Study summary; A new study has been published which investigated whether diet may interact with the effect of cologic® Barrier on depression-related behaviour in rats. The study was carried out by researchers from Aarhus University, Denmark. A previous study from the same researchers already showed that rats become less depressive when they were given Ecologic® Barrier1. In this new study the researchers aimed to find out if a typically Western diet could interfere with this effect since diet is known to have a profound impact on the gut microbiota. Furthermore, they examined three underlying mechanisms that may be involved in reducing depressive symptoms by microbiota-mediated effects. The results showed that Ecologic® Barrier again reduced depressive-related behaviour in rats and that this effect was independently of diet2. These results and previous research suggest that Ecologic® Barrier could be a good potential treatment for depression.
A number of mice studies and a few human studies have now evaluated whether manipulation of the gut microbiota through probiotics can affect behaviour. It appears that probiotics can modulate a wide range of behavioural conditions, including depressive related behaviour. However several questions regarding the underlying mechanisms remain unanswered. One of these questions is whether probiotic treatment may be the concurrent with diet. Diet has a major impact on the gut microbiota. Particularly a Western pattern diet, containing high-fat low-fibre, is associated with changes in the gut microbiota composition and poor microbial diversity.
In this new study the researchers investigated whether the habitual diet may interact with the effect of Ecologic® Barrier on depression-related behaviour and further examined some potentially involved mechanisms underlying the microbe-mediated behavioural effects.
The mechanisms the researchers investigated were:
hippocampal and hypothalamic HPA axis regulationscytokine profile of stimulated immune cells and plasma metabolomics profile.
For their experiments Winclove provided them with Ecologic® Barrier, a multispecies probiotic specifically developed to strengthen the intestinal barrier function and decrease inflammation. Winclove had no further role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.
Forty male rats were randomly assigned to a control or high-fat diet (HFD) for 10 weeks. After 5 weeks on the diet the rats were randomised to placebo or probiotic treatment. The rats in the probiotic group received Ecologic® Barrier (Mixture of 8 bacterial strains: B. bifidum W23, B. lactis W52, L. acidophilus W37, L. brevis W63, L. casei W56, L. salivarius W24, Lc. Lactis W19, Lc. Lactis W58) in a carrier matrix of maize starch, maltodextrins and vegetable protein. The rats in the placebo group were given the matrix only. The experimenter was blinded to treatment groups. The forced swim test (FST) was used to measure depressive-like behaviour in the rats; the more depressed rats are, the less they move.
Ecologic® Barrier significantly (p< 0.001) reduced depressive-related behaviour in the forced swim test by 34% (95% CI: 22-44%). This effect was independently of diet.
Findings on underlying mechanisms:
Probiotic treatment skewed the cytokine production stimulated blood mononuclear cells towards IFNγ. IL2 and IL4 at the expense of TNFα and IL6.
In addition probiotics lowered hippocampal transcript levels of factors involved in HPA axis regulation whereas a high fat diet increased these levels.
A non-targeted plasma metabolomics analysis revealed that probiotics raised the level of indole-3- propionic acid, a potential neuroprotective agent.
The results of this study again confirm the ability of Ecologic® Barrier to reduce depressive related behaviour in rats. The effect of Ecologic® Barrier was not attenuated by consumption of a Western diet.
In addition the researchers found corresponding changes in three physiological systems that could potentially mediate the observed antidepressant-like effect.
profound shifts in the pattern of produced cytokines changes in hippocampal expression of genes related to HPA axis regulation, alterations in concentration of a number of plasma metabolites.
The results of this study are in line with previous pre-clinical studies which also found probiotic intake related to reduction in depressive-like behaviour in rats and mice. Although a lot of pre-clinical evidence supports a role for probiotics in the treatment of depression, human studies with depressed patients are still scarce. However, effects in healthy volunteers have been established by a couple of other studies among which a study with Ecologic® Barrier3 The findings clearly support Ecologic® Barrier as a potential treatment strategy for major depressive disorder.
- Abildgaard et al. Probiotic treatment alters behavior in rats on standard and high fat diet. Acta Neuropsychiatrica 2014;26:1
- Abildgaard et al. Probiotic treatment reduces depressive-like behaviour in rats independently of diet. Psychoneuroendocrinology, article in press.
- Steenbergen et al. A randomized controlled trial to test the effect of multispecies probiotics on cognitive reactivity to sad mood. Brain Behav Immun 2015;48:258-64.