Effects of L-carnitine supplementation on respiratory distress syndrome development and prognosis in premature infants: A single blind randomized controlled trial

Emerging role of metabolic reprogramming in hyperoxia-associated neonatal diseases

Oxygen therapy is common during the neonatal period to improve survival, but it can increase the risk of oxygen toxicity. Hyperoxia can damage multiple organs and systems in newborns, commonly causing lung conditions such as bronchopulmonary dysplasia and pulmonary hypertension, as well as damage to other organs, including the brain, gut, and eyes. These conditions are collectively referred to as newborn oxygen radical disease to indicate the multi-system damage caused by hyperoxia. Hyperoxia can also lead to changes in metabolic pathways and the production of abnormal metabolites through a process called metabolic reprogramming. Currently, some studies have analyzed the mechanism of metabolic reprogramming induced by hyperoxia. The focus has been on mitochondrial oxidative stress, mitochondrial dynamics, and multi-organ interactions, such as the lung-gut, lung-brain, and brain-gut axes. In this article, we provide an overview of the major metabolic pathway changes reported in hyperoxia-associated neonatal diseases and explore the potential mechanisms of metabolic reprogramming. Metabolic reprogramming induced by hyperoxia can cause multi-organ metabolic disorders in newborns, including abnormal glucose, lipid, and amino acid metabolism. Moreover, abnormal metabolites may predict the occurrence of disease, suggesting their potential as therapeutic targets. Although the mechanism of metabolic reprogramming caused by hyperoxia requires further elucidation, mitochondria and the gut-lung-brain axis may play a key role in metabolic reprogramming.

Guidelines for parenteral nutrition in preterm infants: The American Society for Parenteral and Enteral Nutrition

BACKGROUND

Parenteral nutrition (PN) is prescribed for preterm infants until nutrition needs are met via the enteral route, but unanswered questions remain regarding PN best practices in this population.

METHODS

An interdisciplinary committee was assembled to answer 12 questions concerning the provision of PN to preterm infants. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) process was used. Questions addressed parenteral macronutrient doses, lipid injectable emulsion (ILE) composition, and clinically relevant outcomes, including PNALD, early childhood growth, and neurodevelopment. Preterm infants with congenital gastrointestinal disorders or infants already diagnosed with necrotizing enterocolitis or PN-associated liver disease (PNALD) at study entry were excluded.

RESULTS

The committee reviewed 2460 citations published between 2001 and 2023 and evaluated 57 clinical trials. For most questions, quality of evidence was very low. Most analyses yielded no significant differences between comparison groups. A multicomponent oil ILE was associated with a reduction in stage 3 or higher retinopathy of prematurity (ROP) compared to an ILE containing 100% soybean oil. For all other questions, expert opinion was provided.

CONCLUSION

Most clinical outcomes were not significantly different between comparison groups when evaluating timing of PN initiation, amino acid dose, and ILE composition. Future clinical trials should standardize outcome definitions to permit statistical conflation of data, thereby permitting more evidence based recommendations in future guidelines. This guideline has been approved by the ASPEN 2022-2023 Board of Directors.

Upregulating carnitine palmitoyltransferase 1 attenuates hyperoxia-induced endothelial cell dysfunction and persistent lung injury

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a chronic lung disease in premature infants that may cause long-term lung dysfunction. Accumulating evidence supports the vascular hypothesis of BPD, in which lung endothelial cell dysfunction drives this disease. We recently reported that endothelial carnitine palmitoyltransferase 1a (Cpt1a) is reduced by hyperoxia, and that endothelial cell-specific Cpt1a knockout mice are more susceptible to developing hyperoxia-induced injury than wild type mice. Whether Cpt1a upregulation attenuates hyperoxia-induced endothelial cell dysfunction and lung injury remains unknown. We hypothesized that upregulation of Cpt1a by baicalin or L-carnitine ameliorates hyperoxia-induced endothelial cell dysfunction and persistent lung injury.

METHODS

Lung endothelial cells or newborn mice (< 12 h old) were treated with baicalin or L-carnitine after hyperoxia (50% and 95% O2) followed by air recovery.

RESULTS

We found that incubation with L-carnitine (40 and 80 mg/L) and baicalin (22.5 and 45 mg/L) reduced hyperoxia-induced apoptosis, impaired cell migration and angiogenesis in cultured lung endothelial cells. This was associated with increased Cpt1a gene expression. In mice, neonatal hyperoxia caused persistent alveolar and vascular simplification in a concentration-dependent manner. Treatment with L-carnitine (150 and 300 mg/kg) and baicalin (50 and 100 mg/kg) attenuated neonatal hyperoxia-induced alveolar and vascular simplification in adult mice. These effects were diminished in endothelial cell-specific Cpt1a knockout mice.

CONCLUSIONS

Upregulating Cpt1a by baicalin or L-carnitine ameliorates hyperoxia-induced lung endothelial cell dysfunction, and persistent alveolar and vascular simplification. These findings provide potential therapeutic avenues for using L-carnitine and baicalin as Cpt1a upregulators to prevent persistent lung injury in premature infants with BPD.

The Role of l-Carnitine in Mitochondria, Prevention of Metabolic Inflexibility and Disease Initiation

Mitochondria control cellular fate by various mechanisms and are key drivers of cellular metabolism. Although the main function of mitochondria is energy production, they are also involved in cellular detoxification, cellular stabilization, as well as control of ketogenesis and glucogenesis. Conditions like neurodegenerative disease, insulin resistance, endocrine imbalances, liver and kidney disease are intimately linked to metabolic disorders or inflexibility and to mitochondrial dysfunction. Mitochondrial dysfunction due to a relative lack of micronutrients and substrates is implicated in the development of many chronic diseases. l-carnitine is one of the key nutrients for proper mitochondrial function and is notable for its role in fatty acid oxidation. l-carnitine also plays a major part in protecting cellular membranes, preventing fatty acid accumulation, modulating ketogenesis and glucogenesis and in the elimination of toxic metabolites. l-carnitine deficiency has been observed in many diseases including organic acidurias, inborn errors of metabolism, endocrine imbalances, liver and kidney disease. The protective effects of micronutrients targeting mitochondria hold considerable promise for the management of age and metabolic related diseases. Preventing nutrient deficiencies like l-carnitine can be beneficial in maintaining metabolic flexibility via the optimization of mitochondrial function. This paper reviews the critical role of l-carnitine in mitochondrial function, metabolic flexibility and in other pathophysiological cellular mechanisms.

The effects of L-carnitine supplementation on inflammatory factors, oxidative stress, and clinical outcomes in patients with sepsis admitted to the intensive care unit (ICU): study protocol for a double blind, randomized, placebo-controlled clinical trial

BACKGROUND

Sepsis is a common cause for admission to the intensive care unit (ICU), and its incidence has been increasing. It is associated with a significant increase in serum inflammatory biomarkers such as C-reactive protein (CRP) and cytokines such as interleukin 1 (IL-1), IL-6, and tumor necrosis factor (TNF). Sepsis is also associated with pathophysiological changes that include fluid accumulation in the lungs, eventually leading to acute respiratory distress syndrome (ARDS), tissue edema, hypotension, and acute kidney injury (AKI). Conventional therapies include antibiotics, but these may have important adverse effects, so novel therapeutic approaches are required. In animal studies, L-carnitine improves antioxidant status, and in some clinical trials, it has been shown to reduce inflammation. It has also been shown to improve respiratory distress and help maintain coenzyme A homeostasis, metabolic flexibility, promoting the normal function of the tricarboxylic acid (TCA) cycle, and oxidation of fatty acids by peroxisomes. We aim to determine the effects of very high doses of L-carnitine on inflammatory factors, oxidative stress, and clinical outcomes of patients with sepsis in ICU.

METHOD AND DESIGN

In this double-blind, randomized controlled clinical trial, we will use block randomization of 60 patients with sepsis, aged between 20 and 65 years from Al-Zahra Hospital, Isfahan, Iran. The intervention group (n = 30) will receive three capsules of L-carnitine (each capsule contains 1000 mg L-carnitine; totally 3000 mg/day) for 7 days, and a control group (n = 30) will receive a placebo with the same dose and for the same duration in addition to usual care. At baseline, scores for clinical and nutritional status (Acute Physiology and Chronic Health Evaluation II (APACHE II), Sequential Organ Failure Assessment (SOFA), Quick SOFA (qSOFA), and NUTRIC Score) will be assessed. At beginning and end point of the study, inflammatory markers (CRP, erythrocyte sedimentation rate (ESR)), oxidative stress status (total oxidative stress (TOS), total antioxidant capacity (TAC)), and clinical variables will be evaluated also. The mortality rate will be assessed within 28 days of the beginning of the intervention.

DISCUSSION

Because of the anti-inflammatory and antioxidant properties of L-carnitine, it is possible that using a high dose of 3000 mg daily of this nutritional supplement may reduce inflammation and oxidative stress and improve subsequent mortality of critically ill patients with sepsis.

TRIAL REGISTRATION

Iranian Registry of Clinical Trials IRCT20201129049534N1 . Registered on 2 May 2021.

Metabolic dysregulation in bronchopulmonary dysplasia: Implications for identification of biomarkers and therapeutic approaches

Bronchopulmonary dysplasia (BPD) is a common chronic lung disease in premature infants. Accumulating evidence shows that dysregulated metabolism of glucose, lipids and amino acids are observed in premature infants. Animal and cell studies demonstrate that abnormal metabolism of these substrates results in apoptosis, inflammation, reduced migration, abnormal proliferation or senescence in response to hyperoxic exposure, and that rectifying metabolic dysfunction attenuates neonatal hyperoxia-induced alveolar simplification and vascular dysgenesis in the lung. BPD is often associated with several comorbidities, including pulmonary hypertension and neurodevelopmental abnormalities, which significantly increase the morbidity and mortality of this disease. Here, we discuss recent progress on dysregulated metabolism of glucose, lipids and amino acids in premature infants with BPD and in related in vivo and in vitro models. These findings suggest that metabolic dysregulation may serve as a biomarker of BPD and plays important roles in the pathogenesis of this disease. We also highlight that targeting metabolic pathways could be employed in the prevention and treatment of BPD.

Organic Cation Transporters in the Lung-Current and Emerging (Patho)Physiological and Pharmacological Concepts

Organic cation transporters (OCT) 1, 2 and 3 and novel organic cation transporters (OCTN) 1 and 2 of the solute carrier 22 (SLC22) family are involved in the cellular transport of endogenous compounds such as neurotransmitters, l-carnitine and ergothioneine. OCT/Ns have also been implicated in the transport of xenobiotics across various biological barriers, for example biguanides and histamine receptor antagonists. In addition, several drugs used in the treatment of respiratory disorders are cations at physiological pH and potential substrates of OCT/Ns. OCT/Ns may also be associated with the development of chronic lung diseases such as allergic asthma and chronic obstructive pulmonary disease (COPD) and, thus, are possible new drug targets. As part of the Special Issue "Physiology, Biochemistry and Pharmacology of Transporters for Organic Cations", this review provides an overview of recent findings on the (patho)physiological and pharmacological functions of organic cation transporters in the lung.

Fatty Acid Oxidation Protects against Hyperoxia-induced Endothelial Cell Apoptosis and Lung Injury in Neonatal Mice

In neonates, hyperoxia or positive pressure ventilation causes continued lung injury characterized by simplified vascularization and alveolarization, which are the hallmarks of bronchopulmonary dysplasia. Although endothelial cells (ECs) have metabolic flexibility to maintain cell function under stress, it is unknown whether hyperoxia causes metabolic dysregulation in ECs, leading to lung injury. We hypothesized that hyperoxia alters EC metabolism, which causes EC dysfunction and lung injury. To test this hypothesis, we exposed lung ECs to hyperoxia (95% O₂/5% CO₂) followed by air recovery (O₂/rec). We found that O₂/rec reduced mitochondrial oxidative phosphorylation without affecting mitochondrial DNA copy number or mitochondrial mass and that it specifically decreased fatty acid oxidation (FAO) in ECs. This was associated with increased ceramide synthesis and apoptosis. Genetic deletion of carnitine palmitoyltransferase 1a (Cpt1a), a rate-limiting enzyme for carnitine shuttle, further augmented O₂/rec-induced apoptosis. O₂/rec-induced ceramide synthesis and apoptosis were attenuated when the FAO was enhanced by l-carnitine. Newborn mice were exposed to hyperoxia (>95% O₂) between Postnatal Days 1 and 4 and were administered l-carnitine (150 and 300 mg/kg, i.p.) or etomoxir, a specific Cpt1 inhibitor (30 mg/kg, i.p.), daily between Postnatal Days 10 and 14. Etomoxir aggravated O₂/rec-induced apoptosis and simplified alveolarization and vascularization in mouse lungs. Similarly, arrested alveolarization and reduced vessel numbers were further augmented in EC-specific Cpt1a-knockout mice compared with wild-type littermates in response to O₂/rec. Treatment with l-carnitine (300 mg/kg) attenuated O₂/rec-induced lung injury, including simplified alveolarization and decreased vessel numbers. Altogether, enhancing FAO protects against hyperoxia-induced EC apoptosis and lung injury in neonates.

The significant role of carnitine and fatty acids during pregnancy, lactation and perinatal period. Nutritional support in specific groups of pregnant women

BACKGROUND & AIMS

Pregnancy is characterized by a complexity of metabolic processes that may impact fetal health and development. Women's nutrition during pregnancy and lactation is considered important for both mother and infant. This review aims to investigate the significant role of fatty acids and carnitine during pregnancy and lactation in specific groups of pregnant and lactating women.

METHODS

The literature was reviewed using relevant data bases (e.g. Pubmed, Scopus, Science Direct) and relevant articles were selected to provide information and data for the text and associated Tables.

RESULTS

Dynamic features especially of plasma carnitine profile during pregnancy and lactation, indicate an extraordinarily active participation of carnitine in the intermediary metabolism both in pregnant woman and in neonate and may also have implications for health and disease later in life. Maternal diets rich in trans and saturated fatty acids can lead to impairments in the metabolism and development of the offspring, whereas the consumption of long chain-polyunsaturated fatty acids during pregnancy plays a beneficial physiologic and metabolic role in the health of offspring.

CONCLUSIONS

Pregnant women who are underweight, overweight or obese, with gestational diabetes mellitus or diabetes mellitus and those who choose vegan/vegetarian diets or are coming from socially disadvantaged areas, should be nutritionally supported to achieve a higher quality diet during pregnancy and/or lactation.

[Levels of blood free carnitine in preterm infants with different gestational ages and birth weights]

OBJECTIVE

To examine blood concentrations of free carnitine (FC) in preterm infants with different gestational ages (GA) and birth weights (BW).

METHODS

A total of 3 368 preterm infants were enrolled as subjects. According to GA, they were divided into extremely preterm birth (EPTB) group (GA <28 weeks; n=39), very preterm birth (VPTB) group (28 ≤GA <32 weeks; n=405), moderately preterm birth (MPTB) group (32 ≤GA <34 weeks; n=507), and late preterm birth (LPTB) group (34 ≤GA <37 weeks; n=2 417); according to BW, they were divided into extremely low birth weight (ELBW) group (BW <1 000 g; n=36), very low birth weight (VLBW) group (1 000 g ≤BW <1 500 g; n=387), low birth weight (LBW) group (1 500 g ≤BW <2 500 g; n=1 873), and normal birth weight (NBW) group (2 500 g ≤ BW <4 000 g; n=1 072). Blood concentrations of FC were measured between 72 hours and 7 days after birth.

RESULTS

The EPTB and VPTB groups had significantly higher FC concentrations than the MPTB and LPTB groups (P<0.05), and the MPTB group had significantly higher FC concentrations than the LPTB group (P<0.05). The lower limit of the 95% medical reference range of FC increased with the reduction in GA. The ELBW and VLBW groups had significantly higher FC concentrations than the LBW and NBW groups (P<0.05). The LBW group had significantly higher FC concentrations than the NBW group (P<0.05). The lower limit of the 95% medical reference range of FC increased with the reduction in BW.

CONCLUSIONS

There is a significant increase in blood FC concentrations in very/extremely preterm infants and very/extremely low birth weight infants, and tend to decrease with the increases in GA and BW.

OCTN: A Small Transporter Subfamily with Great Relevance to Human Pathophysiology, Drug Discovery, and Diagnostics

OCTN is a small subfamily of membrane transport proteins that belongs to the larger SLC22 family. Two of the three members of the subfamily, namely, OCTN2 and OCTN1, are present in humans. OCTN2 plays a crucial role in the absorption of carnitine from diet and in its distribution to tissues, as demonstrated by the occurrence of severe pathologies caused by malfunctioning or altered expression of this transporter. These findings suggest avoiding a strict vegetarian diet during pregnancy and in childhood. Other roles of OCTN2 are related to the traffic of carnitine derivatives in many tissues. The role of OCTN1 is still unclear, despite the identification of some substrates such as ergothioneine, acetylcholine, and choline. Plausibly, the transporter acts on the control of inflammation and oxidative stress, even though knockout mice do not display phenotypes. A clear role of both transporters has been revealed in drug interaction and delivery. The polyspecificity of the OCTNs is at the base of the interactions with drugs. Interestingly, OCTN2 has been recently exploited in the prodrug approach and in diagnostics. A promising application derives from the localization of OCTN2 in exosomes that represent a noninvasive diagnostic tool.

Metabolic reprogramming in the pathogenesis of chronic lung diseases, including BPD, COPD, and pulmonary fibrosis

The metabolism of nutrient substrates, including glucose, glutamine, and fatty acids, provides acetyl-CoA for the tricarboxylic acid cycle to generate energy, as well as metabolites for the biosynthesis of biomolecules, including nucleotides, proteins, and lipids. It has been shown that metabolism of glucose, fatty acid, and glutamine plays important roles in modulating cellular proliferation, differentiation, apoptosis, autophagy, senescence, and inflammatory responses. All of these cellular processes contribute to the pathogenesis of chronic lung diseases, including bronchopulmonary dysplasia, chronic obstructive pulmonary disease, and pulmonary fibrosis. Recent studies demonstrate that metabolic reprogramming occurs in patients with and animal models of chronic lung diseases, suggesting that metabolic dysregulation may participate in the pathogenesis and progression of these diseases. In this review, we briefly discuss the catabolic pathways for glucose, glutamine, and fatty acids, and focus on how metabolic reprogramming of these pathways impacts cellular functions and leads to the development of these chronic lung diseases. We also highlight how targeting metabolic pathways can be utilized in the prevention and treatment of these diseases.