Variations in Gut Microbiome are Associated with Prognosis of Hypertriglyceridemia-Associated Acute Pancreatitis

The role of gut microbiome and its metabolites in pancreatitis

Gut microbiome plays a vital role in the intestinal ecosystem and has close association with metabolites. Due to the development of metabolomics and microbiomics, recent studies have observed that alteration of either the gut microbiome or metabolites may have effects on the progression of pancreatitis. Several new treatments based on the gut microbiome or metabolites have been studied extensively in recent years. Gut microbes, such as Bifidobacterium, Akkermansia, and Lactobacillus, and metabolites, such as short-chain fatty acids, bile acids, vitamin, hydrogen sulfide, and alcohol, have different effects on pancreatitis. Some preliminary studies about new intervention measures were based on the gut microbiome and metabolites such as diet, prebiotic, herbal medicine, and fecal microbiota transplantation. This review aims to summarize the recent advances about the gut microbiome, metabolites, and pancreatitis in order to determine the potential beneficial role of the gut microbiome and metabolites in pancreatitis.

Potential Applications of Blautia wexlerae in the Regulation of Host Metabolism

Blautia wexlerae (B. wexlerae) is a strong candidate with the potential to become a next-generation probiotics (NGPs) and has recently been shown for the first time to exhibit potential in modulating host metabolic levels and alleviating metabolic diseases. However, the factors affecting the change in abundance of B. wexlerae and the pattern of its abundance change in the associated indications remain to be further investigated. Here, we summarize information from published studies related to B. wexlerae; analyze the effects of food source factors such as prebiotics, probiotics, low protein foods, polyphenols, vitamins, and other factors on the abundance of B. wexlerae; and explore the patterns of changes in the abundance of B. wexlerae in metabolic diseases, neurological diseases, and other diseases. At the same time, the development potential of B. wexlerae was evaluated in the direction of functional foods and special medical foods.

Exploring the interactions of JAK inhibitor and S1P receptor modulator drugs with the human gut microbiome: Implications for colonic drug delivery and inflammatory bowel disease

The gut microbiota is a complex ecosystem, home to hundreds of bacterial species and a vast repository of enzymes capable of metabolising a wide range of pharmaceuticals. Several drugs have been shown to affect negatively the composition and function of the gut microbial ecosystem. Janus Kinase (JAK) inhibitors and Sphingosine-1-phosphate (S1P) receptor modulators are drugs recently approved for inflammatory bowel disease through an immediate release formulation and would potentially benefit from colonic targeted delivery to enhance the local drug concentration at the diseased site. However, their impact on the human gut microbiota and susceptibility to bacterial metabolism remain unexplored. With the use of calorimetric, optical density measurements, and metagenomics next-generation sequencing, we show that JAK inhibitors (tofacitinib citrate, baricitinib, filgotinib) have a minor impact on the composition of the human gut microbiota, while ozanimod exerts a significant antimicrobial effect, leading to a prevalence of the Enterococcus genus and a markedly different metabolic landscape when compared to the untreated microbiota. Moreover, ozanimod, unlike the JAK inhibitors, is the only drug subject to enzymatic degradation by the human gut microbiota sourced from six healthy donors. Overall, given the crucial role of the gut microbiome in health, screening assays to investigate the interaction of drugs with the microbiota should be encouraged for the pharmaceutical industry as a standard in the drug discovery and development process.

Chaiqin Chengqi Decoction as an adjuvant treatment for mild/moderately severe hypertriglyceridemic acute pancreatitis: A retrospective study

BACKGROUND

Hypertriglyceridemia is the third leading cause of acute pancreatitis (AP), and its incidence is increasing. Due to its relatively insidious etiology, it is easy to be ignored in the early stages. In China, Chaiqin Chengqi Decoction (CQCQD) has long been employed for treating AP.

AIM

To evaluate the effectiveness of CQCQD in patients diagnosed with mild/ moderately severe hypertriglyceridemic AP (HTG-AP).

METHODS

In this study, the clinical data of 39 patients with HTG-AP admitted from January 2019 to November 2022 were collected. The changes of blood lipids, gastrointestinal symptoms, and abdominal pain before and after treatment were analyzed and compared between the two groups.

RESULTS

Twenty patients were treated with the conventional HTG-AP regimen, and 19 patients were additionally treated with CQCQD. After receiving treatment, the triglycerides (TG) level of the CQCQD group was lower than that of the CQCQD group (3.14 ± 0.25 mmol/L vs 4.96 ± 0.47 mmol/L, P < 0.01). After 3 d of treatment, the patients in the CQCQD group had more bowel movements than the control group (2.51 ± 0.25 times vs 1.00 ± 0.17 times, P = 0.01). The gastrointestinal function of most patients returned to normal, and the acute gastrointestinal injury score was significantly lower than that of the control group (0.11 ± 0.07 vs 0.42 ± 0.11, P < 0.01).

CONCLUSION

In patients with HTG-AP, CQCQD can significantly reduce the TG level, shorten the recovery time of defecation, significantly improve the gastrointestinal function.

Exploring the Microbial Landscape: Gut Dysbiosis and Therapeutic Strategies in Pancreatitis-A Narrative Review

The gut microbiota is emerging as an important contributor to the homeostasis of the human body through its involvement in nutrition and metabolism, protection against pathogens, and the development and modulation of the immune system. It has therefore become an important research topic in recent decades. Although the association between intestinal dysbiosis and numerous digestive pathologies has been thoroughly researched, its involvement in pancreatic diseases constitutes a novelty in the specialized literature. In recent years, growing evidence has pointed to the critical involvement of the pancreas in regulating the intestinal microbiota, as well as the impact of the intestinal microbiota on pancreatic physiology, which implies the existence of a bidirectional connection known as the "gut-pancreas axis". It is theorized that any change at either of these levels triggers a response in the other component, hence leading to the evolution of pancreatitis. However, there are not enough data to determine whether gut dysbiosis is an underlying cause or a result of pancreatitis; therefore, more research is needed in this area. The purpose of this narrative review is to highlight the role of gut dysbiosis in the pathogenesis of acute and chronic pancreatitis, its evolution, and the prospect of employing the microbiota as a therapeutic intervention for pancreatitis.

The Role of the Gut Microbiome in the Development of Acute Pancreatitis

With the explosion research on the gut microbiome in the recent years, much insight has been accumulated in comprehending the crosstalk between the gut microbiota community and host health. Acute pancreatitis (AP) is one of the gastrointestinal diseases associated with significant morbidity and subsequent mortality. Studies have elucidated that gut microbiota are engaged in the pathological process of AP. Herein, we summarize the major roles of the gut microbiome in the development of AP. We then portray the association between dysbiosis of the gut microbiota and the severity of AP. Finally, we illustrate the promises and challenges that arise when seeking to incorporate the microbiome in acute pancreatitis treatment.

Bibliometric analysis of pancreatic diseases and gut microbiota research from 2002 to 2022

Background

An increasing number of studies have indicated that pancreatic diseases are associated with the structure of the gut microbiota. We aimed to assess the research hotspots and trends in this field through a quantitative method.

Materials and methods

Articles related to pancreatic diseases and the gut microbiota published from 2002 to 2022 were retrieved from the Web of Science database. We visualized the countries/regions, institutions, authors, journals, and keywords using VOSviewer and CiteSpace software. The interplay between pancreatic diseases and the gut microbiota was also analysed.

Results

A total of 129 publications were finally identified. The number of papers increased gradually, and China held the dominant position with respect to publication output. Shanghai Jiao Tong University was the most influential institution. Zeng Yue ranked highest in the number of papers, and Scientific Reports was the most productive journal. The keywords "gut", "bacterial translocation", and "acute pancreatitis" appeared early for the first time, and "gut microbiota", "community", and "diversity" have been increasingly focused on. The predominant pancreatic disease correlated with the gut microbiota was pancreatic inflammatory disease (50.39%). Pancreatic diseases are associated with alterations in the gut microbiota, characterized by a decrease in beneficial bacteria and an increase in harmful bacteria.

Conclusion

This is the first comprehensive bibliometric analysis of all pancreatic diseases and the gut microbiota. The research on the relationship between them is still in the preliminary stage, and the trend is toward a gradual deepening of the research and precise treatment development. The interaction between the gut microbiota and pancreatic diseases will be of increasing concern in the future.

A nomogram for predicting in-hospital overall survival of hypertriglyceridemia-induced severe acute pancreatitis: A single center, cross-sectional study

Background

Hypertriglyceridemia-induced severe acute pancreatitis (HTG-SAP) is a type of pancreatitis characterized by an abnormal elevation of plasma triglyceride. HTG-SAP has been associated with various complications and a high mortality rate. In this study, we established a nomogram for predicting the overall survival (OS) of HTG-SAP patients during hospitalization.

Methods

128 HTG-SAP cases hospitalized at the Affiliated Huadu Hospital, Southern Medical University, from 2019 to 2022 were analyzed retrospectively. A nomogram including prognostic factors correlated with OS during hospitalization was established by multivariate Cox regression analysis. We internally validated the nomogram using time-dependent (at 1-, 2-, and 3- months) survival receiver operating characteristic (SROC) and calibration curve with 500 iterations of bootstrap resampling. Time-dependent decision curve analysis (DCA) was employed to validate the clinical value of the nomogram.

Results

Multivariate Cox regression indicated that serum triglyceride, red blood cell distribution width (RDW), lactic acid, and interleukin-6 (IL6) were independent prognostic factors for OS of HTG-SAP patients during hospitalization and were used to construct a nomogram. The time-dependent area under the curve (AUC) values at 1-, 2-, and 3- months were 0.946, 0.913, and 0.929, respectively, and the Concordance index (C-index) of the nomogram was 0.916 (95%CI 0.871-0.961). The time-dependent calibration curves indicated good consistency between the observed and predicted outcomes. The time-dependent DCAs also revealed that the nomogram yielded a high clinical net benefit. After stratifying the included cases into two risk groups based on the risk score obtained from the nomogram, the high-risk group exhibited a significantly inferior overall survival (OS) compared to the low-risk group (p < 0.0001).

Conclusions

Our nomogram exhibited good performance in predicting the overall survival of HTG-SAP patients during hospitalization.

The Interaction of Microbiome and Pancreas in Acute Pancreatitis

Acute pancreatitis (AP) is a common acute abdomen disease characterized by the pathological activation of digestive enzymes and the self-digestion of pancreatic acinar cells. Secondary infection and sepsis are independent prognosticators for AP progression and increased mortality. Accumulating anatomical and epidemiological evidence suggests that the dysbiosis of gut microbiota affects the etiology and severity of AP through intestinal barrier disruption, local or systemic inflammatory response, bacterial translocation, and the regulatory role of microbial metabolites in AP patients and animal models. Recent studies discussing the interactions between gut microbiota and the pancreas have opened new scopes for AP, and new therapeutic interventions that target the bacteria community have received substantial attention. This review concentrates on the alterations of gut microbiota and its roles in modulating gut-pancreas axis in AP. The potential therapies of targeting microbes as well as the major challenges of applying those interventions are explored. We expect to understand the roles of microbes in AP diagnosis and treatment.

Gut microbiota aggravates neutrophil extracellular traps-induced pancreatic injury in hypertriglyceridemic pancreatitis

Hypertriglyceridemic pancreatitis (HTGP) is featured by higher incidence of complications and poor clinical outcomes. Gut microbiota dysbiosis is associated with pancreatic injury in HTGP and the mechanism remains unclear. Here, we observe lower diversity of gut microbiota and absence of beneficial bacteria in HTGP patients. In a fecal microbiota transplantation mouse model, the colonization of gut microbiota from HTGP patients recruits neutrophils and increases neutrophil extracellular traps (NETs) formation that exacerbates pancreatic injury and systemic inflammation. We find that decreased abundance of Bacteroides uniformis in gut microbiota impairs taurine production and increases IL-17 release in colon that triggers NETs formation. Moreover, Bacteroides uniformis or taurine inhibits the activation of NF-κB and IL-17 signaling pathways in neutrophils which harness NETs and alleviate pancreatic injury. Our findings establish roles of endogenous Bacteroides uniformis-derived metabolic and inflammatory products on suppressing NETs release, which provides potential insights of ameliorating HTGP through gut microbiota modulation.

Composition and functional profiles of gut microbiota reflect the treatment stage, severity, and etiology of acute pancreatitis

Acute pancreatitis (AP) is a type of digestive system disease with high mortality. Previous studies have shown that gut microbiota can participate in developing and treating acute pancreatitis by affecting the host's metabolism. In this study, we followed 20 AP patients to generate longitudinal gut microbiota profiles and activity during disease (before treatment, on the third day of treatment, and 1 month after discharge). We analyzed species composition and metabolic pathways' changes across the treatment phase, severity, and etiology. The diversity of the gut microbiome of patients with AP did not show much variation with treatment. In contrast, the metabolic functions of the gut microbiota, such as the essential chemical reactions that produce energy and maintain life, were partially reinstated after treatment. The severe AP (SAP) patients contained less beneficial bacteria (i.e., Bacteroides xylanisolvens, Clostridium lavalense, and Roseburia inulinivorans) and weaker sugar degradation function than mild AP patients before treatment. Moreover, etiology was one of the drivers of gut microbiome composition and explained the 3.54% variation in species' relative abundance. The relative abundance of pathways related to lipid synthesis was higher in the gut of hyperlipidemia AP patients than in biliary AP patients. The composition and functional profiles of the gut microbiota reflect the severity and etiology of AP. Otherwise, we also identified bacterial species associated with SAP, i.e., Oscillibacter sp. 57_20, Parabacteroides johnsonii, Bacteroides stercoris, Methanobrevibacter smithii, Ruminococcus lactaris, Coprococcus comes, and Dorea formicigenerans, which have the potential to identify the SAP at an early stage. IMPORTANCE Acute pancreatitis (AP) is a type of digestive system disease with high mortality. Previous studies have shown that gut microbiota can participate in the development and treatment of acute pancreatitis by affecting the host's metabolism. However, fewer studies acquired metagenomic sequencing data to associate species to functions intuitively and performed longitudinal analysis to explore how gut microbiota influences the development of AP. We followed 20 AP patients to generate longitudinal gut microbiota profiles and activity during disease and studied the differences in intestinal flora under different severities and etiologies. We have two findings. First, the gut microbiota profile has the potential to identify the severity and etiology of AP at an early stage. Second, gut microbiota likely acts synergistically in the development of AP. This study provides a reference for characterizing the driver flora of severe AP to identify the severity of acute pancreatitis at an early stage.

Current status and advancements in research of gut microecology in acute pancreatitis

Acute pancreatitis (AP) is one of the most common acute abdominal conditions in clinical practice, with increasing incidence and substantial healthcare burden. In recent years, substantial research with high-throughput sequencing technologies has revealed the imbalance between beneficial and pathogenic microbiomes as well as their metabolites during the clinical course of AP. Furthermore, disruption of the intestinal barrier and microbial translocation have been identified as important factors exacerbating systemic inflammatory response and subsequent infectious complications in AP. Maintaining a stable gastrointestinal microecology in patients may help prevent gut-derived infection and attenuate the "second hit" of inflammation induced by AP, thereby improving patient outcomes. This article provides a systematic review of the role of intestinal microbiota and microbial metabolites in the progression of AP, as well as potential therapeutic strategies, in order to offer insights into the understanding of AP pathogenesis and the identification of novel therapeutic targets.

Altered gut microbiota in the early stage of acute pancreatitis were related to the occurrence of acute respiratory distress syndrome

Background

Acute respiratory distress syndrome (ARDS) is the most common cause of organ failure in acute pancreatitis (AP) patients, which associated with high mortality. Specific changes in the gut microbiota have been shown to influence progression of acute pancreatitis. We aimed to determine whether early alterations in the gut microbiota is related to and could predict ARDS occurrence in AP patients.

Methods

In this study, we performed 16S rRNA sequencing analysis in 65 AP patients and 20 healthy volunteers. The AP patients were further divided into two groups: 26 AP-ARDS patients and 39 AP-nonARDS patients based on ARDS occurrence during hospitalization.

Results

Our results showed that the AP-ARDS patients exhibited specific changes in gut microbiota composition and function as compared to subjects of AP-nonARDS group. Higher abundances of Proteobacteria phylum, Enterobacteriaceae family, Escherichia-Shigella genus, and Klebsiella pneumoniae, but lower abundances of Bifidobacterium genus were found in AP-ARDS group compared with AP-nonARDS groups. Random forest modelling analysis revealed that the Escherichia-shigella genus was effective to distinguish AP-ARDS from AP-nonARDS, which could predict ARDS occurrence in AP patients.

Conclusions

Our study revealed that alterations of gut microbiota in AP patients on admission were associated with ARDS occurrence after hospitalization, indicating a potential predictive and pathogenic role of gut microbiota in the development of ARDS in AP patients.

Gut microbiota signature as predictors of adverse outcomes after acute ischemic stroke in patients with hyperlipidemia

Introduction

The alterations of gut microbiota have been associated with multiple diseases. However, the relationship between gut microbiota and adverse outcomes of hyperlipidemic stroke patients remains unclear. Here we determined the gut microbial signature to predict the poor outcome of acute ischemic stroke (AIS) with hyperlipidemia (POAH).

Methods

Fecal samples from hyperlipidemic stroke patients were collected, which further analyzed by 16s rRNA gene sequencing. The diversity, community composition and differential gut microbiota were evaluated. The adverse outcomes were determined by modified Rankin Scale (mRS) scores at 3 months after admission. The diagnostic performance of microbial characteristics in predicting adverse outcomes was assessed by receiver operating characteristic (ROC) curves.

Results

Our results showed that the composition and structure of gut microbiota between POAH patients and good outcome of AIS with hyperlipidemia (GOAH) patients were different. The characteristic gut microbiota of POAH patients was that the relative abundance of Enterococcaceae and Enterococcus were increased, while the relative abundance of Lachnospiraceae, Faecalibacterium, Rothia and Butyricicoccus were decreased. Moreover, the characteristic gut microbiota were correlated with many clinical parameters, such as National Institutes of Health Stroke Scale (NIHSS) score, mean arterial pressure, and history of cerebrovascular disease. Moreover, the ROC models based on the characteristic microbiota or the combination of characteristic microbiota with independent risk factors could distinguish POAH patients and GOAH patients (area under curve is 0.694 and 0.971 respectively).

Conclusions

These findings revealed the microbial characteristics of POAH, which highlighted the predictive capability of characteristic microbiota in POAH patients.

Fighting Fire with Fire: Exosomes and Acute Pancreatitis-Associated Acute Lung Injury

Acute pancreatitis (AP) is a prevalent clinical condition of the digestive system, with a growing frequency each year. Approximately 20% of patients suffer from severe acute pancreatitis (SAP) with local consequences and multi-organ failure, putting a significant strain on patients' health insurance. According to reports, the lungs are particularly susceptible to SAP. Acute respiratory distress syndrome, a severe type of acute lung injury (ALI), is the primary cause of mortality among AP patients. Controlling the mortality associated with SAP requires an understanding of the etiology of AP-associated ALI, the discovery of biomarkers for the early detection of ALI, and the identification of potentially effective drug treatments. Exosomes are a class of extracellular vesicles with a diameter of 30-150 nm that are actively released into tissue fluids to mediate biological functions. Exosomes are laden with bioactive cargo, such as lipids, proteins, DNA, and RNA. During the initial stages of AP, acinar cell-derived exosomes suppress forkhead box protein O1 expression, resulting in M1 macrophage polarization. Similarly, macrophage-derived exosomes activate inflammatory pathways within endothelium or epithelial cells, promoting an inflammatory cascade response. On the other hand, a part of exosome cargo performs tissue repair and anti-inflammatory actions and inhibits the cytokine storm during AP. Other reviews have detailed the function of exosomes in the development of AP, chronic pancreatitis, and autoimmune pancreatitis. The discoveries involving exosomes at the intersection of AP and acute lung injury (ALI) are reviewed here. Furthermore, we discuss the therapeutic potential of exosomes in AP and associated ALI. With the continuous improvement of technological tools, the research on exosomes has gradually shifted from basic to clinical applications. Several exosome-specific non-coding RNAs and proteins can be used as novel molecular markers to assist in the diagnosis and prognosis of AP and associated ALI.

The gut-lung axis in severe acute Pancreatitis-associated lung injury: The protection by the gut microbiota through short-chain fatty acids

The role of gut microbiota in regulating the intestinal homeostasis, as well as the pathogenesis of severe acute pancreatitis-associated lung injury (PALI) is widely recognized. The bioactive functions of metabolites with small molecule weight and the detail molecular mechanisms of PALI mediated by "gut-lung axis" have gradually raised the attentions of researchers. Several studies have proved that short-chain fatty acids (SCFAs) produced by gut microbiome play crucial roles and varied activities in the process of PALI. However, relevant reviews reporting SCFAs in the involvement of PALI is lacking. In this review, we firstly introduced the synthetic and metabolic pathways of SCFAs, as well as the transport and signal transduction routes in brief. Afterwards, we focused on the possible mechanisms and clues of SCFAs to participate in the fight against PALI which referred to the inhibition of pathogen proliferation, anti-inflammatory effects, enhancement of intestinal barrier functions, and the maintenance and regulation of immune homeostasis via pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs). In addition, the latest reported pathological and physiological mechanisms of the gut-lung axis involved in PALI were reviewed. Finally, we summarized the potential therapeutic interventions of PALI by targeting SCFAs, including dietary fiber supplementation, direct supplementation of SCFAs/prebiotics/probiotics, and drugs administration, which is expected to provide new sights for clinical use in the future.

Intestinal Microbiota - An Unmissable Bridge to Severe Acute Pancreatitis-Associated Acute Lung Injury

Severe acute pancreatitis (SAP), one of the most serious abdominal emergencies in general surgery, is characterized by acute and rapid onset as well as high mortality, which often leads to multiple organ failure (MOF). Acute lung injury (ALI), the earliest accompanied organ dysfunction, is the most common cause of death in patients following the SAP onset. The exact pathogenesis of ALI during SAP, however, remains unclear. In recent years, advances in the microbiota-gut-lung axis have led to a better understanding of SAP-associated lung injury (PALI). In addition, the bidirectional communications between intestinal microbes and the lung are becoming more apparent. This paper aims to review the mechanisms of an imbalanced intestinal microbiota contributing to the development of PALI, which is mediated by the disruption of physical, chemical, and immune barriers in the intestine, promotes bacterial translocation, and results in the activation of abnormal immune responses in severe pancreatitis. The pathogen-associated molecular patterns (PAMPs) mediated immunol mechanisms in the occurrence of PALI via binding with pattern recognition receptors (PRRs) through the microbiota-gut-lung axis are focused in this study. Moreover, the potential therapeutic strategies for alleviating PALI by regulating the composition or the function of the intestinal microbiota are discussed in this review. The aim of this study is to provide new ideas and therapeutic tools for PALI patients.

Microbiota in Pancreatic Diseases: A Review of the Literature

The gut microbiota is a critical element in the balance between human health and disease. Its impairment, defined as dysbiosis, is associated with gastroenterological and systemic diseases. Pancreatic secretions are involved in the composition and changes of the gut microbiota, and the gut microbiota may colonize the pancreatic parenchyma and be associated with the occurrence of diseases. The gut microbiota and the pancreas influence each other, resulting in a "gut microbiota-pancreas axis". Moreover, the gut microbiota may be involved in pancreatic diseases, both through direct bacterial colonization and an indirect effect of small molecules and toxins derived from dysbiosis. Pancreatic diseases such as acute pancreatitis, chronic pancreatitis, autoimmune pancreatitis, and pancreatic cancer are common gastroenterological diseases associated with high morbidity and mortality. The involvement of the microbiota in pancreatic diseases is increasingly recognized. Therefore, modifying the intestinal bacterial flora could have important therapeutic implications on these pathologies. The aim of this study is to review the literature to evaluate the alterations of the gut microbiota in pancreatic diseases, and the role of the microbiota in the treatment of these diseases.

The Role of Gut Microbiota and Genetic Susceptibility in the Pathogenesis of Pancreatitis

Pancreatitis is one of the most common inflammatory diseases of the pancreas caused by autodigestion induced by excessive premature protease activation. However, recognition of novel pathophysiological mechanisms remains a still challenge. Both genetic and environmental factors contribute to the pathogenesis of pancreatitis, and the gut microbiota is a potential source of an environmental effect. In recent years, several new frontiers in gut microbiota and genetic risk assessment research have emerged and improved the understanding of the disease. These investigations showed that the disease progression of pancreatitis could be regulated by the gut microbiome, either through a translocation influence or in a host immune response manner. Meanwhile, the onset of the disease is also associated with the heritage of a pathogenic mutation, and the disease progression could be modified by genetic risk factors. In this review, we focused on the recent advances in the role of gut microbiota in the pathogenesis of pancreatitis, and the genetic susceptibility in pancreatitis.