Purple corn anthocyanins retard diabetes-associated glomerulosclerosis in mesangial cells and db/db mice

Diabetic glomerulosclerosis is the hardening of the renal glomeruli that can lead to kidney failure. In the early stage of glomerulosclerosis occur renal mesangial expansion and renal filtration dysfunction. Purple corn has been classified as a functional food and is rich in anthocyanins exerting potential disease-preventive activities. The in vitro study using human renal mesangial cells examined that anthocyanin-rich purple corn butanol fraction (PCB) can attenuate high glucose (HG)-promoted mesangial cell proliferation and matrix accumulation.

Cells were cultured for 3 days in media containing 33 mM glucose in the presence of 1-20 μg/mL PCB. In the in vivo animal study, db/db mice were treated with 10 mg/kg anthocyanin-rich polyphenolic extracts of purple corn (PCE) for 8 weeks.

HG enhanced mesangial production of the fibrosis biomarkers of collagen IV and connective tissue growth factor (CTGF), which was markedly attenuated by adding PCB. Such mesangial fibrosis entailed interleukin-8 activation via eliciting Tyk2-STAT signaling pathway. PCB dampened HG-promoted mesangial hyperplasia that appeared to be attributed to increased expression of platelet-derived growth factor. The 8-week administration of PCE lowered plasma glucose level of db/db mice and ameliorated severe albuminuria. Moreover, PCE lessened collagen fiber accumulation in kidney glomeruli and CTGF expression via retarding TGF-β signaling. Protein expressions of nephrin and podocin, key proteins for filtration barrier function of the glomerular capillary wall, were repressed by treating mice with PCE.

Purple corn may be a potent therapeutic agent for the treatment for diabetes-associated glomerulosclerosis accompanying proteinuria and kidney filtration dysfunction.