Temporal and spatial expression of IGF-I and IGFBP-1 during acute-phase response induced by localized inflammation in rats

Oleic Acid and Eicosapentaenoic Acid Reverse Palmitic Acid-induced Insulin Resistance in Human HepG2 Cells via the Reactive Oxygen Species / JUN Pathway

Oleic acid (OA), a monounsaturated fatty acid (MUFA), has previously been shown to reverse saturated fatty acid palmitic acid (PA)-induced hepatic insulin resistance (IR). However, its underlying molecular mechanism is unclear. In addition, previous studies have shown that eicosapentaenoic acid (EPA), a ω-3 polyunsaturated fatty acid (PUFA), reverses PA-induced muscle IR, but whether EPA plays the same role in hepatic IR and its possible mechanism involved need to be further clarified. Here, we confirmed that EPA reversed PA-induced IR in HepG2 cells and compared the proteomic changes in HepG2 cells after treatment with different free fatty acids (FFAs). A total of 234 proteins were determined to be differentially expressed after PA+OA treatment. Their functions were mainly related to responses to stress and endogenous stimuli, lipid metabolic process, and protein binding. For PA+EPA treatment, the PA-induced expression changes of 1326 proteins could be reversed by EPA, 415 of which were mitochondrial proteins, with most of the functional proteins involved in oxidative phosphorylation (OXPHOS) and tricarboxylic acid (TCA) cycle. Mechanistic studies revealed that the protein encoded by JUN and reactive oxygen species (ROS) play a role in OA- and EPA-reversed PA-induced IR, respectively. EPA and OA alleviated PA-induced abnormal adenosine triphosphate (ATP) production, ROS generation, and calcium (Ca²⁺) content. Importantly, H₂O₂-activated production of ROS increased the protein expression of JUN, further resulting in IR in HepG2 cells. Taken together, we demonstrate that ROS/JUN is a common response pathway employed by HepG2 cells toward FFA-regulated IR.

Insulin-like growth factor binding protein-1 predicts preterm premature rupture of membranes in twin pregnancies

PURPOSE

Mechanisms leading to preterm premature rupture of membranes (PPROM) remain incompletely defined. Based on the elevated occurrence of PPROM in twin gestations and recent studies of the involvement of insulin-like growth factor binding protein-1 (IGFBP-1) in the inhibition of collagen production we hypothesized that serum IGFBP-1 levels might be predictive of susceptibility to PPROM in women with twins.

METHODS

In this prospective study peripheral blood was obtained from 58 women with twin gestations prior to 20 weeks gestation and sera analyzed by ELISA for concentrations of IGFBP-1. Demographic and clinical outcome data were subsequently obtained and associations between IGFBP-1 and PPROM were analyzed by the Mann-Whitney test and receiver operator curve (ROC) analysis.

RESULTS

Eight of our subjects developed PPROM. They did not differ from the other women in demographics, medical history or current pregnancy outcome parameters. However, median IGFBP-1 levels were higher in women who subsequently developed PPROM (59.3 ng/ml) than in the other women (46.6 ng/ml) (p = 0.042). Using a cutoff value of 53.9 ng/ml the circulating IGFBP-1 level predicted development of PPROM with a sensitivity of 74%, specificity of 75%, a negative predictive value of 97% and a positive predictive value of 20%.

CONCLUSIONS

Pending validation in larger studies the findings suggest that determination of serum IGFBP-1 levels in women with twin pregnancies may predict the later development of PPROM.

Factors affecting insulin-regulated hepatic gene expression

Obesity has become a major concern of public health. A common feature of obesity and related metabolic disorders such as noninsulin-dependent diabetes mellitus is insulin resistance, wherein a given amount of insulin produces less than normal physiological responses. Insulin controls hepatic glucose and fatty acid metabolism, at least in part, via the regulation of gene expression. When the liver is insulin-sensitive, insulin can stimulate the expression of genes for fatty acid synthesis and suppress those for gluconeogenesis. When the liver becomes insulin-resistant, the insulin-mediated suppression of gluconeogenic gene expression is lost, whereas the induction of fatty acid synthetic gene expression remains intact. In the past two decades, the mechanisms of insulin-regulated hepatic gene expression have been studied extensively and many components of insulin signal transduction pathways have been identified. Factors that alter these pathways, and the insulin-regulated hepatic gene expression, have been revealed and the underlying mechanisms have been proposed. This chapter summarizes the recent progresses in our understanding of the effects of dietary factors, drugs, bioactive compounds, hormones, and cytokines on insulin-regulated hepatic gene expression. Given the large amount of information and progresses regarding the roles of insulin, this chapter focuses on findings in the liver and hepatocytes and not those described for other tissues and cells. Typical insulin-regulated hepatic genes, such as insulin-induced glucokinase and sterol regulatory element-binding protein-1c and insulin-suppressed cytosolic phosphoenolpyruvate carboxyl kinase and insulin-like growth factor-binding protein 1, are used as examples to discuss the mechanisms such as insulin regulatory element-mediated transcriptional regulation. We also propose the potential mechanisms by which these factors affect insulin-regulated hepatic gene expression and discuss potential future directions of the area of research.

Systemic differential gene regulation of the inter-α-trypsin inhibitor family in acute necrotizing pancreatitis in mice

BACKGROUND

Therapy for systemic complications in severe necrotizing pancreatitis remains symptomatic owing to the unavailability of more specific therapeutic targets. We investigated the differential gene expression in typically affected organs in a mouse model of severe necrotizing pancreatitis.

METHODS

Acute necrotizing pancreatitis was induced in mice by retrograde infusion of taurocholate into the common bile duct. Microarray hybridization was subsequently performed with mRNA isolated from the spleen, liver, intestine, and lungs. Additionally, quantitative real-time polymerase chain reaction was performed to confirm the microarray results.

RESULTS

Severe necrotizing pancreatitis induced widespread changes in gene expression, affecting 27.20% of the genes tested in the spleen and 29.07% in the liver. Fewer genes were differentially regulated in the intestine (10.28%) and the lungs (10.75%). Only 10 genes were found to be upregulated in all 4 organs using microarray analysis. This upregulation in all organs was confirmed by quantitative real-time polymerase chain reaction for only 3 molecules. These molecules were lipocalin 2, insulin-like growth factor binding protein 1, and CD14. Additionally we observed significantly aberrant gene regulation of inter-α-trypsin inhibitor family members in several organs.

CONCLUSIONS

Differential gene regulation in severe necrotizing pancreatitis is far more organ specific than anticipated, with only 3 molecules uniformly regulated systemically. The inter-α-trypsin inhibitor family of molecules appears to play a crucial biologic role in the systemic inflammatory response in acute pancreatitis. Finally, owing to its regulation and function, α1-microglobulin (or bikunin) may be a suitable predictive marker of the systemic inflammatory response syndrome in acute pancreatitis.

Characterization of three IGFBP mRNAs in Atlantic croaker and their regulation during hypoxic stress: potential mechanisms of their upregulation by hypoxia

Insulin-like growth factor-binding proteins (IGFBPs) play important roles in downregulating IGF activity and growth and development in vertebrates under hypoxic stress. However, the mechanisms of hypoxia regulation of IGFBPs in teleost fishes are unknown. The involvement of reactive oxygen species (ROS) and hypoxia-inducible factors (HIFs) in hypoxia upregulation of IGFBPs in Atlantic croaker were investigated. Three croaker IGFBPs, IGFBP-1, IGFBP-2, and IGFBP-5, were cloned and characterized. Chronic hypoxia exposure [dissolved oxygen (DO): 1.7 mg/l for 2-4 wk] caused significant increases in hepatic and neural IGFBP-1 mRNA expression compared with tissue mRNA levels in fish held under normoxic conditions (6.5 mg DO/l). Moreover, longer-term chronic hypoxia exposure (2-2.7 mg DO/l for 15-20 wk) caused significant increases in mRNA levels of all three IGFBPs in both liver and brain tissues. Hypoxia exposure also markedly increased superoxide radical (O(2)(·-), an index of ROS) production and HIF-1α mRNA and HIF-2α protein expression in croaker livers. Pharmacological treatment with an antioxidant attenuated the hypoxia-induced increases in O(2)(·-) production and HIFα mRNA and protein expression as well as the elevation of IGFBP-1 mRNA levels. These results suggest that the upregulation of IGFBP expression under hypoxia stress is due, in part, to alterations in the antioxidant status, which may involve ROS and HIFs.

Conditional ablation of mediator subunit MED1 (MED1/PPARBP) gene in mouse liver attenuates glucocorticoid receptor agonist dexamethasone-induced hepatic steatosis

Glucocorticoid receptor (GR) agonist dexamethasone (Dex) induces hepatic steatosis and enhances constitutive androstane receptor (CAR) expression in the liver. CAR is known to worsen hepatic injury in nonalcoholic hepatic steatosis. Because transcription coactivator MED1/PPARBP gene is required for GR- and CAR-mediated transcriptional activation, we hypothesized that disruption of MED1/PPARBP gene in liver cells would result in the attenuation of Dex-induced hepatic steatosis. Here we show that liver-specific disruption of MED1 gene (MED1(delta Liv)) improves Dex-induced steatotic phenotype in the liver. In wild-type mice Dex induced severe hepatic steatosis and caused reduction in medium- and short-chain acyl-CoA dehydrogenases that are responsible for mitochondrial beta-oxidation. In contrast, Dex did not induce hepatic steatosis in mice conditionally null for hepatic MED1, as it failed to inhibit fatty acid oxidation enzymes in the liver. MED1(delta Liv) livers had lower levels of GR-regulated CAR mRNA compared to wild-type mouse livers. Microarray gene expression profiling showed that absence of MED1 affects the expression of the GR-regulated genes responsible for energy metabolism in the liver. These results establish that absence of MED1 in the liver diminishes Dex-induced hepatic steatosis by altering the GR- and CAR-dependent gene functions.