RESUMO
Alzheimer's disease (AD) is a progressive and incurable neurodegenerative disorder of integrative areas of the brain, characterized by cognitive decline and disability resulting in negative impacts on the family of the patients and the health care services worldwide. AD involves oxidative stress, neuroinflammation and accelerated apoptosis, accompanied by deposition of amyloid-ß peptide plaques and tau protein-based neurofibrillary tangles in the central nervous system. Among the multiple factors that contribute to the onset and evolution of this disease, aging stands out. That is why the prevalence of this disease has increased due to the constant increase in life expectancy. In the hope of finding new, more effective methods to slow the progression of this disease, over the last two decades, researchers have promoted "omics"-based approaches that include the gut microbiota and their reciprocal interactions with different targets in the body. This scientific advance has also led to a better understanding of brain compartments and the mechanisms that affect the integrity of the blood-brain barrier. This review aims to discuss recent advances related to the gut-brain-microbiota axis in AD. Furthermore, considering that AD involves psychiatric symptoms, this review also focuses on the psychiatric factors that interact with this axis (an issue that has not yet been sufficiently addressed in the literature).
RESUMO
The fact that millions of people worldwide suffer from Alzheimer's disease (AD) or Parkinson's disease (PD), the two most prevalent neurodegenerative diseases (NDs), has been a permanent challenge to science. New tools were developed over the past two decades and were immediately incorporated into routines in many laboratories, but the most valuable scientific contribution was the "waking up" of the gut microbiota. Disturbances in the gut microbiota, such as an imbalance in the beneficial/pathogenic effects and a decrease in diversity, can result in the passage of undesired chemicals and cells to the systemic circulation. Recently, the potential effect of probiotics on restoring/preserving the microbiota was also evaluated regarding important metabolite and vitamin production, pathogen exclusion, immune system maturation, and intestinal mucosal barrier integrity. Therefore, the focus of the present review is to discuss the available data and conclude what has been accomplished over the past two decades. This perspective fosters program development of the next steps that are necessary to obtain confirmation through clinical trials on the magnitude of the effects of kefir in large samples.
RESUMO
The mechanisms responsible for cardiovascular and neurodegenerative diseases have been the focus of experimental and clinical studies for decades. The relationship between the gut microbiota and the organs and system tissues represents the research field that has generated the highest number of publications. Homeostasis of the gut microbiota is important to the host because it promotes maturation of the autoimmune system, harmonic integrative functions of the brain, and the normal function of organs related to cardiovascular and metabolic systems. On the other hand, when a gut microbiota dysbiosis occurs, the target organs become vulnerable to the onset or aggravation of complex chronic conditions, such as cardiovascular (e.g., arterial hypertension) and neurodegenerative (e.g., dementia) diseases. In the present brief review, we discuss the main mechanisms involved in those disturbances and the promising beneficial effects that have been revealed using functional food (nutraceuticals), such as the traditional probiotic Kefir. Here, we highlight the current scientific advances, concerns, and limitations about the use of this nutraceutical. The focus of our discussion is the endothelial dysfunction that accompanies hypertension and the neurovascular dysfunction that characterizes ageing-related dementia in patients suffering from Alzheimer's disease.