BRD7 improves glucose homeostasis independent of IRS proteins.

Bromodomain-containing protein 7 (BRD7) has emerged as a player in the regulation of glucose homeostasis. Hepatic BRD7 levels are decreased in obese mice, and the reinstatement of hepatic BRD7 in obese mice has been shown to establish euglycemia and improve glucose homeostasis. Of note, the upregulation of hepatic BRD7 levels activates the AKT cascade in response to insulin without enhancing the sensitivity of the insulin receptor (InsR)-insulin receptor substrate (IRS) axis. In this report, we provide evidence for the existence of an alternative insulin signaling pathway that operates independently of IRS proteins and demonstrate the involvement of BRD7 in this pathway. To investigate the involvement of BRD7 as a downstream component of InsR, we utilized liver-specific InsR knockout mice. Additionally, we employed liver-specific IRS1/2 knockout mice to examine the requirement of IRS1/2 for the action of BRD7. Our investigation of glucose metabolism parameters and insulin signaling unveiled the significance of InsR activation in mediating BRD7's effect on glucose homeostasis in the liver. Moreover, we identified an interaction between BRD7 and InsR. Notably, our findings indicate that IRS1/2 is not necessary for BRD7's regulation of glucose metabolism, particularly in the context of obesity. The upregulation of hepatic BRD7 significantly reduces blood glucose levels and restores glucose homeostasis in high-fat diet-challenged liver-specific IRS1/2 knockout mice. These findings highlight the presence of an alternative insulin signaling pathway that operates independently of IRS1/2 and offer novel insights into the mechanisms of a previously unknown insulin signaling in obesity.

BRD7 deficiency leads to the development of obesity and hyperglycemia.

Obesity is a debilitating disease that has become a global epidemic. Although progress is being made, the underlying molecular mechanism by which obesity develops still remains elusive. Recently, we reported that the expression levels of bromodomain-containing protein 7 (BRD7) are significantly reduced in the liver of obese mice. However, it is not clear whether decreased levels of hepatic BRD7 are directly associated with the development of obesity and disturbance in glucose homeostasis. Here, using heterozygous BRD7 knockout and liver-specific BRD7 knockout mouse models, we report that reduced BRD7 levels lead to increased weight gain with little effect on glucose metabolism. On the other hand, upregulating BRD7 in the liver starting at an early age protects mice from gaining excessive weight and developing glucose intolerance and insulin resistance when challenged with a high-fat diet.

BRD7 regulates the insulin-signaling pathway by increasing phosphorylation of GSK3ß.

Reduced hepatic expression levels of bromodomain-containing protein 7 (BRD7) have been suggested to play a role in the development of glucose intolerance in obesity. However, the molecular mechanism by which BRD7 regulates glucose metabolism has remained unclear. Here, we show that BRD7 increases phosphorylation of glycogen synthase kinase 3ß (GSK3ß) in response to activation of the insulin receptor-signaling pathway shortly after insulin stimulation and the nutrient-sensing pathway after feeding. BRD7 mediates phosphorylation of GSK3ß at the Serine 9 residue and this effect on GSK3ß occurs even in the absence of AKT activity. Using both in vitro and in vivo models, we further demonstrate that BRD7 mediates phosphorylation of ribosomal protein S6 kinase (S6K) and leads to increased phosphorylation of the eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) and, therefore, relieves its inhibition of the eukaryotic translation initiation factor 4E (eIF4E). However, the increase in phosphorylation of 4E-BP1 with BRD7 overexpression is blunted in the absence of AKT activity. In addition, using liver-specific BRD7 knockout (LBKO) mice, we show that BRD7 is required for mTORC1 activity on its downstream molecules. These findings show a novel basis for understanding the molecular dynamics of glucose metabolism and suggest the unique function of BRD7 in the regulation of glucose homeostasis.

Saururus chinensis Baill induces apoptosis through endoplasmic reticulum stress in HepG2 hepatocellular carcinoma cells.

In this study, we examined the mechanism underlying the effect of Saururus chinensis Baill (saururaceae) on hepatocellular carcinoma HepG2 cells. HepG2 cells and Chang cells were exposed to various concentrations of S. chinensis Baill extract (SC-E) for 24 h. SC-E affected more significantly HepG2 cells than Chang cells in terms of cell viability and ATP production. Therefore, current study examined detailed mechanism how SC-E affected HepG2 cell survival. We found that SC-E (75 and 150 µg/ml) induced apoptosis via oxidative stress. SC-E also caused CCAAT-enhancer-binding protein homologous protein (CHOP) activation by dissociating the binding immunoglobulin protein (BiP) from inositol-requiring 1α (IRE1α) in the endoplasmic reticulum (ER) and induced Bax, cytochrome c release to cytosol, caspase-3 activation, and poly ADP ribose polymerase (PARP) cleavage, resulting in HepG2 cell apoptosis. Furthermore, SC-E caused ER Ca(2+) leakage into the cytosol; ER dilation and mitochondrial membrane damage were observed in transmission electron microscopy (TEM). Taken together, our results demonstrated that SC-E induced cancer cell apoptosis specifically through ER stress.

Utility of obesity indicators for metabolically healthy obesity: an observational study using the Korean National Health and Nutrition Examination Survey (2009-2010).

BACKGROUND: Obese individuals who are not at an elevated risk for cardiovascular disease are described as having metabolically healthy obesity (MHO). We sought to identify clinically useful indicators of MHO. METHODS: Records of the Korean National Health and Nutrition Examination Survey (2009-2010) were used to analyze 3,770 obese subjects (body mass index ≥ 25 kg/m2), who were divided into metabolic syndrome and MHO groups. Persons who met less than 3 of the criteria of metabolic syndrome (MS) were defined as having MHO. We estimated age-specific prevalence rates according to the number of MS criteria that were satisfied (patients meeting 0, ≤1, and ≤2 criteria of MS). Receiver operating characteristic analysis was performed to identify the best indicators of MHO. RESULTS: The prevalence of MHO among obese patients decreased with age. When MHO was defined by the fulfillment of ≤2 criteria of MS, the areas under the curves (AUC) for waist circumference and waist-to-height ratio were 0.743 and 0.747 in men and 0.712 and 0.741 in women, respectively. Waist circumference and waist-to-height ratio were the most accurate predictors of MHO for all investigated definitions. CONCLUSIONS: Waist circumference and waist-to-height ratio provide useful indicators for diagnosing MHO, and are more accurate than body mass index, fat percentage, or weight-adjusted appendicular skeletal muscle mass in the Korean population.

A single intratracheal instillation of single-walled carbon nanotubes induced early lung fibrosis and subchronic tissue damage in mice.

Large amounts of nanomaterials may reach both the natural and occupational environments. This represents a potential health hazard. People have forecasted that CNTs may lead to the toxicity such as mesothelioma and fibrosis like asbestos. To identify dominant immune responses induced by SWCNTs, we investigated the composition of bronchioalveolar lavage (BAL) cells, the secretion of cytokine and collagen, histopathology, protein expression, and cell phenotypes over time after a single administration of single-walled carbon nanotubes (SWCNT). In our results, the number of total cells and macrophages remained at the up-regulated level until Day 28, neutrophils rapidly increased at Day 1, and lymphocytes increased from Day 7. In the BAL fluid, pro-inflammatory cytokines rapidly increased at Day 1 and remained at an up-regulated level throughout the experimental period. IL-12 and IL-10 rapidly increased at Day 1 after administration and remained at a similar level until Day 28. IFN-γ and IL-4 reached the maximum at Day 1, and IL-5, TGF-ß, and collagen reached the maximum at Day 7. IL-13 and IL-17 increased in a time-dependent manner. The distribution of B cells and cytotoxic T cells markedly increased at Days 7 and 14, and fibrotic lesions were histopathologically observed at Days 7 and 14. The expressions of caspase-3, p53, COL1A1, COX-2, iNOS, MMP-9, and MMP-2 were also markedly increased at Days 7 and 14. In addition, the expression of mesothelin, iNOS, MMP-9, and p53 was up-regulated until Day 28. Based on these findings, we suggest that a single intratracheal instillation of SWCNTs may induce early lung fibrosis and subchronic tissue damage.