Use of lipid ratios to predict vascular target organ damage in youth.

BACKGROUND: Elevated lipid levels are risk factors for early atherosclerosis. Lipid ratios have emerged as potentially stronger predictors of adverse cardiovascular changes and atherogenic cholesterol. Risk stratification in youth with obesity or type 2 diabetes may be improved by using lipid ratios. We sought to determine if lipid ratios would identify abnormalities in arterial structure and stiffness in adolescents and young adults. METHODS: A total of 762 youth aged 10-24 years had laboratory, anthropometric, blood pressure, and carotid intima-media thickness and arterial stiffness data collected. Subjects were stratified into tertiles (low, mid, high) of lipid ratios and non-high-density lipoprotein cholesterol (HDL-C). Vascular outcomes by tertile were assessed by analyses of variance. General linear models were constructed for each lipid value and included demographics, risk factors and vascular measures. Correlations between lipid markers, vascular measures, and low-density lipoprotein (LDL) particle size and number were conducted. RESULTS: There was a progressive increase in arterial thickness and stiffness across all three lipid ratios and non-HDL-C. The triglyceride to HDL-C (TG/HDL-C) ratio remained an independent predictor of arterial thickness and stiffness after adjusting for other cardiovascular risk factors. TG/HDL-C had the highest correlations with arterial stiffness and small, dense LDL. CONCLUSIONS: Arterial stiffness is increased in youth with high lipid ratios with TG/HDL-C being the most consistent marker of vascular changes. These data suggest that identification of high TG/HDL-C in these individuals may lead to earlier intervention to prevent atherosclerotic cardiovascular disease.

The Effect of Adiposity on Cardiovascular Function and Myocardial Fibrosis in Patients With Duchenne Muscular Dystrophy.

Background Patients with Duchenne muscular dystrophy (DMD) develop cardiomyopathy because of a dystrophin deficiency causing fibrofatty replacement of the myocardium. Corticosteroid use and mobility limitations place these patients at risk for increased adiposity. We sought to determine the association of adiposity with cardiovascular dysfunction in patients with DMD. Methods and Results This was a retrospective review of patients with DMD who underwent both cardiac magnetic resonance imaging and dual-energy x-ray absorptiometry within 1 year. The cardiac magnetic resonance imaging parameters included left ventricular ejection fraction and the presence of late gadolinium enhancement (LGE positive [LGE+]). The adiposity indices, measured by dual-energy x-ray absorptiometry, included percentage of body fat, whole body fat mass indexed to height, and body mass index. A total of 324 patients were identified. Fifty-two percent had LGE+, and 36% had cardiac dysfunction (left ventricular ejection fraction <55%). Patients with cardiac dysfunction had higher whole body fat mass indexed to height and body mass index on univariate analysis (mean difference between patients with and without cardiac dysfunction: +2.9 kg/m, P=0.001; and +1.5 kg/m2, P=0.03, respectively). whole body fat mass indexed to height remained independently associated with cardiac dysfunction on multivariable analysis after adjusting for age, LGE+, and corticosteroid duration. High whole body fat mass indexed to height and percentage of body fat were associated with LGE+ on univariate analysis (mean difference between patients with and without LGE+: +2.0 kg/m, P=0.02; and +2.4%, P=0.02, respectively). Using multivariable analysis, including age and cardiac dysfunction, high percentage of body fat remained independently associated with LGE+. Conclusions This study demonstrates an independent association of adiposity with cardiac dysfunction and LGE+ in patients with DMD. Preventing adiposity may mitigate the later development of ventricular dysfunction in DMD.

Left Ventricular Magnetic Resonance Imaging Strain Predicts the Onset of Duchenne Muscular Dystrophy-Associated Cardiomyopathy.

BACKGROUND: Early detection of left ventricular (LV) dysfunction before the onset of overt Duchenne muscular dystrophy-associated cardiomyopathy (DMDAC) may direct clinical management to slow onset of dysfunction. We aimed to assess whether LV strain will predict those who develop DMDAC. METHODS: We performed a single center retrospective case control study of patients with Duchenne muscular dystrophy who underwent serial cardiac magnetic resonance between 2006 and 2019. Patients with Duchenne muscular dystrophy with an LV ejection fraction ≥55% on ≥1 cardiac magnetic resonance were identified and grouped into age-matched +DMDAC and -DMDAC. Within 3 years, +DMDAC had a subsequent cardiac magnetic resonance with a decline in LV ejection fraction ≥10% and absolute LV ejection fraction ≤50%. -DMDAC maintained an LV ejection fraction ≥55% on serial cardiac magnetic resonances. Two-dimensional and 3-dimensional global radial strain, global circumferential strain (GCS), and global longitudinal strain were measured using tissue tracking software and their ability to predict DMDAC onset was assessed. Multivariable analysis adjusted for late gadolinium enhancement. RESULTS: Thirty +DMDAC and 30 age-matched -DMDAC patients were included with a total of 164 studies analyzed. Before DMDAC onset, 2-dimensional global radial strain and GCS were significantly worse in +DMDAC compared with -DMDAC (25.1±6.0 versus 29.0±6.3, P=0.011; -15.4%±2.4 versus -17.3%±2.6, P=0.003). Three-dimensional GCS and global radial strain had similar findings. Among strain measures, 3-dimensional GCS had the highest area under the curve to predict DMDAC in our cohort. These findings persisted after adjusting for the presence of late gadolinium enhancement. CONCLUSIONS: Reduced global radial strain and GCS may predict those at risk for developing DMDAC before onset of LV dysfunction and its clinical utility warrants further exploration.

Candidate genes contributing to the aggressive phenotype of mantle cell lymphoma.

Mantle cell lymphoma and small lymphocytic lymphoma are lymphocyte cancers that have similar morphologies and a common age of onset. Mantle cell lymphoma is generally an aggressive B cell lymphoma with a short median survival time, whereas small lymphocytic lymphoma is typically an indolent B cell lymphoma with a prolonged median survival time. Using primary tumor samples in bi-directional suppression subtractive hybridization, we identified genes with differential expression in an aggressive mantle cell lymphoma versus an indolent small lymphocytic lymphoma. "Virtual" Northern blot analyses of multiple lymphoma samples confirmed that a set of genes was preferentially expressed in aggressive mantle cell lymphoma compared to indolent small lymphocytic lymphoma. These analyses identified mantle cell lymphoma-specific genes that may be involved in the aggressive behavior of mantle cell lymphoma and possibly other aggressive human lymphomas. Interestingly, most of these differentially expressed genes have not been identified using other techniques, highlighting the unique ability of suppression subtractive hybridization to identify potentially rare or low expression genes.

Pir51, a Rad51-interacting protein with high expression in aggressive lymphoma, controls mitomycin C sensitivity and prevents chromosomal breaks.

Pir51, a protein of unknown function that interacts with Rad51, was identified in a screen for genes that were highly expressed in aggressive mantle cell lymphoma (MCL) versus indolent small lymphocytic lymphoma (SLL) patient samples. We show that Pir51 is a nuclear protein expressed in a variety of cell types and that its expression is regulated during the cell cycle in a pattern nearly identical to Rad51. Also similar to Rad51, Pir51 levels did not change in response to a variety of DNA damaging agents. siRNA depletion of Pir51 did not reduce homologous recombination repair (HRR), but sensitized cells to mitomycin C (MMC)-induced DNA crosslinking and resulted in elevated levels of double-strand breaks (DSBs) in metaphase chromosome spreads and reduced colony formation. Therefore, Pir51 maintains genomic integrity and potentially connects the early response to DNA crosslinks, orchestrated by the ATR kinase and Fanconi Anemia (FA) proteins, to later stages of Rad51-dependent repair. Our results provide the first example of a Rad51-binding protein that influences DNA crosslink repair without affecting homologous recombination repair.

A conserved sequence upstream of the B29 (Ig beta, CD79b) gene interacts with YY1.

The human, murine, and rat B29 (Ig beta, CD79b) genes are highly conserved in sequence and organization and exhibit strict B cell-specific expression. In the human and rat genomes, the B29 gene is located between the skeletal muscle-specific Na-channel alpha subunit (SCN4A) gene and the pituitary-specific growth hormone (GH-N) gene. The human pituitary-specific GH-N gene is controlled by a tissue-specific locus control region (LCR) located just upstream of the B29 promoter that mediates tissue-specific enhancement, histone acetylation, and an open chromatin conformation across the B29 gene in growth hormone (GH)-expressing pituitary cells. Here we show that B29 mRNA is not detected in a GH-expressing pituitary cell line and that GH-N mRNA is not detected in B cells. This differential expression suggests that the B29 gene is insulated or otherwise protected from the regulatory influences of the closely proximal GH LCR. We searched available sequences upstream of the human, mouse, and rat B29 genes and found a highly conserved sequence that fulfills the criteria recently established for non-coding DNA elements potentially involved in gene control. This B29 conserved sequence (BCS) bound ubiquitously expressed nuclear protein complexes. DNase I protection analysis of the BCS revealed a central 'footprinted' core which was confirmed to bind the multifunctional transcription factor, YY1. However, neither the BCS nor the YY1-binding core motif exhibited silencer or enhancer activity in transient transfections or position-independent insulator activity in enhancer-blocking assays. Thus, the BCS may function as a tissue-specific LCR or position-dependent insulator specifically countering the influences of the 5' GH LCR and controlling B29 gene expression.

Gene expression patterns in AIDS versus non-AIDS-related diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is more prevalent and more often fatal in AIDS patients compared to immune-competent individuals. Potential explanations for these differences include distinct tumorigenic mechanisms and/or altered cellular microenvironments. We previously discovered that the TCL1 (T-cell leukemia-1) proto-oncogene is expressed in a high proportion of AIDS-DLBCL compared to DLBCL cases and that aberrant TCL1 expression causes DLBCL in a new transgenic mouse model. Here, we continue to search for other genes that may contribute to the differential pathogenesis of DLBCL in AIDS. Gene subtraction yielded over 1800 potential AIDS-DLBCL candidates, of which about 50% were unknown and not further considered. The remaining 50% of genes were annotated and, when combined with miniarray screening from multiple patient samples, were reduced to 18 candidate genes for extended analysis. These 18 genes showed distinct patterns of expression in both AIDS-DLBCL and DLBCL samples. However, unlike TCL1, none of these genes was preferentially associated with either AIDS-DLBCL or DLBCL. Our data suggest that the increased incidence and severity of AIDS-DLBCL compared to DLBCL is likely due to crippled immune surveillance rather than to markedly different gene expression profiles.

Sp1 transactivation of the TCL1 oncogene.

Cis-regions and trans-factors controlling TCL1 oncogene expression are not known. We identified the functional TCL1 promoter by mapping four transcriptional start sites 24-30 bp downstream of a TATA box. A 424-bp fragment upstream of the major start site showed robust promoter activity comparable with SV40 in both TCL1 expressing and non-expressing cell lines. Additional constructs spanning 10 kb upstream and 20 kb downstream of the start site showed only modest increases in reporter activity indicating that TCL1 expression is primarily controlled by the promoter. Ten putative Sp1-binding sites were identified within 300 bp of the start site, and three of these specifically bound Sp1. A dose-dependent transactivation of the TCL1 promoter with Sp1 addition in Sp1-negative Drosophila SL2 cells was observed, and mutation of the three identified Sp1-binding sites significantly repressed reporter gene expression in 293T cells, confirming a key role for Sp1 in activating the TCL1 promoter in vivo. In TCL1 silent cell lines, CpG DNA methylation was rarely observed at functional Sp1 sites, and methylation of a previously reported NotI restriction site was associated with dense CpG methylation rather than endogenous TCL1 gene silencing. Together, these results indicate that Sp1 mediates transactivation of the TCL1 core promoter and that TCL1 gene silencing is not dependent on mechanisms involving Sp1 and NotI site methylation.