SREBP Processing Inhibitor, Betulin

Toxicity: Toxic (F)

Tang, J.J., et al. 2011. Cell Metab.13, 44.

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A cell-permeable pentacyclic triterpenoid from birch bark extract that interacts with SCAP (SREBP cleavage activating protein) and prevents SREBP (sterol regulatory element-binding protein) Golgi proteolytic activation (1 to 13.55 µM in Rat hepatocytes CRL-1601) via a similar mechanism as oxysterols by inducing the association of SCAP with Insig-1 (insulin-induced gene-1), thereby causing SCAP-SREBPs complex ER retention. Unlike oxysterols, Betulin does not activate LXR to induce concomitant HMGCR (HMG-CoA reductase) degradation and SREBP-1 up-regulation. While both Betulin and HMGCR inhibitor Lovastatin (Cat. No. 438185 ) inhibit cellular cholesterol synthesis (by ~70% in CRL-1601 cultures with respective compound at 13.55 and 1 µM concentration), only Betulin suppresses cellular fatty acid synthesis (by ~55% at 13.55 µM in CRL-1601). Betulin is shown to exhibit comparable in vivo efficacy as Lovastatin (both dosed at 30 mg/kg/day with chow) in ameliorating high fat/cholesterol diet-induced obesity (% fat/lean tissue ratio increase from non-fat diet mice = 167, 44, and 33 in mice consuming fat diet alone, with Lovastatin, with Betulin, respectively). However, only Betulin is demonstrated to lower fasting blood glucose and insulin levels and reduce fat cell size in white adipose tissue in high fat diet mice. Fatostatin (Cat. No. 341329 ) in comparison does not target SCAP via sterol-binding site, nor does it induce SCAP binding to Insig-1.