Morus alba Leaf Bioactives Modulate Peroxisome Proliferator Activated Receptor γ in the Kidney of Diabetic Rat and Impart Beneficial Effect.

Peroxisome proliferator activated receptor gamma (PPARγ) is a ligand-activated nuclear receptor that can be
activated or repressed by several exogenous and endogenous ligands and acts by modulating genes that regulate lipid, glucose,
and insulin homeostasis. In kidney, PPARγ is involved in normal kidney development and other physiological functions. In our
earlier report, we showed that feeding Morus alba leaves to experimental diabetic rats ameliorated diabetic nephropathy and
significantly decreased microalbuminuria. In this paper, we have attempted to look into the molecular mechanism involving
PPARγ modulation by mulberry leaf bioactive compounds by in vitro and in vivo methods and its impact on key inflammatory
markers. In vitro assay by TR-FRET suggested that mulberry leaf extracts can serve as a putative modulator of PPARγ. High
glucose conditions in vitro and in vivo increased PPARγ levels, which were ameliorated by mulberry leaves or their extracts.
Interestingly, PPARγ was significantly phosphorylated at Ser112 by upstream kinases ERK42/44 in kidney of diabetic animals
on feeding mulberry leaves. In vitro studies using MDCK cell line revealed that increased Ser112 phosphorylation was observed
when cells were treated with bound phenolic acid rich extract but not with free phenolic acid rich extracts. HPLC analysis and
bioassay-guided activity revealed that coumaric acid was the bioactive molecule within bound phenolic acid rich extract that was
responsible for increased ERK42/44-mediated phosphorylation at Ser112. Furthermore, mulberry leaf bioactive compounds
showed beneficial effect on the tested inflammatory markers.