Expression analysis of glycerol synthesis-related liver transcripts in rainbow smelt (Osmerus mordax) exposed to a...

Area of Science:

• * Biochemistry and molecular biology
• * Environmental physiology
• * Aquatic animal adaptation

Background:

• * Rainbow smelt (Osmerus mordax) accumulate glycerol to prevent freezing in subzero temperatures.
• * Glyceroneogenesis, a metabolic pathway, is activated by cold and occurs in the liver, branching from glycolysis and gluconeogenesis.

Purpose of the Study:

• * To investigate the metabolic and transcriptomic changes in rainbow smelt during a cold acclimation.
• * To identify genes and pathways involved in glycerol production in response to decreasing temperatures.

Main Methods:

• * Controlled temperature transition from 8°C to 0°C for rainbow smelt.
• * Measurement of carbohydrate and liver transcript levels of 21 genes.
• * Comparison of gene expression and metabolite levels between warm (8°C) and cold (0°C) acclimated smelt.

Main Results:

• * Cold smelt showed lower liver glycogen and higher phosphoglucomutase transcript levels compared to warm smelt.
• * Plasma glycerol levels increased over time in cold smelt, with elevated phosphofructokinase and pyruvate dehydrogenase kinase transcript levels.
• * Increased plasma glucose, liver glucose-6-phosphatase, and lipoprotein lipase transcript levels were observed in cold smelt.

Conclusions:

• * Glycerol production in rainbow smelt is fueled by glycogen degradation.
• * Inhibition of pyruvate oxidation directs metabolic flux towards glycerol synthesis.
• * Upregulation of lipoprotein lipase suggests enhanced lipid breakdown, and glutamine synthetase may aid nitrogen storage for future biosynthesis.