High levels of triglycerides and triglyceride-rich lipoproteins are significant risk factors for cardiovascular diseases. Prevention plans to lower risk include reducing dietary total and saturated fat, but since lifestyle and genetics also play significant roles in developing heart diseases, researchers at the University of Minnesota examined the genetic variations in fatty acid binding proteins and lipid metabolism. Fatty acid binding protein 2 (FABP2) relates absorption and transportation of long chain fatty acids in the intestine. At codon 54 of FABP2, a DNA variation occurs where amino acid alanine is substituted with threonine in the protein.
This allele of threonine at codon 54 (Thr54) can transport a greater amount of fatty acids than alanine, across the intestine into the plasma. Recent studies have found that the threonine allele have higher fasting plasma triglycerides than alanine variants.
Researchers Steven McColley, Angeliki Georgopoulos, Lindsay Young, Mindy Kurzer, Bruce Redmon and Susan Raatz hypothesize that a high-fat diet would reduce triglyceride-rich lipoproteins (TRL) and the threonine-encoding allele (Thr54) would respond by changing the transportation rate. Lipoproteins are the biochemical compounds containing both proteins and lipids that help transport fat inside and outside cells. One of their main functions is to emulsify fat molecules.
The effect of threonine-encoding alleles on triglyceride-rich lipoproteins
For the crossover study, the researchers used 16 healthy postmenopausal women as participants. The participants would undergo three different 8-week isoenergetic diet treatments: high fat, low fat, and low fat plus n-3 fatty acids.
The high fat treatment consisted of a diet where 40% of energy consumed is fat, the low fat treatment consisted of a diet where 20% of energy consumed is fat, and the low-fat plus n-3 fatty acids consisted of a diet where 20% of energy consumed is fat plus 3% as omega-3 fatty acids.
The treatments were assigned in a random order with a regular diet given 6-12 weeks between conditions. Blood samples were collected throughout the process to evaluate triglyceride levels and DNA analysis.
After assessing the data, researchers McColley et al. found that carriers of the Thr54 allele had significantly lower plasma triglycerides, chylomicron triglycerides, very low density lipoprotein and chylomicron remnant triglycerides after taking part in a high-fat diet. Participants with the Ala54 allele (alanine) did not demonstrate significant changes from baseline with any of the diets.