Manish P. Ponda

The Notch pathway in podocytes plays a role in the development of glomerular disease

Albuminuria associated with sclerosis of the glomerulus leads to a progressive decline in renal function affecting millions of people. Here we report that activation of the Notch pathway, which is critical in glomerular patterning, contributes to the development of glomerular disease. Expression of the intracellular domain of Notch1 (ICN1) was increased in glomerular epithelial cells in diabetic nephropathy and in focal segmental glomerulosclerosis. Conditional re-expression of ICN1 in vivo exclusively in podocytes caused proteinuria and glomerulosclerosis. In vitro and in vivo studies showed that ICN1 induced apoptosis of podocytes through the activation of p53. Genetic deletion of a Notch transcriptional partner (Rbpj) specifically in podocytes or pharmacological inhibition of the Notch pathway (with a γ-secretase inhibitor) protected rats with proteinuric kidney diseases. Collectively, our observations suggest that Notch activation in mature podocytes is a new mechanism in the pathogenesis of glomerular disease and thus could represent a new therapeutic target.

Vitamin D May Not Improve Lipid Levels: A Serial Clinical Laboratory Data Study

Background— Vitamin D deficiency is highly prevalent and is associated with dyslipidemia and cardiovascular disease. The impact of correcting vitamin D deficiency on blood lipids, strong cardiovascular disease prognostic factors, is unknown. Methods and Results— To determine relationships between 25-hydroxyvitamin D levels and lipids, we analyzed 4.06 million deidentified patient laboratory test results from September 2009 through February 2011. We performed a cross-sectional study of this population to determine associations between 25-hydroxyvitamin D levels and lipids across clinically defined strata. We also conducted a retrospective cohort study of vitamin D deficient patients to investigate how changes in 25-hydroxyvitamin D levels relate to changes in lipid levels. After exclusions, 107 811 patients with serial testing were selected for cross-sectional analysis. Compared with vitamin D deficient patients (<20 ng/mL), those with optimal levels (≥30 ng/mL) had lower mean total cholesterol (−1.9 mg/dL; 95% confidence interval [95% CI], −1.2 to −2.7; P<0.0001), lower low-density lipoprotein cholesterol (−5.2 mg/dL; 95% CI, −4.5 to −5.8; P<0.0001), higher high-density lipoprotein cholesterol (4.8 mg/dL; 95% CI, 4.5–5.0; P<0.0001), and lower triglycerides (−7.5 mg/dL; 95% CI, −6.2 to −8.7; P<0.0001). For the retrospective cohort analysis, raising vitamin D levels from <20 to ≥30 ng/mL (n=6260), compared with remaining at <20 ng/mL (n=2332), was associated with a mean increase in total cholesterol (0.77 mg/dL; 95% CI, 0.18–1.36; P=0.01) and high-density lipoprotein cholesterol (0.42 mg/dL; 95% CI, 0.08–0.76; P=0.02) but nonsignificant changes in low-density lipoprotein cholesterol (0.32 mg/dL; 95% CI, −0.01 to 0.66; P=0.06) and triglycerides (0.04 mg/dL; 95% CI, −2.16 to 2.23 mg/dL; P=0.97). Conclusions— Although vitamin D deficiency is associated with an unfavorable lipid profile in cross-sectional analyses, correcting for a deficiency might not translate into clinically meaningful changes in lipid concentrations; however, data from intervention trials are required to confirm these findings.Background— Vitamin D deficiency is highly prevalent and is associated with dyslipidemia and cardiovascular disease. The impact of correcting vitamin D deficiency on blood lipids, strong cardiovascular disease prognostic factors, is unknown. Methods and Results— To determine relationships between 25-hydroxyvitamin D levels and lipids, we analyzed 4.06 million deidentified patient laboratory test results from September 2009 through February 2011. We performed a cross-sectional study of this population to determine associations between 25-hydroxyvitamin D levels and lipids across clinically defined strata. We also conducted a retrospective cohort study of vitamin D deficient patients to investigate how changes in 25-hydroxyvitamin D levels relate to changes in lipid levels. After exclusions, 107 811 patients with serial testing were selected for cross-sectional analysis. Compared with vitamin D deficient patients (<20 ng/mL), those with optimal levels (≥30 ng/mL) had lower mean total cholesterol (−1.9 mg/dL; 95% confidence interval [95% CI], −1.2 to −2.7; P <0.0001), lower low-density lipoprotein cholesterol (−5.2 mg/dL; 95% CI, −4.5 to −5.8; P <0.0001), higher high-density lipoprotein cholesterol (4.8 mg/dL; 95% CI, 4.5–5.0; P <0.0001), and lower triglycerides (−7.5 mg/dL; 95% CI, −6.2 to −8.7; P <0.0001). For the retrospective cohort analysis, raising vitamin D levels from <20 to ≥30 ng/mL (n=6260), compared with remaining at <20 ng/mL (n=2332), was associated with a mean increase in total cholesterol (0.77 mg/dL; 95% CI, 0.18–1.36; P =0.01) and high-density lipoprotein cholesterol (0.42 mg/dL; 95% CI, 0.08–0.76; P =0.02) but nonsignificant changes in low-density lipoprotein cholesterol (0.32 mg/dL; 95% CI, −0.01 to 0.66; P =0.06) and triglycerides (0.04 mg/dL; 95% CI, −2.16 to 2.23 mg/dL; P =0.97). Conclusions— Although vitamin D deficiency is associated with an unfavorable lipid profile in cross-sectional analyses, correcting for a deficiency might not translate into clinically meaningful changes in lipid concentrations; however, data from intervention trials are required to confirm these findings. # Clinical Perspective {#article-title-39}

Aldosterone antagonism in chronic kidney disease.

Angiotensin-converting enzyme (ACE) inhibitors are potent members of the arsenal to treat chronic kidney disease (CKD). By reducing blood pressure (BP) and disproportionately decreasing intraglomerular pressure, this class of drugs also reduces proteinuria and slows progression of CKD (1,2). Given the high prevalence of cardiovascular disease in this population, it is noteworthy that ACE inhibitors also decrease the incidence of stroke, myocardial infarction (MI), and cardiovascular mortality in patients who are at high cardiovascular risk (3). More recently, data reporting similar benefits of angiotensin receptor blockers (ARB) support their use in the treatment of CKD as well, especially in individuals with type 2 diabetes (4). Furthermore, one sizable study suggested that the combination of an ACE inhibitor and ARB may be more effective than either agent alone (5). Parving and colleagues (6) called attention to the effects of high-dose ARB therapy, up to three times the recommended dose, as an additional means of effectively interrupting the renin-angiotensin-aldosterone system (RAAS). By logical extension, further blockade of the RAAS by direct antagonism of aldosterone also may prove beneficial. Indeed, aldosterone seems to be a potent effector of renal injury (7–9). In the rare cases of primary aldosteronism and its functional analogue, the even more rare Liddle’s syndrome, the observed renal injury probably is independent of the more proximal elements of the RAAS (10,11). Animal models provide an expeditious tool for assessing pathophysiologic change and the efficacy of intervention. The classic model of primary aldosteronism, the mineralocorticoid–nephrectomy–high-salt model of hypertension, develops systemic and glomerular capillary hypertension and sustains renal damage (12). In the remnant kidney model of CKD, ACE inhibitors and ARB attenuate renal injury (13). However, this protection, which is associated with suppression of aldosterone secretion, is abrogated by exogenous aldosterone infusion with return of …

The Short-Term Effects of Vitamin D Repletion on Cholesterol A Randomized, Placebo-Controlled Trial

Objective—Vitamin D deficiency is common and associated with dyslipidemia. However, it is unclear whether oral vitamin D supplementation improves the lipid profile. Therefore, we conducted a randomized, placebo-controlled trial to determine the short-term effects of vitamin D repletion on the lipid profile. Methods and Results—One hundred fifty-one vitamin D−deficient (25-hydroxyvitamin D <20 ng/mL) adults with elevated risk for cardiovascular disease were randomized to receive either 50 000 IU of vitamin D3 weekly for 8 weeks or placebo. The primary outcome was the change in small low-density lipoprotein (LDL) particle number. Secondary outcomes included changes in other nuclear magnetic resonance−based and chemical lipid fractions. Vitamin D failed to improve the lipid profile. Compared with the placebo, vitamin D repletion did not change small LDL particle number (mean change, +18 nmol/L; 95% CI [−80 to +116 nmol/L]; P=0.63). There were also no changes in the chemical lipid profile: total cholesterol (+5.8 mg/dL, 95% CI [−1.4 to +13.0 mg/dL], P=0.14); LDL cholesterol (+3.8 mg/dL, 95% CI [−2.5 to +10.2 mg/dL], P=0.13); high–density lipoprotein cholesterol (+0.4 mg/dL 95% CI [−1.6 to +2.6 mg/dL], P=0.71); and triglycerides (+7.9 mg/dL 95% CI [−6.5 to +22.3 mg/dL]). In the vitamin D repletion group, exploratory multivariate regression analysis demonstrates that changes in LDL cholesterol were positively correlated with the changes in serum calcium (P<0.001) and inversely with the changes in serum parathyroid hormone (P=0.02). Conclusion—In contrast to the association between low 25-hydroxyvitamin D levels and dyslipidemia, correcting vitamin D deficiency in the short-term does not improve the lipid profile. Repletion of 25-hydroxyvitamin D levels raised serum calcium levels and decreased serum parathyroid hormone levels. These expected physiological responses to vitamin D therapy were correlated with a significant increase in LDL cholesterol. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT01008384.

Relationship of impaired olfactory function in ESRD to malnutrition and retained uremic molecules.

BACKGROUND Olfactory function is impaired in patients with end-stage renal disease (ESRD) and may contribute to uremic anorexia. Only limited correlations of olfactory function and nutritional status were reported. This study examines the relationship of impaired olfactory function to malnutrition and levels of the retained uremic solutes monomethylamine, ethylamine, indoxyl sulfate, and P-cresol sulfate. STUDY DESIGN Cross-sectional observational study. SETTING & PARTICIPANTS 31 stable maintenance hemodialysis patients from an urban outpatient dialysis unit and 18 people with normal renal function participated. PREDICTOR Nutritional status assigned by using Subjective Global Assessment (SGA) score; SGA score of 7 indicates normal nutritional status; SGA score of 5 to 6, mild malnutrition; and SGA score of 3 to 4, moderate malnutrition. OUTCOMES & MEASUREMENTS The primary outcome is olfactory function, assessed using the University of Pennsylvania Smell Identification Test. Levels of retained uremic solutes were measured from a predialysis serum sample. Demographic data and laboratory values for nutritional status, adequacy of dialysis, and inflammation were collected. RESULTS Mean smell scores were 34.9 +/- 1.4 for controls, 33.5 +/- 3.3 for patients with SGA score of 7, 28.3 +/- 5.8 for patients with SGA score of 5 to 6, and 27.9 +/- 4.4 for patients with SGA score of 3 to 4 (P < 0.001 comparing healthy patients with all patients with ESRD). There was no difference in mean smell scores for healthy controls and patients with SGA score of 7. However, patients with lower smell scores had significantly lower SGA scores (P = 0.02) and higher C-reactive protein levels (P = 0.02). Neither smell score nor nutritional status was associated with levels of retained uremic solutes. LIMITATIONS Small sample size, only cross-sectional associations can be described. CONCLUSIONS Our results suggest an association between poor nutritional status and impaired olfactory function in patients with ESRD. Additional research is needed to discover the uremic toxins mediating these processes.

Methylamine clearance by haemodialysis is low

BACKGROUND Dialysis adequacy is currently judged by measures of urea clearance. However, urea is relatively non-toxic and has properties distinct from large classes of other retained solutes. In particular, intracellularly sequestered solutes are likely to behave differently than urea. METHODS We studied an example of this class, the aliphatic amine monomethylamine (MMA), in stable haemodialysis outpatients (n = 10) using an HPLC-based assay. RESULTS Mean MMA levels pre-dialysis in end-stage renal disease subjects were 76 +/- 15 microg/L compared to 32 +/- 4 microg/L in normal subjects (n = 10) (P < 0.001). Mean urea reduction was 62% while the reduction ratio for MMA was 43% (P < 0.01). MMA levels rebounded in the 1 hour post-dialytic period to 85% of baseline, whereas urea levels rebounded only to 47% of baseline. MMA had a much larger calculated volume of distribution compared to urea, consistent with intracellular sequestration. Measures of intra-red blood cell (RBC) MMA concentrations confirmed greater levels in RBCs than in plasma with a ratio of 4.9:1. Because of the intracellular sequestration of MMA, we calculated its clearance using that amount removed from whole blood. Clearances for urea averaged 222 +/- 41 ml/min and for MMA 121 +/- 14 ml/min, while plasma clearance for creatinine was 162 +/- 20 ml/min (P < 0.01, for all differences). Using in vitro dialysis, in the absence of RBCs, solute clearance rates were similar: 333 +/- 6, 313 +/- 8 and 326 +/- 4 ml/min for urea, creatinine and MMA, respectively. These findings suggest that the lower MMA clearance relative to creatinine in vivo is a result of MMA movement into RBCs within the dialyser blood path diminishing its removal by dialysis. CONCLUSION In conclusion, we find that, in conventional haemodialysis, MMA is not cleared as efficiently as urea or creatinine and raise the possibility that RBCs may limit its dialysis not merely by failing to discharge it, but by further sequestering it as blood passes through the dialyser.

Moderate kidney disease inhibits atherosclerosis regression

UNLABELLED Chronic kidney disease (CKD) accelerates cardiovascular disease. The mechanisms that explain this independent, excess risk associated with CKD have not been fully elucidated. OBJECTIVES We propose that impaired regression of atherosclerosis in renal disease represents a novel risk factor for the heightened morbidity and mortality and resistance to treatment observed in patients with CKD. METHODS AND RESULTS Using a transplant model to study atherosclerosis regression, we transplanted atheromatous aortic segments generated in Apolipoprotein E knock-out (ApoE(-/-)) mice, into either control or moderately uremic, normolipidemic, wild-type mice. In non-uremic mice, lesions regressed 55%, whereas lesions in uremic mice increased in size by 17% (p<0.01 for control vs. uremic). The lesions in uremic mice were also characterized by a greater presence of macrophages (36,300 microm(2) vs. 12,600 microm(2), p<0.01). This finding was despite upregulation of chemokine receptor 7 (CCR7), normally a migration factor, in uremic lesion macrophages. Gene expression analysis of lesion macrophages showed relative down-regulation of serum response factor (SRF) target genes in the uremic group, consistent with impaired CCR7 signaling. CONCLUSION Moderate kidney disease inhibits regression of atherosclerosis in a mouse transplant model. This inhibition may be a result of impaired CCR7 signaling.

A randomized clinical trial in vitamin D–deficient adults comparing replenishment with oral vitamin D3 with narrow-band UV type B light: effects on cholesterol and the transcriptional profiles of skin and blood

Background: Vitamin D deficiency, defined as a serum 25-hydroxyvitamin D [25(OH)D] concentration <20 ng/mL, is correlated with a more atherogenic lipid profile. However, oral vitamin D supplementation does not lower LDL-cholesterol concentrations or raise HDL-cholesterol concentrations. This uncoupling between association and causation may result from a failure of oral vitamin D to mimic the effect of dermally synthesized vitamin D in response to ultraviolet type B (UVB) light.Objective: We tested the hypothesis that, in vitamin D-deficient adults, the replenishment of vitamin D with UVB exposure would lower LDL-cholesterol concentrations compared with the effect of oral vitamin D3 supplementation.Design: We performed a randomized clinical trial in vitamin D-deficient adults and compared vitamin D replenishment between subjects who received oral vitamin D3 (n = 60) and those who received narrow-band UVB exposure (n = 58) ≤6 mo.Results: There was no difference in the change from baseline LDL-cholesterol concentrations between oral vitamin D3 and UVB groups (difference in median of oral vitamin D3 minus that of UVB: 1.5 mg/dL; 95% CI: -5.0, 7.0 mg/dL). There were also no differences within groups or between groups for changes in total or HDL cholesterol or triglycerides. Transcriptional profiling of skin and blood, however, revealed significant upregulation of immune pathway signaling with oral vitamin D3 but significant downregulation with UVB.Conclusions: Correcting vitamin D deficiency with either oral vitamin D3 or UVB does not improve the lipid profile. Beyond cholesterol, these 2 modalities of raising 25(OH)D have disparate effects on gene transcription. This trial was registered at clinicaltrials.gov as NCT01688102.

Vitamin D3 Repletion in Chronic Kidney Disease Stage 3: Effects on Blood Endotoxin Activity, Inflammatory Cytokines, and Intestinal Permeability

Background: Vitamin D deficiency is common in the general population and even more prevalent in patients with chronic kidney disease (CKD). Low 25-hydroxyvitamin D [25(OH)D] levels have been associated with cardiovascular disease, though a definitive mechanistic link has not been established. Further, it is unclear if repleting vitamin D mitigates the excess risk observed in epidemiologic studies. Because vitamin D may regulate innate immunity and gut epithelial differentiation, we hypothesized that oral cholecalciferol (D3) would result in decreased blood endotoxin activity, a potential risk factor for cardiovascular disease. Study design, setting & participants, intervention: We studied 12 stable outpatients with CKD stage 3 and 25(OH)D deficiency, who received D3 30,000 units weekly for 8 weeks. The primary endpoint was the change in blood endotoxin activity. Results: Baseline endotoxin activity correlated with 25(OH)D levels (r = –0.60, p = 0.04). Endotoxin activity decreased by 25% from baseline (p = 0.03). Despite the decrease in endotoxin activity, there was no change in intestinal permeability. Conclusion: The results of this study suggest that vitamin D repletion therapy may have an effect on endotoxin activity in early CKD. Further intervention studies using vitamin D in the CKD population are required.

Lipid metabolism in dialysis patients-the story gets more complicated.

Cardiovascular disease continues to be the foremost cause of morbidity and mortality in dialysis patients. Compared with the general population, dialysis patients suffer from an accelerated disease course that is, at least in part, resistant to conventional therapy. While there are a myriad of potential explanations for this resistance, derangements in lipid metabolism probably play an important role. Here, we discuss the significance of altered lipid metabolism in uremia, such as oxidative lipoprotein modification and the pathophysiology of adipose tissue; limitations of conventional approaches to dyslipidemia such as statin therapy and traditional lipid profiles; and areas of investigation with potential for new therapy, such as reverse cholesterol transport.