Involvement of Serum Amyloid A1 in the Pathogenesis of Insulin Resistance in Ovarian Granulosa Cells in Polycystic Ovary Syndrome

Background: Insulin resistance (IR) contributes to ovarian dysfunctions in PCOS patients. Serum amyloid A1 (SAA1) is an acute phase protein produced primarily by the liver in response to inflammation. In addition to its role in inflammation, SAA1 may participate in IR development in peripheral tissues. Yet, expressional regulation of SAA1 in the ovary and its role in the pathogenesis of ovarian IR in PCOS remain elusive. Methods: Follicular fluid and granulosa cells were collected from PCOS and non-PCOS patients with and without IR to measure SAA1 abundance for analysis of its correlation with IR status. The effects of SAA1 on its own expression and insulin signaling pathway were investigated in cultured primary granulosa cells. Results: Ovarian granulosa cells were capable of producing SAA1, which could be induced by SAA1 per se. Moreover, the abundance of SAA1 significantly increased in granulosa cells and follicular fluid in PCOS patients with IR. SAA1 treatment significantly attenuated insulin-stimulated membrane translocation of glucose transporter 4 and glucose uptake in granulosa cells through induction of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression with subsequent inhibition of Akt phosphorylation. These effects of SAA1 could be blocked by inhibitors for toll-like receptors 2/4 (TLR 2/4) and nuclear factor kappa light chain enhancer of activated B (NF-κB). Conclusions: Human granulosa cells are capable of feedforward production of SAA1, which significantly increased in PCOS patients with IR. Excessive SAA1 reduces insulin sensitivity in granulosa cells via induction of PTEN and subsequent inhibition of Akt phosphorylation upon activation of TLR2/4 and NF-κB pathway. These findings highlight that local excessive synthesis of SAA1 is associated with IR development in granulosa cells of PCOS patients.

Serum Amyloid A1 Induces Classically Activated Macrophages: A Role for Enhanced Fibril Formation

AA amyloidosis belongs to the group of amyloid diseases which can follow chronic inflammatory conditions of various origin. The disease is characterized by the deposition of insoluble amyloid fibrils formed by serum amyloid A1 (SAA1) leading eventually to organ failure. Macrophages are intimately involved in the fibrillogenesis as well as in the clearance of amyloid fibrils. In vivo, macrophages may occur as classically (M1) or alternatively activated (M2) macrophages. We investigate here how SAA1 might affect the macrophage phenotype and function. Gene microarray analysis revealed upregulation of 64 M1-associated genes by SAA1. M1-like polarization was further confirmed by the expression of the M1-marker MARCO, activation of the NF-κB transcription factor, and secretion of the M1-cytokines TNF-α, IL-6, and MCP-1. Additionally, we demonstrate here that M1-polarized macrophages exhibit enhanced fibrillogenic activity towards SAA1. Based on our data, we propose reconsideration of the currently used cellular amyloidosis models towards an in vitro model employing M1-polarized macrophages. Furthermore, the data suggest macrophage repolarization as potential intervention strategy in AA amyloidosis.

Serum Amyloid A1/Toll-Like Receptor-4 Axis, an Important Link between Inflammation and Outcome of TBI Patients

Traumatic brain injury (TBI) is one of the leading causes of mortality and disability worldwide without any validated biomarker or set of biomarkers to help the diagnosis and evaluation of the evolution/prognosis of TBI patients. To achieve this aim, a deeper knowledge of the biochemical and pathophysiological processes triggered after the trauma is essential. Here, we identified the serum amyloid A1 protein-Toll-like receptor 4 (SAA1-TLR4) axis as an important link between inflammation and the outcome of TBI patients. Using serum and mRNA from white blood cells (WBC) of TBI patients, we found a positive correlation between serum SAA1 levels and injury severity, as well as with the 6-month outcome of TBI patients. SAA1 levels also correlate with the presence of TLR4 mRNA in WBC. In vitro, we found that SAA1 contributes to inflammation via TLR4 activation that releases inflammatory cytokines, which in turn increases SAA1 levels, establishing a positive proinflammatory loop. In vivo, post-TBI treatment with the TLR4-antagonist TAK242 reduces SAA1 levels, improves neurobehavioral outcome, and prevents blood–brain barrier disruption. Our data support further evaluation of (i) post-TBI treatment in the presence of TLR4 inhibition for limiting TBI-induced damage and (ii) SAA1-TLR4 as a biomarker of injury progression in TBI patients.

MRNA Expression of Adipocytokines and Glucose Transporter Type 4 (GLUT4) in Adipose Tissue in Women With and Without Polycystic Ovary Syndrome

Background: The main feature of polycystic ovary syndrome (PCOS) is hyperandrogenism, adipocytes hypertrophy and chronic low-grade inflammation. It is known that PCOS is closely linked to functional dysfunction in adipose tissue, which in turn are connected with metabolic disturbances such as insulin resistance. However, there is no complete characterization of the adipose tissue in women with PCOS. Aim: To compare the expression of adipocytokines between women with and without PCOS. Materials and Methods: The total number of twenty two participants were enrolled into the study. Study group included ten women with PCOS diagnosed according to the Rotterdam criteria, the control group- twelve women without PCOS. Approximately 3 g of tissue was excised from subcutaneous adipose tissue through a small incision in the suprapubic area. mRNA was isolated and gene expression profiling was performed including following genes: GLUT4, irisin, leptin, omentin, vaspin, adiponectin, visfastin, apelin, serum amyloid A1 and chemerin. Blood samples were taken between 3rd and 5th day of the menstrual cycle to evaluate serum hormonal levels. The oral glucose tolerance test (OGTT) was done simultaneously with the assessment of glucose and insulin plasma levels at 0, 60 and 120 minute. Results: Patients with PCOS presents different mRNA expression of adipocytokines compared with control group. There were statistically significant differences in irisin, leptin, omentin, visfastin, chemerin and serum amyloid A1 expression, that were higher in PCOS. GLUT-4 and adiponectin expression was significantly lower in PCOS patient compared to control. Due to an insufficient measurement of apelin and vaspin gene expression there were not included in following analysis. Conclusions: mRNA expression of adipocytokines in adipose tissue in women with and without polycystic ovary syndrome is different. In women with PCOS, there is a higher expression of genes for most of adipocytokines with lower for adiponectin and GLUT-4.