1
|
Santos F, Díaz-Anadón L, Ordóñez FA, Haffner D. Bone Disease in CKD in Children. Calcif Tissue Int 2021; 108:423-438. [PMID: 33452890 DOI: 10.1007/s00223-020-00787-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Accepted: 12/04/2020] [Indexed: 01/03/2023]
Abstract
This manuscript discusses mineral and bone disorders of chronic kidney disease (MBD-CKD) in pediatric patients with special emphasis on the underlying pathophysiology, the causes and clinical profile of growth retardation, the alterations in the growth plate, the strategies to optimize growth and the medical recommendations for prevention and treatment.
Collapse
Affiliation(s)
- Fernando Santos
- Division of Pediatric Nephrology, Hospital, Universitario Central de Asturias, Avda de Roma s/n, 33011, Oviedo, Asturias, Spain.
- Department of Medicine, University of Oviedo, Oviedo, Asturias, Spain.
| | - Lucas Díaz-Anadón
- Division of Pediatric Nephrology, Hospital, Universitario Central de Asturias, Avda de Roma s/n, 33011, Oviedo, Asturias, Spain
| | - Flor A Ordóñez
- Division of Pediatric Nephrology, Hospital, Universitario Central de Asturias, Avda de Roma s/n, 33011, Oviedo, Asturias, Spain
| | - Dieter Haffner
- Department of Pediatric Kidney, Liver and Metabolic Diseases, Hannover Medical School, Hannover, Germany
| |
Collapse
|
2
|
Okada M, Hiramitsu T, Ichimori T, Goto N, Narumi S, Watarai Y, Sato T, Tominaga Y. Comparison of Pre- and Post-transplant Parathyroidectomy in Renal Transplant Recipients and the Impact of Parathyroidectomy Timing on Calcium Metabolism and Renal Allograft Function: A Retrospective Single-Center Analysis. World J Surg 2020; 44:498-507. [PMID: 31399797 DOI: 10.1007/s00268-019-05124-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
BACKGROUND The effect of parathyroidectomy (PTx) timing on serum calcium (Ca) levels and renal functions in renal transplant recipients with severe hyperparathyroidism (HPT) remains unclear. We retrospectively aimed to investigate and compare the clinical data of patients who underwent pre- and post-transplant PTx and elucidated the impact of PTx timing on serum Ca levels and renal graft outcomes after renal transplantation (RTx). METHODS During January 2000-December 2016, 53 and 55 patients underwent post-transplant PTx (Post-RTx group) and pretransplant PTx (Pre-RTx group), respectively. The serum Ca levels and estimated glomerular filtration rate (eGFR) were assessed in both groups. RESULTS At the end of the follow-up, the serum Ca levels were significantly higher and the incidence of hypocalcemia was significantly lower in the Pre-RTx group than in the Post-RTx group [9.5 vs. 8.9 mg/dL, P < 0.001; 14.5% vs. 34.0%, P = 0.024]. The decrease in the eGFR 12-36 months after RTx was more significant in the Post-RTx group than in the Pre-RTx group (-13.8% vs. -0.9%; P = 0.001). A logistic regression involving age, sex, dialysis period, and serum parathormone level revealed that post-transplant PTx is an independent risk factor for persistent hypocalcemia at the end of the follow-up (P = 0.034) and for a >20% decrease in the eGFR 12-36 months after RTx (P = 0.029). CONCLUSIONS In renal transplant candidates with severe HPT, pretransplant PTx should be considered to prevent persistent hypocalcemia and deterioration of the renal graft function.
Collapse
Affiliation(s)
- Manabu Okada
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan.
| | - Takahisa Hiramitsu
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan
| | - Toshihiro Ichimori
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan
| | - Norihiko Goto
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan
| | - Shunji Narumi
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan
| | - Yoshihiko Watarai
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan
| | - Tetsuhiko Sato
- Department of General Internal Medicine, Nagoya Daini Red Cross Hospital, Nagoya, Japan
| | - Yoshihiro Tominaga
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan
| |
Collapse
|
3
|
Hsu CY, Chen LR, Chen KH. Osteoporosis in Patients with Chronic Kidney Diseases: A Systemic Review. Int J Mol Sci 2020; 21:E6846. [PMID: 32961953 PMCID: PMC7555655 DOI: 10.3390/ijms21186846] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 09/13/2020] [Accepted: 09/16/2020] [Indexed: 02/06/2023] Open
Abstract
Chronic kidney disease (CKD) is associated with the development of mineral bone disorder (MBD), osteoporosis, and fragility fractures. Among CKD patients, adynamic bone disease or low bone turnover is the most common type of renal osteodystrophy. The consequences of CKD-MBD include increased fracture risk, greater morbidity, and mortality. Thus, the goal is to prevent the occurrences of fractures by means of alleviating CKD-induced MBD and treating subsequent osteoporosis. Changes in mineral and humoral metabolism as well as bone structure develop early in the course of CKD. CKD-MBD includes abnormalities of calcium, phosphorus, PTH, and/or vitamin D; abnormalities in bone turnover, mineralization, volume, linear growth, or strength; and/or vascular or other soft tissue calcification. In patients with CKD-MBD, using either DXA or FRAX to screen fracture risk should be considered. Biomarkers such as bALP and iPTH may assist to assess bone turnover. Before initiating an antiresorptive or anabolic agent to treat osteoporosis in CKD patients, lifestyle modifications, such as exercise, calcium, and vitamin D supplementation, smoking cessation, and avoidance of excessive alcohol intake are important. Managing hyperphosphatemia and SHPT are also crucial. Understanding the complex pathogenesis of CKD-MBD is crucial in improving one's short- and long-term outcomes. Treatment strategies for CKD-associated osteoporosis should be patient-centered to determine the type of renal osteodystrophy. This review focuses on the mechanism, evaluation and management of patients with CKD-MBD. However, further studies are needed to explore more details regarding the underlying pathophysiology and to assess the safety and efficacy of agents for treating CKD-MBD.
Collapse
Affiliation(s)
- Chia-Yu Hsu
- Department of Rehabilitation Medicine, Ten-Chan General Hospital, Zhongli, Taoyuan 320, Taiwan;
- Department of Biomedical Engineering, Chung Yuan Christian University, Taoyuan 320, Taiwan
| | - Li-Ru Chen
- Department of Physical Medicine and Rehabilitation, Mackay Memorial Hospital, Taipei 104, Taiwan;
- Department of Mechanical Engineering, National Chiao-Tung University, Hsinchu 300, Taiwan
| | - Kuo-Hu Chen
- Department of Obstetrics and Gynecology, Taipei Tzu-Chi Hospital, The Buddhist Tzu-Chi Medical Foundation, Taipei 231, Taiwan
- Department of Medicine, School of Medicine, Tzu-Chi University, Hualien 970, Taiwan
| |
Collapse
|
4
|
Okada M, Tominaga Y, Hiramitsu T, Ichimori T. Development of Severe Hyperparathyroidism Despite Short-Term Renal Replacement Therapy. World J Surg 2017; 42:425-430. [PMID: 28779382 DOI: 10.1007/s00268-017-4164-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND We occasionally experience cases of severe secondary hyperparathyroidism (SHPT) that require parathyroidectomy (PTX) despite undergoing short-term renal replacement therapy (RRT). Because the characteristics of such cases have never been discussed, we aimed to elucidate the pathophysiology of severe SHPT after short-term RRT by retrospectively analyzing clinical data. METHODS A total of 1013 patients with severe SHPT underwent PTX between January 2007 and April 2016 at Nagoya Daini Red Cross Hospital. Of these patients, 570 underwent RRT for ≥10 years (long RRT group) and 23 for ≤1 year (short RRT group). We retrospectively investigated and compared patient characteristics, preoperative data, subjective symptoms, and bone lesion incidence between the two groups. RESULTS A higher proportion of subjects with congenital or hereditary diseases as primary disease for chronic kidney disease (CKD) (21.7% (5/23) vs. 6.3% (36/570); P = 0.016) and longer predialysis period (21.2 ± 14.0 vs. 10.1 ± 9.2 years; P < 0.001) were observed in the short RRT group than in the long RRT group. Furthermore, lower serum calcium and phosphate levels, heavier parathyroid glands, and severe bone lesions were observed in the short RRT group than in the long RRT group. CONCLUSION Severe SHPT after short-term RRT appeared to occur because of long-term CKD before initiating RRT. Therefore, treating mineral and bone disorders during the early CKD stage might prevent severe SHPT development before initiating RRT.
Collapse
Affiliation(s)
- Manabu Okada
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan. .,Department of Renal Transplant Surgery, Aichi Medical University School of Medicine, Nagakute, Japan.
| | - Yoshihiro Tominaga
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan
| | - Takahisa Hiramitsu
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan
| | - Toshihiro Ichimori
- Department of Transplantation and Endocrine Surgery, Nagoya Daini Red Cross Hospital, 2-9 Myoken-cho, Showa-ku, Nagoya, 4668650, Japan
| |
Collapse
|
5
|
Santos GM, Pantoja CJ, Costa e Silva A, Rodrigues MC, Ribeiro RC, Simeoni LA, Lomri N, Neves FAR. Thyroid hormone receptor binding to DNA and T3-dependent transcriptional activation are inhibited by uremic toxins. NUCLEAR RECEPTOR 2005; 3:1. [PMID: 15807894 PMCID: PMC1087878 DOI: 10.1186/1478-1336-3-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Accepted: 04/04/2005] [Indexed: 12/14/2022]
Abstract
Background There is a substantial clinical overlap between chronic renal failure (CRF) and hypothyroidism, suggesting the presence of hypothyroidism in uremic patients. Although CRF patients have low T3 and T4 levels with normal thyroid-stimulating hormone (TSH), they show a higher prevalence of goiter and evidence for blunted tissue responsiveness to T3 action. However, there are no studies examining whether thyroid hormone receptors (TRs) play a role in thyroid hormone dysfunction in CRF patients. To evaluate the effects of an uremic environment on TR function, we investigated the effect of uremic plasma on TRβ1 binding to DNA as heterodimers with the retinoid X receptor alpha (RXRα) and on T3-dependent transcriptional activity. Results We demonstrated that uremic plasma collected prior to hemodialysis (Pre-HD) significantly reduced TRβ1-RXRα binding to DNA. Such inhibition was also observed with a vitamin D receptor (VDR) but not with a peroxisome proliferator-activated receptor gamma (PPARγ). A cell-based assay confirmed this effect where uremic pre-HD ultrafiltrate inhibited the transcriptional activation induced by T3 in U937 cells. In both cases, the inhibitory effects were reversed when the uremic plasma and the uremic ultrafiltrate were collected and used after hemodialysis (Post-HD). Conclusion These results suggest that dialyzable toxins in uremic plasma selectively block the binding of TRβ1-RXRα to DNA and impair T3 transcriptional activity. These findings may explain some features of hypothyroidism and thyroid hormone resistance observed in CRF patients.
Collapse
Affiliation(s)
- Guilherme M Santos
- Molecular Pharmacology Laboratory, Department of Pharmaceutical Sciences, School of Health Sciences, University of Brasilia, Brazil
- University of Cergy-Pontoise, UFR des Sciences et Techniques, ERRMECe Laboratory, BP222, 2 Ave Adolphe Chauvin, 95302 Cergy-Pontoise, France
| | - Carlos J Pantoja
- Molecular Pharmacology Laboratory, Department of Pharmaceutical Sciences, School of Health Sciences, University of Brasilia, Brazil
| | | | - Maria C Rodrigues
- Molecular Pharmacology Laboratory, Department of Pharmaceutical Sciences, School of Health Sciences, University of Brasilia, Brazil
| | | | - Luiz A Simeoni
- Molecular Pharmacology Laboratory, Department of Pharmaceutical Sciences, School of Health Sciences, University of Brasilia, Brazil
| | - Noureddine Lomri
- University of Cergy-Pontoise, UFR des Sciences et Techniques, ERRMECe Laboratory, BP222, 2 Ave Adolphe Chauvin, 95302 Cergy-Pontoise, France
| | - Francisco AR Neves
- Molecular Pharmacology Laboratory, Department of Pharmaceutical Sciences, School of Health Sciences, University of Brasilia, Brazil
| |
Collapse
|
6
|
Llach F, Fernández E. Overview of renal bone disease: Causes of treatment failure, clinical observations, the changing pattern of bone lesions, and future therapeutic approach. Kidney Int 2003:S113-9. [PMID: 14531783 DOI: 10.1046/j.1523-1755.64.s87.17.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Francisco Llach
- Department of Medicine, Division of Nephrology and Hypertension, Georgetown University Hospital, Washington, DC 20007, USA.
| | | |
Collapse
|
7
|
Fukagawa M, Kazama JJ, Shigematsu T. Skeletal resistance to pth as a basic abnormality underlying uremic bone diseases. Am J Kidney Dis 2001; 38:S152-5. [PMID: 11576943 DOI: 10.1053/ajkd.2001.27426] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Skeletal resistance to parathyroid hormone (PTH) was suggested initially as a mechanism of PTH hypersecretion in uremia. Because of the effective suppression of PTH by recently developed therapeutic modalities, this background abnormality has been uncovered and currently recognized as relative hypoparathyroidism in terms of its relation to bone turnover. Thus, PTH levels two to three times greater than normal are usually required to keep bone turnover normal in uremia. Recent studies suggested that PTH activity may be overestimated using the conventional intact PTH assay. In addition, several steps to osteoclastogenesis are suspected to be disturbed in uremia. Additional studies at cellular and molecular levels are needed to establish preventive and therapeutic modalities for this abnormality.
Collapse
Affiliation(s)
- M Fukagawa
- Division of Nephrology and Dialysis Center, Kobe University School of Medicine, 7-5-2 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.
| | | | | |
Collapse
|
8
|
Lugon JR, André MB, Duarte ME, Rembold SM, Cruz E. Effects of in-center daily hemodialysis upon mineral metabolism and bone disease in end-stage renal disease patients. SAO PAULO MED J 2001; 119:105-9. [PMID: 11391452 PMCID: PMC11164470 DOI: 10.1590/s1516-31802001000300004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
CONTEXT Alternative hemodialysis schedules have been proposed to improve the quality of the dialysis. Nonetheless, their influence upon mineral and bone disorders is unknown. OBJECTIVE To report the impact of a daily hemodialysis schedule upon the lesions of renal osteodystrophy. TYPE OF STUDY Prospective non-controlled study. SETTING Public University Hospital. PARTICIPANTS Five patients treated by daily hemodialysis for at least 24 months. INTERVENTION Daily dialysis sessions were accomplished with non-proportional dialysis machines without an ultrafiltration control device, with blood flow of 300 ml/min, bicarbonate dialysate ([Ca]=3.5 mEq/L) at 500 ml/min, and low-flux membrane dialyzers. Sessions were started at 6:00 p.m. (except Sundays) and lasted 2 hours. MAIN MEASUREMENTS Serum levels of Ca and P from the last 6 months on conventional hemodialysis for the same patients were used for comparison with each semester of daily hemodialysis. Bone biopsies and PTH levels were obtained at the end of the conventional hemodialysis period and then again after 2 years of daily hemodialysis. RESULTS Mean serum calcium was significantly higher during the second and third semesters of daily dialysis [10.0 mg% (SD 0.6), and 10.0 mg% (SD 0.8), respectively] compared to standard dialysis [9.4 mg% (SD 0.8)], p < 0.05. Mean values for phosphorus were significantly lower during every semester of daily hemodialysis [6.3 mg% (SD 1.8), 5.8 mg% (SD 1.7), 6.0 mg% (SD 1.7), and 6.0 mg% (SD 1.8)] compared to standard dialysis [7.2 mg% (SD 2.7)], P < 0.05. Variations in mean Ca x P product followed the same pattern as for phosphorus [59.5 (SD 16.0), 57.1 (SD 16.3), 59.8 (SD 17.7), and 58.31 (SD 20.9) vs. 68.6 (SD 27.3), P < 0.05]. After 2 years on daily hemodialysis, 2 patients who had aplastic lesion were found to have mild bone disorder. In addition, one patient with mixed bone lesion and moderate bone aluminum accumulation had osteitis fibrosa with no aluminum. Intact PTH values at the beginning of study and after 2 years on daily hemodialysis did not differ [134 pg/ml (SD 66) vs. 109 pg/ml (SD 26), P = 0.60, respectively]. CONCLUSIONS Patients treated using daily hemodialysis had better control of serum phosphorus and perhaps a lower risk of metastatic calcifications. Daily hemodialysis also seemed to be beneficial to low turnover bone disease and bone aluminum deposition.
Collapse
Affiliation(s)
- J R Lugon
- Nephrology Division, Department of Internal Medicine, Universidade Federal Fluminense, Niterói, RJ, Brazil.
| | | | | | | | | |
Collapse
|
9
|
Dhondt A, Vanholder R, Van Biesen W, Lameire N. The removal of uremic toxins. KIDNEY INTERNATIONAL. SUPPLEMENT 2000; 76:S47-59. [PMID: 10936799 DOI: 10.1046/j.1523-1755.2000.07606.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Three major groups of uremic solutes can be characterized: the small water-soluble compounds, the middle molecules, and the protein-bound compounds. Whereas small water-soluble compounds are quite easily removed by conventional hemodialysis, this is not the case for many other molecules with different physicochemical characteristics. Continuous ambulatory peritoneal dialysis (CAPD) is often characterized by better removal of those compounds. Urea and creatinine are small water-soluble compounds and the most current markers of retention and removal, but they do not exert much toxicity. This is also the case for many other small water-soluble compounds. Removal pattern by dialysis of urea and creatinine is markedly different from that of many other uremic solutes with proven toxicity. Whereas middle molecules are removed better by dialyzers containing membranes with a larger pore size, it is not clear whether this removal is sufficient to prevent the related complications. Larger pore size has virtually no effect on the removal of protein-bound toxins. Therefore, at present, the current dialytic methods do not offer many possibilities to remove protein-bound compounds. Nutritional and environmental factors as well as the residual renal function may influence the concentration of uremic toxins in the body fluids.
Collapse
Affiliation(s)
- A Dhondt
- Renal Division, Department of Medicine, University Hospital of Gent, Gent, Belgium.
| | | | | | | |
Collapse
|
10
|
Kurokawa K, Fukagawa M. Introduction to Renal Osteodystrophy: Calcium Metabolism in Health and Uremia. Am J Med Sci 1999. [DOI: 10.1016/s0002-9629(15)40546-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|
11
|
Kurokawa K, Fukagawa M. Introduction to renal osteodystrophy: calcium metabolism in health and uremia. Am J Med Sci 1999; 317:355-7. [PMID: 10372833 DOI: 10.1097/00000441-199906000-00001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Affiliation(s)
- K Kurokawa
- Tokai University School of Medicine, Isehara, Kanagawa, Japan.
| | | |
Collapse
|
12
|
Affiliation(s)
- J B Cannata-Andía
- Instituto Reina Sofía de Investigation, Hospital Central de Asturias, Universidad de Oviedo, Spain
| |
Collapse
|
13
|
Affiliation(s)
- P U Massari
- Hospital Privado-Centro Médico de Córdoba, Argentina
| |
Collapse
|
14
|
Abstract
Control of hyperparathyroidism is a major goal of the management of bone diseases in chronic dialysis patients. Severity of hyperparathyroidism has been evaluated mainly by the level of parathyroid hormone (PTH), however, parathyroid size can be another critical marker. Patients with larger parathyroid glands are usually more resistant to calcitriol pulse therapy than those with smaller glands. Large parathyroid glands with nodular hyperplasia are composed of cells more resistant to calcitriol due to lower density of calcitriol receptors. Responsiveness to calcitriol therapy was restored by selective destruction of large parathyroid glands (> 0.5 cm3) by ethanol injections under ultrasonographic guidance. Direct injections of calcitriol solution into enlarged glands were also effective in suppressing PTH and restoring responsiveness to calcitriol. These data suggest that size of parathyroid glands reflects the resistance to calcitriol and that prevention of parathyroid hyperplasia is mandatory for the successful medical management of hyperparathyroidism in chronic renal failure.
Collapse
Affiliation(s)
- M Fukagawa
- First Department of Internal Medicine, University of Tokyo School of Medicine, Japan
| | | |
Collapse
|
15
|
Patel SR, Koenig RJ, Hsu CH. Effect of Schiff base formation on the function of the calcitriol receptor. Kidney Int 1996; 50:1539-45. [PMID: 8914020 DOI: 10.1038/ki.1996.469] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The genomic action of calcitriol is mediated through the interaction of the calcitriol receptor (VDR) with vitamin D response elements (VDREs) of the target genes. We have shown that the interaction of VDRs with VDREs is inhibited by uremic toxins. We hypothesize that uremic toxins form Schiff bases with the lysine residues of the VDR DNA binding domain and inhibit the VDR interaction with the VDRE. In this study, pyridoxal 5'-phosphate was used as a probe to test Schiff base formation as the inhibitory mechanism, since it forms Schiff bases with steroid receptors. Pyridoxal 5'-phosphate inhibited the VDR binding to the VDREs and chemically modified the DNA binding domain of the VDR in vitro. The inhibition was reversed when pyridoxal 5'-phosphate was preincubated with lysine. Further, this chemical agent also blocked the production of chloramphenicol acetyltransferase (CAT) enzyme induced by calcitriol in cells transfected with a constructed VDRE attached to a CAT reporter gene. This finding is consistent with the hypothesis that pyridoxal 5'-phosphate could interact with the VDR and impair its DNA binding within cells. Since induction of 24-hydroxylase synthesis is a receptor mediated process, we studied the effect of pyridoxal 5'-phosphate on the synthesis of renal 24-hydroxylase in rats. When pyridoxal 5'-phosphate was infused to rats, renal 24-hydroxylase activity was suppressed, consequently, degradation of calcitriol was also reduced in these animals. Thus, chemicals capable of Schiff base formation potentially could alter the physiological function of VDR and calcitriol.
Collapse
Affiliation(s)
- S R Patel
- Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, USA
| | | | | |
Collapse
|
16
|
|