A common haplotype of carnitine palmitoyltransferase 1b is associated with the metabolic syndrome.

A Auinger, D Rubin, M Sabandal, U Helwig, A Rüther, S Schreiber, U R Foelsch, F Döring, J Schrezenmeir
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The British journal of nutrition
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The carnitine palmitoyltransferase (CPT) enzyme system facilitates the transport of long-chain fatty acids into mitochondria to provide substrates for β-oxidation. We performed an analysis including three coding SNP in the muscle isoform of the CPT1b gene (rs3213445, rs2269383 and rs470117) and one coding SNP in the CPT2 gene (rs1799821) to find associations with traits of the metabolic syndrome (MetS). Male participants (n 755) from the Metabolic Intervention Cohort Kiel were genotyped and phenotyped for features of the MetS. Participants underwent a glucose tolerance test and a postprandial assessment of metabolic variables after a standardised mixed meal. Carriers of the rare CPT1b 66V (rs3213445) allele had significantly higher γ-glutamyl transpeptidase (GGT), glutamic oxaloacetic transaminase (GOT) and glutamic pyruvate transaminase (GPT) activities (P< 0·0001, P= 0·03 and P= 0·048, respectively) and a higher fatty liver index (FLI, P= 0·026). Fasting and postprandial TAG (P= 0·007 and P= 0·009, respectively) and fasting glucose (P= 0·012) were significantly higher in 66V-allele carriers. The insulin sensitivity index determined after a glucose load was lower in those subjects (P= 0·005). Total cholesterol (P= 0·051) and LDL-cholesterol (P= 0·062) tended to be higher in 66V-allele carriers when compared with I66I homozygotes. Homozygosity of the rare K531E allele presented with lower GGT and GOT activities (P= 0·011 and P= 0·027, respectively). E531E homozygotes tended to have lower GPT and FLI (P= 0·078 and P= 0·052, respectively). CPT2 V368I (rs1799821) genotypic groups did not differ in the investigated anthropometric and metabolic parameters. The present results confirm the association of CPT1b coding polymorphisms with the MetS, with a deleterious effect of the CPT1b I66V and a protective impact of the CPT1b K531E SNP, whereas haplotype analysis indicates a relevance of the E531K polymorphism only.