Novel peroxisome proliferator-activated receptor gamma mutation in a family with familial partial lipodystrophy type 3

Peroxisome proliferator-activated receptor gamma mutation in familial partial lipodystrophy type three: A case report and review of literature

BACKGROUND

Familial partial lipodystrophy disease (FPLD) is a collection of rare genetic diseases featuring partial loss of adipose tissue. However, metabolic difficulties, such as severe insulin resistance, diabetes, hypertriglyceridemia, and hypertension frequently occur alongside adipose tissue loss, making it susceptible to misdiagnosis and delaying effective treatment. Numerous genes are implicated in the occurrence of FPLD, and genetic testing has been for conditions linked to single gene mutation related to FPLD. Reviewing recent reports, treatment of the disease is limited to preventing and improving complications in patients.

CASE SUMMARY

In 2017, a 31-year-old woman with diabetes, hypertension and hypertriglyceridemia was hospitalized. We identified a mutation in her peroxisome proliferator-activated receptor gamma (PPARG) gene, Y151C (p.Tyr151Cys), which results in a nucleotide substitution residue 452 in the DNA-binding domain (DBD) of PPARG. The unaffected family member did not carry this mutation. Pioglitazone, a PPARG agonist, improved the patient's responsiveness to hypoglycemic and antihypertensive therapy. After one year of treatment in our hospital, the fasting blood glucose and glycosylated hemoglobin of the patient were close to normal.

CONCLUSION

We report a rare PPARG mutation, Y151C, which is located in the DBD of PPARG and leads to FPLD, and the preferred agent is PPARG agonists. We then summarized clinical phenotypic characteristics of FPLD3 caused by PPARG gene mutations, and clarified the relationship between different mutations of PPARG gene and the clinical manifestations of this type of FPLD. Additionally, current treatments for FPLD caused by PPARG mutations are reviewed.

Familial partial lipodystrophy resulting from loss-of-function PPARγ pathogenic variants: phenotypic, clinical, and genetic features

The PPARG gene encodes a member of a nuclear receptor superfamily known as peroxisome proliferator-activated gamma (PPARγ). PPARγ plays an essential role in adipogenesis, stimulating the differentiation of preadipocytes into adipocytes. Loss-of-function pathogenic variants in PPARG reduce the activity of the PPARγ receptor and can lead to severe metabolic consequences associated with familial partial lipodystrophy type 3 (FPLD3). This review focuses on recent scientific data related to FPLD3, including the role of PPARγ in adipose tissue metabolism and the phenotypic and clinical consequences of loss-of-function variants in the PPARG gene. The clinical features of 41 PPARG pathogenic variants associated with FPLD3 patients were reviewed, highlighting the genetic and clinical heterogeneity observed among 91 patients. Most of them were female, and the average age at the onset and diagnosis of lipoatrophy was 21 years and 33 years, respectively. Considering the metabolic profile, hypertriglyceridemia (91.9% of cases), diabetes (77%), hypertension (59.5%), polycystic ovary syndrome (58.2% of women), and metabolic-dysfunction-associated fatty liver disease (87,5%). We also discuss the current treatment for FPLD3. This review provides new data concerning the genetic and clinical heterogeneity in FPLD3 and highlights the importance of further understanding the genetics of this rare disease.

Hereditary severe insulin resistance syndrome: Pathogenesis, pathophysiology, and clinical management

Severe insulin resistance has been linked to some of the most globally prevalent disorders, such as diabetes mellitus, nonalcoholic fatty liver disease, polycystic ovarian syndrome, and hypertension. Hereditary severe insulin resistance syndrome (H-SIRS) is a rare disorder classified into four principal categories: primary insulin receptor defects, lipodystrophies, complex syndromes, and obesity-related H-SIRS. Genes such as INSR, AKT2, TBC1D4, AGPAT2, BSCL2, CAV1, PTRF, LMNA, PPARG, PLIN1, CIDEC, LIPE, PCYT1A, MC4R, LEP, POMC, SH2B1, RECQL2, RECQL3, ALMS1, PCNT, ZMPSTE24, PIK3R1, and POLD1 have been linked to H-SIRS. Its clinical features include insulin resistance, hyperglycemia, hyperandrogenism, severe dyslipidemia, fatty liver, abnormal topography of adipose tissue, and low serum leptin and adiponectin levels. Diagnosis of H-SIRS is based on the presence of typical clinical features associated with the various H-SIRS forms and the identification of mutations in H-SIRS-linked genes by genetic testing. Diet therapy, insulin sensitization, exogenous insulin therapy, and leptin replacement therapy have widely been adopted to manage H-SIRS. The rarity of H-SIRS, its highly variable clinical presentation, refusal to be tested for genetic mutations by patients' family members who are not severely sick, unavailability of genetic testing, and testing expenses contribute to the delayed or underdiagnoses of H-SIRS. Early diagnosis facilitates early management of the condition, which results in improved glycemic control and delayed onset of diabetes and other complications related to severe insulin resistance. The use of updated genetic sequencing technologies is recommended, and long-term studies are required for genotype-phenotype differentiation and formulation of diagnostic and treatment protocols.

Case Report: A New Peroxisome Proliferator-Activated Receptor Gamma Mutation Causes Familial Partial Lipodystrophy Type 3 in a Chinese Patient

PURPOSE

Familial partial lipodystrophy type 3 (FPLD3) is an autosomal dominant disease. Patients typically present with loss of adipose tissue and metabolic complications. Here, we reported a Chinese FPLD3 patient with a novel PPARG gene mutation.

METHODS

A 16-year-old female patient and her relatives were assessed by detailed clinical and biochemical examinations. Sequencing was performed by using the extracted DNA. Moreover, we identified FPLD3 patients from previous studies, and according to the protein region affected by the gene mutation. We divided the patients into the DNA-binding domain (DBD) group or the ligand-binding domain (LBD) group, and compared the clinical features between the two groups.

RESULTS

We identified a novel gene mutation affecting the LBD of PPARγ c.929T > C (p.F310S). This mutation leads to the substitution of a phenylalanine by a serine. In our case, subcutaneous fat was significantly diminished in her face, hips and limbs. The patient was also presented with insulin resistance, diabetes mellitus, hypertriglyceridemia, fatty liver, liver dysfunction, albuminuria and diabetic peripheral neuropathy. After literature review, a total of 58 FPLD3 patients were identified and we found no difference in clinical features between the DBD group and LBD group (all P > 0.05).

CONCLUSIONS

A Chinese FPLD3 patient with a novel PPARG gene mutation is described. Our case emphasized the importance of physical examination and genetic testing in young patients with severe metabolic syndromes.

Virtual screening of potentially endocrine-disrupting chemicals against nuclear receptors and its application to identify PPARγ-bound fatty acids

Nuclear receptors (NRs) are key regulators of energy homeostasis, body development, and sexual reproduction. Xenobiotics binding to NRs may disrupt natural hormonal systems and induce undesired adverse effects in the body. However, many chemicals of concerns have limited or no experimental data on their potential or lack-of-potential endocrine-disrupting effects. Here, we propose a virtual screening method based on molecular docking for predicting potential endocrine-disrupting chemicals (EDCs) that bind to NRs. For 12 NRs, we systematically analyzed how multiple crystal structures can be used to distinguish actives and inactives found in previous high-throughput experiments. Our method is based on (i) consensus docking scores from multiple structures at a single functional state (agonist-bound or antagonist-bound), (ii) multiple functional states (agonist-bound and antagonist-bound), and (iii) multiple pockets (orthosteric site and alternative sites) of these NRs. We found that the consensus enrichment from multiple structures is better than or comparable to the best enrichment from a single structure. The discriminating power of this consensus strategy was further enhanced by a chemical similarity-weighted scoring scheme, yielding better or comparable enrichment for all studied NRs. Applying this optimized method, we screened 252 fatty acids against peroxisome proliferator-activated receptor gamma (PPARγ) and successfully identified 3 previously unknown fatty acids with Kd = 100-250 μM including two furan fatty acids: furannonanoic acid (FNA) and furanundecanoic acid (FUA), and one cyclopropane fatty acid: phytomonic acid (PTA). These results suggested that the proposed method can be used to rapidly screen and prioritize potential EDCs for further experimental evaluations.

European lipodystrophy registry: background and structure

BACKGROUND

Lipodystrophy syndromes comprise a group of extremely rare and heterogeneous diseases characterized by a selective loss of adipose tissue in the absence of nutritional deprivation or catabolic state. Because of the rarity of each lipodystrophy subform, research in this area is difficult and international co-operation mandatory. Therefore, in 2016, the European Consortium of Lipodystrophies (ECLip) decided to create a registry for patients with lipodystrophy.

RESULTS

The registry was build using the information technology Open Source Registry System for Rare Diseases in the EU (OSSE), an open-source software and toolbox. Lipodystrophy specific data forms were developed based on current knowledge of typical signs and symptoms of lipodystrophy. The platform complies with the new General Data Protection Regulation (EU) 2016/679 by ensuring patient pseudonymization, informational separation of powers, secure data storage and security of communication, user authentication, person specific access to data, and recording of access granted to any data. Inclusion criteria are all patients with any form of lipodystrophy (with the exception of HIV-associated lipodystrophy). So far 246 patients from nine centres (Amsterdam, Bologna, Izmir, Leipzig, Münster, Moscow, Pisa, Santiago de Compostela, Ulm) have been recruited. With the help from the six centres on the brink of recruitment (Cambridge, Lille, Nicosia, Paris, Porto, Rome) this number is expected to double within the next one or 2 years.

CONCLUSIONS

A European registry for all patients with lipodystrophy will provide a platform for improved research in the area of lipodystrophy. All physicians from Europe and neighbouring countries caring for patients with lipodystrophy are invited to participate in the ECLip Registry.

STUDY REGISTRATION

ClinicalTrials.gov (NCT03553420). Registered 14 March 2018, retrospectively registered.

Is the Mouse a Good Model of Human PPARγ-Related Metabolic Diseases?

With the increasing number of patients affected with metabolic diseases such as type 2 diabetes, obesity, atherosclerosis and insulin resistance, academic researchers and pharmaceutical companies are eager to better understand metabolic syndrome and develop new drugs for its treatment. Many studies have focused on the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ), which plays a crucial role in adipogenesis and lipid metabolism. These studies have been able to connect this transcription factor to several human metabolic diseases. Due to obvious limitations concerning experimentation in humans, animal models—mainly mouse models—have been generated to investigate the role of PPARγ in different tissues. This review focuses on the metabolic features of human and mouse PPARγ-related diseases and the utility of the mouse as a model.

Efficacy and Safety of Metreleptin in Patients with Partial Lipodystrophy: Lessons from an Expanded Access Program

OBJECTIVE

Patients with lipodystrophy have severe metabolic abnormalities (insulin resistance, diabetes, and hypertriglyceridemia) that may increase morbidity and mortality. Metreleptin is approved by the United States Food and Drug Administration for treatment of generalized forms of lipodystrophy. We aimed to determine the efficacy and safety of metreleptin among patients with partial lipodystrophy using an expanded-access model.

METHODS

Study FHA101 (ClinicalTrials.gov identifier: NCT00677313) was an open-label, expanded-access, long-term clinical effectiveness and safety study in 23 patients with partial lipodystrophy and diabetes and/or hypertriglyceridemia with no prespecified leptin level. Metreleptin was administered subcutaneously at 0.02 mg/kg twice daily (BID) at Week 1, followed by 0.04 mg/kg BID at Week 2. Dose adjustments thereafter were based on patient response (maximum dose of 0.08 mg/kg BID). One-year changes in glycated hemoglobin (HbA1c), fasting plasma glucose, triglycerides, alanine and aspartate aminotransferases, and treatment-emergent adverse events (TEAEs) were evaluated.

RESULTS

HbA1c, fasting plasma glucose, and triglycerides were numerically decreased throughout 1 year, with mean (standard error) changes from baseline of -0.88 (0.62)%, -42.0 (22.4) mg/dL, and -119.8 (84.1) mg/dL, respectively, which were greater among patients with higher baseline abnormalities. Liver enzymes did not worsen, and the most frequently observed TEAEs (≥ 10% incidence) were mild to moderate and included nausea (39.1%), hypoglycemia (26.1%), and urinary tract infections (26.1%)-all reported previously. There were no reports of clinically significant immune-related adverse events or new safety signals.

CONCLUSIONS

Our clinical observations document the large heterogeneity and disease burden of partial lipodystrophy syndromes and suggest that metreleptin treatment benefits may extend to patients with partial lipodystrophy. Additional studies are needed to confirm these preliminary findings.