Genetic testing in patients with obesity

Obesity

The role of internists in evaluating obesity is to assess the burden of weight-related disease, mitigate secondary causes of weight gain (medications, sleep deprivation), and solicit patient motivation for weight loss. Internists should assess these factors and emphasize the importance of weight loss for the individual patient. All patients wishing to lose weight should be encouraged to monitor their diet and physical activity and should be referred to high-intensity behavioral programs. Some patients with obesity may also benefit from pharmacotherapy or bariatric surgery.

Recent research trends and updates on nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD), together with metabolic syndrome and obesity, has shown a rapid increase in prevalence worldwide and is emerging as a major cause of chronic liver disease and liver transplantation. Among the various phenotypes of NAFLD, nonalcoholic steatohepatitis (NASH) is highly likely to progress to development of end-stage liver disease and cardiometabolic disease, resulting in liver-related and non-liver-related mortality. Nonetheless, there is no standardized pharmacotherapy against NASH and many drugs are under development in ongoing clinical trials. To develop a successful anti-NASH drug, it is necessary to select an appropriate target population and treatment outcomes depending on whether the mode of action is anti-metabolic, anti-inflammatory or anti-fibrotic. Recently, innovative surrogate markers have been investigated to replace hard outcomes such as liver histology and mortality and reduce the clinical trial duration. Currently, several drugs with fast track designation are being tested in phase III clinical trials, and many other drugs have moved into phase II clinical trials. Both lean NAFLD and typical obese NAFLD have been extensively studied and genetic variants such as PNPLA3 and TM6SF2 have been identified as significant risk factors for lean NAFLD. In the near future, noninvasive biomarkers and effective targeted therapies for NASH and associated fibrosis are required to develop precision medicine and tailored therapy according to various phenotypes of NAFLD.

Assessment and management of severely obese children and adolescents

Approximately 3% of children and adolescents in the UK have severe obesity. The incidence of cardiovascular risk factors such as hypertension, hyperinsulinism and hyperlipidaemia approaches 20% in such individuals. Lifestyle intervention programmes and pharmacotherapy are effective in some individuals, but the relapse rate is high. In exceptional cases, bariatric surgery is effective. This review outlines the scale of the problem, highlights those at risk and discusses referral, current services, appropriate screening and therapeutic interventions.

Whole exome sequencing identifies a homozygous nonsense variation in ALMS1 gene in a patient with syndromic obesity

In the present study we report on genetic analysis in a patient with developmental delay, truncal obesity and vision problem, to find the causative mutation. Whole exome sequencing was performed on genomic DNA extracted from whole blood of the patient which revealed a homozygous nonsense variant (c.2816T>A) in exon 8 of ALMS1 gene that results in a stop codon and premature truncation at codon 939 (p.L939Ter) of the protein. The mutation was confirmed by Sanger sequencing. Exome sequencing was helpful in establishing diagnosis of Alstrom syndrome in this patient. This case highlights the utility of exome sequencing in clinical practice.

The development of youth-onset severe obesity in urban US girls

•

Youth-onset severe obesity warrants particular concern in urban female populations.

•

Among 2226 girls, prevalence was 8.3% at age 7–10, 10.8% at age 12–15 and fairly stable over teen years.

•

Severe obesity prevalence increased more rapidly with age for girls born in 1995 versus 1992.

•

Severely obese girls' BMI grew 2.6 times as fast as normal-BMI peers in the transition to adolescence.

•

Late childhood and early adolescence is a key developmental window for prevention and treatment.

Objective

To understand the incidence and persistence of severe obesity (≥1.2 × 95th BMI percentile-for-age) in girls across the transition to adolescence, and map developmental trajectories of adolescent severe obesity in a high-risk sample.

Methods

We examined ten years of prospectively collected data from a population sample of urban girls (n = 2226; 53% African American, aged 7–10 in 2003–2004). We determined severe obesity prevalence and incidence by age. Logistic regression evaluated for secular trend in the association between age and severe obesity prevalence. Unconditional latent growth curve models (LGCMs) compared BMI development through the adolescence transition between girls with severe obesity versus healthy BMI.

Results

Severe obesity prevalence was 8.3% at age 7–10 and 10.1% at age 16–19 (white: 5.9%; African American: 13.2%; p < 0.001). Age-specific prevalence increased more rapidly among the latest-born, versus earliest-born, girls (p = 0.034). Incidence was 1.3% to 2.4% annually. When we compared 12–15 year-old girls with severe obesity versus healthy BMI, average body weight was already distinct 5 years earlier (16.5 kg versus 25.7 kg; p < 0.001) and the BMI difference between groups increased annually. LGCMs between ages 7–10 and 11–14 indicated an increase of 3.32 kg/m² in the healthy-BMI group and 8.50 kg/m² in the severe obesity group, a 2.6-fold difference.

Conclusions

Youth-onset severe obesity warrants particular concern in urban girls due to high prevalence and an increasing secular prevalence trend. Late childhood and early adolescence may represent a key developmental window for prevention and treatment, but is too late to prevent youth-onset severe obesity entirely.

Early screening of FTO and MC4R variants in newborns of Greek origin

BACKGROUND

Variants of fat mass and obesity associated gene (FTO) and melanocortin-4 receptor gene (MC4R) are related to obesity, overweight and type 2 diabetes.

OBJECTIVES

To examine the presence of FTO and MC4R variants in Greek newborns.

SUBJECTS AND METHODS

A total 1530 newborns of Greek origin were subjected to genetic testing for rs9939609 (FTO) and for rs17782313 (MC4R) variants using dried blood spot (DBS) analysis.

RESULTS

Some 20.2% of newborns carried none of the tested variants. FTO homozygotes and FTO heterozygotes correspond to 18.0% and 45.9% of neonates, respectively. MC4R homozygotes and MC4R heterozygotes were identified in 6.7% and 36.3% of neonates, respectively. Of the infants, 2.2% carried both variants in homozygosity, whereas heterozygotes for both variants correspond to 16.7% of the tested neonates.

CONCLUSION

The results indicate high prevalence of homozygosity and heterozygosity for tested variants. Early screening via DBS may be beneficial in order to adopt a healthy lifestyle.

Effect of genetic and non-genetic factors, including aging, on waist circumference and BMI, and inter-indicator differences in risk assessment

OBJECTIVE

To assess the effect of genetic and non-genetic factors on indicators derived from waist circumference (WC) and body mass index (BMI) as well as inter-indicator differences in risk assessment age-related diseases including diabetes mellitus, coronary heart disease and liver cancer.

METHODS

Height, weight and WC were measured in 100 families (students and their two parents), 41 subjects with regular physical exercise routines, and 170 patients with diabetes mellitus, coronary heart disease or liver cancer. The BMI, waist-height ratio (WHtR) and waist circumference density index (WCDI) were calculated for each subject.

RESULTS

BMI was less affected by genetic factors, while WHtR and WCDI were greatly affected by genetic factors as revealed using multiple regression analysis. BMI, WHtR and WCDI were all sensitive to physical exercise according to ROC analysis; among these factors, the most sensitive indicator was WHtR. However, ROC analysis demonstrated that WCDI was more effective than BMI and WHtR for assessing the risk of three diseases.

CONCLUSIONS

WCDI more accurately reflects the roles of both genetic and non-genetic factors, including aging, which can better predict disease.

Ancestral dichlorodiphenyltrichloroethane (DDT) exposure promotes epigenetic transgenerational inheritance of obesity

BACKGROUND

Ancestral environmental exposures to a variety of environmental factors and toxicants have been shown to promote the epigenetic transgenerational inheritance of adult onset disease. The present work examined the potential transgenerational actions of the insecticide dichlorodiphenyltrichloroethane (DDT) on obesity and associated disease.

METHODS

Outbred gestating female rats were transiently exposed to a vehicle control or DDT and the F1 generation offspring bred to generate the F2 generation and F2 generation bred to generate the F3 generation. The F1 and F3 generation control and DDT lineage rats were aged and various pathologies investigated. The F3 generation male sperm were collected to investigate methylation between the control and DDT lineage male sperm.

RESULTS

The F1 generation offspring (directly exposed as a fetus) derived from the F0 generation exposed gestating female rats were not found to develop obesity. The F1 generation DDT lineage animals did develop kidney disease, prostate disease, ovary disease and tumor development as adults. Interestingly, the F3 generation (great grand-offspring) had over 50% of males and females develop obesity. Several transgenerational diseases previously shown to be associated with metabolic syndrome and obesity were observed in the testis, ovary and kidney. The transgenerational transmission of disease was through both female (egg) and male (sperm) germlines. F3 generation sperm epimutations, differential DNA methylation regions (DMR), induced by DDT were identified. A number of the genes associated with the DMR have previously been shown to be associated with obesity.

CONCLUSIONS

Observations indicate ancestral exposure to DDT can promote obesity and associated disease transgenerationally. The etiology of disease such as obesity may be in part due to environmentally induced epigenetic transgenerational inheritance.

Lean NASH: distinctiveness and clinical implication

INTRODUCTION

Non-alcoholic fatty liver (NAFL) in the absence of overweight and/or obesity, defined by the anthropometric parameter, body mass index (BMI), has been designated as 'lean NASH.' While maintaining a close pathophysiological link with metabolic syndrome (MS) and insulin resistance (IR), the presence of subtle alterations in measures of total body and regional adiposity not exceeding the designed cut-offs, are hallmarks of 'lean NASH.'

MATERIAL AND METHODS

Available literature related to non-alcoholic steatohepatitis (NASH) in lean or non-obese individuals and its pathogenesis in general published in English language journals till the time of manuscript preparation were reviewed and critically analysed.

ANALYSIS

Being a closely related but variant phenotype of NASH, its features metabolically resemble the well-characterized entity 'metabolically obese normal weight (MONW)' individuals. Apart from total body adiposity, distribution of fat in different body compartments has assumed greater pathophysiologic relevance in characterizing 'lean NASH'. Detection of NASH in stringently defined non-obese individuals, by both BMI and waist circumference indices, indicates existence of a subset of NASH in which fat compartmentalization at ectopic sites is not picked up by the anthropometric yardsticks used. Volume [Quantity] and biological behavior of the visceral and deep subcutaneous adipose tissues contribute to this variant of NASH in non-obese subjects. Genetic predisposition to IR and MS along with the environmental influences like childhood nutritional status, dietary composition and gut microbiome possibly play pathogenetic role.

CONCLUSION

The most important concern is in the principles of nomenclature within syndromes where clinical dissimilarities exist despite biological similarities. Till a uniformly acceptable pathophysiological and/or etiology-based classification emerges, the term "lean NASH" would continue to provide us an opportunity to ponder over and refine this subset of fatty liver in non-obese people and potentially significant liver disease.