Lecture 19: Nutrition and the ageing bone

Question 1

Definition osteoporosis =

Answer 1

Progressive, systemic skeletal disease characterized by low bone mass and micro architectural deterioration of bone tissue, with consequent increase in bone fragility and susceptibility of fracture.

Question 2

DEXA can pick up X. Some say density as well, some say not

Answer 2

low bone mass

Question 3

What do osteoclasts and blasts do?

Answer 3

Osteoclast = responsible for resorbing bone (turquoise). They munch away at the surface, leaving a cavity.
Osteoblast = makes new bone matrix

Question 4

Why need osteoblasts and clasts?

Answer 4

• Enables bone to adapt to mechanical loading, - repair damage
• regulate circulating Ca levels
• contribute to acid/base balance

Question 5

Target drug strategies =

Answer 5

regulators of bone turnover

Question 6

Serum calcium/blood values: good marker for calcium homeostasis?

Answer 6

No, The body will do anything to ensure this calcium levels will remain in a small range in the blood. There is no functional marker

Question 7

Explain calcium homeostasis

Answer 7

When blood levels fall, there is an action on PTH:

1. stimulates Ca uptake in kidneys -> active vit D increases Ca uptake in intestines
2. stimulates ca release from bones
   3 blood ca levels rise

Question 8

The three calciotrophic hormones are:

Answer 8

1. PTH
2. 1-25-D (active vit D)
3. Calcitonin (takes calcium from blood and puts it back in bone)

Question 9

Conflicting data: dietary calcium associated, or not associated with risk of fracture.
what can you conclude?

Answer 9

More calcium is not necessarily better, but avoiding a low calcium intake is beneficial for the ageing skeleton.

Question 10

How do you know whether the sun has the right UVB exposure to make vit D

Answer 10

Shadow shorter than your height? Right vit D level!

Question 11

Why is the name vit D confusing?

Answer 11

Vitamin = vital amine, but vit D = pro-hormone. Main source is not diet, but UV exposure

Question 12

Explain vit D uptake by the sun

Answer 12

UVB: absorbed by cholesterol in the skin -> previt D3 -> Vit D3 ->(liver) 25-hydroxyvitamin D3 (clacidiol) ->(kidney) Calcitriol (active vit D)

Question 13

What is the marker for vit D status?

Answer 13

25-hydroxyvitamin D3

Question 14

Can never reach vit D toxic levels via sun, true/false?

Answer 14

true

Question 15

UK guidelines for vit D = 10 microgr/day = less than European committee and EFSA. UK = prevent deficiency, the rest = optimal health.

Answer 15

ok

Question 16

Cycles of rising and falling vit D: bad for health?

Answer 16

If your change in vit D is very high, lost more bone and had increased bone resorption.

Question 17

vit D3 vs D2?

Answer 17

bioavailability seems to be higher in D3. Elevates D3 levels.

Question 18

Vit K: vital for bone health. Why?

Answer 18

 Vit K is vital: it produces an AA called Gla which acts like glue to keep the calcium in bone.

Mechanistically, vit K is very important for bone. But in RCTs, vit K story is not showing a benefit.

Question 19

How does bone help in maintaining the proper pH in the blood? What is the downside of this?

Answer 19

Bone is a huge reserve as alkaline salts. Using these salts to buffer the pH of the blood, might result in gradual decline in bone known as osteoporosis.

Question 20

How does it work that bone buffering can lead to osteoporosis?

Answer 20

When reducing the pH medium in which bone cells operate, bone cells become hyperactive and you lose a lot of bone. As we get older, we become more acidic.

Question 21

DASH study: increasing fruit & veg intake significantly decreased amount of calcium that is lost.

Answer 21

nois