Preferential fat deposition in subcutaneous versus visceral depots is associated with insulin sensitivity

Effects of growth hormone on hepatic insulin sensitivity and glucose effectiveness in healthy older adults

PURPOSE

Growth hormone (GH) replacement decreases insulin sensitivity in healthy individuals. However, the effects of GH on organ-specific insulin sensitivity and glucose effectiveness are not well characterized. The purpose of this study was to evaluate the effects of GH administration for 26 weeks on muscle and hepatic insulin sensitivity and glucose effectiveness in healthy older individuals.

METHODS

This report is from a 26-week randomized, double-blind, placebo-controlled parallel-group trial in healthy, ambulatory, community-dwelling older women and men. We compared surrogate indices of insulin sensitivity [quantitative insulin-sensitivity check index (QUICKI), muscle insulin sensitivity index (MISI), hepatic insulin resistance index (HIRI)] and glucose effectiveness [oral glucose effectiveness index (oGE)] derived from oral glucose tolerance tests (OGTTs) in subjects before and after 26 weeks of administration of GH (n = 17) or placebo (n = 15) as an exploratory outcome.

RESULTS

GH administration for 26 weeks significantly increased fasting insulin concentrations and HIRI but did not significantly change MISI or oGE compared to placebo.

CONCLUSIONS

GH administration for 26 weeks in healthy older subjects impairs insulin sensitivity in the liver but not skeletal muscle and does not alter glucose effectiveness.

The obese adipose tissue microenvironment in cancer development and progression

Obesity is associated with both increased cancer incidence and progression in multiple tumour types, and is estimated to contribute to up to 20% of cancer-related deaths. These associations are driven, in part, by metabolic and inflammatory changes in adipose tissue that disrupt physiological homeostasis both within local tissues and systemically. However, the mechanisms underlying the obesity-cancer relationship are poorly understood. In this Review, we describe how the adipose tissue microenvironment (ATME) evolves during body-weight gain, and how these changes might influence tumour initiation and progression. We focus on multiple facets of ATME physiology, including inflammation, vascularity and fibrosis, and discuss therapeutic interventions that have the potential to normalize the ATME, which might be translationally relevant for cancer prevention and therapy. Given that the prevalence of obesity is increasing on an international scale, translational research initiatives are urgently needed to provide mechanistic explanations for the obesity-cancer relationship, and how to best identify high-risk individuals without relying on crude measures, such as BMI.

Obesity and cardiovascular disease: revisiting an old relationship

A wealth of clinical and epidemiological evidence has linked obesity to a broad spectrum of cardiovascular diseases (CVD) including coronary heart disease, heart failure, hypertension, stroke, atrial fibrillation and sudden cardiac death. Obesity can increase CVD morbidity and mortality directly and indirectly. Direct effects are mediated by obesity-induced structural and functional adaptations of the cardiovascular system to accommodate excess body weight, as well as by adipokine effects on inflammation and vascular homeostasis. Indirect effects are mediated by co-existing CVD risk factors such as insulin resistance, hyperglycemia, hypertension and dyslipidemia. Adipose tissue (AT) quality and functionality are more relevant aspects for cardiometabolic risk than its total amount. The consequences of maladaptive AT expansion in obesity are local and systemic: the local include inflammation, hypoxia, dysregulated adipokine secretion and impaired mitochondrial function; the systemic comprise insulin resistance, abnormal glucose/lipid metabolism, hypertension, a pro-inflammatory and pro-thrombotic state and endothelial dysfunction, all of which provide linking mechanisms for the association between obesity and CVD. The present narrative review summarizes the major pathophysiological links between obesity and CVD (traditional and novel concepts), analyses the heterogeneity of obesity-related cardiometabolic consequences, and provides an overview of the cardiovascular impact of weight loss interventions.

Comparison of visceral fat measurement by dual-energy X-ray absorptiometry to computed tomography in HIV and non-HIV

Background/Objectives

Individuals with HIV are susceptible to visceral fat accumulation, which confers an increased risk of cardiometabolic disease. Advanced software to ascertain visceral fat content from dual-energy X-ray absorptiometry (DXA) has not been validated among this population. We sought to compare DXA with computed tomography (CT) in the measurement of visceral fat cross-sectional area (VAT) in HIV and non-HIV using Bland–Altman analyses.

Subjects/Methods

Data were combined from five previously conducted studies of individuals with HIV (n = 313) and controls without HIV (n = 144) in which paired DXA and CT scans were available. In cross-sectional analyses, DXA-VAT was compared with CT-VAT among participants with and without HIV. In longitudinal analyses, changes in VAT over time were compared between DXA and CT among participants with and without HIV receiving no intervention over 12 months and among individuals with HIV receiving tesamorelin—a medication known to reduce VAT—over 6 months.

Results

In HIV, DXA underestimated VAT compared with CT among individuals with increased visceral adiposity. The measurement bias was −9 ± 47 cm² overall, but became progressively larger with greater VAT (P < 0.0001), e.g., −61 ± 58 cm² among those with VAT ≥ 200 cm². Sex-stratified analyses revealed that the relationship between VAT and measurement bias was especially pronounced in men (P < 0.0001). Longitudinally, DXA underestimated changes in VAT, particularly among those at the extremes of VAT gain or loss (P < 0.0001). In contrast to the cross-sectional findings, the tendency for DXA to underestimate longitudinal changes in VAT was evident in both men and women. Analogous findings were seen among controls in cross-sectional and longitudinal analyses.

Conclusions

DXA underestimated VAT relative to CT in men with and without HIV, who had increased visceral adiposity. DXA also underestimated changes in VAT over time in men and women, irrespective of HIV status. DXA-VAT should be used with caution among both HIV and non-HIV-infected populations.

The associations of fat tissue and muscle mass indices with all-cause mortality in patients undergoing hemodialysis

Protein-energy wasting, which involves loss of fat and muscle mass, is prevalent and is associated with mortality in hemodialysis (HD) patients. We investigated the associations of fat tissue and muscle mass indices with all-cause mortality in HD patients. The study included 162 patients undergoing HD. The fat tissue index (FTI) and skeletal muscle mass index (SMI), which represent respective tissue masses normalized to height squared, were measured by bioimpedance analysis after dialysis. Patients were divided into the following four groups according to the medians of FTI and SMI values: group 1 (G1), lower FTI and lower SMI; G2, higher FTI and lower SMI; G3, lower FTI and higher SMI; and G4, higher FTI and higher SMI. The associations of the FTI, SMI, and body mass index (BMI) with all-cause mortality were evaluated. During a median follow-up of 2.5 years, 29 patients died. The 5-year survival rates were 48.6%, 76.1%, 95.7%, and 87.4% in the G1, G2, G3, and G4 groups, respectively (P = 0.0002). The adjusted hazard ratio values were 0.34 (95% confidence interval [CI] 0.10–0.95, P = 0.040) for G2 vs. G1, 0.13 (95%CI 0.01–0.69, P = 0.013) for G3 vs. G1, and 0.25 (95%CI 0.07–0.72, P = 0.0092) for G4 vs. G1, respectively. With regard to model discrimination, on adding both FTI and SMI to a model with established risk factors, the C-index increased significantly when compared with the value for a model with BMI (0.763 vs. 0.740, P = 0.016). Higher FTI and/or higher SMI values were independently associated with reduced risks of all-cause mortality in HD patients. Moreover, the combination of the FTI and SMI may more accurately predict all-cause mortality when compared with BMI. Therefore, these body composition indicators should be evaluated simultaneously in this population.

A Comparison of Dietary and Caloric Restriction Models on Body Composition, Physical Performance, and Metabolic Health in Young Mice

Time-restricted feeding (TRF), alternate day fasting (ADF), and the dietary restriction model known as the Daniel Fast (DF; a vegan/non-processed food diet plan) have garnered attention recently as nutritional interventions to combat obesity. We compared the effects of various dietary models on body composition, physical performance, and metabolic health in C57BL/6 mice. Sixty young C57BL/6 male mice were assigned a diet of TRF, ADF, DF, caloric restriction (CR), a high-fat Western diet (HF) fed ad libitum, or standard rodent chow for eight weeks. Their body composition, run time to exhaustion, fasting glucose, insulin, and glucose tolerance test area under the glucose curve (AUC) were determined. Compared to the HF group, all groups displayed significantly less weight and fat mass gain, as well as non-significant changes in fat-free mass. Additionally, although not statistically significant, all groups displayed greater run time to exhaustion relative to the HF group. Compared to the HF group, all groups demonstrated significantly lower fasting glucose, insulin, and Homeostatic Model Assessment of Insulin Resistance (HOMA-IR), as well as improved glucose tolerance, and the ADF group displayed the best fasting glucose and glucose tolerance results, with DF having the best HOMA-IR. All investigated fasting protocols may improve body composition, measures of insulin sensitivity, and physical performance compared to a high-fat Western diet. The DF and ADF protocols are most favorable with regards to insulin sensitivity and glucose tolerance. Since our selected dietary protocols have also been investigated in humans with success, it is plausible to consider that these dietary models could prove beneficial to men and women seeking improved body composition and metabolic health.

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

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

Metabolic syndrome is a sequela of radiation exposure in hypothalamic obesity among survivors of childhood brain tumors

Survivors of childhood brain tumors may be at risk for early onset of metabolic syndrome, possibly secondary to surgery and/or radiation exposure. This study examines effects of radiation exposure to hypothalamus-pituitary-adrenal axis (HPA) on metabolic risk among survivors of childhood brain tumors. One hundred forty-two met inclusion criteria; 60 had tumor surgery plus radiation exposure (>1 Gray (Gy)) to HPA. The second subgroup of 82 subjects had surgery only and were not exposed to radiation. Both subgroups had survived for approximately 5 years at the time of study. All had clinical evaluation, vital signs, anthropometry, measurement of body composition by dual X-ray absorptiometry and fasting laboratory assays (metabolic panel, insulin, C-peptide, insulin-like growth factor-1, leptin and adiponectin). Body composition data for both subgroups was compared with the National Health and Nutrition Survey (NHANES) subgroup of similar age, gender and body mass index. Cranial surgery was associated with obesity of similar severity in both subgroups. However, survivors exposed to radiation to the HPA also had increased visceral fat mass and high prevalence of growth hormone deficiency and metabolic syndrome. Fat mass alone did not explain the prevalence of the metabolic syndrome in radiation exposure subgroup. Other factors such as growth hormone deficiency may have contributed to metabolic risk. We conclude that prevalence of metabolic syndrome among subjects exposed to hypothalamic radiation was higher than expected from hypothalamic obesity alone. Radiation exposure may exert untoward endocrinopathies due to HPA exposure that worsens metabolic risk. Early screening for metabolic syndrome in this population is indicated.

Visceral fat is associated with elevation of serum alanine aminotransferase and gamma glutamyltransferase in middle-aged Chinese adults

BACKGROUND : Elevation of hepatic enzymes is associated with insulin resistance, dyslipidaemia and obesity. However, the factors behind elevation of liver enzymes remain unclear. The aim of this study was to compare the role of abdominal visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) in relation with serum alanine aminotransferase (ALT) and gamma glutamyltransferase (GGT) in middle-aged Chinese adults. METHODS : We performed a cross-sectional study on 959 adults aged 40-65 without hepatitis. VAT and SAT were measured at the level of L4-L5 by MRI. Pearson correlation and linear regression were performed to assess the association of VAT/SAT with serum ALT and GGT. Logistic regression was used to evaluate the association of VAT and SAT with high ALT (≥40 U/L) and high GGT (≥35 U/L). RESULTS: VAT had higher correlation coefficient r with ALT and GGT than SAT. VAT, but not SAT, was associated with ALT (males: β=0.15, p=0.01; females: β=0.17, p=0.02) and GGT (males: β=0.39, p<0.0001) in linear regression. VAT remained to be associated with GGT in males (β=0.33, p=0.0001) when was further adjusted. Logistic regression showed that VAT was associated with elevated GGT (OR=2.218, p=0.043) in males but not in females and no such association was observed for SAT. CONCLUSIONS: Increased VAT, but not SAT, was associated with elevation of hepatic enzymes including ALT and GGT. Moreover, VAT was associated with elevated GGT independent of insulin resistance and subcutaneous fat in males.

Involvement of acetyl-CoA-producing enzymes in the deterioration of the functional potential of adipose-derived multipotent cells from subjects with metabolic syndrome

OBJECTIVE

The expansion capacity of white adipose tissue influences the distribution of fat depots in the body, the visceral accumulation of which is linked to metabolic syndrome, regardless of the degree of obesity of the subjects. Alterations in the adipose tissue-derived mesenchymal stem cells (ASCs) may contribute to the adipose tissue remodeling associated with metabolic syndrome and impact the regional distribution of adipose tissue by generating inherently dysfunctional adipocytes. Here we examine the expression levels of acetyl-CoA-producing enzymes and their relationship with the lipogenic, antioxidant and oxidative potential of adipocytes generated from visceral ASCs (adipo-visASCs) and subcutaneous ASCs (adipo-subASCs) from subjects with different metabolic profiles.

MATERIALS/METHODS

Paired samples of visceral and subcutaneous adipose tissue were processed to isolate the respective ASCs from normal-weight (Nw) subjects and obese patients with metabolic syndrome (METS) and without METS (NonMETS). qPCR was used to quantify the expression levels of the genes studied in both adipo-ASCs from the patient groups and those generated after silencing by small interfering RNA of acetyl-CoA-producing enzymes. The accumulation of lipids was quantified by absorbance.

RESULTS

No significant differences in cell yield or CD34⁺CD31^-CD45^- ASC percentage were observed between the different patient groups. Unlike adipo-visASCs, adipo-subASCs from METS patients showed a decrease in expression levels of acetyl-CoA-producing enzymes as well as proteins linked to lipogenesis, antioxidant defense and fatty acid oxidation. Transcriptional silencing of acetyl-CoA-producing enzymes in adipo-subASCs reduced lipid accumulation and affected transcription levels of lipogenic and antioxidant defense proteins.

CONCLUSIONS

Adipo-subASCs may be more susceptible than adipo-visASCs to deterioration of the lipogenic, oxidative and antioxidant potential associated with metabolic syndrome. Intrinsic alterations in transcription levels of acetyl-CoA-producing enzymes may contribute to the metabolic reprogramming of adipo-subASCs from METS patients.

Integrating genetic, transcriptional, and biological information provides insights into obesity

Objective:

Indices of body fat distribution are heritable, but few genetic signals have been reported from genome-wide association studies (GWAS) of computed tomography (CT) imaging measurements of body fat distribution. We aimed to identify genes associated with adiposity traits and the key drivers that are central to adipose regulatory networks.

Subjects:

We analyzed gene transcript expression data in blood from participants in the Framingham Heart Study, a large community-based cohort (n up to 4,303), as well as implemented an integrative analysis of these data and existing biological information.

Results:

Our association analyses identified unique and common gene expression signatures across several adiposity traits, including body mass index, waist-hip ratio, waist circumference, and CT-measured indices, including volume and quality of visceral and subcutaneous adipose tissues. We identified six enriched KEGG pathways and two co-expression modules for further exploration of adipose regulatory networks. The integrative analysis revealed four gene sets (Apoptosis, p53 signaling pathway, Proteasome, Ubiquitin mediated proteolysis) and two co-expression modules with significant genetic variants and 94 key drivers/genes whose local networks were enriched with adiposity-associated genes, suggesting that these enriched pathways or modules have genetic effects on adiposity. Most identified key driver genes are involved in essential biological processes such as controlling cell cycle, DNA repair and degradation of regulatory proteins and are cancer related.

Conclusion:

Our integrative analysis of genetic, transcriptional and biological information provides a list of compelling candidates for further follow-up functional studies to uncover the biological mechanisms underlying obesity. These candidates highlight the value of examining CT-derived and central adiposity traits.

Salivary Leptin Level in Young Adult Males and its Association with Anthropometric Measurements, Fat Distribution and Muscle Mass

Aims: 1) To assess salivary leptin levels in normal-underweight versus overweight and obese healthy adult males aged 18–25 years old. 2) The relative contribution of anthropometric measurements, fat percentage, fat distribution (visceral versus subcutaneous) and total as well as regional muscle mass in arms, trunk and legs respectively in predicting salivary leptin levels. Methods: A total of 92 adult males were classified into two groups based on their body mass index (BMI): normal-underweight, BMI <24.9 kg/m² (n=51); overweight-obese, BMI >25 kg/m² (n=41). Anthropometric measurements such as BMI, waist circumference (WC), hip circumference (HC) and waist-hip ratio (WHR) were measured through standardised methods. Fat percentage, visceral fat level, subcutaneous fat and muscle mass (total and regional) were measured using Karada scan bioelectrical impedance method. Fasting saliva samples were collected and used for assessing salivary leptin concentrations using enzyme-linked immunosorbent assay. Results: Statistical analysis of the data showed a significant difference between the two groups in all of the parameters measured except height and salivary leptin levels. Multiple regression analysis showed that HC, WC and WHR were good predictors for salivary leptin levels in normal-underweight group. However, in the overweight-obese group, height was the most important independent variable that could predict salivary leptin levels as a dependent variable. Conclusions: Predictors for salivary leptin levels in adult healthy males are different in normal-underweight subjects from overweight-obese subjects. The most important predictor for salivary leptin levels is HC in normal weight subjects, while it is height in overweight and obese healthy adult males.

Mitochondrial oxidative stress in obesity: role of the mineralocorticoid receptor

Obesity is a multifaceted, chronic, low-grade inflammation disease characterized by excess accumulation of dysfunctional adipose tissue. It is often associated with the development of cardiovascular (CV) disorders, insulin resistance and diabetes. Under pathological conditions like in obesity, adipose tissue secretes bioactive molecules called 'adipokines', including cytokines, hormones and reactive oxygen species (ROS). There is evidence suggesting that oxidative stress, in particular, the ROS imbalance in adipose tissue, may be the mechanistic link between obesity and its associated CV and metabolic complications. Mitochondria in adipose tissue are an important source of ROS and their dysfunction contributes to the pathogenesis of obesity-related type 2 diabetes. Mitochondrial function is regulated by several factors in order to preserve mitochondria integrity and dynamics. Moreover, the renin-angiotensin-aldosterone system is over-activated in obesity. In this review, we focus on the pathophysiological role of the mineralocorticoid receptor in the adipose tissue and its contribution to obesity-associated metabolic and CV complications. More specifically, we discuss whether dysregulation of the mineralocorticoid system within the adipose tissue may be the upstream mechanism and one of the early events in the development of obesity, via induction of oxidative stress and mitochondrial dysfunction, thus impacting on systemic metabolism and the CV system.

Essential Fatty Acids Linoleic Acid and α-Linolenic Acid Sex-Dependently Regulate Glucose Homeostasis in Obesity

SCOPE

To assess the associations of dietary linoleic acid (LA) and α-linolenic acid (ALA) with type 2 diabetes (T2D) risk in a population-based cohort and further explore the mechanism of action in a high-fat-diet (HFD) induced obese (DIO) mouse model.

METHODS AND RESULTS

The occurrence of T2D among 15 100 Chinese adults from China Health and Nutrition Survey (CHNS, 1997-2011) were followed up for a median of 14 years. The relations of ALA and LA intakes with T2D risk were modified by BMI, with significant associations restricted to obese/overweight subjects. Among them, relative risks (95% confidence intervals) comparing extreme quartiles of intakes were 0.55 (0.32-0.93) in men and 0.53 (0.34-0.85) in women for ALA, while 0.71 (0.41-1.16) in men and 0.56 (0.36-0.89) in women for LA. DIO mice were fed with LA- or ALA-enriched HFD (0.2% wt wt^-1 ) for 15 weeks and then significant sex-dependent changes of gut microbiota were detected. Endotoxemia, systematic and adipose inflammation were relieved in ALA-fed male and LA-fed female mice.

CONCLUSIONS

Long-term intake of LA (for women) and ALA may have a protective effect on T2D development for obese/overweight subjects through sex-specific gut microbiota modulation and gut-adipose axis.

Utility of three novel insulin resistance-related lipid indices for predicting type 2 diabetes mellitus among people with normal fasting glucose in rural China

BACKGROUND

Inexpensive and easily measured indices are needed for the early prediction of type 2 diabetes mellitus (T2DM) in rural areas of China. The aim of this study was to compare triglyceride glucose (TyG), visceral adiposity (VAI), and lipid accumulation product (LAP) with traditional individual measures and their ratios for predicting T2DM.

METHODS

Data for 11 113 people with baseline normal fasting glucose in a rural Chinese cohort were followed for a median of 6.0 years. Cox proportional hazards regression was used to calculate covariate-adjusted hazard ratios (aHRs) and 95% confidence intervals (95% CIs) and receiver operating characteristic analysis was used to compare the ability of traditional measures and TyG, VAI, and LAP at baseline to predict T2DM at follow-up.

RESULTS

Among individual measures, fasting plasma glucose (FPG) and waist circumference (WC) were strongly associated with T2DM. Of all lipid ratios, an elevated triglycerides (TG) to high-density lipoprotein cholesterol (HDL-C) ratio was associated the most with T2DM. Compared with the first quartiles of TyG, VAI, and LAP, their fourth quartiles were associated with T2DM for men (aHR 3.54 [95% CI 2.08-6.03], 2.89 [1.72-4.87], and 5.02 [2.85-8.85], respectively) and women (6.15 [3.48-10.85], 4.40 [2.61-7.42], and 6.49 [3.48-12.12], respectively). For predicting T2DM risk, TyG, VAI, and LAP were mostly superior to the TG:  HDL-C ratio, but did not differ from FPG and WC.

CONCLUSIONS

Prediction of T2DM was not improved by TyG, VAI, and LAP versus FPG or WC alone. Therefore, TyG, VAI, and LAP may not be inexpensive tools for predicting T2DM in rural Chinese people.

Abdominal fat depots, insulin resistance, and incident diabetes mellitus in women with and without HIV infection

OBJECTIVE

The aim of this study was to determine the associations between visceral adipose tissue (VAT) and abdominal subcutaneous adipose tissue (SAT) mass with homeostatic model assessment-insulin resistance (HOMA-IR) and incidence of diabetes mellitus in women with and without HIV infection.

DESIGN

Cross-sectional design for associations between abdominal fat and HOMA-IR; longitudinal design for associations between abdominal fat and incident diabetes.

METHODS

We assessed associations between dual X-ray absorptiometry scan-derived VAT and SAT with HOMA-IR in a subsample from the Women's Interagency HIV Study (n = 226 with and n = 100 without HIV) using linear regression. We evaluated associations of VAT, SAT and HOMA-IR with incident diabetes mellitus using Cox proportional hazards models.

RESULTS

VAT mass was positively associated with log HOMA-IR in fully adjusted linear regression models stratified by HIV serostatus, including adjustment for SAT. During median follow-up of 10.6 years, incidence of diabetes was 1.63 [95% confidence interval (95% CI) 1.15-2.31] and 1.32 [95% CI 0.77-2.28] cases per 100 person-years in women with and without HIV (P = 0.52). In a fully adjusted model, baseline VAT (hazard ratio 2.64 per kg; 95% CI 1.14-6.12; P = 0.023) and SAT (hazard ratio 1.34 per kg; 95% CI 0.73-2.45; P = 0.35) were associated with incident diabetes, but the latter was not statistically significant.

CONCLUSION

VAT mass was independently associated with HOMA-IR in women with and without HIV and was independently associated with future development of diabetes.

Waist-hip ratio as a predictor of myocardial infarction risk: A systematic review and meta-analysis

BACKGROUND AND AIM

Several studies have identified that obesity and being overweight can increase the risk of developing myocardial infarction (MI). However, the predictive value of the central obesity index, that is, the waist-hip ratio (WHR), regarding MI risk remains unclear. This study aimed to provide a systematic review and meta-analysis of WHR as a predictor of MI incidence.

METHODS

This study used relevant keywords and MeSH terms to identify studies of MI risk and WHR from PubMed, Web of Science, Embase, and Cochrane databases in November 2017.

RESULTS

We conducted a meta-analysis of 12 case-control studies in 14 eligible trials and further explored whether the predictive value of WHR on MI risk varies according to sex. The results showed that a high WHR increased MI risk (pooled odds ratio [OR] 2.62, 95% confidence interval [CI] 2.02-3.39, P < 0.00001) and that elevated WHR is more strongly predictive of MI in women than in men (pooled OR 4.63, 95% CI 3.28-6.53 in women; pooled OR 2.71, 95% CI 2.15-3.41 in men).

CONCLUSIONS

MI is significantly associated with increased WHR, with a stronger association among women.

Correlations between the abdominal fat-related parameters and severity of coronary artery disease assessed by computed tomography

Background

Obesity is considered a challenging public problem, which has been proven to be closely associated with coronary artery disease (CAD). Each risk factor of CAD has been separately studied many times in the past, but very few have comprehensively and quantitatively evaluated the relationship between the abdominal fat-related parameters and severity of CAD. The aim of this study was to analyze whether the abdominal fat-related parameters were associated with severity of CAD using abdominal non-enhanced computed tomography (NECT).

Methods

Patients who went through both abdominal NECT and invasive coronary angiography (ICA) were included and retrospectively analyzed. The abdominal fat-related parameters [the ratio of visceral adipose tissue to subcutaneous adipose tissue (VAT/SAT ratio)] and traditional cardiovascular risk factors were evaluated in the participants with or without obstructive CAD. The correlations between the abdominal fat-related parameters and severity of CAD were assessed, and the multivariable logistic regression analysis was performed to investigate the parameters that could be used to predict the severity of CAD.

Results

A total of 223 consecutive subjects (obstructive CAD group, n=117; non-obstructive CAD group, n=106) were analyzed. The VAT/SAT ratio was significantly higher (0.95±0.33 vs. 0.70±0.25, P<0.001) in obstructive CAD (O-CAD) patients than that in non-obstructive CAD (NO-CAD) patients. There was a trend to having nonalcoholic fatty liver disease (NAFLD) in the O-CAD patients than that of NO-CAD (P=0.002); the abdominal aortic calcification (AAC) score in O-CAD patients were higher than that in NO-CAD patients (P<0.001). The multivariable logistic regression analysis demonstrated that VAT/SAT ratio, NAFLD, and AAC score were independent predictors of O-CAD after adjusting the traditional cardiovascular risk factors. The area under the curve (AUC) of the combination of the above risk factors is 0.85, which leads to an increase in AUC than each risk factor alone in differentiating patients with or without O-CAD.

Conclusions

VAT/SAT ratio, NAFLD, and AAC score are correlated with the severity of CAD, indicating their characteristics of being independent risk factors for O-CAD, irrespective of the traditional cardiovascular risk factors. Those CT-derived parameters may make positive contributions to the differentiation of the patients with increased risk of O-CAD.

Abdominal subcutaneous adipose tissue: a favorable adipose depot for diabetes?

Background

Previous studies have documented that visceral adipose tissue is positively associated with the risk of diabetes. However, the association of subcutaneous adipose tissue with diabetes risk is still in dispute. We aimed to assess the associations between different adipose distributions and the risk of newly diagnosed diabetes in Chinese adults.

Methods

The Shanghai Nicheng Cohort Study was conducted among Chinese adults aged 45–70 years. The baseline data of 12,137 participants were analyzed. Subcutaneous and visceral fat area (SFA and VFA) were measured by magnetic resonance imaging. Diabetes was newly diagnosed using a 75 g oral glucose tolerance test.

Results

The multivariable-adjusted odds ratios (OR) and 95% confidence intervals (CI) of newly diagnosed diabetes per 1—standard deviation increase in SFA and VFA were 1.29 (1.19–1.39) and 1.61 (1.49–1.74) in men, and 1.10 (1.03–1.18) and 1.56 (1.45–1.67) in women, respectively. However, the association between SFA and newly diagnosed diabetes disappeared in men and was reversed in women (OR 0.86 [95% CI, 0.78–0.94]) after additional adjustment for body mass index (BMI) and VFA. The positive association between VFA and newly diagnosed diabetes remained significant in both sexes after further adjustment for BMI and SFA. Areas under the receiver operating characteristic curve of newly diagnosed diabetes predicted by VFA (0.679 [95% CI, 0.659–0.699] for men and 0.707 [95% CI, 0.690–0.723] for women) were significantly larger than by the other adiposity indicators.

Conclusions

SFA was beneficial for lower risk of newly diagnosed diabetes in women but was not associated with newly diagnosed diabetes in men after taking general obesity and visceral obesity into account. VFA, however, was associated with likelihood of newly diagnosed diabetes in both Chinese men and women.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0734-8) contains supplementary material, which is available to authorized users.

Racial differences in in vivo adipose lipid kinetics in humans

The storage of lipids in the form of triglycerides (TGs) and the de novo synthesis (lipogenesis) of fatty acids from nonlipid precursors [de novo lipogenesis (DNL)] are important functions of adipose tissue (AT) that influence whole-body metabolism. Yet, few studies have reported in vivo estimates of adipose lipid kinetics in humans. Fifty-two women with obesity (27 African-American and 25 Caucasian; 29.7 ± 5.5 years; BMI 32.2 ± 2.8 kg/m²; 44.3 ± 4.0% body fat) were enrolled in the study. In vivo synthesis (or replacement) of TGs (f_TG) as well as the synthesis of the fatty acid, palmitate [a measure of adipose DNL (f_DNL)], were assessed using an 8 week incorporation of deuterium into lipids (glycerol and palmitate moieties of TGs) in subcutaneous abdominal (scABD) and subcutaneous femoral (scFEM) AT. We report, for the first time, significant race differences in both TG synthesis and absolute DNL, with Caucasians having higher f_TG and f_DNL as compared with African-Americans. The DNL contribution to newly synthesized TG (corrected f_DNL) was not different between races. Interestingly, our findings also show that the scFEM adipose depot had higher TG replacement rates relative to the scABD. Finally, the replacement rate of TG (f_TG) was negatively correlated with changes in body weight over the 8 week labeling period. Our results provide the first evidence that in vivo TG replacement (synthesis and breakdown) rates differ by ethnicity. In addition, TG turnover varies by depot location in humans, implying an increased capacity for TG storage and higher lipolytic activity in the scFEM AT.

Abdominal Subcutaneous Fat: A Favorable or Nonfunctional Fat Depot for Glucose Metabolism in Chinese Adults?

OBJECTIVE

The objective of this study was to assess the associations of abdominal visceral and subcutaneous adipose tissue with blood glucose and beta-cell function.

METHODS

In this study, 11,223 participants without known diabetes were selected for this cross-sectional analysis. Visceral and subcutaneous fat area (VFA and SFA) were measured by magnetic resonance imaging. An oral glucose tolerance test was conducted, and beta-cell function was evaluated.

RESULTS

Men had significantly larger VFA but smaller SFA than women. After controlling for age, linear regression showed that SFA was adversely associated with 0-minute, 30-minute, and 2-hour plasma glucose (PG) and early-, first- and second-phase disposition indices (DIs). After further adjustment for BMI and VFA, some associations of SFA with PG indices and DIs disappeared, while the other associations became significantly weaker in men (2-hour PG: 0.05 and DI_2nd : -0.05) or were reversed in women (0-minute, 30-minute, and 2-hour PG: from -0.07 to -0.04; DI_1st : 0.04, P < 0.05). After adjustment for age, BMI, and SFA, VFA was significantly and adversely associated with PG indices and DIs, with the largest standardized regression coefficients with 2-hour PG.

CONCLUSIONS

The associations of SFA with blood glucose and beta-cell function were clinically insignificant in Chinese adults. VFA had the strongest association with 2-hour PG.

Deep phenotyping in zebrafish reveals genetic and diet-induced adiposity changes that may inform disease risk

The regional distribution of adipose tissues is implicated in a wide range of diseases. For example, proportional increases in visceral adipose tissue increase the risk for insulin resistance, diabetes, and CVD. Zebrafish offer a tractable model system by which to obtain unbiased and quantitative phenotypic information on regional adiposity, and deep phenotyping can explore complex disease-related adiposity traits. To facilitate deep phenotyping of zebrafish adiposity traits, we used pairwise correlations between 67 adiposity traits to generate stage-specific adiposity profiles that describe changing adiposity patterns and relationships during growth. Linear discriminant analysis classified individual fish according to an adiposity profile with 87.5% accuracy. Deep phenotyping of eight previously uncharacterized zebrafish mutants identified neuropilin 2b as a novel gene that alters adipose distribution. When we applied deep phenotyping to identify changes in adiposity during diet manipulations, zebrafish that underwent food restriction and refeeding had widespread adiposity changes when compared with continuously fed, equivalently sized control animals. In particular, internal adipose tissues (e.g., visceral adipose) exhibited a reduced capacity to replenish lipid following food restriction. Together, these results in zebrafish establish a new deep phenotyping technique as an unbiased and quantitative method to help uncover new relationships between genotype, diet, and adiposity.

Human Macrophages Preferentially Infiltrate the Superficial Adipose Tissue

Human abdominal subcutaneous adipose tissue consists of two individual layers—the superficial adipose tissue (SAT) and deep adipose tissue (DAT)—separated by the Scarpa’s fascia. The present study focuses on the analysis of morphological and immunological differences of primary adipocytes, adipose-derived stem cells (ASC), and tissue-infiltrating immune cells found in SAT and DAT. Adipocytes and stromal vascular fraction (SVF) cells were isolated from human SAT and DAT specimens and phenotypically characterized by in vitro assays. Ex vivo analysis of infiltrating immune cells was performed by flow cytometry. Primary adipocytes from SAT are larger in size but did not significantly differ in cytokine levels of LEPTIN, ADIPOQ, RBP4, CHEMERIN, DEFB1, VISFATIN, MCP1, or MSCF. ASC isolated from SAT proliferated faster and exhibited a higher differentiation potential than those isolated from DAT. Flow cytometry analysis indicated no specific differences in the relative numbers of ASC, epithelial progenitor cells (EPC), or CD3⁺ T-cells, but showed higher numbers of tissue-infiltrating macrophages in SAT compared to DAT. Our findings suggest that ASC isolated from SAT have a higher regenerative potential than DAT-ASC. Moreover, spatial proximity to skin microbiota might promote macrophage infiltration in SAT.

The Impact of Abdominal Fat Levels on All-Cause Mortality Risk in Patients Undergoing Hemodialysis

Although an increased body mass index is associated with lower mortality in patients undergoing hemodialysis (HD), known as the “obesity paradox,” the relationship of abdominal fat levels with all-cause mortality has rarely been studied. We investigated the impact of computed-tomography-measured abdominal fat levels (visceral fat area (VFA) and subcutaneous fat area (SFA)) on all-cause mortality in this population. A total of 201 patients undergoing HD were enrolled and cross-classified by VFA and SFA levels according to each cutoff point, VFA of 78.7 cm² and SFA of 93.2 cm², based on the receiver operator characteristic (ROC) curve as following; group 1 (G1): lower VFA and lower SFA, G2: higher VFA and lower SFA, G3: lower VFA and higher SFA, G4: higher VFA and higher SFA. During a median follow-up of 4.3 years, 67 patients died. Kaplan–Meier analysis revealed 10-year survival rates of 29.0%, 50.0%, 62.6%, and 72.4% in G1, G2, G3, and G4 (p < 0.0001), respectively. The adjusted hazard ratio was 0.30 (95% confidence interval [CI] 0.05–1.09, p = 0.070) for G2 vs. G1, 0.37 (95% CI 0.18–0.76, p = 0.0065) for G3 vs. G1, and 0.21 (95% CI 0.07–0.62, p = 0.0035) for G4 vs. G1, respectively. In conclusion, combined SFA and VFA levels were negatively associated with risks for all-cause mortality in patients undergoing HD. These results are a manifestation of the “obesity paradox.”

Androgen excess and metabolic disorders in women with PCOS: beyond the body mass index

BACKGROUND

Insulin resistance is a common feature among women with polycystic ovary syndrome (PCOS), especially in those patients with hyperandrogenism and chronic anovulation. PCOS women are at risk for developing metabolic syndrome, impaired glucose tolerance and type II diabetes mellitus (DM II).

OBJECTIVE

The aim of this review is to explore the existing knowledge of the interplay between androgen excess, pancreatic β-cell function, non-alcoholic fatty liver disease (NAFLD), intra-abdominal and subcutaneous (SC) abdominal adipocytes in PCOS, providing a better comprehension of the molecular mechanisms of diabetologic interest.

METHODS

A comprehensive MEDLINE^® search was performed using relevant key terms for PCOS and DM II.

RESULTS

Insulin-induced hyperandrogenism could impair pancreatic β-cell function, the SC abdominal adipocytes' lipid storage capacity, leading to intra-abdominal adipocyte hypertrophy and lipotoxicity, which in turn promotes insulin resistance, and could enhance NAFLD. Fetal hyperandrogenism exposure prompts to metabolic disorders. Treatment with flutamide showed to partially reverse insulin resistance.

CONCLUSIONS

Metabolic impairment seems not to be dependent only on the total fat mass content and body weight in women with PCOS and might be ascribed to the androgen excess.

Association of Body Mass Index with Risk of Major Adverse Cardiovascular Events and Mortality in People with Diabetes

Background

The relationship between cardiovascular and all-cause mortality and obesity in people with diabetes is still controversial. We investigated the association of body mass index (BMI) with the risk of major adverse cardiovascular events (MACE) and all-cause mortality in people with diabetes.

Methods

In total, 48,438 people with diabetes were enrolled in the Korean National Health Insurance Service-National Health Screening Cohort from 2002 to 2003 and were followed until 2013. Baseline BMI was categorized as underweight (<18.5 kg/m²), normal-weight (18.5–22.9 kg/m²), overweight (23.0–24.9 kg/m²), obese class I (25.0–29.9 kg/m²), and obese class II (≥30.0 kg/m²).

Results

During a median of 10.7 years of follow-up (interquartile range, 10.2–11.2 years), there were 7,360 MACE and 5,766 deaths. Compared to those in the normal-weight group, the fully adjusted hazard ratios (HRs) for MACE were 1.09 (95% confidence interval [CI], 0.92–1.29), 0.91 (95% CI, 0.85–0.97), 0.93 (95% CI, 0.88–0.98), and 0.95 (95% CI, 0.84–1.06) for underweight, overweight, obese class I, and obese class II groups, respectively. The HRs for all-cause mortality were 1.75 (95% CI, 1.54–1.99), 0.74 (95% CI, 0.69–0.79), 0.67 (95% CI, 0.63–0.71), and 0.73 (95% CI, 0.63–0.85) for underweight, overweight, obese class I, and obese class II groups, respectively.

Conclusion

In people with diabetes, underweight people had a higher risk for all-cause mortality, whereas overweight or obese people had a lower risk for MACE and all-cause mortality than those with a normal weight.

Perivascular Adipose Tissue as a Relevant Fat Depot for Cardiovascular Risk in Obesity

Obesity is associated with increased risk of premature death, morbidity, and mortality from several cardiovascular diseases (CVDs), including stroke, coronary heart disease (CHD), myocardial infarction, and congestive heart failure. However, this is not a straightforward relationship. Although several studies have substantiated that obesity confers an independent and additive risk of all-cause and cardiovascular death, there is significant variability in these associations, with some lean individuals developing diseases and others remaining healthy despite severe obesity, the so-called metabolically healthy obese. Part of this variability has been attributed to the heterogeneity in both the distribution of body fat and the intrinsic properties of adipose tissue depots, including developmental origin, adipogenic and proliferative capacity, glucose and lipid metabolism, hormonal control, thermogenic ability, and vascularization. In obesity, these depot-specific differences translate into specific fat distribution patterns, which are closely associated with differential cardiometabolic risks. The adventitial fat layer, also known as perivascular adipose tissue (PVAT), is of major importance. Similar to the visceral adipose tissue, PVAT has a pathophysiological role in CVDs. PVAT influences vascular homeostasis by releasing numerous vasoactive factors, cytokines, and adipokines, which can readily target the underlying smooth muscle cell layers, regulating the vascular tone, distribution of blood flow, as well as angiogenesis, inflammatory processes, and redox status. In this review, we summarize the current knowledge and discuss the role of PVAT within the scope of adipose tissue as a major contributing factor to obesity-associated cardiovascular risk. Relevant clinical studies documenting the relationship between PVAT dysfunction and CVD with a focus on potential mechanisms by which PVAT contributes to obesity-related CVDs are pointed out.

The role of visceral and subcutaneous adipose tissue measurements and their ratio by magnetic resonance imaging in subjects with prediabetes, diabetes and healthy controls from a general population without cardiovascular disease

OBJECTIVE

To study the relationship of area- and volumetric-based visceral and subcutaneous adipose tissue (VAT and SAT) by MRI and their ratio in subjects with impaired glucose metabolism from the general population.

METHODS

Subjects from a population-based cohort with established prediabetes, diabetes and healthy controls without prior cardiovascular diseases underwent 3 T MRI. VAT and SAT were assessed as total volume and area on a single slice, and their ratio (VAT/SAT) was calculated. Clinical covariates and cardiovascular risk factors, such as hypertension and glycemic state were assessed in standardized fashion. Univariate and adjusted analyses were conducted.

RESULTS

Among 384 subjects (age: 56.2 ± 9.2 years, 58.1% male) with complete MRI data available, volumetric and single-slice VAT, SAT and VAT/SAT ratio were strongly correlated (all >r = 0.89). Similarly, VAT/SAT_volume ratio was strongly correlated with VAT_volume but not with SAT (r = 0.72 and r = -0.21, respectively). Significant higher levels of VAT, SAT and VAT/SAT ratio were found in subjects with impaired glucose metabolism (all p ≤ 0.01). After adjustment for potential cardiovascular confounders, VAT_volume and VAT/SAT_volume ratio remained significantly higher in subjects with impaired glucose metabolism (VAT_volume = 6.9 ± 2.5 l and 3.4 ± 2.3 l; VAT/SAT_volume ratio = 0.82 ± 0.34 l and 0.49 ± 0.29 l in patients with diabetes and controls, respectively, all p < 0.02), whereas the association for SAT_volume attenuated. Additionally, there was a decreasing effect of glycemic status on VAT/SAT_volume ratio with increasing body mass index and waist circumference (p < 0.05).

CONCLUSIONS

VAT_volume and VAT/SAT_volume ratio are associated with impaired glucose metabolism, independent of cardiovascular risk factors or MRI-based quantification technique, with a decreasing effect of VAT/SAT_volume ratio in obese subjects. Advances in knowledge: Quantification of VAT_volume and VAT/SAT_volume ratio by MRI represents a reproducable biomarker associated with cardiometabolic risk factors in subjects with impaired glucose metabolism, while the association of VAT/SAT_volume ratio with glycemic state is attenuated in obese subjects.

Insulin resistance in lean and overweight non-diabetic Caucasian adults: Study of its relationship with liver triglyceride content, waist circumference and BMI

Aims

Insulin resistance is the pathophysiological precursor of type 2 diabetes mellitus (DM-2), and its relationship with non-alcoholic fatty liver disease (NAFLD) has been widely studied in patients with obesity or metabolic syndrome using not only ultrasound but also liver biopsies or proton magnetic resonance spectroscopy (H¹-MRS) to assess liver fat content. In contrast, there are no studies on insulin resistance and NAFLD in lean or overweight Caucasian individuals using H¹-MRS or liver biopsies for the quantification of hepatic triglyceride content. Our objectives were to study the presence of insulin resistance in lean and overweight Caucasian adults and investigate its possible relationship with liver triglyceride content, waist circumference (as proxy of visceral adiposity), BMI, and cardiometabolic risk factors.

Methods

A cross-sectional study was conducted in 113 non-obese, non-diabetic individuals classified as overweight (BMI 25–29.9 kg/m²) or lean (BMI 19.5–24.9 kg/m²). Hepatic triglyceride content was quantified by 3T H¹-MRS. NAFLD was defined as hepatic triglyceride content >5.56%. Insulin resistance (HOMA-IR), serum adiponectin, and tumor necrosis factor (TNF) were determined.

Results

HOMA-IR was significantly correlated with hepatic triglyceride content (r:0.76; p<0.0001). The lean-with-NAFLD group had significantly higher HOMA-IR (p<0.001) and lower serum adiponectin (p<0.05) than the overweight-without-NAFLD group. Insulin resistance was independently associated with NAFLD but not with waist circumference or BMI. Regression analysis showed hepatic triglyceride content to be the most important determinant of insulin resistance (p<0.01).

Conclusions

Our findings suggest that NAFLD, once established, seems to be involved in insulin resistance and cardio-metabolic risk factors above and beyond waist circumference and BMI in non-obese, non-diabetic Caucasian individuals.

Relation of Ectopic Fat with Atherosclerotic Cardiovascular Disease Risk Score in South Asians Living in the United States (from the Mediators of Atherosclerosis in South Asians Living in America [MASALA] Study)

Few studies have investigated the association between ectopic fat from different depots and cardiovascular risk scores and their components in the same population, and none have investigated these relations in South Asians. In a cross-sectional analysis of 796 participants in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study who had measurements of visceral, subcutaneous, pericardial, hepatic, and intermuscular fat from abdominal and cardiac computed tomography scans, we used linear regression to determine the associations of 1 standard deviation difference in each ectopic fat depot with pooled cohort risk score and its components. Pericardial and visceral fat were more strongly associated with the pooled cohort risk score (3.1%, 95% confidence interval [CI] 2.5 to 3.7, and 2.7%, 95% CI 2.1 to 3.3, respectively) and components than intermuscular fat (2.3%, 95% CI 1.7 to 3.0); subcutaneous fat was inversely associated with the pooled cohort risk score (-2.6%, 95% CI -3.2 to 1.9) and hepatic fat attenuation was not linearly associated with the pooled cohort risk score when mutually adjusted (-0.3%, 95% CI -0.9 to 0.4). Associations for risk factor components differed by fat depot. In conclusion, subcutaneous and hepatic fat may have different functions than fat stored in other depots in South Asians. Determining whether these relations are heterogeneous by race may help elucidate the mechanisms underlying CVD disparities.

Nonalcoholic Fatty Liver Disease and Metabolic Syndrome

Nonalcoholic fatty liver disease (NAFLD) and metabolic syndrome (MS) are highly prevalent, affecting approximately one-third of the US population. The relationship between NAFLD and MS is complex and may be bidirectionally associated. NAFLD is strongly associated with MS, the components of which include abdominal obesity, hyperglycemia, hypertension, and dyslipidemia. NAFLD associated with certain genetic factors such as the PNPLA3 G allele variant is not accompanied by insulin resistance and MS. Lifestyle modification, including diet and physical activity targeting visceral adiposity, remains the standard of care for patients with NAFLD and MS.

Fibroblast growth factor 21 increases insulin sensitivity through specific expansion of subcutaneous fat

Although the pharmacological effects of fibroblast growth factor 21 (FGF21) are well-documented, uncertainty about its role in regulating excessive energy intake remains. Here, we show that FGF21 improves systemic insulin sensitivity by promoting the healthy expansion of subcutaneous adipose tissue (SAT). Serum FGF21 levels positively correlate with the SAT area in insulin-sensitive obese individuals. FGF21 knockout mice (FGF21KO) show less SAT mass and are more insulin-resistant when fed a high-fat diet. Replenishment of recombinant FGF21 to a level equivalent to that in obesity restores SAT mass and reverses insulin resistance in FGF21KO, but not in adipose-specific βklotho knockout mice. Moreover, transplantation of SAT from wild-type to FGF21KO mice improves insulin sensitivity in the recipients. Mechanistically, circulating FGF21 upregulates adiponectin in SAT, accompanied by an increase of M2 macrophage polarization. We propose that elevated levels of endogenous FGF21 in obesity serve as a defense mechanism to protect against systemic insulin resistance.

FGF21 has a number of beneficial metabolic effects. Here, Li et al. show that FGF21 promotes the healthy expansion of subcutaneous white adipose tissue, promoting the healthy expansion of fat tissue as a regulatory mechanism to maintain systemic insulin sensitivity during nutrient excess.

Associations of Abdominal Subcutaneous and Visceral Fat with Insulin Resistance and Secretion Differ Between Men and Women: The Netherlands Epidemiology of Obesity Study

BACKGROUND

Abdominal obesity is a well-established risk factor for the development of type 2 diabetes. However, sex differences may exist. We aimed to investigate the associations of abdominal subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) with insulin resistance and insulin secretion in men and women.

METHODS

In this cross-sectional analysis of the Netherlands Epidemiology of Obesity study, fasting and postprandial concentrations of glucose and insulin were measured and abdominal fat depots were assessed using magnetic resonance imaging in 2253 participants (53% women). With linear regression analysis, we examined associations of abdominal SAT and VAT with measures of insulin resistance and insulin secretion in men and women, while adjusting for age, ethnicity, education, smoking habits, alcohol consumption, menopausal state and hormone use in women, and models with VAT additionally for total body fat.

RESULTS

Participants had a mean [standard deviation (SD)] age of 56 (6) years, body mass index: 25.9 (3.9) kg/m², VAT: 89 (55) cm², and SAT: 235 (95) cm². In the multivariate models in men, per SD of VAT the homeostatic model assessment of insulin resistance (HOMA-IR) was 20% (95% CI: 14-26) higher, and per SD SAT 21% (15-27) higher. In women, per SD of VAT the HOMA-IR was 40% (29-52) higher, and per SD SAT 12% (6-19) higher. Associations with measures of insulin secretion were weaker than with insulin resistance.

CONCLUSIONS

In men, abdominal SAT and VAT were associated with insulin resistance to a similar extent, whereas in women particularly VAT was associated with insulin resistance and insulin secretion. Future studies need to unravel the mechanisms underlying the metabolic effects of visceral fat in women. Simple and less expensive measures that can distinct abdominal subcutaneous and visceral fat are needed for an improved metabolic risk stratification.

Correlation between obesity and fat-infiltrated axillary lymph nodes visualized on mammography

OBJECTIVE

Using screening mammography, this study investigated the association between obesity and axillary lymph node (LN) size and morphology.

METHODS

We conducted a retrospective review of 188 females who underwent screening mammography at an academic medical centre. Length and width of the LN and hilum were measured in the largest, mammographically visible axillary node. The hilo-cortical ratio (HCR) was calculated as the hilar width divided by the cortical width. Measurements were performed by a board certified breast radiologist and a resident radiology physician. Inter-rater agreement was assessed with Pearson correlation coefficient. We performed multivariable regression analysis for associations of LN measurements with body mass index (BMI), breast density and age.

RESULTS

There was a strong association between BMI and LN dimensions, hilum dimensions and HCR (p < 0.001 for all metrics). There was no significant change in cortex width with increasing BMI (p = 0.15). Increases in LN length and width were found with increasing BMI [0.6 mm increase in length per unit BMI, 95% CI (0.4-0.8), p < 0.001 and0.3 mm increase in width per unit BMI, 95% CI(0.2-0.4), p < 0.001, respectively]. Inter-rater reliability for lymph node and hilum measurements was 0.57-0.72.

CONCLUSION

We found a highly significant association between increasing BMI and axillary LN dimensions independent of age and breast density with strong interobserver agreement. The increase in LN size was driven by expansion of the LN hilum secondary to fat infiltration. Advances in knowledge: This preliminary work determined a relationship between fat infiltrated axillary lymph nodes and obesity.

Body fat distribution is more predictive of all-cause mortality than overall adiposity

AIMS

The relationship between directly measured body fat and all-cause mortality has been rarely studied. The aim of this study was to evaluate the predictive significance of computed tomography (CT)-measured body fat, including both visceral fat area (VFA) and subcutaneous fat area (SFA), for mortality.

METHODS

The study included 36 656 participants who underwent abdominal CT as part of a health check-up at a single university-affiliated healthcare center in 2007 to 2015. Of those, 32 593 participants with data regarding vital status as of May 2016 were included in the final analysis. The main factors evaluated were VFA, SFA and visceral-to-subcutaneous fat area ratio (VSR), and the primary outcome was all-cause mortality.

RESULTS

There were 253 deaths during a mean follow-up of 5.7 years. Increased SFA was associated with decreased all-cause mortality, whereas an increased VFA and VSR were related to increased all-cause mortality. Compared with the predictive power of body mass index (BMI), SFA and VSR showed a larger area under the curve than did BMI. In Kaplan-Meier survival curve analysis, increased SFA and VSR were associated with decreased and increased hazard of all-cause death, respectively. However, in multivariate Cox proportional hazard regression analysis, only VSR was independently associated with all-cause mortality. Moreover, this relationship was paralleled by the harmful impact of increased VSR on metabolic profiles.

CONCLUSION

Increased VSR was an independent predictor of all-cause mortality. This suggests that the location of fat deposits may be more important than the actual amount of body fat.

Salivary adiponectin concentration in healthy adult males in relation to anthropometric measures and fat distribution

Objectives. Body fat content, fat distribution, and adiponectin level are important variables in the development of obesity related complications. Anthropometric indices may provide an economic and faster method in measuring the risk for complications through their predictive effect of fat distribution and adiponectin concentration. We aimed to determine, which of the waist circumference (WC), waist-to-hip ratio (WHR), and body mass index (BMI) may be the best predictor for the total fat percentage (WF), visceral fat level (VF), and subcutaneous whole-body fat (SCWBF). We aimed also to investigate the potential use of the anthropometric measures and fat distribution as predictors for the salivary adiponectin level in the healthy adult males. Subjects. A total of 88 adult males aged between 18−25 years with a wide range of BMI were studied. Anthropometric indices were measured using standardized methods and salivary adiponectin level was assessed using an enzyme-linked immunosorbent assay. Results. In path analysis of the Structural Equation Model (SEM) using IBM@SPSS AMOS, version22, BMI and WC, but not WHR, were strong predictors for WF and SCWBF (p<0.05). BMI but not WC was a strong predictor for VF (p<0.001). WF was strong predictor for SCWBF (p<0.001), but not for VF. BMI, WC, WHR, WF, VF, and SCWBF were poor predictors of the salivary adiponectin level. Conclusion. BMI is the best predictor for the total body fat and fat distribution. However, WHR seems to be of a little value and the salivary adiponectin level independent of BMI and body fat in healthy adult Malay males.

Effects of exenatide twice daily, exenatide once weekly or insulin in patients with type 2 diabetes and baseline HbA1c ≥10.0%: Two pooled analyses including 20 randomised controlled trials

AIMS

Patients with advanced type 2 diabetes (T2D) and high glycated haemoglobin (HbA1c) values can be difficult to treat because of their severe metabolic disease. This pooled analysis examined the treatment effects of exenatide twice daily (BID), exenatide once weekly (QW) and insulin in patients with high baseline HbA1c (≥10.0%).

METHODS

This post hoc analysis used pooled data from 12 and 8 randomised controlled trials of exenatide BID and exenatide QW, respectively. Patients with T2D who completed at least 24 weeks of treatment with exenatide BID, exenatide QW or insulin (insulin glargine, insulin detemir or insulin aspart) were categorised by baseline HbA1c. Patients with HbA1c ≥10.0% were included in the analysis.

RESULTS

Both exenatide and insulin reduced HbA1c (mean ± SE reduction: -2.0% ± 0.2% [exenatide] and -2.1% ± 0.2% [insulin] in the exenatide BID studies, and -2.6% ± 0.1% [exenatide] and -2.1% ± 0.2% [insulin] in the exenatide QW studies; all P < .001). Body weight decreased with exenatide and increased with insulin. Systolic blood pressure decreased with exenatide QW. Insulin dose increased over the course of treatment. The most common adverse events with exenatide were gastrointestinal. Insulin was associated with some hypoglycaemia risk. Hypoglycaemia events occurred infrequently with exenatide when given without sulphonylureas.

CONCLUSIONS

For patients with high HbA1c, treatment with exenatide or insulin both improved glycaemic control. Given the associated weight loss and low risk of hypoglycaemia, exenatide may be a suitable alternative to treatment with insulin in certain patients with T2D and high HbA1c.

Visceral and subcutaneous abdominal adiposity and pulmonary function in 30-year-old adults: a cross-sectional analysis nested in a birth cohort

BACKGROUND

Several studies have verified body fat distribution in association with pulmonary function (PF), mainly waist circumference, but few have used measures able to distinguish abdominal fat compartments. The present study aims to verify the association of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) with PF measures.

METHODS

In 1982, all hospital births occurring in Pelotas, Brazil, were identified and those livebirths have been followed. In 2012-13, the cohort participants were evaluated and VAT and SAT measured using ultrasound; forced expiratory volume in the first second (FEV₁) or forced vital capacity (FVC) were patronized in z-scores stratified by sex. The associations were verified using crude and adjusted linear regressions.

RESULTS

The present analyses comprised 3438 individuals (1721 women). VAT was inversely associated with spirometric parameters, in both crude and adjusted models. SAT showed inverse associations in the crude analyzes in males and a positive trend after adjustment, except for SAT and FVC in males. To each centimeter of VAT, mean adjusted FEV₁ z-scores decreased 0.072 (95% CI -0.107; -0.036) in men and 0.127 (95% CI -0.164; -0.090) in women, and FVC z-scores decreased -0.075 (95% CI -0.111; -0.039) and 0.121 (95% CI -0.158; -0.083), in men and women, respectively.

CONCLUSIONS

VAT has a consistent inverse association with FEV₁ and FVC in both sexes. On the other hand, SAT showed inconsistent results with PF parameters.

Comparison of regional fat measurements by dual-energy X-ray absorptiometry and conventional anthropometry and their association with markers of diabetes and cardiovascular disease risk

Background/Objectives:

Fat distribution is a strong and independent predictor of type 2 diabetes (T2D) and cardiovascular disease (CVD) and is usually determined using conventional anthropometry in epidemiological studies. Dual-energy X-ray absorptiometry (DXA) can measure total and regional adiposity more accurately. Nonetheless, whether DXA provides more precise estimates of cardiovascular risk in relation to total and regional adiposity is not known. We determined the strength of the associations between DXA- and conventional anthropometry determined fat distribution and T2D and CVD risk markers.

Subjects/Methods:

Waist (WC) and hip circumference (HC) and DXA was used to measure total and regional adiposity in 4950 (2119 men) participants aged 29–55 years from the Oxford Biobank without pre-existing T2D or CVD. Cross-sectional associations were compared between WC and HC vs. DXA-determined regional adiposity (all z-score normalised) with impaired fasting glucose, hypertriglyceridemia, hypertension and insulin resistance (IR).

Results:

Following adjustment for total adiposity, upper body adiposity measurements showed consistently increased risk of T2D and CVD risk markers except for abdominal subcutaneous fat in both sexes, and arm fat in men, which showed protective associations. Among upper adiposity depots, visceral fat mass showed stronger odds ratios (OR) ranging from 1.69 to 3.64 compared with WC 1.07–1.83. Among lower adiposity depots, HC showed modest protection for IR in both sexes (men: OR 0.80 (95% confidence interval 0.67, 0.96); women: 0.69 (0.56, 0.86)), whereas gynoid fat and in particular leg fat showed consistent and strong protective effects for all outcomes in both men and women. The differential effect of body fat distribution on CVD and T2D were more pronounced at higher levels of total adiposity.

Conclusions:

Compared with DXA, conventional anthropometry underestimates the associations of regional adiposity with T2D and CVD risk markers. After correcting for overall adiposity, greater subcutaneous fat mass in particular in the lower body is protective relative to greater android or visceral adipose tissue mass.

CT-Derived Body Fat Distribution and Incident Cardiovascular Disease: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Visceral fat has been shown to be associated with increased cardiometabolic risk, but the role of subcutaneous fat remains unclear, and evidence from diverse populations is lacking. We hypothesized that visceral fat, but not subcutaneous fat, would be independently associated with incident cardiovascular disease (CVD) and all-cause mortality.

METHODS

Among 1910 participants from the Multi-Ethnic Study of Atherosclerosis with abdominal fat measurements from computed tomography scans and followed for an average of 9.3 years, we used multivariable Cox proportional hazards models to investigate the relationship of both visceral and subcutaneous fat tertiles with CVD and all-cause mortality. We tested for interaction and performed sensitivity analysis for subgroups and missing values of visceral fat.

RESULTS

Participants had mean age of 65 years, visceral fat 150 cm2, subcutaneous fat 263 cm2, and 50% were female, 21% African American, 13% Asian, and 26% Hispanic. In models adjusted for age, sex, race/ethnicity, income, education, smoking, and subcutaneous fat, there was a statistically significant positive association between visceral fat and CVD, but not mortality. The association for combined CVD may be driven by incident coronary heart disease [tertile 2: hazard ratio, 2.43 (1.38 to 4.28); tertile 3: hazard ratio, 3.00 (1.66 to 5.43)]. Additionally, we found no substantial associations between subcutaneous fat and CVD or mortality. There were no statistically significant interactions by age, sex, or race/ethnicity.

CONCLUSIONS

Visceral fat, but not subcutaneous fat, is significantly associated with increased risk for CVD in a multiethnic cohort. These data support the need for effective strategies for lifestyle changes that prevent and reduce visceral fat.

Comparison of serum vaspin levels and vaspin expression in adipose tissue and smooth muscle tissue in pregnant women with and without gestational diabetes

OBJECTIVE

Vaspin is associated with metabolic parameters and insulin resistance. However, the expression of vaspin in visceral adipose tissue (VAT) in pregnant women with gestational diabetes mellitus (GDM) has not been fully explored, and the contribution of vaspin to the biological mechanisms underlying GDM remains unclear. This study aimed to compare circulating vaspin levels and its expression in different insulin target tissues including subcutaneous adipose tissue (SAT), VAT and smooth muscle tissue (SMT) in pregnant women with and without GDM.

DESIGN

A total of 37 women with GDM (GDM group) and 37 normal pregnant women (control group) were selected. Fasting plasma glucose (FPG), fasting insulin (FINS) and serum vaspin levels were quantified at term, and homeostasis model of assessment2-insulin resistance (HOMA2-IR) values were calculated. RT-qPCR and Western blotting were used to measure mRNA and protein levels of vaspin in VAT, SAT and SMT of 15 GDM women and normal pregnant women.

RESULTS

In the GDM group, serum vaspin concentrations were significantly higher than in the control group. Serum vaspin levels were positively correlated with HOMA2-IR in the GDM group but not in the control group. In the GDM group, vaspin mRNA and protein expression levels in SAT and VAT were both significantly higher than in controls, but no difference was found in SMT. Moreover, relative mRNA but not protein expression levels of vaspin in SAT were highest among the three tissues in both groups.

CONCLUSIONS

Circulating vaspin levels and expression of vaspin in SAT and VAT were higher in GDM women than in normal pregnant women. However, the specific role of vaspin from SAT and VAT in the pathogenesis of GDM needs further study.

Intermittent hypoxia-induced insulin resistance is associated with alterations in white fat distribution

Sleep apnea syndrome is characterized by repetitive upper airway collapses during night leading to intermittent hypoxia (IH). The latter is responsible for metabolic disturbances that rely, at least in part, on abdominal white fat inflammation. Besides qualitative alterations, we hypothesized that IH could also modify body fat distribution, a key factor for metabolic complications. C57BL6 mice exposed to IH (21-5% FiO₂, 60 s cycle, 8 h/day) or air for 6 weeks were investigated for topographic fat alterations (whole-body MRI). Specific role of epididymal fat in IH-induced metabolic dysfunctions was assessed in lipectomized or sham-operated mice exposed to IH or air. Whereas total white fat volume was unchanged, IH induced epididymal adipose tissue (AT) loss with non-significant increase in subcutaneous and mesenteric fat. This was associated with impaired insulin sensitivity and secretion. Epididymal lipectomy led to increased subcutaneous fat in the perineal compartment and prevented IH-induced metabolic disturbances. IH led to reduced epididymal AT and impaired glucose regulation. This suggests that, rather than epididymal AT volume, qualitative fat alterations (i.e. inflammation) could represent the main determinant of metabolic dysfunction. This deterioration of glucose regulation was prevented in epididymal-lipectomized mice, possibly through prevention of IH-induced epididymal AT alterations and compensatory increase in subcutaneous AT.

Body Fat Distribution and the Risk of Incident Metabolic Syndrome: A Longitudinal Cohort Study

The effect of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) area on metabolic syndrome (MS) has been debated. We aimed to evaluate the effects of VAT and SAT on the incidence of MS and its components in a large and apparently healthy Asian population. We performed a longitudinal cohort study of 1,964 subjects who received health screenings over a 5-year follow-up period; 317 incidents of MS (16.1%) were observed during a median follow-up of 4.5 years. The VAT area was significantly associated with a higher incidence of MS; the adjusted HR for incident MS per 1 SD of VAT was 1.50 (95% CI 1.29-1.74), and the adjusted HR of the 5th VAT quintile compared with the 1st quintile was 3.73 (95% CI 2.22-6.28). However, the SAT area was not associated with incident MS. Although the VAT area was longitudinally associated with the incidence of each component of MS, the SAT area was inversely associated with the risk of high blood pressure, fasting blood sugar, and triglycerides, with marginal significance. In conclusion, the VAT area is longitudinally associated with an increased risk of incident MS, while SAT may have a protective effect against the incidence of individual MS components.