Vitamin D receptor expression in human muscle tissue decreases with age

Vitamin D, neurocognitive functioning and immunocompetence

PURPOSE OF REVIEW

Vitamin D deficiency is recognized as one of the most common medical conditions in children and adults. The major causes are inadequate sun exposure and inadequate intakes of dietary and supplemental vitamin D. Vitamin D deficiency and insufficiency defined as a 25-hydroxyvitamin D level less than 20 and 21-29 ng/ml, respectively, have been linked to increased risk for a variety of medical conditions including cancer, heart disease, type II diabetes, infectious diseases, autoimmune diseases, metabolic bone diseases and neurological disorders.

RECENT FINDINGS

The skeletal muscle and brain have a vitamin D receptor and the central nervous system has a capacity to activate vitamin D. Low vitamin D status has been linked to poor performance in neurocognitive testing in elderly. Vitamin D deficiency has been associated with muscle weakness, depression, schizophrenia, Alzheimer's disease, multiple sclerosis and a lower motor neuron-induced muscle atrophy.

SUMMARY

Correcting vitamin D deficiency and preventing vitamin D deficiency in children and adults should be a high priority for healthcare professionals to reduce risk for a wide variety of neurological disorders. Children and adults should take at least 400 international unit IU and 2000 IU vitamin D/day, respectively, to prevent vitamin D deficiency and insufficiency.

Vitamin d status is not associated with outcomes of experimentally-induced muscle weakness and pain in young, healthy volunteers

Vitamin D receptors have been identified in skeletal muscle; and symptoms of vitamin D deficiency include muscle weakness and pain. Moreover, increased serum 25-hydroxyvitamin D (25(OH)D) concentrations have been associated with improved muscle function. To further clarify the importance of vitamin D to muscle, we examined the association between vitamin D status and exercise-induced muscle pain and weakness in healthy people. Muscle damage to the elbow flexors was induced with eccentric exercise (EE) in 48 individuals (22.5 ± 3.2 yrs). Muscle pain ratings following unloaded movement and peak isometric force (IF) were collected before EE and for 4 days post-EE. Linear regression was used to determine if serum 25(OH)D was a predictor of any outcome. In males, R²-values from 0.48 to 1.00. R² for IF ranged from 0 to 0.02 and P-values from 0.48 to 1.00. In females, R² for pain ratings ranged from 0.01 to 0.11 and P-values from 0.14 to 0.59. R² for IF ranged from 0 to 0.04 and P-values from 0.41 to 0.90. In conclusion, vitamin D status did not predict muscle pain or strength after EE-induced muscle damage in young healthy men and women.

Nutritional determinants of mobility

PURPOSE OF REVIEW

In many countries, persons over 65 are one of the fastest growing segments of the population. Mobility disability is one of the major risk factors for morbidity and mortality in this age group. There is increasing evidence that improved nutrition can reduce the risk of developing disability in older age. This review summarizes the recent literature showing the associations between different nutrients and mobility-related outcomes in older adults.

RECENT FINDINGS

Recent studies suggested an association between low intake and low serum concentrations of micronutrients, such as antioxidants and vitamins, with measures of physical performance, muscle strength, and disability in older adults.

SUMMARY

The role of low micronutrients as cross-sectional and longitudinal correlates of mobility disability is consistent with a growing number of studies showing that a diet rich in fruits and vegetables, such as the Mediterranean diet, has a beneficial role in healthy aging.

A prospective study of the associations between 25-hydroxy-vitamin D, sarcopenia progression and physical activity in older adults

OBJECTIVE

Low 25-hydroxyvitamin D (25OHD) levels may be associated with both sarcopenia (the age-related decline in muscle mass and function) and low physical activity (PA). Our objective was to describe prospective associations between 25OHD, muscle parameters, and PA in community-dwelling older adults.

DESIGN

Prospective, population-based study with a mean follow-up of 2·6 ± 0·4 years.

PATIENTS

Six hundred and eighty-six community-dwelling older adults (49% women; mean ± SD 62 ± 7 years old).

MEASUREMENTS

Appendicular lean mass percentage (%ALM) and body fat assessed by Dual-energy X-ray Absorptiometry, leg strength by dynamometer, leg muscle quality (LMQ), PA assessed by pedometer, self-reported sun exposure by questionnaire, and serum 25OHD measured by radioimmunoassay.

RESULTS

Participants with 25OHD ≤50 nM had lower mean %ALM, leg strength, LMQ and PA (all P < 0·05). As a continuous function, baseline 25OHD was a positive independent predictor of change in leg strength (β = 5·74 kg, 95% CI 0·65, 10·82) and LMQ (β = 0·49 kg/kg, 95% CI 0·17, 0·82). Also, change in 25OHD was positively predicted by baseline %ALM (β = 2·03 pM/p.a., 95% CI 0·44, 3·62) leg strength (β = 0·30 pM/p.a., 95% CI 0·06, 0·53), LMQ (β = 4·48 pM/p.a., 95% CI 0·36, 8·61) and PA (β = 2·63 pM/p.a., 95% CI 0·35, 4·92) after adjustment for sun exposure and body fat.

CONCLUSIONS

25OHD may be important for the maintenance of muscle function, and higher skeletal muscle mass and function as well as general PA levels may also be beneficial for 25OHD status, in community-dwelling older adults.

Correlation between Serum 25-Hydroxyvitamin D Levels and Quadriceps Muscle Strength in Elderly Cretans

Vitamin D deficiency is associated with osteomalacic myopathy, and muscle weakness related to vitamin D deficiency has been implicated as a possible risk factor for falls in the elderly. This study investigated the possible correlation between serum 25-hydroxyvitamin D (25[OH]D) concentration and quadriceps muscle strength in ambulatory community dwelling Cretan men ( n = 13) and women ( n = 35) aged ≥ 65 years. Quadriceps muscle strength was measured isometrically using Cybex 6000 apparatus. The mean serum 25(OH)D concentration was significantly higher in men than in women (76.00 versus 49.11 nmol/l, respectively). Serum 25(OH)D values were < 50 nmol/l in 15% of men and in 60% of women. Serum 25(OH)D concentration correlated positively with quadriceps muscle strength. In conclusion, vitamin D deficiency was common in the study participants despite the high levels of sunlight in Crete. Serum 25(OH)D levels were positively correlated with muscle strength.

Extraskeletal effects of vitamin D in older adults: cardiovascular disease, mortality, mood, and cognition

BACKGROUND

Vitamin D insufficiency is prevalent among older adults and may be associated with higher risk for cardiovascular (CV) disease, mortality, depression, and cognitive deficits.

OBJECTIVE

The aim of this article was to review published observational and experimental studies that explored the association between vitamin D insufficiency and CV disease, mortality, mood, and cognition with an emphasis on older adults.

METHODS

PubMed and Web of Science databases were searched for English-language articles from January 1966 through June 2009 relating to vitamin D, using the following MeSH terms: aged, vitamin D deficiency, physiopathology, drug therapy, cardiovascular diseases, blood pressure, mortality, delirium, dementia, cognitive disorders, depression, depressive disorder, seasonal affective disorder, mental disorders, and vitamin D/therapeutic use. Publications had to include patients > or =65 years of age who had > or =1 recorded measurement of 25-hydroxyvitamin D (25[OH]D) or were receiving vitamin D supplementation. All case-control, cohort, and randomized studies were reviewed.

RESULTS

Forty-two case-control, cohort, and randomized trials were identified and included in the review. Based on these publications, the prevalence of vitamin D insufficiency (25[OH]D concentration <30 ng/mL) in communitydwelling older adults (> or =65 years of age) ranged from 40% to 100%. Epidemiologic data and several small randomized trials found a potential association between vitamin D deficiency (25[OH]D concentration <10 ng/mL) and CV disease, including hypertension and ischemic heart disease. Although subgroup analyses of data from the Women's Health Initiative Randomized Trial (the largest randomized, placebo-controlled trial of vitamin D plus calcium therapy) did not find reductions in blood pressure, myocardial infarction, or CV disease-related deaths, intervention contamination limited the findings. Observational studies and a meta-analysis of randomized controlled trials found a mortality benefit associated with higher serum 25(OH)D concentrations or vitamin D(2) or D(3) supplementation (mean dose, 528 IU/d). Observational and small randomized trials found a potential benefit of sunlight or vitamin D on symptoms of depression and cognition, but the findings were limited by methodologic problems.

CONCLUSIONS

Vitamin D insufficiency appears to be highly prevalent among older adults. Evidence from epidemiologic studies and small clinical trials suggests an association between 25(OH)D concentrations and systolic blood pressure, risk for CV disease-related deaths, symptoms of depression, cognitive deficits, and mortality. The Women's Health Initiative Randomized Trial did not find a benefit of vitamin D supplementation on blood pressure, myocardial infarction, or mortality in postmenopausal women.

Independent and combined effects of exercise and vitamin D on muscle morphology, function and falls in the elderly

Regular exercise, particularly progressive resistance training (PRT), is recognized as one of the most effective strategies to prevent age-related muscle loss (sarcopenia), but its effects on muscle function are mixed. However, emerging data indicates that high velocity PRT (fast concentric muscle contractions) is more effective for improving functional outcomes than traditional PRT. In terms of falls prevention, high-challenging balance training programs appear to be most effective. There is also compelling evidence that supplemental vitamin D is an effective therapeutic option for falls prevention. The findings from a recent meta-analysis revealed that supplemental vitamin D at a dose of at least 700–1,000 IU/d or an achieved serum 25(OH)D level of at least 60 nmol/L was associated with reduced falls risk among older individuals. Based on these findings, it is possible that the combination of exercise and vitamin D could have a synergistic effect on muscle morphology and function, particularly since both interventions have been shown to have beneficial effects on type II “fast twitch” muscle fibers and systemic inflammation, which have both been linked to losses in muscle mass and function. Unfortunately however, the findings from the limited number of factorial 2 × 2 design RCTs indicate that additional vitamin D does not enhance the effects of exercise on measures of muscle morphology, function or falls risk. However, none of these trials were adequately powered to detect a “synergistic” effect between the two treatment strategies, but it is likely that if an exercise-by-vitamin D interaction does exist, it may be limited to situations when vitamin D deficiency/insufficiency is corrected. Further targeted research in “high risk” groups is still needed to address this question, and evaluate whether there is a threshold level of serum 25(OH)D to maximize the effects of exercise on muscle and falls risk.

Vitamin D deficiency: appropriate replenishment therapies and the effects of vitamin D toxicity

An 84-year-old patient diagnosed with a vitamin D deficiency was given a prescription for ergocalciferol (vitamin D2) 50,000 units weekly. The prescription was incorrectly filled for ergocalciferol 50,000 units daily. Incorrect therapy continued for two months. The patient's vitamin D level increased from < 7.0 ng/mL to 100 ng/mL over a six-month span. The patient complained of decreased appetite and significant weight loss and presented with an elevated International Normalized Ratio at a pharmacist-run anticoagulation clinic. In conjunction with the physician, the pharmacist discontinued vitamin D therapy and monitored levels.Vitamin D plays an integral role in the body's ability to absorb calcium and regulate calcium homeostasis. Further benefits have been reported regarding the role of vitamin D in muscle strength, cardiovascular health, and in preventing osteoporosis and falls. Vitamin D deficiency is widespread in the older adult population as a result of low dietary intake, decreased sun exposure, decreased intrinsic vitamin D production, and decreased vitamin D receptor activity. Replenishment using high-dose ergocalciferol is one common replenishment therapy. Patients also are able to supplement with nonprescription vitamin D products of varying strengths. While many older patients can be expected to have vitamin D deficiencies, pharmacists should be aware of appropriate replenishment therapies and correct dosing of different vitamin D products. Pharmacists also should be familiar with possible toxic effects of vitamin D, particularly as public awareness of benefits continues to increase.

Vitamin D and fracture prevention

This article discusses the amount of vitamin D supplementation needed and the desirable 25-hydroxyvitamin D level to be achieved for optimal fracture prevention.

Retinoic acid receptor gamma 2 interactions with vitamin D response elements

The vitamin D receptor (VDR) typically binds DNA in a heterodimer complex with the retinoid X receptor (RXR) to direct repeat sequences separated by three base pairs, or vitamin D response elements (VDREs). A modified yeast one-hybrid screen was utilized to search for partner proteins capable of associating with the VDR on a repressor VDRE. Screening of a HeLa cell cDNA library revealed that retinoic acid receptor gamma 2 (RARgamma2) could specifically interact with VDREs, either in the presence or absence of the VDR. Importantly, the A-domain of RARgamma2 appeared to be crucial for this interaction as evidenced by the inability of RARgamma1 to affect reporter gene activity. Transfection data in COS-7 cells revealed the combination of both receptor ligands strongly attenuated transcriptional activation from an enhancer VDRE when RARgamma2 was co-transfected into these cells with the VDR. Furthermore, a VDR/RARgamma2 complex was detected in the mobility shift assay from nuclear extracts of transfected cells. Thus, the data highlight the novel ability of RARgamma2 to interact with VDREs and impact vitamin D activity, which would allow for additional fine-tuning of a transcriptional response depending on ligand availability and expression profile of these nuclear receptors in a given cell type.

Estimated equivalency of vitamin D production from natural sun exposure versus oral vitamin D supplementation across seasons at two US latitudes

BACKGROUND

The relationship between oral vitamin D supplementation and cutaneous photosynthesis is not well understood.

OBJECTIVE

We sought to provide estimates of the equivalency of vitamin D production from natural sun exposure versus oral supplementation.

METHODS

Using the FastRT simulation tool, we determined sun exposure times needed to achieve serum vitamin D(3) concentrations equivalent to 400 or 1000 IU vitamin D for individuals of various Fitzpatrick skin types living in Miami, FL, and Boston, MA, during the months of January, April, July, and October.

RESULTS

Peak ultraviolet B irradiation for vitamin D synthesis occurs around 12 pm Eastern Standard Time (EST). In Boston, MA, from April to October at 12 pm EST an individual with type III skin, with 25.5% of the body surface area exposed, would need to spend 3 to 8 minutes in the sun to synthesize 400 IU of vitamin D. It is difficult to synthesize vitamin D during the winter in Boston, MA. For all study months in Miami, FL, an individual with type III skin would need to spend 3 to 6 minutes at 12 pm EST to synthesize 400 IU. Vitamin D synthesis occurs faster in individuals with lighter Fitzpatrick skin types. The duration to attain 1000 IU of vitamin D is longer in all scenarios.

LIMITATIONS

Results of the computer model are only approximations. In addition, calculations were made based on the assumption that (1/4) of 1 minimal erythema dose directed at (1/4) body surface area is equal to 1000 IU of oral vitamin D.

CONCLUSIONS

Although it may be tempting to recommend intentional sun exposure based on our findings, it is difficult, if not impossible to titrate one's exposure. There are well-known detrimental side effects of ultraviolet irradiation. Therefore, oral supplementation remains the safest way for increasing vitamin D status.

Once-weekly dose of 8400 IU vitamin D(3) compared with placebo: effects on neuromuscular function and tolerability in older adults with vitamin D insufficiency

BACKGROUND

Vitamin D insufficiency, which is prevalent in older individuals, is associated with bone and muscle weakness and falls.

OBJECTIVE

We examined the effects of a weekly dose of 8400 IU vitamin D(3) on postural stability, muscle strength, and safety.

DESIGN

In this double-blind trial, subjects aged > or =70 y with serum 25-hydroxyvitamin D [25(OH)D] concentrations < or =20 but > or =6 ng/mL were randomly assigned to receive a weekly dose of 8400 IU vitamin D(3) (n = 114) or a placebo (n = 112). Mediolateral body sway with eyes open (assessed with the AccuSway(PLUS) platform; Advanced Medical Technology Inc, Watertown, MA) was the primary endpoint. Secondary endpoints included the short physical performance battery (SPPB) and serum 25(OH)D concentrations. An analysis of covariance model was used for treatment comparisons. Safety and tolerability were monitored.

RESULTS

Serum 25(OH)D concentrations rose significantly (from 13.9 to 26.2 ng/mL, P < 0.001) in patients treated with 8400 IU vitamin D(3) but not in patients treated with the placebo. After 16 wk, neither mediolateral sway nor SPPB differed significantly between treatment groups. However, in the post hoc analysis of patients subgrouped by baseline sway (> or = 0.46 compared with <0.46 cm), treatment with 8400 IU vitamin D(3) significantly reduced sway compared with treatment with placebo (P = 0.047) in patients with elevated baseline sway but not in patients with normal baseline sway. Adverse experiences and incidences of hypercalcemia, hypercalciuria, and elevated creatinine were similar with both treatments. In patients treated with 8400 IU vitamin D(3), but not in placebo-treated patients, parathyroid hormone decreased significantly.

CONCLUSIONS

Weekly treatment with 8400 IU vitamin D(3) raised 25(OH)D concentrations in elderly, vitamin D-insufficient individuals. Treatment with 8400 IU vitamin D(3) did not reduce mediolateral sway significantly compared with treatment with placebo in this population, although in post hoc analysis, treatment with 8400 IU vitamin D(3) reduced sway in the subgroup of patients who had elevated sway at baseline. Weekly treatment with 8400 IU vitamin D(3) was well tolerated. This trial was registered at clinicaltrials.gov as NCT00242476.

Effect of age, gender and calciotropic hormones on the relationship between vitamin D receptor gene polymorphisms and bone mineral density

BACKGROUND/OBJECTIVES

Hypovitaminosis D is a major public health problem worldwide and unexpectedly more so in sunny countries. Vitamin D receptor (VDR) gene is associated with inter-individual variance in bone mineral density (BMD). Studies assessing the effect of VDR gene polymorphisms on BMD yielded conflicting results. The aim of this study was to assess the relationship between VDR polymorphisms and BMD in the Lebanese, across age groups and genders and to assess the effect of PTH and lean mass and vitamin D levels on such relationship.

SUBJECTS/METHODS

In total, 203 subjects aged 65-85 years and 336 children aged 10-17 years. Polymorphisms in the VDR gene were assessed with the restriction enzymes BsmI, TaqI and ApaI. Bone mineral content, BMD and lean mass were measured using Dual-Energy X-ray Absorptiometry (DXA). The dominant hand strength was measured in children.

RESULTS

Heterozygote genotype was the most frequent in both age groups. There was no difference in the frequency distribution of genotypes between the young and the elderly. No relationship between VDR genotypes and lean mass was found in either age group. Heterozygote boys had the lowest parathormone (PTH) and heterozygote elderly women had the highest BMD at the spine and forearm.

CONCLUSIONS

In the Lebanese, the relationship between VDR polymorphisms and BMD differs by age. Survival does not seem to differ by VDR genotype. However, further studies are needed to assess the effect of VDR gene polymorphisms on mortality per se and time to mortality, not evaluated in this study.

Serum 25-hydroxyvitamin D is related to indicators of overall physical fitness in healthy postmenopausal women

OBJECTIVE

Inadequate vitamin D status is related to increased adiposity, risk of falls, and muscle weakness, particularly in older people. We hypothesized that serum 25-hydroxyvitamin D [25(OH)D] is related to physical fitness indices (androidal fat, whole body lean mass, balance, strength) in healthy postmenopausal women.

METHODS

Covariates for fitness indices included age or years since menopause, weight, 25(OH)D, energy expenditure, and calcium intake. Overall and regional (androidal fat mass = waist + hip fat) body composition was assessed (N = 242) via dual-energy x-ray absorptiometry.

RESULTS

Regression analyses revealed that 71% of variability (P <or= 0.0001) in androidal fat mass was accounted for by weight (53.0%, P <or= 0.0001), white blood cell (WBC) count (2.0%, P <or= 0.0001), supplemental calcium (1.7%, P = 0.0004), years since menopause (1.1%, P = 0.0034), 25(OH)D (1.0%, P = 0.0051), and vegetable servings (0.6%, P = 0.027); 64% of variability (P <or= 0.0001) in lean mass was accounted for by weight (63.1.%, P <or= 0.0001), WBC count (1.4%, P = 0.0038), and 25(OH)D (1.0%, P = 0.013); 12% of variability (P <or= 0.0001) in balance (right + left leg) was accounted for by age (3.8%, P = 0.0019), 25(OH)D (2.0%, P = 0.025), and WBC count (1.8%, P = 0.032); 14% of variability (P <or= 0.0001) in handgrip strength (right + left) was accounted for by weight (9.3%, P <or= 0.0001), 25(OH)D (2.4%, P = 0.013), WBC count (2.1%, P = 0.019), and age (1.6%, P = 0.044); and 22% of variability (P <or= 0.0001) in torso strength was accounted for by site (15.0%, P <or= 0.0001) and weight (4.6%, P = 0.0003).

CONCLUSIONS

Serum 25(OH)D was the common contributor to physical fitness indices (androidal fat mass, lean mass, balance, handgrip strength) in healthy postmenopausal women.

Role of vitamin d in insulin secretion and insulin sensitivity for glucose homeostasis

Vitamin D functions are not limited to skeletal health benefits and may extend to preservation of insulin secretion and insulin sensitivity. This review summarizes the literature related to potential vitamin D influences on glucose homeostasis and insulin sensitivity. Cross-sectional data provide some evidence that circulating 25-hydroxyvitamin D (25(OH)D) is inversely associated with insulin resistance, although direct measurements of insulin sensitivity are required for confirmation. Reported associations with insulin secretion, however, are contradictory. Available prospective studies support a protective influence of high 25(OH)D concentrations on type 2 diabetes mellitus risk. There is a general lack of consistency in vitamin D intervention outcomes on insulin secretion and sensitivity, likely due to differences in subject populations, length of interventions, and forms of vitamin D supplementation. Vitamin D receptor gene polymorphisms and vitamin D interactions with the insulin like growth factor system may further influence glucose homeostasis. The ambiguity of optimal vitamin D dosing regimens and optimal therapeutic concentrations of serum 25(OH)D limit available intervention studies. Future studies, including cross-sectional and prospective, should be performed in populations at high risk for both vitamin D deficiency and type 2 diabetes mellitus. Well-designed, placebo-controlled, randomized intervention studies are required to establish a true protective influence of vitamin D on glucose homeostasis.

Gait variability detects women in early postmenopause with low bone mineral density

BACKGROUND

Women in early postmenopause and with low bone mineral density (BMD) may exhibit early markers for physical frailty as a result of sarcopenia and osteopenia.

OBJECTIVE

The purpose of this study was to determine whether women in early postmenopause and with low BMD exhibit decreased physical performance and differences in gait variability and fall and fracture rates.

DESIGN

This study was an observational cohort design with participants assigned to groups on the basis of BMD status.

METHODS

Fifty-four women, 31 with low BMD and 23 with normal BMD, participated. This study was conducted in a university research facility. Physical performance was measured by assessment of dynamic balance (timed backward tandem walk test), strength (handheld dynamometry of isometric quadriceps muscle force production), and free gait speed. Gait variability was assessed on the basis of the coefficient of variation for temporal-spatial gait characteristics. Falls and fractures were assessed for the year after initial testing.

RESULTS

Significant between-group differences were found for step time and stance time variability.

LIMITATIONS

The limitations of this study included group assignment on the basis of the results of the most recent bone density scan within the preceding 2 years.

CONCLUSIONS

Women in early postmenopause and with low BMD exhibited increased gait variability in step time and stance time but did not exhibit differences in balance, strength, or gait speed. Gait variability may be more sensitive for detecting differences in women in early postmenopause and with or without low BMD than more typical measures of physical performance.

Effects of resistance exercise and fortified milk on skeletal muscle mass, muscle size, and functional performance in middle-aged and older men: an 18-mo randomized controlled trial

Limited data have suggested that the consumption of fluid milk after resistance training (RT) may promote skeletal muscle hypertrophy. The aim of this study was to assess whether a milk-based nutritional supplement could enhance the effects of RT on muscle mass, size, strength, and function in middle-aged and older men. This was an 18-mo factorial design (randomized control trial) in which 180 healthy men aged 50–79 yr were allocated to the following groups: 1) exercise + fortified milk, 2) exercise, 3) fortified milk, or 4) control. Exercise consisted of progressive RT with weight-bearing impact exercise. Men assigned to the fortified milk consumed 400 ml/day of low-fat milk, providing an additional 836 kJ, 1000 mg calcium, 800 IU vitamin D3, and 13.2 g protein per day. Total body lean mass (LM) and fat mass (FM) (dual-energy X-ray absorptiometry), midfemur muscle cross-sectional area (CSA) (quantitative computed tomography), muscle strength, and physical function were assessed. After 18 mo, there was no significant exercise by fortified milk interaction for total body LM, muscle CSA, or any functional measure. However, main effect analyses revealed that exercise significantly improved muscle strength (∼20–52%, P < 0.001), LM (0.6 kg, P < 0.05), FM (−1.1 kg, P < 0.001), muscle CSA (1.8%, P < 0.001), and gait speed (11%, P < 0.05) relative to no exercise. There were no effects of the fortified milk on muscle size, strength, or function. In conclusion, the daily consumption of low-fat fortified milk does not enhance the effects of RT on skeletal muscle size, strength, or function in healthy middle-aged and older men with adequate energy and nutrient intakes.

Identification of a highly specific and versatile vitamin D receptor antibody

The active form of vitamin D, 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) is critical for regulation of serum calcium and phosphorus levels and for proper maintenance of bone mineralization and neuromuscular function. Biological effects of 1,25(OH)2D3 are mediated through a nuclear steroid hormone receptor, known as the vitamin D receptor (VDR). The discovery of VDR in a number of different cell and tissue types, suggests that the physiological role of vitamin D may extend beyond the regulation of calcium homeostasis and bone function. Unfortunately, identification of tissues expressing VDR has been controversial due to low abundance of the receptor and quality of the antibodies used. Therefore, we elected to characterize a panel of commercially available VDR antibodies in order to identify antibodies with high specificity and sensitivity. To address these objectives, we have used multiple immunoassays to determine VDR expression in tissues from several organs from multiple species employing tissues from VDR knockout mice as critical negative controls. Many of the antibodies tested showed nonspecific binding that can account for divergent reports. However, one antibody, identified as D-6, is highly specific and extremely sensitive. The specificity, sensitivity, and versatility of this antibody make it the preferred antibody for identifying VDR expression in target tissues using immunological methods.

Vitamin D and human skeletal muscle

Vitamin D deficiency is an increasingly described phenomenon worldwide, with well-known impacts on calcium metabolism and bone health. Vitamin D has also been associated with chronic health problems such as bowel and colonic cancer, arthritis, diabetes and cardiovascular disease. In recent decades, there has been increased awareness of the impact of vitamin D on muscle morphology and function, but this is not well recognized in the Sports Medicine literature. In the early 20th century, athletes and coaches felt that ultraviolet rays had a positive impact on athletic performance, and increasingly, evidence is accumulating to support this view. Both cross-sectional and longitudinal studies allude to a functional role for vitamin D in muscle and more recently the discovery of the vitamin D receptor in muscle tissue provides a mechanistic understanding of the function of vitamin D within muscle. The identification of broad genomic and non-genomic roles for vitamin D within skeletal muscle has highlighted the potential impact vitamin D deficiency may have on both under-performance and the risk of injury in athletes. This review describes the current understanding of the role vitamin D plays within skeletal muscle tissue.

Carla Task Force on Sarcopenia: propositions for clinical trials

In the presence of an aging population, public health priorities need to evolve. As the populations gets older, the already existing pathologies have become commonplace with specific geriatric clinical syndromes like frailty, mobility disability, or cognitive impairment, among others. Sarcopenia is a good example for which geriatricians, neurologists, physiologists, nutritionists and epidemiologists need to find a consensual definition and diagnostic tool as well as guidelines for the management of clinical trials and possible treatments. The Carla Sarcopenia Task Force, which met in the south of France (Toulouse) for an expert consensus meeting called "Les Entretiens du Carla", have addressed a series of existing issues to place Sarcopenia into a nosological context: a definition which should be a composite of a change in muscle mass and a change in strength/function depending on either a progressive and chronic wasting process or an acute onset of loss of muscle mass; a recommendation for DXA and the Short Physical Performance Battery as a clinical pragmatic approach of Sarcopenia; a differentiated approach for clinical studies according to prevention or treatment objectives and depending on the sub-groups and target populations; and finally, a summary of therapeutic strategies currently recommended. The aim of "Les Entretiens du Carla", based on an expert meeting panel, was to address a series of unsolved issues in the field of Sarcopenia by combining the expert opinion with a revision of the existing literature on the topic. Through this report, the reader will appreciate the determination to find conclusions on the various issues and further studies to be developed to determine the best multidisciplinary approach needed.

Validated treatments and therapeutic perspectives regarding nutritherapy

Nutritherapy seeks to prevent or correct disease by the use of nutritional supplements including vitamins, trace elements, or macronutrients. This chapter of the "Les Entretiens du Carla" reviews the potential of nutritherapy for the prevention or improvement of sarcopenia, which is the progressive reduction in muscle mass and muscle strength prevalent in late-life. It is critical that we review nutrients and their potential to maintain muscle mass and strength which ultimately will help minimize falls and fractures among the older population. Evidence from randomized-controlled trials will be reviewed for muscle mass as well as important sarcopenia-related endpoints including lower extremity strength and function, as well as falls and fall-related fractures. This chapter will focus on vitamin D as a compelling strategy with evidence for strength gain, fall and fracture prevention from double-blind randomized controlled trials. The other strategy discussed is increased protein intake although longer-term trials and evidence for clinically important endpoints are limited. Today, there is no consistent data on other micronutrients or macronutrients with an established potential to combat sarcopenia.

Fall prevention with supplemental and active forms of vitamin D: a meta-analysis of randomised controlled trials

OBJECTIVE

To test the efficacy of supplemental vitamin D and active forms of vitamin D with or without calcium in preventing falls among older individuals.

DATA SOURCES

We searched Medline, the Cochrane central register of controlled trials, BIOSIS, and Embase up to August 2008 for relevant articles. Further studies were identified by consulting clinical experts, bibliographies, and abstracts. We contacted authors for additional data when necessary. Review methods Only double blind randomised controlled trials of older individuals (mean age 65 years or older) receiving a defined oral dose of supplemental vitamin D (vitamin D(3) (cholecalciferol) or vitamin D(2) (ergocalciferol)) or an active form of vitamin D (1alpha-hydroxyvitamin D(3) (1alpha-hydroxycalciferol) or 1,25-dihydroxyvitamin D(3) (1,25-dihydroxycholecalciferol)) and with sufficiently specified fall assessment were considered for inclusion.

RESULTS

Eight randomised controlled trials (n=2426) of supplemental vitamin D met our inclusion criteria. Heterogeneity among trials was observed for dose of vitamin D (700-1000 IU/day v 200-600 IU/day; P=0.02) and achieved 25-hydroxyvitamin D(3) concentration (25(OH)D concentration: <60 nmol/l v >or=60 nmol/l; P=0.005). High dose supplemental vitamin D reduced fall risk by 19% (pooled relative risk (RR) 0.81, 95% CI 0.71 to 0.92; n=1921 from seven trials), whereas achieved serum 25(OH)D concentrations of 60 nmol/l or more resulted in a 23% fall reduction (pooled RR 0.77, 95% CI 0.65 to 0.90). Falls were not notably reduced by low dose supplemental vitamin D (pooled RR 1.10, 95% CI 0.89 to 1.35; n=505 from two trials) or by achieved serum 25-hydroxyvitamin D concentrations of less than 60 nmol/l (pooled RR 1.35, 95% CI 0.98 to 1.84). Two randomised controlled trials (n=624) of active forms of vitamin D met our inclusion criteria. Active forms of vitamin D reduced fall risk by 22% (pooled RR 0.78, 95% CI 0.64 to 0.94).

CONCLUSIONS

Supplemental vitamin D in a dose of 700-1000 IU a day reduced the risk of falling among older individuals by 19% and to a similar degree as active forms of vitamin D. Doses of supplemental vitamin D of less than 700 IU or serum 25-hydroxyvitamin D concentrations of less than 60 nmol/l may not reduce the risk of falling among older individuals.

Ageing and vitamin D deficiency: effects on calcium homeostasis and considerations for vitamin D supplementation

Vitamin D is a fat-soluble, seco-steroid hormone. In man, the vitamin D receptor is expressed in almost all tissues, enabling effects in multiple systems of the human body. These effects can be endocrine, paracrine and autocrine. The present review summarises the effects of ageing on the vitamin D endocrine system and on Ca homeostasis. Furthermore, consequences for vitamin D supplementation are discussed.

The aging population--is there a role for endocrine interventions?

The expected increase in the aging population will have a significant impact on society and the health system in the coming years and decades. Enhancing healthspan, "healthy aging", and thus extending the time that the elderly are able to function independently is a significant task and is imperative. Age-dependent changes such as weight loss, sarcopenia and anorexia, which contribute to the development of frailty in the elderly are discussed. The role of the age-dependent decrease in growth hormone secretion in this process and the potential benefits and risks of hormonal interventions to delay, prevent or reverse frailty in the elderly are reviewed.

Potential of alfacalcidol for reducing increased risk of falls and fractures

There are no general accepted strategies for combined drug treatments in osteoporosis, while in other important chronic diseases combinations of different medications are used as a rule to improve therapeutic results and reduce the risk of adverse events. It is suggested that the success of combined treatments is related to the different modes of action of the respective single therapies. On the other hand it was shown that a strong antiresorptive bisphosphonate is able to blunt at least in part the effects of anabolic parathyroid hormone peptides Calcitriol, the active vitamin D-hormone and its prodrug alfacalcidol lead to pleiotropic effects on bone remodelling (antiresorptive, anabolic and enhancing mineralization) and in addition to effects on other important target tissues (e.g. gut, parathyroid glands, muscle). With active D-analogs significant improvements in the therapeutic outcome of osteoporosis can be achieved by the resulting improvements of bone quality, calcium absorption and risk reduction of falling. The same beneficial effects cannot be achieved with plain vitamin D due to feedback controlled, limited renal activation or insufficient conversion in the elderly with impairment of renal function. Accordingly alfacalcidol, approved as a treatment for different forms of osteoporosis, is besides adoption as a mono-therapy an interesting candidate for combined therapies. There are interesting preclinical trials and clinical pilote studies in the literature proving that a parallel therapy with selectively anti-osteoclastic bisphophonates and pleiotropically acting D-analogs is able to optimize therapeutic results in osteoporosis. In the AAC-Trial (Alfacalcidol-Alendronate-Combined) we studied 90 patients with established osteoporosis (57 women, 33 men) over two years after alternate allocation to three treatment arms (alfacalcidol plus calcium, alendronate plus plain vitamin D and Ca, and alendronate plus alfacalcidol and Ca). During the 2-year-study we observed the significantly highest lumbar spine and hip BMD increases in the combined treatment group (p < 0.001). The number of patients with new vertebral and non-vertebral fractures after 2 years was 9 with alfacalcidol alone, 10 with alfacalcidol and plain vitamin D and 2 in the group receiving alendronate plus alfacalidol (p < 0.02). Furthermore there was a lower rate of falls and an earlier reduction in back pain in the patients treated with the active combination. This trial confirms the demonstrated highly significant advantages of this combined treatment regimen used in the pilote studies. Especially in patients with severe osteoporosis this interesting combination of two substances with complete different mechanisms of action should be taken into consideration.

Seasonal variance of 25-(OH) vitamin D in the general population of Estonia, a Northern European country

BACKGROUND

Vitamin D has a wide variety of physiological functions in the human body. There is increasing evidence that low serum levels of this vitamin have an important role in the pathogenesis of different skeletal and extra-skeletal diseases. Vitamin D deficiency and insufficiency is common at northern latitudes. There are few population-based studies in the northern European region looking at the issue in a wider age group. We aimed to measure Vitamin D level in the general population of Estonia (latitude 59 degrees N), a North-European country where dairy products are not fortified with vitamin D.

METHODS

The study subjects were a population-based random selection of 367 individuals (200 women and 167 men, mean age 48.9 +/- 12.2 years, range 25-70 years) from the registers of general health care providers. 25-(OH) vitamin D (25(OH)D) level and parathyroid hormone (PTH) were measured in summer and in winter. Additionally age, sex, body mass index (BMI) and self-reported sunbathing habits were recorded.

RESULTS

The mean serum 25(OH)D concentration in winter was 43.7 +/- 15 nmol/L and in summer 59.3 +/- 18 nmol/L (p < 0.0001). In winter 73% of the subjects had 25(OH)D insufficiency (25(OH)D concentration below 50 nmol/L) and 8% had deficiency (25(OH)D below 25 nmol/L). The corresponding percentages in summer were 29% for insufficiency and less than 1% for deficiency. PTH reached a plateau at around 80 nmol/L. BMI and age were inversely associated with 25(OH)D, but lost significance when adjusted for sunbathing habits. A difference in the seasonal 25(OH)D amplitude between genders (p = 0.01) was revealed.

CONCLUSION

Vitamin D insufficiency is highly prevalent throughout the year in a population without vitamin D dairy fortification living at the latitude of 59 degrees N.

Higher serum vitamin D3 levels are associated with better cognitive test performance in patients with Alzheimer's disease

BACKGROUND/AIMS

Recent studies suggest that vitamin D metabolites may be important for preserving cognitive function via specific neuroprotective effects. No large studies have examined the association between vitamin D status and cognition.

METHODS

In this cross-sectional study, we analyzed the serum 25-hydroxyvitamin D(3) levels and Mini-Mental State Examination (MMSE) test scores of 225 older outpatients who were diagnosed as having probable Alzheimer's disease (AD). In addition to the 25-hydroxyvitamin D(3) levels, we analyzed the serum vitamin B(1), B(6) and B(12) levels.

RESULTS

An association was found between MMSE test scores and serum 25-hydroxyvitamin D(3) levels, with a beta-coefficient of 0.05 (p = 0.01). Vitamin-D-sufficient patients had significantly higher MMSE scores as compared to vitamin-D-insufficient ones. No association was found with the other serum vitamin levels.

CONCLUSIONS

These data support the idea that a relationship exists between vitamin D status and cognition in patients with probable AD. However, given the cross-sectional design of this study, no causality can be concluded. Further prospective studies are needed to specify the contribution of vitamin D status to the onset and course of cognitive decline and AD.

Osteoporosis: an evolutionary perspective

Increased life expectancy has led to an overall aging of the population and greater numbers of elderly people. Therefore, the number of people with osteoporosis has increased substantially, accompanied with an epidemic of hip fractures. Osteoporosis is an age-related systemic condition that naturally occurs, among mammals, only in humans. Osteoporosis is known to be highly heritable. However, assuming a genetic determinant for this post-reproductive disease to be transmitted from one generation to the next is counter-intuitive, based on the principles of human evolution, I will attempt to provide an explanation of the phenomenon from the point of view of evolution, selection, and changed environment in humans, which contributed to human longevity, while on other hand, contribute to diseases of civilization, including osteoporosis. There is a need to delve into evolution of human species in search for adaptive patterns to a specific environment that humans are operating in the last couple of millennia, to clarify whether "good" and "bad" genes exist, and how to find and correct them. The answer to the above questions will help us to identify causes of the current epidemic of osteoporosis and to pin-point a tailored treatment.

Vitamin D-deficiency and post-fracture changes in lower extremity function and falls in women with hip fractures

We determined the prevalence of vitamin D deficiency and lower extremity function in women with hip fractures. Women with extremely low vitamin D levels had reduced lower extremity muscle function and increased falls 1 year later. Ensuring vitamin D sufficiency after a hip fracture may improve function and reduce falls.

INTRODUCTION

Hip fractures are the most devastating of fractures, commonly leading to loss of independent ambulation and living. In this retrospective analysis we determined the prevalence of vitamin D deficiency in women with hip fractures and the association between 25-hydroxyvitamin D [25(OH)D] levels and functional impairment one year later.

METHODS

One hundred ten community-dwelling women with hip fractures were recruited from Boston, MA (n = 30) and Baltimore, MD (n = 80) before 1998 and 25(OH)D levels were measured by radioimmunoassay. In a subset of women from Baltimore, a performance measure of the lower extremities using the lower extremity gain scale (LEGS) was measured at 2, 6, and 12 months. Falls, grip strength, chair rise time, walking speed, and balance were also determined.

RESULTS

Vitamin D insufficiency defined as a 25(OH)D 9 ng/mL, those with 25(OH)D

CONCLUSION

Vitamin D sufficiency may have important effects on lower extremity function following hip fractures, without excessive healthcare costs.

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Key Words

• falls
• fracture
• grip strength
• hip
• muscle function
• vitamin d

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MESH Headings

• Accidental Falls
• Aged
• Aged, 80 and over
• Female
• Hand Strength
• Hip Fractures/complications
• Hip Fractures/physiopathology
• Hip Fractures/rehabilitation
• Humans
• Lower Extremity/physiopathology
• Middle Aged
• Recovery of Function
• Retrospective Studies
• Vitamin D Deficiency/complications
• Vitamin D Deficiency/physiopathology

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Grants

• R01 AG18668 NIA NIH HHS
• R01 AG013519 NIA NIH HHS
• R01 AG028114 NIA NIH HHS
• R01 AG13519 NIA NIH HHS
• P60 AG12583 NIA NIH HHS
• R01 AG 12271 NIA NIH HHS
• R01 AG025015 NIA NIH HHS
• R01 AG018668 NIA NIH HHS
• R01 DA013519 NIDA NIH HHS
• P60 AG012583 NIA NIH HHS

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Affiliation(s)

M. S. LeBoff Skeletal Health and Osteoporosis Center and Bone Density Unit, Endocrine, Diabetes, and Hypertension Division, Brigham and Women’s Hospital, 221 Longwood Ave, Boston, MA 02115, USA, e-mail:
W. G. Hawkes Division of Gerontology, Department of Epidemiology and Preventive Medicine, School of Medicine, University of Maryland Baltimore, 660 W. Redwood Street, Suite 200, Baltimore, MD 21201, USA,
J. Glowacki Department of Orthopedic Surgery, Brigham and Women’s Hospital and Harvard Medical School, 221 Longwood Avenue, Boston, MA 02115, USA e-mail:
J. Yu-Yahiro Department of Orthopedics, The Union Memorial Hospital, 3333 N. Calvert Street, Suite 400, Baltimore, MD 21218, USA, e-mail:
S. Hurwitz Center for Clinical Investigation, Brigham and Women’s Hospital, Harvard Medical School, 1620 Tremont St., One Brigham Circle, Boston, MA 02120, USA, e-mail:
J. Magaziner Division of Gerontology, Department of Epidemiology and Preventive Medicine, School of Medicine, University of Maryland Baltimore, 660 W. Redwood Street, Suite 200, Baltimore, MD 21201, USA, e-mail:

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Collaborators Collapse

Genetics of the musculoskeletal system: a pleiotropic approach

The risk of osteoporotic fracture can be viewed as a function of loading conditions and the ability of the bone to withstand the load. Skeletal loads are dominated by muscle action. Recently, it has become clear that bone and muscle share genetic determinants. Involution of the musculoskeletal system manifests as bone loss (osteoporosis) and muscle wasting (sarcopenia). Therefore, the consideration of pleiotropy is an important aspect in the study of the genetics of osteoporosis and sarcopenia. This Perspective will provide the evidence for a shared genetic influence on bone and muscle. We will start with an overview of accumulating evidence that physical exercise produces effects on the adult skeleton, seeking to unravel some of the contradictory findings published thus far. We will provide indications that there are pleiotropic relationships between bone structure/mass and muscle mass/function. Finally, we will offer some insights and practical recommendations as to the value of studying shared genetic factors and will explore possible directions for future research. We consider several related questions that together comprise the general paradigm of bone responses to mechanical loading and the relationship between muscle strength and bone parameters, including the genetic factors that modulate these responses. We believe that further progress in understanding the common genetic etiology of osteoporosis and sarcopenia will provide valuable insight into important biological underpinnings for both conditions and may translate into new approaches to reduce the burdens of both conditions through improved diagnosis, prevention, and early targeted treatment.

10-year case review of nutritional rickets in Children's Hospital of Michigan

Nutritional rickets has been on the rise in the United States. A chart review of patients with nutritional rickets from April 1995 to May 2005 was performed. Fifty-eight subjects were studied (62% males, 38% females, with an age range between 2 and 132 months). Of the subjects, 81% were African Americans and 14% were Arabic; 33% were Christians and 19% were Muslims. An increasing number of cases of nutritional rickets have been noted since 2000. Seventy-nine percent of patients with nutritional rickets presented at the emergency department, and in 69% of the cases, rickets was an incidental finding; 96% of patients were exclusively breast-fed, and none received multivitamin supplements. 25-OH vitamin D levels were below 5 ng/mL in 42% of the patients, all of whom were African Americans. We could document complete resolution of nutritional rickets in only 8 patients, and 3 of these patients showed sequelae of rickets.

Role of vitamin D in the pathogenesis of type 2 diabetes mellitus

Vitamin D deficiency has been shown to alter insulin synthesis and secretion in both humans and animal models. It has been reported that vitamin D deficiency may predispose to glucose intolerance, altered insulin secretion and type 2 diabetes mellitus. Vitamin D replenishment improves glycaemia and insulin secretion in patients with type 2 diabetes with established hypovitaminosis D, thereby suggesting a role for vitamin D in the pathogenesis of type 2 diabetes mellitus. The presence of vitamin D receptors (VDR) and vitamin D-binding proteins (DBP) in pancreatic tissue and the relationship between certain allelic variations in the VDR and DBP genes with glucose tolerance and insulin secretion have further supported this hypothesis. The mechanism of action of vitamin D in type 2 diabetes is thought to be mediated not only through regulation of plasma calcium levels, which regulate insulin synthesis and secretion, but also through a direct action on pancreatic beta-cell function. Therefore, owing to its increasing relevance, this review focuses on the role of vitamin D in the pathogenesis of type 2 diabetes mellitus.

Differential effects of D-hormone analogs and native vitamin D on the risk of falls: a comparative meta-analysis

The aim of this meta-analysis was to compare the antifall efficacy of native vitamin D to that of its hydroxylated analogs alfacalcidol and calcitriol. Randomized clinical trials comparing oral native vitamin D and its analogs alfacalcidol and calcitriol to a placebo were included. Sources included the Cochrane Controlled Trials Register, EMBASE, MEDLINE, a hand search of abstracts, as well as reference lists. The time range was January 1995 to May 2007. Data were abstracted and scored by two investigators. The core analysis was based on double-blind trials, while open trials were included as a robustness analysis. Relative risks (RRs) for falls while allocated to D-hormone analogs or vitamin D were calculated. Publication bias and robustness were formally tested. Fourteen trials including 21,268 subjects were included. Using double-blind data only, vitamin D-hormone analogs provided a statistically significant lower level of risk for falling compared to native vitamin D: RR = 0.79 (95% confidence interval 0.64-0.96) vs. 0.94 (0.87-1.01) (intergroup difference P = 0.049). The dropout rates observed in the two sets of trials were comparable: 0.33% per month. Publication bias investigation did not report any significant trend for selective publication favoring active treatment arms. Upon current evidence, D-hormone analogs seem to prevent falls to a greater extent than their native compound. Long-term, prospective, head-to-head, confirmatory trials are required to address the exact role of vitamin D and D-hormone analogs in the prevention of falls and fractures.

Relationship between serum parathyroid hormone, vitamin D sufficiency, age, and calcium intake

Vitamin D deficiency is extremely common among elderly subjects and it has been associated with poor bone health, and to a number of other conditions. The ideal 25-hydroxy-vitamin D [25(OH)D] concentration, reflecting the size of vitamin D deposits, are generally retained those not associated with any marginal increase in serum parathyroid hormone (PTH). These threshold values vary considerably and this may be due to the interaction of other factors. The aim of the study is to assess whether age and calcium intake interact with the relationship between 25(OH)D and PTH. Data from a survey on the prevalence of hypovitaminosis D in elderly women in Italy were analysed in order to verify whether age and calcium intake were interfering on the 25(OH)D/PTH relationship. A total of 697 women were available for analysis. Serum PTH levels were significantly correlated with age, 25(OH)D and calcium intake (p<0.001) and in a multivariate model they all significantly contributed to explain PTH variance (R(2)=24.4%). In 39 elderly osteoporotic women on a low calcium intake and given vitamin D supplements (2000-3000 IU daily for >8 months) able to increase 25(OH)D levels above 110 nMol/l, PTH levels were maintained below 35 pg/mL. The minimum 25(OH)D levels to be recommended depends largely on the age and the calcium intake. In elderly individuals not taking calcium supplements in order to keep serum PTH levels strictly within the normal range 25(OH)D serum levels should be maintained above ca. 120 nMol/L.

Vitamin D receptor genotypes influence quadriceps strength in chronic obstructive pulmonary disease

BACKGROUND

Quadriceps weakness is an important complication of chronic obstructive pulmonary disease (COPD) and is associated with impaired exercise capacity and greater mortality. Its etiology is multifactorial, and evidence is growing that it is partly determined by genetic susceptibility.

OBJECTIVE

Using an established cohort, we tested whether quadriceps weakness in patients with COPD is influenced by common variations in the gene for the vitamin D receptor.

DESIGN

Vitamin D receptor FokI and BsmI genotypes and the (I/D) angiotensin-converting enzyme (ACE) and bradykinin receptor (+9/-9) genotypes were identified in 107 patients with stable COPD [x +/- SD forced expiratory volume in 1 s (FEV(1)): 34.5 +/- 16.5] and 104 healthy, age-matched control subjects. Quadriceps maximum voluntary contraction force and fat-free mass assessed by bioelectrical impedance analysis were measured.

RESULTS

After adjustment for covariables, both patients and control subjects who were homozygous for the C allele of the FokI polymorphism had less quadriceps strength than did those with > or =1 T allele [41.0 +/- 11.8 compared with 46.0 +/- 13.2 kg (P = 0.01) and 32.5 +/- 11.2 compared with 36.2 +/- 13.1 kg (P = 0.005), respectively]. The b allele of the BsmI polymorphism was associated with greater quadriceps strength in patients-37.0 +/- 13.3, 33.8 +/- 11.6, and 33.8 +/- 11.6 kg for bb, bB, and BB, respectively (P = 0.0005)-but had no effect in healthy control subjects. The effect of BsmI on quadriceps strength was least apparent in patients with the ACE II genotype (P = 0.003).

CONCLUSIONS

The FokI common variants in the VDR gene are associated with skeletal muscle strength in both patients and control subjects, whereas the BsmI polymorphism is associated with strength only in patients.

Therapy of osteoporosis with calcium and vitamin D

Inadequate intakes of vitamin D and calcium lead to reduced calcium absorption, higher bone remodeling rates, and increased bone loss. Vitamin D insufficiency has also been linked to reduced muscle function and increased risk of falling. The mechanisms for the performance and muscle effects are not well understood. Administering vitamin D to those with inadequate vitamin D status has been shown to lower fracture rates in some trials but not in others. The purpose of this presentation is (1) to examine how calcium and vitamin D work in concert, (2) to consider key evidence that increasing vitamin D intake will affect risk of falls and fractures, and (3) to estimate the 25-hydroxyvitamin D [25(OH)D] level needed to achieve maximum fracture protection.

Lack of Association Between Vitamin D Receptor Genotypes and Haplotypes With Fat-Free Mass in Postmenopausal Brazilian Women

The relationship between vitamin D receptor (VDR) ApaI, CDX2, BsmI, FokI, and TaqI polymorphisms and fat-free mass (FFM) were examined in 191 postmenopausal Brazilian women (mean age 67.87 +/- 5.22 years). Participants underwent FFM measurements by dual-energy x-ray absorptiometry (DEXA). Whole-blood-extracted genomic DNA was genotyped to the aforementioned polymorphisms and to ancestry-informative markers through minisequencing, using the SNaPshot Multiplex System. Association between VDR polymorphisms and FFM variables was assessed by analysis of covariance. Haplotypes were estimated, and regression-based, haplotype-specific association tests were carried out with the studied phenotypes. No departure from Hardy-Weinberg equilibrium was detected for any polymorphism. None of the investigated VDR allelic variations, individually or analyzed as haplotypes, was associated with FFM phenotypes. The inclusion of individual African genomic ancestry was used as an attempt to correct for population stratification. Further studies in larger sample population are required to confirm these findings.

Vitamin D and its implications for musculoskeletal health in women: an update

Vitamin D is a hormone that controls phosphorus, calcium, and bone metabolism and neuromuscular function. Vitamin D synthesis is a process in which the skin, liver, and kidney are sequentially involved. The vitamin D pool is completed by the amount taken with food and supplements. Vitamin D deficiency causes osteopenia, precipitates and exacerbates osteoporosis, causes a painful disease, osteomalacia, and increases muscle weakness, which worsens the risk of falls and fractures. A high prevalence of vitamin D insufficiency exists in the apparently healthy population, osteoporotic patients, and patients with prior fractures. Factors contributing to low vitamin D levels include low sunlight exposure, decreased skin synthesis and intestinal absorption, and inadequate diet. The simplest way to correct hypovitaminosis is adequate nutrition and supplements. However, few patients with osteoporosis and/or fractures, receive adequate supplements. Vitamin D insufficiency may alter the regulatory mechanisms of parathyroid hormone and may induce a secondary hyperparathyroidism that increases the risk of osteoporosis and fractures, although the necessary degree of this is not established. Monitoring of serum 25-hydroxyvitamin D levels is the only way to assess vitamin D status. The ideal healthy blood levels of 25-hydroxyvitamin D are controversial, although a range from 30 to 60ng/mL is widely accepted. The role of vitamin D supplementation is to provide humans with the nutrient in an amount closer to the biological norm for our species. This amount of vitamin D results in optimal function of many aspects of health, including balance and muscle strength, thus reducing the risk of fracture beyond what is possible via the quality and quantity of bone itself.