Lipoprotein(a) serum concentrations and apolipoprotein(a) phenotypes in mild and moderate renal failure

Lipid changes and statins in chronic renal insufficiency

It has been known for a long time that chronic kidney disease (CKD) is associated with dyslipidemia, but the full extent of abnormalities has been appreciated only recently, because routine laboratory tests fail to disclose the entire spectrum of lipid abnormalities. Lipids, particularly HDL cholesterol, are predictive of cardiovascular events, but a paradoxic inverse relation between cholesterol concentration and cardiovascular death has been noted in uremic patients. This currently is thought to be explained by the confounding effect of microinflammation and possibly calcification, but this is not definitely proved. Several retrospective analyses that included patients with mild or moderate CKD documented benefit from lowering of cholesterol by statins. In contrast, the Die Deutsche Diabetes Dialyse (4D) study and a small Scandinavian study failed to show a benefit from lowering of cholesterol by statins in ESRD. Pathomechanistically, it is possible that nonclassical pathomechanisms override statin-sensitive mechanisms as also suggested by the observation that statins fail to reduce carotid intima-media thickening. Although, experimentally, exposure to lipids (particularly oxidized lipids) aggravates progression, data on the effect of statins on progression in patients with CKD are not definite. The most likely explanation is that the impact of numerous confounders obscures their effect on progression. The increase in urinary protein excretion of patients who are treated with statins had been a cause of concern, but the underlying mechanism (i.e. interference with proximal tubular reabsorption of protein) meanwhile has been well documented.

Statin therapy is associated with improved outcomes in vascular surgery patients with renal impairment

BACKGROUND

Little is known about the association between baseline kidney function, statin therapy, and outcome after vascular surgery in patients with and without chronic kidney disease.

METHODS

A total of 2126 patients underwent elective major vascular surgery and were divided into 2 categories based on baseline creatinine clearance (CrCl), calculated using the Cockcroft-Gault equation: CrCl > or = 60 mL/min (n = 1358, reference) and CrCl < 60 mL/min (n = 768). Outcome measures were 30-day and long-term all-cause, cardiac, and cerebrocardiovascular mortality. Mean follow-up was 6.0 +/- 3.7 years. Multivariate Cox regression analysis, including potential confounders and propensity score for statin use, was applied. Data are presented as hazard ratios (HRs) with 95% CI.

RESULTS

Thirty-day all-cause, cardiac, and cerebrocardiovascular mortality rates were 3.8% versus 10.2%, 1.3% versus 4.2%, and 2.7% versus 7.8%, respectively, according to the 2 categories of kidney function. In addition, long-term all-cause, cardiac, and cerebrocardiovascular mortality rates were 46.6% versus 72.5%, 14.6% versus 26.4%, and 23.0% versus 40.6%, respectively. Statin therapy was associated with an overall significant improved 30-day and long-term all-cause mortality, independent of other important confounders. However, in patients with a CrCl > or = 60 mL/min, the long-term cardiac and cerebrocardiovascular beneficial effects did not reach statistical significance (HR 0.93, 95% CI 0.61-1.41 and HR 0.89, 95% CI 0.63-1.24, respectively) when compared with patients with a CrCl of < 60 mL/min (HR 0.63, 95% CI 0.41-0.96 and HR 0.67, 95% CI 0.48-0.94, respectively).

CONCLUSIONS

The level of kidney function is an independent predictor of short- and long-term outcome after major noncardiac surgery. In addition, perioperative statin use in patients with kidney disease is associated with a reduction in the short- and long-term all-cause, cardiac, and cerebrocardiovascular mortality.

Renal function and risk of coronary heart disease in general populations: new prospective study and systematic review

BACKGROUND

End-stage chronic kidney disease is associated with striking excesses of cardiovascular mortality, but it is uncertain to what extent renal function is related to risk of subsequent coronary heart disease (CHD) in apparently healthy adults. This study aims to quantify the association of markers of renal function with CHD risk in essentially general populations.

METHODS AND FINDINGS

Estimated glomerular filtration rate (eGFR) was calculated using standard prediction equations based on serum creatinine measurements made in 2,007 patients diagnosed with nonfatal myocardial infarction or coronary death during follow-up and in 3,869 people without CHD in the Reykjavik population-based cohort of 18,569 individuals. There were small and nonsignificant odds ratios (ORs) for CHD risk over most of the range in eGFR, except in the lowest category of the lowest fifth (corresponding to values of <60 ml/min/1.73 m2), in which the OR was 1.33 (95% confidence interval 1.01-1.75) after adjustment for several established cardiovascular risk factors. Findings from the Reykjavik study were reinforced by a meta-analysis of six previous reports (identified in electronic and other databases) involving a total of 4,720 incident CHD cases (including Reykjavik), which yielded a combined risk ratio of 1.41 (95% confidence interval 1.19-1.68) in individuals with baseline eGFR less than 60 ml/min/1.73 m2 compared with those with higher values.

CONCLUSIONS

Although there are no strong associations between lower-than-average eGFR and CHD risk in apparently healthy adults over most of the range in renal function, there may be a moderate increase in CHD risk associated with very low eGFR (i.e., renal dysfunction) in the general population. These findings could have implications for the further understanding of CHD and targeting cardioprotective interventions.

Evidence mounts for a role of the kidney in lipoprotein(a) catabolism

Numerous studies have suggested a role of the kidney in lipoprotein(a) (Lp(a)) catabolism, but direct evidence is still lacking. Frischmann et al. demonstrate that the marked elevation of Lp(a) observed in hemodialysis patients results from a decrease in Lp(a) clearance rather than an increase in Lp(a) production, consistent with the notion that the kidney degrades Lp(a). More studies are needed to prove the biological relevance.

Gender-specific association of adiponectin as a predictor of progression of chronic kidney disease: the Mild to Moderate Kidney Disease Study

Progressive renal vascular sclerosis is a key feature of chronic kidney disease (CKD). Adiponectin, an adipokine with potent anti-inflammatory and antiatherosclerotic properties, is associated with insulin resistance, type II diabetes and cardiovascular disease. In this study, we evaluated the predictive value of adiponectin for the progression of CKD in patients enrolled in the Mild to Moderate Kidney Disease Study. The primary end point was defined as a doubling of the baseline serum creatinine and/or terminal renal failure in 177 patients who completed a prospective follow-up of 7 years. Patients who reached a progression endpoint (n=65) were significantly older, had higher baseline serum creatinine, proteinuria and adiponectin concentrations and more components of the metabolic syndrome. A gender-stratified Cox model revealed adiponectin in men as a significant predictor of progression after adjustment for age, glomerular filtration rate, and proteinuria. Male patients with adiponectin levels above their ROC analysis-derived optimal cutoff of 4 microg/ml had a significantly faster progression than patients below this point. This prospective long-term study in patients with CKD indicates high adiponectin as a novel independent predictor of disease progression in men but not in women. Our observation may be relevant for other conditions of progressive vascular sclerosis and diabetic nephropathy.

Cross-talk between the kidney and the cardiovascular system

In recent years, increasing evidence has been provided that even minor renal dysfunction is a powerful cardiovascular risk factor that induces typical cardiovascular alterations and thus predisposes to coronary heart disease as well as to noncoronary cardiovascular problems. This first had been noted in patients with diabetes but now has been confirmed amply in patients without diabetes as well. Numerous heterogeneous abnormalities have been described in patients with early renal dysfunction (e.g., microalbuminuria, reduced estimated GFR). One final common pathway seems to be endothelial cell dysfunction. The link between albuminuria and generalized endothelial cell dysfunction (as indicated by diminished flow-mediated vasodilation, markers of endothelial cell dysfunction, sloughed off endothelial cells, and high transcapillary albumin escape rate) is unclear. In patients with early renal dysfunction, a long list of classical and nonclassical cardiovascular risk factors have been identified: Elevated asymmetric dimethyl-l-arginine concentrations, markers of microinflammation, oxidative stress, features of metabolic syndrome, abnormal adipokine concentrations, dyslipidemia, inappropriate activation of the renin-angiotensin system, and sympathetic overactivity. The mechanisms that link dysfunction of the kidney and the cardiovascular system are being sought. The most interesting unifying concept, however, is deranged fetal programming linking nephron underdosing to the increased cardiovascular risk.

A potential evidence to explain the reason behind the devastating prognosis of coronary artery disease in uraemic patients: renal insufficiency is associated with poor coronary collateral vessel development

The potential of individuals to develop coronary collateral circulation is often neglected but is of potential major importance in myocardial vulnerability. Likewise, the effect of chronic kidney disease (CKD) on collateral vessel development is not known. The purpose of this study was to evaluate the effect of CKD on collateral development in patients with advanced coronary artery disease. A total of 171 uraemic patients (serum creatinine > or = 1.5 mg/dl, creatinine clearance < 80 mL)/min) who underwent coronary angiography were evaluated in this study. A total of 134 patients met the criteria for the uraemic group and 134 consecutive non-uraemic patients who constituted the control group. The collateral score (CS) was graded according to the Rentrop classification and the collateral score was calculated by summing the Rentrop numbers of every patient. Collateral vessels have also been categorized according to their anatomic locations and collateral connection grades (CC). CC2 collaterals were observed less frequently in the uraemic patients than in the control subjects (11% versus 26%, p=0.03) and CC0 more frequently (31% versus 22%, p<0.05). Epicardial pathway was detected more frequently in the control subjects than in the uraemic patients (31% versus 12%, p=0.03) and septal pathway less frequently (37% versus 54%). There was a significant negative correlation between CS and creatinine (r=-0.68, p<0.01). The mean CS in the uraemic group was significantly lower than the non-uraemic group (1.29+/-0.88 versus 2.18+/-1.3, p<0.001). These results altogether showed that besides the quantity, quality (functional, haemodynamic and anatomic features) of the uraemic collaterals and a network that they constitute is also impaired and different from the collaterals of the patient with normal renal function.

Atherosclerosis and Vascular Calcification in Chronic Renal Failure

Cardiovascular complications are a major clinical problem in patients with chronic kidney disease and end-stage renal failure; cardiac death accounts for approximately 40-50% of all deaths in these patients. Death from cardiovascular causes is up to 20 times more common in uremic patients than in the general population with the risk being even higher than in patients with diabetes mellitus. A high rate of myocardial infarction and excessive cardiac mortality have repeatedly been documented in patients with kidney disease and renal failure. Not only is the prevalence of myocardial infarction high, but also the case fatality rate is significantly higher in uremic patients with and without diabetes, respectively, compared to nonuremic patients. This is of particular interest since the prevalence of coronary atheroma in uremic patients was shown to be approximately 30% by autopsy and coronary angiography studies. Thus, coronary factors, i.e. atherosclerosis, and non-coronary factors may play an important role in the genesis of cardiac complications in the renal patient. In addition, renal failure recently has also be identified as a predictor of mortality in different stages of peripheral vascular disease. In particular, marked differences in the pathogenesis, morphology and course of atherosclerosis and arteriosclerosis under the conditions of renal failure have been documented. Among others increased plaque formation and particularly higher proportion and intensity of vascular calcification have been found in clinical and autopsy studies. In addition to the so-called classical or traditional risk factors, an important role for nonclassical risk factors such as microinflammation, hyperphosphatemia and oxidative stress has been documented in patients with renal failure and is discussed in detail.

Chronic renal failure: a cardiovascular risk factor

The risk of developing cardiovascular disease is greatly increased in patients undergoing renal replacement therapy and, notably, morbidity and mortality due to therapy is much higher in these patients than in the general population. Minimal alterations in renal function, as evidenced by reduced glomerular filtration rate and the presence of albuminuria, have been described as potent cardiovascular risk factors. The classic risk factors only partly explain this difference; hence, we must admit the existence of known and emerging factors associated with increased cardiovascular risk in patients with renal disease. This article provides a review of these factors. It describes the role of hyperphosphoremia and elevated calcium-phosphorous product in the formation of cardiovascular calcifications, the contribution of anemia to left ventricular hypertrophy, and the consequences of accelerated atherogenesis with oxidative stress and a microinflammatory state resulting from endothelial dysfunction. Hyperhomocysteinemia, increased sympathetic nervous system activity, lipoprotein alterations with elevated lipoprotein A, and increases in the concentrations of asymmetrical dimethyl-arginine are other examples of the changes described in this population. Patients with renal disease should be considered to be at high risk for developing cardiovascular disease and candidates for implementation of secondary prevention strategies. It is for this reason that early identification of renal failure, which remains hidden in many cases, is of prime importance.

Apolipoprotein A-IV predicts progression of chronic kidney disease: the mild to moderate kidney disease study

It has not been established firmly whether dyslipidemia contributes independently to the progression of kidney disease. Lipid and lipoprotein parameters, including levels of total, HDL, and LDL cholesterol; triglycerides; lipoprotein(a); apolipoprotein A-IV; and the apolipoprotein E and A-IV polymorphisms, were assessed in 177 patients who had mostly mild to moderate renal insufficiency and were followed prospectively for up to 7 yr. Progression of kidney disease was defined as doubling of baseline serum creatinine and/or terminal renal failure necessitating renal replacement therapy. In univariate analysis, patients who reached a progression end point (n = 65) were significantly older and had higher serum creatinine and proteinuria as well as lower GFR and hemoglobin levels. In addition, baseline apolipoprotein A-IV and triglyceride concentrations were higher and HDL cholesterol levels were lower. Multivariate Cox regression analysis revealed that baseline GFR (hazard ratio 0.714; 95% confidence interval [CI] 0.627 to 0.814 for an increment of 10 ml/min per 1.73 m(2); P < 0.0001) and serum apolipoprotein A-IV concentrations (hazard ratio 1.062; 95% CI 1.018 to 1.108 for an increment of 1 mg/dl; P = 0.006) were significant predictors of disease progression. Patients with apolipoprotein A-IV levels above the median had a significantly faster progression (P < 0.0001), and their mean follow-up time to a progression end point was 53.7 mo (95% CI 47.6 to 59.8) as compared with 70.0 mo (95% CI 64.6 to 75.4) in patients with apolipoprotein A-IV levels below the median. For the apolipoprotein E polymorphism, only the genotype epsilon2/epsilon4 was associated with an increased risk for progression. In summary, this prospective study in patients with nondiabetic primary kidney disease demonstrated that apolipoprotein A-IV concentration is a novel independent predictor of progression.

Cardiovascular risk in patients with mild renal insufficiency: implications for the use of ACE inhibitors

We review the evidence linking mild renal insufficiency (MRI) with increased cardiovascular risk. MRI is associated with a number of cardiovascular risk factors, including nighttime hypertension, and increased levels of lipoprotein (a), homocysteine, asymmetric dimethyl-arginine, and inflammation and insulin resistance markers and mediators. Epidemiologic evidence associates coronary artery disease and nephrosclerosis, a frequent cause of early renal insufficiency in the elderly. In a middle-aged general population MRI was found in 8% of women and 9% of men, but was not associated with cardiovascular disease. Nonetheless, in a representative sample of middle-aged British men the risk of stroke was 60% higher for the sub-group with MRI: in people at high cardiovascular risk (mostly coronary disease), the HOPE study found a 2-fold (unadjusted) or 1.4-fold (adjusted) higher incidence of cardiovascular outcomes with MRI. The combined incidence of cardiovascular death, myocardial infarction and stroke increased with the level of serum creatinine. Several studies have examined the cardiovascular risk associated with MRI in hypertension. In HDFP, as in HOPE, cardiovascular mortality increased with serum creatinine (five-fold difference in cardiovascular mortality between the lowest and the highest creatinine strata). The risk associated with renal insufficiency was independent of other classic cardiovascular risk factors. Two trials of hypertensives with low risk (HOT and a small Italian trial) found that cardiovascular outcomes approximately doubled in subjects with MRI. Another study (MRFIT) found that it was not baseline creatinine, but its increase on follow-up that predicted future cardiovascular disease. These observational data suggest that regardless of etiology MRI is a strong predictor of cardiovascular disease and is found in 10% of populations at low cardiovascular risk and in up to 30% of those at high risk. No prospective therapeutic trials aimed at reducing the cardiovascular burden in people with MRI are available. Subgroup analyses of the HOPE study indicate that angiotensin-converting enzyme (ACE) inhibition with ramipril is beneficial and does not increase the risk of such side effects as acute renal failure or hyperkalemia. Thus the frequent practice of withholding ACE inhibitors from patients with mild renal insufficiency is unwarranted, especially since MRI identifies a group at high risk that appears to benefit most from treatment. Moreover, there is evidence that ACE inhibitors improve renal outcomes in renal insufficiency. Prospective studies should test the predictive power of early renal insufficiency for cardiovascular disease and prognosis with various therapeutic options.

Association between carotid artery intima-media thickness and cardiovascular risk factors in CKD

BACKGROUND

Common carotid artery intima-media thickness (CCA-IMT) correlates with cardiovascular events in the general population and is an independent predictor of cardiovascular mortality in the hemodialysis population. It has not been evaluated extensively in patients with chronic kidney disease.

METHODS

CCA-IMT was measured by using high-resolution B-mode ultrasonography, and glomerular filtration rate (GFR) was measured by means of EDTA clearance. Cardiovascular risk factors assessed included homocysteine and lipoprotein(a) levels, as well as smoking, blood pressure, and cholesterol level.

RESULTS

One hundred fourteen patients were studied; mean measured GFR was 29.6 +/- 18.4 mL/min/1.73 m2 (0.49 +/- 0.31 mL/s). CCA-IMT was significantly elevated (0.59 +/- 0.22 cm) compared with a control group (0.44 +/- 0.08 cm; P = 0.0012). CCA-IMT increases with age (P < 0.0001) and low-density lipoprotein level (P = 0.048) and decreases with high-density lipoprotein level (P = 0.001) and being white (P = 0.014).

CONCLUSION

This study suggests that arterial changes occur early in the course of renal disease progression and may be related to dyslipidemia in the early stages.

New risk factors for atherosclerosis in hypertension: focus on the prothrombotic state and lipoprotein(a)

Although adequate control of blood pressure is of basic importance in cardiovascular prevention in hypertensive patients, correction of additional risk factors is an integral part of their management. In addition to classical risk factors, epidemiological research has identified a number of other conditions that might significantly contribute to cardiovascular risk in the general population and might achieve specific relevance in patients with high blood pressure. In fact, more than 20% of patients with premature cardiovascular events do not have any of the traditional risk factors and, although effective intervention on blood pressure and additional risk factors has significantly reduced cardiovascular morbidity and mortality, the contribution to stroke, coronary artery disease and renal failure is still unacceptably high. Evaluation of new risk factors may further expand our capacity to predict atherothrombotic events when these factors are included along with the traditional ones in the assessment of global cardiovascular risk in hypertensive patients. Because it could be anticipated that the role of these novel factors will become increasingly evident in the future, researchers with an interest in hypertension and physicians dealing with problems related to cardiovascular prevention should give them appropriate consideration. This review summarizes the basic biology and clinical evidence of two emerging risk factors that are reciprocally related and contribute to the development and progression of organ damage in hypertension: the prothrombotic state and lipoprotein(a).

Genetics of the Lp(a)/apo(a) system in an autochthonous Black African population from the Gabon

Plasma lipoprotein(a) (Lp(a)) is a quantitative trait associated with atherothrombotic disease in European and Asian populations. Lp(a) concentrations vary widely within and between populations, with Africans exhibiting on average two- to threefold higher Lp(a) levels and a different distribution compared to Europeans. The apo(a) gene locus on chromosome 6q26-27 (LPA, MIM 152200) has been identified as the major quantitative trait locus (QTL) for Lp(a) concentrations in Europeans and populations of African descent (North American and South African Blacks) but data on autochthonous Black Africans are lacking.Here, we have analysed Lp(a) plasma concentrations, apo(a) isoforms in plasma and four polymorphisms in the LPA gene in 31 African families with 54 children from Gabon. Weighted midparent-offspring regression estimated a heritability h2=0.76. The correlation of Lp(a) levels associated with LPA alleles identical by descent (IBD) resulted in a heritability estimate of 0.801. Our data demonstrate that Lp(a) concentrations are highly heritable in a Central African population without admixture and high Lp(a) (median 43 mg/dl). LPA is the major QTL, explaining most or all of the heritability of Lp(a) in this population.

Factors associated with lipoprotein(a) in chronic kidney disease

BACKGROUND

It is unclear whether lipoprotein(a) (Lp[a]) levels in patients with chronic kidney disease (CKD) are elevated as a result of reduced glomerular filtration rate (GFR) or other factors associated with CKD. The goal of this study is to describe the association of Lp(a) level with GFR in the context of apoprotein(a) (apo[a]) isoform size, race, and other kidney disease-related factors, such as proteinuria, serum albumin level, C-reactive protein (CRP) level, and serum lipid levels.

METHODS

Lp(a) and apo(a) isoforms were measured in serum samples obtained at baseline from 804 participants in the Modification of Diet in Renal Disease study (GFR range, 13 to 55 mL/min/1.73 m2). The cross-sectional association between Lp(a) level and GFR, apo(a) isoform size, race, and other variables was analyzed in univariate and multivariate linear regression.

RESULTS

Median Lp(a) level was greater in blacks than whites (97.5 versus 28.1 nmol/L; P < 0.001). Those with a low-molecular-weight apo(a) isoform size had greater Lp(a) levels than those with a high-molecular-weight apo(a) isoform size (57.5 versus 21.3 nmol/L; P < 0.001). Lp(a) level was not associated with GFR. Low-molecular-weight apo(a), black race, and greater levels of proteinuria, CRP, and triglycerides were independently associated with greater Lp(a) levels.

CONCLUSION

In this population with CKD stages 3 to 4, GFR was not associated with Lp(a) level, whereas other factors related to CKD, such as proteinuria, CRP level, and triglyceride level, as well as genetic factors such as apo(a) isoform size and race, were associated with Lp(a) level.

Minor abnormalities of renal function: a situation requiring integrated management of cardiovascular risk

Changes in renal function related with essential hypertension are associated with an elevated cardiovascular morbidity and mortality. Indices of altered renal function (e.g. microalbuminuria, increased serum creatinine concentrations, decrease in estimated creatinine clearance or overt proteinuria) are independent predictors of cardiovascular morbidity and mortality. The Framingham Heart Study documented the relevance of proteinuria for cardiovascular prognosis in the community. The Intervention as a Goal in Hypertension Treatment (INSIGHT) Study assessed the role of proteinuria as a very powerful risk factor. It has also been shown that microalbuminuria along with primary hypertension poses a high risk for cardiovascular diseases. Recent data indicate that even minor derangements of renal function are associated with the clustering of cardiovascular risk factors observed in metabolic syndrome, that promote progression of atherosclerosis. All these parameters should be routinely evaluated in clinical practice, and considered in any stratification of cardiovascular risk in hypertensive patients. The high prevalence of chronic kidney disease in the general and in the hypertensive populations implies the need for an integrative therapeutic approach to fully protect renal and cardiovascular systems simultaneously.

Asymmetric dimethylarginine and progression of chronic kidney disease: the mild to moderate kidney disease study

Reduced bioavailability of nitric oxide (NO) is thought to play an important role in progression of renal damage. The hypothesis that the endogenous NO synthase inhibitor asymmetric dimethylarginine (ADMA) is involved in progression of kidney disease was tested. Plasma ADMA concentrations and other putative progression factors were assessed in 227 relatively young patients (45.7 +/- 12.6 yr) with nondiabetic kidney diseases and mild to moderate renal failure. Progression assessed as doubling of serum creatinine and/or renal replacement therapy was evaluated prospectively. Baseline plasma ADMA concentrations in renal patients correlated significantly with serum creatinine (r = 0.595), GFR (r = -0.591), age (r = 0.281), and proteinuria (r = 0.184; all P < 0.01). Patients who reached an end point during follow-up were significantly older (P < 0.05) and had significantly higher creatinine, ADMA, and parathyroid hormone blood concentrations and protein excretion rates at baseline, whereas GFR and hemoglobin were significantly lower (all P < 0.01). Cox regression analysis revealed baseline serum creatinine (odds ratio 2.00; 95% confidence interval [CI] 1.61 to 2.49; P < 0.001) and ADMA (odds ratio 1.47; 95% CI 1.12 to 1.93 for an increment of 0.1 mumol/L; P < 0.006) as independent predictors of disease progression. In patients with ADMA levels above median, progression was significantly faster (P < 0.0001), and their mean follow-up time to a progression end point was 52.8 mo (95% CI 46.9 to 58.8) as compared with 71.6 mo (95% CI 66.2 to 76.9) in patients with ADMA levels below the median. The endogenous NO synthase inhibitor ADMA is significantly associated with progression of nondiabetic kidney diseases. Lowering plasma ADMA concentrations may be a novel therapeutic target to prevent progressive renal impairment.

The role of the kidney in lipid metabolism

PURPOSE OF REVIEW

Cellular uptake of plasma lipids is to a large extent mediated by specific membrane-associated proteins that recognize lipid-protein complexes. In the kidney, the apical surface of proximal tubules has a high capacity for receptor-mediated uptake of filtered lipid-binding plasma proteins. We describe the renal receptor system and its role in lipid metabolism in health and disease, and discuss the general effect of the diseased kidney on lipid metabolism.

RECENT FINDINGS

Megalin and cubilin are receptors in the proximal tubules. An accumulating number of lipid-binding and regulating proteins (e.g. albumin, apolipoprotein A-I and leptin) have been identified as ligands, suggesting that their receptors may directly take up lipids in the proximal tubules and indirectly affect plasma and tissue lipid metabolism. Recently, the amnionless protein was shown to be essential for the membrane association and trafficking of cubilin.

SUMMARY

The kidney has a high capacity for uptake of lipid-binding proteins and lipid-regulating hormones via the megalin and cubilin/amnionless protein receptors. Although the glomerular filtration barrier prevents access of the large lipoprotein particles to the proximal tubules, the receptors may be exposed to lipids bound to filtered lipid-binding proteins not associated to lipoprotein particles. Renal filtration and receptor-mediated uptake of lipid-binding and lipid-regulating proteins may therefore influence overall lipid metabolism. The pathological mechanisms causing the pronounced atherosclerosis-promoting effect of uremia may involve impairment of this clearance pathway.

Dyslipidemia and nephrotic syndrome: Recent advances

Patients with nephrotic syndrome (NS) have one of the most pronounced secondary changes in lipoprotein metabolism known, and the magnitude of the changes correlates with the severity of the disease. These changes are of a quantitative as well as a qualitative nature. All apolipoprotein B (apo B)-containing lipoproteins, such as very-low-density lipoproteins (VLDL), intermediate-density lipoproteins (IDL), low-density lipoproteins (LDL), and lipoprotein(a) [Lp(a)], are elevated in nephrotic syndrome. High-density lipoproteins (HDL) are reported to be unchanged or reduced. In addition to these quantitative changes, the lipoprotein composition is markedly changed, with a higher ratio of cholesterol to triglycerides in the apo B-containing lipoproteins and an increase in the proportion of cholesterol, cholesterol ester, and phospholipids compared with proteins. Also apolipoproteins show major changes, with an increase in apolipoprotein A-I, A-IV, B, C, and E. Particularly the changes in apo C-II, which is an activator of the enzyme lipoprotein lipase (LPL), and apo C-III, an inhibitor of LPL, with an increase of the C-III to C-II ratio, might contribute to the impaired lipoprotein catabolism in NS. The mechanisms for these changes in lipoprotein metabolism are discussed in this review as far as they are known. Furthermore, the tremendous elevations of Lp(a) in nephrotic syndrome and its primary and secondary causes are reviewed. Primary causes became recently apparent by a significantly higher frequency of low-molecular-weight apo(a) phenotypes in patients compared with controls. The secondary causes were shown by an increase of Lp(a) in all apo(a) isoform groups. Because Lp(a) is an LDL-like particle that is usually included in the measured or calculated LDL cholesterol fraction, the influence of the extremely high Lp(a) levels in NS on the measurement of LDL cholesterol is discussed.

On the importance of estimating renal function for cardiovascular risk assessment

Microalbuminuria has been shown to predict an increased probability of suffering a cardiovascular event or death. It has also been shown to be decreased by antihypertensive therapy and in particular by drugs counteracting the effects of angiotensin II. In this issue of Journal of Hypertension data, from the LIFE study, are reported indicating for the first time that a decrease in urinary albumin excretion rate is accompanied by a significant decrease in cardiovascular events. This evidence is of great relevance because it constitutes the first evidence showing that regression of an intermediate end-point, microalbuminuria, ensures a better cardiovascular prognosis.

Role of Asymmetrical Dimethylarginine in Renal Microvascular Endothelial Dysfunction in Chronic Renal Failure with Hypertension

We examined whether endothelial function of the renal microcirculation was impaired in a model of chronic renal failure (CRF), and further assessed the role of asymmetrical dimethylarginine (ADMA) and its degrading enzyme, dimethylarginine dimethylaminohydrolase (DDAH), in mediating the deranged nitric oxide (NO) synthesis in CRF. CRF was established in male mongrel dogs by subtotal nephrectomy, and the animals were used in experiments after a period of 4 weeks. The endothelial function of the renal afferent and efferent arterioles was evaluated according to the response to acetylcholine, using an intravital needle-lens charge-coupled device camera. Intrarenal arterial infusion of acetylcholine (0.01 microg/kg/min) elicited 22+/-2% and 20+/-2% dilation of the afferent and efferent arterioles in normal dogs. In dogs with CRF, this vasodilation was attenuated (afferent, 12+/-2%; efferent, 11+/-1%), and the attenuation paralleled the diminished increments in urinary nitrite+nitrate excretion. In the animals with CRF, plasma concentrations of homocysteine (12.2+/-0.7 vs. 6.8+/-0.4 micromol/l) and ADMA were elevated (2.60+/-0.13 vs. 1.50+/-0.08 micromol/l). The inhibition of S-adenosylmethionine-dependent protein arginine N-methyltransferase by adenosine dialdehyde decreased plasma ADMA levels, and improved the acetylcholine-induced changes in urinary nitrite+nitrate excretion and arteriolar vasodilation. Acute methionine loading impaired the acetylcholine-induced renal arteriolar vasodilation in CRF, but not normal dogs, and the impairment in CRF dogs coincided with the changes in plasma ADMA levels. Real-time polymerase chain reaction revealed downregulation of the mRNA expression of DDAH-II in the dogs with CRF. Collectively, these results provide direct in vivo evidence of endothelial dysfunction in canine CRF kidneys. The endothelial dysfunction was attributed to the inhibition of the NO production by elevated ADMA, which involved the downregulation of DDAH-II. The deranged NO metabolic pathway including ADMA and DDAH is a novel mechanism for the aggravation of renal function.

Angiotensin-converting enzyme inhibition and angiotensin II antagonism in nondiabetic chronic nephropathies

Angiotensin II (A II), the main effector of the renin angiotensin system (RAS), plays a central role in the hemodynamic and nonhemodynamic mechanisms of chronic renal disease and is currently the main target of interventions aimed to prevent the onset and progression of chronic nephropathies to end-stage renal disease (ESRD). In addition, to ameliorate glomerular hyperfiltration and size selectivity, reduce protein traffic and prevent glomerular and tubulointerstitial toxicity of ultrafiltered proteins, RAS inhibitors also limit the direct nephrotoxic effects of A II. Thus, both angiotension-converting enzyme (ACE) inhibitors (ACEi) and A II antagonists (ATA) exert a specific nephroprotective effect in both experimental and human chronic renal disease. This effect is time-dependent and is observed across degrees of renal insufficiency. Forced ACEi or ATA uptitration above doses recommended to control arterial hypertension and combined treatment with both agents allow optimization of A II inhibition and maximization of renoprotection. Multifactorial interventions combining RAS inhibition to treatments targeted also to non-RAS mechanisms could even achieve regression of glomerulosclerosis and chronic tubulointerstitial injury. Studies are needed to assess whether renal damage can be reverted to such a point that renal function could be fully prevented from worsening, and possibly improvement. The economic impact of even a partial improvement would be enormous. Moreover, chronic renal insufficiency is an independent risk factor for cardiovascular disease, and effective nephroprotection could also decrease the excess cardiovascular morbidity and mortality associated with chronic nephropathies. In patients with renal insufficiency, ACEi are even more cardioprotective than in those without and are well tolerated. Thus, RAS inhibitor therapy should be offered to all renal patients without specific contraindications, including those closer to renal replacement therapy.

Epidemiology, pathophysiology and therapeutic implications of lipoprotein(a) in kidney disease

Chronic kidney disease is associated with a tremendously increased risk for cardiovascular disease. Traditional risk factors for cardiovascular disease, however, show a diminished predictive power in these patients compared with the general population. This review provides an overview of lipoprotein(a), which is considered a nontraditional risk factor. The characteristic genetic and nongenetic changes of lipoprotein(a) in kidney disease are discussed and set into the context of risk prediction. In particular, genetically determined apolipoprotein(a) polymorphism is a powerful risk predictor for cardiovascular disease and total mortality in these patients. Finally, the limited interventional strategies available to lower lipoprotein(a) are considered.

Development of chronic kidney disease in essential hypertension during long-term therapy

PURPOSE OF REVIEW

This review examines the relevance of the development of chronic kidney disease in long-term hypertensive patients on the cardiovascular prognosis.

RECENT FINDINGS

Recently published guidelines recognize the relevance of the development of chronic kidney disease in the stratification of risk for the hypertensive patient. An adequate assessment of renal function, including an estimation of the glomerular filtration rate, is mandatory in order to ensure an adequate evaluation of the global cardiovascular risk in the hypertensive patient. The presence of subtle elevations in serum creatinine concentrations is a potent predictor of a poor cardiovascular prognosis. The clustering of associated risk factors seems to justify the elevated cardiovascular risk observed in patients with essential hypertension and mild renal function derangement.

SUMMARY

Chronic kidney disease is associated with a significant increase in cardiovascular risk attributable to the simultaneous existence of other risk factors related to the metabolic syndrome. The high prevalence of chronic kidney disease in the general and hypertensive populations forces the recognition of its relevance and the need for an integrated therapeutic approach simultaneously to protect the renal and cardiovascular systems fully.

Relevancia de la insuficiencia renal en el pronóstico cardiovascular de los pacientes con hipertensión arterial esencial

Recently published guidelines recognize the relevance of the finding of chronic kidney disease in the stratification of risk of the hypertensive patient. Determination of the presence of microalbuminuria and estimation of glomerular filtration rate are mandatory in order to ensure an adequate evaluation of global cardiovascular risks in the hypertensive patient. The presence of subtle elevations of serum creatinine concentrations and/or proteinuria are also potent predictors of a poor cardiovascular prognosis. Clustering of associated risk factors seems to justify the elevated cardiovascular risk observed in patients with essential hypertension and mild alterations of renal function.

Renal insufficiency and mortality from acute coronary syndromes

BACKGROUND

Although there is accumulating evidence that renal insufficiency is an independent risk factor for mortality after acute myocardial infarction (AMI), it is not known whether renal dysfunction is associated with an increased mortality rate after a broad range of acute coronary syndromes, including unstable angina.

METHODS

We examined consecutive patients from 24 Veterans Affairs hospitals with confirmed AMI or unstable angina between March 1998 and February 1999, who were categorized into groups according to estimated glomerular filtration rate (GFR). Multivariable regression was used to assess the independent association between GFR and the 7-month mortality rate, adjusting for differences in patient characteristics and treatment.

RESULTS

Of the 2706 patients, 436 (16%) had normal renal function (GFR >90 mL/min/1.73 m(2)), 1169 (43%) had mild renal insufficiency (GFR 60-89 mL/min/1.73 m(2)), 864 (32%) had moderate renal insufficiency (GFR 30-59 mL/min/1.73 m(2)), and 237 (9%) had severe renal insufficiency (GFR <30 mL/min/1.73 m(2)). Patients with renal insufficiency were less likely to undergo coronary angiography or to receive aspirin or beta-blockers at discharge. In multivariable models, renal insufficiency was associated with a higher odds of death (mild renal insufficiency: odds ratio [OR] = 1.76; 95% CI, 0.93-3.33; moderate renal insufficiency: OR = 2.72; 95% CI, 1.43-5.15; and severe renal insufficiency: OR = 6.18; 95% CI, 3.09-12.36; all compared with normal renal function). The associations between renal insufficiency and mortality rate were similar in both the AMI and unstable angina subgroups (P value for interaction =.45).

CONCLUSIONS

Renal insufficiency is common and is associated with higher risks for death in patients with a broad range of ACS at presentation. Future efforts should be dedicated to determining whether more aggressive treatment will optimize outcomes in this patient population.

Creatinine clearance and signs of end-organ damage in primary hypertension

A reduction in renal function is associated with high cardiovascular morbidity and mortality in hypertension. The aim of the present study was to investigate the relationship between creatinine clearance and subclinical organ damage in 957 never previously treated, middle-aged patients with primary hypertension. Renal function was estimated by means of the serum creatinine level using the Cockcroft-Gault formula; left ventricular hypertrophy (LVH) was determined according to electrocardiographic criteria; and retinal vascular changes were evaluated by direct ophthalmoscopy. Creatinine clearance was, on the average, 83+/-21.2 ml/min, and the prevalence of LVH and retinopathy was 13 and 49%, respectively. Creatinine clearance was inversely related to the duration of disease (r=-0.132, P<0.0001), systolic blood pressure (r=-0.110, P=0.001), serum glucose (r=-0.090, P=0.007), total cholesterol (r=-0.196, P<0.0001), and LDL-cholesterol (r=-0.196, P<0.0001). Patients in the lower quintile of creatinine clearance showed a higher prevalence of electrocardiogram (ECG) determined LVH (P=0.04), as well as retinal changes (P=0.02). The risk of having LVH or retinal vascular changes increases significantly with each s.d. decrease in creatinine clearance, regardless of traditional cardiovascular risk factors. Moreover, patients with ECG-determined LVH and retinal changes showed lower creatinine clearance as compared to those with lesser degrees of target organ involvement (P<0.01). In conclusion, a mild reduction in creatinine clearance is associated with preclinical end-organ damage in patients with normal creatinine and primary hypertension. These data may help explain the high cardiovascular mortality observed in patients with renal dysfunction. Routine evaluation of creatinine clearance could be useful for identifying patients at higher cardiovascular risk.

Chronic Renal Insufficiency and Cardiovascular Events in the Elderly: Findings From the Cardiovascular Health Study

In the Cardiovascular Health Study, the authors sought to evaluate the impact of chronic renal insufficiency (CRI) on cardiovascular risk status and outcomes in a representative sample of community-dwelling elderly adults. Defined as a serum creatinine level > or =1.3 mg/dL in women and > or =1.5 mg/dL in men, CRI was present in 647 (11%) of 5808 participants. At baseline, the prevalence of clinical or subclinical cardiovascular disease was 64% in participants with CRI and 43% in those without CRI (odds ratio, 2.34; 95% confidence interval, 1.96-2.80). The incidence of cardiovascular disease events during follow-up was 3% per year in participants with creatinine levels <1.10 mg/dL and increased steadily to reach 7% per year in those with creatinine > or =1.70 mg/dL. Among the possible mediators for the association between CRI and cardiovascular morbidity are inflammatory (C-reactive protein, fibrinogen, and interleukin-6) and hemostatic (factor VII, factor VIII, plasmin-antiplasmin product, and D-dimer) biomarkers, all of which were significantly elevated in Cardiovascular Health Study participants with CRI. Future studies should evaluate the contribution of novel and traditional cardiovascular risk factors to the cardiovascular risk of elderly persons with CRI. The identification of CRI in the elderly and the use of cardiovascular prevention therapies represent a major opportunity to reduce their burden of cardiovascular morbidity.

The apolipoprotein(a) size polymorphism is associated with nephrotic syndrome

BACKGROUND

The atherogenic serum lipoprotein(a) [Lp(a)] is significantly elevated in patients with nephrotic syndrome. The underlying mechanism for this elevation is poorly understood.

METHODS

We investigated in 207 patients with nondiabetic nephrotic syndrome and 274 controls whether the apolipoprotein(a) [apo(a)] kringle-IV repeat polymorphism explains the elevated Lp(a) levels in these patients.

RESULTS

Patients showed a tremendous elevation of Lp(a) concentrations when compared to controls (mean 60.4 vs. 20.0 mg/dL and median 29.8 vs. 6.4 mg/dL, P < 0.0001). Primary and secondary causes contributed to this elevation. The primary causes became apparent by a markedly elevated number of low-molecular-weight apo(a) phenotypes which are usually associated with high Lp(a) levels. This frequency was 35.7% in patients compared to only 24.8% in controls (P= 0.009). In addition, secondary causes by the pathogenetic mechanisms of the nephrotic syndrome itself resulted in a different increase of Lp(a) in the various apo(a) isoform groups. Based on the measured Lp(a) concentrations in each subject, we calculated separately the Lp(a) concentrations arising from the two expressed isoforms by estimating the relative proportion of the two serum isoforms in the sodium dodecyl sulfate (SDS) agarose gel electrophoresis. Low-molecular-weight isoforms were associated with 40% to 75% elevated Lp(a) concentrations when compared to matched isoforms from controls. High-molecular-weight apo(a) isoforms showed 100% to 500% elevated Lp(a) levels compared to matched isoforms from controls. The severity of the nephrotic syndrome as well as the degree of renal impairment did not influence the Lp(a) concentrations.

CONCLUSION

The tremendously increased Lp(a) levels in nephrotic syndrome ar caused by primary genetic as well as disease-related mechanisms.

Relationship between apolipoprotein(a) size polymorphism and coronary heart disease in overweight subjects

BACKGROUND

Overweight is associated with an increased cardiovascular risk which is only partially explained by conventional risk factors. The objective of this study was to evaluate lipoprotein(a) [Lp(a)] plasma levels and apolipoprotein(a) [apo(a)] phenotypes in relation to coronary heart disease (CHD) in overweight subjects.

METHODS

A total of 275 overweight (BMI > or = 27 kg/m2) subjects, of which 155 had experienced a CHD event, 337 normal weight subjects with prior CHD and 103 CHD-free normal weight subjects were enrolled in the study. Lp(a) levels were determined by an ELISA technique and apo(a) isoforms were detected by a high-resolution immunoblotting method.

RESULTS

Lp(a) levels were similar in the three study groups. Overweight subjects with CHD had Lp(a) concentrations significantly higher than those without [median (interquartile range): 20 (5-50.3) versus 12.6 (2.6-38.6) mg/dl, P < 0.05]. Furthermore, overweight subjects with CHD showed a higher prevalence of low molecular weight apo(a) isoforms than those without (55.5% versus 40.8%, P < 0.05) and with respect to the control group (55.5% versus 39.8%, P < 0.05). Stepwise regression analysis showed that apo(a) phenotypes, but not Lp(a) levels, entered the model as significant independent predictors of CHD in overweight subjects.

CONCLUSIONS

Our data indicate that small-sized apo(a) isoforms are associated with CHD in overweight subjects. The characterization of apo(a) phenotypes might serve as a reliable biomarker to better assess the overall CHD risk of each subject with elevated BMI, leading to more intensive treatment of modifiable cardiovascular risk factors.

The Effects of Haemodialysis and Peritoneal Dialysis on Serum Lipoprotein(a) and C-Reactive Protein Levels

Elevated serum lipoprotein(a) is an independent risk factor for coronary artery disease, and C-reactive protein (CRP) is a general and cardiovascular marker in haemodialysis patients. We studied lipoprotein(a) and CRP levels in 48 haemodialysis and 24 continuous ambulatory peritoneal dialysis (CAPD) patients and 20 healthy individuals, after a 12 h fast. Serum lipoprotein(a) levels were elevated in 31.3%, 66.7% and 5% of haemodialysis and CAPD patients and control subjects, respectively. The difference between all groups was significant. Serum CRP levels were high in 43.8%, 58.4% and 5% of haemodialysis and CAPD patients, and healthy subjects, respectively. The mean serum CRP level was significantly different between all groups. Both protein levels were higher in CAPD patients than haemodialysis patients, suggesting that CAPD patients should be more closely monitored for coronary artery disease.

Accelerated coronary artery calcification in mildly reduced renal function of high-risk hypertensives

OBJECTIVE

To examine the effect of mild renal dysfunction on coronary artery calcifications.

METHODS

We examined the progression of coronary atherosclerosis, as measured by dual-section spiral computed tomography, using the total coronary artery calcium score as a quantitative measure of the burden of atherosclerosis. Of 547 high-risk Israeli hypertensive patients, who were participants of the prospective calcification study (a side-arm of the international INSIGHT study), 313 patients completed the 3-year follow-up. Subjects were studied upon entry (on placebo) and again after 3 years of treatment (nifedipine or thiazide). Patients were divided into two groups depending on their creatinine clearance: (i) </= 60 ml/min, renal dysfunction (RD) (n = 53) and (ii) > 60 ml/min, normal renal function group (n = 263).

RESULTS

Blood pressure, hypercholesterolemia, and smoking did not differ between the groups. After 3 years of treatment, blood pressure control was similar, whereas the total coronary artery calcium score progression was two-fold greater in the RD than the normal group (156 +/- 32 versus 64 +/- 8, respectively) (P = 0.006). In a multiple logistic regression analysis, the odds ratio (OR) for total coronary artery calcium score progression was higher for the RD group (2.1) [95% confidence interval (CI) 1.2-3.7]. Gender, body mass index, smoking, cholesterol, family history of ischaemic heart disease and diabetes were not significant predictors. Thiazide-based antihypertensive therapy predicted a faster progression compared to nifedipine (OR 1.66, 95% CI 1.09-2.51).

CONCLUSIONS

Mild renal dysfunction accelerates coronary artery calcifications, above and beyond conventional risk factors.

Apolipoprotein(a) isoform-specific changes of lipoprotein(a) after kidney transplantation

The atherogenic lipoprotein(a) (Lp(a)) is significantly increased in patients with kidney disease. Some studies in hemodialysis patients described this increase to be dependent on the genetic apolipoprotein(a) (apo(a)) isoforms. Only patients who express high molecular weight (HMW) apo(a) isoforms but not those with low molecular weight (LMW) isoforms show a relative increase of Lp(a) when compared to healthy controls matched for apo(a) isoforms. However, this was not confirmed by all studies. We therefore prospectively investigated the changes of Lp(a) deriving from each apo(a) isoform in heterozygotes following kidney transplantation. Lp(a) concentrations were measured by ELISA. To calculate the isoform-specific concentrations and the changes of Lp(a) deriving from each isoform, we densitometrically scanned the apo(a) bands from immunoblots before and after transplantation in 20 patients expressing two apo(a) isoforms. Of these, 10 patients expressed both an LMW and an HMW apo(a) isoform. The other 10 patients expressed only HMW isoforms. Densitometric scanning of apo(a) bands and calculation of isoform-derived Lp(a) concentrations clearly demonstrated that the decrease of Lp(a) following kidney transplantation is caused by changes in the expression of HMW apo(a) isoforms. In some patients, we observed an almost complete disappearance of the HMW apo(a) isoform after transplantation. This study clearly demonstrates that the changes of Lp(a) plasma concentrations in kidney disease depend on the genetically determined size of apo(a). This provides evidence for an interaction of apo(a) genetic variability and kidney function on Lp(a) concentrations.

Management of selected lipid abnormalities: hypertriglyceridemia, isolated low HDL-cholesterol, lipoprotein(a), and lipid abnormalities in renal diseases and following solid organ transplantation

Although the focus in treating lipid disorders is on reducing LDL-C levels, additional lipid-related independent risk factors, such as TG, HDL-C, and Lp(a) levels, should be used clinically to assess cardiovascular risk. Decisions to initiate drug therapy for LDL-C reduction may be influenced by levels of these other lipoprotein fractions. Data supporting intervention to modify these factors are less abundant than for LDL-C reduction, but in certain circumstances. drug therapy targeted at TGs or HDL-C may be appropriate. Patients who have nephrotic syndrome and end-stage renal disease are at particularly high risk for the development of CVD and should be treated aggressively for their lipid disorders. Finally, solid organ transplant recipients are almost always hyperlipidemic and appropriate therapy could reduce cardiovascular events.

Mild renal dysfunction and subclinical cardiovascular damage in primary hypertension

The presence of mild renal dysfunction is associated with high cardiovascular morbidity and mortality rates in patients with primary hypertension. The pathophysiological mechanisms underlying this association are currently unknown. We investigated the relation between mild renal dysfunction and subclinical cardiovascular organ damage in 358 never previously treated patients with primary hypertension. Mild renal dysfunction was defined as a creatinine clearance <60 mL/min and/or the presence of microalbuminuria. Left ventricular mass index and carotid intima-media thickness were assessed by ultrasound scan. The prevalence of mild renal dysfunction, left ventricular hypertrophy, and carotid plaque was 18%, 48%, and 28%, respectively. Mild renal dysfunction was related to the presence of several risk factors, such as older age, higher blood pressure levels and lipid status, and smoking habits. Patients with the highest left ventricular mass and carotid intima-media thickness (upper quartiles) showed a higher prevalence of mild renal dysfunction (P<0.0001). After adjusting for duration of hypertension, mean blood pressure, smoking habits, and age, we found that the risk of left ventricular hypertrophy and/or carotid atherosclerosis increased by 43% with each SD reduction in creatinine clearance, and by 89% with each SD increase in albuminuria. Mild renal dysfunction is associated with preclinical end-organ damage in patients with primary hypertension. These data may help explain the high cardiovascular mortality rates reported in patients with low glomerular filtration rate or with increased albuminuria. The evaluation of creatinine clearance and urinary albumin excretion could be useful for identifying subjects at higher cardiovascular risk.

Cardiovascular risk in patients with mild renal insufficiency

We reviewed the evidence linking mild renal insufficiency (MRI) to an increased cardiovascular risk. A number of cardiovascular risk factors become prevalent with MRI, including night-time hypertension, increase in lipoprotein(a), in homocysteine, in asymmetric dimethyl-arginine (ADMA), markers and mediators of inflammation, and insulin resistance. Also, an epidemiologic association between coronary artery disease and nephrosclerosis, a frequent cause of mild renal insufficiency in the elderly, is documented. In the middle-aged, general population MRI, found in 8% of women and 9% of men, was not associated with cardiovascular disease. However, in a representative sample of middle-aged British men, the risk of stroke was 60% higher for the subgroup of people with MRI; in people at high cardiovascular risk (mostly coronary disease), the HOPE study found a 2-fold (unadjusted), or 1.4-fold (adjusted), higher incidence of cardiovascular outcomes with MRI. The incidence of primary outcome increased with the level of serum creatinine. Several studies determined the cardiovascular risk associated with MRI in hypertension. In HDFP, as in HOPE, cardiovascular mortality increased with higher serum creatinine (five-fold difference in cardiovascular mortality between the lowest and the highest creatinine strata). The risk associated with renal insufficiency was independent from other classic cardiovascular risk factors. In hypertensives with low risk, the HOT, and a small Italian trial found about a doubling in cardiovascular outcomes in MRI. However, in MRFIT, increase in follow-up creatinine predicted future cardiovascular disease, not baseline creatinine. These observational data suggest that MRI, independent of etiology, is a strong predictor of cardiovascular disease, present in 10% of a population at low risk, and up to 30% at high cardiovascular risk. No prospective therapeutic trials, aimed at reducing the cardiovascular burden in people with MRI, are available. Subgroup analyses of the HOPE study indicate that ACE inhibition with ramipril is beneficial without an increased risk for side effects like acute renal failure or hyperkalemia. Thus, the frequent practice of withholding ACE inhibitors from patients with mild renal insufficiency is unwarranted, especially since this identifies a group at high risk that appears to benefit most from treatment. In addition, there is evidence that ACE inhibitors improve renal outcomes in renal insufficiency. Prospective studies should test the predictive power of MRI for cardiovascular disease and therapeutic options.

Why is coronary heart disease of uraemic patients so frequent and so devastating?

On September 6, 2001, Professor Fernando Valderrabano (Hospital Gregorio Marañon, Madrid) died at the age of 59 years. He was a leading figure in Spanish nephrology, a full professor of Medicine/Nephrology at the University Complutense of Madrid, and an outstanding scientist who published more than 300 articles in medical journals. He was a very intelligent and cultured person, and a man of great style who enjoyed a wide range of hobbies and interests in addition to his medical work. All his colleagues and friends mourn his passing.

Influence of concurrent renal dysfunction on outcomes of patients with acute coronary syndromes and implications of the use of glycoprotein IIb/IIIa inhibitors

OBJECTIVES

The purpose of this study was to examine the in-hospital outcome and influence of glycoprotein (GP) IIb/IIIa antagonists on patients with acute coronary syndromes (ACS) across a range of renal function.

BACKGROUND

Recent studies demonstrate increasing cardiovascular risk with progressive renal dysfunction. Previous studies investigating GP IIb/IIIa antagonist use have excluded patients with renal dysfunction.

METHODS

Patients presenting with ACS between January 1999 and May 2000 were identified, and data on demographics, in-hospital management, and clinical events were collected using standardized definitions. Patients were stratified according to renal function assessed by calculated creatinine clearance (CrCl) at presentation. Primary outcome measures included in-hospital mortality and major bleeding events.

RESULTS

Renal insufficiency was present in 312 of 889 patients. There were 40 in-hospital deaths. In non-dialysis-dependent patients, as CrCl worsened, there was a decline in utilization of routine diagnostics and therapeutics, an increase in in-hospital mortality (p = 0.002), and an increase in major bleeding (p = 0.03). Although the use of GP IIb/IIIa antagonists was associated with an increase in major bleeding (p < 0.001), there was a protective effect on in-hospital mortality (p = 0.04) after controlling for CrCl.

CONCLUSIONS

Renal dysfunction is present in a substantial proportion of patients with ACS and is associated with increased in-hospital death. Although GP IIb/IIIa antagonist use in patients with ACS and renal insufficiency resulted in increased bleeding events, its administration was associated with a decreased risk of in-hospital mortality. These preliminary findings need to be confirmed in future randomized clinical trials.

Serum Lipoprotein(a) Concentration and Apo(a) Isoform under The Condition of Renal Dysfunction

A serum lipoprotein(a) (Lp(a)) is an independent risk factor for cardiac events. It is well known that the patients with chronic renal failure (CRF) have a high concentration of serum Lp(a). The purpose of this study was to indicate the relationship between serum Lp(a) concentration and apoprotein(a) (apo(a)) isoforms under the condition of renal dysfunction. One-hundred thirty patients having hypertension, hyperlipidemia, diabetes mellitus and/or CRF were selected in this study. All patients were divided into two groups according to the level of serum creatinine. Serum Lp(a) concentration in the CRF patients (Cr > 2.0 mg/dl) was significantly higher than that in the controls (Cr < 1.2 mg/dl). Many CRF patients had high molecular weight (HMW)-apo(a). This study showed that the increase in HMW-apo(a) was closely accompanied by the increase in serum creatinine levels, and the serum Lp(a) concentration with HMW-apo(a) was higher according to their creatinine levels.

Relationship of renal function to homocysteine and lipoprotein(a) levels: the frequency of the combination of both risk factors in chronic renal impairment

BACKGROUND

Total homocysteine (tHcy) and lipoprotein(a) [Lp(a)] levels have been recognized as risk factors for vascular disease. The combination of elevated tHcy and Lp(a) levels may be particularly atherogenic, although no study has examined the prevalence of the combination of both risk factors in patients with chronic renal impairment.

METHODS

One hundred ninety-seven patients with renal impairment were studied. Patients had glomerular filtration rate (GFR) measured by clearance of chromium 51-labeled EDTA. Blood was obtained for the determination of tHcy, Lp(a), and apolipoprotein(a) [apo(a)] isoform levels.

RESULTS

Patients were divided into five groups according to GFR. Mean tHcy levels in the five groups were as follows: GFR less than 10 mL/min, 30.2 +/- 9.8 (SD) micromol/L; GFR of 10 to 20 mL/min, 26.6 +/- 10.5 micromol/L; GFR of 20 to 30 mL/min, 23.9 +/- 8.6 micromol/L; GFR of 30 to 45 mL/min, 22.2 +/- 8.6 micromol/L; and GFR of 45 to 75 mL/min, 18.2 +/- 9.1 micromol/L compared with control levels of 12.7 +/- 4.6 micromol/L. There was a progressive increase in median Lp(a) levels with declining renal function: median Lp(a) levels for those with a GFR less than 10 mL/min were 37.1 mg/dL (range, 0.6 to 156.0 mg/dL); GFR of 10 to 20 mL/min, 30.3 mg/dL (range, 2.6 to 163.7 mg/dL); GFR of 20 to 30 mL/min, 26.1 mg/dL (range, 0.0 to 164.0 mg/dL); GFR of 30 to 45 mL/min, 20.9 mg/dL (range, 0.0 to 99.8 mg/dL), and GFR of 45 to 75 mL/min, 16.8 mg/dL (range, 2.1 to 81.0 mg/dL) compared with control values of 12.5 mg/dL (range, 0.0 to 88.7 mg/dL).

CONCLUSION

Defining hyperhomocysteinemia as tHcy levels greater than the 90th percentile of controls and elevated Lp(a) level as greater than 30 mg/dL, the frequency of the combination increased with declining renal function. Fifty-eight percent of patients with a GFR less than 10 mL/min had both hyperhomocysteinemia and elevated Lp(a) levels, and even in patients with mild renal impairment, 20% of patients had both risk factors present.

Association of kidney function with serum lipoprotein(a) level: the third National Health and Nutrition Examination Survey (1991-1994)

BACKGROUND

Elevated lipoprotein(a) (Lp[a]) levels have been observed in patients on dialysis therapy. However, few studies explored the relationship between kidney function and Lp(a) levels in patients with mild to moderate chronic kidney disease.

METHODS

We examined the association of estimated glomerular filtration rate (GFR) with Lp(a) level in 7,675 participants in the second phase of the Third National Health and Nutrition Examination Survey.

RESULTS

There was no association between Lp(a) level and estimated GFR in the overall sample (geometric mean, 10.4 mg/dL [95% confidence interval (CI), 9.2 to 11.8] in the group with a GFR of 90 to 149 mL/min/1.73 m2 versus 9.3 mg/dL [95% CI, 7.9 to 11.0] in the group with a GFR of 60 to 89 mL/min/1.73 m2 versus 12.1 mg/dL [95% CI, 9.0 to 15.9] in the group with a GFR of 15 to 59 mL/min/1.73 m2; P = 0.77 for linear trend) or non-Hispanic whites (geometric mean, 8.9 mg/dL [95% CI, 7.8 to 10.2] versus 8.5 mg/dL [95% CI, 7.1 to 10.2] versus 10.9 mg/dL [95% CI, 8.1 to 14.7]; P = 0.54 for linear trend). However, non-Hispanic blacks (geometric mean, 30.4 mg/dL [95% CI, 28.0 to 33.0] versus 35.2 mg/dL [95% CI, 31.4 to 39.4] versus 40.2 mg/dL [95% CI, 27.7 to 58.2]; P = 0.01 for linear trend) and Mexican Americans (geometric mean, 6.2 mg/dL [95% CI, 5.3 to 7.2] versus 7.4 mg/dL [95% CI, 6.4 to 8.5] versus 11.0 mg/dL [95% CI, 5.7 to 20.3]; P = 0.04 for linear trend) showed modestly, but significantly, greater Lp(a) levels with lower GFRs. In a weighed quantile regression model adjusted for age, sex, and race, a lower GFR was associated with greater 95th percentile serum Lp(a) values in the overall sample and non-Hispanic whites and with greater median Lp(a) levels in Mexican Americans.

CONCLUSION

In a cross-section of the US population, a low GFR is associated with only moderately greater Lp(a) levels, and this association may differ by race-ethnicity.

Renal dysfunction as a cardiovascular risk factor

Indices of altered renal function (eg, microalbuminuria, increased serum creatinine concentration, or decrease in estimated creatinine clearance, particularly overt proteinuria) are independent predictors of cardiovascular morbidity and mortality. These parameters should be routinely evaluated in the elderly and in high cardiovascular risk populations, particularly when hypertension is present. Hypertensive kidney damage should be prevented by early aggressive treatment of hypertensive patients with microalbuminuria. To avoid further aggravation of high cardiovascular risk, antihypertensive agents devoid of unwanted metabolic side effects should be used. Epidemiologic information suggests that renal and cardiovascular outcome run parallel in this segment of the population.

Renal protection by antihypertensive therapy

The attainment of adequate renal protection requires strict blood pressure control and a diminution of proteinuria or microalbuminuria to values as near from normalcy as possible. It has been considered that by getting the first, the second could be attained at the same price. Recent data have confirmed that renal protection in hypertensive patients, diabetics or not, requires combination therapy that has to include an angiotensin converting enzyme inhibitor or an angiotensin receptor blocker. A calcium channel blocker can be added to this without renal compromise. A diuretic will also be needed in most cases. Proteinuria will diminish with this combination in particular if up-titration of the drug blocking the effects of angiotensin II is performed. The control of other associated risk factors is also required, in particular smoking and lipids.

Predictive performance of renal function equations for patients with chronic kidney disease and normal serum creatinine levels

Accurate renal function measurements are important for the diagnosis and treatment of kidney disease, proper medication dosing, interpretation of possible uremic symptoms, and decision-making regarding when to initiate renal replacement therapy. Because the use of highly accurate filtration markers to measure renal function has traditionally been limited by cumbersome and costly techniques and the involvement of radioactivity (among other factors), renal function is typically estimated by using specially derived prediction equations. These formulae usually use serum creatinine levels, i.e., a marker of filtration that is insensitive to mild/moderate decreases in GFR. Although attempts have been made to validate certain renal function prediction equations among patients with chronic kidney disease (CKD) with abnormal serum creatinine levels, this is the first study to specifically evaluate the predictive performance of these equations for patients with CKD and serum creatinine levels in the normal range. The results of eight prediction equations for 109 patients with CKD and serum creatinine levels of < or =1.5 mg/dl were compared with standard iohexol GFR values. The most accurate results were obtained with the Cockroft-Gault and Bjornsson equations. The most precise formulae were the Modification of Diet in Renal Disease Study equations, although they were highly biased. Even the most accurate results exhibited levels of error that made them suboptimal for clinical treatment of these patients. These results suggest that measurement of GFR with endogenous or exogenous filtration markers might be the most prudent strategy for the assessment of renal function in the CKD population with normal serum creatinine levels. Further studies are needed to confirm the generalizability of these findings for this patient subgroup.

Hyperlipidemia in kidney disease: causes and consequences

Dyslipidemias are common in patients with chronic kidney disease. The causes vary with the stage of kidney disease, the degree of proteinuria, and the modality of end-stage renal disease treatment. Dyslipidemias have been associated with kidney disease progression, and a number of small, randomized, controlled trials of lipid-lowering agents have been conducted. Unfortunately, the results of these trials, although encouraging, have been inconclusive because of the small numbers of patients enrolled. Dyslipidemias may also contribute to the high incidence of cardiovascular disease in patients with chronic kidney disease. This is most likely for patients with chronic renal insufficiency and for kidney transplant recipients. Less certain is the role of dyslipidemias in the pathogenesis of cardiovascular disease among dialysis patients.