Circulating white blood cell count and measures of adipose tissue inflammation predict higher 24-h energy expenditure

Abstract

Objective: Energy expenditure (EE) and measures of inflammation increase with adiposity, and this obesity-induced chronic and subclinical inflammation was extensively reported to be a cause of insulin resistance. However, whether subclinical inflammation has a role in increasing EE, which may be at the cost of developing insulin resistance, is not clear.

Methods: We investigated the association between circulating white blood cell count (WBC) in a population of Native Americans (n=243) with measurement of EE in a respiratory chamber, and in a subset of the same population (n=34), with gene expression measures of inflammation in subcutaneous abdominal adipose tissue (SAAT). All subjects were healthy on oral glucose tolerance test. Statistically, nonnormally distributed variables were logarithmically transformed before analyses to approximate normal distributions.

Results: WBC was associated with 24-h EE adjusted for age, sex, fat-free mass, and fat mass (r=0.13, P=0.04). In SAAT, tumor necrosis factor-alpha (TNF-alpha), shown as log10-transformed TNF-alpha (r=0.36, P=0.05), and plasminogen activator inhibitor-1 (PAI-1), shown as log10-transformed PAI-1 (lPAI-1; r=0.41, P=0.02), expressions were also positively correlated with adjusted 24-h EE. lPAI-1 was also correlated with adjusted sleep EE (r=0.34, P=0.07).

Conclusions: In conclusion, circulating markers of inflammation (WBC) and markers of inflammation within adipose tissue (TNF-alpha and PAI-1) are positively associated with EE, indicating a role of chronic subclinical inflammation in the regulation of metabolic rate.

Figure 1

Correlation of 24-h energy expenditure with WBC. Adjusted 24-h energy expenditure is positively correlated with white blood cell count (r=0.13, P=0.04). Adj_24EE, 24-h energy expenditure adjusted for age, sex, fat-free mass, and fat mass. WBC, white blood cell count. ○ = female, ● = male.

Figure 2

Correlation of energy expenditure with TNF-α and PAI-1. Adjusted 24-h energy expenditure is positively correlated with TNF-α (r=0.36, P=0.05) (A) and PAI-1 (r=0.41, P=0.02) (B), and adjusted sleeping energy expenditure is positively correlated with PAI-1 (r=0.34, P=0.07) (C). Adj_24EE, 24-h energy expenditure adjusted for age, sex, fat-free mass, and fat mass; Adj_sleep, sleeping energy expenditure adjusted for age, sex, fat-free mass, and fat mass. lTNF-α, lPAI-1 (log10-transformed tumor necrosis factor-α and plasminogen activator inhibitor-1). ○ = female, ● = male.