Variation in adrenergic regulation of lipolysis between omental and subcutaneous adipocytes from obese and non-obese men

FGF21 mediating the Sex-dependent Response to Dietary Macronutrients

Sex is key variable influencing body composition and substrate utilization. At rest, females maintain greater adiposity than males and resist the mobilization of fat. Males maintain greater lean muscle mass and mobilize fat readily. Determining the mechanisms that direct these sex-dependent effects is important for both reproductive and metabolic health. Here, we highlight the fundamental importance of sex in shaping metabolic physiology and assess growing evidence that the hepatokine fibroblast growth factor-21 (FGF21) plays a mechanistic role to facilitate sex-dependent responses to a changing nutritional environment. First, we examine the importance of sex in modulating body composition and substrate utilization. We summarize new data that point toward sex-biased effects of pharmacologic FGF21 administration on these endpoints. When energy is not limited, metabolic responses to FGF21 mirror broader sex differences; FGF21-treated males conserve lean mass at the expense of increased lipid catabolism, whereas FGF21-treated females conserve fat mass at the expense of reduced lean mass. Next, we examine the importance of sex in modulating the endogenous secretion of FGF21 in response to changing macronutrient and energy availability. During the resting state when energy is not limited, macronutrient imbalance increases the secretion of FGF21 more so in males than females. When energy is limited, the effect of sex on both the secretion of FGF21 and its metabolic actions may be reversed. Altogether, we argue that a growing literature supports FGF21 as a plausible mechanism contributing to the sex-dependent mobilization vs preservation of lipid storage and highlight the need for further research.

Adipose tissue as a linchpin of organismal ageing

Ageing is a conserved biological process, modulated by intrinsic and extrinsic factors, that leads to changes in life expectancy. In humans, ageing is characterized by greatly increased prevalence of cardiometabolic disease, type 2 diabetes and disorders associated with impaired immune surveillance. Adipose tissue displays species-conserved, temporal changes with ageing, including redistribution from peripheral to central depots, loss of thermogenic capacity and expansion within the bone marrow. Adipose tissue is localized to discrete depots, and also diffusely distributed within multiple organs and tissues in direct proximity to specialized cells. Thus, through their potent endocrine properties, adipocytes are capable of modulating tissue and organ function throughout the body. In addition to adipocytes, multipotent progenitor/stem cells in adipose tissue play a crucial role in maintenance and repair of tissues throughout the lifetime. Adipose tissue may therefore be a central driver for organismal ageing and age-associated diseases. Here we review the features of adipose tissue during ageing, and discuss potential mechanisms by which these changes affect whole-body metabolism, immunity and longevity. We also explore the potential of adipose tissue-targeted therapies to ameliorate age-associated disease burdens.

The pathophysiology of visceral adipose tissues in cardiometabolic diseases

Central pattern of fat distribution, especially fat accumulation within the intraabdominal cavity increases risks for cardiometabolic diseases. Portal hypothesis combined with a pathological remodeling in visceral fat is considered the major etiological factor explaining the independent contribution of visceral obesity to cardiometabolic diseases. Excessive remodeling in visceral fat during development of obesity leads to dysfunctions in the depot, characterized by hypertrophy and death of adipocytes, hypoxia, inflammation, and fibrosis. Dysfunctional visceral fat secretes elevated levels of fatty acids, glycerol, and proinflammatory and profibrotic cytokines into the portal vein directly impacting the liver, the central regulator of systemic metabolism. These metabolic and endocrine products induce ectopic fat accumulation, insulin resistance, inflammation, and fibrosis in the liver, which in turn causes or exacerbates systemic metabolic derangements. Elucidation of underlying mechanisms that lead to the pathological remodeling and higher degree of dysfunctions in visceral adipose tissue is therefore, critical for the development of therapeutics to prevent deleterious sequelae in obesity. We review depot differences in metabolic and endocrine properties and expendabilities as well as underlying mechanisms that contribute to the pathophysiological aspects of visceral adiposity in cardiometabolic diseases. We also discuss impacts of different weight loss interventions on visceral adiposity and cardiometabolic diseases.

White adipocyte dysfunction and obesity-associated pathologies in humans

The prevalence of obesity and associated chronic diseases continues to increase worldwide, negatively impacting on societies and economies. Whereas the association between excess body weight and increased risk for developing a multitude of diseases is well established, the initiating mechanisms by which weight gain impairs our metabolic health remain surprisingly contested. In order to better address the myriad of disease states associated with obesity, it is essential to understand adipose tissue dysfunction and develop strategies for reinforcing adipocyte health. In this Review we outline the diverse physiological functions and pathological roles of human white adipocytes, examining our current knowledge of why white adipocytes are vital for systemic metabolic control, yet poorly adapted to our current obesogenic environment.

Visceral Adipose Tissue Depth as a Novel Predictor for Gestational Diabetes Mellitus: A Comprehensive Meta-Analysis and Systematic Review

Background and Objectives: The escalating prevalence of gestational diabetes mellitus (GDM) and the limitations associated with utilizing body mass index (BMI) as a predictive measure underscore the imperative need for identifying an optimal early pregnancy predictor. Such a predictor not only mitigates the risk of GDM but also allows for timely implementation of interventions. Materials and Methods: This meta-analysis aimed to explore the association between visceral adipose tissue (VAT) depth and the risk of GDM. A thorough search of PubMed, Embase, and Web of Science databases was conducted up to 30 September 2023. The analysis employed a random-effects model to assess the relationship between VAT depth and the likelihood of GDM. Results: The inclusion criteria encompassed seven studies involving 1315 women, including 225 diagnosed with GDM. Significantly lower VAT depth was observed in the non-GDM group in comparison to the GDM group (Standardized Mean Difference [SMD]: 0.84; 95% Confidence Interval [CI]: 0.52-1.15; p < 0.001). Substantial statistical heterogeneity was noted among studies (I2 = 72.88%, p = 0.001). Through meticulous sensitivity and subgroup analyses, the source of heterogeneity was identified and thoroughly discussed. Subgroup analyses suggest that different GDM diagnostic criteria and VAT definitions all indicate higher VAT depth in GDM patients during early pregnancy. Conclusions: Our findings propose that, during the first trimester, GDM patients exhibit higher VAT depth compared to non-GDM women, highlighting VAT depth as a potential predictive factor for GDM in early pregnancy. This study contributes valuable evidence to the growing body of knowledge surrounding novel predictors for GDM, emphasizing the importance of early intervention strategies.

Adipose organ dysfunction and type 2 diabetes: Role of nitric oxide

Adipose organ, historically known as specialized lipid-handling tissue serving as the long-term fat depot, is now appreciated as the largest endocrine organ composed of two main compartments, i.e., subcutaneous and visceral adipose tissue (AT), madding up white and beige/brown adipocytes. Adipose organ dysfunction manifested as maldistribution of the compartments, hypertrophic, hypoxic, inflamed, and insulin-resistant AT, contributes to the development of type 2 diabetes (T2D). Here, we highlight the role of nitric oxide (NO·) in AT (dys)function in relation to developing T2D. The key aspects determining lipid and glucose homeostasis in AT depend on the physiological levels of the NO· produced via endothelial NO· synthases (eNOS). In addition to decreased NO· bioavailability (via decreased expression/activity of eNOS or scavenging NO·), excessive NO· produced by inducible NOS (iNOS) in response to hypoxia and AT inflammation may be a critical interfering factor diverting NO· signaling to the formation of reactive oxygen and nitrogen species, resulting in AT and whole-body metabolic dysfunction. Pharmacological approaches boosting AT-NO· availability at physiological levels (by increasing NO· production and its stability), as well as suppression of iNOS-NO· synthesis, are potential candidates for developing NO·-based therapeutics in T2D.

Androgen receptor actions on AgRP neurons are not a major cause of reproductive and metabolic impairments in peripubertally androgenized mice

Excess levels of circulating androgens during prenatal or peripubertal development are an important cause of polycystic ovary syndrome (PCOS), with the brain being a key target. Approximately half of the women diagnosed with PCOS also experience metabolic syndrome; common features including obesity, insulin resistance and hyperinsulinemia. Although a large amount of clinical and preclinical evidence has confirmed this relationship between androgens and the reproductive and metabolic features of PCOS, the mechanisms by which androgens cause this dysregulation are unknown. Neuron-specific androgen receptor knockout alleviates some PCOS-like features in a peripubertal dihydrotestosterone (DHT) mouse model, but the specific neuronal populations mediating these effects are undefined. A candidate population is the agouti-related peptide (AgRP)-expressing neurons, which are important for both reproductive and metabolic function. We used a well-characterised peripubertal androgenized mouse model and Cre-loxP transgenics to investigate whether deleting androgen receptors specifically from AgRP neurons can alleviate the induced reproductive and metabolic dysregulation. Androgen receptors were co-expressed in 66% of AgRP neurons in control mice, but only in <2% of AgRP neurons in knockout mice. The number of AgRP neurons was not altered by the treatments. Only 20% of androgen receptor knockout mice showed rescue of DHT-induced androgen-induced anovulation and acyclicity. Furthermore, androgen receptor knockout did not rescue metabolic dysfunction (body weight, adiposity or glucose and insulin tolerance). While we cannot rule out developmental compensation in our model, these results suggest peripubertal androgen excess does not markedly influence Agrp expression and does not dysregulate reproductive and metabolic function through direct actions of androgens onto AgRP neurons.

Discovering cellular programs of intrinsic and extrinsic drivers of metabolic traits using LipocyteProfiler

A primary obstacle in translating genetic associations with disease into therapeutic strategies is elucidating the cellular programs affected by genetic risk variants and effector genes. Here, we introduce LipocyteProfiler, a cardiometabolic-disease-oriented high-content image-based profiling tool that enables evaluation of thousands of morphological and cellular profiles that can be systematically linked to genes and genetic variants relevant to cardiometabolic disease. We show that LipocyteProfiler allows surveillance of diverse cellular programs by generating rich context- and process-specific cellular profiles across hepatocyte and adipocyte cell-state transitions. We use LipocyteProfiler to identify known and novel cellular mechanisms altered by polygenic risk of metabolic disease, including insulin resistance, fat distribution, and the polygenic contribution to lipodystrophy. LipocyteProfiler paves the way for large-scale forward and reverse deep phenotypic profiling in lipocytes and provides a framework for the unbiased identification of causal relationships between genetic variants and cellular programs relevant to human disease.

Of mice and men: Pinpointing species differences in adipose tissue biology

The prevalence of obesity and metabolic diseases continues to rise, which has led to an increased interest in studying adipose tissue to elucidate underlying disease mechanisms. The use of genetic mouse models has been critical for understanding the role of specific genes for adipose tissue function and the tissue’s impact on other organs. However, mouse adipose tissue displays key differences to human fat, which has led, in some cases, to the emergence of some confounding concepts in the adipose field. Such differences include the depot-specific characteristics of visceral and subcutaneous fat, and divergences in thermogenic fat phenotype between the species. Adipose tissue characteristics may therefore not always be directly compared between species, which is important to consider when setting up new studies or interpreting results. This mini review outlines our current knowledge about the cell biological differences between human and mouse adipocytes and fat depots, highlighting some examples where inadequate knowledge of species-specific differences can lead to confounding results, and presenting plausible anatomic explanations that may underlie the differences. The article thus provides critical insights and guidance for researchers working primarily with only human or mouse fat tissue, and may contribute to new ideas or concepts in the important and evolving field of adipose biology.

The acromegaly lipodystrophy

Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are essential to normal growth, metabolism, and body composition, but in acromegaly, excesses of these hormones strikingly alter them. In recent years, the use of modern methodologies to assess body composition in patients with acromegaly has revealed novel aspects of the acromegaly phenotype. In particular, acromegaly presents a unique pattern of body composition changes in the setting of insulin resistance that we propose herein to be considered an acromegaly-specific lipodystrophy. The lipodystrophy, initiated by a distinctive GH-driven adipose tissue dysregulation, features insulin resistance in the setting of reduced visceral adipose tissue (VAT) mass and intra-hepatic lipid (IHL) but with lipid redistribution, resulting in ectopic lipid deposition in muscle. With recovery of the lipodystrophy, adipose tissue mass, especially that of VAT and IHL, rises, but insulin resistance is lessened. Abnormalities of adipose tissue adipokines may play a role in the disordered adipose tissue metabolism and insulin resistance of the lipodystrophy. The orexigenic hormone ghrelin and peptide Agouti-related peptide may also be affected by active acromegaly as well as variably by acromegaly therapies, which may contribute to the lipodystrophy. Understanding the pathophysiology of the lipodystrophy and how acromegaly therapies differentially reverse its features may be important to optimizing the long-term outcome for patients with this disease. This perspective describes evidence in support of this acromegaly lipodystrophy model and its relevance to acromegaly pathophysiology and the treatment of patients with acromegaly.

Change of Computed Tomography-Based Body Composition after Adrenalectomy in Patients with Pheochromocytoma

Despite the potential biological importance of the sympathetic nervous system on fat and skeletal muscle metabolism in animal and in vitro studies, its relevance in humans remains undetermined. To clarify the influence of catecholamine excess on human body composition, we performed a retrospective longitudinal cohort study including 313 consecutive patients with histologically confirmed pheochromocytoma who underwent repeat abdominal computed tomography (CT) scans before and after adrenalectomy. Changes in CT-determined visceral fat area (VFA), subcutaneous fat area (SFA), skeletal muscle area (SMA), and skeletal muscle index (SMI) were measured at the level of the third lumbar vertebra. The mean age of all patients was 50.6 ± 13.6 years, and 171/313 (54.6%) were women. The median follow-up duration for repeat CTs was 25.0 months. VFA and SFA were 14.5% and 15.8% higher, respectively (both p < 0.001), after adrenalectomy, whereas SMA and SMI remained unchanged. Similarly, patients with visceral obesity significantly increased from 103 (32.9%) at baseline to 138 (44.1%) following surgery (p < 0.001); however, the prevalence of sarcopenia was unchanged. This study provides important clinical evidence that sympathetic hyperactivity can contribute to lipolysis in visceral and subcutaneous adipose tissues, but its impact on human skeletal muscle is unclear.

Glucose enhances catecholamine-stimulated lipolysis via increased glycerol-3-phosphate synthesis in 3T3-L1 adipocytes and rat adipose tissue

BACKGROUND

During lipolysis, triglyceride (TG) are hydrolyzed into a glycerol and fatty acids in adipocyte. A significant portion of the fatty acids are re-esterificated into TG, and this is a critical step in promoting lipolysis. Although glycerol-3-phosphate (G3P) is required for triglyceride synthesis in mammalian cell, the substrate for G3P synthesis during active lipolysis is not known. A recent study showed that the inhibition of glucose uptake reduces catecholamine-stimulated lipolysis, suggesting that glucose availability is important in lipolysis in adipocytes. We hypothesized that glucose might play an essential role in generating G3P and thereby promoting catecholamine-stimulated lipolysis in adipocytes. Therefore, we determined the effect of glucose availability on catecholamine-stimulated lipolysis in 3T3-L1 adipocytes and rat adipose tissue.

METHODS AND RESULTS

3T3-L1 adipocytes and rat epididymal fat pads were cultured in a medium with/without glucose during stimulation by isoproterenol. Glycerol release was higher when adipocytes were cultured in a glucose-containing medium than that in a medium without glucose. Measurement of glucose uptake during catecholamine-stimulated lipolysis showed a slight, but significant increase in glucose uptake. We also compared glucose metabolism-related protein, such as glucose transporter 4, hexokinase, glycerol-3-phosphate dehydrogenase and lipase contents between fat tissues that play a critical role in active lipolysis. Epididymal fat exhibited higher lipolytic activity than inguinal fat because of higher lipase and glucose metabolism-related protein contents.

CONCLUSION

We demonstrated that catecholamine-stimulated lipolysis is enhanced in the presence of glucose, and suggests that glucose is one of the primary substrates for G3P in adipocytes during active lipolysis.

Body Composition Changes with Long-term Pegvisomant Therapy of Acromegaly

Context

In active acromegaly, the lipolytic and insulin antagonistic effects of growth hormone (GH) excess alter adipose tissue (AT) deposition, reduce body fat, and increase insulin resistance. This pattern reverses with surgical therapy. Pegvisomant treats acromegaly by blocking GH receptor (GHR) signal transduction and lowering insulin-like growth factor 1 (IGF-1) levels. The long-term effects of GHR antagonist treatment of acromegaly on body composition have not been studied.

Methods

We prospectively studied 21 patients with active acromegaly who were starting pegvisomant. Body composition was examined by whole body magnetic resonance imaging, proton magnetic resonance spectroscopy of liver and muscle and dual-energy x-ray absorptiometry, and endocrine and metabolic markers were measured before and serially during 1.0 to 13.4 years of pegvisomant therapy. The data of patients with acromegaly were compared with predicted and to matched controls.

Results

Mass of visceral AT (VAT) increased to a peak of 187% (1.56-229%) (P < .001) and subcutaneous AT (SAT) to 109% (–17% to 57%) (P = .04) of baseline. These remained persistently and stably increased, but did not differ from predicted during long-term pegvisomant therapy. Intrahepatic lipid rose from 1.75% to 3.04 % (P = .04). Although lean tissue mass decreased significantly, skeletal muscle (SM) did not change. IGF-1 levels normalized, and homeostasis model assessment insulin resistance and HbA1C were lowered.

Conclusion

Long-term pegvisomant therapy is accompanied by increases in VAT and SAT mass that do not differ from predicted, stable SM mass and improvements in glucose metabolism. Long-term pegvisomant therapy does not produce a GH deficiency-like pattern of body composition change.

Acute physical and mental stress resulted in an increase in fatty acids, norepinephrine, and hemodynamic changes in normal individuals: A possible pathophysiological mechanism for hypertension-Pilot study

Hypertension is often associated with metabolic changes. The sustained increase in sympathetic activity is related to increased blood pressure and metabolic changes. Environmental stimuli may be related to increased sympathetic activity, blood pressure, and metabolic changes, especially in genetically predisposed individuals. The aim of this study was to evaluate the response of fatty acids to physical and mental stress in healthy volunteers and the hemodynamic, hormonal, and metabolic implications of these stimuli. Fifteen healthy individuals with a mean age of 31 ± 7 years, of both sexes, were evaluated. They were assessed at baseline and after combined physical and mental stress (isometric exercise test, Stroop color test). Blood samples were collected at baseline and after stimulation for glucose, insulin, fatty acid, and catecholamine levels. Blood pressure, heart rate, cardiac output, systemic vascular resistance, and distensibility of the large and small arteries were analyzed. The data obtained at baseline and after stimuli were from the same individual, being the control itself. Compared to baseline, after physical and mental stress there was a statistically significant increase (p < .05) in free fatty acids, norepinephrine, diastolic blood pressure, peripheral vascular resistance, and distensibility of the large and small arteries. In conclusion, the combination of physical and mental stress raised fatty acids, norepinephrine, diastolic blood pressure, and peripheral vascular resistance in healthy individuals.

Thermogenic adipocytes: lineage, function and therapeutic potential

Metabolic inflexibility, defined as the inability to respond or adapt to metabolic demand, is now recognised as a driving factor behind many pathologies associated with obesity and the metabolic syndrome. Adipose tissue plays a pivotal role in the ability of an organism to sense, adapt to and counteract environmental changes. It provides a buffer in times of nutrient excess, a fuel reserve during starvation and the ability to resist cold-stress through non-shivering thermogenesis. Recent advances in single-cell RNA sequencing combined with lineage tracing, transcriptomic and proteomic analyses have identified novel adipocyte progenitors that give rise to specialised adipocytes with diverse functions, some of which have the potential to be exploited therapeutically. This review will highlight the common and distinct functions of well-known adipocyte populations with respect to their lineage and plasticity, as well as introducing the most recent members of the adipocyte family and their roles in whole organism energy homeostasis. Finally, this article will outline some of the more preliminary findings from large data sets generated by single-cell transcriptomics of mouse and human adipose tissue and their implications for the field, both for discovery and for therapy.

Flow Cytometry of Mouse and Human Adipocytes for the Analysis of Browning and Cellular Heterogeneity

Adipocytes, once considered simple lipid-storing cells, are rapidly emerging as complex cells with many biologically diverse functions. A powerful high-throughput method for analyzing single cells is flow cytometry. Several groups have attempted to analyze and sort freshly isolated adipocytes; however, using an adipocyte-specific reporter mouse, we demonstrate that these studies fail to detect the majority of white adipocytes. We define critical settings required for adipocyte flow cytometry and provide a rigid strategy for analyzing and sorting white and brown adipocyte populations. The applicability of our protocol is shown by sorting mouse adipocytes based on size or UCP1 expression and demonstrating that a subset of human adipocytes lacks the β₂-adrenergic receptor, particularly in the insulin-resistant state. In conclusion, the present study confers key technological insights for analyzing and sorting mature adipocytes, opening up numerous downstream research applications.

Correlation between basal metabolic rate, visceral fat and insulin resistance among type 2 diabetes mellitus with peripheral neuropathy

BACKGROUND

Basal Metabolic Rate (BMR) means the amount of energy utilized by body in physical and psychological resting rate, after a night sleep, awake without any previous physical activity post meal (10 h after last meal) & neutral environment. In people with type 2 diabetes mellitus (T2DM) there is an increase in BMR which is said to be associated with the level of glycaemic control. So, the objective of the study was to find out the correlation between BMR, Insulin resistance and Visceral fat in T2DM with peripheral neuropathy.

MATERIALS & METHODS

A total of 50 participants with T2DM with peripheral neuropathy were included. Age group of 30-75 years were selected for the study. Participants with a known history of neurological disease, locomotor disability, and pregnancy were excluded from the study. Demographic details of the participants like duration of diabetes mellitus, age, Fasting Blood Glucose, Fasting Insulin, HOMA-IR, Glycated Haemoglobin (HBA1c), Neuropathy and Blood pressure values were noted. We measured Basal Metabolic Rate (BMR) by using Mifflin-St Jeor predictive equation in T2DM with peripheral neuropathy.

RESULTS

The mean age of the participants is 60.16 ± 10.62. The mean duration of T2DM 13.44 ± 11.92. In the present study we found a statistical significant correlation between BMR and HOMA IR (r = 0.913*; p = 0.000), BMR & Fasting blood sugar (FBS) (r = 0.281*; p = 0.048), BMR and Visceral fat (VF) (r = 0.332*; p = 0.018).

CONCLUSION

Basal metabolic rate is correlated to Homa-IR, visceral fat, fasting blood sugar and musculoskeletal mass among T2DM with peripheral neuropathy.

The protective effect of neonatal oral administration of oleanolic acid against the subsequent development of fructose-induced metabolic dysfunction in male and female rats

BACKGROUND

Consumption of fructose-rich diets has been implicated in the increasing global prevalence of metabolic syndrome (MetS). Interventions during periods of early ontogenic developmental plasticity can cause epigenetic changes which program metabolism for positive or negative health benefits later in life. The phytochemical oleanolic acid (OA) possesses anti-diabetic and anti-obesity effects. We investigated the potential protective effects of neonatal administration of OA on the subsequent development of high fructose diet-induced metabolic dysfunction in rats.

METHOD

Male and female (N = 112) suckling rats were randomly assigned to four groups and administered orally: distilled water (DW), oleanolic acid (OA; 60 mg/kg), high-fructose solution (HF; 20% w/v) or OA + HF for 7 days. The rats were weaned onto normal commercial rat chow up to day 55. From day 56, half of the rats in each treatment group were continued on plain water and the rest on a high fructose solution as drinking fluid for 8 weeks. On day 110, the rats were subjected to an oral glucose tolerance test and then euthanased on day 112. Tissue and blood samples were collected to determine the effects of the treatments on visceral fat pad mass, fasting plasma levels of cholesterol, insulin, glucose, triglycerides, insulin resistance (HOMA-IR) and glucose tolerance.

RESULTS

Rats which consumed fructose as neonates and then later as adults (HF + F) and those which consumed fructose only in adulthood (DW + F) had significant increases in terminal body mass (females only), visceral fat mass (males and females), serum triglycerides (females only), epididymal fat (males only), fasting plasma glucose (males and females), impaired glucose metabolism (females only), β-cell dysfunction and insulin resistance (males and females) compared to the other treatment groups (P < 0.05). There were no differences in fasting serum cholesterol levels across all treatment groups in both male and female rats (P > 0.05).

CONCLUSION

We conclude that neonatal oral administration of OA during the critical window of developmental plasticity protected against the development of health outcomes associated with fructose-induced metabolic disorders in the rats.

Effects of a combined dietary, exercise and behavioral intervention and sympathetic system on body weight maintenance after intended weight loss: Results of a randomized controlled trial

BACKGROUND

Lifestyle based weight loss interventions are hampered by long-term inefficacy. Prediction of individuals successfully reducing body weight would be highly desirable. Although sympathetic activity is known to contribute to energy homeostasis, its predictive role in body weight maintenance has not yet been addressed.

OBJECTIVES

We investigated, whether weight regain could be modified by a weight maintenance intervention and analyzed the predictive role of weight loss-induced changes of the sympathetic system on long-term weight regain.

DESIGN

156 subjects (age > 18; BMI ≥ 27 kg/m²) participated in a 12-week weight reduction program. After weight loss (T0), 143 subjects (weight loss > 8%) were randomized to a 12-month lifestyle intervention or a control group. After 12 months (T12) no further intervention was performed until month 18 (T18). Weight regain at T18 (regain_BMI) was the primary outcome. Evaluation of systemic and tissue specific estimates of sympathetic system was a pre-defined secondary outcome.

RESULTS

BMI was reduced by 4.67 ± 1.47 kg/m² during the initial weight loss period. BMI maintained low in subjects of the intervention group until T12 (+0.07 ± 2.98 kg/m²; p = 0.58 compared to T0), while control subjects regained +0.98 ± 1.93 kg/m² (p < 0.001 compared to T0). The intervention group regained more weight than controls after ceasing the intervention (1.17 ± 1.34 vs. 0.57 ± 0.93 kg/m²) until T18. Consequently, BMI was not different at T18 (33.49 (32.64; 34.33) vs. 34.18 (33.61; 34.75) kg/m²; p=0.17). Weight loss-induced modification of urinary metanephrine excretion independently predicted regain_BMI (R² = 0.138; p < 0.05). The lifestyle intervention did not modify the course of urinary metanephrines after initial weight loss.

CONCLUSIONS

Our lifestyle intervention successfully maintained body weight during the intervention period. However, no long-term effect could be observed beyond the intervention period. Predictive sympathetic activity was not persistently modified by the intervention, which may partially explain the lack of long-term success of such interventions.

Decreased Serum Adiponectin Level during Catecholamine Crisis in an Obese Patient with Pheochromocytoma

We herein report the case of a 37-year-old man with both pheochromocytoma and visceral fat accumulation and describe the sequential changes in his adiponectin levels throughout the clinical course from catecholamine crisis until the follow-up for adrenalectomy. His adiponectin level decreased during catecholamine crisis and increased after adrenalectomy. However, his adiponectin level decreased again at two years postoperatively when his visceral fat area greatly increased. This case suggests that catecholamines and visceral fat volume may affect adiponectin metabolism in subjects with pheochromocytoma, which may precipitate cardiovascular complications in this endocrine disease.

Heterogeneity of adipose tissue in development and metabolic function

Adipose tissue is a central metabolic organ. Unlike other organs, adipose tissue is compartmentalized into individual depots and distributed throughout the body. These different adipose depots show major functional differences and risk associations for developing metabolic syndrome. Recent advances in lineage tracing demonstrate that individual adipose depots are composed of adipocytes that are derived from distinct precursor populations, giving rise to different populations of energy-storing white adipocytes. Moreover, distinct lineages of energy-dissipating brown and beige adipocytes exist in discrete depots or within white adipose tissue depots. In this Review, we discuss developmental and functional heterogeneity, as well as sexual dimorphism, between and within individual adipose tissue depots. We highlight current data relating to the differences between subcutaneous and visceral white adipose tissue in the development of metabolic dysfunction, with special emphasis on adipose tissue expansion and remodeling of the extracellular matrix. Moreover, we provide a detailed overview of adipose tissue development as well as the consensus and controversies relating to adult adipocyte precursor populations.

Short-Chain Fatty Acids Differentially Affect Intracellular Lipolysis in a Human White Adipocyte Model

BACKGROUND AND AIMS

Gut-derived short-chain fatty acids (SCFA), formed by microbial fermentation of dietary fibers, are believed to be involved in the etiology of obesity and diabetes. Previous data from our group showed that colonic infusions of physiologically relevant SCFA mixtures attenuated whole-body lipolysis in overweight men. To further study potential mechanisms involved in the antilipolytic properties of SCFA, we aimed to investigate the in vitro effects of SCFA incubations on intracellular lipolysis and signaling using a human white adipocyte model, the human multipotent adipose tissue-derived stem (hMADS) cells.

METHODS

hMADS adipocytes were incubated with mixtures of acetate, propionate, and butyrate or single SCFA (acetate, propionate and butyrate) in concentrations ranging between 1 µmol/L and 1 mmol/L. Glycerol release and lipase activation was investigated during basal conditions and following β-adrenergic stimulation.

RESULTS

SCFA mixtures high in acetate and propionate decreased basal glycerol release, when compared to control (P < 0.05), while mixtures high in butyrate had no effect. Also, β-adrenergic receptor mediated glycerol release was not significantly altered following incubation with SCFA mixtures. Incubation with only acetate decreased basal (1 µmol/L) and β-adrenergically (1 µmol/L and 1 mmol/L) mediated glycerol release when compared with control (P < 0.05). In contrast, butyrate (1 µmol/L) slightly increased basal and β-adrenergically mediated glycerol release compared with control (P < 0.05), while propionate had no effect on lipolysis. The antilipolytic effect of acetate was accompanied by a reduced phosphorylation of hormone-sensitive lipase (HSL) at serine residue 650. In addition, inhibition of Gi G proteins following pertussis toxin treatment prevented the antilipolytic effect of acetate.

CONCLUSION

The present data demonstrated that acetate was mainly responsible for the antilipolytic effects of SCFA and acts via attenuation of HSL phosphorylation in a Gi-coupled manner in hMADS adipocytes. Therefore, the modulation of colonic and circulating acetate may be an important target to modulate human adipose tissue lipid metabolism.

Visceral Fat: Higher Responsiveness of Fat Mass and Gene Expression to Calorie Restriction than Subcutaneous Fat

Visceral fat accumulation is accompanied by several metabolic disorders. Here, we investigate the improvement of visceral fat accumulation in the early phase of diet. Hyperlipidemic obese patients received a low-calorie diet (1000 kcal/day) for 14 days. Visceral and subcutaneous fat accumulation was analyzed using ultrasonography. After 14 days of the diet, the average visceral fat of obese patients obviously decreased (P < 0.05), as well as the visceral fat-related secreted proteins, whereas subcutaneous fat did not decrease in these patients. These results show that visceral fat is reduced significantly in the early phase of diet therapy in humans. Therefore, to clarify its mechanism, we analyzed the expression of lipid metabolism-related genes in visceral and subcutaneous fat using obese rats. The Long-Evans Tokushima Otsuka (LETO) rats, as an obese model, were divided into two groups: fasting and non-fasting. The gene expressions in visceral and subcutaneous fat were measured by reverse transcriptase-polymerase chain reaction (RT-PCR). The expression of beta(3)-adrenergic receptor (AR), hormone sensitive lipase (HSL), peroxisome proliferator-activated receptor (PPAR)-gamma, and uncoupling protein (UCP)-2 genes increased by 3.2-, 2.3-, 2.2-, and 2-fold in visceral fat (P < 0.01), but remained almost unchanged in subcutaneous fat. Taken together, the responsiveness of lipid metabolism-related genes to fasting is more sensitive in visceral fat than in subcutaneous fat in rats, suggesting that the different responsiveness to calorie restriction in fat tissues is due to the different induction of metabolism-related gene expression.

Commonalities in the Association between PPARG and Vitamin D Related with Obesity and Carcinogenesis

The PPAR nuclear receptor family has acquired great relevance in the last decade, which is formed by three different isoforms (PPARα, PPARβ/δ, and PPAR ϒ). Those nuclear receptors are members of the steroid receptor superfamily which take part in essential metabolic and life-sustaining actions. Specifically, PPARG has been implicated in the regulation of processes concerning metabolism, inflammation, atherosclerosis, cell differentiation, and proliferation. Thus, a considerable amount of literature has emerged in the last ten years linking PPARG signalling with metabolic conditions such as obesity and diabetes, cardiovascular disease, and, more recently, cancer. This review paper, at crossroads of basic sciences, preclinical, and clinical data, intends to analyse the last research concerning PPARG signalling in obesity and cancer. Afterwards, possible links between four interrelated actors will be established: PPARG, the vitamin D/VDR system, obesity, and cancer, opening up the door to further investigation and new hypothesis in this fascinating area of research.

IgG Autoantibodies Induced by T. cruzi During Pregnancy: Correlation with Gravidity Complications and Early Outcome Assessment of the Newborns

Objective The aim of the present research was to evaluate the correlation of vertically transmitted IgG antibodies induced by T. cruzi and newborn early outcome assessment, mainly birth weight and gestational age. Methods We performed a cross-sectional study with 183 pregnant women (64 with asymptomatic Chagas disease) and their newborns. Both were subjected to complete clinical examination. Peripheral parasitemia was assessed in mother and neonates by parasite detection through microscopic examination of the buffycoat from mother's peripheral and cord blood. Antibodies induced by T. cruzi, such as anti-FRA, anti-B13, anti-p2β and anti-T. cruzi were assessed by immunoassay. Birth weight, general condition evaluation by APGAR Score and gestational age by Capurro Score, were determined in newborns. Results The rate of stillbirth background and pregnancy-induced hypertension were higher in patients with Chagas disease (p = 0.01 and p = 0.02, respectively). Parasitemia was detectable in 17 mothers and 4 newborns. The newborns of mothers with detectable parasitemia presented decreased gestational age (p = 0.006) and body weight (p = 0.04). Mostly all the mothers with Chagas disease and all their newborns have positive values of antibodies induced by T. cruzi; however, only anti-p2β showed to be related to the presence of complication during pregnancy (OR 2.35, p = 0.036), and to low birth weight (OR 1.55, p = 0.02). Conclusions Low birth weight and decreased postnatal estimation of maturity were related to detectable parasitemia in the mother. Also, vertical transmission of T. cruzi-induced autoantibodies might have clinical implication in newborns given the negative association between anti-p2β values and weight.

Attenuated atrial natriuretic peptide-mediated lipolysis in subcutaneous adipocytes of obese type 2 diabetic men

Subjects with obesity seem to display a suboptimal exercise response, which might be due to hormonal disturbances. In the present study, we show the adipose tissue of obese subjects to be less sensitive to atrial natriuretic peptide, a cardiac hormone important during exercise.

Physical Activity and Sedentary Behavior in Metabolically Healthy versus Unhealthy Obese and Non-Obese Individuals - The Maastricht Study

Background

Both obesity and the metabolic syndrome are associated with increased risk of cardiovascular diseases and type 2 diabetes. Although both frequently occur together in the same individual, obesity and the metabolic syndrome can also develop independently from each other. The (patho)physiology of “metabolically healthy obese” (i.e. obese without metabolic syndrome) and “metabolically unhealthy non-obese” phenotypes (i.e. non-obese with metabolic syndrome) is not fully understood, but physical activity and sedentary behavior may play a role.

Objective

To examine objectively measured physical activity and sedentary behavior across four groups: I) “metabolically healthy obese” (MHO); II) “metabolically unhealthy obese” (MUO); III)”metabolically healthy non-obese” (MHNO); and IV) “metabolically unhealthy non-obese” (MUNO).

Methods

Data were available from 2,449 men and women aged 40–75 years who participated in The Maastricht Study from 2010 to 2013. Participants were classified into the four groups according to obesity (BMI≥30kg/m²) and metabolic syndrome (ATPIII definition). Daily activity was measured for 7 days with the activPAL physical activity monitor and classified as time spent sitting, standing, and stepping.

Results

In our study population, 562 individuals were obese. 19.4% of the obese individuals and 72.7% of the non-obese individuals was metabolically healthy. After adjustments for age, sex, educational level, smoking, alcohol use, waking time, T2DM, history of CVD and mobility limitation, MHO (n = 107) spent, per day, more time stepping (118.2 versus 105.2 min; p<0.01) and less time sedentary (563.5 versus 593.0 min., p = 0.02) than MUO (n = 440). In parallel, MHNO (n = 1384) spent more time stepping (125.0 versus 115.4 min; p<0.01) and less time sedentary (553.3 versus 576.6 min., p<0.01) than MUNO (n = 518).

Conclusion

Overall, the metabolically healthy groups were less sedentary and more physically active than the metabolically unhealthy groups. Therefore, physical activity and sedentary time may partly explain the presence of the metabolic syndrome in obese as well as non-obese individuals.

Heterogeneity of white adipose tissue: molecular basis and clinical implications

Adipose tissue is a highly heterogeneous endocrine organ. The heterogeneity among different anatomical depots stems from their intrinsic differences in cellular and physiological properties, including developmental origin, adipogenic and proliferative capacity, glucose and lipid metabolism, insulin sensitivity, hormonal control, thermogenic ability and vascularization. Additional factors that influence adipose tissue heterogeneity are genetic predisposition, environment, gender and age. Under obese condition, these depot-specific differences translate into specific fat distribution patterns, which are closely associated with differential cardiometabolic risks. For instance, individuals with central obesity are more susceptible to developing diabetes and cardiovascular complications, whereas those with peripheral obesity are more metabolically healthy. This review summarizes the clinical and mechanistic evidence for the depot-specific differences that give rise to different metabolic consequences, and provides therapeutic insights for targeted treatment of obesity.

Exercise and the Regulation of Adipose Tissue Metabolism

Adipose tissue is a major regulator of metabolism in health and disease. The prominent roles of adipose tissue are to sequester fatty acids in times of energy excess and to release fatty acids via the process of lipolysis during times of high-energy demand, such as exercise. The fatty acids released during lipolysis are utilized by skeletal muscle to produce adenosine triphosphate to prevent fatigue during prolonged exercise. Lipolysis is controlled by a complex interplay between neuro-humoral regulators, intracellular signaling networks, phosphorylation events involving protein kinase A, translocation of proteins within the cell, and protein-protein interactions. Herein, we describe in detail the cellular and molecular regulation of lipolysis and how these processes are altered by acute exercise. We also explore the processes that underpin adipocyte adaptation to endurance exercise training, with particular focus on epigenetic modifications, control by microRNAs and mitochondrial adaptations. Finally, we examine recent literature describing how exercise might influence the conversion of traditional white adipose tissue to high energy-consuming "brown-like" adipocytes and the implications that this has on whole-body energy balance.

Changes in visceral and subcutaneous fat mass in patients with pheochromocytoma

CONTEXT

Overproduction of catecholamine induces not only hypertension but also glucose intolerance and hyperlipidemia. However, little is known about its effect on visceral and subcutaneous fat.

OBJECTIVE

Our objective was to investigate changes of metabolic factors including visceral and subcutaneous fat areas in patients with pheochromocytoma (Pheo).

DESIGN AND PATIENTS

This was a cross-sectional and longitudinal follow-up study of cases collected from Gunma University Hospital between 2002 and 2013. Forty-two patients with Pheo and 23 with non-functioning adrenal adenoma (NFA) were analyzed before and after adrenalectomy.

RESULTS

Multivariate logistic-regression analysis adjusted by age and gender revealed that glucose intolerance was more common in patients with Pheo than in patients with NFA (21/42, 51% vs. 4/23, 17%, p<0.05). Abdominal visceral fat area (VFA) and subcutaneous fat area (SFA) were significantly lower in patients with Pheo than in those with NFA (80.2±38.7 vs. 124.3±61.8cm(2), p<0.05; 114.6±58.9 vs. 164.3±40.3cm(2), p<0.05, respectively). Significant correlations were observed between fractionated urine noradrenaline level and serum HDL-cholesterol level (r = 0.36, p<0.05), urine normetanephrine level and tumor size (r=0.57, p<0.01), and urine adrenaline level and systolic blood pressure (r=0.35, p<0.05) in Pheo. However, there were no significant correlations between adrenaline and noradrenaline levels and other parameters, including serum LDL-cholesterol and triglyceride levels, and HbA1c. Furthermore, both VFA and SFA, body weight, and BMI were significantly increased, and serum HbA1c as well as HDL-cholesterol levels were decreased after adrenalectomy in Pheo.

CONCLUSION

These findings suggest for the first time that catecholamines might regulate the serum HDL-cholesterol level and both abdominal visceral and subcutaneous fat mass in men.

Detrimental and protective fat: body fat distribution and its relation to metabolic disease

Obesity is linked to numerous comorbidities that include, but are not limited to, glucose intolerance, insulin resistance, dyslipidemia, and cardiovascular disease. Current evidence suggests, however, obesity itself is not an exclusive predictor of metabolic dysregulation but rather adipose tissue distribution. Obesity-related adverse health consequences occur predominately in individuals with upper body fat accumulation, the detrimental distribution, commonly associated with visceral obesity. Increased lower body subcutaneous adipose tissue, however, is associated with a reduced risk of obesity-induced metabolic dysregulation and even enhanced insulin sensitivity, thus, storage in this region is considered protective. The proposed mechanisms that causally relate the differential outcomes of adipose tissue distribution are often attributed to location and/or adipocyte regulation. Visceral adipose tissue effluent to the portal vein drains into the liver where hepatocytes are directly exposed to its metabolites and secretory products, whereas the subcutaneous adipose tissue drains systemically. Adipose depots are also inherently different in numerous ways such as adipokine release, immunity response and regulation, lipid turnover, rate of cell growth and death, and response to stress and sex hormones. Proximal extrinsic factors also play a role in the differential drive between adipose tissue depots. This review focuses on the deleterious mechanisms postulated to drive the differential metabolic response between central and lower body adipose tissue distribution.

Adipose tissue signaling by nuclear receptors in metabolic complications of obesity

In recent years white adipose tissue inflammation has been recognized to be associated with obesity. Adipocytes and adipose tissue associated macrophages (ATMs) secrete bioactive molecules, including adipokines, chemokines/cytokines and free fatty acids that modulate the development of low-grade inflammation and insulin resistance responsible for obesity-related metabolic and cardiovascular diseases. Nuclear receptors, notably peroxisome-proliferator-activated receptors, are sensors of dietary lipids and control transcriptional programs of key metabolic and inflammatory pathways in adipocytes and macrophages. This review focuses on mechanisms by which nuclear receptors maintain white adipose tissue homeostasis. The identification of ATMs as active players in the initiation of chronic inflammation and the links between inflammatory signaling and metabolic dysfunction will be presented, followed by discussion of recent evidence for nuclear receptors in ATM function, with an emphasis on the paracrine interaction between adipocytes and ATMs.

Neuroendocrine circuits governing energy balance and stress regulation: functional overlap and therapeutic implications

Significant comorbidities between obesity-related metabolic disease and stress-related psychological disorders suggest important functional interactions between energy balance and brain stress integration. Largely overlapping neural circuits control these systems, and this anatomical arrangement optimizes opportunities for mutual influence. Here we first review the current literature identifying effects of metabolic neuroendocrine signals on stress regulation, and vice versa. Next, the contributions of reward-driven food intake to these metabolic and stress interactions are discussed. Lastly, we consider the interrelationships between metabolism, stress, and reward in light of their important implications in the development of therapies for metabolism- or stress-related disease.

Regulation of adipocyte lipolysis

In adipocytes the hydrolysis of TAG to produce fatty acids and glycerol under fasting conditions or times of elevated energy demands is tightly regulated by neuroendocrine signals, resulting in the activation of lipolytic enzymes. Among the classic regulators of lipolysis, adrenergic stimulation and the insulin-mediated control of lipid mobilisation are the best known. Initially, hormone-sensitive lipase (HSL) was thought to be the rate-limiting enzyme of the first lipolytic step, while we now know that adipocyte TAG lipase is the key enzyme for lipolysis initiation. Pivotal, previously unsuspected components have also been identified at the protective interface of the lipid droplet surface and in the signalling pathways that control lipolysis. Perilipin, comparative gene identification-58 (CGI-58) and other proteins of the lipid droplet surface are currently known to be key regulators of the lipolytic machinery, protecting or exposing the TAG core of the droplet to lipases. The neuroendocrine control of lipolysis is prototypically exerted by catecholaminergic stimulation and insulin-induced suppression, both of which affect cyclic AMP levels and hence the protein kinase A-mediated phosphorylation of HSL and perilipin. Interestingly, in recent decades adipose tissue has been shown to secrete a large number of adipokines, which exert direct effects on lipolysis, while adipocytes reportedly express a wide range of receptors for signals involved in lipid mobilisation. Recently recognised mediators of lipolysis include some adipokines, structural membrane proteins, atrial natriuretic peptides, AMP-activated protein kinase and mitogen-activated protein kinase. Lipolysis needs to be reanalysed from the broader perspective of its specific physiological or pathological context since basal or stimulated lipolytic rates occur under diverse conditions and by different mechanisms.

Role of adipose tissue in methionine-choline-deficient model of non-alcoholic steatohepatitis (NASH)

Methionine–choline-deficient (MCD) diet is a widely used dietary model of non-alcoholic steatohepatitis (NASH) in rodents. However, the contribution of adipose tissue to MCD-induced steatosis, and inflammation as features of NASH are not fully understood. The goal of this study was to elucidate the role of adipose tissue fatty acid (FA) metabolism, adipogenesis, lipolysis, inflammation and subsequent changes in FA profiles in serum and liver in the pathogenesis of steatohepatitis. We therefore fed ob/ob mice with control or MCD diet for 5 weeks. MCD-feeding increased adipose triglyceride lipase and hormone sensitive lipase activities in all adipose depots which may be attributed to increased systemic FGF21 levels. The highest lipase enzyme activity was exhibited by visceral WAT. Non-esterified fatty acid (NEFA)-18:2n6 was the predominantly elevated FA species in serum and liver of MCD-fed ob/ob mice, while overall serum total fatty acid (TFA) composition was reduced. In contrast, an overall increase of all FA species from TFA pool was found in liver, reflecting the combined effects of increased FA flux to liver, decreased FA oxidation and decrease in lipase activity in liver. NAFLD activity score was increased in liver, while WAT showed no changes and BAT showed even reduced inflammation. Conclusion: This study demonstrates a key role for adipose tissue lipases in the pathogenesis of NASH and provides a comprehensive lipidomic profiling of NEFA and TFA homeostasis in serum and liver. Our findings provide novel mechanistic insights for the role of WAT in progression of MCD-induced liver injury.

•

MCD model of NASH increases lipase activity in WAT as a critical determinant of hepatic FA flux and lipotoxicity.

•

The maximal increase of ATGL and HSL activity is in visceral WAT.

•

Increased lipase activity may be due to enhanced FGF21 signaling.

•

NEFA-18:2n6 is preferentially increased in serum and liver due to lipolysis in WAT.

•

MCD diet enhances the activity of BAT and diminishes its inflammatory markers.

Using a novel coculture model to dissect the role of intramuscular lipid load on skeletal muscle insulin responsiveness under reduced estrogen conditions

Reductions in estrogen function lead to adiposity and peripheral insulin resistance. Significant metabolic changes have been found in adipocytes and skeletal muscle with disruptions in the estrogen-signaling axis; however, it is unclear if intercellular communication exists between these tissues. The purpose of this study was to examine the impact of isolated adipocytes cocultured with single adult skeletal muscle fibers (SMF) collected from control female (SHAM) and ovariectomized female (OVX) mice. In addition, a second purpose was to compare differential effects of primary adipocytes from omental and inguinal adipose depots on SMF from these same groups. OVX SMF displayed greater lipid content, impaired insulin signaling, and lower insulin-induced glucose uptake compared with SHAM SMF without coculture. In the SHAM group, regardless of the adipose depot of origin, coculture induced greater intracellular lipid content compared with control SHAM SMF. The increased lipid in the SMF was associated with impaired insulin-induced glucose uptake when adipocytes were of omental, but not inguinal, origin. Coculture of OVX SMF with omental or inguinal adipocytes resulted in higher lipid content but no further reduction in insulin-induced glucose uptake compared with control OVX SMF. The data indicate that, in the OVX condition, there is a threshold for lipid accumulation in skeletal muscle beyond which there is no further impairment in insulin responsiveness. These results also demonstrate depot-specific effects of adipocyte exposure on skeletal muscle glucose uptake and further implicate a role for increased intracellular lipid storage in the pathogenesis of insulin resistance when estrogen levels are reduced.

Predictive equations overestimate the resting metabolic rate in postmenopausal women

The resting energetic dispenses on postmenopausal stage should be well known in order to elaborate obesity prevention programs.

OBJECTIVE

The aim of this study was to compare the resting metabolic rate (RMR) measured by indirect calorimetry (RMRmeasured) with predictive equations (RMRestimated) and verify which preexisting equation is more indicated for this population, in inactive, postmenopausal women.

DESIGN

43 postmenopausal women volunteered for the present study.

MEASUREMENTS

RMRestimated value was achieved by indirect calorimetry. The predictive equations used were: Harris-Benedict equation (HB), Henry e Ree (HR), Mifflin-St Jeor equation (MSJ), World Health Organization equation (WHO) and Female Brazilian Population (FBP). Body composition was obtained through skinfolds method.

RESULTS

All equations showed significant difference values for kcal/day (p<0.00001) (HB 1313.07±73.46; HR 1310.95±81.41; MSJ 1207.93±93.17; WHO 1375.73±61.01 and FBP 1250.05±73.54 kcal/day) in relation to RMRestimated (1063.79±157.82). The WHO equation was the one which most overestimated the RMR values with a difference of more than 300 kcal/day.

CONCLUSION

None of the equations to approach, in this study showed precision in the estimative of RMR, all prediction equations overestimated RMR values in Brazilians' postmenopausal women, although the MSJ predictive equation showed the greater approximation of RMRmeasured for this population.

Pathophysiology of human visceral obesity: an update

Excess intra-abdominal adipose tissue accumulation, often termed visceral obesity, is part of a phenotype including dysfunctional subcutaneous adipose tissue expansion and ectopic triglyceride storage closely related to clustering cardiometabolic risk factors. Hypertriglyceridemia; increased free fatty acid availability; adipose tissue release of proinflammatory cytokines; liver insulin resistance and inflammation; increased liver VLDL synthesis and secretion; reduced clearance of triglyceride-rich lipoproteins; presence of small, dense LDL particles; and reduced HDL cholesterol levels are among the many metabolic alterations closely related to this condition. Age, gender, genetics, and ethnicity are broad etiological factors contributing to variation in visceral adipose tissue accumulation. Specific mechanisms responsible for proportionally increased visceral fat storage when facing positive energy balance and weight gain may involve sex hormones, local cortisol production in abdominal adipose tissues, endocannabinoids, growth hormone, and dietary fructose. Physiological characteristics of abdominal adipose tissues such as adipocyte size and number, lipolytic responsiveness, lipid storage capacity, and inflammatory cytokine production are significant correlates and even possible determinants of the increased cardiometabolic risk associated with visceral obesity. Thiazolidinediones, estrogen replacement in postmenopausal women, and testosterone replacement in androgen-deficient men have been shown to favorably modulate body fat distribution and cardiometabolic risk to various degrees. However, some of these therapies must now be considered in the context of their serious side effects. Lifestyle interventions leading to weight loss generally induce preferential mobilization of visceral fat. In clinical practice, measuring waist circumference in addition to the body mass index could be helpful for the identification and management of a subgroup of overweight or obese patients at high cardiometabolic risk.

Nutritional, hormonal, and depot-dependent regulation of the expression of the small GTPase Rab18 in rodent adipose tissue

There is increasing evidence that proteins associated with lipid droplets (LDs) play a key role in the coordination of lipid storage and mobilization in adipocytes. The small GTPase, RAB18, has been recently identified as a novel component of the protein coat of LDs and proposed to play a role in both β-adrenergic stimulation of lipolysis and insulin-induced lipogenesis in 3T3-L1 adipocytes. In order to better understand the role of Rab18 in the regulation of lipid metabolism in adipocytes, we evaluated the effects of age, fat location, metabolic status, and hormonal milieu on Rab18 expression in rodent white adipose tissue (WAT). Rab18 mRNA was undetectable at postnatal day 15 (P15), but reached adult levels by P45, in both male and female rats. In adult rats, Rab18 immunolocalized around LDs, as well as within the cytoplasm of mature adipocytes. A weak Rab18 signal was also detected in the stromal-vascular fraction of WAT. In mice, fasting significantly increased, though with a distinct time-course pattern, Rab18 mRNA and protein levels in visceral and subcutaneous WAT. The expression of Rab18 was also increased in visceral and subcutaneous WAT of obese mice (diet-induced, ob/ob, and New Zealand obese mice) compared with lean controls. Rab18 expression in rats was unaltered by castration, adrenalectomy, or GH deficiency but was increased by hypophysectomy, as well as hypothyroidism. When viewed together, our results suggest the participation of Rab18 in the regulation of lipid processing in adipose tissue under both normal and pathological conditions.

Long-term beneficial effect of a 16-week very low calorie diet on pericardial fat in obese type 2 diabetes mellitus patients

Pericardial fat accumulation has been associated with an increased cardiovascular risk. A very low calorie diet (VLCD) improves the cardiovascular risk profile in patients with type 2 diabetes mellitus (T2DM), by improving the metabolic profile, heart function, and triglyceride (TG) stores in (non)adipose tissues. However, long-term effects of a VLCD on pericardial fat volume and tissue-specific TG accumulation have not been documented. The aim of this study was therefore to assess the effects of a 16-week VLCD and of subsequent 14 months follow-up on a regular diet on pericardial fat in relation to other TG stores in obese T2DM patients. We included 14 obese patients with insulin-treated T2DM (mean ± s.e.m.: age 53 ± 2 years; BMI 35 ± 1 kg/m(2)). Pericardial fat and other (non)adipose TG stores were measured using magnetic resonance (MR) imaging and proton spectroscopy before and after a 16-week VLCD and after a 14-month follow-up without dietary interventions. A 16-week VLCD reduced body weight, pericardial fat, hepatic TG content, visceral and subcutaneous abdominal fat volumes to 78, 83, 16, 40, and 53% of baseline values respectively, (all P < 0.05). After an additional 14 months of follow-up on a regular diet, the reduction in pericardial fat volume sustained, despite a substantial regain in body weight, visceral abdominal fat, and hepatic TG content (respectively 90, 83 and 73% of baseline values). In conclusion, VLCD-induced weight loss in obese T2DM patients is accompanied by a substantial decrease in pericardial fat volume, which is sustained even after subsequent weight regain.

Structural and biochemical characteristics of various white adipose tissue depots

It is now widely accepted that white adipose tissue (WAT) is not merely a fuel storage organ, but also a key component of metabolic homoeostatic mechanisms. Apart from its major role in lipid and glucose metabolism, adipose tissue is also involved in a wide array of other biological processes. The hormones and adipokines, as well as other biologically active agents released from fat cells, affect many physiological and pathological processes. WAT is neither uniform nor inflexible because it undergoes constant remodelling, adapting the size and number of adipocytes to changes in nutrients' availability and hormonal milieu. Fat depots from different areas of the body display distinct structural and functional properties and have disparate roles in pathology. The two major types of WAT are visceral fat, localized within the abdominal cavity and mediastinum, and subcutaneous fat in the hypodermis. Visceral obesity correlates with increased risk of insulin resistance and cardiovascular diseases, while increase of subcutaneous fat is associated with favourable plasma lipid profiles. Visceral adipocytes show higher lipogenic and lipolytic activities and produce more pro-inflammatory cytokines, while subcutaneous adipocytes are the main source of leptin and adiponectin. Moreover, adipose tissue associated with skeletal muscles (intramyocellular and intermuscular fat) and with the epicardium is believed to provide fuels for skeletal and cardiac muscle contraction. However, increased mass of either epicardial or intermuscular adipose tissue correlates with cardiovascular risk, while the presence of the intramyocellular fat is a risk factor for the development of insulin resistance. This review summarizes results of mainly human studies related to the differential characteristics of various WAT depots.

Large size cells in the visceral adipose depot predict insulin resistance in the canine model

Adipocyte size plays a key role in the development of insulin resistance. We examined longitudinal changes in adipocyte size and distribution in visceral (VIS) and subcutaneous (SQ) fat during obesity-induced insulin resistance and after treatment with CB-1 receptor antagonist, rimonabant (RIM) in canines. We also examined whether adipocyte size and/or distribution is predictive of insulin resistance. Adipocyte morphology was assessed by direct microscopy and analysis of digital images in previously studied animals 6 weeks after high-fat diet (HFD) and 16 weeks of HFD + placebo (PL; n = 8) or HFD + RIM (1.25 mg/kg/day; n = 11). At 6 weeks, mean adipocyte diameter increased in both depots with a bimodal pattern only in VIS. Sixteen weeks of HFD+PL resulted in four normally distributed cell populations in VIS and a bimodal pattern in SQ. Multilevel mixed-effects linear regression with random-effects model of repeated measures showed that size combined with share of adipocytes >75 µm in VIS only was related to hepatic insulin resistance. VIS adipocytes >75 µm were predictive of whole body and hepatic insulin resistance. In contrast, there was no predictive power of SQ adipocytes >75 µm regarding insulin resistance. RIM prevented the formation of large cells, normalizing to pre-fat status in both depots. The appearance of hypertrophic adipocytes in VIS is a critical predictor of insulin resistance, supporting the deleterious effects of increased VIS adiposity in the pathogenesis of insulin resistance.

Adiponectin Inhibits Spontaneous and Catecholamine-Induced Lipolysis in Human Adipocytes of Non-Obese Subjects Through AMPK-Dependent Mechanisms

Adiponectin is an adipokine increasing glucose and fatty acid metabolism and improving insulin sensitivity. The aim of this study was to investigate the role of adiponectin in the regulation of adipocyte lipolysis. Human adipocytes isolated from biopsies obtained during surgical operations from 16 non-obese and 17 obese subjects were incubated with 1) human adiponectin (20 µg/ml) or 2) 0.5 mM AICAR – activator of AMPK (adenosine monophosphate activated protein kinase). Following these incubations, isoprenaline was added (10-6 M) to investigate the influence of adiponectin and AICAR on catecholamine-induced lipolysis. Glycerol concentration was measured as lipolysis marker. We observed that adiponectin suppressed spontaneous lipolysis by 21 % and isoprenaline-induced lipolysis by 14 % in non-obese subjects. These effects were not detectable in obese individuals, but statistically significant differences in the effect of adiponectin between obese and non-obese were not revealed by two way ANOVA test. The inhibitory effect of AICAR and adiponectin on lipolysis was reversed by Compound C. Our results suggest, that adiponectin in physiological concentrations inhibits spontaneous as well as catecholamine-induced lipolysis. This effect might be lower in obese individuals and this regulation seems to involve AMPK.

Different adipose depots: their role in the development of metabolic syndrome and mitochondrial response to hypolipidemic agents

Adipose tissue metabolism is closely linked to insulin resistance, and differential fat distributions are associated with disorders like hypertension, diabetes, and cardiovascular disease. Adipose tissues vary in their impact on metabolic risk due to diverse gene expression profiles, leading to differences in lipolysis and in the production and release of adipokines and cytokines, thereby affecting the function of other tissues. In this paper, the roles of the various adipose tissues in obesity are summarized, with particular focus on mitochondrial function. In addition, we discuss how a functionally mitochondrial-targeted compound, the modified fatty acid tetradecylthioacetic acid (TTA), can influence mitochondrial function and decrease the size of specific fat depots.

Weight loss and lipolysis promote a dynamic immune response in murine adipose tissue

Obesity elicits an immune response characterized by myeloid cell recruitment to key metabolic organs, including adipose tissue. However, the response of immune cells to nonpathologic metabolic stimuli has been less well studied, and the factors that regulate the metabolic-dependent accumulation of immune cells are incompletely understood. Here we characterized the response of adipose tissue macrophages (ATMs) to weight loss and fasting in mice and identified a role for lipolysis in ATM recruitment and accumulation. We found that the immune response to weight loss was dynamic; caloric restriction of high-fat diet-fed mice led to an initial increase in ATM recruitment, whereas ATM content decreased following an extended period of weight loss. The peak in ATM number coincided with the peak in the circulating concentrations of FFA and adipose tissue lipolysis, suggesting that lipolysis drives ATM accumulation. Indeed, fasting or pharmacologically induced lipolysis rapidly increased ATM accumulation, adipose tissue chemoattractant activity, and lipid uptake by ATMs. Conversely, dietary and genetic manipulations that reduced lipolysis decreased ATM accumulation. Depletion of macrophages in adipose tissue cultures increased expression of adipose triglyceride lipase and genes regulated by FFA, and increased lipolysis. These data suggest that local lipid fluxes are central regulators of ATM recruitment and that once recruited, ATMs form lipid-laden macrophages that can buffer local increases in lipid concentration.

[Adipose tissue. Cellular and molecular principles]

For many decades, cutaneous biology research has primarily focused on the dermis and epidermis. In recent years the subcutaneous far has attracted the attention of basic science, cosmetology and industry. Numerous new approaches are in the process of development, enabling us to better understand assembly, differentiation and function of adipose tissue. To understand these developments a background in the cellular and molecular basics of adipose tissue is indispensable. This state-of the art article provides the needed information.

A microarray analysis of sexual dimorphism of adipose tissues in high-fat-diet-induced obese mice

OBJECTIVE

A sexual dimorphism exists in body fat distribution; females deposit relatively more fat in subcutaneous/inguinal depots whereas males deposit more fat in the intra-abdominal/gonadal depot. Our objective was to systematically document depot- and sex-related differences in the accumulation of adipose tissue and gene expression, comparing differentially expressed genes in diet-induced obese mice with mice maintained on a chow diet.

RESEARCH DESIGN AND METHODS

We used a microarray approach to determine whether there are sexual dimorphisms in gene expression in age-matched male, female or ovariectomized female (OVX) C57/BL6 mice maintained on a high-fat (HF) diet. We then compared expression of validated genes between the sexes on a chow diet.

RESULTS

After exposure to a high fat diet for 12 weeks, females gained less weight than males. The microarray analyses indicate in intra-abdominal/gonadal adipose tissue in females 1642 genes differ by at least twofold between the depots, whereas 706 genes differ in subcutaneous/inguinal adipose tissue when compared with males. Only 138 genes are commonly regulated in both sexes and adipose tissue depots. Inflammatory genes (cytokine-cytokine receptor interactions and acute-phase protein synthesis) are upregulated in males when compared with females, and there is a partial reversal after OVX, where OVX adipose tissue gene expression is more 'male-like'. This pattern is not observed in mice maintained on chow. Histology of male gonadal white adipose tissue (GWAT) shows more crown-like structures than females, indicative of inflammation and adipose tissue remodeling. In addition, genes related to insulin signaling and lipid synthesis are higher in females than males, regardless of dietary exposure.

CONCLUSIONS

These data suggest that male and female adipose tissue differ between the sexes regardless of diet. Moreover, HF diet exposure elicits a much greater inflammatory response in males when compared with females. This data set underscores the importance of analyzing depot-, sex- and steroid-dependent regulation of adipose tissue distribution and function.

Enhancement of lipolytic responsiveness of adipocytes by novel plant extract in rat

Subcutaneous adipocytes accumulate excess energy as triglycerides, but lipolytic response is less sensitive to catecholamines than visceral adipocytes. Obesity also induces catecholamine resistance of adipocytes. We have searched for crude drugs that could enhance the lipolytic response to noradrenalin. In this study, the lipolysis-promoting activities and action mechanisms of a novel plant extract from Hemerocallis fulva (HE) were investigated in isolated adipocytes from rat subcutaneous fat. HE exhibited no lipolysis-promoting activity alone but markedly promoted lipolysis when combined with noradrenaline; however, this synergistic activity was accompanied by no increase of intracellular cAMP production. This activity of HE was also observed when combined with cAMP analogue and was further enhanced by phosphodiesterase inhibitor. PKA inhibitor could reduce these activities of HE. These results indicate that HE is a novel lipolysis-promoting material that can sensitize the lipolytic response of adipocytes to catecholamine and suggest that HE can amplify the intra-cellular signaling pathway related to PKA or modify the other mechanism-regulating lipase activity. This characteristic material could contribute to improvement of adipose mobility in obesity-related disorder or in subcutaneous adiposity and to suppression of body fat accumulation.