Obesity enhances the recruitment of mesenchymal stem cells to visceral adipose tissue.

In obesity, high levels of TNF-α in the bone marrow microenvironment induce the bone marrow-mesenchymal stem cells (BM-MSCs) towards a pro-adipogenic phenotype. Here, we investigated the effect of obesity on the migratory potential of BM-MSCs and their fate towards the adipose tissues. BM-MSCs were isolated from male C57Bl/06 mice with high-fat diet-induced obesity. The migratory potential of the BM-MSCs, their presence in the subcutaneous (SAT) and the visceral adipose tissues (VAT), and the possible mechanisms involved were investigated. Obesity did not affect MSC content in the bone marrow but increased the frequency of MSCs in blood, SAT, and VAT. In these animals, the SAT adipocytes presented a larger area, without any changes in adipokine production or the Sdf-1α gene expression. In contrast, in VAT, obesity increased leptin and IL-10 levels but did not modify the size of the adipocytes. The BM-MSCs from obese animals presented increased spontaneous migratory activity. Despite the augmented expression of Cxcr4, these cells exhibited decreased migratory response towards SDF-1α, compared to that of BM-MSCs from lean mice. The PI3K-AKT pathway activation seems to mediate the migration of BM-MSCs from lean mice, but not from obese mice. Additionally, we observed an increase in the spontaneous migration of BM-MSCs from lean mice when they were co-cultured with BM-HCs from obese animals, suggesting a paracrine effect. We concluded that obesity increased the migratory potential of the BM-MSCs and induced their accumulation in VAT, which may represent an adaptive mechanism in response to chronic nutrient overload.

Obese adipose tissue extracellular vesicles raise breast cancer cell malignancy.

Obesity is a chronic low-grade inflammatory condition that strongly impacts breast cancer. Aside from inflammatory mediators, obese adipose tissue (AT) secretes high amounts of extracellular vesicles (EVs), which are capable of transferring molecules to target cells and promoting cell-to-cell communication. Here, we investigated how soluble mediators and EVs secreted by human obese AT influence MCF-7 and MDA-MB-231 mammary adenocarcinoma cell lines by modulating cell proliferation, migration, invasion, and signaling pathways. Both cell lineages were stimulated with conditioned media (CM) or EVs obtained from cultures of AT explants collected from lean or obese individuals who underwent plastic or bariatric surgeries, respectively. EVs derived from obese AT increased the proliferative potential of both cell lines and further potentiated the migratory and invasive properties of MDA-MB-231 cells. The proliferative effects of CM and EVs on MCF-7 cells were dependent on ERK/MAPK pathway activation, while the migration and invasiveness of MDA-MB-231 cells were dependent on PI3K/AKT pathway activation. Furthermore, CM derived from obese AT potentiated the pro-angiogenic effect of MDA-MB-231 on endothelial cells. We also detected that EVs derived from obese AT were enriched in leptin and bioactive matrix metallopeptidase 9 (MMP9), and stimulation of MDA-MD-231 cells with those EVs or CM derived from obese AT potentiated the release of MMP9 by those cells. Our data indicate that obese AT secretes molecules and EVs with pro-tumoral activities capable of increasing breast cancer cell malignancy and provide strong evidence of the key role of AT-derived EV signaling in the tumor microenvironment.

Chia oil induces browning of white adipose tissue in high-fat diet-induced obese mice.

Previous research suggests that omega-3 fatty acids from animal origin may promote the browning of subcutaneous white adipose tissue. We evaluated if supplementation with a plant oil (chia, Salvia hispanica L.) rich in alpha-linolenic fatty acid (C18:3; ω-3) would promote browning and improve glucose metabolism in animals subjected to an obesogenic diet. Swiss male mice (n = 28) were divided into 4 groups: C: control diet; H: high-fat diet; HC: animals in the H group supplemented with chia oil after reaching obesity; HCW: animals fed since weaning on a high-fat diet supplemented with chia oil. Glucose tolerance, inflammatory markers, and expression of genes and proteins involved in the browning process were examined. When supplemented since weaning, chia oil improved glucose metabolism and promoted the browning process and a healthier phenotype. Results of this study suggested that chia oil has potential to protect against the development of obesity-related diseases.

Up-regulation of phosphatidylinositol 3-kinase and glucose transporter 4 in muscle of rats subjected to maternal undernutrition.

Early postnatal nutrition has been associated with the long-term effects on glucose homeostasis in adulthood. To elucidate the molecular mechanisms by which undernutrition during early life leads to changes in insulin sensitivity, we investigated the insulin signaling in skeletal muscle of rats during development. Offspring of dams fed with either protein-free or normal diets during the first 10 days of lactation were studied from lactation period until adulthood. Early maternal undernutrition impaired secretion of insulin but maintained normal blood glucose levels until adulthood. Insulin receptor (IR) activation after insulin stimulation was decreased during the period of protein restriction. In addition, glucose uptake, insulin receptor substrate 1 (IRS-1) phosphorylation and glucose transporter 4 (GLUT-4) translocation in muscle were reduced in response to insulin during suckling. In contrast, non- or insulin-stimulated glucose uptake and GLUT-4 translocation were found significantly increased in muscle of adult offspring. Finally, basal association of phosphatidylinositol 3-kinase (PI3-kinase) with IRS-1 was increased and was highly stimulated by insulin in muscle from adult rats. Our findings suggest that early postnatal undernutrition increases insulin sensitivity in adulthood, which appears to be directly related to changes in critical steps required for glucose metabolism.