Week 5

Question 1

What are the 4 evolutionary perspectives on developmental plasticity?

Answer 1

1. Fetal programming
2. Predictive adaptive response
3. Thrifty phenotype
4. Capacity-load model

Question 2

Describe the fetal programming hypothesis

Answer 2

If a fetus does not receive proper nutrition, it will react by altering its metabolism. These changes are permanent, and affect chronic disease predisposition

Question 3

What is a key flaw of the fetal programming hypothesis?

Answer 3

Does not factor in adult lifestyle into chronic disease predisposition, which we know plays some role in long-term health

Question 4

How might a fetus alter its metabolism in response to undernutrition? (3)

Answer 4

1. Redistribution of blood
2. Change in oxidation rates of nutritions
3. Altered sensitivity to certain hormones/altered secretions of hormones

Question 5

Name 5 factors which might result in fetal undernutrition

Answer 5

1. Maternal body composition: low energy stores
2. Low maternal dietary intake
3. Suboptimal uteroplacental blood flow
4. Placental transfer
5. Mutations in the fetal genome

Question 6

Describe the predictive-adaptive response

Answer 6

A fetus with a given genotype will predict what its environment will be like and make adjustments to its metabolism accordingly. When the environment is richer (or just different) than predicted, the metabolism will be ill-suited to an environment, resulting in higher rates of chronic disease

Question 7

What are the key problem with the predictive-adaptive response? (2)

Answer 7

1. The fetus is never actually exposed to the environment: mom buffers the environment
2. Does not explain why there are high rates of chronic disease in countries where malnutrition is rare

Question 8

Describe the difference in the thrifty phenotype hypothesis and the fetal programming hypothesis

Answer 8

The difference is in the mechanism

Fetal programming: Change overall metabolism
Thrifty phenotype: Divert metabolism, normal brain and malfunction in less important organs

They have the overall same result but the way that they are proposed to happen is slightly different

Question 9

Describe the thrifty phenotype hypothesis

Answer 9

Adaptive growth restriction: Fetal undernutrition causes the body to divert resources to the most important organs (like the brain) at the expense of lesser organs – protect the brain at all costs

Question 10

Other than the brain, which organs does the body tend to spare in cases of fetal undernutrition? (3)

Answer 10

Liver, pancreas, spleen

Question 11

What organ gets sacrificed and when is largely dependent on… (2)

Answer 11

Age and circumstance

Question 12

True or false: the duration of hyperplasic growth is the same for different organs during fetal growth

Answer 12

False: differs between organs, hence why some organs may be sacrificed based on age and circumstance

Question 13

What were the results of the Minnesota starvation study? How much total body weight was lost? What percentage of this loss was muscle? What percentage of this loss was fat?

Answer 13

Participants lost 25% of their body weight
70% Fat loss
10% Muscle loss
These were only men participating in the study!

Question 14

Why might some people favour fat or muscle loss over the other?

Answer 14

In humans, can very generally be explained by biological sex: Women will lose muscle and men will lose fat – both are beneficial for reproduction but exceptions exist

Question 15

How is muscle reproductively advantageous for human males?

Answer 15

Muscle helps you compete for mates

Question 16

Describe the relative losses in lean and fat mass in men and women during tuberculosis?

Answer 16

Males will preferentially lose lean mass (muscle) and women will preferentially lose fat mass - men and women sacrifice their reproductive stores to run the immune system upon TB infection

Question 17

What is the issue with the observed health data which the thrifty phenotype hypothesis cannot explain?

Answer 17

If fetal birth weight is a predictor of adult health, why is it that there is not a threshold for chronic disease risk?

Question 18

In a study of 8600 Finnish babies, those who were born with low birth weight and later went on to have normal BMI and coronary heart disease displayed what pattern in prepubertal growth?

Answer 18

Huge spike in growth rate from ages 2-11 (hypertrophic growth)

Question 19

Describe the capacity load model

Answer 19

Metabolic load which exceeds the capacity which was established during hyperplasic growth is what predisposes a person to chronic disease

Question 20

Define metabolic load

Answer 20

Lifestyle traits which challenge the capacity for homeostasis (e.g. lack of exercise, high glycemic load-diet)

Question 21

Metabolic growth develops during (hyperplasic/hypertrophic) growth

Answer 21

Hypertrophic

Question 22

Metabolic capacity develops during (hyperplasic/hypertrophic) growth

Answer 22

Hyperplasic

Question 23

Define metabolic capacity

Answer 23

Traits which enhance the ability to maintain homeostasis (e.g. beta cell count, cardiac structure)

Question 24

Typically (smaller/larger) babies have greater metabolic capacity. Why?

Answer 24

Larger

Larger, more productive organs

Question 25

True or false: metabolic capacity can be altered with healthy lifestyle changes

Answer 25

False: metabolic capacity is set for life

Question 26

Why is obesity a risk factor which increases metabolic load?

Answer 26

An obese person has a lot of tissue which requires a lot of energy – demanding to keep up, increases oxidative stress

Question 27

The penalty for high metabolic load is greatest in individuals who…

Answer 27

Have diminished metabolic capacity

Question 28

Birth weight is lost primarily in this tissue

Answer 28

Lean mass (muscle and organ mass) – visceral fat mass is usually preserved

Question 29

Low birthweight babies tend to have (low/high) lean mass and (low high) abdominal fat mass compared to normal birth weight babies

Answer 29

Low lean mass
High abdominal/visceral fat mass

Question 30

How much (%) less lean tissues (muscle and organs) do low birthweight babies tend to have?

Answer 30

25%

Question 31

Why do babies lose lean mass over visceral fat mass?

Answer 31

Fat mass is an energy reserve for immediate survival

Question 32

How does early life undernutrition affect oxidative stress? (increase/decrease)

Answer 32

Increases oxidative stress

Fewer systems in place to manage physiological demands of body’s tissues - fewer B-cells = greater stress, etc.

Question 33

How does early exposure to irreversible oxidative stress influence a fetus’ telomerase?

Answer 33

Accelerates telomerase shortening - result in chromosomal damage sooner

Question 34

In high-income countries, what does the gradient in height look like between high and low status individuals?

Answer 34

Low: shorter
High: taller

Question 35

What model best explains the social gradients in height in high-income countries?

Answer 35

Capacity-load model

Question 36

Describe the relative heights of person 1: Born poor and became rich, and person 2: Born rich and became poor. Who is taller?

What is the overall message of these data?

Answer 36

Born rich and became poor = taller on average

Early life matters in overall adult health

Question 37

In high-income versus low-income countries, are chronic disease rates more an issue of load or capacity?

Answer 37

In high-income: capacity matters, poorer members have the lowest birthweights
In low-income: load matters, richer members have the highest load

Question 38

How can both slow and rapid infant growth elevate the risk for the same diseases?

Answer 38

Slow growth: penalty to capacity
Rapid growth: penalty to load