- Email: [email protected]
Are serum prolyl 4-hydroxylase useful as noninvasive markers of liver fibrosis in patients with biliary atresia?
Journal of Pediatric Surgery (2005) 40, 1366 – 1367
www.elsevier.com/locate/jpedsurg
Correspondence Author’s response To the Editor, Dr Touloukian’s comments reflect the strong leadership in the APSA presidency that has characterized our history. The initiative to reestablish the Executive Council of Pediatric Surgical Organizations is a first step in developing a potential broad-based and rapidly responding body of our peers to address significant issues confronting pediatric surgery, including the educational and training challenges that our article has outlined. Furthermore, the issues that were a part of the initial discussion—curricula for trainees in general surgery and pediatric surgery and CME credits for those posttraining—are both relevant and critically important to our entire field. Hopefully, this body will develop a strategy-based agenda, will meet or converse at a frequency that will permit forward moving decision making, and develop an binstitutional memory Q that can reflect the activity of our entire field. It may be prudent to consider expanding the constituency of this body to include trainee representation and representation from the clinical practice community. In like manner, formalizing a Committee on Women and Family Issues will for the first time address the changing demographics of our trainees and the new entrants into pediatric surgery. However, I would like to challenge Dr Touloukian’s suggestion that curricular reform with b tracking Q could potentially damage the current matching process and that it might be difficult to select institutions that might best serve trainees desiring private practice, an academic position, or even those desiring to be physician scientists. The match in pediatric surgery has served us well, but as we respond to change, there might evolve a need to a better align program and candidate strengths, weaknesses, and goals. Certainly, on the basis of faculty numbers and qualities, case volumes and scope, affiliated medical school/cognate adult residency program strengths, and potential sources for extramural funding for a clinical scholar program, we could quite easily stratify those programs that might be better suited for trainees desiring a focused clinical practice future from those desiring to work in academic surgery. There is precedent in our history (see page 1161 of our article) for pediatric surgery taking the initiative for internal training 0022-3468/$ – see front matter D 2005 Published by Elsevier Inc.
program review over and above that done by the legislative approval bodies. It may be time to do so again. Moritz M. Ziegler The Children’s Hospital Denver, CO 80218-1088, USA E-mail address: [email protected] DOI of original article 10.1016/j.jpedsurg.2005.02.021 doi:10.1016/j.jpedsurg.2005.02.022
Correspondence Are serum prolyl 4-hydroxylase useful as noninvasive markers of liver fibrosis in patients with biliary atresia? Dear Editor, Increased hepatic fibrosis, a prominent feature of major prognostic importance in pediatric liver disorders, results from an imbalance between synthesis and degradation of collagen. A simple, sensitive method for monitoring collagen biosynthesis during the early stage of liver disease may therefore be helpful for predicting prognosis. In our previous communication, we reported the use of type IV collagen and procollagen type III peptide as serum markers of liver fibrosis in biliary atresia (BA). During our research on serum type IV collagen and procollagen type III peptide, we found that their concentrations mimicked changes seen in cytoplasmic enzymes at a cellular level in the liver and changes seen in biliary enzymes in BA [1]. Prolyl 4-hydroxylase (PH)—a key enzyme in the synthesis of collagen—is embedded in the membranes of rough endoplasmic reticulum (RER). Prolyl 4-hydroxylase is postulated to be a regulatory enzyme for collagen biosynthesis, and its activity can rapidly increase through monomer/ tetramer interconversion without synthesis of new enzyme protein [2]. Serum PH levels increase in patients with liver cirrhosis, alcoholic hepatitis, acute hepatitis, hepatocellular carcinoma, and cholestatic diseases. Its concentration in serum is considered to selectively reflect hepatic necrosis because it is only released into the circulation when a cell is destroyed [3]. Thus, when there is hepatocellular damage there is concurrent elevation of serum PH and cytoplasmic
Correspondence enzymes, and when there is cholestasis there is concurrent elevation of serum PH with biliary enzymes, suggesting that a quantitative assay for PH can be used to determine the amount of enzyme released from the liver into the bloodstream [4]. In other words, serum PH is a reliable noninvasive marker for hepatic fibrogenesis and fibrosis. A number of reports have indicated that serum PH levels and serum aminotransferases behave similarly in hepatocellular damage—both clinically and experimentally [5]. However, there appears to be only 1 report on increased hepatic PH activity in BA in the literature, and no reports on serum levels of PH in BA. For this study, 28 patients with BA (mean age, 11.0 F 3.7 years) were divided into 3 groups according to the results of conventional liver function tests. Serum total bilirubin (T-Bil), glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and g-glutamyl transpeptidase (g-GTP) were measured by routine methods. Group I (n = 8) patients were jaundice-free, with normal liver function (T-Bil b2.0 mg/dL; GOT b40 IU/L; GPT b35 IU/L; g-GTP b55 IU/L) and no evidence for severe cholangitis. Group II (n = 10) patients had moderate liver dysfunction (T-Bil b2.0 mg/dL; GOT N40 IU/L; GPT N35 IU/L; g-GTP N55 IU/L). Group III (n = 10) patients had severe liver dysfunction (T-Bil N2.0 mg/dL; GOT N40 IU/L; GPT N35 IU/L; g-GTP N55 IU/L) and were referred to as the bunfavorable prognosisQ group. Ten healthy volunteers (mean age, 10.5 F 2.8 years) served as controls. All subjects were investigated after obtaining parental informed consent to participate in this study. Samples of peripheral venous blood were collected and immediately separated and stored at 808C until they could be assayed. All bloods were fasting specimens taken after each subject had rested for at least 1 hour. Serum immunoreactive PH was measured by a sandwich enzyme immunoassay. Results were expressed in nanograms per milliliter. Serum PH levels (mean F SD) measured were as follows: control, 60.2 F 3.2 ng/mL; group I, 48.0 F 14.1 ng/L; group II, 71.8 F 12.2 ng/mL; and group III, 53.8 F 10.3 ng/mL. There were no significant differences between the patient groups and the control group (Fig. 1). Several papers have reported that the release of PH into serum in response to hepatocellular damage and cholestatic diseases is related to the fact that it is localized in RER membranes—that is, when there is hepatocellular damage, PH may detach from RER membranes and be released into the blood with other cytoplasmic enzymes, and in cholestasis, PH could increase in the blood by a mechanism similar to that which controls the release of biliary enzymes [4]. The lack of increase in serum PH seen in BA probably indicates there is a different etiology for liver fibrosis in BA compared with other liver fibrotic diseases such as altered
1367
Fig. 1 Serum PH levels in patients with BA compared with controls.
membrane permeability, which would allow only cytoplasmic enzymes to pass into the blood but not PH, or, there is no response by PH to cholestasis in BA. Similarly, serum PH does not reflect the extent of cell destruction in the simple way that aminotransferases do because there is no correlation between serum PH and GOT, GPT and g-GTP in groups II and III. This study demonstrates unequivocally that single measurement of serum PH activity in BA is of no value in predicting outcome of progressive liver fibrosis. We conclude that serum PH activity is of no prognostic value in BA.
References [1] Kobayashi H, Miyano T, Horikoshi K, et al. Prognostic value of serum procollagen III peptide and type IV collagen in patients with biliary atresia. J Pediatr Surg 1998;33:112 - 4. [2] Miyabayashi C, Inoue K, Takahara T, et al. Serum prolyl hydroxylase value in liver disease. Jpn J Gastroenterol 1986;83:2181 - 9. [3] Nagai Y, Kato M, Toda G. Selectivity of serum immunoreactive prolyl 4-hydroxylase as a marker for hepatic necrosis. J Gastroenterol Hepatol 1992;7:253 - 6. [4] Nagai Y, Oka H. Human prolyl hydroxylase. Purification, radioimmunoassay and clinical studies in liver diseases. Gastroenterol Jpn 1985;20:53 - 64. [5] Nagai Y, Yoshiba M. Studies on serum immunoreactive prolyl 4-hydroxylase in liver diseases—its elevation both in hepatocellular damage and cholestatic diseases. Clin Chim Acta 1988;175:27 - 36.
Hiroyuki Kobayashi Tsuyoshi Tamura Atsuyuki Yamataka Geoffrey J. Lane Takeshi Miyano Department of Pediatric Surgery Juntendo University School of Medicine Bunkyo-ku, Tokyo 113-8421, Japan E-mail address: [email protected] doi:10.1016/j.jpedsurg.2005.05.020
www.elsevier.com/locate/jpedsurg
Correspondence Author’s response To the Editor, Dr Touloukian’s comments reflect the strong leadership in the APSA presidency that has characterized our history. The initiative to reestablish the Executive Council of Pediatric Surgical Organizations is a first step in developing a potential broad-based and rapidly responding body of our peers to address significant issues confronting pediatric surgery, including the educational and training challenges that our article has outlined. Furthermore, the issues that were a part of the initial discussion—curricula for trainees in general surgery and pediatric surgery and CME credits for those posttraining—are both relevant and critically important to our entire field. Hopefully, this body will develop a strategy-based agenda, will meet or converse at a frequency that will permit forward moving decision making, and develop an binstitutional memory Q that can reflect the activity of our entire field. It may be prudent to consider expanding the constituency of this body to include trainee representation and representation from the clinical practice community. In like manner, formalizing a Committee on Women and Family Issues will for the first time address the changing demographics of our trainees and the new entrants into pediatric surgery. However, I would like to challenge Dr Touloukian’s suggestion that curricular reform with b tracking Q could potentially damage the current matching process and that it might be difficult to select institutions that might best serve trainees desiring private practice, an academic position, or even those desiring to be physician scientists. The match in pediatric surgery has served us well, but as we respond to change, there might evolve a need to a better align program and candidate strengths, weaknesses, and goals. Certainly, on the basis of faculty numbers and qualities, case volumes and scope, affiliated medical school/cognate adult residency program strengths, and potential sources for extramural funding for a clinical scholar program, we could quite easily stratify those programs that might be better suited for trainees desiring a focused clinical practice future from those desiring to work in academic surgery. There is precedent in our history (see page 1161 of our article) for pediatric surgery taking the initiative for internal training 0022-3468/$ – see front matter D 2005 Published by Elsevier Inc.
program review over and above that done by the legislative approval bodies. It may be time to do so again. Moritz M. Ziegler The Children’s Hospital Denver, CO 80218-1088, USA E-mail address: [email protected] DOI of original article 10.1016/j.jpedsurg.2005.02.021 doi:10.1016/j.jpedsurg.2005.02.022
Correspondence Are serum prolyl 4-hydroxylase useful as noninvasive markers of liver fibrosis in patients with biliary atresia? Dear Editor, Increased hepatic fibrosis, a prominent feature of major prognostic importance in pediatric liver disorders, results from an imbalance between synthesis and degradation of collagen. A simple, sensitive method for monitoring collagen biosynthesis during the early stage of liver disease may therefore be helpful for predicting prognosis. In our previous communication, we reported the use of type IV collagen and procollagen type III peptide as serum markers of liver fibrosis in biliary atresia (BA). During our research on serum type IV collagen and procollagen type III peptide, we found that their concentrations mimicked changes seen in cytoplasmic enzymes at a cellular level in the liver and changes seen in biliary enzymes in BA [1]. Prolyl 4-hydroxylase (PH)—a key enzyme in the synthesis of collagen—is embedded in the membranes of rough endoplasmic reticulum (RER). Prolyl 4-hydroxylase is postulated to be a regulatory enzyme for collagen biosynthesis, and its activity can rapidly increase through monomer/ tetramer interconversion without synthesis of new enzyme protein [2]. Serum PH levels increase in patients with liver cirrhosis, alcoholic hepatitis, acute hepatitis, hepatocellular carcinoma, and cholestatic diseases. Its concentration in serum is considered to selectively reflect hepatic necrosis because it is only released into the circulation when a cell is destroyed [3]. Thus, when there is hepatocellular damage there is concurrent elevation of serum PH and cytoplasmic
Correspondence enzymes, and when there is cholestasis there is concurrent elevation of serum PH with biliary enzymes, suggesting that a quantitative assay for PH can be used to determine the amount of enzyme released from the liver into the bloodstream [4]. In other words, serum PH is a reliable noninvasive marker for hepatic fibrogenesis and fibrosis. A number of reports have indicated that serum PH levels and serum aminotransferases behave similarly in hepatocellular damage—both clinically and experimentally [5]. However, there appears to be only 1 report on increased hepatic PH activity in BA in the literature, and no reports on serum levels of PH in BA. For this study, 28 patients with BA (mean age, 11.0 F 3.7 years) were divided into 3 groups according to the results of conventional liver function tests. Serum total bilirubin (T-Bil), glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), and g-glutamyl transpeptidase (g-GTP) were measured by routine methods. Group I (n = 8) patients were jaundice-free, with normal liver function (T-Bil b2.0 mg/dL; GOT b40 IU/L; GPT b35 IU/L; g-GTP b55 IU/L) and no evidence for severe cholangitis. Group II (n = 10) patients had moderate liver dysfunction (T-Bil b2.0 mg/dL; GOT N40 IU/L; GPT N35 IU/L; g-GTP N55 IU/L). Group III (n = 10) patients had severe liver dysfunction (T-Bil N2.0 mg/dL; GOT N40 IU/L; GPT N35 IU/L; g-GTP N55 IU/L) and were referred to as the bunfavorable prognosisQ group. Ten healthy volunteers (mean age, 10.5 F 2.8 years) served as controls. All subjects were investigated after obtaining parental informed consent to participate in this study. Samples of peripheral venous blood were collected and immediately separated and stored at 808C until they could be assayed. All bloods were fasting specimens taken after each subject had rested for at least 1 hour. Serum immunoreactive PH was measured by a sandwich enzyme immunoassay. Results were expressed in nanograms per milliliter. Serum PH levels (mean F SD) measured were as follows: control, 60.2 F 3.2 ng/mL; group I, 48.0 F 14.1 ng/L; group II, 71.8 F 12.2 ng/mL; and group III, 53.8 F 10.3 ng/mL. There were no significant differences between the patient groups and the control group (Fig. 1). Several papers have reported that the release of PH into serum in response to hepatocellular damage and cholestatic diseases is related to the fact that it is localized in RER membranes—that is, when there is hepatocellular damage, PH may detach from RER membranes and be released into the blood with other cytoplasmic enzymes, and in cholestasis, PH could increase in the blood by a mechanism similar to that which controls the release of biliary enzymes [4]. The lack of increase in serum PH seen in BA probably indicates there is a different etiology for liver fibrosis in BA compared with other liver fibrotic diseases such as altered
1367
Fig. 1 Serum PH levels in patients with BA compared with controls.
membrane permeability, which would allow only cytoplasmic enzymes to pass into the blood but not PH, or, there is no response by PH to cholestasis in BA. Similarly, serum PH does not reflect the extent of cell destruction in the simple way that aminotransferases do because there is no correlation between serum PH and GOT, GPT and g-GTP in groups II and III. This study demonstrates unequivocally that single measurement of serum PH activity in BA is of no value in predicting outcome of progressive liver fibrosis. We conclude that serum PH activity is of no prognostic value in BA.
References [1] Kobayashi H, Miyano T, Horikoshi K, et al. Prognostic value of serum procollagen III peptide and type IV collagen in patients with biliary atresia. J Pediatr Surg 1998;33:112 - 4. [2] Miyabayashi C, Inoue K, Takahara T, et al. Serum prolyl hydroxylase value in liver disease. Jpn J Gastroenterol 1986;83:2181 - 9. [3] Nagai Y, Kato M, Toda G. Selectivity of serum immunoreactive prolyl 4-hydroxylase as a marker for hepatic necrosis. J Gastroenterol Hepatol 1992;7:253 - 6. [4] Nagai Y, Oka H. Human prolyl hydroxylase. Purification, radioimmunoassay and clinical studies in liver diseases. Gastroenterol Jpn 1985;20:53 - 64. [5] Nagai Y, Yoshiba M. Studies on serum immunoreactive prolyl 4-hydroxylase in liver diseases—its elevation both in hepatocellular damage and cholestatic diseases. Clin Chim Acta 1988;175:27 - 36.
Hiroyuki Kobayashi Tsuyoshi Tamura Atsuyuki Yamataka Geoffrey J. Lane Takeshi Miyano Department of Pediatric Surgery Juntendo University School of Medicine Bunkyo-ku, Tokyo 113-8421, Japan E-mail address: [email protected] doi:10.1016/j.jpedsurg.2005.05.020