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Context Leptin is an adipokine that signals energy sufficiency. In rodents, leptin deficiency decreases energy expenditure (EE), which is corrected following leptin replacement. In humans, data are mixed regarding leptin-mediated effects on EE. Objective To determine the effects of metreleptin on EE in patients with lipodystrophy. Design, setting, and patients Nonrandomized crossover study of 25 patients with lipodystrophy (National Institutes of Health, 2013-2018). Intervention The initiation cohort consisted of 17 patients without prior exposure to metreleptin, studied before and after 14 days of metreleptin. The withdrawal cohort consisted of 8 previously metreleptin-treated patients, studied before and after 14 days of metreleptin withdrawal. Main outcomes 24-h total energy expenditure (TEE), resting energy expenditure (REE), autonomic nervous system activity [heart rate variability (HrV)], plasma-free triiodothyronine (T3), free thyroxine (T4), epinephrine, norepinephrine, and dopamine. Results In the initiation cohort, TEE and REE decreased by 5.0% (121 ± 152 kcal/day; P = 0.006) and 5.9% (120 ± 175 kcal/day; P = 0.02). Free T3 increased by 19.4% (40 ± 49 pg/dL; P = 0.01). No changes in catecholamines or HrV were observed. In the withdrawal cohort, free T3 decreased by 8.0% (P = 0.04), free T4 decreased by 11.9% (P = 0.002), and norepinephrine decreased by 34.2% (P = 0.03), but no changes in EE, epinephrine, dopamine, or HrV were observed. Conclusions Metreleptin initiation decreased EE in patients with lipodystrophy, but no changes were observed after metreleptin withdrawal. Thyroid hormone was higher on metreleptin in both initiation and withdrawal cohorts. Decreased EE after metreleptin in lipodystrophy may result from reductions in energy-requiring metabolic processes that counteract increases in EE via adipose tissue-specific neuroendocrine and adrenergic signaling.

Leptin is an adipokine that signals energy sufficiency. In rodents, leptin deficiency is associated with decreased body temperature and energy expenditure (EE), which is reversed with leptin replacement. Leptin’s role in EE in humans is unclear; however, one study of 10% weight-reduced healthy subjects suggested that leptin replacement to pre-weight loss levels restored the decline in EE, thyroid hormone, and catecholamines associated with weight loss. Patients with lipodystrophy (LD) are characterized by deficiency of adipose tissue and can serve as models to study effects of leptin deficiency and replacement in humans. We hypothesized that treatment with recombinant leptin (metreleptin) in patients with LD would increase EE, thyroid hormone, and catecholamines. We conducted a non-randomized crossover study of 25 patients with LD who were hospitalized for 19 days on an iso-caloric diet. The initiation cohort consisted of 17 patients with no prior exposure to metreleptin, who were first studied for 5 days without metreleptin (period 1), then were treated with metreleptin for 14 days (period 2). The withdrawal cohort consisted of 8 previously metreleptin-treated patients who were continued on metreleptin for the first 5 days of the study (period 1), then were taken off metreleptin for 14 days (period 2). At the end of each period, we measured 24-hour EE (TEE) and resting EE (REE) using indirect calorimetry and free T3, T4, epinephrine, norepinephrine and dopamine after an 8–12 hour fast. In the leptin initiation cohort, TEE and REE decreased from 2402±383 kcal/day and 1805±332 kcal/day to 2272±396 kcal/day (p=0.003) and 1688±318 kcal/day (p=0.03), respectively. Free T3 increased from median (IQR) 248 (200, 270) pg/mL to 295 (259, 315) (p=0.006). No changes in catecholamines were observed in the initiation cohort. In the withdrawal cohort, free T3 decreased from 295 (267, 331) pg/mL to 265 (237, 323) (p=0.008), free T4 decreased from 1.2 ±0.2 ng/dL to 1.0±0.2 (p=0.002), and norepinephrine decreased from 191±70 pg/mL to 112±47 (p=0.03) after metreleptin withdrawal. No changes in EE, epinephrine or dopamine were observed in the withdrawal cohort. Contrary to previous studies in rodents and healthy humans, we found that introduction of metreleptin reduced EE in patients with LD. Consistent with rodent and prior human data, patients with LD had increased thyroid hormone on metreleptin, which would be expected to increase EE. The discrepancy in EE compared to other models may be due to metreleptin-induced correction of severe metabolic derangements in LD, including reduction in energy-requiring processes such as de novo lipogenesis and gluconeogenesis. These changes may offset increases in leptin-induced mediators of increased EE, such as thyroid hormone.

In the era of newborn screening (NBS) for severe combined immunodeficiency (SCID) and the possibility of gene therapy (GT), it is important to link SCID phenotype to the underlying genetic disease. In western countries, X-linked interleukin 2 receptor gamma chain (IL2RG) and adenosine deaminase (ADA) deficiency SCID are two of the most common types of SCID and can be treated by GT. As a challenge, both IL2RG and ADA genes are highly polymorphic and a gene–based diagnosis may be difficult if the variant is of unknown significance or if it is located in non-coding areas of the genes that are not routinely evaluated with exon-based genetic testing (e.g., introns, promoters, and the 5′and 3′ untranslated regions). Therefore, it is important to extend evaluation to non-coding areas of a SCID gene if the exon-based sequencing is inconclusive and there is strong suspicion that a variant in that gene is the cause for disease. Functional studies are often required in these cases to confirm a pathogenic variant. We present here two unique examples of X-linked SCID with variable immune phenotypes, where IL2R gamma chain expression was detected and no pathogenic variant was identified on initial genetic testing. Pathogenic IL2RG variants were subsequently confirmed by functional assay of gamma chain signaling and maternal X-inactivation studies. We propose that such tests can facilitate confirmation of suspected cases of X-linked SCID in newborns when initial genetic testing is inconclusive. Early identification of pathogenic IL2RG variants is especially important to ensure eligibility for gene therapy.

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.Determine effects of metreleptin on diabetes, hyperlipidemia, nonalcoholic fatty liver disease (NAFLD), growth, and puberty in pediatric patients with lipodystrophy and low leptin.Prospective, single-arm, open-label studies with continuous enrollment since 2000.National Institutes of Health, Bethesda, Maryland.Fifty-three patients aged 6 months to18 years with lipodystrophy, leptin level8 ng/mL (male patients) or12 ng/mL (female patients), and ≥1 metabolic abnormality (diabetes, insulin resistance, or hypertriglyceridemia).Subcutaneous metreleptin injections (0.04 to 0.19 mg/kg/d).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.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; P0.0001), 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.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.

The lipodystrophies represent a class of diseases characterized by leptin deficiency. Leptin deficiency is associated with a severe form of the metabolic syndrome characterized by dyslipidemia, insulin resistance, diabetes, and ovarian dysfunction. Metreleptin is the pharmaceutical derived product that has been approved by the Food and Drug Administration (FDA) to treat the severe metabolic abnormalities of the generalized forms of lipodystrophy. Herein we describe the properties of metreleptin, its use in patients, which includes the administration of the drug and how it may be acquired by medical professionals as well as its safety, tolerability, and properties. Finally, we speculate on future uses and development of metreleptin.

Objective: The purpose of this study is to increase awareness and improve diagnosis of primary immune deficiency (PID) in the heterogenous group of patients with autoimmune cytopenia (AIC) by identifying clinical characteristics and laboratory biomarkers that distinguish PID patients from patients with AIC alone. This is especially relevant in genetically-defined PIDs which may be resistant to conventional therapy and mechanism-based treatment approach is required. Evans syndrome, defined by multi-lineage autoantibodies (two or more positive anti-platelet, anti-neutrophil, or direct Coombs test) is a known risk factor for PID; therefore we also investigate the incidence of PID in a broad cohort of AIC patients with single and multi-lineage cytopenias. Methods: Patients with autoimmune cytopenias (autoimmune hemolytic anemia (AIHA), immune thrombocytopenia (ITP), or autoimmune neutropenia (AIN)) were referred to our Immune Dysregulation clinical team and prospectively enrolled in the study period of 2016-2019. Detailed immune phenotyping (IgG, IgA, IgM, lymphocyte subsets, vaccine titers, lymphocyte proliferation to mitogens/antigens), serum lipopolysaccharide (LPS) and autoantibodies were measured and/or collected by chart review and genetic testing for PID was pursued. Results: From 2016 to 2019, 78 patients were enrolled to our study. The patients were predominantly children (ages 1-82 years, average age 16.82 years). Of 78 patients with AIC, 48 (61%) were diagnosed with underlying PID based on immune phenotyping and/or genetic testing. Of 39 patients with genetic testing to date, 19 (49%) have been diagnosed with genetically-defined PID (pathogenic variants in CTLA-4, NFKB1, ALPS-related genes, WAS, POLE-1, PI3K, CYBB, or 22q11 [partial DiGeorge syndrome]); the remainder were classified as combined immune deficiency or common variable immune deficiency based on immune phenotyping; an additional two patients were classified as ALPS based on clinical history/flow cytometry/family history of ALPS. Lymphocyte subsets (CD4+ T, CD8+ T, CD19+ B, CD56+ NK) and immune globulins (IgG, IgA, IgM) tended to be lower in AIC-PID patients vs AIC-only (p Conclusions: An unexpectedly high fraction of patients with AIC were identified with underlying PID in our Immune Dysregulation program. Routine basic immune evaluation with immunoglobulin levels and lymphocyte subsets expedited diagnosis of PID. Genetic evaluation distinguished a group of patients with AIC-PID and highly elevated LPS level, reflecting high bacterial load, and this may distinguish them from the rest of patients with AIC. The source of bacterial LPS can be multifactorial and is yet to be determined. Our studies continue focusing on biomarkers that can be applied to the heterogenous group of patients with AIC. This will allow early detection and timely initiation of targeted therapies. Disclosures No relevant conflicts of interest to declare.

Obesity is associated with increased blood pressure (BP), which in turn increases the risk of cardiovascular diseases. We found that the increase in leptin levels seen in diet-induced obesity (DIO) drives an increase in BP in rodents, an effect that was not seen in animals deficient in leptin or leptin receptors (LepR). Furthermore, humans with loss-of-function mutations in leptin and the LepR have low BP despite severe obesity. Leptin's effects on BP are mediated by neuronal circuits in the dorsomedial hypothalamus (DMH), as blocking leptin with a specific antibody, antagonist, or inhibition of the activity of LepR-expressing neurons in the DMH caused a rapid reduction of BP in DIO mice, independent of changes in weight. Re-expression of LepRs in the DMH of DIO LepR-deficient mice caused an increase in BP. These studies demonstrate that leptin couples changes in weight to changes in BP in mammalian species.

Type 2 diabetes (T2D) affects ∼10% of the US population, a subset of whom have severe insulin resistance (SIR) (>200 units/d). Treatment of these patients with high-dose insulin presents logistical and compliance challenges. We hypothesized that mild caloric restriction would reduce insulin requirements in patients with T2D and SIR. This was a retrospective study at the National Institutes of Health Clinical Center. Inclusion criteria were as follows: T2D, and insulin dose >200 units/d or >2 units/kg/d. The intervention consisted of mild caloric restriction during a 3 to 6-day hospitalization. The major outcomes were change in insulin dose and blood glucose from admission to discharge. Ten patients met inclusion criteria. Baseline glycated hemoglobin A1c was 10.0 ± 1.6% and body mass index 38.8 ± 9.0 kg/m2. Food intake was restricted from 2210 ± 371 kcal/d preadmission to 1810 ± 202 during the hospital stay (16.5% reduction). Insulin dose decreased from 486 ± 291 units/d preadmission to 223 ± 127 at discharge (44% reduction, P = 0.0025). Blood sugars decreased nonsignificantly in the fasting state (from 184 ± 85 to 141 ± 42, P = 0.20), before lunch (239 ± 68 to 180 ± 76, P = 0.057), and at bedtime (212 ± 95 to 176 ± 48, P = 0.19), and significantly decreased before dinner (222 ± 92 to 162 ± 70, P = 0.016). Mild caloric restriction, an accessible and affordable intervention, substantially reduced insulin doses in patients with T2D and SIR. Further studies are needed to determine if the intervention and results are sustainable outside of a hospital setting.