MR Methodology, Department for Diagnostic and Interventional Neuroradiology, University of Bern, Bern, Switzerland.
Translational Imaging Center (TIC), Swiss Institute for Translational and Entrepreneurial Medicine, Bern, Switzerland.
NMR Biomed. 2024 Aug;37(8):e5123. doi: 10.1002/nbm.5123. Epub 2024 Feb 29.
The liver plays a central role in metabolic homeostasis, as exemplified by a variety of clinical disorders with hepatic and systemic metabolic disarrays. Of particular interest are the complex interactions between lipid and carbohydrate metabolism in highly prevalent conditions such as obesity, diabetes, and fatty liver disease. Limited accessibility and the need for invasive procedures challenge direct investigations in humans. Hence, noninvasive dynamic evaluations of glycolytic flux and steady-state assessments of lipid levels and composition are crucial for basic understanding and may open new avenues toward novel therapeutic targets. Here, three different MR spectroscopy (MRS) techniques that have been combined in a single interleaved examination in a 7T MR scanner are evaluated. H-MRS and C-MRS probe endogenous metabolites, while deuterium metabolic imaging (DMI) relies on administration of deuterated tracers, currently H-labelled glucose, to map the spatial and temporal evolution of their metabolic fate. All three techniques have been optimized for a robust single-session clinical investigation and applied in a preliminary study of healthy subjects. The use of a triple-channel H/H/C RF coil enables interleaved examinations with no need for repositioning. Short-echo-time STEAM spectroscopy provides well resolved spectra to quantify lipid content and composition. The relative benefits of using water saturation versus metabolite cycling and types of respiratory synchronization were evaluated. H-MR spectroscopic imaging allowed for registration of time- and space-resolved glucose levels following oral ingestion of H-glucose, while natural abundance C-MRS of glycogen provides a dynamic measure of hepatic glucose storage. For DMI and C-MRS, the measurement precision of the method was estimated to be about 0.2 and about 16 mM, respectively, for 5 min scanning periods. Excellent results were shown for the determination of dynamic uptake of glucose with DMI and lipid profiles with H-MRS, while the determination of changes in glycogen levels by C-MRS is also feasible but somewhat more limited by signal-to-noise ratio.
肝脏在代谢稳态中起着核心作用，各种具有肝和全身代谢紊乱的临床疾病就是很好的例证。特别值得关注的是，在肥胖症、糖尿病和脂肪肝等高发疾病中，脂质和碳水化合物代谢之间的复杂相互作用。由于获取途径有限且需要进行侵入性操作，这给人体的直接研究带来了挑战。因此，对糖酵解通量进行非侵入性动态评估，以及对脂质水平和组成进行稳态评估，对于基础理解至关重要，并且可能为新的治疗靶点开辟新途径。在此，评估了在 7T 磁共振扫描仪中结合在单次交错检查中的三种不同磁共振光谱（MRS）技术。质子磁共振波谱（H-MRS）和碳磁共振波谱（C-MRS）探测内源性代谢物，而氘代谢成像（DMI）依赖于氘标记示踪剂的给药，目前是 H 标记的葡萄糖，以绘制其代谢命运的时空演变图。所有三种技术都经过优化，可在一次稳健的单次临床研究中使用，并在健康受试者的初步研究中应用。使用三通道 H/H/C RF 线圈可实现无需重新定位的交错检查。短回波时间 STEAM 波谱提供分辨率良好的光谱以定量脂质含量和组成。评估了使用水饱和与代谢物循环和呼吸同步类型的相对益处。H-MRS 波谱成像允许在口服 H-葡萄糖后，对时间和空间分辨的葡萄糖水平进行注册，而天然丰度的糖原 C-MRS 提供了肝葡萄糖储存的动态测量。对于 DMI 和 C-MRS，该方法的测量精度估计分别约为 0.2 和 16 mM，用于 5 分钟扫描周期。DMI 确定葡萄糖的动态摄取以及 H-MRS 确定脂质谱的结果非常出色，而 C-MRS 确定糖原水平变化的结果也是可行的，但受信噪比限制更大。
