Biomedical subjects

Prema B Rapuri

Publications and source records attributed to Prema B Rapuri.

6 recordsLinked to original sources

PubMed2007

Caffeine decreases vitamin D receptor protein expression and 1,25(OH)2D3 stimulated alkaline phosphatase activity in human osteoblast cells.

Of the various risk factors contributing to osteoporosis, dietary/lifestyle factors are important. In a clinical study we reported that women with caffeine intakes >300 mg/day had higher bone loss and women with vitamin D receptor (VDR) variant, tt were at a greater risk for this deleterious effect of caffeine. However, the mechanism of how caffeine effects bone metabolism is not clear. 1,25-Dihydroxy vitamin D(3) (1,25(OH)(2)D(3)) plays a critical role in regulating bone metabolism. The receptor for 1,25(OH)(2)D(3), VDR has been demonstrated in osteoblast cells and it belongs to the superfamily of nuclear hormone receptors. To understand the molecular mechanism of the role of caffeine in relation to bone, we tested the effect of caffeine on VDR expression and 1,25(OH)(2)D(3) mediated actions in bone. We therefore examined the effect of different doses of caffeine (0.2, 0.5, 1.0 and 10mM) on 1,25(OH)(2)D(3) induced VDR protein expression in human osteoblast cells. We also tested the effect of different doses of caffeine on 1,25(OH)(2)D(3) induced alkaline phosphatase (ALP) activity, a widely used marker of osteoblastic activity. Caffeine dose dependently decreased the 1,25(OH)(2)D(3) induced VDR expression and at concentrations of 1 and 10mM, VDR expression was decreased by about 50-70%, respectively. In addition, the 1,25(OH)(2)D(3) induced alkaline phosphatase activity was also reduced at similar doses thus affecting the osteoblastic function. The basal ALP activity was not affected with increasing doses of caffeine. Overall, our results suggest that caffeine affects 1,25(OH)(2)D(3) stimulated VDR protein expression and 1,25(OH)(2)D(3) mediated actions in human osteoblast cells.

Alkaline Phosphatase↗

PubMed2006

An age-related decrease in creatinine clearance is associated with an increase in number of falls in untreated women but not in women receiving calcitriol treatment.

CONTEXT: Decreased calcitriol production due to impaired renal function may be a significant risk factor for falls in normal aging population. OBJECTIVE: The objective of the study was to examine the association between creatinine clearance (CrCl) and the incidence of falls and fallers in groups treated with placebo, calcitriol, estrogen therapy (ET)/estrogen + progestin therapy (HT), and calcitriol + ET/HT. DESIGN: This was a 3-yr, double-blind, placebo-controlled study designed to test the efficacy of calcitriol and ET/HT on bone loss and falls with analysis by intention to treat and post hoc. SETTING: The study was conducted at an academic outpatient center. PARTICIPANTS: Four hundred eighty-nine normal elderly women aged 65-77 yr; 415 women completed the study. INTERVENTION: Subjects were randomized to placebo, calcitriol 0.25 mug twice a day, ET daily (conjugated equine estrogens 0.625 mg), HT (conjugated equine estrogen 0.625 mg + medroxyprogesterone acetate 2.5 mg) and calcitriol + ET/HT. MAIN OUTCOME MEASURES: Cumulative number of falls and fallers were compared between groups with 24-h urine CrCl less than 60 and 60 ml/min or greater. RESULTS: Calcitriol treatment decreased the number of fallers and falls. Low CrCl less than 60 ml/min was a predictor of the number of falls per person but not fallers in the placebo group (P = 0.007). In the low CrCl group (<60 ml/min), the rate of falls decreased on calcitriol by 53% [95% confidence interval (CI) -71% to -22%; P = 0.003], calcitriol + ET/HT by 61% (95% CI -76% to -37%; P = 0.001), and ET/HT by 25% (95% CI: -55% to +24%; not significant). Calcitriol reduced the rate of falls by 30% (95% CI -49% to -4%; P = 0.027) in the CrCl 60 ml/min or greater group. CONCLUSION: Calcitriol treatment decreases falls in all subjects but especially in elderly women with decreased renal function (<60 ml/min) and frequent fallers.

Accidental Falls↗

PubMed2004

Endogenous levels of serum estradiol and sex hormone binding globulin determine bone mineral density, bone remodeling, the rate of bone loss, and response to treatment with estrogen in elderly women.

A total of 489 elderly women aged 65-75 yr who participated in a 3-yr, randomized, blinded osteoporosis trial underwent measurements of serum estradiol, bioavailable estradiol, and SHBG. At baseline, bone mineral density (BMD) was lower at the femoral sites (7-19%, P < 0.05), total body (6-8%, P < 0.05), and spine (5-9%, P = 0.2) in women in the lowest tertile for serum total estradiol [<9 pg/ml (33 pmol/liter)], serum bioavailable estradiol [<2.4 pg/ml (8.8 pmol/liter)], or highest tertile for serum SHBG (>165 nmol/liter), compared with women in the highest tertiles of total estradiol [>13.3 pg/ml (49 pmol/liter)] and bioavailable estradiol [>4 pg/ml (14 pmol/liter)] or lowest tertile for SHBG (<113 nmol/liter). Bone markers were increased in women in the lowest tertile for serum total estradiol (not significant) and bioavailable estradiol (P < 0.05) and highest tertile for SHBG (P < 0.05). In the longitudinal study, the rate of bone loss in the placebo group was significantly higher in total body (P < 0.05) and spine (P < 0.05) in women in the lowest tertile, compared with the highest tertile of serum bioavailable estradiol. After treatment with conjugated equine estrogens 0.625 mg/d, the increase in BMD was 4-6% higher at the femoral sites (P < 0.05), total body (P < 0.05), and spine (not significant), in the lowest tertile, compared with the highest tertile of serum bioavailable estradiol or highest tertile, compared with the lowest tertile of serum SHBG. In summary, small variations in endogenous serum estradiol and high serum SHBG determine differences in BMD and rate of bone loss in elderly women and also affect the response to treatment with estrogen. Women with a serum estradiol level of less than 9 pg/ml (33 pmol/liter) are optimal candidates for estrogen therapy for osteoporosis prevention.

Aged↗

PubMed2003

Protein intake: effects on bone mineral density and the rate of bone loss in elderly women.

BACKGROUND: The role of dietary protein in bone metabolism is controversial. OBJECTIVE: We investigated the associations of dietary protein intake with baseline bone mineral density (BMD) and the rate of bone loss over 3 y in postmenopausal elderly women. DESIGN: Women aged 65-77 y (n = 489) were enrolled in an osteoporosis intervention trial. We studied the associations of protein intake as a percentage of energy with baseline BMD and the rate of bone loss in 96 women in the placebo group (n = 96). We also examined the effect of the interaction of dietary calcium intake with protein intake on BMD. RESULTS: In the cross-sectional study, a higher intake of protein was associated with higher BMD. BMD was significantly higher (P < 0.05) in the spine (7%), midradius (6%), and total body (5%) in subjects in the highest quartile of protein intake than in those in the lower 2 quartiles. This positive association was seen in women with calcium intakes > 408 mg/d. There was no significant effect of protein intake on hip BMD. In the longitudinal study of the placebo group, there was no association between protein intake and the rate of bone loss. CONCLUSIONS: The highest quartile of protein intake (: 72 g/d) was associated with higher BMD in elderly women at baseline only when the calcium intake exceeded 408 mg/d. In the longitudinal study, no association was seen between protein intake and the rate of bone loss, perhaps because the sample size was too small or the follow-up period of 3 y was not long enough to detect changes.

Aged↗

PubMed2002

Effect of discontinuation of estrogen, calcitriol, and the combination of both on bone density and bone markers.

In a 5-yr randomized prospective study we examined the treatment effect of estrogen replacement therapy/hormone replacement therapy (ERT/HRT), calcitriol, ERT/HRT and calcitriol, or placebo for 3 yr and the effect of discontinuation of therapy for 2 more yr on bone mineral density (BMD), calciotropic hormones, markers of bone remodeling, and calcium absorption in 489 elderly women. The treatment phase of the study was double-blinded. After discontinuing therapy for 2 yr, there was rapid bone loss in all 3 treatment groups, and most of the decrease in BMD occurred in the first year. In the ERT/HRT group, spine BMD increased 5.5% in yr 3, decreased 3.2% in yr 4, and decreased 0.7% in yr 5; femoral neck BMD increased 3.7% in yr 3, decreased 2.5% in yr 4, and decreased 0.4% in yr 5; total body BMD increased 2.1% in yr 3, decreased 1.4% in yr 4, and decreased 0.6% in yr 5. In the combination group, spine BMD increased 7.1% in yr 3, decreased 4.3% in yr 4, and decreased 0.3% in yr 5; femoral neck BMD increased 4.5% in yr 3, decreased 3.0% in yr 4, and decreased 0.01% in yr 5; total body BMD increased 2.2% in yr 3, decreased 1.5% in yr 4, and decreased 0.6% in yr 5. In the calcitriol group, spine BMD increased 1.8% in yr 3, decreased 1.8% in yr 4, and showed no change in yr 5; femoral neck BMD increased 0.2% in yr 3, decreased 0.2% in yr 4, and decreased 0.6% in yr 5; total body BMD decreased 0.4% in yr 3, decreased 0.6% in yr 4, and decreased 0.4% in yr 5. Compared with placebo, all treated groups at yr 5 had significantly higher total body BMD; only the combination group had significantly higher spine BMD (3.4%; P < 0.001) and total hip BMD (2.4%; P < 0.01.) compared with the placebo group. Compared with baseline, only spine BMD in the combination group was significantly higher (2.6%; P < 0.001) at yr 5. The increase in calcium absorption and the decrease in serum PTH levels in the calcitriol groups were reversed after discontinuation of treatment, and the decrease in bone markers was reversed in the hormone-treated groups. These results suggest that discontinuation of ERT/HRT and/or calcitriol therapy in elderly women leads to a decrease in much of the BMD gained on treatment; however, in the combination group there was a statistically significant residual effect on spine BMD.

Absorption↗

PubMed2002

Seasonal changes in calciotropic hormones, bone markers, and bone mineral density in elderly women.

Seasonal variation of serum vitamin D metabolites, PTH, bone turnover markers, and bone mineral density (BMD), adjusted for confounding variables, was studied in a cross-sectional population of 251 ambulatory elderly women aged 65-77 yr. A significant (P < 0.05) seasonal change was observed in serum 25 hydroxyvitamin D (25OHD), bone resorption marker (urine N-telopeptide), and BMD of the spine, total body, and mid-radius. Serum 25OHD was significantly lower (P < 0.05) in winter (December, January, February, March) compared with summer (June, July, August, September), with the nadir in February (68.4 +/- 6.74 nmol/liter) and the zenith in August (85.6 +/- 5.12 nmol/liter). Mean serum PTH levels were higher in winter when serum 25OHD was low, and mean serum PTH was lower in summer when serum 25OHD was high, although the seasonal change in serum PTH was not significant. The change in serum 1,25-dihydroxy vitamin D(3) paralleled that of serum 25OHD levels, but the seasonal effect was not significant. Mean 24-h urine N-telopeptide showed a significant seasonal change (P < 0.05); it was about 24% higher in February (zenith) compared with that in August (nadir). The zenith month of urine N-telopeptide levels corresponded to the nadir month of serum 25OHD levels and vice versa. A significant (P < 0.05) inverse correlation was observed between 24-h urine N-telopeptides and serum 25OHD levels. There was a significant (P < 0.05) seasonal change in mean BMD of spine, total body, and mid-radius. These changes paralleled those in serum 25OHD levels. Spine BMD was 8.4% higher in August (zenith) compared with that in February (nadir), whereas total body BMD and mid-radius BMD were 6.1 and 7.6% higher, respectively, in July (zenith) compared with that in January (nadir). There was a nonsignificant increase of 3.6% in total hip BMD. In summary (see Fig. 5), the seasonal changes in vitamin D metabolism in elderly women are closely associated with small changes in serum PTH, changes in bone resorption, and BMD.

Absorption↗