Brain glucose uptake, oxygen metabolism, and blood flow in humans were measured with positron emission tomography, and a resting-state molar ratio of oxygen to glucose consumption of 4.1:1 was obtained. Physiological neural activity, however, increased glucose uptake and blood flow much more (51 and 50 percent, respectively) than oxygen consumption (5 percent) and produced a molar ratio for the increases of 0.4:1. Transient increases in neural activity cause a tissue uptake of glucose in excess of that consumed by oxidative metabolism, acutely consume much less energy than previously believed, and regulate local blood flow for purposes other than oxidative metabolism.

Elevated [(11)C]PIB binding in nondemented subjects suggests that [(11)C]PIB amyloid imaging may be sensitive for detection of a preclinical Alzheimer disease state. Longitudinal studies will be required to determine the association of elevated [(11)C]PIB binding and risk of developing dementia of the Alzheimer type.

These observations suggest that brain amyloid deposition results in low CSF Abeta(42), and that amyloid imaging and CSF Abeta(42) may potentially serve as antecedent biomarkers of (preclinical) AD.

Background-Obesity is a risk factor for impaired cardiac performance, particularly in women. Animal studies suggest that alterations in myocardial fatty acid metabolism and efficiency in obesity can cause decreased cardiac performance.In the present study, we tested the hypothesis that myocardial fatty acid metabolism and efficiency are abnormal in obese women. (rϭ0.58, PϽ0.005). A multivariate, stepwise regression analysis showed that BMI was the only independent predictor of MV O 2 and efficiency (Pϭ0.0005 and PϽ0.05, respectively). Glucose AUC was the only independent predictor of MFAUp, MFAU, and MFAO (PϽ0.05, Ͻ0.005, and Ͻ0.005, respectively). Conclusions-In young women, obesity is a significant predictor of increased MV O 2 and decreased efficiency, and insulin resistance is a robust predictor of MFAUp, MFAU, and MFAO. This increase in fatty acid metabolism and decrease in efficiency is concordant with observations made in experimental models of obesity. These metabolic changes may play a role in the pathogenesis of decreased cardiac performance in obese women.

Our results document the feasibility of PET imaging of prostate cancer with FDHT and suggest that tumor uptake of FDHT is a receptor-mediated process. Positive PET studies were associated with higher PSA levels and thus, presumably, with greater tumor burden.