Rheumatoid arthritis (RA) patients have increased rates of cardiovascular events. However, standard cardiovascular risk assessments, such as lipid profiles, are consistently different in RA patients. Small low-density lipoprotein (LDL) particles have been associated with development of atherosclerosis. Several studies have also demonstrated a correlation between elevated small LDL and markers of inflammation. There have been no studies that have evaluated small LDL particles in active and quiescent RA patients and correlated this with a measurement of blood vessel function.
We investigated small LDL particle concentrations and small vessel elasticity using radial artery tonometry in patients with quiescent or active RA. Small vessel elasticity, as measured by radial artery tonometry, is a marker of vascular function and reduction in small vessel elasticity may be a marker for early atherosclerosis.
35 seropositive RA patients without history of heart disease, diabetes, or active statin therapy were recruited. DAS28 scores were calculated as measurement of RA activity. Laboratory studies included ESR, CRP, and concentration of lipoprotein subclass particles as measured by nuclear magnetic resonance (NMR) spectroscopy. Small vessel elasticity was measured through pulse-wave analysis by radial artery tonometry.
In RA patients with low-disease activity or remission (DAS28-CRP <3.2), there was significantly lower small LDL particle concentration (496 vs. 694nmol/L; p = 0.02) and increased average LDL size (21.5 vs. 21.0nm; p = 0.05) compared to those with active disease. However, this did not coincide with a significant difference in total LDL in the active vs. low-active/remission RA groups (1111 vs. 970nmol/L; p = 0.22) resulting in a significantly higher small LDL to total LDL ratio in the active RA group (0.61 vs. 0.42; p = 0.02). There was no significant correlation between small LDL particle concentration and small vessel elasticity (p = 0.15) nor was their difference in elasticity measurements of RA patients in remission vs. those with active disease (6.13 vs. 7.95ml/mmHgx100, p = 0.24).
A change in LDL particle composition was seen in RA patients with active disease compared to those with low disease activity or clinical remission. This was demonstrated with an increase in small LDL and the proportion of total LDL particles as small LDL in active RA patients without a significant difference in total LDL between these two groups. However the clinical significance of this finding is to be determined as this was not correlated with changes in small vessel elasticity as a marker of early atherosclerosis.