For its studies, the team of the Institute of Experimental Genetics (IEG) used mice that had become obese and had developed type 2 diabetes due to a high-fat diet. Their offspring were obtained solely through in vitro fertilization (IVF) from isolated oocytes and sperm, so that changes in the offspring could only be passed on via these cells. The offspring were carried and born by healthy surrogate mothers. This enabled the researchers to rule out additional factors such as the behavior of the parents and influences of the mother during pregnancy and lactation.
"The results showed that both oocytes and sperm passed on epigenetic information, which particularly in the female offspring led to severe obesity," said Prof. Johannes Beckers, who directed the study. In the male offspring, by contrast, the blood glucose level was more affected than in the female siblings. The data also show that -- like in humans -- the maternal contribution to the change in metabolism in the offspring is greater than the paternal contribution.
Possible explanation for rapid spread of diabetes worldwide
"This kind of epigenetic inheritance of a metabolic disorder due to an unhealthy diet could be another major cause for the dramatic global increase in the prevalence of diabetes since the 1960s," said Prof. Martin Hrabe de Angelis, director of the IEG and initiator of the study. The increase in diabetic patients observed throughout the world can hardly be explained by mutations in the genes themselves (DNA) because the increase has been too fast. Since epigenetic inheritance -- as opposed to genetic inheritance -- is in principle reversible, new possibilities to influence the development of obesity and diabetes arise from these observations, according to the scientists.
In their theories on heredity and evolution, both Jean-Baptiste Lamarck and Charles Darwin explicitly stated that characteristics and traits that parents acquire during their lifetime through interaction with the environment could be passed on to their offspring. It was not until the neo-Darwinist "Synthetic Theory of Evolution," which combines the theories of natural selection by Darwin and of genetics by Gregor Mendel, that the inheritance of acquired traits was rejected. "From the perspective of basic research, this study is so important because it proves for the first time that an acquired metabolic disorder can be passed on epigenetically to the offspring via oocytes and sperm- similar to the ideas of Lamarck and Darwin," said Professor Johannes Beckers.
*Epigenetics: In contrast to genetics, the term epigenetics refers to the inheritance of traits that are not determined in the primary sequence of the DNA (the genes). So far, RNA transcripts and chemical modifications of the chromatin (e.g. on the DNA or the histones) have been considered as carriers of this epigenetic information.
Materials provided by Helmholtz Zentrum München - German Research Center for Environmental Health. Note: Content may be edited for style and length.
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