Diet Dependent Regulation of Developmental Acceleration and Fat Storage
Date Issued
2015
Date
2015
Author(s)
Huang, Mao-Yen
Abstract
The nutrients of diet, such as proteins, fats, carbohydrates, vitamins, and minerals, are essential for development and homeostasis of organisms. Different diets has been shown to alternate organismal life-history, such as development and reproduction, and affect lifespan. However, mechanisms by which the nutrients in complex dietary compositions regulate lifespan and life-history of organism are poorly understood. Here we used Caenorhabditis elegans as a model organism to study this issue. Previous studies have shown that C. elegans fed Comamonas sp. DA1877 has faster developmental rate than those fed Escherichia coli OP50. Using Escherichia coli OP50 or Comamonas sp. DA1877, we investigated how the two diets affect developmental rate differently and the underlying molecular mechanisms. Our results showed that parental worms fed DA1877 produce progeny that grow faster than those fed OP50, the effect of parental diet is also observed in the transcription acetyl-CoA dehydrogenase acdh-1, whose expression is greatly suppressed by DA1877 diet, in the progeny. Next we crossed the transgenic worms fed with different diets and demonstrated that such inherited growth acceleration is mediated by hermaphroditic oocytes. We further tested if the developmental acceleration by DA1877 is caused by the volatile or secreted substances from the bacteria diets. The data indicated that neither the volatiles nor secreted substances from the bacteria diets affect worm developmental rate. Vitamin B12 has been shown recently the key substance in the DA1877 diet for developmental acceleration of C. elegans. To examine whether vitamin B12 is also the cause for developmental acceleration in the progeny, we added vitamin B12 in the parental OP50 diet and tested the expression of acdh-1 in the progeny. Our data showed that the expression of acdh-1 is suppressed both in the parents and the progeny, suggesting vitamin B12 is also the key substance of DA1877 that accelerates the developmental rate in the progeny. Vitamin B12 plays an important role in transmethylation reaction. In budding yeast, methylation of PP2Ac (protein phosphatase 2A catalytic subunit) promotes growth. We tested whether vitamin B12 in DA1877 may activate transmethylation reaction, resulting in the methylation of PP2Ac which in turn accelerates developmental rate in the worms. Our results showed that methionine and S-adenosylmethionine (SAM) supplement, like vitamin B12, increase developmental rate and that the accelerated development is blocked by a mutation of SAM synthesase, sams-1, or PP2Ac RNAi. Moreover, PP2Ac RNAi also suppress the developmental acceleration induced by vitamin B12. In addition, transmethylation reactions are involved in lipid metabolism. We found that not only DA1877 diet but also vitamin B12, SAM, methionine supplements result in decreased lipid droplets in the worms. Together, based on these data, we proposed that vitamin B12 from theDA1877 diet regulates the fat storage and the methylation of PP2Ac through transmethylation reaction to promote developmental rate in C. elegans.
Subjects
diet
C. elegans
development
fat
Type
thesis