Journal of Tongji Medical University 126 I~ ~ ~ ~ ~ q~ r ~ ( #[- ~ ~ ) 17 (2): 126-128, 1997

Lipids, Lipoproteins and Apolipoproteins Abnormalities in Patients undergoing Dialysis YANG Xiao ( ~ ~1~), WANG Huiling (.:t-~N"), ZHU Zhonghua ( $ ~ ) , DENG Anguo (Xl~-~l~l) Department of Nephrology, Xiehe Hospital, Tongji Medical University, Wuhan 430022

Summary: Twenty hemodialysis (HD) patients and 20 patients on continuous am- bulatory peritoneal dialysis (CAPD) were investigated for lipids, lipoproteins and apolipoproteins abnormalities. HD patients had elevated serum triglyceride, de- creased high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A-I (Apo A-I), while CAPD patients had elevated total cholesterol, triglyceride, low-density lipoprotein cholesterol (LDL-C), Apolipoprotein B (Apo B), Apo B/ Apo A-Iratio, and decreased HDL-C, Apo A-I. Because of the molecular sieving effects of peritoneum, CAPD have a negative effect on these abnormalities. CAPD patients might be at greater risk of developing coronary artery disease than HD patients who are also at increased riskas compared with normals. Key words : lipoprotein, apolipoprotein, dialysis

Patients with chronic renal failure often have hypertr iglyceridemia and decreased high-densi ty lipoprotein cholesterol (HDL- C) concentrations [~'2]. While cardiovascular disease is a major cause of high morbidi ty and morta l i ty among these patients [3]. Some studies suggested that abnormal l ipoprotein metabol ism was one of the causes. In China, few reports were available on lipids,. l ipoproteins , especially apolipoproteins metabol ism in patients undergoing dialysis. The purpose of this s tudy is to observe the lipids, l ipoproteins and apolipoproteins ( A p o ) levels in patients on hemodialysis (HD) and patients on continuous ambulato- ry peritoneal dialysis ( C A P D ) , and to s tudy the effects of CAPD on apolipoprotein metabol ism.

1 P A T I E N T S A N D M E T H O D S

Twen ty HD and twenty CAPD patients f rom Xiehe Hospital of Tongji Medical Uni- versi ty were chosen for this study. The HD pat ients were treated two times every week

(4 h each t ime, using polysulfon membrane dialyzer). CAPD patients were t reated with 4 to 5 exchanges daily (2000 ml per ex= change) using dialysate produced by Baxter Company ( Dian6al, Baxter Company , U S A ) . Patients with nephrotic syndrome, diabetes mell i tus , liver disease or thyroid dysfunction were excluded. The underlying disease of dialysis patients were chronic glomerulonephri t is . Thi r ty normals ( f rom population on regular physical checkup in Xiehe Hospi ta l ) were used as the control. Table 1 shows the clinical data of these H D , CAPD patients and controls.

Blood samples for lipids, l ipoproteins and apolipoproteins analysis were obtained at 7 :00 am before breakfast with dialysate retention in CAPD pat ients , and before the dialysis sessions in HD patients and control group. Fifty ml sample from each ex= changed dialysate were obtained for mea- surements of apolipoproteins. Peritoneal clearance of apolipoproteins were calculated as follows :

Peritoneal clearance (ml/min)

Plasma total cholesterol ( T C ) was de- t e rmined by enzymatic methods , triglyc- erides ( T G ) by acetyl acetone chromome- t ry , HDL-C by polyethylene glycol 2 000

Dialysate volume (ml) X Apo concentration in dialysate (g/L)

YANG Xiao, male, born in 1964, Associate Professor

Serum Apo concentration (g/L) XRetention time of dialysate (min) deposition methods. LDL-C were calculated by Friedwald formula. Apo A-I and Apo B in both plasma and diatysatewere measured by electroimmunoassay using antisera to Apo A-I and B provided by Hubei Medical Universi ty.

The statistical significance of the re-

YANG Xiao et al. Lipids, Lipoproteins ~ Apo in Patientson Dialysis 127

suhs were calculated usingstudent 's t test. Data were expressed as x-t-s. Table 1 Clinical data of the HD , CAPD patients and control

n Serum creatinine Serum urea Duration of dialysis Group Age F M (/~mmol/L) (mmol/L) (Months)

HD 8 12 55_+9 520.4• 18.6-+-2.3 10.14-4.2 CAPD 6 14 574-12 459.5-+106.3 16.9-+4.7 12.3-+3.6 Control 20 10 58-+16 76.44-6.5 6.1-+1.9

Table 2 Lipids , lipoproteins and apolipoproteins levels in three groups

TC TG LDL-C HDL-C Apo B Apo A- I Apo B/Apo A- I Group (mmol/L) (mmol/L) (mmol/L) (retool/L) (g/L) (g/L) ratio

(D HD 5.0-+0. 9 2.9-t-2.1 2.8-+t-1.2 0. 9 !0 .1 74-+1-25 108-t-17 0. 69-+--+0. 2 (~)CAPD 7.84-1.4 3.5+1.6 4.9-+t-3.6 0.84-0.3 1504-81 994-35 1.51-++_0.3 @ Control 5.1--4-_0.8 1.5+0. 4 2.9-+t-1.3 1.4_+0. 3 73-t-32 139_+21 0. 534-0. 11

@ vs @ P>0. 05 P<0 . 01 P>0. 05 P<0. 01 P>0. 05 P<0. 01 P<0. 01 @ vs @ P<O. O1 P>O. O1 P<O. O1 P<O. O1 P<O. O1 P<O. O1 P<O. O1 @ vs @ P<O. O1 P<O. 05 P<O. O1 P>O. 05 P<O. O1 P<O. 05 P<O. O1

2 R E S U L T S

Table 2 shows the TC , T G , HDL-C, LDL- C, Apo A-I , and Apo B concentra- tions in the plasma of HD, CAPD patients and controls. The results showed that HD patients had elevated T G , Apo B/Apo A I ratio , and reduced HDL-C and Apo A- I levels, as compared with the control group. CAPD patients showed elevated TC , T G , LDL-C, Apo B. Apo B /Apo A-Iratio , and reduced HDL-C, Apo A-I concentrations. CAPD patients showed the most serious lipids, lipoproteins and apolipoproteins ab- normalities among the three groups. Peri- toneal clearance of Apo A-I and Apo B in patients on CAPD was 0. 061-q-0. 02 (ml / min) and 0. 019-+-0. 003 ( m l / m i n ) , respec- tively. Daily losses of Apo A-I and Apo B into dialysate was 79. 4 ~ 12. 7 ( m g / d a y ) and 25-4-9. 3 rag /day , respectively. Signifi- cant differences were found in peritoneal clearance, daily losses into of Apo A-I dialysate, and Apo B (for them P < 0 . 0 1 ) .

3 DISCUSSION

Previous studies showed that uremic patients had hypertriglyeeridemia and de- creased HDL-C levels, while the plasma TC and LDL-C concentrat ionswere usually re- ported to be normal or only moderately in- creased. The present s tudy indicated that

the lipids, lipoproteins abnormalities in HD patients were similar to that in uremic pa- tients as reported previously ~ 2. ~l. Com- pared with that in HD patients, the abnor- malities in CAPD patients were obvious (ex- cept for H D L - C ) , suggesting that CAPD have stronger unfavorable impacts on lipids and lipoproteins metabolism. The signifi- cantly elevated Apo B-containing fractions in CAPD patients may be due to a combined effect of enhanced very low-density lipopro- teins and chylomieron synthesis resulting from continual glucose absorption from peri- toneum E6'71, and to the reduced activity of lipoprotein lipase and hepatic lipase causing delayed clearance of triglyceride-rieh lipoproteins Csl. Other possible causes in- elude enhanced T G synthesis promoted by using ~adrenergic inhibitors, acetate dialysate, heparin and reduced hepatic blood flowcaused by heart falure Cg'x~

We also found that Apo A-I concentra- tions in CAPD patients were markedly lower than that in control group, while Apo B concentrations in these patients were signifi- cantly higher than those in control group and HD patients. These abnormalities may be partly due to the peritoneal clearance and daily losses into the dialysate of Apo A-I were more significantly greater than that of Apo B. It is well known that the peritoneal membrane has molecular sieving effects. Be- cause the molecu!ar weight of Apo B is greater than that of Apo A-I, it is easier for

128 Journal of Tongji Medical University 17 (2) : 126-128, 1997

A p o A - I to t r a n s p o r t t h r o u g h p e r i t o n e u m . If con t inuous losses of A p o A - I o c c u r , the r i sk of c a r d i o v a s c u l a r d i seases migh t be in- c reas ed in C A P D p a t i e n t s .

In th is s t u d y , we d e m o n s t r a t e d t ha t ab- n o r m a l l i p id s , l i p o p r o t e i n s a n d a p o l i p o p r o - te ins m e t a b o l i s m in H D and C A P D p a t i e n t s were s imi la r to t h o s e in uremic pa t i en t s . M o r e o v e r , C A P D p a t i e n t s were v ic t imized mos t by these a b n o r m a l i t i e s . C A P D m i g h t have a nega t ive effect on c o r o n a r y a r t e r y d i sease due to h y p e r l i p o d e m i a , which is more f r equen t in p a t i e n t s on C A P D t h a n those on HD.

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(Received Sep. 20, 1996)