The application of allostasis and allostatic load in animal species: A scoping review

Abstract

Principles of allostasis and allostatic load have been widely applied in human research to assess the impacts of chronic stress on physiological dysregulation. Over the last few decades, researchers have also applied these concepts to non-human animals. However, there is a lack of uniformity in how the concept of allostasis is described and assessed in animals. The objectives of this review were to: 1) describe the extent to which the concepts of allostasis and allostatic load are applied theoretically to animals, with a focus on which taxa and species are represented; 2) identify when direct assessments of allostasis or allostatic load are made, which species and contexts are represented, what biomarkers are used, and if an allostatic load index was constructed; and 3) detect gaps in the literature and identify areas for future research. A search was conducted using CABI, PubMed, Agricola, and BIOSIS databases, in addition to a complementary hand-search of 14 peer-reviewed journals. Search results were screened, and articles that included non-human animals, as well as the terms “allostasis” or “allostatic” in the full text, were included. A total of 572 articles met the inclusion criteria (108 reviews and 464 peer-reviewed original research). Species were represented across all taxa. A subset of 63 publications made direct assessments of allostatic load. Glucocorticoids were the most commonly used biomarker, and were the only biomarker measured in 25 publications. Only six of 63 publications (9.5%) constructed an allostatic load index, which is the preferred methodology in human research. Although concepts of allostasis and allostatic load are being applied broadly across animal species, most publications use single biomarkers that are more likely indicative of short-term rather than chronic stress. Researchers are encouraged to adopt methodologies used in human research, including the construction of species-specific allostatic load indexes.

Testing the application of plasma glucocorticoids and their ratios as biomarkers of acute and chronic stress in rescued wild koala patients: a pilot study

“…The allostatic load index developed by Beer, et al (2023) included cortisol, DHEAS, cholesterol, non-esterified fatty acids, and fructosamine, which successfully reflected the chronic stress condition of captive giraffes. The use of ALI was rarely done in wildlife (Seeley et al ., 2022), and we recommended future studies to use our study as a starting point to use multiple biomarkers to establish species-specific ALI to assess chronic stress in wildlife.…”

Role of Cortisol in Horse’s Welfare and Health

“…The throughput of this method is also higher than in previously developed methods [8]. This method has been validated and can be effectively used to evaluate the concentration of fecal metabolites of cortisol [124].…”

The One Health approach for allergic diseases and asthma

“…Achieving allostatic correction is key for human health. 59,60 Understanding these complex interactions accounts for the human notion of being stewards to preserve our planet's habitat.…”

“…The efficient regulation of the human host requires anticipating the changing environment and implementing epigenetic modifications in order to respond adequately to external threats. Achieving allostatic correction is key for human health 59,60 . Understanding these complex interactions accounts for the human notion of being stewards to preserve our planet's habitat.…”