Evaluation of organ glucose metabolism by (18)F-FDG accumulation with insulin loading in aged mice compared with young normal mice

It is important to determine the functional changes of organs that occur as a result of aging, the understanding of which may lead to the maintenance of a healthy life. Glucose metabolism in healthy bodies is one of the potential markers used to evaluate the changes of organ function. Thus, information about normal organ glucose metabolism may help to understand the functional changes of organs. [(18)F]-Fluoro-2-deoxy-2-d-glucose ((18)F-FDG), a glucose analog, has been used to measure glucose metabolism in various fields, such as basic medical research and drug discovery. However, glucose metabolism changes in aged animals have not yet been fully clarified. The aim of this study is to evaluate changes in glucose metabolism in organs and brain regions by measuring (18)F-FDG accumulation and (18)F-FDG autoradiography with insulin loading in aged and young wild-type mice. In the untreated groups, the levels of (18)F-FDG accumulation in the blood, plasma, muscle, lungs, spleen, pancreas, testes, stomach, small intestine, kidneys, liver, brain, and brain regions, namely, the cortex, striatum, thalamus, and hippocampus, were all significantly higher in the aged mice. The treated group showed lower (18)F-FDG accumulation levels in the pancreas and kidneys, as well as in the cortex, striatum, thalamus, and hippocampus in the aged mice than the untreated groups, whereas higher (18)F-FDG accumulation levels were observed in those in the young mice. These results demonstrate that insulin loading decreases effect on (18)F-FDG accumulation levels in some organs of the aged mice. Therefore, aging can increase insulin resistance and lead to systemic glucose metabolism dysfunction.