Metabolic syndrome, central obesity and insulin resistance are associated with adverse pathological features in postmenopausal breast cancer

Anticancer effects of metformin and its potential use as a therapeutic agent for breast cancer

Metformin is an orally available, biguanide derivative that is widely used in the treatment of Type 2 diabetes. Recent preclinical data have demonstrated that it can also act as an anticancer agent by activation of AMPK and subsequent inhibition of mTOR. Metformin is currently being investigated in several Phase II/III clinical trials. This article will review the current evidence for its mechanism of action, efficacy in preclinical and clinical models, and toxicity. Ongoing and planned studies evaluating the impact of metformin on breast cancer outcomes are also discussed.

Influence of the metabolic syndrome on leptin and leptin receptor in breast cancer

Obesity and its associated metabolic syndrome (MetS) are recognized risk factors for breast cancer. The molecular basis for this association remains largely unknown. Adipokines, in particular leptin and adiponectin, are thought to form part of the mechanism linking obesity with cancer through their altered expression/production either systemically (endocrine pathway) or locally (paracrine/autocrine pathway). Using quantitative PCR, mRNA expression of adiponectin (AdipoQ) and leptin (Ob) in mammary adipose tissue (MAT), intratumoral leptin and associated ligand receptors (ObR, AdipoR1, and AdipoR2) was examined in 77 patients with complete anthropomorphic and serological data. Expression of Ob in MAT, and ObR in matched tumor tissue was significantly higher in patients with MetS compared to obese only or normal weight cancer patients (P < 0.005). There was no difference in intratumoral leptin adiponectin or its ligand receptors in the same groups. Individual features of MetS correlated with Ob and ObR expression, but not obesity markers (BMI, waist circumference). mRNA expression of leptin (Ob) and ObR, in adipose tissue and matched tumor samples, respectively, appear to be associated with obesity status in breast cancer. Increasing insulin resistance is a predominant feature of this higher Ob/ObR expression observed. These novel data indicate that the MetS may be an amenable risk factor for breast cancer.

Metabolic syndrome and mammographic density: the Study of Women's Health Across the Nation

The metabolic syndrome (MetS) is associated with an increase in breast cancer risk. In our study, we evaluated whether the MetS was associated with an increase in percent mammographic density (MD), a breast cancer risk factor. We used linear regression and mixed models to examine the cross-sectional and longitudinal associations of the MetS and components of the MetS to percent MD in 790 premenopausal and early perimenopausal women enrolled in the Study of Women's Health Across the Nation (SWAN). In cross-sectional analyses adjusted for body mass index (BMI), modest inverse associations were observed between percent MD and the MetS [β = -2.5, standard error (SE) = 1.9, p = 0.19], abdominal adiposity (β = -4.8, SE = 1.9, p = 0.01) and raised glucose (β = -3.7, SE = 2.4, p = 0.12). In longitudinal models adjusted for covariates including age and BMI, abdominal adiposity (β = 0.34, SE = 0.17, p = 0.05) was significantly positively associated with slower annual decline in percent MD with time. In conclusion, our results do not support the hypothesis that the MetS increases breast cancer risk via a mechanism reflected by an increase in percent MD.

Mammalian models of extended healthy lifespan

Over the last two centuries, there has been a significant increase in average lifespan expectancy in the developed world. One unambiguous clinical implication of getting older is the risk of experiencing age-related diseases including various cancers, dementia, type-2 diabetes, cataracts and osteoporosis. Historically, the ageing process and its consequences were thought to be intractable. However, over the last two decades or so, a wealth of empirical data has been generated which demonstrates that longevity in model organisms can be extended through the manipulation of individual genes. In particular, many pathological conditions associated with the ageing process in model organisms, and importantly conserved from nematodes to humans, are attenuated in long-lived genetic mutants. For example, several long-lived genetic mouse models show attenuation in age-related cognitive decline, adiposity, cancer and glucose intolerance. Therefore, these long-lived mice enjoy a longer period without suffering the various sequelae of ageing. The greatest challenge in the biology of ageing is to now identify the mechanisms underlying increased healthy lifespan in these model organisms. Given that the elderly are making up an increasingly greater proportion of society, this focused approach in model organisms should help identify tractable interventions that can ultimately be translated to humans.

Obesity and breast cancer: status of leptin and adiponectin in pathological processes

It is well recognized that obesity increases the risk of various cancers, including breast malignancies in postmenopausal women. Furthermore, obesity may adversely affect tumor progression, metastasis, and overall prognosis in both pre- and postmenopausal women with breast cancer. However, the precise mechanism(s) through which obesity acts is/are still elusive and this relationship has been the subject of much investigation and speculation. Recently, adipose tissue and its associated cytokine-like proteins, adipokines, particularly leptin and adiponectin, have been investigated as mediators for the association of obesity with breast cancer. Higher circulating levels of leptin found in obese subjects could be a growth-enhancing factor as supported by in vitro and preclinical studies, whereas low adiponectin levels in obese women may be permissive for leptin's growth-promoting effects. These speculations are supported by in vitro studies which indicate that leptin promotes human breast cancer cell proliferation while adiponectin exhibits anti-proliferative actions. Further, estrogen and its receptors have a definite impact on the response of human breast cancer cell lines to leptin and adiponectin. More in-depth studies are needed to provide additional and precise links between the in vivo development of breast cancer and the balance of adiponectin and leptin.

Intervening on the side effects of hormone-dependent cancer treatment: the role of strength training

While prostate and breast cancers are both highly prevalent and treatable using hormone suppression therapy, a constellation of side effects ensue, which mimic typical aging effects but at an accelerated pace. Because strength training is considered to be an intervention of choice for addressing the musculoskeletal and metabolic consequences of normal aging in older adults, it may be an effective intervention to attenuate or reverse the side effects of hormone-dependent cancer treatment. This paper provides an overview of the independent effects of strength training on common musculoskeletal and metabolic side effects of hormone-dependent therapy used for prostate and breast cancers. Strength training appears to be an effective complementary therapy for some of the adverse effects of prostate and breast treatment. Future research needs to address potential mechanisms to explain recent findings and to explore the role of strength training in addressing specific risk factors resulting from cancer treatment.

Biomarkers of the metabolic syndrome and breast cancer prognosis

In spite of its public health importance, our understanding of the mechanisms of breast carcinogenesis and progress is still evolving. The metabolic syndrome (MS) is a constellation of biochemical abnormalities including visceral adiposity, hyperglycemia, hyperinsulinemia, dyslipidemia and high blood pressure. The components of the MS have all been related to late-stage disease and even to a poor prognosis of breast cancer through multiple interacting mechanisms. In this review, we aim to present a summary of recent advances in the understanding of the contribution of the MS to breast cancer with the emphasis on the role of biomarkers of the MS in the prognosis of breast cancer.