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

PURPOSE: 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. METHODS: We conducted a cross-sectional study in 108 obese non-diabetic patients. RESULTS: There was an inverse correlation between plasma levels of pro-vitamin A carotenoids (α-carotene, ß-carotene and ß-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 ß-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. CONCLUSION: These results suggest the existence of a favourable effect of ß-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 ß-carotene towards insulin sensitivity would open the way to dietary strategies to prevent metabolic syndrome.

The Medi-RIVAGE study (Mediterranean Diet, Cardiovascular Risks and Gene Polymorphisms): rationale, recruitment, design, dietary intervention and baseline characteristics of participants.

OBJECTIVE: To report the rationale, recruitment, design, dietary intervention and baseline characteristics of participants in the Medi-RIVAGE study (Mediterranean Diet, Cardiovascular Risks and Gene Polymorphisms). DESIGN: A randomised, parallel trial comparing a new nutritional programme with a conventional programme. SETTING: Centre for Detection and Prevention of Arteriosclerosis, Timone University Hospital, Marseille, France, and collaborating teams. SUBJECTS: Two hundred and twelve male and female volunteers with at least one cardiovascular risk factor. INTERVENTION: A Mediterranean-type diet characterised mainly by the quality of fatty acids, amount of fish, vegetable foodstuffs and fibre was proposed and compared with a usually prescribed, low-fat/cholesterol diet. Body mass index, fasting lipids and lipoproteins, apolipoproteins, glucose, insulin and homocysteine were the main outcome measures. Gene polymorphisms of interest were determined. RESULTS: Characteristics of men in the two arms were comparable with regard to sociodemographic variables, and clinical and biological cardiovascular risk factors. There were few differences between the groups of women (cholesterol-related parameters, P<0.05). There was no difference between arms in allelic distribution of the gene polymorphisms studied. Saturated fat and protein intakes were high while carbohydrate and fibre intakes were low, but with no difference between arms. Overall, the nutritional markers were comparable in both arms with few exceptions. Correlations between nutritional intakes and plasma nutrient levels ranged from 0.19 (beta-carotene) to 0.47 (folate). CONCLUSIONS: The comparability of the two arms is notable and warrants a low risk of biases. Current diet departs from the traditional Mediterranean one. The assessment of nutritional intake is validated by correlations obtained between dietary intake and relevant biomarkers. This will be important to estimate participant compliance and to analyse intervention data.