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When glucose–fructose dimers are supplied as the slowly digestible, completely absorbable, low glycemic index (GI) sugar isomaltulose, the detrimental effects of high GI sucrose are avoided. This difference requires the presence of intact glucose-induced insulinotropic peptide receptor (GIPR) and is mediated by the rapid uptake of glucose and the stimulation of GIP release from K cells in the upper small intestine. GIP promotes lipogenesis, fatty liver, insulin resistance, and postprandial inflammation, and reduces fat oxidation in skeletal muscle, partly by hypothalamic interference with energy partitioning and epigenetic programming. GIP is similarly required for the detrimental metabolic effects of other high GI carbohydrates. We therefore propose that the release of GIP in the upper small intestine is an important determinant of the metabolic quality of carbohydrates. [ABSTRACT FROM AUTHOR]

This study examines the effects of summer drought on the composition and profiles of cold-season reserve and soluble carbohydrates in sugar maple (Acer saccharum Marsh.) trees (50–100 years old or ~200 years old) in which the crowns were nondamaged or damaged by the 1998 ice storm. The overall cold season reserve carbohydrate profiles in twig wood tissue of drought-stressed (DS) trees and non-drought-stressed (NDS) trees were generally similar, although differences were observed in the amount of reserve carbohydrates in DS and NDS trees. The cold-season level of starch stored in DS trees in early autumn in the wood tissue was about one-third to one-fifth that in NDS trees. The cold season sugar content in the DS trees was significantly greater than can be attributed to degradation of stored starch, only. The level of sucrose in DS trees remained high throughout the winter until termination of dormancy and dehardening. The concentrations of winter glucose and fructose in DS trees attained peak levels at the time of dormancy termination and declined during dehardening. The profiles of glucose and fructose in DS and damaged DS trees were generally different from that of sucrose throughout the leafless phase. In contrast, profiles of glucose and fructose in NDS trees closely paralleled that of sucrose. Elevated levels of sucrose, glucose, and fructose in DS sugar maple trees during the cold season may function as osmoregulators for freeze protection. Low sugar level or lack of increase in sugar level following dehardening in DS trees may suggest limited change in cellular constituents in adapting to low temperatures. [ABSTRACT FROM AUTHOR]

To assess the effect of the ice storm of January 1998 on sugar maple (Acer saccharum Marsh.) tree health, starch, and soluble sugars in twigs from two damaged sugarbushes (younger: trees 50–100 years old, and older: trees approximately 200 years old) in northern New York were measured throughout the leafless phase (September 1998 – May 1999). Trees severely damaged by the ice storm exhibited signs of recovery during the first growth season (1998), that is, greater numbers of lateral (epicormic) shoots and increased wood production in the current year growth ring of branches at mid-crown, and high concentrations of starch in the twigs at the time of leaf drop. Differences in reserve and soluble sugar profiles between damaged and slightly damaged or undamaged sugar maple trees and between trees of the older sugarbush and those of the younger sugarbush indicate changes in cold season physiology of damaged trees in adapting to or tolerating cold temperature. In damaged trees of the younger and older sugarbushes, the profiles of sucrose, stachyose, raffinose, and xylose were similar to those of corresponding slightly damaged or undamaged trees throughout the cold season, except for late winter sucrose, glucose, and fructose profiles, which exhibited differences in concentration and profile configurations compared with respective slightly damaged or undamaged trees. A lower concentration of sucrose in damaged older tree wood tissue after dehardening in late winter and a lower concentration of "resynthesized" starch just prior to vernal growth were observed. The data indicate that the profiles of individual sugars can provide information on changes in physiological and biochemical processes in damaged trees during the cold season. [ABSTRACT FROM AUTHOR]

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