Featured Research

from universities, journals, and other organizations

Hold the medicinal lettuce

Date:
June 26, 2013
Source:
Johns Hopkins Medicine
Summary:
New research suggests that bits of genetic material from plants eaten by mice can NOT enter the bloodstream intact as previous research from another institution had indicated.

In 2011 and 2012, research from China's Nanjing University made international headlines with reports that after mice ate, bits of genetic material from the plants they'd ingested could make it into their bloodstreams intact and turn the animals' own genes off. The surprising results from Chen-Yu Zhang's group led to speculation that genetic illness might one day be treated with medicinal food, but also to worry that genetically modified foods might in turn modify consumers in unanticipated ways.

Related Articles


Now, though, a research team at Johns Hopkins reports that Zhang's results were likely a false positive that resulted from the technique his group used. The new study, the Johns Hopkins group says, bolsters the case of skeptics who argued that genetic material from food would have little chance of surviving the digestive system, much less crossing the intestinal lining to enter the bloodstream. The study appears in the July issue of RNA Biology.

"It's disappointing in a sense -- it would open up so many therapeutic possibilities if microRNAs from food really could get into our blood and regulate our genes," says Kenneth Witwer, Ph.D., of the Johns Hopkins University School of Medicine's Institute for Basic Biomedical Sciences, who led the new study. But beyond the fact that people won't be picking up prescription lettuce at the pharmacy anytime soon, he adds, the larger lesson is that scientific research's capacity for self-correction is alive and well.

Witwer said his group was intrigued by the earlier results, in which Zhang's group focused on microRNAs, molecules that are a chemical cousin of DNA. Rather than storing genetic information as DNA does, their primary role is to intervene in so-called "gene expression," the process of using genes' blueprints to build proteins. Because they affect whether and how much genes are actually used, microRNAs wield tremendous power, Witwer notes, "so it was startling to think that microRNAs from plants could get into the bloodstream, get into tissues, and regulate genes in those tissues."

Witwer teamed up with colleagues to check the results with a similar experiment of their own. They bought soy-based smoothies at a grocery store and tested their microRNA content, then fed the smoothies to macaques and took samples of the animals' blood.

Knowing that the concentrations of any plant microRNAs in the blood would be too low to measure directly, they used a common technique called polymerase chain reaction (PCR) to bring up the concentration of the genetic material. PCR is designed so that only certain fragments of genetic material in a sample -- the ones researchers choose to target -- will be copied. Zhang's studies had also used PCR to look for plant microRNAs.

Just as Zhang had, the Johns Hopkins team found what appeared to be the targeted plant microRNAs in the macaques' blood. But when they ran the experiment several times, they got highly variable results: Sometimes the microRNAs were present in low concentrations, and sometimes not at all. In addition, the samples from before the macaques drank the smoothies were just as likely to have the microRNAs as were the post-smoothie samples -- a result that just didn't make sense if the source of the microRNAs was the plant material in the drinks.

To Witwer, the results indicated that what he was seeing was not the targeted plant microRNAs, but fragments of the macaques' own genetic material that were similar enough to the targeted segments that the PCR copied them at low levels.

To test this, the team used a new technique in which PCR takes place in tiny aerosolized droplets rather than in a test tube. The advantage, Witwer says, is that by effectively running tens or hundreds of thousands of reactions at the same time, researchers can see whether the outcomes of those reactions are consistent -- in other words, whether the results are meaningful or just a fluke. In this case, the results were all over the place, indicating that plant microRNAs weren't really present.

At the same time, Witwer cautions, it remains possible that very low levels of microRNAs could enter the blood. Even if this happened, though, he says it is unlikely that such small numbers of molecules could affect gene expression. Additional studies will be needed to determine whether low-level transfer occurs and whether any plant RNAs serve a function in the body.


Story Source:

The above story is based on materials provided by Johns Hopkins Medicine. Note: Materials may be edited for content and length.


Journal Reference:

  1. Kenneth W. Witwer, Melissa A. McAlexander, Suzanne E. Queen, Robert J. Adams. Real-time quantitative PCR and droplet digital PCR for plant miRNAs in mammalian blood provide little evidence for general uptake of dietary miRNAs: Limited evidence for general uptake of dietary plant xenomiRs. Landes Bioscience, 2013 [link]

Cite This Page:

Johns Hopkins Medicine. "Hold the medicinal lettuce." ScienceDaily. ScienceDaily, 26 June 2013. <www.sciencedaily.com/releases/2013/06/130626183932.htm>.
Johns Hopkins Medicine. (2013, June 26). Hold the medicinal lettuce. ScienceDaily. Retrieved December 20, 2014 from www.sciencedaily.com/releases/2013/06/130626183932.htm
Johns Hopkins Medicine. "Hold the medicinal lettuce." ScienceDaily. www.sciencedaily.com/releases/2013/06/130626183932.htm (accessed December 20, 2014).

Share This


More From ScienceDaily



More Health & Medicine News

Saturday, December 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

The Best Tips to Curb Holiday Carbs

The Best Tips to Curb Holiday Carbs

Buzz60 (Dec. 19, 2014) It's hard to resist those delicious but fattening carbs we all crave during the winter months, but there are some ways to stay satisfied without consuming the extra calories. Vanessa Freeman (@VanessaFreeTV) has the details. Video provided by Buzz60
Powered by NewsLook.com
Sierra Leone Bikers Spread the Message to Fight Ebola

Sierra Leone Bikers Spread the Message to Fight Ebola

AFP (Dec. 19, 2014) More than 100 motorcyclists hit the road to spread awareness messages about Ebola. Nearly 7,000 people have now died from the virus, almost all of them in west Africa, according to the World Health Organization. Video provided by AFP
Powered by NewsLook.com
Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
The Best Protein-Filled Foods to Energize You for the New Year

The Best Protein-Filled Foods to Energize You for the New Year

Buzz60 (Dec. 19, 2014) The new year is coming and nothing will energize you more for 2015 than protein-filled foods. Fitness and nutrition expert John Basedow (@JohnBasedow) gives his favorite high protein foods that will help you build muscle, lose fat and have endless energy. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins