AUTHOR=Abulmeaty Mahmoud Mustafa Ali , Almajwal Ali M. , Alam Iftikhar , Razak Suhail , ElSadek Mohamed F. , Aljuraiban Ghadeer S. , Hussein Khulood S. , Malash Asmaa M. 

TITLE=Relationship of Vitamin D-Deficient Diet and Irisin, and Their Impact on Energy Homeostasis in Rats

JOURNAL=Frontiers in Physiology

VOLUME=Volume 11 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.00025

DOI=10.3389/fphys.2020.00025

ISSN=1664-042X

ABSTRACT=Background and objective: 
Previous studies have identified the role of irisin and vitamin D in energy homeostasis. However, the effect of irisin and vitamin D on energy regulation has not been thoroughly investigated. Therefore, in this study, the effects of a vitamin D-deficient diet and irisin on total energy expenditure (TEE), food intake, and blood metabolites were investigated in rats.  
Methods: 
Sixteen healthy weaned male albino rats were randomly divided into two groups: a group fed a normal balanced growth diet (group A: n=8) and a group fed a normocalcemic diet that is vitamin D deficient with limited ultraviolet (UV) light exposure (group B, n=8). After six weeks, the volumes of respiratory gases were measured by open-circuit indirect calorimetry. Serum irisin, 25-OHVD3, calcium, insulin, and glucose levels were measured using ELISA. The respiratory quotient (RQ), energy expenditure, and Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) were calculated.
Results: Rats with hypovitaminosis D were hypoirisinemic. Food intake, RQ (to the range of using endogenous fat), and glucose levels reduced significantly, while insulin levels increased. Bodyweight and TEE were non-significant changed. Additionally, irisin was strongly and positively correlated with body weight under normal conditions (r=0.905, p<0.01), and a moderate negative correlation in group B (r=-0.429, p<0.05). TEE and irisin showed no significant correlation.
Conclusions: This study demonstrated that the early changes in energy homeostasis and irisin levels during states of hypovitaminosis D are affected by long-term consumption of a vitamin D-deficient diet with limited UV exposure.