246-OR: A Loss-of-Function Mutation in the Sucrase-Isomaltase Gene Is Linked to a Markedly Healthier Metabolic Profile in Greenlanders

Abstract

Objective: Congenital sucrase-isomaltase deficiency is prevalent in Arctic populations. Recently, a frameshift mutation, c.273-274delAG, in the sucrose-isomaltase encoding gene (SI) was identified. This mutation was predicted to cause complete loss of enzymatic function, and thus is a diagnostic marker for Congenital sucrase-isomaltase deficiency. We aimed to characterize the metabolic health among adult Greenlanders carrying the c.273-274delAG mutation. Material and Methods: We genotyped the c.273-274delAG mutation in two cohorts of Greenlanders comprising 4600 (Cohort I) and 1500 participants (Cohort II), respectively. We assessed the effect of the variant on markers of metabolic health. Results: In cohort I, homozygous carriers of the c.273-274delAG mutation had a markedly healthier metabolic profile than the remaining population, including lower BMI (beta, -2.0 kg/m2, p=3.1x10-5), fat% (-3.3 %, p=0.0004), weight (-4.8 kg, p=0.0005), and levels of triglycerides (-0.27 mmol/l, p=2.3x10-6) and remnant cholesterol (-0.11 mmol/l, p=4.2x10-5). Even though homozygous carriers had a significantly lower consumption of sugar, this did not fully explain the healthier phenotype in these individuals. In cohort II, metabolomics data revealed that particularly HDL metabolism was altered among homozygous carriers of the mutation, and that these individuals had markedly increased levels of circulating acetate (1.78 mmol/l, p=2.1x10-26). Based on these findings, we hypothesize that the observed phenotype is caused by increased fermentation of undigested carbohydrates in the gut, leading to increased amounts of circulating acetate, which increases lipid oxidation and reduces storage of fat. Conclusion: Our results show, that homozygous c.273-274delAG mutation carriers have a markedly healthier metabolic profile, and indicate that SI constitutes a promising new drug target, with potential to prevent obesity and dyslipidemia. Disclosure M.E. Jørgensen: Research Support; Self; Amgen, AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Sanofi-Aventis. Stock/Shareholder; Self; Novo Nordisk A/S. M.K. Andersen: None. L. Skotte: None. E. Jørsboe: None. N. Grarup: None. P. Bjerregaard: None. B. Soborg: None. O. Pedersen: None. B. Feenstra: Employee; Spouse/Partner; Novo Nordisk Inc. N.J.K. Færgeman: None. A. Koch: None. I. Moltke: None. T. Hansen: None. A. Albrechtsen: None.