Moderate replacement of fish oil with palmitic acid-stimulated mitochondrial fusion promotes ß-oxidation by Mfn2 interacting with Cpt1α via its GTPase-domain.

The mitochondrial matrix serves as the principal locale for the process of fatty acids (FAs) ß-oxidation. Preserving the integrity and homeostasis of mitochondria, which is accomplished through ongoing fusion and fission events, is of paramount importance for the effective execution of FAs ß-oxidation. There has been no investigation to date into whether and how mitochondrial fusion directly enhances FAs ß-oxidation. The underlying mechanism of a balanced FAs ratio favoring hepatic lipid homeostasis remains largely unclear. To address such gaps, the present study was conducted to investigate the mechanism through which a balanced dietary FAs ratio enhances hepatic FAs ß-oxidation. The investigation specifically focused on the involvement of Mfn2-mediated mitochondrial fusion in the regulation of Cpt1α in this process. In the present study, the yellow catfish (Pelteobagrus fulvidraco), recognized as a model organism for lipid metabolism, were subjected to eight weeks of in vivo feeding with six distinct diets featuring varying FAs ratios. Additionally, in vitro experiments were conducted to inhibit Mfn2-mediated mitochondrial fusion in isolated hepatocytes, achieved through the transfection of hepatocytes with si-mfn2. Further, deletion mutants for both Mfn2 and Cpt1α were constructed to elucidate the critical regions responsible for the interactions between these two proteins within the system. The key findings were: (1) Substituting palmitic acid (PA) for fish oil (FO) proved to be enhanced in reducing hepatic lipid accumulation. This beneficial effect was primarily attributed to the activation of mitochondrial FAs ß-oxidation; (2) The balanced replacement of PA stimulated Mfn2-mediated mitochondrial fusion by diminishing Mfn2 ubiquitination, thereby enhancing its protein retention within the mitochondria; (3) Mfn2-mediated mitochondrial fusion promoted FAs ß-oxidation through direct interaction between Mfn2 and Cpt1α via its GTPase-domains, which is essential for the maintenance of Cpt1 activity. Notably, the present research results unveil a previously undisclosed mechanism wherein Mfn2-mediated mitochondrial fusion promotes FAs ß-oxidation by directly augmenting the capacity for FA transport into mitochondria (MT), in addition to expanding the mitochondrial matrix. This underscores the pivotal role of mitochondrial fusion in preserving hepatic lipid homeostasis. The present results further confirm that these mechanisms are evolutionarily conserved, extending their relevance from fish to mammals.

FZD2 inhibits the cell growth and migration of salivary adenoid cystic carcinomas.

Several studies have reported that FZD2 regulates tumor biology in a complex manner. The aim of the present study was to identify the role of FZD2 in the cell growth and metastasis of salivary adenoid cystic carcinomas (SACCs). The expression of FZD2 in ACC-83 and ACC-LM cells were measured with real-time PCR. Immunohistochemical staining was used to detect the expression of FZD2 in clinical SACC samples with or without metastasis. Cell proliferation and Transwell assays were performed to explore the effects of FZD2 on cell growth and migration following the silencing of FZD2 with small interference RNAs and the overexpression of FZD2 with plasmid. Our data showed that FZD2 was downregulated in ACC-LM cells, which are an adenoid cystic carcinoma cell line with high metastatic potential, compared to ACC-83 cells, which have low metastatic potential. Additionally, the expression of FZD2 was lower in SACC tissues with metastasis compared to SACC tissues without metastasis (P<0.05). Cell proliferation and migration of ACC-83 cells were increased after the knockdown of FZD2 and decreased following overexpression of FZD2. Knockdown of FZD2 downregulated the expression of PAI-1. Our results suggest that FZD2 may be a tumor suppressor gene in SACCs that inhibits cell growth and migration.

CDH12 promotes the invasion of salivary adenoid cystic carcinoma.

Cadherins are found in almost all living organisms. In addition to their role in the formation and maintenance of normal tissue architecture, cadherins seem to play a crucial role in the cell-cell interactions of cancer cells in tumorigenesis, invasion and metastasis. The aim of the present study was to identify the role of CDH12 in the invasion and metastasis of salivary adenoid cystic carcinoma (SACC). Real-time PCR results showed that CDH12 is abnormally expressed in the highly metastatic SACC cell line ACC-M, compared to ACC-2, a SACC cell line with low metastatic ability. CDH12 expression was significantly higher in clinical samples with metastasis and recurrence than in those without metastasis and recurrence (P<0.05), as demonstrated by immunohistochemical analysis. Overexpression of the CDH12 protein in ACC-M cells infected with an adenovirus vector containing CDH12 enhanced the invasive and migratory ability of ACC-M cells in vitro compared to ACC-M cells infected with empty vector. Likewise, knockdown of CDH12 by small interfering RNA efficiently inhibited the invasion and migration of ACC-M cells in vitro. These results indicate that CDH12 may play an important role in the invasion and metastasis of SACC.

Notch-4 contributes to the metastasis of salivary adenoid cystic carcinoma.

The Notch signaling pathway is important for cell-cell communication; it is involved in gene regulation mechanisms that control multiple cell differentiation processes during embryonic and adult life. Notch is present in all metazoans, and vertebrates possess four different Notch receptors: Notch-1, Notch-2, Notch-3, and Notch-4. The aim of the present study was to identify the role of Notch protein in the metastasis of salivary adenoid cystic carcinoma (SACC). Real-time PCR results showed that Notch-1, Notch-2, and Notch-4 were upregulated in the highly metastatic SACC cell line ACC-M, compared to ACC-2, a SACC cell line with low metastatic ability. Knockdown of Notch-4 by small interfering RNA efficiently inhibited the invasion of ACC-M cells. Notch-4 expression was significantly higher in the clinical samples with metastasis and recurrence compared to that in control (p<0.05), shown by immunohistochemistry analysis. These results indicate that Notch-4 may play an important role in SACC metastasis.