PCLO Variants are Nominally Associated with Early Onset Type 2 Diabetes and Insulin Resistance in Pima Indians

Abstract

Objective: A prior genome-wide association (GWA) study in Pima Indians identified variants within PCLO that were associated with early-onset type 2 diabetes. PCLO encodes a presynaptic cytomatrix protein which functions as a Ca²⁺ sensor that may be involved in insulin secretion and/or insulin action. Therefore, PCLO was analyzed as a candidate gene for type 2 diabetes.

Research Design and Methods: Sequencing of PCLO identified 4 non-synonymous variants and a 10 amino acid insertion. These variants, together with 100 additional variants identified by sequencing or chosen from databases, were genotyped for association analysis in the same 895 subjects analyzed in the prior GWA study (300 cases with diabetes onset at age <25 years, 334 non-diabetic controls age >45, and 261 discordant siblings of the cases or controls for within-family analyses), as well as 415 non-diabetic Pima Indians who had been metabolically phenotyped for predictors of diabetes. Selected variants were further genotyped in a population-based sample of 3501 Pima Indians.

Results: Four variants were modestly associated with early-onset type 2 diabetes in both general and within-family analyses (P=0.004-0.04, recessive model), where the diabetes risk allele was also nominally associated with a lower insulin-mediated glucose disposal rate (P=0.009-0.14, recessive model) in non-diabetic Pima Indians. However, their association with diabetes in the population-based sample was weaker (p=0.02-0.20, recessive model).

Conclusions: Variation within PCLO may have a modest effect on early-onset type 2 diabetes, possibly as a result of reduced insulin action, but has minimal, if any, impact on population-based risk for type 2 diabetes.