Glucose versus Fructose : The Metabolic Difference.
Under the title “F” stands for fructose and fat” an article published in the October 10th 2013 issue of Nature summarizes the results of two studies that appeared in Hepatology (T. Hishomoto et al., 2013) and Nature Communications (T. Lanaspa et al., Nature Commun, 4, 2434, 2013 ). Investigations aimed at exploring further the role of fructose metabolism in obesity. This is a timely investigation in the context of clarifying the cause and effect relationship between an increase in dietary sugar consumption and epidemics of metabolic syndrome. Deciphering the relative contribution of the carbohydrate components (starch, sucrose, glucose, high-fructose corn syrup) is essential in elucidating some of the factors underlying epidemic of obesity and raising public awareness in healthy dietary practices.
The role of fructose on features of metabolic syndrome was assessed using wild-type mice and mice lacking a liver specific fructose metabolizing enzyme : ketohexokinase. Wild-type mice fed with fructose developed severe fatty liver and liver inflammation along with liver fibrosis. The mice that cannot metabolize fructose were protected from inflammation and fibrosis. A further step examined the effect of carbohydrate-rich diets devoid of fructose in mice that cannot metabolize this sugar. These animals appear to be protected from the adverse effects of excess glucose consumption. Mice that cannot metabolize fructose are healthier when placed on carbohydrate-rich diets. Whether such conclusions are also relevant to metabolic syndromes in humans remains to be ascertained. Nevertheless, the calorically equivalence of fructose and glucose should not hide their dramatic metabolic differences.