Annamaria Corsi

A genome-wide association study identifies protein quantitative trait loci (pQTLs)

There is considerable evidence that human genetic variation influences gene expression. Genome-wide studies have revealed that mRNA levels are associated with genetic variation in or close to the gene coding for those mRNA transcripts – cis effects, and elsewhere in the genome – trans effects. The role of genetic variation in determining protein levels has not been systematically assessed. Using a genome-wide association approach we show that common genetic variation influences levels of clinically relevant proteins in human serum and plasma. We evaluated the role of 496,032 polymorphisms on levels of 42 proteins measured in 1200 fasting individuals from the population based InCHIANTI study. Proteins included insulin, several interleukins, adipokines, chemokines, and liver function markers that are implicated in many common diseases including metabolic, inflammatory, and infectious conditions. We identified eight Cis effects, including variants in or near the IL6R (p = 1.8×10−57), CCL4L1 (p = 3.9×10−21), IL18 (p = 6.8×10−13), LPA (p = 4.4×10−10), GGT1 (p = 1.5×10−7), SHBG (p = 3.1×10−7), CRP (p = 6.4×10−6) and IL1RN (p = 7.3×10−6) genes, all associated with their respective protein products with effect sizes ranging from 0.19 to 0.69 standard deviations per allele. Mechanisms implicated include altered rates of cleavage of bound to unbound soluble receptor (IL6R), altered secretion rates of different sized proteins (LPA), variation in gene copy number (CCL4L1) and altered transcription (GGT1). We identified one novel trans effect that was an association between ABO blood group and tumour necrosis factor alpha (TNF-alpha) levels (p = 6.8×10−40), but this finding was not present when TNF-alpha was measured using a different assay , or in a second study, suggesting an assay-specific association. Our results show that protein levels share some of the features of the genetics of gene expression. These include the presence of strong genetic effects in cis locations. The identification of protein quantitative trait loci (pQTLs) may be a powerful complementary method of improving our understanding of disease pathways.

Unexplained anaemia in older persons is characterised by low erythropoietin and low levels of pro-inflammatory markers.

Epidemiological studies report that a third of the cases of anaemia in older persons is unexplained. We compared erythropoietin (EPO), inflammatory markers and major comorbidities between older subjects with normal haemoglobin levels and those with different aetiologic forms of anaemia, including unexplained anaemia. Participants were a representative sample of 964 persons aged ≥65 years, with no evidence of bleeding, complete blood tests, and a complete blood count within 6 h of phlebotomy. Anaemia was defined as haemoglobin <130 g/l in men and 120 g/l in women, and classified as a result of chronic kidney disease, iron deficiency, chronic disease and B12/folate deficiency anaemia, or unexplained anaemia based on standard criteria. Of the 124 anaemic participants, 42 (36·8%) had unexplained anaemia. Participants with anaemia of chronic diseases had significantly higher interleukin‐6 (IL‐6) and C‐reactive protein (CRP) levels, while those with unexplained anaemia had significantly lower CRP than non‐anaemic controls. Iron deficiency anaemia was characterised by significantly higher EPO levels compared with other types of anaemia and normal haemoglobin, B12 and/or folate deficiency. Unexplained anaemia was characterised by unexpectedly low EPO and low lymphocyte count. Unexplained anaemia is associated with reduced kidney EPO response, low levels of pro‐inflammatory markers and low lymphocyte counts.

A common variant of the interleukin 6 receptor (IL-6r) gene increases IL-6r and IL-6 levels, without other inflammatory effects

Interleukin-6 (IL-6) is a key inflammatory cytokine, signalling to most tissues by binding to a soluble IL-6 receptor (sIL-6r), making a complex with gp130. We used 1273 subjects (mean age 68 years) from the InCHIANTI Italian cohort to study common variation in the IL-6r locus and associations with interleukin 6 receptor (IL-6r), IL-6, gp130 and a battery of inflammatory markers. The rs4537545 single nucleotide polymorphism (SNP) tags the functional non-synonymous Asp358Ala variant (rs8192284) in IL-6r (r2=0.89, n=343). Individuals homozygous for the rs4537545 SNP minor allele (frequency 40%) had a doubling of IL-6r levels (132.48 pg/ml, 95% CI 125.13–140.27) compared to the common allele homozygous group (68.31 pg/ml, 95% CI 65.35–71.41): in per allele regression models, the rs4537545 SNP accounted for 20% of the variance in sIL-6r, with P=5.1 × 10−62. The minor allele of rs4537545 was also associated with higher circulating IL-6 levels (P=1.9 × 10−4). There was no association of this variant with serum levels of gp130 or with any of the studied pro- and anti-inflammatory markers. A common variant of the IL-6r gene results in major changes in IL-6r and IL-6 serum levels, but with no apparent effect on gp130 levels or on inflammatory status in the general population.

Vitamin E levels, cognitive impairment and dementia in older persons : the InCHIANTI study

There is conflicting evidence that antioxidants contribute to maintaining cognitive function in elderly subjects. We investigated whether vitamin E plasma levels are related to the presence of dementia and cognitive impairment in a population-based cohort study conducted in Italy. A total of 1033 participants aged at least 65 years received clinical and neuropsychological examinations, donated blood for vitamin E analysis and had their diets assessed. Participants with plasma vitamin E levels in the bottom tertile had a significantly higher probability of being demented (OR 2.6, 95% CI 1.0-7.1) and also of suffering from cognitive impairment (OR 2.2, 95% CI 1.2-4.2) compared to those in the highest vitamin E tertile after adjustment for age, gender, education, lipid levels, energy intake, vitamin E intake, and smoking. This study supports the notion that higher vitamin E plasma levels might provide significant protection against cognitive impairment and dementia in elderly subjects.

Common genetic variation in the gene encoding interleukin-1-receptor antagonist (IL-1RA) is associated with altered circulating IL-1RA levels.

Interleukin-1-receptor antagonist (IL-1RA) modulates the biological activity of the proinflammatory cytokine interleukin-1 (IL-1) and could play an important role in the pathophysiology of inflammatory and metabolic traits. We genotyped seven single nucleotide polymorphisms (SNPs) that capture a large proportion of common genetic variation in the IL-1RN gene in 1256 participants from the Invecchiare in Chianti study. We identified five SNPs associated with circulating IL-1RA levels with varying degrees of significance (P-value range=0.016–4.9 × 10−5). We showed that this association is likely to be driven by one haplotype, most strongly tagged by rs4251961. This variant is only in weak linkage disequilibrium (r2=0.25) with a previously reported variable number of tandem repeats polymorphism (VNTR) in intron-2 although a second variant, rs579543, that tags the VNTR (r2=0.91), may also be independently associated with IL-1RA levels (P=0.03). We found suggestive evidence that the C allele at rs4251961 that lowers IL-1RA levels is associated with an increased IL-1β (P=0.03) level and may also be associated with interferon -γ (P=0.03), α-2 macroglobulin (P=0.008) and adiponectin (P=0.007) serum levels. In conclusion, common variation across the IL-1RN gene is strongly associated with IL-1RA levels.

Serum IL-1β levels in health and disease: a population-based study. ‘The InCHIANTI study’

Interleukin-1 plays a role in normal homeostasis and in the inflammatory response which is deemed to be responsible for the development of major chronic diseases that are highly prevalent in the elderly. Aim of this study is to evaluate the factors influencing the serum levels of Interleukin-1 beta, in a large and representative population. Data were from the InCHIANTI project, a study of factors contributing to the decline of mobility in late life, which sampled people living in two sites in the surroundings of Florence. Blood samples were obtained from 1,292 participants and frozen aliquots were stored at -80 degrees C. The serum levels of several cytokines were measured by enzyme linked immunosorbent assay using an ultrasensitive commercial kit. Interleukin-1 beta serum levels were associated with congestive heart failure (p > 0.001) and angina (p = 0.02), with Ca2+ serum levels (p = 0.02), and with a history of dyslipidemia (p = 0.05). We found no association between serum IL-1beta level and age, sex, consumption of cardioactive drugs and serum levels of IL-1Ra, IL-6, sIL-6R, IL-10 and TNF-alpha. Our data could lend support to the hypothesis that IL-1beta is mainly involved in the functional alterations of cardiomyocytes under conditions marked by mononuclear cell infiltration and by downregulation of calcium.

Relationship Between Low Levels of High-Density Lipoprotein Cholesterol and Dementia in the Elderly. The InChianti Study

BACKGROUND To evaluate the association between plasma lipid fractions and the prevalence of dementia in a large sample of Italian older individuals. METHODS A total of 1051 older community-dwelling individuals (age >/=65 years), enrolled in the InChianti study, were included. Diagnosis of dementia was established at baseline and at the 3-year follow-up using Diagnostic and Statistical Manual of Mental Disorder (Fourth Edition) criteria. Plasma lipids were measured by standardized methods at baseline and after 3 years. RESULTS At baseline, 61 individuals (5.8%) were affected by dementia. Demented individuals showed significantly lower total cholesterol (TC), nonhigh-density lipoprotein cholesterol, and high-density lipoprotein cholesterol (HDL-C) levels compared with controls; no differences were found in triglycerides (TG) and lipoprotein (a) levels. Of the 819 subjects reevaluated at the 3-year follow-up, 81 (9.9%) received a new diagnosis of dementia. Again, demented subjects were characterized by significantly lower TC, non-HDL-C, and HDL-C levels compared with controls, thus confirming the baseline findings. At multivariate logistic regression analysis, HDL-C levels (odds ratio: 0.96, 95% confidence interval: 0.93-0.99), but not TG and non-HDL-C, were associated with dementia independent of important confounders including age, gender, apo E phenotype, stroke, weight loss, interleukin 6 levels, and ankle-brachial index. CONCLUSIONS Among community-dwelling older people, individuals affected by dementia showed significantly lower TC, non-HDL-C, and HDL-C levels; however, at multivariate analysis, only HDL-C was associated with dementia. Our results suggest the existence of an independent relationship between dementia and low HDL-C levels.

Omega-6 and omega-3 fatty acids predict accelerated decline of peripheral nerve function in older persons

Pre‐clinical studies suggest that both omega‐6 and omega‐3 fatty acids have beneficial effects on peripheral nerve function. Rats feed a diet rich in polyunsaturated fatty acids (PUFAs) showed modification of phospholipid fatty acid composition in nerve membranes and improvement of sciatic nerve conduction velocity (NCV). We tested the hypothesis that baseline plasma omega‐6 and omega‐3 fatty acids levels predict accelerated decline of peripheral nerve function. Changes between baseline and the 3‐year follow‐up in peripheral nerve function was assessed by standard surface ENG of the right peroneal nerve in 384 male and 443 female participants of the InCHIANTI study (age range: 24–97 years). Plasma concentrations of selected fatty acids assessed at baseline by gas chromatography. Independent of confounders, plasma omega‐6 fatty acids and linoleic acid were significantly correlated with peroneal NCV at enrollment. Lower plasma PUFA, omega‐6 fatty acids, linoleic acid, ratio omega‐6/omega‐3, arachidonic acid and docosahexanoic acid levels were significantly predicted a steeper decline in nerve function parameters over the 3‐year follow‐up. Low plasma omega‐6 and omega‐3 fatty acids levels were associated with accelerated decline of peripheral nerve function with aging.

Erratum: Omega-6 and Omega-3 fatty acids predict accelerated decline of peripheral nerve function in older persons (European Journal of Neurology (2007) 14, (801-808)

F. Lauretani, S. Bandinelli, B. Benedetta, A. Cherubini, A. D. Iorio, A. Blè, V. Giacomini, A. M. Corsi, J. M. Guralnik and L. Ferrucci Tuscany Regional Health Agency, Florence, Italy; Geriatric Rehabilitation, Azienda Sanitaria Firenze, Florence, Italy; Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA; Institute of Gerontology and Geriatrics, Perugia University Medical School, Perugia, Italy; Laboratory of Clinical Epidemiology, Department of Medicine and Sciences of Aging, University G. D’Annunzio, Chieti, Italy; Longitudinal Studies Section, Clinical Research Branch, National Institute on Aging, Baltimore, MD, USA; and Laboratory of Epidemiology, Demography and Biometry, National Institute on Aging, Bethesda, MD, USA

Understanding the physiological and functional consequences of menopause: The PROSALMEN study

Background and aims: Women live longer and are more often affected by disability and poor health than men. The mechanism underlying this sex-related “mortality-morbidity” paradox is still unclear but it has been suggested that the physiological and functional changes occurring during the menopausal transition play an important role. The aim of PROSALMEN (PROgetto SALute MENopausa: Health in Menopause Project) is to study in great detail how these changes affect the integrity and function of the physiologic subsystems that are relevant to the maintenance of an active and healthy life-style during the aging process. Methods: PROSALMEN is a cross-sectional comparison of age-matched pre- and post-menopausal women. Thirty post-m enopausal women, aged 48–58 years, were enrolled in the study together with 30 age-matched pre-menopausal controls. A number of clinical, biological and functional parameters were collected assessing the integrity and level of function of the physiological subsystems that are important for mobility. Furthermore, we collected information on risk factors, medical conditions and symptoms that frequently develop or become clinically evident after menopause, including the most important elements of the classical post-m enopausal syndrome. Conclusions: This rich dataset will be used to start dissecting the causal pathway leading from menopause to damages in the musculoskeletal system and, in turn, to reduced physical function. The final goal is to understand how and to what extent changes in health behavior and pharmacological treatments in addition to hormone replacement therapy (HRT) may counteract these processes.