Correction of metabolic changes in liver of tumor-bearing mice following curative resection

The hepatic contents of free coenzyme A, acetyl CoA, citrate, and α-oxoglutarate were determined in mice bearing a subcutaneous transplantable C₃H mammary tumor which remained localized. The free CoA and acetyl CoA content of these livers showed significant decreases. A curative resection reverted these changes to normal, but where the resection was unsuccessful, changes in the hepatic content of these metabolites again occurred. Mean spleen weights in animals bearing the tumor were significantly increased, but returned to normal following curative resection. Mean thymus weights did not alter in mice bearing the tumor when the mean weight was 0.55 ± 0.11 (SEM) g, but a sham operation on normal mice induced thymic atrophy, and significant decreases in the hepatic content of citrate. It is suggested that changes in the hepatic contents of free CoA and acetyl CoA in mice bearing this tumor are induced by some product of tumor origin.     

The Effect of Regular Exercise on Development of Sarcoma Tumor and Oxidative Damage in Mice Liver

Regular exercise has the capability of decreasing the incidence and progress of certain cancers. Murine sarcoma, (S-180) cells were transplanted to control (TC), exercise trained (10 week, 1 hour day, 5 times/ week) mice, which had the swimming training terminated at the time of transplantation (ETT), and also to a group of mice that continued to exercise during tumor bearing (ETC). Continuous exercise decreased the size of tumor by about 50%. The accumulation of reactive carbonyl groups (RCD), were not significantly different for any group. The oxidative modification of proteins in the liver of the animals decreased in the exercise- trained non-tumor bearing group compared with control or tumor-bearing groups. No significant alteration was detected in the level of mutant p53. The data indicate that regular exercise retards the development of sarcoma solid tumors and it seems unlikely that massive uncompensated oxidative stress takes place in the tumor.

Key points

• Regular exercise has a capability to reduce the inci-dence and progress of certain cancers.
• Free radicals could act as a promoters and suppres-sors of cancers.
• Exercise can suppress the development of Sarcoma, but the underlying mechanisms are not known.

Key words: Exercise, cancer, oxidative stress, DNA damage, reactive carbonyl derivatives     

Hepatic metastasis alters the immune function of murine liver nonparenchymal cells.

To examine the effect of a single hepatic focus of metastatic colon tumor on the immune function of liver non-parenchymal cells (NPCs) from C57Bl/6 mice, we injected 2.5 x 10(5) liver-derived murine colon adenocarcinoma (LD-MCA-38) cells beneath the liver capsule. Three weeks following injection of the tumor cells, the immune function of the NPCs was studied. The NPCs from tumor-bearing mice exhibited increased cytotoxic and proliferative activity. The NPCs from tumor-bearing mice also contained a greater percentage of CD8+ and T-cell receptor gamma/delta+ liver-associated T lymphocytes. Levels of interleukin 6 and tumor necrosis factor were increased in the NPC supernatant, and interleukin 6 levels were increased in serum from tumor-bearing mice. We conclude that the presence of a single hepatic focus of metastatic tumor results in augmented immune function of murine liver NPCs.     

Prostate epithelial cells utilize glucose and aspartate as the carbon sources for net citrate production

The prostate gland (human, rat ventral prostate) has the major function of accumulating and secreting extremely high levels of citrate. This function requires unique and specialized metabolic pathways associated with prostate secretory epithelial cells by which exogenous substrates must be utilized as the six-carbon sources of citrate. Recent studies demonstrated that aspartate can serve as the four-carbon source of oxalacetate for citrate synthesis. Identification of the two-carbon source of acetyl CoA (AcCoA) had not been established. The present study investigated the probability that exogenous glucose, via pyruvate oxidation, is a physiological source of AcCoA for net citrate production by isolated epithelial cells from rat ventral prostate. Under adequate oxygenation, 5 mM glucose in the presence of aspartate plus glutamate markedly stimulated citrate production. Exogenous and endogenous pyruvate also stimulated net citrate production. We propose that glucose via aerobic glycolysis and pyruvate oxidation provides AcCoA, which condenses with oxalacetate obtained from aspartate transamination for citrate synthesis. Prostate epithelial cells do not readily oxidize citrate, which permits accumulation and secretion of the synthesized citrate.     

Transhepatic neutrophil and monocyte activation during clinical liver transplantation

BACKGROUND: During experimental liver transplantation, neutrophil sequestration results in increased oxygen free radical production and correlates inversely with graft viability. Neutrophil activation in clinical liver transplantation is poorly understood. METHODS: We assessed leukocyte sequestration and transhepatic differences of neutrophil and monocyte CD11b expression, neutrophil free radical production, and plasma concentrations of interleukin 6 and interleukin 8 in nine patients during liver transplantation. RESULTS: Significant hepatic neutrophil sequestration occurred during initial graft rewarming with portal blood, after inferior vena cava declamping, and after hepatic artery declamping (all P<0.05). A positive transhepatic difference (i.e., outcoming - ingoing) in CD11b expression of neutrophils was observed after portal vein declamping (51+/-32 relative fluorescence unit [RFU]) and in CD11b expression of monocytes during initial graft rewarming (67+/-86 RFU, both P<0.05). A transcoronary increase in both unstimulated (74+/-80 RFU) and N-formyl-methionyl-leucylphenylalanine-stimulated (112+/-168 RFU) neutrophil free radical production took place after hepatic artery declamping (both P<0.05). A negative transcoronary difference of interleukin 6 occurred during initial graft rewarming (-192+/-176 pg/ml) and a positive difference of interleukin 8 occurred after hepatic artery declamping (17+/-23 pg/ml, both P<0.05). CONCLUSIONS: Hepatic sequestration and transhepatic activation of neutrophils, and hepatic production of interleukin 8 occur during clinical liver transplantation. A splanchnic influx of interleukin 6 occurs to the graft, possibly modulating neutrophil-mediated graft reperfusion injury.     

Complete devascularization of hepatic lobe with nonresectable hepatoma.

Complete dearterialization of the entire liver was carried out in three patients with nonresectable liver cell carcinoma in whom the right or left portal vein had already obstructed due to tumor thrombosis or invasion. Although remittent fever ensued for two to three weeks postoperatively in all patients, hepatic infaction never occurred in the devascularized hepatic lobes. The effect of the treatment on tumorous lesions appeared satisfactory. The results indicated that the tumor-bearing liver can tolerate nearly complete deprivation of hepatic arterial and portal blood in at least one lobe of the liver if it is not simultaneous.     

Differential effects of rosiglitazone on skeletal muscle and liver insulin resistance in A-ZIP/F-1 fatless mice

To determine the role of adipocytes and the tissue-specific nature in the insulin sensitizing action of rosiglitazone, we examined the effects of 3 weeks of rosiglitazone treatment on insulin signaling and action during hyperinsulinemic-euglycemic clamps in awake A-ZIP/F-1 (fatless), fat-transplanted fatless, and wild-type littermate mice. We found that 53 and 66% decreases in insulin-stimulated glucose uptake and insulin receptor substrate (IRS)-1-associated phosphatidylinositol (PI) 3-kinase activity in skeletal muscle of fatless mice were normalized after rosiglitazone treatment. These effects of rosiglitazone treatment were associated with 50% decreases in triglyceride and fatty acyl-CoA contents in the skeletal muscle of rosiglitazone-treated fatless mice. In contrast, rosiglitazone treatment exacerbated hepatic insulin resistance in the fatless mice and did not affect already reduced IRS-2-associated PI 3-kinase activity in liver. The worsening of insulin action in liver was associated with 30% increases in triglyceride and fatty acyl-CoA contents in the liver of rosiglitazone-treated fatless mice. In conclusion, these data support the hypothesis that rosiglitazone treatment enhanced insulin action in skeletal muscle mostly by its ability to repartition fat away from skeletal muscle.     

Hepatic citrate changes in surgical stress

Hepatic citrate changes in rats were studied in relation to the hypocitricemic response to surgical stress. Following surgery, extraction by the liver of citrate from the circulation was markedly and significantly increased. The decrease in the hepatic vein citrate level as a result of surgery was significantly greater than the decrease in the arterial citrate level. No change in liver tissue citrate content was apparent, indicating that this citrate removed from the circulation did not accumulate in the liver. No corresponding changes in glucose, lactate, and pyruvate could be related to the citrate response to surgery. Consequently, the results strongly indicate that the liver is directly involved in the hypocitricemic response to surgery and that an increased uptake and utilization of citrate by liver cells occurs in response to surgical stress. These studies also revealed that a major source of the citrate in the systemic circulation is derived from splanchnic regions contributing to the portal circulation.     

Prolactin specifically increases pyruvate dehydrogenase Elα in rat lateral prostate epithelial cells

Prolactin is an important regulator of prostate citrate production. In rats this regulatory effect of prolactin is specific for lateral prostate, and has no effect on either ventral or dorsal prostate. The mechanisms by which prolactin regulates prostate citrate production have not been elucidated. Two key regulatory enzymes involved in citrate synthesis by prostate epithelial cells are mitochondrial aspartate aminotransferase (mAAT) which provides oxalacetate, and PDH E1α (pyruvate dehydrogenase) which provides acetyl CoA for citrate synthesis. Our previous studies demonstrated that prolactin regulates mAAT. However, an increase in citrate synthesis would require an increase in both oxalacetate and acetyl CoA. Therefore, we investigated the possibility that prolactin might also regulate PDH E1α in LP epithelial cells. The present studies demonstrate that prolactin administration (1 mg/rat) to rats resulted in an increased level of E1α in LP epithelial cells within 6 hr, but had no effect on the E1α level of VP epithelial cells. In vitro studies demonstrated that exposure of freshly prepared LP epithelial cells to prolactin (0.1–1.0 μg/ml) resulted in increased levels of E1α. Prolactin had no effect on either VP or DP epithelial cells. The stimulatory effect of prolactin on E1α was inhibited by actinomycin and cycloheximide, thereby indicating that prolactin stimulated the biosynthesis of E1α. The studies reveal that prolactin specifically stimulates E1α levels of LP epithelial cells, whereas testosterone specifically stimulates E1α levels of VP epithelial cells. At this time, we propose that the effects of prolactin and testosterone involve increased expression of the E1α gene of LP and VP epithelial cells, respectively.     

The role of the spleen in tumor bearing host: I. Characterization of spleen cells in tumor-bearing mice

Morphologic changes of the spleen and dynamic changes of biologic activity of spleen cells from C₃H/HeJ mice bearing methylcholanthrene induced fibrosarcoma (MCA-F) were investigated in different stages of tumor growth, using local adoptive transfer assay (LATA). The spleen size, weight and the number of spleen cells increased with the tumor growth. In early and late stages of tumor growth, tumor-bearing mice possessed non-specific tumor-enhancing cells which were radioresistant (700 rads), phagocytic and adherent, suggesting that they were macrophages. On the other hand, in middle stages of tumorgenesis, tumor-bearing mice possessed specific cytotosic cells which were radiosensitive (700 rads) and anti-Thy 1.2 serum positive, suggesting that they were T-cells. Thus, the appearance of tumor-enhancing cells was earlier than cytotoxic cells in MCA-F bearing host, and the balance of tumor-enhancing and cytotoxic cells may influence the tumor outgrowth in different stages of tumorgenesis. The spleen serves as a reservoir of factors which either abrogate cell mediated resistance or stimulate neoplastic growth, or as the source of cytotoxic cells, at certain times of tumor burden.     

Protein synthesis in the tumor-influenced hepatocyte

Total body protein turnover is elevated in the Fischer 344 rat bearing a subcutaneous transplantable methylcholanthrene-induced sarcoma. To assess the contribution of the liver, we have measured protein synthesis by hepatocytes freshly isolated from tumor-bearing animals over a range of tumor burdens and from sham-inoculated nontumor bearers. Synthetic rates of total hepatocyte protein were more than twofold greater in hepatocytes from tumor-bearing animals (P less than 0.005) and the increase was proportional to the tumor burden in individual animals (n = 19; r = 0.68; p less than 0.005). When compared with pair-fed nontumor bearers, the differences in rates of total hepatocyte protein synthesis reached statistical significance only when the tumor burden exceeded 5% of total body weight. The stimulation in synthetic rates applied equally to secretory and nonsecretory hepatocyte protein. Furthermore, a lack of net protein accrual in the livers of tumor-bearing animals suggests a concomitant increase in the rate of hepatic protein degradation.     

持续低温氧合机械灌注对小鼠心脏死亡器官捐献供肝的保护作用

目的研究体外持续低温氧合机械灌注对小鼠心脏死亡器官捐献(donation after cardiac death,DCD)供肝的保护作用。方法雄性ICR小鼠根据灌注保存方式不同分为新鲜供肝低温保存组(FC组)、DCD供肝低温保存组(DC组)和DCD供肝低温氧合机械灌注组(DP组),每组6只。低温灌注保存供肝6h后,收集保存过供肝的威斯康星大学保存液(University of Wisconsin solution,UW液),检测丙氨酸转氨酶(ALT)和天冬氨酸转氨酶(AST)水平。收集3组小鼠肝组织,切片,行常规苏木素-伊红(HE)染色,在光学显微镜下观察病理改变,用原位末端脱氧核苷酸转移酶标记法介导的dUTP缺口末端标记(terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling,TUNEL)法观察3组小鼠肝细胞凋亡情况。结果保存6h后,DC组与DP组的UW液中的ALT、AST含量均明显高于FC组(均为P<0.01);DP组的ALT和AST含量均明显低于DC组(均为P<0.01)。光学显微镜下,FC组未见明显坏死区域,DC组肝细胞损伤严重,DP组肝组织未见明显损伤及坏死。荧光显微镜下,FC、DP两组肝细胞凋亡程度轻微,DC组肝细胞形态极不规则,肝细胞坏死严重。结论持续低温氧合机械灌注可减轻肝细胞损伤和凋亡,为DCD肝移植的器官保存研究提供了新的方法。     

Hepatic immunopotentiation by galactose-entrapped liposomal IL-2 compound in the treatment of liver metastases

To activate hepatic sinusoidal lymphocytes (HSL) and increase the local antitumor activity in the liver, we developed a liver-targeted interleukin-2 (IL-2) compound using a galactose residue-entrapped liposome. We prepared various kinds of IL-2-containing liposomes made by the hydration of powdered dimyristoyl-phosphatidylcholine with aqueous recombinant IL-2 followed by the combination with galactose residues to facilitate the selective uptake by liver parenchymal cells bearing galactose receptors. The IL-2 liposomes were given to C3H/He mice followed by the determination of: (1) organ distribution by¹²⁵I-labeled IL-2, (2) antitumor activity of hepatic sinusoidal lymphocytes by⁵¹Cr-release assay, and (3) in vivo antitumor efficacy by the measurement of hepatic metastases. When galactose-entrapped IL-2 liposomes (Gallip-IL-2) were administered, a significantly greater hepatic accumulation of IL-2 was seen for up to 2 weeks compared to IL-2 liposomes or free IL-2. According to these results, the antitumor activity of HSL was significantly augmented. Moreover, when mice with hepatic micrometastases were treated with Gal-lip-IL-2, the area of hepatic metastases was significantly reduced. These findings thus indicate that Gal-lip-IL-2 may enhance the therapeutic efficacy of IL-2 against hepatic metastases and thereby facilitate a more practical daily dosing regimen.     

Hepatic function during xenon anesthesia in pigs

BACKGROUND: Inhalation anesthetics decrease liver perfusion and oxygen consumption by changing the distribution pattern of perfusion between the hepatic artery and the portal vein and by direct effects on liver cells. The effects of xenon on liver perfusion and function have been not investigated until now. METHODS: Fourteen pigs were randomly assigned to two groups to receive either 73-78% xenon or 75% nitrogen in oxygen with additional supplementation of pentobarbital and buprenorphine. Microspheres were used to determine the arterial perfusion of the liver and splanchnic organs. Oxygen contents were measured by catheterization of the portal and a liver vein. Lactate and glucose plasma concentrations were measured in hepatic, mixed venous and arterial blood. Alanine aminotransferase (ALT) and lactate dehydrogenase (LOH) plasma concentrations were measured in arterial blood. Urea production rates were calculated to assess hepatic metabolic function. RESULTS: Significant higher oxygen contents were found in the liver venous blood during xenon anesthesia. No differences were found in any other investigated parameters. CONCLUSION: Higher oxygen content in liver venous blood observed during xenon anesthesia was not induced by changes in hepatic perfusion distribution or by an impairment of liver metabolic capacity. However, it can be explained by similar results known from inhalation anesthesia. Additionally, the effect can be caused by the reduction of plasma catecholamine concentrations during xenon anesthesia.     

Cardiovascular depression secondary to ionic hypocalcemia during hepatic transplantation in humans

Cardiovascular function, serum ionized calcium (Ca+2), and serum citrate were measured intraoperatively in patients (n = 9) undergoing orthotopic hepatic homotransplantation. Serum citrate increased 20-fold (P less than 0.0006) following transfusion of citrated blood products in the absence of a functional liver. Serum ionized calcium decreased (P less than 0.003) with concomitant decreases in cardiac index (P less than 0.005), stroke index (P less than 0.004), and left ventricular stroke work index (P less than 0.001). Hemodynamic depression and ionic hypocalcemia were reversed following the administration of CaCl2. In contrast to patients with normal hepatic function, who may tolerate large amounts of citrated blood, patients with end-stage liver disease demonstrate acute ionic hypocalcemia with concomitant hemodynamic depression when receiving citrated blood products during the course of hepatic transplantation.     

Tricarboxylic Acid Cycle Intermediates in Chronic Renal Failure

In 21 uraemic subjects not yet requiring dialysis, the serumvalues of citrate, fumarate, oxalacetate and malate were significantlyincreased, so that the sum of the concentrations of the TCA-cycleintermediates were increased threefold compared to that of 18control subjects. The replenishment of TCA intermediates could, in theory, occurby several anaplerotic reactions, mainly those catalysed bypyruvate-carboxylase and malic enzyme. The overall pattern detectedin uraemic patients is similar to that observed in rat skeletalmuscle during exercise, in which increased acetyl CoA has beenfound.     

Metformin prevents the development of acute lipid-induced insulin resistance in the rat through altered hepatic signaling mechanisms

Metformin reduces the incidence of progression to type 2 diabetes in humans with obesity or impaired glucose tolerance. We used an animal model to investigate whether metformin could prevent acute lipid-induced insulin resistance and the mechanisms involved. Metformin or vehicle was administered to rats daily for 1 week. Rats were studied basally, after 3.75 h of intralipid-heparin or glycerol infusion, or after 5 h of infusion with a hyperinsulinemic-euglycemic clamp between 3 and 5 h. Metformin had no effect on plasma triacylglycerol or nonesterified fatty acid concentrations and did not alter glucose turnover or gluconeogenic enzyme mRNA after lipid infusion. However, metformin normalized hepatic glucose output and increased liver glycogen during lipid infusion and clamp. Basal liver (but not muscle or fat) AMP-activated protein kinase activity was increased by metformin (by 310%; P < 0.01), associated with increased phosphorylation of acetyl CoA carboxylase. Postclamp liver but not muscle phosphorylated/total Akt protein was increased, whereas basal c-Jun NH2-terminal kinase-1 and -2 protein expression were reduced (by 39 and 53%, respectively; P < 0.05). Metformin also increased hepatic basal IkappaBalpha levels (by 260%; P < 0.001) but had no effect on tyrosine phosphorylation or expression of insulin receptor substrate-1 (IRS-1). In summary, metformin opposes the development of acute lipid-induced insulin resistance in the liver through alterations in multiple signaling pathways.     

The promotion of liver regeneration in mice after a partial hepatectomy as a result of the modulation of macrophage activation by dexmedetomidine

BackgroundThis study investigates the effect of dexmedetomidine (DEX), a highly selective agonist of alpha 2-adrenergic receptors (α2-ARs), on the regulation of hepatic macrophage activation in liver regeneration.MethodsA two-thirds partial hepatectomy (PHx) mouse model was performed. DEX (25 μg/kg) or a vehicle control (saline) was injected i.p. at 30 min before and every 12 h after PHx. The expression of α2B-ARs in the liver was detected using immunofluorescence staining. The effects of DEX on liver regeneration were assessed by Ki67 staining. The gene expression of inflammatory cytokines in isolated hepatic macrophages was quantified 36 h after the PHx.Resultsα2B-ARs colocalized with hepatic macrophages after the PHx. The number of Ki67-positive hepatocytes in the mice treated with DEX was markedly increased (p < 0.05). The increases in Ki67-positive hepatocytes after treatment with DEX were inhibited in the macrophage-depleted mice. DEX treatment inhibited the expression of major pro-inflammatory cytokines interleukin (IL)-1β, IL-6, and tumor necrosis factor and elevated the expression of anti-inflammatory cytokines IL-4, IL-10, and transforming growth factor-β1 in hepatic macrophages 36 h after the PHx (p < 0.05).ConclusionsThe α2B-AR subtype is expressed in hepatic macrophages after a PHx. DEX modulates hepatic macrophage activation toward an anti-inflammatory phenotype via α2B-AR, which promotes the process of liver regeneration.