Independent positive association of plasma β-carotene concentrations with adiponectin among non-diabetic obese subjects

Many epidemiological studies find an inverse correlation between carotenoids intake or carotenoids plasma concentrations and body mass index (BMI), insulin resistance or metabolic syndrome in the general population. However, it is not clear whether these relationships occur in obese population. We conducted a cross-sectional study in 108 obese non-diabetic patients. There was an inverse correlation between plasma levels of pro-vitamin A carotenoids (alpha-carotene, beta-carotene and beta-cryptoxanthin) and both BMI and insulin resistance (estimated by the HOMA-IR). No correlation between plasma concentrations of lycopene or lutein/zeaxanthin and BMI or insulin resistance was found. The inverse association between the three pro-vitamin A carotenoids and HOMA-IR disappeared after adjustment for BMI and waist circumference. Interestingly, we identified a positive association between concentrations of beta-carotene and adiponectin in plasma that was independent of sex, age, smoking status, BMI and waist circumference. To our knowledge, such association has never been described in obese patients. These results suggest the existence of a favourable effect of beta-carotene on insulin sensitivity in obese individuals that could involve a positive regulation of adiponectin, either directly or via its pro-vitamin A activity. The demonstration of the potential benefits of beta-carotene towards insulin sensitivity would open the way to dietary strategies to prevent metabolic syndrome.