Ethnicity-specific differences in L-arginine status in South African men

Abstract

The aetiology for an increasing incidence of hypertensive cardiovascular disease amongst Africans in southern Africa is unclear. Hypertension may be induced by inadequate release of L-arginine-derived nitric oxide impairing vascular tone regulation. In addition, asymmetric dimethylarginine (ADMA) is associated with cardiovascular disease. We compared profiles of L-arginine in African and Caucasian men of similar age with cardiovascular risk factors. We studied 163 Caucasian and 132 African men, respectively, (20 to 70 years) measuring serum L-arginine, ADMA, creatinine, urea, symmetric dimethylarginine (SDMA) and blood pressure. L-arginine levels were significantly lower, whereas blood pressure and pulse wave velocity were significantly higher in African men. Simple linear regression showed ADMA more strongly associated with L-arginine in Caucasians (r ¼ 0.59 vs 0.19), whereas association of SDMA with L-arginine was significant only in Caucasians (r ¼ 0.43 vs 0.001). The stronger association of L-arginine with ADMA in Caucasian men was confirmed by multiple regression analysis (b ¼ 0.46 vs 0.25). Our findings show that the relationship of cardiovascular risk factors with serum L-arginine and some of its catabolites is different in African and Caucasian men and that this may be associated with a relatively higher prevalence of hypertension in African men.

Nitric oxide synthesis capacity, ambulatory blood pressure and end organ damage in a black and white population: the SABPA study

“…The more adverse cardiovascular profile confirms various previous studies indicating the prevalence of cardiovascular disease to be higher in black populations living in South Africa (Van Rooyen et al 2000;LloydSherlock et al 2014;Sliwa et al 2008). However, the more favourable NO synthesis capacity indicated in the black men, challenge our previous findings since we indicated ADMA and SDMA levels to be similar (Schutte et al 2010) and l-arginine levels to be lower (Glyn et al 2012) in black men when compared to white men. When comparing women, previous findings indicated that white women had higher dimethylarginine (ADMA and SDMA) levels than black women (Schutte et al 2010), while in the current study we indicated ADMA levels to be similar and SDMA levels to be higher in white women.…”

“…The above-mentioned discrepancies between previous studies and the present study may be explained by factors such as diet, blood pressure and socioeconomic status. Since l-arginine is a conditionally essential amino acid (Wu and Morris 1998) differences in dietary protein intake may have contributed to the observed lower l-arginine levels in black men when compared to white men (Glyn et al 2012), especially when considering that the black participants of the South African study regarding the role of Sex, Age and Ethnicity on Insulin sensitivity and Cardiovascular Table 3 Forward stepwise multiple regressions with estimated glomerular filtration rate as dependent variable Variables included in the models were: age, waist circumference, ambulatory systolic blood pressure, γ glutamyl transferase, cotinine, C-reactive protein, glycated haemoglobin, triglycerides, total energy expenditure and anti-hypertensive medication with either L-citrulline, L-homoarginine, asymmetric dimethylarginine, symmetric dimethylarginine or dimethylarginine in the model as main independent variables function (SAfrEIC study) were of a lower socioeconomic status when compared to the white participants. However in the present study we obtained a more homogenous socioeconomic group by including only school teachers.…”

“…We have previously indicated that l-arginine levels are lower in black men when compared to white men (Glyn et al 2012). Controversy exists in the literature regarding ADMA levels in black men, with one study performed in the United Kingdom, indicating higher ADMA levels in young black men when compared to white men (Melikian et al 2007), while we previously reported similar ADMA and SDMA levels in black and white men from South Africa (Schutte et al 2010).…”

Exploring the Link Between Cardiovascular Reactivity and End-Organ Damage in African and Caucasian Men: The SABPA Study

“…2 It has been found that the pulse wave velocity (PWV) of muscular arteries is higher in young Africans compared with Caucasians and that there are increased levels of vascular resistance during stress. 6,[13][14][15] Increased reactions to acute psychological stress challenges are implicated in cardiovascular disease: inter alia hypertension, carotid atherosclerosis, and cardiac hypertrophy. [16][17][18][19][20][21][22] It was reported that vascular resistance reactivity in Africans was positively associated with higher α1-adrenergic receptor density and therefore a higher serum calcium sensitivity.…”

L-Arginine Levels among Hypertensive Patients in Sokoto, North Western Nigeria

“…Our finding of an ethnic variation in the level of L-arginine among hypertensive subjects of African descent in Sokoto is consistent with previous report which indicated that the L-arginine is affected by psychosocial distress with higher susceptibility in Black Africans. This interaction may contribute to the higher cardiovascular disease risk in Black Africans [37]. It is becoming particularly clear that there is a 2-to 3-fold racial difference in certain cardiovascular diseases (pre-eclampsia) associated with dysfunctional nitric oxide-mediated vasodilation [38].…”