Abstract: Background Hallmarks of aging in humans and rodents include unfavorable alterations to metabolic and immune system function. There is limited evidence characterizing if this is also true in dogs.
Hypothesis/Objectives Determine if changes in insulin, adiponectin and lymphocytes are associated with age in dogs.
Animals Study 1) 451 companion dogs ages 2-6 years and 7-17 years.
Study 2) 60 research beagles ages < 4 years, 8-10 years, and >10 years.
Methods Study 1) In this cross-sectional observational field study, we measured complete blood counts, fasting insulin and adiponectin levels at a single time point. Associations between these blood-based markers and age were assessed by Spearman correlation.
Study 2) In this cross-sectional observational study, single-time point blood samples were collected for CBC and flow cytometry analyses. Differences between age groups were evaluated using one-way analysis of variance.
Results In Study 1, total lymphocyte counts decreased, insulin increased and adiponectin declined significantly with age, even after adjusting for the effect of weight and BCS (p< 0.001).
In Study 2, total lymphocyte counts and specifically CD3+ T-cells, CD3+/CD4+ T-helper cells and the CD4+/CD8+ ratio were significantly lower in dogs >10 years old compared with dogs < 4 years old (p< 0.001).
Conclusions and Clinical Importance We demonstrate age-related changes in biomarkers of immune and metabolic function in dogs. Importantly, these results mirror age-related changes that are described in rodents and humans. These results support further investigation into these markers as tools to assess negative health outcomes associated with aging in dogs.
