SCP2 variant is associated with alterations in lipid metabolism, brainstem neurodegeneration, and testicular defects

Microglial ER stress response via IRE1α regulates diet-induced metabolic imbalance and obesity in mice

BACKGROUND

Chronic high-fat diet (HFD) feeding triggers hypothalamic inflammation and systemic metabolic dysfunction associated with endoplasmic reticulum (ER) stress. Glial cells, specifically microglia and astrocytes, are central mediators of hypothalamic inflammation. However, the role of Inositol-Requiring Enzyme 1α (IRE1α), a primary ER stress sensor, in glial cells and its contributions to metabolic dysfunction remains elusive.

OBJECTIVES

To investigate the role of IRE1α in microglia in mediating HFD-induced metabolic dysfunction.

METHODS

Using novel conditional knockout mouse models (CX3CR1GFPΔIRE1 and TMEM119ERΔIRE1), we deleted IRE1α in immune cells or exclusively in microglia and studied its impact on metabolic health and hypothalamic transcriptional changes in mice fed with HFD for 16 weeks.

RESULTS

Deleting IRE1α in microglia significantly reduced LPS-induced pro-inflammatory cytokine gene expression in vitro. IRE1α deletion in microglia protected male mice from HFD-induced obesity, glucose intolerance, and hypothalamic inflammation, with no metabolic benefits observed in female mice. RNA-sequencing revealed significant transcriptional reprogramming of the hypothalamus, including upregulation of genes related to mitochondrial fatty acid oxidation, metabolic adaptability, and anti-inflammatory responses.

CONCLUSIONS

Our findings reveal that IRE1α-mediated ER stress response in microglia significantly contributes to hypothalamic inflammation and systemic metabolic dysfunction in response to HFD, particularly in males, demonstrating an important role of microglial ER stress response in diet-induced obesity and metabolic diseases.

Atgl-Dependent Adipocyte Lipolysis Promotes Lipodystrophy and Restrains Fibrogenic Responses during Skin Fibrosis

During skin fibrosis, extracellular matrix proteins are overproduced, and resident lipid-filled mature dermal adipocytes are depleted in both human disease and mouse models. However, the mechanisms underlying this reduction in lipid-filled adipocytes during fibrosis are poorly understood. In this study, we found that adipocyte lipolysis through the rate-limiting enzyme Atgl is required for loss of adipose tissue during skin fibrosis in mice. We found that in 2 fibrotic mouse models, adipocyte lipolysis occurred early during skin fibrosis development, and lipid storage was re-established during fibrosis recovery. In mice lacking Atgl in adipocytes, maintenance of adipocyte lipid storage occurs in both chemical and genetic models of fibrosis development. Transcriptional analysis revealed the upregulation of lipid metabolism/lipolysis genes in the skin of patients with fibrosis. Interestingly, the loss of adipocyte Atgl-driven lipolysis resulted in precocious fibrotic remodeling of the dermal extracellular matrix in bleomycin-treated mice, as indicated by histological and transcriptional changes. These data suggest that dermal adipocyte-derived fatty acids prevent fibrotic extracellular matrix remodeling in fibroblasts during the development of fibrosis. Thus, we suggest that dermal adipocyte-derived fatty acids are released during fibrosis development and delay fibroblast fibrogenic responses, which may hold therapeutic potential for treating fibrotic diseases.

Lipid Oxidation at the Crossroads: Oxidative Stress and Neurodegeneration Explored in Caenorhabditis elegans

Lipid metabolism plays a critical role in maintaining cellular integrity, especially within the nervous system, where lipids support neuronal structure, function, and synaptic plasticity. However, this essential metabolic pathway is highly susceptible to oxidative stress, which can lead to lipid peroxidation, a damaging process induced by reactive oxygen species. Lipid peroxidation generates by-products that disrupt many cellular functions, with a strong impact on proteostasis. In this review, we explore the role of lipid oxidation in protein folding and its associated pathological implications, with a particular focus on findings in neurodegeneration from Caenorhabditis elegans studies, an animal model that remains underutilized. Additionally, we highlight the effectiveness of different methodologies applied in this nematode to deepen our understanding of this intricate process. In the nervous system of any animal, including mammals and invertebrates, lipid oxidation can disturb the delicate balance of cellular homeostasis, leading to oxidative stress, the build-up of toxic by-products, and protein misfolding, key factors in neurodegenerative diseases. This disruption contributes to the pathogenesis of neurodegenerative disorders such as Alzheimer's, Parkinson's, or Huntington's disease. The findings from Caenorhabditis elegans studies offer valuable insights into these complex processes and highlight potential avenues for developing targeted therapies to mitigate neurodegenerative disease progression.

In ovo delivery of oregano essential oil activated xenobiotic detoxification and lipid metabolism at hatch in broiler chickens

In ovo interventions are used to improve embryonic development and robustness of chicks. The objective of this study was to identify the optimal dose for in ovo delivery of oregano essential oil (OEO), and to investigate metabolic impacts. Broiler chickens Ross 308 fertile eggs were injected with 7 levels of OEO (0, 5, 10, 20, 30, 40, and 50 µL) into the amniotic fluid at embryonic d 17.5 (E17.5) (n = 48). Chick quality was measured by navel score (P < 0.05) and/or hatchability rates (P < 0.01) were significantly decreased at doses at or above 10 or 20 µL/egg, respectively, indicating potential toxicity. However, no effects were observed at the 5 µL/egg, suggesting that compensatory mechanisms were effective to maintain homeostasis in the developing embryo. To pursue a better understanding of these mechanisms, transcriptomic analyses of the jejunum were performed comparing the control injected with saline and the group injected with 5 µL of OEO. The transcriptomic analyses identified that 167 genes were upregulated and 90 were downregulated in the 5 µL OEO compared to the control group injected with saline (P < 0.01). Functional analyses of the differentially expressed genes (DEG) showed that metabolic pathways related to the epoxygenase cytochrome P450 pathway associated with xenobiotic catabolic processes were significantly upregulated (P < 0.05). In addition, long-chain fatty acid metabolism associated with ATP binding transporters was also upregulated in the OEO treated group (P < 0.05). The results indicated that low doses of OEO in ovo have the potential to increase lipid metabolism in late stages (E17.5) of embryonic development. In conclusion, in ovo delivery of 5 µL OEO did not show any negative impact on hatchability and chick quality. OEO elevated expression of key enzymes and receptors involved in detoxification pathways and lipid metabolism in the jejunum of hatchling broiler chicks.

The peroxisome: an update on mysteries 3.0

Peroxisomes are highly dynamic, oxidative organelles with key metabolic functions in cellular lipid metabolism, such as the β-oxidation of fatty acids and the synthesis of myelin sheath lipids, as well as the regulation of cellular redox balance. Loss of peroxisomal functions causes severe metabolic disorders in humans. Furthermore, peroxisomes also fulfil protective roles in pathogen and viral defence and immunity, highlighting their wider significance in human health and disease. This has sparked increasing interest in peroxisome biology and their physiological functions. This review presents an update and a continuation of three previous review articles addressing the unsolved mysteries of this remarkable organelle. We continue to highlight recent discoveries, advancements, and trends in peroxisome research, and address novel findings on the metabolic functions of peroxisomes, their biogenesis, protein import, membrane dynamics and division, as well as on peroxisome-organelle membrane contact sites and organelle cooperation. Furthermore, recent insights into peroxisome organisation through super-resolution microscopy are discussed. Finally, we address new roles for peroxisomes in immune and defence mechanisms and in human disorders, and for peroxisomal functions in different cell/tissue types, in particular their contribution to organ-specific pathologies.

Role of STAR and SCP2/SCPx in the Transport of Cholesterol and Other Lipids

Cholesterol is a lipid molecule essential for several key cellular processes including steroidogenesis. As such, the trafficking and distribution of cholesterol is tightly regulated by various pathways that include vesicular and non-vesicular mechanisms. One non-vesicular mechanism is the binding of cholesterol to cholesterol transport proteins, which facilitate the movement of cholesterol between cellular membranes. Classic examples of cholesterol transport proteins are the steroidogenic acute regulatory protein (STAR; STARD1), which facilitates cholesterol transport for acute steroidogenesis in mitochondria, and sterol carrier protein 2/sterol carrier protein-x (SCP2/SCPx), which are non-specific lipid transfer proteins involved in the transport and metabolism of many lipids including cholesterol between several cellular compartments. This review discusses the roles of STAR and SCP2/SCPx in cholesterol transport as model cholesterol transport proteins, as well as more recent findings that support the role of these proteins in the transport and/or metabolism of other lipids.