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AFRICA
Cardiovascular Journal of Africa • ABSTRACTS – SA HEART
®
CONGRESS 2019
S44
Low brain-derived-neurotrophic-factor reflects attenuated retinal vascular function and increased stroke risk: The SABPA study
Annemarie Wentzel*, Leone Malan* Roland von Känel*,
#
, Wayne Smith*,
†
, Roelof van Wyk
‡
and Nicolaas Malan*
*Hypertension in Africa Research Team HART, North-West University, Potchefstroom, South Africa.
#
Department of Consultation-Liaison Psychiatry and
Psychosomatic Medicine, University Hospital Zurich, University of Zurich, Zurich, Switzerland.
†
South African Medical Research Council, Unit for Hypertension
and Cardiovascular Disease, North-West University, Potchefstroom, South Africa.
‡
Surgical Ophthalmologist, Potchefstroom, South Africa
Introduction:
Assessment of retinal vessel function provides an automated approach to non-invasively assess the condition of the cerebral microvasculature
and susceptibility for stroke. Brain-derived neurotrophic factor (BDNF) may constitute a potential link between cerebral and retinal blood flow, specifically
alterations in local perfusion that occur in response to changes in neuronal activity, termed neurovascular coupling. We investigated associations between
retinal vessel function during flicker-light-induced-provocation (FLIP) and systemic BDNF levels.
Methods:
A bi-ethnic cohort of the Sympathetic activity and Ambulatory Blood Pressure in Africans (SABPA) study (n=280), aged 23 - 68 years, was
investigated. Prospective observations for serum BDNF and 24-hour blood pressure (BP) were obtained. During the 3-year follow-up measurements, retinal
vessel calibres were quantified from mydriatic eye fundus images and dynamic retinal vessel responses were determined during FLIP. The University of
California stroke-risk score was applied to assess subclinical 10-year stroke risk.
Results:
Lower BDNF levels (1.3 - 1.8ng/mL) were observed in the total cohort compared to reference ranges (6.97 - 42.6ng/mL). Compared to Caucasians,
Africans showed higher BP and BDNF levels and a greater prevalence of retinopathy (73% vs. 40%). In Africans, arteriolar maximal dilation and maximal
constriction was positively associated with BDNF (p=0.051 and p=0.029). Arteriolar diameter after flicker cessation was positively associated with BDNF
(p<0.001). Arteriolar constriction time was inversely associated with BDNF in Africans (p=0.035), yet positively in the Caucasians (p=0.024). The BDNF cut-point
of 1.5ng/mL was associated with an increased 10-year stroke risk with an odds ratio of 1.56 (95% CI, 0.94; 2.06, p=0.011), irrespective of race or gender.
Conclusion:
The observed attenuation in retinal vessel responses and increased stroke risk may indicate the diminished neuro-protective effect of BDNF
in the SABPA cohort. BDNF may possibly act directly on vascular-smooth-muscle-cells to alter arteriolar vascular resistance and contribute to disturbed
neurovascular coupling and increased stroke risk within the SABPA cohort.
Attenuated retinal vascular dynamics in excessive alcohol consumers: The SABPA study
Annemarie Wentzel*, L Malan* Roland von Känel*,
#
and Nicolaas Malan*
*Hypertension in Africa Research Team HART, North-West University, Potchefstroom, South Africa.
#
Department of Consultation-Liaison Psychiatry and
Psychosomatic Medicine, University Hospital Zurich, University of Zurich, Zurich, Switzerland
Introduction:
Excessive alcohol consumption contributes to microvascular structural and functional modifications. Additionally, in the brain-heart axis,
it influences glial cell function and possibly neurovascular coupling. Due to ethnic and gender disparities in the metabolism and tolerance of alcohol, the
modifications and mechanisms involved may differ. Associations were assessed in excessive alcohol consumers between retinal vasculature and glial markers
[brain-derived neurotrophic factor (BDNF), glial-cell-derived neurotrophic factor (GDNF) and calcium-binding-protein-B (S100B)].
Methods:
A bi-ethnic target population study, the Sympathetic activity and Ambulatory Blood Pressure in Africans (SABPA), was used (n=319). Alcohol
consumption was determined according to previously defined ethnic-specific gamma-glutamyl-transferase (GGT) cut-points, where GGT >19.5U/L and GGT
>55U/L indicated excessive alcohol consumption in Caucasians and Africans, respectively. We assessed ambulatory blood pressure and applied the University
of California 10-year stroke-risk score. Fasting serum BDNF, GDNF and S100B levels were obtained. Retinal vessel calibres were quantified from mydriatic eye
fundus images and dynamic retinal vessel responses were determined during flicker-light-induced-provocation (FLIP).
Results:
Excessive alcohol consumers had higher 24-hour hypertension prevalence (p<0.001), 10-year stroke probability, wider retinal venules and poorer
retinal arteriolar constriction and venular dilation (p<0.001). Lower levels of BDNF, GDNF and S100B (p<0.05) were observed in the excessive alcohol
consumers. In African excessive alcohol consumers, wider retinal venules associated with increased levels of S100B (p=0.019), whilst attenuated retinal
venular dilation inversely associated with S100B (p=0.010). Retinal arteriolar diameter after-FLIP inversely associated with both BDNF (p=0.013) and glycated-
haemoglobin (p=0.048) in the Caucasian excessive alcohol consumers alone.
Conclusion:
The wider venules observed in excessive alcohol consumers is a recognised stroke risk marker. The neurotoxic effect of excessive alcohol
consumption may possibly facilitate apoptosis and attenuate retinal vascular dynamics in the African group. Yet, in the Caucasian group, this effect may
trigger a compensatory, detrimental metabolic response in an attempt to sustain glial health.
Cardiovascular risk profile and acutemental stress alpha or beta-adrenergic responses in a bi-ethnic population: The SABPA study
Annemarie Wentzel*, Leone Malan*, Roland von Känel
#
, Mark Hamer
†
and Nicolaas Malan*
*Hypertension in Africa Research Team HART, North-West University, Potchefstroom, South Africa.
#
Department of Consultation-Liaison Psychiatry
and Psychosomatic Medicine, University Hospital Zurich, Zurich, Switzerland.
†
School Sport, Exercise and Health Sciences, Loughborough University,
Loughborough, United Kingdom
Introduction:
Acute laboratory stressors elicit adrenergic responses identical to that of everyday stress. Whether specific cardio-metabolic and CVD-risk can,
however, be attributed to a predominant alpha or beta-adrenergic response, elicited during acute mental stress, remains to be determined. We aimed to
characterise the specific cardio-metabolic risk profiles of predominant alpha or beta-adrenergic responses, irrespective of age, race and/or gender.
Methods:
The Sympathetic activity and Ambulatory Blood Pressure in Africans (SABPA) study was conducted in a bi-ethnic target population (n=392),
aged 20 - 65 years. An acute mental stress task (STROOP) was administered for 1 minute whilst continuous blood-pressure and 10-lead ECG responses were
obtained. Haemodynamic reactivity profiled participants’responses as optimal alpha-adrenergic [decreases in cardiac output (CO) and arterial compliance
(Cwk)] and beta-adrenergic (increases in CO and Cwk) responses. Of the 392 participants, 48 were optimal alpha-adrenergic and 69 were optimal beta-
adrenergic responders. Fasting blood samples were analysed for cardiac stress and cardio-metabolic risk markers. The University of California stroke-risk score
was used to determine 10-year stroke-risk probability.
Results:
Alpha-adrenergic responders presented with a poorer cardio-metabolic profile, higher levels of glycated haemoglobin, insulin, greater insulin
resistance (HOMA-IR) and lower HDL-cholesterol. Age, race and gender adjusted multivariable logistic regression analyses showed that an alpha-adrenergic