Evaluation of leptin, thought as a cancer-related biomarker, in postmenopausal women.

Abstract

We read with great interest the article by Paxton et al. [1] entitled ‘‘Associations between time spent sitting and cancer-related biomarkers in postmenopausal women: an exploration of effect modifiers’’ in which the investigators reported that the associations between time spent sitting and cancer-related biomarkers were not linear, and no significant associations were found. They added that the relationships between sedentary behavior and cancer-related biomarkers may differ by important factors. We thank the authors for their detailed report. However, we wish to make some comments on leptin, which was evaluated in their study. Leptin, which is an adipocyte-secreted hormone, regulates food intake, energy homeostasis, neuroendocrine function, metabolism, and immune function [2]. Leptin shows circadian variations in its secretion [3]. Leptin rises in the afternoon, peaks at night, and decreases to basal levels in the early morning [3]. The authors did not define the sampling time. In this regard, without defining the sampling time, interpreting the results is problematic. Previous studies showed that certain diseases such as hypertension, cardiovascular diseases, major depression, chronic liver diseases, and several infectious and inflammatory diseases such as rheumatoid arthritis, systemic lupus erythematosus, and Helicobacter pylori infection affect plasma leptin levels [4, 5]. The authors did not mention such contributing factors. In addition, some types of antipsychotics, antidepressants, statins, glucocorticoids, antihypertensive, and antidiabetic drugs affect plasma leptin levels [6, 7]. Also, dietary supplements such as vitamin D, vitamin E, vitamin A, omega-3 fatty acids, linoleic acid, and zinc can affect plasma leptin levels [8, 9]. Bailey et al. [10] reported that supplement use was reported by 49 % of the US population. In this respect, the authors should have stated whether the participants used such drugs and dietary supplements. In conclusion, though this study contributes valuable information to the medical literature, clarifying these concerns will certainly provide a clearer picture when interpreting leptin levels among participants.