|ISSN No. 1606-7754 Vol.16 No.1 April 2008|
Insulin concentration is the main predictor of leptin level: a homogenous type 2 diabetes cohort study in Taiwan
Chung-Hua Hsu1,2; Su-Ching Lin, Kung-Chang Hwang3, Pesus Chou1, Ying-Li Liao4
Community Medicine Research Center and Institute of Public Health, National Yang-Ming University, Taipei1 Branch of Chinese Medicine, Taipei City Hospital2 Department of Pediatrics3, Department of Endocrinology4 Taipei Hospital, Taiwan
We hypothesized that there would be strong association between insulin level and leptin level, and attempted to examine factors affecting plasma leptin level among the homogeneous Type 2 diabetes subjects. The study was conducted from July 2005 through September 2005 in the Taipei Hospital, Taiwan. From 1356 registered diabetes patients, 120 subjects who met the criteria of (1) aged between 20 and 75 years, (2) being Chinese, (3) having Type 2 diabetes for more than one year, (4) having been taking gliclazide and metformin for more than 6 months, were enrolled for this study. Factors affecting plasma leptin level are determined using multiple linear regression analysis. The coefficients obtained by multiple regression analysis with stepwise method showed that gender (β=-0.49, p<0.001), insulin level (β=0.46, p<0.001) and body mass index (BMI)(β=0.21, p=0.003) were the main predictors of leptin concentrations for all type 2 diabetic subjects; insulin level (β=0.50, p<0.001), BMI (β=0.42, p<0.001) and triglyceride (β=0.17, p=0.03) were the main predictors for type 2 diabetic men; and insulin level (β=0.68, p<0.001) was the only predictor for type 2 diabetic women. These initial findings seem to indicate that insulin concentration is the main predictor of leptin level in both male and female type 2 diabetes subjects.
Keywords: Insulin, Leptin, Type 2 diabetes
Leptin is a hormone produced in adipocytes.1 It has been suggested that leptin directs metabolic fuels towards utilization and away from storages.2 The development of Type 2 diabetes in association with obesity, hyperinsulinemia and insulin resistance have been demonstrated. Obesity is associated with a marked increase in circulating leptin concentration.3-4 However, plasma leptin displays a strong correlation with insulin concentration, insulin resistance, metabolic syndrome, dyslipidemia, even after controlling for measures of body fat mass.5-8
The different severity or condition of type 2 diabetes might result in different degree of insulin concentration and resistance. Many studies have demonstrated that taking oral antidiabetic drugs might change the plasma leptin concentration in type 2 diabetes.9-10 To avoid confounders and bias due to different severity of diabetes, we examined a homogenous Chinese cohort who had had type 2 diabetes for more than one year, had been taking gliclazide and metformin for more than six months, and were 20-75 years old.
We hypothesized that there would be strong association between insulin level and leptin level, and attempted to examine factors affecting plasma leptin level among the homogeneous Type 2 diabetes subjects.