The relationship of peritubular capillary density with glomerular volume and kidney function in living kidney donors

BACKGROUND

Peritubular capillary rarefaction plays an important role in the progression of chronic kidney disease. Little is known about the relation between peritubular capillary density, glomerular volume and filtration rate in the healthy kidney.

METHODS

In this single-center study, we included 69 living kidney donors who donated between 2005 and 2008 and had representative renal biopsies available. In all donors, glomerular filtration rate was measured using 125I-Iothalamate before donation and at five years after donation. Before donation, the increase in glomerular filtration rate after dopamine stimulation was measured. Glomerular volume and peritubular capillary density were determined in biopsies taken at the time of transplantation. Pearson's correlation coefficient and linear regression were used to assess relations between parameters.

RESULTS

Mean donor age was 52 ± 11 years and mean measured glomerular filtration rate was 119 ± 22 mL/min before donation and 82 ± 15 mL/min at five years after donation. While peritubular capillary density (measured by either number of peritubular capillaries/50,000 μm2 or number of peritubular capillaries/tubule) was not associated with measured glomerular filtration rate before or after donation, number of peritubular capillaries/tubule was associated with the increase in measured glomerular filtration rate after dopamine stimulation (St.β = 0.33, p = 0.004), and correlated positively with glomerular volume (R = 0.24, p = 0.047). Glomerular volume was associated with unstimulated measured glomerular filtration rate before donation (St.β = 0.31, p = 0.01) and at five years (St.β = 0.30, p = 0.01) after donation, independent of age.

CONCLUSIONS

In summary, peritubular capillary density was not related to unstimulated kidney function before or after kidney donation, in contrast to glomerular volume. However, number of peritubular capillaries/tubule correlated with the increase in glomerular filtration rate after dopamine stimulation in healthy kidneys, and with glomerular volume. These findings suggest that peritubular capillary density and glomerular volume differentially affect kidney function in healthy living kidney donors.

Use of maximal dosage renin-angiotensin-aldosterone system inhibitors in a real life population of complicated type 2 diabetes - contraindications and opportunities

OBJECTIVE

Pharmacological inhibition of the renin-angiotensin-aldosterone-system (RAASi) is the cornerstone of hypertension treatment, renoprotection and secondary prevention of cardiovascular disease in patients with type 2 diabetes. Although there is a dose-dependent effect of RAASi with optimum protection when using maximal dose, little is known on actual use of maximal dosage RAASi in clinical practice. Here we investigate prevalence of maximal dosage RAASi, and contraindications for, optimizing RAASi dosage, in patients with complicated type 2 diabetes in a real-life clinical setting.

RESEARCH DESIGN AND METHODS

We performed a retrospective analysis in 668 patients included in the DIAbetes and LifEstyle Cohort Twente (DIALECT). We grouped patients according to no RAASi, submaximal RAASi and maximal RAASi use. All potassium and creatinine measurements between January 1st 2000 and date of inclusion in DIALECT were extracted from patients files. We identified determinants of maximal RAASi use vs. submaximal RAASi use with multivariate logistic regression analysis.

RESULTS

Mean age was 64 ± 10 years and 61% were men. In total, 460 patients (69%) used RAASi, and 30% used maximal RAASi. Maximal RAASi use was not statistically different between different indications for RAASi (i.e. hypertension, diabetic kidney disease, coronary heart disease and cerebrovascular disease; P > 0.05). Per patient, 2 [1-4] measurements of potassium and 20 [13-31] measurements of creatinine were retrieved, retrospective follow-up time was - 3.0 [-1.4 to -5.7] years. Pre-baseline hyperkalemia > 5.0 mmol/l and acute kidney injury were found in 151 (23%) patients and 119 patients (18%), respectively. Determinants of maximal RAASi were prior acute kidney injury (OR 0.51 (0.30-0.87)), increased albuminuria (OR 1.89 (1.17-3.08)) and total number of used antihypertensives (OR 1.66 (1.33-2.06)).

CONCLUSIONS

Maximal dose RAASi is used in almost one third of complicated type 2 diabetes patients in a real-life setting. The prevalence of contraindications is considerable, but relative in nature, suggesting that it is worthwhile to explore strategies aimed at maximizing RAASi while circumventing the alleged contraindications.

The fish paradox: people with low socio-economic status are not consuming the right type of fish

Background

Fish intake is included in several national food-based dietary guidelines as a component of healthy diet because of its rich source of beneficial omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, heterogeneity among types of fish intake is rarely studied. We investigated the associations of socio-economic status (SES) with total and types of fish intake and validated whether types of fish intake was associated with plasma EPA and DHA.

Methods

From the Lifelines cohort study, 94 246 participants aged 44 ± 13 years old were included to test the association of two SES indicators, i.e., education level and income level, with dietary intakes of total, fatty, lean, fried, and other types of fish. Plasma EPA and DHA were measured in a minor subset of 575 participants (mean age: 50 ± 13 years old). Total and types of fish intake was assessed using Food Frequency Questionnaire. Linear regressions were applied, adjusted for relevant covariates.

Results

After adjusting for covariates, middle and low education were negatively associated with total, fatty, lean, and other fish intake (p < 0.001 for all), and positively associated with fried fish intake (β (SE): 0.04 (0.04), p < 0.001 for middle education; 0.07 (0.04), p < 0.001 for high education), with high education as the reference group. Similar results were observed for income level. In the subset population, total and fatty fish were positively associated with plasma EPA and DHA (p < 0.02 for all). Lean and other fish intake were positively associated with only DHA (p < 0.008 for all), but not EPA, while fried fish was not associated with either EPA or DHA in plasma (p > 0.1 for all).

Conclusions

Lower SES was associated with higher intake of fried fish, which did not seem to be associated with the fish-based EPA and DHA in plasma. Both nutrition education and food price policy could be implemented to increase the awareness and shape people's choice on types of fish.

Key messages

• People with low socio-economic status are consuming the type of fish that is not associated with fish-based omega-3 fatty acids, so nutrition education focusing on avoidance of fried fish is needed.

• Food subsidy programs promoting intake and increasing affordability of healthier fish are needed to improve the nutritional awareness and status of our population.

Effectiveness of a health literacy intervention targeting kidney patients and professionals

Background

Chronic kidney disease (CKD) patients with limited health literacy (LHL) experience a faster kidney decline. To counteract this, we developed Grip on your Kidneys (GoyK). This intervention targets patients’ communication and self-management. It trains health care professionals (HCPs) competences to support patients with LHL. This study aims to test the effectiveness of GoyK on patients’ health and self-management, HCPs’ communication competences, and the quality of consultations.

Methods

A clustered and non-blinded quasi-experimental study was conducted, including 161 patients with mild to severe CKD and 48 HCPs from Dutch general practices and nephrology clinics. Patients (n = 77) and HCPs (n = 30) in the intervention group received GoyK. In the control group, patients (n = 76) had routine visits with HCPs (n = 19). Between March 2021 and June 2022, data were collected with questionnaires and from patient records at baseline (T0), 4 months (T1) and 9 months (T2). Primary outcomes were patients’ self-management and HCPs’ use of health literacy communication strategies.

Preliminary results

At T1, the intervention improved the days per week patients exercised (B = 1.00, 95% confidence interval, CI = 0.35-1.65, P = 0.003), and Likert-scale reported (1-4) fluid intake (B = 0.37, CI = 0.10-0.63, p = 0.006). The intervention had a positive effect on several outcomes related to how patients perceived the consultation quality, and improved the reported use of communication strategies by HCPs at T1 (B = 0.68, CI = 0.35-1.01, p = &lt;0.001). We found no effects on other patient outcomes, like activation for self-management or salt intake.

Conclusions

Our health literacy intervention, targeting CKD patients with LHL and HCPs, improved lifestyle behaviors of patients and the quality of consultations. A further strengthening of other self-management behaviors and on HCPs’ competences is needed, also to reach sustainable effects in the care for patients with LHL.

Key messages

• A health literacy intervention, targeting patients and professionals simultaneously, improved the patients’ self-management and care consultations.

• Training of HCPs improved their competences to support patients with LHL, and care organizations and studies need to implement education on this topic.

Multimorbidity prevalence and patterns and their associations with health literacy among chronic kidney disease patients

Background

Health literacy is the ability to deal with information related to one’s health. Patients with low health literacy have poor disease-management skills for chronic diseases, such as chronic kidney disease (CKD). This could influence the number and combination of their diseases.

Methods

We included adult patients with CKD stages 1–5 from the Lifelines Study (n = 2,742). We assessed the association between low health literacy and the number and patterns of comorbidities, considering them globally and stratified by age and sex, using multinomial logistic regression and latent class analysis, respectively.

Results

Low health literacy was associated with a higher number of comorbidities in the crude models, and after adjustment for age, sex, eGFR, smoking, and BMI. In the crude model, the OR for low health literacy increased from 1.71 (1.25–2.33) for two comorbidities to 2.71 (2.00–3.68) for four comorbidities. In the fully-adjusted model, the associations remained significant with a maximum OR of 1.70 (1.16–2.49) for four comorbidities. The patterns of multimorbidity were similar for low and adequate health literacy, overall and by sex, bur tended to be different for patients older than 65. Older patients with low health literacy had higher comorbidity prevalence and a relatively greater share of cardiovascular, psychiatric, and central nervous system diseases.

Conclusions

Among CKD patients, low health literacy is associated with more multimorbidity. Health literacy is not associated with patterns of multimorbidity in younger patients, but a difference was observed in older ones. Improving low health literacy could be an intervention efficient also in decreasing multimorbidity in CKD patients.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s40620-021-01229-1.

Effects of plasma fatty acids and desaturase activity on metabolic syndrome in a general population

Background

Altered plasma fatty acid (FA) profile and desaturase activities have been associated with several metabolic disease, including MetS. However, their relations have rarely been studied among general population, and no study have included the FA profile in plasma phospholipids (PL) and triglycerides (TG) separately. We investigated the relationship of the FA profile and desaturase activities in plasma PL and TG with MetS, and investigated if there were new characteristics of altered FA profile that could be related to MetS status in a general population.

Methods

Baseline characteristic data from 850 participants (Male: 50.2%) aged 38-68 years who were recruited in the Lifelines Cohort study in the Netherlands were obtained. Individual FA profile was determined in fasting plasma PL and TG, and desaturase activities were estimated from product/precursor ratios. MetS was defined according to International Diabetes Federation in 2006. Logistic regression and odds ratios (OR) were used to examine these relations with the prevalence of MetS, and possible moderation effect of gender in these relation was also investigated.

Results

There was 102 people (12%) who had MetS. After adjustment for several confounders, higher tertiles of PL C18:3 n-6, C18:0, C20:3 n-6, Δ6 desaturase (D6D), and TG C14:0, C16:0, C20:0 were associated with an increasing prevalence of MetS, while higher tertiles of PL C18:1 n-7, C24:1 n-9, C20:0, C24:0, Δ5 desaturase (D5D), stearoyl-CoA desaturase (SCD-18), and TG C24:0, C18:2 n-6, C20:4 n-6, C24:1 n-9, C20:5 n-3, C22:5 n-3, C22:6 n-3, D5D were inversely associated with MetS. Meanwhile, men seemed to be more vulnerable to MetS when having an altered or unfavorable FA profile in both plasma PL and TG.

Conclusions

It is important to increase w-3 and w-6 essential fatty acids intake and decrease saturated fatty acids intake, and monitoring the D5D, D6D, and SCD-18 desaturases as additional fatty acids biomarkers is of equal importance.

Key messages

This study have added the evidence that an altered fatty acids profile was associated with metabolic syndrome (MetS) in a general population. The altered fatty acids profile that was associated with metabolic syndrome differed in plasma PL and TG, which requires further study.

Multimorbidity patterns and its associations with health literacy in chronic kidney disease patients

Background

Health literacy is the ability to deal with information related to one's health. Patients with low health literacy have poor disease-management skills for chronic diseases, such as chronic kidney disease (CKD). This could influence the number and combination of their diseases.

Methods

We included adult patients with CKD stages 1-5 from the Lifelines Study (n = 2,742). We assessed the association between low health literacy and the number and patterns of comorbidities, overall and by age and sex, using multinomial logistic regression and latent class analysis, respectively.

Results

Low health literacy was associated with a higher number of comorbidities in the crude models, and after adjustment for age, sex, eGFR, smoking, and BMI. In the crude model, the OR for low health literacy increased from 1.71 (1.25 to 2.33) for two comorbidities to 2.71 (2.00 to 3.68) for four comorbidities. In the fully-adjusted model, the associations remained significant with a maximum OR of 1.70 (1.16 to 2.49) for four comorbidities. The patterns of multimorbidity were similar for low and adequate health literacy, overall and by sex, and slightly different for patients older than 65. Older patients with low health literacy had higher comorbidity prevalence and a relatively greater share of cardiovascular, psychiatric, and central nervous system diseases.

Conclusions

This study showed that CKD patients have a high prevalence of comorbidities. Patients with low health literacy are more likely to have a higher number of comorbidities than patients with adequate health literacy. Moreover, the multimorbidity patterns are similar for both groups of health literacy, differing slightly at older ages. This age difference suggests that the negative effects of low health literacy develop when aging. Therefore, low health literacy could be an intervention target to decrease multimorbidity along the life course of CKD patients.

Key messages

Among CKD patients, low health literacy is associated with more multimorbidity. Health literacy does not affect patterns of multimorbidity in younger patients, but it does slightly in older ones.

Nutritional Status and Diet in Elderly with Low and High Socioeconomic Status

Background

Socioeconomic status (SES) patterned health disparities have been related to differences in dietary intake, especially in the elderly. Still, it is not known to what extent these differences culminate in vitamin deficiencies, as most studies have assessed nutrient intake, instead of measuring nutritional biomarkers. Hence, we aimed to objectively assess nutritional status in elderly with low and high SES and to investigate whether potential differences therein were mediated by diet.

Methods

1605 individuals (60-75 years) were selected from the LifeLines Cohort Study to create two gender-matched groups with different SES. Nutritional status was assessed by measuring folic acid, vitamin B6, B12, D, A, E and K in the collected samples. SES-groups were defined according to highest completed education as high and low, and dietary quality was assessed the Lifelines Diet Score. Multiple linear regression and logistic regression were first used for the association between SES and vitamin status; and mediation analysis was used to explore the relationship of SES, diet and vitamin status.

Results

The overall prevalence of vitamin deficiency ranged from 4.1% (vitamin B6) to 19.5% (folic acid). The low SES group had significantly poorer status (p ≤ 0.04) of most vitamins, including the B vitamins (i.e., folic acid, B12 and B6) as well as multivitamin deficiencies (p ≤ 0.02). Low SES was independently associated with decreased folic acid, vitamin B6, vitamin B12, and vitamin A serum concentrations (p ≤ 0.03 for all). Diet quality was found to partially mediate the association between SES, and folic acid (39.1%), vitamin B6 (37.1%) and vitamin B12 (37.2%)(P ≤ 0.03).

Conclusions

Low SES is a risk factor for suboptimal nutritional status. The association between SES and nutritional status can be partially explained by diet quality, suggesting that policy makers can mitigate socioeconomic inequality in nutritional status by improving diet quality among elderly.

Key messages

Revealed that low SES was a risk factor for a suboptimal nutritional status among the elderly and a possible self-reinforcing trap has formed which causes low SES and hidden hunger to persist. Highlighted the importance of diet quality in socioeconomically patterned health disparities and indicating the need for SES-tailored public health strategies.

Associations of ultra-processed food and its consumption patterns with incident type 2 diabetes

Background

To study the associations of the consumption of ultra-processed food (UPF) and its underlying habitual consumption patterns with incident type 2 diabetes (T2D) in a large population-based cohort.

Methods

In 70 421 participants (35-70 years, 58.6% women) from the Lifelines cohort study, dietary intake was assessed with a food frequency questionnaire. Principal component analysis (PCA) was performed to derive UPF consumption patterns. UPF was related to incident diabetes with adjustments for confounders, including overall diet quality.

Results

During a median follow-up of 41 months, the intake of UPF was associated with higher risk of type 2 diabetes (1128 cases, OR for a 10% increment in UPF intake 1.33 [95% CI 1.26, 1.41]), and remained significant after adjustment for confounders. PCA revealed four habitual UPF consumption patterns. A pattern high in cold savory snacks (OR 1.16 [95% CI 1.09, 1.22]) and a pattern high in warm savory snacks (OR 1.15 [95% CI 1.08, 1.21]) were associated with an increased diabetes risk; a pattern high in traditional Dutch cuisine was not associated with diabetes risk (OR 1.05 [95% CI 0.97, 1.14]); while a pattern high in sweet snacks and pastries was inversely associated with diabetes risk (OR 0.82 [95% CI 0.76, 0.89]). There was a clear inverse association between diabetes risk at baseline and the sweet snacks and pastries pattern (β = -0.104 [95% CI -0.113, -0.094]).

Conclusions

A higher consumption of UPF was associated with higher risk of type 2 diabetes. For consumption patterns, this association was most pronounced for the patterns that were high in savory snacks. Our findings emphasize that in addition to promoting the consumption of healthy food products, discouraging the consumption of UPF, specifically savory snacks, should be considered as part of future diabetes prevention strategies.

Key messages

Ultra-processed foods intake was associated with increased risk of type 2 diabetes. Consumption patterns of ultra-processed foods should be the focus for future policies.

Using Structural Equation Modelling to Untangle Pathways of Factors Associated with Type 2 Diabetes

Background

Risk factors for type 2 diabetes (T2D) are multi-facet and interrelated. We aimed to apply structural equation modelling to examine and quantify pathways of modifiable risk factors related to incident type 2 diabetes.

Methods

Analysis was based on 68 649 participants (35-80 years, without diabetes at baseline) from the Lifelines cohort study. We proposed a conceptual model that illustrates the pathways of risk factors related to incident type 2 diabetes: socio-economic status (income and education) → lifestyle behaviors (diet quality, physical activity, TV watching, and smoking) → clinical markers (blood lipids and obesity status) → incident type 2 diabetes. Structural equation modeling was performed to test this proposed model.

Results

After a median follow-up of 41 months, 1124 new cases of type 2 diabetes were identified. The best-fitting model indicated that among all modifiable risk factors included, waist circumference had the biggest direct effect on type 2 diabetes (β: 0.213 ), followed by HDL-cholesterol (β: -0.141). Less TV watching and more physical activity were found to play an important role in improving clinical markers that were directly associated with type 2 diabetes. Education had the biggest direct effects on all lifestyle behaviors.

Conclusions

Using this innovative approach, our analysis provides a more nuanced assessment of the interplay of type 2 diabetes risk factors, compared to traditional risk estimates. Our results indicated that reducing large waist circumference may be prioritized as the main target for the prevention of type 2 diabetes, and lifestyle interventions are urgently warranted with additional support for those with a low education.

Key messages

Our study elucidated the multiple causal pathways to type 2 diabetes in a prospective setting. Our results identified the most critical targets for future prevention strategies for type 2 diabetes.

[Sodium restriction in heart failure: where are the data?]

Mahtani et al. review the evidence for sodium restriction in heart failure. The paucity of solid studies is striking, but deplorably in line with the paucity of high-quality studies on lifestyle management in general. One hard endpoint study (Sodium-HF) is underway. Promising results were obtained in the GOURMET study, which integrated sodium restriction into a broader nutritional approach that simultaneously targeted malnutrition, a major problem in heart failure. Targeting overall nutritional status - rather than single nutrients - matches current trends in nutrition guidelines, and deserves further exploration. Using fresh products and avoiding processed foods is the main step towards an overall healthier diet with less sodium. Dietary improvement, with its clinical benefit, is feasible in most patients by means of adequate support and feedback. Hopefully, the emergence of 'lifestyle medicine' will, with clinical and scientific effort, allow for the health potential of nutrition to be translated into clinical benefit for patients.

Anabolic competence: Assessment and integration of the multimodality interventional approach in disease-related malnutrition

Disease-related malnutrition (DRM) is a frequent clinical problem, characterized by loss of lean body mass and decreased function, including muscle function and immunocompetence. In DRM, nutritional intervention is necessary, but it has not consistently been shown to be sufficient. Other factors, for example, physical activity and hormonal or metabolic influencers of the internal milieu, are also important in the treatment of DRM. A prerequisite for successful treatment of DRM is the positive balance between anabolism and catabolism. The aim of this review was to approach DRM using this paradigm of anabolic competence, for conceptual and practical reasons. Anabolic competence is defined as "that state which optimally supports protein synthesis and lean body mass, global aspects of muscle and organ function, and immune response." Anabolic competence and interdisciplinary, multimodality interventions create a practical foundation to approach DRM in a proactive comprehensive way. Here, we describe the paradigm of anabolic competence, and its operationalization by measuring factors related to anabolic competence and suited for clinical management of patients with DRM.

Effects of Direct Renin Blockade on Renal & Systemic Hemodynamics and on RAAS Activity, in Weight Excess and Hypertension: A Randomized Clinical Trial

Aim

The combination of weight excess and hypertension significantly contributes to cardiovascular risk and progressive kidney damage. An unfavorable renal hemodynamic profile is thought to contribute to this increased risk and may be ameliorated by direct renin inhibition (DRI). The aim of this trial was to assess the effect of DRI on renal and systemic hemodynamics and on RAAS activity, in men with weight excess and hypertension.

Methods

A randomized, double-blind, cross-over clinical trial to determine the effect of DRI (aliskiren 300 mg/day), with angiotensin converting enzyme inhibition (ACEi; ramipril 10 mg/day) as a positive control, on renal and systemic hemodynamics, and on RAAS activity (n = 15).

Results

Mean (SEM) Glomerular filtration rate (101 (5) mL/min/1.73m²) remained unaffected by DRI or ACEi. Effective renal plasma flow (ERPF; 301 (14) mL/min/1.73m²) was increased in response to DRI (320 (14) mL/min/1.73m², P = 0.012) and ACEi (317 (15) mL/min/1.73m², P = 0.045). Filtration fraction (FF; 34 (0.8)%) was reduced by DRI only (32 (0.7)%, P = 0.044). Mean arterial pressure (109 (2) mmHg) was reduced by DRI (101 (2) mmHg, P = 0.008) and ACEi (103 (3) mmHg, P = 0.037). RAAS activity was reduced by DRI and ACEi. Albuminuria (20 [9–42] mg/d) was reduced by DRI only (12 [5–28] mg/d, P = 0.030).

Conclusions

In men with weight excess and hypertension, DRI and ACEi improved renal and systemic hemodynamics. Both DRI and ACEi reduced RAAS activity. Thus, DRI provides effective treatment in weight excess and hypertension.

Trial Registration

Dutch trial register, registration number: 2532 www.trialregister.nl

[Is a once-daily dose of furosemide effective? Literature study into rational for dosing of short-acting diuretic]

- Furosemide is a widely used short-acting diuretic with a steep dose-response curve.- Furosemide is commonly prescribed once daily, but because of its short-acting nature it is questionable if a once-daily regiment is effective.- Different physiological and pathophysiological principles influence the effect and period of efficacy of furosemide.- Studies in both healthy subjects and different patient categories do demonstrate efficacy of furosemide once daily, but also that furosemide prescribed twice daily is more effective.- It is advised to combine furosemide treatment with a sodium-restricted diet, because this enhances the effects of the diuretic treatment.

Concordance of dietary sodium intake and concomitant phosphate load: Implications for sodium interventions

BACKGROUND AND AIMS

Both a high dietary sodium and high phosphate load are associated with an increased cardiovascular risk in patients with chronic kidney disease (CKD), and possibly also in non-CKD populations. Sodium and phosphate are abundantly present in processed food. We hypothesized that (modulation of) dietary sodium is accompanied by changes in phosphate load across populations with normal and impaired renal function.

METHODS AND RESULTS

We first investigated the association between sodium and phosphate load in 24-h urine samples from healthy controls (n = 252), patients with type 2 diabetes mellitus (DM, n = 255) and renal transplant recipients (RTR, n = 705). Secondly, we assessed the effect of sodium restriction on phosphate excretion in a nondiabetic CKD cohort (ND-CKD: n = 43) and a diabetic CKD cohort (D-CKD: n = 39). Sodium excretion correlated with phosphate excretion in healthy controls (R = 0.386, P < 0.001), DM (R = 0.490, P < 0.001), and RTR (R = 0.519, P < 0.001). This correlation was also present during regular sodium intake in the intervention studies (ND-CKD: R = 0.491, P < 0.001; D-CKD: R = 0.729, P < 0.001). In multivariable regression analysis, sodium excretion remained significantly correlated with phosphate excretion after adjustment for age, gender, BMI, and eGFR in all observational cohorts. In ND-CKD and D-CKD moderate sodium restriction reduced phosphate excretion (31 ± 10 to 28 ± 10 mmol/d; P = 0.04 and 26 ± 11 to 23 ± 9 mmol/d; P = 0.02 respectively).

CONCLUSIONS

Dietary exposure to sodium and phosphate are correlated across the spectrum of renal function impairment. The concomitant reduction in phosphate intake accompanying sodium restriction underlines the off-target effects on other nutritional components, which may contribute to the beneficial cardiovascular effects of sodium restriction. (f) Registration numbers: Dutch Trial Register NTR675, NTR2366.

[Is a salt-restricted diet now up for discussion?]

A recent meta-analysis published in The Lancet related sodium excretion to mortality in both hypertensive and normotensive subjects. High salt excretion, measured in a spot urine test, was related to increased mortality in hypertensive subjects only, whereas low sodium excretion was related to increased mortality in both hypertensive and normotensive subjects. Here we discuss practical consequences of this analysis. The data underline the importance of salt restriction in hypertension; the analysis also shows that there is a lower limit to salt restriction. Since salt intake cannot be assessed adequately from the sodium content of a single urine sample, 24-hour urine collection is advised in subjects on a salt-restricted diet. A 24-hour urine collection allows checking for unnecessarily strict salt restriction or, as will more often be the case, shows the patient that adequate salt restriction has not yet been attained.

Hepatic syndecan-1 changes associate with dyslipidemia after renal transplantation

Syndecan-1 is a transmembrane heparan sulfate (HS) proteoglycan present on hepatocytes and involved in uptake of triglyceride-rich lipoproteins via its HS polysaccharide side chains. We hypothesized that altered hepatic syndecan-1 metabolism could be involved in dyslipidemia related to renal transplantation. In a rat renal transplantation model elevated plasma triglycerides were associated with fivefold increased expression of hepatic syndecan-1 mRNA (p < 0.01), but not protein. Expression of syndecan-1 sheddases (ADAM17, MMP9) and heparanase was significantly up-regulated after renal transplantation (all p < 0.05). Profiling of HS side chains revealed loss of hepatic HS upon renal transplantation accompanied by significant decreased functional capacity for VLDL binding (p = 0.02). In a human renal transplantation cohort (n = 510), plasma levels of shed syndecan-1 were measured. Multivariate analysis showed plasma syndecan-1 to be independently associated with triglycerides (p < 0.0001) and inversely with HDL cholesterol (p < 0.0001). Last, we show a physical association of syndecan-1 to HDL from renal transplant recipients (RTRs), but not to HDL from healthy controls. Our data suggest that after renal transplantation loss of hepatic HS together with increased syndecan-1 shedding hampers lipoprotein binding and uptake by the liver contributing to dyslipidemia. Our data open perspectives toward improvement of lipid profiles by targeted inhibition of syndecan-1 catabolism in renal transplantation.

Sex specific association between carnosinase gene CNDP1 and cardiovascular mortality in patients with type 2 diabetes (ZODIAC-22)

INTRODUCTION

Homozygosity for a 5-leucine repeat (5L-5L) in the carnosinase gene (CNDP1) has been associated with a reduced prevalence of diabetic nephropathy in cross-sectional studies in patients with type 2 diabetes, particularly in women. Prospective studies on mortality are not available. This study investigated whether 5L-5L was associated with mortality and progression of renal function loss and to what extent this effect is modified by sex.

METHODS

In a prospective cohort of patients with type 2 diabetes, a Cox proportional hazard model was used to compare 5L-5L with other genotypes regarding (cardiovascular) mortality. Renal function slopes were obtained by within-individual linear regression of the estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease (MDRD) equation, and were compared between 5L-5L and other genotypes.

RESULTS

871 patients were included (38% with 5L-5L). After 9.5 years of follow-up, hazards ratios (HR) for all-cause and cardiovascular mortality in 5L-5L versus other genotypes were 1.09 [95% confidence interval (CI) 0.88-1.36] and 1.12 (95% CI 0.79-1.58), respectively. There was a significant interaction between CNDP1 and sex for the association with cardiovascular mortality (p = 0.01), not for all-cause mortality (p = 0.32). Adjusted HR in 5L-5L for cardiovascular mortality was 0.69 (95% CI 0.39-1.23) in men and 1.77 (95% CI 1.12-2.81) in women. The slopes of eGFR-MDRD did not significantly differ between 5L-5L and other genotypes.

CONCLUSIONS

The association between CNDP1 and cardiovascular mortality was sex-specific, with a higher risk in women with 5L-5L genotype. CNDP1 was not associated with all-cause mortality or change in eGFR.

Receptor for advanced glycation end products (RAGE) polymorphisms are associated with systemic lupus erythematosus and disease severity in lupus nephritis

OBJECTIVE

Interaction of advanced glycation end products (AGEs) with their receptors (RAGE) plays an important role in inflammation in auto-immune diseases. Several functional polymorphisms of RAGE have been described. In this study we analysed the role of RAGE polymorphisms in disease susceptibility for systemic lupus erythematosus (SLE). In addition, we investigated whether these polymorphisms in SLE are associated with serum levels of soluble RAGE (sRAGE), renal involvement (lupus nephritis (LN)) and its outcome.

METHODS

For this cross-sectional study DNA samples of 97 SLE patients, 114 LN patients and 429 healthy controls (HC) were genotyped for four RAGE polymorphisms: -429 T/C, -374 T/A, 2184 A/G and Gly82Ser. Differences in genotype frequencies and allele frequencies were tested between patients and HCs. In SLE patients, sRAGE was measured by enzyme-linked immunosorbent assay (ELISA). In addition, association of genotypes with sRAGE and disease severity in LN was analysed.

RESULTS

The C allele of -429 T/C, the T allele of -374 T/A and the G allele of 2184 A/G were significantly more prevalent in SLE and LN compared with HC. In LN, the C allele of RAGE -429 T/C, the A allele of -374 T/A and the G allele of RAGE 2184 A/G polymorphism were significantly associated with more proteinuria and worse renal function during the first two years of treatment. No association of genotype with sRAGE was found.

CONCLUSION

RAGE polymorphisms are associated with susceptibility to SLE and LN. In addition, some of these polymorphisms are likely to be associated with disease severity and initial response to treatment in LN.

Association of complement C3 gene variants with renal transplant outcome of deceased cardiac dead donor kidneys

Local renal complement activation by the donor kidney plays an important role in the pathogenesis of renal injury inherent to kidney transplantation. Contradictory results were reported about the protective effects of the donor C3F allotype on renal allograft outcome. We investigated the influence of the donor C3F allotype on renal transplant outcome, taking all different donor types into account. C3 allotypes of 1265 donor-recipient pairs were determined and divided into four genotypic groups according to the C3F allotype of the donor and the recipient. The four genotypic groups were analyzed for association with primary nonfunction (PNF), delayed graft function, acute rejection, death-censored graft survival and patient survival. Considering all donor types, multivariable analysis found no association of the donor C3F allotype with renal allograft outcome. Also, for living and deceased brain-dead donors, no association with allograft outcome was found. Post hoc subgroup analysis within deceased cardiac dead (DCD) donors revealed an independent protective association of donor C3F allotype with PNF. This study shows that the donor C3F allotype is not associated with renal allograft outcome after kidney transplantation. Subgroup analysis within DCD donors revealed an independent protective association of the donor C3F allotype with PNF, which is preliminary and warrants further validation.

Former smoking is a risk factor for chronic kidney disease after lung transplantation

Chronic kidney disease (CKD) is a common complication after lung transplantation (LTx). Smoking is a risk factor for many diseases, including CKD. Smoking cessation for >6 months is required for LTx enlistment. However, the impact of smoking history on CKD development after LTx remains unclear. We investigated the effect of former smoking on CKD and mortality after LTx. CKD was based on glomerular filtration rate (GFR) ((125) I-iothalamate measurements). GFR was measured before and repeatedly after LTx. One hundred thirty-four patients never smoked and 192 patients previously smoked for a median of 17.5 pack years. At 5 years after LTx, overall cumulative incidences of CKD-III, CKD-IV and death were 68.5%, 16.3% and 34.6%, respectively. Compared to never smokers, former smokers had a higher risk for CKD-III (hazard ratio [HR] 95% confidence interval [95%CI]= 1.69 [1.27-2.24]) and IV (HR = 1.90 [1.11-3.27]), but not for mortality (HR = 0.99 [0.71-1.38]). Adjustment for potential confounders did not change results. Thus, despite cessation, smoking history remained a risk factor for CKD in LTx recipients. Considering the increasing acceptance for LTx of older recipients with lower baseline renal function and an extensive smoking history, our data suggest that the problem of post-LTx CKD may increase in the future.

Donor kidney adapts to body dimensions of recipient: no influence of donor gender on renal function after transplantation

Female kidneys and kidneys from small donors have been suggested to perform worse after kidney transplantation. Here, we evaluate the impact of gender and body dimensions on posttransplantation GFR in living donor transplantation. Two hundred and ninety-three donor-recipient pairs, who were transplanted at our center were evaluated. All pairs had detailed renal function measurement ((125) I-iothalamate and (131) I-hippuran) 4 months predonation in the donor and 2.5 months posttransplantation in donor and recipient. For 88 pairs, 5 years of recipient follow-up was available. Delta GFR was calculated as (recipient GFR-donor single kidney GFR). Recipients of both male and female kidneys had similar renal function at early and long term after transplantation. Male recipients had higher ERPF, ΔGFR and ΔERPF at both time points. Kidneys of donors smaller than their recipient had higher ΔGFR and ΔERPF than kidneys of larger donors at both time points (p < 0.05). In multivariate analysis, ΔGFR was predicted by donor/recipient BSA-ratio together with transplantation related factors (R(2) 0.19), irrespective of donor and recipient gender. In conclusion, in living donor transplantation, female kidneys perform as well as male donor kidneys. Kidneys adapt to the recipient's body size and demands, independent of gender, without detrimental effects in renal function and outcome up to mid-long term.

Rat Ace allele variation determines susceptibility to AngII-induced renal damage

INTRODUCTION

Ace b/l polymorphism in rats is associated with differential tissue angiotensin-converting enzyme (ACE) expression and activity, and susceptibility to renal damage. Same polymorphism was recently found in outbred Wistar rat strain with b allele accounting for higher renal ACE, and provided a model for studying renin-angiotensin-aldosterone system (RAAS) response behind the innate high or low ACE conditions.

METHODS

We investigated the reaction of these alleles on chronic angiotensin II (AngII) infusion. Wistar rats were selected to breed male homozygotes for the b (WU-B) or l allele (WU-L) (n = 12). For each allele, one group (n = 6) received AngII infusion via an osmotic minipump (435 ng/kg/min) for 3 weeks. The other group (n = 6) served as a control.

RESULTS

WU-B had higher ACE activity at baseline then WU-L. Interestingly, baseline renal ACE2 expression and activity were higher in WU-L. AngII infusion induced the same increase in blood pressure in both genotypes, no proteinuria, but caused tubulo-interstitial renal damage with increased α-SMA and monocyte/macrophage influx only in WU-B (p < 0.05). Low ACE WU-L rats did not develop renal damage.

CONCLUSION

AngII infusion causes proteinuria-independent renal damage only in rats with genetically predetermined high ACE while rats with low ACE seemed to be protected against the detrimental effect of AngII. Differences in renal ACE2, mirroring those in ACE, might be involved.

A polymorphism in the gene encoding carnosinase (CNDP1) as a predictor of mortality and progression from nephropathy to end-stage renal disease in type 1 diabetes mellitus

AIMS/HYPOTHESIS

Homozygosity for a five leucine repeat (5L-5L) in the carnosinase gene (CNDP1) has been found to be cross-sectionally associated with a low frequency of diabetic nephropathy (DN), mainly in type 2 diabetes. We prospectively investigated in patients with type 1 diabetes whether: (1) 5L-5L is associated with mortality; (2) there is an interaction of 5L-5L with DN or sex for prediction of mortality; and (3) 5L-5L is associated with progression to end-stage renal disease (ESRD).

METHODS

In this prospective study in white European patients with type 1 diabetes, individuals with DN were defined by persistent albuminuria ≥ 300 mg/24 h. Controls without nephropathy were defined by persistent (>15 years) normoalbuminuria < 30 mg/24 h. Leucine repeats were assessed with a fluorescent DNA analysis system. Onset of ESRD was defined by need to start chronic dialysis or kidney transplantation.

RESULTS

The study involved 916 patients with DN and 1,170 controls. During follow-up for 8.8 years, 107 patients (14%) with 5L-5L died compared with 182 patients (13.8%) with other genotypes (p = 0.99). There was no significant interaction of 5L-5L with DN for prediction of mortality (p = 0.57), but a trend towards interaction with sex (p = 0.08). In patients with DN, HR for ESRD in 5L-5L vs other genotypes was not constant over time, with increased risk for 5L-5L beyond 8 years of follow-up (p = 0.03).

CONCLUSIONS/INTERPRETATION

CNDP1 polymorphism was not associated with mortality, and nor was there an interaction of this polymorphism with DN for prediction of mortality in patients with type 1 diabetes. CNDP1 polymorphism predicts progression to ESRD in patients with DN, but only late after baseline measurements.

Donor and recipient origin of mesenchymal and endothelial cells in chronic renal allograft remodeling

Chronic transplant dysfunction (CTD) is the leading cause for limited kidney graft survival. Renal CTD is characterized by interstitial and vascular remodeling leading to interstitial fibrosis, tubular atrophy and transplant vasculopathy (TV). The origin of cells and pathogenesis of interstitial and vascular remodeling are still unknown. To study graft-versus-recipient origin of interstitial myofibroblasts, vascular smooth muscle cells (SMCs) and endothelial cells (ECs), we here describe a new rat model for renal CTD using Dark Agouti kidney donors and R26 human placental alkaline phosphatase transgenic Fischer344 recipients. This model showed the development of CTD within 12 weeks after transplantation. In interstitial remodeling, both graft- and recipient-derived cells contributed to a similar extent to the accumulation of myofibroblasts. In arteries with TV, we observed graft origin of neointimal SMCs and ECs, whereas in peritubular and glomerular capillaries, we detected recipient EC chimerism. These data indicate that, within the interstitial and vascular compartments of the transplanted kidney, myofibroblasts, SMCs and ECs involved in chronic remodeling are derived from different sources and suggest distinct pathogenetic mechanisms within the renal compartments.

Nephrectomy elicits impact of age and BMI on renal hemodynamics: lower postdonation reserve capacity in older or overweight kidney donors

Renal functional reserve could be relevant for the maintenance of renal function after kidney donation. Low-dose dopamine induces renal vasodilation with a rise in glomerular filtration rate (GFR) in healthy subjects and is thought to be a reflection of reserve capacity (RC). Older age and higher body mass index (BMI) may be associated with reduced RC. We therefore investigated RC in 178 consecutive living kidney donors (39% males, age 48 +/- 11 years, BMI 25.5 +/- 4.1). RC was determined as the rise in GFR ((125)I-iothalamate), 4 months before and 2 months after donor nephrectomy. Before donor nephrectomy, GFR was 114 +/- 20 mL/min, with a reduction to 72 +/- 12 mL/min after donor nephrectomy. The dopamine-induced rise in GFR of 11 +/- 10% was reduced to 5 +/- 7% after donor nephrectomy (p < 0.001). Before donor nephrectomy, older age and higher BMI did not affect reserve capacity. After donor nephrectomy, the response of GFR to dopamine independently and negatively correlated with older age and higher BMI. Moreover, postdonation reserve capacity was absent in obese donors. The presence of overweight had more impact on loss of RC in younger donors. In conclusion, donor nephrectomy unmasked an age- and overweight-induced loss of reserve capacity. Younger donors with obesity should be carefully monitored.

Analysis of C1q polymorphisms suggests association with systemic lupus erythematosus, serum C1q and CH50 levels and disease severity

BACKGROUND

Several findings link systemic lupus erythematosus (SLE) with C1q, the first molecule of the classical complement pathway. Polymorphisms of the C1qA gene are associated with low serum C1q levels in patients with cutaneous LE, but C1q polymorphisms have not been studied in patients with systemic lupus.

OBJECTIVE

To determine whether polymorphisms of the C1q genes are associated with SLE, disease phenotypes, serum C1q and CH50 levels.

METHODS

DNA for genetic analysis was obtained from 103 Caucasian patients with SLE and their family members. Five tag single nucleotide polymorphisms (tag SNPs) served as unique markers for underlying SNPs in the genes of the C1q protein. The pedigree disequilibrium test (PDT) was applied to trios to determine association of markers with SLE, SLE phenotypes, low serum C1q and low CH50. Single SNP association and haplotype analysis was also performed.

RESULTS

The PDT revealed a significant association of the tag SNP rs631090 (covering the C1qB gene) with SLE (p = 0.02). Rs631090 was moderately associated with low serum C1q levels (p = 0.06). In addition, the tag SNPs rs292001 and rs294183 were associated with more severe SLE (Systemic Lupus Erythematosus International Collaborating Clinics (SLICC) damage index score>0; p = 0.007 and p = 0.02, respectively). Haplotype analysis and single SNP association analysis showed no significant associations, but additional analyses revealed that marker rs587585 is associated with low serum C1q and CH50 levels.

CONCLUSIONS

C1q polymorphisms are associated with SLE, serum C1q and CH50 levels in a stable founder population of patients with SLE. Although the studied population was small and allele frequencies were low, this is the first study to suggest an association of C1q polymorphisms with SLE.

Body mass index and glomerular hyperfiltration in renal transplant recipients: cross-sectional analysis and long-term impact

Obesity is a risk factor for renal graft loss. Higher body mass index (BMI) in native kidneys is associated with glomerular hyperfiltration. Whether higher BMI in renal transplants is associated with hyperfiltration is unknown. We investigated the impact of BMI on renal hemodynamics 1 year post-transplant. We analyzed glomerular filtration rate (GFR, (125)I-iothalamate) and effective renal plasma flow (ERPF, (131)I-hippurate) in 838 kidney transplants. Data were analyzed for all patients and for the subpopulation without diabetes. Long-term impact of BMI and renal hemodynamics were explored by Cox-regression. With higher BMI GFR and filtration fraction (FF) increased significantly. Multivariate analysis supported impact of BMI on GFR (adjusted r(2) of the model 0.275) and FF (adjusted r(2) of the model 0.158). This association was not explained by diabetes mellitus. On Cox-regression analysis, lower GFR and higher FF were independent determinants of overall graft loss and graft loss by patient mortality. Lower GFR and higher BMI were determinants of death-censored graft loss, with borderline contribution of higher FF. In renal transplants higher BMI is independently associated with higher GFR and FF one year posttransplant, suggesting glomerular hyperfiltration with altered afferent-efferent balance. Mechanisms underlying the long-term prognostic impact of hyperfiltration deserve further exploration.

Predictive capacity of pre-donation GFR and renal reserve capacity for donor renal function after living kidney donation

Kidney transplantation from living donors is important to reduce organ shortage. Reliable pre-operative estimation of post-donation renal function is essential. We evaluated the predictive potential of pre-donation glomerular filtration rate (GFR) (iothalamate) and renal reserve capacity for post-donation GFR in kidney donors. GFR was measured in 125 consecutive donors (age 49 +/- 11 years; 36% male) 119 +/- 99 days before baseline GFR (GFRb) and 57 +/- 16 days after donation (GFRpost). Reserve capacity was assessed as GFR during stimulation by low-dose dopamine (GFRdopa), amino acids (GFRAA) and both (GFRmax). GFRb was 112 +/- 18, GFRdopa 124 +/- 22, GFRAA 127 +/- 19 and GFRmax 138 +/- 22 mL/min. After donation, GFR remained 64 +/- 7%. GFRpost was predicted by GFRb(R2 = 0.54), GFRdopa(R2 = 0.35), GFRAA(R2 = 0.56), GFRmax(R2 = 0.55)and age (R2 = -0.22; p < 0.001 for all). Linear regression provided the equation GFRpost = 20.01 + (0.46*GFRb). Multivariate analysis predicted GFRpost by GFRb, age and GFRmax(R2 = 0.61, p < 0.001). Post-donation renal function impairment (GFR < or = 60 mL/min/1.73 m2) occurred in 31 donors. On logistic regression, GFRb, body mass index (BMI) and age were independent predictors for renal function impairment, without added value of reserve capacity. GFR allows a relatively reliable prediction of post-donation GFR, improving by taking age and stimulated GFR into account. Long-term studies are needed to further assess the prognostic value of pre-donation characteristics and to prospectively identify subjects with higher risk for renal function loss.

Obesity and Renal Hemodynamics

Obesity is a risk factor for renal damage in native kidney disease and in renal transplant recipients. Obesity is associated with several renal risk factors such as hypertension and diabetes that may convey renal risk, but obesity is also associated with an unfavorable renal hemodynamic profile independent of these factors, and that may exert effects on renal damage as well. In animal models of obesity-associated renal damage, micro-puncture studies showed glomerular hypertension and hyperfiltration. In humans an elevated glomerular filtration rate has been demonstrated in several studies, sometimes associated with hyperperfusion as well, independent of blood pressure or the presence of diabetes. An elevated filtration fraction was found in several studies, consistent with glomerular hypertension. This renal hemodynamic profile resembles the hyperfiltration pattern in diabetes and is therefore assumed to be a pathogenetic factor in renal damage. Of note, the association between body mass index and renal hemodynamics is not limited to overt obesity or overweight, but is also present across the normal range, without a particular threshold. Multiple factors are assumed to contribute to these renal hemodynamic alterations, such as insulin resistance, the renin-angiotensin system and the tubulo-glomerular responses to increased proximal sodium reabsorption, and possibly also inappropriate activity of the sympathetic nervous system and increased leptin levels. Obesity has a high world-wide prevalence. On a population-basis, therefore, its contribution to long-term renal risk may be considerable, especially as it is usually clustered with risk factors like hypertension and insulin resistance. In short-term studies the renal hemodynamic alterations in obesity and the associated proteinuria were reversible by weight loss, and renin-angiotensin system-blockade, respectively. These interventions are therefore likely to have the potential to limit the renal risks of obesity.

Renal ACE2 expression in human kidney disease

Angiotensin-converting enzyme 2 (ACE2) is a recently discovered homologue of angiotensin-converting enzyme (ACE) that is thought to counterbalance ACE. ACE2 cleaves angiotensin I and angiotensin II into the inactive angiotensin 1-9, and the vasodilator and anti-proliferative angiotensin 1-7, respectively. ACE2 is known to be present in human kidney, but no data on renal disease are available to date. Renal biopsies from 58 patients with diverse primary and secondary renal diseases were studied (hypertensive nephropathy n = 5, IgA glomerulopathy n = 8, minimal change nephropathy n = 7, diabetic nephropathy n = 8, focal glomerulosclerosis n = 5, vasculitis n = 7, and membranous glomerulopathy n = 18) in addition to 17 renal transplants and 18 samples from normal renal tissue. Immunohistochemical staining for ACE2 was scored semi-quantitatively. In control kidneys, ACE2 was present in tubular and glomerular epithelium and in vascular smooth muscle cells and the endothelium of interlobular arteries. In all primary and secondary renal diseases, and renal transplants, neo-expression of ACE2 was found in glomerular and peritubular capillary endothelium. There were no differences between the various renal disorders, or between acute and chronic rejection and control transplants. ACE inhibitor treatment did not alter ACE2 expression. In primary and secondary renal disease, and in transplanted kidneys, neo-expression of ACE2 occurs in glomerular and peritubular capillary endothelium. Further studies should elucidate the possible protective mechanisms involved in the de novo expression of ACE2 in renal disease.