Relationship between urinary cGMP excretion and serum total cholesterol levels in a general population

Hypercholesterolemia impairs endothelial function. However, the critical level of serum total cholesterol at which endothelial dysfunction occurs is unknown at present. We investigated cross-sectionally the correlation between urinary excretion of cyclic guanosine 3′,5′ monophosphate (cGMP), a second messenger of nitric oxide (NO) and serum total cholesterol concentrations in a general population sample of Japanese men and women. The samples comprised 1541 subjects (788 men and 753 women) aged 40–79 years, who participated in cardiovascular risk surveys between 1997 and 2002 and underwent a 24 h urine collection. Urinary excretion of cGMP was measured using a 125I-labeled cGMP radioimmunoassay and was adjusted for urinary creatinine excretion (nmol/mmol creatinine). The mean urinary cGMP excretion correlated linearly and inversely with serum total cholesterol level: mean cGMP excretion adjusted for age, sex and cardiovascular risk factors was 61.7, 53.6, 50.8, 49.2, 47.3 and 46.4 nmol/mmol for total cholesterol levels <4.14, 4.14–4.64, 4.65–5.16, 5.17–5.68, 5.69–6.20 and ≥6.21 mmol/L, respectively (p = 0.007). This relation was more evident among individuals with end-organ damage, among subjects with higher C-reactive protein (CRP) levels and among postmenopausal women. Our data suggest a reduction of NO bioactivity with higher serum total cholesterol levels, even within clinically normal cholesterol levels.