Regulation of postnatal growth and adiposity Flashcards
What does postnatal growth depend on?
‘growth’ vs ‘development’
Catch-up growth
What things come under adiposity?
- Adipogenesis
- Measuring adiposity
- Body fat distribution
- Programming of adiposity
Is Growth related to development?
Yes but is not synonymous
Define growth
Quantitative increase in physical size or mass
Everyone begins like with their own genetic potential. What will this determine?
This determines its target mature size
Genetic potential is determined by environment
In what two ways does growth occur?
Cell hyperplasia/ proliferation: increase in cell number
Cell hypertrophy: enlargement of cells or accumulation of extracellular material
Define development
A progression of changes (quantitative or qualitative) that lead form an undifferentiated or immature state to a highly organise, specialised and mature state
Where is there a switch in the relative importance of growth versus development?
Switch from lots of development in early life to more growth in later life
Stem cells are pluripotent which can become different types of cells
Excess growth e.g., obesity, muscle, tumours, in animals (wrong sort of growth)
How is growth measured?
Tell me about this
Growth charts (centile charts)
Each of these curved lines are called ‘centiles’ and show how your child is growing and developing in relation to other children their age
Boys and girls use different charts due to different growth rates over childhood
Weights and heights that are anywhere within the centile line on the chart are considered normal
Based on population norms
50 percentile line is bang on track for growth
Tell me about ‘catch-up’ growth and the centile charts
Why is catch-up growth bad news in the long-term?
Catch up growth can affect metabolism and the type of growth that’s going on
Refeeding causes the effects seen on the diagram as was used to delayed and then suddenly get influx which the body wasn’t expecting
Seen in animal studies as well
Accelerated post-natal catch-up growth is related to what in childhood?
Obesity
Define adipogenesis
The formation of fat or fatty tissue
What are the types of fat?
White fat
Brown fat
Tell me about white fat
White fat- store lipids
Have a scant ring of cytoplasm surrounding a single large lipid droplet (uniocular)
Nuclei are flattened and eccentric within the cell
Some mitochondria
Main function is to store energy in the form of triglycerides
Tell me about brown fat
Brown fat
Are polygonal in shape
Contain multiple lipid droplets of varying size (multiocular)
Nuclei are round and almost centrally located
High content of mitochondria
Burn lipids to produce heat due to presence of UCP1 protein
What are some factors which determine the prevalence, mass and activity of brown adipose tissue (BAT)?
Does it increase or decrease BAT?
- Outdoor temperature; increases cold
- Sex; female increase (more BAT in females)
- Adiposity; excess fat decrease
- Diabetes status; diabetes decrease
- Age; aging decrease
In children 5% of body mass is brown fat
Obese people have more white and brown fat
How is BAT activated?
What can be used to measure adiposity and what is the formula for that?
BMI (body mass index)= weight (Kg) / Height (m) x Height (m)
What are some other methods used to measure body fat?
Bioelectrical impedance: uses an electrical current to estimate fat based on its reactance and resistance properties
Skin-fold thickness: measure amount of subcutaneous fat
Dual-energy X-ray absorptiometry (DEXA)
Underwater weighing: computes body volume as the difference between body weight measured in air and weight measured during water submersion
Computerise tomography (CT)
Its the body fat distribution that counts, tell me about the different body shapes and which ones are better?
Apple shape vs Pear shape
More fat in abdomen is more damaging that fat below the waist
Apple shape is more metabolically damaging than pear shape
Hip to weight ratio can give idea of relative ratio
Apple shape
- More visceral fat
- Higher risk of weight-related health problems
Pear shape
- Less visceral fat
- Lower risk of weight related health problems
Compare Visceral vs Subcutaneous fat
More visceral fat= higher risk of metabolic and cardiovascular diseases
Subcutaneous fat is not as metabolically damaging as one with more visceral fat
Name the adipokines that are released from the adipose tissue and their physiological functions
What can visceral obesity lead to?
Provide examples?
Why is this the case?
Visceral obesity leads to inflammation and disease (All problems of having more adipose tissue in abdominal space)
- Lot of adipose tissue in abdominal space have good access to good portal circulation i.e., liver which has important roles. If adipokines enter here, then it can affect the function of the liver
- Pro-inflammatory state, prothrombic start, prohypertensive due to increased release of cytokines
- Ectopic fat deposition is laying fat where there shouldn’t be fat stored
