Fluctuations of neuronal activities in the brain may underlie relatively slow components of neurofunctional alterations, which can be modulated by food intake and related systemic metabolic statuses. Glutamatergic neurotransmission plays a major role in the regulation of excitatory tones in the central nervous system, although just how dietary elements contribute to the tuning of this system remains elusive. Here, we provide the first demonstration by bimodal positron emission tomography (PET) and magnetic resonance spectroscopy (MRS) that metabotropic glutamate receptor subtype 5 (mGluR5) ligand binding and glutamate levels in human brains are dynamically altered in a manner dependent on food intake and consequent changes in plasma glucose levels. The brain-wide modulations of central mGluR5 ligand binding and glutamate levels and profound neuronal activations following systemic glucose administration were further proven by PET, MRS, and intravital two-photon microscopy, respectively, in living rodents. The present findings consistently support the notion that food-associated glucose intake is mechanistically linked to glutamatergic tones in the brain, which are translationally accessible in vivo by bimodal PET and MRS measurements in both clinical and non-clinical settings.

大脑中神经元活动的波动可能是神经功能改变相对缓慢的组成部分的基础，这可以通过食物摄入和相关的全身代谢状态进行调节。谷氨酸能神经传递在中枢神经系统兴奋性的调节中起着重要作用，尽管饮食元素如何促进该系统的调节仍然难以捉摸。在这里，我们通过双峰正电子发射断层扫描 (PET) 和磁共振波谱 (MRS) 首次证明了人类大脑中代谢型谷氨酸受体亚型 5 (mGluR5) 配体结合和谷氨酸水平的动态变化取决于食物摄入量和随之而来的血浆葡萄糖水平的变化。PET、MRS 和活体双光子显微镜分别在活啮齿动物中进一步证明了全身葡萄糖给药后中枢 mGluR5 配体结合和谷氨酸水平的全脑调节以及深刻的神经元激活。目前的研究结果一致支持这样一种观点，即食物相关的葡萄糖摄入量与大脑中的谷氨酸能在机械上相关，这是可转化的在临床和非临床环境中通过双峰 PET 和 MRS 测量在体内进行。