Intestinal Consumption of Intravenously Administered Fuels

Abstract

Total parenteral nutrition has been extensively used to feed patients with a variety of gastrointestinal diseases, but little attention has focused on the nutritional requirements of the gut. To investigate intestinal consumption of intravenously administered nutrients, uptake of three principal fuels determined from in vitro studies was quantitated in seven awake, unrestrained dogs. Portal blood flow was measured by a dye dilution technique and, simultaneously, substrate samples were obtained from chronic indwelling arterial and portal venous catheters. Studies were performed during a postabsorptive basal period and during separate infusions of glutamine (0.10 mmol/kg X min), glucose (0.10 mmol/kg X min), and beta-hydroxybutyrate, (0.40 mmol/kg X min). During the basal period there was a significant arterial-portal vein gradient for glucose (144 +/- 26 mumol/liter) and glutamine (49 +/- 11 mumol/liter). These substances were taken up by the gut at rates of 4.11 +/- 1.23 and 1.43 +/- 0.19 mumol/kg X min, respectively. No significant uptake of beta-hydroxybutyrate was determined in the basal studies (0.27 +/- 0.10 mumol/kg X min). During substrate infusion, gut glucose uptake was unchanged (2.68 +/- 1.67 mumol/kg X min, NS), but consumption of glutamine (4.60 +/- 0.66 mumol/kg X min, p less than 0.001) and beta-hydroxybutyrate (4.33 +/- 0.71 mumol/kg X min, p less than 0.001) increased significantly. During parenteral feedings in patients with gastrointestinal disorders, circulating levels of beta-hydroxybutyrate and glutamine are often low, and glutamine is absent from standard amino acid solutions. Current parenteral formulation may not provide appropriate fuels for the gastrointestinal tract.

Paradigms for Mechanical Signal Transduction in the Intestinal Epithelium

“…It might therefore be postulated that these cells cannot exist without apical nutrients, and that this is why parenteral nutrition fails to support the gut. However, the enterocyte can derive nutrition luminally or by submucosal perfusion [70, 71]. Moreover, cultured intestinal epithelial cells survive quite nicely in culture if supplied with basal nutrients, and indeed appear to differentiate and proliferate more readily than if nutrients are only supplied apically [72].…”

Effect of low-dose oral glutamine on painful stomatitis during bone marrow transplantation

“…[4][5][6][7] The intestine utilizes glutamine as its primary energy source, and glutamine has been shown to be an essential dietary component for support and maintenance of intestinal growth and function. [8][9][10] Supplementation of TPN with glutamine has been shown to decrease villous atrophy associated with exclusive feeding via TPN. 11,12 Nutritionally depleted patients have been shown to have decreased plasma glutamine and mucosal glutamine.…”

Gut Glutamine Metabolism at Different Stages of Sepsis in Rats

“…Previous studies on rats have indicated that glutamine is the principal fuel utilized by the gut, 8,9 and that approximately 25% of circulating glutamine is extracted by the small intestine under normal conditions, 26 with most of the uptake occurring in the epithelial cells that line the villi. 8,27 Therefore, glutamine may be an essential component for the maintenance of gut structure and function, particularly during the catabolic state.…”

“…[5][6][7] The intestinal tract plays an important physiologic and metabolic role during the catabolic state. Glutamine is the principal fuel used by the gut 8,9 and may be an essential component for the maintenance of gut structure and function. 10 Therefore, much attention has been focused on gut glutamine metabolism in the catabolic state, and some of the effects of glutamine supplementation have been demonstrated in animal and clinical studies.…”