Tumor necrosis factor-alpha mediates hyperglycemia-augmented gut barrier dysfunction in endotoxemia.
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OBJECTIVE
To examine whether hyperglycemia would augment gut barrier dysfunction and inflammatory responses in endotoxemic rats, and simultaneously to clarify the roles of tumor necrosis factor (TNF)-alpha in alterations of gut mucosal permeability associated with hyperglycemia.
METHODS
Prospective randomized animal study.
METHODS
University research laboratory.
METHODS
: Male Wistar rats treated with lipopolysaccharide (LPS) injection.
METHODS
After LPS injection (4 mg/kg), rats were randomly allocated into group S (n = 6), group G (n = 7), or group GI (n = 8) with continuous infusion of different fluid solutions: normal saline, 40% glucose or 10% glucose mixed with insulin, respectively. Blood glucose, insulin, and proinflammatory cytokines, accompanied by gut mucosal permeability using an in situ loop preparation of gut with fluorescence isothiocyanate-conjugated dextran, were measured. Bacterial growth or alterations in mesenteric lymph nodes and cecal contents were also assessed. We further determined the roles of TNF-alpha using an inhibitor of TNF-alpha converting enzyme in gut barrier dysfunction under the same experimental settings.
RESULTS
Hyperglycemia over 400 mg/dL was achieved and kept in group G during the study period whereas normoglycemia was preserved in group S and GI, the latter of which showed the similar extent of hyperinsulinemia to group G. Plasma concentrations of fluorescence-labeled dextran and TNF-alpha in group G were significantly higher vs. group S and GI, and the number of bacteria found in mesenteric lymph nodes in group G was greater compared with group S. Intestinal environments including microflora and organic acids were not altered by blood glucose or insulin level. Inhibiting conversion of membrane-bound to soluble type of TNF-alpha restored gut mucosal permeability augmented by hyperglycemia.
CONCLUSIONS
These findings indicate that hyperglycemia deteriorates LPS-elicited gut barrier dysfunction and bacterial translocation independently of plasma insulin level, and that TNF-alpha mediates such mucosal dysfunction of gut in endotoxemia.
