SCIENTIA MEDICA Effects of regular physical exercise on skin blood flow and cardiovascular risk factors in overweight and obese subjects

Objective: it is well known that low omentin levels and reduced bioavailability of nitric oxide (NO) are outgrowth of obesity. Besides, in obese subjects, microvascular dysfunction can be an initial stage of cardiovascular diseases. This situation can be evaluated with skin laser–Doppler flowmetry (LDF). Methods: in this study we investigated the effects of 12 weeks moderate physical exercise on microvascular reactivity and plasma levels of omentin and NO in 25 overweight and obese subjects. Control group was composed of 28 sedentary participants who were neither obese nor overweight. Microvascular reactivity was handled by measurement of skin blood flow from the ring finger of the right hand with LDF, which is a non–invasive method for evaluation. With this method, it was aimed to examine the post–occlusive reactive hyperemia response of the patients. None of the participants in both groups have never followed a regular exercise schedule in their life span. Results: with regular exercise, there was a statistically significant decrease in glucose (p=0.008), cholesterol (p=0.05), and triglyceride (p=0.048) levels, while body mass index, high–density lipoprotein, and low–density lipoprotein levels did not change significantly in overweight/obese group. Also, the omentin level significantly increased (p=0.01), but NO level did not change significantly. Mo-reover, the amount of change in omentin and NO levels measured before and after the physical exercise were significantly correlated (r=0.57). Considering the microcirculation, rest flow (p=0.001) and peak flow value of LDF (p=0.001) incre- ased after the physical exercise. Conclusion: our study shows that moderate physical exercise affects microvas- cular reactivity and plasma levels of omentin in overweight and obese subjects.


Introduction
Cardiovascular diseases are significant reasons of morbidity and mortality in obese individuals.
Endothelial dysfunction and atherosclerosis are highly likely severe consequences of obesity induced cardiovascular diseases (1). In obesity, increased free fatty acids can cause mitochondrial dysfunction and free oxygen radical formation and eventually endothelial dysfunction. As a result of increased free fatty acids and accompanying activated inflammatory pathways, insulin resistance and oxidative stress may be generated.
Depending on this, bioavailability of endothelium-derived nitric oxide (NO) reduces and by this way NO-dependent vascular dilatation may deteriorate (2). Moreover, obesity leads to malfunction in particularly visceral type of adipose tissue. Adipose tissue has been widely conside-

Material and method
In this research, male and female subjects who were diagnosed as obese or overweight,  RF and PF were detected as 151.13 and 330.71, respectively. On contrary to that, RF and PF of the same subject were detected as 375.68 and 557.39, respectively, after completing the exercise schedule (not illustrated) (p=0.001 and p=0.002). AH; arterial hyperaemia, AO; arterial occlusion, PF; peak flow, PU; perfusion unit, RF; rest flow, TH1; time to half before hyperaemia, the time it takes after the release of the occlusion for perfusion to reach the midpoint between no flow and peak flow, TH2; half time of hyperaemia, the time it takes after the release of the occlusion, post-hyperaemia, for perfusion to reach the midpoint between peak flow and baseline, TM; time to peak flow, TR; time to recovery.

Statistical method
The Kolmogorov-Smirnov test was used for detecting whether the data ranks in a normal distribution or not. The Mann-Whitney U and Wilcoxon tests were used to compare non-normally distributed variables in two independent groups and two dependent groups, respectively. Nevertheless, no significant difference was found among weight, BMI, HDL, and LDL.
As for the Table 2 As we hope, there was a statistically significant difference between RF (p=0.001) and PF (p=0.002) measurements of the overweight/obese group before starting exercise schedule and the control group, the measurements were lower in the overweight/obese group before starting exercise accordingly (Figure 1). However, those measurements did not differ from each other when the control group and the overweight/obese group fulfilled the 12-week exercise schedule were compared ( Table 2).  showed parallelism with each other (16). In the study carried out with the coronary artery patients and healthy controls, the post occlusive reactive hyperaemia and microcirculation response were evaluated, and it was found that in coronary artery patients the vasodilation response was detected to be decreased. Since it is not invasive, simple to use and can be repeatable, it is thought that LDF also could be used in the patients' diagnosis and follow up (17). In obese subjects it was shown with LDF that acetylcholine-induced endothelium dependent vasodilation response was found to be decreased (18). On contrary to that, in both aerobic or anaerobic exercising athletes, it was observed to be increased (19,20). In hypertensive overweight subjects the physical exercise increased the endothelium-dependent vasodilation by increasing the post ischemic peak value that was measured with LDF (21). In our study, in obese subjects, RF and PF rates measured with LDF were specified to be increased after physical exercise of which reason is thought hypothetically to be an increase in endothelium-dependent vasodilation.
In a similar study, it was shown that in overweight and obese subjects the forearm blood flow response to acetylcholine increased after physical exercise. However, there was no change in BMI, similar to our study (22).
Obesity decreases NO bioavailability and thus

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it was thought that the vascular endothelia loses its anti-atherogenic feature and NO dependent dilation deteriorates (2). Regular physical exercise probably increases NO bioavailability depending upon the increase in endothelial NO synthase (eNOS) and antioxidant defence capacity (16,23).
In overweight children, active dance exercise for 12 weeks caused an increase in flow mediated dilation without changing the NO production (24). Similarly, the NO levels overweight/obese subjects did not increase significantly related to the physical exercise in our study but in LDF, the vasodilation enhanced.
Omentin is an adipocytokine secreted by adipose tissue and it is thought that, its lower levels

Conflicts of interest disclosure
The authors declare no competing interests relevant to the content of this study.

Authors' contributions
All the authors declare to have made substantial contributions to the conception, or design, or acquisition, or analysis, or interpretation of data; and drafting the work or revising it critically for important intellectual content; and to approve the version to be published.

Availability of data and responsibility for the results
All the authors declare to have had full access to the available data and they assume full responsibility for the integrity of these results.