Association between serum uric acid levels and coronary flow reserve in hypertensive patients without concomitant risk factors

Is Low Serum Klotho Level Associated with Alterations in Coronary Flow Reserve?

BACKGROUND

The Klotho gene, described as an "aging suppressor" gene, encodes a single-pass transmembrane protein. The extracellular part of Klotho is cleaved and released into the circulation where it may function as a vasculoprotective hormone. Coronary flow reserve (CFR) is accepted as a marker of coronary microvascular dysfunction when epicardial coronary stenosis is absent. There are no data regarding the relationship between serum Klotho levels and disorders in coronary microcirculation in healthy adults. We aimed to investigate the association between serum Klotho levels and alterations in coronary microcirculation in healthy adults using echocardiographic measurements of CFR.

METHODS

Thirty-four healthy volunteers (median age: 34 [27-39], 14 males) were enrolled in this study. The study population was divided into two subgroups according to the median value of serum Klotho levels: a high Klotho (HK) group (n = 17, median age: 34 [30-38]; 6 males) and a low Klotho (LK) group (n = 17, median age: 32 [26-39]; 8 males). The analysis of coronary flow velocities was performed by transthoracic Doppler echocardiography.

RESULTS

Hyperemic diastolic peak flow velocities and CFR were significantly higher in the HK group than in the LK group (70 [66-92] versus 61 [47-66], P = 0.003 and 3.0 [2.6-3.8] versus 2.2 [1.7-2.8], respectively, P = 0.001). Serum Klotho levels were positively correlated with CFR (P < 0.001).

CONCLUSION

Serum Klotho levels correlate with CFR in a healthy population. Low serum Klotho levels may potentially identify patients with impaired CFR.

The relationship between asymptomatic organ damage, and serum soluble tumor necrosis factor-like weak inducer of apoptosis (sTWEAK) and Interleukin-17A (IL-17A) levels in non-diabetic hypertensive patients

Background

This study aimed to measure the serum soluble tumor necrosis factor-like weak inducer of apoptosis (sTWEAK) and interleukin-17A (IL-17A) levels in hypertensive patients with/without asymptomatic organ damage (AOD), as well as to determine the relationship between the serum sTWEAK and IL17-A levels, and carotid intima media thickness (CIMT), proteinuria, retinopathy, and the left ventricle mass index (LVMI).

Methods

The study included 159 patients diagnosed with and followed-up for primary hypertension (HT); 79 of the patients had AOD (61 female and 18 male) and 80 did not (52 female and 28 male). sTWEAK and IL-17A levels were measured in all patients.

Results

The sTWEAK level was significantly lower in the patients with AOD than in those without AOD (858.4 pg/mL vs. 1151.58 pg/mL, P = 0.001). The sTWEAK level was negatively correlated with the mean microalbuminuria level and LVMI. The median IL-17A level was significantly higher in the patients with AOD than in those without AOD (2.34 pg/mL vs. 1.80 pg/mL, P = 0.001). There was a positive correlation between mean IL-17A level, and mean microalbuminuria level, CIMT, and LVMI. Multivariate logistic regression analysis showed that patient age, sTWEAK level, and mean 24-h systolic blood pressure were predictors of AOD.

Conclusions

The sTWEAK level was lower and IL-17A level was higher in the patients with AOD. It remains unknown if sTWEAK and IL-17A play a role in the pathophysiology of AOD. Prospective observational studies are needed to determine the precise role of sTWEAK and IL-17A in the development of target organ damage.

The effects of hyperuricaemia on flow-mediated and nitroglycerin-mediated dilatation in high-risk patients

BACKGROUND AND AIMS

Uric acid is emerging as one of the newer risk markers to consider in the cardiovascular risk assessment because it is demonstrated to be associated with adverse cardiovascular outcomes, particularly in high cardiovascular risk patients. One of the proposed mechanisms involving hyperuricaemia is the development of vascular damage. The aim of this study is to examine the role of hyperuricaemia on vascular function in patients with high cardiovascular risk.

METHODS AND RESULTS

We examined the clinical significance of hyperuricaemia in relation to vasomotor response of the brachial artery by using high-resolution ultrasound in 304 subjects with coronary artery disease and/or diabetes. Nitroglycerin-mediated dilatation (NMD) was significantly lower in the hyperuricaemic group compared with the normouricaemic group (12.8 ± 6.9% vs. 16.2 ± 7.7%, p < 0.001), but no significant difference was observed in flow-mediated dilatation (FMD) between the two groups [3.78 (95% CR: 1.5-9.9) vs. 3.88 (95% CR: -2.6 to 9.9), p = 0.78]. Multivariate analysis demonstrated that smoking was the strongest predictor of FMD (b = -0.81, p = 0.02); and that smoking (b = -2.62, p = 0.003), SBP (b = -0.11, p = 0.001), hyperuricaemia (b = -2.11, p = 0.02) and use of nitrates (b = -3.30, p = 0.001) were independent predictors of NMD.

CONCLUSION

High cardiovascular risk patients with hyperuricaemia had a lower NMD than those with normouricaemia. Importantly, hyperuricaemia was independently associated with NMD after multivariable adjustments. To further understand the pathophysiological mechanisms involving hyperuricaemia, particularly in the context of impaired NMD, further experimental and clinical studies are needed.