A novel brain-penetrant oral UGT8 inhibitor decreases in vivo galactosphingolipid biosynthesis in murine Krabbe disease

Neuroimmunology in globoid cell leukodystrophy: A comprehensive review including treatments, models, and neuroimmune mechanisms underlying neuropathology

Globoid cell leukodystrophy (GLD), or Krabbe's disease, is a fatal genetic demyelinating disease of the central nervous system (CNS) caused by loss-of-function mutations in galactosylceramidase (GALC). As a result of the loss of GALC enzymatic activity, there is an accumulation of a toxic lipid called galactosylsphingosine, or psychosine. Current treatments have focused on restoring GALC function as a means to reduce psychosine accumulation, which show promise, however, still have limited success at improving behavioral or cognitive deficits in infants with GLD. Recent studies have discovered a role for T cells in GLD, indicating that there is a previously understudied role for the adaptive immune system as a contributing factor to GLD pathophysiology. This review aims to provide a comprehensive discussion of the current field of GLD research including treatment advances and GLD pathophysiology, with a focus on the role of neuroimmunological mechanisms contributing to GLD.

Long-chain sulfatide enrichment is an actionable metabolic vulnerability in intraductal papillary mucinous neoplasm (IPMN)-associated pancreatic cancers

BACKGROUND

We conducted an integrated cross-species spatial assessment of transcriptomic and metabolomic alterations associated with progression of intraductal papillary mucinous neoplasms (IPMNs), which are bona fide cystic precursors of pancreatic ductal adenocarcinoma (PDAC).

OBJECTIVE

We aimed to uncover biochemical and molecular drivers that underlie malignant progression of IPMNs to PDAC.

DESIGN

Matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry (MS)-based spatial imaging and Visium spatial transcriptomics (ST) was performed on human resected IPMN/PDAC tissues (n=23) as well as pancreata from a mutant Kras;Gnas mouse model of IPMN/PDAC. Functional studies in murine IPMN/PDAC-derived Kras;Gnas cells were performed using CRISPR/cas9 technology, small interfering RNAs, and pharmacological inhibition.

RESULTS

MALDI-MS analyses of patient tissues revealed long-chain hydroxylated sulfatides to be selectively enriched in the neoplastic epithelium of IPMN/PDAC. Integrated ST analyses showed cognate transcripts involved in sulfatide biosynthesis, including UGT8, Gal3St1, and FA2H, to co-localise with areas of sulfatide enrichment. Genetic knockout or pharmacological inhibition of UGT8 in Kras;Gnas IPMN/PDAC cells decreased protein expression of FA2H and Gal3ST1 with consequent alterations in mitochondrial morphology and reduced mitochondrial respiration. Small molecule inhibition of UGT8 elicited anticancer effects via ceramide-mediated compensatory mitophagy and activation of intrinsic apoptosis pathways. In vivo, UGT8 inhibition suppressed tumour growth in allograft models of murine IPMN/PDAC cells derived from Kras;Gnas and Kras;Tp53;Gnas mice.

CONCLUSION

Our work identifies enhanced sulfatide metabolism as an early metabolic alteration in cystic precancerous lesions of the pancreas that persists through invasive neoplasia and a potential actionable vulnerability in IPMN-derived PDAC.

Role of Galactosylceramide Metabolism in Satellite Glial Cell Dysfunction and Neuron-Glia Interactions in Painful Diabetic Peripheral Neuropathy

Diabetic peripheral neuropathy (DPN) is a prevalent and disabling complication of diabetes, with painful diabetic peripheral neuropathy (PDPN) being its most severe subtype due to chronic pain and resistance to treatment. Satellite glial cells (SGCs), critical for maintaining dorsal root ganglion (DRG) homeostasis, undergo significant structural and functional changes under pathological conditions. This study investigated the role of galactosylceramide (GalCer), a key sphingolipid, in SGC dysfunction and neuron-glia interactions during DPN progression. Using a rat model of PDPN, we employed single-cell RNA sequencing (scRNA-seq), targeted mass spectrometry, and immunofluorescence analysis. The PDPN group exhibited transcriptional activation and structural reorganization of SGCs, characterized by increased SGC abundance and glial activation, evidenced by elevated Gfap expression. Functional enrichment analyses revealed disruptions in sphingolipid metabolism, including marked reductions in GalCer levels. Subclustering identified vulnerable SGC subsets, such as Cluster a, with dysregulated lipid metabolism. The depletion of GalCer impaired SGC-neuron communication, destabilizing DRG homeostasis and amplifying neurodegeneration and neuropathic pain. These findings demonstrate that GalCer depletion is a central mediator of SGC dysfunction in PDPN, disrupting neuron-glia interactions and exacerbating neuropathic pain. This study provides novel insights into the molecular mechanisms of DPN progression and identifies GalCer metabolism as a potential therapeutic target.

The glial UDP-glycosyltransferase Ugt35b regulates longevity by maintaining lipid homeostasis in Drosophila

Lipid droplets (LDs) are dynamic organelles essential for lipid storage and organismal survival. Studies have highlighted the importance of glial function in brain LD formation during aging; however, the genes and mechanisms involved remain elusive. Here, we found that Ugt35b, a member of the uridine diphosphate (UDP)-glycosyltransferases that catalyze the transfer of glycosyl groups to acceptors, is highly expressed in glia and crucial for Drosophila lifespan. By integrating multiomics data, we demonstrated that glial Ugt35b plays key roles in regulating glycerolipid and glycerophospholipid metabolism in the brain. Notably, we found that Ugt35b and Lsd-2 are co-expressed in glia and confirmed their protein interaction in vivo. Knockdown of Ugt35b significantly reduced LD formation by downregulating Lsd-2 expression, while overexpression of Lsd-2 partially rescued the shortened lifespan in glial Ugt35b RNAi flies. Our findings reveal the crucial role of glial Ugt35b in regulating LD formation to maintain brain lipid homeostasis and support Drosophila lifespan.

From pathological mechanisms in Krabbe disease to cutting-edge therapy: A comprehensive review

Since its initial documentation by Knud Krabbe in 1916, numerous studies have scrutinized the characteristics of Krabbe disease (KD) until the identification of the mutation in the GALC gene. In alignment with that, we investigated the natural history of KD spanning eight decades to gain a deeper understanding of the evolutionary trajectory of its mechanisms. Through our comprehensive analysis, we unearthed additional novel elements in molecular biology involving the micropathological mechanism of the disease. This review offers an updated perspective on the metabolic disorder that defines KD. Recently, extracellular vesicles (EVs), autophagy impairment, and α-synuclein have emerged as pivotal players in the neuropathological processes. EVs might serve as a cellular mechanism to avoid or alleviate the detrimental impacts of excessive toxic psychosine levels, and extracting EVs could contribute to synapse dysfunction. Autophagy impairment was found to be independent of psychosine and reliant on AKT and B-cell lymphoma 2. Additionally, α-synuclein has been recognized for inducing cellular death and dysfunction in common biological pathways. Our objective is to assess the effectiveness of advanced therapies in addressing this particular condition. While hematopoietic stem cells have been a primary treatment, its administration proves challenging, particularly in the presymptomatic phase. In this review, we have compiled information from over 10 therapy trials, comparing them based on their benefits and disadvantage.

Globoid Cell Leukodystrophy (Krabbe Disease): An Update

Globoid cell leukodystrophy or Krabbe is a disease that affects children as well as adults who have mutations in the gene encoding the enzyme galactosylceramidase/galctocerebrosidase (GALC), resulting in the deposition of the toxic lipid D-galactosyl-beta1-1' sphingosine (GalSph or psychosine). Several therapeutic modalities were used to treat patients with Krabbe disease, including hematopoietic stem cell transplantation, enzyme replacement therapy, autophagy activators, intravenous immunoglobulin, and inhibitors of the Pyroptosis process, among many other approaches. In this article, I will briefly discuss the disease in both human and animal model, describe recent clinical observations as well as methods utilizing genetic analysis for diagnosis, and finally review recent advances in treating this rare and devastating disease.

The development of a broad-spectrum retaining β-exo-galactosidase activity-based probe

Acid β-galactosidase (GLB1) and galactocerebrosidase (GALC) are retaining exo-β-galactosidases involved in lysosomal glycoconjugate metabolism. Deficiency of GLB1 may result in the lysosomal storage disorders GM1 gangliosidosis, Morquio B syndrome, and galactosialidosis, and deficiency of GALC may result in Krabbe disease. Activity-based protein profiling (ABPP) is a powerful technique to assess the activity of retaining glycosidases in relation to health and disease. This work describes the use of fluorescent and biotin-carrying activity-based probes (ABPs) to assess the activity of both GLB1 and GALC in cell lysates, culture media, and tissue extracts. The reported ABPs, which complement the growing list of retaining glycosidase ABPs based on configurational isomers of cyclophellitol, should assist in fundamental and clinical research on various β-galactosidases, whose inherited deficiencies cause debilitating lysosomal storage disorders.

The Uridine diphosphate (UDP)-glycosyltransferases (UGTs) superfamily: the role in tumor cell metabolism

UDP-glycosyltransferases (UGTs), important enzymes in biotransformation, control the levels and distribution of numerous endogenous signaling molecules and the metabolism of a wide range of endogenous and exogenous chemicals. The UGT superfamily in mammals consists of the UGT1, UGT2, UGT3, and UGT8 families. UGTs are rate-limiting enzymes in the glucuronate pathway, and in tumors, they are either overexpressed or underexpressed. Alterations in their metabolism can affect gluconeogenesis and lipid metabolism pathways, leading to alterations in tumor cell metabolism, which affect cancer development and prognosis. Glucuronidation is the most common mammalian conjugation pathway. Most of its reactions are mainly catalyzed by UGT1A, UGT2A and UGT2B. The body excretes UGT-bound small lipophilic molecules through the bile, urine, or feces. UGTs conjugate a variety of tiny lipophilic molecules to sugars, such as galactose, xylose, acetylglucosamine, glucuronic acid, and glucose, thereby inactivating and making water-soluble substrates, such as carcinogens, medicines, steroids, lipids, fatty acids, and bile acids. This review summarizes the roles of members of the four UGT enzyme families in tumor function, metabolism, and multiple regulatory mechanisms, and its Inhibitors and inducers. The function of UGTs in lipid metabolism, drug metabolism, and hormone metabolism in tumor cells are among the most important topics covered.

Human iPSC-derived astrocytes generated from donors with globoid cell leukodystrophy display phenotypes associated with disease

Globoid cell leukodystrophy (Krabbe disease) is a fatal neurodegenerative, demyelinating disease caused by dysfunctional activity of galactosylceramidase (GALC), leading to the accumulation of glycosphingolipids including psychosine. While oligodendrocytes have been extensively studied due to their high levels of GALC, the contribution of astrocytes to disease pathogenesis remains to be fully elucidated. In the current study, we generated induced pluripotent stem cells (iPSCs) from two donors with infantile onset Krabbe disease and differentiated them into cultures of astrocytes. Krabbe astrocytes recapitulated many key findings observed in humans and rodent models of the disease, including the accumulation of psychosine and elevated expression of the pro-inflammatory cytokine IL-6. Unexpectedly, Krabbe astrocytes had higher levels of glucosylceramide and ceramide, and displayed compensatory changes in genes encoding glycosphingolipid biosynthetic enzymes, suggesting a shunting away from the galactosylceramide and psychosine pathway. In co-culture, Krabbe astrocytes negatively impacted the survival of iPSC-derived human neurons while enhancing survival of iPSC-derived human microglia. Substrate reduction approaches targeting either glucosylceramide synthase or serine palmitoyltransferase to reduce the sphingolipids elevated in Krabbe astrocytes failed to rescue their detrimental impact on neuron survival. Our results suggest that astrocytes may contribute to the progression of Krabbe disease and warrant further exploration into their role as therapeutic targets.