No change in calcium absorption in adult Pakistani population before and after vitamin D administration using strontium as surrogate

Strontium Regulates the Proliferation and Differentiation of Isolated Primary Bovine Chondrocytes via the TGFβ/SMAD Pathway

The present study evaluated the effects of strontium (Sr) on proliferation and differentiation of chondrocytes isolated from dairy cows, and whether Sr exerts its effects via transforming growth factor β (TGFβ) signaling. The chondrocytes were isolated from patellar cartilage from newborn Holstein bull calves (n = 3, 1 day old, 38.0 ± 2.8 kg, fasting) within 15 min after euthanasia, and treated with different concentrations of Sr (0, 0.1, 1, and 10 μg/ml, as SrCl₂·6H₂O). After pretreatment with or without activin receptor-like kinase 5 (ALK5) inhibitor (10 μM SB-505124) for 4 h, chondrocytes were incubated with Sr for another 4 h. Overall effects of Sr were evaluated relative to NaCl as the control. In contrast, the 1 μg/ml Sr-treated group served as the control to determine effects of preincubating with SB-505124. Western blot and qRT-PCR were used for measuring expression of proliferation-, differentiation-, and TGFβ1-responsive factors. Data were analyzed using one-way ANOVA in GraphPad Prism 7.0. Incubation with all doses of Sr increased TGFβ1/ALK5-induced SMAD3 phosphorylation, and at 10 μg/ml it inhibited ALK1-induced SMAD1/5/9 phosphorylation. Expression of mRNA and protein of the proliferation-responsive factors type Ⅱ Collagen α1 (COL2A1) and aggrecan (ACAN) was induced by Sr at 1 μg/ml. In contrast, Sr at 10 μg/ml inhibited the expression of differentiation-responsive factors type Ⅹ Collagen α1 (COL10A1) and secreted phosphoprotein 1 (SPP1), and at 1 μg/ml it had the same effect on alkaline phosphatase (ALPL) mRNA and protein levels. Cells were stained with PI/RNase Staining buffer to assess cell cycle activity using flow-cytometry. Incubation with Sr at 1 and 10 μg/ml induced an increase in the number of cells in the S-phase, leading to an increase in the proliferation index. Incubation with SB-505124 inhibited phosphorylation of SMAD3. Abundance of ACAN and COL2A1 mRNA and protein was lower when cells were pre-incubated with SB-505124. Overall, data indicated that Sr promotes proliferation and inhibits differentiation of primary chondrocytes by directing TGFβ1 signaling towards SMAD3 phosphorylation rather than SMAD1/5/9 phosphorylation. Whether these effects occur in vivo remains to be determined and could impact future application of Sr as an experimental tool in livestock.

Vitamin D deficiency in Pakistani population: critical overview from 2008 to 2018

Purpose

The purpose of this paper is to access the present situation of the Pakistani population that suffers from vitamin D deficiency.

Design/methodology/approach

A review-based study was conducted based on publications from Pakistan between the years 2008 and 2018. The publications were archived from Pub Med and Google Scholar databases. A total of 18 publications were shortlisted, based on the cutoff values of vitamin D sufficiency, insufficiency and deficiency.

Findings

As per the data, 38.5 per cent of the participants were males, 48.7 per cent were females and 12.8 per cent of the studies have not mentioned the genders of the participants. The cumulative results show that 58.17 per cent (95 per cent CI: 52.17, 64.16) of the population is vitamin D-deficient and 26.65 per cent (95 per cent CI: 21.63, 31.66) is insufficient in vitamin D. The highest level of vitamin D deficiency was reported from Sindh (62.15 per cent), followed by Khyber Pakhtunkhwa (60.57 per cent), Punjab (51.75 per cent) and the Federal Capital (49.25 per cent). Moreover, Cochran’s Q test indicated considerable heterogeneity (p= >0.001) with regard to Vitamin D deficiency (VDD) prevalence found among samples from the selected studies.

Originality/value

The present analysis suggests that more than half of the Pakistani population suffers from VDD, which, thus, should be considered as an epidemic and treated likewise.

COMPARISON OF VITAMIN D REPLACEMENT STRATEGIES WITH HIGH-DOSE INTRAMUSCULAR OR ORAL CHOLECALCIFEROL: A PROSPECTIVE INTERVENTION STUDY

OBJECTIVE

To ascertain the frequency of correction of vitamin D deficiency (VDD) with single or multiple doses of oral (p.o.) and intramuscular (i.m.) administration of 2 high-dose preparations of vitamin D3 (VD3).

METHODS

This was a prospective intervention study conducted in an ambulatory care setting. One hundred participants with VDD (25-hydroxy vitamin D [25-OHD] <20 ng/mL) were randomized to receive a dose of 600,000 or 200,000 IU of VD3 via a p.o. or i.m. route. The main outcome measure was serum 25-OHD levels at 2, 4, and 6 months after the intervention. The same dose was repeated in participants if 25-OHD remained <30 ng/mL at 2 and 4 months.

RESULTS

At 2 months, VDD was corrected in 93.8% of participants in Group 1 (600,000 IU i.m.); 83.3% in Group 2 (600,000 IU p.o.), 87.5% in Group 3 (200,000 IU i.m.), and 70.6% in Group 4 (200,000 IU p.o.). The mean changes from baseline in vitamin D levels at 2 months were 29.6 ± 13.7, 19.8 ± 12.3, 18.3 ± 10.6, and 13.7 ± 7.8 ng/mL in Groups 1, 2, 3, and 4, respectively. The mean levels remained significantly higher from baseline in all groups at all time points during the 6 months of observation. The mean 25-OHD level achieved in Group 1 was significantly higher than all other groups at 6 months.

CONCLUSION

Two months after the intervention, VDD was corrected in more than 70% of participants with a single dose of either 600,000 or 200,000 IU given p.o. or i.m.

25-Hydroxyvitamin D level does not reflect intestinal calcium absorption: an assay using strontium as a surrogate marker

There is conflicting evidence as to the optimal serum 25-hydroxyvitamin D [25(OH)D] concentration for intestinal calcium absorption (Abs-Ca). Our purpose was to assess the relationship between vitamin D status and Abs-Ca in postmenopausal women. Fifty volunteers with low bone mass were grouped according to their serum 25(OH)D concentration as follows: mild deficient, <50 nmol/L (DEF) and sufficient, ≥75 nmol/L (SUF). The subjects were submitted to an oral strontium overload test to assess their Abs-Ca. Fasting blood samples were obtained to perform the relevant hormonal and biochemical tests. After the subjects received the test solution, blood samples were drawn at 30, 60, 120, and 240 min to determine the strontium concentrations. Abs-Ca was indirectly expressed as the area under the serum strontium concentration curve (AUC). A repeated measures ANOVA was performed to determine the differences among the groups. Pearson's correlation and multiple linear regression analysis were used to study the associations between the variables. The mean 25(OH)D and 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations differed between the groups (SUF vs. DEF) as follows: 98.7 ± 18.2 vs. 38.4 ± 8.5 nmol/L (p < 0.001) and 36.2 ± 10.2 vs. 24.9 ± 4.6 pg/mL (p < 0.001), respectively. There was no statistically significant difference between the groups for parathyroid hormone and AUC. Only 1,25(OH)2D influenced the strontium absorption in the last 2 h of the test. In the studied population, no correlation between levels of 25(OH)D and Abs-Ca was found. Only 1,25(OH)2D influenced Abs-Ca as measured by a strontium absorption test.

The relationship between serum 25-hydroxy vitamin D, parathormone and bone mineral density in Indian population

OBJECTIVES

Vitamin D deficiency (VDD) is a global problem. Not all patients with VDD have clinical manifestations or secondary hyperparathyroidism. We studied the interaction between serum 25-hydroxy vitamin D (25OHD), parathormone (PTH) and bone mineral density (BMD) in Indian adolescents and adults.

DESIGN

Population survey.

PATIENTS

A total of 1829 adolescents and 1346 adults aged 50 years and above were analysed in this study.

MEASUREMENTS

Serum biochemistry, 25OHD, PTH and BMD were estimated. Subjects were grouped according to quartiles of serum PTH. VDD was defined as severe (25OHD ≤ 5 ng/ml), moderate (25OHD ≤ 10 ng/ml) and mild (25OHD ≤ 20 ng/ml) and secondary hyperparathyroidism (SHPT) when serum PTH levels >65 pg/ml.

RESULTS

Only 30-40% of subjects with moderate and severe VDD, respectively, had SHPT. BMD decreased from Quartile 1 to Quartile 4 of PTH at all sites among adolescents and adults, with only a marginal decline in serum 25OHD levels between these quartiles. Further, within each PTH quartile, there was no difference in BMD according to categories of VDD. Analysing BMD in the different PTH quartiles, the PTH cut-offs beyond which BMD showed a significant decline, was 35 pg/ml in adolescents and 53 pg/ml in adults.

CONCLUSIONS

Less than half of the subjects with VDD have SHPT. BMD levels start to decline at PTH values currently considered to be normal. These data suggest the need to redefine SHPT in different age groups keeping in mind the relationship between PTH and BMD. This may also influence the decision to supplement subjects with VDD.

Assessing the effect of dietary calcium intake and 25 OHD status on bone turnover in women in Pakistan

SUMMARY

Bone health assessed in three towns of Karachi, Pakistan in females showed poor calcium intake, vitamin D deficiency, secondary hyperparathyroidism, and high bone turnover. Correlates of high bone turnover included females residing in Saddar Town, underweight females less than 30 years of age from low socio-economic status, and secondary hyperparathyroidism.

AIMS

To assess bone health and association of dietary calcium and 25 hydroxy vitamin D with bone turnover in the community-dwelling females of Karachi.

METHODS

Bone health was assessed in three randomly selected towns of Karachi, Pakistan. One premenopausal female fulfilling the inclusion criteria from each household was included in the study. Dietary calcium was assessed through a food frequency questionnaire and biochemical markers including calcium, phosphates, albumin, magnesium, creatinine, and SGPT, intact parathyroid hormone, 25 hydroxy vitamin D, and N-telopeptide of type I collagen were measured to assess the bone health.

RESULTS

Three hundred and five females were included from three towns. Overall, 90.5% of females had vitamin D deficiency with 42.6 and 23.3% having secondary hyperparathyroidism and high bone turn over respectively. Prevalence of vitamin D deficiency, secondary hyperparathyroidism, and high bone turnover was significantly different among towns. Mean vitamin D levels were significantly low and iPTH levels significantly high in females with high bone turnover. Calcium intake was not significantly different among females with normal, high, and low bone turnover. Correlates of high bone turnover included females residing in Saddar Town, underweight females less than 30 years of age belonging to low socio-economic status, and secondary hyperparathyroidism.

CONCLUSION

Compromised bone health is seen in community-dwelling females of Karachi. There is a need to perform large-scale community-based studies in all age groups to understand the interplay of markers in our population to understand the impact of these variables translating into the risk of osteoporosis.

Optimal vitamin D status: a critical analysis on the basis of evidence-based medicine

CONTEXT

Public health authorities around the world recommend widely variable supplementation strategies for adults, whereas several professional organizations, including The Endocrine Society, recommend higher supplementation.

METHODS

We analyzed published randomized controlled clinical trials to define the optimal intake or vitamin D status for bone and extraskeletal health.

CONCLUSIONS

The extraskeletal effects of vitamin D are plausible as based on preclinical data and observational studies. However, apart from the beneficial effects of 800 IU/d of vitamin D3 for reduction of falls in the elderly, causality remains yet unproven in randomized controlled trials (RCTs). The greatest risk for cancer, infections, cardiovascular and metabolic diseases is associated with 25-hydroxyvitamin D (25OHD) levels below 20 ng/mL. There is ample evidence from RCTs that calcium and bone homeostasis, estimated from serum 1,25-dihydroxyvitamin D and PTH, calcium absorption, or bone mass, can be normalized by 25OHD levels above 20 ng/mL. Moreover, vitamin D supplementation (800 IU/d) in combination with calcium can reduce fracture incidence by about 20%. Such a dose will bring serum levels of 25OHD above 20 ng/mL in nearly all postmenopausal women. Based on calculations of the metabolic clearance of 25OHD, a daily intake of 500-700 IU of vitamin D3 is sufficient to maintain serum 25OHD levels of 20 ng/mL. Therefore, the recommendations for a daily intake of 1500-2000 IU/d or serum 25OHD levels of 30 ng or higher for all adults or elderly subjects, as suggested by The Endocrine Society Task Force, are premature. Fortunately, ongoing RCTs will help to guide us to solve this important public health question.