Experimental observations on maternal reproductive rate and offspring characteristics

Starting from a clone of Philodina roseola (Rotifera, Bdelloidea) six homogeneous animals have been reared. From them three different age cohorts have been studied in order to determine their life tables. Cohorts and parental life schedules are compared and discussed. A sort of correlation between offspring fecundity and life span and maternal rate of egg production could be established.     

Aging modulates susceptibility to mouse liver Mallory-Denk body formation

Mallory-Denk bodies (MDBs) are hepatocyte cytoplasmic inclusions found in several liver diseases and consist primarily of the cytoskeletal proteins, keratins 8 and 18 (K8/K18). Recent evidence indicates that the extent of stress-induced protein misfolding, a K8>K18 overexpression state, and transglutaminase-2 activation promote MDB formation. In addition, the genetic background and gender play an important role in mouse MDB formation, but the effect of aging on this process is unknown. Given that oxidative stress increases with aging, the authors hypothesized that aging predisposes to MDB formation. They used an established mouse MDB model-namely, feeding non-transgenic male FVB/N mice (1, 3, and 8 months old) with 3,5 diethoxycarbonyl-1,4-dihydrocollidine for 2 months. MDB formation was assessed using immunofluorescence staining and biochemically by demonstrating keratin and ubiquitin-containing crosslinks generated by transglutaminase-2. Immunofluorescence staining showed that old mice had a significant increase in MDB formation compared with young mice. MDB formation paralleled the generation of high molecular weight ubiquitinated keratin-containing complexes and induction of p62. Old mouse livers had increased oxidative stress. In addition, 20S proteasome activity and autophagy were decreased, and endoplasmic reticulum stress was increased in older livers. Therefore, aging predisposes to experimental MDB formation, possibly by decreased activity of protein degradation machinery.     

Generation and functional characterization of knock-in mice harboring the cardiac troponin I-R21C mutation associated with hypertrophic cardiomyopathy

The R21C substitution in cardiac troponin I (cTnI) is the only identified mutation within its unique N-terminal extension that is associated with hypertrophic cardiomyopathy (HCM) in man. Particularly, this mutation is located in the consensus sequence for β-adrenergic-activated protein kinase A (PKA)-mediated phosphorylation. The mechanisms by which this mutation leads to heart disease are still unclear. Therefore, we generated cTnI knock-in mouse models carrying an R21C mutation to evaluate the resultant functional consequences. Measuring the in vivo levels of incorporated mutant and WT cTnI, and their basal phosphorylation levels by top-down mass spectrometry demonstrated: 1) a dominant-negative effect such that, the R21C+/- hearts incorporated 24.9% of the mutant cTnI within the myofilament; and 2) the R21C mutation abolished the in vivo phosphorylation of Ser(23)/Ser(24) in the mutant cTnI. Adult heterozygous (R21C+/-) and homozygous (R21C+/+) mutant mice activated the fetal gene program and developed a remarkable degree of cardiac hypertrophy and fibrosis. Investigation of cardiac skinned fibers isolated from WT and heterozygous mice revealed that the WT cTnI was completely phosphorylated at Ser(23)/Ser(24) unless the mice were pre-treated with propranolol. After propranolol treatment (-PKA), the pCa-tension relationships of all three mice (i.e. WT, R21C+/-, and R21C+/+) were essentially the same. However, after treatment with propranolol and PKA, the R21C cTnI mutation reduced (R21C+/-) or abolished (R21C+/+) the well known decrease in the Ca(2+) sensitivity of tension that accompanies Ser(23)/Ser(24) cTnI phosphorylation. Altogether, the combined effects of the R21C mutation appear to contribute toward the development of HCM and suggest that another physiological role for the phosphorylation of Ser(23)/Ser(24) in cTnI is to prevent cardiac hypertrophy.     

Stress‐associated H3K4 methylation accumulates during postnatal development and aging of rhesus macaque brain

Epigenetic modifications are critical determinants of cellular and developmental states. Epigenetic changes, such as decreased H3K27me3 histone methylation on insulin/IGF1 genes, have been previously shown to modulate lifespan through gene expression regulation. However, global epigenetic changes during aging and their biological functions, if any, remain elusive. Here, we examined the histone modification H3K4 dimethylation (H3K4me2) in the prefrontal cortex of individual rhesus macaques at different ages by chromatin immunoprecipitation, followed by deep sequencing (ChIP‐seq) at the whole genome level. Through integrative analysis of the ChIP‐seq profiles with gene expression data, we found that H3K4me2 increased at promoters and enhancers globally during postnatal development and aging, and those that correspond to gene expression changes in cis are enriched for stress responses, such as the DNA damage response. This suggests that metabolic and environmental stresses experienced by an organism are associated with the progressive opening of chromatin. In support of this, we also observed increased expression of two H3K4 methyltransferases, SETD7 and DPY30, in aged macaque brain.     

The extreme longevity of Arctica islandica is associated with increased peroxidation resistance in mitochondrial membranes

The deleterious reactive carbonyls released upon oxidation of polyunsaturated fatty acids in biological membranes are believed to foster cellular aging. Comparative studies in mammals and birds have shown that the susceptibility to peroxidation of membrane lipids peroxidation index (PI) is negatively correlated with longevity. Long‐living marine molluscs are increasingly studied as longevity models, and the presence of different types of lipids in the membranes of these organisms raises questions on the existence of a PI–longevity relationship. We address this question by comparing the longest living metazoan species, the mud clam Arctica islandica (maximum reported longevity = 507 year) to four other sympatric bivalve molluscs greatly differing in longevity (28, 37, 92, and 106 year). We contrasted the acyl and alkenyl chain composition of phospholipids from the mitochondrial membranes of these species. The analysis was reproduced in parallel for a mix of other cell membranes to investigate whether a different PI–longevity relationship would be found. The mitochondrial membrane PI was found to have an exponential decrease with increasing longevity among species and is significantly lower for A. islandica. The PI of other cell membranes showed a linear decrease with increasing longevity among species and was also significantly lower for A. islandica. These results clearly demonstrate that the PI also decreases with increasing longevity in marine bivalves and that it decreases faster in the mitochondrial membrane than in other membranes in general. Furthermore, the particularly low PI values for A. islandica can partly explain this species’ extreme longevity.     

Age-associated elevation in TLR5 leads to increased inflammatory responses in the elderly

Aging is accompanied by a progressive decline in immune function. Studies have shown age-related decreases in the expression and signaling efficiency of Toll-like receptors (TLRs) in monocytes and dendritic cells and dysregulation of macrophage TLR3. Using a multivariable mixed effect model, we report a highly significant increase in TLR5-induced production of IL-8 from monocytes of older individuals (P < 0.0001). Elevated IL-8 is accompanied by increased expression of TLR5, both protein and mRNA, and by increased levels of TLR5-mediated phosphorylation of MAPK p38 and ERK. We noted incomplete activation of NF-κB in response to TLR5 signaling in monocytes of elderly donors, as reflected by the absence of an associated increase in the production of TNF-α. Elevated TLR5 may provide a critical mechanism to enhance immune responsiveness in older individuals.     

Lifelong rapamycin administration ameliorates age-dependent cognitive deficits by reducing IL-1β and enhancing NMDA signaling

Understanding the factors that contribute to age-related cognitive decline is imperative, particularly as age is the major risk factor for several neurodegenerative disorders. Levels of several cytokines increase in the brain during aging, including IL-1β, whose levels positively correlate with cognitive deficits. Previous reports show that reducing the activity of the mammalian target of rapamycin (mTOR) extends lifespan in yeast, nematodes, Drosophila, and mice. It remains to be established, however, whether extending lifespan with rapamycin is accompanied by an improvement in cognitive function. In this study, we show that 18-month-old mice treated with rapamycin starting at 2 months of age perform significantly better on a task measuring spatial learning and memory compared to age-matched mice on the control diet. In contrast, rapamycin does not improve cognition when given to 15-month-old mice with pre-existing, age-dependent learning and memory deficits. We further show that the rapamycin-mediated improvement in learning and memory is associated with a decrease in IL-1β levels and an increase in NMDA signaling. This is the first evidence to show that a small molecule known to increase lifespan also ameliorates age-dependent learning and memory deficits.     

Caloric restriction may reverse age-related autonomic decline in humans

Caloric restriction (CR) retards aging in laboratory rodents. No information is available on the effects of long-term CR on physiologic markers of aging and longevity in humans. Heart rate variability (HRV) is a marker for cardiac autonomic functioning. The progressive decline in HRV with aging and the association of higher HRV with better health outcomes are well established. Heart rate variability assessment is a reliable tool by which the effects of CR on autonomic function can be assessed. Time- and frequency-domain analyses compared 24-h HRV in 22 CR individuals aged 35-82 years and 20 age-matched controls eating Western diets (WD). The CR group was significantly leaner than the WD group. Heart rate was significantly lower, and virtually, all HRV values were significantly higher in the CR group than in the WD group (P < 0.002). Heart rate variability in the CR individuals was comparable with published norms for healthy individuals 20 years younger. In addition, when differences in heart rate (HR) and HRV between CR and WD were compared with previously published changes in HRV induced in healthy adults given atenolol, percent differences in each measure were generally similar in direction and magnitude and suggested declines in sympathetic and increases in parasympathetic modulation of HR and increased circadian variability associated with CR. These findings provide evidence that CR has direct systemic effects that counter the expected age-associated changes in autonomic function so that HRV indexes in CR individuals are similar to those of individuals 20 years younger eating WDs.     

MFG-E8 activates proliferation of vascular smooth muscle cells via integrin signaling

An accumulation of milk fat globule EGF-8 protein (MFG-E8) occurs within the context of arterial wall inflammatory remodeling during aging, hypertension, diabetes mellitus, or atherosclerosis. MFG-E8 induces VSMC invasion, but whether it affects VSMC proliferation, a salient feature of arterial inflammation, is unknown. Here, we show that in the rat arterial wall in vivo, PCNA and Ki67, markers of cell cycle activation, increase with age between 8 and 30 months. In fresh and early passage VSMC isolated from old aortae, an increase in CDK4 and PCNA, an increase in the acceleration of cell cycle S and G2 phases, decrease in the G1/G0 phase, and an increase in PDGF and its receptors confer elevated proliferative capacity, compared to young VSMC. Increased coexpression and physical interaction of MFG-E8 and integrin αvβ5 occur with aging in both the rat aortic wall in vivo and in VSMC in vitro. In young VSMC in vitro, MFG-E8 added exogenously, or overexpressed endogenously, triggers phosphorylation of ERK1/2, augmented levels of PCNA and CDK4, increased BrdU incorporation, and promotes proliferation, via αvβ5 integrins. MFG-E8 silencing, or its receptor inhibition, or the blockade of ERK1/2 phosphorylation in these cells reduces PCNA and CDK4 levels and decelerates the cell cycle S phase, conferring a reduction in proliferative capacity. Collectively, these results indicate that MFG-E8 in a dose-dependent manner coordinates the expression of cell cycle molecules and facilitates VSMC proliferation via integrin/ERK1/2 signaling. Thus, an increase in MFG-E8 signaling is a mechanism of the age-associated increase in aortic VSMC proliferation.