| Co-Investigator(Kenkyū-buntansha) |
MIYASHITA Kazuhisa Wakayama Medical University, School of Medicine, Department of Hygiene, Professor, 医学部, 教授 (50124889)
ARITA Mikio Wakayama Medical University, School of Health and Nursing Science, Professor, 保健看護学部, 教授 (40168018)
MORIOKA Ikuharu Wakayama Medical University, School of Health and Nursing Science, Professor, 保健看護学部, 教授 (70264877)
GOWA Yoshiaki Osaka International University, Department of Human Health Science, Professor, 人間科学学部, 教授 (40248050)
TOMIDA Kotaro Wakayama University, Faculty of Economics, Associate Professor, 経済学部, 助教授 (50197935)
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| Research Abstract |
In this study, we investigated the effect of adolescent growth, obesity and adipocytokines on the insulin resistance and blood insulin levels, and then examined the relationships of obesity and its metabolic consequences with early arterial wall changes in healthy adolescents. The results are as follows ;
The blood insulin levels and insulin resistance (homeostasis model assessment) elevated temporarily with adolescent growth. The age-related variation of insulin was closely related to pubertal stage, which was determined according to the maximum incremental age of body height. Independent of these growth-specific variations, the obese subjects tended to have insulin resistance and higher insulin levels more than non-obese subjects. Over weight, excess body fat and larger waist circumference were correlated with insulin resistance and insulin levels. Of the indices, the main factor relevant to insulin resistance was the abdominal visceral fat indexed by the maximum preperitioneal fat th
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ickness using ultrasonography.
Leptin, an adipocytokine secreted from adipose tissue, regulates body fat balance by decreasing food intake and stimulating energy expenditure. In adolescents, there was a large variation in serum leptin levels according to age and sex. The leptin levels in girls increased progressively with age, whereas those in boys were extremely low and tended to decrease with age. A highly positive correlation was observed between insulin resistance and serum leptin levels, especially in obese subjects. The association persisted despite controlling for percent body fat, triglycerides, HDL cholesterol in multivariate analysis. Therefore, elevated leptin levels are likely related to insulin resistance independent of excess body fat and high levels of blood lipid and lipoproteins.
Compared to the subjects without insulin resistance, those with insulin resistance had significantly higher systolic and diastolic blood pressures, triglycerides and atherogenic index, and significantly lower HDL cholesterol. Furthermore, a longitudinal analysis found that the subjects with elevated insulin levels (sex-, age-specific top quartiles) were at increased risk for showing elevated blood pressure in later years. These findings suggest that insulin resistance and hyperinsulinemia adversely affect the metabolic risk factors for cardiovascular disease even in adolescents.
The effects of the clustering of metabolic syndrome variables in adolescents on the early arterial wall changes were evaluated. The brachial-ankle pulse wave velocity (baPWV) was measured as an index of arterial stiffness. In adolescents, the baPWV was higher in boys versus girls. In linier regression analyses adjusted for sex and age, the baPWV was significantly associated with all adiposity measures, systolic and diastolic blood pressure, triglycerides, HDL cholesterol, and insulin. The number of metabolic syndrome variables clustering, including high levels (sex-, age-specific top quartiles) of waist-height ratio, mean blood pressure, total-to-HDL cholesterol ratio, and homeostasis model assessment of insulin resistance, demonstrated a graded association with the baPWV. These findings suggest that adiposity and its metabolic consequences are associated with the evolution of arterial stiffness in adolescents. This fact indicates the need for monitoring arterial stiffness in childhood and emphasizes the importance of strategies to control adiposity and metabolic disturbances early in life. Less
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