Leendert H. Oterdoom

High urinary excretion of kidney injury molecule-1 is an independent predictor of graft loss in renal transplant recipients

Background. Chronic transplant dysfunction is characterized by renal function decline and proteinuria. Kidney injury molecule (KIM)-1, a transmembrane tubular protein with unknown function, is undetectable in normal kidneys, but markedly induced after injury. Urinary KIM-1 excretion has been quantified as biomarker of renal damage. We prospectively studied whether urinary KIM-1 predicts graft loss, independent of renal function and proteinuria. Methods. Renal transplant recipients (n=145) visiting our outpatient clinic between August 2001 and July 2003 collected 24-hour urine samples for assessment of baseline urinary KIM-1 excretion (microsphere-based Luminex technology), and were followed for graft loss. Results. Recipients participated at a median (interquartile range) of 6.0 (2.5–12.0) years posttransplant in baseline measurements. Follow-up beyond baseline was 4.0 (3.2–4.5) years. Urinary KIM-1 excretion was 0.72 (0.42–1.37) ng per 24 hours. Occurrence of graft loss increased over tertiles of KIM-1 excretion: 3 (6.3%), 11 (22.4%), and 17 cases (35.4%; P=0.001), respectively. High KIM-1 excretion was associated with proteinuria, low creatinine clearance, and high donor age (all P<0.01). In multivariate Cox regression analyses, prediction of graft loss by KIM-1 appeared independent of creatinine clearance, proteinuria, and donor age. Hazard ratios (95% CI) for the second and third tertile of KIM-1 excretion were 3.6 (0.9–13.5) and 5.1 (1.5–17.8) in the final model. Conclusions. Urinary excretion of KIM-1 is an independent predictor of long-term graft loss and therefore a promising new biomarker in early prediction of graft loss.

Urinary creatinine excretion, an indirect measure of muscle mass, is an independent predictor of cardiovascular disease and mortality in the general population

OBJECTIVE Low muscle mass often indicates poor health, but the relation with cardiovascular disease (CVD) is unknown. Skeletal muscles are responsible for approximately 75% of insulin stimulated whole body glucose disposal and therefore insulin resistance could underlie the relation between muscle mass and CVD. We aimed to determine whether muscle mass, as reflected by 24h urinary creatinine excretion, is associated with CVD and whether this depends on insulin resistance. METHODS The study was performed in the prospective, community-based, observational cohort of the PREVEND study in Groningen, the Netherlands. 24h creatinine excretion was assessed in 4044 women and 4048 men. Outcome events were incidence of major adverse cardiovascular events (MACE) and all-cause mortality, with a follow-up of 7.5 [7.3-7.9] years. Insulin resistance was estimated using fasting insulin and HOMA. RESULTS In women every doubling of creatinine excretion was associated with an approximate 60% decrease in risk for MACE (hazard ratio (HR) 0.41 [95%CI 0.26-0.64], P<0.001) and 50% decrease in risk for all-cause mortality (HR: 0.52 [0.31-0.90], P=0.02) independent of age, smoking, CVD history, race, fasting insulin concentrations and components of the metabolic syndrome. In men every doubling of creatinine excretion was borderline associated with an approximately 25% decrease in risk for MACE (HR: 0.74 [0.53-1.03], P=0.07) and independently associated with a 55% decreased risk for all-cause mortality (HR: 0.45 [0.32-0.62], P<0.001). CONCLUSIONS Low creatinine excretion, as indirect measure of low muscle mass, is associated with MACE and all-cause mortality in the general population, independent of insulin resistance. Perhaps protein-calorie malnutrition or physical activity could underlie the association between muscle mass and CVD.

Urinary creatinine excretion reflecting muscle mass is a predictor of mortality and graft loss in renal transplant recipients

Background. Insulin resistance has been implicated to underlie both excess cardiovascular disease and chronic transplant dysfunction after renal transplantation. Skeletal muscle mainly determines peripheral insulin resistance, and could therefore affect outcome. Methods. All transplant recipients at our outpatient clinic with a functioning graft more than 1 year were invited to participate between 2001 and 2003. Mortality and death censored graft loss were recorded until August 2007. We used 24 hr urine creatinine excretion as measure of muscle mass. Cox regression was used to analyze the prospective data. Results. Six hundred four renal transplant recipients (age 51±12 years, 55% men) were studied. Creatinine excretion was 10.1±2.6 mmol/24 hr in women and 13.6±3.4 mmol/24 hr in men. During follow-up of 5.3 (4.7–5.7) years, 95 recipients died and 42 suffered graft loss. Determinants of creatinine excretion were weight, sex, age, height, cumulative prednisolone doses, and diabetes (r2=0.45). Creatinine excretion was associated with both mortality (3rd vs. 1st tertile Hazard ratio: 0.4 [95% confidence interval 0.2–0.7], P=0.003) and graft loss (3rd vs. 1st tertile Hazard ratio: 0.4 [95% confidence interval 0.1–0.9], P=0.03) independent of age, sex, serum creatinine, proteinuria, insulin resistance related factors, time after transplantation, and duration of dialysis. Conclusions. Creatinine excretion as measure of muscle mass is associated with mortality and graft loss after renal transplantation, independent of insulin resistance and its related factors. We speculate that preservation of muscle mass by stimulating exercise, sufficient diet, and less use of corticosteroids may be relevant for improving prognosis in renal transplant recipients.

Circulating Markers of Endothelial Dysfunction Interact With Proteinuria in Predicting Mortality in Renal Transplant Recipients

Background. Proteinuria is associated with endothelial dysfunction (ED) and increased mortality. We investigated whether urinary protein excretion (UPE) is correlated with markers of ED and whether these markers affect the association of proteinuria with mortality in renal transplant recipients (RTR). Methods. Six hundred four RTR with a functioning graft for more than 1 year were included. RTR were divided according to UPE: less than 0.3, 0.3 to 1.0, and more than 1.0 g/24 hr. Soluble intercellular adhesion molecule type 1 (sICAM-1) and soluble vascular cellular adhesion molecule type 1 (sVCAM-1) were measured using ELISA. Results. UPE (0.2 [0.0–0.5] g/24 hr), sICAM-1 (603 (514–721) ng/mL), and sVCAM-1 (952 [769–1196] ng/mL) were measured at 6.0 (2.6–11.4) years posttransplant. During follow-up for 5.3 (4.7–5.7) years, 94 (16%) RTR died. UPE was correlated with sVCAM-1 (standardized &bgr;=0.13, P=0.001) but not with sICAM-1 (standardized &bgr;=0.04, P=0.3). RTR with UPE more than 1.0 g/24 hr and high sICAM-1 (hazard ratio=4.7, 95% confidence interval 2.3–9.7, P<0.0001) or sVCAM-1 (hazard ratio=4.2, 95% confidence interval 2.0–8.6, P=0.0001) concentrations were at increased risk for death, whereas RTR with UPE more than 1.0 g/24 hr and low concentrations of sICAM-1 and sVCAM-1 were not. Conclusions. In RTR, UPE is correlated with sVCAM-1 but not with sICAM-1. Furthermore, RTR with proteinuria and high concentrations of sICAM-1 or sVCAM-1 have an increased risk for death, compared with RTR without proteinuria, whereas this is not the case in RTR with proteinuria but low concentrations of sICAM-1 and sVCAM-1. These results suggest that ED plays a role in the association of proteinuria with mortality after renal transplantation.

Determinants of Insulin Resistance in Renal Transplant Recipients

Background. Insulin resistance is considered to play an important role in the development of cardiovascular disease, which limits long-term renal transplant survival. Renal transplant recipients are more insulin-resistant compared with healthy controls. It is not known to date which factors relate to this excess insulin resistance. Therefore, we investigated which factors are related to insulin resistance long-term after renal transplantation. Methods. All renal transplant recipients at our outpatient clinic with a functioning graft for more than one year were invited to participate. We excluded diabetic recipients. Recipient, donor, and transplant characteristics were collected as putative determinants. We used fasting insulin, homeostasis model assessment index, and McAuley’s index as valid estimates of insulin resistance. Linear regression models were created to investigate independent determinants of all indexes. Results. A total of 483 recipients (57% male, 50±12 years) were analyzed at a median (interquartile range) time of 6.0 (2.6–11.6) years posttransplant. The most consistent determinants across all three indices were body mass index (P<0.001), waist-to-hip ratio (P<0.001), and prednisolone dose (P<0.05). Independent associations were present for total cholesterol (P<0.001), high-density lipoprotein cholesterol (P<0.001), creatinine clearance (P<0.05), recipient age (P<0.001), and gender (P≤0.002). No independent associations were present for transplant-related factors such as acute rejection treatment or cytomegalovirus seropositivity. Conclusions. Our results indicate that obesity, distribution of obesity, and prednisolone treatment are the predominant determinants of insulin resistance long term after transplantation. Insulin resistance after renal transplantation could be managed favorably by weight and prednisolone dose reduction, which may reduce cardiovascular disease.

N-terminal pro-B-type natriuretic peptide and mortality in renal transplant recipients versus the general population.

Background. Mortality rates are higher in renal transplant recipients (RTR) than in the general population (GP). It is unknown what risk factors account for this difference. Methods. We prospectively followed a cohort of 606 RTR for 3026 person-years, during which 95 died. A GP cohort of 3234 subjects was followed for 24,940 person-years, during which 130 died. Results. All investigated risk factors, except ethnicity, body mass index, and total cholesterol, differed significantly between cohorts, with an adverse risk profile in the RTR. The age-adjusted and gender-adjusted hazard ratio for mortality in RTR was 6.2 (95% confidence interval [CI] 4.6–8.3) compared with GP, which was reduced to 2.4 (95% CI 1.6–3.6), 4.3 (95% CI 3.0–6.1), and 5.0 (95% CI 3.5–7.3) after additional adjustment for differences in N-terminal pro-B-type natriuretic peptide (NT-proBNP), creatinine clearance, and need for antihypertensive medication, respectively (all P<0.001), whereas adjustment for variables more related to atherosclerosis, including history of cardiovascular disease, diabetes, and high-density lipoprotein cholesterol, did not affect the difference in mortality between RTR and GP. Associations of NT-proBNP, creatinine clearance, and the use of antihypertensive medication with mortality were significantly steeper in RTR than in GP. Risk for mortality was similar for RTR and GP with low NT-proBNP (<100 pg/mL). Conclusions. Elevated NT-proBNP, low creatinine clearance, and need for antihypertensive medication are stronger risk factors for mortality in RTR than in GP. The increased mortality seen in the RTR population may well be related to cardiac failure rather than “accelerated atherosclerosis.”

Low levels of sRAGE are associated with increased risk for mortality in renal transplant recipients

Objective. Infusion of the soluble form of the receptor for advanced glycation end-products (sRAGE) was protective against atherosclerosis and nephropathy in animal models. In this study we investigated determinants of endogenous sRAGE in renal transplant recipients and whether sRAGE was associated with mortality and graft loss. Methods and Results. A total of 591 patients participated at a median time of 6 years after transplantation. Independent determinants of sRAGE were mycophenolate mofetil medication (&bgr;=−0.21, P<0.001), creatinine clearance (&bgr;=−0.15, P<0.001), BMI (&bgr;=−0.12, P=0.003) and fasting insulin concentration (&bgr;=−0.14, P=0.001). Low sRAGE levels were associated with a 2–3 times higher risk for mortality especially after correction for creatinine clearance (P=0.006). Conclusion. A lack of sRAGE is a risk factor for mortality in renal transplant recipients. The putatively protective role of sRAGE and in particular its association with mycophenolate mofetil usage needs further investigation.

Plasma Procalcitonin Is an Independent Predictor of Graft Failure Late After Renal Transplantation

Background. Chronic low-grade inflammation is involved in chronic transplant dysfunction after renal transplantation. Procalcitonin (PCT), known to reflect microbial inflammation, may also reflect ongoing noninfectious chronic low-grade inflammation in organ parenchyma, including transplanted kidneys. We aimed to compare predictive performance of plasma PCT for development of graft failure in renal transplant recipients (RTR) with that of high-sensitivity C-reactive protein (hsCRP), an established marker of systemic chronic low-grade inflammation. Methods. We included 575 RTR with functioning grafts for more than or equal to 1 year at a median (interquartile range) time of 6.1 (2.9–11.7) years posttransplant. PCT was determined using an ultrasensitive immunoluminometric assay and hsCRP using high-sensitivity enzyme-linked immunosorbent assay. Results. Median (interquartile range) plasma PCT and hsCRP concentrations were 0.023 (0.017–0.036) ng/mL and 2.1 (0.8–4.9) mg/L, respectively. After a median (interquartile range) of 5.2 (4.5–5.7) years of follow-up, incidence of graft failure was 0.5%, 2.6%, and 18.5% according to increasing PCT tertiles (P<0.001 by log-rank test). Area under the curve of receiver operating characteristic analysis of PCT for prediction of graft failure was significantly higher than that of hsCRP (0.84 vs. 0.56, P<0.001). After adjustment for potential confounders, PCT remained an independent predictor of graft failure (hazard ratio=2.3 [95% confidence interval 1.4–3.7] per doubling PCT, P=0.0004), whereas this was not the case for hsCRP. Conclusion. We identified plasma PCT as a strong and an independent predictor of graft failure in RTR. These data suggest that PCT in RTR reflects ongoing inflammation in parenchyma of transplanted kidneys. Further studies are required to investigate whether PCT could be of use as an early biomarker for chronic transplant dysfunction.

Skin-autofluorescence is an independent predictor of graft loss in renal transplant recipients.

Background. Skin-autofluorescence (skin-AF) noninvasively measures the tissue accumulation of advanced glycation end products (AGEs). AGEs are nephrotoxic and potential effectors of cardiovascular mortality. We investigated whether skin-AF predicted graft loss after kidney transplantation. Methods. A total of 302 renal transplant recipients were enrolled at a median time of 6.1 (2.6-12.1) years after transplantation and were subsequently followed up for first occurrence of graft loss (i.e., graft failure or all-cause mortality) for 5.2 (4.6-5.4) years. The association of baseline skin-AF with graft loss was investigated with univariable and multivariable Cox-regression and receiver-operator-characteristic curve analyses. Results. Baseline skin-AF was 2.7±0.8 arbitrary units. Skin-AF predicted graft loss in a univariable Cox regression analysis (Hazard ratios 2.40 [1.75-3.29], P<0.001) and in a multivariable model (Hazard ratios 1.83 [1.22-2.75], P=0.003), adjusted for other identified risk-factors, including patient age, creatinine clearance, protein excretion, high sensitivity C-reactive protein (hsCRP), and human leukocyte antigen-DR mismatching. The area under the receiver-operator-characteristic curve for skin-AF as predictor of graft loss was significantly different from 0.5. Skin-AF was also a significant predictor of graft failure and mortality as separate end points. Conclusions. We conclude that skin-AF is an independent predictor of graft loss in kidney transplant recipients. Although skin-AF is not a direct measurement for AGEs, we believe that our results do support the hypothesis that accumulation of AGEs in renal transplant recipients contributes to the development of graft loss.

Fasting insulin is a stronger cardiovascular risk factor in women than in men

Diabetes is a stronger risk factor for cardiovascular disease (CVD) in women than in men. It is not known whether there is also a sex difference in the association between hyperinsulinaemia, reflecting insulin resistance, and CVD. Fasting insulin was assessed with a specific assay in 6916 fasting, non-diabetic subjects of the PREVEND study without a prior history of CVD. Major Adverse Cardiovascular Events (MACE) (defined as CVD morbidity and CVD mortality) were prospectively recorded after the baseline survey. Cox-regression models were used to investigate the association of fasting insulin with subsequent development of MACE. Fasting insulin was 54 [38-77]pmol/l in women (age 48+/-12yrs) and 57 [40-88] pmol/l in men (age 49+/-13yrs). During follow-up for 7.5 [6.9-7.8]yrs, 98 cardiovascular events were recorded in 3626 women and 242 events in 3290 men. There was a significant (P<0.001) interaction between sex and fasting insulin for MACE, with the strongest association in women. In women, there was a logarithmic association for insulin with MACE, independent of age, alcohol consumption, and smoking (HR=1.50 [95% CI 1.17-1.91] per doubling of insulin, P=0.001). In men, for a similar multivariate model, there was a logarithmic association (HR=1.13 [95% CI [0.97-1.32] per doubling of insulin, P=0.1). Further adjustment for components of the insulin resistance syndrome weakened the association more in men than in women. With HOMA instead of insulin, results were essentially similar. In parallel with diabetes, fasting hyperinsulinaemia reflecting insulin resistance in non-diabetic subjects is associated with an increased risk for cardiovascular disease, which is more pronounced in women than in men.