Kidney expression of the ecto-nucleotida pirophosftase / fosphodiesterase 1 (ENPP1) gene according to the different genotypes of the ENPP1 K121Q polymorphism

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: MON 818-841-Diabetes Pathophysiology & Complications
Basic/Clinical
Monday, June 17, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board MON-823
Daisy Crispim*1, Denise Alves Sortica2, Guilherme Pozzueco Zaffari2, Mariana Palazzo Carpena2, Letícia de Almeida Brondani2 and Luis Henrique Canani3
1Clinical Hospital from Porto Alegre, Porto Alegre, Brazil, 2Hospital de Clínicas de Porto Alegre, Porto Alegre, Brazil, 3Hosp de Clinicas - Porto Alegre, Porto Alegre, Brazil
Introduction: ENPP1 is one of the five cell membrane proteins that contain an active site that catalyzes the extracellular release of nucleoside-5-nucleotide phosphatases and their products. This protein is expressed in several tissues, including kidney and, when in increased levels, inhibits the tyrosine kinase activity of the insulin receptor, causing insulin resistance. The Q allele of K121Q polymorphism (rs1044498) in the ENNP1gene has been associated with diabetic nephropathy in different populations.

Objective: To analyze whether ENPP1gene expression and protein concentration in human kidney tissue samples differs between different genotypes of K121Q polymorphism in non-diabetic subjects.

Methods: Renal biopsies and peripheral blood were collected from 107 individuals who underwent therapeutic radical nephrectomy. The genotyping of the K121Q polymorphism in these 107 samples was performed by Real-time PCR using TaqMan MGB probes. ENPP1gene expression was evaluated in a sub-group of 35 individuals (14 with the K/K genotype, 12 K/Q and 9 Q/Q) using RT-qPCR. ENPP1 protein distributions and intensities were analyzed in 67 individuals (28 K/K, 30 K/Q and 9 Q/Q) using immunohistochemistry technique. Ten fields of each sample were photographed, and the intensity of ENPP1 immunostaining was analyzed independently by two researchers using the Image Pro Plus version 4.5 program. The project was approved by the research ethics committee and patients signed an informed consent form.

Results: The genotype frequencies of the K121Q polymorphism are in Hardy-Weinberg equilibrium (P=0.076). Among the 107 patients included in the study, 10 had the K/K genotype (9.3%), 33 had the K/Q genotype (30.8%) and 64 had the K/K genotype (59.8%). The ENPP1 gene expression in the kidney did not differ significantly between Q allele carriers and subjects with the K/K genotype [10.1 (1.14 – 37.78)] vs. [7.52 (1.25 – 135.5) arbitrary units, respectively; P=0.158]. ENPP1 immunoreactivity was observed only in the distal tubules of the kidneys. Likewise gene expression data, ENPP1 immunoreactivity in kidney was not different in subjects carrying the Q allele and subjects with the K/K genotype [894.2 (187.9 – 1993.6) vs. 778.0 (89.6 – 2321.9) pixels, respectively; P=0.241].

Conclusion: These data suggest that the K121Q polymorphism is not associated with changes in ENPP1 expression in the human kidney.

Nothing to Disclose: DC, DAS, GPZ, MPC, LDAB, LHC

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

Sources of Research Support: Financial Support: FIPE-HCPA FAPERGS, CNPq.