THE INCREASE OF PLASMA HOMOCYSTEINE CONCENTRATIONS WITH AGE IS PARTLYDUE TO THE DETERIORATION OF RENAL-FUNCTION AS DETERMINED BY PLASMA CYSTATIN-C

One of the main determinants of plasma homocysteine in healthy subject s is serum creatinine. In the present study, we therefore investigated the relation between plasma homocysteine concentration, serum creatin ine and a new marker for glomerular filtration rate, plasma cystatin C concentration. Cystatin C reflects the glomerular filtration better t han serum creatinine and is not related to the muscle mass and formati on of creatinine. The study group consisted of 255 healthy subjects fr om a well-defined area in the southern part of Sweden. The concentrati on of plasma homocysteine was increased in men compared to women. This difference disappeared when men and women were stratified by serum cr eatinine values. Statistically significant correlations were noted bet ween plasma homocysteine and age, plasma cystatin C and serum creatini ne. It is shown that plasma homocysteine is not only correlated to ser um creatinine as a result of renal function but also as a result of th e relationship between homocysteine production and creatine-creatinine synthesis. Using linear regression we were able to show that plasma c ystatin C had a higher explanatory value than age. Serum creatinine sh owed a lower explanatory power than age. The findings in the present s tudy might suggest that the increase of plasma homocysteine concentrat ion with age could be partly due to the deterioration of renal functio n.