Hemodynamic responses to exercise in obese children and adolescents before and after overweight reduction

OBJECTIVE

To determine the change of hemodynamic parameters in graded bicycle exercise testing in obese children before and after overweight reduction.

METHODS

Forty-two obese children (mean age 11 years) and 40 healthy, lean children underwent graded bicycle exercise testing (1, 1.5, 2, 2.5 Watt/kg) recording the heart rate (HR) and blood pressure (BP) before exercise (T1), at maximum load (T2), and 6 min after ending the exercise (T3). Furthermore, the increase of the patient's heart rate within each ramp (I-HR) and the individual maximum load (Watt/kg) were recorded. After participating in an one-year outpatient intervention program for obese children, the study group underwent exercise testing again. Furthermore, we analyzed the lipid and insulin levels in the study group before and after overweight reduction and correlated the changes of the hemodynamic parameters to the changes of the insulin and lipid levels.

RESULTS

The obese children had significantly (p<0.05) higher systolic blood pressure values at T1, T2, and T3 as compared to the lean children. The I-HR was significantly (p<0.05) higher in the study group. HR and BP at T1, T2, and T3, and the lipid and insulin values improved significantly in the study group after overweight reduction. The changes of HR and BP did not correlate to the changes of insulin and lipids.

CONCLUSION

Compared to lean children, obese children demonstrated a significantly lower exercise capacity of the cardiovascular system, which improved after participating in an obesity intervention program. Overweight reduction influences the hemodynamic and metabolic changes of childhood obesity positively and thereby leads to an improvement of the cardiovascular risk factor profile.

Tyrosinase inhibition by extracts and constituents of Sideroxylon inerme L. stem bark, used in South Africa for skin lightening

OBJECTIVE

To investigate the stem bark of Sideroxylon inerme L. and its compounds for tyrosinase-inhibition activity and to evaluate the mechanism involved of the most potent compounds in tyrosinase inhibition.

MATERIALS AND METHODS

Three different extracts (acetone, methanol and dichloromethane) of Sideroxylon inerme L. were evaluated for their inhibitory effect in vitro on the monophenolase and diphenolase activated forms of tyrosinase, using a colorimetric procedure. This test was used for bioactivity-guided isolation of two active compounds using column chromatography and TLC. Active extracts were also investigated for their inhibitory effect on melanogenesis in cultured B16 melanoma cells. Antioxidant activities of the methanolic extract of Sideroxylon inerme and purified compounds were investigated using the 1,2-diphenyl-2-picrylhydrazyl (DPPH) antioxidant assay. The inhibition of tyrosinase activity relative to the inhibition of its activity at the transcriptional level was also studied by determination of the degree of expression of mRNAs for this gene by using extract of Sideroxylon inerme-treated cells (B16F10) and semi-quantitative RT-PCR.

RESULTS

Methanolic and acetonic extracts of the stem bark of Sideroxylon inerme showed significant inhibition of monophenolase activity (IC50 values of 63 microg/ml and 82 microg/ml, respectively). The methanolic extract also exhibited 37% reduction of melanin content at 6.2 microg/ml in melanocytes without being significantly toxic to the cells. Examination for inhibition of monophenoloxidase in situ on TLC, followed by column chromatographic purification of the stem bark extract of Sideroxylon inerme, resulted in the isolation of two active compounds, epigallocatechin gallate and procyanidin B1, with IC50 values against monophenolase of 30 microg/ml and > 200 microg/ml, respectively. Epigallocatechin gallate exhibited a greater anti-tyrosinase activity than arbutin. Sideroxylon inerme bark extracts, epigallocatechin gallate and procyanidin B1 exhibited antioxidant DPPH radical scavenging activities with EC50 values of 1.54 microg/ml, 1.33 microg/ml and 1.68 microg/ml, respectively and were not particularly cytotoxic. During mechanism studies it was evident that at the transcription level, Sideroxylon inerme (25 microg/ml) was acting as a potent tyrosinase inhibitor compared to controls (untreated cells and kojic acid).

CONCLUSION

The bark extract of Sideroxylon inerme and the two isolated compounds warrant further investigation in clinical studies to be considered as skin-depigmenting agents.

Characteristics and risk factors of tobacco consumption among University of Sharjah students, 2005

This study aimed to estimate the prevalence, patterns and risk factors of tobacco consumption among a stratified random sample of students at University of Sharjah, United Arab Emirates (UAE), during 2005. The overall reported smoking prevalence among 1057 sampled students was 15.1%; cigarette smokers were 9.4% and waterpipe smokers 5.6%. While women comprised only 8.9% of cigarette smokers, they were 26.2% of waterpipe smokers. Multiple linear regression analysis showed that the most important predictors for smoking among the students were: male sex, having a smoking friend, having a smoking family member (father/mother/both), non-UAE nationality and older age. There is a need to intensify efforts to prevent young people from starting smoking and to help young smokers to stop.