Breast Cancer Endocrine Therapy Promotes Weight Gain With Distinct Adipose Tissue Effects in Lean and Obese Female Mice

Estrogen receptors in mitochondrial metabolism: age-related changes and implications for pregnancy complications

Estrogen hormones are primarily associated with their role as female sex hormones responsible for primary and secondary sexual development. Estrogen receptors are known to undergo age-dependent decreases due to age-related changes in hormone production. In the mitochondria, estrogen functions by reducing the production of reactive oxygen species in the electron transport chain, inhibiting apoptosis, and regulating mitochondrial DNA content. Moreover, estrogen receptors may be the key components in maintaining mitochondrial membrane potential and structure. Although estrogen plays a crucial role in the development of pregnancy, our understanding of how estrogen receptors change with aging during pregnancy remains limited. During pregnancy, estrogen levels are significantly elevated, with a corresponding upregulation of estrogen receptors, which play various roles in pregnancy. However, the exact role of estrogen receptors in pregnancy complications remains to be further investigated. The paper reviews the role of estrogen receptors in the regulation of mitochondrial metabolism and in pregnancy complications, with a special focus on the effect of age-related changes on estrogen levels and estrogen receptors function. We also address how estrogen maintains mitochondrial function, including reducing the production of reactive oxygen species in the electron transport chain, inhibiting apoptosis, regulating mitochondrial DNA content, and maintaining mitochondrial membrane potential and structure. However, the effects of estrogen on mitochondria-endoplasmic reticulum contacts have not been well studied. Based on these emergent roles in mitochondria, the differential roles of estrogen receptors in pregnancy complications are of great relevance. The paper emphasizes the association between maternal health and estrogen receptors and indicates the need for future research to elucidate the interdependence of estrogen receptor-regulated maternal health with mitochondrial function and their relationship with the gut microbiome. Overall, we summarize the important role of estrogen receptors during pregnancy and highlight the need for further research to better understand the role of estrogen receptors in aging and pregnancy complications. This not only helps to reveal the mechanism underlying the role of estrogen in maternal health but also has potential clinical implications for the development of new therapies targeting age-related diseases and pregnancy complications.

Postnatal Tamoxifen Exposure Induces Long-Lasting Changes to Adipose Tissue in Adult Mice

Tamoxifen (TAM) is commonly administered to a variety of inducible or conditional transgenic mice that contain Cre recombinase fused with ER. While the impacts of adult TAM treatment are well documented in the field of adipose biology, the long-term effects of postnatal TAM treatment on adult life are still understudied. In this study, we investigated whether postnatal TAM treatment had long-lasting effects on adult body composition and adiposity in male and female mice, fed either with chow or a high-fat diet (HFD). We found that postnatal, but not adult, TAM treatment had long-lasting impacts on female mice, resulting in lower body weight, lower fat mass, and smaller adipocytes. In contrast, postnatal exposure to TAM impaired male but not female cold-induced adipose beiging capacity. Interestingly, upon HFD feeding, the sex-dependent effects of TAM on adult life disappeared, and both female and male mice showed a more obese phenotype with impaired glucose tolerance. These findings suggest that postnatal TAM injection exerts a long-lasting impact on adipose tissue in adult life in a sex- and diet-dependent manner.

Machine learning predicts the risk of osteoporosis in patients with breast cancer and healthy women

OBJECTIVE

In this study, we investigated the effects of endocrine therapy and related drugs on the body composition and bone metabolism of patients with breast cancer. Additionally, using body composition-related indicators in machine learning algorithms, the risks of osteoporosis in patients with breast cancer and healthy women were predicted.

METHODS

We enrolled postmenopausal patients with breast cancer who were hospitalized in a tertiary hospital and postmenopausal women undergoing health checkups in our hospital between 2019 and 2021. The basic information, body composition, bone density-related indicators, and bone metabolism-related indicators of all the study subjects were recorded. Machine learning models were constructed using cross-validation.

RESULTS

Compared with a healthy population, the body composition of patients with breast cancer was low in bone mass, protein, body fat percentage, muscle, and basal metabolism, whereas total water, intracellular fluid, extracellular fluid, and waist-to-hip ratio were high. In patients with breast cancer, the bone mineral density (BMD), Z value, and T value were low and the proportion of bone loss and osteoporosis was high. BMD in patients with breast cancer was negatively correlated with age, endocrine therapy status, duration of medication, and duration of menopause, and it was positively correlated with body mass index (BMI) and basal metabolism. The parameters including body composition, age, hormone receptor status, and medication type were used for developing the machine learning model to predict osteoporosis risk in patients with breast cancer and healthy populations. The model showed a high accuracy in predicting osteoporosis, reflecting the predictive value of the model.

CONCLUSIONS

Patients with breast cancer may have changed body composition and BMD. Compared with the healthy population, the main indicators of osteoporosis in patients with breast cancer were reduced nonadipose tissue, increased risk of edema, altered fat distribution, and reduced BMD. In addition to age, duration of treatment, and duration of menopause, body composition-related indicators such as BMI and basal metabolism may be considerably associated with BMD of patients with breast cancer, suggesting that BMD status can be monitored in clinical practice by focusing on changes in the aforementioned indexes, which may provide a way to prevent preclinical osteoporosis.

Diabetes mellitus in breast cancer survivors: metabolic effects of endocrine therapy

Breast cancer is the most common invasive malignancy in the world, with millions of survivors living today. Type 2 diabetes mellitus (T2DM) is also a globally prevalent disease that is a widely studied risk factor for breast cancer. Most breast tumours express the oestrogen receptor and are treated with systemic therapies designed to disrupt oestrogen-dependent signalling. Since the advent of targeted endocrine therapy six decades ago, the mortality from breast cancer has steadily declined; however, during the past decade, an elevated risk of T2DM after breast cancer treatment has been reported, particularly for those who received endocrine therapy. In this Review, we highlight key events in the history of endocrine therapies, beginning with the development of tamoxifen. We also summarize the sequence of reported adverse metabolic effects, which include dyslipidaemia, hepatic steatosis and impaired glucose tolerance. We discuss the limitations of determining a causal role for breast cancer treatments in T2DM development from epidemiological data and describe informative preclinical studies that suggest complex mechanisms through which endocrine therapy might drive T2DM risk and progression. We also reinforce the life-saving benefits of endocrine therapy and highlight the need for better predictive biomarkers of T2DM risk and preventive strategies for the growing population of breast cancer survivors.

Barriers and facilitators of healthy lifestyle and perspectives towards the development of weight loss programmes. Focus groups with post-treatment breast cancer survivors in Greece

The present study aimed to identify the factors that prohibit or enable breast cancer survivors from adopting a healthy lifestyle, as well as to record patients' suggestions towards developing a weight-loss lifestyle intervention. Twenty-three breast cancer survivors participated in four online, semi-structured focus groups in Greece. All discussions were video-recorded and transcribed verbatim. Participants were 50⋅5 ± 7⋅4 years old with a current mean BMI of 29⋅1 ± 3⋅4 kg/m2. Four main themes emerged from thematic analysis: (1) dietary and lifestyle practices, (2) the effects of cancer on body weight, (3) the impact of cancer on psychology, and (4) the effect of the environment on body weight. Lack of information from healthcare professionals and lack of time were the main barriers to body weight management, whereas the main facilitators were support from their social environment, along with a comfortable physical environment, and the facility of technology. Participants suggested that an effective weight-loss lifestyle intervention should include psychological and social support, guidance and education, collaboration, flexible recommendations, personalised goals, and a follow-up plan. The needs of breast cancer survivors need to be considered when designing weight-loss lifestyle interventions. A personalised approach may prove more effective in promoting a healthy lifestyle and improving patients' care.

Sex Differences in the Skeletal Muscle Response to a High Fat, High Sucrose Diet in Rats

Men are diagnosed with type 2 diabetes at lower body mass indexes than women; the role of skeletal muscle in this sex difference is poorly understood. Type 2 diabetes impacts skeletal muscle, particularly in females who demonstrate a lower oxidative capacity compared to males. To address mechanistic differences underlying this sex disparity, we investigated skeletal muscle mitochondrial respiration in female and male rats in response to chronic high-fat, high-sugar (HFHS) diet consumption. Four-week-old Wistar Rats were fed a standard chow or HFHS diet for 14 weeks to identify sex-specific adaptations in mitochondrial respirometry and characteristics, transcriptional patterns, and protein profiles. Fat mass was greater with the HFHS diet in both sexes when controlled for body mass (p < 0.0001). Blood glucose and insulin resistance were greater in males (p = 0.01) and HFHS-fed rats (p < 0.001). HFHS-fed males had higher mitochondrial respiration compared with females (p < 0.01 sex/diet interaction). No evidence of a difference by sex or diet was found for mitochondrial synthesis, dynamics, or quality to support the mitochondrial respiration sex/diet interaction. However, transcriptomic analyses indicate sex differences in nutrient handling. Sex-specific differences occurred in PI3K/AKT signaling, PPARα/RXRα, and triacylglycerol degradation. These findings may provide insight into the clinical sex differences in body mass index threshold for diabetes development and tissue-specific progression of insulin resistance.

Obesity and Risk of Recurrence in Patients With Breast Cancer Treated With Aromatase Inhibitors

Importance

Clinical studies confirm that obesity is a risk factor for recurrence in postmenopausal women with hormone receptor-positive (HR+) breast cancer. Evidence suggests that women with obesity do not obtain similar protection from aromatase inhibitors as women with healthy weight.

Objective

To examine the associations of body mass index (BMI) with recurrence.

Design, Setting, and Participants

The cohort study was conducted using data from the Danish Breast Cancer Group and enrolled postmenopausal women diagnosed with stage I to III HR+ breast cancer from 1998 through 2016. Data analysis was conducted from November 2022 to April 2023.

Exposures

BMI was classified as (1) healthy weight (18.5-24.9), (2) overweight (25.0-29.9), (3) obesity (30.0-34.9), and (4) severe obesity (≥35.0) using the World Health Organization guidelines. Healthy weight was considered the reference group in statistical analyses.

Main Outcomes and Measures

Follow-up began 6 months after breast cancer surgery and continued until the first event of recurrence, contralateral breast cancer, new primary malignant neoplasm, death, emigration, end of clinical follow-up at 10 years, or September 25, 2018. Cox regression was used to estimate crude and adjusted hazard ratios with 95% CIs, adjusting for patient, tumor, and treatment characteristics.

Results

A total of 13 230 patients (median [IQR] age at diagnosis, 64.4 [58.6-70.2] years) with information on BMI were enrolled. There were 1587 recurrences with a median (IQR) potential estimated follow-up of 6.2 (3.6-8.5) years. Multivariable analyses revealed increased recurrence hazards associated with obesity (adjusted hazard ratio, 1.18 [95% CI, 1.01-1.37]) and severe obesity (adjusted hazard ratio, 1.32 [95% CI, 1.08-1.62]) vs patients with healthy weight. Patients with overweight had a greater risk, but the results were not statistically significant (adjusted hazard ratio, 1.10 [95% CI, 0.97-1.24]).

Conclusions and Relevance

In this study, obesity was associated with an increased risk of breast cancer recurrence among postmenopausal patients with HR+ early-stage breast cancer treated with aromatase inhibitors. Physicians should be aware of the significance of obesity on breast cancer outcomes to secure optimal treatment benefit in all patients.

Changes in m6A in Steatotic Liver Disease

Fatty liver disease is one of the major causes of morbidity and mortality worldwide. Fatty liver includes non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH), now replaced by a consensus group as metabolic dysfunction-associated steatotic liver disease (MASLD). While excess nutrition and obesity are major contributors to fatty liver, the underlying mechanisms remain largely unknown and therapeutic interventions are limited. Reversible chemical modifications in RNA are newly recognized critical regulators controlling post-transcriptional gene expression. Among these modifications, N6-methyladenosine (m6A) is the most abundant and regulates transcript abundance in fatty liver disease. Modulation of m6A by readers, writers, and erasers (RWE) impacts mRNA processing, translation, nuclear export, localization, and degradation. While many studies focus on m6A RWE expression in human liver pathologies, limitations of technology and bioinformatic methods to detect m6A present challenges in understanding the epitranscriptomic mechanisms driving fatty liver disease progression. In this review, we summarize the RWE of m6A and current methods of detecting m6A in specific genes associated with fatty liver disease.

The 'omics of obesity in B-cell acute lymphoblastic leukemia

The obesity pandemic currently affects more than 70 million Americans and more than 650 million individuals worldwide. In addition to increasing susceptibility to pathogenic infections (eg, SARS-CoV-2), obesity promotes the development of many cancer subtypes and increases mortality rates in most cases. We and others have demonstrated that, in the context of B-cell acute lymphoblastic leukemia (B-ALL), adipocytes promote multidrug chemoresistance. Furthermore, others have demonstrated that B-ALL cells exposed to the adipocyte secretome alter their metabolic states to circumvent chemotherapy-mediated cytotoxicity. To better understand how adipocytes impact the function of human B-ALL cells, we used a multi-omic RNA-sequencing (single-cell and bulk transcriptomic) and mass spectroscopy (metabolomic and proteomic) approaches to define adipocyte-induced changes in normal and malignant B cells. These analyses revealed that the adipocyte secretome directly modulates programs in human B-ALL cells associated with metabolism, protection from oxidative stress, increased survival, B-cell development, and drivers of chemoresistance. Single-cell RNA sequencing analysis of mice on low- and high-fat diets revealed that obesity suppresses an immunologically active B-cell subpopulation and that the loss of this transcriptomic signature in patients with B-ALL is associated with poor survival outcomes. Analyses of sera and plasma samples from healthy donors and those with B-ALL revealed that obesity is associated with higher circulating levels of immunoglobulin-associated proteins, which support observations in obese mice of altered immunological homeostasis. In all, our multi-omics approach increases our understanding of pathways that may promote chemoresistance in human B-ALL and highlight a novel B-cell-specific signature in patients associated with survival outcomes.

Estrogen receptor alpha deficiency in cardiomyocytes reprograms the heart-derived extracellular vesicle proteome and induces obesity in female mice

Dysregulation of estrogen receptor alpha (ERα) has been linked with increased metabolic and cardiovascular disease risk. Here, we generate and characterize cardiomyocyte-specific ERα knockout (ERαHKO) mice to assess the role of ERα in the heart. The most striking phenotype was obesity in female ERαHKO but not male ERαHKO mice. Female ERαHKO mice showed cardiac dysfunction, mild glucose and insulin intolerance and reduced ERα gene expression in skeletal muscle and white adipose tissue. Transcriptomic, proteomic, lipidomic and metabolomic analyses revealed evidence of contractile and/or metabolic dysregulation in heart, skeletal muscle and white adipose tissue. We show that heart-derived extracellular vesicles from female ERαHKO mice contain a distinct proteome associated with lipid and metabolic regulation, and have the capacity to metabolically reprogram the target skeletal myocyte proteome with functional impacts on glycolytic capacity and reserve. This multi-omics study uncovers a cardiac-initiated and sex-specific cardiometabolic phenotype regulated by ERα and provides insights into extracellular vesicle-mediated interorgan communication.

Behavioral and transcriptomic effects of the cancer treatment tamoxifen in mice

Introduction

Tamoxifen is a common treatment for estrogen receptor-positive breast cancer. While tamoxifen treatment is generally accepted as safe, there are concerns about adverse effects on cognition.

Methods

We used a mouse model of chronic tamoxifen exposure to examine the effects of tamoxifen on the brain. Female C57/BL6 mice were exposed to tamoxifen or vehicle control for six weeks; brains of 15 mice were analyzed for tamoxifen levels and transcriptomic changes, and an additional 32 mice were analyzed through a battery of behavioral tests.

Results

Tamoxifen and its metabolite 4-OH-tamoxifen were found at higher levels in the brain than in the plasma, demonstrating the facile entry of tamoxifen into the CNS. Behaviorally, tamoxifen-exposed mice showed no impairment in assays related to general health, exploration, motor function, sensorimotor gating, and spatial learning. Tamoxifen-treated mice showed a significantly increased freezing response in a fear conditioning paradigm, but no effects on anxiety measures in the absence of stressors. RNA sequencing analysis of whole hippocampi showed tamoxifen-induced reductions in gene pathways related to microtubule function, synapse regulation, and neurogenesis.

Discussion

These findings of the effects of tamoxifen exposure on fear conditioning and on gene expression related to neuronal connectivity suggest that there may be CNS side effects of this common breast cancer treatment.

Factors associated with weight gain after breast cancer: Results from a community-based survey of Australian women

PURPOSE

Weight gain after breast cancer is common. The aim of this study was to determine factors associated with weight gain after breast cancer in Australian women.

METHODS

A cross-sectional online survey was conducted between November 2017 and January 2018. Women living in Australia who self-identified as having breast cancer or ductal carcinoma in-situ were eligible. We created stepwise linear and logistic regression models to evaluate predictors for absolute and clinically significant (≥5%) weight gain respectively.

RESULTS

Data from 276 women were analysed. Most were Caucasian and 92% had been diagnosed with Stage 0-III breast cancer. Absolute weight gain was associated with hot flushes, being in the menopausal transition at diagnosis, being less physically active than at diagnosis, lower eating self-efficacy when watching television or using a computer, and higher self-efficacy when anxious or nervous (F-ratio = 3.26, R²-adjusted = 0.16, p < .001). Clinically significant weight gain was associated with tamoxifen use (OR 2.7), being less physically active than at diagnosis (OR 3.1), and lower eating self-efficacy when watching television or using a computer (OR 0.82) (Chi-square 64.94, df = 16, p < .001). Weight gain was not associated with chemotherapy, radiotherapy, aromatase inhibitor use, number of lymph nodes removed, or body mass index at diagnosis.

CONCLUSIONS

Interventions to prevent weight gain after breast cancer, particularly aiming to maintain physical activity, should be targeted at women receiving tamoxifen. The role of eating self-efficacy, especially attentive eating, in managing weight after breast cancer should be explored.

Neonatal intake of Omega-3 fatty acids enhances lipid oxidation in adipocyte precursors

Establishing metabolic programming begins during fetal and postnatal development, and early-life lipid exposures play a critical role during neonatal adipogenesis. We define how neonatal consumption of a low omega-6 to -3 fatty acid ratio (n6/n3 FA ratio) establishes FA oxidation in adipocyte precursor cells (APCs) before they become adipocytes. In vivo, APCs isolated from mouse pups exposed to the low n6/n3 FA ratio had superior FA oxidation capacity, elevated beige adipocyte mRNAs Ppargc1α, Ucp2, and Runx1, and increased nuclear receptor NR2F2 protein. In vitro, APC treatment with NR2F2 ligand-induced beige adipocyte mRNAs and increased mitochondrial potential but not mass. Single-cell RNA-sequencing analysis revealed low n6/n3 FA ratio yielded more mitochondrial-high APCs and linked APC NR2F2 levels with beige adipocyte signatures and FA oxidation. Establishing beige adipogenesis is of clinical relevance, because fat depots with energetically active, smaller, and more numerous adipocytes improve metabolism and delay metabolic dysfunction.

Barriers and enablers of weight management after breast cancer: a thematic analysis of free text survey responses using the COM-B model

Background

Weight gain is common after breast cancer. The aim of this study was to identify and describe the barriers to and enablers of successful weight management for women with breast cancer.

Methods

This was a combined inductive and deductive framework analysis of free text responses to an anonymous cross-sectional survey on weight after breast cancer. Women were recruited mainly through the Breast Cancer Network Australia Review and Survey Group. We applied deductive thematic analysis to free text responses to questions on barriers, enablers, research priorities, and one open-ended question at the end of the survey using the Capability, Opportunity, Motivation and Behaviour (COM-B) model as a framework. Subthemes that arose from the inductive analysis were mapped onto the COM-B model framework. Findings were used to identify behaviour change intervention functions.

Results

One hundred thirty-three women provided free text responses. Most women were of Caucasian origin and had been diagnosed with non-metastatic breast cancer, with a mean age of 59.1 years. Women's physical capability to adopt and sustain healthy lifestyle habits was significantly affected by treatment effects and physical illness, and some lacked psychological capability to self-regulate the face of stress and other triggers. Limited time and finances, and the social impact of undergoing cancer treatment affected the ability to control their diet. Frustration and futility around weight management were prominent. However, some women were confident in their abilities to self-regulate and self-monitor lifestyle behaviours, described support from friends and health professionals as enablers, and welcomed the physical and psychological benefits of being active in the context of embracing transformation and self-care after cancer.

Conclusion

Women need specific advice and support from peers, friends and families and health professionals. There is a substantial gap in provision of supportive care to enable women to adopt and sustain healthy lifestyles. Environmental restructuring (including financial support), incentivization (creating an expectation of looking and feeling better), persuasion and coercion (aiming to prevent recurrence), and equipping women with specific knowledge and skills, would also facilitate optimal lifestyle behaviours and weight management.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-13980-6.

The association between adiposity and anti-proliferative response to neoadjuvant endocrine therapy with letrozole in post-menopausal patients with estrogen receptor positive breast cancer

The impact of adiposity on the efficacy of endocrine treatment in patients with estrogen receptor positive breast cancer is poorly investigated. Here, we retrospectively investigated in a cohort of 56 patients whether body mass index and/or mammary adiposity are associated with anti-proliferative response in the neoadjuvant setting. Anti-proliferative response was defined as high Ki67 at baseline (Ki67_bl) and low Ki67 at surgery (Ki67_srg), using the 14% cut-off. Mammary adipocyte size was assessed on hematoxylin and eosin slides from the surgical samples using digital pathology. A higher proportion of tumors with an anti-proliferative response was observed in patients with obesity (54.5%) as compared to patients with normal weight (9.0%) and patients with overweight (40.0%) (p = 0.031), confirmed by multivariable regression analysis adjusted for baseline Ki67 (OR, obese vs normal weight: 13.76, 95%CI: 1.49–207.63, p = 0.020). Larger adipocyte diameter was identified as predictor of anti-proliferative response (OR per increase in diameter of 5 μm for adipocytes distant from the tumor: 2.24, 95%CI: 1.01–14.32, p = 0.046). This study suggests that anti-proliferative response to neoadjuvant letrozole might be more frequent in patients with increased systemic or mammary adiposity.