Academic journal article Iranian Journal of Public Health

Effects of Aerobic Exercise on Serum Retinol Binding Protein4, Insulin Resistance and Blood Lipids in Obese Women

Academic journal article Iranian Journal of Public Health

Effects of Aerobic Exercise on Serum Retinol Binding Protein4, Insulin Resistance and Blood Lipids in Obese Women

Article excerpt

Introduction

Obesity is known as a risk factor for the develop-ment of metabolic disorders such as chronic inflammation, insulin resistance, dyslipidemia, arterial hypertension and atherosclerosis (1). Most of obese individuals are in danger of metabolic syndrome (2). Adipiokins are secreted proteins from adipose tissue. The production of some of the adipiokins is resulted from obesity, type2 diabetics, and metabolic syndrome (3). Retinol binding protein 4 (RBP4) is a type of adipokine related to the family of lipocalin proteins which transports vitamin A (retinol) to serum (4). RBP4 protein is synthesized mainly in the liver and adipose tissue (5). Adipose tissue may be a less important source for RBP4 concentrations in humans than animals (6). Although serum level of RBP4 in obesity, type2 diabetes, and metabolic syndrome is increased, the report is not accurate concentrations (7). Recently, higher RBP4 levels in obese and overweigh individuals have been re- ported (6). Besides, after adjustment for age, se-rum RBP4 had a positive relation with waist circumference, total abdominal fat and visceral fat. Visceral fat and LDL-C levels are independently influenced by RBP4 (8).RBP4 could be a bridge between obesity and insulin resistance (7). Cho et al (7) showed that human obesity is increased with RBP4 serum levels, and BMI is significantly higher than those of lean controls. In this study, there was not any relationship between plasma levels and the amount or percentage of body fat. Furthermore, the study by Broch et al (3) con-cluded that there was no relationship among insulin resistance, RBP4, and anthropometric measure-ments such as waist circumference, hip circum-ference, WHR, BMI, and fat mass. But RBP4 is related to blood pressure, triglycerides and LDL-C levels. RBP4 levels is related to systolic blood pressure, and obesity-related biochemical parame-ters (fasting glucose, fasting insulin, total choles-terol, LDL-C and insulin resistance index), even after adjustment for age and fat.

It is likely that increase in RBP4 level, will lead to increased in insulin resistance, dyslipidemia, and cardiovascular diseases (8).

Some studies in humans' RBP4 levels have shown inversely correlated insulin sensitivity and HDL-C levels. It is a point to mention that with some components of metabolic syndrome including BMI, triglyceride levels and systolic blood pres-sure there was a positive relationship (7, 8-13). Aerobic exercise will reduce the RBP4 levels in menopause women with type2 diabetes, middle-aged women, and young women (14, 15). A study showed that in response to four week exercise training in a wide age range of patients, RBP4 level was reduced (15). Moreover, Choy et al., af-ter three months of exercise training did not ob-serve significant differences in the levels of RBP4 in Korean women (16). As noted, obesity is one effective factor in increasing the levels of RBP4 in humans. Studies have also shown that the RBP4 level is much higher in obese people than in lean ones. Therefore, weight loss will reduce serum concentrations of RBP4 (3, 12). Studies have shown that a 5% weight loss, will lead to an in-creased insulin resistance index. Only slightly, the RBP4 gene will reduces fat tissue. And RBP4 level is not affected by this amount of weight loss (6, 12). Other studies have described that improve-ment in metabolism after exercise can reduce RBP4 levels (6). This also improves insulin sensitivity caused by exercise training in humans which are associated with lower levels RBP4 (17). Another study showed that a decrease in body fat caused by exercise, leads to a decreased level of RBP4 (14).

According to the controversial studies on the exercise effect and RBP4 levels, few studies which have been done in this area, and because the exact mechanism of exercise effect on 4RBP reduction is not clear this study was designed.

Materials and Methods

This is a quasi-experimental research method. …

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