The bone remodelling process, performed by the Bone Multicellular Unit (BMU) is a key multi-hierarchically regulated process, which provides and supports various functionality of bone tissue. It is also plays a critical role in bone disorders, as well as bone tissue healing following damage. Improved modelling of bone turnover processes could play a significant role in helping to understand the underlying cause of bone disorders and thus develop more effective treatment methods. Moreover, despite extensive research in the field of bone tissue engineering, bonescaffold development is still very empirical. The development of improved methods of modelling the bone remodelling process should help to develop new implant designs which encourage rapid osteointegration. There are a number of limitations with respect to previous research in the field of mathematical modelling of the bone remodelling process, including the absence of an osteocyte loop of regulation. It is within this context that this research presented in this thesis utilises a range of modelling methods to develop a framework for bone remodelling which can be used to improve treatment methods for bone disorders. The study concentrated on dynamic and steady state variables that in perspective can be used as constraints for optimisation problem considering bone remodelling or tissue remodelling with the help of the grafts/scaffolds.The cellular and combined allosteric-regulation approaches to modelling of bone turnover, based on the osteocyte loop of regulation, have been studied. Both approaches have been studied different within wide range of rate parameters. The approach to the model validation has been considered, including a statistical approach and parameter reduction approach. From a validation perspective the cellular class of modes is preferable since it has fewer parameters to validate. The optimal control framework for regulation of remodelling has been studied. Future work in to improve the models and their application to bone scaffold design applications have been considered. The study illustrates the complexity of formalisation of the metabolic processes and the relations between hierarchical subsystems in hard tissue where a relatively small number of cells are active. Different types/modes of behaviour have been found in the study: relaxational, periodical and chaotic modes. All of these types of behaviour can be found, in bone tissue. However, a chaotic or periodic modes are ones of the hardest to verify although a number of periodical phenomena have been observed empirically in bone and skeletal development. Implementation of the allosteric loop into cellular model damps other types of behaviour/modes. In this sense it improves the robustness, predictability and control of the system. The developed models represent a first step in a hierarchical model of bone tissue (system versus local effects). The limited autonomy of any organ or tissue implies differentiation on a regulatory level as well as physiological functions and metabolic differences. Implementation into the cellular phenomenological model of allosteric-like loop of regulation has been performed. The results show that the robustness of regulation can be inherited from the phenomenological model. An attempt to correlate the main bone disorders with different modes of behaviour has been undertaken using Paget’s disorder in bone, osteoporosis and some more general skeleton disorders which lead to periodical changes in bone mass, reported by some authors. However, additional studies are needed to make this hypothesis significant. The study has revealed a few interesting techniques. When studying a multidimensional phenomenon, as a bone tissue is, the visualisation and data reduction is important for analysis and interpretation of results. In the study two novel technical methods have been proposed. The first is the graphical matrix method to visualise/project the multidimensional phase space of variables into diagonal matrix of regular combination of two-dimensional graphs. This significantly simplifies the analysis and, in principle, makes it possible to visualise the phase space higher than three-dimensional. The second important technical development is the application of the Monte-Carlo method in combination with the regression method to study the character and stability of the equilibrium points of a dynamic system. The advantage of this method is that it enables the most influential parameters that affect the character and stability of the equilibrium point to be identified from a large number of the rate parameters/constants of the dynamic system. This makes the interpretation of parameters and conceptual verification of the model much easier.

No description available.

Tenofovir disoproxil fumarate (TDF) is a nucleotide reverse transcriptase inhibitor and a prodrug of tenofovir (TFV). It is the currently recommended first line combination treatment of human immunodeficiency virus (HIV) infection in adults. Various clinical studies have associated treatment with a TDF-containing antiretroviral therapy (ART) regimen with reduced bone mineral density (BMD) and renal dysfunction. Hardly any studies to date have correlated plasma TFV concentration with markers of renal function and bone turnover (BTM). This knowledge is also unavailable in the South African public health care system. Hence, the correlations between plasma TFV concentration and renal function markers and BTM in HIV-infected women were investigated. Renal function markers and BTM in HIV-infected women were compared with those in HIV-uninfected control women. A pilot cross-sectional sub-study within the Prospective Urban and Rural Epidemiology (PURE) South Africa study was conducted. Sixty women participated, of which 30 HIV-infected women were matched for age and body mass index with 30 HIV-uninfected ones. Ethics approval was obtained from the North-West University, Human Research Ethics committee (NWU-00016-10-A1) on 12 April 2013 to conduct this sub-study and the North West Department of Health, Mmabatho on 08 August 2013 to access patient health information. A validated high-performance liquid chromatography tandem mass spectrometry method was developed to analyse TFV in plasma. Renal markers measured were the estimated glomerular filtration rate (eGFR), creatinine clearance (CrCl), albuminuria, serum creatinine (SCr), serum urea, serum uric acid, glucosuria, urine sodium (UNa) and maximum tubular reabsorption of phosphate (TmPO4/GFR). The BTM markers measured included C-terminal telopeptide (CTx), alkaline phosphatase (ALP), parathyroid hormone (PTH), total vitamin D (VitD), serum calcium (SrCa), serum phosphate (SrP) and BMD. BMD was assessed using the DTX-200 peripheral DXA system (Osteometer MediTech, Hawthorn, California, USA). Renal and bone markers were analysed on Elecsys® 2010 and COBAS INTERGRA® 400 plus (Roche Diagnostics, Switzerland). Baseline data for HIV-infected participants with regard to CD4+ cell count, SCr prior to TDF initiation, time since TDF initiation, weight prior to TDF initiation and time since HIV diagnosis were collected retrospectively from participants’ public health care files. Statistical analyses applied were linear regression, analysis of covariance, the Mann-Whitney U test, paired t-test and unpaired t-test. IBM® SPSS® Statistics software 22 was used to perform all the statistical analyses. The median and interquartile range of plasma TFV concentration was 113 (74-139.4) ng/mL (n=25) and no TFV was detected in five participants’ plasma. Adjusted analyses showed TFV concentration to be associated with albuminuria (adjusted r2 = 0.339; p = 0.001). Values of CrCl, eGFR and albuminuria (p = 0.032; p = 0.038; p = 0.048, respectively) were significantly higher in HIV-infected women compared to HIV-uninfected women. CrCl [112 (84-137) mL/min] and eGFR [134 (93-153) mL/min/1.73m2] values were abnormally high in HIV-infected women. There was also an increase in both CrCl and eGFR (p = 0.008; p < 0.001, respectively) from baseline to median follow-up of 16.6 (8.8-23.4) months in HIV-infected women. At a TFV plasma concentration of ≥ 120 ng/mL, CTx and ALP correlated positively (r = 0.704; p = 0.016). ALP (112 ± 28 U/L; p < 0.001), CTx (0.68 ± 0.4 ng/mL; p = 0.027) and PTH (56.3 ± 32 pg/mL; p = 0.050) were higher in HIV-infected women compared to HIV-uninfected women. CD4+ cell count increased from baseline to follow-up in HIV-infected women (+250 cells/mm3; p = 0.001). In HIV-infected women on a TDF-based regimen, TFV plasma concentration is associated with an increase in albuminuria, while perturbations in BTM equilibrium occur at ≥ 120 ng/mL of TFV plasma concentration. Abnormally higher CrCl and eGFR are present in HIV-infected women, seen as glomerular hyperfiltration compared with HIV-uninfected women. There was immunological improvement with TDF-based ART in HIV-infected women. Longitudinal studies with larger sample sizes are needed to confirm these findings. / MSc (Pharmacology), North-West University, Potchefstroom Campus, 2015

Tenofovir disoproxil fumarate (TDF) is a nucleotide reverse transcriptase inhibitor and a prodrug of tenofovir (TFV). It is the currently recommended first line combination treatment of human immunodeficiency virus (HIV) infection in adults. Various clinical studies have associated treatment with a TDF-containing antiretroviral therapy (ART) regimen with reduced bone mineral density (BMD) and renal dysfunction. Hardly any studies to date have correlated plasma TFV concentration with markers of renal function and bone turnover (BTM). This knowledge is also unavailable in the South African public health care system. Hence, the correlations between plasma TFV concentration and renal function markers and BTM in HIV-infected women were investigated. Renal function markers and BTM in HIV-infected women were compared with those in HIV-uninfected control women. A pilot cross-sectional sub-study within the Prospective Urban and Rural Epidemiology (PURE) South Africa study was conducted. Sixty women participated, of which 30 HIV-infected women were matched for age and body mass index with 30 HIV-uninfected ones. Ethics approval was obtained from the North-West University, Human Research Ethics committee (NWU-00016-10-A1) on 12 April 2013 to conduct this sub-study and the North West Department of Health, Mmabatho on 08 August 2013 to access patient health information. A validated high-performance liquid chromatography tandem mass spectrometry method was developed to analyse TFV in plasma. Renal markers measured were the estimated glomerular filtration rate (eGFR), creatinine clearance (CrCl), albuminuria, serum creatinine (SCr), serum urea, serum uric acid, glucosuria, urine sodium (UNa) and maximum tubular reabsorption of phosphate (TmPO4/GFR). The BTM markers measured included C-terminal telopeptide (CTx), alkaline phosphatase (ALP), parathyroid hormone (PTH), total vitamin D (VitD), serum calcium (SrCa), serum phosphate (SrP) and BMD. BMD was assessed using the DTX-200 peripheral DXA system (Osteometer MediTech, Hawthorn, California, USA). Renal and bone markers were analysed on Elecsys® 2010 and COBAS INTERGRA® 400 plus (Roche Diagnostics, Switzerland). Baseline data for HIV-infected participants with regard to CD4+ cell count, SCr prior to TDF initiation, time since TDF initiation, weight prior to TDF initiation and time since HIV diagnosis were collected retrospectively from participants’ public health care files. Statistical analyses applied were linear regression, analysis of covariance, the Mann-Whitney U test, paired t-test and unpaired t-test. IBM® SPSS® Statistics software 22 was used to perform all the statistical analyses. The median and interquartile range of plasma TFV concentration was 113 (74-139.4) ng/mL (n=25) and no TFV was detected in five participants’ plasma. Adjusted analyses showed TFV concentration to be associated with albuminuria (adjusted r2 = 0.339; p = 0.001). Values of CrCl, eGFR and albuminuria (p = 0.032; p = 0.038; p = 0.048, respectively) were significantly higher in HIV-infected women compared to HIV-uninfected women. CrCl [112 (84-137) mL/min] and eGFR [134 (93-153) mL/min/1.73m2] values were abnormally high in HIV-infected women. There was also an increase in both CrCl and eGFR (p = 0.008; p < 0.001, respectively) from baseline to median follow-up of 16.6 (8.8-23.4) months in HIV-infected women. At a TFV plasma concentration of ≥ 120 ng/mL, CTx and ALP correlated positively (r = 0.704; p = 0.016). ALP (112 ± 28 U/L; p < 0.001), CTx (0.68 ± 0.4 ng/mL; p = 0.027) and PTH (56.3 ± 32 pg/mL; p = 0.050) were higher in HIV-infected women compared to HIV-uninfected women. CD4+ cell count increased from baseline to follow-up in HIV-infected women (+250 cells/mm3; p = 0.001). In HIV-infected women on a TDF-based regimen, TFV plasma concentration is associated with an increase in albuminuria, while perturbations in BTM equilibrium occur at ≥ 120 ng/mL of TFV plasma concentration. Abnormally higher CrCl and eGFR are present in HIV-infected women, seen as glomerular hyperfiltration compared with HIV-uninfected women. There was immunological improvement with TDF-based ART in HIV-infected women. Longitudinal studies with larger sample sizes are needed to confirm these findings. / MSc (Pharmacology), North-West University, Potchefstroom Campus, 2015

Lycopene is a potent carotenoid antioxidant shown to decrease the risk of chronic diseases associated with oxidative stress and has recently begun to be studied in relation to osteoporosis. However, studies specifically associating intervention with lycopene and a decreased risk for osteoporosis have not yet been conducted, and the mechanisms by which lycopene affects bone have yet to be elucidated. The purpose of this thesis was to explore the hypotheses that supplementation with lycopene would increase antioxidant capacity while decreasing oxidative stress parameters; subsequently decreasing bone turnover markers, and thus the risk of osteoporosis in postmenopausal women. Specifically, experiments were designed to determine whether lycopene acts in its antioxidant capacity to improve bone health, and to delineate the mechanisms of these effects. These hypotheses were investigated through a cross-sectional study, a randomized controlled clinical study, and in vitro studies on human osteoblast cells. The results presented in this thesis demonstrate that intervention with the potent antioxidant lycopene significantly increased concentrations of the 5-cis isomer and resulted in significantly decreased oxidative stress parameters in postmenopausal women. This decrease in oxidative stress parameters resulted in significantly decreased concentrations of the bone resorption marker crosslinked N-telopeptides of type I collagen (NTx). The typical diet of participants included a relatively low intake of lycopene, and the corresponding serum lycopene concentrations were not as effective in decreasing biomarkers of oxidative stress and bone resorption as those obtained from supplementation with lycopene to increase 5-cis serum lycopene. Studies on the paraoxonase enzyme suggest that lycopene is most effective in quenching oxidative stress to decrease bone turnover markers when the internal antioxidant defenses are insufficient or decremented. Mechanisms demonstrated by the in vitro findings suggest that cis lycopene is capable of both preventing and repairing the damaging effects of oxidative stress in osteoblasts. Overall, this thesis provides evidence that lycopene acts through its antioxidant capacity to decrease oxidative stress parameters and bone turnover markers, and may, therefore, reduce the risk for osteoporosis. Based on these findings, the consumption of lycopene by women to improve overall bone health should be considered.

Lycopene is a potent carotenoid antioxidant shown to decrease the risk of chronic diseases associated with oxidative stress and has recently begun to be studied in relation to osteoporosis. However, studies specifically associating intervention with lycopene and a decreased risk for osteoporosis have not yet been conducted, and the mechanisms by which lycopene affects bone have yet to be elucidated. The purpose of this thesis was to explore the hypotheses that supplementation with lycopene would increase antioxidant capacity while decreasing oxidative stress parameters; subsequently decreasing bone turnover markers, and thus the risk of osteoporosis in postmenopausal women. Specifically, experiments were designed to determine whether lycopene acts in its antioxidant capacity to improve bone health, and to delineate the mechanisms of these effects. These hypotheses were investigated through a cross-sectional study, a randomized controlled clinical study, and in vitro studies on human osteoblast cells. The results presented in this thesis demonstrate that intervention with the potent antioxidant lycopene significantly increased concentrations of the 5-cis isomer and resulted in significantly decreased oxidative stress parameters in postmenopausal women. This decrease in oxidative stress parameters resulted in significantly decreased concentrations of the bone resorption marker crosslinked N-telopeptides of type I collagen (NTx). The typical diet of participants included a relatively low intake of lycopene, and the corresponding serum lycopene concentrations were not as effective in decreasing biomarkers of oxidative stress and bone resorption as those obtained from supplementation with lycopene to increase 5-cis serum lycopene. Studies on the paraoxonase enzyme suggest that lycopene is most effective in quenching oxidative stress to decrease bone turnover markers when the internal antioxidant defenses are insufficient or decremented. Mechanisms demonstrated by the in vitro findings suggest that cis lycopene is capable of both preventing and repairing the damaging effects of oxidative stress in osteoblasts. Overall, this thesis provides evidence that lycopene acts through its antioxidant capacity to decrease oxidative stress parameters and bone turnover markers, and may, therefore, reduce the risk for osteoporosis. Based on these findings, the consumption of lycopene by women to improve overall bone health should be considered.

The aim of the study was to investigate the association between depression and low bone mineral density (BMD) in premenopausal females. The rationale for the study was that depression is often characterized by cortisol hypersecretion. The role of cortisol includes effects on bone metabolism and the immune system: cortisol is a bone resorption agonist through its support of osteoclastogenesis. The release of pro-inflammatory cytokines, (especially IL-1, IL-6 and TNF-alpha) which induce cortisol secretion, also pushes the balance of bone remodelling in favour of resorption, consequently causing loss of bone mineral density. Significant results have been reported in studies of various groups across the USA, Europe and Asia, indicating a causal role for depression in osteoporosis. However, some studies could not support this association. With both osteoporosis and depression representing growing public health concerns in South Africa, the aim of this study was to examine the association between depression and loss of BMD in a South African sample with varying levels of depression. The study was approached from two starting points: the first used low BMD as the departure point and the second was undertaken from the diagnosis of depression. This was achieved by first investigating women where the primary concern was possible low BMD (referred to as Study 1) and secondly by assessing women whose primary diagnosis was clinically confirmed major depression (Study 2). Study 1 involved investigation of BMD in a volunteer-based sample of 40 premenopausal women drawn from three different sources. All volunteers underwent a DEXA scan, were assessed for depression and supplied saliva for cortisol analysis. Study 2 examined the BMD of five psychiatric patients diagnosed with severe, recurrent major depression and four healthy controls. These volunteers were required to undergo the same testing as subjects in Study 1. In addition, blood and urine samples were taken to examine bone turnover markers (bone specific alkaline phosphate, osteocalcin, urine pyridinoline cross-linked C-telopeptide and deoxypyridinoline). The pro-inflammatory status of the psychiatric patients was compared to reference ranges. The latter served as a small exploratory study and an introduction to further avenues of research. Study 1 revealed no clear general association between depression and bone density on DEXA scores. However, a correlation was found between left femoral neck BMD and depression in those women with low BMD only. Significant differences were found though between subjects with normal and low BMD in terms of body mass index (BMI) and contraception use. Study 2 on the other hand, indicated a trend of association between depression and low BMD: subjects suffering with severe major depression were noted to have lower bone density (on DEXA) and higher bone turnover (as measured by markers of bone turnover) as well as higher cortisol levels than healthy controls. In addition, depressed subjects exhibited elevated IL-1-alpha levels but normal TNF-alpha levels when compared to normative data. In conclusion, the study indicated that the effect of depression on bone density is dependent on the intensity and duration of depression. IL-1-alpha and cortisol may be instrumental in this loss of BMD. / Dissertation (MSc)--University of Pretoria, 2008. / Physiology / unrestricted

The purpose of this randomized controlled trial was to investigate temporal skeletal responses to short-term high intensity physical activity. Twenty-eight normal active females [age: 20.7 +/- 2.1 yr (mean +/- SD)] were randomized into exercise (EX, n = 15) or control (CN, n = 13) groups. The exercise group trained 6 days/wk for 6 wk, which consisted of maximal isokinetic knee flexion/extension 3 days/wk, combined with 3 days/wk running. The purpose was to expose the tibiae to a period of abruptly increased loading forces. Tibial bending stiffness (EIMRTA), and serum concentrations of biochemical markers of bone formation [osteocalcin (OC)], and bone resorption [n-telopeptide of type I collagen (NTx)] were measured at baseline, 2 wks, 4 wks, and 6 wks. Isokinetic concentric knee extension/flexion peak torque, as well as total body and site-specific bone mineral density (BMD) were measured at baseline and 6 wk. After training, the exercise group significantly increased (p < 0.05) isokinetic concentric peak torque for the dominant (13.6%) and non-dominant (5.7%) quadriceps, as well as dominant (7.7%) and non-dominant (9.5%) hamstrings, compared to the controls. No differences for total body or site-specific BMD were noted. A two-way multivariate repeated measures ANOVA revealed no timeâ ¢group interactions for composite tibial bending stiffness [(EIMRTA); p = 0.57] or the biochemical markers of bone turnover [(OC and NTx); p = 0.15] across the four sampling periods. While there were no main effects for group, a trend for time (p = 0.051) for composite EIMRTA was observed. The exercise group demonstrated a 20% increase in EIMRTA from baseline (74.8 +/- 22.3 Nm2) to 6 wk (89.8 +/- 24 Nm2), compared to controls who demonstrated a 4% increase (Baseline 86.5 +/- 23.8 Nm2; 6 wk 90 +/- 23.7 Nm2). Significant group differences (p = 0.05) were noted for OC, but not NTx. Differences (p < 0.05) for OC were observed at baseline [13.2 +/- 2.4 ng/ml (CN), 15.6 +/- 2.7 ng/ml (EX)], and follow-up ANCOVA revealed no differences for subsequent sampling periods. Main effects for time were found for OC and NTx (p < 0.001). Main effects for time in OC were attributable to changes in the exercise group (p < 0.01) and NTx (p < 0.01), but not the control group. / Ph. D.

Introduction: This study investigated the systemic response of serum bone alkaline phosphatase (SBAP) and urinary N-telopeptide (UNTX) to tobacco exposure and environmental tobacco smoke (ETS) and the possible effect modification (and variability) of this response by racial/ethnic origin. Methods: Data (n=5411) were obtained from the National Health and Nutrition Examination Survey, with data analysis done on adults aged ≥ 20years. Outcome variables were SBAP and UNTX. Independent variable was tobacco exposure measured using serum cotinine levels and adjusted for covariates. Generalized linear models were used to explore associations. Results: A percentage increase in log transformed serum cotinine was associated with a 0.005 percentage increase in log transformed SBAP (CI: 0.002, 0.008) and 0.02 percentage increase in log transformed UNTX (CI: −0.01, 0.04) with interaction between cotinine and race/ethnicity (p=0.01). Stratifying by race/ethnicity, tobacco exposure was associated with significant decreases in UNTX among non-Hispanic Whites–0.008(−0.014, −0.002) and Mexican Americans −0.014 (−0.025, −0.002) only. Categories of serum cotinine were associated with a monotonic increase in SBAP (p for trend <0.001) and monotonic non-linear decrease in UNTX (p for trend>0.05). Conclusions: Tobacco and environmental tobacco exposure are associated with SBAP and increased bone formation. The response of UNTX to these exposures is modified by race/ethnicity with non-Hispanic Whites and Mexican-Americans less sensitive to the resorptive effects of tobacco exposure on bone.

In the United States, osteoporosis results in about 1.5 million annual fractures, costing approximately $15 billion. Calcitonin is safe and effective in slowing osteoporotic bone loss, but its effect is transient. The current studies were designed to explore the dose-dependent effects of salmon calcitonin on bone turnover in ovariectomized rats and to determine if the decrease in therapeutic effectiveness of calcitonin demonstrated over time with higher doses is due to oversuppression of bone turnover. Doses of 5, 15, & 50 IU/kg BW/day of calcitonin were compared to placebo in 12-week-old ovariectomized and sham-ovariectomized Sprague-Dawley rats for 24 weeks. The spinal bone mineral content (BMC) as measured by DXA in ovariectomized subjects receiving 5 & 15 IU/kg of calcitonin was not significantly different from sham-ovariectomized subjects, while spinal BMC of subjects receiving 50 IU/kg was significantly lower than shamovariectomized subjects (p<0.05). Femoral BMC of ovariectomized subjects was significantly lower than sham-ovariectomized subjects (p<0.05), but no significant differences were noted between treatment groups. Scanning electron microscopy (SEM) demonstrated a decrease in number and density of trabeculae and in cortical thickness when comparing femurs from ovariectomized with sham-ovariectomized subjects. SEM of subjects receiving 50 IU/kg displayed greater bone loss than other groups. No significant differences were noted between groups for levels of urinary helical peptides or serum pyridinoline [ELISA], indicators of bone resorption. Urinary calcium excretion [capillary ion electrophoresis] was significantly higher in subjects receiving 50 IU/kg of calcitonin than other ovariectomized subjects (p<0.05). Serum levels of osteocalcin [RIA], an indicator of bone formation, were significantly higher in subjects receiving 5 IU/kg of calcitonin than control subjects and those receiving 50 IU/kg (p<0.05). Production of antibodies to calcitonin [ELISA] by subjects in this study did not correlate with changes in bone turnover or bone density. The results of this study do not provide evidence higher doses of calcitonin result in oversuppression of bone turnover. However, urinary calcium excretion affected bone resorption in a reverse dose-dependent manner, suggesting the calciuric effect may be responsible for less effective outcomes seen with higher doses of calcitonin.