Serum leptin and leptin binding activity in children and adolescents with hypothalamic dysfunction

The clinical significance of inflammatory mediators in predicting obesity and progression-free survival in patients with adult-onset Craniopharyngioma

BACKGROUND

Craniopharyngioma (CP) is a rare malformational tumor characterized by high rates of recurrence and morbid obesity. However, the role of inflammatory mediators in obesity and the prognosis of patients with CP remains unknown. Therefore, the present study aimed to analyze associations of inflammatory mediators with weight-related outcomes and the prognosis of patients with CP.

METHODS

A total of 130 consecutive patients with CP were included in this study. The expression levels of seven inflammatory mediators and the plasma leptin concentration were investigated. Clinical parameters, weight changes, new-onset obesity, and progression-free survival (PFS) were recorded. The relationships between inflammatory mediators, clinicopathologic parameters, weight-related outcomes, and PFS were explored.

RESULTS

Compared with those in normal pituitary tissue, the expressions of inflammatory mediators in tumor tissue were higher. Higher expression levels of CXCL1 and CXCL8 were identified as independent risk factors for significant weight gain, and CXCL1 and TNF were identified as independent risk factors for new-onset postoperative obesity. Poor PFS was associated with higher expression levels of CXCL1, CXCL8, IL1A, IL6, and TNF.

CONCLUSION

The present study revealed that inflammatory mediators are associated with morbid obesity in patients with CP. Inflammatory mediators may be the critical bridge between elevated leptin and weight-related outcomes. Additionally, PFS was associated with the expression of inflammatory mediators. Further research is needed to elucidate the underlying mechanisms of inflammatory mediators and their potential as targets for novel therapies for CP.

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.

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.

Clinical Significance of Plasma Leptin and Its Receptors mRNA Expression in Craniopharyngiomas: A Prospective Study

Craniopharyngioma (CP) is a benign tumor with a high rate of obesity and frequent recurrence. Moreover, the role of leptin/leptin receptors axis in obesity and the prognosis of CP is still unknown. Plasma leptin concentration and mRNA expression of leptin receptors were assessed in patients with CP. Moreover, the association between leptin/leptin receptors axis, weight-related outcomes, and progression-free survival (PFS) were explored in CP patients. Leptin receptors overexpressed in CP tumor tissue were compared to normal brain tissue (p < 0.05); compared to healthy controls, the concentration of leptin was elevated in CP with or without matched age, sex, and body mass index (BMI) (p < 0.05). The high plasma leptin level was an independent risk predictor for significant weight gain (adjusted odds ratio (aOR) = 2.29, and p = 0.030) and new-onset obesity (aOR = 6.64, and p = 0.016). High plasma leptin level (adjusted hazard ratio (aHR) = 3.74, and p = 0.011) and leptin receptor (LEPR) mRNA expression (aHR = 3.12, and p = 0.045) were independent risk factors for poor PFS in CP. Inappropriately elevated leptin relative to BMI and its failure to inhibit further weight gain indicate the existence of leptin resistance in patients with CP. Leptin and LEPR were independent predictors for PFS of patients with CP. The leptin/leptin receptors axis may be a potential therapeutic target for obesity in patients with CP.

Leptin Elevation as a Risk Factor for Slipped Capital Femoral Epiphysis Independent of Obesity Status

BACKGROUND

Slipped capital femoral epiphysis (SCFE) is strongly associated with childhood obesity, yet the prevalence of obesity is orders of magnitude greater than the prevalence of SCFE. Therefore, it is hypothesized that obesity is not, by itself, a sufficient condition for SCFE, but rather one component of a multifactorial process requiring preexisting physeal pathology. Leptin elevation is seen to varying degrees in patients with obesity, and as leptin has been shown to cause physeal pathology similar to the changes seen in SCFE, we propose that leptin may be a factor distinguishing between patients with SCFE and equally obese children without hip abnormalities.

METHODS

Serum leptin levels were obtained from 40 patients with SCFE and 30 control patients with approximate body mass index (BMI) matching. BMI percentiles were calculated according to Centers for Disease Control and Prevention population data by patient age and sex. Patients were compared by demographic characteristics, leptin levels, odds of leptin elevation, and odds of SCFE.

RESULTS

The odds of developing SCFE was increased by an odds ratio of 4.9 (95% confidence interval [CI], 1.31 to 18.48; p < 0.02) in patients with elevated leptin levels, regardless of obesity status, sex, and race. When grouping patients by their obesity status, non-obese patients with SCFE showed elevated median leptin levels at 5.8 ng/mL compared with non-obese controls at 1.7 ng/mL (p = 0.006). Similarly, obese patients with SCFE showed elevated median leptin levels at 17.9 ng/mL compared with equally obese controls at 10.5 ng/mL (p = 0.039). Serum leptin levels increased in association with obesity (p < 0.001), with an increase in leptin of 0.17 ng/mL (95% CI, 0.07 to 0.27 ng/mL) per BMI percentile point.

CONCLUSIONS

To our knowledge, this study is the first to clinically demonstrate an association between elevated serum leptin levels and SCFE, regardless of BMI. This adds to existing literature suggesting that SCFE is a multifactorial process and that leptin levels may have profound physiological effects on the development of various disease states. Despite a strong association with adiposity, leptin levels vary between patients of equal BMI and may be a vital resource in prognostication of future obesity-related comorbidities.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Hypothalamic Obesity in Craniopharyngioma Patients: Disturbed Energy Homeostasis Related to Extent of Hypothalamic Damage and Its Implication for Obesity Intervention

Hypothalamic obesity (HO) occurs in patients with tumors and lesions in the medial hypothalamic region. Hypothalamic dysfunction can lead to hyperinsulinemia and leptin resistance. This review is focused on HO caused by craniopharyngiomas (CP), which are the most common childhood brain tumors of nonglial origin. Despite excellent overall survival rates, CP patients have substantially reduced quality of life because of significant long-term sequelae, notably severe obesity in about 50% of patients, leading to a high rate of cardiovascular mortality. Recent studies reported that both hyperphagia and decreased energy expenditure can contribute to severe obesity in HO patients. Recognized risk factors for severe obesity include large hypothalamic tumors or lesions affecting several medial and posterior hypothalamic nuclei that impact satiety signaling pathways. Structural damage in these nuclei often lead to hyperphagia, rapid weight gain, central insulin and leptin resistance, decreased sympathetic activity, low energy expenditure, and increased energy storage in adipose tissue. To date, most efforts to treat HO have shown disappointing long-term success rates. However, treatments based on the distinct pathophysiology of disturbed energy homeostasis related to CP may offer options for successful interventions in the future.

Elevated leptin expression in rat model of traumatic spinal cord injury and femoral fracture

BACKGROUND

Few studies have reported a relationship between leptin induced by spinal cord injury (SCI) and healing bone tissue.

OBJECTIVE

To observe serum and callus leptin expression within the setting of fracture and traumatic SCI.

METHODS

Seventy-two male Sprague Dawley rats were randomized equally into four groups: control, SCI group, fracture group, and fracture/SCI group. Rats were sacrificed at 7, 14, 21, and 28 days post-fracture/SCI. Serum leptin was detected using radioimmunoassay at 1, 7, 14, 21, and 28 days, and callus formation was measured radiologically at 14, 21, and 28 days. Callus leptin was analyzed by means of immunohistochemistry.

RESULTS

Serum leptin in the fracture group, SCI group, and combined fracture/SCI group were all significantly increased compared to control group at the 1, 7, 14, and 2-day time points (P < 0.05). Serum leptin in the combined fracture/SCI group was significantly higher than in the fracture group at 7, 14, and 21 days (P < 0.05), and higher than in SCI groups at 14 and 21days after operation (P < 0.05). The percentage of leptin-positive cells in the fracture/SCI callus, and callus volume was significantly higher than in the fracture-only group (P < 0.001).

CONCLUSIONS

Overall, elevated leptin expression was demonstrated within healing bone especially in the 21 days of a rat model combining fracture and SCI. A close association exists between leptin levels and the degree of callus formation in fractures.

Elevated leptin expression in a rat model of fracture and traumatic brain injury

A few studies have reported a relationship between leptin induced by brain injury and healing of bone tissue. Our objective was to measure serum and callus leptin expression within the setting of fracture and traumatic brain injury (TBI). Sixty-four male Sprague-Dawley rats were randomised equally into four groups: control, TBI group, fracture group and fracture/TBI group. Rats were sacrificed at 2, 4, 8 and 12 weeks after fracture/TBI. Serum leptin was detected using radio-immunoassay, and callus formation was measured radiologically. Callus leptin was analysed with immunohistochemistry. Serum leptin was significantly increased in the fracture, TBI and combined fracture/TBI groups compared with the control group at 2 weeks (P &lt; 0.05). Serum leptin was significantly higher in the combined fracture/TBI group than in the fracture and TBI groups at 4 and 8 weeks (P &lt; 0.05). The percentage of leptin-positive cells in the callus and callus volume were significantly higher in the fracture/TBI group than in the fracture-only group (P &lt; 0.001). Thus, we demonstrated elevated leptin expression within healing bone, particularly in the first 8 weeks of a rat model combining fracture and TBI. A close association exists between leptin levels and the degree of callus formation in fractures.

The role of leptin, soluble leptin receptor, resistin, and insulin secretory dynamics in the pathogenesis of hypothalamic obesity in children

INTRODUCTION

In this study, we have investigated the role of leptin, soluble leptin receptor(sOb-R), resistin, and insulin secretory dynamics in the development of hypothalamic obesity.

MATERIALS AND METHODS

Children who had hypothalamo-pituitary tumor were divided into two groups. First group included obese-overweight (hypothalamic obese = HOB group, n = 23) and second group included non-obese children (hypothalamic non-obese = HNOB group, n = 16). Exogenously obese-overweight children (OB group, n = 22) were included as controls. Basal and second-hour serum glucose and insulin in oral glucose tolerance test (OGTT), basal serum leptin, sOb-R, resistin levels, and homeostasis model assessment (HOMA) indexes were compared between the groups.

RESULTS

Age, sex, and pubertal status were similar in study groups. Median and interquartile ranges of body mass index (BMI) z scores were similar in HOB and OB groups (2.0 (1.5-2.1) and 2.1 (1.8-2.3), respectively). Serum leptin levels corrected for BMI were highest and total leptin/sOb-R ratios (free leptin index (FLI)) tended to be higher in HOB than HNOB and OB groups, indicating leptin resistance (leptin/BMI, 4.0 (1.6-5.2), 1.5 (0.8-3.1), and 2.5 (1.8-3.5); FLI, 2.0 (0.8-3.5), 0.6 (0.3-1.2), and 1.5 (1-2.3) in HOB, HNOB, and OB groups; respectively). Serum resistin levels were similar in groups (2.6 (1.9-3.1), 2.8 (1.7-3.4), and 3.0 (2.2-3.5) ng/ml in HOB, HNOB, and OB groups, respectively). Basal serum glucose, basal and second-hour insulin levels in OGTT, and HOMA index were higher in OB group than the HOB and HNOB groups, indicating insulin resistance in simple obesity; however, increment of insulin to same glycemic load in OGTT was highest in the HOB group indicating insulin dysregulation (p < 0.05).

CONCLUSION

Hypothalamic obesity seems to be related to both dysregulated afferent (leptin) and efferent (insulin) neural outputs through the autonomic nervous system resulting in energy storage as fat.

Free and total leptin serum levels and soluble leptin receptors levels in two models of genetic obesity: the Prader-Willi and the Down syndromes

Alterations in energy balance and feeding behavior and the subsequent high frequency of obesity are hallmarks of 2 chromosomal diseases: the Prader-Willi syndrome (PWS) and the Down syndrome (DS). Leptin, an important regulator of food intake and energy homeostasis, circulates in 2 forms: a free, therefore active, fraction and a fraction bound to the soluble leptin receptor, whose bioavailability consequently participates in the regulation of leptin action. To investigate the possible role of the free-bound leptin balance in the pathogenesis of obesity in PWS and DS, we enrolled 7 obese women with DS, 5 obese women with PWS, 7 obese women, and 7 normal-weight healthy control women. Basal hormonal concentrations, total and free leptin levels, and leptin receptors levels were measured in plasma samples obtained from the 4 groups. No significant differences were observed in the hormonal milieu. Women with DS exhibited lower total leptin concentrations (P<.01), comparable leptin receptor level and, therefore, lower free leptin values (P<.01) when compared with obese controls, then resembling the profile peculiar to normal-weight control women. At variance, subjects with PWS did not differ from obese controls regarding both leptin and leptin receptor levels. Our data suggest that, whereas subjects with PWS have a leptin assessment corresponding to their degree of obesity, subjects with DS may have a defect in the secretion of leptin that could at least partially account for this form of syndromal obesity.

Physical activity energy expenditure may mediate the relationship between plasma leptin levels and worsening insulin resistance independently of adiposity

Leptin regulates a constellation of neuroendocrine processes that control energy homeostasis. The infusion of leptin in rodents lacking endogenous leptin promotes physical activity energy expenditure (PAEE) and improves insulin signaling, whereas hyperleptinemia is associated with physical inactivity and insulin resistance (IR). We tested whether baseline leptin levels predict changes in PAEE and IR over time, independent of obesity. We also assessed whether the relationship between leptin and change in IR is mediated by PAEE. The population consisted of 288 nondiabetic UK Caucasian adults (mean age: 49.4 yr; SD: 0.7 yr), in whom leptin, insulin, glucose, PAEE (via heart rate monitoring with individual calibration by indirect calorimetry), and anthropometric characteristics had been measured at baseline and 5 yr later. In linear regression models, baseline leptin levels inversely predicted follow-up PAEE ( P = 0.033). On average, individuals with low leptin levels (below sex-specific median) increased their daily activity 35% more during the 5-yr follow-up period than those with above-median leptin levels. Baseline leptin level also predicted worsening IR (fasting, 30-min, and 2-h insulins, and homeostasis model assessment-IR; all P < 0.01). Associations were independent of potential confounders, such as adiposity, age, and sex. Including baseline PAEE as a cofactor in the leptin-insulin models reduced the strength (1–4% reduction) and significance of the associations, suggesting that PAEE mediates the leptin-insulin relationships. Hyperleptinemia predicts a relative decline in PAEE and worsening insulin resistance, possibly via shared molecular pathways.

Study of serum factors potentially involved in the pathogenesis of heterotopic bone formation after severe brain injury

OBJECTIVE

To look for serum factors detectable early after head injury and predictive of heterotopic bone formation.

PATIENTS AND METHODS

In this prospective study of a homogeneous population of 31 men with severe brain injury, blood samples were obtained 3 months after the accident, and levels of serum factors influenced by bone metabolism were compared between patients with and without heterotopic bone formation. As extensive fractures can influence serum factors, the patients without heterotopic bone formation were divided into two groups based on whether they had major fractures. Radionuclide bone scanning was used to validate patient classification.

RESULTS

The group with heterotopic bone formation had significantly higher serum alkaline phosphatase levels (P < 0.01) and significantly lower serum leptin levels (P < 0.01), as compared to the other two groups. Body mass index and serum creatinine were comparable in the three groups.

CONCLUSION

Leptin may be associated with the development of heterotopic bone formation. The antiosteogenic effect of leptin mediated by hypothalamic neurons may be impaired by hypothalamic damage related to severe brain injury.