Effects of Oral Administration of Insulin-Like Growth Factor-I on Circulating Concentration of Insulin-Like Growth Factor-I and Growth of Internal Organs in Weanling Mice

Clinical outcome and gut development after insulin-like growth factor-1 supplementation to preterm pigs

BACKGROUND

Elevation of circulating insulin-like growth factor-1 (IGF-1) within normal physiological levels may alleviate several morbidities in preterm infants but safety and efficacy remain unclear. We hypothesized that IGF-1 supplementation during the first 1-2 weeks after preterm birth improves clinical outcomes and gut development, using preterm pigs as a model for infants.

METHODS

Preterm pigs were given vehicle or recombinant human IGF-1/binding protein-3 (rhIGF-1, 2.25 mg/kg/d) by subcutaneous injections for 8 days (Experiment 1, n = 34), or by systemic infusion for 4 days (Experiment 2, n = 19), before collection of blood and organs for analyses.

RESULTS

In both experiments, rhIGF-1 treatment increased plasma IGF-1 levels 3-4 fold, reaching the values reported for term suckling piglets. In Experiment 1, rhIGF-1 treatment increased spleen and intestinal weights without affecting clinical outcomes like growth, blood biochemistry (except increased sodium and gamma-glutamyltransferase levels), hematology (e.g., red and white blood cell populations), glucose homeostasis (e.g., basal and glucose-stimulated insulin and glucose levels) or systemic immunity variables (e.g., T cell subsets, neutrophil phagocytosis, LPS stimulation, bacterial translocation to bone marrow). The rhIGF-1 treatment increased gut protein synthesis (+11%, p < 0.05) and reduced the combined incidence of all-cause mortality and severe necrotizing enterocolitis (NEC, p < 0.05), but had limited effects on intestinal morphology, cell proliferation, cell apoptosis, brush-border enzyme activities, permeability and levels of cytokines (IL-1β, IL-6, IL-8). In Experiment 2, rhIGF-1 treated pigs had reduced blood creatine kinase, creatinine, potassium and aspartate aminotransferase levels, with no effects on organ weights (except increased spleen weight), blood chemistry values, clinical variables or NEC.

CONCLUSION

Physiological elevation of systemic IGF-1 levels for 8 days after preterm birth increased intestinal weight and protein synthesis, spleen weight and potential overall viability of pigs, without any apparent negative effects on recorded clinical parameters. The results add further preclinical support for safety and efficacy of supplemental IGF-1 to hospitalized very preterm infants.

In Vivo Anti-Inflammatory Effects and Related Mechanisms of Processed Egg Yolk, a Potential Anti-Inflammaging Dietary Supplement

Egg-yolk based supplements have demonstrated biological effects. We have developed a novel processed egg-yolk (PEY) complement, and we have tested whether it has inflammation modulatory properties. These were evaluated in a lipopolysaccharide (LPS)-challenge in 1-month male rats by in vivo circulating cytokine profiles measured by multiplexing techniques. Cell culture was used to explore ex vivo properties of derived serum samples. We explored growth factor composition, and mass-spectrometry metabolome and lipidome analyses of PEY to characterize it. PEY significantly prevented LPS-induced increase in IL-1 β, TNF-α, and MCP-1. Further, serum from PEY-treated animals abrogated LPS-induced iNOS build-up of the Raw 264.7 macrophage-like cell line. Immunochemical analyses demonstrated increased concentrations of insulin-like growth factor 1 (IGF-1), connective tissue growth factor (CTGF), and platelet-derived growth factor (PDGF) in the extract. PEY vs. egg-yolk comparative metabolomic analyses showed significative differences in the concentrations of at least 140 molecules, and in 357 in the lipidomic analyses, demonstrating the complexity of PEY. Globally, PEY acts as an orally-bioavailable immunomodulatory extract that may be of interest in those conditions associated with disarranged inflammation, such as inflammaging.

Effect of human milk formula with bovine colostrum supplementation on bone mineral density in infant cynomolgus macaques

Insulin-like growth factor 1 (IGF1) is a regulator of human growth during infancy and childhood, known to promote bone and muscle growth as well as lipid accumulation. This study aimed to investigate the effects of formula milk with or without IGF1 supplementation (in the form of pure IGF1 or bovine colostrum) on growth and body composition in infant cynomolgus macaques during the first 6 months of life. Three groups of infants were nursery-reared and received formula milk with or without IGF1 or bovine colostrum supplementation for 4 months, and a fourth group consisting of breast-fed infants was included for comparison (n=6 for each group). Ranked-based analysis of covariance was used to detect differences between adjusted means for sex. No differences in weight, height, fat mass, and fat-free mass could be detected between groups. However, bone mineral density (BMD) was significantly different between groups at the end of formula feeding. Infants that received bovine colostrum supplementation displayed higher mean BMD than infants of all other groups, with no differences between the latter three groups. In conclusion, our results suggest that supplementation with bovine colostrum can enhance BMD in formula-fed infants, an effect that apparently does not depend on IGF1. Bovine colostrum supplementation could be beneficial for long-term bone health in infants with suboptimal bone growth.

Risk factors and growth factors in ROP

Retinopathy of prematurity (ROP) is a multifactorial disease which incidence is increasing with increasing survival of very preterm infants. Pathogenic pathway is characterised by abnormal retinal vascular development modulated by vascular growth factors: low IGF-1 in the first phase and high VEGF in the second phase. Many causal factors are able to influence retinal vascularization: gestational age, birth weight, oxygen administration, perinatal bacterial or fungal infections, and blood transfusions. All risk factors, both oxygen and not-oxygen-regulated, have been studied considering the whole period from hospital birth to the hospital discharge, but it is possible that postnatal risk factors may be determinant in a time-dependent way. Analysis of factors involved in the pathogenesis of ROP suggests that their action begins long before anatomical clinical features become appreciable and this is strengthened by the essential role of risk factors from the first two to four weeks of life, thus preventive strategies in very preterm infants should be carried out since birth.

Beneficial effect of insulin-like growth factor-1 on hypoxemic renal dysfunction in the newborn rabbit

Acute normocapnic hypoxemia can cause functional renal insufficiency by increasing renal vascular resistance (RVR), leading to renal hypoperfusion and decreased glomerular filtration rate (GFR). Insulin-like growth factor 1 (IGF-1) activity is low in fetuses and newborns and further decreases during hypoxia. IGF-1 administration to humans and adult animals induces pre- and postglomerular vasodilation, thereby increasing GFR and renal blood flow (RBF). A potential protective effect of IGF-1 on renal function was evaluated in newborn rabbits with hypoxemia-induced renal insufficiency. Renal function and hemodynamic parameters were assessed in 17 anesthetized and mechanically ventilated newborn rabbits. After hypoxemia stabilization, saline solution (time control) or IGF-1 (1 mg/kg) was given as an intravenous (i.v.) bolus, and renal function was determined for six 30-min periods. Normocapnic hypoxemia significantly increased RVR (+16%), leading to decreased GFR (-14%), RBF (-19%) and diuresis (-12%), with an increased filtration fraction (FF). Saline solution resulted in a worsening of parameters affected by hypoxemia. Contrarily, although mean blood pressure decreased slightly but significantly, IGF-1 prevented a further increase in RVR, with subsequent improvement of GFR, RBF and diuresis. FF indicated relative postglomerular vasodilation. Although hypoxemia-induced acute renal failure was not completely prevented, IGF-1 elicited efferent vasodilation, thereby precluding a further decline in renal function.

The impact of enteral insulin-like growth factor 1 and nutrition on gut permeability and amino acid utilization

The intestine serves numerous purposes. In addition to digestion and absorption, the intestine functions as an organ that provides specific and nonspecific protection against pathological bacteria and noxious agents. At birth, and certainly when birth occurs prematurely, these functions are not yet fully developed. This article addresses the specific needs of the neonatal gut to perform these functions adequately and describes efforts to modulate intestinal barrier function by preterm formula supplemented with insulin-like growth factor 1.

Effect of enteral IGF-1 supplementation on feeding tolerance, growth, and gut permeability in enterally fed premature neonates

OBJECTIVES

The gastrointestinal tract of the premature newborn functions suboptimally with regard to digestion, absorption, and feeding tolerance. Human milk contains trophic factors, such as insulin-like growth factor-1 (IGF-1), that are believed to stimulate gut growth and function. The objective of this double blind, randomized, controlled trial was to assess the effects of enteral IGF-1 supplementation on whole body growth measured by weight gain (in grams per kilogram per day), days to regain birth weight, and anthropometrical characteristics, and gut maturation and permeability (measured by sugar absorption tests).

PATIENTS AND METHODS

The study included 60 premature infants (birth weight 750-1250 g) during the first month of life. Patients received either standard infant formula or standard infant formula supplemented with IGF-1 in a concentration twice that of human colostrum (10 microg/100 mL of formula). Primary endpoints were days to full enteral feeding, days to regain birth weight, and growth rate. Sugar absorption tests were performed weekly to assess the secondary endpoints gut permeability and maturation.

RESULTS

None of the primary endpoints differed to statistical significance between groups at any point. However, gut permeability was significantly lower in the IGF-1 supplement group on day 14 compared with the control group. At day 21, lactulose/mannitol excretion ratios were (again) comparable between the groups.

CONCLUSIONS

Although gut permeability showed a faster decrease in the IGF-1 supplement group, our data do not support IGF-1 supplementation to infant formula.

Fetal and amniotic insulin-like growth factor-I supplements improve growth rate in intrauterine growth restriction fetal sheep

To date, there is no known prenatal treatment for intrauterine growth restriction (IUGR). IGF-I is an important regulator of fetal growth and circulating IGF-I concentrations are reduced in IUGR fetuses. We investigated whether any of three different methods of fetal IGF-I administration would reverse IUGR in sheep. Animals were randomized into five groups: control (n = 17), IUGR + saline (SAL, n = 17), IUGR + iv IGF-I (IGF-IV, n = 14), IUGR + intraamniotic IGF-I (IGF-AF, n = 14), or IUGR + intraamniotic IGF-I with nutrients (IGF-NUT, n = 16). Weekly IGF-I dose was 360 microg in each treatment group. IUGR was induced by placental embolization between 93 and 99 d and treatment was from 100-128 d gestation (term = 147 d). Embolization caused asymmetrical IUGR with reduced fetal growth rates and body and organ weights, but increased brain to liver weight ratio, at post mortem. Embolized fetuses were also hypoxemic and hypoglycemic and had reduced circulating IGF-I and insulin concentrations. IGF-AF and IGF-IV significantly increased fetal growth rates, but only IGF-AF significantly increased fetal liver weight, compared with saline-treated fetuses. Fetal weights and brain to liver weight ratios in all IGF-I-treated fetuses were intermediate between the control and SAL groups. Addition of nutrients reduced the effects of amniotic IGF-I treatment and increased fetal hemoglobin and lactate concentrations. Treatments did not change fetal plasma IGF-I and insulin concentrations. This is the first report of an intrauterine treatment significantly increasing fetal growth rate in established IUGR. Amniotic IGF-I administration may provide the basis for a clinically applicable prenatal treatment for the IUGR fetus.