Preterm Birth Is Associated with Higher Uric Acid Levels in Adolescents

Duration of Simultaneous Exposure to High-Risk and Lower-Risk Nephrotoxic Antimicrobials in the Neonatal Intensive Care Unit (NICU) and Future Adolescent Kidney Health

OBJECTIVE

To determine whether greater duration of simultaneous exposure to antimicrobials with high nephrotoxicity risk combined with lower-risk antimicrobials (simultaneous exposure) in the neonatal intensive care unit (NICU) is associated with worse later kidney health in adolescents born preterm with very low birth weight (VLBW).

STUDY DESIGN

Prospective cohort study of participants born preterm with VLBW (<1500 g) as singletons between January 1, 1992, and June 30, 1996. We defined simultaneous exposure as a high-risk antimicrobial, such as vancomycin, administered with a lower-risk antimicrobial on the same date in the NICU. Outcomes were serum creatinine, estimated glomerular filtration rate (eGFR), and first-morning urine albumin-creatinine ratio (ACR) at age 14 years. We fit multivariable linear regression models with days of simultaneous exposure and days of nonsimultaneous exposure as main effects, adjusting for gestational age, birth weight, and birth weight z-score.

RESULTS

Of the 147 out of 177 participants who had exposure data, 97% received simultaneous antimicrobials for mean duration 7.2 days (SD 5.6). No participant had eGFR <90 ml/min/1.73 m2. The mean ACR was 15.2 mg/g (SD 38.7) and 7% had albuminuria (ACR >30 mg/g). Each day of simultaneous exposure was associated only with a 1.04-mg/g higher ACR (95% CI 1.01 to 1.06).

CONCLUSIONS

Despite frequent simultaneous exposure to high-risk combined with lower-risk nephrotoxic antimicrobials in the NICU, there were no clinically relevant associations with worse kidney health identified in adolescence. Although future studies are needed, these findings may provide reassurance in a population thought to be at increased risk of chronic kidney disease.

Differences in maternal and neonatal cardiometabolic markers and placenta status by foetal sex. The GESTAFIT project

Aims:

To explore the differences in some maternal-neonatal metabolic markers and placenta status by foetal sex.

Methods:

One hundred thirty-nine Caucasian pregnant women from the GESTAFIT project and their new-borns were included in the present cross-sectional study. Serum cardiometabolic markers (i.e. lipid and glycaemic profile and uric acid) were analysed at late pregnancy and at birth. In placenta, telomeres length, proportion of deleted mitochondrial-DNA and mitochondrial-DNA density, some minerals and interleukin 8, epidermal growth factor, fibroblast growth factor-2 and vascular endothelial growth factor were measured. The study was run between November 2015 and April 2018.

Results:

Mothers carrying a male showed higher serum triglycerides than mothers carrying a female at late pregnancy (p < .05). Serum total and low-density lipoprotein cholesterol were greater in males’ umbilical cord blood artery compared to females’ new-borns (both, p < .05). Mothers of males and male new-borns presented higher uric acid than mothers of females and female new-borns at birth (p < .05). Female’s placentas presented greater placental-newborn weight ratio, manganese content and fibroblast growth factor-2 (all, p ⩽ .05), and evidence of statistical significance in telomeres length, which were 17% longer (p = .076).

Conclusion:

Our findings show weak differences in some cardiometabolic and placental status markers by foetal sex. Notwithstanding, we observed a slightly more proatherogenic profile in both, mothers carrying males’ foetuses and male new-borns. We also found lower serum uric acid and better placenta status in mothers carrying a female. These findings indicate that foetal sex might need to be considered for a more personalized follow-up of pregnancies.

The Long-Term Effect of Preterm Birth on Renal Function: A Meta-Analysis

The preterm-born adult population is ever increasing following improved survival rates of premature births. We conducted a meta-analysis to investigate long-term effects of preterm birth on renal function in preterm-born survivors. We searched PubMed and EMBASE to identify studies that compared renal function in preterm-born survivors and full-term-born controls, published until 2 February 2019. A random effects model with standardized mean difference (SMD) was used for meta-analyses. Heterogeneity of the studies was evaluated using Higgin’s I² statistics. Risk of bias was assessed using the Newcastle–Ottawa quality assessment scale. Of a total of 24,388 articles screened, 27 articles were finally included. Compared to full-term-born controls, glomerular filtration rate and effective renal plasma flow were significantly decreased in preterm survivors (SMD −0.54, 95% confidence interval (CI), −0.85 to −0.22, p = 0.0008; SMD −0.39, 95% CI, −0.74 to −0.04, p = 0.03, respectively). Length and volume of the kidneys were significantly decreased in the preterm group compared to the full-term controls (SMD −0.73, 95% CI, −1.04 to −0.41, p < 0.001; SMD −0.82, 95% CI, −1.05 to −0.60, p < 0.001, respectively). However, serum levels of blood urea nitrogen, creatinine, and cystatin C showed no significant difference. The urine microalbumin to creatinine ratio was significantly increased in the preterm group. Both systolic and diastolic blood pressures were also significantly elevated in the preterm group, although the plasma renin level did not differ. This meta-analysis demonstrates that preterm-born survivors may be subject to decreased glomerular filtration, increased albuminuria, decreased kidney size and volume, and hypertension even though their laboratory results may not yet deteriorate.

Serum uric acid and blood pressure among adolescents: data from the Nutrition and Health Survey in Taiwan (NAHSIT) 2010-2011

PURPOSE

Elevated serum uric acid (UA) is frequently observed in adults with high blood pressure (BP); however, data from adolescents are limited. We examined the association between serum UA and BP in a nationally representative sample of Taiwan adolescents.

MATERIAL AND METHODS

Some 1384 participants, aged 14-19 years, from the Nutrition and Health Survey in Taiwan 2010-2011 were included for the study. Elevated BP was defined as systolic or diastolic BP ≥120/80 mmHg. The analyses examined the relationship between serum UA and BP using linear regression and odds ratios of having an elevated BP using logistic regression.

RESULTS

In this study population, the mean age was 16.0 years, mean serum UA was 5.8 mg/dL, 22.5% were obese (body mass index ≥24 kg/m²) and 9.8% had an elevated BP. Compared to girls, boys are more likely to be obese and to have higher serum UA and BP. After full adjustments, systolic BP, diastolic BP and mean arterial pressure increased 0.45, 0.48 and 0.47 mmHg, respectively, for each 1-mg/dL increase in UA (p = 0.07, 0.03 and 0.02, respectively). The odds of having an elevated BP were 3.4 times higher in subjects of the upper tertile of serum UA than those of the lower tertile (p = 0.02).

CONCLUSION

Adolescents with factors as male, obesity, and UA ≥5.5 mg/dL were prone to have an elevated BP, regardless of age and family history of hypertension. The present study found that serum UA levels are significantly correlated to BP in Taiwanese adolescents.

[Asymptomatic Hyperuricemia and Risk Of Cardiovascular and Renal Diseases]

Asymptomatic hyperuricemia (HU) is common in the population and significantly contributes to the general cardiovascular risk. Despite extensive study of this condition there is still no conclusive answers to questions about detection of asymptomatic HU and its effect on the risk for development and progression of cardiovascular and kidney diseases. This review summarizes key information about these issues, which has been accumulated by the present time.

Influence of race on the effect of premature birth on salivary cortisol response to stress in adolescents

BACKGROUND

Adolescents born preterm have altered hypothalamic-pituitary-adrenal axis function with a blunted cortisol stress response, however, the influences of intrauterine growth restriction and race are unclear.

METHODS

We measured salivary cortisol before and 20 min after a maximal-exercise stress test and calculated the cortisol stress response. We used linear regression to compare cortisol stress responses between preterm and term groups, adjusting for birth weight z-score and maternal hypertension, and examined effect modification by race and sex.

RESULTS

We evaluated 171 adolescents born preterm with very low birth weight and 50 born term. Adolescents born preterm had reduced cortisol stress response compared to term (0.03 vs. 0.08 μg/dL, p = 0.04). This difference was race dependent: non-Black adolescents born preterm had significantly reduced cortisol stress response compared to those born at term (adjusted β: -0.74; 95% CI -1.34, -0.15), while there was no difference in Black adolescents (0.53; -0.16, 1.22). Sex did not modify the relationship.

CONCLUSIONS

Adolescents born preterm exhibit a reduced salivary cortisol response to exercise stress, suggesting long-term alterations in the hypothalamic-pituitary-adrenal axis. This relationship was evident in non-Black but not in Black adolescents, suggesting that race may modify the influence of preterm birth on stress alterations of the hypothalamic-pituitary-adrenal axis.

Association of circulating uric acid and angiotensin-(1-7) in relation to higher blood pressure in adolescents and the influence of preterm birth

Elevated serum uric acid increases the risk of hypertension, and individuals born preterm have higher blood pressure (BP) and uric acid, but the mechanisms remain unclear. Preclinical studies demonstrate uric acid increases BP via increased renin-angiotensin system (RAS) expression, especially angiotensin (Ang) II, but the association of uric acid with Ang-(1–7) is unknown. Ang-(1–7), an alternative RAS product, counteracts Ang II by stimulating sodium excretion, vasodilation, and nitric oxide, thus contributing to lower BP. Plasma Ang-(1–7) is lower in preterm-born adolescents. We hypothesized uric acid is associated with a higher ratio of Ang II to Ang-(1–7) in plasma, especially in preterm-born adolescents. We measured BP, serum uric acid, and plasma RAS components in a cross-sectional analysis of 163 14-year-olds (120 preterm, 43 term). We estimated the associations between uric acid and the RAS using generalized linear models adjusted for sex, obesity, sodium intake, and fat intake, stratified by birth status. Uric acid was positively associated with Ang II/Ang-(1–7) (adjusted β (aβ): 0.88 mg/dl, 95% CI 0.17 to 1.58), plasma renin activity (aβ: 0.32 mg/dl, 95% CI 0.07 to 0.56), and aldosterone (aβ: 1.26 mg/dl, 95% CI 0.18 to 2.35), and inversely with Ang-(1–7) (aβ: −1.11 mg/dl, 95% CI −2.39 to 0.18); preterm birth did not modify these associations. Higher Ang II/Ang-(1–7) was associated with higher uric acid in adolescents. As preterm birth is associated with higher BP and uric acid, but lower Ang-(1–7), the imbalance between uric acid and Ang-(1–7) may be an important mechanism for the development of hypertension.

Association between pre-and postnatal growth and longitudinal trends in serum uric acid levels and blood pressure in children aged 3 to 7 years

Background

Uric acid has been identified as an important factor in the development of hypertension. If low birth weight (LBW) combined with catch-up growth (CUG) is associated with continuously elevated serum uric acid levels (SUA) level trajectories, LBW children who experience CUG may have an increased risk of hypertension later in life. Therefore, this cohort study analyzed longitudinal trends in SUA levels and changes in blood pressure in relation to pre- and postnatal growth over an extended follow-up period.

Methods

This prospective cohort study of 364 children from the Ewha Birth and Growth Cohort assessed the effects of pre- and postnatal growth status on SUA at 3, 5, and 7 years of age using a linear mixed model and the change in blood pressure over the 7-year follow-up period using a generalized linear model (analysis of covariance). CUG was defined as a change in weight (between birth and age 3) with a z-score > 0.67 for LBW subjects. The multivariate model considered sex, gestational age, and uric acid, height, and weight at 3 years of age.

Results

Children with LBW and CUG had higher SUA for the first 7 years of life compared to the normal birth weight group. This trend was particularly evident when comparing LBW children at term to children with normal birth weight. Within the group with LBW at term, children with greater CUG had higher SUA than children with normal birth weight, and this difference increased with age. Changes in the systolic blood pressure between 3 and 7 years of age were higher by 7.9 mmHg in children who experienced LBW and CUG compared with those who had a normal birth weight after adjusting for sex, gestational age, and height, weight, and uric acid at 3 years of age (p-value = 0.08).

Conclusions

The uric acid levels and changes in systolic blood pressure were consistently higher among LBW children who experienced CUG compared with NBW children for the first 7 years of life. LBW children who experienced greater weight gain from birth to age 3 had even higher uric acid levels compared with NBW children.

Effects of Prenatal Growth Status on Subsequent Childhood Renal Function Related to High Blood Pressure

BACKGROUND

Hypertension is one of the major causes of chronic diseases. The effect on high blood pressure (BP) with fetal growth restriction is now well-established. Recent studies suggest that a reduced number of nephrons programmed during the intrauterine period contribute to a subsequently elevated BP, due to a permanent nephron deficit. However, few studies have examined this in children. We investigated the effects of low birth weight (LBW) and preterm birth on the renal function markers related to a high BP in childhood.

METHODS

We used data from 304 children aged 7-12 years who participated in the 2014 Ewha Birth and Growth Cohort survey in Korea. We assessed the serum uric acid, cystatin C, blood urea nitrogen (BUN), creatinine levels, and the estimated glomerular filtration rate (eGFR) in childhood. Anthropometric characteristics, BP in childhood, birth weight and gestational age were collected.

RESULTS

The serum uric acid was significantly higher in LBW children (4.0 mg/dL) than in normal birth weight children (3.7 mg/dL). The cystatin C levels were highest among children who were very preterm (0.89 mg/dL) compared with those who were not (preterm, 0.84 mg/dL; normal, 0.81 mg/dL), although the result was only borderline significant (P for trend = 0.06). Decreased birth weight was found to be significantly associated with an increased serum BUN level in childhood. In the analysis of the effects of renal function on BP, subjects with an eGFR lower than the median value had a significantly higher diastolic BP in childhood (difference = 2.4 mmHg; P < 0.05).

CONCLUSION

These findings suggest that LBW and preterm birth are risk factors for increased serum levels of renal function markers in childhood. Reduced eGFR levels were significantly associated with elevated diastolic BP in childhood. It is necessary to identify vulnerable individuals during their life and intervene appropriately to reduce the risk of an increased BP in the future.

Fetal programming and the angiotensin-(1-7) axis: a review of the experimental and clinical data

Hypertension is the primary risk factor for cardiovascular disease that constitutes a serious worldwide health concern and a significant healthcare burden. As the majority of hypertension has an unknown etiology, considerable research efforts in both experimental models and human cohorts has focused on the premise that alterations in the fetal and perinatal environment are key factors in the development of hypertension in children and adults. The exact mechanisms of how fetal programming events increase the risk of hypertension and cardiovascular disease are not fully elaborated; however, the focus on alterations in the biochemical components and functional aspects of the renin-angiotensin (Ang) system (RAS) has predominated, particularly activation of the Ang-converting enzyme (ACE)-Ang II-Ang type 1 receptor (AT1R) axis. The emerging view of alternative pathways within the RAS that may functionally antagonize the Ang II axis raise the possibility that programming events also target the non-classical components of the RAS as an additional mechanism contributing to the development and progression of hypertension. In the current review, we evaluate the potential role of the ACE2-Ang-(1-7)-Mas receptor (MasR) axis of the RAS in fetal programming events and cardiovascular and renal dysfunction. Specifically, the review examines the impact of fetal programming on the Ang-(1-7) axis within the circulation, kidney, and brain such that the loss of Ang-(1-7) expression or tone, contributes to the chronic dysregulation of blood pressure (BP) and cardiometabolic disease in the offspring, as well as the influence of sex on potential programming of this pathway.

Renal function and blood pressure are altered in adolescents born preterm

BACKGROUND

Preterm birth increases the risk of hypertension and kidney disease. However, it is unclear when changes in blood pressure (BP) and renal function become apparent and what role obesity and sex play. We hypothesized adolescents born preterm have higher BP and worse kidney function compared to term in an obesity- and sex-dependent manner.

METHODS

Cross-sectional analysis of 14-year-olds born preterm with very low birth weight (n = 96) compared to term (n = 43). We used generalized linear models to estimate the associations among preterm birth and BP, estimated glomerular filtration rate (eGFR), and ln (x) urinary albumin-to-creatinine ratio (ACR), stratified by overweight/obesity (OWO, body mass index (BMI) ≥ 85th percentile) and sex.

RESULTS

Compared to term, preterm-born adolescents had higher systolic blood pressure (SBP) and diastolic blood pressure (DBP) (adjusted β (aβ) 3.5 mmHg, 95% CI - 0.1 to 7.2 and 3.6 mmHg, 95% CI 0.1 to 7.0), lower eGFR (β - 8.2 mL/min/1.73 m², 95% CI - 15.9 to - 0.4), and higher ACR (aβ 0.34, 95% CI - 0.04 to 0.72). OWO modified the preterm-term difference in DBP (BMI < 85th percentile aβ 5.0 mmHg, 95% CI 0.7 to 9.2 vs. OWO 0.2 mmHg, 95% CI - 5.3 to 5.6) and ACR (OWO aβ 0.72, 95% CI 0.15 to 1.29 vs. BMI < 85th percentile 0.17, 95% CI - 0.31 to 0.65). Sex modified the preterm-term ACR difference (female aβ 0.52, 95% CI 0.001 to 1.04 vs. male 0.18, 95% CI - 0.36 to 0.72).

CONCLUSIONS

Prematurity was associated with higher BP and reduced renal function that were detectable in adolescence. OWO and sex may modify the strength of these relationships.

Birthweight and serum uric acid in American adolescents

Elevated serum uric acid is associated with hypertension and chronic kidney disease. We evaluated the relationship between birthweight and uric acid in a nationally representative sample of 5390 US adolescents aged 12-15 in the National Health and Nutrition Examination Survey from 1999 to 2012. There was an inverse association between birthweight and uric acid after adjustment for sex, age, race, obesity, and dietary sodium intake. Each 1 kg increase in birthweight was associated with decreased uric acid by 0.11 mg/dL (95% CI: -0.16 to -0.06; model R²  = 0.32). This relationship was stronger in adolescents with elevated blood pressure (β = -0.25; 95% CI: -0.44 to -0.06; R²  = 0.50) but persisted in adolescents with normal blood pressure (β = -0.10; 95% CI: -0.15 to -0.05; R²  = 0.31). In conclusion, lower birthweight is associated with higher uric acid in US adolescents. These findings may support the hypothesis that reduced nephron number is associated with elevated uric acid.