11.2 - Metabolic And Endocrine Control During Special Circumstances

Question 1

What fuel sources are normally available in the blood and available under special conditions?

Answer 1

Normally

• glucose
• fatty acids (except in RBC, brain and CNS)

Special conditions

• amino acids from muscle mass, converted to glucose or ketone bodies
• ketone bodies from fatty acids, used when glucose short as brain can use it
• lactate, made in anaerobic metabolism in body

Question 2

What happening 2 hours after feeding?

Answer 2

Immediate metabolism supported by glucose

Speed up growth and repair process

Make glycogen as rapidly as possible

Increase fat stores

Question 3

What happens 2-10 hours after feeding?

Answer 3

Glucose and fats no longer being absorbed

Maintain blood glucose by drawing on glycogen stores
Support other metabolic activity with fatty acids released from stores
Preserve blood glucose for brain

Question 4

What happens 8-10 hours after feeding?

Answer 4

Glycogen stores depleted = need to make more glucose

Continue to support metabolism with fatty acids

Question 5

What happens during starvation?

Answer 5

Need to reduce protein breakdown

Fatty acid metabolism produces ketone bodies

Brain becomes able to metabolise ketone bodies = reduces need for glucose.

Question 6

What do anabolic hormones do?

Answer 6

Promote fuel storage e.g insulin

Lack of insulin = catabolic state

Question 7

What do catabolic hormones do?

Answer 7

Promote release from stores and utilisation

E.g glucagon, adrenaline, cortisol, growth hormone and thyroid hormone

Question 8

What does insulin stop and promote?

Answer 8

Stop

• gluconeogenesis
• glycogenolysis
• lipolysis
• ketogenesis
• proteolysis

Go

• GLUT4 transporter for muscle uptake
• glycolysis
• glycogen synthesis
• protein synthesis

Question 9

What does feeding promote?

Answer 9

Amino acid uptake and protein synthesis in liver and muscle

Promotes lipogenesis and storage. Of fatty acids as triacylglycerol in adipose

Question 10

What do you get from fasting?

Answer 10

Glycogenolysis
Lipolysis
Gluconeogenesis - glycerol from fat provided. Kidney also starts doing this also.

Cortisol is released which prevents most cells from using glucose and fatty acids are preferentially metabolised.

Liver starts making ketone bodies and brain starts to utilise these sparing glucose requirement from protein

Question 11

What are the two main phases of metabolic adaptation during pregnancy?

Answer 11

Anabolic

• early pregnancy
• increase in maternal fat stores and small increase in insulin sensitivity
• nutrients stored to meet futur demands of rapid foetal growth

Catabolic

• late pregnancy
• decreased insulin sensitivity (increased resistance)
• tissues use fatty acids to save glucose
• increased resistance to insulin = increase maternal glucose and free fatty acid conc
• allows greater substrate availability for foetal growth.

Question 12

What’s the fetoplacental unit?

Answer 12

Placenta, fetal adrenal glands and fetal liver make an endocrine entity called the fetoplacental unit

Question 13

What hormones does the placenta release to control the maternal hypothalamic pituitary axis?

Answer 13

Hypothalamic

• CRH
• GnRH
• TRH
• GHRH

Pituitary like

• ACTH
• Human chorionic gonadotropin
• human chorion thyrotropi
• human placental lactogen

Question 14

What happens to insulin levels in the second half of pregnancy?

Answer 14

Maternal insulin increases

Anti insulin hormones increases at a faster rate

Therefore the insulin/anti insulin ratio falls

Cells therefore have decreased insulin sensitivity

Question 15

What are anti insulin hormones?

Answer 15

cause transient hyperglycaemia after meals because Of increased insulin resistance

Hypoglycaemia can occur between meals and at night because of the continuous fetal draw of Glucose

NB: maternal ant pit becomes desensitised to CRH so more ACTH and cortisol is around

Question 16

Whats insulin secretion like in pregnancy?

Answer 16

Increased appetite = more glucose in ingested

Oestrogen and progesterone increase sensitivity of maternal pancreatic B cells to blood glucose

• B cell hyperplasia
• B cell hypertrophy

Leads to increased insulin synthesis and secretion
If B cells don’t respond normally, blood glucose may become seriously high and gestational diabetes may develop

Question 17

What are the underlying causes of gestational diabetes?

Answer 17

1) autoantibodies similar to those characteristic of type 1 DM
2) genetic susceptibility to maturity onset of diabeties
3) B cell dysfunction in setting of obesity and chronic insulin resistance

Question 18

What are the clinical implications of gestational diabetes?

Answer 18

• Increased incidence of miscarriage
• Incidence of congenital malformation is 4x higher
• Fetal macrosomia (large body) = could get shoulder dystopia (shoulder gets stuck during birth)
• Associated with gestational hypertension and preeclampsia
• risk minimised if diagnosed and managed

Question 19

What makes someone more at risk of gestational diabeties?

Answer 19

Higher insulin resistance before pregnancy

Also age as fat to lean body mass ratio increases and insulin resistance increases with age (over 25)

BMI over 25 kg/m2

More common in Asians, black and Hispanic groups

If you have gestational diabetes during pregnancy will probably develop type 2 later in life.

Question 20

What’s the management for gestational diabeties?

Answer 20

Dietary modification

Insulin injections if persistent hyperglycaemia

Regular ultrasound scans to asses fetal growth

Question 21

What metabolic responses occur during excersise?

Answer 21

Increased energy demands met by mobilisation of energy stores

Glucose supply to brain maintain

End products of metabolism are removed asap

Question 22

How are atp stores replenished in exercise ?

Answer 22

Muscle creatine phosphate stores rapidly replenish

Glycolysis supplied atp - 2 per glucose

• using muscle glycogen in intensive excersise that’s anaerobic
• oxygen can be supplied from complete oxidation of glucose and glycogen stores from muscle and liver in long excersise e.g jogging

Oxidative phosphorylation - but needs oxygen

Question 23

What’s the role of the liver in blood glucose conc?

Answer 23

Excersise increases hepatic blood glucose production through glycogenolysis and gluconeogenesis

Liver recycles lactate produced by anaerobic metabolism

Rate of glucose production from liver is insufficient to meet full demands,
Needs to be maintained for brain

EXTRA

Muscle takes glucose from GLUT4 from insulin and GLUT 1 (always active )
Excersise also have insulin independant process of glucose uptake

Question 24

How are fatty acids used as fuel?

Answer 24

In aerobic conditions

• slow release from adipose tissue
• limited carrying capacity in blood
• capacity limited by uptake across mitochondrial membrane

Low rate of atp production but high capacity for sustained production

Question 25

How is energy produced in a sprint?

Answer 25

Anaerobic respiration and muscle store of glycogen , helps to spare blood glucose for brain

Question 26

How is energy used in 1500 m distance race?

Answer 26

Three phases

• initially creatine phosphate and anaerobic glycogen metabolism
• long middle phase in which ATP is made aerobically from muscle glycogen
• anaerobic metabolism of glycogen and produce lactate

Question 27

How is energy made in a marathon?

Answer 27

Aerobic mainly, uses muscle and liver glycogen and fatty acids

Insulin levels slowly fall
Glucagon Levels rise and do their thing

Adrenaline for glycogenolysis and lipolysis and more growth hormone for lipolysis and gluconeogenesis

Cortisol rises slowly for lipolysis and gluconeogenesis

Question 28

What are the benefits of excersise?

Answer 28

• less adipose more muscle
• glucose tolerance improves
• more insulin sensitive tissues
• less blood triglycerides
• blood pressure falls
• psychological effects