S10 Metabolic and Endocrine Control during Special Circumstances Flashcards
(38 cards)
What fuel sources are normally available in the blood?
Glucose (stored as glycogen in liver and skeletal muscle)
Fatty acids (stored at TAG in adipose tissue)
Which fuel sources are availed under special conditions?
Amino acids - converted to glucose or ketone bodies
Ketone bodies - from fatty acids - brain can use this
Lactate - product of anaerobic metabolism in muscle - can be converted back into glucose in the Cori cycle by liver or utilised for TCA cycle by other tissues
What are the anabolic hormones involved in metabolic control?
Insulin
And growth hormone in terms of the fact it increases protein synthesis
What are the catabolic hormones involved in metabolic control?
- glucagon
- adrenaline
- cortisol
- growth hormone - increases lipolysis and gluconeogenesis
- thyroid hormones
Which metabolic processes does insulin lead to the inhibition of?
- gluconeogenesis
- glycogenolysis
- lipolysis
- ketogenesis
- proteolysis
Which metabolic processes does insulin lead to the activation of?
- glucose uptake in muscle and adipose (GLUT4)
- glycolysis
- glycogen synthesis
- protein synthesis
What metabolic processes occur in energy starvation?
- Reduction of blood glucose stimulates the release of cortisol from the adrenal cortex and glucagon from the pancreas
- These stimulate gluconeogenesis and fat and protein breakdown
- Reduced insulin levels and anti-insulin effects of cortisol prevent cells from using glucose - fatty acids are metabolised instead
- The liver starts producing ketone bodies and the brain utilise these instead of glucose
- The kidneys start to contribute to gluconeogenesis
- When fat stored are depleted, protein is used as fuel
- If death occurs, it is because of loss of muscle mass
Why must increase in protein content of diet be gradual if someone is malnourished?
Otherwise get refereeing syndrome (ammonia poisoning)
What are the two main phases of metabolic adaptation during pregnancy?
- anabolic phase - predatory increase in maternal nutrient stores especially adipose
- catabolic phase - maternal metabolism adapts to meet an increasing demand by fetal-placental unit
What happens in the anabolic phase of pregnancy?
- increase in maternal fat stores
- small increase in insulin sensitivity
- nutrients are stored to meet future demands of rapid fetal growth and lactation after birth
This is early pregnancy
What happens in the catabolic phase of pregnancy?
- decreased insulin sensitivity/increased insulin resistance - increase in maternal glucose and free fatty acid concentration - more substrate available for fetal growth
- maternal tissues use fatty acids instead of glucose
Occurs in late pregnancy
What happens in placental transfer?
Most substances are transferred by simple diffusion down concentration gradients
- glucose transfer is by facilitated diffusion via GLUT1 transporters
What is a fetoplacental unit?
In pregnancy, the placenta, fetal adrenal glands and fetal liver control maternal metabolism to ensure the fetus’ survival.
The placenta secretes lots of proteins that can control the maternal hypothalamic pituitary axi
What are anti-insulin hormones in pregnancy? What is the effect on the mother?
Hormones secreted by the placenta that have anti-insulin effects on the maternal metabolism
E.g. corticotropin releasing hormone, human placental lactogen, progesterone
Transient hyperglycaemia after meals due to increases insulin resistance
But hypoglycaemia can occur between meals and at night due to continuous fetal draw of glucose
What effect do oestrogens and progesterone have on pancreatic beta-cells?
They increase the sensitivity of maternal pancreatic beta-cells to blood glucose - so increased insulin synthesis and secretion.
- if the beta-cells don’t respond normally, blood glucose can become very high and gestational diabetes can develop
What is gestational diabetes?
A disease in which pancreatic beta-cells don’t produce enough insulin to meet the increased requirement in late pregnancy
What are 3 underlying causes of gestational diabetes?
- autoantibodies similar to those of type 1 diabetes mellitus
- genetic susceptibility similar to maturity onset diabetes (rare)
- beta-cell dysfunction linked to obesity and chronic insulin resistance e.g. evolving type 2 diabetes mellitus - common
What are the clinical implications of gestational diabetes?
- increases risk if miscarriage
- increases risk of congenital malformation
- fetal macrosomia can occur - large bodied baby
- disproportionate amount of adipose around the shoulders and chest - shoulder dystocia - shoulders could get stuck during birth
- gestational hypertension and pre-eclampsia
These can reduced if it is diagnosed and managed
What plays a role in determining if a women’s develops gestational diabetes or not?
Their starting point in terms of insulin resistance before pregnancy
Risk factors:
- maternal age over 25 years
- BMI of 25kg/m2 or above
- more common in Asian, black and Hispanic ethnic groups
- personal/family history of diabetes
- family history of macrosomia
How do you manage gestational diabetes?
- dietary modification
- insulin injection
- regular ultrasounds to assess the fetal growth and wellbeing
In which body systems are there rapid adaptations when someone goes from rest to exercise?
- MSK
- CVS
- respiratory system
- temperature regulation
When someone is exercising, what does the metabolic response need to ensure?
- increased energy demands of skeletal and cardiac muscle are met by mobilisation of energy stores
- there are minimal disturbances to metabolic homeostasis - keep rate of mobilisation = to rate of utilisation
- glucose supply to the brain is maintained
- the end products of metabolism are removed ASAP
What needs to be rapidly resynthesised to meet metabolic demands on cells during exercise?
ATP
Where does the energy come from used in exercise?
- muscle creatine phosphate stored can quickly replenish ATP
- glycolysis
- oxidation phosphorylation
