Hypoxia and adipocyte physiology: implications for adipose tissue dysfunction in obesity

Enhancing adipose tissue plasticity: progenitor cell roles in metabolic health

Adipose tissue demonstrates considerable plasticity and heterogeneity, enabling metabolic, cellular and structural adaptations to environmental signals. This adaptability is key for maintaining metabolic homeostasis. Impaired adipose tissue plasticity can lead to abnormal adipose tissue responses to metabolic cues, which contributes to the development of cardiometabolic diseases. In chronic obesity, white adipose tissue undergoes pathological remodelling marked by adipocyte hypertrophy, chronic inflammation and fibrosis, which are linked to local and systemic insulin resistance. Research data suggest that the capacity for healthy or unhealthy white adipose tissue remodelling might depend on the intrinsic diversity of adipose progenitor cells (APCs), which sense and respond to metabolic cues. This Review highlights studies on APCs as key determinants of adipose tissue plasticity, discussing differences between subcutaneous and visceral adipose tissue depots during development, growth and obesity. Modulating APC functions could improve strategies for treating adipose tissue dysfunction and metabolic diseases in obesity.

Hypoxia and aging: molecular mechanisms, diseases, and therapeutic targets

Aging is a complex biological process characterized by the gradual decline of cellular functions, increased susceptibility to diseases, and impaired stress responses. Hypoxia, defined as reduced oxygen availability, is a critical factor that influences aging through molecular pathways involving hypoxia-inducible factors (HIFs), oxidative stress, inflammation, and epigenetic modifications. This review explores the interconnected roles of hypoxia in aging, highlighting how hypoxic conditions exacerbate cellular damage, promote senescence, and contribute to age-related pathologies, including cardiovascular diseases, neurodegenerative disorders, cancer, metabolic dysfunctions, and pulmonary conditions. By examining the molecular mechanisms linking hypoxia to aging, we identify key pathways that serve as potential therapeutic targets. Emerging interventions such as HIF modulators, antioxidants, senolytics, and lifestyle modifications hold promise in mitigating the adverse effects of hypoxia on aging tissues. However, challenges such as the heterogeneity of aging, lack of reliable biomarkers, and safety concerns regarding hypoxia-targeted therapies remain. This review emphasizes the need for personalized approaches and advanced technologies to develop effective antiaging interventions. By integrating current knowledge, this review provides a comprehensive framework that underscores the importance of targeting hypoxia-induced pathways to enhance healthy aging and reduce the burden of age-related diseases.

Obesity-induced neuronal senescence: Unraveling the pathophysiological links

Obesity is one of the most prevalent and increasing metabolic disorders and is considered one of the twelve risk factors for dementia. Numerous studies have demonstrated that obesity induces pathophysiological changes leading to cognitive decline; however, the underlying molecular mechanisms are yet to be fully elucidated. Various biochemical processes, including chronic inflammation, oxidative stress, insulin resistance, dysregulation of lipid metabolism, disruption of the blood-brain barrier, and the release of adipokines have been reported to contribute to the accumulation of senescent neurons during obesity. These senescent cells dysregulate neuronal health and function by exhibiting a senescence-associated secretory phenotype, inducing neuronal inflammation, deregulating cellular homeostasis, causing mitochondrial dysfunction, and promoting microglial infiltration. These factors act as major risks for the occurrence of neurodegenerative diseases and cognitive decline. This review aims to focus on how obesity upregulates neuronal senescence and explores both pharmacological and non-pharmacological interventions for preventing cognitive impairments, thus offering new insights into potential therapeutic strategies.

Remodeling of white adipose tissue microenvironment against obesity by phytochemicals

Obesity is a kind of chronic disease due to a long-term imbalance between energy intake and expenditure. In recent years, the number of obese people around the world has soared, and obesity problem should not be underestimated. Obesity is characterized by changes in the adipose microenvironment, mainly manifested as hypertrophy, chronic inflammatory status, hypoxia, and fibrosis, thus contributing to the pathological changes of other tissues. A plethora of phytochemicals have been found to improve adipose microenvironment, thus prevent and resist obesity, providing a new research direction for the treatment of obesity and related diseases. This paper discusses remodeling of the adipose tissue microenvironment as a therapeutic avenue and reviews the progress of phytochemicals in fighting obesity by improving the adipose microenvironment.

Fiery Connections: Macrophage-Mediated Inflammation, the Journey from Obesity to Type 2 Diabetes Mellitus and Diabetic Kidney Disease

The high prevalence of diabetes mellitus (DM) poses a significant public health challenge, with diabetic kidney disease (DKD) as one of its most serious consequences. It has become increasingly clear that type 2 DM (T2D) and the complications of DKD are not purely metabolic disorders. This review outlines emerging evidence related to the step-by-step contribution of macrophages to the development and progression of DKD in individuals who specifically develop T2D as a result of obesity. The macrophage is a prominent inflammatory cell that contributes to obesity, where adipocyte hypertrophy leads to macrophage recruitment and eventually to the expansion of adipose tissue. The recruited macrophages secrete proinflammatory cytokines, which cause systemic inflammation, glucose dysregulation, and insulin sensitivity, ultimately contributing to the development of T2D. Under such pathological changes, the kidney is susceptible to elevated glucose and thereby activates signaling pathways that ultimately drive monocyte recruitment. In particular, the early recruitment of proinflammatory macrophages in the diabetic kidney produces inflammatory cytokines/chemokines that contribute to inflammation and tissue damage associated with DKD pathology. Macrophage activation and recruitment are crucial inciting factors that also persist as DKD progresses. Thus, targeting macrophage activation and function could be a promising therapeutic approach, potentially offering significant benefits for managing DKD at all stages of progression.

Inhibition of Adipocyte-Derived FABP4 Reduces Adipocyte Inflammation, Improves Angiogenesis, and Facilitates Wound Healing in Metabolic Dysfunctions

Dermal white adipose tissue may participate in the wound-healing process. Obesity-mediated chronic low-grade inflammation impairs wound healing by suppressing vascularity. Given that FABP4 is upregulated in the skin tissue of animals with obesity, this study aimed to investigate the effects of FABP4 inhibition on wound healing in mice with high-fat diet-induced metabolic dysfunction in vivo. The interaction between adipocyte-derived FABP4 and vascular endothelial cell function was also investigated. In mice with high-fat diet-induced metabolic dysfunction, FABP4 inhibition increased angiogenesis and facilitated wound healing with reduced wound inflammation. FABP4 inhibition not only attenuated systemic inflammation, decreased body weight, and reduced insulin resistance but also improved the sizes of adipocytes and hypoxic conditions in dermal white adipose tissue. In vitro hypoxia was used to induce adipocyte inflammation, and the supernatants from hypoxia-stimulated adipocytes impaired the function and angiogenetic capability of human dermal microvascular endothelial cells (HDMECs). Both of them were improved by FABP4 inhibition. Altogether, FABP4 inhibition reduced systemic and adipocyte inflammation, improved vascular endothelial cell function, and facilitated wound healing in metabolic dysfunctions. Given the complex involvement of wound healing, future studies may be required to validate FABP4 as a potential therapeutic target for wound repair in metabolic dysfunctions.

Metabolomics in human SGBS cells as new approach method for studying adipogenic effects: Analysis of the effects of DINCH and MINCH on central carbon metabolism

Growing evidence suggests that exposure to certain metabolism-disrupting chemicals (MDCs), such as the phthalate plasticizer DEHP, might promote obesity in humans, contributing to the spread of this global health problem. Due to the restriction on the use of phthalates, there has been a shift to safer declared substitutes, including the plasticizer diisononyl-cyclohexane-1,2-dicarboxylate (DINCH). Notwithstanding, recent studies suggest that the primary metabolite monoisononyl-cyclohexane-1,2-dicarboxylic acid ester (MINCH), induces differentiation of human adipocytes and affects enzyme levels of key metabolic pathways. Given the lack of methods for assessing metabolism-disrupting effects of chemicals on adipose tissue, we used metabolomics to analyze human SGSB cells exposed to DINCH or MINCH. Concentration analysis of DINCH and MINCH revealed that uptake of MINCH in preadipocytes was associated with increased lipid accumulation during adipogenesis. Although we also observed intracellular uptake for DINCH, the solubility of DINCH in cell culture medium was limited, hampering the analysis of possible effects in the μM concentration range. Metabolomics revealed that MINCH induces lipid accumulation similar to peroxisome proliferator-activated receptor gamma (PPARG)-agonist rosiglitazone through upregulation of the pyruvate cycle, which was recently identified as a key driver of de novo lipogenesis. Analysis of the metabolome in the presence of the PPARG-inhibitor GW9662 indicated that the effect of MINCH on metabolism was mediated at least partly by a PPARG-independent mechanism. However, all effects of MINCH were only observed at high concentrations of 10 μM, which are three orders of magnitudes higher than the current concentrations of plasticizers in human serum. Overall, the assessment of the effects of DINCH and MINCH on SGBS cells by metabolomics revealed no adipogenic potential at physiologically relevant concentrations. This finding aligns with previous in vivo studies and supports the potential of our method as a New Approach Method (NAM) for the assessment of adipogenic effects of environmental chemicals.

Plasma Uric Acid, Lactate, and Osmolality in Colorectal Cancer

A complex evaluation of colorectal cancer (CRC) in relation to screening, diagnosis, stage determination, prognosis, and treatment requires valuable biomarkers. The aim of this study was to measure selected biomarkers—uric acid (UA), lactate, Na+, Cl−, and osmolality—in CRC patients and to assess their diagnostic value to distinguish between CRC and healthy controls. Plasma lactate (2.21 ± 0.11 vs. 2.88 ± 0.19, p < 0.01), Na+ (130.79 ± 0.42 vs. 133.23 ± 0.25, p < 0.001), Cl− (102.59 ± 0.45 vs. 103.94 ± 0.23, p < 0.01), and osmolality (266.44 ± 0.86 vs. 271.72 ± 0.62, p < 0.001) were found to be significantly lower in CRC patients as compared to the healthy controls group. Among them, with satisfactory diagnostic potential, were plasma Na+ concentrations and osmolality (AUCNa+ = 0.752, p < 0.0001; AUCosmolality = 0.757, p < 0.05), respectively. UA concentrations were detected at higher concentrations in CRC patients (333.67 ± 13.05 vs. 295.88 ± 13.78, p < 0.05). The results of this study contribute to the elucidation of molecular mechanisms of CRC pathogenesis and the role of studied metabolic parameters in this process. Plasma uric acid, lactate, and osmolality parameters can be used for screening and monitoring colorectal cancer. Further studies are required to elucidate the molecular mechanisms of their action in cancer development. The action of circulating plasma lactate may be different from those locally produced in the tumor microenvironment.

Exploring the Effect of Acute and Regular Physical Exercise on Circulating Brain-Derived Neurotrophic Factor Levels in Individuals with Obesity: A Comprehensive Systematic Review and Meta-Analysis

Obesity is a major global health concern linked to cognitive impairment and neurological disorders. Circulating brain-derived neurotrophic factor (BDNF), a protein crucial for neuronal growth and survival, plays a vital role in brain function and plasticity. Notably, obese individuals tend to exhibit lower BDNF levels, potentially contributing to cognitive decline. Physical exercise offers health benefits, including improved circulating BDNF levels and cognitive function, but the specific impacts of acute versus regular exercise on circulating BDNF levels in obesity are unclear. Understanding this can guide interventions to enhance brain health and counter potential cognitive decline in obese individuals. Therefore, this study aimed to explore the impact of acute and regular physical exercise on circulating BDNF in individuals with obesity. The target population comprised individuals classified as overweight or obese, encompassing both acute and chronic protocols involving all training methods. A comprehensive search was conducted across computerized databases, including PubMed, Academic Search Complete, and Web of Science, in August 2022, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Initially, 98 studies were identified, from which 16 studies, comprising 23 trials, met the selection criteria. Substantial heterogeneity was observed for both acute (I2 = 80.4%) and long-term effects (I2 = 88.7%), but low risk of bias for the included studies. A single session of exercise increased circulating BDNF levels among obese patients compared to the control group (ES = 1.25, 95% CI = 0.19 to 2.30, p = 0.021). However, with extended periods of physical exercise, there was no significant increase in circulating BDNF levels when compared to the control group (ES = 0.49, 95% CI = -0.08 to 1.06, p = 0.089). These findings highlight the need to consider exercise duration and type when studying neurobiological responses in obesity and exercise research. The study's results have implications for exercise prescription in obesity management and highlight the need for tailored interventions to optimize neurotrophic responses. Future research should focus on elucidating the adaptive mechanisms and exploring novel strategies to enhance BDNF modulation through exercise in this population. However, further research is needed considering limitations such as the potential age-related confounding effects due to diverse participant ages, lack of sex-specific analyses, and insufficient exploration of how specific exercise parameters (e.g., duration, intensity, type) impact circulating BDNF.

HIF1α Elevations at Tissue and Serum Levels and Their Association With Metabolic Disorders in Children With Obesity

OBJECTIVE

We aimed to examine the expression profile and circulating level of hypoxia-inducible factor 1 alpha (HIF1α) in children and the relationships with metabolic disorders.

METHODS

A total of 519 children were recruited, with paired subcutaneous and omental adipose tissues collected from 17 children and serum samples from the remaining children. All children underwent anthropometric and biochemical analyses. The mRNA, protein, and serum levels of HIF1α were determined by real-time PCR, immunohistochemistry, and enzyme-linked immunosorbent assay, respectively.

RESULTS

Both HIF1α mRNA and protein levels, especially in omental adipose tissue, were increased in overweight or obese (OV/OB) children (P < .05). Likewise, serum HIF1α level was remarkably higher in OV/OB children than in normal-weight children (P < .05). Serum HIF1α level was positively correlated with BMI z-score, fat mass percentage, waist to height ratio, systolic blood pressure, alanine aminotransferase, total triglycerides, uric acid, and homeostasis model assessment of insulin resistance (IR). Furthermore, a binary logistic regression analysis of serum HIF1α level indicated that the risks for IR, nonalcoholic fatty liver disease (NAFLD), and metabolic syndrome remained significant in the presence of all potential confounding variables. Finally, the area under the receiver operating characteristic curves for serum HIF1α level in children who were diagnosed with IR, NAFLD, and metabolic syndrome were 0.698 (95% CI, 0.646-0.750; P < .001), 0.679 (95% CI, 0.628-0.731; P < .001), and 0.900 (95% CI, 0.856-0.945; P < .001).

CONCLUSION

HIF1α expression is higher in the adipose tissue, especially omental, of children with obesity than in children with normal weight. Elevated serum HIF1α level is associated with adiposity and metabolic disorder, which may predict a higher risk of obesity complications.

Adipocyte Glucocorticoid Receptor Activation With High Glucocorticoid Doses Impairs Healthy Adipose Tissue Expansion by Repressing Angiogenesis

In humans, glucocorticoids (GCs) are commonly prescribed because of their anti-inflammatory and immunosuppressive properties. However, high doses of GCs often lead to side effects, including diabetes and lipodystrophy. We recently reported that adipocyte glucocorticoid receptor (GR)-deficient (AdipoGR-KO) mice under corticosterone (CORT) treatment exhibited a massive adipose tissue (AT) expansion associated with a paradoxical improvement of metabolic health compared with control mice. However, whether GR may control adipose development remains unclear. Here, we show a specific induction of hypoxia-inducible factor 1α (HIF-1α) and proangiogenic vascular endothelial growth factor A (VEGFA) expression in GR-deficient adipocytes of AdipoGR-KO mice compared with control mice, together with an increased adipose vascular network, as assessed by three-dimensional imaging. GR activation reduced HIF-1α recruitment to the Vegfa promoter resulting from Hif-1α downregulation at the transcriptional and posttranslational levels. Importantly, in CORT-treated AdipoGR-KO mice, the blockade of VEGFA by a soluble decoy receptor prevented AT expansion and the healthy metabolic phenotype. Finally, in subcutaneous AT from patients with Cushing syndrome, higher VEGFA expression was associated with a better metabolic profile. Collectively, these results highlight that adipocyte GR negatively controls AT expansion and metabolic health through the downregulation of the major angiogenic effector VEGFA and inhibition of vascular network development.

ARTICLE HIGHLIGHTS

Adipose Tissue Hypoxia in Obesity: Clinical Reappraisal of Hypoxia Hypothesis

Obese subjects exhibit lower adipose tissue oxygen consumption in accordance with the lower adipose tissue blood flow. Thereby, compared to lean subjects, obese individuals have almost half lower capillary density and more than half lower vascular endothelial growth factor (VEGF). The VEGF expression together with hypoxia-inducible transcription factor-1 alpha (HIF-1α) activity also requires phosphatidylinositol 3-kinase (PI3K) and mammalian target of rapamycin (mTOR)-mediated signaling. Especially HIF-1α is an important signaling molecule for hypoxia to induce the inflammatory responses. Hypoxia contributes to several biological functions, such as angiogenesis, cell proliferation, apoptosis, inflammation, and insulin resistance (IR). Pathogenesis of obesity-related comorbidities is attributed to intermittent hypoxia (IH), which is mostly observed in visceral obesity. Proinflammatory phenotype of the adipose tissue is a crucial link between IH and the development of IR. Inhibition of adaptive unfolded protein response (UPR) in hypoxia increases β cell death. Moreover, deletion of HIF-1α worsens β cell function. Oxidative stress, as well as the release of proinflammatory cytokines/adipokines in obesity, is proportional to the severity of IH. Reactive oxygen species (ROS) generation at mitochondria is responsible for propagation of the hypoxic signal; however, mitochondrial ROS production is required for hypoxic HIF-1α protein stabilization. Alterations in oxygen availability of adipose tissue directly affect the macrophage polarization and are responsible for the dysregulated adipocytokines production in obesity. Hypoxia both inhibits adipocyte differentiation from preadipocytes and macrophage migration from the hypoxic adipose tissue. Upon reaching a hypertrophic threshold beyond the adipocyte fat loading capacity, excess extracellular matrix (ECM) components are deposited, causing fibrosis. HIF-1α initiates the whole pathological process of fibrosis and inflammation in the obese adipose tissue. In addition to stressed adipocytes, hypoxia contributes to immune cell migration and activation which further aggravates adipose tissue fibrosis. Therefore, targeting HIF-1α might be an efficient way to suppress hypoxia-induced pathological changes in the ECM. The fibrosis score of adipose tissue correlates negatively with the body mass index and metabolic parameters. Inducers of browning/beiging adipocytes and adipokines, as well as modulations of matrix remodeling enzyme inhibitors, and associated gene regulators, are potential pharmacological targets for treating obesity.

Next-Cell Hypothesis: Mechanism of Obesity-Associated Carcinogenesis

Higher body fat content is related to a higher risk of mortality, and obesity-related cancer represents approximately 40% of all cancer patients diagnosed each year. Furthermore, epigenetic mechanisms are involved in cellular metabolic memory and can determine one's predisposition to being overweight. Low-grade chronic inflammation, a well-established characteristic of obesity, is a central component of tumor development and progression. Cancer-associated adipocytes (CAA), which enhance inflammation- and metastasis-related gene sets within the cancer microenvironment, have pro-tumoral effects. Adipose tissue is a major source of the exosomal micro ribonucleic acids (miRNAs), which modulate pathways involved in the development of obesity and obesity-related comorbidities. Owing to their composition of cargo, exosomes can activate receptors at the target cell or transfer molecules to the target cells and thereby change the phenotype of these cells. Exosomes that are released into the extracellular environment are internalized with their cargo by neighboring cells. The tumor-secreted exosomes promote organ-specific metastasis of tumor cells that normally lack the capacity to metastasize to a specific organ. Therefore, the communication between neighboring cells via exosomes is defined as the "next-cell hypothesis." The reciprocal interaction between the adipocyte and tumor cell is realized through the adipocyte-derived exosomal miRNAs and tumor cell-derived oncogenic miRNAs. The cargo molecules of adipocyte-derived exosomes are important messengers for intercellular communication involved in metabolic responses and have very specific signatures that direct the metabolic activity of target cells. RNA-induced silencing regulates gene expression through various mechanisms. Destabilization of DICER enzyme, which catalyzes the conversion of primary miRNA (pri-miRNA) to precursor miRNA (pre-miRNA), is an important checkpoint in cancer development and progression. Interestingly, adipose tissue in obesity and tumors share similar pathogenic features, and the local hypoxia progress in both. While hypoxia in obesity leads to the adipocyte dysfunction and metabolic abnormalities, in obesity-related cancer cases, it is associated with worsened prognosis, increased metastatic potential, and resistance to chemotherapy. Notch-interleukin-1 (IL-1)-Leptin crosstalk outcome is referred to as "NILCO effect." In this chapter, obesity-related cancer development is discussed in the context of "next-cell hypothesis," miRNA biogenesis, and "NILCO effect."

A low-carbohydrate diet with different fatty acids' sources in the treatment of obesity: Impact on insulin resistance and adipogenesis

BACKGROUND

The search for nutritional intervention strategies against obesity has grown, highlighting the low-carbohydrate diet model. However, little is known about the impact of the quality of fatty acids consumed in this diet. Thus, we aim to investigate the influence of fatty acid quality on dietary strategy on obesity.

METHODS

Male Swiss mice were diet-induced to obesity. Afterward, mice consume a low-carb diet with different types of fat: saturated, polyunsaturated ω-3, ω-6, and monounsaturated ω-9 fatty acids. Weight gain and food consumption were monitored weekly. An oral glucose tolerance test was performed and blood and tissue samples were collected for analysis of insulin resistance markers. Protein expression of insulin signaling pathway molecules, lipid metabolism, mitochondrial function, macrophage polarization, and cytokine production were analyzed.

RESULTS

The high-fat diet was able to induce obesity and glucose intolerance. The switch to a low-carbohydrate dietary pattern reversed the glucose intolerance, with better results in the ω-3 and ω-9 groups. After the low-carbohydrate diet, groups ω-3 and ω-9 presented improved fasting serum glucose, insulin, and HOMA indexes. The low-carbohydrate diet also increased the activity of insulin pathway proteins such as IR, IRS1, and AKT. Furthermore, the ω-3 diet group showed greater activity of mitochondrial complexes and AMPK signaling pathway proteins. The ω-6 and ω-9 -rich diet induced M2-type macrophage polarization, as well as cytokine production modulation by the low-carbohydrate diet in the ω-3 and ω-9 groups.

CONCLUSIONS

Consuming a low-carbohydrate diet pattern promotes weight loss and improves glucose intolerance in obesity. Also, the quality of lipids has a direct influence, demonstrating that the consumption of ω-3 polyunsaturated and ω-9 monounsaturated lipids can lead to more favorable outcomes for the improvement of glucose intolerance, lipid metabolism, and anti-inflammatory effects.

Human Preadipocytes Differentiated under Hypoxia following PCB126 Exposure during Proliferation: Effects on Differentiation, Glucose Uptake and Adipokine Profile

Persistent organic pollutants (POPs) accumulation and hypoxia are two factors proposed to adversely alter adipose tissue (AT) functions in the context of excess adiposity. Studies have shown that preadipocytes exposure to dioxin and dioxin-like POPs have the greatest deleterious impact on rodent and immortalized human preadipocyte differentiation, but evidence on human preadipocytes is lacking. Additionally, hypoxia is known to strongly interfere with the dioxin-response pathway. Therefore, we tested the effects of pre-differentiation polychlorinated biphenyl (PCB)126 exposure at 10 µM for 3 days and subsequent differentiation under hypoxia on human subcutaneous adipocytes (hSA) differentiation, glucose uptake and expression of selected metabolism- and inflammation-related genes. Pre-differentiation PCB126 exposure lowered the adenosine triphosphate (ATP) content, glucose uptake and leptin expression of mature adipocytes but had limited effects on differentiation under normoxia (21% O2). Under hypoxia (3% O2), preadipocytes ability to differentiate was significantly reduced as reflected by significant decreased lipid accumulation and downregulation of key adipocyte genes such as peroxisome proliferator-activated receptor gamma (PPARγ) and adiponectin. Hypoxia increased glucose uptake and glucose transporter 1 (GLUT1) expression but abolished the adipocytes insulin response and GLUT4 expression. The expression of pro-inflammatory adipokine interleukin-6 (IL-6) was slightly increased by both PCB126 and hypoxia, while IL-8 expression was significantly increased only following the PCB126-hypoxia sequence. These observations suggest that PCB126 does not affect human preadipocyte differentiation, but does affect the subsequent adipocytes population, as reflected by lower ATP levels and absolute glucose uptake. On the other hand, PCB126 and hypoxia exert additive effects on AT inflammation, an important player in the development of chronic diseases such as type 2 diabetes and cardiovascular diseases.

Adipocyte-derived extracellular vesicles: bridging the communications between obesity and tumor microenvironment

By the year 2035 more than 4 billion people might be affected by obesity and being overweight. Adipocyte-derived Extracellular Vesicles (ADEVs/ADEV-singular) are essential for communication between the tumor microenvironment (TME) and obesity, emerging as a prominent mechanism of tumor progression. Adipose tissue (AT) becomes hypertrophic and hyperplastic in an obese state resulting in insulin resistance in the body. This modifies the energy supply to tumor cells and simultaneously stimulates the production of pro-inflammatory adipokines. In addition, obese AT has a dysregulated cargo content of discharged ADEVs, leading to elevated amounts of pro-inflammatory proteins, fatty acids, and carcinogenic microRNAs. ADEVs are strongly associated with hallmarks of cancer (proliferation and resistance to cell death, angiogenesis, invasion, metastasis, immunological response) and may be useful as biomarkers and antitumor therapy strategy. Given the present developments in obesity and cancer-related research, we conclude by outlining significant challenges and significant advances that must be addressed expeditiously to promote ADEVs research and clinical applications.

Anthocyanins ameliorate obesity-associated metainflammation: Preclinical and clinical evidence

The growing rates of obesity worldwide call for intervention strategies to help control the pathophysiological consequences of weight gain. The use of natural foods and bioactive compounds has been suggested as such a strategy because of their recognized antioxidant and anti-inflammatory properties. For example, polyphenols, especially anthocyanins, are candidates for managing obesity and its related metabolic disorders. Obesity is well known for the presence of metainflammation, which has been labeled as an inflammatory activation that leads to a variety of metabolic disorders, usually related to increased oxidative stress. Considering this, anthocyanins may be promising natural compounds able to modulate several intracellular mechanisms, mitigating oxidative stress and metainflammation. A wide variety of foods and extracts rich in anthocyanins have become the focus of research in the field of obesity. Here, we bring together the current knowledge regarding the use of anthocyanins as an intervention tested in vitro, in vivo, and in clinical trials to modulate metainflammation. Most recent research applies a wide variety of extracts and natural sources of anthocyanins, in diverse experimental models, which represents a limitation of the research field. However, the literature is sufficiently consistent to establish that the in-depth molecular analysis of gut microbiota, insulin signaling, TLR4-triggered inflammation, and oxidative stress pathways reveals their modulation by anthocyanins. These targets are interconnected at the cellular level and interact with one another, leading to obesity-associated metainflammation. Thus, the positive findings with anthocyanins observed in preclinical models might directly relate to the positive outcomes in clinical studies. In summary and based on the entirety of the relevant literature, anthocyanins can mitigate obesity-related perturbations in gut microbiota, insulin resistance, oxidative stress and inflammation and therefore may contribute as a therapeutic tool in people living with obesity.

13C-Metabolic flux analysis of 3T3-L1 adipocytes illuminates its core metabolism under hypoxia

Hypoxia has been identified as a major factor in the pathogenesis of adipose tissue inflammation, which is a hallmark of obesity and obesity-linked type 2 diabetes mellitus. In this study, we have investigated the impact of hypoxia (1% oxygen) on the physiology and metabolism of 3T3-L1 adipocytes, a widely used cell culture model of adipose. Specifically, we applied parallel labeling experiments, isotopomer spectral analysis, and ¹³C-metabolic flux analysis to quantify the impact of hypoxia on adipogenesis, de novo lipogenesis and metabolic flux reprogramming in adipocytes. We found that 3T3-L1 cells can successfully differentiate into lipid-accumulating adipocytes under hypoxia, although the production of lipids was reduced by about 40%. Quantitative flux analysis demonstrated that short-term (1 day) and long-term (7 days) exposure to hypoxia resulted in similar reprogramming of cellular metabolism. Overall, we found that hypoxia: 1) reduced redox and energy generation by more than 2-fold and altered the patterns of metabolic pathway contributions to production and consumption of energy and redox cofactors; 2) redirected glucose metabolism from pentose phosphate pathway and citric acid cycle to lactate production; 3) rewired glutamine metabolism, from net glutamine production to net glutamine catabolism; 4) suppressed branched chain amino acid consumption; and 5) reduced biosynthesis of odd-chain fatty acids and mono-unsaturated fatty acids, while synthesis of saturated even-chain fatty acids was not affected. Together, these results highlight the profound impact of extracellular microenvironment on adipocyte metabolic activity and function.

The effect of the ketogenic diet on Acne: Could it be a therapeutic tool?

Acne is a chronic inflammatory disease of the pilosebaceous unit resulting from androgen-induced increased sebum production, altered keratinization, inflammation, and bacterial colonization of the hair follicles of the face, neck, chest and back by Propionibacterium acnes. Overall, inflammation and immune responses are strongly implicated in the pathogenesis of acne. Although early colonization with Propionibacterium acnes and family history may play an important role in the disease, it remains unclear exactly what triggers acne and how treatment affects disease progression. The influence of diet on acne disease is a growing research topic, yet few studies have examined the effects of diet on the development and clinical severity of acne disease, and the results have often been contradictory. Interestingly, very low-calorie ketogenic diet (VLCKD) has been associated with both significant reductions in body weight and inflammatory status through the production of ketone bodies and thus it has been expected to reduce the exacerbation of clinical manifestations or even block the trigger of acne disease. Given the paucity of studies regarding the implementation of VLCKD in the management of acne, this review aims to provide evidence from the available scientific literature to support the speculative use of VLCKD in the treatment of acne.

Hypoxia as a Double-Edged Sword to Combat Obesity and Comorbidities

The global epidemic of obesity is tightly associated with numerous comorbidities, such as type II diabetes, cardiovascular diseases and the metabolic syndrome. Among the key features of obesity, some studies have suggested the abnormal expansion of adipose-tissue-induced local endogenous hypoxic, while other studies indicated endogenous hyperoxia as the opposite trend. Endogenous hypoxic aggravates dysfunction in adipose tissue and stimulates secretion of inflammatory molecules, which contribute to obesity. In contrast, hypoxic exposure combined with training effectively generate exogenous hypoxic to reduce body weight and downregulate metabolic risks. The (patho)physiological effects in adipose tissue are distinct from those of endogenous hypoxic. We critically assess the latest advances on the molecular mediators of endogenous hypoxic that regulate the dysfunction in adipose tissue. Subsequently we propose potential therapeutic targets in adipose tissues and the small molecules that may reverse the detrimental effect of local endogenous hypoxic. More importantly, we discuss alterations of metabolic pathways in adipose tissue and the metabolic benefits brought by hypoxic exercise. In terms of therapeutic intervention, numerous approaches have been developed to treat obesity, nevertheless durability and safety remain the major concern. Thus, a combination of the therapies that suppress endogenous hypoxic with exercise plans that augment exogenous hypoxic may accelerate the development of more effective and durable medications to treat obesity and comorbidities.

Physiological Oxygen Levels Differentially Regulate Adipokine Production in Abdominal and Femoral Adipocytes from Individuals with Obesity Versus Normal Weight

Adipose tissue (AT) inflammation may increase obesity-related cardiometabolic complications. Altered AT oxygen partial pressure (pO₂) may impact the adipocyte inflammatory phenotype. Here, we investigated the effects of physiological pO₂ levels on the inflammatory phenotype of abdominal (ABD) and femoral (FEM) adipocytes derived from postmenopausal women with normal weight (NW) or obesity (OB). Biopsies were collected from ABD and FEM subcutaneous AT in eighteen postmenopausal women (aged 50-65 years) with NW (BMI 18-25 kg/m², n = 9) or OB (BMI 30-40 kg/m², n = 9). We compared the effects of prolonged exposure to different physiological pO₂ levels on adipokine expression and secretion in differentiated human multipotent adipose-derived stem cells. Low physiological pO₂ (5% O₂) significantly increased leptin gene expression/secretion in ABD and FEM adipocytes derived from individuals with NW and OB compared with high physiological pO₂ (10% O₂) and standard laboratory conditions (21% O₂). Gene expression/secretion of IL-6, DPP-4, and MCP-1 was reduced in differentiated ABD and FEM adipocytes from individuals with OB but not NW following exposure to low compared with high physiological pO₂ levels. Low physiological pO₂ decreases gene expression and secretion of several proinflammatory factors in ABD and FEM adipocytes derived from individuals with OB but not NW.

Management of NAFLD in primary care settings

Non-alcoholic fatty liver disease (NAFLD) affects at least 25% of the general population and is an increasingly important cause of cirrhosis and hepatocellular carcinoma. Although it is the research focus of the hepatology field, it is clear that primary care physicians are seeing the majority of NAFLD patients and are in a pivotal position to provide quality care. In this article, we review the role of primary care in the management of NAFLD. NAFLD is common in patients with diabetes, obesity and other metabolic risk factors. Abdominal ultrasonography is the most commonly used method to diagnose fatty liver. Simple fibrosis scores have high negative predictive values in excluding advanced liver fibrosis and future liver-related events and can be used in primary care as initial evaluation. An abnormal result should be followed by subsequent workup or specialist referral. Primary care is the ideal setting to institute multidisciplinary care, especially the involvement of dietitians and physical activity trainers in lifestyle intervention, as well as initiating the discussion of bariatric surgery in patients with severe obesity. Although specific drug treatment for steatohepatitis would require a more precise diagnosis, metabolic drugs that improve both steatohepatitis and cardiovascular outcomes (e.g. glucagon-like peptide-1 receptor agonists) may be considered in patients with NAFLD.

IL10/AMPK pathway was associated with the hippocampal anti-inflammatory response to high-sugar and high-fat diet withdrawal

OBJECTIVE

The present experimental study aimed to evaluate the effect of consuming an obesogenic diet (OD) on serum and hippocampal inflammation and proteins related to energy metabolism, alongside, we evaluated how the same parameters responded to an OD withdrawal.

SUBJECTS

Thirty male 60-days-old Wistar rats were used.

METHODS

The control group (n = 10) was fed the control diet across the whole experiment. The remaining animals were fed a high-sugar/high-fat (HSHF) diet for 30 days (n = 20) and half of them were placed on the control diet for 48 h (n = 10) afterwards.

RESULTS

OD intake decreased hippocampal AMPK phosphorylation, although, it did not increase serum inflammation and only increased hippocampal pNFκBp65 levels without any increase in the cytokines assessed. Moreover, OD withdrawal led to higher inflammatory markers in the serum and hippocampus and higher hippocampal AMPK phosphorylation. The mediation models applied suggested that the effect of OD withdrawal on hippocampal inflammation was driven by serum inflammation, which activated the hippocampal IL10/AMPK anti-inflammatory pathway as a response.

CONCLUSION

Our analyses suggest that OD withdrawal increases serum inflammation with hippocampal consequent inflammatory alterations. Despite the general assumption that improving diet improves health, this may not be immediate.

Altered adipose tissue macrophage populations in people with HIV on integrase inhibitor-containing antiretroviral therapy

OBJECTIVE

Antiretroviral therapy (ART) extends the life of people with HIV (PWH), but these individuals are at increased risk for obesity, dyslipidemia, diabetes, and cardiovascular disease. These comorbidities may be a consequence of HIV-related chronic inflammation and/or adverse effects of ART on tissue regulatory adipose tissue macrophages (ATMs). We sought to determine the effects of HIV/ART on metabolically beneficial ATM populations and functions.

DESIGN

We examined subcutaneous ATMs from PWH on integrase inhibitor-containing ART ( n  = 5) and uninfected persons ( n  = 9). We complemented these studies with ex vivo and in vitro analyses of peripheral blood mononuclear cell (PBMC) and murine macrophage lipid metabolism and fatty acid oxidation gene expression.

METHODS

ATM populations were examined by flow cytometry. Macrophage lipid metabolism and fatty acid oxidation gene expression were examined by Seahorse assay and quantitative PCR.

RESULTS

Adipose tissue from PWH had reduced populations of metabolically activated CD9 + ATMs compared to that of uninfected controls ( P  < 0.001). PBMCs of PWH had lower fatty acid metabolism compared to those of uninfected controls ( P  < 0.01). Analysis of murine macrophages revealed that dolutegravir reduced lipid metabolism ( P  < 0.001) and increased expression of the fatty acid beta-oxidation enzyme enoyl-CoA hydratase, short chain 1 ( P  < 0.05).

CONCLUSIONS

We report the loss of metabolically beneficial ATM populations in PWH on ART, altered fatty acid metabolism of blood immune cells, and evidence that dolutegravir alters macrophage fatty acid metabolism. Future studies should examine direct or indirect effects and mechanisms of dolutegravir, and other integrase inhibitors and ART classes, on fatty acid beta-oxidation.

Of mice and men: Considerations on adipose tissue physiology in animal models of obesity and human studies

The ever-increasing burden of obesity demands a better pathophysiological understanding, especially regarding adipose tissue pathophysiology. Animal models of obesity are of great importance in investigating potential mechanisms and implications of obesity. Many issues should be considered while interpreting the preclinical results as anatomical and pathophysiological differences exist among species. Importantly, the natural history of obesity development differs considerably. An important example of conflicting results among preclinical models and human physiological studies is that of adipose tissue oxygenation, where rodent models almost unanimously have shown the presence of hypoxia in the adipose tissue of obese animals while human studies have yielded conflicting results to date. Other issues which require further clarification before generalizing preclinical data in humans include adipose tissue browning, endocrine function and fibrosis. The aim of this mini-review is to synopsize similarities and differences between rodent models and humans, which should be taken into consideration in obesity studies.

Reducing VEGFB expression regulates the balance of glucose and lipid metabolism in mice via VEGFR1

In recent years, studies have demonstrated that vascular endothelial growth factor B (VEGFB) can affect the metabolism of fatty acids and glucose, and it is expected to become a target for the diagnosis and treatment of metabolic diseases such as obesity and diabetes. At present, the specific mechanism that VEGFB regulates lipid and glucose metabolism balance is not completely understood. The present study used systemic VEGFB gene-knockout mice to investigate the effects of downregulation of the VEGFB gene on lipid metabolism and insulin secretion, and to explore the mechanism of the VEGFB pathway involved in the regulation of glucose and lipid metabolism. The morphological changes in the liver and pancreas of mice after VEGFB gene deletion were observed under a light microscope and a scanning electron microscope, and the effects of VEGFB gene deletion on lipid metabolism and blood glucose balance were detected by a serological technique. The detection indexes included total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol. Simultaneously, fasting blood glucose, glycosylated hemoglobin A1c (HbA1c), fasting insulin and glucagon were measured. Insulin sensitivity was assessed by using the insulin tolerance tests and glucose tolerance tests, and function of β-cell islets was evaluated by using the insulin resistance index (HOMA-IR) and pancreatic β-cell secretion index (HOMA-β). Τhe protein expression changes of vascular endothelial growth factor receptor 1 (VEGFR1) and vascular endothelial growth factor receptor 2 (VEGFR2) in mouse islets were detected by western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) after the VEGFB gene was knocked down to analyze the mechanism of VEGFB that may be involved in glucose and lipid metabolism. It was observed that after VEGFB was knocked down, mouse hepatocytes exhibited steatosis and increased secretory vesicles in islet cells. The lipid metabolism indexes such as TG, TC and LDL increased significantly; however, the levels of FBS, postprandial blood glucose and HbA1c decreased, whereas the glucose tolerance increased. Serum insulin secretion increased and HOMA-IR decreased since VEGFB was knocked down. Western blotting and RT-qPCR results revealed that the expression levels of VEGFR1 and neuropilin-1 decreased after the VEGFB gene was knocked down, while the expression levels of VEGFA and VEGFR2 increased. The absence of VEGFB may be involved in the regulation of glucose and lipid metabolism in mice by activating the VEGFA/VEGFR2 signaling pathway. VEGFB is expected to become a new target for the treatment of metabolic diseases such as obesity and diabetes. At present, the mechanism of VEGFB involved in regulating lipid metabolism and glucose metabolism is not completely clear. It was identified that downregulating VEGFB improved lipid metabolism and insulin resistance. The role of VEGFB/VEGFR1 pathway and other family members in regulating glucose and lipid metabolism was detected, which provided a theoretical and experimental basis for VEGFB to affect the regulation of glucose and lipid metabolism balance.

Regulatory Effects of Metformin, an Antidiabetic Biguanide Drug, on the Metabolism of Primary Rat Adipocytes

Metformin is a biguanide compound commonly applied in humans with type 2 diabetes. The drug affects different tissues, including fat tissue. The direct influence of metformin on cells of fat tissue, i.e., adipocytes, is poorly elucidated. In the present study, the short-term (4-h) effects of metformin on lipogenesis, glucose transport, lipolysis, and lactate release in primary rat adipocytes were explored. It was demonstrated that metformin reduced insulin-induced lipogenesis and increased glucose transport into adipocytes. The tested compound also decreased lactate release from fat cells. It was shown that metformin substantially limited lipolysis stimulated by epinephrine (adrenergic receptor agonist) and dibutyryl-cAMP (direct activator of protein kinase A). Moreover, metformin decreased the lipolytic process triggered by DPCPX (adenosine A1 receptor antagonist). In the case of each lipolytic stimulator, the drug evoked a similar inhibitory effect in the presence of 3 and 12 mM glucose. The lipolytic response of adipocytes to epinephrine was also found to be reduced by metformin when glucose was replaced by alanine. It was demonstrated that the tested compound limits the release of both glycerol and fatty acids from fat cells. The results of the present study provided evidence that metformin significantly affects the metabolism of primary rat adipocytes. Its action covers processes related to lipid accumulation and release and occurs after relatively short-term exposure.

Ceiling culture of human mature white adipocytes with a browning agent: A novel approach to induce transdifferentiation into beige adipocytes

Excess and dysfunctional adipose tissue plays an important role in metabolic diseases, including obesity, atherosclerosis and type 2 diabetes mellitus. In mammals, adipose tissue is categorized into two types: white and brown. Adult brown tissue is mainly composed of beige adipocytes, which dispose of stored energy as heat and have become increasingly popular as a therapeutic target for obesity. However, there is still a paucity of cell models that allow transdifferentiation of mature white adipocytes into beige adipocytes, as seen in vivo. Here, we describe a novel, ceiling culture-based model of human mature white adipocytes, which transdifferentiate into beige adipocytes under the mechanical force and hypoxia of ceiling culture. We also show that the use of rosiglitazone and rapamycin can modulate transdifferentiation, up and down regulating expression of beige adipocyte-specific genes, respectively. Rosiglitazone additionally facilitated the upregulation of fatty acid lipolysis and oxidation genes. Finally, these beige adipocytes derived from dedifferentiated adipocytes exhibited a progenitor-specific phenotype, with higher expression of mature adipocyte-specific genes than adipocyte-derived stem cells. Overall, we report a novel approach to conveniently cultivate beige adipocytes from white adipocytes in vitro, suitable for mechanistic studies of adipose biology and development of cell and drug therapies in the future.

Lactate Is a Key Mediator That Links Obesity to Insulin Resistance via Modulating Cytokine Production From Adipose Tissue

Numerous evidence indicates that inflammation in adipose tissue is the primary cause of systemic insulin resistance induced by obesity. Obesity-associated changes in circulating LPS level and hypoxia/HIF-1α activation have been proposed to be involved in boosting obesity-induced inflammation. However, there is poor understanding of what triggers obesity-induced inflammation. In this study, we pinpoint lactate as a key trigger to mediate obesity-induced inflammation and systemic insulin resistance. Specific deletion of Slc16a1 that encodes MCT1, the primary lactate transporter in adipose tissues, robustly elevates blood levels of proinflammatory cytokines and aggravates systemic insulin resistance without alteration of adiposity in mice fed high-fat diet. Slc16a1 deletion in adipocytes elevates intracellular lactate level while reducing circulating lactate concentration. Mechanistically, lactate retention due to Slc16a1 deletion initiates adipocyte apoptosis and cytokine release. The locally recruited macrophages amplify the inflammation by release of proinflammatory cytokines to the circulation, leading to insulin resistance in peripheral tissues. This study, therefore, indicates that lactate within adipocytes has a key biological function linking obesity to insulin resistance, and harnessing lactate in adipocytes can be a promising strategy to break this link.

The Obese Brain: Mechanisms of Systemic and Local Inflammation, and Interventions to Reverse the Cognitive Deficit

Overweight and obesity are now considered a worldwide pandemic and a growing public health problem with severe economic and social consequences. Adipose tissue is an organ with neuroimmune-endocrine functions, which participates in homeostasis. So, adipocyte hypertrophy and hyperplasia induce a state of chronic inflammation that causes changes in the brain and induce neuroinflammation. Studies with obese animal models and obese patients have shown a relationship between diet and cognitive decline, especially working memory and learning deficiencies. Here we analyze how obesity-related peripheral inflammation can affect central nervous system physiology, generating neuroinflammation. Given that the blood-brain barrier is an interface between the periphery and the central nervous system, its altered physiology in obesity may mediate the consequences on various cognitive processes. Finally, several interventions, and the use of natural compounds and exercise to prevent the adverse effects of obesity in the brain are also discussed.

Relative Contributions of Pseudohypoxia and Inflammation to Peritoneal Alterations with Long-Term Peritoneal Dialysis Patients

Long-term peritoneal dialysis (PD) is associated with alterations in peritoneal function, like the development of high small solute transfer rates and impaired ultrafiltration. Also morphologic changes can develop, the most prominent being loss of mesothelium, vasculopathy and interstitial fibrosis. Current research suggests peritoneal inflammation as the driving force for these alterations. In this review the available evidence for inflammation is examined and a new hypothesis is put forward consisting of high glucose-induced pseudohypoxia. Hypoxia of cells is characterized by a high NADH/NAD+ ratio in their cytosol. Pseudohypoxia is similar, but occurs when excessive amounts of glucose are metabolized, as is the case for peritoneal interstitial cells in PD. The glucose- induced high NADH/NAD+ ratio upregulates the hypoxia-inducible factor-1 gene, which stimulates not only the glucose transporter-1 gene, but also many profibrotic genes like TGFβ, VEGF, PAI-1 and CTGF, all known to be involved in the development of peritoneal fibrosis. This review discusses the causes and consequences of pseudohypoxia in PD and the available options for treatment and prevention. Reducing peritoneal exposure to the excessively high dialysate glucose load is the cornerstone to avoid the pseudohypoxia-induced alterations. This can partly be done by the use of icodextrin, or by combinations of low molecular weight osmotic agents, all in a low dose. The addition of alanyl-glutamine to the dialysis solution needs further clinical investigation.

Delivery of miRNAs to the adipose organ for metabolic health

Despite the increasing prevalence of obesity and diabetes, there is no efficient treatment to combat these epidemics. The adipose organ is the main site for energy storage and plays a pivotal role in whole body lipid metabolism and energy homeostasis, including remodeling and dysfunction of adipocytes and adipose tissues in obesity and diabetes. Thus, restoring and balancing metabolic functions in the adipose organ is in demand. MiRNAs represent a novel class of drugs and drug targets, as they are heavily involved in the regulation of many cellular and metabolic processes and diseases, likewise in adipocytes. In this review, we summarize key regulatory activities of miRNAs in the adipose organ, discuss various miRNA replacement and inhibition strategies, promising delivery systems for miRNAs and reflect the future of novel miRNA-based therapeutics to target adipose tissues with the ultimate goal to combat metabolic disorders.

Gold nanoparticles and obese adipose tissue microenvironment in cancer treatment

The epidemiological correlation between obesity and cancer is well characterized, but the biological mechanisms which regulate tumor development and response to therapy in obese cancer patients remain unclear. The tumor microenvironment plays an important role in protecting cancer cells by altering the delivery of anticancer therapy to the tumor tissue, reducing the efficacy of treatment. Obese tumor microenvironment provides additional benefits to the survival of tumor cells against anticancer therapies by altering the extracellular matrix composition, angiogenesis processes and the immune cells profile. Nanotechnology, and in particular gold nanoparticles, are being researched as a theranostic strategy for cancer treatment due to their ability to sensitize cancer cells to radiation and photodynamic therapy, enhance delivery of drugs to tumor cells, and in diagnostic applications. Adipose tissue and the obese tumor microenvironment may alter the activity of nanotherapeutics. In this article, we reviewed the current state of our understanding about the mechanisms by which the obese tumor microenvironment may alter the delivery and efficacy of anti-cancer treatments, and why the use of gold nanoparticles may represent an interesting strategy for cancer treatment in the obesity setting.

Adipokines: inflammation and the pleiotropic role of white adipose tissue

I had been working on the endocrine and signalling role of white adipose tissue (WAT) since 1994 following the identification of the ob (Lep) gene(1), this after some 15 years investigating the physiological role of brown adipose tissue. The ob gene, a mutation in which it is responsible for the profound obesity of ob/ob (Lepob/Lepob) mice, is expressed primarily in white adipocytes and encodes the pleiotropic hormone leptin. The discovery of this adipocyte hormone had wide-ranging implications, including that white fat has multiple functions that far transcend the traditional picture of a simple lipid storage organ.

Inflammatory mechanisms linking obesity and tendinopathy

Chronic tendinopathy is a debilitating tendon disorder with disappointing treatment outcomes. This review focuses on the potential roles of chronic low-grade inflammation in promoting tendinopathy in obesity. A systematic literature search was performed to identify all clinical studies supporting the actions of obesity-associated inflammatory mediators in the development of tendinopathy. The mechanisms of obesity-induced chronic inflammation in adipose tissue are firstly reviewed. Common inflammatory mediators potentially linking obesity and the development of tendinopathy, and their association with mechanical overuse, are discussed, along with pre-clinical evidences and a systematic literature search on clinical studies. The potential contribution of local adipose tissues in the promotion of inflammation, pain and tendon degeneration is then discussed. The future research directions are proposed.

Translational potential statement

Better understanding of the roles of obesity-associated inflammatory mediators on tendons will clarify the pathophysiological drivers of tendinopathy in patients with obesity and identify possible treatment targets. Further studies on the mechanisms of obesity-induced chronic inflammation on tendon are a promising direction for the treatment of tendinopathy.

Obesity and Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) is characterized by upper airway collapse during sleep. Chronic intermittent hypoxia, sleep fragmentation, and inflammatory activation are the main pathophysiological mechanisms of OSA. OSA is highly prevalent in obese patients and may contribute to cardiometabolic risk by exerting detrimental effects on adipose tissue metabolism and potentiating the adipose tissue dysfunction typically found in obesity. This chapter will provide an update on: (a) the epidemiological studies linking obesity and OSA; (b) the studies exploring the effects of intermittent hypoxia and sleep fragmentation on the adipose tissue; (c) the effects of OSA treatment with continuous positive airway pressure (CPAP) on metabolic derangements; and (d) current research on new anti-diabetic drugs that could be useful in the treatment of obese OSA patients.

DNA demethylase ALKBH1 promotes adipogenic differentiation via regulation of HIF-1 signaling

DNA 6-adenine methylation (6mA), as a novel adenine modification existing in eukaryotes, shows essential functions in embryogenesis and mitochondrial transcriptions. ALKBH1 is a demethylase of 6mA and plays critical roles in osteogenesis, tumorigenesis, and adaptation to stress. However, the integrated biological functions of ALKBH1 still require further exploration. Here, we demonstrate that knockdown of ALKBH1 inhibits adipogenic differentiation in both human mesenchymal stem cells (hMSCs) and 3T3-L1 preadipocytes, while overexpression of ALKBH1 leads to increased adipogenesis. Using a combination of RNA-seq and N6-mA-DNA-IP-seq analyses, we identify hypoxia-inducible factor-1 (HIF-1) signaling as a crucial downstream target of ALKBH1 activity. Depletion of ALKBH1 leads to hypermethylation of both HIF-1α and its downstream target GYS1. Simultaneous overexpression of HIF-1α and GYS1 restores the adipogenic commitment of ALKBH1-deficient cells. Taken together, our data indicate that ALKBH1 is indispensable for adipogenic differentiation, revealing a novel epigenetic mechanism that regulates adipogenesis.

Recent Developments in Extracellular Matrix Remodeling for Fat Grafting

Remodeling of the extracellular matrix (ECM), which provides structural and biochemical support for surrounding cells, is vital for adipose tissue regeneration after autologous fat grafting. Rapid and high-quality ECM remodeling can improve the retention rate after fat grafting by promoting neovascularization, regulating stem cells differentiation, and suppressing chronic inflammation. The degradation and deposition of ECM are regulated by various factors, including hypoxia, blood supply, inflammation, and stem cells. By contrast, ECM remodeling alters these regulatory factors, resulting in a dynamic relationship between them. Although researchers have attempted to identify the cellular sources of factors associated with tissue regeneration and regulation of the microenvironment, the factors and mechanisms that affect adipose tissue ECM remodeling remain incompletely understood. This review describes the process of adipose ECM remodeling after grafting and summarizes the factors that affect ECM reconstruction. Also, this review provides an overview of the clinical methods to avoid poor ECM remodeling. These findings may provide new ideas for improving the retention of adipose tissue after fat transplantation.

Regulatory modules of human thermogenic adipocytes: functional genomics of large cohort and Meta-analysis derived marker-genes

Background

Recently, ProFAT and BATLAS studies identified brown and white adipocytes marker genes based on analysis of large databases. They offered scores to determine the thermogenic status of adipocytes using the gene-expression data of these markers. In this work, we investigated the functional context of these genes.

Results

Gene Set Enrichment Analyses (KEGG, Reactome) of the BATLAS and ProFAT marker-genes identified pathways deterministic in the formation of brown and white adipocytes. The collection of the annotated proteins of the defined pathways resulted in expanded white and brown characteristic protein-sets, which theoretically contain all functional proteins that could be involved in the formation of adipocytes. Based on our previously obtained RNA-seq data, we visualized the expression profile of these proteins coding genes and found patterns consistent with the two adipocyte phenotypes. The trajectory of the regulatory processes could be outlined by the transcriptional profile of progenitor and differentiated adipocytes, highlighting the importance of suppression processes in browning. Protein interaction network-based functional genomics by STRING, Cytoscape and R-Igraph platforms revealed that different biological processes shape the brown and white adipocytes and highlighted key regulatory elements and modules including GAPDH-CS, DECR1, SOD2, IL6, HRAS, MTOR, INS-AKT, ERBB2 and 4-NFKB, and SLIT-ROBO-MAPK. To assess the potential role of a particular protein in shaping adipocytes, we assigned interaction network location-based scores (betweenness centrality, number of bridges) to them and created a freely accessible platform, the AdipoNET (https//adiponet.com), to conveniently use these data. The Eukaryote Promoter Database predicted the response elements in the UCP1 promoter for the identified, potentially important transcription factors (HIF1A, MYC, REL, PPARG, TP53, AR, RUNX, and FoxO1).

Conclusion

Our integrative approach-based results allowed us to investigate potential regulatory elements of thermogenesis in adipose tissue. The analyses revealed that some unique biological processes form the brown and white adipocyte phenotypes, which presumes the existence of the transitional states. The data also suggests that the two phenotypes are not mutually exclusive, and differentiation of thermogenic adipocyte requires induction of browning as well as repressions of whitening. The recognition of these simultaneous actions and the identified regulatory modules can open new direction in obesity research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08126-8.

Crossroads between Estrogen Loss, Obesity, and Heart Failure with Preserved Ejection Fraction

The prevalence of obesity and heart failure with preserved ejection fraction (HFpEF) increases significantly in postmenopausal women. Although obesity is a risk factor for left ventricular diastolic dysfunction (LVDD), the mechanisms that link the cessation of ovarian hormone production, and particularly estrogens, to the development of obesity, LVDD, and HFpEF in aging females are unclear. Clinical, and epidemiologic studies show that postmenopausal women with abdominal obesity (defined by waist circumference) are at greater risk for developing HFpEF than men or women without abdominal obesity. The study presents a review of clinical data that support a mechanistic link between estrogen loss plus obesity and left ventricular remodeling with LVDD. It also seeks to discuss potential cell and molecular mechanisms for estrogen-mediated protection against adverse adipocyte cell types, tissue depots, function, and metabolism that may contribute to LVDD and HFpEF.

Hyperlipidemia and Obesity's Role in Immune Dysregulation Underlying the Severity of COVID-19 Infection

Obesity and hyperlipidemia are known to be risk factors for various pathological disorders, including various forms of infectious respiratory disease, including the current Coronavirus outbreak termed Coronavirus Disease 19 (COVID-19). This review studies the effects of hyperlipidemia and obesity on enhancing the inflammatory response seen in COVID-19 and potential therapeutic pathways related to these processes. In order to better understand the underlying processes of cytokine and chemokine-induced inflammation, we must further investigate the immunomodulatory effects of agents such as Vitamin D and the reduced form of glutathione as adjunctive therapies for COVID-19 disease.

Oxygen in Metabolic Dysfunction and Its Therapeutic Relevance

Significance: In recent years, a number of studies have shown altered oxygen partial pressure at a tissue level in metabolic disorders, and some researchers have considered oxygen to be a (macro) nutrient. Oxygen availability may be compromised in obesity and several other metabolism-related pathological conditions, including sleep apnea-hypopnea syndrome, the metabolic syndrome (which is a set of conditions), type 2 diabetes, cardiovascular disease, and cancer. Recent Advances: Strategies designed to reduce adiposity and its accompanying disorders have been mainly centered on nutritional interventions and physical activity programs. However, novel therapies are needed since these approaches have not been sufficient to counteract the worldwide increasing rates of metabolic disorders. In this regard, intermittent hypoxia training and hyperoxia could be potential treatments through oxygen-related adaptations. Moreover, living at a high altitude may have a protective effect against the development of abnormal metabolic conditions. In addition, oxygen delivery systems may be of therapeutic value for supplying the tissue-specific oxygen requirements. Critical Issues: Precise in vivo methods to measure oxygenation are vital to disentangle some of the controversies related to this research area. Further, it is evident that there is a growing need for novel in vitro models to study the potential pathways involved in metabolic dysfunction to find appropriate therapeutic targets. Future Directions: Based on the existing evidence, it is suggested that oxygen availability has a key role in obesity and its related comorbidities. Oxygen should be considered in relation to potential therapeutic strategies in the treatment and prevention of metabolic disorders. Antioxid. Redox Signal. 35, 642-687.

LACTATE CAN BE A MARKER OF METABOLIC SYNDROME IN SEVERE OBESITY?

Background:

In the last decades, numerous studies have confirmed the importance of lactate - by-product to the nutrient signal of the intracellular redox state - to regulatory functions in energy metabolism.

Aim:

To evaluate changes in blood lactate in patients with severe obesity and its correlation with body composition and metabolic profile.

Methods:

Twenty-four people with severe obesity (BMI=40 kg/m²) were evaluated in a prospective case-control study before and six months after Roux-in-Y gastric bypass. The blood lactate, total cholesterol, and fractions, C-reactive protein and HOMA-IR were analyzed after 12 h fasting. Body mass composition was evaluated by bioelectrical impedance and respiratory quotient was measured by indirect calorimetry.

Results:

The initial lactate level was 2.5±1.1 mmol/l and returned to normal level (1.9±3.6 mmol/l, p=0.0018) after surgery. This reduction was positively correlated with a decrease in BMI (p=0.0001), % free fat mass (p=0,001), % fat mass (p=0.001) and HOMA-IR (p=0.01). There was normalization of lactatemia in 70% of patients. There was no correlation between lactatemia and C-reactive protein.

Conclusions:

There was a significant improvement of metabolic parameters, normalization of blood lactate, fat mass loss, although these individuals remained with a high BMI.

Hypoperfusion of the infrapatellar fat pad and its relationship to MRI T2* relaxation time changes in a 5/6 nephrectomy model

The purpose of present study was to longitudinally investigate the alterations in infrapatellar fat pad (IPFP) vascularity in 5/6 nephrectomized rats by using dynamic contrast enhanced (DCE) MRI and IPFP degeneration by using MRI T2* relaxation time. Twelve male Sprague–Dawley rats were assigned to a control group and a 5/6 nephrectomy CKD group. The right knees of all rats were longitudinally scanned by 4.7 T MRI, and serial changes in the IPFP were assessed at 0, 8, 16, 30, and 44 weeks by DCE-MRI (parameters A, k_el and k_ep) and MRI T2* mapping. After MRI measurements, knee specimens were obtained and evaluated histologically. The CKD group had IPFPs with lower blood volume A and lower permeability k_ep values from 16 weeks (p < 0.05), lower venous washout k_el value from 30 weeks (p < 0.001), and significantly higher T2* values reflecting adipocyte degeneration beginning at 16 weeks (p < 0.05). The histopathological results confirmed the MRI findings. Hypoperfusion and adipocytes degeneration related to CKD were demonstrated in a rodent 5/6 nephrectomy model. DCE parameters and MRI T2* can serve as imaging biomarkers of fat pad degeneration during CKD progression.

Contribution of Adipose Tissue Oxidative Stress to Obesity-Associated Diabetes Risk and Ethnic Differences: Focus on Women of African Ancestry

Adipose tissue (AT) storage capacity is central in the maintenance of whole-body homeostasis, especially in obesity states. However, sustained nutrients overflow may dysregulate this function resulting in adipocytes hypertrophy, AT hypoxia, inflammation and oxidative stress. Systemic inflammation may also contribute to the disruption of AT redox equilibrium. AT and systemic oxidative stress have been involved in the development of obesity-associated insulin resistance (IR) and type 2 diabetes (T2D) through several mechanisms. Interestingly, fat accumulation, body fat distribution and the degree of how adiposity translates into cardio-metabolic diseases differ between ethnicities. Populations of African ancestry have a higher prevalence of obesity and higher T2D risk than populations of European ancestry, mainly driven by higher rates among African women. Considering the reported ethnic-specific differences in AT distribution and function and higher levels of systemic oxidative stress markers, oxidative stress is a potential contributor to the higher susceptibility for metabolic diseases in African women. This review summarizes existing evidence supporting this hypothesis while acknowledging a lack of data on AT oxidative stress in relation to IR in Africans, and the potential influence of other ethnicity-related modulators (e.g., genetic-environment interplay, socioeconomic factors) for consideration in future studies with different ethnicities.

Contribution of RAGE axis activation to the association between metabolic syndrome and cancer

Far beyond the compelling proofs supporting that the metabolic syndrome represents a risk factor for diabetes and cardiovascular diseases, a growing body of evidence suggests that it is also a risk factor for different types of cancer. However, the involved molecular mechanisms underlying this association are not fully understood, and they have been mainly focused on the individual contributions of each component of the metabolic syndrome such as obesity, hyperglycemia, and high blood pressure to the development of cancer. The Receptor for Advanced Glycation End-products (RAGE) axis activation has emerged as an important contributor to the pathophysiology of many clinical entities, by fueling a chronic inflammatory milieu, and thus supporting an optimal microenvironment to promote tumor growth and progression. In the present review, we intend to highlight that RAGE axis activation is a crosswise element on the potential mechanistic contributions of some relevant components of metabolic syndrome into the association with cancer.

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.

Adipokines and Metabolic Regulators in Human and Experimental Pulmonary Arterial Hypertension

Pulmonary hypertension (PH) is associated with meta-inflammation related to obesity but the role of adipose tissue in PH pathogenesis is unknown. We hypothesized that adipose tissue-derived metabolic regulators are altered in human and experimental PH. We measured circulating levels of fatty acid binding protein 4 (FABP-4), fibroblast growth factor -21 (FGF-21), adiponectin, and the mRNA levels of FABP-4, FGF-21, and peroxisome proliferator-activated receptor γ (PPARγ) in lung tissue of patients with idiopathic PH and healthy controls. We also evaluated lung and adipose tissue expression of these mediators in the three most commonly used experimental rodent models of pulmonary hypertension. Circulating levels of FABP-4, FGF-21, and adiponectin were significantly elevated in PH patients compared to controls and the mRNA levels of these regulators and PPARγ were also significantly increased in human PH lungs and in the lungs of rats with experimental PH compared to controls. These findings were coupled with increased levels of adipose tissue mRNA of genes related to glucose uptake, glycolysis, tricarboxylic acid cycle, and fatty acid oxidation in experimental PH. Our results support that metabolic alterations in human PH are recapitulated in rodent models of the disease and suggest that adipose tissue may contribute to PH pathogenesis.

Intermittent Hypoxia Mediates Caveolae Disassembly That Parallels Insulin Resistance Development

Repetitive complete or incomplete pharyngeal collapses are leading to chronic intermittent hypoxia (CIH), a hallmark feature of obstructive sleep apnea (OSA) syndrome responsible for many metabolic disorders. In humans, an association between OSA and insulin resistance has been found independently of the degree of obesity. Based on our previous work showing that hypoxia applied to adipocytes led to cellular insulin resistance associated with caveolae flattening, we have investigated the effects of CIH on caveolae structuration in adipose tissue. Original exploratory experiences demonstrate that 6 weeks-exposure of lean mice to CIH is characterized by systemic insulin resistance and translates into adipocyte insulin signaling alterations. Chronic intermittent hypoxia also induces caveolae disassembly in white adipose tissue (WAT) illustrated by reduced plasma membrane caveolae density and enlarged caveolae width, concomitantly to WAT insulin resistance state. We show that CIH downregulates caveolar gene and protein expressions, including cavin-1, cavin-2, and EHD2, underlying molecular mechanisms responsible for such caveolae flattening. Altogether, we provide evidences for adipose tissue caveolae disassembly following CIH exposure, likely linked to cavin protein downregulation. This event may constitute the molecular basis of insulin resistance development in OSA patients.

Towards precision medicine: defining and characterizing adipose tissue dysfunction to identify early immunometabolic risk in symptom-free adults from the GEMM family study

Interactions between macrophages and adipocytes are early molecular factors influencing adipose tissue (AT) dysfunction, resulting in high leptin, low adiponectin circulating levels and low-grade metaflammation, leading to insulin resistance (IR) with increased cardiovascular risk. We report the characterization of AT dysfunction through measurements of the adiponectin/leptin ratio (ALR), the adipo-insulin resistance index (Adipo-IRi), fasting/postprandial (F/P) immunometabolic phenotyping and direct F/P differential gene expression in AT biopsies obtained from symptom-free adults from the GEMM family study. AT dysfunction was evaluated through associations of the ALR with F/P insulin-glucose axis, lipid-lipoprotein metabolism, and inflammatory markers. A relevant pattern of negative associations between decreased ALR and markers of systemic low-grade metaflammation, HOMA, and postprandial cardiovascular risk hyperinsulinemic, triglyceride and GLP-1 curves was found. We also analysed their plasma non-coding microRNAs and shotgun lipidomics profiles finding trends that may reflect a pattern of adipose tissue dysfunction in the fed and fasted state. Direct gene differential expression data showed initial patterns of AT molecular signatures of key immunometabolic genes involved in AT expansion, angiogenic remodelling and immune cell migration. These data reinforce the central, early role of AT dysfunction at the molecular and systemic level in the pathogenesis of IR and immunometabolic disorders.