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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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Presentation Transcript
overview
Overview
  • Definition
  • Experiment
  • Method
  • Results
  • Discussion
  • Importance of Study
insulin like growth factor
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.
experiment
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
method
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
results
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
addition of rh igf i igfbp 3
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
discussion
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
importance of study
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