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Adi M, Ghanbari F, Downie ML, Hung A, Robinson-Cohen C, Manousaki D. Effects of 25-Hydroxyvitamin D Levels on Renal Function: A Bidirectional Mendelian Randomization Study. J Clin Endocrinol Metab 2023; 108:1442-1451. [PMID: 36510827 PMCID: PMC10413421 DOI: 10.1210/clinem/dgac724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 12/07/2022] [Accepted: 12/08/2022] [Indexed: 12/15/2022]
Abstract
CONTEXT Observational studies investigating the role of vitamin D in renal function have yielded inconsistent results. OBJECTIVE We tested whether 25-hydroxyvitamin D (25[OH]D) serum levels are associated with renal function, and inversely, whether altered renal function causes changes in 25(OH)D, using Mendelian randomization (MR). METHODS In this two-sample MR study, we used single nucleotide polymorphisms (SNP) associated with 25(OH)D in 443 734 Europeans and evaluated their effects on estimated glomerular filtration rate (eGFR), blood urea nitrogen (BUN), chronic kidney disease (CKD) risk and progression in genome-wide association studies totaling over 1 million Europeans. To control for pleiotropy, we also used SNPs solely in DHCR7, CYP2R1, and GC, all genes with known roles in vitamin D metabolism. We performed a reverse MR, using SNPs for the above indices of renal function to study causal effects on 25(OH)D levels. RESULTS We did not find robust evidence supporting effects of 25(OH)D on eGFR, BUN, and CKD or its progression. Our inverse variance weighted MR demonstrated a 0.56 decrease in standardized log-transformed 25(OH)D (95% CI -0.73, -0.41; P = 2.89 × 10-12) per unit increase in log-transformed eGFR. Increased BUN was associated with increased 25(OH)D (β = 0.25, 95% CI 0.15, 0.36; P = 4.12 × 10-6 per unit increase in log-transformed BUN). Finally, genetically predicted CKD conferred a 0.05 increase in standardized log-transformed 25(OH)D level (95% CI 0.04, 0.06; P = 1.06 × 10-13). Other MR methods confirmed the findings of the main analyses. CONCLUSION Genetically predicted CKD, increased BUN, and decreased eGFR are associated with increased 25(OH)D levels, but we found no causal effect of 25(OH)D on renal function in Europeans.
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Affiliation(s)
- Manel Adi
- Department of Biochemistry and Molecular Medicine, University of Montreal, Montreal, QC H3T1J4, Canada
| | - Faegheh Ghanbari
- Research Center of the Sainte-Justine University Hospital, University of Montreal, Montreal, QC H3TAC5, Canada
| | - Mallory L Downie
- Department of Renal Medicine, University College London, London NW32PF, UK
| | - Adriana Hung
- Department of Medicine, Vanderbilt University Medical Center, Veterans Administration Tennessee Valley Healthcare System, Nashville, TN 37212, USA
| | | | - Despoina Manousaki
- Department of Biochemistry and Molecular Medicine, University of Montreal, Montreal, QC H3T1J4, Canada
- Research Center of the Sainte-Justine University Hospital, University of Montreal, Montreal, QC H3TAC5, Canada
- Department of Pediatrics, University of Montreal, Montreal, QC H3T1C5, Canada
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Nemeth Z, Patonai A, Simon-Szabó L, Takács I. Interplay of Vitamin D and SIRT1 in Tissue-Specific Metabolism-Potential Roles in Prevention and Treatment of Non-Communicable Diseases Including Cancer. Int J Mol Sci 2023; 24:ijms24076154. [PMID: 37047134 PMCID: PMC10094444 DOI: 10.3390/ijms24076154] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Revised: 03/13/2023] [Accepted: 03/16/2023] [Indexed: 04/14/2023] Open
Abstract
The importance of the prevention and control of non-communicable diseases, including obesity, metabolic syndrome, type 2 diabetes, cardiovascular diseases, and cancer, is increasing as a requirement of the aging population in developed countries and the sustainability of healthcare. Similarly, the 2013-2030 action plan of the WHO for the prevention and control of non-communicable diseases seeks these achievements. Adequate lifestyle changes, alone or with the necessary treatments, could reduce the risk of mortality or the deterioration of quality of life. In our recent work, we summarized the role of two central factors, i.e., appropriate levels of vitamin D and SIRT1, which are connected to adequate lifestyles with beneficial effects on the prevention and control of non-communicable diseases. Both of these factors have received increased attention in relation to the COVID-19 pandemic as they both take part in regulation of the main metabolic processes, i.e., lipid/glucose/energy homeostasis, oxidative stress, redox balance, and cell fate, as well as in the healthy regulation of the immune system. Vitamin D and SIRT1 have direct and indirect influence of the regulation of transcription and epigenetic changes and are related to cytoplasmic signaling pathways such as PLC/DAG/IP3/PKC/MAPK, MEK/Erk, insulin/mTOR/cell growth, proliferation; leptin/PI3K-Akt-mTORC1, Akt/NFĸB/COX-2, NFĸB/TNFα, IL-6, IL-8, IL-1β, and AMPK/PGC-1α/GLUT4, among others. Through their proper regulation, they maintain normal body weight, lipid profile, insulin secretion and sensitivity, balance between the pro- and anti-inflammatory processes under normal conditions and infections, maintain endothelial health; balance cell differentiation, proliferation, and fate; and balance the circadian rhythm of the cellular metabolism. The role of these two molecules is interconnected in the molecular network, and they regulate each other in several layers of the homeostasis of energy and the cellular metabolism. Both have a central role in the maintenance of healthy and balanced immune regulation and redox reactions; therefore, they could constitute promising targets either for prevention or as complementary therapies to achieve a better quality of life, at any age, for healthy people and patients under chronic conditions.
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Affiliation(s)
- Zsuzsanna Nemeth
- Department of Internal Medicine and Oncology, Semmelweis University, Koranyi S. u 2/a, 1083 Budapest, Hungary
| | - Attila Patonai
- Department of Surgery, Transplantation and Gastroenterology, Semmelweis University, Ulloi u. 78, 1082 Budapest, Hungary
| | - Laura Simon-Szabó
- Department of Molecular Biology, Semmelweis University, Tuzolto u. 37-47, 1094 Budapest, Hungary
| | - István Takács
- Department of Internal Medicine and Oncology, Semmelweis University, Koranyi S. u 2/a, 1083 Budapest, Hungary
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Kritmetapak K, Losbanos L, Berent TE, Ashrafzadeh-Kian SL, Algeciras-Schimnich A, Hines JM, Singh RJ, Kumar R. Hyperphosphatemia with elevated serum PTH and FGF23, reduced 1,25(OH) 2D and normal FGF7 concentrations characterize patients with CKD. BMC Nephrol 2021; 22:114. [PMID: 33784965 PMCID: PMC8011073 DOI: 10.1186/s12882-021-02311-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 03/12/2021] [Indexed: 12/26/2022] Open
Abstract
BACKGROUND Hyperphosphatemia confers adverse cardiovascular outcomes, and commonly occurs in late-stage CKD. Fibroblast growth factor 7 (FGF7) is a phosphaturic peptide which decreases renal phosphate transport in vitro and in vivo. Serum FGF7 concentrations are reduced in hyperphosphatemic patients with hypophosphatasia and are elevated in some hypophosphatemic patients with tumor-induced osteomalacia. No data, however, are available on whether circulating FGF7 concentrations increase to compensate for phosphate retention in CKD patients. METHODS This was a cross-sectional study performed among 85 adult patients with varying estimated glomerular filtration rates (eGFR). We measured serum intact FGF7 (iFGF7) concentration using an iFGF7 immunoassay and determined its associated factors. Relationships between eGFR and mineral metabolism biomarkers [phosphate, iFGF7, iFGF23, parathyroid hormone (PTH), and 1,25-dihydroxyvitamin D (1,25(OH)2D)] were explored. RESULTS For eGFRs of ≥ 60 (n = 31), 45-59 (n = 16), 30-44 (n = 11), 15-29 (n = 15), and < 15 mL/min/1.73 m2 (n = 12), median (IQ25-75) iFGF7 concentrations were 46.1 (39.2-56.9), 43.1 (39.0-51.5), 47.3 (38.3-66.5), 47.7 (37.7-55.8), and 49.6 (42.5-65.6) pg/mL, respectively (P = 0.62). Significant increases in serum iFGF23, PTH, and phosphate were observed at eGFRs of < 33 (95 % CI, 26.40-40.05), < 29 (95 % CI, 22.51-35.36), and < 22 mL/min/1.73 m2 (95 % CI, 19.25-25.51), respectively, while significant decreases in serum 1,25(OH)2D were observed at an eGFR of < 52 mL/min/1.73 m2 (95 % CI, 42.57-61.43). No significant correlation was found between serum iFGF7 and phosphate, iFGF23, PTH or 1,25(OH)2D. In multivariable analyses, body mass index (per 5 kg/m2 increase) was independently associated with the highest quartile of serum iFGF7 concentration (OR, 1.20; 95 % CI, 1.12-1.55). CONCLUSIONS Compensatory decreases in circulating 1,25(OH)2D and increases in circulating iFGF23 and PTH, but not iFGF7, facilitate normalization of serum phosphate concentration in early stages of CKD. Whether other circulating phosphaturic peptides change in response to phosphate retention in CKD patients deserves further study.
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Affiliation(s)
- Kittrawee Kritmetapak
- Division of Nephrology and Hypertension, Department of Internal Medicine, Mayo Clinic, 200 1st Street SW, MN, 55905, Rochester, USA.,Division of Nephrology, Department of Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - Louis Losbanos
- Division of Nephrology and Hypertension, Department of Internal Medicine, Mayo Clinic, 200 1st Street SW, MN, 55905, Rochester, USA
| | - Taylor E Berent
- Division of Nephrology and Hypertension, Department of Internal Medicine, Mayo Clinic, 200 1st Street SW, MN, 55905, Rochester, USA
| | | | - Alicia Algeciras-Schimnich
- Clinical Immunoassay Laboratory, Mayo Clinic, MN, Rochester, USA.,Department of Laboratory Medicine and Pathology, Mayo Clinic, MN, Rochester, USA
| | - Jolaine M Hines
- Immunochemical Core Laboratory, Mayo Clinic, MN, Rochester, USA
| | - Ravinder J Singh
- Department of Laboratory Medicine and Pathology, Mayo Clinic, MN, Rochester, USA
| | - Rajiv Kumar
- Division of Nephrology and Hypertension, Department of Internal Medicine, Mayo Clinic, 200 1st Street SW, MN, 55905, Rochester, USA. .,Department of Biochemistry and Molecular Biology, Mayo Clinic, MN, Rochester, USA.
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Kritmetapak K, Pongchaiyakul C. Parathyroid Hormone Measurement in Chronic Kidney Disease: From Basics to Clinical Implications. Int J Nephrol 2019; 2019:5496710. [PMID: 31637056 PMCID: PMC6766083 DOI: 10.1155/2019/5496710] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 09/04/2019] [Indexed: 11/18/2022] Open
Abstract
Accurate measurement of parathyroid hormone (PTH) is crucial for therapeutic decision-making in patients with chronic kidney disease-mineral and bone disorder (CKD-MBD). The second-generation PTH assays, often referred to as "intact PTH" assays, are the current standard and most available assays in clinical practice. However, intact PTH assays measure both full-length biologically active PTH and heterogeneous PTH fragments in the circulation, providing the equivocal value of PTH measurement in patients with CKD-MBD. Due to the variability of PTH assays, preanalytical sample errors, and the phenomenon of end-organ PTH hyporesponsiveness, current CKD-MBD guidelines recommend a wide range for serum PTH targets (2-9 the upper normal limit of the intact PTH assay) in dialysis patients to diminish the risk of developing adynamic bone disease. Nevertheless, a sizeable proportion of CKD patients still experience renal osteodystrophy despite having serum PTH levels within the recommended range. The primary cause of this inconsistency is the analytical interference of various PTH fragments and oxidized PTH forms that considerably accumulate in CKD patients. Therefore, a new mass spectrometry-based assay, which is capable of specifically measuring the whole spectra of PTH fragments, can potentially improve diagnostic accuracy for renal osteodystrophy. However, the effects of different PTH fragments on bone metabolism, vascular calcification, and mortality in CKD patients warrant further research.
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Affiliation(s)
- Kittrawee Kritmetapak
- Division of Nephrology, Department of Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
| | - Chatlert Pongchaiyakul
- Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
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Li HJ, Groden C, Hoenig MP, Ray EC, Ferreira CR, Gahl W, Novacic D. Case report: extreme coronary calcifications and hypomagnesemia in a patient with a 17q12 deletion involving HNF1B. BMC Nephrol 2019; 20:353. [PMID: 31500578 PMCID: PMC6734489 DOI: 10.1186/s12882-019-1533-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2019] [Accepted: 08/23/2019] [Indexed: 01/30/2023] Open
Abstract
Background 17q12 deletion syndrome encompasses a broad constellation of clinical phenotypes, including renal magnesium wasting, maturity-onset diabetes of the young (MODY), renal cysts, genitourinary malformations, and neuropsychiatric illness. Manifestations outside of the renal, endocrine, and nervous systems have not been well described. Case presentation We report a 62-year-old male referred to the Undiagnosed Diseases Program (UDP) at the National Institutes of Health (NIH) who presented with persistent hypermagnesiuric hypomagnesemia and was found to have a 17q12 deletion. The patient exhibited several known manifestations of the syndrome, including severe hypomagnesemia, renal cysts, diabetes and cognitive deficits. Coronary CT revealed extensive coronary calcifications, with a coronary artery calcification score of 12,427. Vascular calcifications have not been previously reported in this condition. We describe several physiologic mechanisms and a review of literature to support the expansion of the 17q12 deletion syndrome to include vascular calcification. Conclusion Extensive coronary and vascular calcifications may be an extension of the 17q12 deletion phenotype, particularly if hypomagnesemia and hyperparathyroidism are prevalent. In patients with 17q12 deletions involving HNF1B, hyperparathyroidism and hypomagnesemia may contribute to significant cardiovascular risk.
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Affiliation(s)
- Howard J Li
- Harvard Medical School, Boston, MA, 02115, USA.,National Institute of Mental Health, NIH, Bethesda, MD, 20892, USA
| | - Catherine Groden
- Undiagnosed Diseases Program, Office of the Clinical Director and National Human Genome Research Institute, NIH, Bethesda, MD, 20892, USA
| | - Melanie P Hoenig
- Harvard Medical School, Boston, MA, 02115, USA.,Division of Nephrology, Beth Israel Deaconess Medical Center, Boston, MA, 02215, USA
| | - Evan C Ray
- Renal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PA, 15261, USA
| | - Carlos R Ferreira
- Medical Genetics Branch, National Human Genome Research Institute, NIH, Bethesda, MD, USA
| | - Willam Gahl
- Undiagnosed Diseases Program, Office of the Clinical Director and National Human Genome Research Institute, NIH, Bethesda, MD, 20892, USA.,Medical Genetics Branch, National Human Genome Research Institute, NIH, Bethesda, MD, USA
| | - Danica Novacic
- Undiagnosed Diseases Program, Office of the Clinical Director and National Human Genome Research Institute, NIH, Bethesda, MD, 20892, USA.
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6
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Leung EKY, Lee CC, Angelos P, Kaplan EL, Grogan RH, Sarracino DA, Krastins B, Lopez MF, Karrison T, Yeo KTJ. Analytical Differences in Intraoperative Parathyroid Hormone Assays. J Appl Lab Med 2019; 3:788-798. [PMID: 31639754 DOI: 10.1373/jalm.2018.026815] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 12/07/2018] [Indexed: 11/06/2022]
Abstract
BACKGROUND We compared the rates of intraoperative parathyroid hormone (PTH) decline using the Siemens Immulite® Turbo PTH and Roche Elecsys® short turnaround time PTH assays in 95 consecutive surgical patients to investigate analytical and turnaround time (TAT) differences between the tests performed in the operating room (OR) vs the central clinical chemistry laboratory (CCL). METHODS Serial blood samples from 95 patients undergoing parathyroidectomy were collected and measured using the 2 immunoassays. Specimens from the first 15 patients were measured simultaneously in the OR and CCL and used for the TAT study. In addition to 2 baseline samples, specimens were collected at 5, 10, and 15 min (for some patients, >15 min) after parathyroidectomy. RESULTS In the TAT study, a significant difference was observed (OR median 20 min vs CCL median 27 min; P < 0.05). Of the 95 patient series, slower rates of parathyroid hormone decrease were observed in approximately 20% of the patients when comparing the Roche with the Immulite immunoassay. CONCLUSIONS There was a slightly longer TAT in the CCL compared with running the assay directly within the OR (median difference of approximately 7 min). For a majority of the patients, both methods showed equivalent rates of PTH decline; however, for approximately 20% of the patients, there was a slower rate of PTH decline using the Roche assay.
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Affiliation(s)
- Edward K Y Leung
- Department of Pathology, Pritzker School of Medicine, The University of Chicago, Chicago, IL;
| | - Christine C Lee
- Department of Pathology, Pritzker School of Medicine, The University of Chicago, Chicago, IL
| | - Peter Angelos
- Endocrine Surgery Research Program, Department of Surgery, Section of Endocrine Surgery, The University of Chicago Medical Center, Chicago, IL
| | - Edwin L Kaplan
- Endocrine Surgery Research Program, Department of Surgery, Section of Endocrine Surgery, The University of Chicago Medical Center, Chicago, IL
| | - Raymon H Grogan
- Endocrine Surgery Research Program, Department of Surgery, Section of Endocrine Surgery, The University of Chicago Medical Center, Chicago, IL
| | - David A Sarracino
- BRIMS (Biomarker Research Initiative in MS), Thermo Fisher Scientific, Cambridge, MA
| | | | | | - Theodore Karrison
- Department of Public Health Sciences, Biostatistics Laboratory, The University of Chicago, Chicago, IL
| | - Kiang-Teck J Yeo
- Department of Pathology, Pritzker School of Medicine, The University of Chicago, Chicago, IL
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Role of Vitamin D in Uremic Vascular Calcification. BIOMED RESEARCH INTERNATIONAL 2017; 2017:2803579. [PMID: 28286758 PMCID: PMC5329659 DOI: 10.1155/2017/2803579] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 12/26/2016] [Accepted: 01/16/2017] [Indexed: 12/16/2022]
Abstract
The risk of cardiovascular death is 10 times higher in patients with CKD (chronic kidney disease) than in those without CKD. Vascular calcification, common in patients with CKD, is a predictor of cardiovascular mortality. Vitamin D deficiency, another complication of CKD, is associated with vascular calcification in patients with CKD. GFR decline, proteinuria, tubulointerstitial injury, and the therapeutic dose of active form vitamin D aggravate vitamin D deficiency and reduce its pleiotropic effect on the cardiovascular system. Vitamin D supplement for CKD patients provides a protective role in vascular calcification on the endothelium by (1) renin-angiotensin-aldosterone system inactivation, (2) alleviating insulin resistance, (3) reduction of cholesterol and inhibition of foam cell and cholesterol efflux in macrophages, and (4) modulating vascular regeneration. For the arterial calcification, vitamin D supplement provides adjunctive role in regressing proteinuria, reverse renal osteodystrophy, and restoring calcification inhibitors. Recently, adventitial progenitor cell has been linked to be involved in the vascular calcification. Vitamin D may provide a role in modulating adventitial progenitor cells. In summary, vitamin D supplement may provide an ancillary role for ameliorating uremic vascular calcification.
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Felsenfeld AJ, Levine BS, Rodriguez M. Pathophysiology of Calcium, Phosphorus, and Magnesium Dysregulation in Chronic Kidney Disease. Semin Dial 2015; 28:564-77. [DOI: 10.1111/sdi.12411] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Arnold J. Felsenfeld
- Department of Medicine; VA Greater Los Angeles Healthcare System and the David Geffen School of Medicine at UCLA; Los Angeles California
| | - Barton S. Levine
- Department of Medicine; VA Greater Los Angeles Healthcare System and the David Geffen School of Medicine at UCLA; Los Angeles California
| | - Mariano Rodriguez
- Nephrology Service; IMIBIC; Hospital Universitario Reina Sofia; University of Cordoba; Cordoba Spain
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10
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Abstract
Chronic kidney disease (CKD) has been recognized as a significant global health problem because of the increased risk of total and cardiovascular morbidity and mortality. Vitamin D deficiency or insufficiency is common in patients with CKD, and serum levels of vitamin D appear to have an inverse correlation with kidney function. Growing evidence has indicated that vitamin D deficiency may contribute to deteriorating renal function, as well as increased morbidity and mortality in patients with CKD. Recent studies have suggested that treatment with active vitamin D or its analogues can ameliorate renal injury by reducing fibrosis, apoptosis, and inflammation in animal models; this treatment also decreases proteinuria and mortality in patients with CKD. These renoprotective effects of vitamin D treatment are far beyond its classical role in the maintenance of bone and mineral metabolism, in addition to its pleiotropic effects on extra-mineral metabolism. In this review, we discuss the altered metabolism of vitamin D in kidney disease, and the potential renoprotective mechanisms of vitamin D in experimental and clinical studies. In addition, issues regarding the effects of vitamin D treatment on clinical outcomes are discussed.
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Affiliation(s)
- Chang Seong Kim
- Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea
| | - Soo Wan Kim
- Department of Internal Medicine, Chonnam National University Medical School, Gwangju, Korea
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11
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Abstract
PURPOSE OF REVIEW Regulation of calcium homeostasis during a lifetime is a complex process reflecting a balance among intestinal calcium absorption, bone calcium influx and efflux, and renal calcium excretion. Perturbations can result in hypocalcemia or hypercalcemia and adaptations in calcium handling must occur during growth and aging. RECENT FINDINGS Study of the calcium sensing receptor in the thick ascending limb of Henle and TRPV5 in the distal tubule continues to provide insights into regulation of renal calcium excretion. Hypercalcemia-induced secretion of calcitonin via activation of the calcium-sensing receptor may protect against the development of hypercalcemia. A calcilytic was shown to increase serum calcium by decreasing renal calcium excretion. Ezrin, a cross-linking protein important for renal phosphate handling, is also involved in the regulation of intestinal calcium absorption. Increased 1,25-hydroxyvitamin D (1,25D) values were shown to protect against the development of hypocalcemia by increasing calcium efflux and decreasing calcium influx in bone. Finally, fibroblast growth factor 23 stimulation, which should result in suppression of 1,25D, was shown to be prevented in a model of vitamin D deficiency in which maintenance of 1,25D is important in minimizing hypocalcemia. SUMMARY Recent information has provided new insights on how intestinal, bone and renal mechanisms are regulated to maintain calcium homeostasis.
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Kopic S, Geibel JP. Gastric acid, calcium absorption, and their impact on bone health. Physiol Rev 2013; 93:189-268. [PMID: 23303909 DOI: 10.1152/physrev.00015.2012] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Calcium balance is essential for a multitude of physiological processes, ranging from cell signaling to maintenance of bone health. Adequate intestinal absorption of calcium is a major factor for maintaining systemic calcium homeostasis. Recent observations indicate that a reduction of gastric acidity may impair effective calcium uptake through the intestine. This article reviews the physiology of gastric acid secretion, intestinal calcium absorption, and their respective neuroendocrine regulation and explores the physiological basis of a potential link between these individual systems.
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Affiliation(s)
- Sascha Kopic
- Department of Surgery and Cellular and Molecular Physiology, Yale School of Medicine, New Haven, Connecticut, USA
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Alvarez J, Wasse H, Tangpricha V. Vitamin D supplementation in pre-dialysis chronic kidney disease: A systematic review. DERMATO-ENDOCRINOLOGY 2012; 4:118-27. [PMID: 22928067 PMCID: PMC3427190 DOI: 10.4161/derm.20014] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Vitamin D deficiency is associated with a variety of skeletal, cardiometabolic, and immunologic co-morbidities that are present in chronic kidney disease (CKD). We performed a systematic review to investigate the effects of vitamin D supplementation, in the form of ergocalciferol or cholecalciferol, on various health outcomes in early CKD. Seventeen clinical trials were identified, only two of which were randomized, placebo controlled trials. The majority of studies supplementing with > 2,000 IU/day of cholecalciferol achieved optimal vitamin D status, whereas studies supplementing with ergocalciferol were less consistent. Studies varied widely in their effects on lowering serum parathyroid hormone concentrations. Few studies investigated effects of vitamin D treatment on other clinical health indicators in early CKD. Rigorous studies are necessary to investigate optimal vitamin D dosing strategies in early CKD for the maintenance of adequate vitamin D status, management of secondary hyperparathyroidism and improvement of non-skeletal related clinical outcomes.
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14
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Qazi RA, Martin KJ. Vitamin D in kidney disease: pathophysiology and the utility of treatment. Rheum Dis Clin North Am 2012; 38:115-23. [PMID: 22525847 DOI: 10.1016/j.rdc.2012.03.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
CKD is associated with decreased vitamin D metabolites, both the storage form 25(OH)D and the active form 1,25-dihydroxyvitamin D. This contributes to hyperparathyroidism, and increased levels of PTH mobilize minerals from the skeleton and increase the risk for fractures. Treatment with vitamin D sterols efficiently reduces secondary hyperparathyroidism of CKD. Observational studies suggest survival and other potential benefits of vitamin D treatment in the CKD population. These observations need to be verified with controlled prospective trials.
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Affiliation(s)
- Rizwan A Qazi
- Division of Nephrology, Saint Louis University, Saint Louis, MO 63110, USA.
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15
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D'Amour P. Acute and chronic regulation of circulating PTH: significance in health and in disease. Clin Biochem 2012; 45:964-9. [PMID: 22569597 DOI: 10.1016/j.clinbiochem.2012.04.029] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2012] [Revised: 04/16/2012] [Accepted: 04/26/2012] [Indexed: 11/26/2022]
Abstract
Circulating human parathyroid hormone (PTH) is immunoheterogenous. It is composed of 80% carboxyl-terminal (C) fragments and of 20% PTH(1-84). This composition contrasts with the biological activity of the hormone, which is only related to PTH(1-84), creating a paradox between circulating PTH composition and PTH bioactivity. PTH molecular forms are either secreted by the parathyroid glands or generated by the peripheral metabolism of PTH(1-84) in the liver. The kidney has a major role in the disposal of C-PTH fragments. Secretion of PTH molecular forms by the parathyroid glands is highly regulated under a variety of clinical conditions, suggesting that C-PTH fragments could exert some biological effects of their own. Recent data suggest that C-PTH fragments can exert biological actions opposite to those of PTH(1-84) by acting on a C-PTH receptor not yet cloned. They can decrease calcium concentration, phosphate excretion, bone resorption and 1,25(OH)₂ synthesis. The clinical implications of this new concept are reviewed.
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Affiliation(s)
- Pierre D'Amour
- Centre de Recherche, Centre Hospitalier de l'Université de Montréal-CRCHUM, Hôpital Saint-Luc, Department of Medicine, Université de Montréal, Montréal, Québec, Canada.
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Martin KJ, González EA. Long-term management of CKD-mineral and bone disorder. Am J Kidney Dis 2012; 60:308-15. [PMID: 22520454 DOI: 10.1053/j.ajkd.2012.01.027] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 01/04/2012] [Indexed: 02/07/2023]
Abstract
Chronic kidney disease-mineral and bone disorder (CKD-MBD) is the term used to describe the abnormalities of bone and mineral metabolism that occur in the setting of kidney disease. The spectrum of these abnormalities is wide, ranging from severe high-turnover bone disease on one end to marked low bone turnover bone disease on the other. Similarly, some patients have severe vascular calcifications while others do not, and the values for biochemistry determinations, including calcium, phosphorus, and parathyroid hormone, also may vary widely among patients. This variability may be influenced by such things as the chronicity of the particular kidney disease, effects of therapies such as corticosteroids on modifying the course of kidney disease, and comorbid conditions, such as diabetes, heart disease, age, and osteoporosis. The heterogeneity of CKD-MBD makes strict protocol-driven therapeutic approaches difficult; accordingly, considerable individualized therapy is required. Using a case history, we explore several of the variables and difficulties involved in patient management.
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Affiliation(s)
- Kevin J Martin
- Division of Nephrology, Saint Louis University, St. Louis, MO, USA.
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Darabian S, Rattanasompattikul M, Hatamizadeh P, Bunnapradist S, Budoff MJ, Kovesdy CP, Kalantar-Zadeh K. Cardiorenal syndrome and vitamin D receptor activation in chronic kidney disease. Kidney Res Clin Pract 2012; 31:12-25. [PMID: 26889405 PMCID: PMC4715094 DOI: 10.1016/j.krcp.2011.12.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Revised: 11/22/2011] [Accepted: 11/22/2011] [Indexed: 02/05/2023] Open
Abstract
Cardiorenal syndrome (CRS) refers to a constellation of conditions whereby heart and kidney diseases are pathophysiologically connected. For clinical purposes, it would be more appropriate to emphasize the pathophysiological pathways to classify CRS into: (1) hemodynamic, (2) atherosclerotic, (3) uremic, (4) neurohumoral, (5) anemic–hematologic, (6) inflammatory–oxidative, (7) vitamin D receptor (VDR) and/or FGF23-, and (8) multifactorial CRS. In recent years, there have been a preponderance data indicating that vitamin D and VDR play an important role in the combination of renal and cardiac diseases. This review focuses on some important findings about VDR activation and its role in CRS, which exists frequently in chronic kidney disease patients and is a main cause of morbidity and mortality. Pathophysiological pathways related to suboptimal or defective VDR activation may play a role in causing or aggravating CRS. VDR activation using newer agents including vitamin D mimetics (such as paricalcitol and maxacalcitol) are promising agents, which may be related to their selectivity in activating VDR by means of attracting different post-D-complex cofactors. Some, but not all, studies have confirmed the survival advantages of D-mimetics as compared to non-selective VDR activators. Higher doses of D-mimetic per unit of parathyroid hormone (paricalcitol to parathyroid hormone ratio) is associated with greater survival, and the survival advantages of African American dialysis patients could be explained by higher doses of paricalcitol (>10 μg/week). More studies are needed to verify these data and to explore additional avenues for CRS management via modulating VDR pathway.
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Affiliation(s)
- Sirous Darabian
- Harold Simmons Center for Kidney Disease Research and Epidemiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA; St. John Cardiovascular Reserach Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA
| | - Manoch Rattanasompattikul
- Harold Simmons Center for Kidney Disease Research and Epidemiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA
| | - Parta Hatamizadeh
- Harold Simmons Center for Kidney Disease Research and Epidemiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA
| | | | - Matthew J Budoff
- St. John Cardiovascular Reserach Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA
| | | | - Kamyar Kalantar-Zadeh
- Harold Simmons Center for Kidney Disease Research and Epidemiology, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA, USA; David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; UCLA School of Public Health, Los Angeles, CA, USA
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Abstract
In chronic kidney disease (CKD), abnormalities in vitamin D metabolism contribute to the development of mineral and skeletal disorders, elevations in parathyroid hormone (PTH), hypertension, systemic inflammation, renal and cardiovascular damage. CKD induces a progressive loss of the capacity of the kidney not only to convert 25-hydroxyvitamin D [25(OH)D] to circulating calcitriol, the vitamin D hormone, but also to maintain serum 25(OH)D levels for non-renal calcitriol synthesis. The resulting calcitriol and 25(OH)D deficiency associates directly with accelerated disease progression and death. This chapter presents our understanding of the pathophysiology behind 25(OH)D and calcitriol deficiency in CKD, of the adequacy of current recommendations for vitamin D supplementation and PTH suppression, and of potential markers of renal and cardiovascular lesions unrelated to PTH suppression, a knowledge required for the design of trials to obtain evidence-based recommendations for vitamin D and calcitriol replacement that improve outcomes at all stages of CKD.
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Affiliation(s)
- Adriana Dusso
- Division of Experimental Nephrology, IRBLleida (Lleida Institute for Biomedical Research), Avda Rovira Roure 80, Lleida, Spain.
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Defective renal maintenance of the vitamin D endocrine system impairs vitamin D renoprotection: a downward spiral in kidney disease. Kidney Int 2011; 79:715-29. [PMID: 21270766 DOI: 10.1038/ki.2010.543] [Citation(s) in RCA: 102] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
In kidney disease, the progressive loss of renal capacity to produce calcitriol, the vitamin D hormone, is a key contributor to elevations in parathyroid hormone (PTH) and mineral and skeletal disorders predisposing to renal and cardiovascular damage, ectopic calcifications, and high mortality rates. Thus, the safe correction of calcitriol deficiency to suppress PTH has been the treatment of choice for decades. However, recent epidemiological and experimental data suggest that calcitriol replacement may improve outcomes through renal and cardioprotective actions unrelated to PTH suppression. Furthermore, a striking incidence of vitamin D deficiency occurs in kidney disease and associates more strongly than calcitriol deficiency with a higher risk for kidney disease progression and death. Despite the translational relevance of these findings, no prospective trials are currently available in support of the efficacy of vitamin D supplementation and/or calcitriol replacement to safely halt/moderate renal disease progression. This review updates the pathophysiology behind the vicious cycle by which kidney injury impairs the maintenance of normal vitamin D and calcitriol levels, which in turn impedes vitamin D/calcitriol renoprotective actions, a requirement for the design of prospective trials to improve current recommendations for vitamin D interventions at all stages of kidney disease.
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Adriaansen J, Perez P, Zheng C, Collins MT, Baum BJ. Human parathyroid hormone is secreted primarily into the bloodstream after rat parotid gland gene transfer. Hum Gene Ther 2011; 22:84-92. [PMID: 20977345 DOI: 10.1089/hum.2010.097] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Hypoparathyroidism is a hormone deficiency syndrome that leads to low blood calcium levels and for which current replacement therapy is inadequate. Gene transfer to salivary glands leads to safe and abundant secretion of therapeutic protein into either saliva or the bloodstream. We previously reported the successful transduction of rat submandibular glands with an adenoviral vector encoding human parathyroid hormone (Ad.hPTH), but unfortunately most of the hPTH was secreted into saliva. Because submandibular and parotid glands are morphologically and functionally different, we hypothesized that hPTH sorting might be different in parotid glands. After 2 days, the pattern of hPTH secretion from transduced parotid glands of intact rats was reversed from that of transduced submandibular glands, that is, most transgenic hPTH was detected in serum (5 × 10(10) viral particles per gland; the saliva-to-serum ratio of total hPTH secreted was 0.04). Vector copies were localized to the targeted parotid glands, with none detected in liver or spleen. Ad.hPTH next was administered to parotid glands of parathyroidectomized rats. Two days after delivery no hPTH was detectable in saliva, but high levels were found in serum, leading to normalization of serum calcium and a significant increase in the urinary phosphorus-to-creatinine ratio. This study demonstrates for the first time differential sorting of transgenic hPTH between submandibular and parotid glands, suggesting that hPTH may be a valuable model protein for understanding the molecular basis of transgenic secretory protein sorting in these exocrine glands. We also show the clinical potential of salivary gland hPTH gene therapy for patients with hypoparathyroidism.
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Affiliation(s)
- J Adriaansen
- Gene Transfer Section, Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892-1190, USA
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D'Amour P, Rousseau L, Hornyak S, Yang Z, Cantor T. Influence of Secondary Hyperparathyroidism Induced by Low Dietary Calcium, Vitamin D Deficiency, and Renal Failure on Circulating Rat PTH Molecular Forms. Int J Endocrinol 2011; 2011:469783. [PMID: 21747853 PMCID: PMC3124668 DOI: 10.1155/2011/469783] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2011] [Accepted: 04/14/2011] [Indexed: 11/24/2022] Open
Abstract
Rats(r) with secondary hyperparathyroidism were studied to define the relationship between vitamin D metabolites and rPTH levels measured by 3 different rat ELISAs. Controls and renal failure (RF) rats were on a normal diet, while 2 groups on a low-calcium (-Ca) or a vitamin D-deficient (-D) diet. RF was induced surgically. Mild RF rats had normal calcium and 25(OH)D but reduced 1,25(OH)(2)D levels (P < .001) with a 2.5-fold increased in rPTH (P < .001). Severe RF rats and those on a -Ca or -D diet had reduced calcium (P < .01) and 25(OH)D levels (P < .05), with rPTH increased by 2 (-Ca diet; P < .05), 4 (-D diet; P < .001), and 20-folds (RF; P < .001) while 1,25(OH)(2)D was high (-Ca diet: P < .001) or low (-D diet, RF: P < .001). 25(OH)D and 1,25(OH)(2)D were positively and negatively related on the -Ca and -D diets, respectively. rPTH molecular forms behaved as expected in RF and on -Ca diet, but not on -D diet with more C-rPTH fragments when less were expected. This may be related to the short-time course of this study compared to prior studies.
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Affiliation(s)
- Pierre D'Amour
- Centre de Recherche, Centre Hospitalier de l'Université de Montréal (CRCHUM), Hôpital Saint-Luc Département de Médecine, Université de Montréal, Montréal, QC, Canada H2X 1P1
- *Pierre D'Amour:
| | - Louise Rousseau
- Centre de Recherche, Centre Hospitalier de l'Université de Montréal (CRCHUM), Hôpital Saint-Luc Département de Médecine, Université de Montréal, Montréal, QC, Canada H2X 1P1
| | | | - Zan Yang
- Scantibodies Laboratory Inc., Santee, CA 92071, USA
| | - Tom Cantor
- Scantibodies Laboratory Inc., Santee, CA 92071, USA
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D'Amour P, Rousseau L, Hornyak S, Yang Z, Cantor T. Rat parathyroid hormone (rPTH) ELISAs specific for regions (2-7), (22-34) and (40-60) of the rat PTH structure: influence of sex and age. Gen Comp Endocrinol 2010; 168:312-7. [PMID: 20627105 DOI: 10.1016/j.ygcen.2010.07.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 07/02/2010] [Accepted: 07/04/2010] [Indexed: 11/26/2022]
Abstract
Rat (r) PTH ELISAs were used to study the influence of age and sex on rPTH levels and circulating PTH molecular forms separated by HPLC. Standard curves and saturation analysis were undertaken to define epitopes. Rats were sacrificed at approximately 27, 47 and 75days. Relevant biochemical parameters and 25(OH) vitamin D were measured. Differences between sexes were analyzed by Kruskal-Wallis ANOVA, followed by Dunn's test. Epitopes were localized in regions 2-7, 22-34 and 40-60 of rPTH structure for whole (W), total (T) and carboxyl (C) rPTH ELISAs. The W-rPTH assay only detected rPTH(1-84) and N-PTH in circulation while the T-PTH assay further detected large C-rPTH fragments. The C-rPTH assay detected all circulating rPTH molecular forms including smaller C-rPTH fragments. In both sexes, weight (p<0.001), ionized calcium, creatinine, albumin and 25(OH)D values (p<0.001) increased with age, while phosphate and alkaline phosphatase decreased (p<0.001). In male rats, W-rPTH remained unchanged, while T-rPTH rose slightly (p<0.05) and C-rPTH declined by half with time (p<0.001). In female rats, W-rPTH (p<0.05), T-rPTH (p<0.001) and C-rPTH (p<0.01) all increased in older animals. In both sexes, C-rPTH/W-rPTH and C-rPTH/T-rPTH ratios decreased between 25 and 47 days, to rise again between 47 and 75 days. The initial decrease may represent an adaptation to weaning and a change of diet between 25 and 47 days while the rise corresponds to higher calcium and 25(OH)D levels between 47 and 75 days. These changes were more pronounced in female rats, indicating an influence of sex on PTH molecular form secretion or metabolism.
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Affiliation(s)
- Pierre D'Amour
- Centre de recherche, Centre hospitalier de l'Université de Montréal- Hôpital Saint-Luc, Montréal, Québec, Canada.
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Qazi RA, Martin KJ. Vitamin D in kidney disease: pathophysiology and the utility of treatment. Endocrinol Metab Clin North Am 2010; 39:355-63, table of contents. [PMID: 20511057 DOI: 10.1016/j.ecl.2010.02.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Vitamin D physiology has gained more importance and publicity than any of its counterparts in the water- and fat-soluble vitamin groups combined. This is partly because vitamin D deficiency is still widely prevalent in the developed world and the beneficial effects are thought to extend beyond the regulation of calcium and phosphorus homeostasis alone. Vitamin D deficiency becomes even more important in the various stages of chronic kidney disease (CKD); CKD itself is also on the increase. How vitamin D physiology is altered in CKD and how the various treatment modalities can alter the morbidity and mortality associated with CKD is the topic of discussion for this article.
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Affiliation(s)
- Rizwan A Qazi
- Division of Nephrology, Saint Louis University, Saint Louis, MO 63110, USA.
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Koshikawa M, Nishiguchi K, Yorifuji S, Shimazu K, Takaori K, Mori K, Eguchi E, Okada K, Tanaka A, Kuwahara T. Amino terminal cleavage of PTH(1–84) to PTH(7–84) is regulated by serum calcium concentration via calcium-sensing receptor in hemodialysis patients. Clin Exp Nephrol 2010; 14:233-8. [DOI: 10.1007/s10157-010-0264-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2009] [Accepted: 01/06/2010] [Indexed: 11/24/2022]
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Parathyroid Hormone and Parathyroid Hormone–Related Peptide in the Regulation of Calcium Homeostasis and Bone Development. Endocrinology 2010. [DOI: 10.1016/b978-1-4160-5583-9.00056-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Adriaansen J, Zheng C, Perez P, Baum BJ. Production and sorting of transgenic, modified human parathyroid hormone in vivo in rat salivary glands. Biochem Biophys Res Commun 2009; 391:768-72. [PMID: 19944067 DOI: 10.1016/j.bbrc.2009.11.135] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Accepted: 11/20/2009] [Indexed: 10/20/2022]
Abstract
Polarized salivary epithelial cells can sort secretory proteins towards either the basolateral or apical pole. Transgenic human parathyroid hormone (hPTH) exclusively sorts apically in rat submandibular glands. To help understand this specific process we modified the hPTH cDNA sequence and delivered the cDNAs to glands in vivo using adenoviral (Ad) vectors. The Ad vectors encoded: (1) the native form of hPTH (Ad.pre-pro-hPTH1-84), (2) the native sequence, but with the pro-segment deleted (Ad.pre-hPTH1-84), and (3) a sequence containing the pre-segment followed by the first 34 amino acids of hPTH (Ad.pre-hPTH1-34). hPTH production and sorting were studied after two days. All constructs were effectively transcribed in targeted glands. However, the pre-hPTH1-84 modification led to reduced hPTH secretion and production, while no immunoreactive hPTH resulted from pre-hPTH1-34 cDNA infusion. The pre-hPTH1-84 modification had no effect on apical sorting. These in vivo results show that the signal responsible for hPTH's apical sorting does not reside in the pro-segment and that deleting both the pro-segment and the carboxyl-terminal region severely impairs post-translational processing of hPTH.
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Affiliation(s)
- Janik Adriaansen
- Molecular Physiology and Therapeutics Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892-1190, USA
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Jean G, Souberbielle JC, Chazot C. Monthly cholecalciferol administration in haemodialysis patients: a simple and efficient strategy for vitamin D supplementation. Nephrol Dial Transplant 2009; 24:3799-805. [PMID: 19622574 DOI: 10.1093/ndt/gfp370] [Citation(s) in RCA: 91] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND There is growing evidence of the usefulness of vitamin D supplementation in dialysis patients who are most often vitamin D deficient. Due to the long half-life of vitamin D, there is much interest in administering it intermittently for long-term adherence. However, there are no data to indicate which dosage would be most efficient. Objective. The aim was to assess the long-term efficiency and safety of a monthly oral dose of cholecalciferol (100 000 IU) in vitamin D-deficient haemodialysis (HD) patients. METHODS HD patients with a serum 25-hydroxyvitamin D (25(OH)D) level <75 nmol/L were enrolled in a 15-month prospective study. The exclusion criteria were as follows: use of any vitamin D derivatives, prescription of cinacalcet and bisphosphonates, uncontrolled hypercalcaemia (>2.55 mmol/L), hyperphosphataemia (>2 mmol/L) and severe secondary hyperparathyroidism (SHPT; serum PTH >600 pg/mL). Biological data were recorded in the following months: M-3, M0, M1, M3, M9 and M15. We aimed to maintain stable levels of the phosphate binder and oral and dialysate calcium during the course of the study. RESULTS Of the 250 patients screened, 161 were enrolled, and the results from 107 were recorded at the end of the study. Of these 107 patients, 56% were males, and the average age of the patient group was 66.4 +/- 15 years. Diabetics accounted for 36% of the total patients. The dialysis schedule ranged from 3 x 5 to 3 x 8 h, with a mean dialysate calcium concentration of 1.48 +/- 0.6 mmol/L. After 15 months, the mean serum 25(OH)D level increased from 32 +/- 13 to 105.8 +/- 27 nmol/L (P < 0.001) and plateaued after M3. Of the patients, 91% had a level higher than the target level (>75 nmol/L), while none had levels >200 nmol/L. The serum calcitriol (1,25(OH)(2)D) level increased from 13.7 +/- 14 to 45 +/- 13 pmol/L (P < 0.001) and plateaued after M9. The levels of serum PTH (median 295-190 pg/mL, P < 0.001), bone alkaline phosphatase (20.5 +/- 9-17.1 +/- 7 microg/L, P < 0.05) and beta-cross-laps (2.5 +/- 1-2.07 +/- 0.8 microg/L, P < 0.05) decreased significantly. No significant changes were observed in the values of the following: calcaemia, phosphataemia, blood pressure, serum albumin, haemoglobin and C-reactive protein. CONCLUSIONS Long-term monthly administration of oral cholecalciferol (100 000 IU) was a safe, effective, inexpensive and simple method for correcting vitamin D deficiency in almost 90% of the HD patients in this study and led to optimal compliance. The most evident consequences were a slight decrease in the levels of PTH and bone markers and an increase in the level of serum 1,25(OH)(2)D.
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Affiliation(s)
- Guillaume Jean
- Centre de Rein Artificiel, 42 avenue du 8 mai 1945, 69160, Tassin Demi-lune, France.
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Isakova T, Gutiérrez OM, Wolf M. A blueprint for randomized trials targeting phosphorus metabolism in chronic kidney disease. Kidney Int 2009; 76:705-16. [PMID: 19606082 DOI: 10.1038/ki.2009.246] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The diagnosis of chronic kidney disease (CKD) confers dismal clinical outcomes regardless of whether patients are initiating dialysis and face a median survival of only 2-3 years or they have earlier-stage CKD and face a risk of death that is greater than the risk of progression to dialysis. These poor outcomes are driven by extraordinarily high rates of cardiovascular disease that historically have not responded to risk-factor modification strategies proven to attenuate risk in the general population. Nor have measures aimed at increasing the dose or quality of dialysis made an appreciable dent in mortality. Still worse, interventions that were expected to be beneficial resulted in increased mortality in recent trials. Although this apparent lack of progress in advancing the care of CKD is discouraging, resignation is not an option. On the contrary, with the rising rates of CKD worldwide, there is an urgent need to rigorously test novel therapeutic strategies in randomized trials. The breadth of accumulating evidence linking disordered phosphorus metabolism to adverse outcomes spans in vitro, animal, and human studies, and positions phosphorus management as an attractive target for intervention. Although opinion-based practice guidelines promote phosphorus management strategies that are widely accepted in dialysis patients, there is a clear need to perform randomized controlled trials to prove or disprove the benefits of therapy. Perhaps even more important, the discovery of fibroblast growth factor 23 (FGF23) and its potential as a novel diagnostic to identify disordered phosphorus metabolism at an early, subclinical state has presented the opportunity to develop placebo-controlled randomized trials in pre-dialysis CKD patients with normal serum phosphate levels. This commentary considers the justification and challenges for such trials and presents a 'first-draft' blueprint of distinct trial approaches to initiate a dialog that will ultimately culminate in studies aimed at improving survival across the spectrum of CKD.
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Affiliation(s)
- Tamara Isakova
- Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA
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Lavi-Moshayoff V, Silver J, Naveh-Many T. Human PTH gene regulation in vivo using transgenic mice. Am J Physiol Renal Physiol 2009; 297:F713-9. [PMID: 19570881 DOI: 10.1152/ajprenal.00161.2009] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
To study the regulation of the human PTH (hPTH) gene in vivo, we generated transgenic mice with the hPTH gene expressed in the mouse parathyroid using a bacterial artificial chromosome (BAC) containing the hPTH gene within its 144-kb chromosomal region. The BAC construct maintains the native hPTH gene surrounding sequences and isolates it from positional effects. The transgenic mice had normal levels of serum mouse PTH (mPTH) in addition to both intact and bioactive hPTH. Despite the presence of both mPTH and hPTH, serum calcium and 1,25(OH)(2) vitamin D levels were normal. The lack of response to hPTH may be due to tachyphylaxis of the mPTH receptor (PTH1R) and/or impaired recognition of the mPTH1R. In contrast, the regulation of hPTH levels in the mouse was intact. A calcium-depleted diet increased serum mPTH and both intact and bioactive hPTH. mPTH and hPTH mRNA levels were also markedly increased. The calcimimetic R-568 dramatically decreased mPTH and hPTH serum levels. Administered recombinant fibroblast growth factor (FGF)23 decreased hPTH. Therefore, the regulation of hPTH gene expression and serum hPTH levels is intact in the transgenic mice, indicating preservation of the signal transduction of the parathyroid calcium receptor and the Klotho-FGF receptor between mouse and man.
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Affiliation(s)
- Vardit Lavi-Moshayoff
- Nephrology Services, Hadassah Hebrew University Medical Center, P. O. Box 12000, Jerusalem, Israel 91120
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Eastell R, Arnold A, Brandi ML, Brown EM, D'Amour P, Hanley DA, Rao DS, Rubin MR, Goltzman D, Silverberg SJ, Marx SJ, Peacock M, Mosekilde L, Bouillon R, Lewiecki EM. Diagnosis of asymptomatic primary hyperparathyroidism: proceedings of the third international workshop. J Clin Endocrinol Metab 2009; 94:340-50. [PMID: 19193909 DOI: 10.1210/jc.2008-1758] [Citation(s) in RCA: 229] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
OBJECTIVE Asymptomatic primary hyperparathyroidism (PHPT) is a common clinical problem. The purpose of this report is to guide the use of diagnostic tests for this condition in clinical practice. PARTICIPANTS Interested professional societies selected a representative for the consensus committee and provided funding for a one-day meeting. A subgroup of this committee set the program and developed key questions for review. Consensus was established at a closed meeting that followed. The conclusions were then circulated to the participating professional societies. EVIDENCE Each question was addressed by a relevant literature search (on PubMed), and the data were presented for discussion at the group meeting. CONSENSUS PROCESS Consensus was achieved by a group meeting. Statements were prepared by all authors, with comments relating to accuracy from the diagnosis subgroup and by representatives from the participating professional societies. CONCLUSIONS We conclude that: 1) reference ranges should be established for serum PTH in vitamin D-replete healthy individuals; 2) second- and third-generation PTH assays are both helpful in the diagnosis of PHPT; 3) DNA sequence testing can be useful in familial hyperparathyroidism or hypercalcemia; 4) normocalcemic PHPT is a variant of the more common presentation of PHPT with hypercalcemia; 5) serum 25-hydroxyvitamin D levels should be measured and, if vitamin D insufficiency is present, it should be treated as part of any management course; and 6) the estimated glomerular filtration rate should be used to determine the level of kidney function in PHPT: an estimated glomerular filtration rate of less than 60 ml/min.1.73 m2 should be a benchmark for decisions about surgery in established asymptomatic PHPT.
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Affiliation(s)
- R Eastell
- University of Sheffield, Sheffield, United Kingdom.
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Analysis of CYP27B1, encoding 25-hydroxyvitamin D-1alpha-hydroxylase, as a candidate tumor suppressor gene in primary and severe secondary/tertiary hyperparathyroidism. J Bone Miner Res 2009; 24:102-4. [PMID: 18767934 PMCID: PMC2689078 DOI: 10.1359/jbmr.080903] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
CYP27B1, encoding 25-hydroxyvitamin D-1alpha-hydroxylase, converts 25-hydroxyvitamin D to its active form, 1,25-dihydroxyvitamin D, and is expressed primarily in the kidney but also in nontraditional sites including the parathyroid glands. Whereas the role of locally produced 1,25-dihydroxyvitamin D is not yet clear, it is possible that it contributes importantly to vitamin D-mediated inhibition of parathyroid cell growth, so CYP27B1 can be considered a candidate parathyroid tumor suppressor gene in that its acquired inactivation in a parathyroid cell could confer a tumorigenic growth advantage. Expression of CYP27B1 has also been reported to be altered in parathyroid neoplasms. Because detection of inactivating mutations is the central criterion for validating a candidate tumor suppressor, we directly sequenced the coding region and all splice sites of CYP27B1 in 31 sporadic parathyroid adenomas and 31 parathyroid tumors from patients with refractory secondary/tertiary hyperparathyroidism. No nonsense, frameshift, or other inactivating mutations were found, and there was no sign of homozygous deletion. Our findings indicate that CYP27B1 does not commonly serve as a classical tumor suppressor gene in the development of sporadic parathyroid adenomas or of refractory secondary/tertiary hyperparathyroidism.
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Abstract
Abnormalities in vitamin D metabolism play a major role in the pathogenesis of secondary hyperparathyroidism in chronic kidney disease. The gradual and progressive decline in 1,25-dihydroxyvitamin D in the course of chronic kidney disease is the result of several mechanisms that limit the ability of the failing kidney to maintain the levels of 1,25-dihydroxyvitamin D despite increasing levels of parathyroid hormone. Recent observations have indicated that chronic kidney disease seems to be associated with a high incidence of nutritional vitamin D insufficiency or deficiency as manifested by decreased levels of 25-hydroxyvitamin D. This contributes to the inability to maintain the levels of 1,25-dihydroxyvitamin D; therefore, current practice guidelines suggest repleting vitamin D status by the administration of native vitamin D as a first step in the therapy of the abnormalities of bone and mineral metabolism in chronic kidney disease. The efficacy of this therapy is extremely variable, and active vitamin D sterols may be required, especially as kidney disease progresses. The importance of the abnormal vitamin D metabolism is being investigated vigorously in view of the observations that vitamin D may have important biologic actions in many tissues in addition to bone and parathyroid. Thus, observational data have suggested potential survival benefits of vitamin D sterol administration in this clinical setting, and experimental data have suggested a potential beneficial effect of vitamin D sterols on the progression of kidney disease. Further work is required to define the mechanisms involved and to examine the effects of vitamin D therapy on outcomes in randomized, controlled trials.
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Affiliation(s)
- Wisam Al-Badr
- Division of Nephrology, Saint Louis University, St. Louis, Missouri, USA
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D'Amour P. Lessons from a second- and third-generation parathyroid hormone assays in renal failure patients. J Endocrinol Invest 2008; 31:459-62. [PMID: 18560265 DOI: 10.1007/bf03346391] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- P D'Amour
- Research Center, Centre hospitalier de l'Université de Montréal (CHUM) - Hôpital Saint-Luc and Department of Medicine, University of Montréal, Montréal, Québec, Canada.
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