A pilot study of FDG PET/CT detects a link between brown adipose tissue and breast cancer

An update on the secretory functions of brown, white, and beige adipose tissue: Towards therapeutic applications

Adipose tissue, including white adipose tissue (WAT), brown adipose tissue (BAT), and beige adipose tissue, is vital in modulating whole-body energy metabolism. While WAT primarily stores energy, BAT dissipates energy as heat for thermoregulation. Beige adipose tissue is a hybrid form of adipose tissue that shares characteristics with WAT and BAT. Dysregulation of adipose tissue metabolism is linked to various disorders, including obesity, type 2 diabetes, cardiovascular diseases, cancer, and infertility. Both brown and beige adipocytes secrete multiple molecules, such as batokines, packaged in extracellular vesicles or as soluble signaling molecules that play autocrine, paracrine, and endocrine roles. A greater understanding of the adipocyte secretome is essential for identifying novel molecular targets in treating metabolic disorders. Additionally, microRNAs show crucial roles in regulating adipose tissue differentiation and function, highlighting their potential as biomarkers for metabolic disorders. The browning of WAT has emerged as a promising therapeutic approach in treating obesity and associated metabolic disorders. Many browning agents have been identified, and nanotechnology-based drug delivery systems have been developed to enhance their efficacy. This review scrutinizes the characteristics of and differences between white, brown, and beige adipose tissues, the molecular mechanisms involved in the development of the adipocytes, the significant roles of batokines, and regulatory microRNAs active in different adipose tissues. Finally, the potential of WAT browning in treating obesity and atherosclerosis, the relationship of BAT with cancer and fertility disorders, and the crosstalk between adipose tissue with circadian system and circadian disorders are also investigated.

Importance of temperature on immuno-metabolic regulation and cancer progression

Cancer immunotherapies emerge as promising strategies for restricting tumour growth. The tumour microenvironment (TME) has a major impact on the anti-tumour immune response and on the efficacy of the immunotherapies. Recent studies have linked changes in the ambient temperature with particular immuno-metabolic reprogramming and anti-cancer immune response in laboratory animals. Here, we describe the energetic balance of the organism during change in temperature, and link this to the immune alterations that could be of relevance for cancer, as well as for other human diseases. We highlight the contribution of the gut microbiota in modifying this interaction. We describe the overall metabolic response and underlying mechanisms of tumourigenesis in mouse models at varying ambient temperatures and shed light on their potential importance in developing therapeutics against cancer.

Oncogenic role of an uncharacterized cold-induced zinc finger protein 726 in breast cancer

The unobtrusive cold environmental temperature can be linked to the development of cancer. This study, for the first time, envisaged cold stress-mediated induction of a zinc finger protein 726 (ZNF726) in breast cancer. However, the role of ZNF726 in tumorigenesis has not been defined. This study investigated the putative role of ZNF726 in breast cancer tumorigenic potency. Gene expression analysis using multifactorial cancer databases predicted overexpression of ZNF726 in various cancers, including breast cancer. Experimental observations found that malignant breast tissues and highly aggressive MDA-MB-231 cells showed an elevated ZNF726 expression as compared to benign and luminal A type (MCF-7), respectively. Furthermore, ZNF726 silencing decreased breast cancer cell proliferation, epithelial-mesenchymal transition, and invasion accompanied by the inhibition of colony-forming ability. Concordantly, ZNF726 overexpression significantly demonstrated opposite outcomes than ZNF726 knockdown. Taken together, our findings propose cold-inducible ZNF726 as a functional oncogene demonstrating its prominent role in facilitating breast tumorigenesis. An inverse correlation between environmental temperature and total serum cholesterol was observed in the previous study. Furthermore, experimental outcomes illustrate that cold stress elevated cholesterol content hinting at the involvement of the cholesterol regulatory pathway in cold-induced ZNF726 gene regulation. This observation was bolstered by a positive correlation between the expression of cholesterol-regulatory genes and ZNF726. Exogenous cholesterol treatment elevated ZNF726 transcript levels while knockdown of ZNF726 decreased the cholesterol content via downregulating various cholesterol regulatory gene expressions (e.g., SREBF1/2, HMGCoR, LDLR). Moreover, an underlying mechanism supporting cold-driven tumorigenesis is proposed through interdependent regulation of cholesterol regulatory pathway and cold-inducible ZNF726 expression.

Metabolic crosstalk between thermogenic adipocyte and cancer cell: Dysfunction and therapeutics

As one of the largest endocrine organs with a wide distribution in organisms, adipose tissue secretes multiple adipokines, cytokines, metabolites, and exosomes to promote tumour development. Elaborating the crosstalk between cancer cells and adipocytes provides a tissue-level perspective of cancer progression, which reflects the heterogeneity and complexity of human tumours. Three main types of adipose tissues, white, brown, and beige adipose tissue, have been described. Thermogenic capacity is a prominent characteristic of brown and beige adipocytes. Most studies so far mainly focus on the contribution of white adipocytes to the tumour microenvironment. However, the role of thermogenic adipose tissue in malignant cancer behaviour has been largely overlooked. Recently, emerging evidence suggests that beige/brown adipocytes play a key role in the development and progression of various cancers. This review focuses on the bidirectional communication between tumour cells and thermogenic adipocytes and the therapeutic strategies to disrupt this interaction.

Crosstalk between Depression and Breast Cancer via Hepatic Epoxide Metabolism: A Central Comorbidity Mechanism

Breast cancer (BC) is a serious global challenge, and depression is one of the risk factors and comorbidities of BC. Recently, the research on the comorbidity of BC and depression has focused on the dysfunction of the hypothalamic–pituitary–adrenal axis and the persistent stimulation of the inflammatory response. However, the further mechanisms for comorbidity remain unclear. Epoxide metabolism has been shown to have a regulatory function in the comorbid mechanism with scattered reports. Hence, this article reviews the role of epoxide metabolism in depression and BC. The comprehensive review discloses the imbalance in epoxide metabolism and its downstream effect shared by BC and depression, including overexpression of inflammation, upregulation of toxic diols, and disturbed lipid metabolism. These downstream effects are mainly involved in the construction of the breast malignancy microenvironment through liver regulation. This finding provides new clues on the mechanism of BC and depression comorbidity, suggesting in particular a potential relationship between the liver and BC, and provides potential evidence of comorbidity for subsequent studies on the pathological mechanism.

Brown fat activation demonstrated on FDG PET/CT predicts survival outcome

PURPOSE

The purpose of this study was to compare the survival of patients with and without BAT activity on FDG PET/CT.

METHODS

PET/CT exams from 3937 breast cancer patients were retrospectively reviewed for bilateral symmetric elongated FDG activity in the neck and chest, typical of BAT activation. A control group of age-matched (± 1 year) breast cancer patients who underwent PET/CT the same week was also enrolled for comparison. Kaplan-Meier curves of progression-free survival (PFS) and overall survival (OS) for BAT positive patients and the control group were calculated. Further sub-analysis was performed to account for the hormonal changes associated with menopause.

RESULTS

2.0% (80/3937) of the breast cancer patients who underwent PET/CT demonstrated BAT activation, and 80 additional patients were analyzed for comparison as the group without BAT activity. Mean follow-up was 76 months (range 1-225 months). There were 4 recurrences in the BAT group, compared to 12 in the control. The mean PFS for the BAT group was 127 months, which was significantly lower than the mean PFS of 180 months in the control (p = 0.047). Sub-analysis of premenopausal women again showed longer PFS for the BAT group (129 vs. 196 months, p = 0.095) while no difference was found in postmenopausal women (mean 102 vs. 135 months, p = 0.360). Presence of BAT activity was also a significant predictor variable for PFS on Cox regression.

CONCLUSION

Patients with BAT activity showed longer progression-free survival than those without, emphasizing the need for further evaluation of its role in metabolism, treatment response, tumor microenvironment and long-term prognosis.

The evolving view of thermogenic fat and its implications in cancer and metabolic diseases

The incidence of metabolism-related diseases like obesity and type 2 diabetes mellitus has reached pandemic levels worldwide and increased gradually. Most of them are listed on the table of high-risk factors for malignancy, and metabolic disorders systematically or locally contribute to cancer progression and poor prognosis of patients. Importantly, adipose tissue is fundamental to the occurrence and development of these metabolic disorders. White adipose tissue stores excessive energy, while thermogenic fat including brown and beige adipose tissue dissipates energy to generate heat. In addition to thermogenesis, beige and brown adipocytes also function as dynamic secretory cells and a metabolic sink of nutrients, like glucose, fatty acids, and amino acids. Accordingly, strategies that activate and expand thermogenic adipose tissue offer therapeutic promise to combat overweight, diabetes, and other metabolic disorders through increasing energy expenditure and enhancing glucose tolerance. With a better understanding of its origins and biological functions and the advances in imaging techniques detecting thermogenesis, the roles of thermogenic adipose tissue in tumors have been revealed gradually. On the one hand, enhanced browning of subcutaneous fatty tissue results in weight loss and cancer-associated cachexia. On the other hand, locally activated thermogenic adipocytes in the tumor microenvironment accelerate cancer progression by offering fuel sources and is likely to develop resistance to chemotherapy. Here, we enumerate current knowledge about the significant advances made in the origin and physiological functions of thermogenic fat. In addition, we discuss the multiple roles of thermogenic adipocytes in different tumors. Ultimately, we summarize imaging technologies for identifying thermogenic adipose tissue and pharmacologic agents via modulating thermogenesis in preclinical experiments and clinical trials.

Brown adipose tissue (BAT) activation at 18F-FDG PET/CT: correlation with clinicopathological characteristics in breast cancer

Background

There is conflicting results of few published human 18F-FDG PET/CT studies about BAT activation in breast cancer (BC). The aim of the study is to evaluate the association between the levels of BAT metabolic activity detected by 18F-FDG PET/CT and clinicopathological characteristics of a tumor in patients with primary BC.

Results

BAT was activated in 16 out of 157 (10.2%) consecutive female patients with BC who underwent 18F-FDG PET/CT for initial evaluation. The majority of patients (15/16) had bilateral uptake in the supraclavicular regions. The mean values of the highest SUVmax and total metabolic activity (TMA) of activated BAT were 13.3 ± 9.9 and 79.6 ± 45, respectively. Median outdoor temperature was significantly lower in the activated BAT group (P value=0.035). Patients with BAT activation tended to have a lower median primary tumor size and primary SUVmax, but not statistically significant than those without BAT activation. BAT activation was significantly more frequent among younger age groups (14/16) and patients with lower body mass index (BMI) (10/16), but it was insignificantly more frequent among estrogen receptor-positive (ER+), progesterone receptor-positive (PR+), human epidermal growth factor receptor2 negative (HER2-), invasive ductal carcinoma (IDC), grade II, luminal B subtype, high Ki-67 expression level, patients with positive nodal metastasis, and in patients without distant metastasis. TMA was significantly higher among HER2+ patients (P value=0.019), but insignificantly higher among the younger age groups, stages I and II, invasive lobular carcinoma (ILC), grade I, luminal B subtype, ER+, PR−, higher Ki-67 expression level, patients with positive nodal, and distant metastasis. BMI and patient’s age were the significant independent predictor factors for BAT activation on multivariate regression analysis.

Conclusion

BAT activation in young age females is sex hormone-dependent, positively associated with less aggressive molecular subtypes of BC, less frequent in patients with distant metastasis. BAT activation may be a prognostic factor that carries a better prognosis in BC.

Brown Adipose Tissue in Breast Cancer Evaluated by [18F] FDG-PET/CT

PURPOSE

Recently brown adipose tissue (BAT) activation has been proposed to have a possible role in breast cancer. The aim of this study was to evaluate BAT activation in patients with breast cancer and its relationship with molecular characteristics of tumor.

PROCEDURES

The study group comprised 79 patients with histologically proven ductal breast carcinoma (51 ± 13 years). Data on distribution, intensity (SUVmax), and total metabolic activity (TMA) of BAT were obtained from [¹⁸F] FDG-PET/CT. Clinical and biochemical data were obtained from the database.

RESULTS

BAT activation was present in 12 of the 79 patients (15.2 %). Patients with BAT activation were younger and had a lower body mass index (BMI) (p < 0.05 and p < 0.0005, respectively) and showed less frequently metastasis (p < 0.05). No significant differences were found in estrogen receptor (ER), progesterone receptor (PgR), Ki67, grade, and in molecular subtypes. In patients younger than 55 years and with a BMI < 26, no significant differences were observed between patients with and without BAT activation. In the 12 patients with BAT activation, a significant inverse correlation was observed between TMA and BMI (r = - 0.64, p < 0.05). TMA and SUVmax were higher in grade 2 than in grade 3 patients. No significant differences were found in both TMA and SUVmax between patients with and without lymph node metastases. A significant difference in both TMA and SUVmax was observed among different molecular types, with luminal B patients showing higher values.

CONCLUSIONS

In conclusion, the present study suggests a relation between BAT activation and positive known prognostic factor in breast cancer, such as intermediate tumor grade and luminal B cancer type.

A systematic review of imaging studies of human brown adipose tissue

Brown adipose tissue (BAT) is involved in energy dissipation and has been linked to weight loss, insulin sensitivity, and reduced risk of atherosclerotic disease. BAT is found most often in the supraclavicular region, as well as mediastinal and paravertebral areas, and it is predominantly seen in young persons. BAT is activated by cold temperature and the sympathetic nervous system. In humans, BAT was initially detected via 2-deoxy-2-[¹⁸ F]fluoro-d-glucose (FDG) positron emission tomography/computed tomography (PET/CT), a high-resolution molecular imaging modality used to identify and stage malignancies. Recent studies have shown that BAT can be localized using conventional imaging modalities, such as CT or magnetic resonance imaging, as well as radiotracers used for single-photon emission CT. In this systematic review, we have summarized the evidence for BAT detection in humans using various imaging techniques.

Brown adipose tissue is associated with cardiometabolic health

White fat stores excess energy, whereas brown and beige fat are thermogenic and dissipate energy as heat. Thermogenic adipose tissues markedly improve glucose and lipid homeostasis in mouse models, although the extent to which brown adipose tissue (BAT) influences metabolic and cardiovascular disease in humans is unclear^1,2. Here we retrospectively categorized 134,529 ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography scans from 52,487 patients, by presence or absence of BAT, and used propensity score matching to assemble a study cohort. Scans in the study population were initially conducted for indications related to cancer diagnosis, treatment or surveillance, without previous stimulation. We report that individuals with BAT had lower prevalences of cardiometabolic diseases, and the presence of BAT was independently correlated with lower odds of type 2 diabetes, dyslipidemia, coronary artery disease, cerebrovascular disease, congestive heart failure and hypertension. These findings were supported by improved blood glucose, triglyceride and high-density lipoprotein values. The beneficial effects of BAT were more pronounced in individuals with overweight or obesity, indicating that BAT might play a role in mitigating the deleterious effects of obesity. Taken together, our findings highlight a potential role for BAT in promoting cardiometabolic health.

Can the aging influence cold environment mediated cancer risk in the USA female population?

Cancer is one of the most debilitating diseases worldwide. Cancer incidence and/or death depends on several intrinsic and extrinsic factors (e.g., dietary habits, socio-behavioral activities, physical inactivity, smoking, alcohol consumption, gender, races/ethnicities and age). Various studies have found that an inverse relationship subsists between environmental temperature and cancer risk. Furthermore, this negative relationship was found to be more consistent in the USA female population. This research mainly focuses on influence of aging on cold environment mediated cancer risk for overall and various anatomical site-specific cancers. Age-specific county-wise data of cancer incidence rate (CIR) in the USA female population was selected in this study. Statistical analysis found a negative correlation between the average annual temperature (AAT) and CIR in all anatomical sites (AAS; overall) as well as different anatomical site-specific cancers (e.g., breast, melanoma, leukaemia, pancreas, bladder, uterus, thyroid and non-Hodgkin's lymphoma (NHL), except for cervical cancer) in different age groups (e.g., less than 50 years, 50 plus years, less than 65 years and 65 plus years). In addition, an inverse relationship between the AAT and CIR was found in case of paediatric cancer. However, all the results obtained from the linear model based statistical analysis proposed that the older age-group of females particularly above 65 years seems to be more prone to cold temperature linked cancer risk. For example, age-specific cold linked cancer incidence appears to be more inclined in case of breast cancer in the age-group of 65 plus years. This study, for first time, proposes that aging may have a positive influence on the relationship between cancer incidence and environment temperature.

Cold-hearted: A case for cold stress in cancer risk

A negative correlation exists between environmental temperature and cancer risk based on both epidemiological and statistical analyses. Previously, cold stress was reported to be an effective cause of tumorigenesis. Several studies have demonstrated that cold temperature serves as a potential risk factor in cancer development. Most recently, a link was demonstrated between the effects of extreme cold climate on cancer incidence, pinpointing its impact on tumour suppressor genes by causing mutation. The underlying mechanism behind cold stress and its association with tumorigenesis is not well understood. Hence, this review intends to shed light on the role of associated factors, genetic and/or non-genetic, which are modulated by cold temperature, and eventually influence tumorigenic potential. While scrutinizing the effect of cold exposure on the body, the expression of certain genes, e.g. uncoupled proteins and heat-shock proteins, were elevated. Biological chemicals such as norepinephrine, thyroxine, and cholesterol were also elevated. Brown adipose tissue, which plays an essential role in thermogenesis, displayed enhanced activity upon cold exposure. Adaptive measures are utilized by the body to tolerate the cold, and in doing so, invites both epigenetic and genetic changes. Unknowingly, these adaptive strategies give rise to a lethal outcome i.e., genesis of cancer. Concisely, this review attempts to draw a link between cold stress, genetic and epigenetic changes, and tumorigenesis and aspires to ascertain the mechanism behind cold temperature-mediated cancer risk.

Brown adipose tissue and cancer progression

OBJECTIVE

The purpose of our study was to determine the role of brown adipose tissue (BAT) in cancer progression.

MATERIALS AND METHODS

Our study was approved by our institutional review board and Health Insurance Portability and Accountability Act-compliant. Our study group comprised 132 cancer patients (116 f, 16 m; mean age 50 ± 16 years) who underwent F18-FDG PET/CT per standard clinical protocol, for staging or surveillance of cancer. We included patients who were BAT-positive on PET/CT and had clinical follow-up data available for at least 12 months or until tumor recurrence or tumor-related death, whichever occurred first. BAT volume by PET/CT was quantified by PET-CT Viewer shareware. Clinical information including tumor type, tumor recurrence, survival, and outside temperature at time of scan were recorded. Cox proportional hazard models were used to determine longitudinal associations between BAT volume and tumor recurrence/mortality.

RESULTS

There were 55 tumor recurrences/tumor-related deaths over a median follow-up period of 71 (33; 110 interquartile range) months. Higher BAT volume was associated with an increased likelihood of tumor recurrence/tumor-associated mortality after adjustment for covariates (p = 0.03).

CONCLUSION

BAT volume, assessed using routine PET/CT, is a predictor of tumor recurrence/mortality in patients with cancer, independent of other factors that can influence BAT activity, such as sex, age, BMI, or tumor type.

Pheochromocytoma and Paraganglioma Patients With Poor Survival Often Show Brown Adipose Tissue Activation

CONTEXT

Pheochromocytomas/paragangliomas (PPGLs) are neuroendocrine tumors that can secrete norepinephrine (NE). Brown adipose tissue (BAT) activation is mediated through the action of NE on β-adrenoceptors (β-ARs). In some malignancies, BAT activation is associated with higher cancer activity.

OBJECTIVE

To study the relationship between BAT activation and PPGL clinical outcomes.

DESIGN

A retrospective case-control study that included 342 patients with PPGLs who underwent 18F-fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography (18F-FDG PET/CT) imaging at the National Institutes of Health (NIH). We excluded all patients with parasympathetic tumors and those who underwent 18F-FDG PET/CT after PPGL resection. Scans of 205 patients were reviewed by 2 blinded nuclear medicine physicians; 16 patients had BAT activation on 18F-FDG PET/CT [7.80%; age 27.50 (15.00-45.50) years; 10 female/6 male; body mass index [BMI] 24.90 [19.60-25.35] kg/m2). From the remaining 189 patients, we selected 36 matched controls (age 34.4 [25.4-45.5] years; 21 female/15 male; BMI 25.0 [22.0-26.0] kg/m2).

PRIMARY OUTCOME MEASURE

Overall survival.

RESULTS

The presence of active BAT on 18F-FDG PET/CT was associated with decreased overall survival when compared with the control group (HRz 5.80; 95% CI, 1.05-32.05; P = 0.02). This association remained significant after adjusting for the SDHB mutation. Median plasma NE in the BAT group was higher than the control group [4.65 vs 0.55 times above the upper limit of normal; P < 0.01]. There was a significant association between higher plasma NE levels and mortality in PPGLs in both groups.

CONCLUSIONS

Our findings suggest that the detection of BAT activity in PPGL patients is associated with higher mortality. We suggest that BAT activation could either be reflecting or contributing to a state of increased host stress that may predict poor outcome in metastatic PPGL.

PET imaging study of brown adipose tissue (BAT) activity in mice devoid of receptor for advanced glycation end products (RAGE)

Brown adipose tissue (BAT) is responsible for adaptive thermogenesis. We previously showed that genetic deficiency of receptor for advanced glycation end products (RAGE) prevented the effects of high-fat diet (HFD). This study was to compare BAT activity in RAGE knock out (Ager^-/-, RKO) and wild-type (WT) mice after treated with HFD or LFD. [¹⁸F]FDG PET-CT imaging under identical cold-stimulated conditions and mean standard uptake values (SUV_mean), ratio of SUV_iBAT/SUV_muscle (SUVR, muscle as the reference region) and percentage ID/g were used for BAT quantification. The results showed that [¹⁸F]FDG uptake (e.g., SUVR) in WT-HFD mice was significantly reduced (three-fold) as compared to that in WT-LFD (1.40 +/- 0.07 and 4.03 +/- 0.38; P = 0.004). In contrast, BAT activity in RKO mice was not significantly affected by HFD, with SUVR_RKO-LFD: 2.14 +/- 0.10 and SUVR_RKO-LFD: 1.52 +/- 0.13 (P = 0.3). The uptake in WT-LFD was almost double of that in RKO-LFD (P = 0.004); however, there was no significant difference between RKO-HFD and WT-HFD mice (P = 0.3). These results, corroborating our previous findings on the measurement of mRNA transcripts for UCP1 in the BAT, suggest that RAGE may contribute to altered energy expenditure and provide a protective effect against HFD by Ager deletion (Ager ^-/-).

The Effects of Adipocytes on the Regulation of Breast Cancer in the Tumor Microenvironment: An Update

Obesity is a global pandemic and it is well evident that obesity is associated with the development of many disorders including many cancer types. Breast cancer is one of that associated with a high mortality rate. Adipocytes, a major cellular component in adipose tissue, are dysfunctional during obesity and also known to promote breast cancer development both in vitro and in vivo. Dysfunctional adipocytes can release metabolic substrates, adipokines, and cytokines, which promote proliferation, progression, invasion, and migration of breast cancer cells. The secretion of adipocytes can alter gene expression profile, induce inflammation and hypoxia, as well as inhibit apoptosis. It is known that excessive free fatty acids, cholesterol, triglycerides, hormones, leptin, interleukins, and chemokines upregulate breast cancer development. Interestingly, adiponectin is the only adipokine that has anti-tumor properties. Moreover, adipocytes are also related to chemotherapeutic resistance, resulting in the poorer outcome of treatment and advanced stages in breast cancer. Evaluation of the adipocyte secretion levels in the circulation can be useful for prognosis and evaluation of the effectiveness of cancer therapy in the patients. Therefore, understanding about functions of adipocytes as well as obesity in breast cancer may reveal novel targets that support the development of new anti-tumor therapy. In this systemic review, we summarize and update the effects of secreted factors by adipocytes on the regulation of breast cancer in the tumor microenvironment.

Preliminary investigation of brown adipose tissue assessed by PET/CT and cancer activity

OBJECTIVE

To determine the role of brown adipose tissue (BAT) in cancer activity.

MATERIALS AND METHODS

The study group comprised 142 patients (121 female, 21 male; mean age, 49 ± 16 years) who underwent F18-FDG PET/CT (PET/CT) for staging or surveillance of cancer and who were BAT-positive on PET/CT. BAT volume by PET/CT, abdominal (visceral and subcutaneous) fat and paraspinous muscle cross-sectional areas (CSA) were assessed. Groups with and without active cancer on PET/CT were compared using a two-sided paired t test. Linear regression analyses between BAT and body composition parameters were performed.

RESULTS

There were 62 patients (54 female, eight male) who had active cancer on PET/CT and 80 patients (67 female, 13 male) without active cancer. Groups were similar in age and BMI (p ≥ 0.4), abdominal fat and muscle CSA, fasting glucose, and outside temperature at time of scan (p ≥ 0.2). Patients who had active cancer on PET/CT had higher BAT volume compared to patients without active cancer (p = 0.009). In patients without active cancer, BAT was positively associated with BMI and abdominal fat depots (r = 0.46 to r = 0.59, p < 0.0001) while there were no such associations in patients with active cancer (p ≥ 0.1). No associations between BAT and age or muscle CSA were found (p ≥ 0.1).

CONCLUSIONS

BAT activity is greater in patients with active cancer compared to age-, sex-, and BMI-matched BAT-positive patients without active cancer, suggesting a possible role of BAT in cancer activity.

Impact of diverse chemotherapeutic agents and external factors on activation of brown adipose tissue in a large patient collective

Increased activity of brown adipose tissue (BAT) activity in adults is thought to prevent obesity. Therefore, regulators of BAT activity might serve as anti-obesity therapy in future, but are not investigated thoroughly up to now. In our study, we assessed retrospectively the association of BAT activity with several external factors and diverse chemotherapeutic and immunosuppressive agents in a collective of 702 patients. The patients underwent at least two clinically indicated PET/CT examinations in the course of different oncological and inflammatory diseases. BAT activity was identified according to predefined PET/CT criteria in all examinations. In multivariate analysis, the type of disease, the disease activity and the therapeutic regimen did not influence BAT activity. In contrast, sex and age were confirmed as independent factors for BAT activity. For the association of therapeutic agents with BAT activity, we examined 53 different disease-related agents, which were applied to patients without initial BAT activity between their PET/CT examinations. Out of these, cytarabine therapy was significantly associated with increased new onset of BAT activity. Cytarabine is a therapeutic agent for lymphoma patients. Further targeted studies might investigate the usefulness of Cytarabine serving as possible therapeutic approach against obesity via BAT regulation.

A New Personalized Cooling Protocol to Activate Brown Adipose Tissue in Young Adults

Brown adipose tissue (BAT) activity is induced when humans are exposed to cold. Therefore, cold exposure prior to the ¹⁸F-FDG-PET/CT scan is used as a tool to quantify BAT. Several cooling protocols, including fixed and personalized ones are currently in use. The aim of the present study was to determine the effect of a new personalized cooling protocol where the shivering threshold was measured on a separate day, on BAT volume and activity in young adults. A total of 47 adults (n = 28 women) aged 22 ± 2 years participated in the study. We determined participants' shivering threshold (visually and self-reported) using a water perfused cooling vest in an air-conditioned cold room. 48–72 h later, participants wore the cooling vest set at ~4°C above the shivering threshold for 60 min prior to injection of ¹⁸F-FDG and ~5°C above the shivering threshold for ~60 min after injection, until PET/CT scan. We quantified BAT following BARCIST 1.0 recommendations. We identified 40 participants (85%, n = 25 women) as PET+ and 7 (n = 3 women) as PET–. The PET+ group presented significantly higher BAT volume and activity than PET– group (all P < 0.05). PET+ women had higher BAT mean activity than PET+ men (SUV_mean: 5.0 ± 1.6 vs. 3.6 ± 0.9 g/ml respectively, P = 0.003), and there were no significant sex differences in BAT volume (P = 0.161). A total of 9 out of 47 participants did not shiver during the shivering threshold test. Our findings are similar to previous cold-stimulated human BAT studies; therefore, we conclude that our personalized cooling protocol is able to activate BAT in young adults.

Interfacial Adipose Tissue in Systemic Sclerosis

Purpose of Review

This review provides a summary of recent insights into the role of the local white adipose tissue (WAT) in systemic sclerosis.

Recent Findings

Adipocytes located in an interfacial WAT area adjacent to fibrotic lesions have an intermediate phenotype and special properties implicated in fibrotic pathology in systemic sclerosis (SSc). The important role of these cells is recognized in different pathologies, such as wound healing, psoriasis, breast cancer, and prostate cancer. Additionally, both immature and mature adipocytes are involved in the appearance of fibroblast-like cells but exhibit different phenotypes and synthetic properties.

Summary

Adipocytes from interfacial WAT adjacent to the fibrotic area in SSc are phenotypically different from bulk adipocytes and are involved in pathogenesis of SSc. Immature and mature adipocytes from this WAT layer differentiate into various types of fibroblast-like cells, making the local ratio of immature to mature adipocytes in interfacial WAT of particular importance in SSc pathogenesis.

Implication of atypical supraclavicular F18-fluorodeoxyglucose uptake in patients with breast cancer: Association between brown adipose tissue and breast cancer

It has been reported that F18-fluorodeoxyglucose (FDG) uptake in the neck and supraclavicular lesions represents activated brown adipose tissue (BAT). In the present study, the association between BAT activity, detected by FDG-positron emission tomography (PET), and the clinicopathological features of patients with breast cancer was investigated. The cases of 156 consecutive patients with breast cancer who underwent FDG-PET preoperatively were analyzed. The distribution and intensity of atypical FDG uptake in the neck and/or supraclavicular region was reviewed. The intensity was graded as follows: 1, weak; 2, moderate; and 3, intense. Among the 156 patients, 70 (44.9%) exhibited grade 1 intensity, 65 (41.7%) exhibited grade 2 intensity and 21 (13.5%) exhibited grade 3 intensity. The intensity of FDG was significantly associated with human epidermal growth factor receptor 2 (HER2) expression and progesterone expression. Among the 156 patients, 6 (3.8%) had recurrent disease. Multivariate analysis revealed that showing a low grade of atypical FDG uptake was the only independent risk factor of short-term recurrence, and none of the patients with recurrent disease had atypical FDG uptake that may reflect the activation of BAT. These results indicated that the presence of BAT is associated with HER2 expression and the absence of BAT may be a prognostic factor for breast cancer.

Factors influencing brown fat activation in FDG PET/CT: a retrospective analysis of 15,000+ cases

OBJECTIVE

Brown fat can exhibit high uptake of fluorine-18 fludeoxyglucose (¹⁸F-FDG) on positron emission tomography (PET) and interferes with interpretation of the scan. The goal of this study was to identify factors that may influence brown adipose tissue (BAT) activation.

METHODS

A retrospective study of ¹⁸F-FDG PET scans was performed using a database of 15,109 PET/CT reports. BAT activation reported by nuclear medicine physicians and factors influencing BAT activation were gathered. The data were analyzed using in-house software.

RESULTS

The total reported BAT activation was 3.6%. BAT activation was reported significantly more often in patients who were female (p < 0.0001), younger (p < 0.0001), with lower body mass index (p < 0.0001), with lower blood glucose levels (p = 0.01), indicated for breast cancer (p = 0.004), not administered chemotherapy recently before the scan (p < 0.0001) and shown to have BAT activation in a previous scan (p < 0.0001). BAT activation was also reported significantly more for lower outdoor temperatures (p < 0.0001) and for late morning scans than for afternoon (p = 0.005) and early morning (p = 0.001) scans.

CONCLUSION

This retrospective study of 15,109 scans highlights multiple factors contributing to BAT activation on ¹⁸F-FDG PET. The identification of new factors influencing BAT and confirmation of previously identified factors with a larger data set can be used to more accurately identify patients at risk for BAT activation so that prevention strategies can be implemented. Advances in knowledge: This study presents new factors associated with higher incidence of BAT activation, such as time of day, previous BAT activation and breast cancer. Conversely, recent chemotherapy was associated with reduced incidence of BAT activation.

Local adipocyte cancer cell paracrine loop: can "sick fat" be more detrimental?

This review article focuses on the emerging role of tumor resident adipocytes. It provides in vitro and in vivo evidence that they are essential for cancer development/progression. In addition to systemic effects, their tumor-promoting impact is dependent on local functions, notably via a complex adipocyte cancer cell paracrine loop (ACCPL). Indeed, this event leads to dramatic phenotypic and/or functional modifications of both cell types as well as of the extracellular matrix. Adipocytes undergo delipidation leading to adipocytes/cancer-associated adipocytes/cancer-associated fibroblasts de-differentiation processes. In turn, cancer cell aggressiveness is exacerbated through increased proliferation, migration, and invasion properties. This is accompanied by intense tissue remodeling, conducting to the occurrence of the tumor stroma. The molecular pathways involved in ACCPL remain largely unknown. Nevertheless, several clues are starting to emerge. Moreover, obesity is currently a sign of increased risk and poor prognosis in human carcinomas. How adiposopathy might impact tumors and specifically the ACCPL is still under investigation. However, available experimental, epidemiological, and clinical data allow to draw some directions. Interestingly, there are numerous similarities between the ACCPL-induced and obesity-related molecular alterations. It might, therefore, be hypothesized that obesity provides a "constitutively active" local permissive environment for cancer cells. Improving our knowledge about ACCPL in both lean and obese patients remains a challenging task. Indeed, deciphering the cellular and molecular mechanisms behind ACCPL might provide new targets for improving diagnosis/prognosis and the design of innovative therapeutic strategies, and even, in case of obesity, for preventing cancer.

Metabolically Active Brown Fat Mimicking Pericardial Metastasis on PET/CT: The Discriminating Role of Cardiac Magnetic Resonance Imaging

Metabolically active mediastinal brown adipose tissue may be mistakenly diagnosed as a malignancy on 18F-fluoro-2-deoxy-D-glucose (FDG)/positron emission tomography (PET). We report the case of a patient with locally recurrent breast carcinoma in which staging PET/CT revealed a suspicious pericardial lesion for which the patient was referred to our centre. The novelty of this case resides in the fact that by tissue characterization, cardiac magnetic resonance imaging allowed the determination that the lesion corresponded to brown fat, a reassuring finding with important impact on management, because the presence of pericardial metastasis would have disqualified this patient for curative resection of her cancer recurrence.

Increased Expression of Beige/Brown Adipose Markers from Host and Breast Cancer Cells Influence Xenograft Formation in Mice

The initiation and progression of breast cancer is a complex process that is influenced by heterogeneous cell populations within the tumor microenvironment. Although adipocytes have been shown to promote breast cancer development, adipocyte characteristics involved in this process remain poorly understood. In this study, we demonstrate enrichment of beige/brown adipose markers, contributed from the host as well as tumor cells, in the xenografts from breast cancer cell lines. In addition to uncoupling protein-1 (UCP1) that is exclusively expressed in beige/brown adipocytes, gene expression for classical brown (MYF5, EVA1, and OPLAH) as well as beige (CD137/TNFRSF9 and TBX1) adipocyte markers was also elevated in the xenografts. Enrichment of beige/brown characteristics in the xenografts was independent of the site of implantation of the breast tumor cells. Early stages of xenografts showed an expansion of a subset of mammary cancer stem cells that expressed PRDM16, a master regulator of brown adipocyte differentiation. Depletion of UCP1(+) or Myf5(+) cells significantly reduced tumor development. There was increased COX2 (MT-CO2) expression, which is known to stimulate formation of beige adipocytes in early xenografts and treatment with a COX2 inhibitor (SC236) reduced tumor growth. In contrast, treatment with factors that induce brown adipocyte differentiation in vitro led to larger tumors in vivo. A panel of xenografts derived from established breast tumor cells as well as patient tumor tissues were generated that expressed key brown adipose tissue-related markers and contained cells that morphologically resembled brown adipocytes.

IMPLICATIONS

This is the first report demonstrating that beige/brown adipocyte characteristics could play an important role in breast tumor development and suggest a potential target for therapeutic drug design.

The influence of sex steroids on adipose tissue growth and function

Obesity remains a major global health concern. Understanding the metabolic influences of the obesity epidemic in the human population on maintenance of a healthy weight and metabolic profile is still of great significance. The importance and role of white adipose tissue has been long established, particularly with excess adiposity. Brown adipose tissue (BAT), however, has only recently been shown to contribute significantly to the metabolic signature of mammals outside the previously recognised role in small mammals and neonates. BAT's detection in adults has led to a renewed interest and is now considered to be a potential therapeutic target to prevent excess white fat accumulation in obesity, a theory further promoted by the recent discovery of beige fat. Adipose tissue distribution varies significantly between genders. Pre-menopausal females often show enhanced lower and peripheral fat deposition in adiposity deposition compared to the male profile of central and visceral fat accumulation with obesity. This sex disparity is partly attributed to the different effects of sex hormone profiles and interactions on the adipose tissue system. In this review, we explore this intricate relationship and show how modifications in the effects of sex hormones impact on both brown and white adipose tissues. We also discuss the impact of sex hormones on activation of the hypothalamic-pituitary-adrenal (HPA) axis and how the three pathways between adiposity, HPA and sex steroids can have a major contribution to the prevention or maintenance of obesity and therefore on overall health.

Positron Emission Tomography in Breast Cancer

Gradually, FDG-PET/CT has been strengthening within the diagnostic algorithms of oncological diseases. In many of these, PET/CT has shown to be useful at different stages of the disease: diagnosis, staging or re-staging, treatment response assessment, and recurrence. Some of the advantages of this imaging modality versus CT, MRI, bone scan, mammography, or ultrasound, are based on its great diagnostic capacity since, according to the radiopharmaceutical used, it reflects metabolic changes that often occur before morphological changes and therefore allows us to stage at diagnosis. Moreover, another advantage of this technique is that it allows us to evaluate the whole body so it can be very useful for the detection of distant disease. With regard to breast cancer, FDG-PET/CT has proven to be important when recurrence is suspected or in the evaluation of treatment response. The technological advancement of PET equipment through the development of new detectors and equipment designed specifically for breast imaging, and the development of more specific radiopharmaceuticals for the study of the different biological processes of breast cancer, will allow progress not only in making the diagnosis of the disease at an early stage but also in enabling personalized therapy for patients with breast cancer.

A link between cold environment and cancer

Many risk factors such as smoking and change of life style have been shown to promote genetic and adaptive epigenetic changes responsible for tumorigenesis. This study brings environmental temperature as a cancer causing factor to light. The cancer mortality rate (CMR) of a country was correlated with 17 different variables. Multivariate analysis of a total of 188 countries found that the average annual temperature (AAT) of a country might have a significant contribution to cancer death when compared with other factors such as alcohol and meat consumption. Univariate analysis found a negative correlation between AAT and CMR. All these countries were categorized into three temperature zones (zone I, -2 to 11.5 °C; number of countries, 38; zone II, 11.6 to 18.6 °C; number of countries, 32; and zone III, 18.7 to 30 °C; number of countries, 118). Out of the top-most 50 countries having the highest CMR, 26 (68.42 %), 10 (31.25 %), and 14 (11.66 %) belong to zone I, zone II, and zone III, respectively. Out of the least 50 countries having the lowest CMR, 1 (2.63 %), 4 (12.5 %), and 45 (37.5 %) belong to zone I, zone II, and zone III, respectively. CMR is low in those countries situated near to the Torrid zone (33(°) N to 23.5(°)S), but it is high for those countries situated away from these two latitudes. These data indicate that cold temperature may have a contribution in increasing tumorigenesis. High metabolic stress, which is the result of maintaining our body temperature against a cold environment, could be the possible cause for the higher cancer mortality.

Adipocyte-derived players in hematologic tumors: useful novel targets?

INTRODUCTION

Adipocytes and their products play essential roles in tumor establishment and progression. As the main cellular component of the bone marrow, adipocytes may contribute to the development of hematologic tumors.

AREAS COVERED

This review summarizes experimental data on adipocytes and their interaction with various cancer cells. Special focus is set on the interactions of bone marrow adipocytes and normal and transformed cells of the hematopoietic system such as myeloma and leukemia cells. Current in vitro and in vivo data are summarized and the potential of novel therapeutic targets is critically discussed.

EXPERT OPINION

Targeting lipid metabolism of cancer cells and adipocytes in combination with standard therapeutics might open novel therapeutic avenues in these cancer entities. Adipocyte-derived products such as free fatty acids and specific adipokines such as adiponectin may be vital anti-cancer targets in hematologic malignancies. However, available data on lipid metabolism is currently mostly referring to peripheral fat cell/cancer cell interactions and results need to be evaluated specifically for the bone marrow niche.