Systemic Ghrelin Treatment Induces Rapid, Transient, and Asymmetric Changes in the Metabolic Activity of the Mouse Brain

INTRODUCTION

Ghrelin regulates a variety of functions by acting in the brain. The targets of ghrelin in the mouse brain have been mainly mapped using immunolabeling against c-Fos, a transcription factor used as a marker of cellular activation, but such analysis has several limitations. Here, we used positron emission tomography in mice to investigate the brain areas responsive to ghrelin.

METHODS

We analyzed in male mice the brain areas responsive to systemically injected ghrelin using positron emission tomography imaging of 18F-fluoro-2-deoxyglucose (18F-FDG) uptake, an indicator of metabolic rate. Additionally, we studied if systemic administration of fluorescent ghrelin or native ghrelin displays symmetric accessibility or induction of c-Fos, respectively, in the brain of male mice.

RESULTS

Ghrelin increased 18F-FDG uptake in few specific areas of the isocortex, striatum, pallidum, thalamus, and midbrain at 0-10-min posttreatment. At the 10-20 and 20-30 min posttreatment, ghrelin induced mixed changes in 18F-FDG uptake in specific areas of the isocortex, striatum, pallidum, thalamus, and midbrain, as well as in areas of the olfactory areas, hippocampal and retrohippocampal regions, hypothalamus, pons, medulla, and even the cerebellum. Ghrelin-induced changes in 18F-FDG uptake were transient and asymmetric. Systemically administrated fluorescent-ghrelin-labeled midline brain areas known to contain fenestrated capillaries and the hypothalamic arcuate nucleus, where a symmetric labeling was observed. Ghrelin treatment also induced a symmetric increased c-Fos labeling in the arcuate nucleus.

DISCUSSION/CONCLUSION

Systemically injected ghrelin transiently and asymmetrically affects the metabolic activity of the brain of male mice in a wide range of areas, in a food intake-independent manner. The neurobiological bases of such asymmetry seem to be independent of the accessibility of ghrelin into the brain.

Head-to-head comparison of cerebral blood flow single-photon emission computed tomography and 18 F-fluoro-2-deoxyglucose positron emission tomography in the diagnosis of Alzheimer disease

BACKGROUND

Clinical diagnosis of Alzheimer disease (AD) is only 70% accurate. Reduced cerebral blood flow (CBF) and metabolism in parieto-temporal and posterior cingulate cortex may assist diagnosis. While widely accepted that ¹⁸ F-fluoro-2-deoxyglucose positron emission tomography (¹⁸ F-FDG PET) has superior accuracy to CBF-SPECT for AD, there are very limited head-to-head data from clinically relevant populations and these studies relied on clinical diagnosis as the reference standard.

AIMS

To compare directly the accuracy of CBF-SPECT and ¹⁸ F-FDG PET in patients referred for diagnostic studies in detecting β-amyloid PET confirmed AD.

METHODS

A total of 126 patients, 56% with mild cognitive impairment and 44% with dementia, completed both CBF-SPECT and ¹⁸ F-FDG PET as part of their diagnostic assessment, and subsequently underwent β-amyloid PET for research purposes. Transaxial slices and Neurostat 3D-SSP analyses of ¹⁸ F-FDG PET and CBF-SPECT scans were independently reviewed by five nuclear medicine clinicians blinded to all other data. Operators selected the most likely diagnosis and their diagnostic confidence. Accuracy analysis used final diagnosis incorporating β-amyloid PET as the reference standard.

RESULTS

Clinicians reported high diagnostic confidence in 83% of ¹⁸ F-FDG PET compared to 67% for CBF-SPECT (P = 0.001). All reviewers showed individually higher accuracy using ¹⁸ F-FDG PET. Based on majority read, the combined area under the receiver operating characteristic curve in diagnosing AD was 0.71 for ¹⁸ F-FDG PET and 0.61 for CBF-SPECT (P = 0.02). The sensitivity of ¹⁸ F-FDG PET and CBF-SPECT was 76% versus 43% (P < 0.001), while specificity was 74% versus 83% (P = 0.45).

CONCLUSIONS

¹⁸ F-FDG PET is superior to CBF-SPECT in detecting AD among patients referred for the assessment of cognitive impairment.

Relationship between the maximum standardized uptake value of fluoro-2-deoxyglucose-positron emission tomography/computed tomography and clinicopathological characteristics in tongue squamous cell carcinoma

Aim

Tongue carcinoma is one of the most common oral and maxillofacial malignant tumors worldwide, maximum standardized uptake value (SUVmax) in ¹⁸ F-fluoro-2-deoxyglucose-positron emission tomography/computed tomography (PET/CT) has been widely used in cancer research; however, there are few systematical reports on the relationship between SUVmax and clinicopathological characteristics in tongue squamous cell carcinoma (TSCC). This study aimed to investigate the relationship between them and whether SUV parameters can predict lymph node metastasis.

Materials and Methods

PET/CT manifestations and clinicopathological features of 52 patients with TSCC confirmed by pathology were retrospectively analyzed. Single-factor and multiple regression analyses were conducted on possible factors influencing TSCC SUVmax, including sex, age, smoking history, tumor location and size, histological differentiation, and tumor node metastasis (TNM) stages, T stages, and N stages. Diagnostic performance of SUVmax for lymph node metastasis was measured by the area under the receiver operating characteristic curve, and sensitivity and specificity were determined by Youden's J statistic.

Results

SUVmax was correlated with sex, tumor location and size, and TNM stages, T stages, and N stages (P < 0.05) but was not correlated with histological differentiation, smoking history, and age (P > 0.05). Sex, tumor location, tumor size, and N stage were influencing factors independent of TSCC SUVmax (P < 0.05). TSCC SUVmax had predictive value for lymph node metastasis. When the cutoff value was 6.57, the diagnostic efficiency was the highest, with the sensitivity being 79.2% and the specificity being 85.7%.

Conclusions

SUVmax was higher among male patients with TSCC with posterior tumor location, larger tumor size, and lymph node metastasis, and TSCC SUVmax was important in predicting lymph node metastasis.

Maximum standardized uptake value in 18F-fluoro-2-deoxyglucose positron emission tomography is associated with advanced tumor factors in esophageal cancer

Positron emission tomography/computed tomography (PET/CT) with ¹⁸F-fluoro-2-deoxyglucose (FDG-PET/CT) has become established in cancer imaging, and derived maximum standardized uptake values (SUVmax) add functional information regarding cancer, including esophageal squamous cell carcinoma (ESCC). The aim of the present study was to determine the clinical significance and association of tumor progression using SUVmax derived from PET/CT images in patients with ESCC. In total, 101 patients with ESCC were assessed using FDG-PET/CT and the SUVmax was then compared with the clinical backgrounds and prognoses of the patients. Endoscopic ESCC biopsy specimens were obtained in order to analyze mRNA expression relative to tumor progression. The results showed that values for SUVmax were significantly higher in patients with tumor progression factors, particularly those with lymph node metastasis. Analysis of receiver operating characteristics curves revealed an optimum SUVmax cut-off value of 10.26 for node-positive disease. Patients with SUVmax ≥10.26 had gene alterations with epithelial-mesenchymal transition (EMT) and significantly worse overall survival (P=0.0012). A higher SUVmax in patients with ESCC was associated with lymph node metastasis and a poorer prognosis. Thus, the SUVmax may reflect the potential of EMT in patients with ESCC.

¹⁸F-fluoro-2-deoxyglucose uptake on PET CT and glucose transporter 1 expression in colorectal adenocarcinoma

AIM

To evaluate the correlation between the level of (18)F-fluoro-2-deoxyglucose ((18)F-FDG) uptake and glucose transporter 1 (GLUT1) expression in colorectal adenocarcinoma (CRA).

METHODS

Forty four patients with resected CRA and preoperative (18)F-FDG positron emission tomography - computed tomography data were investigated in this study. Comparison of maximum standardized uptake value (SUVmax) of the lesion was made with GLUT1 expression by immunohistochemistry and various clinicopathologic factors including tumor volume, invasion depth, gross finding, and lymph node metastasis.

RESULTS

SUVmax was 14.45 ± 7.0 in negative GLUT1 expression cases, 15.51 ± 5.7 in weak GLUT1 expression cases, and 16.52 ± 6.8 in strong GLUT1 expression cases, and there was no correlation between between GLUT1 expression and SUVmax. SUVmax was significantly correlated with tumor volume (P < 0.001). However, there was no significant differences in SUVmax and GLUT1 expression among other clinicopathologic factors.

CONCLUSION

GLUT1 expression does not correlates significantly with (18)F-FDG uptake in CRA. (18)F-FDG uptake was increased with tumor volume, which is statistically significant.