Is the Risk and Nature of CVD the Same in Type 1 and Type 2 Diabetes?

The incidence of both type 1 and type 2 diabetes is increasing globally, most likely explained by environmental changes, such as changing exposures to foods, viruses, and toxins, and by increasing obesity. While cardiovascular disease (CVD) mortality has been declining recently, this global epidemic of diabetes threatens to stall this trend. CVD is the leading cause of death in both type 1 and type 2 diabetes, with at least a two- to fourfold increased risk in patients with diabetes. In this review, the risk factors for CVD are discussed in the context of type 1 and type 2 diabetes. While traditional risk factors such as dyslipidemia, hypertension, and obesity are greater in type 2 patients than in type 1 diabetes, they explain only about half of the increased CVD risk. The role for diabetes-specific risk factors, including hyperglycemia and kidney complications, is discussed in the context of new study findings.     

Study on the polymorphisms and promoter methylation and expression of the glutathione Stransferases P1 gene in hepatocellular carcinoma

Objective To study the relationship between hepatocellular carcinoma (HCC) and the polymorphisms, promoter methylation, and expression of glutathione S-transferases P1 gene (GST)P1 gene. Methods Using methylation -special PCR (MSP), the methylated status of CpG islands of GSTP1 gene in tumor tissues of 53 HCC and its adjacent nontumor tissues were studied. The en-     

PGC-1β promotes enterocyte lifespan and tumorigenesis in the intestine

The mucosa of the small intestine is renewed completely every 3–5 d throughout the entire lifetime by small populations of adult stem cells that are believed to reside in the bottom of the crypts and to migrate and differentiate into all the different populations of intestinal cells. When the cells reach the apex of the villi and are fully differentiated, they undergo cell death and are shed into the lumen. Reactive oxygen species (ROS) production is proportional to the electron transfer activity of the mitochondrial respiration chain. ROS homeostasis is maintained to control cell death and is finely tuned by an inducible antioxidant program. Here we show that peroxisome proliferator-activated receptor-γ coactivator-1β (PGC-1β) is highly expressed in the intestinal epithelium and possesses dual activity, stimulating mitochondrial biogenesis and oxygen consumption while inducing antioxidant enzymes. To study the role of PGC-1β gain and loss of function in the gut, we generated both intestinal-specific PGC-1β transgenic and PGC-1β knockout mice. Mice overexpressing PGC-1β present a peculiar intestinal morphology with very long villi resulting from increased enterocyte lifespan and also demonstrate greater tumor susceptibility, with increased tumor number and size when exposed to carcinogens. PGC-1β knockout mice are protected from carcinogenesis. We show that PGC-1β triggers mitochondrial respiration while protecting enterocytes from ROS-driven macromolecule damage and consequent apoptosis in both normal and dysplastic mucosa. Therefore, PGC-1β in the gut acts as an adaptive self-point regulator, capable of providing a balance between enhanced mitochondrial activity and protection from increased ROS production.The intestine represents the interface between the organism and its luminal environment and is constantly challenged by mechanical stress, diet-derived toxins and oxidants, and endogenously generated reactive oxygen species (ROS), which can induce serious damage to all biological molecules and cell structures (1). To preserve cellular integrity and tissue homeostasis, the intestine possesses self-renewing capacity via the continuous migration of new enterocytes that undergo differentiation from the crypt to the apical compartment of the villus, where they become competent to apoptosis and are shed into the lumen. ROS accumulation within intestinal epithelial cells promotes apoptotic cell death in the differentiated compartment (2). The mitochondrial electron transport chain is a major site of ROS production in the cells. Under physiological conditions, the balance between ROS generation and detoxification is controlled by a set of cellular enzymes including superoxide dismutase and catalase. Important components of the ROS-scavenging pathways are linked to mitochondrial oxidative metabolism via the peroxisome proliferator-activated receptor-γ coactivators 1α and 1β (PGC-1α and PGC-1β), apparently enabling cells to maintain normal redox status in response to changing oxidative capacity (3). PGC-1α and PGC-1β are master regulators of mitochondrial biogenesis and oxidative metabolism as well as antioxidant defense. Both PGC-1α and PGC-1β are preferentially expressed in tissues with high oxidative capacity where they participate, through mitochondrial biogenesis, in the metabolic response to high energy demand (4), such as cold-adapted thermogenesis in brown adipose tissue (5), fiber-type switching in striated muscle (6), and fatty acid β oxidation and gluconeogenesis in liver during a fasting state (7, 8). The increase in mitochondrial biogenesis and activity stimulated by PGC-1 proteins may cause an increase in the production of ROS. However, PGC-1α also has been shown to increase the expression of the major mitochondrial antioxidant enzyme superoxide dismutase 2 (Sod2) (3, 9). Therefore, PGC-1α is able to upgrade aerobic energy metabolism while preserving ROS homeostasis, by simultaneously promoting ROS formation and detoxification. Recently, it has been shown in Drosophila that the PGC-1α homolog spargel is able to induce mitochondrial function and oxygen consumption, which is coupled to the induction of scavenger systems and ROS reduction, finally leading to increased longevity (10). On the other hand, in the differentiated intestinal epithelium of mice, PGC-1α induces mitochondrial biogenesis and oxygen consumption, but it is not able to induce the ROS-scavenging apparatus, thus promoting ROS-dependent apoptotic cell death (2).PGC-1β is highly similar to PGC-1α, both in amino acid sequence and ability to regulate several metabolic pathways (8, 11). Therefore, in the present study we focus on the function of PGC-1β in the intestinal epithelium, giving special attention to the effect of this coactivator in enterocyte homeostasis. We first show that PGC-1β is highly expressed in intestinal epithelium with an almost ubiquitous pattern of localization along the entire crypt–villus axis. To study its activation, we generated mice overexpressing PGC-1β selectively in the enterocytes. We show that in these cells PGC-1β enhances mitochondrial biogenesis and respiration and induces a parallel increase in antioxidant enzymes, such as Sod2 and glutathione peroxidase 4 (Gpx4), as well as peroxiredoxins. As a result, the intestinal morphology is severely affected, with significant increases in enterocyte longevity and mucosal villi length. Concomitantly, PGC-1β overexpression leads to a significant increase in tumor number and size in two distinct models of intestinal carcinogenesis. Moreover, to confirm the role of PGC-1β activity in the intestine, we also generated intestinal-specific PGC-1β (iPGC-1β) knockout mice that, in line with the evidence from transgenic mice, show reduced expression of several metabolic pathways and mitochondrial antioxidant systems as well as decreased susceptibility to tumors. Indeed, tumors may use adaptive mechanisms to keep their ROS burden within a range that permits their growth and survival. In such contest, PGC-1β acts as a gatekeeper of redox status, allowing enterocyte survival and, in cancer-promoting conditions, tumor progression.     

sICAM-1 and TNF-α in Asthma and Rhinitis: Relationship with the Presence of Atopy

Background. A genetically determined overproduction of specific immunoglobulin E (IgE) underlies many diseases like asthma or allergic rhinitis. IgE as well as tumor necrosis factor-α (TNF-α), and intercellular adhesion molecule-1 (ICAM-1) play a critical role in the induction and maintenance of inflammation. While the correlation between IgE and atopy is inseparable, little is known about the correlation of atopy with markers of inflammation. Objective. We investigated the relationship between the serum concentrations of TNF-α, soluble ICAM-1 (sICAM-1), and the presence of atopy in patients with persistent rhinitis or asthma. Methods. Serum concentrations of sICAM-1, TNF-α, and total IgE were investigated in 64 adults with persistent allergic rhinitis, 17 subjects with nonatopic rhinitis, 90 patients with asthma, and 21 healthy individuals. Atopy was diagnosed on the basis of positive family history, skin prick tests, and serum IgE concentration. Results. Total IgE concentration was significantly higher in patients with atopic rhinitis or asthma when compared with nonatopic patients and healthy individuals and was the highest in patients suffering from severe atopic asthma who were not treated with systemic glucocorticosteroids. Although there were marked alterations in IgE in atopic and nonatopic patients, there were no significant differences between atopic and corresponding groups of nonatopic rhinitic and asthmatic patients in sICAM-1 and TNF-α concentrations. (sICAM-1 in rhinitis: atopic vs. nonatopic patients: 224.02 and 221.08 ng/ml, respectively, p > .05; in mild/moderate asthma: atopic vs. nonatopic: 306.22 and 326.39 ng/ml, respectively, p > .05; severe asthma without oral corticosteroids therapy: atopic vs. nonatopic: 418.03 and 468.09 ng/ml, respectively, p > .05; and severe asthma with oral corticosteroids therapy: atopic vs. nonatopic: 320.66 and 308.09 ng/ml, respectively, p > .05). Conclusions. Concentrations of sICAM-1 and TNF-α are significantly higher in patients with asthma compared with those observed in patients with rhinitis, but they are independent of the presence of atopy.     

PDK1 coordinates survival pathways and β-adrenergic response in the heart

The 3-phosphoinositide-dependent kinase-1 (PDK1) plays an important role in the regulation of cellular responses in multiple organs by mediating the phosphoinositide 3-kinase (PI3-K) signaling pathway through activating AGC kinases. Here we defined the role of PDK1 in controlling cardiac homeostasis. Cardiac expression of PDK1 was significantly decreased in murine models of heart failure. Tamoxifen-inducible and heart-specific disruption of Pdk1 in adult mice caused severe and lethal heart failure, which was associated with apoptotic death of cardiomyocytes and β₁-adrenergic receptor (AR) down-regulation. Overexpression of Bcl-2 protein prevented cardiomyocyte apoptosis and improved cardiac function. In addition, PDK1-deficient hearts showed enhanced activity of PI3-Kγ, leading to robust β₁-AR internalization by forming complex with β-AR kinase 1 (βARK1). Interference of βARK1/PI3-Kγ complex formation by transgenic overexpression of phosphoinositide kinase domain normalized β₁-AR trafficking and improved cardiac function. Taken together, these results suggest that PDK1 plays a critical role in cardiac homeostasis in vivo by serving as a dual effector for cell survival and β-adrenergic response.     

NLRP1 haplotypes associated with vitiligo and autoimmunity increase interleukin-1β processing via the NLRP1 inflammasome

Nuclear localization leucine-rich-repeat protein 1 (NLRP1) is a key regulator of the innate immune system, particularly in the skin where, in response to molecular triggers such as pathogen-associated or damage-associated molecular patterns, the NLRP1 inflammasome promotes caspase-1–dependent processing of bioactive interleukin-1β (IL-1β), resulting in IL-1β secretion and downstream inflammatory responses. NLRP1 is genetically associated with risk of several autoimmune diseases including generalized vitiligo, Addison disease, type 1 diabetes, rheumatoid arthritis, and others. Here we identify a repertoire of variation in NLRP1 by deep DNA resequencing. Predicted functional variations in NLRP1 reside in several common high-risk haplotypes that differ from the reference by multiple nonsynonymous substitutions. The haplotypes that are high risk for disease share two substitutions, L155H and M1184V, and are inherited largely intact due to extensive linkage disequilibrium across the region. Functionally, we found that peripheral blood monocytes from healthy subjects homozygous for the predominant high-risk haplotype 2A processed significantly greater (P < 0.0001) amounts of the IL-1β precursor to mature bioactive IL-1β under basal (resting) conditions and in response to Toll-like receptor (TLR) agonists (TLR2 and TLR4) compared with monocytes from subjects homozygous for the reference haplotype 1. The increase in basal release was 1.8-fold greater in haplotype 2A monocytes, and these differences between the two haplotypes were consistently observed three times over a 3-mo period; no differences were observed for IL-1α or TNFα. NLRP1 RNA and protein levels were not altered by the predominant high-risk haplotype, indicating that altered function of the corresponding multivariant NLRP1 polypeptide predisposes to autoimmune diseases by activation of the NLRP1 inflammasome.     

Role of the β1 integrin molecule in T-cell activation and migration

β1 integrins play crucial roles in a variety of cell processes such as adhesion, migration, proliferation, and differentiation of lymphocytes. To understand the molecular mechanisms of these various biological effects, it is particularly important to analyze cell signaling through the β1 integrins. Our previous study showed that PLC-γ, pp125FAK (focal adhesion kinase), pp105, paxillin, p59fyn, p56lck, and ERK1/2 are phosphorylated in their tyrosine residues upon engagement of β1 integrins. We identified pp105 as Cas (Crk-associated substrate)-related protein and successfully cloned its cDNA. pp105 is a Cas homologue predominantly expressed in the cells of lymphoid lineage, which led us to designate it Cas-L. Like p130Cas, Cas-L contains a single SH3 domain and multiple SH2-binding sites (YXXP motif), which are suggested to bind SH2 domains of Crk, Nck, and SHPTP2. Subsequent studies revealed that pp125FAK binds Cas-L on its SH3 domain and phosphorylates its tyrosine residues upon β1 integrin stimulation. Since Cas-L is preferentially expressed in lymphocytes, it is conceivable that Cas-L plays an important role in lymphocyte-specific signals. We have shown that Cas-L is involved in the T-cell receptor (TCR)/CD3 signaling pathway as well as the β1 integrin signaling pathway. Cas-L is transiently phosphorylated following CD3 crosslinking and tyrosine-phosphorylated Cas-L binds to Crk and C3G. Furthermore, a Cas-L mutant (Cas-LΔSH3), which lacks the binding site for FAK, is still tyrosine-phosphorylated upon CD3 crosslinking but not upon β1 integrin crosslinking, suggesting that FAK is not involved in CD3-dependent Cas-L phosphorylation. Finally, we have identified a crucial role of Cas-L in β1 integrin-mediated T-cell co-stimulation. We have found that this co-stimulatory pathway is impaired in the Jurkat T-cell line, and that the expression level of Cas-L is reduced in the Jurkat cells compared to peripheral T-cells. The transfection of Cas-L cDNA into Jurkat cells restored the β1 integrin-mediated co-stimulation, while the transfection of Cas-LΔSH3 mutant failed to do so, which contrasts with the case of CD3-mediated signaling. These results indicate that Cas-L plays a key role, through the association and phosphorylation by FAK, in β1 integrin-mediated T-cell co-stimulation. Moreover, tyrosine phosphorylation of Cas-L is critical for T-cell receptor and β1 integrin-induced T-lymphocyte migration. Taken together, Cas-L might be the bi-modal docking protein which assembles the signals through β1 integrins and TCR/CD3, and which participates in a variety of T-cell functions. Received: August 24, 1999 / Accepted: August 31, 1999     

Z α-1 antitrypsin deficiency and the endoplasmic reticulum stress response

The serine proteinase inhibitor α-1 antitrypsin (AAT) is produced principally by the liver at the rate of 2 g/d. It is secreted into the circulation and provides an antiprotease protective screen throughout the body but most importantly in the lung, where it can neutralise the activity of the serine protease neutrophil elastase. Mutations leading to deficiency in AAT are associated with liver and lung disease. The most notable is the Z AAT mutation, which encodes a misfolded variant of the AAT protein in which the glutamic acid at position 342 is replaced by a lysine. More than 95% of all individuals with AAT deficiency carry at least one Z allele. ZAAT protein is not secreted effectively and accumulates intracellularly in the endoplasmic reticulum (ER) of hepatocytes and other AAT-producing cells. This results in a loss of function associated with decreased circulating and intrapulmonary levels of AAT. However, the misfolded protein acquires a toxic gain of function that impacts on the ER. A major function of the ER is to ensure correct protein folding. ZAAT interferes with this function and promotes ER stress responses and inflammation. Here the signalling pathways activated during ER stress in response to accumulation of ZAAT are described and therapeutic strategies that can potentially relieve ER stress are discussed.     

Interleukin-1β and interleukin-1α stimulate the plasminogen activator activity and prostaglandin E2 levels of human synovial cells

Monocyte—macrophage polypeptides (monokines) cause synovial cells to increase the levels of putative mediators of destruction and inflammation. This interaction may account for some of the properties of rheumatoid pannus. We report here that samples of purified human interleukin-1β(IL-1β) and recombinant IL-1β stimulate both the plasminogen activator activity and prostaglandin E₂ levels of human synovial fibroblast-like cells. The same holds true for purified pig IL-1 (catabolin) and recombinant murine IL-1. The elevation in plasminogen activator activity was inhibited by indomethacin, and this suggests that endogenous prostanoids are important in the IL-1-mediated stimulation of proteinase activity.