Many studies have highlighted the benefits of a carotenoid-rich diet on health( Footnote 1 ). However, it is not clear to date whether carotenoids and/or their breakdown products are responsible for the observed health benefits. Currently, two human enzymes have been identified and cloned, which catalyse the centric (β-carotene monooxygenase-1; BCMO1) and eccentric (BCDO2) cleavage of carotenes( Footnote 2 ). BCMO1- or BCDO2-knock-out mice develop an obese phenotype independent of the type of diet (standard or high-fat), suggesting that these enzymes play a major role in lipid homeostasis( Footnote 3 ). Previous studies have identified several single nucleotide polymorphisms (SNP) in the coding region of BCMO1 that are common in the UK population, leading to a reduced catalytic activity of the corresponding enzyme in vitro ( Footnote 4 ). Here, an investigation was conducted into whether genetic variations exist in the BCDO2 gene as well, and whether these variations could influence the postprandial response in human volunteers.
Primers were designed to cover each of the twelve exons of the BCDO2 gene and were used to amplify DNA using a high-fidelity polymerase. Resulting PCR products were then screened for the presence of SNP by denaturing HPLC and identified by sequencing. Allelic frequency of the SNP were determined and analysed in relation to biological variables and β-carotene absorption through an on-going collaboration with the University of Reading.
The data in the Table show that women carrying a specific mutant allele in the BCDO2 gene display reduced fasting HDL-cholesterol and elevated TAG compared with the wild type. Functionality of the identified SNP is currently under investigation. These data need to be confirmed in other populations, and mechanistic studies in animal models such as knock-out mice are warranted to understand the metabolic pathways involved in these observations.
