Role of long-chain fatty acids in the postnatal induction of genes coding for liver mitochondrial beta-oxidative enzymes

Breastfeeding-Related Health Benefits in Children and Mothers: Vital Organs Perspective

Breast milk (BM) is a constantly changing fluid that represents the primary source of nutrition for newborns. It is widely recognized that breastfeeding provides benefits for both the child and the mother, including a lower risk of ovarian and breast cancer, type 2 diabetes mellitus, decreased blood pressure, and more. In infants, breastfeeding has been correlated with a lower risk of infectious diseases, obesity, lower blood pressure, and decreased incidence of respiratory infections, diabetes, and asthma. Various factors, such as the baby's sex, the health status of the mother and child, the mother's diet, and the mode of delivery, can affect the composition of breast milk. This review focuses on the biological impact of the nutrients in BM on the development and functionality of vital organs to promote the benefit of health.

Hallmarks of the human intestinal microbiome on liver maturation and function

As one of the most metabolically complex systems in the body, the liver ensures multi-organ homeostasis and ultimately sustains life. Nevertheless, during early postnatal development, the liver is highly immature and takes about 2 years to acquire and develop almost all of its functions. Different events occurring at the environmental and cellular levels are thought to mediate hepatic maturation and function postnatally. The crosstalk between the liver, the gut and its microbiome has been well appreciated in the context of liver disease, but recent evidence suggests that the latter could also be critical for hepatic function under physiological conditions. The gut-liver crosstalk is thought to be mediated by a rich repertoire of microbial metabolites that can participate in a myriad of biological processes in hepatic sinusoids, from energy metabolism to tissue regeneration. Studies on germ-free animals have revealed the gut microbiome as a critical contributor in early hepatic programming, and this influence extends throughout life, mediating liver function and body homeostasis. In this seminar, we describe the microbial molecules that have a known effect on the liver and discuss how the gut microbiome and the liver evolve throughout life. We also provide insights on current and future strategies to target the gut microbiome in the context of hepatology research.

The health implications of birth by Caesarean section

Since the first mention of fetal programming of adult health and disease, a plethora of programming events in early life has been suggested. These have included intrauterine and postnatal events, but limited attention has been given to the potential contribution of the birth process to normal physiology and long-term health. Over the last 30 years a growing number of studies have demonstrated that babies born at term by vaginal delivery (VD) have significantly different physiology at birth to those born by Caesarean section (CS), particularly when there has been no exposure to labour, i.e. pre-labour CS (PLCS). This literature is reviewed here and the processes involved in VD that might programme post-natal development are discussed. Some of the effects of CS are short term, but longer term problems are also apparent. We suggest that VD initiates important physiological trajectories and the absence of this stimulus in CS has implications for adult health. There are a number of factors that might plausibly contribute to this programming, one of which is the hormonal surge or "stress response" of VD. Given the increasing incidence of elective PLCS, an understanding of the effects of VD on normal development is crucial.

Postnatal hepatic fatty acid oxidative capacity of preterm pigs receiving TPN does not differ from that of term pigs and is not affected by supplemental arachidonic and docosahexaenoic acids

To improve pediatric care of preterm infants, a better understanding of the metabolic processes associated with immaturity is needed. To this end, preterm and term pigs were delivered and administered either a control, a low-PUFA [0.3 and 0.6% of total lipids as docosahexaenoic acid (DHA) and arachidonic acid (AA), respectively], or a high-PUFA (5 and 11% of total lipids as DHA and AA, respectively) parenteral solution. Hepatic oxidative capacity and carnitine palmitoyltransferase (CPT) mRNA and activity in the presence or absence of malonyl-CoA were determined after 6 d. Oxidation of [1-(14)C]-palmitate or [1-(14)C]-glucose was similar in liver homogenates isolated from preterm and term pigs receiving the control solution. Oxidative capacity for either substrate did not differ with parenteral solution in preterm pigs, whereas in term pigs, glucose oxidation was 64% greater when the high-PUFA solution was administered relative to the control (P < 0.05). In preterm pigs, CPT I mRNA determined after 6 d of parenteral feeding were 1.5-fold greater (P < 0.05) than newborn estimates irrespective of solution administered, whereas CPT I mRNA were only greater for term pigs receiving the low- and high-PUFA solutions (66 and 115%, respectively; P < 0.05) relative to newborn estimates. Malonyl-CoA-sensitive CPT activity did not differ between preterm and term pigs or parenteral solution. Postnatal adaptations demonstrated by parenterally fed term neonates are present following preterm birth and are not improved by the provision of DHA and AA to parenteral solutions.

Clinical features and insulin regulation in infants with a syndrome of prolonged neonatal hyperinsulinism

OBJECTIVES

To characterize the clinical features and insulin regulation in infants with hypoglycemia due to prolonged neonatal hyperinsulinism.

STUDY DESIGN

Data were collected on 26 infants with hypoglycemia due to neonatal hyperinsulinism that later resolved. Acute insulin response (AIR) tests to calcium, leucine, glucose, and tolbutamide were performed in 11 neonates. Results were compared to children with genetic hyperinsulinism due to mutations of the adenosine triphosphate-dependent potassium (K(ATP)) channel and glutamate dehydrogenase (GDH).

RESULTS

Among the 26 neonates, there were significantly more males, small-for-gestational-age infants, and cesarean deliveries. Only 5 of the 26 had no identifiable risk factor. Hyperinsulinism was diagnosed at a median age of 13 days (range, 2 to 180 days) and resolved by a median age of 181 days (range, 18 to 403 days). Diazoxide was effective in 19 of the 21 neonates treated. In the 11 neonates tested, the AIRs to calcium, leucine, glucose, and tolbutamide resembled those in normal controls and differed from genetic hyperinsulinism due to K(ATP) channel and GDH mutations.

CONCLUSIONS

We define a syndrome of prolonged neonatal hyperinsulinism that is responsive to diazoxide, persists for several months, and resolves spontaneously. AIR tests suggest that both the K(ATP) channel and GDH have normal function.

Metabolic adaptation at birth

After birth, the neonate must make a transition from the assured continuous transplacental supply of glucose to a variable fat-based fuel economy. The normal infant born at term accomplishes this transition through a series of well-coordinated metabolic and hormonal adaptive changes. The patterns of adaptation in the preterm infant and the baby born after intrauterine growth restriction are, however, different to that of a full-term neonate, with the risk for former groups that there will be impaired counter-regulatory ketogenesis. There is much less precise linkage of neonatal insulin secretion to prevailing blood glucose concentrations. These patterns of metabolic adaptation are further influenced by feeding practices.

Control of gene expression by fatty acids

The last decade provided evidence that major (glucose, fatty acids, amino acids) or minor (iron, vitamin, etc.) dietary constituents regulated gene expression in an hormonal-independent manner. This review focuses on molecular mechanisms by which fatty acids control the expression genes encoding regulatory protein involved in their own metabolism. Nonesterified fatty acids or their CoA derivatives seem to be the main signals involved in the transcriptional effect of long-chain fatty acids. The effects of fatty acids are mediated either directly owing to their specific binding to various nuclear receptors (PPAR, LXR, HNF-4alpha) leading to changes in the trans-activating activity of these transcription factors, or indirectly as the result of changes in the abundance of regulatory transcription factors (SREBP-1c, ChREBP, etc.). The relative contribution of each transcription factor in fatty acid-induced positive or negative gene expression is discussed.

Natural progress of blood glucose in full-term low-grade low-birthweight infants

BACKGROUND

Although various authors have suggested the risk of hypoglycemia in practical medicine for low-birthweight infants is exaggerated, convincing evidence using recent definitions of hypoglycemia is not documented.

METHODS

To evaluate the risk of hypoglycemia in low grade low-birthweight infants (LGLBWI) (2100 g < birthweight < 2500 g) whose only abnormality is low-birthweight, whole blood glucose (BGw) was measured five times (0, 0.5, 1, and 4 h after birth and just before the first bottle feeding) in 49 LGLBWI and 38 normal birthweight infants.

RESULTS

Whole blood glucose was not lower in LGLBWI with a gestational age of 38-40 weeks (GT38LGLBWI) than in normal birthweight individuals with a gestational age of 38-40 weeks at each of the five measuring times. No case of GT38LGLBWI, not even in small for gestational age infants, required treatment for hypoglycemia. The BGw was significantly lower in 37-week gestational age LGLBWI than in GT38LGLBWI at 0.5 h and 1 h after birth (P < 0.05). However, in all cases with low BGw value (below 30 mg/dL at 1 h after birth), BGw value increased naturally to the normal level 1.5 h after birth. No symptoms of hypoglycemia were observed.

CONCLUSIONS

In the care of hypoglycemia in LGLBWI, attention should be paid first to gestational age, namely, tendency to prematurity. In this study, however, no hypoglycemia that required treatment was found among full-term normal LGLBWI, even those who were small for gestational age. Frequent blood glucose measurement for those infants is therefore unnecessary.

Nutritional factors that affect the postnatal metabolic adaptation of full-term small- and large-for-gestational-age infants

OBJECTIVE

To document metabolic adaptation to ex utero life in small- (SGA) and large-for-gestational-age (LGA) infants in relation to fetal nutrition and postnatal feeding practices.

METHODS

In a prospective study, 65 SGA (< or = second centile) and 39 LGA (> or = 98th centile) full-term infants were recruited. Anthropometry was performed within the first 48 hours. There was full support of breastfeeding and close clinical observation. Blood glucose and ketone body (kb) concentrations were measured prefeed for the first 7 postnatal days. Infants were exclusively breastfed (BF), breastfed with formula milk supplementation (FS), or exclusively formula milk fed (FF).

RESULTS

Within the SGA group, a measure of "thinness," the midarm circumference/head circumference ratio, was significantly correlated to the number of episodes of blood glucose < 2.00 mmol/L. Epoch (age at sampling) analysis in this group showed no difference in blood glucose levels across the different feeding groups but revealed a statistically significant greater kb concentration for infants who were exclusively breastfed. For SGA infants, the median peak kb concentration (peak kb) was significantly different for BF, FS, and FF groups. Multiple regression analysis for the SGA group demonstrated that peak kb concentration was negatively related to the volume of formula milk, independent of blood glucose levels and neonatal anthropometry. For LGA infants, low blood glucose levels were offset by kb concentrations equivalent to those observed in infants who were appropriate for gestational age.

CONCLUSION

Neonatal ability to generate kb when blood glucose values are low depends more on successful breastfeeding than on size for gestational age or neonatal nutritional status. Routine blood glucose monitoring of LGA infants with no additional risk factors is not necessary. Routine formula milk supplementation for LGA and SGA infants should not be recommended.

Hypoglycemia and the breastfed neonate

Healthy, full-term infants are functionally and metabolically programmed to make the transition from their intrauterine dependent environment to their extrauterine existence without the need for metabolic monitoring or interference with the natural breastfeeding process. Full-term infants are equipped with homeostatic mechanisms that preserve adequate energy substrate to the brain and other vital organs. Thermal stability and early, properly guided, frequent, exclusive breastfeeding are the keys to success. Thus, routine screening for blood glucose concentrations or feeding sugar water is not necessary and potentially counterproductive to the establishment of a healthy mother-infant dyad.

Fatty acid import into mitochondria

The mitochondrial carnitine system plays an obligatory role in beta-oxidation of long-chain fatty acids by catalyzing their transport into the mitochondrial matrix. This transport system consists of the malonyl-CoA sensitive carnitine palmitoyltransferase I (CPT-I) localized in the mitochondrial outer membrane, the carnitine:acylcarnitine translocase, an integral inner membrane protein, and carnitine palmitoyltransferase II localized on the matrix side of the inner membrane. Carnitine palmitoyltransferase I is subject to regulation at the transcriptional level and to acute control by malonyl-CoA. The N-terminal domain of CPT-I is essential for malonyl-CoA inhibition. In liver CPT-I activity is also regulated by changes in the enzyme's sensitivity to malonyl-CoA. As fluctuations in tissue malonyl-CoA content are parallel with changes in acetyl-CoA carboxylase activity, which in turn is under the control of 5'-AMP-activated protein kinase, the CPT-I/malonyl-CoA system is part of a fuel sensing gauge, turning off and on fatty acid oxidation depending on the tissue's energy demand. Additional mechanism(s) of short-term control of CPT-I activity are emerging. One proposed mechanism involves phosphorylation/dephosphorylation dependent direct interaction of cytoskeletal components with the mitochondrial outer membrane or CPT-I. We have proposed that contact sites between the outer and inner mitochondrial membranes form a microenvironment which facilitates the carnitine transport system. In addition, this system includes the long-chain acyl-CoA synthetase and porin as components.

Essential fatty acid metabolism in the micropremie

Lipids are structural components of all tissues and are indispensable for cell membrane synthesis. The brain, retina, and other neural tissues are particularly rich in LCPUFAs, affecting neural structural development and function. LCPUFAs serve also as specific precursors for eicosanoid production (prostaglandins, prostacyclins, thromboxanes, and leukotrienes). These autocrine and paracrine mediators are powerful regulators of numerous cell and tissue functions (e.g., thrombocyte aggregation, inflammatory reactions, and leukocyte functions, vasoconstriction and vasodilatation, blood pressure, bronchial constriction, uterine contraction). Dietary lipid intake affects cholesterol metabolism at an early age and is associated with cardiovascular morbidity and mortality in later life. Over recent years, the role of fatty acids in modulating signal transduction and regulating gene expression have been described, emphasizing the complex of fatty acid effects. Dietary fatty acids, especially LCPUFA, can have significant effects in the modulation of developmental processes affecting the clinical outcomes of extremely premature infants.

Essential fatty acids in early life: structural and functional role

Essential fatty acids (EFA) are structural components of all tissues and are indispensable for cell membrane synthesis; the brain, retina and other neural tissues are particularly rich in long-chain polyunsaturated fatty acids (LCPUFA). These fatty acids serve as specific precursors for eicosanoids that regulate numerous cell and organ functions. Results from animal and recent human studies support the essential nature of n-3 EFA in addition to the well-established role of n-6 EFA for human subjects, particularly in early life. The most significant effects relate to neural development and maturation of sensory systems. Recent studies using stable-isotope-labelled tracers demonstrate that even preterm infants are able to form arachidonic acid (AA) and docosahexaenoic acid (DHA), but that synthesis is extremely low. Intracellular fatty acids or their metabolites regulate transcriptional activation of gene expression during adipocyte differentiation, and retinal and nervous system development. Regulation of gene expression by LCPUFA occurs at the transcriptional level and is mediated by nuclear transcription factors activated by fatty acids. These nuclear receptors are part of the steroid hormone receptor family. Two types of polyunsaturated fatty acid responsive transcription factors have been characterized, the peroxisome proliferator-activated receptor (PPAR) and the hepatic nuclear factor 4alpha. DHA also has significant effects on photoreceptor membranes involved in the signal transduction process, rhodopsin activation, and rod and cone development. Comprehensive clinical studies have shown that dietary supplementation with marine oil or single-cell oils, sources of LCPUFA, results in increased blood levels of DHA and AA, as well as an associated improvement in visual function in formula-fed premature infants to match that of human milk-fed infant. Recent clinical trials convincingly support LCPUFA supplementation of preterm infant formulations and possibly term formula to mimic human milk composition.

Regulation of gene expression by fatty acids

Long-chain fatty acids regulate the transcription of several genes encoding proteins involved in energetic metabolism. This review discusses the relative contribution of free fatty acids or their coenzyme A ester as metabolite signals and the possibility that the control of gene transcription could be independent of the activation of peroxisome proliferator-activated receptors.