The Stimulatory Effect of Fructose on Ethanol Metabolism

Scholz, Roland; Schwabe, U.; Plauk, Christiane; Nohl, Hans

doi:10.1159/000175623

Cited by 13 publications

(5 citation statements)

References 27 publications

(19 reference statements)

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“…Glucose was the major end product of fructose metabolism in hepatocytes from both fed and starved rats. Glucose and lactate production accounted for the fructose metabolized, leaving little room for the production of glycerol, in agreement with results reported by others (Scholz et al, 1975).…”

Section: Metabolic Changessupporting

confidence: 92%

“…A stimulatory effect of fructose on ethanol oxidation has been reported by many authors (for review, see Scholz et al, 1975). We found no activation by fructose of the rate of ethanol oxidation in hepatocytes from either fed or starved rats (when incubated with lactate, pyruvate and glucose as in the present experiments).…”

Section: Metabolic Changessupporting

confidence: 75%

“…The most obvious explanation for a = 0.10 in cells from fed rats with or without fructose is a more extensive cycling of hydrogen in the reactions catalysed by aldolase and triosephosphate isomerase, because of the increased concentration of substrate for these reactions as compared with cells from starved rats (Scholz et al, 1975).…”

Section: Fate Of Labelling From [2-3h]lactatementioning

confidence: 99%

“…Fructose is rapidly metabolized by the liver, gives rise to a large increase in the concentration of pyruvate (Mapungwana & Davies, 1982) and enhances the rate of the glucose/glucose 6-phosphate and fructose 6-phosphate/fructose 1,6-bisphosphate substrate cycles (Clark et al, 1979). Furthermore, fructose stimulates ethanol metabolism in hepatocytes with a sub-optimal supply of precursors of the malate-aspartate hydrogen shuttle (Scholz et al, 1975;Cornell, 1983a). The effect of fructose addition was therefore examined in the present experiments.…”

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confidence: 99%

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The reversibility of cytosolic dehydrogenase reactions in hepatocytes from starved and fed rats. Effect of fructose

Vind¹,

Grunnet²

1984

Biochemical Journal

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The metabolism of [2-3H]lactate was studied in isolated hepatocytes from fed and starved rats metabolizing ethanol and lactate in the absence and presence of fructose. The yields of 3H in ethanol, water, glucose and glycerol were determined. The rate of ethanol oxidation (3 mumol/min per g wet wt.) was the same for fed and starved rats with and without fructose. From the detritiation of labelled lactate and the labelling pattern of ethanol and glucose, we calculated the rate of reoxidation of NADH catalysed by lactate dehydrogenase, alcohol dehydrogenase and triosephosphate dehydrogenase. The calculated flux of reducing equivalents from NADH to pyruvate was of the same order of magnitude as previously found with [3H]ethanol or [3H]xylitol as the labelled substrate [Vind & Grunnet (1982) Biochim. Biophys. Acta 720, 295-302]. The results suggest that the cytoplasm can be regarded as a single compartment with respect to NAD(H). The rate of reduction of acetaldehyde and pyruvate was correlated with the concentration of these metabolites and NADH, and was highest in fed rats and during fructose metabolism. The rate of reoxidation of NADH catalysed by lactate dehydrogenase was only a few per cent of the maximal activity of the enzymes, but the rate of reoxidation of NADH catalysed by alcohol dehydrogenase was equal to or higher than the maximal activity as measured in vitro, suggesting that the dissociation of enzyme-bound NAD+ as well as NADH may be rate-limiting steps in the alcohol dehydrogenase reaction.

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Section: Metabolic Changessupporting

confidence: 92%

Section: Metabolic Changessupporting

confidence: 75%

Section: Fate Of Labelling From [2-3h]lactatementioning

confidence: 99%

mentioning

confidence: 99%

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The reversibility of cytosolic dehydrogenase reactions in hepatocytes from starved and fed rats. Effect of fructose

Vind¹,

Grunnet²

1984

Biochemical Journal

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“…Parts of the data were presented at the International Symposium on Sugars and Sugar Substitutes, 3 -5 October 1974, in Munich [57].…”

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confidence: 99%

Mechanism of the Stimulatory Effect of Fructose on Ethanol Oxidation in Perfused Rat Liver

Scholz

Nohl

1976

Eur J Biochem

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The stimulatory effect of fructose on ethanol oxidation was studied in livers from fasted rats perfused with Krebs-Henseleit-bicarbonate buffer in a non-recirculating system. Two series of experiments were performed : (A) ethanol was infused with stepwise increasing concentrations (0.1 -20 mM) in the presence of 4 mM fructose; (B) fructose was infused with stepwise increasing concentrations (0.5 -10 mM) in the presence of 2 mM ethanol. From measured metabolic rates the following parameters were calculated : energy-rich phosphates consumed for fructose metabolism which were provided from oxidative phosphorylation (A -P) ; reducing equivalents derived from stimulated ethanol utilization which were disposed by mitochondrial oxidation ( A 2H). Under the various conditions studied a linear relationship between these parameters was observed. The ratio d -P/A2H was about 2.0. It is suggested that fructose stimulates ethanol oxidation indirectly by increasing the energy consumption of the liver due to the production of glucose from fructose. Consequently, the rate of oxidative phosphorylation is increased and, therefore, the capacity of the respiratory chain for oxidizing reducing equivalents derived from ethanol is enhanced. The data support the more general hypothesis that the rate of ethanol oxidation depend upon the rate of hepatic energy consumption in a given metabolic state.The rate-controlling factor in ethanol metabolism is still a subject of debate. Previously, it was suggested that the rate of ethanol oxidation is limited by the activity of hepatic alcohol dehydrogenase [l -41. However, this concept has been questioned, since it was observed that the rate of ethanol elimination varied with the metabolic state [5-71 and could be stimulated by various compounds, e.g. pyruvate [l, 6-91, fructose [8 -221, or dinitrophenol [23], and that peroxidatic processes play an important role in ethanol metabolism at high concentrations [24-261. The present concept of rate-control is the following.

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Ethanol Metabolism in Perfused Liver and Isolated Hepatocytes with Associated Methodologies

Williamson¹,

Tischler²

1979

Biochemistry and Pharmacology of Ethanol

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The Stimulatory Effect of Fructose on Ethanol Metabolism

Cited by 13 publications

References 27 publications

The reversibility of cytosolic dehydrogenase reactions in hepatocytes from starved and fed rats. Effect of fructose

The reversibility of cytosolic dehydrogenase reactions in hepatocytes from starved and fed rats. Effect of fructose

Mechanism of the Stimulatory Effect of Fructose on Ethanol Oxidation in Perfused Rat Liver

Ethanol Metabolism in Perfused Liver and Isolated Hepatocytes with Associated Methodologies

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