Differences in the time course of the metabolic response of B and non-B pancreatic islet cells to D-glucose and metabolized or non-metabolized hexose esters.
The early (min </= 1) and late (min 45) changes in NAD(P)H fluorescence caused by alpha-D-glucose pentaacetate, beta-L-glucose pentaacetate, and beta-D-galactose pentaacetate (1.7 mM each), alone or together with either L-leucine (10.0 mM) or D-glucose (8.3 mM), were monitored in purified pancreatic B and non-B rat islet cells. Whilst D-glucose caused a rapid increase in the NAD(P)H signal in B-cells, but not so in non-B cells, alpha-D-glucose pentaacetate, but not the two other monosaccharide esters, rapidly augmented the NAD(P)H signal in both B and non-B cells. After 45 min, the NAD(P)H signal was increased by either D-glucose in both B and non-B islet cells or alpha-D-glucose pentaacetate. At this late time, beta-L-glucose pentaacetate also increased the NAD(P)H signal in B cells exposed to L-leucine. These findings emphasize the relevance of differences in the time course of D-glucose uptake by B and non-B islet cells as a determinant of rapid changes in redox state. They also provide further support for the role of intracellular Ca(2+) regulating the activity of key Ca(2+)-responsive mitochondrial dehydrogenases. Last, they reinforce the view that the effects of hexose pentaacetates upon insulin and glucagon release entail a dual modality, linked either to the catabolism of their hexose moiety or to a direct effect of the esters themselves upon a stereospecific receptor system.
Mercan
D
D
Laboratory of Experimental Medicine, Brussels Free University, Brussels, Belgium.
Kadiata
M M
MM
Malaisse
W J
WJ
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002469:Cell Separation; D004952:Esters / Q000494:pharmacology; D005690:Galactose / Q000031:analogs & derivatives* / Q000494:pharmacology; D005947:Glucose / Q000031:analogs & derivatives* / Q000494:pharmacology; D007515:Islets of Langerhans / Q000166:cytology* / Q000187:drug effects*; D008928:Mitochondria / Q000201:enzymology; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D051381:Rats; D013237:Stereoisomerism
D004952:Esters; D009243:NAD; C105128:glucose pentaacetate; D009249:NADP; C026877:galactose peracetate; D005947:Glucose; D002118:Calcium; D005690:Galactose