The Metabolism of Fructose in Man §¶

The metabolism of fructose has been studied with varying intensity and enthusiasm since Kulzu in 1874 first reported that diabetic patients were able to utilize fructose given orally better than other sugars. Although Naunyn' confirmed these results, he maintained that tolerance for fructose was eventually lost, and Joslin,11 as late as 1946, stated that in his experiments "at first the fructose was well-utilized, but later hyperglycemia and glycosuria usually followed." Interestingly enough, however, the same authors found that a diet containing Jerusalem artichokes, which on digestion yield fructose, could be taken for a period of at least three years without the subject losing his ability to utilize it more efficiently as compared with an equal amount of starch. The advent of insulin eliminated much of the clinical interest in fructose as an adjunct in the treatment of diabetes mellitus in man. Despite the inconsistent and often contradictory results reported in patients, it seemed clear in experimental diabetes in animals that fructose was handled differently from glucose and did not require the intervention of insulin. Minkowski1 in 1893 observed that fructose, in contrast to glucose, led to the formation of glycogen in the liver when given to depancreatized dogs. In 1929 Cori' studied the utilization in muscle of known amounts of intravenously injected fructose and glucose in eviscerated, depancreatized rats. By subsequently analyzing the entire carcasses for free sugar, he found that 39 per cent of the fructose and only 10 per cent of the glucose had disappeared in one hour. The injection of insulin resulted in a marked increase in the rate of disappearance of glucose but had no effect on the metabolism of fructose. A possible explanation for these findings lies in the