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Lidgard B, Hoofnagle AN, Zelnick LR, de Boer IH, Fretts AM, Kestenbaum BR, Lemaitre RN, Robinson-Cohen C, Bansal N. High-Density Lipoprotein Lipidomics in Chronic Kidney Disease. Clin Chem 2023; 69:273-282. [PMID: 36644946 PMCID: PMC10069017 DOI: 10.1093/clinchem/hvac216] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 11/17/2022] [Indexed: 01/17/2023]
Abstract
BACKGROUND Patients with chronic kidney disease (CKD) have dysfunctional high-density lipoprotein (HDL) particles as compared with the general population. Understanding the lipid composition of HDL may provide mechanistic insight. We tested associations of estimated glomerular filtration rate (eGFR) and albuminuria with relative HDL abundance of ceramides, sphingomyelins, and phosphatidylcholines in participants with CKD. METHODS We studied 490 participants with CKD from the Seattle Kidney Study. HDL was isolated from plasma; targeted lipidomics was used to quantify the relative abundance of ceramides, sphingomyelins, and phosphatidylcholines per 10 µg of total HDL protein. We evaluated the associations of eGFR and albuminuria with levels of individual lipids and lipid classes (including 7 ceramides, 6 sphingomyelins, and 24 phosphatidylcholines) using multivariable linear regression, controlling for multiple comparisons via the false discovery rate. RESULTS The mean (SD) eGFR was 45 (24) mL/min/1.73 m2; the median (IQR[interquartile range]) albuminuria was 108 (16, 686) mg/g (12.2 [1.8, 77.6] mg/mmol) urine creatinine. After adjusting for demographics, past medical history, laboratory values, and medication use, eGFR was not associated with higher relative abundance of any class of lipids or individual lipids. Greater albuminuria was significantly associated with a higher relative abundance of total ceramides and moderate-long R-chain sphingomyelins, ceramides 22:0 and 24:1, hexosylceramide 16:0, sphingomyelin 16:0, and phosphatidylcholines 29:0, 30:1, and 38:2; the strongest association was for hexosylceramide 16:0 (increase per doubling of urine albumin to creatinine ratio 0.022 (95% CI, 0.012-0.032). CONCLUSIONS Greater albuminuria was significantly associated with specific alterations in the lipid composition of HDL in participants with CKD.
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Ogudu U, Nwaiwu O, Fasipe OJ. A comparative evaluation of fixed dose and separately administered combinations of lisinopril and hydrochlorothiazide in treatment-naïve adult hypertensive patients in a rural Nigerian community. INTERNATIONAL JOURNAL OF CARDIOLOGY CARDIOVASCULAR RISK AND PREVENTION 2022; 14:200144. [PMID: 36097516 PMCID: PMC9463461 DOI: 10.1016/j.ijcrp.2022.200144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 06/25/2022] [Accepted: 07/23/2022] [Indexed: 12/03/2022]
Abstract
Background Antihypertensive drugs administered as fixed dose combination (FDC) therapy compared to separately administered combination therapy have been proposed to improve treatment compliance/adherence, and therefore the efficacy of blood pressure (BP) control treatment. Aim The aim of this present study is to compare the blood pressure control, renal end-organ protection and medication compliance/adherence in patients receiving FDC and those receiving separately administered combinations of Lisinopril and Hydrochlorothiazide in treatment-naive hypertensive adult patients in a rural Nigerian community. Method ology: This randomized two-arm prospective longitudinal 8-week parallel-group study was carried-out for 6-month at the Ajegunle Community between April 2018 and October 2018. Efficacy variables included the changes from baseline in mean sitting systolic BP (MSSBP) and mean sitting diastolic BP (MSDBP). Medication safety, compliance/adherence and renal end-organ protection were assessed. Results The baseline characteristics of the two groups were similar. Prevalence of hypertension was found to be 32.9%. The mean blood pressure of all the participants was 165.6 ± 16.5 mmHg and 98.5 ± 11.5 mmHg for systolic BP and diastolic BP respectively, while the mean pulse rate of the participants was 85.0 ± 13.4 beats/min. At the 8-week end point, both regimens had achieved significant reductions from baseline in MSSBP (−33.18 and −37.16 mm Hg, respectively; both, P < 0.05) and MSDBP (−12.97 and −17.53 mm Hg; both, P < 0.05). Both regimens were generally well tolerated. Adherence was better in the FDC arm and there was no any reported case of proteinuria occurrence in both arms. Conclusion The high prevalence of hypertension in the community shows that there is unmet need in diagnosis and awareness of the disease. Both combination therapies were well tolerated; but the FDC antihypertensive therapy resulted in statistically significant amount of BP reductions than the separately administered combination antihypertensive therapy. Making FDCs available and affordable will help many hypertensive patients to achieve their target BP control goals easily.
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Olszewska-Słonina DM. Serum Arylsulfatase and Acid Phosphatase Activity in Patients with Metabolic Syndrome as a Result of Oxidative Damage to Lysosomes. Protein Pept Lett 2021; 28:1246-1258. [PMID: 34931962 DOI: 10.2174/0929866528666210712095134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2021] [Revised: 05/06/2021] [Accepted: 05/16/2021] [Indexed: 11/22/2022]
Abstract
BACKGROUND Metabolic and clinical disorders forming the complex of interrelated abnormalities is known as metabolic syndrome (METs). OBJECTIVE Our goal was to assess the dependence of serum arylsulfatase (AS) and acid phosphatase (ACP) activities on anthropometric and biochemical parameters in patients with METs. METHODS In 142 patients with METs (IDF criteria), consisting of different components in different sequences (hypertension, diabetes, lipid disorders), and in 65 healthy participants, basic biochemical parameters were determined in laboratory tests. The activity of serum hydrolases was determined using Bessey's (ACP) and Roy's (AS) methods. RESULTS The AS activity is correlated with waist-to-hip ratio (WHR) (more strongly in women and in most advanced METs), BMI (in men), and triglycerides (TG) (in women, participants with I degree obesity, and those with three METs components). The ACP activity correlated with the WHR of patients with II degree obesity, TG in those with III degree of obesity, and total cholesterol (TC) in those with four METs components. CONCLUSION Increased AS activity in patients with METs compared to lower AS activity in the control group may be due to decreased lysosomal function and related to the amount of adipose tissue. Low activity of ACP in the blood serum of patients with METs compared to high activity of ACP in the control group may indicate exhaustion of the lysosomal apparatus and loss of hydrolytic activity. The increase in TG and TC in groups with an increasing number of METs-defining components may be due to the abnormal lysosomal degradation of these compounds.
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Affiliation(s)
- Dorota M Olszewska-Słonina
- Department of Pathobiochemistry and Clinical Chemistry, Faculty of Pharmacy, L. Rydygier Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Torun, Bydgoszcz,Poland
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Comper WD, Russo LM, Vuchkova J. Are filtered plasma proteins processed in the same way by the kidney? J Theor Biol 2016; 410:18-24. [PMID: 27647256 DOI: 10.1016/j.jtbi.2016.09.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Revised: 08/24/2016] [Accepted: 09/15/2016] [Indexed: 11/19/2022]
Abstract
In order to understand the mechanism of albuminuria we have explored how other plasma proteins are processed by the kidney as compared to inert molecules like Ficolls. When fractional clearances are plotted versus protein radius there is a remarkable parallelism between protein (molecular weight range 30-150kDa) clearance in healthy controls, in Dent's disease, in nephrotic states and the clearance of Ficolls. Although there are significant differences in the levels of fractional clearances in these states. Dent's disease results in a 2-fold increase in the fractional clearance of proteins as compared to healthy controls whereas in nephrotic states there is a further 3-fold increase in fractional clearance. Previous thinking that albumin uptake was controlled primarily by the megalin/cubilin receptor does not explain the albumin urinary excretion data and is therefore an incorrect concept. Protein clearance in nephrotic states approach the fractional clearance of inert Ficolls for a given radius. It therefore appears that there are two pathways processing these proteins. A low capacity pathway associated with megalin/cubilin that degrades filtered protein (that is inhibited in Dent's disease) and a high capacity pathway that retrieves the filtered protein and returns it to the blood supply (without retrieval nephrotic protein excretion will occur and this will account for hypoproteinemia). On the other hand low molecular weight proteins (<20kDa) are processed entirely differently by the kidney. They are not retrieved but are comprehensively degraded in the kidney with the degradation products predominantly returned to the blood supply.
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Affiliation(s)
- W D Comper
- SalAqua Diagnostics, New York and Kantum Diagnostics, NH, United States.
| | - L M Russo
- Systems Biology, Massachusetts General Hospital, Boston, United States
| | - J Vuchkova
- Department Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
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Mitchell BI, Byron MM, Ng RC, Chow DC, Ndhlovu LC, Shikuma CM. Elevation of Non-Classical (CD14+/lowCD16++) Monocytes Is Associated with Increased Albuminuria and Urine TGF-β1 in HIV-Infected Individuals on Stable Antiretroviral Therapy. PLoS One 2016; 11:e0153758. [PMID: 27097224 PMCID: PMC4838224 DOI: 10.1371/journal.pone.0153758] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 04/04/2016] [Indexed: 12/30/2022] Open
Abstract
OBJECTIVE High rates of albuminuria are observed among HIV-infected individuals on stable antiretroviral therapy (ART). Though pro-inflammatory and pro-fibrotic responses are described as components of albuminuria in the general population, it is unclear how these responses are associated to albuminuria in ART-treated chronic HIV. We investigated the relationship of monocyte subsets and urine inflammatory and fibrotic biomarkers to albuminuria in ART-treated HIV-infected participants. DESIGN AND METHODS Cross-sectional analyses were performed on Hawaii Aging with HIV-cardiovascular disease study cohort participants who were required at entry to be ≥40 years old and on ART ≥3 months. Monocyte subpopulations were determined in banked peripheral blood mononuclear cells (PBMC) using multi-parametric flow-cytometry. Entry random urine samples were assessed for albumin-to-creatinine ratios (UACR). Urine samples were measured for inflammatory and fibrotic biomarkers using Luminex technology. RESULTS Among 96 HIV-infected subjects with measured UACR (87% male, 59% Caucasian, and 89% undetectable HIV RNA with median CD4 of 495.5 cells/μL), 18 patients (19%) had albuminuria. Non-classical (CD14low/+CD16++) monocytes were significantly elevated in subjects with albuminuria (p = 0.034) and were correlated to UACR (r = 0.238, p = 0.019). Elevated non-classical monocyte counts were significant predictors of worsening albuminuria, independent of traditional- and ART-associated risk factors (β = 0.539, p = 0.007). Urine TGF-β1 and collagen-IV were significantly higher in albuminuric compared to non-albuminuric participants (TGF-β1; p = 0.039 and collagen-IV; p = 0.042). Urine TGF-β1 was significantly correlated with non-classical monocyte counts (r = 0.464, p = 0.017). CONCLUSION Alterations in monocyte subpopulations and urine pro-fibrotic factors may play a role in kidney dysfunction during chronic HIV infection and warrants further study.
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Affiliation(s)
- Brooks I. Mitchell
- Department of Tropical Medicine, University of Hawaii, Honolulu, Hawaii, United States of America
- Hawaii Center for AIDS, University of Hawaii, Honolulu, Hawaii, United States of America
- * E-mail:
| | - Mary Margaret Byron
- Department of Tropical Medicine, University of Hawaii, Honolulu, Hawaii, United States of America
| | - Roland C. Ng
- Department of Medicine, University of Hawaii, Honolulu, Hawaii, United States of America
| | - Dominic C. Chow
- Hawaii Center for AIDS, University of Hawaii, Honolulu, Hawaii, United States of America
- Department of Medicine, University of Hawaii, Honolulu, Hawaii, United States of America
| | - Lishomwa C. Ndhlovu
- Department of Tropical Medicine, University of Hawaii, Honolulu, Hawaii, United States of America
- Hawaii Center for AIDS, University of Hawaii, Honolulu, Hawaii, United States of America
| | - Cecilia M. Shikuma
- Department of Tropical Medicine, University of Hawaii, Honolulu, Hawaii, United States of America
- Hawaii Center for AIDS, University of Hawaii, Honolulu, Hawaii, United States of America
- Department of Medicine, University of Hawaii, Honolulu, Hawaii, United States of America
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Russo LM, Srivatsan S, Seaman M, Suleiman H, Shaw AS, Comper WD. Albuminuria associated with CD2AP knockout mice is primarily due to dysfunction of the renal degradation pathway processing of filtered albumin. FEBS Lett 2013; 587:3738-41. [PMID: 24140342 DOI: 10.1016/j.febslet.2013.09.045] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 09/21/2013] [Accepted: 09/26/2013] [Indexed: 01/15/2023]
Abstract
Here we address the assumption that the massive intact albuminuria accompanying mutations of structural components of the slit diaphragm is due to changes in glomerular permeability. The increase in intact albumin excretion rate in Cd2ap knockout mice by >100-fold was not accompanied by equivalent changes in urine flow rate, glomerular filtration rate or increases in dextran plasma clearance rate, which demonstrates that changes in glomerular permeability alone could not account for the increase in intact albumin excretion. The albuminuria could be accounted for by inhibition of the tubule degradation pathway associated with degrading filtered albumin. There are remarkable similarities between these results and all types of podocytopathies in acquired and toxin-induced renal disease, and nephrotic states seen in mice with podocyte mutations.
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Affiliation(s)
- Leileata M Russo
- SalAqua Inc, Suite 277, 331 W 57th St, New York, NY 10019, United States
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Glomerular and tubular dysfunctions and their relationship to adiponectin and oxidative stress in obese subjects. Int J Organ Transplant Med 2012. [DOI: 10.1016/j.hkjn.2012.09.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
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Nakhjavani M, Morteza A, Jenab Y, Ghaneei A, Esteghamati A, Karimi M, Farokhian A. Gender difference in albuminuria and ischemic heart disease in type 2 diabetes. Clin Med Res 2012; 10:51-6. [PMID: 22031479 PMCID: PMC3355738 DOI: 10.3121/cmr.2011.1021] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECTIVE The value of urinary albumin excretion in the prediction of myocardial ischemia in men and women with type 2 diabetes is not well understood. We questioned whether gender influences the albuminuria-ischemic heart disease relationship in patients with type 2 diabetes. METHODS We designed a matched case-control study of 926 patients with albuminuria (cases) and 926 age and body mass index matched patients without albuminuria (controls). Ischemic heart disease was defined as the presence of (1) history of angina pectoris or angina equivalent symptoms and critical care unit admission, (2) myocardial infarction and/or electrocardiographic evidence of Q-wave myocardial infarction, (3) coronary revascularization and/or stenting, (4) positive myocardial single-photon emission computed tomography scan, (5) ischemic ST-segment or T-wave changes, and (6) positive stress testing. RESULTS Patients with albuminuria had a lower glomerular filtration rate and a longer diabetes duration than patients without albuminuria. In the group of cases, there were a greater number of men with ischemic heart disease (120 of 370; 32.4%) compared to women (97 of 559; 17.4%) (P<0.001). The odds ratio of having ischemic heart disease according to the presence or absence of albuminuria was 1.25 [95% CI: 1.01-1.56] (P<0.05) in all studied populations, 0.79 [95% CI: 0.51-1.21] (P=0.14) in women, and 2.84 [95% CI: 1.68-4.79] (P<0.001) in men. We showed that diabetes duration, high-density lipoprotein, low-density lipoprotein, and hemoglobin A(1c) influence albuminuria in women, while diabetes duration, fasting blood sugar, and diastolic blood pressure influence albuminuria in men. CONCLUSIONS Men with albuminuria are at increased risk of ischemic heart disease compared to women. This may be related to the role of high-density lipoprotein on the albuminuria-gender relationship.
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Affiliation(s)
- Manouchehr Nakhjavani
- Endocrinology and Metabolism Research Center-EMRC, Vali-Asr Hospital, Tehran University of Medical Sciences, PO Box 13145-784, Tehran, Iran.
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Speeckaert MM, Speeckaert R, Van De Voorde L, Delanghe JR. Immunochemically unreactive albumin in urine: fiction or reality? Crit Rev Clin Lab Sci 2011; 48:87-96. [PMID: 21871001 DOI: 10.3109/10408363.2011.591366] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Urinary albumin measurements are currently not standardized due to a lack of a reference method and reference (primary and secondary [matrix]) material. Multiple molecular forms of albumin in urine are identified. Modification of albumin by proteolysis during passage through the urinary tract and chemical modification during specimen storage leads to the formation of albumin fragments. Multiple methods have been developed to quantify albuminuria and significant different results are reported dependent on the available assay. The current point of view of the National Kidney Disease Education Program - IFCC Working Group on Standardization of Albumin considers the immunoassay with polyclonal sera as the primary method of quantifying urine albumin. This article reviews the process of albumin fragmentation and focuses on the controversial topic of immuno-unreactive, nonimmunoreactive, or immunochemically nonreactive albumin fractions and its consequences for albumin analysis. We conclude that at present there are no hard arguments for measuring immunochemically unreactive albumin in urine. Immunoassays using polyclonal antisera for the detection of urinary albumin remain the gold standard. The development of a reference measurement procedure remains one of the challenges for the future.
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Affiliation(s)
- Marijn M Speeckaert
- Department of Clinical Chemistry, University of Ghent, Faculty of Medicine, Belgium
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10
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The role of obesity in kidney disease: recent findings and potential mechanisms. Int Urol Nephrol 2011; 43:771-84. [PMID: 21544651 DOI: 10.1007/s11255-011-9974-1] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2010] [Accepted: 04/15/2011] [Indexed: 01/10/2023]
Abstract
Obesity epidemic is in rise in almost every industrialized country and continues to be a growing problem worldwide. In fact, obesity per se has been recognized as a chronic disease. Consequently, there has been a cascade of metabolic changes initiated by the markedly risen prevalence that contributes to the increased incidence of diabetes, hypertension, and cardiovascular disease. Moreover, obesity is also associated with an increased risk of chronic kidney disease (CKD). The majority of the studies indicate a direct relationship between body mass index (BMI) and CKD risk. Moreover, current evidence emphasized the fact that central obesity measurements, such as waist circumference, could be a better predictor of CKD progression and mortality than BMI. The detrimental effects of obesity on kidney outcome have been recognized in nondialysis-dependent (NDD)-CKD patients. However, survival in overweight or obese CKD patients undergoing maintenance hemodialysis is paradoxically opposed compared with the general population. This "reverse epidemiology," however, is valid mainly for the inflammated end-stage renal disease (ESRD) patients. In fact, renal transplant recipients with higher BMI have inferior patient and graft survival compared to patients with lower BMI. This review also provides perspectives concerning the mechanisms associated with obesity, such as the renin-angiotensin-aldosterone system (RAAS) activation, and the role of leptin, adiponectin, fetuin-A, and adipose tissue, as factors that contribute to the development of CKD. Prevention strategies for CKD patients are also discussed and should be considered by clinicians.
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Toth P, Koller A, Pusch G, Bosnyak E, Szapary L, Komoly S, Marko L, Nagy J, Wittmann I. Microalbuminuria, indicated by total versus immunoreactive urinary albumins, in acute ischemic stroke patients. J Stroke Cerebrovasc Dis 2010; 20:510-6. [PMID: 20813547 DOI: 10.1016/j.jstrokecerebrovasdis.2010.03.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2010] [Revised: 03/03/2010] [Accepted: 03/09/2010] [Indexed: 12/12/2022] Open
Abstract
Microalbuminuria, assessed by measuring immunoreactive albumin, is common in patients with cerebrovascular disease and is associated with increased risk of stroke. Total urinary albumin (t-uAlb) comprises both immunoreactive albumin (ir-uAlb) and nonimmunoreactive albumin (nir-uAlb). We hypothesized that t-uAlb is a more sensitive indicator of microalbuminuria than ir-uAlb, and that measurement of t-uAlb will increase the prevalence of microalbuminuria in ischemic stroke patients compared with measurement of ir-uAlb and will show a stronger correlation with the severity of stroke and oxidative stress. In urine samples from 98 patients with ischemic stroke, the albumin-to-creatinine ratios t-uAlb/uCreat and ir-uAlb/uCreat were measured by high-performance liquid chromatography (HPLC) and immunoturbidimetry (IT), and the nir-uAlb/uCreat ratio was calculated. Urinary ortho-tyrosine (o-Tyr/uCreat), an indicator of oxidative stress, was measured by HPLC. The severity of stroke was scored based on the National Institutes of Health Stroke Scale (NIHSS). The prevalence of microalbuminuria detected by HPLC was significantly higher than that detetcted by IT (66.3 vs 36.7%). Although all forms of albumin showed significant correlation with stroke severity (t-uAlb: r = 0.24, P < .05 ir-uAlb: r = 0.25, P < .05 nir-uAlb: r = 0.29, P < .05), only nir-uAlb was found to be an independent predictor of stroke severity (B = 0.20, β = 0.35, P < .05). In addition, t-uAlb/uCreat and nir-uAlb/uCreat had a significant correlation with o-Tyr/uCreat (r = 0.336, P < .05 and r = 0.358, P < .05 respectively), whereas ir-uAlb/uCreat did not (r = 0.22, P > .05). Our data suggest that in acute ischemic stroke patients, t-uAlb is a more sensitive indicator of microalbuminuria than the presently used ir-uAlb. Future studies should aim to elucidate the underlying mechanisms for the relationship among urinary albumins and cerebrovascular diseases and the role of urinary albumins in risk stratification for stroke.
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Affiliation(s)
- Peter Toth
- Department of Physiology, New York Medical College, Valhalla, New York, USA
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Abstract
The classic mechanism to explain albumin excretion in diabetes has been permeability defects in the glomerular filter. However, a new concept has emerged that albuminuria can be explained by the two major pathways the proximal tubular cell uses to process filtered albumin. Specifically, albumin permeability through the glomerular filter is only governed by size selectivity. Most of the filtered albumin is retrieved by the proximal tubular cell and returned to the peritubular blood supply. Albuminuria in the nephrotic range would arise from retrieval pathway dysfunction. The small quantities of filtered albumin that are not retrieved undergo obligatory lysosomal degradation before urinary excretion as small peptide fragments. This pathway is sensitive to metabolic factors responsible for hypertrophy and fibrosis, particularly molecules such as angiotensin II and transforming growth factor-beta1, whose production is stimulated by hyperglycemic environments. Dysfunction in this degradation pathway may lead to albuminuria below the nephrotic range.
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Affiliation(s)
- Wayne D Comper
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
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Wolf G. Antiproteinuric response to dual blockade of the renin–angiotensin system in primary glomerulonephritis. ACTA ACUST UNITED AC 2008; 4:474-5. [DOI: 10.1038/ncpneph0904] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Accepted: 06/25/2008] [Indexed: 11/09/2022]
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Comper WD, Hilliard LM, Nikolic-Paterson DJ, Russo LM. Disease-dependent mechanisms of albuminuria. Am J Physiol Renal Physiol 2008; 295:F1589-600. [PMID: 18579704 DOI: 10.1152/ajprenal.00142.2008] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The mechanism of albuminuria is perhaps one of the most complex yet important questions in renal physiology today. Recent studies have directly demonstrated that the normal glomerulus filters substantial amounts of albumin and that charge selectivity plays little or no role in preventing this process. This filtered albumin is then processed by proximal tubular cells by two distinct pathways; dysfunction in either one of these pathways gives rise to discrete forms of albuminuria. Most of the filtered albumin is returned to the peritubular blood supply by a retrieval pathway. Albuminuria in the nephrotic range would arise from retrieval pathway dysfunction. The small quantities of filtered albumin that are not retrieved undergo obligatory lysosomal degradation before urinary excretion as small peptide fragments. This degradation pathway is sensitive to metabolic factors responsible for hypertrophy and fibrosis, particularly molecules such as angiotensin II and transforming growth factor-beta1, whose production is stimulated by hyperglycemic and hypertensive environments. Dysfunction in this degradation pathway leads to albuminuria below the nephrotic range. These new insights into albumin filtration and processing argue for a reassessment of the role of podocytes and the slit diaphragm as major direct determinants governing albuminuria, provide information on how glomerular morphology and "tubular" albuminuria may be interrelated, and offer a new rationale for drug development.
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Affiliation(s)
- Wayne D Comper
- Dept. of Biochemistry and Molecular Biology, Monash Univ., Clayton, Victoria, Australia.
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Galle J, Schwedhelm E, Pinnetti S, Boger RH, Wanner C. Antiproteinuric effects of angiotensin receptor blockers: telmisartan versus valsartan in hypertensive patients with type 2 diabetes mellitus and overt nephropathy. Nephrol Dial Transplant 2008; 23:3174-83. [DOI: 10.1093/ndt/gfn230] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Affiliation(s)
- Anund Hallén
- Department of Medical Biochemistry and Microbiology, Uppsala University, Biomedical Center, Uppsala, Sweden
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Zhu S, Liu Y, Wang L, Meng QH. Transforming growth factor- 1 is associated with kidney damage in patients with essential hypertension: renoprotective effect of ACE inhibitor and/or angiotensin II receptor blocker. Nephrol Dial Transplant 2008; 23:2841-6. [DOI: 10.1093/ndt/gfn159] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Li H, Liu JP. Mechanisms of action of TGF-beta in cancer: evidence for Smad3 as a repressor of the hTERT gene. Ann N Y Acad Sci 2007; 1114:56-68. [PMID: 17934056 DOI: 10.1196/annals.1396.016] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Transforming growth factor-beta (TGF-beta) induces cell differentiation and suppresses cell proliferation, but the mechanisms underlying the actions of TGF-beta remain to be fully elucidated. Recent studies suggest that TGF-beta suppresses neoplastic cell development by employing Smad3 protein to repress the gene of human telomerase reverse transcriptase (hTERT). In human breast cancer cells, TGF-beta induces rapid phosphorylation and subsequent entry of Smad3 into the nucleus. In the nucleus, Smad3 binds to the hTERT gene promoter directly and inhibits hTERT gene transcription activity. By interacting with c-myc, Smad3 also represses the c-myc gene. Thus, TGF-beta prevents continuous cell proliferation by switching off telomerase activity through Smad3 repression of the hTERT gene and the action of c-myc. Modulating the interface between Smad3 and the hTERT gene, and the potential feedback loop from telomeres to Smad3 via Smurf2, may represent a novel approach to regulate cell lifespan of proliferation.
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Affiliation(s)
- He Li
- Department of Immunology, AMREP, Monash Medical School, Commercial Road, Prahran, Victoria 3181, Australia.
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Martinelli R, Santos CVCD, Albuquerque ML, Silva AM, Rodrigues LE. In vivo effect of enalapril on lysosomal compartment isolated from kidney and liver of rats. J Renin Angiotensin Aldosterone Syst 2007; 8:105-9. [PMID: 17907097 DOI: 10.3317/jrass.2007.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
INTRODUCTION Angiotensin II (Ang II) inhibitory agents such as angiotensin-converting enyzme (ACE) inhibitors have been used as antihypertensive and anti-proteinuric drugs, attenuating the progression and inducing regression of glomerulosclerosis. The mechanisms related to the renoprotective effects of the ACE-inhibitors, although partly related to the blockade of the renin-angiotensin system (RAS), are not completely understood. Their effects on many cellular functions and intracellular components have not been directly studied. The aim of the present studies was to investigate the effect of enalapril on lysosomal activity. MATERIAL AND METHODS Two groups of Wistar rats were studied. The experimental group received enalapril, 50 mg/L, in the drinking water; the control group was submitted to the same conditions except for enalapril. After two weeks of treatment, each animal was sacrificed and samples of liver and kidney were individually collected, homogenised and subjected to differential centrifugation. The supernatant was utilised for evaluation of ortophosphoric-monoester phosphohydrolase as a marker of lysosome stability and the results expressed as specific units of phosphatase activity. RESULTS The mean specific activities of the lysosomal compartment isolated from kidneys of enalapril-treated rats showed a mean specific activity that was 17.6% higher than the control group; no: difference was found in the liver. CONCLUSION The present studies suggests that the beneficial effect of enalapril is not related to effects on lysosomal membrane.
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Affiliation(s)
- Reinaldo Martinelli
- Renal Service, Federal University of Bahia, Medical School, Salvador, Bahia, Brazil.
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Santos AMR, Pomin VH, Stelling MP, Guimarães MAM, Cardoso LR, Mourão PAS. The renal clearance of dextran sulfate decreases in puromycin aminonucleoside-induced glomerulosclerosis: A puzzle observation. Clin Chim Acta 2007; 383:116-25. [PMID: 17599817 DOI: 10.1016/j.cca.2007.05.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2006] [Revised: 05/08/2007] [Accepted: 05/09/2007] [Indexed: 10/23/2022]
Abstract
BACKGROUND Puromycin aminonucleoside-induced nephrosis is characterized by increased renal excretion of plasma proteins. We employed this experimental model to study the urinary clearance of dextran sulfate. METHODS The dextran sulfate eliminated by the urine was determined using a metachromatic assay. Polysaccharide fragments were analyzed by chromatographic and electrophoretic procedures. Disaccharide composition of the glomerular heparan sulfate was assessed using digestion with specific lyases. RESULTS In normal rats dextran sulfate is partially degraded to lower molecular weight fragments and only then eliminated by the urine. Surprisingly, in puromycin aminonucleoside-induced glomerulosclerosis the molecular size of the fragments of dextran sulfate found in the urine is the same or even lower than in control animals in spite of the marked proteinuria. Furthermore, urinary excretion of dextran sulfate decreases in the experimentally induced nephrosis. This observation cannot be totally attributed to a reduced number of physiologically active nephrons since the glomerular filtration rate decreases approximately 32% after puromycin aminonucleoside administration while the urinary excretion of 8 kDa-dextran sulfate decreases 3-fold. The glomerular heparan sulfate shows reduced sulfation when compared with normal animals. Possibly puromycin aminonucleoside decreases the activity of kidney endoglycosidases, which reduce the molecular size of the sulfated polysaccharide, leading to a decrease in its renal clearance. Reduced sulfation of the glomerular heparan sulfate in the puromycin aminonucleoside-induced nephrosis does not alter the size of the dextran sulfate eliminated by the kidney, as suggested for protein. CONCLUSIONS Each pathological process induces a particular modification in the kidney, which in turn can affect the renal selectivity to specific macromolecules in different ways.
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Affiliation(s)
- Ana M R Santos
- Laboratório de Tecido Conjuntivo, Hospital Universitário Clementino Fraga Filho, Universidade Federal do Rio de Janeiro, Caixa Postal 68041, Rio de Janeiro, RJ, 21941-590, Brazil
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Russo LM, del Re E, Brown D, Lin HY. Evidence for a role of transforming growth factor (TGF)-beta1 in the induction of postglomerular albuminuria in diabetic nephropathy: amelioration by soluble TGF-beta type II receptor. Diabetes 2007; 56:380-8. [PMID: 17259382 DOI: 10.2337/db06-1018] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Transforming growth factor-beta (TGF-beta) has previously been implicated in the progression of diabetic nephropathy, including the onset of fibrosis and albuminuria. Here we report for the first time the use of a high-affinity TGF-beta1 binding molecule, the soluble human TGF-beta type II receptor (sTbetaRII.Fc), in the treatment of diabetic nephropathy in 12-week streptozotocin-induced diabetic Sprague-Dawley rats. In vitro studies using immortalized rat proximal tubule cells revealed that 50 pmol/l TGF-beta1 disrupted albumin uptake (P < 0.001 vs. control), an inhibition significantly reversed by the use of the sTbetaRII.Fc (1,200 pmol/l). In vivo studies demonstrated that treatment with sTbetaRII.Fc reduced urinary albumin excretion by 36% at 4 weeks, 59% at 8 weeks (P < 0.001), and 45% at 12 weeks (P < 0.01 for diabetic vs. treated). This was correlated with an increase in megalin expression (P < 0.05 for diabetic vs. treated) and a reduction in collagen IV expression following sTbetaRII.Fc treatment (P < 0.001 for diabetic vs. treated). These changes occurred independently of changes in blood glucose levels. This study demonstrates that the sTbetaRII.Fc is a potential new agent for the treatment of fibrosis and albuminuria in diabetic nephropathy and may reduce albuminuria by reducing TGF-beta1-induced disruptions of renal proximal tubule cell uptake of albumin.
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Affiliation(s)
- Leileata M Russo
- Program in Membrane Biology, Division of Nephrology, Department of Medicine, Massachusetts General Hospital/Harvard Medical School, Simches Research Center, 185 Cambridge Street, Boston, MA 02114, USA.
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Polkinghorne KR, Su Q, Chadban SJ, Shaw JE, Zimmet PZ, Atkins RC. Population prevalence of albuminuria in the Australian Diabetes, Obesity, and Lifestyle (AusDiab) study: immunonephelometry compared with high-performance liquid chromatography. Am J Kidney Dis 2006; 47:604-13. [PMID: 16564938 DOI: 10.1053/j.ajkd.2005.12.034] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2005] [Accepted: 12/09/2005] [Indexed: 11/11/2022]
Abstract
BACKGROUND Microalbuminuria is an independent risk factor for cardiovascular morbidity and mortality in the general population. Standard immunochemical urinary albumin assays detect immunoreactive albumin, whereas high-performance liquid chromatography (HPLC) detects both immunoreactive and immunounreactive albumin. METHODS Using data from the Australian Diabetes, Obesity, and Lifestyle cohort study of randomly selected community-based Australian adults, spot urine samples were tested for albuminuria (spot urine albumin-creatinine ratio [ACR]: normal, < 30 mg/g; microalbuminuria, 30 to 300 mg/g; and macroalbuminuria, > 300 mg/g) by using both immunonephelometry (IN) and HPLC (n = 10,010). RESULTS Bland-Altman analysis showed significant bias, with a greater ACR by means of HPLC, particularly at lower levels of ACR. Mean ACR was 15.8 mg/g (95% confidence interval [CI], 12.3 to 19.2) by means of IN compared with 30.0 mg/g (95% CI, 27.0 to 35.0) by means of HPLC. The prevalence of microalbuminuria was 4 times greater by means of HPLC compared with IN (20% versus 5.5%). In all demographic and comorbid subgroups associated with microalbuminuria, the prevalence of microalbuminuria increased by 2 to 4 times. A total of 1,743 subjects (17.4%) classified as normoalbuminuric by means of IN were reclassified as microalbuminuric by means of HPLC. Using multivariate logistic regression, women, patients with untreated and treated hypertension, and those with impaired glucose tolerance or diabetes were associated significantly with a change in category from normoalbuminuric to microalbuminuria by means of HPLC. CONCLUSION HPLC measures significantly more urinary albumin within the normoalbuminuria and microalbuminuria range, resulting in a significant increase in prevalence of microalbuminuria. Longitudinal studies are needed to determine whether the extra individuals identified by means of HPLC are at increased risk for developing hard clinical outcomes (renal and cardiovascular).
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Abstract
Albumin is the most abundant protein in serum and contributes to the maintenance of oncotic pressure as well as to transport of hydrophobic molecules. Although albumin is a large anionic protein, it is not completely retained by the glomerular filtration barrier. In order to prevent proteinuria, albumin is reabsorbed along the proximal tubules by receptor-mediated endocytosis, which involves the binding proteins megalin and cubilin. Endocytosis depends on proper vesicle acidification. Disturbance of endosomal acidification or loss of the binding proteins leads to tubular proteinuria. Furthermore, endocytosis is subject to modulation by different signaling systems, such as protein kinase A (PKA), protein kinase C (PKC), phosphatidylinositol 3-kinase (PI3-K) and transforming growth factor beta (TGF-beta). In addition to being reabsorbed in the proximal tubule, albumin can also act as a profibrotic and proinflammatory stimulus, thereby initiating or promoting tubulo-interstitial diseases.
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Affiliation(s)
- Michael Gekle
- Physiologisches Institut, University of Würzburg, 97070 Würzburg, Germany.
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Teppo AM, Honkanen E, Finne P, Törnroth T, Grönhagen-Riska C. Increased urinary excretion of alpha1-microglobulin at 6 months after transplantation is associated with urinary excretion of transforming growth factor-beta1 and indicates poor long-term renal outcome. Transplantation 2004; 78:719-24. [PMID: 15371675 DOI: 10.1097/01.tp.0000131816.51366.6b] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND Albumin and alpha1-microglobulin (alpha1M) are absorbed by two specific receptors in tubular epithelial cells. Any cell injury will disturb the reabsorption of these proteins, The increased urinary excretions of albumin or alpha1M could thus serve as a marker of subclinical graft lesions and as an early indicator of chronic allograft dysfunction. METHODS We measured 24-hour urinary excretions of albumin, alpha1M, and transforming growth factor (TGF)-beta1 at 6 months after transplantation in 79 renal-graft recipients and recorded the changes in 24-hour creatinine clearance an average 51 (range 14-72) posttransplant follow-up months. RESULTS At 6 months from transplantation, 46 of 79 (58%) patients were normoalbuminuric, 25 (32%) microalbuminuric, and 8 (10%) macroalbuminuric. In normoalbuminuric patients, urinary alpha1M/creatinine ratio was 10 times, and TGF-beta1/creatinine ratio approximately 5 times, higher than in the healthy subjects but lower than in albuminuric patients. In all patients, urinary alpha1M correlated with urinary TGF-beta1 (r=0.508, P<0.001), with albumin (r=0.220, P<0.05), and with the annual changes in 24-hour creatinine clearance (r=-0.273, P<0.05). During follow-up, renal function deteriorated in 20 of 33 (60%) patients with alpha1M/creatinine ratio greater than 5 mg/mmol, but only in 1 of 46 (2%) patients whose ratio was less than 5 mg/mmol (P<0.01), giving the ratio 5 mg/mmol or greater a 95% sensitivity to detect patients with poor long-term outcome. CONCLUSIONS We show proximal tubular injury, measured by increased urinary alpha1M, to be present even in normoalbuminuric patients and to be associated with increased excretion of TGF-beta1 and with the annual deterioration of glomerular filtration rate. These findings show increased alpha1M/creatinine ratio to be an early and sensitive indicator of poor long-term outcome in renal-transplant patients.
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Affiliation(s)
- Anna-Maija Teppo
- Department of Medicine, Division of Nephrology, Helsinki University Hospital, Helsinki, Finland
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Russo LM, Comper WD, Osicka TM. Mechanism of albuminuria associated with cardiovascular disease and kidney disease. Kidney Int 2004:S67-8. [PMID: 15485423 DOI: 10.1111/j.1523-1755.2004.09218.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The major underlying factors associated with tissue damage and fibrosis in cardiovascular and kidney disease are the up-regulation and action of growth factors such as transforming growth factor-beta (TGF-beta) and cytokines produced in response to changes in systemic factors, particularly blood pressure or hyperglycemia. This study identifies the relationship of elevated levels of TGF-beta to increased levels of intact albumin in the urine (micro- and macroalbuminuria). This mechanism may be directly linked to the effect of TGF-beta on albumin uptake and the lysosomal breakdown of filtered albumin by proximal tubular cells prior to excretion.
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Affiliation(s)
- Leileata M Russo
- Program in Membrane Biology, Renal Unit, Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, USA
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Das UN. Long-chain polyunsaturated fatty acids interact with nitric oxide, superoxide anion, and transforming growth factor-beta to prevent human essential hypertension. Eur J Clin Nutr 2004; 58:195-203. [PMID: 14749737 DOI: 10.1038/sj.ejcn.1601766] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Patients with uncontrolled essential hypertension have elevated concentrations of superoxide anion (O(2)(-*)), hydrogen peroxide (H(2)O(2)), lipid peroxides, endothelin, and transforming growth factor-beta (TGF-beta) with a simultaneous decrease in endothelial nitric oxide (eNO), superoxide dismutase (SOD), vitamin E, and long-chain polyunsaturated fatty acids (LCPUFAs). Physiological concentrations of angiotensin II activate NAD(P)H oxidase and trigger free radical generation (especially that of O(2)(-*)). Normally, angiotensin II-induced oxidative stress is abrogated by adequate production and release of eNO, which quenches O(2)(-*) to restore normotension. Angiotensin II also stimulates the production of endothelin and TGF-beta. TGF-beta enhances NO generation, which in turn suppresses TGF-beta production. Thus, NO has a regulatory role on TGF-beta production and is also a physiological antagonist of endothelin. Antihypertensive drugs suppress the production of O(2)(-*) and TGF-beta and enhance eNO synthesis to bring about their beneficial actions. LCPUFAs suppress angiotensin-converting enzyme (ACE) activity, reduce angiotensin II formation, enhance eNO generation, and suppress TGF-beta expression. Perinatal supplementation of LCPUFAs decreases insulin resistance and prevents the development of hypertension in adult life, whereas deficiency of LCPUFAs in the perinatal period results in raised blood pressure later in life. Patients with essential hypertension have low concentrations of various LCPUFAs in their plasma phospholipid fraction. Based on this, it is proposed that LCPUFAs serve as endogenous regulators of ACE activity, O(2)(-*), eNO generation, and TGF-beta expression. Further, LCPUFAs have actions similar to statins, inhibit (especially omega-3 fatty acids) cyclooxygenase activity and suppress the synthesis of proinflammatory cytokines, and activate the parasympathetic nervous system, all actions that reduce the risk of major vascular events. Hence, it is proposed that availability of adequate amounts of LCPUFAs during the critical periods of growth prevents the development of hypertension in adulthood.
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Affiliation(s)
- U N Das
- EFA Sciences LLC, Norwood, MA 02062, USA.
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Chagnac A, Weinstein T, Herman M, Hirsh J, Gafter U, Ori Y. The effects of weight loss on renal function in patients with severe obesity. J Am Soc Nephrol 2003; 14:1480-6. [PMID: 12761248 DOI: 10.1097/01.asn.0000068462.38661.89] [Citation(s) in RCA: 381] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Severe obesity is associated with increased renal plasma flow (RPF) and glomerular filtration rate (GFR). The aim of the present study was to examine whether weight loss may reverse glomerular dysfunction in obese subjects without overt renal disease. Renal glomerular function was studied in eight subjects with severe obesity (body mass index [BMI] 48.0 +/- 2.4) before and after weight loss. Nine healthy subjects served as controls. GFR and RPF were determined by measuring inulin and PAH clearance. In the obese group, GFR (145 +/- 14 ml/min) and RPF (803 +/- 39 ml/min) exceeded the control value by 61% (90 +/- 5 ml/min, P = 0.001) and 32% (610 +/- 41 ml/min, P < 0.005), respectively. Consequently, filtration fraction was increased. Mean arterial pressure, although normal, was higher than in the control group (101 +/- 4 versus 86 +/- 2 mmHg, P < 0.01). After weight loss, BMI decreased by 32 +/- 4%, to 32.1 +/- 1.5 (P = 0.001). GFR and RPF decreased to 110 +/- 7 ml/min (P = 0.01) and 698 +/- 42 ml/min (P < 0.02), respectively. Albumin excretion rate decreased from 16 microg/min (range, 4 to 152 microg/min) to 5 microg/min (range, 3 to 37 microg/min) (P < 0.01). Fractional clearance of albumin decreased from 3.2 x 10(-6) (range, 1.1 to 23 x 10(-6)) to 1.2 x 10(-6) (range, 0.5 to 6.8 x 10(-6)) (P < 0.02). This study shows that obesity-related glomerular hyperfiltration ameliorates after weight loss. The improvement in hyperfiltration may prevent the development of overt obesity-related glomerulopathy.
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Affiliation(s)
- Avry Chagnac
- Department of Nephrology, Rabin Medical Center-Golda Campus, Tel Aviv University Medical School, Petah Tikva, Israel.
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Wohlfarth V, Drumm K, Mildenberger S, Freudinger R, Gekle M. Protein uptake disturbs collagen homeostasis in proximal tubule-derived cells. KIDNEY INTERNATIONAL. SUPPLEMENT 2003:S103-9. [PMID: 12694321 DOI: 10.1046/j.1523-1755.63.s84.13.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Interstitial fibrosis is of major importance for the deterioration of renal function, leading to uremia. Interaction of filtered proteins with proximal tubular cells is important for the onset and development of tubulointerstitial damage. METHODS We investigated the effects of protein endocytosis on collagen homeostasis and signaling pathways of proximal tubule-derived cells (OK cells, LLC-PK1 cells), which express the endocytic machinery typical for the proximal tubule (megalin and cubilin), and compared it to renal epithelial cells with low endocytic activity (MDCK, IHKE1, NHE3-deficient OK cells). Collagen homeostasis was assessed by proline incorporation, ELISA, and Western blot. Matrix metalloproteinase (MMP) activity was assessed by gelatinase assay. Signaling pathways were monitored by reporter gene assay. RESULTS Albumin, glycated albumin, fatty acid-free albumin, or globulins led to an increase of secreted collagen (types I, III, and IV) in OK and LLC-PK1 cells. In cells with low protein uptake activity, albumin exposure inhibited collagen secretion. Western blot analysis showed an increase of cellular collagen. MMP activity was significantly decreased by albumin exposure. Furthermore, albumin exposure led to activation of the NF-kappa B-, AP1-, NFAT-, SRE-, and CRE-pathways. Inhibition of NF-kappa B, PKC, or PKA partially reversed the effects of albumin. In addition, inhibition of albumin endocytosis reduced collagen secretion and activation of the signaling pathways. Discussion. The data show that endocytic uptake of proteins disturbs collagen homeostasis in proximal tubular cells. This disturbed matrix homeostasis probably supports the progression of interstitial fibrosis, which is of importance for the development of renal insufficiency.
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Affiliation(s)
- Verena Wohlfarth
- Physiologisches Institut, Universität Würzburg, Würzburg, Germany
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Russo LM, Brammar GC, Jerums G, Comper WD, Osicka TM. The effect of ramipril on albumin excretion in diabetes and hypertension: the role of increased lysosomal activity and decreased transforming growth factor-beta expression. J Hypertens 2003; 21:419-28. [PMID: 12569274 DOI: 10.1097/00004872-200302000-00035] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Albumin excretion is modulated post-filtration by lysosomal processing that produces a spectrum of albumin-derived material in urine, much of which is not detected by conventional immunoassays. This study aimed to determine the efficacy of ramipril treatment (+ RAM) after 24 weeks on total albumin excretion (intact plus albumin-derived peptides) in spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats with (d) and without (c) diabetes. METHODS Intact albumin excretion was analysed by radioimmunoassay and total albumin excretion was analysed by measuring radioactivity derived from circulating [ C]albumin. Renal lysosomal activity was determined by urinary [ H]dextran sulphate desulphation. Renal transforming growth factor-beta 1 (TGF-beta 1), TGF-beta inducible gene-h3 (beta ig-h3) and angiotensinogen mRNA production were analysed by real time reverse transcriptase-polymerase chain reaction. RESULTS Hypertension (SHR-c and SHR-d) resulted in a significant increase in intact albumin excretion, which was significantly reduced by ramipril treatment (P < 0.05 for SHR-c + RAM and 0.001 for SHR-d + RAM compared to non-treated). This was accompanied by a significant decrease in blood pressure (P < 0.001 for SHR-c + RAM and SHR-d + RAM), renal beta ig-h3 mRNA production (P < 0.05 for SHR-c + RAM and SHR-d + RAM), and an increase in lysosomal activity. Diabetes (WKY-d and SHR-d) primarily caused a significant increase in total albumin excretion, predominantly in the form of albumin-derived fragments in the WKY-d group and intact albumin in the SHR-d group. Ramipril treatment reduced total albumin excretion in the WKY-d + RAM group (P < 0.001). CONCLUSIONS Ramipril prevents increases in both intact albumin and total albumin excretion in hypertensive and diabetic states, respectively.
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Affiliation(s)
- Leileata M Russo
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
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Kamimura M, Orth SR. Altered tubular albumin degradation in the pathogenesis of albuminuria: additional experimental evidence challenging the paradigm of glomerular capillary leakage. J Hypertens 2003; 21:269-71. [PMID: 12569255 DOI: 10.1097/00004872-200302000-00016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Tanner GA, Tielker MA, Connors BA, Phillips CL, Tanner JA, Evan AP. Atubular glomeruli in a rat model of polycystic kidney disease. Kidney Int 2002; 62:1947-57. [PMID: 12427119 DOI: 10.1046/j.1523-1755.2002.00689.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Autosomal-dominant polycystic kidney disease (ADPKD) is associated with a progressive decline in glomerular filtration rate (GFR) that often leads to end-stage renal disease. The basis for this decline in GFR is poorly understood. METHODS Glomeruli in heterozygous Han:SPRD rats with ADPKD and their normal litter mates were studied by light microscopy, using serial sectioning techniques. The connections of the renal corpuscles to proximal tubules were classified as normal, atrophied, or absent (atubular glomerulus). Renal corpuscles also were examined by scanning electron microscopy. Single nephron glomerular blood flows were determined using microspheres. RESULTS In the kidneys of six-month-old rats with ADPKD, 50% of the glomeruli were atubular and another 26% were associated with atrophied neck segments; these glomeruli were most often smaller in size than normal. About 16% of the glomeruli were hypertrophied and had normal connections to proximal tubules. Sclerotic changes in cystic kidney glomeruli were usually mild or moderate, and belied the failure of glomerular function. Glomerular blood flow in the cystic kidneys averaged half of normal and was markedly heterogeneous; the majority of small glomeruli displayed very low blood flows and a few showed relatively high blood flows. Fewer glomerular abnormalities were found in rats treated for five months with potassium citrate in their drinking water. CONCLUSIONS The diminished GFR in the rat with ADPKD can be accounted for largely by the formation of atubular glomeruli. Compensatory glomerular hypertrophy also is present and may contribute to the progression of the renal disease.
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Affiliation(s)
- George A Tanner
- Department of Cellular and Integrative Physiology, Indiana UniversitySchool of Medicine, Indianapolis, Indiana, USA.
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Russo LM, Bakris GL, Comper WD. Renal handling of albumin: a critical review of basic concepts and perspective. Am J Kidney Dis 2002; 39:899-919. [PMID: 11979334 DOI: 10.1053/ajkd.2002.32764] [Citation(s) in RCA: 159] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Biochemical and physiological processes that underlie the mechanism of albuminuria are completely reassessed in this article in view of recent discoveries that filtered proteins undergo rapid degradation during renal passage and the resulting excreted peptide fragments are not detected by conventional urine protein assays. This means that filtered protein and/or albumin levels in urine have been seriously underestimated. The concept that albuminuria is a result of changes in glomerular permeability is questioned in light of these findings and also in terms of a critical examination of charge selectivity, shunts, or large-pore formation and hemodynamic effects. The glomerulus appears to function merely in terms of size selectivity alone, and for albumin, this does not change significantly in disease states. Intensive albumin processing by a living kidney occurs through cellular processes distal to the glomerular basement membrane. Failure of this cellular processing primarily leads to albuminuria. This review brings together recent data about urinary albumin clearance and current knowledge of receptors known to process albumin in both health and disease states. We conclude with a discussion of topical and controversial issues associated with the proposed new understanding of renal handling of albumin.
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Affiliation(s)
- Leileata M Russo
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
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