Genetic variants associated with altered plasma levels of C-reactive protein are not associated with late-life cognitive ability in four Scottish samples

Neurology-related protein biomarkers are associated with cognitive ability and brain volume in older age

Identifying biological correlates of late life cognitive function is important if we are to ascertain biomarkers for, and develop treatments to help reduce, age-related cognitive decline. Here, we investigated the associations between plasma levels of 90 neurology-related proteins (Olink® Proteomics) and general fluid cognitive ability in the Lothian Birth Cohort 1936 (LBC1936, N = 798), Lothian Birth Cohort 1921 (LBC1921, N = 165), and the INTERVAL BioResource (N = 4451). In the LBC1936, 22 of the proteins were significantly associated with general fluid cognitive ability (β between -0.11 and -0.17). MRI-assessed total brain volume partially mediated the association between 10 of these proteins and general fluid cognitive ability. In an age-matched subsample of INTERVAL, effect sizes for the 22 proteins, although smaller, were all in the same direction as in LBC1936. Plasma levels of a number of neurology-related proteins are associated with general fluid cognitive ability in later life, mediated by brain volume in some cases.

A systematic review of existing peripheral biomarkers of cognitive aging: Is there enough evidence for biomarker proxies in behavioral modification interventions?: An initiative in association with the nutrition, exercise and lifestyle team of the Canadian Consortium on Neurodegeneration in Aging

Peripheral biomarkers have shown significant value in predicting brain health and may serve as a useful proxy measurement in the assessment of evidence-based lifestyle behavior modification programs, including physical activity and nutrition programs, that aim to maintain cognitive function in late life. The aim of this systematic review was to elucidate which peripheral biomarkers are robustly associated with cognitive function among relatively healthy non-demented older adults. Following the standards for systematic reviews (PICO, PRIMSA), and employing MEDLINE and Scopus search engines, 222 articles were included in the review. Based on the review of biomarker proxies of cognitive health, it is recommended that a comprehensive biomarker panel, or biomarker signature, be developed as a clinical end point for behavior modification trials aimed at enhancing cognitive function in late life. The biomarker signature should take a multisystemic approach, including lipid, immune/inflammatory, and metabolic biomarkers in the biological signature index of cognitive health.

The protected survivor model: Using resistant successful cognitive aging to identify protection in the very old

For some cardiovascular risk factors, association with risk for cognitive impairment observed in early old age is reduced, or paradoxically even reversed, as age of outcome increases. Successful cognitive aging is intact cognition in the oldest-old; we define resistant successful cognitive aging as successful cognitive aging despite high risk. The protected survivor model posits that a minority of the general population has a protective factor that mitigates the negative effect of a risk factor on successful cognitive aging for the unprotected majority. As age increases, differential failure rates increase the proportion of survivors with protection. Among the unprotected, the proportion with low risk increases, but among those with protection, high risk and low risk do not differ. Due to differential mortality, half the survivors are eventually protected - a majority among those with high risk, and a minority among those with low risk. According to the protective survivor model, an example of Simpson's paradox, the association of the risk factor with survival does not change within an individual, but the association in the surviving population changes as its age increases. We created quantitative illustrations of a simplified protected survivor model applied to successful cognitive aging to explain how the usual association of a risk factor with cognitive decline is reversed in the very old. In the illustrations, probability of subsequent survival was higher for survivors with high risk (mostly protected) than low risk (mostly not protected), an example of Simpson's paradox. Resistance to disease despite the presence of risk factors is consistent with the presence of countervailing protection. Based on the protected survivor model, we hypothesize that studies seeking protective factors against cognitive decline will be more effective by limiting a successful cognitive aging sample to resistant successful cognitive aging - to contrast with a sample without successful cognitive aging.

Serum High-Sensitive C-Reactive Protein Level and CRP Genetic Polymorphisms Are Associated with Abdominal Aortic Aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA) development involves an inflammatory process with a potential genetic background. C-reactive protein (CRP) is an acute phase protein and was elevated in patients with AAA. The aim of this study was to investigate the association among serum high-sensitive CRP (hsCRP) concentration, its CRP genetic polymorphisms, and AAA.

METHODS

Serum hsCRP concentrations and abdominal aorta diameters were measured, and correlation analysis between them was performed in 155 unrelated participants with AAA and 310 non-AAA controls. Tagging single nucleotide polymorphisms (SNPs) in the CRP gene (rs1417938, rs1130864, rs1205, rs1800947) were identified via HapMap. Stratification analysis was performed to evaluate the effects of SNPs on the concentration of serum hsCRP. The association between 4 SNPs and AAA was assessed by unconditional logistic regressions.

RESULTS

Elevated serum hsCRP level was found to be an independent risk factor for AAA (odds ratio [OR] = 3.91, 95% confidence interval [CI]: 2.45, 6.23) after adjustment for confounding factors. Concentrations of serum hsCRP were significant different (P = 0.01) in 4 subgroups derived from participants with abdominal aorta diameter <20 mm, 20-29 mm, 30-54 mm, and ≥55 mm. Stratification analysis revealed there was significant high frequency of elevated hsCRP levels in subjects carrying rs1205-CC genotype compared with those carrying rs1205-TT or CT genotypes (P = 0.004, OR = 2.31, 95% CI: 1.30, 4.11), suggesting that the genotype CC of rs1205 was associated with higher serum hsCRP levels. However, the frequency of rs1205-CC in AAA patients (15.3%) was similar to control subjects (17.6%), and we could not confirm rs1205-CC was the genetic risk factor of AAA (OR = 1.18, 95% CI: 0.69, 2.01). Moreover, we found another CRP polymorphism rs1417938-TT had a significantly higher likelihood of AAA than the AT genotype (OR = 2.07, 95% CI: 1.06, 4.03) for the first time, indicating there was perhaps a role for rs14117938-T polymorphism that correlates with AAA.

CONCLUSIONS

Serum hsCRP may be related to the presence of AAA and abdominal aorta diameter. Genetic polymorphisms in CRP gene could influence the concentration of serum hsCRP and the likelihood of AAA, but the causal relationship between AAA and CRP should be demonstrated further.

Evaluating the physiological reserves of older patients with cancer: the value of potential biomarkers of aging?

Aging of an individual entails a progressive decline of functional reserves and loss of homeostasis that eventually lead to mortality. This process is highly individualized and is influenced by multiple genetic, epigenetic and environmental factors. This individualization and the diversity of factors influencing aging result in a significant heterogeneity among people with the same chronological age, representing a major challenge in daily oncology practice. Thus, many factors other than mere chronological age will contribute to treatment tolerance and outcome in the older patients with cancer. Clinical/comprehensive geriatric assessment can provide information on the general health status of individuals, but is far from perfect as a prognostic/predictive tool for individual patients. On the other hand, aging can also be assessed in terms of biological changes in certain tissues like the blood compartment which result from adaptive alterations due to past history of exposures, as well as intrinsic aging processes. There are major signs of 'aging' in lymphocytes (e.g. lymphocyte subset distribution, telomere length, p16INK4A expression), and also in (inflammatory) cytokine expression and gene expression patterns. These result from a combination of the above two processes, overlaying genetic predispositions which contribute significantly to the aging phenotype. These potential "aging biomarkers" might provide additional prognostic/predictive information supplementing clinical evaluation. The purpose of the current paper is to describe the most relevant potential "aging biomarkers" (markers that indicate the biological functional age of patients) which focus on the biological background, the (limited) available clinical data, and technical challenges. Despite their great potential interest, there is a need for much more (validated) clinical data before these biomarkers could be used in a routine clinical setting. This manuscript tries to provide a guideline on how these markers can be integrated in future research aimed at providing such data.

Association study of candidate gene polymorphisms and obesity in a young Mexican-American population from South Texas

BACKGROUND AND AIMS

Obesity is increasingly a health problem and a risk factor for diabetes in young Mexican-American populations. Genetic association studies in older, mostly non-Hispanic populations have reported that polymorphisms in the candidate genes HSD11B1, CRP, ADIPOQ, PPARG, ANKK1, ABCC8 and SERPINF1 are associated with obesity or diabetes. We analyzed the polymorphisms rs846910, rs1205, rs1501299, rs1801282, rs1800497, rs757110 and rs1136287 in these candidate genes, for association with obesity and metabolic traits in a young Mexican-American population from south Texas.

METHODS

Genotyping of the seven common SNPs were performed by allelic discrimination assays in 448 unrelated Mexican Americans (median age = 16 years) from south Texas. χ(2) tests and regression analyses using additive models were used for genetic association analyses adjusting for covariates; p values were corrected for multiple testing by permutation analyses.

RESULTS

rs1800497 (ANKK1) shows association with waist circumference (p = 0.009) and retains the association (p = 0.03) after permutation testing. Analysis of metabolic quantitative traits shows that rs846910 (HSD11B1) was associated with HOMA-IR (p = 0.04) and triglycerides (p = 0.03), and rs1205 (CRP) with HOMA-IR (p = 0.03) and fasting glucose levels (p = 0.007). However, the quantitative traits associations are not maintained after permutation analysis. None of the other SNPs in this study showed associations with obesity or metabolic traits in this young Mexican-American population.

CONCLUSIONS

We report a potential association between rs1800497 (linked to changes in brain dopamine receptor levels) and central obesity in a young Mexican-American population.

C-reactive protein and genetic variants and cognitive decline in old age: the PROSPER study

BACKGROUND

Plasma concentrations of C-reactive protein (CRP), a marker of chronic inflammation, have been associated with cognitive impairment in old age. However, it is unknown whether CRP is causally linked to cognitive decline.

METHODS AND FINDINGS

Within the Prospective Study of Pravastatin in the Elderly at Risk (PROSPER) trial, with 5680 participants with a mean age of 75 years, we examined associations of CRP levels and its genetic determinants with cognitive performance and decline over 3.2 years mean follow-up. Higher plasma CRP concentrations were associated with poorer baseline performance on the Stroop test (P = 0.001) and Letter Digit Tests (P<0.001), but not with the immediate and delayed Picture Learning Test (PLT; both P>0.5). In the prospective analyses, higher CRP concentrations associated with increased rate of decline in the immediate PLT (P = 0.016), but not in other cognitive tests (all p>0.11). Adjustment for prevalent cardiovascular risk factors and disease did not change the baseline associations nor associations with cognitive decline during follow-up. Four haplotypes of CRP were used and, compared to the common haplotype, carrierships associated strongly with levels of CRP (all P<0.007). In comparison to strong associations of apolipoprotein E with cognitive measures, associations of CRP haplotypes with such measures were inconsistent.

CONCLUSION

Plasma CRP concentrations associate with cognitive performance in part through pathways independent of (risk factors for) cardiovascular disease. However, lifelong exposure to higher CRP levels does not associate with poorer cognitive performance in old age. The current data weaken the argument for a causal role of CRP in cognitive performance, but further study is warranted to draw definitive conclusions.

Genetic variation in C-reactive protein in relation to colon and rectal cancer risk and survival

C-reactive protein (CRP), a biomarker of inflammation, has been shown to be influenced by genetic variation in the CRP gene. In this study, we test the hypothesis that genetic variation in CRP influences both the risk of developing colon and rectal cancer and survival. Two population-based studies of colon cancer (n = 1,574 cases, 1,970 controls) and rectal (n = 791 cases, 999 controls) were conducted. We evaluated four CRP tagSNPs: rs1205 (G > A, 3' UTR); rs1417938 (T > A, intron); rs1800947 (G > C, L184L); and rs3093075 (C > A, 3' flanking). The CRP rs1205 AA genotype was associated with an increased risk of colon cancer (OR 1.3, 95%CI 1.1-1.7), whereas the rs3093075 A allele was associated with a reduced risk of rectal cancer (OR 0.7, 95%CI 0.5-0.9). The strongest association for the rs1205 polymorphism and colon cancer was observed among those with KRAS2 mutations (OR 1.5, 95%CI 1.1-2.0). The CRP rs1205 AA genotype also was associated with an increased risk of CIMP+ rectal tumors (OR 2.5, 95%CI 1.2-5.3); conversely, the rs1417938 A allele was associated with a reduced risk of CIMP+ rectal tumors (OR 0.5, 95%CI 0.3-0.9). We observed interactions between CRP rs1800947 and BMI and family history of CRC in modifying risk of both colon and rectal cancer. These data suggest that genetic variation in the CRP gene influences risk of both colon and rectal cancer development.

Association between erythrocyte sedimentation rate and IQ in Swedish males aged 18-20

OBJECTIVE

To investigate if signs of inflammation are associated with performance on a contemporaneous IQ-test in males aged 18-20.

DESIGN

Cohort study using data from the conscript register on performance on an IQ-test and on erythrocyte sedimentation rates (ESR) measured in 1969/70. Data on cardiovascular risk factors measured at conscription and national register data on childhood circumstances at age 10 were considered as potential sources of confounding. Data from national registers was linked to the cohort in order to explore long term associations between ESR at age 18-20 and mortality between the years 1971-2006.

SETTING

49,321 Swedish males aged 18-20, screened for general health and for mental and physical capacity at compulsory conscription examination before military service.

RESULTS

We found an inverse correlation between ESR and performance on an IQ-test. While an association was observed across IQ bands and ESR ranges, independent of cardiovascular risk factors or childhood circumstances, the association was slightly attenuated by adjustment for childhood socioeconomic position (SEP). An association between childhood SEP and ESR was detected that remained after adjusting for IQ. The ESR was also associated with future mortality following adjustment for childhood SEP.

CONCLUSIONS

Low-grade inflammation, as indicated by the ESR, is associated with reduced cognitive abilities already at age 18-20.

Variation in the uric acid transporter gene (SLC2A9) and memory performance

Understanding human cognitive ageing is important to improve the health of an increasing elderly population. Serum uric acid levels have been linked to many ageing illnesses and are also linked to cognitive functioning, though the direction of the association is equivocal. SLC2A9, a urate transporter, influences uric acid levels. This study first tested four SLC2A9 SNPs, previously associated with uric acid levels, in approximately 1000 Scots: the Lothian Birth Cohort 1936 (LBC1936). These participants were tested on general cognitive ability at ages 11 and 70. At age 70, they took a battery of diverse cognitive tests. Two replication cohorts were investigated. First, the LBC1921, who were tested on general cognitive ability at age 11. At ages 79 (n = 520), 83 (n = 281) and age 87 (n = 177), they completed cognitive ability test batteries. Second, the Edinburgh Type 2 Diabetes Study (ET2DS) were tested for cognitive abilities aged between 60 and 75 years (n = 1066). All analyses were adjusted for age, gender, body mass index and either childhood cognitive ability test score (LBC) or vocabulary-a measure of prior cognitive ability in ET2DS. Significant associations were detected with SLC2A9 and a general memory factor in LBC1936 and other individual cognitive ability tests (lowest P = 0.0002). The association with logical memory replicated in LBC1921 at all ages (all P < 0.05). These associations were not replicated in ET2DS (all P > 0.1). If the positive associations withstand, then this study could suggest that higher uric acid levels may be associated with increased performance on memory-related tasks.

Association between raised inflammatory markers and cognitive decline in elderly people with type 2 diabetes: the Edinburgh Type 2 Diabetes Study

OBJECTIVE

To determine whether circulating levels of the inflammatory markers C-reactive protein (CRP), interleukin (IL)-6, and tumor necrosis factor (TNF)-alpha are associated with cognitive ability and estimated lifetime cognitive decline in an elderly population with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A cross-sectional study of 1,066 men and women aged 60-75 years with type 2 diabetes and living in Lothian, Scotland (the Edinburgh Type 2 Diabetes Study), was performed. Seven cognitive tests were used to measure abilities in memory, nonverbal reasoning, information processing speed, executive function, and mental flexibility. The results were used to derive a general intelligence factor (g). A vocabulary-based test was administered as an estimate of peak prior cognitive ability. Results on the cognitive tests were assessed for statistical association with inflammatory markers measured in a venous blood sample at the time of cognitive testing.

RESULTS

Higher IL-6 and TNF-alpha levels were associated with poorer age- and sex-adjusted scores on the majority of the individual cognitive tests. They were also associated with g using standardized regression coefficients -0.074 to -0.173 (P < 0.05). After adjusting for vocabulary, education level, cardiovascular dysfunction, duration of diabetes, and glycemic control, IL-6 remained associated with three of the cognitive tests and with g.

CONCLUSIONS

In this representative population of people with type 2 diabetes, elevated circulating levels of inflammatory markers were associated with poorer cognitive ability. IL-6 levels were also associated with estimated lifetime cognitive decline.

Associations between polymorphisms in five inflammation-related genes and cognitive ability in older persons

Several studies have found associations between inflammatory biomarker levels and cognitive ability. This study tested the relationship between polymorphisms in genes that are associated with or encode the biomarkers and cognitive ability and estimated lifetime cognitive change. Data came from the aspirin for asymptomatic atherosclerosis trial (n = 2091, mean age = 67.2 years ). Twelve single nucleotide polymorphisms (SNPs) were genotyped from five genes (IL-1alpha, IL-1beta, IL-6, HNF-1A and F13A1). Cognition was assessed via administration of a five-test battery of psychometric tests, which were used to derive a general intelligence factor, g. A vocabulary-based cognitive test was also administered and adjusted for in the analysis to enable an estimation of lifetime cognitive change. Age- and sex-adjusted analyses yielded one weakly significant association between the IL-1alpha rs2856838 SNP and a measure of mental flexibility/processing speed (P = 0.044). Adjustment for the vocabulary-based scores resulted in a single, significant association between the IL-1alpha rs3783546 SNP and a measure of processing speed (P = 0.048). There is little evidence to suggest an association between SNPs in the inflammation-related genes IL-1alpha, IL-1beta, IL-6, TCF-1 and F13A1 and cognition in an elderly population of community-dwelling Scottish citizens.