OBJECTIVES: Epigenetic is one of the possible mechanisms of transmit parental metabolic stress to offspring. tRNA modification or fragmentation is a promising candidate. We investigated the molecular mechanism of intergeneration transmission of diet-induced metabolic stress. METHODS: Male mice fed with control diet (CD) or high-fat diet (HFD) for 9 weeks. Body weight, amount of food intake and organ weights were measured. Metabolism-related proteins and gene expression were measured in testis and liver. tRNA methylation in sperm was investigated by bisulfite conversion-based sequencing. We analyzed publicly available omics data to profile changes of high-fat diet feeding. To explain mTOR activity linked to angiogenin (ANG) gene expression, we treated compound C (CC) or rapamycin (RP) in cell lines. RESULTS: We showed mTOR negative regulators were down regulated in HFD from analysis of transcriptome data from liver and sperm. Consistently, analysis on sperm metabolome data revealed that free amino acid level and tRNA amino-acyl biosynthesis pathway was up-regulated in HFD. Increased a level of phospho-mTOR protein was confirmed in testis, but not phospho-AMPK protein. Next, we measured tRNA modification-related gene expression levels in testis and liver. Expression of Dnmt2 and NSun2 related in tRNA methylation was elevated in HFD in testis and liver. However, expression of ANG related with tRNA cleavage was only increased in testis. In addition, methylation status in sperm tRNA-Asp-GTC was no different between diets. The data suggested that tRNA cleavage with ANG, rather than tRNA methylation process, was more likely involved in transmit transgenerational effect to offspring. Finally, we investigated changing mTOR activity could affect to Angiogenin gene expression level. Treatment with CC showed increased Angiogenin gene expression level, but RP treatment showed no change. CONCLUSIONS: Our data suggested that diet-induced alteration of mTOR activity led to upregulation of Angiogenin expression in sperm, which might be a key of transgenerational mechanism. FUNDING SOURCES: This study was supported by the National Research Foundation of Korea the Korean National Cancer Center. EL is grateful for financial support from Hyundai Motor Chung Mong-Koo Foundation and BK21 FOUR (Fostering Outstanding Universities for Research).
