Unravelling the nutritional threads with novel associations of cognitive functions and telomerase.

BackgroundShorter telomere length (TL) has been associated with poor health behaviors, increased risks of chronic diseases and early mortality. Excessive shortening of telomere is a marker of accelerated aging and can be influenced by oxidative stress and nutritional deficiency. Plasma n6:n3 polyunsaturated fatty acid (PUFA) ratio may impact cell aging. Increased dietary intake of marine n-3 PUFA is associated with reduced telomere attrition. However, the effect of plasma PUFA on leukocyte telomere length (LTL) and its interaction with genetic variants are not well established.MethodsA nested coronary artery disease (CAD) case-control study comprising 711 cases and 638 controls was conducted within the Singapore Chinese Health Study (SCHS). Samples genotyped with the Illumina ZhongHua-8 array. Plasma n-3 and n-6 PUFA were quantified using mass spectrometry (MS). LTL was measured with quantitative PCR method. Linear regression was used to test the association between PUFA and LTL. The interaction between plasma PUFAs and genetic variants was assessed by introducing an additional term (PUFA×genetic variant) in the regression model. Analysis was carried out in cases and controls separately and subsequently meta-analyzed using the inverse-variance weighted method. We further assessed the association of PUFA and LTL with CAD risk by Cox Proportional-Hazards model and whether the effect of PUFA on CAD was mediated through LTL by using structural equation modeling.ResultsHigher n6:n3 ratio was significantly associated with shorter LTL (p = 0.018) and increased CAD risk (p = 0.005). These associations were mainly driven by elevated plasma total n-3 PUFAs, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) (p < 0.05). There was a statistically significant interaction for an intergenic single nucleotide polymorphism (SNP) rs529143 with plasma total n-3 PUFA and DHA on LTL beyond the genome-wide threshold (p < 5 × 10− 8). Mediation analysis showed that PUFA and LTL affected CAD risk independently.ConclusionsHigher plasma n6:n3 PUFA ratio, and lower EPA and DHA n-3 PUFAs were associated with shorter LTL and increased CAD risk in this Chinese population. Furthermore, genetic variants may modify the effect of PUFAs on LTL. PUFA and LTL had independent effect on CAD risk in our study population.

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), long-chain n-3 PUFAs important for brain and heart function, can be obtained from dietary fish products or by liver synthesis from alpha-linolenic acid (alpha-LNA). Their daily human dietary requirements are not clear, and their liver synthesis rates in humans and nonhumans are unknown. We estimated whole-body (presumably liver) synthesis rates in unanesthetized rats by infusing [U-(13)C]alpha-LNA intravenously for 2 h and measuring labeled and unlabeled n-3 PUFA in arterial plasma using negative chemical ionization GC-MS. Newly synthesized esterified [(13)C]DHA, [(13)C]EPA, and [(13)C]docosapentaenoic acid (DPA) appeared in arterial plasma after 60 min of infusion, then their concentrations rose in an S-shaped manner. Esterified concentration x plasma volume data were fit with a sigmoidal equation, whose peak first derivatives provided synthesis rates of unlabeled EPA, DPA, and DHA equal to 8.40, 6.27, and 9.84 mumol/day, respectively. The DHA synthesis rate exceeded the published daily rat brain DHA consumption rate by 30-fold, suggesting that liver synthesis from alpha-LNA could maintain brain DHA homeostasis were DHA absent from the diet. This stable isotope infusion method could be used to quantify whole-body DHA synthesis rates in human subjects.

BackgroundTelomeres play a crucial role in cellular survival and its length is a predictor for onset of chronic non-communicable diseases. Studies on association between telomeres and obesity in children have brought discrepant results and the underlying mechanisms and influential factors are to be elucidated. This study aimed to investigate changes in telomere length and telomerase reverse transcriptase (TERT) DNA methylation, and further to determine their correlation with n-3 polyunsaturated fatty acids (PUFAs) in preschool children with obesity.MethodsForty-six preschool children with obesity aged 3 to 4 years were included in the study, with equal numbers of age- and gender-matched children with normal weight as control. Leukocyte telomere length was determined by the ratio of telomeric product and single copy gene obtained using real-time qPCR. DNA methylation of TERT promoter was analyzed by bisulfite sequencing. Fatty acids in erythrocytes were measured by gas chromatography with a total of 15 fatty acids analyzed. The total saturated fatty acids (SFAs), total n-6 PUFAs, total n-3 PUFAs, and the ratio of arachidonic acid (AA) to docosahexaenoic acid (DHA) were calculated. Then the correlation between leukocyte telomere length, TERT promoter methylation and fatty acids was determined.ResultsIn preschool children with obesity, leukocyte telomeres were shortened and had a negative association with the body mass index. The methylated fractions in 13 of 25 CpG sites in the TERT promoter were increased by approximately 3 to 35% in the children with obesity compared to the normal weight children. Erythrocyte lauric acid and total SFAs, lenoleic acid and total n-6 PUFAs were higher, and DHA was lower in the children with obesity than those in the children with normal weight. Correlative analysis showed that leukocyte telomere length had a positive association with total SFAs and DHA, and a negative association with the AA/DHA ratio. However, no association between erythrocyte DHA and the TERT promoter methylation was found.ConclusionThese data indicate that the reduced body DHA content and increased AA/DHA ratio may be associated with shortened leukocyte telomeres in child obesity, which is probably not involved in the TERT promoter methylation.

Mechanisms responsible for telomere maintenance are been recently elucidated: many cancers harbor mutations in alpha thalassemia/mental retardation syndrome X-linked (ATRX) gene resulting in a phenomenon known as alternative lengthening of telomeres (ALT) or point mutations in the promoter of the telomerase reverse transcriptase (TERT) gene leading to an increased telomerase expression. ATRX and TERT mutations have been recently identified also in brain tumors. In gliomas, a molecular stratification based on IDH and ATRX mutational status and 1p/19q codeletion has been suggested. ATRX mutations have been observed mainly in astrocytic tumors and TERT promoter mutations mainly in oligodendroglial tumors. Aim of our study was to evaluate the expression of both ATRX and TERT in WHO grade II gliomas and in their resected recurrences, related to a set of confirmed molecular markers and to clinical data. We performed an immunohistochemical analysis of ATRX and TERT expression in 30 grade II gliomas (astrocytomas, oligoastrocytomas and oligodendroglioma) and in their respective recurrences (grade III-IV). Also evaluation of IDH1 and p53 status and 1p/19q LOH were carried out. Loss of expression of ATRX protein has been associated to the mutated gene and ALT phenotype, while expression of TERT protein could be related to TERT promoter mutations. We found a loss of ATRX expression in 70% of cases; recurrences showed the same pattern of ATRX expression. In the most part of cases ATRX loss was associated to IDH1 and p53 mutation and intact 1p/19q, as previously observed. In the major part of cases with ATRX loss of expression TERT was not detected. TERT high expression was observed in about 30% of grade II gliomas at the first surgery, minor expression of TERT was found in grade III-IV recurrent tumors. In most case high expression of TERT was associated to 1p/19q deletion. We observed a statistically significant correlation between TERT high expression and a better outcome. Our study of protein expression of both ATRX and TERT in low grade gliomas and in their recurrences in relationship with established molecular markers and follow-up data, confirm the possibility of using immunohistochemistry in routine diagnostic procedures for better define this subset of neoplasm.

Telomere biology and its maintenance in schizophrenia spectrum disorders: Exploring links to cognition

Increased dietary ratios of ω6/ω3 polyunsaturated fatty acids have been implicated in the pathogenesis of Crohn's disease (CD), but epidemiologic data are limited. We investigated whether variants of genes that control polyunsaturated fatty acid metabolism (CYP4F3, FADS1, and FADS2), along with the dietary ratio of ω6/ω3, confers susceptibility to CD. Based on data from 182 children newly diagnosed with CD and 250 controls, we found that children who consumed a higher dietary ratio of ω6/ω3 were susceptible for CD if they were also carriers of specific variants of CYP4F3 and FADS2 genes. Our findings implicate diet-gene interactions in the pathogenesis of CD.

Beneficial physiological effects of long-chain n-3 polyunsaturated fatty acids are widely accepted but the mechanism(s) by which these fatty acids act remains unclear. Herein, we report the presence, distribution, and regulation of the levels of n-3 epoxy-fatty acids by soluble epoxide hydrolase (sEH) and a direct antinociceptive role of n-3 epoxy-fatty acids, specifically those originating from docosahexaenoic acid (DHA). The monoepoxides of the C18:1 to C22:6 fatty acids in both the n-6 and n-3 series were prepared and the individual regioisomers purified. The kinetic constants of the hydrolysis of the pure regioisomers by sEH were measured. Surprisingly, the best substrates are the mid-chain DHA epoxides. We also demonstrate that the DHA epoxides are present in considerable amounts in the rat central nervous system. Furthermore, using an animal model of pain associated with inflammation, we show that DHA epoxides, but neither the parent fatty acid nor the corresponding diols, selectively modulate nociceptive pathophysiology. Our findings support an important function of epoxy-fatty acids in the n-3 series in modulating nociceptive signaling. Consequently, the DHA and eicosapentaenoic acid epoxides may be responsible for some of the beneficial effects associated with dietary n-3 fatty acid intake.

Telomerase reverse transcriptase (TERT) promoter mutations occur frequently in cancer, have been associated with increased TERT expression and cell proliferation, and could potentially influence therapeutic regimens for melanoma. As the role of TERT expression in malignant melanoma and the non-canonical functions of TERT remain understudied, we aimed to extend the current knowledge on the impact of TERT promoter mutations and expression alterations in tumor progression by analyzing several highly annotated melanoma cohorts. Using multivariate models, we found no consistent association for TERT promoter mutations or TERT expression with the survival rate in melanoma cohorts under immune checkpoint inhibition. However, the presence of CD4+ T cells increased with TERT expression and correlated with the expression of exhaustion markers. While the frequency of promoter mutations did not change with Breslow thickness, TERT expression was increased in metastases arising from thinner primaries. As single-cell RNA-sequencing (RNA-seq) showed that TERT expression was associated with genes involved in cell migration and dynamics of the extracellular matrix, this suggests a role of TERT during invasion and metastasis. Co-regulated genes found in several bulk tumors and single-cell RNA-seq cohorts also indicated non-canonical functions of TERT related to mitochondrial DNA stability and nuclear DNA repair. This pattern was also evident in glioblastoma and across other entities. Hence, our study adds to the role of TERT expression in cancer metastasis and potentially also immune resistance.

The amount and distribution of [(13)C]docosahexaenoic acid (DHA) in plasma, platelet, and erythrocyte lipid classes were followed as a function of time (1 to 72 h) in young adults after ingestion of a single dose of [(13)C]DHA esterified in a phosphatidylcholine (PC), in using gas chromatography combustion;-isotope ratio mass spectrometry. [(13)C]DHA first appeared in plasma non-esterified fatty acids (NEFA) and triglycerides (TG), with a maximal appearance at 6 h and a further decline, then being delayed 3-fold compared to [(13)C]DHA ingested in triglycerides. Lysophosphatidylcholine (LPC) was also enriched in [(13)C]DHA, due mainly to earlier hepatic secretion, and plateaued at 6 h, whereas phosphatidylethanolamine (PE) and phosphatidylcholine (PC) containing [(13)C]DHA plateaued at 9 h. The labeling of erythrocyte and platelet phospholipids exhibited different kinetics, probably involving different metabolic pathways for [(13)C]DHA incorporation in cell membranes. Computation of the relative contribution of LPC and NEFA for delivery of [(13)C]DHA to blood cells showed that the supply to platelets occurred through NEFA. In contrast, [(13)C]DHA was carried by both LPC and NEFA to erythrocytes, which differs from what was previously been observed after intake of triglycerides labeled with [(13)C]DHA where LPC was the only source of [(13)C]DHA for erythrocytes. We conclude that the lipid form of ingested DHA affects markedly its kinetics and partly its metabolic fate.

Fish intake, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and in some cases alpha-linolenic acid (ALA) have been associated with reduced risk of cardiovascular events and death. The association between n-3 fatty acids in plasma lipids and the progression of coronary artery atherosclerosis was assessed among women with established coronary artery disease (CAD). A prospective cohort study involved postmenopausal women (n = 228) participating in the Estrogen Replacement and Atherosclerosis Trial. Quantitative coronary angiography was performed at baseline and after 3.2 +/- 0.6 (mean +/- SD) years. Women with plasma phospholipid (PL) DHA levels above the median, compared with below, exhibited less atherosclerosis progression, as expressed by decline in minimum coronary artery diameter (-0.04 +/- 0.02 and -0.10 +/- 0.02 mm, respectively; P = 0.007) or increase in percentage stenosis (1.34 +/- 0.76% and 3.75 +/- 0.74%, respectively; P = 0.006), and had fewer new lesions [2.0% (0.5-3.5%) of measured segments (95% confidence interval) and 4.2% (2.8-5.6%), respectively; P = 0.009] after adjustments for cardiovascular risk factors. Similar results were observed for DHA in the triglycerides (TGs). EPA and ALA in plasma lipids were not significantly associated with atherosclerosis progression. Consistent with higher reported fish intake, higher levels of plasma TG and PL DHA are associated with less progression of coronary atherosclerosis in postmenopausal women with CAD.

Decision letter: Common genetic variations in telomere length genes and lung cancer: a Mendelian randomisation study and its novel application in lung tumour transcriptome

Editor's evaluation: Common genetic variations in telomere length genes and lung cancer: a Mendelian randomisation study and its novel application in lung tumour transcriptome

Amyloid β and Tumorigenesis: Amyloid β-Induced Telomere Dysfunction in Tumor Cells

Cytochromes P450 (CYPs) metabolize polyunsaturated long-chain fatty acids (PUFA-LC) to several classes of oxygenated metabolites. Through use of human recombinant CYPs, we recently showed that CYP1A1, -2C19, -2D6, -2E1, and -3A4 are mainly hydroxylases, whereas CYP1A2, -2C8, -2C9, and -2J2 are mainly epoxygenases of arachidonic acid (AA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), respectively. It is worth noting that the last double bond of these PUFAs, i.e., omega6 in AA or omega3 in EPA and DHA, respectively, was preferentially epoxidized. In this study, we have characterized the stereoselectivity of this epoxidation reaction by comparison with the PUFA-LC epoxide stereoisomers obtained from the enantioselective bacterial CYP102A1 F87V. The stereoselectivity of the epoxidation of the last olefin of AA (omega6), EPA (omega3), or DHA (omega3) differed between the CYP isoforms but was similar for EPA and DHA. These data give additional insight into the PUFA-LC epoxide enantiomers generated by the hepatic CYPs.

Telomere maintenance is a fundamental hallmark of cancer. Most tumors maintain telomere length via reactivation of telomerase reverse transcriptase (TERT) expression. Identifying imaging biomarkers of TERT can enable non-invasive assessment of tumor proliferation and response to therapy. Deuterium magnetic resonance spectroscopy (DMRS) following administration of 2H-labeled substrates recently emerged as a novel, clinically translatable method of monitoring metabolic activity in vivo. The goal of this study was to delineate metabolic reprogramming associated with TERT expression and to leverage this information for non-invasive imaging of tumor burden and treatment response in gliomas. Our results indicate that TERT expression is associated with elevated levels of the redox metabolite NADH in glioblastomas and oligodendrogliomas. Mechanistically, TERT expression is associated with inhibitory phosphorylation and cytosolic sequestration of FOXO1. FOXO1, in turn, negatively regulates nicotinamide phosphoribosyl transferase (NAMPT), which is the rate-limiting enzyme in NAD+ biosynthesis. As a result, TERT upregulates NAMPT, resulting in elevated steady-state pools of NAD+ and NADH. Concomitantly, FOXO1 negatively regulates the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase, which converts NAD+ to NADH. As a result, TERT upregulates the NADH/NAD+ ratio. Since elevated NADH and NADH/NAD+ ratio drive pyruvate conversion to lactate, we then examined whether DMRS-based imaging of [U-2H]-pyruvate metabolism reports on TERT expression in gliomas. Our results indicate that doxycycline-inducible TERT silencing significantly reduces lactate production from [U-2H]-pyruvate in tumor-bearing mice. Importantly, [U-2H]-pyruvate metabolism to lactate differentiates tumor from normal brain in vivo, including at clinical field strength (3T). Furthermore, [U-2H]-pyruvate reports on early response to treatment with TERT inhibitors or with radiochemotherapy in mice bearing orthotopic patient-derived gliomas at early timepoints before radiographic alterations can be visualized by magnetic resonance imaging. Collectively, our studies integrate a mechanistic understanding of TERT biology with innovative imaging that has the potential to improve assessment of tumor burden and treatment response for glioma patients.