Author Affiliations: Department of Geriatrics and Metabolic Diseases, Second University of Naples, Naples, Italy.
The adiponectin adipocyte-secreted adipokine has both insulin-enhancer and anti-inflammatory properties1 and is the most consistent biochemical predictor of type 2 diabetes mellitus. Higher adiponectin levels are consistently associated with a lower risk of type 2 diabetes in 13 prospective studies of diverse populations with a total of 14 598 participants and 2623 incident cases of type 2 diabetes, with a relative risk of 0.72 (95% confidence interval, 0.67-0.78) per 1-log μg/mL increment in adiponectin levels.2 Identification of lifestyle changes able to increase adiponectin circulating levels may help refine the strategy against the current diabetes epidemics.
This was a post hoc analysis of randomized controlled trials3- 5 to see whether adiponectin levels were related to success in achieving lifestyle changes. A total of 410 subjects (219 men and 191 women) were originally randomized to an intervention group, based on improvement of quality of diet and increased physical activity, or to a control group (general information about healthy food choices and exercise). The goals of the dietary intervention were a reduction in intake of saturated fat to less than 10% of energy consumed, an increase in intake of monounsaturated fat to 10% or more of energy consumed, and an increase in fiber intake to at least 15 g per 1000 kcal. The goal of physical activity was moderate exercise for at least 30 min/d for at least 5 d/wk. Frequent ingestion of whole-grain products, vegetables, fruits, nuts, low-fat milk, and olive oil was recommended. The subjects also received individual guidance on increasing their level of physical activity: endurance exercise (such as walking, jogging, swimming, aerobic ball games, or skiing) was recommended. The study subjects were ranked according to their success in achieving the goals of the intervention at the 4-year examination. We calculated the percentage of subjects in both groups who had an adiponectin level of 1 μg/mL or more above the median of the sample in each success score category (0, no goal achieved; 1, dietary goal achieved; 2, physical activity goal achieved; and 3, dietary + physical activity goals achieved). Adiponectin levels were assayed with a radioimmunoassay from Linco Research, St Charles, Missouri, which has an intra-assay coefficient of variation of 1.78% to 6.21%.
At baseline, the mean (SD) age of subjects in the intervention and control groups was 41 (6.6) and 41.2 (6.8) years, respectively, and the mean (SD) body mass index (calculated as weight in kilograms divided by height in meters squared) was 32.4 (5.5) and 32.6 (6.2), respectively. At 4 years, 155 subjects in both groups were still in the program. The median (interquartile range) of plasma adiponectin concentration was 6.1 (3.5-9.1) μg/mL. The Figure shows the numbers of subjects who achieved the goals in each group, as well as the percentage of subjects in each category with adiponectin concentrations of 1 μg/mL or more above the median. The figures were adjusted for weight changes. Absolute numbers of people at goals were significantly lower in the control group; however, percentage values did not show any difference between groups, suggesting that achievement of the goal resulted in raised adiponectin levels independent of the group assignment.
Subjects achieving adiponectin levels of 1 μg/mL or more above the median at the end of follow-up, according to the success score. *Data are given as number at goal/number not at goal in each category.
This study provides evidence that circulating adiponectin levels, in the range of those suggested to offer protection from type 2 diabetes, can be obtained by successful lifestyle changes. Our estimate of the effect of the intervention can be considered conservative, since all subjects in the control group also had benefits from the general health advice. The recent results of the long-term Women's Antioxidant Cardiovascular Study,6 which showed no effect from generous doses supplement intake of vitamins A and C and beta carotene on primary prevention of type 2 diabetes, further stress the importance of lifestyle changes for diabetes prevention. Successful lifestyle changes are associated with increased circulating levels of adiponectin in overweight subjects.
Correspondence: Dr Esposito, Department of Geriatrics and Metabolic Diseases, Second University of Naples, Piazza L. Miraglia, 80138 Naples, Italy (firstname.lastname@example.org).
Author Contributions:Study concept and design: Esposito and Giugliano. Acquisition of data: Esposito and Giugliano. Drafting of the manuscript: Esposito and Giugliano. Critical revision of the manuscript for important intellectual content: Esposito and Giugliano. Statistical analysis: Giugliano. Administrative, technical, and material support: Esposito. Study supervision: Esposito and Giugliano.
Financial Disclosure: None reported.
Funding/Support: This work was supported in part by a grant from the Second University of Naples, Naples, Italy.
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