LIGHT (TNFSF14) inhibits glucose uptake of adipocytes by downregulating GLUT4 expression via AKT signaling pathway

LIGHT/TNFSF14 Affects Adipose Tissue Phenotype

LIGHT/TNFSF14 is linked to several signaling pathways as a crucial member of a larger immunoregulatory network. It is primarily expressed in inflammatory effector cells, and high levels of LIGHT have been reported in obesity. Thus, with the aim of deepening the knowledge of the role of LIGHT on adipose tissue phenotype, we studied wild-type (WT), Tnfsf14-/-, Rag-/- and Rag-/Tnfsf14- (DKO) mice fed a normal diet (ND) or high-fat diet (HFD). Our results show that, although there is no significant weight gain between the mice with different genotypes, it is significant within each of them. We also detected an increase in visceral White Adipose Tissue (vWAT) weight in all mice fed HFD, together with the lowest levels of vWAT weight in Tnfsf14-/- and DKO mice fed ND with respect to the other strain. Inguinal WAT (iWAT) weight is significantly affected by genotype and HFD. The least amount of iWAT was detected in DKO mice fed ND. Histological analysis of vWAT showed that both the genotype and the diet significantly affect the adipocyte area, whereas the number is affected only by the genotype. In iWAT, the genotype and the diet significantly affect mean adipocyte area and number; interestingly, the area with the least adipocyte was detected in DKO mice fed ND, suggesting a potential browning effect due to the simultaneous lack of mature lymphocytes and LIGHT. Consistently, Uncoupling Protein 1 (UCP1) staining of iWAT demonstrated that few positive brown adipocytes appeared in DKO mice. Furthermore, LIGHT deficiency is associated with greater levels of UCP1, highlighting the lack of its expression in Rag-/- mice. Liver examination showed that all mice fed HFD had a steatotic liver, but it was particularly evident for DKO mice. In conclusion, our study demonstrates that the adipose tissue phenotype is affected by LIGHT levels but also much more by mature lymphocytes.

Assessment of Novel Oligopeptides from Rapeseed Napin (Brassica napus) in Protecting HepG2 Cells from Insulin Resistance and Oxidative Stress

Oligopeptides (Thr-His-Leu-Pro-Lys (THLPK), His-Pro-Leu-Lys (HPLK), Leu-Pro-Lys (LPK), His-Leu-Lys (HLK), and Leu-His-Lys (LHK)) are newly identified from rapeseed napin (Brassica napus) protein-derived hydrolysates with the capability of upregulating glucose transporter-4 (GLUT4) expression and translocation. However, whether each of them enhances GLUT4 expression and translocation and their specific mechanisms remain unclear. Here, we assess the effects of the oligopeptides against insulin resistance (IR) and oxidative stress in hepatocytes and screen out the most antidiabetic one. Specifically, compared with other oligopeptides, LPK not only remarkably elevated glucose consumption to 8.45 mmol/L protein; superoxide dismutase (SOD) activity to 319 U/mg protein; GLUT4 expression and translocation; and phosphorylated level of insulin receptor substrate-1 (IRS-1), phosphatidylinositol 3-kinase (PI3K), and protein kinase B (Akt) (P < 0.05) but also remarkably attenuated the reactive oxygen species (ROS) level to 2255, lactate dehydrogenase (LDH) activity to 20.5 U/mg protein, malondialdehyde (MDA) content to 241 nmol/mg protein, and NO content to 1302 μmol/mL protein (P < 0.05). These findings demonstrated that antidiabetic oligopeptide LPK possessed the most potential to protect HepG2 cells from IR and oxidative stress via activating IRS-1/PI3K/Akt/GLUT4 and regulating common oxidative markers in vitro.

Monascus-fermented grain vinegar enhances glucose homeostasis through the IRS-1/PI3K/Akt and AMPK signaling pathways in HepG2 cell and db/db mice

MV was reported to have beneficial effects in ameliorating insulin resistance in db/db mice, but the intrinsic mechanisms for glucose homeostasis are unclear. This study examined the anti-diabetic mechanism of MV using HepG2 cells and C57BL/KsJ-db/db mice. MV increased insulin sensitivity by promoting insulin-dependent glucose uptake and activating glycogen accumulation in HepG2 cells. Furthermore, the glucose homeostasis was enhanced in db/db mice administered 1 mg/kg/day of MV for eight weeks by activating the IRS-1/PI3K/Akt and AMPK pathways in the skeletal muscle and liver tissue. In addition, MV promoted glycogen synthesis by regulating the key enzymes, including GSK-3β and GS, and suppressed gluconeogenesis by inhibiting the mRNA expressions of G6pase and PEPCK. These findings show that MV regulates both signaling pathways and improves the glucose metabolism disorder. Thus, MV might be an alternative functional food or nutraceutical in ameliorating T2DM.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01146-4.

Realigning the LIGHT signaling network to control dysregulated inflammation

Advances in understanding the physiologic functions of the tumor necrosis factor superfamily (TNFSF) of ligands, receptors, and signaling networks are providing deeper insight into pathogenesis of infectious and autoimmune diseases and cancer. LIGHT (TNFSF14) has emerged as an important modulator of critical innate and adaptive immune responses. LIGHT and its signaling receptors, herpesvirus entry mediator (TNFRSF14), and lymphotoxin β receptor, form an immune regulatory network with two co-receptors of herpesvirus entry mediator, checkpoint inhibitor B and T lymphocyte attenuator, and CD160. Deciphering the fundamental features of this network reveals new understanding to guide therapeutic development. Accumulating evidence from infectious diseases points to the dysregulation of the LIGHT network as a disease-driving mechanism in autoimmune and inflammatory reactions in barrier organs, including coronavirus disease 2019 pneumonia and inflammatory bowel diseases. Recent clinical results warrant further investigation of the LIGHT regulatory network and application of target-modifying therapeutics for disease intervention.