Slug, a Cancer-Related Transcription Factor, is Involved in Vascular Smooth Muscle Cell Transdifferentiation Induced by Platelet-Derived Growth Factor-BB During Atherosclerosis.

Background Heart attacks and stroke often result from occlusive thrombi following the rupture of vulnerable atherosclerotic plaques. Vascular smooth muscle cells (VSMCs) play a pivotal role in plaque vulnerability because of their switch towards a proinflammatory/macrophage-like phenotype when in the context of atherosclerosis. The prometastatic transcription factor Slug/Snail2 is a critical regulator of cell phenotypic transition. Here, we aimed to investigate the role of Slug in the transdifferentiation process of VSMCs occurring during atherogenesis. Methods and Results In rat and human primary aortic smooth muscle cells, Slug protein expression is strongly and rapidly increased by platelet-derived growth factor-BB (PDGF-BB). PDGF-BB increases Slug protein without affecting mRNA levels indicating that this growth factor stabilizes Slug protein. Immunocytochemistry and subcellular fractionation experiments reveal that PDGF-BB triggers a rapid accumulation of Slug in VSMC nuclei. Using pharmacological tools, we show that the PDGF-BB-dependent mechanism of Slug stabilization in VSMCs involves the extracellular signal-regulated kinase 1/2 pathway. Immunohistochemistry experiments on type V and type VI atherosclerotic lesions of human carotids show smooth muscle-specific myosin heavy chain-/Slug-positive cells surrounding the prothrombotic lipid core. In VSMCs, Slug siRNAs inhibit prostaglandin E2 secretion and prevent the inhibition of cholesterol efflux gene expression mediated by PDGF-BB, known to be involved in plaque vulnerability and/or thrombogenicity. Conclusions Our results highlight, for the first time, a role of Slug in aortic smooth muscle cell transdifferentiation and enable us to consider Slug as an actor playing a role in the atherosclerotic plaque progression towards a life-threatening phenotype. This also argues for common features between acute cardiovascular events and cancer.

The flanking peptides issue from the maturation of the human islet amyloid polypeptide (hIAPP) slightly modulate hIAPP-fibril formation but not hIAPP-induced cell death.

Type 2 diabetes mellitus is a disease characterized by the formation of amyloid fibrillar deposits consisting mainly in human islet amyloid polypeptide (hIAPP), a peptide co-produced and co-secreted with insulin. hIAPP and insulin are synthesized by pancreatic ß cells initially as prehormones resulting after sequential cleavages in the mature peptides as well as the two flanking peptides (N- and C-terminal) and the C-peptide, respectively. It has been suggested that in the secretory granules, the kinetics of hIAPP fibril formation could be modulated by some internal factors. Indeed, insulin is known to be a potent inhibitor of hIAPP fibril formation and hIAPP-induced cell toxicity. Here we investigate whether the flanking peptides could regulate hIAPP fibril formation and toxicity by combining biophysical and biological approaches. Our data reveal that both flanking peptides are not amyloidogenic. In solution and in the presence of phospholipid membranes, they are not able to totally inhibit hIAPP-fibril formation neither hIAPP-membrane damage. In the presence of INS-1 cells, a rat pancreatic ß-cell line, the flanking peptides do not modulate hIAPP fibrillation neither hIAPP-induced cell death while in the presence of human islets, they have a slightly tendency to reduce hIAPP fibril formation but not its toxicity. These data demonstrate that the flanking peptides do not strongly contribute to reduce mature hIAPP amyloidogenesis in solution and in living cells, suggesting that other biochemical factors present in the cells must act on mature hIAPP fibril formation and hIAPP-induced cell death.

NOV/CCN3: A New Adipocytokine Involved in Obesity-Associated Insulin Resistance.

Identification of new adipokines that potentially link obesity to insulin resistance represents a major challenge. We recently showed that NOV/CCN3, a multifunctional matricellular protein, is synthesized and secreted by adipose tissue, with plasma levels highly correlated with BMI. NOV involvement in tissue repair, fibrotic and inflammatory diseases, and cancer has been previously reported. However, its role in energy homeostasis remains unknown. We investigated the metabolic phenotype of NOV(-/-) mice fed a standard or high-fat diet (HFD). Strikingly, the weight of NOV(-/-) mice was markedly lower than that of wild-type mice but only on an HFD. This was related to a significant decrease in fat mass associated with an increased proportion of smaller adipocytes and to a higher expression of genes involved in energy expenditure. NOV(-/-) mice fed an HFD displayed improved glucose tolerance and insulin sensitivity. Interestingly, the absence of NOV was associated with a change in macrophages profile (M1-like to M2-like), in a marked decrease in adipose tissue expression of several proinflammatory cytokines and chemokines, and in enhanced insulin signaling. Conversely, NOV treatment of adipocytes increased chemokine expression. Altogether, these results show that NOV is a new adipocytokine that could be involved in obesity-associated insulin-resistance.

Inhibition of the Inflammasome NLRP3 by Arglabin Attenuates Inflammation, Protects Pancreatic ß-Cells from Apoptosis, and Prevents Type 2 Diabetes Mellitus Development in ApoE2Ki Mice on a Chronic High-Fat Diet.

Intraperitoneal injection of arglabin (2.5 ng/g of body weight, twice daily, 13 weeks) into female human apolipoprotein E2 gene knock-in (ApoE2Ki) mice fed a high-fat Western-type diet (HFD) reduced plasma levels of glucose and insulin by ∼20.0% ± 3.5% and by 50.0% ± 2.0%, respectively, in comparison with vehicle-treated mice. Immunohistochemical analysis revealed the absence of active caspase-3 in islet sections from ApoE2Ki mice fed a HFD and treated with arglabin. In addition, arglabin reduced interleukin-1ß (IL-1ß) production in a concentration-dependent manner in Langerhans islets isolated from ApoE2Ki mice treated with lipopolysaccharide (LPS) and with cholesterol crystals. This inhibitory effect is specific for the inflammasome NOD-like receptor family, pyrin domain-containing 3 (NLRP3) because IL-1ß production was abolished in Langerhans islets isolated from Nlrp3(-/-) mice. In the insulin-secreting INS-1 cells, arglabin inhibited, in a concentration-dependent manner, the maturation of pro-IL-1ß into biologically active IL-1ß probably through the inhibition of the maturation of procaspase-1 into active capsase-1. Moreover, arglabin reduced the susceptibility of INS-1 cells to apoptosis by increasing Bcl-2 levels. Similarly, autophagy activation by rapamycin decreased apoptosis susceptibility while autophagy inhibition by 3-methyladenin treatment promoted apoptosis. Arglabin further increased the expression of the autophagic markers Bcl2-interacting protein (Beclin-1) and microtubule-associated protein 1 light chain 3 II (LC3-II) in a concentration-dependent manner. Thus, arglabin reduces NLRP3-dependent inflammation as well as apoptosis in pancreatic ß-cells in vivo and in the INS-1 cell line in vitro, whereas it increases autophagy in cultured INS-1 cells, indicating survival-promoting properties of the compound in these cells. Hence, arglabin may represent a new promising compound to treat inflammation and type 2 diabetes mellitus development.

Glucocorticoids Inhibit Basal and Hormone-Induced Serotonin Synthesis in Pancreatic Beta Cells.

Diabetes is a major complication of chronic Glucocorticoids (GCs) treatment. GCs induce insulin resistance and also inhibit insulin secretion from pancreatic beta cells. Yet, a full understanding of this negative regulation remains to be deciphered. In the present study, we investigated whether GCs could inhibit serotonin synthesis in beta cell since this neurotransmitter has been shown to be involved in the regulation of insulin secretion. To this aim, serotonin synthesis was evaluated in vitro after treatment with GCs of either islets from CD1 mice or MIN6 cells, a beta-cell line. We also explored the effect of GCs on the stimulation of serotonin synthesis by several hormones such as prolactin and GLP 1. We finally studied this regulation in islet in two in vivo models: mice treated with GCs and with liraglutide, a GLP1 analog, and mice deleted for the glucocorticoid receptor in the pancreas. We showed in isolated islets and MIN6 cells that GCs decreased expression and activity of the two key enzymes of serotonin synthesis, Tryptophan Hydroxylase 1 (Tph1) and 2 (Tph2), leading to reduced serotonin contents. GCs also blocked the induction of serotonin synthesis by prolactin or by a previously unknown serotonin activator, the GLP-1 analog exendin-4. In vivo, activation of the Glucagon-like-Peptide-1 receptor with liraglutide during 4 weeks increased islet serotonin contents and GCs treatment prevented this increase. Finally, islets from mice deleted for the GR in the pancreas displayed an increased expression of Tph1 and Tph2 and a strong increased serotonin content per islet. In conclusion, our results demonstrate an original inhibition of serotonin synthesis by GCs, both in basal condition and after stimulation by prolactin or activators of the GLP-1 receptor. This regulation may contribute to the deleterious effects of GCs on beta cells.

Ketosis-prone type 2 diabetes mellitus and human herpesvirus 8 infection in sub-saharan africans.

CONTEXT: An atypical form of type 2 diabetes mellitus (DM-2) is revealed by ketosis (ketosis-prone type 2 diabetes mellitus), frequently occurring in individuals who are black and of African origin, and characterized by an acute onset requiring transient insulin therapy. Its sudden onset suggests precipitating factors. OBJECTIVE: To investigate the putative role of human herpesvirus 8 (HHV-8) in the pathogenesis of ketosis-prone DM-2. DESIGN, SETTING, AND PARTICIPANTS: A cross-sectional study in which antibodies were searched against latent and lytic HHV-8 antigens using immunofluorescence. The presence of HHV-8 in genomic DNA was investigated in 22 of the participants at clinical onset of diabetes. We also tested whether HHV-8 was able to infect human pancreatic beta cells in culture in vitro. The study was conducted at Saint-Louis University Hospital, Paris, France, from January 2004 to July 2005. All participants were black and of African origin: 187 were consecutive diabetic patients of whom 81 had ketosis-prone DM-2 and 106 had nonketotic DM-2, and 90 individuals were nondiabetic control participants who were matched for age and sex. MAIN OUTCOME MEASURES: Seroprevalence of HHV-8 and percentage of patients with HHV-8 viremia at onset in ketosis-prone DM-2. RESULTS: HHV-8 antibodies were found in 71 patients (87.7%) with ketosis-prone DM-2 vs 16 patients (15.1%) with nonketotic DM-2 (odds ratio, 39.9; 95% confidence interval, 17.1-93.4; P < .001) and 36 of the control participants (40.0%) (odds ratio, 10.7; 95% confidence interval, 4.9-23.4; P < .001). HHV-8 in genomic DNA was present in 6 of 13 patients with ketosis-prone DM-2 tested at acute onset and in 0 of 9 patients with nonketotic DM-2. HHV-8 proteins were present in human islet cells that were cultured for 4 days in the presence of HHV-8. CONCLUSIONS: In this preliminary cross-sectional study, the presence of HHV-8 antibodies was associated with ketosis-prone DM-2 in patients of sub-Saharan African origin. Longitudinal studies are required to understand the clinical significance of these findings.