Biogenesis and Function of Peroxisomes in Human Disease with a Focus on the ABC Transporter

Mimicomes: Mimicking Multienzyme System by Artificial Design

Enzymes are widely distributed in organelles of cells, which are capable of carrying out specific catalytic reactions. In general, several enzymes collaborate to facilitate complex reactions and engage in vital biochemical processes within cells, which are also called cascade systems. The cascade systems are highly efficient, and their dysfunction is associated with a multitude of endogenous diseases. The advent of nanotechnology makes it possible to mimic these cascade systems in nature and realize partial functions of natural biological processes both in vitro and in vivo. To emphasize the significance of artificial cascade systems, mimicomes is first proposed, a new concept that refers to the artificial cascade catalytic systems. Typically, mimicomes are able to mimic specific natural biochemical catalytic processes or facilitate the overall catalytic efficiency of cascade systems. Subsequently, the evolution and development of different types of mimicomes in recent decades are elucidated exhaustedly, from the natural enzyme-based mimicomes (immobilized enzyme and vesicle mimicomes) to the nanozyme-based mimicomes and enzyme-nanozyme hybrid mimicomes. In conclusion, the remaining challenges in the design of multifunctional mimicomes and their potential applications are summarized, offering insights into their future prospects.

GTPBP2 in-frame deletion in canine model with non-syndromic progressive retinal atrophy

Progressive retinal atrophy (PRA), caused by aberrant functioning of rod/cone photoreceptors, leads to blindness affecting mammals, including dogs. We identified a litter of three Labrador retrievers affected by non-syndromic PRA; the parents and three other siblings were unaffected. Homozygosity mapping and whole-genome sequencing detected a homozygous 3-bp deletion in the coding region of GTPBP2, located in CFA12 (NC_049233.1:12,264,348_12,264,350del, c.1606_1608del, p.Ala536del). The variant was absent from the online European Variation Archive (EVA) database, the Dog Biomedical Variants Database Consortium, and the Dog10k database. We tested 91 non-affected dogs from the same kennel and found 75 wild-type (WT) and 16 carriers, all clinically normal, and 569 Labradors from the general population (USA), all WT. GTPBP2 is associated with Jaberi-Elahi syndrome (JES) in Homo sapiens, and splice variants in Mus musculus are associated with neurodegeneration; in both cases photoreceptor degeneration may be included in its manifestation. Heterologous cellular systems were transfected with cDNA encoding WT or A536del mutant GTPBP2 protein and immunoblot analysis of total cell lysate with anti-GTPBP2 antibodies showed that the expression level of the GTPBP2 mutant protein A536del is slightly but not significantly reduced compared to WT. Immunofluorescent methods and confocal analysis of cells transfected with WT or A536del GTPBP2 protein revealed that the WT form is diffuse throughout the cytosol, while the mutant form resulted in the formation of cytoplasmic aggregates in ~70-80% of cells. The deleted amino acid falls within a conserved interval outside the GTP domain of GTPBP2, suggesting a potentially novel role of the sequence on cellular localization of the protein.

From gene to therapy: a review of deciphering the role of ABCD1 in combating X-Linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (X-ALD) is a severe genetic disorder caused by ABCD1 mutations, resulting in the buildup of very-long-chain fatty acids, leading to significant neurological decline and adrenal insufficiency. Despite advancements in understanding the mechanisms of X-ALD, its pathophysiology remains incompletely understood, complicating the development of effective treatments. This review provides a comprehensive overview of X-ALD, with a focus on the genetic and biochemical roles of ABCD1 and the impacts of its mutations. Current therapeutic approaches are evaluated, discussing their limitations, and emphasizing the need to fully elucidate the pathogenesis of X-ALD. Additionally, this review highlights the importance of international collaboration to enhance systematic data collection and advance biomarker discovery, ultimately improving patient outcomes with X-ALD.

Application of PPAR Ligands and Nanoparticle Technology in Metabolic Steatohepatitis Treatment

Metabolic dysfunction-associated steatotic liver disease/steatohepatitis (MASLD/MASH) is a major disease worldwide whose effective treatment is challenging. Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear receptor superfamily and function as ligand-activated transcription factors. To date, three distinct subtypes of PPARs have been characterized: PPARα, PPARβ/δ, and PPARγ. PPARα and PPARγ are crucial regulators of lipid metabolism that modulate the transcription of genes involved in fatty acid (FA), bile acid, and cholesterol metabolism. Many PPAR agonists, including natural (FAs, eicosanoids, and phospholipids) and synthetic (fibrate, thiazolidinedione, glitazar, and elafibranor) agonists, have been developed. Furthermore, recent advancements in nanoparticles (NPs) have led to the development of new strategies for MASLD/MASH therapy. This review discusses the applications of specific cell-targeted NPs and highlights the potential of PPARα- and PPARγ-targeted NP drug delivery systems for MASLD/MASH treatment.

Frameshift Variant in AMPD2 in Cirneco dell'Etna Dogs with Retinopathy and Tremors

While the manifestations of many inherited retinal disorders are limited to loss of vision, others are part of a syndrome that affects multiple tissues, particularly the nervous system. Most syndromic retinal disorders are thought to be recessively inherited. Two dogs out of a litter of Cirneco dell' Etna dogs, both males, showed signs of retinal degeneration, along with tremors and signs described as either atypical seizures or paroxysmal dyskinesias, while the other two male littermates were normal. We named this oculo-neurological syndrome CONS (Cirneco oculo-neurological syndrome), and undertook homozygosity mapping and whole-genome sequencing to determine its potential genetic etiology. Notably, we detected a 1-bp deletion in chromosome 6 that was predicted to cause a frameshift and premature stop codon within the canine AMPD2 gene, which encodes adenosine monophosphate deaminase, an enzyme that converts adenosine 5'-monophosphate (AMP) to inosine 5'-monophosphate (IMP). Genotyping of the available Cirneco population suggested perfect segregation between cases and controls for the variant. Moreover, this variant was absent in canine genomic databases comprised of thousands of unaffected dogs. The AMPD2 genetic variant we identified in dogs presents with retinal manifestations, adding to the spectrum of neurological manifestations associated with AMPD2 variants in humans.

Recent research on inherited metabolic diseases in children

With the improvement in the research level and the diagnosis and treatment technology of inherited metabolic diseases (IMD), the research on pediatric IMD in China has made great progress, but there is still some distance from the international level. Due to the vast territory of China and the uneven distribution of medical resources, the regional characteristics of IMD remain unclear in China, and there are many problems and difficulties in early diagnosis and treatment. Therefore, it is necessary to improve the understanding of pediatric IMD among pediatricians, so as to improve the diagnosis and treatment level, achieve an early identification, diagnosis, and treatment of pediatric IMD, and effectively reduce the fatality and disability rates of children with IMD. This article reviews the research progress of IMD in children in China, and analyzes the features of representative IMDs. Citation:Chinese Journal of Contemporary Pediatrics, 2022, 24(3): 326-331.

Uncurtaining the pivotal role of ABC transporters in diabetes mellitus

The metabolic disorders are the edge points for the initiation of various diseases. These disorders comprised of several diseases including diabetes, obesity, and cardiovascular complications. Worldwide, the prevalence of these disorders is increasing day by day. The world's population is at higher threat of developing metabolic disease, especially diabetes. Therefore, there is an impregnable necessity of searching for a newer therapeutic target to reduce the burden of these disorders. Diabetes mellitus (DM) is marked with the dysregulated insulin secretion and resistance. The lipid and glucose transporters portray a pivotal role in the metabolism and transport of both of these. The excess production of lipid and glucose and decreased clearance of these leads to the emergence of DM. The ATP-binding cassette transporters (ABCT) are important for the metabolism of glucose and lipid. Various studies suggest the key involvement of ABCT in the pathologic process of different diseases. In addition, the involvement of other pathways, including IGF signaling, P13-Akt/PKC/MAPK signaling, and GLP-1 via regulation of ABCT, may help develop new treatment strategies to cope with insulin resistance dysregulated glucose metabolism, key features in DM.

Syndromic Inherited Retinal Diseases: Genetic, Clinical and Diagnostic Aspects

Inherited retinal diseases (IRDs), which are among the most common genetic diseases in humans, define a clinically and genetically heterogeneous group of disorders. Over 80 forms of syndromic IRDs have been described. Approximately 200 genes are associated with these syndromes. The majority of syndromic IRDs are recessively inherited and rare. Many, although not all, syndromic IRDs can be classified into one of two major disease groups: inborn errors of metabolism and ciliopathies. Besides the retina, the systems and organs most commonly involved in syndromic IRDs are the central nervous system, ophthalmic extra-retinal tissues, ear, skeleton, kidney and the cardiovascular system. Due to the high degree of phenotypic variability and phenotypic overlap found in syndromic IRDs, correct diagnosis based on phenotypic features alone may be challenging and sometimes misleading. Therefore, genetic testing has become the benchmark for the diagnosis and management of patients with these conditions, as it complements the clinical findings and facilitates an accurate clinical diagnosis and treatment.

Peroxisomal Cofactor Transport

Peroxisomes are eukaryotic organelles that are essential for growth and development. They are highly metabolically active and house many biochemical reactions, including lipid metabolism and synthesis of signaling molecules. Most of these metabolic pathways are shared with other compartments, such as Endoplasmic reticulum (ER), mitochondria, and plastids. Peroxisomes, in common with all other cellular organelles are dependent on a wide range of cofactors, such as adenosine 5′-triphosphate (ATP), Coenzyme A (CoA), and nicotinamide adenine dinucleotide (NAD). The availability of the peroxisomal cofactor pool controls peroxisome function. The levels of these cofactors available for peroxisomal metabolism is determined by the balance between synthesis, import, export, binding, and degradation. Since the final steps of cofactor synthesis are thought to be located in the cytosol, cofactors must be imported into peroxisomes. This review gives an overview about our current knowledge of the permeability of the peroxisomal membrane with the focus on ATP, CoA, and NAD. Several members of the mitochondrial carrier family are located in peroxisomes, catalyzing the transfer of these organic cofactors across the peroxisomal membrane. Most of the functions of these peroxisomal cofactor transporters are known from studies in yeast, humans, and plants. Parallels and differences between the transporters in the different organisms are discussed here.

Mapping the Associations of the Plasma Lipidome With Insulin Resistance and Response to an Oral Glucose Tolerance Test

CONTEXT

Insulin resistance (IR) remains a global health challenge. Lipidomics offers an opportunity to identify biomarkers and better understand mechanisms of IR associated with abnormal lipid metabolism.

OBJECTIVE

The objective of this article is to determine plasma lipid species associated with indices of IR and evaluate the lipidome response to an oral glucose tolerance test (OGTT).

DESIGN AND SETTING

This study was community based and cross-sectional.

PARTICIPANTS AND SAMPLE

Plasma samples (collected at 0 and 120 min during an OGTT) from nonobese, young adults age 18 to 34 years (n = 246) were analyzed using liquid chromatography-tandem mass spectrometry.

MAIN OUTCOME MEASURES

The associations between indices of IR and lipid classes and species (with a sex interaction term), or changes in lipid levels during an OGTT, were tested using linear models (adjusted for age, sex, body mass index, total cholesterol, high-density lipoprotein cholesterol, and triglycerides).

RESULTS

Some (213) and (199) lipid species were associated with the homeostatic model assessment of insulin resistance and insulin area under curve (AUC), respectively. Alkylphosphatidylcholine (10), alkenylphosphatidylcholine (23), and alkylphosphatidylethanolamine (6) species were associated with insulin AUC in men only. Species of phosphatidylcholine (7) and sphingomyelin (5) were associated in women only. In response to an OGTT, a perturbation in the plasma lipidome, particularly in acylcarnitine species, was observed; and the changes in many lipid species were associated with insulin AUC.

CONCLUSIONS

The plasma lipidome and changes in lipid levels during an OGTT were associated with indices of IR. These findings underlie the involvement of molecular lipid species in the pathogenesis of IR and possibly crosstalk between IR and sex-specific regulation of lipid metabolism.

Staying in Healthy Contact: How Peroxisomes Interact with Other Cell Organelles

Peroxisomes share extensive metabolic connections with other cell organelles. Membrane contact sites (MCSs) establish and maintain such interactions, and they are vital for organelle positioning and motility. In the past few years peroxisome interactions and MCSs with other cellular organelles have been explored extensively, resulting in the identification of new MCSs, the tethering molecules involved, and their functional characterization. Defective tethering and compartmental communication can lead to pathological conditions that can be termed 'organelle interaction diseases'. We review peroxisome-organelle interactions in mammals and summarize the most recent knowledge of mammalian peroxisomal organelle contacts in health and disease.