Kaempferol alleviates palmitic acid-induced lipid stores, endoplasmic reticulum stress and pancreatic β-cell dysfunction through AMPK/mTOR-mediated lipophagy

• Published in: The Journal of nutritional biochemistry 2018-07, Vol.57, p.212-227
• Main Authors: Varshney, Ritu, Varshney, Rajat, Mishra, Rutusmita, Gupta, Sumeet, Sircar, Debabrata, Roy, Partha
• Format: Article
• Language: English
• Subjects: Diabetes; ER stress; Insulin; Kaempferol; Lipophagy; Pancreatic β-cells
• ISSN: 0955-2863; 1873-4847
• DOI: 10.1016/j.jnutbio.2018.02.017

Kaempferol, a natural flavonoid, has the beneficial effects of preserving pancreatic β-cell mass and function, but its action on β-cell lipid metabolism still remains elusive. Recently, autophagy has been reported to play a major role in lipid metabolism in various cell types, but its role in pancreatic β-cell's lipid metabolism is rarely reported. Here, we investigated the role of kaempferol-induced autophagy in inhibition of lipid stores, ER stress and β-cell dysfunction in palmitic acid-challenged RIN-5F cells and isolated pancreatic islets. The lipid-lowering effect of kaempferol was determined by Oil Red O staining, triglyceride assay, BODIPY labeling, RT-PCR and immunoblot analysis of PLIN2 (the lipid droplet coat protein) expression. Further, the involvement of AMPK/mTOR-mediated lipophagy was established by pharmacological and genetic inhibitors of autophagy and AMPK. The co-localization studies of lipid droplets with autophagosomes/lysosomes by BODIPY-MDC-LysoTracker co-staining, LC3/BODIPY labeling and LC3/PLIN2 double immunolabeling further strengthened the findings. Kaempferol treatment exhibited decreased lipid stores and increased co-localization of lipid droplets with autophagosomes and lysosomes in palmitic acid–challenged β-cells. Moreover, inhibition of autophagy led to decreased co-localization and increased lipid droplets accumulation. Kaempferol-induced alleviation of ER stress and β-cell dysfunctions was established by immunoblot analysis of CHOP-10 (a key mediator of cell death in response to ER stress) and insulin content/secretion analysis respectively. Together, these findings suggest that kaempferol prevents ectopic lipid accumulation and ER stress, thus restoring β-cell function through AMPK-mediated lipophagy. The current data implies that kaempferol may be a potential therapeutic candidate to prevent obesity-linked diabetic complications.