Amniotic fluid glycine-valine ratio and neonatal morbidity in fetal growth restriction

Interplay Between Plasma Glycine and Branched-Chain Amino Acids Contributes to the Development of Hypertension and Coronary Heart Disease

BACKGROUND

Higher levels of plasma glycine are linked to a reduced risk, while increased levels of total branched-chain amino acids (tBCAAs) are associated with a higher risk of essential hypertension and coronary heart disease (CHD). As these metabolic components are interconnected, analyzing the tBCAAs/glycine ratio may help to understand their interplay in the pathogenesis of cardiovascular disease.

METHODS

The Cox regression approach was combined with the development of novel genetic tools for assessments of associations between plasma metabolomic data (glycine, tBCAAs, and tBCAAs/glycine ratio) from the UK Biobank and the development of hypertension and CHD. Genome-wide association study was performed on 186 523 White UK Biobank participants to identify new independent genetic instruments for the 2-sample Mendelian randomization analyses. P-gain statistic >10 identified instruments associated with tBCAAs/glycine ratio significantly stronger compared with individual amino acids. Outcomes of genome-wide association study on hypertension and CHD were derived from the UK Biobank (nonoverlapping sample), FinnGen, and CARDIoGRAMplusC4D.

RESULTS

The tBCAAs/glycine ratio was prospectively associated with a higher risk of developing hypertension and CHD (hazard ratio quintile Q5 versus Q1, 1.196 [95% CI, 1.109-1.289] and 1.226 [95% CI, 1.160-1.296], respectively). Mendelian randomization analysis demonstrated that tBCAAs/glycine ratio (P-gain >10) was a risk factor for hypertension (meta-analyzed inverse-variance weighted causal estimate 0.45 log odds ratio/SD (95% CI, 0.26-0.64) and CHD (0.48 [95% CI, 0.29-0.67]) with an absolute effect significantly larger compared with the effect of glycine (-0.06 [95% CI, -0.1 to -0.03] and -0.08 [95% CI, -0.11 to -0.05], respectively) or tBCAAs (0.22 [95% CI, 0.09-0.34] and 0.12 [95% CI, 0.01-0.24], respectively).

CONCLUSIONS

The total BCAAs/glycine ratio is a key element of the metabolic signature contributing to hypertension and CHD, which may reflect biological pathways shared by glycine and tBCAAs.

Biomarkers for Macrosomia Prediction in Pregnancies Affected by Diabetes

Large birthweight, or macrosomia, is one of the commonest complications for pregnancies affected by diabetes. As macrosomia is associated with an increased risk of a number of adverse outcomes for both the mother and offspring, accurate antenatal prediction of fetal macrosomia could be beneficial in guiding appropriate models of care and interventions that may avoid or reduce these associated risks. However, current prediction strategies which include physical examination and ultrasound assessment, are imprecise. Biomarkers are proving useful in various specialties and may offer a new avenue for improved prediction of macrosomia. Prime biomarker candidates in pregnancies with diabetes include maternal glycaemic markers (glucose, 1,5-anhydroglucitol, glycosylated hemoglobin) and hormones proposed implicated in placental nutrient transfer (adiponectin and insulin-like growth factor-1). There is some support for an association of these biomarkers with birthweight and/or macrosomia, although current evidence in this emerging field is still limited. Thus, although biomarkers hold promise, further investigation is needed to elucidate the potential clinical utility of biomarkers for macrosomia prediction for pregnancies affected by diabetes.

A predictor of small-for-gestational-age infant: oral glucose challenge test

OBJECTIVE

This study was performed to investigate the role of first-hour 50-g oral glucose challenge test (GCT) parameters in predicting the risk of delivering a small-for-gestational-age infant and to determine the accuracy of estimated fetal weight.

METHODS

We screened 2,643 pregnant women >20 years of age and excluded 552 patients according to exclusion criteria. Newborns were assigned to three groups as SGA(n:100), AGA(n:100), and LGA(n:100) according to birth weight. All mothers received 50-g GCT in their 24-28th weeks of gestation. We examined the relationship between birthweight and test results.

RESULTS

First-hour serum glucose level after the test significantly predicted babies with small for gestational age. Optimal cutoff value was obtained at a level of 74.5 mg/dl with 67% sensitivity and 55% specificity. The estimated fetal weight of Hadlock 5 formula was strongly correlated with the birth weight (Pearson r = 0.89).

CONCLUSION

Our study revealed that 50-g oral glucose challenge test may predict small-for-gestational-age cases with 67% sensitivity, and our data revealed that there is a significant correlation between estimated fetal weight of Hadlock 5 formula and the birth weight.

Characterization of dietary protein-dependent amino acid metabolism by linking free amino acids with transcriptional profiles through analysis of correlation

This study aims to characterize diet-dependent amino acid metabolism by linking profiles of amino acids concentrations (“aminograms”) with transcript datasets through the analysis of correlation. We used a dietary model of protein restriction-to-excess, where rats were fed diets with different levels of casein (5, 10, 15, 20, 30, 50, and 70%) for 2 wk. Twenty-five different amino acids in the plasma, liver, kidney, small intestine, and muscle and 71 gene transcripts in these compartments were measured together with general physiological variables. Under low-protein diet (LPD) conditions, the plasma aminogram for EAA was similar to that of the liver and the small intestine, respectively. Under the high-protein diet (HPD), however, the plasma aminogram for EAA became like that of muscle, while that of NEAA was similar with that of both liver and muscle. To assess the impact of gene expressions in each tissue on the plasma aminograms, correlations were obtained between aminograms and transcripts in each tissue under a diet with different protein levels. Based on the correlations obtained, amino acids and transcripts were systematically connected and then a metabolite-to-gene network was constructed for either LPD or HPD condition. The networks obtained and some other metabolically meaningful relationships such as ureagenesis and serine metabolism clearly illustrated activation of either body protein breakdown with LPD or amino acid catabolism with HPD.

The fetal response to chronic placental insufficiency

Fetal growth restriction is most commonly caused by failure of the placenta to meet the increasing demands for oxygen and substrate of the developing fetus, resulting in common fetal compensatory responses. Understanding these responses is helpful in developing a management strategy that will optimize pregnancy outcome.

Fetal growth restriction due to placental disease

Normal fetal growth depends on the genetically predetermined growth potential and its modulation by the health of the fetus, placenta and the mother. Fetuses that are small because of intrauterine growth restriction (IUGR) are at higher risk for poor perinatal and long-term outcome than those who are appropriately grown. Of the many potential underlying processes that may result in IUGR, placental disease is clinically the most relevant. Fetal cardiovascular and behavioral responses to placental insufficiency and the metabolic status are interrelated. The concurrent evaluation of fetal biometry, amniotic fluid volume, heart rate patterns, arterial and venous Doppler, and biophysical variables therefore allow the most comprehensive fetal evaluation in IUGR. In the absence of successful intrauterine therapy, the timing of delivery is perhaps the most critical aspect of the antenatal management. A discussion of the fetal responses to placental insufficiency and a management protocol that accounts for multiple Doppler and biophysical parameters as well as gestational age is provided in this review.