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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent evidence suggests a pathogenetic link between hypertension and insulin resistance. In addition, disturbances of vitamin D/parathyroid hormone axis have been reported in various hypertensive and insulin-resistant states. Chronic renal failure is characterized by high incidence of hypertension, insulin resistance and disturbances in the vitamin D/parathyroid hormone axis. Preliminary studies in both patients and rats with end-stage renal disease who were hypertensive, insulin resistant and 1,25-dihydroxycholecalciferol deficient with hyperparathyroidism; parenteral administration of pharmacological doses of 1,25-dihydroxycholecalciferol led to reversal of hypertension and insulin resistance without significant changes in serum calcium or parathyroid hormone concentrations. Thus, vitamin D deficiency may be an important factor in the pathogenesis of hypertension and insulin resistance in end-stage renal disease.
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PMID:The vitamin D/parathyroid hormone axis in the pathogenesis of hypertension and insulin resistance in uremia. 146 50

The metabolism of Ca2+ is profoundly disturbed in the spontaneously hypertensive rat (SHR), compared with its normotensive control, the Wistar-Kyoto rat. This is true for the whole animal as well as at the cellular and the subcellular level. Many apparently discrepant results of the literature could be due to differences in age, gender, strain, and type of diet. It is possible that the SHR has initially an epithelial (and a nonepithelial) Ca2+ transport defect. This could in turn lead to a more or less efficient stimulation of calcitriol synthesis and a compensatory increase in calcium absorption during early life. With the maturation of the animal, however, a state of calcium and vitamin D deficiency would prevail. In this scheme, the observed defect of epithelial Ca2+ transport in the SHR is primary in nature, reflecting some perturbation of Ca2+ handling by the cell, and the changes of vitamin D metabolism and hyperparathyroidism are secondary. Altered cellular Ca2+ permeability and a compromised ability of the cell to remove or sequester Ca2+ may be relevant to the pathogenesis and maintenance of hypertension. Parathyroid gland overfunction and vitamin D deficiency may also be involved in the elevation of arterial pressure. Our knowledge of such interactions is however still incomplete. Much more has to be learnt about the probable link between alterations of Ca2+ metabolism and elevated blood pressure.
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PMID:Disturbances of calcium metabolism in experimental hypertension. 218 94

Hypophosphatemia has been documented in patients with hypertension and in spontaneously hypertensive rats compared with genetically matched control Wistar-Kyoto rats. However, renal tubular reabsorption is increased in spontaneously hypertensive rats. Therefore, it was hypothesized that decreased serum phosphate levels in spontaneously hypertensive rats may be related to a decrease in the intestinal transport of phosphate. To test this hypothesis, sodium-dependent phosphate uptake by jejunal brush-border membrane vesicles of spontaneously hypertensive rats and genetically matched Wistar-Kyoto rats was determined. Phosphate uptake consisted of two components: sodium-independent passive diffusion across the brush border and sodium-dependent, carrier-mediated uptake. The initial rate of uptake in spontaneously hypertensive and Wistar-Kyoto rats was linear up to 20 seconds. The initial rate and time course of jejunal sodium-dependent phosphate uptake was decreased in adult spontaneously hypertensive rats compared with corresponding mean values in Wistar-Kyoto rats. This decrease was secondary to a decrease in Vmax rather than Km, suggesting tha the number and/or the activity of the sodium-phosphate transporters is decreased. Sodium-dependent phosphate uptake was pH dependent, with greater uptake at pH 6.0 than at pH 7.4. However, uptake values were lower in spontaneously hypertensive rats than in Wistar-Kyoto rats at all pH levels tested. In contrast, sodium-dependent phosphate uptake in weanling rats (prehypertensive state) was not significantly different between spontaneously hypertensive and Wistar-Kyoto rats. Vitamin D deficiency in both spontaneously hypertensive and Wistar-Kyoto rats decreased Vmax and Km of sodium-dependent phosphate uptake, whereas 1,25(OH)2 vitamin D3 administration increased Vmax and Km in both spontaneously hypertensive and Wistar-Kyoto rats. These results suggest that the hypophosphatemia seen in adult spontaneously hypertensive rats is secondary to a decrease in sodium-dependent phosphate uptake compared with controls. The sodium phosphate transporter in spontaneously hypertensive rats is responsive to vitamin D administration.
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PMID:Intestinal phosphate transport in spontaneously hypertensive rats and genetically matched controls. 234 21

This article begins with a discussion on changes in the maternal calcium-parathyroid axis in response to pregnancy, followed by calcium disorders that can take place during pregnancy. Hypercalcemia and its subsequent disorders, including hyperparathyroidism, hypocalciuric hypercalcemia, and thyroid disease, are reviewed. Also, hypocalcemia and its subsequent disorders, including hypoparathyroidism, vitamin D deficiency, and hypomagnesemia, are addressed. Concluding the article are discussions on bone status and osteoporosis, calcium metabolism in pregnancy-induced hypertension and preeclampsia, and nephrolithiasis in pregnancy.
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PMID:Calcium disorders of pregnancy. 778 23

Environmental factors are important in the aetiology of glucose intolerance, type II diabetes and IHD. The lack of vitamin D, which is necessary for adequate insulin secretion, relates demographically to increased risk of myocardial infarction. These disorders are connected, degenerative vascular disease increasing with glucose intolerance and diabetes and, with its risk factors, comprising syndrome 'X'. Evidence is presented suggesting that vitamin D deficiency may be an avoidable risk factor for syndrome 'X', adding another preventative measure to current recommendations which are aimed at reducing the worldwide epidemic of these disorders. Experimentally, vitamin D deficiency progressively reduces insulin secretion; glucose intolerance follows and becomes irreversible. Relationships between vitamin D status, glucose tolerance and 30 min insulin secretion during oral glucose tolerance tests are reported in British Asians; insulin secretion, but not glycaemia, improving with short-term supplementation. Studies showing reduction in blood pressure and in risk of heart attack and diabetes with exercise (usually outdoor), rarely consider the role of vitamin D status. Glycaemia and insulin secretion in elderly European men, however, relate to vitamin D status, independent of season or physical activity. Prolonged supplementation can improve glycaemia. Hypertension improves with vitamin D treatment with or without initial deficiency. Vitamin D status and climate are reviewed as risk factors for myocardial infarction; the risk reducing with altitude despite increasing cold. Glycaemia and fibrinogenaemia improve with insulin secretion increases in summer. Variation in vitamin D requirements could arise from genetic differences in vitamin D processing since bone density can vary with vitamin D-receptor genotype. Vitamin D receptors are present in islet beta cells and we report insulin secretion in healthy Asians differing profoundly with the Apa I genotype, being independent of vitamin D status. Those at risk of vitamin D deficiency include the elderly, those living indoors or having a covered-up style of dress, especially dark-skinned immigrants, and pregnant women, and these are groups recognized as being at increased risk of diabetes.
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PMID:Inadequate vitamin D status: does it contribute to the disorders comprising syndrome 'X'? 962 22

Vitamin D is one of the oldest hormones that have been made in the earliest life forms for over 750 million years. Phytoplankton, zooplankton, and most plants and animals that are exposed to sunlight have the capacity to make vitamin D. Vitamin D is critically important for the development, growth, and maintenance of a healthy skeleton from birth until death. The major function of vitamin D is to maintain calcium homeostasis. It accomplishes this by increasing the efficiency of the intestine to absorb dietary calcium. When there is inadequate calcium in the diet to satisfy the body's calcium requirement, vitamin D communicates to the osteoblasts that signal osteoclast precursors to mature and dissolve the calcium stored in the bone. Vitamin D is metabolized in the liver and then in the kidney to 1,25-dihydroxyvitamin D [1,25(OH)(2)D]. 1,25(OH)(2)D receptors (VDR) are present not only in the intestine and bone, but in a wide variety of other tissues, including the brain, heart, stomach, pancreas, activated T and B lymphocytes, skin, gonads, etc. 1,25(OH)(2)D is one of the most potent substances to inhibit proliferation of both normal and hyperproliferative cells and induce them to mature. It is also recognized that a wide variety of tissues, including colon, prostate, breast, and skin have the enzymatic machinery to produce 1,25(OH)(2)D. 1,25(OH)(2)D and its analogs have been developed for treating the hyperproliferative disease psoriasis. Vitamin D deficiency is a major unrecognized health problem. Not only does it cause rickets in children, osteomalacia and osteoporosis in adults, but may have long lasting effects. Chronic vitamin D deficiency may have serious adverse consequences, including increased risk of hypertension, multiple sclerosis, cancers of the colon, prostate, breast, and ovary, and type 1 diabetes. There needs to be a better appreciation of the importance of vitamin D for overall health and well being.
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PMID:Vitamin D: A millenium perspective. 1252 May 30

Vitamin D is metabolised by a hepatic 25-hydroxylase into 25-hydroxyvitamin D (25(OH)D) and by a renal 1alpha-hydroxylase into the vitamin D hormone calcitriol. Calcitriol receptors are present in more than thirty different tissues. Apart from the kidney, several tissues also possess the enzyme 1alpha-hydroxylase, which is able to use circulating 25(OH)D as a substrate. Serum levels of 25(OH)D are the best indicator to assess vitamin D deficiency, insufficiency, hypovitaminosis, adequacy, and toxicity. European children and young adults often have circulating 25(OH)D levels in the insufficiency range during wintertime. Elderly subjects have mean 25(OH)D levels in the insufficiency range throughout the year. In institutionalized subjects 25(OH)D levels are often in the deficiency range. There is now general agreement that a low vitamin D status is involved in the pathogenesis of osteoporosis. Moreover, vitamin D insufficiency can lead to a disturbed muscle function. Epidemiological data also indicate a low vitamin D status in tuberculosis, rheumatoid arthritis, multiple sclerosis, inflammatory bowel diseases, hypertension, and specific types of cancer. Some intervention trials have demonstrated that supplementation with vitamin D or its metabolites is able: (i) to reduce blood pressure in hypertensive patients; (ii) to improve blood glucose levels in diabetics; (iii) to improve symptoms of rheumatoid arthritis and multiple sclerosis. The oral dose necessary to achieve adequate serum 25(OH)D levels is probably much higher than the current recommendations of 5-15 microg/d.
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PMID:Vitamin D in preventive medicine: are we ignoring the evidence? 1272 May 76

It is remarkable that phytoplankton and zooplankton have been producing vitamin D for more than 500 million years. The role of vitamin D in lower non-vertebrate life forms is not well understood. However, it is critically important that most vertebrates obtain an adequate source of vitamin D, either from exposure to sunlight or from their diet, in order to develop and maintain a healthy mineralized skeleton. Vitamin D deficiency is an unrecognized epidemic in most adults who are not exposed to adequate sunlight. This can precipitate and exacerbate osteoporosis and cause the painful bone disease osteomalacia. Once vitamin D is absorbed from the diet or made in the skin by the action of sunlight, it is metabolized in the liver to 25-hydroxyvitamin D [25(OH)D] and then in the kidney to 1,25-dihydroxyvitamin D [1,25(OH)2D]. 1,25(OH)2D interacts with its nuclear receptor (VDR) in the intestine and bone in order to maintain calcium homeostasis. The VDR is also present in a wide variety of other tissues. 1,25(OH)2D interacts with these receptors to have a multitude of important physiological effects. In addition, it is now recognized that many tissues, including colon, breast and prostate, have the enzymatic machinery to produce 1,25(OH)2D. The insights into the new biological functions of 1,25(OH)2D in regulating cell growth, modulating the immune system and modulating the renin-angiotensin system provides an explanation for why diminished sun exposure at higher latitudes is associated with increased risk of dying of many common cancers, developing type 1 diabetes and multiple sclerosis, and having a higher incidence of hypertension. Another calciotropic hormone that is also produced in the skin, parathyroid hormone-related peptide, is also a potent inhibitor of squamous cell proliferation. The use of agonists and antagonists for PTHrP has important clinical applications for the prevention and treatment of skin diseases and disorders of hair growth.
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PMID:Evolution and function of vitamin D. 1289 11

Primary hyperparathyroidism (pHPT) has changed its clinical features in the last decade becoming a mild biochemical disease, in which the classical fibrous cystic osteitis is a rare complication. The more frequent bone involvement in primary hyperparathyroidism is observed at the distal 1/3 of the radius, where the cortical bone is primarily represented. However, lumbar and femoral osteopenia or osteoporosis prevalently affect hyperparathyroid post-menopausal women. We report two, otherwise healthy, young male patients, who presented a painful jaw swelling. In both patients standard radiographic imaging revealed a low-density well-defined lesion, which caused jaw bone destruction. High levels of serum calcium (14.1-16.6 mg/dl, n.v. 8.1-10.4) and PTH (1172-1928 pg/ml, n.v. 10-65) indicated the presence of pHPT associated with hypertension, asymptomatic renal involvement and osteoporosis with normal serum 25-hydroxyvitamin D levels in both patients. A single huge parathyroid adenoma was successfully removed and within 2 months jaw lesions were almost completely re-mineralized without any other therapeutic intervention in both patients. In conclusion, although brown jaw tumors are a rare complication of the hyperparathyroidism, they should be considered and identified in young patients with severe pHPT. Moreover, such a complication seems to be independent from vitamin D deficiency, suggesting the involvement of other pathogenetic factors.
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PMID:Brown jaw tumors: today's unusual presentation of primary hyperparathyroidism. 1459 21

Patients with end-stage renal disease have markedly increased risk for death from cardiovascular disease. Renal failure is associated with multiple metabolic and endocrinologic abnormalities, and these alterations are involved in advanced atherosclerosis and high cardiovascular risk. Increased insulin resistance index by homeostasis model assessment (HOMA-IR), a simple index of insulin resistance, was an independent predictor of cardiovascular mortality in nondiabetic patients on maintenance hemodialysis. Renal failure impairs lipoprotein metabolism leading to the atherogenic lipoprotein profile characterized by increased triglyceride-rich remnant lipoproteins such as intermediate-density lipoprotein, an independent factor of increased aortic stiffness. Non-high-density lipoprotein cholesterol, the sum of cholesterol of intermediate-density lipoprotein and other apoB-containing lipoproteins, is an independent factor associated with increased arterial thickness and a predictor of cardiovascular death in hemodialysis patients. The risk for cardiovascular death in hemodialysis patients is associated closely with hypertension and malnutrition, but not with obesity. The constellation of insulin resistance, dyslipidemia, hypertension, and malnutrition in renal failure suggests the presence of another type of metabolic syndrome promoting cardiovascular disease. In addition, vitamin D deficiency and abnormalities in calcium, phosphate, and parathyroid hormone levels increase the death risk from cardiovascular disease in renal failure. It is expected that treatment of these metabolic and endocrinologic alterations would improve the survival of patients with renal failure.
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PMID:Roles of metabolic and endocrinological alterations in atherosclerosis and cardiovascular disease in renal failure: another form of metabolic syndrome. 1549 Apr 3


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