Effects of PPAR and RXR ligands in semaphorin 6B gene expression of human MCF-7 breast cancer cells.

This study tests the hypothesis that the activators of peroxisome proliferator-activated receptors (PPARs) and 9-cis-retinoic acid receptor (RXR) regulate human semaphorin 6B (Sema6B) gene expression. The human MCF-7 breast adenocarcinoma cell line was chosen because it expresses Sema6B at a high level. The Sema6B mRNA level was analyzed by RT-PCR and the semaphorin 6B protein content was determined using a polyclonal antibody that we have produced and characterized.

Sphingomyelin/cholesterol ratio: an important determinant of glucose transport mediated by GLUT-1 in 3T3-L1 preadipocytes.

Sphingomyelin pathway has been linked with insulin signaling through insulin-dependent GLUT-4 glucose transporter, but a relationship between sphingomyelin and the GLUT-1 transporter responsible for the basal (insulin-independent) glucose transport has not been clearly established. As GLUT-1 is mainly distributed to the cell surface, we explored the effects of changes in membrane sphingomyelin content on glucose transport through GLUT-1. The addition of exogenous sphingomyelin or glutathione (an inhibitor of endogenous sphingomyelinase) to the culture medium increased membrane sphingomyelin and cholesterol contents.

Erythrocyte membrane phospholipid composition is related to hyperinsulinemia in obese nondiabetic women: effects of weight loss.

The complex mechanisms by which obesity predisposes to insulin resistance are not clearly understood. According to a cell membrane hypothesis of insulin resistance, the defects in insulin action could be related to changes in membrane properties. The purpose of this work was to examine the relationship between 2 markers of insulin resistance (fasting plasma insulin [FPI] and homeostasis model assessment [HOMA IR]) and erythrocyte membrane lipid composition.