Quantitative trait locus analysis of circulating adhesion molecules in hyperlipidemic apolipoprotein E-deficient mice

Abstract

Circulating soluble adhesion molecules have been suggested as useful markers to predict several clinical conditions such as atherosclerosis, type 2 diabetes, obesity, and hypertension. To determine genetic factors influencing plasma levels of soluble vascular cell adhesion molecule-1 (VCAM-1) and P-selectin, quantitative trait locus (QTL) analysis was performed on an intercross between C57BL/6J (B6) and C3H/HeJ (C3H) mouse strains deficient in apolipoprotein E-deficient (apoE-/-). Female F2 mice were fed a western diet for 12 weeks. One significant QTL, named sVcam1 (71 cM, LOD 3.9), on chromosome 9 and three suggestive QTLs on chromosomes 5, 13 and 15 were identified to affect soluble VCAM-1 levels. Soluble P-selectin levels were controlled by one significant QTL, named sSelp1 (8.5 cM, LOD 3.4), on chromosome 16 and two suggestive QTLs on chromosomes 10 and 13. Both adhesion molecules showed significant or an apparent trend of correlations with body weight, total cholesterol, and LDL/VLDL cholesterol levels in the F2 population. These results indicate that plasma VCAM-1 and P-selectin levels are complex traits regulated by multiple genes, and this regulation is conferred, at least partially, by acting on body weight and lipid metabolism in hyperlipidemic apoE-/- mice.

Figure 1

Plasma soluble VCAM-1 (A) and P-selectin (B) levels in Western diet-fed female B6.apoE^-/- (B6), C3H.apoE^-/- (C3H), F₁, and F₂ mice. Each dot represents an individual value of one mouse. Mean ± SD of each group is shown on the figure. The horizontal lines denote means.

Figure 2

Distributions of plasma soluble VCAM-1 and P-selectin levels in female F₂ mice derived from B6.apoE^−/− and C3H.apoE^−/− mice. Mice were fed a Western diet for 12 weeks.

Figure 3

Genomewide scans for main effect loci affecting plasma levels of soluble VCAM-1 (A) and P-selectin (B) in F₂ mice. Chromosomes 1 through X are represented numerically on the X-axis. The Y-axis represents the LOD score. The horizontal broken lines represents the suggestive (P = 0.63) and significant (P = 0.05) levels as determined by permutation tests using 1,000 permutations.

Figure 4

Detailed LOD score plots of significant and suggestive QTLs for soluble VCAM-1 and P-selectin. The X-axis depicts the plot positions in cM for each chromosome and Y-axis depicts the LOD score. A: Soluble VCAM-1 QTLs on chromosomes 9, 5, 13, and 15; B: Soluble P-Selectin QTLs on chromosomes 16, 10, and 13.

Figure 5

The allele effects at different QTLs in the F₂ offspring on soluble VCAM-1 (A-D) and P-Selectin levels (E-G). Chromosome number and the QTL position in cM are given for each QTL. Homozygosity for B6 alleles is represented by BB, homozygosity for C3H alleles is represented by CC, and heterozygote at a locus is represented by BC.

Figure 6

mRNA levels of Thpo, Adipoq, and Gapdh in endothelial cells from B6 and C3H mice analyzed by RT-PCR. Each lane represents an individual mouse.