Authors: Piaggi P, Thearle MS, Bogardus C, Krakoff J
Journal: J Clin Endocrinol Metab. 2015 Jan 5:jc20143582. [Epub ahead of print]
Context: Increased adiposity and insulin resistance are associated with hyperglycemia and previous studies have reported that higher glucoses are associated with lower rates of weight gain. One possible mechanism is via increased energy expenditure (EE). Objective: To assess the relationships between changes in EE during spontaneous weight gain and concomitant changes in glucose levels. Design and Participants: Body composition, metabolic and glycemic data were available from non-diabetic Native Americans who underwent two measurements of 24-h EE during eucaloric feeding in a metabolic chamber (N=144; time between measurements: 5.0±3.3 years) or resting EE by ventilated hood system during the euglycemic-hyperinsulinemic clamp (N=261; 4.5±3.2 years). Long-term follow-up data (8.3±4.3 years) for weight and body composition were available in 131 and 122 subjects, respectively. Main Outcome Measures: 24-h EE and respiratory quotient (RQ), resting (RMR) and sleeping (SMR) metabolic rates, glucose and insulin levels, basal glucose output (BGO). Results: Weight gain-associated increase in fasting plasma glucose (FPG) levels was accompanied with decreased 24-h RQ (partial R=-0.24, P=0.002) and increased 24-h EE, RMR, SMR and fat oxidation after accounting for changes in body composition (partial R: 0.12 to 0.19, all P≤0.05). Upon weight gain, BGO tended to increase (P=0.07) while insulin infusion induced a decrease in EE (P=0.04). Higher baseline FPG predicted lower rates of future weight gain (partial R=-0.18, P=0.04). Conclusions: Higher FPG after weight gain was associated with greater-than-expected increase in EE. The rise in BGO and the insulin-induced EE suppression at follow-up indicate that increased hepatic gluconeogenesis may be an important mediator of EE changes associated with weight gain.
Authors: Wentzensen N, Walker JL, Gold MA, Smith KM, Zuna RE, Mathews C, Dunn ST, Zhang R, Moxley K, Bishop E, Tenney M, Nugent E, Graubard BI, Wacholder S, Schiffman M
Journal: J Clin Oncol. 2015 Jan 1;33(1):83-9. doi: 10.1200/JCO.2014.55.9948
PURPOSE: Women with abnormal cervical cancer screening results are referred to colposcopy and biopsy for diagnosis of cervical cancer precursors (high-grade squamous intraepithelial lesions [HSILs]). Colposcopy with a single biopsy can miss identification of HSILs. No systematic study has quantified the improved detection of HSIL by taking multiple lesion-directed biopsies.
METHODS: The Biopsy Study was an observational study of 690 women referred to colposcopy after abnormal cervical cancer screening results. Up to four directed biopsies were taken from distinct acetowhite lesions and ranked by colposcopic impression. A nondirected biopsy of a normal-appearing area was added if fewer than four directed biopsies were taken. HSIL identified by any biopsy was the reference standard of disease used to evaluate the incremental yield and sensitivity of multiple biopsies.
RESULTS: In the overall population, sensitivities for detecting HSIL increased from 60.6% (95% CI, 54.8% to 66.6%) from a single biopsy to 85.6% (95% CI, 80.3% to 90.2%) after two biopsies and to 95.6% (95% CI, 91.3% to 99.2%) after three biopsies. A significant increase in sensitivity of multiple biopsies was observed in all subgroups. The highest increase in yield of HSIL was observed for women with a high-grade colposcopic impression, HSIL cytology, and human papillomavirus (HPV) type 16 positivity. Only 2% of all HSILs diagnosed in the participants were detected by biopsies of normal-appearing transformation zone.
CONCLUSION: Collection of additional lesion-directed biopsies during colposcopy increased detection of histologic HSIL, regardless of patient characteristics. Taking additional biopsies when multiple lesions are present should become the standard practice of colposcopic biopsy.
Authors: Andres SN, Appel CD, Westmoreland JW, Williams JS, Nguyen Y, Robertson PD, Resnick MA, Williams RS
Journal: Nat Struct Mol Biol. 2015 Jan 12. doi: 10.1038/nsmb.2945. [Epub ahead of print]
Ctp1 (also known as CtIP or Sae2) collaborates with Mre11-Rad50-Nbs1 to initiate repair of DNA double-strand breaks (DSBs), but its functions remain enigmatic. We report that tetrameric Schizosaccharomyces pombe Ctp1 contains multivalent DNA-binding and DNA-bridging activities. Through structural and biophysical analyses of the Ctp1 tetramer, we define the salient features of Ctp1 architecture: an N-terminal interlocking tetrameric helical dimer-of-dimers (THDD) domain and a central intrinsically disordered region (IDR) linked to C-terminal 'RHR' DNA-interaction motifs. The THDD, IDR and RHR are required for Ctp1 DNA-bridging activity in vitro, and both the THDD and RHR are required for efficient DSB repair in S. pombe. Our results establish non-nucleolytic roles of Ctp1 in binding and coordination of DSB-repair intermediates and suggest that ablation of human CtIP DNA binding by truncating mutations underlie the CtIP-linked Seckel and Jawad syndromes.
Authors: Clausen AR, Lujan SA, Burkholder AB, Orebaugh CD, Williams JS, Clausen MF, Malc EP, Mieczkowski PA, Fargo DC, Smith DJ, Kunkel T
Journal: Nat Struct Mol Biol. 2015 Jan 26. doi: 10.1038/nsmb.2957. [Epub ahead of print]
Ribonucleotides are frequently incorporated into DNA during replication in eukaryotes. Here we map genome-wide distribution of these ribonucleotides as markers of replication enzymology in budding yeast, using a new 5' DNA end-mapping method, hydrolytic end sequencing (HydEn-seq). HydEn-seq of DNA from ribonucleotide excision repair-deficient strains reveals replicase- and strand-specific patterns of ribonucleotides in the nuclear genome. These patterns support the roles of DNA polymerases α and δ in lagging-strand replication and of DNA polymerase ɛ in leading-strand replication. They identify replication origins, termination zones and variations in ribonucleotide incorporation frequency across the genome that exceed three orders of magnitude. HydEn-seq also reveals strand-specific 5' DNA ends at mitochondrial replication origins, thus suggesting unidirectional replication of a circular genome. Given the conservation of enzymes that incorporate and process ribonucleotides in DNA, HydEn-seq can be used to track replication enzymology in other organisms.
Authors: Qiu C, McCann KL, Wine RN, Baserga SJ, Hall TM
Journal: Proc Natl Acad Sci U S A. 2014 Dec 15. pii: 201407634. [Epub ahead of print]
Pumilio/feminization of XX and XO animals (fem)-3 mRNA-binding factor (PUF) proteins bind sequence specifically to mRNA targets using a single-stranded RNA-binding domain comprising eight Pumilio (PUM) repeats. PUM repeats have now been identified in proteins that function in pre-rRNA processing, including human Puf-A and yeast Puf6. This is a role not previously ascribed to PUF proteins. Here we present crystal structures of human Puf-A that reveal a class of nucleic acid-binding proteins with 11 PUM repeats arranged in an "L"-like shape. In contrast to classical PUF proteins, Puf-A forms sequence-independent interactions with DNA or RNA, mediated by conserved basic residues. We demonstrate that equivalent basic residues in yeast Puf6 are important for RNA binding, pre-rRNA processing, and mRNA localization. Thus, PUM repeats can be assembled into alternative folds that bind to structured nucleic acids in addition to forming canonical eight-repeat crescent-shaped RNA-binding domains found in classical PUF proteins.
Authors: Nichols HB, DeRoo LA, Scharf DR, Sandler DP
Journal: J Natl Cancer Inst. 2014 Dec 3;107(1). pii: dju354. doi: 10.1093/jnci/dju354. Print 2015 Jan.
BACKGROUND: Tamoxifen has been US Food and Drug Administration-approved for primary prevention of breast cancer since 1998 but has not been widely adopted, in part because of increased risk of serious side effects. Little is known about the risk-benefit profiles of women who use chemoprevention outside of a clinical trial. We examined characteristics associated with initiation and discontinuation of tamoxifen for primary prevention of breast cancer within a large cohort of women with a first-degree family history of breast cancer.
METHODS: This research was conducted within The Sister Study, a cohort of 50884 US and Puerto Rican women age 35 to 74 years enrolled from 2003 to 2009. Eligible women were breast cancer-free at enrollment and had a sister who had been diagnosed with breast cancer. Participants reported tamoxifen use, ages started and stopped taking tamoxifen, and total duration of use at enrollment. We identified 788 tamoxifen users and 3131 nonusers matched on age and year of enrollment who had no history of contraindicating factors (stroke, transient ischemic attack, cataract, endometrial or uterine cancer). Characteristics associated with tamoxifen initiation were evaluated with multivariable conditional logistic regression. All statistical tests were two-sided.
RESULTS: Based on published risk-benefit indices, 20% of women who used tamoxifen had insufficient evidence that the benefits of tamoxifen outweigh the risk of serious side effects. After 4.5 years, 46% of women had discontinued tamoxifen.
CONCLUSIONS: While the majority of women who used tamoxifen for primary prevention of breast cancer were likely to benefit, substantial discontinuation of tamoxifen before five years and use by women at risk of serious side effects may attenuate benefits for breast cancer prevention.
Authors: Baumann MH, Solis E Jr, Watterson LR, Marusich JA, Fantegrossi WE, Wiley JL
Journal: J Neurosci. 2014 Nov 12;34(46):15150-8. doi: 10.1523/JNEUROSCI.3223-14.2014
The abuse of synthetic psychoactive substances known as "designer drugs," or "new psychoactive substances" (NPS), is increasing at an alarming rate. NPS are purchased as alternatives to traditional illicit drugs of abuse and are manufactured to circumvent laws regulating the sale and use of controlled substances. Synthetic cathinones (i.e., "bath salts") and synthetic cannabinoids (i.e., "spice") are two types of NPS that have received substantial media attention. Although low recreational doses of bath salts or spice compounds can produce desirable effects, high doses or chronic exposure often leads to dangerous medical consequences, including psychosis, violent behaviors, tachycardia, hyperthermia, and even death. Despite the popularity of NPS, there is a paucity of scientific data about these drugs. Here we provide a brief up-to-date review describing the mechanisms of action and neurobiological effects of synthetic cathinones and cannabinoids.
Authors: Pratto F, Brick K, Khil P, Smagulova F, Petukhova GV, Camerini-Otero RD
Journal: Science. 2014 Nov 14;346(6211):1256442. doi: 10.1126/science.1256442
DNA double-strand breaks (DSBs) are introduced in meiosis to initiate recombination and generate crossovers, the reciprocal exchanges of genetic material between parental chromosomes. Here, we present high-resolution maps of meiotic DSBs in individual human genomes. Comparing DSB maps between individuals shows that along with DNA binding by PRDM9, additional factors may dictate the efficiency of DSB formation. We find evidence for both GC-biased gene conversion and mutagenesis around meiotic DSB hotspots, while frequent colocalization of DSB hotspots with chromosome rearrangement breakpoints implicates the aberrant repair of meiotic DSBs in genomic disorders. Furthermore, our data indicate that DSB frequency is a major determinant of crossover rate. These maps provide new insights into the regulation of meiotic recombination and the impact of meiotic recombination on genome function.
Authors: Freudenthal BD, Beard WA, Perera L, Shock DD, Kim T, Schlick T, and Wilson SH
Journal: Nature. 2014 Nov 17. doi: 10.1038/nature13886.
Oxidative stress promotes genomic instability and human diseases. A common oxidized nucleoside is 8-oxo-7,8-dihydro-2'-deoxyguanosine, which is found both in DNA (8-oxo-G) and as a free nucleotide (8-oxo-dGTP). Nucleotide pools are especially vulnerable to oxidative damage. Therefore cells encode an enzyme (MutT/MTH1) that removes free oxidized nucleotides. This cleansing function is required for cancer cell survival and to modulate Escherichia coli antibiotic sensitivity in a DNA polymerase (pol)-dependent manner. How polymerases discriminate between damaged and non-damaged nucleotides is not well understood. This analysis is essential given the role of oxidized nucleotides in mutagenesis, cancer therapeutics, and bacterial antibiotics. Even with cellular sanitizing activities, nucleotide pools contain enough 8-oxo-dGTP to promote mutagenesis. This arises from the dual coding potential where 8-oxo-dGTP(anti) base pairs with cytosine and 8-oxo-dGTP(syn) uses its Hoogsteen edge to base pair with adenine. Here we use time-lapse crystallography to follow 8-oxo-dGTP insertion opposite adenine or cytosine with human pol β, to reveal that insertion is accommodated in either the syn- or anti-conformation, respectively. For 8-oxo-dGTP(anti) insertion, a novel divalent metal relieves repulsive interactions between the adducted guanine base and the triphosphate of the oxidized nucleotide. With either templating base, hydrogen-bonding interactions between the bases are lost as the enzyme reopens after catalysis, leading to a cytotoxic nicked DNA repair intermediate. Combining structural snapshots with kinetic and computational analysis reveals how 8-oxo-dGTP uses charge modulation during insertion that can lead to a blocked DNA repair intermediate.
Authors: Memoli MJ, Czajkowski L, Reed S, Athota R, Bristol T, Proudfoot K, Fargis S, Stein M, Dunfee RL, Shaw PA, Davey RT, Taubenberger JK
Journal: Clin Infect Dis. 2014 Nov 20. pii: ciu924. [Epub ahead of print]
BACKGROUND: Healthy volunteer wild-type influenza challenge models offer a unique opportunity to evaluate multiple aspects of this important virus. Such studies have not been performed in the U.S. in over a decade, limiting our capability to investigate this virus and develop countermeasures. We have completed the first ever wild-type influenza A challenge study under an IND. This dose finding study will lead to further development of this model both for A(H1N1)pdm09 and other strains of influenza.
METHODS: Volunteers were admitted to an isolation unit at the NIH Clinical Center for a minimum of 9 days. A reverse genetics, cell-based, GMP produced, wild-type A(H1N1)pdm09 virus was administered intranasally. Escalating doses were given until a dose was reached that produced disease in a minimum of 60% of volunteers.
RESULTS: An optimal dose of 107 TCID50 was reached which caused mild to moderate influenza disease in 69% of individuals with mean viral shedding for 4-5 days and significant rises in convalescent influenza antibody titers. Viral shedding preceded symptoms by 12-24 hours and terminated 2-3 days prior to symptom resolution, indicating that individuals may be infectious before symptom development. As expected nasal congestion and rhinorrhea were most common, but interestingly, fever was observed in only 10%.
CONCLUSION: This study represents the first healthy volunteer influenza challenge model using a GMP-produced wild-type virus under an IND. This unique clinical research program will facilitate future studies of influenza pathogenesis, animal model validation, and the rapid, efficient, and cost-effective evaluation of efficacy of novel vaccines and therapeutics.