Aging is associated with hypoxia and oxidative stress in adipose tissue: implications for adipose function

Fibroblast growth factor 21 resistance is associated with body shape in patients with type 2 diabetes complicating hypertension

Objectives

Obesity, especially abdominal obesity, increases the prevalence of metabolic and cardiovascular disease (CVD). Fibroblast growth factor 21 (FGF21) has been identified as a critical regulator playing a therapeutic role in diabetes and its complications. This study aims to evaluate the relationship between serum FGF21 levels and body shape parameters in patients with hypertension (HP) and type 2 diabetes mellitus (T2DM).

Methods

Serum FGF21 levels were determined in 1,003 subjects, including 745 patients with T2DM, and 258 individuals were selected as a healthy control in this cross-sectional study.

Results

Serum FGF21 levels were significantly higher in T2DM patients with HP than those without [534.9 (322.6-722.2) vs. 220.65 (142.8-347.55) pg/ml, p < 0.001], and levels in both of these two groups were significantly increased compared with that of healthy control [123.92 (67.23-219.32) pg/ml, all p < 0.001]. These differences were also observed in body shape parameters, including weight, waistline, body mass index (BMI), body shape index (ABSI), and the percentage of abdominal obesity. Serum FGF21 levels in T2DM patients were positively correlated with body shape parameters, including weight, waistline, neck circumference, BMI, ABSI, percent of abdominal obesity, and triglyceride, while negatively with estimated glomerular filtration rate (all p < 0.01). The significance remained stable when adjusted for age and T2DM duration. In addition, both serum FGF21 concentrations and waistline were independently associated with HP in T2DM patients after the adjustment for risk factors (all p < 0.05). ROC analysis for FGF21 levels of 745 patients with T2DM identified 411.33 pg/ml as an optimal cut-off point to predict HP, with a sensitivity and specificity of 66.0% and 84.9%, respectively.

Conclusions

FGF21 resistance occurs in patients of HP in T2DM, and positively correlates with body shape parameters (especially waistline and BMI). High levels of FGF21 may be a compensatory reaction to offset HP.

Age-related changes to adipose tissue and peripheral neuropathy in genetically diverse HET3 mice differ by sex and are not mitigated by rapamycin longevity treatment

Neural communication between the brain and adipose tissues regulates energy expenditure and metabolism through modulation of adipose tissue functions. We have recently demonstrated that under pathophysiological conditions (obesity, diabetes, and aging), total subcutaneous white adipose tissue (scWAT) innervation is decreased ('adipose neuropathy'). With advanced age in the C57BL/6J mouse, small fiber peripheral nerve endings in adipose tissue die back, resulting in reduced contact with adipose-resident blood vessels and other cells. This vascular neuropathy and parenchymal neuropathy together likely pose a physiological challenge for tissue function. In the current work, we used the genetically diverse HET3 mouse model to investigate the incidence of peripheral neuropathy and adipose tissue dysregulation across several ages in both male and female mice. We also investigated the anti-aging treatment rapamycin, an mTOR inhibitor, as a means to prevent or reduce adipose neuropathy. We found that HET3 mice displayed a reduced neuropathy phenotype compared to inbred C56BL/6 J mice, indicating genetic contributions to this aging phenotype. Compared to female HET3 mice, male HET3 mice had worse neuropathic phenotypes by 62 weeks of age. Female HET3 mice appeared to have increased protection from neuropathy until advanced age (126 weeks), after reproductive senescence. We found that rapamycin overall had little impact on neuropathy measures, and actually worsened adipose tissue inflammation and fibrosis. Despite its success as a longevity treatment in mice, higher doses and longer delivery paradigms for rapamycin may lead to a disconnect between life span and beneficial health outcomes.

Role of a small GTPase Cdc42 in aging and age-related diseases

A small GTPase, Cdc42 is evolutionarily one of the most ancient members of the Rho family, which is ubiquitously expressed and involved in a wide range of fundamental cellular functions. The crucial role of Cdc42 includes regulation of the actin cytoskeleton, cell polarity, morphology and migration, endocytosis and exocytosis, cell cycle, and proliferation in many different cell types. Many studies have provided compelling yet contradicting evidence that Cdc42 dysregulation plays an important role in cellular and tissue aging. Furthermore, Cdc42 is a critical factor in the development and progression of aging-related pathologies, such as neurodegenerative and cardiovascular disorders, diabetes type 2, and aging-related disorders of the joints and bones, and the inhibition of the Cdc42 demonstrates potentially significant therapeutic and anti-aging effects in animal models of aging and disease. However, regulation of Cdc42 expression and activity is very complex and depends on many factors, such as the origin and complexity of the tissues, hormonal status, etc. Therefore, this review is focused on current advances in understanding the underlying cellular and molecular mechanisms associated with Cdc42 activity and regulation of senescence in different cell types since they may provide a foundation for novel therapeutic strategies and targeted drugs to reverse the aging process and treat aging-associated disorders.

Adipose Tissue Plasticity in Aging

As a dynamic endocrine organ, white adipose tissue (WAT) stores lipids and plays a critical role in maintaining whole-body energy homeostasis and insulin sensitivity. A large group of the population over 65 years old suffer from increased WAT mass, especially in the visceral location. Visceral adiposity accelerates aging through promoting age-associated chronic conditions, significantly shortening life expectancy. Unlike WAT, brown adipose tissue (BAT) functions as an effective energy sink that burns and disposes of excess lipids and glucose upon activation of thermogenesis. Unfortunately, the thermogenic activity of BAT declines during aging. New appreciation of cellular and functional remodeling of WAT and BAT during aging has emerged in recent years. Efforts are underway to explore the potential underlying mechanisms behind these age-associated alterations in WAT and BAT and the impact of these alterations on whole-body metabolism. Lastly, it is intriguing to translate our knowledge obtained from animal models to the clinic to prevent and treat age-associated metabolic disorders. © 2022 American Physiological Society. Compr Physiol 12: 4119-4132, 2022.

Adipose tissue and ovarian aging: Potential mechanism and protective strategies

Ovarian aging occurs approximately 10 years prior to the natural age-associated functional decline of other organ systems. With the increase of life expectancy worldwide, ovarian aging has gradually become a key health problem among women. Therefore, understanding the causes and molecular mechanisms of ovarian aging is very essential for the inhibition of age-related diseases and the promotion of health and longevity in women. Recently, studies have revealed an association between adipose tissue (AT) and ovarian aging. Alterations in the function and quantity of AT have profound consequences on ovarian function because AT is central for follicular development, lipid metabolism, and hormonal regulation. Moreover, the interplay between AT and the ovary is bidirectional, with ovary-derived signals directly affecting AT biology. In this review, we summarize the current knowledge of the complex molecular mechanisms controlling the crosstalk between the AT and ovarian aging, and further discuss how therapeutic targeting of the AT can delay ovarian aging.

An Avocado Extract Enriched in Mannoheptulose Prevents the Negative Effects of a High-Fat Diet in Mice

Beginning at 16 weeks of age and continuing for 44 weeks, male C57BL/6J were fed either a control (CON) diet; a high-fat (HF) diet (60% unsaturated); or the HF diet containing an extract of unripe avocados (AvX) enriched in the 7-carbon sugar mannoheptulose (MH), designed to act as a glycolytic inhibitor (HF + MH). Compared to the CON diet, mice on the HF diet exhibited higher body weights; body fat; blood lipids; and leptin with reduced adiponectin levels, insulin sensitivity, VO2max, and falls from a rotarod. Mice on the HF + MH diet were completely protected against these changes in the absence of significant diet effects on food intake. Compared to the CON diet, oxidative stress was also increased by the HF diet indicated by higher levels of total reactive oxygen species, superoxide, and peroxynitrite measured in liver samples by electron paramagnetic resonance spectroscopy, whereas the HF + MH diet attenuated these changes. Compared to the CON, the HF diet increased signaling in the mechanistic target of the rapamycin (mTOR) pathway, and the addition of the MH-enriched AvX to this diet attenuated these changes. Beyond generating further interest in the health benefits of avocados, these results draw further new attention to the effects of this rare sugar, MH, as a botanical intervention for preventing obesity.

Senolytic effects of quercetin in an in vitro model of pre-adipocytes and adipocytes induced senescence

The dysfunction of adipose tissue with aging and the accumulation of senescent cells has been implicated in the pathophysiology of chronic diseases. Recently interventions capable of reducing the burden of senescent cells and in particular the identification of a new class of drugs termed senolytics have been object of extensive investigation. We used an in vitro model of induced senescence by treating both pre-adipocytes as well as mature adipocytes with hydrogen peroxide (H₂O₂) at a sub-lethal concentration for 3 h for three consecutive days, and hereafter with 20 uM quercetin at a dose that in preliminary experiments resulted to be senolytic without cytotoxicity. H₂O₂ treated pre-adipocytes and adipocytes showed typical senescence-associated features including increased beta-galactosidase activity (SA-ß-gal) and p21, activation of ROS and increased expression of pro-inflammatory cytokines. The treatment with quercetin in senescent pre-adipocytes and adipocytes was associated to a significant decrease in the number of the SA-β-gal positive cells along with the suppression of ROS and of inflammatory cytokines. Besides, quercetin treatment decreased miR-155-5p expression in both models, with down-regulation of p65 and a trend toward an up-regulation of SIRT-1 in complete cell extracts. The senolytic compound quercetin could affect AT ageing by reducing senescence, induced in our in vitro model by oxidative stress. The downregulation of miRNA-155-5p, possibly through the modulation of NF-κB and SIRT-1, could have a key role in the effects of quercetin on both pre-adipocytes and adipocytes.

Aging adipose: Depot location dictates age-associated expansion and dysfunction

Adipose tissue has a variety of diverse functions that maintain energy homeostasis. In conditions of excess energy availability, adipose tissue increases its lipid storage and communicates the nutritional abundance to various organs in the body. In conditions of energy depletion, such as fasting, cold exposure, or prolonged exercise, triglycerides stored in adipose tissue are released as free fatty acids to support the shift to catabolic metabolism. These diverse functions of storage, communication, and energy homeostasis are shared between numerous adipose depots including subcutaneous, visceral, brown, beige, intramuscular, marrow, and dermal adipose tissue. As organisms age, the cellular composition of these depots shifts to facilitate increased inflammatory cell infiltration, decreased vasculature, and increased adipocyte quantity and lipid droplet size. The purpose of this review is to give a comprehensive overview of the molecular and cellular changes that occur in various aged adipose depots and discuss their impact on physiology. The molecular signature of aged adipose leads to higher prevalence of metabolic disease in aged populations including type 2 diabetes, cardiovascular disease, Alzheimer's disease, and certain types of cancer.

Role of NLRP3 Inflammasome Activation in Obesity-Mediated Metabolic Disorders

NLRP3 inflammasome is one of the multimeric protein complexes of the nucleotide-binding domain, leucine-rich repeat (NLR)-containing pyrin and HIN domain family (PYHIN). When activated, NLRP3 inflammasome triggers the release of pro-inflammatory interleukins (IL)-1β and IL-18, an essential step in innate immune response; however, defective checkpoints in inflammasome activation may lead to autoimmune, autoinflammatory, and metabolic disorders. Among the consequences of NLRP3 inflammasome activation is systemic chronic low-grade inflammation, a cardinal feature of obesity and insulin resistance. Understanding the mechanisms involved in the regulation of NLRP3 inflammasome in adipose tissue may help in the development of specific inhibitors for the treatment and prevention of obesity-mediated metabolic diseases. In this narrative review, the current understanding of NLRP3 inflammasome activation and regulation is highlighted, including its putative roles in adipose tissue dysfunction and insulin resistance. Specific inhibitors of NLRP3 inflammasome activation which can potentially be used to treat metabolic disorders are also discussed.

Is Adipose Tissue the Fountain of Youth? The Impact of Adipose Stem Cell Aging on Metabolic Homeostasis, Longevity, and Cell-Based Therapies

Aging is driven by four interlinked processes: (1) low-grade sterile inflammation; (2) macromolecular and organelle dysfunction, including DNA damage, telomere erosion, and mitochondrial dysfunction; (3) stem cell dysfunction; and (4) an accumulation of senescent cells in tissues. Adipose tissue is not immune to the effects of time, and all four of these processes contribute to a decline of adipose tissue function with advanced age. This decline is associated with an increase in metabolic disorders. Conversely, optimally functioning adipose tissue generates signals that promote longevity. As tissue-resident progenitor cells that actively participate in adipose tissue homeostasis and dysregulation, adipose stem cells (ASCs) have emerged as a key feature in the relationship between age and adipose tissue function. This review will give a mechanistic overview of the myriad ways in which age affects ASC function and, conversely, how ASC function contribute to healthspan and lifespan. A central mediator in this relationship is the degree of resilience of ASCs to maintain stemness into advanced age and the consequent preservation of adipose tissue function, in particular subcutaneous fat. The last sections of this review will discuss therapeutic options that target senescent ASCs to extend healthspan and lifespan, as well as ASC-based therapies that can be used to treat age-related pathologies, and collectively, these therapeutic applications may transform the way we age.

The Potential Benefit of Monitoring Oxidative Stress and Inflammation in the Prevention of Non-Communicable Diseases (NCDs)

The significant increase in worldwide morbidity and mortality from non-communicable diseases (NCDs) indicates that the efficacy of existing strategies addressing this crisis may need improvement. Early identification of the metabolic irregularities associated with the disease process may be a key to developing early intervention strategies. Unhealthy lifestyle behaviours are well established drivers of the development of several NCDs, but the impact of such behaviours on health can vary considerably between individuals. How can it be determined if an individual's unique set of lifestyle behaviours is producing disease? Accumulating evidence suggests that lifestyle-associated activation of oxidative and inflammatory processes is primary driver of the cell and tissue damage which underpins the development of NCDs. However, the benefit of monitoring subclinical inflammation and oxidative activity has not yet been established. After reviewing relevant studies in this context, we suggest that quantification of oxidative stress and inflammatory biomarkers during the disease-free prodromal stage of NCD development may have clinical relevance as a timely indicator of the presence of subclinical metabolic changes, in the individual, portending the development of disease. Monitoring markers of oxidative and inflammatory activity may therefore enable earlier and more efficient strategies to both prevent NCD development and/or monitor the effectiveness of treatment.

How does adipose tissue contribute to inflammageing?

Across aging, white adipose tissue (WAT) undergoes significant changes in quantity and distribution, with an increase in visceral adipose tissue, ectopic fat deposition and a decline in gluteofemoral subcutaneous depot. In particular, WAT becomes dysfunctional with an increase in production of inflammatory peptides and a decline of those with anti-inflammatory activity and infiltration of inflammatory cells. Moreover, dysfunction of WAT is characterized by preadipocyte differentiation decline, increased oxidative stress and mitochondrial dysfunction, reduction in vascularization and hypoxia, increased fibrosis and senescent cell accumulation. WAT changes represent an important hallmark of the aging process and may be responsible for the systemic pro-inflammatory state ("inflammageing") typical of aging itself, leading to age-related metabolic alterations. This review focuses on mechanisms linking age-related WAT changes to inflammageing.

Aging differentially impacts vasodilation and angiogenesis in arteries from the white and brown adipose tissues

Aging adipose tissues (ATs) manifest reduced vascularity and increased hypoxia and inflammation that contribute to local and systemic metabolic dysfunction. However, the mechanisms that underlie these age-related changes are incompletely understood. In this study, we sought to examine insulin-stimulated vasodilation and angiogenesis in the arterial vasculature from three major AT depots, perigonadal white (pgWAT), subcutaneous white (scWAT) and brown (BAT) from young and old mice. Here, we demonstrate that in young mice, insulin-stimulated vasodilation is lower in feed arteries from pgWAT compared to scWAT (p < 0.05), but no differences were found between feed arteries in other AT depots (p > 0.05). Insulin-stimulated vasodilation was lower in old compared to young feed arteries from all three AT depots (p < 0.05 for all). In the presence of endothelial nitric oxide synthase inhibitor, L-NAME, insulin-stimulated vasodilation was decreased in young (p < 0.05), but was unaffected in old (p > 0.05) from all AT depots. We also observed no age-related differences in endothelium-independent dilation, as assessed by sodium nitroprusside (p > 0.05). We next investigated angiogenic capacity of the vasculature in these AT depots. In young mice, BAT vasculature demonstrated the highest angiogenic potential, followed by pgWAT and scWAT. We found that aging decreased angiogenic sprout formation in pgWAT and BAT (both p < 0.05), but increased angiogenic potential in scWAT (p < 0.05), indicating dissimilar impact of aging on angiogenesis in different AT depots. Collectively, these data suggest that aging leads to a consistent impairment in insulin-stimulated vasodilation and reduction in NO bioavailability in all three AT, although aging differentially impacts angiogenic capacity across different AT depots.

Age-Dependent Changes of Adipokine and Cytokine Secretion From Rat Adipose Tissue by Endogenous and Exogenous Toll-Like Receptor Agonists

White adipose tissue but recently also brown adipose tissue have emerged as endocrine organs. Age-associated obesity is accompanied by prolonged and elevated lipopolysaccharide (LPS)-induced sickness symptoms and increased cytokine and adipokine levels in the circulation partially originating from adipose tissue. In the present study, ex vivo fat explants were used to investigate how the exogenous pathogen-associated molecular pattern (PAMP) LPS or the endogenous danger-associated molecular patterns (DAMPs) high mobility group box-1 protein (HMGB1) and biglycan modulate the release of cytokines and adipokines/batokines and, thus, could influence systemic and/or local inflammation. The response of adipose tissue (epididymal, retroperitoneal, subcutaneous, and brown) was compared between young lean and old obese rats (2 vs. 24 months old). LPS induced a strong interleukin (IL)-6 and tumor necrosis factor (TNF) alpha release into the supernatant of all adipose tissue types investigated. HMGB1 (subcutaneous) and biglycan (retroperitoneal) led to an increased release of IL-6 and TNFalpha (HMGB1) and decreased visfatin and adiponectin (biglycan) secretion from epididymal adipose tissue (young rats). Visfatin was also decreased by HMGB1 in retroperitoneal adipose tissue of old rats. We found significantly higher leptin (all fat pads) and adiponectin (subcutaneous) levels in supernatants of adipose tissue from old compared to young rats, whereas visfatin secretion showed the opposite. The expression of the biglycan receptor Toll-like receptor (TLR) 2 as well as the LPS and HMGB1 receptors TLR4 and receptor for advanced glycation end products (RAGE) were reduced with age (TLR4/RAGE) and by stimulation with their ligands (subcutaneous). Overall, we revealed that adipokines/adipose-tissue released cytokines show some modulation of their release caused by mediators of septic (batokines) and sterile inflammation with potential implication for acute and chronic disease. Moreover, aging may increase or decrease the release of fat-derived mediators. These data show that DAMPS and LPS locally modulate cytokine secretion while only DAMPS but not LPS can locally alter adipokine secretion during inflammation.

Long-term, high-fat feeding exacerbates short-term increases in adipose mitochondrial reactive oxygen species, without impairing mitochondrial respiration

White adipose tissue (WAT) dysfunction in obesity is implicated in the onset of whole body insulin resistance. Alterations in mitochondrial bioenergetics, namely impaired mitochondrial respiration and increased mitochondrial reactive oxygen species (mtROS) production, have been suggested to contribute to this metabolic dysregulation. However, techniques investigating mitochondrial function are classically normalized to tissue weight, which may be confounding when considering obesity-related adipocyte hypertrophy. Furthermore, the effect of long-term high-fat diet (HFD) on mtROS in WAT has yet to be elucidated. Therefore, we sought to determine the HFD-mediated temporal changes in mitochondrial respiration and mtROS emission in WAT. C57BL/6N mice received low-fat diet or HFD for 1 or 8 wk and changes in inguinal WAT (iWAT) and epididymal WAT (eWAT) were assessed. While tissue weight-normalized mitochondrial respiration was reduced in iWAT following 8-wk HFD-feeding, this effect was mitigated when adipocyte cell size and/or number were considered. These data suggest HFD does not impair mitochondrial respiratory capacity per adipocyte within WAT. In support of this assertion, within eWAT compensatory increases in lipid-supported and maximal succinate-supported respiration occurred at 8 wk despite cell hypertrophy and increases in WAT inflammation. Although these data suggest impairments in mitochondrial respiration do not contribute to HFD-mediated WAT phenotype, lipid-supported mtROS emission increased following 1-wk HFD in eWAT, while both lipid and carbohydrate-supported mtROS were increased at 8 wk in both depots. Combined, these data establish that while HFD does not impair adipocyte mitochondrial respiratory capacity, increased mtROS is an enduring physiological occurrence within WAT in HFD-induced obesity.

High-fat diet induced obesity and age influence the telomere shelterin complex and telomerase gene expression in mouse adipose tissue

Obesity and aging are linked to inflammation and increased risk of chronic disease. Telomeres are the endcaps of chromosomes that are regulated by telomerase, the enzyme that elongates telomeres, as well as a protein complex known as shelterin. Telomere dysfunction is associated with inflammation, aging, and disease. However, the effect of high-fat diet (HFD) induced obesity and advancing age on the shelterin complex and telomerase in adipose tissue is unknown. The present study investigated the effects of obesity and aging on C57BL/6J mice adipose tissue mRNA expression of shelterin complex genes. Young (YG) mice (3 mo) were randomly assigned to be fed either a high-fat diet (YG + HFD; 60% kcal from fat) or a low-fat diet (YG + LFD; 10% kcal from fat). A subset of mice were aged until 16 months. Body weight and epididymal white adipose tissue (EWAT) weight increased with age or a HFD. There was a trend for increased Terf2 expression, as expression was increased in HFD + YG by ~47% and aged mice by ~80%. Pot1b expression was increased in aged mice by ~35%-60% compared to YG, independent of diet. mTert, the gene that codes for the catalytic subunit of telomerase, was significantly elevated in aged mice. Changes in telomere associated gene expression was accompanied by changes in expression of inflammatory markers Mcp1 and Tnfα. These findings suggest obesity and age impact expression of shelterin complex and telomerase related genes in adipose, perhaps altering telomere function in adipose tissue thereby increasing inflammation and risk of chronic disease.

Pathophysiological implications of hypoxia in human diseases

Oxygen is essentially required by most eukaryotic organisms as a scavenger to remove harmful electron and hydrogen ions or as a critical substrate to ensure the proper execution of enzymatic reactions. All nucleated cells can sense oxygen concentration and respond to reduced oxygen availability (hypoxia). When oxygen delivery is disrupted or reduced, the organisms will develop numerous adaptive mechanisms to facilitate cells survived in the hypoxic condition. Normally, such hypoxic response will cease when oxygen level is restored. However, the situation becomes complicated if hypoxic stress persists (chronic hypoxia) or cyclic normoxia-hypoxia phenomenon occurs (intermittent hypoxia). A series of chain reaction-like gene expression cascade, termed hypoxia-mediated gene regulatory network, will be initiated under such prolonged or intermittent hypoxic conditions and subsequently leads to alteration of cellular function and/or behaviors. As a result, irreversible processes occur that may cause physiological disorder or even pathological consequences. A growing body of evidence implicates that hypoxia plays critical roles in the pathogenesis of major causes of mortality including cancer, myocardial ischemia, metabolic diseases, and chronic heart and kidney diseases, and in reproductive diseases such as preeclampsia and endometriosis. This review article will summarize current understandings regarding the molecular mechanism of hypoxia in these common and important diseases.

Structural Elements of the Biomechanical System of Soft Tissue

In living organisms, forces are constantly generated and transmitted throughout tissue. Such forces are generated through interaction with the environment and as a result of the body’s endogenous movement. If these internally or externally originating forces exceed the ability of tissues to cope with the applied forces, (i.e. “tissue thresholds”), they will cause force-related tissue harm. However, biotensegrity systems act to prevent these forces from causing structural damage to cells and tissues. The mechanism and structure of soft tissues that enable them to maintain their integrity and prevent damage under constantly changing forces is still not fully understood. The current anatomical and physical knowledge is insufficient to assess and predict how, why, where, and when to expect force-related tissue harm.

When including the concept of tensegrity and the related principles of the hierarchical organisation of the elements of the subcellular tensional homeostatic structure into current biomechanical concepts, it increases our understanding of the events in force handling in relation to the onset of force-related tissue harm: Reducing incident forces in tissue to a level that is not harmful to the involved structures is achieved by dissipation, transduction and transferring the force in multiple dimensions. To enable this, the biomechanical systems must function in a continuous and consistent way from the cellular level to the entire body to prevent local peak forces from causing harm. In this article, we explore the biomechanical system with a focus on biotensegrity concepts across several organisational levels, describing in detail how it may function and reflecting on how this might be applied to patient management.

Identification and Application of Gene Expression Signatures Associated with Lifespan Extension

Several pharmacological, dietary, and genetic interventions that increase mammalian lifespan are known, but general principles of lifespan extension remain unclear. Here, we performed RNA sequencing (RNA-seq) analyses of mice subjected to 8 longevity interventions. We discovered a feminizing effect associated with growth hormone regulation and diminution of sex-related differences. Expanding this analysis to 17 interventions with public data, we observed that many interventions induced similar gene expression changes. We identified hepatic gene signatures associated with lifespan extension across interventions, including upregulation of oxidative phosphorylation and drug metabolism, and showed that perturbed pathways may be shared across tissues. We further applied the discovered longevity signatures to identify new lifespan-extending candidates, such as chronic hypoxia, KU-0063794, and ascorbyl-palmitate. Finally, we developed GENtervention, an app that visualizes associations between gene expression changes and longevity. Overall, this study describes general and specific transcriptomic programs of lifespan extension in mice and provides tools to discover new interventions.

Peroxisomal regulation of redox homeostasis and adipocyte metabolism

Peroxisomes are ubiquitous cellular organelles required for specific pathways of fatty acid oxidation and lipid synthesis, and until recently their functions in adipocytes have not been well appreciated. Importantly, peroxisomes host many oxygen-consumption reactions and play a major role in generation and detoxification of reactive oxygen species (ROS) and reactive nitrogen species (RNS), influencing whole cell redox status. Here, we review recent progress in peroxisomal functions in lipid metabolism as related to ROS/RNS metabolism and discuss the roles of peroxisomal redox homeostasis in adipogenesis and adipocyte metabolism. We provide a framework for understanding redox regulation of peroxisomal functions in adipocytes together with testable hypotheses for developing therapies for obesity and the related metabolic diseases.

The db mutation improves memory in younger mice in a model of Alzheimer's disease

Alzheimer's disease (AD) is the most common age-related neurodegenerative disease, while obesity is a major global public health problem associated with the metabolic disorder type 2 diabetes mellitus (T2DM). Chronic obesity and T2DM have been identified as invariant risk factors for dementia and late-onset AD, while their impacts on the occurrence and development of AD remain unclear. As shown in our previous study, the diabetic mutation (db, Lepr^db/db) induces mixed or vascular dementia in mature to middle-aged APP^ΔNL/ΔNL x PS1^P264L/P264L knock-in mice (db/AD). In the present study, the impacts of the db mutation on young AD mice at 10 weeks of age were evaluated. The db mutation not only conferred young AD mice with severe obesity, impaired glucose regulation and activated mammalian target of rapamycin (mTOR) signaling pathway in the mouse cortex, but lead to a surprising improvement in memory. At this young age, mice also had decreased cerebral Aβ content, which we have not observed at older ages. This was unlikely to be related to altered Aβ synthesis, as both β- and γ-secretase were unchanged. The db mutation also reduced the cortical IL-1β mRNA level and IBA1 protein level in young AD mice, with no significant effect on the activation of microglia and astrocytes. We conclude that the db mutation could transitorily improve the memory of young AD mice, a finding that may be partially explained by the relatively improved glucose homeostasis in the brains of db/AD mice compared to their counterpart AD mice, suggesting that glucose regulation could be a strategy for prevention and treatment of neurodegenerative diseases like AD.

Adipose oxidative stress and protein carbonylation

Increased oxidative stress and abundance of reactive oxygen species (ROS) are positively correlated with a variety of pathophysiologies, including cardiovascular disease, type 2 diabetes, Alzheimer's disease, and neuroinflammation. In adipose biology, diabetic obesity is correlated with increased ROS in an age- and depot-specific manner and is mechanistically linked to mitochondrial dysfunction, endoplasmic reticulum (ER) stress, potentiated lipolysis, and insulin resistance. The cellular quality control systems that homeostatically regulate oxidative stress in the lean state are down-regulated in obesity as a consequence of inflammatory cytokine pressure leading to the accumulation of oxidized biomolecules. New findings have linked protein, DNA, and lipid oxidation at the biochemical level, and the structures and potential functions of protein adducts such as carbonylation that accumulate in stressed cells have been characterized. The sum total of such regulation and biochemical changes results in alteration of cellular metabolism and function in the obese state relative to the lean state and underlies metabolic disease progression. In this review, we discuss the molecular mechanisms and events underlying these processes and their implications for human health and disease.

Loss of Malat1 does not modify age- or diet-induced adipose tissue accretion and insulin resistance in mice

Several studies have suggested that signals emerging from white adipose tissue can contribute to the control of longevity. In turn, aging is associated with perturbed regulation and partitioning of fat depots and insulin resistance. However, the exact mechanisms involved in these relationships remain undetermined. Using RAP-PCR on adipose tissue of young and old male mice coupled with qPCR validation, we have uncovered the long non-coding RNA Malat1 as a gene robustly downregulated in visceral white adipose tissue (vWAT) during normal aging in male mice and men. Reductions in Malat1 expression in subcutaneous WAT (scWAT) were also observed in genetic (ob and db) as well as diet-induced models of obesity. Based on these findings, Malat1+/+ and Malat1-/- mouse littermates were thus probed to detect whether loss of Malat1 would impact age or diet-induced gain in fat mass and development of glucose intolerance. Contrary to this hypothesis, male and female Malat1-deficient mice gained as much weight, and developed insulin resistance to a similar extent as their Malat1+/+ littermates when studied up to eight months old on regular chow or a high-fat, high-sucrose diet. Moreover, we observed no marked difference in oxygen consumption, food intake, or lipid profiles between Malat1+/+ and Malat1-/- mice. Therefore, we conclude that the overall metabolic impact of the absence of Malat1 on adipose tissue accretion and glucose intolerance is either physiologically not relevant upon aging and obesity, or that it is masked by as yet unknown compensatory mechanisms.

Grape Seed Proanthocyanidin Extract Prevents Ovarian Aging by Inhibiting Oxidative Stress in the Hens

Oxidative stress is an important inducement in ovarian aging which results in fecundity decline in human and diverse animals. As a potent antioxidant, grape seed proanthocyanidin extract (GSPE) was investigated to ameliorate chicken ovarian aging in this study. Firstly, ovarian antioxidant capacity of hens at different ages (90, 150, 280, and 580 days old) was compared to elucidate its age-related changes. Subsequently, a D-gal-induced (2.5 mg/mL) aging ovarian model was established and the cultured ovarian tissues were treated with GSPE at 5 μg/mL for 72 h to evaluate the putative attenuating effects of GSPE on ovarian aging. Meanwhile, ovaries of D280 (young) and D580 (old) were treated with GSPE for 72 h in culture to verify the protective effects of GSPE on natural aging ovary. The results showed that GSPE could rescue the antioxidant capacity decline by increasing the antioxidase activities and their gene expression in either D-gal-induced or natural aging ovaries. Moreover, GSPE could maintain the homeostasis between cell proliferation and apoptosis in the D-gal-induced and natural aging ovaries, as well as alleviate D-gal-induced nucleus chromatin condensation in the ovarian granulosa cells. In conclusion, GSPE treatment can effectively prevent the ovarian aging process in hens by reducing oxidative stress.

The role of declining adaptive homeostasis in ageing

Adaptive homeostasis is "the transient expansion or contraction of the homeostatic range for any given physiological parameter in response to exposure to sub-toxic, non-damaging, signalling molecules or events, or the removal or cessation of such molecules or events" (Davies, 2016). Adaptive homeostasis enables biological systems to make continuous short-term adjustments for optimal functioning despite ever-changing internal and external environments. Initiation of adaptation in response to an appropriate signal allows organisms to successfully cope with much greater, normally toxic, stresses. These short-term responses are initiated following effective signals, including hypoxia, cold shock, heat shock, oxidative stress, exercise-induced adaptation, caloric restriction, osmotic stress, mechanical stress, immune response, and even emotional stress. There is now substantial literature detailing a decline in adaptive homeostasis that, unfortunately, appears to manifest with ageing, especially in the last third of the lifespan. In this review, we present the hypothesis that one hallmark of the ageing process is a significant decline in adaptive homeostasis capacity. We discuss the mechanistic importance of diminished capacity for short-term (reversible) adaptive responses (both biochemical and signal transduction/gene expression-based) to changing internal and external conditions, for short-term survival and for lifespan and healthspan. Studies of cultured mammalian cells, worms, flies, rodents, simians, apes, and even humans, all indicate declining adaptive homeostasis as a potential contributor to age-dependent senescence, increased risk of disease, and even mortality. Emerging work points to Nrf2-Keap1 signal transduction pathway inhibitors, including Bach1 and c-Myc, both of whose tissue concentrations increase with age, as possible major causes for age-dependent loss of adaptive homeostasis.

Fibroblast growth factor 21 delayed endothelial replicative senescence and protected cells from H2O2-induced premature senescence through SIRT1

Vascular aging is an independent risk factor for age-related diseases, including atherosclerosis. Fibroblast growth factor 21 (FGF21) has been widely recognized as a metabolic regulator that is elevated in response to caloric and nutritional restrictions. Recent studies have demonstrated its emerging role as a pro-longevity hormone, but its effects on the senescence of human umbilical vascular endothelial cells (HUVECs) remain unclear. In the present study, we explored the anti-senescence effects and underlying mechanism of FGF21 on HUVECs. Co-cultivation of HUVECs with 5 ng/mL FGF21 significantly attenuated the phenotype changes of cells during in vitro subculture, including increased senescent population, decreased proliferation rate, decreased SIRT1 and elevated P53 and P21 protein levels. FGF21 also protected HUVECs from H₂O₂-induced cell damage, including premature cell senescence, intracellular accumulation of reactive oxygen species, increased DNA damage, decreased SIRT1 protein level and elevated protein levels of VCAM-1, ICAM-1, P53 and P21. Transient knockdown of SIRT1 in HUVECs significantly suppressed the protective effects of FGF21 for the rescue of H₂O₂-induced premature senescence and DNA damage, which suggests that the anti-senescence effect of FGF21 on HUVECs is SIRT1-dependent. These results support the potential of FGF21 as a therapeutic target for postponing vascular aging and preventing age-related vascular diseases.

Age-dependent obesity and mitochondrial dysfunction

Aging is associated with progressive visceral white adipose tissue (WAT) expansion both in human and mouse. Importantly, WAT enlargement is initiated early in life, suggesting that molecular mechanisms underlying age-dependent obesity are activated at early stages of lifetime. Our recent study found that age-dependent obesity was associated with a specific decline in mitochondrial complex IV activity, which leads to reduced fatty acid oxidation and subsequent adipocyte hypertrophy. At the molecular level, global mitochondrial complex IV inhibition was driven by hypoxia-inducible factor-1α (HIF1α)-mediated repression of some of its key subunits, including cytochrome c oxidase 5b (Cox5b). In this commentary, we compare age-dependent WAT responses with those observed in the high fat diet model of extreme obesity. Furthermore, we discuss the potential scenarios that could initiate age-dependent WAT expansion as well as the mechanisms by which HIF1α could be activated in WAT.

Systematic review of patient factors affecting adipose stem cell viability and function: implications for regenerative therapy

BACKGROUND

The applications for fat grafting have increased recently, within both regenerative and reconstructive surgery. Although fat harvesting, processing and injection techniques have been extensively studied and standardised, this has not had a big impact on the variability of outcome following fat grafting. This suggests a possible larger role of patient characteristics on adipocyte and adipose-derived stem cell (ADSC) viability and function. This systematic review aims to collate current evidence on the effect of patient factors on adipocyte and ADSC behaviour.

METHODS

A systematic literature review was performed using MEDLINE, Cochrane Library and EMBASE. It includes outcomes observed in in vitro analyses, in vivo animal studies and clinical studies. Data from basic science work have been included in the discussion to enhance our understanding of the mechanism behind ADSC behaviour.

RESULTS

A total of 41 papers were included in this review. Accumulating evidence indicates decreased proliferation and differentiation potential of ADSCs with increasing age, body mass index, diabetes mellitus and exposure to radiotherapy and Tamoxifen, although this was not uniformly seen across all studies. Gender, donor site preference, HIV status and chemotherapy did not show a significant influence on fat retention. Circulating oestrogen levels have been shown to support both adipocyte function and graft viability. Evidence so far suggests no significant impact of total cholesterol, hypertension, renal disease, physical exercise and peripheral vascular disease on ADSC yield.

CONCLUSIONS

A more uniform comparison of all factors highlighted in this review, with the application of a combination of tests for each outcome measure, is essential to fully understand factors that affect adipocyte and ADSC viability, as well as functionality. As these patient factors interact, future studies looking at adipocyte viability need to take them into consideration for conclusions to be meaningful. This would provide crucial information for surgeons when deciding appropriate volumes of lipoaspirate to inject, improve patient selection, and counsel patient expectations with regards to outcomes and likelihood for repeat procedures. An improved understanding will also assist in identification of patient groups that would benefit from graft enrichment and cryopreservation techniques.

Adipose-specific ablation of Nrf2 transiently delayed high-fat diet-induced obesity by altering glucose, lipid and energy metabolism of male mice

Nuclear factor E2-related factor 2 (NRF2) is a well-known master controller of the cellular adaptive antioxidant and detoxification response. Recent studies demonstrated altered glucose, lipid and energy metabolism in mice with a global Nrf2 knockout. In the present study, we aim to determine the effects of an adipose-specific ablation of Nrf2 (ASAN) on diet-induced obesity (DIO) in male mice. The 6-week-old adipose-specific Nrf2 knockout (NK) and its Nrf2 control (NC) mice were fed with either control diet (CD) or high-fat diet (HFD) for 14 weeks. NK mice exhibited transiently delayed body weight (BW) growth from week 5 to week 11 of HFD feeding, higher daily physical activity levels and preferential use of fat over carbohydrates as a source of energy at week 8 of the CD-feeding period. After 14 weeks of feeding, NK mice showed comparable results with NC mice with respect to the overall BW and body fat content, but exhibited reduced blood glucose, reduced number but increased size of adipocytes, accompanied with elevated expression of many genes and proteins in the visceral fat related to glucose, lipid and energy metabolism (e.g. Fgf21, Pgc1a). These results indicated that NRF2 is an important mediator for glucose, lipid and energy metabolism in adipose tissue, and ASAN could have beneficial effect for prevention of DIO during the early development of mice.

Free Radical-derived Oxysterols: Novel Adipokines Modulating Adipogenic Differentiation of Adipose Precursor Cells

CONTEXT

Increased oxidative stress in adipose tissue emerges as an inducer of obesity-linked insulin resistance. Here we tested whether free-radical derived oxysterols are formed by, and accumulate in, human adipocytes. Moreover, we asked whether increased accumulation of oxysterols characterizes the adipose cells of obese patients with type 2 diabetes (T2D) (OBT2D) compared with lean, nondiabetic controls (CTRLs). Finally, we studied the effects of the free radical-derived oxysterols on adipogenic differentiation of adipose-derived stem cells (ASCs).

MAIN OUTCOME MEASURES

Adipocytes and ASCs were isolated from sc abdominal adipose tissue biopsy in four OBT2D and four CTRL subjects. Oxysterols in adipocytes were detected by gas chromatography/mass spectrometry. The cellular and molecular effects of oxysterols were then evaluated on primary cultures of ASCs focusing on cell viability, adipogenic differentiation, and "canonical" WNT and MAPK signaling pathways.

RESULTS

7-ketocholesterol (7κ-C) and 7β-hydroxycholesterol were unambiguously detected in adipocytes, which showed higher oxysterol accumulation (P < .01) in OBT2D, as compared with CTRL individuals. Notably, the accumulation of oxysterols in adipocytes was predicted by the adipose cell size of the donor (R² = 0.582; P < .01). Challenging ASCs with free radical-derived type I (7κ-C) and type II (5,6-Secosterol) oxysterols led to a time- and concentration-dependent decrease of cell viability. Meaningfully, at a non-toxic concentration (1μM), these bioactive lipids hampered adipogenic differentiation of ASCs by sequential activation of WNT/β-catenin, p38-MAPK, ERK1/2, and JNK signaling pathways.

CONCLUSION

Free radical-derived oxysterols accumulate in the "diabetic" fat and may act as novel adipokines modulating the adipogenic potential of undifferentiated adipose precursor cells.

Adaptive phenotypic response to climate enabled by epigenetics in a K-strategy species, the fish Leucoraja ocellata (Rajidae)

The relative importance of genetic versus epigenetic changes in adaptive evolution is a hotly debated topic, with studies showing that some species appear to be able to adapt rapidly without significant genetic change. Epigenetic mechanisms may be particularly important for the evolutionary potential of species with long maturation times and low reproductive potential ('K-strategists'), particularly when faced with rapidly changing environmental conditions. Here we study the transcriptome of two populations of the winter skate (Leucoraja ocellata), a typical 'K-strategist', in Atlantic Canada; an endemic population in the southern Gulf of St Lawrence and a large population on the Scotian Shelf. The endemic population has been able to adapt to a 10°C higher water temperature over short evolutionary time (7000 years), dramatically reducing its body size (by 45%) significantly below the minimum maturation size of Scotian Shelf and other populations of winter skate, as well as exhibiting other adaptations in life history and physiology. We demonstrate that the adaptive response to selection has an epigenetic basis, cataloguing 3653 changes in gene expression that may have enabled this species to rapidly respond to the novel environment. We argue that the epigenetic augmentation of species evolutionary potential (its regulation though gene expression) can enable K-strategists to survive and adapt to different environments, and this mechanism may be particularly important for the persistence of sharks, skates and rays in the light of future climate change.

Dynamic gene expression profiles during postnatal development of porcine subcutaneous adipose

A better understanding of the control of lipogenesis is of critical importance for both human and animal physiology. This requires a better knowledge of the changes of gene expression during the process of adipose tissue development. Thus, the objective of the current study was to determine the effects of development on subcutaneous adipose tissue gene expression in growing and adult pigs. Here, we present a comprehensive investigation of mRNA transcriptomes in porcine subcutaneous adipose tissue across four developmental stages using digital gene expression profiling. We identified 3,274 differential expressed genes associated with oxidative stress, immune processes, apoptosis, energy metabolism, insulin stimulus, cell cycle, angiogenesis and translation. A set of universally abundant genes (ATP8, COX2, COX3, ND1, ND2, SCD and TUBA1B) was found across all four developmental stages. This set of genes may play important roles in lipogenesis and development. We also identified development-related gene expression patterns that are linked to the different adipose phenotypes. We showed that genes enriched in significantly up-regulated profiles were associated with phosphorylation and angiogenesis. In contrast, genes enriched in significantly down-regulated profiles were related to cell cycle and cytoskeleton organization, suggesting an important role for these biological processes in adipose growth and development. These results provide a resource for studying adipose development and promote the pig as a model organism for researching the development of human obesity, as well as being used in the pig industry.

Effect of lipopolysaccharides on adipogenic potential and premature senescence of adipocyte progenitors

The elevation of circulating LPS has been associated with obesity and aging. However, whether and how LPS contributes to adipose tissue dysfunction is unclear. In this study, we investigated the effect of LPS on the adipogenic capacity and cellular senescence of adipocyte progenitors. Stromal-vascular cells were isolated from inguinal adipose tissue of C57BL/6 mice and treated with LPS during the different time periods of adipocyte differentiation. We found that LPS treatment for 24 h prior to the induction of differentiation led to the most profound effect on the inhibition of adipogenesis, as evidenced by the morphological changes and the decreased mRNA expression of adipocyte marker genes. In addition, LPS induced features of premature senescence of SV cells, including the activation of p53, the elevation of SA-β-gal activity, and increased hydrogen peroxide production, but not telomere length. Upon LPS treatment, SV cells also developed senescence-associated secretory phenotype (SASP), as demonstrated by the increased expression of TNFα, IL-1β, IL-6, MCP-1, and VEGFα. Blocking LPS-induced NF-κB activation and cytokine production by Bay 11-7082 failed to rescue the impaired adipogenesis and the reduction in PPARγ and Zfp423 expression. On the contrary, rosiglitazone had little effect on cytokine production but corrected the defective adipogenic potential. In conclusion, we demonstrate that LPS inhibits adipogenesis by disrupting the differentiation of adipocyte progenitors in a NF-κB-independent manner; LPS also induces premature senescence of adipocyte progenitors. Our data suggest that LPS could be a potential contributor to the defective adipogenesis and the development of cellular senescence in adipose tissue during obesity and aging.

Hypoxia, Oxidative Stress and Fat

Metabolic disturbances in white adipose tissue in obese individuals contribute to the pathogenesis of insulin resistance and the development of type 2 diabetes mellitus. Impaired insulin action in adipocytes is associated with elevated lipolysis and increased free fatty acids leading to ectopic fat deposition in liver and skeletal muscle. Chronic adipose tissue hypoxia has been suggested to be part of pathomechanisms causing dysfunction of adipocytes. Hypoxia can provoke oxidative stress in human and animal adipocytes and reduce the production of beneficial adipokines, such as adiponectin. However, time-dose responses to hypoxia relativize the effects of hypoxic stress. Long-term exposure of fat cells to hypoxia can lead to the production of beneficial substances such as leptin. Knowledge of time-dose responses of hypoxia on white adipose tissue and the time course of generation of oxidative stress in adipocytes is still scarce. This paper reviews the potential links between adipose tissue hypoxia, oxidative stress, mitochondrial dysfunction, and low-grade inflammation caused by adipocyte hypertrophy, macrophage infiltration and production of inflammatory mediators.

Longevity GWAS Using the Drosophila Genetic Reference Panel

We used 197 Drosophila melanogaster Genetic Reference Panel (DGRP) lines to perform a genome-wide association analysis for virgin female lifespan, using ~2M common single nucleotide polymorphisms (SNPs). We found considerable genetic variation in lifespan in the DGRP, with a broad-sense heritability of 0.413. There was little power to detect signals at a genome-wide level in single-SNP and gene-based analyses. Polygenic score analysis revealed that a small proportion of the variation in lifespan (~4.7%) was explicable in terms of additive effects of common SNPs (≥2% minor allele frequency). However, several of the top associated genes are involved in the processes previously shown to impact ageing (eg, carbohydrate-related metabolism, regulation of cell death, proteolysis). Other top-ranked genes are of unknown function and provide promising candidates for experimental examination. Genes in the target of rapamycin pathway (TOR; Chrb, slif, mipp2, dredd, RpS9, dm) contributed to the significant enrichment of this pathway among the top-ranked 100 genes (p = 4.79×10(-06)). Gene Ontology analysis suggested that genes involved in carbohydrate metabolism are important for lifespan; including the InterPro term DUF227, which has been previously associated with lifespan determination. This analysis suggests that our understanding of the genetic basis of natural variation in lifespan from induced mutations is incomplete.

The impact of ageing on adipose structure, function and vasculature in the B6D2F1 mouse: evidence of significant multisystem dysfunction

The critical influence of the white adipose tissue (WAT) on metabolism is well-appreciated in obesity, but adipose tissue dysfunction as a mechanism underlying age-associated metabolic dysfunction requires elucidation. To explore this possibility, we assessed metabolism and measures of epididymal (e)WAT mitochondria and artery function in young (6.1 ± 0.4 months) and old (29.6 ± 0.2 months) B6D2F1 mice. There were no group differences in average daily oxygen consumption, fasted blood glucose or plasma free fatty acids, but fasted plasma insulin and the homeostatic model assessment of insulin resistance (HOMA-IR%) were higher in the old (∼50-85%, P < 0.05). Tissue mass (P < 0.05) and adipocyte area were lower (∼60%) (P < 0.01) and fibrosis was greater (sevenfold, P < 0.01) in eWAT with older age. The old also exhibited greater liver triglycerides (∼60%, P < 0.05). The mitochondrial respiratory oxygen flux after the addition of glutamate and malate (GM), adenosine diphosphate (d), succinate (S) and octanoyl carnitine (O) were one- to twofold higher in eWAT of old mice (P < 0.05). Despite no change in the respiratory control ratio, substrate control ratios of GMOd/GMd and GMOSd/GMd were ∼30-40% lower in old mice (P < 0.05) and were concomitant with increased nitrotyrosine (P < 0.05) and reduced expression of brown adipose markers (P < 0.05). Ageing reduced vascularity (∼50%, P < 0.01), angiogenic capacity (twofold, P < 0.05) and expression of vascular endothelial growth factor (∼50%, P < 0.05) in eWAT. Finally, endothelium-dependent dilation was lower (P < 0.01) in isolated arteries from eWAT arteries of the old mice. Thus, metabolic dysfunction with advancing age occurs in concert with dysfunction in the adipose tissue characterized by both mitochondrial and arterial dysfunction.

Inhibition of age-related cytokines production by ATGL: a mechanism linked to the anti-inflammatory effect of resveratrol

Ageing is characterized by the expansion and the decreased vascularization of visceral adipose tissue (vAT), disruption of metabolic activities, and decline of the function of the immune system, leading to chronic inflammatory states. We previously demonstrated that, in vAT of mice at early state of ageing, adipocytes mount a stress resistance response consisting in the upregulation of ATGL, which is functional in restraining the production of inflammatory cytokines. Here, we found that, in the late phase of ageing, such an adaptive response is impaired. In particular, 24-months-old mice and aged 3T3-L1 adipocytes display affected expression of ATGL and its downstream PPARα-mediated lipid signalling pathway, leading to upregulation of TNFα and IL-6 production. We show that the natural polyphenol compound resveratrol (RSV) efficiently suppresses the expression of TNFα and IL-6 in an ATGL/PPARα dependent manner. Actually, adipocytes downregulating ATGL do not show a restored PPARα expression and display elevated cytokines production. Overall the results obtained highlight a crucial function of ATGL in inhibiting age-related inflammation and reinforce the idea that RSV could represent a valid natural compound to limit the onset and/or the exacerbation of the age-related inflammatory states.

Aging differentially alters the expression of angiogenic genes in a tissue-dependent manner

Organ functions are altered and impaired during aging, thereby resulting in increased morbidity of age-related diseases such as Alzheimer's disease, diabetes, and heart failure in the elderly. Angiogenesis plays a crucial role in the maintenance of tissue homeostasis, and aging is known to reduce the angiogenic capacity in many tissues. Here, we report the differential effects of aging on the expression of angiogenic factors in different tissues, representing a potentially causes for age-related metabolic disorders. PCR-array analysis revealed that many of angiogenic genes were down-regulated in the white adipose tissue (WAT) of aged mice, whereas they were largely up-regulated in the skeletal muscle (SM) of aged mice compared to that in young mice. Consistently, blood vessel density was substantially reduced and hypoxia was exacerbated in WAT of aged mice compared to that in young mice. In contrast, blood vessel density in SM of aged mice was well preserved and was not different from that in young mice. Moreover, we identified that endoplasmic reticulum (ER) stress was strongly induced in both WAT and SM during aging in vivo. We also found that ER stress significantly reduced the expression of angiogenic genes in 3T3-L1 adipocytes, whereas it increased their expression in C2C12 myotubes in vitro. These results collectively indicate that aging differentially affects the expression of angiogenic genes in different tissues, and that aging-associated down-regulation of angiogenic genes in WAT, at least in part through ER stress, is potentially involved in the age-related adipose tissue dysfunction.

Transcriptional impact of dietary methionine restriction on systemic inflammation: relevance to biomarkers of metabolic disease during aging

Calorie restriction (CR) without malnutrition increases lifespan and produces significant improvements in biomarkers of metabolic health. The improvements are attributable in part to effects of CR on energy balance, which limit fat accumulation by restricting energy intake. Normal age-associated increases in adiposity and insulin resistance are associated with development of a systemic proinflammatory state, while chronic CR limits fat deposition and expression of inflammatory markers. Dietary methionine restriction (MR) has emerged as an effective CR mimetic because it produces a comparable extension in lifespan. MR also reduces adiposity through a compensatory increase in energy expenditure that effectively limits fat accumulation, but essentially nothing is known about the effects of MR on systemic inflammation. Here, we review the relationships between these two interventions and discuss their transcriptional impact. In addition, using tissues from rats after long-term consumption of CR or MR diets, transcriptional profiling was used to examine retrospectively the systems biology of 59 networks of molecules annotated to inflammation. Transcriptional effects of both diets occurred primarily in white adipose tissue and liver, and the responses to MR were far more robust than those to CR. The primary transcriptional targets of MR in both liver and white adipose tissue were phagocytes and macrophages, where expression of genes associated with immune cell infiltration and quantity was reduced. These findings support the conclusion that anti-inflammatory responses produced by CR and MR are not strictly dependent upon reduced adiposity but are significantly influenced by the metabolic mechanisms through which energy balance is altered.

Adipose tissue oxygenation: Effects on metabolic function

With the increasing prevalence of obesity there is a concomitant increase in white adipose tissue dysfunction, with the tissue moving toward a proinflammatory phenotype. Adipose tissue hypoxia has been proposed as a key underlying mechanism triggering tissue dysfunction but data from human, in vivo studies, to support this hypothesis is limited. Human adipose tissue oxygenation has been investigated by direct assessment of tissue oxygen tension (pO2) or by expression of hypoxia-sensitive genes/protein in lean and obese subjects but findings are inconsistent. An obvious read-out of hypoxia is the effect on intermediary metabolism, and we have investigated the functional consequences, in terms of a "metabolic signature" of human adipose tissue hypoxia in vivo. Here, we discuss the different approaches used and the importance of integrative physiological techniques to try and elucidate what defines adipose tissue hypoxia in humans.

Elucidation of molecular mechanisms of physiological variations between bovine subcutaneous and visceral fat depots under different nutritional regimes

Adipose tissue plays a critical role in energy homeostasis and metabolism. There is sparse understanding of the molecular regulation at the protein level of bovine adipose tissues, especially within different fat depots under different nutritional regimes. The objective of this study was to analyze the differences in protein expression between bovine subcutaneous and visceral fat depots in steers fed different diets and to identify the potential regulatory molecular mechanisms of protein expression. Subcutaneous and visceral fat tissues were collected from 16 British-continental steers (15.5 month old) fed a high-fat diet (7.1% fat, n=8) or a control diet (2.7% fat, n=8). Protein expression was profiled using label free quantification LC-MS/MS and expression of selected transcripts was evaluated using qRT-PCR. A total of 682 proteins were characterized and quantified with fat depot having more impact on protein expression, altering the level of 51.0% of the detected proteins, whereas diet affected only 5.3%. Functional analysis revealed that energy production and lipid metabolism were among the main functions associated with differentially expressed proteins between fat depots, with visceral fat being more metabolically active than subcutaneous fat as proteins associated with lipid and energy metabolism were upregulated. The expression of several proteins was significantly correlated to subcutaneous fat thickness and adipocyte size, indicating their potential as adiposity markers. A poor correlation (r=0.245) was observed between mRNA and protein levels for 9 genes, indicating that many proteins may be subjected to post-transcriptional regulation. A total of 8 miRNAs were predicted to regulate more than 20% of lipid metabolism proteins differentially expressed between fat depots, suggesting that miRNAs play a role in adipose tissue regulation. Our results show that proteomic changes support the distinct metabolic and physiological characteristics observed between subcutaneous and visceral adipose tissue depots in cattle.

Adipocytokines in relation to cardiovascular disease

Adipose tissue can be considered as a huge gland producing paracrine and endocrine hormones, the adipo(cyto)kines. There is growing evidence that these adipo(cyto)kines may link obesity to cardiovascular diseases. The excessive adipocyte hypertrophy in obesity induces hypoxia in adipose tissue. This leads to adiposopathy, the process that converts "healthy" adipose tissue to "sick" adipose tissue. This is accompanied by a change in profile of adipo(cyto)kines released, with less production of the "healthy" adipo(cyto)kines such as adiponectin and omentin and more release of the "unhealthy" adipo(cyto)kines, ultimately leading to the development of cardiovascular diseases. The present review provides a concise and general overview of the actual concepts of the role of adipo(cyto)kines in endothelial dysfunction, hypertension, atherosclerosis and heart diseases. The knowledge of these concepts may lead to new tools to improve health in the next generations.

Proline oxidase-adipose triglyceride lipase pathway restrains adipose cell death and tissue inflammation

The nutrient-sensing lipolytic enzyme adipose triglyceride lipase (ATGL) has a key role in adipose tissue function, and alterations in its activity have been implicated in many age-related metabolic disorders. In adipose tissue reduced blood vessel density is related to hypoxia state, cell death and inflammation. Here we demonstrate that adipocytes of poorly vascularized enlarged visceral adipose tissue (i.e. adipose tissue of old mice) suffer from limited nutrient delivery. In particular, nutrient starvation elicits increased activity of mitochondrial proline oxidase/dehydrogenase (POX/PRODH) that is causal in triggering a ROS-dependent induction of ATGL. We demonstrate that ATGL promotes the expression of genes related to mitochondrial oxidative metabolism (peroxisome proliferator-activated receptor-α, peroxisome proliferator-activated receptor-γ coactivator-1α), thus setting a metabolic switch towards fat utilization that supplies energy to starved adipocytes and prevents cell death, as well as adipose tissue inflammation. Taken together, these results identify ATGL as a stress resistance mediator in adipocytes, restraining visceral adipose tissue dysfunction typical of age-related metabolic disorders.

Prolonged diet induced obesity has minimal effects towards brain pathology in mouse model of cerebral amyloid angiopathy: implications for studying obesity-brain interactions in mice

Cerebral amyloid angiopathy (CAA) occurs in nearly every individual with Alzheimer's disease (AD) and Down's syndrome, and is the second largest cause of intracerebral hemorrhage. Mouse models of CAA have demonstrated evidence for increased gliosis contributing to CAA pathology. Nearly two thirds of Americans are overweight or obese, with little known about the effects of obesity on the brain, although increasingly the vasculature appears to be a principle target of obesity effects on the brain. In the current study we describe for the first time whether diet induced obesity (DIO) modulates glial reactivity, amyloid levels, and inflammatory signaling in a mouse model of CAA. In these studies we identify surprisingly that DIO does not significantly increase Aβ levels, astrocyte (GFAP) or microglial (IBA-1) gliosis in the CAA mice. However, within the hippocampal gyri a localized increase in reactive microglia were increased in the CA1 and stratum oriens relative to CAA mice on a control diet. DIO was observed to selectively increase IL-6 in CAA mice, with IL-1β and TNF-α not increased in CAA mice in response to DIO. Taken together, these data show that prolonged DIO has only modest effects towards Aβ in a mouse model of CAA, but appears to elevate some localized microglial reactivity within the hippocampal gyri and selective markers of inflammatory signaling. These data are consistent with the majority of the existing literature in other models of Aβ pathology, which surprisingly show a mixed profile of DIO effects towards pathological processes in mouse models of neurodegenerative disease. The importance for considering the potential impact of ceiling effects in pathology within mouse models of Aβ pathogenesis, and the current experimental limitations for DIO in mice to fully replicate metabolic dysfunction present in human obesity, are discussed. This article is part of a Special Issue entitled: Animal Models of Disease.

Oxidative stress in the etiology of age-associated decline in glucose metabolism

One of the most common pathologies in aging humans is the development of glucose metabolism dysfunction. The high incidence of metabolic dysfunction, in particular type 2 diabetes mellitus, is a significant health and economic burden on the aging population. However, the mechanisms that regulate this age-related physiological decline, and thus potential preventative treatments, remain elusive. Even after accounting for age-related changes in adiposity, lean mass, blood lipids, etc., aging is an independent factor for reduced glucose tolerance and increased insulin resistance. Oxidative stress has been shown to have significant detrimental impacts on the regulation of glucose homeostasis in vitro and in vivo. Furthermore, oxidative stress has been shown to be modulated by age and diet in several model systems. This review provides an overview of these data and addresses whether increases in oxidative stress with aging may be a primary determinant of age-related metabolic dysfunction.