Structural and functional properties of deep abdominal subcutaneous adipose tissue explain its association with insulin resistance and cardiovascular risk in men

Towards a consensus atlas of human and mouse adipose tissue at single-cell resolution

Adipose tissue (AT) is a complex connective tissue with a high relative proportion of adipocytes, which are specialized cells with the ability to store lipids in large droplets. AT is found in multiple discrete depots throughout the body, where it serves as the primary repository for excess calories. In addition, AT has an important role in functions as diverse as insulation, immunity and regulation of metabolic homeostasis. The Human Cell Atlas Adipose Bionetwork was established to support the generation of single-cell atlases of human AT as well as the development of unified approaches and consensus for cell annotation. Here, we provide a first roadmap from this bionetwork, including our suggested cell annotations for humans and mice, with the aim of describing the state of the field and providing guidelines for the production, analysis, interpretation and presentation of AT single-cell data.

Association among measurements obtained using portable ultrasonography with sex, body mass index, and age in a large sample of adult population

BACKGROUND

The assessment of the site-specific distribution of subcutaneous tissues (ST) represents an important addition to the body composition (BC) estimation. In this context, ultrasound stands out as a valuable method. However, the absence of reference values complicates both the interpretation of the obtained parameters and the monitoring of their changes during nutritional interventions or training programs.

METHODS

A total of 6,270 ultrasound images obtained with a technique using a non-diagnostic B-mode 2.5 MHz ultrasound probe (BodyMetrixTM, IntelaMetrix, Inc., Livermore, CA, USA) were obtained from adult men and women and analysed by grouping them according to sex, body mass index (BMI), and age. The thicknesses of total (tSAT), superficial (sSAT), and deep (dSAT) subcutaneous adipose tissue and muscle (MT), their ratios (sSAT/dSAT and MT/SAT), and muscle echogenicity (EG) were measured at the abdomen, thigh, chest, triceps, and hip sites.

RESULTS

Women exhibited greater tSAT, sSAT, dSAT, and EG (p < 0.001) and lower MT (p < 0.001), sSAT/dSAT (p = 0.008 for the abdomen and p < 0.001 for the thigh), and MT/SAT (p < 0.001) compared to men at both the abdomen and thigh sites. SAT-related parameters showed significant correlations with BMI, with thicknesses correlating positively and ratios negatively (p < 0.001). Muscle-related parameters correlated significantly with age, with MT and EG showing positive correlations and MT/SAT showing negative correlations (p < 0.001) in both sexes. Among SAT parameters, dSAT showed the strongest association with BMI in both men and women.

CONCLUSIONS

This study is the first to report the mean values of SAT-related quantitative and qualitative measurements (thickness and EG) in various body sites assessed through ultrasound and their associations with sex, BMI, and age in a large cohort. These findings could prove valuable in clinical practice for precise monitoring of nutritional and/or training interventions, as well as for a more comprehensive evaluation of nutritional status.

Analysis of Physiological Oxygen Concentrations in Different Abdominal Fat Layers by Body Mass Index

BACKGROUND

Physiological oxygen concentration in adipose tissue is closely linked to metabolic disorders such as chronic inflammation and insulin resistance. However, the nature of the variation in the oxygen levels of adipose tissue with body mass index (BMI) and depths of abdominal fat remain unclear. Therefore, this study aimed to elucidate the patterns of oxygen concentration in adipose tissue layers according to BMI.

METHODS

In this study, patients undergoing abdominal fat removal surgery were divided into the normal-weight (NW) or overweight-obese (OW) groups based on their BMI. Oxygen concentrations in abdominal superficial (sSAT) and deep subcutaneous adipose tissue (dSAT) were measured. The oxygen consumption rate, mean cell area, and capillary density in both tissue layers were compared between the two groups. Furthermore, the interaction between these three variables, BMI, and adipose tissue oxygen concentration, was analyzed using linear regression.

RESULTS

A total of 42 patients were recruited in this study and we observed that oxygen concentration in the sSAT was significantly lower than in the dSAT, irrespective of BMI. In terms of the oxygen concentration in the dSAT, OW's was significantly lower than that of NW's. Linear regression analysis revealed a significant correlation between dSAT oxygen concentration and BMI, mean adipocyte area, and vascular density.

CONCLUSION

Individuals who are obese have significantly lower oxygen levels in the deep abdominal adipose tissue, and this is influenced by BMI, adipocyte area, and capillary density.

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Type 2 Diabetes Mellitus: New Pathogenetic Mechanisms, Treatment and the Most Important Complications

Type 2 diabetes mellitus (T2DM), a prevalent chronic disease affecting over 400 million people globally, is driven by genetic and environmental factors. The pathogenesis involves insulin resistance and β-cell dysfunction, mediated by mechanisms such as the dedifferentiation of β-cells, mitochondrial dysfunction, and oxidative stress. Treatment should be based on non-pharmacological therapy. Strategies such as increased physical activity, dietary modifications, cognitive-behavioral therapy are important in maintaining normal glycemia. Advanced therapies, including SGLT2 inhibitors and GLP-1 receptor agonists, complement these treatments and offer solid glycemic control, weight control, and reduced cardiovascular risk. Complications of T2DM, such as diabetic kidney disease, retinopathy, and neuropathy, underscore the need for early diagnosis and comprehensive management to improve patient outcomes and quality of life.

Association of body composition and survival in patients with locally advanced breast cancer: a historical cohort study

BACKGROUND

Altered body composition has been attributed to major health problems globally, particularly in patients with cancer. To date, there have not been sufficient indices for body compositions in predicting the survival of locally advanced breast cancer (LABC).

PURPOSE

To assess the association between body composition and overall survival (OS) as well as disease-free survival (DFS) in patients with LABC.

MATERIAL AND METHODS

A retrospective study was conducted of patients with LABC diagnosed between 2010 and 2018. Body composition parameters, including skeletal muscle and adiposity parameters, were measured using computed tomography at the L3 vertebra using in-house software developed by MATLAB and freeware Python 3.6.13. The association between body composition and OS and DFS were analyzed using a log-rank test and multivariate Cox-proportional hazard regression.

RESULTS

Of 199 patients, 72 (36%) died during the follow-up period (range = 3.8-150.7 months). Median survival was 101 months. Low visceral-to-subcutaneous ratio ≤0.3 (adjusted hazard ratio [aHR] = 2.57, 95% confidence interval [CI] = 1.51-4.37; aHR = 2.46, 95% CI = 1.33-4.56), and high composite fat (aHR = 3.26, 95% CI = 1.69-6.29; aHR = 2.19, 95% CI = 1.11-4.3) were associated with lower OS and DFS. Positive lymph nodes ≥3, progesterone receptor negative, and total radiation dose >5000 cGy significantly decreased both OS and DFS. A history of previous treatment before body composition assessment and surgery had a protective effect on OS and DFS. No association of sarcopenia, body mass index, and adiposity areas with survival outcomes was observed.

CONCLUSION

Low visceral-to-subcutaneous ratio and high composite fat were independent prognostic factors for OS and DFS in patients with LABC. However, other body composition parameters showed no effect on survival.

Body adipose tissue depots and treatment outcomes for women with breast cancer: A systematic review

BACKGROUND & AIMS

Excessive adipose tissue is associated with poorer prognosis in women with breast cancer (BC). However, several body adiposity depots, such as visceral (VAT), subcutaneous (SAT), intermuscular (IMAT), and gluteofemoral adipose tissues (GFAT) may have heterogeneous metabolic roles and health effects in these patients. This systematic review aims to evaluate the impact of different body adipose tissue depots, assessed via computed tomography (CT), on treatment outcomes for women with BC. We hypothesize that distinct body adipose tissue depots may be associated differently with outcomes in patients with BC.

METHODS

A comprehensive bibliographical search was conducted using PubMed, Embase, Cochrane Library, Scopus, and Web of Science databases (until January 2024). The methodological quality of the included studies was assessed using the Newcastle-Ottawa Scale.

RESULTS

The final sample comprised 23 retrospective studies (n = 12,462), with fourteen presenting good quality. A lack of standardization in CT body adipose tissue depots measurement and outcome presentation precluded quantitative analysis. Furthermore, most included studies had heterogeneous clinical characteristics. Survival and treatment response were the most prevalent outcomes. VAT (n = 19) and SAT (n = 17) were the most frequently evaluated depots and their increase was associated with worse outcomes, mainly in terms of survival. IMAT (n = 4) presented contradictory findings and a higher GFAT (n = 1) was associated with better outcomes.

CONCLUSION

This systematic review found an association between increased VAT and SAT with worse outcomes in patients with BC. However, due to the heterogeneity of the included studies, further research with homogeneous methodologies is necessary to better understand the impact of body adipose tissue depots on treatment outcomes. Such knowledge could lead to improved care for this patient population.

Estimation of the Impact of Abdominal Adipose Tissue (Subcutaneous and Visceral) on the Occurrence of Carbohydrate and Lipid Metabolism Disorders in Patients with Obesity-A Pilot Study

Obesity represents a significant global public health concern. The excessive accumulation of abdominal adipose tissue is often implicated in the development of metabolic complications associated with obesity. Our study aimed to investigate the impact of particular deposits of abdominal adipose tissue on the occurrence of carbohydrate and lipid metabolism complications. We established cut-off points for visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and the VAT/SAT ratio at which selected metabolic complications of obesity-related diseases (disorders of carbohydrate and/or lipid metabolism) occur. We conducted an observational study involving 91 subjects with first- and second-degree obesity, accounting for gender differences. Anthropometric measurements were taken, body composition analysis (BIA) was conducted, and biochemical determinations were made. Our findings suggest that commonly used parameters for assessing early metabolic risk, such as BMI or waist circumference, may overlook the significant factor of body fat distribution, as well as gender differences. Both visceral and subcutaneous adipose tissue were found to be important in estimating metabolic risk. We identified the cut-off points in women in terms of their elevated fasting glucose levels and the presence of insulin resistance (HOMA-IR: homeostasis model assessment of insulin resistance) based on SAT, VAT, and the VAT/SAT ratio. In men, cut-off points were determined for the presence of insulin resistance (HOMA-IR) based on VAT and the VAT/SAT ratio. However, the results regarding lipid disorders were inconclusive, necessitating further investigation of a larger population.

Sex-specific association of visceral and subcutaneous adipose tissue volumes with systemic inflammation and innate immune cells in people living with obesity

BACKGROUND AND AIMS

Obesity predisposes to metabolic and cardiovascular diseases. Adipose tissue inflammation and systemic inflammation contribute to these complications. There are strong sex differences in adipose tissue distribution and in systemic inflammation. Women have more subcutaneous adipose tissue (SAT) and less visceral adipose tissue (VAT) than men. We explored the sex differences in the association between the different adipose compartments and inflammatory markers that are important in cardiometabolic disease pathophysiology.

METHODS

Single-center observational cohort study with 302 individuals with a BMI ≥ 27 kg/m2. We were unable to acquire MRI data from seven individuals and from another 18 the MRI data were not usable, resulting in 277 people (155 men, 122 women), aged 55-81 years.

INTERVENTION

We performed the following measurements: abdominal magnetic resonance imaging to measure VAT, and SAT (deep and superficial) volumes; circulating leukocyte counts and cytokine production capacity of peripheral blood mononuclear cells (PBMCs), circulating cytokines, adipokines, and targeted proteomics; abdominal sSAT biopsies for histology and gene expression.

RESULTS

Only in women, (s)SAT volume was associated with circulating leukocytes, monocytes, and neutrophils. Circulating IL-6 and IL-18BP were associated with SAT volume in women and VAT in men. Several circulating proteins, including monocyte-colony-stimulating factor 1 and hepatocyte growth factor, are associated with sSAT in women and VAT in men. Only in women, SAT volume is associated with SAT expression of inflammatory proteins, including leptin, CD68, TNFα and IL-1α.

CONCLUSION

In women living with obesity, abdominal SAT volume, especially sSAT, is associated with circulating leukocytes and inflammatory proteins. In men, these parameters mainly show associations with VAT volume. This could be because only in women, sSAT volume is associated with sSAT expression of inflammatory proteins. These findings underscore that future research on adipose tissue in relation to cardiometabolic and cardiovascular disease should take sex differences into account.

Adipose Tissue in Cardiovascular Disease: From Basic Science to Clinical Translation

The perception of adipose tissue as a metabolically quiescent tissue, primarily responsible for lipid storage and energy balance (with some endocrine, thermogenic, and insulation functions), has changed. It is now accepted that adipose tissue is a crucial regulator of metabolic health, maintaining bidirectional communication with other organs including the cardiovascular system. Additionally, adipose tissue depots are functionally and morphologically heterogeneous, acting not only as sources of bioactive molecules that regulate the physiological functioning of the vasculature and myocardium but also as biosensors of the paracrine and endocrine signals arising from these tissues. In this way, adipose tissue undergoes phenotypic switching in response to vascular and/or myocardial signals (proinflammatory, profibrotic, prolipolytic), a process that novel imaging technologies are able to visualize and quantify with implications for clinical prognosis. Furthermore, a range of therapeutic modalities have emerged targeting adipose tissue metabolism and altering its secretome, potentially benefiting those at risk of cardiovascular disease.

Birth weight, skeletal maturity and dietary patterns are associated with body composition compartments differently in male and female physically active adolescents

Background: Adequate body composition is important for health and performance of physically active adolescents; however, some factors can influence body composition. Aim: The purpose of this study was to evaluate the association between body composition and birth weight, skeletal maturity and dietary patterns, in male (n = 124) and female (n = 107) physically active adolescents. Methods: Birth weight was obtained from health booklets. Dual-energy X-ray absorptiometry (DXA) was used to estimate fat mass (FM), fat-free mass (FFM), visceral adipose tissue (VAT) and abdominal adipose tissue (ASAT). Skeletal maturity was assessed by a hand and fist scanner using DXA. Food intake was assessed using a food frequency questionnaire and dietary patterns by factorial analysis. Results: Seventy one percent (male = 16%, female = 55%) of the participants were mature. Two dietary patterns (in natura/minimally processed and processed/ultra-processed) were identified. In males, FM (>15%, P = 0.043) and ASAT (>30%, P = 0.042) were higher in those with low-median compared to high-median birth weight. FFM (>24%) was higher in skeletally mature compared to those immatures (P = 0.001), and VAT (>28%) was higher in processed/ultra-processed compared to in natura/minimally processed dietary patterns (P = 0.015). In females, FFM (>9%) was higher in those with low-median compared to high-median birth weight (P = 0.019); and FFM (>16%), FM (>28%) and ASAT (>45%) were higher in skeletally mature compared to those immatures (P = 0.001). Conclusion: Our results may contribute to a better understanding of the complex association among body composition, birth weight, skeletal maturity and dietary patterns and in physically active adolescents, differently according to sex.

A fully convolutional neural network for comprehensive compartmentalization of abdominal adipose tissue compartments in MRI

BACKGROUND

Existing literature has highlighted structural, physiological, and pathological disparities among abdominal adipose tissue (AAT) sub-depots. Accurate separation and quantification of these sub-depots are crucial for advancing our understanding of obesity and its comorbidities. However, the absence of clear boundaries between the sub-depots in medical imaging data has challenged their separation, particularly for internal adipose tissue (IAT) sub-depots. To date, the quantification of AAT sub-depots remains challenging, marked by a time-consuming, costly, and complex process.

PURPOSE

To implement and evaluate a convolutional neural network to enable granular assessment of AAT by compartmentalization of subcutaneous adipose tissue (SAT) into superficial subcutaneous (SSAT) and deep subcutaneous (DSAT) adipose tissue, and IAT into intraperitoneal (IPAT), retroperitoneal (RPAT), and paraspinal (PSAT) adipose tissue.

MATERIAL AND METHODS

MRI datasets were retrospectively collected from Singapore Preconception Study for Long-Term Maternal and Child Outcomes (S-PRESTO: 389 women aged 31.4 ± 3.9 years) and Singapore Adult Metabolism Study (SAMS: 50 men aged 28.7 ± 5.7 years). For all datasets, ground truth segmentation masks were created through manual segmentation. A Res-Net based 3D-UNet was trained and evaluated via 5-fold cross-validation on S-PRESTO data (N = 300). The model's final performance was assessed on a hold-out (N = 89) and an external test set (N = 50, SAMS).

RESULTS

The proposed method enabled reliable segmentation of individual AAT sub-depots in 3D MRI volumes with high mean Dice similarity scores of 98.3%, 97.2%, 96.5%, 96.3%, and 95.9% for SSAT, DSAT, IPAT, RPAT, and PSAT respectively.

CONCLUSION

Convolutional neural networks can accurately sub-divide abdominal SAT into SSAT and DSAT, and abdominal IAT into IPAT, RPAT, and PSAT with high accuracy. The presented method has the potential to significantly contribute to advancements in the field of obesity imaging and precision medicine.

Feasibility of adipose-derived therapies for hair regeneration: Insights based on signaling interplay and clinical overview

Dermal white adipose tissue (dWAT) is a dynamic component of the skin and closely interacts with the hair follicle. Interestingly, dWAT envelops the hair follicle during anagen and undergoes fluctuations in volume throughout the hair cycle. dWAT-derived extracellular vesicles can significantly regulate the hair cycle, and this provides a theoretical basis for utilizing adipose tissue as a feasible clinical strategy to treat hair loss. However, the amount and depth of the available literature are far from enough to fully elucidate the prominent role of dWAT in modulating the hair growth cycle. This review starts by investigating the hair cycle-coupled dWAT remodeling and the reciprocal signaling interplay underneath. Then, it summarizes the current literature and assesses the advantages and limitations of clinical research utilizing adipose-derived therapies for hair regeneration.

Metabolic phenotyping in people living with obesity: Implications for dietary prevention

Given the increasing number of people living with obesity and related chronic metabolic disease, precision nutrition approaches are required to increase the effectiveness of prevention strategies. This review addresses these approaches in different metabolic phenotypes (metabotypes) in obesity. Although obesity is typically associated with an increased cardiometabolic disease risk, some people with obesity are relatively protected against the detrimental effects of excess adiposity on cardiometabolic health, also referred to as 'metabolically healthy obesity' (MHO). Underlying mechanisms, the extent to which MHO is a transient state as well as lifestyle strategies to counteract the transition from MHO to metabolically unhealthy obesity (MUO) are discussed. Based on the limited resources that are available for dietary lifestyle interventions, it may be reasonable to prioritize interventions for people with MUO, since targeting high-risk patients for specific nutritional, lifestyle or weight-loss strategies may enhance the cost-effectiveness of these interventions. Additionally, the concept of tissue insulin resistant (IR) metabotypes is discussed, representing distinct etiologies towards type 2 diabetes (T2D) as well as cardiovascular disease (CVD). Recent evidence indicates that these tissue IR metabotypes, already present in individuals with obesity with a normal glucose homeostasis, respond differentially to diet. Modulation of dietary macronutrient composition according to these metabotypes may considerably improve cardiometabolic health benefits. Thus, nutritional or lifestyle intervention may improve cardiometabolic health, even with only minor or no weight loss, which stresses the importance of focusing on a healthy lifestyle and not on weight loss only. Targeting different metabotypes towards T2D and cardiometabolic diseases may lead to more effective lifestyle prevention and treatment strategies. Age and sex-related differences in tissue metabotypes and related microbial composition and functionality (fermentation), as important drivers and/or mediators of dietary intervention response, have to be taken into account. For the implementation of these approaches, more prospective trials are required to provide the knowledge base for precision nutrition in the prevention of chronic metabolic diseases.

Fatty Liver Index (FLI) Identifies Not Only Individuals with Liver Steatosis but Also at High Cardiometabolic Risk

A fatty liver index (FLI) greater than sixty (FLI ≥ 60) is an established score for metabolic dysfunction-associated steatotic liver disease (MASLD), which carries a high risk for diabetes and cardiovascular disease, while a FLI ≤ 20 rules out the presence of steatosis. Thus, we investigated whether FLI was associated with cardiometabolic risk factors, i.e., visceral (VAT), subcutaneous (SC), epicardial (EPI), extrapericardial (PERI), and total cardiac (CARD-AT) adipose tissue, hepatic fat ((by magnetic resonance imaging, MRI, and spectroscopy, MRS), and insulin resistance (IR, HOMA-IR and OGIS-index), and components of metabolic syndrome. All individuals with FLI ≥ 60 had MASLD, while none with FLI ≤ 20 had steatosis (by MRS). Subjects with FLI ≥ 60 had a higher BMI and visceral and cardiac fat (VAT > 1.7 kg, CARD-AT > 0.2 kg). FLI was positively associated with increased cardiac and visceral fat and components of metabolic syndrome. FLI, VAT, and CARD-AT were all associated with IR, increased blood pressure, cholesterol, and reduced HDL. For FLI ≥ 60, the cut-off values for fat depots and laboratory measures were estimated. In conclusion, FLI ≥ 60 identified not only subjects with steatosis but also those with IR, abdominal and cardiac fat accumulation, increased blood pressure, and hyperlipidemia, i.e., those at higher risk of cardiometabolic diseases. Targeted reduction of FLI components would help reduce cardiometabolic risk.

Visceral adipose tissue and residual cardiovascular risk: a pathological link and new therapeutic options

Obesity is a heterogeneous disease that affects almost one-third of the global population. A clear association has been established between obesity and cardiovascular disease (CVD). However, CVD risk is known to be related more to the local distribution of fat than to total body fat. Visceral adipose tissue (VAT) in particular has a high impact on CVD risk. This manuscript reviews the role of VAT in residual CV risk and the available therapeutic strategies for decreasing residual CV risk related to VAT accumulation. Among the many pathways involved in residual CV risk, obesity and particularly VAT accumulation play a major role by generating low-grade systemic inflammation, which in turn has a high prognostic impact on all-cause mortality and myocardial infarction. In recent years, many therapeutic approaches have been developed to reduce body weight. Orlistat was shown to reduce both weight and VAT but has low tolerability and many drug-drug interactions. Naltrexone-bupropion combination lowers body weight but has frequent side effects and is contraindicated in patients with uncontrolled hypertension. Liraglutide and semaglutide, glucagon-like peptide 1 (GLP-1) agonists, are the latest drugs approved for the treatment of obesity, and both have been shown to induce significant body weight loss. Liraglutide, semaglutide and other GLP-1 agonists also showed a positive effect on CV outcomes in diabetic patients. In addition, liraglutide showed to specifically reduce VAT and inflammatory biomarkers in obese patients without diabetes. GLP-1 agonists are promising compounds to limit inflammation in human visceral adipocytes.

Unraveling White Adipose Tissue Heterogeneity and Obesity by Adipose Stem/Stromal Cell Biology and 3D Culture Models

The immune and endocrine dysfunctions of white adipose tissue are a hallmark of metabolic disorders such as obesity and type 2 diabetes. In humans, white adipose tissue comprises distinct depots broadly distributed under the skin (hypodermis) and as internal depots (visceral). Depot-specific ASCs could account for visceral and subcutaneous adipose tissue properties, by regulating adipogenesis and immunomodulation. More importantly, visceral and subcutaneous depots account for distinct contributions to obesity and its metabolic comorbidities. Recently, distinct ASCs subpopulations were also described in subcutaneous adipose tissue. Interestingly, the superficial layer closer to the dermis shows hyperplastic and angiogenic capacities, whereas the deep layer is considered as having inflammatory properties similar to visceral. The aim of this focus review is to bring the light of recent discoveries into white adipose tissue heterogeneity together with the biology of distinct ASCs subpopulations and to explore adipose tissue 3D models revealing their advantages, disadvantages, and contributions to elucidate the role of ASCs in obesity development. Recent advances in adipose tissue organoids opened an avenue of possibilities to recreate the main cellular and molecular events of obesity leading to a deep understanding of this inflammatory disease besides contributing to drug discovery. Furthermore, 3D organ-on-a-chip will add reproducibility to these adipose tissue models contributing to their translation to the pharmaceutical industry.

Association of physical activity with increased PI3K and Akt mRNA levels in adipose tissues of obese and non-obese adults

Phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway regulates glucose and lipid metabolism. We examined the association of PI3K and Akt expression in visceral (VAT) and subcutaneous adipose tissue (SAT) with daily physical activity (PA) in non-diabetic obese and non-obese adults. In this cross-sectional study, we included 105 obese (BMI ≥ 30 kg/m²) and 71 non-obese (BMI < 30 kg/m²) subjects (aged/ ≥ 18 years). PA was measured using a valid and reliable International Physical Activity Questionnaire(IPAQ)-long-form, and the metabolic equivalent of task(MET) was calculated. Real-time PCR was performed to analyze the mRNA relative expression. VAT PI3K expression had a lower level in obese compared to non-obese (P = 0.015), while its expression was higher in active individuals than inactive ones (P = 0.029). SAT PI3K expression was increased in active individuals compared to inactive ones (P = 0.031). There was a rise in VAT Akt expression in the actives compared to the inactive participants (P = 0.037) and in non-obese/active compared to non-obese/inactive individuals (P = 0.026). Obese individuals had a decreased expression level of SAT Akt compared to non-obsesses (P = 0.005). VAT PI3K was directly and significantly associated with PA in obsesses (β = 1.457, P = 0.015). Positive association between PI3K and PA suggests beneficial effects of PA for obese individuals that can be partly described by PI3K/Akt pathway acceleration in adipose tissue.

Comparison of therapeutic effects of mesenchymal stem cells derived from superficial and deep subcutaneous adipose tissues

BACKGROUND

Fibrosis is a common histological feature in the process from chronic organ injury to organ failure. Chronic tissue injury causes inflammatory cell infiltration into the injured tissue. The persistence of this inflammatory cell infiltration leads to fibrosis and organ failure. Adipose-derived mesenchymal stem cells (ASCs) have received much attention as a regenerative therapeutic tool to prevent progression from organ injury to failure. Subcutaneous abdominal adipose tissue is divided into superficial and deep layers by a superficial fascia. Adipose tissue easily collected by liposuction is usually obtained from a deep layer, so ASCs derived from a deep layer are generally used for regenerative medicine. However, no research has been conducted to investigate differences in the therapeutic effects of ASCs from the superficial and deep layers (Sup-ASCs and Deep-ASCs, respectively). Therefore, we compared the therapeutic potencies of Sup-ASCs and Deep-ASCs.

METHODS

ASCs were isolated from superficial and deep subcutaneous abdominal adipose tissues collected from patients who underwent breast reconstruction. We first compared cell characteristics, such as morphology, cell proliferation, cell surface markers, adipogenic and osteogenic differentiation, cell senescence markers, and expression of coagulation and anticoagulant factors between Sup-ASCs and Deep-ASCs. Furthermore, we compared their ability to promote polarization of M2 macrophages and to inhibit transforming growth factor (TGF)-β/Smad signaling using THP-1 cells and TGF-β1 stimulated HK-2 cells incubated with conditioned media from Sup-ASCs or Deep-ASCs. In in vivo experiments, after renal ischemia-reperfusion injury (IRI) procedure, Sup-ASCs or Deep-ASCs were injected through the abdominal aorta. At 21 days post-injection, the rats were sacrificed and their left kidneys were collected to evaluate fibrosis. Finally, we performed RNA-sequencing analysis of Sup-ASCs and Deep-ASCs.

RESULTS

Sup-ASCs had greater proliferation and adipogenic differentiation compared with Deep-ASCs, whereas both ASC types had similar morphology, cell surface markers, senescence markers, and expression of coagulation and anticoagulant factors. Conditioned media from Sup-ASCs and Deep-ASCs equally promoted polarization of M2 macrophages and suppressed TGF-β/Smad signaling. Moreover, administration of Sup-ASCs and Deep-ASCs equally ameliorated renal fibrosis induced by IRI in rats. RNA-sequencing analysis revealed no significant difference in the expression of genes involved in anti-inflammatory and anti-fibrotic effects between Sup-ASCs and Deep-ASCs.

CONCLUSIONS

These results indicate that both Sup-ASCs and Deep-ASCs can be used effectively and safely as an intravascular ASC therapy for organ injury.

Sex differences in body composition in people with prediabetes and type 2 diabetes as compared with people with normal glucose metabolism: the Maastricht Study

AIMS/HYPOTHESIS

Obesity is a major risk factor for type 2 diabetes. However, body composition differs between women and men. In this study we investigate the association between diabetes status and body composition and whether this association is moderated by sex.

METHODS

In a population-based cohort study (n=7639; age 40-75 years, 50% women, 25% type 2 diabetes), we estimated the sex-specific associations, and differences therein, of prediabetes (i.e. impaired fasting glucose and/or impaired glucose tolerance) and type 2 diabetes (reference: normal glucose metabolism [NGM]) with dual-energy x-ray absorptiometry (DEXA)- and MRI-derived measures of body composition and with hip circumference. Sex differences were analysed using adjusted regression models with interaction terms of sex-by-diabetes status.

RESULTS

Compared with their NGM counterparts, both women and men with prediabetes and type 2 diabetes had more fat and lean mass and a greater hip circumference. The differences in subcutaneous adipose tissue, hip circumference and total and peripheral lean mass between type 2 diabetes and NGM were greater in women than men (women minus men [W-M] mean difference [95% CI]: 15.0 cm2 [1.5, 28.5], 3.2 cm [2.2, 4.1], 690 g [8, 1372] and 443 g [142, 744], respectively). The difference in visceral adipose tissue between type 2 diabetes and NGM was greater in men than women (W-M mean difference [95% CI]: -14.8 cm2 [-26.4, -3.1]). There was no sex difference in the percentage of liver fat between type 2 diabetes and NGM. The differences in measures of body composition between prediabetes and NGM were generally in the same direction, but were not significantly different between women and men.

CONCLUSIONS/INTERPRETATION

This study indicates that there are sex differences in body composition associated with type 2 diabetes. The pathophysiological significance of these sex-associated differences requires further study.

The association between serum copper and obesity and all-cause mortality: the NHANES 2011-2016

Excessive serum copper has multiple effects on human health, while the association between copper and obesity remains unclear. The objective of this study is to examine the associations of serum copper concentrations with obesity and adiposity measures, including body fat composition and distribution among adults in the USA. This analysis utilized data from the National Health and Nutrition Examination Survey (NHANES) (2011-2016). A total of 7285 adults aged 18 years or older who had serum copper measures were included in this cross-sectional study. Multi-linear regression and logistic regression were used to estimate the independent risky effect of copper on fat deposition and all-cause mortality. Moreover, these associations were analyzed in stratification analysis by gender, age, and physical activity (PA). Generally, we found that participants who were females, non-Hispanic Black, or with inactive PA tended to have a higher serum level of copper. In addition, we observed positive associations between serum copper and adiposity measurements. Furthermore, a serum copper level higher than 133.9 μg/dL was a risk factor for all-cause mortality, which doubled the odds ratio of all-cause mortality compared to the normal serum copper level. Serum copper was positively associated with fat deposition of whole body and regional parts, and all-cause mortality. Furthermore, the effects of copper on fat distribution were also significant and could be modified by age, gender, and PA.

Changes in abdominal adipose tissue depots assessed by MRI correlate with hepatic histologic improvement in non-alcoholic steatohepatitis

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) is prevalent in adults with obesity and can progress to cirrhosis. In a secondary analysis of prospectively acquired data from the multicenter, randomized, placebo-controlled FLINT trial, we investigated the relationship between reduction in adipose tissue compartment volumes and hepatic histologic improvement.

METHODS

Adult participants in the FLINT trial with paired liver biopsies and abdominal MRI exams at baseline and end-of-treatment (72 weeks) were included (n = 76). Adipose tissue compartment volumes were obtained using MRI.

RESULTS

Treatment and placebo groups did not differ in baseline adipose tissue volumes, or in change in adipose tissue volumes longitudinally (p = 0.107 to 0.745). Deep subcutaneous adipose tissue (dSAT) and visceral adipose tissue volume reductions were associated with histologic improvement in NASH (i.e., NAS [non-alcoholic fatty liver disease activity score] reductions of ≥2 points, at least 1 point from lobular inflammation and hepatocellular ballooning, and no worsening of fibrosis) (p = 0.031, and 0.030, respectively). In a stepwise logistic regression procedure, which included demographics, treatment group, baseline histology, baseline and changes in adipose tissue volumes, MRI hepatic proton density fat fraction (PDFF), and serum aminotransferases as potential predictors, reductions in dSAT and PDFF were associated with histologic improvement in NASH (regression coefficient = -2.001 and -0.083, p = 0.044 and 0.033, respectively).

CONCLUSIONS

In adults with NASH in the FLINT trial, those with greater longitudinal reductions in dSAT and potentially visceral adipose tissue volumes showed greater hepatic histologic improvements, independent of reductions in hepatic PDFF.

CLINICAL TRIAL NUMBER

NCT01265498.

IMPACT AND IMPLICATIONS

Although central obesity has been identified as a risk factor for obesity-related disorders including insulin resistance and cardiovascular disease, the role of central obesity in non-alcoholic steatohepatitis (NASH) warrants further clarification. Our results highlight that a reduction in central obesity, specifically deep subcutaneous adipose tissue and visceral adipose tissue, may be related to histologic improvement in NASH. The findings from this analysis should increase awareness of the importance of lifestyle intervention in NASH for clinical researchers and clinicians. Future studies and clinical practice may design interventions that assess the reduction of deep subcutaneous adipose tissue and visceral adipose tissue as outcome measures, rather than simply weight reduction.

Favorable fatty acid composition in adipose tissue in healthy Iraqi- compared to Swedish-born men - a pilot study using MRI assessment

Middle Eastern immigrants are at high-risk for insulin resistance. Fatty acid composition (FAC) plays an important role in the development of insulin resistance but has not been investigated in people of Middle Eastern ancestry. Here, the aim was to assess the FAC in visceral and subcutaneous adipose tissue (VAT and SAT) in healthy Iraqi- and Swedish-born men using a magnetic resonance imaging (MRI) method.This case-control study included 23 Iraqi- and 15 Swedish-born middle-aged men, without cardiometabolic disease. Using multi-echo MRI of the abdomen, the fractions of saturated, monounsaturated, and polyunsaturated fatty acids (fSFA, fMUFA, and fPUFA) were estimated in VAT and SAT. SAT was further analyzed in deep and superficial compartments (dSAT and sSAT).

In all depots, fPUFA was significantly higher and fSFA significantly lower in Iraqi men, independently of age and BMI. In both Iraqi- and Swedish-born men, higher fPUFA and lower fMUFA were found in sSAT vs. dSAT. Among Iraqi men only, higher fPUFA and lower fMUFA were found in SAT vs. VAT.Iraqi-born men presented a more favorable abdominal FAC compared to Swedish-born men. This MRI method also revealed different FACs in different abdominal depots. Our results may reflect a beneficial FAC in Middle Eastern immigrants.

  

Cooling down with Entresto. Can sacubitril/valsartan combination enhance browning more than coldness?

BACKGROUND

It is a growing importance to induce a new treatment approach to encourage weight loss but also to improve maintenance of lost weight. It has been shown that promotion of brown adipose tissue (BAT) function or acquisition of BAT characteristics in white adipose tissue (terms referred as "browning") can be protective against obesity.

MAIN TEXT

Amongst numerous established environmental influences on BAT activity, cold exposure is the best interested technique due to its not only effects on of BAT depots in proliferation process but also de novo differentiation of precursor cells via β-adrenergic receptor activation. A novel combination drug, sacubitril/valsartan, has been shown to be more efficient in reducing cardiovascular events and heart failure readmission compared to conventional therapy. Also, this combination of drugs increases the postprandial lipid oxidation contributing to energy expenditure, promotes lipolysis in adipocytes and reduces body weight. To date, there is no research examining potential of combined sacubitril/valsartan use to promote browning or mechanisms in the basis of this thermogenic process.

CONCLUSION

Due to the pronounced effects of cold and sacubitril/valsartan treatment on function and metabolism of BAT, the primary goal of further research should focused on investigation of the synergistic effects of the sacubitril/valsartan treatment at low temperature environmental conditions.

Generation of a genetically modified pig model with CREBRFR457Q variant

Obesity is among the strongest risk factors for type 2 diabetes (T2D). The CREBRF missense allele rs373863828 (p. Arg457Gln, p. R457Q) is associated with increased body mass index but reduced risk of T2D in people of Pacific ancestry. To investigate the functional consequences of the CREBRF variant, we introduced the corresponding human mutation R457Q into the porcine genome. The CREBRF^R457Q pigs displayed dramatically increased fat deposition, which was mainly distributed in subcutaneous adipose tissue other than visceral adipose tissue. The CREBRF^R457Q variant promoted preadipocyte differentiation. The increased differentiation capacity of precursor adipocytes conferred pigs the unique histological phenotype that adipocytes had a smaller size but a greater number in subcutaneous adipose tissue (SAT) of CREBRF^R457Q variant pigs. In addition, in SAT of CREBRF^R457Q pigs, the contents of the peroxidative metabolites 4-hydroxy-nonenal and malondialdehyde were significantly decreased, while the activity of antioxidant enzymes, such as glutathione peroxidase, superoxide dismutase, and catalase, was increased, which was in accordance with the declined level of the reactive oxygen species (ROS) in CREBRF^R457Q pigs. Together, these data supported a causal role of the CREBRF^R457Q variant in the pathogenesis of obesity, partly via adipocyte hyperplasia, and further suggested that reduced oxidative stress in adipose tissue may mediate the relative metabolic protection afforded by this variant despite the related obesity.

Chromatin accessibility landscape of stromal subpopulations reveals distinct metabolic and inflammatory features of porcine subcutaneous and visceral adipose tissue

Background

Fat accumulation in visceral adipose tissue (VAT) confers increased risk for metabolic disorders of obesity, whereas accumulation of subcutaneous adipose tissue (SAT) is associated with lower risk and may be protective. Previous studies have shed light on the gene expression profile differences between SAT and VAT; however, the chromatin accessibility landscape differences and how the cis-regulatory elements govern gene expression changes between SAT and VAT are unknown.

Methods

Pig were used to characterize the differences in chromatin accessibility between the two adipose depots-derived stromal vascular fractions (SVFs) using DNase-sequencing (DNase-seq). Using integrated data from DNase-seq, H3K27ac ChIP-sequencing (ChIP-seq), and RNA-sequencing (RNA-seq), we investigated how the regulatory locus complexity regulated gene expression changes between SAT and VAT and the possible impact that these changes may have on the different biological functions of these two adipose depots.

Results

SVFs form SAT and VAT (S-SVF and V-SVF) have differential chromatin accessibility landscapes. The differential DNase I hypersensitive site (DHS)-associated genes, which indicate dynamic chromatin accessibility, were mainly involved in metabolic processes and inflammatory responses. Additionally, the Krüppel-like factor family of transcription factors were enriched in the differential DHSs. Furthermore, the chromatin accessibility data were highly associated with differential gene expression as indicated using H3K27ac ChIP-seq and RNA-seq data, supporting the validity of the differential gene expression determined using DNase-seq. Moreover, by combining epigenetic and transcriptomic data, we identified two candidate genes, NR1D1 and CRYM, could be crucial to regulate distinct metabolic and inflammatory characteristics between SAT and VAT. Together, these results uncovered differences in the transcription regulatory network and enriched the mechanistic understanding of the different biological functions between SAT and VAT.

Human white adipose tissue: A highly dynamic metabolic organ

Recent technological developments have allowed determination of the age of fat cells and their lipids in adult humans. In contrast to prior views, this has demonstrated a high turnover rate of the fat cells (10%/year) and their unilocular lipid droplets (six times/10 years). Fat cell turnover is increased in obesity and when adipose tissue is composed of many but small adipocytes (hyperplasia, a benign adipose phenotype). While fat mass gain increases adipocyte number and size, only the latter is altered (decreased) after weight loss, which may facilitate weight regain. Fat cell lipid turnover is attenuated in subjects with excess body fat. In the subcutaneous region, this dysregulation occurs already in the overweight state while in the visceral depot, it is only observed in severe obesity. This may explain why the latter depot is particularly pernicious in the overweight/obese state as it allows for more rapid lipid fluxes between visceral fat and the liver. Adipose lipid turnover decreases during ageing due to impaired breakdown (lipolysis) of stored triglycerides. If this decline is not compensated by reduced adipocyte lipid uptake, bodyweight will increase over time. In concordance with this, low lipolysis rates are a risk factor for future weight gain and glucose intolerance. Adipose lipid turnover is also decreased in insulin resistance and certain forms of dyslipidemia. Altogether, adult human adipose tissue is in a highly dynamic state. Alterations in the turnover of fat cells and their lipids are therefore novel factors to consider in the pathophysiology of common metabolic disorders.

Aerobic training reduces pancreatic fat content and improves β-cell function: A randomized controlled trial using IDEAL-IQ magnetic resonance imaging

AIMS

To explore the effects of six months of moderate-intensity aerobic exercise on pancreatic fat content and its impact on β-cell function.

MATERIALS AND METHODS

A total of 106 patients with type 2 diabetes mellitus were randomized to either a moderate-intensity aerobic training group (three times a week, including 5 min warm-up, 50 min aerobic dancing, and 5 min relaxation, n = 53) or control group (n = 53) with 6-month intervention. The primary endpoint was change in pancreatic fat content. An intention-to-treat analysis was conducted.

RESULTS

Eighty-six patients completed the study with 43 patients in the aerobic training group. The average age, HbA1c, and pancreatic fat content for all participants (106 patients) were 66.39 ± 5.59 years, 7.05 ± 1.24%, and 10.35 ± 9.20%, respectively. Nearly half (49.06%) of patients were males. Subjects in the aerobic training group saw a significant reduction in pancreatic fat content when compared to controls (p = 0.001). In logistic regression models containing age, diabetes duration, change in BMI, smoking/drinking status, changes in lipid indices, and other abdominal fat content, only reduction in pancreatic fat content (p < 0.05) was an independent protective factor for β-cell function and HbA1c.

CONCLUSIONS

Six months of moderate-intensity aerobic training significantly reduced the pancreatic fat content. The reduction of pancreatic fat content was an independent protective factor for β-cell function and HbA1c.

Keeping It Local in Metabolic Disease: Adipose Tissue Paracrine Signaling and Insulin Resistance

Alterations in adipose tissue composition and function are associated with obesity and contribute to the development of type 2 diabetes. While the significance of this relationship has been cemented, our understanding of the multifaceted role of adipose tissue in metabolic heath and disease continues to evolve and expand. Heterogenous populations of cells that make up adipose tissue throughout the body generate diverse secretomes containing a mosaic of bioactive compounds with vast structural and signaling capabilities. While there are many reports highlighting the important role of adipose tissue endocrine signaling in insulin resistance and type 2 diabetes, the direct, local, paracrine effect of adipose tissue has received less attention. Recent studies have begun to underscore the importance of considering anatomically discrete adipose depots for their specific impact on local microenvironments and metabolic function in neighboring tissues as well as regulation of whole-body physiology. This article highlights the important role of adipose tissue paracrine signaling on metabolic function and insulin sensitivity in nearby tissues and organs, specifically focusing on visceral, pancreatic, subcutaneous, intermuscular, and perivascular adipose tissue depots.

Mechanotransduction regulates inflammation responses of epicardial adipocytes in cardiovascular diseases

Adipose tissue is a crucial regulator in maintaining cardiovascular homeostasis by secreting various bioactive products to mediate the physiological function of the cardiovascular system. Accumulating evidence shows that adipose tissue disorders contribute to several kinds of cardiovascular disease (CVD). Furthermore, the adipose tissue would present various biological effects depending on its tissue localization and metabolic statuses, deciding the individual cardiometabolic risk. Crosstalk between adipose and myocardial tissue is involved in the pathophysiological process of arrhythmogenic right ventricular cardiomyopathy (ARVC), cardiac fibrosis, heart failure, and myocardial infarction/atherosclerosis. The abnormal distribution of adipose tissue in the heart might yield direct and/or indirect effects on cardiac function. Moreover, mechanical transduction is critical for adipocytes in differentiation, proliferation, functional maturity, and homeostasis maintenance. Therefore, understanding the features of mechanotransduction pathways in the cellular ontogeny of adipose tissue is vital for underlining the development of adipocytes involved in cardiovascular disorders, which would preliminarily contribute positive implications on a novel therapeutic invention for cardiovascular diseases. In this review, we aim to clarify the role of mechanical stress in cardiac adipocyte homeostasis and its interplay with maintaining cardiac function.

Obesity, Body Composition, and Sex Hormones: Implications for Cardiovascular Risk

Cardiovascular disease (CVD) continues to be the leading cause of death in adults, highlighting the need to develop novel strategies to mitigate cardiovascular risk. The advancing obesity epidemic is now threatening the gains in CVD risk reduction brought about by contemporary pharmaceutical and surgical interventions. There are sex differences in the development and outcomes of CVD; premenopausal women have significantly lower CVD risk than men of the same age, but women lose this advantage as they transition to menopause, an observation suggesting potential role of sex hormones in determining CVD risk. Clear differences in obesity and regional fat distribution among men and women also exist. While men have relatively high fat in the abdominal area, women tend to distribute a larger proportion of their fat in the lower body. Considering that regional body fat distribution is an important CVD risk factor, differences in how men and women store their body fat may partly contribute to sex-based alterations in CVD risk as well. This article presents findings related to the role of obesity and sex hormones in determining CVD risk. Evidence for the role of sex hormones in determining body composition in men and women is also presented. Lastly, the clinical potential for using sex hormones to alter body composition and reduce CVD risk is outlined. © 2022 American Physiological Society. Compr Physiol 12:1-45, 2022.

Comparison between handheld ultrasound and regional and whole-body dual energy x-ray absorptiometry (DXA) for body fat assessment

OBJECTIVES

To determine the extent of agreement between a handheld ultrasound (US) attached to an android tablet and the reference method dual energy x-ray absorptiometry (DXA) for the measurement of adiposity.

METHODS

A whole-body DXA scan and abdominal adipose tissue thickness measurements using a handheld US were obtained from 104 adults (63 females, 41 males). Body fat percent (BF%), total fat mass (kg), and trunk fat mass (kg) were obtained from DXA. Subcutaneous adipose tissue (SAT), superficial subcutaneous adipose tissue (SSAT), and deep subcutaneous adipose tissue (DSAT) thickness were obtained from US. Sex-specific total fat mass, trunk fat mass, and BF% estimates by US were compared with DXA. Spearman's correlations and Bland-Altman plots were used to assess agreement between the methods.

RESULTS

US SAT correlated strongly with total fat mass for both females (r_s = 0.74) and males (r_s = 0.87) as did trunk fat mass (females, r_s = 0.81; males, r_s = 0.83); as did SSAT and DSAT (females: r_s = 0.65 and r_s = 0.66; males: r_s = 0.63 and r_s = 0.85, respectively, all p-values < 0.0001). Bland-Altman plots demonstrated strong agreement for total and trunk fat mass for both males and females. For BF%, acceptable limits of agreement were observed for males but not for females, substantial proportional bias as indicated by a negative slope was noted for BF% using SAT (r = -0.298, p = 0.0177).

CONCLUSION

The handheld US and technique to analyze abdominal adipose tissue thickness showed strong agreement with DXA results and generated highly comparable estimates for total and trunk fat mass for both sexes.

Impact of Different Adipose Depots on Cardiovascular Disease

ABSTRACT

Adipose tissue (AT)-derived factors contribute to the regulation of cardiovascular homeostasis, thereby playing an important role in cardiovascular health and disease. In obesity, AT expands and becomes dysfunctional, shifting its secretory profile toward a proinflammatory state associated with deleterious effects on the cardiovascular system. AT in distinct locations (ie, adipose depots) differs in crucial phenotypic variables, including inflammatory and secretory profile, cellular composition, lipolytic activity, and gene expression. Such heterogeneity among different adipose depots may explain contrasting cardiometabolic risks associated with different obesity phenotypes. In this respect, central obesity, defined as the accumulation of AT in the abdominal region, leads to higher risk of cardiometabolic alterations compared with the accumulation of AT in the gluteofemoral region (ie, peripheral obesity). The aim of this review was to provide an updated summary of clinical and experimental evidence supporting the differential roles of different adipose depots in cardiovascular disease and to discuss the molecular basis underlying the differences of adipose depots in the regulation of cardiovascular function.

Distinct opposing associations of upper and lower body fat depots with metabolic and cardiovascular disease risk markers

BACKGROUND

To examine the associations of total and regional adiposity with metabolic and cardiovascular disease (CVD) risk markers.

METHODS

This cross-sectional study included 1080 (53.8% men, aged 39-44 years) individuals from South India. Anthropometry (height, weight, waist and hip circumference), body composition assessment using dual-energy X-ray absorptiometry (DXA), blood pressure (BP), and plasma glucose, insulin and lipids were measured. Regression analysis was used to examine associations of standardized fat measurements with type 2 diabetes (T2D), insulin resistance (IR), hypertension and hypertriglyceridemia and continuous measurements of BP, glucose, insulin, HOMA-IR and lipids. Contour plots were constructed to visualize the differential effect of upper and lower fat depots.

RESULTS

DXA-measured fat depots were positively associated with metabolic and CVD risk markers. After adjusting for fat mass index, upper body fat remained positively, while lower body fat was negatively associated with risk markers. A one standard deviation (SD) increase in android fat showed higher odds ratios (ORs) for T2D (6.59; 95% CI 3.17, 13.70), IR (4.68; 95% CI 2.31, 9.50), hypertension (2.57; 95% CI 1.56, 4.25) and hypertriglyceridemia (6.39; 95% CI 3.46, 11.90) in men. A 1 SD increase in leg fat showed a protective effect with ORs for T2D (0.42; 95% CI 0.24, 0.74), IR (0.31; 95% CI 0.17, 0.57) and hypertriglyceridemia (0.61; 95% CI 0.38, 0.98). The magnitude of the effect was greater with DXA-measured fat compared with anthropometry.

CONCLUSION

At any level of total body fat, upper and lower body fat depots demonstrate opposite risk associations with metabolic and CVD risk markers in Asian Indians.

Hepatic steatosis is associated with anthropometry, cardio-metabolic disease risk, sex, age and urbanisation, but not with ethnicity in adult Kenyans

OBJECTIVE

We aimed to determine the associations of non-alcoholic fatty liver disease (NAFLD) with cardio-metabolic risk factors for diabetes in adult Kenyans.

METHODS

A cross-sectional study was undertaken among rural and urban Kenyans of different ethnic origin. Ultrasonography scanning (USS) methods were used for the assessment of hepatic fat accumulation for NAFLD assessment and abdominal fat distribution, and simple anthropometry measurements were performed. All participants underwent a 2-h oral glucose tolerance test, and biochemical, haemodynamic and lifestyle data were obtained. Multivariate logistic regression analyses were used to assess sex, age, residency and ethnic differences in the association between NAFLD and various metabolic parameters.

RESULTS

In total, 743 individuals (59.1% women) with a mean age of 38.0 (range 18-68) years participated in the study. Overall, 118 individuals (15.9%) had NAFLD, of whom 94.1% had mild steatosis. Age >40 years was significantly associated with having NAFLD compared with <30 years of age with no difference found in NAFLD between ethnic groups (Luo, Kamba, Maasai). All body composition and clinical measurements were associated with NAFLD (p < 0.045 for OR).

CONCLUSION

Finding lower odds for NAFLD in men was unexpected, as was the lack of differences in NAFLD among the ethnic groups, while higher odds for NAFLD with increasing age and in urban vs. rural populations was expected. Especially the sex-specific results warrant further studies in black African populations on biology of body composition for having NAFLD, and whether this translates into insulin resistance and higher risk of diabetes and consequently cardiovascular disease in black African women.

Associations between skeletal muscle echo intensity and thickness in relation to glucose homeostasis in healthy and glucose impaired older males

BACKGROUND

Aging-related changes in muscle composition and mass may predispose older adults to developing insulin resistance. Ultrasound echo intensity and thickness are surrogates of muscle composition and mass, however, their associations with glucose homeostasis are not well established. We examined how muscle echo intensity and thickness correlate with markers of glucose homeostasis in older (≥65 years) males with normal (n = 22) or impaired (n = 10) glucose control.

METHODS

Echo intensity was measured for the biceps brachii, rectus abdominis, and rectus femoris. Muscle thickness was evaluated for the biceps brachii + brachioradialis, rectus abdominis, and rectus femoris + vastus intermedius. Glucose homeostasis was evaluated using a 2-h oral glucose tolerance test.

RESULTS

In older males with normal glucose homeostasis, higher echo intensity of the rectus abdominis and rectus femoris was moderately (r = 0.36 to 0.59) associated with 2-h glucose. On the contrary, higher muscle echo intensity of the rectus abdominis, biceps brachii, and rectus femoris was moderately-to-strongly (r = -0.36 to -0.79) associated with indices of better glucose homeostasis in the impaired group. Rectus abdominis muscle thickness was moderately associated (r = 0.36) with better glucose tolerance in the normal glucose homeostasis; however, in the glucose impaired group, muscle thickness was associated with (r = 0.37 to 0.73) with poorer glucose homeostasis.

CONCLUSIONS

Muscle echo intensity displays divergent associations with glucose homeostasis in older males with normal compared to impaired glucose control. Larger muscle thickness was associated with poorer glucose homeostasis in the glucose impaired group, but rectus abdominis muscle thickness was correlated with better homeostasis in healthy older males.

Automated Segmentation of Visceral, Deep Subcutaneous, and Superficial Subcutaneous Adipose Tissue Volumes in MRI of Neonates and Young Children

Purpose

To develop and evaluate an automated segmentation method for accurate quantification of abdominal adipose tissue (AAT) depots (superficial subcutaneous adipose tissue [SSAT], deep subcutaneous adipose tissue [DSAT], and visceral adipose tissue [VAT]) in neonates and young children.

Materials and Methods

This was a secondary analysis of prospectively collected data, which used abdominal MRI data from Growing Up in Singapore Towards healthy Outcomes, or GUSTO, a longitudinal mother-offspring cohort, to train and evaluate a convolutional neural network for volumetric AAT segmentation. The data comprised imaging volumes of 333 neonates obtained at early infancy (age ≤2 weeks, 180 male neonates) and 755 children aged either 4.5 years (n = 316, 150 male children) or 6 years (n = 439, 219 male children). The network was trained on images of 761 randomly selected volumes (neonates and children combined) and evaluated on 100 neonatal volumes and 227 child volumes by using 10-fold validation. Automated segmentations were compared with expert-generated manual segmentation. Segmentation performance was assessed using Dice scores.

Results

When the model was tested on the test datasets across the 10 folds, the model had strong agreement with the ground truth for all testing sets, with mean Dice similarity scores for SSAT, DSAT, and VAT, respectively, of 0.960, 0.909, and 0.872 in neonates and 0.944, 0.851, and 0.960 in children. The model generalized well to different body sizes and ages and to all abdominal levels.

Conclusion

The proposed segmentation approach provided accurate automated volumetric assessment of AAT compartments on MR images of neonates and children.Keywords Pediatrics, Deep Learning, Convolutional Neural Networks, Water-Fat MRI, Image Segmentation, Deep and Superficial Subcutaneous Adipose Tissue, Visceral Adipose TissueClinical trial registration no. NCT01174875 Supplemental material is available for this article. © RSNA, 2021.

Extracellular cystine influences human preadipocyte differentiation and correlates with fat mass in healthy adults

Plasma cysteine is associated with human obesity, but it is unknown whether this is mediated by reduced, disulfide (cystine and mixed-disulfides) or protein-bound (bCys) fractions. We investigated which cysteine fractions are associated with adiposity in vivo and if a relevant fraction influences human adipogenesis in vitro. In the current study, plasma cysteine fractions were correlated with body fat mass in 35 adults. Strong positive correlations with fat mass were observed for cystine and mixed disulfides (r ≥ 0.61, P < 0.001), but not the quantitatively major form, bCys. Primary human preadipocytes were differentiated in media containing cystine concentrations varying from 10-50 μM, a range similar to that in plasma. Increasing extracellular cystine (10-50 μM) enhanced mRNA expression of PPARG2 (to sixfold), PPARG1, PLIN1, SCD1 and CDO1 (P = 0.042- < 0.001). Adipocyte lipid accumulation and lipid-droplet size showed dose-dependent increases from lowest to highest cystine concentrations (P < 0.001), and the malonedialdehyde/total antioxidant capacity increased, suggesting increased oxidative stress. In conclusion, increased cystine concentrations, within the physiological range, are positively associated with both fat mass in healthy adults and human adipogenic differentiation in vitro. The potential role of cystine as a modifiable factor regulating human adipocyte turnover and metabolism deserves further study.

Superficial vs Deep Subcutaneous Adipose Tissue: Sex-Specific Associations With Hepatic Steatosis and Metabolic Traits

CONTEXT

Subcutaneous adipose tissue (SAT) is not homogeneous, as the fascia scarpa separates the deep SAT (dSAT) from the superficial SAT (sSAT).

OBJECTIVE

The aim of this study is to evaluate the sex-specific associations of sSAT and dSAT with hepatic steatosis and metabolic syndrome in overweight individuals.

METHODS

We recruited 285 individuals with a body mass index (BMI) greater than or equal to 27 and aged 55 to 81 years. Abdominal magnetic resonance imaging was performed around level L4 to L5 to measure visceral adipose tissue (VAT), dSAT, and sSAT volumes. The amount of hepatic fat was quantified by MR spectroscopy.

RESULTS

Men had significantly higher volumes of VAT (122.6 cm3 vs 98.7 cm3, P < .001) and had only half the volume of sSAT compared to women adjusted for BMI (50.3 cm3 in men vs 97.0 cm3 in women, P < .001). dSAT correlated significantly with hepatic fat content in univariate analysis (standardized β = .190, P < .05), while VAT correlated significantly with hepatic steatosis in a multivariate model, adjusted for age, alcohol use, and other abdominal fat compartments (standardized β = .184, P = .037). Moreover, dSAT in men correlated negatively with HDL cholesterol (standardized β = -0.165, P = .038) in multivariate analyses. In women with a BMI between 30 and 40, in a multivariate model adjusted for age, alcohol use, and other abdominal fat compartments, VAT correlated positively (standardized β = -.404, P = .003), and sSAT negatively (standardized β = -.300, P = .04) with hepatic fat content.

CONCLUSION

In men, dSAT is associated with hepatic steatosis and adverse metabolic traits, such as lower HDL cholesterol levels, whereas in women with obesity sSAT shows a beneficial relation with respect to hepatic fat content.

Abdominal subcutaneous adipose tissue negatively associates with subclinical coronary artery disease in men with psoriasis

Objective

Understand the relationship between abdominal subcutaneous adipose tissue (ASAT) and coronary atherosclerosis defined as noncalcified and lipid-rich necrotic core burden in psoriasis.

Methods

We performed a cross-sectional study of 232 participants (92 women) with psoriasis and without known cardiovascular disease. Participants underwent coronary computed tomography angiography to characterize coronary atherosclerosis burden and low dose abdominal computed tomography to quantify subcutaneous and visceral adipose tissue. Fat depot volumes were first adjusted for each participant's BMI (ASAT_adjBMI).

Results

In women, there was a positive correlation between ASAT_adjBMI and systemic inflammation as assessed by hs-C-reactive protein (r=0.30; p=.004) and GlycA (r=0.29; p=.007) as well as total cholesterol (r=0.24; p=.02) and low-density lipoprotein cholesterol (r=0.22; p=.04). In men, ASAT_adjBMI correlated with hs-C-reactive protein (r=0.18; p=.04) and insulin resistance (r=0.17; p=.04). In models fully adjusted for traditional cardiovascular risk factors, ASAT_adjBMI negatively associated with noncalcified and lipid-rich necrotic core burden in men (β= -0.17; p=.03, β= -0.20; p=.03, respectively), but not women (β= -0.06; p=.57, β= 0.09; p=.49, respectively) with psoriasis.

Conclusions

For a given BMI, ASAT negatively associated with coronary atherosclerosis burden in male participants with psoriasis. The observed sex-specific effects warrant further study of ASAT in states of chronic inflammation.

A novel conjunctive microenvironment derived from human subcutaneous adipose tissue contributes to physiology of its superficial layer

Background

In human subcutaneous adipose tissue, the superficial fascia distinguishes superficial and deep microenvironments showing extensions called retinacula cutis. The superficial subcutaneous adipose tissue has been described as hyperplastic and the deep subcutaneous adipose tissue as inflammatory. However, few studies have described stromal-vascular fraction (SVF) content and adipose-derived stromal/stem cells (ASCs) behavior derived from superficial and deep subcutaneous adipose tissue. In this study, we analyzed a third conjunctive microenvironment: the retinacula cutis superficialis derived from superficial subcutaneous adipose tissue.

Methods

The samples of abdominal human subcutaneous adipose tissue were obtained during plastic aesthetic surgery in France (Declaration DC-2008-162) and Brazil (Protocol 145/09).

Results

The SVF content was characterized in situ by immunofluorescence and ex vivo by flow cytometry revealing a high content of pre-adipocytes rather in superficial subcutaneous adipose tissue microenvironment. Adipogenic assays revealed higher percentage of lipid accumulation area in ASCs from superficial subcutaneous adipose tissue compared with retinacula cutis superficialis (p < 0.0001) and deep subcutaneous adipose tissue (p < 0.0001). The high adipogenic potential of superficial subcutaneous adipose tissue was corroborated by an up-regulation of adipocyte fatty acid-binding protein (FABP4) compared with retinacula cutis superficialis (p < 0.0001) and deep subcutaneous adipose tissue (p < 0.0001) and of C/EBPα (CCAAT/enhancer-binding protein alpha) compared with retinacula cutis superficialis (p < 0.0001) and deep subcutaneous adipose tissue (p < 0.0001) microenvironments. Curiously, ASCs from retinacula cutis superficialis showed a higher level of adiponectin receptor gene compared with superficial subcutaneous adipose tissue (p = 0.0409), widely known as an anti-inflammatory hormone. Non-induced ASCs from retinacula cutis superficialis showed higher secretion of human vascular endothelial growth factor (VEGF), compared with superficial (p = 0.0485) and deep (p = 0.0112) subcutaneous adipose tissue and with adipogenic-induced ASCs from superficial (p = 0.0175) and deep (p = 0.0328) subcutaneous adipose tissue. Furthermore, ASCs from retinacula cutis superficialis showed higher secretion of Chemokine (C–C motif) ligand 5 (CCL5) compared with non-induced (p = 0.0029) and induced (p = 0.0089) superficial subcutaneous adipose tissue.

Conclusions

This study highlights the contribution to ASCs from retinacula cutis superficialis in their angiogenic property previously described for the whole superficial subcutaneous adipose tissue besides supporting its adipogenic potential for superficial subcutaneous adipose tissue.

Indirect Predictors of Visceral Adipose Tissue in Women with Polycystic Ovary Syndrome: A Comparison of Methods

Visceral adipose tissue (VAT) accumulation, is a part of a polycystic ovary syndrome (PCOS) phenotype. Dual-energy x-ray absorptiometry (DXA) provides a gold standard measurement of VAT. This study aimed to compare ten different indirect methods of VAT estimation in PCOS women. The study included 154 PCOS and 68 age- and BMI-matched control women. Subjects were divided into age groups: 18-30 y.o. and 30-40 y.o. Analysis included: body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR), waist/height 0.5 (WHT.5R), visceral adipose index (VAI), lipid accumulation product (LAP), and fat mass index (FMI). VAT accumulation, android-to-gynoid ratio (A/G), and total body fat (TBF) was measured by DXA. ROC analysis revealed that WHtR, WHT.5R, WC, BMI, and LAP demonstrated the highest predictive value in identifying VAT in the PCOS group. Lower cut-off values of BMI (23.43 kg/m2) and WHtR (0.45) were determined in the younger PCOS group and higher thresholds of WHtR (0.52) in the older PCOS group than commonly used. Measuring either: WHtR, WHT.5R, WC, BMI, or LAP, could help identify a subgroup of PCOS patients at high cardiometabolic risk. The current observations reinforce the importance of using special cut-offs to identify VAT, dependent on age and PCOS presence.

Adipose Tissue-Endothelial Cell Interactions in Obesity-Induced Endothelial Dysfunction

Obesity has a strong impact on the pathogenesis of cardiovascular disease, which raises enthusiasm to understand how excess adiposity causes vascular injury. Adipose tissue is an essential regulator of cardiovascular system through its endocrine and paracrine bioactive products. Obesity induces endothelial dysfunction, which often precedes and leads to the development of cardiovascular diseases. Connecting adipose tissue-endothelial cell interplay to endothelial dysfunction may help us to better understand obesity-induced cardiovascular disease. This Mini Review discussed (1) the general interactions and obesity-induced endothelial dysfunction, (2) potential targets, and (3) the outstanding questions for future research.

Obesity and Heart Failure with Preserved Ejection Fraction

Obese heart failure with preserved ejection fraction (HFpEF) is a distinct HFpEF phenotype. Sodium retention, high circulating neurohormone levels, alterations in energy substrate metabolism, group 3 pulmonary hypertension, pericardial restraint, and systemic inflammation are central pathophysiologic mechanisms. Confirming the diagnosis may be challenging and high suspicion is required. Reduction of visceral adipose tissue, via caloric restriction and/or bariatric surgery, may improve outcomes in obese HFpEF patients. Furthermore, mineralocorticoid receptor inhibition, neprilysin inhibition, and sodium-glucose cotransporter 2 inhibition can ameliorate the effects of adiposity on the cardiovascular system, allowing for promising new treatment targets for the obese HFpEF phenotype.

Association between abdominal fat and mortality in patients undergoing cardiovascular surgery

BACKGROUND

Obesity is associated with reduced postoperative mortality in patients undergoing cardiovascular surgery. However, body mass index cannot differentiate abdominal fat composition. This study evaluated the relationships between total abdominal, subcutaneous, and visceral fat composition and postoperative mortality in East Asian patients undergoing cardiovascular surgery.

METHODS

Adult patients who underwent cardiovascular surgery between October 2004 and December 2016 were retrospectively included. Total, subcutaneous and visceral fat areas were measured from cross-sectional computed tomography images. The relationships between each fat composition and mortality were evaluated.

RESULTS

A total of 3,661 patients were analyzed, and overall mortality was 19.9% (729 died) during the 4.6 year median follow-up period. The risks of all-cause and cardiac-cause mortality decreased as subcutaneous fat composition increased (adjusted hazard ratio [aHR], 0.997; 95% confidence interval [CI], 0.994-1.000 and aHR, 0.994; 95% CI, 0.989-0.999; P = .02 and = .01, respectively). No association was detected between the total and visceral fat area and mortality.

CONCLUSIONS

Reduced abdominal subcutaneous fat, but not the total or visceral fat composition was associated with higher all-cause and cardiac-cause mortality after cardiovascular surgery in East Asian patients, consisting mainly of normal or overweight patients.

Effects of short-term dietary restriction on plasma metabolites and the subcutaneous fat area according to metabolic status in obese individuals: a case-control study

BACKGROUND

Research elucidating the metabolic mechanisms that differentiate subtypes of obesity has been increasing. We aimed to investigate the effects of a 12-week dietary intervention on the metabolomic profiles of obese subjects.

METHODS

Subjects followed a 12-week dietary restriction protocol consisting of a 300 kcal/day reduction in their usual caloric intake. Twenty-nine obese subjects were included and divided into two groups: the metabolic status maintenance group (n = 17, controls) and the metabolic status improvement group (n = 12, tests). We analyzed the somatometric and biochemical parameters and performed ultra-performance liquid chromatography-mass spectrometry analysis of the plasma metabolites.

RESULTS

At 12 weeks, the fat percentage, whole fat area (WFA), subcutaneous fat area (SFA) at the L1 vertebra, and the levels of triglycerides, gamma-glutamyltransferase (gamma-GT), and leptin were markedly decreased in the metabolic status improvement group, while the level of high-density lipoprotein cholesterol increased compared with that in the metabolic status maintenance group. Metabolomic profiling at 12 weeks showed substantial differences in 4-aminobutyraldehyde (p = 0.005) and 4'-apo-β-carotenal (p = 0.024) between the two groups. Furthermore, an AUC value of 0.89 was obtained for the following seven featured biomarkers: triglycerides, gamma-GT, leptin, fat percentage, WFA, and SFA at the L1 vertebra, and 4-aminobutyraldehyde.

CONCLUSIONS

We demonstrated that 4-aminobutyraldehyde and related regional fat distribution parameters were strongly associated with obesity according to metabolic status. Thus, these biomarkers are potentially valuable in confirming the efficacy of short-term interventions and predicting metabolic status in obese individuals.

TRIALS REGISTRATION

This study was registered at ClinicalTrials.gov under NCT03135132 (registered 1 May 2017-retrospectively registered).

Different Indicators of Adiposity and Fat Distribution and Cardiometabolic Risk Factors in Patients with Type 2 Diabetes

OBJECTIVE

This study aimed to evaluate the effect of adiposity and fat distribution on the odds of elevated cardiovascular risk factors among adults with type 2 diabetes mellitus.

METHODS

The present cross-sectional study included 2,427 adults with type 2 diabetes mellitus. Body fat was assessed by dual-energy x-ray absorptiometry. Multivariate-adjusted logistic regression was used to estimate effects of adiposity parameters on elevated hemoglobin A_1c (HbA_1c , ≥7.0%), hypertension (blood pressure ≥140/90 mmHg), and elevated low-density lipoprotein (LDL) cholesterol (≥2.6 mmol/L).

RESULTS

The multivariable-adjusted odds ratio (OR) for elevated HbA_1c was 0.82 (95% CI: 0.70-0.96) for each SD increase in leg fat mass. The multivariable-adjusted OR for hypertension was 1.15 (95% CI: 1.00-1.32) for each SD increase in android fat mass. Multivariable-adjusted ORs for elevated LDL cholesterol ranged from 1.16 (95% CI: 1.00-1.35) to 1.27 (95% CI: 1.06-1.51) for each SD increase in arm and android fat mass and percentage of total, truncal, arm, and android fat. Each SD increase in BMI, truncal-to-leg fat ratio, and android-to-gynoid fat ratio was significantly associated with increased risks of elevated HbA_1c , hypertension, and elevated LDL cholesterol.

CONCLUSIONS

Subcutaneous fat in the lower body was associated with a more favorable glycemic profile, but not blood pressure or lipid profile, whereas central adiposity was associated with poor control of cardiovascular risk factors among patients with type 2 diabetes mellitus.

Dysmetabolic adipose tissue in obesity: morphological and functional characteristics of adipose stem cells and mature adipocytes in healthy and unhealthy obese subjects

The way by which subcutaneous adipose tissue (SAT) expands and undergoes remodeling by storing excess lipids through expansion of adipocytes (hypertrophy) or recruitment of new precursor cells (hyperplasia) impacts the risk of developing cardiometabolic and respiratory diseases. In unhealthy obese subjects, insulin resistance, type 2 diabetes, hypertension, and obstructive sleep apnoea are typically associated with pathologic SAT remodeling characterized by adipocyte hypertrophy, as well as chronic inflammation, hypoxia, increased visceral adipose tissue (VAT), and fatty liver. In contrast, metabolically healthy obese individuals are generally associated with SAT development characterized by the presence of smaller and numerous mature adipocytes, and a lower degree of VAT inflammation and ectopic fat accumulation. The remodeling of SAT and VAT is under genetic regulation and influenced by inherent depot-specific differences of adipose tissue-derived stem cells (ASCs). ASCs have multiple functions such as cell renewal, adipogenic capacity, and angiogenic properties, and secrete a variety of bioactive molecules involved in vascular and extracellular matrix remodeling. Understanding the mechanisms regulating the proliferative and adipogenic capacity of ASCs from SAT and VAT in response to excess calorie intake has become a focus of interest over recent decades. Here, we summarize current knowledge about the biological mechanisms able to foster or impair the recruitment and adipogenic differentiation of ASCs during SAT and VAT development, which regulate body fat distribution and favorable or unfavorable metabolic responses.

Association of Body Composition with Type 2 Diabetes: A Retrospective Chart Review Study

This study analyzed the body composition of individuals with type 2 diabetes (T2DM). In this retrospective chart review study, body composition was measured through multifrequency bioelectrical impedance analysis (InBody 770). Body composition assessments were conducted in individuals with T2DM, who were aged ≥18 years. The parameters included body mass index (BMI), body fat mass (BFM), fat-free mass (FFM), visceral fat area, percent body fat (PBF), appendicular skeletal muscle mass (ASM), and skeletal muscle index (SMI). One-way ANOVA and independent t-tests were used to calculate differences in body composition distribution by age and sex. A total of 2404 participants were recruited. The prevalence of overall low muscle mass and sarcopenic obesity was 28.0% and 18.7%, respectively, which increased with age. The overall prevalence of obesity when PBF was used was 71.5%, which was higher than that when BMI was applied (32.4%). The normal BMI group exhibited a prevalence of low muscle mass of 55.6% and sarcopenic obesity of 34.8%. For both men and women, bodyweight, BFM, FFM, ASM, and SMI all decreased with age. The prevalence of low muscle mass and sarcopenic obesity was high in older adults and people with normal BMI. Using BMI to assess obesity and determine insufficient muscle mass underestimates the prevalence of obesity and neglects the problems of sarcopenia and high body fat in people with normal BMI.