Consequences of stopping and restarting leptin in an adolescent with lipodystrophy

Lipodystrophies in non-insulin-dependent children: Treatment options and results from recombinant human leptin therapy

Lipodystrophy is a general definition containing different pathologies which, except for those observed in insulin-treated subjects falling outside the scope of this paper, are characterized by total or partial lack of body fat, that, according to the amount of missing adipose tissue, are divided in generalized or partial lipodystrophy. These diseases are characterized by leptin deficiency, which often leads to metabolic derangement, causing insulin resistance, dyslipidemia, and increasing cardiovascular risk. In this narrative review, we presentend the clinical presentation of different types of lipodystrophies and metabolic unbalances related to disease in children and adolescents, focusing on the main treatment options and the novel results from recombinant human leptin (metreleptin) therapy. Milestones in the management of lipodystrophy include lifestyle modification as diet and physical activity, paired with hypoglycemic drugs, insulin, hypolipidemic drugs, and other drugs with the aim of treating lipodystrophy complications. Metreleptin has been recently approved for pediatric patients with general lipodystrophy (GL)> 2 years of age and for children with partial lipodystrophy (PL)> 12 years of age not controlled with conventional therapies. New therapeutic strategies are currently being investigated, especially for patients with PL forms, specifically, liver-targeted therapies. Further studies are needed to achieve the most specific and precise treatment possible.

Treatment Options for Lipodystrophy in Children

Lipodystrophy includes a heterogeneous group of rare diseases characterized by different amounts of adipose tissue loss and several metabolic complications, including hypertriglyceridemia, steatohepatitis and particularly insulin resistance, that may lead to severe morbidity and, sometimes, mortality. Therefore, therapy for lipodystrophy primarily consists of a conventional approach that involves standard treatments of metabolic abnormalities. Given the evidence of leptin deficiency in lipodystrophy syndromes, leptin replacement therapy has been considered as a treatment option. Long-term studies on the use of therapy with a methionylated analog of human leptin, metreleptin, first on animals and subsequently on human patients, demonstrated enormous improvements of patients' clinical features and metabolic conditions. Recently, metreleptin was approved by Food and Drug Administration (FDA) for the treatment of generalized lipodystrophy and by European Medicines Agency (EMA) for the treatment of both generalized and partial lipodystrophy. However, further research is being conducted for new and different therapeutic agents, especially helpful for the treatment of patients with partial lipodystrophy, as some of them do not have access to metreleptin therapy or show poor response.

Metreleptin treatment of non-HIV lipodystrophy syndromes

Lipodystrophy syndromes (LS) constitute a group of rare diseases of the adipose tissue, characterized by a complete or selective deficiency of the fat mass. These disorders are associated with important insulin resistance, cardiovascular and metabolic comorbidities that impact patient's survival and quality of life. Management is challenging and includes diet, physical activity, and specific pharmacological treatment of LS-associated comorbidities. Because of a common pathophysiology involving decreased concentration of the adipokine leptin, efforts have been made to develop therapeutic strategies with leptin replacement therapy. Metreleptin, a recombinant human leptin analogue, has been proposed in hypoleptinemic patients since the beginning of 2000's. The treatment leads to an improvement in metabolic parameters, more important in generalized than in partial LS forms. In this review, the current knowledge about the development of the drug, its outcomes in the treatment of lipodystrophic patients as well as the peculiarities of its use will be presented.

Association between genetically determined leptin and blood lipids considering alcohol consumption: a Mendelian randomisation study

OBJECTIVES

The objective of this study was to evaluate the association of genetically determined leptin with lipids.

DESIGN

We conducted a Mendelian randomisation study to assess a potential causal relationship between serum leptin and lipid levels. We also evaluated whether alcohol drinking modified the associations of genetically determined leptin with blood lipids.

SETTING AND PARTICIPANTS

3860 participants of the Framingham Heart Study third generation cohort.

RESULTS

Both genetic risk scores (GRSs), the GRS generated using leptin loci independent of body mass index (BMI) and GRS generated using leptin loci dependent of BMI, were positively associated with log-transformed leptin (log-leptin). The BMI-independent leptin GRS was associated with log-transformed triglycerides (log-TG, β=-0.66, p=0.01), but not low-density lipoprotein cholesterol (LDL-C, p=0.99), high-density lipoprotein cholesterol (HDL-C, p=0.44) or total cholesterol (TC, p=0.49). Instrumental variable estimation showed that per unit increase in genetically determined log-leptin was associated with 0.55 (95% CI: 0.05 to 1.00) units decrease in log-TG. Besides significant association with log-TG (β=-0.59, p=0.009), the BMI-dependent GRS was nominally associated with HDL-C (β=-10.67, p=0.09) and TC (β=-28.05, p=0.08). When stratified by drinking status, the BMI-dependent GRS was associated with reduced levels of LDL-C (p=0.03), log-TG (p=0.004) and TC (p=0.003) among non-current drinkers only. Significant interactions between the BMI-dependent GRS and alcohol drinking were identified for LDL-C (p=0.03), log-TG (p=0.03) and TC (p=0.02).

CONCLUSION

These findings together indicated that genetically determined leptin was negatively associated with lipid levels and the association may be modified by alcohol consumption.

Fatty liver in lipodystrophy: A review with a focus on therapeutic perspectives of adiponectin and/or leptin replacement

Lipodystrophy is a group of clinically heterogeneous, inherited or acquired, disorders characterized by complete or partial absence of subcutaneous adipose tissue that may occur simultaneously with the pathological, ectopic, accumulation of fat in other regions of the body, including the liver. Fatty liver adds significantly to hepatic and extra-hepatic morbidity in patients with lipodystrophy. Lipodystrophy is strongly associated with severe insulin resistance and related comorbidities, such as hyperglycemia, hyperlipidemia and nonalcoholic fatty liver disease (NAFLD), but other hepatic diseases may co-exist in some types of lipodystrophy, including autoimmune hepatitis in acquired lipodystrophies, or viral hepatitis in human immunodeficiency virus (HIV)-associated lipodystrophy. The aim of this review is to summarize evidence linking lipodystrophy with hepatic disease and to provide a special focus on potential therapeutic perspectives of leptin replacement therapy and adiponectin upregulation in lipodystrophy.

Long-term effectiveness and safety of metreleptin in the treatment of patients with partial lipodystrophy

PURPOSE

To evaluate the effects of metreleptin in patients with partial lipodystrophy (PL).

METHODS

Patients aged ≥ 6 months with PL, circulating leptin < 12.0 ng/mL, and diabetes mellitus, insulin resistance, or hypertriglyceridemia received metreleptin doses (once or twice daily) titrated to a mean of 0.124 mg/kg/day. Changes from baseline to month 12 in glycated hemoglobin (HbA1c) and fasting serum triglycerides (TGs; co-primary endpoints), fasting plasma glucose (FPG), and liver volume were evaluated. Additional assessments included the proportions of patients achieving target decreases in HbA1c or fasting TGs at month 12, long-term treatment effects, and treatment-emergent adverse events (TEAEs).

RESULTS

Significant (p < 0.05) reductions in HbA1c (-0.6%), fasting TGs (-20.8%), FPG (-1.2 mmol/L), and liver volume (-13.4%) were observed in the overall PL population at month 12. In a subgroup of patients with baseline HbA1c ≥ 6.5% or TGs ≥ 5.65 mmol/L, significant (p < 0.05) reductions were seen in HbA1c (-0.9%), fasting TGs (-37.4%), FPG (-1.9 mmol/L), and liver volume (-12.4%). In this subgroup, 67.9% of patients had a ≥ 1% decrease in HbA1c or ≥ 30% decrease in fasting TGs, and 42.9% had a ≥ 2% decrease in HbA1c or ≥ 40% decrease in fasting TGs. Long-term treatment in this subgroup led to significant (p < 0.05) reductions at months 12, 24, and 36 in HbA1c, fasting TGs, and FPG. Metreleptin was well tolerated with no unexpected safety signals. The most common TEAEs were abdominal pain, hypoglycemia, and nausea.

CONCLUSIONS

In patients with PL, treatment with metreleptin was well tolerated and resulted in improvements in glycemic control, hypertriglyceridemia, and liver volume.

Pathogenesis of NASH: The Impact of Multiple Pathways

Purpose of review

Advancing our understanding of the mechanisms that underlie NASH pathogenesis.

Recent findings

Recent findings on NASH pathogenesis have expanded our understanding of its complexity including: (1) there are multiple parallel hits that lead to NASH; (2) the microbiota play an important role in pathogenesis, with bacterial species recently shown to accurately differentiate between NAFL and NASH patients; (3) the main drivers of liver cell injury are lipotoxicity caused by free fatty acids (FFAs) and their derivatives combined with mitochondrial dysfunction; (4) decreased endoplasmic reticulum (ER) efficiency with increased demand for protein synthesis/folding/repair results in ER stress, protracted unfolded protein response, and apoptosis; (5) upregulated proteins involved in multiple pathways including JNK, CHOP, PERK, BH3-only proteins, and caspases result in mitochondrial dysfunction and apoptosis; and (6) subtypes of NASH in which these pathophysiological pathways vary may require patient subtype identification to choose effective therapy.

Summary

Recent pathogenesis studies may lead to important therapeutic advances, already seen in patients treated with ACC, ASK1 and SCD1 inhibitors and FXR agonists. Further advancing our understanding of mechanisms underlying NASH pathogenesis and the complex interplay between them will be crucial for developing effective therapies.

Update on Therapeutic Options in Lipodystrophy

PURPOSE OF REVIEW

The purpose of this review is to summarize the therapeutic approach for lipodystrophy syndromes with conventional treatment options and metreleptin therapy in detail and to point out the current investigational treatments in development.

RECENT FINDINGS

The observation of leptin deficiency in patients with lipodystrophy and the potential of leptin replacement to rescue metabolic abnormalities in animal models of lipodystrophy were followed by the first clinical study of leptin therapy in patients with severe lipodystrophy. This and several other long-term studies demonstrated important benefits of recombinant human leptin (metreleptin) to treat metabolic abnormalities of lipodystrophy. These studies ultimately led to the recent FDA approval of metreleptin for the treatment of generalized lipodystrophy and EMA approval for both generalized and partial lipodystrophy. Additional research efforts in progress focus on novel treatment options, predominantly for patients with partial lipodystrophy. Current treatment of generalized lipodystrophy includes metreleptin replacement as an adjunct to diet and standard treatment approach for metabolic consequences of lipodystrophy. Beyond metreleptin, a number of different compounds and treatment modalities are being studied for the treatment of partial lipodystrophy.

Long-term effectiveness and safety of metreleptin in the treatment of patients with generalized lipodystrophy

PURPOSE

The purpose of this study is to summarize the effectiveness and safety of metreleptin in patients with congenital or acquired generalized lipodystrophy.

METHODS

Patients (n = 66) aged ≥6 months had lipodystrophy, low circulating leptin, and ≥1 metabolic abnormality (diabetes mellitus, insulin resistance, or hypertriglyceridemia). Metreleptin dose (once or twice daily) was titrated to a mean dose of 0.10 mg/kg/day with a maximum of 0.24 mg/kg/day. Means and changes from baseline to month 12 were assessed for glycated hemoglobin (HbA1c), fasting triglycerides (TGs), and fasting plasma glucose (FPG). Additional assessments included the proportions of patients achieving target decreases in HbA1c or fasting TGs at months 4, 12, and 36, medication changes, and estimates of liver size. Treatment-emergent adverse events (TEAEs) were recorded.

RESULTS

Significant mean reductions from baseline were seen at month 12 for HbA1c (-2.2%, n = 59) and FPG (-3.0 mmol/L, n = 59) and mean percent change in fasting TGs (-32.1%, n = 57) (all p ≤ 0.001). Reductions from baseline over time in these parameters were also significant at month 36 (all p < 0.001, n = 14). At month 4, 34.8% of patients had a ≥1% reduction in HbA1c and 62.5% had a ≥30% reduction in fasting TGs; at month 12, 80% of patients had a ≥1% decrease in HbA1c or ≥30% decrease in TGs, and 66% had a decrease of ≥2% in HbA1c or ≥40% decrease in TGs. Of those on medications, 41%, 22%, and 24% discontinued insulin, oral antidiabetic medications, or lipid-lowering medications, respectively. Mean decrease in liver volume at month 12 was 33.8% (p < 0.001, n = 12). Most TEAEs were of mild/moderate severity.

CONCLUSIONS

In patients with generalized lipodystrophy, long-term treatment with metreleptin was well tolerated and resulted in sustained improvements in hypertriglyceridemia, glycemic control, and liver volume.

Effects of Metreleptin in Pediatric Patients With Lipodystrophy

CONTEXT

Lipodystrophy syndromes are rare disorders of deficient adipose tissue. Metreleptin, a human analog of leptin, improved metabolic abnormalities in mixed cohorts of children and adults with lipodystrophy and low leptin.

OBJECTIVE

Determine effects of metreleptin on diabetes, hyperlipidemia, nonalcoholic fatty liver disease (NAFLD), growth, and puberty in pediatric patients with lipodystrophy and low leptin.

DESIGN

Prospective, single-arm, open-label studies with continuous enrollment since 2000.

SETTING

National Institutes of Health, Bethesda, Maryland.

PATIENTS

Fifty-three patients aged 6 months to <18 years with lipodystrophy, leptin level <8 ng/mL (male patients) or <12 ng/mL (female patients), and ≥1 metabolic abnormality (diabetes, insulin resistance, or hypertriglyceridemia).

INTERVENTION

Subcutaneous metreleptin injections (0.04 to 0.19 mg/kg/d).

MAIN OUTCOME MEASURES

Change in A1c, lipid, and transaminase levels after a mean ± standard deviation (SD) of 12 ± 0.2 months and 61 ± 39 months. Changes in liver histology, growth, and pubertal development throughout treatment.

RESULTS

After 12 months, the A1c level (mean ± SD) decreased from 8.3% ± 2.4% to 6.5% ± 1.8%, and median triglyceride level decreased from 374 mg/dL [geometric mean (25th,75th percentile), 190, 1065] to 189 mg/dL (112, 334; P < 0.0001), despite decreased glucose- and lipid-lowering medications. The median [geometric mean (25th,75th percentile)] alanine aminotransferase level decreased from 73 U/L (45, 126) to 41 U/L (25, 59; P = 0.001), and that of aspartate aminotransferase decreased from 51 U/L (29, 90) to 26 U/L (18, 42; P = 0.0002). These improvements were maintained over long-term treatment. In 17 patients who underwent paired biopsies, the NAFLD activity score (mean ± SD) decreased from 4.5 ± 2.0 to 3.4 ± 2.0 after 3.3 ± 3.2 years of metreleptin therapy (P = 0.03). There were no clinically significant changes in growth or puberty.

CONCLUSION

Metreleptin lowered A1c and triglyceride levels, and improved biomarkers of NAFLD in pediatric patients with lipodystrophy. These improvements are likely to reduce the lifetime burden of disease.

A Report of Three Cases With Acquired Generalized Lipodystrophy With Distinct Autoimmune Conditions Treated With Metreleptin

CONTEXT

Acquired generalized lipodystrophy (AGL) is associated with leptin deficiency as a result of adipose tissue loss and hypertriglyceridemia, insulin resistance, and hepatic steatosis. It may coexist with other autoimmune diseases such as Hashimoto's thyroiditis, rheumatoid arthritis, hemolytic anemia, and chronic active hepatitis. Metreleptin therapy has been shown to improve metabolic abnormalities in lipodystrophy, but the effect on AGL patients with active autoimmune disease is unknown.

CASE DESCRIPTION

We report 3 cases of pediatric patients with AGL and distinct active autoimmune diseases who were treated with metreleptin over a period of 4-6 years. Case 1 is a 9-year-old girl with active juvenile dermatomyositis, who was successfully treated with leptin with no worsening of her dermatomoysitis. Case 2 is a 16-year-old female with Graves' disease, who could discontinue all her antidiabetic medication completely with improved triglyceride levels. Case 3 is an 11-year-old boy with active autoimmune hepatitis and chronic urticaria, whose hyperphagia has resolved and his liver enzymes and hepatosplenomegaly have improved.

CONCLUSION

Metreleptin therapy is of considerable clinical benefit to reduce insulin resistance and hypertriglyceridemia and did not appear to alter the clinical course of autoimmune disease nor clinical efficacy of immunosuppressive treatments. Our observations suggest that risk or presence of autoimmune disease should not lead to withholding of metreleptin treatment from patients with AGL, but should prompt close clinical follow up in light of cautionary preclinical data.

Leptin in nonalcoholic fatty liver disease: a narrative review

Leptin, the first described adipokine, interplays with hepatic metabolism. The aim of this review was to summarize available data on the association between leptin and nonalcoholic fatty liver disease (NAFLD). Leptin has a potential dual action on NAFLD experimental models, exerting a possible anti-steatotic, but also a proinflammatory and profibrogenic action. Observational clinical studies have shown higher or similar leptin levels between simple steatosis and nonalcoholic steatohepatitis (NASH) compared with controls. Interventional studies showed that circulating leptin diminishes together with body mass index after successful weight loss following lifestyle modifications or bariatric surgery. Studies providing evidence for the effect of other medications on leptin levels in NAFLD populations are limited and of low power. Data from small studies claim that recombinant leptin administration had a possibly beneficial effect on steatosis, but not fibrosis, in NAFLD patients with hypoleptinemia. Although the aforementioned dual leptin action has not yet been validated in humans, leptin administration in NAFLD patients with normoleptinemia or hyperleptinemia is discouraged. Further well-controlled studies in cautiously selected populations are needed to elucidate whether leptin has any prognostic and therapeutic role in NAFLD patients.

Leptin replacement therapy for the treatment of non-HAART associated lipodystrophy syndromes: a meta-analysis into the effects of leptin on metabolic and hepatic endpoints

The clinical manifestations of lipodystrophy syndromes (LS) are hypoleptinemia, hyperglycemia, insulin resistance, dyslipidemia and hepatic steatosis. Leptin replacement therapy (LRT) is effective at improving these pathologies. Currently, there are no data compiling the evidence from the literature, and demonstrating the effect of LRT in LS patients. A systematic review of the MEDLINE and Cochrane Library databases was conducted to identify studies assessing the effect of LRT on metabolic and hepatic endpoints in patients with LS not associated with highly active antiretroviral therapy (HAART) use. Standardized mean differences (SMD) and 95% confidence intervals of pooled results were calculated for overall changes in glucose homeostasis, lipid profile, and hepatic physiology, using an inverse-variance random-effects model. After screening, 12 studies were included for review. Meta-analysis of results from 226 patients showed that LRT decreased fasting glucose [0.75 SMD units (range 0.36‐1.13), p=0.0001], HbA1c [0.49 (0.17‐0.81), p=0.003], triglycerides [1.00 (0.69‐1.31), p<0.00001], total cholesterol [0.62 (0.21‐1.02), p=0.003], liver volume [1.06 (0.51‐1.61), p=0.0002] and AST [0.41 (0.10‐0.73) p=0.01]. In patients with non-HAART LS, LRT improves the outcome of several metabolic and hepatic parameters. Studies were limited by small populations and therefore large prospective trials are needed to validate these findings.

20 years of leptin: leptin and reproduction: past milestones, present undertakings, and future endeavors

The association between leptin and reproduction originated with the leptin-mediated correction of sterility in ob/ob mice and initiation of reproductive function in normal female mice. The uncovering of a central leptin pathway regulating food intake prompted the dissection of neuroendocrine mechanisms involving leptin in the metabolic control of reproduction. The absence of leptin receptors on GnRH neurons incited a search for intermediary neurons situated between leptin-responsive and GnRH neurons. This review addresses the most significant findings that have furthered our understanding of recent progress in this new field. The role of leptin in puberty was impacted by the discovery of neurons that co-express kisspeptin, neurokinin B, and dynorphin and these could act as leptin intermediates. Furthermore, the identification of first-order leptin-responsive neurons in the premammilary ventral nucleus and other brain regions opens new avenues to explore their relationship to GnRH neurons. Central to these advances is the unveiling that agouti-related protein/neuropeptide Y neurons project onto GnRH and kisspeptin neurons, allowing for a crosstalk between food intake and reproduction. Finally, while puberty is a state of leptin sensitivity, mid-gestation represents a state of leptin resistance aimed at building energy stores to sustain pregnancy and lactation. The mechanisms underlying leptin resistance in pregnancy have lagged; however, the establishment of this natural state is significant. Reproduction and energy balance are tightly controlled and backed up by redundant mechanisms that are critical for the survival of our species. It will be the goal of the following decade to shed new light on these complex and essential pathways.

Metreleptin for metabolic disorders associated with generalized or partial lipodystrophy

Lipodystrophy is a group of acquired and inherited disorders characterized by selective loss of adipose tissue. Despite wide genotypic and phenotypic variety, many patients with lipodystrophy have similar metabolic complications including insulin resistance, diabetes mellitus, hypertriglyceridemia and hepatic steatosis. Often, these metabolic abnormalities are severe and difficult to treat with conventional glucose and lipid-lowering therapies. Lack of adipose tissue also results in marked hypoleptinemia, and there has recently been much interest in using leptin-replacement therapy to treat the metabolic complications of lipodystrophy. Administration of metreleptin, the human recombinant leptin analogue, has been shown in prospective, open-label studies to improve glucose control, dyslipidemia and steatohepatitis. This article summarizes the current evidence for the safety and efficacy of leptin-replacement therapy in patients with lipodystrophy.

Direct and indirect effects of leptin on adipocyte metabolism

Leptin is hypothesized to function as a negative feedback signal in the regulation of energy balance. It is produced primarily by adipose tissue and circulating concentrations correlate with the size of body fat stores. Administration of exogenous leptin to normal weight, leptin responsive animals inhibits food intake and reduces the size of body fat stores whereas mice that are deficient in either leptin or functional leptin receptors are hyperphagic and obese, consistent with a role for leptin in the control of body weight. This review discusses the effect of leptin on adipocyte metabolism. Because adipocytes express leptin receptors there is the potential for leptin to influence adipocyte metabolism directly. Adipocytes also are insulin responsive and receive sympathetic innervation, therefore leptin can also modify adipocyte metabolism indirectly. Studies published to date suggest that direct activation of adipocyte leptin receptors has little effect on cell metabolism in vivo, but that leptin modifies adipocyte sensitivity to insulin to inhibit lipid accumulation. In vivo administration of leptin leads to a suppression of lipogenesis, an increase in triglyceride hydrolysis and an increase in fatty acid and glucose oxidation. Activation of central leptin receptors also contributes to the development of a catabolic state in adipocytes, but this may vary between different fat depots. Leptin reduces the size of white fat depots by inhibiting cell proliferation both through induction of inhibitory circulating factors and by contributing to sympathetic tone which suppresses adipocyte proliferation. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.