Common genetic factors for uncontrolled eating mechanisms

OBJECTIVE

Reward-based eating drives are putative mechanisms of uncontrolled eating implicated in obesity and disordered eating (e.g., binge eating). Uncovering the genetic and environmental contributions to reward-related eating, and their genetic correlation with BMI, could shed light on key mechanisms underlying eating and weight-related disorders.

METHOD

We conducted a classical twin study to examine how much variance in uncontrolled eating phenotypes and body mass index (BMI) was explained by genetic factors, and the extent that these phenotypes shared common genetic factors. 353 monozygotic twins and 128 dizygotic twins completed the Reward-based Eating Drive 13 scale, which measures three distinct uncontrolled eating phenotypes (loss of control over eating, preoccupation with thoughts about food, and lack of satiety), and a demographic questionnaire which included height and weight for BMI calculation. We estimated additive genetic (A), common environmental (C), and unique environmental (E) factors for each phenotype, as well as their genetic correlations, with a multivariate ACE model. A common pathway model also estimated whether genetic variance in the uncontrolled eating phenotypes was better explained by a common latent uncontrolled eating factor.

RESULTS

There were moderate genetic correlations between uncontrolled eating phenotypes and BMI (.26-.41). Variance from the uncontrolled eating phenotypes was also best explained by a common latent uncontrolled eating factor that was explained by additive genetic factors (52%).

DISCUSSION

These results suggest that uncontrolled eating phenotypes are heritable traits that also share genetic variance with BMI. This has implications for understanding the cognitive mechanisms that underpin obesity and disordered eating.

PUBLIC SIGNIFICANCE

Our study clarifies the degree to which uncontrolled eating phenotypes and BMI are influenced by shared genetics and shows that vulnerability to uncontrolled eating traits is impacted by common genetic factors.

Leveraging Online Treatment to Re-examine the Association Between Alcohol Use and Disinhibition

BACKGROUND

Cognitive disinhibition underpins alcohol and drug use problems. Although higher-risk substance use is consistently associated with poorer disinhibition, current findings may be limited by narrow recruitment methods, which over-represent individuals engaged in traditional treatment services with more severe presentations. We embedded a novel gamified disinhibition task (the Cognitive Impulsivity Suite; CIS) in a national online addiction support service ( https://www.counsellingonline.org.au/ ).

METHOD

Participants aged 18 to 64 ( N = 137; 109 women) completed the Alcohol-Use Disorders Identification Test (AUDIT) and Drug Use Disorders Identification Test (DUDIT) along with the CIS, which measures three aspects of disinhibition (Attentional Control, Information-Sampling, and Feedback Monitoring/Shifting). The majority of the sample comprised people with alcohol use, and AUDIT scores were differentiated into ‘higher-risk’ or ‘lower-risk’ groups using latent-class analysis. These classes were then regressed against CIS performance measures.

RESULTS

Compared to lower-risk, higher-risk alcohol use was associated with poorer attentional control and feedback monitoring/shifting. While higher-risk alcohol use was associated with slower information accumulation, this was only observed for older adults, who appeared to compensate with a more conservative response criterion.

CONCLUSIONS

Our results reveal novel relationships between higher-risk alcohol use and specific aspects of disinhibition in participants who sought online addiction help services.

The influence of stress on the neural underpinnings of disinhibited eating: a systematic review and future directions for research

Disinhibited eating involves overconsumption and loss of control over food intake, and underpins many health conditions, including obesity and binge-eating related disorders. Stress has been implicated in the development and maintenance of disinhibited eating behaviours, but the mechanisms underlying this relationship are unclear. In this systematic review, we examined how the impact of stress on the neurobiological substrates of food-related reward sensitivity, interoception and cognitive control explains its role in disinhibited eating behaviours. We synthesised the findings of functional magnetic resonance imaging studies including acute and/or chronic stress exposures in participants with disinhibited eating. A systematic search of existing literature conducted in alignment with the PRISMA guidelines identified seven studies investigating neural impacts of stress in people with disinhibited eating. Five studies used food-cue reactivity tasks, one study used a social evaluation task, and one used an instrumental learning task to probe reward, interoception and control circuitry. Acute stress was associated with deactivation of regions in the prefrontal cortex implicated in cognitive control and the hippocampus. However, there were mixed findings regarding differences in reward-related circuitry. In the study using a social task, acute stress associated with deactivation of prefrontal cognitive control regions in response to negative social evaluation. In contrast, chronic stress was associated with both deactivation of reward and prefrontal regions when viewing palatable food-cues. Given the small number of identified publications and notable heterogeneity in study designs, we propose several recommendations to strengthen future research in this emerging field.

Cognitive training and remediation interventions for substance use disorders: a Delphi consensus study

AIMS

Substance use disorders (SUD) are associated with cognitive deficits that are not always addressed in current treatments, and this hampers recovery. Cognitive training and remediation interventions are well suited to fill the gap for managing cognitive deficits in SUD. We aimed to reach consensus on recommendations for developing and applying these interventions.

DESIGN, SETTING AND PARTICIPANTS

We used a Delphi approach with two sequential phases: survey development and iterative surveying of experts. This was an on-line study. During survey development, we engaged a group of 15 experts from a working group of the International Society of Addiction Medicine (Steering Committee). During the surveying process, we engaged a larger pool of experts (n = 54) identified via recommendations from the Steering Committee and a systematic review.

MEASUREMENTS

Survey with 67 items covering four key areas of intervention development: targets, intervention approaches, active ingredients and modes of delivery.

FINDINGS

Across two iterative rounds (98% retention rate), the experts reached a consensus on 50 items including: (i) implicit biases, positive affect, arousal, executive functions and social processing as key targets of interventions; (ii) cognitive bias modification, contingency management, emotion regulation training and cognitive remediation as preferred approaches; (iii) practice, feedback, difficulty-titration, bias modification, goal-setting, strategy learning and meta-awareness as active ingredients; and (iv) both addiction treatment work-force and specialized neuropsychologists facilitating delivery, together with novel digital-based delivery modalities.

CONCLUSIONS

Expert recommendations on cognitive training and remediation for substance use disorders highlight the relevance of targeting implicit biases, reward, emotion regulation and higher-order cognitive skills via well-validated intervention approaches qualified with mechanistic techniques and flexible delivery options.

Proof-of-concept trial of Goal Management Training+ to improve executive functions and treatment outcomes in methamphetamine use disorder

BACKGROUND

Deficits in executive function are common in methamphetamine use disorder (MUD), likely contributing to difficulties in sustained treatment success. Cognitive remediation interventions are designed to treat such deficits but have not been adapted to the needs of people with MUD. This study presents a proof-of-concept trial to evaluate a new cognitive remediation program for MUD, Goal Management Training⁺ (GMT⁺).

METHODS

This was a cluster-randomised crossover trial comparing GMT⁺ with a psychoeducation-based control (Brain Health Workshop; BHW). GMT⁺ is a therapist-administered group-based cognitive remediation for executive dysfunction comprising four 90-minute weekly sessions and daily journal activities. BHW is a lifestyle psychoeducation program matched to GMT⁺ for therapist involvement, format, and duration. Participants (n = 36; GMT n = 17; BHW n = 19) were recruited from therapeutic communities in Victoria, Australia. Primary outcomes included intervention acceptability, feasibility, and improvements in self-reported executive function. Secondary outcomes included cognitive tests of executive function, severity of methamphetamine dependence, craving, and quality of life. We performed mixed linear modelling and calculated Hedges' g effect sizes.

RESULTS

GMT⁺ participant ratings and program retention indicated high acceptability. There was no difference between GMT⁺ and BHW on self-reported executive function (g = 0.06). Cognitive tasks suggested benefits of GMT⁺ on information gathering (g = 0.88) and delay-discounting (g = 0.80). Severity of methamphetamine dependence decreased more in GMT⁺ (g = 1.47).

CONCLUSIONS

GMT⁺ was well-accepted but did not improve self-reported executive functioning. Secondary outcomes suggested GMT⁺ was beneficial for objective cognitive performance and severity of dependence.

The Hunger Games: Homeostatic State-Dependent Fluctuations in Disinhibition Measured with a Novel Gamified Test Battery

Food homeostatic states (hunger and satiety) influence the cognitive systems regulating impulsive responses, but the direction and specific mechanisms involved in this effect remain elusive. We examined how fasting, and satiety, affect cognitive mechanisms underpinning disinhibition using a novel framework and a gamified test-battery. Thirty-four participants completed the test-battery measuring three cognitive facets of disinhibition: attentional control, information gathering and monitoring of feedback, across two experimental sessions: one after overnight fasting and another after a standardised meal. Homeostatic state was assessed using subjective self-reports and biological markers (i.e., blood-derived liver-expressed antimicrobial protein 2 (LEAP-2), insulin and leptin). We found that participants who experienced greater subjective hunger during the satiety session were more impulsive in the information gathering task; results were not confounded by changes in mood or anxiety. Homeostatic state did not significantly influence disinhibition mechanisms linked to attentional control or feedback monitoring. However, we found a significant interaction between homeostatic state and LEAP-2 on attentional control, with higher LEAP-2 associated with faster reaction times in the fasted condition only. Our findings indicate lingering hunger after eating increases impulsive behaviour via reduced information gathering. These findings identify a novel mechanism that may underpin the tendency to overeat and/or engage in broader impulsive behaviours.

Alternative cutting methods to minimize transfer of nervous system tissue during steak preparation from bone-in short loins

Fresh beef products, such as steaks, may become contaminated with potential specified risk materials (SRMs), such as central nervous system tissue, during the fabrication of bone-in loin subprimals. The objective of this study was to evaluate current and alternative cutting methods that could be used to minimize the transfer of nervous system tissue (NST) tissue during preparation of steaks from bone-in short loins. Bone-in short loins were cut according to three methods. (i) Cutting method I-The vertebral column bones were removed prior to cutting the loin into steaks from the medial (vertebral column) to lateral (flank) side. (ii) Cutting method II--The loin was cut into steaks from the vertebral column side to the flank side prior to removal of the vertebral column bones. (iii) Cutting method III--The loin was cut into steaks from the flank side to the vertebral column side prior to removal of the vertebral column bones. Results indicated that surface areas along the vertebral column cutting line had detectable (0.10 and 0.22% NST/100 cm2) and, thus, higher potential SRM contamination than resulting steak surfaces or the cutting blade. Overall, there were no detectable (<0.10% NST/100 cm2) differences in NST contamination of steaks produced by the three cutting methods. Immunohistochemical evaluation of areas on excised and ground steak surfaces indicated that regardless of cutting method, there was generally "no" to "moderate" staining, suggesting that detectable (0.137 to 0.201% NST) contamination from these samples was most likely due to peripheral nerve detection. These results imply that steaks may be cut from bone-in short loins prior to removal of the vertebral column bones without affecting the transfer of NST to resulting steaks at concentrations <0.10% NST/100 cm2.

W mutant mice with mild or severe developmental defects contain distinct point mutations in the kinase domain of the c-kit receptor

Mutations at the mouse W/c-kit locus lead to intrinsic defects in stem cells of the melanocytic, hematopoietic, and germ cell lineages. W alleles vary in the overall severity of phenotype that they confer, and some alleles exhibit an independence of pleiotropic effects. To elucidate the molecular basis for these biological differences, we analyzed the c-kit locus and the c-kit-associated autophosphorylation activities in five different W mutants representative of a range of W phenotypes. Mast cell cultures derived from mice or embryos homozygous for each W allele were deficient in c-kit autophosphorylation activity, the extent of which paralleled the severity of phenotype conferred by a given W allele both in vivo and in an in vitro mast cell coculture assay. The mildly dominant, homozygous viable alleles W44 and W57 were found to express reduced levels of an apparently normal c-kit protein. In contrast, c-kit kinase defects conferred by the moderately dominant, homozygous viable alleles W41 or W55 or the homozygous lethal allele, W37, were attributed to single-point mutations within the kinase domain of the c-kit polypeptide, which result in point substitutions of amino acid residues highly conserved in the family of protein tyrosine kinases. The nature and location of these amino acid substitutions account for the relative severity of phenotypes conferred by these W alleles and demonstrate that the pleiotropic developmental defects associated with the W/c-kit locus arise as the result of dominant loss-of-function mutations in a transmembrane receptor tyrosine kinase.

Analysis of lens cell fate and eye morphogenesis in transgenic mice ablated for cells of the lens lineage

Transgenic mice carrying the diphtheria toxin A gene driven by mouse gamma 2-crystallin promoter sequences manifest microphthalmia due to ablation of fiber cells in the ocular lens. Here we map ablation events in the lens by crossing animals hemizygous for the ablation construct with transgenic mice homozygous for the in situ lacZ reporter gene driven by identical gamma 2-crystallin promoter sequences. By comparing the spatial distribution of lacZ-expressing cells and the profile of gamma-crystallin gene expression in the lenses of normal and microphthalmic offspring, the contributions of specific cell types to lens development were examined. The results suggest that phenotypically and developmentally distinct populations of lens fiber cells are able to contribute to the lens nucleus during organogenesis. We also show that dosage of the transgene and its site of integration influence the extent of ablation. In those mice homozygous for the transgene and completely lacking cells of the lens lineage, we show that the sclera, cornea, and ciliary epithelium are reduced in size but, otherwise, reasonably well formed. In contrast, the anterior chamber, iris, and vitreous body are not discernible while the sensory retina is highly convoluted and extensively fills the vitreous chamber.