Recent shifts in the genomic ancestry of Mexican Americans may alter the genetic architecture of biomedical traits

People in the Americas represent a diverse continuum of populations with varying degrees of admixture among African, European, and Amerindigenous ancestries. In the United States, populations with non-European ancestry remain understudied, and thus little is known about the genetic architecture of phenotypic variation in these populations. Using genotype data from the Hispanic Community Health Study/Study of Latinos, we find that Amerindigenous ancestry increased by an average of ~20% spanning 1940s-1990s in Mexican Americans. These patterns result from complex interactions between several population and cultural factors which shaped patterns of genetic variation and influenced the genetic architecture of complex traits in Mexican Americans. We show for height how polygenic risk scores based on summary statistics from a European-based genome-wide association study perform poorly in Mexican Americans. Our findings reveal temporal changes in population structure within Hispanics/Latinos that may influence biomedical traits, demonstrating a need to improve our understanding of admixed populations.

A genome-wide association and admixture mapping study of bronchodilator drug response in African Americans with asthma

Short-acting β₂-adrenergic receptor agonists (SABAs) are the most commonly prescribed asthma medications worldwide. Response to SABAs is measured as bronchodilator drug response (BDR), which varies among racial/ethnic groups in the U.S^{1, 2}. However, the genetic variation that contributes to BDR is largely undefined in African Americans with asthma³. To identify genetic variants that may contribute to differences in BDR in African Americans with asthma, we performed a genome-wide association study (GWAS) of BDR in 949 African American children with asthma, genotyped with the Axiom World Array 4 (Affymetrix, Santa Clara, CA) followed by imputation using 1000 Genomes phase III genotypes. We used linear regression models adjusting for age, sex, body mass index (BMI) and genetic ancestry to test for an association between BDR and genotype at single nucleotide polymorphisms (SNPs). To increase power and distinguish between shared vs. population-specific associations with BDR in children with asthma, we performed a meta-analysis across 949 African Americans and 1,830 Latinos (Total=2,779). Lastly, we performed genome-wide admixture mapping to identify regions whereby local African or European ancestry is associated with BDR in African Americans. We identified a population-specific association with an intergenic SNP on chromosome 9q21 that was significantly associated with BDR (rs73650726, p=7.69×10⁻⁹). A trans-ethnic meta-analysis across African Americans and Latinos identified three additional SNPs within the intron of PRKG1 that were significantly associated with BDR (rs7903366, rs7070958, and rs7081864, p≤5×10⁻⁸). Our results failed to replicate in three additional populations of 416 Latinos and 1,615 African Americans. Our findings indicate that both population specific and shared genetic variation contributes to differences in BDR in minority children with asthma, and that the genetic underpinnings of BDR may differ between racial/ethnic groups.

Stress and Bronchodilator Response in Children with Asthma

RATIONALE

Stress is associated with asthma morbidity in Puerto Ricans (PRs), who have reduced bronchodilator response (BDR).

OBJECTIVES

To examine whether stress and/or a gene regulating anxiety (ADCYAP1R1) is associated with BDR in PR and non-PR children with asthma.

METHODS

This was a cross-sectional study of stress and BDR (percent change in FEV1 after BD) in 234 PRs ages 9-14 years with asthma. We assessed child stress using the Checklist of Children's Distress Symptoms, and maternal stress using the Perceived Stress Scale. Replication analyses were conducted in two cohorts. Polymorphisms in ADCYAP1R1 were genotyped in our study and six replication studies. Multivariable models of stress and BDR were adjusted for age, sex, income, environmental tobacco smoke, and use of inhaled corticosteroids.

MEASUREMENTS AND MAIN RESULTS

High child stress was associated with reduced BDR in three cohorts. PR children who were highly stressed (upper quartile, Checklist of Children's Distress Symptoms) and whose mothers had high stress (upper quartile, Perceived Stress Scale) had a BDR that was 10.2% (95% confidence interval, 6.1-14.2%) lower than children who had neither high stress nor a highly stressed mother. A polymorphism in ADCYAP1R1 (rs34548976) was associated with reduced BDR. This single-nucleotide polymorphism is associated with reduced expression of the gene for the β2-adrenergic receptor (ADRB2) in CD4(+) lymphocytes of subjects with asthma, and it affects brain connectivity of the amygdala and the insula (a biomarker of anxiety).

CONCLUSIONS

High child stress and an ADCYAP1R1 single-nucleotide polymorphism are associated with reduced BDR in children with asthma. This is likely caused by down-regulation of ADRB2 in highly stressed children.

Communicating with parents of premature infants: who is the informant?

OBJECTIVES

To determine what sources of information are most helpful for neonatal intensive care unit (NICU) parents, who provides NICU parents with the information, and also what expectations parents have regarding obtaining information.

STUDY DESIGN

A 19-item questionnaire was given to the parents of infants 32 weeks or younger prior to discharge from the NICU.

RESULTS

Out of the 101 parents who consented, almost all of the parents (96%) felt that 'the medical team gave them the information they needed about their baby' and that the 'neonatologist did a good job of communicating' with them (91%). However, the nurse was chosen as 'the person who spent the most time explaining the baby's condition, 'the best source of information,' and the person who told them 'about important changes in their baby's condition' (P<0.01).

CONCLUSION

Although the neonatologist's role in parent education is satisfactory, the parents identified the nurses as the primary source of information.

Immaturity or starvation? Longitudinal study of leptin levels in premature infants

OBJECTIVE

Leptin, the protein product of the ob gene, is a potential placental growth factor and is integral to the body's system of energy regulation as shown in animal models. Premature infants are especially vulnerable to changes in energy regulation, and several studies have demonstrated a rapid fall in leptin values at birth. The purpose of the present investigation was to measure leptin levels in premature infants throughout hospitalization.

METHODS

Eligible infants were less than 32 weeks' gestation, appropriate for gestational age, and hospitalized at Christiana Hospital Special Care Nursery. Serum samples for leptin analysis were drawn within 24 h of birth and twice a week thereafter until discharge. Concurrent growth measurements were obtained with each leptin sample. Body mass index, ponderal index, and midarm circumference/head circumference ratios were calculated to assess growth.

RESULTS

Leptin levels were low and remained low for the duration of the premature infants' hospitalization (mean +/- SD = 1.35 +/- 0.63 ng/ml/ml, range 0-3.06). After controlling for weight, there was a small (r(2) = 0.1, p < 0.00001) but significant correlation between leptin and postnatal age after 4 days of age. Despite an increase in caloric intake during the study period, there was no relationship between leptin and caloric intake. There were significant negative correlations between measurements of growth and both leptin and the leptin/weight ratio. Maternal diabetes and the use of steroids had small but significant effects on the leptin/weight ratio.

CONCLUSION

In this population of predominantly female premature infants, leptin levels were very low as compared to term infants, children and adults, and did not change appreciably over the study period. The low leptin levels seen in these premature infants are similar to those levels seen in malnourished adults, anorexics, and in animal models of starvation. We speculate that a critical adipose store needs to be reached before increased amounts of leptin can be adequately produced. Persistently low leptin levels may also reflect an immaturity in the hypothalamic-pituitary-adrenal axis.

Effect of sleep position on apnea and bradycardia in high-risk infants

OBJECTIVE

The purpose of this investigation was to investigate, in high-risk infants, the occurrence of abnormalities in documented monitor downloads during the side versus prone position.

STUDY DESIGN

Forty infants admitted to the A. I. duPont Hospital for Children with diagnoses associated with sudden infant death syndrome were included in this investigation. During an overnight hospitalization, infants were placed on home apnea monitors, with computer memory to capture alarms for apnea > 20 seconds, age-defined bradycardia, and tachycardia. Infants were studied for 12 hours. Each infant was assigned to 6 hours of prone and side during the 12-hour period, with order of position randomly assigned by random number generation. Differences between the two positions in alarm frequency and significant events, as determined by a blinded interpreting physician were analyzed by Fisher exact test, with p < 0.05. Power analysis necessitated 20 patients in each group, with beta error of 0.2.

RESULTS

Eleven episodes of apnea occurred in the prone position, and 16 in the side position (p = NS). The mean numbers of apnea events per tracing in the prone position was 0.27 +/- 0.84 and 0.39 +/- 1.1 in the side position (p = 0.58). The mean number of bradycardia events per tracing in the prone position was 0.44 +/- 1.45 and 0.49 +/- 1.94 in the side position (p = 0.9).

CONCLUSION

Clinicians need to be cautious when recommending the side or prone position in this group of high-risk infants. The results in this investigation provide support for the Back to Sleep Campaign recommendations to be applied, not only to healthy term infants, but higher risk infants as well. Studies of the high-risk infant in the supine position are warranted.

Placental leptin: an important new growth factor in intrauterine and neonatal development?

BACKGROUND

Leptin, the protein product of the ob gene, is produced by the adipocyte and seems to function as a link between adiposity, satiety, and activity. Leptin has also been found to be necessary for pubertal development, conception, and pregnancy in mice, and is increased in prepubertal children, independent of adiposity, suggesting a role in childhood growth and development. This study investigated 100 mother/newborn pairs to determine the role of leptin in neonatal development. Placental tissue was assayed for leptin mRNA to evaluate it as a source of leptin production in utero.

METHODS

One hundred mother/newborn pairs were enrolled in this study. Radioimmunoassay was performed for leptin on maternal venous and newborn cord blood. Leptin concentrations were measured in 43 children in Tanner stages 1 and 2 as a control group. Placental tissue was obtained from five mothers and assayed for leptin mRNA by reverse transcription/polymerase chain reaction (RT/PCR). Human placental cell lines JAR and JEG-3 were also assayed for leptin mRNA expression.

RESULTS

Leptin was present in all newborns studied at a mean concentration of 8.8 ng/mL (+/-9.6 standard deviations). Leptin concentrations in cord blood correlated with newborn weight (r = .51), body mass index (BMI) (r = .48), and arm fat (r = .42). There was no correlation between leptin and insulin. When statistically covarying for adiposity for newborns and Tanner stages 1 and 2 children, newborns had greater concentrations of leptin (mean, 10.57 ng/mL) than children (mean, 3.04 ng/mL). Leptin was present in all mothers at a mean value of 28.8 ng/mL (+/-22.2 standard deviations). Leptin concentration correlated with prepregnancy BMI (r = .56), BMI at time of delivery (r = .74), and arm fat (r = .73). Maternal leptin correlated with serum insulin (r = .49). There was no correlation between maternal and newborn leptin concentrations. Thirteen percent of newborns had higher leptin concentrations than their mothers. Placental tissue from five separate placentas expressed leptin mRNA at comparable or greater levels than adipose tissue. Two human trophoblastic placental cell lines, JAR and JEG-3, also expressed leptin mRNA.

CONCLUSIONS

The correlation between leptin and adiposity found in children and adults was also found in newborns. Serum leptin concentrations in newborns were increased more than three-fold compared with children in Tanner stages 1 and 2 when controlling for adiposity, suggesting that leptin concentrations in the newborn are not explained by adiposity alone. Maternal leptin concentrations correlated with measures of adiposity at delivery but did not correlate with newborn adiposity or leptin. Leptin mRNA was expressed both in placental tissue and in two human placental cell lines. These data suggest that leptin has a role in intrauterine and neonatal development and that the placenta provides a source of leptin for the growing fetus.

Plasma lecithin: cholesterol acyltransferase and plasma lipolytic activity in preterm infants given total parenteral nutrition with 10% or 20% Intralipid

The effect of 10% or 20% Intralipid on lipid clearing enzymes, plasma lipids and apoproteins was investigated during the first 5 days after birth in 37 premature infants maintained on total parenteral nutrition; 21 infants received 20% and 16 received 10% Intralipid, respectively. Lipid was infused over a 20-h period at rates of 1, 2 and 3 g/kg/day on consecutive days. Plasma lecithin: cholesterol acyltransferase (LCAT) activity was low and increased significantly (p<0.05) only during infusions of 3 g/kg/day in both groups of infants. Plasma lipolytic activity was generally not affected by the regimen or preparation (10% or 20%) of Intralipid infused, except for higher (p<0.05) levels at 3 g/kg/day of 20% compared with prelipid infusion. Plasma triglyceride concentrations wer similar after 10% or 20% Intralipid, whereas plasma total cholesterol was significantly higher during infusion of 2 and 3 g/kg/day of 10% compared with 20% Intralipid. The efficient clearing of 20% Intralipid might be related to the lower lecithin: triglyceride ration which is compatible with the low LCAT activity of premature infants.

Soluble interleukin-2 receptor as a predictor of neonatal sepsis

We prospectively measured soluble interleukin-2 receptor levels in 56 premature infants with suspected sepsis and demonstrated significant differences between those with positive results on blood, urine, or cerebrospinal fluid cultures, and those with negative results. Soluble interleukin-2 receptor levels can be used to facilitate the diagnosis of sepsis in premature infants with negative blood culture results.

Use of [13C]bicarbonate infusion for measurement of CO2 production

To determine whether infusion of 13C-labeled bicarbonate can be used to measure rates of CO2 production (VCO2), seven healthy adults received 6-h primed continuous intravenous infusions of NaH13CO3 and L-[1-14C]leucine in the post-absorptive state while VCO2 was measured by indirect calorimetry. Indirect calorimetry and the use of specific activity and rate of 14CO2 expired yielded identical values of VCO2: 8.97 +/- 0.82 and 8.80 +/- 0.83 mmol/min, respectively (P = NS). The concentration of NaH13CO3 in the infusates and the 13C enrichment in breath CO2 were determined using gas chromatography-isotope ratio mass spectrometry. The rate of appearance of CO2 measured using the NaH13CO3 infusion rate and the steady-state breath 13CO2 enrichments was 11.41 +/- 1.56 mmol/min, which was higher (P < 0.001) than that determined by either of the other two methods. When corrected for the recovery of labeled CO2 during the infusion of NaH13CO3 by use of published values, rate of appearance of CO2 was 9.24 +/- 0.78 mmol/min, which did not differ from VCO2 determined using the other two methods. We conclude that infusion of NaH13CO3 can be used to determine VCO2. This method should be useful to study the oxidation of substrates in populations such as ventilator-dependent neonates, in whom indirect calorimetry is laborious and inaccurate.

Recent advances in parenteral nutrition

With the modifications described in this article, some of the precise elements in parenteral nutrition have been elucidated. With these changes, this form of nutrition has provided the essential calories and trace elements necessary for very-low-birthweight infants, as well as infants who have required surgery. As further research is done in this area, it is anticipated that even more adjustments to parenteral nutrition will be made, in order to provide optimal caloric vitamin, and trace element intake and establish the optimal manner in which these are administered.

Human mammary gland function at the onset of lactation: medium-chain fatty acid synthesis

The onset of medium-chain fatty acid synthesis in the human mammary gland was investigated. Colostrum and serum were collected from 31 healthy women and the fatty acid composition of total lipid was analyzed by gas-liquid chromatography. Although colostrum/serum ratios for most fatty acids range from 0.7-2.4, very low levels of 10:0 and 12:0 were present in serum lipids as compared to much higher concentrations of these fatty acids in colostrum lipids (colostrum/serum ratio 16.23 and 17.11 for 10:0 and 12:0, respectively). We have previously found that medium-chain fatty acid levels are very low in prepartum mammary secretions (6-10 wk before term delivery) but are higher and similar in colostrum of women who deliver preterm (3-14 wk) or at full term. The data indicate that parturition, irrespective of length of pregnancy, is the trigger for medium-chain fatty acid synthesis in the human mammary gland.

Soluble interleukin-2 receptor levels in infants with bronchopulmonary dysplasia

Soluble interleukin-2 receptors (sIL2R) in plasma have been identified as a marker of lymphocyte activation. Lymphocyte activation as a manifestation of inflammation may be important in the pathogenesis of bronchopulmonary dysplasia (BPD). To test the hypothesis that infants with BPD have higher sIL2R levels, 12 infants with or at risk of developing BPD (GA +/- SD, 27 +/- 5 weeks; BW +/- SD 1,053 +/- 733 g) had plasma sIL2R levels determined and were compared to 20 infants being ventilated for respiratory distress syndrome (RDS) (GA +/- SD, 28 +/- 3.5 weeks; BW +/- SD, 1,133 +/- 390 g: P = NS for both GA and BW, t test). Tracheal aspirates in both groups were also analyzed for sIL2R levels. To control for the effects of postnatal age (PNA) and study weight (SW) on the sIL2R levels, another group of 16 nonventilated babies (NVB) had plasma analyzed for sIL2R (PNA +/- SD: 39 +/- 40 days NVB vs. 48 +/- 36 days BPD; P = NS); (SW +/- SD: 1391 +/- 250 g NVB vs. 1212 +/- 700 g BPD; P = NS). The following data were obtained for the plasma sIL2R levels (mean +/- SEM U/mL): RDS controls, 1,231 +/- 80; BPD infants, 1,790 +/- 120; NVB controls, 1,319 +/- 76; P = 0.0005 RDS vs. BPD and P = 0.002 BPD vs. NVB. There was no significant difference in the sIL2R levels for the infants at risk of developing BPD vs. the infants with established BPD. Also, when analyzed separately, infants at risk of BPD and the infants with established BPD had higher sIL2R levels than the RDS and NVB controls. No differences were noted in the tracheal sIL2R levels in the BPD vs. RDS groups. These data indicate that infants with BPD had significantly higher sIL2R levels in plasma than either RDS or NVB controls. Therefore, lymphocyte activation may play a role in the pathogenesis of BPD.

Prolonged apnea and oxyhemoglobin desaturation in asymptomatic premature infants

Seventy-eight longitudinal four-channel recordings of heart rate, thoracic impedance, nasal thermistry, and pulse oximetry were performed on 26 asymptomatic premature infants (gestational age, 29.9 +/- 1.58 weeks; birth weight, 1,753 +/- 226 grams; postconceptional age, 34.3 +/- 2.0 weeks; postnatal age, 4.41 +/- 2.40 weeks; all values mean +/- SD). Tracings were scored for central and obstructive apnea, bradycardia, periodic breathing, apnea density, and prolonged apnea. The studies demonstrated 585 episodes (7.41/recording) of oxyhemoglobin desaturation with less than 90%. Recordings had a mean of 16.1 episodes of central apnea, 3.04 episodes of obstructive apnea, and 2.34 episodes of bradycardia. Periodic breathing and short obstructive apneas correlated significantly with the total number of oxyhemoglobin desaturations of less than 80% and 90%. Episodes of prolonged apnea were seen in 20 of 78 recordings. In the latter a significantly higher number of total desaturations (less than 90%), desaturations less than 80% and 90% in association with apnea and with bradycardia, longer desaturations, desaturations during sleep, and isolated bradycardia were observed. Variations in heart rate, thoracic impedance, nasal air flow, and pulse oximetry are associated with episodes of oxyhemoglobin desaturation in asymptomatic premature infants. These infants, although asymptomatic, may be at risk for impaired tissue oxygenation.

Milk and blood fatty acid composition during two lactations in the same woman

Fatty acid composition of colostrum, milk, and serum was studied during two consecutive lactations in the same woman. There were marked differences between milk and serum: medium chain fatty acids (C6:0-C14:0) were higher in milk (8.36-21.37%) than in serum (1.59-9.6%) throughout lactation. The high milk-serum ratio of medium chain fatty acids (up to 28.4, 30.2, and 6.2 for 10:0, 12:0, and 14:0, respectively) indicates synthesis in the mammary gland. Long-chain polyunsaturated fatty acids (C20:1-C22:6) of the n - 3 and n - 6 series were higher in serum (6.76-12.53%) than in milk (1.57-4.42%). With the exception of colostrum, the fatty acid composition of milk and serum changed little during lactation and was similar in two consecutive lactations in the same woman. Comparison of milk and serum fatty acids provides a noninvasive approach for the assessment of the synthetic activity of the human mammary gland.

Lecithin:cholesterol acyltransferase (LCAT) activity during lipid infusion in premature infants

Plasma cholesterol and lecithin concentrations are regulated by the serum enzyme lecithin: cholesterol acyltransferase (LCAT). LCAT activity is low in cord blood of premature infants, suggesting that in these infants the hypercholesterolemia associated with Intralipid infusion might be due to low LCAT activity. The serum LCAT activity has not been quantitated in preterm infants receiving intravenous fat emulsions. We have therefore quantitated LCAT activity in eleven premature infants maintained on total parenteral nutrition (TPN). Ten infants were studied during the first 2 weeks after birth; they received daily infusions of Intralipid at a rate of 0.5-2.0 g/kg/day over 15 h. One infant received 3.8 g/kg/day during the second week. In addition to LCAT, serum apoprotein A1 (the cofactor of LCAT), cholesterol, triglycerides, and free fatty acids were quantitated. Blood specimens were taken before the start of the infusion and 15-45 min before its completion. The LCAT activity and apoprotein A1 concentrations remained, respectively, 21-24% and 30-35% of adult levels. However, serum cholesterol levels remained in the normal range during the fat infusion. It remains to be established whether low LCAT activity and apoprotein A1 levels are due to the administration of Intralipid (which lowers LCAT activity in rats), to the lack of enteral feedings, or to prematurity per se. Our data suggest that administration of Intralipid at a rate not exceeding 1-2 g/kg/day does not impair the clearing of Intralipid-lecithin and the metabolism of cholesterol.

Case report: congenital syphilis associated with persistent pulmonary hypertension of the newborn

A Newborn infant with prenatally acquired syphilis and persistent pulmonary hypertension is described. The patient had clinical, serologic, and radiologic evidence of syphilis at birth. He demonstrated right to left shunting of blood at the level of the foramen ovale, and responded to hyperventilation. Despite adequate oxygenation with hyperventilation, the patient expired after five days of therapy due to a progressive pneumonia and hypotension. The clinician should be aware of this unusual mode of presentation and anticipate the potential need for early aggressive intervention.

Closure of the ductus arteriosus with indomethacin in ventilated neonates with respiratory distress syndrome. Effects of pulmonary compliance and ventilation

The reported effects of indomethacin on pulmonary compliance are variable depending upon the patient population and on the degree to which indomethacin resulted in successful ductal closure. Eleven fluid-restricted, furosemide-treated premature infants being mechanically ventilated for respiratory distress syndrome (RDS) who also had a significant patent ductus arteriosus (PDA) had pulmonary function testing performed before and after successful closure of the PDA. The diagnosis of a significant PDA was made by clinical and echocardiographic criteria. Indomethacin was administered at a dosage of 0.2 mg/kg/dose every 12 to 18 h for 1 to 3 doses. To control for the 48-h time interval to achieve ductal closure, nine premature infants being ventilated for RDS but who did not have a significant PDA also had pulmonary function evaluations performed before and after the 48 h. Also, to control for the independent effect of fluid restriction and diuretic therapy on pulmonary compliance, eight such premature infants with a PDA had pulmonary function evaluations performed at a 48-h interval. Successful closure of the ductus with indomethacin was associated with an improvement in compliance and ventilation parameters in all infants in the indomethacin-treated infants. In the indomethacin-treated group, the mean percent improvements were noted in the following parameters: CLdyn, 59.2%; CLI, 78.3%; CLE, 63.3%; VT, 63.3%; VE, 54.6%. There were no significant changes in the pulmonary functions in the 48-h RDS or the 48-h PDA fluid-restricted, furosemide-treated control groups. In conclusion, successful closure of the ductus with indomethacin causes a significant improvement in compliance and ventilation parameters in infants being mechanically ventilated for RDS.

Effect of fat infusions on platelet concentration in premature infants

Critically ill premature infants often require lipid emulsions with parenteral nutrition until enteral feedings can be safely initiated. Because thrombocytopenia has been listed as a potential side effect of fat emulsions, we examined the effect of varying doses of intravenous fat infusions on platelet concentrations in premature infants. An initial validation study demonstrated no artifactual effect of fat infusions on the electronic cell counter method of platelet enumeration. We observed no adverse effect of fat emulsions administered at doses of 0.8 to 3.3 g/kg/day on platelet concentration either during short-term (48 hr) or long-term study periods (4 weeks).

Effect of heparin dose and infusion rate on lipid clearance and bilirubin binding in premature infants receiving intravenous fat emulsions

The effect of heparin dose and infusion rate on plasma lipids, lipases, and unbound bilirubin was investigated in 22 premature infants with physiologic jaundice. Infants were randomly assigned to receive low or high intravenous doses (24 vs 137.3 U/day) of heparin. Each patient then received 2 g/kg/day of 10% Intralipid on 2 successive days: one day during a 15-hour period and the other day over 24 hours, with the order assigned randomly. The results demonstrate a significantly greater change in serum-free fatty acids in infants receiving the high heparin dose during the 15-hour lipid infusion period. Lipoprotein lipase activity rose more with the high heparin dose and equally at either infusion rate. We conclude that lipid infusions of 2 g/kg/day with low heparin dosage infused over 24 hours resulted in less elevation in serum-free fatty acids. There were no adverse effects on unbound bilirubin at either infusion rate or heparin dosage.

Total parenteral nutrition with intralipid in premature infants receiving TPN with heparin: effect on plasma lipolytic enzymes, lipids, and glucose

Plasma lipolytic activity (lipoprotein lipase and hepatic lipase), free fatty acids (FFA), triglycerides, cholesterol, and glucose levels were measured in 21 premature infants [gestational age 26-37 weeks (mean +/- SEM 30.4 +/- 0.63 weeks), aged 1-8 days (mean +/- SEM 3.00 +/- 0.35 days)]. All infants were maintained on total parenteral nutrition with heparin (1 U/ml) and were given Intralipid, 1, 2, and 3 g/kg/day, over 15 h on days 1, 2, and 3, respectively. Blood samples were drawn before and at the end of Intralipid administration. Baseline plasma lipolytic activity, before the start of lipid infusion, was 1.54 +/- 0.24 U/ml (1 U = 1 mumol [3H]oleic acid released from tri[3H]olein/h). Lipolytic activity increased after lipid infusion to 4.04 +/- 0.96, 4.32 +/- 0.63, and 6.09 +/- 1.00 U/ml on days 1, 2, and 3 of the study. Hepatic lipase amounted to 38-47% of total lipolytic activity. During the 3 days of lipid infusion, there were dose-dependent increases in plasma FFA, triglyceride, and cholesterol. Whereas FFA and triglyceride concentrations returned to prelipid infusion levels 9 h after stopping the infusion of Intralipid, 1, 2, or 3 g/kg, there was a cumulative increase in plasma cholesterol and glucose concentrations. The close correlation between FFA concentrations and plasma lipolytic activity (r = 0.655, p less than 0.001) suggests considerable intravascular lipolysis. The positive correlation between plasma FFA and triglycerides (r = 0.632, p less than 0.001) and FFA and cholesterol (r = 0.582, p less than 0.001) indicate, however, that intravascular lipolysis does not prevent the lipemia associated with Intralipid infusion to low birth weight infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous administration of lipid emulsions to premature infants

This article describes the mechanisms responsible for hydrolysis and clearance of triglyceride from the circulation and focuses on the factors that affect lipid clearance in the newborn infant. The potential beneficial and adverse effects of IV lipid administration to premature infants are reviewed in detail. Several practical considerations for IV lipid administration are also discussed.

The effect of 15-hour fat infusions of varying dosage on bilirubin binding to albumin

Intravenous fat emulsions (1, 2, and 3 g/kg) were administered over 15 hr to 20 appropriate for gestational age premature infants with physiologic hyperbilirubinemia to determine the effect of fat infusions on the serum free fatty acid:albumin molar ratio (F/A) and on unbound bilirubin. Significant increases (p less than 0.05) in F/A occurred with each increase in lipid dose in infants less than 30 wk gestation, but not in infants greater than or equal to 30 wk gestation. There was a direct linear correlation (r = 0.65, p less than 0.001) between F/A ratio and unbound bilirubin (estimated fluorometrically by the ratio of albumin-bound bilirubin/reserve bilirubin binding capacity, B/R). The largest increases in unbound bilirubin (albumin-bound bilirubin/reserve bilirubin binding capacity) were seen in infants with F/A greater than 4.0. The gestational age of infants with F/A greater than 4.0 was significantly less (p less than 0.01) than infants with F/A less than 4.0 (28.7 +/- 0.47 vs. 31.1 +/- 0.40 wk, mean +/- SEM). In 10/58 infusions there was a fall in unbound bilirubin, unrelated to birthweight, gestational age, postnatal age, however, during these infusions the end-infusion F/A was greater than or equal to 3.0. We conclude that 1 g/kg of lipid emulsion infused over a 15-hr period has minimal risk of decreasing bilirubin binding in premature infants less than 30 wk gestation. As doses of 2 or 3 g/kg are used, these infants may be at risk of decreased bilirubin binding, due to elevations in the F/A ratio. Monitoring of the F/A ratio may identify infants at risk for decreased bilirubin binding during lipid infusion and provide guidelines for determining the appropriate lipid dose.