Adipogenic function of mouse tetranectin and identification of its functional domain

Insight into the function of tetranectin in human diseases: A review and prospects for tetranectin-targeted disease treatment

Tetranectin (TN), a serum protein, is closely associated with different types of cancers. TN binds plasminogen and promotes the proteolytic activation of plasminogen into plasmin, which suggests that TN is involved in remodeling the extracellular matrix and cancer tissues during cancer development. TN is also associated with other diseases, such as developmental disorders, cardiovascular diseases, neurological diseases, inflammation, and diabetes. Although the functional mechanism of TN in diseases is not fully elucidated, TN binds different proteins, such as structural protein, a growth factor, and a transcription regulator. Moreover, TN changes and regulates protein functions, indicating that TN-binding proteins mediate the association between TN and diseases. This review summarizes the current knowledge of TN-associated diseases and TN functions with TN-binding proteins in different diseases. In addition, potential TN-targeted disease treatment by inhibiting the interaction between TN and its binding proteins is discussed.

Tetranectin targeting by epigallocatechin gallate suppresses colon cancer cell proliferation

Tetranectin is a serum protein that binds to plasminogen and enhances its proteolytic activation, which underlies the involvement of tetranectin in the development of several carcinomas including colon cancer. In the present study, structure-based in silico screening of natural products showed that epigallocatechin gallate with anticancer effects binds to tetranectin. Binding to epigallocatechin gallate to tetranectin was confirmed by intrinsic fluorescence quenching assays and isothermal titration calorimetry. Furthermore, epigallocatechin gallate efficiently inhibited the activity of tetranectin to enhance the activation of plasminogen. We also found that tetranectin enhanced the proliferation of CT-26 colon cancer cells. Epigallocatechin gallate showed its cytotoxic effect on CT-26 cells due to its binding to tetranectin and the consequent suppression of the cell proliferation. These results demonstrate that the anticancer effect of epigallocatechin gallate is mediated, at least in part, by inhibiting tetranectin as a binding target.

Adipogenic function of tetranectin mediated by enhancing mitotic clonal expansion via ERK signaling

Tetranectin (TN), an adipogenic serum protein, enhances adipocyte differentiation, however, its functional mechanism has yet to be elucidated. In the present study, we investigated the adipogenic function of TN by using medium containing TN-depleted fetal bovine serum (TN-del-FBS) and recombinant mouse TN (mTN). The adipocyte differentiation of 3T3-L1 cells was significantly enhanced by mTN supplementation essentially at differentiation induction, which indicated a potential role of the protein in the early differentiation phase. The adipogenic effect of mTN was more significant with insulin in the differentiation induction cocktail, implicating their close functional relationship. mTN enhanced not only the proliferation of growing cells, but also mitotic clonal expansion (MCE) that is a prerequisite for adipocyte differentiation in the early phase. Consistently, mTN increased the phosphorylation of ERK in the early phase of adipocyte differentiation. Results of this study demonstrate that the adipogenic function of mTN is mediated by enhancing MCE via ERK signaling.

Docosahexaenoic Acid Suppresses Expression of Adipogenic Tetranectin through Sterol Regulatory Element-Binding Protein and Forkhead Box O Protein in Pigs

Tetranectin (TN), a plasminogen-binding protein originally involved in fibrinolysis and bone formation, was later identified as a secreted adipokine from human and rat adipocytes and positively correlated with adipogenesis and lipid metabolism in adipocytes. To elucidate the nutritional regulation of adipogenic TN from diets containing different sources of fatty acids (saturated, n-6, n-3) in adipocytes, we cloned the coding region of porcine TN from a cDNA library and analyzed tissue expressions in weaned piglets fed with 2% soybean oil (SB, enriched in n-6 fatty acids), docosahexaenoic acid oil (DHA, an n-3 fatty acid) or beef tallow (BT, enriched in saturated and n-9 fatty acids) for 30 d. Compared with tissues in the BT- or SB-fed group, expression of TN was reduced in the adipose, liver and lung tissues from the DHA-fed group, accompanied with lowered plasma levels of triglycerides and cholesterols. This in vivo reduction was also confirmed in porcine primary differentiated adipocytes supplemented with DHA in vitro. Then, promoter analysis was performed. A 1956-bp putative porcine TN promoter was cloned and transcription binding sites for sterol regulatory-element binding protein (SREBP)-1c or forkhead box O proteins (FoxO) were predicted on the TN promoter. Mutating binding sites on porcine TN promoters showed that transcriptional suppression of TN by DHA on promoter activity was dependent on specific response elements for SREBP-1c or FoxO. The inhibited luciferase promoter activity by DHA on the TN promoter coincides with reduced gene expression of TN, SREBP-1c, and FoxO1 in human embryonic kidney HEK293T cells supplemented with DHA. To conclude, our current study demonstrated that the adipogenic TN was negatively regulated by nutritional modulation of DHA both in pigs in vivo and in humans/pigs in vitro. The transcriptional suppression by DHA on TN expression was partly through SREBP-1c or FoxO. Therefore, down-regulation of adipogenic tetranectin associated with fibrinolysis and adipogenesis may contribute to the beneficial effects of DHA on ameliorating obesity-induced metabolic syndromes such as atherosclerosis and adipose dysfunctions.

Serum proteome assessment in nonalcoholic fatty liver disease in children: a preliminary study

OBJECTIVES

Nonalcoholic fatty disease (NAFLD) affects 3-10% of the pediatric population, making it the most common chronic liver disease among children. The aim of the study is to identify potential biomarkers enabling the diagnosis of NAFLD and monitoring the course of the disease.

METHODS

Proteome analysis was performed in a group of 30 patients (19 boys and 11 girls) in total, of whom 16 children had previously diagnosed NAFLD based on the abdominal ultrasound after excluding other diseases of this organ.

RESULTS

A total of 297 proteins have been identified. Thirty-seven proteins (responsible for inflammation, stress response, and regulation of this process) differentiating both experimental groups were identified. Up-regulated proteins included afamin, retinol-binding protein-4, complement components, and hemopexin; while serum protease inhibitors, clusterin, immunoglobulin chains, and vitamin D binding protein were found in the down-regulated group. The correlation between selected proteins and indicators of noninvasive assessment of liver fibrosis (APRI, FIB-4) as well as differences between the serum proteome of patients with normal weight, overweight, and obesity were also assessed.

CONCLUSION

The plasma protein profile is significantly altered in nonalcoholic liver disease in children and may prove to be a valuable source of biomarkers to evaluate the extent of liver disease.