Effects of exogenous homocysteine on cellular proliferation and extracellular matrix production in cultured rat mesangial cells

SUMMARY: Homocysteine (HCY) is a thiol‐containing amino acid produced as a result of the demethylation of methionine. It has been proved that elevated HCY is associated with a high risk of arteriosclerotic cardiovascular disease. Although hyperhomocysteinaemia is observed frequently in patients with end‐stage renal disease, its role in the process of glomerulosclerosis is not clear. This study investigated the effects of exogenous HCY on proliferation, phenotype change and extracellular matrix production in rat mesangial cells (MCs). The results revealed that DNA synthesis in MCs, measured by the [³H]‐thymidine uptake, did not increase significantly when the cells were treated with HCY at concentrations of 5 × 10^?5, 5 × 10^?4 or 1 × 10^?3 mol/L, even though thymidine incorporation in MCs increased two‐ to fourfold using 20% fetal calf serum‐RPMI medium or platelet‐derived growth factor (20 ng/mL). A dose‐dependent increase in thymidine incorporation in vascular smooth muscle cells was also found when these cells were treated with HCY at similar concentrations (P < 0.01). The cell cycle was not changed when MCs were stimulated by HCY at different doses (5 × 10^?5, 5 × 10^?4 and 1 × 10^?3 mol/L) or at different time points (24, 48 and 72 h). Additionally, increased extracellular signal‐regulated kinase was observed in MCs induced by PDGF (10 ng/mL), but not by HCY (0.5 mmol/L) for 2–60 min. α‐Smooth muscle actin, detected using Western blot analysis, was not changed when MCs were exposed to 0.5 mmol/L HCY for 6, 12, 18, 24 and 36 h. Fibronectin and laminin, which are detected in the supernatant of cultured MCs by inhibition enzyme‐linked immunosorbent assay, were not changed when MCs were exposed to HCY (5 × 10^?4 mol/L) for 2, 4, 6 or 8 days. These results suggest that HCY has no effect on proliferation, phenotype change or extracellular matrix production in MCs. This indicates that HCY may not be a key factor contributing to the process of glomerulosclerosis.     

半胱氨酸蛋白酶抑制剂C对肝硬化患者肾功能早期损害的实验评价

目的探讨血清半胱氨酸蛋白酶抑制剂C(Cys C)对肝硬化患者肾功能早期损害的诊断价值。方法测定67例肝硬化患者和32名健康对照者的血清肌酐(Cr)、尿素(Urea)、肌酐清除率(Ccr)和Cys C水平,并将患者按性别、Ch ild-Pugh分级或Ccr水平进行分组评价。结果肝硬化患者血清Ccr和Cys C水平与对照组比较差异有显著性(P<0.001),但Cr和Urea差异无显著性。不同性别患者Ccr、Cr和Cys C水平与对照组比较差异有显著性(P<0.05~0.001),但Urea无差异。肝硬化患者Ch ild-Pugh分级各亚组Ccr、Cr、Urea和Cys C水平与健康对照组比较差异有显著性(P<0.05~0.001)。以Ccr 70 m l/m in为界点将患者分为Ⅰ和Ⅱ亚组,并与对照组比较,结果表明仅Cys C水平差异有显著性(P<0.001),Cys C水平Ⅰ和Ⅱ2亚组间差异也有显著性(P<0.001)。受试者工作特征曲线(ROC曲线)显示Cys C诊断有效性优于Cr和Urea。结论血清Cr和Urea难以对肝硬化患者肾功能轻度受损进行诊断,Ccr虽能作出早期指示,却过高估计试验结果,而Cys C能较准确地作出早期检测,提示其可能是潜在的肝硬化患者肾功能早期损害的指标。     

Ambulatory Blood Pressure in Patients with Mesangial Proliferative Glomerulonephritis

Twenty-four-hour ambulatory blood pressure was measured in seven normotensive and 10 hypertensive patients with biopsy proven mesangial proliferative glomerulonephritis (MPG). In normotensive patients, the nocturnal blood pressure variation was seen with a nightly drop in blood pressure while in hypertensive patients with MPG, 24-h blood pressure level was increased both at day- and night-time, but a nocturnal change in blood pressure was also observed in these patients. The pattern of blood pressure variation was not, however, different from the normotensive patients. None of the hypertensive patients with MPG was a so-called non-dipper, showing the same level of blood pressure both at day- and night-time. The hypertensive patients had a rapid increase in blood pressure in the early morning hours from 06.00 to 09.00 h, followed by a relatively abrupt decrease in blood pressure in the evening hours. The patients with high blood pressure were treated with antihypertensive drugs; all patients started with captopril 25 mg once a day, later increasing to twice daily. If the correction of the high blood pressure was not achieved with this drug, amlodipine 5 or 10 mg was added with or without furosemide. Most of the patients needed more than one drug. In all patients, a normal 24-h ambulatory blood pressure could be obtained. The lack of nightly non-dippers in the present hypertensive patients may be explained by a relatively short history of renal disease and the presence of normal or moderately reduced glomerular filtration rate. The abrupt rise in blood pressure during the early morning hours may be due to activation of the renin-angiotensin or sympathetic nervous system in the hypertensive patients with MPG.     

The kidney of spiny mice (Acomys cahirinus): Electron microscopy of glomerular changes associated with ageing and tubular glycogen accumulation during hyperglycemia

Summary Glomeruli and tubules of the kidney of normoglycemic and diabetic spiny mice were studied with the electron microscope. Progressive thickening of the basement membranes of glomerular capillaries with a concomitant increase in the deposition of basement-membrane-like mesangial matrix occurred with age. Focal hemispherical thickenings of the basement membrane on its epithelial side were observed with increasing frequency in older animals. The plasma membrane of adjacent foot processes exhibited features suggestive of pinocytosis. Collagen fibers in electronlucent areas surrounded by mesangial matrix were regularly seen in animals beyond the age of twelve months. In diabetic animals, the alterations of the glomerular capillary basement membranes and of the mesangial region appeared to be more pronounced but no specific lesions were observed. This negative finding may be related to the relatively short duration of the diabetic state. Measurements of the thickness of glomerular capillary basement membranes showed a significant age-dependent increase in basement membrane width and indicated that this process may be accelerated in diabetic animals. Examination of the renal tubules of diabetic animals showed a characteristic segmental pattern of glycogen storage in epithelial cells with considerable variations in the degree of glycogen infiltration between different segments but also between individual cells of a given segment. The most surprising feature associated with glycogen storage was the occurrence of lysosomes filled with glycogen. The mechanisms responsible for the accumulation of glycogen within lysosomes are unknown but may be related to an increase in glycogen turnover in cells actively involved in the reabsorption of glucose or to an impairment of lysosomal function secondary to diabetes.Supported in part by the Fonds National Suisse de la Recherche Scientifique, Berne, Switzerland (Grants No. 5344 and 4848.3), and by a grant-in-aid through Zyma S.A., Nyon, Switzerland.     

Cystatin C blood level as a risk factor for death after heart surgery.

AIMS: Pre-operative renal dysfunction is a known risk factor for mortality and morbidity after heart surgery. Despite limited accuracy, serum creatinine is widely used to estimate glomerular filtration rate (GFR). Cystatin C is more accurate for assessing GFR. The aim of the present study was to assess associations between GFR estimated from serum cystatin C levels before heart surgery and hospital mortality, hospital morbidity, and 1 year mortality. METHODS AND RESULTS: In a prospective single-centre observational study, clinical risk factors for morbidity and mortality were recorded and serum creatinine and cystatin C levels were measured in patients admitted for heart surgery. Hospital mortality and morbidity and 1 year mortality were recorded. Over an 8 month period, 499 patients were screened, among whom 376 (74.5%) were included in the study. Hospital mortality was 5.6% (21 patients) and 1 year mortality was 10.2%. Hospital morbidity, defined by a length of stay above the 75th percentile, was 22.1% (83 patients). In the multivariable analysis, GFR estimated from serum cystatin C, but not GFR estimated from serum creatinine, was an independent risk factor for hospital morbidity/mortality (odds ratio per 10 mL/min of GFR decrease, 1.20 (1.07-1.34), P = 0.001) and for 1 year mortality (hazards ratio per 10 mL/min of GFR decrease, 1.26 (1.09-1.46), P = 0.002). CONCLUSION: Pre-operative GFR estimation from serum cystatin C may provide a better risk assessment than pre-operative GFR estimation from serum creatinine in patients scheduled for heart surgery.     

Association analysis of podocyte slit diaphragm genes as candidates for diabetic nephropathy

Aims/hypothesis The slit diaphragm is an adhesion and signalling protein complex linking the interdigitating podocyte foot processes in the kidney glomerulus, and mutations in slit diaphragm-associated genes result in severe proteinuria. Here we report a genetic association analysis of four slit diaphragm genes, LRRC7, KIRREL, NPHS2 and ACTN4, in a Finnish diabetic nephropathy cohort. Materials and methods A total of 40 single nucleotide polymorphisms (SNPs) were genotyped in 1103 patients with type 1 diabetes. The patients were classified according to their renal status, and the genotype data were analysed in a cross-sectional case–control setting. To confirm positive associations, four SNPs were genotyped in 1,025 additional patients with type 1 diabetes. Results No associations with diabetic nephropathy were observed for any of the analysed SNPs. The SNPs were not associated with the time from the onset of diabetes to the diagnosis of nephropathy or with glomerular filtration rate or AER as quantitative variables. In a sex-specific sub-analysis, the variants rs979972 and rs749701 in the first intron of ACTN4 were nominally associated with diabetic nephropathy in females, with odds ratios of 1.81 (95% CI 1.18–2.79, p = 0.007) and 1.93 (95% CI 1.26–2.96, p = 0.003) respectively. Conclusions/interpretation Our study has not found any evidence that common variants in LRRC7, KIRREL, NPHS2 and ACTN4 contribute to susceptibility to diabetic nephropathy in Finnish patients with type 1 diabetes. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

Relationship of renal size to nephropathy in Type 1 (insulin-dependent) diabetes

Summary Thirty-five patients with Type 1 (insulin-dependent) diabetes mellitus and 90 normal subjects had renal size (renal area index) determined by X-ray and also had examination of renal biopsies by light and electron microscopy. Renal area index of 206±32 cm²/1.73 m² (mean±SD) in the Type 1 diabetic patients exceeded that in the normal subjects (180±25 cm²/1.73 m², p<0.001). In the diabetic patients, the renal area index correlated with creatinine clearance (r=+0.43, p<0.05), but did not correlate with urinary albumin excretion, or the electron microscopic measurements of percentage total mesangium and glomerular basement membrane width. In diabetic patients with clinical nephropathy or severe glomerulopathy on biopsy, the kidneys may remain large. Thus, renal size does not indicate the severity of diabetic renal lesions on biopsy.     

Independance of glucagon and insulin handling by the isolated perfused dog kidney

Summary The effect of raising arterial plasma glucagon concentrations on kidney glucagon uptake was investigated using an isolated dog kidney perfused with whole blood. In addition, the effect of insulin on the magnitude of glucagon uptake by the kidney was studied at various glucagon concentrations. Renal vein plasma glucagon (V) has been found to be proportional to renal artery plasma glucagon (A). V and A were highly significantly correlated. In the absence of exogenous insulin infusion, V equalled 0.733±0.034 A, while in the presence of insulin V equalled 0.747±0.015 A. When kidney glucagon uptake was measured directly it increased as a function of arterial plasma glucagon. The calculated regression lines were similar in the presence and in the absence of insulin. The mean clearance rate of glucagon by the kidney was similar at low, medium or high concentrations of glucagon and was not affected by the presence of insulin at a mean concentration of 335.7±15.7 U/ml. At this concentration of insulin, kidney insulin uptake was not affected by glucagon at concentrations ranging from 32 to 1600 pg/ml. Comparison of kidney glucagon uptake at similar arterial plasma glucagon concentrations, but with different renal plasma flows, indicated that kidney glucagon uptake is more dependant on arterial plasma glucagon concentration than on the quantity of glucagon entering the kidney per minute. It is concluded that: 1) kidney glucagon uptake increases as a function of arterial plasma glucagon concentration; 2) the clearance rate of glucagon is similar at low, medium or high arterial concentrations of glucagon; 3) at concentration of 300–350 U/ml, insulin does not affect kidney glucagon uptake, and 4) at concentrations of glucagon up to 1600 pg/ml, renal insulin uptake is not affected by glucagon. These studies indicate that insulin and glucagon are handled independantly by the kidney of the dog.     

A copper(II)-selective chelator ameliorates diabetes-evoked renal fibrosis and albuminuria, and suppresses pathogenic TGF-β activation in the kidneys of rats used as a model of diabetes

AIMS/HYPOTHESIS: The selective Cu(II) chelator triethylenetetramine (TETA) extracts systemic Cu(II) into the urine of diabetic humans and rats as a model of diabetes, and in the process also normalises hallmarks of diabetic heart disease. However, the role of Cu and its response to TETA in animals with diabetic nephropathy were previously unknown. Here, we report the effects of TETA treatment on Cu and other essential elements, as well as on indices of renal injury and known pathogenic molecular processes, in kidneys from a rat model of diabetes. METHODS: Rats at 8 weeks after streptozotocin-induction of diabetes were treated with oral TETA (34 mg/day in drinking water) for a further 8 weeks and then compared with untreated diabetic control animals. RESULTS: Renal tissue Cu was substantively elevated by diabetes and normalised by TETA, which also suppressed whole-kidney and glomerular hypertrophy without lowering blood glucose. The urinary albumin: creatinine ratio was significantly elevated in the rat model of diabetes but lowered by TETA. Total collagen was also elevated in diabetic kidneys and significantly improved by TETA. Furthermore, renal cortex levels of TGF-beta1, MAD homologue (SMAD) 4, phosphorylated SMAD2, fibronectin-1, collagen-III, collagen-IV, plasminogen activator inhibitor-1 and semicarbazide-sensitive amine oxidase all tended to be elevated in diabetes and normalised by TETA. CONCLUSIONS/INTERPRETATION: Dysregulation of renal Cu homeostasis may be a key event eliciting development of diabetic nephropathy. Selective Cu(II) chelation can protect against pathogenic mechanisms that lead to or cause diabetic nephropathy and might be clinically useful in the treatment of early-stage diabetic kidney disease.     

Is serum cystatin-C a reliable marker for metabolic syndrome?

Purpose

Chronic kidney disease and metabolic syndrome are recognized as major cardiovascular risk factors. It has been shown that cystatin C has a stronger association with mortality risk than creatinine-based estimations of glomerular filtration rate. We measured cystatin values in dyslipidemic patients and looked for correlations between renal function, cystatin, and metabolic syndrome.

Methods

There were 925 dyslipidemic patients prospectively included in this cross-sectional study and evaluated over 10 months. Each visit included clinical and biological assessment.

Results

Most patients exhibited cardiovascular risk factors other than dyslipidemia: hypertension in 34%, diabetes in 11%, and smoking in 18%. Mean triglycerides were 149 ± 136 mg/dL, mean high-density lipoprotein cholesterol 54 ± 14 mg/dL, and low-density lipoprotein 167 ± 48 mg/dL. Metabolic syndrome was present in 238 (26%) patients. Plasma creatinine did not differ between control group and metabolic syndrome patients (80 ± 26 vs 82 ± 20 μmol/L, respectively, P = .2), but creatinine clearance evaluated by abbreviated Modification of Diet in Renal Disease Study formula was lower in the metabolic syndrome group than in the non-metabolic-syndrome group (83.3 ± 18.8 mL/min/1.73m² vs 86.8 ± 16.9 mL/min/1.73m², respectively, P <.007). Cystatin value was significantly higher in metabolic syndrome patients than in others (0.86 ± 0.23 vs 0.79 ± 0.20 mg/L, respectively, P <.0001), independently of serum creatinine level and creatinine clearance. Furthermore, there was a progressive increase in cystatin, as a function of the number of metabolic syndrome components.

Conclusions

Our study shows that cystatin is associated with metabolic syndrome in dyslipidemic patients. Cystatin may be an interesting marker of metabolic syndrome and of increased cardiovascular and renal risk.