Plasma biomarkers of mouse aging

Effect of senolytic drugs in young female mice chemically induced to estropause

AIMS

This study aimed to assess metabolic responses and senescent cell burden in young female mice induced to estropause and treated with senolytic drugs.

MAIN METHODS

Estropause was induced by 4-vinylcyclohexene diepoxide (VCD) injection in two-month-old mice. The senolytics dasatinib and quercetin (D + Q) or fisetin were given by oral gavage once a month from five to 11 months of age.

KEY FINDINGS

VCD-induced estropause led to increased body mass and reduced albumin concentrations compared to untreated cyclic mice, without affecting insulin sensitivity, lipid profile, liver enzymes, or total proteins. Estropause decreased catalase activity in adipose tissue but had no significant effect on other redox parameters in adipose and hepatic tissues. Fisetin treatment reduced ROS levels in the hepatic tissue of estropause mice. Estropause did not influence senescence-associated beta-galactosidase activity in adipose and hepatic tissues but increased senescent cell markers and fibrosis in ovaries. Senolytic treatment did not decrease ovarian cellular senescence induced by estropause.

SIGNIFICANCE

Overall, the findings suggest that estropause leads to minor metabolic changes in young females, and the senolytics D + Q and fisetin had no protective effects despite increased ovarian senescence.

Reduced protein intake and aging affects the sustainment of hematopoiesis by impairing bone marrow mesenchymal stem cells

Protein malnourishment (PM) is common among the elderly, but how aging and PM impact hematopoiesis is not fully understood. This study aimed to assess how aging and PM affect the hematopoietic regulatory function of bone marrow (BM) mesenchymal stem cells (MSCs). Young and aged male C57BL/6J mice were fed with normoproteic or hypoproteic diets and had their nutritional, biochemical, and hematological parameters evaluated. BM MSCs were characterized and had their secretome, gene expression, autophagy, reactive oxygen species production (ROS), and DNA double-stranded breaks evaluated. The modulation of hematopoiesis by MSCs was assayed using in vitro and in vivo models. Lastly, BM invasiveness and mice survival were evaluated after being challenged with leukemic cells of the C1498 cell line. Aging and PM alter biochemical parameters, changing the peripheral blood and BM immunophenotype. MSC autophagy was affected by aging and the frequencies for ROS and DNA double-stranded breaks. Regarding the MSCs' secretome, PM and aging affected CXCL12, IL-6, and IL-11 production. Aging and PM up-regulated Akt1 and PPAR-γ while down-regulating Cdh2 and Angpt-1 in MSCs. Aged MSCs increased C1498 cell proliferation while reducing their colony-forming potential. PM and aging lowered mice survival, and malnourishment accumulated C1498 cells at the BM. Finally, aged and/or PM MSCs up-regulated Sox2, Nanog, Pou5f1, and Akt1 expression while down-regulating Cdkn1a in C1498 cells. Together, aging and PM can induce cell-intrinsic shifts in BM MSCs, creating an environment that alters the regulation of hematopoietic populations and favoring the development of malignant cells.

Progress in the study of aging marker criteria in human populations

The use of human aging markers, which are physiological, biochemical and molecular indicators of structural or functional degeneration associated with aging, is the fundamental basis of individualized aging assessments. Identifying methods for selecting markers has become a primary and vital aspect of aging research. However, there is no clear consensus or uniform principle on the criteria for screening aging markers. Therefore, we combine previous research from our center and summarize the criteria for screening aging markers in previous population studies, which are discussed in three aspects: functional perspective, operational implementation perspective and methodological perspective. Finally, an evaluation framework has been established, and the criteria are categorized into three levels based on their importance, which can help assess the extent to which a candidate biomarker may be feasible, valid, and useful for a specific use context.

Causal Effects of Plasma Haptoglobin Levels on Alzheimer's Disease: A Two-Sample Mendelian Randomization Study

BACKGROUND

A connection between plasma levels of haptoglobin (Hp) and Alzheimer's disease (AD) has been shown in several observational studies. It is debatable, nonetheless, how the two are related causally.

OBJECTIVE

To establish the causal relationship between Hp and AD using a two-sample Mendelian randomization (MR) study.

METHODS

From the extensive genome-wide association studies and FinnGen dataset, summaries and statistics pertaining to AD were gathered. We investigated the possibility of a causal link between Hp and AD using a two-sample MR study. Inverse variance weighting was used as the primary analytical technique, and it was supported by the joint application of complementary analyses and fixed effects meta-analysis to combine results from various sources.

RESULTS

Genetically determined Hp was causally associated with AD [odds ratio (OR), 1.05; 95% confidence interval (CI), 1.02 to 1.09; p = 8.96×10-4]; Inverse variance-weighted estimates coming from different data sources were combined in a meta-analysis with consistent findings (OR, 1.03; 95% CI, 1.01 to 1.05; p = 2.00×10-3). The outcomes of the inverse MR analysis showed that AD had no appreciable causal impact on Hp.

CONCLUSION

The present MR analysis shows that higher plasma Hp leads to an increased risk of AD. Strategies for plasma Hp testing may open up new doors for the early diagnosis and prevention of AD.

Relationship of Haptoglobin Phenotypes With Sarcopaenia in Patients With Congestive Heart Failure

BACKGROUND

Systemic inflammation in patients with chronic heart failure (CHF) contributes to age-related muscle loss or sarcopaenia. However, the relationship of plasma haptoglobin (Hp), an acute-phase reactant, with muscle and physical health in CHF is unknown.

METHODS

This study investigated the associations of plasma haptoglobin levels and phenotypes with handgrip strength (HGS), appendicular skeletal muscle index (ASMI) and physical capacity in healthy controls (n=67) and CHF patients (n=61) aged 55-73 years.

RESULTS

Patients with CHF had higher plasma Hp levels and higher proportions of Hp2-2 phenotype when compared with healthy controls. Plasma Hp2-1 and Hp2-2 levels were negatively associated with HGS and ASMI in healthy controls and CHF (both p<0.05). A negative association of plasma Hp2-2 with gait speed and plasma Hp2-1 with daily steps count was also found in CHF (p<0.05). Patients with Hp2 phenotype showed higher expressions of inflammation and oxidative stress markers, as well as low scores on quality of life parameters.

CONCLUSIONS

Circulating Hp may be a valuable biomarker for assessing muscle health and physical capacity in CHF.

High salt diet-induced proximal tubular phenotypic changes and sodium-glucose cotransporter-2 expression are coordinated by cold shock Y-box binding protein-1

High salt diet (HSD) is a hallmark of blood pressure elevations, weight gain and diabetes onset in the metabolic syndrome. In kidney, compensatory mechanisms are activated to balance salt turnover and maintain homeostasis. Data on the long-term effects of HSD with respect to tubular cell functions and kidney architecture that exclude confounding indirect blood pressure effects are scarce. Additionally we focus on cold shock Y-box binding protein-1 as a tubular cell protective factor. A HSD model (4% NaCl in chow; 1% NaCl in water) was compared to normal salt diet (NSD, standard chow) over 16 months using wild type mice and an inducible conditional whole body knockout for cold shock Y-box binding protein-1 (BL6J/N, Ybx1). HSD induced no difference in blood pressure over 16 months, comparing NSD/HSD and Ybx1 wild type/knockout. Nevertheless, marked phenotypic changes were detected. Glucosuria and subnephrotic albuminuria ensued in wild type animals under HSD, which subsided in Ybx1-deficient animals. At the same time megalin receptors were upregulated. The sodium-glucose cotransporter-2 (SGLT2) was completely downregulated in wild type HSD animals that developed glucosuria. In Ybx1 knockouts, expression of AQP1 and SGLT2 was maintained under HSD; proximal tubular widening and glomerular tubularization developed. Concurrently, amino aciduria of neutral and hydrophobic amino acids was seen. In vitro translation confirmed that YB-1 translationally represses Sglt2 transcripts. Our data reveal profound effects of HSD primarily within glomeruli and proximal tubular segments. YB-1 is regulated by HSD and orchestrates HSD-dependent changes; notably, sets reabsorption thresholds for amino acids, proteins and glucose.

Age-dependent transcriptional alterations in cardiac endothelial cells

Aging is a significant risk factor for cardiovascular disease. Despite the fact that endothelial cells play critical roles in cardiovascular function and disease, the molecular impact of aging on this cell population in many organ systems remains unknown. In this study, we sought to determine age-associated transcriptional alterations in cardiac endothelial cells. Highly enriched populations of endothelial cells (ECs) isolated from the heart, brain, and kidney of young (3 mo) and aged (24 mo) C57/BL6 mice were profiled for RNA expression via bulk RNA sequencing. Approximately 700 cardiac endothelial transcripts significantly differ by age. Gene set enrichment analysis indicated similar patterns for cellular pathway perturbations. Receptor-ligand comparisons indicated parallel alterations in age-affected circulating factors and cardiac endothelial-expressed receptors. Gene and pathway enrichment analyses show that age-related transcriptional response of cardiac endothelial cells is distinct from that of endothelial cells derived from the brain or kidney vascular bed. Furthermore, single-cell analysis identified nine distinct EC subtypes and shows that the Apelin Receptor-enriched subtype is reduced with age in mouse heart. Finally, we identify age-dysregulated genes in specific aged cardiac endothelial subtypes.

Plasma proteomic profiling of young and old mice reveals cadherin-13 prevents age-related bone loss

The blood exhibits a dynamic flux of proteins that are secreted by the tissues and cells of the body. To identify novel aging-related circulating proteins, we compared the plasma proteomic profiles of young and old mice using tandem mass spectrometry. The expression of 134 proteins differed between young and old mice. We selected seven proteins that were expressed at higher levels in young mice, and confirmed their plasma expression in immunoassays. The plasma levels of anthrax toxin receptor 2 (ANTXR2), cadherin-13 (CDH-13), scavenger receptor cysteine-rich type 1 protein M130 (CD163), cartilage oligomeric matrix protein (COMP), Dickkopf-related protein 3 (DKK3), periostin, and secretogranin-1 were all confirmed to decrease with age. We then investigated whether any of the secreted proteins influenced bone metabolism and found that CDH-13 inhibited osteoclast differentiation. CDH 13 treatment suppressed the receptor activator of NF-κB ligand (RANKL) signaling pathway in bone marrow-derived macrophages, and intraperitoneal administration of CDH-13 delayed age-related bone loss in the femurs of aged mice. These findings suggest that low plasma CDH-13 expression in aged mice promotes aging-associated osteopenia by facilitating excessive osteoclast formation. Thus, CDH-13 could have therapeutic potential as a protein drug for the prevention of osteopenia.

Peroxiredoxin2 Deficiency Aggravates Aging-Induced Insulin Resistance and Declines Muscle Strength

This study examined the role of peroxiredoxin2 (Prx2) in aging-induced insulin resistance and reduction in skeletal muscle function in young (2-month-old) and old (24-month-old) Prx2 knockout (KO) and wild-type mice. Plasma insulin levels increased with aging in Prx2 KO mice but not in wild-type mice. Insulin sensitivity in the whole-body and skeletal muscle as assessed with the hyperinsulinemic-euglycemic clamp was lower in Prx2 KO mice than in wild-type mice in the old group but was not significantly different between the two genotypes in the young group. Insulin-induced activation of intracellular signaling molecules was also suppressed in old Prx2 KO mice compared to their wild-type littermates. Oxidative stress, inflammation, and p53 expression levels in skeletal muscle were higher in Prx2 KO mice than in wild-type mice in the old group but were not different between the two genotypes in the young group. p53 expression was negatively correlated with skeletal muscle insulin sensitivity in old mice. Skeletal muscle mass was similar between the two genotypes but grip strength was reduced in old Prx2 KO mice compared to old wild-type mice. These results suggest that Prx2 plays a protective role in aging-induced insulin resistance and declines in muscle strength by suppressing oxidative stress.

Biomarkers mapping of neuropathic pain in a nerve chronic constriction injury mice model

Neuropathic pain is caused by a lesion or disease of the somatosensory nervous system and has a considerable impact on the quality of life. Neuropathic pain has a dynamic and complex aetiology and gives heterogeneous symptoms across patients; therefore, it represents an important clinical challenge. Current pharmacological treatment includes tricyclic antidepressant serotonin-noradrenaline uptake inhibitors such as duloxetine, pregabalin, and gabapentin. However, these drugs do not show efficacy in all patients suffering from neuropathic pain. In this work we used a nerve chronic constriction injury mice model based on the ligation of sciatic nerve to analyse, by two-dimensional electrophoresis and mass spectrometry, blood proteins significantly altered by neuropathic pain one-week after surgery. A sham-ligated group of mice acting as control and a group of ligated mice treated with gabapentin were also analysed. The results indicated that four haptoglobin isoforms were significantly more expressed, while transthyretin and alpha-2-macroglobulin expression decreased in the serum of the murine neuropathic pain model with respect to the control mice. Interestingly, the treatment with the gabapentin reversed these conditions. The outcomes of this study can provide a further understanding of the pathophysiological meaning of the biomarkers involved in neuropathic pain.

Aging Systemic Milieu Impairs Outcome after Ischemic Stroke in Rats

Compelling evidence indicates that factors in the blood can profoundly reverse aging-related impairments, as exposure of aged mice to young blood rejuvenates adult stem cell function, improves cognition, and ameliorates cardiac hypertrophy. Systemic factors from mice can also extend the life span of a partner exposed to a lethal treatment or disease. These findings suggest that the systemic milieu of a healthy young partner may be beneficial for an aged organism. However, it is unknown whether a healthy young systemic milieu can improve functional recovery after ischemic stroke. Intraperitoneal administration of young plasma into aged rats after ischemic stroke induced by distal middle cerebral artery occlusion (dMCAO) reduced infarct volume and motor impairment, compared with vehicle group. On the contrary, intraperitoneal administration of plasma from aged rats into young ischemic rats worsened brain injury and motor deficits. Using a proteomic approach, we found that haptoglobin levels were significantly increased in serum of aged rats and that intraperitoneal administration of haptoglobin impaired outcome after ischemic stroke in young rats. Our data suggest that the aging systemic milieu plays a critical role in functional outcome after ischemic stroke.

Every-other-day feeding extends lifespan but fails to delay many symptoms of aging in mice

Dietary restriction regimes extend lifespan in various animal models. Here we show that longevity in male C57BL/6J mice subjected to every-other-day feeding is associated with a delayed onset of neoplastic disease that naturally limits lifespan in these animals. We compare more than 200 phenotypes in over 20 tissues in aged animals fed with a lifelong every-other-day feeding or ad libitum access to food diet to determine whether molecular, cellular, physiological and histopathological aging features develop more slowly in every-other-day feeding mice than in controls. We also analyze the effects of every-other-day feeding on young mice on shorter-term every-other-day feeding or ad libitum to account for possible aging-independent restriction effects. Our large-scale analysis reveals overall only limited evidence for a retardation of the aging rate in every-other-day feeding mice. The data indicate that every-other-day feeding-induced longevity is sufficiently explained by delays in life-limiting neoplastic disorders and is not associated with a more general slowing of the aging process in mice.

Dietary restriction can extend the life of various model organisms. Here, Xie et al. show that intermittent periods of fasting achieved through every-other-day feeding protect mice against neoplastic disease but do not broadly delay organismal aging in animals.

The impact of growth hormone on proteomic profiles: a review of mouse and adult human studies

Growth hormone (GH) is a protein that is known to stimulate postnatal growth, counter regulate insulin's action and induce expression of insulin-like growth factor-1. GH exerts anabolic or catabolic effects depending upon on the targeted tissue. For instance, GH increases skeletal muscle and decreases adipose tissue mass. Our laboratory has spent the past two decades studying these effects, including the effects of GH excess and depletion, on the proteome of several mouse and human tissues. This review first discusses proteomic techniques that are commonly used for these types of studies. We then examine the proteomic differences found in mice with excess circulating GH (bGH mice) or mice with disruption of the GH receptor gene (GHR^-/-). We also describe the effects of increased and decreased GH action on the proteome of adult patients with either acromegaly, GH deficiency or patients after short-term GH treatment. Finally, we explain how these proteomic studies resulted in the discovery of potential biomarkers for GH action, particularly those related with the effects of GH on aging, glucose metabolism and body composition.

Common methods of biological age estimation

At present, no single indicator could be used as a golden index to estimate aging process. The biological age (BA), which combines several important biomarkers with mathematical modeling, has been proposed for >50 years as an aging estimation method to replace chronological age (CA). The common methods used for BA estimation include the multiple linear regression (MLR), the principal component analysis (PCA), the Hochschild's method, and the Klemera and Doubal's method (KDM). The fundamental differences in these four methods are the roles of CA and the selection criteria of aging biomarkers. In MLR and PCA, CA is treated as the selection criterion and an independent index. The Hochschild's method and KDM share a similar concept, making CA an independent variable. Previous studies have either simply constructed the BA model by one or compared the four methods together. However, reviews have yet to illustrate and compare the four methods systematically. Since the BA model is a potential estimation of aging for clinical use, such as predicting onset and prognosis of diseases, improving the elderly's living qualities, and realizing successful aging, here we summarize previous BA studies, illustrate the basic statistical steps, and thoroughly discuss the comparisons among the four common BA estimation methods.

Increased levels of hyper-stable protein aggregates in plasma of older adults

Proteins that misfold into hyper-stable/degradation-resistant species during aging may accumulate and disrupt protein homeostasis (i.e., proteostasis), thereby posing a survival risk to any organism. Using the method diagonal two-dimensional (D2D) SDS-PAGE, which separates hyper-stable SDS-resistant proteins at a proteomics level, we analyzed the plasma of healthy young (<30 years) and older (60-80 years) adults. We discovered the presence of soluble SDS-resistant protein aggregates in the plasma of older adults, but found significantly lower levels in the plasma of young adults. We identified the inflammation-related chaperone protein haptoglobin as the main component of the hyper-stable aggregates. This observation is consistent with the growing link between accumulations of protein aggregates and aging across many organisms. It is plausible higher amounts of SDS-resistant protein aggregates in the plasma of older adults may reflect a compromise in proteostasis that may potentially indicate cellular aging and/or disease risk. The results of this study have implications for further understanding the link between aging and the accumulation of protein aggregates, as well as potential for the development of aging-related biomarkers. More broadly, this novel application of D2D SDS-PAGE may be used to identify, quantify, and characterize the degradation-resistant protein aggregates in human plasma or any biological system.

Oxidative stress response and Nrf2 signaling in aging

Increasing oxidative stress, a major characteristic of aging, has been implicated in a variety of age-related pathologies. In aging, oxidant production from several sources is increased, whereas antioxidant enzymes, the primary lines of defense, are decreased. Repair systems, including the proteasomal degradation of damaged proteins, also decline. Importantly, the adaptive response to oxidative stress declines with aging. Nrf2/EpRE signaling regulates the basal and inducible expression of many antioxidant enzymes and the proteasome. Nrf2/EpRE activity is regulated at several levels, including transcription, posttranslation, and interactions with other proteins. This review summarizes current studies on age-related impairment of Nrf2/EpRE function and discusses the changes in Nrf2 regulatory mechanisms with aging.

Proteome analysis in the assessment of ageing

Based on demographic trends, the societies in many developed countries are facing an increasing number and proportion of people over the age of 65. The raise in elderly populations along with improved health-care will be concomitant with an increased prevalence of ageing-associated chronic conditions like cardiovascular, renal, and respiratory diseases, arthritis, dementia, and diabetes mellitus. This is expected to pose unprecedented challenges both for individuals and societies and their health care systems. An ultimate goal of ageing research is therefore the understanding of physiological ageing and the achievement of 'healthy' ageing by decreasing age-related pathologies. However, on a molecular level, ageing is a complex multi-mechanistic process whose contributing factors may vary individually, partly overlap with pathological alterations, and are often poorly understood. Proteome analysis potentially allows modelling of these multifactorial processes. This review summarises recent proteomic research on age-related changes identified in animal models and human studies. We combined this information with pathway analysis to identify molecular mechanisms associated with ageing. We identified some molecular pathways that are affected in most or even all organs and others that are organ-specific. However, appropriately powered studies are needed to confirm these findings based in in silico evaluation.

Effects of age and sex on the hematology and blood chemistry of Tibetan macaques (Macaca thibetana)

Tibetan macaques (Macaca thibetana), also known as Chinese stump-tailed macaques, are a threatened primate species. Although Tibetan macaques are Old World monkeys in the genus of Macaca, limited age- and sex-related physiologic data are available for this particular species. We used 69 apparently healthy Tibetan male and female macaques to explore the effect of age and sex on physiologic parameters. Somatometric measurements, biochemistry, and hematologic parameters were analyzed. Significant age-related differences were found for weight, BMI, RBC count, Hgb, Hct, neutrophils, eosinophil count, ALT, AST, ALP, GGT, creatine kinase (muscle and brain subtypes), LDH, α-amylase, creatinine, apolipoprotein A1, total protein, albumin, cholesterol, HDL, and potassium. Significant differences by sex were noted for weight, BMI, ALT, total bilirubin, and indirect bilirubin. An interaction between age and sex accounted for statistically significant differences in the values for weight, BMI, and lymphocyte and eosinophil counts. These physiologic data will provide veterinarians and researchers with important age- and sex-specific reference ranges for evaluating experimental results from Tibetan macaques.

Proteomic profiles reveal age-related changes in coelomic fluid of sea urchin species with different life spans

Sea urchins have a different life history from humans and traditional model organisms used to study the process of aging. Sea urchins grow indeterminately, reproduce throughout their life span and some species have been shown to exhibit negligible senescence with no increase in mortality rate at advanced ages. Despite these properties, different species of sea urchins are reported to have very different natural life spans providing a unique model to investigate cellular mechanisms underlying life span determination and negligible senescence. To gain insight into the biological changes that accompany aging in these animals, proteomic profiles were examined in coelomic fluid from young and old sea urchins of three species with different life spans: short-lived Lytechinus variegatus, long-lived Strongylocentrotus franciscanus and Strongylocentrotus purpuratus which has an intermediate life span. The proteomic profiles of cell-free coelomic fluid were complex with many proteins exhibiting different forms and extensive post-translational modifications. Approximately 20% of the protein spots on 2-D gels showed more than two-fold change with age in each of the species. Changes that are consistent with age in all three species may prove to be useful biomarkers for age-determination for these commercially fished marine invertebrates and also may provide clues to mechanisms of negligible senescence. Among the proteins that change with age, the ectodomain of low-density lipoprotein receptor-related protein 4 (LRP4) was significantly increased in the coelomic fluid of all three sea urchin species suggesting that the Wnt signaling pathway should be further investigated for its role in negligible senescence.

Mouse models of growth hormone action and aging: a proteomic perspective

Growth hormone (GH) is a protein secreted by the anterior pituitary and circulates throughout the body to exert important actions on growth and metabolism. GH stimulates the secretion of insulin-like growth factor-I (IGF-I) that mediates some of the growth promoting actions of GH. The GH/IGF-I axis has recently been recognized as important in terms of longevity in organisms ranging from Caenorhabditis elegans to mice. For example, GH transgenic mice possess short lifespans while GH receptor null (GHR-/-) mice have extended longevity. Thus, the actions of GH (or IGF-I) or lack thereof impact the aging process. In this review, we summarize the proteomic analyses of plasma and white adipose tissue in these two mouse models of GH action, i.e. GH transgenic and GHR-/- mice. At the protein level, we wanted to establish novel plasma biomarkers of GH action as a function of age and to determine differences in adipose tissue depots. We have shown that these proteomic approaches have not only confirmed several known physiological actions of GH, but also resulted in novel protein biomarkers and targets that may be indicative of the aging process and/or new functions of GH. These results may generate new directions for GH and/or aging research.

Decreased insulin sensitivity and increased oxidative damage in wasting adipose tissue depots of wild-type mice

Unintentional weight loss (wasting) in the elderly is a major health concern as it leads to increased mortality. Several studies have focused on muscle loss, but little is known about the mechanisms giving rise to loss of fat mass at old ages. To investigate potential mechanisms, white adipose tissue (WAT) characteristics and proteomic profiles were compared between adult (10-12-month-old) and aged (22-24-month-old) wild-type mice. Four individual WAT depots were analyzed to account for possible depot-specific differences. Proteomic profiles of WAT depots, along with body weights and compositions, plasma levels of insulin, leptin and adiponectin, insulin tolerance, adipocyte sizes, and products of oxidative damage in each WAT depot were determined. We found that lean mass remained constant while fat mass and insulin tolerance were decreased in old age, as were adipocyte sizes in the WAT depots. Proteomic results showed increased levels of enolase, pyruvate dehydrogenase E1β, NAD(+)-dependent isocitrate dehydrogenase α, and ATP synthase subunit β, and decreased levels of carbonic anhydrase 3 in WAT of aged mice. These data suggest increased aerobic glucose oxidation in wasting WAT, consistent with decreased insulin signaling. Also, Cu/Zn superoxide dismutase and two chaperones were increased in aged WAT depots, indicating higher stress resistance. In agreement, lipid peroxidation (HNE-His adducts) increased in old age, although protein oxidation (carbonyl groups) showed no increase. In conclusion, features of wasting WAT were similar in the four depots, including decreased adipocyte sizes and alterations in protein expression profiles that indicated decreased insulin sensitivity and increased lipid peroxidation.

Proteomic screening of glycoproteins in human plasma for frailty biomarkers

The application of proteomics methodology for analyzing human blood samples is of increasing importance as a noninvasive method for understanding, detecting, and monitoring disease. In particular, glycoproteomic analysis may be useful in the study of age-related diseases and syndromes, such as frailty. This study demonstrates the use of methodology for isolating plasma glycoproteins using lectins, comparing the glycoproteome by frailty status using two-dimensional polyacrylamide gel electrophoresis and identifying glycoproteins using mass spectrometry. In a pilot study, we found seven glycoproteins to differ by at least twofold in prefrail compared with nonfrail older adults, including haptoglobin, transferrin, and fibrinogen, consistent with known inflammatory and hematologic changes associated with frailty. Enzyme-linked immunosorbent assay analysis found that plasma transferrin concentration was increased in frail and prefrail older adults compared with nonfrail, confirming our proteomic findings. This work provides evidence for using a reproducible methodology for conducting clinical proteomic comparative studies of age-related diseases.

Age- and sex-associated plasma proteomic changes in growth hormone receptor gene-disrupted mice

Growth hormone receptor gene-disrupted (GHR-/-) mice are dwarf, insulin sensitive, and long lived despite being obese. In order to identify characteristics associated with their increased longevity, we studied age-related plasma proteomic changes in these mice. Male and female GHR-/- mice and their littermate controls were followed longitudinally at 8, 16, and 24 months of ages for plasma proteomic analysis. Relative to control littermates, GHR-/- mice had increased levels of apolipoprotein A-4 and retinol-binding protein-4 and decreased levels of apolipoprotein E, haptoglobin, and mannose-binding protein-C. Female GHR-/- mice showed decreased inflammatory cytokines including interleukin-1β and monocyte chemotactic protein-1. Additionally, sex differences were found in specific isoforms of apolipoprotein E, RBP-4, haptoglobin, albumin, and hemoglobin subunit beta. In conclusion, we find plasma proteomic changes in GHR-/- mice that favor a longer life span as well as sex differences indicative of an improved health span in female mice.

Novel serum protein biomarkers indicative of growth hormone doping in healthy human subjects

The detection of recombinant human growth hormone (rhGH) is difficult due to its short half-life; therefore, novel and robust biomarkers of rhGH abuse are needed. In this study, serum samples derived from subjects treated with rhGH in a randomized, double blind, placebo-controlled crossover study were analyzed by 2-DE coupled with MS. Eight healthy male subjects aged 23.2±0.6 years were injected with rhGH (2 mg/day) or saline for 7 days with serum samples drawn at days 0, 3, and 8. Protein intensities were quantified and analyzed for differences between rhGH and placebo treatments. Proteins that showed significant changes were identified and confirmed by Western blotting. These included specific isoforms of α-1 antitrypsin and transthyretin that increased; and inter-α-trypsin inhibitor heavy chain H4, apolipoprotein A-1, and hemoglobin β chain that decreased. These proteins represent novel biomarkers of short-term rhGH exposure and may lead to a new method for detecting rhGH doping.

Proteomic changes in the heart of diet-induced pre-diabetic mice

The development of type 2 diabetes (T2D) is strongly associated with obesity. In humans, T2D increases the risk for end organ complications. Among these, heart disease has been ranked as the leading cause of death. We used a proteomic methodology to test the hypothesis that a pre-diabetic state generated by high-fat diet leads to changes in proteins related to heart function and structure. Over 300 protein spots were resolved by two-dimensional gel electrophoresis (2-DE). Fifteen protein spots were found to be altered (7 decreased and 8 increased) in pre-diabetic hearts. The protein spots were then identified by mass spectrometry and immunoblots. Among the decreased proteins, 3 are involved in heart structure (one isoform of desmin, troponin T2 and α-cardiac actin), 3 are involved in energy metabolism (mitochondrial ATP synthase β subunit, adenylate kinase and creatine kinase) and one is a component of the citric acid cycle (isocitrate dehydrogenase 3). In contrast, proteins involved in fatty acid oxidation (two isoforms of peroxisomal enoyl-CoA hydratase) and the citric acid cycle (three isoforms of malate dehydrogenase) were increased in pre-diabetic hearts. The results suggest that changes in the levels of several heart proteins may have implications in the development of the cardiac phenotype associated to T2D.

Plasma proteomic profiles of bovine growth hormone transgenic mice as they age

Attenuation of the growth hormone (GH)/insulin-like growth factor-1 (IGF-1) axis results in extended lifespan in many organisms including mice. Conversely, GH transgenic mice have excess GH action and die prematurely. We have studied bovine (b) GH transgenic mice (n = 9) and their wild type (WT) littermates (n = 8) longitudinally and have determined several age-related changes. Compared to WT mice, bGH mice lost fat mass, became hypoglycemic and had lower insulin levels at older ages despite being hyperinsulinemic when young. To examine plasma protein differences in bGH mice relative to controls, samples at 2, 4, 8, 12 and 16 months of age were analyzed by two-dimensional gel electrophoresis followed by identification using mass spectrometry. We found several differences in plasma proteins of bGH mice compared to controls, including increased apolipoprotein E (five isoforms), haptoglobin (four isoforms) and mannose-binding protein-C (one out of three isoforms), and decreased transthyretin (six isoforms). In addition, clusterin (two out of six isoforms) and haptoglobin (four isoforms) were up-regulated in bGH mice as a function of age. Finally, alpha-2 macroglobulin (seven isoforms) was altered in an isoform-specific manner with two isoforms increased and two decreased in bGH mouse plasma compared to controls. In conclusion, identification of these proteins suggests that bGH mice exhibit an increased inflammatory state with an adverse lipid profile, possibly contributing to their diminished life expectancy. Also, these newly discovered plasma proteins may be indicative or 'biomarkers' of a shortened lifespan.

Serum proteome changes in acromegalic patients following transsphenoidal surgery: novel biomarkers of disease activity

CONTEXT

Transsphenoidal adenomectomy is the primary treatment for acromegaly. However, assessment of the therapeutical outcome remains problematic since the existing biomarkers of disease activity frequently show discordant results.

OBJECTIVE

To discover novel serum biomarkers of disease activity in acromegalic patients before and after surgery.

DESIGN

Serum samples of eight newly diagnosed acromegaly patients before and after transsphenoidal surgery were analyzed for proteomic changes by two-dimensional gel electrophoresis. Protein spots displaying statistically significant changes, pre- versus post-surgery, were identified by mass spectrometry (MS), tandem MS (MS/MS), and western blot analysis.

RESULTS

Six protein spots displaying decreased intensities after surgery were identified as transthyretin (two isoforms), haptoglobin α2, β-hemoglobin, and apolipoprotein A-1 (two isoforms). One protein spot, identified as complement C4B precursor, was increased after the surgery.

CONCLUSIONS

Seven serum protein spots were differentially expressed following surgery in acromegalic patients. The identified proteins represent potential novel biomarkers to assess the effectiveness of surgical treatment in acromegalic individuals. Future studies will validate the use of the identified proteins as biomarkers of disease activity after medical treatment of acromegaly.