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A Single Complex Agpat2 Allele in a Patient With Partial Lipodystrophy.

ABSTRACT: Genetic lipodystrophies are a group of rare syndromes associated with major metabolic complications - including severe insulin resistance, type 2 diabetes mellitus, and hypertriglyceridemia - which are classified according to the distribution of adipose tissue. Lipodystrophies can be present at birth or develop during life and can range from local to partial and general. With at least 18 different genes implicated so far, definite diagnosis can be challenging due to clinical and genetic heterogeneity. In an adult female patient with clinical and metabolic features of partial lipodystrophy we identified via whole genome sequencing (WGS) a single complex AGPAT2 allele [V67M;V167A], functionally equivalent to heterozygosity. AGPAT2 encodes for an acyltransferase implicated in the biosynthesis of triacylglycerol and glycerophospholipids. So far homozygous and compound heterozygous mutations in AGPAT2 have only been associated with generalized lipodystrophy. A SNP risk score analysis indicated that the index patient is not predisposed to lipodystrophy based on her genetic background. The partial phenotype in our patient is therefore more likely associated to the genetic variants in AGPAT2. To test whether the resulting double-mutant AGPAT2 protein is functional we analyzed its in vitro enzymatic activity via mass spectrometry. The resulting AGPAT2 double mutant is enzymatically inactive. Our data support the view that the current classification of lipodystrophies as strictly local, partial or generalized may have to be re-evaluated and viewed more as a continuum, both in terms of clinical presentation and underlying genetic causes. Better molecular understanding of lipodystrophies may lead to new therapies to treat adipose tissue dysfunction in common and rare diseases.

SUBMITTER: Broekema MF

PROVIDER: S-EPMC6168662 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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A Single Complex <i>Agpat2</i> Allele in a Patient With Partial Lipodystrophy.

Broekema Marjoleine F MF Massink Maarten P G MPG De Ligt Joep J Stigter Edwin C A ECA Monajemi Houshang H De Ridder Jeroen J Burgering Boudewijn M T BMT van Haaften Gijs W GW Kalkhoven Eric E

Frontiers in physiology 20180926

Genetic lipodystrophies are a group of rare syndromes associated with major metabolic complications - including severe insulin resistance, type 2 diabetes mellitus, and hypertriglyceridemia - which are classified according to the distribution of adipose tissue. Lipodystrophies can be present at birth or develop during life and can range from local to partial and general. With at least 18 different genes implicated so far, definite diagnosis can be challenging due to clinical and genetic heteroge ...[more]

PMID: 30319454

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Project description:Abstract Background: Congenital generalized lipodystrophy (CGL) is a rare inherited disease characterized by widespread loss of subcutaneous fat and severe metabolic abnormalities. Metreleptin, a synthetic analog of leptin, is a treatment modality that has been shown to decrease fasting triglycerides, fasting glucose, and HbA1c. Metformin use in infants has only been described in a few case reports of CGL and Donohue syndrome (insulin receptor mutation), and there is no established dosing for this age group. We report metreleptin, insulin, and metformin use in an infant with type 1 CGL who presented with marked hypertriglyceridemia, hypoleptinemia, hyperglycemia, and transaminitis. Clinical Case: A 2-month-old African American female born SGA at term presented to her primary care physician for a well child check where she was noted to have poor weight gain, hyperphagia, and abdominal distension. She was subsequently admitted for failure to thrive with weight z-score of -2.17 and length z-score of -0.15. Initial labs were notable for triglycerides of 5,167 mg/dL, HDL 10 mg/dL, blood glucose 324 mg/dL, ALT 212 units/L, AST 215 units/L, and bicarbonate of 17 mmol/L. A random insulin level was elevated at 257 mcIU/mL. Adiponectin was undetectable and leptin was low at 0.3 ng/mL. Hemoglobin A1c was in diabetes mellitus range at 8.9%. She was started on detemir 1.0 units/kg/day on day 1 (titrated to a maximum dose of 4.4 units/kg/day) and metformin 50 mg/kg/day on day 3 of hospitalization. By day 4, triglycerides decreased to 758 mg/dL, AST to 119 units/L and ALT to 124 units/L. Pre-prandial glucoses improved ranging from 113 to 138 mg/dL. As her insurance denied coverage for detemir, she was discharged home on glargine 0.7 units/kg/day and metformin suspension. One month later, she was started on subcutaneous metreleptin, and glargine was discontinued. At 5 months of age, she had triglycerides 229 mg/dl, normal liver enzymes, and normal blood glucoses while on 0.056 mg/kg/day of subcutaneous metreleptin and metformin. Medications were well tolerated without side effects. She had improved growth and met all developmental milestones. Genetic evaluation revealed that she was homozygous for a pathogenic variant, c.589-2A>G; p.Gln196fs*228 (rs116807569), in the AGPAT2 gene. Conclusion: Leptin is important in regulation of lipid and glucose metabolism, and patients with CGL are deficient due to lack of adipose tissue. Metabolic abnormalities, including stabilization of glucoses and improved hypertriglyceridemia, in our patient markedly improved with initiation of metreleptin, metformin, and insulin. We present successful dosing of these treatment modalities without adverse reactions in an infant with CGL.

Project description:ObjectivesLMNA variants have been previously associated with cardiac abnormalities independent of lipodystrophy. We aimed to assess cardiac impact of familial partial lipodystrophy (FPLD) to understand the role of laminopathy in cardiac manifestations.Study designRetrospective cohort study.MethodsClinical data from 122 patients (age range: 13-77, 101 females) with FPLD were analysed. Mature human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) from a patient with an LMNA variant were studied as proof-of-concept for future studies.ResultsSubjects with LMNA variants had a higher prevalence of overall cardiac events than others. The likelihood of having an arrhythmia was significantly higher in patients with LMNA variants (OR: 3.77, 95% CI: 1.45-9.83). These patients were at higher risk for atrial fibrillation or flutter (OR: 5.78, 95% CI: 1.04-32.16). The time to the first arrhythmia was significantly shorter in the LMNA group, with a higher HR of 3.52 (95% CI: 1.34-9.27). Non-codon 482 LMNA variants were more likely to be associated with cardiac events (vs. 482 LMNA: OR: 4.74, 95% CI: 1.41-15.98 for arrhythmia; OR: 17.67, 95% CI: 2.45-127.68 for atrial fibrillation or flutter; OR: 5.71, 95% CI: 1.37-23.76 for conduction disease). LMNA mutant hiPSC-CMs showed a higher frequency of spontaneous activity and shorter action potential duration. Functional syncytia of hiPSC-CMs displayed several rhythm alterations such as early afterdepolarizations, spontaneous quiescence and spontaneous tachyarrhythmia, and significantly slower recovery in chronotropic changes induced by isoproterenol exposure.ConclusionsOur results highlight the need for vigilant cardiac monitoring in FPLD, especially in patients with LMNA variants who have an increased risk of developing cardiac arrhythmias. In addition, hiPSC-CMs can be studied to understand the basic mechanisms for the arrhythmias in patients with lipodystrophy to understand the impact of specific mutations.

Dataset Information

A Single Complex Agpat2 Allele in a Patient With Partial Lipodystrophy.

Publications

A Single Complex <i>Agpat2</i> Allele in a Patient With Partial Lipodystrophy.

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