Astrocytic BDNF signaling within the ventromedial hypothalamus regulates energy homeostasis.

Brain-derived neurotrophic factor (BDNF) is essential for maintaining energy and glucose balance within the central nervous system. Because the study of its metabolic actions has been limited to effects in neuronal cells, its role in other cell types within the brain remains poorly understood. Here we show that astrocytic BDNF signaling within the ventromedial hypothalamus (VMH) modulates neuronal activity in response to changes in energy status. This occurs via the truncated TrkB.T1 receptor. Accordingly, either fasting or central BDNF depletion enhances astrocytic synaptic glutamate clearance, thereby decreasing neuronal activity in mice. Notably, selective depletion of TrkB.T1 in VMH astrocytes blunts the effects of energy status on excitatory transmission, as well as on responses to leptin, glucose and lipids. These effects are driven by increased astrocytic invasion of excitatory synapses, enhanced glutamate reuptake and decreased neuronal activity. We thus identify BDNF/TrkB.T1 signaling in VMH astrocytes as an essential mechanism that participates in energy and glucose homeostasis.

The ginseng pimple: an inflammatory papule following ginseng consumption.

Ginseng is a popular herbal remedy derived from the plant roots of the Panax genus and has been used in traditional Asian medicine for thousands of years. In the United States, it has become increasingly popular and is taken for many conditions, including as an immune enhancer. Cutaneous adverse effects have been reported to occur following ginseng consumption, although detailed clinical descriptions are limited. A 60-year-old woman who repeatedly developed inflammatory papules following ginseng consumption is described and the characteristics of ginseng use in healthcare are reviewed.