Abstract
Background: L-Arginine (LA) is an amino acid, which when combined with oxygen, catalyses nitric oxide (NO), a potent vasodilator that is important for vascular regulation (1). Due to the anti-athrogenic properties of NO (2), there has been increasing interest in the potential therapeutic use of LA to treat vascular disease. Both long (3) and short-term (4) supplementation have been linked to improvements in vascular function in the systemic circulation. However, less is known about its influence on the cerebral vasculature.
Methods: Eight healthy males (age: 21 ± 1 years; body mass index: 24.3 ± 3.4 kg.m2) participated in this single-blinded randomised placebo-controlled trial. Middle cerebral artery velocity (MCAv; transcranial Doppler ultrasound), mean arterial pressure (MAP; photoplethsmography) and end-tidal carbon dioxide (CO2; capnography) were continuously recorded throughout each testing session, which was preceded by either a 3-day oral supplementation of LA (x7 500mg capsules per day) or placebo powder (flour). Cerebrovascular resistance (CVR) and cerebrovascular conductance (CVC) were calculated as MAP/MCAv and MCAv/MAP respectively, following 5 minutes seated rest. Cerebrovascular reactivity to CO2 was assessed in response to 3 minutes of breathing 5% CO2 (balanced air; CVRCO2HYPER) and following 3 minutes of controlled hyperventilation (15 breaths per minute; CVRCO2HYPO). Cerebrovascular range was calculated as CVRCO2HYPER + CVRCO2HYPO. A 7-day "washout" period was followed between trials. Exhaled nitric oxide (ozone-based chemiluminescence) was measured on the morning of each visit. Following confirmation of distribution of normality (Shapiro-W-Wilk Tests), data were analysed using paired samples t-tests. Significance was established at P < 0.05 and data are expressed as mean ± SD.
Results: Supplementation with LA elevated exhaled NO (Figure 1; P < 0.05). However, this did not confer any changes in cerebrovascular function (Table 1).
Conclusion: These findings indicate that short-term oral supplementation of LA does not impact cerebrovascular function in healthy young adults. Whether LA supplementation influences cerebrovascular function in clinically relevant populations remains to be fully elucidated.
Methods: Eight healthy males (age: 21 ± 1 years; body mass index: 24.3 ± 3.4 kg.m2) participated in this single-blinded randomised placebo-controlled trial. Middle cerebral artery velocity (MCAv; transcranial Doppler ultrasound), mean arterial pressure (MAP; photoplethsmography) and end-tidal carbon dioxide (CO2; capnography) were continuously recorded throughout each testing session, which was preceded by either a 3-day oral supplementation of LA (x7 500mg capsules per day) or placebo powder (flour). Cerebrovascular resistance (CVR) and cerebrovascular conductance (CVC) were calculated as MAP/MCAv and MCAv/MAP respectively, following 5 minutes seated rest. Cerebrovascular reactivity to CO2 was assessed in response to 3 minutes of breathing 5% CO2 (balanced air; CVRCO2HYPER) and following 3 minutes of controlled hyperventilation (15 breaths per minute; CVRCO2HYPO). Cerebrovascular range was calculated as CVRCO2HYPER + CVRCO2HYPO. A 7-day "washout" period was followed between trials. Exhaled nitric oxide (ozone-based chemiluminescence) was measured on the morning of each visit. Following confirmation of distribution of normality (Shapiro-W-Wilk Tests), data were analysed using paired samples t-tests. Significance was established at P < 0.05 and data are expressed as mean ± SD.
Results: Supplementation with LA elevated exhaled NO (Figure 1; P < 0.05). However, this did not confer any changes in cerebrovascular function (Table 1).
Conclusion: These findings indicate that short-term oral supplementation of LA does not impact cerebrovascular function in healthy young adults. Whether LA supplementation influences cerebrovascular function in clinically relevant populations remains to be fully elucidated.
| Original language | English |
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| Title of host publication | Proceedings of The Physiological Society |
| Publisher | The Physiological Society |
| Volume | 37 |
| Publication status | Published - 1 Jul 2016 |
| Event | Joint Meeting of the American Physiological Society and The Physiological Society - Convention Centre, Dublin, Ireland Duration: 29 Jul 2016 → 31 Jul 2016 |
Conference
| Conference | Joint Meeting of the American Physiological Society and The Physiological Society |
|---|---|
| Abbreviated title | Physiology 2016 |
| Country/Territory | Ireland |
| City | Dublin |
| Period | 29/07/16 → 31/07/16 |