Lipids and lipid-activated vitamins in chronic cholestatic diseases

Mitochondrial cholesterol: Metabolism and impact on redox biology and disease

Cholesterol is a crucial component of membrane bilayers by regulating their structural and functional properties. Cholesterol traffics to different cellular compartments including mitochondria, whose cholesterol content is low compared to other cell membranes. Despite the limited availability of cholesterol in the inner mitochondrial membrane (IMM), the metabolism of cholesterol in the IMM plays important physiological roles, acting as the precursor for the synthesis of steroid hormones and neurosteroids in steroidogenic tissues and specific neurons, respectively, or the synthesis of bile acids through an alternative pathway in the liver. Accumulation of cholesterol in mitochondria above physiological levels has a negative impact on mitochondrial function through several mechanisms, including the limitation of crucial antioxidant defenses, such as the glutathione redox cycle, increased generation of reactive oxygen species and consequent oxidative modification of cardiolipin, and defective assembly of respiratory supercomplexes. These adverse consequences of increased mitochondrial cholesterol trafficking trigger the onset of oxidative stress and cell death, and, ultimately, contribute to the development of diverse diseases, including metabolic liver diseases (i.e. fatty liver disease and liver cancer), as well as lysosomal disorders (i.e. Niemann-Pick type C disease) and neurodegenerative diseases (i.e. Alzheimer's disease). In this review, we summarize the metabolism and regulation of mitochondrial cholesterol and its potential impact on liver and neurodegenerative diseases.

Mechanism for development of malnutrition in primary biliary cholangitis

Primary biliary cholangitis (PBC) is a chronic cholestatic liver disease that is associated with impaired biliary excretion processes. Along with the development of cholestasis, there is a deficient flow of bile acids into the intestinal lumen causing malnutrition (MN) that is manifested in deficiencies of both macro- and micronutrients. The mechanism for development of trophological insufficiency is multifactorial. However, the trigger of MN in PBC is impaired enterohepatic circulation of bile acids. The ingress of bile acids with a detergent effect into the general bloodstream, followed by elimination via the kidneys and skin, triggers a cascade of metabolic disturbances, which leads to the gradual development and progression of calorie MN. The latter gradually transforms into protein-calorie MN (PСM) (as marasmus) due to the insufficient entry of bile acids into the duodenum, which is accompanied by a decrease in the emulsification, hydrolysis, and absorption of fats and fat-soluble vitamins, as well as disturbance of intestinal motility and bacterial overgrowth. Fat-soluble vitamin deficiencies complement PСM with vitamin and mineral MN. The development of hepatocellular failure enhances the progression of PСM due to the impaired protein synthetic function of hepatocytes in the advanced stage of PBC, which results in deficiency of not only the somatic but also the visceral pool of proteins. A mixed PСM form of marasmus and kwashiorkor develops. Early recognition of energy, protein, micronutrient, and macronutrient deficiencies is of great importance because timely nutritional support can improve liver function and quality of life in patients with PBC. In this case, it is important to know what type (energy, protein-calorie, vitamin, and vitamin-mineral) and form (marasmus, marasmus-kwashiorkor) of MN is present in the patient and how it is associated with the stage of the disease. Therefore, it is recommended to screen all patients with PBC for MN, from the early asymptomatic stage of the disease in order to identify and avoid preventable complications, such as fatigue, malaise, performance decrement, sarcopenia, osteoporosis, and hepatic encephalopathy, which will be able to provide appropriate nutritional support for correction of the trophological status.

Sensory Axonopathy Associated With Vitamin E Deficiency

Vitamin E deficiency can be observed in patients with malabsorption syndromes or inherited diseases such as ataxia. It is unusual for it to be a result of dietary insufficiency due to its presence in a wide variety of foods. Patients with vitamin E deficiency can present with neuromuscular disorders such as ataxia, hyporeflexia, spinocerebellar syndrome, as well as loss of vibration and proprioceptive sensation. Herein, we are presenting a case in which a previously healthy adult with no family history of genetic defects and malabsorption syndrome presented with a characteristic sensory axonopathy associated with vitamin E deficiency without any evidence of fat malabsorption. Patient reported a markedly improvement of symptoms after three-month supplementation of vitamin E. The unique part of this case was that the patient presented with neuropathic pain associated with vitamin E deficiency without any family history of inherited deficiency or any malabsorption syndrome.

Exploring the temporal dynamics of inhibition of return using steady-state visual evoked potentials

Inhibition of return is characterized by delayed responses to previously attended locations when the interval between stimuli is long enough. The present study employed steady-state visual evoked potentials (SSVEPs) as a measure of attentional modulation to explore the nature and time course of input- and output-based inhibitory cueing mechanisms that each slow response times at previously stimulated locations under different experimental conditions. The neural effects of behavioral inhibition were examined by comparing post-cue SSVEPs between cued and uncued locations measured across two tasks that differed only in the response modality (saccadic or manual response to targets). Grand averages of SSVEP amplitudes for each condition showed a reduction in amplitude at cued locations in the window of 100-500 ms post-cue, revealing an early, short-term decrease in the responses of neurons that can be attributed to sensory adaptation, regardless of response modality. Because primary visual cortex has been found to be one of the major sources of SSVEP signals, the results suggest that the SSVEP modulations observed were caused by input-based inhibition that occurred in V1, or visual areas earlier than V1, as a consequence of reduced visual input activity at previously cued locations. No SSVEP modulations were observed in either response condition late in the cue-target interval, suggesting that neither late input- nor output-based IOR modulates SSVEPs. These findings provide further electrophysiological support for the theory of multiple mechanisms contributing to behavioral cueing effects.

The MBOAT7 rs641738 variant is associated with an improved outcome in primary sclerosing cholangitis

BACKGROUND AND AIMS

Primary sclerosing cholangitis (PSC) is a chronic cholestatic disease that causes liver cirrhosis, leading to liver failure. Additionally, PSC is a risk factor for cholangiocarcinoma. Its mechanism is unknown, and liver transplantation remains the sole curative option. The membrane bound O-acyltransferase domain containing 7 (MBOAT7) rs641738 and rs626283 variant alleles have been associated with both an accelerated progression of the disease and a higher risk for developing a more severe phenotype in many chronic hepatic diseases. Thus, we analysed their effect on long-term outcomes and laboratory parameters in PSC patients.

METHODS

We determined MBOAT7 genotypes and estimated the actuarial survival rate free of liver transplantation, using the Kaplan-Meier estimator. The differences between the estimates were analysed using the log-rank test. Patient blood was drawn and analysed for different serum parameters including cholestatic markers. Additionally, MBOAT7 RNA expression in human hepatic cell lines MZCHA1 (a biliary adenocarcinoma cell line), HepG2 (a hepatocellular carcinoma cell line), LX-2 (hepatic stellate cell line) and H-69 (cholangiocyte cell line) was analysed.

RESULTS

Transplant-free survival was significantly prolonged in carriers of two rs641738 variant alleles, which was referred to as the TT genotype (mean 19.6 years; 95% confidence interval [CI]: 16.3-22.9 years) compared to the CC (mean 15.4 years, 95% CI 12.8-18.0 years) and heterozygous genotypes (mean 13.2 years, 95% CI 11.4-15.0 years) (P=0.017). This effect was restricted to male patients. We confirmed the high expression of MBOAT7 in hepatic stellate cells and found that MBOAT7 is less expressed in biliary epithelial cell lines, compared to parenchymal hepatic cells.

CONCLUSIONS

Unlike other chronic liver diseases, carrying two MBOAT7 variant alleles does not seem to affect PSC patients negatively, but seems to have a positive effect on transplant-free survival. This study could help improve individual prognosis in PSC patients and give some new perspective on the involvement of the immune system in PSC.

Impact of Microbes on the Pathogenesis of Primary Biliary Cirrhosis (PBC) and Primary Sclerosing Cholangitis (PSC)

Primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) represent the major clinical entities of chronic cholestatic liver diseases. Both disorders are characterized by portal inflammation and slowly progress to obliterative fibrosis and eventually liver cirrhosis. Although immune-pathogenic mechanisms have been implicated in the pathogenesis of PBC and PSC, neither disorder is considered to be a classical autoimmune disease, as PSC and PBC patients do not respond to immune-suppressants. Furthermore, the decreased bile flow resulting from the immune-mediated tissue assault and the subsequent accumulation of toxic bile products in PBC and PSC not only perpetuates biliary epithelial damage, but also alters the composition of the intestinal and biliary microbiota and its mutual interactions with the host. Consistent with the close association of PSC and inflammatory bowel disease (IBD), the polyclonal hyper IgM response in PBC and (auto-)antibodies which cross-react to microbial antigens in both diseases, an expansion of individual microbes leads to shifts in the composition of the intestinal or biliary microbiota and a subsequent altered integrity of epithelial layers, promoting microbial translocation. These changes have been implicated in the pathogenesis of both devastating disorders. Thus, we will discuss here these recent findings in the context of novel and alternative therapeutic options.

Primary biliary cirrhosis: Clinical and laboratory criteria for its diagnosis

Primary biliary cirrhosis (PBC) is a chronic progressive cholestatic granulomatous, and destructive inflammatory lesion of small intralobular and septal bile ducts, which is likely to be caused by an autoimmune mechanism with a the presence of serum antimitochondrial antibodies and a potential tendency to progress to cirrhosis. Despite the fact that the etiology of this disease has been unknown so far, there has been a considerable body of scientific evidence that can reveal the clinical and laboratory signs of PBC and the individual components of its pathogenesis and elaborate diagnostic criteria for the disease and its symptomatic therapy. Deficiencies in autoimmune tolerance are critical factors for the initiation and perpetuation of the disease. The purpose of this review is to summarize the data available in the literature and the author’s findings on clinical and laboratory criteria for the diagnosis of PBC. This review describes the major clinical manifestations of the disease and the mechanisms of its development. It presents the immunological, biochemical, and morphological signs of PBC and their significance for its diagnosis. A great deal of novel scientific evidence for the problem of PBC has been accumulated. However, the inadequate efficiency of therapy for the disease lends impetus to the quest for its etiological factors and to further investigations of its pathogenetic mechanisms and, on this basis, to searches for new methods for its early diagnosis.

Serum metabolic signatures of primary biliary cirrhosis and primary sclerosing cholangitis

BACKGROUND & AIMS

A greater understanding of cholestatic disease is necessary to advance diagnostic tools and therapeutic options for conditions such as primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC). The purpose of this study was to determine and compare the serum metabolomes of patients with PBC (n = 18) or PSC (n = 21) and healthy controls (n = 10) and to identify metabolites that may differentiate these two cholestatic diseases.

METHODS AND RESULTS

Using a mass spectrometry-based, non-targeted biochemical profiling approach, we identified 420 serum metabolites, 101 that differed significantly (P ≤ 0.05) between PBC and control groups, 115 that differed significantly between PSC and control groups, and 56 that differed significantly between PSC and PBC groups. Random forest classification analysis was able to distinguish patients with PBC or PSC with 95% accuracy with selected biochemicals reflective of protein and amino acid metabolism identified as the major contributors. Metabolites related to bile acid metabolism, lipid metabolism, inflammation, and oxidative stress/lipid peroxidation were also identified as differing significantly when comparing the disease groups and controls, with some of these pathways differentially affected in the PBC and PSC groups.

CONCLUSION

In this study, we identified novel metabolic changes associated with cholestatic disease that were both consistent and different between PBC and PSC. Validation studies in larger patient cohorts are required to determine the utility of these biochemical markers for diagnosis and therapeutic monitoring of patients with PBC and PSC.

Primary Biliary Cirrhosis and Primary Sclerosing Cholangitis: a Review Featuring a Women's Health Perspective

Primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC) are two major types of chronic cholestatic liver disease. Each disorder has distinguishing features and variable progression, but both may ultimately result in cirrhosis and hepatic failure. The following offers a review of PBC and PSC, beginning with a general overview of disease etiology, pathogenesis, diagnosis, clinical features, natural course, and treatment. In addition to commonly associated manifestations of fatigue, pruritus, and fat-soluble vitamin deficiency, select disease-related topics pertaining to women's health are discussed including metabolic bone disease, hyperlipidemia and cardiovascular risk, and pregnancy-related issues influencing maternal disease course and birth outcomes. This comprehensive review of PBC and PSC highlights some unique clinical considerations in the care of female patients with cholestatic liver disease.

Serum lipids in primary sclerosing cholangitis

BACKGROUND

Limited data are available regarding the serum lipids in primary sclerosing cholangitis.

AIMS

To determine the lipid levels in patients with primary sclerosing cholangitis.

METHODS

We monitored the serum lipid levels annually for up to 6 years in 157 patients included in three previous trials of ursodeoxycholic acid.

RESULTS

The baseline lipid values were: total cholesterol=207 mg/dL (127-433); high-density lipoprotein=56 mg/dL (26-132); low-density lipoprotein=129 mg/dL (48-334); triglycerides=102 mg/dL (41-698). Cirrhotic stage was associated with lower levels of total cholesterol (186 mg/dL vs. 217 mg/dL, p=.02). A significant correlation between the liver biochemistries and total and low-density lipoprotein cholesterol levels was observed. Ursodeoxycholic acid, as compared to placebo, significantly decreased total (-27 mg/dL vs. 22 mg/dL, p=.0004) and low-density lipoprotein cholesterol (-24 mg/dL vs. 17 mg/dL, p=.0001). After extended follow-up, small changes in the lipid levels were noticed. The incidence of coronary artery disease was 4%.

CONCLUSIONS

Our findings suggest that the lipid levels in primary sclerosing cholangitis are often above levels where treatment with lipid-lowering agents is recommended. However, primary sclerosing cholangitis patients seem to have no elevated risk for cardiovascular events. The correlation of total and low-density lipoprotein cholesterol with liver biochemistries implies that mechanisms linked to cholestasis may regulate cholesterol metabolism.

Prevalence and treatment of hyperlipidemia in patients with chronic hepatitis C infection

BACKGROUND

Patients with chronic hepatitis C (HCV) infection can also have hyperlipidemia. Glucose intolerance has been associated with HCV infection and treating hyperlipidemia in this and other high-risk groups is warranted. We hypothesized that hyperlipidemia is common in patients with hepatitis C and that it is under-treated for fear of worsening liver function.

DESIGN

From the Stratton Veterans Affairs Medical Center computerized database, we collected information on patients with HCV infection enrolled in hepatology clinic. We collected information on age, sex, duration of HCV infection, concomitant diagnoses, medications they were on, laboratory values including hepatic function, glucose, and lipid levels. We collected information on the lipid levels and various cardiovascular risk factors.

METHODS

This is a retrospective study involving record review. We analyzed the data collected from the records for prevalence of high cholesterol (as defined by the National Cholesterol Education Program) and for prevalence of various cardiovascular risk factors. We analyzed prevalence of treatment of hyperlipidemia in various risk groups. In the patients who were treated for hyperlipidemia, we collected information on any worsening hepatic function that led to treatment discontinuation.

RESULTS

Six hundred and twenty-eight (70.5%) out of 891 patients with hepatitis C had hyperlipidemia. Of the 628 patients who had hyperlipidemia, 81 (12.7%) had positive antibody and RNA not tested; 162 (25.4%) had positive antibody but negative RNA testing; and 385 (61.3%) had positive testing for viral RNA. Two hundred and eighty-four (45.2%) of 628 patients with hyperlipidemia were eligible for treatment to lower it. Of 146 patients with hyperlipidemia and diabetes mellitus or arterial disease who were qualified for treatment (LDL >99), 95 (65.1%) were treated with lipid-lowering medication. Of 148 patients with hyperlipidemia and without diabetes or arterial disease who were qualified for treatment, 64 (43.3%) were treated with lipid-lowering medication.

CONCLUSION

A high prevalence of hyperlipidemia in patients infected with HCV is observed. Prevalence is highest among those who are positive for viral RNA. About half the patients with hyperlipidemia were eligible for treatment with drugs to lower it. Treatment of hyperlipidemia with medication though surprisingly common could improve.