Electrocardiographic response to enzyme replacement therapy for Pompe disease

PURPOSE

Electrocardiogram (ECG) abnormalities are universal in infantile Pompe disease or glycogen storage disease type II, a fatal genetic muscle disorder caused by deficiency of acid alpha-glucosidase (GAA). Hallmarks of this disease include a shortened PR interval, an increased QT dispersion (QTd), and large left ventricular (LV) voltages. We evaluated the effect of recombinant human GAA (rhGAA) enzyme replacement therapy (ERT) on these ECG parameters in patients with infantile-onset Pompe disease.

METHODS

A total of 134 ECGs were evaluated from 19 patients (5 females and 14 males) with a median age of 5.5 months at the time of enrollment in open-label clinical trials exploring the safety and efficacy of ERT at a single center from 1999 to 2004. rhGAA was purified from genetically engineered Chinese hamster ovary cells overproducing GAA and infused intravenously at doses ranging from 10 mg/kg per week to 20 to 40 mg/kg every 2 weeks in patients with infantile-onset Pompe disease. The PR interval, QTd (longest to shortest QT), and LV voltage (SV1 + RV6) were blindly determined by two independent observers.

RESULTS

The median follow-up period was 6 months (range 2-30 months). The PR interval lengthened from 83 (42-110) ms to 107 (95-130) ms (P < .001), and the QTd decreased from 83 (40-125) ms to 53 (20-80) ms (P = .003). There were significant decreases in LV voltage (67 [17-83] mV vs. 48 [18-77] mV, P = .03), which correlated with decrease in LV mass on two-dimensional echocardiogram. There was no evident change in the QTc interval (429 [390-480] ms vs. 413 [370-450] ms, P = not significant).

CONCLUSION

rhGAA ERT for infantile Pompe disease results in an increase in PR interval and a decrease in both the QTd and the LV voltage. These results suggest that these ECG parameters may be useful markers of the severity of cardiac disease and the response to ERT treatment in patients with infantile Pompe disease.

Evasion of immune responses to introduced human acid alpha-glucosidase by liver-restricted expression in glycogen storage disease type II

Glycogen storage disease type II (GSD-II; Pompe disease) is caused by a deficiency of acid alpha-glucosidase (GAA; acid maltase) and manifests as muscle weakness, hypertrophic cardiomyopathy, and respiratory failure. Adeno-associated virus vectors containing either a liver-specific promoter (LSP) (AAV-LSPhGAApA) or a hybrid CB promoter (AAV-CBhGAApA) to drive human GAA expression were pseudotyped as AAV8 and administered to immunocompetent GAA-knockout mice. Secreted hGAA was detectable in plasma between 1 day and 12 weeks postadministration with AAV-LSPhGAApA and only from 1 to 8 days postadministration for AAV-CBGAApA. No anti-GAA antibodies were detected in response to AAV-LSPhGAApA (<1:200), whereas AAV-CBhGAApA provoked an escalating antibody response starting 2 weeks postadministration. The LSP drove approximately 60-fold higher GAA expression than the CB promoter in the liver by 12 weeks following vector administration. Furthermore, the detected cellular immunity was provoked by AAV-CBhGAApA, as detected by ELISpot and CD4+/CD8+ lymphocyte immunodetection. GAA activity was increased to higher than normal and glycogen content was reduced to essentially normal levels in the heart and skeletal muscle following administration of AAV-LSPhGAApA. Therefore, liver-restricted GAA expression with an AAV vector evaded immunity and enhanced efficacy in GSD-II mice.

Amylopectinosis disease isolated to the heart with normal glycogen branching enzyme activity and gene sequence

We report a 17-month-old female patient with a rare cause of cardiomyopathy secondary to accumulation of amylopectin-like material (fibrillar glycogen) isolated to the heart. Evidence of amylopectinosis isolated to cardiac myocytes in this patient was demonstrated by histology and electron microscopy. Glycogen content, glycogen branching enzyme (GBE) activity, as well as phosphofructokinase enzyme activities measured in liver, skeletal muscle, fibroblasts and ex-transplanted heart tissue were all in the normal to lower normal ranges. Normal skeletal muscle and liver tissue histology and GBE activity, normal GBE activity in skin fibroblasts, plus normal GBE gene sequence in this patient exclude the classical branching enzyme deficiency (type IV GSD). We believe that this is an as yet uncharacterized and novel phenotype of GSD associated with cardiomyopathy, in which there is an imbalance in the regulation of glycogen metabolism limited to the heart.

Improved efficacy of gene therapy approaches for Pompe disease using a new, immune-deficient GSD-II mouse model

Glycogen storage disease type II (GSD-II) is a lysosomal storage disorder in which the lack of human acid-alpha glucosidase (hGAA) activity results in massive accumulations of glycogen in cardiac and skeletal muscle fibers. Affected individuals die of cardiorespiratory failure secondary to the skeletal and/or cardiac muscle involvement. Recombinant hGAA enzyme replacement therapy (ERT) is currently in clinical trials and, although promising, ERT may be limited by large-scale production issues and/or the need for frequent infusions. These limitations could be circumvented or augmented by gene therapy strategies. Previous findings in our lab demonstrated that hepatic targeting of a modified adenovirus vector expressing human GAA was able to correct the glycogen accumulation in multiple affected muscles in the GAA-KO mice, by virtue of high-level, hepatic secretion of hGAA. However, although the vector persisted and expressed hGAA for 6 months in the liver, plasma hGAA was not detectable beyond 10 dpi (days postinjection), and reaccumulation of glycogen was observed. Two possibilities may have contributed to this phenomenon, the shut down of the CMV promoter and/or the onset of high levels of anti-hGAA antibodies. In order to test these and other possibilities, we have now developed an immune-deficient mouse model of GSD-II by interbreeding GAA-KO mice with severe combined immune-deficient (SCID) mice, generating double knockout, GAA-KO/SCID mice. In this new mouse model, we evaluated the efficacy of an [E1-, polymerase-] AdhGAA vector, in the absence of anti-hGAA antibody responses. After intravenous injection, GAA detection in the plasma was prolonged for at least 6 months secondary to the lack of anti-hGAA antibody production in all of the treated mice. GAA-KO/SCID mice treated with high doses of viral vector demonstrated longer durations of glycogen correction in both skeletal and cardiac muscles, relative to mice injected with lower doses of the vector. Notably, within 2 weeks of vector injection, muscle strength and coordination was normalized, and the improved muscle function persisted for at least 6 months. In summary, this new mouse model of GSD-II now makes it possible to assess the full potential for efficacy of any GAA-expressing vector (and/or ERT) contemplated for use in GSD-II gene therapy, without the negative influence that anti-hGAA antibodies entail.

Association between urokinase-plasminogen activator gene T4065C polymorphism and risk of mitral valve prolapse

BACKGROUND

Abnormalities of collagen and elastic fibers were found in floppy mitral valves (FMV). Urokinase-plasminogen activator (PLAU) was suggested to be involved in the pathogenesis of elastin and collagen degradation in arterial aneurysm. The role of PLAU genetic variant in mitral valve prolapse (MVP) has not been studied. We, therefore, performed a case-controlled study investigating the possible relation between the PLAU gene polymorphisms and risk of MVP in Taiwan Chinese.

METHODS

We studied 100 patients with MVP diagnosed by echocardiography and 106 age- and sex-matched normal control subjects. The T4065C and T3995C polymorphisms of the PLAU gene were identified by polymerase chain reaction (PCR)-based restriction analysis.

RESULTS

There was a significant difference in either the genotype distribution or allelic frequencies between MVP cases and controls for PLAU gene T4065C polymorphism (P = 0.0001 and 0.0002, respectively). An odds ratio for risk of MVP associated with PLAU T4065C TC genotype was 6.03 (95% confidence interval 2.11-14.83). An odds ratio for risk of MVP associated with PLAU T4065C T allele was 4.99 (95% confidence interval 1.93-12.91). There was no significant difference in either the genotype distribution or allelic frequencies between MVP cases and controls for PLAU T3995C polymorphism. Further categorization of the MVP patients into mild and severe subgroups revealed no statistical difference between these two subgroups for PLAU T4065C and T3995C polymorphisms.

CONCLUSIONS

This study shows that patients with MVP have a higher frequency of PLAU T4065C TC genotype and T allele that supports a role of the PLAU T4065C polymorphism in determining the risk of MVP among the Chinese population in Taiwan.

Hypertension and impaired glycine handling in mice lacking the orphan transporter XT2

A family of orphan transporters has been discovered that are structurally related to the Na(+)-Cl(-)-dependent neurotransmitter transporters, including the dopamine transporter. One member of this family, the mouse XT2 gene, is predominantly expressed in the kidney and has 95% homology to rat ROSIT (renal osmotic stress-induced Na(+)-Cl(-) organic solute cotransporter). To study the physiological functions of this transporter, we generated XT2-knockout mice by gene targeting. XT2(-/-) mice develop and survive normally with no apparent abnormalities. To attempt to identify potential substrates for XT2, we screened urine from XT2-knockout mice by high-pressure liquid chromatography and mass spectrometry and found significantly elevated concentrations of glycine. To study glycine handling, XT2(+/+) and XT2(-/-) mice were injected with radiolabeled glycine, and urine samples were collected to monitor glycine excretion. After 2 h, XT2(-/-) mice were found to excrete almost twice as much glycine as the XT2(+/+) controls (P = 0.03). To determine whether the absence of the XT2 transporter affected sodium and fluid homeostasis, we measured systolic blood pressure by computerized tail-cuff manometry. Systolic blood pressure was significantly higher in XT2(-/-) mice (127 +/- 3 mmHg) than in wild-type controls (114 +/- 2 mmHg; P < 0.001). This difference in systolic blood pressure was maintained on high and low salt feeding. To examine whether the alteration in blood pressure and the defect in glycine handling were related, we measured systolic blood pressure in the XT2(-/-) mice during dietary glycine supplementation. Glycine loading caused systolic blood pressure to fall in the XT2(-/-) mice from 127 +/- 3 to 115 +/- 3 mmHg (P < 0.001), a level virtually identical to that of the wild-type controls. These data suggest that the XT2 orphan transporter is involved in glycine reabsorption and that the absence of this transporter is sufficient to cause hypertension.

Association between COL3A1 collagen gene exon 31 polymorphism and risk of floppy mitral valve/mitral valve prolapse

BACKGROUND

Collagen structure is a key element in mitral valves. Collagen defects were proposed as the primary events causing floppy mitral valves (FMV). The role of collagen genetic variant in floppy mitral valve/mitral valve prolapse (FMV/MVP) has not been well studied. The purpose of this study is to investigate the possible relationship between the collagen gene polymorphisms and risk of FMV/MVP among the Chinese population in Taiwan.

METHODS

We studied 100 patients with FMV/MVP diagnosed by echocardiography and 243 age- and sex-matched normal control subjects. The polymorphisms of exon 31 and exon 52 of the collagen type III-alpha1 gene (COL3A1) were identified by polymerase chain reaction (PCR)-based restriction analysis.

RESULTS

There was a significant difference in either the genotype distribution (P<0.0001) or allelic frequencies (P<0.0001) between FMV/MVP cases and controls for COL3A1 exon 31 polymorphism. An odds ratio for risk of FMV/MVP associated with COL3A1 exon 31 GG genotype was 7.42 (95% confidence interval 4.40-12.52). An odds ratio for risk of FMV/MVP associated with COL3A1 exon 31 G allele was 2.28 (95% confidence interval 1.57-3.29). There was no significant difference in the distribution of COL3A1 exon 52 genotypes (P=0.31) and allelic frequencies (P=0.32) between FMV/MVP cases and controls. Further categorization of the FMV/MVP patients into mild and severe subgroups revealed no statistical difference from the controls for exon 31 or exon 52 polymorphism.

CONCLUSIONS

This study shows that patients with FMV/MVP have higher frequency of COL3A1 exon 31 GG genotype that supports a role of the COL3A1 exon 31 polymorphism in determining the risk of FMV/MVP among the Chinese population in Taiwan.

Lack of association between perlecan gene intron 6 BamHI polymorphism and risk of mitral valve prolapse in Taiwan Chinese

Abnormalities of proteoglycan, collagen, and elastic fibers were found in floppy mitral valves. Perlecan is one of the three major classes of heparan sulfate proteoglycans within the cardiovascular system. The role of perlecan genetic variant in mitral valve prolapse (MVP) has not been studied. We therefore performed a case-controlled study investigating the possible relation between the perlecan gene intron 6 BamHI polymorphism and MVP among the Chinese population in Taiwan. We studied 100 patients with MVP diagnosed by echocardiography and 100 age- and sex-matched normal control subjects. The perlecan gene intron 6 BamHI polymorphism was identified by polymerase chain reaction-based restriction analysis. There were no significant differences in either the genotype distribution or allelic frequencies between MVP cases and controls for perlecan gene intron 6 BamHI polymorphism (P = 0.20 and 0.76, respectively). Further categorization of the MVP patients into mild and severe subgroups also revealed no statistical difference from controls for perlecan gene intron 6 BamHI polymorphism. It is concluded that perlecan gene intron 6 BamHI polymorphism is not a suitable genetic marker of MVP in Taiwan Chinese.

[Isoelectric focusing analysis of Echinococcus multilocularis protoscolex antigens]

OBJECTIVE

To understand the components of the crude antigens of Echinococcus multilocularis protoscoleces.

METHODS

Isoelectric focusing was carried out to fractionate the protein components of E. multilocularis protoscoleces. The individual fractions were collected and subjected to SDS-PAGE, the gels were analyzed by a gel analysis system.

RESULTS

The pI values of individual fractions varied from 4.0 to 8.5, while the molecule weights of main protein bands were 72/73, 62/63, 42/44, 35/36, 34 and 21/22 kDa.

CONCLUSION

An alternative separation method of crude antigens of Echinococcus multilocularis was established.

Arsenic trioxide in comparison with chemotherapy and bone marrow transplantation for the treatment of relapsed acute promyelocytic leukaemia

BACKGROUND

The best overall treatment strategy for patients with acute promyelocytic leukaemia (APL) in relapse with chemotherapy, bone marrow transplantation (BMT) or arsenic trioxide (As(2)O(3)) based therapy remains undefined.

PATIENTS AND METHODS

We reviewed the clinical course and treatment outcome of 143 APL cases seen in four major hospitals in Hong Kong over a 10-year period.

RESULTS

Complete remission (CR) was attained in 113 cases (79%) with all-trans retinoic acid (ATRA) and chemotherapy. Relapse occurred at a median of 16 months in 54 cases, with a 3-year disease free survival of 56%. Post-relapse treatment was successful in 41 cases (76%), giving an actuarial 3-year overall survival (OS) of 81% from CR1. Three different protocols were used: chemotherapy alone (n = 19), allogeneic BMT (n = 14) and an As(2)O(3)-based regimen (n = 21). Chemotherapy was associated with the highest treatment-related mortality (TRM) at 53%, giving a CR2 rate of 47%. TRM was 36% for BMT. The CR2 rate for the As(2)O(3)-based regimen was 100%, with no TRM. However, 38% of As(2)O(3) treated patients had subsequent relapses, which were further salvaged in 75% by combined As(2)O(3) plus ATRA. The actuarial OS for the three protocols leveled off by 2 years at 82% for As(2)O(3), 43% for BMT and 23% for chemotherapy (P = 0.0004).

CONCLUSIONS

Our results suggest that As(2)O(3) may be superior to chemotherapy and BMT for the treatment of APL in relapse.

Multiple muscles in the AMD quail can be "cross-corrected" of pathologic glycogen accumulation after intravenous injection of an [E1-, polymerase-] adenovirus vector encoding human acid-alpha-glucosidase

BACKGROUND

Previously, in murine models of acid maltase deficiency (AMD), we demonstrated that intravenous administration of an improved adenovirus (Ad) vector encoding human acid alpha glucosidase (hGAA) resulted in liver transduction, followed by high-level hepatocyte-mediated secretion of hGAA into the plasma space. The hGAA secreted by the liver was taken up and targeted to muscle cell lysosomes. The levels of hGAA achieved by this approach resulted in clearance of lysosomal glycogen accumulations; in some muscle tissues the effect was prolonged (>6 months). We next wished to demonstrate whether this approach could be generalized across divergent species. To accomplish this goal, we determined whether a similar approach would also result in efficacy, but in a quail model of AMD.

METHODS

An [E1-, E2b-]Ad vector encoding hGAA was intravenously injected into AMD quails. At several time points thereafter, plasma, liver, and multiple muscle tissues were assayed for evidence of hGAA gene expression, liver-mediated hGAA secretion, uptake of hGAA by skeletal muscles, and evidence of glycogen correction in AMD skeletal muscles. These results were compared with those obtained from mock-injected AMD or wild-type quails.

RESULTS

Intravenous [E1-, E2b-]Ad/hGAA vector injection resulted in high-level liver transduction and hepatic secretion of precursor forms of hGAA. The hepatically secreted hGAA was found to not only be efficiently taken up by cardiac and skeletal muscles, but was also proteolytically cleaved and processed equivalently to the quail-GAA protein detected in wild-type quails. The observations suggest that the signals regulating muscle cell uptake (but not proteolytic cleavage) of lysosomal enzymes are conserved and recognized across divergent species of vertebrates. Importantly, once localized to skeletal muscle lysosomes, the hGAA was able to effectively clear the glycogen accumulations present in AMD quail muscles.

CONCLUSIONS

Adenovirus-mediated transduction of the hGAA gene, followed by hepatic secretion, uptake, and cross-correction of the pathologic glycogen accumulation noted in multiple muscles of both the AMD mouse and AMD quail, adds support to the notion that gene transfer strategies (Ad-mediated or other agents) targeting liver tissues with the hGAA gene are likely to be highly efficacious in humans affected by AMD.

Consolidation therapy with autologous blood stem cell transplantation in a patient with primary plasma cell leukaemia

Primary plasma cell leukaemia (PPCL) is a rare form of plasma cell dyscrasia. Conventional melphalan-based treatment is often ineffective, with a reported median survival of 2-7 months only. We report a 53-year-old man with PPCL who was treated with four cycles of combination chemotherapy including vincristine, adriamycin and dexamethasone that resulted in a good partial remission. High-dose melphalan 200 mg/m2 and autologous peripheral blood stem cell (PBSC) rescue was then given 6 months after diagnosis. Maintenance interferon-alpha was started 8 weeks after transplantation with good drug compliance. Complete remission was achieved and molecular remission was documented 11 months after autologous PBSC transplantation. In conclusion, high-dose therapy followed by autologous stem cell rescue is a feasible option for PPCL that can result in a reasonably sustained remission.

Association between angiotensin I-converting enzyme gene insertion/deletion polymorphism and mitral valve prolapse syndrome

BACKGROUND

Some studies have reported that patients with mitral valve prolapse syndrome (MVPS) also have a disorder in the autonomic or neuroendocrine function, which can cause a host of related symptoms. A potential role of the renin-angiotensin system in the pathogenesis of MVPS has been addressed. However, the role of angiotensin I-converting enzyme (ACE) genetic variant in MVPS has not been studied. We therefore performed a case-control study investigating the possible relation between ACE gene polymorphisms and MVPS in Taiwan Chinese.

METHODS

We studied 100 patients with MVPS diagnosed by echocardiography and 100 age- and sex-matched normal control patients. ACE gene insertion/deletion (I/D), A-240T, and G2350A polymorphisms were identified by polymerase chain reaction-based restriction analysis.

RESULTS

There was a significant difference in the distribution of ACE I/D genotypes (P =.003) and allelic frequencies (P =.001) between MVPS cases and control patients. An odds ratio for the risk of MVPS associated with the ACE II genotype was 2.14 (95% CI 1.20-3.80 ). An odds ratio for the risk of MVPS associated with ACE I allele was 1.96 (95% CI 1.30-2.97). The A-240T and G2350A polymorphisms of the ACE gene showed no association with MVPS (P =.20, P =.13, respectively).

CONCLUSIONS

This study showed that patients with MVPS have a higher frequency of ACE II genotype, which supports a role of the ACE I/D gene polymorphism in determining the risk of MVPS among the Chinese population in Taiwan.

Association between angiotensinogen gene M235T polymorphism and mitral valve prolapse syndrome in Taiwan Chinese

BACKGROUND AND AIM OF THE STUDY

It has been reported that patients with mitral valve prolapse syndrome (MVPS) also have a disorder in autonomic or neuroendocrine function which can cause many related symptoms. Although a potential role of the reninangiotensin system in the pathogenesis of MVPS has been addressed, the role of the angiotensinogen (AGT) genetic variant in MVPS has not been studied. Thus, a case-controlled study was performed to investigate the possible relationship between AGT gene polymorphisms and MVPS.

METHODS

A total of 100 patients with MVP diagnosed by echocardiography and 100 age- and sex-matched normal control subjects was studied. AGT gene M235T and T174M polymorphisms were identified by polymerase chain reaction-based restriction analysis.

RESULTS

There was a significant difference in the distribution of AGT gene M235T genotypes (p <0.001) and allelic frequencies (p <0.001) between MVPS cases and controls. An Odds Ratio (OR) for risk of MVPS associated with M235T TT genotype was 8.55 (95% CI 4.51-16.18). An OR for risk of MVPS associated with the T allele at the M235T locus of the AGT gene was 3.27 (95% CI 2.05-5.22). The T174M polymorphism of AGT gene showed no association with MVPS (p = 0.94).

CONCLUSION

These findings suggest that the M235T polymorphism of the AGT gene is associated with MVPS in the Chinese population of Taiwan. The association of the TT genotype with MVPS is more noteworthy than an overall increase in the frequency of the T allele at the M235T locus.

Investigation of Notch3 as a candidate gene for bipolar disorder using brain hyperintensities as an endophenotype

The purpose of the study was to consider MRI hyperintensities as a potential endophenotype for bipolar disorder (BPD) and to investigate Notch3 (CADASIL) as a candidate gene for BPD. MRI scans were performed on 21 members of a family with a high incidence of BPD. Two-point and multipoint linkage analyses were performed and two exons of Notch3 were investigated with SSCP. Fifteen of 21 family members had MRI hyperintensities, including all bipolar patients and six family members with no affective illness. Two-point linkage analysis yielded negative results for all models. Multipoint linkage analysis yielded negative results except for Model 1a, in which a maximal LOD score was -1.24. A mutation screen of Exons 3 and 4 was negative. Notch3 does not appear to be a candidate gene for BPD in this family.

Delivery of glucose-6-phosphatase in a canine model for glycogen storage disease, type Ia, with adeno-associated virus (AAV) vectors

Therapy in glycogen storage disease type Ia (GSD Ia), an inherited disorder of carbohydrate metabolism, relies on nutritional support that postpones but fails to prevent long-term complications of GSD Ia. In the canine model for GSD Ia, we evaluated the potential of intravenously delivered adeno-associated virus (AAV) vectors for gene therapy. In three affected canines, liver glycogen was reduced following hepatic expression of canine glucose-6-phosphatase (G6Pase). Two months after AAV vector administration, one affected dog had normalization of fasting glucose, cholesterol, triglycerides, and lactic acid. Concatamerized AAV vector DNA was confirmed by Southern blot analysis of liver DNA isolated from treated dogs, as head-to-tail, head-to-head, and tail-to-tail concatamers. Six weeks after vector administration, the level of vector DNA signal in each dog varied from one to five copies per cell, consistent with variation in the efficiency of transduction within the liver. AAV vector administration in the canine model for GSD Ia resulted in sustained G6Pase expression and improvement in liver histology and in biochemical parameters.

Thyroid diseases in pregnancy

INTRODUCTION

Changes in thyroid function in pregnancy encompass both hyper- and hypothyroidism. Failure to maintain euthyroidism may place both mother and foetus at higher risk of adverse obstetrical outcomes. This review examines the differences between physiological and pathological thyroid dysfunction during pregnancy and their management.

METHODS

Data were obtained from relevant clinical studies and review articles listed in MEDLINE. Additional cross-references from selected articles were identified.

RESULTS

In hyperthyroidism, the challenge lies in differentiating gestational transient thyrotoxicosis (GTT) from actual pathological states during the first trimester. GTT is thought to be due to elevation of isoforms of human chorionic gonadotropin (hCG) which may exert potent thyrotrophic effects. While thionamides are safe, the lowest possible dose should be used together with close monitoring of maternal thyroid function in order to avoid over-treatment. Surgery for thyroid nodules may be safely performed during the second trimester. Conversely, diagnosing hypothyroid states, particularly subclinical hypothyroidism and postpartum thyroiditis (PPT), require a high index of suspicion. High levels of thyroid peroxidase antibodies (TPOAb) and thyroid stimulating hormone (TSH) in early pregnancy may be predictive of PPT and subsequent permanent hypothyroidism. Clinicians must recognise the need to increase thyroxine replacement as maternal hypothyroidism may adversely affect the IQ scores of children. The association between thyroid autoimmunity and recurrent abortions remain unclear.

CONCLUSION

Regardless of the aetiology of thyroid dysfunction, the key to management lies in individualized therapy in close collaboration with the obstetrician.

Nomenclature of the GLUT/SLC2A family of sugar/polyol transport facilitators

The recent identification of several additional members of the family of sugar transport facilitators (gene symbol SLC2A, protein symbol GLUT) has created a heterogeneous and, in part, confusing nomenclature. Therefore, this letter provides a summary of the family members and suggests a systematic nomenclature for SLC2A and GLUT symbols.

Molecular characterization of glycogen storage disease type III

Deficiency of the glycogen debranching enzyme (gene, AGL) causes glycogen storage disease type III (GSD-III), an autosomal recessive disease affecting glycogen metabolism. Most GSD-III patients have AGL deficiency in both the liver and muscle (type IIIa), but some have it in the liver but not muscle (type IIIb). Cloning of human AGL cDNAs and determination of the genomic structure and mRNA isoforms of AGL have allowed for the study of GSD-III at the molecular level. In turn, the resulting information has greatly facilitated our understanding of the molecular basis of this storage disease with remarkable clinical and enzymatic variability. In this review, we summarize all 31 GSD-III mutations in the literature and discuss their clinical and laboratory implications. Most of the mutations are nonsense mutations caused by a nucleotide substitution or small insertion or deletion; only one is caused by a missense amino acid change. Some important genotype-phenotype correlation have emerged, in particular, that exon 3 mutations (17delAG and Q6X) are specifically associated with GSD-IIIb. Three other mutations have appeared to have some phenotype correlation. Specifically, the splice mutation IVS32-12A>G was found in GSD-III patients having mild clinical symptoms, while the mutations 3965delT and 4529insA are associated with a severe phenotype and early onset of clinical manifestations. A molecular diagnostic scheme has been proposed to diagnose GSD-III noninvasively. The characterization of AGL mutations in GSD-III patients has also helped the structure-function analysis of this bifunctional enzyme important for glycogen metabolism.

Comparing fasting plasma glucose against two-hour post-load glucose concentrations for the diagnosis of diabetes mellitus and glucose intolerance in Singaporean hospital patients

INTRODUCTION

Several studies have assessed the impact of the 1997 American Diabetes Association (ADA) recommendation, of using fasting plasma glucose (FPG) concentration, to diagnose diabetes mellitus in population-based cohorts. However, data concerning the impact of this recommendation in the hospital setting are limited. As the performance characteristics of diagnostic tests vary depending on the prevalence of diabetes in the population studied, we have examined the clinical impact of adopting the ADA recommendations in comparison to the traditional 2-hour post-load glucose (2HPG) concentration used by the World Health Organisation (WHO) in diagnosing diabetes and other categories of glucose intolerance in Singaporean hospital patients.

MATERIALS AND METHODS

We analysed the results of the standard 75 g oral glucose tolerance test (OGTT) performed on 625 patients in our hospital from 1994 to 1999.

RESULTS

The prevalence of diabetes amongst these 625 patients was 36.8% (230) based on the ADA recommendation of using FPG, 42.8% (263) on using the 2HPG and 52.0% (325) on using the full 1998 WHO criteria. The degree of agreement (kappa) in establishing the diagnosis of diabetes between the FPG and 2HPG cut-offs was 0.48. Ninety-five (15.2%) individuals had diabetes based on the 2HPG alone, 62 (9.9%) based on the FPG alone and 168 (26.9%) based on both the FPG and 2HPG. Eighty-six (13.8%) individuals had impaired fasting glucose (IFG) and 123 (19.7%) had impaired glucose tolerance (IGT). The kappa-value between IFG and IGT was 0.08.

CONCLUSION

Fasting plasma glucose concentration was an inadequate parameter in diagnosing diabetes and intermediate categories of glucose intolerance in our cohort of subjects. Our findings suggest that the OGTT remains an important diagnostic tool for classifying glucose tolerance in our hospital patients.

Reoperative Snodgrass procedure

PURPOSE

We examine the results of a reoperative Snodgrass procedure for complex hypospadias.

MATERIALS AND METHODS

A total of 25 patients with hypospadias in whom repair had failed underwent a reoperative Snodgrass procedure. Mean patient age and number of prior repairs were 11.4 years and 2.5, respectively. Before this treatment the meatus was at the distal shaft in 10 cases, mid shaft in 9, proximal shaft in 4 and penoscrotal junction in 2. Preoperatively the associated complications were fistulas in 13 patients, residual chordee in 12 and diverticulum in 1. In 8 cases the fistula was incorporated into the hypospadiac opening and treated as a longer defect. The urethral plates were, subjectively, surgically altered or unaltered in 7 and 18 patients, respectively. In 8 patients (group A) the previous repair(s) did not involve dissection of the urethral plate (unaltered) nor was there a fistula. The remaining 17 patients were classified as group B. The neourethra was then reconstructed as the Snodgrass technique. Followup urethral calibration was performed in 17 patients.

RESULTS

Mean followup period was 13.7 months. Mean length and size of neourethra were 19.9 mm. and 14Fr, respectively. There were 7 (28%) postoperative fistulas of the neourethra. The incidences of postoperative fistula of the neourethra were 0% and 41.2% in groups A and B, respectively (p <0.01). Statistically the surgically altered urethral plate and the presence of a preoperative fistula were 2 independent factors predicting a higher postoperative fistula rate. The overall postoperative meatal stenosis rate was 13 (52%) with 3 (37.5%) in group A and 10 (58.8%) in group B, respectively (p >0.05). The meatal stenosis was treated with simple dilation in 11 cases and meatoplasty during subsequent fistula repair in 2. Stricture at the anastomostic site between the normal urethra and neourethra was noted in 2 patients. Fistula repair was successfully performed 6 months later in 4 patients.

CONCLUSIONS

The Snodgrass procedure is a viable option for the treatment of previously failed hypospadias repair. It was highly effective in patients with a surgically unaltered urethral plate and no preoperative fistula.

Tumor necrosis factor alpha -238 and -308 polymorphisms do not associate with insulin resistance in hypertensive subjects

It is well established that, as a group, patients with essential hypertension are characterized by insulin resistance. Previous studies have shown that a biallelic polymorphism in the tumor necrosis factor (TNF)alpha promoter position -308 and -238 might be involved in the insulin resistance state in diabetic and/or nondiabetic subjects. We determined these polymorphisms in 235 nondiabetic hypertensive subjects and 246 unrelated normotensive controls. Fasting plasma glucose, insulin, lipoprotein, leptin, and TNFalpha concentrations were measured, in addition to plasma glucose and insulin responses to a 75-g oral glucose tolerance test (OGTT). Insulin sensitivity was also determined by an insulin suppression test in 69 hypertensive and 76 normotensive individuals. The results showed no association of these genotypic distributions between hypertensive and normotensive individuals both at -308 (GG, GA, and AA were 80.9%, 17.9%, and 1.3% in hypertensives, 84.2%, 15.4%, and 0.4% in normotensives, chi(2) = 1.68, P =.432) and at -238 (GG, GA, and AA were 98.3%, 1.7%, and 0% in hypertensives, 96.7%, 3.3%, and 0% in normotensives, chi(2) = 1.19, P =.276) sites. These results did not change even after adjustment for values of age and body mass index (BMI). Anthropometric measurements, fasting plasma glucose, insulin, lipoprotein concentrations, glucose, and insulin responses to OGTT, TNFalpha, and leptin concentrations were similar between the genotype at the -308 site both in hypertensive and normotensive groups. Insulin sensitivity, either measured by an insulin suppression test or homeostasis model assessment (HOMA) index, did not differ between the genotype at the -308 site in subjects with hypertension or normotension. Fasting plasma TNFalpha (10.2 alpha 0.5 pg/mL v 10.1 +/- 0.5 pg/mL, P =.928) concentrations did not differ between hypertensive and normotensive subjects even after adjustment for body fat and BMI values. We conclude that TNFalpha promoter gene polymorphisms at position -238 and -308 do not play a major role in the pathogenesis of insulin resistance in Chinese subjects with or without hypertension.