Cell growth, calcium binding proteins

Q13 Osteomalacia and osteoporosis are complications of celiac disease. The mineral in bone is mainly calcium phosphate a supply of calcium is therefore needed for bone growth and replacement. Calcium is absorbed by active mechanisms in the duodenum and jejunum, facilitated by a metabolite of vitamin D. It is also passively absorbed in the ileum and specific calcium binding proteins are present in the intestinal epithelial cells. Loss of absorptive cells and calcium binding proteins markedly decreases calcium uptake and limits its availability for bone growth and repair. 

C, which is found in complement proteins FI, F2, and F3, first found in fibronectin I, the immunoglobulin superfamily domain N, found in some growth factor receptors E, a module homologous to the calcium-binding E-F hand domain and LB, a lectin module found in some cell surface proteins. (Adapted from Baron, M., Norman, D., and Campbell, I., 1991, Protein modnles. Trends in Biochemical Sciences 16 13—1 7.)... 

Mechanism of Action Acts as a coenzyme for various metabolic functions, including fat and carbohydrate metabolism and protein synthesis. Therapeutic Effect Necessary for cell growth and replication, hematopoiesis, and myelin synthesis. Pharmacokinetics In the presence of calcium, absorbed systemically in lower half of ileum. Initially, bound to intrinsicfactor this complex passes down intestine, binding to receptor sites on ileal mucosa. Protein binding High, Metabolized in the liver. Primarily eliminated unchanged in urine. Half-life 6 days. 

Kim et al. (1999) and Jung et al. (2005) reported that fish peptides are capable of accelerating calcium absorption. Further, researchers have identified that fish protein hydrolysates possess hormone-like peptides and growth factors to accelerate calcium absorption (Fouchereau-Peron et al., 1999). These peptides are capable of binding to cell surface receptors on osteoclasts and involved mainly in calcium metabolism by decreasing the number of osteoclasts. Therefore, these peptides could be used in the treatment of osteoporosis and Paget s disease (Table 15.3). 

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