Infected mice fed a diet supplemented with 5% L-glutamine (total 6.9%) had significantly less gastric inflammation and hyperplasia than those fed a diet with 1.9% glutamine, Susan J. Hagen, Ph.D., of Beth Israel Deaconess Medical Center in Boston, and colleagues found.
Supplemental L-glutamine also appeared to improve early immune response to H. pylori infection, they reported in the May 2009 Journal of Nutrition.
Glutamine is a nonessential amino acid found in beef, chicken, fish, eggs, dairy products, and some grains and vegetables. L-glutamine -- the biologically active isomer of glutamine -- is also widely available in commercial dietary supplements promoted for bodybuilding.
"Glutamine supplementation may be an alternative therapy for reducing H. pylori-associated pathology," the researchers said.
Antibiotics plus a proton pump inhibitor are the recommended first-line treatment to eradicate H. pylori, which reduces the inflammation that promotes gastric cancer development.
However, a recent review suggested that regimens for H. pylori eradication are losing efficiency, largely due to drug resistance.
Dr. Hagen's group also noted that cost, side effects, and patient compliance hamper mass treatment strategies, while eradication therapy is not recommended for asymptomatic patients or those with dyspepsia without ulcer disease.
Given the interest in alternatives such as vaccines and dietary strategies, the researchers looked at dietary glutamine, which they had previously shown protects against cell death from H. pylori-produced ammonia.
They divided 105 mice into two groups fed either a standardized diet with 1.9% glutamine or the same diet with supplemental L-glutamine replacing carbohydrates for 5% of total calories.
After two weeks on these diets, the mice were further allocated to an uninfected sham group or infection with H. pylori.
Throughout the 20-week follow-up period, the diet groups remained similar in weight gain and mean H. pylori colonization levels.
This was reassuring, Dr. Hagen's group noted, because the bacteria also use glutamine to produce ammonia.
"One concern we had originally was that H. pylori growth and colonization would be enhanced by a L-glutamine-containing diet and H. pylori-related pathology would be more severe with this diet regime," they wrote.
While serum antibody levels to the bacteria were unaffected by extra glutamine in the mouse diet, some early immune responses were elevated in gastric tissues, though these effects dissipated by week 20.
Among the T-helper 1 cytokines, the proinflammatory interleukin-1b increased significantly more with L-glutamine by six weeks postinfection than with a low glutamine diet (P<0.05).
The same was true at six weeks for T-helper 2 cytokines interleukin-4, interleukin-10, and transforming growth factor-b (all P<0.05).
This immune modulation was reflected in greater inflammation in gastric tissue on histopathology at six weeks among infected L-glutamine group mice.
But by week 20, the L-glutamine diet resulted in lower inflammation levels than the control diet.
While all the infected mice showed the expected histopathology changes in the stomach, mean scores for foveolar hyperplasia and hyperplastic gland length were lower with L-glutamine supplementation at 20 weeks compared with controls (P<0.05).
These results suggested that "mucosal barrier disruption and immune cell recruitment were reduced, rather than facilitated, by L-glutamine," the researchers concluded.
They noted that a higher level of dietary glutamine might offer even greater protection, with further study warranted.
|The study was supported by grants from the National Institutes of Health.
- Reviewed by Dori F. Zaleznik, MD Associate Clinical Professor of Medicine, Harvard Medical School, Boston