Identification of the dichotomous role of age-related LCK in calorie restriction revealed by integrative analysis of cDNA microarray and interactome

Sex-Mediated Differences in TNF Signaling- and ECM-Related Gene Expression in Aged Rat Kidney

Aging leads to the functional decline of an organism, which is associated with age and sex. To understand the functional change of kidneys depending on age and sex, we carried out a transcriptome analysis using RNA sequencing (RNA-Seq) data from rat kidneys. Four differentially expressed gene (DEG) sets were generated according to age and sex, and Gene Ontology analysis and overlapping analysis of Kyoto Encyclopedia of Genes and Genomes pathways were performed for the DEG sets. Through the analysis, we revealed that inflammation- and extracellular matrix (ECM)-related genes and pathways were upregulated in both males and females during aging, which was more prominent in old males than in old females. Furthermore, quantitative real-time PCR analysis confirmed that the expression of tumor necrosis factor (TNF) signaling-related genes, Birc3, Socs3, and Tnfrsf1b, and ECM-related genes, Cd44, Col3a1, and Col5a2, which showed that the genes were markedly upregulated in males and not females during aging. Also, hematoxylin-eosin (H&E) staining for histological analysis showed that renal damage was highly shown in old males rather than old females. In conclusion, in the rat kidney, the genes involved in TNF signaling and ECM accumulation are upregulated in males more than in females during aging. These results suggest that the upregulation of the genes may have a higher contribution to age-related kidney inflammation and fibrosis in males than in females.

Chronic Inflammation as an Underlying Mechanism of Ageing and Ageing-Related Diseases

Age-related chronic inflammation is characterized as the unresolved low-grade inflammatory process underlying the ageing process and various age-related diseases. In this chapter, we review the age-related changes in the oxidative stress-sensitive pro-inflammatory NF-κB signaling pathways causally linked with chronic inflammation during ageing based on senoinflammation schema. We describe various age-related dysregulated pro- and anti-inflammatory cytokines, chemokines, and senescence-associated secretory phenotype (SASP), and alterations of inflammasome, specialized pro-resolving lipid mediators (SPM), and autophagy as major players in the chronic inflammatory intracellular signaling network. A better understanding of the molecular, cellular, and systemic mechanisms involved in chronic inflammation in the ageing process would provide further insights into the potential anti-inflammatory strategies.

Anti-aging Effects of Calorie Restriction (CR) and CR Mimetics based on the Senoinflammation Concept

Chronic inflammation, a pervasive feature of the aging process, is defined by a continuous, multifarious, low-grade inflammatory response. It is a sustained and systemic phenomenon that aggravates aging and can lead to age-related chronic diseases. In recent years, our understanding of age-related chronic inflammation has advanced through a large number of investigations on aging and calorie restriction (CR). A broader view of age-related inflammation is the concept of senoinflammation, which has an outlook beyond the traditional view, as proposed in our previous work. In this review, we discuss the effects of CR on multiple phases of proinflammatory networks and inflammatory signaling pathways to elucidate the basic mechanism underlying aging. Based on studies on senoinflammation and CR, we recognized that senescence-associated secretory phenotype (SASP), which mainly comprises cytokines and chemokines, was significantly increased during aging, whereas it was suppressed during CR. Further, we recognized that cellular metabolic pathways were also dysregulated in aging; however, CR mimetics reversed these effects. These results further support and enhance our understanding of the novel concept of senoinflammation, which is related to the metabolic changes that occur in the aging process. Furthermore, a thorough elucidation of the effect of CR on senoinflammation will reveal key insights and allow possible interventions in aging mechanisms, thus contributing to the development of new therapies focused on improving health and longevity.

Novel Role of Lck in Leptin-Induced Inflammation and Implications for Renal Aging

Aging is associated with increased fat mass and elevated serum leptin levels (hyperleptinemia), causing proinflammation in the kidneys where it plays a primary role in the removal of endogenous leptin from the circulation. Lymphocyte-specific kinase (Lck) is a positive regulator of inflammatory signaling and a potential treatment target for age-related diseases, but its role in leptin signaling is unknown. Here, we investigated how Lck influences hyperleptinemia-induced inflammation in kidney tissues from 6- and 21-month-old rats. Results indicate that Lck expression and activation increased significantly in aged rat kidneys, especially at renal tubules. Furthermore, we identified interactions between Lck and short leptin-receptor isoforms, suggesting that Lck is a protein tyrosine kinase regulating leptin signaling. We further investigated whether increased Lck expression in renal tubular epithelial cells and macrophage infiltration are associated with leptin-induced inflammation. We then demonstrated that leptin activates Lck and proinflammatory transcription factors (STAT3 and NF-κB), while Lck knockdown modulates the expression of both transcription factors. Collectively, these data implicate that Lck leads to development of leptin-induced renal inflammation during aging. Inhibition of this protein tyrosine kinase may therefore be an appropriate therapeutic option for protection against age-related hyperleptinemia.

Vascular Dysfunction and Insulin Resistance in Aging

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Insulin was discovered in 1922 by Banting and Best. Since that time, extensive research on the mechanisms of insulin activity and action has continued. Currently, it is known that the role of insulin is much greater than simply regulating carbohydrate metabolism. Insulin in physiological concentration is also necessary to maintain normal vascular function.

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Insulin resistance is defined as a pathological condition characterized by reduced sensitivity of skeletal muscles, liver, and adipose tissue, to insulin and its downstream metabolic effects under normal serum glucose concentrations. There are also selective forms of insulin resistance with unique features, including vascular insulin resistance. Insulin resistance, both classical and vascular, contributes to vascular impairment resulting in increased risk of cardiovascular disease. Furthermore, in the elderly population, additional factors including redistribution of fat concentrations, low-grade inflammation, and decreased self-repair capacity [or cell senescence] amplify the vascular abnormalities related to insulin resistance.

Modulation of senoinflammation by calorie restriction based on biochemical and Omics big data analysis

Aging is a complex and progressive process characterized by physiological and functional decline with time that increases susceptibility to diseases. Aged-related functional change is accompanied by a low-grade, unresolved chronic inflammation as a major underlying mechanism. In order to explain aging in the context of chronic inflammation, a new integrative concept on age-related chronic inflammation is necessary that encompasses much broader and wider characteristics of cells, tissues, organs, systems, and interactions between immune and non-immune cells, metabolic and non-metabolic organs. We have previously proposed a novel concept of senescent (seno)-inflammation and provided its frameworks. This review summarizes senoinflammation concept and additionally elaborates modulation of senoinflammation by calorie restriction (CR). Based on aging and CR studies and systems-biological analysis of Omics big data, we observed that senescence associated secretory phenotype (SASP) primarily composed of cytokines and chemokines was notably upregulated during aging whereas CR suppressed them. This result further strengthens the novel concept of senoinflammation in aging process. Collectively, such evidence of senoinflammation and modulatory role of CR provide insights into aging mechanism and potential interventions, thereby promoting healthy longevity. [BMB Reports 2019; 52(1): 56-63].

Redefining Chronic Inflammation in Aging and Age-Related Diseases: Proposal of the Senoinflammation Concept

Age-associated chronic inflammation is characterized by unresolved and uncontrolled inflammation with multivariable low-grade, chronic and systemic responses that exacerbate the aging process and age-related chronic diseases. Currently, there are two major hypotheses related to the involvement of chronic inflammation in the aging process: molecular inflammation of aging and inflammaging. However, neither of these hypotheses satisfactorily addresses age-related chronic inflammation, considering the recent advances that have been made in inflammation research. A more comprehensive view of age-related inflammation, that has a scope beyond the conventional view, is therefore required. In this review, we discuss newly emerging data on multi-phase inflammatory networks and proinflammatory pathways as they relate to aging. We describe the age-related upregulation of nuclear factor (NF)-κB signaling, cytokines/chemokines, endoplasmic reticulum (ER) stress, inflammasome, and lipid accumulation. The later sections of this review present our expanded view of age-related senescent inflammation, a process we term "senoinflammation", that we propose here as a novel concept. As described in the discussion, senoinflammation provides a schema highlighting the important and ever-increasing roles of proinflammatory senescence-associated secretome, inflammasome, ER stress, TLRs, and microRNAs, which support the senoinflammation concept. It is hoped that this new concept of senoinflammation opens wider and deeper avenues for basic inflammation research and provides new insights into the anti-inflammatory therapeutic strategies targeting the multiple proinflammatory pathways and mediators and mediators that underlie the pathophysiological aging process.

Modulation of senoinflammation by calorie restriction based on biochemical and Omics big data analysis

Aging is a complex and progressive process characterized by physiological and functional decline with time that increases susceptibility to diseases. Aged-related functional change is accompanied by a low-grade, unresolved chronic inflammation as a major underlying mechanism. In order to explain aging in the context of chronic inflammation, a new integrative concept on age-related chronic inflammation is necessary that encompasses much broader and wider characteristics of cells, tissues, organs, systems, and interactions between immune and non-immune cells, metabolic and non-metabolic organs. We have previously proposed a novel concept of senescent (seno)-inflammation and provided its frameworks. This review summarizes senoinflammation concept and additionally elaborates modulation of senoinflammation by calorie restriction (CR). Based on aging and CR studies and systems-biological analysis of Omics big data, we observed that senescence associated secretory phenotype (SASP) primarily composed of cytokines and chemokines was notably upregulated during aging whereas CR suppressed them. This result further strengthens the novel concept of senoinflammation in aging process. Collectively, such evidence of senoinflammation and modulatory role of CR provide insights into aging mechanism and potential interventions, thereby promoting healthy longevity. [BMB Reports 2019; 52(1): 56-63].

Distinguishing normal brain aging from the development of Alzheimer's disease: inflammation, insulin signaling and cognition

As populations age, prevalence of Alzheimer's disease (AD) is rising. Over 100 years of research has provided valuable insights into the pathophysiology of the disease, for which age is the principal risk factor. However, in recent years, a multitude of clinical trial failures has led to pharmaceutical corporations becoming more and more unwilling to support drug development in AD. It is possible that dependence on the amyloid cascade hypothesis as a guide for preclinical research and drug discovery is part of the problem. Accumulating evidence suggests that amyloid plaques and tau tangles are evident in non-demented individuals and that reducing or clearing these lesions does not always result in clinical improvement. Normal aging is associated with pathologies and cognitive decline that are similar to those observed in AD, making differentiation of AD-related cognitive decline and neuropathology challenging. In this mini-review, we discuss the difficulties with discerning normal, age-related cognitive decline with that related to AD. We also discuss some neuropathological features of AD and aging, including amyloid and tau pathology, synapse loss, inflammation and insulin signaling in the brain, with a view to highlighting cognitive or neuropathological markers that distinguish AD from normal aging. It is hoped that this review will help to bolster future preclinical research and support the development of clinical tools and therapeutics for AD.

Inflammation, insulin signaling and cognitive function in aged APP/PS1 mice

Cognitive dysfunction and neuroinflammation are typical in Alzheimer's disease (AD), but are also associated with normal aging, albeit less severely. Insulin resistance in the brain has been demonstrated in AD patients and is thought to be involved in AD pathophysiology. Using 15-18 month-old APP/PS1 mice, this study measured peripheral and central insulin signaling and sensitivity, inflammatory markers in brain and plasma and oxidative stress and synapse density in the brain. Novel object recognition, Morris water maze and reversal water maze tasks were performed to assess cognitive function in aged APP/PS1 mice and wild type littermates. Glucose tolerance and insulin sensitivity were similar in APP/PS1 mice and wild type controls, however IRS-1 pSer⁶¹⁶ was increased in cortex and dentate gyrus of APP/PS1 mice. Recognition and spatial memory was impaired in both APP/PS1 and wild type mice, however learning impairments were apparent in APP/PS1 mice. Expression of GLP-1 receptor, ERK2, IKKβ, mTOR, PKCθ, NF-κB1 and TLR4 was similar between aged APP/PS1 mice and age-matched wild types. Compared to age-matched wild type mice, IFNγ and IL-4 were increased in brains of APP/PS1 mice. These results suggest that normal aging may be associated with enhanced neuroinflammation, oxidative stress, and cognitive decline, however distinctions are apparent in the brain of APP/PS1 mice in terms of inflammation and insulin signaling and in certain cognitive domains. Demarcation of pathological events that distinguish AD from normal aging will allow for improvements in diagnostic tools and the development of more effective therapeutics.

Effects of MHY908, a New Synthetic PPARα/γ Dual Agonist, on Inflammatory Responses and Insulin Resistance in Aged Rats

Insulin resistance is common with aging and is associated with the inflammatory response in both humans and rodents. A number of peroxisome proliferator-activated receptor (PPAR) α/γ dual agonists have been tested for their abilities to attenuate insulin resistance and type 2 diabetes. However, there is no study on the effects of PPARα/γ dual agonists on inflammation and insulin resistance during aging. In the present study, we investigated the ability of 2-[4-(5-chlorobenzothiazothiazol-2-yl)phenoxy]-2-methyl-propionic acid (MHY908), a newly synthesized novel PPARα/γ dual agonist, to suppress the inflammatory response and attenuate insulin resistance in aged rats. Twenty-month-old rats were divided into four groups: ad libitum fed, ad libitum fed supplemented with MHY908 (1 mg and 3 mg/kg/day for 4 weeks), and 40% calorie restricted. Six-month-old ad libitum fed rats were used as an age control. The aged rats supplemented with MHY908 showed reduced serum glucose, triglyceride, and insulin levels, as well as reduced liver triglyceride levels. MHY908 brought about a reduction in endoplasmic reticulum stress and activation of the c-Jun N-terminal kinase in the livers of aged rats, which consequently improved insulin signaling. In the kidneys of aged rats, the efficacy of MHY908 as a potent anti-inflammatory agent was shown by its suppression of NF-κB activation through inhibition of the Akt/IκB kinase signaling pathway. Therefore, the major finding of this study is that MHY908 acts as a therapeutic agent against age-related inflammation associated with insulin resistance by activating PPARα and PPARγ, thus attenuating endoplasmic reticulum stress.

Age-related inflammation and insulin resistance: a review of their intricate interdependency

Chronic inflammation is a major risk factor underlying aging and the associated diseases of aging; of particular interest is insulin resistance during aging. Chronic inflammation impairs normal lipid accumulation, adipose tissue function, mitochondrial function, and causes endoplasmic reticulum (ER) stress, which lead to insulin resistance. However, some studies show that insulin resistance itself amplifies chronic inflammation. The activity of the insulin-dependent Akt signaling pathway is highlighted because of its decrease in insulin-sensitive organs, like liver and muscle, which may underlie insulin resistance and hyperinsulinemia, and its increased levels in non-metabolic organs, such as kidney and aorta. In that the prevalence of obesity has increased substantially for all age groups in recent years, our review summarizes the data showing the involvement of chronic inflammation in obesity-induced insulin resistance, which perpetuates reciprocal interactions between the chronic inflammatory process and increased adiposity, thereby accelerating the aging process.

A functional link between heme oxygenase-1 and tristetraprolin in the anti-inflammatory effects of nicotine

Nicotine stimulates the cholinergic anti-inflammatory pathway and prevents excessive inflammation by inhibiting the release of inflammatory cytokines from macrophages. We have previously reported that heme oxygenase-1 (HO-1) and tristetraprolin (TTP) are induced by nicotine and mediate the anti-inflammatory function of nicotine in macrophages. However, it was not clear whether the two molecules are functionally linked. In this study, we sought to determine whether HO-1 associates with TTP to mediate the anti-inflammatory effects of nicotine. Inhibition of HO-1 activity or HO-1 expression attenuated the effects of nicotine on STAT3 activation, TTP induction, and TNF-α production in LPS-treated macrophages. Induction of HO-1 expression increased the level of TTP in the absence of nicotine. In an LPS-induced endotoxemia model, HO-1 deficiency blocked the effects of nicotine on the STAT3 phosphorylation, TTP induction, and LPS-induced TNF-α production in the liver. Downregulation of STAT3 by siRNA attenuated the effect of nicotine on TTP expression and TNF-α production but did not affect the nicotine-mediated induction of HO-1. In TTP knockout mice, nicotine treatment enhanced HO-1 expression and STAT3 activation but failed to inhibit LPS-induced TNF-α production. Our results suggest that HO-1 and TTP are functionally linked in mediating the anti-inflammatory effects of nicotine; HO-1 is necessary for the induction of TTP by nicotine. This novel nicotine-HO-1-TTP signaling pathway provides new possibilities for the treatment of inflammatory diseases.