Will We Still Need Liver Biopsies to Diagnose Biliary Atresia in a Few Years?

A recent study (C Lertudomphonwanit, R Moura, L Fei, Y Zhang, S Gutta, L Yang, KE Bove, P Shivakumar, JA Bezerra. Sci Transl Med. 2017; 9: eaan8462) may change how we diagnose biliary atresia (BA) and provides an insight into potential pathogenesis. Link to studyLarge-scale proteomics identifies MMP-7 as a sentinel of epithelial injury and of biliary atresia

Using large-scale proteomics, the authors screened 1129 proteins in a discovery cohort (n=70) of patients with BA.  They identified several proteins that were increased with BA. Matrix metalloproteinase-7 (MMP-7) was the lead biomarker.  Subsequently, they used two additional validation cohorts.  Human subjects were infants in enrolled in the Prospective Database of Infants with Cholestasis (PROBE) which is part of the NIDDK-funded ChiLDRen (www.childrennetwork.org).

Key findings:

  • 76 proteins were significantly overexpressed or underexpressed in BA compared with children with intrahepatic cholestasis (IHC).
  • MMP-7 was more accurate than gamma glutamyltranspeptidase (GGT).  The combination of MMP-7 and GGT had a AUROC of 0.94 in validation cohorts.
  • The authors further studied the role of MMP-7 by immunostaining and found it primarily was detected in cholangiocytes of intrahepatic bile ducts in infants with BA.  It was also identified in a few hematopoietic cells.
  • MMP-7 expression in the liver did not correlate with fibrosis.
  • MMP-7 serum levels increased in neonatal mice after bile duct epithelial injury induced by intraperitoneal rotavirus administration.
  • Using a mice model, they found that a MMP-7 inhibitor (batimastat) could block the development of BA in a mouse model (in 86% of cases) compared with 0% in control mice.
  • Overall, the authors note that coupled with GGT, MMP-7 serum levels result in “sensitivity and specificity of 97 and 94% respectively, at optimal cutoff, which provided positive and negative predictive values of 85 and 99% respectively, if one considers the prevalence of BA of 25.9% among infants with conjugated hyperbilirubinemia.”

My take: More work is needed.  However, these values suggest that MMP-7 and GGT combined may be more accurate than a liver biopsy in the diagnosis of BA.

Related blog posts:

South Kaibab Trail, Grand Canyon

#NASPGHAN17 IBD Treat to Target and Tight Control

More information from this year’s annual NASPGHAN meeting.

This blog entry has abbreviated/summarized these presentations. Though not intentional, some important material is likely to have been omitted; in addition, transcription errors are possible as well.

IBD Treat to Target: Treat the Patient or Treat the Disease

Robert Baldassano  Children’s Hospital of Philadelphia

I missed the first few minutes of this presentation, even though I had highlighted this as one of my top priorities.  So, if anyone reading this post has some additional comments, they are certainly welcome.

Key points:

  • Do not rely on symptoms alone to assess patient improvement.
  • Best surrogate marker: calprotectin.  Frequent calprotectin levels can help determine objective improvement; it is much more helpful than CRP as ~25% of patients do not elevate their CRP levels
  • Therapeutic drug monitoring is important in improving outcomes. Dose optimization improves response rate and durability of infliximab response.
  • Evolving targets in ulcerative colitis.  Even histologic activity, in the absence of endoscopic activity, is associated with relapsing disease
  • Dr. Baldassano indicated that he no longer is starting patients on thiopurine therapy. There are “36 phase 3 trials underway.” Thus, many promising options for those who may burn through current treatments
  • This lecture reviewed data from the RISK study showing that early (1st 90 days w/in diagnosis) TNF therapy helps prevent penetrating disease (related post: CCFA Update 2017/RISK study)

Another presentation by Philip Minar et al (Cincinnati Children’s Hospital Medical Center) shows that CD64 suppression is an early biomarker of response to infliximab therapy.

New Biomarker for Crohn’s Disease (Plus Two)

A recent study identifies a new biomarker for Crohn’s disease (CD) (Inflamm Bowel Dis 2014; 20: 1037-48).

The authors examined a cohort of 208 newly diagnosed pediatric CD and 43 non-IBD controls for ileal/rectal expression of FcγRIA mRNA.  In addition, in a smaller cohort of 26 newly diagnosed CD patients, 83 established CD patients and 30 non-IBD controls the authors measured peripheral blood polymorphonuclear neutrophil (PMN) CD64 index.

Key findings:

  • Ileal FcγRIA mRNA expression was significantly elevated in CD compared with non-IBD controls
  • PMN CD64 was significantly elevated in CD compared with non-IBD controls and correlated with mucosal injury as measured by the simple endoscopic score for CD.
  • Patients in clinical remission with a PMN CD64 <1 had a high rate of sustained remission (95%) whereas only 56% had sustained remission if PMN CD64 was >1.

Take-home point: This study shows in pediatrics, as in adults IBD patients, that PMN CD64 index is associated with mucosal inflammation; high levels are associated with clinical relapse.  Serum biomarkers are likely to complement stool biomarkers like fecal calprotectin.

One other point the authors make: “studies have found that 57% to 59% of CD have concurrent IBS.”  Thus, there is a need for biomarkers to distinguish whether patients with clinical symptoms are experiencing an inflammatory relapse.

Related blog post: Calprotectin: Part of diagnostic algorithm for IBD 

Two other studies in same issue:

“Alterations in the Intestinal Microbiome (Dysbiosis) as a Predictor of Relapse After Infliximab Withdrawal in Crohn’s disease” pages 978-86.  N=33 CD patients. Key finding: “CD-associated dysbiosis, characterized by a decrease in Firmicutes, correlates with the time-to-relapse after infliximab withdrawal.”

“Tissue Studies in Screened First-degree Relatives Reveal a Distinct Crohn’s Disease Phenotype” pages 1049-56. N=38 asymptomatic relatives. Key finding: based on histologic scoring 61% were normal, 26% had minor lesions, and 13% had evidence of active disease. This study indicates that screening relatives may identify a subset with early biologic disease.

Natural laws not patentable: the case with Prometheus

While most individuals might think of greek mythology or the recent movie when hearing the word “Prometheus,” pediatric gastroenterologists might think of the company that performs a number of useful diagnostic tests.  Recently, Prometheus has had a legal setback (NEJM 2012; 365: 2338-40). 

Since the 1990s, Prometheus has tested for azathioprine (& 6-mercaptopurine) metabolites.  A therapeutic level of 6-thioguanine (6-TG), a metabolite for these drugs, is recognized as generally between 230-400 pmol per 8×10(to the 8th) red cells.  Levels outside this range often require drug adjustments.

When the Mayo clinic started to offer a slightly different assay, priced 25% below Prometheus’s test, Prometheus sued for patent infringement.  The court held that “if a law of nature is not patentable, then neither is a process reciting a law of nature;”  hence, Prometheus’s patent was rejected.

There are implications of this lawsuit on the use of a large number of biomarkers.  For example, patents for BRCA DNA sequences that increase the risk for cancer will probably be overturned.  Industry groups argue that denying patents will halt progress as companies will not be able to recoup investments in biomarker development.  Congress could consider passing laws allowing exclusive marketing of these innovations.  Alternatively, adequate funding through the NIH (National Institutes of Health) could allow development of biomarkers without the need for patents; in fact, 100 projects are in progress at this time.

MicroRNA signature for eosinophilic esophagitis

In a previous post discussing MicroRNAs (miRNAs) (MicroRNAs and biliary atresia), I stated that “Despite this intriguing research, it not clear whether or when miRNAs will have an important role in bedside management.”  Well, as more articles emerge on miRNAs, it is becoming clear that miRNAs will have a role in clinical medicine; the questions are when and what cost.

The latest study (J Allergy Clin Immunol 2012; 129: 1064-75) by Lu et al from Cincinnati shows how this technique can identify a specific signature for eosinophilic esophagitis (EoE) and how miRNAs can serve as a biomarker for disease response.  The investigators took plasma and esophageal biopsy specimens from patients with EoE, reflux esophagitis, and healthy controls; they used an array comprising 677 miRNAs.  254 miRNAs were expressed at greater than background levels, but 21 upregulated miRNAs and 11 downregulated miRNAs were markedly different.

To quickly understand how useful this technology could become requires a glance at the “heat maps” showing the expression profile of the 21 upregulated miRNAs and the 11 downregulated miRNAs, comparing EoE with healthy controls (Figures 1 & 3).  In addition, in Figure 3, it is readily apparent that the expression pattern is completely different from reflux esophagitis.  Furthermore, this figure demonstrates visually a normal-appearing pattern in patients who respond to fluticasone.

Other figures in the article and in the appendix demonstrate the complex relationships between these specific miRNAs and target genes.

Key points:

  • miRNAs from tissue or blood could serve as biomarkers for the presence of EoE and response to therapy
  • Of the identified miRNAs, miR-21 and miR-223 strongly correlate with esophageal eosinophilia as well as previously described EoE transcriptome
  • Plasma miRNAs that are most differentiated in EoE include miR-146a, miR-146b, and miR-223.

Related posts:

Guidelines for Eosinophilic Esophagitis

Eosinophilic Esophagitis -Six Food Group Diet

The undiscovered country

MicroRNAs and biliary atresia

The human genome may encode over 1000 microRNAs (miRNAs), which may target about 60% of mammalian genes and are abundant in many human cell types. MicroRNAs are a class of short (18-23 nucleotide) noncoding RNA molecules which act as a negative regulator of target mRNA stability and translation.  This month the interaction of miRNAs with biliary atresia is examined (JPGN 2012; 54: 186-92).

Using a mouse model, the authors identify miRNA-29 overexpression associated with the downregulation of two mRNA targets related to biliary atresia pathogenesis.  The research has several limitations, including the use of adult mice.  The reason why I highlight this study is that miRNAs are helping elucidate basic disease mechanisms and identifying new therapeutic targets.  Some of these same investigators published “Circulating microRNA is a biomarker of pediatric Crohn disease.” (JPGN: 2011;  53(1): 26-33).  In this study, 11 CD-associated serum miRNA were identified with encouraging diagnostic potential.  These specific miRNAs were found in Crohn disease patients but not in controls and patients with celiac disease.  The sensitivity for Crohn disease was over 80%.

Despite this intriguing research, it not clear whether or when miRNAs will have an important role in bedside management.

Additional references:

Four advances for intestinal failure

Several advances in the management of intestinal failure have the potential to improve the outlook for our intestinal failure (IF) (aka Short Bowel Syndrome) patients (JPEN 2012; 36: 36S-42S).

Although IF patients already have improving survival with rates of 80-95% over followup ranging from 1-5 years, many still do not survive, primarily due to bacterial infections or chronic liver disease.  Ongoing research has made some promising steps in the management of these pediatric patients.  This article focuses on four of these steps.

1. Citrulline monitoring

  • Major source of citrulline is enterocyte production.  Citrulline is an amino acid not encoded in human genetic code; it is present in some proteins as a product of posttranslational modification.
  • Watermelon is one of few dietary sources.
  • Useful biomarker for bowel length/absorption –independent of inflammatory markers
  • Levels >15-20 μmol/L indicate good likelihood of achieving enteral autonomy
  • Levels <12μmol/L indicate a very low likelihood of achieving enteral autonomy

2. Teduglutide therapy

  • Analog of glucagon-like peptide 2 (GLP-2) but harder to degrade (longer half-life)
  • Preliminary studies in adults indicate improvement in absorption and villous histology after subcutaneous administration for three weeks.  Improvements reverse when drug is discontinued.
  • Since GLP-2 is produced by colon & increased in IF (if colon present), unclear whether exogenous administration will be as beneficial in patients with residual colon

3. Lipid minimization &/or fish oil lipids

  • Cholestasis increases in patients receiving more than 1 g/kg/day of intralipids (soy based).
  • Fish oil (Omegaven) has shown benefit in lowering cholestasis in numerous case reports.  This may be due the high content of anti-inflammatory ω-3 fatty acids.
  • Another preparation SMOFLipid is a mixed formulation and may be safer than pure fish oil; randomized controlled studies of both of these lipid formulations are underway.
  • Fish oil has not been shown to improve histology
  • Parenteral nutrition associated liver disease (PNALD) may improve with lowering lipids & may not need omegaven

4. Ethanol locks

  • May be beneficial in treating and preventing central line infections.  In both situations, in small studies, ethanol locks lowered incidence of recurrent infections.
  • Six studies involving 75 patients (66 pediatric patients) lowered infection rates from approximately 10 per 1000 catheter days to 2 per 1000 catheter days.
  • Ethanol concentrations were mostly 70% in these studies, though 25% has been used.
  • Dwell times ranged from 2-14 hours.
  • Randomized studies are in progress.
  • Fewer infections should reduce the likelihood of death from sepsis and death due to loss of venous access.

Additional references:

  • -NEJM 2010; 362: 181.  Letter to editor describes use of fish oil in (n=125) Boston pediatric patients.
  • -JPGN 2009; 48: 209. n=12. SBS.9/12 improved with omegaven. 3 had transplant (L-ITx). No controls.
  • -NEJM 2009; 361: 998. Intestinal Rx.  Review claims ~90% 1yr survival. 47% 5yr, 61% 3yr (expecting to go higher)
  • -JPGN 2009; 48: 334. Isolated liver w SBS feasible IF 50cm small bowel remaining or 30cm w ICV, 50% enteral nutrition >4 weeks with good growth, no dysmotility.
  • -Pediatrics 2008; 121: e678. n=18. use of fish oil improved cholestasis compared to historical controls.
  • -Gastroenterology 2008; 135: 61, 303. Survival of ITx (vs. HAL).  In many conditions, better off from survival standpoint without Tx. Tx if failure of TPN (severe liver dz/thrombosis of >/= 2 central veins, multiple bouts of sepsis/frequent dehydration), high risk of death, severe short bowel (<10cm in infants and <20cm in adults), pseudoobstruction, unwillingness to accept long-term tpn. 93% of TPN patients who did not have TPN-complications had 93% survival rate.  Thus, TPN is first line Rx as survival and quality of life often better.
  • -Pediatrics 2006; 118: e197-e201.  Reversal of TPN-AC c IV omega-3 fatty acids (fish oil-derived) instead of intralipids
  • -Liver Transplantation 2006; 12: 1062, 1040. Liver transplant alone reasonable to consider in some SBS patients who tolerate >50% enteral therapy and are less than 2 years old.
  • -Gastroenterology 2006; 130. Supp 1. Summary of NIH workshop on intestinal failure. TX Indications: Liver disease, thrombosis of major veins, recurrent catheter-related sepsis, frequent severe dehydration/electrolyte imbalance.
  • -JPGN 2005; 41: 47A (pg507). Poor prognosis: <40cm, needing >40kcal/kg PN, increased bili (>150 μmol/L)
  • -J Pediatr 2005; 146: 542. Serum citrulline > 19 μ/L associated with bowel adaptation/weaning off HAL.
  • -J Pediatr 2004; 145: 157-163. Survival of SBS with as little as 15
  • -Arch Pediatr Adolesc Med 2006; 160: 104953.  Use of ethanol lock (70%, 08-1.4mL for 12-24hrs, then withdraw). n=51.  High success rate in salvaging line
  • -J Pediatr 2001; 139: 27-33. Review of 30 pts. 3 of 30 pts with bowel length 40cm or less able to wean PN.
  • -Gastroenterology 2001; 120: 806-815. Glucagon-like peptide 2 improves nutrient absorption marginally.