Week 8 readings summary Flashcards
why does NAFL develop?
If delivery of lipids to the liver outweighs the sum of the hepatic lipid oxidation and secretion, the intrahepatic lipid (IHL) content increases, causing NAFLD
4 conditions where IHL accumulates
Increased hepatic NEFA uptake due to higher fasting and/or postprandial plasma NEFA concentrations
Low partition of fatty acids to skeletal muscle (low chylomicron clearance by muscle and low NEFA uptake)
Elevated DNL; activated by elevated plasma glucose and insulin concentrations
Limited capacity to increase hepatic VLDL-TAG secretion and hepatic mitochondrial oxidation
what effect does aerobic exercise training have on IHL content?
- aerobic training decreases IHL content in the absence of weight loss
- (one study showed no change in IHL content in overweight men, but exercise was limited)
what effect does resistance exercise training have on IHL content?
- reduces IHL in obese and sedentary
- in adolescents, boys showed improvement in resistance and aerobic, girls only in aerobic
why does exercise effect IHL conc?
energy expenditure increases due to PA, inducing negative energy balance, which results in the mobilisation of hepatic lipids as a substrate to fuel the energy deficit
but IHL is lowered by affecting one of more pathways (this is known because weight loss is not always seen, as so cant all be due to the reason explained above)
how does exercise training affect plasma NEFA (which in turn causes a decrease in IHL content)?
increase in plasma NEFA uptake by skeletal muscle
some evidence for decrease in fasting and/or plasma NEFA
how does exercise training affect Dietary TAG (which in turn causes a decrease in IHL content)?
Increase in LPL-mediated TAG uptake by skeletal muscle
Decrease in HL-mediated TAG uptake by liver
how does exercise training affect DNL (which in turn causes a decrease in IHL content)?
Decrease in plasma insulin, a key player for the activation of DNL
In diabetes, exercise can decrease plasma glucose and hence decrease DNL
how does exercise training affect VLDL metabolism (which in turn causes a decrease in IHL content)?
decrease in hepatic VLDL as a consequence of lower hepatic TAG accumulation
how does exercise training affect mitochondrial oxidation (which in turn causes a decrease in IHL content)?
increase in hepatic CS and cytochrome C indicative for increases in hepatic mitochondria content and oxidative phosphorylation
how does a single bout of exercise affect IHL and why?
increases IHL content due to elevated plasma NEFA during exercise and in the post-exercise period
