-/- mice during the light cycle, but not during the dark cycle, indicating a circadian related metabolic shift towards fat utilization in the growth hormone deficient mice. The novel CRISPR/Cas9 GHRH-/- mice are exhibiting the consistent and unique physiological and metabolic characteristics, which might mediate the longevity effects of growth hormone deficiency in mice.


ANCOVA: analysis of covariance; AUC: area under the curve; BMC: bone mineral content; BMD: bone mineral density; DXA: dual-energy X-ray absorptiometry; ESC: embryonic stem cell; GH: growth hormone; GHRH: growth hormone-releasing hormone; GHR/GHBP: GH receptor/GH-binding protein; Pit1: pituitary factor-1; PRL: prolactin; Prop-1: Prophet of Pit-1; RER: respiratory exchange ratio; TSH: thyroid-stimulating hormone; VCO2: carbon dioxide production; VO2: oxygen consumption.