Assessing Unintended Health Effects of Genetically Engineered Foods

whooshdisguisingBiotechnology

Dec 14, 2012 (4 years and 11 months ago)

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Approaches to Assessing
Unintended Health Effects of
Genetically Engineered Foods


Understanding the Science
Behind the Approach

Ann L. Yaktine, Ph.D.

Institute of Medicine

The National Academies


The USDA, FDA, and EPA asked the National
Academies to convene a committee of experts
to:




Outline science
-
based approaches for
assessing or predicting unintended health
effects of genetically engineered foods, and




Compare the potential for unintended effects
of GE foods with those derived from
conventional and other methods of genetic
modification.


Safety of Genetically Engineered
Foods: Approaches to Assessing
Unintended Effects

The Task to the Study Panel


Focus on mechanisms

by which
unintended changes in composition of
food occur as a result of various breeding
and propagation methods


Assess the extent

to which these
mechanisms are likely to lead to
significant compositional changes in food


Assess methods to detect

unintended
changes in food in order to determine
potential human health effects


Identify appropriate scientific questions

and methods for determining unintended
changes in food from GE organisms


Outline methods to assess

the potential
short
-

and long
-
term human
consequences of such changes

The study focused on scientific
approaches and methodology used
to predict and assess unintended
effects.

Defining the Science

What is Genetic Engineering?

One type of genetic modification that
involves an intended
targeted
change
in a gene sequence to achieve a
specific result through the use of
recombinant DNA

(rDNA) technology.

rDNA Techniques


Microbial Vectors


Electroporation


Microinjection


Transposable Elements

TCGATAGCGCAAAACTAA

ATGCCAAGCA

TCAA

TCAA

ATGCCAAGCA

Genetic engineering is targeted, that is, the
gene sequence is specific and the insertion
site is known.

ATGCCAAGCA

CATATTCTC

TCGATAGCGCAAAACTAA

Non
-
GE Techniques of Genetic
Modification


Mutation Breeding:



Radiation Mutagenesis



Chemical Mutagenesis


Induced mutagenesis causes random
changes in the DNA sequence.

ATGCCAA

CATATTCTC

AGCGCAAAACTAA

TCGA

GCA

Other Non
-
GE Techniques of
Genetic Modification


Simple Selection


Crossing


Interspecies Crossing



The progeny of cross
-
breeding cannot
always be predicted.

Targeted
,
Non
-
Targeted
, and
Conventional

Methods of Genetic
Modification All Have the Potential
to Produce Unintended Effects.


Genetic Engineering (Targeted Genetic
Modification)



Impact of expressing proteins from an
unrelated species?


Brazil nut gene into soybean



Effects of new proteins operating through
unexpected pathways?




Non
-
targeted Genetic Modification


Cannot predict outcome due to random
changes to the gene sequence





Conventional Crossing


Expression pattern of new traits cannot
always be predicted


Lenape potato




Mechanisms of genetic engineering
overlap with those of other types of
genetic modification.



Techniques used to alter the genetic
composition of an organism are
mechanistically different.


Why is predicting an unintended effect
difficult?

It is unlikely that all methods
of either genetic engineering
or conventional breeding will
have equal probability for
unintended effects.

It is more likely that the product
of the modification rather than
the process itself will produce an
unintended effect.

What Scientific Approaches Can Be
Used to Identify Compositional
Changes in Food that May Lead to
an Unintended Effect?


Targeted Quantitative Analysis



Profiling (Untargeted) Analysis

Targeted Analysis


Predefined
Compounds


Amino acids


Lipids


Vitamins


Other nutrients,
toxicants, allergens


Isolated for Analysis


Quantified

Profiling Analysis


Multiple Compounds
in a Sample


Compounds
Identified and
Quantified:


Electrophoretic
separation


Spectrometry


Genomic, proteomic,
etc.

Profiling:

Genomics and Proteomics


Genomic technology can measure the
level of thousands of transcripts
simultaneously


Proteomic analysis detects and
quantifies individual or groups of
proteins

Toxicity Testing



Agronomic Comparisons



Feeding Trials

Application, Validation, and
Limitations of Tools for
Identifying and Predicting
Unintended Effects

Any adverse health effect from
unintended compositional changes
will be a consequence of:


The inherent toxicity of the compound


Allergens


Toxins/toxicants


Anti
-
nutrients



The level of dietary exposure


Exposure to high
-
level consumers


Food habits related to culture


Effect of food preparation/processing

Agronomic Comparison


Agronominc traits are evaluated in the
laboratory, greenhouse, and field

APPLICATION



Varieties with unusual
features are discarded

LIMITATION



Not sufficient for
identifying all
unintended changes

Feeding Trials

Test Animals are Fed Modified Whole Foods
or Food Extracts

APPLICATION



Compares nutritional
quality of GE crop
with its conventional
counterpart

LIMITATIONS



Nutrient requirements
of animal models


Volume of food that
can be administered


Limited test dosage
and exposure time

Food is a Complex Mixture

The use of targeted and non
-
targeted
(profiling) methods to assess the
safety of genetically modified foods is
increasing, however, there are
limitations to our ability to interpret
and utilize the information generated.


The complexity of food composition
challenges the ability of modern
analytical chemistry and bioinformatics
to identify compositional changes and
determine their biological relevance.

Looking to the Future

Although the array of analytical and
epidemiological techniques has increased,

gaps remain in our ability to:


Identify compositional changes that result
from genetic modification


Determine the biological relevance of such
changes to human health


Devise appropriate scientific methods to
predict and assess unintended effects

Recommendations from the Study

Develop and employ:



Standardized Sampling Methodologies



Validation Procedures



Performance
-
based Techniques for Targeted
Analysis and Profiling



Integrated Database of Food Composition from
Industrial and Regulatory Agency Sources

Standardized Sampling
Methodologies

Should include:



Comparison of modified foods to unmodified
varieties developed under a variety of
environmental conditions



Comparison of modified foods to commonly
consumed commercial varieties

Validation Procedures

The tracking potential of all

genetically modified foods should be improved ,
including:



Pre
-
market to post
-
market feedback loop



Dietary survey tools

Performance
-
Based Techniques for
Targeted Analysis and Profiling


Scientific methods to detect unintended
compositional changes must be continually
scrutinized for accuracy, validity, and application



Current databases of novel and naturally
-
occurring compounds must be improved and
expanded

Acknowledgements

The Institute of Medicine and the Division of
Earth and Life Sciences, The National
Academies

The Committee to Identify and Assess
Unintended Effects of GE Foods on Human
Health, Dr. Bettie Sue Masters, Chair