Apolipoprotein(a) is Present in Urine and Its Excretion is Decreased in Patients with Renal Failure

Abstract

To investigate the relation between renal function and concentrations of lipoprotein(a) [Lp(a)] in serum, we measured Lp(a) in samples of serum and urine from patients with diabetes mellitus and in samples sent to a laboratory center for measurements of creatinine clearance. Serum Lp(a) concentrations were significantly increased in subjects with obvious renal dysfunction (serum creatinine > or = 176.8 mumol/L) compared with normal control subjects. Urinary Lp(a) excretion was decreased in subjects with obvious renal dysfunction compared with subjects without obvious renal dysfunction (serum creatinine < or = 88.4 mumol/L) and was negatively and positively correlated with serum creatinine and creatinine clearance, respectively. More than 80% of urinary Lp(a) was recovered in the d > 1.21 kg/L fraction. At least six bands for apolipoprotein(a) [apo(a)] fragments, which were smaller than native apo(a) in serum, were observed in urine by immunoblotting, and some of these were also detected in serum. Degraded apo(a) fragments are probably present in urine, and their excretion decreases in parallel with decreases in the glomerular filtration rate.

In vivo kinetics of lipoprotein(a) in homozygous Watanabe heritable hyperlipidaemic rabbits

“…In this study the Lp(a)/LDL ratio in the kidney of control rabbits was far less than I , and in WHHL rabbits close to 1 which does not support our earlier hypothesis. With that respect the research of Oida et al [29] is noteworthy who showed that Lp(a) or fragments thereof are secreted in the urine in kidney patients; urinary excretion of Lp(a) decreased in parallel with the decrease in the glomerular filtration rate. In our study we tried to collect rabbit urine in order to assay such fragments, but for practicable reasons it was almost impossible to obtain representative samples.…”

Decrease in lipoprotein(a) after renal transplantation is related to the glucocorticoid dose

“…Blood samples may not always have been drawn before dialysis treatment, which is known to be of influence on the Lp(a) concentrations [29]. Apo(a) fragments have been detected in urine [30] and their excretion is reduced in patients with renal failure. It is therefore feasible that ESRD is associated with increased I, 26,668-615 plasma levels of such apo(a) fragments, which may be differentially assessed by the various immunoassays.…”

Decreased urinary apolipoprotein (a) excretion in patients with impaired renal function

“…It is apparent from recent work that apo(a) immunoreactivity is found in urine [21][22][23]. However, it is not intact Lp(a) that is secreted but rather apo(a) fragments.…”