I’ve been meaning to write on this paper, from David Sinclair and co-workers, on the mechanism of resveratrol action. The backstory is so long and convoluted that you’re going to have to set aside some time to catch up if you’re just joining it (paging back through this category archive will give you some play-by-play). But the basics are that resveratrol came on the scene as an activator of the enzyme SIRT1, which connection was later called into question by work that showed a lot of artifacts in the assay conditions used to establish it.
This new paper may well clear some of that up. The fluorescent tagged peptides that were producing the false positive may well be mimicking the natural protein partners, if this analysis is correct. SIRT1, as it turns out, recognizes a hydrophobic domain in the same region of each, which can be the fluorescent tag, or native hydrophobic amino acids themselves.
So it appears that resveratrol (and other synthetic sirtuin activators) are acting allosterically on the protein. This work found a single SIRT1 amino acid mutant (E230K) that doesn’t affect SIRT1’s catalytic activity, but does completely mess with resveratrol’s ability to activate it (the other compounds in this class show the same effect). That makes for a neat story, and it would resolve several questions about the molecular mechanism of action.
But it leaves open the bigger questions: is SIRT1 a human drug target? Do activators exert beneficial effects, and do different ones have different profiles in living systems? There’s already plenty of evidence for some of these; the problem is, the evidence points both ways (much of this is summed up and linked to in this post). Resveratrol itself is not, I would say, an appropriate molecule to answer the detailed questions (other than “What does effects does resveratrol itself have?”). It does not have particularly good pharmacokinetic properties, for one thing, and it is known to hit a lot of other things besides SIRT1 (Sinclair himself has referred to it as a “dirty molecule”, and I agree).
So it’s the follow-on sitruin activators that GSK has that are the real vehicles for answering these very interesting (and potentially important, and potentially lucrative) questions. A quick look at Clinicaltrials.gov shows that work has been done on SRT2104 and SRT2379, but many of these studies have been complete for a year or two now. (Here’s the one that’s listed as ongoing – it and several others have an anti-inflammatory bent). All we can deduce is that at least two SRT compounds are being (or recently have been) evaluated in the clinic. Fierce Biotech has a bit more from Sirtris CEO George Vlasuk:
About those clinical trials: GSK’s massive investment in Sirtris has yet to lead to a drug or a prime-time drug candidate. Sirtris has ended clinical development of multiple synthetic compounds after initial human studies, Vlasuk said. And his team is hunting for the precise mechanism for activating SIRT1 in hopes of creating more potent compounds than resveratrol to treat diseases.
Hmm. I thought that maybe this new Science paper was the precise mechanism. But maybe not? The story continues. . .