Effect of carbohydrates upon fluorescence of reduced pyridine nucleotides from perifused isolated pancreatic islets

Abstract

In perifused pancreatic islets, the fluorescence of reduced pyridine nucleotides (NAD(P)H) was measured continuously. Elevation of glucose concentration in the medium from 0-5 mM to 20 mlVl led to an increase in l~AD(P)H-fluorescence beginning 10-20 sec after change of medium. Perifusion with calcium-free media had no influence on this effect. It was, however, partially or completely blocked by 2-deoxy D-glucose, D-glucosamine, or D-mannoheptulose. D-mannose, but not D-fructose and L-lactate, enhanced ~qAD(P)I-I-fluorescence from pancreatic islets. Pyruvate caused but a small fluorescence increase. From these observations it is concluded that D-glucose leads to the increase of NAD(P)I-i-fluorescence by mediation of the phosphoglyceraldehyde dehydrogenase reaction.

Involvement of Per–Arnt–Sim (PAS) kinase in the stimulation of preproinsulin and pancreatic duodenum homeobox 1 gene expression by glucose

“…Exposure of ␤ cells to glucose also leads to increased concentrations of a number of molecules, which may conceivably interact with PAS domains (38) and affect a change in PASK tertiary structure and hence phosphorylation state. These include reduced pyridine nucleotides (39,40), ATP and ADP (11,41), and Ca 2ϩ (42), in addition to a range of glycolytic intermediates, amino acids (43), and fatty acids (44), as well as a decrease in O 2 tension (45) and membrane potential (46). Identification of those parameters that play a role in regulating PASK activity requires further investigation.…”

Oscillatory control of insulin secretion

“…Oxygen oscillations with similar temporal properties as those of [Ca 2+ ] i have later been demonstrated with intra-islet electrodes (Jung et al, 1999a;Jung et al, 1999b;Jung et al, 2000;Ortsäter et al, 2000), and found to correlate with oscillations in glucose consumption (Jung et al, 2000) and insulin release (Ortsäter et al, 2000). Oscillations in NAD(P)H have been observed in single rat β-cells (Pralong et al, 1994) but have been difficult to catch in islets (Panten et al, 1973;Gilon and Henquin, 1992). It was not until recently that NAD(P)H oscillations were convincingly demonstrated in islets (Luciani et al, 2006) (Krippeit-Drews et al, 2000) and with temporal characteristics similar to that of the NAD(P)H oscillations (Luciani et al, 2006).…”

Effects of glucose on the cytosolic ration of reduced/oxidized nicotinamide-adenine dinucleotide phosphate in rat islets of Langerhans

“…Effects on insulin release of agents known to modify the extent of reduction of nicotinamide nucleotides were noted by Ammon & Steinke (1972) and by Deery & Taylor (1973). An increase in the extent of reduction of nicotinamide nucleotides in intact perifused islets of Langerhans was observed when the concentration of glucose in the perifusion medium was increased from 3 to 20mM (Panten et al, 1973). Such changes have been correlated with rates of insulin release under various conditions (Panten et al, 1973(Panten et al, , 1974.…”

“…An increase in the extent of reduction of nicotinamide nucleotides in intact perifused islets of Langerhans was observed when the concentration of glucose in the perifusion medium was increased from 3 to 20mM (Panten et al, 1973). Such changes have been correlated with rates of insulin release under various conditions (Panten et al, 1973(Panten et al, , 1974. However, with the technique used, it was not possible ascertain the cellular location and identity of the reduced nicotinamide nucleotides.…”