In vertebrates, PTH receptor 1 (PTH1R) plays a pivotal role in control of bone development and homeostasis; however, how it is regulated is poorly defined. Here we report that Kindlin-2 binds to and modulates PTH1R to regulate bone mass and PTH actions. Deleting Kindlin-2 expression using the 10-kb mouse Dmp1-Cre severely impairs the anabolic effects of intermittent PTH on bone in adult mice with or without ovariectomy. Of particular interest, Kindlin-2 and Pth1r double heterozygous mice (Dmp1- Cre; Kindlin-2 f/+ ; Pth1r f/+ ), but not either singly heterozygous mice (Dmp1- Cre; Kindlin-2 f/+ or Dmp1-Cre; Pth1r f/+ ), display severe osteopenia and fail to increase bone mass in response to administration of intermittent PTH. Mechanistically, Kindlin-2 interacts with the C-terminal cytoplasmic region of PTH1R. When overexpressed, this region efficiently inhibits the endogenous PTH/PTH1R signaling in osteoblasts, which is reversed by introduction of a point mutation that abolishes the Kindlin-2 interaction. Furthermore, Kindlin-2 loss inhibits PTH-induced CREB phosphorylation and cAMP production in vitro and in bone. PTH upregulates, while estrogen deficiency downregulates, expression of Kindlin-2 in vitro and in bone. Collectively, we demonstrate that interplay between Kindlin-2 and PTH1R regulates bone mass by modulating PTH1R and provide a potential therapeutic target for metabolic bone diseases

Presented for the degree of Doctor of Science of University of the Uiituatersrand. October, 1964. / ffiy interest in iron metabolism was initially aroused in 1948 by a young patient with idiopathic haemochromatosis who was admitted to Professor Elliott*© ward while I was serving my medical internship, With the support of the Council for Scientific and Industrial Research it was possible to carry out radioisotopic studies on this patient and over the next four years a number of other subjects with the same disease ware investigated. As the study continued, attention was also directed to the siderosis which is so common in adult Bantu, and to the Iron overload which results from the administration of repeated blood transfusions to subjects with refractory anaemias. / IT2018

A dissertation submitted to the Faculty of Medicine, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree Master of Science in Medicine. Johannesburg, 1995 / HLA-linked haemochromatosis is the result of an inborn error of metabolism inherited as an autosomal recessive gene, closely linked to the HLA locus on chromosome six. In this condition iron absorption is inappropriately high leading to iron overload. Integral to the pathogenesis of this disorder and in contrast to other causes of iron overload, is the relatively modest accumulation of iron within cells of both the small intestine and the reticuloendothelial system and the excessive deposition of iron in parenchymal cells of the liver and other organs. This observation has led to the suggestion that the primary defect(s) could be present in either the gut, the liver, the reticuloendothelial system or all three. Abnormalities in iron uptake by cells, iron transport through and between cells and iron storage in cells have all been suggested as possible mechanisms responsible for the abnormal absorption and distribution of iron in haemochromatosis. Malfunction of the iron transport protein transferrin or its receptor could be responsible for abnormal distribution and iron loading while an abnormality of ferritin iron storage could explain why some cells appear to be unable to store iron and others are iron overloaded. / IT2018

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Dissertation (PhD)--University of Stellenbosch, 2003. / 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. / AFRIKAANSE OPSOMMING: Die Effek van Statiene op Been en Mineraal Metabolisme Beide statiene en aminobisfosfonate verminder die prenelasie van proteïene wat betrokke is in die sitoskeletale organisasie en aktivering van gepolariseerde en beweeglike selle. Gevolglik is dit gepostuleer dat statiene ‘n invloed sal hê op been metabolisme. Ons het die effekte van verskillende dossisse van simvastatien (1, 5, 10 en 20mg/Kg/dag), mondelings toegedien oor 12 weke aan intakte vroulike Sprague-Dawley rotte, en die effek van simvastatien 20mg/Kg/dag op skyn- en ge-ovariektomeerde rotte, op femorale been mineral digtheid (BMD) en kwantitatiewe been histomorfometrie (KBH), vergeleke met kontroles, ondersoek. Op ‘n soortgelyke manier is die effek van atorvastatien (2,5mg/Kg/day) en pravastatien (10mgKg/dag) op BMD ondersoek en vergelyk met kontroles. BMD is verminder deur simvastatien 1mg/Kg/dag (p = 0.042), atorvastatien (p = 0.0002) en pravastatien (p = 0.002). Die effekte op KBH parameters het verskil met verskillende dossisse van simvastatien (ANOVA; p = 0.00012). KBH parameters van beide been vormasie en resorpsie is vergelykend en merkbaar verhoog deur simvastatien 20mg/Kg/dag in twee onafhanklike groepe van intakte rotte en is vergesel deur ‘n relatiewe onveranderde BMD. Met laer dossisse het simvastatien 1mg/Kg/dag been vormasie verminder terwyl been resorpsie verhoog is en is weerspieël deur ‘n merkbaar verminderde BMD. Ge-ovariektomeerde diere wat simvastatien 20mg/Kg/dag ontvang het, het geen verandering in BMD relatief tot die onbehandelde geovariektomeerde kontroles getoon nie, en die toename in been vormasie was kleiner as in die skyngeopereerde rotte wat simvastatien ontvang het en daar was geen verandering in been resorpsie nie. Die dosis-respons kurwes vir simvastatien vir been vormasie en resorpsie het van mekaar verskil. Uit hierdie studies word die volgende gevolgtrekkings gea) lae-dosis simvastatien (1mg/Kg/dag), atorvastatien 2.5mg/Kg/dag en pravastatien 10mg/Kg/dag verminder BMD in knaagdiere; b) 1mg/Kg/dag simvastatien verminder been vormasie en verhoog been resorpsie en veroorsaak gevolglik ‘n velaging in die BMD; c) 20mg/Kg/dag simvastatien verhoog been vormasie en resorpsie met ‘n gevolglike onveranderde BMD; d) die effekte van simvastatien op KBH verskil met verskillende dossisse; e) die dosis-repons kurwes van been resorpsie en been vormasie veskil van mekaar f) die effekte van simvastatien wat waargeneem in intakte rotte word nie gesien in ge-ovariektomeerde rotte nie; g) simvastatien kannie die verlies van been wat veroorsaak word deur ovariektomie voorkom nie.

published_or_final_version / Community Medicine / Doctoral / Doctor of Philosophy

Cyclopropenoid fatty acids (CPFA), which are a group of fatty acids produced by plants of the order Malvales, are known to induce adverse physiological effects when administered to a variety of animal species. A structurally strained cyclopropene ring is present in all CPFA and is believed responsible for the toxic action of these fatty acids. Dietary consumption of CPFA by mammals, poultry and fish has resulted in toxic responses including hepatic damage, impaired reproductive capabilities and sizeable alterations in lipid metabolism. Furthermore, CPFA have been identified as mildly carcinogenic and strongly cocarcinogenic towards rainbow trout (Salmo gairdneri). The mechanism by which CPFA enhance carcinogenesis is currently not understood. The research in this thesis has therefore been directed toward obtaining a better understanding as to how CPFA induce toxic responses in rainbow trout. Hepatic plasma membranes were isolated from both control trout and trout which had consumed dietary CPFA. The plasma membranes were then compared via the use of electron microscopy, chromatographic analysis of phospholipid and fatty acid content, two dimensional polyacrylamide gel electrophoresis of proteins, and Western blot analysis of concanavalin A sensitive glycoproteins. Electron micrographs revealed that control plasma membranes appeared more homogeneous than CPFA membranes and were characterized by more membrane sheets and less vesicularization. The analysis of enzyme activities revealed that CPFA caused a decrease in whole liver glucose-6-phosphatase activity and that control plasma membranes expressed slightly higher glucose-6-phosphatase and 5'-nucleotidase activities as compared to CPFA membranes. Although dietary CPFA appeared to have no effect on the phospholipid content of the plasma membranes, significant alterations in the fatty acid profiles of ethanolamine and choline phospholipids were observed. CPFA caused a decrease in palmitic, palmitoleic and oleic acids while the level of stearic and docosahexaenoic acids subsequently increased. Differences between the protein content of control and CPFA plasma membranes were made clear through the analysis of electrophoretic and Western blotting data. Membranes isolated from fish fed CPFA contained several proteins of high molecular weight (above 66,000 daltons) and other proteins of high isoelectric point that were not present in control plasma membranes. Additionally, two families of glycoproteins which had previously been identified as microsomal in origin were detected only in CPFA plasma membranes. A discussion concerning the possible causes and biological ramifications of the observed subcellular alterations caused by CPFA insult is also presented in this thesis. / Graduation date: 1989