Environment & Energy
Related: About this forumNucleic Acid Invaders from Food Confirmed
Just as many of us suspected all along.
New research confirms that DNA fragments derived from meals, large enough to carry complete genes, can escape degradation and enter the human circulatory system, and so can RNA, raising serious concerns over new nucleic acids introduced into the human food chain via genetically modified organisms.
A study led by Sándor Spisák who holds a joint appointment at Hungarian Academy of Sciences in Budapest and Harvard Medical School Boston, Massachusetts in the USA analysed over 1,000 human adult samples from four independent studies, and found DNA fragments derived from food in all plasma samples, some large enough to code for complete genes.
Previous animal feeding studies have demonstrated that a minor proportion of fragmented dietary DNA may resist digestion, but the degradation of long chains of DNA and the possible uptake and transport into the bloodstream are not at all understood. Circulating cell free DNA (cfDNA) in the human bloodstream, first described in 1948, are mostly double-stranded molecules with a wide range of fragment sizes from 180 - 21 k bp.
Most people think cfDNA are from apoptotic cells (resulting from programmed cell-death), and in different diseases such as inflammation, autoimmune, trauma and cancer, necrotic cells (from non-programmed cell death) may increase the amount. In fact, both DNA and RNA are found circulating in the bloodstream, and there is good evidence that they are actively secreted from living cells as a nucleic acid intercommunication system.
Ruh-roh...
mike_c
(36,214 posts)So if some nucleic acid oligomers are directly absorbed into the bloodstream-- and the mechanism for that is unclear (epithelial M cells? enteroendocrine cells?)-- then it's likely that they have ALWAYS done so, and there is no selective disadvantage to it, or perhaps there are damage prevention mechanisms in place. Prion diseases make a similar argument on the expression product side, i.e. the misfolded template proteins must be absorbed intact in order to model misfolding of endogenous proteins, but the fact that infectious prion diseases are rare suggests that at least some steps in the process are highly regulated and protected.
GliderGuider
(21,088 posts)A lot of the outcome depends on what's in those fragments.
mike_c
(36,214 posts)...reason for not panicking just yet. I've also seen the argument that this is part of vertebrate immune system maintenance, i.e. that exposure to dietary epitopes helps to keep the immune system tuned to respond specifically to easily encountered environmental components, although that argument would seem to apply to polypeptide oligomers more than NAs.
Whether or not "what's in those fragments" is meaningful at all depends entirely upon whether there is any plausible means for expressing gene products from them. I certainly would not rule that out, but it also doesn't seem to be a common source of pathogenicity, either.
GliderGuider
(21,088 posts)I don't know how great the potential for uptake is, not being a microbiologist. But if a scientist who holds a joint appointment with the Hungarian Academy of Sciences and Harvard Medical School is concerned, maybe it's not outrageous that I'm concerned as well.