The Impact of Iron Deficiency During Development on Mammalian Target of Rapamycin Signaling, Neuronal Structure, and Learning and Memory Behavior

University of Minnesota Ph.D. dissertation. November 2010. Major: Neuroscience. Advisor: Michael Georgieff. 1 computer file (PDF); v, 99 pages.Iron deficiency (ID) is the most common micronutrient deficiency, affecting an estimated 2 billion people world wide including 20-30% of pregnant women and their offspring. Many human studies have demonstrated negative effects of early life ID on learning and memory which persist beyond the period of ID despite of prompt iron treatment, observations which are supported by rodent models of early iron deficiency anemia (IDA). In spite of a large, observational literature the mechanisms through which early ID causes acute and persistent brain dysfunction are largely unknown. Mammalian target of rapamycin (mTOR) signaling is an attractive candidate for mediating the effects of early ID because it integrates cellular metabolic status to regulate fundamental aspects of cellular growth and differentiation. The overall goal of the current studies is to understand the role of iron in regulating mTOR signaling during a critical period of development in the hippocampus by using unique genetic mouse models of hippocampal ID to: 1) Determine when iron is required for hippocampal development 2) Determine the role of iron in mTOR signaling 3) Manipulate iron and mTOR to determine effects on hippocampal structure and behavior. The findings from these experiments demonstrate that mTOR signaling is upregulated by neuronal ID during the same period that rapid hippocampal development requires large amounts of iron. Additionally, rescue of behavioral outcomes in adult animals following restoration of mTOR signaling (through either timely iron repletion or pharmacological suppression) provides functional evidence for a connection between mTOR and the persistent effects of early ID

Genome-Wide Analyses of Metal Responsive Genes in Caenorhabditis elegans

Metals are major contaminants that influence human health. Many metals have physiologic roles, but excessive levels can be harmful. Advances in technology have made toxicogenomic analyses possible to characterize the effects of metal exposure on the entire genome. Much of what is known about cellular responses to metals has come from mammalian systems; however the use of non-mammalian species is gaining wider attention. Caenorhabditis elegans is a small round worm whose genome has been fully sequenced and its development from egg to adult is well characterized. It is an attractive model for high throughput screens due to its short lifespan, ease of genetic mutability, low cost, and high homology with humans. Research performed in C. elegans has led to insights in apoptosis, gene expression, and neurodegeneration, all of which can be altered by metal exposure. Additionally, by using worms one can potentially study mechanisms that underline differential responses to metals in nematodes and humans, allowing for identification of novel pathways and therapeutic targets. In this review, toxicogenomic studies performed in C. elegans exposed to various metals will be discussed, highlighting how this non-mammalian system can be utilized to study cellular processes and pathways induced by metals. Recent work focusing on neurodegeneration in Parkinson’s disease will be discussed as an example of the usefulness of genetic screens in C. elegans and the novel findings that can be produced

Biomarkers of Nutrition for Development (BOND)—Iron Review

This is the fifth in the series of reviews developed as part of the Biomarkers of Nutrition for Development (BOND) program. The BOND Iron Expert Panel (I-EP) reviewed the extant knowledge regarding iron biology, public health implications, and the relative usefulness of currently available biomarkers of iron status from deficiency to overload. Approaches to assessing intake, including bioavailability, are also covered. The report also covers technical and laboratory considerations for the use of available biomarkers of iron status, and concludes with a description of research priorities along with a brief discussion of new biomarkers with potential for use across the spectrum of activities related to the study of iron in human health. The I-EP concluded that current iron biomarkers are reliable for accurately assessing many aspects of iron nutrition. However, a clear distinction is made between the relative strengths of biomarkers to assess hematological consequences of iron deficiency versus other putative functional outcomes, particularly the relationship between maternal and fetal iron status during pregnancy, birth outcomes, and infant cognitive, motor and emotional development. The I-EP also highlighted the importance of considering the confounding effects of inflammation and infection on the interpretation of iron biomarker results, as well as the impact of life stage. Finally, alternative approaches to the evaluation of the risk for nutritional iron overload at the population level are presented, because the currently designated upper limits for the biomarker generally employed (serum ferritin) may not differentiate between true iron overload and the effects of subclinical inflammation

Geriatric assessment in older alloHCT recipients: association of functional and cognitive impairment with outcomes

Use of allogeneic hematopoietic cell transplantation (alloHCT) is increasing in older patients with hematologic malignancies. Studies suggest that geriatric assessment (GA), incorporating functional measures such as instrumental activities of daily living (IADL), delineates subtle age-related impairments that enhance risk-stratification. The objective of this multi-institutional retrospective study was to evaluate the prognostic utility of GA metrics collected pre-alloHCT. Eligibility criteria included age ≥50 and pre-alloHCT GA inclusive of at least IADL. Beyond IADL, additional geriatric metrics were collected where available and included Medical Outcomes Study Physical Health score (MOS-PH), Timed Up and Go (TUG), and cognition by Blessed Orientation Memory Concentration (BOMC). Three hundred thirty subjects were included, with a median age of 63 (range 50 to 77). Impairments were frequent: 36% had at least 1 IADL impairment; 14% had TUG ≥13.5 seconds; and 17% had cognitive impairment (BOMC ≥ 7). Median MOS-PH score was 80. IADL and age were not significantly associated with nonrelapse mortality (NRM) or overall survival (OS). In multivariate analysis, only impaired cognition and Hematopoietic Cell Transplant-Comorbidity Index score ≥3 showed an independent association with 1-year NRM (subdistribution hazard ratio [SHR], 2.36; P = .01; and SHR, 2.19; P = .009, respectively). Cognitive impairment independently conferred inferior 1-year OS (hazard ratio, 1.94; P = .01). In a preplanned subgroup analysis in 224 patients aged ≥60 years, cognitive impairment remained the sole GA metric predictive of NRM (2-year NRM: SHR, 2.72; P = .007). These data suggest that cognitive impairment elevates risk of post-alloHCT NRM in older patients

Corrigendum to ‘Current Use and Trends in Hematopoietic Cell Transplantation in the United States’ [Transplantation and Cellular Therapy 26/8 (2020) e177-e182]

Corrigendum to "Current Use and Trends in Hematopoietic Cell Transplantation in the United States

Current Use of and Trends in Hematopoietic Cell Transplantation in the United States

Hematopoietic cell transplantation (HCT) is a well-established treatment to control and/or cure many malignant and nonmalignant diseases involving the hematopoietic system and some solid tumors. We report information about HCT procedures performed in the United States in 2018 and analyze trends and outcomes of HCT as reported to the Center for International Blood and Marrow Transplant Research (CIBMTR). Overall, compared with 2017, the number of allogeneic HCTs performed in the United States increased by 1%, and the number of autologous HCTs decreased by 5%. Key findings are fewer autologous HCTs performed for non-Hodgkin lymphoma and increasing numbers of haploidentical HCTs, nearly all of which use post-transplantation cyclophosphamide for graft-versus-host disease prophylaxis. There is a continuing increase in HCT in adults age >70 years, particularly for acute myelogenous leukemia and myelodysplastic syndromes. Survival rates by disease, disease stage, donor type, and age are presented. This report, prepared annually by the CIBMTR, provides a snapshot of current transplant activity in the United States

Comprehensive Prognostication in Critically Ill Pediatric Hematopoietic Cell Transplant Patients: Results from Merging the Center for International Blood and Marrow Transplant Research (CIBMTR) and Virtual Pediatric Systems (VPS) Registries

Critically ill pediatric allogeneic hematopoietic cell transplant (HCT) patients may benefit from early and aggressive interventions aimed at reversing the progression of multiorgan dysfunction. Therefore, we evaluated 25 early risk factors for pediatric intensive care unit (PICU) mortality to improve mortality prognostication. We merged the Virtual Pediatric Systems and Center for International Blood and Marrow Transplant Research databases and analyzed 936 critically ill patients ≤21 years of age who had undergone allogeneic HCT and subsequently required PICU admission between January 1, 2009, and December 31, 2014. Of 1532 PICU admissions, the overall PICU mortality rate was 17.4% (95% confidence interval [CI], 15.6% to 19.4%) but was significantly higher for patients requiring mechanical ventilation (44.0%), renal replacement therapy (56.1%), or extracorporeal life support (77.8%). Mortality estimates increased significantly the longer that patients remained in the PICU. Of 25 HCT- and PICU-specific characteristics available at or near the time of PICU admission, moderate/severe pre-HCT renal injury, pre-HCT recipient cytomegalovirus seropositivity, <100-day interval between HCT and PICU admission, HCT for underlying acute myeloid leukemia, and greater admission organ dysfunction as approximated by the Pediatric Risk of Mortality 3 score were each independently associated with PICU mortality. A multivariable model using these components identified that patients in the top quartile of risk had 3 times greater mortality than other patients (35.1% versus 11.5%, P < .001, classification accuracy 75.2%; 95% CI, 73.0% to 77.4%). These data improve our working knowledge of the factors influencing the progression of critical illness in pediatric allogeneic HCT patients. Future investigation aimed at mitigating the effect of these risk factors is warranted

Hippocampus specific iron deficiency alters competition and cooperation between developing memory systems

Iron deficiency (ID) is the most common gestational micronutrient deficiency in the world, targets the fetal hippocampus and striatum and results in long-term behavioral abnormalities. These structures primarily mediate spatial and procedural memory, respectively, in the rodent but have interconnections that result in competition or cooperation during cognitive tasks. We determined whether ID-induced impairment of one alters the function of the other by genetically inducing a 40% reduction of hippocampus iron content in late fetal life in mice and measuring dorsal striatal gene expression and metabolism and the behavioral balance between the two memory systems in adulthood. Slc11a2hipp/hipp mice had similar striatum iron content, but 18% lower glucose and 44% lower lactate levels, a 30% higher phosphocreatine:creatine ratio, and reduced iron transporter gene expression compared to wild type (WT) littermates, implying reduced striatal metabolic function. Slc11a2hipp/hipp mice had longer mean escape times on a cued task paradigm implying impaired procedural memory. Nevertheless, when hippocampal and striatal memory systems were placed in competition using a Morris Water Maze task that alternates spatial navigation and visual cued responses during training, and forces a choice between hippocampal and striatal strategies during probe trials, Slc11a2hipp/hipp mice used the hippocampus-dependent response less often (25%) and the visual cued response more often (75%) compared to WT littermates that used both strategies approximately equally. Hippocampal ID not only reduces spatial recognition memory performance but also affects systems that support procedural memory, suggesting an altered balance between memory systems