Lopinavir co-induces insulin resistance and ER stress in human adipocytes.

HIV-protease inhibitors (PIs) markedly decreased mortality of HIV-infected patients. However, their use has been associated with occurence of metabolic abnormalities the causes of which are not well understood. We report here that lopinavir, one of the most prescribed PI, dose-dependently co-induced insulin resistance and ER stress in human adipocytes obtained from differentiation of precursor cells. Insulin resistance was subsequent to IRS1 phosphorylation defects and resulted in a concentration-dependent decrease of glucose uptake. The major ER stress pathway involved was the phosphorylation of eIF2-alpha. Salubrinal, a selective eIF2-alpha dephosphorylation inhibitor, induced insulin resistance by targeting IRS1 phosphorylation at serine 312 and acted synergistically with LPV when both drugs were used in combination. This study points out the key role of eIF2-alpha phosphorylation in the development of PI-associated insulin resistance and ER stress. Thus, this protein represents a promising therapeutic target for development of new PIs devoid of adverse metabolic effects.

Arachidonic acid and prostacyclin signaling promote adipose tissue development: a human health concern?

High fat intake is associated with fat mass gain through fatty acid activation of peroxisome proliferator-activated receptors delta and gamma, which promote adipogenesis. We show herein that, compared to a combination of specific agonists to both receptors or to saturated, monounsaturated, and omega-3 polyunsaturated fatty acids, arachidonic acid (C20:4, omega-6) promoted substantially the differentiation of clonal preadipocytes. This effect was blocked by cyclooxygenase inhibitors and mimicked by carbacyclin, suggesting a role for the prostacyclin receptor and activation of the cyclic AMP-dependent pathways that regulate the expression of the CCAAT enhancer binding proteins beta and delta implicated in adipogenesis. During the pregnancy-lactation period, mother mice were fed either a high-fat diet rich in linoleic acid, a precursor of arachidonic acid (LO diet), or the same isocaloric diet enriched in linoleic acid and alpha-linolenic acid (LO/LL diet). Body weight from weaning onwards, fat mass, epididymal fat pad weight, and adipocyte size at 8 weeks of age were higher with LO diet than with LO/LL diet. In contrast, prostacyclin receptor-deficient mice fed either diet were similar in this respect, indicating that the prostacyclin signaling contributes to adipose tissue development. These results raise the issue of the high content of linoleic acid of i) ingested lipids during pregnancy and lactation, and ii) formula milk and infant foods in relation to the epidemic of childhood obesity.

Adipocyte differentiation of multipotent cells established from human adipose tissue.

In this study multipotent adipose-derived stem cells isolated from human adipose tissue (hMADS cells) were shown to differentiate into adipose cells in serum-free, chemically defined medium. During the differentiation process, hMADS cells exhibited a gene expression pattern similar to that described for rodent clonal preadipocytes and human primary preadipocytes. Differentiated cells displayed the key features of human adipocytes, i.e., expression of specific molecular markers, lipolytic response to agonists of beta-adrenoreceptors (beta2-AR agonist > beta1-AR agonist >> beta3-AR agonist) and to the atrial natriuretic peptide, insulin-stimulated glucose transport, and secretion of leptin and adiponectin. hMADS cells were able to respond to drugs as inhibition of adipocyte differentiation was observed in the presence of prostaglandin F2alpha, tumour necrosis factor-alpha, and nordihydroguaiaretic acid, a natural polyhydroxyphenolic antioxidant. Thus, for the first time, human adipose cells with normal karyotype and indefinite life span have been established. They represent a novel and valuable tool for studies of fat tissue development and metabolism.