Sensing Dietary Deficits
One of an animal's most important tasks is selecting an adequate diet. This requires an ability to detect specific nutrients in foods; your text describes how a few nutrients are detected by their taste, while in other cases learning is involved, based on the effects that follow eating a food. Recent research has illuminated how the brain detects indispensable amino acids (IAC), nine amino acids the body requires for synthesizing proteins. A rat will turn away from a food lacking an amino acid it needs within just 20 minutes of beginning to eat. At the same time, activity increases in the anterior piriform cortex (APC), the brain area responsible. Researchers at the University of California, Davis took the research a step further by recording from APC slices placed in nutrient baths that either contained all nine IACs or lacked one of them. When one of the amino acids was missing, the researchers recorded an increase in excitatory postsynaptic potentials. This suggests that the APC can detect IAC levels directly, thus monitoring conditions in its own environment. Journal of Neuroscience, Vol 31, 1583-1590.
Dramatic Increase in Diabetes Projected
Researchers at the U.S. Centers for Disease Control and Prevention are projecting that the number of new cases of diabetes will continue to increase, even if preventive interventions are undertaken. Using data on prediabetes and diabetes incidence in the United States, current life expectancy, and population increases among high-risk subgroups, they estimate that diabetes prevalence will increase from its 2010 level of 14% to 25%-28% of the population by 2050. Population Health Metrics, 2010, 8:29.
Another Epigenetic Effect on Weight
In the Application on p 177 ("The Epigenetics of Weight Regulation"), you learn that starvation during the World War II German blockade of western Holland resulted in the birth of underweight babies, even into the second generation; the cause turned out to be decreased methylation of a gene involved in growth (IGF2). Research just published indicates that dietary restriction can also have the opposite effect. In two studies, British researchers monitored the diet of pregnant mothers, then assessed gene methylation in the babies from DNA samples taken from the umbilical cord. Six or nine years later (depending on the study), researchers checked body fat in the children. A low carbohydrate diet during pregnancy was associated with higher levels of fat in the children, and with excess methylation of their RXRa genes, which are involved in fat metabolism and fat cell development. As the percentage of RXRa genes that were methylated increased from 40% to 80%, the children's percentage of body fat went from 17% to 21%. While this appears to be in conflict with the Dutch hunger winter results, remember that the circumstances there involved more severe deprivation of all nutrients. Diabetes, April 6, 2011, (doi: 10.2337/db10-0979).
Anti-Anorexia Advocate Dies
Isabelle Caro, a former fashion model who battled anorexia from the time she was 12, has died in her native France. Caro was best known for a billboard ad in which she posed nude, with her back to the camera and her gaunt face and prominent ribs showing. In 2008 she released an autobiography called "The Little Girl Who Did Not Want to Get Fat." In her blog she described herself as "a little invisible snowflake in a strong blizzard who is fighting, fighting to finally live, despite years of suffering, and who is crying out to the entire world to say that anorexia is a hell from which you must escape while you still have time." CNN World, December 30, 2010.