The growing prevalence of obesity in western societies represents a critical public health concern to millions of people, yet the factors controlling the buildup of fat within our bodies are not completely understood. The involuntary functions of organs such as the heart, stomach and intestines are regulated by the autonomic nervous system. This system is divided into two parts - the sympathetic nervous system (SNS) and parasympathetic nervous system (PSNS). The SNS controls our body's reactions during "fight or flight" situations where heart rate, blood pressure, and energy usage are increased. The primary source of stored energy in mammals are fat deposits and if energy needs cannot be met during "fight or flight" situations, signals sent from the brain via the SNS to fat cells a process known as SNS innervation - induces the breakdown of fat and the release of extra fuel. On the other hand, the PSNS controls our body during "rest and digest" situations where the body is relaxed and digestion is increased. While it has been demonstrated that dual SNS and PSNS innervation exists in most organs, no such innervation by the PSNS has been demonstrated for fat cells. If present, PSNS innervation may begin to explain the complex mechanisms underlying the buildup of fatty tissue.

A study reported in the November 4 issue of the Journal of Clinical Investigation (JCI) by Felix Kreier and colleagues from the Netherlands Institute for Brain Research in Amsterdam revealed, for the first time, that PSNS innervation of fatty tissue does indeed occur. The authors removed nerves from the sympathetic branch of the nervous system of rats and injected multiple abdominal fat compartments with molecular tagged pseudorabies virus. The replication of viral particles resulted in infections occurring only along the chain of functionallyconnected neurons of the PSNS from the fatty tissue to the brain. "Before this work, there was
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Contact: Brooke Grindlinger
science_editor@the-jci.org
212-342-9006
Journal of Clinical Investigation
5-Nov-2002

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