Impact of antiretroviral treatment on (13) C-methionine metabolism as a marker of hepatic mitochondrial function: a longitudinal study

The characterisation of hepatic mitochondrial function in patients with non-alcoholic fatty liver disease (NAFLD) using the 13C-ketoisocaproate breath test

Hepatic mitochondrial function (HMF) assessed by the ¹³C-ketoisocaproate breath test (¹³C-KICA BT) has been previously shown to be significantly associated with the severity of biopsy proven non-alcoholic fatty liver disease (NAFLD). However, it is uncertain whether any perturbation in HMF relates specifically to severity of liver disease or factors associated with metabolic syndrome within (NAFLD). Our aim was to investigate whether there was any change in HMF assessed by ¹³C-KICA BT in patients with NAFLD compared to control subjects, and to assess the factors that are independently associated with HMF.

METHODS

77 patients with NAFLD and 11 healthy control subjects were studied. HMF was assessed using ¹³C-KICA BT and expressed as cumulative % ¹³C-dose recovered on breath over 1 h (cPDR over 1 h). Liver fat and fibrosis was assessed by transient elastography. Multivariable linear regression modelling was undertaken to test the independence of associations with HMF.

RESULTS

HMF (cPDR over 1 h) was lower in NAFLD compared to controls [13.4% (4.8) v. 21.0% (6.3); p < 0.0001)]. In NAFLD, HMF was lower in patients with diabetes versus no diabetes [12.7% (3.4) v. 14.3% (6.1); p = 0.003)]. Regression modelling showed age (β = -0.08; p = 0.01), waist circumference (β = -0.08; p = 0.01), hip circumference (β = -0.04; p = 0.01), aspartate aminotransferase (AST) (β = -0.05; p = 0.01) and diabetes status (β = -1.81; p = 0.01) were independently associated with HMF (R² = 41.5%; p < 0.0001).

CONCLUSIONS

In patients with NAFLD (compared to healthy subjects), there was a reduction in HMF assessed by the ¹³C-KICA BT. Furthermore, in patients with NAFLD, HMF is independent and inversely associated with age, waist and hip circumference, AST and diabetes status.

Molecular changes in hepatic metabolism and transport in cirrhosis and their functional importance

Liver cirrhosis is the common endpoint of many hepatic diseases and represents a relevant risk for liver failure and hepatocellular carcinoma. The progress of liver fibrosis and cirrhosis is accompanied by deteriorating liver function. This review summarizes the regulatory and functional changes in phase I and phase II metabolic enzymes as well as transport proteins and provides an overview regarding lipid and glucose metabolism in cirrhotic patients. Interestingly, phase I enzymes are generally downregulated transcriptionally, while phase II enzymes are mostly preserved transcriptionally but are reduced in their function. Transport proteins are regulated in a specific way that resembles the molecular changes observed in obstructive cholestasis. Lipid and glucose metabolism are characterized by insulin resistance and catabolism, leading to the disturbance of energy expenditure and wasting. Possible non-invasive tests, especially breath tests, for components of liver metabolism are discussed. The heterogeneity and complexity of changes in hepatic metabolism complicate the assessment of liver function in individual patients. Additionally, studies in humans are rare, and species differences preclude the transferability of data from rodents to humans. In clinical practice, some established global scores or criteria form the basis for the functional evaluation of patients with liver cirrhosis, but difficult treatment decisions such as selection for transplantation or resection require further research regarding the application of existing non-invasive tests and the development of more specific tests.

Bortezomib-induced acute interstitial nephritis

Acute interstitial nephritis (AIN) is one of the important causes of acute kidney injury (AKI) resulting from inflammatory tubulointerstitial injury induced by medications, infections and systemic diseases. Bortezomib has been increasingly used especially in renal related indications such as multiple myeloma and monoclonal gammopathy of renal significance. Severe allergic reactions from bortezomib treatment including AIN have not been described in the literature. We report a 47-year-old white man who developed biopsy-proven allergic AIN after treatment with bortezomib for his C3 glomerulonephritis. The patient's kidney function improved after treatment with glucocorticoid therapy and discontinuation of bortezomib, but worsened with recurrent AKI episode after re-initiation of bortezomib. His renal function improved after glucocorticoid therapy and discontinuation of bortezomib. To our knowledge, this is the first report of a biopsy-proven AIN from bortezomib.

Clinical utility of 13C-liver-function breath tests for assessment of hepatic function

13C-Liver-function breath tests have been used in clinical diagnostics and, to a limited extent, to investigate hepatic function. From a practical perspective, tests such as the 13C-aminopyrine and 13C-methacetin breath tests are simple to administer, safe, and relatively inexpensive to perform. Surprisingly, they have not entered the mainstream of clinical practice, because they are perceived to lack the specificity and adequate precision needed to give accurate results in real time. The dynamic nature of 13C-liver-function breath tests, their possible versatility in terms of assessing a range of different liver functions, and the ease with which they can be repeated to follow relative changes in liver function with time, all imply the potential for wider clinical application. Therefore, there is a need for these tests to be critically evaluated and their potential clinical application be tested systematically against defined objectives. We describe refinements in the methodology of the tests and propose several situations in which currently reliable methods for assessment of liver function do not exist and where 13C-liver-function breath tests might be of use. We propose that use has been constrained by practical methodological considerations which could be addressed to offer tests better suited to routine application in the out-patient or community setting.

HIV-Antiretroviral Therapy Induced Liver, Gastrointestinal, and Pancreatic Injury

The present paper describes possible connections between antiretroviral therapies (ARTs) used to treat human immunodeficiency virus (HIV) infection and adverse drug reactions (ADRs) encountered predominantly in the liver, including hypersensitivity syndrome reactions, as well as throughout the gastrointestinal system, including the pancreas. Highly active antiretroviral therapy (HAART) has a positive influence on the quality of life and longevity in HIV patients, substantially reducing morbidity and mortality in this population. However, HAART produces a spectrum of ADRs. Alcohol consumption can interact with HAART as well as other pharmaceutical agents used for the prevention of opportunistic infections such as pneumonia and tuberculosis. Other coinfections that occur in HIV, such as hepatitis viruses B or C, cytomegalovirus, or herpes simplex virus, further complicate the etiology of HAART-induced ADRs. The aspect of liver pathology including liver structure and function has received little attention and deserves further evaluation. The materials used provide a data-supported approach. They are based on systematic review and analysis of recently published world literature (MedLine search) and the experience of the authors in the specified topic. We conclude that therapeutic and drug monitoring of ART, using laboratory identification of phenotypic susceptibilities, drug interactions with other medications, drug interactions with herbal medicines, and alcohol intake might enable a safer use of this medication.

Hepatic mitochondrial dysfunction in Friedreich ataxia

BACKGROUND

Mitochondrial dysfunction due to respiratory chain impairment is a key feature in pathogenesis of Friedreich ataxia. Friedreich ataxia affects the nervous system, heart and pancreas.

METHODS

We assessed hepatic mitochondrial function by (13)C-methionine-breath-test in 16 Friedreich ataxia patients and matched healthy controls.

RESULTS

Patients exhaled significantly smaller amounts of (13)CO(2) over 90 minutes. Maximal exhaled percentage dose of (13)CO(2) recovery was reduced compared to controls.

CONCLUSIONS

(13)C-methionine-breath-test indicates subclinical hepatic mitochondrial dysfunction in Friedreich ataxia but did not correlate with GAA repeat lengths, disease duration or disease severity.

The non-invasive (13)C-methionine breath test detects hepatic mitochondrial dysfunction as a marker of disease activity in non-alcoholic steatohepatitis

Introduction

Mitochondrial dysfunction plays a central role in the general pathogenesis of non-alcoholic fatty liver disease (NAFLD), increasing the risk of developing steatosis and subsequent hepatocellular inflammation. We aimed to assess hepatic mitochondrial function by a non-invasive ¹³C-methionine breath test (MeBT) in patients with histologically proven NAFLD.

Methods

118 NAFLD-patients and 18 healthy controls were examined by MeBT. Liver biopsy specimens were evaluated according to the NASH scoring system.

Results

Higher grades of NASH activity and fibrosis were independently associated with a significant decrease in cumulative ¹³C-exhalation (expressed as cPDR(%)). cPDR_1.5h was markedly declined in patients with NASH and NASH cirrhosis compared to patients with simple steatosis or borderline diagnosis (cPDR1.5h: 3.24 ± 1.12% and 1.32 ± 0.94% vs. 6.36 ± 0.56% and 4.80 ± 0.88% respectively; p < 0.001). ¹³C-exhalation further declined in the presence of advanced fibrosis which was correlated with NASH activity (r = 0.36). The area under the ROC curve (AUROC) for NASH diagnosis was estimated to be 0.87 in the total cohort and 0.83 in patients with no or mild fibrosis (F0-1).

Conclusion

The ¹³C-methionine breath test indicates mitochondrial dysfunction in non-alcoholic fatty liver disease and predicts higher stages of disease activity. It may, therefore, be a valuable diagnostic addition for longitudinal monitoring of hepatic (mitochondrial) function in non-alcoholic fatty liver disease.