Causes of dysregulation of lipid metabolism in chronic renal failure

Role of SN1 lipases on plasma lipids in metabolic syndrome and obesity

OBJECTIVE

To assess the phospholipase activity of endothelial (EL) and hepatic lipase (HL) in postheparin plasma of subjects with metabolic syndrome (MS)/obesity and their relationship with atherogenic and antiatherogenic lipoproteins. Additionally, to evaluate lipoprotein lipase (LPL) and HL activity as triglyceride (TG)-hydrolyses to complete the analyses of SN1 lipolytic enzymes in the same patient.

APPROACH AND RESULTS

Plasma EL, HL, and LPL activities were evaluated in 59 patients with MS and 36 controls. A trend toward higher EL activity was observed in MS. EL activity was increased in obese compared with normal weight group (P=0.009) and was negatively associated with high-density lipoprotein-cholesterol (P=0.014 and P=0.005) and apolipoprotein A-I (P=0.045 and P=0.001) in control and MS group, respectively. HL activity, as TG-hydrolase, was increased in MS (P=0.025) as well as in obese group (P=0.017); directly correlated with low-density lipoprotein-cholesterol (P=0.005) and apolipoprotein B (P=0.003) and negatively with high-density lipoprotein-cholesterol (P=0.021) in control group. LPL was decreased in MS (P<0.001) as well as in overweight and obese compared with normal weight group (P=0.015 and P=0.004, respectively); inversely correlated %TG-very low-density lipoproteins (P=0.04) and TG/apolipoprotein B index (P=0.013) in control group. These associations were not found in MS.

CONCLUSIONS

We describe for the first time EL and HL activity as phospholipases in MS/obesity, being both responsible for high-density lipoprotein catabolism. Our results elucidate part of the remaining controversies about SN1 lipases activity in MS and different grades of obesity. The impact of insulin resistance on the activity of the 3 enzymes determines the lipoprotein alterations observed in these states.

Response of Angiopoietin-like Proteins 3 and 4 to Hemodialysis

Background/Aim

Patients on chronic hemodialysis (cHD) have decreased activity of lipoprotein lipase (LPL). Angiopoietin-like proteins (ANGPTL) 3 and 4 have been shown to inactivate LPL. The aim of this study was to investigate the levels of the ANGPTLs in plasma of cHD-patients and to evaluate if cHD may alter these levels.

Material and methods

Baseline data were collected from cHD patients (n = 23), and controls (n = 23) and samples were analyzed from 17 patients during low-flux or high-flux HD, and from ultrafiltrate (n = 5). The levels of ANGPTL3 and 4, LPL and triglycerides were studied in a cross-over design on cHD with local citrate compared to tinzaparin as anticoagulant.

Results

The level of ANGPTL3 was higher than ANGPTL4 in patients and controls (p<0.01); the ANGPTL3 was 2.0 and ANGPTL4 was 3.3-fold higher in cHD versus controls. The levels of ANGPTL4 increased during cHD. After 180 min of HD the values had decreased again. When the dialysis was performed with high-flux filter, the mean level of ANGPTL4 at 180 min was below the value observed before cHD (p = 0.003). There was immunoreaction for ANGPTL4 in UFs when using high-flux, but not with low-flux, filter. ANGPTL3 was not detectable in UF. On cHD with citrate, no LPL activity was released into the blood

Conclusions

ANGPTL3 and ANGPTL4 were increased in HD patients. Anticoagulation with tinzaparin during cHD causes release of ANGPTL4 from tissues into blood. cHD using high-flux filters, to some extent, removed ANGPTL4. With citrate the levels of ANGPTL4 decreased.

Renal function is ameliorated in a diabetic nephropathy rat model through a duodenal-jejunal bypass

AIMS

Diabetes surgery is growing in popularity and has been shown to have marked effects on diabetes. However, several studies have shown it may induce some renal injury, and, currently, the impact of diabetes surgery on renal function is unclear. In this study, we examined renal function and histological changes in rats with diabetic nephropathy (DN) following a duodeno-jejunal bypass (DJB) operation.

METHODS

Rats with streptozotocin (STZ)-induced diabetes were randomly assigned to 3 groups: DJB group (DJB), Sham-DJB group (S-DJB) and diabetes group (DM). Six age-matched normal rats were assigned as the control group. DJB and sham surgery were performed. Body weight, food intake, glucose levels, lipid parameters, cystatin C (Cys_C) levels, serum and urinary creatinine, 24h urine albumin excretion rate (UAER) and glomerular filtration rate (GFR) were measured. Histological analysis and immunohistochemical studies of renal sections were also performed.

RESULTS

DJB ameliorated renal function by improving UAER, GFR and Cys_C levels 4 and 8 weeks after surgery. It also improved lipid metabolism by decreasing fasting total serum cholesterol (TC) and triglyceride (TG) levels. Immuno-staining of synaptopodin showed podocyte injury was also improved in DJB glomeruli compared with sham and DM groups. Histological analysis showed that the mesangial expansion was not significantly prevented 8 weeks after DJB surgery.

CONCLUSION

DJB ameliorated renal function in UAER and GFR but not mesangial expansion in a DN rat model. The improvement of renal function may be attributed to reversing the injury or loss of podocytes after DJB surgery.

The thyroid and the kidney: a complex interplay in health and disease

Thyroid hormones may directly affect the kidney and altered kidney function may also contribute to thyroid disorders. The renal manifestations of thyroid disorders are based on hemodynamic alterations or/and to direct effects of thyroid hormones. The renin-angiotensin system plays a crucial role in the cross-talk between the thyroid and the kidney. Hypothyroidism may be accompanied by an increase of serum creatinine and reduction of glomerular filtration rate (GFR), whereas hyperthyroidism may increase GFR. Treatment of thyroid disorders may lead to normalization of GFR. Primary and subclinical hypothyroidism and low triiodothyronine (T3) syndrome are common features in patients with chronic kidney disease (CKD). In addition low levels of thyroid hormones may predict a higher risk of cardiovascular and overall mortality in patients with end-stage renal disease. The causal nature of this correlation remains uncertain. In this review, special emphasis is given to the thyroid pathophysiology, its impact on kidney function and CKD and the interpretation of laboratorial findings of thyroid dysfunction in CKD.

Vitamin E tocotrienol supplementation improves lipid profiles in chronic hemodialysis patients

PURPOSE

Chronic hemodialysis patients experience accelerated atherosclerosis contributed to by dyslipidemia, inflammation, and an impaired antioxidant system. Vitamin E tocotrienols possess anti-inflammatory and antioxidant properties. However, the impact of dietary intervention with Vitamin E tocotrienols is unknown in this population.

PATIENTS AND METHODS

A randomized, double-blind, placebo-controlled, parallel trial was conducted in 81 patients undergoing chronic hemodialysis. Subjects were provided daily with capsules containing either vitamin E tocotrienol-rich fraction (TRF) (180 mg tocotrienols, 40 mg tocopherols) or placebo (0.48 mg tocotrienols, 0.88 mg tocopherols). Endpoints included measurements of inflammatory markers (C-reactive protein and interleukin 6), oxidative status (total antioxidant power and malondialdehyde), lipid profiles (plasma total cholesterol, triacylglycerols, and high-density lipoprotein cholesterol), as well as cholesteryl-ester transfer protein activity and apolipoprotein A1.

RESULTS

TRF supplementation did not impact any nutritional, inflammatory, or oxidative status biomarkers over time when compared with the baseline within the group (one-way repeated measures analysis of variance) or when compared with the placebo group at a particular time point (independent t-test). However, the TRF supplemented group showed improvement in lipid profiles after 12 and 16 weeks of intervention when compared with placebo at the respective time points. Normalized plasma triacylglycerols (cf baseline) in the TRF group were reduced by 33 mg/dL (P=0.032) and 36 mg/dL (P=0.072) after 12 and 16 weeks of intervention but no significant improvement was seen in the placebo group. Similarly, normalized plasma high-density lipoprotein cholesterol was higher (P<0.05) in the TRF group as compared with placebo at both week 12 and week 16. The changes in the TRF group at week 12 and week 16 were associated with higher plasma apolipoprotein A1 concentration (P<0.02) and lower cholesteryl-ester transfer protein activity (P<0.001).

CONCLUSION

TRF supplementation improved lipid profiles in this study of maintenance hemodialysis patients. A multi-centered trial is warranted to confirm these observations.

High density lipoprotein cholesterol levels are an independent predictor of the progression of chronic kidney disease

OBJECTIVES

Patients with chronic kidney disease (CKD) often present with reduced plasma HDL cholesterol (HDL-C) levels. Whether this reduction in an epiphenomenon or is involved in disease progression is unclear. The aim of this study was to investigate the relation between HDL-C levels/function and CKD progression in patients with different degrees of disease.

DESIGN

A total of 176 patients with CKD [glomerular filtration rate (GFR) 50.3 ± 29.1 mL min⁻¹] were recruited and followed for up to 84 months. Lipid profile, metabolic status and kidney function were evaluated at predetermined times. Age-matched control subjects were selected from the PLIC study (n = 453). Scavenger receptor class B member 1 (SR-BI) and ATP-binding cassette transporter A1 (ABCA-1)-dependent efflux of cholesterol were measured in CKD patients and in age-matched control subjects.

RESULTS

Low HDL-C levels, diabetes and hypertension were associated with reduced GFR. At follow-up, low HDL-C levels were associated with earlier entry in dialysis or doubling of the plasma creatinine level (P = 0.017); HDL-C levels were the only lipid parameter that affected the progression of CKD (hazard ratio 0.951, 95% confidence interval 0.917-0.986, P = 0.007), independently of the presence of diabetes. Only SR-BI-mediated serum cholesterol efflux was significantly reduced in the group of CKD patients with low HDL-C levels compared to the control group.

CONCLUSIONS

CKD patients with low levels of plasma HDL-C have a poor prognosis. HDL functionality is also impaired in renal dysfunction. These data support the relevance of HDL in influencing CKD progression.

Targeting the transcription factor Nrf2 to ameliorate oxidative stress and inflammation in chronic kidney disease

Oxidative stress and inflammation are mediators in the development and progression of chronic kidney disease (CKD) and its complications, and they are inseparably linked as each begets and amplifies the other. CKD-associated oxidative stress is due to increased production of reactive oxygen species (ROS) and diminished antioxidant capacity. The latter is largely caused by impaired activation of Nrf2, the transcription factor that regulates genes encoding antioxidant and detoxifying molecules. Protective effects of Nrf2 are evidenced by amelioration of oxidative stress, inflammation, and kidney disease in response to natural Nrf2 activators in animal models, while Nrf2 deletion amplifies these pathogenic pathways and leads to autoimmune nephritis. Given the role of impaired Nrf2 activity in CKD-induced oxidative stress and inflammation, interventions aimed at restoring Nrf2 may be effective in retarding CKD progression. Clinical trials of the potent Nrf2 activator bardoxolone methyl showed significant improvement in renal function in CKD patients with type 2 diabetes. However, due to unforeseen complications the BEACON trial, which was designed to investigate the effect of this drug on time to end-stage renal disease or cardiovascular death in patients with advanced CKD, was prematurely terminated. This article provides an overview of the role of impaired Nrf2 activity in the pathogenesis of CKD-associated oxidative stress and inflammation and the potential utility of targeting Nrf2 in the treatment of CKD.

Triglyceride-cholesterol imbalance across lipoprotein subclasses predicts diabetic kidney disease and mortality in type 1 diabetes: the FinnDiane Study

BACKGROUND

Circulating cholesterol (C) and triglyceride (TG) levels are associated with vascular injury in type 1 diabetes (T1DM). Lipoproteins are responsible for transporting lipids, and alterations in their subclass distributions may partly explain the increased mortality in individuals with T1DM.

DESIGN AND SUBJECTS

A cohort of 3544 individuals with T1DM was recruited by the nationwide multicentre FinnDiane Study Group. At baseline, six very low-density lipoprotein VLDL, one intermediate-density lipoprotein IDL, three low-density lipoprotein LDL and four higher high-density lipoprotein HDL subclasses were quantified by proton nuclear magnetic resonance spectroscopy. At follow-up, the baseline data were analysed for incident micro- or macroalbuminuria (117 cases in 5.3 years), progression from microalbuminuria (63 cases in 6.1 years), progression from macroalbuminuria (109 cases in 5.9 years) and mortality (385 deaths in 9.4 years). Univariate associations were tested by age-matched cases and controls and multivariate lipoprotein profiles were analysed using the self-organizing map (SOM).

RESULTS

TG and C levels in large VLDL were associated with incident albuminuria, TG and C in medium VLDL were associated with progression from microalbuminuria, and TG and C in all VLDL subclasses were associated with mortality. Large HDL-C was inversely associated with mortality. Three extreme phenotypes emerged from SOM analysis: (i) low C (<3% mortality), (ii) low TG/C ratio (6% mortality), and (iii) high TG/C ratio (40% mortality) in all subclasses.

CONCLUSIONS

TG-C imbalance is a general lipoprotein characteristic in individuals with T1DM and high vascular disease risk.

High-density lipoprotein in uremic patients: metabolism, impairment, and therapy

Several studies have shown that HDL has altered antioxidant and anti-inflammatory effects in chronic uremia, either by the reduction in its antioxidant enzymes or by the impairment of their activity. Systemic oxidative stress, which is highly prevalent in chronic kidney disease (CKD) patients, has been shown to decrease antioxidant and anti-inflammatory effects of HDL and even transform it into a pro-oxidant and pro-inflammatory agent. For this reason, we believe that the propensity for accelerated cardiovascular disease in CKD is facilitated by a few key features of this disease, namely, oxidative stress, inflammation, hypertension, and disorders of lipid metabolism. In a nutshell, oxidative stress and inflammation enhance atherosclerosis leading to increased cardiovascular mortality and morbidity in this population. In this detailed review, we highlight the current knowledge on HDL dysfunction and impairment in chronic kidney disease as well as the available therapy.

Endothelial Lipase Activity Predicts High-Density Lipoprotein Catabolism in Hemodialysis

Objective—

A novel phospholipase assay was used to measure for the first time the behavior of endothelial and hepatic phospholipase activities in postheparin human plasma of hemodialyzed patients and its relationship with atherogenic and antiatherogenic lipoprotein levels.

Methods and Results—

Endothelial and hepatic phospholipase activity was assessed in a total SN1-specific phospholipase assay, using (1-decanoylthio-1-deoxy-2-decanoyl-sn-glycero-3-phosphoryl) ethylene glycol as the substrate. Hemodialyzed patients presented lower values of total and hepatic phospholipase activity than controls: 4.4 (1.9–9.0) versus 7.5 (3.6–18.0) and 2.6 (0.7–6.2) versus 6.6 (1.3–15.2) μmol of fatty acid released per milliliter of postheparin plasma per hour, respectively ( P <0.001); however, endothelial lipase (EL) phospholipase activity was increased in patients: 1.7 (0.8–3.0) versus 1.1 (0.1–2.7) μmol of fatty acid released per milliliter of postheparin plasma per hour ( P =0.008). EL was negatively associated with high-density lipoprotein (HDL)-cholesterol ( r =–0.427; P =0.001), and apolipoprotein A-I levels, total phospholipase, and hepatic lipase activity were directly associated with low-density lipoprotein-cholesterol and apolipoprotein B. The association of EL and HDL-cholesterol remained significant when adjusting for waist circumference (β=–0.26; P =0.05), and the effect of hepatic lipase on low-density lipoprotein-cholesterol continued after adjusting for age (β=0.46; P = 0.001).

Conclusion—

Our results support the hypothesis that EL is the predominant enzyme responsible for lipolytic catabolism of HDLs in hemodialyzed patients and resolve the apparent paradox observed between low hepatic lipase activity and decreased HDL-cholesterol levels observed in these patients. In addition, the ability to assess total hepatic lipase and EL phospholipase activity in plasma will increase our knowledge of the mechanisms involved in controlling HDL levels and cardiovascular risk in hemodialyzed patients, as well as other populations with low levels of HDL-cholesterol.

The contribution of thyroid dysfunction on cardiovascular disease in patients with chronic kidney disease

Accelerated atherosclerosis and arterial stiffness are the two leading causes of increased cardiovascular disease in patients with chronic kidney disease. Dysfunctional thyroid hormone metabolism has been suggested to play a role in atherosclerosis and arterial stiffness. Changes in cardiac contractility and output, myocardial oxygen demand, systemic and peripheral vascular resistance, blood pressure and lipid profile, increased inflammatory burden and endothelial dysfunction may be responsible for thyroid hormone-related cardiovascular disease. This article focuses on the mechanistic insights of this association and provides a concise review of the current literature.

Dysregulation of hepatic fatty acid metabolism in chronic kidney disease

BACKGROUND

Chronic kidney disease (CKD) results in hypertriglyceridemia which is largely due to impaired clearance of triglyceride-rich lipoproteins occasioned by downregulation of lipoprotein lipase and very low-density lipoprotein (LDL) receptor in the skeletal muscle and adipose tissue and of hepatic lipase and LDL receptor-related protein in the liver. However, data on the effect of CKD on fatty acid metabolism in the liver is limited and was investigated here.

METHODS

Male Sprague-Dawley rats were randomized to undergo 5/6 nephrectomy (CRF) or sham operation (control) and observed for 12 weeks. The animals were then euthanized and their liver tissue tested for nuclear translocation (activation) of carbohydrate-responsive element binding protein (ChREBP) and sterol-responsive element binding protein-1 (SREBP-1) which independently regulate the expression of key enzyme in fatty acid synthesis, i.e. fatty acid synthase (FAS) and acyl-CoA carboxylase (ACC) as well as nuclear Peroxisome proliferator-activated receptor alpha (PPARα) which regulates the expression of enzymes involved in fatty acid oxidation and transport, i.e. L-FABP and CPT1A. In addition, the expression of ATP synthase α, ATP synthase β, glycogen synthase and diglyceride acyltransferase 1 (DGAT1) and DGAT2 were determined.

RESULTS

Compared with controls, the CKD rats exhibited hypertriglyceridemia, elevated plasma and liver tissue free fatty acids, increased nuclear ChREBP and reduced nuclear SREBP-1 and PPARα, upregulation of ACC and FAS and downregulation of L-FABP, CPT1A, ATP synthase α, glycogen synthase and DGAT in the liver tissue.

CONCLUSION

Liver in animals with advanced CKD exhibits ChREBP-mediated upregulation of enzymes involved in fatty acid synthesis, downregulation of PPARα-regulated fatty acid oxidation system and reduction of DGAT resulting in reduced fatty acid incorporation in triglyceride.

Perilipin-1 in hemodialyzed patients: association with history of coronary heart disease and lipid profile

Perilipin-1 surrounds lipid droplets in both adipocytes and in atheroma plaque foam cells and controls access of lipases to the lipid core. In hemodialysis (HD) patients, dyslipidemia, malnutrition, inflammation and atherosclerosis are common. Thirty-six HD patients and 28 healthy volunteers were enrolled into the study. Ten HD patients suffered from coronary heart disease (CHD). Perilipin-1, triglycerides, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol (HDL-C), body mass index, albumin, geriatric nutritional risk index, normalized protein catabolic rate, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were measured. Perilipin-1 did not differ between HD patients and healthy volunteers. IL-6 and TNF-α were higher in HD patients. The evaluated nutritional markers and the markers of inflammation did not differ between HD patients with high perilipin-1 levels and HD patients with low perilipin-1 levels. Regarding the lipid profile, only HDL-C differed between HD patients with high perilipin-1 levels and HD patients with low perilipin-1 levels, and it was higher in the first subgroup. Perilipin-1 was significantly higher in HD patients without CHD. Perilipin-1 is detectable in the serum of HD patients and it is associated with increased HDL-C and decreased incidence of CHD.

Effects of lipoprotein-associated phospholipase A2 on arginase/nitric oxide pathway in hemodialysis patients

Lipoprotein-associated phospholipase A2 (Lp-PLA2) and arginase are recently described inflammatory biomarkers associated with cardiovascular disease. In this study, we aimed to investigate the possible effects of serum Lp-PLA2 mass levels on arginase/nitric oxide (NO) pathway as a cardiovascular risk marker in hemodialysis (HD) patients. Forty-three HD patients and 15 healthy subjects were included in this study. Lipid profile, high sensitivity C-reactive protein (hs-CRP), albumin, creatinine, body mass index (BMI), Lp-PLA2 and total nitrite levels, and arginase activity were determined in serum samples from patients and control subjects. Lp-PLA2 levels were found to be positively correlated with arginase, triglycerides, total cholesterol, low-density lipoprotein-cholesterol, and age and negatively correlated with high-density lipoprotein-cholesterol and total nitrite levels, while there was no correlation with BMI and hs-CRP, albumin, and creatinine levels in HD patients. We conclude that elevated Lp-PLA2 mass levels may contribute to impaired arginase/NO pathway in HD patients and that increased the arginase activity and Lp-PLA2 mass levels with decreased total nitrite levels seem to be useful biochemical markers in terms of reflecting endothelial dysfunction and associated cardiovascular risks in HD patients.

HDL-associated enzymes and proteins in hemodialysis patients

OBJECTIVES

To evaluate HDL-associated proteins and enzymes and their relation with lipoprotein profile and inflammatory markers in chronic renal patients on hemodialysis.

DESIGN AND METHODS

We studied 53 patients under hemodialysis and 32 healthy subjects as controls. We compared plasma lipids, Apoprotein-AI and hs-CRP, as a marker of chronic inflammation. We evaluated proteins and enzymes associated to HDL, involved in several points of lipoprotein metabolism: CETP, paraoxonase and LpPLA2 activities. Hepatic lipase was measured in postheparin plasma.

RESULTS

Patients showed higher triglycerides and lower LDL-, HDL- and total-cholesterol than controls (p<0.05). Also, in comparison with controls, Apoprotein-AI, paraoxonase and hepatic lipase were lower, while CETP was higher (p<0.03). LpPLA2 did not show changes between groups.

CONCLUSION

Beyond plasma lipid-lipoprotein profile, other factors could contribute to induce a pro-oxidative and pro-inflammatory status. The protective role of HDL does not only depend on its concentration, but also on its functionality.

Is zinc-α2-glycoprotein a cardiovascular protective factor for patients undergoing hemodialysis?

BACKGROUND

Zinc-α2-glycoprotein (ZAG) is a lipid mobilizing factor. Its anti-inflammatory action and expression pattern suggest that ZAG could act by protecting against the obesity-associated disorders. In hemodialysis (HD) patients, ZAG levels were described to be elevated but its effects on markers of inflammation and LDL oxidation are still unclear. We investigated the relationship between ZAG and markers of systemic inflammation and LDL atherogenic modification profile in HD patients.

METHODS

Forty-three patients regularly on HD were studied and compared to 20 healthy subjects. Plasma ZAG, adiponectin, electronegative LDL [LDL(-)], an atherosclerotic negatively charged LDL subfraction, and anti-LDL(-) autoantibodies levels were measured by ELISA. Markers of inflammation and atherogenic cell recruitment (TNF-α, interleukin-6, VCAM-1, ICAM-1, MCP-1 and PAI-1) were also determined.

RESULTS

Inflammatory markers and atherogenic cell recruitment were higher in HD patients when compared to healthy subjects. ZAG levels were also higher in HD patients (151.5 ± 50.1 mg/l vs 54.6 ± 23.0 mg/l; p<0.0001) and its levels were negatively correlated with TNF-α (r=-0.39; p=0.001) and VCAM-1 (r=-0.52; p<0.0001) and, positively correlated with anti-LDL(-) autoantibodies (r=0.38; p=0.016). On multivariate analyses, plasma ZAG levels were independently associated with VCAM-1 (p=0.01).

CONCLUSION

ZAG is inversely associated with markers of pro-atherogenic factors linked to systemic inflammation and oxidative stress. Thus, this adipokine may constitute a novel marker of a favorable metabolic profile regarding cardiovascular risk factors in HD population.

Lipoprotein lipase deficiency in chronic kidney disease is accompanied by down-regulation of endothelial GPIHBP1 expression

BACKGROUND

Chronic renal failure (CRF) is associated with hypertriglyceridemia and impaired clearance of very low density lipoprotein (VLDL) and chylomicrons which are largely due to lipoprotein lipase (LPL) deficiency/dysfunction. After its release from myocytes and adipocytes, LPL binds to the endothelium in the adjacent capillaries where it catalyzes hydrolysis of triglycerides in VLDL and chylomicrons. The novel endothelium-derived molecule, glycosylphosphatidylinositol-anchored binding protein 1 (GPIHBP1), plays a critical role in LPL metabolism and function by anchoring LPL to the endothelium and binding chylomicrons. GPIHBP1-deficient mice and humans exhibit severe hypertriglyceridemia and diminished heparin-releasable LPL, pointing to the critical role of GPIHBP1 in regulation of LPL activity. Given its central role in regulation of LPL activity and triglyceride metabolism, we explored the effect of chronic kidney disease (CKD) on GPIHBP1 expression.

METHODS

Expression of GPIHBP1 and LPL were determined by reverse transcriptase-polymerase chain reaction, Western blot and immunohistochemical analyses in the adipose tissue, skeletal muscle and myocardium of rats 12 weeks after 5/6 nephrectomy (CRF) or sham-operation (control).

RESULTS

Compared to the controls, the CRF group exhibited severe hypertriglyceridemia, significant reduction of the skeletal muscle, myocardium and adipose tissue LPL mRNA and protein abundance. This was accompanied by parallel reductions of GPIHBP1 mRNA abundance and immunostaining in the tested tissues.

CONCLUSIONS

LPL deficiency in CKD is associated with and compounded by GPIHBP1 deficiency. Together these abnormalities contribute to impaired clearance of triglyceride-rich lipoproteins, diminished availability of lipid fuel for energy storage in adipocytes and energy production in myocytes and consequent hypertriglyceridemia, cachexia, muscle weakness and atherosclerosis.

Effects of alpha-lipoic acid supplementation on inflammation, oxidative stress, and serum lipid profile levels in patients with end-stage renal disease on hemodialysis

OBJECTIVE

We examined the effects of alpha-lipoic acid (ALA) supplementation on inflammation, oxidative stress, and serum lipid profile levels in hemodialysis (HD) patients.

DESIGN

This was a double-blinded, randomized, placebo-controlled clinical trial.

SETTING

The present study involved HD centers in Tabriz, Iran.

PATIENTS

Participants included 63 patients with end-stage renal disease (43 men and 20 women; age range: 22-79 years) undergoing maintenance HD.

INTERVENTION

HD patients were randomly assigned into the supplemented group (n = 31), receiving a daily dose of ALA (600 mg), or a control group (n = 32), receiving placebo for 8 weeks.

MAIN OUTCOME MEASURES

High sensitivity C-reactive protein (hsCRP), malondialdehyde, total antioxidant status, total cholesterol, triglyceride, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) were measured at baseline and after 8 weeks of supplementation.

RESULTS

At the end of intervention, 11 patients were excluded from the study. HsCRP levels decreased by 18.7% in the supplemented group after 8 weeks of supplementation, and the reduction was significant in comparison with the placebo group (P < .05); this finding was also significant after adjusting for baseline values of hsCRP. The mean malondialdehyde and total antioxidant status levels did not change significantly in the 2 groups during the study. The mean high-density lipoprotein cholesterol concentrations increased significantly in the supplemented group at the end of the study (P < .05); however, this improvement was not statistically significant as compared with the placebo group. No significant alterations were observed in the other lipid profile parameters within each group during the study.

CONCLUSION

ALA supplementation significantly reduced hsCRP levels, which is a risk factor for cardiovascular disease in HD patients.

Characteristics of low-density and high-density lipoprotein subclasses in pediatric renal transplant recipients

Renal transplant recipients often suffer from dyslipidemia which is one of the principal risk factors for cardiovascular disease. This study sought to determine characteristics of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles and their associations with carotid intima-media thickness (cIMT) in a group of pediatric renal transplant recipients. We also examined the influence of immunosuppressive therapy on measured LDL and HDL particle characteristics. HDL size and subclass distribution were determined using gradient gel electrophoresis, while concentrations of small, dense LDL (sdLDL)-cholesterol (sdLDL-C) and sdLDL-apolipoprotein B (sdLDL-apoB) using heparin-magnesium precipitation method in 21 renal transplant recipients and 32 controls. Renal transplant recipients had less HDL 2b (P < 0.001), but more HDL 3a (P < 0.01) and 3b (P < 0.001) subclasses. They also had increased sdLDL-C (P < 0.01) and sdLDL-apoB (P < 0.05) levels. The proportion of the HDL 3b subclasses was a significant predictor of increased cIMT (P < 0.05). Patients treated with cyclosporine had significantly higher sdLDL-C and sdLDL-apoB concentrations (P < 0.05) when compared with those on tacrolimus therapy. Pediatric renal transplant recipients have impaired distribution of HDL and LDL particles. Changes in the proportion of small-sized HDL particles are significantly associated with cIMT. Advanced lipid testing might be useful in evaluating the effects of immunosuppressive therapy.

Atorvastatin and low-density lipoprotein cholesterol in type 2 diabetes mellitus patients on hemodialysis

BACKGROUND AND OBJECTIVES

Patients undergoing maintenance hemodialysis are at high cardiovascular risk. Lowering LDL-cholesterol with statins reduces the incidence rate of cardiovascular events in patients with chronic kidney disease. In contrast, two randomized, prospective, placebo-controlled trials have been completed in hemodialysis patients that showed no significant effects of statins on cardiovascular outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A post hoc analysis was conducted of the 4D (Die Deutsche Diabetes Dialyze) study to investigate whether LDL-cholesterol at baseline is predictive of cardiovascular events and whether the effect of atorvastatin on clinical outcomes depends on LDL-cholesterol at baseline.

RESULTS

High concentrations of LDL-cholesterol by tendency increased the risks of cardiac endpoints and all-cause mortality. Concordantly, atorvastatin significantly reduced the rates of adverse outcomes in the highest quartile of LDL-cholesterol (≥145 mg/dl, 3.76 mmol/L). The hazard ratios and 95% confidence intervals were 0.69 (0.48 to 1.00) for the composite primary endpoint, 0.58 (0.34 to 0.99) for cardiac death, 0.48 (0.25 to 0.94) for sudden cardiac death, 0.62 (0.33 to 1.17) for nonfatal myocardial infarction, 0.68 (0.47 to 0.98) for all cardiac events combined, and 0.72 (0.52 to 0.99) for death from all causes, respectively. No such decrease was seen in any of the other quartiles of LDL-cholesterol at baseline.

CONCLUSIONS

In patients with type 2 diabetes mellitus undergoing hemodialysis, atorvastatin significantly reduces the risk of fatal and nonfatal cardiac events and death from any cause if pretreatment LDL-cholesterol is >145 mg/dl (3.76 mmol/L).

The effect of prolonged oral exposure of cockerels to disinfectant (Iodosteryl(®)) on induction of oxidative stress and liver damage

This study was designed to investigate the effect of prolonged oral exposure of cockerels to disinfectant (Iodosteryl(®)) present in drinking water and its ability to induce liver damage and oxidative stress. Thirty-two healthy birds were used for this study. They were grouped into four groups of eight per group. Group I received 10 ml/kg body weight of physiological saline. Groups II, III and IV received 1 part per million, 2 part per million and 4 part per million of Iodosteryl(®) in their drinking water for six weeks. The results revealed significant (P<0.05) increase in alanine aminotransferase, aspartate aminotransferase and alkaline phosphatase activities in a dose-dependent manner in birds administered with Iodosteryl(®) when compared with control. Significant (P<0.05) increase in sodium and potassium ions was obtained from birds that received Iodosteryl(®) (4 part per million) compared with control. Also, there was significant (P<0.05) increase in total cholesterol, triglycerides, high density lipoprotein and low density lipoprotein levels in all treatment groups (1, 2 and 4 part per million) compared with control. Serum blood urea nitrogen levels increased significantly (P<0.05) in a dose-dependent manner. Biologic markers of oxidative stress (malondialdehyde and hydrogen peroxide generation) increased significantly with concomitant significant (P<0.05) decrease in serum glutathione level in a dose-dependent manner when compared with control. Histological sections revealed hepatic congestion, vacuolation and fibrosis at varying concentration of Iodosteryl(®). Overall, Iodosteryl(®) induced hepatic damage, increased oxidative stress and decreased antioxidant defense system; hence exposure of both animals and humans to prolonged iodine disinfectant is potentially harmful.

Paraoxonase-1 and ischemia-modified albumin in patients with end-stage renal disease

End-stage renal disease (ESRD) with and/or without treatment by hemodialysis (HD) is associated with accelerated atherosclerosis, leading to cardiovascular disease (CVD) including acute coronary syndromes. Therefore, the regulation of CVD is a crucial issue for ESRD patients. Given the recent reports that paraoxonase-1 (PON-1) and ischemia-modified albumin (IMA) could predict CVD-related mortality in ESRD, the two recent biomarkers may be useful for preventive strategies for CVD. This review paper presents current data on the relationships between PON-1, IMA, and ESRD. Many studies have shown that circulating PON-1 activity is lower in ESRD patients, and we have shown that its levels increase after HD. Although circulating IMA levels can increase before HD in ESRD patients, there remains to be little data. Our pilot study has shown a significant inverse correlation between PON-1 and IMA in ESRD patients. Although the pathogenic link between PON-1 and IMA remains speculative, considering both biomarkers may provide new insights into the prevention of CVD in ESRD patients.

Hemodialysis alters lipid profiles, total antioxidant capacity, and vitamins A, E, and C concentrations in humans

Although hemodialysis (HD) is essential for end-stage renal disease patients, at the same time it causes oxidative stress and long-term pro-atherosclerotic effects. This study aimed to determine lipid profile as well as the total antioxidant capacity (TAC) and vitamins A, E, and C in HD patients. The study enrolled 31 patients (50.3 ± 14.9 years old) undergoing maintenance 4-hour HD three times per week with a polysulfone membrane dialyzer for a mean of 76.1 months (range, 7-120 months) and 31 healthy individuals (47.8 ± 13.9 years old). Lipid profiles were determined spectrophotometrically using commercially available kits. Total antioxidant capacity was determined by ferric reducing/antioxidant power assay, levels of vitamins A and E were assayed using high-pressure liquid chromatography, and the level of vitamin C was measured by a photometric method. Our results showed that before HD, the levels of TAC and vitamin A were significantly higher than in normal subjects, whereas the levels of high-density lipoprotein (HDL) and vitamin C were lower than in control subjects (P < .001). There was no significant difference between normal subjects and patients before dialysis regarding low-density lipoprotein (LDL) and vitamin E levels (P > .05). After HD, the levels of HDL-cholesterol, vitamins E and C, and TAC decreased significantly (P < .001), but the decreased level of vitamin A still remained higher than controls (P < .05), whereas the levels of LDL were significantly higher than controls (P < .001). In conclusion, alterations in the lipoprotein profiles and antioxidant markers following HD suggest an increased risk of atherosclerosis in these patients.

Lipids-induced apoptosis is aggravated by acyl-coenzyme A: cholesterol acyltransferase inhibitor

OBJECTIVE

To investigate the role of acyl-coenzyme A: cholesterol acyltransferase inhibitor (ACATI) in apoptosis induced by lipids and whether lipids-induced apoptosis is accompanied by increase of free cholesterol in endoplasmic reticulum (ER), in order to further understand the mechanism of lipids-induced apoptosis in advanced atherosclerosis.

METHODS

Human vascular smooth muscle cells (VSMCs) and phorbol 12-myristate 13-acetate (PMA) differentiated THP-1 macrophages were used. Tritiated thymidine incorporation was applied to detect cell proliferation. Cytotoxicity was assessed by lactate dehydrogenase (LDH) release. 4',6-diamidino-2-phenylindole (DAPI) staining, caspase-3, -7 assay, and Annexin-V/propidium iodide (PI) staining were used to detect apoptosis. High performance liquid chromatography was used in intracellular free cholesterol and cholesterol ester assay. ER free cholesterol was quantified.

RESULTS

Different lipids had different effects on proliferation and cytotoxicity of VSMCs. 25-hydroxycholesterol (25OHC) had biphasic effects on the proliferation of VSMCs. At low concentration, it stimulated cell proliferation, but turned to proliferation inhibition as concentration reached 15 mug/mL. 25OHC and acetylated low density lipoprotein (AcLDL) could respectively induce apoptosis in human VSMCs and PMA differentiated THP-1 macrophages, which was aggravated by ACATI, accompanied by increase of intracellular free cholesterol content. There was also an increase of cholesterol content in ER with AcLDL-induced apoptosis in THP-1 macrophages.

CONCLUSIONS

Lipids could induce apoptosis, accompanied by increase of intracellular free cholesterol content, which could be augmented by ACATI, suggesting that insults resulting in ER free cholesterol rise might be the initiator of apoptosis.

Amelioration of nephropathy with apoA-1 mimetic peptide in apoE-deficient mice

BACKGROUND

There is mounting evidence that dyslipidaemia may contribute to development and progression of renal disease. For instance, hyperlipidaemia in apolipoprotein E-deficient (apoE(-/-)) mice is associated with glomerular inflammation, mesangial expansion and foam cell formation. ApoA-1 mimetic peptides are potent antioxidant and anti-inflammatory compounds which are highly effective in ameliorating atherosclerosis and inflammation in experimental animals. Given the central role of oxidative stress and inflammation in progression of renal disease, we hypothesized that apoA-1 mimetic peptide, D-4F, may attenuate renal lesions in apoE(-/-) mice.

METHODS

Twenty-five-month-old female apoE(-/-) mice were treated with D-4F (300 µg/mL in drinking water) or placebo for 6 weeks. Kidneys were harvested and examined for histological and biochemical characteristics.

RESULTS

Compared with the control mice, apoE(-/-) mice showed significant proteinuria, tubulo-interstitial inflammation, mesangial expansion, foam cell formation and up-regulation of oxidative [NAD(P)H oxidase subunits] and inflammatory [NF-κB, MCP-1, PAI-1 and COX-2] pathways. D-4F administration lowered proteinuria, improved renal histology and reversed up-regulation of inflammatory and oxidative pathways with only minimal changes in plasma lipid levels.

CONCLUSIONS

The apoE(-/-) mice develop proteinuria and glomerular and tubulo-interstitial injury which are associated with up-regulation of oxidative and inflammatory mediators in the kidney and are ameliorated by the administration of apoA-1 mimetic peptide. These observations point to the role of oxidative stress and inflammation in the pathogenesis of renal disease in hyperlipidaemic animals and perhaps humans.