Glomerular matrix
protein accumulation, mediated largely by mesangial cells, is central to the pathogenesis of
diabetic kidney disease. Our previous studies showed that the membrane microdomains caveolae and their marker
protein caveolin-1 regulate matrix
protein synthesis in mesangial cells in response to diabetogenic stimuli, and that
caveolin-1 knockout mice are protected against
diabetic kidney disease. In a screen to identify the molecular mechanism underlying this protection, we also established that secreted antifibrotic
glycoprotein follistatin is significantly upregulated by
caveolin-1 deletion.
Follistatin potently neutralizes
activins, members of the
transforming growth factor-β superfamily. A role for
activins in
diabetic kidney disease has not yet been established. Therefore, in vitro, we confirmed the regulation of
follistatin by
caveolin-1 in primary mesangial cells and showed that
follistatin controls both basal and
glucose-induced matrix production through
activin inhibition. In vivo, we found
activin A upregulation by immunohistochemistry in both mouse and human
diabetic kidney disease. Importantly, administration of
follistatin to type 1 diabetic Akita mice attenuated early
diabetic kidney disease, characterized by
albuminuria, hyperfiltration, basement membrane thickening, loss of endothelial glycocalyx and podocyte
nephrin, and glomerular matrix accumulation. Thus,
activin A is an important mediator of high
glucose-induced profibrotic responses in mesangial cells, and
follistatin may be a potential novel
therapy for the prevention of
diabetic kidney disease.