Doctoral Degrees (General Internal Medicine)

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Browsing Doctoral Degrees (General Internal Medicine) by browse.metadata.advisor "Hulley, P. A."

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    The effect of statins on bone and mineral metabolism
    (Stellenbosch : University of Stellenbosch, 2003-04) Maritz, Frans Jacobus; Hough, F. S.; Hulley, P. A.; University of Stellenbosch. Faculty of Health Sciences. Dept. of Internal Medicine.
    ENGLISH ABSTRACT: The Effect of Statins on Bone and Mineral Metabolism Both statins and amino-bisphosphonates reduce the prenylation of proteins which are involved in cytoskeletal organization and activation of polarized and motile cells. Consequently statins have been postulated to affect bone metabolism. We investigated the effects of different doses of simvastatin (1,5,10 and 20mg/Kg/day), administered orally over 12 weeks to intact female Sprague-Dawley rats, and the effect of simvastatin 20mg/Kg/day in sham and ovariectomised rats, on femoral bone mineral density (BMD) and quantitative bone histomorphometry (QBH), compared to controls. Similarly, the affect of atorvastatin (2,5mg/Kg/day) and pravastatin (10mg/Kg/day) on BMD was investigated and compared to controls. BMD was decreased by simvastatin 1mg/Kg/day (p = 0.042), atorvastatin (p = 0,0002) and pravastatin (p = 0.002). The effect on QBH parameters differed with different doses of simvastatin (ANOVA; p = 0.00012). QBH parameters of both bone formation and resorption were equivalently and markedly increased by simvastatin 20mg/Kg/day in two independent groups of intact rats, and reflected by a relatively unchanged BMD. At lower doses, simvastatin 1mg/Kg/day decreased bone formation while increasing bone resorption as reflected by a marked decrease in BMD. Ovariectomised animals receiving simvastatin 20mg/Kg/day showed no change in BMD relative to the untreated ovariectomised controls, their increase in bone formation was smaller than in sham-operated rats receiving simvastatin and there was no change in bone resorption. The dose response curves of simvastatin for bone formation and resorption differed from each other. From these studies it is concluded that:- a) low-dose simvastatin (1mg/Kg/day), atorvastatin 2.5mg/Kg/day) and pravastatin 10mg/Kg/day) decrease BMD in rodents;b) 1mg/Kg/day simvastatin decreases bone formation and increases bone resorption and is reflected by a reduced BMD; c) 20mg/Kg/day simvastatin increases bone formation and resorption and results in an unchanged BMD; d) the effects of simvastatin on QBH differ at different dosages; e) the dose-response curves for QBH parameters of bone resorption and bone formation differ from each other; f) the effects of simvastatin seen in intact rats are not observed in ovariectomised rats; g) simvastatin is unable to prevent the bone loss caused by ovariectomy.