BACKGROUND/OBJECTIVES While excessive food consumption represents a key factor in the development of obesity, the underlying mechanisms are still unclear. Ghrelin, a gut-brain hormone involved in the regulation of appetite, is impaired in obesity. In addition to its role in eating behavior, this hormone was shown to affect brain regions controlling reward, including the striatum and prefrontal cortex, and there is strong evidence of impaired reward processing in obesity. The present study investigated the possibility that disrupted reward-related brain activity in obesity relates to ghrelin deficiency. SUBJECTS/METHODS Fifteen severely obese subjects (BMI > 35 kg/m2) and fifteen healthy non-obese control subjects (BMI < 30 kg/m2) were recruited. A guessing-task paradigm, previously shown to activate the ventral striatum, was used to assess reward-related brain neural activity by functional magnetic resonance imaging (fMRI). Fasting blood samples were collected for the measurement of circulating ghrelin. RESULTS Significant activations in the ventral striatum, ventromedial prefrontal cortex and extrastriate visual cortex were elicited by the fMRI task in both obese and control subjects. In addition, greater reward-related activations were present in the dorsolateral prefrontal cortex, and precuneus/posterior cingulate of obese subjects compared to controls. Obese subjects exhibited longer choice times after repeated reward and lower circulating ghrelin levels than lean controls. Reduced ghrelin levels significantly predicted slower post-reward choices and reward-related hyperactivity in dorsolateral prefrontal cortices in obese subjects. CONCLUSION This study provides evidence of association between circulating ghrelin and reward-related brain activity in obesity and encourages further exploration of the role of ghrelin system in altered eating behavior in obesity.

中文翻译：

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奖励相关的大脑活动和行为与肥胖患者的外周生长素释放肽水平有关

背景/目的 虽然过度的食物消耗是肥胖发展的关键因素，但其潜在机制仍不清楚。Ghrelin 是一种参与调节食欲的肠脑激素，在肥胖症中受损。除了在饮食行为中的作用外，这种激素还被证明会影响控制奖赏的大脑区域，包括纹状体和前额叶皮层，并且有强有力的证据表明肥胖症的奖赏处理受损。本研究调查了肥胖中与奖励相关的大脑活动中断与生长素释放肽缺乏有关的可能性。对象/方法 招募了 15 名严重肥胖受试者 (BMI > 35 kg/m2) 和 15 名健康非肥胖对照受试者 (BMI < 30 kg/m2)。一个猜测任务范式，以前显示激活腹侧纹状体，用于通过功能磁共振成像 (fMRI) 评估与奖励相关的大脑神经活动。收集空腹血样用于测量循环生长素释放肽。结果 肥胖和对照受试者的 fMRI 任务均引起腹侧纹状体、腹内侧前额叶皮层和纹外视觉皮层的显着激活。此外，与对照组相比，肥胖受试者的背外侧前额叶皮层和楔前叶/后扣带回中存在更大的奖励相关激活。与精益对照组相比，肥胖受试者在重复奖励后表现出更长的选择时间和更低的循环生长素释放肽水平。降低的生长素释放肽水平显着预测了肥胖受试者背外侧前额叶皮质的较慢的后奖励选择和奖励相关的过度活跃。