Regulation of oxygen saturation in retinal blood vessels in response to dynamic exercise

Acute effects of high-intensity interval training on cognition and retinal microcirculation in experienced amateur boxers

BACKGROUND

Limited and contradictory data are available regarding the acute effects of endurance exercises on cognition and retinal microcirculation. Thus, we aimed to evaluate the acute effects of sport-specific high-intensity interval training (HIIT) on cognition and retinal vessel diameters in experienced amateur boxers.

METHODS

Eleven young (age 22.8±2.9 years) men with 10.7±4.8 years of boxing experience completed two sessions in random order: high-intensity intermittent punching load and passive rest. Cardiovascular response, retinal vessel diameters, and cognitive performance were evaluated at baseline, during exercise, and immediately after each session.

RESULTS

Increased heart rate during intermittent punching load (P<0.05) reaching 91.2±3.7% of the maximal heart rate was observed. The HIIT improved cognitive flexibility and inhibitory control (P<0.05), while the working memory and motor speed were not affected. Significant dilatation of temporal retinal venules (P<0.05) was observed after the HIIT compared with the values before the HIIT, resulting in a decreased arteriolar-to-venular diameter ratio (P<0.05).

CONCLUSIONS

At the functional level, an improvement in executive function due to intermittent high intensity punching load was observed, while at the physiological level, retinal venular dilatation was observed in experienced amateur boxers.

Effects of etanercept on the apoptosis of ganglion cells and expression of Fas, TNF-α, caspase-8 in the retina of diabetic rats

AIM

To evaluate the effects of etanercept on the expression of Fas, tumor necrosis factor-alpha (TNF-α) and caspase-8 in the early stage of the apoptotic pathway in diabetic rats, and to explore the therapeutic effect of etanercept on diabetic retinopathy.

METHODS

A total of 60 Sprague-Dawley (SD) rats were randomly and evenly divided into 3 groups with 20 rats each, including control group, and diabetic groups with or without treatment. Streptozotocin (STZ)-induced diabetic rats were established for diabetic groups. Blood glucose and body weight were measured weekly. All the rats were sacrificed at the 12wk after treatment. The expressions of Fas, TNF-α and caspase-8 in rat retina were quantitatively detected by PCR and Western blot. The leakage of Evan blue was adopted to measure the retinal vascular leakage quantitatively, and to compare it among different groups. TUNEL method was used to compare the amount of apoptotic bodies quantitatively in rat retina ganglion cells under electron microscope.

RESULTS

The expressions of Fas, TNF-α and caspase-8 in each group were compared via PCR and Western blot, in which the diabetic group with treatment was lower than those without treatment (P<0.01), but all the diabetic groups were higher than the control group (P<0.01). Evans blue leakage in the diabetic treatment group was lower than those without treatment (P<0.01), but those in the control group was the lowest compared with the other two groups (P<0.01). TUNEL method showed that the apoptotic bodies of retina in the diabetic treatment group was lower than those without treatment (P<0.01), while those in the control group was the lowest compared with the other two groups (P<0.01).

CONCLUSION

Etanercept can effectively reduce the expression of Fas, TNF-α and caspase-8, as well as the retinal leakage and retinal cell apoptosis in diabetic rats.

Retinal vessel oxygen saturation and vessel diameter in healthy individuals during high-altitude exposure

PURPOSE

To assess changes of retinal vessel oxygen saturation and vessel diameter in healthy individuals during high-altitude exposure.

METHODS

Retinal oxygen saturation and vessel diameter were obtained at sea level (SL, 40 m) and high altitude (HA, 3681 m) on 17 healthy individuals from Beijing (six males, 28.06 ± 8.06 years) using Oxymap T1 and then compared with 21 residents from Yushu (10 males, 28.63 ± 6.00 years). Systemic and ocular parameters were also measured before and after high-altitude exposure. Data were presented as mean ± SD and analysed using paired and independent Student t-test with significance accepted at p < 0.05.

RESULTS

Short-term high-altitude exposure of Beijing Group significantly affected all the systemic and ocular parameters, as well as retinal oxygen saturation and vessel diameter ranging from overall quadrant to different quadrants, other than retinal venous oxygen saturation and retinal arterial diameter. However, these changes were not evident in those permanently living at HA. Pearson's correlation analysis revealed correlations between retinal oxygen saturation and systemic and ocular parameters (all p < 0.05). The multivariate linear regression analysis indicated that retinal arterial oxygen saturation was significantly associated with arterial peripheral arterial oxygen saturation (SpO₂ ) and subfoveal choroidal thickness.

CONCLUSION

Short-term exposure to HA induces retinal microcirculation disturbance and auto-regulatory response in healthy individuals, which is probably attributed to arterial SpO₂ and endothelial dysfunction under hypoxic conditions.

Effect of a maximal treadmill test on intraocular pressure and ocular perfusion pressure: The mediating role of fitness level

Objectives:

We compared the impact of a maximal treadmill test on intraocular pressure and ocular perfusion pressure between trained and untrained individuals.

Methods:

Based on the maximal aerobic capacity (relative VO2 max), 31 military helicopter pilots were divided into groups of trained (n = 16; VO2 max = 57.06 ± 1.66) and untrained (n = 15; VO2 max = 43.42 ± 1.19) individuals. Intraocular pressure and blood pressure were collected before effort, just after volitional exhaustion and after 5 and 15 min of recovery.

Results:

The maximal treadmill test induced significant changes on intraocular pressure (p < 0.001, η2 = 0.52) and ocular perfusion pressure (p < 0.001, η2 = 0.60). Intraocular pressure and ocular perfusion pressure increased just after volitional exhaustion (effect size = 0.88 and 1.59, respectively), and these values returned to baseline levels after 5 (effect size = 0.87 and 1.26, respectively) and 15 (effect size = 1.23 and 1.91, respectively) min of recovery. The untrained group exhibited higher intraocular pressure and ocular perfusion pressure values in comparison with the trained group just after volitional exhaustion (effect size = 1.43 and 0.11 for intraocular pressure and effect size = 2.81 and 0.96 for ocular perfusion pressure). Five minutes of recovery was insufficient to reach baseline intraocular pressure and ocular perfusion pressure values only for the untrained group (effect size = 0.91 and 0.72, respectively).

Conclusion:

Our findings reveal that fitness level modulates the intraocular pressure and ocular perfusion pressure responses to a maximal treadmill test, being high fitness levels desirable in order to attenuate the impact of maximal efforts on these indices. These outcomes may be of clinical relevance for the management of glaucoma patients or those at risk, although future studies are needed to test these results in a clinical population.

Retinal oxygen saturation as a non-invasive estimate for mixed venous oxygen saturation and cardiac output

PURPOSE

To investigate the correlation between retinal vessel oxygen saturation and mixed venous oxygen saturation (SvO_2-mixed ) and cardiac output (CO).

METHODS

Retinal arterial (SaO_2-retinal ) and venous (SvO_2-retinal ) oxygen saturation were measured non-invasively with dual-wavelength retinal oximetry in subjects receiving invasive measurements of SvO_2-mixed and CO through right heart catheterization. Correlations were analysed using Spearman's rank correlation coefficients and linear regression models.

RESULTS

Fourteen patients (median age 62.7 years, range: 21-77) were included in the analysis. When adjusted for age, SvO_2-retinal showed a positive correlation with SvO_2-mixed (β = 0.80, p = 0.003). Retinal arteriovenous oxygen saturation difference was significantly correlated with the inverse of CO (Spearman's ρ = 0.59, p = 0.026).

CONCLUSION

This pilot study provides proof of concept for the use of retinal oximetry as a non-invasive tool to assess systemic cardiovascular function.

Acute and chronic effects of soccer game on the retinal vessel diameters in middle-aged adults

BACKGROUND

Although changes in retinal vessel diameter is a new biomarker for the evaluation of cardiovascular risk factors, limited information is available regarding the effects of endurance exercises on retinal microcirculation. Thus, we aimed to evaluate both chronic and acute effects of soccer game on the diameters of retinal vessels in middle-aged players.

METHODS

Retinal vessel diameters were measured in 12 middle-aged amateur players (44.4±7.0 years of age) with more than four years of soccer playing experience and 12 age-matched sedentary adults (49.7±7.1 years of age). In soccer players, diameters were also measured immediately after the soccer game. Cardiovascular risk profiles (anthropometry and body composition and blood pressure [BP]) and physical activity levels were also measured.

RESULTS

Soccer players had wider retinal vessels than controls (P<0.05), resulting in greater arteriolar-to-venular diameter ratio (AVR) (P<0.05). Greater sports-related physical activity, lower body mass index (BMI) and fat mass were observed for soccer players compared to the controls (P<0.05), whereas BP did not differ. Physical activity level correlated positively with temporal retinal arteriolar (TRA) diameter and with AVR (P<0.05), whereas TRA diameter correlated negatively with BMI and fat mass (P<0.05). A significant correlation between temporal retinal venule (TRV) diameter and TRA diameter (P<0.05) was observed. The acute soccer game increased BP (P<0.05) and induced TRV dilatation (P<0.05).

CONCLUSIONS

In middle-aged amateur soccer players, improvement of the retinal microcirculation was observed. Cardiovascular risk factors and physical inactivity were associated with adverse retinal microvascular alterations. In terms of acute effects, soccer play causes venular, but not arteriolar dilatation for middle-aged adults.