final biochem paper - Osteoporosis is a disorder...

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Osteoporosis is a disorder characterized by loss of bone mass which leads to fragility fractures. Several converging pathogenic mechanisms cause bone mass loss and microarchitectural deterioration of skeletal structure. These mechanisms, coupled with an increase risk of falls, contribute to a high incidence of fragility fractures in osteoporotic patients. Skeletal fragility can result from: (a) failure to achieve a skeleton of optimal mass and strength during growth; (b) excessive bone resorption resulting in loss of bone mass and deterioration of microarchitecture; and (c) inadequate bone formation response to increased resorption in bone remodeling (Raisz 2005). Recent literature reveals not only that vitamin D plays a crucial role in reducing excessive bone resorption and promoting bone formation, thus contributing to healthier bones and lowering risk of osteoporosis, but also that vitamin D status is inadequate in Canadians across the country aged 35+. The established benefits of vitamin D for bone health, coupled with the apparent deficiency in vitamin D among Canadians, points to the pressing need to initiate a major campaign with the goal of improving vitamin D status and reducing risk of osteoporosis in Canadians. We will begin by exploring the mechanisms underlying the connection between vitamin D intake and improved bone strength. After briefly outlining the sources of vitamin D and its active form calcitriol, we will investigate the role of calcitriol in inhibiting parathyroid hormone (PTH) synthesis and increasing calcium absorption in the intestine and kidney. We will then delineate how these actions result in stronger bones, which will involve elucidation of bone structure and mineralization. Following this, we will examine a recent scientific study on calicitriol’s role in promoting osteoblastic activity and increasing osteocalcin production by osteoblasts, which further contributes to bone health. Having established the biochemical basis relating vitamin D to osteoporotic risk, we will examine the epidemiological evidence for vitamin D deficiency in Canadians, and offer revised recommendations for adequate vitamin D intake. Moreover, we will explore the role of genetics, specifically vitamin D receptor (VDR) polymorphisms, in predicting risk of osteoporosis. Lastly, we will evaluate the main basic science and epidemiological sources used to support our opinion to initiate this campaign. 1
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The Role of Vitamin D in Improving Bone Health I) Vitamin D: From the Diet and the Sun to its Active Form Vitamin D can be obtained through consumption of foods from animal sources, especially liver, beef, veal, and eggs. Dairy products such as milk, cheese, and butter and some saltwater fish, including herring, salmon, tuna, and sardines are also significant sources. Selected foods are also fortified with vitamin D, including milk, yogurt, cheese, margarine, orange juice, breads and cereals. Dietary vitamin D 3 is absorbed along with fat and with the aid of bile salts via passive diffusion into the intestinal cell. Within the intestinal cell, vitamin D
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This note was uploaded on 07/06/2011 for the course BIOCHEMIST BIOCHEM 3N taught by Professor Drmacdonald during the Fall '10 term at McMaster University.

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final biochem paper - Osteoporosis is a disorder...

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