Phenylpropenoic acid glucoside phytochemical augments pancreatic beta cell mass in high-fat diet-fed mice and protects beta cells from ER stress-induced apoptosis

Scope: A major goal of diabetes therapy is to identify novel drugs that preserve or expand
pancreatic beta cell mass. Here, we examined the effect of a phenylpropenoic acid glucoside
(PPAG) phytochemical on the beta cell mass, and via whichmechanism this effect is established.
Methods and results: Mice were fed a high-fat and fructose-containing diet to induce obesity
and hyperglycemia. PPAG treatment protected obese mice from diet-induced hyperglycemia
and resulted in a tripling of beta cell mass. The effect of the phytochemical on beta cell
mass was neither due to increased proliferation, as determined by Ki67 immunostaining,
nor to neogenesis, which was assessed by genetic lineage tracing. TUNEL staining revealed
suppressed apoptosis in PPAG-treated obese mice. In vitro, PPAG protected beta cells from
palmitate-induced apoptosis. It protected beta cells against ER stress by increasing expression
of antiapoptotic B-cell lymphoma 2 (BCL2) protein without affecting proapoptotic signals.
Conclusions: We identified an antidiabetic phytochemical compound that protects pancreatic
beta cells from ER stress and apoptosis induced by high-fat diet/lipotoxicity. At the tissue
level, this led to a tripling of beta cell mass. At the molecular level, the protective effect of the
phytochemical was mediated by increasing BCL2 expression in beta cells.