Sarcopenia, obesity, and natural killer cell immune senescence in aging: altered cytokine levels as a common mechanism. Aging (Albany NY). 2012;4:535-546. [PMID: 22935594 PMCID: PMC3461341 DOI: 10.18632/aging.100482]

Proinflammatory status influences NK cells subsets in the elderly

Aging is associated to dysfunctional changes in the immune system, a process termed immunosenescence. Elderly individuals usually present chronic low level inflammation, likely as the consequence of continued exposure to antigens combined with poor immune function, increases in production of pro-inflammatory cytokines by effector memory and senescent T cells and macrophages. This condition not only results from, but also drives immunosenescence. Aging affects all cell components of the immune system, including NK cells and its different subsets (CD56dimCD16+, CD56brightCD16+/- and CD56-CD16+). In particular, the percentage of total NK cells is increased in healthy aging and centenarians, whereas there is a decrease in the CD56bright NK cell subset and an expansion of CD56-CD16+ NK cells. However, the causes of these alterations on NK cells in old donors are not fully understood. In this work we analyse NK cell subsets in the elderly in relation with markers of inflammation and health status. The results show that there is a positive correlation between the number of total NK cells and the body mass index (BMI), while the number of CD56bright NK cells negatively correlates with the levels of C-reactive protein (CRP), supporting that chronic inflammation is involved in the decrease of this NK cell subset.

Studies that shed new light on aging

I will first discuss how all aging models that assume that the aged cell has irreversibly lost its youthful capabilities through such mechanisms as accumulated dysfunction, accumulated damage, and/or accumulation of toxic byproducts of metabolism have been shown to be incorrect. I will then briefly discuss models of aging and propose an experiment that would distinguish between those models and provide a basis for organismic rejuvenation.

Targeting T cell immunometabolism for cancer immunotherapy; understanding the impact of the tumor microenvironment

The immune system has a key role to play in controlling cancer initiation and progression. T cell activation, which is central to anti-tumor immune responses, coincides with changes in cellular metabolism. Naïve T cells predominantly require an ATP generating metabolic profile, whereas proliferating effector T cells require anabolic metabolic profiles that promote rapid growth and proliferation. Furthermore, specific T cell subsets require distinct energetic and biosynthetic pathways to match their functional requirements. The often hostile tumor microenvironment can affect T cell immune responses by altering the resulting cellular metabolism. Tailoring immune responses by manipulating cellular metabolic pathways may provide an exciting new option for cancer immunotherapy. T cell responses might also be skewed via metabolic manipulation to treat the complications of obesity-associated inflammation, which is a rapidly growing global health problem and a major risk factor for many malignancies. In this review, the diverse metabolic requirements of T cells in anti-tumor immunity are discussed, as well as the profound influence of the tumor microenvironment and the possible avenues for manipulation to enhance anti-tumor immunity.

Shaping of NK cell subsets by aging

NK cells are key players in the innate immune response against virus infection and tumors. Here we describe the current knowledge on age-associated changes in NK cells and the role of persistent CMV infection in configuring NK cell compartment in the elderly. Aging but not CMV causes a redistribution of NK cell subsets as shown by a decrease of CD56bright cells and an increase of CD56-CD16+ NK cells. On the contrary the changes in CD56dimCD16+ NK cells are compatible with the accumulation of CD57+ long-lived NK cells that can also be observed in young CMV-seropositive individuals. NK cell function and dynamics in the elderly will be related not only with age but also with exposure to pathogens, especially CMV.

Obesity-related inflammation: implications for older adults

The combination of age-related increases in obesity and inflammation can lead to chronic disease, decreased strength, and physical disability. Lifestyle interventions that include moderate caloric restriction along with aerobic and resistance exercise have shown improvements in metabolic outcomes, strength, and physical function in obese older adults. Although few weight loss studies have addressed diet quality, evidence summarized in this review suggests that encouraging intake of antioxidant-rich fruits and vegetables, high-quality protein, low-glycemic index carbohydrates, and omega-3 fatty acids may further ameliorate obesity-related inflammation. Future controlled trials are indicated to examine the effects of incorporating these foods into multimodal weight loss interventions.

Skeletal muscle area correlates with body surface area in healthy adults

AIM

Depletion of skeletal muscle mass (sarcopenia) predicts survival in patients with cancer or liver cirrhosis. Recently, many reports have used computed tomography (CT) to measure muscle area to define sarcopenia. However, the definition of sarcopenia using CT has not been fully determined. The aim of this study was to establish formulae to calculate the standard area of skeletal muscle.

METHODS

Forty-five healthy adults (24 men and 21 women, aged 21-66 years) who wished to donate part of their liver for transplantation underwent CT. Cross-sectional areas (cm(2) ) of skeletal muscle were measured at the caudal end of the third lumbar vertebra. Regression analysis was performed to establish formulae to calculate the standard area of skeletal muscle. A validation conducted on 30 other healthy adults was performed to check the accuracy of formulae.

RESULTS

Men had a median skeletal muscle area of 155.0 cm(2) (range, 114.0-203.0), compared with 111.7 cm(2) (range, 89.8-139.3) in women (P < 0.001). Furthermore, skeletal muscle area significantly correlated with body surface area (BSA) in men (P < 0.0001, r(2)  = 0.60) and women (P < 0.0001, r(2)  = 0.78). The formulae to calculate skeletal muscle area were 126.9 × BSA - 66.2 in men and 125.6 × BSA - 81.1 in women. The estimated muscle area significantly correlated with actual muscle area in men (P = 0.003, r(2)  = 0.64) and women (P = 0.0001, r(2)  = 0.70).

CONCLUSION

Sarcopenia can be defined by the difference between measured data and calculated data using our new formulae.

Natural killer (NK) cell deficit in coronary artery disease: no aberrations in phenotype but sustained reduction of NK cells is associated with low-grade inflammation

Although reduced natural killer (NK) cell levels have been reported consistently in patients with coronary artery disease (CAD), the clinical significance and persistence of this immune perturbation is not clarified. In this study we characterized the NK cell deficit further by determining (i) differentiation surface markers and cytokine profile of NK cell subsets and (ii) ability to reconstitute NK cell levels over time. Flow cytometry was used to analyse NK cell subsets and the intracellular cytokine profile in 31 patients with non-ST elevation myocardial infarction (non-STEMI), 34 patients with stable angina (SA) and 37 healthy controls. In blood collected prior to coronary angiography, the proportions of NK cells were reduced significantly in non-STEMI and SA patients compared with controls, whereas NK cell subset analyses or cytokine profile measurements did not reveal any differences across groups. During a 12-month follow-up, the proportions of NK cells increased, although not in all patients. Failure to reconstitute NK cell levels was associated with several components of metabolic syndrome. Moreover, interleukin (IL)-6 levels remained high in patients with sustained NK cell deficit, whereas a decline in IL-6 (P < 0·001) was seen in patients with a pronounced increase in NK cells. In conclusion, we found no evidence that reduction of NK cells in CAD patients was associated with aberrations in NK cell phenotype at any clinical stage of the disease. Conversely, failure to reconstitute NK cell levels was associated with a persistent low-grade inflammation, suggesting a protective role of NK cells in CAD.

Aging and HIV/AIDS: pathogenetic role of therapeutic side effects

The intersection of aging and HIV/AIDS is a looming 'epidemic within an epidemic.' This paper reviews how HIV/AIDS and its therapy cause premature aging or contribute mechanistically to HIV-associated non-AIDS illnesses (HANA). Survival with HIV/AIDS has markedly improved by therapy combinations containing nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors, and protease inhibitors (PIs) called HAART (highly active antiretroviral therapy). Because NRTIs and PIs together prevent or attenuate HIV-1 replication, and prolong life, the population of aging patients with HIV/AIDS increases accordingly. However, illnesses frequently associated with aging in the absence of HIV/AIDS appear to occur prematurely in HIV/AIDS patients. Theories that help to explain biological aging include oxidative stress (where mitochondrial oxidative injury exceeds antioxidant defense), chromosome telomere shortening with associated cellular senescence, and accumulation of lamin A precursors (a nuclear envelop protein). Each of these has the potential to be enhanced or caused by HIV/AIDS, antiretroviral therapy, or both. Antiretroviral therapy has been shown to enhance events seen in biological aging. Specifically, antiretroviral NRTIs cause mitochondrial dysfunction, oxidative stress, and mitochondrial DNA defects that resemble features of both HANA and aging. More recent clinical evidence points to telomere shortening caused by NRTI triphosphate-induced inhibition of telomerase, suggesting telomerase reverse transcriptase (TERT) inhibition as being a pathogenetic contributor to premature aging in HIV/AIDS. PIs may also have a role in premature aging in HIV/AIDS as they cause prelamin A accumulation. Overall, toxic side effects of HAART may both resemble and promote events of aging and are worthy of mechanistic studies.

Soluble Fas ligand is associated with natural killer cell dynamics in coronary artery disease

OBJECTIVE

Apoptosis of natural killer (NK) cells is increased in patients with coronary artery disease (CAD) and may explain why NK cell levels are altered in these patients. Soluble forms of Fas and Fas ligand (L) are considered as markers of apoptosis. Here, we investigated whether plasma levels of Fas and FasL were associated with NK cell apoptosis and NK cell levels in CAD patients.

METHODS

Fas and FasL in plasma were determined by ELISA in 2 cohorts of CAD patients; one longitudinal study measuring circulating NK cells and apoptotic NK cells by flow cytometry 1 day, 3 months and 12 months after a coronary event and one cross-sectional study measuring NK cell apoptosis ex vivo. Both studies included matched healthy controls. Fas and FasL were also determined in supernatants from NK cells undergoing cytokine-induced apoptosis in cell culture.

RESULTS

In the 12-month longitudinal study, plasma FasL increased by 15% (p<0.001) and NK cell levels by 31% (p<0.05) while plasma Fas did not change. Plasma FasL and NK cell levels were significantly related at 3 months and 12 months, r=0.40, p<0.01. Furthermore, plasma FasL, but not plasma Fas, correlated with NK cell apoptosis ex vivo in CAD patients, r=0.54, p<0.05. In vitro, cytokine-induced apoptosis of NK cells resulted in abundant release of FasL.

CONCLUSION

In CAD patients, FasL in plasma is associated with both apoptotic susceptibility of NK cells and dynamic changes in circulating NK cells. NK cells are also themselves a potential source of soluble FasL. Our findings link NK cell status to a soluble marker with possible atheroprotective effects thereby supporting a beneficial role of NK cells in CAD.

Is obesity a marker of robustness in vulnerable hospitalized aged populations? Prospective, multicenter cohort study of 1 306 acutely ill patients

BACKGROUND

The "obesity paradox" is poorly understood in vulnerable older hospitalized populations.

OBJECTIVES

To prospectively analyze the impact of body mass index (BMI) and comorbidities on early (6-week), one- and two-year mortality.

DESIGN

Prospective multicenter study with a two-year follow-up of old patients participating in the SAFES cohort study.

SETTINGS

Nine university hospitals in France.

PARTICIPANTS

Patients aged 75 or older hospitalized in medical divisions through the emergency department.

MEASUREMENT

Inpatients' characteristics were obtained through a comprehensive geriatric assessment of inpatients, conducted in the first week of hospitalization. All-cause mortalities at 6-week, one- and two-year were determined using bivariable and multivariable Cox proportional hazard model.

RESULTS

The SAFES cohort included 1,306 patients, aged 85±6 years, with a majority of women (65%). One- and two-year mortality were inversely associated with BMI ≥30 kg/m2 while early mortality was not, and positively associated with age, burden of comorbidities, walking disorders, level of dependency and presence of a dementia syndrome. Survival rates between patients in low (< 18.0 kg/m2) and intermediate (18-24.9 and 25-29.9 kg/m2) BMI categories were not significant.

CONCLUSION

While our findings seem to confirm the reality of the "obesity paradox" in vulnerable older hospitalized population, the exact understanding of underlying mechanisms and even the truthfulness of this paradoxical relationship are still fraught with considerable methodological, epidemiological and metabolic challenges.

Life-long endurance exercise in humans: circulating levels of inflammatory markers and leg muscle size

Human aging is associated with a loss of skeletal muscle and an increase in circulating inflammatory markers. It is unknown whether endurance training (Tr) can prevent these changes. Therefore we studied 15 old trained (O-Tr) healthy males and, for comparison, 12 old untrained (O-Un), 10 Young-Tr (Y-Tr) and 12 Young-Un (Y-Un). Quadriceps size, VO2 peak, CRP, IL-6, TNF-α and its receptors, suPAR, lipid profile, leucocytes and glucose homeostasis were measured. Tr was associated with an improved insulin profile (p<0.05), and lower leucocyte (p<0.05) and triglyceride levels (p<0.05), independent of age. Aging was associated with poorer glucose control (p<0.05), independent of training. The age-related changes in waist circumference, VO2 peak, cholesterol, LDL, leg muscle size, CRP and IL-6 were counteracted by physical activity (p<0.05). A significant increase in suPAR with age was observed (p<0.05). Most importantly, life-long endurance exercise was associated with a lower level of the inflammatory markers CRP and IL-6 (p<0.05), and with a greater thigh muscle area (p<0.05), compared to age-matched untrained counterparts. These findings in a limited group of individuals suggest that regular physical endurance activity may play a role in reducing some markers of systemic inflammation, even within the normal range, and in maintaining muscle mass with aging.

FoxO1 controls lysosomal acid lipase in adipocytes: implication of lipophagy during nutrient restriction and metformin treatment

Finding new molecular pathways and strategies modulating lipolysis in adipocytes is an attractive goal of the current research. Indeed, it is becoming clear that several human age-related pathologies are caused by adipose tissue expansion and altered lipid metabolism. In the present work, we show that transcription factor forkhead homeobox type protein O1 (FoxO1) is upregulated by nutrient restriction (NR) in adipocytes and exerts the transcriptional control of lipid catabolism via the induction of lysosomal acid lipase (Lipa). An increased autophagy and colocalization of lipid droplets (LDs) with lysosomes was observed implying lipophagy in Lipa-mediated LDs degradation. Interestingly, we found that metformin (Metf), a biguanide drug commonly used to treat type-2 diabetes, exerts effects comparable to that of NR. Actually, it was able to elicit FoxO1-dependent Lipa induction as well as LDs degradation through lipophagy. Moreover, we demonstrate that, during NR or Metf treatment, free fatty acids released by Lipa are directed toward AMP-activated protein kinase-mediated mitochondrial oxidation, thus maintaining energetic homeostasis in adipocytes. In conclusion, our data show that lysosomal-mediated lipid catabolism is activated by NR in adipocytes and give further support to the use of Metf as a NR mimetic to combat age-related diseases associated with altered lipid metabolism.

Killer Immunoglobulin-like Receptors (KIR) haplogroups A and B track with Natural Killer Cells and Cytokine Profile in Aged Subjects: Observations from Octo/Nonagenarians in the Belfast Elderly Longitudinal Free-living Aging STudy (BELFAST)

BACKGROUND

Natural Killer Cells (NK) play an important role in detection and elimination of virus-infected, damaged or cancer cells. NK cell function is guided by expression of Killer Immunoglobulin-like Receptors (KIRs) and contributed to by the cytokine milieu. KIR molecules are grouped on NK cells into stimulatory and inhibitory KIR haplotypes A and B, through which NKs sense and tolerate HLA self-antigens or up-regulate the NK-cytotoxic response to cells with altered HLA self-antigens, damaged by viruses or tumours. We have previously described increased numbers of NK and NK-related subsets in association with sIL-2R cytokine serum levels in BELFAST octo/nonagenarians. We hypothesised that changes in KIR A and B haplotype gene frequencies could explain the increased cytokine profiles and NK compartments previously described in Belfast Elderly Longitudinal Free-living Aging STudy (BELFAST) octo/nonagenarians, who show evidence of ageing well.

RESULTS

In the BELFAST study, 24% of octo/nonagenarians carried the KIR A haplotype and 76% KIR B haplotype with no differences for KIR A haplogroup frequency between male or female subjects (23% v 24%; p=0.88) or for KIR B haplogroup (77% v 76%; p=0.99). Octo/nonagenarian KIR A haplotype carriers showed increased NK numbers and percentage compared to Group B KIR subjects (p=0.003; p=0.016 respectively). There were no KIR A/ B haplogroup-associated changes for related CD57+CD8 (high or low) subsets. Using logistic regression, KIR B carriers were predicted to have higher IL-12 cytokine levels compared to KIR A carriers by about 3% (OR 1.03, confidence limits CI 0.99-1.09; p=0.027) and 14% higher levels for TGF-β (active), a cytokine with an anti-inflammatory role, (OR 1.14, confidence limits CI 0.99-1.09; p=0.002).

CONCLUSION

In this observational study, BELFAST octo/nonagenarians carrying KIR A haplotype showed higher NK cell numbers and percentage compared to KIR B carriers. Conversely, KIR B haplotype carriers, with genes encoding for activating KIRs, showed a tendency for higher serum pro-inflammatory cytokines compared to KIR A carriers. While the findings in this study should be considered exploratory they may serve to stimulate debate about the immune signatures of those who appear to age slowly and who represent a model for good quality survivor-hood.

[Gender aspects of malnutrition and associated sequelae. Prevention and therapy]

Malnutrition is related to a range of secondary complications. The prevalence of many of these sequelae is higher in elderly women than in men, thus resulting in a higher level of impairment and reduced quality of life. Multiple factors lead to the development of malnutrition and socioeconomic causes, such as poverty among the elderly and isolation, are more common in elderly women. The age-associated loss of muscle mass is more pronounced in women than in men and the risk of developing sarcopenia and frailty is increased. The prevalence of sarcopenic obesity is higher in women than in men. Malnutrition increases the risk of osteoporosis and about 80 % of all osteoporosis patients are women. Furthermore, low serum levels of vitamin D correlate more closely to a poorer cognitive outcome in elderly women than they do in men. The prevention, early diagnosis and therapy of malnutrition is of great clinical importance, particularly to preserve physical functional capacity and thus quality of life in elderly women.

Immunological and nutritional factors in elderly people in low-level care and their association with mortality

Background

This study examines associations between markers of nutritional status and lymphocyte subsets and seeks to determine if lymphocyte profile is predictive of survival in elderly Australians residing in aged care facilities. Aged yet still ambulatory subjects (n = 88, 73% female) living in low-level care and requiring minimal assistance were studied for 143 weeks. At baseline when participants were aged (mean ± SD) 86.0 ± 5.9 years, dietary intake was determined by 3-day weighed food record, body composition was assessed by dual energy X-ray absorptiometry (DXA) and a venous blood sample was taken.

Results

At baseline assessment, study participants were consuming nutrient-poor diets and most had symptoms of chronic disease. Although overweight, 40% exhibited sarcopenia. Markers of nutritional status did not relate closely to immune cell numbers (absolute or relative), which on average were within the normal range. Men had lower numbers of CD3⁺CD4⁺ cells (CD4⁺ T cells), a higher proportion of CD3⁻ CD16^± CD56^± (natural killer (NK) cells) and a higher ratio of NK: CD4⁺ T cells than women (all P < 0.05). The main age-related changes evident were decreased T cells, particularly low CD4⁺ T cell counts, and increased numbers of CD19⁺ (B-cell) and NK cells. During the 143 week duration of follow-up, about one quarter of the study participants died, with death more likely in men than women (P < 0.01). Poor survival was predicted by the presence of decreased numbers of CD4⁺ T cells (hazard ratio (HR) 0.919, P < 0.01) and expanded numbers of NK cells (HR 1.085, P < 0.05) in the blood, and therefore the presence of a high NK: CD4⁺ T cell ratio (HR 30.521, P < 0.01).

Conclusions

The NK: CD4⁺ T cell ratio may potentially have clinical utility for predicting longevity in elderly populations. Further studies are needed in other elderly populations to confirm this finding.

The relationship between visceral obesity and colorectal cancer

SUMMARY The prevalence of obesity continues to rise globally and physicians and healthcare systems have to prepare for rising rates of obesity-associated disease. Aside from cardiovascular disease and diabetes, recent evidence suggests a strong association between obesity and the development of cancer, including colorectal cancer. Using BMI as a marker for obesity, excess body fat is associated with an increased risk of colorectal cancer; however, this relationship appears to be stronger among males and more consistent for colon rather than rectal cancer. Epidemiologic literature evaluating the risk of obesity on colorectal cancer survival using BMI is less consistent. Recent evidence suggests that visceral fat plays a greater role in the development of disease. Current research on the effect of visceral obesity on colorectal cancer outcomes is in its infancy, but may drive a new wave of practice for this ever-growing population of colorectal cancer patients.

Rat retinal transcriptome: effects of aging and AMD-like retinopathy

Pathogenesis of age-related macular degeneration (AMD), the leading cause of vision loss in the elderly, remains poorly understood due to the paucity of animal models that fully replicate the human disease. Recently, we showed that senescence-accelerated OXYS rats develop a retinopathy similar to human AMD. To identify alterations in response to normal aging and progression of AMD-like retinopathy, we compared gene expression profiles of retina from 3- and 18-mo-old OXYS and control Wistar rats by means of high-throughput RNA sequencing (RNA-Seq). We identified 160 and 146 age-regulated genes in Wistar and OXYS retinas, respectively. The majority of them are related to the immune system and extracellular matrix turnover. Only 24 age-regulated genes were common for the two strains, suggestive of different rates and mechanisms of aging. Over 600 genes showed significant differences in expression between the two strains. These genes are involved in disease-associated pathways such as immune response, inflammation, apoptosis, Ca ( 2+) homeostasis and oxidative stress. The altered expression for selected genes was confirmed by qRT-PCR analysis. To our knowledge, this study represents the first analysis of retinal transcriptome from young and old rats with biologic replicates generated by RNA-Seq technology. We can conclude that the development of AMD-like retinopathy in OXYS rats is associated with an imbalance in immune and inflammatory responses. Aging alters the expression profile of numerous genes in the retina, and the genetic background of OXYS rats has a profound impact on the development of AMD-like retinopathy.

Sarcopenic obesity and endocrinal adaptation with age

In normal aging, changes in the body composition occur that result in a shift toward decreased muscle mass and increased fat mass. The loss of muscle mass that occurs with aging is termed sarcopenia and is an important cause of frailty, disability, and loss of independence in older adults. Age-related changes in the body composition as well as the increased prevalence of obesity determine a combination of excess weight and reduced muscle mass or strength, recently defined as sarcopenic obesity. Weight gain increases total/abdominal fat, which, in turn, elicits inflammation and fatty infiltration in muscle. Sarcopenic obesity appears to be linked with the upregulation of TNF-α, interleukin (IL)-6, leptin, and myostatin and the downregulation of adiponectin and IL-15. Multiple combined exercise and mild caloric restriction markedly attenuate the symptoms of sarcopenic obesity. Intriguingly, the inhibition of myostatin induced by gene manipulation or neutralizing antibody ameliorates sarcopenic obesity via increased skeletal muscle mass and improved glucose homeostasis. In this review, we describe the possible influence of endocrinal changes with age on sarcopenic obesity.