Altered renal and platelet arachidonic acid metabolism in cirrhosis

Urinary excretion rates of prostaglandin (PG) E2, PGF2 alpha, 6-keto-PGF1 alpha, and thromboxane (TX) B2 were evaluated in three groups of cirrhotic patients [without ascites (group 1, 13 cases), with ascites and normal renal function (group 2, 15 cases), and with ascites and renal failure (group 3, 5 cases)] and in 14 healthy controls. All urinary arachidonate metabolites were significantly increased in group 2 patients. Patients with renal failure showed lower PGE2, PGF2 alpha, and TXB2 values than those from group 2; PGF2 alpha values were also lower than controls. Platelet TXA2 production during whole blood clotting was significantly reduced in all groups of patients. Administration of low-dose aspirin and sulindac, two cyclooxygenase inhibitors selectively sparing renal cyclooxygenase activity, effectively inhibited platelet TXA2 production without affecting urinary TXB2 excretion, thus ruling out platelets as a possible source of urinary TXB2. We conclude that patients with ascites and normal renal function show an overall activation of the renal PG system. Renal production of vasodilating PGE2 and PGI2 may be involved in supporting renal function in these patients. A reduced platelet synthesis of proaggregatory TXA2 also occurs in cirrhotic patients. This may play a role in the bleeding tendency of cirrhosis.     

Influence of calcium-channel blockers on platelet function and arachidonic acid metabolism

Available data indicate that platelet function and arachidonic acid metabolism are important factors in hemostasis and regulation of vascular tone. Plasma membrane and intracellular mobilization of calcium ions are intimately related to platelet activation and release of platelet contents. Release of arachidonic acid from membrane phospholipids as well as subsequent synthesis and release of vasoconstrictor thromboxane A2 are also regulated by movement of calcium ions. Adenosine 3':5'-cyclic phosphate in turn controls levels of free calcium ions in platelets and regulates calcium-dependent reactions. Slow-channel calcium blockers, such as verapamil, diltiazem and nifedipine, inhibit platelet activation in vitro, and decrease platelet adhesion intravascularly. These agents have also been shown to decrease platelet nucleotide release and thromboxane A2 generation. Some preliminary data suggest that calcium blockers also increase generation of vasodilator and platelet antiaggregant prostacyclin, which could contribute to decrease in platelet function. These effects of calcium blockers on platelet function and arachidonic acid metabolism could contribute in part to their efficacy in patients with ischemic heart disease.     

Platelet arachidonic acid metabolism and platelet function in ten patients with chronic myelogenous leukemia

We have compared the pathways of arachidonic acid (C 20:4) metabolism in platelets from ten patients with Philadelphia chromosome-positive CML with those of seven normal subjects. Platelets were incubated with 3H-arachidonic acid, gel-filtered, and treated with thrombin (5 U/ml). The cyclooxygenase and lipoxygenase-derived products and free arachidonic acid released from the platelets were separated by high pressure liquid chromatography and their radioactivity determined. The total uptake of 3H-C 20:4 by platelets from CML patients did not differ from controls, but the release of radioactivity in response to thrombin was significantly lower (p < 0.01) in CML patients (32.3% +/- 4.9% of total radioactivity was released from control platelets; 19.0% +/- 7.4% from CML platelets). Both cyclooxygenase and lipoxygenase-derived products were reduced, but there was no specific pattern of abnormality. Although there was no direct correlation between either the WBC or platelet count and impairment of platelet C 20:4 metabolism, the platelets from three patients with accelerated disease released the lowest total amount of 3H-C 20:4 metabolites. In a single patient, studied before and after successful chemotherapy (hydroxyurea), severe abnormalities in platelet arachidonic acid metabolism returned to normal after treatment.     

Altered bile acid metabolism in primary biliary cirrhosis

Selected aspects of bile acid metabolism were assessed in six women with primary biliary cirrhosis and varying degrees of cholestasis. Urinary bile acid excretion was markedly increased and correlated highly with serum levels. In three patients in whom urinary bile acids were separated by chromatography, the majority of urinary bile acids were monosulfated (34%, 42%, 32%) or polysulfated and/or glucuronidated (30%, 20%, 38%). The monosulfates of chenodeoxycholic acid were conjugated at either the 3 position (67%, 68%, 73%) or the 7 position (33%, 32%, 27%); similarly, the monosulfates of cholic acid were conjugated at the 3 position (65%, 58%, 68%) or the 7 position (35%, 42%, 32%). The position of sulfation was not markedly influenced by the mode of amidation with glycine or taurine. Chenodeoxycholic exchangeable pool size, turnover rate, and synthesis were measured by isotope dilution and found to be well within normal limits, despite the cholestasis. The fraction of chenodeoxycholic acid synthesis excreted in urine ranged from 9 to 48%; 4–38% of chenodeoxycholic acid synthesis was sulfated. These data indicate that the major abnormalities in bile acid metabolism in patients with cholestasis secondary to primary biliary cirrhosis are formation of sulfated bile acids in greatly increased amounts, elevation of blood levels of primary bile acids, and a shift to renal excretion as a major mechanism for bile acid elimination. Chenodeoxycholic acid synthesis continues at its usual rate despite cholestasis. Whether these changes, including the formation of 7-monosulfated bile acids, occur in other forms of cholestasis and whether either the persistance of unchanged chenodeoxycholic acid synthesis or the formation of such novel conjugates has any pathophysiological significance remain to be investigated.Supported by NIH grant AM 21506 to the University of California and grant RR 00585 and NIH grants AM 19448 and AM 16770 to the Mayo Clinic and Mayo Foundation. In addition, research at the University of California was supported by grants-in-aid from the Rorer Company, the Eli Lilly Company, and the Canada Packers Limited Company.     

肝硬化与肺功能异常的关系

目的:了解肝硬化患者肺功能异常与肝病之间的关系.方法:选取2007-05/2008-03我院及中山大学附属第一医院住院肝硬化患者50例.肺功能检测患者第一秒用力呼气量(FEV1)、一秒率(FEV1/FVC),单次呼吸法检测肺一氧化碳弥散量(DLCO)、比弥散量(KCO,即单位肺泡的DLCO).将肝硬化患者分别按患者肝掌、蜘蛛痣、显性黄疸、白蛋白减低、脾亢、门静脉增宽等的异常与否分成阳性组(+)和阴性组(-),比较组间FEV1、FEV1/FVC、DLCO、KCO均值的差异.结果:约34%患者出现通气功能障碍,以限制性通气为主:有72%的患者出现弥散功能减退,为最主要的肺功能改变.Child-Pugh积分与KCO呈负相关(r=-0.351,P<0.05);白蛋白水平与FEV1、KCO呈正相关(r=0.334,0.336,均P<0.05);门静脉宽度与FEV1、DLCO呈负相关(r=-0.389,-0.417,均P<0.05);脾厚度与DLCO、KCO呈负相关(r=-0.644,-0.536,均P<0.01).血红蛋白浓度和脾脏厚度是DLCO的独立预测因子(P<0.05).结论:弥散障碍在肝硬化患者中发生率较高,门静脉高压的长期作用与之有密切关系.     

Altered lipid metabolism in preeclampsia and HELLP syndrome: links to enhanced platelet reactivity and fetal growth

Normal pregnancy is a physiological condition of balanced hypercoagulability. However, in preeclamptic pregnancies, the coagulation and fibrinolytic cascades are highly activated, accompanied by pathological blood rheology and endothelial dysfunction. This may result in disseminated intravascular coagulation (DIC). Atherosclerosis research showed that lipids may interfere with coagulation and cause endothelial dysfunction. Therefore, we analyzed the lipoprotein distribution and platelet counts in uncomplicated preeclamptic and HELLP syndrome pregnancies. In addition, a correlation between the fetal circulation determined by Doppler velocimetry and the maternal lipid metabolism was investigated. Fasting serum was collected from 24 women in the third trimester of uncomplicated pregnancies, 9 women with severe preeclampsia, and 6 women with HELLP syndrome. Cholesterol (CH), triglycerides (TGs), and apolipoproteins were analyzed in serum and in very-low-density (VLDL), intermediate-density (IDL), low-density (LDL), and high-density (HDL) lipoproteins separated by ultra-centrifugation. Compared with normal pregnancies, TGs in serum, VLDL, IDL, LDL, and HDL were significantly increased in preeclampsia; no difference in CH concentrations was observed. During HELLP syndrome, IDL-TGs were increased compared with normal pregnancies. There was no clear correlation between fetal hemodynamics and maternal lipid metabolism, but there was a significant negative correlation between maternal platelet counts and serum TG levels. Because TG-rich particles may play an important role in thrombin generation and may induce platelet aggregation, the observed changes in lipoprotein metabolism in preeclampsia and HELLP syndrome may contribute to the coagulopathy seen in these conditions.     

Role of arachidonic acid metabolism in human platelet activation and irreversible aggregation

Previous studies from our laboratory have demonstrated that the aggregation response of platelets inhibited by agents blocking cyclooxygenase activity could be restored to a normal state of sensitivity by prior stimulation of alpha-adrenergic receptors. Since cyclooxygenase activity and thromboxane synthesis are not absolutely required for irreversible platelet aggregation, it is important to define precisely what role this pathway serves in platelet physiology. The present study has evaluated the influence of agents that selectively block arachidonic acid conversion at different steps of synthesis. Inhibition of peroxidase, cyclooxygenase, lipoxygenase, and thromboxane synthetase blocked the second wave response of platelets to several agonists, but did not cause dissociation of aggregates preformed by prior exposure to arachidonate (AA) or adenosine diphosphate. Phospholipase (A2/C) inhibitors, similar to prostaglandin inhibitors, blocked the second wave response of platelets to the action of agonists and, in addition, caused dissociation of aggregates induced by aggregating agents. Results of our study demonstrate that when single agonists are tested at threshold concentrations, products of arachidonate metabolism may play a role in the activation process. However, continued generation of these metabolites does not appear to be essential for the maintenance of irreversible aggregation. When a combination of agents or high concentration of physiological agonists are used, both activation and irreversible aggregation can be secured independent of prostaglandin synthesis or the release reaction.     

Renal function and cognitive impairment in patients with liver cirrhosis

Objective. Cognitive impairment is a common problem in patients with liver cirrhosis. Its pathogenesis is multifactorial and ammonia is considered to play a central role. Renal function has been shown to be important for ammonia metabolism in cirrhosis. Although renal dysfunction is common in cirrhotic patients, its effect on cognitive function is largely unexplored. Material and methods. A total of 128 consecutive cirrhotic patients were prospectively evaluated for the presence of cognitive dysfunction according to the West-Haven criteria and by means of two psychometric tests. Serum creatinine, sodium and potassium as well as plasma ammonia concentrations were assessed. Glomerular filtration rate was also measured by ⁵¹Cr- EDTA clearance in a subgroup of patients. Results. Forty-one patients (32%) were found to have cognitive dysfunction (clinical evaluation and/or psychometric tests). Sixteen patients (13%) found with serum creatinine levels above reference values had cognitive dysfunction more frequently than patients with creatinine within the normal range (69% versus 31%; p=0.001), but did not differ in aetiology or severity of cirrhosis (p>0.1). Patients with loop diuretics versus without did not differ in creatinine values (p>0.1). Multivariate analysis showed that cognitive dysfunction was related to hospital admission at inclusion in the study, international normalized ratio and serum creatinine (p<0.05 for all), but not to potassium or sodium levels. Plasma ammonia concentration was related to serum creatinine (r=0.26, p=0.004) and the glomerular filtration rate (r=?0.44, p=0.023). Conclusions. Renal dysfunction seems to be related to cognitive impairment in patients with liver cirrhosis and might be implicated in the pathogenesis of hepatic encephalopathy.     

Renal function and cognitive impairment in patients with liver cirrhosis

OBJECTIVE: Cognitive impairment is a common problem in patients with liver cirrhosis. Its pathogenesis is multifactorial and ammonia is considered to play a central role. Renal function has been shown to be important for ammonia metabolism in cirrhosis. Although renal dysfunction is common in cirrhotic patients, its effect on cognitive function is largely unexplored. MATERIAL AND METHODS: A total of 128 consecutive cirrhotic patients were prospectively evaluated for the presence of cognitive dysfunction according to the West-Haven criteria and by means of two psychometric tests. Serum creatinine, sodium and potassium as well as plasma ammonia concentrations were assessed. Glomerular filtration rate was also measured by (51)Cr- EDTA clearance in a subgroup of patients. RESULTS: Forty-one patients (32%) were found to have cognitive dysfunction (clinical evaluation and/or psychometric tests). Sixteen patients (13%) found with serum creatinine levels above reference values had cognitive dysfunction more frequently than patients with creatinine within the normal range (69% versus 31%; p = 0.001), but did not differ in aetiology or severity of cirrhosis (p >0.1). Patients with loop diuretics versus without did not differ in creatinine values (p >0.1). Multivariate analysis showed that cognitive dysfunction was related to hospital admission at inclusion in the study, international normalized ratio and serum creatinine (p <0.05 for all), but not to potassium or sodium levels. Plasma ammonia concentration was related to serum creatinine (r = 0.26, p = 0.004) and the glomerular filtration rate (r = -0.44, p = 0.023). CONCLUSIONS: Renal dysfunction seems to be related to cognitive impairment in patients with liver cirrhosis and might be implicated in the pathogenesis of hepatic encephalopathy.     

The influence of albumin and calcium on human platelet arachidonic acid metabolism

The effects of in vitro changes in calcium and albumin on human platelet arachidonic acid metabolism were evaluated. Hypoalbuminemia enhanced the conversion of released 14C-arachidonic acid from prelabeled platelet phospholipids to the metabolites of the platelet cyclooxygenase and lipoxygenase pathways. This effect was, however, associated with a decreased release of arachidonic acid in the presence of hypoalbuminemia, such that the overall conversion of released 14C- arachidonic acid to platelet thromboxane B2 was similar in the presence of physiologic albumin concentration (3.5 g/dl) or at decreased albumin concentrations of 0.7 and 0.0 g/dl. External calcium was shown to be important for optimal platelet arachidonic acid release, with maximal release occurring at 1 mM calcium.     

Platelet function abnormalities in response to arachidonic acid in the acute phase of myocardial infarction

The aggregation of platelets to arachidonic acid was studied serially in patients admitted to the hospital with suspected acute myocardial infarction (MI) and no history of platelet-altering drug ingestion. Of 17 patients studied within the first 48 hours after MI, 16 had a marked decrease in aggregation, to 0.5 mM arachidonic acid (15 +/- 12% compared with 64 +/- 15% for control subjects, p less than 0.01). The exception was a patient with documented coronary artery spasm who was receiving nifedipine at the time of MI. He had a delayed but normal final percent aggregation. The aggregation response returned to normal at 2 to 4 days and was slightly above normal at 6 to 10 days (change not statistically significant). Thromboxane B2 formation correlated with the response of patients' platelets to arachidonic acid (38 +/- 15 ng in the low responders versus 161 +/- 30 ng/3 X 10(8) platelets/4 min in the normal responders, p less than 0.05). Low responding platelets after washing had normal adenosine diphosphate and adenosine triphosphate contents and aggregated and formed thromboxane B2 normally with arachidonic acid. The plasma of patients with MI was found to inhibit platelet aggregation and thromboxane B2 formation to arachidonic acid.     

肝硬化患者体表胃电图参数与肝功能损害程度的相关性研究

探讨肝硬化患者体表胃电图参数变化与肝功能及检验指标间的关系。对63例肝硬化患者和20例健康志愿者进行体表胃电图记录和化验检查。将健康对照组、Child-pugh分级A级、B级、C级四级受试者进行两两比较,主频和胃电节律紊乱百分比均有显著差异;胃电节律紊乱百分比与肝功能检验指标进行相关性分析,发现白蛋白和血小板计数与胃电节律紊乱百分比存在直线负相关关系(r分别为-0.723和-0.704)。1.肝硬化患者存在明显胃电节律紊乱,并随肝功能损害程度加重而加重;2.白蛋白和血小板计数与肝硬化患者胃电节律紊乱关系密切,可用于判断肝硬化患者胃动力障碍情况。     

Transcellular metabolism of arachidonic acid: increased platelet thromboxane generation in the presence of activated polymorphonuclear leukocytes.

Human polymorphonuclear leukocytes (PMN) activated by n-formyl-methionyl-leucyl-phenylalanine (fMLP), in the presence of cytochalasin B, are able to induce activation of coincubated autologous platelets "via" cathepsin G released from the azurophilic granules. However, thromboxane (Tx) B2 production in this system cannot be completely explained by cathepsin G-stimulated platelet arachidonate metabolism. Indeed, the amount of TxB2 found in supernatants of platelet/PMN suspensions challenged with 1 mumol/L fMLP was twofold to fourfold higher than that measured when platelets were stimulated by supernatants from fMLP-activated PMN. In the present report, we analyzed the possibility that PMN-induced TxB2 production in this system is the result of transcellular metabolism of arachidonic acid (AA) between fMLP-activated PMN and cathepsin G-stimulated platelets. 3H-AA-labeled PMN were used to test if a transfer of AA or metabolite(s) occur from PMN to platelets. Our results showed that: (1) 3H-TxB2 and 3H-12-HHT are synthesized when 3H-AA-labeled PMN are activated mixed to unlabeled platelets; (2) total radioactivity released by fMLP-stimulated PMN is increased in the presence of platelets, whereas the membrane content of unesterified 3H-AA is reduced; (3) platelet cyclooxygenase inhibition completely prevents 3H-TxB2 synthesis; and (4) inhibition of cathepsin G-induced platelet activation with the antiprotease eglin C blocks the formation of 3H-TxB2. These data show that in the experimental system used, platelets use PMN-derived unmetabolized AA to synthesize TxB2.     

Plasma amino acid response to protein ingestion in patients with liver cirrhosis

The metabolic effects of a protein-rich meal were studied for 3 h in 10 controls and in 20 cirrhotic patients. After protein ingestion, blood glucose did not vary significantly. Insulin and glucagon levels rose in controls and, more markedly, in cirrhotics. Aromatic amino acids and tryptophan increased more in cirrhotics as a result of their decreased liver function. Similarly, branched-chain amino acids increased by 153 +/- 14 nmol/ml X min (mean +/- SE) in controls and by 259 +/- 27 nmol/ml X min in cirrhotics (p less than 0.02), in the presence of a markedly increased insulin response. Branched-chain amino acid metabolism mainly occurs in skeletal muscle under insulin control; in cirrhosis, it might be reduced as a consequence of insulin resistance. To support this hypothesis, the effects of the protein meal were compared with those of an oral glucose load in 15 cirrhotic patients. Branched-chain amino acid response to protein ingestion significantly correlated with blood glucose response to oral glucose (r = 0.714), and with insulin resistance during the glucose tolerance test, when assessed by the insulinogenic index (r = 0.628). Similarly, in 8 patients, increased branched-chain amino acid response also correlated with the index of tissue sensitivity to insulin obtained by means of the glucose clamp technique during continuous insulin infusion (r = -0.809). We conclude that liver cirrhosis is characterized by an abnormal branched-chain amino acid response to protein ingestion, which matches the well-known intolerance to oral glucose. Both alterations are possibly due to decreased peripheral insulin activity on substrates.     

Effect of ursodeoxycholic acid (UDCA) therapy for compensatory liver cirrhosis on liver function tests and serum bile acid metabolism]

Effect of ursodeoxycholic acid (600 mg/day 12 weeks) on liver function tests and bile acid metabolism were investigated in 6 patients with compensatory liver cirrhosis (CLC) and 6 with chronic active hepatitis (CAH). Serial determination of serum GOT, GPT and gamma-GTP after the initiation of UDCA revealed significant reduction in mean levels of these enzymes after 4 weeks, and further improvement was observed at the end of the 12-weeks treatment regimen (CLC: 79.3%, 81.1%, 51.5% of initial values, respectively, CAH: 61.2%, 59.3%, 42.8%). On the other hand, after UDCA administration, serum total bile acid increased and UDCA became the predominant bile acid in CLC and CAH patients. Other endogenous bile acids decreased in both groups, but reduction rate of serum chenodeoxycholic acid level in CLC was smaller than that in CAH group (CLC: 86.1% of initial values, respectively, CAH: 54.2%). During UDCA treatment, apparent side effect was not observed. We suggest that UDCA administration might constitute effective treatment for compensatory liver cirrhosis as well as chronic hepatitis.     

Abnormal polyunsaturated fatty acid patterns of serum lipids in alcoholism and cirrhosis: arachidonic acid deficiency in cirrhosis.

Patterns of polyunsaturated fatty acids of serum phospholipids were measured for groups of alcoholics without cirrhosis, alcoholics with cirrhosis, cirrhotics without alcoholism, and a control population. Alcoholics without cirrhosis showed increased polyunsaturated fatty acids derived from linoleic and linolenic acids, but in cirrhotics these products were decreased. Alcoholism accentuated the abnormal polyunsaturated fatty acid pattern of cirrhosis. In alcohol abuse without cirrhosis, the level of 20:3 omega 9 (20 acyl carbon atoms:3 double bonds, omega, 9 carbon atoms beyond last double bond) was significantly increased, despite adequate levels of linoleic and arachidonic acids. Liver involvement appears necessary for development of deficiencies of polyunsaturated fatty acids in serum phospholipids, of which arachidonic acid deficiency is of the largest magnitude.     

Androgen metabolism in cirrhosis of the liver

Androgen metabolism was studied in male patients with cirrhosis of the liver. The plasma level, metabolic clearance, and production rates of testosterone were decreased while the conversion ratio and rate transport constant of testosterone to androstenedione was increased. Administration of testosterone produced a marked increase in the metabolic clearance rate of testosterone indicating that parenchymal hepatic dysfunction per se was not the cause for the reduced clearance rate. Moreover, the patients were found to have normal testicular reserve for the biosynthesis of testosterone as indicated by an almost fourfold increase in the plasma concentration of testosterone following the administration of human chorionic gonadotropin. These data demonstrate that the reduced production rate of testosterone in male cirrhotics is not due primarily to testicular disease but possibly reflects hypothalamic-pituitary suppression secondary to increased circulating estrogens. The increase in the rate of conversion of testosterone to androstenedione, found in the present study, is consistent with this hypothesis. The present investigation thus provides quantitative data on the hypogonadal state in cirrhosis and suggests possible mechanisms for the alteration in androgen metabolism.