Scientific Results: The companion dog as a model for inflammaging: a cross-sectional pilot study

September 6, 2024 - 9 minutes read

Posts in our Scientific Results series introduce recent papers published in the scientific literature by members of the Dog Aging Project research team. Follow this series to learn more about the scientific questions we’re asking, the kinds of results we’re getting, and what it all means for you and your dog.

Who worked on this research?

Sarah M. Schmid
Jessica M. Hoffman
Jena Prescott
Holley Ernst
Daniel E. L. Promislow
Dog Aging Project Consortium
Kate E. Creevy

  • Schmid, Sarah-web
  • Environmental head shot of Jessica Hoffman (Postdoctoral Fellow, Biology) and Dr. Steven Austad, PhD (Distinguished Professor/Chair, Biology) standing in Volker Lab, 2019.
  • PrescottJena-2016S
  • Ernst, Holley
  • Daniel-Promislow-300-x-250
  • DAP Logo
  • Creevy-Kate

Where was it published?

Geroscience

 What is this paper about?

Aging is complicated, and so is our relationship with the process. We are bombarded, it seems, on every side with anti-aging creams, foods, and supplements to combat the outward signs of aging for us and our furry friends. But what about the inner processes of aging?

For decades, scientists have been studying why we age and how we can slow down the effects. Although aging is a complex process, research suggests that inflammation is at the center. Inflammation is the body’s protective reaction to injury, disease, or irritation.  Short-term, inflammation can be helpful to fight off microbial invaders or diseases. However, chronic, low-level inflammation can play a role in the development of a host of diseases in humans, including type 2 diabetes, heart disease, Alzheimer’s, cancer, and even depression. It is this chronic, sterile (meaning there is no infection to fight off), low-level inflammation that contributes to aging.

Inflammaging can be studied by looking at what are known as inflammatory mediators (or biomarkers) in the blood. You may have seen some of these in your own lab results, such as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, and C-reactive protein (CRP).In humans, these biomarkers are associated with an increased risk of frailty, morbidity, and mortality.

Few studies have measured these inflammatory markers in companion dogs, and most have focused on single breeds or single geographical areas. The Dog Aging Project offers a unique opportunity to evaluate inflammaging in companion dogs. We enroll tens of thousands of dogs from all over the United States of all sizes, breeds, and ages. To more closely evaluate inflammaging in companion dogs, the Dog Aging Project created the Precision Cohort, whereby we collect blood samples annually to evaluate inflammatory markers. Some of this cohort have recently completed their fourth year of samples. And they come from across the entire United States, giving us a broad geographic region. While our long-term goal is to evaluate these inflammatory markers longitudinally, or in the same dog over time, we first needed to determine which inflammatory mediators correlate most with age.

Thus, we started with a pilot study. This was a small-scale version of the methods and procedures we would like to use to investigate our questions about inflammaging in a larger, longitudinal study. The smaller study allowed us to develop procedures to enhance the rigor and reproduction of our research. We wanted to test our process rather than find definitive answers. We aimed to include dogs representing a variety of breeds across a large geographical area. As inflammatory markers such as CRP and IL-6 can increase with disease, we made sure to only include healthy dogs. We confirmed the included dogs were healthy through careful review of their veterinary medical records and assessment of routine blood work (complete blood count, chemistry panel) and urine. As adiposity, or having too much fatty tissue in the body, has been shown to increase inflammatory markers in people, we determined body condition scores (BCS- a measure of canine obesity)in all study participants. Since BCS was not always noted in the veterinary medical records, we had dog owners send in pictures of their dogs (one from above, one from the side) so we could assign BCS in the same way across all study participants.

For our pilot study, we measured a variety of inflammatory markers  in 47 dogs (21 male, 26 female.) These included cytokines (IL-2, IL-6, IL-8, and TNF-α), C reactive protein (CRP), blood cell counts, and biochemical parameters. We then determined whether the concentrations of these inflammatory biomarkers in the blood were correlated with age, body weight, BCS, or sex.  Our results demonstrated that some of these markers, specifically IL-6 and TNF-α, increased with age in companion dogs, similar to what has been shown in people. This gives more evidence to the strength of the companion dog as a model for human aging.

What do these results mean for me and my dog?

We were able to replicate some of the age-induced changes in inflammatory markers seen in people, including increases in IL-6 and TNF-α with age. However, some of these findings conflict with previous studies on dogs, indicating the need to continue this research with more extensive and diverse populations. Our findings support the continued measurement of IL-6 and TNF-α within the Dog Aging Project Precision Cohort. With each study, we hope to move closer to understanding how inflammaging affects morbidity and mortality in our canine companions. For this, we depend on our Dog Aging Project Pack’s continued contributions and, especially, the dedicated members of our Precision Cohort.

Where can I learn more?

Schmid, S.M., Hoffman, J.M., Prescott, J. et al. The companion dog as a model for inflammaging: a cross-sectional pilot study. GeroScience (2024). https://doi.org/10.1007/s11357-024-01217-w

You can also check out our previous blog post, Fountain of Youth- Understanding Inflammaging and Why We Age

 

Abstract

Inflammaging, the chronic, progressive proinflammatory state associated with aging, has been associated with multiple negative health outcomes in humans. The pathophysiology of inflammaging is complex; however, it is often characterized by high serum concentrations of inflammatory mediators such as tumor necrosis factor alpha (TNF-α), interleukin (IL)-6, and C-reactive protein (CRP). Few studies have evaluated the effects of age on inflammatory cytokines in companion dogs, and most of these studies included dogs of a single breed. In this cross-sectional study, we measured multiple circulating inflammatory markers and hematological parameters in banked serum samples from 47 healthy companion dogs of various breeds enrolled in the Dog Aging Project. Using univariate linear models, we investigated the association of each of these markers with age, sex, body weight, and body condition score (BCS), a measure of obesity in the dog. Serum IL-6, IL-8, and TNF-α concentrations were all positively associated with age. Lymphocyte count was negatively associated with age. Platelet count had a negative association with body weight. IL-2, albumin, cholesterol, triglyceride, bilirubin, S100A12, and NMH concentrations were not associated with age, weight, BCS, or sex after adjustment for multiple comparisons. Our findings replicate previous findings in humans, including increases in IL-6 and TNF-α with age, giving more evidence to the strength of the companion dog as a model for human aging.

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