Factors associated with circulating concentrations of irisin in the general population cohort of the ABCD study.

OBJECTIVE: Animal studies have shown that irisin is a myokine secreted following physical exercise, and that it induces the remodeling of white adipose tissue toward brown adipose tissue. Therefore, a protective role of irisin against obesity, diabetes, and other metabolic and cardiovascular conditions has been hypothesized. However, data in humans are contradictory and few data are available concerning the general population. DESIGN: We aimed to evaluate the association between serum irisin concentrations and habitual physical activity, as well as other metabolic and cardiovascular factors in a general population in a Mediterranean area. METHODS: We considered 858 consecutive individuals included in the ABCD (Alimentazione, Benessere Cardiovascolare e Diabete) study (ISRCTN15840340), a longitudinal observational single-center study of a cohort representative of the general population of Palermo, Sicily. Irisin serum concentrations (Phoenix Europe, Germany), habitual physical activity (HPA) level, and other blood and clinical variables were measured. RESULTS: The irisin serum concentrations were not normally distributed in the cohort (Shapiro-Wilk test=0.94; P<0.001). A significant association between irisin concentrations and HPA was observed (P<0.001). Irisin concentrations were higher in women than in men (P<0.01), and significantly correlated with serum concentrations of HDL-cholesterol (P<0.05) and hs-C-reactive protein (hs-CRP; P<0.05). Binary logistic regression analysis demonstrated that high (⩾ median value) irisin serum concentrations were significantly associated with female gender (OR=1.63; 95% CI=1.16-2.28), high serum hs-CRP concentrations (OR=1.61; 95% CI=1.02-2.54) and the HPA level (OR=1.42; 95% CI=1.02-1.96). CONCLUSIONS: Our study confirms, in a cohort of a general population, that irisin concentrations gradually increase with the usual level of habitual physical activity.

Association of dietary patterns with insulin resistance and clinically silent carotid atherosclerosis in apparently healthy people.

BACKGROUND/OBJECTIVES: Dietary habits are important determinants of individual cardiovascular and metabolic risk. This study investigated the association between dietary patterns and asymptomatic carotid atherosclerosis, defined as the presence of plaques and/or increased intima-media thickness, and metabolic biomarkers of insulin resistance, including the homeostasis model assessment of insulin resistance (HOMA-IR) and the trygliceride/high-density lipoprotein (HDL)-cholesterol (Tg/HDL) ratio in a cohort of adults without known diabetes or atherosclerotic cardiovascular disease. SUBJECTS/METHODS: Nine hundred and twenty-nine randomly selected participants were cross-sectionally investigated. Each participant answered a food frequency questionnaire, and underwent high-resolution ultrasonographic evaluation of both carotid arteries. Laboratory blood measurements were obtained in a subsample of 507 participants. RESULTS: A dietary pattern that could be defined as unhealthy (high consumption of soft drinks, fried foods, seed oils, cured meats, butter, red meat and sweets) was identified in 21% of the cohort, whereas 34% of the cohort exhibited a dietary pattern that resembled the Mediterranean diet (high intakes of fruit, milk and cheese, olive oil, vegetables, pasta and bread). Intermediate habits characterized the remaining 45%. After adjusting for age, body mass index (BMI), waist circumference, glycated hemoglobin (HbA1c) and hypertension on treatment, the Mediterranean dietary pattern was associated with significantly lower HOMA-IR (ß-coefficient=-0.51; P=0.003). After adjusting for gender, BMI and HbA1c, the unhealthy dietary pattern was associated with a significantly higher Tg/HDL-cholesterol ratio (ß-coefficient=0.43; P=0.006). No significant association was found between dietary patterns and carotid atherosclerosis. CONCLUSIONS: This study suggests that, independent of measures of adiposity, a Mediterranean dietary pattern is associated with lower insulin resistance.