Mitochondrial GCN5L1 regulates cytosolic redox state and hepatic gluconeogenesis via glycerol phosphate shuttle GPD2

Increased hepatic gluconeogenesis and type 2 diabetes mellitus

Abnormally increased hepatic gluconeogenesis is a significant contributor to hyperglycemia in the fasting state in patients with type 2 diabetes mellitus (T2DM) due to insulin resistance. Metformin, the most prescribed drug for the treatment of T2DM, is believed to exert its effect mainly by reducing hepatic gluconeogenesis. Here, we discuss how increased hepatic gluconeogenesis contributes to T2DM and we review newly revealed mechanisms underlying the attenuation of gluconeogenesis by metformin. In addition, we analyze the recent findings on new determinants involved in the regulation of gluconeogenesis, which might ultimately lead to the identification of novel and targeted treatment strategies for T2DM.

Zhuangyao Jianshen Wan ameliorates senile osteoporosis in SAMP6 mice through Modulation of the GCN5L1-mediated PI3K/Akt/wnt signaling pathway

Background

Senile osteoporosis (SOP) is a systemic bone disease characterized by increased susceptibility to fractures. However, there is currently no effective treatment for SOP. The Zhuangyao Jianshen Wan (ZYJSW) pill is traditionally believed to possess kidney-nourishing and bone-strengthening effects, demonstrating efficacy in treating fractures. Despite this, its effectiveness and mechanism in SOP remain unclear. This study aims to investigate the therapeutic potential of ZYJSW in treating SOP in senescence accelerated mouse prone 6 (SAMP6, P6) mice, and elucidate the underlying mechanisms.

Methods

Four-month-old SAMP6 mice were categorized into six groups: the model group (SAMP6), low, medium, and high-dose ZYJSW treatment groups, calcitriol treatment (positive control 1) group, and metformin treatment (positive control 2) group. Gastric administration was carried out for 15 weeks, and a normal control group comprising four-month-old Senescence-Accelerated Mouse Resistant 1 (SAMR1) mice. Changes in body weight, liver and kidney function, bone protective effects, and muscle quality were evaluated using various assays, including H&E staining, Goldner staining, bone tissue morphology analysis, Micro-CT imaging, and biomechanical testing. Qualitative analysis and quality control of ZYJSW were performed via LC-MS/MS analysis. To explore mechanisms, network pharmacology and proteomics were employed, and the identified proteins were validated by Western blotting.

Results

Oral administration of ZYJSW to P6 mice exerted preventive efficacy against osteopenia, impaired bone microstructure, and poor bone and muscle quality. ZYJSW attenuated the imbalance in bone metabolism by promoting bone formation, as evidenced by the upregulation of key factors such as Runt-related transcription factor 2 (RUNX2), Bone Morphogenetic Protein (BMP2), Osteoprotegerin (OPG) and Osteocalcin (OCN), while simultaneously inhibiting bone resorption through the downregulation of TNF receptor associated factor 6 (TRAF6), Tartrate resistant acid phosphatase (TRAP), Receptor activator for nuclear factor-κB ligand (RANKL) and Cathepsin K (CTSK). Additionally, ZYJSW enhanced muscle structure and function by counteracting the elevation of Ubiquitin (Ub), Muscle RING-finger protein-1 (Murf-1), F-Box Protein 32 (FBOX32), and Myogenin (Myog). Network pharmacology predictions, proteomics analysis corroborated by published literature demonstrated the role of ZYJSW involving in safeguarding mitochondrial biogenesis. This was achieved by suppressing GCN5L1 expression, contributing to the heightened expression of TFAM, PGC-1α, and nuclear respiratory factor-1 (NRF-1) proteins. ZYJSW also positively modulated Wnt signaling pathways responsible for bone formation, due to regulating expressions of key components like β-catenin, GSK-3β, and LRP5. In addition, ZYJSW causes the downregulation of the PI3K/Akt pathway by inhibiting the phosphorylation of both PI3K and Akt.

Conclusions

The study highlights the significance of ZYJSW in preserving the health of both bone and muscle in P6 mice, potentially through the regulation of the GCN5L1-mediated PI3K/Akt/Wnt signaling pathway.

The translational potential of this article

Our research provides evidence and a mechanistic rationale for ZYJSW as a candidate for SOP treatment, offering insights for further exploration and strategy development.

Glycerol 3-phosphate dehydrogenases (1 and 2) in cancer and other diseases

The glycerol 3-phosphate shuttle (GPS) is composed of two different enzymes: cytosolic NAD+-linked glycerol 3-phosphate dehydrogenase 1 (GPD1) and mitochondrial FAD-linked glycerol 3-phosphate dehydrogenase 2 (GPD2). These two enzymes work together to act as an NADH shuttle for mitochondrial bioenergetics and function as an important bridge between glucose and lipid metabolism. Since these genes were discovered in the 1960s, their abnormal expression has been described in various metabolic diseases and tumors. Nevertheless, it took a long time until scientists could investigate the causal relationship of these enzymes in those pathophysiological conditions. To date, numerous studies have explored the involvement and mechanisms of GPD1 and GPD2 in cancer and other diseases, encompassing reports of controversial and non-conventional mechanisms. In this review, we summarize and update current knowledge regarding the functions and effects of GPS to provide an overview of how the enzymes influence disease conditions. The potential and challenges of developing therapeutic strategies targeting these enzymes are also discussed.

Adapting to stress: The effects of hibernation and hibernacula temperature on the hepatic transcriptome of Rhinolophus pusillus

Hibernation, a survival strategy in mammals for extreme climates, induces physiological phenomena such as ischemia-reperfusion and metabolic shifts that hold great potential for advancements in modern medicine. Despite this, the molecular mechanisms underpinning hibernation remain largely unclear. This study used RNA-seq and Iso-seq techniques to investigate the changes in liver transcriptome expression of Rhinolophus pusillus during hibernation and active periods, as well as under different microhabitat temperatures. We identified 11 457 differentially expressed genes during hibernation and active periods, of which 395 showed significant differential expression. Genes associated with fatty acid catabolism were significantly upregulated during hibernation, whereas genes related to carbohydrate metabolism and glycogen synthesis were downregulated. Conversely, immune-related genes displayed differential expression patterns: genes tied to innate immunity were significantly upregulated, while those linked to adaptive immunity and inflammatory response were downregulated. The analysis of transcriptomic data obtained from different microhabitat temperatures revealed that R. pusillus exhibited an upregulation of genes associated with lipid metabolism in lower microhabitat temperature. This upregulation facilitated an enhanced utilization rate of triglyceride, ultimately resulting in increased energy provision for the organism. Additionally, R. pusillus upregulated gluconeogenesis-related genes regardless of the microhabitat temperature, demonstrating the importance of maintaining blood glucose levels during hibernation. Our transcriptomic data reveal that these changes in liver gene expression optimize energy allocation during hibernation, suggesting that liver tissue adaptively responds to the inherent stress of its function during hibernation. This study sheds light on the role of differential gene expression in promoting more efficient energy allocation during hibernation. It contributes to our understanding of how liver tissue adapts to the stressors associated with this state.