Apolipoprotein C-III (
ApoC-III) plays an important role in the metabolism of
triglyceride-rich
lipoproteins and is known to be elevated in patients with
uremia. To investigate the role of
apoC-III in uremic
dyslipidemia, we examined
apoC-III,
triglyceride levels and
lipoprotein particles containing both
apoB and
apoC-III (LP-Bc) in 27 uremic patients prior to dialysis (predialysis), 30 patients on
hemodialysis (HD) and 31 patients on
peritoneal dialysis (PD). All three groups of patients had elevated levels of plasma
apoC-III (20+/-7 mg/dl for predialysis, 18+/-5 for HD and 22+/-8 for PD, compared to 11+/-3 mg/dl for control subjects [p<0/01 for all comparisons]).
ApoC-III was positively correlated with plasma
triglycerides in PD patients (r = 0.86, p<0.0001), HD patients (r = 0.67, p<0.0001) and predialysis patients (r = 0.60, p<0.001) as well as in all patients combined (r = 0.75, p<0.0001).
ApoC-III was also positively correlated with levels of LP-Bc in all three groups of patients, although this correlation was less strong (r = 0.46, p<0.0001 for all patients combined). In predialysis and PD patients, the majority of
apoC-III was found in
heparin precipitable
lipoproteins, whereas the majority of
apoC-III in HD patients was found in HDL, indicating less efficient lipolysis in predialysis and PD patients in comparison with HD. These data support the hypothesis that the elevation of
apoC-III in
uremia can alter the metabolism of
triglyceride-rich
lipoproteins, leading to an elevation in
triglycerides and LP-Bc. Understanding the mechanism(s) of elevated
apoC-III in
uremia may help to clarify the causes of uremic
dyslipidemia.