Ectopic fat stores: housekeepers that can overspill into weapons of lean body mass destruction

Fat-enlarged axillary lymph nodes are associated with node-positive breast cancer in obese patients

PURPOSE

Obesity associated fat infiltration of organ systems is accompanied by organ dysfunction and poor cancer outcomes. Obese women demonstrate variable degrees of fat infiltration of axillary lymph nodes (LNs), and they are at increased risk for node-positive breast cancer. However, the relationship between enlarged axillary nodes and axillary metastases has not been investigated. The purpose of this study is to evaluate the association between axillary metastases and fat-enlarged axillary nodes visualized on mammograms and breast MRI in obese women with a diagnosis of invasive breast cancer.

METHODS

This retrospective case-control study included 431 patients with histologically confirmed invasive breast cancer. The primary analysis of this study included 306 patients with pre-treatment and pre-operative breast MRI and body mass index (BMI) > 30 (201 node-positive cases and 105 randomly selected node-negative controls) diagnosed with invasive breast cancer between April 1, 2011, and March 1, 2020. The largest visible LN was measured in the axilla contralateral to the known breast cancer on breast MRI. Multivariate logistic regression models were used to assess the association between node-positive status and LN size adjusting for age, BMI, tumor size, tumor grade, tumor subtype, and lymphovascular invasion.

RESULTS

A strong likelihood of node-positive breast cancer was observed among obese women with fat-expanded lymph nodes (adjusted OR for the 4th vs. 1st quartile for contralateral LN size on MRI: 9.70; 95% CI 4.26, 23.50; p < 0.001). The receiver operating characteristic curve for size of fat-enlarged nodes in the contralateral axilla identified on breast MRI had an area under the curve of 0.72 for predicting axillary metastasis, and this increased to 0.77 when combined with patient and tumor characteristics.

CONCLUSION

Fat expansion of axillary lymph nodes was associated with a high likelihood of axillary metastases in obese women with invasive breast cancer independent of BMI and tumor characteristics.

Pathogenesis of obesity and cardiometabolic diseases: From the legacy of Ancel Keys to current concepts

Several areas of research into the prevention and treatment of obesity today can be traced to one or more of the scientific works pioneered by Ancel Keys between the 1930s to 1970s in fields that cut across the physiology of extremes and public health nutrition. These range from his classical studies into how body and mind respond to chronic exposure to hypoxia in "The Physiology of Life at High Altitudes" or to simulated famine under controlled laboratory conditions in "The Biology of Human Starvation", the impact of diet and lifestyle on cardiovascular morbidity and mortality in "The Seven Countries Study," to the "Indices of Relative Weight and Obesity" in which he identified what has since been the most widely utilized diagnostic tool to monitor obesity across populations worldwide and which he coined as the body mass index. The contribution of Ancel Keys to medical sciences through his observations, analytical approaches, and research output of his classic studies, and how these have (and continue) to impact on a plethora of current concepts in obesity research today, are embodied in the eight review articles that constitute this supplement reporting the proceedings of the 10th Fribourg Obesity Research Conference. The aim of this introductory paper is to put into perspective the legacy of Ancel Keys to current concepts that are encapsulated in these review articles that cover research areas that include (i) the diagnosis of obesity for health risks; (ii) the role of dietary fat types in the pathogenesis of obesity and cardiometabolic diseases; (iii) the rationale, efficacy and safety of low carbohydrate ketogenic diets, or the therapeutic potential of hypoxic conditioning, in weight management programs; (iv) the psychological and physiological basis of the "famine reaction" that counters therapeutic dieting and facilitates weight regain; and (v) the potential impact of weight cycling and yoyo dieting on risks for later obesity and cardiometabolic diseases.

Inflammation and metabolism: the role of adiposity in sarcopenic obesity

Sarcopenic obesity is characterised by the double burden of diminished skeletal muscle mass and the presence of excess adiposity. From a mechanistic perspective, both obesity and sarcopenia are associated with sub-acute, chronic pro-inflammatory states that impede metabolic processes, disrupting adipose and skeletal functionality, which may potentiate disease. Recent evidence suggests that there is an important cross-talk between metabolism and inflammation, which has shifted focus upon metabolic-inflammation as a key emerging biological interaction. Dietary intake, physical activity and nutritional status are important environmental factors that may modulate metabolic-inflammation. This paradigm will be discussed within the context of sarcopenic obesity risk. There is a paucity of data in relation to the nature and the extent to which nutritional status affects metabolic-inflammation in sarcopenic obesity. Research suggests that there may be scope for the modulation of sarcopenic obesity with alterations in diet. The potential impact of increasing protein consumption and reconfiguration of dietary fat composition in human dietary interventions are evaluated. This review will explore emerging data with respect to if and how different dietary components may modulate metabolic-inflammation, particularly with respect to adiposity, within the context of sarcopenic obesity.

Characterization of the mouse white adipose tissue redox environment and associations with perinatal environmental exposures to bisphenol A and high-fat diets

White adipose tissue (WAT) plays an important role in obesity pathophysiology. Redox signaling underlies several aspects of WAT physiology; however, the thiol redox environment of WAT has not yet been fully characterized. Dietary and endocrine disrupting chemical (EDC) exposures during development can transiently impact the cellular redox environment, but it is unknown whether these exposures can reprogram the WAT thiol redox environment. To characterize the WAT thiol redox environment, we took a descriptive approach and measured thiol redox parameters using high-performance liquid chromatography in mouse mesenteric (mWAT), gonadal (gWAT) and subinguinal (sWAT) depots. Cysteine (CYSS:CYS) and glutathione (GSSG:GSH) redox potentials (Eh) were more oxidizing in gWAT and sWAT than mWAT. Increased body weight, relative WAT weight and age were associated with oxidizing GSSG:GSH Eh in mWAT in a sex-specific manner. Body weight and relative WAT weight were also positively associated with GSSG:GSH Eh in sWAT. We carried out a second mouse study with perinatal exposures to bisphenol A (BPA) and Mediterranean and Western high-fat diets (HFDs) to determine whether early-life chemical and dietary factors have long-lasting impacts on mWAT redox parameters. Mice exposed to Mediterranean HFD or BPA had more oxidizing GSSG:GSH mWAT Eh than controls, with more pronounced differences in females. These findings suggest an important role for the thiol redox environment in WAT physiology. Observed sex-specific and depot-specific differences in thiol redox parameters are consistent with known WAT physiology. Lastly, mWAT GSSG:GSH Eh may be reprogrammed by developmental exposure to HFDs and EDCs, which may have implications for obesity risk.

Caffeic Acid Phenethyl Ester Regulates PPAR's Levels in Stem Cells-Derived Adipocytes

Hypertrophic obesity inhibits activation of peroxisome proliferators-activated receptor gamma (PPARγ), considered the key mediator of the fully differentiated and insulin sensitive adipocyte phenotype. We examined the effects of Caffeic Acid Phenethyl Ester (Cape), isolated from propolis, a honeybee hive product, on Adipose Stem Cells (ASCs) differentiation to the adipocyte lineage. Finally we tested the effects of Cape on insulin-resistant adipocytes. Quantification of Oil Red O-stained cells showed that lipid droplets decreased following Cape treatment as well as radical oxygen species formation. Additionally, exposure of ASC to high glucose levels decreased adiponectin and increased proinflammatory cytokines mRNA levels, which were reversed by Cape-mediated increase of insulin sensitivity. Cape treatment resulted in decreased triglycerides synthesis and increased beta-oxidation. Exposure of ASCs to Lipopolysaccharide (LPS) induced a reduction of PPARγ, an increase of IL-6 levels associated with a well-known stimulation of lipolysis; Cape partially attenuated the LPS-mediated effects. These observations reveal the main role of PPARγ in the adipocyte function and during ASC differentiation. As there is now substantial interest in functional food and nutraceutical products, the observed therapeutic value of Cape in insulin-resistance related diseases should be taken into consideration.

Neto JMD, Marçal AC, Machado UF, Camargo EA, Santos MRV, Brito LC. Modelo de obesidade induzida por dieta hiperlipídica e associada à resistência à ação da insulina e intolerância à glicose

OBJETIVO: Validar um modelo de obesidade induzida por dieta hiperlipídica, de baixo custo, fácil reprodutibilidade, que mimetizasse características observadas no humano e viabilizasse posteriores proposições terapêuticas. MATERIAIS E MÉTODOS: Dezesseis camundongos Swiss receberam dieta padrão (DP) ou dieta hiperlipídica (DH), durante 10 semanas. RESULTADOS: Embora o grupo DP tenha apresentado maior consumo de água (p < 0,01) e ração (p < 0,001), o grupo DH apresentou maior ganho de peso corpóreo (p < 0,5) e aumento de coxins adiposos (p < 0,001), favorecendo maior índice de adiposidade (p < 0,001), glicemia (p < 0,01) e área sob a curva nos testes de tolerância à insulina (p < 0,001) e à glicose (p < 0,01). CONCLUSÃO: Validou-se um modelo de obesidade induzida por dieta hiperlipídica associada à resistência à ação da insulina e à intolerância à glicose, em um período de 10 semanas.

Osteocyte apoptosis and lipid infiltration as mechanisms of alcohol-induced bone loss

AIMS

We carried out an in vivo study to assess the relationship between increase in adiposity in the marrow and osteocyte apoptosis in the case of alcohol-induced bone loss.

METHODS AND RESULTS

After alcohol treatment, the number of apoptotic osteocytes was increased and lipid droplets were accumulated within the osteocytes, the bone marrow and the cortical bone micro-vessels. At last, we found an inverse correlation between bone mineral density and osteocyte apoptosis and strong significant correlations between the osteocyte apoptotic number and lipid droplet accumulation in osteocyte and bone micro-vessels.

CONCLUSION

These data show that alcohol-induced bone loss is associated with osteocyte apoptosis and lipid accumulation in the bone tissue. This lipid intoxication, or 'bone steatosis', is correlated with lipid accumulation in bone marrow and blood micro-vessels.

A translational view of the genetics of lipodystrophy and ectopic fat deposition

A wide range of lipodystrophy syndromes exist, each with varying clinical presentations, and yet cumulatively they underscore the importance of adipocyte biology in human metabolism. Loss of the ability to retain excess lipids in "classical" adipose tissue stores can lead to the overdevelopment of ectopic fat stores, often creating severe perturbations of both glucose and lipid homeostasis. Linkage analysis and candidate sequencing efforts have successfully identified responsible mutations for multiple forms of lipodystrophy. Recently, the reduction in the cost of DNA sequencing has resulted in discovery of many novel mutations within both known and novel loci. In this review, we present the steps involved in clinical characterization of a suspected lipodystrophy case, an overview of the clinical manifestations, molecular findings, and pathogenic basis of different forms of lipodystrophy, a discussion of therapeutic options for lipodystrophy patients, and an examination of genetic advances that will be used to identify additional pathogenic mechanisms.

Effect of birth weight and postnatal weight gain on body composition in early infancy: The Generation R Study

BACKGROUND

Rapid postnatal weight gain is associated with obesity and type 2 diabetes in later life. The influence of rapid weight gain on body composition in early infancy is still unknown and the critical periods of weight gain for later disease are debated.

AIMS

To investigate the effect of birth weight and rapid weight gain on body composition in the first 6 months of life.

STUDY DESIGN

The Generation R Study, a population-based prospective cohort study from fetal life onwards.

SUBJECTS AND OUTCOME MEASURES

We measured body fat and fat distribution by skinfold thickness at the age of 6 weeks and 6 months in 909 Dutch term infants. Analyses were adjusted for current body mass index, sex and maternal socioeconomic status, pre-pregnancy body mass index, height and duration of breastfeeding.

RESULTS

Upward postnatal weight percentile change was associated with increased skinfold thickness, percentage body fat at 6 weeks and 6 months and a larger truncal/peripheral fat ratio at 6 months (p<0.01 for all). Birth weight was inversely associated with truncal/peripheral fat ratio (p<0.01) but not with relative body fat at 6 months.

CONCLUSION

During early postnatal rapid weight gain infants do not grow in all body tissues in equal measure. Instead, they acquire relatively large amounts of fat, which is preferentially distributed to the truncal region. Long term observational studies have to assess if such changes in body composition persist into adulthood.

Skeletal changes associated with the onset of type 2 diabetes in the ZDF and ZDSD rodent models

The incidence and prevalence of type 2 diabetes (T2D) continue to escalate at an unprecedented rate in the United States, particularly among populations with high rates of obesity. The impact of T2D on bone mass, geometry, architecture, strength, and resistance to fracture has yet to be incontrovertibly characterized because of the complex and heterogeneous nature of this disease. This study utilized skeletally mature male diabetic rats of the commonly used Zucker diabetic fatty (ZDF) and Zucker diabetic Sprague-Dawley (ZDSD) strains as surrogate models to assess alterations in bone attributable to T2D-like states. After the animals were euthanized, bone data were collected using dual-energy X-ray absorptiometry, peripheral quantitative tomography, and micro-CT imaging modalities and via three-point bending or compression mechanical testing methods. ZDF and ZDSD diabetic rats exhibited lower bone mineral densities, which coincided with declines in structural strength and increased fragility at the femoral midshaft and the L4 vertebral body in response to monotonic loading. Vertebral trabecular morphology was compromised in both diabetic rodent strains, and ZDSD diabetic rats exhibited additional phenotypic impairments to bone material properties at the spine. Because the metabolic origin of the T2D-like state that develops in the ZDSD rat strain is highly relevant to adult-onset diabetes, it is a particularly attractive novel model for future preclinical research.

Intricacies of fat

One of the most exciting cell biology fields of study concerns the physiology and pathology of fat. The basic assumptions once held concerning the function of adipose tissue have been shown to be oversimplified or sometimes completely wrong. Fat does more than store excess energy; it is actually the largest endocrine organ in the body, and it may be one of the most active. Adipocytes release hormones and other molecules that act on nearby tissues and travel through the vasculature to distant sites, such as the brain, skeletal muscle, and liver. Under conditions of normal weight, those signals help the body to suppress hunger, utilize glucose, and decrease the risk of cardiovascular disease. However, under conditions of obesity, the hormones (or the proteins that bind the hormones) become abnormal and can result in states of chronic inflammation leading to diabetes and heart disease. In addition, excessive fat can lead to the accumulation of lipid droplets in nonfat cells, including skeletal and cardiac muscle. Although some lipid droplets are used as an immediate source of energy for cells, large numbers of stored droplets can cause cellular damage and cell death. The purposes of this article are to review the normal and deviant signals released by fat cells, to draw a link between those signals and chronic diseases such as diabetes, and to discuss the role of exercise in reversing some of the deviant signaling perpetrated by excess fat.

Regulation of fat storage via suppressed thermogenesis: a thrifty phenotype that predisposes individuals with catch-up growth to insulin resistance and obesity

Catch-up growth during infancy and childhood is increasingly recognized as a major risk factor for later development of insulin-related complications and chronic diseases, namely abdominal obesity, type 2 diabetes and cardiovascular disease. As catch-up growth per se is characterized by insulin resistance, hyperinsulinaemia and an accelerated rate of fat storage (i.e., catch-up fat) even in the absence of hyperphagia, the possibility arises that suppressed thermogenesis in certain organs/tissues - for the purpose of enhancing the efficiency of catch-up fat - also plays a role in the pathophysiological consequences of catch-up growth. Here, the evidence for the existence of an adipose-specific control of thermogenesis, the suppression of which contributes to catch-up fat, is reviewed. Recent findings suggest that such suppression of thermogenesis is accompanied by hyperinsulinaemia, insulin resistance in skeletal muscle and insulin hyperresponsiveness in adipose tissue, all of which precede the appearance of excess body fat, central fat distribution and elevations in intramyocellular triglyceride or circulating lipid concentrations. These findings underscore a role for suppressed thermogenesis per se as an early event in the pathophysiology of catch-up growth. It is proposed that, in its evolutionary adaptive role to spare glucose for the rapid rebuilding of an adequate fat reserve (for optimal survival capacity during intermittent famine), suppressed thermogenesis in skeletal muscle constitutes a thrifty phenotype that confers to the phase of catch-up growth its high sensitivity to the development of insulin resistance and hyperinsulinaemia. In the context of the complex interactions between earlier reprogramming and a modern lifestyle characterized by nutritional abundance and low physical activity, this thrifty 'catch-up fat phenotype' is a central event that predisposes individuals with catch-up growth to abdominal obesity, type 2 diabetes and cardiovascular disease.

Alpha-lipoic acid prevents lipotoxic cardiomyopathy in acyl CoA-synthase transgenic mice

Alpha-lipoic acid (alpha-LA) mimics the hypothalamic actions of leptin on food intake, energy expenditure, and activation of AMP-activated protein kinase (AMPK). To determine if, like leptin, alpha-LA protects against cardiac lipotoxicity, alpha-LA was fed to transgenic mice with cardiomyocyte-specific overexpression of the acyl CoA synthase (ACS) gene. Untreated ACS-transgenic mice died prematurely with increased triacylglycerol content and dilated cardiomyopathy, impaired systolic function and myofiber disorganization, apoptosis, and interstitial fibrosis on microscopy. In alpha-LA-treated ACS-transgenic mice heart size, echocardiogram and TG content were normal. Plasma TG fell 50%, hepatic-activated phospho-AMPK rose 6-fold, sterol regulatory element-binding protein-1c declined 50%, and peroxisome proliferator-activated receptor-gamma cofactor-1alpha mRNA rose 4-fold. Since food restriction did not prevent lipotoxicity, we conclude that alpha-LA treatment, like hyperleptinemia, protects the heart of ACS-transgenic mice from lipotoxicity.