Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Non-human Molecule Is Absorbed by Eating Red Meat According to Study by UCSD Researchers

30.09.2003


A non-human, cellular molecule is absorbed into human tissues as a result of eating red meat and milk products, according to a study by researchers at the University of California, San Diego (UCSD) School of Medicine, published online the week of September 29, 2003 in Proceedings of the National Academy of Sciences. The researchers also showed that the same foreign molecule generates an immune response that could potentially lead to inflammation in human tissues.

Several previous studies have linked ingestion of red meat to cancer and heart disease, and possibly to some disorders involving inflammation. However, that research has primarily focused on the role of red-meat saturated fats and on products that arise from cooking. The UCSD study is the first to investigate human dietary absorption of a cell-surface molecular sugar called N-glycolylneuraminic acid (Neu5Gc), which is found in non-human mammals. Not produced in humans, Neu5Gc occurs naturally in lamb, pork and beef, the so-called “red meats”. Levels are very low or undetectable in fruits, vegetables, hen’s eggs, poultry and fish.

Conducting laboratory studies with human tissue, followed by tests in three adult subjects, the UCSD team provided the first proof that people who ingest Neu5Gc absorb some of it into their tissues. In addition, they demonstrated that many humans generate an immune response against the molecule, which the body sees as a foreign invader.



The study’s senior author, Ajit Varki, M.D., UCSD professor of medicine and cellular and molecular medicine, and co-director of the UCSD Glycobiology Research and Training Center, said that although it is unlikely that the ingestion of Neu5Gc alone would be primarily responsible for any specific disease, “it is conceivable that gradual Neu5Gc incorporation into the cells of the body over a lifetime, with subsequent binding of the circulating antibodies against Neu5Gc (the immune response), could contribute to the inflammatory processes involved in various diseases.”

He added that another potential medical barrier related to Neu5Gc might occur in organ transplantation.

“Over the past decade, the number of patients waiting for organ transplantation has more than tripled, with little increase in the number of donor organs. This has led to an exploration of using animal organs for transplantation into humans, a process called xenotransplantation,” Varki said. “However, the leading donor candidate is the pig, an animal in which Neu5Gc happens to be very common. The current study raises the possibility that human antibodies against Neu5Gc might recognize the Neu5Gc in the pig organ and facilitate its rejection.”

In describing the research approach taken by his team, Varki explained that humans do not produce Neu5Gc because they lack the gene responsible for its production.** And yet, other researchers have reported small amounts of Neu5Gc in human cancer tissues.

To verify the existence of Neu5Gc in human cancers, Varki’s collaborator, Elaine Muchmore, M.D., UCSD professor of medicine and associate chief of staff for education at the San Diego VA Healthcare System, developed an antibody that would be attracted by, and bind to Neu5Gc on tissue samples. The antibody was purified by Pam Tangvoranuntakul, B.S., the study’s first author and a Ph.D. student in Varki’s lab.

Working with Nissi Varki, M.D., UCSD professor of pathology and medicine, Tangvoranuntakul found that the antibody stained not only human cancers, but also some healthy human tissues. They found that small amounts of Neu5Gc were present in blood vessels and secretory cells, such as the mucous membranes. A further chemical analysis by Sandra Diaz, a Varki research associate, confirmed the presence of Neu5Gc in human tissue.

Meanwhile, an analysis of healthy human tissue by postdoctoral fellow Pascal Gagneux, Ph.D., and Tangvoranuntakul determined that most people had circulating antibodies in the blood that recognized Neu5Gc, and thus could potentially initiate an inflammatory immune response.

In the absence of any known molecular mechanism that would produce Neu5Gc in humans, the group reasoned that the small amounts of Neu5Gc found in human tissue could arise from human ingestion of Neu5Gc in dietary sources. Postdoctoral fellow Muriel Bardor, Ph.D., showed that when human cells in culture were exposed to Neu5Gc, they easily absorbed and incorporated it onto their own surfaces.

However, to study the possibility of dietary absorption, it was necessary to carry out an ingestion study in healthy people. Because the researchers were hesitant to give a potentially harmful substance to humans, Ajit Varki volunteered to be the first subject, followed by Muchmore and Gagneux.

When the three volunteers drank Neu5Gc purified from pork sources and dissolved in water, there were no immediate ill effects. An analysis of the volunteers’ urine, blood, serum (the clear liquid that can be separated from clotted blood), hair and saliva, both before ingestion and regularly for several days after, determined that the human body eliminates most of the Neu5Gc, but retains and metabolically absorbs small amounts of the foreign sugar. At approximately two days following ingestion, the Neu5Gc levels were two to three times the baseline level prior to ingestion. By four to eight days following ingestion, the levels had dropped nearly to baseline.

The authors cautioned that a causal relationship between Neu5Gc expression in human tissues with any human disease would be premature and scientifically speculative at best. Instead, they said their findings point to the need for population-level analyses of the presence of Neu5Gc in human tissues in relationship to disease incidence, and the mechanisms of human incorporation and antibody response against this sugar.

The study was supported by grants to Varki from the National Institutes of Health (NIH) and the G. Harold and Leila Y. Mathers Charitable Foundation. Some human studies were done in the UCSD General Clinical Research Center, which is also supported by the NIH.

Sue Pondrom | UCSD
Further information:
http://health.ucsd.edu/news/2003/09_29_Varki.html

More articles from Life Sciences:

nachricht Quality control in immune communication: Chaperones detect immature signaling molecules in the immune system
20.09.2019 | Technische Universität München

nachricht Moderately Common Plants Show Highest Relative Losses
20.09.2019 | Universität Rostock

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: 'Nanochains' could increase battery capacity, cut charging time

How long the battery of your phone or computer lasts depends on how many lithium ions can be stored in the battery's negative electrode material. If the battery runs out of these ions, it can't generate an electrical current to run a device and ultimately fails.

Materials with a higher lithium ion storage capacity are either too heavy or the wrong shape to replace graphite, the electrode material currently used in...

Im Focus: Stevens team closes in on 'holy grail' of room temperature quantum computing chips

Photons interact on chip-based system with unprecedented efficiency

To process information, photons must interact. However, these tiny packets of light want nothing to do with each other, each passing by without altering the...

Im Focus: Happy hour for time-resolved crystallography

Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in the city have developed a new method to watch biomolecules at work. This method dramatically simplifies starting enzymatic reactions by mixing a cocktail of small amounts of liquids with protein crystals. Determination of the protein structures at different times after mixing can be assembled into a time-lapse sequence that shows the molecular foundations of biology.

The functions of biomolecules are determined by their motions and structural changes. Yet it is a formidable challenge to understand these dynamic motions.

Im Focus: Modular OLED light strips

At the International Symposium on Automotive Lighting 2019 (ISAL) in Darmstadt from September 23 to 25, 2019, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, a provider of research and development services in the field of organic electronics, will present OLED light strips of any length with additional functionalities for the first time at booth no. 37.

Almost everyone is familiar with light strips for interior design. LED strips are available by the metre in DIY stores around the corner and are just as often...

Im Focus: Tomorrow´s coolants of choice

Scientists assess the potential of magnetic-cooling materials

Later during this century, around 2060, a paradigm shift in global energy consumption is expected: we will spend more energy for cooling than for heating....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Optical Technologies: International Symposium „Future Optics“ in Hannover

19.09.2019 | Event News

Society 5.0: putting humans at the heart of digitalisation

10.09.2019 | Event News

Interspeech 2019 conference: Alexa and Siri in Graz

04.09.2019 | Event News

 
Latest News

Quality control in immune communication: Chaperones detect immature signaling molecules in the immune system

20.09.2019 | Life Sciences

Moderately Common Plants Show Highest Relative Losses

20.09.2019 | Life Sciences

The Fluid Fingerprint of Hurricanes

20.09.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>