Biomedical subjects
C A Stanley
Publications and source records attributed to C A Stanley.
First prenatal diagnosis of the carnitine transporter defect.
We report the first attempt at prenatal diagnosis of the carnitine transporter defect in a fetus at high risk of having the disorder. Analysis of cultured CVS after prolonged culture predicted that the fetus was not affected but might be heterozygous for the carnitine transporter defect, but chromosome 15 satellite DNA markers showed no paternal contribution, suggesting that the CVS cells assayed were of predominantly maternal origin. Subsequent assay of cultured amniocytes predicted that the fetus would be affected, and this was confirmed in the newborn period. We conclude that prenatal diagnosis of the carnitine transporter defect is possible, but where results depend on extended culture of CVS, molecular studies should be performed to confirm genetic contributions from both parents.
Endocardial fibroelastosis and primary carnitine deficiency due to a defect in the plasma membrane carnitine transporter.
Endocardial fibroelastosis (EFE) has previously been shown to be associated with tissue carnitine deficiency, although the basis for the carnitine deficiency has not been documented. A patient with the classical features of EFE and marked deficiency of carnitine in heart muscle, skeletal muscle, and liver is presented in this report. Cultured skin fibroblasts from both parents demonstrated levels of carnitine uptake at 50% of the normal rate. This is consistent with heterozygosity for the plasma membrane carnitine transporter defect, indicating likely homozygosity for this recently recognized inborn error in the index patient.
Mutations in the sulonylurea receptor gene are associated with familial hyperinsulinism in Ashkenazi Jews.
Familial hyperinsulinism (HI) is a disorder of pancreatic beta-cell function characterized by persistent hyperinsulinism despite severe hypoglycemia. To define the molecular genetic basis of HI in Ashkenazi Jews, 25 probands were screened for mutations in the sulfonylurea receptor (SUR1) gene by single-strand conformation polymorphism (SSCP) analysis of genomic DNA and subsequent nucleotide sequence analyses. Two common mutations were identified: (I) a novel in-frame deletion of three nucleotides (nt) in exon 34, resulting in deletion of the codon for F1388 (delta F1388) and (II) a previously described g-->a transition at position-9 of the 3' splice site of intron 32 (designated 3992-9g-->a). Together, these mutations are associated with 88% of the HI chromosomes of the patients studied. 86Rb+ efflux measurements of COSm6 cells co-expressing Kir6.2 and either wild-type or delta F1388 SUR1 revealed that the F1388 mutation abolished ATP-sensitive potassium channel (KATP) activity in intact cells. Extended haplotype analyses indicated that the delta F1388 mutation was associated with a single specific haplotype whereas the 3992-9g-->a mutation was primarily associated with a single haplotype but also occurred in the context of several other different haplotypes. These data suggest that HI in Ashkenazi Jews is predominantly associated with mutations in the SUR1 gene and provide evidence for the existence of at least two founder HI chromosomes in this population.
Acute fatty liver of pregnancy, hemolysis, elevated liver enzymes, and low platelets syndrome, and long chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency.
BACKGROUND: The similarity of the hepatic pathology in acute fatty liver of pregnancy (AFLP) to that seen in children with inherited disorders of intramitochondrial fatty acid oxidation (FAO) suggests that there may be a genetic basis for some cases of AFLP. OBJECTIVE: The purpose of this study was to examine patients with AFLP and their offspring to determine if there were women with AFLP who were heterozygous for the FAO defect, long chain 3-hydroxyacyl CoA dehydrogenase (LCHAD) deficiency. METHODS: We evaluated 12 women previously diagnosed with AFLP. Provocative fasting studies and skin biopsies for examination of their cultured skin fibroblasts were performed to search for a generalized defect in FAO both in vivo and in vitro. Cultured skin fibroblasts from AFLP patients, their children, and their husbands were also examined specifically for LCHAD activity. RESULTS: Of 12 women with a previous episode of AFLP, eight had reduced LCHAD activity consistent with being heterozygous for LCHAD deficiency. The eight heterozygotes had a total of nine pregnancies complicated by AFLP. In seven of those nine pregnancies, the women developed severe preeclampsia and hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome. Of the nine offspring delivered from these pregnancies, four were confirmed to be affected with homozygous LCHAD deficiency. Three other deceased infants were presumed to be LCHAD-deficient based on clinical findings, postmortem examination, and confirmed heterozygote parents. The remaining two infants delivered after pregnancies complicated by AFLP had LCHAD activity in the heterozygous range and are healthy at 18 and 24 months of age. Consistent with the known autosomal recessive nature of this defect, five tested husbands of LCHAD heterozygous women with a history of AFLP and affected infants also showed reduced LCHAD activity. CONCLUSIONS: These studies indicate that a significant subgroup of women with AFLP are heterozygous for LCHAD deficiency and that careful observation of their offspring for signs of this disorder is warranted. Severe preeclampsia appears to increase the risk of AFLP in LCHAD heterozygous women.
Glycine and L-carnitine therapy in 3-methylcrotonyl-CoA carboxylase deficiency.
Genetic deficiency of 3-methylcrotonyl-CoA carboxylase (3-MCC) is a rare inborn error of leucine metabolism producing an organic acidaemia. With accumulation of 3-methylcrotonyl-CoA, there is increased production of 3-hydroxyisovaleric acid, the glycine conjugate (3-methylcrotonylglycine), and the carnitine conjugate (3-hydroxyisovalerylcarnitine). The conjugates represent endogenous detoxification products. We studied excretion rates of these conjugates at baseline and with glycine and carnitine therapy in an 8-year-old girl with 3-MCC deficiency. Her preadmission diet was continued. Plasma and urine samples were obtained after 24 h of each of the following: L-carnitine 100 mg/kg per day and glycine 100, 175 and 250 mg/kg per day. Plasma and urinary carnitine levels were reduced by 80% and 50%, respectively with abnormal urinary excretion patterns. These normalized with carnitine therapy. Acylcarnitine excretion increased with carnitine therapy. The glycine conjugate, 3-methylcrotonylglycine (3-MCG), was the major metabolite excreted at all times and its excretion increased with glycine therapy. Clearly, in 3-MCC deficiency the available glycine and carnitine pools are not sufficient to meet the potential for conjugation of accumulated metabolites, suggesting a possible therapeutic role for glycine and carnitine therapy in this disorder.
Recombinant mapping of the familial hyperinsulinism gene to an 0.8 cM region on chromosome 11p15.1 and demonstration of a founder effect in Ashkenazi Jews.
A gene for autosomal recessive familial hyperinsulinism (HI) (OMIM: 256450), a neonatal metabolic disease characterized by inappropriate insulin secretion in the presence of severe hypoglycemia, was recently mapped to a 6.6 cM interval between the markers D11S926 and D11S928 on chromosome 11p in 15 families (1). In the current study we evaluated six additional families and five new markers, and further localized the gene between D11S419 and D11S1310. Using genotype data from CEPH Version 7 and data generated from this study, this region was estimated to be 0.8 cM in length. Significant linkage disequilibrium between markers and the HI gene was observed over a region of 10.3 cM (11 pter-D11S926-D11S1308-11pcen) for Ashkenazi Jewish chromosomes. Haplotype analysis showed that 12 of 36 HI chromosomes, versus one of 36 non-HI chromosomes, bore a specific haplotype for D11S419-D11S902-D11S921 (p < 0.0007), strongly suggesting a founder effect in this ethnic group.
Familial hyperinsulinism maps to chromosome 11p14-15.1, 30 cM centromeric to the insulin gene.
Familial hyperinsulinism (HI) is the most common cause of persistent neonatal hyperinsulinaemic hypoglycemia. Linkage analysis in 15 families (12 Ashkenazi Jewish, 2 consanguineous Arab, 1 non-Jewish Caucasian) mapped HI to chromosome 11p14-15.1 (lod score = 9.5, theta = 0 at D11S921). Recombinants localized the disease locus to the 6.6 cM interval between D11S926 and D11S928. In Jewish families, association (p = 0.003) with specific D11S921/D11S419 haplotypes suggested a founder effect. This locus, which is important for normal glucose-regulated insulin secretion, represents a candidate gene for studies of other diseases of beta-cell dysfunction including non-insulin-dependent diabetes mellitus (NIDDM).
Genetic disorders of mitochondrial fatty acid oxidation.
Genetic diseases of mitochondrial fatty acid oxidation have recently emerged as important disorders to consider in the differential diagnosis of hypoglycemia, cardiomyopathy, or skeletal muscle weakness in infants and children. A total of 16 different defects have been identified over the past decade that involve almost all of the possible enzyme steps in the pathway. One of these disorders, medium-chain acyl-coenzyme A dehydrogenase deficiency has a frequency as high as 1 in 10,000 births and is the single most common genetic defect of intermediary metabolism. The disorders are frequently mistaken for Reye syndrome or sudden infant death syndrome. Improved methods have simplified the diagnosis of some of the fatty acid oxidation defects. However, recognition of these disorders remains challenging. Rapid advances have continued to be made over the past year in defining clinical phenotypes, diagnostic methods, and therapeutic strategies. Familiarity with this new group of disorders is becoming increasingly important for general pediatricians as well as subspecialists in metabolism, endocrinology, gastroenterology, cardiology, neurology, and genetics.
In vitro and in vivo effects of granulocyte colony-stimulating factor on neutrophils in glycogen storage disease type 1B: granulocyte colony-stimulating factor therapy corrects the neutropenia and the defects in respiratory burst activity and Ca2+ mobilization.
Children with glycogen storage disease (GSD) type 1b are susceptible to recurrent bacterial infections and have chronic neutropenia accompanied by phagocytic cell dysfunction including decreased superoxide anion (O2-) generation, calcium (Ca2+) mobilization, and chemotactic activity. Granulocyte colony-stimulating factor (G-CSF), a cytokine that corrects neutropenia in other diseases, in vitro enhances f-Met-Leu-Phe-triggered neutrophil O2- generation. Short-term pretreatment (15 min) of GSD 1b neutrophils with G-CSF increased the rate of O2- production (p < 0.01); however, this rate was still significantly below the rate of O2- production in control neutrophils. Recombinant human G-CSF (5 micrograms/kg/d) was administered s.c. to a GSD 1b patient. Before treatment, absolute neutrophil counts were < 500/mm3. Two d after G-CSF administration, the absolute neutrophil counts increased to 1333 and remained in the normal range during a 12-mo follow-up period. In vivo, G-CSF therapy increased f-Met-Leu-Phe-stimulated O2- production to 52% of control after 1 mo, and by mo 4, O2- production reached control levels. Our previous studies (J Clin Invest 56:196-202, 1990) demonstrated that decreased O2- production in neutrophils was associated with impaired Ca2+ mobilization. In vivo administration of G-CSF increased f-Met-Leu-Phe-triggered Ca2+ mobilization by neutrophils to 43% of control by mo 1 of G-CSF therapy and to 93% of control by mo 4, thus paralleling the improvements in O2- generation. In contrast, G-CSF therapy had no effect on the defective neutrophil chemotaxis. In summary, G-CSF therapy produced a rapid increase in circulating neutrophils and a gradual correction of O2- production.(ABSTRACT TRUNCATED AT 250 WORDS)
Acute fatty liver of pregnancy and long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency.
The pathogenesis of acute fatty liver of pregnancy is unknown, but similarities in the clinical presentation and the histological appearance of the liver with those found in children with metabolic defects in the intramitochondrial beta-oxidation pathway of the liver suggest that a disturbance in hepatic fatty acid oxidation may play a role. We report a woman with acute fatty liver of pregnancy who gave birth to a seemingly normal full-term infant who was seen at 4 mo of age with hypoglycemia, coma and profound hepatic steatosis. The infant had a defect in fatty acid oxidation, long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency, and the mother proved to be heterozygous for this metabolic condition. We hypothesize that the interaction of an affected fetus with a female heterozygous for this defect in fatty acid oxidation in the late third trimester accounts for some cases of acute fatty liver of pregnancy.
Impairment of calcium mobilization in phagocytic cells in glycogen storage disease type 1b.
Patients with glycogen storage disease (GSD) type 1b, in contrast to patients with GSD 1a, are susceptible to recurrent bacterial infections suggesting defective phagocytic function. We have demonstrated a selective defect in respiratory burst activity but not in degranulation by phagocytic cells in GSD 1b but not in GSD 1a. The respiratory burst abnormality in phagocytic cells from GSD 1b patients was associated with impaired calcium mobilization, whereas these processes were normal in GSD 1a patients. Therefore, the alteration in calcium mobilization was an indication of a signalling defect in phagocytic cells from GSD 1b. However, calcium mobilization was normal in lymphocytes, indicating that defective calcium mobilization was not a global finding in circulating leukocytes, but was specific to phagocytic cells. Calcium mobilization in response to ionomycin was reduced suggesting decreased calcium stores in GSD 1b neutrophils. Therefore, altered phagocytic cell function in GSD 1b patients appears to be associated with diminished calcium mobilization and defective calcium stores. This defective calcium signalling was associated with a selective defect in respiratory burst activity but not degranulation.
Short- and long-term use of octreotide in the treatment of congenital hyperinsulinism.
Octreotide, a long-acting analog of somatostatin that inhibits insulin release, has the potential to control hypoglycemia in infants with congenital hyperinsulinism. To examine the efficacy and side effects of octreotide, we evaluated therapy between 1988 and 1993 in 16 infants who did not respond to diazoxide. In nine patients with onset of severe hypoglycemia in the first days of life, octreotide was helpful in stabilizing plasma glucose levels and allowed reductions in the rates of glucose infusion; however, glucose control was inadequate to avoid subtotal pancreatectomy. In two of these nine patients postoperatively and in seven other infants, a trial of long-term treatment with octreotide was undertaken. Four were treated successfully for up to 4.3 years. Octreotide therapy was not associated with thyroid deficiency and caused only transient malabsorption. All patients receiving long-term therapy had some decrease in linear growth and two had subnormal plasma concentrations of insulin-like growth factor I and insulin-like growth factor binding protein 3 compatible with suppression of growth hormone by octreotide. Resistance to octreotide therapy, even with increasing doses, occurred in all patients. These results suggest that octreotide may aid in the acute or long-term treatment of congenital hyperinsulinism in a limited number of selected cases.
Detection of inborn errors of fatty acid oxidation from acylcarnitine analysis of plasma and blood spots with the radioisotopic exchange-high-performance liquid chromatographic method.
Sixty-one plasma samples from patients with inborn errors of fatty acid oxidation and from control subjects were analyzed in a blinded fashion for acylcarnitines by the radioisotopic exchange-high-performance liquid chromatographic method. All samples from patients with medium-chain acyl-coenzyme A dehydrogenase (MCAD) deficiency (n = 30), some of which had been stored in a frozen state for several years, showed a prominent octanoylcarnitine peak. In all blood spots from 11 patients with MCAD deficiency, octanoylcarnitine was also detected. Control plasma specimens and blood spots contained small amounts of octanoylcarnitine; however, the octanoylcarnitine/acetylcarnitine ratio differentiated patients with MCAD deficiency. Longer-chain acylcarnitines were found in plasma of all three patients with defects in long-chain fatty acid oxidation. Plasma and blood spots from a patient with multiple acyl-coenzyme A dehydrogenase deficiency contained C4-acylcarnitine, hexanoylcarnitine, octanoylcarnitine, and decanoylcarnitine. The results suggest that the method may be highly sensitive in detecting MCAD deficiency and other defects in fatty acid oxidation from plasma or blood spots.
Renal handling of carnitine in secondary carnitine deficiency disorders.
Reduced plasma and tissue concentrations of carnitine, a cofactor required for fatty acid oxidation, are present in patients with inherited disorders of mitochondrial acyl-CoA oxidation that are associated with accumulations of acylcarnitines. To determine whether the secondary carnitine deficiency in these patients is due to excessive urinary loss of acylcarnitines, the development of carnitine deficiency was examined in patients with four different acyl-CoA oxidation disorders, including medium-chain and long-chain fatty acyl-CoA dehydrogenase deficiencies, isovaleric acidemia, and propionic acidemia. After a 3-mo period of treatment with oral carnitine to raise plasma total carnitine concentrations to or above normal, patients were started on a carnitine-free diet and the changes in plasma total and free carnitine levels and urinary total and free carnitine excretion were followed for 5 d. Patients with all four disorders showed a return of plasma carnitine levels and urinary carnitine excretion to baseline within 2 to 4 d. The rapidity of these changes could not be explained solely by excessive acylcarnitine wasting. Continued excretion of free carnitine in all patients indicated the additional presence of an impairment in renal transport of free carnitine. Consistent with this interpretation, estimates of renal thresholds for free carnitine gave values that were less than that for a control child in all four disorders and ranged as low as one half those reported in normal individuals. These results suggest that secondary carnitine deficiency in the acyl-CoA oxidation disorders is due to indirect as well as direct effects of accumulated acylcarnitines.(ABSTRACT TRUNCATED AT 250 WORDS)
Interferon-gamma corrects the respiratory burst defect in vitro in monocyte-derived macrophages from glycogen storage disease type 1b patients.
Glycogen storage disease (GSD) type 1b is accompanied by decreased respiratory burst activity in peripheral blood phagocytic cells (i.e. monocytes and neutrophils). To elucidate whether this depressed respiratory burst was due to an intrinsic defect of phagocytic cells or due in part to in vivo host factors, we examined superoxide anion (O2-) production in monocytes from five GSD 1b patients cultured 9 d in vitro to allow for differentiation into macrophages (MDM). O2- production in MDM was measured in response to concanavalin A, fMet-Leu-Phe, and phorbol myristate acetate (PMA) stimulation. GSD 1b MDM had significantly depressed O2- generation with fMet-Leu-Phe and concanavalin A stimulation; however, unlike peripheral blood monocytes, GSD 1b MDM responded to PMA stimulation with O2- production comparable to healthy control donors. The cytokine interferon-gamma (IFN-gamma) has been shown to enhance O2- production in MDM. When GSD 1b MDM were cultured in the presence of IFN-gamma (1 x 10(5) U/L), O2- production in response to fMet-Leu-Phe, concanavalin A, and PMA was enhanced to rates similar to those of control MDM cultured in the presence of IFN-gamma. Thus, the respiratory burst defect observed in circulating phagocytic cells is also present in vitro in cultured GSD 1b MDM. However, in contrast to circulating phagocytic cells, depressed O2- production in GSD 1b MDM is selective to receptor-mediated activation, but not to PMA stimulation. This defect is correctable after short-term treatment with IFN-gamma, suggesting a role for IFN-gamma in treating the phagocytic defect in this disease.