In most, but not all, affected children, a period of normal development is followed by an irreversible brain injury triggered by a nonspecific illness. If children with GA-I reach 5 years of age without suffering brain injury they usually never show symptoms of the disease. New research using a mouse model of GA-I (Gcdh “/ “ mice) by William Zinnanti and colleagues at Penn State, Hershey, has provided insight into the mechanisms underlying injury and age-dependent susceptibility to the disease and suggested a way to monitor children with the disease.

Gcdh “/ “ mice do not develop disease if lysine and tryptophan are excluded from their diet. Exposure to lysine in the diet caused brain damage in both young and adult mice, but the extent of the damage was much greater in the young mice. This was shown to be because lysine uptake is enhanced in the immature brain compared with the adult brain and so more intermediates of lysine degradation accumulated, thereby increasing the susceptibility to brain damage. Treating young Gcdh “/ “ mice with homoarginine, to limit brain uptake of lysine, and glucose, to limit lysine degradation, substantially decreased brain damage caused by exposure to lysine in the diet. Furthermore, brain injury was preceded by decreases in glutamate and GABA in the brain that could be monitored by proton nuclear magnetic resonance spectroscopy, providing hope that a way of monitoring children with GA-I to predict the onset of brain injury might be developed.

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Researchers have known for some time that metabolic status and food preferences can vary from person to person and even between different cultures. The recent growth of the new field of proteome research, which focuses on characterizing the structure and function of the complete set of proteins produced by our genes, has allowed scientists to gain a deeper understanding of the metabolic changes that occur when foods are digested, Kochhar says.

There's a lot of information in metabolism that can be used to improve health and this information is just now being explored and tapped, the researcher says.

In the future, a test for determining one's metabolic type could be performed as part of a blood or urine test during a regular visit to the doctor, Kochhar predicts. But a reliable test to measure one's metabolic type may be five years away, as more research is still needed in this area, he notes.

Women were not included in the current study in order to avoid any metabolic variations linked to the menstrual cycle, which has been shown in studies by others to influence metabolic differences, Kochhar says. But the researchers plan to include women in future clinical trials on metabolic responses to chocolate to determine if there is a gender-specific response to the treat.

In addition to providing a better understanding of individual metabolic types, the current study could also lead to the discovery of additional biomarkers that can identify new health benefits linked to chocolate and other foods, says Kochhar, whose research was funded by Nestl?©.

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