Pathogenesis of dyslipoproteinemia in renal insufficiency: the role of lipoprotein lipase and hepatic lipase

Lipoprotein Metabolism Abnormalities in Patients with Chronic Renal Insufficiency

Patients with chronic renal insufficiency (CRI) on hemodialysis develop lipoprotein abnormalities that may contribute to increased risk for atherosclerosis. The objective of this study was to assess the atherogenic risk of chronic renal insufficiency patients and dialysis treated patients (DTP) by measuring total cholesterol (TC), triglycerides (TG), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C) and calculating the risk factor ratio: TC/HDL-C and LDL-C/HDL-C. The examined group consisted of 18 chronic renal insufficiency patients and 60 patients on hemodialysis. The results were compared to a control group of 85 voluntary blood donors. Serum lipid parameters were examined by standard methods. All lipid parameters in hemodialysis patients were statistically different as compared to the control group (p<0.05) while chronic renal insufficiency patients showed significant difference only in triglycerides and HDL-cholesterol. Hypertriglyceridemia was present in both examined groups of patients and HDL-cholesterol was lower within both groups. All calculated atherogenic ratios were higher for patients than the control group. Lipid parameters were compared between chronic renal insufficiency and hemodialysis patients, but statistically significant difference was obtained only for HDL-cholesterol (p<0.05). The increased values of triglycerides and lower HDL-cholesterol in chronic renal insufficiency patients contribute to high incidence of cardiovascular disease. Chronic renal insufficiency patients have impaired reverse cholesterol transport from peripheral cells to lipoproteins, decreased levels of HDL-cholesterol, hypertriglyceridemia prevalence of small, dense LDL and increased levels of potentially atherogenic remnant particles.

Different effects of low weight molecular heparin and unfractioned heparin on lipid profile and coagulation at haemodialysis patients

Each haemodialysis treatment requires the application of anticoagulation medicines, which will prevent coagulation in extracorporal blood circulation. In this study we try to determine the quality of admitted anticoagulant and his effect on lipid profile on hemodialysis patients after twelve months. We were applying standard heparin and low weight molecular heparin (LWMH). During our study we was analyzed effect of anticoagulant therapy on lipid profile of hemodialysis patients. In that parameters was included triglycerides, cholesterol, lipoprotein fractions, complete blood count, Hgb, HCT; All of these parameters was analyzed in correlation with duration of hemodialysis treatment, sex and age of the patients. Our research was carried out as a prospective study, for the period of 12 months. In the study were included 60 patients (34M/26F), who were on chronic hemodialysis program. All patients were divided into two groups. The first group of patients was included 27 patients (15M/12F) who were treated with standard heparin. The second group was included 33 patients (19M/14F) treated with LWMH (enoxaparin). The average length of hemodialysis was 4.15 +/- 0.52 years. Each patient had a protocol in which is marked parameters such as flushing dialysator, creating fibrin-ring in vein and arterial dropper and the time it takes to stop the bleeding. In the results the average age amounted to 58.54 +/- 2.24 years. The average value of cholesterol in the blood was 5.38 +/- 2.26. Values of HDL-cholesterol in patients treated with LWMH were significantly lower (P<or=0.05) in the treated group compared to standard heparin. There were no significant statistical differences between both groups in relation to the level of LDL cholesterol in the blood. (p ns). LWMH had a better effect on the irrigation system and dialysator on both sex equally, compared with standard heparin. LWMH is in the female dialysis population has led to improvements in lipid profile. After the first six months of study in male patients treated with standard heparin in relation to the female part of the observed patients was significantly better anticoagulation effect in the first half of the study (1.85 +/- 0.05 compared to 2.09 +/- 0.10) (P<or=0.001). Average rating blood clots were statistically significant for standard heparin (p<or=0,001) with 1,86 at the beginning the value is fell to 1.41, while for LWMH with 1.85 at the beginning of the study amounted to 1.52 grade average. (P<or=0.05). The results of our study show that LWMH had a better rinsing effect of dialysis systems and dialysator in both sex equally, compared to standard unfractioned heparin. When the male part of the respondents in the first six months of standard heparin had a better evaluation of blood clots than women in the same group, and also better than the group on enoxaparin for both gender. LWMH in female dialysis population has led to improved lipid profiles. Patients treated with standard heparin had a statistically significant reduction in the rate of blood clots than patients who received enoxaparin (LWMH). Such differences were minimal, which can be interpreted by the fact that LWMH still derivative of the standard heparin.

Lipid management in chronic kidney disease, hemodialysis, and transplantation

Recent studies have shown the spectrum of dyslipidemia in patients who have chronic kidney disease (CKD) or end-stage renal disease to be different from that of the general population. This article discusses the pathophysiology of dyslipidemia in CKD, dialysis, and renal transplant patients, the therapeutic options, and their association with clinical outcomes. Whenever possible, comparisons are made to outcomes in the general population.

The potential role of sterol regulatory element binding protein transcription factors in renal injury

The disturbed lipid metabolism is a permanent finding in renal failure. It is supposed to be a main reason for the accelerated atherosclerosis and high cardiovascular and cerebrovascular mortality of patients with renal failure. Sterol regulatory element binding proteins (SREBPs) are the transcription factors involved in the regulation of lipid homeostasis. They are responsible for the transcription activation of genes associated with the synthesis of fatty acids, triglycerides, and cholesterol. SREBP-1 gene expression in adipose tissue and SREBP-2 in liver are significantly elevated in renal failure. This is accompanied with the up-regulation of genes encoding enzymes of both fatty acids and cholesterol synthesis and significant serum lipid enhancement. Moreover, it has been shown that a destructive accumulation of lipids in the kidney structures is associated with enhanced kidney SREBP gene expression and increased lipid production. This was found even in the absence of any abnormalities in serum lipids. One may suppose that SREBP transcription factors play an important role in disturbed lipid metabolism in renal failure.

Upregulation of lipogenic enzymes genes expression in white adipose tissue of rats with chronic renal failure is associated with higher level of sterol regulatory element binding protein-1

Chronic renal failure (CRF) frequently results in hypertriglyceridemia and elevated plasma concentration of very-low-density lipoprotein (VLDL). These abnormalities are thought to be primarily due to depressed lipoprotein lipase and hepatic lipase activities, as well as impaired clearance of plasma lipoproteins. Some results suggest that not only lipoproteins catabolism but also their overproduction might contribute to hypertriglyceridemia in CRF. Because sterol regulatory element binding protein (SREBP) plays an important role in the regulation of lipid homeostasis, increased level of this transcription factor might be involved in modulating lipid metabolism in CRF. The purpose of the present study is to determine whether there is an altered regulation of the SREBP-1 in CRF rats and whether the altered regulation of SREBP-1 is associated with the upregulation of lipogenic enzymes genes expression in CRF rats. In the white adipose tissue (WAT) of CRF rats, marked increases in the microsomal (precursor) and nuclear (mature) forms of SREBP-1 have been found. The increase in SREBP-1 was associated with an increased level of lipogenic enzymes (acetyl-coenzyme A [CoA] carboxylase [ACC], adenosine triphosphate-citrate lyase [ACL], fatty acid synthase [FAS], glucose 6-phosphate dehydrogenase [G6PDH], 6-phosphogluconate dehydrogenase [6PGDH], and malic enzyme [ME]) genes expression. In turn, this was associated with an increased rate of fatty acids synthesis in WAT and a significant increase in plasma triacylglycerol (TAG) and VLDL concentration. Our study indicates that WAT SREBP-1 expression is increased in CRF rats and that SREBP-1 may play an important role in the increased fatty acid synthesis. These results reveal another facet of disturbed lipid metabolism in CRF.

Lipoprotein particle abnormalities and the impaired lipolysis in renal insufficiency

BACKGROUND

Increased concentrations of very low- (VLDL) and intermediate-density (IDL) lipoproteins in chronic renal failure (CRF) are thought to result from a defect(s) in degradation of plasma triglyceride (TG)-rich lipoproteins. The purpose of this study was to identify lipoprotein abnormalities associated with the reduced lipolytic rate constant, k1, of combined VLDL and IDL substrate from renal patients and asymptomatic controls.

METHODS

The VLDL + IDL were isolated from 18 predialytic patients (CRF-I), 8 patients on hemodialysis (CRF-II) and 10 asymptomatic controls. The lipolytic rate constant (k1) of VLDL + IDL was measured by an assay using bovine milk lipoprotein lipase and determination of TG before and after incubation by gas chromatography (GC). Neutral lipids were measured by GC and apolipoproteins by electroimmunoassays; the apolipoprotein-defined TG-rich lipoproteins including Lp-B:C, Lp-B:C:E and Lp-A-II:B:C:D:E were determined by immunoaffinity chromatography.

RESULTS

The k1 values of VLDL + IDL were significantly (P < 0.001) lower in CRF-I and CRF-II patients (0.0341 and 0.0352 min-1, respectively) than controls (0.0515 min-1). The levels of apolipoproteins B, C-III and E, and TG-rich Lp-B:C, Lp-B:C:E and Lp-A-II:B:C:D:E particles normalized to 100 mg TG per VLDL + IDL were significantly higher in both groups of CRF patients than in controls. All three TG-rich lipoproteins were characterized by significantly increased percent contents of free (FC) and esterified (CE) cholesterol and a decreased percentage of TG. The k1 values of the combined CRF-I and CRF-II patient groups showed significant negative correlations (P < 0.001) with FC (r=-0.81) and CE (r=-0.63) and a positive correlation with TG (r=0.72). Among lipoprotein particles, only Lp-A-II:B:C:D:E levels showed a significant negative correlation with k1 values (r=-0.47, P < 0.03).

CONCLUSIONS

This study shows that the abnormal neutral lipid composition of all three TG-rich lipoprotein particles and increased concentrations of Lp-A-II:B:C:D:E particles represent the main factors affecting the in vitro lipolytic rates of VLDL + IDL substrate in both the CRF patients before dialysis and patients on hemodialysis.