T-kininogen: a biomarker of aging in Fisher 344 rats with possible implications for the immune response

Cognitive Reserve in Model Systems for Mechanistic Discovery: The Importance of Longitudinal Studies

The goal of this review article is to provide a resource for longitudinal studies, using animal models, directed at understanding and modifying the relationship between cognition and brain structure and function throughout life. We propose that forthcoming longitudinal studies will build upon a wealth of knowledge gleaned from prior cross-sectional designs to identify early predictors of variability in cognitive function during aging, and characterize fundamental neurobiological mechanisms that underlie the vulnerability to, and the trajectory of, cognitive decline. Finally, we present examples of biological measures that may differentiate mechanisms of the cognitive reserve at the molecular, cellular, and network level.

Proteomics Analysis to Identify and Characterize the Biomarkers and Physical Activities of Non-Frail and Frail Older Adults

Globally, the proportion of older adults is increasing. Older people face chronic conditions such as sarcopenia and functional decline, which are often associated with disability and frailty. Proteomics assay of potential serum biomarkers of frailty in older adults. Older adults were divided into non-frail and frail groups (n = 6 each; 3 males in each group) in accordance with the Chinese-Canadian Study of Health and Aging Clinical Frailty Scale. Adults were measured for grip power and the 6-min walk test for physical activity, and venous blood was sampled after adults fasted for 8 h. Ultra-high-performance liquid chromatography-tandem mass spectrometry was used for proteomics assay. The groups were compared for levels of biomarkers by t test and Pearson correlation analysis. Non-frail and frail subjects had mean age 77.5±0.4 and 77.7±1.6 years, mean height 160.5±1.3 and 156.6±2.9 cm and mean weight 62.5±1.2 and 62.8±2.9 kg, respectively. Physical activity level was lower for frail than non-frail subjects (grip power: 13.8±0.4 vs 26.1±1.2 kg; 6-min walk test: 215.2±17.2 vs 438.3±17.2 m). Among 226 proteins detected, for 31, serum levels were significantly higher for frail than non-frail subjects; serum levels of Ig kappa chain V-III region WOL, COX7A2, and albumin were lower. The serum levels of ANGT, KG and AT were 2.05-, 1.76- and 2.22-fold lower (all p < 0.05; Figure 1A, 2A and 3A) for non-frail than frail subjects and were highly correlated with grip power (Figure 1B, 2B and 3B). Our study found that ANGT, KG and AT levels are known to increase with aging, so degenerated vascular function might be associated with frailty. In total, 226 proteins were revealed proteomics assay; levels of angiotensinogen (ANGT), kininogen-1 (KG) and antithrombin III (AT) were higher in frail than non-frail subjects (11.26±2.21 vs 5.09±0.74; 18.42±1.36 vs 11.64±1.36; 22.23±1.64 vs 9.52±0.95, respectively, p < 0.05). These 3 factors were highly correlated with grip power (p < 0.05), with higher correlations between grip power and serum levels of ANGT (r = -0.89), KG (r = -0.90), and AT (r = -0.84). In conclusion, this is the first study to demonstrate a serum proteomic profile characteristic of frailty in older adults. Serum ANGT, KG and AT levels could be potential biomarkers for monitoring the development and progression of frailty in older adults.

Comparative proteomic analysis of the aging soleus and extensor digitorum longus rat muscles using TMT labeling and mass spectrometry

Sarcopenia describes an age-related decline in skeletal muscle mass, strength, and function that ultimately impairs metabolism and leads to poor balance, frequent falling, limited mobility, and a reduction in quality of life. Here we investigate the pathogenesis of sarcopenia through a proteomic shotgun approach. In brief, we employed tandem mass tags to quantitate and compare the protein profiles obtained from young versus old rat slow-twitch type of muscle (soleus) and a fast-twitch type of muscle (extensor digitorum longus, EDL). Our results disclose 3452 and 1848 proteins identified from soleus and EDL muscles samples, of which 78 and 174 were found to be differentially expressed, respectively. In general, most of the proteins were structural related and involved in energy metabolism, oxidative stress, detoxification, or transport. Aging affected soleus and EDL muscles differently, and several proteins were regulated in opposite ways. For example, pyruvate kinase had its expression and activity different in both soleus and EDL muscles. We were able to verify with existing literature many of our differentially expressed proteins as candidate aging biomarkers and, most importantly, disclose several new candidate biomarkers such as the glioblastoma amplified sequence, zero β-globin, and prolargin.

Development of a serum profile for healthy aging

Increasing numbers of Americans are reaching 85 years of age or older, yet there are no reliable biomarkers to predict who will live this long. The goal of this pilot study therefore was: (1) to identify a potential serum pattern that could identify proteins involved in longevity and (2) to determine if this pattern was a marker of longevity in an independent sample of individuals. Serum samples were analyzed in three cohorts of individuals (n = 12 in each) aged 20-34, 60-74, and ≥ 90 years who participated in The Louisiana Healthy Aging Study. The 12 most abundant proteins were removed and the remaining proteins separated by two-dimensional gel electrophoresis. Gels were matched and the intensity of each spot quantified. Multivariate discriminant analysis was used to identify a serum pattern that could separate these three age cohorts. Seven protein spots were found that correctly distinguished the subjects into the three groups. However, these spots were not as successful in discriminating the ages in a second set of 15 individuals as only eight of these subjects were placed into their correct group. These preliminary results show that the proteomics approach can be used to identify potential proteins or markers that may be involved in the aging process and/or be important determinants of longevity.

Kininogens: More than cysteine protease inhibitors and kinin precursors

Two kininogens are found in mammalian sera: HK (high molecular weight kininogen) and LK (low molecular weight kininogen) with the exception of the rat which encompasses a third kininogen, T-Kininogen (TK). Kininogens are multifunctional glycosylated molecules related to cystatins (clan IH, family I25). They harbor three cystatin domains but only two of them are tight-binding inhibitors of cysteine cathepsins. HK and LK, but not TK, are precursors of potent peptide hormones, the kinins, which are released proteolytically by tissue and plasma kallikreins. Besides these classical features novel functions of kininogens have been recently discovered; they are described in the second part of this review. HKa, which corresponds to the kinin-free two-chain HK and its isolated domain D5 (kininostatin), possesses angiostatic and pro-apoptotic properties, inhibits the proliferation of endothelial cells and participates in the regulation of angiogenesis. Moreover, some HK-derived peptides display potent and broad-spectrum microbicidal properties against both Gram-positive and Gram-negative bacteria, and thus may offer a promising alternative to conventional antibiotic therapy. Of seminal interest, a kininogen-derived peptide inhibits activation of the contact phase system of coagulation and protects mice with invasive Streptococcus pyogenes infection from pulmonary lesions. On the other hand, TK is a biomarker of aging at the end of lifespan of elderly rats. However, although TK has been initially identified as an acute phase reactant, and earlier known as alpha-l-acute phase globulin, the increase of TK in liver and plasma is not known to relate to any inflammatory event during the senescence process.

The release of sympathetic neurotransmitters is impaired in aged rats after an inflammatory stimulus: a possible link between cytokine production and sympathetic transmission

Aging results in a general decline in the response to external insults, including acute inflammatory challenges. In young animals, the inflammatory response requires activation of the sympathetic system, including neurotransmitters such as ATP, and catecholamines (epinephrine and norepinephrine). To test whether aging affects activation of this axis, and whether this in turn might affect cytokine release, we administered lipopolysaccharide (LPS) i.p. to adult, middle-aged and aged Fisher 344 rats (6-, 15- and 23-month old, respectively) and evaluated the early (0-12h) serum levels of Neuropeptide-Y (NP-Y), ATP and vanillyl mandelic acid (VMA, as an indirect measurement of catecholamine levels). In addition, we evaluated the association between these factors and serum levels of the cytokines tumor necrosis factor-alpha (TNFalpha) and interleukin-10 (IL-10). Induction of both ATP and NP-Y was markedly reduced in the serum of aged animals, when compared to their younger counterparts, while induction of VMA was not affected by age. In spite of these changes, serum levels of TNFalpha and IL-10 were strongly hyper induced and delayed in aged rats. The results suggest that during aging there is a dysregulation in sympathetic neurotransmitter regulatory mechanisms, and this might play a role in the impairment of the inflammatory response.

Differential proteomics in the aging Noble rat ventral prostate

Incidence of prostatic diseases increases dramatically with age which may be related to a decline in androgen support. However, the key mechanisms underlying prostate aging remain unclear. In the present study, we investigated the aging process in the ventral prostate (VP) of Noble rats by identifying differentially expressed prostate proteins between 3- and 16-month-old animals using ICAT and MS. In total, 472 proteins were identified with less than a 1% false positive rate, among which 34 were determined to have a greater than two-fold increase or 1.7-fold decrease in expression in the aged VPs versus their younger counterparts. The majority of the differentially expressed proteins identified have not been previously reported to be associated with prostate aging, and they fall into specific functional categories, including oxidative stress/detoxification, chaperones, protein biosynthesis, vesicle transport, and intracellular trafficking. The expression of GST, ferritin, clusterin, kininogen, oxygen regulated protein 150, spermidine synthase, ADP ribosylation factor, and cyclophilin B was verified by Western blot analyses on samples used for the ICAT study, as well as on those obtained from an independent group of animals comprised of three age groups. To the best of our knowledge, this is the first study on the proteome of the aging rat prostate.