Joint health, mobility and the microbiome

While the link between the microbiome and digestive, or even skin problems may seem obvious, the connection between the microbes in our dog’s guts and the health of their joints might seem more of a stretch. However, there are several well-researched mechanisms linking the microbiome to joint conditions such as arthritis, and so it is now well accepted that the microbes in our dogs’ intestines can play a major role in the health of their joints, their mobility, and enjoyment of activity.

Reactive arthritis has been known to be triggered by small bowel bacterial overgrowths of specific strains. There has also been immune cross-reactivity found between small bowel bacteria and cartilage. Another theory involves increased intestinal permeability (leaky gut) causing exposure of the immune system to the gut microbiome^[1]. It is also thought that gut dysbiosis might promote musculoskeletal disorders through intestinal absorption of various vitamins and nutrients, or lack of absorption. Osteoclasts (cells involved in bone breakdown) might be indirectly stimulated by gut microbiota via IGF-1 (insulin-like growth factor 1) levels in the blood. But the main link between them is through inflammation^[2]. An increased risk of developing inflammatory joint disease has been found with the presence of certain bacterial species in the microbiome, as well as through inflammatory cytokines (signals) from the microbiome itself. They may also be involved in low-grade inflammation in post-traumatic arthritis.

The risk of a dog, or a human, developing arthritis increases with age. Interestingly, with age, the microbiome undergoes some changes too, leading to a decrease in biodiversity and metabolic potential, so a state of dysbiosis. These changes have been linked with increased inflammatory cytokines and matrix metalloproteinases circulating in the blood, as well as increased intestinal permeability. This in turn leads to an increase in systemic inflammation in the body, known as ‘inflammaging’, and so the risk of osteoarthritis increases in older animals.^[3] With this in mind, we can hopefully start working to maintain the health of the microbiome from an early age, and throughout our pets’ lives, to keep their joints healthier for longer, keeping our geriatric pets more mobile and better able to enjoy their later life. We may even be able to develop new ways to treat and manage arthritis, which would be great for pets and people alike. Research in this area is still in its early stages, but a recent study on rats found that probiotic administration might significantly reduce pro-inflammatory cytokine production in knee cartilage^[4].

In sports medicine in people, there has been a lot of research into the gut-joint axis over recent years. They have found that physical exercise could modulate the gut microbiota, improve production of short chain fatty acids, boost intestinal mucosal (lining) immunity, modify the bile acid profile and improve bacterial ratios within the biome. They have also found that the risk of gastrointestinal disease might be decreased with low intensity exercise, showing a direct correlation between skeletal muscle and the gut microbiome.^[5] A further slightly different link through the nervous system, the microbiome and joint disease has also been hypothesised: gut dysbiosis might regulate the microglial activation in the trigeminal nerve system (one of the facial nerves), and act as a mediator of inflammation in the temporomandibular joint^[6]. Another area of research has looked at specific bacteria and their influence on joint health. One in particular found that an abundance of certain bacterial species can be linked with increased joint pain and severity of arthritis symptoms. This is thought to be related to macrophage (white blood cell) mediated inflammation, triggered by endotoxin production by the gut microbiome^[7].

Knowing all of this, we can now see how influential the gut microbiome is in the body. If it can affect the immune system and inflammation, then it can affect every single system in the body, especially as the body ages. With arthritis being so common in older dogs, and even many younger ones, this makes it even more important that we keep the microbiome of our pets in tip top condition. This way we can help our pets to live their lives with the highest quality of life possible, for as long as possible.

References

^[1] Bedaiwi MK, Inman RD. Microbiome and probiotics: link to arthritis. Curr Opin Rheumatol. 2014 Jul;26(4):410-5. doi: 10.1097/BOR.0000000000000075. PMID: 24841227.

^[2] Ferrillo M, Giudice A, Migliario M, Renó F, Lippi L, Calafiore D, Marotta N, de Sire R, Fortunato L, Ammendolia A, Invernizzi M, de Sire A. Oral-Gut Microbiota, Periodontal Diseases, and Arthritis: Literature Overview on the Role of Probiotics. Int J Mol Sci. 2023 Feb 27;24(5):4626. doi: 10.3390/ijms24054626. PMID: 36902056; PMCID: PMC10003001.

^[3] Mohr AE, Jäger R, Carpenter KC, Kerksick CM, Purpura M, Townsend JR, et al. The athletic gut microbiota. J Int Soc Sports Nutr [Internet]. 2020 Dec 12;17(1):24

^[4] Korotkyi O.H., Vovk A.A., Dranitsina A.S., Falalyeyeva T.M., Dvorshchenko K.O., Fagoonee S., Ostapchenko L.I. The influence of probiotic diet and chondroitin sulfate administration on Ptgs2, Tgfb1 and Col2a1 expression in rat knee cartilage during monoiodoacetate-induced osteoarthritis. Minerva Med. 2019;110:419–424.

^[5] de Sire A, de Sire R, Petito V, Masi L, Cisari C, Gasbarrini A, Scaldaferri F, Invernizzi M. Gut-Joint Axis: The Role of Physical Exercise on Gut Microbiota Modulation in Older People with Osteoarthritis. Nutrients. 2020 Feb 22;12(2):574. doi: 10.3390/nu12020574. PMID: 32098380; PMCID: PMC7071456.

^[6] Ma Y, Liu S, Shu H, Crawford J, Xing Y, Tao F. Resveratrol alleviates temporomandibular joint inflammatory pain by recovering disturbed gut microbiota. Brain Behav Immun. 2020 Jul;87:455-464. doi: 10.1016/j.bbi.2020.01.016. Epub 2020 Jan 27. PMID: 32001342; PMCID: PMC9444375.

^[7] Boer CG, Radjabzadeh D, Medina-Gomez C, Garmaeva S, Schiphof D, Arp P, Koet T, Kurilshikov A, Fu J, Ikram MA, Bierma-Zeinstra S, Uitterlinden AG, Kraaij R, Zhernakova A, van Meurs JBJ. Intestinal microbiome composition and its relation to joint pain and inflammation. Nat Commun. 2019 Oct 25;10(1):4881. doi: 10.1038/s41467-019-12873-4. PMID: 31653850; PMCID: PMC6814863.