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The Case for Single Gene Effects on Human Obesity
Published in Claude Bouchard, The Genetics of Obesity, 2020
There are several genetic syndromes in humans for which obesity is a prominent symptom. These include the Prader-Willi, Borjeson-Forssman-Lehmann, Bardet-Biedl, Biemond, Pickwickian, and Cohen syndromes.3 Prader-Willi syndrome is one of the best understood in terms of its genetic causes. It is commonly due to deletions in chromosome region 15ql1— 12, although in some cases no deletions may be detected cytogenetically. Deletions visible under a light microscope probably involve the loss of at least 2 to 5 million base pairs of DNA. Disorders caused by such deletions are called contiguous gene syndromes because their phenotypes are probably due to the deletion of three to ten genes and regulatory sequences. Deletions associated with Prader-Willi syndrome suggest that genes in chromosome region 15q 11-12 may affect appetite and/or satiety cues that mediate food intake. A variety of other genes involved in carbohydrate metabolism, lipid metabolism and storage, and endocrine function may be deleted in other human syndromes. The existence of genetic obesity syndromes is important because it indicates that altering one or a few genes can cause obesity in humans. Once the obesity-relevant genes from these syndromes are identified, it will be possible to determine whether normal variation in the same genes causes obesity in people with a normal chromosome complement.
The Pathophysiology of Childhood Obesity
Published in Fima Lifshitz, Childhood Nutrition, 2020
Children with other genetic abnormalities are also prone to obesity. Children with Down’s syndrome tend to be mentally retarded, slow growers, and obese. The high prevalence of obesity in these children may be due to excess food intake or a low requirement for energy through reduced physical activity.47 Children with Prader-Willi syndrome are also characterized by obesity.9 It was suggested that a low metabolic rate caused the obesity in these children.74 Schoeller and colleagues58 utilized the doubly labeled water method to determine body composition and total daily energy expenditure in children with Prader-Willi syndrome. Lower energy requirements of these children was due to less fat-free mass and not to an unusually low metabolic rate. It is important to utilize body composition techniques not dependent on assumptions about fat distribution, such as the doubly labeled water method, in order to prevent misinterpreting the amount of fat-free mass. Overestimating the amount of fat-free mass would predict excessive energy requirements in these children.
Patterns of Inheritance: Mendelian and Non-Mendelian
Published in Merlin G. Butler, F. John Meaney, Genetics of Developmental Disabilities, 2019
Merlin G. Butler, Michael Begleiter, Shannon Lillis, Molly Lund, F. John Meaney
Several common genetic syndromes show the effects of genomic imprinting. Prader–Willi and Angelman syndromes are two disorders caused by alterations of chromosome 15. Prader–Willi syndrome is characterized by obesity, short stature, hypogonadism, mental deficiency, and food seeking behaviors (7,8) (Fig. 13). Greater than 95% of individuals with Prader–Willi syndrome are caused by a paternally derived deletion of the 15q11–q13 region or from maternal disomy 15 (both 15s from the mother) which results from a trisomy 15 fetus and loss of the paternal chromosome 15 early in the pregnancy. Angelman syndrome is characterized by short stature, severe mental retardation, seizures, lack of speech, ataxia, and distinctive facial features (8,9) (Fig. 14). Greater than 75% of cases of Angelman syndrome are caused by deletions of 15q11–q13 derived from the maternal chromosome 15 or paternal disomy 15 (both 15s from the father). Both of these syndromes can also be caused by a mutation or defect in the imprinting center which controls the activity of genes in the region (10). This results in a failure of the female-to-male or male-to-female switch in imprinting during gameto genesis. A sperm cell with a persistent female imprint would lead to a child with Prader–Willi syndrome and an egg cell with a persistent male imprint would cause Angelmansyndrome.
Improvement of Planning Abilities in Adults with Prader-Willi Syndrome: A Randomized Controlled Trial
Published in Developmental Neurorehabilitation, 2021
Séverine Estival, Virginie Laurier, Fabien Mourre, Virginie Postal
Prader-Willi Syndrome is a neurodevelopmental genetic disorder characterized by various expressions of endocrine, neurologic, cognitive and behavioral symptoms.1 The disorder is caused by the loss of expression of the imprinted genes from the 15q11q13 region of the paternal chromosome 15.2 Approximately 60% of cases are due to the deletion of the whole 15q11q13 region (type I deletion) or a part of it (type II deletion) and in 35% of cases, the entire 15th maternal chromosome is duplicated and the paternal chromosome is lost (uniparental maternal disomy).3 PWS is characterized by infantile hypotonia, mental retardation, feeding difficulty in infancy that evolves to an extreme drive to eat in childhood, dysmorphic features, short stature, hypogonadism, sleep apnea, diabetes, and severe maladaptive behaviors including obsessive, compulsive, and oppositional behaviors.4,5 Speech and language skills are also reported to be often impaired.6 Intellectual disability and deficit in executive functions are well documented in PWS: deficits in inhibition, switching, updating, cognition estimation, planning7–13 Executive functions (EF) are essential to allow a flexible and context-appropriate behavior when facing a new or complex situation.14,15 Planning is conceived as a higher cognitive function that implies the effective inhibition, updating and shifting processes.16
Sedentary behavior and children with physical disabilities: a scoping review
Published in Disability and Rehabilitation, 2021
Felipe Ganz, Nevin Hammam, Lesley Pritchard
Most of the studies compared sedentary behavior patterns of children with and without physical disabilities. Studies conducted with children with juvenile idiopathic arthritis and Down syndrome demonstrated that they spend more time sedentary than their peers who are typically developing [20,36]. Castner et al. [23] reported that children with Prader–Willi syndrome spend no more time sedentary than children with non-syndromal obesity and Foerste et al. [26] reported that children with non-syndromal obesity are more sedentary than those with Prader–Willis syndrome and Trisomy 21. Two studies evaluated the relationship between sedentary time and age. Children with Down syndrome 14 and 15 years are more sedentary than younger children (8–11 years of age) [25]. Older children with acquired brain injury also appear to be more sedentary [19].
From leptin to lasers: the past and present of mouse models of obesity
Published in Expert Opinion on Drug Discovery, 2021
Joshua R. Barton, Adam E. Snook, Scott A. Waldman
Prader Willi Syndrome is caused by deficient expression of the Prader Willi Critical Region (PWCR) of chromosome 15q11.2-q13 [91]. PWS usually is caused by the loss of a paternally imprinted region of chromosome 15 by paternal deletion, maternal uniparental disomy of chromosome 15, or imprinting defect. Angelman Syndrome is caused by the loss of the maternally imprinted region on the q arm of chromosome 15, and is phenotypically similar to PWS until two years of age, when hyperphagia and obesity become apparent in PWS [91]. Feeding behaviors in PWS are classically divided into two phases: poor feeding and hypotonia in infancy, with a reversal to hyperphagia and obesity that occurs between 18 and 36 months [92]. More recently, the nutritional phases of PWS have been divided into 4 main phases, with phase 3 (8 years old – adulthood) characterized by insatiable hunger [92]. During this phase, individuals with PWS seem unable to feel full. The compulsion to eat can be so severe that individuals with PWS have been reported to gain up to 20lbs in one weekend, and can eat to the point of life-threatening gastric rupture [93]. Complications from obesity account for the majority of mortality in individuals with PWS [94].