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ABSTRACT: BACKGROUND AND AIMS: Studies investigating insulin resistance (IR) in chronic hepatitis C virus (HCV) infection have used surrogate measures of IR that have limited reliability. We aimed to describe the distribution and risk factors associated with IR and its change over time in HCV using direct measurement. METHODS: One hundred two non-cirrhotic, non-diabetic, HCV-infected subjects underwent clinical, histologic, and metabolic evaluation, and 27 completed repeat evaluation at 6 months. Insulin-mediated glucose uptake was measured by steady-state plasma glucose (SSPG) concentration during the insulin suppression test. RESULTS: Three subjects with diabetes were excluded and 95 completed all testing. SSPG ranged from 39 to 328 mg/dL (mean 135 mg/dL) and was stable over time (mean SSPG change -0.3 mg/dL). SSPG was associated with Latino ethnicity (Coef 67, 95 % CI 37-96), BMI (Coef 19 per 5 kg/m(2), 95 % CI 5-32), ferritin (Coef 1.4 per 10 ng/ml, 95 % CI 0.2-2.5), male gender (Coef -48, 95 % CI -80 to -16), and HDL (Coef -16, 95 % CI -28 to -5 mg/dL). Current tobacco use (Coef 55, 95 % CI 19-90), steatosis (Coef -44, 95 % CI -86 to -3), and increases in BMI (Coef 30 per 5 kg/m(2), 95 % CI 6-53) and triglyceride (Coef 3.5 per 10 mg/dL, 95 % CI 0.3-6.7) predicted change in SSPG. CONCLUSIONS: There was a wide spectrum of insulin resistance in our HCV population. Host factors, rather than viral factors, appeared to more greatly influence insulin action and its change in HCV.
Digestive Diseases and Sciences 10/2012; · 2.12 Impact Factor
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ABSTRACT: Insulin resistance, as measured by surrogate markers, is associated with lower response to hepatitis C virus (HCV) therapy and may improve with HCV eradication. We prospectively evaluated the impact of directly measured insulin resistance and abnormal glucose metabolism on achieving sustained virologic response (SVR) with HCV therapy and assessed whether SVR results in improved insulin sensitivity and fasting glucose.
A total of 50 noncirrhotic, nondiabetic, HCV-infected patients (27 untreated, 23 treated with pegylated interferon/ribavirin, nonrandomized) underwent clinical and histologic evaluation and 75-g oral glucose tolerance test. Insulin sensitivity was assessed directly with insulin suppression test by measuring steady-state plasma glucose (SSPG) concentration during a 240-min infusion of octreotide, glucose, and insulin. Of the subjects, 43 had at least one follow-up evaluation.
Patient characteristics were median age 48, 57% male, and 52% white. SVR was achieved in 61% (14 of 23) of treated subjects. SVR was independently associated with HCV genotypes 2 and 3 (odds ratio 8.8 [95% CI 1.2-61.7]) but was not strongly associated with insulin sensitivity. When controlling for elapsed time between measurements, being on interferon, and BMI, SSPG decreased by 36 mg/dL (-88 to 16) in those with SVR and decreased by 28 mg/dL (-93 to 38) in those without SVR, compared with the untreated group. BMI (coefficient 9.1 per 5 units; 95% CI 5.3-12.9) and interferon use (coefficient 56; 95% CI 6.8-105) were associated with SSPG.
Insulin resistance does not appear to be strongly associated with SVR. HCV therapy may improve insulin resistance regardless of virologic response; however, BMI and interferon use were clearly associated with insulin resistance.
Diabetes care 03/2012; 35(5):1090-4. · 8.09 Impact Factor
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Gastroenterology 11/2011; 142(1):8-11. · 11.68 Impact Factor
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ABSTRACT: Stress signaling, both within and outside the endoplasmic reticulum, has been linked to metabolic dysregulation and hepatic steatosis. Methionine-choline-deficient (MCD) diets cause severe fatty liver disease and have the potential to cause many types of cellular stress. The purpose of this study was to characterize hepatic stress in MCD-fed mice and explore the relationship between MCD-mediated stress and liver injury.
Stress signaling was examined in mice fed MCD formulas for 4-21 days. Signaling also was evaluated in mice fed MCD formulas supplemented with clofibrate, which inhibits hepatic triglyceride accumulation. The role of the pro-apoptotic stress protein C/EBP homologous protein (CHOP) in MCD-mediated liver injury was assessed by comparing the responses of wild-type and CHOP-deficient mice to an MCD diet.
MCD feeding caused steatohepatitis coincident with the activation of cJun N-terminal kinase and caspase-12. In contrast, MCD feeding did not activate inositol-requiring protein-1 and actually suppressed the expression of X-box protein-1s. MCD feeding caused weak stimulation of double-stranded RNA-activated protein kinase-like endoplasmic reticulum-resident kinase, but robust activation of general control nonderepressible-2, followed by the phosphorylation of eukaryotic initiating factor-2α and induction of CHOP. Clofibrate eliminated MCD-mediated hepatic steatosis but did not inhibit diet-induced stress. CHOP deficiency did not alleviate, and in fact worsened, MCD-mediated liver disease.
MCD feeding causes an integrated stress response in the liver rather than a classic unfolded protein response. This stress response does not by itself lead to liver injury. CHOP, despite its identity as a mediator of stress-related cell death, does not play a central role in the pathogenesis of MCD-mediated liver disease.
Gastroenterology 11/2010; 139(5):1730-9, 1739.e1. · 11.68 Impact Factor
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ABSTRACT: Methionine-choline-deficient (MCD) diets cause steatohepatitis in rodents and are used to model fatty liver disease in human beings. Recent studies have identified sucrose as a major contributor to MCD-related liver disease through its ability to promote hepatic de novo lipogenesis.
To determine whether glucose and fructose, the two constitutents of sucrose, differ in their capacity to provoke steatohepatitis when incorporated individually into MCD formulas.
MCD and control formulas prepared with either glucose or fructose as the sole source of carbohydrate were fed to mice for 21 days. Liver injury was assessed biochemically and histologically together with hepatic gene expression and fatty acid analysis.
Mice fed MCD formulas developed similar degrees of hepatic steatosis whether they contained glucose or fructose. By contrast, mice fed MCD-fructose developed significantly more hepatocellular injury than mice fed MCD-glucose, judged by histology, apoptosis staining and serum alanine aminotransferase. Liver injury in MCD-fructose mice coincided with an exaggerated rise in the ratio of long-chain saturated to unsaturated fatty acids in the liver. Notably, hepatic inflammation was not enhanced in mice fed MCD-fructose, correlating instead with hepatic lipid peroxidation, which was equivalent in the two MCD groups.
Fructose is more cytotoxic than glucose when used as the source of carbohydrate in MCD formulas.
The data suggest the enhanced cytotoxicity of fructose in the MCD model is related to its ability to stimulate de novo lipogenesis, which yields harmful long-chain saturated fatty acids.
Liver international: official journal of the International Association for the Study of the Liver 09/2010; 30(8):1229-39. · 3.82 Impact Factor
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ABSTRACT: No concrete, causal, mechanistic theory is available to explain how different hepatic zonation patterns of P450 isozyme levels and hepatotoxicity emerge following dosing with different compounds. We used the synthetic method of modeling and simulation to discover, explore, and experimentally challenge concrete mechanisms that show how and why biomimetic zonation patterns can emerge and change within agent-based analogues, expecting that those mechanisms may have counterparts in rats. Mobile objects map to compounds. One analogue represents a cross-section through a lobule. It is comprised of 460 identical, quasi-autonomous functional units called sinusoidal segments (SSs). SSs detect and respond to compound-generated response signals and the local level of an endogenous gradient. Each SS adapts by using those signals to adjust (or not) the probability that it will clear a detected compound during the next simulation cycle. The adjustment decision is based on the value of a biomimetic algorithm that is based on an assumed, evolution imposed, genetic mandate that normal hepatocytes resist increasing the cost of their actions. The algorithm estimates the long-term, discounted cost to a given SS of continuing to use its current clearance effort. Upon compound exposure, lobular analogues developed a variety of clearance and hepatotoxicity patterns that were strikingly similar to those reported in the literature. A degree of quantitative validation was achieved against data on hepatic zonation of CYP1A2 mRNA expression caused by three different doses of TCDD (2,3,7,8-tetracholorodibenzo-p-dioxone).
Journal of Theoretical Biology 08/2010; 265(4):718-33. · 2.21 Impact Factor
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ABSTRACT: Studies using surrogate estimates show high prevalence of insulin resistance in hepatitis C infection. This study prospectively evaluated the correlation between surrogate and directly measured estimates of insulin resistance and the impact of obesity and ethnicity on this relationship. Eighty-six nondiabetic, noncirrhotic patients with hepatitis C virus (age = 48 +/- 7 years, 74% male, 44% white, 22% African American, 26% Latino, 70% genotype 1) were categorized into normal-weight (body mass index [BMI] < 25, n = 30), overweight (BMI = 25-29.9, n = 38), and obese (BMI > or = 30, n = 18). Insulin-mediated glucose uptake was measured by steady-state plasma glucose (SSPG) concentration during a 240-minute insulin suppression test. Surrogate estimates included: fasting glucose and insulin, glucose/insulin, homeostasis model assessment (HOMA-IR), quantitative insulin sensitivity check index (QUICKI), insulin (I-AUC) and glucose (G-AUC) area under the curve during oral glucose tolerance test, and the Belfiore and Stumvoll indexes. All surrogate estimates correlated with SSPG, but the magnitude of correlation varied (r = 0.30-0.64). The correlation coefficients were highest in the obese. I-AUC had the highest correlation among all ethnic and weight groups (r = 0.57-0.77). HOMA-IR accounted for only 15% of variability in SSPG in the normal weight group. The common HOMA-IR cutoff of < or =3 to define insulin resistance had high misclassification rates especially in the overweight group independent of ethnicity. HOMA-IR > 4 had the lowest misclassification rate (75% sensitivity, 88% specificity). Repeat HOMA-IR measurements had higher within-person variation in the obese (standard deviation = 0.77 higher than normal-weight, 95% confidence interval = 0.25-1.30, P = 0.005). CONCLUSION: Because of limitations of surrogate estimates, caution should be used in interpreting data evaluating insulin resistance especially in nonobese, nondiabetic patients with HCV.
Hepatology 07/2010; 52(1):38-46. · 11.66 Impact Factor
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Jacquelyn J Maher
Gastroenterology 02/2010; 138(4):1244-6. · 11.68 Impact Factor
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ABSTRACT: Methionine-choline-deficient (MCD) diets cause steatohepatitis in rodents and are used to study the pathophysiology of fatty liver disease in human beings. The most widely used commercial MCD formulas not only lack methionine and choline but also contain excess sucrose and fat. The objective of this study was to determine whether dietary sucrose in the MCD formula plays a role in the pathogenesis of MCD-related liver disease. We prepared two custom MCD formulas, one containing sucrose as the principal carbohydrate and the other substituting sucrose with starch. Mice fed the sucrose-enriched formula developed typical features of MCD-related liver disease, including hepatic steatosis, hepatocellular apoptosis, alanine aminotransferase elevation, lipid peroxidation, and hepatic inflammation. In contrast, mice fed MCD-starch were significantly protected against liver injury. MCD-sucrose and MCD-starch mice displayed identical diet-related abnormalities in hepatic fatty acid uptake and triglyceride secretion. Hepatic de novo lipogenesis and triglyceride synthesis, however, were 2 times higher in MCD-sucrose mice than MCD-starch mice (P < 0.01). Hepatic lipid analysis revealed accumulation of excess saturated fatty acids in MCD-sucrose mice that correlated with hepatocellular injury. Overall, the results indicate that dietary sucrose is critical to the pathogenesis of MCD-mediated steatohepatitis. They suggest that saturated fatty acids, which are products of de novo lipogenesis, are mediators of hepatic toxicity in this model of liver disease.
The Journal of Lipid Research 03/2009; 50(10):2072-82. · 5.56 Impact Factor
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Jacquelyn J Maher
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ABSTRACT: The clinical syndrome of acetaminophen-induced liver injury represents the combined result of drug toxicity and a potent innate immune response that follows drug-induced cell death. In this issue of the JCI, Imaeda and colleagues report that DNA released from dying hepatocytes is a key stimulus of innate immune activation in the acetaminophen-treated mouse liver (see the related article beginning on page 305). They present evidence indicating that hepatocyte DNA promotes immune activation by acting as a danger-associated molecular pattern (DAMP) that stimulates cytokine production in neighboring sinusoidal endothelial cells via Tlr9 and the Nalp3 inflammasome.
Journal of Clinical Investigation 03/2009; 119(2):246-9. · 15.39 Impact Factor
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ABSTRACT: Prolonged hepatic warm ischemia during surgery remains a significant problem, particularly in the setting of liver resection and reduced remaining liver mass. The goal of the present study is to evaluate the effect of passive cooling caused by exposure to ambient conditions on hepatic injury in rats during warm ischemia followed by hepatectomy.
The left and median lobes of male rats were exposed to 75 min of ischemia under either normothermic (37 degrees C) or mildly hypothermic (34 degrees C) conditions. After 75 min of ischemia, the right lobe was resected, leaving the animal with only the remaining ischemic lobes. Animals were allowed to survive indefinitely or sacrificed at 4 h after reperfusion for determination of injury and inflammatory gene expression.
Survival was already markedly higher in mildly hypothermic rats than normothermic rats at 24 h. Short passive cooling for the time course of the ischemic event significantly increased the hepatic induction of heat shock proteins 70 and 32 (both 3-fold versus normothermia, P<0.05) in response to ischemia/reperfusion whereas it significantly decreased the induction of tumor necrosis factor-alpha (TNF-alpha) and macrophage inflammatory protein-2 (MIP-2) in the liver. Biochemical markers of hepatic injury were significantly lower in the passive cooling group than in normothermic animals: aspartate aminotransferase (AST) serum concentrations were 9277+/-3461IU/L versus 15106+/-4104IU/L (P<0.01), and alanine aminotransferase (ALT) levels 5986+/-2246IU/L versus 9429+/-3643IU/L (P<0.01).
We demonstrated in a clinically relevant model of hepatic ischemia/reperfusion that mild hypothermia significantly reduces hepatic injury and improves survival.
Journal of Surgical Research 10/2008; 158(1):43-52. · 2.25 Impact Factor
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ABSTRACT: Obesity is an inflammatory disorder characterized by heightened activity of the innate immune system. Innate immune activation is central to the development of obesity-related insulin resistance; it also plays an important role in obesity-related tissue damage, such as that seen in atherosclerosis. Recent research has implicated the innate immune system in the pathophysiology of obesity-related liver disease. This review summarizes how innate immune processes, occurring both within and outside the liver, cause not only insulin resistance but also end-organ damage in the form of nonalcoholic fatty liver disease.
Hepatology 09/2008; 48(2):670-8. · 11.66 Impact Factor
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ABSTRACT: Tryptophan 2,3-dioxygenase (TDO), a liver-specific cytosolic hemoprotein, is the rate-limiting enzyme in L-tryptophan catabolism and thus a key serotonergic determinant. Glucocorticoids transcriptionally activate the TDO gene with marked enzyme induction. TDO is also regulated by heme, its prosthetic moiety, as its expression and function are significantly reduced after acute hepatic heme depletion. Here we show in primary rat hepatocytes that this impairment is not due to faulty transcriptional activation of the TDO gene but rather due to its posttranscriptional regulation by heme. Accordingly, in acutely heme-depleted hepatocytes, the de novo synthesis of TDO protein is markedly decreased (>90%) along with that of other hepatic proteins. This global suppression of de novo hepatic protein syntheses in these heme-depleted cells is associated with a significantly enhanced phosphorylation of the alpha-subunit of the eukaryotic initiation factor eIF2 (eIF2alpha), as monitored by the phosphorylated eIF2alpha/total eIF2alpha ratio. Heme supplementation reversed these effects, indicating that heme regulates TDO induction by functional control of an eIF2alpha kinase. A cDNA was cloned from heme-depleted rat hepatocytes, and DNA sequencing verified its identity to the previously cloned rat brain heme-regulated inhibitor (HRI). Proteomic, biochemical, and/or immunoblotting analyses of the purified recombinant protein and the immunoaffinity-captured hepatic protein confirmed its identity as a rat heme-sensitive eIF2alpha kinase. These findings not only document that a hepatic HRI exists and is physiologically relevant but also implicate its translational shut-off of key proteins in the pathogenesis and symptomatology of the acute hepatic heme-deficient conditions clinically known as the hepatic porphyrias.
Journal of Pharmacology and Experimental Therapeutics 01/2008; 323(3):979-89. · 3.83 Impact Factor
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ABSTRACT: Methionine-choline-deficient (MCD) diets that cause steatohepatitis in rodents are typically enriched in polyunsaturated fat. To determine whether the fat composition of the MCD formula influences the development of liver disease, we manufactured custom MCD formulas with fats ranging in PUFA content from 2% to 59% and tested them for their ability to induce steatohepatitis. All modified-fat MCD formulas caused identical degrees of hepatic steatosis and resulted in a similar distribution of fat within individual hepatic lipid compartments. The fatty acid composition of hepatic lipids, however, reflected the fat composition of the diet. Mice fed a PUFA-rich MCD formula showed extensive hepatic lipid peroxidation, induction of proinflammatory genes, and histologic inflammation. When PUFAs were substituted with more saturated fats, lipid peroxidation, proinflammatory gene induction, and hepatic inflammation all declined significantly. Despite the close relationship between PUFAs and hepatic inflammation in mice fed MCD formulas, dietary fat had no impact on MCD-mediated damage to hepatocytes. Indeed, histologic apoptosis and serum alanine aminotransferase levels were comparable in all MCD-fed mice regardless of dietary fat content. Together, these results indicate that dietary PUFAs promote hepatic inflammation but not hepatotoxicity in the MCD model of liver disease. These findings emphasize that individual dietary nutrients can make specific contributions to steatohepatitis.
The Journal of Lipid Research 09/2007; 48(8):1885-96. · 5.56 Impact Factor
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ABSTRACT: Mammalian hepatic cytochromes P450 (P450s) are endoplasmic reticulum (ER)-anchored hemoproteins engaged in the metabolism of numerous xeno- and endobiotics. P450s exhibit widely ranging half-lives, utilizing both autophagic-lysosomal (ALD) and ubiquitin-dependent 26S proteasomal (UPD) degradation pathways. Although suicidally inactivated hepatic CYPs 3A and "native" CYP3A4 in Saccharomyces cerevisiae are degraded via UPD, the turnover of native hepatic CYPs 3A in their physiological milieu has not been elucidated. Herein, we characterize the degradation of native, dexamethasone-inducible CYPs 3A in cultured primary rat hepatocytes, using proteasomal (MG-132 and MG-262) and ALD [NH4Cl and 3-methyladenine (3-MA)] inhibitors to examine their specific degradation route. Pulse-chase with immunoprecipitation analyses revealed a basal 52% 35S-CYP3A loss over 6 h, which was stabilized by both proteasomal inhibitors. By contrast, no corresponding CYP3A stabilization was detected with either ALD inhibitor NH4Cl or 3-MA. Furthermore, MG-262-induced CYP3A stabilization was associated with its polyubiquitylation, thereby verifying that native CYPs 3A were also degraded via UPD. To identify the specific participants in this process, cellular proteins were cross-linked in situ with paraformaldehyde (PFA) in cultured hepatocytes. Immunoblotting analyses of CYP3A immunoprecipitates after PFA-cross-linking revealed the presence of p97, a cytosolic AAA ATPase instrumental in the extraction and delivery of ubiquitylated ER proteins for proteasomal degradation. Such native CYP3A-p97 interactions were greatly magnified after CYP3A suicidal inactivation (which accelerates UPD), and/or proteasomal inhibition, and were confirmed by proteomic and confocal immunofluorescence microscopic analyses. These findings clearly reveal that native CYPs 3A undergo UPD and implicate a role for p97 in this process.
Biochemistry 08/2007; 46(26):7793-803. · 3.42 Impact Factor
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Jacquelyn J Maher
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ABSTRACT: Alcoholic hepatitis is a disease with a wide range of severity. Patients with severe disease have short-term mortality rates above 35%. In these high-risk patients, pharmacologic therapy is an important adjunct to supportive medical care and has been proved to improve survival. Given the benefit of drug treatment, it is important to identify patients at risk of early mortality from alcoholic hepatitis. A number of validated scoring systems are useful for this purpose, including the Maddrey Discriminant Function, the Model of End-Stage Liver Disease score, and the Glasgow Alcoholic Hepatitis score. Patients judged by one or more of these criteria to have severe alcoholic hepatitis should be treated with corticosteroids or pentoxifylline, provided they have no contraindications for this treatment. Adequate nutrition is also critical and should be provided by tube feeding if necessary. A prompt decline in serum bilirubin indicates a favorable response to therapy. Patients who do not exhibit a reduction in serum bilirubin within 1 week are considered nonresponders and have a 6-month mortality rate of 50% or higher.
Current Gastroenterology Reports 04/2007; 9(1):39-46.
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ABSTRACT: Lipogenic diets that are completely devoid of methionine and choline (MCD) induce hepatic steatosis. MCD feeding also provokes systemic weight loss, for unclear reasons. In this study, we found that MCD feeding causes profound hepatic suppression of the gene encoding stearoyl-coenzyme A desaturase-1 (SCD-1), an enzyme whose regulation has significant effects on metabolic rate. Within 7 days of MCD exposure, hepatic SCD-1 mRNA decreased to nearly undetectable levels. By day 21, SCD-1 protein was absent from hepatic microsomes and fatty acids showed a decrease in monounsaturated species. These changes in hepatic SCD-1 were accompanied by signs of hypermetabolism. Calorimetry revealed that MCD-fed mice consumed 37% more energy than control mice (P = 0.0003). MCD feeding also stimulated fatty acid oxidation, although fatty oxidation genes were not significantly upregulated. Interestingly, despite their increased metabolic rate, MCD-fed mice did not increase their food consumption, and as a result, they lost 26% of their body weight in 21 days. In summary, MCD feeding suppresses SCD-1 in the liver, which likely contributes to hypermetabolism and weight loss. MCD feeding also induces hepatic steatosis, by an independent mechanism. Viewed together, these two disparate consequences of MCD feeding (weight loss and hepatic steatosis) give the appearance of an unusual form of lipodystrophy.
The Journal of Lipid Research 11/2006; 47(10):2280-90. · 5.56 Impact Factor
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ABSTRACT: Obese Zucker rats demonstrate increased susceptibility to hepatic ischemia-reperfusion injury. This study evaluates the effect of mild systemic hypothermia on ischemia-induced acute fulminant necrosis during warm ischemia and reperfusion, and investigates blood metabolic profiles under normothermic and mildly hypothermic conditions.
The left and median hepatic lobes of male, obese, Zucker rats were exposed to 75 minutes of ischemia under either normothermic (36.9 +/- 0.3 degrees C) or mildly hypothermic (33.3 +/- 0.1 degrees C) conditions followed by 8 hours of reperfusion. Animals were killed and tissue and blood were harvested for analysis of histology, liver enzymes, and metabolic 1H-NMR spectroscopy.
Liver enzyme activities were significantly higher in the normothermic group when compared with mildly hypothermic animals. Histologic analysis showed greater than 75% necrosis in the normothermic group, whereas in the mildly hypothermic group necrosis was less than 25%. Blood from normothermic animals contained greater concentrations of lactate (190%, P = .001) and lower concentrations of glucose (60%, P = .01) than hypothermic animals; hepatic osmolyte betaine was also increased in blood from the normothermic group (220%, P = .0002). In addition, normothermic rats had increased concentrations of circulating fatty acids, triglycerides, glutamate, succinate, and acetate when compared with the hypothermic.
Mild hypothermia decreased hepatic necrosis in obese rats. NMR blood profiles indicate that hypothermia protects hepatic metabolism.
Surgery 10/2006; 140(3):404-12. · 3.10 Impact Factor
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ABSTRACT: Alpha-naphthylisothiocyanate (ANIT) is a hepatotoxicant that causes acute cholestatic hepatitis with infiltration of neutrophils around bile ducts and necrotic hepatocytes. The objective of this study was to determine whether the beta2-integrin CD18, which plays an important role in leukocyte invasion and cytotoxicity, contributes to ANIT-induced hepatic inflammation and liver injury. Mice with varying levels of leukocyte CD18 expression were treated with ANIT and monitored for hepatic neutrophil influx and liver injury over 48 h. Mice that were partially deficient in CD18 (30% of normal levels) developed periportal inflammation and widespread hepatic necrosis after ANIT treatment in a pattern identical to that in wild-type (WT) mice. In contrast, mice that completely lack CD18 (CD18 null) were resistant to ANIT toxicity. Forty-eight hours after ANIT, CD18-null mice displayed 60% lower serum alanine aminotransferase (ALT) levels and 75% less hepatic necrosis, as shown by morphometry, than WT mice. This was true despite evidence that ANIT still provoked hepatic neutrophil influx in CD18-null mice. WT mice could also be protected from ANIT-induced hepatocellular necrosis, by depleting the animals of neutrophils. Notably, neither CD18-null mice nor neutrophil-depleted WT mice exhibited any attenuation of bile duct injury or cholestasis due to ANIT. We conclude from these experiments that neutrophils invade ANIT-treated livers in a CD18-independent fashion but utilize CD18 to induce hepatocellular cytotoxicity. The results emphasize that neutrophil-mediated amplification of ANIT-induced liver injury is directed toward hepatocytes rather than cholangiocytes. In fact, the data indicate that the majority of ANIT toxicity toward hepatocytes in vivo is neutrophil driven.
AJP Gastrointestinal and Liver Physiology 09/2006; 291(2):G355-63. · 3.43 Impact Factor
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Betty Y Y Tam,
Kevin Wei,
John S Rudge,
Jana Hoffman,
Joceyln Holash,
Sang-ki Park,
Jenny Yuan,
Colleen Hefner,
Cecile Chartier,
Jeng-Shin Lee, [......],
Lisa Ma,
Uma Sundram,
Grace Wu,
Joseph A Garcia,
Stanley L Schrier, Jacquelyn J Maher,
Randall S Johnson,
George D Yancopoulos,
Richard C Mulligan,
Calvin J Kuo
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ABSTRACT: Vascular endothelial growth factor (VEGF) exerts crucial functions during pathological angiogenesis and normal physiology. We observed increased hematocrit (60-75%) after high-grade inhibition of VEGF by diverse methods, including adenoviral expression of soluble VEGF receptor (VEGFR) ectodomains, recombinant VEGF Trap protein and the VEGFR2-selective antibody DC101. Increased production of red blood cells (erythrocytosis) occurred in both mouse and primate models, and was associated with near-complete neutralization of VEGF corneal micropocket angiogenesis. High-grade inhibition of VEGF induced hepatic synthesis of erythropoietin (Epo, encoded by Epo) >40-fold through a HIF-1alpha-independent mechanism, in parallel with suppression of renal Epo mRNA. Studies using hepatocyte-specific deletion of the Vegfa gene and hepatocyte-endothelial cell cocultures indicated that blockade of VEGF induced hepatic Epo by interfering with homeostatic VEGFR2-dependent paracrine signaling involving interactions between hepatocytes and endothelial cells. These data indicate that VEGF is a previously unsuspected negative regulator of hepatic Epo synthesis and erythropoiesis and suggest that levels of Epo and erythrocytosis could represent noninvasive surrogate markers for stringent blockade of VEGF in vivo.
Nature Medicine 08/2006; 12(7):793-800. · 22.46 Impact Factor
