Friday, 26 September 2008

Clever, no?

If we eat a meal consisting mainly of carbohydrates, then insulin is the dominant hormone released, while glucagon is suppressed.  Insulin duly stimulates glucose uptake by peripheral cells, as well as glycogen synthesis in the liver and muscles.  In addition, hepatic gluconeogenesis and ketogenesis are inhibited by insulin, a process facilitated by the low levels of glucagon.  Lastly, fat storage occurs in adipose tissue.

On the other hand, if we eat a meal consisting mainly of protein, both insulin and glucagon are raised.  The reason that insulin levels are boosted
 is that the hormone stimulates amino acid uptake and protein synthesis.  In other words, the hormone is anabolic with regards to protein, which makes sense, as the right time to increase protein production is surely when you've just taken in a whole lot of amino acids!  However, without enough carbohydrates in our hypothetical meal, there is the very real risk of insulin causing hypoglycaemia.  To counteract this risk, glucagon is also secreted, which causes a stimulation of hepatic gluconeogenesis.  This balances the opposing glucose-lowering effects of insulin, thereby preventing hypoglycaemia.

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