Interleukin-6 and C-reactive protein, successful aging, and mortality : the PolSenior study

BACKGROUND: In the elderly, chronic low-grade inflammation (inflammaging) is a risk factor for the development of aging-related diseases and frailty. Using data from several thousand Eastern Europeans aged 65 years and older, we investigated whether the serum levels of two proinflammatory factors, interleukin-6 (IL-6) and C-reactive protein (CRP), were associated with physical and cognitive performance, and could predict mortality in successfully aging elderly. RESULTS: IL-6 and CRP levels systematically increased in an age-dependent manner in the entire study group (IL-6: n = 3496 individuals, p < 0.001 and CRP: n = 3632, p = 0.003), and in the subgroup of successfully aging individuals who had never been diagnosed with cardiovascular disease, myocardial infarction, stroke, type 2 diabetes, or cancer, and had a Mini Mental State Examination (MMSE) score ≥24 and a Katz Activities of Daily Living (ADL) score ≥5 (IL-6: n = 1258, p < 0.001 and CRP: n = 1312, p < 0.001). In the subgroup of individuals suffering from aging-related diseases/disability, only IL-6 increased with age (IL-6: n = 2238, p < 0.001 and CRP: n = 2320, p = 0.249). IL-6 and CRP levels were lower in successfully aging individuals than in the remaining study participants (both p < 0.001). Higher IL-6 and CRP levels were associated with poorer physical performance (lower ADL score) and poorer cognitive performance (lower MMSE score) (both p < 0.001). This association remained significant after adjusting for age, gender, BMI, lipids, estimated glomerular filtration rate, and smoking status. Longer survival was associated with lower concentrations of IL-6 and CRP not only in individuals with aging-related diseases/disability (HR = 1.063 per each pg/mL, 95 % CI: 1.052-1.074, p < 0.001 and HR = 1.020 per each mg/L, 95 % CI: 1.015-1.025, p < 0.001, respectively) but also in the successfully aging subgroup (HR = 1.163 per each pg/mL, 95 % CI: 1.128-1.199, p < 0.001 and HR = 1.074 per each mg/L, 95 % CI: 1.047-1.100, p < 0.001, respectively). These associations remained significant after adjusting for age, gender, BMI, lipids and smoking status. The Kaplan-Meier survival curves showed similar results (all p < 0.001). CONCLUSIONS: Both IL-6 and CRP levels were good predictors of physical and cognitive performance and the risk of mortality in both the entire elderly population and in successfully aging individuals

In Vitro Aggregation Behavior of a Non-Amyloidogenic λ Light Chain Dimer Deriving from U266 Multiple Myeloma Cells

Excessive production of monoclonal light chains due to multiple myeloma can induce aggregation-related disorders, such as light chain amyloidosis (AL) and light chain deposition diseases (LCDD). In this work, we produce a non-amyloidogenic IgE λ light chain dimer from human mammalian cells U266, which originated from a patient suffering from multiple myeloma, and we investigate the effect of several physicochemical parameters on the in vitro stability of this protein. The dimer is stable in physiological conditions and aggregation is observed only when strong denaturating conditions are applied (acidic pH with salt at large concentration or heating at melting temperature Tm at pH 7.4). The produced aggregates are spherical, amorphous oligomers. Despite the larger β-sheet content of such oligomers with respect to the native state, they do not bind Congo Red or ThT. The impossibility to obtain fibrils from the light chain dimer suggests that the occurrence of amyloidosis in patients requires the presence of the light chain fragment in the monomer form, while dimer can form only amorphous oligomers or amorphous deposits. No aggregation is observed after denaturant addition at pH 7.4 or at pH 2.0 with low salt concentration, indicating that not a generic unfolding but specific conformational changes are necessary to trigger aggregation. A specific anion effect in increasing the aggregation rate at pH 2.0 is observed according to the following order: SO4−≫Cl−>H2PO4−, confirming the peculiar role of sulfate in promoting protein aggregation. It is found that, at least for the investigated case, the mechanism of the sulfate effect is related to protein secondary structure changes induced by anion binding

Contribution of Electrostatics in the Fibril Stability of a Model Ionic-Complementary Peptide

In this work we quantified the role of electrostatic interactions in the self-assembly of a model amphiphilic peptide (RADA 16-I) into fibrillar structures by a combination of size exclusion chromatography and molecular simulations. For the peptide under investigation, it is found that a net charge of +0.75 represents the ideal condition to promote the formation of regular amyloid fibrils. Lower net charges favor the formation of amorphous precipitates, while larger net charges destabilize the fibrillar aggregates and promote a reversible dissociation of monomers from the ends of the fibrils. By quantifying the dependence of the equilibrium constant of this reversible reaction on the pH value and the peptide net charge, we show that electrostatic interactions contribute largely to the free energy of fibril formation. The addition of both salt and a charged destabilizer (guanidinium hydrochloride) at moderate concentration (0.3–1 M) shifts the monomer-fibril equilibrium toward the fibrillar state. Whereas the first effect can be explained by charge screening of electrostatic repulsion only, the promotion of fibril formation in the presence of guanidinium hydrochloride is also attributed to modifications of the peptide conformation. The results of this work indicate that the global peptide net charge is a key property that correlates well with the fibril stability, although the peptide conformation and the surface charge distribution also contribute to the aggregation propensity

NGS Reveals Molecular Pathways Affected by Obesity and Weight Loss-Related Changes in miRNA Levels in Adipose Tissue

Both obesity and weight loss may cause molecular changes in adipose tissue. This study aimed to characterize changes in adipose tissue miRNome in order to identify molecular pathways affected by obesity and weight changes. Next generation sequencing (NGS) was applied to identify microRNAs (miRNAs) differentially expressed in 47 samples of visceral (VAT) and subcutaneous (SAT) adipose tissues from normal-weight (N), obese (O) and obese after surgery-induced weight loss (PO) individuals. Subsequently miRNA expression was validated by real-time PCR in 197 adipose tissues and bioinformatics analysis performed to identify molecular pathways affected by obesity-related changes in miRNA expression. NGS identified 344 miRNAs expressed in adipose tissues with ≥5 reads per million. Using &gt;2 and &lt;−2 fold change as cut-offs we showed that the expression of 54 miRNAs differed significantly between VAT-O and SAT-O. Equally, between SAT-O and SAT-N, the expression of 20 miRNAs differed significantly, between SAT-PO and SAT-N the expression of 79 miRNAs differed significantly, and between SAT-PO and SAT-O, the expression of 61 miRNAs differed significantly. Ontological analyses disclosed several molecular pathways regulated by these miRNAs in adipose tissue. NGS-based miRNome analysis characterized changes of the miRNA profile of adipose tissue, which are associated with changes of weight possibly responsible for a differential regulation of molecular pathways in adipose tissue when the individual is obese and after the individual has lost weight

Scheme of aggregation mechanism.

<p><i>D*</i> represents the salt-induced or temperature-induced intermediate dimer prone to aggregate.</p

Light chain structural changes induced by salt addition monitored by CD (A) and ANS binding (B).

<p>Experiments were performed at 20°C for a 0.3 g/L protein solution in 25 mM PBS at pH 7.4 (…) and in 20 mM HCl buffer at pH 2.0 without salt (▵), with 0.15 M NaCl (–),0.15 M Na₂SO₄ (―), 0.45 M NaCl (○), 0.49 M NaH₂PO₄ (□) and 0.5 M Na₂SO₄ (×).</p

FTIR secondary structure analysis.

<p>Thin film ATR-FTIR spectra of native light chain dimer (–) and of light chain aggregates obtained after one month incubation in 20 mM HCl at pH 2.0 with 0.45 M NaCl (―), with 0.15 M Na₂SO₄ (…), or with 0.49 M NaH₂PO₄ () (runs 4, 8, and 6 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0033372#pone-0033372-t001" target="_blank">Table 1</a>).</p