I found this study on glucose uptake and working out... Since I'm the carb nazi, i thought I might wanna post this here.. <B>
Pauliina Peltoniemi
INSULIN-STIMULATED GLUCOSE UPTAKE IN SKELETAL MUSCLE DURING EXERCISE
Studies in different degrees of glucose tolerance</B>
Turku PET Centre, Department of Medicine, University of Turku, Turku, Finland
Supervisors: Prof. Juhani Knuuti, Prof. Pirjo Nuutila, Prof. Hannele Yki-Järvinen
Despite greater awareness of the important clinical benefits of exercise to increase glucose uptake and insulin
sensitivity in the skeletal muscle, the cellular and molecular mechanisms responsible for these phenomena
are still not fully understood. Based on animal studies there is growing evidence that exercise-induced
increment in glucose uptake does not, in contrast to insulin, involve the activation of key insulin signaling
mediators, such as insulin receptor substrate-1 (IRS-1) in skeletal muscle. This could suggest that good
insulin sensitivity, even when due to physical training, does not necessarily increase the ability of exercise to
stimulate glucose uptake. On the other hand, the previous data proposing that exercise can increase glucose
uptake independent of insulin raise the possibility that exercise could increase glucose uptake normally also
in skeletal muscle of insulin resistant subjects. However, no data are presently available determining the
association between insulin sensitivity or insulin resistance and the ability of an acute bout of exercise to
enhance skeletal muscle glucose uptake <I>in vivo </I>in humans. Positron emission tomography (PET) can be used
to quantitatively and accurately measure regional metabolism and perfusion in human skeletal muscle and it
overcomes most of physical limitations of other imaging or invasive techniques by enabling true
quantification of physiological processes. Rates of glucose uptake, blood flow and oxygen consumption can
be quantitated directly and noninvasively in human skeletal muscle using [18F]FDG, [15O]H2O, [15O]O2 and
PET. PET also allows the examination of skeletal muscle metabolism and perfusion during acute exercise
thus enables to study the effects of exercise to stimulate glucose uptake and blood flow simultaneously in
resting and exercising legs under identical metabolic conditions. Moreover, recent methodological
developments of reconstruction procedures have enabled the quantification of flow and glucose uptake
heterogeneity in pixel-by-pixel level in human skeletal muscle. The present study was designed to investigate
the effects of acute exercise on skeletal muscle glucose uptake and blood flow in healthy subjects with
different degree of glucose tolerance and in patients with type 1 diabetes. Furthermore, the goal was to
determine the distribution of skeletal muscle blood flow and glucose uptake in patients with type 1 diabetes
and normal subjects and whether exercise alters the distributions of glucose uptake and blood flow in skeletal
muscle. We also examined the value of lumped constant (LC) for [18F]FDG directly in human skeletal
muscle by combining two independent methods FDG PET and microdialysis.
Pauliina Peltoniemi
INSULIN-STIMULATED GLUCOSE UPTAKE IN SKELETAL MUSCLE DURING EXERCISE
Studies in different degrees of glucose tolerance</B>
Turku PET Centre, Department of Medicine, University of Turku, Turku, Finland
Supervisors: Prof. Juhani Knuuti, Prof. Pirjo Nuutila, Prof. Hannele Yki-Järvinen
Despite greater awareness of the important clinical benefits of exercise to increase glucose uptake and insulin
sensitivity in the skeletal muscle, the cellular and molecular mechanisms responsible for these phenomena
are still not fully understood. Based on animal studies there is growing evidence that exercise-induced
increment in glucose uptake does not, in contrast to insulin, involve the activation of key insulin signaling
mediators, such as insulin receptor substrate-1 (IRS-1) in skeletal muscle. This could suggest that good
insulin sensitivity, even when due to physical training, does not necessarily increase the ability of exercise to
stimulate glucose uptake. On the other hand, the previous data proposing that exercise can increase glucose
uptake independent of insulin raise the possibility that exercise could increase glucose uptake normally also
in skeletal muscle of insulin resistant subjects. However, no data are presently available determining the
association between insulin sensitivity or insulin resistance and the ability of an acute bout of exercise to
enhance skeletal muscle glucose uptake <I>in vivo </I>in humans. Positron emission tomography (PET) can be used
to quantitatively and accurately measure regional metabolism and perfusion in human skeletal muscle and it
overcomes most of physical limitations of other imaging or invasive techniques by enabling true
quantification of physiological processes. Rates of glucose uptake, blood flow and oxygen consumption can
be quantitated directly and noninvasively in human skeletal muscle using [18F]FDG, [15O]H2O, [15O]O2 and
PET. PET also allows the examination of skeletal muscle metabolism and perfusion during acute exercise
thus enables to study the effects of exercise to stimulate glucose uptake and blood flow simultaneously in
resting and exercising legs under identical metabolic conditions. Moreover, recent methodological
developments of reconstruction procedures have enabled the quantification of flow and glucose uptake
heterogeneity in pixel-by-pixel level in human skeletal muscle. The present study was designed to investigate
the effects of acute exercise on skeletal muscle glucose uptake and blood flow in healthy subjects with
different degree of glucose tolerance and in patients with type 1 diabetes. Furthermore, the goal was to
determine the distribution of skeletal muscle blood flow and glucose uptake in patients with type 1 diabetes
and normal subjects and whether exercise alters the distributions of glucose uptake and blood flow in skeletal
muscle. We also examined the value of lumped constant (LC) for [18F]FDG directly in human skeletal
muscle by combining two independent methods FDG PET and microdialysis.