The Pharmaceutical Journal
Vol 277 No 7409 p78-83
15 July 2006

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Building bones with nutraceuticals

David Appleton and Brian Lockwood discuss bone, osteoporosis and nutraceuticals that can help treat and slow the process of bone depletion

David Appleton, MPharm, is a preregistration student and Brian Lockwood, PhD, MRPharmS, is senior lecturer in pharmacy School of Pharmacy and Pharmaceutical Sciences, University of Manchester

SUMMARY

Our skeletons provide us with a strong yet light protective framework, due to a unique structure comparable to reinforced concrete. Bone is not merely an inert material, however, but a highly dynamic metabolic reservoir of calcium ions. The skeleton stores 99 per cent of all calcium ions contained in the body. There are two main types of bone in the skeleton. These are distinguished by their microscopic architecture:

· Cortical bone is hard and dense, and comprises the shafts of the long bones which bear most of the body’s weight.

· Cancellous or trabecular bone is found in the ends of long bones, vertebrae and pelvis. This has a honeycomb like appearance, with plates known as trabeculae arranged in such a way as to provide resistance to forces. There is also a greater internal surface area and blood supply than in cortical bone, which means it is involved in calcium homeostasis.

Bone consists of an organic phase (matrix) and an inorganic mineral phase, together with a highly varied population of cells responsible for its development and maintenance. The matrix is composed of structural proteins, collagen and mucopolysaccharides, which provide resistance and flexibility. The main mineral present is hydroxyapatite (crystalline calcium phosphate) which is responsible for the rigidity and compressibility of bone.

Bone growth (modelling) begins in fetal development and continues to between 25–40 years of age when peak bone mass is said to be attained. During puberty there is an accelerated period of growth where most of this mass is laid down. The timing and nature of this process is initially dictated by genetic factors, followed by environmental factors in adulthood, which are described below.

After modelling there follows a process of consolidation, known as remodelling, which is necessary to allow the skeleton to respond to external forces and maintain body mineral levels. Up to 10 per cent of existing bone per year3 is restructured, at sites known as bone multicellular units.

Bone multicellular units consist of teams of osteoblasts and osteoclasts acting in a co-ordinated fashion under the influence of numerous cellular factors. The resorption process follows a clear series of stages lasting approximately 100 days:

· Osteoclasts initiate remodelling through specific activation of their membrane receptors. They attach to internal bone surfaces and secrete protons and enzymes which degrade and release minerals from the tissue.

· Osteoblasts then replace the resorbed material with immature matrix protein (osteoid), which later becomes mineralised.

Examples of factors necessary for co-ordinating osteoblasts and osteoclasts include:

· Calcium availability
· Mechanical forces experienced by the skeleton
· Endocrine, autocrine and paracrine factors

The last category is of particular significance once peak bone mass is attained.

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