Increased Body Mass Index Augments Endothelial Injury and Clinical Outcomes after Hematopoietic Stem Cell Transplantation.

Higher body mass index (BMI) is characterized as a chronic inflammatory state with endothelial dysfunction. Endothelial injury after allogeneic hematopoietic stem cell transplantation (allo-HSCT) puts patients at risk for such complications as transplantation-associated thrombotic microangiopathy (TA-TMA) and acute graft-versus-host-disease (aGVHD). To evaluate the impact of increased BMI on endothelial injury after allo-HSCT in pediatric and young adult patients, we conducted a retrospective cohort study evaluating 476 consecutive allo-HSCT children and young adult recipients age 0 to 20 years. Our analysis was subdivided based on distinct age categories (<2 years and 2 to 20 years). BMI was considered as a variable but was also expressed in standard deviations from the mean adjusted for age and sex (z-score), based on established criteria from the World Health Organization (age <2 years) and the Centers for Disease Control and Prevention (age 2 to 20 years) to account for differences associated with age. Primary endpoints included the incidences of TA-TMA and aGVHD. Increased BMI z-score was associated with TA-TMA after allo-HSCT in patients age <2 years (median, 18.1; IQR, 17 to 20; P = .006) and in patients age 2 to 20 years (median, 18.7; IQR, 16 to 21.9; P = .02). Higher BMI z-score correlated with TA-TMA risk in both age groups, with a BMI z-score of .9 in the younger cohort and .7 (IQR, -.4 to 1.6; P = .04) in the older cohort. Increased BMI z-score was associated with an increased risk of TA-TMA in a multivariate analysis of the entire cohort (odds ratio [OR], 1.2; 95% confidence interval [CI], 1.05 to 1.37; P = .008). Multivariate analysis also demonstrated that patients with BMI in the 85th percentile or greater had an increased risk of developing TA-TMA compared to those with a lower BMI percentile (OR, 2.66; 95% CI, 1.62 to 4.32; P < .001). Baseline and day +7 ST2 levels were elevated in subjects with TA-TMA compared to those without TA-TMA in both age groups. Baseline sC5b-9 concentration was not correlated with BMI z-score, but sC5b-9 concentration was increased markedly by 7 days post-allo-HSCT in patients age <2 years who later developed TA-TMA compared to those who never developed TA-TMA (P = .001). The median BMI z-score was higher for patients with aGVHD compared to patients without aGVHD (.7 [range, -3.9 to 3.9] versus .2 [range, -7.8 to 5.4]; P = .03). We show that high BMI is associated with augmented risk of endothelial injury after HSCT, specifically TA-TMA. These data identify a high-risk population likely to benefit from early interventions to prevent endothelial injury and prompt treatment of established endothelial injury.

Intestinal permeability in patients undergoing stem cell transplantation correlates with systemic acute phase responses and dysbiosis.

Intestinal permeability may correlate with adverse outcomes during hematopoietic stem cell transplantation (HSCT), but longitudinal quantification with traditional oral mannitol and lactulose is not feasible in HSCT recipients because of mucositis and diarrhea. A modified lactulose:rhamnose (LR) assay is validated in children with environmental enteritis. Our study objective was to quantify peri-HSCT intestinal permeability changes using the modified LR assay. The LR assay was administered before transplant, at day +7 and +30 to 80 pediatric and young adult patients who received allogeneic HSCT. Lactulose and rhamnose were detected using urine mass spectrometry and expressed as an L:R ratio. Metagenomic shotgun sequencing of stool for microbiome analyses and enzyme-linked immunosorbent assay analyses of plasma lipopolysaccharide binding protein (LBP), ST2, REG3α, claudin1, occludin, and intestinal alkaline phosphatase were performed at the same timepoints. L:R ratios were increased at day +7 but returned to baseline at day +30 in most patients (P = .014). Conditioning regimen intensity did not affect the trajectory of L:R (P = .39). Baseline L:R ratios did not vary with diagnosis. L:R correlated with LBP levels (r2 = 0.208; P = .0014). High L:R ratios were associated with lower microbiome diversity (P = .035), loss of anaerobic organisms (P = .020), and higher plasma LBP (P = .0014). No adverse gastrointestinal effects occurred because of LR. Intestinal permeability as measured through L:R ratios after allogeneic HSCT correlates with intestinal dysbiosis and elevated plasma LBP. The LR assay is well-tolerated and may identify transplant recipients who are more likely to experience adverse outcomes.

Transcriptome analysis in acute gastrointestinal graft-versus host disease reveals a unique signature in children and shared biology with pediatric inflammatory bowel disease.

We performed transcriptomic analyses on freshly frozen (n=21) and paraffin-embedded (n=35) gastrointestinal (GI) biopsies from children with and without acute acute GI graft-versus-host disease (GvHD) to study differential gene expressions. We identified 164 significant genes, 141 upregulated and 23 downregulated, in acute GvHD from freshy frozen biopsies. CHI3L1 was the top differentially expressed gene in acute GvHD, involved in macrophage recruitment and bacterial adhesion. Mitochondrial genes were among the top downregulated genes. Immune deconvolution identified a macrophage cellular signature. Weighted gene co-expression network analysis showed enrichment of genes in the ERK1/2 cascade. Transcriptome data from 206 ulcerative colitis (UC) patients were included to uncover genes and pathways shared between GvHD and UC. Comparison with the UC transcriptome showed both shared and distinct pathways. Both UC and GvHD transcriptomes shared an innate antimicrobial signature and FCγ1RA/CD64 was upregulated in both acute GvHD (log-fold increase 1.7, P=0.001) and UC. Upregulation of the ERK1/2 cascade pathway was specific to GvHD. We performed additional experiments to confirm transcriptomics. Firstly, we examined phosphorylation of ERK (pERK) by immunohistochemistry on GI biopsies (acute GvHD n=10, no GvHD n=10). pERK staining was increased in acute GvHD biopsies compared to biopsies without acute GvHD (P=0.001). Secondly, plasma CD64, measured by enzyme-linked immunsorbant assay (n=85) was elevated in acute GI GvHD (P<0.001) compared with those without and was elevated in GVHD compared with inflammatory bowel disease (n=47) (P<0.001), confirming the upregulated expression seen in the transcriptome.

Tryptophan metabolism is dysregulated in individuals with Fanconi anemia.

Fanconi anemia (FA) is a complex genetic disorder associated with progressive marrow failure and a strong predisposition to malignancy. FA is associated with metabolic disturbances such as short stature, insulin resistance, thyroid dysfunction, abnormal body mass index (BMI), and dyslipidemia. We studied tryptophan metabolism in FA by examining tryptophan and its metabolites before and during the stress of hematopoietic stem cell transplant (HSCT). Tryptophan is an essential amino acid that can be converted to serotonin and kynurenine. We report here that serotonin levels are markedly elevated 14 days after HSCT in individuals with FA, in contrast to individuals without FA. Kynurenine levels are significantly reduced in individuals with FA compared with individuals without FA, before and after HSCT. Most peripheral serotonin is made in the bowel. However, serotonin levels in stool decreased in individuals with FA after transplant, similar to individuals without FA. Instead, we detected serotonin production in the skin in individuals with FA, whereas none was seen in individuals without FA. As expected, serotonin and transforming growth factor ß (TGF-ß) levels were closely correlated with platelet count before and after HSCT in persons without FA. In FA, neither baseline serotonin nor TGF-B correlated with baseline platelet count (host-derived platelets), only TGF-B correlated 14 days after transplant (blood bank-derived platelets). BMI was negatively correlated with serotonin in individuals with FA, suggesting that hyperserotonemia may contribute to growth failure in FA. Serotonin is a potential therapeutic target, and currently available drugs might be beneficial in restoring metabolic balance in individuals with FA.

Endothelial injury, F-actin and vitamin-D binding protein after hematopoietic stem cell transplant and association with clinical outcomes.

Endothelial injury after hematopoietic stem cell transplant is an important initiating factor for early transplant toxicities of thrombotic microangiopathy and acute graft versus host disease. We hypothesized that release of the angiopathic molecule filamentous actin from hematopoietic cells lysed during conditioning prior to stem cell transplant would be associated with clinical outcomes. We detected filamentous actin in the blood of 52% of stem cell transplant recipients in the first 14 days after transplant, and children with detectable filamentous actin had significantly elevated risk of thrombotic microangiopathy (p= 0.03) and non-relapse mortality (p= 0.04). Filamentous actin is cleared from the circulation by vitamin D binding protein so we expected that higher levels of vitamin D binding protein would improve outcomes. In a cohort of 190 children receiving allogeneic transplant, risk of thrombotic microangiopathy was reduced in those with serum concentrations of vitamin D binding protein above the median at day 30 (10% vs 31%, p=0.01), and graft versus host disease and non-relapse mortality were reduced in those with levels above the median at day 100 (3% vs 18%, p=0.04 and 0% vs 15%, p=0.002). Western blot analyses demonstrated actin-vitamin D binding protein complexes in the blood, which cleared by day 21-28. Our data support modulation of cytokine secretion and macrophage phenotype by vitamin D binding protein later after transplant. Taken together, our data identify an association between filamentous-actin, a mediator of endothelial damage, and vitamin D binding protein, an actin scavenger, as modifiers of risk of clinical consequences of endothelial injury.

Metabolic networks of the human gut microbiota.

The human gut microbiota controls factors that relate to human metabolism with a reach far greater than originally expected. Microbial communities and human (or animal) hosts entertain reciprocal exchanges between various inputs that are largely controlled by the host via its genetic make-up, nutrition and lifestyle. The composition of these microbial communities is fundamental to supply metabolic capabilities beyond those encoded in the host genome, and contributes to hormone and cellular signalling that support the dynamic adaptation to changes in food availability, environment and organismal development. Poor functional exchange between the microbial communities and their human host is associated with dysbiosis, metabolic dysfunction and disease. This review examines the biology of the dynamic relationship between the reciprocal metabolic state of the microbiota-host entity in balance with its environment (i.e. in healthy states), the enzymatic and metabolic changes associated with its imbalance in three well-studied diseases states such as obesity, diabetes and atherosclerosis, and the effects of bariatric surgery and exercise.