Effects of reduced renal mass on tissue lipids and renal injury in hyperlipidemic rats

Relieving lipid accumulation through UCP1 suppresses the progression of acute kidney injury by promoting the AMPK/ULK1/autophagy pathway

Rationale: Acute kidney injury (AKI) is a serious clinical emergency with an acute onset, rapid progression, and poor prognosis. Recent evidence suggests that AKI is accompanied by significant metabolic abnormalities, including alterations in lipid metabolism. However, the specific changes in lipids in AKI, and their role and regulation mechanisms are currently unclear.

Methods: Quantitative metabolomics was performed in AKI models to reveal the differences of lipid metabolism-related products. Regulated pathway was detected by western blot, qRT-PCR, immunoblot analysis and immunohistochemistry.

Results: The present study systematically analyzes the changes in lipid composition in AKI for the first time and find that the degree of lipid accumulation was highly correlated with uncoupling protein 1 (UCP1). Importantly, relieving lipid accumulation in AKI by upregulating UCP1 can significantly inhibit the progression of AKI through promoting AMPK/ULK1/autophagy pathway.

Conclusions: The present findings suggest that lipid accumulation in AKI is directly regulated by UCP1, which can activate cell autophagy and thus significantly inhibit disease progression. It will provide new ideas and targets for the treatment of AKI.

Influence of 3D-Calculated Parenchymal Volume Loss on Renal Function After Partial Nephrectomy

Background: Our study aims to evaluate the influence of potential determinants of glomerular filtration rate (GFR) decrease after partial nephrectomy (PN), including renal parenchymal loss and other clinical, tumoral, and surgical factors. Materials and Methods: Eighty-six patients who had undergone PN and for whom preoperative and postoperative computerized tomography scans were available were selected. We calculated the preoperative total kidney volumes, tumor volumes, and postoperative total kidney volumes 1 year after surgery using a three-dimensional (3D) volume segmentation method. Factors that may be potential determinants of percent GFR decrease were also evaluated, including patient age, type of procedure (laparoscopic vs. open), comorbidity index, preoperative GFR, tumor size and volume, RENAL nephrometry score, warm ischemia time, and 3D calculated renal parenchymal loss. Clinical, surgical, and tumor parameters potentially associated with renal parenchymal loss were evaluated. Results: The mean age of the patients was 58 years, the mean tumor diameter was 3.6 cm, and the mean tumor volume was 11.7 cc. The mean percent of renal parenchymal loss was 22.3%, and the mean percent of GFR loss was 17.3%. The renal parenchymal loss was strongly associated with age (r = 0.702, P = .02), Charlson comorbidities index (r = 0.768, P < .001), and RENAL nephrometry score (r = 0.812, P < .001). In multivariate logistic regression analysis, older age, higher Charlson comorbidities index, higher percent renal parenchymal loss, and higher RENAL nephrometry score were independently associated with higher percent of GFR loss. Conclusion: Of all the factors analyzed, RENAL score and Charlson comorbidities index were the most accurate predictors of postoperative parenchymal loss. Also, the percent decrease in GFR at late time points was associated with renal volume preservation and quality of the remnant parenchyma.

Chronic exercise provides renal-protective effects with upregulation of fatty acid oxidation in the kidney of high fructose-fed rats

Excessive fructose intake causes metabolic syndrome and lipid accumulation in the kidney and leads to renal dysfunction and damage. Exercise (Ex) improves lipids regulation, but the mechanisms are unclarified in the kidney. In the present study, male Sprague-Dawley rats were allocated to groups fed with control or high-fructose (HFr) diet. Part of rats in each group underwent aerobic treadmill Ex for 12 wk. Drug treatment was performed as the fenofibrate gavage during the last 4 wk on HFr diet-fed rats. Renal function, histological changes, and expression of regulators involved in fatty acid (FA) metabolism were assessed. In CON diet-fed groups, Ex did not affect renal function or histology and significantly increased renal expression of FA β-oxidation regulators including acyl-CoA dehydrogenases (CADs), acyl-CoA oxidase, peroxisome proliferator-activated receptor (PPAR)-α, and PPAR-γ coactivator (PGC)-1α and lipogenic factors including acetyl-CoA carboxylase (ACCα), FA synthase (FAS), and sterol regulatory element-binding protein 1c. HFr caused albuminuria, lipid accumulation, and renal pathohistological changes, which were attenuated by Ex but not by fenofibrate. HFr decreased renal expression of medium- and short-chain CADs and PPAR-α and increased renal expression of ACCα, FAS, and sterol regulatory element-binding protein 1c. Ex increased expression of CADs, carnitine palmitoyltransferase type I, acyl-CoA oxidase, PPAR-α, and PGC-1α and decreased renal expression of ACCα and FAS in HFr diet-fed rats. The Ex-induced FA metabolism alteration was similar to that in the fenofibrate-treated group. In conclusion, the present study indicates that Ex enhanced renal FA metabolism, which might protect the kidney in lipid dysregulation diseases.

Sesamin Ameliorates High-Fat Diet-Induced Dyslipidemia and Kidney Injury by Reducing Oxidative Stress

The study explored the protective effect of sesamin against lipid-induced renal injury and hyperlipidemia in a rat model. An animal model of hyperlipidemia was established in Sprague-Dawley rats. Fifty-five adult Sprague-Dawley rats were divided into five groups. The control group was fed a standard diet, while the other four groups were fed a high-fat diet for 5 weeks to induce hyperlipidemia. Three groups received oral sesamin in doses of 40, 80, or 160 mg/(kg·day). Seven weeks later, the blood lipids, renal function, antioxidant enzyme activities, and hyperoxide levels in kidney tissues were measured. The renal pathological changes and expression levels of collagen type IV (Col-IV) and α-smooth muscle actin (α-SMA) were analyzed. The administration of sesamin improved the serum total cholesterol, triglyceride, low-density lipoprotein cholesterol, apolipoprotein-B, oxidized-low-density lipoprotein, and serum creatinine levels in hyperlipidemic rats, while it increased the high-density lipoprotein cholesterol and apolipoprotein-A levels. Sesamin reduced the excretion of 24-h urinary protein and urinary albumin and downregulated α-SMA and Col-IV expression. Moreover, sesamin ameliorated the superoxide dismutase activity and reduced malondialdehyde levels in kidney tissue. Sesamin could mediate lipid metabolism and ameliorate renal injury caused by lipid metabolism disorders in a rat model of hyperlipidemia.

Relation of serum lipids and lipoproteins with progression of CKD: The CRIC study

BACKGROUND AND OBJECTIVES

Hyperlipidemia is common in patients with CKD. The objective of this study was to evaluate whether measures of plasma lipids and lipoproteins predict progression of kidney disease in patients with CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Prospective cohort study in adults (n=3939) with CKD aged 21-74 years recruited between 2003 and 2008 and followed for a median of 4.1 years. At baseline, total cholesterol, triglycerides, very-low-density lipoprotein cholesterol (VLDL-C), LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), apoA-I , apoB, and lipoprotein(a) [Lp(a)] were measured. The outcomes were composite end point of ESRD or 50% decline in eGFR from baseline (rate of change of GFR).

RESULTS

Mean age of the study population was 58.2 years, and the mean GFR was 44.9 ml/min per 1.73 m(2); 48% of patients had diabetes. None of the lipid or lipoprotein measures was independently associated with risk of the composite end point or rate of change in GFR. However, there were significant (P=0.01) interactions by level of proteinuria. In participants with proteinuria<0.2 g/d, 1-SD higher LDL-C was associated with a 26% lower risk of the renal end point (hazard ratio [HR], 0.74; 95% confidence interval [95% CI], 0.59 to 0.92; P=0.01), and 1-SD higher total cholesterol was associated with a 23% lower risk of the renal end point (HR, 0.77; 95% CI, 0.62 to 0.96; P=0.02). In participants with proteinuria>0.2 g/d, neither LDL-C (HR, 0.98; 95% CI, 0.98 to 1.05) nor total cholesterol levels were associated with renal outcomes. Treatment with statins was reported in 55% of patients and was differential across lipid categories.

CONCLUSIONS

In this large cohort of patients with CKD, total cholesterol, triglycerides, VLDL-C, LDL-C, HDL-C, apoA-I, apoB, and Lp(a) were not independently associated with progression of kidney disease. There was an inverse relationship between LDL-C and total cholesterol levels and kidney disease outcomes in patients with low levels of proteinuria.

Effects of unilateral nephrectomy on renal function in male Spontaneously Diabetic Torii fatty rats: a novel obese type 2 diabetic model

The Spontaneously Diabetic Torii (SDT) fatty rat is a new model for obese type 2 diabetes. The aim of the present study was to investigate the effect of 1/2 nephrectomy (Nx) on renal function and morphology and on blood pressure in SDT fatty rats. Male SDT fatty rats underwent 1/2 Nx or a sham operation (Sham). Subsequently, animals were studied with respect to renal function and histological alterations. Induction of 1/2 Nx in SDT fatty rats led to functional and morphological damage to the remnant kidney and to hypertension, which are considered main characteristics of chronic kidney disease, at a younger age compared with the sham group. In conclusion, the SDT fatty rat is useful in investigations to elucidate the pathogenesis of human diabetic nephropathy and in new drug discovery.

Association of reduced renal function with hepatitis B virus infection and elevated alanine aminotransferase

BACKGROUND AND OBJECTIVES

Clinically, hepatitis B virus (HBV) infection is observed to be associated with nephropathy. However, previous population-based studies failed to show an association between HBV infection and CKD. Therefore, this cross-sectional study was designed to further explore this association.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A representative sample of 6854 Chinese adults aged 30-75 years was tested for levels of serum hepatitis B surface antigen, alanine aminotransferase (ALT), creatinine, urinary albumin/creatinine ratio, and potential CKD risk factors.

RESULTS

Neither HBV infection nor elevated ALT (ALT+; ≥ sex-specific 90th percentile of ALT levels of noninfected persons) was significantly associated with reduced estimated GFR (eGFR < 60 ml/min per 1.73 m(2)). Compared with noninfected persons, HBV-infected persons with ALT+, but not those with ALT- (P=0.26), were more likely to have reduced eGFR (odds ratio, 4.07; 95% confidence interval, 1.18-14.0; P=0.03). Further analysis with a general linear model revealed a significant difference in eGFR (mean ± SEM) between HBV-infected and noninfected persons (87.8±0.8 versus 90.2±0.4 ml/min per 1.73 m(2); P=0.002). This difference was mainly derived from that between HBV-infected persons with ALT+ and noninfected persons, with an average difference in eGFR of -4.5 (95% confidence interval, -0.9 to -8.1; P=0.01). HBV infection and ALT+, alone or in combination, were not significantly associated with albuminuria or CKD.

CONCLUSIONS

HBV infection with elevated ALT, rather than HBV infection alone, was associated with reduced renal function.

Residual renal function after partial or radical nephrectomy for renal cell carcinoma

Renal cell carcinoma (RCC) is often detected incidentally and early. Currently, open partial nephrectomy and laparoscopic total nephrectomy form competing technologies. The former is invasive, but nephron-sparing; the other is considered less invasive but with more loss of renal mass. Traditionally, emphasis has been placed on oncologic outcomes. However, a patient with an excellent oncologic outcome may suffer from morbidity and mortality related to renal failure. Animal models with hypertension and diabetic renal disease indicate accelerated progression of pre-existing disease after nephrectomy. Patients with RCC are older and they have a high prevalence of diabetes and hypertension. The progression of renal failure may also be accelerated after a nephrectomy. Our analysis of the available literature indicates that renal outcomes in RCC patients after surgery are relatively poorly defined. A strategy to systematically evaluate the renal function of patients with RCC, with joint discussion between the nephrologist and the oncologic team, is strongly advocated.

Apolipoprotein E polymorphism and the progression of diabetic nephropathy in type 2 diabetes

BACKGROUND/AIMS

Three different apo E alleles (E2, E3 and E4) produce apo E isoproteins, which regulate the metabolism of lipoproteins. This study investigated the apo E polymorphisms as a prognostic factor for the development of diabetic nephropathy (DN).

METHODS

A total of 525 type 2 diabetic patients were enrolled to participate in this prospective observational study. Apo E gene polymorphisms were analyzed by polymerase chain reaction. The progression of DN was defined as a shift to a higher stage of DN or a doubling of the baseline serum creatinine level by the end of the study.

RESULTS

The mean follow-up period was 42.4 months. The patients whose DN progressed had significantly higher urine albumin/creatinine ratios and fewer used diuretics than those in whom DN did not progress. In the Cox regression analysis, the apo E4 carriers were found to be at greater risk of progression of DN than non-apo E4 carriers (p = 0.007, hazard ratio 2.252). After adjusting for confounding factors, apo E4 carriers remained at increased risk of progression to more severe DN (p = 0.002, hazard ratio 2.820).

CONCLUSION

Our study suggests the apo E4 carrier might serve as a predictor of DN progression in Taiwan.

Changing prevalence of glomerular diseases in Korean adults: a review of 20 years of experience

BACKGROUND

The prevalence of glomerular diseases differs according to geographic area, race, age and indications for a renal biopsy. This study was conducted to evaluate the distribution and changing patterns of renal diseases during the past 20 years in a large patient population in Korea.

METHODS

Patients aged 16 years or older who underwent a renal biopsy at Severance Hospital in the Yonsei University Health System from 1987 to 2006 were enrolled. All medical records were reviewed retrospectively.

RESULTS

In total, 1818 patients (M:F = 1.02:1) were reviewed. Glomerulonephritis (GN) comprised 85.9% of the total biopsied cases. The most common primary GN was IgA nephropathy (IgAN) (28.3%), which was followed by minimal change disease (MCD) (15.5%), membranous nephropathy (MN) (12.3%), focal segmental glomerulosclerosis (FSGS) (5.6%) and membranoproliferative GN (MPGN) (4.0%). The most common secondary GN was lupus nephritis (8.7%). The most common idiopathic nephrotic syndrome was MCD (38.5%), which was followed by MN and IgAN. Among 128 (7.4%) patients who were HBsAg-positive, MN (30.5%) and MPGN (21.1%) were the most common GN. When the incidence rates between 1987-91 and 2002-06 were compared, IgAN increased from 25.6 to 34.5%, while MCD (from 23.2 to 7.0%) and MPGN (from 6.7 to 1.7%) decreased significantly (P < 0.01).

CONCLUSIONS

IgAN was the most common primary GN, and MCD was the most common cause of nephrotic syndrome. In the 5-year quartile comparison, the relative frequency of IgAN increased, while the relative frequency of MCD and MPGN decreased significantly during the past 20 years.

Hepatitis C virus infection and the prevalence of renal insufficiency

BACKGROUND

Hepatitis C virus (HCV) is associated with pathologic changes in the kidney. However, the association between HCV and renal dysfunction is not well defined.

DESIGN, SETTING, PARTICIPANTS, AND MEASUREMENTS

This study estimated the prevalence of renal insufficiency among veterans who received care through the Veterans Affairs Puget Sound Health Care System. The study population consisted of veterans who underwent HCV antibody testing between January 1, 1999, and December 31, 2004, and had at least one primary care or medical subspecialty visit and at least one outpatient creatinine measurement within the 18 mo before antibody testing. Veterans were excluded when they had a history of chronic dialysis, creatinine >5 mg/dl, or renal transplantation. Study data were extracted from the electronic medical record. Renal insufficiency was defined as a creatinine level > or =1.5 mg/dl. Multivariate logistic regression was performed to estimate the risk for renal insufficiency associated with HCV. Among 25,782 eligible veterans, 1928 were HCV antibody positive and 23,854 were HCV antibody negative.

RESULTS

Although the proportion with renal insufficiency was lower for antibody-positive versus -negative veterans (4.8 versus 6.0%), after adjustment for age, race, gender, diabetes, and hypertension, HCV-positive veterans had a 40% higher odds for renal insufficiency (odds ratio 1.40; 95% confidence interval 1.11 to 1.76) as compared with HCV-negative veterans.

CONCLUSIONS

HCV was associated with an increased prevalence of renal insufficiency.

YM440, a novel hypoglycemic agent, protects against nephropathy in Zucker fatty rats via plasma triglyceride reduction

The novel hypoglycemic agent, YM440 ((Z)-1,4-bis{4-[(3,5-dioxo-1,2,4-oxadiazolidin-2-yl) methyl] phenoxy}but-2-ene) is a ligand of the peroxisome proliferator-activated receptor, (PPAR) gamma. YM440 has been shown to counteract insulin resistance in diabetic rodent models. However, it is not clear whether this compound has a significant effect on hyperlipidemia in vivo. Hyperlipidemia has been reported to be a risk factor for the early development of renal disease. The aim of this study is to examine the effects of chronic treatment with YM440 on hyperlipidemia and renal injury in obese Zucker fatty (ZF) rats. Treatment of 8-week-old ZF rats with YM440 (100 mg/kg/day) for 16 weeks decreased plasma triglyceride and cholesterol concentrations. YM440 markedly reduced the rate of progression of both albuminuria and proteinuria. YM440 normalized urinary N-acetyl-beta-D-glucosaminidase (NAG) activity, which is a marker for renal proximal tubular damage, and ameliorated the rise in systolic blood pressure compared to the vehicle control. YM440 also blocked the development of nephromegaly. Histological analyses revealed that both glomerular area expansion and tubular cast accumulation gradually lessened in YM440-treated ZF rats. Regression analyses between the plasma triglyceride levels and the renal parameters (urinary protein excretion and albumin excretion) indicated that the renal parameters correlated positively with the plasma triglyceride levels. In conclusion, the hypolipidemic effects of YM440 prevent renal injury in ZF rats. YM440 might be useful for preventing the early development of diabetic nephropathy in subjects with type 2 diabetes by ameliorating metabolic control problems.

Chronic nephropathies of cocaine and heroin abuse: a critical review

Renal disease in cocaine and heroin users is associated with the nephrotic syndrome, acute glomerulonephritis, amyloidosis, interstitial nephritis, and rhabdomyolysis. The pathophysiologic basis of cocaine-related renal injury involves renal hemodynamic changes, glomerular matrix synthesis and degradation, and oxidative stress and induction of renal atherogenesis. Heroin is the most commonly abused opiate in the United States. Previous studies identified a spectrum of renal diseases in heroin users. The predominant renal lesion in black heroin users is focal segmental glomerulosclerosis and in white heroin users is membranoproliferative glomerulonephritis. Although the prevalence of heroin use in the United States has increased, the incidence of "heroin nephropathy" has declined. Because reports of heroin nephropathy predated the surveillance of hepatitis C virus and HIV, the varied findings might be related to the spectrum of viral illnesses that are encountered in injection drug users. Socioeconomic conditions, cultural and behavioral practices, or differences in genetic susceptibilities may be more associated with the development of nephropathy in heroin users than the drug's pharmacologic properties. Administration of cocaine in animal models results in nonspecific glomerular, interstitial, and tubular cell lesions, but there is no animal model of heroin-associated renal disease. The heterogeneity of responses that are associated with heroin is not consistent with a single or simple notion of nephropathogenesis. There are no well-designed, prospective, epidemiologic studies to assess the incidence and the prevalence of renal disease in populations of opiate users and to establish the validity of a syndrome such as heroin nephropathy. It is concluded although there is a paucity of evidence to support a heroin-associated nephropathy, the evidence from in vitro cellular and animal studies to support the existence of cocaine-induced renal changes is more convincing.

Pivotal role of xanthine oxidase in the initiation of tubulointerstitial renal injury in rats with hyperlipidemia

Hyperlipidemia can induce or aggravate renal tubulointerstitial injury. Experiments in a complex rat model with chronic glomerulonephritis and long-standing, coexisting hyperlipidemia suggested that induction of xanthine oxidase (XO), with increased oxygen radical generation, is involved in aggravation of tubulointerstitial injury. To separate the role of XO in the initial events of lipid-mediated tubulointerstitial injury, short-term experiments with diet-induced hyperlipidemia over 21 and 35 days were performed in otherwise healthy rats. XO expression in relation to the antioxidant enzymes was examined in the cortical tubulointerstitium (TIS) and proximal tubules (PT). Subsequent experiments with XO inhibition were performed, examining tubulointerstitial infiltration with ED1-positive cells and expression of adhesion molecules and monocyte chemoattractant protein-1 (MCP-1) as indicators of early injurious events. Hyperlipidemia increased XO activity in TIS by 40 and 86%, and in PT by 28 and 90% at days 21 and 35, compared with controls on regular diet. This increased activity was associated with increased reactive oxygen species. Among the antioxidant enzymes, glutathione peroxidase activity increased in TIS by 40% and in PT by 90%. Histological evaluation showed a three-fold increase in ED1-positive cells and increased MCP-1 and vascular cell adhesion molecule-1 (VCAM-1) expression at day 35 in the TIS. Inhibition of XO prevented tubulointerstitial ED1 cell infiltration, together with a decreased expression of MCP-1 and VCAM-1. These results point to an important role for XO in the early stage of hyperlipidemia-associated renal injury, mediating macrophage infiltration by a putatively redox-dependent upregulation of MCP-1 and VCAM-1.

Effects of statin therapy on the progression of chronic kidney disease

Statins are lipid-lowering agents that specifically, competitively, and reversibly inhibit 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the enzyme that catalyzes the conversion of HMG-CoA to mevalonic acid, the rate-limiting step in the formation of cholesterol. A large body of evidence from numerous, well-controlled, randomized trials demonstrates that statins significantly reduce fatal and nonfatal cardiovascular events in the general population. Cardiovascular benefits of statins have been conventionally attributed to reduction in levels of low-density lipoprotein cholesterol. More recently, subanalyses of large clinical trials suggest that statins may also prove beneficial in ameliorating the progression of kidney disease through their cholesterol-dependent and/or cholesterol-independent (pleiotropic) effects. This review focuses on the role of statin therapy in the progression of chronic kidney disease, the published trials that study the effect of antilipidemic agents on nephropathy, and the emerging pleiotropic effects of statins on the kidneys.

Increased sensitivity of the obese Zucker rat to deoxycorticosterone-salt-induced hypertension

OBJECTIVE

The objective of this study was to test the hypothesis that obesity increases the sensitivity of rats to experimentally induced hypertension.

DESIGN AND METHODS

To induce hypertension, unilaterally nephrectomized lean and obese Zucker rats were injected with 25 mg/kg of deoxycorticosterone acetate (DOCA) twice weekly for 5 weeks and given water containing 1% NaCl to drink. Unilaterally nephrectomized control rats were injected with vehicle and drank tap water. Systolic blood pressure (SBP) was measured by the tail cuff method. Renal histology and urinary albumin excretion were used to assess the effects of the experimental treatment on the kidney.

RESULTS

Obese rats exhibited a significant rise in SBP at 4 days after the start of DOCA-salt treatment. In contrast, SBP of DOCA-treated lean rats was not significantly elevated from pretreatment measurements until day 22. Moreover, SBP was significantly higher during the plateau phase of blood pressure development in obese DOCA-salt treated rats (196 mmHg) than in correspondingly treated lean rats (150 mmHg). Both obesity and DOCA-salt treatment promoted glomerulosclerosis and mild tubulointerstitial damage in the kidney with DOCA-salt treatment exacerbating the effect of obesity. Urinary albumin excretion was significantly greater in obese control rats compared with lean controls and in DOCA-treated obese rats relative to vehicle-treated obese rats.

CONCLUSION

Results of this study indicate that obese Zucker rats are more sensitive to mineralocorticoid-induced hypertension than lean rats. This study provides experimental evidence supporting the epidemiological findings that obesity is a risk factor for the development of hypertension.

Effect of dietary linoleic acid on the progression of chronic renal failure in rats

The role of linoleic acid in chronic renal failure (CRF) is controversial. In the present study 21 male Wistar rats submitted to 5/6 renal mass reduction (R) and 16 normal controls (C) were fed a supplement (S) or normal (N) linoleic acid diet for 60 days starting 10 days after CRF. As expected, serum creatinine, cholesterol and triglycerides (mean +/- SEM) were higher in the CRF groups compared to the C groups (P<0.05). The RS group presented lower cholesterol (84 +/- 4 vs 126 +/- 13 mg%) and triglyceride (88 +/- 9 vs 132 +/- 19 mg%) levels compared to the RN group. Proteinuria and kidney weight did not differ between CRF groups. Glomerular area increased 78% in RS and 100% in RN compared to control rats. Glomerular sclerosis index tended to be lower in RS (27%) compared to RN (38%), tubulointerstitial damage was similar between CRF groups (RS = 1.91 +/- 0.2 and RN = 2.14 +/- 0.3), and mesangial fractional volume increased to the same extent in both CRF groups. The data suggest that a linoleic acid-enriched diet did not protect against the progression of CRF after 60 days.

Characteristics of progressive renal disease

Virtually all renal diseases progress to terminal renal failure relatively independently of the initial disease. Arresting the rate of the deterioration of kidney failure has a great impact on reducing the number of patients reaching the stage of expensive renal replacement therapy. Understanding the mechanisms of the progression of kidney disease has greatly been improved during recent years. The nature of the progressive renal damage with various etiologies includes various well-known factors where hemodynamics, renin-angiotensin system (RAS) and progressive proteinuria play the central roles. Proteinuria has to be shown as an independent risk factor for renal disease progression. Also, disturbances in lipid metabolism as well as the later structural lesions contribute to the progression. Various modalities have been used for the prevention of progressive renal disease, e.g. low-protein diet, antihypertensive therapy, antifibrotic therapy. Many recent experimental and clinical studies have shown that besides the systemic blood pressure lowering effect, RAS blocking agents provide renal protective effects via direct, hemodynamic, and indirect, non-hemodynamic, pathways: (1) lowering intraglomerular capillary hydraulic pressure, and increasing the glomerular ultrafiltration coefficient; (2) lowering proteinuria; (3) lowering hyperlipidemia; (4) diminishing kidney growth; (5) diminishing infiltration of macrophages; (6) downregulation of proinflammatory cytokines. Therefore, RAS blocking agents are widely prescribed not only for antihypertensive but also for renoprotective purposes in diabetic and non-diabetic nephropathies.

Effect of the lipoprotein lipase activator NO-1886 on adriamycin-induced nephrotic syndrome in rats

Hyperlipidemia associated with nephrotic syndrome may play a role in the deterioration of renal function. Tsutsumi et al have previously reported that the novel compound NO-1886 increases lipoprotein lipase (LPL) activity, resulting in a reduction of plasma triglycerides and an elevation of high-density lipoprotein (HDL) cholesterol in normal rats. The aim of this study was to ascertain whether NO-1886 suppresses the renal injury by treatment of the hyperlipidemia in an Adriamycin (Kyowa Hakko Kogyo, Tokyo, Japan) induced nephrosis rat model fed a high-protein diet that induced renal dysfunction and tubulointerstitial injury. Administration of Adriamycin caused hyperlipidemia, proteinuria, and edema with ascites in rats in 4 weeks. Furthermore, a combination of Adriamycin and a high-protein diet increased plasma creatinine and blood urea nitrogen (BUN) and decreased plasma albumin. Histologically, in Adriamycin-treated rats, marked interstitial cellular infiltration, tubular lumen dilation, and tubular cast formation in the kidney were observed. NO-1886 decreased plasma triglyceride and increased HDL cholesterol in Adriamycin-induced nephrotic rats. NO-1886 treatment reduced plasma creatinine and BUN levels and increased plasma albumin in Adriamycin-treated rats; it also ameliorated the ascites and proteinuria. Histologically, NO-1886-treated rats showed a quantitatively significant preservation of tubulointerstitial lesions. These data suggest that NO-1886 may have a protective effect against Adriamycin-induced nephrosis with tubulointerstitial nephritis in rats by a modification of the plasma lipid disorder.

Interstitial fibrosis in hypercholesterolemic rats: role of oxidation, matrix synthesis, and proteolytic cascades

Uninephrectomized rats with diet-induced hypercholesterolemia develop interstitial inflammation and fibrosis after 8 to 12 weeks. Fibrosis has been associated with the accumulation of lipid peroxidation products within the tubulointerstitium, along with increased renal mRNA levels for transforming growth factor beta-1 (TCF-beta 1), some matrix proteins, and the tissue inhibitor of metalloproteinases (TIMP-1). However, mRNA levels for urokinase-type plasminogen activator (uPA) have been found to be decreased. The purpose of the present study was to determine whether antioxidant therapy could attenuate interstitial fibrosis in hypercholesterolemic rats and to determine changes in the pattern of renal gene expression induced by antioxidant therapy. Three groups of uninephrectomized rats were studied after 12 weeks of feeding standard rat chow, an atherogenic diet (standard chow plus 4% cholesterol/1% cholic acid), or an atherogenic diet supplemented with high doses of the antioxidants probucol and vitamin E. Rats fed the atherogenic diet developed hypercholesterolemia and a 56% increase in total kidney collagen compared with rats fed standard chow. In comparison, the hypercholesterolemic rats treated with antioxidants had normal levels of renal lipid peroxidation products and a normal kidney collagen content. In contrast, there were no significant differences in urinary albumin excretion rates or the number of interstitial macrophages between the two hypercholesterolemic groups. Compared with the untreated hypercholesterolemic group, antioxidant therapy induced significant reductions in renal mRNA levels for procollagen III (to 60% of untreated levels), collagen IV (60%), and TIMP-1 (20%), while uPA levels were significantly increased (to 210%). Paradoxically, antioxidant therapy was associated with a significant increase in renal TGF-beta 1 mRNA levels (to 150%), although TGF-beta 1 protein expression shifted from interstitial to tubular epithelial cells in predominance. The results of the present study demonstrate the efficiency of antioxidant therapy in preventing renal interstitial fibrosis in hypercholesterolemic rats with a single kidney. Based on changes in renal gene expression at the mRNA level, impaired matrix protein synthesis and increased intrarenal activity of the metalloproteinases and uPA/plasmin may play a role in the attenuation of fibrosis.

Interstitial inflammation and fibrosis in rats with diet-induced hypercholesterolemia

Abnormalities in lipid metabolism appear to play a pathogenic role in progressive renal disease. To elucidate the cellular and molecular basis of renal interstitial fibrosis in uninephrectomized rats with diet-induced hypercholesterolemia, we fed experimental rats with standard rat chow supplemented with 4% cholesterol and 1% cholic acid. Control rats were fed an isocaloric diet. Groups of 7 control and 7 experimental rats were killed after 4, 8, and 12 weeks. Hypercholesterolemic rats developed albuminuria; serum creatinine was elevated at 12 weeks. By 12 weeks numerous oil red O-positive cells were present throughout the interstitium and to a lesser extent in tubules. Total renal lipid-peroxidation products were significantly increased (172 +/- 15, 198 +/- 28, and 197 +/- 13 mmol malondialdehyde/kidney at 4, 8, and 12 weeks vs. 123 +/- 17, 144 +/- 6, and 125 +/- 10 mmol in controls). Immunostaining revealed oxidatively modified lipoproteins within tubular and interstitial cells. The interstitial disease was characterized by an interstitial infiltrate of monocytes. Significant increases were detected in renal cortical mRNA levels for monocyte chemoattractant protein-1 (MCP-1), osteopontin, and vascular cell adhesion molecule-1 (VCAM-1), associated with changes in the pattern of immunostaining for each encoded proteins. Total kidney collagen was significantly increased at 12 weeks (9.8 +/- 0.9 mg/kidney vs. 7.8 +/- 0.9 mg in controls). At 12 weeks there was a significant increase in interstitial immunostaining for collagen I, collagen III, collagen IV, fibronectin and tenascin. A significant threefold increase in renal cortical mRNA levels for transforming growth factor beta-1 (TGF-beta 1) at 4 and 12 weeks was associated with the appearance of TGF-beta 1-positive interstitial cells. Renal matrix protein mRNA levels were measured at 4, 8, and 12 weeks. The only statistically significant elevations were procollagen alpha 1(I) and procollagen alpha 1(III) at weeks 8 and 12. In contrast, renal cortical mRNA levels for the tissue inhibitor of metalloproteinases-1 (TIMP-1) were significantly increased at 4, 8 and 12 weeks (1.4 +/- 0.5, 2.7 +/- 0.9 and 2.7 +/- 1.4 arbitrary densitometric units, respectively, vs. 1.0 +/- 0.4, 1.0 +/- 0.5 and 1.0 +/- 0.4 units for controls), and urokinase-type plasminogen activator (muPA) mRNA levels were significantly decreased at 4, 8, and 12 weeks (0.4 +/- 0.1 arbitrary densitometric units for all three experimental groups vs. 1.0 +/- 0.4, 1.0 +/- 0.3, and 1.0 +/- 0.4 units for the control groups). In summary, rats with diet-induced hypercholesterolemia develop renal interstitial fibrosis over several weeks. Following the accumulation of lipids within tubulointerstitial cells, interstitial nephritis develops. The fibrotic phase is characterized by modest changes in matrix protein mRNA levels, up-regulated TIMP-1, and down-regulated muPA levels, suggesting that altered matrix degradation plays a role in the interstitial fibrogenesis in this model.

Increased frequency of apolipoprotein epsilon 2 allele in non-insulin dependent diabetic (NIDDM) patients with nephropathy

The genetic polymorphism of apolipoprotein E (epsilon 2, epsilon 3 and epsilon 4) is associated with lipid abnormalities. It has been suggested that lipid abnormalities may contribute to the development and progression of kidney diseases, including diabetic nephropathy. Thus, in this study we compared the apo E allele frequencies among 146 non-insulin-dependent diabetic (NIDDM) patients with nephropathy, 135 NIDDM patients without nephropathy and 576 of the general Japanese population. The epsilon 2 allele frequency was significantly higher in diabetic patients with nephropathy (7.2%) and with renal failure (9.7%) than in diabetic patients without nephropathy (2.6%) and in the general Japanese population (3.7%). It is concluded that there is a possibility that the epsilon 2 allele is associated with nephropathy in NIDDM.

Effects of pravastatin on lipid levels, in vitro oxidizability of non-HDL lipoproteins and microalbuminuria in IDDM patients

The effects of pravastatin on plasma lipid levels, in vitro oxidizability of the non-HDL fraction, metabolic control, urinary albumin excretion, and four serum enzymes (SGPT, SGOT, GT and CPK) were studied in 20 insulin-dependent diabetic patients (IDDM) with incipient nephropathy. The patients were divided into two groups and the study was carried out by a crossover design. After 12 weeks pravastatin treatment (20 mg daily), plasma cholesterol, LDL-cholesterol and apolipoprotein B (Apo B) decreased by 22, 19 and 15%, respectively. The thiobarbituric acid reactive substances (TBARS) formation and the oxidation lagtime of the non-HDL fraction during the in vitro incubation with copper were not changed before and after treatment. The HbA1c and blood glucose levels, urinary albumin excretion, SGOT, SGPT and GT were not influenced by pravastatin treatment. CPK activity was elevated after 12 weeks of pravastatin treatment, and this elevation persisted even after the 12 weeks placebo period. So, pravastatin could be used as an effective drug for IDDM patients with incipient nephropathy, but close monitoring of the CPK activity is recommended.

Acquired essential fatty acid depletion in the remnant kidney: amelioration with U-63557A

Previous studies have demonstrated an association between renal cortical fatty acid composition and experimental models of renal injury. The present study was designed to extend these observations to the remnant kidney and to investigate the hypothesis that increased endogenous turnover of arachidonic acid metabolites results in the depletion of progenitor fatty acids. Remnant kidney cortex demonstrated a relative reduction of the essential fatty acids, linoleate and arachidonate (20 +/- 7.2% and 11 +/- 0.3%, respectively), nine weeks after subtotal nephrectomy. In addition, the monounsaturated fatty acid, oleate, was increased (48 +/- 10.6%) while its saturated progenitor, stearate, was decreased (13 +/- 4.3%). Serial evaluation of dienoic prostanoids revealed a significant increase in the renal excretion of TXB2 in rats with remnant kidneys (27 +/- 3.0, 29 +/- 1.1, and 34 +/- 3.3 ng/day vs. 21 +/- 0.8, 20 +/- 1.5, and 22 +/- 3.3 ng/day in control rats, at 3, 6, and 9 weeks, respectively). Moreover, TXB2 excretion inversely correlated with dienoic progenitor fatty acids [18:2(n-6), r2 = 0.76; 20:4(n-6), r2 = 0.79], suggesting that these events are biochemically coupled. Endogenous turnover of precursor fatty acids, confirmed by an increase in renal TXB2 excretion, preceded overt depletion of essential fatty acids by several weeks. Importantly, blockade of endogenous synthesis of TXA2 with the specific TXA2 synthase antagonist, U-63557A, restored the essential fatty acid composition to normal and ameliorated progressive glomerular destruction. Moreover, the ancillary fatty acid disturbances were attenuated by administration of U-63557A.(ABSTRACT TRUNCATED AT 250 WORDS)

The combination of lovastatin and enalapril in a model of progressive renal disease

Puromycin-induced nephrotic syndrome is an animal model of progressive renal disease. Both angiotensin converting enzyme inhibitors and lipid-lowering agents have been used to preserve renal structure and function in this model, although neither completely prevents progression. We tested the hypothesis that the combination of the two agents would be more protective than either alone. Rats were divided into five groups; all were uninephrectomized. Four groups were given puromycin at a dose of 10 mg/100 g body weight (BW) with additional doses of 4 mg/100 g BW given intraperitoneally at 4, 5, and 6 weeks thereafter. One group was given enalapril (EN) 50 mg/l dissolved in the drinking water; the second received lovastatin (L) 15 mg/kg given daily by gavage; the third received both agents; the fourth was left untreated, and the final group received no puromycin and served as the control group. Eight weeks after the initial dose of puromycin, glomerular filtration rate (GFR), as inulin clearance, and protein excretion were determined and blood was collected for cholesterol and triglycerides. Blood pressure was not different between any of the groups. At the end of the study period, serum cholesterol [mean +/- SD, 252 +/- 185 mg/dl (L), 135 +/- 101 mg/dl (L + EN)] and triglycerides (239 +/- 200, 148 +/- 158 mg/dl) were significantly lower (P < 0.001) in the lovastatin-treated groups than in the untreated puromycin group (535 +/- 255 mg/dl and 579 +/- 561 mg/dl, cholesterol and triglyceride, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein E2, renal failure and lipid abnormalities in non-insulin-dependent diabetes mellitus

The association of apolipoprotein E (apo E) genetic polymorphism, particularly apo E2, with renal failure (plasma creatinine > or = 1.4 mg/dl, and urinary albumin excretion index > or = 300 mg/g.creatinine and/or persistent proteinuria) was investigated in 57 non-insulin-dependent diabetic (NIDDM) patients. Apo E2 allele frequency was significantly higher in diabetic patients with renal failure (9.6%) than in diabetic patients without renal failure (3.2%) and in the general Japanese population (3.7%). This finding suggests that apo E2 is associated with renal failure in NIDDM. In addition, to elucidate the association of apo E2 with lipid abnormalities, plasma lipid and lipoprotein levels were compared among the apo E2 (E2/2 and E3/2) and E3/3 groups of NIDDM with renal failure (n = 27) and the apo E2 (E3/2) and E3/3 groups of NIDDM with normoalbuminuria (n = 34). In diabetic patients, the apo E2 group with renal failure had significantly higher levels of plasma total cholesterol (T-chol), very-low-density lipoprotein (VLDL)-chol, triglyceride (TG), VLDL-TG and apo E than the apo E3/3 group with renal failure, and had significantly higher levels of plasma T-chol, VLDL-chol, TG and VLDL-TG than the apo E2 and E3/3 groups with normoalbuminuria. Furthermore, the apo E2 group with renal failure had significantly higher ratios of VLDL-(chol/TG) and VLDL-chol/TG (an index of remnants in plasma) than the apo E3/3 group with renal failure and the apo E2 and E3/3 groups with normoalbuminuria. These results suggest that apo E2 leads to the accumulation of TG-rich lipoprotein and remnants in plasma. It is concluded that apo E2 is associated with renal insufficiency in NIDDM and that apo E2 may be a factor that aggravates lipid abnormalities in NIDDM with renal failure.

Effect of chronic cholesterol loading in the development of acute ischemic renal failure in rats

The effect of chronic cholesterol loading and lovastatin administration in renal artery clamping acute renal failure in rats is not known. Acute renal failure was induced by 60-min left renal artery clamping immediately after right nephrectomy. The changes in renal function after renal artery clamping in the hyperlipidemic rats were unexpected. The acute renal failure in the cholesterol-loaded groups was less severe than in the nonhyperlipidemic rats. The lovastatin administration had some favorable effect on renal function after ischemia; however, this effect was not additive to the high dietary cholesterol administration. Our results seems to favor the concept that in this special form of experimental renal ischemic acute renal failure, serum cholesterol levels, elevated through diet, may have protective effects with respect to renal tubular lesions during or following the acute ischemic insult.

Cholesterol: a renal risk factor in diabetic nephropathy?

In a prospective follow-up of 30 patients with type 1 diabetes and nephropathy, serum cholesterol, triglycerides, apolipoprotein Al and B, and lipoprotein(a) were determined to study their relationship to the rate of decline in glomerular filtration rate. The patients had proteinuria and advanced nephropathy with a mean +/- SD glomerular filtration rate of 39 mL/min/1.73 m2. The decline in glomerular filtration rate was determined during 2.5 +/- 0.5 years. High serum cholesterol, triglycerides, and apolipoprotein B were correlated to a more rapid deterioration in kidney function. The rate of decline in glomerular filtration rate was 1.0 +/- 2.5 mL/min/yr in the 10 patients with the lowest cholesterol level, compared with 4.5 +/- 3.2 mL/min/yr in the patients with the highest serum cholesterol (P = 0.015). The combined effect of the measured lipids, blood pressure, type of antihypertensive treatment, protein intake, proteinuria, and hemoglobin A1C on the rate of decline in glomerular filtration rate was assessed by multiple regression analysis. The measured factors together had a high explanatory power for the rate of decline in glomerular filtration rate. In this model, 73% of the variation in decline in glomerular filtration rate was explained by the measured variables (multiple r2 = 0.73). Low cholesterol and treatment with an angiotensin-converting enzyme inhibitor were the strongest predictors of a favorable renal prognosis. This suggests that hypercholesterolemia is an important risk factor for diabetic nephropathy.

Hypertension, hyperlipidemia, and renal damage

Experimental studies have demonstrated that a number of factors participate in the progression of renal disease. Systemic and glomerular hypertension have been shown to be critical factors in renal injury. Hyperlipidemia that frequently coexists with renal disease also has been suggested as an important participatory factor in nephron damage. Interestingly, both hypertension and hyperlipidemia seem to evoke glomerular growth, a factor that has also been postulated to be involved in glomerular and tubular destruction. Recently, experimental and clinical data suggest that an important interaction occurs between hyperlipidemia and hypertension. Not only do they frequently coexist, but hypertension dramatically exaggerates hyperlipidemic injury, and hyperlipidemia alters systemic and glomerular vascular production of vasoactive substances which maintain basal vascular tone. Thus, these recent observations underscore the interactive potential of the various risk factors that participate in progression of renal disease. They also suggest that multiple interventional strategies may be needed to optimally prevent progressive nephron loss.

In vivo NMR imaging and spectroscopic investigation of renal pathology in lean and obese rat kidneys

Diabetic nephropathy is a major cause of end-stage renal failure. While our understanding of the pathogenesis of nephropathy is incomplete, progressive glomerular injury appears to play a significant role in the decline of renal function. Proton NMR spectroscopy and imaging techniques were used to address changes in renal pathology associated with glomerular mesangial expansion in vivo in kidneys from spontaneously obese and lean (control) littermate Zucker rats. Fully functioning rat kidneys were surgically exposed and externalized for direct NMR signal detection via a coil placed around the organ. High-resolution (78 microns in plane) proton images were obtained at 4.7 T magnetic field strength revealing fine structure within the well-defined cortical and medullary regions. The obese rat kidney images were distinct in appearance from the lean kidney images and exhibited marked cortical expansion as well as increased overall kidney size. Enlargement of mean glomerular diameter was verified histologically in the obese kidneys as compared with the lean kidneys. Proton T1 and T2 relaxation times were determined from the entire kidney using standard spectroscopic techniques, and from specific regions within the kidney from multiple T1- and T-2 weighted images. Additionally, image contrast enhancement resulting from saturation transfer between protons in restricted-mobility environments and mobile water protons within the kidney was investigated in the lean and obese rat kidneys using magnetization-transfer imaging techniques. At the early stage of renal injury examined in this study, diseased and healthy kidneys could not be differentiated on the basis of relaxation times alone. The magnitude of saturation transfer obtained in cortical tissue in the lean and obese kidneys was also not statistically significantly different. However, the magnitude of saturation transfer achieved in the medullary tissue of obese kidneys was statistically significantly less than that achieved in lean kidneys.

Interactions of LDL and modified LDL with mesangial cells and matrix

Hyperlipidemia may play a role in the progression of diabetic and other renal diseases. Low density lipoprotein (LDL) and other proteins including extracellular matrix components undergo nonenzymatic glycation in vivo. We examined the effects of glycation of LDL as occurs in diabetes (4 to 8%) on binding and uptake by mesangial cells and their proliferation. The glycation of LDL (g-LDL) significantly decreased its binding and uptake by mesangial cells by 15 to 20%, indicating that glycated LDL binds to the LDL receptor, but with lower affinity than LDL. Both LDL and g-LDL modestly stimulated [3H] thymidine incorporation into mesangial cells at 5 to 10 micrograms/ml. Native, oxidized (Ox-LDL) and glycated LDL all bound to the extracellular matrix generated by rat mesangial cells in culture. The binding of LDL, Ox-LDL and g-LDL to mesangial matrix was two to four times higher than to mesangial cells. Binding of LDL and g-LDL was significantly higher to glycolaldehyde modified matrix, which serves as an in vitro model for nonenzymatic glycation end-product cross-linking of matrix which occurs in long-standing diabetes. Based on these findings, we propose that glycation of LDL decreases its binding and uptake by the LDL receptor of mesangial cells and may slow its catabolism. Furthermore, LDL bound to extracellular mesangial matrix can undergo oxidation and generate cytotoxic LDL components. This process may be further enhanced by advanced glycation of the mesangial matrix in diabetes, contributing to glomerular pathology.

Plasma lipoproteins and renal function during simvastatin treatment in diabetic nephropathy

The aim of this study was to assess the effect of simvastatin on plasma lipoproteins and renal function in hypercholesterolaemic Type 1 (insulin-dependent) diabetic patients with diabetic nephropathy. Twenty-six hypercholesterolaemic (total cholesterol greater than or equal to 5.5 mmol/l) Type 1 diabetic patients with nephropathy were enrolled in a double-blind randomized placebo-controlled study for 12 weeks. The active treatment group (n = 14) received simvastatin (10-20 mg/day) for 12 weeks while the remaining 12 patients received treatment with placebo. The results during simvastatin treatment (baseline vs 12 weeks): total cholesterol 6.6 vs 4.8 mmol/l (p less than 0.01), LDL-cholesterol 4.25 vs 2.57 mmol/l (p less than 0.01) and apolipoprotein B 1.37 vs 1.06 mmol/l (p less than 0.01). HDL-cholesterol, and apolipoprotein A-I remained unchanged. Total cholesterol, LDL-cholesterol, HDL-cholesterol, apolipoprotein A-I, apolipoprotein B remained unchanged during placebo treatment. Albuminuria measured during the simvastatin and the placebo treatment (baseline vs 12 weeks) (the data are logarithmically transformed before analysis because of their positively skewed transformation; geometric mean (x/divided by antilog SE) is indicated) was 458 (x/divided by 1.58) vs 393 (x/divided by 1.61) and 481 (x/divided by 1.62) vs 368 (x/divided by 1.78 micrograms/min (NS). Glomerular filtration rate during simvastatin and placebo treatment (baseline vs 12 weeks) was 64 vs 63 and 72 vs 74 ml.min-1.1.73 m-2, respectively. Two patients receiving simvastatin treatment were withdrawn, one due to gastrointestinal side effects and one due to myalgia.(ABSTRACT TRUNCATED AT 250 WORDS)

Impact of dietary fatty acid supplementation on renal injury in obese Zucker rats

We previously reported that renal injury in hyperlipidemic, obese Zucker rats was associated with a relative deficiency of tissue polyunsaturated fatty acids (PUFA). In the present study 10-week-old obese Zucker rats were pair fed regular chow or chow containing either 20% sunflower oil rich in n-6 PUFA, fish oil rich in n-3 PUFA, coconut oil medium-chain saturated fatty acid, or beef tallow long-chain saturated fatty acid. At 34 weeks of age there were comparable reductions in albuminuria, mesangial matrix expansion, and glomerulosclerosis in the fish oil and sunflower oil groups. While both fish oil and sunflower oil reduced serum triglycerides, and improved the composition of triglyceride-enriched lipoproteins, only fish oil decreased serum cholesterol. The effect of the dietary fatty acid supplementation on fatty acid profiles were similar in isolated glomeruli and cortical tissue. In general, the amelioration in injury in the fish oil and sunflower oil fed rats was most closely linked to glomerular levels of PUFA, either n-6 or n-3. These data suggest that hyperlipidemia and abnormalities in tissue FA are closely linked, and that dietary supplementation with PUFA may ameliorate chronic, progressive renal injury.

Effects of dietary fatty acids in an animal model of focal glomerulosclerosis

The obese Zucker rat develops hyperlipidemia, proteinuria and focal glomerulosclerosis without prior changes in renal hemodynamics. To study the effects of oral fatty acid intake on the development of renal injury in this model, rats were fed standard chow or chow supplemented with either 14% fish oil or 14% beef tallow after unilateral nephrectomy at the age of 10 weeks. At 32 weeks post-nephrectomy animals were sacrificed and renal tissue saved to assess histology and glomerular eicosanoid production. Fish-oil treated rats had lower mean plasma cholesterol levels and developed less proteinuria than control or tallow-fed animals although there was no difference in plasma creatinine or blood pressure. Histological analysis showed significantly fewer sclerosed glomeruli in the fish oil group (4.0 +/- 0.8% vs. control 19.4 +/- 4.1%, P less than 0.0005 and vs. beef tallow 10.8 +/- 1.9%, P less than 0.005). Glomeruli derived from rats on fish oil supplements produced smaller amounts of prostaglandin (PG)E2 and of the stable metabolites of PGI2 (6-oxo-PGF1 alpha), PGF2 (PGF2 alpha) and thromboxane (TX)A2 (TXB2) than those from tallow-fed animals. This study demonstrates that oral fatty acid intake may influence the development of glomerulosclerosis. The apparent beneficial effects of fish oil have not been fully defined, but may relate to favorable changes in plasma lipid concentration and renal eicosanoid production.

On the natural tendency to progressive loss of remaining kidney function in patients with impaired renal function

Patients who lose more than 50% of their functioning renal mass are at risk to develop progressive deterioration of their remaining kidney function, even though the process that caused the original loss of kidney function may no longer be present. The glomerular capillary hyperperfusion, hypertension, and hyperfiltration that occur in the surviving nephrons may play an important role in the natural tendency for renal function to deteriorate. Nevertheless, recent studies suggest that these glomerular hemodynamic events may not be the final common pathway for the natural deterioration of renal function, as was once thought. With regard to the general management of patients with impaired renal function, recent evidence suggests that controlling systemic blood pressure, reducing dietary protein and phosphorus intake, and controlling hyperlipidemia may be effective in slowing the loss of renal function.

Renal injury of diet-induced hypercholesterolemia in rats

Abnormalities in lipid metabolism frequently accompany renal disease and may be important in the pathogenesis of progressive renal injury. In the present study, the effects of a high cholesterol diet on renal histology, cortical lipids, and glomerular hemodynamic function were examined in normal rats with and without reduced renal mass. Cholesterol feeding for 19 weeks increased serum cholesterol from 66 +/- 10 mg/dl to 256 +/- 93 mg/dl in two-kidney rats, and from 73 +/- 15 mg/dl to 407 +/- 274 mg/dl in nephrectomy rats (P less than 0.01). Both sham-operated and unilateral nephrectomy rats fed a high cholesterol diet had a greater amount of glomerulosclerosis and tubulointerstitial damage than rats fed standard chow. Cortical cholesteryl esters were increased by the cholesterol diet, and correlated with the amount of glomerulosclerosis (r = 0.90, P less than 0.01) and tubulointerstitial injury (r = 0.64, P less than 0.05). Cholesterol feeding and nephrectomy both caused alterations in tissue essential fatty acids, and a panel of specific monoclonal antibodies indicated that renal injury and cortical lipid alterations were associated with an increase in glomerular macrophages. Finally, micropuncture experiments carried out in a separate group of rats fed high cholesterol for 8 to 10 weeks demonstrated increases in glomerular capillary pressure. These results suggest that additional investigations may ultimately determine how cholesterol deposition, altered fatty acid metabolism, macrophages, and increased glomerular pressure might combine to cause chronic progressive renal injury.

Circadian assessment of lipids in the hyperphagic obese rat compared with lean litter-mates

Time and feeding influences on cholesterol, triglyceride, glucose and insulin levels, and serum cholinesterase activity were assessed in a genetically-hyperlipidemic hyperphagic obese rat model, and compared with its lean litter-mate. Following a 28-day acclimation to a 12-hr light/dark cycle, blood samples were obtained every 2 hr from rats via tail bleed for a 24-hr period. Synchronization with other animal studies was established by endogenous serum cortisol levels [acrophase 18-20 hr after light onset (HALO) in both groups]. Triglycerides cholesterol, insulin and glucose levels were significantly elevated in obese versus lean rats. Obese rats were observed to feed throughout the 24-hr cycle, whereas lean litter-mates ate only during the dark cycle. No circadian rhythmicity was found in glucose levels with either rat group. Insulin levels were not correlated. Although triglyceride levels peaks at 13 HALO in lean rats, no pattern was observed in obese rats. Cholesterol levels were unchanged with time in either group. Cholinesterase activity followed a circadian rhythm in the lean, but not obese, rats with an acrophase estimated at 8 HALO. In contrast to previous reports, enzyme activity was not correlated with triglyceride levels in either rat group. Circadian similarities in insulin levels between rat groups suggest changes in insulin metabolism and/or secretion which are likely to be independent of feeding or activity. Conversely, triglyceride levels remained elevated throughout the 24-hr period in obese rats, whereas significant increases were observed in lean rats during the dark active cycle. These data suggest that triglyceride levels, and not insulin and cholesterol levels, are most likely dependent on feeding patterns.