# Activation of the hypothalamic–pituitary–adrenal axis by exogenous and endogenous GDF15

## TL;DR

GDF15 activates the body's stress response by stimulating the HPA axis, especially in cases of cellular damage not involving inflammation.

## Contribution

GDF15 is shown to be a key signal for activating the HPA axis in response to non-inflammatory cellular stress.

## Key findings

- GDF15 activates the HPA axis in mice and rats, increasing corticosterone levels.
- GDF15 is essential for the HPA response to toxins that do not trigger a strong cytokine response.
- Blocking the GDF15 receptor prevents the corticosterone response to GDF15 administration.

## Abstract

GDF15, a hormone produced by a wide variety of cells undergoing different types of stress, acts on a receptor in the brain where it transmits signals that are perceived by the organism as aversive. We now report an action of GDF15, whereby it activates the endocrine stress response and increases circulating levels of the principal glucocorticoid (a “stress” steroid). By studying mice genetically deficient in GDF15, we also demonstrate that GDF15 is a key signal through which damage due to toxic chemicals activates the steroid stress response. GDF15 is currently being explored as an antiobesity drug and examination of the degree and duration of the steroid effect will need to be incorporated into any human trials.

An acute increase in the circulating concentration of glucocorticoid hormones is essential for the survival of severe somatic stresses. Circulating concentrations of GDF15, a hormone that acts in the brain to reduce food intake, are frequently elevated in stressful states. We now report that GDF15 potently activates the hypothalamic–pituitary–adrenal (HPA) axis in mice and rats. A blocking antibody to the GDNF-family receptor α-like receptor completely prevented the corticosterone response to GDF15 administration. In wild-type mice exposed to a range of stressful stimuli, circulating levels of both corticosterone and GDF15 rose acutely. In the case of Escherichia coli or lipopolysaccharide injections, the vigorous proinflammatory cytokine response elicited was sufficient to produce a near-maximal HPA response, regardless of the presence or absence of GDF15. In contrast, the activation of the HPA axis seen in wild-type mice in response to the administration of genotoxic or endoplasmic reticulum toxins, which do not provoke a marked rise in cytokines, was absent in Gdf15−/− mice. In conclusion, consistent with its proposed role as a sentinel hormone, endogenous GDF15 is required for the activation of the protective HPA response to toxins that do not induce a substantial cytokine response. In the context of efforts to develop GDF15 as an antiobesity therapeutic, these findings identify a biomarker of target engagement and a previously unrecognized pharmacodynamic effect, which will require monitoring in human studies.