Obesity is the most significant chronic healthcare crisis facing the United States, as well as other countries. Already 1 out of every 3 adults, and 1 out of every 6 children or adolescents, in the U.S. is obese! Leptin is a hormone that has received considerable attention since its discovery in 1994 for its role in regulating metabolism (like a thermostat, or adipostat) and implications for obesity. High leptin levels are associated with feeling satiated and an active metabolism. Though many overweight people have high levels of circulating leptin, it’s been found that their hypothalamic neurons do not receive the signal – a phenomenon known as “leptin resistance.” An animal model that mirrors this is db/db mice, which lack leptin receptors on the surface of they hypothalamic neurons and are therefore morbidly obese (see image).
Reporting in Science this past week, researchers at Harvard Medical School transplanted neurons with the leptin receptor into the hypothalami of db/db mice and as a result were able to partially restore leptin sensitivity and ameliorate their obesity. Two to three months after transplanting 15,000 (a relatively small number) fluorescently-tagged, leptin sensitive neurons into the db/db mice hypothalami, they observed statistically significant drops in blood sugar levels, leptin concentration, and fat mass. In terms of the mechanism and implications, the team concludes: Read more »
This picture shows the view from my office window in Boston: Dull, dreary, and depressing — at least on overcast days like today. Lack of light is one of the reasons that people feel mentally foggy.
One of the bloggers I follow, Rachel Zimmerman of WBUR’s CommonHealth blog, recently wrote that she’s been drinking three times as much coffee as usual. In addition to imbibing more caffeine, I’ve been trying to boost my spirits and alertness with mid-day runs to the snack machine (not the best strategy, in case you’re wondering).
At this time of year, many people aren’t just foggy and sad — they’ve got SAD, or seasonal affective disorder. About half a million Americans — women more often than men — are diagnosed with seasonal affective disorder each year. Many others experience at least some of the symptoms, which include loss of pleasure and energy, inability to concentrate, feelings of worthlessness, and an uncontrollable urge to eat sugar and high-carbohydrate foods (in my case, chocolate chip cookies).
Bright white light therapy remains a mainstay of treatment for seasonal affective disorder. That’s because the light acts on cells in the retina, the tissue located at the back of the eye that sends visual information to the brain. The hypothalamus, which helps control the sleep-wake cycle, is one part of the brain that receives this information. During the winter months, when people tend to stay indoors more, days are shorter, and the weather becomes overcast, our exposure to natural light diminishes. That disrupts the sleep-wake cycle, as well as other circadian rhythms. The result can be symptoms of seasonal affective disorder. Read more »
*This blog post was originally published at Harvard Health Blog*