Abstract: Objective To investigate the changes of lipid metabolism and stress response of adult C. elegans exposed to non-freezing low temperature and explore the possible mechanism. Methods The survival rate and activity of adult C. elegans cultured at 20 ℃ or 4 ℃ were observed. Lipid metabolism of the cultured adult C. elegans was evaluated using oil red O staining and by detecting the expressions of the genes related with lipid metabolism. The effects of low temperature exposure on stress level of adult C. elegans were evaluated using mitochondrial fluorescence staining and by detecting the expression levels of stress-related genes and antioxidant genes at both the mRNA and protein levels. Results The lifespan and activity of adult C. elegans exposed to low temperature were significantly reduced with decreased lipid accumulation (P<0.05) and decreased expressions of genes related with fatty acid synthesis and metabolism (fat-5, fat-6, fat-7, fasn-1, nhr-49, acs-2 and aco-1; P<0.01). Cold stress significantly increased the expressions of heat shock proteins hsp-70 and hsp16.2 (P<0.05) but lowered the number of mitochondria (P<0.0001) and the expressions of atfs-1, sod-2, sod-3 and gpx-1 (P<0.05). Knockout of fat-5, nhr-49 or both fat-5 and fat-6 obviously enhanced the sensitivity of C. elegans to cold stress as shown by further reduced activity (P<0.05) and reduced survival rate at 24 h (P<0.0001) under cold stress. Conclusion Exposure to a low temperature at 4 ℃ results in lowered lipid metabolism of adult C. elegans accompanied by a decreased mitochondrial number and quality control ability, which triggers high expressions of stress-related genes and causes reduction of antioxidant capacity, thus callsing lowered activity and reduced lifespan of C. elegans.

Key words: cold stress; C. elegans; lipid metabolism; stress response