The balancing act of appetite and burning fat
A staggering 8\;% of health costs in Europe are due to obesity-related diseases; genetic, socioeconomic and environmental factors can contribute to an individual being overweight or underweight. The EU-funded TOR and neurogenesis project has just finished investigations into the influence of the central nervous system (CNS) on weight gain. As the control centre for energy balance throughout the body, the brain must be able to pick up signals from the CNS through a variety of sensory inputs. Information on the balance between energy from stores such as fat cells compared with that on tap from food just eaten reaches the hypothalamus. Signals from this area of the brain regulate body weight and food intake. Sensor mechanisms that gauge levels of adenosine triphosphate (ATP), the cell's molecular energy store also signal to the hypothalamus. A fuel-sensing mechanism, the mammalian target of rapamycin (mTOR) signalling cascade, is implicated in integrating the information about the hormones leptin and insulin involved in energy balance and nutrient signals. The project team hypothesised that a cell signalling protein ciliary neurotrophic factor (CNTF) may be involved in hypothalamic control. This small molecule, a so-called cytokine, can reduce weight even during diet-induced obesity. Interestingly, weight loss continues even after the therapy has been discontinued due to this appetite controller. The TOR and neurogenesis researchers have found that more CNTF means greater activity for mTOR in the rat hypothalamus. Furthermore, mice with defective mTOR signalling do not respond to CNTF. Future research will focus on what types of cells are activated in the hypothalamus during CNTF therapy and whether mTOR signalling is needed for long-term action of CNTF. The project's research has far-reaching significance as there is a distinct lack of efficient anti-obesity treatments. Targeting the biochemical nuts and bolts of appetite control and energy balance promises to deliver pharmaceutical answers to obesity.
