Response: The Effect of 12 Weeks Aerobic, Resistance, and Combined Exercises on Omentin-1 Levels and Insulin Resistance among Type 2 Diabetic Middle-Aged Women (Diabetes Metab J 2017;41:205-12).

We appreciate Dr. Kim's interest and comments on our article entitled “The effect of 12 weeks aerobic, resistance, and combined exercises on omentin-1 levels and insulin resistance among type 2 diabetic middle-aged women” which was published in Diabetes and Metabolism Journal [1].

Omentin is an adipokine, which is expressed and secreted from adipose tissue [2]. Among total body fat storages, visceral adipose tissue (VAT) is distinct in omentin secretion. Serum omentin concentration is related to obesity and type 2 diabetes mellitus [3]. In addition, recent studies reported that omentin level in the bloodstream is increased by lifestyle modification or exercise [45]. To understand what is the exact mechanisms of rise in omentin-1 secretion when the above interventions are applied and whether fat depots is only a causal link between lifestyle and change in omentin production or both healthy lifestyle (including physical exercise) and change in fat depots are the main causes for this achievement, measurement of body fat storage is indispensable. In this regard, we completely agree with Dr. Kim that measurement of abdominal circumference could have improved our understanding of the effect of exercise on central obesity and omentin secretion. However, because of cultural and religious sensitivities, we preferred not to measure abdominal circumference of female participants as otherwise, we would have significant decrease in participation rate. Anyhow, due to the following reasons we believe our decision did not critically limit the findings of our study.

VAT can be divided into omental, mesenteric, retroperitoneal, gonadal, and pericardial [6]. As Yang et al. [7] suggested, omental fat expresses and secrets much greater omentin compare to other VAT components and subcutaneous adipose tissue (SAT). Abdominal circumference is a good meter for change in SAT and mesenteric but not omental fat and in return omentin production [8]. Indeed, more accurate methods for measuring different parts of VAT are high-resolution magnetic resonance imaging and computerized tomography scan. Not of these methods were decided to be used in our study due to high costs and potential side effects [910].

As suggested by Dr. Kim, We also believe more studies are needed to clarify the mechanisms that physical exercise affect omentin secretion from visceral fat depots.