The Effect of IGF 2 BP 2 Gene Polymorphisms on Pioglitazone Response in Chinese Type 2 Diabetes Patients

Genome-wide association studies identified that insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2) genetic polymorphisms are related to type 2 diabetes mellitus (T2DM) in several populations. This study aimed to investigate whether the IGF2BP2 gene rs1470579 and rs4402960 polymorphisms were associated with T2DM and pioglitazone efficacy in Chinese T2DM patients.  A total of 281 T2DM patients and 111 healthy volunteers were enrolled to identify the IGF2BP2 gene rs1470579 and rs4402960 polymorphisms; 86 patients were randomly selected and given a 12-week pioglitazone treatment (30 mg/ day). Fasting plasma glucose, postprandial plasma glucose (PPG), glycated hemoglobin, serum triglycerides (TG), total cholesterol, low-density lipoprotein cholesterol and highdensity lipoprotein cholesterol (HDL-C) were determined before and after pioglitazone treatment.  The results showed that the IGF2BP2 gene rs1470579 and rs4402960 polymorphisms were associated with T2DM in a Chinese Received: April 10, 2014  May 6, 2014  2014 Prof. Qiong Huang Institute of Clinical Pharmacology, Anhui Medical University Key Laboratory of Anti-Inflammatory and Immune Medicine, Ministry of Education Hefei, Anhui 230032 (PR China) E-Mail qionghuang @ 126.com  Th is is an Open Access article licensed under the terms of the Creative Commons Attribution-NonCommercial 3.0 Unported license (CC BY-NC) (www.karger.com/OA-license), applicable to the online version of the article only. Distribution permitted for non-commercial purposes only. Zhang /Pei /Yang  /Zhao  /Mu /Huang  /Zhu Pharmacology 2014;94:115–122 DOI: 10.1159/000363414 116 environmental factors [3–5] . Genetic studies such as high-throughput technology genome-wide association studies have identified some new loci related to T2DM in recent years [6–11] . It has been proved that the insulinlike growth factor 2 mRNA-binding protein 2 (IGF2BP2) gene rs1470579 and rs4402960 polymorphisms [6] are associated with susceptibility to and the development of T2DM. This association was also replicated in Asian populations [7–9] . IGF2BP2 is an mRNA-binding protein which is involved in RNA location, stability and translation  . IGF2BP2 regulates insulin-like growth factor 2 (IGF2) translation by binding to the 5 ′ UTR of the IGF2 mRNA. IGF2 also plays an important role in the growth and insulin signaling pathways [11] . IGF2BP2 gene rs1470579and rs4402960-mutated carriers showed a moderately increased risk of T2DM in genome-wide association study results. T2DM patients with different IGF2BP2 genotypes showed various levels of insulin secretion. It has been demonstrated that variants in the IGF2BP2 gene affect first-phase insulin secretion and the disposition index detected by hyperglycemic clamps  . Thiazolidinediones (TZD) are insulin-sensitizing agents which could decrease fasting plasma glucose (FPG) and postprandial plasma glucose (PPG) levels by increasing glucose uptake in the peripheral tissue  . Pioglitazone is a new TZD, and the only available one which has been widely used for T2DM therapy [13, 14] . The therapeutic efficacy of pioglitazone showed individual differences. It has been proved that T2DM patients with different peroxisome proliferator-activated receptor-γ [15] or resistin [16] genotypes showed distinctive effects in multiple-dose pioglitazone therapy. In this study, we intended to investigate the effect of the IGF2BP2 gene rs1470579 and rs4402960 polymorphisms on the therapeutic efficacy of pioglitazone in Chinese T2DM patients.  The study group included 281 unrelated T2DM patients from the First and Third Affiliated Hospitals of the Anhui Medical University and 111 unrelated normoglycemic control subjects from the First Affiliated Hospital of the Anhui Medical University. The inclusion criteria were as follows: (1) T2DM was diagnosed in accordance with World Health Organization criteria in 1999 (FPG ≥ 7.0 mmol/l or 2-hour PPG ≥ 11.1 mmol/l); (2) body mass index (BMI) between 19 and 30; (3) no prior TZD use, and (4) no change in medication in the previous 3 months. Normoglycemic control subjects were selected by an FPG <6.1 mmol/l and a 2-hour PPG <7.8 mmol/l. The exclusion criteria were as follows: (1) type 1 diabetes mellitus; (2) ischemic heart disease, congestive heart failure, kidney or liver diseases; (3) insulin treatment or other drugs which affect the glucose metabolism (such as glucocorticoids), and (4) pregnancy or lactation in women. A total of 86 T2DM patients, who received a daily dose of 30 mg oral pioglitazone (Kasiping, Hangzhou, China) for 12 consecutive weeks, were recruited from the Third Xiangya Hospital of the Central South University and the Third Affiliated Hospital of the Anhui Medical University. These patients were advised to maintain the same levels of energy intake and physical activity. The local ethics committee approved the protocol, and all subjects signed the informed consent form before the study started. We also applied for clinical admission to the Chinese Clinical Trial Register (No. ChiCTR-RNC-12001949).  Venous blood samples of the subjects were collected in the fasting state and 2 h after a standardized breakfast at week 0 and week 12 (the end of administration). The BMI was calculated as the weight in kilograms divided by body height in meters squared. Concentrations of FPG, total cholesterol (TC) and triglyceride (TG) were determined by enzymatic colorimetric assay. The highdensity lipoprotein cholesterol (HDL-C) concentration was measured by lipoprotein electrophoresis. The low-density lipoprotein cholesterol (LDL-C) concentration was calculated according to the Friedewald formula  . Plasma HbA 1c levels were measured by high-performance liquid chromatography assay. Genotyping Genomic DNA was isolated from peripheral blood leukocytes using the Promega DNA Purification Kit (Promega, USA). The IGF2BP2 gene rs4402960 and rs1470579 polymorphisms were genotyped using the polymerase chain reaction-restriction fragment length polymorphism method. All the primers and reagents were previously described  . Statistical Analysis All analyses were performed with SPSS software (version 17.0 for Windows; SPSS Inc., Chicago, Ill., USA). Measurement data are expressed as means ± SD (95% CI). The Hardy-Weinberg equilibrium and frequencies were assessed with a Pearson χ 2 test. Continuous variables were compared using Student’s t test between the T2DM and control groups. Nonnormally distributed data were analyzed by the Mann-Whitney test. OR were calculated using a logistic regression analysis while adjusting for BMI, TG and LDL. Differences between before and after pioglitazone treatment were analyzed by paired t tests. Statistical power was calculated by the power calculator software PASS (www.ncss.com). A p value <0.05 was considered to be statistically significant.