by E. Mironchik-Frankenberg, DVM.
Introduction:
We’ve devoted much time over the past few months to discussion of inflammatory conditions that affect pets. Of all the body systems that impact our daily lives, in both humans and our pets, the gastrointestinal system (aka the GI tract or “the gut”) is probably the one we are most acutely aware of…regular feeding and elimination urges occur multiple times daily, and any disturbance to this process has an immediate impact.
The gastrointestinal tract is the main part of the digestive system, which includes all of the organs that are involved in eating and processing food. It begins with the mouth and includes the esophagus, stomach, liver, pancreas, intestines, rectum, and anus.1
In people, the most common inflammatory GI tract disorder is Inflammatory Bowel Disease, or IBD, which is typically classified as either ulcerative colitis or Crohn’s disease.
In pets, inflammatory disease can affect the GI tract and its associated organs, such as the pancreas and liver. Some notable examples include IBD, colitis, pancreatitis, and hepatitis. Inflammatory bowel disease is an umbrella term used to describe a group of conditions characterized by inflammation of the GI tract with persistent or recurrent GI signs. Inflammatory bowel diseases are the most common cause of chronic vomiting and diarrhea in dogs and cats.3
In both people and pets, these disorders can be serious, frustratingly difficult to manage, and have a severe impact on the patient’s quality of life.
GI functions:
From an overall health perspective, the GI tract is one of the body’s most vital organs. It has two main functions: digestion of food and host defense. The gut has the most extensive immune system in the body.8 It acts as one of the host body’s main defensive shields by protecting it from foreign invaders like bacteria and viruses. An important component of this system is the intestinal “microbiome.” The microbiome is the complex ecosystem of viruses, bacteria, fungi, and protozoa that live within the intestinal tract of mammalian species. A normal, balanced microbiome is crucial for maintaining overall health. It does this in several ways:5
- Modulating the immune system
- Keeping dangerous invaders in check by regulating the epithelial barrier, the critical protective lining of the gut
- Providing nutrients to the host by metabolizing and fermenting food
Dysbiosis, is a situation that occurs when the gut microbiome is imbalanced or disturbed. This can lead to a wide range of abnormalities and has far reaching consequences. It is currently thought that this alteration of the gut environment and development of dysbiosis may allow the overgrowth of pathogenic bacteria and the induction of intestinal injury and inflammation in IBD.9
Individuals with severe GI disease and disruption of the GI immune system can have many other complications and far-reaching consequences. Therefore, a healthy GI system is necessary for a healthy life.
Inflammatory Bowel Disease in Pets:
For this article, we will focus on Inflammatory Bowel Disease. The exact causes of IBD are unknown, however, we know that alteration of the normal microbiome plays a crucial role. In addition, there are multiple factors that can also contribute to persistent GI inflammation, including:3
Genetics. Some breeds of dogs and cats may be predisposed.
Environmental factors. Stress, diet, and pharmaceuticals can trigger inflammation.
The immune system and immune responses. Dysfunction in the immune system can lead to imbalance and lack of host defenses, creating a snowball effect and allowing GI bacteria to gain access to the blood and tissues.
Because it can be difficult to determine the underlying cause of the inflammation, diagnosis is time-consuming, costly, and can require multiple steps and procedures. A diagnosis of IBD is primarily one of exclusion, which means it requires elimination of the many other infectious and other causes that mimic IBD, such as intestinal parasites, bacterial or viral infection, toxin exposure, drug reaction, cancer, or non-gastrointestinal causes.
Whatever the underlying causes, clinical signs range from mild to severe, and can include anorexia(lack of appetite), vomiting, diarrhea, bloody stool, weight loss and general malaise. 3,4
Treatment goals:
Overall, the goals of therapy are to reduce diarrhea and vomiting, promote appetite and weight gain, and decrease intestinal inflammation. If a specific cause can be identified, such as a parasitic infection, it should be eliminated first.4
Diet change, prolonged antibiotics, anti-inflammatory medications, and/or immunosuppressive drugs are typically employed in a step wise fashion. Unfortunately, the drugs themselves can have side effects and there is a negative feedback cycle in which prolonged use of these drugs can negatively affect the normal health and balance of the intestinal microbiome. This necessitates even more drug therapy which can lead to a vicious cycle of persistent dysbiosis and enhanced intestinal inflammation.3
How can cannabis help?
Gastrointestinal disorders are a frequent reason for medical cannabis use in people.2
We know that the Endocannabinoid system, or ECS, is widely distributed throughout the GI tract. There is currently much interest and scientific research into the complex connection between the ECS, the microbiome, the GI nervous system, the immune system, gastrointestinal function, and overall health.
Current thinking suggests that the ECS serves as a communication bridge between bacteria and the host, relaying signals back and forth in a symbiotic, mutually beneficial relationship.6
The extent of the GI ECS is extremely complex and still not well understood, but cannabinoid receptors (CB1 and CB2), endocannabinoids, and their associated enzymes are present throughout the GI system.8 ECS components modulate numerous vital GI functions, including energy intake and appetite, metabolism and insulin sensitivity, GI motility, esophageal sphincter function, gastric acid secretion, gastric emptying, the intestinal microbiome, colon motility and transit time, visceral sensitivity, inflammation, and pain. 7,8 In addition, there are notable effects attributed to the ECS in liver and pancreatic function.7
While there may be significant species differences in the activity of the ECS and cannabis use in these disease processes, we know that it can be of significant benefit to humans. Research has shown that activation of the CB1 and CB2 receptors in animal models of colitis reduces inflammation.2 Existing research has already demonstrated the extent of the ECS in the GI tract of dogs and cats.10,11 Taking into consideration these facts, combined with the fact that cannabinoid receptors have a protective role in inflammatory bowel disease,11 provides an anatomical basis to support the use of cannabinoid receptor agonists in relieving many of the signs and dysfunction resulting from inflammatory GI conditions in these species. In addition, there is already much evidence to support the anti-inflammatory ability of cannabinoids and their benefit in easing the secondary signs of GI disease, such as nausea, inappetence, and pain. Therefore, it is reasonable to assume that cannabinoid use may benefit our pets with these conditions. While this author is unaware of any clinical trial results in companion animals as of yet, hopefully that will change in the near future and research results will soon be available to support this.
Conclusion:
Diseases that affect the GI tract can have a profound daily impact on the lives of not only the pet, but caregivers and family members as well. Because these conditions can necessitate lifelong management, finding an effective treatment and tolerable routine is imperative for a good quality of life for all involved. While there is still much we need to learn, it’s clear that cannabis may provide a worthwhile option and potentially effective solution.
Coming next: Inflammation part 4; Skin disorders
References:
- https://www.merckvetmanual.com/dog-owners/digestive-disorders-of-dogs/introduction-to-digestive-disorders-of-dogs
- https://www.projectcbd.org/medicine/cannabis-gastrointestinal-disorders
- https://todaysveterinarypractice.com/inflammatory-bowel-disease-dogs-cats/
- https://www.merckvetmanual.com/digestive-system/diseases-of-the-stomach-and-intestines-in-small-animals/chronic-enteropathies-in-small-animals
- https://todaysveterinarypractice.com/intestinal-microbes-digestive-system-disease-dogs/
- https://www.projectcbd.org/wellness/gut-microbiota-endocannabinoid-system
- Role of Cannabis and Its Derivatives in Gastrointestinal and Hepatic Disease. https://www.gastrojournal.org/article/S0016-5085(20)30563-1/fulltext or https://www.sciencedirect.com/science/article/pii/S0016508520305631
- Cannabinoid CB2 receptors in the gastrointestinal tract: a regulatory system in states of inflammation. https://bpspubs.onlinelibrary.wiley.com/doi/full/10.1038/sj.bjp.0707486
- Humoral immune responses against gut bacteria in dogs with inflammatory bowel disease. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6675102/
- Localization of cannabinoid and cannabinoid related receptors in the cat gastrointestinal tract https://link.springer.com/article/10.1007/s00418-020-01854-0
- Localization of cannabinoid receptors CB1, CB2, GPR55, and PPARα in the canine gastrointestinal tract https://pubmed.ncbi.nlm.nih.gov/29882158/
