Hepatocyte nuclear factor-4α interacts with other hepatocyte nuclear factors in regulating transthyretin gene expression

The Journey of Human Transthyretin: Synthesis, Structure Stability, and Catabolism

Transthyretin (TTR) is a homotetrameric protein mainly synthesised by the liver and the choroid plexus whose function is to carry the thyroid hormone thyroxine and the retinol-binding protein bound to retinol in plasma and cerebrospinal fluid. When the stability of the tetrameric structure is lost, it breaks down, paving the way for the aggregation of TTR monomers into insoluble fibrils leading to transthyretin (ATTR) amyloidosis, a progressive disorder mainly affecting the heart and nervous system. Several TTR gene mutations have been characterised as destabilisers of TTR structure and are associated with hereditary forms of ATTR amyloidosis. The reason why also the wild-type TTR is intrinsically amyloidogenic in some subjects is largely unknown. The aim of the review is to give an overview of the TTR biological life cycle which is largely unknown. For this purpose, the current knowledge on TTR physiological metabolism, from its synthesis to its catabolism, is described. Furthermore, a large section of the review is dedicated to examining in depth the role of mutations and physiological ligands on the stability of TTR tetramers.

Pattern of serum protein capillary electrophoretogram in SARS- CoV-2 infection

Background and aims

Monoclonal/biclonalgammopathy of unknown significance (MGUS/BGUS) is observed in COVID-19. This study was conducted to determine the changes in serum protein electrophoresis (SPEP) in COVID-19.

Materials and methods

In this descriptive (cross-sectional) study, serum inflammatory markers (CRP, IL-6 and ferritin) were measured and SPEP was carried out by capillary electrophoresis method in 35 controls and 30 moderate & 58 severe COVID-19 cases.

Results

Serum inflammatory markers were increased in COVID-19 cases with severity. M−band(s), β-γ bridging and pre-albumin band(s) on SPEP were observed in 15.5, 11 & 12% of severe cases and 3, 4 & 0% moderate COVID-19 cases respectively. Area under curve (AUC) of α 1 and α 2 bands of SPEP increased significantly in severe COVID-19.

Conclusions

We conclude that SPEP changes like the appearance of M−band(s) indicating MGUS(BGUS), β- γ bridging indicating the presence of fast-moving immunoglobulins, pre-albumin band indicating the rise in serum transthyretin level and the increase in AUC of α 1 and α 2 bands indicating the rise in positive acute phase reactants occur in COVID-19. The occurrence and magnitude of these changes are higher in severe COVID-19 than that in moderate COVID-19. The diagnostic and prognostic significance of these SPEP changes are worth exploring.

Beyond Val30Met transthyretin (TTR): variants associated with age-at-onset in hereditary ATTRv amyloidosis

OBJECTIVES

V30M in transthyretin (TTR) gene is causative for hereditary ATTRv amyloidosis (familial amyloid polyneuropathy). ATTRv amyloidosis shows a wide variation in age-at-onset (AO) between clusters, families, and among generations. We aim at identifying genetic modifiers of disease onset that may contribute to this variability in Portuguese patients by identifying other variants in TTR locus, beyond the ATTRv amyloidosis causing variant that could play a regulatory role in its expression level.

METHODS

We analysed DNA samples of 330 ATTRV30M carriers (299 patients, 31 aged-asymptomatic carriers aged >40 years) from 120 families currently under follow-up. A generalised estimating equation analysis (GEE) was used to take into account non-independency of AO between relatives. An intensive in silico analysis was performed in order to understand a possible regulation of gene expression.

RESULTS

We found 11 rare variants in the promoter, coding and intron/exon boundaries of the TTR gene associated with the onset of symptoms before and after age 40 years, namely 2 novel ones and a tandem CA-dinucleotide repeat. Furthermore, of the 4 common variants found, one was significantly associated with AO and may influence the constitutive splicing of TTR pre-mRNA. The seven ATTRV30M/V30M homozygous do not carry any of the variants identified in this study, including the common ones. In silico analysis disclosed significant alterations in the mechanism of splicing, transcription factors and miRNAs binding.

CONCLUSIONS

Variants within the promoter region may modify disease expressivity and variants in the 3'UTR can impact the efficacy of novel therapeutic interventions. Importantly, the putative mechanisms of regulation of gene expression within the TTR gene deserve to be better explored, in order to be used in the future as potential therapeutical targets.

Differential Diagnosis of Cachexia and Refractory Cachexia and the Impact of Appropriate Nutritional Intervention for Cachexia on Survival in Terminal Cancer Patients

Cancer cachexia subsequently shifts to refractory cachexia, however, it is not easy to properly differentiate them in clinical settings. Patients considered refractory cachexia may include cachectic patients with starvation. This study aimed to identify these cachectic patients and to evaluate the effect of nutritional intervention for them. Study subjects were terminal cancer patients admitted for palliative care and were judged refractory cachexia in the last five years. We retrospectively examined to find useful indices for identifying such cachectic patients and for evaluating the effect of nutritional intervention. Out of 223 patients in refractory cachexia, 26 were diagnosed cachexia with starvation after symptom management. Comparing before and one week after this management, Palliative Performance Scale (PPS) and transthyretin significantly improved (p < 0.0001, p = 0.0002, respectively) Then, we started nutritional intervention for these cachectic patients and divided into effective group (n = 17) and non-effective group (n = 9) using the criteria for cachexia. Comparing between the two groups, PPS significantly improved2 weeks after intervention in effective group (p = 0.006). Survival time was significantly longer in effective group (p = 0.008). PPS and transthyretin were useful for differential diagnosis of cachexia and refractory cachexia. PPS was useful for evaluating nutritional intervention for cachectic patients. Appropriate nutritional intervention improved survival.

HNF‑4α downregulation promotes tumor migration and invasion by regulating E‑cadherin in renal cell carcinoma

Renal cell carcinoma (RCC) is the most common malignant disease of the kidneys in adults. Patients with metastatic RCC have an unusually poor prognosis and exhibit resistance to all current therapies. Therefore, it is necessary to explore novel molecules involved in the progression of RCC and to identify effective therapeutic targets. Hepatocyte nuclear factor-4α (HNF-4α) serves an important role in hepatocyte differentiation and is involved in the progression of liver cancer; however, the functional role of HNF-4α has not been well established in RCC. The present study reported that HNF-4α expression was markedly downregulated in RCC tissue samples compared with in normal controls by immunohistochemistry and RNA-sequencing analysis. Statistical analysis demonstrated that HNF-4α downregulation was significantly associated with tumor stage, recurrence, metastasis and poor prognosis in patients with RCC. Furthermore, wound-healing and Transwell assays revealed that downregulation of HNF-4α promoted cell migration and invasion by transcriptionally regulating E-cadherin in RCC. Finally, a positive correlation was revealed between HNF-4α expression and E-cadherin expression, and patients with low E-cadherin expression also had a poor prognosis. These findings may provide novel insights into the biological effects of HNF-4α and lay the foundation for the discovery of molecular therapeutic targets in RCC.

Low Transthyretin Levels Predict Poor Prognosis in Cancer Patients in Palliative Care Settings

OBJECTIVES

Although transthyretin (TTR) is a nutritional indicator and is influenced by systemic inflammation, it may be a good prognostic indicator for cancer patients in palliative care settings. This study investigates the correlation between low TTR levels and survival among cancer patients in palliative care settings.

METHODS

This was a sub-analysis of a prospective, multicenter cohort study. Patients who had advanced-stage cancer and who were newly referred to palliative care services were eligible to participate; however, those receiving anti-tumor therapy were excluded. Survival analyses were performed to clarify predictors of poor prognosis.

RESULTS

A total of 144 patients were enrolled (45.1% female; median age, 72 years). Cox regression analysis revealed that low TTR levels (<10.9 mg/l) (hazard ratio 1.74, P = 0.025), poor muscle power (1.71, P = 0.045), and fatigue (1.89, P = 0.024) were predictors of poor prognosis. Median survival in patients with low TTR levels (<10.9 mg/l) was 26 days, which was significantly shorter than those with high TTR levels (≥10.9 mg/l) (50 days; P < 0.001).

CONCLUSION

Low TTR levels may be indicators for poor prognosis among cancer patients in palliative care settings.

MicroRNA regulation of Transthyretin in trophoblast differentiation and Intra-Uterine Growth Restriction

Placental trophoblast cells produce various cytokines, transporters vital to normal embryogenesis. Transthyretin (TTR) aids trans-placental passage of maternal thyroxin (TH) to fetal circulation. Inadequate TH delivery leads to developmental abnormality. Regulation of TTR biosynthesis in placenta is critical for normal embryo development. We showed here that TTR transcripts were expressed more in fetal placenta. Using bioinformatic analysis and confirmation with dual-luciferase reporter assays, we found that miR-200a-3p and miR-141-3p inhibited TTR expression by directly binding to the 3'UTR of TTR, which is reversed by mutation in the microRNA binding site. Differentiation of human trophoblast BeWo cells was associated with decreased TTR transcript and protein levels with concomitant increase in the levels of both microRNAs. Interestingly, ectopic overexpression of the microRNA mimics abrogated thyroxin uptake by BeWo cells, which was reversed by the corresponding inhibitors. Furthermore, in a rat model of intra-uterine growth restriction (IUGR), TTR expression decreased significantly in placenta with reciprocal rise in miR-141-3p but not 200a-3p. In human IUGR placenta, TTR transcript and protein levels were significantly lower associated with high expression of miR-141-3p but not 200a-3p. These data provides new insight into physiological role of miR-141-3p in regulating TTR during trophoblast differentiation and IUGR.

Analysis of gene expression and regulation implicates C2H9orf152 has an important role in calcium metabolism and chicken reproduction

The reproductive system of a female bird is responsible for egg production. The genes highly expressed in oviduct are potentially important. From RNA-seq analysis, C2H9orf152 (an orthologous gene of human C9orf152) was identified as highly expressed in chicken uterus. To infer its function, we obtained and characterized its complete cDNA sequence, determined its spatiotemporal expression, and probed its transcription factor(s) through pharmaceutical approach. Data showed that the complete cDNA sequence was 1468bp long with a 789bp of open reading frame. Compared to other tested tissues, this gene was highly expressed in the oviduct and liver tissues, especially uterus. Its expression in uterus was gradually increased during developmental and reproductive periods, which verified its involvement in the growth and maturity of reproductive system. In contrast, its expression was not significant different between active and quiescent uterus, suggesting the role of C2H9orf152 in reproduction is likely due to its long-term effect. Moreover, based on its 5'-flanking sequence, Foxd3 and Hnf4a were predicted as transcription factors of C2H9orf152. Using berberine or retinoic acid (which can regulate the activities of Hnf4a and Foxd3, respectively), we demonstrated suppression of C2H9orf152 by the chemicals in chicken primary hepatocytes. As retinoic acid regulates calcium metabolism, and Hnf4a is a key nuclear factor to liver, these findings suggest that C2H9orf152 is involved in liver function and calcium metabolism of reproductive system. In conclusion, C2H9orf152 may have a long-term effect on chicken reproductive system by regulating calcium metabolism, suggesting this gene has an important implication in the improvement of egg production and eggshell quality.

Mebiolgel, a thermoreversible polymer as a scaffold for three dimensional culture of Huh7 cell line with improved hepatocyte differentiation marker expression and HCV replication

PURPOSE

A novel three dimensional (3D) culture system purely synthesised from co-polymer which is free from biological contamination for Huh7 cell cultivation and hepatitis C virus (HCV) replication has been attempted.

MATERIALS AND METHODS

Mebiolgel, a thermo-reversible gelation polymer was used as a 3D scaffold for culturing Huh7, a liver carcinoma cell line used in our study. The 3D culture of the cells were infected with cell culture derived HCV.

RESULT

The scaffold supported the cell growth as 3D spheroids for up to 63 days. Moreover mebiolgel was found to be improving the hepatocyte differentiation of Huh7 cells at the transcript level. Three dimensional culture was susceptible for HCV infection, and this was confirmed by detecting the HCV replication intermediate viral core antigen.

CONCLUSION

Mebiolgel based culture system was proven to be suited for 3D culture of Huh7 cells by improvising liver specific genotypic expression and was susceptible for HCV replication. Since mebiolgel based Huh 7 express better hepatocyte differentiation markers genotypically, this can be implemented as an alternate for primary hepatocytes in studies such as viral isolation from patient serum.

Hepatocytes: a key cell type for innate immunity

Hepatocytes, the major parenchymal cells in the liver, play pivotal roles in metabolism, detoxification, and protein synthesis. Hepatocytes also activate innate immunity against invading microorganisms by secreting innate immunity proteins. These proteins include bactericidal proteins that directly kill bacteria, opsonins that assist in the phagocytosis of foreign bacteria, iron-sequestering proteins that block iron uptake by bacteria, several soluble factors that regulate lipopolysaccharide signaling, and the coagulation factor fibrinogen that activates innate immunity. In this review, we summarize the wide variety of innate immunity proteins produced by hepatocytes and discuss liver-enriched transcription factors (e.g. hepatocyte nuclear factors and CCAAT/enhancer-binding proteins), pro-inflammatory mediators (e.g. interleukin (IL)-6, IL-22, IL-1β and tumor necrosis factor-α), and downstream signaling pathways (e.g. signal transducer and activator of transcription factor 3 and nuclear factor-κB) that regulate the expression of these innate immunity proteins. We also briefly discuss the dysregulation of these innate immunity proteins in chronic liver disease, which may contribute to an increased susceptibility to bacterial infection in patients with cirrhosis.

The systemic amyloid precursor transthyretin (TTR) behaves as a neuronal stress protein regulated by HSF1 in SH-SY5Y human neuroblastoma cells and APP23 Alzheimer's disease model mice

Increased neuronal synthesis of transthyretin (TTR) may favorably impact on Alzheimer's disease (AD) because TTR has been shown to inhibit Aβ aggregation and detoxify cell-damaging conformers. The mechanism whereby hippocampal and cortical neurons from AD patients and APP23 AD model mice produce more TTR is unknown. We now show that TTR expression in SH-SY5Y human neuroblastoma cells, primary hippocampal neurons and the hippocampus of APP23 mice, is significantly enhanced by heat shock factor 1 (HSF1). Chromatin immunoprecipitation (ChIP) assays demonstrated occupation of TTR promoter heat shock elements by HSF1 in APP23 hippocampi, primary murine hippocampal neurons, and SH-SY5Y cells, but not in mouse liver, cultured human hepatoma (HepG2) cells, or AC16 cultured human cardiomyocytes. Treating SH-SY5Y human neuroblastoma cells with heat shock or the HSF1 stimulator celastrol increased TTR transcription in parallel with that of HSP40, HSP70, and HSP90. With both treatments, ChIP showed increased occupancy of heat shock elements in the TTR promoter by HSF1. In vivo celastrol increased the HSF1 ChIP signal in hippocampus but not in liver. Transfection of a human HSF1 construct into SH-SY5Y cells increased TTR transcription and protein production, which could be blocked by shHSF1 antisense. The effect is neuron specific. In cultured HepG2 cells, HSF1 was either suppressive or had no effect on TTR expression confirming the differential effects of HSF1 on TTR transcription in different cell types.

Proteomic serum profile of fatigued men receiving localized external beam radiation therapy for non-metastatic prostate cancer

CONTEXT

Fatigue is the most distressing side effect of radiation therapy, and its progression etiology is unknown.

OBJECTIVES

This study describes proteome changes from sera of fatigued men with non-metastatic prostate cancer receiving external beam radiation therapy (EBRT).

METHODS

Fatigue scores, measured by the Functional Assessment of Chronic Illness Therapy-Fatigue, and serum were collected from 12 subjects at baseline (before EBRT) and at midpoint (Day 21) of EBRT. Depleted sera from both time points were analyzed using two-dimensional difference gel electrophoresis, and up/down regulated proteins were identified using liquid chromatography-tandem mass spectrometry. Western blot analyses confirmed the protein changes observed.

RESULTS

Results showed that apolipoprotein (Apo)A1, ApoE, and transthyretin (TTR) consistently changed from baseline (Day 0) to midpoint (Day 21). The mean ApoE level of subjects with high change in fatigue (HF: n = 9) increased significantly from baseline to midpoint and were higher than in subjects with no change in fatigue. The mean ApoA1 level was higher in HF subjects at baseline and at midpoint than in no fatigue subjects at both time points. The mean TTR level of no fatigue subjects was higher at baseline and midpoint than in HF subjects.

CONCLUSION

These ApoE, ApoA1, and TTR results may assist in understanding pathways that can explain fatigue progression etiology in this clinical population.

The role of microRNAs in hepatocyte nuclear factor-4alpha expression and transactivation

Hepatocyte nuclear factor (HNF)-4α is a key member of the transcription factor network regulating hepatocyte differentiation and function. Genetic and molecular evidence suggests that expression of HNF-4α is mainly regulated at the transcriptional level. Activation of HNF-4A gene involves the interaction of distinct sets of transcription factors and co-transcription factors within enhancer and promoter regions. Here we study the inhibitory effect of microRNAs (miRNAs) on the 3'-untranslated region (3'-UTR) of HNF-4A mRNA. The potential recognition elements of a set of miRNAs were identified utilizing bioinformatics analysis. The family members of miR-34 and miR-449, including miR-34a, miR-34c-5p and miR-449a, share the same target elements located at two distinct locations within the 3'-UTR of HNF-4A. The over-expression of miR-34a, miR-34c-5p or miR-449a in HepG2 cells led to a significant decrease in the activity of luciferase reporter carrying 3'-UTR of HNF-4A. The repressive effect on reporter activity was partially or fully eliminated when one or two of the binding site(s) for miR-34a/miR-34c-5p/miR-449a were deleted within the 3'-UTR. The protein level of HNF-4α was dramatically reduced by over-expression of miR-34a, miR-34c-5p and miR-449a, which correlates with a decrease in the binding activity of HNF-4α and transactivation of HNF-4α target genes. These results suggest that the recognition sites of miR-34a, miR-34c-5p and miR-449a within 3'-UTR of HNF-4A are functional. The mechanism of down-regulation of the binding activity and transactivation of HNF-4α by the miRNAs involves the decrease in HNF-4α protein level via miRNAs selectively targeting HNF-4A 3'-UTR, leading to the translational repression of HNF-4α expression.

Transthyretin blocks retinol uptake and cell signaling by the holo-retinol-binding protein receptor STRA6

Vitamin A is secreted from cellular stores and circulates in blood bound to retinol-binding protein (RBP). In turn, holo-RBP associates in plasma with transthyretin (TTR) to form a ternary RBP-retinol-TTR complex. It is believed that binding to TTR prevents the loss of RBP by filtration in the kidney. At target cells, holo-RBP is recognized by STRA6, a plasma membrane protein that serves a dual role: it mediates uptake of retinol from extracellular RBP into cells, and it functions as a cytokine receptor that, upon binding holo-RBP, triggers a JAK/STAT signaling cascade. We previously showed that STRA6-mediated signaling underlies the ability of RBP to induce insulin resistance. However, the role that TTR, the binding partner of holo-RBP in blood, plays in STRA6-mediated activities remained unknown. Here we show that TTR blocks the ability of holo-RBP to associate with STRA6 and thereby effectively suppresses both STRA6-mediated retinol uptake and STRA6-initiated cell signaling. Consequently, TTR protects mice from RBP-induced insulin resistance, reflected by reduced phosphorylation of insulin receptor and glucose tolerance tests. The data indicate that STRA6 functions only under circumstances where the plasma RBP level exceeds that of TTR and demonstrate that, in addition to preventing the loss of RBP, TTR plays a central role in regulating holo-RBP/STRA6 signaling.

Transcriptional regulation of N-acetylglutamate synthase

The urea cycle converts toxic ammonia to urea within the liver of mammals. At least 6 enzymes are required for ureagenesis, which correlates with dietary protein intake. The transcription of urea cycle genes is, at least in part, regulated by glucocorticoid and glucagon hormone signaling pathways. N-acetylglutamate synthase (NAGS) produces a unique cofactor, N-acetylglutamate (NAG), that is essential for the catalytic function of the first and rate-limiting enzyme of ureagenesis, carbamyl phosphate synthetase 1 (CPS1). However, despite the important role of NAGS in ammonia removal, little is known about the mechanisms of its regulation. We identified two regions of high conservation upstream of the translation start of the NAGS gene. Reporter assays confirmed that these regions represent promoter and enhancer and that the enhancer is tissue specific. Within the promoter, we identified multiple transcription start sites that differed between liver and small intestine. Several transcription factor binding motifs were conserved within the promoter and enhancer regions while a TATA-box motif was absent. DNA-protein pull-down assays and chromatin immunoprecipitation confirmed binding of Sp1 and CREB, but not C/EBP in the promoter and HNF-1 and NF-Y, but not SMAD3 or AP-2 in the enhancer. The functional importance of these motifs was demonstrated by decreased transcription of reporter constructs following mutagenesis of each motif. The presented data strongly suggest that Sp1, CREB, HNF-1, and NF-Y, that are known to be responsive to hormones and diet, regulate NAGS transcription. This provides molecular mechanism of regulation of ureagenesis in response to hormonal and dietary changes.