Loss of the glucocorticoid receptor in zebrafish improves muscle glucose availability and increases growth.

08:00 EDT 2nd April 2019 | BioPortfolio

Summary of "Loss of the glucocorticoid receptor in zebrafish improves muscle glucose availability and increases growth."

Chronic stress and the associated elevation in corticosteroid levels increase muscle protein catabolism. We hypothesized that the GR-regulated restriction of muscle glucose availability may play a role in the increased protein catabolism during chronic stress. To test this, we generated a ubiquitous GR knockout (GRKO) zebrafish to determine the physiological consequence of glucocorticoid stimulation on muscle metabolism and growth. Adult GRKO zebrafish had higher body mass, and this corresponded with an increased protein and lipid, but not carbohydrate content. GRKO fish were hypercortisolemic, but they elicited a higher cortisol response to an acute stressor. However, the stressor-induced increase in plasma glucose level observed in the wildtype was completely abolished in the GRKO fish. Also, the muscle, but not liver, capacity for glucose uptake was enhanced in the GRKO fish, and this corresponded with a higher hexokinase activity in the mutants. Zebrafish lacking GR also showed a higher capacity for protein synthesis, including increased phosphorylation of eIF4B, higher expression of heat shock protein cognate 70, and total protein content. A chronic fasting stressor reduced body mass and muscle protein content in adult zebrafish, but this decrease was attenuated in the GRKO compared to the wildtype fish. Metabolomics analysis revealed that the free pool of amino acid substrates used for oxidation and gluconeogenesis were lower in the fasted GRKO fish muscle compared to the wildtype. Altogether, chronic stressor-mediated GR signalling limits muscle glucose uptake, and this may play a role in protein catabolism, leading to the growth suppression in fish.


Journal Details

This article was published in the following journal.

Name: American journal of physiology. Endocrinology and metabolism
ISSN: 1522-1555


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Medical and Biotech [MESH] Definitions

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A glucose transport protein found in mature MUSCLE CELLS and ADIPOCYTES. It promotes transport of glucose from the BLOOD into target TISSUES. The inactive form of the protein is localized in CYTOPLASMIC VESICLES. In response to INSULIN, it is translocated to the PLASMA MEMBRANE where it facilitates glucose uptake.

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