Although STZ-injected mice showed increased SPHK1 and connective tissue growth factor expression in tubules after 30 days, SPHK1 deficiency further aggravated the DKD fibrosis phenotype, thus the role of sphingolipids in diabetic TECs and the effect of MtROS in this process remain unclear [49]. Here, SPHK1 is linked to diabetic kidney disease.