Leptin and Metabolic Syndrome in Obese and Non-Obese Children

Abstract

Metabolic syndrome is characterized by a clustering of metabolic abnormalities: insulin resistance - hyperinsulinemia, dyslipidemia (high triglycerides and low HDL - cholesterol serum concentrations), impaired glucose tolerance and/or type 2 diabetes, and hypertension. The aim of this study was to analyse the role of different variables of metabolic syndrome, including leptin, in 74 non-obese children and 68 children with non-syndromal obesity. As metabolic syndrome variables, we have included body mass index, waist circumference, trunk-to-total skinfolds (%), systolic blood pressure, diastolic blood pressure, glucose, uric acid, fasting insulin, triglycerides and high-density lipoprotein-cholesterol (HDL-C). Factor analysis showed 4 factors in each group. In non-obese children, waist circumference, BMI, fasting insulin, triglycerides, trunk-to-total skinfolds (%), leptin and uric acid loaded positively on factor 1, and HDL-C loaded negatively on this factor; systolic and diastolic blood pressure had high positive loadings in factor 2; HDL-C and leptin showed positive loadings and triglycerides and uric acid, negative loadings in factor 3; and, finally, glucose and insulin showed positive loadings in factor 4. These four factors explained 72.16 % of the total variance in the non-obese group. In obese children, BMI, waist circumference, leptin, diastolic blood pressure and systolic blood pressure loaded positively on factor 1; diastolic blood pressure, trunk-to-total skinfolds (%), uric acid and systolic blood pressure showed high positive loadings in factor 2; fasting insulin, glucose and triglycerides showed positive loadings in factor 3; and, finally, triglycerides showed positive loadings and HDL-C negative loadings in factor 4. These four factors explained 74.18 % of the total variance in the obese group. Our results point to a different homeostatic control of metabolic syndrome characteristics in obese and non-obese children. Leptin seems to play a key underlying role in metabolic syndrome, especially in the obese group.

Hormones regulating lipid metabolism and plasma lipids in childhood obesity

“…4,12 In our study, leptin plasma concentrations were positively associated to anthropometric markers of fat mass and also to basal energy expenditure, which corroborates that, also in prepubertal children, leptin resistance is markedly evident. Leptin has been shown to be associated to insulin by other investigators in childhood and adult life.…”

“…9 Typical alterations of the metabolic syndrome may begin early in childhood, as they have been reported in prepubertal children 10,11 and adolescence. 12 However, the etiology of insulin resistance and its associated biochemical alterations, particularly those affecting lipid metabolism, continue to be a matter of debate. Changes in leptin, insulin and adiponectin, associated to obesity and their effects on lipid metabolism, may explain the alterations in plasma lipids and other characteristic features of the metabolic syndrome.…”

Relationships of physical activity with metabolic syndrome features and low-grade inflammation in adolescents

“…It is well established that adipocyte secretion products participate in the metabolic features associated with obesity. It has been suggested that leptin and sTNF-α R1 could reduce insulin sensitivity [10,35,36]. In addition to TNF-α, which is a proinflammatory cytokine, leptin might also contribute indirectly to systemic inflammation [10].…”

Body composition in adolescents: measurements and metabolic aspects

“…This cluster of metabolic abnormalities that already appears in obese children and adolescents increases the risk of cardiovascular diseases. 14,26,27 Obese children and adolescents with impaired glucose tolerance have peripheral insulin resistance and insulin secretion abnormalities that cause major defects in lipid and carbohydrate metabolism. Early in the natural history of type 2 diabetes in obese young people, insulin resistance as prediabetes status is related to an increased visceral fat more than to excess body fat.…”

“…Other metabolic abnormalities, associated with excess adiposity and implicated in cardiovascular morbidity and mortality, have also shown direct relations with central fat distribution in children and adolescents: greater plasma hemostatic factor concentrations; 30 increased intramyocellular lipid content; 28 low HDL-cholesterol and high LDL-cholesterol, ApoA1/ApoB and triglycerides plasma levels; 26,31,32 and hypertension. 26,31,32 Metabolic syndrome is characterized in childhood and adolescence by a clustering of several independent cardiovascular risk factors, 26,33 which appears in 8.9% of obese children (defined by the simultaneous presence of four risk factors).…”