Lipid droplet - mitochondria coupling: A novel lipid metabolism regulatory hub in diabetic nephropathy

Functional interplay of lipid droplets and mitochondria

Our body stores energy mostly in form of fatty acids (FAs) in lipid droplets (LDs). From there the FAs can be mobilized and transferred to peroxisomes and mitochondria. This transfer is dependent on close opposition of LDs and mitochondria and peroxisomes and happens at membrane contact sites. However, the composition and the dynamics of these contact sites is not well understood, which is in part due to the dependence on the metabolic state of the cell and on the cell- and tissue-type. Here, we summarize the current knowledge on the contacts between lipid droplets and mitochondria both in mammals and in the yeast Saccharomyces cerevisiae, in which various contact sites are well studied. We discuss possible functions of the contact site and their implication in disease.

Database-Driven Spatially Resolved Lipidomics Highlights Heterogeneous Metabolic Alterations in Type 2 Diabetic Mice

Spatially resolved lipidomics is pivotal for detecting and interpreting lipidomes within spatial contexts using the mass spectrometry imaging (MSI) technique. However, comprehensive and efficient lipid identification in MSI remains challenging. Herein, we introduce a high-coverage, database-driven approach combined with air-flow-assisted desorption electrospray ionization (AFADESI)-MSI to generate spatial lipid profiles across whole-body mice. Using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS), we identified 2868 unique lipids in the serum and various organs of mice. Subsequently, we systematically evaluated the distinct ionization properties of the lipids between LC-MS and MSI and created a detailed MSI database containing 14 123 ions. This method enabled the visualization of aberrant fatty acid and phospholipid metabolism across organs in a diabetic mouse model. As a powerful extension incorporated into the MSIannotator tool, our strategy facilitates the rapid and accurate annotation of lipids, providing new research avenues for probing spatially resolved heterogeneous metabolic changes in response to diseases.

SIRT6's function in controlling the metabolism of lipids and glucose in diabetic nephropathy

Diabetic nephropathy (DN) is a complication of diabetes mellitus (DM) and the main cause of excess mortality in patients with type 2 DM. The pathogenesis and progression of DN are closely associated with disorders of glucose and lipid metabolism. As a member of the sirtuin family, SIRT6 has deacetylation, defatty-acylation, and adenosine diphosphate-ribosylation enzyme activities as well as anti-aging and anticancer activities. SIRT6 plays an important role in glucose and lipid metabolism and signaling, especially in DN. SIRT6 improves glucose and lipid metabolism by controlling glycolysis and gluconeogenesis, affecting insulin secretion and transmission and regulating lipid decomposition, transport, and synthesis. Targeting SIRT6 may provide a new therapeutic strategy for DN by improving glucose and lipid metabolism. This review elaborates on the important role of SIRT6 in glucose and lipid metabolism, discusses the potential of SIRT6 as a therapeutic target to improve glucose and lipid metabolism and alleviate DN occurrence and progression of DN, and describes the prospects for future research.

Targeting Renal Proximal Tubule Cells in Obesity-Related Glomerulopathy

As a metabolic disorder, obesity can cause secondary kidney damage, which is called obesity-related glomerulopathy (ORG). As the incidence of obesity increases worldwide, so does the incidence of end-stage renal disease (ESRD) caused by ORGs. However, there is still a lack of effective strategies to prevent and delay the occurrence and development of ORG. Therefore, a deeper understanding and elaboration of the pathogenesis of ORG is conducive to the development of therapeutic drugs for ORG. Here, we review the characteristics of pathological lesions of ORG and describe the roles of lipid metabolism disorders and mitochondrial oxidative stress in the development of ORG. Finally, we summarize the current available drugs or compounds for the treatment of ORG and suggested that ameliorating renal lipid metabolism and mitochondrial function may be potential therapeutic targets for ORG.

FAM210A mediates an inter-organelle crosstalk essential for protein synthesis and muscle growth in mouse

Mitochondria are not only essential for energy production in eukaryocytes but also a key regulator of intracellular signaling. Here, we report an unappreciated role of mitochondria in regulating cytosolic protein translation in skeletal muscle cells (myofibers). We show that the expression of mitochondrial protein FAM210A (Family With Sequence Similarity 210 Member A) is positively associated with muscle mass in mice and humans. Muscle-specific Myl1Cre-driven Fam210a knockout (Fam210aMKO) in mice reduces mitochondrial density and function, leading to progressive muscle atrophy and premature death. Metabolomic and biochemical analyses reveal that Fam210aMKO reverses the oxidative TCA cycle towards the reductive direction, resulting in acetyl-CoA accumulation and hyperacetylation of cytosolic proteins. Specifically, hyperacetylation of several ribosomal proteins leads to disassembly of ribosomes and translational defects. Transplantation of Fam210aMKO mitochondria into wildtype myoblasts is sufficient to elevate protein acetylation in recipient cells. These findings reveal a novel crosstalk between the mitochondrion and ribosome mediated by FAM210A.

Protective Effect of Astragaloside IV against Cadmium-Induced Damage on Mouse Renal Podocytes (MPC5)

In this study, we investigated the protective effect of Astragaloside IV (Ast) on mouse podocytes and its possible mechanism of action by constructing a cadmium-induced mouse renal podocytes model. We investigated the effects of cadmium (Cd) toxicity on cell number, morphology, the mitochondrial status of subcellular organelles, protein and gene levels, and the protective effects of Ast by constructing a model of Cd-induced damage to mouse renal podocytes (MPC5) and giving Ast protection at the same time. The results showed that exposure of MPC5 cells to CdCl₂ culture medium containing 6.25 μM concentration acted with low cell mortality, but the mortality of MPC5 cells increased with the prolongation of cadmium exposure time. Given Ast, the death rate in the low dose group (12.5 μM) was significantly reduced, while the death rate in the medium dose group (25 μM) was extremely significantly reduced. In comparison to the control group, the Cd-exposed group exhibited a significant increase of 166.7% in malondialdehyde (MDA) content and a significant decrease of 17.1% in SOD activity. The mitochondrial membrane potential was also reduced to varying degrees. However, in the Ast-protected group compared to the Cd-exposed group, the MDA content significantly decreased by 20.8%, the SOD activity decreased by 7.14%, and the mitochondrial membrane potential showed a significant increase. Fluorescence staining of mitochondrial membrane potential indicated that Cd exposure caused mitochondrial apoptosis. In the 12-h cadmium-exposed group, the protein expression of Nephrin in mice significantly decreased by 33.4%. However, the expression of the Desmin protein significantly increased by 67.8%, and the expression of the autophagy protein LC3-II significantly increased by 55.5%. Meanwhile, the expression of PINK1, a mitochondrial autophagy pathway protein, was significantly increased in the 12 h and 24 h cadmium exposure groups. The mRNA level of PINK1 was significantly increased, and that of Parkin was decreased in the 48 h cadmium exposure group. Compared to the Cd-exposed group, the Ast group showed more significant improvements in the expression of podocyte structure, functional proteins, and mitochondrial autophagy pathway proteins. The immunological assay of mitochondrial autophagic pathway proteins further indicated that Cd-induced damage to MPC5 cells might be associated with the dysregulation of mitochondrial autophagy.

Probiotic Bifidobacterium breve MCC1274 Protects against Oxidative Stress and Neuronal Lipid Droplet Formation via PLIN4 Gene Regulation

Consumption of Bifidobacterium breve MCC1274 has been shown to improve memory and prevent brain atrophy in populations with mild cognitive impairment (MCI). Preclinical in vivo studies using Alzheimer's disease (AD) models indicate that this probiotic protects against brain inflammation. There is growing evidence that lipid droplets are associated with brain inflammation, and lipid-associated proteins called perilipins could play an important role in neurodegenerative diseases such as dementia. In this study, we found that B. breve MCC1274 cell extracts significantly decreased the expression of perilipin 4 (PLIN4), which encodes a lipid droplet docking protein whose expression is known to be increased during inflammation in SH-SY5Y cells. Niacin, an MCC1274 cell extract component, increased PLIN4 expression by itself. Moreover, MCC1274 cell extracts and niacin blocked the PLIN4 induction caused by oxidative stress in SH-SY5Y cells, reduced lipid droplet formation, and prevented IL-6 cytokine production. These results offer a possible explanation for the effect of this strain on brain inflammation.