Environmental modulation of the inhibitory action of D-mannoheptulose upon D-glucose metabolism in isolated rat pancreatic islets

✍ Scribed by Sally Picton; Willy J. Malaisse

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 106 KB
• Volume: 17
• Category: Article
• ISSN: 0263-6484
• DOI: 10.1002/(sici)1099-0844(199903)17:1<65::aid-cbf812>3.0.co;2-t

✦ Synopsis

In pancreatic islets prepared from fed rats and incubated at a low concentration (1 . 7 mM) of D-glucose, D-mannoheptulose (10 . 0 mM) virtually fails to aect the metabolism of the hexose. Likewise, in islets from starved rats, the relative extent of the inhibitory action of D-mannoheptulose upon D-glucose metabolism is much more marked at high (16 . 7 mM) than low (1 . 7 mM) hexose concentration. Nevertheless, despite decreasing the metabolism of D-glucose, starvation augments the sensitivity to D-mannoheptulose in the islets incubated at a low concentration of the hexose. D-galactose, but not D-fructose, also augments the inhibitory action of D-mannoheptulose upon D-glucose metabolism in islets prepared from fed rats and exposed to the low concentration of D-glucose. A comparable situation prevails in islets exposed to 2-ketoisocaproate. Forskolin, however, which decreases D-glucose catabolism in the islets from fed rats exposed to 1 . 7 mM D-glucose, fails to aect signi®cantly the inhibitory action of D-mannoheptulose on D-glucose metabolism. It is proposed that hexoses transported by the same carrier as D-glucose and non-glucidic nutrient secretagogues somehow increase D-mannoheptulose uptake by the islet cells. The latter two conditions may be operative in islets exposed to a high concentration of D-glucose, this accounting for the exquisite sensitivity to D-mannoheptulose of glucose-stimulated islets.