Ju-yi Li

TNF-α stimulates endothelial palmitic acid transcytosis and promotes insulin resistance

Persistent elevation of plasma TNF-α is a marker of low grade systemic inflammation. Palmitic acid (PA) is the most abundant type of saturated fatty acid in human body. PA is bound with albumin in plasma and could not pass through endothelial barrier freely. Albumin-bound PA has to be transported across monolayer endothelial cells through intracellular transcytosis, but not intercellular diffusion. In the present study, we discovered that TNF-α might stimulate PA transcytosis across cardiac microvascular endothelial cells, which further impaired the insulin-stimulated glucose uptake by cardiomyocytes and promoted insulin resistance. In this process, TNF-α-stimulated endothelial autophagy and NF-κB signaling crosstalk with each other and orchestrate the whole event, ultimately result in increased expression of fatty acid transporter protein 4 (FATP4) in endothelial cells and mediate the increased PA transcytosis across microvascular endothelial cells. Hopefully the present study discovered a novel missing link between low grade systemic inflammation and insulin resistance.

Siglec-5 is a novel marker of critical limb ischemia in patients with diabetes

Critical Limb Ischemia (CLI) is common but uncommonly diagnosed. Improved recognition and early diagnostic markers for CLI are needed. Therefore, the aim of our study was to identify plasma biomarkers of CLI in patients with type 2 diabetes mellitus (T2DM). In this study, antibody-coated glass slide arrays were used to determine the plasma levels of 274 human cytokines in four matched cases of diabetes with and without CLI. Potential biomarkers were confirmed in an independent cohort by ELISA. After adjusting for confounding risk factors, only plasma level of Siglec-5 remained significantly associated with an increased odds ratio (OR) for diabetes with CLI by binary logistic regression analysis. Receiver operating characteristic (ROC) curve analysis revealed the optimal cut-off points for Siglec-5 was 153.1 ng/ml. After entering Siglec-5, the AUC was 0.99, which was higher than that of confounding risk factors only (AUC = 0.97, P < 0.05). Siglec-5 was expressed in plaques, but not in healthy artery wall in T2DM patients. Elevated plasma Siglec-5 was independently associated with CLI in T2DM. Plasma Siglec-5 levels are implicated as an early diagnostic marker of CLI in T2DM patients and it may become a target for the prevention or treatment of CLI in diabetes.

Cavin-1 regulates caveolae-mediated LDL transcytosis: crosstalk in an AMPK/eNOS/ NF-κB/Sp1 loop

Caveolae are specialized lipid rafts structure in the cell membrane and critical for regulating endothelial functions, e.g. transcytosis of macromolecules like low density lipoprotein (LDL) etc. Specifically, the organization and functions of caveolae are mediated by structure protein (caveolin-1) and adapter protein (cavin-1). The pathogenic role of caveolin-1 is well studied; nevertheless, mechanisms whereby cavin-1 regulates signaling transduction remain poorly understood. The aim of this study was designed to explore the role of cavin-1 in caveolae-mediated LDL transcytosis across endothelial cells. We reported here that cavin-1 knockdown mediated by small interfering RNA (siRNA) caused a significant decrease of LDL transcytosis. Moreover, cavin-1 knockdown increased the activity of endothelial nitric oxide synthase (eNOS) and the production of nitric oxide (NO). Consequently, an eNOS inhibitor, N-Nitro-L-Arginine Methyl Ester (L-NAME), not only suppressed the activity of specificity protein (Sp1) and nuclear factor kappa B (NF-κB), but also inhibited both activities via activating adenosine 5‘-monophosphate- activated protein kinase (AMPK). In conclusion, we proposed an AMPK/eNOS/NF-κB/Sp1 circuit loop was formed to regulate caveolae residing proteins’ expression, e.g. LDL receptor (LDLR), caveolin-1, eNOS, thereby to regulate caveolae-mediated LDL transcytosis in endothelial cells.

MiR-323b-5p acts as a novel diagnostic biomarker for critical limb ischemia in type 2 diabetic patients

Type 2 diabetes mellitus (T2DM) is a major contributor to peripheral artery disease (PAD), especially in cases that advance to critical limb ischemia (CLI). Accumulating evidence indicates that miRNAs play an important role in the development of PAD and T2DM. Due to the limited value of current diagnostic methods for CLI in T2DM patients, we compared the miRNA expression profiles of Chinese T2DM patients with or without CLI to find out whether distinctive miRNAs could serve as potential diagnostic biomarkers. We statistically identified 7 miRNAs (hsa-miR-200b-3p, hsa-miR-2115-3p, hsa-miR-431-5p, hsa-miR-486-5p, hsa-miR-210-3p, hsa-miR-1264, hsa-miR-323b-5p) which were up-regulated in the CLI group, whereas other 4 miRNAs (hsa-miR-5579-3p, hsa-miR-665, hsa-miR-4285, hsa-miR-500a-3p) were down-regulated. Our validation test suggested a relatively high diagnostic accuracy of serum hsa-miR-323b-5p levels for the detection of CLI in T2DM patients, with a sensitivity of 62.67% and a specificity of 80.65%. The area under the curve (AUC) for miR-323b-5p + confounding risk factors was 0.94 (95% CI: 0.884–0.994, P < 0.001), which was higher than that for miR-323b-5p. Taken together, our results indicate that circulating hsa-miR-323b-5p could be a promising serum biomarker for the diagnosis of critical limb ischemia in type 2 diabetic patients.

Polymorphisms in the Osteopontin Are Associated with Susceptibility to Ankylosing Spondylitis in a Han Chinese Population

The aim of this study was to investigate whether osteopontin (OPN) variants are associated with susceptibility to ankylosing spondylitis (AS) in a Chinese population. Polymorphisms at the 9175th position in exon 7 of OPN and rs17524488 were genotyped using direct sequencing in 186 unrelated AS patients and 188 ethnically matched healthy controls. Serum concentration of OPN was measured by enzyme-linked immunosorbent assay (ELISA) in all participants. AS patients displayed significantly higher OPN serum levels than the controls (P < 001). A heterozygous, novel 9175 T>A in exon 7 of the OPN gene was found in this study. In healthy controls, subjects carrying the rs17524488 G/G genotype of the OPN display significantly higher OPN serum levels than the GG/GG genotype (P < 0.05). Plasma OPN level is implicated as an early diagnostic marker of AS. The novel 9175th- (exon 7) position polymorphism of OPN and rs17524488 were related to susceptibility to AS in a Chinese population, the rs17524488 G/G genotype may be involved in the pathogenesis of AS, and the precise molecular mechanism underlying the influence of OPN polymorphisms on the development of AS remains to be determined in the further prospective studies.