GUT BRAIN AXIS


“GUT BRAIN AXIS” :

by : Paolo Manzelli pmanzelli.lre@gmail.com,    S.Vincenzo (LI) 06th/JAN/2013

 Hank Osuna (Science &Art)

http://graphics8.nytimes.com/images/2012/06/19/science/19MICR/19MICR-articleInline.jpg

Premise:

The “Gut Brain Axis” interactions effects the “memory-based immune adaptive system” that responds to each new encounter with the gene-expression of microbial world on the basis of past interactions.

Therefore the adaptive immune system evolved in humans not only to mount defenses against micro-organisms but because of their need to recognize and manage the symbiosis with the many complex communities of beneficial microbes, in particular to those that live in the intestinal tract . It is well known that the enteric microbiota interacts with the gut-microbiome to form essential relationships that govern metabolic homeostasis.

Furthermore the regulation of the microbiome–gut–brain axis is essential for maintaining both symbiosis and the relative homeostasis of gut metabolic functionality, and this includes the memory processes of enteric brain (ENS) but also is inclusive of the bi-directional signalling with the central brain (CNS)

Therefore the ability of gut microbiota to communicate with the two brains
(ENS<–> CNS) and thus modulate their activity of neurotransmission is emerging as an exciting concept in health and disease prevention. .

Despite the unique bacterial fingerprint of each individual ( e.g  Microbiome symilarly to genome is an unique fingerprint of each person) , there appears to be a certain composition of biodiversity in gut-microbial balance confers a health gut benefits for a large spectrum of population .

It is, therefore, reasonable to note that a decrease in bio-diversity the gastrointestinal bacteria will lead to deterioration in gastrointestinal, neuro-endocrine and/or immune relationships and ultimately the dysbiosis based on the decrease of biodiversity in microbiome determines various metabolic and immunologic diseases.

Thus FUTURE HORIZON OF NUTRITION studies focusing on the impact to the enteric microbiota of the host and also to the central nervous system interactivity on the dysbiosis are essential to scientific understanding of the influence of this complex “gut-brain axis” system.

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Man is a “Super – Organism” because the complete genetics is not only determined by the Nuclear DNA of each cell, but  is inclusive of  the complemented expression and functions of Mitochondrial DNA, and through the symbiosis of Microbiome  e.g  the genetic of bacteria having a determinant effect in the primary metabolism of food. Most scientific literature show how  microbes living in our gut, where they work as a complex metabolic organ and provide bio-chemical transformations not encoded in our nuclear human genome.

The Microbiome /Microbiota healty functionality. .

Recent studies of the human microbiome have revealed that even healthy individuals differ remarkably in the microbes that occupy habitats such as the gut, skin and vagina. Much of this bio-diversity is important to establish epigenetic adaptation to the environment. Diet represent the most important relationship environment starting  from early microbial exposure to food.

In order to  characterize the human microbial communities composition and genetics , the Human Microbiome Project (HMP)  as an important result put in evidence that  the genetic diversity (microbiome)  and composition  of the types of  microbes (microbiota)  vary widely  among healthy subjects living in western society. (1)

There’s very broad variation in these bacteria in different person  , so that we can think that “each genome has associated a symbiotic personalized microbiome”.  This main result of the  HMP  gives severely limits our ability to define a “normal” microbiome profile to get a model of an “healty gut microbiome”  that can be preferred through modulating the composition of microbiota on the basis of different diets.

Bacterial colonization of the intestine is dynamic in relation to the changes of diets and so that is critical the symbiosis between genome and microbiome . As a consequence no- personalized diets  favor the risk of dysbiosis  by changing the normal  metabolic homeostasis, and producing many diseases such as the immune and endocrine systems. Besides it is emerging that the influence of the dysbiosis of gut –microbiome also extends some disturbances to the modulation of neural development.

Furthermore, it become very important to understand how the symbiosis genome-microbiome can be maintained  in a stable coordination for the prevention of an healty life and ageing

As a matter of fact recent research demonstrates that the overall balance in composition of the microbiota, together with the influence of pivotal genetic of bacterial species can induce specific responses, that can effect to  adult neural functions both in peripherally ENS and to the centrally CNS. Many studies have clearly demonstrate that effects of dysbiosis of commensal gut bacteria  include drastic lose of protection from  infection and procures bowel inflammation ads a consequence abnormal  modulation of behavioral responses giving stress and pain. There is now robust evidence that gut bacteria influence interactively the enteric nervous system, an also produces effects that may contribute to afferent signaling to the central brain. The vagus nerve has also emerged as an important means of communicating signals from the CNS to gut bacteria. Further understanding of the interactivity underlying microbiome-gut and brain communication (e.g. “ Gut-Brain Axis”) will provide with new insight into the symbiotic relationship between gut microbiota and the human hosts and therefore may identify and implement the potential of microbial-based knowledge for improving preventive or therapeutic strategies to aid the treatment of physiological and psychological  disorders. (2)

In particular it is known that the enteric brain works through the enteric sensory nerves stimulate gut motility and pain perception. These enteric  neurons in the intestinal tract are arranged in two  layers (plexuses) sandwiched between the two tubes of muscle that form the digestive tract. Hence the enteric  neurons control the gut, contracting the muscle to propel or mix its contents, as well as triggering secretion of water and enzymes to aid digestion and absorb nutrients. Viceversa gut bacteria interact with enteric neurons and the mucous membrane of the digestive tract though changes in bacteria metabolic activities that may alter anxiety-like behaviors and memory function. Furthermore signals produced by the metabolic microbiome-products (as for instance SCFA (= Short Chain Fatty Acids) can indeed travel interactively to the central brain via several different routes, including via vagal and spinal sensory nerves, and this changes in communication interactivity may be effect in altering  function in the central nervous system. Often interventions in substituting the microflora ( by fecal transplantation -3 ) seems to  be  effective for improving language, cognitive abilities, adaptive behavior, and social skills, and reducing anxiety and aggression in autism. But those results in relation to autism till now demonstrate some contracdictory research findings due the complexity of such interactive communication  and bio-chemical interaction .(4)

Recently  a  team of Australian researchers studied more than 50 children with autism and discovered ”no” significant differencies in gut microbes and also in the bacteria present in the digestive systems. This study contradicts some earlier research that has found that autistic children have microbiomes that differ from those of other kids. So that at the status of the art in this field that search to clarify the relationship effects between “ Microbiome and  Autism” there are so many contradictory among research findings, probably because they are seen  across too many different specific research fields.

The human microbiome serves as the interface between our genes and the evolution of environmental exposures. Therefore  future horizons  of the knowledge of  microbiome’s symbiosis  thus may offer  of providing new insights into our neuro-development, and perhaps to understand better even a variety of neuropsychiatric diseases ranging from affective disorders to autism.(5)

In conclusion more research findings are necessary to go beyond the  central question in psychiatry and understand  the relative role of genes and environment in shaping behavior.

BIBLIO ON LINE

(1)   – http://www.ncbi.nlm.nih.gov/pubmed/22699609

(2)   – http://www.ncbi.nlm.nih.gov/pubmed/22638926

(3)   – Bacteriotherapy or total gut flora fecal transplant : https://autismitsgutstupid.wordpress.com/2012/01/18/bacteriotherapy-fecal-transplant/#comment-3237

(4)   -http://blogs.plos.org/wonderland/2012/11/08/on-autism-gut-microbes-and-contradictory-research-findings/

(5)   http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3139398/

(6)   http://scienceline.org/2011/11/fecal-transplants-the-scoop-on-therapeutic-poop/

(7)   http://theconversation.edu.au/can-a-gut-bacteria-imbalance-really-cause-autism-9128

 

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