Preterm infants may be at risk of necrotizing enterocolitis (NEC) due to deficiency of transforming growth factor-β 2 (TGF-β2) in the developing intestine. We hypothesized that low epithelial TGF-β2expression in preterm intestine and during NEC results from diminished autocrine induction of TGF-β2in these cells. Premature baboons delivered at 67% gestation were treated per current norms for human preterm infants. NEC was diagnosed by clinical and radiological findings. Inflammatory cytokines, TGF-β2, Smad7, Ski, and strawberry notch N (SnoN)/Ski-like oncoprotein (SKIL) was measured using quantitative reverse transcriptase-polymerase chain reaction, immunoblots, and immunohistochemistry. Smad7 effects were examined in transfected IEC6 intestinal epithelial cells in vitro. Findings were validated in archived human tissue samples of NEC. NEC was recorded in seven premature baboons. Consistent with existing human data, premature baboon intestine expressed less TGF-β2than term intestine. TGF-β2expression was regulated in epithelial cells in an autocrine fashion, which was interrupted in the premature intestine and during NEC due to increased expression of Smad7. LPS increased Smad7 binding to the TGF-β2promoter and was associated with dimethylation of the lysine H3K9, a marker of transcriptional silencing, on the nucleosome of TGF-β2. Increased Smad7 expression in preterm intestine was correlated with the deficiency of SnoN/SKIL, a repressor of the Smad7 promoter. Smad7 inhibits autocrine expression of TGF-β2in intestinal epithelial cells in the normal premature intestine and during NEC. Increased Smad7 expression in the developing intestine may be due to a developmental deficiency of the SnoN/SKIL oncoprotein.

Premature infants develop hyperglycemia shortly after birth, increasing their morbidity and death. Surviving infants have increased incidence of diabetes as young adults. Our understanding of the biological basis for the insulin resistance of prematurity and developmental regulation of glucose production remains fragmentary. The objective of this study was to examine maturational differences in insulin sensitivity and the insulin-signaling pathway in skeletal muscle and adipose tissue of 30 neonatal baboons using the euglycemic hyperinsulinemic clamp. Preterm baboons (67% gestation) had reduced peripheral insulin sensitivity shortly after birth (M value 12.5 ± 1.5 vs 21.8 ± 4.4 mg/kg · min in term baboons) and at 2 weeks of age (M value 12.8 ± 2.6 vs 16.3 ± 4.2, respectively). Insulin increased Akt phosphorylation, but these responses were significantly lower in preterm baboons during the first week of life (3.2-fold vs 9.8-fold). Preterm baboons had lower glucose transporter-1 protein content throughout the first 2 weeks of life (8%-12% of term). In preterm baboons, serum free fatty acids (FFAs) did not decrease in response to insulin, whereas FFAs decreased by greater than 80% in term baboons; the impaired suppression of FFAs in the preterm animals was paired with a decreased glucose transporter-4 protein content in adipose tissue. In conclusion, peripheral insulin resistance and impaired non-insulin-dependent glucose uptake play an important role in hyperglycemia of prematurity. Impaired insulin signaling (reduced Akt) contributes to the defect in insulin-stimulated glucose disposal. Counterregulatory hormones are not major contributors.

Background Transient neonatal hyperglycemia has been reported in up to 80% of extremely preterm human infants. We hypothesize that severe hyperglycemia (HG) is associated with increased morbidity and mortality in preterm baboons. Methods Sixty six baboons born at 67% of gestation were studied. Hyperglycemia was defined as serum glucose level ≥ 150mg/dL during the first week of life. Animals were stratified into 2 groups: severe HG (≥8 events) and non-severe HG (<8 events). Results Hyperglycemia developed in 65/66 (98%) of the baboons included. A total of 3,386 glucose measurements were obtained. The mean serum glucose level was 159±69 mg/dL for the severe HG group and 130±48 mg/dL for the non-severe HG group during the first week of life. No differences were found in gender, birth weight, sepsis, PDA, or oxygenation/ventilation indices between groups. Severe HG was associated with early death even after controlling for sepsis, postnatal steroid exposure and catecholamine utilization. Conclusion Hyperglycemia is common in preterm baboons and is not associated with short term morbidity. Severe hyperglycemia occurring in the first week of life is associated with early death in preterm baboons.

Objective We hypothesize that prenatal exposure to glucocorticoids (GCs) will negatively alter the insulin signal transduction pathway and has differing effects on the fetus according to gestational age at exposure. Methods Twenty-three fetal baboons were delivered from twenty-three healthy, non-diabetic mothers. Twelve preterm (0.67 gestational age) and eleven near term (0.95 gestational age) baboons were euthanized immediately after delivery. Half of the pregnant baboons at each gestation received two doses of intramuscular betamethasone 24-hours apart (170 μg.kg−1) before delivery, while the other half received no intervention. Vastus lateralis muscle was obtained from postnatal animals to measure protein content and gene expression of insulin receptor (IR)-β, IR-β Tyr 1361 phosphorylation (pIR-β), IR substate-1 (IRS-1), IRS-1 tyrosine phosphorylation (pIRS-1), p85 subunit of PI3-kinase (p85), Akt (Protein Kinase B), phospho-Akt Ser473 (pAkt), Akt-1, Akt-2, and glucose transporters (GLUT1 and GLUT4). Results Skeletal muscle from preterm baboons exposed to glucocorticoids had markedly reduced protein content of Akt and Akt-1 (respectively, 73% and 72% from 0.67 gestational age Control, P<0.001); IR-β and pIR-β were decreased (respectively, 94% and 85%, P<0.01) in the muscle of premature GC exposed fetuses, but not in term fetuses. GLUT1 and GLUT4 tended to increase with GC exposure in preterm animals (P=0.09), while GLUT4 increased 6.0 fold in term animals after GC exposure (P<0.05). Conclusion Exposure to a single course of antenatal GCs during fetal life alters the insulin-signaling pathway in fetal muscle in a manner dependent on the stage of gestation.

Background Premature birth occurs when nephrogenesis is incomplete and has been linked to increased renal pathologies in the adult. Metabolic factors complicating preterm birth may have additional consequences for kidney development. Here, we evaluated the effects of prematurity and hyperglycemia on nephrogenesis in premature baboons when compared to term animals. Methods Baboons were delivered prematurely (67% gestation; n=9) or at term (n=7) and survived 2–4 weeks. Preterm animals were classified by glucose control during the first five days of life (DOL): normoglycemic (PtN; serum glucose 50–100mg/dL, n=6) and hyperglycemic (PtH; serum glucose 150–250mg/dL, n=3). Kidneys were assessed histologically for glomeruli relative area, maturity, size, and overall morphology. Kidney lysates were evaluated for oxidative damage with 4-hydroxynonenal (4-HNE) antibody. Results Histological examination revealed decreased glomeruli relative area (p<0.05), fewer glomerular generations (p<0.01), and increased renal corpuscle area (p<0.001) in preterm compared to term animals. Numbers of apoptotic glomeruli were similar between groups. PtH kidneys exhibited reduced nephrogenic zone width (p<0.0001), increased numbers of mature glomeruli (p<0.05), and increased 4-HNE staining compared to PtN kidneys. Conclusion Prematurity interrupts normal kidney development, independent of glomerular cell apoptosis. When prematurity is complicated by hyperglycemia; kidney development shifts towards accelerated maturation and increased oxidative stress.