Recombinant Methionyl Human Leptin Research Articles

Acquired partial lipoatrophy as graft-versus-host disease and treatment with metreleptin: two case reports

IntroductionAcquired partial lipoatrophy has been reported after bone marrow transplantation during childhood; however, no adult cases have previously been reported. We herein report two adult cases of acquired partial lipoatrophy after transplantation.Case presentationA 28-year-old Japanese woman developed diabetic ketoacidosis and received insulin therapy after bone marrow transplantation. She manifested partial lipoatrophy of the extremities, prominent insulin resistance, hyperglycemia, hypertriglyceridemia, and fatty liver. A 40-year-old Japanese woman underwent liver transplantation from a living donor for alcoholic liver disease after abstinence from alcohol. She newly developed non-alcoholic steatohepatitis and diabetes. Non-alcoholic steatohepatitis progressed to liver failure, and a second liver transplantation from a brain-dead donor was performed at 42 years of age. She demonstrated loss of subdermal fat of the upper and lower extremities, prominent insulin resistance, hyperglycemia, and hypertriglyceridemia. In both cases, the injection of recombinant methionyl human leptin reversed all of the metabolic abnormalities.ConclusionsAcquired partial lipoatrophy after transplantation is a manifestation of chronic graft-versus-host disease in adults. This entity is associated with diabetes with prominent insulin resistance and severe hypertriglycemia and can be successfully treated with metreleptin for the long term.

New advances in the treatment of generalized lipodystrophy: role of metreleptin.

Recombinant methionyl human leptin or metreleptin is a synthetic leptin analog that has been trialed in patients with leptin-deficient conditions, such as leptin deficiency due to mutations in the leptin gene, hypothalamic amenorrhea, and lipodystrophy syndromes. These syndromes are characterized by partial or complete absence of adipose tissue and hormones derived from adipose tissue, most importantly leptin. Patients deficient in leptin exhibit a number of severe metabolic abnormalities such as hyperglycemia, hypertriglyceridemia, and hepatic steatosis, which can progress to diabetes mellitus, acute pancreatitis, and hepatic cirrhosis, respectively. For the management of these abnormalities, multiple therapies are usually required, and advanced stages may be progressively difficult to treat. Following many successful trials, the US Food and Drug Administration approved metreleptin for the treatment of non-HIV-related forms of generalized lipodystrophy. Leptin replacement therapy with metreleptin has, in many cases, reversed these metabolic complications, with improvements in glucose-insulin-lipid homeostasis, and regression of fatty liver disease. Besides being effective, a daily subcutaneous administration of metreleptin is generally safe, but the causal association between metreleptin and immune complications (such as lymphoma) is still unclear. Moreover, further investigation is needed to elucidate mechanisms by which metreleptin leads to the development of anti-leptin antibodies. Herein, we review clinical aspects of generalized lipodystrophy and the pharmacological profile of metreleptin. Further, we examine studies that assessed the safety and efficacy of metreleptin, and outline some clinical perspectives on the drug.

Diagnosis and management of lipodystrophy: a practical update

Lipodystrophy is a group of rare conditions characterized by partial or complete loss of subcutaneous adipose tissue. Lipodystrophy is associated with metabolic derangements including severe insulin resistance, diabetes, hypertriglyceridemia, pancreatitis, nonalcoholic fatty liver disease and, in females, hyperandrogenism, polycystic ovarian syndrome and subfertility. The underlying cause may be genetic or acquired. Patients may present in childhood or adulthood. The diagnosis is frequently delayed, especially in partial lipodystrophy. Avoidance of excess dietary energy intake, despite the often lean appearance of the patient, is the current mainstay of treatment, aiming to avoid short- and long-term complications, while allowing normal growth in children. Early involvement of a specialized multidisciplinary team in the diagnosis and management of patients with lipodystrophy may enable evidence-based management guidelines to be developed. The timely diagnosis of lipodystrophy is becoming more important as novel treatment options such as recombinant methionyl human leptin therapy has recently been approved for use in some patients.

Selective capacity of metreleptin administration to reconstitute CD4 + T-cell number in females with acquired hypoleptinemia

Leptin is an adipocyte-derived hormone that controls food intake and reproductive and immune functions in rodents. In uncontrolled human studies, low leptin levels are associated with impaired immune responses and reduced T-cell counts; however, the effects of leptin replacement on the adaptive immune system have not yet been reported in the context of randomized, controlled studies and/or in conditions of chronic acquired leptin deficiency. To address these questions, we performed a randomized, double-blinded, placebo-controlled trial of recombinant methionyl-human leptin (metreleptin) administration in replacement doses in women experiencing the female triad (hypothalamic amenorrhea) with acquired chronic hypoleptinemia induced by negative energy balance. Metreleptin restored both CD4(+) T-cell counts and their in vitro proliferative responses in these women. These changes were accompanied by a transcriptional signature in which genes relevant to cell survival and hormonal response were up-regulated, and apoptosis genes were down-regulated in circulating immune cells. We also observed that signaling pathways involved in cell growth/survival/proliferation, such as the STAT3, AMPK, mTOR, ERK1/2, and Akt pathways, were activated directly by acute in vivo metreleptin administration in peripheral blood mononuclear cells and CD4(+) T-cells both from subjects with chronic hypoleptinemia and from normoleptinemic, lean female subjects. Our data show that metreleptin administration, in doses that normalize circulating leptin levels, induces transcriptional changes, activates intracellular signaling pathways, and restores CD4(+) T-cell counts. Thus, metreleptin may prove to be a safe and effective therapy for selective CD4(+) T-cell immune reconstitution in hypoleptinemic states such as tuberculosis and HIV infection in which CD4(+) T cells are reduced.

Therapeutic use of recombinant methionyl human leptin

Recombinant methionyl human leptin (r-metHuLeptin) was first used as a replacement therapy in patients bearing inactivating mutations in the leptin gene. In this indication, it was shown since 1999 to be very efficient in inducing a dramatic weight loss in rare children and adults with severe obesity due to the lack of leptin. These first clinical trials clearly showed that r-metHuLeptin acted centrally to reduce food intake, inducing loss of fat mass, and to correct metabolic alterations, immune and neuroendocrine defects. A few years later, r-metHuLeptin was also shown to reverse the metabolic complications associated with lipodystrophic syndromes, due to primary defects in fat storage, which induce leptin deficiency. The beneficial effects, which could be mediated by central and/or peripheral mechanisms, are thought to mainly involve the lowering effects of leptin on ectopic lipid storage, in particular in liver and muscles, reducing insulin resistance. Interestingly, r-metHuLeptin therapy also reversed the hypothalamic-pituitary-gonadal axis dysfunctions associated with hypothalamic amenorrhea. However, if r-metHuLeptin treatment has been shown to be dramatically efficient in leptin-deficient states, its very limited effect in inducing weight loss in common obese patients revealed that, in patients with adequate leptin secretion, mechanisms of leptin resistance and leptin tolerance prevent r-metHuLeptin from inducing any additional effects. This review will present the current data about the effects of r-metHuLeptin therapy in humans, and discuss the recent perspectives of this therapy in new indications.

Long-term metreleptin treatment increases bone mineral density and content at the lumbar spine of lean hypoleptinemic women

Strenuously exercising young women with hypothalamic amenorrhea are hypoleptinemic and have low bone mineral density (BMD) and content (BMC), which predispose them to increased fracture risk. Short-term leptin replacement in these women corrects many neuroendocrine abnormalities and increases circulating levels of bone formation markers. Whether treatment with recombinant methionyl human leptin (metreleptin) for a long period improves BMD and BMC remains unknown. We studied 20 strenuously exercising young women with hypoleptinemia (leptin concentration <5 ng/mL) and hypothalamic amenorrhea of at least 6 months' duration. Eleven were randomized to metreleptin (initial dose, 0.08 mg/[kg·d] for 3 months; altered thereafter to 0.12 mg/kg for lack of efficacy or 0.04 mg/[kg d] for more than 5% weight loss) and 9 were randomized to placebo for 9 months. After a 3-month washout period, subjects were reexamined at the 1-year time point. Six subjects elected to continue on open-label metreleptin treatment for another 12 months. Two subjects dropped out after 18 months, and 4 completed the entire 2-year study. The BMD and BMC of the total body, lumbar spine (L1-L4), hip, and radius were assessed by using dual-energy x-ray absorptiometry at baseline and at 3, 6, 9, 12, 18, and 24 months of treatment. Metabolic and hormonal parameters and bone markers were measured in blood and urine. Metreleptin significantly increased BMC (P = .034) and tended to increase BMD (P = .069) at the lumbar spine at 9 months in the entire study group (intention-to-treat analysis). In subjects who completed the entire 2-year study (n = 4), metreleptin significantly increased BMD (P = .024) and BMC (P = .049) at the lumbar spine by 4% to 6%. Changes were not significant at the whole body, hip, and radius. Changes in hormonal and metabolic parameters and bone markers were moderate during the first year of treatment, but metreleptin further increased insulin-like growth factor 1 and decreased cortisol and cross-linked C-terminal telopeptide of type 1 collagen concentrations in serum during the second year of treatment (P < .05). The incremental area under the estradiol concentration curve over the 2-year course of the study correlated positively with the corresponding increase in lumbar spine BMD (ρ = 0.42, P = .039). Long-term metreleptin administration in strenuously exercising young women with hypothalamic amenorrhea and hypoleptinemia increases lumbar spine BMD and BMC and alters bone remodeling milieu to favor bone accretion. Results from this pilot study should be confirmed by future, larger clinical trials and need to be extended by studying bone microarchitecture and fracture risk.

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.

Recombinant Human Leptin Treatment Does Not Improve Insulin Action in Obese Subjects With Type 2 Diabetes

OBJECTIVELeptin therapy improves insulin sensitivity in people with leptin deficiency, but it is not known whether it improves insulin action in people who are not leptin deficient. The purpose of the current study was to determine whether leptin treatment has weight loss–independent effects on insulin action in obese subjects with type 2 diabetes.RESEARCH DESIGN AND METHODSWe conducted a randomized, placebo-controlled trial in obese subjects (BMI: 35.4 ± 0.6 kg/m2; mean ± SE) with newly diagnosed type 2 diabetes. Subjects were randomized to treatment with placebo (saline), low-dose (30 mg/day), or high-dose (80 mg/day) recombinant methionyl human (r-Met hu) leptin for 14 days. Multiorgan insulin sensitivity before and after treatment was evaluated by using the hyperinsulinemic-euglycemic clamp procedure in conjunction with stable isotopically labeled tracer infusions to measure glucose, glycerol, and fatty acid kinetics.RESULTSLow-dose and high-dose leptin treatment resulted in a threefold (P < 0.01) and 150-fold (P < 0.001) increase in basal plasma leptin concentrations, respectively. However, neither low-dose nor high-dose therapy had an effect on insulin-mediated suppression of glucose, glycerol, or palmitate rates of appearance into plasma compared with placebo. In addition, leptin treatment did not increase insulin-mediated stimulation of glucose disposal compared with placebo (14.3 ± 3.1, 18.4 ± 3.6, 16.7 ± 2.4 vs. 17.5 ± 2.5, 20.7 ± 3.0, 19.1 ± 3.3 μmol/kg body wt/min before vs. after treatment in the placebo, low-dose, and high-dose leptin groups, respectively).CONCLUSIONSr-Met hu leptin does not have weight loss–independent, clinically important effects on insulin sensitivity in obese people with type 2 diabetes.

Leptin treatment reduces body fat but does not affect lean body mass or the myostatin-follistatin-activin axis in lean hypoleptinemic women

Animal studies in vivo indicate that leptin treatment in extremely leptin-sensitive ob/ob mice reduces body weight exclusively by reducing fat mass and that it increases muscle mass by downregulating myostatin expression. Data from human trials are limited. Therefore, we aimed at characterizing the effects of leptin administration on fat mass, lean body mass, and circulating regulators of muscle growth in hypoleptinemic and presumably leptin-sensitive human subjects. In an open-label, single-arm trial, seven lean, strenuously exercising, amenorrheic women with low leptin concentrations (≤5 ng/ml) were given recombinant methionyl human leptin (metreleptin; 0.08 mg·kg(-1)·day(-1)) for 10 wk. In a separate randomized, double-blind, placebo-controlled trial, seven women were given metreleptin (initial dose: 0.08 mg·kg(-1)·day(-1) for 3 mo, increased thereafter to 0.12 mg·kg(-1)·day(-1) if menstruation did not occur), and six were given placebo for 9 mo. Metreleptin significantly reduced total body fat by an average of 18.6% after 10 wk (P < 0.001) in the single-arm trial and by 19.5% after 9 mo (placebo subtracted; P for interaction = 0.025, P for metreleptin = 0.004) in the placebo-controlled trial. There were no significant changes in lean body mass (P ≥ 0.33) or in serum concentrations of myostatin (P ≥ 0.35), follistatin (P ≥ 0.30), and activin A (P ≥ 0.20) whether in the 10-wk trial or the 9-mo trial. We conclude that metreleptin administration in lean hypoleptinemic women reduces fat mass exclusively and does not affect lean body mass or the myostatin-follistatin-activin axis.

Leptin replacement improves postprandial glycemia and insulin sensitivity in human immunodeficiency virus–infected lipoatrophic men treated with pioglitazone: a pilot study

Highly active antiretroviral therapy (HAART)–induced lipoatrophy is characterized by hypoleptinemia and insulin resistance. Evidence suggests that pioglitazone and recombinant methionyl human leptin (metreleptin) administration has beneficial effects in human immunodeficiency virus (HIV)–infected lipoatrophic patients. This proof-of-concept study aimed at evaluating whether the combination of metreleptin and pioglitazone has favorable effects, above and beyond pioglitazone alone, on both metabolic outcomes and peripheral lipoatrophy in HIV-infected patients on HAART. Nine HIV-positive men with at least 6 months of HAART exposure, clinical evidence of lipoatrophy, and low leptin concentrations (≤4 ng/mL) were placed on pioglitazone treatment (30 mg/d per os) and were randomized to receive either metreleptin (0.04 mg/kg subcutaneously once daily; n = 5) or placebo (n = 4) for 3 months in a double-blinded fashion. Compared with placebo, metreleptin reduced fasting serum insulin concentration, increased adiponectin concentration, reduced the homeostasis model assessment index of insulin resistance, and attenuated postprandial glycemia in response to a mixed meal (all P ≤ .02), but did not affect trunk and peripheral fat mass. HIV control was not affected, and no major adverse effects were observed. Metreleptin administration in HIV-positive, leptin-deficient patients with lipoatrophy treated with pioglitazone improves postprandial glycemia and insulin sensitivity. Results from this pilot study should be confirmed in larger clinical trials.

Human Recombinant Leptin Administration as a Potential Obesity Therapy

Obesity is an escalating global health problem and established cardiovascular risk factor for the development of cardiovascular and metabolic diseases. Leptin derived from the adipose tissue acts centrally to suppress appetite and increase energy expenditure, therefore leptin resistance is considered as an important mechanism for the onset and maintenance of obesity; Leptin analogues as well as leptin receptor blockers have been candidates for the treatment of obesity, however clinical trials in obese populations have yielded variable results. Given specific circumstances in obese subjects could optimize the beneficial actions of the hormone and minimize its deleterious effects. In this review, human recombinant leptin (pegylated polyethylene glycol recombinant human leptin (PEG-OB) and recombinant methionyl human leptin (r-metHuLeptin) is developed to control resistant and morbid obesity will be discussed. Keywords: Obesity, leptin, pegylated human recombinant leptin, recombinant methionyl human leptin, myocardial hypertrophy, dyslipidemia, hyperleptinemia, hypothalamic pro-opiomelanocortin, anorectic effects, neuroendocrine, hypothalamus, thermogenesis, sympathoectomy, retinopathy, nephropathy, genetic mutation, myocardium, atherosclerosis, thrombosis, arterial hypertension, neointinal hyperplasia, blood-brain barrier, norepinephrine spillover, melanocortin system, neuropeptide mediators, Pegylated Polyethylene Glycol, pramlintide, triglyceride, somatotropic axes, plasminogen activator, adiponectin, ghrelin

Efficacy of leptin therapy in the different forms of human lipodystrophy

Lipodystrophy is a rare disorder characterised by loss of adipose tissue, hypoleptinaemia, severe insulin resistance, diabetes and dyslipidaemia. The aims of this study were to determine whether leptin replacement in lipodystrophy patients ameliorates their metabolic abnormalities over an extended period of time and whether leptin therapy is effective in the different forms of lipodystrophy. We conducted an open-label prospective study of patients with acquired forms of lipodystrophy and inherited forms of lipodystrophy secondary to mutations in the AGPAT2, SEIPIN (also known as BSCL2), LMNA and PPARgamma (also known as PPARG) genes. Between July 2000 and November 2008, 48 patients with lipodystrophy were treated with s.c. recombinant methionyl human leptin. Serum triacylglycerol and HbA(1c) levels declined dramatically with leptin therapy. Among 35 patients with data at baseline and 12 months, serum triacylglycerol fell by 59% (from 10.18 +/- 2.67 mmol/l to 4.16 +/- 0.99 mmol/l [means +/- SE]; p = 0.008) and HbA(1c) decreased by 1.5 percentage points (from 8.4 +/- 0.3% to 6.9 +/- 0.3%; p < 0.001). A significant reduction was seen in total cholesterol and a trend towards reduction was observed in LDL-cholesterol at 12 months. HDL-cholesterol was unchanged. Among generalised lipodystrophy patients, proteinuria diminished with leptin replacement. Patients with both acquired and inherited forms of lipodystrophy experienced decreases in serum triacylglycerol and HbA(1c) levels. Leptin replacement in lipodystrophy patients leads to significant and sustained improvements in glycaemic control and dyslipidaemia. Leptin is effective in the various forms of lipodystrophy, whether they are acquired or inherited, generalised or partial. ClinicalTrials.gov ID NCT00025883 This work was supported by intramural research funding from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) of the National Institutes of Health (NIH).

Leptin and insulin sensitivity: reply to Oral and Burant

present data that support the hypothesis that the increase in insulin sensitivity, while off recombinant methionyl human leptin, can be attributed to the rapid expansion of the adipose tissue mass. Furthermore, these authors cite the positive effects of leptin therapy on insulin sensitivity of lipodystrophic patients and of patients with mutations of the insulin receptor. As discussed in our article (7), there are limitations to those examples. In lipodystrophic patients there is marked insulin resistance, which is absent in leptin deficiency; on the contrary, prior to treatment our patients did not exhibit pronounced insulin resistance, even in the context of morbid obesity (4). In mutations of the insulin receptor there is defective signaling, which again is absent in leptin deficiency. Therefore, those examples cannot be directly compared with our data. We agree that our study does not allow us to conclude that leptin therapy by itself has a direct effect, worsening insulin sensitivity; as we discussed extensively, such an effect could be indirect through other actions of leptin. Additionally, as commented extensively in our paper, rapid weight gain is a confounding factor that needs to be minimized in future studies. Nevertheless, the uniqueness of our patients (complete absence of leptin and of leptin resistance and normal insulin sensitivity) allows us to suggest that leptin may worsen insulin sensitivity either directly or indirectly. The adipoinsular axis has many complex interactions that need to be elucidated (1). It is possible that leptin may lead to changes in insulin sensitivity but not to overall glucose homeostasis. In clinical research studies, the weight of leptindeficient patients should ideally be kept stable during the onand off-leptin euglycemic hyperinsulinemic clamps. However, it is unethical to allow excessive weight regain after leptin therapy is temporarily discontinued. Alternatively, one could restrict the patients to a rigid isocaloric diet at all times. However, it is virtually impossible for leptin-deficient patients to maintain such a diet while off leptin. The limitations of clinical research in living patients are such that not all possible variables can be controlled for at the same time. Given the constraints of patient-oriented investigation, we still believe that our results provide some of the clearest evidence that in humans leptin worsens insulin resistance, and we stand by our comment that hyperleptinemia may mediate the increased insulin resistance of obesity. Others have independently come to the same conclusion (2). We agree that further studies are needed to clarify the acute and chronic effects of leptin on insulin sensitivity. To determine whether the rapid increase in adipose tissue mass is responsible for the increase in insulin sensitivity, we plan to determine glucose uptake by performing euglycemic hyperinsulinemic clamps with radiolabeled glucose. In addition, patients will be advised to maintain isocaloric diets as much as possible. By continuing to investigate the effects of leptin on insulin sensitivity, we may be able to elucidate the roles of leptin on the adipoinsular axis. As a last word, the regulation of human glucose homeostasis is of fundamental relevance to the survival of our species. Therefore, the hallmark of such regulation is extensive redundancy, as evidenced by a vast network of signals that determine overall glucose utilization (3, 5). The specific contribution of each signal to glucose homeostasis is not necessarily fixed and immutable but may vary across time and across individuals or groups of individuals with different disorders in the context of their overall metabolic milieu.

Cellular Immunity Before and After Leptin Replacement Therapy

The few identified leptin-deficient children have immune deficiency. To evaluate whether a newly-identified leptin-deficient boy has immune defects; to assess the immune changes during leptin replacement. A 5 year-old boy with congenital leptin deficiency was evaluated before, 2 weeks and 6 weeks after the initiation of recombinant methionyl human leptin. Thymic volume was measured by computed tomography. Humoral immunity was assessed by measuring levels of several immunoglobulins. Cellular immunity was evaluated by the analysis of lymphocyte proliferation in response to mitogens. Lymphocyte subsets were quantified by flow cytometry. At baseline, thymic volume was increased. The lymphocyte subsets count and humoral/cellular immunities were normal. After treatment, proliferative response to mitogens increased by 1.5- to 3-fold, and lymphocyte count decreased by 17%. Immune defects are not an obligatory feature of congenital leptin deficiency. Even in the absence of significant immune defects, leptin replacement therapy enhanced T-cell responsiveness.

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 Replacement Improves Cognitive Development

BackgroundLeptin 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.ObjectiveTo evaluate the effect of leptin on neurocognitive development.MethodologyA 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 FindingsPrior 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.ConclusionsWe 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 RegistrationClinicalTrials.gov NCT00659828

Deconvolution of Insulin Secretion, Insulin Hepatic Extraction Post-hepatic Delivery Rates and Sensitivity during 24-hour Standardized Meals: Time Course of Glucose Homeostasis in Leptin Replacement Treatment

Minimally invasive methodology, mathematical model, and software for analysis of glucose homeostasis by deconvolution of insulin secretion, hepatic extraction, post-hepatic delivery, and sensitivity from 24-hour standardized meals test have been developed and illustrated by the study of glucose homeostasis of a genetically based leptin-deficient patient before and after leptin replacement treatment. The only genetically leptin-deficient adult man identified in the world was treated for 24 months with recombinant methionyl human leptin. Blood was collected every 7 minutes for 24 hours, with standardized meals consumed during the 4 visits: at baseline, one-week, 18-months, and 24-months after initiation of the treatment. Concentrations of insulin, C-peptide, and plasma glucose were measured. Insulin secretion was obtained by deconvolution of C-peptide data. Hepatic insulin extraction was determined based on our modifications of the insulin kinetics model . Insulin sensitivity for each of the four meals was calculated by using the minimal glucose model approach. Hepatic extraction of insulin was the first element of glucose homeostasis to respond to leptin replacement treatment and increased 2-fold after one week of treatment. Insulin secretion and delivery rates decreased more than 2-fold and insulin sensitivity increased 10-fold after 24 months of treatment. Computer programs for analysis of 24-hour insulin secretion, extraction, delivery, and action are available upon request.

Leptin Does Not Mediate Short-Term Fasting-Induced Changes in Growth Hormone Pulsatility but Increases IGF-I in Leptin Deficiency States

States of acute and chronic energy deficit are characterized by increased GH secretion and decreased IGF-I levels. The objective of the study was to determine whether changes in levels of leptin, a key mediator of the adaptation to starvation, regulate the GH-IGF system during energy deficit. We studied 14 healthy normal-weight men and women during three conditions: baseline fed and 72-h fasting (to induce hypoleptinemia) with administration of placebo or recombinant methionyl human leptin (r-metHuLeptin) (to reverse the fasting associated hypoleptinemia). We also studied eight normal-weight women with exercise-induced chronic energy deficit and hypothalamic amenorrhea at baseline and during 2-3 months of r-metHuLeptin treatment. GH pulsatility, IGF levels, IGF and GH binding protein (GHBP) levels were measured. During short-term energy deficit, measures of GH pulsatility and disorderliness and levels of IGF binding protein (IGFBP)-1 increased, whereas leptin, insulin, IGF-I (total and free), IGFBP-4, IGFBP-6, and GHBP decreased; r-metHuLeptin administration blunted the starvation-associated decrease of IGF-I. In chronic energy deficit, total and free IGF-I, IGFBP-6, and GHBP levels were lower, compared with euleptinemic controls; r-metHuLeptin administration had no major effect on GH pulsatility after 2 wk but increased total IGF-I levels and tended to increase free IGF-I and IGFBP-3 after 1 month. The GH/IGF system changes associated with energy deficit are largely independent of leptin deficiency. During acute energy deficit, r-metHuLeptin administration in replacement doses blunts the starvation-induced decrease of IGF-I, but during chronic energy deficit, r-metHuLeptin administration increases IGF-I and tends to increase free IGF-I and IGFBP-3.

Leptin Does Not Directly Regulate the Pancreatic Hormones Amylin and Pancreatic Polypeptide

Leptin and the pancreatic hormones amylin and pancreatic polypeptide are being evaluated alone or in combination for the treatment of obesity, but their physiological regulation has not yet been fully elucidated. Thus, we examined whether amylin and pancreatic polypeptide are regulated by caloric intake and/or short- and long-term energy deprivation and whether any potential regulation is mediated by changes in leptin levels. We measured circulating levels of amylin and pancreatic polypeptide after 1) a 75-g glucose load in 28 healthy, normal-weight women, 2) 72-h complete energy deficiency (severe hypoleptinemia) with administration of either placebo or replacement-dose recombinant methionyl human leptin (r-metHuLeptin) in normal-weight men (n = 6) and women (n = 7), and 3) chronic mild energy deficiency (mild hypoleptinemia) in 7 women with hypothalamic amenorrhea before and after r-metHuLeptin administration for 3 months. Amylin and pancreatic polypeptide levels increased 15 min after a 75-g glucose load and remained elevated at 60 and 120 min (P < 0.0001). Fasting for 72 h decreased leptin (to 21%) and amylin (to 67%) of baseline but not pancreatic polypeptide levels. Normalizing leptin levels with r-metHuLeptin did not alter the fasting-induced decrease in amylin and had no effect on pancreatic polypeptide levels. Neither amylin nor pancreatic polypeptide levels were different in leptin-deficient women with hypothalamic amenorrhea compared with weight-matched control subjects, and normalization of leptin levels with r-metHuLeptin treatment did not alter amylin or pancreatic polypeptide levels. Circulating amylin levels increase after a glucose load and decrease in response to short-term complete fasting, but these changes are not mediated by leptin.

Pharmacokinetics of Subcutaneous Recombinant Methionyl Human Leptin Administration in Healthy Subjects in the Fed and Fasting States

Recombinant methionyl human leptin (r-metHuLeptin) has demonstrated efficacy in improving hormonal and metabolic parameters in leptin-deficient states, and it has been suggested that leptin replacement may reverse metabolic adaptations during weight loss interventions. The pharmacokinetics of subcutaneously administered r-metHuLeptin have been recently published, but whether pharmacokinetic parameters are altered by short-term fasting, adiposity and/or gender has not yet been evaluated. The objective of this study was to characterize pharmacokinetic parameters following subcutaneous r-metHuLeptin administration at doses in the physiological to supra-physiological to pharmacological range in the fed state and during 3-day complete fasting in lean and obese subjects, including both men and women. We analysed pharmacokinetic profiles in five lean men, five obese men and five lean women following subcutaneous administration of physiological (0.01 mg/kg), supra-physiological (0.1 mg/kg) and pharmacological (0.3 mg/kg) doses of r-metHuLeptin given once in the fed state and once daily during 3-day complete caloric deprivation (fasting). With r-metHuLeptin administration at 0.01 mg/kg, leptin concentrations ranged up to approximately 7 ng/mL in lean men, approximately 20 ng/mL in obese men and approximately 30 ng/mL in lean women in the fed state. There was a significant effect of 3-day fasting: it decreased baseline leptin concentrations, peak serum concentration (C(max)) and area under the serum concentration-time curve from time zero to infinity (AUC(infinity)) [all p < 0.0001] and increased clearance (p < 0.001), most prominently in lean men (p < 0.0001 across the groups). Administration of r-metHuLeptin at 0.1 mg/kg resulted in leptin concentrations up to approximately 70 ng/mL in lean men, approximately 100 ng/mL in obese men and approximately 150 ng/mL in lean women in the fed state. At this dose, there was a similar effect of fasting on the pharmacokinetic parameters as well as a decrease in the terminal-phase elimination half-life (p = 0.02), consistent with increased clearance, but the effect of fasting was less pronounced overall than with the 0.01 mg/kg dose. With r-metHuLeptin administration at 0.3 mg/kg, leptin concentrations ranged up to approximately 150 ng/mL in lean men, approximately 300 ng/mL in obese men and approximately 400 ng/mL in lean women in the fed state. At this dose, fasting increased clearance to a lesser degree (p = 0.046), mainly in lean men, suggesting that the fasting-induced increase in leptin clearance by the kidneys can plateau. Within each group, the subjects lost approximately 3-4 kg of bodyweight after 3 days of fasting (all p < 0.0001), but the amount and time course of weight loss did not differ according to the dose of r-metHuLeptin administered or the circulating leptin concentrations achieved. Short-term fasting in healthy individuals results in increased clearance of leptin; this contributes to hypoleptinaemia, which may serve as a signal to increase energy intake in the setting of caloric restriction. Obese individuals with greater energy stores at baseline have a blunted response to the fasting-induced increase in leptin clearance. Also, women have a differential response to fasting, with primarily decreased leptin production rather than increased clearance. These findings and the resulting formulas for calculating doses for r-metHuLeptin administration have important implications for future therapeutic use of r-metHuLeptin in conjunction with hypocaloric diets for the treatment of obesity.