Obesity and diabetes Flashcards
what are the energy stores in the body
plasma glucose - used by all cells, small store
glycogen (liver) - for plasma glucose homeostasis, highly hydrated
glycogen (muscle) - used only within muscle, can be rapidly mobilised and can provide ATP anaerobically, highly hydrated
triacylglycerol (adipose, muscle) - big energy yield, not hydrated, requires O2, cant be used by brain
protein - convertible to glucose and ketone bodies, all protein is functional
what occurs during fasting
breakdown of liver glycogen in the first defence against hypoglycaemia
as fasting continues gluconeogenesis becomes important (process where glucose is formed from amino acids, glycerol and lactate)
TAG breakdown then occurs which is an important fuels for muscles, kidney etc but cannot fuel the brain
in the liver non-esterified fatty acids (nefa), the mobilised form of fatty acids, is oxidised to acetyl-coA, most of which forms ketone bodies, they are fuels for many tissues including the brain and levels raise overnight
which reaction is irreversible
the pyruvate kinase reaction in glycolysis
lactate or pyruvate to glucose therefore goes by a TCA intermediate, oxaloacetate
what are the sources of plasma glucose during starvation
dietary carbs, then liver glycogen, then gluconeogenesis aftr a day or so
because protein breakdown is functionally costly and life limiting, TAG breakdown become the main source of energy (nefa for muscles, kidney etc, and ketone bodies for the brain, this spares the requirement for glucose
changes in plasma concentration after a meal
starch digestion quickly raises the glucose concentration to a peak which then rapidly declines as tissue removes glucose from plasma
glucose stimulates release of insulin, this promotes glucose uptake and utilisation
this fall in glucose then decreases insulin secretion
nefa is high during fasting and falls during feeding as the breakdown of TAG is inhibited by insulin
impact of insulin on liver muscle and adipose
liver - increases glycogen synthesis, decreases glycogenolysis, decreases gluconeogenesis
muscle - increases glucose uptake, glycogen synthesis and protein synthesis, decreases glycogenolysis
adipose - increases glucose uptake and TAG synthesis, decreases lipolysis
describe type 1 diabetes
insulin dependent, there is a failure of insulin production
early and rapid onset
weight loss, hyperglycaemia, ketonaemia \ (due to increased lipolysis)
polydipsia (excessive thirst), polyuria and metabolic acidaemia (build-up of acid in blood)
describe type 2 diabetes
loss of insulin sensitivity
slow onset, later in life
frequently associated with obesity
hyperglycaemia (increased TAG synthesis)
retinopathy, nephropathy (deterioration of kidney function), neuropathy, heart disease, circulatory problems
mechanism of metformin
drug used to treat type 2
inhibits gluconeogenesis
activates amp-activated protein kinase
acts on intestine
more effective when taken orally
metabolic effects of amp-activated kinase
increases - glucose uptake, glycolysis, fatty acid oxidation, mitochondrial biogenesis
inhibits - gluconeogenesis, glycogen synthesis, cholesterol synthesis, fatty acid synthesis, TAG synthesis, protein synthesis, rRNA synthesis
describe metabolic condition
characterised by obesity (particularly increased abdo fat)
high plasma TAG, low HDL, insulin resistance, glucose intolerance
long-term effects are increased BP, CVD, and risk of stroke
what is notable about the microbiome
provides a significant fraction of the total energy intake, through fermentation of complex dietary carbohydrates in the large intestine
what is leptin
peptide hormone secreted by adipose tissue
circulating levels correlate with body fat content
leptin receptors in the hypothalamus control the production of peptides that control appetite, satiety (feeling full) and rate of oxidative metabolism
what is congenital leptin deficiency
produces obesity in humans, can be reversed by daily injections of leptin
however the plasma leptin concentration is correlated with BMI, so leptin injections cannot be used to treat obesity in humans with normal leptin expression
what other horones affect digestion
ghrelin - secreted by gastric cells, increases hunger (orexigenic), inhibits insulin secretion and levels fall after feeding
cholecystokinin - secreted by duodenum, stimulates secretion of digestive enzymes and bile, slows gastric emptying, decreases hunger
gastric inhibitory peptide - secreted by duodenum and jejunum, inhibits gastric acidification, slows digestion, stimulates insulin secretion
peptide YY - secreted by ileum and colon anti orexigenic (decreases hunger)
