Hypertrophic cardiomyopathy and dysregulation of cardiac energetics in a mouse model of biliary fibrosis

Elevated plasma bile acids coincide with cardiac stress and inflammation in young Cyp2c70-/- mice

BACKGROUND

High plasma bile acids (BAs), for instance due to intrahepatic cholestasis of pregnancy or neonatal cholestasis, are associated with cardiac abnormalities. Here, we exploited the variability in plasma BA levels in Cyp2c70-/- mice with a human-like BA composition to investigate the acute effects of elevated circulating BAs on the heart.

METHODS

RNA sequencing was performed on hearts of 3-week-old Cyp2c70-/- mice lacking mouse-specific BA species that show features of neonatal cholestasis. Cardiac transcriptomes were compared between wild-type pups, Cyp2c70-/- pups with low or high plasma BAs, and Cyp2c70-/- pups from dams that were perinatally treated with ursodeoxycholic acid (UDCA).

RESULTS

We identified 1355 genes that were differentially expressed in hearts of Cyp2c70-/- mice with high versus low plasma BAs with enrichment of inflammatory processes. Strikingly, expression of 1053 (78%) of those genes was normalized in hearts of pups of UDCA-treated dams. Moreover, 645 cardiac genes strongly correlated to plasma BAs, of which 172 genes were associated with cardiovascular disease.

CONCLUSIONS

Elevated plasma BAs alter gene expression profiles of hearts of mice with a human-like BA profile, revealing cardiac stress and inflammation. Our findings support the notion that high plasma BAs induce cardiac complications in early life.

IMPACT

Cyp2c70-/- mice with a human-like bile acid composition show features of neonatal cholestasis but the extrahepatic consequences hereof have so far hardly been addressed Elevated plasma bile acids in Cyp2c70-/- pups coincide with cardiac stress and inflammation Perinatal treatment with UDCA prevents dysregulated cardiac gene expression patterns in Cyp2c70-/- pups.

Inhibition of fatty acid uptake by TGR5 prevents diabetic cardiomyopathy

Diabetic cardiomyopathy is characterized by myocardial lipid accumulation and cardiac dysfunction. Bile acid metabolism is known to play a crucial role in cardiovascular and metabolic diseases. Takeda G-protein-coupled receptor 5 (TGR5), a major bile acid receptor, has been implicated in metabolic regulation and myocardial protection. However, the precise involvement of the bile acid-TGR5 pathway in maintaining cardiometabolic homeostasis remains unclear. Here we show decreased plasma bile acid levels in both male and female participants with diabetic myocardial injury. Additionally, we observe increased myocardial lipid accumulation and cardiac dysfunction in cardiomyocyte-specific TGR5-deleted mice (both male and female) subjected to a high-fat diet and streptozotocin treatment or bred on the diabetic db/db genetic background. Further investigation reveals that TGR5 deletion enhances cardiac fatty acid uptake, resulting in lipid accumulation. Mechanistically, TGR5 deletion promotes localization of CD36 on the plasma membrane through the upregulation of CD36 palmitoylation mediated by the palmitoyl acyltransferase DHHC4. Our findings indicate that the TGR5-DHHC4 pathway regulates cardiac fatty acid uptake, which highlights the therapeutic potential of targeting TGR5 in the management of diabetic cardiomyopathy.

Bile Acids and Bilirubin Role in Oxidative Stress and Inflammation in Cardiovascular Diseases

Bile acids (BAs) and bilirubin, primarily known for their role in lipid metabolism and as heme catabolite, respectively, have been found to have diverse effects on various physiological processes, including oxidative stress and inflammation. Indeed, accumulating evidence showed that the interplay between BAs and bilirubin in these processes involves intricate regulatory mechanisms mediated by specific receptors and signaling pathways under certain conditions and in specific contexts. Oxidative stress plays a significant role in the development and progression of cardiovascular diseases (CVDs) due to its role in inflammation, endothelial dysfunction, hypertension, and other risk factors. In the cardiovascular (CV) system, recent studies have suggested that BAs and bilirubin have some opposite effects related to oxidative and inflammatory mechanisms, but this area of research is still under investigation. This review aims to introduce BAs and bilirubin from a biochemical and physiological point of view, emphasizing their potential protective or detrimental effects on CVDs. Moreover, clinical studies that have assessed the association between BAs/bilirubin and CVD were examined in depth to better interpret the possible link between them.

Taurocholic acid ameliorates hypertension through the activation of TGR5 in the hypothalamic paraventricular nucleus

Diets rich in taurine can increase the production of taurine-conjugated bile acids, which are known to exert antihypertensive effects. Despite their benefits to the heart, kidney and arteries, their role in the central nervous system during the antihypertensive process remains unclear. Since hypothalamic paraventricular nucleus (PVN) plays a key role in blood pressure regulation, we aimed to investigate the function of bile acids in the PVN. The concentration of bile acids in the PVN of spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto rats (WKY) fed with normal chow was measured using LC-MS/MS, which identified taurocholic acid (TCA) as the most down-regulated bile acid. To fully understand the mechanism of TCA's functions in the PVN, bi-lateral PVN micro-infusion of TCA was carried out. TCA treatment in the PVN led to a significant reduction in the blood pressure of SHRs, with decreased plasma levels of norepinephrine and improved morphology of cardiomyocytes. It also decreased the number of c-fos+ neurons, reduced the inflammatory response, and suppressed oxidative stress in the PVN of the SHRs. Most importantly, the TGR5 receptors in neurons and microglia were activated. PVN infusion of SBI-115, a TGR5 specific antagonist, was able to counteract with TCA in the blood pressure regulation of SHRs. In conclusion, TCA supplementation in the PVN of SHRs can activate TGR5 in neurons and microglia, reduce the inflammatory response and oxidative stress, suppress activated neurons, and attenuate hypertension.

Safety and efficacy of Single-Pass Albumin Dialysis (SPAD), Prometheus, and Molecular Adsorbent Recycling System (MARS) liver haemodialysis vs. Standard Medical Therapy (SMT): meta-analysis and systematic review

Introduction

Because not all liver dysfunction patients are suitable for transplantations and there is a shortage of grafts, liver support therapies have gained interest. In this regard, extracorporeal albumin dialysis devices such as single-pass albumin dialysis (SPAD), Prometheus, and molecular adsorbent recycling system (MARS) have been valuable in supplementing standard medical therapy (SMT). However, the efficacy and safety of these devices is often questioned.Aim: We performed a systematic review to summarize the efficacy and safety of MARS, SPAD, and Prometheus as supportive treatments for liver dysfunction.

Material and methods

PubMed, Medline, Cochrane Library, Web of Science, and Google Scholar electronic databases were extensively searched for all randomized trials published in English. In addition, meta-analytic analyses were performed with Review Manager software, and Cochrane's risk of bias tool embedded in this software was used for bias assessment.

Results

Twelve trials including a total of 653 patients were eligible for inclusion. Subgroup analyses of data from these trials revealed that MARS and Prometheus were associated with significant removal of bilirubin (MD = -5.14 mg/dl; 95% CI: -7.26 - -3.02; p < 0.00001 and MD = -8.11 mg/dl; 95% CI: -12.40 - -3.82; p = 0.0002, respectively) but not bile acids and ammonia when compared to SMT. Furthermore, MARS was as effective as Prometheus and SPAD in the reduction of bilirubin (MD = 2.98 mg/dl; 95% CI: -4.26 - 10.22; p = 0.42 and MD = 0.67 mg/dl; 95% CI: -2.22 - 3.56; p = 0.65), bile acids (MD = -17.06 µmol/l; 95% CI: -64.33 - 30.20; p = 0.48 and MD = 16.21 µmol/l; 95% CI: -17.26 - 49.68; p = 0.34), and ammonia (MD = 26 µmol/l; 95% CI: -12.44 - 64.44; p = 0.18). In addition, MARS had a considerable effect in improving hepatic encephalopathy (HE) (RR = 1.54; 95% CI: 1.15-2.05; p = 0.004). However, neither MARS nor Prometheus had a mortality benefit compared to SMTRR (0.86; 95% CI: 0.71-1.03; p = 0.11 and RR = 0.87; 95% CI: 0.66-1.14; p = 0.31, respectively).

Conclusions

MARS, SPAD, and Prometheus, as liver support therapies, are equally effective in reducing albumin-bound and water-soluble substances. Moreover, MARS is associated with HE improvement. However, none of the therapies was associated with a significant reduction in mortality or adverse events.

Bile acid metabolism and signaling in health and disease: molecular mechanisms and therapeutic targets

Bile acids, once considered mere dietary surfactants, now emerge as critical modulators of macronutrient (lipid, carbohydrate, protein) metabolism and the systemic pro-inflammatory/anti-inflammatory balance. Bile acid metabolism and signaling pathways play a crucial role in protecting against, or if aberrant, inducing cardiometabolic, inflammatory, and neoplastic conditions, strongly influencing health and disease. No curative treatment exists for any bile acid influenced disease, while the most promising and well-developed bile acid therapeutic was recently rejected by the FDA. Here, we provide a bottom-up approach on bile acids, mechanistically explaining their biochemistry, physiology, and pharmacology at canonical and non-canonical receptors. Using this mechanistic model of bile acids, we explain how abnormal bile acid physiology drives disease pathogenesis, emphasizing how ceramide synthesis may serve as a unifying pathogenic feature for cardiometabolic diseases. We provide an in-depth summary on pre-existing bile acid receptor modulators, explain their shortcomings, and propose solutions for how they may be remedied. Lastly, we rationalize novel targets for further translational drug discovery and provide future perspectives. Rather than dismissing bile acid therapeutics due to recent setbacks, we believe that there is immense clinical potential and a high likelihood for the future success of bile acid therapeutics.

Evaluation of Electrocardiogram Parameters and Heart Rate Variability During Blood Pressure Elevation by Phenylephrine in Cirrhotic Rats

Cirrhotic cardiomyopathy is a myocardial disease that may go undetected in the early stages due to peripheral vasodilatation. The aim of the study was to evaluate the electrocardiogram (ECG) and heart rate variability (HRV) after raising blood pressure by phenylephrine injection in rats with liver cirrhosis. Twenty male Sprague-Dawley rats were divided into the Sham and common bile duct ligation (CBDL) groups. After 44 days, animals were anesthetized and the right femoral artery and vein catheterized. After a steady-state period, a bolus injection of phenylephrine (PHE, 10 μg/μl/IV, baroreflex maneuver) was followed by a slow injection of PHE (100 μg/ml/5 min/IV, sustained maneuver). Rapid and slow injections of PHE resulted in a greater increase in mean arterial pressure (MAP) and a weaker bradycardia response in the CBDL group than in the Sham group. ECG analysis showed increased QT, QTc, JT, and T peak to T end in the CBDL group, which remained unchanged after PHE injection. On the other hand, the parasympathetic indices of the HF band and RMSSD, and the sympathetic index of the LF band after PHE injection were lower in the CBDL group than in the Sham group.ECG data indicated prolonged ventricular depolarization and repolarization, independent of blood pressure levels in cirrhosis. On the other hand, after PHE injection, the parasympathetic and sympathetic components of HRV decreased, regardless of the duration of elevated blood pressure. We suggest that HRV analysis can provide a useful approach to assess cardiac dysfunction associated with elevated blood pressure in cirrhosis.

TGR5 signalling in heart and brain injuries: focus on metabolic and ischaemic mechanisms

The heart and brain are the core organs of the circulation and central nervous system, respectively, and play an important role in maintaining normal physiological functions. Early neuronal and cardiac damage affects organ function. The relationship between the heart and brain is being continuously investigated. Evidence-based medicine has revealed the concept of the "heart- brain axis," which may provide new therapeutic strategies for certain diseases. Takeda protein-coupled receptor 5 (TGR5) is a metabolic regulator involved in energy homeostasis, bile acid homeostasis, and glucose and lipid metabolism. Inflammation is critical for the development and regeneration of the heart and brain during metabolic diseases. Herein, we discuss the role of TGR5 as a metabolic regulator of heart and brain development and injury to facilitate new therapeutic strategies for metabolic and ischemic diseases of the heart and brain.

How non-alcoholic fatty liver disease and cirrhosis affect the heart

Liver diseases affect the heart and the vascular system. Cardiovascular complications appear to be a leading cause of death in patients with non-alcoholic fatty liver disease (NAFLD) and cirrhosis. The predominant histological changes in the liver range from steatosis to fibrosis to cirrhosis, which can each affect the cardiovascular system differently. Patients with cirrhotic cardiomyopathy (CCM) and NAFLD are at increased risk of impaired systolic and diastolic dysfunction and for suffering major cardiovascular events. However, the pathophysiological mechanisms behind these risks differ depending on the nature of the liver disease. Accurate assessment of symptoms by contemporary diagnostic modalities is essential for identifying patients at risk, for evaluating candidates for treatment, and prior to any invasive procedures. This review explores current perspectives within this field.

From dried bear bile to molecular investigation of differential effects of bile acids in ex vivo and in vitro models of myocardial dysfunction: Relevance for neuroinflammation

Bile acids have been known to have both beneficial and detrimental effects on heart function, and as a consequence this can affect the brain. Inflammation is a key factor linking the heart and the brain, bile acids can reduce inflammation in the heart and, as a consequence, neuroinflammation, which may be due to the activation of different peripheral and central cellular and molecular mechanisms. Herein, we compile data published so far and summarise evidence demonstrating the effects of bile acids on myocardial cell viability and function, and its related mechanisms, in ex vivo and in vitro studies conducted in homeostatic state or in models of cardiovascular diseases. Studies show that ursodeoxycholic acid (UDCA) and tauroursodeoxycholic acid (TUDCA) do not affect the viability or contraction of cardiomyocytes in homeostatic state, and while UDCA has the capability to prevent the effect of hypoxia on reduced cell viability and beating rate, TUDCA can protect endoplasmic reticulum (ER) stress-induced apoptosis and cardiac contractile dysfunction. In contrast, deoxycholic acid (DCA) decreases contraction rate in homeostatic state, but it also prevents hypoxia-induced inflammation and oxidative stress, whereas lithocholic acid (LCA) can rescue doxazosin-induced apoptosis. Moreover, glycodeoxycholic acid (GDCA), cholic acid (CA), chenodeoxycholic acid (CDCA), glycocholic acid (GCA), taurocholic acid (TCA), taurochenodeoxycholic acid (TCDCA) and taurodeoxycholic acid (TDCA) decrease contraction, whereas CDCA decreases cell viability in homeostatic conditions. The mechanisms underlying the aforementioned contrasting effects involve a differential regulation of the TGR5, M2R and FXR receptors, as well as the cAMP signalling pathway. Overall, this review confirms the therapeutic potential of certain types of bile acids: UDCA, TUDCA, and potentially LCA, in cardiovascular diseases. By reducing inflammation in the heart, bile acids can improve heart-brain communication and promote overall health. Additional investigations are required to better elucidate mechanisms of action and more personalized clinical therapeutic doses.

The Crosstalk between Gut Microbiota and Bile Acids Promotes the Development of Non-Alcoholic Fatty Liver Disease

Recently the roles of gut microbiota are highly regarded in the pathogenesis of nonalcoholic fatty liver disease (NAFLD). The intestinal bacteria regulate the metabolism of bile acids depending on bile salt hydrolase (BSH), 7-dehydroxylation, hydroxysteroid dehydrogenase (HSDH), or amide conjugation reaction, thus exerting effects on NAFLD development through bile acid receptors such as farnesoid X receptor (FXR), Takeda G-protein-coupled bile acid protein 5 (TGR5), and vitamin D receptor (VDR), which modulate nutrient metabolism and insulin sensitivity via interacting with downstream molecules. Reversely, the composition of gut microbiota is also affected by the level of bile acids in turn. We summarize the mutual regulation between the specific bacteria and bile acids in NAFLD and the latest clinical research based on microbiota and bile acids, which facilitate the development of novel treatment modalities in NAFLD.

Cirrhotic Cardiomyopathy Following Bile Duct Ligation in Rats-A Matter of Time?

Cirrhotic patients often suffer from cirrhotic cardiomyopathy (CCM). Previous animal models of CCM were inconsistent concerning the time and mechanism of injury; thus, the temporal dynamics and cardiac vulnerability were studied in more detail. Rats underwent bile duct ligation (BDL) and a second surgery 28 days later. Cardiac function was assessed by conductance catheter and echocardiography. Histology, gene expression, and serum parameters were analyzed. A chronotropic incompetence (Pd31 < 0.001) and impaired contractility at rest and a reduced contractile reserve (Pd31 = 0.03, Pdob-d31 < 0.001) were seen 31 days after BDL with increased creatine (Pd35, Pd42, and Pd56 < 0.05) and transaminases (Pd31 < 0.001). A total of 56 days after BDL, myocardial fibrosis was seen (Pd56 < 0.001) accompanied by macrophage infiltration (CD68: Pgroup < 0.001) and systemic inflammation (TNFα: Pgroup < 0.001, white blood cell count: Pgroup < 0.001). Myocardial expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) was increased after 31 (Pd31 < 0.001) and decreased after 42 (Pd42 < 0.001) and 56 days (Pd56 < 0.001). Caspase-3 expression was increased 31 and 56 days after BDL (Pd31 = 0.005; Pd56 = 0.005). Structural changes in the myocardium were seen after 8 weeks. After the second surgery (second hit), transient myocardial insufficiency with secondary organ dysfunction was seen, characterized by reduced contractility and contractile reserve.

Elevated bile acids are associated with left ventricular structural changes in biliary atresia

BACKGROUND

In children with biliary atresia (BA), pathologic structural changes within the heart, which define cirrhotic cardiomyopathy, are associated with adverse perioperative outcomes. Despite their clinical relevance, little is known about the pathogenesis and triggers of pathologic remodeling. Bile acid excess causes cardiomyopathy in experimental cirrhosis, but its role in BA is poorly understood.

METHODS

Echocardiographic parameters of left ventricular (LV) geometry [LV mass (LVM), LVM indexed to height, left atrial volume indexed to BSA (LAVI), and LV internal diameter (LVID)] were correlated with circulating serum bile acid concentrations in 40 children (52% female) with BA listed for transplantation. A receiver-operating characteristic curve was generated to determine optimal threshold values of bile acids to detect pathologic changes in LV geometry using Youden index. Paraffin-embedded human heart tissue was separately analyzed by immunohistochemistry for the presence of bile acid-sensing Takeda G-protein-coupled membrane receptor type 5.

RESULTS

In the cohort, 52% (21/40) of children had abnormal LV geometry; the optimal bile acid concentration to detect this abnormality with 70% sensitivity and 64% specificity was 152 µmol/L (C-statistics=0.68). Children with bile acid concentrations >152 µmol/L had ∼8-fold increased odds of detecting abnormalities in LVM, LVM index, left atrial volume index, and LV internal diameter. Serum bile acids positively correlated with LVM, LVM index, and LV internal diameter. Separately, Takeda G-protein-coupled membrane receptor type 5 protein was detected in myocardial vasculature and cardiomyocytes on immunohistochemistry.

CONCLUSION

This association highlights the unique role of bile acids as one of the targetable potential triggers for myocardial structural changes in BA.

Emerging Roles of Gut Microbial Modulation of Bile Acid Composition in the Etiology of Cardiovascular Diseases

Despite advances in preventive measures and treatment options, cardiovascular disease (CVD) remains the number one cause of death globally. Recent research has challenged the traditional risk factor profile and highlights the potential contribution of non-traditional factors in CVD, such as the gut microbiota and its metabolites. Disturbances in the gut microbiota have been repeatedly associated with CVD, including atherosclerosis and hypertension. Mechanistic studies support a causal role of microbiota-derived metabolites in disease development, such as short-chain fatty acids, trimethylamine-N-oxide, and bile acids, with the latter being elaborately discussed in this review. Bile acids represent a class of cholesterol derivatives that is essential for intestinal absorption of lipids and fat-soluble vitamins, plays an important role in cholesterol turnover and, as more recently discovered, acts as a group of signaling molecules that exerts hormonal functions throughout the body. Studies have shown mediating roles of bile acids in the control of lipid metabolism, immunity, and heart function. Consequently, a picture has emerged of bile acids acting as integrators and modulators of cardiometabolic pathways, highlighting their potential as therapeutic targets in CVD. In this review, we provide an overview of alterations in the gut microbiota and bile acid metabolism found in CVD patients, describe the molecular mechanisms through which bile acids may modulate CVD risk, and discuss potential bile-acid-based treatment strategies in relation to CVD.

Lithocholic acid promotes skeletal muscle regeneration through the TGR5 receptor

<p indent="0mm">Lithocholic acid (LCA) is a classical secondary bile acid formed by the metabolism of gut microbiota. The TGR5 receptor (also known as G protein-coupled receptor 1, GPBAR1) is an important bile acid membrane receptor that mediates a variety of metabolic processes <italic>in vivo</italic>. In recent years, most studies have focused on the role of bile acid receptors in the intestine and liver. However, there are few reports on its effect on skeletal muscle regeneration, and the specific mechanism remains unclear. Therefore, it is necessary to investigate the mechanism of the TGR5 receptor in the regulation of skeletal muscle regeneration. The results demonstrate that muscle injection with LCA significantly reduces the necrosis rate of injured muscle and improves muscle injury. Moreover, treatment of C2C12 cells with LCA significantly increases AKT/mTOR/FoxO3 phosphorylation through the TGR5 receptor, enhances MyoG transcription and reduces FBXO32 transcription. These findings indicate that LCA can activate the TGR5/AKT signaling pathway, inhibit protein degradation and promote protein synthesis to enhance the myogenic process and promote skeletal muscle regeneration. </p>.

Subclinical cardiac abnormalities in children with biliary atresia correlate with outcomes after liver transplantation

Objective

There are subclinical cardiac abnormalities (SCA) in children with biliary atresia (BA). However, data on the consequences of these cardiac changes after liver transplantation (LT) remain controversial in the pediatric field. We aimed to determine the relationship between outcomes and the subclinical cardiac abnormalities in pediatric patients with BA based on two-dimensional echocardiography (2DE) parameters.

Methods

A total of 205 children with BA were enrolled in this study. The relationship between 2DE parameters and outcomes, including death and serious adverse events (SAE) after LT, was analyzed by regression analysis. Using receiver operator characteristic (ROC) curves to determine the optimal cut-off values of 2DE parameters for outcomes. Differences in the AUCs were compared using DeLong's test. The Kaplan -Meier method with log-rank testing was used to evaluate survival outcomes between groups.

Results

Left ventricular mass index (LVMI) and relative wall thickness (RWT) were found to be independently associated with SAE (OR: 1.112, 95% CI: 1.061 - 1.165, P < 0.001 and OR: 1.193, 95% CI: 1.078 - 1.320, P = 0.001, respectively). The cutoff value of LVMI for predicting the SAE was 68 g/m2.7 (AUC = 0.833, 95% CI 0.727-0.940, P < 0.001), and the cutoff value of RWT for predicting the SAE was 0.41 (AUC = 0.732, 95% CI 0.641-0.823, P < 0.001). The presence of subclinical cardiac abnormalities (LVMI > 68 g/m2.7, and/or RWT > 0.41) was associated with lower patient survival (1-year, 90.5% vs 100.0%; 3-year, 89.7% vs 100.0, log-rank P = 0.001). and higher incidence of SAE events.

Conclusions

Subclinical cardiac abnormalities were correlated with post-LT mortality and morbidity in children with BA. LVMI can predict the occurrence of death and serious adverse events after liver transplantation.

The Role of Bile Acids in the Human Body and in the Development of Diseases

Bile acids are specific and quantitatively important organic components of bile, which are synthesized by hepatocytes from cholesterol and are involved in the osmotic process that ensures the outflow of bile. Bile acids include many varieties of amphipathic acid steroids. These are molecules that play a major role in the digestion of fats and the intestinal absorption of hydrophobic compounds and are also involved in the regulation of many functions of the liver, cholangiocytes, and extrahepatic tissues, acting essentially as hormones. The biological effects are realized through variable membrane or nuclear receptors. Hepatic synthesis, intestinal modifications, intestinal peristalsis and permeability, and receptor activity can affect the quantitative and qualitative bile acids composition significantly leading to extrahepatic pathologies. The complexity of bile acids receptors and the effects of cross-activations makes interpretation of the results of the studies rather difficult. In spite, this is a very perspective direction for pharmacology.

Preserved Left Ventricular Function despite Myocardial Fibrosis and Myopathy in the Dystrophin-Deficient D2.B10-Dmdmdx/J Mouse

Duchenne muscular dystrophy involves an absence of dystrophin, a cytoskeletal protein which supports cell structural integrity and scaffolding for signalling molecules in myocytes. Affected individuals experience progressive muscle degeneration that leads to irreversible loss of ambulation and respiratory diaphragm function. Although clinical management has greatly advanced, heart failure due to myocardial cell loss and fibrosis remains the major cause of death. We examined cardiac morphology and function in D2.B10-Dmd^mdx/J (D2-mdx) mice, a relatively new mouse model of muscular dystrophy, which we compared to their wild-type background DBA/2J mice (DBA/2). We also tested whether drug treatment with a specific blocker of mitochondrial permeability transition pore opening (Debio-025), or ACE inhibition (Perindopril), had any effect on dystrophy-related cardiomyopathy. D2-mdx mice were treated for six weeks with Vehicle control, Debio-025 (20 mg/kg/day), Perindopril (2 mg/kg/day), or a combination (n = 8/group). At 18 weeks, compared to DBA/2, D2-mdx hearts displayed greater ventricular collagen, lower cell density, greater cell diameter, and greater protein expression levels of IL-6, TLR4, BAX/Bcl2, caspase-3, PGC-1α, and notably monoamine oxidases A and B. Remarkably, these adaptations in D2-mdx mice were associated with preserved resting left ventricular function similar to DBA/2 mice. Compared to vehicle, although Perindopril partly attenuated the increase in heart weight and collagen at 18 weeks, the drug treatments had no marked impact on dystrophic cardiomyopathy.

Pathogenic Mechanisms Underlying Cirrhotic Cardiomyopathy

Cardiac dysfunction associated with cirrhosis in the absence of preexisting heart disease is a condition known as cirrhotic cardiomyopathy (CCM). Cardiac abnormalities consist of enlargement of cardiac chambers, attenuated systolic and diastolic contractile responses to stress stimuli, and repolarization changes. CCM may contribute to cardiovascular morbidity and mortality after liver transplantation and other major surgeries, and also to the pathogenesis of hepatorenal syndrome. The underlying mechanisms of CCM are poorly understood and as such medical therapy is an area of unmet medical need. The present review focuses on the pathogenic mechanisms responsible for development of CCM. The two major concurrent mechanistic pathways are the inflammatory phenotype due to portal hypertension, and protein/lipid synthetic/metabolic defects due to cirrhosis and liver insufficiency. The inflammatory phenotype arises from intestinal congestion due to portal hypertension, resulting in bacteria/endotoxin translocation into the systemic circulation. The cytokine storm associated with inflammation, particularly TNFα acting via NFκB depresses cardiac function. They also stimulate two evanescent gases, nitric oxide and carbon monoxide which produce cardiodepression by cGMP. Inflammation also stimulates the endocannabinoid CB-1 pathway. These systems inhibit the stimulatory beta-adrenergic contractile pathway. The liver insufficiency of cirrhosis is associated with defective synthesis or metabolism of several substances including proteins and lipids/lipoproteins. The protein defects including titin and collagen contribute to diastolic dysfunction. Other protein abnormalities such as a switch of myosin heavy chain isoforms result in systolic dysfunction. Lipid biochemical changes at the cardiac sarcolemmal plasma membrane result in increased cholesterol:phospholipid ratio and decreased membrane fluidity. Final common pathway changes involve abnormal cardiomyocyte intracellular ion kinetics, particularly calcium. In conclusion, cirrhotic cardiomyopathy is caused by two pathways of cellular and molecular dysfunction/damage due to hepatic insufficiency and portal hypertension.

Mechanistic insights into the pathophysiology of cirrhotic cardiomyopathy

Myocardial dysfunction in end stage cirrhotic liver disease, termed cirrhotic cardiomyopathy, is a long known, but little understood comorbidity seen in ∼50% of adults and children who present for liver transplantation. Structural, functional, hemodynamic and electrocardiographic aberrations that occur in the heart as a direct consequence of a damaged liver, is associated with multi-organ failure and increased mortality and morbidity in patients undergoing surgical procedures such as porto-systemic shunt placement and liver transplantation. Despite its clinical significance and rapid advances in science and pharmacotherapy, there is yet no specific treatment for this disease. This may be due to a lack of understanding of the pathogenesis and mechanisms behind how a cirrhotic liver causes cardiac pathology. This review will focus specifically on insights into the molecular mechanisms that drive this liver-heart interaction. Deeper understanding of the etio-pathogenesis of cirrhotic cardiomyopathy will allow us to design and test treatments that can be targeted to prevent and/or reverse this co-morbid consequence of liver failure and improve health care delivery and outcomes in patients with cirrhosis.

Impact of nutritional status on prevalence of left ventricular hypertrophy in children undergoing liver transplant

OBJECTIVE

We sought to (1) determine the prevalence of cardiac changes in patients with ESLD awaiting OLT (2) determine relationship between nutritional indices and cardiac changes.

METHODS

Retrospective review of transthoracic ECHO, clinical and nutritional information of pediatric patients evaluated for OLT. ECHO was analyzed for LVH, defined as LVMI > 95 g/m^2.7 and/or RWT > 0.42. These findings were correlated with age, ESLD etiology, growth and nutritional parameters as well as pre- and post-OLT.

RESULTS

Sixty-five patients were included, all had normal left ventricular systolic function. Nine patients (14%) had LVMI > 95 g/m^2.7 , five patients (8%) had RWT > 0.42, none met both criteria. None had thickened interventricular septal wall. Fourteen patients (20%) had significant left ventricular dilation. Nutritional deprivation was modestly present-weight under third percentile in 22%, length under third percentile in 24%, and both weight and length under third percentile in 17%. There were 12 patients (17%) with MUAC below two standard deviations for age; of these one had an elevated LVMI and another had an RWT > 0.42.

CONCLUSIONS

In this contemporary cross-sectional evaluation, a smaller proportion of patients with ESLD had LVH in contrast to prior studies. Despite a comparable disease burden, our cohort had better nutritional status. Though there was a trend between nutritional and LVH indices, this correlation may be better assessed prospectively in a larger cohort.

Acute myocardial injury secondary to severe acute liver failure: A retrospective analysis supported by animal data

To investigate whether acute liver failure (ALF) leads to secondary acute myocardial injury, 100 ALF patients that were retrospectively identified in a single center based on ICD 10 codes and 8 rats from an experimental study that died early after bile duct ligation (BDL) were examined. Creatine kinase (CK), creatine kinase-MB isoenzyme (CKMB) and cardiac troponin-I (cTnI) were analyzed as markers of myocardial injury. For histological analysis, hematoxylin-eosin (HE), elastic Van Gieson (EVG), CD41 and myeloperoxidase were used to stain rat hearts. Major adverse cardiac events (MACEs) were a critical factor for mortality (p = 0.037) in human ALF. Deceased patients exhibited higher levels of CKMB than survivors (p = 0.023). CKMB was a predictor of mortality in ALF (p = 0.013). Animals that died early after BDL exhibited increased cTnI, CKMB, tumor necrosis factor α (TNFα) and interleukin-6 (IL-6) levels compared to controls (cTnI: p = 0.011, CKMB: p = 0.008, TNFα: p = 0.003, IL-6: p = 0.006). These animals showed perivascular lesions and wavy fibers, microthrombi and neutrophilic infiltration in the heart. MACEs are decisive for mortality in human ALF, and elevated CKMB values indicate that this might be due to structural myocardial damage. Accordingly, CKMB was found to have predictive value for mortality in ALF. The results are substantiated by data from a rat BDL model demonstrating diffuse myocardial injury.

Risk of Heart Disease after Cholecystectomy: A Nationwide Population-Based Cohort Study in South Korea

The aim of the study is to evaluate the risk of heart disease in individuals who underwent cholecystectomy. This was a retrospective cohort study using the National Health Insurance Service database of South Korea. A total of 146,928 patients who underwent cholecystectomy and 268,502 age- and sex-matched controls were compared. Multivariate Cox proportional hazard regression analysis was used to estimate the hazard ratio (HR) and 95% confidence interval (CI) for heart disease after cholecystectomy. In results, a previous history of cholecystectomy increased the risk of heart disease (congestive heart failure [CHF], myocardial infarction [MI], atrial fibrillation [AF]) (adjusted HR [aHR]: 1.40, 95% CI: [1.36–1.44]). The increased risk was particularly seen for CHF (1.22 [1.16–1.29]) but not for MI and AF (p > 0.05). In the subgroup analyses, cholecystectomy was associated with an increased risk of MI in patients aged <65 years (1.49 [1.16–1.92] and 1.18 [1.05–1.35] in patients aged 40–49 and 50–64 years, respectively), but not in those aged ≥ 65 years (0.932 [0.838–1.037]). Moreover, the risk of MI was increased in patients without diabetes mellitus (DM) (1.16 [1.06–1.27]); however, it was decreased in patients with DM (0.83 [0.72–0.97]). In contrast, cholecystectomy did not modify the risk of AF in the subgroup analyses (all p > 0.05). In conclusion, a history of cholecystectomy is associated with an increased risk of CHF. Cholecystectomy may increase the risk of MI in the younger population without DM. These findings suggest that the alteration of bile metabolism and homeostasis might be potentially associated with the development of some heart diseases.

TGR5 Expression Is Associated with Changes in the Heart and Urinary Bladder of Rats with Metabolic Syndrome

Adipose-derived cytokines may contribute to the inflammation that occurs in metabolic syndrome (MetS). The Takeda G protein-coupled receptor (TGR5) regulates energy expenditure and affects the production of pro-inflammatory biomarkers in metabolic diseases. Etanercept, which acts as a tumor necrosis factor (TNF)-α antagonist, can also block the inflammatory response. Therefore, the interaction between TNF-α and TGR5 expression was investigated in rats with high-fat diet (HFD)-induced obesity. Heart tissues isolated from the HFD-induced MetS rats were analyzed. Changes in TGR5 expression were investigated with lithocholic acid (LCA) as the agonist. Betulinic acid (BA) was used to activate TGR5 in urinary bladders. LCA was more effective in the heart tissues of HFD-fed rats, although etanercept alleviated the function of LCA. STAT3 activation and higher TGR5 expression were observed in the heart tissues collected from HFD-fed rats. Thus, cardiac TGR5 expression is promoted by HFD through STAT3 activation in rats. Moreover, the urinary bladders of female rats fed a HFD showed a low response, which was reversed by etanercept. Relaxation by BA in the bladders was more marked in HFD-fed rats. The high TGR5 expression in HFD-fed rats was characterized using a mRNA assay, and the increased cAMP levels were found to be stimulated by BA in the isolated bladders. Therefore, TGR5 expression increases with a HFD in both the hearts and urinary bladders. Collectively, cytokine-medicated TGR5 activation was observed in the hearts and urinary bladders of rats.

Advances in cirrhotic cardiomyopathy

PURPOSE OF REVIEW

Cirrhotic cardiomyopathy (CCM) is a well-recognized entity. When patients with CCM encounter challenges such as liver transplantation, overt cardiac dysfunction manifests, leading to morbidity and mortality. Although revised diagnostic criteria for CCM have recently been proposed, these still need to be validated.

RECENT FINDINGS

Previous reviews have summarized the mechanisms of CCM, such as abnormalities of the β-adrenergic pathway, cardiac plasma membrane biophysical and biochemical properties, and electrophysiological changes. Cardiomyocyte apoptosis, inflammation, and oxidative stress also play important roles. The present review details further mechanisms of CCM, which include myosin heavy chain isoform shifts and abnormalities in cellular calcium transients. Additionally, we review recent studies on therapeutic strategies. Recent work underscores the importance of CCM in the natural history of the immediate and medium-term postoperative period after liver transplantation. Appropriate management strategies for CCM remain the area of greatest unmet need, requiring much further research.

SUMMARY

CCM is a clinically relevant syndrome affecting patients with cirrhosis, leading to increased morbidity and mortality. New diagnostic criteria have been recently proposed by an expert working group. The pathogenic mechanisms remain incompletely clarified and optimal management strategies need much further study.

Overexpression of TGR5 alleviates myocardial ischemia/reperfusion injury via AKT/GSK-3β mediated inflammation and mitochondrial pathway

Ischemia/reperfusion (I/R) injury reduces cell proliferation, triggers inflammation, promotes cell apoptosis and necrosis, which are the leading reasons of morbidity and mortality in patients with cardiac disease. TGR5 is shown to express in hearts, but its functional role in I/R-induced myocardial injury is unclear. In the present study, we aimed to explore the underlying molecular mechanism of TGR5 in hypoxia/reoxygenation (H/R)-induced cardiomyocyte injury in vitro. The results showed that TGR5 was significantly up-regulated in H9C2 (rat cardiomyocyte cells) and human cardiomyocytes (HCMs) after H/R. Overexpression of TGR5 significantly improved cell proliferation, alleviated apoptosis rate, the activities of caspase-3, cleaved caspases-3 and Bax protein expression levels, and increased Bcl-2 level. Overexpression of TGR5 significantly up-regulated ROS generation, stabilized the mitochondrial membrane potential (MMP), and reduced the concentration of intracellular Ca²⁺ as well as cytosolic translocation of mitochondrial cytochrome c (cyto-c). Meanwhile, overexpressed TGR5 also enhanced the mRNA and protein levels of interleukin (IL)-10, and decreased the mRNA and protein levels of IL-6 and tumor necrosis factor α (TNF-α). The shTGR5+H/R group followed opposite trends. In addition, overexpressed TGR5 induced an increase in the levels of p-AKT and p-GSK-3β. The protective effects of TGR5 were partially reversed by AKT inhibitor MK-2206. Taken together, these results suggest that TGR5 attenuates I/R-induced mitochondrial dysfunction and cell apoptosis as well as inflammation, and these protections may through AKT/GSK-3β pathway.

Activation of TGR5 restores AQP2 expression via the HIF pathway in renal ischemia-reperfusion injury

Renal ischemia-reperfusion (I/R) injury is associated with markedly reduced protein expression of aquaporins (AQPs). Membrane G protein-coupled bile acid receptor-1 (TGR5) has shown protective roles in some kidney diseases. The purpose of the current study was to investigate whether activation of TGR5 prevented the decreased protein expression of AQPs in rodents with renal I/R injury and potential mechanisms. TGR5 agonist lithocholic acid (LCA) treatment reduced polyuria after renal I/R injury in rats. LCA prevented the decreased abundance of AQP2 protein and upregulated hypoxia-inducible factor (HIF)-1α protein expression, which were associated with decreased protein abundance of NF-κB p65 and IL-1β. After renal I/R, mice with tgr5 gene deficiency exhibited further decreases in AQP2 and HIF-1α protein abundance and increases of IL-1β and NF-κB p65 protein expression compared with wild-type mice. In primary cultured inner medullary collecting duct cells with hypoxia/reoxygenation, LCA induced markedly increased protein expression of AQP2 and HIF-1α, which were partially prevented by the PKA inhibitor H89. FG4592, a prolyl-4-hydroxylase domain-containing protein inhibitor, increased HIF-1α and AQP2 protein abundance in association with decreased NF-κB p65 protein expression in inner medullary collecting duct cells with hypoxia/reoxygenation. In conclusion, TGR5 stimulation by LCA prevented downregulation of renal AQPs in kidney with I/R injury, likely through activating HIF-1α signaling and suppressing inflammatory responses.NEW & NOTEWORTHY Stimulation of the membrane G protein-coupled bile acid receptor TGR5 by lithocholic acid (LCA) reduced polyuria in rats with renal ischemia-reperfusion (I/R) injury. LCA increased abundance of aquaporin-2 (AQP2) protein and upregulated hypoxia-inducible factor (HIF)-1α protein expression in association with decreased NF-κB p65 and IL-1β. After I/R, mice with tgr5 gene deficiency exhibited more severe decreases in AQP2 and HIF-1α protein abundance and inflammatory responses. TGR5 activation exhibits a protective role in acute renal injury induced by I/R.

Overview of bile acid signaling in the cardiovascular system

Bile acids (BAs) are classically known to play a vital role in the metabolism of lipids and in absorption. It is now well established that BAs act as signaling molecules, activating different receptors (such as farnesoid X receptor, vitamin D receptor, Takeda G-protein-coupled receptor 5, sphingosine-1-phosphate, muscarinic receptors, and big potassium channels) and participating in the regulation of energy homeostasis and lipid and glucose metabolism. In addition, increased BAs can impair cardiovascular function in liver cirrhosis. Approximately 50% of patients with cirrhosis develop cirrhotic cardiomyopathy. Exposure to high concentrations of hydrophobic BAs has been shown to be related to adverse effects with respect to vascular tension, endothelial function, arrhythmias, coronary atherosclerotic heart disease, and heart failure. The BAs in the serum BA pool have relevant through their hydrophobicity, and the lipophilic BAs are more harmful to the heart. Interestingly, ursodeoxycholic acid is a hydrophilic BA, and it is used as a therapeutic drug to reverse and protect the harmful cardiac effects caused by hydrophobic elevated BAs. In order to elucidate the mechanism of BAs and cardiovascular function, abundant experiments have been conducted in vitro and in vivo. The aim of this review was to explore the mechanism of BAs in the cardiovascular system.

Myocardial Dysfunction in Cirrhotic Cardiomyopathy is Associated with Alterations of Phospholamban Phosphorylation and IL-6 Levels

BACKGROUND

Decreased cardiac contractility has been observed in cirrhosis, but the mechanisms that initiate and maintain cardiac dysfunction are not entirely understood.

AIM OF THE STUDY

We test the hypothesis that cirrhotic cardiomyopathy is related to deterioration of myocardial contractility due to alterations in calcium-handling proteins expression. In addition, we evaluated whether cardiac pro-inflammatory cytokine levels are associated with this process.

METHODS

Cirrhosis was induced by thioacetamide (TAA, 100 mg/kg/i.p., twice weekly for eight weeks). The myocardial performance was evaluated in isolated left ventricle papillary muscles under basal conditions and after inotropic challenge. The cardiac calcium handling protein expression was detected by Western blotting. Cardiac TNF-α and IL-6 levels were measured by ELISA.

RESULTS

Thioacetamide induced liver cirrhosis, which was associated with cirrhotic cardiomyopathy characterized by in vivo left ventricular diastolic and systolic dysfunction as well as cardiac hypertrophy. In vitro baseline myocardial contractility was lower in cirrhosis. Also, myocardial responsiveness to post-rest contraction stimulus was declined. Protein expression for RYR2, SERCA2, NCX, pPBL Ser¹⁶ and L-type calcium channel was quantitatively unchanged; however, pPBL Thr¹⁷ was significantly lower while IL-6 was higher.

CONCLUSIONS

Our study demonstrates that cirrhotic cardiomyopathy is associated with decreased cardiac contractility with alteration of phospholamban phosphorylation in association with higher cardiac pro-inflammatory IL-6 levels. These findings provided molecular and functional insights about the effects of liver cirrhosis on cardiac function.

Impaired myosin isoform shift and calcium transients contribute to cellular pathogenesis of rat cirrhotic cardiomyopathy

BACKGROUND & AIMS

Cirrhotic cardiomyopathy is a recently recognized entity, but detailed cellular and molecular mechanisms remain unclarified. We aimed to elucidate the role of myosin heavy chain isoform shifts and their relation to calcium transients in the contractile kinetics of cirrhotic rats.

METHODS

Cirrhosis was induced in male Lewis Brown-Norway rats by bile duct ligation (BDL). Myosin heavy chain (MHC) isoform distribution was evaluated by gel electrophoresis. Contractile force, Ca²⁺ transients and cell shortening were studied at varied frequency and extracellular [Ca²⁺ ]. T-tubular integrity was analysed by power spectrum analysis of images of myocytes stained with di-8-ANEPPS.

RESULTS

Compared with sham controls, the phenotypes of cirrhotic rats were as follows: (a) alpha-myosin heavy chain shifted to beta-MHC isoform; (b) mild loss of T-tubular integrity in myocytes; (c) a reduced maximum and rate of rise of the Ca²⁺ transient (max F/F_o ); (d) a reduction in both the rate of rise and fall of contraction; (e) decreased maximal force-generating capacity; (f) loss of the inotropic effect of increased stimulus frequency; (g) unchanged sensitivity of force development to varied extracellular [Ca²⁺ ] and (h) increased spontaneous diastolic sarcomere length fluctuations.

CONCLUSION

Cardiomyocytes and ventricular trabeculae in a cirrhotic rat model showed features of typical heart failure including systolic and diastolic prolongation, impaired force-frequency relation and decreased force-generating capacity. Impaired myosin isoform shift and calcium transients are important contributory mechanisms underlying the pathogenesis of the heart failure phenotype seen in cirrhosis.

Molecular Physiology of Bile Acid Signaling in Health, Disease, and Aging

Over the past two decades, bile acids (BAs) have become established as important signaling molecules that enable fine-tuned inter-tissue communication from the liver, their site of production, over the intestine, where they are modified by the gut microbiota, to virtually any organ, where they exert their pleiotropic physiological effects. The chemical variety of BAs, to a large extent determined by the gut microbiome, also allows for a complex fine-tuning of adaptive responses in our body. This review provides an overview of the mechanisms by which BA receptors coordinate several aspects of physiology and highlights new therapeutic strategies for diseases underlying pathological BA signaling.

Interplay of Liver-Heart Inflammatory Axis and Cannabinoid 2 Receptor Signaling in an Experimental Model of Hepatic Cardiomyopathy

BACKGROUND AND AIMS

Hepatic cardiomyopathy, a special type of heart failure, develops in up to 50% of patients with cirrhosis and is a major determinant of survival. However, there is no reliable model of hepatic cardiomyopathy in mice. We aimed to characterize the detailed hemodynamics of mice with bile duct ligation (BDL)-induced liver fibrosis, by monitoring echocardiography and intracardiac pressure-volume relationships and myocardial structural alterations. Treatment of mice with a selective cannabinoid-2 receptor (CB₂ -R) agonist, known to attenuate inflammation and fibrosis, was used to explore the impact of liver inflammation and fibrosis on cardiac function.

APPROACH AND RESULTS

BDL induced massive inflammation (increased leukocyte infiltration, inflammatory cytokines, and chemokines), oxidative stress, microvascular dysfunction, and fibrosis in the liver. These pathological changes were accompanied by impaired diastolic, systolic, and macrovascular functions; cardiac inflammation (increased macrophage inflammatory protein 1, interleukin-1, P-selectin, cluster of differentiation 45-positive cells); and oxidative stress (increased malondialdehyde, 3-nitrotyrosine, and nicotinamide adenine dinucleotide phosphate oxidases). CB₂ -R up-regulation was observed in both livers and hearts of mice exposed to BDL. CB₂ -R activation markedly improved hepatic inflammation, impaired microcirculation, and fibrosis. CB₂ -R activation also decreased serum tumor necrosis factor-alpha levels and improved cardiac dysfunction, myocardial inflammation, and oxidative stress, underlining the importance of inflammatory mediators in the pathology of hepatic cardiomyopathy.

CONCLUSIONS

We propose BDL-induced cardiomyopathy in mice as a model for hepatic/cirrhotic cardiomyopathy. This cardiomyopathy, similar to cirrhotic cardiomyopathy in humans, is characterized by systemic hypotension and impaired macrovascular and microvascular function accompanied by both systolic and diastolic dysfunction. Our results indicate that the liver-heart inflammatory axis has a pivotal pathophysiological role in the development of hepatic cardiomyopathy. Thus, controlling liver and/or myocardial inflammation (e.g., with selective CB₂ -R agonists) may delay or prevent the development of cardiomyopathy in severe liver disease.

Protective role of cardiac-specific overexpression of caveolin-3 in cirrhotic cardiomyopathy

Cirrhotic cardiomyopathy is a clinical syndrome in patients with liver cirrhosis characterized by blunted cardiac contractile responses to stress and/or heart rate-corrected QT (QTc) interval prolongation. Caveolin-3 (Cav-3) plays a critical role in cardiac protection and is an emerging therapeutic target for heart disease. We investigated the protective role of cardiac-specific overexpression (OE) of Cav-3 in cirrhotic cardiomyopathy. Biliary fibrosis was induced in male Cav-3 OE mice and transgene negative (TG_neg) littermates by feeding a diet containing 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC; 0.1%) for 3 wk. Liver pathology and blood chemistries were assessed, and stress echocardiography, telemetry, and isolated heart perfusion studies to assess adrenergic responsiveness were performed. Cav-3 OE mice showed a similar degree of hyperdynamic contractility, pulmonary hypertension, and QTc interval prolongation as TG_neg mice after 3 wk of DDC diet. Blunted systolic responses were shown in both DDC-fed Cav-3 OE and TG_neg hearts after in vivo isoproterenol challenge. However, QTc interval prolongation after in vivo isoproterenol challenge was significantly less in DDC-fed Cav-3 OE hearts compared with DDC-fed TG_neg hearts. In ex vivo perfused hearts, where circulatory factors are absent, isoproterenol challenge showed hearts from DDC-fed Cav-3 OE mice had better cardiac contractility and relaxation compared with DDC-fed TG_neg hearts. Although Cav-3 OE in the heart did not prevent cardiac alterations in DDC-induced biliary fibrosis, cardiac expression of Cav-3 reduced QTc interval prolongation after adrenergic stimulation in cirrhosis.NEW & NOTEWORTHY Prevalence of cirrhotic cardiomyopathy is up to 50% in cirrhotic patients, and liver transplantation is the only treatment. However, cirrhotic cardiomyopathy is associated with perioperative morbidity and mortality after liver transplantation; therefore, management of cirrhotic cardiomyopathy is crucial for successful liver transplantation. This study shows cardiac myocyte specific overexpression of caveolin-3 (Cav-3) provides better cardiac contractile responses and less corrected QT prolongation during adrenergic stress in a cirrhotic cardiomyopathy model, suggesting beneficial effects of Cav-3 expression in cirrhotic cardiomyopathy.

What Every Intensivist should Know about Impairment of Cardiac Function and Arrhythmias in Liver Disease Patients: A Review

Objectives

Impairment of cardiac function and arrhythmias often coexist in patients with liver diseases. Many studies have proved this coexistence and put forward various theories toward its pathophysiology. This narrative review tries to find the answers with supporting evidence on five main questions:

Materials and methods

Clinical evidence was obtained by using search engines, namely, Cochrane Library, PubMed, and Google Scholar. Studies published in journals in the English language, between January 1969 and December 2019, which mentioned the relationship between cardiac arrhythmia and liver disease, were included. We used the keywords: jaundice, bilirubin, arrhythmia, ECG, QTc interval, QT dispersion, liver, and cirrhosis. Relevant animal or human studies answering the five main questions were extracted and reviewed.

Conclusion

The evidence included in our review sheds light on the fact that approximately 50% of liver cirrhosis cases develop cirrhotic cardiomyopathy (CC) and there has been an association between liver abnormalities and cardiac pathology. The present review also supports that there exists a strong association between high levels of serum bilirubin levels and cardiac arrhythmias, QTc value can be relied upon as a risk factor for predicting imminent arrhythmias, and that it is associated with mortality. Its basic pathophysiology can be explained by the potential action of bile acids in prolonging the QT interval. It also causes cardiac hypertrophy and apoptosis of cardiomyocytes leading to cardiac dysfunction.

How to cite this article

Arya S, Kumar P, Tiwari B, Belwal S, Saxena S, Abbas H. What Every Intensivist should Know about Impairment of Cardiac Function and Arrhythmias in Liver Disease Patients: A Review. Indian J Crit Care Med 2020;24(12):1251–1255.

Activation of TGR5 Partially Alleviates High Glucose-Induced Cardiomyocyte Injury by Inhibition of Inflammatory Responses and Oxidative Stress

High glucose- (HG-) induced cardiomyocyte injury is the leading cause of diabetic cardiomyopathy, which is associated with the induction of inflammatory responses and oxidative stress. TGR5 plays an important role in the regulation of glucose metabolism. However, whether TGR5 has cardioprotective effects against HG-induced cardiomyocyte injury is unknown. Neonatal mouse cardiomyocytes were isolated and incubated in a HG medium. Protein and mRNA expression was detected by western blotting and RT-PCR, respectively. Cell apoptosis was determined by Hoechst 33342 staining and flow cytometry. After treatment of cells with HG, TGR5-selective agonist INT-777 reduced the increase in expression of proinflammatory cytokines and NF-κB, whereas pretreatment of cells with TGR5 shRNA significantly reduced the inhibitory effects of INT-777. We also found that INT-777 increased the protein expression of Nrf2 and HO-1. In the presence of TGR5 shRNA, the expression of Nrf2 and HO-1 was reduced, indicating that TGR5 may exert an antioxidant effect partially through the Nrf2/HO-1 pathway. Furthermore, INT-777 treatment inhibited HG-induced ROS production and apoptosis that were attenuated in the presence of TGR5 shRNA or ZnPP (HO-1 inhibitor). Activation of TGR5 has cardioprotective effects against HG-induced cardiomyocyte injury and could be a pharmacological target for the treatment of diabetic cardiomyopathy.

Predictors, burden and impact of cardiac arrhythmias among patients hospitalized with end-stage liver disease

BACKGROUND

Cirrhotic cardiomyopathy, hyperammonemia, and hepatorenal syndrome predispose to cardiac arrhythmias in End-stage liver disease (ESLD).

OBJECTIVES

Among ESLD hospitalizations, we evaluate the distribution and predictors of arrhythmias and their impact on hospitalization outcomes.

METHODS

We selected ESLD records from the Nationwide Inpatient Sample (2007-2014), identified concomitant arrhythmias (tachyarrhythmias and bradyarrhythmias), and their demographic and comorbid characteristics, and estimated the effect of arrhythmia on outcomes (SAS 9.4).

RESULTS

Of 57,119 ESLD hospitalizations, 6,615 had arrhythmias with higher odds with increasing age, males, jaundice, hepatorenal syndrome, alcohol use, and cardiopulmonary disorders. The most common arrhythmias were atrial fibrillation, cardiac arrest/asystole, and ventricular tachycardia. After propensity-matching (arrhythmia: no-arrhythmia, 6,609:6,609), arrhythmias were associated with 200% higher mortality, 1.7-days longer stay, $32,880 higher cost, and higher rates of shock, respiratory and kidney failures.

CONCLUSIONS

Due to worse outcomes with arrhythmias, there is a need for better screening and follow-up of ESLD patients for dysrhythmias.

TGR5 activation ameliorates hyperglycemia-induced cardiac hypertrophy in H9c2 cells

Left ventricular hypertrophy is an independent risk factor in diabetic patients. TGR5 is shown to express in hearts, but its functional role in diabetes-induced cardiac hypertrophy remained unclear. The current study investigated the role of TGR5 on high glucose-induced hypertrophy of H9C2 cells. After incubation with a high level of glucose, H9C2 cells showed hypertrophic responses. Activation of TGR5 by lithocholic acid (LCA) ameliorated cell hypertrophy and enhanced SERCA2a and phosphorylated phospholamban (PLN) expression in H9C2 cells. Triamterene inhibited these effects at an effective dose to block TGR5. However, LCA failed to modify the free radical elevation induced by high-glucose in the H9c2 cells. Moreover, PKA inhibitors, but not an Epac blocker, markedly improved hyperglycemia-induced hypertrophy and attenuated the increased SERCA2a expression by LCA; it also attenuated the phosphorylated PLN and SERCA2a protein expression levels in high glucose-treated H9C2 cells. In conclusion, TGR5 activation stimulated protein kinase A (PKA) to enhance PLN phosphorylation, which activated SERCA2a to remove Ca²⁺ from cytosol to sarcoplasmic reticulum in addition to the reduction of calcineurin/NFAT pathway signaling to ameliorate the hyperglycemia-induced cardiac hypertrophy shown in cardiomyocytes. TGR5 may service as a new target in the control of diabetic cardiomyopathy.

Micro-utrophin Improves Cardiac and Skeletal Muscle Function of Severely Affected D2/mdx Mice

Duchenne muscular dystrophy (DMD) is an X-linked muscle-wasting disease caused by mutations in the dystrophin gene. DMD boys are wheelchair-bound around 12 years and generally survive into their twenties. There is currently no effective treatment except palliative care, although personalized treatments such as exon skipping, stop codon read-through, and viral-based gene therapies are making progress. Patients present with skeletal muscle pathology, but most also show cardiomyopathy by the age of 10. A systemic therapeutic approach is needed that treats the heart and skeletal muscle defects in all patients. The dystrophin-related protein utrophin has been shown to compensate for the lack of dystrophin in the mildly affected BL10/mdx mouse. The purpose of this investigation was to demonstrate that AAV9-mediated micro-utrophin transgene delivery can not only functionally replace dystrophin in the heart, but also attenuate the skeletal muscle phenotype in severely affected D2/mdx mice. The data presented here show that utrophin can indeed alleviate the pathology in skeletal and cardiac muscle in D2/mdx mice. These results endorse the view that utrophin modulation has the potential to increase the quality life of all DMD patients whatever their mutation.

TGR5 activation induces cytoprotective changes in the heart and improves myocardial adaptability to physiologic, inotropic, and pressure-induced stress in mice

INTRODUCTION

Administration of cholic acid, or its synthetic derivative, 6-alpha-ethyl-23(S)-methylcholic acid (INT-777), activates the membrane GPCR, TGR5, influences whole body metabolism, reduces atherosclerosis, and benefits the cardiovascular physiology in mice. Direct effects of TGR5 agonists, and the role for TGR5, on myocardial cell biology and stress response are unknown.

METHODS

Mice were fed chow supplemented with 0.5% cholic acid (CA) or 0.025% INT-777, a specific TGR5 agonist, or regular chow for 3 weeks. Anthropometric, biochemical, physiologic (electrocardiography and echocardiography), and molecular analysis was performed at baseline. CA and INT-777 fed mice were challenged with acute exercise-induced stress, acute catecholamine-induced stress, and hemodynamic stress induced by transverse aortic constriction (TAC) for a period of 8 weeks. In separate experiments, mice born with constitutive deletion of TGR5 in cardiomyocytes (CM-TGR5^del ) were exposed to exercise, inotropic, and TAC-induced stress.

RESULTS

Administration of CA and INT-777 supplemented diets upregulated TGR5 expression and activated Akt, PKA, and ERK1/2 in the heart. CA and INT-777 fed mice showed improved exercise tolerance, improved sensitivity to catecholamine and attenuation in pathologic remodeling of the heart under hemodynamic stress. In contrast, CM-TGR5^del showed poor response to exercise and catecholamine challenge as well as higher mortality and signs of accelerated cardiomyopathy under hemodynamic stress.

CONCLUSIONS

Bile acids, specifically TGR5 agonists, induce cytoprotective changes in the heart and improve myocardial response to physiologic, inotropic, and hemodynamic stress in mice. TGR5 plays a critical role in myocardial adaptability, and TGR5 activation may represent a potentially attractive treatment option in heart failure.

Heart and bile acids - Clinical consequences of altered bile acid metabolism

Cardiac dysfunction has an increased prevalence in diseases complicated by liver cirrhosis such as primary biliary cholangitis and primary sclerosing cholangitis. This observation has led to research into the association between abnormalities in bile acid metabolism and cardiac pathology. Approximately 50% of liver cirrhosis cases develop cirrhotic cardiomyopathy. Bile acids are directly implicated in this, causing QT interval prolongation, cardiac hypertrophy, cardiomyocyte apoptosis and abnormal haemodynamics of the heart. Elevated maternal serum bile acids in intrahepatic cholestasis of pregnancy, a disorder which causes an impaired feto-maternal bile acid gradient, have been associated with fatal fetal arrhythmias. The hydrophobicity of individual bile acids in the serum bile acid pool is of relevance, with relatively lipophilic bile acids having a more harmful effect on the heart. Ursodeoxycholic acid can reverse or protect against these detrimental cardiac effects of elevated bile acids.

Bile acids and cardiovascular function in cirrhosis

Cirrhotic cardiomyopathy and the hyperdynamic syndrome are clinically important complications of cirrhosis, but their exact pathogenesis is still partly unknown. Experimental models have proven the cardiotoxic effects of bile acids and recent studies of their varied receptor-mediated functions offer new insight into their involvement in cardiovascular dysfunction in cirrhosis. Bile acid receptors such as farnesoid X-activated receptor and TGR5 are currently under investigation as potential therapeutic targets in a variety of pathological conditions. These receptors have also recently been identified in cardiomyocytes, vascular endothelial cells and smooth muscle cells where they seem to play an important role in cellular metabolism. Chronic cholestasis leading to abnormal levels of circulating bile acids alters the normal signalling pathways and contributes to the development of profound cardiovascular disturbances. This review summarizes the evidence regarding the role of bile acids and their receptors in the generation of cardiovascular dysfunction in cirrhosis.

Bile acid receptors in the biliary tree: TGR5 in physiology and disease

Bile salts represent signalling molecules with a variety of endocrine functions. Bile salt effects are mediated by different receptor molecules, comprising ligand-activated nuclear transcription factors as well as G protein-coupled membrane-bound receptors. The farnesoid X receptor (FXR) and the plasma membrane-bound G protein-coupled receptor TGR5 (Gpbar-1) are prototypic bile salt receptors of both classes and are highly expressed in the liver including the biliary tree as well as in the intestine. In liver, TGR5 is localized in different non-parenchymal cells such as sinusoidal endothelial cells, Kupffer cells, hepatic stellate cells and small and large cholangiocytes. Through TGR5 bile salts can mediate choleretic, cell-protective as well as proliferative effects in cholangiocytes. A disturbance of these signalling mechanisms can contribute to the development of biliary diseases. In line with the important role of TGR5 for bile salt signalling, TGR5 knockout mice are more susceptible to cholestatic liver damage. Furthermore, in absence of TGR5 cholangiocyte proliferation in response to cholestasis is attenuated and intrahepatic and extrahepatic bile ducts show increased cell damage, underscoring the role of the receptor for biliary physiology. Decreased TGR5 expression may also contribute to the development or progression of cholangiopathies like primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC) since reduced TGR5-dependent cell-protective mechanisms such as bicarbonate secretion renders cholangiocytes more vulnerable towards bile salt toxicity. Nevertheless, TGR5 overexpression or constant stimulation of the receptor can promote cholangiocyte proliferation leading to cyst growth in polycystic liver disease or even progression of cholangiocarcinoma. Not only the stimulation of TGR5-mediated pathways by suitable TGR5 agonists but also the inhibition of TGR5 signalling by the use of antagonists represent potential therapeutic approaches for different types of biliary diseases. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Bile acid excess induces cardiomyopathy and metabolic dysfunctions in the heart

Cardiac dysfunction in patients with liver cirrhosis is strongly associated with increased serum bile acid concentrations. Here we show that excess bile acids decrease fatty acid oxidation in cardiomyocytes and can cause heart dysfunction, a cardiac syndrome that we term cholecardia. Farnesoid X receptor; Small Heterodimer Partner double knockout mice, a model for bile acid overload, display cardiac hypertrophy, bradycardia, and exercise intolerance. In addition, double knockout mice exhibit an impaired cardiac response to catecholamine challenge. Consistent with this decreased cardiac function, we show that elevated serum bile acids reduce cardiac fatty acid oxidation both in vivo and ex vivo. We find that increased bile acid levels suppress expression of proliferator-activated receptor-γ coactivator 1α, a key regulator of fatty acid metabolism, and that proliferator-activated receptor-γ coactivator 1α overexpression in cardiac cells was able to rescue the bile acid-mediated reduction in fatty acid oxidation genes. Importantly, intestinal bile acid sequestration with cholestyramine was sufficient to reverse the observed heart dysfunction in the double knockout mice.

CONCLUSIONS

Decreased proliferator-activated receptor-γ coactivator 1α expression contributes to the metabolic dysfunction in cholecardia so that reducing serum bile acid concentrations may be beneficial against the metabolic and pathological changes in the heart. (Hepatology 2017;65:189-201).

The role of bile acids in metabolic regulation

Bile acids (BA), long believed to only have lipid-digestive functions, have emerged as novel metabolic modulators. They have important endocrine effects through multiple cytoplasmic as well as nuclear receptors in various organs and tissues. BA affect multiple functions to control energy homeostasis, as well as glucose and lipid metabolism, predominantly by activating the nuclear farnesoid X receptor and the cytoplasmic G protein-coupled BA receptor TGR5 in a variety of tissues. However, BA also are aimed at many other cellular targets in a wide array of organs and cell compartments. Their role in the pathogenesis of diabetes, obesity and other 'diseases of civilization' becomes even more clear. They also interact with the gut microbiome, with important clinical implications, further extending the complexity of their biological functions. Therefore, it is not surprising that BA metabolism is substantially modulated by bariatric surgery, a phenomenon contributing favorably to the therapeutic effects of these surgical procedures. Based on these data, several therapeutic approaches to ameliorate obesity and diabetes have been proposed to affect the cellular targets of BA.

Renal Impairment with Sublethal Tubular Cell Injury in a Chronic Liver Disease Mouse Model

The pathogenesis of renal impairment in chronic liver diseases (CLDs) has been primarily studied in the advanced stages of hepatic injury. Meanwhile, the pathology of renal impairment in the early phase of CLDs is poorly understood, and animal models to elucidate its mechanisms are needed. Thus, we investigated whether an existing mouse model of CLD induced by 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) shows renal impairment in the early phase. Renal injury markers, renal histology (including immunohistochemistry for tubular injury markers and transmission electron microscopy), autophagy, and oxidative stress were studied longitudinally in DDC- and standard diet-fed BALB/c mice. Slight but significant renal dysfunction was evident in DDC-fed mice from the early phase. Meanwhile, histological examinations of the kidneys with routine light microscopy did not show definitive morphological findings, and electron microscopic analyses were required to detect limited injuries such as loss of brush border microvilli and mitochondrial deformities. Limited injuries have been recently designated as sublethal tubular cell injury. As humans with renal impairment, either with or without CLD, often show almost normal tubules, sublethal injury has been of particular interest. In this study, the injuries were associated with mitochondrial aberrations and oxidative stress, a possible mechanism for sublethal injury. Intriguingly, two defense mechanisms were associated with this injury that prevent it from progressing to apparent cell death: autophagy and single-cell extrusion with regeneration. Furthermore, the renal impairment of this model progressed to chronic kidney disease with interstitial fibrosis after long-term DDC feeding. These findings indicated that DDC induces renal impairment with sublethal tubular cell injury from the early phase, leading to chronic kidney disease. Importantly, this CLD mouse model could be useful for studying the pathophysiological mechanisms of sublethal tubular cell injury.

Molecular adsorbent recirculating system and single-pass albumin dialysis in liver failure--a prospective, randomised crossover study

Background

The aim of extracorporeal albumin dialysis (ECAD) is to reduce endogenous toxins accumulating in liver failure. To date, ECAD is conducted mainly with the Molecular Adsorbents Recirculating System (MARS). However, single-pass albumin dialysis (SPAD) has been proposed as an alternative. The aim of this study was to compare the two devices with a prospective, single-centre, non-inferiority crossover study design with particular focus on reduction of bilirubin levels (primary endpoint) and influence on paraclinical and clinical parameters (secondary endpoints) associated with liver failure.

Methods

Patients presenting with liver failure were screened for eligibility and after inclusion were randomly assigned to be started on either conventional MARS or SPAD (with 4 % albumin and a dialysis flow rate of 700 ml/h). Statistical analyses were based on a linear mixed-effects model.

Results

Sixty-nine crossover cycles of ECAD in 32 patients were completed. Both systems significantly reduced plasma bilirubin levels to a similar extent (MARS: median −68 μmol/L, interquartile range [IQR] −107.5 to −33.5, p = 0.001; SPAD: −59 μmol/L, −84.5 to +36.5, p = 0.001). However, bile acids (MARS: −39 μmol/L, −105.6 to −8.3, p < 0.001; SPAD: −9 μmol/L, −36.9 to +11.4, p = 0.131), creatinine (MARS: −24 μmol/L, −46.5 to −8.0, p < 0.001; SPAD: −2 μmol/L, −9.0 to +7.0/L, p = 0.314) and urea (MARS: −0.9 mmol/L, −1.93 to −0.10, p = 0.024; SPAD: −0.1 mmol/L, −1.0 to +0.68, p = 0.523) were reduced and albumin-binding capacity was increased (MARS: +10 %, −0.8 to +20.9 %, p < 0.001; SPAD: +7 %, −7.5 to +15.5 %, p = 0.137) only by MARS. Cytokine levels of interleukin (IL)-6 and IL-8 and hepatic encephalopathy were altered by neither MARS nor SPAD.

Conclusions

Both procedures were safe for temporary extracorporeal liver support. While in clinical practice routinely assessed plasma bilirubin levels were reduced by both systems, only MARS affected other paraclinical parameters (i.e., serum bile acids, albumin-binding capacity, and creatinine and urea levels). Caution should be taken with regard to metabolic derangements and electrolyte disturbances, particularly in SPAD using regional citrate anti-coagulation.

Trial registration

German Clinical Trials Register (www.drks.de) DRKS00000371. Registered 8 April 2010.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-1159-3) contains supplementary material, which is available to authorized users.

Cardiac imaging in patients with chronic liver disease

Cirrhotic cardiomyopathy (CCM) is characterized by an impaired contractile response to stress, diastolic dysfunction and the presence of electrophysiological abnormalities, and it may be diagnosed at rest in some patients or demasked by physiological or pharmacological stress. CCM seems to be involved in the development of hepatic nephropathy and is associated with an impaired survival. In the field of cardiac imaging, CCM is not yet a well-characterized entity, hence various modalities of cardiac imaging have been applied. Stress testing with either physiologically or pharmacologically induced circulatory stress has been used to assess systolic dysfunction. Whereas echocardiography with tissue Doppler is by far the most preferred method to detect diastolic dysfunction with measurement of E/A- and E/E'-ratio. In addition, echocardiography may also possess the potential to evaluate systolic dysfunction at rest by application of new myocardial strain techniques. Experience with other modalities such as cardiac magnetic resonance imaging and cardiac computed tomography is limited. Future studies exploring these imaging modalities are necessary to characterize and monitor the cardiac changes in cirrhotic patients.