Elevated Plasma Homocysteine and Low Vitamin B-6 Status in Nonsupplementing Older Women with Rheumatoid Arthritis

Abstract

Objective The purpose of this study was to determine if nonsupplementing older women (aged ≥55 years) with rheumatoid arthritis had higher plasma homocysteine and lower B-vitamin status compared to healthy controls. Elevated plasma homocysteine, a risk factor for cardiovascular disease, may help explain why individuals with rheumatoid arthritis have an increased risk of cardiovascular disease. Methods Older, free-living women were classified as rheumatoid arthritis (n=18) or healthy control (n=33). Participants were not using B-vitamin supplements. Fasting blood samples were measured for pyridoxal 5′phosphate (PLP) (the metabolically active coenzyme form of vitamin B-6), folate, red blood cell folate, vitamin B-12, transcobalamin II, homocysteine, C-reactive protein, and lipid concentrations. Participants completed 7-day weighed food records, the Stanford Health Assessment Questionnaire (HAQ), and a visual analog pain scale. Results PLP concentrations were lower in the rheumatoid arthritis vs healthy control participants (4.93±3.85 vs 11.35±7.11 ng/mL [20±16 vs 46±29 nmol/L]; P<0.01) whereas plasma homocysteine was higher in the rheumatoid arthritis group (1.63±0.74 vs 1.15±0.38 mg/L [12.1±5.5 vs 8.5±2.8 μmol/L]; P=0.02). Red blood cell folate concentrations were lower in the rheumatoid arthritis vs healthy control participants [414±141 vs 525±172 ng/mL [938±320 vs 1,190±390 nmol/L]; P=0.02). No significant differences were found for plasma folate, vitamin B-12, and transcobalamin II. An inverse correlation was found between PLP concentrations and the HAQ disability index ( r=−0.37; P<0.01). A positive correlation was found between homocysteine concentrations and the HAQ disability index ( r=0.36; P=0.01). Total cholesterol and low-density lipoprotein cholesterol levels were lower in the rheumatoid arthritis group (cholesterol 191±43 vs 218±33 mg/dL [4.95±1.11 vs 5.65±0.85 mmol/L]; P=0.02; low-density lipoprotein cholesterol 110±36 vs 137±29 mg/dL [2.85±0.93 vs 3.55±0.75 mmol/L]; P<0.01). No significant differences were seen between groups for protein (g/day), fat (g/day), cholesterol (mg/day), folate (μg/day), vitamin B-12 (μg/day), and vitamin B-6 (mg/day) dietary intakes. Conclusions Poor vitamin B-6 status and elevated plasma homocysteine concentrations were seen in older women with rheumatoid arthritis compared to healthy controls and may contribute to their increased risk of cardiovascular disease.