Microanalysis of eating behavior of three leptin deficient adults treated with leptin therapy

The leptin gene's polymorphism and how it relates to the Awassi sheep's physical characteristics

The study was conducted at the sheep and goat research station, at Al-Shatrah District, Thi-Qar Agriculture Directorate, Thi-Qar Governorate, from 1/11/2021 to 30/6/2022 for one production season. A total of 100 animals were used, consisting of 50 parents and 50 lambs, males and females; the ages of the ewes ranged from 3 to 5 years old. The sheep data used in the experiment were collected from the station records. The genetic part was also completed in the Marshes Research Laboratory at the University of Thi-Qar. The study aimed at the genetic polymorphism of the leptin gene and its relationship to the body dimensions of the Awassi sheep. The nitrogenous base sequence analysis of the leptin gene indicated a size of 260 base pairs, with a change in location 119 in the studied area. The homozygous CC genotype was more significant than the number of animals; the frequency of the C and T alleles was 0.65 and 0.35, respectively. There was no significant effect between the three genetic polymorphisms resulting from the mutation at site 119 of the studied plot on the body dimensions of the newborns as well as at weaning. Keywords: Polymorphism, leptin gene, body dimensions, Awassi sheep.

Eating behaviour in contrasting adiposity phenotypes: Monogenic obesity and congenital generalized lipodystrophy

Most known types of nonsyndromic monogenic obesity are caused by rare mutations in genes of the leptin-melanocortin pathway controlling appetite and adiposity. In contrast, congenital generalized lipodystrophy represents the most extreme form of leanness in humans caused by recessive mutations in four genes involved in phospholipid/triglyceride synthesis and lipid droplet/caveolae structure. In this disease, the inability to store triglyceride in adipocytes results in hypoleptinemia and ectopic hepatic and muscle fat accumulation leading to fatty liver, hypertriglyceridemia and severe insulin resistance. As a result of hypoleptinemia, patients with lipodystrophy show alterations in eating behaviour characterized by constant increased energy intake. As it occurs in obesity caused by genetic leptin deficiency, exogenous leptin rapidly reduces hunger scores in patients with congenital generalized lipodystrophy, with additional beneficial effects on glucose homeostasis and metabolic profile normalization. The melanocortin-4 receptor agonist setmelanotide has been used in the treatment of monogenic obesities. There is only one report on the effect of setmelanotide in a patient with partial lipodystrophy resulting in mild reductions in hunger scores, with no improvements in metabolic status. The assessment of contrasting phenotypes of obesity/leanness represents an adequate strategy to understand the pathophysiology and altered eating behaviour associated with adipose tissue excessive accumulation/paucity.

Beneficial effects of leptin substitution on impaired eating behavior in lipodystrophy are sustained beyond 150 weeks of treatment

AIM

Metreleptin treatment in lipodystrophy patients improves eating behavior with increased satiety and reduced hunger. However, no data are available whether effects are maintained beyond 52 weeks of treatment.

METHODS

A prospective study with measurements at baseline and at >150 weeks of metreleptin treatment was performed. Five female lipodystrophy patients with indication for metreleptin were included. Behavioral aspects of hunger- and satiety regulation were assessed by validated eating behavior questionnaires and visual analog scales assessing hunger and satiety feelings before and after a standardized meal.

RESULTS

Hunger rated on visual analog scales at 120 min after the meal significantly decreased from 46 ± 10 mm at baseline to 17 ± 6 mm at long-term assessment. Furthermore, satiety at 5 and 120 min after the meal significantly increased from baseline to long-term assessment (5 min: 70 ± 7 mm to 87 ± 3 mm; 120 min: 43 ± 10 mm to 79 ± 8 mm). On the Three Factor Eating Questionnaire, the mean value of factor 3 (hunger) significantly decreased from 9.2 ± 0.2 at baseline to 2.6 ± 1.5 at long-term assessment. In the Inventory of Eating Behavior and Weight Problems Questionnaire, mean values for scale 2 (strength and triggering of desire to eat) and scale 7 (cognitive restraint of eating) significantly decreased from baseline (31.6 ± 4.8 and 11.4 ± 2.2, respectively) to long-term assessment (14.0 ± 2.1 and 10.0 ± 1.9).

CONCLUSION

First evidence is presented that long-term metreleptin treatment of >150 weeks has sustained effects on eating behavior with increased satiety, as well as reduced hunger and hunger-related measures.

Centrally Acting Agents for Obesity: Past, Present, and Future

For many years, obesity was believed to be a condition of overeating that could be resolved through counseling and short-term drug treatment. Obesity was not recognized as a chronic disease until 1985 by the scientific community, and 2013 by the medical community. Pharmacotherapy for obesity has advanced remarkably since the first class of drugs, amphetamines, were approved for short-term use. Most amphetamines were removed from the obesity market due to adverse events and potential for addiction, and it became apparent that obesity pharmacotherapies were needed that could safely be administered over the long term. This review of central nervous system (CNS) acting anti-obesity drugs evaluates current therapies such as phentermine/topiramate, which act through multiple neurotransmitter pathways to reduce appetite. In the synergistic mechanism of bupropion/naltrexone, naltrexone blocks the feed-back inhibitory circuit of bupropion to give greater weight loss. Lorcaserin, a selective agonist of a serotonin receptor that regulates food intake, and the glucagon-like-peptide-1 (GLP-1) receptor agonist liraglutide are reviewed. Future drugs include tesofensine, a potent triple reuptake inhibitor in Phase III trials for obesity, and semaglutide, an oral GLP-1 analog approved for diabetes and currently in trials for obesity. Another potential new pharmacotherapy, setmelanotide, is a melanocortin-4 receptor agonist, which is still in an early stage of development. As our understanding of the communication between the CNS, gut, adipose tissue, and other organs evolves, it is anticipated that obesity drug development will move toward new centrally acting combinations and then to drugs acting on peripheral target tissues.

Impact of short-term refeeding on appetite and meal experiences in new onset adolescent eating disorders

Restrictive eating disorders (ED) are increasing and represent a serious risk to the health of adolescent females. Restrictive ED in youth are often treated through aggressive short-term refeeding. Although evidence supports that this intervention is the "gold standard" for improving ED outcomes in youth, little research has specifically probed appetite and meal-related responses to this type of intensive, short-term refeeding in newly diagnosed individuals. Information about appetite and meal-related dysfunction could provide valuable insights regarding treatment-interfering features of ED in both acute inpatient and longer-term outpatient treatment. The purpose of this study was to evaluate the hunger, fullness, olfactory, and gustatory responses of adolescents with newly-diagnosed restrictive ED and to probe how and when these responses are altered by refeeding. Using a quasi-experimental ecologically valid methodology, this study described and compared profiles of hunger, fullness, olfactory, and gustatory responses in adolescent females (n = 15) with newly diagnosed restrictive ED at hospital admission (i.e., severe malnutrition) and after medical refeeding, in comparison to healthy controls (n = 15). Results showed that newly diagnosed (i.e., malnourished) adolescents with ED showed significantly different meal-related experiences than controls. Refeeding improved some of these differences, but not all. Following refeeding, females with ED continued to show lower hunger, greater fullness, and lower pleasantness of smell ratings compared to controls. Unpleasantness of taste ratings maladaptively increased, such that females who were re-fed reported more aversive scents than pre-treatment. Profiles of meal-related responses were also identified and compared between groups. The applicability of these findings are discussed within the context of critical periods of change during refeeding treatment and potentially promising intervention targets that might enhance treatment outcomes for adolescents with newly onset, restrictive ED.

Leptin signaling as a therapeutic target of obesity

INTRODUCTION

Leptin is a hormone with a key role in food intake and body weight homeostasis. Congenital leptin deficiency (CLD) is a rare disease that causes hyperphagia and early severe obesity. However, common obesity conditions are associated with hyperleptinemia and leptin resistance.

AREAS COVERED

The main signaling pathways activated by leptin as well as the mechanisms underlying the regulatory actions of leptin on food intake and on lipid and glucose metabolism are reviewed. The potential mechanisms involving leptin resistance and the main regulatory hormonal and nutritional factors controlling leptin production/functions are also analyzed. The pathophysiology of leptin in human obesity, and especially the trials analyzing effects of leptin replacement therapy in patients with CLD or in subjects with common obesity and in post-obese weight-reduced subjects are also summarized.

EXPERT OPINION

The use of drugs or specific bioactive food components with anti-inflammatory properties to reduce the inflammatory state associated with obesity, especially at the hypothalamus, may help to overcome leptin resistance. Research should also be focused on investigating dietary strategies, food supplements or drugs capable of avoiding or reversing the leptin fall during weight management, in order to promote sustained body weight lowering and weight loss maintenance.

Leptin treatment: facts and expectations

Leptin has key roles in the regulation of energy balance, body weight, metabolism, and endocrine function. Leptin levels are undetectable or very low in patients with lipodystrophy, hypothalamic amenorrhea, and congenital leptin deficiency (CLD) due to mutations in the leptin gene. For these patients, leptin replacement therapy with metreleptin (a recombinant leptin analog) has improved or normalized most of their phenotypes, including normalization of endocrine axes, decrease in insulin resistance, and improvement of lipid profile and hepatic steatosis. Remarkable weight loss has been observed in patients with CLD. Due to its effects, leptin therapy has also been evaluated in conditions where leptin levels are normal or high, such as common obesity, diabetes (types 1 and 2), and Rabson-Mendenhall syndrome. A better understanding of the physiological roles of leptin may lead to the development of leptin-based therapies for other prevalent disorders such as obesity-associated nonalcoholic fatty liver disease, depression and dementia.

Plasma leptin concentrations are highly correlated to emotional states throughout the day

Previous work has shown that leptin appears to regulate the plasma levels of hormones such as adrenocorticotropic hormone (ACTH) and cortisol in humans and that it has antidepressant effects in animals. It is unknown whether fluctuations in circulating leptin levels are correlated to changes in human emotions. This study was conducted to determine whether minute-to-minute fluctuations in the plasma concentrations of human leptin were associated with psychological variables. Leptin was sampled every 7 min throughout the day in 10 healthy subjects (five men and five women) studied in a clinical research center, and visual analog scales were applied every hour. We found highly significant correlations between fluctuations in plasma leptin concentrations and three psychological variables: sadness, carbohydrate craving and social withdrawal. We showed that during the course of the day increases in leptin levels are associated with decreased search for starchy foods, decreased feelings of sadness and increased social withdrawal. Our findings support the hypothesis that during the course of the day as leptin levels increase individuals subjectively feel happier (less sad) and have less inclination to interact socially. Conversely, when leptin levels decrease, we show increases in sadness and social cooperation, which might facilitate the search for food. We suggest that increased human leptin levels may promote positive feelings and that decreased leptin levels might modulate inner states that motivate and facilitate the search for nutrients.

Effects of a novel MC4R agonist on maintenance of reduced body weight in diet-induced obese mice

OBJECTIVE

The physiology of the weight-reduced (WR) state suggests that pharmacologic agents affecting energy homeostasis may have greater efficacy in WR individuals. Our aim was to establish a protocol that allows for evaluation of efficacy of weight maintenance agents and to assess the effectiveness of AZD2820, a novel melanocortin 4 receptor (MC4R) agonist in such a paradigm.

METHODS

MC4R agonist was administered in stratified doses to mice who were either fed high-fat diet ad libitum (AL) throughout the study; or stabilized at a 20% reduced body weight (BW), administered the drug for 4 weeks, and thereafter released from caloric restriction while continuing to receive the drug (WR).

RESULTS

After release of WR mice to AL feeding, the high-dose group (53.4 nmol/day) regained 12.4% less BW than their vehicle-treated controls since the beginning of drug treatment. In WR mice, 10.8 nmol/day of the agonist was sufficient to maintain these animals at 95.1% of initial BW versus 53.4 nmol/day required to maintain the BW of AL animals (94.5%).

CONCLUSIONS

In the WR state, the MC4R agonist was comparably efficacious to a five-fold higher dose in the AL state. This protocol provides a model for evaluating the mechanisms and quantitative efficacy of weight-maintenance strategies and agents.

The role of leptin in the control of insulin-glucose axis

Obesity and diabetes mellitus are great public health concerns throughout the world because of their increasing incidence and prevalence. Leptin, the adipocyte hormone, is well known for its role in the regulation of food intake and energy expenditure. In addition to the regulation of appetite and satiety that recently has attracted much attentions, insight has also been gained into the critical role of leptin in the control of the insulin-glucose axis, peripheral glucose and insulin responsiveness. Since the discovery of leptin, leptin has been taken for its therapeutic potential to obesity and diabetes. Recently, the therapeutic effects of central leptin gene therapy have been reported in insulin-deficient diabetes in obesity animal models such as ob/ob mise, diet-induced obese mice, and insulin-deficient type 1 diabetes mice, and also in patients with inactivating mutations in the leptin gene. Herein, we review the role of leptin in regulating feeding behavior and glucose metabolism and also the therapeutic potential of leptin in obesity and diabetes mellitus.

Effects of leptin deficiency and replacement on cerebellar response to food-related cues

Leptin affects eating behavior partly by altering the response of the brain to food-related stimuli. The effects of leptin on brain structure have been observed in the cerebellum, where leptin receptors are most densely expressed, but the function of leptin in the cerebellum remains unclear. We performed a nonrandomized, prospective interventional study of three adults with genetically mediated leptin deficiency. FMRI was recorded three times each year during years 5 and 6 of leptin replacement treatment. Session 1 of each year occurred after 10 months of continuous daily replacement, session 2 after 33-37 days without leptin, and session 3 at 14-23 days after daily replacement was restored. Statistical parametric mapping software (SPM5) was employed to contrast the fMRI blood oxygenation level-dependent response to images of high-calorie foods versus images of brick walls. Covariate analyses quantified the effects of the duration of leptin replacement and concomitant changes in body mass on the cerebral responses. Longer duration of replacement was associated with more activation by food images in a ventral portion of the posterior lobe of the cerebellum, while simultaneous decreases in body mass were associated with decreased activation in a more dorsal portion of the same lobe. These findings indicate that leptin replacement reversibly alters neural function within the posterior cerebellum and modulates plasticity-dependent brain physiology in response to food cues. The results suggest an underexplored role for the posterior cerebellum in the regulation of leptin-mediated processes related to food intake.

Effects of leptin replacement alone and with exendin-4 on food intake and weight regain in weight-reduced diet-induced obese rats

Weight loss in obese humans produces a relative leptin deficiency, which is postulated to activate potent orexigenic and energy conservation mechanisms to restrict weight loss and promote weight regain. Here we determined whether leptin replacement alone or with GLP-1 receptor agonist exendin-4 attenuates weight regain or promotes greater weight loss in weight-reduced diet-induced obese (DIO) rats. Forty percent restriction in daily intake of a high-fat diet in DIO rats for 4 wk reduced body weight by 12%, body fat by 29%, and plasma leptin by 67% and normalized leptin sensitivity. When food restriction ended, body weight, body fat, and plasma leptin increased rapidly. Daily administration of leptin [3-h intraperitoneal (ip) infusions (4 nmol·kg(-1)·h(-1))] at onset and end of dark period for 3 wk did not attenuate hyperphagia and weight regain, nor did it affect mean daily meal sizes or meal numbers. Exendin-4 (50 pmol·kg(-1)·h(-1)) infusions during the same intervals prevented postrestriction hyperphagia and weight regain by normalizing meal size. Coadministration of leptin and exendin-4 did not reduce body weight more than exendin-4 alone. Instead, leptin began to attenuate the inhibitory effects of exendin-4 on food intake, meal size, and weight regain by the end of the second week of administration. Plasma leptin in rats receiving leptin was sevenfold greater than in rats receiving vehicle and 17-fold greater than in rats receiving exendin-4. Together, these results do not support the hypothesis that leptin replacement alone or with exendin-4 attenuates weight regain or promotes greater weight loss in weight-reduced DIO rats.

The use of functional MRI to study appetite control in the CNS

Functional magnetic resonance imaging (fMRI) has provided the opportunity to safely investigate the workings of the human brain. This paper focuses on its use in the field of human appetitive behaviour and its impact in obesity research. In the present absence of any safe or effective centrally acting appetite suppressants, a better understanding of how appetite is controlled is vital for the development of new antiobesity pharmacotherapies. Early functional imaging techniques revealed an attenuation of brain reward area activity in response to visual food stimuli when humans are fed—in other words, the physiological state of hunger somehow increases the appeal value of food. Later studies have investigated the action of appetite modulating hormones on the fMRI signal, showing how the attenuation of brain reward region activity that follows feeding can be recreated in the fasted state by the administration of anorectic gut hormones. Furthermore, differences in brain activity between obese and lean individuals have provided clues about the possible aetiology of overeating. The hypothalamus acts as a central gateway modulating homeostatic and nonhomeostatic drives to eat. As fMRI techniques constantly improve, functional data regarding the role of this small but hugely important structure in appetite control is emerging.

Leptin reverses declines in satiation in weight-reduced obese humans

BACKGROUND

Individuals who are weight-reduced or leptin deficient have a lower energy expenditure coupled with higher hunger and disinhibition and/or delayed satiation compared with never-weight-reduced control subjects. Because exogenous leptin inhibits feeding in congenitally leptin-deficient humans, reduced leptin signaling may reduce the expression of feeding inhibition in humans.

OBJECTIVE

The objective was to test the hypothesis that reduced leptin signaling may reduce the expression of feeding inhibition (ie, blunt satiation) in humans by examining the effects of leptin repletion on feeding behavior after weight loss.

DESIGN

Ten obese humans (4 men, 6 women) were studied as inpatients while they received a weight-maintaining liquid-formula diet. Satiation was studied by measuring intake and ratings of appetite-related dispositions 3 h after ingestion of 300 kcal of the liquid-formula diet. The subjects were studied at each of 3 time periods: 1) while they maintained their usual weight (Wt(initial)) and then after weight reduction and stabilization at 10% below initial weight and while they received 5 wk of either 2) twice-daily injections of placebo (Wt(-10%placebo)) or 3) "replacement doses" of leptin (Wt(-10%leptin)) in a single-blind crossover design with a 2-wk washout period between treatments. Energy expenditure was also measured at each study period.

RESULTS

Both energy expenditure and visual analog scale ratings that reflect satiation were significantly lower at Wt(-10%placebo) than at Wt(initial) and Wt(-10%leptin).

CONCLUSION

The results are consistent with the hypothesis that the absence of leptin signaling after weight loss may blunt the expression of feeding inhibition in humans.

Ten years of leptin replacement therapy

Leptin is a pleiotropic cytokine-like hormone that is involved in the regulation of energy intake and expenditure, neuroendocrine function, immunity and lipid and glucose metabolism. The few humans with genetically based leptin deficiency provide a unique model to assess those effects. We have identified five Turkish patients (one male and two female adults; one boy and one girl) with congenital leptin deficiency due to a missense mutation in the leptin gene. Four of these patients were treated with physiological doses of recombinant methionyl human leptin. Body composition, brain structure and function, behaviour, immunity and endocrine and metabolic parameters were evaluated before and during treatment. Our results showed that leptin has peripheral, hypothalamic and extra-hypothalamic effects. Within the endocrine system, leptin regulates the circadian rhythms of cortisol, thyroid-stimulating hormone, luteinizing hormone and follicle-stimulating hormone. In the brain, leptin controls energy balance and body weight, and plays a role on neurogenesis and brain function. Leptin is a key element of the adiposinsular axis, enhances immune response, and regulates inflammation, coagulation, fibrinolysis and platelet aggregation. Our 10-year experience in treating these unique patients provided valuable data on the peripheral and central effects of leptin. Those results can be taken into account for the development of leptin-based therapies for other diseases.

Energy intake in weight-reduced humans

Almost anyone who has ever lost weight can attest that it is harder to sustain weight loss than to lose weight. Maintenance of a 10% or greater reduced body weight is accompanied by decreases in energy expenditure to levels significantly below what is predicted solely on the basis of weight and body composition changes. This disproportionate decline in energy expenditure would not be sufficient to account for the over 80% recidivism rate to pre-weight loss levels of body fatness after otherwise successful weight reduction if there were a corresponding reduction in energy intake. In fact, reduced body weight maintenance is accompanied by increased energy intake above that required to maintain reduced weight. The failure to reduce energy intake in response to decreased energy output reflects decreased satiation and perception of how much food is eaten and multiple changes in neuronal signaling in response to food which conspire with the decline in energy output to keep body energy stores (fat) above a CNS-defined minimum (threshold). Much of this biological opposition to sustained weight loss is mediated by the adipocyte-derived hormone "leptin."

Pharmacological management of appetite expression in obesity

For obese individuals, successful weight loss and maintenance are notoriously difficult. Traditional drug development fails to exploit knowledge of the psychological factors that crucially influence appetite, concentrating instead on restrictive criteria of intake and weight reduction, allied to a mechanistic view of energy regulation. Drugs are under development that may produce beneficial changes in appetite expression in the obese. These currently include glucagon-like peptide-1 analogs such as liraglutide, an amylin analog davalintide, the 5-HT(2C) receptor agonist lorcaserin, the monoamine re-uptake inhibitor tesofensine, and a number of combination therapies such as pramlintide and metreleptin, bupropion and naltrexone, phentermine and topiramate, and bupropion and zonisamide. However, the effects of these treatments on eating behavior remain poorly characterized. Obesity is typically a consequence of overconsumption driven by an individual's natural sensitivity to food stimuli and the pleasure derived from eating. Intuitively, these processes should be effective targets for pharmacotherapy, and behavioral analysis can identify drugs that selectively affect desire to eat, enjoyment of eating, satiation or postmeal satiety. Rational interventions designed specifically to modulate these processes could limit the normally aversive consequences of caloric restriction and maximize an individual's capacity to successfully gain control over their appetite.

Changes in insulin sensitivity during leptin replacement therapy in leptin-deficient patients

Leptin replacement rescues the phenotype of morbid obesity and hypogonadism in leptin-deficient adults. However, leptin's effects on insulin resistance are not well understood. Our objective was to evaluate the effects of leptin on insulin resistance. Three leptin-deficient adults (male, 32 yr old, BMI 23.5 kg/m(2); female, 42 yr old, BMI 25.1 kg/m(2); female, 46 yr old, BMI 31.7 kg/m(2)) with a missense mutation of the leptin gene were evaluated during treatment with recombinant methionyl human leptin (r-metHuLeptin). Insulin resistance was determined by euglycemic hyperinsulinemic clamps and by oral glucose tolerance tests (OGTTs), whereas patients were on r-metHuLeptin and after treatment was interrupted for 2-4 wk in the 4th, 5th, and 6th years of treatment. At baseline, all patients had normal insulin levels, C-peptide, and homeostatic model assessment of insulin resistance index, except for one female diagnosed with type 2 diabetes. The glucose infusion rate was significantly lower with r-metHuLeptin (12.03 +/- 3.27 vs. 8.16 +/- 2.77 mg.kg(-1).min(-1), P = 0.0016) but did not differ in the 4th, 5th, and 6th years of treatment when all results were analyzed by a mixed model [F(1,4) = 0.57 and P = 0.5951]. The female patient with type 2 diabetes became euglycemic after treatment with r-metHuLeptin and subsequent weight loss. The OGTT suggested that two patients showed decreased insulin resistance while off treatment. During an off-leptin OGTT, one of the patients developed a moderate hypoglycemic reaction attributed to increased posthepatic insulin delivery and sensitivity. We conclude that, in leptin-deficient adults, the interruption of r-metHuLeptin decreases insulin resistance in the context of rapid weight gain. Our results suggest that hyperleptinemia may contribute to mediate the increased insulin resistance of obesity.

Leptin reverses weight loss-induced changes in regional neural activity responses to visual food stimuli

Increased hunger and food intake during attempts to maintain weight loss are a critical problem in clinical management of obesity. To determine whether reduced body weight maintenance is accompanied by leptin-sensitive changes in neural activity in brain regions affecting regulatory and hedonic aspects of energy homeostasis, we examined brain region-specific neural activity elicited by food-related visual cues using functional MRI in 6 inpatient obese subjects. Subjects were assessed at their usual weight and, following stabilization at a 10% reduced body weight, while receiving either twice daily subcutaneous injections of leptin or placebo. Following weight loss, there were predictable changes in neural activity, many of which were reversed by leptin, in brain areas known to be involved in the regulatory, emotional, and cognitive control of food intake. Specifically, following weight loss there were leptin-reversible increases in neural activity in response to visual food cues in the brainstem, culmen, parahippocampal gyrus, inferior and middle frontal gyri, middle temporal gyrus, and lingual gyrus. There were also leptin-reversible decreases in activity in response to food cues in the hypothalamus, cingulate gyrus, and middle frontal gyrus. These data are consistent with a model of the weight-reduced state as one of relative leptin deficiency.

Leptin replacement improves cognitive development

Background

Leptin changes brain structure, neuron excitability and synaptic plasticity. It also regulates the development and function of feeding circuits. However, the effects of leptin on neurocognitive development are unknown.

Objective

To evaluate the effect of leptin on neurocognitive development.

Methodology

A 5-year-old boy with a nonconservative missense leptin gene mutation (Cys-to-Thr in codon 105) was treated with recombinant methionyl human leptin (r-metHuLeptin) at physiologic replacement doses of 0.03 mg/kg/day. Cognitive development was assessed using the Differential Ability Scales (DAS), a measure of general verbal and nonverbal functioning; and selected subtests from the NEPSY, a measure of neuropsychological functioning in children.

Principal Findings

Prior to treatment, the patient was morbidly obese, hypertensive, dyslipidemic, and hyperinsulinemic. Baseline neurocognitive tests revealed slower than expected rates of development (developmental age lower than chronological age) in a majority of the areas assessed. After two years, substantial increases in the rates of development in most neurocognitive domains were apparent, with some skills at or exceeding expectations based on chronological age. We also observed marked weight loss and resolution of hypertension, dyslipidemia and hyperinsulinemia.

Conclusions

We concluded that replacement with r-metHuLeptin is associated with weight loss and changes in rates of development in many neurocognitive domains, which lends support to the hypothesis that, in addition to its role in metabolism, leptin may have a cognitive enhancing role in the developing central nervous system.

Trial Registration

ClinicalTrials.gov NCT00659828

Collective and individual functions of leptin receptor modulated neurons controlling metabolism and ingestion

Two known types of leptin-responsive neurons reside within the arcuate nucleus: the agouti gene-related peptide (AgRP)/neuropeptide Y (NPY) neuron and the proopiomelanocortin (POMC) neuron. By deleting the leptin receptor gene (Lepr) specifically in AgRP/NPY and/or POMC neurons of mice, we examined the several and combined contributions of these neurons to leptin action. Body weight and adiposity were increased by Lepr deletion from AgRP and POMC neurons individually, and simultaneous deletion in both neurons (A+P LEPR-KO mice) further increased these measures. Young (periweaning) A+P LEPR-KO mice exhibit hyperphagia and decreased energy expenditure, with increased weight gain, oxidative sparing of triglycerides, and increased fat accumulation. Interestingly, however, many of these abnormalities were attenuated in adult animals, and high doses of leptin partially suppress food intake in the A+P LEPR-KO mice. Although mildly hyperinsulinemic, the A+P LEPR-KO mice displayed normal glucose tolerance and fertility. Thus, AgRP/NPY and POMC neurons each play mandatory roles in aspects of leptin-regulated energy homeostasis, high leptin levels in adult mice mitigate the importance of leptin-responsiveness in these neurons for components of energy balance, suggesting the presence of other leptin-regulated pathways that partially compensate for the lack of leptin action on the POMC and AgRP/NPY neurons.

Potential therapies based on antidiabetic peptides

Since adipose tissue was shown to be more than a storage organ, the many cytokines it produces have been identified, along with their roles in energy homeostasis, appetite, and insulin resistance. Concurrently, numerous gut hormones with a diversity of effects have been discovered. They include, amongst many others, peptide YY, ghrelin and oxyntomodulin. As these peptides have been investigated, the potential for their use as novel anti-obesity and antidiabetic therapies has been realized. In this chapter we describe the actions of four of the peptides that have been proposed as the basis for promising new therapies for diabetes: leptin, adiponectin, obestatin and peptide YY. They each have an effect on appetite and, directly or indirectly, on glucose metabolism. We synthesize available data for these peptides and consider the therapeutic potential of each.

Leptin replacement alters brain response to food cues in genetically leptin-deficient adults

A missense mutation in the ob gene causes leptin deficiency and morbid obesity. Leptin replacement to three adults with this mutation normalized body weight and eating behavior. Because the neural circuits mediating these changes were unknown, we paired functional magnetic resonance imaging (fMRI) with presentation of food cues to these subjects. During viewing of food-related stimuli, leptin replacement reduced brain activation in regions linked to hunger (insula, parietal and temporal cortex) while enhancing activation in regions linked to inhibition and satiety (prefrontal cortex). Leptin appears to modulate feeding behavior through these circuits, suggesting therapeutic targets for human obesity.

Effects of leptin replacement on macro- and micronutrient preferences

BACKGROUND

The mechanisms underlying food choices are complex and involve neuroendocrine and biochemical signaling. Among neuroendocrine signals, leptin may play a prominent role in food preference.

OBJECTIVE

This study was designed to obtain an understanding of the effects of leptin replacement on macro- and micronutrient preferences in leptin-deficient adults.

DESIGN

We studied the effects of leptin replacement on three adults with genetic leptin deficiency during the initial 12 months of treatment. Dietary intake was measured in our study by weighed food consumption records. Nutrient intake was calculated using a nutrition analysis software.

RESULTS

After leptin replacement was started, all patients had initially a marked reduction in food intake. The reduction in caloric intake differentially affected intake of macro- and micronutrients. There was an initial shift toward a higher percentage consumption of fats and a decrease in the intake of carbohydrates. Significant differences also occurred in 7 distinct types of macronutrients, 12 vitamins, 11 minerals and 1 amino acid.

CONCLUSIONS

We documented several specific leptin-induced changes in macro- and micronutrients intake during the course of leptin-replacement treatment, the majority of which were not related to the decrease in total caloric consumption.

Effects of leptin on intake of specific micro- and macronutrients in a woman with leptin gene deficiency studied off and on leptin at stable body weight

In this report, we examine the effects of leptin on the intake of specific macro- and micronutrients in a female patient with leptin gene deficiency. The patient was studied off and on leptin at stable body weight, within the normal to mildly overweight range. The data were obtained by detailed dietary assessments, measuring dietary intakes by weighed food and fluid consumption records, and analyzed using nutrition analysis software. Overall, significant differences were found in the off versus on leptin treatment periods in the following categories: (i) macronutrients: kilocalories, protein, carbohydrates, monounsaturated fats, MFA 18:1 oleic and total fiber; (ii) vitamins: vitamin C, pyridoxine and pantothenic acid; (iii) minerals: potassium, magnesium, copper and chromium; and amino acids: threonine, lysine and histidine. The nutritional data from this study indicates a direct link between the effects of leptin and ingestion of several specific micronutrients. The mechanisms underlying these effects warrant further investigation and study.

Genetics of human obesity

This chapter presents the current state of knowledge in the field of the genetics of human obesity. The molecular approach has proved to be powerful in defining new syndromes associated with obesity. The pivotal role of leptin and melanocortin pathways has been recognized, but only in rare cases of obesity. In the more common form of obesity a multitude of polymorphisms located in genes and candidate regions throughout the genome regulate an individual's susceptibility to weight gain in a permissive environment. The effects are often uncertain and the results not always confirmed. Combining these single nucleotide polymorphisms and defining the associated risks for obesity will be a real challenge in the future. It is now necessary to integrate data of various origins (environment, genotype, expression) to clarify this field.

Genetics of human obesity

We present the knowledge acquired in the field of the genetics of human obesity. The molecular approach proved to be powerful to define new syndromes associated to obesity. The pivotal role of leptin and melanocortin pathways were recognized but in rare obesity cases. In the commoner form of obesities, a multitude of polymorphisms located in genes and candidate regions participate in an individual susceptibility to weight gain in a permissive environment. The effects are often uncertain and the results not always confirmed. It is now necessary to integrate data of various origins (environment, genotype, expression) to clarify the domain.

Adipocytokines: leptin--the classical, resistin--the controversical, adiponectin--the promising, and more to come

With the growing prevalence of obesity, scientific interest in the biology of adipose tissue has been extended to the secretory products of adipocytes, since they are increasingly shown to affect several aspects in the pathogenesis of obesity-related diseases. The cloning of the ob gene is consistent with this concept and suggests that body fat content in adult rodents is regulated by a negative feedback loop centred in the hypothalamus. In recent years, a number of additional signalling molecules secreted by adipose tissue have been discovered, commonly referred to as 'adipocytokines'. Among these, adiponectin is perhaps the most interesting and promising compound for the clinician since it has profound protective actions in the pathogenesis of diabetes and cardiovascular disease. Adiponectin is low in obese subjects and, in particular, insulin-resistant patients. In contrast, resistin seems to be of greater relevance in relation to the immune stress response than in the regulation of glucose homeostasis. However, inflammatory processes have recently been connected with the development of atherosclerosis. Finally, little is known regarding the clinical relevance of visfatin. Recent research has revealed many functions of adipocytokines extending far beyond metabolism, such as immunity, cancer and bone formation. This report aims to review some of the recent topics of adipocytokine research that may be of particular importance.