Metabolism of Fructose:
Sucrose, a disaccharide, is composed of equal amounts of fructose and glucose. High fructose corn syrup, as the name implies, is higher in fructose than glucose. Fructose and glucose are both monosaccharides.
Now the question is the ability of the human body cells to metabolize fructose in comparison to glucose. The name High fructose corn syrup that gives the impression that it contains a large amount of fructose. The content of fructose is only 55% versus 50% in sucrose. Sucrose is pure disaccharide of only glucose and fructose. The reason HFCS has more than 50% fructose is because the glucose extracted from corn starch is enzymatically treated ( Man is entering the picture) to convert some of the glucose to fructose. This treatment of the corn starch is done to make the sugar sweeter which is why it is so popular in the food industry. The enzymatically treatment is not done by the body but is artificially administered to increase the level of fructose. Any disorder and/or dysfunction attributed to the consumption of fructose can manifest whether one consumes cane sugar or beet sugar or HFCS. Plain old sucrose is the enemy.
Glucose metabolism is subject to a negative feedback system. When the hypothalamus metabolizes glucose a signaling pathway is initiated that results in the suppression of food intake and the ultimate release of glucose in the process of digestion. This feedback system prevents you from eating too much food. Changes in neuropeptide expression results in suppressed food intake while simultaneously increasing overall energy expenditure for the many very active cells that comprise muscle and neural tissue, for example. This is normal since an energy supply is necessary for active cells.
This is in contrast to fructose metabolism. The brain and the liver possess a unique set of transporters and enzymes that enable fructose to bypass a very important reaction that controls the rate limiting step in glycolysis that is critical in the regulation of ATP production and consumption. Glycogen is a stored sugar chemical in the liver that, when broken down, releases glucose into the bloodstream from the liver. If there is nothing ready to use the excess glucose it is converted to fat. You don't want that!
When the hypothalamus fructose metabolism bypasses the above regulatory step its metabolism rapidly depletes ATP in the hypothalamus. This leads to a series of chemical reactions that make the effects of glucose metabolism and fructose metabolism very different even though they utilize the same signaling pathway to control food intake. Keep this in mind. It is important to understand why fructose can lead to diabetes and obesity.
Fructose is highly correlated with the development of diabetes, obesity and a metabolic syndrome. Fructose metabolism differs from glucose metabolism in that fructose causes the formation of uric acid. A chemical is acted upon by uric acid that causes a very rapid depletion of ATP, the main source of chemical energy for body cells. When the body senses the loss of stored ATP it signals for food intake to manufacture the ATP it senses it, the body , needs. This chemical is not subject to feedback inhibition such as is the case for glucose metabolism. This results in a very large ATP depletion. This cycle repeats itself and more food is taken in and the breakdown product are stored as fat. You, in other words, get fatter and fatter. Since the liver is the source for the majority of fructose metabolism the depletion of ATP, in the liver, has a direct effect on other liver metabolic procedures. An increase in uric acid formation takes place after a series of chemical changes in the liver.
This increase in the level of serum uric acid is directly associated with the prediction for the development of obesity and hypertension. Gout is another disorder that is associated with the excess production of uric acid. Increased consumption of HFCS can lead to an increase in the symptoms of gout.
The metabolic syndrome results in laboratory test animals resulted in increases in obesity, visceral fat accumulation, fatty liver and elevated insulin levels. Changes in other chemicals after fructose consumption may account for increased food intake that could result in weight gain.
Keep in mind the consumption of any of the basic sources of sugar from sugar cane, sugar beets and corn starch all contain fructose. Abuse of sugar, any sugar, intake has serious effects on your health.
Jim
