Gender affects reperfusion injury in rat liver

Increase in post-reperfusion sensitivity to tissue plasminogen activator-mediated fibrinolysis during liver transplantation is associated with abnormal metabolic changes and increased blood product utilisation

BACKGROUND

Increased systemic fibrinolytic activity can occur in liver transplant recipients after the donor graft is reperfused. However, it remains unclear whether this is related solely to tissue plasminogen activator (t-PA) levels or whether unique metabolic changes can alter t-PA activity and enhance fibrinolytic activity. We hypothesise that an increase in sensitivity to t-PA-mediated fibrinolysis (StF) following liver reperfusion is associated with specific metabolic abnormalities.

MATERIALS AND METHODS

Liver transplant recipients had serial blood samples analysed with a modified thrombelastography assay using exogenous t-PA to measure sensitivity/resistance to fibrinolysis with the lysis 30 min after maximum clot strength (tLY30). Paired plasma samples were analysed with mass spectroscopy-based metabolomics. The tLY30 was correlated to metabolites using Spearman's rho. StF was defined as a tLY30 change of >8.5% from the anhepatic phase to 30 min after reperfusion based on the distribution of tLY30 in a healthy control population.

RESULTS

StF occurred in 53% of patients. Cohorts had similar MELD scores (18 vs 16, p=0.876) and tLY30 at baseline (p=0.867) and anhepatic phase of surgery (p=0.463). Thirty min after reperfusion, the tLY30 was 73% in patient with StF vs 33% in those without StF 33% (p=0.006). StF was associated with increased red blood cell transfusions (p=0.035), during the first 2 hours of reperfusion. Nine metabolites demonstrated a correlation with tLY30 (p<0.05).

DISCUSSION

StF is a transient event that resolves within 2 hours of graft reperfusion and is associated with increased blood product use. This phenomenon correlates with derangements in citric acid cycle, purine and amino acid metabolism. Future research is needed to determine whether these metabolites are biomarkers or mechanistically linked to increased sensitivity to t-PA-mediated fibrinolytic activity following graft reperfusion.

Development of a Predictive Model for Hyperglycemia in Nondiabetic Recipients After Liver Transplantation

Background

Posttransplant hyperglycemia has been associated with increased risks of transplant rejection, infections, length of stay, and mortality.

Methods

To establish a predictive model to identify nondiabetic recipients at risk for developing postliver transplant (LT) hyperglycemia, we performed this secondary, retrospective data analysis of a single-center, prospective, randomized, controlled trial of glycemic control among 107 adult LT recipients in the inpatient period. Hyperglycemia was defined as a posttransplant glucose level greater than 200 mg/dL after initial discharge up to 1 month following surgery. Candidate variables with P less than 0.10 in univariate analyses were used to build a multivariable logistic regression model using forward stepwise selection. The final model chosen was based on statistical significance and additive contribution to the model based on the Bayesian Information Criteria.

Results

Forty-three (40.2%) patients had at least 1 episode of hyperglycemia after transplant after the resolution of the initial postoperative hyperglycemia. Variables selected for inclusion in the model (using model optimization strategies) included length of hospital stay (odds ratio [OR], 0.83; P < 0.001), use of glucose-lowering medications at discharge (OR, 3.76; P = 0.03), donor female sex (OR, 3.18; P = 0.02) and donor white race (OR, 3.62; P = 0.01). The model had good calibration (Hosmer-Lemeshow goodness-of-fit test statistic = 9.74, P = 0.28) and discrimination (C-statistic = 0.78; 95% confidence interval, 0.65-0.81, bias-corrected C-statistic = 0.78).

Conclusions

Shorter hospital stay, use of glucose-lowering medications at discharge, donor female sex and donor white race are important determinants in predicting hyperglycemia in nondiabetic recipients after hospital discharge up to 1 month after liver transplantation.

Effect of Γ-aminobutyric acid on kidney injury induced by renal ischemia-reperfusion in male and female rats: Gender-related difference

Background:

The most important cause of kidney injury is renal ischemia/reperfusion injury (IRI), which is gender-related. This study was designed to investigate the protective role of Γ-aminobutyric acid (GABA (against IRI in male and female rats.

Materials and Methods:

Thirty-six female and male wistar rats were assigned to six experimental groups. The IRI was induced by clamping renal vessels for 45 min then was performed reperfusion for 24 h. The group sex posed to IRI were pretreated with GABA and were compared with the control groups.

Results:

Serum levels of creatinine and blood urea nitrogen, kidney weight, and kidney tissue damage score increased in the IRI alone groups, (P < 0.05), while GABA decreased these parameters in female significantly (P < 0.05), but not in male rats. Uterus weight decreased significantly in female rats treated with GABA. Testis weight did not alter in male rats. Serum level of nitrite and kidney level of malondialdehyde (MDA) had no significant change in both female and male rats. Kidney level of nitrite increased significantly in female rats experienced IRI and serum level of MDA increased significantly in males that were exposed to IRI (P < 0.05).

Conclusion:

GABA could ameliorate kidney injury induced by renal IRI in a gender dependent manner.

Female donor to male recipient gender discordance results in inferior graft survival: a prospective study of 1,042 liver transplants

BACKGROUND

The influence of donor-recipient gender mismatch on outcomes after liver transplantation (LT) is controversial. The aim of this study was to evaluate the effect of donor and recipient gender discordance on graft survival.

METHODS

All patients who underwent primary LT from 1994-2012 at a single-center were identified prospectively. Clinico-demographic data were collected at the time of LT and last follow-up. Gender match included both male donor to male recipient (MM) and female donor to female recipient (FF), while gender mismatch included female donor to male recipient (FM) and male donor to female recipient (MF). Survival curves for graft survival were generated using Kaplan-Meier method and compared by log-rank test. Unadjusted and multivariate adjusted COX regression analyzing graft survival at up to 10 years post-transplant was performed.

RESULTS

A total of 1,042 subjects fulfilled the criteria. Graft survival in patients receiving a donor-recipient gender match was better than those receiving a gender mismatch (P = 0.047). Female-to-male transplants had the worst graft survival of all combinations (P < 0.001); this difference was maintained in multivariate regression after adjustment for recipient and donor variables (hazards ratio 2.09, P = 0.013).

CONCLUSION

Female-to-male liver transplants are associated with a statistically significant poorer graft survival as compared with other donor-recipient gender groups.

Role of endogenous vitamin E in renal ischemic preconditioning process: differences between male and female rats

BACKGROUND

Antioxidants such as α-tocopherol (vitamin E) and β-carotene (vitamin A) play an important role in protective effect of repeated brief periods of ischemia, namely ischemic preconditioning (IPC). Values of these antioxidants were investigated and compared after induction of ischemia reperfusion (IR) and kidney IPC in both male and female rats.

METHODS

Forty eight Wistar rats were divided randomly into six groups of 8: groups A and B (male and female controls, respectively), group C (male IR or IR cases), group D (female IR cases) and groups E and F (male and female IPC cases, respectively). In groups C and D, ischemia was induced by clamping of left renal arteries for 45 min. In groups E and F, rats underwent four cycles of 4 min of arterial clamping and 11 min of de-clamping before final 45 min ischemia induction. Afterward, serum was collected to assess the blood urea nitrogen, creatinine and vitamins E and A values. Renal tissues were obtained for histological assessments.

RESULTS

α-tocopherol levels in male and female rats showed a significant increase in IPC compared with IR group (P<0.01) and also in female IPC compared with male IPC group. β-carotene levels had no significant variations. Histological evaluation showed that IR-induced renal injuries were less in female rats. Also, protective effects of IPC were more in female rats (P<0.01).

CONCLUSIONS

Renal IPC reduced damages in both male and female rats, but tissue injuries in females were decreased much more along with the increase of endogenous vitamin E.

The current state of knowledge of hepatic ischemia-reperfusion injury based on its study in experimental models

The present review focuses on the numerous experimental models used to study the complexity of hepatic ischemia/reperfusion (I/R) injury. Although experimental models of hepatic I/R injury represent a compromise between the clinical reality and experimental simplification, the clinical transfer of experimental results is problematic because of anatomical and physiological differences and the inevitable simplification of experimental work. In this review, the strengths and limitations of the various models of hepatic I/R are discussed. Several strategies to protect the liver from I/R injury have been developed in animal models and, some of these, might find their way into clinical practice. We also attempt to highlight the fact that the mechanisms responsible for hepatic I/R injury depend on the experimental model used, and therefore the therapeutic strategies also differ according to the model used. Thus, the choice of model must therefore be adapted to the clinical question being answered.

Gender-dependent oxidative variations in liver of aged rats

A shift from redox regulation to oxidative damage is known to contribute organ dysfunction and aging-related disorders. Exposure to reactive oxygen species throughout the life-span increases the incidence of several liver diseases. A redox basis of the loss of antioxidant capacity of aged livers has not been fully elucidated in both genders. In the current study, we investigated the gender-dependent relations between protein carbonyl (PCO), a commonly used marker of protein oxidation and other protein oxidation parameters such as advanced oxidation protein products (AOPP) and total thiol (T-SH). Our study also covered other oxidative stress markers, such as malondialdehyde (MDA), lipid hydroperoxides (LHP), and glutathione (GSH) in liver tissue of the male and female aged rats. PCO and AOPP levels in old male and female rats were significantly higher than those in the young control groups (P < 0.001 and P < 0.01, respectively for male rats; P < 0.001 for both parameters in female rats). On the other hand, T-SH levels were not found to be different between young and old rat groups. Plasma MDA levels of old male and female rats were significantly higher compared to those of the young control groups (P < 0.01 and P < 0.001, respectively). LHP levels were only found out to be significantly higher in old female rats when compared to those in young male rats. GSH levels in old male and female rats were significantly lower than in the corresponding young control groups (P < 0.01 for male rats; P < 0.05 for female rats). Our results demonstrated greater susceptibility to hepatic oxidative damage in females than in males. This appears to contradict the general assumption that females are less susceptible to oxidative injury than males are.

Experimental Models of Temporary Normothermic Liver Ischemia

Hepatic ischemia/reperfusion injury has so far been investigated in various experimental models. A clinical transfer of experimental results is, however, problematic because of anatomical and physiological differences and also the inevitable simplification of experimental work. The choice of model must therefore be adapted to the clinical question to be answered. The simplest procedure for inducing normothermic ischemia is to clamp the hepatoduodenal ligament. Models that do not avert portal congestion are regarded as unsuitable. Our current understanding of the pathogenesis of ischemia/reperfusion injury depends mainly on studies whose authors have investigated either global liver ischemia with a portocaval shunt, spleen transposition and in the isolated perfused system, or partial ischemia. This review is a critical examination of various approaches to the study of normothermic hepatic ischemia in experimental animals.

The effect of estrogen on hepatic microcirculation after ischemia/reperfusion

BACKGROUND AND AIMS

Gender dimorphism in clinical manifestation of sepsis, hemorrhage, and trauma is still under investigation. Several experimental studies have indicated a protective effect of estrogen. Nonetheless, the effect of gender on hepatic ischemia/reperfusion remains controversially discussed, and the influence of estrogen is still unclear. In the present study, we investigated whether hepatic ischemia/reperfusion (I/R) injury is gender-dependent and if hepatic microvascular reperfusion injury can be prevented by estrogen.

MATERIALS AND METHODS

Eight female and eight male Sprague-Dawley rats were subjected to 90 min left lobar ischemia followed by 60 min reperfusion. Additional six males were pretreated with 17beta-estradiol 24 h before I/R. Six female and six male rats served as nonischemic sham animals. By means of intravital microscopy, sinusoidal perfusion, leukocyte-endothelial cell interaction, and Kupffer cell activity were analyzed. Finally, arterial blood and liver tissue samples were taken for histomorphological analysis and liver enzyme determination.

RESULTS

After hepatic ischemia/reperfusion, animals revealed a significant gender-specific impairment of hepatic microcirculation, whereas Kupffer cell depression, sinusoidal perfusion failure, leukocyte-endothelial cell interaction within post sinusoidal venules, and parenchymal liver cell damage were more pronounced in male animals. Pretreatment with estrogen caused a normalization of Kupffer cell dysfunction and an amelioration of sinusoidal perfusion failure and venular leukocyte-endothelial cell interaction. However, estrogen did not protect from manifestation of post ischemic parenchymal cell damage.

CONCLUSION

Hepatic ischemia and reperfusion generate a gender-specific occurrence of microvascular injury, which seems to be partially mediated by estrogen. However, additional factors may contribute to the initial post ischemic parenchymal cell damage.

Effects of short-term moderate alcohol administration on oxidative stress and nutritional status in healthy males

The effects of moderate amounts of different alcoholic beverages on oxidative stress and nutritional parameters were investigated in 40 healthy subjects. Ethanol 40 g/day was administered at the two main meals for 30 days by beer (group A), wine (group B) or spirit (group C); controls (group D) maintaned abstinence. Malondyaldeide (MDA), adenosine-triphosphate (ATP), reduced-glutathione (GSH), E-vitamin and nutritional status were evaluated at the start (T0) and the end (T1) of the study. At T1 controls did not present significant changes in the assessed parameters, while a significant increase of malondyaldeide (MDA) and a significant decrease of reduced-glutathione and E-vitamin in group A, B and C and of ATP in group C were observed. Fat mass (FM) increased slightly in group A and B and decreased in group C. Ethanol decreased antioxidant parameters and increased lipoperoxidation parameters. However some of these changes appeared attenuated when ethanol was consumed in beer or wine. Finally, short-term moderate ethanol intake appeared to influence the FM, although it was not able to significantly affect nutritional or body composition.

Impact of donor gender on male rat recipients of small-for-size liver grafts

The aim of this study was to assess the impact of donor gender on small-for-size (SFS) liver transplantation in male recipients using a rat model. Adult female or male Lewis rats were used as donors and male Lewis rats as recipients. Size-matched (SM) and SFS liver grafts from either male or female donors were transplanted into male recipients. Animals receiving SFS grafts were sacrificed at postoperative week 1, week 4, and week 12, respectively (n = 6-8 per group), those receiving SM grafts after 3 months. The cumulative survival rate (SVR) in the female-to-male (F-M) SFS group was significantly lower (62%; 13 of 21) compared with the male-to-male (M-M) group (90%; 18 of 20) (P < 0.05). Spontaneous death occurred in the F-M SFS combination either in the early postoperative period (<3 weeks) in animals with confluent hepatic necrosis or in the late postoperative period (>8 weeks) in animals with biliary obstruction. In contrast, no death was observed in the early posttransplantation period after M-M liver transplantation. The relative graft size in the SM F-M group was significantly higher (graft-to-recipient weight ratio [GRWR] 2.40% +/- 0.8%) than in the SFS M-M group (GRWR 1.35% +/- 0.2%; P < 0.001). Regardless of graft size, the outcome was worse in terms of SVR as well as regarding the incidence and severity of biliary complications in F-M compared with M-M liver transplantation. In conclusion, male recipients of female livers had a less favorable outcome irrespective of graft size. Confluent hepatic necrosis as well as biliary obstruction were perceived as consequence of a severe perfusion problem in F-M liver transplantation, which was possibly related to an enhancement of ischemia-reperfusion (I/R) injury by the lack of estrogen in male recipients of female grafts.

Programming of hepatic antioxidant capacity and oxidative injury in the ageing rat

Exposure to undernutrition in fetal life increases the susceptibility of humans and animals to major disease states in adult life. Studies of rodents exposed to protein restriction during fetal life indicate that lifespan is reduced, a finding that is the opposite of the well-documented improvement in longevity noted with post-weaning caloric restriction. The maternal low-protein (MLP) model of rat pregnancy therefore provides a suitable vehicle to consider how nutrition in fetal life may programme mechanisms of ageing. Pregnant rats were fed control (n = 7) or MLP diet (n = 7) throughout pregnancy. At birth, increased oxidation of hepatic proteins was noted, and this appeared related to activity of glutathione reductase. Older offspring were studied at 4, 16, 30 and 44 weeks of age and analyses revealed that MLP exposure in utero produced sex-specific differences in oxidant:antioxidant balance. In male offspring, MLP increased protein carbonyl concentrations in the liver (P = 0.013) and increased glutathione peroxidase activity (P = 0.018). These programmed changes were absent in the female offspring. The data support the hypothesis that reduced lifespan in rats subject to prenatal protein restriction is a consequence of enhanced oxidative processes promoting apoptosis and loss of tissue function. Mechanisms of ageing appear to be subject to nutritional programming during early development.

Lower liver transplant success in females: gender differences in metabolic response to global ischemia

BACKGROUND

Research has shown that gender plays a significant role in the metabolic processes of different organs and that transplanting livers of females into male or female recipients has significantly higher failure rates. To understand why, this study examined whether gender differences exist in various metabolic responses of livers to ischemia.

METHODS

The following metabolic liver parameters in Sprague-Dawley rats (male, n = 14; and female, n = 18) were examined; adenosine triphosphate (ATP) and lactate expressed as micromoles/g dry weight, and hydrogen ion content [H+] expressed as 10(-8) mol/L. In vivo liver biopsy specimens were compared with ischemic biopsy specimens at 3, 10, 15, 30, and 45 minutes (37 degrees C).

RESULTS

In vivo female ATP values (9.9 +/- 0.8) were similar to males (9.8 +/- 0.9) and both had early, rapid decline during ischemia reaching 20% of baseline by 10 minutes of ischemia. In contrast, male liver lactate accumulation peaked by 3 minutes and at much lower levels (35 +/- 13), whereas female liver lactate peaked by 10 minutes at 71 +/- 11. For the rest of the ischemic period, female livers exhibited significantly (P < .05) greater lactate accumulation. Female liver H+ levels also increased to higher levels (55 +/- 10) than the male livers (37 +/- 7) and this pattern was significantly (P < .05) different from 10 minutes onward.

CONCLUSIONS

Although livers of females ultimately have similar ATP profiles to livers of males, they experienced more rapid and greater degree of tissue lactate and H+ accumulation during ischemia. Therefore, female livers have increased acidosis during ischemia, which could adversely affect transplant outcome.

Real time endoscopic imaging of oxyradical generation in pig stomach during ischemia-reperfusion

BACKGROUND

Oxygen-free radicals generation is considered to be a major cause of gastric injury during reperfusion. Chemiluminescence has been used to assess real-time free radical release on the surface of isolated organs.

AIMS

To evaluate the combined use of chemiluminescence and gastroendoscopy techniques and to assess the real-time production of free radicals during ischemic damage of the gastric wall in an animal model.

PATIENTS AND METHODS

For the experiment, an optical junction was set up between a fibroendoscope and a luminograph apparatus. Three pigs were submitted to gastrofibroendoscopy before, during and after 30 min of clamping of the coeliac artery. Under basal conditions, at the end of the ischemic phase and at the beginning of reperfusion, 1 mM of lucigenin, a specific superoxide enhancer, was injected in the left gastric artery of the animal. The endoscopic live images and chemiluminescence emission were recorded and successively superimposed to measure rate and spatial distribution of photon emission (photons/s).

RESULTS

Free radical production was not observed under basal conditions or during the ischemic phase, but significantly increased during reperfusion reaching a maximum peak after 15 min (0.6+/-0.2 photons x 10(5)/s) and decreased progressively thereafter. The superimposition of live and chemiluminescence images allowed the determination of the regional production rate and distribution of photons.

CONCLUSIONS

Preliminary observations, in an animal model, on an innovative imaging system which allows the visualization of rate and spatial distribution of reactive oxygen species formation are presented. This new endoscopic technique could be useful for the assessment of oxidative gastric mucosal injury in several gastric diseases; however, further studies remain necessary to determine the applicability of this technique in humans.