Hypovitaminosis D and Valvular Calcification in Patients With Dilated Cardiomyopathy

CLINICAL INVESTIGATION

Hypovitaminosis D and Valvular Calcification in Patients With Dilated Cardiomyopathy Dwight A. Dishmon, MD, Jimmy L. Dotson, MD, Ahmad Munir, MD, Maeda D. Nelson, RN, BSN, Syamal K. Bhattacharya, PhD, Ivan A. D’Cruz, MD, Richard C. Davis, MD, PhD and Karl T. Weber, MD

Abstract: Background: In patients with dilated (idiopathic) cardiomyopathy (DCM), little is known about the presence of valvular calcification and its association with hypovitaminosis D, which may predispose affected tissues to calcification. Our objectives were 2-fold: to conduct a retrospective assessment of echocardiographic evidence of valvular calcification in patients with DCM who were known to have hypovitaminosis D (25(OH)D ⬍30 ng/mL) and to conduct a prospective assessment of serum 25(OH)D in patients with DCM, who had demonstrated echocardiographic evidence of valvular calcification. Methods: The retrospective study consisted of 48 African American patients (34 men, 14 women; 52.3 ⫾ 1.5 years) having DCM and ejection fraction ⬍35% with serum creatinine ⬍2.0 mg/dL and 25(OH)D ⬍30 ng/mL; and 20 white patients in the prospective study (20 men; 71.0 ⫾ 3.0 years) having DCM and ejection fraction ⬍35% with serum creatinine ⬍2.0 mg/dL and echocardiographic evidence of valvular calcification. In the retrospective study, a transthoracic echocardiogram was obtained to address mitral valvular and annular calcification, aortic valvular calcification, and sinotubular calcification; whereas in the prospective study, serum 25(OH)D level was monitored in patients with known valvular calcification. Serum parathyroid hormone (PTH) was monitored in both studies. Results: In the retrospective study, hypovitaminosis D was found in 19 patients (31%) with valvular calcification and in whom serum PTH was increased (83 ⫾ 8 pg/mL). In the prospective study, 15 of 20 elderly patients (80%) with known DCM and valvular calcification were found to have hypovitaminosis D (25(OH)D ⬍30 ng/mL), whereas serum PTH was normal (43 ⫾ 4 pg/mL). Conclusions: In patients with DCM without marked renal dysfunction, valvular calcification was seen more frequently and associated with hypovitaminosis D, whereas in elderly patients with valvular calcification, hypovitaminosis D is common, suggesting that the duration of vitamin D deficiency may determine the extent of valvular calcification. The role of hypovitaminosis D in the appearance of valvular calcification deserves further study. Key Indexing Terms: Hypovitaminosis D; Valvular calcification; Dilated cardiomyopathy; Echocardiography. [Am J Med Sci 2009; 337(5):312–316.]

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he prevalence of vitamin D deficiency (ie, hypovitaminosis D) is relatively high in the United States and worldwide.1 Levels of the principal storage form of vitamin D, 25-hyFrom the Division of Cardiovascular Diseases (DAD, JLD, AM, MDN, SKB, Department of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee; Department of Surgery (SKB), University of Tennessee Health Science Center, Memphis, Tennessee; and Department of Veterans Affairs Medical Center (AM, IAD, RCD), Memphis, Tennessee. Submitted July 3, 2008; accepted in revised form August 20, 2008. Presented, in part, at the annual scientific session of the Southern Society for Clinical Investigation, February 21–23, 2008. Correspondence: Karl T. Weber, MD, Division of Cardiovascular Diseases, University of Tennessee Health Science Center, 956 Court Avenue, Suite A312, Memphis, TN 38163 (E-mail: [email protected]). IAD, RCD, KTW),

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droxyvitamin D (25(OH)D), are low in up to one half of otherwise healthy adults.2,3 The causes of hypovitaminosis D are multifactorial and most importantly include inadequate exposure to sunlight. The vital role of calcium and vitamin D in the maintenance of skeletal health has been well established. There is cumulative evidence that vitamin D has extraosseous manifestations. Clinical studies have demonstrated multiple associations between hypovitaminosis D and plasma renin activity, blood pressure, and calcification involving the coronaries and other vascular beds.4 Furthermore, ecological studies have revealed an increased incidence of hypertension and cardiovascular disease as the latitude from the equator rises, a phenomenon attributed to a higher prevalence of vitamin D deficiency in regions with less sunlight exposure.4 Even though vitamin D is most recognized for its effects on the skeletal system, vitamin D receptors have demonstrated versatility in their expression in various tissues, including the endothelium, vascular smooth muscle cells, and cardiomyocytes.5 In vitro, activated 1,25-dihydroxyvitamin D (1,25(OH)D2) regulates the growth of vascular smooth muscle cells and cardiomyocytes, directly suppresses renin gene expression, and inhibits cytokine release from lymphocytes.4 Of particular clinical relevance, the principal biologic effect of vascular smooth muscle cells is the production of inhibitors of calcification.5 These roles reflect the variability and versatility of vitamin D on the cardiovascular system. Vascular calcification occurs in patients with atherosclerosis, ischemic cardiomyopathy, osteoporosis, and chronic kidney disease. In each of these conditions, vascular calcification is independently associated with increased cardiovascular risk.5 In the general population, presence of vascular calcification carries a poor 5-year prognosis.6 It has been suggested that valvular calcification may be another potential manifestation of hypovitaminosis D.7 Similarities have been shown between vascular atherosclerosis and chronic degenerative changes in the aortic and mitral valves.8,9 Related to atherosclerosis, the initiating event for valvular disease is thought to be injury or endothelial dysfunction.10 Boon et al11 found an association of both mitral and annular calcification, as well as aortic valvular calcification with age and vascular risk factors. Age, female sex, diabetes mellitus, hypertension, and hypercholesterolemia were strongly associated with mitral and aortic valvular calcification, with odds ratios between 2.2 and 2.8.11 Little is known regarding the relationship between hypovitaminosis D and valvular calcification in patients with dilated cardiomyopathy (DCM). The aforementioned clinical and experimental findings led us to hypothesize that DCM, valvular calcification, and hypovitaminosis D must be correlated. Our objectives were 2-fold: (1) to conduct a retrospective assessment of echocardiographic evidence of valvular calcification in patients with

The American Journal of the Medical Sciences • Volume 337, Number 5, May 2009

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FIGURE 1. Parasternal short-axis view on a transthoracic echocardiogram showing a normal appearing aortic valve with clearly defined leaflets (open arrow) and calcification in the margins of aortic valve leaflets with lack of crisp definition (solid arrow).

DCM and who were known to have hypovitaminosis D (defined as 25(OH)D ⬍30 ng/mL) and (2) to conduct a prospective assessment of serum 25(OH)D in patients with DCM who had known echocardiographic evidence of valvular calcification.

METHODS Data were collected both retrospectively and prospectively. The patient populations included in this study, approved by the respective institutional review boards at the University of Tennessee Health Science Center and Veterans Affairs Medical Center, consisted of 48 patients in the retrospective study and 20 patients in the prospective study. Retrospective Study The 48 patients (34 men, 14 women; 52.3 ⫾ 1.5 years) in the retrospective study were inpatients and outpatients treated by the Cardiology Service at the Regional Medical Center in Memphis, TN. Demographic and clinical data were obtained from the patients’ records. Each of these patients had DCM with an ejection fraction (EF) ⬍35%, serum creatinine ⬍2.0 mg/dL, and clinically established hypovitaminosis D (defined as a serum 25(OH)D level ⬍30 ng/mL). Three experienced echocardiologists interpreted the echocardiograms for evidence of valvular calcification. Valvular calcification (see Figures 1–3) was defined by the presence of echodense calcium on the mitral valve or annulus, on the aortic valve or annulus, or in the sinotubular junction as previously reported.12 No tricuspid or pulmonary valvular or annular calcification was documented. All of these patients were African American and none were obese. Prospective Study The 20 patients (20 men; 71.0 ⫾ 3.0 years) in the prospective study were inpatients and outpatients at the Veter-

FIGURE 2. Parasternal long-axis view on a transthoracic echocardiogram showing a normal appearing posterior mitral annulus (open arrow) and calcification of the posterior mitral annulus, extending into the base of the posterior mitral leaflet (solid arrow). © 2009 Lippincott Williams & Wilkins

FIGURE 3. Parasternal long-axis view on a transthoracic echocardiogram showing normal appearing aortic root and sinotubular junction (open arrow) and calcification of the sinotubular junction (solid arrow).

ans Affairs Hospital in Memphis, TN, who had DCM and echocardiographic evidence of valvular calcification. The aforementioned definition for the echocardiographic presence of calcification was also pertinent to this study. Serum 25(OH)D levels were subsequently obtained in these patients. Patients in this group were all men and predominantly white. All patients had a serum creatinine ⬍2.0 mg/dL. Exclusion Criteria In both groups, none of the patients was receiving therapies that could have altered the hypothalamic-pituitary axis, and consequently parathyroid function and vitamin D levels. None was receiving growth hormone, insulin, thyroxin, estrogen, or a glucocorticoid, and none had any disorder affecting bone metabolism, including rheumatoid arthritis, osteomalacia, primary hyperparathyroidism, Paget disease, hyperthyroidism, osteogenesis imperfecta, gastric resection, inflammatory bowel disease, or a history of fragility fractures. We did not adjust for comorbid states, such as hyperlipidemia, diabetes mellitus, or hypertension. Furthermore, no adjustments were made for body mass index, cigarette smoking, or specific medical or pharmacologic treatments. The lowest recordable 25(OH)D level, below the limits of detection, was ⬍7.0 ng/mL for both groups. For calculation purposes, in those patients in whom a level of ⬍7.0 ng/mL was obtained, a value of 6.9 ng/mL was used. Serum parathyroid hormone (PTH) was monitored by standard methodology.

RESULTS Retrospective Study The retrospective study consisted of 48 younger patients (52.3 ⫾ 1.5 years) with DCM and hypovitaminosis D. In this population of middle-aged African Americans, we would not implicate senescent skin and its reduced efficiency in generating vitamin D. Nineteen (31%) patients were found to have valvular calcification of whom 9 had calcification involving the aortic valve or annulus, 8 had calcification of the mitral valve or annulus, and 4 had calcification localized to the sinotubular ridge. Of the 19 patients with echocardiographic calcification, 2 patients had calcification involving both the aortic and mitral valves. Ninety-six percent of patients had hypovitaminosis D as defined by a 25(OH) vitamin D level ⬍30 ng/mL. The average 25(OH)D for the entire group was 13.2 ng/mL (range ⬍7– 54.1). There was no 25(OH)D data available on 12 patients—5 patients with calcification versus 7 patients without calcification. The mean 25(OH)D level in patients with calcification was 11.7 ng/mL versus 23.6 ng/mL in those without calcification. Two patients had a 25(OH)D level ⬎30 ng/mL (mean 42.5). Neither of those patients had any echocardiographic

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evidence of calcification. Four additional patients had 25(OH)D level ⬎20 ng/mL. Of those patients, only 1 patient (a 74-yearold woman) had valvular calcification. The mean 25(OH)D levels for patients with aortic valve, mitral valve, and sinotubular ridge calcification were 11.1, 17.9, and 15.4 ng/mL, respectively. Patients with aortic valve calcification tended to be older (average age 61 years) compared with patients with mitral valve and sinotubular ridge calcification (average 53 and 56 years, respectively). The average EF for the entire group was 26%. Serum PTH (mean ⫾ SEM) for the 48 African American patients in this retrospective study was 83 ⫾ 8 pg/mL (normal ⬍65 pg/mL). In those with valvular calcification it was 88 ⫾ 13 pg/mL. Prospective Study In the prospective study, 15 of 20 (80%) elderly patients (71.0 ⫾ 3.0 years) with known DCM and valvular calcification were found to have hypovitaminosis D (25(OH)D ⬍30 ng/mL). The mean 25(OH)D level for the group was 22.25 ng/mL (range ⬍7.0 – 63.1). There were a total of 31 calcific lesions among these patients. Thirteen patients had calcification of the aortic valve, 12 patients had calcification involving the mitral valve, and 6 patients had calcification involving the sinotubular ridge. Of these individuals, 10 patients had calcification involving a combination of the aortic and mitral valves (7 patients), aortic valve and sinotubular ridge (1 patient), or aortic valve, mitral valve, and sinotubular ridge (1 patient). Four of 5 patients with calcification involving more than 1 site had 25(OH)D level in the normal range. Three patients had hemodynamically significant aortic stenosis (mean gradient ⬎35 mm Hg), whereas no patients revealed significant mitral stenosis. Serum PTH (mean ⫾ SEM) for the 20 white patients in this prospective study with valvular calcification was 43 ⫾ 4 pg/mL (normal ⬍65 pg/mL).

DISCUSSION Our retrospective study revealed 31% of middle-aged African American patients with DCM and hypovitaminosis D had associated valvular calcification. Furthermore, 80% of elderly men with DCM and valvular calcification were found to have hypovitaminosis D. The presence of valvular/annular calcification is clinically relevant as evidenced by an increased prevalence and risk of severe coronary disease, stroke, and cardiac death in patients with annular calcification, particularly, mitral annular calcification.13 Mitral annular calcification, in particular, may result in mitral stenosis, mitral regurgitation, atrial dysrhythmias, infective endocarditis, and heart block.14,15 Furthermore, calcific aortic valve disease is increasing in prevalence (primarily because of an aging population) and has become the most common predictor for surgical valve replacement.16 Furthermore, it has been documented that over a short period of time (5 years), approximately 9% of patients with aortic valve sclerosis will progress to aortic valve stenosis.17 Extraskeletal manifestations of vitamin D and the high prevalence of hypovitaminosis D have largely been unrecognized by physicians and patients alike.18 This community-based study convincingly implicates an association between DCM, valvular calcification, and hypovitaminosis D. The high prevalence of hypovitaminosis D in African Americans enrolled in the prospective study was quite striking and in keeping with our previous findings.19 Limited cutaneous synthesis due to inadequate exposure to sunlight and pigmented skin, where melanin is a natural sunscreen that mandates longer sunlight exposure for the skin to initiate vitamin D steroidogenesis, and inadequate dietary

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intake, are the primary causes of hypovitaminosis D.4 Serum 25(OH)D is regarded as the best indicator of vitamin D status in patients without kidney disease for numerous reasons: (1) it is the substrate for the renal and nonrenal production of 1,25(OH)D; (2) it has a much longer biologic half-life (several weeks) than 1,25(OH)D; and (3) it circulates in much higher concentrations. Serum 25(OH)D is reflective of the composite production of vitamin D from endogenous and exogenous sources, including ultraviolet B radiation and dietary intake.4 Vitamin D deficiency can affect the parathyroid glands by triggering secondary hyperparathyroidism (SHPT). PTH, elaborated in response to ionized hypocalcemia because of hypovitaminosis D, promotes hypertrophy of cardiomyocytes and vascular remodeling in addition to proinflammatory effects, such as the release of cytokines by vascular smooth muscle cells.4 Relatively high levels of 25(OH)D (⬎30 ng/mL) and 1,25(OH)2D3 are required to maintain normal PTH levels, to maximize intestinal and renal calcium absorption, and to minimize disturbances in calcium homeostasis.20 Nonetheless, optimal levels of serum 25(OH)D for cardiovascular protection may differ from those required for bone metabolism or normal PTH physiology. Serum PTH levels were elevated in our African American cohort with hypovitaminosis D and in the subset with valvular calcification. Serum PTH levels were not elevated in our elderly prospective cohort followed at the Veterans Affairs Hospital with valvular calcification. The prevalence of hypovitaminosis D and SHPT in African Americans residing in Memphis has recently been reported and likely has a multifactorial basis.19 The contribution of elevations in PTH to valvular calcification is presently uncertain. Some studies have shown a strong correlation between cardiovascular risk factors and calcification of the mitral and aortic valves.21,22 Valvular calcification has, in turn, been linked to aortic and coronary calcification.23 In populationbased studies, the prevalence of aortic valvular and mitral valvular calcification have been reported to be 28% and 13%, respectively.21,24 Likewise, the prevalence of mitral valvular/ annular calcification may be as high as 36% in patients with end-stage renal disease.25 To date, however, there has not been a strong association established between the presence of cardiac calcification, whether myocardial or valvular, and any biomarker of parathyroid or renal function. Despite the association of cardiac calcific deposits with primary and SHPT, renal disease, hypercalcemia, and (in this case) hypovitaminosis D, no linear correlation between lab values and the degree of calcification present has been clearly established. Vitamin D deficiency has been associated with adverse effects on cardiac function and the appearance of congestive heart failure. In southeast England, a potentially fatal, reversible DCM has been seen in dark-skinned, exclusively breast-fed infants, particularly, toward the end of winter.26 In a recent report, conducted in Memphis during winter and summer months, we found reduced 25(OH)D levels (⬍30 ng/mL) in the majority of African Americans having DCM and reduced EF, with or without decompensated failure.19 Study limitations include nonmonitoring of atherosclerotic burden. Patients with mitral annular calcification are reported to have a significantly higher prevalence of aortic atheromatous disease than matched controls.27 Protruding atheromas with a thickness ⬎4 mm were also more prevalent in patients with mitral annular calcification. It has been postulated that mitral and aortic annular/valvular calcification, coronary artery calcification, and aortic atheroma may all be a part of the spectrum of atherosclerosis.28,29 Despite sharing common risk Volume 337, Number 5, May 2009

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factors, the link between atherosclerosis and calcific valvular sclerosis is less evident when the cellular and molecular biology of valvular sclerosis with calcification is considered. The major cellular component and determinant of collagen synthesis in heart valve leaflets are myofibroblasts (or valvular interstitial cells). The turnover of collagen by these cells is regulated by auto-/paracrine properties of locally generated angiotensin peptides and, in turn, the fibrogenic cytokine transforming growth factor-␤1.30 –33 Calcification of the collagenous matrix involves bone morphogenic proteins.34 Moreover, vitamin D deficiency is associated with an activation of the circulating renin-angiotensin-aldosterone system and cardiac fibrosis appears in vitamin D receptor knockout mice.35,36 Renin-angiotensin-aldosterone system activation accounts for salt avidity together with salt and water retention when patients with DCM have symptomatic heart failure.37 The management of hypovitaminosis D in our patients could proceed in a number of directions. One approach could be to increase sunlight exposure with reliance on the skin to enhance steroidogenesis and the liver to generate vitamin D. It has been reported that exposure of the skin to suberythemal (nontanning) doses of ultraviolet B light derived from a lamp source (also known as phototherapy) can be as effective as oral vitamin D3 in raising 25(OH)D levels and suppressing parathyroid levels.38 Alternatively, vitamin D could be supplemented in pharmacologic doses. Schleithoff et al39 have reported that 9 months of treatment with vitamin D3 led to an improvement in serum 25(OH)D levels in patients with heart failure and hypovitaminosis D. Witte et al40 found that patients with heart failure treated for 9 months with multiple micronutrients that included vitamin D had improved exercise tolerance and overall quality of life. The efficacy of phototherapy versus high-dose vitamin D supplementation in African American patients with DCM and hypovitaminosis D remains to be explored. In summary, hypovitaminosis D with echocardiographic evidence of valvular calcification was found in one third of middle-aged African Americans with DCM, but no renal failure. In elderly white men having DCM with valvular calcification, hypovitaminosis D was found in 80%. These findings call into question the importance of hypovitaminosis D in leading to the pathobiologic process presenting as aortic and/or mitral valvular calcification and which may be a time-dependent process. It no longer may be appropriate to consider it a passive degenerative process.41 REFERENCES 1. Holick MF. High prevalence of vitamin D inadequacy and implications for health. Mayo Clin Proc 2006;81:353–73. 2. Chapuy MC, Preziosi P, Maamer M, et al. Prevalence of vitamin D insufficiency in an adult normal population. Osteoporos Int 1997;7: 439 – 43. 3. Nesby-O’Dell S, Scanlon KS, Cogswell ME, et al. Hypovitaminosis D prevalence and determinants among African American and white women of reproductive age: third National Health and Nutrition Examination Survey, 1988 –1994. Am J Clin Nutr 2002;76:187–92. 4. Wang TJ, Pencina MJ, Booth SL, et al. Vitamin D deficiency and risk of cardiovascular disease. Circulation 2008;117:503–11. 5. Zittermann A, Schleithoff SS, Koerfer R. Vitamin D and vascular calcification. Curr Opin Lipidol 2007;18:41– 6. 6. Towler DA, Clemens TL. Vitamin D and cardiovascular medicine. In: Feldman D, Pike JW, Glorieux FH, editors. Vitamin D. 2nd ed. San Diego (CA): Elsevier Academic Press; 2005. p. 899 –910. 7. Shiraki M, Miyagawa A, Akiguchi I, et al. Evidence of hypovitamin-

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osis D in patients with mitral ring calcification. Jpn Heart J 1988;29: 801– 8. 8. Otto CM, Kuusisto J, Reichenbach DD, et al. Characterization of the early lesion of ‘degenerative’ valvular aortic stenosis. Histological and immunohistochemical studies. Circulation 1994;90:844 –53. 9. Walton KW, Williamson N, Johnson AG. The pathogenesis of atherosclerosis of the mitral and aortic valves. J Pathol 1970;101: 205–20. 10. Mohler ER III. Mechanisms of aortic valve calcification. Am J Cardiol 2004;94:1396 – 402. 11. Boon A, Cheriex E, Lodder J, et al. Cardiac valve calcification: characteristics of patients with calcification of the mitral annulus or aortic valve. Heart 1997;78:472– 4. 12. D’Cruz IA, Calderon E, Clark R. Transthoracic echocardiographic visualization of calcification of the sinotubular ridge of the ascending aorta. Echocardiography 1998;15:425– 8. 13. Atar S, Jeon DS, Luo H, et al. Mitral annular calcification: a marker of severe coronary artery disease in patients under 65 years old. Heart 2003;89:161– 4. 14. Nestico PF, Depace NL, Morganroth J, et al. Mitral annular calcification: clinical, pathophysiology, and echocardiographic review. Am Heart J 1984;107:989 –96. 15. Benjamin EJ, Plehn JF, D’Agostino RB, et al. Mitral annular calcification and the risk of stroke in an elderly cohort. N Engl J Med 1992;327:374 –9. 16. Passik CS, Ackermann DM, Pluth JR, et al. Temporal changes in the causes of aortic stenosis: a surgical pathologic study of 646 cases. Mayo Clin Proc 1987;62:119 –23. 17. Novaro GM, Katz R, Aviles RJ, et al. Clinical factors, but not C-reactive protein, predict progression of calcific aortic-valve disease: the Cardiovascular Health Study. J Am Coll Cardiol 2007;50:1992– 8. 18. Grant WB, Holick MF. Benefits and requirements of vitamin D for optimal health: a review. Altern Med Rev 2005;10:94 –111. 19. Alsafwah S, LaGuardia SP, Nelson MD, et al. Hypovitaminosis D in African Americans residing in Memphis, Tennessee with and without heart failure. Am J Med Sci 2008;335:292–7. 20. Holick MF, Siris ES, Binkley N, et al. Prevalence of vitamin D inadequacy among postmenopausal North American women receiving osteoporosis therapy. J Clin Endocrinol Metab 2005;90:3215–24. 21. Maher ER, Young G, Smyth-Walsh B, et al. Aortic and mitral valve calcification in patients with end-stage renal disease. Lancet 1987;2: 875–7. 22. Agmon Y, Khandheria BK, Meissner I, et al. Aortic valve sclerosis and aortic atherosclerosis: different manifestations of the same disease? Insights from a population-based study. J Am Coll Cardiol 2001;38: 827–34. 23. Yamamoto H, Shavelle D, Takasu J, et al. Valvular and thoracic aortic calcium as a marker of the extent and severity of angiographic coronary artery disease. Am Heart J 2003;146:153–9. 24. Fox CS, Parise H, Vasan RS, et al. Mitral annular calcification is a predictor for incident atrial fibrillation. Atherosclerosis 2004;173: 291– 4. 25. Tangpricha V, Koutkia P, Rieke SM, et al. Fortification of orange juice with vitamin D: a novel approach for enhancing vitamin D nutritional health. Am J Clin Nutr 2003;77:1478 – 83. 26. Maiya S, Sullivan I, Allgrove J, et al. Hypocalcaemia and vitamin D deficiency: an important, but preventable, cause of life-threatening infant heart failure. Heart 2008;94:581– 4. 27. Matsumura Y, Takata J, Yabe T, et al. Atherosclerotic aortic plaque detected by transesophageal echocardiography: its significance and limitation as a marker for coronary artery disease in the elderly. Chest 1997;112:81– 6.

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Dishmon et al

28. Wexler L, Brundage B, Crouse J, et al. Coronary artery calcification: pathophysiology, epidemiology, imaging methods, and clinical implications. A statement for health professionals from the American Heart Association. Writing Group. Circulation 1996;94:1175–92.

35. Yuan W, Pan W, Kong J, et al. 1,25-Dihydroxyvitamin D3 suppresses renin gene transcription by blocking the activity of the cyclic AMP response element in the renin gene promoter. J Biol Chem 2007;282: 29821–30.

29. Goldbarg SH, Elmariah S, Miller MA, et al. Insights into degenerative aortic valve disease. J Am Coll Cardiol 2007;50:1205–13.

36. Simpson RU, Hershey SH, Nibbelink KA. Characterization of heart size and blood pressure in the vitamin D receptor knockout mouse. J Steroid Biochem Mol Biol 2007;103:521– 4.

30. Sun Y, Diaz-Arias AA, Weber KT. Angiotensin-converting enzyme, bradykinin and angiotensin II receptor binding in rat skin, tendon and heart valves: an in vitro quantitative autoradiographic study. J Lab Clin Med 1994;123:372–7. 31. Weber KT. Extracellular matrix remodeling in heart failure. A role for de novo angiotensin II generation. Circulation 1997;96:4065– 82. 32. Katwa LC, Tyagi SC, Campbell SE, et al. Valvular interstitial cells express angiotensinogen, cathepsin D, and generate angiotensin peptides. Int J Biochem Cell Biol 1996;28:807–21. 33. Jian B, Narula N, Li QY, et al. Progression of aortic valve stenosis: TGF-beta1 is present in calcified aortic valve cusps and promotes aortic valve interstitial cell calcification via apoptosis. Ann Thorac Surg 2003;75:457– 65. 34. O’Brien KD, Kuusisto J, Reichenbach DD, et al. Osteopontin is expressed in human aortic valvular lesions. Circulation 1995;92:2163– 8.

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37. Selektor Y, Weber KT. The salt-avid state of congestive heart failure revisited. Am J Med Sci 2008;335:209 –18. 38. Chel VG, Ooms ME, Popp-Snijders C, et al. Ultraviolet irradiation corrects vitamin D deficiency and suppresses secondary hyperparathyroidism in the elderly. J Bone Miner Res 1998;13:1238 – 42. 39. Schleithoff SS, Zittermann A, Stu¨ttgen B, et al. Low serum levels of intact osteocalcin in patients with congestive heart failure. J Bone Miner Metab 2003;21:247–52. 40. Witte KK, Nikitin NP, Parker AC, et al. The effect of micronutrient supplementation on quality-of-life and left ventricular function in elderly patients with chronic heart failure. Eur Heart J 2005;26:2238 – 44. 41. Demer LL, Tintut Y. Vascular calcification: pathobiology of a multifaceted disease. Circulation 2008;117:2938 – 48.

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