The balance between leptin and adiponectin in the control of carcinogenesis - focus on mammary tumorigenesis. Biochimie. 2012;94:2164-2171. [PMID: 22728769 DOI: 10.1016/j.biochi.2012.06.013]

Interplay of adipokines and myokines in cancer pathophysiology: Emerging therapeutic implications

Excess body weight constitutes a worldwide health problem with epidemic proportions impacting on the risk and prognosis of several disease states including malignancies. It is believed that the metabolic changes associated with weight gain, particularly visceral obesity, and physical inactivity could lead to dysfunctional adipose and muscle tissues causing insulin resistance, low-grade chronic inflammation and abnormal secretion of adipokines and myokines. The complex paracrine and endocrine interconnection between adipokines and myokines reflects a yin-yang balance with important implications in processes such as lipolysis control, insulin sensitivity and prevention from obesity-driven chronic low-grade inflammation and cancer promotion through anti-inflammatory adipokines and myokines. Furthermore, the complex pathophysiology of cancer cachexia is based on the interplay between muscle and adipose tissue mediated by free fatty acids, various adipokines and myokines. The purpose of this editorial is to explore the role of the adipose and muscle tissue interplay in carcinogenesis, cancer progression and cachexia, and to examine the mechanisms underpinning their association with malignancy. Understanding of the mechanisms connecting the interplay of adipokines and myokines with cancer pathophysiology is expected to be of importance in the development of therapeutic strategies against cancer cachexia. Advances in the field of translational investigation may lead to tangible benefits to obese and inactive persons who are at increased risk of cancer as well as to cancer patients with cachexia.

Leptin's role in lipodystrophic and nonlipodystrophic insulin-resistant and diabetic individuals

Leptin is an adipocyte-secreted hormone that has been proposed to regulate energy homeostasis as well as metabolic, reproductive, neuroendocrine, and immune functions. In the context of open-label uncontrolled studies, leptin administration has demonstrated insulin-sensitizing effects in patients with congenital lipodystrophy associated with relative leptin deficiency. Leptin administration has also been shown to decrease central fat mass and improve insulin sensitivity and fasting insulin and glucose levels in HIV-infected patients with highly active antiretroviral therapy (HAART)-induced lipodystrophy, insulin resistance, and leptin deficiency. On the contrary, the effects of leptin treatment in leptin-replete or hyperleptinemic obese individuals with glucose intolerance and diabetes mellitus have been minimal or null, presumably due to leptin tolerance or resistance that impairs leptin action. Similarly, experimental evidence suggests a null or a possibly adverse role of leptin treatment in nonlipodystrophic patients with nonalcoholic fatty liver disease. In this review, we present a description of leptin biology and signaling; we summarize leptin's contribution to glucose metabolism in animals and humans in vitro, ex vivo, and in vivo; and we provide insights into the emerging clinical applications and therapeutic uses of leptin in humans with lipodystrophy and/or diabetes.

Oxidative stress associated to dysfunctional adipose tissue: a potential link between obesity, type 2 diabetes mellitus and breast cancer

Diabetes mellitus and breast cancer are two important health problems. Type 2 diabetes (T2DM) and obesity are closely linked with both being associated with breast cancer. Despite abundant epidemiological data, there is no definitive evidence regarding the mechanisms responsible for this association. The proposed mechanisms by which diabetes affects breast cancer risk and prognosis are the same as the mechanisms hypothesised for the contribution of obesity to breast cancer risk. The obesity-induced inflammation promoted by adipose tissue dysfunction is a key feature, which is thought to be an important link between obesity and cancer. Inflammation induces an increase in free radicals and subsequently promotes oxidative stress, which may create a microenvironment favourable to the tumor development in obese persons. Oxidative stress is also proposed as the link between obesity and diabetes mellitus. Therefore, obesity-related oxidative stress could be a direct cause of neoplastic transformation associated with obesity and T2DM in breast cancer cells. This review is focused on the role of obesity-related oxidative stress in the context of chronic inflammation, on the time of breast cancer onset and progression, which provide targets for preventive and therapeutic strategies in the fields of diabetes and obesity-related breast cancer.

Obesity-associated adipokines correlate with survival in epithelial ovarian cancer

OBJECTIVES

Obesity impacts outcome in women with epithelial ovarian cancer (EOC), although its exact role and the molecular mechanisms remain poorly defined. Adipocytes secrete leptin and adiponectin, and the leptin to adiponectin (L:A) ratio is correlated with poor survival in other malignancies. We hypothesized that the L:A ratio is associated with survival in women with EOC.

METHODS

We queried the institutional tumor registry for patients with advanced stage EOC and identified a cohort of 161 women with banked fasting prediagnostic serum samples. Patients underwent cytoredutive surgery followed by platinum-based chemotherapy. Sera were assayed for leptin and adiponectin, and clinico-pathologic data were abstracted. Standard statistical tests were performed.

RESULTS

161 patients met inclusion criteria. We identified a significant correlation between BMI and leptin and the L:A ratio, but not adiponectin, in this cohort (r=0.46, 0.46, and -0.13, respectively; p=0.001, 0.001, and 0.106). Women with low L:A ratios demonstrated statistically longer disease-specific survival (57 months) compared to those with median or high levels (49 and 37 months, respectively; p=0.02). On multivariate analysis, we determined that BMI and age, but not L:A ratio, retained significance as independent prognostic factors for survival (p=0.04, 0.004, and 0.895, respectively).

CONCLUSIONS

In this cohort, the L:A ratio correlated statistically with clinical outcome, but did not independently predict survival. Obesity remains a modifiable risk factor in women with EOC. Further studies are needed to determine if leptin and/or adiponectin may be potential therapeutic targets in obese women with EOC.