Fat tissue, aging, and cellular senescence

Expression of lipogenic markers is decreased in subcutaneous adipose tissue and adipocytes of older women and is negatively linked to GDF15 expression

In aging, the capacity of subcutaneous adipose tissue (SAT) to store lipids decreases and this results in metabolically unfavorable fat redistribution. Triggers of this age-related SAT dysfunction may include cellular senescence or endoplasmic reticulum (ER) stress. Therefore, we compared lipogenic capacity of SAT between young and older women and investigated its relation to senescence and ER stress markers. Samples of SAT and corresponding SAT-derived primary preadipocytes were obtained from two groups of women differing in age (36 vs. 72 years, n = 15 each) but matched for fat mass. mRNA levels of selected genes (lipogenesis: ACACA, FASN, SCD1, DGAT2, ELOVL6; senescence: p16, p21, NOX4, GDF15; ER stress-ATF4, XBP1s, PERK, HSPA5, GADD34, HYOU1, CHOP, EDEM1, DNAJC3) were assessed by qPCR, protein levels of GDF15 by ELISA, and mitochondrial function by the Seahorse Analyzer. Compared to the young, SAT and in vitro differentiated adipocytes from older women exhibited reduced mRNA expression of lipogenic enzymes. Out of analyzed senescence and ER stress markers, the only gene, whose expression correlated negatively with the expression of lipogenic enzymes in both SAT and adipocytes, was GDF15, a marker of not only senescence but also mitochondrial dysfunction. In line with this, inhibition of mitochondrial ATP synthase in adipocytes strongly upregulated GDF15 while reduced expression of lipogenic enzymes. Moreover, adipocytes from older women had a tendency for diminished mitochondrial capacity. Thus, a reduced lipogenic capacity of adipocytes in aged SAT appears to be linked to mitochondrial dysfunction rather than to ER stress or accumulation of senescent cells.

The Role of Curcumin in the Modulation of Ageing

It is believed that postponing ageing is more effective and less expensive than the treatment of particular age-related diseases. Compounds which could delay symptoms of ageing, especially natural products present in a daily diet, are intensively studied. One of them is curcumin. It causes the elongation of the lifespan of model organisms, alleviates ageing symptoms and postpones the progression of age-related diseases in which cellular senescence is directly involved. It has been demonstrated that the elimination of senescent cells significantly improves the quality of life of mice. There is a continuous search for compounds, named senolytic drugs, that selectively eliminate senescent cells from organisms. In this paper, we endeavor to review the current knowledge about the anti-ageing role of curcumin and discuss its senolytic potential.

Mechanisms of obesity-induced metabolic and vascular dysfunctions

Obesity has reached epidemic proportions and its prevalence is climbing. Obesity is characterized by hypertrophied adipocytes with a dysregulated adipokine secretion profile, increased recruitment of inflammatory cells, and impaired metabolic homeostasis that eventually results in the development of systemic insulin resistance, a phenotype of type 2 diabetes. Nitric oxide synthase (NOS) is an enzyme that converts L-arginine to nitric oxide (NO), which functions to maintain vascular and adipocyte homeostasis. Arginase is a ureohydrolase enzyme that competes with NOS for L-arginine. Arginase activity/expression is upregulated in obesity, which results in diminished bioavailability of NO, impairing both adipocyte and vascular endothelial cell function. Given the emerging role of NO in the regulation of adipocyte physiology and metabolic capacity, this review explores the interplay between arginase and NO, and their effect on the development of metabolic disorders, cardiovascular diseases, and mitochondrial dysfunction in obesity. A comprehensive understanding of the mechanisms involved in the development of obesity-induced metabolic and vascular dysfunction is necessary for the identification of more effective and tailored therapeutic avenues for their prevention and treatment.

Characterization and Optimization of the Seeding Process of Adipose Stem Cells on the Polycaprolactone Scaffolds

The purpose of the current study was to evaluate the usefulness of adipose-derived stem cells (ASCs) for bone injury therapy. Lipoaspirates were collected from the abdomen regions of 17 healthy female donors (mean age 49 ± 6 years) using Coleman technique or Body-jet liposuction. In the present study, the primary objective was the in vitro characteristics of human ASCs. The secondary objective was the optimization of the cell seeding process on 3D-printed scaffolds using polycaprolactone (PCL) or polycaprolactone covered with tricalcium phosphate (PCL + 5% TCP). Biological evaluation of human ASC showed high efficiency of isolation obtaining a satisfying amount of homogeneous cell populations. Results suggest that ASCs can be cultured in vitro for a long time without impairing their proliferative capacity. Growth kinetics shows that the highest number of cells can be achieved in passage 5 and after the 16^th passage; there is a significant decrease of cell numbers and their proliferative potential. The percentage of colony forming units from the adipose stem cells is 8% ± 0.63% (p < 0.05). It was observed that the accumulation of calcium phosphate in the cells in vitro, marked with Alizarin Red S, was increased along with the next passage. Analysis of key parameters critically related to the cell seeding process shows that volume of cell suspension and propagation time greatly improve the efficiency of seeding both in PCL and PCL + 5% TCP scaffolds. The cell seeding efficiency did differ significantly between scaffold materials and cell seeding methods (p < 0.001). Increased seeding efficiency was observed when using the saturation of cell suspension into scaffolds with additional incubation. Alkaline phosphatase level production in PCL + 5% TCP scaffold was better than in PCL-only scaffold. The study results can be used for the optimization of the seeding process and quantification methods determining the successful implementation of the preclinical model study in the future tissue engineering strategies.

Diabetes and Aging: From Treatment Goals to Pharmacologic Therapy

Diabetes is becoming one of the most widespread health burning problems in the elderly. Worldwide prevalence of diabetes among subjects over 65 years was 123 million in 2017, a number that is expected to double in 2045. Old patients with diabetes have a higher risk of common geriatric syndromes, including frailty, cognitive impairment and dementia, urinary incontinence, traumatic falls and fractures, disability, side effects of polypharmacy, which have an important impact on quality of life and may interfere with anti-diabetic treatment. Because of all these factors, clinical management of type 2 diabetes in elderly patients currently represents a real challenge for the physician. Actually, the optimal glycemic target to achieve for elderly diabetic patients is still a matter of debate. The American Diabetes Association suggests a HbA1c goal <7.5% for older adults with intact cognitive and functional status, whereas, the American Association of Clinical Endocrinologists (AACE) recommends HbA1c levels of 6.5% or lower as long as it can be achieved safely, with a less stringent target (>6.5%) for patients with concurrent serious illness and at high risk of hypoglycemia. By contrast, the American College of Physicians (ACP) suggests more conservative goals (HbA1c levels between 7 and 8%) for most older patients, and a less intense pharmacotherapy, when HbA1C levels are ≤6.5%. Management of glycemic goals and antihyperglycemic treatment has to be individualized in accordance to medical history and comorbidities, giving preference to drugs that are associated with low risk of hypoglycemia. Antihyperglycemic agents considered safe and effective for type 2 diabetic older patients include: metformin (the first-line agent), pioglitazone, dipeptidyl peptidase 4 inhibitors, glucagon-like peptide 1 receptor agonists. Insulin secretagogue agents have to be used with caution because of their significant hypoglycemic risk; if used, short-acting sulfonylureas, as gliclazide, or glinides as repaglinide, should be preferred. When using complex insulin regimen in old people with diabetes, attention should be paid for the risk of hypoglycemia. In this paper we aim to review and discuss the best glycemic targets as well as the best treatment choices for older people with type 2 diabetes based on current international guidelines.

Lipectomy associated to obesity produces greater fat accumulation in the visceral white adipose tissue of female compared to male rats

BACKGROUND

Mobility of fat deposited in adipocytes among different fatty territories can play a crucial role in the pathogenesis of obesity-related diseases. Our goal was to investigate which of the remaining fat pads assume the role of accumulating lipids after surgical removal of parietal WAT (lipectomy; LIPEC) in rats of both sexes displaying MSG-induced obesity.

METHODS

The animals entered the study straight after birth, being separated according to gender and randomly divided into CON (control, saline-treated) and MSG (monosodium glutamate-treated) groups. Next, the animals underwent LIPEC or sham-operated surgery (SHAM). Obesity was induced by the injection of MSG (4 mg/g/day) during neonatal stage (2nd to 11th day from birth). LIPEC was performed on the 12th week, consisting in the withdrawal of parietal WAT. On the 16th week, the following WATs were isolated and collected: peri-epididymal-WAT (EP-WAT); parametrial-WAT (PM-WAT); omental-WAT (OM-WAT); perirenal-WAT (PR-WAT) and retroperitoneal-WAT (RP-WAT).

RESULTS

The adiposity index was significantly increased in both male (3.2 ± 0.2** vs 1.8 ± 0.1) and female (4.9 ± 0.7* vs 2.6 ± 0.3) obese rats compared to their respective control groups. LIPEC in obese animals produced fat accumulation in visceral fat sites in a more accentuated manner in female (3.6 ± 0.3** vs 2.8 ± 0.3 g/100 g) rather than in male (1.8 ± 0.2* vs 1.5 ± 0.1 g/100 g) rats compared to obese non-lipectomized animals. Among the visceral WATs, the greater differences were observed between gonadal WATs of obese lipectomized rats, with higher accumulation having been observed in PM-WAT (2.8 ± 0.3* vs 2.1 ± 0.2 g/100 g) rather than in EP-WAT (1.0 ± 0.1 ± 0.9 ± 0.1 g/100 g) when compared to obese non-lipectomized animals.

CONCLUSIONS

The results of the present study led us to conclude that obesity induced by MSG treatment occurs differently in male and female rats. When associated with parietal LIPEC, there was a significant increase in the deposition of visceral fat, which was significantly higher in obese female rats than in males, indicating that fat mobility among WATs in lipectomized-obese rats can occur more expressively in particular sites of remaining WATs.

L1 drives IFN in senescent cells and promotes age-associated inflammation

Retrotransposable elements are deleterious at many levels, and the failure of host surveillance systems for these elements can thus have negative consequences. However, the contribution of retrotransposon activity to ageing and age-associated diseases is not known. Here we show that during cellular senescence, L1 (also known as LINE-1) retrotransposable elements become transcriptionally derepressed and activate a type-I interferon (IFN-I) response. The IFN-I response is a phenotype of late senescence and contributes to the maintenance of the senescence-associated secretory phenotype. The IFN-I response is triggered by cytoplasmic L1 cDNA, and is antagonized by inhibitors of the L1 reverse transcriptase. Treatment of aged mice with the nucleoside reverse transcriptase inhibitor lamivudine downregulated IFN-I activation and age-associated inflammation (inflammaging) in several tissues. We propose that the activation of retrotransposons is an important component of sterile inflammation that is a hallmark of ageing, and that L1 reverse transcriptase is a relevant target for the treatment of age-associated disorders.

Aging Disrupts Muscle Stem Cell Function by Impairing Matricellular WISP1 Secretion from Fibro-Adipogenic Progenitors

Research on age-related regenerative failure of skeletal muscle has extensively focused on the phenotypes of muscle stem cells (MuSCs). In contrast, the impact of aging on regulatory cells in the MuSC niche remains largely unexplored. Here, we demonstrate that aging impairs the function of mouse fibro-adipogenic progenitors (FAPs) and thereby indirectly affects the myogenic potential of MuSCs. Using transcriptomic profiling, we identify WNT1 Inducible Signaling Pathway Protein 1 (WISP1) as a FAP-derived matricellular signal that is lost during aging. WISP1 is required for efficient muscle regeneration and controls the expansion and asymmetric commitment of MuSCs through Akt signaling. Transplantation of young FAPs or systemic treatment with WISP1 restores the myogenic capacity of MuSCs in aged mice and rescues skeletal muscle regeneration. Our work establishes that loss of WISP1 from FAPs contributes to MuSC dysfunction in aged skeletal muscles and demonstrates that this mechanism can be targeted to rejuvenate myogenesis.

Sarcopenia: Aging-Related Loss of Muscle Mass and Function

Sarcopenia is a loss of muscle mass and function in the elderly that reduces mobility, diminishes quality of life, and can lead to fall-related injuries, which require costly hospitalization and extended rehabilitation. This review focuses on the aging-related structural changes and mechanisms at cellular and subcellular levels underlying changes in the individual motor unit: specifically, the perikaryon of the α-motoneuron, its neuromuscular junction(s), and the muscle fibers that it innervates. Loss of muscle mass with aging, which is largely due to the progressive loss of motoneurons, is associated with reduced muscle fiber number and size. Muscle function progressively declines because motoneuron loss is not adequately compensated by reinnervation of muscle fibers by the remaining motoneurons. At the intracellular level, key factors are qualitative changes in posttranslational modifications of muscle proteins and the loss of coordinated control between contractile, mitochondrial, and sarcoplasmic reticulum protein expression. Quantitative and qualitative changes in skeletal muscle during the process of aging also have been implicated in the pathogenesis of acquired and hereditary neuromuscular disorders. In experimental models, specific intervention strategies have shown encouraging results on limiting deterioration of motor unit structure and function under conditions of impaired innervation. Translated to the clinic, if these or similar interventions, by saving muscle and improving mobility, could help alleviate sarcopenia in the elderly, there would be both great humanitarian benefits and large cost savings for health care systems.

The Impact of Aging on Adipose Function and Adipokine Synthesis

During the last 40 years, there has been a world-wide increase in both the prevalence of obesity and an increase in the number of persons over the age of 60 due to a decline in deaths from infectious disease and the nutrition transition in low and middle income nations. While the increase in the elderly population indicates improvements in global public health, this population may experience a diminished quality of life due to the negative impacts of obesity on age-associated inflammation. Aging alters adipose tissue composition and function resulting in insulin resistance and ectopic lipid storage. A reduction in brown adipose tissue activity, declining sex hormones levels, and abdominal adipose tissue expansion occur with advancing years through the redistribution of lipids from the subcutaneous to the visceral fat compartment. These changes in adipose tissue function and distribution influence the secretion of adipose tissue derived hormones, or adipokines, that promote a chronic state of low-grade systemic inflammation. Ultimately, obesity accelerates aging by enhancing inflammation and increasing the risk of age-associated diseases. The focus of this review is the impact of aging on adipose tissue distribution and function and how these effects influence the elaboration of pro and anti-inflammatory adipokines.

From White to Brown - Adipose Tissue Is Critical to the Extended Lifespan and Healthspan of Growth Hormone Mutant Mice

Growth hormone (GH) is a metabolic hormone that has major functions in the liver, muscle, and adipose tissue (AT). In the past 20 years, numerous studies have demonstrated that decreased growth hormone (GH) action is clearly linked to alterations in longevity. Therefore, it is not surprising that mechanisms underlying the extended longevity of GH-mutant animals include alterations in AT function. This Review aims to describe the basics of AT biology, GH secretion and action, and the effects of altered GH signaling in mice and humans. Lastly, this Review discusses the intersection of GH and AT, and how the influence of GH on AT may play a critical role in determining lifespan and healthspan.

Obesity May Accelerate the Aging Process

Lines of evidence from several studies have shown that increases in life expectancy are now accompanied by increased disability rate. The expanded lifespan of the aging population imposes a challenge on the continuous increase of chronic disease. The prevalence of overweight and obesity is increasing at an alarming rate in many parts of the world. Further to increasing the onset of metabolic imbalances, obesity leads to reduced life span and affects cellular and molecular processes in a fashion resembling aging. Nine key hallmarks of the aging process have been proposed. In this review, we will review these hallmarks and discuss pathophysiological changes that occur with obesity, that are similar to or contribute to those that occur during aging. We present and discuss the idea that obesity, in addition to having disease-specific effects, may accelerate the rate of aging affecting all aspects of physiology and thus shortening life span and health span.

The Dual Role of the Pervasive "Fattish" Tissue Remodeling With Age

Human aging is characterized by dramatic changes in body mass composition that include a general increase of the total fat mass. Within the fat mass, a change in the proportions of adipose tissues also occurs with aging, affecting body metabolism, and playing a central role in many chronic diseases, including insulin resistance, obesity, cardiovascular diseases, and type II diabetes. In mammals, fat accumulates as white (WAT) and brown (BAT) adipose tissue, which differ both in morphology and function. While WAT is involved in lipid storage and immuno-endocrine responses, BAT is aimed at generating heat. With advancing age BAT declines, while WAT increases reaching the maximum peak by early old age and changes its distribution toward a higher proportion of visceral WAT. However, lipids tend to accumulate also within lipid droplets (LDs) in non-adipose tissues, including muscle, liver, and heart. The excess of such ectopic lipid deposition and the alteration of LD homeostasis contribute to the pathogenesis of the above-mentioned age-related diseases. It is not clear why age-associated tissue remodeling seems to lean toward lipid deposition as a "default program." However, it can be noted that such remodeling is not inevitably detrimental. In fact, such a programmed redistribution of fat throughout life could be considered physiological and even protective, in particular at extreme old age. In this regard, it has to be considered that an excessive decrease of subcutaneous peripheral fat is associated with a pro-inflammatory status, and a decrease of LD is associated with lipotoxicity leading to an increased risk of insulin resistance, type II diabetes and cardiovascular diseases. At variance, a balanced rate of fat content and distribution has beneficial effects for health and metabolic homeostasis, positively affecting longevity. In this review, we will summarize the present knowledge on the mechanisms of the age-related changes in lipid distribution and we will discuss how fat mass negatively or positively impacts on human health and longevity.

Contribution of Adipose Tissue Inflammation to the Development of Type 2 Diabetes Mellitus

The objective of this comprehensive review is to summarize and discuss the available evidence of how adipose tissue inflammation affects insulin sensitivity and glucose tolerance. Low-grade, chronic adipose tissue inflammation is characterized by infiltration of macrophages and other immune cell populations into adipose tissue, and a shift toward more proinflammatory subtypes of leukocytes. The infiltration of proinflammatory cells in adipose tissue is associated with an increased production of key chemokines such as C-C motif chemokine ligand 2, proinflammatory cytokines including tumor necrosis factor α and interleukins 1β and 6 as well as reduced expression of the key insulin-sensitizing adipokine, adiponectin. In both rodent models and humans, adipose tissue inflammation is consistently associated with excess fat mass and insulin resistance. In humans, associations with insulin resistance are stronger and more consistent for inflammation in visceral as opposed to subcutaneous fat. Further, genetic alterations in mouse models of obesity that reduce adipose tissue inflammation are-almost without exception-associated with improved insulin sensitivity. However, a dissociation between adipose tissue inflammation and insulin resistance can be observed in very few rodent models of obesity as well as in humans following bariatric surgery- or low-calorie-diet-induced weight loss, illustrating that the etiology of insulin resistance is multifactorial. Taken together, adipose tissue inflammation is a key factor in the development of insulin resistance and type 2 diabetes in obesity, along with other factors that likely include inflammation and fat accumulation in other metabolically active tissues. © 2019 American Physiological Society. Compr Physiol 9:1-58, 2019.

T Cells in Adipose Tissue in Aging

Similar to obesity, aging is associated with visceral adiposity and insulin resistance. Inflammation in adipose tissue, mainly evidenced by increased accumulation and proinflammatory polarization of T cells and macrophages, has been well-documented in obesity and may contribute to the associated metabolic dysfunctions including insulin resistance. Studies show that increased inflammation, including inflammation in adipose tissue, also occurs in aging, so-called "inflamm-aging." Aging-associated inflammation in adipose tissue has some similarities but also differences compared to obesity-related inflammation. In particular, conventional T cells are elevated in adipose tissue in both obesity and aging and have been implicated in metabolic functions in obesity. However, the changes and also possibly functions of regulatory T cells (Treg) in adipose tissue are different in aging and obesity. In this review, we will summarize recent advances in research on the changes of these immune cells in adipose tissue with aging and obesity and discuss their possible contributions to metabolism and the potential of these immune cells as novel therapeutic targets for prevention and treatment of metabolic diseases associated with aging or obesity.

Urothelial Senescence in the Pathophysiology of Diabetic Bladder Dysfunction-A Novel Hypothesis

Diabetic bladder dysfunction (DBD) is a well-recognized and common symptom affecting up to 50% of all diabetic patients. DBD has a broad range of clinical presentations ranging from overactive to underactive bladder symptoms that develops in middle-aged to elderly patients with long standing and poorly controlled diabetes. Low efficacy of current therapeutics and lifestyle interventions combined with high national healthcare costs highlight the need for more research into bladder dysfunction pathophysiology and novel treatment options. Cellular senescence is an age-related physiologic process in which cells undergo irreversible growth arrest induced by replicative exhaustion and damaging insults. While controlled senescence negatively regulates cell proliferation and promotes tissue regeneration, uncontrolled senescence is known to result in tissue dysfunction through enhanced secretion of inflammatory factors. This review presents previous scientific findings and current hypotheses that characterize diabetic bladder dysfunction. Further, we propose the novel hypothesis that cellular senescence within the urothelial layer of the bladder contributes to the pro-inflammatory/pro-oxidant environment and symptoms of diabetic bladder dysfunction. Our results show increased cellular senescence in the urothelial layer of the bladder; however, whether this phenomenon is the cause or effect of DBD is unknown. The urothelial layer of the bladder is made up of transitional epithelia specialized to contract and expand with demand and plays an active role in transmission by modulating afferent activity. Transition from normal functioning urothelial cells to secretory senescence cells would not only disrupt the barrier function of this layer but may result in altered signaling and sensation of bladder fullness; dysfunction of this layer is known to result in symptoms of frequency and urgency. Future DBD therapeutics may benefit from targeting and preventing early transition of urothelial cells to senescent cells.

Pleiotropic effects of metformin: Shaping the microbiome to manage type 2 diabetes and postpone ageing

Metformin is the first-choice therapy to lower glycaemia and manage type 2 diabetes. Continuously emerging epidemiological data and experimental models are showing additional protective effects of metformin against a number of age-related diseases (ARDs), e.g., cardiovascular diseases and cancer. This evidence has prompted the design of a specific trial, i.e., the Targeting Aging with Metformin (TAME) trial, to test metformin as an anti-ageing molecule. However, a unifying or prevailing mechanism of action of metformin is still debated. Here, we summarize the epidemiological data linking metformin to ARD prevention. Then, we dissect the deeply studied mechanisms of action explaining its antihyperglycemic effect and the putative mechanisms supporting its anti-ageing properties, focusing on studies using clinically pertinent doses. We hypothesize that the molecular observations obtained in different models with metformin could be indirectly mediated by its effect on gut flora. Novel evidence suggests that metformin reshapes the human microbiota, promoting the growth of beneficial bacterial species and counteracting the expansion of detrimental bacterial species. In turn, this action would influence the balance between pro- and anti-inflammatory circulating factors, thereby promoting glycaemic control and healthy ageing. This framework may reconcile diverse observations, providing information for designing further studies to elucidate the complex interplay between metformin and the metabiome harboured in mammalian body compartments, thereby paving the way for innovative, bacterial-based therapeutics to manage type 2 diabetes and foster a longer healthspan.

Macrophages in the Aging Liver and Age-Related Liver Disease

The number of individuals aged 65 or older is projected to increase globally from 524 million in 2010 to nearly 1. 5 billion in 2050. Aged individuals are particularly at risk for developing chronic illness, while being less able to regenerate healthy tissue and tolerate whole organ transplantation procedures. In the liver, these age-related diseases include non-alcoholic fatty liver disease, alcoholic liver disease, hepatitis, fibrosis, and cirrhosis. Hepatic macrophages, a population comprised of both Kupffer cells and infiltrating monocyte derived macrophages, are implicated in several chronic liver diseases and also play important roles in the homeostatic functions of the liver. The effects of aging on hepatic macrophage population dynamics, polarization, and function are not well understood. Studies performed on macrophages derived from other aged sources, such as the bone marrow, peritoneal cavity, lungs, and brain, demonstrate general reductions in autophagy and phagocytosis, dysfunction in cytokine signaling, and altered morphology and distribution, likely mediated by epigenetic changes and mitochondrial defects, that may be applicable to hepatic macrophages. This review highlights recent findings in macrophage developmental biology and function, particularly in the liver, and discusses the role of macrophages in various age-related liver diseases. A better understanding of the biology of aging that influences hepatic macrophages and thus the progression of chronic liver disease will be crucial in order to develop new interventions and treatments for liver disease in aging populations.

Autophagy and the cell biology of age-related disease

Macroautophagy (autophagy) is a conserved lysosomal degradation process essential for cellular homeostasis and adaption to stress. Accumulating evidence indicates that autophagy declines with age and that impaired autophagy predisposes individuals to age-related diseases, whereas interventions that stimulate autophagy often promote longevity. In this Review, we examine how the autophagy pathway restricts cellular damage and degeneration, and the impact of these functions towards tissue health and organismal lifespan.

Follistatin-Like 1 Is Downregulated in Morbidly and Super Obese Central-European Population

Follistatin-like 1 (FSTL1) is a secreted adipomyokine with a possible link to obesity; however, its connection to extreme obesity currently remains unknown. In order to analyze such association for the very first time, we employed a unique cohort of morbidly and super obese individuals with a mean BMI of 44.77 kg/m² and measured the levels of circulating FSTL1. We explored the 3′ UTR of FSTL1 to locate a genetic variant which impairs microRNA binding. We located and investigated such SNP (rs1057231) in relation to the FSTL1 protein level, obesity status, and other body composition parameters. We observed a significant decline in FSTL1 level in obese subjects in comparison to nonobese ones. The evaluated SNP was found to correlate with FSTL1 only in nonobese subjects. The presented results were not affected by sex since both males and females expressed FSTL1 equally. We suggest that the FSTL1 decrease observed in extremely obese subjects is a result of adipogenesis reduction accompanied by a senescence of preadipocytes which otherwise willingly express FSTL1, increased adipocyte apoptosis, and epigenetic FSTL1 silencing.

The Dysfunctional MDM2-p53 Axis in Adipocytes Contributes to Aging-Related Metabolic Complications by Induction of Lipodystrophy

Profound loss and senescence of adipose tissues are hallmarks of advanced age, but the underlying cause and their metabolic consequences remain obscure. Proper function of the murine double minute 2 (MDM2)-p53 axis is known to prevent tumorigenesis and several metabolic diseases, yet its role in regulation of adipose tissue aging is still poorly understood. In this study, we show that the proximal p53 inhibitor MDM2 is markedly downregulated in subcutaneous white and brown adipose tissues of mice during aging. Genetic disruption of MDM2 in adipocytes triggers canonical p53-mediated apoptotic and senescent programs, leading to age-dependent lipodystrophy and its associated metabolic disorders, including type 2 diabetes, nonalcoholic fatty liver disease, hyperlipidemia, and energy imbalance. Surprisingly, this lipodystrophy mouse model also displays premature loss of physiological integrity, including impaired exercise capacity, multiple organ senescence, and shorter life span. Transplantation of subcutaneous fat rejuvenates the metabolic health of this aging-like lipodystrophy mouse model. Furthermore, senescence-associated secretory factors from MDM2-null adipocytes impede adipocyte progenitor differentiation via a non-cell-autonomous manner. Our findings suggest that tight regulation of the MDM2-p53 axis in adipocytes is required for adipose tissue dynamics and metabolic health during the aging process.

An update on physical health and economic consequences of overweight and obesity

Overweight and obesity (OW and OB) have been on the increase globally and posed health risks to the world's population of all ages, including pre-born babies, children, adolescents, adults and elderly people, via their comorbid conditions. Excellent examples of comorbidities associated with obesity include cancer, cardiovascular diseases (CVD) and type 2 diabetes mellitus (T2DM). In this article, we aimed to review and update scientific evidence regarding the relationships between obesity and its common physical health consequences, including CVD, T2DM, hypertension, ischemic stroke, cancer, dyslipidemia and reproductive disorders. In addition, the economic burden of OW and OB will be discussed. Abundant evidence is found to support the associations between obesity and other diseases. In general, the odd ratios, risk ratios or hazard ratios are often higher in OW and OB people than in the normal-weight ones. However, the molecular mechanism of how OW and OB induce the development of other diseases has not been fully understood. Figures also showed that obesity and its-related disorders exert enormous pressure on the economy which is projected to increase. This review highlights the fact that obesity can lead to numerous lethal health problems; therefore, it requires a lot of economic resources to fight against this epidemic.

Fisetin is a senotherapeutic that extends health and lifespan

BACKGROUND

Senescence is a tumor suppressor mechanism activated in stressed cells to prevent replication of damaged DNA. Senescent cells have been demonstrated to play a causal role in driving aging and age-related diseases using genetic and pharmacologic approaches. We previously demonstrated that the combination of dasatinib and the flavonoid quercetin is a potent senolytic improving numerous age-related conditions including frailty, osteoporosis and cardiovascular disease. The goal of this study was to identify flavonoids with more potent senolytic activity.

METHODS

A panel of flavonoid polyphenols was screened for senolytic activity using senescent murine and human fibroblasts, driven by oxidative and genotoxic stress, respectively. The top senotherapeutic flavonoid was tested in mice modeling a progeroid syndrome carrying a p16INK4a-luciferase reporter and aged wild-type mice to determine the effects of fisetin on senescence markers, age-related histopathology, disease markers, health span and lifespan. Human adipose tissue explants were used to determine if results translated.

FINDINGS

Of the 10 flavonoids tested, fisetin was the most potent senolytic. Acute or intermittent treatment of progeroid and old mice with fisetin reduced senescence markers in multiple tissues, consistent with a hit-and-run senolytic mechanism. Fisetin reduced senescence in a subset of cells in murine and human adipose tissue, demonstrating cell-type specificity. Administration of fisetin to wild-type mice late in life restored tissue homeostasis, reduced age-related pathology, and extended median and maximum lifespan.

INTERPRETATION

The natural product fisetin has senotherapeutic activity in mice and in human tissues. Late life intervention was sufficient to yield a potent health benefit. These characteristics suggest the feasibility to translation to human clinical studies. FUND: NIH grants P01 AG043376 (PDR, LJN), U19 AG056278 (PDR, LJN, WLL), R24 AG047115 (WLL), R37 AG013925 (JLK), R21 AG047984 (JLK), P30 DK050456 (Adipocyte Subcore, JLK), a Glenn Foundation/American Federation for Aging Research (AFAR) BIG Award (JLK), Glenn/AFAR (LJN, CEB), the Ted Nash Long Life and Noaber Foundations (JLK), the Connor Group (JLK), Robert J. and Theresa W. Ryan (JLK), and a Minnesota Partnership Grant (AMAY-UMN#99)-P004610401-1 (JLK, EAA).

Maternal obesity impairs skeletal development in adult offspring

Intrauterine or early postnatal high-fat diet (HFD) has substantial influences on adult offspring health; however, studies of HFD-induced maternal obesity on regulation of adult offspring bone formation are sparse. Here, we investigated the effects of HFD-induced maternal obesity on both fetal and adult offspring skeletal development. We found that HFD-induced maternal obesity significantly decreased fetal skeletal development, but enhanced fetal osteoblastic cell senescence signaling and significantly increased the expression of inflammatory factors of the senescence-associated secretory phenotype (SASP) in osteo-progenitors. It was found that p300/CBP activation led to H3K27 acetylation to increase the expression of senescence-related genes and PPARγ in embryonic mouse osteogenic calvarial cells from HFD obese dams. These results were recapitulated in human umbilical cord mesenchymal stem cells (UC MSCs) isolated from offspring of pregnant obese and lean mothers following delivery. Regardless of postnatal HFD challenge, adult offspring from HFD obese dams showed significantly suppressed bone formation. Such early involution of bone formation of adult offspring from HFD obese dams may at least in part due to histone acetylation, i.e., epigenetic regulation of genes involved in cell senescence signaling in pre-osteoblasts from prenatal development. These findings indicate fetal pre-osteoblastic cell senescence signaling is epigenetically regulated by maternal obesity to repress bone formation in adult offspring in rodents and suggest that at least some of these effects may also manifest in humans.

Loss of periostin occurs in aging adipose tissue of mice and its genetic ablation impairs adipose tissue lipid metabolism

Remodeling of the extracellular matrix is a key component of the metabolic adaptations of adipose tissue in response to dietary and physiological challenges. Disruption of its integrity is a well-known aspect of adipose tissue dysfunction, for instance, during aging and obesity. Adipocyte regeneration from a tissue-resident pool of mesenchymal stem cells is part of normal tissue homeostasis. Among the pathophysiological consequences of adipogenic stem cell aging, characteristic changes in the secretory phenotype, which includes matrix-modifying proteins, have been described. Here, we show that the expression of the matricellular protein periostin, a component of the extracellular matrix produced and secreted by adipose tissue-resident interstitial cells, is markedly decreased in aged brown and white adipose tissue depots. Using a mouse model, we demonstrate that the adaptation of adipose tissue to adrenergic stimulation and high-fat diet feeding is impaired in animals with systemic ablation of the gene encoding for periostin. Our data suggest that loss of periostin attenuates lipid metabolism in adipose tissue, thus recapitulating one aspect of age-related metabolic dysfunction. In human white adipose tissue, periostin expression showed an unexpected positive correlation with age of study participants. This correlation, however, was no longer evident after adjusting for BMI or plasma lipid and liver function biomarkers. These findings taken together suggest that age-related alterations of the adipose tissue extracellular matrix may contribute to the development of metabolic disease by negatively affecting nutrient homeostasis.

Age-Related Changes in Glucose Metabolism, Hyperglycemia, and Cardiovascular Risk

Aging and diabetes mellitus are 2 well-known risk factors for cardiovascular disease (CVD). During the past 50 years, there has been an dramatic increase in life expectancy with a simultaneous increase in the prevalence of diabetes mellitus in the older population. This large number of older individuals with diabetes mellitus is problematic given that CVD risk associated with aging and diabetes mellitus. In this review, we summarize epidemiological data relating to diabetes mellitus and CVD, with an emphasis on the aging population. We then present data on hyperglycemia as a risk factor for CVD and review the current knowledge of age-related changes in glucose metabolism. Next, we review the role of obesity in the pathogenesis of age-related glucose dysregulation, followed by a summary of the results from major randomized controlled trials that focus on cardiovascular risk reduction through glycemic control, with a special emphasis on older adults. We then conclude with our proposed model of aging that body composition changes and insulin resistance link possible dysregulation of physiological pathways leading to obesity and diabetes mellitus-both forms of accelerated aging-and risks for CVD.

MiR27a Promotes the Development of Macrophage-like Characteristics in 3T3-L1 Preadipocytes

Recruitment and polarization of classically activated (M1) macrophages within adipose tissue contribute to chronic low-grade inflammation in obesity. Adipose tissue precursor cells exhibit the capacity to develop macrophage-like characteristics and adipocyte-derived miR27a is known to promote reprogramming of somatic cells. It was unknown whether exogenous addition of miR27a promote the development of macrophage-like characteristics of adipose precursor cells. We examined macrophage surface antigen, phagocytosis and migration ability in 3T3-L1 preadipocytes transfected with miR27a mimics. Transfection of 3T3-L1 preadipocytes with miR27a mimics increased phagocytosis and migration and increased the number of cells expressing the macrophage makers F4/80 and MHC compared to controls. M2 and CD206 macrophage markers were unaltered. In addition, transfection of 3T3-L1 preadipocytes with miR27a mimics reduced PPARγ expression, activated NF-κB and promoted secretion of the inflammatory cytokines MCP-1, TNF-α and IL-1β compared to controls. The level of anti-inflammatory factors Arg-1, IL-10, Ym1 and Fizz1 were unaltered. Secretion of miR27a was increased in conditioned medium prepared from palmitic acid-treated differentiated 3T3-L1 adipocytes compared to controls. Incubation of 3T3-L1 preadipocytes with this conditioned medium increased phagocytosis and migration compared to controls. Finally, conditioned medium prepared from differentiated 3T3-L1 adipocytes transfection with miR27a inhibitors reduced phagocytosis and migration in 3T3-L1 preadipocytes compared to controls. The data indicate that PPARγ agonists may reverse the activation of NF-κB pathway mediated by miR27a overexpression and reduce phagocytosis and migration of adipose precursor cells. In addition, miR27a may promote the development of macrophage-like characteristics in 3T3-L1 preadipocytes.

p53 Functions in Adipose Tissue Metabolism and Homeostasis

As a tumor suppressor and the most frequently mutated gene in cancer, p53 is among the best-described molecules in medical research. As cancer is in most cases an age-related disease, it seems paradoxical that p53 is so strongly conserved from early multicellular organisms to humans. A function not directly related to tumor suppression, such as the regulation of metabolism in nontransformed cells, could explain this selective pressure. While this role of p53 in cellular metabolism is gradually emerging, it is imperative to dissect the tissue- and cell-specific actions of p53 and its downstream signaling pathways. In this review, we focus on studies reporting p53’s impact on adipocyte development, function, and maintenance, as well as the causes and consequences of altered p53 levels in white and brown adipose tissue (AT) with respect to systemic energy homeostasis. While whole body p53 knockout mice gain less weight and fat mass under a high-fat diet owing to increased energy expenditure, modifying p53 expression specifically in adipocytes yields more refined insights: (1) p53 is a negative regulator of in vitro adipogenesis; (2) p53 levels in white AT are increased in diet-induced and genetic obesity mouse models and in obese humans; (3) functionally, elevated p53 in white AT increases senescence and chronic inflammation, aggravating systemic insulin resistance; (4) p53 is not required for normal development of brown AT; and (5) when p53 is activated in brown AT in mice fed a high-fat diet, it increases brown AT temperature and brown AT marker gene expression, thereby contributing to reduced fat mass accumulation. In addition, p53 is increasingly being recognized as crucial player in nutrient sensing pathways. Hence, despite existence of contradictory findings and a varying density of evidence, several functions of p53 in adipocytes and ATs have been emerging, positioning p53 as an essential regulatory hub in ATs. Future studies need to make use of more sophisticated in vivo model systems and should identify an AT-specific set of p53 target genes and downstream pathways upon different (nutrient) challenges to identify novel therapeutic targets to curb metabolic diseases.

[Antioxidant and anti-inflammatory modulation of exercise during aging]

Aging is characterised by a gradual loss of the functional reserve. This, along with the fostering of sedentary habits and the increase in risk factors, causes a deterioration of antioxidant defences and an increase of the circulatory levels of inflammatory and oxidative markers, boosting a low-rate chronic inflammation, defined as inflamm-aging. This phenomenon is present in the aetiopathology of chronic diseases, as well as in cognitive deterioration cases associated with aging. The objective of this review is to describe the modulation of antioxidant and anti-inflammatory effects of physical exercise of moderate intensity and volume in the elderly. Evidence of its effectiveness as a non-pharmacological resource is presented, which decreases some deleterious effects of aging. This is mainly due to its neuroprotective action, the increase in circulating anti-inflammatory markers, and the improvement of antioxidant defence derived from its practice.

Fat depot-specific differences of macrophage infiltration and cellular senescence in obese bovine adipose tissues

Obesity is associated with the chronic inflammation and senescence of adipose tissues. Macrophage is a key mediator of chronic inflammation that infiltrates obese adipose tissue and stimulates metabolic disorders. However, the fat depot-specific differences of macrophage infiltration and senescence, especially the influence on intramuscular adipose tissue, have remained unclear. We investigated the fat depot-specific differences of macrophage infiltration and senescence in obese bovine adipose tissue from three different anatomical sites (subcutaneous, intramuscular and visceral). Macrophage infiltrations and crown-like structures were observed in visceral adipose tissue, although there were few macrophages in subcutaneous and intramuscular adipose tissues. The positive reaction of senescence marker SA-βgal activity was observed in visceral adipose tissue. In contrast, the activity of SA-βgal in subcutaneous and intramuscular adipose tissues were low. The expression of p53 gene, the master regulator of cellular senescence, in visceral adipose tissue was higher than that of subcutaneous and intramuscular adipose tissue. At the cellular level, p53 gene expression was negatively correlated with the size of subcutaneous adipocytes. In contrast, p53 gene expressions were positively correlated with the size of intramuscular and visceral adipocytes. These results indicate that anatomical sites of obese adipose tissue affect macrophage infiltration and the senescent state in a fat depot-specific manner.

Determinants of body fat distribution in humans may provide insight about obesity-related health risks

Obesity increases the risks of developing cardiovascular and metabolic diseases and degrades quality of life, ultimately increasing the risk of death. However, not all forms of obesity are equally dangerous: some individuals, despite higher percentages of body fat, are at less risk for certain chronic obesity-related complications. Many open questions remain about why this occurs. Data suggest that the physical location of fat and the overall health of fat dramatically influence disease risk; for example, higher concentrations of visceral relative to subcutaneous adipose tissue are associated with greater metabolic risks. As such, understanding the determinants of the location and health of adipose tissue can provide insight about the pathological consequences of obesity and can begin to outline targets for novel therapeutic approaches to combat the obesity epidemic. Although age and sex hormones clearly play roles in fat distribution and location, much remains unknown about gene regulation at the level of adipose tissue or how genetic variants regulate fat distribution. In this review, we discuss what is known about the determinants of body fat distribution, and we highlight the important roles of sex hormones, aging, and genetic variation in the determination of body fat distribution and its contribution to obesity-related comorbidities.

Senolytics improve physical function and increase lifespan in old age

Physical function declines in old age, portending disability, increased health expenditures, and mortality. Cellular senescence, leading to tissue dysfunction, may contribute to these consequences of aging, but whether senescence can directly drive age-related pathology and be therapeutically targeted is still unclear. Here we demonstrate that transplanting relatively small numbers of senescent cells into young mice is sufficient to cause persistent physical dysfunction, as well as to spread cellular senescence to host tissues. Transplanting even fewer senescent cells had the same effect in older recipients and was accompanied by reduced survival, indicating the potency of senescent cells in shortening health- and lifespan. The senolytic cocktail, dasatinib plus quercetin, which causes selective elimination of senescent cells, decreased the number of naturally occurring senescent cells and their secretion of frailty-related proinflammatory cytokines in explants of human adipose tissue. Moreover, intermittent oral administration of senolytics to both senescent cell-transplanted young mice and naturally aged mice alleviated physical dysfunction and increased post-treatment survival by 36% while reducing mortality hazard to 65%. Our study provides proof-of-concept evidence that senescent cells can cause physical dysfunction and decreased survival even in young mice, while senolytics can enhance remaining health- and lifespan in old mice.

Age Alters Chromatin Structure and Expression of SUMO Proteins under Stress Conditions in Human Adipose-Derived Stem Cells

Adult stem cells play a critical role in tissue homeostasis and repair. Aging leads to a decline in stem cells’ regenerative capacity that contributes significantly to the maintenance of organ and tissue functions. Age-dependent genomic and epigenetic modifications together play a role in the disruption of critical cellular pathways. However, the epigenetic mechanisms responsible for the decline of adult stem cell functions remain to be well established. Here, we investigated age-dependent, genome-wide alterations in the chromatin accessibility of primary human adipose-derived stem cells (ASCs) in comparison to age-matched fibroblasts via ATAC-seq technology. Our results demonstrate that aging ASCs possess globally more stable chromatin accessibility profiles as compared to aging fibroblasts, suggesting that robust regulatory mechanisms maintain adult stem cell chromatin structure against aging. Furthermore, we observed age-dependent subtle changes in promoter nucleosome positioning in selective pathways during aging, concurrent with altered small ubiquitin-related modifier (SUMO) protein expression under stress conditions. Together, our data suggest a significant role for nucleosome positioning in sumoylation pathway regulation in stress response during adult stem cell aging. The differences described here between the chromatin structure of human ASCs and fibroblasts will further elucidate the mechanisms regulating gene expression during aging in both stem cells and differentiated cells.

With Great Age Comes Great Metastatic Ability: Ovarian Cancer and the Appeal of the Aging Peritoneal Microenvironment

Age is one of the biggest risk factors for ovarian cancer. Older women have higher rates of diagnosis and death associated with the disease. In mouse models, it was shown that aged mice had greater tumor burden than their younger counterparts when intraperitoneally injected with ovarian tumor cells. While very few papers have been published looking at the direct link between ovarian cancer metastasis and age, there is a wealth of information on how age affects metastatic microenvironments. Mesothelial cells, the peritoneal extracellular matrix (ECM), fibroblasts, adipocytes and immune cells all exhibit distinct changes with age. The aged peritoneum hosts a higher number of senescent cells than its younger counterpart, in both the mesothelium and the stroma. These senescent cells promote an inflammatory profile and overexpress Matrix Metalloproteinases (MMPs), which remodel the ECM. The aged ECM is also modified by dysregulated collagen and laminin synthesis, increases in age-related crosslinking and increasing ovarian cancer invasion into the matrix. These changes contribute to a vastly different microenvironment in young and aged models for circulating ovarian cancer cells, creating a more welcoming “soil”.

Peripheral Lymphocytes, Obesity, and Metabolic Syndrome in Young Adults: An Immunometabolism Study

BACKGROUND

Obesity is characterized by a low-intensity chronic inflammatory process in which immune system cells interact in a complex network, which affects systemic metabolic processes. This raises interest in analyzing possible changes in the proportions of immune system cells in individuals with obesity with and without metabolic syndrome (MS), in relation to their body composition.

METHODS

Circulating cells were analyzed with flow cytometry in young adults: monocytes, granulocytes, lymphocytes (T, B, and natural killer [NK]), TCD4⁺CD62^-, TCD8⁺CD28^-, and naive and memory cells of TCD3⁺ and TCD4⁺. Body composition was obtained by bioelectrical impedance analysis and dual-energy X-ray absorptiometry, and metabolic parameters.

RESULTS

A total of 169 persons were evaluated: 20% presented normal body mass index (BMI); 49% was overweight, and 31% had obesity; 28% had MS. It was observed that with an increase in BMI and visceral adipose tissue increase (VATI), body composition and biochemical variables were negatively altered. With regard to cell subpopulations, total lymphocytes increased and granulocytes and NK lymphocytes decreased in patients with MS and VATI. Memory cells increased with BMI and VATI. In individuals with MS, monocytes, and NK lymphocytes comprised a negative association with VAT, fat mass, and skeletal muscle mass (SMM). In individuals with MS and VATI, a negative correlation was observed between monocytes and SMM.

CONCLUSIONS

Significant changes were detected in the subpopulations of lymphocytes, suggesting that weight gain, SMM, and VAT accumulation gave rise to immunological changes at the peripheral level, and the presence of increased memory cells could be related to low-intensity chronic inflammation.

Methods of Isolation, Characterization and Expansion of Human Adipose-Derived Stem Cells (ASCs): An Overview

Considering the increasing interest in adipose-derived stem cells (ASCs) in regenerative medicine, optimization of methods aimed at isolation, characterization, expansion and evaluation of differentiation potential is critical to ensure (a) the quality of stem cells also in terms of genetic stability; (b) the reproducibility of beneficial effects; and (c) the safety of their use. Numerous studies have been conducted to understand the mechanisms that regulate ASC proliferation, growth and differentiation, however standard protocols about harvesting and processing techniques are not yet defined. It is also important to note that some steps in the procedures of harvesting and/or processing have been reported to affect recovery and/or the physiology of ASCs. Even considering the great opportunity that the ASCs provide for the identification of novel molecular targets for new or old drugs, the definition of homogeneous preparation methods that ensure adequate quality assurance and control, in accordance with current GMPs (good manufacturing practices), is required. Here, we summarize the literature reports to provide a detailed overview of the methodological issues underlying human ASCs isolation, processing, characterization, expansion, differentiation techniques, recalling at the same time their basilar principles, advantages and limits, in particular focusing on how these procedures could affect the ASC quality, functionality and plasticity.

The Na/K-ATPase Oxidant Amplification Loop Regulates Aging

As aging involves oxidant injury, we examined the role of the recently described Na/K-ATPase oxidant amplification loop (NKAL). First, C57Bl6 old mice were given a western diet to stimulate oxidant injury or pNaKtide to antagonize the NKAL. The western diet accelerated functional and morphological evidence for aging whereas pNaKtide attenuated these changes. Next, human dermal fibroblasts (HDFs) were exposed to different types of oxidant stress in vitro each of which increased expression of senescence markers, cell-injury, and apoptosis as well as stimulated the NKAL. Further stimulation of the NKAL with ouabain augmented cellular senescence whereas treatment with pNaKtide attenuated it. Although N-Acetyl Cysteine and Vitamin E also ameliorated overall oxidant stress to a similar degree as pNaKtide, the pNaKtide produced protection against senescence that was substantially greater than that seen with either antioxidant. In particular, pNaKtide appeared to specifically ameliorate nuclear oxidant stress to a greater degree. These data demonstrate that the NKAL is intimately involved in the aging process and may serve as a target for anti-aging interventions.

Mitochondria and Reactive Oxygen Species in Aging and Age-Related Diseases

Aging has been linked to several degenerative processes that, through the accumulation of molecular and cellular damage, can progressively lead to cell dysfunction and organ failure. Human aging is linked with a higher risk for individuals to develop cancer, neurodegenerative, cardiovascular, and metabolic disorders. The understanding of the molecular basis of aging and associated diseases has been one major challenge of scientific research over the last decades. Mitochondria, the center of oxidative metabolism and principal site of reactive oxygen species (ROS) production, are crucial both in health and in pathogenesis of many diseases. Redox signaling is important for the modulation of cell functions and several studies indicate a dual role for ROS in cell physiology. In fact, high concentrations of ROS are pathogenic and can cause severe damage to cell and organelle membranes, DNA, and proteins. On the other hand, moderate amounts of ROS are essential for the maintenance of several biological processes, including gene expression. In this review, we provide an update regarding the key roles of ROS-mitochondria cross talk in different fundamental physiological or pathological situations accompanying aging and highlighting that mitochondrial ROS may be a decisive target in clinical practice.

Premature Physiologic Aging as a Paradigm for Understanding Increased Risk of Adverse Health Across the Lifespan of Survivors of Childhood Cancer

The improvement in survival of childhood cancer observed across the past 50 years has resulted in a growing acknowledgment that simply extending the lifespan of survivors is not enough. It is incumbent on both the cancer research and the clinical care communities to also improve the health span of survivors. It is well established that aging adult survivors of childhood cancer are at increased risk of chronic health conditions, relative to the general population. However, as the first generation of survivors age into their 50s and 60s, it has become increasingly evident that this population is also at risk of early onset of physiologic aging. Geriatric measures have uncovered evidence of reduced strength and speed and increased fatigue, all components of frailty, among survivors with a median age of 33 years, which is similar to adults older than 65 years of age in the general population. Furthermore, frailty in survivors independently increased the risk of morbidity and mortality. Although there has been a paucity of research investigating the underlying biologic mechanisms for advanced physiologic age in survivors, results from geriatric populations suggest five biologically plausible mechanisms that may be potentiated by exposure to cancer therapies: increased cellular senescence, reduced telomere length, epigenetic modifications, somatic mutations, and mitochondrial DNA infidelity. There is now a critical need for research to elucidate the biologic mechanisms of premature aging in survivors of childhood cancer. This research could pave the way for new frontiers in the prevention of these life-changing outcomes.

A delayed proinflammatory response of human preadipocytes to PCB126 is dependent on the aryl hydrocarbon receptor

Inflammation in adipose tissue is recognized as a causative factor in the development of type II diabetes. Adipocyte hypertrophy as well as bacterial and environmental factors have been implicated in causing inflammation in mature adipocytes. Exposure to persistent organic pollutants such as polychlorinated biphenyls (PCBs) has been associated with the development of type II diabetes. We show here that PCB126, a dioxin-like PCB, activates a robust proinflammatory state in fat cell precursors (preadipocytes). The response was found to be dependent on aryl hydrocarbon receptor (AhR) activation, although induction of the response was delayed compared to upregulation of CYP1A1, a classic AhR-responsive gene. Treatment of preadipocytes with a nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) inhibitor partially attenuated the PCB126-induced inflammatory response and partly, but not completely, ameliorated disruption of adipogenesis caused by PCB126. Our results indicate a role for PCB126 in mediating an inflammatory response through AhR in preadipocytes that interferes with adipogenesis.

Selective elimination of senescent cells by mitochondrial targeting is regulated by ANT2

Cellular senescence is a form of cell cycle arrest that limits the proliferative potential of cells, including tumour cells. However, inability of immune cells to subsequently eliminate senescent cells from the organism may lead to tissue damage, inflammation, enhanced carcinogenesis and development of age-related diseases. We found that the anticancer agent mitochondria-targeted tamoxifen (MitoTam), unlike conventional anticancer agents, kills cancer cells without inducing senescence in vitro and in vivo. Surprisingly, it also selectively eliminates both malignant and non-cancerous senescent cells. In naturally aged mice treated with MitoTam for 4 weeks, we observed a significant decrease of senescence markers in all tested organs compared to non-treated animals. Mechanistically, we found that the susceptibility of senescent cells to MitoTam is linked to a very low expression level of adenine nucleotide translocase-2 (ANT2), inherent to the senescent phenotype. Restoration of ANT2 in senescent cells resulted in resistance to MitoTam, while its downregulation in non-senescent cells promoted their MitoTam-triggered elimination. Our study documents a novel, translationally intriguing role for an anticancer agent targeting mitochondria, that may result in a new strategy for the treatment of age-related diseases and senescence-associated pathologies.

Secretion of autoimmune antibodies in the human subcutaneous adipose tissue

The adipose tissue (AT) contributes to systemic and B cell intrinsic inflammation, reduced B cell responses and secretion of autoimmune antibodies. In this study we show that adipocytes in the human obese subcutaneous AT (SAT) secrete several pro-inflammatory cytokines and chemokines, which contribute to the establishment and maintenance of local and systemic inflammation, and consequent suboptimal immune responses in obese individuals, as we have previously shown. We also show that pro-inflammatory chemokines recruit immune cells expressing the corresponding receptors to the SAT, where they also contribute to local and systemic inflammation, secreting additional pro-inflammatory mediators. Moreover, we show that the SAT generates autoimmune antibodies. During the development of obesity, reduced oxygen and consequent hypoxia and cell death lead to further release of pro-inflammatory cytokines, “self” protein antigens, cell-free DNA and lipids. All these stimulate class switch and the production of autoimmune IgG antibodies which have been described to be pathogenic. In addition to hypoxia, we have measured cell cytotoxicity and DNA damage mechanisms, which may also contribute to the release of “self” antigens in the SAT. All these processes are significantly elevated in the SAT as compared to the blood. We definitively found that fat-specific IgG antibodies are secreted by B cells in the SAT and that B cells express mRNA for the transcription factor T-bet and the membrane marker CD11c, both involved in the production of autoimmune IgG antibodies. Finally, the SAT also expresses RNA for cytokines known to promote Germinal Center formation, isotype class switch, and plasma cell differentiation. Our results show novel mechanisms for the generation of autoimmune antibody responses in the human SAT and allow the identification of new pathways to possibly manipulate in order to reduce systemic inflammation and autoantibody production in obese individuals.