Ian R. Holzman

Bio: Ian R. Holzman is an academic researcher from Icahn School of Medicine at Mount Sinai. The author has contributed to research in topics: Gestational age & Low birth weight. The author has an hindex of 25, co-authored 50 publications receiving 2807 citations. Previous affiliations of Ian R. Holzman include Boston Children's Hospital.

Butyrate enhances the intestinal barrier by facilitating tight junction assembly via activation of AMP-activated protein kinase in Caco-2 cell monolayers.

Abstract: Butyrate, one of the SCFA, promotes the development of the intestinal barrier. However, the molecular mechanisms underlying the butyrate regulation of the intestinal barrier are unknown. To test the hypothesis that the effect of butyrate on the intestinal barrier is mediated by the regulation of the assembly of tight junctions involving the activation of the AMP-activated protein kinase (AMPK), we determined the effect of butyrate on the intestinal barrier by measuring the transepithelial electrical resistance (TER) and inulin permeability in a Caco-2 cell monolayer model. We further used a calcium switch assay to study the assembly of epithelial tight junctions and determined the effect of butyrate on the assembly of epithelial tight junctions and AMPK activity. We demonstrated that the butyrate treatment increased AMPK activity and accelerated the assembly of tight junctions as shown by the reorganization of tight junction proteins, as well as the development of TER. AMPK activity was also upregulated by butyrate during calcium switch-induced tight junction assembly. Compound C, a specific AMPK inhibitor, inhibited the butyrate-induced activation of AMPK. The facilitating effect of butyrate on the increases in TER in standard culture media, as well as after calcium switch, was abolished by compound C. We conclude that butyrate enhances the intestinal barrier by regulating the assembly of tight junctions. This dynamic process is mediated by the activation of AMPK. These results suggest an intriguing link between SCFA and the intracellular energy sensor for the development of the intestinal barrier.

Effects of butyrate on intestinal barrier function in a Caco-2 cell monolayer model of intestinal barrier.

Abstract: Production of short-chain fatty acids (SCFA) in the intestinal lumen may play an important role in the maintenance of the intestinal barrier. However, overproduction/accumulation of SCFA in the bowel may be toxic to the intestinal mucosa and has been hypothesized to play a role in the pathogenesis of neonatal necrotizing enterocolitis (NEC). By using a Caco-2 cell monolayer model of intestinal barrier, we report here that the effect of butyrate on the intestinal barrier is paradoxical. Butyrate at a low concentration (2 mM) promotes intestinal barrier function as measured by a significant increase in transepithelial electrical resistance (TER) and a significant decrease in inulin permeability. Butyrate at a high concentration (8 mM) reduces TER and increases inulin permeability significantly. Butyrate induces apoptosis and reduces the number of viable Caco-2 cells in a dose-dependent manner. Intestinal barrier function impairment induced by high concentrations of butyrate is most likely related to butyrate-induced cytotoxicity due to apoptosis. We conclude that the effect of butyrate on the intestinal barrier is paradoxical; i.e. whereas low concentrations of butyrate may be beneficial in promoting intestinal barrier function, excessive butyrate may induce severe intestinal epithelial cell apoptosis and disrupt intestinal barrier.

Statewide NICU Central-Line-Associated Bloodstream Infection Rates Decline After Bundles and Checklists

Abstract: OBJECTIVE: In 2008, all 18 regional referral NICUs in New York state adopted central-line insertion and maintenance bundles and agreed to use checklists to monitor maintenance-bundle adherence and report checklist use. We sought to confirm whether adopting standardized bundles and using central-line maintenance checklists reduced central-line–associated bloodstream infections (CLABSI). METHODS: This was a prospective cohort study that enrolled all neonates with a central line who were hospitalized in any of 18 NICUs. Each NICU reported CLABSI and central-line utilization data and checklist use. We used χ2 to compare CLABSI rates in the preintervention (January to December 2007) versus the postintervention (March to December 2009) periods and Poisson regression to model adjusted CLABSI rates. RESULTS: Each study period included more than 55 000 central-line days and more than 200 000 patient-days. CLABSI rates decreased 67% statewide (risk ratio: 0.33 [95% confidence interval: 0.27–0.41]; P CONCLUSIONS: Although standardizing central-line care elements led to a significant statewide decline in NICU CLABSIs, site of care remains an independent risk factor. Using maintenance checklists reduced CLABSIs.

Reduction of maternal-infant transmission of human immunodeficiency virus type 1 with zidovudine treatment. Pediatric AIDS Clinical Trials Group Protocol 076 Study Group.

Abstract: Background and Methods Maternal-infant transmission is the primary means by which young children become infected with human immunodeficiency virus type 1 (HIV). We conducted a randomized, double-blind, placebo-controlled trial of the efficacy and safety of zidovudine in reducing the risk of maternal-infant HIV transmission. HIV-infected pregnant women (14 to 34 weeks' gestation) with CD4+ T-lymphocyte counts above 200 cells per cubic millimeter who had not received antiretroviral therapy during the current pregnancy were enrolled. The zidovudine regimen included antepartum zidovudine (100 mg orally five times daily), intrapartum zidovudine (2 mg per kilogram of body weight given intravenously over a one-hour period, then 1 mg per kilogram per hour until delivery), and zidovudine for the newborn (2 mg per kilogram orally every six hours for six weeks). Infants with at least one positive HIV culture of peripheral-blood mononuclear cells were classified as HIV-infected. Results From April 1991 through Decemb...

Management of Hyperbilirubinemia in the Newborn Infant 35 or More Weeks of Gestation

Abstract: Jaundice occurs in most newborn infants. Most jaundice is benign, but because of the potential toxicity of bilirubin, newborn infants must be monitored to identify those who might develop severe hyperbilirubinemia and, in rare cases, acute bilirubin encephalopathy or kernicterus. The focus of this guideline is to reduce the incidence of severe hyperbilirubinemia and bilirubin encephalopathy while minimizing the risks of unintended harm such as maternal anxiety, decreased breastfeeding, and unnecessary costs or treatment. Although kernicterus should almost always be preventable, cases continue to occur. These guidelines provide a framework for the prevention and management of hyperbilirubinemia in newborn infants of 35 or more weeks of gestation. In every infant, we recommend that clinicians 1) promote and support successful breastfeeding; 2) perform a systematic assessment before discharge for the risk of severe hyperbilirubinemia; 3) provide early and focused follow-up based on the risk assessment; and 4) when indicated, treat newborns with phototherapy or exchange transfusion to prevent the development of severe hyperbilirubinemia and, possibly, bilirubin encephalopathy (kernicterus).

Human nutrition, the gut microbiome and the immune system.

Abstract: Marked changes in socio-economic status, cultural traditions, population growth and agriculture are affecting diets worldwide. Understanding how our diet and nutritional status influence the composition and dynamic operations of our gut microbial communities, and the innate and adaptive arms of our immune system, represents an area of scientific need, opportunity and challenge. The insights gleaned should help to address several pressing global health problems.

Review article: the role of butyrate on colonic function

Abstract: BACKGROUND: Butyrate, a short-chain fatty acid, is a main end-product of intestinal microbial fermentation of mainly dietary fibre. Butyrate is an important energy source for intestinal epithelial cells and plays a role in the maintenance of colonic homeostasis. AIM: To provide an overview on the present knowledge of the bioactivity of butyrate, emphasizing effects and possible mechanisms of action in relation to human colonic function. METHODS: A PubMed search was performed to select relevant publications using the search terms: 'butyrate, short-chain fatty acid, fibre, colon, inflammation, carcinogenesis, barrier, oxidative stress, permeability and satiety'. RESULTS: Butyrate exerts potent effects on a variety of colonic mucosal functions such as inhibition of inflammation and carcinogenesis, reinforcing various components of the colonic defence barrier and decreasing oxidative stress. In addition, butyrate may promote satiety. Two important mechanisms include the inhibition of nuclear factor kappa B activation and histone deacetylation. However, the observed effects of butyrate largely depend on concentrations and models used and human data are still limited. CONCLUSION: Although most studies point towards beneficial effects of butyrate, more human in vivo studies are needed to contribute to our current understanding of butyrate-mediated effects on colonic function in health and disease.