SERUM APELIN IN CHILDREN AND ADOLESCENTS WITH TYPE 1 DM: RELATION TO GLUCOSE METABOLISM AND INSULIN SENSITIVITY

Abstract

Diabetes Mellitus is a group of metabolic diseases characterized by hyperglycemia resulting from defect in insulin secretion, insulin action, or both (American Diabetes Association, 2007). Apelin is a bioactive peptide, first isolated from bovine stomach (Tatemoto et al., 1998). This peptide is the endogenous ligand of the G-protein-coupled receptor APJ. Apelin is derived from preproapelin, a 77-amino-acid precursor, which is subsequently cleaved by endopeptidases into several active molecular forms, such as apelin-36, apelin-13 and apelin-12 (Lee et al., 2000). Apelin mRNA is expressed in several tissues: including several regions of the central nervous system, in the heart, placenta, lung, mammary gland and gastrointestinal tract (Wang et al., 2004; Masri et al., 2005). It has been shown that apelin is an adipokine produced and secreted by white adipose tissue in humans and mice (Boucher et al., 2005). Given its hypotensive effect and its effect on cardiac contractility, apelin also appears to be involved in cardiovascular function (Tatemoto et al., 2001; Szokodi et al., 2002). Other studies suggest that apelin plays a role in the central nervous system and particularly in the regulation of food intake and water balance but the results of the different studies are conflicting (Valle et al., 2008; Clarke et al., 2009). Moreover, apelin is involved in energy metabolism, it has been demonstrated that this adipokine improves insulin sensitivity in insulin resistant obese mice and that this effect is explained by an increase in glucose uptake in skeletal muscle (Dray et al., 2008; Yue et al., 2010). Apelin synthesis is stimulated by insulin and plasma apelin levels were reported to be increased in obesity in association with hyperinsulinemia (Boucher et al., 2005). The present study is a cross sectional observational case control study that was conducted at the Pediatric Diabetes Clinic, Children's Hospital, Ain Shams University. The study included 60 patients with type 1 diabetes mellitus and 30 age and sex matched healthy individuals as a control group. The diabetic group is further divided into 2 equal subgroups; controlled and uncontrolled diabetics according to HbA1c%. All patients included in this study were subjected to: full history taking, complete physical examination and laboratory investigations including: fasting blood glucose, HbA1c, fasting serum lipid profile (HDL, LDL, triglyceride and total cholesterol), fasting serum insulin and serum apelin.