Noninvasive biomarkers for acute hepatotoxicity induced by 1,3-dichloro-2-propanol: hyperpolarized 13C dynamic MR spectroscopy

In vivo Hyperpolarized Metabolic Imaging to Monitor the Progression of Hepatitis B Virus (HBV)-Related Hepatitis to Liver Fibrosis

PURPOSE

This study aimed to assess metabolic changes to monitor the progression from normal liver to hepatitis B virus (HBV)-related hepatitis and liver fibrosis using hyperpolarized 13C magnetic resonance imaging (MRI).

PROCEDURES

Hepatitis was induced in mice (n = 16) via hydrodynamic injection of HBV 1.2 plasmid (25 μg). Among them, liver fibrosis was induced in the mice (n = 8) through weight-adapted administration of thioacetamide with ethanol. Normal control mice (n = 8) were injected with a phosphate buffer solution. Subsequently, a hyperpolarized 13C MRI was performed on the mouse liver in vivo. The level of hepatitis B surface antigen (HBsAg) in blood serum was measured. Statistical analysis involved comparing the differential metabolite ratios, blood biochemistry values, and body weight among the three groups using the Kruskal-Wallis one-way analysis of variance.

RESULTS

HBsAg was absent in the normal and fibrosis groups, while it was detected in the hepatitis group. The ratios of [1-13C] lactate/pyruvate, [1-13C] alanine/pyruvate, [1-13C] lactate/total carbon, and [1-13C] alanine/total carbon were significantly lower in the normal control group than in the hepatitis and fibrosis groups (p < 0.05). Moreover, these ratios were significantly higher in the fibrosis group than in the hepatitis group (p < 0.05). However, no significant differences were observed in either [1-13C] pyruvate-hydrate/pyruvate or [1-13C] pyruvate-hydrate/total carbon among the three groups.

CONCLUSIONS

The levels of [1-13C] lactate and [1-13C] alanine in vivo may serve as valuable indicators for differentiating between HBV-related hepatitis, liver fibrosis, and normal liver.

Detection of early-stage NASH using non-invasive hyperpolarized 13C metabolic imaging

Non-alcoholic steatohepatitis (NASH) is characterized from its early stages by a profound remodeling of the liver microenvironment, encompassing changes in the composition and activities of multiple cell types and associated gene expression patterns. Hyperpolarized (HP) 13C MRI provides a unique view of the metabolic microenvironment, with potential relevance for early diagnosis of liver disease. Previous studies have detected changes in HP 13C pyruvate to lactate conversion, catalyzed by lactate dehydrogenase (LDH), with experimental liver injury. HP ∝ -ketobutyrate ( ∝ KB) is a close molecular analog of pyruvate with modified specificity for LDH isoforms, specifically attenuated activity with their LDHA-expressed subunits that dominate liver parenchyma. Building on recent results with pyruvate, we investigated HP ∝ KB in methionine-choline deficient (MCD) diet as a model of early-stage NASH. Similarity of results between this new agent and pyruvate (~ 50% drop in cytoplasmic reducing capacity), interpreted together with gene expression data from the model, suggests that changes are mediated through broad effects on intermediary metabolism. Plausible mechanisms are depletion of the lactate pool by upregulation of gluconeogenesis (GNG) and pentose phosphate pathway (PPP) flux, and a possible shift toward increased lactate oxidation. These changes may reflect high levels of oxidative stress and/or shifting macrophage populations in NASH.

Hyperpolarized carbon 13 MRI in liver diseases: Recent advances and future opportunities

Hyperpolarized carbon-13 magnetic resonance imaging (HP ¹³ C MRI) is a recently translated metabolic imaging technique. With dissolution dynamic nuclear polarization (d-DNP), more than 10 000-fold signal enhancement can be readily reached, making it possible to visualize real-time metabolism and specific substrate-to-metabolite conversions in the liver after injecting carbon-13 labelled probes. Increasing evidence suggests that HP ¹³ C MRI is a potential tool in detecting liver abnormalities, predicting disease progression and monitoring response treatment. In this review, we will introduce the recent progresses of HP ¹³ C MRI in diffuse liver diseases and liver malignancies and discuss its future opportunities from a clinical perspective, hoping to provide a comprehensive overview of this novel technique in liver diseases and highlight its scientific and clinical potential in the field of hepatology.

Metabolic Changes in Different Stages of Liver Fibrosis: In vivo Hyperpolarized 13C MR Spectroscopy and Metabolic Imaging

PURPOSE

The objective was to assess metabolic changes in different stages of liver fibrosis using hyperpolarized C-13 magnetic resonance spectroscopy (MRS) and metabolic imaging.

PROCEDURES

Mild and severe liver fibrosis were induced in C3H/HeN mice (n = 14) by injecting thioacetamide (TAA). Other C3H/HeN mice (n = 7) were injected with phosphate buffer saline (PBS) (7.4 pH) as normal controls. Hyperpolarized C-13 MRS was performed on the livers of the mice, which was accompanied by intravoxel incoherent motion (IVIM) diffusion-weighted imaging with 12 b values. The differential metabolite ratios, apparent diffusion coefficient values, and IVIM parameters among the three groups were analyzed by a one-way analysis of variance test.

RESULTS

The ratios of [1-¹³C]lactate/pyruvate, [1-¹³C]lactate/total carbon (tC), [1-¹³C]alanine/pyruvate, and [1-¹³C] alanine/tC were significantly higher in both the mild and severe fibrosis groups than in the normal control group (p < 0.05). While the [1-¹³C]lactate/pyruvate and [1-¹³C]lactate/tC ratios were not significantly different between mild and severe fibrosis groups, the ratios of [1-¹³C]alanine/pyruvate and [1-¹³C]alanine/tC were significantly higher in the severe fibrosis group than in the mild fibrosis group (p < 0.05). In addition, D^* showed a significantly lower value in the severe fibrosis group than in the normal or mild fibrosis groups and negatively correlated with the levels of [1-¹³C] lactate and [1-¹³C]alanine.

CONCLUSIONS

Our findings suggest that it might be possible to differentiate mild from severe liver fibrosis using the cellular metabolic changes with hyperpolarized C-13 MRS and metabolic imaging.

Thermal processing food-related toxicants: a review

Heterocyclic aromatic amines, acrylamide, 5-hydroxymethylfurfural, furan, polycyclic aromatic hydrocarbons, nitrosamines, acrolein, chloropropanols and chloroesters are generated toxicants formed in some foodstuffs, mainly starchy and protein-rich food during thermal treatment such as frying, roasting and baking. The formation of these chemical compounds is associated with development of aromas, colors and flavors. One of the challenges facing the food industry today is to minimize these toxicants without adversely affecting the positive attributes of thermal processing. To achieve this objective, it is essential to have a detailed understanding of the mechanism of formation of these toxicants in processed foods. All reviewed toxicants in that paper are classified as probable, possible or potential human carcinogens and have been proven to be carcinogenic in animal studies. The purpose of that review is to summarize some of the most frequent occurring heat-generated food toxicants during conventional heating, their metabolism and carcinogenicity. Moreover, conventional and microwave heating were also compared as two different heat treatment methods, especially how they change food chemical composition and which thermal food toxicants are formed during specific method.

Time-course metabolic changes in high-fat diet-induced obesity rats: A pilot study using hyperpolarized (13)C dynamic MRS

The purpose of this study was to investigate the time-course metabolic changes based on hyperpolarized (13)C magnetic resonance spectroscopy (MRS) in high-fat diet (HFD)-induced obesity rats and the correlation between metabolic and serum enzyme levels. Sprague-Dawley rats were fed either HFD (60% fat) or normal diet (10% fat) for 6weeks. A HyperSense DNP was used to hyperpolarize [1-(13)C] pyruvic acid and the hyperpolarized (13)C MRS was examined every 2weeks in the course of 6weeks using a 3T GE MR750 scanner. The body weight of HFD-induced obese rats was significantly increased compared to normal rats at the 6th week after the onset of feeding (p=0.05). Simultaneously, the HFD-induced obese rats showed significantly increased levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and low-density lipoprotein (LDL)-cholesterol compared to normal rats (p≤0.05). In the dynamic (13)C MR spectra acquired at the 6th week, the obese rats showed significantly increased ratios of [1-(13)C] lactate/[1-(13)C] pyruvate and [1-(13)C] alanine/[1-(13)C] pyruvate (p=0.05). The (13)C spectral outcomes are positively correlated with the enzyme levels of ALT and LDH in the HFD-induced obesity. The [1-(13)C] lactate and [1-(13)C] alanine are potentially considered as noninvasive biomarkers for the HFD-induced obesity.