Monogenic forms of childhood obesity due to mutations in the leptin gene

Syndromic and Monogenic Obesity: New Opportunities Due to Genetic-Based Pharmacological Treatment

Obesity is a significant health problem with a continuously increasing prevalence among children and adolescents that has become a modern pandemic during the last decades. Nowadays, the genetic contribution to obesity is well-established. For this narrative review article, we searched PubMed and Scopus databases for peer-reviewed research, review articles, and meta-analyses regarding the genetics of obesity and current pharmacological treatment, published in the English language with no time restrictions. We also screened the references of the selected articles for possible additional articles in order to include most of the key recent evidence. Our research was conducted between December 2022 and December 2023. We used the terms "obesity", "genetics", "monogenic", "syndromic", "drugs", "autosomal dominant", "autosomal recessive", "leptin-melanocortin pathway", and "children" in different combinations. Recognizing the genetic background in obesity can enhance the effectiveness of treatment. During the last years, intense research in the field of obesity treatment has increased the number of available drugs. This review analyzes the main categories of syndromic and monogenic obesity discussing current data on genetic-based pharmacological treatment of genetic obesity and highlighting the necessity that cases of genetic obesity should follow specific, pharmacological treatment based on their genetic background.

Precision medicine of obesity as an integral part of type 2 diabetes management - past, present, and future

Obesity is a complex and heterogeneous condition that leads to various metabolic complications, including type 2 diabetes. Unfortunately, for some, treatment options to date for obesity are insufficient, with many people not reaching sustained weight loss or having improvements in metabolic health. In this Review, we discuss advances in the genetics of obesity from the past decade-with emphasis on developments from the past 5 years-with a focus on metabolic consequences, and their potential implications for precision management of the disease. We also provide an overview of the potential role of genetics in guiding weight loss strategies. Finally, we propose a vision for the future of precision obesity management that includes developing an obesity-centred multidisease management algorithm that targets both obesity and its comorbidities. However, further collaborative efforts and research are necessary to fully realise its potential and improve metabolic health outcomes.

Genetics and epigenetics in the obesity phenotyping scenario

Obesity is a common complex trait that elevates the risk for various diseases, including type 2 diabetes and cardiovascular disease. A combination of environmental and genetic factors influences the pathogenesis of obesity. Advances in genomic technologies have driven the identification of multiple genetic loci associated with this disease, ranging from studying severe onset cases to investigating common multifactorial polygenic forms. Additionally, findings from epigenetic analyses of modifications to the genome that do not involve changes to the underlying DNA sequence have emerged as key signatures in the development of obesity. Such modifications can mediate the effects of environmental factors, including diet and lifestyle, on gene expression and clinical presentation. This review outlines what is known about the genetic and epigenetic contributors to obesity susceptibility, along with the albeit limited therapeutic options currently available. Furthermore, we delineate the potential mechanisms of actions through which epigenetic changes can mediate environmental influences and the related opportunities they present for future interventions in the management of obesity.

Bioleptin as a useful marker of metabolic status in children with diabetes mellitus type 1

Introduction

The purpose of our study was tomeasure the level of leptin and biologically active leptin (bioLEP) in children with type 1 diabetes, depending on the duration of diabetes and its degree of metabolic control.

Methods

The study included 94 children (58 boys and 36 girls). In a group of children with diabetes, 40 patients were newly diagnosed with type 1 diabetes, 40 children who have diabetes for more than a year (20 with good metabolic control and 20 with poor metabolic control). The control group consisted of 14 healthy children. The serum level of leptin and bioLEP was measured using a sandwich enzyme-linked immunosorbent assay. To our knowledge, this is the first study to describe bioLEP levels among diabetic children with different forms of disease control.

Results

Lower levels of leptin were found in children with diabetes compared to healthy children. Furthermore, we found a statistically higher concentration of leptin in the group of children with newly diagnosed diabetes compared to children from the diabetic group with poor metabolic control and lower than healthy children (11.19 vs. 7.84 and 20.94 ng/mL). Moreover, children in the metabolically well-controlled group had statistically lower levels of this hormone (5.11 ng/mL) than healthy children. Leptin concentrations differed significantly between underweight, overweight, and obese children.

Discussion

In our study, the level of bioLEP differed significantly between children in the newly diagnosed diabetes group and children in the long-term, poorly controlled diabetes group and healthy controls. Despite many studies published in recent years, many aspects of leptin secretion, action, and mechanisms of its influence on carbohydrate and fat metabolism are still to be clarified. In our opinion, studies evaluating the status of bioLEP in diabetes can also contribute to a better understanding of the mechanisms regulating metabolism.

A National Multicenter Study of Leptin and Leptin Receptor Deficiency and Systematic Review

CONTEXT

Homozygous leptin (LEP) and leptin receptor (LEPR) variants lead to childhood-onset obesity.

OBJECTIVE

To present new cases with LEP and LEPR deficiency, report the long-term follow-up of previously described patients, and to define, based on all reported cases in literature, genotype-phenotype relationships.

METHODS

Our cohort included 18 patients (LEP = 11, LEPR = 7), 8 of whom had been previously reported. A systematic literature review was conducted in July 2022. Forty-two of 47 studies on LEP/LEPR were selected.

RESULTS

Of 10 new cases, 2 novel pathogenic variants were identified in LEP (c.16delC) and LEPR (c.40 + 5G > C). Eleven patients with LEP deficiency received metreleptin, 4 of whom had been treated for over 20 years. One patient developed loss of efficacy associated with neutralizing antibody development. Of 152 patients, including 134 cases from the literature review in addition to our cases, frameshift variants were the most common (48%) in LEP and missense variants (35%) in LEPR. Patients with LEP deficiency were diagnosed at a younger age [3 (9) vs 7 (13) years, P = .02] and had a higher median body mass index (BMI) SD score [3.1 (2) vs 2.8 (1) kg/m2, P = 0.02], which was more closely associated with frameshift variants (P = .02). Patients with LEP deficiency were more likely to have hyperinsulinemia (P = .02).

CONCLUSION

Frameshift variants were more common in patients with LEP deficiency whereas missense variants were more common in LEPR deficiency. Patients with LEP deficiency were identified at younger ages, had higher BMI SD scores, and had higher rates of hyperinsulinemia than patients with LEPR deficiency. Eleven patients benefitted from long-term metreleptin, with 1 losing efficacy due to neutralizing antibodies.

Rare Antagonistic Leptin Variants and Severe, Early-Onset Obesity

Hormone absence or inactivity is common in congenital disease, but hormone antagonism remains controversial. Here, we characterize two novel homozygous leptin variants that yielded antagonistic proteins in two unrelated children with intense hyperphagia, severe obesity, and high circulating levels of leptin. Both variants bind to the leptin receptor but trigger marginal, if any, signaling. In the presence of nonvariant leptin, the variants act as competitive antagonists. Thus, treatment with recombinant leptin was initiated at high doses, which were gradually lowered. Both patients eventually attained near-normal weight. Antidrug antibodies developed in the patients, although they had no apparent effect on efficacy. No severe adverse events were observed. (Funded by the German Research Foundation and others.).

360-Degree Perspectives on Obesity

Alarming statistics show that the number of people affected by excessive weight has surpassed 2 billion, representing approximately 30% of the world's population. The aim of this review is to provide a comprehensive overview of one of the most serious public health problems, considering that obesity requires an integrative approach that takes into account its complex etiology, including genetic, environmental, and lifestyle factors. Only an understanding of the connections between the many contributors to obesity and the synergy between treatment interventions can ensure satisfactory outcomes in reducing obesity. Mechanisms such as oxidative stress, chronic inflammation, and dysbiosis play a crucial role in the pathogenesis of obesity and its associated complications. Compounding factors such as the deleterious effects of stress, the novel challenge posed by the obesogenic digital (food) environment, and the stigma associated with obesity should not be overlooked. Preclinical research in animal models has been instrumental in elucidating these mechanisms, and translation into clinical practice has provided promising therapeutic options, including epigenetic approaches, pharmacotherapy, and bariatric surgery. However, more studies are necessary to discover new compounds that target key metabolic pathways, innovative ways to deliver the drugs, the optimal combinations of lifestyle interventions with allopathic treatments, and, last but not least, emerging biological markers for effective monitoring. With each passing day, the obesity crisis tightens its grip, threatening not only individual lives but also burdening healthcare systems and societies at large. It is high time we took action as we confront the urgent imperative to address this escalating global health challenge head-on.

Proteome and genome integration analysis of obesity

ABSTRACT

The prevalence of obesity has increased worldwide in recent decades. Genetic factors are now known to play a substantial role in the predisposition to obesity and may contribute up to 70% of the risk for obesity. Technological advancements during the last decades have allowed the identification of many hundreds of genetic markers associated with obesity. However, the transformation of current genetic variant-obesity associations into biological knowledge has been proven challenging. Genomics and proteomics are complementary fields, as proteomics extends functional analyses. Integrating genomic and proteomic data can help to bridge a gap in knowledge regarding genetic variant-obesity associations and to identify new drug targets for the treatment of obesity. We provide an overview of the published papers on the integrated analysis of proteomic and genomic data in obesity and summarize four mainstream strategies: overlap, colocalization, Mendelian randomization, and proteome-wide association studies. The integrated analyses identified many obesity-associated proteins, such as leptin, follistatin, and adenylate cyclase 3. Despite great progress, integrative studies focusing on obesity are still limited. There is an increased demand for large prospective cohort studies to identify and validate findings, and further apply these findings to the prevention, intervention, and treatment of obesity. In addition, we also discuss several other potential integration methods.

Neuroendocrine and neuroimmune mechanisms underlying comorbidity of pain and obesity

Pain and obesity, as well as their associated impairments, are major health concerns. Understanding the relationship between the two is the focus of a growing body of research. However, early researches attribute increased mechanical stress from excessive weight as the main factor of obesity-related pain, which not only over-simplify the association, but also fail to explain some controversial outcomes arising from clinical investigations. This review focuses on neuroendocrine and neuroimmune modulators importantly involved in both pain and obesity, analyzing nociceptive and anti-nociceptive mechanisms based on neuroendocrine pathways including galanin, ghrelin, leptin and their interactions with other neuropeptides and hormone systems which have been reported to play roles in pain and obesity. Mechanisms of immune activities and metabolic alterations are also discussed, due to their intense interactions with neuroendocrine system and crucial roles in the development and maintenance of inflammatory and neuropathic pain. These findings have implications for health given rising rates of obesity and pain-related diagnoses, by providing novel weight-control and analgesic therapies targeted on specific pathways.

Structural insights into the mechanism of leptin receptor activation

Leptin is an adipocyte-derived protein hormone that promotes satiety and energy homeostasis by activating the leptin receptor (LepR)-STAT3 signaling axis in a subset of hypothalamic neurons. Leptin signaling is dysregulated in obesity, however, where appetite remains elevated despite high levels of circulating leptin. To gain insight into the mechanism of leptin receptor activation, here we determine the structure of a stabilized leptin-bound LepR signaling complex using single particle cryo-EM. The structure reveals an asymmetric architecture in which a single leptin induces LepR dimerization via two distinct receptor-binding sites. Analysis of the leptin-LepR binding interfaces reveals the molecular basis for human obesity-associated mutations. Structure-based design of leptin variants that destabilize the asymmetric LepR dimer yield both partial and biased agonists that partially suppress STAT3 activation in the presence of wild-type leptin and decouple activation of STAT3 from LepR negative regulators. Together, these results reveal the structural basis for LepR activation and provide insights into the differential plasticity of signaling pathways downstream of LepR.

Functionally Significant Variants in Genes Associated with Abdominal Obesity: A Review

The high prevalence of obesity and of its associated diseases is a major problem worldwide. Genetic predisposition and the influence of environmental factors contribute to the development of obesity. Changes in the structure and functional activity of genes encoding adipocytokines are involved in the predisposition to weight gain and obesity. In this review, variants in genes associated with adipocyte function are examined, as are variants in genes associated with metabolic aberrations and the accompanying disorders in visceral obesity.

Recent Advances in the Knowledge of the Mechanisms of Leptin Physiology and Actions in Neurological and Metabolic Pathologies

Excess body weight is frequently associated with low-grade inflammation. Evidence indicates a relationship between obesity and cancer, as well as with other diseases, such as diabetes and non-alcoholic fatty liver disease, in which inflammation and the actions of various adipokines play a role in the pathological mechanisms involved in these disorders. Leptin is mainly produced by adipose tissue in proportion to fat stores, but it is also synthesized in other organs, where leptin receptors are expressed. This hormone performs numerous actions in the brain, mainly related to the control of energy homeostasis. It is also involved in neurogenesis and neuroprotection, and central leptin resistance is related to some neurological disorders, e.g., Parkinson's and Alzheimer's diseases. In peripheral tissues, leptin is implicated in the regulation of metabolism, as well as of bone density and muscle mass. All these actions can be affected by changes in leptin levels and the mechanisms associated with resistance to this hormone. This review will present recent advances in the molecular mechanisms of leptin action and their underlying roles in pathological situations, which may be of interest for revealing new approaches for the treatment of diseases where the actions of this adipokine might be compromised.

Obesity and diabetes: the final frontier

INTRODUCTION

Obesity is a key target in the treatment and prevention of diabetes and independently to reduce the burden of cardiovascular disease. We reviewed the options now available and anticipated to deal with obesity.

AREAS COVERED

We considered the epidemiology, genetics, and causation of obesity and the relationship to diabetes, and the dietary, pharmaceutical, and surgical management of the condition. The literature search covered both popular media via Google Search and the academic literature as indexed on PubMed with search terms including obesity, childhood obesity, adipocytes, insulin resistance, mechanisms of satiety, bariatric surgery, GLP-1 receptor agonists, and SGLT2 inhibitors.

EXPERT OPINION

Although bariatric surgery has been the primary approach to treating obese individuals, the emergence of agents impacting the brain satiety centers now promises effective, non-invasive treatment of obesity for individuals with and without diabetes. The GLP-1 receptor agonists have assumed the primary role in treating obesity with significant weight loss. Long-term results with semaglutide and tirzepatide are now approaching the success seen with bariatric surgery. Future agents combining the benefits of satiety control and thermogenesis to dissipate caloric excess are under investigation.

The promise of new anti-obesity therapies arising from knowledge of genetic obesity traits

Obesity is a multifactorial and complex disease that often manifests in early childhood with a lifelong burden. Polygenic and monogenic obesity are driven by the interaction between genetic predisposition and environmental factors. Polygenic variants are frequent and confer small effect sizes. Rare monogenic obesity syndromes are caused by defined pathogenic variants in single genes with large effect sizes. Most of these genes are involved in the central nervous regulation of body weight; for example, genes of the leptin-melanocortin pathway. Clinically, patients with monogenic obesity present with impaired satiety, hyperphagia and pronounced food-seeking behaviour in early childhood, which leads to severe early-onset obesity. With the advent of novel pharmacological treatment options emerging for monogenic obesity syndromes that target the central melanocortin pathway, genetic testing is recommended for patients with rapid weight gain in infancy and additional clinical suggestive features. Likewise, patients with obesity associated with hypothalamic damage or other forms of syndromic obesity involving energy regulatory circuits could benefit from these novel pharmacological treatment options. Early identification of patients affected by syndromic obesity will lead to appropriate treatment, thereby preventing the development of obesity sequelae, avoiding failure of conservative treatment approaches and alleviating stigmatization of patients and their families.

Genetic obesity: an update with emerging therapeutic approaches

Based on the genetic contribution, childhood obesity can be classified into 3 groups: common polygenic obesity, syndromic obesity, and monogenic obesity. More genetic causes of obesity are being identified along with the advances in the genetic testing. Genetic obesities including syndromic and monogenic obesity should be suspected and evaluated in children with early-onset morbid obesity and hyperphagia under 5 years of age. Patients with syndromic obesity have early-onset severe obesity associated specific genetic syndromes including Prader-Willi syndrome, Bardet-Biedle syndrome, and Alstrom syndrome. Syndromic obesity is often accompanied with neurodevelopmental delay or dysmorphic features. Nonsyndromic monogenic obesity is caused by variants in single gene which are usually involved in the regulation of hunger and satiety associated with the hypothalamic leptin-melanocortin pathway in central nervous system. Unlike syndromic obesity, patients with monogenic obesity usually show normal neurodevelopment. They would be presented with hyperphagia and early-onset severe obesity with additional clinical symptoms including short stature, red hair, adrenal insufficiency, hypothyroidism, hypogonadism, pituitary insufficiencies, diabetes insipidus, increased predisposition to infection or intractable recurrent diarrhea. Identifying patients with genetic obesity is critical as new innovative therapies including melanocortin 4 receptor agonist have become available. Early genetic evaluation enables to identify treatable obesity and provide timely intervention which may eventually achieve favorable outcome by establishing personalized management.

Leptin in Human Milk-One of the Key Regulators of Nutritional Programming

Breast milk is the optimal food for infants and toddlers, providing basic nutrients. It is also a source of many biologically active substances. Among them are hormones responsible for metabolic balance. One of the hormones taken in with breast milk by a breastfed baby is leptin. This hormone is involved in the regulation of appetite, informing the brain about the body’s energy resources. Having the correct mechanisms related to the action of leptin is a factor reducing the risk of obesity. The natural presence of leptin in the composition of breast milk suggests that it has a specific role in shaping the health of a breastfed child. Obesity as a disease of civilization affects more and more people, including children. The development of this disease is multifaceted and determined by many factors, including genetic and environmental factors such as eating habits and low physical activity. Behind obesity, there are complex mechanisms in which many elements of the human body are involved. Understanding the effects of breastfeeding as a natural source of leptin can help prevent childhood obesity and development of this disease in future life.

Biomarkers Predictive of Metabolic Syndrome and Cardiovascular Disease in Childhood Cancer Survivors

The improvement in childhood cancer treatments resulted in a marked improvement in the survival of pediatric cancer patients. However, as survival increased, it was also possible to observe the long-term side effects of cancer therapies. Among these, metabolic syndrome is one of the most frequent long-term side effects, and causes high mortality and morbidity. Consequently, it is necessary to identify strategies that allow for early diagnosis. In this review, the pathogenetic mechanisms of metabolic syndrome and the potential new biomarkers that can facilitate its diagnosis in survivors of pediatric tumors are analyzed.

Resistin in Urine and Breast Milk: Relation to Type of Feeding and Anthropometry at 1-Month

Breast milk contains adipokines such as resistin and leptin and is known for its protective effect against obesity and insulin resistance. This pilot study aims to evaluate the correlation between resistin levels, feeding types (breast milk and formula), and anthropometric parameters in healthy 1-month-old term infants. Urine and breast milk samples were collected from 32 infants and their mothers at 1 month postpartum. Twelve infants were included in the breastfed group, while thirteen infants comprised the breastfed-dominant mix-fed group, and seven infants the formula-dominant mix-fed group. Using ELISA kits, we analyzed resistin levels in the infants' urine and the mothers' breast milk, and leptin levels in breast milk. Urinary resistin levels among the three groups were not significantly different. There was no correlation between the following: urinary resistin levels in the breastfed group with resistin levels in breast milk; resistin levels in urine with infant's body weight and weight gain; resistin levels in breast milk with weight, age, and BMI of mothers and leptin levels in breast milk. This study suggests that the type of feeding does not affect resistin levels in term infants and resistin level does not affect growth in early infancy.

Early-onset severe obesity due to homozygous p.R105W (c313C> T) mutation in leptin gene in Turkish siblings: Two cases reports

Congenital leptin deficiency (CLD) is a rare cause of monogenic form obesity due to homozygous or compound heterozygous mutations in the LEP gene. To date, nine pathogenic mutations have been reported. In this study, we present are; an 18-year-old morbidly obese girl and a 14-year-old obese brother, both with homozygous mutation in the LEP gene [p.R105W (c313C> T)] and their data after three years of recombinant leptin treatment. To date, few cases of CLD have been reported in the literature. The cases reported here were siblings who were not diagnosed despite presentation at the clinic due to obesity in childhood, and diagnosis was delayed until adolescence. Clinicians need to consider CLD, a monogenic form of obesity in children with early severe obesity onset, especially if they are the child of a consanguineous marriage.

A fresh look to the phenotype in mono-allelic likely pathogenic variants of the leptin and the leptin receptor gene

Leptin (LEP) and leptin receptor (LEPR) play a major role in energy homeostasis, metabolism, and reproductive function. While effects of biallelic likely pathogenic variants (-/-) on the phenotype are well characterized, effects of mono-allelic likely pathogenic variants (wt/-) in the LEP and LEPR gene on the phenotype compared to wild-type homozygosity (wt/wt) have not been systematically investigated. We identified in our systematic review 44 animal studies (15 on Lep, 29 on Lepr) and 39 studies in humans reporting on 130 mono-allelic likely pathogenic variant carriers with 20 distinct LEP variants and 108 heterozygous mono-allelic likely pathogenic variant carriers with 35 distinct LEPR variants. We found indications for a higher weight status in carriers of mono-allelic likely pathogenic variant in the leptin and in the leptin receptor gene compared to wt/wt, in both animal and human studies. In addition, animal studies showed higher body fat percentage in Lep and Lepr wt/- vs wt/wt. Animal studies provided indications for lower leptin levels in Lep wt/- vs. wt/wt and indications for higher leptin levels in Lepr wt/- vs wt/wt. Data on leptin levels in human studies was limited. Evidence for an impaired metabolism in mono-allelic likely pathogenic variants of the leptin and in leptin receptor gene was not conclusive (animal and human studies). Mono-allelic likely pathogenic variants in the leptin and in leptin receptor gene have phenotypic effects disposing to increased body weight and fat accumulation.

Leptin gene-targeted editing in ob/ob mouse adipose tissue based on the CRISPR/Cas9 system

Gene therapy has become the most effective treatment for monogenic diseases. Congenital LEPTIN deficiency is a rare autosomal recessive monogenic obesity syndrome caused by mutations in the Leptin gene. Ob/ob mouse is a monogenic obesity model, which carries a homozygous point mutation of C to T in Exon 2 of the Leptin gene. Here, we attempted to edit the mutated Leptin gene in ob/ob mice preadipocytes and inguinal adipose tissues using CRISPR/Cas9 to correct the C to T mutation and restore the production of LEPTIN protein by adipocytes. The edited preadipocytes exhibit a correction of 5.5% of Leptin alleles and produce normal LEPTIN protein when differentiated into mature adipocytes. The ob/ob mice display correction of 1.67% of Leptin alleles, which is sufficient to restore the production and physiological functions of LEPTIN protein, such as suppressing appetite and alleviating insulin resistance. Our study suggests CRISPR/Cas9-mediated in situ genome editing as a feasible therapeutic strategy for human monogenic diseases, and paves the way for further research on efficient delivery system in potential future clinical application.

Tissue-Specific Effects of Leptin on Glucose and Lipid Metabolism

The discovery of leptin was intrinsically associated with its ability to regulate body weight. However, the effects of leptin are more far-reaching and include profound glucose-lowering and anti-lipogenic effects, independent of leptin's regulation of body weight. Regulation of glucose metabolism by leptin is mediated both centrally and via peripheral tissues and is influenced by the activation status of insulin signaling pathways. Ectopic fat accumulation is diminished by both central and peripheral leptin, an effect that is beneficial in obesity-associated disorders. The magnitude of leptin action depends upon the tissue, sex, and context being examined. Peripheral tissues that are of particular relevance include the endocrine pancreas, liver, skeletal muscle, adipose tissues, immune cells, and the cardiovascular system. As a result of its potent metabolic activity, leptin is used to control hyperglycemia in patients with lipodystrophy and is being explored as an adjunct to insulin in patients with type 1 diabetes. To fully understand the role of leptin in physiology and to maximize its therapeutic potential, the mechanisms of leptin action in these tissues needs to be further explored.

The infundibular peptidergic neurons and glia cells in overeating, obesity, and diabetes

Dysfunctional regulation of energy homeostasis results in increased bodyweight and obesity, eventually leading to type 2 diabetes mellitus. The infundibular nucleus (IFN) of the hypothalamus is the main regulator of energy homeostasis. The peptidergic neurons and glia cells of the IFN receive metabolic cues concerning energy state of the body from the circulation. The IFN can monitor hormones like insulin and leptin and nutrients like glucose and fatty acids. All these metabolic cues are integrated into an output signal regulating energy homeostasis through the release of neuropeptides. These neuropeptides are released in several inter- and extrahypothalamic brain regions involved in regulation of energy homeostasis. This review will give an overview of the peripheral signals involved in the regulation of energy homeostasis, the peptidergic neurons and glial cells of the IFN, and will highlight the main intra-hypothalamic projection sites of the IFN.

Impact of Genetic Variations and Epigenetic Mechanisms on the Risk of Obesity

Rare genetic obesity disorders are characterized by mutations of genes strongly involved in the central or peripheral regulation of energy balance. These mutations are effective in causing the early onset of severe obesity and insatiable hunger (hyperphagia), suggesting that the genetic component can contribute to 40–70% of obesity. However, genes’ roles in the processes leading to obesity are still unclear. This review is aimed to summarize the current knowledge of the genetic causes of obesity, especially monogenic obesity, describing the role of epigenetic mechanisms in obesity and metabolic diseases. A comprehensive understanding of the underlying genetic and epigenetic mechanisms, with the metabolic processes they control, will permit adequate management and prevention of obesity.

Preconception leptin levels and pregnancy outcomes: A prospective cohort study

OBJECTIVE

Obesity has become a major, worldwide public health issue and is associated with a greater risk of adverse pregnancy outcomes. Leptin, a hormone produced by adipocytes, is elevated in individuals with obesity and may mediate the association between obesity and pregnancy outcomes. Though leptin levels during pregnancy have been associated with pregnancy outcomes, less is understood regarding preconception levels. Therefore, the objective of this study was to evaluate associations between preconception leptin levels and adverse pregnancy outcomes.

METHODS

This was a prospective cohort study nested within a large randomized controlled trial conducted at four medical centres in the United States. A total of 1078 women completed the parent study; this analysis involved women who became pregnant during that study (n = 776). Patients were healthy women, ages 18 to 40, attempting to conceive, with 1 to 2 prior pregnancy losses. Participants were followed for less than or equal to 6 cycles while trying to conceive and throughout pregnancy if they conceived. Preconception leptin concentrations were measured in serum collected at baseline then categorized by tertiles (using the lowest as reference group). Weighted log-binomial regression estimated risk ratios (RR) and 95% confidence intervals (CIs) for pregnancy loss, preterm delivery (PTD), gestational diabetes (GDM), and hypertensive disorders in pregnancy, adjusting for age, waist-to-hip ratio (WHR), and body mass index (BMI).

RESULTS

The mean (SD) BMI in this cohort was 25.4 ± 6.0. GDM (RR 18.37; 95% CI, 2.39-141.55) and hypertensive disorders of pregnancy (RR 2.35; 95% CI, 1.20-4.61) risks were higher among women in the high tertile after adjusting for age and WHR. The associated risk persisted when adjusting for BMI for GDM but was attenuated for hypertensive disorders in pregnancy. Leptin levels were not associated with risk of pregnancy loss or PTD.

CONCLUSIONS

Women with higher baseline preconception leptin levels had a higher likelihood of experiencing some adverse pregnancy outcomes including GDM and hypertensive disorders of pregnancy. These findings warrant further evaluation, especially in light of the association between leptin and obesity.

Relative leptin deficiency in children with severe early-onset obesity (SEOO) - results of the Early-onset Obesity and Leptin - German-Polish Study (EOL-GPS)

Background Severe early-onset obesity (SEOO) in children is a common feature of monogenic obesity. Gene defects of the leptin-melanocortin pathway can be analysed biochemically and genetically. The aim of this study was to search for children with leptin deficiency or biologically inactive leptin in a cohort of children with SEOO and to study associations between leptin parameters and anthropometric data. Methods The cohort included n = 50 children with SEOO (22 boys) who were recruited at one of four study centres (Germany: Ulm; Poland: Katowice, Szczecin, Rzeszow) between October 2015 and October 2017. Weight (kg) and height (m) were measured, Tanner stage was obtained and a fasting serum blood sample was taken. Serum levels of total leptin (LEP, ng/mL), biologically active leptin (bioLEP, ng/mL) and soluble leptin receptor (sLEPR, ng/mL) were measured. The body mass index (BMI [kg/m2]), BMI z-score (World Health Organization [WHO]), quotient of bioLEP/LEP and leptin-standard deviation score (LEP-SDS) (Tanner stage, BMI and sex-adjusted) were calculated. Results We did not find any child with leptin deficiency or biologically inactive leptin in our cohort. The serum LEP and bioLEP levels were strongly correlated with age (r = 0.50, p < 0.05) and BMI (r = 0.70; p < 0.0001). Girls had higher LEP and bioLEP levels (49.7 ± 35.9 vs. 37.1 ± 25.5 ng/mL, p > 0.05) as well as lower LEP-SDS than boys (-1.77 ± 2.61 vs. -1.40 ± 2.60, p > 0.05). sLEPR levels were negatively correlated with BMI values (r = -0.44; p < 0.05), LEP (r = -0.39; p < 0.05) and bioLEP levels (r = -0.37; p < 0.05). Interestingly, there was a strong inverse relationship between LEP-SDS and BMI (r = -0.72, p < 0.001). Conclusions In this cohort with SEOO, we identified no new cases of children with leptin deficiency or bioinactive leptin. A strong negative correlation between the LEP-SDS and BMI values could be interpreted as relative leptin deficiency in children with SEOO. In case this hypothesis can be confirmed, these children would benefit from a substitution therapy with methionyl human leptin (metreleptin™).

Methylphenidate in children with monogenic obesity due to LEPR or MC4R deficiency improves feeling of satiety and reduces BMI-SDS-A case series

BACKGROUND

The clinical phenotype of patients with monogenic obesity due to mutations in the leptin receptor (LEPR) or melanocortin 4 receptor (MC4R) gene is characterized by impaired satiety and hyperphagia, leading to extreme, sometimes life-threatening weight gain.

SUBJECTS/METHODS

In a case series, we analysed the effect of an off-label methylphenidate (MPH) use for 1 year as an individual treatment approach on eating behaviour (Child Eating Behaviour Questionnaire [CEBQ]), appetite (visual analogue scales) and body mass index (BMI) trajectories in five patients with severe obesity due to mutations in the LEPR (n = 3) or MC4R (n = 2) gene.

RESULTS

After 1 year use of MPH (20 mg/day divided in two to three doses), BMI (Δ BMI_T0-T1x¯ : -0.7 ± 0.9 kg/m² ), BMI standard deviation score (SDS) (Δ BMI-SDS_T0-T1x¯ : -0.32 ± 0.20), and %BMIP95 (Δ %BMIP95_T0-T1x¯ : -6.6 ± 7.8%) decreased. BMI-SDS velocity decreased from +0.17 ± 0.22 to -0.30 ± 0.20. Appetite and CEBQ subscale scores for "food responsiveness" and "enjoyment of food" decreased. We observed adverse effects with increase in self-reported frequency of disordered sleep, nervousness, hyperactivity, and tics.

CONCLUSIONS

The observed decrease in BMI trajectories with MPH use for one year is clinically meaningful in this group of patients, since the natural course would have been associated with a pronounced increase in BMI, leading to comorbidities and complications over time.

Monogenic leptin deficiency in early childhood obesity

BACKGROUND

Early childhood obesity is a public health problem worldwide. It affects different aspects of physical and mental child's health. Identifying the etiologies, especially treatable and preventable causes, can direct health professionals toward proper management. Analysis of serum leptin levels and leptin gene mutations is a rapid and easy step toward the diagnosis of congenital leptin deficiency that is considered an important cause in early childhood obesity.

OBJECTIVES

The aim of this study was to diagnose monogenic leptin deficiency in Egyptian children presenting with early onset obesity (EOO).

METHODS

The current cross-sectional study included 80 children who developed obesity during the first year of life with BMI > 2 SD (for age and sex). The studied population was subjected to history taking, auxological assessment, serum leptin assay, and leptin gene sequencing.

RESULTS

Ten cases had leptin deficiency (12.5%), while 18 cases showed elevated leptin levels (22.5%). Leptin gene variants in the coding region were identified in 30% of the leptin-deficient group: two novel homozygous disease-causing variants (c.104 T > G and c.34 delC) and another previously reported homozygous pathogenic variant (c.313C > T).

CONCLUSION

Leptin deficiency is considered a significant cause of monogenic obesity in Egyptian children with early-onset obesity as the diagnosis of these patients would be a perfect target for recombinant leptin therapy.

Preconception Leptin and Fecundability, Pregnancy, and Live Birth Among Women With a History of Pregnancy Loss

Context

With the increase of obesity, it is imperative to understand the neuroendocrine mechanisms, including the neuroendocrine hormone leptin, by which obese or overweight women are at increased risk for subfertility and infertility.

Objective

The objective was to examine associations between preconception serum leptin concentrations, fecundability, pregnancy, and live birth.

Design

Secondary analysis of a prospective cohort among women with prior pregnancy losses.

Setting

The study was conducted at four US medical centers (2006 to 2012).

Intervention

Not available.

Materials and Methods

Preconception serum leptin concentrations were measured at baseline, and women were followed for up to six menstrual cycles, and throughout pregnancy if they conceived. Discrete Cox proportional hazard regression models were used to assess fecundability odds ratios (FORs) and log-binomial regression to estimate risk ratios (RRs) for pregnancy and live birth. Models were adjusted for age, physical activity, treatment arm, and adiposity, either by measured waist-to-hip ratio or body mass index (BMI).

Results

High leptin concentrations were associated with decreased fecundability (FOR 0.72, 95% CI 0.58, 0.90), reduced risk of pregnancy (RR 0.87, 95% CI 0.78, 0.96) and live birth (RR 0.76, 95% CI 0.65, 0.89) comparing the upper to the lower tertile. However, adjustment for BMI in lieu of waist-to-hip ratio nullified observed associations.

Conclusions

In women with a history of pregnancy loss, relations between higher preconception leptin and fecundability were attenuated after adjustment for BMI, although not after adjustment for other markers of adiposity. Leptin may serve as a complementary marker of adiposity for assessment of obesity and reproductive outcomes.

Antioxidants protect against diabetes by improving glucose homeostasis in mouse models of inducible insulin resistance and obesity

AIMS/HYPOTHESIS

In the context of diabetes, the health benefit of antioxidant treatment has been widely debated. In this study, we investigated the effect of antioxidant treatment during the development of insulin resistance and hyperphagia in obesity and partial lipodystrophy.

METHODS

We studied the role of antioxidants in the regulation of insulin resistance using the tamoxifen-inducible fat-specific insulin receptor knockout (iFIRKO) mouse model, which allowed us to analyse the antioxidant's effect in a time-resolved manner. In addition, leptin-deficient ob/ob mice were used as a hyperphagic, chronically obese and diabetic mouse model to validate the beneficial effect of antioxidants on metabolism.

RESULTS

Acute induction of insulin receptor knockout in adipocytes changed the substrate preference to fat before induction of a diabetic phenotype including hyperinsulinaemia and hyperglycaemia. In healthy chow-fed animals as well as in morbidly obese mice, this diabetic phase could be reversed within a few weeks. Furthermore, after the induction of insulin receptor knockout in mature adipocytes, iFIRKO mice were protected from subsequent obesity development through high-fat diet feeding. By genetic tracing we show that the persistent fat mass loss in mice after insulin receptor knockout in adipocytes is not caused by the depletion of adipocytes. Treatment of iFIRKO mice with antioxidants postponed and reduced hyperglycaemia by increasing insulin sensitivity. In ob/ob mice, antioxidants rescued both hyperglycaemia and hyperphagia.

CONCLUSIONS/INTERPRETATION

We conclude that fat mass reduction through insulin resistance in adipocytes is not reversible. Furthermore, it seems unlikely that adipocytes undergo apoptosis during the process of extreme lipolysis, as a consequence of insulin resistance. Antioxidants have a beneficial health effect not only during the acute phase of diabetes development, but also in a temporary fashion once chronic obesity and diabetes have been established.

The Effects of Laparoscopic Sleeve Gastrectomy on the Parameters of Leptin Resistance in Obesity

Obesity is a growing public health problem worldwide. Bariatric surgical procedures achieve the most sustainable and efficacious outcomes in the treatment of morbid obesity. However, little is known about the underlying molecular pathways modulated by these surgical interventions. Since leptin resistance is implicated in the pathogenesis of obesity, we herein report the effects of laparoscopic sleeve gastrectomy (LSG) on the serum levels of leptin and leptin receptor, in addition to its overall effect on leptin resistance. This was an interventional and follow-up clinical study. In the first part, patients attending the general surgery outpatient clinics at our university hospital were first stratified according to their Body-Mass Index (BMI) into cases (n = 38) with BMI ≥ 35 who were scheduled to undergo LSG, and controls (n = 75) with a normal BMI. Serum leptin and leptin receptor levels were measured by sandwich ELISA technique. A leptin resistance index was estimated by adjusting leptin to BMI ratio to leptin receptor concentration. In the second part of the study, cases who underwent LSG were followed up one year postoperatively to assess their BMI and serum leptin and leptin receptor levels. Leptin to BMI ratio was significantly higher, while serum leptin receptor was significantly lower, in obese patients compared to controls. This translated into a significantly higher leptin resistance index in obese patients. LSG resulted in a significant reduction of BMI, leptin to BMI ratio, and leptin resistance index, as it significantly increased leptin receptor levels. In conclusion, LSG showed significant decrease in leptin resistance in obese patients after one year. Further studies are needed to determine the clinical impact of this finding on LSG outcomes.

Visceral fat and insulin resistance - what we know?

One of the most significant challenges of current medicine is the increasing prevalence of obesity worldwide that is accompanied by a wide range of chronic health complications and increased mortality. White adipose tissue actively contributes to metabolic regulation by production of a variety of hormones and cytokines, commonly referred to as adipokines. The spectrum and quantity of adipokines produced by the adipose tissue of obese patients is directly or indirectly involved in much obesity-related pathology (type 2 diabetes mellitus, cardiovascular disease, inflammatory response). One of the underlying mechanisms linking obesity, diabetes, and cardiovascular complications is subclinical inflammation, primarily arising in visceral adipose tissue. Adipocyte size, number and polarization of lymphocytes and infiltrated macrophages are closely related to metabolic and obesity-related diseases. The storage capacity of hypertrophic adipocytes in obese patients is limited. This results in chronic energy overload and leads to increased apoptosis of adipocytes that in turn stimulates the infiltration of visceral adipose tissue by immune cells, in particular macrophages. These cells produce many proinflammatory factors; while the overall production of anti-inflammatory cytokines and adipokines is decreased. The constant release of proinflammatory factors into the circulation then contributes to a subclinical systemic inflammation, which is directly linked to the metabolic and cardiovascular complications of obesity.

Relevance of polymorphisms in MC4R and BDNF in short normal stature

Background

Variation in genes of the leptinergic-melanocortinergic system influence both body weight and height. Because short normal stature (SNS) is characterized by reduced body height, delayed maturation and leanness, allelic variation of genes in this pathway are hypothesized to affect this common condition.

Methods

We analyzed the coding regions of LEP, MC4R, MRAP2 and BDNF in 185 children with SNS (height < 5th percentile) to search for non-synonymous and frameshift variants. For association studies (two-sided χ²-tests) population-based data sets (ExAC, EVS and KORA) were used. Cyclic AMP accumulation, cell surface expression, central expression and MAP kinase activation were assayed in vitro to determine the functional implications of identified variants.

Results

We detected eleven variants predicted to be protein-altering, four in MC4R, four in BDNF, and three in MRAP2. No variants were found in LEP. In vitro analysis implied reduced function for the MC4R variant p.Met215Ile. Loss-of-function is contrary to expectations based on obesity studies, and thus does not support that this variant is relevant for SNS. The minor SNP alleles at MC4R p.Val103Ile and BDNF p.Val66Met were nominally associated with SNS.

Conclusion

Taken together, although genes of the leptinergic-melanocortinergic system are important for normal growth, our data do not support the involvement of rare mutations in LEP, MC4R, MRAP2 or BDNF in short normal stature.

Electronic supplementary material

The online version of this article (10.1186/s12887-018-1245-1) contains supplementary material, which is available to authorized users.

Uncovering the molecular mechanisms behind disease-associated leptin variants

The pleiotropic hormone leptin has a pivotal role in regulating energy balance by inhibiting hunger and increasing energy expenditure. Homozygous mutations found in the leptin gene are associated with extreme obesity, marked hyperphagia, and impaired immune function. Although these mutations have been characterized in vivo, a detailed understanding of how they affect leptin structure and function remains elusive. In the current work, we used NMR, differential scanning calorimetry, molecular dynamics simulations, and bioinformatics calculations to characterize the effects of these mutations on leptin structure and function and binding to its cognate receptor. We found that mutations identified in patients with congenital leptin deficiency not only cause leptin misfolding or aggregation, but also cause changes in the dynamics of leptin residues on the receptor-binding interface. Therefore, we infer that mutation-induced leptin deficiency may arise from several distinct mechanisms including (i) blockade of leptin receptor interface II, (ii) decreased affinity in the second step of leptin's interaction with its receptor, (iii) leptin destabilization, and (iv) unsuccessful threading through the covalent loop, leading to leptin misfolding/aggregation. We propose that this expanded framework for understanding the mechanisms underlying leptin deficiency arising from genetic mutations may be useful in designing therapeutics for leptin-associated disorders.

Obesity genetics: insights from the Pakistani population

The Pakistani population is extensively diverse, indicating a genetic admixture of European and Central/West Asian migrants with indigenous South Asian gene pools. Pakistanis are organized in different ethnicities/castes based on cultural, linguistic and geographical origin. While Pakistan is facing a rapid nutritional transition, the rising prevalence of obesity is driving a growing burden of health complications and mortality. This represents a unique opportunity for the research community to study the interplay between obesogenic environmental changes and obesity predisposing genes in the time frame of one generation. This review recapitulates the ancestral origins of Pakistani population, the societal determinants of the rise in obesity and its governmental management. We describe the contribution of syndromic, monogenic non-syndromic and polygenic obesity genes identified in the Pakistani population. We then discuss the utility of gene identification approaches based on large consanguineous families and original gene × environment interaction study designs in discovering new obesity genes and causal pathways. Elucidation of the genetic basis of obesity in the Pakistani population may result in improved methods of obesity prevention and treatment globally.

Early childhood BMI trajectories in monogenic obesity due to leptin, leptin receptor, and melanocortin 4 receptor deficiency

OBJECTIVE

To evaluate whether early childhood body mass index (BMI) is an appropriate indicator for monogenic obesity.

METHODS

A cohort of n = 21 children living in Germany or Austria with monogenic obesity due to congenital leptin deficiency (group LEP, n = 6), leptin receptor deficiency (group LEPR, n = 6) and primarily heterozygous MC4 receptor deficiency (group MC4R, n = 9) was analyzed. A control group (CTRL) was defined that consisted of n = 22 obese adolescents with no mutation in the above mentioned genes. Early childhood (0-5 years) BMI trajectories were compared between the groups at selected time points.

RESULTS

The LEP and LEPR group showed a tremendous increase in BMI during the first 2 years of life with all patients displaying a BMI >27 kg/m² (27.2-38.4 kg/m²) and %BMI_P95 (percentage of the 95th percentile BMI for age and sex) >140% (144.8-198.6%) at the age of 2 years and a BMI > 33 kg/m² (33.3-45.9 kg/m²) and %BMI_P95 > 184% (184.1-212.6%) at the age of 5 years. The MC4R and CTRL groups had a later onset of obesity with significantly lower BMI values at both time points (p < 0.01).

CONCLUSION

As result of the investigation of early childhood BMI trajectories in this pediatric cohort with monogenic obesity we suggest that BMI values >27.0 kg/m² or %BMI_P95 > 140% at the age of 2 years and BMI values >33.0 kg/m² or %BMI_P95> 184% at the age of 5 years may be useful cut points to identify children who should undergo genetic screening for monogenic obesity due to functionally relevant mutations in the leptin gene or leptin receptor gene.

CRISPR-Cas9-mediated generation of obese and diabetic mouse models

Mouse models of obesity (ob/ob) and diabetes (db/db) in which the leptin (Lep) and leptin receptor (Lepr) genes have been mutated, respectively, have contributed to a better understanding of human obesity and type 2 diabetes and to the prevention, diagnosis, and treatment of these metabolic diseases. In this study, we report the first CRISPR-Cas9-induced Lep and Lepr knockout (KO) mouse models by co-microinjection of Cas9 mRNA and sgRNAs that specifically targeted Lep or Lepr in C57BL/6J embryos. Our newly established Lep and Lepr KO mouse models showed phenotypic disorders nearly identical to those found in ob/ob and db/db mice, such as an increase in body weight, hyperglycemia, and hepatic steatosis. Thus, Cas9-generated Lep and Lepr KO mouse lines will be easier for genotyping, to maintain the lines, and to use for future obesity and diabetes research.

Ethnic and population differences in the genetic predisposition to human obesity

Obesity rates have escalated to the point of a global pandemic with varying prevalence across ethnic groups. These differences are partially explained by lifestyle factors in addition to genetic predisposition to obesity. This review provides a comprehensive examination of the ethnic differences in the genetic architecture of obesity. Using examples from evolution, heritability, admixture, monogenic and polygenic studies of obesity, we provide explanations for ethnic differences in the prevalence of obesity. The debate over definitions of race and ethnicity, the advantages and limitations of multi-ethnic studies and future directions of research are also discussed. Multi-ethnic studies have great potential to provide a better understanding of ethnic differences in the prevalence of obesity that may result in more targeted and personalized obesity treatments.

Frühkindlicher BMI-Verlauf bei monogener Adipositas

Hintergrund

Monogene Adipositasformen haben eine geschätzte Prävalenz von 1–5 % in der Gruppe der extrem adipösen Patienten. Bereits im frühen Kindesalter zwischen monogener Adipositas und anderen Adipositasformen zu unterscheiden, stellt eine Herausforderung für Kinderärzte dar. Insbesondere stellt sich die Frage, wann weiterführende Diagnostik indiziert ist.

Fragestellung

Können Body Mass Index (BMI) und BMI-Verlauf als Parameter herangezogen werden, um eine monogene Adipositas auf Basis einer Mutation des Leptin- oder Leptinrezeptorgens frühzeitig zu diagnostizieren?

Material und Methoden

Frühkindliche BMI-Verläufe (0–5 Jahre) von n = 21 Patienten mit monogener Adipositas aufgrund von Leptindefizienz (LEP, n = 6), Leptinrezeptordefizienz (LEPR, n = 6) und MC4-Rezeptordefizienz (MC4R, n = 9) wurden analysiert. BMI-Werte im Alter von 2 und 5 Jahren, Zeitpunkte der Vorsorgen U7 und U9 in Deutschland, wurden zwischen den Gruppen verglichen.

Ergebnisse

Patienten mit funktionellem Leptinmangel oder Leptinrezeptordefekt zeigen den stärksten BMI-Anstieg in den ersten beiden Lebensjahren. Ihr BMI ist im Alter von 2 Jahren >25 kg/m2 [27,2–38,4 kg/m2] und im Alter von 5 Jahren >30 kg/m2 [33,3–45,9 kg/m2]. Bei Patienten mit MC4R-Defekt manifestierte sich die Adipositas zu einem späteren Zeitpunkt mit signifikant niedrigeren BMI-Werten im Alter von 2 bzw. 5 Jahren (p < 0,01).

Diskussion

Unsere Ergebnisse zeigen, dass ein BMI > 25 kg/m2 im Alter von 2 Jahren und ein BMI > 30 kg/m2 im Alter von 5 Jahren Hinweis auf das Vorliegen einer monogenen Adipositas auf Basis einer Mutation des Leptin- oder Leptinrezeptorgens ist. Bei diesen Patienten sollte eine weiterführende Diagnostik (Bestimmung von Leptin, bioaktivem Leptin, Molekulargenetik) frühzeitig erfolgen.

Biology of obesity and weight regain: Implications for clinical practice

BACKGROUND AND PURPOSE

Weight loss is recommended as first-line therapy for many chronic illnesses, including obesity. Most patients who do successfully lose weight are unable to maintain their reduced weight. Recent research findings are reviewed and synthesized to explain the biology of obesity, adaptation to weight loss, and weight regain.

FINDINGS

Weight regain is a common consequence of successful weight loss. Current obesity management strategies fail to take into consideration the underlying genetic and environmental causes of obesity. Available treatment modalities create a negative energy balance that stimulates integrated, persistent neurologic, endocrine, muscle, and adipose tissue adaptation to restore body weight and fat mass, independent of lifestyle changes.

IMPLICATIONS FOR PRACTICE

Understanding the pathophysiology of obesity and weight loss alters nurse practitioners' responsibilities in caring for patients with obesity. They are responsible for expanding assessment and intervention strategies and offering people with obesity realistic expectations for weight loss and regain. They are obligated to explain weight regain when it occurs to minimize patient frustration. Nurse practitioners have the opportunity to adopt new approaches to patient advocacy, especially in the areas of public policy to improve diagnostic tools and adjunctive therapy for people with obesity.

Monogene Adipositas

Autosomal-rezessiv vererbte Mutationen in den Genen für Leptin, Leptinrezeptor, Proopiomelanocortin (POMC) und Prohormon-Convertase (PC1) führen zu einer ausgeprägten frühkindlichen Adipositas. Patienten mit biologisch inaktivem Leptin oder Leptinmangel können mit humanem rekombinanten Leptin erfolgreich behandelt werden. Für die anderen Patienten hat sich die Behandlung mit einem α‑MSH-Analogon als erfolgreich erwiesen (POMC-Patienten) bzw. befindet sich derzeit in Erprobung.

Kodominant vererbte Mutationen im MC4R-Gen stellen die häufigste Form der monogenen Adipositas dar. Eine kausale Therapie ist hier allerdings nicht möglich.

Es sind inzwischen noch weitere, autosomal-rezessiv vererbte Genmutationen identifiziert worden, die ebenfalls mit einer ausgeprägten Adipositas assoziiert sind. Die meisten dieser Mutationen liegen in Genen, die in die Signaltransduktion von MC4R oder dem Leptinrezeptor involviert sind. Auch für diese Patienten gibt es aktuell noch keine kausale Therapie.

Schlussfolgerung: Bei Patienten mit extremer frühkindlicher Adipositas sollte eine molekulargenetische Diagnostik eingeleitet werden, da die Diagnosestellung für die Betroffenen und ihre Familie eine enorme Erleichterung bedeuten kann. Außerdem gewinnen die Familien Klarheit über das Wiederholungsrisiko und eventuell ist sogar eine kausale oder zumindest optimierte Therapie möglich.

High-fat diet increases pain behaviors in rats with or without obesity

Obesity is associated with increased risk for chronic pain. Basic mechanisms for this association are poorly understood. Using a milder version of a radicular pain model, local inflammation of the dorsal root ganglion (DRG), we observed marked increases in mechanical and cold allodynia in rats of both sexes that were maintained on a high-fat diet (HFD) for 6 weeks prior to DRG inflammation. Notably, this increase in pain-related behaviors occurred in both Long-Evans and Sprague-Dawley rats despite the fact that the 6-week HFD exposure induced obesity (e.g., increased insulin, leptin, weight, and percent body fat) in the Long-Evans, but not Sprague-Dawley, strains. This suggested that HFD, rather than obesity per se, increased pain behaviors. Increased pain behaviors were observed even after a much shorter (1 week) exposure to the HFD but the effect was smaller. HFD also increased behavioral responses and paw swelling to paw injection of complete Freund’s adjuvant, a model of peripheral inflammatory pain. No change was detected in plasma cytokine levels in HFD rats. However, increased macrophage infiltration of the DRG was observed in response to the HFD, absent any pain model. The results suggest that HFD can increase pain even when it does not cause obesity.

Correlation of disease severity with body weight and high fat diet in the FATZO/Pco mouse

Obesity in many current pre-clinical animal models of obesity and diabetes is mediated by monogenic mutations; these are rarely associated with the development of human obesity. A new mouse model, the FATZO mouse, has been developed to provide polygenic obesity and a metabolic pattern of hyperglycemia and hyperinsulinemia, that support the presence of insulin resistance similar to metabolic disease in patients with insulin resistance/type 2 diabetes. The FATZO mouse resulted from a cross of C57BL/6J and AKR/J mice followed by selective inbreeding for obesity, increased insulin and hyperglycemia. Since many clinical studies have established a close link between higher body weight and the development of type 2 diabetes, we investigated whether time to progression to type 2 diabetes or disease severity in FATZO mice was dependent on weight gain in young animals. Our results indicate that lighter animals developed metabolic disturbances much slower and to a lesser magnitude than their heavier counterparts. Consumption of a diet containing high fat, accelerated weight gain in parallel with disease progression. A naturally occurring and significant variation in the body weight of FATZO offspring enables these mice to be identified as low, mid and high body weight groups at a young age. These weight groups remain into adulthood and correspond to slow, medium and accelerated development of type 2 diabetes. Thus, body weight inclusion criteria can optimize the FATZO model for studies of prevention, stabilization or treatment of type 2 diabetes.

Glucose dysregulation and response to common anti-diabetic agents in the FATZO/Pco mouse

The FATZO/Pco mouse is the result of a cross of the C57BL/6J and AKR/J strains. The crossing of these two strains and the selective inbreeding for obesity, insulin resistance and hyperglycemia has resulted in an inbred strain exhibiting obesity in the presumed presence of an intact leptin pathway. Routinely used rodent models for obesity and diabetes research have a monogenic defect in leptin signaling that initiates obesity. Given that obesity and its sequelae in humans are polygenic in nature and not associated with leptin signaling defects, the FATZO mouse may represent a more translatable rodent model for study of obesity and its associated metabolic disturbances. The FATZO mouse develops obesity spontaneously when fed a normal chow diet. Glucose intolerance with increased insulin levels are apparent in FATZO mice as young as 6 weeks of age. These progress to hyperglycemia/pre-diabetes and frank diabetes with decreasing insulin levels as they age. The disease in these mice is multi-faceted, similar to the metabolic syndrome apparent in obese individuals, and thus provides a long pre-diabetic state for determining the preventive value of new interventions. We have assessed the utility of this new model for the pre-clinical screening of agents to stop or slow progression of the metabolic syndrome to severe diabetes. Our assessment included: 1) characterization of the spontaneous development of disease, 2) comparison of metabolic disturbances of FATZO mice to control mice and 3) validation of the model with regard to the effectiveness of current and emerging anti-diabetic agents; rosiglitazone, metformin and semaglutide.

CONCLUSION

Male FATZO mice spontaneously develop significant metabolic disease when compared to normal controls while maintaining hyperglycemia in the presence of high leptin levels and hyperinsulinemia. The disease condition responds to commonly used antidiabetic agents.

Measurement of immunofunctional leptin to detect and monitor patients with functional leptin deficiency

CONTEXT AND AIMS

Functional leptin deficiency is characterized by high levels of circulating immunoreactive leptin (irLep), but a reduced bioactivity of the hormone due to defective receptor binding. As a result of the fact that affected patients can be successfully treated with metreleptin, it was aimed to develop and validate a diagnostic tool to detect functional leptin deficiency.

METHODS

An immunoassay capable of recognizing the functionally relevant receptor-binding complex with leptin was developed (bioLep). The analytical quality of bioLep was validated and compared to a conventional assay for immune-reactive leptin (irLep). Its clinical relevance was evaluated in a cohort of lean and obese children and adults as well as in children diagnosed with functional leptin deficiency and their parents.

RESULTS

In the clinical cohort, a bioLep/irLep ratio of 1.07 (range: 0.80-1.41) was observed. Serum of patients with non-functional leptin due to homozygous amino acid exchanges (D100Y or N103K) revealed high irLep but non-detectable bioLep levels. Upon treatment of these patients with metreleptin, irLep levels decreased, whereas levels of bioLep increased continuously. In patient relatives with heterozygous amino acid exchanges, a bioLep/irLep ratio of 0.52 (range: 0.48-0.55) being distinct from normal was observed.

CONCLUSIONS

The new bioLep assay is able to diagnose impaired leptin bioactivity in severely obese patients with a homozygous gene defect and in heterozygous carriers of such mutations. The assay serves as a diagnostic tool to monitor leptin bioactivity during treatment of these patients.

GENETIC AND EPIGENETIC CAUSES OF OBESITY

Obesity is a complex, heritable trait influenced by the interplay of genetics, epigenetics, metagenomics and the environment. With the increasing access to high precision diagnostic tools for genetic investigations, numerous genes influencing the phenotype have been identified, especially in early onset severe obesity. This review summarizes the current knowledge on the known genetic causes of obesity and the available therapeutic options. Furthermore, we discuss the role and potential mechanism of epigenetic changes that may be involved as mediators of the environmental influences and that may provide future opportunities for intervention.

GENETIC AND EPIGENETIC CAUSES OF OBESITY

Obesity is a complex, heritable trait influenced by the interplay of genetics, epigenetics, metagenomics and the environment. With the increasing access to high precision diagnostic tools for genetic investigations, numerous genes influencing the phenotype have been identified, especially in early onset severe obesity. This review summarizes the current knowledge on the known genetic causes of obesity and the available therapeutic options. Furthermore, we discuss the role and potential mechanism of epigenetic changes that may be involved as mediators of the environmental influences and that may provide future opportunities for intervention.