Ethanol stimulates glycogenolysis and inhibits both glycogenesis via gluconeogenesis and from exogenous glucose in perfused rat liver

AIMS: Although it is commonly recognized that ethanol suppresses gluconeogenesis, the influence of alcohol intake on blood glucose levels remains controversial. Ethanol may act on both glucose production and glucose consumption in the liver. Thus, we studied each effect of ethanol on glucose oxidation, gluconeogenesis, glycogenesis and glycogenolysis in the liver. METHODS: The rat liver was isolated and cyclically perfused with a medium containing 50 mmol/l ethanol. RESULTS: Ethanol enhanced 14C-glucose oxidation in the liver from 1.09 +/- 0.11 to 1.41 +/- 0.14 micromol for 20 min (p < 0.05). Gluconeogenesis from 14C-lactate was markedly reduced by ethanol from 8.0 +/- 1.3 to 1.5 +/- 0.6 micromol for 12 min (p < 0.01). Ethanol increased glycogenolysis (net hepatic glucose output, 0.47 +/- 0.10 vs. 0.22 +/- 0.04 mmol/30 min, p < 0.01), and then decreased hepatic glycogen content (179 +/- 38 vs. 273 +/- 39 mg in the presence of 1 mU/ml insulin after 30 min of perfusion, p < 0.05). Ethanol decreased the direct glycogenesis from 14C-glucose from 0.55 +/- 0.08 to 0.33 +/- 0.05 micromol per 100 mg glycogen for 30 min (p < 0.01). Ethanol inhibited the indirect glycogenesis from 14C-lactate from 0.21 +/- 0.04 to 0.09 +/- 0.01 micromol per 100 mg glycogen for 30 min (p < 0.01). DISCUSSION: The influence of ethanol on the blood glucose regulation by the liver seems to be different between fasted and fed states. Namely, ethanol has both the hypoglycemic effects through decreased gluconeogenesis and increased glucose oxidation and the hyperglycemic effects through decreased glycogenesis and increased glycogenolysis.     

Differential effects of alcohol upon gluconeogenesis from lactate in young and old hepatocytes

The purpose of this study was to determine the effect of age upon hepatic gluconeogenesis (HGN) from lactate in the presence of various concentrations of alcohol from young (3 months) and old (24 months) male rats. After a 24-hour fast, livers were perfused with collagenase and the hepatocytes were isolated. Aliquots of the cell suspension were placed in Krebs-Henseleit buffer and incubated with lactate, [U-(14)C]lactate, and nine different concentrations of ethanol (EtOH) for 30 min. Dose-effect curves were generated for the determination of maximal and half-maximal alcohol-induced inhibition on gluconeogenesis. There were no significant differences in basal HGN (lactate only and no EtOH) between young and old hepatocytes, 86.9+/-6.3 nmol/mg protein/30 min. The addition of ethanol significantly reduced HGN from lactate in both groups. At the highest ethanol concentration (15 mM), the glucose production was inhibited more from old, 46.1+/-1.2 nmol/mg protein/30 min, compared to young hepatocytes, 56.0+/-1.6 nmol/mg protein/30 min. The greater age-related reduction in HGN was confirmed by the minimal glycogenolysis, and the concomitant decline in [U-(14)C]glucose production, lactate uptake, and [U-(14)C]lactate uptake. The results suggest that alcohol elicits a greater inhibition upon HGN from lactate in old compared to young liver cells.     

非酒精性脂肪性肝病大鼠肝脏解偶联蛋白2表达及其与能量贮备的关系

目的探讨非酒精性脂肪性肝病(NAFLD)大鼠肝脏线粒体解偶联蛋白2(UCP2)表达及其与能量贮备的关系。方法模型组SD大鼠给予高脂肪高胆固醇饮食饲养,分批于实验第8、12、16、24 周处死,同期设普通饮食饲养大鼠作对照。免疫组织化学和逆转录聚合酶链反应(RT-PCR)检测肝脏UCP2 mRNA转录及其蛋白表达。荧光测定法检测肝脏三磷酸腺苷(ATP)含量。结果模型组大鼠8周呈现单纯性脂肪肝,12-24周从脂肪性肝炎进展为脂肪性肝炎伴肝纤维化。免疫组织化学和RT-PCR显示,随着造模时间延长,模型组肝脏UCP2表达逐渐增强,UCP mRNA转录于24周达高峰,较对照组升高4.2倍, t=16.474,P<0.01;模型组肝脏ATP含量则随造模时间延长而逐渐减低,24周为(1.99±0.66) ×108μmol/g,对照组为(2.97±0.48)×108μmol/g,t=3.248,P<0.01。模型组肝脏UCP2 mRNA 转录的相对数值与其ATP含量呈密切负相关,r=-0.93,P<0.01。结论持续24周高脂饮食成功复制大鼠NAFLD模型,模型大鼠肝脏UCP2表达增强而ATP含量减少,两者之间关系密切。     

Effects of nicardipine and nisoldipine on myocardial metabolism, coronary blood flow and oxygen supply in angina pectoris

The effects of the calcium antagonists nicardipine and nisoldipine on left ventricular (LV) metabolism were analyzed in 32 patients with angina pectoris. Measurements were made at a fixed heart rate under the basal state and during a cold pressor test (CPT). After administration of the drugs, coronary blood flow increased significantly and the mean aortic pressure decreased by 10% (p less than 0.01) in the basal state and by 11% (p less than 0.01) during CPT. Despite the reduction in pressure-rate product, myocardial oxygen consumption was unchanged in the basal state (18 +/- 4 vs 19 +/- 4 ml/min, difference not significant) and during CPT (21 +/- 5 vs 21 +/- 5 ml/min, difference not significant); this discrepancy between a reduced pressure-rate product and an unchanged oxygen consumption was also noted when nicardipine was given after propranolol (0.1 mg/kg; 12 patients). Both agents also increased LV lactate uptake, particularly during CPT (+13 mumol/min, p less than 0.05 vs control CPT) and reduced LV glutamine production. In 10 patients in whom 14C-lactate was infused, the chemical LV lactate extraction ratio increased more than the 14C-lactate extraction ratio after administration of the drugs, indicating a reduction in LV lactate production. The data are consistent with the hypothesis that nicardipine and nisoldipine improve perfusion and aerobic metabolism in chronically ischemic areas, resulting in an augmented oxygen consumption and in a reduced lactate production.     

Influence of sex and beta2 adrenergic receptor haplotype on resting and terbutaline-stimulated whole body lipolysis

beta 2 adrenergic receptors ( beta 2 ARs) are important mediators of lipolysis. The beta 2 AR gene is highly polymorphic. To determine the contribution of beta 2 AR polymorphisms to variability in whole body lipolysis, we compared basal and terbutaline-stimulated lipolytic rates (Ra) using tracer techniques in 14 healthy, non-obese males (n=7) and females (n=7) who were homozygous for Cys-19/Arg16/Gln27 or Arg-19/Gly16/Glu27 haplotypes. Fasting (overnight) Ra values were higher in females compared to males. Mean+/-SD Ra, Ra/body weight, Ra/fat free mass, Ra/fat, and Ra/energy expenditure rates in males and females were 155+/-46 vs 311+/-111 micromol/min (P=.007); 2.0+/-0.61 vs 5.2+/-2.3 micromol/(min kg) (P=.006); 2.5+/-0.75 vs 7.8+/-3.4 micromol/(min kg) (P=.003); 10+/-3.7 vs 17+/-7.4 micromol/(min kg) (P=.09); and 144+/-45.5 vs 392+/-111 micromol/d (P=.0001), respectively. Mean+/-SD basal glycerol concentrations were higher in females compared to males: 62+/-5.6 vs 36+/-17 micromol/L (P=.003). Basal glycerol concentrations and Ra values were similar by beta2 AR haplotype. Basal glucose and insulin concentrations tended to be higher in males compared to females and were similar by haplotype. Terbutaline-stimulated changes in glycerol concentrations were variable and are not related to either sex or haplotype. We conclude that compared to haplotype, sex is a more important determinant of basal lipolysis after a 12-hour fast in healthy, non-obese individuals.     

Effects of exercise on plasma high-density lipoprotein cholesteryl ester metabolism in male and female miniature swine

We studied the effects of exercise on high-density lipoprotein (HDL) cholesteryl ester (CE) metabolism in 6 male and 6 female miniature pigs fed a commercial swine diet supplemented with cholesterol and fat. The diets were fed for a total period of 20 weeks. During the last 12 weeks of the feeding period, the pigs were exercised on a motorized treadmill 5 days per week for 45 min/d at a speed of 9.5 to 10.0 km/h at 0% grade. Homologous HDL preparations were radiolabeled with cholesteryl (1-14C)oleate and intravenously administered to the pigs, followed by blood sampling at the appropriate time points and measurement of radiolabeled HDL CE. This was performed while the animals were sedentary and after the exercise period. Plasma cholesterol increased after the exercise protocol from 7.21 +/- 1.90 to 8.50 +/- 2.81 mmol/L (mean +/- SD, n = 6) in the females and from 8.11 +/- 3.61 to 10.07 +/- 3.61 in the males. HDL CE transport rates in female pigs were significantly lower (23%) after the exercise protocol (118 +/- 14 v 91 +/- 14 micromol/h/L plasma). HDL CE transport rates in the males were also lower (11%) after exercise (90 +/- 20 v 80 +/- 18 micromol/h/L plasma), but this effect was not statistically significant. Further, the residence time or life span of HDL CE was significantly longer after the exercise protocol in both male and female pigs. Thus, the results of this study suggest that exercise reduces the transport rate of HDL CE and prolongs the life span of HDL CE in hypercholesterolemic pigs.     

Coronary microembolization does not induce acute preconditioning against infarction in pigs-the role of adenosine

OBJECTIVE: After coronary microembolization (ME) adenosine is released from ischemic areas of the microembolized myocardium. This adenosine dilates vessels in adjacent nonembolized myocardium and increases coronary blood flow. For ischemic preconditioning (IP) to protect the myocardium against infarction, an increase in the interstitial adenosine concentration (iADO) prior to the subsequent ischemia/reperfusion is necessary. We hypothesized that the adenosine release after ME is sufficient to increase iADO and protect the myocardium against infarction from subsequent ischemia/reperfusion. We have therefore compared myocardial protection by either coronary microembolization or ischemic preconditioning prior to ischemia/reperfusion. METHODS: In anesthetized pigs, the left anterior descending (LAD) was cannulated and perfused from an extracorporeal circuit. In 11 pigs, sustained ischemia was induced by 85% inflow reduction for 90 min (controls). Two other groups of pigs were subjected either to IP (n = 8; 10-min ischemia/15-min reperfusion) or coronary ME (n = 9; i.c. microspheres; 42 microm ?; 3000 x ml(-1) x min inflow) prior to sustained ischemia. Coronary venous adenosine concentration (vADO) and iADO (microdialysis) were measured. Infarct size was determined after 2-h reperfusion by triphenyl tetrazolium chloride staining. RESULTS: In pigs subjected to IP, infarct size was reduced to 2.6 +/- 1.1% (mean +/- S.E.M.) vs. 17.0 +/- 3.2% in controls. iADO was increased from 2.4 +/- 1.3 to 13.1 +/- 5.8 micromol x l(-1) during the reperfusion following IP. In pigs subjected to ME, at 10 min after ME, coronary blood flow (38.6 +/- 3.6 to 53.6 +/- 4.3 ml x min(-1)) and vADO (0.25 +/- 0.04 to 0.48 +/- 0.07 micromol x l(-1)) were increased. However, iADO (2.0 +/- 0.5 at baseline vs. 2.3 +/- 0.6 micromol x l(-1) at 10 min after ME) did not increase. Infarct size induced by sustained ischemia following ME (22.5 +/- 5.2%) was above that of controls for any given subendocardial blood flow. CONCLUSION: ME released adenosine into the vasculature and increased coronary blood flow. The failure of iADO to increase with ME possibly explains the lack of protection against infarction after ME.     

Effect of diet and red wine consumption on serum total antioxidant capacity (TAC), dehydroepiandrosterone-sulphate (DHEAS) and insulin-like growth factor-1 (IGF-1) in Italian centenarians

The traditional mediterranean diet is associated with a hope for longer survival. It has also been shown that the red wine possesses a protective effect against the oxidative stress. We studied TAC, the DHEAS and the IGF-1 in a group of 26 healthy centenarians, 17 women and 9 men, of the age range of 100--105 years. Furthermore, we analyzed also serum urate and bilirubin levels between drinkers and abstainers. Most of centenarian subjects have been moderate wine consumers (<500 ml/day of red wine). These subjects were subdivided as follows: (i) Group A: those who had maintained the style of their dietary habits as compared to the previous years (n=3 males, 10 females); (ii) Group B: those who actually consumed a diet being deficient compared to that of the previous years, but remained moderate drinkers of red wine (n=3 males, 4 females); and (iii) Group C: those who actually consumed a diet being deficient compared to that of the previous years, and at the same time, were abstainers in wine consumption (n=3 males, 3 females). The results show that in men three of the studied parameters decreased from Group A to C to considerable extents, as follows (mean+/-S.D.). TAC: 302.4+/-32.3; 142.0+/-24.1 and 96.4+/-20.1 micromol/l; DHEAS: 3.35+/-0.81; 2.52+/-0.18 and 1.34+/-0.14 micromol/l; IGF-1: 85.7+/-6.7; 76.6+/-6.7 and 65.6+/-2.6 ng/ml, respectively. For the same parameters, the results in the women were: TAC: 258.4+/-12.2; 182.1+/-14.0 and 107.6+/-10.0 micromol/l; DHEAS: 3.85+/-0.16; 2.34+/-0.19 and 2.05+/-0.04 micromol/l; IGF-1: 89.7+/-6.7; 76.6+/-4.7 and 64.2+/-2.7 ng/ml, respectively. We did not find any significant difference in the other serum parameters between drinkers (n=14) and abstainers (n=3) (urate: 267.6+/-52.9, and 289.5+/-80.1; bilirubin: 9.81+/-4.29 and 7.18+/-2.89 micromol/l, respectively). Our data suggest that the deteriorated diet caused a reduction of TAC, DHEAS and IGF-1 in the centenarians. However, red vine consumption exerted a protective effect against this trend, even if this protection is not reaching statistical significance in some cases (in men), which is due most probably to the lower number of male subjects in the study.     

Effect of macronutrient composition of the diet on the regulation of lipolysis in adipose tissue at rest and during exercise: microdialysis study

The aim of the present study was to elucidate, using a microdialysis technique, whether modifications in the proportion of fat in the diet influence lipid mobilization from adipose tissue in situ. Nine healthy volunteers (age, 23.4 +/- 0.2 years; body mas index [BMI], 23.5 +/- 1.6 kg/m(2)) were fed, in random order, with a high-fat diet (HFD) (65% of energy content fat, 15% protein, 20% carbohydrate) or a high-carbohydrate diet (HCD) (70% carbohydrate, 15% protein, 15% fat) for 5 days, with a washout period of 10 days between the diets. Subjects were studied in the fasting state on the morning following days 4 and 5 of each diet. We measured the concentration of extracellular glycerol (EGC) in adipose tissue in response to (1) pharmacologic stimulation with isoprenaline (1 and 10 micromol/L) in situ, (2) stimulation with intravenous infusion of epinephrine (0.0375 microg/min/kg body weight), and (3) submaximal aerobic exercise (50% V*O2max, 60-minute duration). No effect of the diet composition was found in the increases of EGC in response to isoprenaline (area under the curve [AUC]: HFD, 1,534 +/- 370 micromol/90 min; HCD, 1,108 +/- 465 micromol/90 min; not significant [NS]) or epinephrine stimulations (AUC: HFD, 190 +/- 92 micromol/30 min; HCD, 251 +/- 298 micromol/30 min; NS). The exercise-induced increase in EGC was higher during the HFD (AUC: HFD, 1,641 +/- 181 micromol/60 min; HCD, 963 +/- 156 micromol/60 min; P <.05) and was associated with a higher exercise-induced response of norepinephrine (P <.05) and epinephrine (P =.056) and lower insulinemia during exercise. The results suggest that macronutrient composition of diet does not affect the beta-adrenergic responsiveness of adipose tissue to catecholamine action at rest. During exercise, the HFD promotes higher lipolysis in adipose tissue and this is associated with a higher catecholamine response and lower insulinemia.     

Impact of aging on substrate metabolism by the human heart

BACKGROUND: Results of studies in experimental animals have shown that, with age, myocardial fatty acid metabolism decreases, and glucose metabolism increases. Whether similar changes occur in humans is unknown. METHODS: Seventeen healthy younger normal volunteers (six males, 26 +/- 5 years) and 19 healthy older volunteers (nine males, 67 +/- 5 years) underwent positron emission tomography (PET) under resting conditions in the fasted state. Myocardial blood flow (MBF), myocardial oxygen consumption (MVO(2)), myocardial fatty acid utilization (MFAU) and oxidation (MFAO), and myocardial glucose utilization (MGU) were quantified by PET with (15)O-water, (11)C-acetate, (11)C-palmitate, and(11)C-glucose, respectively. RESULTS: Although MBF was similar between the groups, MVO(2) was higher in the older subjects (5.6 +/- 1.6 micromol/g/min) compared with younger subjects (4.6 +/- 1.0 micromol/g/min, p < 0.04). Rates of MFAU and MFAO (corrected for MVO(2)) were significantly lower in older subjects than in younger subjects (MFAU/MVO(2): 35 +/- 10 vs. 51 +/- 20 nmol free fatty acids (FFA)/nmol O(2) x 10(-3), p < 0.005, and MFAO/MVO(2): 33 +/- 10 vs. 48 +/- 18 nmol FFA/nmol O(2) x 10(-3), p < 0.004). In contrast, the rates of MGU corrected for MVO(2) did not differ between the groups. CONCLUSIONS: With aging, humans exhibit a decline in MFAU and MFAO. Although absolute rates of MGU do not increase, by virtue of the decline in MFAU there is likely an increase in relative contribution of MGU to substrate metabolism. The clinical significance of this metabolic switch awaits further study.     

Hibernating myocardium retains metabolic and contractile reserve despite regional reductions in flow,function, and oxygen consumption at rest

Hibernating myocardium, characterized by reductions in flow and function at rest, has limited contractile reserve in response to increases in external workload. We hypothesized that this attenuation of function reflects an adaptive downregulation that prevents the development of metabolic evidence of ischemia during stress. To test this hypothesis, pigs were chronically instrumented with a proximal left anterior descending artery stenosis for 3 months, resulting in severe anteroapical hypokinesis with reduced resting perfusion (0.78+/-0.05 versus 0.94+/-0.07 mL x min(-1)x g(-1) in remote, P<0.01; and 0.99+/-0.08 in controls, P<0.05). Open-chest studies confirmed resting dysfunction compared with normal controls (segment shortening 9.2+/-2.2% versus 23.5+/-1.1%, P<0.05). Resting myocardial oxygen consumption was reduced (63+/-3 versus 77+/-6 microL x g(-1) x min(-1) in controls, P<0.05), yet lactate consumption was normal. Although subendocardial perfusion failed to increase during graded, intravenous epinephrine infusion (n=8), peak segment shortening (to 17.3+/-3.1%, P<0.05) and oxygen consumption (to 90+/-6 microL x g(-1) x min(-1), P<0.01) increased from the depressed resting levels. There was no lactate production in hibernating myocardium, and lactate uptake increased during stress (0.7+/-0.1 to 1.2+/-0.1 micromol x g(-1) x min(-1), P<0.05). The absence of metabolic evidence of ischemia was also confirmed during atrial pacing to a rate of 120 bpm (n=8). Thus, despite reductions in function and oxygen consumption at rest, hibernating myocardium retains the ability to increase metabolism without the development of acute ischemia. This supports the hypothesis that the downregulation of oxygen consumption and function in hibernating myocardium is an adaptive response that prevents a supply-demand imbalance during submaximal increases in cardiac workload when coronary flow reserve is limited.     

Net hepatic lactate balance following mixed meal feeding in the four-day fasted conscious dog

The present experiments were undertaken to determine whether four days of fasting and marked hepatic glycogen depletion would alter the effect of mixed meal feeding on net hepatic lactate balance in the conscious dog. Dogs were fasted for four days and were then fed a mixed meal over a ten-minute period. Net hepatic glucose and lactate balance were monitored for the next eight hours using the A-V difference technique. The arterial plasma glucose level rose to a maximum of 121 +/- 3 mg/dL three hours after feeding and then decreased. Net hepatic glucose output declined to 0.44 +/- 0.44 mg/kg/min but the liver never became a net consumer of glucose. The arterial blood lactate level rose from 678 +/- 71 to 1000 +/- 158 mumol/L as the liver switched from net lactate uptake (12.2 +/- 2.0 mumol/kg/min) to net lactate production (4.3 +/- 1.7 mumol/kg/min). Over the course of the eight-hour postprandial period 25 g of glycogen were deposited in the liver. The net hepatic uptake of the gluconeogenic amino acids rose from 6.1 +/- 1.2 mumol/kg/min to a peak of 15.4 +/- 4.3 mumol/kg/min one hour after feeding. Net hepatic uptake of glycerol fell from 3.0 +/- 0.3 mumol/kg/min to an average of 1.5 +/- 0.4 mumol/kg/min. The plasma insulin level increased from 13 +/- 2 microU/mL at 3.5 hours and fell to 32 +/- 7 microU/mL by 8 hours. The plasma glucagon level rose from 22 +/- 3 pg/mL to 93 +/- 12 pg/mL 1.5 hours after feeding and fell to 68 +/- 6 pg/mL 8 hours after feeding.(ABSTRACT TRUNCATED AT 250 WORDS)     

Swim training increases glucose output from liver perfused in situ with glucagon in fed and fasted rats

The effect of endurance swim training (3 hours per day, 5 days/week, for 10 weeks) on hepatic glucose production (HGP) in liver perfused in situ for 60 minutes with glucagon and insulin was studied in Sprague-Dawley rats. The experiments were performed in fed rats and in rats fasted for 24 hours, but with lactate (8 mmol/L) added to the perfusion medium. Liver glycogen content was significantly lower in fasted than fed rats (fasted untrained and trained: 14 +/- 4 and 11 +/- 3 micromol glycosyl U/g of liver wet weight (WW); fed untrained and trained: 205 +/- 11 and 231 +/- 11 micromol glycosyl U/g of liver WW; not significantly different in trained and untrained rats). Glucagon increased HGP in the 4 experimental groups, but the increases were more rapid and pronounced in trained than in untrained rats in both fed and fasted states. HGP values (area under the curve [AUC] in micromol/g of liver WW) were significantly higher in trained fed (112.1 +/- 7.1 v 85.9 +/- 12.2 in untrained rats) than in trained fasted rats (50.8 +/- 4.4 v 34.7 +/- 3.6 in untrained rats). When compared with untrained rats, the total amount of glucose released by the liver in response to glucagon in trained rats was approximately 30% higher in the fed state and approximately 45% larger in the fasted state. These results indicate that endurance training increases the response of both glycogenolysis and gluconeogenesis to glucagon.     

Effects of Aging and Testosterone Administration on Liver Alcohol Dehydrogenase Activity in Male Fischer 344 Rats

The activity of alcohol dehydrogenase was measured in liver cytosolic fractions of male Fischer 344 rats at ages representing young adulthood, middle age, and old age. The activities were 1.7 +/- 0.1, 2.3 +/- 0.1, and 2.6 +/- 0.2 mumol/min/g liver in rats aged 4-5, 14-15, and 24-25 months, respectively. Hepatic alcohol dehydrogenase activity in female rats (3.4 +/- 0.2 mumol/min/g liver) was the same in young as in old rats. Castration increased alcohol dehydrogenase activity in young males to levels found in females, and testosterone administration reversed the effect. However, neither physiological nor pharmacological doses of the hormone restored the elevated enzyme activities of old male rats to levels found in young male rats.     

Glutathione protects the rat liver against reperfusion injury after hypothermic preservation.

BACKGROUND & AIMS: The extracellular generation of reactive oxygen species (ROS) by Kupffer cells contributes to reperfusion injury of the liver allograft. The endogenous antioxidant glutathione (GSH) can detoxify these ROS; however, this effect might be limited by the low extracellular concentration of GSH. We therefore investigated whether an increase of extracellular GSH protects the liver against reperfusion injury after cold preservation. METHODS: Livers of male Sprague-Dawley rats subjected to 24 hours of cold ischemia in University of Wisconsin solution (4 degrees C) were reperfused for 2 hours in the absence (controls) or presence of 0.5, 1, 2, or 4 mmol/L GSH (n = 4-6 each). RESULTS: Two hours after starting reperfusion of control livers, the sinusoidal release of lactate dehydrogenase and purine nucleoside phosphorylase increased to 247 +/- 96 and 27 +/- 13 mU. min(-1). g liver(-1), respectively, but only to 76 +/- 43 and 10 +/- 4 mU. min(-1). g liver(-1) in the presence of 4 mmol/L GSH. This cytoprotective effect was confirmed histologically by a marked reduction of trypan blue staining of hepatocytes. Compared with control livers, postischemic bile flow was significantly enhanced by GSH (0.15 +/- 0.02 vs. 0.41 +/- 0.11 microL. min(-1). g liver(-1)), indicating improved liver function. During reperfusion of control livers, intracellular GSH content declined from 4.5 +/- 0.3 to 2.3 +/- 0.1 micromol/g liver, but only to 3.8 +/- 0.4 micromol/g liver in the presence of 4 mmol/L GSH. Reperfusion of untreated livers was accompanied by a prolonged increase of portal pressure to maximally 12.5 +/- 1.9 cm H2O, which was significantly attenuated by 4 mmol/L GSH (7.2 +/- 1.4 cm H2O). Similar cytoprotective and hemodynamic effects were observed with 2 mmol/L GSH, but not with 0.5 and 1 mmol/L GSH. CONCLUSIONS: Treatment of cold-preserved livers with GSH upon reperfusion prevents damage of hepatocytes, deterioration of the hepatic circulation, and loss of intracellular GSH. In view of these protective effects and its low toxicity in humans, GSH should be considered a candidate drug for prevention of ROS-related reperfusion injury of the liver allograft.     

Inhibition of glucose production and stimulation of bile flow by R (+)-alpha-lipoic acid enantiomer in rat liver

AIMS/BACKGROUND: R (+)-alpha-lipoic acid (RLA) has been suggested for the treatment of liver diseases, but has also been shown to improve glucose utilization in diabetic patients. Because detailed information of RLA action on carbohydrate metabolism in intact liver is lacking, we examined concentration-dependent effects of RLA on hepatic glucose production. METHODS: RLA (10(-6-)10(-3) mol L(-1)) or buffer (control) was infused in isolated livers of fasted rats during recirculating perfusion for 90 min (n = 4-6/group). Hepatic glucose and lactate fluxes and bile secretion were continuously monitored. RESULTS: RLA reduced lactate (10 mmol L(-1))-dependent glucose production in concentration-dependent fashion (R = - 0.780, P < 0.001) by up to 67% compared with control (0.36 +/- 0.02 micromol min(-1) g(-1)). In parallel, RLA dose dependently decreased lactate uptake (R = - 0.592, P < 0.001) also by up to 67% (control: 0.58 +/- 0.08 micromol min(-1) g(-1)). RLA (10(-4) mol L(-1) and 10(-3) mol L(-1)) stimulated bile flow by approximately 20 and approximately 50%, respectively (P < 0.02 vs. control). After 10(-3) mol L(-1) RLA infusion, liver glycogen was approximately 3 fold higher (5.2 +/- 1.1 vs. control: 1.8 +/- 0.2 micromol g(-1), P < 0.002). Also at low lactate concentrations (1 mmol L(-1)), 10(-3) mol L(-1) RLA reduced glucose production by approximately 53% and lactate uptake by approximately 60%, but stimulated bile secretion by approximately 50% (P < 0.05). CONCLUSION: RLA reduces hepatic glucose release by inhibiting lactate-dependent glucose production in a concentration-dependent fashion.     

The effects of carbohydrate variation in isocaloric diets on glycogenolysis and gluconeogenesis in healthy men

To evaluate the effect of dietary carbohydrate content on postabsorptive glucose metabolism, we quantified gluconeogenesis and glycogenolysis after 11 days of high carbohydrate (85% carbohydrate), control (44% carbohydrate), and very low carbohydrate (2% carbohydrate) diets in six healthy men. Diets were eucaloric and provided 15% of energy as protein. Postabsorptive glucose production was measured by infusion of [6,6-2H2]glucose, and fractional gluconeogenesis was measured by ingestion of 2H2O. Postabsorptive glucose production rates were 13.0 +/- 0.7, 11.4 +/- 0.4, and 9.7 +/- 0.4 micromol/kg x min after high carbohydrate, control, and very low carbohydrate diets, respectively (P < 0.001 among the three diets). Gluconeogenesis was about 14% higher after the very low carbohydrate diet (6.3 +/- 0.2 micromol/kg x min; P = 0.001) compared to the control diet, but was not different between the high carbohydrate and control diets (5.5 +/- 0.3 vs. 5.5 +/- 0.2 micromol/kg x min). The rates of glycogenolysis were 7.5 +/- 0.5, 5.9 +/- 0.3, and 3.4 +/- 0.3 micromol/kg x min, respectively (P < 0.001 among the three diets). We conclude that under eucaloric conditions in healthy subjects, dietary carbohydrate content affects the rate of postabsorptive glucose production mainly by modulation of glycogenolysis. In contrast, dietary carbohydrate content affects the postabsorptive rate of gluconeogenesis minimally, as evidenced by only a slight increase in gluconeogenesis during severe carbohydrate restriction.     

Biliary cholesterol and bile acid excretion do not increase in hamsters fed cereal-based diets containing cholesterol

The major compensatory responses to increased cholesterol consumption are decreased cholesterol synthesis and increased cholesterol excretion through the bile either as free cholesterol or bile acids. The objective of this study was to test the hypothesis that biliary cholesterol excretion is increased in hamsters fed low levels of cholesterol reflecting normal human intake. The hypothesis was based on observations that hamsters generally resist changes in bile acid synthesis when fed large amounts of cholesterol; therefore, increased biliary cholesterol excretion represents a potentially significant pathway for elimination of excess cholesterol in this species. Hamsters were fed modified NIH-07 cereal-based diets containing 0.02%, 0.03%, and 0.05% cholesterol (0.04, 0.06, and 0.10 mg cholesterol/kcal, respectively). The primary response to increasing amounts of dietary cholesterol was downregulation of whole-body cholesterol synthesis, reduced from 3.93+/-0.14 micromol x d(-1) x 100 g(-1) body weight in hamsters fed 0.02% cholesterol to 0.52+/-0.14 micromol x d(-1) x 100 g(-1) in the 0.05% cholesterol group. Biliary cholesterol excretion was also slightly reduced in hamsters fed 0.05% cholesterol, whereas bile acid excretion was not altered by dietary cholesterol. Despite a pronounced downregulation of whole-body cholesterol synthesis, liver and plasma cholesterol concentrations increased in hamsters fed 0.05% cholesterol. The data indicate that increased biliary cholesterol excretion is not a major compensatory route of cholesterol excretion in hamsters consuming cholesterol. Furthermore, cholesterol added to the diet at 0.05% appears to be the approximate threshold at which compensatory mechanisms can prevent increases in liver and plasma cholesterol in male Syrian hamsters. Consequently, this species may be an appropriate animal model for "hyperresponding" individuals in the human population.     

大鼠肝组织核因子-κB活性变化与过氧化物酶体增殖物激活受体γ表达的关系

目的 观察不同病因所致的脂肪性肝病大鼠肝组织核因子-κB(NF-κB)的活性变化,过氧化物酶体增殖物激活受体γ(PPAR γ)的表达,及其相互关系在脂肪性肝病炎症反应中的作用。方法40只Wistar 大鼠随机分为正常对照组、酒精组、高脂组和酒精加高脂4组,每组10只大鼠,16周断头处死,用HE、苏丹Ⅳ、Masson三色染色观察肝组织光镜下的病理改变和超微结构的变化。用电泳迁移率分析、逆转录聚合酶链反应观察各组大鼠肝组织NF-κB的活性变化与PPAR γ mRNA的表达、各生物化学指标间的相互关系。 结果 模型组大鼠肝组织均表现有不同程度的脂肪变性、炎症、坏死和纤维化,以酒精加高脂组病理损害最重。酒精组和酒精加高脂组的NF-κB活性(142±16.32,238±19.14)明显高于正常对照组(73±9.24,F值分别为6.36、17.93,P值均<0.01)和单纯高脂组(84±10.38,F值分别为5.96、16.20,P值均<0.01),酒精加高脂组的NF-κB活性显著高于酒精组(F=6.23,P<0.01),而高脂组和正常对照组比较差异无统计学意义。酒精组、高脂组和酒精加高脂组大鼠肝组织PPAR γmRNA的表达(0.2530±0.069,0.3647±0.082,0.1226±0.054)均较正常对照组(0.8097±0.094)有不同程度的减弱(F值分别为15.43、7.24、21.45,P值均<0.01)。相关分析显示:酒精组和酒精加高