Paper entitled 'SIDT1-dependent absorption in the stomach mediates host uptake of dietary and orally administered microRNAs' published on Cell research on Aug 17. [Photo/WeChat account of BSC]

A research team led by Professor Zhang Chenyu from the Nanjing University in Nanjing -- the capital city of East China's Jiangsu province -- reported its latest findings in a paper published in the respected journal Cell Research on Aug 17, according to a statement on the WeChat public account of Biophysical Society of China, or BSC.

The paper, entitled 'SIDT1-dependent absorption in the stomach mediates host uptake of dietary and orally administered microRNAs', reveals a major mechanism underlying the absorption of dietary microRNAs.

BSC officials said it uncovers an unexpected role of the stomach and sheds light on developing small RNA therapeutics by oral delivery.

Dietary microRNAs have been shown to be absorbed by mammals and regulate host gene expressions, but the absorption mechanism remains unknown, they said.

In the paper, the team showed that SIDT1 expressed on gastric pit cells in the stomach is required for the absorption of dietary microRNAs. It found that SIDT1-deficient mice showed reduced basal levels and impaired dynamic absorption of dietary microRNAs.

Notably, team members identified the stomach as the primary site for dietary microRNA absorption, which is dramatically attenuated in the stomachs of SIDT1-deficient mice. Mechanistic analyses revealed that the uptake of exogenous microRNAs by gastric pit cells is SIDT1 and low-pH dependent. Furthermore, it was found that oral administration of plant-derived miR2911 retards liver fibrosis -- and this protective effect was abolished in SIDT1-deficient mice.

In the present study, the team tested how and where SIDT1 performs its functions. In addition, the team identified SIDT1 as an RNA transporter that mediates dietary miRNA absorption in the mammalian stomach.

It was found that the stomach's highly acidic environment is crucial for SIDT1-dependent absorption of miRNAs. Notably, dietary miRNAs absorbed via SIDT1 can exert biological functions in the host and oral administration of plant-derived miR2911 retards liver fibrosis, which is abolished by SIDT1 deficiency.