Glutamine-based oral rehydration solutions: the magic bullet revisited?

Protective effects of alanyl-glutamine supplementation against nelfinavir-induced epithelial impairment in IEC-6 cells and in mouse intestinal mucosa

PURPOSE

Human Immunodeficiency Virus (HIV) protease inhibitors (PI) remain a crucial component of highly active therapy (HAART) and recently have been demonstrated to have potent antitumor effect on a wide variety of tumor cell lines. However, discontinuation of therapy is an important issue, which may be related to various side-effects, especially diarrhea. The aim of this study was to evaluate the effects of nelfinavir (NFV), an HIV PI, and of alanyl-glutamine (AQ) supplementation, on intestinal cell migration, proliferation, apoptosis and necrosis, using IEC-6 cells and on intestinal crypt depth, villus length, villus area, mitotic index and apoptosis in Swiss mice.

METHODS

Migration was evaluated at 12 and 24 h after injury using a wound healing assay. Cellular proliferation was measured indirectly at 24 and 48 h using tetrazolium salt WST-1. Apoptosis and necrosis were measured by flow cytometry using the Annexin V assay. Intestinal morphometry and mitotic index in vivo were assessed following a seven-day treatment with 100 mg/kg of NFV, given orally. In vivo proliferation and apoptosis were evaluated by intestinal crypt mitotic index and immunohistochemistry, respectively.

RESULTS

In vitro, AQ supplementation enhanced IEC-6 cell migration and proliferation, following challenge with NFV. In vivo, AQ increased intestinal villus length, villus area, crypt depth and cell proliferation and cell migration, following treatment with NFV. AQ did not decrease cell death induced by NFV both in vivo and in vitro.

CONCLUSIONS

AQ supplementation is potentially beneficial in preventing the effects of PIs, such as NFV, in the intestinal tract.

Wasting and intestinal barrier function in children taking alanyl-glutamine-supplemented enteral formula

OBJECTIVE

We examined the effect of a diet supplemented with alanyl-glutamine (AG) or placebo glycine (G) on intestinal barrier function and growth in children in northeastern Brazil.

PATIENTS AND METHODS

One hundred seven children ages 7.9 to 82.2 months with a weight-for-age (WAZ), height-for-age (HAZ), or weight-for-height (WHZ) z-score less than -1 were studied. From July 2003 to November 2004, 51 study patients received AG (24 g/d) and 56 received G (25 g/d; isonitrogenic concentration) control for 10 days. Lactulose/mannitol excretion ratio was used as a measure of intestinal permeability and was performed on days 1 and 10 of nutritional supplementation. Weight and height were measured on days 1, 10, 30, and 120 of the protocol.

RESULTS

The patients were similar on admission with regard to age, sex, birth weight, nutritional status, lactulose/mannitol ratio, and serum concentrations of glutamine and arginine. The percentage of lactulose urinary excretion significantly improved (decreased) in children receiving AG for 10 days but not in those receiving glycine controls. AG significantly increased cumulative change over 120 days in WHZ and WAZ scores but not HAZ scores after adjustment for age and season in comparison with the placebo glycine group.

CONCLUSIONS

Children tolerated AG-supplemented enteral formula well, and it significantly improved cumulative WHZ and WAZ over 120 days in comparison with children in the placebo glycine group. The data also suggested a beneficial effect of AG in the barrier function paracellular pathway, albeit with reduced mannitol excretion. Thus, although the effect of AG on reduced mannitol concentration requires clarification, AG appears to improve nutrition and barrier function.

The use of oral rehydration solutions in children and adults

The observation that the intestinal Na(+)-glucose cotransporter remains intact in most diarrheal illnesses led to development of the life-saving, low-cost technology of oral rehydration salt (ORS) solutions. The primary therapeutic role of ORS solutions is in prevention and treatment of dehydration during management of acute gastroenteritis. Successful oral rehydration therapy involves early use of ORS with maintenance or timely resumption of regular feeding. Since the inception of the oral rehydration approach more than three decades ago, the widespread use of ORS solutions has revolutionized the management and outcomes of acute gastroenteritis in children and adults. The efficacy of the World Health Organization ORS solution and of commercial ORS formulations has been enhanced by reducing osmolarity. Newer formulations of ORS are under active investigation, with promise of added benefits, including promotion of intestinal healing. This article reviews fluid and electrolyte transport in the gastrointestinal tract, the pathophysiologic mechanisms of acute diarrhea, and the basis and formulation of current and newer ORS solutions. Guidelines for efficacious use of ORS in the management of acute gastroenteritis and short gut syndrome are also provided.

Proabsorptive effect of gum arabic in isotonic solutions orally administered to rats: effect on zinc and other solutes

We have previously shown that the addition of gum arabic (GA) to oral rehydration solution (ORS) enhances water and electrolyte absorption during jejunal perfusion in rats under anesthesia. This study investigates whether GA by oral administration could be equally effective in rats. Isotonic solutions containing 25 g/L GA (AG), or without GA (A0) were administered via oral tube to lightly anesthetized adult female rats. Similar experiments were conducted with hypertonic solutions containing no GA (B0), or either 10 (B10) or 50 g/L GA (B50). Blood concentrations of sodium, glucose, glutamate, zinc, and tritiated water were determined at 0, 15, 30, 60, 90, 120, and 180 minutes, and results between treatments were compared. Administration of the isotonic, GA-containing solution (AG) resulted in a higher blood zinc level than with the isotonic GA-free solution (A0) from 15 minutes throughout 180 minutes. Blood zinc at 15 minutes (means +/- SEM) was as follows: for A0: 69.3 +/- 2.0, for AG: 83.4 +/- 3.5 nmol/L, P=0.002. At 180 minutes, A0: 52.6 +/- 1.8; AG: 68.1 +/- 4.6 nmol/L, P=0.004. The corresponding areas under the curve (AUC) were as follows: for A0: 10,737 +/- 214; for AG: 13,919 +/- 765 nmol x min/L, P<0.001). Glucose, glutamate, sodium, and tritiated water body distribution presented no differences in blood concentrations. For sodium and tritiated water body distribution, there was a significant time effect (P<0.0001). In hypertonic solutions, blood zinc levels declined over time, possibly due to their osmotic, counter-absorptive action, thus obscuring possible opposite effects of GA. GA appears to be an effective enhancer of zinc absorption when orally administered in isotonic solutions to laboratory animals. This proabsorptive capacity could be attributed to some of the physicochemical and biochemical properties of GA and suggest possible applications of GA in liquid formulas and solid food preparations.

Towards a better oral rehydration fluid

Improvements in characteristics of solutions used for oral rehydration therapy, to provide significant reductions in amount and duration of diarrhea, are expected to contribute to wider use of these fluids. Recent studies suggest that these may come about from reducing the osmolality of the solution, and by providing short chain fatty acids for better fluid absorption from the colon. This article briefly reviews the physiology of intestinal and colonic absorption in diarrhea, and indicates the further studies that are needed to translate the above advances into universal practice for the treatment of diarrhea.