Hello, and welcome to our Animal Care Learning Alliance webinar, the gastrointestinal microbiome and its effects. The intestinal microbiome is a topic that is garnering increasing interest and research focus due to a tide of evidence demonstrating influences external to the GI tract across multiple body systems. The purpose of this webinar is to explore some of the functions and influences that the intestinal microbiome has and ask ourselves whether there are any clinical implications for us as vets now or in the future.
The definition of the intestinal microbiome is the total collection of microbial organisms within the gastrointestinal tract of a host animal. This is predominantly bacteria but also includes viruses, fungi, and protozoa. We've included some fun facts with regards to the human intestinal microbiome, but what about dogs?
It seems logical that microbiome composition would vary between species to match their ecological niche and the dietary implications that it presents. It also makes sense that variations may occur in response to a changing environment, seasonal food availability, for example. The consistency of variation between breeds within species suggests there may be a genetic component, however, this is further supported by observed signatures of microbial heritability.
Is there perhaps potential to identify individual whose genotype encourages an intestinal microbiome that gives them some kind of advantage that is useful clinically? This is the basis for the development of prokanica. Dogs with renowned iron stomachs were initially studied by Doctor Beasley when developing the product and deciding which lactobaci strains to include.
What does the intestinal microbiome actually do for the host? Let's start with the immediate effects within the gut. It is well known that mammalian species can't digest plant materials such as cellulose, but various bacterial species can.
This has led to the development of the symbiotic relationship and the evolution of fermentation specialists such as ruminants. This more efficient conversion of plant material to energy is felt by most mammalian species. However, exploitation of a wide range of ecological niches that would otherwise not support the mammalian biodiversity that they do.
One of the products of cellulose digestion are short chain fatty acids, namely acetate. Propionate and butyrate. These compounds have many functions within the gut for the host, for the microbiome itself, and across the body.
They provide direct nutrition to cholonocytes and are instrumental in biastic metabolism. Acetate is the main source of energy for the bacteria of the microbiome. And butyrate is essential for maintaining oxygen balance in the gut, protecting the entire population from dysbiosis, which is defined as alterations to the population numbers, diversity and function.
Short chain fatty acids travel to peripheral tissues where they are involved in cholesterol metabolism and lipogenesis and therefore appetite regulation. So even though we are talking about the local effects of the microbiome here, you can already start to see how the effects spread beyond the gut. Another non-digestible substance that the intestinal microbiome are instrumental in managing is endogenous intestinal mucus.
While another important function of bacterial species such as bifidobacterial and some lactobacillus species is the production of vitamins, particularly B group vitamins, effectively supplying them into the gut for their host to use. One important local effect of the intestinal microbiome is pathogen exclusion. This function is provided by the commensals and is delivered by different mechanisms including inhibition achieved by the production of antimicrobial peptides or AMPs, displacement and competition.
One of the most basic ways to prevent infection by a pathogens is though is by ensuring that there are no physical weak spots in the intestinal mucosa that could allow entry. Remember that the epithelial layer of the gut lining is just a single cell thick. It is here that the previously discussed short chain fatty acids produced by some bacterial species within the intestinal microbiome come into play again.
These compounds not only provide direct nutrition for the intestinal mucosal cells, allowing them to maintain normal function, but also alter tight junction integrity. With higher levels of some short chain fatty acids being associated with conferred protection against infection with enteropathogens. Short chain fatty acids have an influence on mucin cells too, promoting mucus production and so enhancing the physical barrier it provides against pathogens.
The power of those short term fatty acids goes further though, with their effects being seen on inflammatory cells, acting as signal molecules to alter levels of hemopoietic and non-hemopoietic inflammatory cell lines and down regulating pro-inflammatory cytokines. This isn't just observed locally with many anti-inflammatory effects being demonstrated across the body. One example being the prevention of bacterial induced preterm labour in pregnant women by decreasing the chemotaxis and inflammatory gene expression in neutrophils.
Back to the gut though. Some members of the intestinal microbiome, particularly Lactobacillus species, generate metabolites that combines the Ayl hydrocarbon receptor AHR on host cells. This receptor has a role in regulating mucosal immune responses, and deficiencies in AHL ligands has been shown to alter the microbiome composition and reduce the amount of AMPs produced as a result.
We've already started seeing how the intestinal microbiome and the compounds and metabolites it produces have effects beyond the gut, and there is new evidence continually being published of wider effects across the body. Let's look at some specific body systems and disease processes and see where, where there are potential therapeutic implications in some of the research findings out there. The intestinal microbiome seems to play a role in the development and progression of obesity, and there seem to be many different metabolites and mechanisms involved affecting immune energy and hormone regulation.
Even if we just look at short chain fatty acids as an example, there is a wealth of evidence of the variety of ways they exert an impact on weight management across the body. Randomised controlled trials have shown that higher production of SCFAs correlates with lower diet-induced obesity and with reduced insulin resistance. Butyrate and propionate seems to control gut hormones and reduce appetite and food intake in mice.
And studies in identical twins have ruled out a genetic factor too. The evidence goes on. Most studies of overweight and obese people show a dysbiosis characterised by lower diversity in their intestinal microbiome.
This link seems to correlate across multiple mammalian species. Does it mean that addressing dysbiosis could be a viable tool in our arsenal for tackling the growing obesity problem in pets? Accumulating data now indicates that the gut microbiota also communicates with the central nervous system, possibly through neural endocrine and immune pathways and thereby influences brain function and behaviour.
For example, there is strong evidence that some species and the intestinal microbiome regulates the production and metabolism of serotonin and its precursor amino acid tryptophan. Some microbiota have a direct antioxidant effect, reducing oxidative stress, a key factor for prognosis in many neurological disorders and following traumatic brain injuries. Studies in germ-free animals suggest a role for the gut microbiota in the regulation of mental health disorders, mood, cognition, and pain.
There are even suggestions that modulation of the gut microbiota may be a viable strategy for developing novel therapeutics for complex CLS disorders. Indeed, there is already evidence in humans that altering the intestinal microbiome has positive effects on mental health conditions. There is now expanding evidence for the view that enteric microbiota plays a role in early programming and later response to chronic and acute stress.
Suggesting that microbiomemodulation from an early age could have positive cognitive effects later. In life. Could this have relevance in reducing canine behaviour problems?
Perhaps one study looking at a population of 31 fighting dogs demonstrated an association between gut microbiome structure and dog aggression, so maybe. Neoplastic disease has naturally been part of the research focus for the effects that the intestinal microbiome has with obvious hope that modulation may be beneficial in neoplastic disease processes. It has been shown that the intestinal microbiome changes considerably in humans and dogs with various neoplastic diseases.
Whether this is a result of the disease process or causative or both is undefined, but some intestinal bacteria have been implicated in the development of some neoplastic diseases. It is therefore potential to look at reducing risk by modulating the intestinal microbiome by reducing or eliminating these species. There is some promising evidence formulations containing lactic acid bacteria have been shown to reduce the incidence of chemically mediated hepatocellular carcinoma and colon cancer in rats.
And butyrate has been shown to induce apoptosis of colon cancer cells. A common and often frustrating problem seen in small animal clinical practise is cani atopic dermatitis. There is evidence from multiple studies to suggest that modulating the intestinal microbiome can significantly improve pruits and visible skin lesions in atopic dogs.
And it is well recognised as having similar positive effects in humans with atopic dermatitis. These results are really encouraging as gastrointestinal support products are widely accepted as safe for long-term administration in dogs with very low risk of side effects. Indeed, none were noted in these studies.
And this is not the case for many current therapeutics. Another area of investigation in dogs, specifically in major organ support. One exciting pilot study has demonstrated the effects that various species of Lactobacillus has on glomer a filtration rate in dogs with chronic kidney disease.
The study showed that GFR measured through the plasma clearance of Iohexol is increased in dogs treated with the lactobacillus strains compared with dogs treated with standard therapy. Decline of GFR over time was also slowed. The same strains have demonstrated efficacy in humans for the prevention, treatment, and maintenance of remission of pouchitis and ulcerative colitis.
Accelerate healing of gastric ulcers and reduce portal pressure in patients with cirrhosis. Recently these strains have also been used in dogs with idiopathic inflammatory bowel disease, with promising results too. We've already touched on some effects of the intestinal microbiome that are relevant during pregnancy and early life.
The dramatic hormonal shifts that occur during pregnancy with resultant unique inflammatory and immune changes alter gut function and bacterial composition. Oestrogen and progesterone impact the composition of the gut microbiome through their effect on bacterial metabolism and growth and virulence of pathogenic bacteria. Human and animal studies have shown that the microbial diversity in the gut at the start of pregnancy appears to be similar to that of nonpregnant women or animals.
Yet as the pregnancy advances, there are sometimes dramatic changes in the population. In humans, the abundance of gut bacteria associated with inflammatory states increased in nearly 70% of women. Although dramatic changes in microbiome composition during pregnancy seem normal.
Both mother and foetus seem very sensitive to changes outside this norm. Negative dysbiosis during pregnancy, for example, as a result of antibiotic use, has been shown to increase the chances of chronic intestinal disorders for both mother and foetus and can even impact foetal brain development. It was thought that neonate mammals were sterile in utero and gained the seed population of their own microbiome during delivery.
Evidence of maternal microorganisms being present in the meconium and in the cord blood suggests that actually the process of building an intestinal microbiome begins before birth. Evidence suggests the placenta and amniotic fluid is involved in this. Lactation is another source of bacteria for the development of the neonates intestinal microbiome.
Milk is being increasingly recognised as non-sterile, with many maternal microbiome bacteria species shown to be present in the breast milk of humans. So the microbiome of mum is important for her own health but also vitally important for her offspring, and it starts before birth. As discussed previously with stress response, early microbiome composition can have impacts later in life.
For example, in humans, modulation of the maternal microbiome during pregnancy has been shown to reduce the incidence of cutaneous allergic reactions in infants with effects lasting into later life. As interesting as all these findings are, what can you take from them as a small animal clinician? We've only touched upon a fraction of it, but the evidence of the wide ranging effects of the intestinal microbiome hopefully lead to a conclusion that it is an important aspect of health.
As with any other important body system, preventative health is the best way to maintain its function. Evidence suggests that it is worth doing from an early age, maybe even before birth. A logical way to do this is via bacterial gut support products and indeed most research where the intestinal microbiome was modulated in some way did so using these products.
We've not covered it in great detail today, but there are many things that can influence the intestinal microbiome, both positively and negatively. Being conscious of the effects of stress, for example, and providing advice to owners about supporting their dog's intestinal microbiome in scenarios like changes of environment. Another obvious influence is diet.
In a study performed comparing dogs fed a commercial extruded canine diet, and those fed a raw diet, significant differences in their microbiome were observed, with the raw dogs having higher incidence of Clostridium perfringences and E. Coli than the commercial food group. This is another example of how diet goes beyond nutrition, and advice that is sympathetic to the microbiome should be included in dietary recommendations.
This includes switching diets gradually to try and reduce the risk of dysbiosis and consider the addition of bacterial GI support products. Physical assaults to the intestinal microbiome, such as antibiotic administration, can also lead to severe dysbiosis that can take years to return to normal with no intervention. It's already standard practise in some clinics to prescribe bacterial gut support products for administration after a course of antibiotics.
It is a very real possibility that modulation of the intestinal microbiome will be included in therapeutic protocols in the future as further research is conducted. If you are going to use a bacterial gut support product to maintain or modulate the intestinal microbiome, one key difference between those commercially available is the bacterial species included. Prokanicare is the first GI support product available in the UK to be developed from the intestinal bacteria of healthy dogs and contains 3 canine strains of live Lactobacillus.
Safety is paramount, and Lactobacillus species have been certified by the EFSA to present no pathologic or antimicrobial resistance risk. They're typically sensitive to antibiotics, and the genome of Lactobacillus species does not naturally receive foreign DNA, so development of resistance is extremely difficult. Many commercially available canine GI support products are of porine, avian, or human origin.
This is important as it has been demonstrated that adhesion of gastrointestinal bacteria to epithelial cells of the gut is host specific. The strains of Lactobacillus bacteria found in prokanica have also been shown to promote indigenous intestinal commensal populations and reduce numbers of potentially pathogenic bacteria. They do this by a mechanisms unique to each strain including inhibition, competitive exclusion, and displacement.
Thank you for watching this webinar. A link to a summary sheet will be posted in the comments section. And references to papers are available upon request.
