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Protein Restriction: Effects on IGF and Bone Formation

Protein Restriction: Effects on IGF and Bone Formation. By Keisha Smith Endocrinology. Overview. Definition Experiment Method Results Discussion Importance of Study. Insulin-Like Growth Factor. Made by osteoblasts, chondrocytes and osteocytes and stored predominantly in bone matrix.

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Protein Restriction: Effects on IGF and Bone Formation

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  1. Protein Restriction:Effects on IGF and Bone Formation By Keisha Smith Endocrinology

  2. Overview • Definition • Experiment • Method • Results • Discussion • Importance of Study

  3. Insulin-Like Growth Factor • Made by osteoblasts, chondrocytes and osteocytes and stored predominantly in bone matrix. • Stimulate cartilage growth, osteoblast proliferation, collagen deposition and bone mineralization.

  4. Experiment • Hypothesis • Low protein consumption common in the elderly • decreases areal bone mineral density • decreases IGF • is related to bone loss and osteoporosis. • Focus • Effect of IGF-I on bone proliferation in adult female rats with protein restricted diet

  5. Method • First, rats all fed similarly • 15% casein for 14 days • Second, rats split into two groups • isocaloric diet of 15% casein or 2.5% casein for 14 days • Third, rats injected with rhIGF-I/IGFBP-3 • to determine the effect of IGF-I • 14 days after injection, rats killed • to obtain analytical samples of cortical and trabecular bone endosteal resorption activity. • Blood and urine samples obtained • measure bone resorption activity

  6. Results • Low protein diet showed decrease in • Body weight and organs • Mineralizing surfaces and bone formation rate in the periosteum of cortical bone • Bone resorption in cancellous bone • Plasma osteocalcin • Plasma IGF-I • Urinary deoxypyridinoline excretion levels

  7. Body Weights

  8. Bone Formation

  9. Group 1 increases cortical periosteal bone formation activities increases osteoblast recruitment and activity, mineralizing surfaces and bone formation in cancellous bone increases plasma osteocalcin Group 2 no significant increase no significant increase no significant change in plasma osteocalcin Addition of rhIGF-I/IGFBP-3

  10. Discussion • Low protein intake and osteocalcin levels may be an indicator of decreased bone formation activity • Low protein intake suppresses the osteoblastic cells response to IGF-I in both cortical bone • Dietary protein restriction impairs periosteal bone formation in cortical bone without any significant change in cancellous bone

  11. Importance of Study • Protein restriction causes drastic changes in body weight, decreased plasma IGF-I, osteocalcin and bone resorption • Results suggest that giving IGF-I to patients with protein deficiency may not be beneficial

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