Freezing stress adaptations: Critical elements to activate Nrf2 related antioxidant defense in liver and skeletal muscle of the freeze tolerant wood frogs

2021 ◽  
Vol 254 ◽  
pp. 110573 ◽  
Author(s):  
Jing Zhang ◽  
Aakriti Gupta ◽  
Kenneth B. Storey
Keyword(s):  
Skeletal Muscle ◽  
Antioxidant Defense ◽  
Freezing Stress ◽  
Wood Frogs ◽  
Critical Elements ◽  
Freeze Tolerant

Skeletal muscle uncoupling-induced longevity in mice is linked to increased substrate metabolism and induction of the endogenous antioxidant defense system

2013 ◽  
Vol 304 (5) ◽  
pp. E495-E506 ◽  
Author(s):  
S. Keipert ◽  
M. Ost ◽  
A. Chadt ◽  
A. Voigt ◽  
V. Ayala ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Skeletal Muscle ◽  
Antioxidant Defense ◽  
Antioxidant Defense System ◽  
Mapk Signaling ◽  
Redox Signaling ◽  
Defense System ◽  
High Fat ◽  
Substrate Metabolism ◽  
Endogenous Antioxidant

Ectopic expression of uncoupling protein 1 (UCP1) in skeletal muscle (SM) mitochondria increases lifespan considerably in high-fat diet-fed UCP1 Tg mice compared with wild types (WT). To clarify the underlying mechanisms, we investigated substrate metabolism as well as oxidative stress damage and antioxidant defense in SM of low-fat- and high-fat-fed mice. Tg mice showed an increased protein expression of phosphorylated AMP-activated protein kinase, markers of lipid turnover (p-ACC, FAT/CD36), and an increased SM ex vivo fatty acid oxidation. Surprisingly, UCP1 Tg mice showed elevated lipid peroxidative protein modifications with no changes in glycoxidation or direct protein oxidation. This was paralleled by an induction of catalase and superoxide dismutase activity, an increased redox signaling (MAPK signaling pathway), and increased expression of stress-protective heat shock protein 25. We conclude that increased skeletal muscle mitochondrial uncoupling in vivo does not reduce the oxidative stress status in the muscle cell. Moreover, it increases lipid metabolism and reactive lipid-derived carbonyls. This stress induction in turn increases the endogenous antioxidant defense system and redox signaling. Altogether, our data argue for an adaptive role of reactive species as essential signaling molecules for health and longevity.

DNA methylation and regulation of DNA methyltransferases in a freeze-tolerant vertebrate

2020 ◽  
Vol 98 (2) ◽  
pp. 145-153 ◽  
Author(s):  
Jing Zhang ◽  
Liam J. Hawkins ◽  
Kenneth B. Storey
Keyword(s):  
Dna Methylation ◽  
Transcriptional Repression ◽  
Freeze Tolerance ◽  
Dna Methyltransferases ◽  
Wood Frog ◽  
Activity Levels ◽  
Wood Frogs ◽  
Metabolic Role ◽  
Freeze Tolerant

The wood frog is one of the few freeze-tolerance vertebrates. This is accomplished in part by the accumulation of cryoprotectant glucose, metabolic rate depression, and stress response activation. These may be achieved by mechanisms such as DNA methylation, which is typically associated with transcriptional repression. Hyperglycemia is also associated with modifications to epigenetic profiles, indicating an additional role that the high levels of glucose play in freeze tolerance. We sought to determine whether DNA methylation is affected during freezing exposure, and whether this is due to the wood frog’s response to hyperglycemia. We examined global DNA methylation and DNA methyltransferases (DNMTs) in the liver and muscle of frozen and glucose-loaded wood frogs. The results showed that levels of 5-methylcytosine (5mC) increased in the muscle, suggesting elevated DNA methylation during freezing. DNMT activities also decreased in muscle during thawing, glucose loading, and in vitro glucose experiments. Liver DNMT activities were similar to muscle; however, a varied response to DNMT levels and a decrease in 5mC highlight the metabolic role the liver plays during freezing. Glucose was also shown to decrease DNMT activity levels in the wood frog, in vitro, elucidating a potentially novel regulatory mechanism. Together these results suggest an interplay between freeze tolerance and hyperglycemic regulation of DNA methylation.

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