ベツリノール

解説ベツリンC30H50O2(442.70)．ルパン骨格をもつ五環性トリテルペンジオール．シラカバBetula albaの樹皮成分(24％ 以上)．ヤマグルマ科Trocodendron aralioides，カバノキ科Corylus avellana，マメ科Vicia faba，そのほか多くの植物にも含まれている．無色の針状晶．融点250 ℃．[α]15D＋20°(ピリジン)．エタノール，クロロホルム，エーテル，ベンゼンに易溶，酢酸に可溶，冷水に難溶．

説明Sterol regulatory element binding protein 2 (SREBP-2) regulates cholesterol synthesis by activating the transcription of genes for HMG-CoA reductase and other enzymes of the cholesterol synthetic pathway. When cellular sterol levels are high, SREBP is bound by SCAP and Insig to ER membranes as a glycosylated precursor protein. Upon cholesterol depletion, the protein is cleaved to its active form and translocated into the nucleus to stimulate transcription of genes involved in the uptake and synthesis of cholesterol. Betulin, the precursor of betulinic acid, is a pentacyclic triterpene found in the bark of birch trees. Betulin inhibits the SREBP-driven pathway of cholesterol and fatty acid biosynthesis by promoting SCAP–Insig binding which prevents the activation and release of SREBP-2 from the ER. At 15-30 mg/kg/day, betulin has been shown to decrease lipid levels and increase insulin sensitivity in mice fed a western-type diet. In an atherosclerosis disease model, 30 mg/kg/day betulin can reduce the size and improve the stability of atherosclerotic plaques in LDLR-knockout mice. At 2.5-5 μg/ml betulin, in combination with cholesterol, demonstrates anticancer effects by inducing apoptosis in Jurkat cells, A549 lung carcinoma cells, and HeLa cervical carcinoma cells.

使用Betulin may be used in the preparation of betulinic acid, which shows anti-HIV, antimalarial and anti-inflammatory activities.

一般的な説明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 ameliorate 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.