JBC, Vol. 251, Issue 19, 5936-5943, Oct, 1976
Stimulus-secretion coupling of glucose-induced insulin release. Metabolism of alpha- and beta-D-glucose in isolated islets
W. J. Malaisse, A. Sener, M. Koser and A. Herchuelz
Alpha-D-Glucose is known to exert more marked insulinotropic action than
B-D-glucose. Both anomers are phosphorylated at the same rate by rat islet
homogenates. The islet glucose-6-phosphate dehydrogenase displays a
preferential affinity towards beta-D-glucose-6-phosphate, and this
coincides with a higher sorbitol content in the islets exposed to
beta-D-glucose. On the contrary, the islet phosphoglucose isomerase is
stereospecific for alpha-D-glucose 6-phosphate and, hence, the
concentration of glucose 6-phosphate is lower and that of the alpha-anomer
to lactate and CO2 is also higher than that of beta-D-glucose. This
increased glycolytic flux is associated with a more marked inhibitory
action on 14Ca efflux, a more pronounced stimulation of 45Ca net uptake and
a higher rate of insulin release in the islets exposed to alpha-D-glucose.
The more marked insulinotropic action of alpha- as a distinct from
beta-D-glucose is thus compatible with the view that glycolysis represents
the key component of the sensor device through which glucose is identified
in the pancreatic B-cell as a stimulus for insulin release.
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