Impact of social connectedness on weight loss outcomes in an online program

Obesity is linked to many negative health consequences. While online behavioral weight loss programs (BWL) are an effective treatment for obesity, weight losses are modest. Social connectedness has been found to improve weight loss outcomes and previous findings suggests that it may be especially important for people of color. The present study investigated the impact of social connectedness (structural connectedness, or network size; relationship quality, and functional connectedness, or social support) on weight loss outcomes in an online BWL program and whether Black race or Hispanic ethnicity moderates the relationship between social connectedness and weight loss. Participants (N = 387) enrolled in a 16-week online BWL program and completed measures of social connectedness before treatment and had their weight measured. Individuals with less structural connectedness (smaller social networks) had greater weight losses. Further, higher levels of functional connectedness (affectionate support, positive support, and relationship quality) mediated the relationship between smaller network size and better weight loss outcomes. Black race / Hispanic ethnicity did not moderate the relationship between social connectedness and weight loss. These findings suggest that the quality of one's relationships, not the size of one's social network, is important for weight loss. Future studies may examine whether online BWL programs that build relationship quality and affectionate and positive support in participants' existing social networks improve overall weight loss outcomes.

Impact of income and perceived stress on engagement and weight loss outcomes in an online behavioral weight loss program

Lower income is associated with greater stress, and stress has been shown to undermine treatment engagement and weight loss outcomes in face-to-face interventions. The present study examined whether lower income predicts treatment engagement and weight loss outcomes during an online behavioral weight loss (BWL) intervention. A total of N = 260 participants (79.2% female; 50.7 ± 11.9 years of age; 60.3% non-Hispanic White) were enrolled into an online BWL program and had their income, stress, program engagement, and weight measured. Results showed that stress fully mediated the effect of income on engagement in the online program. Further, lower income predicted poorer weight loss outcomes, and this effect was partially mediated by perceived stress. This is the first study to demonstrate that lower income is associated with poorer engagement and weight loss outcomes in an online weight loss program, underscoring the need for systems-level stress reduction programs and individual level stress management tools, particularly for individuals with lower income.

Episodic future thinking, delay discounting, and exercise during weight loss maintenance: The PACE trial

OBJECTIVES

Weight loss maintenance (WLM) is the next major challenge in obesity treatment. While most individuals who lose weight intend to keep their weight off, weight regain is common. Temporal Self-Regulation Theory posits that whether intentions lead to behavior depends on self-regulatory capacity, including delay discounting (DD; the tendency to discount a larger future reward in favor of a smaller immediate reward). Episodic Future Thinking (EFT; mental imagery of a future event for which a health goal is important) may improve DD and promote behavior change. Described herein is a trial protocol designed to examine whether EFT improves DD within the context of weight loss maintenance.

METHOD

Participants who lose ≥5% of initial body weight in an online behavioral weight loss intervention will be randomly assigned to a standard weight loss maintenance program (WLM-STD) or a weight loss maintenance program plus EFT (WLM + EFT). Both interventions involve periodic phone and in-person treatment sessions. Participants in WLM + EFT will engage in daily EFT training via smartphone. To control for contact, participants in WLM-STD will engage in daily Healthy Thinking (reviewing strategies for weight management) on their smartphone. Our primary hypothesis is that WLM + EFT will yield better improvements in DD compared to WLM-STD. We will also explore whether DD mediates the relationship between intervention allocation and physical activity (secondary outcome). Weight and contextual variables will be explored.

CONCLUSIONS

This study is the first to test whether EFT improves DD within the context of weight loss maintenance; results from this experimental medicine approach could have important implications for understanding the impact of both EFT and DD on sustained behavior change. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Slowing down and taking a second look: Inhibitory deficits associated with binge eating are not food-specific

Poor inhibitory control may contribute to the maintenance of binge eating (BE) among overweight and obese individuals. However, it is unknown whether deficits are general or specific to food (versus other attractive non-food stimuli), or whether observed deficits are attributable to increased depressive symptoms in BE groups. In the current study, we hypothesized that individuals with BE would display inhibitory control deficits, with more pronounced deficits occurring when food stimuli were used. Overweight or obese participants with (n = 25) and without (n = 65) BE completed a Stop Signal Task (SST) with distinct task blocks featuring food-specific stimuli, positive non-food stimuli, or neutral stimuli. The BE group exhibited poorer inhibitory control across SST stimuli types (p = .003, ηp(2)=.10), but deficits did not differ by stimuli type (p = .68, ηp(2) < .01). Including depression as a covariate did not significantly alter results. Results suggest individuals with BE display inhibitory control deficits compared to controls; however, deficits do not appear to be specific to stimuli type. Furthermore, inhibitory control deficits do not appear to be associated with mood disturbance in the BE group. Replication and further research is needed to guide treatment targets.

Bacteriophage P22 portal protein is part of the gauge that regulates packing density of intravirion DNA

The complex double-stranded DNA bacteriophages assemble DNA-free protein shells (procapsids) that subsequently package DNA. In the case of several double-stranded DNA bacteriophages, including P22, packaging is associated with cutting of DNA from the concatemeric molecule that results from replication. The mature intravirion P22 DNA has both non-unique (circularly permuted) ends and a length that is determined by the procapsid. In all known cases, procapsids consist of an outer coat protein, an interior scaffolding protein that assists in the assembly of the coat protein shell, and a ring of 12 identical portal protein subunits through which the DNA is presumed to enter the procapsid. To investigate the role of the portal protein in cutting permuted DNA from concatemers, we have characterized P22 portal protein mutants. The effects of several single amino acid changes in the P22 portal protein on the length of the DNA packaged, the density to which DNA is condensed within the virion, and the outer radius of the capsid have been determined. The results obtained with one mutant (NT5/1a) indicate no change (+/- 0.5%) in the radius of the capsid, but mature DNA that is 4.7% longer and a packing density that is commensurately higher than those of wild-type P22. Thus, the portal protein is part of the gauge that regulates the length and packaging density of DNA in bacteriophage P22. We argue that these findings make models for DNA packaging less likely in which the packing density is a property solely of the coat protein shell or of the DNA itself.

Nucleotide sequence of the bacteriophage P22 genes required for DNA packaging

The mechanism of DNA packaging by dsDNA viruses is not well understood in any system. In bacteriophage P22 only five genes are required for successful condensation of DNA within the capsid. The products of three of these genes, the portal, scaffolding, and coat proteins, are structural components of the precursor particle, and two, the products of genes 2 and 3, are not. The scaffolding protein is lost from the structure during packaging, and only the portal and coat proteins are present in the mature virus particle. These five genes map in a contiguous cluster at the left end of the P22 genetic map. Three additional genes, 4, 10, and 26, are required for stabilizing of the condensed DNA within the capsid. In this report we present the nucleotide sequence of 7461 bp of P22 DNA that contains the five genes required for DNA condensation, as well as a nonessential open reading frame (ORF109), gene 4, and a portion of gene 10. N-terminal amino acid sequencing of the encoded proteins accurately located the translation starts of six genes in the sequence. Despite the fact that most of these proteins have striking analogs in the other dsDNA bacteriophage groups, which perform highly analogous functions, no amino acid sequence similarity between these analogous proteins has been found, indicating either that they diverged a very long time ago or that they are the products of spectacular convergent evolution.

Fine structure genetic and physical map of the gene 3 to 10 region of the bacteriophage P22 chromosome

The mechanism by which dsDNA is packaged by viruses is not yet understood in any system. Bacteriophage P22 has been a productive system in which to study the molecular genetics of virus particle assembly and DNA packaging. Only five phage encoded proteins, the products of genes 3, 2, 1, 8 and 5, are required for packaging the virus chromosome inside the coat protein shell. We report here the construction of a detailed genetic and physical map of these genes, the neighboring gene 4 and a portion of gene 10, in which 289 conditional lethal amber, opal, temperature sensitive and cold sensitive mutations are mapped into 44 small (several hundred base pair) intervals of known sequence. Knowledge of missense mutant phenotypes and information on the location of these mutations allows us to begin the assignment of partial protein functions to portions of these genes. The map and mapping strains will be of use in the further genetic dissection of the P22 DNA packaging and prohead assembly processes.

Characterization of persistent poliovirus mutants selected in human neuroblastoma cells

Six Sabin-derived persistent poliovirus mutants were selected in human neuroblastoma IMR-32 cells. The mutants had a titer 30 to 10(5) times lower in nonneural HEp-2c cells than in IMR-32 cells. When the growth cycles of persistent viruses in the two cell lines were compared, the most striking feature was a delay of 2 to 4 hr in virus release from HEp-2c cells. In Hep-2c cells, type 1 mutants could spontaneously establish a persistent infection in the absence of any exogenous viral inhibitor. Mutations at a rate of 1 every 210 nucleotides had accumulated in the genome of the type 1 mutants selected in neuroblastoma cells, modifying cell specificity and conferring the ability to persist in some nonneural cells. These results indicate that mutants of poliovirus with highly modified biological properties can be selected in vitro in cells of neural origin.

Structure of the Drosophila DNA topoisomerase II gene. Nucleotide sequence and homology among topoisomerases II

We have determined the nucleotide sequence of the Drosophila DNA topoisomerase II gene. Data from primer extension and S1 nuclease protection experiments were combined with comparisons of genomic and cDNA sequences to determine the structure of the mature messenger RNA. This message has a large open reading frame of 4341 nucleotides. The length of the predicted protein is 1447 amino acids with a molecular weight of 164,424. Topoisomerase II can be divided into three domains: (1) an N-terminal region with homology to the B (ATPase) subunit of the bacterial type II topoisomerase, DNA gyrase; (2) a central region with homology to the A (breaking and rejoining) subunit of DNA gyrase; (3) a C-terminal region characterized by alternating stretches of positively and negatively charged amino acids. DNA topoisomerase II from the fruit fly shares significant sequence homology with those from divergent sources, including bacteria, bacteriophage T4 and yeasts. The location and distribution of homologous stretches in these sequences are analyzed.

Functional expression of a Drosophila gene in yeast: genetic complementation of DNA topoisomerase II

Since DNA topoisomerase II (EC 5.99.1.3) is an essential enzyme in yeast, heterologous topoisomerase II gene expression in yeast cells can provide a system for analyzing the structure and function of topoisomerase II genes from other species. A series of yeast expression plasmids was constructed in which segments of the cDNA sequences encoding Drosophila DNA topoisomerase II were inserted under the transcriptional control of yeast GAL1 promoter. Expression of the functional form of Drosophila topoisomerase II cDNA can complement conditionally lethal, temperature-sensitive mutations in the yeast topoisomerase II gene (TOP2), as well as mutations in which the TOP2 locus was disrupted. The survival of these yeast cells depends upon the continuous expression of Drosophila topoisomerase II. Repression of Drosophila gene expression by glucose causes these yeast cells to cease dividing after a few generations. In addition to these genetic complementation data, the expression of the Drosophila topoisomerase II gene in yeast cells with a disruption in TOP2 can also be detected by immunochemical methods with an antibody specific for Drosophila topoisomerase II.

Isolation and characterization of the gene encoding Drosophila DNA topoisomerase II

We have isolated the gene coding for the Drosophila type II DNA topoisomerase by immunochemically screening a Drosophila cDNA library constructed with a phage lambda expression vector, lambda gt11. The identity of the cloned gene is confirmed by the analysis of an antigenic fusion protein produced in Escherichia coli and by the in vitro translation of its RNA. The gene is 5.1 kilobases in length, the expected size for a gene encoding topoisomerase II (Mr 170,000), and it is divided into five exons. By in situ hybridization to the polytene chromosomes from salivary glands, we have mapped it to chromosome 2L at 37D.

Plasmid vectors useful in the study of translation initiation signals

The construction and characterization of plasmid vectors useful in the analysis of translation initiation signals in Escherichia coli and in the construction of lacZ gene hybrids are described. Transcription on the vectors proceeds from a cAMP-independent lac promoter through several restriction sites into a truncated lacZ structural gene lacking its first eight codons. Because this gene has no translation initiation signal, its level of expression is extremely low. A DNA fragment containing a translation start signal can be inserted between the promoter and truncated lacZ gene to produce a hybrid protein with functional beta-galactosidase activity. The vectors described here differ in sequence between the EcoRI cloning site and the lacZ gene to allow easy, in-frame joining of DNA containing a translation initiation signal to the lacZ gene. Cells containing plasmids can be screened directly for in-frame inserts by colony color on indicator plates.