Tuesday, January 17, 2012

Resveratrol: One step forward, two steps back

Resveratrol is in the news again but this time for all the wrong reasons.  No, it didn't just break up with a pop star or get busted for breaking probation.  Stunning allegations from the University of Connecticut suggest that a significant percentage of Dipak Das' (UConn professor and Director of the Cardiovascular Research Center) scientific research on RES may suffer from scientific fraud (see here for just one article).  I looked at some of the (60,000 page!) report and it looks like much of the fraud was based on images of Western blots that had been altered or fabricated.  I have long complained about figures of Western blots in various publications where only the bands of interest are shown with no molecular weight markers or anything.  This is like buying a car based on a picture you see on the internet.  Yes, there is a band there but you have no idea how good the antibody is that you are using to probe with, if the protein runs at the right place on the gel, etc.  In Das' case, it looks like random bands were just pasted on there.  No bueno, pal, no bueno.

Does this mean that resveratrol is now demoted to a worthless contamination in an otherwise tasty glass of wine?  Um, no.  I'll admit I have read some of Das' stuff and it has influenced some of my opinions about RES, but there are a whole host of researchers out there that have demonstrated how RES impacts biological pathways and (in my opinion) there is very clear evidence that it has a significant effect if the dose is high enough.  Unfortunately, cases like this place a stigma on research involving RES and could hinder progress towards understanding the physiological benefit of this molecule.

Ok, so now on to better news.  My favorite wine goddess maker, Kerith Overstreet from Bruliam Wines, has a new blog post on the cardioprotective properties of wine. It's pretty funny (you can check it out here) but in it she highlights not RES, but oligomeric proanthocyanidins (OPCs).  If you recall an early post I made on the magic of winemaking (here), you may recognize OPC as another term for polymerized flavinoids, which include tannins such as catechin.  Most OPCs originate from the grape skin, so the amount of OPC in any given bottle can vary dramatically.  The final levels depend, in part, on how long the grape skins are left in the fermentation since it is the rising alcohol content that ultimately extracts the monomeric proanthocyanidins from the grape.  Therefore, craft is a big variable in determining the benefit of wine to the drinker (we are all counting on you, Kerith!) Interestingly, Das was involved in a company called Dry Creek Nutrition, that was trying to purify and sell proanthocyanidins.  In light of the Das debacle, maybe OPCs are the new RES!

Wednesday, January 11, 2012

Discovery of an upside down, carnivorous plant in Brazil

I've always been a fan of carnivorous plants.  Pitcher plants, Venus flytraps... very cool.  An article just published in PNAS describes a very bizarre plant that has been recently characterized as carnivorous.  The flowering plant, from the genus Philcoxia, is a pathetic specimen.  Found in dry savannas of the cerrado in central Brazil, the stems are leafless, which means it resembles many of my potted plants here at the house.

It turns out that the leaves of Philcoxia are actually underground! Most plants would find this adaptation ridiculous.  The primary function of a leaf is to capture sunlight and produce energy through photosynthesis.  What kind of freakish plant would put the leaf underground where there is no light?  A murderous plant, of course.

What Pereira et al. show in the PNAS paper (abstract) is that the leaves of Philcoxia have evolved to trap and eat nematodes in the soil.  The data to support this comes from an elegant study using nematodes that had been fed nitrogen-15 (15N), an isotope of natural nitrogen.  Releasing the nematodes in the vicinity of the plant, they measured the change in 15N in the leaves after two days.  They show that the absorbed 15N increases from nearly undetectable levels before the experiment to about 15% of all nitrogen content by Day 2.  They talk in the methods about how they extensively washed and dried the leaves to remove all traces of 'nematode remains', but the greatest risk in this experiment is that the 15N they are measuring is simply from the residue of dead worms on the leaves.  Nevertheless, they also show that the leaves are covered  with a sticky sap and that enzymes on the surface are available to break down the corpse for consumption, as found in other carnivorous plants. Interestingly, the glands that produce the sap are also similar to those found on other carnivorous plants.  So, it certainly seems plausible that another plant has found its way to the dark side.  Better call NCIS (that's Nematode Criminal Investigative Service).

Maybe I'll just start telling people that the dead plants I have around my house are rare Philcoxia from central Brazil and that they are supposed to look dead.  Maybe I'll tell them that I have re-engineered them to eat, um, larger prey. I wonder if carnivory could be engineered into grass?  That would keep the neighbor's dog off of the yard!! Ahh, the possibilities...