The APOE -219G/T and +113G/C polymorphisms affect insulin resistance among Turks

Alzheimer Disease Associated Loci: APOE Single Nucleotide Polymorphisms in Marmara Region

Alzheimer's disease (AD) is a major global health challenge, especially among individuals aged 65 or older. According to population health studies, Turkey has the highest AD prevalence in the Middle East and Europe. To accurately determine the frequencies of common and rare APOE single nucleotide polymorphisms (SNPs) in the Turkish population residing in the Marmara Region, we conducted a retrospective study analyzing APOE variants in 588 individuals referred to the Bursa Uludag University Genetic Diseases Evaluation Center. Molecular genotyping, clinical exome sequencing, bioinformatics analysis, and statistical evaluation were employed to identify APOE polymorphisms and assess their distribution. The study revealed the frequencies of APOE alleles as follows: ε4 at 9.94%, ε2 at 9.18%, and ε3 at 80.68%. The gender-based analysis in our study uncovered a tendency for females to exhibit a higher prevalence of mutant genotypes across various SNPs. The most prevalent haplotype observed was ε3/ε3, while rare APOE SNPs were also identified. These findings align with global observations, underscoring the significance of genetic diversity and gender-specific characteristics in comprehending health disparities and formulating preventive strategies.

Examining the effects of the CLU and APOE polymorphisms' combination on coronary artery disease complexed with type 2 diabetes mellitus

AIMS

Coronary artery disease (CAD) and type 2 diabetes mellitus (T2DM) are important and increasing public health problems. This study aimed to identify the impact of APOE and CLU gene polymorphisms on the prevalence of both diseases, along with the effect of these polymorphisms on lipid profile and glucose metabolism.

METHODS

736 CAD patients (≥50 stenosis) and 549 non-CAD subjects (≤30 stenosis) were genotyped for APOE (rs429358 and rs7412) and CLU (rs11136000) gene polymorphisms using hydrolysis probes in real-time PCR. Blood samples of the individuals were drawn before coronary angiography and biochemical analyses were done. The associations between the polymorphisms and the selected parameters were assessed using statistical analysis.

RESULTS

In this study, the ε2 and ε4 isoforms of apoE were associated with serum lipid levels and TC/HDL-C and LDL-C/HDL-C ratios in analysis adjusted for several confounders and in crude analysis. It was observed that CLU T allele carrier non-CAD subjects had lower glycosylated hemoglobin levels. Furthermore, the effects of APOE and CLU polymorphisms were assessed on CAD and T2DM presence. In crude and multiple logistic regression analyses, the ε2 isoform carriers had a lower risk for CAD complexed with T2DM. When the combinational effects of APOE and CLU polymorphisms were examined, the ε2 and T allele carriers had decreased risk for CAD complexed with T2DM compared to non-carriers.

CONCLUSIONS

In conclusion, the combination of APOE and CLU polymorphisms is associated with CAD-DM status along with the APOE ε2 isoform by itself, and the apoE isoforms are strongly associated with serum lipid levels.

Peripheral TREM2 mRNA levels in early and late-onset Alzheimer disease's patients

'Triggering receptor expressed on myeloid cells 2' (TREM2) gene is involved in Alzheimer's disease (AD) and TREM2 mRNA expression is known to be increased in the peripheral blood cells of AD patients. In this study, we examined the expression levels of TREM2 mRNA in peripheral leukocytes of early and late-onset AD patients. We have also investigated the effect of the presence of APOE ε4 allele on TREM2 expression. TREM2 mRNA expression was analyzed in 30 early-onset AD (EOAD) patients, 38 late-onset AD (LOAD) patients, and in their age-matched controls by using quantitative real-time polymerase chain reaction. TREM2 levels in LOAD patients were higher than EOAD. Also, in elderly controls significantly higher TREM2 levels were found compared with young controls. Moreover, APOE ε4 carriers in LOAD patients exhibited significantly higher TREM2 expression levels than APOE ε4 non-carriers and elderly controls. Also, correlation analysis showed that TREM2 mRNA expression was increased by age. The differential expression of TREM2 mRNA levels between EOAD and LOAD patients might be independent of the AD disease status and results from an age-related increase in TREM2 expression. In LOAD patients, increased age and the presence of APOE ε4 allele further increase TREM2 expression. Taken together, we can suggest that age is a factor that increases TREM2 expression, and TREM2 and APOE ε4 may interact together in the pathogenesis of LOAD.

Association of apolipoprotein E gene polymorphisms with blood lipids and their interaction with dietary factors

BACKGROUND

Several candidate genes have been identified in relation to lipid metabolism, and among these, lipoprotein lipase (LPL) and apolipoprotein E (APOE) gene polymorphisms are major sources of genetically determined variation in lipid concentrations. This study investigated the association of two single nucleotide polymorphisms (SNPs) at LPL, seven tagging SNPs at the APOE gene, and a common APOE haplotype (two SNPs) with blood lipids, and examined the interaction of these SNPs with dietary factors.

METHODS

The population studied for this investigation included 660 individuals from the Prevention of Cancer by Intervention with Selenium (PRECISE) study who supplied baseline data. The findings of the PRECISE study were further replicated using 1238 individuals from the Caerphilly Prospective cohort (CaPS). Dietary intake was assessed using a validated food-frequency questionnaire (FFQ) in PRECISE and a validated semi-quantitative FFQ in the CaPS. Interaction analyses were performed by including the interaction term in the linear regression model adjusted for age, body mass index, sex and country.

RESULTS

There was no association between dietary factors and blood lipids after Bonferroni correction and adjustment for confounding factors in either cohort. In the PRECISE study, after correction for multiple testing, there was a statistically significant association of the APOE haplotype (rs7412 and rs429358; E2, E3, and E4) and APOE tagSNP rs445925 with total cholesterol (P = 4 × 10^- 4 and P = 0.003, respectively). Carriers of the E2 allele had lower total cholesterol concentration (5.54 ± 0.97 mmol/L) than those with the E3 (5.98 ± 1.05 mmol/L) (P = 0.001) and E4 (6.09 ± 1.06 mmol/L) (P = 2 × 10^- 4) alleles. The association of APOE haplotype (E2, E3, and E4) and APOE SNP rs445925 with total cholesterol (P = 2 × 10^- 6 and P = 3 × 10^- 4, respectively) was further replicated in the CaPS. Additionally, significant association was found between APOE haplotype and APOE SNP rs445925 with low density lipoprotein cholesterol in CaPS (P = 4 × 10^- 4 and P = 0.001, respectively). After Bonferroni correction, none of the cohorts showed a statistically significant SNP-diet interaction on lipid outcomes.

CONCLUSION

In summary, our findings from the two cohorts confirm that genetic variations at the APOE locus influence plasma total cholesterol concentrations, however, the gene-diet interactions on lipids require further investigation in larger cohorts.

Apolipoprotein E gene polymorphism modifies fasting total cholesterol concentrations in response to replacement of dietary saturated with monounsaturated fatty acids in adults at moderate cardiovascular disease risk

Background

Consumption of ≤10% total energy from fat as saturated fatty acids (SFA) is recommended for cardiovascular disease risk reduction in the UK; however there is no clear guidance on the optimum replacement nutrient. Lipid-associated single-nucleotide polymorphisms (SNPs) have been shown to modify the lipid responses to dietary fat interventions. Hence, we performed a retrospective analysis in 120 participants from the Dietary Intervention and VAScular function (DIVAS) study to investigate whether lipoprotein lipase (LPL) and apolipoprotein E (APOE) SNPs modify the fasting lipid response to replacement of SFA with monounsaturated (MUFA) or n-6 polyunsaturated (PUFA) fatty acids.

Methods

The DIVAS study was a randomized, single-blinded, parallel dietary intervention study performed in adults with a moderate cardiovascular risk who received one of three isoenergetic diets rich in SFA, MUFA or n-6 PUFA for 16 weeks.

Results

After the 16-week intervention, a significant diet-gene interaction was observed for changes in fasting total cholesterol (P = 0.001). For the APOE SNP rs1064725, only TT homozygotes showed a significant reduction in total cholesterol after the MUFA diet (n = 33; −0.71 ± 1.88 mmol/l) compared to the SFA (n = 38; 0.34 ± 0.55 mmol/l) or n-6 PUFA diets (n = 37; −0.08 ± 0.73 mmol/l) (P = 0.004). None of the interactions were statistically significant for the other SNPs.

Conclusions

In summary, our findings have demonstrated a greater sensitivity of the APOE SNP rs1064725 to dietary fat composition, with a total cholesterol lowering effect observed following substitution of SFA with MUFA but not n-6 PUFA. Further large intervention studies incorporating prospective genotyping are required to confirm or refute our findings.

Trial registration

The trial was registered at www.clinicaltrials.gov as NCT01478958.

Electronic supplementary material

The online version of this article (10.1186/s12944-017-0606-3) contains supplementary material, which is available to authorized users.

APOE ε4 allele modifies the association of lead exposure with age-related cognitive decline in older individuals

BACKGROUND

Continuing chronic and sporadic high-level of lead exposure in some regions in the U.S. has directed public attention to the effects of lead on human health. Long-term lead exposure has been associated with faster cognitive decline in older individuals; however, genetic susceptibility to lead-related cognitive decline during aging has been poorly studied.

METHODS

We determined the interaction of APOE-epsilon variants and environmental lead exposure in relation to age-related cognitive decline. We measured tibia bone lead by K-shell-x-ray fluorescence, APOE-epsilon variants by multiplex PCR and global cognitive z-scores in 489 men from the VA-Normative Aging Study. To determine global cognitive z-scores we incorporated multiple cognitive assessments, including word list memory task, digit span backwards, verbal fluency test, sum of drawings, and pattern comparison task, which were assessed at multiple visits. We used linear mixed-effect models with random intercepts for individual and for cognitive test.

RESULTS

An interquartile range (IQR:14.23μg/g) increase in tibia lead concentration was associated with a 0.06 (95% confidence interval [95%CI]: -0.11 to -0.01) lower global cognition z-score. In the presence of both ε4 alleles, one IQR increase in tibia lead was associated with 0.57 (95%CI: -0.97 to -0.16; p-value for interaction: 0.03) lower total cognition z-score. A borderline association was observed in presence of one ε4 allele (Estimate-effect per 1-IQR increase: -0.11, 95%CI: -0.22, 0.01) as well as lack of association in individuals without APOE ε4 allele.

CONCLUSIONS

Our findings suggest that individuals carrying both ε4 alleles are more susceptible to lead impact on global cognitive decline during aging.

WITHDRAWN: Impact of apolipoprotein E gene polymorphism and additional gene-obesity interaction on type 2 diabetes risk in a Chinese Han old population

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Influence of multiple APOE genetic variants on cognitive function in a cohort of older men - results from the Normative Aging Study

BACKGROUND

APOE is the biomarker with the greatest known influence on cognitive function; however, the effect of complex haplotypes involving polymorphisms rs449647, rs405509, rs440446, rs429358 and rs7412 has never been studied in older populations.

METHODS

We evaluated APOE polymorphisms using multiplex PCR for genotyping and Mini-Mental State Examination (MMSE) to evaluate cognitive function in 819 individuals from VA Normative Aging Study.

RESULTS

Combinatorial analysis of all polymorphisms and individual analysis of polymorphisms rs449647, rs405509, rs440446 and rs7412 did not show any association with cognitive performance. Polymorphism rs429358 was associated with better cognitive performance (odds of MMSE ≤ 25 = 0.63, 95% CI 0.42-0.95; p = 0.03) in the oldest subsample (5th quintile of age) (odds of MMSE ≤ 25 = 0.34; 95% CI 0.13-0.86; p = 0.02). APOE allele ε4 was also associated with better cognitive performance (odds of MMSE ≤ 25 = 0.61, 95% CI 0.40-0.94; p = 0.02), also in the oldest subsample (odds of MMSE ≤ 25 = 0.35, 95% CI 0.14-0.90; p = 0.03).

CONCLUSIONS

These results suggest a beneficial effect of polymorphism rs429358 in the oldest men.

Diverging sex-specific long-term effects of cigarette smoking on fasting insulin and glucose levels in non-diabetic people

OBJECTIVES

We determined in non-diabetic persons the associations of current smoking with future glucose and insulin concentrations.

DESIGN AND METHODS

Middle-aged non-diabetic adults (n=1071) were studied in whom these values were measured at baseline and 5.2-years later.

RESULTS

Age-adjusted fasting insulin concentrations in 137 smoking men remained lower than never smokers at both surveys. While age-adjusted fasting glucose values in male never smokers declined at follow-up (p=0.037), they rose in male smokers. In 94 female smokers, age-adjusted fasting insulin values marginally declined, and fasting glucose was reduced (by 0.09 mmol/L, p=0.055) during follow-up. In contrast in never-smoking women, insulin and glucose concentrations rose (p<0.001 in both). Age-adjusted insulin levels in former smokers exhibited similar trends as never smokers. Trends were essentially unchanged when adjustment included body mass index. Current male smokers demonstrated evidence of reduced insulin sensitivity, female smokers of improved one, as assessed by QUICKI.

CONCLUSION

Smoking among Turks induces at long-term lower fasting insulin levels which represent improved insulin sensitivity in women, yet a reduced one in men.