Heritability of Endurance Traits from Animal Research Models
J. Timothy Lightfoot, Monica J. Hubal, Stephen M. Roth in Routledge Handbook of Sport and Exercise Systems Genetics, 2019
This chapter focuses on treadmill running and swimming as a means to assess endurance exercise capacity and as an exercise paradigm to elicit responses to endurance training. Starting with a founder population of heterogeneous N:National Institutes of Health rats, Koch and Britton developed a two-way artificial selection model of endurance running capacity based on maximal treadmill running performance. After 11 generations of selection, high-capacity runner and low-capacity runner selected lines differed by approximately 660 m in treadmill running endurance. J. Timothy Lightfoot et al. screened several strains of mice for endurance exercise performance using a graded treadmill test and identified DBA/2J and BALB/cJ as low- and high-performing strains. Data from animal models confirm that endurance exercise capacity and responses to training are heritable traits and these traits are determined by multiple genetic factors. The high heritability estimates for endurance exercise capacity in inbred mice suggest that a high percentage of the variation in exercise capacity is determined by genetic factors.
The Genetic Alibi
Roy J. Shephard in Obesity: A Kinesiologist’s Perspective, 2018
This chapter examines methods of assessing the genetic component of obesity. It looks at methods used when estimating the heritability of obesity and attempts to reach a consensus on the extent of the influence in the general population. The chapter explores briefly some of the likely underlying mechanisms. Classical quantitative studies of heritability were often based on differences in the characteristics of monozygotic and dizygotic twin-pairs. The analysis of data from family studies is based on the calculation of correlations between various familial relationships. Animal studies may exploit single-gene mutations in small mammals, whether these have occurred spontaneously, or are the result of exposure to radiation or mutagenic chemicals. Studies of genetic markers have looked for a greater than expected frequency of specific genetic variants in individuals who are overweight or obese. The weakness of the genetic alibi is illustrated by the FTO genotype, associated with fat accumulation.
Development of Comorbid PTSD and Substance Use Disorders
Anka A. Vujanovic, Sudie E. Back in Posttraumatic Stress and Substance Use Disorders, 2019
This chapter reviews the predominant etiological models for posttraumatic stress disorder (PTSD)/substance use disorder (SUD) and is written with several key assumptions in mind. It discusses evidence for explanatory models of PTSD/SUD, with the understanding that there is no single best model, but complementary explanations across multiple models. The chapter aims to understand the etiological and maintenance factors contributing to the onset of comorbid PTSD/SUD. The shared liability model suggests that PTSD and SUD frequently co-occur due to common familial risk. Substance use phenotypes have generally demonstrated higher heritability rates compared to trauma and PTSD phenotypes. The self-medication hypothesis presumes that individuals with a history of trauma and/or PTSD are at increased risk for SUD due to repeated use of substances to cope with trauma-related symptoms. Several prospective, epidemiological studies have been conducted to examine patterns of association between PTSD and SUD.
Heritability analysis of IgG4 antibodies in autoimmune thyroid disease
Published in Autoimmunity, 2014
I. M. Outschoorn, M. V. Talor, C. L. Burek, W. H. Hoffman, N. R. Rose
A study of IgG4 autoantibody levels in juvenile thyroid disease patients showed evidence of heritability using the ROMP screening method. These levels increased with time despite the fact that total IgG antibody decreased with time. Evidence of heritability was demonstrated only in patients with high titers of autoantibodies to both thyroglobulin (Tg) and thyroperoxidase (TPO) unlike family members who may show high titers of one or the other and be asymptomatic at the time of sampling. Since high and low IgG4 levels give different heritability plots, these findings may represent a more severe fibrotic form of thyroiditis with a distinct genetic background. Hence a simple predictive approach is offered by this screening tool for the disease in patients and family members which may be helpful in the future to identify IgG4-related thyroiditis early in the course of disease without the requirement for biopsy.
Heritability and environmental effects for self-reported periods with stuttering: A twin study from Denmark
Published in Logopedics Phoniatrics Vocology, 2011
Corrado Fagnani, Steen Fibiger, Axel Skytthe, Jacob V. B. Hjelmborg
Genetic influence for stuttering was studied based on adult self-reporting. Using nation-wide questionnaire answers from 33,317 Danish twins, a univariate biometric analysis based on the liability threshold model was performed in order to estimate the heritability of stuttering. The self-reported incidences for stuttering were from less than 4% for females to near 9% for males. Both probandwise concordance rate and tetrachoric correlation were substantially higher for monozygotic compared to dizygotic pairs, indicating substantial genetic influence on individual liability. Univariate biometric analyses showed that additive genetic and unique environmental factors best explained the observed concordance patterns. Heritability estimates for males/females were 0.84/0.81. Moderate unique environmental effects were also found.
Estimation of heritability and familial correlation in myopia is not affected by past sun exposure
Published in Ophthalmic Genetics, 2019
Jason Charng, Paul G. Sanfilippo, Gareth Lingham, Louis J. Stevenson, David A. Mackey, Seyhan Yazar
Purpose: To consider the effect of including past sun exposure in estimating heritability and familial correlation of myopia-related traits. Methods: We calculate familial correlation and heritability of anterior chamber depth (ACD), axial length (AL), corneal curvature (CC), and spherical equivalent (SphE), with or without past sun exposure as a covariate, in a large number of unrelated nuclear families from the Raine Study (parents: Gen1, offspring: Gen2) residing in Perth, Australia, a city with a high amount of daily sunlight. Past sun exposure was objectively measured using conjunctival ultraviolet autofluorescence (CUVAF) photography. Results: When sun exposure was not included in the analysis, both familial correlation (correlation±SE; ACD: 0.308 ± 0.065, AL: 0.374 ± 0.061, CC: 0.436 ± 0.063, SphE: 0.281 ± 0.070) and heritability (ACD: 0.606 ± 0.104, AL: 0.623 ± 0.098, CC: 0.793 ± 0.079, SphE: 0.591 ± 0.106) were significant for all traits (all P < .001). However, there was no significant change in both familial correlation and heritability estimates when sun exposure was included as an additional covariate. Conclusions: Past sun exposure does not affect the estimation of the additive genetic component in myopia-related traits.
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