BACKGROUND: Cholesterol metabolism is tightly regulated at the cellular level. 
This study was to measure the expression levels of ATP-binding cassette 
transporter A1 (ABCA1) and G1 (ABCG1), scavenger receptor class B type I (SR-BI) 
and class A (SRA), and CD36 mRNAs in peripheral blood mononuclear cells (PBMCs) 
in response to 100-km ultramarathon event and determine any correlation between 
these ABC transporters/scavenger receptor expression levels and plasma 
cholesterol homeostasis.
MATERIALS AND METHODS: Twenty-six participants were enrolled. Blood was drawn 
from each individual 1 week prior, immediately after, and 24 hours after the 
race. The expression levels of ABCA1, ABCG1, SR-BI, SRA and CD36 in PBMCs were 
measured by using real-time quantitative reverse transcription polymerase chain 
reaction.
RESULTS: Plasma triglyceride levels were significantly increased immediately 
after the race and dropped at 24-hour post-race compared with pre-race values. 
The 100-km ultramarathon boosted high-density lipoprotein cholesterol (HDL-C) 
levels and decreased low-density lipoprotein cholesterol (LDL-C) levels 24-hour 
post-race. The expression levels of ABCA1, ABCG1 and SR-BI were markedly 
decreased, whereas that of CD36 was slightly but significantly upregulated in 
runners' PBMCs immediately after the race. Ultramarathon resulted in immediate 
large-scale stimulation of inflammatory cytokines with increased plasma 
interleukin-6 and tumour necrosis factor-alpha levels. Moreover, by using in 
vitro models with human monocytic cell lines, incubation of runners' plasma 
immediately after the race significantly downregulated ABCA1 and ABCG1, and 
upregulated CD36 expression in these cells.
CONCLUSIONS: ABCA1, ABCG1 and CD36 gene expressions in PBMCS might be associated 
with endurance exercise-induced plasma cholesterol homeostasis and systemic 
inflammatory response.