The macroenzymes: a clinical review

Significant elevations of serum amylase caused by macroamylase: Case reports and detection possibilities

BACKGROUND

The presence of isolated elevated serum amylase levels can be caused by high molecular mass complexes. We describe 13 cases of hyperamylasemia detected in adult patients without clinical symptoms of a pancreatic disorder. Five of them were thoroughly examined using different tools for the detection of macrocomplexes.

METHODS

We performed both screening and more advanced methods of macroamylase detection, including polyethylene glycol precipitation, sample storage at 4°C and separation by gel filtration.

RESULTS

The presence of macroamylase in the suspected samples was confirmed by the methods described, except for the sample storage at 4°C. In this method, the enzyme activity did not decrease. The polyethylene glycol precipitation activity (% PPA) averaged 89.1% for amylase, whereas the control samples averaged 30.7%. Gel filtration chromatography confirmed an IgA macroamylase peak in three samples and an IgG macroamylase peak in two samples.

CONCLUSION

The presence of macroamylase should be suspected whenever the clinical history and condition of the patient do not match the measured enzyme value to avoid diagnostic errors and unnecessary invasive examinations. The presence of macrocomplexes is considered a benign process that may occur in apparently healthy individuals. Cooperation between clinicians and laboratory staff is necessary.

Clinical Significance of Transient Asymptomatic Elevations in Aminotransferase (TAEAT) in Oncology

Monitoring for liver injury remains an important aspect of drug safety assessment, including for oncotherapeutics. When present, drug-induced liver injury may limit the use or result in the discontinuation of these agents. Drug-induced liver injury can exhibit with a wide spectrum of clinical and biochemical manifestations, ranging from transient asymptomatic elevations in aminotransferases (TAEAT) to acute liver failure. Numerous oncotherapeutics have been associated with TAEAT, with published reports indicating a phenomenon in which patients may be asymptomatic without overt liver injury despite the presence of grade ≥3 aminotransferase elevations. In this review, we discuss the occurrence of TAEAT in the context of oncology clinical trials and clinical practice, as well as the clinical relevance of this phenomenon as an adverse event in response to oncotherapeutics and the related cellular and molecular mechanisms that may underlie its occurrence. We also identify several gaps in knowledge relevant to the diagnosis and the management of TAEAT in patients receiving oncotherapeutics, and identify areas warranting further study to enable the future development of consensus guidelines to support clinical decision-making.

Troponin interference with special regard to macrocomplex formation

Biomarkers, such as troponin-T and troponin-I, are regarded as the gold standard laboratory parameter for diagnosing many cardiological diseases. These parameters have been approved for clinical use. Many cardiological guidelines recommend the analysis of troponins in the majority of cardiological disease diagnoses and to also gain prognostic information. Nonetheless, many medical circumstances could cause false troponin elevations. In this article, we focus on troponin artifacts, particularly macro-immune complex formation, as important interference factors. Therefore, we performed a literature search from 2006 to 06/2021.

Asymptomatic HyperCKemia: A Diagnostic Trap

Elevated creatine kinase (CK) levels are the most sensitive indicator of muscle injury. Levels >5000 U/L warns physicians to initiate aggressive hydration and prevent renal failure. We present a rare case of asymptomatic hyperCkemia with levels >80 times the upper limit of normal (ULN), refractory to fluid resuscitation. Our patient was found to have elevated macroenzymes- macroCkemia, causing decreased clearance of CK. The objective of this case report is to bring to attention a rare and benign cause of CK elevation which can lead to diagnostic and therapeutic errors.

The Utility of Elevated Serum Lactate Dehydrogenase in Current Clinical Practice

OBJECTIVE

Because of its wide tissue distribution, elevation of serum lactate dehydrogenase (LD) is a nonspecific finding. Although serum LD is still included in the prognosis and staging of metastatic melanoma and germ cell tumors, its nonspecificity has led to decreased usefulness.

METHODS

In this study, we analyzed the serum LD assays performed in a 726-bed hospital during a 1-year period and reviewed charts of patients with serum LD of >3 standard deviations (SD).

RESULTS

Of 312 patients with elevated serum LD, only 9 were patients with melanoma and germ cell tumors. The other 303 patients had other malignancies, chronic conditions, and sepsis.

CONCLUSION

Elevated serum LD (even >3 SD) is an extremely nonspecific finding that does not contribute to clinical management in a majority of patients. As such, serum LD testing should be retired from routine clinical order sets and restricted in use.

Persistent elevation of aspartate aminotransferase in a child after incomplete Kawasaki disease: a case report and literature review

BACKGROUND

Interpretation of abnormalities in liver function tests, especially in asymptomatic children, is a common problem faced by clinicians. Isolated elevation of aspartate aminotransferase may further puzzle physicians. Macro-aspartate aminotransferase (AST) results from complexes AST produces with other plasma components, such as immunoglobulin. To our knowledge, this is the first report on a case of macro-AST-associated incomplete Kawasaki disease (KD). It is to make physicians aware of this benign condition and help to prevent extensive, unnecessary investigations and invasive workups.

CASE PRESENTATION

A 16-month old boy with a 7-day history of fever was admitted to our pediatric ward for pyrexia workup. After complete investigations, KD was confirmed by a pediatric rheumatologist. During his admission and serial follow-up tests, an isolated AST elevation was noted. Comprehensive tests were performed and using the polyethylene glycol (PEG) precipitation method, macro-AST was confirmed. The patient has been followed up for 3 years, and so far, the benign nature of this condition has been confirmed.

CONCLUSION

Clinicians should consider testing for macro-AST when elevated AST is the only abnormal lab finding. Although an uncommon finding, macro-AST may be seen in both children and adults. There are many reasons for this phenomenon, including resolved acute hepatitis or in some cases, inflammatory bowel disease, hepatic malignancy, monoclonal gammapathy, celiac disease, or KD; however, it may be observed in asymptomatic healthy children as well. Using the PEG precipitation method, a definitive diagnosis can be made. In none of these conditions does macro-AST have any prognostic significance. An appreciation of macro-AST may prevent the need for more invasive investigations to which patients may be unnecessarily subjected. It is important to recognize this condition as benign and assure patients that no specific treatment is required.

Persistent Increase in Serum Alkaline Phosphatase in a Patient with Monoclonal Gammopathy of Undefined Significance

We report the finding of alkaline phosphatase-immunoglobulin complex (macro-alkaline phosphatase (macro-ALP)) in a patient with persistently increased ALP activity. The identification of macro-ALP is important to rule out pathological causes of increased ALP activity and to avoid unnecessary diagnostic investigation. The patient was subsequently diagnosed with vitamin D deficiency, gallstone pancreatitis, and monoclonal gammopathy of undefined significance (MGUS). Macro-ALP can coexist with disease that can increase serum ALP activity. We report, for the first time, a case of macro-ALP in a patient with a monoclonal protein (M-protein).

A heterozygous mutation in GOT1 is associated with familial macro-aspartate aminotransferase

BACKGROUND & AIMS

Macro-aspartate aminotransferase (macro-AST) manifests as a persistent elevation of AST levels, because of association of the protein with immunoglobulins in the circulation. Macro-AST is a rare, benign condition without a previously confirmed genetic basis.

METHODS

Whole exome sequencing (WES)-based screening was performed on 32 participants with suspected familial macro-AST, while validation of variants was performed on an extended cohort of 92 probands and 1,644 healthy controls using Taqman genotyping.

RESULTS

A missense variant (p.Gln208Glu, rs374966349) in glutamate oxaloacetate transaminase 1 (GOT1) was found, as a putative causal variant predisposing to familial macro-AST. The GOT1 p.Gln208Glu mutation was detected in 50 (54.3%) of 92 probands from 20 of 29 (69%) families, while its prevalence in healthy controls was only 0.18%. In silico analysis demonstrated that the amino acid at this position is not conserved among different species and that, functionally, a negatively charged glutamate on the GOT1 surface could strongly anchor serum immunoglobulins.

CONCLUSIONS

Our data highlight that testing for the p.Gln208Glu genetic variant may be useful in diagnosis of macro-AST.

LAY SUMMARY

Higher than normal levels of aspartate aminotransferase (AST) in the bloodstream may be a sign of a health problem. Individuals with macro-AST have elevated blood AST levels, without ongoing disease and often undergo unnecessary medical tests before the diagnosis of macro-AST is established. We found a genetic variant in the GOT1 gene associated with macro-AST. Genetic testing for this variant may aid diagnosis of macro-AST.

Distribution of serum concentrations reported for macroenzyme aspartate aminotransferase (macro-AST)

Background

The presence of macroenzyme (M) is often the explanation of an isolated elevation of aspartate aminotransferase (AST). Where M is identified, it is reasonable for the clinician to ask where an individual patient's result fits in with known concentrations of M. In this context, we conducted a survey of literature to examine the distribution of reported serum concentrations of macro-AST. We also analyzed the distribution data to examine whether elevations were consistent with simple alteration of circulatory half-life (t_1/2) of M relative to normal AST.

Methods

Distributions of M were compiled from the literature. These distributions were compared to predictions based on fixed changes in t_1/2 applied to the reference interval for AST.

Results

There was a bimodal distribution of literature values for M (n =51), comprised roughly of populations A (M <200 U/L; 60% of total) and B (M >200 U/L; 40% of total). The two distributions were reasonably well characterized by a simple projection to the right of the reference interval for AST according to increased t_1/2 (A: t_1/2 =3.3 days; B: t_1/2 =19.8 days) relative to AST (t_1/2 =0.7 days).

Conclusions

Knowledge of distributions for M may be useful in discussion with clinicians regarding significance of M for individual patients. Distributions for M were consistent with the simplest explanation for elevated AST due strictly to an extended circulatory lifetime for M. Caveats to analysis, however, include selection within literature data mainly for patients with various co-morbidities.

[Macro-AST and myeloma: An incidental association?]

INTRODUCTION

Macro-AST is recognized as a classical aetiology of isolated and persistent increase of serum aspartate aminotransferase (AST) levels. Macro-AST are high molecular weight complexes associating AST and a macromolecule, often an immunoglobulin. Although those macroenzymes of unknown pathogenesis are usually non-pathogenic, association with several diseases, including autoimmune diseases and liver diseases has been described.

CASE REPORT

We report here the case of a 45-year-old patient with previously normal liver enzymes in whom an AST elevation and an IgA monoclonal gammopathy were discovered concomitantly. Following the diagnosis of multiple myeloma, we could evidence in the patient's serum a complex between AST and the monoclonal IgA. AST levels course followed closely the progression of monoclonal gammopathy.

CONCLUSION

This is the first report demonstrating a clear link between macro-AST and a monoclonal gammopathy.

Persistently raised aspartate aminotransferase (AST) due to macro-AST in a rheumatology clinic

Macrocomplexes between immunoglobins and aspartate aminotransferase (macro-AST) may result in persistently increased AST concentration. The presence of macro-AST in patients has been implicated in unnecessary investigations of abnormal liver function tests. We report the case of a 44-year-old female who presented to the rheumatology clinic with a 12-months' history of constant widespread pain affecting her limbs and was found to have an elevated AST concentration. Further information from her GP revealed a 14-years' history of elevated AST with otherwise normal liver function. Previous abdominal ultrasound and two liver biopsies carried out 2 years apart were normal. This prompted further analytical investigation by the biochemistry department which identified macro-AST as the cause. This case illustrates that persistently raised isolated AST concentration with no other abnormal indices may warrant macroenzyme analysis potentially avoiding unnecessary invasive investigations.

A macro-enzyme cause of an isolated increase of alkaline phosphatase

BACKGROUND

Macroenzyme complexes of serum enzymes and antibody can increase the circulating enzymatic activity and may lead to unnecessary additional testing and procedures. Laboratory physicians and scientists need to be aware of techniques to identify macroenzyme complexes when suspected.

CASE REPORT

To investigate the possibility of a macro-alkaline phosphatase in the serum of a 74 year old male with persistently increased alkaline phosphatase we coupled a protein A/G agarose affinity chromatography technique with isoenzyme electrophoresis to look for the presence of macro-alkaline phosphatase.

RESULTS

The majority of the alkaline phosphatase activity in the patient's serum sample was bound to the column and only a minor fraction (25%) of alkaline phosphatase activity was present in the column flow-through. The alkaline phosphatase activity was also found to co-elute with the immunoglobulins in the patient sample. The alkaline phosphatase activity in a control serum sample concurrently treated in the same manner did not bind to the column and was found in the column flow-through.

CONCLUSION

The use of protein A/G agarose affinity chromatography is a rapid and simple method that can be applied to the investigation of other macro-enzyme complexes.

Detection of creatine kinase macroenzymes

BACKGROUND

It is vital to detect macroenzymes in patients' plasma or serum since their presence may lead to spurious elevation of enzyme activity, thereby causing diagnostic confusion. Our service for macroenzyme detection has been made available to laboratories throughout the UK. This report describes our laboratory's experience with macro-creatine kinase (CK) detection over a 10-year period.

METHODS

In each sample received, the presence of macro-CK was looked for by both polyethylene glycol percent precipitable activity (%PPA) and isoenzyme electrophoresis (IsoEP). The accumulated findings over 10 years were reviewed.

RESULTS

Out of a total number of 255 requests received from throughout the UK, 30 patients (11.8%) were found to be positive for macro-CK (28 type 1 and 2 type 2). Among those found to be positive, the total CK elevation was relatively modest and the %PPA positively correlated with macro-CK by IsoEP and densitometry (Spearman r(s) = 0.631). The upper reference limit for %PPA of CK could be increased from 37% to 45% after assessment by both an International Federation of Clinical Chemistry-approved calculation and by receiver operating characteristic curve analysis.

CONCLUSIONS

Adoption of this change would allow for a more cost-effective investigation protocol. More than 80% of those positive for macro-CK type 1 (immunoglobulin bound) were female, which conforms to findings in many autoimmune processes.

Chronic asymptomatic hyperamylasemia unrelated to pancreatic diseases

PURPOSE

This study was addressed to assess the clinical characteristics of patients presenting with chronic hyperamylasemia unrelated to pancreatic diseases (CHUPD). Almost all patients presenting with chronic hyperamylasemia undergo expensive, long, difficult, and often unnecessarily repeated diagnostic procedures. This is in conjunction with the poor knowledge of the fact that besides hyperenzymemia secondary to pancreatic diseases and systemic illnesses, various non-pathological forms of chronic hyperamylasemia without relevant pathologic consequence can occur in clinical practice.

MATERIAL AND METHODS

Data of all patients with CHUPD were retrospectively reviewed (June 1997-December 2009). Fifty one patients were included in the study; median follow up was 48 months (range 8-112 months). Their pre-enrolment diagnoses were: chronic pancreatitis in 31 cases (60.7%) and recurrent pancreatitis in 13 cases (25.4%); the remaining 7 patients (13.7%) were without a specific diagnosis.

RESULTS

Our observations, supported by diagnostic procedures (Ca19-9 serum levels, abdominal ultrasonography, computed tomography and magnetic resonance, endoscopic retrograde cholangiopancreatography, and endoscopic ultrasonography) revealed that CHUPD was secondary to: a) benign pancreatic hyperamylasemia, 20 patients (39.2%); b) macroamylasemia, 18 patients (35.2 %) and c) salivary hyperamylasemia, 13 patients (25.4%).

CONCLUSIONS

Due to the poor familiarity with CHUPD, the occurrence of this condition quite frequently leads to unnecessarily repeated diagnostic procedures.

Macroenzyme creatine kinase in the era of modern laboratory medicine

Among the conditions in which creatine kinase (CK)-MB activity is elevated in the absence of myocardial injury or infarction, macroenzyme (macro) CK merits special attention from clinicians. We present 2 cases, 1 with macro CK type 1 and the other with macro CK type 2, to stress the common clinical situations and diagnostic dilemma that clinicians encounter when evaluating patients with macro CK. Moreover, the rare conditions associated with macro CK, and the phenomenon of spuriously high CK-MB activity out of proportion to total CK, are discussed. The biochemical characteristics, clinical significance and potential implications of macro CK are reviewed within the scope of modern laboratory medicine.

Prevalence and long-term course of macro-aspartate aminotransferase in children

OBJECTIVES

To investigate the prevalence, association with clinical conditions, and long-term course of macro-aspartate aminotransferase (macro-AST).

STUDY DESIGN

Forty-four children with an isolated elevation of serum AST were screened for macro-AST with electrophoresis and % polyethylene glycol (PEG) precipitable activity (PPA).

RESULTS

All children were healthy, except they had elevated AST values. Seventeen children (38.6%) were macro-AST-positive. They had higher AST values than the 27 children who were macro-AST-negative (P = .001). Values <67.1% PPA and >82.2% PPA were associated with a very low probability of being macro-AST-positive and macro-AST-negative, respectively. Thirty-eight children underwent clinical and laboratory follow-up (mean, 4.7 +/- 3.8; range, 1-16 years). All remained symptom-free. AST levels decreased significantly only in children who were macro-AST-negative (P = .006). Macroenzyme persisted in 6 of the 9 children who were macro-AST-positive after 6.0 +/- 4.1 years.

CONCLUSIONS

Macro-AST was present in more than one-third of children with an isolated increase of AST levels. The lack of pathological correlates in a long period argues for the benign nature of this phenomenon in childhood. We suggest that our %PPA thresholds can be used as a screening test and that electrophoresis be reserved for confirming positive screen test results and cases in which %PPA levels are of intermediate discriminant accuracy.

A paediatric case of macro aspartate aminotransferase

Macroenzymes are enzymes in plasma that have a higher molecular mass than the corresponding enzyme normally present under (patho) physiological conditions. Macro species have been described for most routinely measured enzymes, but with only a few reports of macro species with aspartate aminotransferase (AST), and in particular very few reports in children and adolescents. Routine biochemical analysis in a 15-year-old girl presenting with lower back pain revealed an isolated raised AST as part of a liver function test profile. Polyethylene glycol precipitation and gel filtration chromatography showed this to be a macro species.

Macro-creatine kinase and macro-lactate dehydrogenase in a girl with ulcerative colitis

We report the case of a girl affected by ulcerative colitis with high serum levels of creatine kinase and lactate dehydrogenase due to the presence of macroenzymes. Our observation suggests that the knowledge of this association may be helpful when evaluating ulcerative colitis patients with unexplained isolated elevation of one or more serum enzyme activities.

Macroenzyme Creatine Kinase (Ck) Type 2 in HIV-Infected Patients is Significantly Associated with Tdf and Consists of Ubiquitous Mitochondrial Ck

Objective

To evaluate the prevalence and origin of macroenzyme creatine kinase type 2 (Macro CK2) in HIV-1-infected patients on antiretroviral treatment.

Design

CK, CK-MB activity and protein weight, electrophoretic behaviour, glomerular filtration rate (GFR), aspartate aminotransferase (AST), alanine aminotransferase (ALT), bone alkaline phosphatase (AP), (2-microglobulin serum levels and proteinuria were analysed in 468 HIV-infected outpatients. Sera with detectable Macro CK2 were further analysed using immunoblotting.

Results

CK-MB isoenzyme activity and mass concentration revealed the presence of Macro CK2 in 32/408 (7.8%) outpatients. Tenofovir DF (TDF) treatment was a prominent common feature in these patients. Prospective examination of sera from 41 patients collected prior to and during TDF exposure showed Macro CK2 in 20/41 (48%) TDF-treated patients and in 0/19 control sera from patients with TDF-free regimens. Macro CK2 was not present prior to TDF exposure. Patients with Macro CK2 showed a significant elevation of serum (2-microglobulin levels. GFR, AST/ALT ratio, bone AP and proteinuria remained unchanged. Electrophoresis and immunoblotting demonstrated that the Macro CK2 in TDF-treated patients consisted of the ubiquitous (uMtCK) and not the sarcomeric type (sMtCK) of mitochondrial CK (MtCK).

Conclusions

Macro CK2 consisting of uMtCK is associated with the use of TDF-containing regimens. Whether the appearance of uMtCK in these patients reflects mitochondrial damage remains to be clarified.

Immunoglobulin G has a role for systemic protein modulation in vivo: a new concept of protein homeostasis

The constant level of various proteins including albumin and cellular components in intravascular pool in vivo is strictly controlled by an unknown homeostatic mechanism, although there are fluctuations seen in pathologic conditions. Because the majority of the IgG in the serum is regarded as self-reactive natural autoantibodies, IgG may have a role to react with all proteins in vivo. It is hypothesized that like an immune system, a homeostatic mechanism for the protein pool also has a sensitive role to identify and memorize the extent and repertoire of both normal and pathogenic proteins on an individual basis, and IgG may be one of the major players in performing these functions. This hypothesis may explain the unresolved clinical observations as followed: (1) the marked increased IgG levels observed in self-limiting diseases presumed to come from immunological insults such as acute poststreptococcal glomerulonephritis and Kikuchi-Fujimoto disease, (2) an immediate reduction of all protein levels except immunoglobulins after intravenous immunoglobulin (IVIG) treatment in Kawasaki disease, (3) a unified explanation for the variety of immunomodulating effects exerted by IVIG, (4) the IgG-enzyme complexes observed in benign conditions such as macroamylasemia and hyperphosphatasemia, and (5) the marked decreased IgG level, which is correlated with the albumin level in minimal change nephrotic syndrome. IgG may be a 'watch-dog' for the disturbances of protein homeostasis in vivo. IgG may control the pathogenic proteins that appeared in disordered states, and it may help prevent the loss of proteins in case of nephrotic syndrome.

Development of macro-aspartate aminotransferase in a patient undergoing specific allergen injection immunotherapy

Macro-aspartate aminotransferase (macro-AST), a complex between normal AST and an immunoglobulin, is recognized as a cause of isolated elevation of AST. Though its pathogenesis is unknown, previous reports have been suggestive of an autoimmune process. We describe a case of macro-AST formation in a patient with previously normal liver enzymes in whom an isolated AST elevation was discovered after initiation of specific allergen injection immunotherapy (SIT) for allergic rhinitis. We propose that SIT in this otherwise healthy patient led to the formation of macro-AST as a consequence of antibody cross-reaction (molecular mimicry). Awareness of this possible mechanism of macroenzyme development may be helpful to physicians evaluating patients with isolated elevations in AST.

Observation and identification of lactate dehydrogenase anomaly in a postburn patient

OBJECTIVE

Lactate dehydrogenase (LDH) anomaly is one of the macroenzymes. Macroenzymes are enzymes in serum that have formed high molecular mass complexes, either by self polymerisation or by association with other serum components. The aim of this study was to identify the properties of LDH anomaly and observe the changes from admission to discharge in a postburn patient with LDH anomaly in his serum.

METHODS

LDH isoenzymes of the serum were electrophoretically fractionated with terylene cellulose acetate supporting media; LDH anomaly was identified by counter immunoelectrophoresis.

RESULTS

An abnormal LDH-4 band and an extra band on the cathode of LDH-5 were observed in the serum of this patient and were found to be part of an LDH-IgG complex. As his symptoms improved, the patient's LDH anomaly gradually disappeared. The appearance and disappearance of the anomaly seemed to be related to the progression of the patient's burns.

CONCLUSION

In clinical practice, it is important to keep in mind the possibility of an LDH anomaly in patients when the LDH level is abnormally high or does not seem to be related to the clinical state. Early discovery of an LDH anomaly in a patient's serum may be useful for diagnosis and treatment.

Macro-aspartate aminotransferase (macro-AST). A 12-year follow-up study in a young female

We describe a case of chronic elevation of serum aspartate aminotransferase (AST) activity due to the presence of a macro-enzyme form of AST (macro-AST) in a young female followed up for 12 years. This biochemical abnormality, although generally detected in acute and chronic hepatitis, malignancies and autoimmune disease, was not associated with any particular illness and did not seem to be congenital, as normal AST concentrations were reported in the patient's family members. Moreover, the normal or quasi-normal values of AST associated with peak levels observed in our case suggest that this phenomenon has a fluctuating behaviour rather than persisting for many months or years. In conclusion, we believe that it is important: 1) to reassure the patient with macro-AST, as this condition has a benign evolution and does not require any specific treatment; 2) to keep in mind this biochemical abnormality in all cases of unexplained AST elevation in order to avoid unnecessary invasive diagnostic procedures.

Macro-aspartate aminotransferase in a female with antibodies to hepatitis C virus

Persistent elevation of aspartate aminotransferase (AST) activity in serum due to the presence of a macroenzyme form of AST (macro-AST) may lead to diagnostic confusion in many clinical conditions, particularly those associated with chronic liver disease. We describe a case of macro-AST arising in an adult female with a false-positive hepatitis C virus (HCV) RNA test result that was not accompanied by other biochemical or histologic evidence of liver disease. The presence of macro-AST in serum was confirmed utilizing size-exclusion, high performance liquid chromatography (HPLC) and Protein G-agarose beads to precipitate immune complexes of AST and immunoglobulin G followed by centrifugation and AST activity measurements in the supernatant. A brief review of the clinical enzymology of AST and methods used to quantify serum macro-AST activity is provided.

Effect of timing of urea feeding on the yield and quality of embryos in lactating dairy cows

High protein diets, which lead to excess production of nonprotein nitrogen such as ammonia and urea, have been associated with reduced fertility in dairy cows. In this study we test the hypothesis that diets containing high levels of quickly degradable urea nitrogen (QDN) compromise embryo development. Lactating dairy cows were fed mixed silage and concentrates twice daily. At 60 days postpartum, a synchronized estrus was induced and the cows were subsequently superovulated and inseminated using a standard protocol. On Day 7 after insemination, the uteri were flushed and embryos retrieved. At the start of treatment, cows were randomly allocated into three nutritional groups: control (CONT, n = 8), long (L-) QDN (n = 8) and short (S-) QDN (n = 9). The L-QDN cows were fed a supplement of urea from 10 days before insemination, and the S-QDN cows were fed the supplement from insemination until embryo collection. Both L- and S-QDN diets produced significant increases in plasma ammonia and urea 3 h post-feeding. The S-QDN but not the L-QDN diet was associated with a significant reduction in embryo yield. Embryo quality was also significantly reduced in the S-QDN cows. This study indicates that there is no deleterious effect on the yield and quality of embryos recovered 7 days after breeding when QDN feeding is initiated during the previous midluteal phase. However, introduction of a similar diet 10 days later, at the time of insemination, was deleterious. We suggest that QDN is toxic to embryos but cows can adjust within 10 days.

Macroamylasemia in patients with celiac disease

OBJECTIVE

Macroamylasemia is considered to be rarely associated with celiac disease (CD). We have evaluated patients in whom macroamylasemia or elevated total amylase (TA) led to the diagnosis of CD. These cases served as a catalyst for examining the prevalence of elevated TA and macroamylase (MA) in patients with active CD.

METHOD

Total amylase and MA measurements were performed in the sera of 124 celiac patients with positive antiendomysium and tissue transglutaminase tests, in 100 patients on gluten-free diet (GFD) with negative serology test results, and in the sera of 89 healthy controls. Macroamylasemia was measured by using the PEG precipitation method.

RESULTS

Twenty-three newly diagnosed celiac patients had elevated serum amylase levels (>2 SD above the controls). The average TA and MA levels were significantly elevated in both celiac groups. The nonprecipitated amylase levels (pancreatic and salivary amylase fractions) were not different from those of the controls. Three controls (3.4%), 21 newly diagnosed celiac (16.8%), and seven patients on GFD (7%) had significantly elevated MA activity in their sera.

CONCLUSIONS

A significant percentage of the newly diagnosed patients with CD have macroamylasemia. Serum MA remained elevated in some patients on strict GFD. In addition, in the presence of an elevated amylase or MA the possibility of CD should be considered.

[Macro-CK disclosing disseminated epidermoid carcinoma of the pyriform sinus in a patient with dermatomyositis]

INTRODUCTION

The association between dermatomyositis and cancer is clearly established, but its frequency remains difficult to define.

EXEGESIS

We report the case of an association between a dermatomyositis and a cancer of the piriform antrum. Four months after surgical treatment and radiotherapy, the increased macro-CK level gave us reason to suspect a cancer relapse with pulmonary, hepatic, splenic and renal metastases without progressive clinical signs.

CONCLUSION

Mitochondrial macro-CK detection must evoke the presence of neoplasia with or without metastasis, which would be a poor prognosis, as has been shown in our patient.

Prolonged Hyperlipasemia Attributable to a Novel Type of Macrolipase

Background: We present the case of an 80-year-old woman who was admitted to hospital with an intermittent volvulus of the right colon. A total colectomy was performed. Initially, serum amylase and lipase increased concordantly, but after a few weeks amylase normalized (85 U/L), whereas lipase increased to 3764 U/L. This discrepancy and persistence of hyperlipasemia suggested a macromolecular form of lipase.

Methods: The nature of the macromolecular complex was studied using high-pressure liquid gel-permeation chromatography, affinity chromatography, (immuno)electrophoresis, and immunodiffusion.

Results: Gel-permeation chromatography revealed a macrolipase, with a molecular mass &gt;900 kDa, that contributed up to 56% of total serum lipase activity. Butanol extraction of the specimen did not alter the elution profile. The thermostabilities of pancreatic lipase and the macroform were similar, whereas activation energy (Ea) was lower in the macromolecular lipase (28 ± 4 kJ · mol−1 · K−1 vs 48 ± 7 kJ · mol−1 · K−1 (P = 0.02). Agarose electrophoresis showed a broad band of lipase activity at the application site. Protein A-Sepharose affinity gel chromatography excluded IgG-linked lipase. Agarose electrophoresis and immunofixation excluded linkage to other immunoglobulins. Radial immunodiffusion did not show lipase activity in the immunoglobulin precipitation bands. Radial immunodiffusion with α2-macroglobulin (α2-MG) antibodies showed a diffuse spot of lipase activity within the precipitation band, suggesting a macromolecular association between lipase and α2-MG. Affinity gel chromatography against α2-MG showed lipase activity in the α2-MG-bound fractions.

Conclusion: This is the first report of a macrolipase in which an association between α2-MG and lipase is described.

Macroaspartasemia as a cause of isolated elevation of aspartate aminotransferase--its biochemical and physiological characteristics

OBJECTIVES

The increase of serum aspartate aminotransferase (AST) is generally found in hepatic, cardiac, muscular disease and hemolytic disorders of the red blood cell (RBC). The elevation of its activity is suspected in pathological conditions of these organs. However, instances without any of those conditions rarely exist.

METHODS

The experimental samples were obtained from a normal person's hemolysed RBC, a hepatitis patient and a macroaspartatemic female's serum. They were studied with exclusion chromatography, electrophoresis of AST and changes of AST activity due to Polyethylene Glycol (PEG) and various conditions on storage.

RESULTS

1) The patterns of AST activity by exclusion chromatography are similar to the hemolysed RBC and the hepatitis's serum but differs by the isolated AST elevation. 2) The AST activity with addition of PEG and different anti-immunoglobulin subtypes to different serums are slightly decreased in hepatitis but markedly decreased with PEG and anti-IgG in macroaspartatemia. 3) The patterns of AST activity in electrophoresis are single band-cytosomal AST (cAST)-from hemolysed RBC and two bands-mitochondrial AST (mAST) and cAST-from hepatitis, the major being cAST and the minor mAST. Even though there are two bands, the major one is atypical and the minor corresponds to mAST in macroaspartatemia. 4) The changes of AST activity on storage according to time and temperature show to be stable over 4 weeks at room temperature and cooled condition, and 9 weeks under frozen state in macroaspartatase.

CONCLUSION

Concluding from the above findings, macroaspartatemia is an enzyme-immunoglobulin complex composed of cAST with IgG. MacroAST might be stabler than usual AST at physical conditions.