Patterns of Gene and Metabolite Define the Effects of Extracellular Osmolality on Kidney Collecting Duct

To investigate the effects of changes in extracellular
osmolality on the function of kidney collecting duct cells, particularly
on water and sodium reabsorption in the conditions of diuresis and
antidiuresis, we generated transcriptome and metabolome profiles of
primary cultured inner medullary collecting duct (IMCD) cells. They
were grown in hyperosmolar culture medium (640 mOsm) for 4 days and
then exposed to either reduced (300 mOsm) or same osmolality for 1
or 2 days more. Integrated analysis of the transcriptome and metabolome
revealed that decreased extracellular osmolality was associated with
decreased levels of organic osmolytes, glucose, intermediates of citric
acid cycle, and branched-chain amino acids (BCAA) in IMCD cells, along
with significantly decreased gene expression and protein abundance
of P-type transporters (ATP1B1), ABC transporters (ABCC5 and ABCG1),
and insulin signaling pathways (IRS2). Quantitative real-time RT-PCR
and semiquantitative immunoblotting confirmed the changes of transcript
levels of differentially expressed genes and protein levels. Taken
together, integrated analysis of omics data demonstrated that water
and sodium reabsorption could be reduced by decreased extracellular
osmolality per se, through decreased levels of ABC transporters and
IRS2, which play a potential role in the transport of organic osmolytes,
BCAA, glucose, and trafficking of epithelial sodium channel.