Wk 7 L1 - Osteoporosis Flashcards
(13 cards)
LO
- Understand the mechanisms behind osteoporosis
- Explain how nutrition impacts bone health in ageing
population - Impact of hormone deprivation in bone health
WHO definition
progressive disease that weakens bones, increasing the risk of fractures.
the prevention of this disease and its associated fractures is considered essential to the maintenance of health, quality of life, and independence in the elderly population
Bone remodelling
Events stimulate the activation phase
Osteoclasts
Osteoblasts
Osteocytes
Osteoclasts
Derived from hematopoietic pre-cursor cells e.g., by RANKL, and attach to the bone surface
Resorb bone matrix by secreting acid to demineralize and proteases to breakdown collagen matrix
Minerals and fragments of bone matrix type I collagen (CTx) are released into the circulation during matrix degradation
Then undergo apoptosis
Macrophages clear away the debris
Osteoblasts
Derived from mesenchymal lineage
Deposit osteoids to fill the cavity, and then mineralize it after
They secrete various proteins (P1NP) during matrix formation
They then differentiate into osteocytes, and are
embedded in bone matrix
Others undergo apoptosis or become bone-
lining cells.
Osteocytes
Form a canalicular network between each other
Can sense mechanical forces (mechano-sensing cells) and respond to load in tissue
Releases factors which increase (RANKL) or decrease (OPG) osteoclast formation and activity
Release factors which inhibit (Sclerostin) osteoblast differentiation and activity
Osteoporosis
Osteoclasts activity increases, resulting in
more bone resorption than bone formation
Bone homeostasis - Nutrients
Bone is a major calcium storage site
Calcium release and retrieval is monitored by hormones: Calcitonin and Parathyroid Hormones
Calcium
- Low Calcium intake has been associated with the osteoporosis risks
- Calcium absorption decreases with age
- Aus intake guildlines increase as we age
Vitamin D
Vitamin D deficiency increases the risk of osteoporosis
Older adults are at risk of vitamin D deficiency
Potential reasons:
- Decreased production capacity
- Decreased absorption capacity
- Decreased sun exposure
Doses recomended to increase with age
Bone homeostasis - Estrogens
Estrogens (E2) are involved in bone homeostasis, through direct and indirect effects on osteoblasts and osteoclasts
In males, E2 is produced from testosterone, conversion by the aromatase enzyme
Effects of hormone deprivation on bones - Menopause
After menopause women experience a reduction in ovarian E2 production
Leads to a rapid bone loss; ~3-5% annually for 5-10 years
factors influence the onset and severity of osteoporosis: genetic, exercise, BMI,
smoking, nutrition, etc.
Effects of hormone deprivation on bones - Men with low T
Some men have hypogonadal T due to medical treatment and developmental factors
Reduction in T also leads to a reduction in estradiol levels
Low T increases risk of having osteoporosis
E2 and T deficiency increases rate of bone remodeling;
- osteoclastogenesis, osteoblastogenesis, bone resorption, and bone formation
- BUT, bone resorption is higher
