Sex steroids play a key role in bone turnover and preserving BMD; hence, gender-affirming hormone treatment (HT) in transgender people affects bone metabolism. Most studies have looked into the effect of HT on changes in BMD; however, they do not provide insights into changes in bone metabolism caused by HT. This study investigated changes in bone turnover markers (BTMs) and sclerostin, as well as their correlations with change in BMD in transwomen and transmen during the first year of HT. Transwomen received estradiol and antiandrogens; transmen received testosterone. Sclerostin; P1NP; alkaline phosphatase (ALP); CTx; and BMD of the total hip, the femoral neck, and the lumbar spine were evaluated at baseline and after 1 year of HT. There were 121 transwomen (median age 30 years, interquartile range [IQR] 24 to 41 years) and 132 transmen (median age 24 years, IQR 21 to 33 years) included in the study. In transwomen, ALP decreased in 19% (95% CI, -21 to-16), CTx in 11% (95% CI, -18 to-4), and sclerostin in 8% (95%CI, -13 to-4) of study participants after 1 year of HT. In contrast, in transmen P1NP, ALP, and sclerostin increased in 33% (95% CI, 24 to 42), 16% (95% CI, 12 to 20), and 15% (95% CI, 10 to 20) of study participants, respectively, after 1 year of HT. No age differences were seen in transwomen, whereas in transmen aged ≥50 years a decrease in all BTMs was found in contrast with the other age groups. These transmen had low estrogen concentration at the start of HT based on their postmenopausal state before the start of HT; their estradiol concentrations increased during testosterone treatment. Changes in BTMs and BMD were weakly correlated (correlation coefficient all <0.30). To conclude, 1 year of HT resulted in decreased bone turnover in transwomen and older transmen, whereas it increased in younger transmen. The decrease in bone resorption in older transmen shows the importance of estrogen as a key regulator of bone turnover. © 2019 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals, Inc.

Osteogenesis imperfecta (OI) is a heterogeneous group of rare inherited bone and connective tissue disorders resulting from defect in collagen synthesis or function. It is characterized by bone fragility, which shows wide range of severities. The heterozygous mutations in the genes coding type I collagen are responsible to 80% of the OI cases. Metabolic bone markers relating type I collagen production or degraded products of mature collagen fiber may provides important information on the pathophysiology of OI. Typically, P1NP which is bone formation marker shows significant reduction and CTX or NTX shows relatively high level in type I OI. The other applications of metabolic bone markers in the management of OI will be discussed.

Background: There are limited data on vitamin D status of Sichuan province, and no investigation has been carried out on the correlations of 25(OH)D and BTMs between healthy Hans and Tibetans of Sichuan province. This study aimed to examine 25(OH)D levels around Sichuan province and to assess differences by ethnicity, age, gender, sunlight exposure, geographic location, and seasons.

Methods: Blood samples from 2317 healthy adults aged of 18 to 75 years and of Han and Tibetan ethnicities were collected in six regions and during four seasons. Serum 25(OH)D₂ and 25(OH)D₃ levels were measured by LC-MS/MS method. Serum total P1NP and β-CTX were measured by immunoassay.

Results: Participants aged 18-40 years showed significantly lower 25(OH)D levels than participants aged 41-75 years old (P < .0001). The median serum 25(OH)D level for males was significantly higher than that of females (P < .0001). Serum 25(OH)D levels among four seasons and different districts varied significantly (P < .0001). In addition, the 25(OH)D level of Tibetans was significantly lower than that of Hans, while the serum total P1NP and β-CTX levels of Tibetans were significantly higher than those of Hans (P < .0001).

Conclusion: Adult population was more common to have vitamin D deficiency/insufficiency among Tibetans, females, north regions and in spring and winter.

Keywords: bone turnover marker; epidemiological study; ethnic difference; liquid chromatography-tandem mass spectrometry; vitamin D.

Background: Cherubism is a rare autosomal dominant genetic condition caused by mutations in the SH3BP2 gene. This disease is characterized by osteolysis of the jaws, with the bone replaced by soft tissue rich in fibroblasts and multinuclear giant cells. SH3BP2 is a ubiquitous adaptor protein yet the consequences of SH3BP2 mutation have so far been described as impacting only face. Cherubism mouse models have been generated and unlike human patients, the knock-in mice exhibit systemic bone loss together with a systemic inflammation.

Case presentation: In light of these observations, we decided to search for a systemic cherubism phenotype in a 6-year-old girl with an aggressive cherubism. We report here the first case of cherubism with systemic manifestations. Bone densitometry showed low overall bone density (total body Z-score = - 4.6 SD). Several markers of bone remodelling (CTx, BALP, P1NP) as well as inflammation (TNFα and IL-1) were elevated. A causative second-site mutation in other genes known to influence bone density was ruled out by sequencing a panel of such genes.

Conclusions: If this systemic skeletal cherubism phenotype should be confirmed, it would simplify the treatment of severe cherubism patients and allay reservations about applying a systemic treatment such as those recently published (tacrolimus or imatinib) to a disease heretofore believed to be localised to the jaws.

Keywords: Bone loss phenotype; Case report; Cherubism; SH3BP2 protein; Systemic inflammation.

OBJECTIVE

There is a lack of data on the effects of prolactin on calcium metabolism and bone turnover in hyperprolactinemia of various origins. The aim of this study was to compare the influence of medicamentous and physiological hyperprolactinemia on bone turnover in female rats.

METHODS

Experimental animals (18 weeks old, Wistar female rats) were divided as follows: the group P - 9 rats, 3 weeks pregnant; the group M3-10 rats that were intramuscularly administrated sulpirid (10 mg/kg) twice daily for 3 weeks, the group M6 - 10 rats that were intramuscularly administrated with sulpirid (10 mg/kg) twice daily for 6 weeks, and age matched nulliparous rats as the control group: 10 rats, 18-week-old (C1) and 7 rats, 24 weeks old (C2). Laboratory investigations included serum ionized calcium and phosphorus, urinary calcium and phosphorous excretion, osteocalcin and serum procollagen type 1 N-terminal propeptide (P1NP).

RESULTS

Experimental animals in the group P compared to the control group, displayed lower mean serum ionized calcium (0.5 +/- 0.2 vs 1.12 +/- 0.04 mmol/L; p < 0.001); higher mean serum phosphorus (2.42 +/- 0.46 vs 2.05 +/- 0.2 mmol/L; p < 0.05); increased urinary calcium (3.90 +/- 0.46 vs 3.05 +/- 0.58; p < 0.01) and significantly increased P1NP (489.22 +/- 46.77 vs 361.9 +/- 53.01 pg/mL; p < 0.001). Experimental animals in the group M3 had significantly decreased P1NP, compared to the contol group. Prolongated medicamentous hyperprolactinemia (the group M6) induced increased serum ionized calcium (1.21 +/- 0.03 vs 1.15 +/- 0.02 mmol/L; p < 0.001); decreased serum phosphorus (1.70 +/- 0.13 vs 1.89 +/- 0.32 mmol/L; p < 0.001); decreased osteocalcin and P1NP.

CONCLUSIONS

Physiological hyperprolactinemia does not have such harmful effect on bone metabolism as medicamentous hyperprolactinemia. Chronic medicamentous hyperprolactinemia produces lower serum levels of bone formation markers. Assessment of bone turnover markers in prolongated medicamentous hyperprolactinemia provides an opportunity for earlier diagnosis of bone metabolism disturbances and should be considered as mandatory.

OBJECTIVE

Hyperprolactinaemia in pregnancy leads to mild and reversible changes in the maternal skeletal system, and medicamentous hyperprolactinemia causes more detrimental effects. We conducted an experimental study to evaluate differences between Prlr gene expression in the duodenum, vertebrae and kidneys during physiological and medicamentous hyperprolactinaemia, which could influence calcium homeostasis.

METHODS

Experimental animals (18 weeks old, Wistar female rats) were divided as follows: group P (nine rats that were 3 weeks pregnant), group M (ten rats that were intramuscularly administrated sulpiride (10 mg/kg) twice daily for 3 weeks), and the control group (C, ten age-matched nulliparous rats, 18-week-old). Laboratory investigations included measurements of serum ionized calcium, phosphorus, urinary calcium and phosphorus excretion, osteocalcin (OC), serum procollagen type 1 N-terminal propeptide (P1NP), vitamin D, parathyroid hormone (PTH) and prolactin (PRL). Relative quantification of gene expression for prolactin receptors in the duodenum, vertebrae and kidneys was determined using real-time PCR.

RESULTS

Expression of the Prlr gene was significantly higher in the duodenum (p < 0.001) and lower in vertebrae (p < 0.001) and kidneys (p < 0.01) in rats with physiological hyperprolactinaemia (PHP) than in the control group. Significantly lower Prlr expression in the duodenum was verified (p < 0.001), along with increased Prlr gene expression in vertebrae (p < 0.001) and kidneys (p < 0.01), in rats with medicamentous hyperprolactinaemia (MHP) than in the C group.

CONCLUSIONS

Downregulation of Prlr gene expression in the duodenum may explain the diminished intestinal calcium absorption in medicamentous hyperprolactinaemia. Prolactin takes calcium from the skeletal system following increased Prlr gene expression in the vertebrae to maintain calcium homeostasis, which increases the harmful effect on bone metabolism compared to that of physiological hyperprolactinaemia.

OBJECTIVE

There is limited information on the impact of recombinant human growth hormone (rhGH) on the muscle-bone unit in children with Crohn's disease (CD). In this pilot study, we report on the effects of rhGH on bone formation, dual-energy X-ray absorptiometry (DXA) total body (TB) bone mineral density adjusted for height and lumbar spine (LS) bone mineral apparent density (BMAD), and body composition.

METHODS

Prospective study of 8 children with CD (6 male), aged 14.8 years (9.0-16.4), who received rhGH for 24 months. Serum procollagen type 1 N-terminal propeptide (P1NP) was measured at baseline and at 6 months. DXA was performed every 6 months.

RESULTS

Six months of rhGH led to improvement in P1NP SDS adjusted for bone age from -3.6 (-7.9 to -0.9) to -2.4 (-3.7 to 0.4) (p = 0.01). At baseline, reduction in LS-BMAD and TB lean mass SDS was observed being -1.2 (-3.6 to 0.8) (p = 0.01 vs. zero) and -0.8 (-2.4 to 3.0) (p = 0.11 vs. zero), respectively. No significant changes were seen in DXA bone and muscle parameters over the 24 months.

CONCLUSIONS

Twenty-four months of therapy with rhGH in CD did not lead to an improvement in DXA BMD and lean mass, despite improvement in P1NP and linear growth.

Background: Bone turnover and metabolic indicators are related to age and gender. Age and gender should be matched in subjects in disease control research of bone turnover and metabolism, but strict matching of gender and age increases the difficulty and cost of the research. Therefore, the aim of this study was to solve it is necessary to strictly match age and gender in clinical research in bone metabolism.

Methods: A cross-sectional study was conducted from the data were extracted from the HIS of ZhuJiang Hospital. Data relating to seven bone turnover and metabolic indicators from 1036 patients between January 2018 and October 2019 were analyzed.

Results: P1NP, β-CTx and 25(OH)D were significant different in individuals younger than 20 years of age. ALP was significantly higher in those under 20 years of age and lower at age 20-39 compared with other age groups. The concentrations of Ca and P were different among the groups aged 0-19, 20-39, and 40-59 years of age groups but exhibited no difference above 60 years of age. PTH expression was not dependent on age. P1NP, β-CTx and PTH concentrations were not significantly different between the genders within the same age group. ALP was significantly different between genders within the age range 20-59 years. Ca and 25(OH)D were significantly different between the genders for those older than 60. Serum P was significantly different in the two genders for those aged 40-79. Patients received both alfacalcidol and calcium treatment differently from the others in P1NP, β-CTx, Serum Ca, P and ALP.

Conclusion: P1NP and β-CTx were highly correlated with age. If these two indictors require analysis in a case control study, the patients and controls should be strictly matched by age under 20 years. The demarcation point for ALP was 40 years of age. Ca and P were strongly recommended strict matching according to age in disease research. The difference in P1NP, β-CTx, 25(OH)D and ALP between genders depends on age differences. Medication history should be considered in bone turnover and metabolic clinical research.

Keywords: Age; Bone metabolic; Bone turnover; Children; Gender.

Numerous observational studies have reported that serum urate concentration positively correlates with bone density and reduced risk of fractures. The aim of this study was to examine whether soluble urate directly influences bone remodelling.

In laboratory studies, the in vitro effects of soluble urate were examined in osteoclast, osteoblast and osteocyte assays at a range of urate concentrations consistent with those typically observed in humans (up to 0.70 mmol/L). The clinical relevance of the in vitro assay findings was assessed using serial procollagen-1 N-terminal propeptide (P1NP) and Month 12 bone density data from a randomised controlled trial of allopurinol dose escalation in people with gout.

Addition of urate in the RAW264.7 cell osteoclastogenesis assay led to small increases in osteoclast formation (ANOVA p = 0.018), but no significant difference in bone resorption. No significant effects on osteoclast number or activity were observed in primary cell osteoclastogenesis or resorption assays. Addition of urate did not alter viability or function in MC3T3-E1 pre-osteoblast, primary human osteoblast, or MLO-Y4 osteocyte assays. In the clinical trial analysis, reducing serum urate over a 12 month period by allopurinol dose escalation did not lead to significant changes in P1NP or differences in bone mineral density.

Addition of soluble urate at physiological concentrations does not influence bone remodelling in vitro. These data, together with clinical trial data showing no effect of urate-lowering on P1NP or bone density, do not support a direct role for urate in influencing bone remodelling.

Objective: To investigate the effect of malnutrition during pregnancy on bone development in rat pups with intrauterine growth restriction (IUGR). Methods: IUGR offspring were induced with a 10% low protein diet, while the control group was given a 21% protein diet during pregnancy. Serum biomarkers including bone glutamyl protein (BGP), amino-terminal propeptide of type 1 procollagen (P1NP), cross linked N-telopeptide of type I collagen (NTX), and insulin like growth factor 1 (IGF-1) levels were measured at 7, 21 and 56 d. Left femurs taken at 56 d were used for bone histomorphometry analysis by micro-computed tomography (micro-CT). Results: Compared with the control group, the IUGR group had lower IGF-1 and BGP levels at 7 and 21 d, and higher P1NP and NTX levels at 7 d. The IUGR group had thinner trabecular thickness (Tb.Th), lower trabecular number (Tb.N), and increased trabecular separation (Tb.Sp) at 56 d. Conclusion: The effect of IUGR on bone development may persist after birth.

Phenylalanine hydroxylase (PAH) deficiency is a genetic disorder characterized by deficiency of the PAH enzyme. Patients follow a phenylalanine-restricted diet low in intact protein, and must consume synthetic medical food (MF) to supply phenylalanine-free protein. We assessed relationships between dietary intake and nutrient source (food or MF) on bone mineral density (BMD) and bone turnover markers (BTM) in PAH deficiency. Blood from 44 fasted females 11-52 years of age was analyzed for plasma phenylalanine, serum BTM [CTx (resorption), P1NP (formation)], vitamin D, and parathyroid hormone (PTH). BTM ratios were calculated to assess resorption relative to formation (CTx/P1NP). Dual energy X-ray absorptiometry measured total BMD and age-matched Z-scores. Three-day food records were analyzed for total nutrient intake, nutrients by source (food, MF), and compliance with MF prescription. Spearman's partial coefficients (adjusted for age, BMI, energy intake, blood phenylalanine) assessed correlations. All had normal BMD for age (Z-score>>-2). Sixty-four percent had high resorption and normal formation indicating uncoupled bone turnover. CTx/P1NP was positively associated with food phenylalanine (r 2 = 0.39; p-value = 0.017), energy (r 2 = 0.41; p-value = 0.011) and zinc (r 2 = 0.41; p-value = 0.014). CTx/P1NP was negatively associated with MF fat (r 2 = -0.44; p-value = 0.008), MF compliance (r 2 = -0.34; p-value = 0.056), and positively with food sodium (r 2 = 0.43; p-value = 0.014). CTx/P1NP decreased significantly with age (p-value = 0.002) and higher PTH (p-value = 0.0002). Phenylalanine was not correlated with any bone indicator. Females with PAH deficiency had normal BMD but elevated BTM, particularly resorption. More favorable ratios were associated with nutrients from MF and compliance. Younger females had less favorable BTM ratios. Promoting micronutrient intake through compliance with MF may impact bone metabolism in patients with PAH deficiency.

CONCLUSIONS

Bone mineral density was normal in 44 females with PAH deficiency; however, bone turnover markers suggested uncoupling of bone resorption and formation, particularly in younger patients. Adequate nutrient intake from medical food and overall medical food compliance may positively impact bone turnover.

Bones have been suggested to be a target for glucagon-like peptide -1 (GLP-1); however, studies of the effects on human bones so far have given diverging results. We hypothesized that GLP-1, together with glucagon-like peptide-2 and glucose-dependent insulinotropic polypeptide, plays a role in the gut-bone axis. We examined the acute effect of three GLP-1 receptor ligands [GLP-1 (7-36)amide, GLP-1 (9-36)amide, and exenatide] on markers of bone remodeling. Eight healthy, normal-weight participants, with a mean age of 24.3 years, were studied for 4 days in a double-blinded, randomized clinical trial. Blood was collected before and after s.c. injection of GLP-1 (7-36)amide (1.5 nmol/kg), GLP-1 (9-36)amide (1.5 nmol/kg), exenatide (2.4 nmol/subject), or saline. Plasma was analyzed for bone markers and for osteoprotegerin (OPG), PTH, and IGF-1 levels. All ligands were tested in vitro for their cAMP-inducing activity on the human GLP-1 receptor. GLP-1 (7-36)amide decreased CTX-levels, compared with placebo (area under the curve [AUC] ±SD 0 to 120 min = -2143 ± 1294 % × min versus -883 ± 1557 % × min; p < 0.05). No difference was observed between placebo and GLP-1 (9-36)amide, or between placebo and exenatide, although exenatide had a similar potency as GLP-1 (7-36)amide for cAMP formation in vitro (EC₅₀ of 0.093 and 0.054 nmol/L). However, exenatide reached maximum plasma concentration at 90 min versus 15 min for GLP-1 (7-36)amide, and plasma CTX was significantly decreased during the second hour of the study after exenatide injections compared with placebo (AUC ±SD -463.1 ± 218 % × min and -136 ± 91 % × min; p < 0.05). There was no effect of the injections on bone formation markers (P1NP and osteocalcin) or on OPG, PTH and IGF-1 levels. In conclusion, we show that GLP-1 receptor agonists, but not the primary metabolite GLP-1 (9-36)amide, decrease bone resorption, and suggest that GLP-1 may be part of the gut-bone axis. © 2019 The Authors. JBMR Plus is published by Wiley Periodicals, Inc. on behalf of the American Society for Bone and Mineral Research.

Purpose/Introduction: Osteoporosis (OP) and cardiovascular (CV) disease emerge as closely related conditions, showing common risk factors and/or pathophysiological mechanisms. The aim of this study was to evaluate the association between bone health markers (BHM) and individual CV risk factors and overall CV risk (FRAMINGHAM-FRS, and PROCAM scores) in a general adult population.

METHODS

In 103 subjects (21 males; age: 56 ± 12 years), vitamin D (25(OH)D), osteocalcin (OC), bone alkaline phospatase (BALP), procollagen I aminoterminal propeptide (P1NP), CTx-telopeptide, as well clinical history and life style were evaluated.

RESULTS

Aging (p < 0.001) and glycemia (p < 0.05) emerged as independent 25(OH)D predictors. Aging (p < 0.001), male sex (p < 0.05), and obesity (p < 0.05) represented independent OC determinants. Aging (p < 0.05) was the only independent BALP determinant. After multivariate adjustment, low 25(OH)D (<20 ng/mL) (Odds ratio OR (95% confidence intervals CI)) (5 (1.4-18) p < 0.05) and elevated OC (>75th percentile-16.6 ng/mL) (6.7 (1.9-23.8) p < 0.01) were found to be significant FRS predictors, while subjects with elevated OC and/or BALP (>75th percentile-9.8 μg/L) showed a higher CV risk as estimated by PROCAM (3.6 (1.2-10.7) p < 0.05). CTx and P1NP did not significantly correlate with CV risk factors or scores.

CONCLUSIONS

As we go further into bone and CV physiology, it is evident that a close relationship exists between these diseases. Further studies are needed to investigate mechanisms by which bone turnover markers are related to metabolic risk and could modulate CV risk. This knowledge may help to develop possible multiple-purpose strategies for both CV disease and OP prevention and treatment.

The biochemical bone formation marker aminoterminal type 1 procollagen propeptide (total P1NP) was determined in 91 serum samples from healthy male donors aged 19 to 60 years, by using an "Elecsys Total P1NP" kit of reagents ("Roche-Diagnostics", Germany) on an "Elecsys 2010" electric chemiluminescence analyzer ("Roche-Hitachi", Japan). A relationship was found between the serum concentration of total P1NP and the age of the examined males. At the age of 19-20 years, the content of the propeptide is highest, at the age of 21-24 years, it decreased by 1.5-2 times, by the age of 30 years, there is its moderate decrease, which is then followed by its stabilization. The detected age-related changes reflect accelerated bone metabolism in young males during formation of the bone mass peak. The findings may be used as references in measuring male total P1NP on Elecsys automatic analyzers.

OBJECTIVE

The aim of this study was to characterize the mesenchymal stromal cells (MSCs) and endothelial progenitor cells (EPCs) mobilization, and bone turnover in osteoporotic fracture healing in ovariectomized mice.

METHODS

In total, 112 female C57/BL mice were divided into two groups. The first group was sham-operated (SO), and the other group was ovariectomized (OVX). After three weeks, the right femora of the mice were fractured under anesthesia and internally fixed with steel pin. Peripheral blood and bone marrow were was collected for flow cytometry analysis, at 0 hours (h), 12 h, 24 h, 72 h and 168 h after fracture. MSCs and EPCs levels were assessed using cell surface antigens in different combinations (CD44+ CD34-CD45-, and CD34+ KDR+CD45-) by flow cytometry. At 0, 14, 28 and 42 days after fracture, sera were assayed for circulating levels of procollagen type I-N-terminal propeptide (P1NP) and C-terminal telopeptide of type I-collagen (CTX) by ELISA. Femurs were harvested at 2 weeks and 6 weeks after fracture for X-ray radiography, micro-computed tomography (micro-CT) and histology.

RESULTS

Our results showed that bone marrow and peripheral blood MSCs numbers of the OVX mice were significantly lower than the SO mice, at 12 h, 24 h and 72 h after fracture. In addition, circulating P1NP and CTX levels of the OVX mice were significantly higher than the SO mice, at 2 and 4 weeks.

CONCLUSIONS

Results of the present study revealed disorders of bone marrow MSCs mobilization and bone turnover may partially account for the delay of osteoporotic fracture healing.

In the original publication of the article, the last row of Table 1 was published incorrectly as "Serum P1NP (μmol/L), median (IQR)^b : Romosozumab, 25 (18, 34); Teriparatide, 25 (20, 33)". The correct row should be read as "Serum P1NP (μg/L), median (IQR)^b : Romosozumab, 25 (18, 34); Teriparatide, 25 (20, 33)".

Elevated urine net acid excretion (NAE), indicative of subclinical metabolic acidosis, has been associated with higher bone turnover. Urine citrate, which is a common clinical measure, changes in response to acid-base status but its association with bone turnover is uncertain.

We evaluated the association between change in urine citrate and change in bone turnover and calcium excretion.

A total of 233 healthy men and women ≥60 years old were randomly assigned to 1.0 mmol/kg/d potassium bicarbonate (KHCO3), 1.5 mmol/kg/d KHCO3, or placebo for 84 days.

Urine citrate, NAE, N-telopeptide of collagen type-I (NTX), calcium excretion, and serum amino-terminal propeptide of type 1 procollagen (P1NP) were measured before and after intervention.

Urine citrate increased dose dependently after KHCO3 supplementation (P trend < 0.001). The urine citrate change was significantly inversely associated with P1NP change (P = 0.021) but not with change in NTX (P = 0.051) or calcium excretion (P = 0.652). The NAE change was positively associated with change in NTX and calcium excretion (P ≤ 0.003) but not with change in P1NP (P = 0.051). When the urine citrate change and NAE change were included in the same model, the urine citrate change was not associated with change in NTX, calcium excretion, or serum P1NP (P ≥ 0.086), whereas change in NAE remained associated with change in NTX and calcium excretion (P ≤ 0.003).

Urine citrate may not be a suitable alternative to NAE when assessing acid-base status in relation to bone turnover in older adults.

As the most common metabolic bone disease worldwide, osteoporosis and its associated morbidities have garnered significant attention as a public health concern and economic burden. The condition is characterized by progressive loss of bone mass and destruction of bone microarchitecture, both of which are independent risk factors for skeletal fragility and fracture. The primary goal of managing osteoporosis is the prevention of these fractures, termed fragility or low-trauma fractures, as they are the disease’s main source of morbidity and mortality. Consequently, the primary goal of osteoporosis management is fracture prevention, with early diagnosis being crucial. Unfortunately, osteoporosis is commonly indetectable clinically before a fracture event, and early indicators of disease are difficult to assess radiographically. This highlights the need for methods that allow early detection of loss of bone integrity to mitigate further disease progress and subsequent fracture. The pathogenesis of osteoporosis stems from detrimental alterations in the homeostasis of bone turnover, leading to decreased bone strength by loss of mass and quality. There are multiple known mechanisms capable of causing such derangement of the balance between bone breakdown and formation and are dependent on the individual risk factors of each patient, such as low estrogen state, advanced age, long term corticosteroid use or other disease states such as systemic inflammation, thyroid, and parathyroid disease. The most commonly utilized method for identifying osteoporosis is through T-score determination, a quantified measure of bone marrow density (BMD) using dual-energy x-ray absorptiometry (DXA). A BMD, represented by T-score, of the spine or hip greater than or equal to 2.5 standard deviations below the average for that of healthy young women is considered diagnostic. BMD values are also used to determine and monitor management, in addition to establishing fracture risk, despite profuse data showing that the majority of patients experiencing fragility fractures do not have a T-score indicating osteoporotic bone density. As a result, it is recognized that BMD is insufficient as a sole means for comprehensively evaluating bone strength. Moreover, BMD is not particularly useful as a singular surveillance tool of treatment response, as changes in density may be slow or minimal. This is particularly apparent within the first year of treatment, where serial DEXA scans are ineffective at detecting BMD change. Due to the limitations of BMD, researchers have explored other possible tools to support osteoporosis management, with bone turnover markers being a topic of particular interest. Bone turnover biomarkers (BTMs) are byproducts produced from the bone remodeling process that can be measured in urine or serum and are indicative of the rate of bone turnover. BTMs are classified as either markers of bone formation such as total alkaline phosphatase (total ALP, bone-specific alkaline phosphatase (B-ALP), procollagen type 1 N-terminal propeptide (P1NP), osteocalcin (O), and procollagen type 1 C-terminal propeptide (P1CP), or as markers of bone resorption such as hydroxyproline (HYP), pyridinoline, tartrate-resistant acid phosphatase 5b (TRAP 5b), deoxypyridinoline (DPD), carboxy-terminal cross-linked telopeptide of type 1 collagen (CTX-1), and amino-terminal cross-linked telopeptide of type 1 collagen (NTX-1). There is limited specificity with these markers, as BTMs are reflective of the rate of bone turnover in general. However, unlike DXA measurements, BTM levels show appreciable, rapid response to changes in turnover rate, making them of great use clinically for monitoring treatment response and adherence in osteoporotic patients from the onset of treatment initiation. Although all BTMs can shift in response to osteoporotic disease processes, the International Osteoporosis Foundation (IOF) and International Federation of Clinical Chemistry (IFCC) have recommended serum P1NP and CTX-1 as bone formation and resorption reference markers, respectively, for use in fracture risk prediction and monitoring of osteoporosis treatment. Studies looking at BTMs in various cohorts have shown that elevated markers are associated with increased bone turnover, which increases the deterioration of bone quality and, thus, the risk of fragility fracture. This correlation shows promise in osteoporosis management, where bone turnover biomarkers (BTMs) have already proved to be of clinical use as adjuvant tools for fragility fracture risk stratification and treatment response, as well as adherence monitoring. However, there is currently insufficient evidence to establish their ability to fulfill these roles without the concomitant assessment of BMD with DXA, nor their use as an independent diagnostic tool. As such, more research is needed to establish their utility, as well as how to adjust for the multiple physiological and pathological factors that can influence levels.

Daily assumption of antiretroviral drugs and HIV-related immune activation lead to important side effects, which are particularly evident in vertically infected patients. Bone homeostasis impairment and reduction of bone mineral density (BMD) is one of the most important side effects. Primary aim of this study is to assess the prevalence of bone homeostasis alterations in a group of vertically infected patients; secondary aim is to analyze the relationship between bone homeostasis alterations and anthropometric data, severity of HIV infection, and antiretroviral therapy. We studied 67 patients with vertically transmitted HIV-1 (aged 6-31 years), followed by the Pediatric Infectious Disease Unit of the University Hospital of Padua, Italy. We analyzed bone turnover markers (P1NP and CTx) and we performed lumbar spine and femoral dual energy X-ray absorption densitometry (DXA). Personal and anthropometric data and information on HIV-infection severity and antiretroviral therapy were collected for all patients. We found that BMD values recorded by DXA showed a significant correlation with age, race, BMI, physical activity, and antiretroviral therapy duration. P1NP was increased in 43% of patients, while CTX in 61% of them. P1NP alteration was related to age, race, BMI, physical activity, therapy duration, and ever use of protease inhibitors and nucleotide reverse transcriptase inhibitors. CTX alteration was found to be correlated only with age. In conclusion, our study confirms that a wide percentage of HIV vertically infected patients show reduced BMD and impaired bone homeostasis. Strict monitoring is needed in order to early identify and treat these conditions.

CONCLUSIONS

Inhibition of sympathetic signaling to bone reduces bone resorption in rodents. In contrast, we show that pharmacological reduction of the sympathetic tone increases bone resorption in humans in vivo. This effect does not appear to be mediated via a direct pharmacological effect on the osteoclast.

BACKGROUND

Inhibition of sympathetic signaling to bone reduces bone resorption in rodents. It is uncertain whether a similar role for the sympathetic nervous system exists in humans. The sympathetic tone can be reduced by clonidine, which acts via alpha-2-adrenergic receptors in the brainstem. Our objective was to determine the effect of clonidine on bone turnover in humans.

METHODS

The acute effect of a single oral dose of 0.3 mg clonidine on serum bone turnover markers (C-terminal cross-linking telopeptides of collagen type I (CTx), a marker for bone resorption, and procollagen type 1 N propeptide (P1NP), a marker for bone formation) was determined in a randomized crossover design in 12 healthy volunteers, aged 18-70 years. In addition, we assessed the effect of clonidine on the number of tartrate-resistant acid phosphatase-positive multinucleated cells (TRAcP(+) MNCs) and bone resorption.

RESULTS

CTx concentrations increased after clonidine treatment compared to the control condition (p = 0.035). P1NP concentrations were not affected by clonidine (p = 0.520). In vitro, clonidine had no effect on the number of TRAcP(+) MNCs (p = 0.513) or on bone resorption (p = 0.996).

CONCLUSIONS

We demonstrated that clonidine increases bone resorption in humans in vivo. This effect does not appear to be mediated via a direct effect on the osteoclast.

Paget's disease of bone (PDB) is a chronic disorder characterized by localized bone regions with excessive bone turnover. Although oral risedronate (17.5 mg daily for 8 weeks) was recently approved in Japan, its efficacy is not well understood. We retrospectively examined the efficacy of oral risedronate in PDB patients in a clinical setting. Eleven patients whose serum alkaline phosphatase (ALP) level exceeded the upper limit of the normal range were treated. Patients whose ALP levels normalized and remained so for 12 months after therapy initiation were defined as responders. Treatment was repeated if bone pain recurred or if serum ALP levels increased at least 25% above the nadir. Six patients (55%) were responsive to the therapy. A higher prevalence of skull lesions, higher serum calcium levels at treatment initiation and antecedent treatments of bisphosphonates were predictors of resistance against the therapy. Fresh frozen serum samples obtained from some treatment sessions were evaluated for metabolic bone markers such as bone-specific ALP (BAP), type I procollagen N-terminal pro-peptide (PINP), N-treminal crosslinking telopeptide of type I collagen and C-treminal crosslinking telopeptide of type I collagen (CTX). A significant reduction of P1NP preceded that of serum ALP levels in the responders, which was followed by a similar occurrence for BAP and osteocalcin (BGP) levels. A temporary decrease in CTX levels was noted. No significant changes in markers (including ALP level) were observed in non-responder and repeat-treatment groups. P1NP levels may be more useful than ALP levels in assessing treatment efficacy. Repeat treatment effectiveness for the repeat-treatment group was limited.

Introduction: We previously found lower bone mass but similar bone turnover in pre-pubertal children living with HIV (CLWH) on a ritonavir-boosted lopinavir (LPV/r)-based vs. efavirenz-based antiretroviral therapy regimen 2 years after switch. Here, we evaluate if bone turnover differed between the groups close to the time of switch.

Methods: Samples from 108 children remaining on LPV/r and 104 children switched to efavirenz were available for analysis 8 weeks post-randomization. Bone turnover markers, including C-telopeptide of type 1 collagen (CTx), procollagen type-I N-terminal propeptide (P1NP), and osteocalcin were measured. Markers of immune activation were also measured, including IL-6, TNF-alpha, soluble CD14 and high-sensitivity C-reactive protein (CRP).

Results: Eight weeks post-randomization, we did not detect differences in CTx (1.42 vs. 1.44 ng/mL, p = 0.85) or P1NP concentrations (622 vs. 513 ng/mL, p = 0.68) between treatment groups. At 8 weeks, the treatment groups also had similar levels of IL-6, TNF-alpha, soluble CD14 and high-sensitivity CRP. Osteocalcin (ng/mL) was higher in the LPV/r than efavirenz group both at 8 weeks (88.6 vs. 67.3, p = 0.001) and 2 years (67.6 vs. 49.8, p = 0.001).

Conclusions: Overall, we failed to detect difference in bone turnover by P1NP and CTx in virologically-suppressed CLWH on different regimens at a time point close to the switch. We did observe higher levels of total osteocalcin in children remaining on LPV/r compared to children switched to efavirenz. Future studies should focus on uncovering the mechanism and determining whether perturbation in undercarboxylated osteocalcin could explain some of the bone side effects noted with protease inhibitors.

Keywords: Bone; Bone turnover markers; Osteocalcin; Protease inhibitors.

Widely distributed osteosclerosis is an unusual radiographic finding with multiple causes. A 42-year-old premenopausal Spanish woman gradually acquired dense bone diffusely affecting her axial skeleton and focally affecting her proximal long bones. Systemic lupus erythematosus (SLE) diagnosed in adolescence had been well controlled. She had not fractured or received antiresorptive therapy, and she was hepatitis C virus antibody negative. Family members had low bone mass. Lumbar spine bone mineral density (BMD) measured by dual-photon absorptiometry (DPA) at age 17 years, while receiving glucocorticoids, was 79% the average value of age-matched controls. From ages 30 to 37 years, dual-energy X-ray absorptiometry (DXA) BMD Z-scores steadily increased in her lumbar spine from +3.8 to +7.9, and in her femoral neck from -1.4 to -0.7. Serum calcium and phosphorus levels were consistently normal, 25-hydroxyvitamin D (25OHD) <20 ng/mL, and parathyroid hormone (PTH) sometimes slightly increased. Her reduced estimated glomerular filtration rate (eGFR) was 38 to 55 mL/min. Hypocalciuria likely reflected positive mineral balance. During increasing BMD, turnover markers (serum bone-specific alkaline phosphatase [ALP], procollagen type 1 N propeptide [P1NP], osteocalcin [OCN], and carboxy-terminal cross-linking telopeptide of type 1 collagen [CTx], and urinary amino-terminal cross-linking telopeptide of type 1 collagen [NTx and CTx]) were 1.6- to 2.8-fold above the reference limits. Those of bone formation seemed increased more than those of resorption. FGF-23 was slightly elevated, perhaps from kidney disease. Serum osteoprotegerin (OPG) and TGFβ1 levels were normal, but sclerostin (SOST) and receptor activator of nuclear factor kappa-B ligand (RANKL) were elevated. Serum multiplex biomarker profiling confirmed a high level of SOST and RANKL, whereas Dickkopf-1 (DKK-1) seemed low. Matrix metalloproteinases-3 (MMP-3) and -7 (MMP-7) were elevated. Iliac crest biopsy revealed tetracycline labels, no distinction between thick trabeculae and cortical bone, absence of peritrabecular fibrosis, few osteoclasts, and no mastocytosis. Then, for the past 3 years, BMD Z-scores steadily decreased. Skeletal fluorosis, mastocytosis, myelofibrosis, hepatitis C-associated osteosclerosis, multiple myeloma, and aberrant phosphate homeostasis did not explain her osteosclerosis. Mutation analysis of the LRP5, LRP4, SOST, and osteopetrosis genes was negative. Microarray showed no notable copy number variation. Perhaps her osteosclerosis reflected an interval of autoimmune-mediated resistance to SOST and/or RANKL. © 2016 American Society for Bone and Mineral Research.