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

Arginine metabolomics in mood disorders

Alterations of nitric oxide (NO) homeostasis have been described in mood disorders. However, the analytical challenges associated with the direct measurement of NO have prompted the search for alternative biomarkers of NO synthesis. We investigated the published evidence of the association between these alternative biomarkers and mood disorders (depressive disorder or bipolar disorder). Electronic databases were searched from inception to the June 30, 2023. In 20 studies, there was a trend towards significantly higher asymmetric dimethylarginine (ADMA) in mood disorders vs. controls (p = 0.072), and non-significant differences in arginine (p = 0.29), citrulline (p = 0.35), symmetric dimethylarginine (SDMA; p = 0.23), and ornithine (p = 0.42). In subgroup analyses, the SMD for ADMA was significant in bipolar disorder (p < 0.001) and European studies (p = 0.02), the SMDs for SDMA (p = 0.001) and citrulline (p = 0.038) in European studies, and the SMD for ornithine in bipolar disorder (p = 0.007), Asian (p = 0.001) and American studies (p = 0.005), and patients treated with antidepressants (p = 0.029). The abnormal concentrations of ADMA, SDMA, citrulline, and ornithine in subgroups of mood disorders, particularly bipolar disorder, warrant further research to unravel their pathophysiological role and identify novel treatments in this group (The protocol was registered in PROSPERO: CRD42023445962).

Circadian blood pressure variability and asymmetric dimethylarginine in patients with glaucoma: cross-sectional study of The LIGHT cohort

OBJECTIVE

Glaucoma is reportedly associated with asymmetric dimethylarginine (ADMA) and circadian blood pressure (BP) variability, including night-time SBP. We determined whether ADMA level is associated with night-time SBP in patients with glaucoma.

METHODS

In this cross-sectional study, we measured the serum ADMA level and ambulatory BP of 163 patients with glaucoma and 705 participants without glaucoma. Based on the tertiles of serum ADMA level, the patients were divided into three groups: low, intermediate, and high-ADMA. Night-time SBP was determined based on ambulatory BP measured every 30 min for 48 h. The nondipper BP pattern was defined as having a night-time mean SBP decline of less than 10% relative to the mean daytime SBP.

RESULTS

In the glaucoma group, the night-time SBP in the high-ADMA group was significantly higher than in the low-ADMA group (123.0 and 114.4 mmHg, respectively; P  = 0.003). Multivariable analysis adjusted for the potential confounders showed the night-time SBP, and the odds ratio for nondipper in the high-ADMA group were also significantly higher than in the low-ADMA group ( P  = 0.030 and P  = 0.021, respectively). Significant associations between continuous serum ADMA levels with night-time SBP and nondipper were also found ( P  = 0.002 and 0.006, respectively). In the control group, however, no significant associations were found between serum ADMA levels and night-time SBP and nondipper. A significant interaction effect of the serum ADMA levels and glaucoma on nondipper was found ( P  = 0.004).

CONCLUSION

Serum ADMA level was significantly associated with the disturbance of circadian BP variability in patients with glaucoma.

Phenotypic characteristics of asthma and morbidity are associated with distinct longitudinal changes in L-arginine metabolism

BACKGROUND

The L-arginine metabolome is dysregulated in asthma, though it is not understood how longitudinal changes in L-arginine metabolism differ among asthma phenotypes and relate to disease outcomes.

OBJECTIVES

To determine the longitudinal associations between phenotypic characteristics with L-arginine metabolites and their relationships with asthma morbidity.

METHODS

This is a prospective cohort study of 321 patients with asthma followed semiannually for over 18 months with assessments of plasma L-arginine metabolites, asthma control, spirometry, quality of life and exacerbations. Metabolite concentrations and ratios were transformed using the natural logarithm.

RESULTS

There were many differences in L-arginine metabolism among asthma phenotypes in the adjusted models. Increasing body mass index was associated with increased asymmetric dimethylarginine (ADMA) and depleted L-citrulline. Latinx was associated with increased metabolism via arginase, with higher L-ornithine, proline and L-ornithine/L-citrulline levels, and was found to have higher L-arginine availability compared with white race. With respect to asthma outcomes, increasing L-citrulline was associated with improved asthma control and increasing L-arginine and L-arginine/ADMA were associated with improved quality of life. Increased variability in L-arginine, L-arginine/ADMA, L-arginine/L-ornithine and L-arginine availability index over 12 months were associated with increased exacerbations, OR 4.70 (95% CI 1.35 to 16.37), OR 8.69 (95% CI 1.98 to 38.08), OR 4.17 (95% CI 1.40 to 12.41) and OR 4.95 (95% CI 1.42 to 17.16), respectively.

CONCLUSIONS

Our findings suggest that L-arginine metabolism is associated with multiple measures of asthma control and may explain, in part, the relationship between age, race/ethnicity and obesity with asthma outcomes.

Reduction of acetate synthesis, enhanced arginine export, and supply of precursors, cofactors, and energy for improved synthesis of L-arginine by Escherichia coli

L-arginine (L-Arg) is a semi-essential amino acid with many important physiological functions. However, achieving efficient manufacture of L-Arg on an industrial scale using Escherichia coli (E. coli) remains a major challenge. In previous studies, we constructed a strain of E. coli A7, which had good L-Arg production capacity. In this study, E. coli A7 was further modified, and E. coli A21 with more efficient L-Arg production capacity was obtained. Firstly, we reduced the acetate accumulation of strain A7 by weakening the poxB gene and overexpressing acs gene. Secondly, we improved the L-Arg transport efficiency of strains by overexpressing the lysE gene from Corynebacterium glutamicum (C. glutamicum). Finally, we enhanced the supplies of precursors for the synthesis of L-Arg and optimized the supplies of cofactor NADPH and energy ATP in strain. After fermentation in a 5-L bioreactor, the L-Arg titer of strain A21 was found to be 89.7 g/L. The productivity was 1.495 g/(L·h) and the glucose yield was 0.377 g/g. Our study further narrowed the titer gap between E. coli and C. glutamicum in the synthesis of L-Arg. In all recent studies on the L-Arg production by E. coli, this was the highest titer recorded. In conclusion, our study further promotes the efficient mass synthesis of L-Arg by E. coli. KEY POINTS: • The acetate accumulation of starting strain A7 was decreased. • Overexpression of gene lysE of C. glutamicum enhanced L-Arg transport in strain A10. • Enhance the supplies of precursors for the synthesis of L-Arg and optimize the supplies of cofactor NADPH and energy ATP. Finally, Strain A21 was detected to have an L-Arg titer of 89.7 g/L in a 5-L bioreactor.

Metabolic engineering of Escherichia coli for efficient production of l-arginine

As a semi-essential amino acid, l-arginine (l-Arg) plays an important role in food, health care, and medical treatment. At present, the main method of producing l-Arg is the use of microbial fermentation. Therefore, the selection and breeding of high-efficiency microbial strains is the top priority. To continuously improve the l-Arg production performance of the strains, a series of metabolic engineering strategies have been tried to transform the strains. The production of l-Arg by metabolically engineered Corynebacterium glutamicum (C. glutamicum) reached a relatively high level. Escherichia coli (E. coli), as a strain with great potential for l-Arg production, also has a large number of research strategies aimed at screening effective E. coli for producing l-Arg. E. coli also has a number of advantages over C. glutamicum in producing l-Arg. Therefore, it is of great significance to screen out excellent and stable E. coli to produce l-Arg. Here, based on recent research results, we review the metabolic pathways of l-Arg production in E. coli, the research progress of l-Arg production in E. coli, and various regulatory strategies implemented in E. coli.

The association of PAI-1 with 24 h blood pressure in young healthy adults is influenced by smoking and alcohol use: The African-PREDICT study

BACKGROUND AND AIMS

The association between plasminogen activator inhibitor-1 (PAI-1) and blood pressure is well established, but it is debatable whether raised PAI-1 levels precede or result from raised blood pressure. Furthermore, it is unclear whether this association already exists in the absence of overt hypertension and to what degree it is influenced by health behaviours. Our aim was to investigate the association of 24 h blood pressure with PAI-1 activity (PAI-1_act) in a young, healthy cohort, and to assess the influence of alcohol consumption and smoking on these associations.

METHODS AND RESULTS

Healthy black and white men and women (aged 20-30 years, n = 1156) were cross-sectionally analysed. Statistical analysis was performed first split by ethnicity and sex and then by alcohol consumption and smoking. Regression analyses adjusted for age revealed positive associations of 24 h blood pressure with PAI-1_act in most groups (p < 0.05). In multivariate-adjusted analyses, significance was lost in all groups except black men, who also had higher monocyte chemoattractant protein-1 (MCP-1) and von Willebrand factor antigen (vWF_ag) compared to white men (both p < 0.001). Analyses in black men, split by self-reported alcohol use and smoking, revealed 24 h blood pressure-PAI-1_act associations only in alcohol users (24 h SBP [B = 4.22, p < 0.001], DBP [B = 2.04, p = 0.015] and PP [B = 2.18, p = 0.013]) and smokers (24 h SBP [B = 6.10, p < 0.001] and PP [B = 4.33, p = 0.001]).

CONCLUSION

Our findings support a positive association between 24 h blood pressure and PAI-1, particularly in individuals with higher MCP-1 and vWF_ag levels. Furthermore, smoking and alcohol consumption play an important role in modifying the association between blood pressure and PAI-1.

Leptin and the Retinal Microvasculature in Young Black and White Adults: The African-PREDICT Study

BACKGROUND

Leptin is a vasoactive peptide that has been linked to diseases associated with macrovascular deterioration. What is still uncertain is its involvement in the microvasculature. Since microvascular changes are presumed to precede macrovascular deterioration, we examined whether measures of the retinal microvasculature are associated with leptin in healthy, young Black and White individuals.

METHOD

We included 283 Black and 289 White men and women (aged 20-30 years). We determined serum leptin, calculated central retinal artery and vein equivalents and arterio-venous ratio. We also measured retinal vessel responses to light flicker provocation.

RESULTS

Black men were leaner and had lower leptin than White men, whereas Black women had increased adiposity and leptin compared to White women (all p<0.001). Black groups had narrower retinal arteries, and greater maximum arteriolar and venular dilations in response to light flicker than the White groups (p<0.001). Arterio-venous ratio associated negatively with leptin (all p≤0.044) in all groups (except Black women), but was lost upon adjustment for body mass index and other covariates. We found an inverse association between maximal venular dilation and leptin only in Black men in single and multiple regression analyses (Std β= -0.22; R²=0.05; p=0.035). No associations were found between other retinal measures with leptin in the other groups.

CONCLUSION

We found an independent, negative association between retinal vein dilation with leptin in healthy, young Black men, suggesting a potential detrimental role for leptin in regulating microvascular responses in a population group known to be at greater risk of cardiovascular disease development.

An Ethnic Comparison of Arginine Dimethylation and Cardiometabolic Factors in Healthy Black and White Youth: The ASOS and African-PREDICT Studies

Proteinic arginine dimethylation (PADiMe) is a major post-translational modification. Proteolysis of asymmetric and symmetric PADiMe products releases asymmetric dimethylarginine (ADMA) and symmetric dimethylarginine (SDMA), respectively, two endogenous atherogenic substances. SDMA, ADMA, and its major metabolite dimethylamine (DMA) are eliminated by the kidney. The urinary concentrations of DMA+ADMA, SDMA, and DMA+ADMA+SDMA are useful measures of the whole-body asymmetric and symmetric PADiMe, respectively. Urinary (DMA+ADMA)/SDMA is an index of the asymmetric to symmetric PADiMe balance. In two bi-ethnic studies, the ASOS (39 black boys, 41 white boys) and the African-PREDICT (292 black young men, 281 white young men) studies, we investigated whether ethnicity is a major determinant of PADiMe, and whether PADiMe is associated with blood pressure and ethnicity-dependent growth and inflammatory factors, including HDL. DMA, ADMA, and SDMA were measured in spot urine samples by gas chromatography-mass spectrometry, and their excretion was corrected for creatinine excretion. In black boys, creatinine-corrected DMA, DMA+ADMA, and DMA+ADMA+SDMA concentrations were lower by 11.7%, 9.5%, and 7.6% (all p < 0.05), respectively, compared to the white boys, and 3.4%, 2.0%, and 1.8% lower (all p < 0.05), respectively, in black compared to white men. (DMA+ADMA)/SDMA did not differ between black boys and black men, but was higher in white boys compared to white men. ADMA did not differ between black and white boys, or between black and white men. Creatinine-corrected SDMA excretion was lower in black boys compared to white boys (by 8%) and to white men (by 3.1%). None of the PADiMe indices were associated with blood pressure in either study. IGF-binding protein 3 correlated inversely with all PADiMe indices in the black men only. Our study showed that asymmetric proteinic arginine dimethylation is higher in white boys than in black boys, and that this difference disappears in adulthood. ADMA metabolism and SDMA excretion were lower in the black subjects compared to the white subjects, suggesting ethnicity-dependent hepatic and renal elimination of ADMA and SDMA in the childhood. The results of our study may have clinical relevance beyond atherosclerosis, such as in growth and inflammation, which have not been sufficiently addressed thus far.

Arginine Derivatives in Cerebrovascular Diseases: Mechanisms and Clinical Implications

The amino acid L-arginine serves as substrate for the nitric oxide synthase which is crucial in vascular function and disease. Derivatives of arginine, such as asymmetric (ADMA) and symmetric dimethylarginine (SDMA), are regarded as markers of endothelial dysfunction and have been implicated in vascular disorders. While there is a variety of studies consolidating ADMA as biomarker of cerebrovascular risk, morbidity and mortality, SDMA is currently emerging as an interesting metabolite with distinct characteristics in ischemic stroke. In contrast to dimethylarginines, homoarginine is inversely associated with adverse events and mortality in cerebrovascular diseases and might constitute a modifiable protective risk factor. This review aims to provide an overview of the current evidence for the pathophysiological role of arginine derivatives in cerebrovascular ischemic diseases. We discuss the complex mechanisms of arginine metabolism in health and disease and its potential clinical implications in diverse aspects of ischemic stroke.

Retinal vessel caliber and caliber responses in true normotensive black and white adults: The African-PREDICT study

PURPOSE

Globally, a detrimental shift in cardiovascular disease risk factors and a higher mortality level are reported in some black populations. The retinal microvasculature provides early insight into the pathogenesis of systemic vascular diseases, but it is unclear whether retinal vessel calibers and acute retinal vessel functional responses differ between young healthy black and white adults.

METHODS

We included 112 black and 143 white healthy normotensive adults (20-30 years). Retinal vessel calibers (central retinal artery and vein equivalent (CRAE and CRVE)) were calculated from retinal images and vessel caliber responses to flicker light induced provocation (FLIP) were determined. Additionally, ambulatory blood pressure (BP), anthropometry and blood samples were collected.

RESULTS

The groups displayed similar 24 h BP profiles and anthropometry (all p > .24). Black participants demonstrated a smaller CRAE (158 ± 11 vs. 164 ± 11 MU, p < .001) compared to the white group, whereas CRVE was similar (p = .57). In response to FLIP, artery maximal dilation was greater in the black vs. white group (5.6 ± 2.1 vs. 3.3 ± 1.8%; p < .001).

CONCLUSIONS

Already at a young age, healthy black adults showed narrower retinal arteries relative to the white population. Follow-up studies are underway to show if this will be related to increased risk for hypertension development. The reason for the larger vessel dilation responses to FLIP in the black population is unclear and warrants further investigation.

Asymmetric dimethylarginine and symmetric dimethylarginine prospectively relates to carotid wall thickening in black men: the SABPA study

The relationship of both asymmetric (ADMA) and symmetric (SDMA) dimethylarginine with carotid wall thickness is inconclusive especially among black populations. We aimed to compare carotid intima media thickness (cIMT) and dimethylarginine levels in 75 black and 91 white men at baseline and after a 3-year follow-up, and to investigate associations of percentage change in cIMT with percentage change in dimethylarginine levels (ADMA and SDMA). Plasma levels of ADMA and SDMA were determined with a liquid chromatography mass spectrometry method and B-mode ultrasonography was used to determine the cIMT at baseline and follow-up. In black men, mean cIMT (p = 0.79) and ADMA levels (p = 0.67) remained the same, but SDMA levels were lower (p < 0.001) when comparing baseline and follow-up. In white men, cIMT increased (p < 0.001), but both mean ADMA and SDMA levels decreased (p < 0.001) over time. In black men, percentage change in cIMT was positively associated with percentage change in ADMA (R ² = 0.49; β = 0.46; p < 0.001) and percentage change in SDMA (R ² = 0.46; β = 0.41; p < 0.001). These associations were absent in the white men. Despite lower mean SDMA and similar ADMA and cIMT in black men, percentage change in cIMT was independently associated with percentage change in ADMA and percentage change in SDMA. These results suggest an important role for ADMA and SDMA lowering strategies to delay carotid wall thickening, especially in black populations prone to the development of cardiovascular disease.

Arginine-Nitric Oxide Metabolites and Cardiac Dysfunction in Patients With Breast Cancer

BACKGROUND

Oxidative/nitrosative stress and endothelial dysfunction are hypothesized to be central to cancer therapeutics-related cardiac dysfunction (CTRCD). However, the relationship between circulating arginine-nitric oxide (NO) metabolites and CTRCD remains unstudied.

OBJECTIVES

This study sought to examine the relationship between arginine-NO metabolites and CTRCD in a prospective cohort of 170 breast cancer patients treated with doxorubicin with or without trastuzumab.

METHODS

Plasma levels of arginine, citrulline, ornithine, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine (SDMA), and N-monomethylarginine (MMA) were quantified at baseline, 1 month, and 2 months after doxorubicin initiation. Determinants of baseline biomarker levels were identified using multivariable linear regression, and Cox regression defined the association between baseline levels and 1- or 2-month biomarker changes and CTRCD rate in 139 participants with quantitated echocardiograms at all time points.

RESULTS

Age, hypertension, body mass index, and African-American race were independently associated with ≥1 of baseline citrulline, ADMA, SDMA, and MMA levels. Decreases in arginine and citrulline and increases in ADMA were observed at 1 and 2 months (all p < 0.05). Overall, 32 participants experienced CTRCD over a maximum follow-up of 5.4 years. Hazard ratios for ADMA and MMA at 2 months were 3.33 (95% confidence interval [CI]: 1.12 to 9.96) and 2.70 (95% CI: 1.35 to 5.41), respectively, and 0.78 (95% CI: 0.64 to 0.97) for arginine at 1 month.

CONCLUSIONS

In breast cancer patients undergoing doxorubicin therapy, early alterations in arginine-NO metabolite levels occurred, and early biomarker changes were associated with a greater CTRCD rate. Our findings highlight the potential mechanistic and translational relevance of this pathway to CTRCD.

Improvement of the ammonia assimilation for enhancing L-arginine production of Corynebacterium crenatum

There are four nitrogen atoms in L-arginine molecule and the nitrogen content is 32.1%. By now, metabolic engineering for L-arginine production strain improvement was focused on carbon flux optimization. In previous work, we obtained an L-arginine-producing Corynebacterium crenatum SDNN403 (ARG) through screening and mutation breeding. In this paper, a strain engineering strategy focusing on nitrogen supply and ammonium assimilation for L-arginine production was performed. Firstly, the effects of nitrogen atom donor (L-glutamate, L-glutamine and L-aspartate) addition on L-arginine production of ARG were studied, and the addition of L-glutamine and L-aspartate was beneficial for L-arginine production. Then, the glutamine synthetase gene glnA and aspartase gene aspA from E. coli were overexpressed in ARG for increasing the L-glutamine and L-aspartate synthesis, and the L-arginine production was effectively increased. In addition, the L-glutamate supply re-emerged as a limiting factor for L-arginine biosynthesis. Finally, the glutamate dehydrogenase gene gdh was co-overexpressed for further enhancement of L-arginine production. The final strain could produce 53.2 g l^-1 of L-arginine, which was increased by 41.5% compared to ARG in fed-batch fermentation.

Cardiovascular function is not associated with creatine kinase activity in a black African population: The SABPA study

Background

Higher creatine kinase (CK) activity is associated with the development of cardiovascular disease in black African populations. We compared CK activity and investigated associations of blood pressure with CK activity in black and white men as well as black and white women.

Methods

Ambulatory blood pressure, total peripheral resistance and pulse wave velocity of 197 black and 208 white participants were determined and serum CK activity was measured.

Results

Blood pressure and pulse wave velocity were higher in black men and women (all p < 0.001) when compared to their white counterparts. CK activity only varied between black and white women (75.9 U/l vs 62.8 U/l, p = 0.009), even after adjusting for age, body mass index and physical activity. Despite the worse cardiovascular profile of black men and women, and the higher CK activity in the black women, we were unable to link blood pressure, pulse wave velocity or total peripheral resistance with CK activity, in the black African population. In white men, total peripheral resistance was associated with CK activity (R² = 0.32; β = 0.25; p = 0.009), whereas systolic blood pressure (R² = 0.46; β = 0.17; p = 0.03) and pulse pressure (R² = 0.31; β = 0.21; p = 0.01) were associated with CK activity in white women.

Conclusions

The lack of associations in the black African population suggests that the link between a worse cardiovascular profile and CK activity may be overshadowed by other contributing factors. Whereas, the established link between cardiovascular function and CK activity in the white groups may be the result of enhanced smooth muscle cell contractility and/or attenuated nitric oxide synthesis capacity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0315-2) contains supplementary material, which is available to authorized users.