Modern Medical Laboratory Journal

Researchers from the Max Planck Institute for Metabolism Research and Harvard Medical School have now shown a synaptic amplifier of hunger for regaining body weight in the hypothalamus. Restricting caloric intake effectively reduces body weight, but most dieters fail long-term adherence to caloric deficit and eventually regain lost weight. Hypothalamic circuits that control hunger drive critically determine body weight; yet, how weight loss sculpts these circuits to motivate food consumption until lost weight is regained remains unclear. In this study, researchers probe the contribution of synaptic plasticity in discrete excitatory afferents on hunger-promoting AgRP neurons. They reveal a crucial role for activity-dependent, remarkably long-lasting amplification of synaptic activity originating from paraventricular hypothalamus thyrotropin-releasing (PVH^TRH) neurons in long-term body weight control. Silencing PVH^TRH neurons inhibits the potentiation of excitatory input to AgRP neurons and diminishes concomitant regain of lost weight. Brief stimulation of the pathway is sufficient to enduringly potentiate this glutamatergic hunger synapse and triggers an NMDAR-dependent gaining of body weight that enduringly persists. Identification of this activity-dependent synaptic amplifier provides a previously unrecognized target to combat regain of lost weight. 
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