Biomedical subjects

Frankie B Stentz

Publications and source records attributed to Frankie B Stentz.

8 recordsLinked to original sources

PubMed2006

Palmitic acid-induced activation of human T-lymphocytes and aortic endothelial cells with production of insulin receptors, reactive oxygen species, cytokines, and lipid peroxidation.

Diabetic conditions are associated with hyperglycemia and hyperlipidemia, but the role of saturated fatty acids (SFA) vs. unsaturated fatty acids (UFA) in activation of T-lymphocytes and human aortic endothelial cells (HAEC) is not known. We investigated in vitro effects of various concentrations of SFA (palmitate) and UFA (oleic, linoleic, linolenic, and arachidonic) acids in activation of these cells. These cells in presence of palmitate, but not UFA, exhibited time, and concentration-dependent emergence of insulin receptors, GLUT 4 expression, generation of ROS, cytokines, lipid peroxidation, and IRS-1. We conclude that both T-lymphocytes and HAEC share common characteristics in exhibiting activation of these cells to palmitate, but not to UFA, by developing insulin receptors and becoming insulin responsive tissues, a hitherto unknown response to palmitate. We hypothesize that these events may serve as protective defense mechanisms against acute effects of glucotoxicity and lipotoxicity in these cells.

Aorta↗

PubMed2005

De novo emergence of insulin-stimulated glucose uptake in human aortic endothelial cells incubated with high glucose.

Elevated glucose concentrations have profound effects on cell function. We hypothesized that incubation of human aortic endothelial cells (HAEC) with high glucose increases insulin signaling and develops the appearance of insulin-stimulated glucose uptake by the cells. Compared with 5 mM glucose, incubation of HAEC with 30 mM glucose for up to 48 h increased in a time-dependent manner expression of insulin receptor, insulin receptor substrate (IRS)-1, IRS-2, and GLUT1 proteins. High glucose also increased the specific binding of (125)I-labeled insulin in HAEC accompanied by accelerated production of interleukin (IL)-6 and IL-8. Short-term stimulation by 50 microU/ml insulin did not activate [(14)C]glucose uptake by HAEC incubated in 5 mM glucose. However, an addition of insulin to high glucose-exposed endothelial cells led to a significant increase in [(14)C]glucose uptake in a glucose concentration- and time-dependent fashion, reaching a plateau at 48 h of incubation. Furthermore, incubation of HAEC with 30 mM glucose resulted in a new insulin-stimulated extracellular signal-regulated kinase-1/2 mitogen-activated protein kinase phosphorylation and increased lipid peroxidation and production of reactive oxygen species. These studies show for the first time that high glucose increases expression of insulin receptors and downstream elements of the insulin-signaling pathway and transforms "insulin-resistant" aortic endothelial cells into "insulin-sensitive" tissue regarding glucose uptake.

Aorta↗

PubMed2005

Hyperglycemia-induced activation of human T-lymphocytes with de novo emergence of insulin receptors and generation of reactive oxygen species.

Upon activation by phytohemagglutine (PHA), T-lymphocytes (T-cells) express receptors for growth factors, insulin, IGF-1 and IL2 and become insulin sensitive. Diabetic ketoacidosis (DKA) is associated with in vivo emergence of these growth factor receptors without incubation with PHA. As DKA consists of multiple metabolic alterations, in addition to hyperglycemia, we investigated the in vitro effect of different concentrations of glucose (5, 15, and 30 mM) in isolated CD4 of human T-cells at various time intervals (0, 24, 48, and 72 h). Hyperglycemia, but not euglycemia, resulted in de novo emergence of growth factor receptors in a dose- and time-dependent fashion. The activation was also associated with incremental changes in GLUT 4, IRS-1, proinflammatory cytokines, and oxidative stress components. We propose that activation of T-cells with development of insulin receptors in hyperglycemic conditions may serve as a mechanism for control of glucose entry into these cells, thus, protecting them against glucose toxicity.

CD4-Positive T-Lymphocytes↗

PubMed2004

Transcriptome and proteome expression in activated human CD4 and CD8 T-lymphocytes.

T-lymphocytes (T-cells) are unique in that unlike monocytes, they have no insulin receptors, and are insulin insensitive, but upon activation with antigens develop insulin, IGF-1, and IL-2 receptors, and become insulin sensitive tissues. In vivo activation of these cells has now been demonstrated in patients with diabetic ketoacidosis. We analyzed the genomics and proteomics of activated and non-activated CD4+ and CD8+ T-cells of normal subjects using Affymetrix microarray gene chips and proteomes by SELDI-TOF mass spectrometry analysis. Genes for IL-2, insulin, and IGF-1 receptors were increased at least 2-fold in activated vs non-activated T-cells. Using an expression array containing the entire human genome of 39,500 genes, we evaluated approximately 27,000 genes relevant in physiologic and cellular ontologies. Of these, approximately 10,500 genes were increased in activated cells, compared to about 7,000, which were decreased, and approximately 9500, which were unchanged. Among activated ontologies were signal transduction pathways such as IRS-1, IRS-2, Akt, and glycolytic pathways. To our knowledge this is the first report of an hitherto unreported event. Possible implications of these processes are discussed in the light of their physiological significance.

Adult↗

PubMed2004

Diabetic ketoacidosis induces in vivo activation of human T-lymphocytes.

Diabetic ketoacidosis (DKA) is an inflammatory state associated with immune responses in polymorphonuclear cells (PMN). Activation of subgroup of T-lymphocytes in PMN of DKA patients, however, is not known. We studied in vivo activation of CD4 and CD8 lymphocytes by measuring de novo growth factor receptor for insulin, IGF-1, and IL-2 in eight patients on admission and at resolution of DKA, and compared them with matched controls. The presence of these receptors was demonstrated in all patients' lymphocytes on admission, but not in control subjects. This event was associated with increased levels of thiobarbituric acid-reacting material and dichlorofluorescien, as markers of oxidative stress. Based on these new findings and works in the literature, we hypothesize that hyperglycemia/ketosis results in increased reactive oxygen species, leading to increased levels of cytokines and emergence of growth factor receptors. We propose DKA changes the T-lymphocytes to insulin sensitive tissues as a compensatory mechanism.

CD4-Positive T-Lymphocytes↗

PubMed2004

De novo emergence of growth factor receptors in activated human CD4+ and CD8+ T lymphocytes.

Using phytohemagglutinin (PHA)-activated human T lymphocytes, we have demonstrated de novo emergence of growth factor receptors (insulin, insulin-like growth factor-1 [IGF-1], and interleukin-2 [IL-2]) in the CD4(+) and CD8(+) subsets determined by flow cytometry. This activation was also associated with development of insulin-degrading activity (IDA) in a time-dependent fashion. These events, which are actinomycin- and cycloheximide-sensitive, occur only in activated, but not nonactivated, CD4(+) and CD8(+) lymphocytes. The emergence of these receptors, as well as IDA, which is preceded by CD69 emergence, reaches a plateau by 72 hours and is comparable in both subsets. The IDA is localized in the cytosol, and insulin binding is limited to the cell membrane. T-lymphocyte activation also initiates expression of the IL-2 gene with the transcription of IL-2 mRNA, the level of which is further enhanced by 38% with the addition of insulin. In these activated lymphocytes, insulin binding to its receptor also caused an 83% upregulation of phosphorylated insulin receptor substrate-1 (IRS-1). In situ development of these growth factor receptors and signal transduction mechanisms in T lymphocytes upon activation, such as by proinflammatory cytokines or oxidative stress, could be an important defense mechanism in various disease states in man.

CD4-Positive T-Lymphocytes↗

PubMed2004

Proinflammatory cytokines, markers of cardiovascular risks, oxidative stress, and lipid peroxidation in patients with hyperglycemic crises.

Acute and chronic hyperglycemia are proinflammatory states, but the status of proinflammatory cytokines and markers of oxidative stress and cardiovascular risks is not known in hyperglycemic crises of diabetic ketoacidosis (DKA) and nonketotic hyperglycemia (NKH). We studied 20 lean and 28 obese patients with DKA, 10 patients with NKH, and 12 lean and 12 obese nondiabetic control subjects. We measured 1) proinflammatory cytokines (tumor necrosis factor-alpha, interleukin [IL]-6, IL1-beta, and IL-8), 2) markers of cardiovascular risk (C-reactive protein [CRP], homocysteine, and plasminogen activator inhibitor-1 [PAI-1]), 3) products of reactive oxygen species (ROS; thiobarbituric acid [TBA]-reacting material, and dichlorofluorescein [DCF]), and 4) cortisol, growth hormone (GH), and free fatty acids (FFAs) on admission (before insulin therapy) and after insulin therapy and resolution of hyperglycemia and/or ketoacidosis. Results were compared with lean and obese control subjects. Circulating levels of cytokines, TBA, DCF, PAI-1, FFAs, cortisol, and GH on admission were significantly increased two- to fourfold in patients with hyperglycemic crises compared with control subjects, and they returned to normal levels after insulin treatment and resolution of hyperglycemic crises. Changes in CRP and homocysteine in response to insulin therapy did not reach control levels after resolution of hyperglycemia. We conclude that DKA and NKH are associated with elevation of proinflammatory cytokines, ROS, and cardiovascular risk factors in the absence of obvious infection or cardiovascular pathology. Return of these values to normal levels with insulin therapy demonstrates a robust anti-inflammatory effect of insulin.

Adult↗

PubMed2003

Activated T lymphocytes in Type 2 diabetes: implications from in vitro studies.

The number of subjects with Type 2 diabetes (DM2) has risen significantly in the last ten years. Obtaining sufficient human tissue to study this disease process as well as many other diseases is generally difficult. T lymphocytes offer a unique opportunity for these studies. Although resting human peripheral T-lymphocytes are devoid of insulin receptors, these receptors emerge upon activation of cells by specific antigens or mitogens. Concomitant with the insulin receptors, two other growth factor receptors (IGF-1 and IL-2) also emerge on the T lymphocyte cell surface along with intracellular signal transduction mechanisms and insulin degrading enzyme (IDE). After binding to its receptor, insulin has been shown to exert its classical effects on carbohydrate metabolism in the stimulated T- cell; thereby, validating the use of activated T-lymphocytes for studying the pathogenesis of metabolic and immune disorders and the mechanism(s) by which insulin exerts its effects. In activated T-lymphocytes, insulin stimulates glucose uptake, glucose oxidation, pyruvate flux and pyruvate dehydrogenase activity, amino acid transport, lipid metabolism and protein synthesis. Through its ability to enhance nutrient uptake and raise the levels of intermediary cellular metabolism, insulin is believed to maintain the allo-activated state of lymphocytes, enhance T-Lymphocyte responsiveness, and support or possibly promote the actions of immuno-derived regulatory growth and differential factors. Since insulin enhances energy requirements and protein synthesis necessary for appropriate T-cell functions, defects in insulin action may lead to inappropriate immunoresponses in various metabolic states such as in diabetes. Studies from our lab have found insulin binding, processing, and responsiveness in phytohemagglutinin(PHA)-activated T-cells are reflective of the donor's glycemic status and ambient insulin levels in subjects with Type 1 and Type 2 diabetes (DM2) and other insulin resistant states. Our studies show that patients with diabetic ketoacidosis and hyperglycemia have increased proinflammatory cytokines and activated CD4+ and CD8+ T lymphocytes. The diabetic state, where effective insulin concentrations are low and both glucose and free fatty acids are high, provides an environment of oxidative stress and activation of the inflammatory pathways. The mechanisms underlying insulin action, in general, or in the CD4+ and CD8+ T-lymphocytes, in particular, have not been clearly elucidated. Due to the accessibility of obtaining these cells from patients, activated T-lymphocytes offer the potential of studying diabetes and other disease in human subjects.

Diabetes Mellitus, Type 2↗