- Email: [email protected]
Haemorrhagic shock encephalopathy and sudden infant death
202
The reason why fluorescences obtained by the interference filter and halogen lights were weaker than those obtained with standard fluorescence microscopy and a mercury lamp is that the intensity of fluorescence is proportional to the excitation energy.9,10 However, fluorescences emitted by the interference system were strong enough to detect all the parasites tested, and the system is much cheaper than standard fluorescence microscopes. Additionally, I have been able to detect parasites more clearly using the interference filter in a daylight illuminated light microscope than a halogen illuminated microscope (unpublished). The interference filter could possibly be used as an FITC filter for immunological investigations since it transmits an excitation wavelength of FITC (490nm). By contrast, a commercially available FITC filter can be used for this system only if its red diffraction beam of 645-700 nm (known as "red light for contrasting dark-field") is suppressed by an additional filter.9,10 Use of three suppression filters with the FITC filter (Olympus) is essential to obtain results similar to those for the AO filter (unpublished); moreover, these four filters could not be used in daylight illuminated microscopes. Improvement of the filter system to obtain a more intense fluorescence is now in progress. I thank Prof A. Ishii, Okayama University, Japan, for his valuable suggestions, and Dr P. F. Billingsley, Imperial College, London, for his
SHORT REPORTS
Haemorrhagic shock encephalopathy and sudden infant death
critical appraisal of the manuscript. This study received financial support from the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases.
REFERENCES 1. Voller A, Draper CC. Immunodiagnosis and seroepidemiology of malaria. Br Med Bull 1982; 38: 173-77. 2. Bruce-Chwatt LJ. From Laveran’s discovery to DNA probes: new trends in diagnosis of malaria. Lancet 1987; ii: 1509-11. 3. Barker RH, Suebsang L, Roney W. Specific DNA probe for the diagnosis of P falciparum malaria. Science 1986; 231: 1434-36. 4. Kawamoto F, Mizuno S, Fujioka H, et al. Simple and rapid staining for detection of Entamoeba cysts and other protozoans with fluorochromes. Jpn J Med Sci Biol 1987; 40: 35-46. 5. Kawamoto F, Kumada N. Fluorescent probes for detection of protozoan parasites. Parasitol Today 1987; 3: 284-86. 6. Spielman A, Prerrone JB, Teklehaimanot A, et al. Malaria diagnosis by direct observation of centrifuged samples of blood. Am J Trop Med Hyg 1988; 39: 337-42. 7. Rickman LS, Long GW, Oberst R, et al. Rapid diagnosis of malaria by acridine orange staining of centrifuged parasites. Lancet 1989; i: 68-71. 8. Rygaard J, Olsen W. Interference filters for improved immunofluorescence microscopy. Acta Path Microbiol Scand 1969; 76: 146-49. 9. Fluorescence microscopy. In: Kawamura A Jr, ed. Fluorescent antibody techniques and their applications. Tokyo: University of Tokyo Press, 1977: 95-114. 10. Rost FW. Fluorescence microscopy. In: Everson Pearse AG, ed. Histochemistry theoretical and applied. Vol 1. Preparative and optical technology. Edinburgh: Churchill Livingstone, 1980: 346-78.
On admission she had convulsions and bloody diarrhoea. Haemoglobin fell from 11-2 g/dl to 8-9 g/dl the next day. White cell count was 24-2 x 109/1 with a lymphocytosis, and platelet count fell from 338 x 109/1 to 35 x 109/1. Prothrombin time (international normalised ratio 7-4), activated partial thromboplastin time (137 s), and fibrin degradation products (160 mg/1 [normal range 2’1-7’9]) were raised. There was an acidosis (pH 7-23, pCOz 2-2 kPa, and bicarbonate 69 mmol/1) although blood urea (14-6 mmol/1) returned to normal after fluid replacement. Serum ell-antitrypsin rose to 868 IU/1 (normal < 40) the day after admission and an electroencephalogram showed repeated bursts of multifocal
paroxysmal activity. In 2 pairs of non-identical twins, haemorrhagicshock encephalopathy syndrome developed in 1 co-twin while the other died of sudden infant death syndrome. The twin pairs were aged 3 and 4 months, respectively, and no cause was identified. We suggest that stress protein deficiency may underlie both syndromes.
The haemorrhagic-shock encephalopathy syndrome was first described in 19831 but its cause remains unknown. The reasons for childhood deaths from sudden infant death syndrome (SIDS) are also uncertain in many cases. We describe 2 pairs of non-identical twins in whom 1 co-twin was found unexpectedly dead while the other went on to manifest the haemorrhagic-shock encephalopathy
syndrome. Case 1. A previously healthy female twin born at 34 weeks’ gestation to unrelated parents was found at 3 months of age to be hot, tachypnoeic, and hypotonic in the early hours of the morning. Both the mother and an elder sibling of the infant were recovering from chickenpox. There was no recent history of immunisation or drug intake. The father’s cousin had died from SIDS.
Circulatory support was maintained with colloid (blood and plasma) in the first 48 h, dopamine, and phenoxybenzamine. She was cooled to 32°C, hyperventilated for 3 days, and ventilated for another 6 days. Seizures were controlled with chlormethiazole. Minor bleeding continued despite fresh frozen plasma and vitamin K. Ampicillin, cefotaxime, zoster immune globulin, acyclovir, and cimetidine were also given. The patient recovered but with a residual spastic diplegia. The other twin, a boy, was well at the time his sister became ill but was found dead in his cot 1 h later. Necropsy revealed laryngotracheitis and enteritis with microvesicular fatty change in the liver. Case 2. A male twin was bom at 27 weeks’ gestation (1 06 kg) and was ventilated for 12 h after birth. Aged 4 months he was recovering from an upper respiratory tract infection, which had been treated with a cough suppressant, when he was found one morning febrile and vomiting. After hospital admission he became apnoeic and was ventilated. He had an undetectable blood glucose and was treated with intravenous dextrose. Haemoglobin was 9-6 g/dl, white cell count 42-7 x 109/1, and platelet count 537 x 109/1. Serum sodium was 159 mmol/l, potassium 6-9 mmol/1, and urea 11 -4 mmol/1. Seizures were treated with phenobarbitone, a blood transfusion was given (30 ml), and intravenous penicillin and gentamicin were started. Inotropic support was with dopamine, dobutamine, and adrenaline. The patient had bloody diarrhoea, bleeding from venepuncture sites, acute renal failure, and a metabolic acidosis (minimum pH 692). The platelet count fell (64 x 109/1) and prothrombin time (29 s),
203
activated partial thromboplastin time (69 s), and thrombin time (18 s) increased. Fibrin degradation products were present. Serum creatinine concentration rose to 197 umol/1 and peritoneal dialysis was started. An electroencephalogram showed no cerebral activity. Treatment was withdrawn and the patient died 36 h after initial hospital admission. Necropsy showed haemorrhagic cortical infarction, haemorrhagic infarction of the adrenal glands, and a mononuclear infiltrate in the lungs. At the same time as the onset of his acute illness his twin sister was found dead. Necropsy examination was unremarkable.
A relation between SIDS and haemorrhagic-shock encephalopathy syndrome has been reported in a child who
survived the latter but who died 3 months later from SIDS.2 Similarities between the two conditions include median age of onset (5 months),2 male preponderanceand a winter
peak.3 Common
pathways for these conditions may be overheating, infection, and metabolic abnormalities. Overheating and underventilation, caused by overwrapping or excessive clothing and leading to febrile apnoea, may be an important cause of cot death.4 4 of 39 patients with haemorrhagic-shock encephalopathy syndrome were thought to be overwrapped and admission temperature, recorded in 19 infants, was > 39°C in 10.2 The infants we report, however, were not excessively covered in clothes or bedding. Respiratory tract infection accompanies death in 40-75% of cases of SIDS’ and several explanations of how such infection may lead to cot deaths have been suggested.6 A prodromal illness was seen in 73% of cases of haemorrhagic-shock encephalopathy although no virus has been consistently identified.2 Moreover, infection can inherent metabolic disorder. Inborn metabolic errors-eg, medium chain acyl Co-A dehydrogenase (MCAD) deficiency, may account for up to 10% of cases of SIDS.’MCAD deficiency has been implicated in an acute illness resembling Reye’s syndrome.8 2 patients initially diagnosed with Reye’s syndrome were later confirmed as
unmask
an
having haemorrhagic-shock encephalopathy.2 Although a deficiency of protease inhibitors, such as al-antitrypsin, may be an important factor in the pathogenesis of haemorrhagicshock encephalopathy9 we found no evidence of a deficit. We suggest that a deficiency of cell stress (formerly called heat-shock) proteins could provide the causal link between these two conditions. Stress protein synthesis is increased after various stresses act on a cell—eg, a sudden rise in temperature, hypoxia, viral infection, nutrient deprivation, and irradiation.10 We propose that abnormalities in stress proteins could result in deficient cytoprotective responses and lead to cot death or the widespread cell damage of the haemorrhagic-shock encephalopathy syndrome. This deficit may be unmasked by overheating, infection, or metabolic disturbances such as hypoglycaemia. A study of stress proteins in these two conditions together with measurement of gene transcriptional activity with available gene probes will enable this hypothesis to be tested further. REFERENCES 1 Levin
M, Kay JDS, Gould JD, et al. Haemorrhagic shock and encephalopathy: a new syndrome with a high mortality in young
2.
children. Lancet 1983; ii: 64-67. Joint British Paediatric Association
and Communicable Disease Surveillance Centre surveillance scheme for haemorrhagic shock encephalopathy syndrome: surveillance report for 1982-84. Br Med J
1985; 290: 1578-79. 3 Sofer
S, Philllip M, Hershkowits J, Bennett H. Hemorrhagic shock and encephalopathy syndrome. Its association with hyperthermia. Am J Dis
Child 1986; 140: 1252-54. 4 Stanton AN. Overheating and
cot
death. Lancet 1984; ii: 1199-201.
5.
Shannon DC, Kelly DH. SIDS and near-SIDS. N Engl J Med 1982; 306:
6.
Anonymous. Respiratory infection and sudden infant death. Lancet 1989;
7.
Emery JL,
959-65.
ii: 1191-92. Howat AJ, Variend S, Vawter GF. Investigation of inborn errors of metabolism in unexpected infant deaths. Lancet 1988; ii:
29-31. 8. Roe CR,
Millington DS, Maltby DA, Kinnebrew P. Recognition of medium-chain acyl-CoA dehydrogenase deficiency in asymptomatic siblings of children dying of sudden infant death or Reye-like syndromes.J Pediatr 1986; 108: 13-18. 9. Levin M, Pincott JR, Hjelm M, et al. Hemorrhagic shock and encephalopathy: clinical, pathologic, and biochemical features. J Pediatr 1989; 114: 194-203. 10. Young RA, Elliott TJ. Stress proteins, infection, and immune surveillance. Cell 1989; 59: 5-8. ADDRESSES Departments of Paediatrics (J. Q Trounce, MRCP, D. I Johnston, MD) and Pathology (J Lowe, MRCPath), University Hospital, Nottingham; and Department of Paediatrics (B W. Lloyd, MD), North Middlesex Hospital, London. Correspondence to Dr J. Q. Trounce, Royal Alexandra Hospital for Sick Children, Dyke Road, Brighton, East Sussex, BN1 3JN, UK
Lipoprotein(a) reduction by N-acetylcysteine Lipoprotein(a), a complex of low-density lipoprotein disulphide bridges with apo(a), is
linked by associated
atherosclerotic disease when present high plasma concentrations. In vitro, N-acetylcysteine (NAC) dissociates this complex. In two patients with high Lp(a) levels NAC lowered plasma Lp(a) from 58 to 20 mg/dl and from 59 to 18 mg/dl: reductions of this order have not hitherto been achieved either by drugs or by diet. with
at very
High plasma lipoprotein(a) (Lp[a]) concentrations are associated with an increased risk for atherosclerotic and thrombotic disease. 1-3 This cholesterol-rich lipoprotein consists of low-density lipoprotein attached to the large glycoprotein apo(a) by one or more disulphide bonds. Lp(a) levels are highly heritable and largely determined by the apo(a) gene locus on chromosome 6q. Current hypolipidaemic regimens do not satisfactorily lower plasma Lp(a). Low-fat diets or diets enriched in monounsaturated fatty acids or m-6 polyunsaturated fatty acids have no effect and fish-oil-based diets cause only a modest reduction.’ Most drugs are ineffective though niacin has some value.5 If high levels of Lp(a) do adversely affect health, a safe, effective Lp(a)-lowering regimen is needed. We hypothesised that disulphide bond reducing agents might be effective-by dissociating apo(a) from Lp(a) and/or by inhibiting Lp(a) formation. The studies reported here are with N-acetylcysteine (NAC), a mild reducing agent that has been used clinically in man for other purposes. To test whether NAC can dissociate apo(a) from Lp(a) in vitro, was prepared from a patient with high Lp(a) levels by a combination of density gradient ultracentrifugation and column chromatography.’ Purified Lp(a) was incubated for 1 h at 37°C with 10 mm dithiothreitol or 2% 2-mercaptoethanol, two reducing agents known to dissociate Lp(a), or 1% or 0-5% NAC. The preparation was then delipidated and subjected to polyacrylamide gel electrophoresis followed by transfer to ’Immobilon P’
Lp(a)
The reason why fluorescences obtained by the interference filter and halogen lights were weaker than those obtained with standard fluorescence microscopy and a mercury lamp is that the intensity of fluorescence is proportional to the excitation energy.9,10 However, fluorescences emitted by the interference system were strong enough to detect all the parasites tested, and the system is much cheaper than standard fluorescence microscopes. Additionally, I have been able to detect parasites more clearly using the interference filter in a daylight illuminated light microscope than a halogen illuminated microscope (unpublished). The interference filter could possibly be used as an FITC filter for immunological investigations since it transmits an excitation wavelength of FITC (490nm). By contrast, a commercially available FITC filter can be used for this system only if its red diffraction beam of 645-700 nm (known as "red light for contrasting dark-field") is suppressed by an additional filter.9,10 Use of three suppression filters with the FITC filter (Olympus) is essential to obtain results similar to those for the AO filter (unpublished); moreover, these four filters could not be used in daylight illuminated microscopes. Improvement of the filter system to obtain a more intense fluorescence is now in progress. I thank Prof A. Ishii, Okayama University, Japan, for his valuable suggestions, and Dr P. F. Billingsley, Imperial College, London, for his
SHORT REPORTS
Haemorrhagic shock encephalopathy and sudden infant death
critical appraisal of the manuscript. This study received financial support from the UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases.
REFERENCES 1. Voller A, Draper CC. Immunodiagnosis and seroepidemiology of malaria. Br Med Bull 1982; 38: 173-77. 2. Bruce-Chwatt LJ. From Laveran’s discovery to DNA probes: new trends in diagnosis of malaria. Lancet 1987; ii: 1509-11. 3. Barker RH, Suebsang L, Roney W. Specific DNA probe for the diagnosis of P falciparum malaria. Science 1986; 231: 1434-36. 4. Kawamoto F, Mizuno S, Fujioka H, et al. Simple and rapid staining for detection of Entamoeba cysts and other protozoans with fluorochromes. Jpn J Med Sci Biol 1987; 40: 35-46. 5. Kawamoto F, Kumada N. Fluorescent probes for detection of protozoan parasites. Parasitol Today 1987; 3: 284-86. 6. Spielman A, Prerrone JB, Teklehaimanot A, et al. Malaria diagnosis by direct observation of centrifuged samples of blood. Am J Trop Med Hyg 1988; 39: 337-42. 7. Rickman LS, Long GW, Oberst R, et al. Rapid diagnosis of malaria by acridine orange staining of centrifuged parasites. Lancet 1989; i: 68-71. 8. Rygaard J, Olsen W. Interference filters for improved immunofluorescence microscopy. Acta Path Microbiol Scand 1969; 76: 146-49. 9. Fluorescence microscopy. In: Kawamura A Jr, ed. Fluorescent antibody techniques and their applications. Tokyo: University of Tokyo Press, 1977: 95-114. 10. Rost FW. Fluorescence microscopy. In: Everson Pearse AG, ed. Histochemistry theoretical and applied. Vol 1. Preparative and optical technology. Edinburgh: Churchill Livingstone, 1980: 346-78.
On admission she had convulsions and bloody diarrhoea. Haemoglobin fell from 11-2 g/dl to 8-9 g/dl the next day. White cell count was 24-2 x 109/1 with a lymphocytosis, and platelet count fell from 338 x 109/1 to 35 x 109/1. Prothrombin time (international normalised ratio 7-4), activated partial thromboplastin time (137 s), and fibrin degradation products (160 mg/1 [normal range 2’1-7’9]) were raised. There was an acidosis (pH 7-23, pCOz 2-2 kPa, and bicarbonate 69 mmol/1) although blood urea (14-6 mmol/1) returned to normal after fluid replacement. Serum ell-antitrypsin rose to 868 IU/1 (normal < 40) the day after admission and an electroencephalogram showed repeated bursts of multifocal
paroxysmal activity. In 2 pairs of non-identical twins, haemorrhagicshock encephalopathy syndrome developed in 1 co-twin while the other died of sudden infant death syndrome. The twin pairs were aged 3 and 4 months, respectively, and no cause was identified. We suggest that stress protein deficiency may underlie both syndromes.
The haemorrhagic-shock encephalopathy syndrome was first described in 19831 but its cause remains unknown. The reasons for childhood deaths from sudden infant death syndrome (SIDS) are also uncertain in many cases. We describe 2 pairs of non-identical twins in whom 1 co-twin was found unexpectedly dead while the other went on to manifest the haemorrhagic-shock encephalopathy
syndrome. Case 1. A previously healthy female twin born at 34 weeks’ gestation to unrelated parents was found at 3 months of age to be hot, tachypnoeic, and hypotonic in the early hours of the morning. Both the mother and an elder sibling of the infant were recovering from chickenpox. There was no recent history of immunisation or drug intake. The father’s cousin had died from SIDS.
Circulatory support was maintained with colloid (blood and plasma) in the first 48 h, dopamine, and phenoxybenzamine. She was cooled to 32°C, hyperventilated for 3 days, and ventilated for another 6 days. Seizures were controlled with chlormethiazole. Minor bleeding continued despite fresh frozen plasma and vitamin K. Ampicillin, cefotaxime, zoster immune globulin, acyclovir, and cimetidine were also given. The patient recovered but with a residual spastic diplegia. The other twin, a boy, was well at the time his sister became ill but was found dead in his cot 1 h later. Necropsy revealed laryngotracheitis and enteritis with microvesicular fatty change in the liver. Case 2. A male twin was bom at 27 weeks’ gestation (1 06 kg) and was ventilated for 12 h after birth. Aged 4 months he was recovering from an upper respiratory tract infection, which had been treated with a cough suppressant, when he was found one morning febrile and vomiting. After hospital admission he became apnoeic and was ventilated. He had an undetectable blood glucose and was treated with intravenous dextrose. Haemoglobin was 9-6 g/dl, white cell count 42-7 x 109/1, and platelet count 537 x 109/1. Serum sodium was 159 mmol/l, potassium 6-9 mmol/1, and urea 11 -4 mmol/1. Seizures were treated with phenobarbitone, a blood transfusion was given (30 ml), and intravenous penicillin and gentamicin were started. Inotropic support was with dopamine, dobutamine, and adrenaline. The patient had bloody diarrhoea, bleeding from venepuncture sites, acute renal failure, and a metabolic acidosis (minimum pH 692). The platelet count fell (64 x 109/1) and prothrombin time (29 s),
203
activated partial thromboplastin time (69 s), and thrombin time (18 s) increased. Fibrin degradation products were present. Serum creatinine concentration rose to 197 umol/1 and peritoneal dialysis was started. An electroencephalogram showed no cerebral activity. Treatment was withdrawn and the patient died 36 h after initial hospital admission. Necropsy showed haemorrhagic cortical infarction, haemorrhagic infarction of the adrenal glands, and a mononuclear infiltrate in the lungs. At the same time as the onset of his acute illness his twin sister was found dead. Necropsy examination was unremarkable.
A relation between SIDS and haemorrhagic-shock encephalopathy syndrome has been reported in a child who
survived the latter but who died 3 months later from SIDS.2 Similarities between the two conditions include median age of onset (5 months),2 male preponderanceand a winter
peak.3 Common
pathways for these conditions may be overheating, infection, and metabolic abnormalities. Overheating and underventilation, caused by overwrapping or excessive clothing and leading to febrile apnoea, may be an important cause of cot death.4 4 of 39 patients with haemorrhagic-shock encephalopathy syndrome were thought to be overwrapped and admission temperature, recorded in 19 infants, was > 39°C in 10.2 The infants we report, however, were not excessively covered in clothes or bedding. Respiratory tract infection accompanies death in 40-75% of cases of SIDS’ and several explanations of how such infection may lead to cot deaths have been suggested.6 A prodromal illness was seen in 73% of cases of haemorrhagic-shock encephalopathy although no virus has been consistently identified.2 Moreover, infection can inherent metabolic disorder. Inborn metabolic errors-eg, medium chain acyl Co-A dehydrogenase (MCAD) deficiency, may account for up to 10% of cases of SIDS.’MCAD deficiency has been implicated in an acute illness resembling Reye’s syndrome.8 2 patients initially diagnosed with Reye’s syndrome were later confirmed as
unmask
an
having haemorrhagic-shock encephalopathy.2 Although a deficiency of protease inhibitors, such as al-antitrypsin, may be an important factor in the pathogenesis of haemorrhagicshock encephalopathy9 we found no evidence of a deficit. We suggest that a deficiency of cell stress (formerly called heat-shock) proteins could provide the causal link between these two conditions. Stress protein synthesis is increased after various stresses act on a cell—eg, a sudden rise in temperature, hypoxia, viral infection, nutrient deprivation, and irradiation.10 We propose that abnormalities in stress proteins could result in deficient cytoprotective responses and lead to cot death or the widespread cell damage of the haemorrhagic-shock encephalopathy syndrome. This deficit may be unmasked by overheating, infection, or metabolic disturbances such as hypoglycaemia. A study of stress proteins in these two conditions together with measurement of gene transcriptional activity with available gene probes will enable this hypothesis to be tested further. REFERENCES 1 Levin
M, Kay JDS, Gould JD, et al. Haemorrhagic shock and encephalopathy: a new syndrome with a high mortality in young
2.
children. Lancet 1983; ii: 64-67. Joint British Paediatric Association
and Communicable Disease Surveillance Centre surveillance scheme for haemorrhagic shock encephalopathy syndrome: surveillance report for 1982-84. Br Med J
1985; 290: 1578-79. 3 Sofer
S, Philllip M, Hershkowits J, Bennett H. Hemorrhagic shock and encephalopathy syndrome. Its association with hyperthermia. Am J Dis
Child 1986; 140: 1252-54. 4 Stanton AN. Overheating and
cot
death. Lancet 1984; ii: 1199-201.
5.
Shannon DC, Kelly DH. SIDS and near-SIDS. N Engl J Med 1982; 306:
6.
Anonymous. Respiratory infection and sudden infant death. Lancet 1989;
7.
Emery JL,
959-65.
ii: 1191-92. Howat AJ, Variend S, Vawter GF. Investigation of inborn errors of metabolism in unexpected infant deaths. Lancet 1988; ii:
29-31. 8. Roe CR,
Millington DS, Maltby DA, Kinnebrew P. Recognition of medium-chain acyl-CoA dehydrogenase deficiency in asymptomatic siblings of children dying of sudden infant death or Reye-like syndromes.J Pediatr 1986; 108: 13-18. 9. Levin M, Pincott JR, Hjelm M, et al. Hemorrhagic shock and encephalopathy: clinical, pathologic, and biochemical features. J Pediatr 1989; 114: 194-203. 10. Young RA, Elliott TJ. Stress proteins, infection, and immune surveillance. Cell 1989; 59: 5-8. ADDRESSES Departments of Paediatrics (J. Q Trounce, MRCP, D. I Johnston, MD) and Pathology (J Lowe, MRCPath), University Hospital, Nottingham; and Department of Paediatrics (B W. Lloyd, MD), North Middlesex Hospital, London. Correspondence to Dr J. Q. Trounce, Royal Alexandra Hospital for Sick Children, Dyke Road, Brighton, East Sussex, BN1 3JN, UK
Lipoprotein(a) reduction by N-acetylcysteine Lipoprotein(a), a complex of low-density lipoprotein disulphide bridges with apo(a), is
linked by associated
atherosclerotic disease when present high plasma concentrations. In vitro, N-acetylcysteine (NAC) dissociates this complex. In two patients with high Lp(a) levels NAC lowered plasma Lp(a) from 58 to 20 mg/dl and from 59 to 18 mg/dl: reductions of this order have not hitherto been achieved either by drugs or by diet. with
at very
High plasma lipoprotein(a) (Lp[a]) concentrations are associated with an increased risk for atherosclerotic and thrombotic disease. 1-3 This cholesterol-rich lipoprotein consists of low-density lipoprotein attached to the large glycoprotein apo(a) by one or more disulphide bonds. Lp(a) levels are highly heritable and largely determined by the apo(a) gene locus on chromosome 6q. Current hypolipidaemic regimens do not satisfactorily lower plasma Lp(a). Low-fat diets or diets enriched in monounsaturated fatty acids or m-6 polyunsaturated fatty acids have no effect and fish-oil-based diets cause only a modest reduction.’ Most drugs are ineffective though niacin has some value.5 If high levels of Lp(a) do adversely affect health, a safe, effective Lp(a)-lowering regimen is needed. We hypothesised that disulphide bond reducing agents might be effective-by dissociating apo(a) from Lp(a) and/or by inhibiting Lp(a) formation. The studies reported here are with N-acetylcysteine (NAC), a mild reducing agent that has been used clinically in man for other purposes. To test whether NAC can dissociate apo(a) from Lp(a) in vitro, was prepared from a patient with high Lp(a) levels by a combination of density gradient ultracentrifugation and column chromatography.’ Purified Lp(a) was incubated for 1 h at 37°C with 10 mm dithiothreitol or 2% 2-mercaptoethanol, two reducing agents known to dissociate Lp(a), or 1% or 0-5% NAC. The preparation was then delipidated and subjected to polyacrylamide gel electrophoresis followed by transfer to ’Immobilon P’
Lp(a)