Telomere shortening over 6 years is associated with increased subclinical carotid vascular damage and worse cardiovascular prognosis in the general population

INTRODUCTION

Leucocyte telomere length (LTL) is an important determinant of telomere function and cellular replicative capacity. The aim of the present study was to examine prospectively the associations between telomere shortening (TS) and both the progression of atherosclerosis and the incidence of cardiovascular events (CVEs).

MATERIALS AND METHODS

Leucocyte telomere length was measured by quantitative polymerase chain reaction to determine the ratio of telomere length to single-copy gene (T/S) in 768 subjects (462 female and 306 male) enrolled in a large general population survey [the Progressione della Lesione Intimale Carotidea (PLIC study)]. Common carotid artery intima-media thickness was determined at baseline and after 6 years of follow-up, and the associations between TS and the progression of atherosclerosis and incidence of CVEs were evaluated.

RESULTS

Mean LTL was 1.25 ± 0.92 T/S (median 1.14) at baseline and 0.70 ± 0.37 T/S (median 0.70) after 6 years of follow-up. Median 6-year LTL change was -0.46 T/S [interquartile range (IQR) -0.57 to 1.06], equating to -0.078 T/S [IQR(-0.092 to 0.176)] per year. Of note, telomere lengthening occurred in 30.4% of subjects. After adjustment for classical cardiovascular disease (CVD) risk factors (age, gender, smoking, physical activity, alcohol consumption, systolic blood pressure, glucose levels, lipid profile and therapies), TS was associated with incident subclinical carotid vascular damage [hazard ratio (HR) 5.19, 95% confidence interval (CI) 1.20-22.4, P = 0.028]. Finally, subjects in whom LTL shortened over time showed an increased risk of incident CVE, compared to those in whom LTL lengthened (HR 1.69, CI 1.02-2.78, P = 0.041).

CONCLUSION

These data indicate that TS is associated with increased risk of subclinical carotid vascular damage and increased incidence of CVEs beyond CVD risk factors in the general population, whereas LTL lengthening is protective.

Upregulation of gingival tissue miR-200b in obese periodontitis subjects

Increased local immune and inflammatory responses in obese individuals with periodontitis may explain the aggressive clinical presentation and altered treatment response when compared to that of normal weight subjects. Our goal was to identify any differences in microRNA (miRNA) expression profiles of gingival tissue in periodontitis when obesity is present, which may suggest novel molecular pathways that this miRNA network may affect. Total RNA was extracted from gingival tissue biopsies collected from normal weight and obese individuals with periodontitis; miRNA expression profiling was performed with Affymetrix GeneChip miRNA 3.0 arrays; and results were validated with quantitative reverse transcription polymerase chain reaction (qRT-PCR). In silico identification of previously confirmed miRNA gene targets was conducted through miRTarBase and miRWalk databases, and pathway enrichment analysis identified enriched miRNA gene sets. Expression of selected genes in the same biopsy samples was tested with qRT-PCR. The gingival tissue miRNA profile of obese patients, compared to that of normal weight patients, showed 13 upregulated and 22 downregulated miRNAs, among which miR-200b was validated by qRT-PCR to be significantly increased in obesity. Functional analysis of 51 experimentally validated miR-200b gene targets identified enrichment of genes involved in cell motility, differentiation, DNA binding, response to stimulus, and vasculature development pathways not previously identified in the obesity-specific disease profile. Furthermore, the expression of the miR-200b gene targets ZEB1/2, GATA2, and KDR was confirmed by qRT-PCR as being lower in obese patients with periodontitis versus normal weight patients, suggesting a role of miR-200b in regulation of a set of gene targets and biological pathways relevant to wound healing and angiogenesis. Functional studies to explore the role of miR-200b in the above processes may offer new insights on putative therapeutic targets for this group of patients.

Variants of ADRA2A are associated with fasting glucose, blood pressure, body mass index and type 2 diabetes risk: meta-analysis of four prospective studies

AIMS/HYPOTHESIS

We quantified the effect of ADRA2A (encoding α-2 adrenergic receptor) variants on metabolic traits and type 2 diabetes risk, as reported in four studies.

METHODS

Genotype data for ADRA2A single nucleotide polymorphisms (SNPs) rs553668 and rs10885122 were analysed in >17,000 individuals (1,307 type 2 diabetes cases) with regard to metabolic traits and type 2 diabetes risk. Two studies (n = 9,437), genotyped using the Human Cardiovascular Disease BeadChip, provided 12 additional ADRA2A SNPs.

RESULTS

Rs553668 was associated with per allele effects on fasting glucose (0.03 mmol/l, p = 0.016) and type 2 diabetes risk (OR 1.17, 95% CI 1.04-1.31; p = 0.01). No significant association was observed with rs10885122. Of the 12 SNPs, several showed associations with metabolic traits. Overall, after variable selection, rs553668 was associated with type 2 diabetes risk (OR 1.38, 95% CI 1.09-1.73; p = 0.007). rs553668 (per allele difference 0.036 mmol/l, 95% CI 0.008-0.065) and rs17186196 (per allele difference 0.066 mmol/l, 95% CI 0.017-0.115) were independently associated with fasting glucose, and rs17186196 with fasting insulin and HOMA of insulin resistance (4.3%, 95% CI 0.6-8.1 and 4.9%, 95% CI 1.0-9.0, respectively, per allele). Per-allele effects of rs491589 on systolic and diastolic blood pressure were 1.19 mmHg (95% CI 0.43-1.95) and 0.61 mmHg (95% CI 0.11-1.10), respectively, and those of rs36022820 on BMI 0.58 kg/m(2) (95% CI 0.15-1.02).

CONCLUSIONS/INTERPRETATION

Multiple ADRA2A SNPs are associated with metabolic traits, blood pressure and type 2 diabetes risk. The α-2 adrenergic receptor should be revisited as a therapeutic target for reduction of the adverse consequences of metabolic trait disorders and type 2 diabetes.

Polymorphism of the heme oxygenase-1 gene and cerebral aneurysms

Inflammation is thought to play an important role in intracranial aneurysm formation. Heme-oxygenase-1(HO-1) is a novel anti-inflammatory factor. A length polymorphic variant of the HO-1 gene promoter region, comprising (GT)n dinucleotide repeats, is associated with altered levels of gene transcription: long (= 36 GT) repeats are associated with decreased HO-1. We hypothesized that patients with aneurysmal subarachnoid haemorrhage were more likely to have long repeats than controls. Sixty-nine patients with aneurysms and 230 age-matched controls were genotyped, and allelic repeats were classed as <36 (short and medium repeats) and >36 (long repeats). Patients were more likely to have =36 repeats than controls (8 v. 4%, p = 0.037. Control patients without aneurysms were more likely to have short alleles. Thus, facilitated up-regulation of HO-1 may be a protective anti-inflammatory factor against the development of intracranial aneurysms, whilst a propensity to a more pro-inflammatory state may put individuals at risk. However, because of the relatively small sample size and modest statistical significance, the data must be interpreted with caution and the association needs to be confirmed in further samples.

Association of the hormone sensitive lipase -60C > G variant with fasting insulin levels in healthy young men

BACKGROUND AND AIM

Hormone sensitive lipase (HSL) is the rate-limiting enzyme in triglyceride intracellular lipolysis, generating free fatty acids for energy utilisation. HSL is also expressed in pancreatic beta-cells where its activity may affect insulin secretion. We previously identified an HSL promoter variant, -60C > G, which in vitro exhibits 40% reduced promoter activity.

METHODS AND RESULTS

In this study we examined the association of the HSL -60C > G on fasting lipid, insulin and glucose levels and the response to an oral fat tolerance test and an oral glucose tolerance test in 744 healthy young men participating in the second European Atherosclerosis Study. There was no case control difference in frequency of the rare -60G allele, however there was a North-to-South gradient in the frequency of the -60G allele, ranging from 0.037 (95% CI 0.01-0.07) in the Baltic regions to 0.087 (95% CI 0.05-0.12) in the South of Europe. When the group was analysed as a whole, there was no significant difference in fasting lipid or glucose values, body mass index, waist/hip ratio or blood pressure and no significant heterogeneity between cases and controls. There was, however, a significant association with fasting insulin measures [-60CC (n = 608) 11.95 mU/L vs -60 CG + GG (n = 79) 10.62 mU/L p = 0.01] and with the homeostasis model assessment of insulin resistance (HOMA-IR) (p = 0.04) and the homeostatic assessment of beta-cells function (HOMA-B); (p = 0.008).

CONCLUSION

Even in these healthy young men, HSL-60 C > G allele was associated with effects on fasting insulin measures, and differences in insulin resistance and beta-cells function.

Variation in the promoter of the human hormone sensitive lipase gene shows gender specific effects on insulin and lipid levels: results from the Ely study

We previously identified a hormone sensitive lipase (HSL) promoter variant, -60C>G, which in vitro exhibits 40% reduced promoter activity. In this study we examined the effect of the -60C>G on glycemic and lipid measures in the population based Ely study of metabolic function and insulin resistance in 218 middle-aged men and 276 middle-aged women. Adipose tissue HSL is the rate-limiting step in triglyceride lipolysis, generating free fatty acids for energy utilization. HSL is also expressed in pancreatic beta-cells where its activity therefore may affect insulin secretion. In the women, carriers of the HSL -60G allele had significantly lower fasting insulin levels (P=0.0005) and a lower total area under the curve for insulin during the oral glucose tolerance test (P=0.005). There was no demonstrable association in men with these measures of insulin sensitivity but carriers of the -60G allele had significantly lower fasting non-esterified fatty acid (NEFA) levels (P=0.025) and higher low density lipoprotein cholesterol levels (P=0.02) than men who were non-carriers. This study provides additional evidence for a role for HSL in the development of insulin resistance, from which carriers of the -60G allele, associated here with markers of insulin sensitivity in women, and with lower NEFA levels in men, might be protected.

Effect of microsomal triglyceride transfer protein gene variants (-493G > T, Q95H and H297Q) on plasma lipid levels in healthy middle-aged UK men

Microsomal triglyceride transfer protein (MTP) plays a central role in the synthesis of lipoproteins by shuttling lipids between phospholipid membranes to apoB. We have examined the effect of three MTP gene variants, -493G > T, Q95H and H297Q, in 2831 healthy UK middle-aged men. The rare allele frequencies were: 0.25 (95% CI 0.24-0.26) for -493T, 0.054 (95% CI 0.05-0.06) for 95H and 0.32 (95% CI 0.31-0.33) for 297Q. The three variants were in strong allelic association in all pairwise combinations (p < 0.001). None of the variant sites were associated with significant differences in cholesterol, triglyceride, apoB or apoAI levels. When stratified by tertiles of triglycerides for the H297Q variant alone there was a significant effect on apoB levels in men in the top tertile (p = 0.01). Considering the -493G > T and H297Q genotype in combination on baseline levels, individuals with three or four rare alleles had 6.6% higher mean apoB levels compared to the rest (p = 0.007). Therefore, homozygosity for 297Q at higher triglyceride (Tg) levels, or in combination with -493G > T, is associated with a raising effect on apoB levels, suggesting the importance of modest differences in MTP activity in determining hepatic secretion of lipoproteins in healthy men.

Familial lipoprotein lipase (LPL) deficiency: a catalogue of LPL gene mutations identified in 20 patients from the UK, Sweden, and Italy

The aim of this study was to identify mutations in the lipoprotein lipase (LPL) gene in 20 unrelated patients with familial lipoprotein deficiency (FLLD) and to investigate the genotype/phenotype relationship. The previously reported G188E mutation (Monsalve et al., J Clin Invest 86:728-734, 1990) was screened for and found to be present in seven individuals (12/40 alleles). In addition, three patients were heterozygous for the 2.0 kb insertion (Langlois et al., Proc Nalt Acad Sci US 86:948-952, 1989). Two approaches were taken for new mutation detection; single-strand conformation polymorphism and sequencing to identify micro-mutations in the proximal promoter and exons 1-9 of the LPL gene and Southern blotting to identify gross mutations. Ten different point mutations were found (W86G, A158T, H183Q, G188E, S193R, P207L, L252X, N291S, M301T, L303P). Additionally, a two nucleotide deletion in exon 6 (delta1006-1007), a six nucleotide deletion in exon 8 (delta1441-1447), and a silent substitution in the wobble position of codon E118 were identified. In vitro mutagenesis and expression in COS-B cells suggested that the A158T and S193R substitutions virtually abolished enzyme activity. In analysing the genotype/phenotype relationship, there was no strong association between age at diagnosis, severity of symptoms, lipid levels, and the nature/position of the mutation. Triglyceride levels, however, were higher in compound heterozygotes compared to true homozygotes, possibly reflecting increased instability of heterodimers. Overall, 29 of 40 (72.5%) mutant alleles were identified. Failure to identify the mutation in 11 alleles might reflect the inadequacy of the method or the possibility that mutations lie within regions of the gene not screened in the study because of lack of availability of sequence.

Identification of genetic variation in the human hormone-sensitive lipase gene and 5' sequences: homology of 5' sequences with mouse promoter and identification of potential regulatory elements

Hormone-sensitive lipase (HSL) plays a crucial role in triglyceride hydrolysis in adipose tissue and exhibits cholesterol hydrolase activity in steroidogenic tissue and macrophages. Thus, common genetic variation in the HSL gene could affect both energy metabolism and atherogenesis. Using overlapping single-strand conformational polymorphism analysis (SSCP), a common single base change (T/C) in intron 4 [allele frequency 0.012 (95% CI 0.007-0. 018)] and a variable CA repeat in intron 6 with 9 alleles (heterozygosity index = 0.66) were identified. Sequence of 1.123 kb upstream from the reported 5'UTR (1) which includes intron B, exon B, and 159 bp of the promoter (2) was obtained and a single common nucleotide change, -60C/G [allele frequency 0.052 (95% CI 0.039-0. 064)], identified. Preliminary in vitro studies show that the -60G construct has 38.5% lower luciferase activity compared to the -60C construct (P = 0.035), suggesting a functional change affecting HSL gene expression. The 5' sequence shows 57-59% homology with the mouse promoter with higher homology at potential regulatory motifs. Thus, the 1.7 kb of 5' sequences is well conserved and may play a part in the regulation of HSL gene expression.