Serum antioxidant concentrations and metabolic syndrome are associated among U.S. adolescents in recent national surveys

Abstract

Specific micronutrients, including retinol, retinyl esters, carotenoids [α-carotene, β-carotene (cis+trans), β-cryptoxanthin, lutein+zeaxanthin, and total lycopene], vitamin E, and vitamin C have antiinflammatory and antioxidant effects, properties shown to reduce oxidative stress, a process that accompanies the pathogenesis of many chronic diseases. It is still largely unknown whether they are associated with the occurrence of metabolic syndrome (MetS) in the adolescent U.S. population. MetS was defined by the International Diabetes Federation (IDF) criteria. Other non-MetS outcomes relying on blood measurements were elevated HOMA-IR, C-reactive protein (CRP), and hyperuricemia. We tested associations between serum antioxidants and MetS outcomes among adolescents aged 12-19 y using cross-sectional data from NHANES 2001-2006 (n = 782-4285). IDF MetS prevalence was estimated at 7% among boys and 3% among girls. In adjusted models, adolescents with MetS had consistently lower carotenoid concentrations compared with their counterparts without MetS. Total carotenoids were also inversely related to HOMA-IR and CRP. Vitamin C was inversely related to uric acid level and MetS binary outcome. Retinol+retinyl esters exhibited an inverse relationship with CRP and a positive relationship with uric acid and HOMA-IR as well as MetS binary outcome. Vitamin E had no association with MetS, particularly after controlling for serum cholesterol and TG. In conclusion, among U.S. adolescents, serum carotenoid concentrations were inversely associated with MetS status, HOMA-IR, and CRP, whereas serum vitamin C was inversely related to MetS status and serum uric acid. Vitamin E had no consistent association with MetS, whereas retinol+retinyl esters had a positive relationship with HOMA-IR, uric acid, and MetS, while being inversely related to CRP. These associations need further study.

FIGURE 1

Adjusted β and 95% CI of major serum antioxidant concentrations (expressed as quartiles, Q2, Q3, Q4 vs. Q1) and MetS (IDF definition) count outcome (A), HOMA-IR (log_e-transformed) (B), CRP concentration (log_e-transformed), and uric acid concentration (log_e-transformed) among U.S. adolescents (NHANES 2003–2006). Ranges for each antioxidant quartile were (μmol/L): retinol+retinyl esters (Q1: 0.461–1.399; Q2: 1.399–1.646; Q3: 1.647–1.918; Q4: 1.918–5.334); total carotenoids (Q1: 0.172–0.816; Q2: 0.817–1.038; Q3: 1.038–1.308; Q4: 1.309–7.877); vitamin E (Q1: 1.9–15.4; Q2: 15.4–17.6; Q3: 17.6–20.5; Q4: 20.5–68.8); vitamin C (Q1: 0.6–43.2; Q2: 43.7–59.1; Q3: 59.6–73.2; Q4: 73.8–212.9). (A) Analysis was based on multiple zero-inflated Poisson regression models that simultaneously included all antioxidant exposures and adjusted for socio-demographic factors: age, sex, race/ethnicity, and PIR, dietary intakes (total energy intake, alcohol, caffeine, β-carotene, vitamin C, vitamin E, and dietary supplement use), and serum concentrations of folate, vitamin B-12, 25(OH)D, total cholesterol, and TG. (B–D) Analysis was based on multiple OLS regression models that simultaneously included all antioxidant exposures and adjusted for covariates listed in A. P-trends were estimated using a model in which antioxidant status variables were entered in their ordinal scale. IDF, International Diabetes Federation; MetS, metabolic syndrome; 25(OH)D, 25-hydroxyvitamin D; OLS, ordinary least square; PIR, poverty income ratio.