Congratulations to Dr. Xiangning Chen

Congratulations to Dr. Xiangning Chen. She publicly defended her thesis, Light modulates glucose and lipid metabolism via the sympathetic nervous system. Her PhD journey comes to an end after five vigorous years.

Abstract: Epidemiologic and animal studies show that aberrant light conditions are a major risk factor for diseases such as diabetes and obesity. The common view in the field is that aberrant light exerts detrimental effects on glucose and lipid homeostasis through the misalignment of the circadian clock with activities that follow the solar day. Our results in mice, however, reveal a direct effect of light on glucose and lipid homeostasis independent of circadian misalignment, and likely, by regulating the sympathetic nervous system. We show that dark rearing from birth caused glucose and lipid metabolic defects that manifested at different stages across the life of animals and were exacerbated with age in males, but not females. These metabolic defects result as a consequence of blunted sympathetic activity in dark reared mice.  Remarkably, the metabolic defects caused by dark rearing for 10 months could be partially alleviated by a 5-week exposure to a regular light-dark cycle.

To understand how light controls the sympathetic nervous system, we are currently investigating the role of different intrinsically photosensitive retinal ganglion cells (ipRGCs) in the light-brain-sympathetic circuit using acute light stimulation. Further, we are using a retrograde tracing to define the underlying neural circuits by which light signals impinging on the retina are relayed to the periphery to influence glucose and lipid homeostasis.

These studies will lead to new knowledge about how light modulates glucose metabolism and the potential impact of environmental light on metabolic diseases, as well as the underlying circuits and mechanisms.

Rejji Kuruvilla, Xiangning Chen, Haiqing Zhao, & Samar Hattar (from left to right) celebrate Chen’s public defense.