Every cell in your body requires a constant supply of glucose for energy. Since glucose is transported around the body to those cells, blood sugar levels in the blood need to be regulated. In fact, blood glucose needs to maintained within fairly strict limits because problems will result if those levels get too low (hypoglycaemia), or too high (hyperglycaemia).
The regulation of blood sugar level is a feedback mechanism – something that is common in your body, and largely under hormonal influence.
Over a 24 hour period, normal blood glucose levels show slight variations, with slight increases after meals, but this should drop again to a lower constant level. Over night, or after fasting, a healthy individual will show only slight reductions in blood sugar levels. So, how does the body regulate blood sugar?
Here is a diagram of the overall process:
Blood Sugar Levels Rise
If blood sugar levels increase (e.g. after a meal), the beta cells of the islets of Langerhans in the pancreas produce insulin. The insulin has an effect on various organs of the body, increasing cell permeability to glucose and increasing enzyme activity in the cells allowing the glucose to be taken up and stored.
The liver and muscle tissue converts glucose to glycogen and stores it. This helps reduce the levels of sugar in the blood. In addition, the breakdown of fats in fat cells is inhibited, so that glucose will be used preferentially for energy.
Blood Sugar Levels Fall
The alpha cells in the islets of Langerhans of the pancreas product glucagon. Glucagon is “antagonistic” to insulin, basically having the opposite effect on the organs of the body. Glucagon increases the conversion of stored glycogen into glucose in the liver and muscles thereby increasing blood sugar levels.
Glucagon also increases the uptake of amino acids and glycerol into the liver so that more glucose can be synthesized.
The importance of glycogen as stored energy
Since all of the cells in your body require a continuous supply of energy, it is important that your body stores excess “energy” eaten during meals so that it can be used when food is less plentiful. Excess glucose is converted to glycogen by the mechanisms we saw above.
Glycogen is stored in the liver and the muscles. When your body is active, energy requirements increase and stored glycogen can be converted to glucose to be used as energy. If stored glycogen levels get too low however, cortisol is secreted from the adrenal cortex, and this stimulates the conversion of proteins and fats into glucose so energy levels can be maintained.
NOTE: People who cannot regulate their blood sugar levels are diabetic. Many require daily injections of insulin (although this depends on the type of diabetes). Scientists have turned to recombinant DNA technology to manufacture enough insulin to supply the diabetic population, including some novel solutions like Humalog and Novolog. It's almost identical to human insulin but acts much more quickly. If you are interested, you can read more about Humalog & Novolog.