Physical activity modulates the effect of a lipoprotein lipase mutation (D9N) on plasma lipids and lipoproteins

We investigated interactions between a mutation (D9N) in the lipoprotein lipase (LPL) gene and physical activity, as well as other lifestyle factors, on lipid traits in a population-based sample of Dutch men and women (n = 379). We used questionnaire information to classify physical activity, alcohol consumption, and smoking habits, while overweight was defined as a body mass index (BMI) > 25 kg/m2. Non-fasting blood samples were used for the determination of lipid traits and the D9N genotype. Fifteen subjects (4%) carried the mutation. They presented with higher levels of total cholesterol, apolipoprotein (apo) B and triglycerides compared to non-carriers. While no interactions with overweight, alcohol consumption, and smoking were found, a strong interaction between the D9N mutation and physical activity became apparent. Physically inactive D9N carriers (n = 5) had considerably higher total cholesterol (+2 mmol/l, p < or = 0.0001) and apo B levels (+63 mg/dl, p < or = 0.0001) compared to non-carriers of this mutation, whereas their high-density lipoprotein (HDL)-cholesterol concentrations were lower (-0.22 mmol/l, p < 0.05). This was not the case for physically active D9N carriers (n = 10). In conclusion, a common variant of the LPL gene (D9N) adversely affects plasma lipid and lipoprotein profiles. However, the unfavorable consequences may be counteracted by physical activity.     

Giant Asian honeybee or Bambara stings causing myocardial infarction,bowel gangrene and fatal anaphylaxis in Sri Lanka: a case series

The sting of Giant Asian honeybee (Apis dorsata) or Bambara in Sinhala and Karunge Kulavi in Tamil is a common environmental hazard in Sri Lanka known to cause immediate allergic reactions, which could be fatal in sensitized individuals. We reported myocardial infarction, bowel gangrene and fatal anaphylaxis in a prospectively proven case series and the association of these uncommon complications with delayed removal of stingers from the patients' skin.     

The expression of type III hyperlipoproteinemia: involvement of lipolysis genes

Type III hyperlipoproteinemia (HLP) is mainly found in homozygous apolipoprotein (APO) E2 (R158C) carriers. Genetic factors contributing to the expression of type III HLP were investigated in 113 hyper- and 52 normolipidemic E2/2 subjects, by testing for polymorphisms in APOC3, APOA5, HL (hepatic lipase) and LPL (lipoprotein lipase) genes. In addition, 188 normolipidemic Dutch control panels (NDCP) and 141 hypertriglyceridemic (HTG) patients were genotyped as well. No associations were found for four HL gene polymorphisms and two LPL gene polymorphisms and type III HLP. The frequency of the rare allele of APOC3 3238 G>C and APOA5 −1131 T>C (in linkage disequilibrium) was significantly higher in type III HLP patients when compared with normolipidemic E2/2 subjects, 15.6 vs 6.9% and 15.1 vs 5.8%, respectively, (P<0.05). Furthermore, the frequencies of the APOA5 c.56 G>C polymorphism and LPL c.27 G>A mutation were higher in type III HLP patients, though not significant. Some 58% of the type III HLP patients carried either the APOA5 −1131 T>C, c.56 G>C and/or LPL c.27 G>A mutation as compared to 27% of the normolipidemic APOE2/2 subjects (odds ratio 3.7, 95% confidence interval=1.8–7.5, P<0.0001). The HTG patients showed similar allele frequencies of the APOA5, APOC3 and LPL polymorphisms, whereas the NDCP showed similar allele frequencies as the normolipidemic APOE2/2. Patients with the APOC3 3238 G>C/APOA5 −1131 T>C polymorphism showed a more severe hyperlipidemia than patients without this polymorphism. Polymorphisms in lipolysis genes associate with the expression and severity of type III HLP in APOE2/2.     

Common genetic variants do not associate with CAD in familial hypercholesterolemia

In recent years, multiple loci dispersed on the genome have been shown to be associated with coronary artery disease (CAD). We investigated whether these common genetic variants also hold value for CAD prediction in a large cohort of patients with familial hypercholesterolemia (FH). We genotyped a total of 41 single-nucleotide polymorphisms (SNPs) in 1701 FH patients, of whom 482 patients (28.3%) had at least one coronary event during an average follow up of 66 years. The association of each SNP with event-free survival time was calculated with a Cox proportional hazard model. In the cardiovascular disease risk factor adjusted analysis, the most significant SNP was rs1122608:G>T in the SMARCA4 gene near the LDL-receptor (LDLR) gene, with a hazard ratio for CAD risk of 0.74 (95% CI 0.49–0.99; P-value 0.021). However, none of the SNPs reached the Bonferroni threshold. Of all the known CAD loci analyzed, the SMARCA4 locus near the LDLR had the strongest negative association with CAD in this high-risk FH cohort. The effect is contrary to what was expected. None of the other loci showed association with CAD.     

Detection of genomic deletions of PKP2 in arrhythmogenic right ventricular cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited myocardial disease that predominantly affects the right ventricle and is associated with ventricular arrhythmias that may lead to sudden cardiac death. Mutations within at least seven separate genes have been identified to cause ARVC, however a genetic culprit remains elusive in approximately 50% of cases. Although negative genetic testing may be secondary to pathogenic mutations within undiscovered genes, an alternative explanation may be the presence of large deletions or duplications involving known genes. These large copy number variants may not be detected with standard clinical genetic testing which is presently limited to direct DNA sequencing. We describe two cases of ARVC possessing large deletions involving plakophilin‐2 (PKP2) identified with microarray analysis and/or multiplex ligation‐dependent probe amplification (MLPA) that would have been classified as genotype negative with standard clinical genetic testing. A deletion of the entire coding region of PKP2 excluding exon 1 was identified in patient 1 and his son. In patient 2, MLPA analysis of PKP2 revealed deletion of the entire gene with subsequent microarray analysis demonstrating a de novo 7.9 Mb deletion of chromosome 12p12.1p11.1. These findings support screening for large copy number variants in clinically suspected ARVC cases without clear disease causing mutations following initial sequencing analysis.     

Episodic variations of prolactin, thyroid-stimulating hormone, luteinizing hormone, melatonin and cortisol in infertile women with subclinical hypothyroidism

Preliminary data have suggested that female infertility due to corpus luteum insufficiency may be caused by subclinical hypothyroidism [exaggerated thyroid-stimulating hormone (TSH) response to thyrotrophin- releasing hormone (TRH) stimulation]. L-Thyroxine supplementation has been recommended to achieve pregnancies in subclinical hypothyroid women. This controlled study was carried out in order to investigate the biochemical diagnosis of subclinical hypothyroidism as a possible infertility factor. Five infertile patients (aged 25-36 years) with subclinical hypothyroidism (n = 4, stimulated TSH >20 microU/ml) or primary hypothyroidism (n = 1) and five healthy controls (aged 22-39 years) with normal thyroid function (stimulated TSH <15 microU/ml), regular cycles and no history of infertility were studied in the early follicular phase. In the pre-study evaluation, eight of 23 volunteers (34.8%) had to be excluded because of subclinical hypothyroidism with stimulated TSH values (TSHs) >15 microU/ml. Cycle function of patients and controls was compared by the method of LH pulse pattern analysis. Therefore blood samples were drawn every 10 min during a 24 h period. Sleep was recorded from midnight to 7 a.m. Repetition of the TRH tests at the end of the 24 h blood sampling period confirmed the difference in stimulated TSH values of the two study groups. Pulse analysis for luteinizing hormone (LH), TSH and prolactin showed no differences between patients and controls for pulse frequency, amplitude, height, length, area under curve (AUC) and the 24 h mean. Even the hypothyroid patient had a normal LH pulse pattern. Additional measurement of melatonin in pooled sera every 30 min gave the well-documented diurnal profiles during day and night for both groups. Patients had significantly higher melatonin values at seven time points during the night. Peaks for LH, TSH, prolactin and cortisol were correlated with the sleep stages wake, rapid eye movement, 1 + 2 and 3 + 4. We concluded that corpus luteum insufficiency in female infertility cannot be explained by subclinical hypothyroidism and thus should not be treated with L-thyroxine for fertility reasons.      

Assisted reproductive technology and complex chromosomal rearrangements: the limits of ICSI

Complex chromosomal rearrangements are very rare events in the human population. According to our knowledge on the consequences of simple reciprocal translocations for male fertility, translocations involving three or more chromosomes are thought to lead to severe reproductive impairments in terms of meiotic disturbance or chromosomal imbalance of gametes. We report the case of a 48 year old man whose sperm count revealed either oligozoospermia (<10(3) spermatozoa/ml) or azoospermia. He was referred to the laboratory for in-vitro fertilization after intracytoplasmic sperm injection. Cytogenetic investigations showed a complex chromosomal rearrangement involving firstly a translocation between the short arm of chromosome 7 and the long arm of chromosome 13 and secondly a translocation between the short arm of the same chromosome 13 and the short arm of chromosome 9. Diagnosis was ascertained by fluorescence in-situ hybridization and staining of the nucleolar organizer regions. Theoretical study of the translocated chromosomes predicted a 'chain' configuration of the hexavalent at the pachytene stage of meiosis. In all, 32 modes of segregation were considered and only one resulted either in a normal or a balanced gamete karyotype. Genetic counselling and choice of appropriate artificial reproduction technique are discussed.      

The GAP-related domain of tuberin, the product of the TSC2 gene, is a target for missense mutations in tuberous sclerosis

Tuberous sclerosis is an autosomal dominant trait in which the dysregulation of cellular proliferation and differentiation results in the development of hamartomatous growths in many organs. The TSC2 gene is one of two genes determining tuberous sclerosis. Inactivating germline mutations of TSC2 in patients with tuberous sclerosis and somatic loss of heterozygosity at the TSC2 locus in the associated hamartomas indicate that TSC2 functions as a tumour suppressor gene and that loss of function is critical to expression of the tuberous sclerosis phenotype. The TSC2 product, tuberin, has a region of homology with the GTPase activating protein rap1GAP and stimulates the GTPase activity of rap1a and rab5a in vitro. Here we show that the region of homology between tuberin and human rap1GAP and the murine GAP mSpa1 is more extensive than previously reported and spans approximately 160 amino acid residues encoded within exons 34-38 of the TSC2 gene. Single strand conformation polymorphism analysis of these exons in 173 unrelated patients with tuberous sclerosis and direct sequencing of variant conformers together with study of additional family members enabled characterisation of disease associated mutations in 14 cases. Missense mutations, which occurred in exons 36, 37 and 38 were identified in eight cases, four of whom shared the same recurrent change P1675L. Each of the five different missense mutations identified was shown to occur de novo in at least one sporadic case of tuberous sclerosis. The high proportion of missense mutations detected in the region of the TSC2 gene encoding the GAP-related domain supports its key role in the regulation of cellular growth.