Triglycerides and systolic blood pressure negatively mediate the direct relationship of vitamin D status to resting energy expenditure: A cross sectional analysis

Abstract

Background and aims: We determined whether individual components of metabolic syndrome (MetS) mediated the direct association of vitamin D status (25OHD) on resting energy expenditure (REE).

Methods: Multiple linear regression determined predictors of REE from data on 180 men and women from two ethnic groups. We then modelled a mediation pathway through components of MetS on the direct association between 25OHD and REE. The mediation modelling used the PROCESS SPSS Macro (version 4.0) based on 5000 bootstrapped samples, with the adjustment for different sets of covariates.

Results: REE was significantly predicted by age, fat mass (FM), fat free mass (FFM), ethnicity, inverse ln insulin, 25OHD, triglycerides (TG), systolic blood pressure (SBP) and, to some extent, by time of REE measurements (p < 0.094). Adjustment for all these covariates, resulted in a negative indirect mediation effect of TG [β coefficient (bootstrapped SE): 0.95 (0.519); bootstrapped 95% CI: 2.172, -0.165; p < 0.05] and a concurrent negative mediation of SBP [β coefficient (bootstrapped SE): 0.72(0.484); bootstrapped 95% CI: 1.851, -0.011; p < 0.05]. There remained a positive direct pathway from 25OHD to REE [β coefficient (S.E): 4.715 (2.129); p = 0.028], however the total effect of 25OHD was dampened [β coefficient (S.E): 3.04 (2.126); p = 0.154].

Conclusions: Independent of insulin sensitivity, a negative mediation by TG and SBP dampened the overall effect of 25OHD on REE.

Keywords: Insulin sensitivity; Mediation; Metabolic syndrome; Resting energy expenditure; Systolic blood pressure; Triglycerides; Vitamin D.