Reed A. Dimmitt

Serum cytosolic β-glucosidase activity in a rat model of necrotizing enterocolitis

The diagnosis of necrotizing enterocolitis (NEC) is made from a combination of clinical and radiographic findings. There are no useful screening biochemical markers of intestinal injury. The serum concentration of cytosolic β-glucosidase (CBG), an enzyme found primarily in enterocytes, is markedly elevated in animal models of ischemia and bowel obstruction. We hypothesized that in a rat model of NEC, serum CBG activity would significantly increase before microscopic evidence of severe intestinal injury. Cohorts of 2-wk-old Sprague-Dawley rats (n = 10/cohort) were anesthetized and underwent laparotomy with occlusion of the superior mesenteric artery (SMA). Platelet-activating factor (200 μg/animal) was injected in the proximal duodenum. Serum and intestinal samples were obtained at time 0 (control) and 30, 60, and 90 min of ischemia (I) and after 90 min of I followed by 60 min of reperfusion (I/R). Histopathologic injury was categorized as either no or minimal injury or mural necrosis by two masked investigators and CBG activity was measured by ELISA. Data were analyzed with Fishers exact test and ANOVA. Only the I/R group had significantly greater mural necrosis compared with the control group (90%versus 0%, respectively, p < 0.001). In contrast, CBG activity was significantly elevated after only 90 min of I and after I/R (15.1 ± 5.6 and 16.4 ± 4.3 units/mL, respectively, p < 0.05). We conclude that serum CBG is elevated before transmural intestinal injury in this model and may have utility as an early marker of ischemia in patients at risk for NEC.

A Potential Biomarker in the Cord Blood of Preterm Infants Who Develop Retinopathy of Prematurity

Preterm infants are at risk of developing sepsis, necrotizing enterocolitis (NEC), chronic lung disease (CLD), and retinopathy of prematurity (ROP). We used high-throughput mass spectrometry to investigate whether cord blood proteins can be used to predict development of these morbidities. Cord blood plasma from 44 infants with a birth weight of <1500 g was analyzed by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF). Six infants developed ROP ≥stage II, 10 CLD, three sepsis, and one NEC. We detected 814 protein signals representing 330 distinct protein species. Nineteen biomarkers were associated with development of ≥stage II ROP [false-discovery rate (FDR) <5%] and none with CLD. Several proteins with molecular weight (Mr) 15–16 kD and pI 4–5 were detected with increased abundance in infants with ROP, while similar Mr proteins with pI 7–9 were less abundant in these patients. Sodium dodecylsulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and sequence analysis identified these proteins as α-, β-, and γ-globin chains. Partial deamidation of Asn139 in β-globin chains was observed only in the pI 4–5 proteins. We conclude that there are several promising biomarkers for the risk of ROP. Deamidation of globin chains is especially promising and may indicate underlying prenatal pathologic mechanisms in ROP. Validation studies will be undertaken to determine their clinical utility.