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Metabolic effects of ethanol in per used rat liver
... This would account for the undiminished total ketogenesis and the decreased ketone body specific activity. Ethanol increased the p-hydroxybutyrate : acetoacetate ratio, as previously observed (17,19). The ethanol-induced increase in palmitate esterification was found to result from enhanced formation of diglycerides, triglycerides, and phospholipids ( Table 3). ...
... The mechanisms by which ethanol elevated esterification and decreased oxidation to C02 and ketone bodies therefore appear closely related. Ethanol markedly increases the NADH : NAD ratio in the liver cytosol (17,19,24). Although energy is immediately available from ethanol oxidation (19), oxygen consumption is unaltered in the presence of long-chain fatty acids (see Results and Ref. 19). ...
... Ethanol markedly increases the NADH : NAD ratio in the liver cytosol (17,19,24). Although energy is immediately available from ethanol oxidation (19), oxygen consumption is unaltered in the presence of long-chain fatty acids (see Results and Ref. 19). Ethanol increased the mitochondrial NADH :NAD ratio in the liver cells as evidenced by the increased p-hydroxybutyrate:acetoacetate ratio ( Table 2). ...
Ethanol inhibited the oxidation and enhanced the esterification of albumin-bound [1-¹⁴C]palmitate incubated with isolated rat liver cells. Ethanol decreased the conversion of [1-¹⁴C]palmitate to ¹⁴CO2 and ¹⁴C-labeled ketone bodies and enhanced the incorporation of [¹⁴C]palmitate into glycerolipids, especially triglyceride; cholesteryl ester synthesis was unaffected. The half-maximal effective ethanol concentration for each of these processes was 6–10 μg/ml and a maximum effect was produced by about 50 μg/ml. Ethanol oxidation was required for each of these alterations, since the effects were completely abolished by pyrazole. The energy obtainable from ethanol oxidation was in excess of the energy deficit from decreased fatty acid oxidation. However, ethanol did not affect O2 consumption, indicating that ethanol oxidation replaced the oxidation of both fatty acids and other substrates. Ethanol inhibited the citric acid cycle in the intact liver cells by 20–30%. The major site of inhibition was α-ketoglutarate oxidation. Results suggest that ethanol inhibited α-ketoglutarate dehydrogenase in the mitochondria of hepatocytes by elevating the mitochondrial NADH:NAD ratio. A minor site of inhibition of ethanol oxidation was detected between succinate and citrate. It is suggested that ethanol inhibits fatty acid oxidation in hepatocytes by competitive substrate oxidation, resulting in an increased availability of long-chain free fatty acids; this thereby enhances esterification, leading to accumulation of liver triglyceride.
... ) (Veech et al, 1972) (Greenbaum et al, 1971) (Lagunas et al, 1970) (Rawat, 1968) (Veech et al, 1973) (Williamson et al, 1967) (Baquer et al, 1976) (Casazza et al, 1986) (Casazza & Veech, 1986a) (Parrilla et al, 1975) (Williamson et al, 1969) (Schofield et al, 1987) 9.19E-02 2.33E-01 cytosol 9.08E-02 2.16E-01 mitochondrion 6.38E-03 9.98E-02 Acetate 1.05746036 1.05746036 cell (Murthy & Steiner, 1973) (Knowles et al, 1974) ) (Richards et al, 1975) 5.66E-03 9.64E-03 cytosol 4.85E-03 8.26E-03 mitochondrion 4.85E-03 8.26E-03 Acetylglutamate 0.01637939 0.32056798 cell (Saheki et al, 1977) (Shigesada & Tatibana, 1971) (Zollner, 1981) (Saheki et al, 1978) 1.88E-01 3.23E-01 cytosol (Shigesada & Tatibana, 1971) 1.61E-01 2.75E-01 mitochondrion (Shigesada & Tatibana, 1971) 1.66E-01 2.83E-01 Acetyl coenzyme A 0.02620702 0.27222539 cell (Menahan et al, 1981) (Start & Newsholme, 1968) (Siess et al, 1978) (Greenbaum et al, 1971) (Kondrup & Grunnet, 1973) (Lagunas et al, 1970) (Rawat, 1968) (Veech et al, 1973) (Albe et al, 1990) (Baquer et al, 1976) (Siess et al, 1977) (Parrilla et al, 1975) (Williamson et al, 1969) 3.75E-02 1.11E-01 0.03332383 1.36 cytosol (Siess et al, 1978) (Siess et al, 1978) (Garland et al, 1965) (Siess et al, 1977) 1.81E-02 6.11E-02 0.006402 2.74 mitochondrion (Siess et al, 1976) (Siess et al, 1978) (Matsuishi et al, 1991) (Garland et al, 1965) (Siess et al, 1977) (Latipaa et al, 1986) (Lopes-Cardozo & van den Bergh, 1974a) (Eaton et al, 1994) 1.15E-01 3.02E-01 ...
... ) (Veech et al, 1972) (Greenbaum et al, 1971) (Lagunas et al, 1970) (Rawat, 1968) (Veech et al, 1973) (Williamson et al, 1967) (Baquer et al, 1976) (Casazza et al, 1986) (Casazza & Veech, 1986a) (Parrilla et al, 1975) (Williamson et al, 1969) (Schofield et al, 1987) 9.19E-02 2.33E-01 cytosol 9.08E-02 2.16E-01 mitochondrion 6.38E-03 9.98E-02 Acetate 1.05746036 1.05746036 cell (Murthy & Steiner, 1973) (Knowles et al, 1974) ) (Richards et al, 1975) 5.66E-03 9.64E-03 cytosol 4.85E-03 8.26E-03 mitochondrion 4.85E-03 8.26E-03 Acetylglutamate 0.01637939 0.32056798 cell (Saheki et al, 1977) (Shigesada & Tatibana, 1971) (Zollner, 1981) (Saheki et al, 1978) 1.88E-01 3.23E-01 cytosol (Shigesada & Tatibana, 1971) 1.61E-01 2.75E-01 mitochondrion (Shigesada & Tatibana, 1971) 1.66E-01 2.83E-01 Acetyl coenzyme A 0.02620702 0.27222539 cell (Menahan et al, 1981) (Start & Newsholme, 1968) (Siess et al, 1978) (Greenbaum et al, 1971) (Kondrup & Grunnet, 1973) (Lagunas et al, 1970) (Rawat, 1968) (Veech et al, 1973) (Albe et al, 1990) (Baquer et al, 1976) (Siess et al, 1977) (Parrilla et al, 1975) (Williamson et al, 1969) 3.75E-02 1.11E-01 0.03332383 1.36 cytosol (Siess et al, 1978) (Siess et al, 1978) (Garland et al, 1965) (Siess et al, 1977) 1.81E-02 6.11E-02 0.006402 2.74 mitochondrion (Siess et al, 1976) (Siess et al, 1978) (Matsuishi et al, 1991) (Garland et al, 1965) (Siess et al, 1977) (Latipaa et al, 1986) (Lopes-Cardozo & van den Bergh, 1974a) (Eaton et al, 1994) 1.15E-01 3.02E-01 ...
... Adenosine diphosphate 1.13251754 4.60962719 cell (Hems & Brosnan, 1970) (Veech et al, 1972) (Start & Newsholme, 1968) (Siess et al, 1978) (Greenbaum et al, 1971) (Lagunas et al, 1970) (Elbers et al, 1974) (Veech et al, 1973) (Albe et al, 1990) (Aw et al, 1987) (Kauffman et al, 1977) (Baquer et al, 1976) (Casazza et al, 1986) ) (Jackson et al, 1980) (Siess et al, 1977) (Keiding, 1973) (Parrilla et al, 1975) (Sestoft, 1974) ) (Woods & Krebs, 1973) (Williamson et al, 1969) (Siess et al, 1978) 2.06E+00 3.71E+00 0.2899039 3.7 cytosol (Tischler et al, 1977) (Elbers et al, 1974) (Aw et al, 1987) (Siess et al, 1977) (Soboll et al, 1978) 1.17E+00 2.32E+00 0.3655542 15.7122574 mitochondrion (Siess et al, 1978) (Tischler et al, 1977) (Zuurendonk & Tager, 1974) (Elbers et al, 1974) (Aw et al, 1987) (Siess et al, 1977) (Soboll et al, 1978) (Siess, 1985) 5.31E+00 8.35E+00 ...
... The primary objective of our group was to develop a robust and realistic mathematical model as the blood brain barrier, to affect a large number of organs and biological processes [66]. Ethanol is not known to be formed in the mammalian body nor it is present in any of the natural food sources, therefore strong metabolic processes involving allosteric or back regulation (such as for lactate, glucose) are absent [37,39]. [61,63], and those which support the findings that the predominant mechanism for ethanol metabolism is NADPH dependent hydrogen peroxide (H 2 O 2 ) production (by the microsomal electron transport) followed by the peroxidation of alcohol to acetaldehyde by catalase [60,62]. ...
... The excess NADH affects the lactate to pyruvate ratios, driving the equilibrium reaction towards lactate. Thus more pyruvate goes to lactate, which results in low gluconeogenic fluxes [35,39,40,51,53]. ...
... High NADH concentration also inhibits enzymes of the TCA cycle, further deteriorating metabolic functions. Acetaldehyde not converted to acetic acid can bind to cysteine, a constituent of the anti 7 which results in low gluconeogenic fluxes [35,39,40,51,53]. These pathways are Metabolic pathways showing important regulatory steps in the comprehensive model of ethanol metabolism. ...
... Nearly five decades ago, studies by Williamson et al., Lefevre et al., and Krebs et al. have demonstrated the potential for ethanol (EtOH) to enhance plasma ketone concentration, in conjunction with high fat diet or fatty acid utilization in the liver [13][14][15]. In particular, EtOH plus high fat diet for ∼4-6 days enhances ketonemia in human subjects much higher than that observed with EtOH or high fat diet alone [14]. ...
... Previous studies in human subjects have shown that EtOH consumption in concomitance with high fat diet results in a marked increase in plasma ketone concentration [14]. In addition, in rat liver perfusion studies and liver slice preparations, EtOH exposure increases ketone body formation only in the presence of exogenous fatty acids [13,14]. These seminal findings from earlier studies suggest that under in vivo conditions, fatty acids derived from dietary fat and/or adipose tissue lipolysis contribute to EtOH-induced hepatic ketogenesis. ...
... Moreover, a signifi cant increase in citrate concentration has been observed in the kidney, liver and pancreas of alloxan-treated mice, an effect that has been ascribed to a concurrent inhibition of mitochondrial aconitase, the enzyme immediately next to CS in the TCA cycle (Boquist et al. 1985 ). The oxidation of EtOH by the liver and other tissues possessing ADH activity increases the supply of reducing equivalents in the form of NADH which, after transport into the mitochondria, can inhibit the TCA cycle at the CS and isocitrate dehydrogenase steps (Williamson et al. 1969 ). When provided singly, before and after the induction of diabetes, both EtOH and TAU were found to increase the diabetic CS activity twofold. ...
... In addition, the simultaneous availability of EtOH and TAU demonstrated a greater elevating effect on the diabetic CS activity than either treatment alone. Since neither EtOH nor TAU altered the baseline value of CS to a signifi cant extent, it is safe to assume that at their protecting by infl uencing a diabetes-mediated change such as that of the ratios of pyridine nucleotides (as NAD + /NADH) and of ATP/ADP (Obrosova and Stevens 1999 ;Williamson et al. 1969 ). ...
This study has comparatively evaluated ethanol and taurine for their effects on diabetes-induced changes in the activities of enzymes related to the classical and alternative pathways of glucose metabolism, both separately and in combination with each other, in the rat. The experiments were carried out using male Sprague-Dawley rats, 310–340 g in weight, assigned to groups of six. Ethanol, as a 5 % (v/v) solution, was freely available from days 1 to 28 in place of the drinking water. Diabetes was induced on day 15 with streptozotocin, 60 mg/kg i.p. in 10 mM citrate buffer pH 4.5. Taurine, 2.4 mM/kg, was given by oral gavage alongside ethanol. Kidneys were collected on day 29 and made into homogenates in PBS pH 7.4, which were used to assay enzymes related to glycolysis (HK, GK-like, PFK-1, PK, GAPDH), gluconeogenesis (PC, cPEPCK, FBPase, G6Pase), Krebs cycle (CS), malate shuttle (cMDH), pentose phosphate pathway (G6PDH, 6PGDH) and polyol pathway (AR, SDH) as well as the glucose and glycogen contents. Diabetes increased the enzyme activities of glycolysis (≥55 %), gluconeogenesis (≥162 %), malate shuttle (>125 %), pentose phosphate pathway (>200 %), AR (~110 %) and glycogenesis (~235 %), lowered the activity of the Krebs cycle (by 73 %), and increased the glycogen/glucose ratio (~300 %). The daily consumption of a low concentration of ethanol or an oral dosing with taurine generally resulted in a significant protection against the changes in the activities of metabolic pathways associated with glucose metabolism when given before the induction of diabetes, being about equipotent in their effects, their individual protective effects became enhanced when available concurrently.
... While ALDH2 is primarily responsible for acetaldehyde metabolism, ALDH1, which is encoded by Aldh1a1 gene, also contributes to its oxidation (Agarwal, 2001). NAD + and NADP + are cofactors required for ethanol metabolism, which increases hepatic NADH/NAD + and NADPH/NADP + ratios respectively in the liver (Williamson et al., 1969). A small fraction of ingested ethanol can form additional metabolites through an enzyme-catalyzed non-oxidizing pathway. ...
... Redox regulation of gluconeogenesis varies with the carbon source. In particular, a more reduced cytosol (i.e., increased cytosolic [NADH]:[NAD + ]) inhibits gluconeogenesis from lactate and glycerol 19,20 but not from alanine and pyruvate 21,22 . The key difference between these substrates is the increased sensitivity of lactate and glycerol to a reduced cytosol and thus increased cytosolic [NADH]:[NAD + ], since these substrates, unlike pyruvate or alanine, will themselves reduce the cytosol ( Supplementary Fig. 1a). ...
Metformin, the universal first-line treatment for type 2 diabetes, exerts its therapeutic glucose-lowering effects by inhibiting hepatic gluconeogenesis. However, the primary molecular mechanism of this biguanide remains unclear, though it has been suggested to act, at least partially, by mitochondrial complex I inhibition. Here we show that clinically relevant concentrations of plasma metformin achieved by acute intravenous, acute intraportal or chronic oral administration in awake normal and diabetic rats inhibit gluconeogenesis from lactate and glycerol but not from pyruvate and alanine, implicating an increased cytosolic redox state in mediating metformin's antihyperglycemic effect. All of these effects occurred independently of complex I inhibition, evidenced by unaltered hepatic energy charge and citrate synthase flux. Normalizing the cytosolic redox state by infusion of methylene blue or substrates that contribute to gluconeogenesis independently of the cytosolic redox state abrogated metformin-mediated inhibition of gluconeogenesis in vivo. Additionally, in mice expressing constitutively active acetyl-CoA carboxylase, metformin acutely decreased hepatic glucose production and increased the hepatic cytosolic redox state without altering hepatic triglyceride content or gluconeogenic enzyme expression. These studies demonstrate that metformin, at clinically relevant plasma concentrations, inhibits hepatic gluconeogenesis in a redox-dependent manner independently of reductions in citrate synthase flux, hepatic nucleotide concentrations, acetyl-CoA carboxylase activity, or gluconeogenic enzyme protein expression.
... Ethanol ingestion produces rapid and profound changes in hepatic, and specifically in mitochondrial metabolism. These changes include a swift increase in alcohol metabolism (SIAM) [125,126] by the formation of NADH from cytosolic alcohol dehydrogenase (ADH) and mitochondrial acetaldehyde dehydrogenase (ACDH). The increases mitochondrial respiration and accelerates mitochondrial oxygen consumption [127]. ...
Metabolism is an interconnecting network of metabolite consumption and creation. Metabolomics has focused on metabolite concentrations in metabolic networks. Fluxomics is also required in the study of metabolism and quantifies the flux of substrate through each reaction step or a series of reaction steps (i.e., metabolic pathway or cycle), and ultimately is required for energy balance equations of the system. The primary noninvasive method of quantifying fluxes in living systems is by in vivo ¹³C nuclear magnetic resonance (NMR) spectroscopy. The present state of noninvasive in vivo NMR technology allows for just four simultaneous flux measurements of metabolic pathways: gluconeogenesis, glycogen synthesis, glycolysis, and citric acid cycle. Since the liver is the gatekeeper and metabolic center for the animal, in vivo fluxomics of liver is extensively reviewed. Additionally, other organ systems studies are discussed demonstrating interorgan cycles, such as the Cori and Randall cycles. This review discusses the basics of in vivo fluxomics focusing on the general details of the NMR experimental protocol and required hardware/software needed to analyze the data.
... Alcohol metabolism is known to significantly slow the TCA cycle when fatty acids are available in mice 26 and rats. 32 We observed changes in the metabolite lactate, which is consistent with the data presented by Bradford et al. Higher levels of lactate correlate with hypoxia. ...
Fatty liver is significantly associated with hepatic cirrhosis and liver cancer. Excessive alcohol consumption causes alcoholic fatty liver disease (AFLD). Ginger has been reported to exhibit antioxidant potential and hepatoprotective activity. In the present study, a mouse model for AFLD was developed by employing male C57BL/6 mice who were fed an alcohol-containing liquid diet (Lieber-DeCarli diet) ad libitum. In the treatment groups, ginger essential oil (GEO) and citral were orally administered every day for 4 weeks. Serum biochemical analysis, antioxidant enzyme activity analysis, and histopathological evaluation revealed that GEO and citral exhibited hepatoprotective activity against AFLD. Metabolites in serum samples were profiled by high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS). Metabolomic data indicated the amounts of metabolites such as D-glucurono-6,3-lactone, glycerol-3-phosphate, pyruvic acid, lithocholic acid, 2-pyrocatechuic acid, and prostaglandin E1 were increased after alcohol administration, but the levels were recovered in treatment groups. Our analysis indicated that ginger possesses hepatoprotective properties against AFLD. Further, these metabolites can serve as early non-invasive candidate biomarkers in the clinical application of AFLD for health management.
... Isotope studies have been used to evaluate total respiratory carbon dioxide production, and also strongly suggest that during ethanol metabolism the activity of the citric acid cycle is inhibited, and that cerebral glucose utilization decreases. The sites of inhibition were identified as the citrate synthase and isocitrate dehydrogenase steps, and the citrate content was decreased (Williamson et al., 1969). On-line 31 P-nuclear magnetic resonance (NMR) spectroscopy showed that long-term exposure to ethanol reduces the levels of adenosine triphosphate (ATP) and phosphocreatine (Fonseca et al., 2001). ...
Event-related potential (ERP) is a reliable neuroelectric measure of brain activity that helps to confirm the assessment of mental status and cognitive impairment. Many studies have reported that alcoholics show a significantly lower ERP P300 amplitude than the norm. In the present study, ERP P300 waves were measured to evaluate the effect of citric acid on cognitive function during excessive alcohol consumption in healthy adults. Five volunteers were selected through clinical interview, physical examination, and psychiatric assessment for participation in this study. In a double-blind placebo-controlled before-after design, each subject was treated with 5 ml/kg body weight alcohol, 5 ml/kg body weight alcohol and 1 mg citric acid, or a placebo on three separate occasions, one week apart. ERP P300, blood biochemical indicators, blood alcohol concentrations (BACs) and acetaldehyde concentrations were assessed. Repeated measure analysis of variance (ANOVA) with a within-subjects factor was used to evaluate differences in blood biochemical indicators, BACs, blood acetaldehyde concentrations, and ERP P300 in the three sessions of assessments. Several blood biochemical indicators showed significant differences between treatments, including the levels of cholinesterase (CHE), total bile acid (TBA), triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), and glycylproline dipeptidyl aminopeptidase (GPDA). BACs after consumption of alcohol alone or citric acid with alcohol were significantly higher compared to those after placebo treatment (P<0.05). There were no significant differences in blood acetaldehyde concentrations between the treatments. The P300 amplitudes on the frontal (Fz), central (Cz), and parietal (Pz) regions of the scalp after consumption of alcohol were significantly lower than those after consumption of the placebo or citric acid with alcohol (P<0.05), while there were no significant differences between the latter two treatments. The results of this study suggest that citric acid could reduce the decline in ERP P300 amplitude and cognitive ability induced by acute alcohol consumption. It may also affect some blood biochemical indicators, but the specific mechanisms need further research.
Xylitol metabolism and its interaction with lactate metabolism has been investigated in perfused livers from fasted rats. Xylitol (5 mm) served as a strong reductant for cytosolic NAD systems as shown by increased ratios of lactate to pyruvate, α-glycerophosphate to dihydroxyacetone-P, and triose phosphates to 3-P-glycerate. The mitochondrial NAD system, as monitored by changes of the β-hydroxybutyrate to acetoacetate ratio, was less affected, particularly when xylitol was added in the presence of lactate, suggesting a limitation in the rate of transport of NADH from cytosol to mitochondria. Xylitol also caused an increased reduction of bound NAD as determined analytically and by increased pyridine nucleotide fluorescence measured by surface fluorometry. The latter technique showed that half-maximum reduction was obtained with 0.4 mm xylitol, suggesting that xylitol was metabolized principally to d-xylulose via the low Km cytosolic NAD-linked xylitol dehydrogenase.
In the perfused liver xylitol was converted mainly to glucose, after phosphorylation of d-xylulose to d-xylulose-5-P and metabolism via the pentose phosphate pathway. Lactate uptake and conversion to glucose were strongly inhibited by xylitol. This effect was interpreted as resulting from the increased cytosolic NADH:NAD ratio which caused pyruvate levels to fall. An observed decrease of acetyl coenzyme A levels may also contribute to diminished flux through pyruvate carboxylase. Xylitol uptake was less affected by the presence of lactate, presumably because of the lower midpotential of NAD-xylitol dehydrogenase (-236 mvolts) compared with that of lactate dehydrogenase (-216 mvolts). Ketone body production from endogenous fatty acids was inhibited equally by lactate and xylitol. The production of ketone bodies from added oleic acid was marginally inhibited by xylitol, suggesting the absence of a specific antiketogenic effect in the isolated liver. Xylitol metabolism was not associated with any increased rate of respiration, showing that reoxidation of NADH produced by xylitol dehydrogenase caused an inhibition of the citric acid cycle. Total adenine nucleotide levels diminished slightly during xylitol metabolism, but the ATP:ADP ratio was not appreciably changed.
A relatively simple procedure was devised for the purification of phosphofructokinase from rabbit liver extracts. The enzyme was purified more than 2600-fold with a yield of close to 50%.
Liver phosphofructokinase migrates faster on zone electrophoresis than rabbit skeletal muscle phosphofructokinase. It also differs from muscle enzyme in stability, molecular weight, and kinetic properties. The liver enzyme behaves on Sepharose chromatography as a polymer of various states of aggregation with the largest aggregate having a particle weight of many millions.
A comparison of the kinetic properties of liver and muscle phosphofructokinase revealed similarities in pH optimum, cation activation, and substrate affinity at pH 8.2. On the other hand, striking differences in kinetic control properties were observed at pH 7.0. The liver enzyme was more inhibited by ATP, less sensitive to the deinhibiting action of AMP, ADP, and cyclic 3',5'-AMP, less inhibited by citrate, phosphoenolpyruvate, phosphocreatine, 2-phosphoglycerate, and 3-phosphoglycerate, and more inhibited by 2,3-diphosphoglycerate than muscle phosphofructokinase.
The results suggest that liver phosphofructokinase is less suited for anaerobic energy production than the skeletal muscle enzyme and may not be subject to the same control mechanism in vivo.
Die Tatsache, daß dieses Thema an einer Internistentagung diskutiert wird, ist ein Beweis für das zunehmende Interesse der Inneren Medizin für die Angio-logie, und zwar nicht nur für Krankheiten der coronaren, renalen und cerebralen Gefäße, sondern auch für solche der Gliedmassenarterien und -venen, für die bisher in erster Linie die chirurgischen Kliniken zuständig waren. Die z. Z. noch vereinzelten angiologischen Teams medizinischer Kliniken haben sich bereits aufs beste bewährt.
Since the discovery of the process of oxidative phosphorylation, biochemical textbooks have tacitly assumed that most, if not all, of mammalian mitochondrial respiration is tightly coupled to ATP turnover, so that any increase in cellular oxygen uptake (JO) must necessarily indicate an augmented demand for ATP. On the other hand, much evidence has now accrued that the increase in JO observed when hepatocytes are presented with substrates, particularly fatty acids (Berry, 1974a; Williamson et al., 1969; Debeer et al., 1974; Berry et al., 1983a), cannot be wholly or even mainly accounted for by increased utilization of ATP in biosynthetic processes such as gluconeogenesis and urea formation (Berry, 1974a; Berry et al., 1983a; Hems et al., 1966; Krebs et al., 1964). The mechanism by which oxygen consumption is stimulated to a greater extent than predicted from any increased metabolic activity of the cells has not been established unequivocally. Possibilities include uncoupling of the mitochondria (Scholz et al., 1984; Soboll and Stucki, 1985), changes in eficiency of coupling, perhaps by alterations in the H+/e- ratio of mitochondrial proton pumping (Nicholls, 1974; Pietrobon et al., 1981), induction of futile cycles of ATP synthesis and hydrolysis (Debeer et al., 1974; Newsholme and Crabtree, 1976; Katz and Rognstad, 1976; Plomp et al., 1985), or stimulation of some other pathway such as reversed electron flow (Berry et al., 1983a). None of these explanations seems entirely satisfactory.
In liver the mixed function oxidation system is located in the membranes of the smooth endoplasmic reticulum. It requires NADPH and molecular oxygen to convert a wide variety of compounds into more polar (i.e., hydroxylated or dealkylated) derivatives. In our studies the increased oxygen uptake of perfused liver following the addition of a suitable substrate, e.g., aminopyrine, was used to estimate the rate of this microsomal process (1).
The increasing number of reports indicating an inverse association between cardiovascular morbidity or mortality and moderate alcohol intake (Gordon and Kannell, 1983; Kagan et al., 1981; Klatsky et al., 1974; Kozarevic et al., 1982; Salonen et al., 1983) represent a perplexing dilemma for the providers of health care (Ashley, 1984; Lieber, 1984; Popham et al., 1983).
Beim Menschen führt Alkoholabusus zu einer Fettleber und Hyperlipoproteinämie vom Typ IV mit Vermehrung der Serumpräbetalipoproteine und Triglyceride.
Alcoholic liver disease is a major health problem, and specific therapies are lacking because we still do not understand how alcohol causes liver damage. The purpose of this chapter is to evaluate the evidence for and against the hypothesis that hypoxia is involved in this disease. We shall review hepatic oxygen uptake, ethanol metabolism and adaptations, and hypoxic tissue damage in general briefly.
BATELLI and STERN of Geneva seem to have been the first to give a clear demonstration that various organs in the body can oxidize alcohol. This happened in 1910. They found that the liver from many species of animal has a high capacity for metabolizing alcohol, but that to some extent the kidneys could also perform the oxidation. Their investigations were carried out using minced tissue preparations. In the same year, HAMILL (1910) showed that a rabbit heart perfused with a RINGER solution containing alcohol removed a part of the alcohol during the experiment. FISHER (1916) made a similar observations some years later in experiments with cat hearts, as did KLEWITZ (1923) with rabbit hearts.
Obwohl zahlreiche Studien über den Effekt von Äthanol auf die Blutglucosekonzentration am Menschen durchgeführt wurden [3, 5, 7], weiß man relativ wenig über seinen Effekt auf die Glucoseneubildung. Die wenigen am Menschen über die Gluconeogenese erhobenen Daten stammen aus Tracer-Studien von Kreisberg [9], wobei man den Gesamtanteil der Gluconeogenesepräkursoren an der Glucoseneubildung und den der Glykogenolyse nicht erfassen konnte. Die bisher mit der Kathetertechnik an der menschlichen Leber vorgenommenen Untersuchungen hatten andere Fragestellungen zum Ziel [16].
The metabolic activity of an organ, e.g., the liver, will create gradients of oxygen, substrates, hormones, and products of metabolism along the capillaries. These concentration gradients will tend to subdivide the organ into zones of different metabolic activity at the capillary level. In many organs, e.g., muscles and brain, capillaries seem to be organized so as to minimize the zonation effect of the longitudinal capillary gradients, since adjacent parallel capillaries are perfused in opposite directions.
Chronic ethanol ingestion has been shown to affect most cytoplasmic organelles of the hepatocyte, both morphologically and functionally. Some of these changes appear to be injurious i.e., they result in decreased function, while others are probably adaptive and lead to enhanced function.
Ethyl alcohol (ethanol), which is, a nutrient, a tranquilizer, an euphoristic beverage, is also a toxic responsible of so much human degradation, a social plague increasing the death rate among the adult population (Fig. 1). Very curiously, its metabolic effects, which are certainly in relation with its aforementioned properties, do not draw the scientific attention they deserve, althrough the consumption of ethanol is a widespread fact.
Experiments on ethanol oxidation in humans have demonstrated (Figure 1) that oral ethanol loads of 0.7 g/kg body weight cause an ethanol concentration in the serum of 0.1 g/100 ml (1). This ethanol level decreases linearly with time. Curve 1 demonstrates the degradation of ethanol concentration in a normal subject with a rate of 90 mg kg-1h-1. Curve 2 shows the conversion of serum ethanol in a human with atypical alcohol dehydrogenase (18). Although carriers of atypical ADH have a specific ADH activity which is about five times higher than normal persons, ethanol is metabolized at a normal rate of 141 mg kg-1h-1. Children with glycogenosis type I (without liver glucose-6-phosphatase activity) oxidize ethanol about four times faster than do normal children (20), i.e., at a rate of 460 mg kg-1h-1. This is demonstrated in curve 3 (Figure 1).
Fig. 1
Ethanol oxidation in a normal subject (1), a person with atypical ADH (2) and a child with glycogenosis type I (3).
The hypoglycemic effect of ethanol is well established (1–5). However, several observations indicate that a decrease in blood glucose levels following ethanol administration is dependent upon the nutritional state. In dogs and adult men the hypoglycemic effect of ethanol is observed mainly in subjects fasted for several days (2,5). Moreover, studies with liver slices from fed rats showed that gluconeogenesis from alanine was stimulated by ethanol, whereas in the fasted state the effect was inconsistent (6). On the other hand, it has been reported that gluconeogenesis from several substrates was suppressed in isolated perfused livers from fasted rats by ethanol (7,8). These discrepancies suggest that the inhibitory effect of ethanol on glucose production is not absolute, but is dependent upon the metabolic state of the liver.
As early as 1918, Feigl described hyperlipemia in association with alcoholism. This original observation has been widely confirmed but it is only recently that the biochemical mechanisms involved have been studied.
Ethanol exerts different effects on hepatic cellular metabolism depending mainly on the dose and duration of intake. Following the ingestion of a substantial amount of ethanol, its presence alters a number of hepatic functions either because of the change in the hepatic redox state — NADH/NAD ratio — (resulting for instance in reduction of lipid oxidation), or because ethanol when present at high concentrations will inhibit a variety of microsomal functions involving particularly drug metabolism. These effects are not observed at low ethanol concentrations. Furthermore chronic ethanol consumption, at least in its early stages, produces adaptive metabolic changes in the endoplasmic reticulum which result primarily in increased metabolism of drugs and accelerated lipoprotein production. More extended periods of ethanol intake result in damage to cell organelles in what can be considered a third stage of the alcohol effect, namely that of injury (primarily to the mitochondria) possibly involving the effects of acetaldehyde, the first product of ethanol metabolism. Prolongation of ethanol-induced injury eventually culminates in hepatic lesions such as alcoholic hepatitis and cirrhosis. The purpose of this chapter is to describe the metabolic abnormalities which characterize each of these stages of alcohol-induced changes in the liver.
This chapter discusses the properties and methods of assay of fructosediphosphatase (FDPase). It also discusses the purification of FDPase from different sources such as liver, kidney, muscles, and Candida utilis. The requirement of FDPase for gluconeogenesis has been firmly established by the observations with bacterial and human mutants referred to in an earlier section. However, the role of this enzyme in the regulation of carbohydrate metabolism remains to be clarified. Control of gluconeogenesis in liver appears to be exerted primarily a t the steps leading to the formation of phosphoenolpyruvate, but evidence has accumulated which suggests that control is also exerted at the level of fructose 1,6-diphosphate. Adenosine monophosphate (AMP), which is a specific inhibitor of FDPase in every organism examined except the slime mold, is also an activator of phosphofructokinase. High levels would therefore stimulate glycolysis, while low concentrations would favor gluconeogenesis. However, the levels of AMP have been found not to fluctuate significantly in fed or fasted animals, and other factors must therefore contribute to the metabolic control by this substance. One such factor may be the concentration of FDP, which itself inhibits FDPase, and which greatly enhances the inhibition by AMP. An additional regulatory mechanism is suggested by the low activity of purified FDPases in the neutral pH range and by the increases in neutral FDPase activity brought about by reagents, which modify sulfhydryl groups in the protein, particularly physiological agents such as CoA, acyl carrier protein, or homocystine.
Previous studies in our laboratory (1–3), have indicated that the major rate limiting factor in ethanol metabolism in the intact liver cell is the rate of mitochondrial reoxidation to NAD+ of NADH produced in the oxidation of ethanol. This has now been confirmed in several laboratories (4–8). In this process oxygen is utilized and water is formed. The capacity of mitochondria to oxidize reducing equivalents is related to the relative availability of phosphate acceptor (ADP), or more generally to the phosphorylation potential (ATP/ADP × Pi) (9–12). Mitochondrial uncouplers such as dinitrophenol (DNP), carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone (FCCP) and arsenate allow the mitochondria to oxidize reducing equivalents independently of phosphate acceptor availability and thus they increase the rate of oxygen consumption (13). Accordingly, the rate of ethanol metabolism has been shown to be increased by uncoupling agents both in vivo (2,4) and in vitro in liver slices (1, 14), perfused liver (3,5) and isolated hepatocytes (8). Figure 1 shows the effect of DNP on the rate of ethanol metabolism by perfused rat liver.
Ethanol is not only produced by yeast but can also be found in mammals in trace amounts (McManus et al., 1966). Bacterial fermentation in the gut is one way in which it is produced (Krebs and Perkins, 1970). How-ever, it is primarily an exogenous compound that is readily absorbed from the gastrointestinal tract. Only 2-10% of ethanol absorbed is eliminated through the kidneys and lungs; the rest is oxidized in the body, principally in the liver. The rate of ethanol removal from the blood is, indeed, remarkably decreased or halted by hepatectomy or procedures damaging the liver (Thompson, 1956). Moreover, the predominant role of liver for ethanol metabolism was shown directly in individuals with portacaval shunts undergoing hepatic vein catheterization (Winkler et al., 1969). Extrahepatic metabolism of ethanol is relatively small (Forsander and Raiha Niels, 1960; Larsen, 1959), except for the stomach (vide infra.) This relative organ specificity probably explains why, despite the existence of intracellular mechanisms to maintain homeostasis, ethanol disposal produces striking metabolic imbalances in the liver. These effects are aggravated by the lack of a feedback mechanism to adjust the rate of ethanol oxidation to the metabolic state of the hepatocyte and the inability of ethanol, unlike other major sources of calories, to be stored in the liver or to be metabolized or stored to a significant degree in peripheral tissues (Table 1.1). The hepatocyte contains three main pathways for ethanol metabolism, each located in a different subcellular compartment: the alcohol dehydrogenase pathway of the cytosol (or soluble frac-tion of the cell), the microsomal ethanol-oxidizing sys-tem located in the endoplasmic reticulum, and catalase located in the peroxisomes (Fig. 1.1).
Brown adipose tissue is thermogenically active when coupling of oxidative phosphorylation is loosened. Brown‐adipose‐tissue mitochondria when freshly isolated are uncoupled. They are brought to a coupled state by oxidation of endogenous fatty acids, after which addition of exogenous fatty acids produces a burst of oxygen consumption. This does not correspond to that theoretically required for complete oxidation of the added fatty acid to carbon dioxide and water.
Oxidation by coupled mitochondria of ¹⁴ C‐labelled palmitic acid in the presence of malate leads to labelling of water‐soluble intermediates.
These intermediates are identified as citric acid cycle intermediates, amino acids arising from transamination, and acetyl L‐carnitine.
It is found that in coupled and uncoupled conditions the ratio of acetyl L‐carnitine to other intermediates is altered. Uncoupling reduces the formation of acetyl L‐carnitine and increases entry of acetyl groups into the citric acid cycle.
A control mechanism for this process and its possible correlation with the physiological function of brown adipose tissue are discussed.
Gluconeogenesis is reviewed from the standpoints of its functions and relationships to general metabolism, the biochemical mechanisms involved in its control, and its alterations in various physiologic and pathologic conditions. Its functions are discussed in relationship to cerebral metabolism, the Cori cycle, the alanine cycle, and ammonia production by the kidney. The pathways of glucose synthesis from major physiologic substrates are outlined. Control mechanisms for gluconeogenesis, which appear to operate under physiologic conditions, are discussed. Particular attention is paid to regulation of the following processes or enzymes: supply of substrate from peripheral tissues, substrate uptake by the liver, transport of metabolites across the mitochondrial membranes, pyruvate carboxylase, pyruvate dehydrogenase, the Krebs cycle, P-enolpyruvate carboxykinase, pyruvate kinase, fructose-1, 6-diphosphatase, P-fructokinase, glucose 6-phosphatase, glucokinase, phosphorylase, and glycogen synthetase. In addition, the effects of changes in ATP, ADP, AMP, cyclic AMP, the [free NADH] / [free NAD+] ratio, Ca++, and H+ are considered. Changes in gluconeogenesis in various situations are described with particular reference to studies in man. An attempt is made to identify hormonal and other factors responsible for alterations in metabolism. The situations considered include the following: brief and prolonged starvation, diabetes and insulin treatment, fetal and neonatal development, pregnancy and lactation, exercise, obesity, glucocorticoid deficiency and excess, alcohol hypoglycemia, hypoxia, and fatty acid infusion. The effects of certain hypoglycemic agents on gluconeogenesis are also described. Some general conclusions are drawn regarding the possible roles and mechanisms of action of glucagon, insulin, adrenal steroids, the sympathetic nervous system, and fatty acids in the control of gluconeogenesis in vivo. Areas needing further research are outlined.
Zusammenfassung Die Chromosomenanalyse eines 4 Monate alten weiblichen Säuglings mit rotatorischem Spontannystagmus, Sehschwäche (Blindheit ?) und hochgradigem motorischem und geistigem Entwicklungsrückstand ergibt ein E-Trisomie-Mosaik mit gleichzeitiger Translokation C/E. Der 2 1/2 jährige Bruder dieses Kindes zeigt die gleiche klinische Symptomatik, die cytogenetische Untersuchung erweckt den Verdacht auf das Vorliegen derselben chromosomalen Aberration. Die Karyotypen der Eltern sind normal. Cytogenetischer Befund und seine Beziehung zur Klinik werden diskutiert.
Beim Kultur-pH 6,2 weist die beobachtete Wachstumskurve von Acetobacter rancens mit Athanol als Kohlenstoffsubstrat zwei Wachstumsphasen auf. Im Laufe der ersten Phase ist die Fähigkeit der Zellen für die Oxydierung des Azetats viel geringer als diejenige, welche nach dem Verschwinden des Athanols aus dem Kulturmedium beobachtet wird.
Die Bestimmung der Enzyme des Glyoxylsäurezyklus und des Zitronensäurezyklus im Laufe der Anpassung der Zellen an die Oxydierung des Azetats, erlaubte es nachzuweisen, dass die spezifische Aktivität der Mehrheit der Enzyme steigt, wenn das Athanol durch das Azetat im Kulturmedium ersetzt wird.
Das Athanol inhibiert auch die Oxydierung des Azetats durch ruhende Zellen. Diese Inhibition ist ungefähr konstant für eine Konzentration von Athanol zwischen 7,5 mM und 300 mM.
Leitenzym des Peroxysoms–einer phylogenetisch alten, jedoch erst seit einigen Jahren bekannten Zellorganelle – ist Katalase, ein Hämoprotein, welches Wasserstoffperoxid sowohl katalatisch als auch peroxidatisch umsetzt. In den Peroxysomen ist die Katalase u.a. mit H2O2-liefernden Oxidasen vergesellschaftet. Auch in Gewebszellen, beispielsweise der Leber und der Niere, läuft ein Teil der Sauerstoffreduktion über die Bildung von H2O2. Drehscheibe des peroxysomalen H2O2-Umsatzes ist das aktive Intermediat, Katalase-Fe3+-H2O2 (Komplex I), das sich durch spezifische Absorptionsbanden auszeichnet. Die Organphotometrie an der intakten, hämoglobinfrei durchströmten Rattenleber zur selektiven Messung des Komplexes I ermöglicht einen direkten Einblick in die Dynamik des im Nanomolbereich ablaufenden H2O2-Umsatzes. Endrogen bildet 1 g Leber etwa 50 nmol H2O2 pro min. Die Wechselzahl, die im stationären Zustand bei < 10 min−1 in der Zelle gegenüber > 108 min−1 am isolierten Enzym bei Substratüberschuß liegt, kann durch intrazelluläre Stimulation der H2O2-Produktion (z. B. durch Glykolat oder Urat) auf etwa 102min−1 gebracht werden. Die bei den niedrigen Wechselzahlen gegenüber dem katalatischen Weg begünstigte peroxidatische Oxidation von Wasserstoffdonoren (z. B. Methanol und äthanol) hat im normalen Metabolismus und bei pathologischen Zuständen Bedeutung.
The dose-dependent effect of ethanol on the hepatic metabolism of the perfused rat liver has been investigated by (a) 31P-NMR spectroscopy for the follow-up of intracellular phosphorylated metabolites and (b) HPLC for compounds released in the effluents. Perfusion of livers from fed rats with ethanol induced an increase in the level of sn-glycerol 3-phosphate and net accumulations of 3.30 ± 0.33 and 0.69 ± 0.15 μmol × g−1 wet liver were reached after 20 min, for 70 mM and 0.5 mM ethanol, respectively. sn-Glycerol-3-phosphate accumulation was fully detected by 31P NMR as indicated by comparing quantitations based on NMR and biochemical assays. Ethanol administration up to a concentration of 10 mM induced a dose-dependent decrease in the release of lactate + pyruvate by the liver. Lactate release decreased from 1129 ± 39 to 674 ± 84 nmol × min−1× g−1, while pyruvate decreased from 230 ± 9 to 6.2 ± 0.4 nmol × min−1× g−1, after 20 min of perfusion with 10 mM ethanol. Nevertheless, the flux through 6-phosphofructo-1-kinase, as measured by both the accumulation of sn-glycerol 3-phosphate and release of lactate + pyruvate, was not affected in the early phase of ethanol oxidation. Finally, data obtained from oxygen consumption, the release of acetate and the accumulation of sn-glycerol 3-phosphate do not support the involvement of the microsomal ethanol-oxidizing system in the catalysis of ethanol oxidation, even at high doses of alcohol.
hind-limb ischaemia;thermoregulation;environmental temperatures;oxidative degradation;pyruvate oxidation
Changes in metabolic rates (oxygen consumption, ketogenesis, 14CO2 production from labelled fatty acids, glycolysis) following the addition of octanoate or oleate were studied in isolated livers from fed and starved rats perfused with Krebs-Henseleit bicarbonate buffer in a non-recirculating system. The following results were obtained.1The infusion of fatty acids Caused a large increase in the rate of oxygen consumption. The effect was greater with octanoate than with oleate and was half-maximal with fatty acid concentrations (free plus albumin bound) around 0.1 mM.2The effects of oleate were only partially suppressed when the perfusate contained albumin concentrations near the physiological range.3When fatty acids were oxidized at high rates, the glycolytic rate was diminished by 50%.4The increase in oxygen consumption could not be explained fully by the increased ATP demand for fatty acid metabolism or by a compensation for the diminished extramitochondrial ATP generation.5In the presence of phenylalkyl oxirane carboxylic acid, an inhibitor of the transport of long-chain acyl-CoA derivates into the mitochondria, ketogenesis and 14CO2 production from labelled oleate were strongly inhibited, whereas the increase in oxygen consumption was only slightly affected.6In the presence of antimycin A, the increase in oxygen consumption due to fatty acids was totally abolished.7Following pretreatment of rats with ciprofibrate (induction of enzymes for peroxisomal β-oxidation of long-chain fatty acids), ketogenesis (but not 14CO2 production) from oleate was enhanced threefold. The increase in oxygen consumption, however, was not affected.In conclusion, the increase in hepatic oxygen consumption due to addition of fatty acids reflects a mitochondrial process; it is, in part, independent of the ATP demand of the cell. An uncoupling-like effect of fatty acids on the respiratory chain and its possible physiological significance in ketogenesis are discussed.
Introduction Alcohol Elimination Rates and Alcohol-Metabolizing Capacity of Man Significant Pathways and Enzymes of Alcohol Metabolism Liver Alcohol Dehydrogenase Liver Aldehyde Dehydrogenase Factors that Limit and Accelerate Rates of Alcohol Metabolism Effects of Chronic Ethanol Ingestion Summary and Conclusions
The effect of fatty acids on the interconversion of pyruvate dehydrogenase between its active (nonphosphorylated) and inactive (phosphorylated) forms was measured in rat liver mitochondria respiring in state 3 with pyruvate plus malate and 2‐oxoglutarate plus malate and during state 4 to state 3 transition in the presence of different substrates. The content of intramitochondrial adenine nucleotides was determined in the parallel experiments.
Decrease of the intramitochondrial ATP/ADP ratio with propionate and its increase with palmitoyl‐ l ‐carnitine in state 3 is accompanied by a shift of the steady‐state of the pyruvate dehydrogenase system towards the active or the inactive form, respectively.
Transition from the high energy state (state 4) to the active respiration (state 3) in mitochondria oxidizing 2‐oxoglutarate or palmitoyl‐ l ‐carnitine causes an increase of the amount of the active form of pyruvate dehydrogenase due to the decrease of ATP/ADP ratio in the matrix.
No change in ATP/ADP ratio can be observed in the presence of octanoate in mitochondria oxidizing pyruvate or 2‐oxoglutarate in state 3 or during state 4 to state 3 transition. Simultaneously, no significant change in phosphorylation state of pyruvate dehydrogenase occurs and a low amount of the enzyme in the active form is present with octanoate or octanoate plus 2‐oxoglutarate. Pyruvate abolishes this effect of octanoate and shifts the steady‐state of pyruvate dehydrogenase system towards the active form.
These results indicate that fatty acids influence the interconversion of pyruvate dehydrogenase mainly by changing intramitochondrial ATP/ADP ratio. However, the comparison of the steady‐state level of the pyruvate dehydrogenase system in the presence of different substrates in various metabolic conditions provides some evidence that accumulation of acetyl‐CoA and high level of NADH may promote the phosphorylation of pyruvate dehydrogenase.
Pyruvate exerts its protective effect against phosphorylation of pyruvate dehydrogenase in the presence of fatty acids of short, medium or long chain in a manner which depends on its concentration. It is suggested that in isolated mitochondria pyruvate counteracts the effect of acetyl‐CoA and NADH on pyruvate dehydrogenase kinase.
Reversible hyperlipoproteinemia may be observed after ethanol loads in healthy man before any ethanol-induced disease is being established. Different pathogenetic ways to this acute ethanol-induced hyperlipoproteinemia have been investigated or postulated in recent years. Two main sites have appeared: changes in the metabolism of lipids and their precursors which depend from actual oxidation of ethanol in the liver, and ethanol-induced activation of lipolysis in adipose tissue, transmitted by the sympathico-adrenal system. The changes in liver metabolism during ethanol oxidation have been well confirmed in many experiments, they nevertheless do not seem to lead to hyperlipoproteinemia in many experimental designs in animals and after drinkable amounts of ethanol in healthy man when lipolysis of adipose tissue is blocked and no food is ingested. After the intake of a fatty meal these triglycerides are becoming importance as a source of fatty acids. A possible increased de novo synthesis of palmitic acid may to a minor degree contribute to hypertrigly-ceridemia.
1. In der vorliegenden Arbeit wurde untersucht, ob für die Fetteinlagerung in die Leber durch Alkoholzufuhr vorwiegend eine Neusynthese von Fettsäuren als Folge von Stoffwechseländerungen in der Leber durch die Alkoholoxydation selbst verantwortlich ist oder eine Mobilisierung von Fettsäuren aus dem peripheren Fettgewebe. Zu diesem Zweck wurde der Einfluß von Äthanol auf den Gehalt an Metaboliten und Coenzymen des energieliefernden Stoffwechsels sowie von Triglyceriden in der Leber von Ratten bestimmt, bei denen die Alkoholoxydation normal oder durch Fütterung einer proteinarmen Kost stark eingeschränkt war. 2. Alkohol führt bei normal ernährten Ratten in kurzer Zeit zu einer deutlichen Zunahme der Reduktion des cytoplasmatischen NAD-Systems der Leber, gemessen an den Quotienten Lactat/Pyruvat undα-Glycerophosphat/Dihydroxyacetonphosphat. Der Reduktionsgrad des mitochondrialen NAD-Systems nimmt, gemessen an dem Quotientenβ-Hydroxybutyrat/Acetoacetat nach Alkoholzufuhr initial weniger ausgeprägt zu. Er steigt jedoch, im Gegensatz zu dem des cytoplasmatischen NAD-Systems, mit der Dauer der Alkoholeinwirkung weiter an. Der Quotient NADH/NAD, der sich aus dem Gehalt der Leber an NADH und NAD berechnet, nimmt unter Alkohol ebenfalls zu. 3. Der Triglyceridgehalt der Leber steigt unter Äthanoleinwirkung bei normal ernährten Ratten innerhalb von 12 Std auf das 4fache des Ausgangswertes an. 6. Aus den Ergebnissen wird geschlossen, daß die Fettsäuren für die vermehrte Triglycerideinlagerung in die Leber nach akuter Alkoholgabe vorweigend extrahepatischen Ursprungs sind. Die Fetteinlagerung ist weitgehend unabhängig von Stoffwechseländerungen in der Leber durch die Alkoholoxydation selbst.
The economic cost to society from alcohol abuse and alcoholism in the United States was an estimated $148billion in 1992.
When adjusted for inflation and population, the estimates are generally comparable with cost estimates produced over the past
20 years. The current estimates are significantly greater than the most recent detailed estimates developed for 1985— about
42% above increases due to population growth and inflation. Between 1985 and 1992, inflation accounted for about 37.5% and
population growth for 7.1% increases. Changes in prevalence have been associated with a modest reduction in alcohol costs.
Though crime rates did not materially change over this period, criminal justice expenditures more than doubled overall, even
after adjustment forprice increases. The balance ofchanges are due tonewfindings and/or methodology indicating larger impacts
than previously estimated. It is estimated that 45.1% ofcosts are borne by alcohol abusers and/or members of their households,
38.6% are borne by government, 10.2% by private insurance, and 6.0% by victims of alcohol-related trauma (motor vehicle crashes
plus crime). The costs staying in the household of the abusers may be materially incident on persons other than the abuser,
e.g., spouses, children.
This chapter describes the development of the Alcohol Use Disorders Identification Test (AUDIT) among various Mexican populations,
the evaluations that followed the World Health Organization international research project from where this screening instrument
was derived, its use in nonclinical settings, modifications introduced in its wording, the development of a short version,
and validity and reliability tests. It also describes rates of hazardous, harmful, and dependent drinkers and biobehavioral
consequences of abuse among various Mexican populations. Data drawn from different samples showed adequate levels of specificity
and sensitivity. Findings from general population samples confirmed previous observations in general practice: That the AUDIT
could capture not only regular consumption at hazardous levels, but also episodic heavy drinking. Data from an International
Labor Office/World Health Organization project on model programs for alcohol prevention in the workplace showed that it was
possible to derive a short version, easily used for intervention programs, that differentiated categories of drinkers at various
risk levels. Rates of problem drinkers in clinical samples varied between 28 and 43% for males and 3.6 and 4.8% among females.
Hazardous drinking varied between 0.7 and 15.5% among males and females in general populations and reached 44% in a sample
of male workers; in clinical settings, harmful drinking ranged from 7 to 16% among males and dependence from 3 to 10%.
1)
In rats fed a standard diet or a protein restricted diet the effect of acute and chronic ethanol administration on liver content
of adenine nucleotides was studied. In the long-term experiments the total liver content of NAD and NADP was additionally
determined.
2)
A single oral ethanol load does not significantly influence the total adenine nucleotide content. Liver AMP content increases
immediately following ethanol ingestion about 2-fold and remains elevated for 12 hours. ATP content and ATP/ADP ratio are
significantly reduced within 30 minutes after ethanol administration. Both return to initial values after 2 hours and decrease
again thereafter.
3)
The increase in the AMP content is dose dependent, i.e. it is more pronounced after small doses of ethanol and is not observed
when blood ethanol concentrations are very high. The elevation of the AMP levels during ethanol oxidation is interpreted as
a consequence of increased ATP consumption and of inhibition of citric acid cycle.
4)
In animals fed nearly protein-free diet, total adenine nucleotide content and ATP content are distinctly reduced. An increase
in AMP concentration is not observed in these rats where ethanol oxidation is markedly inhibited.
5)
Chronic ethanol application does neither in rats kept on a standard diet nor in those fed a protein restricted regimen affect
the liver content of total adenine nucleotides or ATP. Similarly the total content of NAD and NADP shows no major changes.
6)
It is concluded that the relatively small alterations in total liver adenine nucleotide content and in the different adenine
nucleotide fractions are not important for ethanol-induced fat accumulation or other disturbances in the liver.
1. The aim of this study is to elucidate the origin of fatty acids accumulating as triglycerides in the liver following acute ethanol administration. In order to clarify this problem the effect of ethanol on the content of metabolites and coenzymes of the fatty acid and carbohydrate metabolism in liver and blood was assessed in man and in experimental animals.
2. Metabolic changes induced by the oxidation of ethanol in the liver of rats fed a standard diet (marked increase in the reduction of the cytoplasmic NAD-system in the liver, measured by the lactate/pyruvate,α-glycerophosphate/dihydroxyacetonephosphate, and NADH/NAD ratios and increase of the acetyl-CoA content of the liver) can already be observed during the initial phase after a single oral load of ethanol.
3. The pronounced accumulation of triglycerides in the liver following ethanol administration begins after a rather long lag period. This coincides with an increase in the concentration of free fatty acids in the plasma.
4. In animals fed a protein-deficient diet (0.5% protein) the activity of liver alcohol dehydrogenase decreases to about 15% of the control values within 3 weeks. Under these conditions, ethanol oxidation is extremely slow when measured by blood elimination rate. This inhibition of ethanol oxidation caused by protein deficiency has been confirmed in man.
5. Due to the reduced ethanol oxidation rate, metabolic changes induced by the oxidation of ethanol itself (increase of the reduction state of the cytoplasmic NAD-system and the hepatic content of acetyl-CoA) are not observed or at least much less pronounced in rats kept on a protein deficient diet than in normal control animals. Conversely the accumulation of triglycerides in the liver is even more marked in the former. Theβ-hydroxybutyrate/acetoacetate ratio and the concentration of these ketone bodies are also more elevated in liver and blood of protein deficient animals.
6. Inhibition of lipolysis by adrenalectomy or application ofβ-receptor blocking agents diminishes the accumulation of triglycerides in the liver following acute ethanol administration. Under these conditions metabolic changes induced by the ethanol oxidation itself (increase in the lactate/pyruvate and NADH/NAD ratios) are similar to those observed in control animals.
7. Acute ethanol administration to rats fed a standard diet increases the liver content of long-chain acyl-CoA esters. In protein deficient rats, ethanol application results in extremely high long-chain acyl-CoA levels. The marked increase in the long-chain acyl-CoA/free CoA ratio suggests a feed-back inhibition of fatty acid synthesis at the acetyl-CoA carboxylase reaction.
8. Increased production ofα-glycerophosphate has been suggested to play a role in the preferential formation of triglycerides after acute ethanol administration. To elucidate this problem the effect of ethanol on hyperthyroid rats has been investigated. Hyperthyroidism inducesα-glycerophosphate oxidase a 20 to 30-fold and inhibits the elevation of hepaticα-glycerophosphate content caused by ethanol. Correspondingly, the ethanol-induced triglyceride accumulation in the liver was found to be distinctly lower than in euthyroid controls.
9. In man, acute ethanol administration leads to analogous changes of the redox couples lactate/pyruvate andβ-hydroxy-butyrate/acetoacetate and other metabolic alterations as observed in animal experiments.
10. It is concluded from these results that acute ethanol administration does not enhance hepatic fatty acid synthesis. Stimulated peripheral lipolysis is assumed to be the major source of the fatty acids which accumulate in the liver after acute ethanol intoxication. Both the marked elevation of hepaticα-glycerophosphate content and the increased fatty acid supply from adipose tissue are suggested to be of significance for the predominant triglyceride formation in the liver.
Even a moderate does of alcohol infused into fasted and fed rabbits (1.95 g/kg for over 2 h) induces a change in myocardial lipid metabolism. Such metabolic alterations were studied by measuring fatty acid oxidation and esterification by homogenates prepared from the hearts of these rabbits, and also by analyzing fatty acid composition of heart triglyceride. Ethanol administration resulted in depressed fatty acid oxidation and enhanced esterification. These metabolic derangements were restored towards the control value by the addition of carnitine in the incubation medium. The fatty acid analysis using gas chromatography was performed with rabbit heart triglyceride, adipose tissue, plasma FFA and rabbit food, each of them showing a slightly different composition. Ethanol was infused into either fed or fasted animals and the fatty acid composition of cardiac triglyceride was examined. There was very little difference in ethanol-induced compositional changes between the two dietary states of the animals, although in both instances the content of heart triglyceride was increased three hours after cessation of ethanol infusion. However, fatty acid composition of heart triglyceride greatly changed and showed a close resemblance to that of the plasma FFA, suggesting that the source of the increased fatty acid moiety in the myocardium is plasma FFA and that heart triglyceride undergoes turnover at a considerably high rate. However, this altered composition of cardiac triglyceride returned towards the pre-infusion pattern at a very slow pace. In particular, unsaturated fatty acid levels did not rise to the control value during a 2-week observation period, indicating that transacylation and desaturation processes in the organ, as well as re-arrangement or exchange of the acyl moiety of complex lipids among organs, are gradual.
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