Beneficial Outcomes of Sleeve Gastrectomy in a Morbidly Obese Patient With Bardet-Biedl Syndrome

Differentiating monogenic and syndromic obesities from polygenic obesity: Assessment, diagnosis, and management

Background

Obesity is a multifactorial neurohormonal disease that results from dysfunction within energy regulation pathways and is associated with increased morbidity, mortality, and reduced quality of life. The most common form is polygenic obesity, which results from interactions between multiple gene variants and environmental factors. Highly penetrant monogenic and syndromic obesities result from rare genetic variants with minimal environmental influence and can be differentiated from polygenic obesity depending on key symptoms, including hyperphagia; early-onset, severe obesity; and suboptimal responses to nontargeted therapies. Timely diagnosis of monogenic or syndromic obesity is critical to inform management strategies and reduce disease burden. We outline the physiology of weight regulation, role of genetics in obesity, and differentiating characteristics between polygenic and rare genetic obesity to facilitate diagnosis and transition toward targeted therapies.

Methods

In this narrative review, we focused on case reports, case studies, and natural history studies of patients with monogenic and syndromic obesities and clinical trials examining the efficacy, safety, and quality of life impact of nontargeted and targeted therapies in these populations. We also provide comprehensive algorithms for diagnosis of patients with suspected rare genetic causes of obesity.

Results

Patients with monogenic and syndromic obesities commonly present with hyperphagia (ie, pathologic, insatiable hunger) and early-onset, severe obesity, and the presence of hallmark characteristics can inform genetic testing and diagnostic approach. Following diagnosis, specialized care teams can address complex symptoms, and hyperphagia is managed behaviorally. Various pharmacotherapies show promise in these patient populations, including setmelanotide and glucagon-like peptide-1 receptor agonists.

Conclusion

Understanding the pathophysiology and differentiating characteristics of monogenic and syndromic obesities can facilitate diagnosis and management and has led to development of targeted pharmacotherapies with demonstrated efficacy for reducing body weight and hunger in the affected populations.

Bardet-Biedl syndrome: A clinical overview focusing on diagnosis, outcomes and best-practice management

Bardet-Biedl syndrome (BBS) is a genetic disorder characterized by early-onset obesity, polydactyly, genital and kidney anomalies, developmental delay and vision loss due to rod-cone dystrophy. BBS is an autosomal recessive disorder with >20 implicated genes. The genotype-phenotype relationship in BBS is not clear, and there may be additional modifying factors. The underlying mechanism is dysfunction of primary cilia. In BBS, receptor trafficking in and out of the cilia is compromised, affecting multiple organ systems. Along with early-onset obesity, hyperphagia is a prominent symptom and contributes significantly to clinical morbidity and caregiver burden. While there is no cure for BBS, setmelanotide is a new pharmacotherapy approved for treatment of obesity in BBS. The differential diagnosis for BBS includes other ciliopathies, such as Alstrom syndrome, and other genetic obesity syndromes, such as Prader-Willi syndrome. Careful clinical history and genetic testing can help determine the diagnosis and a multidisciplinary team is necessary to guide clinical management.

Bardet-Biedl syndrome: A focus on genetics, mechanisms and metabolic dysfunction

Bardet-Biedl syndrome (BBS) is a rare, monogenic, multisystem disorder characterized by retinal dystrophy, renal abnormalities, polydactyly, learning disabilities, as well as metabolic dysfunction, including obesity and an increased risk of type 2 diabetes. It is a primary ciliopathy, and causative mutations in more than 25 different genes have been described. Multiple cellular mechanisms contribute to the development of the metabolic phenotype associated with BBS, including hyperphagia as a consequence of altered hypothalamic appetite signalling as well as alterations in adipocyte biology promoting adipocyte proliferation and adipogenesis. Within this review, we describe in detail the metabolic phenotype associated with BBS and discuss the mechanisms that drive its evolution. In addition, we review current approaches to the metabolic management of patients with BBS, including the use of weight loss medications and bariatric surgery. Finally, we evaluate the potential of targeting hypothalamic appetite signalling to limit hyperphagia and induce clinically significant weight loss.

Towards precision medicine in bariatric surgery prescription

Obesity is a complex, multifactorial and chronic disease. Bariatric surgery is a safe and effective treatment intervention for obesity and obesity-related diseases. However, weight loss after surgery can be highly heterogeneous and is not entirely predictable, particularly in the long-term after intervention. In this review, we present and discuss the available data on patient-related and procedure-related factors that were previously appointed as putative predictors of bariatric surgery outcomes. In addition, we present a critical appraisal of the available evidence on which factors could be taken into account when recommending and deciding which bariatric procedure to perform. Several patient-related features were identified as having a potential impact on weight loss after bariatric surgery, including age, gender, anthropometrics, obesity co-morbidities, eating behavior, genetic background, circulating biomarkers (microRNAs, metabolites and hormones), psychological and socioeconomic factors. However, none of these factors are sufficiently robust to be used as predictive factors. Overall, there is no doubt that before we long for precision medicine, there is the unmet need for a better understanding of the socio-biological drivers of weight gain, weight loss failure and weight-regain after bariatric interventions. Machine learning models targeting preoperative factors and effectiveness measurements of specific bariatric surgery interventions, would enable a more precise identification of the causal links between determinants of weight gain and weight loss. Artificial intelligence algorithms to be used in clinical practice to predict the response to bariatric surgery interventions could then be created, which would ultimately allow to move forward into precision medicine in bariatric surgery prescription.

Laparoscopic Sleeve Gastrectomy in a Morbidly Obese Pediatric Patient With Bardet-Biedl Syndrome

Data on the effect of bariatric surgery for syndromic obesity are lacking. This case report presents the preoperative evaluation and perioperative outcomes of a 7-year-old pediatric patient with Bardet-Biedl syndrome (BBS) who underwent sleeve gastrectomy. The male patient was referred to our department for the surgical treatment of his obesity. His preoperative body mass index (BMI) was 55.2 kg/m² (weight, 83.5 kg), and he was above the 99^th percentile for age and gender. The patient underwent laparoscopic sleeve gastrectomy. The postoperative period was uneventful. Six months after the operation, the patient's weight decreased to 50 kg (BMI, 28.72 kg/m²). Weight loss was maintained until 3 years after surgery. Dyslipidemia and nonalcoholic fatty liver disease were significantly alleviated. Laparoscopic sleeve gastrectomy may be a safe and effective treatment for morbid BBS-related obesity in pediatric patients. Further data are needed to confirm the long-term efficacy and safety of bariatric surgery in BBS.

An evaluation of setmelanotide injection for chronic weight management in adult and pediatric patients with obesity due to Bardet-Biedl syndrome

INTRODUCTION

Bardet-Biedl Syndrome (BBS) is a rare, multisystemic ciliopathy with an incidence of obesity of 89%. Mutations in genes encoding BBS proteins are linked to reduced leptin sensitivity of hypothalamic POMC neurons and reduced activation of the melanocortin-4 receptor (MC4R) pathway due to deficient α-MSH production by hypothalamic POMC neurons. The MC4R pathway is involved in controlling body weight and energy metabolism, and its disruption is linked to hyperphagia and obesity. Setmelanotide is an MC4R agonist that counteracts deficiencies in the MC4R pathway of individuals with BBS.

AREAS COVERED

Data from clinical trials were reviewed along with information available from setmelanotide's approval for treatment of obesity in people ages ≥6y with a clinical diagnosis of BBS.

EXPERT OPINION

Setmelanotide is available as a daily injectable that can be used for amelioration of obesity in people with Bardet-Biedl syndrome. Its cost is substantial, which may limit its use, but among those who respond, setmelanotide can reduce body mass dramatically and potentially improve comorbid conditions associated with obesity. Setmelanotide treatment has generally tolerable side effects, primarily injection site reactions and nausea/vomiting that generally improve with continued use; almost all people using setmelanotide experience marked skin darkening due to off-target activation of cutaneous MC1R.

Bardet-Biedl Syndrome: Current Perspectives and Clinical Outlook

The Bardet Biedl syndrome (BBS) is a rare inherited disorder considered a model of non-motile ciliopathy. It is in fact caused by mutations of genes encoding for proteins mainly localized to the base of the cilium. Clinical features of BBS patients are widely shared with patients suffering from other ciliopathies, especially autosomal recessive syndromic disorders; moreover, mutations in cilia-related genes can cause different clinical ciliopathy entities. Besides the best-known clinical features, as retinal degeneration, learning disabilities, polydactyly, obesity and renal defects, several additional clinical signs have been reported in BBS, expanding our understanding of the complexity of its clinical spectrum. The present review aims to describe the current knowledge of BBS i) pathophysiology, ii) clinical manifestations, highlighting both the most common and the less described features, iii) current and future perspective for treatment.

Critical review of bariatric surgical outcomes in patients with Prader-Willi syndrome and other hyperphagic disorders

OBJECTIVE

The aim of this study was to review bariatric procedure outcomes among patients with Prader-Willi syndrome (PWS), melanocortin 4 receptor (MC4R) mutations, Bardet-Biedl syndrome, and hypothalamic obesity.

METHODS

Systematic published literature review used the following search terms: "Prader-Willi syndrome," "Bardet-Biedl syndrome," "hyperphagia," "bariatric surgery," "MC4R"/"melanocortin 4 receptor", "hypothalamic obesity," and "bariatric procedure." Information collected included demographics, genetics, anthropometry, procedure type, outcomes, and complications, with inclusion of case series and clinical reports given the rarity of the disorders. For PWS, postoperative weight-change percentage and BMI up to 14 years following surgery were analyzed using general linear mixed models, with descriptive outcomes for other conditions.

RESULTS

A total of 54 publications were identified, with variable follow-up periods for 202 patients (114 with PWS, 43 with MC4R mutations, 7 with Bardet-Biedl syndrome, and 38 with hypothalamic obesity) among bariatric procedures. Weight loss of patients with PWS was greatest within 1 year of surgery, with weight-change percentage not significantly different from 0 at 5 years. Long-term results in other conditions were variable and featured suboptimal weight loss and increased reoperation risk.

CONCLUSIONS

Bariatric procedures among hyperphagic individuals, including those with PWS, report variable results and outcomes. Benefits of bariatric surgery may be less durable in hyperphagic disorders in comparison with other patients with severe obesity.

Benefits of weight loss of 10% or more in patients with overweight or obesity: A review

OBJECTIVE

Modest weight loss (5%-10%) is clinically meaningful in patients with overweight or obesity. However, greater weight loss may be required to achieve improvements in or remission of certain weight-related complications. Therefore, this study reviewed the effect of large weight loss (≥10%). Most studies reporting large weight loss and relevant outcomes used bariatric surgery or lifestyle modifications.

RESULTS

Benefits of large weight loss were observed in patients with various overweight- or obesity-related complications, including improvements in comorbidities such as type 2 diabetes and hypertension. Improvements in glucose metabolism and cardiovascular risk factors were observed in patients who achieved large weight loss through lifestyle interventions or pharmacotherapy (phentermine/topiramate 15/92 mg once daily or subcutaneous semaglutide 2.4 mg once weekly). Other benefits associated with large weight loss included reduced cancer risk and improvements in knee osteoarthritis, sleep apnea, fertility-related end points, and health-related quality of life. While costly, bariatric surgery is currently the most cost-effective intervention, although most weight-management programs are deemed cost-effective.

CONCLUSIONS

Overall, large weight loss has a major beneficial impact on overweight- and obesity-related complications. Large weight loss should be the main treatment target when modest weight loss has had insufficient effects on obesity-related complications and for patients with severe obesity.

Bardet-Biedl syndrome: Weight patterns and genetics in a rare obesity syndrome

BACKGROUND

Bardet-Biedl syndrome (BBS) is a rare genetic disorder that severely inhibits primary cilia function. BBS is typified by obesity in adulthood, but pediatric weight patterns, and thus optimal periods of intervention, are poorly understood.

OBJECTIVES

To examine body mass differences by age, gender, and genotype in children and adolescents with BBS.

METHODS

We utilized the largest international registry of BBS phenotypes. Anthropometric and genetic data were obtained from medical records or participant/family interviews. Participants were stratified by age and sex categories. Genotype and obesity phenotype were investigated in a subset of participants with available data.

RESULTS

Height and weight measurements were available for 552 unique individuals with BBS. The majority of birth weights were in the normal range, but rates of overweight or obesity rapidly increased in early childhood, exceeding 90% after age 5. Weight z-scores in groups >2 years were above 2.0, while height z-scores approached 1.0, but were close to 0.0 in adolescents. Relative to those with the BBS10 genotype, the BBS1 cohort had a lower BMI z-score in the 2-5 and 6-11 age groups, with similar BMI z-scores thereafter. Children with biallelic loss of function (LOF) genetic variants had significantly higher BMI z-scores compared to missense variants.

CONCLUSION

Despite normal birth weight, most individuals with BBS experience rapid weight gain in early childhood, with high rates of overweight/obesity sustained through adolescence. Children with LOF variants are disproportionally affected. Our findings support the need for earlier recognition and initiation of weight management therapies in BBS.

Effect of setmelanotide, a melanocortin-4 receptor agonist, on obesity in Bardet-Biedl syndrome

AIM

To report an analysis of ~1 year of setmelanotide treatment for obesity and hunger, as well as metabolic and cardiac outcomes, in individuals with Bardet-Biedl syndrome (BBS).

MATERIALS AND METHODS

Individuals aged 12 years and older with BBS received once-daily setmelanotide. The dose was titrated every 2 weeks to establish the individual therapeutic dose (≤3 mg); treatment continued for an additional 10 weeks. Participants who lost 5 kg or more (or ≥5% of body weight if <100 kg at baseline) continued into the 52-week extension phase. The primary outcome was mean percent change from baseline in body weight at 3 months. Hunger scores and safety were secondary outcomes.

RESULTS

From February 2017 and February 2018, 10 individuals were screened; eight completed the 3-month treatment phase and seven completed the extension phase. Mean percent change in body weight from baseline to 3 months was -5.5% (90% CI, -9.3% to -1.6%; n = 8); change from baseline was -11.3% (90% CI, -15.5% to -7.0%; n = 8) at 6 months and -16.3% (90% CI, -19.9% to -12.8%; n = 7) at 12 months. All participants reported at least one treatment-emergent adverse event (AE), most commonly injection-site reaction. No AEs led to study withdrawal or death. Most, morning, and average hunger scores were reduced across time points.

CONCLUSIONS

Setmelanotide reduced body weight and hunger in individuals with BBS and had a safety profile consistent with previous reports. Setmelanotide may be a treatment option in individuals with BBS-associated obesity and hyperphagia.

Bariatric Surgery for Monogenic Non-syndromic and Syndromic Obesity Disorders

PURPOSE OF REVIEW

The global prevalence of obesity has increased rapidly over the last decades, posing a severe threat to human health. Currently, bariatric surgery is the most effective therapy for patients with morbid obesity. It is unknown whether this treatment is also suitable for patients with obesity due to a confirmed genetic defect (genetic obesity disorders). Therefore, this review aims to elucidate the role of bariatric surgery in the treatment of genetic obesity.

RECENT FINDINGS

In monogenic non-syndromic obesity, an underlying genetic defect seems to be the most important factor determining the efficacy of bariatric surgery. In syndromic obesity, bariatric surgery result data are scarce, and even though some promising follow-up results have been reported, caution is required as patients with more severe behavioral and developmental disorders might have poorer outcomes. There is limited evidence in support of bariatric surgery as a treatment option for genetic obesity disorders; hence, no strong statements can be made regarding the efficacy and safety of these procedures for these patients. However, considering that patients with genetic obesity often present with life-threatening obesity-related comorbidities, we believe that bariatric surgery could be considered a last-resort treatment option in selected patients.

Bardet-Biedl Syndrome Caused by Skipping of SCLT1 Complicated by Microvesicular Steatohepatitis

We treated the case of a 22-year-old male patient with liver dysfunction. At 1 year of age, hepatic fibrosis was suspected. In addition, due to the presence of retinitis pigmentosa, renal failure, obesity, mental retardation, and hypogonadism, he was diagnosed with Bardet-Biedl syndrome (BBS). Skipping of exons 14 and 17 in the sodium channel and clathrin linker 1 (SCLT1) gene was observed. At 22 years of age, the liver enzyme levels were further elevated and a diagnosis of microvesicular steatohepatitis was made. Insulin resistance, a reduction of muscle mass, an impairment of the fatty acid metabolism, and hyperleptinemia in this syndrome may cause steatohepatitis.