Alzheimer’s disease (AD) is an inflammatory condition considered one of the most common forms of senile dementia, and previous research in mice has shown that changes in gut bacteria could enhance inflammation and amyloidosis. Besides this, metabolic alterations such as insulin resistance and glucose metabolism dysregulation and altered lipid metabolism have also been linked to the development of AD. Studies in humans indicate a relationship between probiotics and cognitive function under certain circumstances. However, to date no study has considered gut microbiota manipulation in AD patients.
A recent study, led by Dr. Mahmoud Salami from the Physiology Research Centre at Kashan University of Medical Sciences in Kashan (Iran), has found that a daily dose of probiotic Lactobacillus and Bifidobacterium bacteria taken over 12 weeks may improve cognitive function in elderly Alzheimer’s patients.
The researchers conducted a randomized, double-blind and controlled trial with 60 elderly AD patients (60-95 years old) to assess the effects of probiotic supplementation on cognitive function and metabolic status. The patients were randomly divided into two groups (n=30 in each group) treated with either a fermented dairy product (probiotic group) or milk (control group). The probiotic supplementation consisted of administering 200 ml/day of a probiotic milk containing Lactobacillus acidophilus, L. casei, Bifidobacterium bifidum, and L. fermentum (2 x 109 colony forming units/g for each) for 12 weeks. Each participant underwent a test for mental function called the mini-mental status exam (MMSE), which is a standard measure for grading cognitive state, used worldwide. The MMSE questionnaire includes tasks like giving the current date, counting backwards from 100 by sevens, naming objects, repeating a phrase, and copying a picture, among others. Fasting blood samples were also obtained for determining biochemical parameters before and after the treatment.
The probiotic-treated patients showed a moderate but significant improvement in the MMSE score (from 8.7 to 10.6, out of a maximum of 30) after 12 weeks intervention, whereas in the control group the average score on the MMSE questionnaire did not significantly change (from 8.5 to 8.0).
In addition, treatment with probiotics in Alzheimer’s patients also resulted in lower levels of serum triglycerides, Very Low Density Lipoprotein (VLDL), plasma malondialdehyde (a biomarker of oxidative stress) and serum high-sensitivity C-reactive protein (hs-CRP, a powerful marker of inflammation). Furthermore, there was a reduction in the homeostasis model of assessment-estimated insulin resistance and in the quantitative insulin sensitivity check index – two common measures of insulin resistance – and in the activity of Beta cells, the insulin-producing cells in the pancreas.
To sum up, this is the first time that probiotic supplementation has been shown to benefit cognitive function and metabolic status in AD patients. Further human studies and longer follow-up periods are needed in order to test the beneficial effects of probiotics in this population.
Akbari E, Asemi Z, Daneshvar Kakhaki R, et al. Effect of probiotic supplementation on cognitive function and metabolic status in Alzheimer’s disease: a randomized, double-blind and controlled trial. Front Aging Neurosci. 2016; 8:256. doi: 10.3389/fnagi.2016.00256.