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Cardiac Magnetic Resonance Imaging (CMRI), the gold standard approach for characterizing myocardial infarction (MI), frequently relies on Late Gadolinium Enhancement (LGE) using gadolinium-based contrast agents (GBCA). Whereas novel GBCAs targeting specific molecules have not yet entered clinical practice, chemical exchange saturation transfer (CEST) MRI shows promise for detecting various endogenous molecules. This study explored the potential of natural D-glucose as a biodegradable MRI contrast agent for imaging MI on day 7 by employing glucose-weighted CEST MRI (glucoCEST). In vivo, the application of cardiac glucoCEST MTR (asymmetric magnetization transfer ratio) mapping delineated distinct pre- and post-glucose infusion states in both healthy (n=8) and MI-induced mice (n=6) at 9.4T. This approach resulted in significant alterations in glucoCEST contrast, effectively identifying MI regions analogous to conventional LGE and immunohistochemical staining. Ex vivo mass spectrometry imaging confirmed elevated C-glucose and gadolinium accumulation in the MI region after exogenous administration, suggesting the potential of glucoCEST MRI for MI detection. Our preclinical study on MI demonstrated that cardiac glucoCEST MRI utilizing natural D-glucose as a biodegradable contrast agent effectively differentiates between MI regions, Remote myocardium (RM), and healthy myocardium. The results were comparable to those obtained using LGE imaging.

2-Deoxy-D-glucose (2DG) is a known surrogate molecule that is useful for inferring glucose uptake and metabolism. Although 13C-labeled 2DG can be detected by nuclear magnetic resonance (NMR), its low sensitivity for detection prohibits imaging to be performed. Using chemical exchange saturation transfer (CEST) as a signal-amplification mechanism, 2DG and the phosphorylated 2DG-6-phosphate (2DG6P) can be indirectly detected in 1H magnetic resonance imaging (MRI). We showed that the CEST signal changed with 2DG concentration, and was reduced by suppressing cerebral metabolism with increased general anesthetic. The signal changes were not affected by cerebral or plasma pH, and were not correlated with altered cerebral blood flow as demonstrated by hypercapnia; neither were they related to the extracellular glucose amounts as compared with injection of D- and L-glucose. In vivo 31P NMR revealed similar changes in 2DG6P concentration, suggesting that the CEST signal reflected the rate of glucose assimilation. This method provides a new way to use widely available MRI techniques to image deoxyglucose/glucose uptake and metabolism in vivo without the need for isotopic labeling of the molecules.

•Fiber photometry with FRET biosensors complements MRI with cell-specific data.•Data from FRET fiber photometry are consistent with two-photon microscopy ones.•The DGE signal contains a vascular component at short times after injection.•3OMG produces a positive DGE response but depletes intracellular glucose. Glucose is the main energy source in the brain and its regulated uptake and utilization are important biomarkers of pathological brain function. Glucose Chemical Exchange Saturation Transfer (GlucoCEST) and its time-resolved version Dynamic Glucose-Enhanced MRI (DGE) are promising approaches to monitor glucose and detect tumors, since they are radioactivity-free, do not require 13C labeling and are is easily translatable to the clinics. The main principle of DGE is clear. However, what remains to be established is to which extent the signal reflects vascular, extracellular or intracellular glucose. To elucidate the compartmental contributions to the DGE signal, we coupled it with FRET-based fiber photometry of genetically encoded sensors, a technique that combines quantitative glucose readout with cellular specificity. The glucose sensor FLIIP was used with fiber photometry to measure astrocytic and neuronal glucose changes upon injection of D-glucose, 3OMG and L-glucose, in the anaesthetized murine brain. By correlating the kinetic profiles of the techniques, we demonstrate the presence of a vascular contribution to the signal, especially at early time points after injection. Furthermore, we show that, in the case of the commonly used contrast agent 3OMG, the DGE signal actually anticorrelates with the glucose concentration in neurons and astrocytes.

A correlation between the abnormal cerebral glucose metabolism and the progression of Alzheimer’s disease (AD) has been found in previous studies, suggesting that glucose alterations may be used to predict the histopathological diagnosis in AD. In this study, we investigated the dynamic changes of cerebral glucose uptake in vivo using MR glucose chemical exchange saturation transfer (glucoCEST) imaging in a rat model of AD with an intracerebroventricular (i.c.v) injection of amyloid Aβ-protein (25–35), confirmed by Morris water maze and Nissl staining. In total, 6 rats in the AD group and 6 rats in the control group that were given an injection of sterile normal saline were included. At 28 days after injection, all rats performed a 7.0 T MR exanimation, including glucoCEST, diffusion tensor imaging (DTI) and hippocampus magnetic resonance spectra (MRS), to detect the possible metabolic and structural changes in the rat brain. A significantly elevated brain glucoCEST signal in the brain of AD rats was observed, and a decreased brain glucose uptake was also explored during the progression of glucose infusion compared with those in rats of the control group. In addition, there is a significant positive correlation between glucoCEST enhancement (GCE) and myo-Inosito (Ins) in the AD group and the control group ( P < 0.05). A significantly reduced number of neurons in the cortex and hippocampus in AD rats combined with the significantly longer escape and a decreased number of crossings were verified at 28 days after Aβ25–35 injection by Nissl staining and Morris water maze, respectively. Our results indicated that an abnormal brain glucose mechanism in AD rats could be detected by glucoCEST imaging, suggesting a new method to explore the occurrence and progress of diabetes-related AD or dementia.