PBL 1: Extremes of the food world Flashcards
What happens to glucose levels when you are starved?
Starved - glucose levels are low meaning glucagon levels are low and insulin is inhibited. Glucagon acts to activate gluconeogenesis in the liver as well as glycogenolysis to increase glucose levels. It also inhibits glucose uptake in cells.
However this only lasts for 24 hours without further carb intake and then starvation becomes prolonged where fat metabolism and ketone production occurs. The body also begins to reduce its demand for glucose and energy by switching off.
What compounds are used for gluconeogenesis?
Gluconeogenic amino acids (from muscles) Carbon compounds Glycerol lactate Pyruvate
What happens to glucose levels when you are fed?
Glucose levels are high meaning insulin is secreted. Insulin acts to reduce blood glucose levels through inhibiting the release of glucagon, inhibiting gluconeogenesis, inhibiting glycogenolysis and promoting glucose uptake.
What is the dominant energy source?
Lipids
Which organs cannot use lipids as an energy source?
Brain
Renal medulla
RBCs
What happens to lipids levels when you are in starvation?
Glucose levels are low meaning glucagon is released. Glucagon acts to promote lipolysis via activation of hormone sensitive lipase breaking down triglycerides into glycerol and fatty acids. Free fatty acids then get converted into ketones through beta oxidation. This means it can replace 50% of the brain’s energy use reducing the demand for glucose.
However if this is prolonged = ketoacidosis as acetoacetate builds up
What are the benefits of beta oxidation during starvation?
Formation of ketones to replace 50% of brain’s energy use reducing its demand for glucose
Protein usage is decreased so there is less muscle wasting
What is ketogenesis at the expense of?
Oxaloacetate
What is the main differences between marasmus and kwashiorkor?
Marasmus is when calories and proteins are lost whereas kwashiorkor is when there are mostly proteins lost as opposed to other compounds.
This means in marasmus you tend to not get any oedema whereas in kwashiorkor you do get ascites and oedema.
Onset of marasmus is months to years whereas kwashiorkor is weeks to months
Mortality is high for kwashiorkor but low for marasmus
What are the features of marasmus?
Forms in childhood
Calories and proteins lost
Onset is months to years
Mortality low Muscle wasting Hypoglycaemic Body temperature falls Hb falls Plasma albumin falls
What are the features of kwashiorkor?
Grossly proteins lost Adequate calories can be just 1 amino acid lost Swollen abdomen = ascites Weeks to months onset High mortality Enlarged liver Skin lesions Hair loss
Who is at risk of getting kwashiorkor?
Weaning babies at risk as lose protein from mother’s breast milk
How does ascites occur?
In kwashiorkor there is a protein deficiency - commonly this is albumin. This means there is reduced oncotic activity meaning water moves out from the cells into the EC space of the abdomen
In regards to the table, explain why:
- haemoglobin is low?
- WBC is low?
- platelet count is low?
- albumin is low?
- Na/Mg/P is low?
- Hb is low as there is a deficiency of protein intake and so less amino acids available to produce Hb
- WBCs are low as there is immunodeficiency due to the malnutrition, low energy levels mean immune responses are poorly activated and maintained
- Platelets are low as thiamine (B1) is low due to malnutrition
- Albumin is low due to low protein intake
- Sodium, magnesium and phosphate are low due to refeeding syndrome
Why are low WBCs such a large problem?
Immunodeficiency meaning many die of common infections as energy needed for activation and maintenance of immune responses
- susceptible to HIV/AIDS/TB/malaria/diarrhoea (which only causes further malnutrition)
What is the weight watchers diet?
Aim to reduce overall calorie intake
Point based system
Switch from glucose metabolism to fat metabolism to burn fat
No ketogenesis
What is the Low GI diet?
Low glycemic index diet
Controversial
Stick to low GI foods which take longer to digest so stay fuller for longer and sugar is released over time = reduce overall food intake
Also reduce insulin secretion so fat storage reduced
What is the glycemic index?
Measure of how much food changes blood glucose levels
Low GI = small rise in blood glucose levels
What is the Atkins diet?
Ketogenic diet
Restrict carbohydrates in diet so insulin levels stay low and fat is not stored
Slight intake of carbs to prevent gluconeogenesis from body’s proteins (no muscle wasting)
Protein intake mainly
Linked closely to starvation as get ketogenesis
How long can the body live in a starved state?
2 months
What is the refeeding syndrome?
A potentially fatal shift in fluids and electrolytes when malnourished patients are fed
What is the mechanism of refeeding syndrome?
Increases in glucose when fed = insulin increased and glucagon decreased = glycogen/fat/protein synthesis AND phosphate, magnesium, thiamine are taken into cells = water follows = potassium absorbed via Na+/K+/ATP symporter = glucose moves into cells = serum levels of nutrients decrease = malnutrition
What is the result of refeeding syndrome?
Changes in metabolism B1 deficiency Sodium/fluid imbalance Hypokalaemia Hypophosphatemia Hypomagnesia
Why do kwashiorkor children have a fatty liver?
Liver cannot make proteins (apolipoproteins) to transport the fats so get accumulated in the liver
