Association of Lipin 1 gene polymorphisms with measures of energy and glucose metabolism

Objective: To examine the importance of lipin 1 (LPIN1) gene variation in energy and glucose metabolism. Transgenic animal models have shown that lipin, a protein encoded by the LPIN1 gene, promotes fat synthesis and storage in adipose tissue while decreasing energy expenditure and lipid oxidation in skeletal muscle. Lpin 1 was identified as the mutated gene in the fatty liver dystrophy mouse, which exhibits lipin deficiency and features of human lipodystrophy. Research Methods and Procedures: We genotyped five LPIN 1 polymorphisms and tested for association with resting metabolic rate (RMR), fat oxidation, fasting plasma insulin and glucose concentration, and obesity-related phenotypes, including BMI, body fat percentage, sum of six skinfolds, and waist circumference in 712 subjects of the Quebec Family Study. Results: The strongest results were generation- specific. In parents, RMR of the G/G IVS 13 + 3333A>G homozygotes was 107 kcal/d higher than in A/A homozygotes and 39 kcal/d higher than in A/G heterozygotes (p = 0.0003). In offspring, carriers of the C allele of the IVS18 + 181C>T variant had significantly higher (p < 0.0003) insulin levels than T/T homozygotes. These associations remained significant after adjusting for multiple testing. Several other associations between body composition measures and the IVS18 + 181C>T variant were significant (p = 0.05 to 0.003), suggesting a strong pattern of relationships. Discussion: These findings support the hypothesis that sequence variation in the LPIN 1 gene contributes to variation in RMR and obesity-related phenotypes potentially in an age-dependent manner.