Androgen receptor (AR) gene CAG trinucleotide repeat length associated with body composition measures in non-syndromic obese, non-obese and Prader-Willi syndrome individuals

Adolescent obesity in the past decade: A systematic review of genetics and determinants of food choice

Background and purpose:

As the incidence of global obesity increases, concerns about adverse health outcomes in adolescents continues to rise. The complexity and expense of this problem require early recognition and specific preventive treatments. Knowledge of genetics and determinants of food choices contributing to adolescent obesity warrants further examination. The primary goal was to appraise the literature from the past decade (2007–2017) on the current state of food choice and genetic determinants of adolescent overweight/obesity in the United States. The secondary goal was to determine trends in the literature and areas for future research.

Methods:

A systematic review of research studies in the United States from 2007 to 2017 was completed. Database searches were conducted using CINAHL, Embase, PsycINFO, PsycArticles, PubMed, Scopus, Academic Search Complete, Web of Science, BIOSIS, and the Cochrane Library. A total of 535 studies were selected. Of these, 283 studies focused on determinants of food choices and 165 studies focused on genetic factors.

Conclusions:

A total of 41 full-text articles included in this literature review contained studies limited exclusively to adolescents. Stress factors related to food choices demonstrated a new trend being explored. The need for precision health, the application of genetic information, could uncover ways food choices affect adolescent obesity.

Implications for practice:

The etiology of adolescent obesity requires that nurses gain knowledge of genetics and food choice determinants to inform personalized treatments for adolescents, which may establish effective interventions that promote healthy weight achievement.

Neuroanatomical and molecular correlates of cognitive and behavioural outcomes in hypogonadal males

Robust epidemiological, clinical and laboratory evidence supports emerging roles for the sex steroids in such domains as neurodevelopment, behaviour, learning and cognition. Regions of the mammalian brain that are involved in cognitive development and memory do not only express the classical nuclear androgen receptor, but also the non-genomic membrane receptor, which is a G protein-coupled receptor that mediates some rapid effects of the androgens on neurogenesis and synaptic plasticity. Under physiological conditions, hippocampal neurons do express the enzyme aromatase, and therefore actively aromatize testosterone to oestradiol. Although glial expression of the aromatase enzyme is minimal, increased expression following injury suggests a role for sex steroids in neuroprotection. It is therefore plausible to deduce that low levels of circulating androgens in males would perturb neuronal functions in relation to cognition and memory, as well as neural repair following injury. The present review is an overview of some roles of the sex steroids on cognitive function in males, and the neuroanatomical and molecular underpinnings of some behavioural and cognitive deficits characteristic of such genetic disorders noted for low androgen levels, including Klinefelter syndrome, Bardet-Biedl syndrome, Kallman syndrome and Prader-Willi syndrome. Recent literature in relation to some behavioural and cognitive changes secondary to surgical and pharmacological castration are also appraised.

Single Gene and Syndromic Causes of Obesity: Illustrative Examples

Obesity is a significant health problem in westernized societies, particularly in the United States where it has reached epidemic proportions in both adults and children. The prevalence of childhood obesity has doubled in the past 30 years. The causation is complex with multiple sources, including an obesity promoting environment with plentiful highly dense food sources and overall decreased physical activity noted for much of the general population, but genetic factors clearly play a role. Advances in genetic technology using candidate gene approaches, genome-wide association studies, structural and expression microarrays, and next generation sequencing have led to the discovery of hundreds of genes recognized as contributing to obesity. Polygenic and monogenic causes of obesity are now recognized including dozens of examples of syndromic obesity with Prader-Willi syndrome, as a classical example and recognized as the most common known cause of life-threatening obesity. Genetic factors playing a role in the causation of obesity will be discussed along with the growing evidence of single genes and the continuum between monogenic and polygenic obesity. The clinical and genetic aspects of four classical but rare obesity-related syndromes (ie, Prader-Willi, Alström, fragile X, and Albright hereditary osteodystrophy) will be described and illustrated in this review of single gene and syndromic causes of obesity.