Yunyun Cheng

Fatty acid composition of milk triacylglycerol (TAG) is important for neonatal growth. We previously identified a synonymous mutation widely distributed in human populations, IGF-1 c.258A > G, which decreased milk TAG content in gene-edited mice. So far, the acyl chain composition of affected TAGs, underlying molecular mechanism, and cross-species conservation remain unclear. Here, integrated transcriptomic and metabolomic analyses of mouse mammary glands revealed that this mutation downregulates IGF-1 expression and elevates lipoprotein lipase (LPL) activity, and potential associations between IGF 1 and peroxisome proliferator-activated receptor γ (PPARG), fatty acid synthase (FASN) and lipin 1 (LPIN1). Association analysis in 295 Bama pigs carrying this gene polymorphism showed reduced milk lipid content in sows; further, correspondingly lower litter weight was significantly associated with the genotype. Integrated metabolomic profiling of mouse mammary glands and porcine milk demonstrated insufficient production of lauric and myristic acids. Accordingly, supplementing these two fatty acids restored TAG content. Mechanistically, IGF-1 promotes triacylglycerol-containing medium-chain fatty acid (MCFA-TAG) synthesis by activating the PPARG-FASN/LPIN1 axis, whereas increased LPL activity indirectly suppresses this axis through long-chain fatty acid accumulation. Together, our results reveal the molecular mechanism whereby this mutation affects milk lipid synthesis, providing insights into the regulation of MCFA-TAG synthesis.

Introduction: Ionizing radiation (IR)-induced liver fibrosis is one of the most serious complications of radiotherapy for liver cancer, and the core of its development lies in the activation of hepatic stellate cells (HSCs). The insulin-like growth factor 1 receptor (IGF1R) is commonly known as a growth-promoting kinase receptor that plays a critical role in cell differentiation and tissue reorganization, as well as in promoting the activation of HSCs, tentatively. Additionally, there has been a resurgence of interest in its role in DNA damage repair; nevertheless, the underlying mechanism remains poorly understood. Considering that DNA damage and repair are the most serious radiation injury events, the aim of this study was to explore the mechanism of IGF1R in the activation of HSCs by regulating DNA damage repair. Method and results: In this study, we first confirmed that IR induced the activation of HSCs, along with DNA damage and the upregulation of DNAdependent protein kinase catalytic subunit (DNA-PKcs) and IGF1R expressions. Then we indicated that the radiation-induced activation of HSCs and DNA damage repair were promoted by the activation or overexpression of IGF1R, either alone or together with DNA-PKcs activation, mechanistically through IGF1R–DNAPKcs interactions. The process is primarily facilitated by the nuclear translocation of IGF1R, which promotes PRKDC transcription at the mRNA level. Moreover, it involves an interaction with DNA-PKcs in the cytoplasm at the protein level, which, in turn, facilitates the entry of DNA-PKcs into the nucleus and subsequent promotion of DNA damage repair. Discussion: Our findings suggest that the inhibition of the IGF1R-promoted, DNA-PKcs-dependent non-homologous end joining (NHEJ) repair mode is a promising strategy to prevent the activation of HSCs. To the best of our knowledge, the present study is pioneering in its exploration of the mechanism by which IGF1R mediates radiation-induced activation of HSCs by regulating DNA-PKcs.

Introduction: Bone injury is a common side effect and a long-term response in radiotherapy-induced osteoblast damage, often characterized by reduced osteoblast proliferation and differentiation. Despite its clinical relevance, studies on radiation-induced bone injury are limited, and the molecular mechanisms underlying ionizing radiation (IR)-induced osteoblast damage remain largely unclear. Objectives: This study aimed to establish a radiation-induced osteoblast injury model, screen and identify related factors involved in the radiation injury of osteoblasts. Methods: The optimal IR damage conditions were first determined by measuring cell proliferation, cycle, apoptosis, and differentiation and mineralization abilities in a radiation-induced osteoblast injury model. Subsequently, differentially expressed genes were screened through RNA sequencing of radiation-damaged MC3T3-E1 cells. Results: Mouse double minute 2 homolog (MDM2) was the most significantly upregulated gene post-IR treatment, suggesting its key role in responses to IR. Meanwhile, cell apoptosis, cell cycle regulation, and several pathways, including the phosphoinositide 3-kinase/protein kinase B signaling pathway and signaling pathways involved in the cell cycle, were enriched. Furthermore, the role of MDM2 in radiation-induced osteoblast proliferation, differentiation, and DNA damage was investigated, followed by the identification of key pathway alterations under conditions of MDM2 knockdown and IR treatment. Conclusion: MDM2 knockdown alleviated IR damage in MC3T3-E1 cells by promoting cell proliferation, reducing cell cycle arrest and apoptosis rates, and reversing osteoblast differentiation. These effects may be due to the alleviation of DNA damage.

Liver fibrosis is induced by persistent stimulation of various factors, resulting from complex multicellular interactions and multifactorial networks. Without intervention, it can progress to cirrhosis and even liver cancer. Current understanding suggests that liver fibrosis is reversible, making it crucial to explore effective therapeutic strategies for its alleviation. Although the activation and proliferation of hepatic stellate cells (HSCs) play a pivotal role in liver fibrosis, the importance of hepatocytes, cholangiocytes, liver sinusoidal endothelial cells (LSECs) and immune cells cannot be ignored, the interactions of these cells with HSCs are worth discussing. Therefore, based on the diversity of cell composition in the liver organ, this review summarizes the impact of the parenchymal and nonparenchymal hepatic cells on liver fibrosis, including hepatocytes, cholangiocytes, hepatic macrophages, T cells, NK cells, B cells and LSECs, as well as the fibroblast subpopulations. And further discussed the interactions of these cells with HSCs and illustrated intercellular signal transduction among these cells in contributing to liver fibrosis. Clarifying the roles and interactions of various cells in the development of liver fibrosis will be helpful to explore effective strategies for the treatment of liver fibrosis.

Senile osteoporosis (SOP) is a multifactorial, age-related progressive phenomenon with a considerable morbidity and mortality. IGF-1 is an important regulator of bone reconstruction and metabolism throughout life. Nevertheless, our previous study unexpectedly found there is no change in the peak bone mass with a altered IGF-1 gene expression leaded by IGF-1 c.258 A > G synonymous mutation. Considering its involvement in the cellular senescence, we suspected c.258 A > G may participate in SOP. Therefore, the effect of IGF-1 c.258 A > G on SOP was firstly detected, the changes of bone formation and bone resorption index in SOP mice with two genotypes indicated it improved SOP. Then, the in vitro study confirmed the mutation ameliorates SOP by promoting the growth and development of senescent osteoblasts. At last, co-culture of osteoblast and osteoclast further verified the mutation prevents SOP by increasing the bone formation capacity of senescent osteoblasts. Collectively, this study illuminated the role of IGF-1 c.258 A > G in ameliorating SOP.

Background and Objective Bone injury is a common side effect of radiotherapy to tumors, which is a long-term response after damage to osteoblasts, especially reducing osteoblasts proliferation and differentiation. Currently, there are few studies on radiation-induced bone injury, the molecules involved in the ionizing radiation (IR) induced osteoblasts damage remain need to be excavated. Therefore, this study aims to establish a radiation induced osteoblast injury model, to screen and identify relevant factors involved in radiation injury of osteoblast through RNA-sequencing. Methods The MC3T3-E1 cells were administered a total dose of 0, 2, 4, 6, 8 Gy (2.22 Gy/min) X ray radiation. The cell proliferation was detected by CCK-8 assay and clonogenic assay, the cell cycle and apoptosis were detected by flow cytometry. The osteoblasts differentiation was estimated by ALP staining and the mineralization capacity was evaluated by alizarin red staining. The related gene expression levels were confirmed by RT-qPCR and western blot assay. The DNA damage and repair foci were detected by the immunofluorescence of γ-H2AX and 53BP1. Results In this study, the optimal IR damage conditions (8Gy, 2.22Gy/min) were firstly determined by measuring cell proliferation, cell cycle, cell apoptosis and further cell differentiation and mineralization abilities and the related genes ( p-AKT , p-ERK1/2 , cyclinB , BAX , BCL2 , ALP , OPN , RUNX2 , Collagen1 ) expression level changes in radiation-induced osteoblast injury model. Then, we screened 26 differentially expressed genes after the RNA-sequencing of the 8 Gy-irradiated MC3T3-E1 cells, and they were mainly involved in DNA damage and repair, cell apoptotic progress and cell cycle regulation, meanwhile, participated in several main pathway including PI3K-AKT signaling pathway, p53 signaling pathway and signaling pathway involved in cell cycle and cell senescence. We focused on verifying the differential expression genes and confirmed the MDM2, NOTCH1, CDKN1A and GCLC were upregulated after IR treatment, suggesting the key roles in the response of the IR. In addition, regarding on our sequencing results, the DNA damage and repair were also verified and the results suggested that IR induced DNA damage and repair in MC3T3-E1 cells. Conclusions In summary, IR damaged MC3T3-E1 cells by inhibiting cell proliferation, impacting cell cycle process, inducing cell apoptosis and affecting the osteoblasts differentiation, which maybe due to the DNA damage and the differential expression of the key genes (MDM2, NOTCH1, CDKN1A and GCLC ) .

Bone injury is a common side effect of radiotherapy to tumors, which is a long-term response after damage to osteoblasts, especially reducing osteoblasts proliferation and differentiation. Currently, there are few studies on radiation-induced bone injury, the molecules involved in the ionizing radiation (IR) induced osteoblasts damage remain need to be excavated. In this study, the optimal IR damage conditions (8Gy, 2.22Gy/min) were firstly determined by measuring cell proliferation, cell cycle, cell apoptosis and further cell differentiation and mineralization abilities and the related genes (p-AKT, p-ERK1/2, cyclinB, BAX, BCL2, ALP, OPN, RUNX2, Collagen1) expression level changes in radiation-induced osteoblast injury model. Then, we screened 26 differentially expressed genes after the RNA-sequencing of the 8 Gy-irradiated MC3T3-E1 cells, and they were mainly involved in DNA damage and repair, cell apoptotic progress and cell cycle regulation, meanwhile, participated in several main pathway including PI3K-AKT signaling pathway, p53 signaling pathway and signaling pathway involved in cell cycle and cell senescence. We focused on verifying the differential expression genes and confirmed the MDM2, NOTCH1, CDKN1A and GCLC were upregulated after IR treatment, suggesting the key roles in the response of the IR. In addition, regarding on our sequencing results, the DNA damage and repair were also verified and the results suggested that IR induced DNA damage and repair in MC3T3-E1 cells. In summary, IR damaged MC3T3-E1 cells by inhibiting cell proliferation, impacting cell cycle process, inducing cell apoptosis and affecting the osteoblasts differentiation, which maybe due to the DNA damage and the differential expression of the key genes (MDM2, NOTCH1, CDKN1A and GCLC ).