Metabolic 3: metabolic response to stress vs starvation Flashcards
how does simple starvation differ from catabolic weight loss ?
simple starvation = metabolic adaptation and lean tissue conserved
catabolic weight loss = lean tissue breakdown which continues despite nutritional intake.
what is anorexia nervosa and how does it affect the body?
Nutritional deficiency, severe Severe restriction of nutritional intake Despite extremely low body weight Glucose: Low Starvation ketosis Physiological response for alternative energy supply
what changes would you see in urea and ketones in starvation?
Serum analysis showed increased urea, ketones
High urea indicates protein (muscle) breakdown & /or AKI
Ketones indicate use of an alternative energy supply from TG - FFA breakdown
In liver FFA for energy & conversion to ketones
what happens to glucose metabolism in starvation?
Low glucose causes decline in insulin & increase in glucagon release
Resulting in degradation: glycogen, fat stores, protein
To maintain glucose supply to cells without mitochondria: RBCs Brain requires some glucose
Brain adapts further to ketones for energy
describe normal glucose metabolism
Postprandial increase blood glucose
Stimulates insulin release
Insulin mediates glucose uptake into skeletal muscle, fat tissue
Suppresses hepatic gluconeogenesis
describe the process of ketoacidosis and what stimulates it.
Liver production of ketones
Stimulated by low insulin & high glucagon
Secondary to low glucose: fasting, low carbohydrate diet, diabetes
Lipase activated
Fat stores - triglycerides - long chain fatty acids & glycerol
Fatty acids transported to liver
name the 2 main ketone bodies
beta-hydroxybutyric acid
acetoacetic acid
describe the process of a fasting ketosis
which is the major ketone?
Liver generation of ketones is the physiological response to fasting
Mild ketosis ~1mmol/L after 12h fast
Fasting for 20 days: 8 - 10mmol/L
β-hydroxy butyrate is major ketone
Synthesis matches utilization : in brain, muscle, kidney
what are the 3 stabalisation methods in a fasting ketosis ?
Stabilization:3 mechanisms:
Stimulation insulin release, despite low glucose
Increased sensitivity of adipose tissue to insulin inhibitory effect on fatty acid release
Direct inhibition of lipolysis by ketones
No adverse effects with fasting ketosis.
why do we need to give nutritional support in critical illness?
Catabolism exceeds anabolism
Carbohydrates are preferred energy
Fat mobilization is impaired
Protein administration to decrease breakdown of muscle protein
List the sepsis 6
Give 1) oxygen 2) fluids 3) antibiotics Take 1) urine output 2) blood cultures 3) lactate
why is there lactic acidosis in sepsis?
Usual cause is Tissue hypoperfusion Impaired tissue oxygenation, leading to increased anaerobic metabolism Hypovolemia Cardiac failure Sepsis Cardiopulmonary arrest
list the hypermetabolic response to injury/trauma/surgical/critically ill
Increased blood pressure & heart rate Peripheral insulin resistance Increased protein and lipid catabolism Increased resting energy expenditure Increased body temperature Total body protein loss Muscle wasting Acute-phase protein response
what happens to glucose in critically unwell patient?
High catecholamines, cortisol
Increased gluconeogenesis Catecholamines:
Enhance glycogen breakdown
Impair glucose disposal via alterations of the insulin-signaling pathway; & GLUT4 translocation in muscle & adipose tissue, resulting in peripheral insulin resistance
why is there insulin resistance in critical illness?
Skeletal muscle is responsible for 75% of whole-body insulin-stimulated glucose uptake
Decreases in muscle contribute to this persistent insulin resistance
