In 1971, Japanese biochemist Akira Endo began screening thousands of fungal fermentation broths for cholesterol synthesis inhibitors. His hypothesis: fungi would have evolved molecules to inhibit sterol synthesis in microbial competitors. After examining over 6,000 broths, Endo found compactin (mevastatin) in Penicillium citrinum — the first HMG-CoA reductase inhibitor. He received the Lasker Prize in 2008.
The target: HMG-CoA reductase, the regulatory bottleneck
The mevalonate pathway (18 steps from acetyl-CoA to cholesterol) has one rate-limiting regulatory step: the reduction of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) to mevalonate by HMG-CoA reductase. Statins are competitive inhibitors that structurally mimic HMG-CoA at the transition state — the pharmacophore 3,5-dihydroxyheptanoate portion binds with 6–8 orders of magnitude greater affinity than the natural substrate.
The real mechanism: LDL receptor upregulation
When HMG-CoA reductase is inhibited, hepatic cholesterol falls, releasing the SREBP-2 transcription factor from the ER → nuclear translocation → activation of the LDL receptor gene. More LDL receptors on hepatocyte surface → greater clearance of circulating LDL particles → 40–60% reduction in plasma LDL. The main mechanism of statins is not directly inhibiting cholesterol synthesis but upregulating the LDL receptor — accelerating LDL clearance from plasma.
Pleiotropic effects
Benefits beyond LDL reduction include anti-inflammatory effects (reduced PCR-us; inhibition of Rho/Ras isoprenylation → reduced NF-κB activation), plaque stabilization (increased collagen content, reduced intraplaque inflammation), and endothelial effects (increased eNOS expression → more nitric oxide → vasodilation).