Guar Gum, Type of Dietary Fiber, Eases MS Severity in Mouse Model
Supplement as part of MS diet alters immune response in symptomatic animals
Guar gum, a type of dietary fiber that can be taken as a supplement, lessened inflammation and disease severity in a mouse model of multiple sclerosis (MS), a new study reports.
While fiber-rich diets have long been recommended to improve overall health, these findings help pinpoint which fibers have the greatest impact on immune system responses and should be part of dietary interventions for people with MS.
The study, “Inhibition of Th1 activation and differentiation by dietary guar gum ameliorates experimental autoimmune encephalomyelitis,” was published in Cell Reports.
Although no special or particular diet is favored for people with MS, studies generally show the disease to be less severe in people with healthy, well-balanced food choices. Most dietary recommendations for MS suggest that patients should eat plenty of fiber, which can help ease inflammation — but there are many kinds of fiber, and they are rarely considered individually.
“Dietary fibres are potent modulators of immune responses and can control inflammation in multiple diseases, but they’re a very biochemically diverse family. Our study gives us a clearer window into the potential of several sources of fibre in maintaining immune health,” Lisa Osborne, PhD, an assistant professor in the department of microbiology and immunology at the University of British Columbia (UBC) and a study co-author, said in a university press release.
Guar gum among 4 types of dietary fiber tested in EAE mice
To learn more, Osborne and colleagues conducted a series of experiments in mice with experimental autoimmune encephalitis (EAE), a common mouse model of MS.
Starting two weeks before EAE induction, the mice were fed either a standard diet containing 5% cellulose fiber, a diet with no fiber at all, or diets supplemented with 30% of one of four types of fiber: resistant starch, inulin, pectin, or guar gum.
After EAE was induced, the disease progressed similarly in mice on all of the diets, with one notable exception — mice given the guar gum diet had delayed symptom onset and lesser disease severity over a 15-day monitoring period.
“Guar gum supplementation significantly delayed symptom onset, limited disease incidence, and reduced cumulative disease severity in symptomatic mice over” those 15 days, the researchers wrote.
“Experts have consistently been saying fibre is good for you — and a variety of fibre sources is important to immune health — but there hasn’t been very much critical work into identifying how the body responds to different fibre types. It’s fascinating that this particular source has such an impact,” said Naomi Fettig, a PhD student at UCB and first author of the study.
Guar gum, also called guaran, is extracted from guar beans, which are mainly grown in India and Pakistan. The fiber is commonly used as an additive to thicken and stabilize food in parts of the world.
“Guar beans aren’t that common in western diets, and the gum isn’t used at these high levels as an additive in the west,” Fettig said.
Further analyses showed mice fed the guar gum diet had fewer inflammatory immune cells in their central nervous systems (CNS, the brain and spinal cord). MS is caused by inflammation in the CNS.
Results also showed that guar gum supplementation led to increased production of anti-inflammatory molecules called short-chain fatty acids (SCFAs) by microbes in the gut. But other fibers also led to an increase in SCFA production, so these differences cannot account for the effects only seen with guar gum.
“These data suggest that delayed EAE onset in guar gum-supplemented mice is a consequence of impaired immune cell recruitment to the CNS,” the researchers wrote.
Diet supplement’s benefits with MS may lie in CD4 T-cell changes
Further experimentation revealed that the guar gum diet led to reduced activation of a type of immune cell called CD4 T-cells. These cells grew less rapidly in mice fed the guar gum diet, and fewer of them showed signs of a pro-inflammatory process called Th1 polarization. The guar gum diet did not affect Th17 polarization, another type of inflammatory process in CD4 T-cells.
“These data reveal a previously unappreciated role for the dietary fiber guar gum as a selective modifier of CD4+ T cell activation and Th1, but not Th17, polarization,” the researchers wrote.
CD4 T-cells from guar gum-fed mice also showed reduced expression of genes coding for chemokine receptors and integrins, which these immune cells need to move through the body and to get into the CNS.
“These data suggest that in addition to inhibiting CD4+ T cell activation, proliferation, and Th1 polarization, guar gum interferes with expression of an array of chemokine receptors and integrins and limits CD4+ T cell migratory potential,” the researchers wrote.
In a final set of experiments, the researchers showed that T-cells from mice given guar gum were diminished in their ability to induce EAE in mice on a control diet, showing that the protective effects of the diet are at least partly due to their effect on T-cells.
A noted study limitation is that the doses of guar gum used were higher than would realistically given to people.
“Incorporating guar beans might be challenging to achieve at the doses we gave to mice, but a guar gum derivative, partially hydrolyzed guar gum, is commercially available as a prebiotic,” Osborne said.
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