Preclinical evidence of Yinchenhao decoction on cholestasis: A systematic review and meta-analysis of animal studies

Metabolomics and serum pharmacochemistry combined with network pharmacology uncover the potential effective ingredients and mechanisms of Yin-Chen-Si-Ni Decoction treating ANIT-induced cholestatic liver injury

ETHNOPHARMACOLOGICAL RELEVANCE

Yin-Chen-Si-Ni Decoction is a classical traditional Chinese medicine (TCM) prescription that is used clinically for treating cholestatic liver injury (CLI) and other hepatic diseases. However, the material basis and underlying mechanisms of YCSND are not clear.

AIM OF THE STUDY

To investigate effective components and mechanisms of YCSND in the treatment of CLI using serum pharmacochemistry, metabolomics, and network pharmacology.

MATERIALS AND METHODS

Biochemical indicators, liver index, and histopathology analysis were adopted to evaluate the protective effect of YCSND on ANIT-induced CLI rats. Then, a UPLC-Q-Exactive Orbitrap MS/MS analysis of the migrant components in serum and liver including prototype and metabolic components was performed in YCSND. In addition, a study of the endogenous metabolites using serum and liver metabolomics was performed to discover potential biomarkers, metabolic pathways, and associated mechanisms. Further, the network pharmacology oriented by in vivo migrant components was also used to pinpoint the active ingredients, core targets, and signaling pathways of YCSND. Finally, molecular docking and molecular dynamics simulation (MDS) were used to predict the binding ability between components and core targets, and a real-time qPCR (RT-qPCR) experiment was used to measure the mRNA expression of the core target genes.

RESULTS

Pharmacodynamic studies suggest that YCSND could exert obvious hepatoprotective effects on CLI rats. Furthermore, 68 compounds, comprising 32 prototype components and 36 metabolic components from YCSND, were found by serum pharmacochemistry analysis. Network pharmacology combining molecular docking and MDS showed that apigenin, naringenin, 18β-glycyrrhetinic acid, and isoformononetin have better binding ability to 6 core targets (EGFR, AKT1, IL6, MMP9, CASP3, PPARG). Additionally, PI3K, TNF-α, MAPK3, and six core target genes in liver tissues were validated with RT-qPCR. Metabolomics revealed the anti-CLI effects of YCSND by regulating four metabolic pathways of primary bile acid and biosynthesis, phenylalanine, tyrosine and tryptophan biosynthesis, taurine and hypotaurine metabolism, and arachidonic acid metabolism. Integrating metabolomics and network pharmacology identified four pathways related to CLI, including the PI3K-Akt, HIF-1, MAPK, and TNF signaling pathway, which revealed multiple mechanisms of YCSND against CLI that might involve anti-inflammatory and apoptosis.

CONCLUSION

The research based on serum pharmacochemistry, network pharmacology, and metabolomics demonstrates the beneficial hepatoprotective effects of YCSND on CLI rats by regulating multiple components, multiple targets, and multiple pathways, and provides a potent means of illuminating the material basis and mechanisms of TCM prescriptions.

Liver cirrhosis: current status and treatment options using western or traditional Chinese medicine

Liver cirrhosis arises from liver fibrosis and necroinflammation caused by various mechanisms of hepatic injury. It is a prevalent condition in clinical practice characterized by hepatocellular dysfunction, portal hypertension, and associated complications. Despite its common occurrence, the etiology and pathogenesis of liver cirrhosis remain incompletely understood, posing a significant health threat. Effective prevention of its onset and progression is paramount in medical research. Symptoms often include discomfort in the liver area, while complications such as sarcopenia, hepatic encephalopathy, ascites, upper gastrointestinal bleeding, and infection can arise. While the efficacy of Western medicine in treating liver cirrhosis is uncertain, Chinese medicine offers distinct advantages. This review explores advancements in liver cirrhosis treatment encompassing non-pharmacological and pharmacological modalities. Chinese medicine interventions, including Chinese medicine decoctions, Chinese patent medicines, and acupuncture, exhibit notable efficacy in cirrhosis reversal and offer improved prognoses. Nowadays, the combination of Chinese and Western medicine in the treatment of liver cirrhosis also has considerable advantages, which is worthy of further research and clinical promotion. Standardized treatment protocols based on these findings hold significant clinical implications.

Optimized therapeutic potential of Yinchenhao decoction for cholestatic hepatitis by combined network meta-analysis and network pharmacology

BACKGROUND

Cholestatic hepatitis is recognized as a significant contributor to the development of liver fibrosis and cirrhosis. As a well-known classic formula for the treatment of cholestatic hepatitis, Yinchenhao decoction (YCHD) is widely used in countries in Asia, including China, Japan, and Korea. However, in recent years, a risk of liver injury has been reported from Rheum palmatum L. and Gardenia jasmonoides J.Ellis which are the main ingredients of YCHD. Therefore, the question arises whether YCHD is still safe enough for the treatment of cholestatic hepatitis or whether an optimized ratio of ingredients should be applied. These is inevitable questions for the clinical application of YCHD.

PURPOSE

To provide a scientific basis for the clinical application of YCHD through a combination of meta-analysis and network pharmacology and to find the best ratio of components to ensure optimal therapeutic efficacy and safety. At the same time, a deeper understanding of the mechanisms of YCHD was explored.

METHODS

We retrieved relevant trials from various databases including PubMed, Web of Science, EMBASE, Cochrane Library, China National Knowledge Infrastructure (CNKI), VIP and Wanfang databases up to August 2023. After screening for inclusion and exclusion criteria, we assessed efficiency, ALT, AST, and TBIL as outcome parameters. The relevant data underwent a network meta-analysis using STATA 16.0 software. Based on network pharmacology, we screened the disease targets, active ingredients, and targets related to YCHD. The targets were visualized using Cytoscape 3.9.1. Then, potential mechanisms were explored based on bioinformatic techniques.

RESULTS

Twenty eligible studies were finally screened and a total of 1,591 patients who fulfilled the inclusion criteria were enrolled in the study. The meta-analysis results indicated that TG-c (treatment group c) [(Artemisia capillaris Thunb. : Gardenia jasminoides J.Ellis : Rheum palmatum L. = 10:5:2-10:5:3) + CT] was the most promising therapeutic approach, demonstrating superior efficacy and notable improvements in both AST and TBIL levels. For ALT, TG-d [(Artemisia capillaris : Gardenia jasminoides : Rheum palmatum = 5:1:1-5:2:1) + CT] exhibited the greatest potential as optimal therapy option. Based on the surface under the cumulative ranking curve (SUCRA) values, TG-c was the best therapy in terms of efficiency and improvement in TBIL levels, while TG-d was the most effective in reducing ALT levels. For AST levels, TG-e [(Artemisia capillaris : Gardenia jasminoides : Rheum palmatum = 5:2:2-5:3:3) + CT] was the most effective therapy. The comprehensive analysis revealed that TG-c exhibited the most pronounced efficacy. Combined network pharmacology, GO enrichment analysis and KEGG pathway enrichment analysis displayed that the key target genes of Artemisia capillaris, Rheum palmatum, and Gardenia jasminoides were closely involved in inflammation response, bile transport, apoptosis, oxidative stress, and regulation of leukocyte migration. Notably, bile secretion dominated the common pathway of the three herbs. On the other hand, Artemisia capillaris exhibited a unique mode of action by regulating the IL-17 signaling pathway, which may play a crucial role in its effectiveness.

CONCLUSION

Based on our findings, the optimal TG-C demonstrated the most favorable overall therapeutic efficacy by increasing the dosage of Artemisia capillaris while reducing the dosage of Gardenia jasminoides and Rheum palmatum. This is attributed to the potent ability of Artemisia capillaris. to effectively modulate the IL-17 signaling pathway, thereby exerting a beneficial therapeutic effect. Conversely, Gardenia jasminoides and Rheum palmatum may potentially enhance the activation of the NF-кB signaling pathway, thereby elevating the risk of hepatotoxicity.

Yinchenhao Decoction Protects Against Acute Liver Injury in Mice With Biliary Acute Pancreatitis by Regulating the Gut Microflora-Bile Acids-Liver Axis

Background and Aims: Acute liver injury (ALI) often follows biliary acute pancreatitis (BAP), but the exact cause and effective treatment are unknown. The aim of this study was to investigate the role of the gut microflora-bile acids-liver axis in BAP-ALI in mice and to assess the potential therapeutic effects of Yinchenhao decoction (YCHD), a traditional Chinese herbal medicine formula, on BAP-ALI. Methods: Male C57BL/6 mice were allocated into three groups: negative control (NC), BAP model, and YCHD treatment groups. The severity of BAP-ALI, intrahepatic bile acid levels, and the gut microbiota were assessed 24 h after BAP-ALI induction in mice. Results: Our findings demonstrated that treatment with YCHD significantly ameliorated the severity of BAP-ALI, as evidenced by the mitigation of hepatic histopathological changes and a reduction in liver serum enzyme levels. Moreover, YCHD alleviated intrahepatic cholestasis and modified the composition of bile acids, as indicated by a notable increase in conjugated bile acids. Additionally, 16S rDNA sequencing analysis of the gut microbiome revealed distinct alterations in the richness and composition of the microbiome in BAP-ALI mice compared to those in control mice. YCHD treatment effectively improved the intestinal flora disorders induced by BAP-ALI. Spearman's correlation analysis revealed a significant association between the distinct compositional characteristics of the intestinal microbiota and the intrahepatic bile acid concentration. Conclusions: These findings imply a potential link between gut microbiota dysbiosis and intrahepatic cholestasis in BAP-ALI mice and suggest that YCHD treatment may confer protection against BAP-ALI via the gut microflora-bile acids-liver axis.

An UHPLC-QTOF-MS-based strategy for systematic profiling of chemical constituents and associated in vivo metabolites of a famous traditional Chinese medicine formula, Yinchenhao decoction

Yinchenhao decoction (YCHD), a famous traditional Chinese medicine formula, has been applied for relieving jaundice in China for more than 1800 years. However, the material basis for YCHD is still unclear, and the chemical composition and metabolism characteristic in vivo are undefined, making the potential effective constituents and mechanism of action unclear. Herein, an ultrahigh-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS)-based strategy was applied for the chemical profiling of YCHD, as well as their in vivo prototypes and global metabolites that defined the metabolome. Our results showed that a total of 139 chemicals were identified in YCHD, including 28 organic acids, 12 monoterpenoids, five diterpenes, three triterpenoids, 17 iridoids, 23 anthraquinones, 26 flavonoids, four coumarins and 21 other types. Moreover, 58 prototypes and 175 metabolites were found in rat biological samples after oral administration of YCHD; those distributed in plasma, liver, intestine and feces were suggested to be potentially effective substances. Oxidation, hydrogenation, decarboxylation and conjugations with methyl, sulfate and glucuronate were considered as the predominant metabolic pathways in vivo. In conclusion, this is a systemic study of chemical constituents and in vivo metabolome profiles of YCHD, contributing to the material basis understanding and further mechanism research.

Yinchen Linggui Zhugan decoction ameliorates high fat diet-induced nonalcoholic fatty liver disease by modulation of SIRT1/Nrf2 signaling pathway and gut microbiota

Yinchen Linggui Zhugan decoction (YLZD) is an effective and classical traditional herbal prescription for treating the nonalcoholic fatty liver disease (NAFLD) and has been proven to be effective in the regulation of lipid metabolism disorder and attenuate inflammation for a NAFLD rat model. However, the exact underlying mechanism has not been elucidated. In the current study, a NAFLD rat model was established using a high-fat diet (HFD) for 10 weeks, followed by YLZD treatment with 1.92 g/kg/day for 4 weeks to explore the mechanisms of YLZD. Our results showed that YLZD decreased the hepatic lipid deposition, restored the liver tissue pathological lesions, inhibited the expression of oxidative stress, and decreased the inflammatory cytokines levels. Meanwhile, the genes and proteins expressions of SIRT1/Nrf2 signaling pathway together with downstream factors including HO-1 and NQO1 were elevated in the YLZD treated NAFLD rats. For further elaborating the upstream mechanism, short-chain fatty acids (SCFAs) in serum and feces were measured by liquid chromatograph mass spectrometer and gas chromatograph mass spectrometer, and the differences in gut microbiota of rats in each group were analyzed through high-throughput sequencing of 16S rRNA. The results demonstrated that the contents of butyric acid (BA) and total SCFAs in YLZD-treated NAFLD rats were significantly increased in serum and feces. 16S rRNA sequencing analysis illustrated that YLZD intervention led to a modification of the gut microbiota composition, with a decrease of Oribacterium, Lactobacillus and the ratio of Firmicutes/Bacteroides, as well as the increase in SCFAs-producing bacteria such as Christensenellaceae, Clostridia, Muribaculaceae, and Prevotellaceae. Spearman rank correlation analysis indicated that BA and total SCFAs were negatively co-related with oxidative stress-related factors and inflammatory cytokines, while they were positively co-related with SIRT1/Nrf2 pathway related genes and proteins. Furthermore, in vitro study confirmed that BA effectively reduced oxidative stress by activating SIRT1/Nrf2 signaling pathway in L02 cells. Together, the present data revealed YLZD could ameliorate HFD-induced NAFLD in rats by the modulation of SIRT1/Nrf2 signaling pathway and gut microbiota.

Mechanism and Active Components of Qingre Lidan Tablets Alleviate Intrahepatic Cholestasis by Activating the Farnesoid X Receptor

Background

Qingre Lidan tablets (QLTs) are a compound preparation of Chinese medicine that have long been used clinically to treat poor bile circulation caused by the inflammation and obstruction of the gallbladder and bile duct and to relieve jaundice and other symptoms. However, its material basis and mechanism are still unclear. The purpose of this study was to investigate the mechanism and active components of QLTs for treating intrahepatic cholestasis (IHC) in rat models.

Methods

In vivo experiments verified the effect of QLTs on alpha-naphthyl isothiocyanate (ANIT)-induced IHC models in rats. The mRNA and protein expression levels of farnesoid X receptor (FXR), bile salt export pump (BSEP), and multidrug-associated protein 2 (MRP2) in the rat liver were detected. UPLC/Q-TOF-MS was used to separate and identify the monomers in QLTs, and a dual-luciferase reporter assay was used to select effective the monomers that stimulate FXR. Among the selected monomers, baicalein was used as a representative to verify the effect on rat IHC models.

Results

QLTs and baicalein significantly reduced the serum biochemical indicators reflecting the changes in liver function among IHC rats and remitted the ANIT-induced liver histopathological changes. The expression levels of FXR, BSEP, and MRP2 in the liver were significantly increased after QLT treatment in a dose-dependent manner. Moreover, six types of active components that activate FXR were selected in QLTs, namely baicalein, wogonin, baicalein II, emodin, dibutyl phthalate, and diisooctyl phthalate.

Conclusions

QLTs and the active component, baicalein, can alleviate IHC in model rats.

Distinct common signatures of gut microbiota associated with damp-heat syndrome in patients with different chronic liver diseases

Background: Chronic hepatitis B (CHB) and non-alcoholic fatty liver disease (NAFLD) are prevalent in China. According to traditional Chinese medicine (TCM) theory, damp-heat (DH) syndrome is common in chronic liver disease. However, the biological characteristics related to quantitative diagnosis remain to be determined. This study aimed to identify the consistent alterations in the gut microbiota associated with DH syndrome in patients with CHB or NAFLD. Methods: A total of 405 individuals were recruited, of which 146 were participants who met the consistent TCM diagnosis by three senior TCM physicians and were typical syndromes. All participants were required to provide fresh stool and serum samples. The gut microbiota was assessed by fecal 16S rRNA gene sequencing, and the serum metabolite profiles of participants were quantified by an ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) system. DH syndrome-related bacteria taxa were identified based on the 146 individuals with typical syndromes and validated in all 405 volunteers. Results: The results showed that CHB and NAFLD patients with typical TCM DH syndrome had consistently elevated serum total bile acid (TBA) levels. Significant alterations in microbial community were observed according to TCM syndromes identification. A total of 870 microbial operational taxonomic units and 21 serum metabolites showed the same variation trends in both the CHB and NAFLD DH syndrome groups. The functional analysis predicts consistent dysregulation of bile acid metabolism. Five genera (Agathobacter, Dorea, Lachnospiraceae_NC2004_group, Subdoligranulum, and unclassified_c__Clostridia) significantly decreased in abundance in patients with DH syndrome. We utilize these five genera combined with TBA to construct a random forest classifier model to predict TCM diagnosis. The diagnostic receiver-operator characteristic (ROC) areas for DH syndrome were 0.818 and 0.791 in internal tenfold cross-validation and the test set based on all 405 individuals, respectively. Conclusion: There are common signatures of gut microbiota associated with DH syndrome in patients with different chronic liver diseases. Serum TBA combined with DH-related genera provides a good diagnostic potential for DH syndrome in chronic liver disease.

Promising traditional Chinese medicine for the treatment of cholestatic liver disease process (cholestasis, hepatitis, liver fibrosis, liver cirrhosis)

ETHNOPHARMACOLOGICAL RELEVANCE

Cholestatic liver disease (CLD) is mainly characterized by cholestasis. If not treated, it will deteriorate to cholestatic hepatitis, liver fibrosis, liver cirrhosis, and even liver failure. CLD has a high clinical incidence, and limited treatment with single therapy. In the long-term clinical exploration, traditional Chinese medicine (TCM) has been corroborated with unique therapeutic effects on the CLD process.

AIM OF THIS REVIEW

This paper summarizes the effective single and compound TCMs for the treatment of CLD. According to 4 important clinical stages of CLD: cholestasis, hepatitis, liver fibrosis, liver cirrhosis, pharmacological effects and mechanisms of 5 typical TCM examples are reviewed, aims to provide basis for clinical drug selection in different processes of CLD.

MATERIALS AND METHODS

Relevant scientific articles regarding therapeutic effects of TCM for the CLD were collected from different databases. We collated three single herbs including Artemisia scoparia Waldst. et Kit. or Artemisia capillaris Thunb. (Artemisiae Scopariae Herba, Yin Chen in Chinese), Paeonia lactiflora Pall. or Paeonia veitchii Lynch. (Paeoniae radix rubra, Chi Shao in Chinese), Poria cocos (Schw.) Wolf (Poria, Fu Ling in Chinese), and two compound herbs of Huang Qi Decoction (HQD) and Yin Chen Hao Decoction (YCHD) to studied and analyzed.

RESULTS

We proposed five promising TCMs treatments for the important developmental stages of CLD. Among them, Yin Chen is an essential medicine for protecting liver and gallbladder, and its TCM prescription is also a promising strategy for cholestasis. Based on clinical evidence, high-dose application of Chi Shao is a clinical special treatment of cholestasis hepatitis. Fu Ling can regulate immune cells and increase antibody levels in serum, which is expected to be an emerging therapy to prevent cholestatic liver fibrosis to cirrhosis. HQD can be used as routine clinical medicine for liver fibrosis. In addition, YCHD can exert better comprehensive advantages with multiple components, can treat the whole course of CLD and prevent it from developing to the end-stage.

CONCLUSION

Yin Chen, Chi Shao, Fu Ling, HQD and YCHD have shown good clinical efficacy in controlling the development of CLD. Clinically, it is easier to curb the development of CLD by adopting graded diagnosis and treatment measures. We suggest that CLD should be risk stratified in clinical treatment to ensure personalized treatment for patients, so as to slow down the development of the disease.

Yinchenhao Decoction ameliorates the high-carbohydrate diet induced suppression of immune response in largemouth bass (Micropterus salmoides)

Yinchenhao Decoction (YD), a Chinese herbal medicine, has been traditionally used for treatment of metabolic liver diseases. A 10-week feeding trail was carried out to examine the effects of YD supplementation in a high carbohydrate diet (HCD) on liver histopathology, immune response, disease resistance, and expression of genes associated with endoplasmic reticulum stress, autophagy, apoptosis, necroptosis and inflammation in juvenile largemouth. A diet containing 9% carbohydrate was used as a low carbohydrate diet (LCD), and a HCD was formulated to contain 18% carbohydrate and supplemented with 0, 0.5, 1, 2 or 4% YD (HCD, HCD+0.5YD, HCD+1YD, HCD+2YD and HCD+4YD). Triplicate groups of fish (5.6 ± 0.2 g) were feed the test diets to visual satiety for 10 weeks. The highest survival rate after Nocardia seriolae challenge was recorded for the HCD+4YD group. YD application led to reduced ACP, AKP, AST and ALT activities. HCD-induced cells swelling, ruptured cell membrane, migrated nuclei and increasing inflammatory cells in hepatocytes were mitigated by YD addition. Moreover, YD decreased the expressions of pro-inflammation genes (TNF-α, IL-1β, IL-8, hepcidin1, NF-κB, COX2, CD80 and CD83) and increased the mRNA levels of anti-inflammation genes (IL-10 and IKBα). The mode of liver cell death was preferably changed to programed apoptosis rather than uncontrolled necroptosis by application of YD in HCD. Furthermore, the expression of UPR genes (IRE1, Eif2α, ATF6, XBP1 and GRP78/Bip) and autophagy genes (LC3-2, BNIP3 and P62) was increased by YD supplementation. In summary, our results demonstrated that YD addition in HCD enhances UPR, autophagy and programed apoptosis maintaining the homeostasis, and decreases uncontrolled necroptosis and inflammation, ultimately leading to improved immune response in largemouth bass.

Chlorogenic acid improves diabetic retinopathy by alleviating blood-retinal-barrier dysfunction via inducing Nrf2 activation

As one of the major diabetic microvascular complications, diabetic retinopathy (DR) is mainly initiated by the blood-retinal barrier (BRB) dysfunction. Chlorogenic acid (CGA) is a natural polyphenolic compound in Lonicerae Japonicae Flos, which traditionally has the beneficial function for eyes and is commonly included in many anti-diabetic formulas. In this study, the potential protective mechanism of CGA against DR was investigated. Streptozotocin (STZ) was used to induce diabetes in mice. CGA attenuated BRB dysfunction and reversed endothelial-mesenchymal transition (EndoMT) and epithelial-mesenchymal transition (EMT) in retinas in vivo. CGA inhibited microglia activation and reduced tumor necrosis factor (TNF)α release both in vivo and in vitro. CGA promoted nuclear factor erythroid 2-related factor 2 (Nrf2) activation and prevented EndoMT/EMT in TNFα-treated human retinal endothelial cells (HRECs) or retinal pigment epithelial APRE19 cells. CGA alleviated endothelial/epithelial barrier oxidative injury in HRECs or APRE19 cells stimulated with TNFα, but this effect was disappeared in cells co-incubated with Nrf2 inhibitor. Additionally, the CGA-supplied alleviation on BRB damage and EndoMT/EMT was markedly weakened in retinas from STZ-treated Nrf2 knock-out mice. All results suggest that CGA improves DR through attenuating BRB injury by reducing microglia-initiated inflammation and preventing TNFα-induced EndoMT/EMT and oxidative injury via inducing Nrf2 activation.

Preclinical Evidence of Berberine on Non-Alcoholic Fatty Liver Disease: A Systematic Review and Meta-Analysis of Animal Studies

As lifestyle and diet structure impact our health, non-alcoholic fatty liver disease (NAFLD) is prevalent all over the world. Some phytomedicines containing berberine (BBR) have been extensively used for centuries in Ayurvedic and traditional Chinese medicine. The goal of this systematic review is to investigate the preclinical evidence of BBR on NAFLD models. The following relevant databases, including Web of Science, PubMed, the Cochrane Library, and Embase, were retrieved from inception to May 2021. The content involved BBR on different animal models for the treatment of NAFLD. The SYstematic Review Center for Laboratory animal Experimentation (SYRCLE) Animal Experiment Bias Risk Assessment Tool was used to assess the methodological quality and RevMan 5.4 software was used to conduct the meta-analysis based on the Cochrane tool. A total of 31 studies involving 566 animals were included, of which five models and five animal breeds were reported. The results showed that TC, TG, ALT, AST, HDL-C, LDL-C, FBG, FINS, and FFA in the group treated with BBR were significantly restored compared with those in the model group. HOMA-IR had a significant downward trend, but the result was not significantly different (P = 0.08). The subgroup analysis of the different models and different animal breeds indicated that BBR could ameliorate the aforementioned indicator levels, although some results showed no significant difference. Finally, we summarized the molecular mechanisms by which berberine regulated NAFLD/NASH, mainly focusing on activating the AMPK pathway, improving insulin sensitivity and glucose metabolism, regulating mitochondrial function, reducing inflammation and oxidative stress, regulating cell death and ER stress, reducing DNA methylation, and regulating intestinal microenvironment and neurotoxicity. The preclinical evidence suggested that BBR might be an effective and promising drug for treating NAFLD/NASH. In addition, further studies with more well-designed researches are needed to confirm this conclusion.