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Regulation of Carbohydrate Metabolism by 2,5-anhydro-D-mannitol
Patricio T. Riquelme, Mary Ellen Wernette-Hammond, Nancy M. Kneer and Henry A. Lardy
Proceedings of the National Academy of Sciences of the United States of America
Vol. 80, No. 14, [Part 1: Biological Sciences] (Jul. 15, 1983), pp. 4301-4305
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/14014
Page Count: 5
You can always find the topics here!Topics: Gluconeogenesis, Hepatocytes, Lactates, Diabetes, Diabetes complications, Biochemistry, Phosphates, Incubation, Enzymes, Cellular metabolism
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In hepatocytes isolated from fasted rats, 2,5-anhydromannitol inhibits gluconeogenesis from lactate plus pyruvate and from substrates that enter the gluconeogenic pathway as triose phosphate. This fructose analog has no effect, however, on gluconeogenesis from xylitol, a substrate that enters the pathway primarily as fructose 6-phosphate. The sensitivity of gluconeogenesis to 2,5-anhydromannitol depends on the substrate metabolized; concentrations of 2,5-anhydromannitol required for 50% inhibition increase in the order lactate plus pyruvate < dihydroxyacetone < glycerol < sorbitol < fructose. The inhibition by 2,5-anhydromannitol of gluconeogenesis from dihydroxyacetone is accompanied by an increase in lactate formation and by two distinct crossovers in gluconeogenic-glycolytic metabolite patterns--i.e., increases in pyruvate concentrations with decreases in phosphoenolpyruvate and increases in fructose-1,6-bisphosphate concentrations with little change in fructose 6-phosphate. In addition, 2,5-anhydromannitol blocks the ability of glucagon to stimulate gluconeogenesis and inhibit lactate production from dihydroxyacetone. 2,5-Anhydromannitol decreases cellular fructose 2,6-bisphosphate content in hepatocytes; therefore the effects of the fructose analog are not mediated by fructose 2,6-bisphosphate, a naturally occurring allosteric regulator. 2,5-Anhydromannitol also inhibits gluconeogenesis in hepatocytes isolated from fasted diabetic rats, but higher concentrations of the analog are required.
Proceedings of the National Academy of Sciences of the United States of America © 1983 National Academy of Sciences