The metabolic consequences of prematurity

Pulsatile Leucine Administration during Continuous Enteral Feeding Enhances Skeletal Muscle Mechanistic Target of Rapamycin Complex 1 Signaling and Protein Synthesis in a Preterm Piglet Model

BACKGROUND

Continuous feeding does not elicit an optimal anabolic response in skeletal muscle but is required for some preterm infants. We reported previously that intermittent intravenous pulses of leucine (Leu; 800 μmol Leu·kg-1·h-1 every 4 h) to continuously fed pigs born at term promoted mechanistic target of rapamycin complex 1 (mTORC1) activation and protein synthesis in skeletal muscle.

OBJECTIVES

The aim was to determine the extent to which intravenous Leu pulses activate mTORC1 and enhance protein synthesis in the skeletal muscle of continuously fed pigs born preterm.

METHODS

Pigs delivered 10 d preterm was advanced to full oral feeding >4 d and then assigned to 1 of the following 4 treatments for 28 h: 1) ALA (continuous feeding; pulsed with 800 μmol alanine·kg-1·h-1 every 4 h; n = 8); 2) L1× (continuous feeding; pulsed with 800 μmol Leu·kg-1·h-1 every 4 h; n = 7); 3) L2× (continuous feeding; pulsed with 1600 μmol Leu·kg-1·h-1 every 4 h; n = 8); and 4) INT (intermittent feeding every 4 h; supplied with 800 μmol alanine·kg-1 per feeding; n = 7). Muscle protein synthesis rates were determined with L-[2H5-ring]Phenylalanine. The activation of insulin, amino acid, and translation initiation signaling pathways were assessed by Western blot.

RESULTS

Peak plasma Leu concentrations were 134% and 420% greater in the L2× compared to the L1× and ALA groups, respectively (P < 0.01). Protein synthesis was greater in the L2× than in the ALA and L1× groups in both the longissimus dorsi and gastrocnemius muscles (P < 0.05) but not different from the INT group (P > 0.10). Amino acid signaling upstream and translation initiation signaling downstream of mTORC1 largely corresponded to the differences in protein synthesis.

CONCLUSIONS

Intravenous Leu pulses potentiate mTORC1 activity and protein synthesis in the skeletal muscles of continuously fed preterm pigs, but the amount required is greater than in pigs born at term.

Blood-Biomarkers for Glucose Metabolism in Preterm Infants

This was an exploratory, prospective, longitudinal, cohort study that aimed to establish "healthy" reference levels related to growth parameters and glucose metabolites in preterm infants. This was conducted to further investigate growth and metabolic disturbances potentially related to neonatal illness. The study sample consisted of 108 preterm infants born before 32 weeks in 2018-2019 in the Capital Region of Denmark. Repetitive blood samples were acquired at the neonatal wards, while clinical data were obtained from the regional hospital medical record system. Thirty-four "healthy" preterm infants (31%) were identified. The "ill" infants were divided into four subgroups dependent on gestational age and small for gestational age. Reference levels for the growth parameters and metabolic biomarkers glucose, albumin, and adiponectin, and two glucose control indicators, glycated albumin and fructosamine, were determined for the "healthy" and "ill" subgroups. The "ill" extremely preterm infants had increased glucose levels (mean difference 0.71 mmol/L, 95% CI 0.23; 1.18 mmol/L) and glycated albumin (corrected; %) (mean difference 0.92 mmol/L, 95% CI 0.38 mmol/L;1.47 mmol/L) compared to the "healthy" infants. In "ill" extremely preterm infants and "ill" very preterm infants born small for gestational age, levels of biomarkers containing proteins were decreased. In the "Ill" extremely preterm infants and infants born small for gestational age, postnatal growth was continuously decreased throughout the postconceptional period. The short-term glucose-control indicator, glycated albumin (corrected; %), reflected well the high glucose levels due to its correction for the depleted plasma-protein pool.

LRP6 Bidirectionally Regulates Insulin Sensitivity through Insulin Receptor and S6K Signaling in Rats with CG-IUGR

OBJECTIVE

Intrauterine growth restriction followed by postnatal catch-up growth (CG-IUGR) increases the risk of insulin resistance-related diseases. Low-density lipoprotein receptor-related protein 6 (LRP6) plays a substantial role in glucose metabolism. However, whether LRP6 is involved in the insulin resistance of CG-IUGR is unclear. This study aimed to explore the role of LRP6 in insulin signaling in response to CG-IUGR.

METHODS

The CG-IUGR rat model was established via a maternal gestational nutritional restriction followed by postnatal litter size reduction. The mRNA and protein expression of the components in the insulin pathway, LRP6/β-catenin and mammalian target of rapamycin (mTOR)/S6 kinase (S6K) signaling, was determined. Liver tissues were immunostained for the expression of LRP6 and β-catenin. LRP6 was overexpressed or silenced in primary hepatocytes to explore its role in insulin signaling.

RESULTS

Compared with the control rats, CG-IUGR rats showed higher homeostasis model assessment for insulin resistance (HOMA-IR) index and fasting insulin level, decreased insulin signaling, reduced mTOR/S6K/ insulin receptor substrate-1 (IRS-1) serine307 activity, and decreased LRP6/β-catenin in the liver tissue. The knockdown of LRP6 in hepatocytes from appropriate-for-gestational-age (AGA) rats led to reductions in insulin receptor (IR) signaling and mTOR/S6K/IRS-1 serine307 activity. In contrast, LRP6 overexpression in hepatocytes of CG-IUGR rats resulted in elevated IR signaling and mTOR/S6K/IRS-1 serine307 activity.

CONCLUSION

LRP6 regulated the insulin signaling in the CG-IUGR rats via two distinct pathways, IR and mTOR-S6K signaling. LRP6 may be a potential therapeutic target for insulin resistance in CG-IUGR individuals.

Early-life determinants of childhood plasma insulin levels: implications for primordial prevention of diabetes

BACKGROUND

We earlier reported prematurity as an independent risk factor for elevated insulin levels. Investigation is still lacking on the influence of prenatal and perinatal factors on childhood insulin levels.

METHODS

In this secondary analysis of a prospective birth cohort, plasma insulin levels were measured at birth and early childhood. Regression models identified early-life factors associated with the primary outcome: log-transformed childhood plasma insulin levels.

RESULTS

One thousand one hundred and nine children had insulin levels at birth and 825 at both time points. Compared to term, preterm infants had higher plasma insulin levels (geometric mean) at birth (612, 95% CI 552-679 vs. 372, 95% CI 345-402 pmol/ml) and in early childhood (547, 95% CI 494-605 vs. 445, 95% CI 417-475 pmol/ml). Factors associated with higher early childhood insulin levels included higher insulin level at birth, black race, female sex, maternal smoking during pregnancy, maternal perceived stress, in utero drug exposure, maternal pregestational diabetes mellitus, and maternal preconception overweight and obesity.

CONCLUSIONS

In this high-risk US birth cohort, we identified multiple prenatal and perinatal risk factors for higher early childhood insulin levels, in addition to prematurity. These findings lend support to primordial preventive strategies for diabetes mellitus.

IMPACT

In this secondary analysis of a large prospective study from a high-risk racially diverse cohort, we identify biological and social factors that contribute to elevated levels of plasma insulin in early childhood. Our study also investigates factors affecting plasma insulin in preterm infants along with comorbidities commonly seen during the neonatal intensive care stay. Our work reaffirms the importance of Developmental Origins of Health and Disease with regards to in utero programming of insulin levels. Our work supports the possibility that primordial preventive strategies for diabetes mellitus in high-risk populations may need to begin as early as the prenatal period.

Prematurity blunts the insulin- and amino acid-induced stimulation of translation initiation and protein synthesis in skeletal muscle of neonatal pigs

Extrauterine growth restriction in premature infants is largely attributed to reduced lean mass accretion and is associated with long-term morbidities. Previously, we demonstrated that prematurity blunts the feeding-induced stimulation of translation initiation signaling and protein synthesis in skeletal muscle of neonatal pigs. The objective of the current study was to determine whether the blunted feeding response is mediated by reduced responsiveness to insulin, amino acids, or both. Pigs delivered by cesarean section preterm (PT; 103 days, n = 25) or at term (T; 112 days, n = 26) were subject to euinsulinemic-euaminoacidemic-euglycemic (FAST), hyperinsulinemic-euaminoacidemic-euglycemic (INS), or euinsulinemic-hyperaminoacidemic-euglycemic (AA) clamps four days after delivery. Indices of mechanistic target of rapamycin complex 1 (mTORC1) signaling and fractional protein synthesis rates were measured after 2 h. Although longissimus dorsi (LD) muscle protein synthesis increased in response to both INS and AA, the increase was 28% lower in PT than in T. Upstream of mTORC1, Akt phosphorylation, an index of insulin signaling, was increased with INS but was 40% less in PT than in T. The abundances of mTOR·RagA and mTOR·RagC, indices of amino acid signaling, increased with AA but were 25% less in PT than in T. Downstream of mTORC1, eIF4E·eIF4G abundance was increased by both INS and AA but attenuated by prematurity. These results suggest that preterm birth blunts both insulin- and amino acid-induced activation of mTORC1 and protein synthesis in skeletal muscle, thereby limiting the anabolic response to feeding. This anabolic resistance likely contributes to the high prevalence of extrauterine growth restriction in prematurity.NEW & NOTEWORTHY Extrauterine growth faltering is a major complication of premature birth, but the underlying cause is poorly understood. Our results demonstrate that preterm birth blunts both the insulin-and amino acid-induced activation of mTORC1-dependent translation initiation and protein synthesis in skeletal muscle, thereby limiting the anabolic response to feeding. This anabolic resistance likely contributes to the reduced accretion of lean mass and extrauterine growth restriction of premature infants.

Trends and Correlates of Overweight among Pre-School Age Children, Adolescent Girls, and Adult Women in South Asia: An Analysis of Data from Twelve National Surveys in Six Countries over Twenty Years

Overweight has become a global pandemic and is associated with a rise in diet-related non-communicable diseases and associated co-morbidities. Most of the world’s undernourished people live in South Asia, yet the number of overweight and obese individuals in this region is growing. This study explores trends and correlates of overweight among pre-school age children, adolescent girls, and adult women in South Asia. Using pooled data from 12 national surveys in six countries, generalized linear mixed models were run to analyze relationships. Overweight children had significantly higher odds than non-overweight children of having an overweight mother (Adjusted Odds Ratio: 1.34, p < 0.01). Overweight adolescent girls were more likely to come from a wealthier household (Adjusted Prevalence Ratio (APR): 2.46, p < 0.01) in an urban area (1.74, p < 0.01), and have formal education (1.22, p < 0.01), compared to non-overweight girls. Similar relationships were seen among overweight vs. non-overweight adult women. In Bangladesh, India, and Nepal, overweight among girls and women increased over time, while differentials associated with household wealth, urban residence, and formal education attenuated over time. Overweight and obesity are becoming more prevalent across South Asia in a context of persisting undernutrition. Once a condition of the wealthier, more educated and urban, rates of overweight are increasing among poorer, less educated, and rural women. This requires immediate attention to ‘multi-use’ policies and programmes.

Prenatal exposure to endocrine disrupting chemicals and risk of being born small for gestational age: Pooled analysis of seven European birth cohorts

BACKGROUND AND AIMS

There is evidence that endocrine disrupting chemicals (EDCs) have developmental effects at environmental concentrations. We investigated whether some EDCs are associated with the adverse birth outcome Small for Gestational Age (SGA).

METHODS

We used PCB 153, p,p'-DDE, HCB, PFOS and PFOA measured in maternal, cord blood or breast milk samples of 5446 mother-child pairs (subset of 693 for the perfluorinated compounds) from seven European birth cohorts (1997-2012). SGA infants were those with birth weight below the 10th percentile for the norms defined by gestational age, country and infant's sex. We modelled the association between measured or estimated cord serum EDC concentrations and SGA using multiple logistic regression analyses. We explored effect modification by child's sex and maternal smoking during pregnancy.

RESULTS

Among the 5446 newborns, 570 (10.5%) were SGA. An interquartile range (IQR) increase in PCB 153 was associated with a modestly increased risk of SGA (odds ratio (OR) of 1.05 [95% CI: 1.04-1.07]) that was stronger in girls (OR of 1.09 [95% CI: 1.04-1.14]) than in boys (OR of 1.03 [95% CI: 1.03-1.04]) (p-interaction = 0.025). For HCB, we found a modestly increased odds of SGA in girls (OR of 1.04 [95% CI: 1.01-1.07] per IQR increase), and an inverse association in boys (OR of 0.90 [95% CI: 0.85-0.95]) (p-interaction = 0.0003). Assessment of the HCB-sex-smoking interaction suggested that the increased odds of SGA associated with HCB exposure was only in girls of smoking mothers (OR of 1.18 [95% CI: 1.11-1.25]) (p-interaction = 0.055). Higher concentrations of PFOA were associated with greater risk of SGA (OR of 1.64 [95% CI: 0.97-2.76]). Elevated PFOS levels were associated with increased odds of SGA in newborns of mothers who smoked during pregnancy (OR of 1.63 [95% CI: 1.02-2.59]), while an inverse association was found in those of non-smoking mothers (OR of 0.66 [95% CI: 0.61-0.72]) (p-interaction = 0.0004). No significant associations were found for p,p'-DDE.

CONCLUSIONS

Prenatal environmental exposure to organochlorine and perfluorinated compounds with endocrine disrupting properties may contribute to the prevalence of SGA. We found indication of effect modification by child's sex and smoking during pregnancy. The direction of the associations differed by chemical and these effect modifiers, suggesting diverse mechanisms of action and biological pathways.

Losing the war against obesity: the need for a developmental perspective

Developed countries are struggling to control epidemics of obesity and related chronic diseases; thus, we can expect only limited success from applying the current approaches to the developing world, which is experiencing an alarming increase in such disorders. This failure results in part from the fact that our focus on adult life-styles, although important, ignores data that suggest that biological and cultural factors operating early in life affect adult health status. To stem the rising obesity burden in developing countries, scientists and policy-makers must address obesity-promoting factors from early development to adulthood.

Breast-feeding and childhood hospitalizations for infections

BACKGROUND

Infectious disease is a leading cause of morbidity and hospitalization for infants and children. During infancy, breast-feeding protects against infectious diseases, particularly respiratory infections, gastrointestinal infections, and otitis media. Little is known about the longer-term impact of breast-feeding on infectious disease in children.

METHODS

We investigated the relationship between infant feeding and childhood hospitalizations from respiratory and gastrointestinal infections in a population-based birth cohort of 8327 children born in 1997 and followed for 8 years. The main outcomes were public hospital admissions for respiratory infections, gastrointestinal infections, and all infectious diseases. Cox regression was used to assess time to first hospitalization.

RESULTS

Breast-feeding only (no formula-feeding) for 3 or more months was associated with a lower risk of hospital admission in the first 6 months of life for respiratory infections (hazard ratio = 0.64 [95% confidence interval = 0.42-0.97]), gastrointestinal infections (0.51 [0.25-1.05]), and any infection (0.61 [0.44-0.85]), adjusted for sex, type of hospital at birth, and household income. Partial breast-feeding (both breast-feeding and formula-feeding) in the first 3 months also reduced hospitalizations from infections but with smaller effect sizes. Beyond 6 months of age, there was no association between breast-feeding status at 3 months and hospitalization for infectious disease.

CONCLUSIONS

Giving breast milk and no formula for at least 3 months substantially reduced hospital admissions for many infectious diseases in the first 6 months of life, when children are most vulnerable.

[Clinical predictors of growth response in the first year of treatment with a fixed dose of growth hormone in children born small for gestational age]

OBJECTIVE

To identify clinical predictors associated with catch-up growth in the first year of treatment with somatropin (rhGH) in a group of children born small for gestational age (SGA).

SUBJECTS AND METHODS

Thirty nine children who have been on rhGH therapy for at least one year (0.33 mg/kg/week) were evaluated. The clinical parameters analyzed were chronological age (CA), bone age (BA), target height and standard deviations scores (SDS) of birth weight and length, height, weight and growth rate.

RESULTS

rhGH therapy was associated with a first year height increment of 0.67 SDS (p < 0.01). BA and birth weight SDS were predictive of growth response, with statistical difference in height SDS variation between prepubertal and pubertal subgroups (p = 0.016).

CONCLUSION

These data show a significant growth response with a fixed rhGH dose, those children who started rhGH in prepubertal ages presented the best outcomes.

Reduction of IGF-binding protein-3 as a potential marker of intra-uterine growth restriction

BACKGROUND

Growth factor-binding proteins influence the growth of infants starting in utero. Adaptation of the fetus to an adverse uterine environment is associated with changes in the growth hormone-growth factor-insulin axis.

AIMS

To evaluate serum levels of IGF-I and IGFBP-3 in small and appropriate for gestational age newborn infants.

METHODS

Fifty-four newborn infants, small (SGA, n=28) or appropriate (AGA, n=26) for gestational age were matched by gestational age and sex. Blood was collected on the first day of life, and anthropometric measurements were taken at birth. The serum levels of IGF-I and IGFBP-3 were compared, and correlated with the anthropometric measurements.

RESULTS

On the first day of life, mean serum IGFBP-3 levels were significantly lower in SGA babies and correlated with weight, length, head circumference, and ponderal index (weight/length 3) (P<0.0001). In contrast, no associations were found between IGF-I serum levels and these anthropometric measurements.

CONCLUSION

Our data show that SGA babies have significantly reduced IGFBP-3 concentrations at birth.

Physical growth of preterm girls with visual impairment

The aim of this study was to estimate pubertal age and to assess the level of physical development of preterm girls with defective vision. The study material - anthropometric data (body height and weight, BMI) and information on the age of menarche were collected from 155 subjects with defective vision (partially sighted and blind). Median age at menarche was estimated by probit analysis. The girls, ranging in age from 7-18 years, attended Centers for Blind and Partially Sighted Children in Wroclaw and Cracow (Poland). 22% of the subjects were prematurely born, were born with low birth mass and their sight defect diagnosed as retinopathy due to prematurity (ROP). The girls with ophthalmic impairments were shorter and lighter than their age peers from the reference data. Blind girls reached pubertal age 2 months earlier than the partially sighted (Me=13.31 and Me=13.44) and, the preterm subjects entered puberty 6 months earlier than the full-term girls, irrespective of degree of defect (Me=12.93 and Me=13.42, respectively). The results suggest that earlier puberty is associated with visual impairment. The results show also that irrespective of the degree of defect, preterm girls reach menarche significantly earlier than those who were full-term. It seems possible that mechanisms responsible for earlier puberty in the preterm subjects and with low body mass play an important a role in sexual maturation in girls with sight dysfunction. There appears to be a need to pursue further studies in this sphere.

Clinical-radiological features of fractures in premature infants--a review

Premature infants are more vulnerable to bone fractures than term infants for numerous reasons, directly or indirectly related to prematurity. Although the reported incidence of fractures in this vulnerable population is somewhat inconsistent, the increased risk is clear. Metabolic disorders, genetic disease, accidental trauma, and non-accidental injury can all account for fractures in premature infants, so that determining the etiology is of importance. This increased risk does not appear to continue into childhood. Thus, most of these fractures would be found in children <3 years of age, often within the first year of life. Unfortunately, this is the same age group in which the majority of non-accidental injury (NAI) cases, frequently presenting with fractures, are seen. Further confounding the diagnosis is the possibility of previously undiagnosed fractures from trauma during delivery, and fractures due to bone weakening by metabolic diseases. A multi-dimensional approach using a combination of diagnostic procedures is necessary to properly identify the location of the fractures, the bone structure and characteristics, and the history with regards to family situation and medical treatment. This paper reviews the potential factors related to fractures in premature infants and the differential diagnoses of child abuse fractures.

Feeding preterm infants after hospital discharge: a commentary by the ESPGHAN Committee on Nutrition

Survival of small premature infants has markedly improved during the last few decades. These infants are discharged from hospital care with body weight below the usual birth weight of healthy term infants. Early nutrition support of preterm infants influences long-term health outcomes. Therefore, the ESPGHAN Committee on Nutrition has reviewed available evidence on feeding preterm infants after hospital discharge. Close monitoring of growth during hospital stay and after discharge is recommended to enable the provision of adequate nutrition support. Measurements of length and head circumference, in addition to weight, must be used to identify those preterm infants with poor growth that may need additional nutrition support. Infants with an appropriate weight for postconceptional age at discharge should be breast-fed when possible. When formula-fed, such infants should be fed regular infant formula with provision of long-chain polyunsaturated fatty acids. Infants discharged with a subnormal weight for postconceptional age are at increased risk of long-term growth failure, and the human milk they consume should be supplemented, for example, with a human milk fortifier to provide an adequate nutrient supply. If formula-fed, such infants should receive special postdischarge formula with high contents of protein, minerals and trace elements as well as an long-chain polyunsaturated fatty acid supply, at least until a postconceptional age of 40 weeks, but possibly until about 52 weeks postconceptional age. Continued growth monitoring is required to adapt feeding choices to the needs of individual infants and to avoid underfeeding or overfeeding.

Environmental influences during development and their later consequences for health and disease: implications for the interpretation of empirical studies

Early experience has a particularly great effect on most organisms. Normal development may be disrupted by early environmental influences; individuals that survive have to cope with the damaging consequences. Additionally, the responses required to cope with environmental challenges in early life may have long-term effects on the adult organism. A further set of processes, those of developmental plasticity, may induce a phenotype that is adapted to the adult environment predicted by the conditions of early life. A mismatch between prediction and subsequent reality can cause severe health problems in those human societies where economic circumstances and nutrition are rapidly improving. Understanding the underlying mechanisms of plasticity is, therefore, clinically important. However, to conduct research in this area, developmental plasticity must be disentangled from disruption and the adverse long-term effects of coping. The paper reviews these concepts and explores ways in which such distinctions may be made in practice.