A Pilot Study of Associations Between Visceral Fat, IL-6, and Urinary F(2)-Isoprostanes in Older Adults Exposed to a Diet Intervention

BACKGROUND: Short-term markers of successful visceral adipose tissue (VAT) loss are needed. Urinary F(2)-isoprostanes might serve as a marker for intensified lipid metabolism, whereas circulating IL-6 might stimulate fat oxidation and enhance mobilization of VAT. OBJECTIVES: This pilot study was designed to explore the hypotheses that 1) reduction in VAT is associated with increase in IL-6, and 2) that increases in urinary F(2)-isoprostanes are associated with increases in IL-6 and reduction in VAT. METHODS: Eighteen participants (aged 60–75 y, BMI 30–40 kg/m(2)) were randomly assigned to either a very-low-carbohydrate diet (VLCD; <10:25:>65% energy from carbohydrate:protein:fat) or a low-fat diet (LFD; 55:25:20%) for 8 wk. Changes in fat distribution were assessed by MRI. Four urinary F(2)-isoprostane isomers were quantified in 24-h urine collection using LC-MS/MS analyses. Changes in 4 F(2)-isoprostane isomers were summarized using factor analysis (Δ-F(2)-isoprostane factor). Statistical significance was set at P < 0.1. RESULTS: Within the VLCD group, change in VAT was inversely associated with change in IL-6 (r = −0.778, P = 0.069) and Δ-F(2)-isoprostane factor (r = −0.690, P = 0.086), demonstrating that participants who maintained higher concentrations of F(2)-isoprostane factor across the intervention showed greater decreases in VAT. A positive relation between Δ-F(2)-isoprostane factor and change in IL-6 was observed (r = 0.642, P = 0.062). In the LFD group, no significant associations between changes in VAT, F(2)-isoprostane factor, or IL-6 were observed. CONCLUSIONS: Results from this exploratory study in older adults with obesity suggest that, in the context of a VLCD, IL-6 could be involved in VAT mobilization, and urinary F(2)-isoprostanes could reflect intensified oxidation of mobilized fatty acids. Trial registration: This study is registered at clinicaltrials.gov as NCT02760641.