Obesity-associated genetic variants in young Asian Indians with the metabolic syndrome and myocardial infarction

OBJECTIVE

Associations between obesity-related polymorphisms and the metabolic syndrome in 485 young ( ≤ 45 Years) Asian Indian patients with acute myocardial infarction (AMI), and 300 matched controls were assessed.

METHODS

Genetic variants included the adiponectin 45T→G and 276G→T, LEPR K109R and Q223R, MC4R-associated C→T and FTO A→T polymorphisms.

RESULTS

The metabolic syndrome, as defined by NCEP ATP III and IDF criteria, was diagnosed in 61 and 60% of patients, respectively. No relationship was found between the obesity-associated polymorphisms and the metabolic syndrome, or between AMI patients and controls. The MC4R-associated TT genotype occurred more frequently in patients with lower triglyceride levels (p = 0.024), while the adiponectin 45 TT genotype occurred more commonly in patients with normal fasting glucose levels (p = 0.004). The LEPR Q223R TT genotype was associated with low high-density lipoprotein (HDL) cholesterol levels (p = 0.003).

CONCLUSION

The metabolic syndrome occurs commonly in young Asian Indian patients with AMI. No relationship was found between any obesity-associated polymorphism and the metabolic syndrome. Particular genotypes may exert protective or disadvantageous effects on individual components of the metabolic syndrome.

Prognostic value of N-terminal-pro-brain natriuretic peptide measurements in patients with acute coronary syndromes

BACKGROUND

The aim of this study was to examine the prognostic value of admission N-terminal-pro-brain natriuretic peptide (NT-proBNP) measurements for the outcome of adverse events, and to compare it with that of cardiac troponin T in the assessment of risk in patients with acute coronary syndrome (ACS) during the hospital stay and at six months following hospital discharge.

METHODS

The study population consisted of 200 Asian Indian patients admitted with a diagnosis of ACS to the Coronary Care Unit at RK Khan Hospital, Durban, South Africa. A reference group comprising 100 healthy Indian individuals drawn from the same community and who did not suffer from cardiovascular disease was also analysed.

RESULTS

The majority of patients presented with ST segment elevation myocardial infarction (STEMI) (71%), whereas 14.5% had non-ST segment elevation MI (NSTEMI), and the remaining 14.5% had unstable angina. Patients had multiple risk factors for coronary heart disease (CHD) including hypertension (59%), hypercholesterolaemia (59%), smoking (57%), diabetes mellitus (51%), obesity (46%), and a strong family history of CHD (55%). NT-proBNP levels were significantly increased in patients with STEMI (p = 0.005) and NSTEMI (p = 0.002) who developed adverse events during their hospital stay, compared with those who did not. At the six-month followup, although NT-proBNP levels were higher in patients with STEMI and NSTEMI who developed adverse events, these differences were not statistically significant. No differences in troponin T levels were detected in patients with STEMI and NSTEMI who developed adverse events, compared to those who did not, either during the hospital stay, or at six months after release. At hospital admission, 24% of patients with unstable angina who had elevated NT-proBNP levels and normal troponin T concentrations developed adverse events, compared to 38% at six months. NT-proBNP levels in the reference group were comparable with those reported in other populations.

CONCLUSION

This study demonstrated that elevation in admission NT-proBNP levels is an important determinant of acute and intermediate cardiac risk in patients with ACS. NT-proBNP concentrations were superior to those of troponin T as prognostic markers in both STEMI and NSTEMI. In a low-risk group of patients with unstable angina and negative troponin T concentrations, elevated NT-proBNP levels constituted a risk for the development of adverse cardiovascular events. Therefore, NT-proBNP should be included in the risk assessment of ACS to provide guidance for further therapeutic strategies.

Plasminogen activator inhibitor type 1 (PAI-1) and platelet glycoprotein IIIa (PGIIIa) polymorphisms in young Asian Indians with acute myocardial infarction

BACKGROUND

The relationship between polymorphisms in the genes for plasminogen activator inhibitor type 1(PAI-1) and platelet glycoprotein IIIa (PGIIIa), clinical and environmental features, and the risk of premature coronary heart disease (CHD) in Asian Indian subjects living in South Africa, has been investigated.

METHODS

The prevalence of the PAI-1 promoter 4G/5G and the PGIIIa PI A1A2 polymorphisms was examined in 195 unrelated Asian Indian patients ( <or= 45 years) who presented with myocardial infarction (MI). Results were compared with those from 107 unaffected siblings (18-45 years) and 300 healthy age- and race-matched control subjects.

RESULTS

Overall, neither the PAI-1 4G/5G nor the PGIIIa PI A1A2 polymorphism demonstrated an independent risk for MI. No synergistic effect was observed between these two polymorphisms when analysed together. There was a marginal association between the 4G allele of the PAI-1 gene and the risk of MI in individuals who smoked compared with non-smokers (26 vs 11%; p = 0.028; OR 2.74; 95% CI 1.04-8.47). The PGIIIa PI A2 allele was, however, strongly associated with a previous history of MI (17 vs 6%; p = 0.004; OR 3.00; 95% CI 1.38-6.46), as well as the severity of disease as determined by angiography (single/double- vs triple-vessel disease: 3% vs 15%; p = 0.020; OR 0.19; 95% CI 0.02-0.92).

CONCLUSION

In young Asian Indians who smoke, the PAI-1 4G allele is a mild risk factor for the development of MI. The PGIIIa PI A2 allele constitutes a significant risk for individuals who have a previous history of MI, as well as serving as an indicator for the severity of CHD.

Coagulation gene polymorphisms as risk factors for myocardial infarction in young Indian Asians

BACKGROUND

The relationship between pro-coagulant gene polymorphisms, clinical features and the risk of premature coronary heart disease (CHD) in Indian Asian subjects resident in South Africa has been investigated.

METHODS

The prevalence of the beta-fibrinogen -455G/A and -148C/T, and the factor VII 10 bp 5' promoter insertion/deletion and R353Q polymorphisms were examined in 195 unrelated Indian Asian patients (< or = 45 years) who presented with myocardial infarction (MI). Results were compared with those from 107 unaffected siblings (18-45 years) and 300 healthy age- and race-matched control subjects.

RESULTS

Overall, none of the polymorphisms examined here showed any association with MI. However, when stratified according to obesity, patients with a BMI > 30 kg/m2 had a significantly higher frequency of the beta-fibrinogen variant alleles, compared with non-obese patients (19% vs 9%; p = 0.025) and controls (19% vs 9%; p = 0.003). Furthermore, the highest frequency of variant alleles occurred in obese smokers (24%), compared with 4% in non-obese non-smokers (p = 0.003) and 9% in control subjects (p < 0.001). The factor VII R353Q and promoter insertion variants, on the other hand, were associated with higher HDL and lower LDL levels (p = 0.034 and 0.04, respectively).

CONCLUSION

In young Indian Asians who are both obese and smoke, the beta-fibrinogen genetic polymorphisms -455G-->A and -148C-->T, which are in linkage disequilibrium, are significant risk factors for the development of MI. Factor VII genetic variants, namely the 10 bp promoter insertion/deletion and R353Q polymorphisms, may possibly play a protective role through their association with elevated HDL and low LDL levels, respectively.

Demographic data and outcome of acute coronary syndrome in the South African Asian Indian population

Significant differences in the prevalence of coronary heart disease (CHD) exist with respect to gender, age and ethnicity. The disease has been reported to be higher in Indian populations that have emigrated from the Indian subcontinent. The aim of this study was to examine differences in major cardiovascular risk factors and clinical outcome in South African Asian Indians of different age groups and gender, who presented with acute coronary syndromes (ACS). The study cohort consisted of 2 290 consecutive patients, admitted between 1996 and 2002, who were divided into three age subgroups: young ( </= 45 years; 20%), middle age (> 45 to </= 65 years; 59%), and old age (> 65 years; 21%). All three age groups were predominantly male, but this was more evident in the younger (88%) and middle age groups (71%), and became less striking as the proportion of females increased with age. Smoking was more common in young men compared with young women (p < 0.01). Diabetes mellitus (21%) and hypertension (18%) were seen less frequently in young patients but this was confined to men only. Total cholesterol was elevated in 65 to 70% of all patients while high-density lipoprotein (HDL) levels were significantly lower in men compared with women for all age subsets. Hospital mortality was extremely low in young (1%) and middle-aged patients (2%), but was expectedly higher in older patients (8%; p < 0.0001). A family history of CHD was the most common familial vascular disease seen. Young patients were more often subjected to diagnostic and therapeutic interventions. They had more aggressive disease, with 48% of those subjected to angiographic studies having triple vessel disease (TVD), and 14% undergoing coronary artery bypass grafting (CABG). Triple vessel disease was also detected most commonly in middle-aged (64%) and old patients (75%). In conclusion, significant differences in risk factor status were found in South African Indians between genders and for different age groups. Also, young Indians in this study differed markedly from other young population groups with CHD, in that they frequently had premature atherosclerosis with diffuse and aggressive disease.

Prolactin as a tumour marker in cancer of the cervix

The aim of this study was to determine the possible usefulness of prolactin as a tumour marker in cancer of the cervix. Serum prolactin levels were measured using an enzyme linked immunosorbent assay in 105 women divided into malignant, pre-malignant and control groups. Elevated levels of prolactin were found in 42.9% of patients with malignant disease, 22.9% of controls and 14.2% of individuals with premalignant disease. The differences were not statistically significant. Although prolactin levels were found to be elevated in some patients with malignant disease of the cervix, further studies are needed to establish whether this is of clinical significance.

T594M mutation of the epithelial sodium channel beta-subunit gene in pre-eclampsia and eclampsia in Black South African women

The possible role of the beta-subunit of the epithelial sodium channel T594M polymorphism in hypertensive disorders of pregnancy has not been examined. This study compared Black South African women with pre-eclampsia (n= 204), early onset pre-eclampsia (n= 67), eclampsia (n= 120) and gestational hypertension (n= 78) with 338 women from the same ethnic group who had full-term normotensive pregnancies, for the presence of the T594M polymorphism. The variant allele was detected in 1.7% to 3.8% of the various patient groups and in 3.6% of the control group reflecting no significant difference. These results suggest that the T594M polymorphism in the sodium channel beta-subunit is not associated with the pathogenesis of pre-eclampsia or gestational hypertension.

Lp(a) and apoE polymorphisms in young South African Indians with myocardial infarction

The lipoprotein(a) [Lp(a)] and apolipoprotein E (apoE) polymorphisms have been shown to be important genetic determinants of cardiovascular risk. Their effect on coronary heart disease (CHD) is less clear, particularly in Asian Indians who are at high risk for this disease. The aim of this study was to examine the association of the Lp(a) promoter pentanucleotide repeat polymorphism and the apoE codon 112 and 158 genotypes in 195 young South African Indian patients (< or = 45 years) with myocardial infarction (MI). Results were compared with 300 healthy age-matched control subjects drawn from the same community and 107 unaffected siblings (18-45 years). In addition, fasting lipograms were performed on all patients and a detailed history of conventional risk factors and family background was obtained. Of the six different Lp(a) alleles detected, the 8-repeat sequence was most frequently seen. However, no difference in frequencies existed between patient and control groups. The most frequently occurring apoE genotype in the three study groups was E3/E3 (patients 71%; siblings 70%; controls 70%). A significant difference in the E3/E4 genotype was seen between patients and controls (23% vs 14%; p = 0.018) and between siblings and controls (24% vs 14%; p = 0.027). These patients were also more likely to have significantly higher low-density lipoprotein (LDL) and lower high-density lipoprotein (HDL) levels (p = 0.005 and 0.045, respectively). No association was observed between any of the Lp(a) or apoE genotypes and conventional risk factors such as smoking, diabetes, hypertension, obesity or a family history of CHD. In conclusion, the apoE3/E4 genotype is strongly associated with the incidence of myocardial infarction in young South African Indians. This genotype also adversely affects LDL and HDL cholesterol levels, both of which contribute to premature atherosclerosis. In contrast, the Lp(a) pentanucleotide repeat polymorphism does not appear to have any aetiological role in MI in this population.

Renin-angiotensin system and associated gene polymorphisms in myocardial infarction in young South African Indians

The renin-angiotensin system plays an important role in cardiovascular regulation. Abnormalities in genetic components of this system, such as the angiotensin-converting enzyme (ACE) gene, angiotensin II type 1 (AT1) receptor gene and angiotensinogen (AGT) gene, may cause a variety of adverse cardiovascular effects. It was the aim of this study, therefore, to investigate the involvement of the ACE insertion/deletion (I/D), AT1 receptor 1166 A->C and AGT M235T polymorphisms as predisposing factors for myocardial infarction (MI) in 195 young South African Indians (</= 45 years). Results were compared with those obtained I n 107 unaffected siblings (18-45 years old) and 300 healthy age- and race-matched control subjects. The distribution of the ACE genotypes was the same in each of the three study groups (p-value ranged between 0.83 and 0.98). No differences were observed in the 1166 A->C AT1 receptor polymorphism with respect to both genotype and allelotype (p > 0.70), or in the genotype or allele frequency distribution of the AGT M235T polymorphism (p > 0.44). However, a significant in crease was noted for both the AT1 receptor C variant (p = 0.025) and the AGT T variant (p = 0.047) in hypertensive patients compared with those who were normotensive. In conclusion, results of this study indicate that the ACE I/D, the 1166 A->C AT1 receptor and AGT M235T polymorphisms do not confer any increased risk for MI in young South African Indians.

P53 codon 72 polymorphism and BRCA 1 and 2 mutations in ovarian epithelial malignancies in black South Africans

Mutations in the BRCA and p53 tumor suppressor genes are implicated in the oncogenesis of ovarian tumors although their exact roles remain unclear. Despite recognized ethnic differences in the frequency of ovarian cancer and in genetic polymorphisms between populations, studies carried out so far have focused almost entirely on Caucasian subjects. In this study, undertaken at King Edward VIII Hospital, Durban, South Africa, we examined blood and/or primary epithelial ovarian tumor tissue from 75 black South African women for the presence of the three most commonly occurring BRCA 1 and 2 mutations (185delAG, 5382insC and 6174delT). The p53 codon 72 allele status was also examined and results were compared to a reference cohort comprising 340 ethnically matched subjects. None of the BRCA 1 or 2 mutations were detected in the patient group. The codon 72 Arg allele frequency in lymphocytic DNA was not significantly different compared with the control group. In contrast, in ovarian tumor DNA, the Arg allele was found significantly more frequently than in the controls; this was observed in terms of both Arg allele frequency (45% vs. 31%; P = 0.017) and Arg homozygosity (20% vs. 9%; P = 0.039). Tumors with the more aggressive serous papillary cystadenomatous histology had a markedly higher Arg frequency (45%) than the mucinous cystadenomas (25%). The higher frequency of the Arg allele detected in this study in black South Africans with ovarian tumors suggests a possible role in malignant transformation and may constitute a risk factor for ovarian and other epithelial cancers through mechanisms yet to be elucidated.

P53 codon 72 polymorphism and BRCA 1 and 2 mutations in ovarian epithelial malignancies in black South Africans

Mutations in the BRCA and p53 tumor suppressor genes are implicated in the oncogenesis of ovarian tumors although their exact roles remain unclear. Despite recognized ethnic differences in the frequency of ovarian cancer and in genetic polymorphisms between populations, studies carried out so far have focused almost entirely on Caucasian subjects. In this study, undertaken at King Edward VIII Hospital, Durban, South Africa, we examined blood and/or primary epithelial ovarian tumor tissue from 75 black South African women for the presence of the three most commonly occurring BRCA 1 and 2 mutations (185delAG, 5382insC and 6174delT). The p53 codon 72 allele status was also examined and results were compared to a reference cohort comprising 340 ethnically matched subjects. None of the BRCA 1 or 2 mutations were detected in the patient group. The codon 72 Arg allele frequency in lymphocytic DNA was not significantly different compared with the control group. In contrast, in ovarian tumor DNA, the Arg allele was found significantly more frequently than in the controls; this was observed in terms of both Arg allele frequency (45% vs. 31%; P = 0.017) and Arg homozygosity (20% vs. 9%; P = 0.039). Tumors with the more aggressive serous papillary cystadenomatous histology had a markedly higher Arg frequency (45%) than the mucinous cystadenomas (25%). The higher frequency of the Arg allele detected in this study in black South Africans with ovarian tumors suggests a possible role in malignant transformation and may constitute a risk factor for ovarian and other epithelial cancers through mechanisms yet to be elucidated.

Risk factors and methylenetetrahydrofolate reductase gene polymorphisms in a young South African Indian-based population with acute myocardial infarction

Although coronary heart disease (CHD) is extremely common in South African Indians, there is little published data on the possible causes leading to myocardial infarction (MI) in young Indians. The aim of this study was to identify common environmental risk factors and to examine the relationship between two polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) gene, the 677 C right arrow-hooked T and 1298 A right arrow-hooked C in young South African Indians with MI. Demographic and risk factor data were obtained from245 patients </= 45 years with MI who were admitted to the RK Khan Hospital, Durban. Venous blood from 195 of the 245 patients with MI, as well as from the sublings of the MI patients (n = 107), and 300 healthy age-matched Indian control subjects, were collectd from genetic analysis. Cigarette smoking was the most important risk factor, occurring in three-quarters of patients, followed by dyslipidaemia in half of the subjects. Diabetes (19%) and hypertension (22%) were found not to be major risk factors for MI. A strong familial link was observed not only for a history of CHD (54%), but also for diabetes (42%) and hypertension (41%). No difference was found in the thermolabile variant of the MTFHR gene (677 C right arrow-hooked T) or the second variant 1298 A right arrow-hooked C between controls and patients with MI or their siblings. The two polymorphisms did not appear to work in synergy, neither was there any relationship to common risk factors for CHD. In conclusion, smoking, dyslipidaemia and obesity were the most common phenotypic risk factors for MI. Neither the 667 C right arrow-hooked T nor the 1298 A right arrow-hooked C MTFHR variants appeared to be risk factors for premature CHD in this group.

Absence of Factor V Leiden, thrombomodulin and prothrombin gene variants in Black South African women with pre-eclampsia and eclampsia

It has been suggested that gene aberrations may contribute to vascular endothelial dysfunction of pre-eclampsia in Caucasian and Japanese women. This study was undertaken to examine the association between pre-eclampsia in Black Zulu speaking South African women and the Factor 5 Leiden mutation. 100 patients with pre-eclampsia comprised the study group. The control group comprised 110 normotensive pregnant women of the same population group. Genotyping was performed to detect the G or A allele at residue 506 of the Factor V gene, and the C or T allele at residue 455 of the thrombomodulin gene. Our findings demonstrate that these particularly genetic loci are of little use in disease association studies for pre-eclampsia in homogenous Zulu speaking Africans.

P53 codon 72 polymorphism and human papillomavirus type in relation to cervical cancer in South African women

The usefulness of the arginine (Arg) residue at codon 72 of the p53 tumor suppressor gene as a marker for the risk of cervical cancer remains unclear. Studies to date have focused mainly on Caucasian subjects despite marked ethnic variations in both the p53 polymorphism and the frequency of cervical carcinoma. Furthermore, not all studies have taken into account the type of human papillomavirus (HPV) infection present. In this study, undertaken at King Edward VIII Hospital, Durban, South Africa, we determined the p53 codon 72 status in 281 black South African women with cervical cancer and 340 ethnically matched healthy control subjects. In addition, HPV DNA was confirmed in 190 cervical tumors and the viral type determined. Results showed that overall more cancer patients than control subjects had an Arg allele at codon 72 with respect to both genotype and allelotype (P < 0.05). A significantly higher (P < 0.001) Arg allele frequency (55%) was also observed in patients whose tumors contained low or intermediate risk HPV DNA compared with control subjects (31%); the Arg homozygosity rate was 34% and 9% in patients and controls, respectively (P < 0.001). In contrast, patients harboring HPV 16/18 infections showed no differences in p53 status compared with controls. It would appear that, in the absence of HPV 16/18 infections, the Arg allele at codon 72 of the p53 tumor suppressor gene may constitute a risk factor for carcinogenesis of the cervix.

Polymorphisms in various coagulation genes in black South African women with placental abruption

This pilot study examined Factor V Leiden (R506Q), prothrombin (20210G-->A), thrombomodulin (A455V) and MTHFR (677C-->T) in 100 Zulu-speaking black South African women with placental abruption and 217 controls. The Factor V Leiden and prothrombin variant gene alleles were not detected in either patient or control groups. The thrombomodulin polymorphic variant was not seen in the patient group but three heterozygotes (1%) were found in the controls. No homozygotes for the MTHFR T677 variant were detected in the patients but two (1%) were noted in the controls; the normal and heterozygote genotype and allele frequencies for this polymorphism were similar in the two groups.

Biochemical and molecular diagnosis of glutaric aciduria type 1 in a black South African male child: case report

Glutaric aciduria type 1 (GA-1) is an inborn error of metabolism caused by a deficiency of the mitochondrial enzyme glutaryl-Co enzyme A dehydrogenase. GA-1 is not uncommon amongst Caucasians but to the best of our knowledge, it has previously not been reported in black African children. We present a case of GA-1 in a black South African boy who was referred to hospital at the age of five years and ten 10 months with dyskinesia and dystonia accompanied by chorea and athetosis. Radiological examination revealed enlarged basal cisterns with bilateral fluid collection around the sylvian fissures suggestive of GA-1. Analysis of urine showed raised levels of glutaric acid at 520 micromol/mmol creatinine (normal <2.0), 3-hydroxyglutaric acid at 113 micromol/mmol creatinine (normal <3.0) and a low blood carnitine level of 31.5 micromol/l (normal 35-84). A definitive diagnosis was reached through DNA analysis which revealed homozygosity for an A293T mutation in the glutaryl-Co-enzyme A dehydrogenase (GCDH) gene.

Collagen Ialpha1 and vitamin D receptor gene polymorphisms in South African whites, blacks and Indians

OBJECTIVE

To determine whether polymorphic differences exist between black, white and Indian South Africans in genes associated with bone mineral density and osteoporosis.

DESIGN

Genes selected were the vitamin D receptor (Apa I and Taq I polymorphisms) and collagen (Sp I transcription factor polymorphism) using standard molecular biology techniques.

SETTING

Department of Chemical Pathology, Nelson R Mandela School of Medicine, University of Natal, Durban, South Africa.

SUBJECTS

Healthy male and female blood donors living in the Durban metropolitan region, South Africa. The group comprised black Africans (n=264), white Caucasians (n=247) and Asians of Indian origin (n=194).

RESULTS

No significant differences in genotypes were seen between white and Indian subjects. Blacks had a significantly higher frequency of the TT Taq I genotype and a significantly lower frequency of the Ss Sp I genotype. No ss genotype was detected in blacks.

CONCLUSION

The very low frequency of the collagen Sp I s allele and higher frequency of the VDR T allele in blacks may be associated with the lower incidence of osteoporosis in this ethnic group.

Apolipoprotein E polymorphism in South African Zulu women with preeclampsia

OBJECTIVES

Apolipoprotein E may contribute to the hypertiglyceridemia and consequent endothelial dysfunction of preeclampsia. We carried out a study to determine whether the apolipoprotein E genotype plays any role as a risk factor for preeclampsia in a black South African population with a high incidence of preeclampsia.

DESIGN

A descriptive, prospective study design was used.

SETTING

King Edward VIII Hospital, a tertiary care, referral academic hospital in Durban, South Africa.

PATIENTS AND PARTICIPANTS

One hundred three South African Zulu women with preeclampsia and 110 healthy normotensive women attending the antenatal clinic were recruited.

MAIN OUTCOME MEASURES

The relationship between the apolipoprotein E allele and genotype frequencies to preeclampsia as well as adverse perinatal outcome.

RESULTS

The frequencies of varepsilon2 and varepsilon4 alleles (0. 19 and 0.25, respectively) were much higher than those reported in other population groups. However, there was no significant difference in the apolipoprotein E genotype and allele frequencies between the study and the control groups. The varepsilon2/2 genotype was associated with increased risk of perinatal death (p = 0.047).

CONCLUSION

The study suggests that, despite the high incidence of both preeclampsia and the varepsilon2 and varepsilon4 alleles in South African Zulu women, apolipoprotein E genotype does not appear to be a risk factor for preeclampsia in this population.

5,10 methylenetetrahydrofolate reductase polymorphism in black South African women with pre-eclampsia

The polymorphic C677T mutation in the gene encoding 5,10 methylenetetrahydrofolate reductase has been shown to be a risk factor for pre-eclampsia in Japanese and European women when inherited as a homozygous trait. We attempted to verify these findings in a black African population with a high incidence of pre-eclampsia. No difference in frequency of the T-allele was observed in 105 women with pre-eclampsia, compared with 110 healthy pregnant normotensive women. Only one woman with pre-eclampsia was TT homozygous, suggesting that methylenetetrahydrofolate reductase polymorphism is not an important factor in the pathogenesis of pre-eclampsia in black South African women.

HMG-CoA reductase is not the site of the primary defect in phytosterolemia

Phytosterolemia is an autosomal recessive disorder characterized by the excessive absorption, reduced excretion, and consequent high tissue and plasma levels of plant sterols, by the presence of tendon xanthomas, and by premature atherosclerosis. Low HMG-CoA reductase (HRase) activity and mass have been reported in liver and mononuclear leucocytes and low mRNA levels in liver from phytosterolemic subjects. These results led to the proposal that the primary defect in this condition involves the HRase gene locus. We examined this hypothesis in phytosterolemic subjects and heterozygous parents from four unrelated families. A variable number tandem repeat (VNTR) polymorphism of the HRase gene in the three informative families and a ScrFI restriction fragment length polymorphism (RFLP) within intron 2 of the gene in one of these families, segregated independently of the disease phenotype. Biological parentage was confirmed in the family in whom both polymorphisms failed to segregate with the disorder. These results conclusively exclude the HRase gene locus as the site of the primary defect in phytosterolemia. The study was extended by examining plasma levels of mevalonic acid and lathosterol, both markers of cholesterol biosynthesis, in response to cholestyramine, a bile acid sequestrant that is known to up-regulate HRase. Oral administration of cholestyramine resulted in a substantial (7.7-fold) increase in mevaIonic acid levels in two phytosterolemic subjects, compared with a 2.2-fold rise in their obligate heterozygote parents and a 2.3-fold increase in three healthy control subjects. The lathosterol/cholesterol (L/C) ratio showed a quantitatively similar response. Baseline levels of mevalonate and the L/C ratio were low in the phytosterolemic patients in conformity with reports of reduced cholesterol biosynthesis and HRase activity in this disorder. These functional data provide support for the concept that the primary defect in phytosterolemia does not affect a trans gene locus responsible for the constitutive expression or regulation of HMG-CoA reductase.

Molecular diagnosis of multiple endocrine neoplasia type 2A

OBJECTIVE

To identify by means of genetic analyses individuals who are at risk of developing medullary thyroid cancer that is a component of multiple endocrine neoplasia.

SUBJECTS

A three-generation kindred with clinically and biochemically diagnosed medullary thyroid cancer.

METHOD

Identification of a heterozygote mutation by nucleic acid sequencing and restriction analyses.

RESULTS

A heterozygote T-->C (Cys-->Arg) mutation at codon 618 in exon 10 of the RET proto-oncogene was identified in 4 family members who had previously been diagnosed with medullary thyroid cancer. The same mutation was also found in one of the proband's presymptomatic children who subsequently underwent a pre-emptive thyroidectomy. The genetic diagnosis was confirmed by histology. No mutations were detected in any other family members.

CONCLUSION

Identification of heterozygote germline mutations in multiple endocrine neoplasia is direct, highly accurate and cost-effective. This study demonstrates that, appropriately used, molecular diagnosis can supersede conventional biochemical methods in the management of patients with inherited cancers.

Relation between retinoblastoma and p53 proteins in human papilloma viruses 16/18 positive and negative cancers of the uterine cervix

AIM

To ascertain the extent of retinoblastoma protein (pRB) expression in comparison to p53 protein and human papilloma viruses (HPV) 16/18 status in cervical carcinomas.

METHODS

Fifty cases of invasive cervical carcinoma were HPV typed for genotypes 16 and 18 using consensus primers by polymerase chain reaction (PCR). Immunohistochemistry for pRB and p53 was done on formalin fixed tissue using microwave antigen retrieval and commercially available antibodies.

RESULTS

Forty five cases were squamous carcinomas, three were adenocarcinomas, and two were adenosquamous carcinomas. Thirty one cases were HPV 16 positive and one was HPV 18. Sixteen cases showed +4 pRB expression and a further 11 were +3 positive. Seven cases were negative. Only five cases (10%) showed +4 p53 immunostaining, while seven were negative and 15 were +1. Of the 16 pRB +4 positive cases, one was negative for p53 and a further seven were +1 positive. This inverse pattern of staining between pRB and p53 had a p value of < 0.001. No correlation was observed between HPV 16/18 status and p53 and/or pRB staining.

CONCLUSIONS

pRB is expressed in the majority of cases of cervical cancer (86%), with more than 75% (+4) of the tumour cell population being positive in 16 cases (32%). There appears to be a general inverse pattern of staining between pRB (high) and p53 (low) in cervical cancer. The expression of both pRB and p53 proteins is independent of the HPV 16/18 status of the tumour.

Variations in c-erbB-2 proto-oncogene status in breast cancer tumors as detected by two different cDNA probes

We examined 232 breast carcinomas for c-erbB-2 amplification by Southern analysis using two different cDNA probes. Using these same probes, 95 of these tumors were also examined for mRNA expression by Northern analysis. Amplification was detected in 20 and 17% of the tumors with the probes pHER 2 and pCER 204, respectively, but only 10% showed amplification with both probes. A significantly higher incidence (p < 0.01) of mRNA overexpression was detected with the pHER 2 probe (34%) compared with the pCER 204 probe (16%), with only 11% of tumors demonstrating overexpression with both probes. A total of 10 tumors (11%) exhibited amplification as well as overexpression with pHER 2, whereas significantly fewer (3%) manifested both abnormalities with the larger pCER 204 probe (p < 0.05). Amplification of c-erbB-2, as detected with the pHER 2 probe but not with the pCER 204 probe, was significantly associated with the absence of both estrogen and progesterone receptors (p < 0.05 and p < 0.01, respectively). No relationship was found with other clinical prognostic indicators, such as nodal involvement and metastases. As determined by either probe, overexpression was not associated with prognostic indicators. There was no significant difference in the c-erbB-2 status of tumors from different racial groups.

Apolipoprotein E allele frequencies in a South African Indian female population

Coronary heart disease is common amongst South Africans of Indian (Asian) ancestry. As part of an investigation into risk factors in premenopausal and post-menopausal Indian nurses, we determined the apolipoprotein E genotype by means of restriction isotyping on 173 healthy nurses between the ages of 25-55 years. The apolipoprotein E allele frequencies on 346 chromosomes were: epsilon 2, 1.2% (95% confidence interval 0.06-2.66); epsilon 3, 87.6% (95% confidence interval 84.1-91.1 and epsilon 4, 11.3% (95% confidence interval 7.94-14.60). No epsilon 2/2 homozygotes were encountered. Our results demonstrate an extremely low frequency of the epsilon 2 allele, a low-normal apo epsilon 4 and a high epsilon 3 allele frequency. It is unlikely that apolipoprotein E polymorphism contributes to the high incidence of coronary heart disease in this population.

Enzyme immunoassay of oestrogen and progesterone receptors in uterine and intrauterine tissue during human pregnancy and labour

Oestrogen and progesterone receptors were studied in the non-pregnant state, in early pregnancy and at term using monoclonal antibody enzyme immunoassays. Receptors for both steroids were found in tissues from non-pregnant patients and patients in early pregnancy. At term oestrogen receptors were undetectable in all tissues studied. Progesterone receptors were undetectable in chorion, amnion and placenta at term, while present in extremely low concentrations in decidua and myometrium.

Changes in the binding characteristics of oestrogen and progesterone in uterine and intrauterine tissue with the progression of human pregnancy

The binding characteristics of oestrogen and progesterone in intrauterine tissue were studied in the non-pregnant state and throughout pregnancy using sucrose density gradient centrifugation and titration analyses. High affinity receptors for these steroids which were present in high concentrations in tissue from non-pregnant patients and patients in early pregnancy, decreased with the advance of pregnancy to undetectable levels at term. Non-saturable binding to progesterone detected in term tissue was identified as albumin and cortisol binding globulin.

Decreased concentrations and affinities of oestrogen and progesterone receptors of intrauterine tissue in human pregnancy

Cytoplasmic and nuclear receptors for oestrogen and progesterone were measured in non-pregnant myometrium and endometrium and compared to concentrations found in decidua of ectopic pregnancy (6-8 weeks gestation) and therapeutic abortions (8-16 weeks). Amnion, chorion, placenta, decidua and myometrium at full term pregnancy were also assayed for the same receptors. High affinity binding was confirmed in the non-pregnant tissue; in early pregnancy, decreases in concentrations of cytoplasmic receptors were demonstrated, these decreases becoming more marked as pregnancy progressed in the 1st trimester. Nuclear receptor concentrations were not significantly different. Significant decreases in the occurrence of positive receptors with the progression of pregnancy were also demonstrated for cytoplasmic and nuclear oestrogen and nuclear progesterone receptors. Tissue at full term pregnancy had no detectable receptors, irrespective of whether the patients were in labour or not. Increasing the range of the labelled steroids failed to demonstrate any low affinity binding sites and pre-assay removal of endogenous hormones also had no effect on receptor status. When endogenous hormones were removed, displaceable binding was demonstrated in the presence of excess unlabelled ligand. However, this binding did not conform with receptor dynamics on Scatchard analysis. Heating the cytosol prior to assay or failure to remove endogenous steroid hormones eliminated this binding. Cytosolic oestrogen and progesterone levels increased significantly in the decidua of therapeutic abortions, whilst term pregnant tissue had the highest concentration of endogenous hormones.

Breast cancer prognosis in three different racial groups in relation to steroid hormone receptor status

Follow-up studies on 466 patients over a 5-year period showed Whites to have an overall significantly longer disease-free interval and survival than Blacks and Asians. No racial differences in prognosis were seen in patients with Stage II disease (p greater than 0.2) but in Stage III, White patients had significantly longer disease-free periods than Blacks or Asians; the same was not true of survival. Whites had a 67% incidence of cytoplasmic estrogen receptor (CER) positive tumors compared with only 49% in Blacks and 41% in Asians. When tumors were assayed for CER, nuclear estrogen receptor (NER), and cytoplasmic progesterone receptor (CPR), there were no racial differences in the proportions of tumors containing all 3 receptors, but significant variations were found in neoplasms with no receptors and in those with apparently defective receptors. In White patients receptor status had no influence on prognosis (p greater than 0.3). Black patients whose tumors contained both CER and NER had a significantly better time to recurrence than those whose tumors lacked these receptors, while in Asian women the presence of CER alone, or CER together with NER, or CER, NER, and CPR, was indicative of a significantly longer disease-free period.

Estrogen and progesterone receptors in breast cancer among women of different racial groups

No differences in steroid hormone receptor status were detected in premenopausal breast cancer patients of different races. In postmenopausal women, 65% of Whites were found to have tumors positive for cytoplasmic estrogen receptors (CER) compared with 58, 52, and 41% in women of mixed race, Blacks, and Asians, respectively. The proportions of tumors which contained a full complement of receptors (CER, nuclear estrogen receptors, and cytoplasmic progesterone receptors) were similar in Blacks, Whites, and Asians in each menopausal group. In postmenopausal patients, significantly fewer White women had tumors devoid of all receptors, while having a higher incidence of tumors with an abnormal or defective receptor distribution. Neither the stage of the disease nor the degree of nodal involvement appeared to affect receptor status in any population group, but very large tumors had fewer receptors. White patients with large neoplasms had a significantly higher incidence of CER than Blacks or Asians. Similar observations were made for White patients presenting with Stage III disease, whose tumors were greater of histological Grade I tumors were positive for CER, compared with Grade III neoplasms. Indications are that receptor status is inherent to the natural history of the disease and is not influenced by clinical features.

Clinical patterns of presentation of breast cancer in women of different racial groups in South Africa

The ages at presentation of white patients with breast cancer were found to be significantly higher than those of blacks, Indians and coloureds; 73% of white women fell into the postmenopausal group, in marked contrast to only 35% of Indians, while blacks and coloureds had similar proportions of pre- and post-menopausal patients. A significantly higher incidence of poorly differentiated tumours was seen in Indian and black patients. Blacks showed a significant tendency to present with more advanced disease, while whites were generally diagnosed at a much earlier stage.

The sex hormone profile of male patients with breast cancer

The mean total serum oestradiol level was found to be significantly increased in 8 patients with carcinoma of the breast when compared with 8 healthy reference subjects matched for race, sex and age. The calculated mean free oestradiol index was also higher in these patients. There were no significant differences, however, between the levels of LH, FSH, prolactin. DHEA-S, testosterone and SHGB in the 2 groups. The patients showed a significantly increased LH response to GnRH while there was no difference in the FSH response. Only 1/7 patients had a tumour devoid of steroid hormone receptors. It may be that an increased level of circulating oestradiol-17 beta is an important factor in the aetiology of hormone-dependent male breast cancer.

Cytoplasmic and nuclear estrogen and progesterone receptors in male breast cancer

Cytoplasmic estrogen receptors were detected in 12 of 13 male breast cancer tumors. There was no significant correlation of receptor levels with the age of the patient, size and histological grading of the tumor, and stage and nodal involvement of the disease. Nuclear estrogen receptors were found in eight of 10 tumors and six of nine patients had tumors positive for cytoplasmic progesterone receptors, two of which were also found to contain nuclear progesterone receptors. The presence of cytoplasmic progesterone receptors, in addition to cytoplasmic and nuclear estrogen receptors, may be indicative of truly hormone-dependent tumors in male breast cancer. Treatment offered to patients included surgery, X-ray therapy, chemotherapy, and orchiectomy, but as yet, no general conclusions of the efficacy of the therapeutic regime can be drawn.

Nuclear and cytoplasmic oestrogen receptors in squamous carcinoma of the cervix

Nuclear and cytoplasmic oestrogen receptors (REN and REC) were sought in 5 normal cervices and in 43 specimens of squamous carcinoma of the cervix. All 3 tissues components of the 5 normal cervices contained both REN and REC. Thirty-five (81%) of the tumours contained receptors, but in only 9 (21%) were they found in both subcellular compartments. Twenty-four tumours (56%) had only REC and 2 had only REN. The potential therapeutic significance of these findings is not yet known, but it seems possible that tumours with an intact receptor mechanism might benefit from oestrogen therapy and have a more favourable prognosis.

Nuclear and cytoplasmic oestrogen receptors in human mammary carcinoma

Methods for the measurement of cytoplasmic and nuclear oestrogen receptors (CER and NER) are described. CERs and NERs were found to be labile at ambient temperatures; the receptors are stable for up to 1 year when stored in liquid nitrogen. Over a period of 5 years, 51% of the breast adenocarcinomas examined in women proved to be positive for CER; four adenocarcinomas of the breast obtained from men were all positive for CER; in those tumours examined for both CER and NER, 46% proved positive for CER and 30% positive for NER; no tumour was found to be positive for NER and negative for CER. In older female patients, the percentage of patients positive for oestrogen receptors increased and they were present in higher concentrations; in younger Indian women the same tendency was observed. The percentages of receptor-positive tumours in Indians, Blacks and Whites are similar. Neither the stage of the tumour nor the presence of nodal metastases influenced receptor positivity; there was no significant difference in the time to recurrence between receptor-positive and receptor-negative patients in the small number with reliable follow-up data.