Adipose Tissue Quality in Aging: How Structural and Functional Aspects of Adipose Tissue Impact Skeletal Muscle Quality

Sarcobesity: New paradigms for healthy aging related to taurine supplementation, gut microbiota and exercise

Enigmatic sarcopenic obesity is still a challenge for science and adds to the global public health burden. The progressive accumulation of body fat combined with a dysfunctional skeletal muscle structure and composition, oxidative stress, mitochondrial dysfunction, and anabolic resistance, among other aggravating factors, together represent the seriousness and complexity of treating the metabolic disorder of sarcobesity in aging. For this reason, further studies are needed that encourage the support of therapeutic management. It is along these lines that we direct the reader to therapeutic approaches that demonstrate important, but still obscure, outcomes in the physiological conditions of sarcobesity, such as the role of taurine in modulating inflammatory and antioxidant mechanisms in muscle and adipose tissue, as well as the management of gut microbiota, able to systemically re-establish the structure and function of the gut-muscle axis, in addition to the merits of physical exercise as an instrument to improve muscular health and lifestyle quality.

Moderate resistance training reduces intermuscular adipose tissue and risk factors of atherosclerotic cardiovascular disease for elderly patients with type 2 diabetes

AIM

This study aimed to assess the impact of moderate resistance training on intermuscular adipose tissue (IMAT) in elderly patients with type 2 diabetes and the independent effect of IMAT reduction on metabolic outcomes.

METHODS

In this randomized controlled trial, 85 patients with type 2 diabetes were assigned to either the resistance training group (42 participants) or the control group (43 participants) for a 6-month intervention. The primary outcome was changes in IMAT measured by computed tomography scan and magnetic resonance imaging using the interactive decomposition of water and fat with echo asymmetry and least squares qualification sequence. Secondary outcomes included changes in metabolic parameters.

RESULTS

Thirty-seven participants in each group completed the study. The IMAT area (measured by a computed tomography scan) in the resistance group decreased from 5.176 ± 1.249 cm2 to 4.660 ± 1.147 cm2, which is a change of -0.512 ± 0.115 cm2, representing a 9.89% decrease from the least-squares adjusted mean at baseline, which was significantly different from that of the control group (a change of 0.587 ± 0.115 cm2, a 10.34% increase). The normal attenuation muscle area (representing normal muscle density) in the resistance group increased from 82.113 ± 8.776 cm2 to 83.054 ± 8.761 cm2, a change of 1.049 ± 0.416 cm2, a 1.3% increase, which was significantly different from that of the control group (a change of -1.113 ± 0.416 cm2, a 1.41% decrease). Homeostasis model assessment 2 of beta cell function (HOMA2-β; increased from 52.291 ± 24.765 to 56.368 ± 21.630, a change of 4.135 ± 1.910, a 7.91% increase from baseline) and ratio of insulin increase to blood glucose increase at 30 min after the oral glucose tolerance test (∆I30/∆G30; increased from 4.616 ± 1.653 to 5.302 ± 2.264, a change of 0.715 ± 0.262, a 15.49% increase) in the resistance group were significantly improved compared with those in the control group, which had a change of -3.457 ± 1.910, a 6.05% decrease in HOMA2-β, and a change of -0.195 ± 0.262, a 3.87% decrease in ∆I30/∆G30, respectively. Adjusting for sex, age, diabetes duration, baseline IMAT, and the dependent variable at baseline, linear regression showed that the change in IMAT area was not related to the change in HOMA2 insulin resistance (β = -0.178, p = .402) or the change in HOMA2-β (β = -1.891, p = .197), but was significantly related to the changes in ∆I30/∆G30 (β = -0.439, p = .047), 2-h postprandial glucose (β = 1.321, p = .026), diastolic blood pressure (β = 2.425, p = .018), normal attenuation muscle area (β = -0.907, p = .019) and 10-year risk of atherosclerotic cardiovascular disease (β = 0.976, p = .002).

CONCLUSION

Low-level, moderate resistance training reduces IMAT content. Even a small reduction in IMAT may be related to a decrease in risk factors for atherosclerotic cardiovascular disease, but this small reduction may not be sufficient to reduce insulin resistance.

Antioxidative and anti-diabetic effects of Tapinanthus cordifolius leaf extract on high-fat diet and streptozotocin-induced type 2 diabetic rats

Type 2 diabetes mellitus (T2DM) remains a global health concern despite current treatment options. This study investigated the potential of Tapinanthus cordifolius (TC) leaf extract as a therapeutic agent for T2DM. T2DM was induced in rats using a high-fat diet and streptozotocin. Diabetic rats received daily oral administration of TC extract (200, 400, or 800 mg/kg) and metformin (400 mg/kg) or remained untreated for 21 days. Blood glucose levels, body weight, diabetic symptoms, oxidative stress markers, and gene expression of metabolic regulators were assessed. TC treatment significantly reduced blood glucose levels and restored body weight in diabetic rats, comparable to the effects of metformin. TC also increased antioxidant enzyme activities (SOD, GST, and CAT) and decreased lipid peroxidation in various tissues. Furthermore, TC upregulated gene expression of glucose transporter type 4 (GLUT-4) and adiponectin receptor 2 (ADIPOR-2) while downregulating pro-inflammatory cytokines TNF-α and IL-6. This study provides the first in vivo evidence supporting TC leaf extract's anti-diabetic and antioxidant efficacy. The findings suggest that TC holds promise as a natural therapeutic agent for managing T2DM through multiple mechanisms, including improved glycemic control, enhanced insulin sensitivity, and protection against oxidative stress and tissue damage. In conclusion, this study validates the ethnobotanical use of TC as an anti-diabetic agent. Further research is warranted to isolate the bioactive compounds responsible for these effects.

Sarcopenic obesity in patients awaiting liver transplant: Unique challenges for nutritional recommendations

Sarcopenic obesity increases the risk of mortality in patients with liver disease awaiting liver transplantation and in the post-transplant period. Nutrition recommendations for individuals with sarcopenia differ from recommendations for patients with obesity or sarcopenic obesity. While these nutrition guidelines have been established in non-cirrhotic patients, established guidelines for liver transplant candidates with sarcopenic obesity are lacking. In this paper, we review existing literature on sarcopenic obesity in patients with chronic liver disease and address opportunities to improve nutritional counseling in patients awaiting liver transplantation.

Percutaneous biopsies of skeletal muscle and adipose tissue in individuals older than 70: methods and outcomes in the Study of Muscle, Mobility and Aging (SOMMA)

Biopsies of muscle and adipose tissue (AT) are useful tools to gain insights into the aging processes in these tissues. However, they are invasive procedures and their risk/benefit profile in older adults can be altered by sarcopenia, frailty, poor healing, and multimorbidity. Their success rates, safety, and tolerability in a geriatric population have not been reported in detail. Investigators in the Study of Muscle, Mobility, and Aging (SOMMA) performed biopsies of muscle and AT in older adults and prospectively collected data on biopsy success rates, safety, and tolerability. We report here the methods and outcomes of these two procedures. In total, 861 participants (aged 70-94) underwent percutaneous biopsies of the Vastus lateralis muscle with a Bergstrom needle. A subset (n = 241) also underwent percutaneous biopsies of the abdominal subcutaneous AT with the tumescent liposuction technique. Success rate was assessed by the percentage of biopsies yielding adequate specimens for analyses; tolerability by pain scores; and safety by frequency of adverse events. All data were prospectively collected. The overall muscle biopsy success rate was 97.1% and was modestly lower in women. The AT biopsy success rate was 95.9% and slightly lower in men. Minimal or no pain was reported in 68% of muscle biopsies and in 83% of AT biopsies. Adverse events occurred in 2.67% of muscle biopsies and 4.15% of AT biopsies. None was serious. In older adults, percutaneous muscle biopsies and abdominal subcutaneous AT biopsies have an excellent safety profile, often achieve adequate tissue yields for analyses, and are well tolerated.

Risk factors for intracellular fatty accumulation in rotator cuff muscle: a histologic analysis

BACKGROUND

Fatty accumulation in rotator cuff muscles has been associated with shoulder dysfunction, risk of repair failure, and poor postoperative outcomes. This study sought to assess risk factors associated with true fatty accumulation based on histologic analysis and determine whether preoperative function directly correlated with this fatty rotator cuff accumulation.

METHODS

Supraspinatus muscle biopsy specimens obtained prospectively from patients undergoing arthroscopic rotator cuff repair were stained with LipidTOX to quantify lipid accumulation. Two-step cluster analysis with Goutallier classification was used to define the fatty and non-fatty rotator cuff groups. We further performed a receiver operating characteristic curve analysis to confirm the group cutoff values.

RESULTS

In total, 51 patients (aged 60.1 ± 10.5 years) were included. There were 19 high-grade partial tears, 10 small tears, 7 medium tears, 10 large tears, and 5 massive tears. Both cluster and receiver operating characteristic curve analyses yielded a cutoff value of 30% LipidTOX/4',6-diamidino-2-phenylindole (DAPI) separating the fatty vs. non-fatty groups. In the univariate analysis, patients with fatty rotator cuffs were aged 63.2 years on average compared with 59.7 years in the non-fatty group (P = .038). Female patients made up 57.1% of the fatty cohort, which was statistically higher than the non-fatty group (P = .042). Massive and large tears were more likely to occur in the fatty group (P = .005). In the multivariate analysis, full tendon tears had the largest predictive status of falling into the fatty group (odds ratio, 15.4; P = .008), followed by female sex (odds ratio, 4.9; P = .036). Patients in the fatty group had significantly higher American Shoulder and Elbow Surgeons scores (P = .048) and lower visual analog scale scores (P = .002).

DISCUSSION AND CONCLUSION

This prospective histologic assessment revealed that full-thickness rotator cuff tears and female sex were the largest risk factors for intracellular lipid accumulation. Although tear size correlated with fatty accumulation, the sex disparity is a noteworthy finding that warrants further research.

Comprehensive Matrisome Profiling of Human Adipose Tissue for Soft Tissue Reconstruction

For effective translation of research from tissue engineering and regenerative medicine domains, the cell-instructive extracellular matrix (ECM) of specific tissues must be accurately realized. As adipose tissue is gaining traction as a biomaterial for soft tissue reconstruction, with highly variable clinical outcomes obtained, a quantitative investigation of the adipose tissue matrisome is overdue. In this study, the human adipose tissue matrisome is profiled using quantitative sequential windowed acquisition of all theoretical fragment ion spectra - mass spectrometry (SWATH-MS) proteomics across a cohort of 13 fat-grafting patients, to provide characterization of ECM proteins within the tissue, and to understand human population variation. There are considerable differences in the expression of matrisome proteins across the patient cohort, with age and lipoaspirate collection technique contributing to the greatest variation across the core matrisome. A high abundance of basement membrane proteins (collagen IV and heparan sulfate proteoglycan) is detected, as well as fibrillar collagens I and II, reflecting the hierarchical structure of the tissue. This study provides a comprehensive proteomic evaluation of the adipose tissue matrisome and contributes to an enhanced understanding of the influence of the matrisome in adipose-related pathologies by providing a healthy reference cohort and details an experimental pipeline that can be further exploited for future biomaterial development.

Lipodystrophy as a target to delay premature aging

Lipodystrophy syndromes are rare diseases characterized by low levels and an abnormal distribution of adipose tissue, caused by diverse genetic or acquired causes. These conditions commonly exhibit metabolic complications, including insulin resistance, diabetes, hypertriglyceridemia, nonalcoholic fatty liver disease, and adipose tissue dysfunction. Moreover, genetic lipodystrophic laminopathies exhibit a premature aging phenotype, emphasizing the importance of restoring adipose tissue distribution and function. In this opinion, we discuss the relevance of adipose tissue reestablishment as a potential approach to alleviate premature aging and age-related complications in genetic lipodystrophy syndromes.

Reappraisal of Adipose Tissue Inflammation in Obesity

Chronic low-grade inflammation is a central component in the pathogenesis of obesity-related expansion of adipose tissue and complications in other metabolic tissues. Five different signaling pathways are defined as dominant determinants of adipose tissue inflammation: These are increased circulating endotoxin due to dysregulation in the microbiota-gut-brain axis, systemic oxidative stress, macrophage accumulation, and adipocyte death. Finally, the nucleotide-binding and oligomerization domain (NOD) leucine-rich repeat family pyrin domain-containing 3 (NLRP3) inflammasome pathway is noted to be a key regulator of metabolic inflammation. The NLRP3 inflammasome and associated metabolic inflammation play an important role in the relationships among fatty acids and obesity. Several highly active molecules, including primarily leptin, resistin, adiponectin, visfatin, and classical cytokines, are abundantly released from adipocytes. The most important cytokines that are released by inflammatory cells infiltrating obese adipose tissue are tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), monocyte chemoattractant protein 1 (MCP-1) (CCL-2), and IL-1. All these molecules mentioned above act on immune cells, causing local and then general inflammation. Three metabolic pathways are noteworthy in the development of adipose tissue inflammation: toll-like receptor 4 (TLR4)/phosphatidylinositol-3'-kinase (PI3K)/Protein kinase B (Akt) signaling pathway, endoplasmic reticulum (ER) stress-derived unfolded protein response (UPR), and inhibitor of nuclear factor kappa-B kinase beta (IKKβ)-nuclear factor kappa B (NF-κB) pathway. In fact, adipose tissue inflammation is an adaptive response that contributes to a visceral depot barrier that effectively filters gut-derived endotoxin. Excessive fatty acid release worsens adipose tissue inflammation and contributes to insulin resistance. However, suppression of adipose inflammation in obesity with anti-inflammatory drugs is not a rational solution and paradoxically promotes insulin resistance, despite beneficial effects on weight gain. Inflammatory pathways in adipocytes are indeed indispensable for maintaining systemic insulin sensitivity. Cannabinoid type 1 receptor (CB1R) is important in obesity-induced pro-inflammatory response; however, blockade of CB1R, contrary to anti-inflammatory drugs, breaks the links between insulin resistance and adipose tissue inflammation. Obesity, however, could be decreased by improving leptin signaling, white adipose tissue browning, gut microbiota interactions, and alleviating inflammation. Furthermore, capsaicin synthesized by chilies is thought to be a new and promising therapeutic option in obesity, as it prevents metabolic endotoxemia and systemic chronic low-grade inflammation caused by high-fat diet.

Coexistence of muscle atrophy and high subcutaneous adipose tissue radiodensity predicts poor prognosis in hepatocellular carcinoma

Introduction

We aimed to assess the prognostic implications of muscle atrophy and high subcutaneous adipose tissue (SAT) radiodensity in patients with hepatocellular carcinoma (HCC).

Methods

In this retrospective study, muscle atrophy was assessed using the psoas muscle index (PMI) obtained from computed tomography. SAT radiodensity was evaluated based on radiodensity measurements. Survival and multivariate analyses were performed to identify factors associated with prognosis. The impact of muscle atrophy and high SAT radiodensity on prognosis was determined through survival analysis.

Results

A total of 201 patients (median age: 71 years; 76.6% male) with HCC were included. Liver cirrhosis was observed in 72.6% of patients, and the predominant Child-Pugh grade was A (77.1%). A total of 33.3% of patients exhibited muscle atrophy based on PMI values, whereas 12.9% had high SAT radiodensity. Kaplan-Meier survival analysis demonstrated that patients with muscle atrophy had significantly poorer prognosis than those without muscle atrophy. Patients with high SAT radiodensity had a significantly worse prognosis than those without it. Muscle atrophy, high SAT radiodensity, the Barcelona Clinic Liver Cancer class B, C, or D, and Child-Pugh score ≥ 6 were significantly associated with overall survival. Further classification of patients into four groups based on the presence or absence of muscle atrophy and high SAT radiodensity revealed that patients with both muscle atrophy and high SAT radiodensity had the poorest prognosis.

Conclusion

Muscle atrophy and high SAT radiodensity are significantly associated with poor prognosis in patients with HCC. Identifying this high-risk subgroup may facilitate the implementation of targeted interventions, including nutritional therapy and exercise, to potentially improve clinical outcomes.

Muscle quality and not quantity as a predictor of survival in head and neck squamous cell carcinoma

BACKGROUND

Sarcopenia is frequent in head and neck squamous cell carcinoma (HNSCC), as a consequence of malnutrition related to risk factors or tumoral mass. Treatment is associated with toxicities that lead to reduced calories intake and muscle mass wasting. Sarcopenia has been negatively associated with tumor control and survival outcomes.

PURPOSE

Our aim is to evaluate the prognostic impact of sarcopenia on overall survival (OS) and progression free survival (PFS) in HNSCC patients undergoing chemoradiation therapy within a prospective clinical trial of chemoradiation vs induction chemotherapy followed by radiation and cetuximab (INTERCEPTOR).

MATERIALS AND METHODS

On baseline CT or MRI, we investigated the association between OS and PFS with radiological markers of sarcopenia, measured at the third cervical vertebra level. We studied paravertebral skeletal muscles area (cm2), muscle density (HU), muscle index (cm2/m2), and intermuscular adipose tissue (IMAT) area (cm2).

RESULTS

Imaging of 128 patients was evaluable. We found out that higher body mass index (BMI) was associated with better OS (p = 0.02), and PFS (p = 0.04). Skeletal muscle area (p = 0.02), and IMAT (p = 0.02) were negatively associated with PFS. IMAT was positively correlated with muscle area (Correlation coefficient 0.6, CI95% 0.47-0.7), and negatively associated with muscle density (Correlation coefficient -0.37, CI95% -0.53 - -0.18).

CONCLUSIONS

IMAT can be used as predictor of PFS in HNC patients undergoing chemoradiation therapy. The amount of intermuscular fat deposits induces alterations of muscle quality, without alterations of muscle quantity, influencing patients' prognosis.

Physiological Approaches Targeting Cellular and Mitochondrial Pathways Underlying Adipose Organ Senescence

The adipose organ is involved in many metabolic functions, ranging from the production of endocrine factors to the regulation of thermogenic processes. Aging is a natural process that affects the physiology of the adipose organ, leading to metabolic disorders, thus strongly impacting healthy aging. Cellular senescence modifies many functional aspects of adipose tissue, leading to metabolic alterations through defective adipogenesis, inflammation, and aberrant adipocytokine production, and in turn, it triggers systemic inflammation and senescence, as well as insulin resistance in metabolically active tissues, leading to premature declined physiological features. In the various aging fat depots, senescence involves a multiplicity of cell types, including mature adipocytes and immune, endothelial, and progenitor cells that are aging, highlighting their involvement in the loss of metabolic flexibility, one of the common features of aging-related metabolic disorders. Since mitochondrial stress represents a key trigger of cellular senescence, and senescence leads to the accumulation of abnormal mitochondria with impaired dynamics and hindered homeostasis, this review focuses on the beneficial potential of targeting mitochondria, so that strategies can be developed to manage adipose tissue senescence for the treatment of age-related metabolic disorders.

The role of skeletal muscle mass on cardiovascular disease risk: an emerging role on modulating lipid profile

PURPOSE OF REVIEW

The purpose of this review was to present updated evidence on the role of skeletal muscle mass on cardiometabolic health.

RECENT FINDINGS

Increased lean, and especially skeletal, muscle mass has been associated with better cardiometabolic health in various epidemiological studies, even in younger age groups. In addition, the link between skeletal muscle mass and adult lipid profile is of interest. A preliminary analysis using the data from the ATTICA prospective cohort study (2002-2022) supports this association.

SUMMARY

Skeletal muscle mass has many metabolic functions (i.e., glucose, insulin and protein metabolism, mitochondrial function, arterial stiffness, inflammation, oxidative stress, brain function, hormone status). Given its associations with the lipid profile and overall cardiometabolic risk, skeletal muscle mass stands among the emerging risk factors for cardiovascular diseases. In addition to only using body mass index or fat distribution, more studies should evaluate lean mass and its prognostic and predictive ability regarding chronic diseases.

Characteristic and fate determination of adipose precursors during adipose tissue remodeling

Adipose tissues are essential for actively regulating systemic energy balance, glucose homeostasis, immune responses, reproduction, and longevity. Adipocytes maintain dynamic metabolic needs and possess heterogeneity in energy storage and supply. Overexpansion of adipose tissue, especially the visceral type, is a high risk for diabetes and other metabolic diseases. Changes in adipocytes, hypertrophy or hyperplasia, contribute to the remodeling of obese adipose tissues, accompanied by abundant immune cell accumulation, decreased angiogenesis, and aberrant extracellular matrix deposition. The process and mechanism of adipogenesis are well known, however, adipose precursors and their fate decision are only being defined with recent information available to decipher how adipose tissues generate, maintain, and remodel. Here, we discuss the key findings that identify adipose precursors phenotypically, with special emphasis on the intrinsic and extrinsic signals in instructing and regulating the fate of adipose precursors under pathophysiological conditions. We hope that the information in this review lead to novel therapeutic strategies to combat obesity and related metabolic diseases.

Significant Interactions between Adipokines and Vitamin D Combined with the Estimated Glomerular Filtration Rate: A Geriatric Case Study

Vitamin D deficiency is an important issue in the worldwide population, especially in older people. According to the World Health Organization data, in 2030, 1 in 6 people in the world will be 60 years old or older. The main storage site for vitamin D is adipose tissue. Further, 25(OH)D regulates the expression of adipogenic genes and apoptosis of adipocytes and directly influences the secretion of the appetite-regulating hormone-leptin. Thus, we investigated the impact of the serum concentrations of leptin, adiponectin, omentin, ghrelin, visfatin, and biochemical parameters on vitamin D and estimated glomerular filtration rate (eGFR) in geriatric females. Our studies indicate that the leptin, visfatin and ghrelin are linked with vitamin D concentration and the eGFR rate in the geriatric females. (1) Background: Vitamin D deficiency is common in older people, and researchers are looking for a link between vitamin D deficiency and the occurrence of diseases in advanced age. The study aimed to evaluate the association between serum 25(OH)D levels and clinical variables in older females. (2) Methods: We investigated the impact of the serum concentrations of leptin, adiponectin, omentin, ghrelin, visfatin, and biochemical parameters on vitamin D and estimated the glomerular filtration rate (eGFR) in 74 geriatric females. (3) Results: We observed a significantly higher concentration of creatinine and visfatin in the G2 stage (eGFR = 60-89 mL/min./1.73 m²). We performed an additional analysis to exclude the effect of vitamin D supplementation and obtained a significantly higher vitamin D concentration in the G2 stage. We found significantly lower vitamin D concentrations in older people. In addition, in a person with low levels of vitamin D, we observed significantly lower levels of albumin and ghrelin. Older patients (80 to 89 years old) had significantly lower levels of vitamin D, albumin, insulin, HOMA-IR, and ghrelin than younger patients (60 to 69 years old). Spearman's correlations performed to examine the relationship between clinical variables seemed to confirm previous results. According to ROC curve analysis, leptin concentration was the strongest predictor of vitamin D fluctuations (the area under the curve, AUC = 0.685; with 79.5% sensitivity and 51.4% specificity; p = 0.0291). However, visfatin reached the most accurate AUC^ROC = 0.651 with 84.2% sensitivity and 49.1% specificity for predicting effects on eGFR. (4) Conclusions: The results suggest that serum levels of leptin, visfatin, and ghrelin are linked with vitamin D concentration and the eGFR rate in the population of geriatric females.

Beyond energy balance regulation: The underestimated role of adipose tissues in host defense against pathogens

Although the adipose tissue (AT) is a central metabolic organ in the regulation of whole-body energy homeostasis, it is also an important endocrine and immunological organ. As an endocrine organ, AT secretes a variety of bioactive peptides known as adipokines - some of which have inflammatory and immunoregulatory properties. As an immunological organ, AT contains a broad spectrum of innate and adaptive immune cells that have mostly been studied in the context of obesity. However, overwhelming evidence supports the notion that AT is a genuine immunological effector site, which contains all cell subsets required to induce and generate specific and effective immune responses against pathogens. Indeed, AT was reported to be an immune reservoir in the host's response to infection, and a site of parasitic, bacterial and viral infections. In addition, besides AT's immune cells, preadipocytes and adipocytes were shown to express innate immune receptors, and adipocytes were reported as antigen-presenting cells to regulate T-cell-mediated adaptive immunity. Here we review the current knowledge on the role of AT and AT's immune system in host defense against pathogens. First, we will summarize the main characteristics of AT: type, distribution, function, and extraordinary plasticity. Second, we will describe the intimate contact AT has with lymph nodes and vessels, and AT immune cell composition. Finally, we will present a comprehensive and up-to-date overview of the current research on the contribution of AT to host defense against pathogens, including the respiratory viruses influenza and SARS-CoV-2.

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.

SARS-CoV-2 infection induces persistent adipose tissue damage in aged golden Syrian hamsters

Coronavirus disease 2019 (COVID-19, caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2)) is primarily a respiratory illness. However, various extrapulmonary manifestations have been reported in patients with severe forms of COVID-19. Notably, SARS-CoV-2 was shown to directly trigger white adipose tissue (WAT) dysfunction, which in turn drives insulin resistance, dyslipidemia, and other adverse outcomes in patients with COVID-19. Although advanced age is the greatest risk factor for COVID-19 severity, published data on the impact of SARS-CoV-2 infection on WAT in aged individuals are scarce. Here, we characterized the response of subcutaneous and visceral WAT depots to SARS-CoV-2 infection in young adult and aged golden hamsters. In both age groups, infection was associated with a decrease in adipocyte size in the two WAT depots; this effect was partly due to changes in tissue's lipid metabolism and persisted for longer in aged hamsters than in young-adult hamsters. In contrast, only the subcutaneous WAT depot contained crown-like structures (CLSs) in which dead adipocytes were surrounded by SARS-CoV-2-infected macrophages, some of them forming syncytial multinucleated cells. Importantly, older age predisposed to a unique manifestation of viral disease in the subcutaneous WAT depot during SARS-CoV-2 infection; the persistence of very large CLSs was indicative of an age-associated defect in the clearance of dead adipocytes by macrophages. Moreover, we uncovered age-related differences in plasma lipid profiles during SARS-CoV-2 infection. These data suggest that the WAT's abnormal response to SARS-CoV-2 infection may contribute to the greater severity of COVID-19 observed in elderly patients.

Altered Adipocyte Cell Size Distribution Prior to Weight Loss in the R6/2 Model of Huntington's Disease

BACKGROUND

Metabolic alterations contribute to disease onset and prognosis of Huntington's disease (HD). Weight loss in the R6/2 mouse model of HD is a consistent feature, with onset in mid-to-late stage of disease.

OBJECTIVE

In the present study, we aimed to investigate molecular and functional changes in white adipose tissue (WAT) that occur at weight loss in R6/2 mice. We further elaborated on the effect of leptin-deficiency and early obesity in R6/2 mice.

METHODS

We performed analyses at 12 weeks of age; a time point that coincides with the start of weight loss in our R6/2 mouse colony. Gonadal (visceral) and inguinal (subcutaneous) WAT depot weights were monitored, as well as adipocyte size distribution. Response to isoprenaline-stimulated glycerol release and insulin-stimulated glucose uptake in adipocytes from gonadal WAT was assessed.

RESULTS

In R6/2 mice, WAT depot weights were comparable to wildtype (WT) mice, and the response to insulin and isoprenaline in gonadal adipocytes was unaltered. Leptin-deficient R6/2 mice exhibited distinct changes compared to leptin-deficient WT mice. At 12 weeks, female leptin-deficient R6/2 mice had reduced body weight accompanied by an increased proportion of smaller adipocytes, while in contrast; male mice displayed a shift towards larger adipocyte sizes without a significant body weight reduction at this timepoint.

CONCLUSIONS

We here show that there are early sex-specific changes in adipocyte cell size distribution in WAT of R6/2 mice and leptin-deficient R6/2 mice.

Adipose tissue aging is regulated by an altered immune system

Adipose tissue is a widely distributed organ that plays a critical role in age-related physiological dysfunctions as an important source of chronic sterile low-grade inflammation. Adipose tissue undergoes diverse changes during aging, including fat depot redistribution, brown and beige fat decrease, functional decline of adipose progenitor and stem cells, senescent cell accumulation, and immune cell dysregulation. Specifically, inflammaging is common in aged adipose tissue. Adipose tissue inflammaging reduces adipose plasticity and pathologically contributes to adipocyte hypertrophy, fibrosis, and ultimately, adipose tissue dysfunction. Adipose tissue inflammaging also contributes to age-related diseases, such as diabetes, cardiovascular disease and cancer. There is an increased infiltration of immune cells into adipose tissue, and these infiltrating immune cells secrete proinflammatory cytokines and chemokines. Several important molecular and signaling pathways mediate the process, including JAK/STAT, NFκB and JNK, etc. The roles of immune cells in aging adipose tissue are complex, and the underlying mechanisms remain largely unclear. In this review, we summarize the consequences and causes of inflammaging in adipose tissue. We further outline the cellular/molecular mechanisms of adipose tissue inflammaging and propose potential therapeutic targets to alleviate age-related problems.

Effect of Obesity and High-Density Lipoprotein Concentration on the Pathological Characteristics of Alzheimer's Disease in High-Fat Diet-Fed Mice

The typical pathological features of Alzheimer's disease (AD) are the accumulation of amyloid plaques in the brain and reactivity of glial cells such as astrocytes and microglia. Clinically, the development of AD and obesity are known to be correlated. In this study, we analyzed the changes in AD pathological characteristics in 5XFAD mice after obesity induction through a high-fat diet (HFD). Surprisingly, high-density lipoprotein and apolipoprotein AI (APOA-I) serum levels were increased without low-density lipoprotein alteration in both HFD groups. The reactivity of astrocytes and microglia in the dentate gyrus of the hippocampus and fornix of the hypothalamus in 5XFAD mice was decreased in the transgenic (TG)-HFD high group. Finally, the accumulation of amyloid plaques in the dentate gyrus region of the hippocampus was also significantly decreased in the TG-HFD high group. These results suggest that increased high-density lipoprotein level, especially with increased APOA-I serum level, alleviates the pathological features of AD and could be a new potential therapeutic strategy for AD treatment.

Targeted erasure of DNA methylation by TET3 drives adipogenic reprogramming and differentiation

DNA methylation is a crucial epigenetic modification in the establishment of cell-type-specific characteristics. However, how DNA methylation is selectively reprogrammed at adipocyte-specific loci during adipogenesis remains unclear. Here, we show that the transcription factor, C/EBPδ, and the DNA methylation eraser, TET3, cooperatively control adipocyte differentiation. We perform whole-genome bisulfite sequencing to explore the dynamics and regulatory mechanisms of DNA methylation in adipocyte differentiation. During adipogenesis, DNA methylation selectively decreases at adipocyte-specific loci carrying the C/EBP binding motif, which correlates with the activity of adipogenic promoters and enhancers. Mechanistically, we find that C/EBPδ recruits a DNA methylation eraser, TET3, to catalyse DNA demethylation at the C/EBP binding motif and stimulate the expression of key adipogenic genes. Ectopic expression of TET3 potentiates in vitro and in vivo adipocyte differentiation and recovers downregulated adipogenic potential, which is observed in aged mice and humans. Taken together, our study highlights how targeted reprogramming of DNA methylation through cooperative action of the transcription factor C/EBPδ, and the DNA methylation eraser TET3, controls adipocyte differentiation.

Nutrients and the Circadian Clock: A Partnership Controlling Adipose Tissue Function and Health

White adipose tissue (WAT) is a metabolic organ with flexibility to retract and expand based on energy storage and utilization needs, processes that are driven via the coordination of different cells within adipose tissue. WAT is comprised of mature adipocytes (MA) and cells of the stromal vascular cell fraction (SVF), which include adipose progenitor cells (APCs), adipose endothelial cells (AEC) and infiltrating immune cells. APCs have the ability to proliferate and undergo adipogenesis to form MA, the main constituents of WAT being predominantly composed of white, triglyceride-storing adipocytes with unilocular lipid droplets. While adiposity and adipose tissue health are controlled by diet and aging, the endogenous circadian (24-h) biological clock of the body is highly active in adipose tissue, from adipocyte progenitor cells to mature adipocytes, and may play a unique role in adipose tissue health and function. To some extent, 24-h rhythms in adipose tissue rely on rhythmic energy intake, but individual circadian clock proteins are also thought to be important for healthy fat. Here we discuss how and why the clock might be so important in this metabolic depot, and how temporal and qualitative aspects of energy intake play important roles in maintaining healthy fat throughout aging.

Weight Loss and Exercise Differentially Affect Insulin Sensitivity, Body Composition, Cardiorespiratory Fitness, and Muscle Strength in Older Adults With Obesity: A Randomized Controlled Trial

BACKGROUND

Aging-related disease risk is exacerbated by obesity and physical inactivity. It is unclear how weight loss and increased activity improve risk in older adults. We aimed to determine the effects of diet-induced weight loss with and without exercise on insulin sensitivity, VO2peak, body composition, and physical function in older obese adults.

METHODS

Physically inactive older (68.6 ± 4.5 years) obese (body mass index 37.4 ± 4.9 kg/m2) adults were randomized to health education control (HEC; n = 25); diet-induced weight loss (WL; n = 31); or weight loss and exercise (WLEX; n = 28) for 6 months. Insulin sensitivity was measured by hyperinsulinemic-euglycemic clamp, body composition by dual-energy X-ray absorptiometry and MRI, strength by isokinetic dynamometry, and VO2peak by graded exercise test.

RESULTS

WLEX improved (p < .05) peripheral insulin sensitivity (+75 ± 103%) versus HEC (+12 ± 67%); WL (+36 ± 47%) versus HEC did not reach statistical significance. WLEX increased VO2peak (+7 ± 12%) versus WL (-2 ± 24%) and prevented reductions in strength and lean mass induced by WL (p < .05). WLEX decreased abdominal adipose tissue (-16 ± 9%) versus HEC (-3 ± 8%) and intermuscular adipose tissue (-15 ± 13%) versus both HEC (+9 ± 15%) and WL (+2 ± 11%; p < .01).

CONCLUSIONS

Exercise with weight loss improved insulin sensitivity and VO2peak, decreased ectopic fat, and preserved lean mass and strength. Weight loss alone decreased lean mass and strength. Older adults intending to lose weight should perform regular exercise to promote cardiometabolic and functional benefits, which may not occur with calorie restriction-induced weight loss alone.

Non-alcoholic fatty liver disease: a multi-system disease influenced by ageing and sex, and affected by adipose tissue and intestinal function

In recent years, a wealth of factors are associated with increased risk of developing non-alcoholic fatty liver disease (NAFLD) and NAFLD is now thought to increase the risk of multiple extra-hepatic diseases. The aim of this review is first to focus on the role of ageing and sex as key, poorly understood risk factors in the development and progression of NAFLD. Secondly, we aim to discuss the roles of white adipose tissue (WAT) and intestinal dysfunction, as producers of extra-hepatic factors known to further contribute to the pathogenesis of NAFLD. Finally, we aim to summarise the role of NAFLD as a multi-system disease affecting other organ systems beyond the liver. Both increased age and male sex increase the risk of NAFLD and this may be partly driven by alterations in the distribution and function of WAT. Similarly, changes in gut microbiota composition and intestinal function with ageing and chronic overnutrition are likely to contribute to the development of NAFLD both directly (i.e. by affecting hepatic function) and indirectly via exacerbating WAT dysfunction. Consequently, the presence of NAFLD significantly increases the risk of various extra-hepatic diseases including CVD, type 2 diabetes mellitus, chronic kidney disease and certain extra-hepatic cancers. Thus changes in WAT and intestinal function with ageing and chronic overnutrition contribute to the development of NAFLD – a multi-system disease that subsequently contributes to the development of other chronic cardiometabolic diseases.

DNA Methylation Modulates Aging Process in Adipocytes

Aging has been recognized to be a highly complex biological health problem with a high risk of chronic diseases, including type 2 diabetes, atherosclerosis, chronic bronchitis or emphysema, cancer and Alzheimer's disease. Particularly, age-related turnover in adipose tissue is a major contributor to metabolic syndromes and shortened lifespan. Adipocytes undergo senescence in early stage, which results in adipose tissue metabolic dysfunction, redistribution, and inflammation. The well-established association between DNA methylation (DNAm) and aging has been observed in the past few decades. Indeed, age-related alteration in DNAm is highly tissue-specific. This review intends to summarize the advancements how DNAm changes coupled with aging process in adipose tissue, by which DNAm regulates cellular senescence, metabolic function, adipokine secretion and beiging process in adipocytes. Elucidation of the effect of DNAm on adipose aging would have great potential to the development of epigenetic therapeutic strategies against aging-related diseases in clinical settings.

State of Knowledge on Molecular Adaptations to Exercise in Humans: Historical Perspectives and Future Directions

For centuries, regular exercise has been acknowledged as a potent stimulus to promote, maintain, and restore healthy functioning of nearly every physiological system of the human body. With advancing understanding of the complexity of human physiology, continually evolving methodological possibilities, and an increasingly dire public health situation, the study of exercise as a preventative or therapeutic treatment has never been more interdisciplinary, or more impactful. During the early stages of the NIH Common Fund Molecular Transducers of Physical Activity Consortium (MoTrPAC) Initiative, the field is well-positioned to build substantially upon the existing understanding of the mechanisms underlying benefits associated with exercise. Thus, we present a comprehensive body of the knowledge detailing the current literature basis surrounding the molecular adaptations to exercise in humans to provide a view of the state of the field at this critical juncture, as well as a resource for scientists bringing external expertise to the field of exercise physiology. In reviewing current literature related to molecular and cellular processes underlying exercise-induced benefits and adaptations, we also draw attention to existing knowledge gaps warranting continued research effort. © 2021 American Physiological Society. Compr Physiol 12:3193-3279, 2022.

Skeletal muscle transcriptome response to a bout of endurance exercise in physically active and sedentary older adults

Age-related declines in cardiorespiratory fitness and physical function are mitigated by regular endurance exercise in older adults. This may be due, in part, to changes in the transcriptional program of skeletal muscle following repeated bouts of exercise. However, the impact of chronic exercise training on the transcriptional response to an acute bout of endurance exercise has not been clearly determined. Here, we characterized baseline differences in muscle transcriptome and exercise-induced response in older adults who were active/endurance trained or sedentary. RNA-sequencing was performed on vastus lateralis biopsy specimens obtained before, immediately after, and 3 h following a bout of endurance exercise (40 min of cycling at 60%-70% of heart rate reserve). Using a recently developed bioinformatics approach, we found that transcript signatures related to type I myofibers, mitochondria, and endothelial cells were higher in active/endurance-trained adults and were associated with key phenotypic features including V̇o_2peak, ATP_max, and muscle fiber proportion. Immune cell signatures were elevated in the sedentary group and linked to visceral and intermuscular adipose tissue mass. Following acute exercise, we observed distinct temporal transcriptional signatures that were largely similar among groups. Enrichment analysis revealed catabolic processes were uniquely enriched in the sedentary group at the 3-h postexercise timepoint. In summary, this study revealed key transcriptional signatures that distinguished active and sedentary adults, which were associated with difference in oxidative capacity and depot-specific adiposity. The acute response signatures were consistent with beneficial effects of endurance exercise to improve muscle health in older adults irrespective of exercise history and adiposity.NEW & NOTEWORTHY Muscle transcript signatures associated with oxidative capacity and immune cells underlie important phenotypic and clinical characteristics of older adults who are endurance trained or sedentary. Despite divergent phenotypes, the temporal transcriptional signatures in response to an acute bout of endurance exercise were largely similar among groups. These data provide new insight into the transcriptional programs of aging muscle and the beneficial effects of endurance exercise to promote healthy aging in older adults.

Sarcopenic Dysphagia, Malnutrition, and Oral Frailty in Elderly: A Comprehensive Review

Frailty is a highly prevalent condition in the elderly that has been increasingly considered as a crucial public health issue, due to the strict correlation with a higher risk of fragility fractures, hospitalization, and mortality. Among the age-related diseases, sarcopenia and dysphagia are two common pathological conditions in frail older people and could coexist leading to dehydration and malnutrition in these subjects. “Sarcopenic dysphagia” is a complex condition characterized by deglutition impairment due to the loss of mass and strength of swallowing muscles and might be also related to poor oral health status. Moreover, the aging process is strictly related to poor oral health status due to direct impairment of the immune system and wound healing and physical and cognitive impairment might indirectly influence older people’s ability to carry out adequate oral hygiene. Therefore, poor oral health might affect nutrient intake, leading to malnutrition and, consequently, to frailty. In this scenario, sarcopenia, dysphagia, and oral health are closely linked sharing common pathophysiological pathways, disabling sequelae, and frailty. Thus, the aim of the present comprehensive review is to describe the correlation among sarcopenic dysphagia, malnutrition, and oral frailty, characterizing their phenotypically overlapping features, to propose a comprehensive and effective management of elderly frail subjects.

COVID-19 in Joint Ageing and Osteoarthritis: Current Status and Perspectives

COVID-19 is a trending topic worldwide due to its immense impact on society. Recent trends have shifted from acute effects towards the long-term morbidity of COVID-19. In this review, we hypothesize that SARS-CoV-2 contributes to age-related perturbations in endothelial and adipose tissue, which are known to characterize the early aging process. This would explain the long-lasting symptoms of SARS-CoV-2 as the result of an accelerated aging process. Connective tissues such as adipose tissue and musculoskeletal tissue are the primary sites of aging. Therefore, current literature was analyzed focusing on the musculoskeletal symptoms in COVID-19 patients. Hypovitaminosis D, increased fragility, and calcium deficiency point towards bone aging, while joint and muscle pain are typical for joint and muscle aging, respectively. These characteristics could be classified as early osteoarthritis-like phenotype. Exploration of the impact of SARS-CoV-2 and osteoarthritis on endothelial and adipose tissue, as well as neuronal function, showed similar perturbations. At a molecular level, this could be attributed to the angiotensin-converting enzyme 2 expression, renin-angiotensin system dysfunction, and inflammation. Finally, the influence of the nicotinic cholinergic system is being evaluated as a new treatment strategy. This is combined with the current knowledge of musculoskeletal aging to pave the road towards the treatment of long-term COVID-19.

Interactive effects of aging and aerobic capacity on energy metabolism-related metabolites of serum, skeletal muscle, and white adipose tissue

Aerobic capacity is a strong predictor of longevity. With aging, aerobic capacity decreases concomitantly with changes in whole body metabolism leading to increased disease risk. To address the role of aerobic capacity, aging, and their interaction on metabolism, we utilized rat models selectively bred for low and high intrinsic aerobic capacity (LCRs/HCRs) and compared the metabolomics of serum, muscle, and white adipose tissue (WAT) at two time points: Young rats were sacrificed at 9 months of age, and old rats were sacrificed at 21 months of age. Targeted and semi-quantitative metabolomics analysis was performed on the ultra-pressure liquid chromatography tandem mass spectrometry (UPLC-MS) platform. The effects of aerobic capacity, aging, and their interaction were studied via regression analysis. Our results showed that high aerobic capacity is associated with an accumulation of isovalerylcarnitine in muscle and serum at rest, which is likely due to more efficient leucine catabolism in muscle. With aging, several amino acids were downregulated in muscle, indicating more efficient amino acid metabolism, whereas in WAT less efficient amino acid metabolism and decreased mitochondrial β-oxidation were observed. Our results further revealed that high aerobic capacity and aging interactively affect lipid metabolism in muscle and WAT, possibly combating unfavorable aging-related changes in whole body metabolism. Our results highlight the significant role of WAT metabolism for healthy aging.

Pim1 knockout alleviates sarcopenia in aging mice via reducing adipogenic differentiation of PDGFRα+ mesenchymal progenitors

BACKGROUND

Sarcopenia widely exists in elderly people and triggers numerous age-related events. The essential pathologic change lies in the increased intramuscular adipose tissue after aging with no exception to non-obese objects. Pim1 appears to be associated with adipogenic differentiation in recent studies, inspiring us to explore whether it regulates adipogenesis in aging muscles and affects sarcopenia.

METHODS

Wild-type and Pim1 knockout C57/BL6J mice were randomized into young and old groups. Histo-pathological and molecular biological methods were applied to assess the intramuscular adipose tissue content, the atrophy and regeneration, and the expressions of Pim1 and adipogenic transcription factors. PDGFRα+ mesenchymal progenitors were separated and their replicative aging model were established. Different time of adipogenic induction and different amounts of Pim1 inhibitor were applied, after which the adipogenic potency were evaluated. The expressions of Pim1 and adipogenic transcription factors were measured through western blotting.

RESULTS

The aging mice demonstrated decreased forelimb grip strength (P = 0.0003), hanging impulse (P < 0.0001), exhaustive running time (P < 0.0001), tetanic force (P = 0.0298), lean mass (P = 0.0008), and percentage of gastrocnemius weight in body weight (P < 0.0001), which were improved by Pim1 knockout (P = 0.0015, P = 0.0222, P < 0.0001, P = 0.0444, P = 0.0004, and P = 0.0003, respectively). To elucidate the mechanisms, analyses showed that Pim1 knockout decreased the fat mass (P = 0.0005) and reduced the intramuscular adipose tissue content (P = 0.0008) by inhibiting the C/EBPδ pathway (P = 0.0067) in aging mice, resulting in increased cross-sectional area of all and fast muscle fibres (P = 0.0017 and 0.0024 respectively), decreased levels of MuRF 1 and atrogin 1 (P = 0.0001 and 0.0329 respectively), and decreased content of Pax7 at the basal state (P = 0.0055). In vitro, senescent PDGFRα+ mesenchymal progenitors showed significantly increased the intracellular adipose tissue content (OD510) compared with young cells after 6 days of adipogenic induction (P < 0.0001). The Pim1 expression was elevated during adipogenic differentiation, and Pim1 inhibition significantly reduced the OD510 in senescent cells (P = 0.0040) by inhibiting the C/EBPδ pathway (P = 0.0047).

CONCLUSIONS

Pim1 knockout exerted protective effects in sarcopenia by inhibiting the adipogenic differentiation of PDGFRα+ mesenchymal progenitors induced by C/EBPδ activation and thus reducing the intramuscular adipose tissue content in aging mice. These results provide a potential target for the treatment of sarcopenia.

Shatavari Supplementation in Postmenopausal Women Improves Handgrip Strength and Increases Vastus lateralis Myosin Regulatory Light Chain Phosphorylation but Does Not Alter Markers of Bone Turnover

Shatavari has long been used as an Ayurvedic herb for women's health, but empirical evidence for its effectiveness has been lacking. Shatavari contains phytoestrogenic compounds that bind to the estradiol receptor. Postmenopausal estradiol deficiency contributes to sarcopenia and osteoporosis. In a randomised double-blind trial, 20 postmenopausal women (68.5 ± 6 years) ingested either placebo (N = 10) or shatavari (N = 10; 1000 mg/d, equivalent to 26,500 mg/d fresh weight shatavari) for 6 weeks. Handgrip and knee extensor strength were measured at baseline and at 6 weeks. Vastus lateralis (VL) biopsy samples were obtained. Data are presented as difference scores (Week 6-baseline, median ± interquartile range). Handgrip (but not knee extensor) strength was improved by shatavari supplementation (shatavari +0.7 ± 1.1 kg, placebo -0.4 ± 1.3 kg; p = 0.04). Myosin regulatory light chain phosphorylation, a known marker of improved myosin contractile function, was increased in VL following shatavari supplementation (immunoblotting; placebo -0.08 ± 0.5 a.u., shatavari +0.3 ± 1 arbitrary units (a.u.); p = 0.03). Shatavari increased the phosphorylation of Akt^ser473 (Akt^ser473 (placebo -0.6 ± 0.6 a.u., shatavari +0.2 ± 1.3 a.u.; p = 0.03) in VL. Shatavari supplementation did not alter plasma markers of bone turnover (P1NP, β-CTX) and stimulation of human osteoblasts with pooled sera (N = 8 per condition) from placebo and shatavari supplementation conditions did not alter cytokine or metabolic markers of osteoblast activity. Shatavari may improve muscle function and contractility via myosin conformational change and further investigation of its utility in conserving and enhancing musculoskeletal function, in larger and more diverse cohorts, is warranted.

Mitochondrial dysfunction plays an essential role in remodeling aging adipose tissue

Aging is characterized by several physiological changes in the human body, such as the remodeling/redistribution of body fat, highlighted by the increase in fat in the abdominal region due to reduced fat in the peripheral limbs. Abdominal fat is related to metabolic complications and an increased risk for developing diseases such as obesity, type 2 diabetes mellitus, and hypertension. Understanding this process is crucial for developing new therapeutic strategies able to mitigate its impact. This redistribution of fat has been associated with lower activation of brown adipose tissue over the years of life. Brown adipose tissue differs from white adipose tissue, mainly because it produces heat, increasing energy expenditure. Current evidence points to morphological and functional changes in mitochondria during aging, a key mechanism for understanding the dysmetabolic and pro-inflammatory phenotype associated with senescence. Therefore, this minireview will focus on how aging-induced mitochondrial changes are involved in the remodeling/redistribution of body fat.

Exogenous parathyroid hormone attenuates ovariectomy-induced skeletal muscle weakness in vivo

Osteoporosis commonly affects the elderly and is associated with significant morbidity and mortality. Loss of bone mineral density induces muscle atrophy and increases fracture risk. However, muscle lipid content and droplet size are increased by aging and mobility impairments, inversely correlated with muscle function, and a cause of reduced motor function. Teriparatide, the synthetic form of human parathyroid hormone (PTH) 1-34, has been widely used to treat osteoporosis. Although PTH positively affects muscle differentiation in vitro, the precise function and mechanisms of muscle mass and power preservation are still poorly understood, especially in vivo. In this study, we investigated the effect of PTH on skeletal muscle atrophy and dysfunction using an ovariectomized murine model. Eight-week-old female C57BL/6J mice were ovariectomized or sham-operated. Within each surgical group, the mice were divided into PTH injection or control subgroups. Motor function was evaluated based on grip strength, treadmill running, and lactic acid concentration. PTH receptor was expressed in skeletal muscle cells and myoblasts. PTH inhibited ovariectomy-induced bone loss but not uterine atrophy or increased body weight; PTH not only abolished ovariectomy-induced reduction in grip strength and maximum running speed, but also significantly reduced the ovariectomy-induced increase in lactic acid concentration (compared with that observed in the vehicle control). PTH also abrogated the ovariectomy-induced reduction in the oxidative capacity of muscle fibers, their cross-sectional area, and intramyocellular lipid content, and induced cell proliferation, cell migration, and muscle differentiation, while reducing lipid secretion by C2C12 myoblasts via the Wnt/β-catenin pathway. PTH significantly ameliorated muscle weakness and attenuated exercise-induced lactate levels in ovariectomized mice. Our in vitro study demonstrated that PTH/Wnt signaling regulated the proliferation, migration, and differentiation of myoblasts and also reduced lipid secretion in myoblasts. Thus, PTH could regulate several aspects of muscle function and physiology, and may represent a novel therapeutic strategy for patients with osteoporosis.

Does Physical Dance Training with Virtual Games Change Muscle Quality of Community-Dwelling Older Women?

Objective: The aim of the study is to analyze the effects of physical dance training with a virtual game on muscle quality (MQ) of community-dwelling older women. Materials and Methods: In total, 46 older women participated in the study and were assigned to either a control group (CG, n = 25, 71 ± 5 years) or training group (TG, n = 21, 69 ± 4 years). The following assessments were performed at baseline and after 12 weeks: quadriceps, ankle plantar flexor, and dorsiflexor isokinetic peak torque (PT) (Biodex System 4 Dynamometer); quadriceps cross-sectional area (CSA) measured using magnetic resonance imaging; intramuscular noncontractile tissue (IMNCT) (Image-Pro Plus 4.5.0.29 for Windows); and MQ (ratio of quadriceps PT to CSA). Each week for 12 weeks, the TG undertook three 40-minute sessions of physical training with the "Dance Central" game for Xbox 360^® with Kinect, while the CG was instructed to maintain usual activities of daily living. Results: The TG increased quadriceps eccentric PT at 60°/s (P = 0.04) and ankle plantar flexor concentric PT at 60°/s (P = 0.02) when compared with the CG. No significant difference in quadriceps CSA, IMNCT, and MQ was observed. Conclusion: Physical dance training with virtual games can increase quadriceps and ankle plantar flexor strength without changing IMNCT and MQ of community-dwelling older women. Trial number: RBR-8xkwyp (ensaiosclinicos.gov.br-Brazilian Clinical Trials Registry).

Age-related change in shear elastic modulus of the thoracolumbar multifidus muscle in healthy Beagle dogs using ultrasound shear wave elastography

Background

Multifidus muscle stiffness decreases in patients with lumbar intervertebral disk herniation; however, age-related changes in humans have not been reported.

Objectives

The reliability of ultrasound shear wave elastography in dogs, and changes in the shear elastic modulus of the thoracolumbar multifidus muscle with aging in dogs, were investigated.

Methods

Twelve beagle dogs were divided into 2 groups based on the age of onset of intervertebral disk herniation: young (aged not exceeding 2 years; 1.3 ± 0.6 years old, n = 5) and adult (4.9 ± 1.2 years old, n = 7). The shear elastic modulus of the multifidus muscle, from the thirteenth thoracic spine to the fourth lumbar spine, was measured using ultrasound shear wave elastography. The length, cross-sectional area and muscle to fat ratio of the multifidus muscle, and the grade of intervertebral disk degeneration, were assessed using radiographic and magnetic resonance imaging examinations.

Results

The length and cross-sectional area of the multifidus muscle increased caudally. In the young group, the shear elastic modulus of the multifidus muscle of the thirteenth thoracic spine was less than that of the third lumbar spine. In the adult group, the shear elastic modulus of the multifidus muscle of first and third lumbar spine was lower than that of the same site in the young group.

Conclusions

Ultrasound can be used to measure shear wave elastography of the thoracolumbar multifidus in dogs. If the multifidus muscle stiffness decreases, we should consider age-related change.

Age-Dependent Remodeling in Infrapatellar Fat Pad Adipocytes and Extracellular Matrix: A Comparative Study

The infrapatellar fat pad (IFP) is actively involved in knee osteoarthritis (OA). However, a proper description of which developmental modifications occur in the IFP along with age and in absence of joint pathological conditions, is required to adequately describe its actual contribution in OA pathophysiology. Here, two IFP sources were compared: (a) IFP from healthy young patients undergoing anterior-cruciate ligament (ACL) reconstruction for ACL rupture (n = 24); (b) IFP from elderly cadaver donors (n = 23). After histopathological score assignment to confirm the absence of inflammatory features (i.e., inflammatory infiltrate and increased vascularity), the adipocytes morphology was determined; moreover, extracellular matrix proteins were studied through histology and Second Harmonic Generation approach, to determine collagens content and orientation by Fast Fourier Transform and OrientationJ. The two groups were matched for body mass index. No inflammatory signs were observed, while higher area, perimeter, and equivalent diameter and volume were detected for the adipocytes in the elderly group. Collagen III displayed higher values in the young group and a lower total collagen deposition with aging was identified. However, collagen I/III ratio and the global architecture of the samples were not affected. A higher content in elastic fibers was observed around the adipocytes for the ACL-IFPs and in the septa cadaver donor-IFPs, respectively. Age affects the characteristics of the IFP tissue also in absence of a pathological condition. Variable mechanical stimulation, depending on age-related different mobility, could be speculated to exert a role in tissue remodeling.

A moderate intensity exercise program improves physical function and oxidative damage in older women with and without sarcopenic obesity

BACKGROUND AND OBJECTIVES

The excess of body fat and muscle mass loss in adulthood results in sarcopenic obesity, which is associated with disability and poor physical condition. A relationship among obesity, sarcopenia and oxidative stress also has been established. These aspects limit a good muscle function which is crucial in the independence of older women with and without sarcopenic obesity. This study had as objective to design a moderate intensity exercise program for older women with sarcopenic obesity, and to examine its effects on oxidative damage and physical function. We hypothesized that the exercise program will reduce oxidative damage and to improve the physical function of older women with sarcopenic obesity.

METHODS

Thirty healthy women (68 ± 5.05 years old) and 30 women with sarcopenic obesity (68.06 ± 5.75 years old) from the Integral Development of the Family rest home participated in the evaluation. The participants underwent evaluations of body composition, physical fitness (timed up-and-go [TUG] test, reaction time, gait speed, flexibility and muscle strength) and oxidative stress (oxidative damage to lipid and protein as well as evaluation of the antioxidant system) before and after of moderate intensity exercise program. The program consisted of warm-up, flexibility; aerobic exercises of moderate intensity (VO₂ max and HR max between 60% and 70%); isotonic exercises of low intensity with progressive weight (250 g of initial weight, with increase every two weeks until reaching 750 g of final weight) and global stretching at the end of each section. The program was monitored on a personal basis and undertaken three times a week over three months.

RESULTS

In both groups, the program induced a five-fold increase in muscle strength, an increase in flexibility and improvement of fragility parameters (TUG and gait speed) (P ≤ 0.001, respectively). Furthermore, this exercise program decreased oxidative damage and increased antioxidant defense (P ≤ 0.001) to a greater extent in the sarcopenic group.

CONCLUSION

It was concluded that moderate intensity exercise is an effective approach to promote changes in body composition, physical fitness and to reduce oxidative damage in older women with and without sarcopenic obesity. These findings might have important implications for the prevention or treatment of sarcopenic obesity in older people.

The muscle to bone axis (and viceversa): An encrypted language affecting tissues and organs and yet to be codified?

Skeletal muscles and bone tissue form the musculoskeletal apparatus, a complex system essential for the voluntary movement. The loss of muscle mass and muscle strength is often associated with a loss of bone mass, in a "hazardous duet" which implies the co-existence of sarcopenia-osteoporosis and exposes patients to a deterioration in quality of life and increased mortality. From the mechanostat theory to the recent definition of the osteosarcopenia syndrome, many aspects of muscle-bone interaction have been investigated in recent decades. The mechanical interaction is now accepted, considering the close anatomical relationship between the two tissues, however, much remains to be discovered regarding the biochemical muscle-bone interaction. Skeletal muscle has been defined as an endocrine organ capable of exerting an action on other tissues. Myokines, bioactive polypeptides released by the muscle, could represent the encrypted message in the communication between muscle and bone. These two tissues have a reciprocal influence on their metabolisms and respond in a similar way to the multiple external factors. The aim of this review is to stimulate the understanding of the encrypted language between muscle and bone, highlighting the role of catabolic pathways and oxidative stress in the musculoskeletal apparatus to elucidate the shared mechanisms and the similarity of response to the same stimuli by different tissues. Our understanding of muscle-bone interactions it could be useful to identify and develop new strategies to treat musculoskeletal diseases, together with pharmacological, nutritional and exercise-based approaches, which are already in use for the treatment of these pathologies.

Oral Nutritional Supplement with β-hydroxy-β-methylbutyrate (HMB) Improves Nutrition, Physical Performance and Ameliorates Intramuscular Adiposity in Pre-Frail Older Adults: A Randomized Controlled Trial

OBJECTIVES

Supplementation of high protein oral nutrition shakes supplemented with β-hydroxy-β-methylbutyrate (HP-HMB) has been shown to improve muscle mass, muscle strength, and physical performance in older adults, but the roles of HP-HMB supplementation on the intramuscular adiposity remained unknown. This 12-week randomized controlled trial evaluated the changes of muscle mass, muscle strength, physical performance and intramuscular adiposity among community-dwelling pre-frail older persons.

METHODS

This was an open-label, parallel group, randomized controlled trail that enrolled 70 community-dwelling pre-frail older persons without active or uncontrolled conditions, disability or dementia. The intervention group was provided with two services of HP HMB (Ensure® Plus Advance containing 3g HMB) per day for 12 weeks, and the control group was provided with professional nutritional counselling for sufficient protein intake. All participants received functional assessments, laboratory tests and magnetic resonance imaging (MRI) of the dominant leg before and after study. Intramuscular adipose tissue (IMAT) and the mid-thigh cross-sectional area (CSA) of muscle were obtained by MRI, and the IMAT-to-CSA ratio was calculated to evaluate intramuscular adiposity.

RESULTS

Overall, 62 participants (mean age: 71.1±3.8 years, 69.4% female) completed the study (HP-HMB group: 29, control group: 33) and comparisons of baseline characteristics between groups were not statistically different. For the primary outcome, HP-HMB group showed significant improvements in the CSA of mid-thigh muscle (mean increase of CSA: 149.1±272.3 for HMB group vs -22.9±309.1 mm2 for control group, P=0.045). The improvement of MNA-SF was borderline (0.28±0.75 vs. -0.15±0.94, P=0.064), but serum levels of Vit D were significantly increased in the HMB group (3.83±8.18 vs. -1.30±4.81 ng/mL, P=0.002). Moreover, the body weight and BMI were significantly increased in the HMB group (1.10±1.18 vs. 0.24±1.13 kg, P=0.005; 0.56±0.68 vs. 0.22±0.47 kg/m2, P=0.019). In particular, the IMAT-to-CSA ratio was reduced in the HMB group (-0.38±1.21 vs. -0.02±2.56 %, P=0.06). Using the generalized estimating equation, we found that SPPB score in chair rise test was significantly improved (β=0.71, 95% C.I.0.09-1.33, P=0.026).

CONCLUSIONS

The 12-week supplementation with high protein oral nutrition shake supplemented with 3g HMB per day significantly increased muscle mass, as well as nutritional status and physical performance, and ameliorated the intramuscular adiposity of pre-frail older persons. Further study is needed to explore the long-term benefits of HP-HMB supplementation on muscle and metabolic health for older adults.

Sarcopenia during COVID-19 lockdown restrictions: long-term health effects of short-term muscle loss

The COVID-19 pandemic is an extraordinary global emergency that has led to the implementation of unprecedented measures in order to stem the spread of the infection. Internationally, governments are enforcing measures such as travel bans, quarantine, isolation, and social distancing leading to an extended period of time at home. This has resulted in reductions in physical activity and changes in dietary intakes that have the potential to accelerate sarcopenia, a deterioration of muscle mass and function (more likely in older populations), as well as increases in body fat. These changes in body composition are associated with a number of chronic, lifestyle diseases including cardiovascular disease (CVD), diabetes, osteoporosis, frailty, cognitive decline, and depression. Furthermore, CVD, diabetes, and elevated body fat are associated with greater risk of COVID-19 infection and more severe symptomology, underscoring the importance of avoiding the development of such morbidities. Here we review mechanisms of sarcopenia and their relation to the current data on the effects of COVID-19 confinement on physical activity, dietary habits, sleep, and stress as well as extended bed rest due to COVID-19 hospitalization. The potential of these factors to lead to an increased likelihood of muscle loss and chronic disease will be discussed. By offering a number of home-based strategies including resistance exercise, higher protein intakes and supplementation, we can potentially guide public health authorities to avoid a lifestyle disease and rehabilitation crisis post-COVID-19. Such strategies may also serve as useful preventative measures for reducing the likelihood of sarcopenia in general and in the event of future periods of isolation.

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.

The impact of disease-related immobilization on thigh muscle mass and strength in older hospitalized patients

Background

We assessed the quantitative changes in muscle mass and strength during 2 weeks of hospitalization in immobile and mobile acutely ill hospitalized older adults.

Methods

Forty-one patients (82.4 ± 6.6 years, 73.0% females) participated in this prospective longitudinal observational study. Mobility status was defined according to walking ability as described in the Barthel-Index. Functional status, including handgrip strength and isometric knee-extension strength, and mid-thigh magnetic resonance imaging (MRI) measurements of cross-sectional area (CSA) were conducted on admission and at discharge.

Results

Twenty-two participants (54%) were immobile and 19 (46%) mobile. In all, 54.0 and 12.0% were at risk of malnutrition and malnourished, respectively. The median time between baseline and follow-up for MRI scans were 13 days in mobile and immobile participants (P = 0.072). Mid-thigh muscle and subcutaneous fat CSA significantly decreased by 3.9cm² (5.0%, P = 0.002) and 5.3cm² (5.7%, P = 0.036) during hospitalization whereas intermuscular fat remained unchanged in immobile subjects. No significant changes were observed in mobile patients. In a regression analysis, mobility was the major independent risk factor for changes in mid-thigh muscle CSA as a percentage of initial muscle area (P = 0.022) whereas other variables such as age (P = 0.584), BMI (P = 0.879), nutritional status (P = 0.835) and inflammation (P = 0.291) were not associated with muscle mass changes. There was a significant decrease in isometric knee extension strength (P = 0.002) and no change in handgrip strength (P = 0.167) in immobile patients whereas both parameters increased significantly over time in mobile patients (P = 0.048 and P = 0.012, respectively).

Conclusions

Two weeks of disease-related immobilization result in a significant loss of thigh muscle mass and muscle strength in older patients with impaired mobility. Concomitantly, there was a significant reduction of subcutaneous adipose tissue in immobile older hospitalized patients whereas no changes were observed in intermuscular fat among these patients. These data highlight the importance of mobility support in maintaining muscle mass and function in older hospitalized patients.

Predicted Skeletal Muscle Mass and 4-Year Cardiovascular Disease Incidence in Middle-Aged and Elderly Participants of IKARIA Prospective Epidemiological Study: The Mediating Effect of Sex and Cardiometabolic Factors

The sex-specific effect of skeletal muscle mass (SMM) index (SMI) on 4-year first fatal/non-fatal cardiovascular disease (CVD) event in free-of-disease individuals was examined. In 2009, n = 1411 inhabitants (mean age = 64(12)) from Ikaria were selected. Follow-up was performed in 2013. SMI was created to reflect SMM through appendicular skeletal muscle mass (indirectly calculated through formulas) divided by body mass index (BMI). Fifteen and six tenths percent of participants exhibited CVD (19.8% in men/12% in women, p = 0.002). Significant U-shape trends were observed in participants >65 years old and women irrespective to age confirmed through multi-adjusted Cox regression analysis; in age >65 years, Hazard Ratio (HR)_{(2nd vs. 1st SMI tertile)} = 0.80, 95% Confidence Interval (95%CI) (0.45, 0.96) and in women HR_{(2nd vs. 1st SMI tertile)} = 0.71, 95% CI (0.33, 0.95), while, as for the 3rd SMI tertile, no significant trends were observed. Mediation analysis revealed that mediators of the aforementioned associations in men were the arterial distensibility and total testosterone, while, in women, inflammation, insulin resistance, and arterial distensibility. High SMM accompanied by obesity may not guarantee lower CVD risk. Specific cardiometabolic factors seem to explain this need for balance between lean and fat mass.

Exercise intolerance and rapid skeletal muscle energetic decline in human age-associated frailty

BACKGROUND

Physical frailty in older individuals is characterized by subjective symptoms of fatigue and exercise intolerance (EI). Objective abnormalities in skeletal muscle (SM) mitochondrial high-energy phosphate (HEP) metabolism contribute to EI in inherited myopathies; however, their presence or link to EI in the frail older adult is unknown.

METHODS

Here, we studied 3 groups of ambulatory, community-dwelling adults with no history of significant coronary disease: frail older (FO) individuals (81 ± 2.7 years, mean ± SEM), nonfrail older (NFO) individuals (79 ± 2.0 years), and healthy middle-aged individuals, who served as controls (CONT, 51 ± 2.1 years). Lower extremity SM HEP levels and mitochondrial function were measured with ³¹P magnetic resonance (MR) techniques during graded multistage plantar flexion exercise (PFE). EI was quantified by a 6-minute walk (6MW) and peak oxygen consumption during cardiopulmonary testing (peak VO₂).

RESULTS

During graded exercise, FO, NFO, and CONT individuals all fatigued at similar SM HEP levels, as measured by ³¹P-MR. However, FO individuals fatigued fastest, with several-fold higher rates of PFE-induced HEP decline that correlated closely with shorter exercise duration in the MR scanner and with 6MW distance and lower peak oxygen consumption on cardiopulmonary testing (P < 0.001 for all). SM mitochondrial oxidative capacity was lower in older individuals and correlated with rapid HEP decline but less closely with EI.

CONCLUSION

Several-fold faster SM energetic decline during exercise occurs in FO individuals and correlates closely with multiple measures of EI. Rapid energetic decline represents an objective, functional measure of SM metabolic changes and a potential new target for mitigating frailty-associated physical limitations.

FUNDING

This work was supported by NIH R21 AG045634, R01 AG063661, R01 HL61912, the Johns Hopkins University Claude D. Pepper Older Americans Independence Center P30AG021334, and the Clarence Doodeman Endowment in Cardiology at Johns Hopkins.

Rapid exercise-induced skeletal muscle high-energy phosphate decline occurs in frail, older individuals and is closely linked to exercise intolerance and fatigue.