Metabolic States & Metabolic Rate

Absorptive state

fed state → 4 hours after eating began → absorption of nutrients → nutrients can be used immediately to meet energy needs (excess can be stored)

Post absorptive state

fasting state → between meals when GI tract is empty → energy source is supplied by breaking down reserves to maintain blood glucose level

Absorptive state → anabolism vs catabolism

anabolism exceeds catabolism → focus more on using incoming nutrients and storing excess/ building

Absorptive state - carbohydrates

glucose is the major energy fuel → converted to fat or glycogen to be stored (glycogenesis + lipogenesis)

Absorptive state - triglycerides

most glycerol and fatty acids are convereted to triglycerides to be stored

energy source for muscles and liver cells (hepatocytes)

Absorptive state - amino acids

amino acids are used in protein synthesis

excess are deaminated → then stored as fat or used for ATP (in the liever)

Hormonal control of absorptive state

Insulin → secreted when blood glucose level is elevated/ high

hypoglycemic (lowers blood sugar) hormone

Insulin effect on metabolism

• glucose

• glucose oxidation, glucogenesis, lipogenesis, glucoconeogenesis

• Amino acid

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• moves glucose into muscle or adipose cells (brain and liver take glucose without insulin)

• stimulates glucose oxidation (glucose →atp)

• stimulates glucogenesis and lipogenesis (glucose → glycogen and triglyceride for energy storage)

• inhibits gluconeogeneisis (prevent liver from making new glucose when glucose is already high)

• active transport of amino acids to tissue cells + promotes protein synthesis

Diabetes mellitus

inadequate insulin production or abnormal insulin receptors

→ glucose becomes unavailable to cells (can’t enter) → high blood glucose → kidney can’t reabsorb it so it spills into urine

→ fats and proteins are used for energy instead

Effects of fats and proteins being used from diabetes mellitus (3)

1. weight loss

2. protein waste

3. fat breakdown → lots of acetyl CoA → ketogenesis → lots of ketone bodies → lowers blood pH (metabolic acidosis)

Post absorbtive state - catabolism vs anabolism

catabolism of fat, glycogen, and protein exceeds anabolism → focused more on breaking down stored nutrients

Goal of post absorptive state

maintain blood glucose levels / make glucose available to blood

+
promote use of fat for energy (glucose sparing )

Glucose sparing

saving glucose for organs that need it most → use fat as energy instead (fatty acids)

Sources of blood glucose during post absorptive state (fasting)

• glycogenolysis in liver and skeletal muscle (glycogen → glucose)

• lipolysis in adipose tissue and liver → breaks down triglyceride into glycerol and fatty acid → glycerol can be used for glyconeogensis (production of glucose from non carbs) in the liver

• Catabolism of cellular protein → glucose

Hormonal control of postabsorptive state

• what stimulates it to be released (2)

• what does it promote (2)

glucagon - hyperglycemic hormone (raises blood glucose)

• stimulated by declining blood glucose level and rising amino acid level

• promotes glycogenolysis + gluconeogenesis in liver (increase glucose)

  • promotes lipolysis in adipose tissue (fatty acid and glycerol increased in blood

Neural control of postabsorptive state

sympathetic nervous system interacts with hormones to control events in post absorptive state

ex: epinephrine and cortisol