Tasteful Science

This is very cool, chocolate in the shape of a constituent molecule of chocolate.

The full story is here.

Randy Old Goats

So, sometime ago, I posted about the news that the MHRA had ordered Gillian McKeith to stop making claims about a product that contained an extract of Horny Goat Weed. Now, over at badscience, some discussion is going on about other products with similar claims.

For example, from healthydirect.co.uk:

The perfect aphrodisiac and vitalising tonic for both men and women. Can support or improve any of the following: • Libido/Sexual Desire • Energy & Stamina • Erectile Dysfunction • Sperm Production • Sensory Stimulation

So, this has got me wondering, what is the evidence for the effect of horny goat weed?

Just as a background to the research, I stopped off at the wikipedia article on Horny Goat Weed (I wanted to know the latin name). The wikipedia article claims that an extract, known as icariin, promotes the formation of nitric oxide and that it also acts as an inhibitor of an enzyme, PDE5. It also gets something rather wrong, where the article claims:

Viagra, a popular pharmaceutical, works by blocking the production of the PDE-5 enzyme.

It actually works by blocking the activity of PDE-5, not the production of the enzyme. Both inhibition of Nitric Oxide synthesis and PDE5 activity are viable mechanisms for inducing erections in men, but does it work?

Going to pubmed and searching for "Epimedium" returns eight pages of results, limiting these to English language returns four pages. Scanning through these results there are two articles that may be of interest.

First, one study demonstrated that doses ranging from 300 microgrammes to 10,000 microgrammes, injected directly into the region of the penis known as the corpus cavernosum, resulted in an increase in blood pressure in the rat penis (Chen and Chiu, 2006).

Second, a study demonstrated that, when incubated with extract, strips of rabbit penile tissue relaxed (Chiu et al, 2006).

So, some evidence that it may work through the mechanism claimed, but no evidence that it produces an effect by oral dosing, even in animals. Next up, the wikipedia article claims that the active component is a compound known as icariin. So, what is the evidence there? A couple of articles report icariin having an in vitro IC50 of around 1 micromolar against PDE5 (Ning et al, 2006 and Xin et al, 2003) which is a reasonable potency.

However, there is nothing on the compounds pharmacokinetics in humans or even rodents. So, all this in vitro work, interesting though it is, may be of no use if the compound is not absorbed by the intestine.

So, final word? There is no evidence to support the use of Horny Goat Weed at the moment. It has a plausible mechanism though, and further research may determine its efficacy.

References

Chen KK, Chiu JH.
Effect of Epimedium brevicornum Maxim extract on elicitation of
penile erection in the rat.
Urology. 2006 Mar;67(3):631-5.
PMID: 16527595

Chiu JH, Chen KK, Chien TM, Chiou WF, Chen CC, Wang JY, Lui WY, Wu CW.Epimedium brevicornum Maxim extract relaxes rabbit corpus cavernosum through multitargets on nitric oxide/cyclic guanosine monophosphate signaling pathway.
Int J Impot Res. 2006 Jul-Aug;18(4):335-42. Epub 2006 Jan 5.
PMID: 16395327

Ning, H., Xin, Z., Lin, G., Banie, L., Lue, T.F., Lin, C., et al.
Effects of icariin on phosphodiesterase-5 activity in vitro and cyclic guanosine monophosphate level in cavernous smooth muscle cells. Urology,(2006) 68(6), 1350-4.
PMID: 17169663 Xin, Z.C., Kim, E.K., Lin, C.S., Liu, W.J., Tian, L., Yuan, Y.M., et al. Effects of icariin on cGMP-specific PDE5 and cAMP-specific PDE4 activities. Asian journal of andrology,(2003) 5(1), 15-8.PMID: 12646997

I am wrong

I am wrong. Brilliantly, repeatedly and gloriously wrong. Today I wrote this. Today, less than 24 hours later, I will contradict myself. Because, sometimes 'traditional' knowledge does tell us something new.

I rather enjoy browsing DissectMedicine, Nature's equivalent to Digg. It's a nice idea however, it is sometimes taken over by spammers, those that want to pursue their own flakey agenda. So, when I see a story about a herbal extract that can treat obesity, submitted by a user with the name of the extract, linking to a page that sells the extract, I assume it's bunk.

However, I am uptight enough to dig a little deeper. First off, pubmed. Which returns absolutely nothing. Not a good start but it's always worth digging a little deeper. So, off to google. The first hit (that isn't an advert) is a BBC news story. The story is entirely uncritical and mentions that the rights have been licensed to a British pharmaceutical company that specialises in natural products, Phytopharm.

On their site is a Q&A sheet about their developement of Hoodia extract, which mentions a clinical trial. So, if a clinical trial has been performed, it may be on the register. But it isn't. If it isn't on the register, then it's not likely to be published because a lot of medical journals now insist that trials are registered before hand as a pre-requisite for publication. So, no chance of getting the results that way.

So, am I wrong? I want to believe that there's something in it. I tend to trust authority (a minor failing of mine probably), so I tend to believe Phytopharm when they say positive results were achieved. But I can't be sure without seeing the numbers. So, if anyone from Phytopharm is reading this, do drop me a line, I'd love to know more. Also, if you are reading this, do you want to give me a job? I'm looking for a new job at the moment, and it's a quick and easy way to shut me up!


As an aside, I'm trying out a footer that should allow this post to be submitted to DissectMedicine, let's see how it works.

The BBC has an interesting headline, Wine 'allows guilt free gluttony'. This is reporting on a very interesting story prepublished in nature. I don't understand the use of the quotation marks here. None of the sources quoted in the story are quoted as saying that, so who said "allows guilt free gluttony"?

Beyond the nit-picking of a BBC headline, the story is very interesting. As many people know, restricting calorific intake in fruit flies and mice to one third of normal, prolongs survival. This is fine in laboratory conditions, where infectious disease is much less common, but some people have been quick to apply these findings to humans to recommend this diet to extend human lifespan.

Now, building on previous research, a natural product has been identified which has a similar effect in mice, through a similar mechanism. In mice fed a high calorie diet, resveratrol returns the survival rate to mice fed a normal calorie diet. As usual, In The Pipeline has the interesting details.

Now, according to the wikipedia article, red wine contains this compound, thus taking us full circle. So, needing little encouragement to slosh some red wine down my gullet, how much do I need to drink to stay slim? Well, the mice in the article were fed 22 mg/kg/day. Which is a fair amount. I guess I weigh about 80 kg, so that's 1760 mg I would need to consume per day. Non-mescadine red wine apparantly contains up to 5.8 mg/l, so based on that, I would need to consume 303 litres of red wine to feel the benefit. I suspect, however, that the ethanol may undo the benefit I may gain from my resveratrol. No matter! Muscadine type red wine, apparantly contains 40 mg/l, so I need only consume 44 litres of the stuff a day, far better!

Sadly, there is still no quick fix here, and red wine does not allow guilt-free gluttony.

New blog toy!

Well google have released a new toy for us all to play with! Of course being a total google fanboy I can't resist the temptation, and so, if you scroll down the page, way down, just past the technorati tool, is the Science and Progress search box. It's got a few sites indexed to it and I'll keep adding them as I can.

Enjoy!