Interstrain differences in the progression of nonalcoholic steatohepatitis to fibrosis in mice are associated with altered hepatic iron metabolism

SLC40A1 in iron metabolism, ferroptosis, and disease: A review

Solute carrier family 40 member 1 (SLC40A1) plays an essential role in transporting iron from intracellular to extracellular environments. When SLC40A1 expression is abnormal, cellular iron metabolism becomes dysregulated, resulting in an overload of intracellular iron, which induces cell ferroptosis. Numerous studies have confirmed that ferroptosis is closely associated with the development of many diseases. Here, we review recent findings on SLC40A1 in ferroptosis and its association with various diseases, intending to explore new directions for research on disease pathogenesis and new therapeutic targets for prevention and treatment. This article is categorized under: Cancer > Genetics/Genomics/Epigenetics Metabolic Diseases > Molecular and Cellular Physiology.

Mineral metabolism and ferroptosis in non-alcoholic fatty liver diseases

Nonalcoholic fatty liver disease (NAFLD) has become the most prevalent chronic liver disease worldwide. Minerals including iron, copper, zinc, and selenium, fulfil an essential role in various biochemical processes. Moreover, the identification of ferroptosis and cuproptosis further underscores the importance of intracellular mineral homeostasis. However, perturbation of minerals has been frequently reported in patients with NAFLD and related diseases. Interestingly, studies have attempted to establish an association between mineral disorders and NAFLD pathological features, including oxidative stress, mitochondrial dysfunction, inflammatory response, and fibrogenesis. In this review, we aim to provide an overview of the current understanding of mineral metabolism (i.e., absorption, utilization, and transport) and mineral interactions in the pathogenesis of NAFLD. More importantly, this review highlights potential therapeutic strategies, challenges, future directions for targeting mineral metabolism in the treatment of NAFLD.

Antifibrotic activities of Scutellariae Radix extracts and flavonoids: Comparative proteomics reveals distinct and shared mechanisms

BACKGROUND

Scutellariae Radix (SR), the root of Scutellaria baicalensis Georgi, and SR flavonoids have antifibrotic activities. It remains obscure, however, amongst SR aqueous extract (SRA), SR methanolic extract (SRM) and five major SR flavonoids (baicalein, baicalin, wogonoside, wogonin and oroxyloside), which ones are the most promising antifibrotics and what their mechanisms are.

PURPOSE

To compare the antifibrotic activities of SR extracts and flavonoids, and the proteomic signatures of selected SR extract and flavonoid, versus IN1130 phosphate, an antifibrotic positive control (abbreviated as IN1130), in TGF-β1-induced in vitro model of fibrosis in NRK-49F renal fibroblasts.

METHODS

Isobaric labelling-based mass spectrometry was used for proteomic studies. Differentially expressed proteins were further analyzed using Gene Ontology annotation enrichment, protein-protein interaction network analysis and pathway analysis. Selected proteins of interest were validated by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Baicalein was the SR flavonoid with the best efficacy-toxicity ratio. SRM contained 8-fold more flavonoids and was more potently antifibrotic than SRA. Proteomic analysis of cells treated by TGF-β1, with or without baicalein (40 and 80 μM), SRM (40 and 80 μg/ml) and IN1130 (1 μM) suggested that baicalein, SRM and IN1130 all repressed TGF-β1-induced ribosomal proteins in cell lysates, while baicalein and SRM, but not IN1130, regulated the intracellular lysosome pathway; secretomic analysis suggested that 40 and 80 μg/ml SRM and 80 μM baicalein, but not IN1130 and 40 μM baicalein increased ribosomal proteins in conditioned media, whereas only baicalein regulated the lysosome pathway. ELISA verified secretomic findings that baicalein, SRM and IN1130 repressed TGF-β1-induced PAI-1 (Serpine1), Plod2, Ctgf (Ccn2), Ccl2 and Ccl7; baicalein and IN1130, but not SRM, reversed TGF-β1-induced Cyr61 (Ccn1) and Tsku; only baicalein reversed TGF-β1 repression of Mmp3; only IN1130 reversed TGF-β1-repressed Nov (Ccn3). ELISA validated cell-lysate proteomic findings that baicalein, SRM and IN1130 all reversed TGF-β1-induced Enpp1; only IN1130 reversed TGF-β1-induced Impdh2 and Sqstm1 and TGF-β1-repressed Aldh3a1. Baicalein and SRM induced Ccdc80, while only baicalein induced Tfrc.

CONCLUSION

Baicalein, SRM and IN1130 repress TGF-β1-induced fibrogenesis in renal fibroblasts by regulating overlapping protein targets and biological pathways. Our findings offer a comprehensive view of shared, drug- and dose-specific pharmacological and toxicological mechanisms and provide a valuable resource for further research and development of more efficacious and safer antifibrotics.

MiR-223 as a Regulator and Therapeutic Target in Liver Diseases

MicroRNAs (miRNAs) are endogenous non-coding single-stranded small molecule RNAs consisting of 20–24 nucleotides that are highly conserved in species evolution. Expression of miRNAs is strictly tissue-specific, and it is chronological in fungi and plants, as well as in animals. MiR-223 has been shown to play a key role in innate immunity, and dysregulation of its expression contributes to the pathogenesis of multiple inflammatory diseases, and cancers. In this article the biosynthesis and functions of miR-223 in innate immunity are reviewed, and the role of miR-223 in liver physiopathology and therapeutic prospects are highlighted.

Current Trends of Essential Trace Elements in Patients with Chronic Liver Diseases

Essential trace elements play crucial roles in the maintenance of health, since they are involved in many metabolic pathways. A deficiency or an excess of some trace elements, including zinc, selenium, iron, and copper, frequently causes these metabolic disorders such as impaired glucose tolerance and dyslipidemia. The liver largely regulates most of the metabolism of trace elements, and accordingly, an impairment of liver functions can result in numerous metabolic disorders. The administration or depletion of these trace elements can improve such metabolic disorders and liver dysfunction. Recent advances in molecular biological techniques have helped to elucidate the putative mechanisms by which liver disorders evoke metabolic abnormalities that are due to deficiencies or excesses of these trace elements. A genome-wide association study revealed that a genetic polymorphism affected the metabolism of a specific trace element. Gut dysbiosis was also responsible for impairment of the metabolism of a trace element. This review focuses on the current trends of four trace elements in chronic liver diseases, including chronic hepatitis, liver cirrhosis, nonalcoholic fatty liver disease, and autoimmune liver diseases. The novel mechanisms by which the trace elements participated in the pathogenesis of the chronic liver diseases are also mentioned.

Liraglutide improves hepatic steatosis and metabolic dysfunctions in a 3-week dietary mouse model of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis (NASH) is an emerging health problem worldwide. However, efficacious pharmacological treatment for NASH is lacking. A major issue for preclinical evaluation of potential therapeutics for NASH is the limited number of appropriate animal models, i.e., models that do not require long-term dietary intervention and adequately mimic disease progression in humans. The present study aimed to evaluate a 3-wk dietary mouse model of NASH and validate it by studying the effects of liraglutide, a compound in advanced clinical development for NASH. C57BL6/J mice were fed a diet high in fat (60%), cholesterol (1.25%), and cholic acid (0.5%), along with 2% hydroxypropyl-β-cyclodextrin in drinking water (HFCC-CDX diet). Histological and biological parameters were measured at 1 and 3 wk. After 1-wk diet induction, liraglutide was administrated daily for 2 wk and then NASH-associated phenotypic aspects were evaluated in comparison with control mice. Prior to treatment with liraglutide, mice fed the HFCC-CDX diet for 1 wk developed liver steatosis and had increased levels of oxidative-stress markers and hepatic and systemic inflammation. For mice not treated with liraglutide, these aspects were even more pronounced after 3 wk of the dietary period, with additional liver insulin resistance and fibrosis. Liraglutide treatment corrected the diet-induced alterations in glucose metabolism and significantly reduced hepatic steatosis and inflammation. This study provides a novel 3-wk dietary model of mice that rapidly develop NASH features, and this model will be suitable for evaluating the therapeutic efficacy of compounds in preclinical drug development for NASH.NEW & NOTEWORTHY We propose a diet high in fat (60%), cholesterol (1.25%), and cholic acid (0.5%) along with 2% hydroxypropyl-β-cyclodextrin in drinking water (HFCC-CDX diet) as a new dietary model of nonalcoholic steatohepatitis. We used the HFCC-CDX model to reproduce the main features of disease development in humans for the purpose of facilitating the rapid screening of drug candidates and prioritizing the more promising candidates for advanced preclinical assessment and subsequent clinical trials.

Iron Metabolism in Cancer

Demanded as an essential trace element that supports cell growth and basic functions, iron can be harmful and cancerogenic though. By exchanging between its different oxidized forms, iron overload induces free radical formation, lipid peroxidation, DNA, and protein damages, leading to carcinogenesis or ferroptosis. Iron also plays profound roles in modulating tumor microenvironment and metastasis, maintaining genomic stability and controlling epigenetics. in order to meet the high requirement of iron, neoplastic cells have remodeled iron metabolism pathways, including acquisition, storage, and efflux, which makes manipulating iron homeostasis a considerable approach for cancer therapy. Several iron chelators and iron oxide nanoparticles (IONPs) has recently been developed for cancer intervention and presented considerable effects. This review summarizes some latest findings about iron metabolism function and regulation mechanism in cancer and the application of iron chelators and IONPs in cancer diagnosis and therapy.

Stress of Strains: Inbred Mice in Liver Research

Inbred mice are the most popular animals used for in vivo liver research. These mice are genetically defined, readily available, less expensive to maintain than larger animals, and enjoy a broad array of commercial reagents for scientific characterization. C57BL/6 mice are the most commonly used strain. However, other strains discussed, including BALB/c, C3H, A/J, and FVB/N, may be better suited to a particular disease model or line of investigation. Understanding the phenotypes of different inbred mouse strains facilitates informed decision making during experimental design. Model systems influenced by strain-dependent phenotype include tissue regeneration, drug-induced liver injury (DILI; e.g., acetaminophen), fibrosis (e.g., carbon tetrachloride, CCl₄), Fas-induced apoptosis, cholestasis, alcohol-induced liver disease and cirrhosis, nonalcoholic fatty liver disease and steatohepatitis (NAFLD/NASH), and hepatocellular carcinoma (HCC). Thoughtful consideration of the strengths and weaknesses of each inbred strain in a given model system will lead to more robust data and a clearer understanding of translational relevance to human liver disease.

Role of microRNAs in alcohol-induced liver disorders and non-alcoholic fatty liver disease

MicroRNAs (miRNAs) are small non-coding RNAs that regulate multiple physiological and pathological functions through the modulation of gene expression at the post-transcriptional level. Accumulating evidence has established a role for miRNAs in the development and pathogenesis of liver disease. Specifically, a large number of studies have assessed the role of miRNAs in alcoholic liver disease (ALD) and non-alcoholic fatty liver disease (NAFLD), two diseases that share common underlying mechanisms and pathological characteristics. The purpose of the current review is to summarize and update the body of literature investigating the role of miRNAs in liver disease. In addition, the potential use of miRNAs as biomarkers and/or therapeutic targets is discussed. Among all miRNAs analyzed, miR-34a, miR-122 and miR-155 are most involved in the pathogenesis of NAFLD. Of note, these three miRNAs have also been implicated in ALD, reinforcing a common disease mechanism between these two entities and the pleiotropic effects of specific miRNAs. Currently, no single miRNA or panel of miRNAs has been identified for the detection of, or staging of ALD or NAFLD. While promising results have been shown in murine models, no therapeutic based-miRNA agents have been developed for use in humans with liver disease.

Role of miR-223 in the pathophysiology of liver diseases

MiRNAs are small, noncoding RNAs, which can regulate gene expression posttranscriptionally, and they have emerged as key factors in disease biology by aiding in disease development and progression. MiR-223 is highly conserved during evolution and it was first described as a modulator of hematopoietic lineage differentiation. MiR-223 has an essential part in inflammation by targeting the nuclear factor-κB pathway and the nucleotide-binding oligomerization domain-like receptor protein 3 inflammasome. Recent studies have shown that miR-223 expression is deregulated in various types of liver diseases, including hepatitis virus infections, alcohol-induced liver injury, drug-induced liver injury, non-alcoholic fatty liver disease, cirrhosis, and hepatocellular carcinoma. As inflammatory and immune factors are involved in the occurrence and progress of liver diseases, deregulated miR-223 may participate in the pathogenesis of these conditions by influencing neutrophil infiltration, macrophage polarization, and inflammasome activation. This review first summarizes the present understanding of the biological functions of miR-223, including its gene location and transcription regulation, as well as its physiological role in hematopoietic differentiation. This review then focuses on the role of miR-223 in liver pathophysiology and its potential applications as a diagnostic biomarker and therapeutic target in liver diseases.

A tiny RNA molecule involved with gene regulation may offer an appealing target for diagnosing and treating various liver diseases. MicroRNA-223 (miR-223) was first identified as controlling gene activity in a wide variety of immune cells. A review from researchers led by Yanning Liu at China’s Zhejiang University in Hangzhou details how abnormal miR-223 also contributes to liver damage in a variety of conditions, although questions still remain about how it functions in different liver disorders. The authors highlight studies linking miR-223 with the development of fibrosis and cirrhosis, and with the inflammatory response to injury from drugs, alcohol, or infection. This could make this microRNA a useful diagnostic biomarker. The authors also identify therapeutic opportunities to modulate this molecule, referring to several studies on the manipulation of miR-223 to treat hepatitis.

Updates on Dietary Models of Nonalcoholic Fatty Liver Disease: Current Studies and Insights

Nonalcoholic fatty liver disease (NAFLD) is a disease of increasing interest, as its prevalence is on the rise. NAFLD has been linked to metabolic syndrome, which is becoming more common due to the Western diet. Because NAFLD can lead to cirrhosis and related complications including hepatocellular carcinoma, the increasing prevalence is concerning, and medical therapy aimed at treating NAFLD is of great interest. Researchers studying the effects of medical therapy on NAFLD use dietary mouse models. The two main types of mouse model diets are the methionine- and choline-deficient (MCD) diet and the Western-like diet (WD). Although both induce NAFLD, the mechanisms are very different. We reviewed several studies conducted within the last 5 years that used MCD diet or WD mouse models in order to mimic this disease in a way most similar to humans. The MCD diet inconsistently induces NAFLD and fibrosis and does not completely induce metabolic syndrome. Thus, the clinical significance of the MCD diet is questionable. In contrast, WD mouse models consisting of high fat, cholesterol, and a combination of high-fructose corn syrup, sucrose, fructose, or glucose not only lead to metabolic syndrome but also induce NAFLD with fibrosis, making these choices most suitable for research.

Utilization of animal models to investigate nonalcoholic steatohepatitis-associated hepatocellular carcinoma

Nonalcoholic fatty liver disease (NAFLD) comprises a spectrum of liver disorders with fat accumulation from simple fatty liver, nonalcoholic steatohepatitis (NASH), fibrosis/cirrhosis and NAFLD/NASH-associated hepatocellular carcinoma (HCC). NASH is a progressive form of NAFLD and requires medical attention. One of 5-10 NASH patients may progress to end-state liver disease (ESLD or cirrhosis) in 5-10 years; meanwhile, life-threatening complications of ESLD and HCC account for major mortality. An increasing burden of NAFLD in clinics, elucidation of its pathogenesis and progression, and assessment of the efficacy of potential therapeutics demand reliable animal models. Most NASH-associated HCC occurs in cirrhotic subjects; however, HCC does appear in NASH patients without cirrhosis. Lipotoxicity, oxidant stress, insulin resistance, endoplasmic reticulum stress, altered adipokine and lymphokine profiles and gut microbiome changes affect NAFLD progression and constitute key pathobiologic interplays. How these factors promote malignant transformation in a microenvironment of steatotic inflammation and fibrosis/cirrhosis, and lead to development of neoplasms is one of critical questions faced in the hepatology field. The present review summarizes the characteristics of emerging rodent NASH-HCC models, and discusses the challenges in utilizing these models to unveil the mysteries of NASH-associated HCC development.

Genetics of metabolic syndrome: potential clues from wild-derived inbred mouse strains

The metabolic syndrome (MetS) is a complex constellation of metabolic abnormalities including obesity, abnormal glucose metabolism, dyslipidemia, and elevated blood pressure that together substantially increase risk for cardiovascular disease and Type 2 diabetes. Both genetic and environmental factors contribute to the development of MetS, but this process is still far from understood. Human studies have revealed only part of the underlying basis. Studies in mice offer many strengths that can complement human studies to help elucidate the etiology and pathophysiology of MetS. Here we review the ways mice can contribute to MetS research. In particular, we focus on the information that can be obtained from studies of the inbred strains, with specific focus on the phenotypes of the wild-derived inbred strains. These are newly derived inbred strains that were created from wild-caught mice. They contain substantial genetic variation that is not present in the classical inbred strains, have phenotypes of relevance for MetS, and various mouse strain resources have been created to facilitate the mining of this new genetic variation. Thus studies using wild-derived inbred strains hold great promise for increasing our understanding of MetS.

Serum microRNAs as predictors for liver fibrosis staging in hepatitis C virus-associated chronic liver disease patients

Accurate staging of liver fibrosis is important for clinical decision making and personalized management. Liver fibrosis is influenced by patients' genomics, including IFNL3 genotype and microRNA expression. However, incorporating microRNAs into fibrosis prediction algorithms has not been investigated. We examined the potential of eight selected serum microRNAs; miR-122, miR-126, miR-129, miR-199a, miR-155, miR-203a, miR-221, and miR-223 as non-invasive biomarkers to stage liver fibrosis in HCV-associated chronic liver disease (HCV-CLD). 145 Egyptian HCV-CLD patients were divided according to Metavir fibrosis scores. MicroRNAs and IFNL3 rs12979860 genotype were assayed by RT-qPCR and allelic discrimination techniques, respectively. Serum miR-122 was downregulated, whereas miR-203a and miR-223 were upregulated in significant fibrosis (≥F2) compared with no/mild fibrosis (F0-F1). Serum miR-126, miR-129, miR-203a, and miR-223 were upregulated in severe fibrosis (≥F3) and cirrhosis (F4) compared with F0-F2 and F0-F3, respectively. miR-221 was upregulated in ≥F3, but unchanged in F4. miR-155, miR-199a, and IFNL3 rs12979860 genotype were not significantly different in all comparisons. Differentially expressed serum microRNAs discriminated ≥F2, ≥F3, and F4 by receiver-operating-characteristic analysis. Multivariate logistic analysis revealed a model combining miR-129, miR-223, AST, and platelet count with high diagnostic accuracy for ≥F3 (AUC=0.91). The model also discriminated F4 (AUC=0.96) and ≥F2 (AUC=0.783), and was superior to APRI and FIB-4 in discriminating ≥F3 and F4, but not ≥F2. In conclusion, combining serum microRNAs with baseline predictors could serve as a new non-invasive algorithm for staging HCV-associated liver fibrosis. Additional studies are required to confirm this model and test its significance in liver fibrosis of other etiologies.

Strain- and time-dependent alterations in hepatic iron metabolism in a murine model of nonalcoholic steatohepatitis

Nonalcoholic steatohepatitis is a common liver disease that is often accompanied by dysregulated iron metabolism. The aim of the study was to test the hypothesis that aberrant iron metabolism in nonalcoholic steatohepatitis is modulated by genetic susceptibility to inflammation and oxidative stress. Hepatic histology and iron content were assessed in 3 inbred strains of mice (C57BL/6, BALB/c, and C3H/HeJ) fed an atherogenic diet (AD). Hepatic expression of genes relevant to iron metabolism, inflammation, and oxidative stress were quantitated by real-time reverse transcription-polymerase chain reaction. At 6 weeks on the AD, histologic injury and induction of inflammatory and oxidative stress-associated gene expression were most pronounced in C57BL/6. At 18 weeks on the AD, these parameters were similar in C57BL/6 and BALB/c. Atherogenic diet-fed C3H/HeJ showed milder responses at both time points. The AD was associated with decreased hepatic iron concentrations in all strains at 6 and 18 weeks. The decrease in hepatic iron concentrations did not correlate with changes in hepcidin expression and was not associated with altered expression of iron transporters. These findings are similar to those observed in models of obesity-induced steatosis and indicate that hepatic steatosis can be associated with depletion of iron stores that is not explained by upregulation of hepcidin expression by inflammation.

SIGNIFICANCE OF THE STUDY

Nonalcoholic steatohepatitis (NASH) is a common liver disease that often accompanies the metabolic syndrome. The latter condition has been linked to iron deficiency and diminished intestinal iron absorption, likely the result of hepcidin upregulation by chronic inflammation. Paradoxically, some NASH patients accumulate excess hepatic iron, which may increase fibrosis and cancer risk. Iron accumulation has been attributed to suppression of hepcidin by oxidative stress. The objective of this study was to investigate the contributions of inflammation and oxidative stress to altered hepatic iron metabolism in a murine model of NASH using inbred strains of mice with differing susceptibilities to injury.

Relationship between iron overload and nonalcoholic fatty liver disease: An update

As a component of the multiple hits, iron overload plays an important role in the development of nonalcoholic fatty liver disease (NAFLD). Iron overload could affect glucose, lipid, energy metabolism and inflammatory reaction. This paper reviews the relationship between iron overload and nonalcoholic fatty liver disease, in order to clarify how and why iron overload influences the progression of NAFLD.

Mechanistically linked serum miRNAs distinguish between drug induced and fatty liver disease of different grades

Hepatic steatosis is characterised by excessive triglyceride accumulation in the form of lipid droplets (LD); however, mechanisms differ in drug induced (DIS) and/or non-alcoholic fatty liver disease (NAFLD). Here we hypothesized distinct molecular circuits of microRNA/LD-associated target genes and searched for mechanistically linked serum and tissue biomarkers that would distinguish between DIS and human NAFLD of different grades. We analysed >800 rat hepatic whole genome data for 17 steatotic drugs and identified 157 distinct miRNAs targeting 77 DIS regulated genes. Subsequently, genomic data of N = 105 cases of human NAFLD and N = 32 healthy controls were compared to serum miRNA profiles of N = 167 NAFLD patients. This revealed N = 195 tissue-specific miRNAs being mechanistically linked to LD-coding genes and 24 and 9 miRNAs were commonly regulated in serum and tissue of advanced and mild NAFLD, respectively. The NASH serum regulated miRNAs informed on hepatic inflammation, adipocytokine and insulin signalling, ER-and caveolae associated activities and altered glycerolipid metabolism. Conversely, serum miRNAs associated with blunt steatosis specifically highlighted activity of FOXO1&HNF4α on CPT2, the lipid droplet and ER-lipid-raft associated PLIN3 and Erlin1. Altogether, serum miRNAs informed on the molecular pathophysiology of NAFLD and permitted differentiation between DIS and NAFLD of different grades.

Whole genome and normalized mRNA sequencing reveal genetic status of TK6, WTK1, and NH32 human B-lymphoblastoid cell lines

Closely related TK6, WTK1, and NH32 human B-lymphoblastoid cell lines differ in their p53 functional status. These lines are used frequently in genotoxicity studies and in studies aimed at understanding the role of p53 in DNA repair. Despite their routine use, little is known about the genetic status of these cells. To provide insight into their genetic composition, we sequenced and analyzed the entire genome of TK6 cells, as well as the normalized transcriptomes of TK6, WTK1, and NH32 cells. Whole genome sequencing (WGS) identified 21,561 genes and 5.17×10(6) small variants. Within the small variants, 50.54% were naturally occurring single nucleotide polymorphisms (SNPs) and 49.46% were mutations. The mutations were comprised of 92.97% single base-pair substitutions and 7.03% insertions or deletions (indels). The number of predicted genes, SNPs, and small mutations are similar to frequencies observed in the human population in general. Normalized mRNA-seq analysis identified the expression of transcripts bearing SNPs or mutations for TK6, WTK1, and NH32 as 2.88%, 2.04%, and 1.71%, respectively, and several of the variant transcripts identified appear to have important implications in genetic toxicology. These include a single base deletion mutation in the ferritin heavy chain gene (FTH1) resulting in a frame shift and protein truncation in TK6 that impairs iron metabolism. SNPs in the thiopurine S-methyltransferase (TPMT) gene (TPMT*3A SNP), and in the xenobiotic metabolizing enzyme, NADPH quinine oxidoreductase 1 (NQO1) gene (NQO1*2 SNP), are both associated with decreased enzyme activity. The clinically relevant TPMT*3A and NQO1*2 SNPs can make these cell lines useful in pharmacogenetic studies aimed at improving or tailoring drug treatment regimens that minimize toxicity and enhance efficacy.

Nonalcoholic Fatty Liver Disease: Correlation of the Liver Parenchyma Fatty Acid with Intravoxel Incoherent Motion MR Imaging-An Experimental Study in a Rat Model

Purpose

To prospectively evaluate the changes in fatty acid concentration after administrating a 60% high-fat diet to a non-alcoholic fatty liver disease rat model and to perform a correlation analysis between fatty acid with molecular diffusion (D_true), perfusion-related diffusion (D_fast), and perfusion fraction (P_fraction).

Material and Methods

This prospective study was approved by the appropriate ethics committee. Ten male Sprague-Dawley rats were fed a 60% high-fat diet until the study was finished. Point-resolved spectroscopy sequence ¹H-MRS with TR = 1,500 msec, TE = 35 msec, NEX = 64, and 8×8×8 mm³ voxel was used to acquire magnetic resonance spectroscopy (MRS) data. Diffusion-weighted imaging was performed on a two-dimensional multi-b value spin echo planar image with the following parameters: repetition time msec/echo time msec, 4500 /63; field of view, 120×120 msec²; matrix, 128×128; section thickness, 3 mm; number of repetition, 8; and multiple b value, 0, 25, 50, 75, 100, 200, 500, 1000 sec/mm². Baseline magnetic resonance imaging and magnetic resonance spectroscopy data (control) were acquired. ¹H proton MRS and diffusion-weighted imaging were obtained every 2 weeks for 8 weeks. The individual contributions of the true molecular diffusion and the incoherent motions of water molecules in the capillary network to the apparent diffusion changes were estimated using a least-square nonlinear fitting in MatLab. A Wilcoxon signed-rank test with the Kruskal-Wallis test was used to compare each week’s fatty acid mean quantification. Spearman’s correlation coefficient was used to evaluate the correlation between each fatty acid (e.g., total lipid (TL), total saturated fatty acid (TSFA), total unsaturated fatty acid (TUSFA), total unsaturated bond (TUSB), and polyunsaturated bond (PUSB)) and intravoxel incoherent motion (IVIM) mapping images (e.g., D_true, D_fast, and P_fraction).

Results

The highest mean TL value was at week 8 (0.278 ± 0.10) after the administration of the 60% high-fat diet, followed by weeks 6, 4, 2, and 0. The concentration level (16.99±2.29) of TSFA at week 4 was the highest. No significant differences in the concentrations of TUSFA, TUSB, or PUSB were observed in different weeks.

Conclusion

After the administration of the 60% high-fat diet in nonalcoholic fatty liver disease model, TL and TSFA depositions had significant changes. The mean concentrations of TUSFA, TUSB, PUSB did not significantly change. Total unsaturated fatty acid and polyunsaturated bond showed positive correlations with D_true and P_fraction.

An overview of molecular basis of iron metabolism regulation and the associated pathologies

Iron is essential for several vital biological processes. Its deficiency or overload drives to the development of several pathologies. To maintain iron homeostasis, the organism controls the dietary iron absorption by enterocytes, its recycling by macrophages and storage in hepatocytes. These processes are mainly controlled by hepcidin, a liver-derived hormone which synthesis is regulated by iron levels, inflammation, infection, anemia and erythropoiesis. Besides the systemic regulation of iron metabolism mediated by hepcidin, cellular regulatory processes also occur. Cells are able to regulate themselves the expression of the iron metabolism-related genes through different post-transcriptional mechanisms, such as the alternative splicing, microRNAs, the IRP/IRE system and the proteolytic cleavage. Whenever those mechanisms are disturbed, due to genetic or environmental factors, iron homeostasis is disrupted and iron related pathologies may arise.