Lecture 7

Question 1

Osteoporosis risk increases with age

Answer 1

• 10 times more common in women than men
• estrogen is a potent stimulant for osteoblast activity and bone formation
• however, obese post menopausal women can still produce estrogen because the enzyme aromatase is expressed in obese adipose tissue

Question 2

BMI and osteoporosis risk

Answer 2

Very low BMI (underweight):
- increased risk for fragility related fractures

Very high GMI (obese):
- site specific increased risk of fractures + inflammation driven increases in bone resorption (TNFa, IL-6)

• obesity causes greater mechanical stress on bones and bone mass increases to accommodate BUT eventually increases in bone mass CANNOT MATCH increases in fat mass
• 20% increases risk fracture for ankle and upper leg in obese women (+5 kg increases ankle fracture risk 5%)
• fewer hip-spine and upper body fractures (some protection)

Question 3

How obesity influences bone status

Answer 3

Adverse effects:
- inflammatory cytokines (TNFa, IL-6) produced in obese adipose tissue, can stimulate osteoclasts (increased bone resorption)
- 25-hydroxyvitamin D levels are reduced (liver precursor to vitamin D (calcitriol)
- serum PTH levels increase

Beneficial effects:
- increased BMI increases mechanical load on bones which stimulates bone formation BUT there’s a limit
- estrogen stimulates osteoclast apoptosis, estrogen is synthesized in obese adipose tissue via increased aromatase expression

Question 4

Metabolic syndrome

Answer 4

Cluster of medical disorders that, when presented together, increase risk of CVD and diabetes

Ex:
- obesity
- high blood glucose
- low HDL
- hypertension
- high blood pressure

• 1 in 5 Canadians have it, increased with age

Question 5

Calcium role in diabetes and metabolic syndrome

Answer 5

• Combined high intake of vit D and calcium decreases risk of type 2 diabetes by 33%

-trend of low dairy product intake = higher incidence of obesity, diabetes, hypertension, dislipidemia and vice versa

Question 6

Calcium role in weight loss

Answer 6

Getting RDA of calcium and vit D reduces body weight, waist circumference, fat mass (not BMI)

• calcium intake could be correlated with weight loss response, risk of diabetes, and metabolic syndrome
• how could calcium (combined w vit D work?):
  — increases fecal fat excretion (decreasing lipid absorption in SI)
  — favours or promotes fat oxidation in adipose tissue
  — calcium specific effects on appetite
  — high protein content of milk increases fullness, reduces food intake, stimulates GI hormones

MORE RESEARCH NEEDED