Hypothalamic Obesity: 4 Years of the International Registry of Hypothalamic Obesity Disorders

Evaluating the effectiveness and underlying mechanisms of incretin-based treatments for hypothalamic obesity: A narrative review

Background

Hypothalamic obesity represents a clinical condition within the broader spectrum of obesity that frequently eludes detection and appropriate diagnosis. This subset of obesity is characterized by a dearth of established predictive markers and a paucity of standardized therapeutic protocols. The advent and rising prominence of glucagon-like peptide-1 (GLP-1) receptor agonists in the obesity treatment landscape present novel therapeutic avenues for hypothalamic obesity management. Nonetheless, critical inquiries persist concerning the efficacy of GLP-1 receptor (GLP-1R) agonists in this context, particularly regarding their central mechanisms of action and specific impact on hypothalamic obesity.

Methods

In this narrative review, we concentrate on analyzing research papers that delineate the detection and function of GLP-1 receptors across various hypothalamic and cerebral regions. Additionally, we examine clinical research papers and reports detailing the application of GLP-1 receptor agonists in treating hypothalamic obesity. Furthermore, we include a concise presentation of a clinical case from our unit for contextual understanding.

Results

Currently, the clinical evidence supporting the efficacy of GLP-1 receptor agonists in hypothalamic obesity, as well as the diverse characteristics of this obesity subtype, remains insufficient. Preliminary data suggest that GLP-1R agonists might offer an effective treatment option, albeit with variable outcomes, particularly in younger patient cohorts. From a mechanistic perspective, the presence of GLP-1 receptors in various hypothalamic and broader brain regions potentially underpins the efficacy of GLP-1R agonists, even in instances of hypothalamic damage. Nevertheless, additional research is imperative to establish the functional relevance of these receptors in said brain regions.

Conclusion

GLP-1R agonists represent a potential therapeutic option for patients with hypothalamic obesity. However, further clinical and basic/translational research is essential to validate the efficacy of these drugs across different presentations of hypothalamic obesity and to understand the functionality of GLP-1R in the diverse brain regions where they are expressed.

Setmelanotide for the treatment of acquired hypothalamic obesity: a phase 2, open-label, multicentre trial

BACKGROUND

Hypothalamic obesity resulting from hypothalamic damage might affect melanocortin signalling. We investigated the melanocortin-4 receptor agonist setmelanotide for treatment of hypothalamic obesity.

METHODS

This phase 2, open-label, multicentre trial was done in five centres in the USA. Eligible patients were aged between 6 and 40 years with obesity and history of hypothalamic injury or diagnosis of a non-malignant tumour affecting the hypothalamus that was treated with surgery, chemotherapy, or radiation. Setmelanotide was titrated up to a dose of 3·0 mg and administered subcutaneously once a day for a total duration of 16 weeks. The primary endpoint was the proportion of patients with a reduction in BMI of at least 5% from baseline after 16 weeks, compared with a historic control rate of less than 5% in this population. The primary endpoint was analysed using the full analysis set, which includes all patients with baseline data who received at least one dose of setmelanotide. Safety was assessed in all patients who received at least one dose of study drug. This trial is registered with ClinicalTrials.gov (NCT04725240) and is complete.

FINDINGS

Between June 6, 2021, and Jan 13, 2022, 19 patients were screened for inclusion. One patient was excluded, and 18 were enrolled and received at least one dose of setmelanotide. Patients were primarily White (n=14 [78%]) and male (n=11 [61%]). Enrolled patients had a mean age of 15·0 years (SD 5·3) and a mean BMI of 38·0 kg/m2 (SD 6·5). Of 18 patients enrolled, 16 (89%) of 18 patients completed the study and met the primary endpoint of reduction in BMI of at least 5% from baseline after 16 weeks (p<0·0001). The mean reduction in BMI across all patients was 15% (SD 10). A composite proportion of patients had a clinically meaningful change (89%, 90% CI 69-98%; p<0·0001), comprising a reduction in BMI Z score of at least 0·2 points for patients younger than 18 years (92%, 68-100%; p<0·0001) and reduction in bodyweight of at least 5% for patients aged 18 years or older (80%, 34-99%; p<0·0001). Patients aged 12 years or older had a mean reduction in hunger score of 45%. Frequent adverse events included nausea (61%), vomiting (33%), skin hyperpigmentation (33%), and diarrhoea (22%). Of 14 patients who continued treatment in a long-term extension study (NCT03651765), 12 completed at least 12 months of treatment at the time of publication and had a mean change in BMI of -26% (SD 12) from index trial baseline.

INTERPRETATION

These findings support setmelanotide as a novel effective treatment of hypothalamic obesity.

FUNDING

Rhythm Pharmaceuticals.

Appetite- and Weight-Regulating Neuroendocrine Circuitry in Hypothalamic Obesity

Since hypothalamic obesity (HyOb) was first described over 120 years ago by Joseph Babinski and Alfred Fröhlich, advances in molecular genetic laboratory techniques have allowed us to elucidate various components of the intricate neurocircuitry governing appetite and weight regulation connecting the hypothalamus, pituitary gland, brainstem, adipose tissue, pancreas, and gastrointestinal tract. On a background of an increasing prevalence of population-level common obesity, the number of survivors of congenital (eg, septo-optic dysplasia, Prader-Willi syndrome) and acquired (eg, central nervous system tumors) hypothalamic disorders is increasing, thanks to earlier diagnosis and management as well as better oncological therapies. Although to date the discovery of several appetite-regulating peptides has led to the development of a range of targeted molecular therapies for monogenic obesity syndromes, outside of these disorders these discoveries have not translated into the development of efficacious treatments for other forms of HyOb. This review aims to summarize our current understanding of the neuroendocrine physiology of appetite and weight regulation, and explore our current understanding of the pathophysiology of HyOb.

Acquired hypothalamic obesity: A clinical overview and update

Hypothalamic obesity (HO) is a rare and complex disorder that confers substantial morbidity and excess mortality. HO is a unique subtype of obesity characterized by impairment in the key brain pathways that regulate energy intake and expenditure, autonomic nervous system function, and peripheral hormonal signalling. HO often occurs in the context of hypothalamic syndrome, a constellation of symptoms that follow from disruption of hypothalamic functions, for example, temperature regulation, sleep-wake circadian control, and energy balance. Genetic forms of HO, including the monogenic obesity syndromes, often impact central leptin-melanocortin pathways. Acquired forms of HO occur as a result of tumours impacting the hypothalamus, such as craniopharyngioma, surgery or radiation to treat those tumours, or other forms of hypothalamic damage, such as brain injury impacting the region. Risk for severe obesity following hypothalamic injury is increased with larger extent of hypothalamic damage or lesions that contain the medial and posterior hypothalamic nuclei that support melanocortin signalling pathways. Structural damage in these hypothalamic nuclei often leads to hyperphagia, central insulin and leptin resistance, decreased sympathetic activity, low energy expenditure, and increased energy storage in adipose tissue, the collective effect of which is rapid weight gain. Individuals with hyperphagia are perpetually hungry. They do not experience fullness at the end of a meal, nor do they feel satiated after meals, leading them to consume larger and more frequent meals. To date, most efforts to treat HO have been disappointing and met with limited, if any, long-term success. However, new treatments based on the distinct pathophysiology of disturbed energy homeostasis in acquired HO may hold promise for the future.

Caregiver Burden and Its Relationship to Health-Related Quality of Life in Craniopharyngioma Survivors

CONTEXT

Craniopharyngioma (CP) is a rare brain tumor associated with severe comorbidities that reduce survivor health-related quality of life (HRQOL). However, CP impact on caregivers is unknown.

OBJECTIVE

To measure caregiver burden and examine its relationship to survivor HRQOL and other determinants in CP.

METHODS

Eighty-two participants who self-identified as caregivers of CP survivors responded to an online survey including caregiver-reported Pediatric Quality of Life Inventory (PedsQL), and the Zarit Burden Interview (ZBI).

RESULTS

Caregivers reported an average of 13 out of 29 health conditions in survivors following tumor treatment, including excess weight, hypopituitarism, fatigue, mood, cognition, social issues, temperature dysregulation, visual impairment, and sleep problems. Strikingly, 70% of survivors who experienced obesity also experienced hyperphagia. ZBI scores were moderate with a median of 37. PedsQL total scores were poor with a median of 46.2. ZBI scores were independent of caregiver level of education and care duration. Both scores were independent of income, survivor age, gender, age at diagnosis, or tumor recurrence. In contrast, both scores depended on the number (P < .001) and the type of survivor health problems, with significantly worse scores for caregivers or survivors with symptoms of hypothalamic dysfunction (P < .001) including hyperphagia but not obesity. PedsQL total scores significantly predicted ZBI scores (P < .001).

CONCLUSION

Survivor poly-symptomatology predicted and incurred significant caregiver burden. Our study separated hyperphagia and obesity and identified hyperphagia and other hypothalamic dysfunction symptoms as understudied issues. Altogether, these findings draw particular attention to the unmet needs of CP survivors and their caregivers.

Treatment of hypothalamic obesity in people with hypothalamic injury: new drugs are on the horizon

Hypothalamic obesity (HO) is a complex and rare disorder affecting multiple regulatory pathways of energy intake and expenditure in the brain as well as the regulation of the autonomic nervous system and peripheral hormonal signaling. It can be related to monogenic obesity syndromes which often affect the central leptin-melanocortin pathways or due to injury of the hypothalamus from pituitary and hypothalamic tumors, such as craniopharyngioma, surgery, trauma, or radiation to the hypothalamus. Traditional treatments of obesity, such as lifestyle intervention and specific diets, are still a therapeutic cornerstone, but often fail to result in meaningful and sustained reduction of body mass index. This review will give an update on pharmacotherapies of HO related to hypothalamic injury. Recent obesity drug developments are promising for successful obesity intervention outcomes.

Hypothalamic integrity is necessary for sustained weight loss after bariatric surgery: A prospective, cross-sectional study

OBJECTIVE

The hypothalamus is the main integrator of peripheral and central signals in the control of energy homeostasis. Its functional relevance for the effectivity of bariatric surgery is not entirely elucidated. Studying the effects of bariatric surgery in patients with hypothalamic damage might provide insight.

SUMMARY BACKGROUND DATA

Prospective study to analyze the effects of bariatric surgery in patients with hypothalamic obesity (HO) vs. matched patients with common obesity (CO) with and without bariatric surgery.

METHODS

65 participants were included (HO-surgery: n = 8, HO-control: n = 10, CO-surgery: n = 12, CO-control: n = 12, Lean-control: n = 23). Body weight, levels of anorexic hormones, gut microbiota, as well as subjective well-being/health status, eating behavior, and brain activity (via functional MRI) were evaluated.

RESULTS

Patients with HO lost significantly less weight after bariatric surgery than CO-participants (total body weight loss %: 5.5 % vs. 26.2 %, p = 0.0004). After a mixed meal, satiety and abdominal fullness tended to be lowest in HO-surgery and did not correlate with levels of GLP-1 or PYY. Levels of PYY (11,151 ± 1667 pmol/l/h vs. 8099 ± 1235 pmol/l/h, p = 0.028) and GLP-1 (20,975 ± 2893 pmol/l/h vs. 13,060 ± 2357 pmol/l/h, p = 0.009) were significantly higher in the HO-surgery vs. CO-surgery group. Abundance of Enterobacteriaceae and Streptococcus was increased in feces of HO and CO after bariatric surgery. Comparing HO patients with lean-controls revealed an increased activation in insula and cerebellum to viewing high-caloric foods in left insula and cerebellum in fMRI.

CONCLUSIONS

Hypothalamic integrity is necessary for the effectiveness of bariatric surgery in humans. Peripheral changes after bariatric surgery are not sufficient to induce satiety and long-term weight loss in patients with hypothalamic damage.

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.

A Survey of Patient-Relevant Outcomes in Pediatric Craniopharyngioma: Focus on Hypothalamic Obesity

CONTEXT

Individuals treated for pediatric craniopharyngioma, a rare, grade 1 brain tumor, frequently develop hypothalamic obesity, a complication often recalcitrant to intervention. Although hypothalamic obesity is known to adversely impact quality of life, less is known about how caregivers and patients experience this condition.

OBJECTIVE

Our goal was to examine the approaches that families take towards weight management and the impact on social function in individuals with craniopharyngioma and obesity. Individuals with craniopharyngioma without obesity were included as a comparison.

SUBJECTS AND METHODS

Adult caregivers of children <18y with craniopharyngioma completed a web-based survey posted by a patient advocacy organization between February and July 2020. Questions related to the child's diagnosis, medications, lifestyle modifications, and social function along with research priorities. Descriptive statistics were generated. Linear regression was used to assess the independent effects of obesity and other covariates on social function.

RESULTS

Of 106 respondents, 60 (57%) reported their child had obesity at the time of survey completion. In contrast, only 6 (5.7%) had obesity prior to craniopharyngioma diagnosis. A majority (92%) of those with obesity had tried limiting calories or carbohydrates; 31% and 69% found these helpful, respectively. Thirty-eight percent had tried weight loss medications (stimulants, metformin, GLP1R-agonists, and topiramate) and 48% found at least one helpful. Both stimulant and anti-depressant use were reported more frequently with obesity. An index (T-score) reflecting social function was lower in the cohort than a population reference, 41 (SD 11) vs. 50 (SD 10), p<0.001. In a linear model, both older age and obesity were independently associated with greater social impairment. Ninety-four percent of respondents caring for a child with obesity (and 79% of all respondents) identified "improving treatments and prevention for hypothalamic obesity" as a key research priority.

CONCLUSIONS

Only a minority of individuals with hypothalamic obesity had trialed medication, even though many reported that lifestyle modification was inadequate. Furthermore, social function was significantly impaired overall in survivors compared to a reference cohort, and even more so in individuals with obesity. These findings highlight the opportunity to improve social functioning as an additional potential benefit of improved treatments for hypothalamic obesity.

The Effects of Oxytocin on Appetite Regulation, Food Intake and Metabolism in Humans

The hypothalamic peptide oxytocin and its receptor are involved in a range of physiological processes, including parturition, lactation, cell growth, wound healing, and social behavior. More recently, increasing evidence has established the effects of oxytocin on food intake, energy expenditure, and peripheral metabolism. In this review, we provide a comprehensive description of the central oxytocinergic system in which oxytocin acts to shape eating behavior and metabolism. Next, we discuss the peripheral beneficial effects oxytocin exerts on key metabolic organs, including suppression of visceral adipose tissue inflammation, skeletal muscle regeneration, and bone tissue mineralization. A brief summary of oxytocin actions learned from animal models is presented, showing that weight loss induced by chronic oxytocin treatment is related not only to its anorexigenic effects, but also to the resulting increase in energy expenditure and lipolysis. Following an in-depth discussion on the technical challenges related to endogenous oxytocin measurements in humans, we synthesize data related to the association between endogenous oxytocin levels, weight status, metabolic syndrome, and bone health. We then review clinical trials showing that in humans, acute oxytocin administration reduces food intake, attenuates fMRI activation of food motivation brain areas, and increases activation of self-control brain regions. Further strengthening the role of oxytocin in appetite regulation, we review conditions of hypothalamic insult and certain genetic pathologies associated with oxytocin depletion that present with hyperphagia, extreme weight gain, and poor metabolic profile. Intranasal oxytocin is currently being evaluated in human clinical trials to learn whether oxytocin-based therapeutics can be used to treat obesity and its associated sequela. At the end of this review, we address the fundamental challenges that remain in translating this line of research to clinical care.

Cephalocaudal tumor diameter is a predictor of diabetes insipidus after endoscopic transsphenoidal surgery for non-functioning pituitary adenoma

PURPOSE

Diabetes insipidus (DI) develops commonly after endoscopic transsphenoidal surgery (ETS). We retrospectively investigated the incidence, onset, duration and predictors of DI after ETS in patients with non-functioning pituitary adenoma (NFPA).

METHODS

A total of 168 patients who underwent ETS to remove NFPAs were included. Various perioperative data on demographics, comorbidities, previous treatments, perioperative hormone deficiencies, tumor characteristics, surgery, anesthesia, intraoperative fluid balance, perioperative laboratory findings, postoperative complications, readmission and hospital length of stay were collected and analyzed. Patients were diagnosed with DI and treated with desmopressin when they showed urine output > 5 mL/kg/hr with a serum sodium concentration > 145 mmol/L or an increase ≥ 3 mmol/L in serum sodium concentration between two consecutive tests after surgery. DI was considered permanent when desmopressin was prescribed for > 6 months after surgery.

RESULTS

Seventy-seven (45.8%) patients experienced postoperative DI and 10 (6.0%) patients suffered from permanent DI. The median onset of DI and the median duration of transient DI were postoperative day 1 and 5 days, respectively. In multivariable logistic regression analysis, cephalocaudal tumor diameter (odds ratio [95% confidence interval] 2.59 [1.05-6.36], P = 0.038) was related to postoperative DI. In receiver operating characteristic analysis, its area under the curve was 0.68 (95% confidence interval 0.59-0.76, P < 0.001). Its optimal cutoff value that maximized the sum of sensitivity and specificity for postoperative DI was 2.7 cm.

CONCLUSIONS

Postoperative DI was observed in 45.8% of patients undergoing ETS to remove NFPAs. A large cephalocaudal tumor diameter was predictive of postoperative DI in such patients.

Methylphenidate improves weight control in childhood brain tumor survivors with hypothalamic obesity

BACKGROUND

Hypothalamic obesity causes unrelenting weight gain for childhood brain tumor survivors. No single therapy has proven effective for treatment. We aimed to evaluate effectiveness of long-term methylphenidate therapy on body mass index (BMI) change in children with hypothalamic obesity.

METHODS

A retrospective analysis included children with a history of brain tumor and hypothalamic obesity receiving methylphenidate (10-60 mg/day) for hypothalamic obesity. Subjects were evaluated for BMI trajectory before and after methylphenidate start. Given that z-scores can be skewed in severely obese children, we calculated BMI as a percent of the BMI at the 95th percentile for the child's age and gender (BMI% 95th).

RESULTS

Twelve patients with hypothalamic obesity completed methylphenidate therapy for at least 6 months (median 3.1 years, range 1.0-5.8 years). All subjects had a suprasellar tumor (nine [75%] with craniopharyngioma) and pituitary dysfunction. Pretreatment median BMI percent of the 95th percentile was 125.6% (interquartile range [IQR] 25-75: 115.3-138.3%) with BMI z-score of 2.4 (IQR 25-75: 2.1-2.6). Following methylphenidate treatment, there was a 69.9% reduction in the median slope of BMI change. Eleven of 12 patients (92%) had a reduction in the slope of their BMI change on methylphenidate treatment. Postmethylphenidate median BMI percent of the 95th percentile decrease to 115.2% (IQR 25-75: 103.6-121.2%) with median BMI z-score of 2.1 (IQR 25-75: 1.8-2.2). Mild side effects were noted in six patients.

CONCLUSIONS

Methylphenidate use reduced and sustained BMI change in children with hypothalamic obesity. Stimulant therapy is an effective first-line agent for treatment of hypothalamic obesity.

Laparoscopic Sleeve Gastrectomy on Severe Obesity after Intracranial Germinoma Treatment: A Case Report

Hypothalamic obesity is a clinical syndrome characterized by severe and refractory obesity that is caused by hypothalamic function impairment. Recently, bariatric surgery has been attempted for patients with hypothalamic obesity after craniopharyngioma, but experiences have not yet been accumulated in other hypothalamic disorders. Here, we report the case of a 39-year-old male patient with panhypopituitarism who received laparoscopic sleeve gastrectomy (LSG) after intracranial germinoma treatment. The patient was diagnosed with intracranial germinoma at age 15 and achieved complete remission after radiotherapy (total 50 Gy). He was obese during diagnosis [body mass index (BMI), 29.2 kg/m²], and his obesity gradually worsened after the intracranial germinoma treatment, and LSG was considered when his BMI was 48.6 kg/m². After 1 month of hospitalized diet-exercise program, LSG was performed. After LSG, his BMI gradually decreased and reached 38.8 kg/m² on the day of discharge (6 weeks after the surgery). Five months after LSG, his insulin resistance improved, but insulin hypersecretion remained. Fifteen months after the surgery, his BMI was 31.2 kg/m², with marked decrease in visceral and subcutaneous fat areas (from 393.8 cm² and 168.2 cm² before the surgery to 111.5 cm² and 56.3 cm², respectively.). To our knowledge, this is the first case of LSG for hypothalamic obesity after intracranial germinoma treatment. Although the pathophysiology of hypothalamic obesity is different from that of primary obesity, LSG could be a successful therapeutic choice for patients with hypothalamic obesity after the intracranial germinoma treatment.