Mae Sheikh-Ali

Hyperglycemia-induced endoplasmic reticulum stress in endothelial cells

OBJECTIVE Hyperglycemia-induced endothelial cell dysfunction in vascular disease can occur due to increased oxidative stress and a concomitant increase in endoplasmic reticulum (ER) stress. To investigate whether these cellular stresses are independent or causally linked, we determined whether or not specific glycolytic intermediates that induce oxidative stress also induce ER stress. METHODS Human umbilical vein endothelial cells were treated with dextrose, partially metabolizable (e.g., fructose and galactose) and non-metabolizable sugars (e.g., 3-O-methyglucose), and various intermediates of the glycolytic and tricarboxylic acid pathways. Activation of the unfolded protein response and subsequent generation of ER stress was measured by the ER stress-responsive alkaline phosphatase method, and superoxide (SO) generation was measured using the hydro-ethidene-fluorescence method. The mitochondrial origin of the SO and the generation of ER stress by dextrose and the intermediate metabolites were confirmed with experiments using allopurinol and diphenyleneiodonium chloride to block SO generation by xanthine oxidase and nicotinamide adenosine dinucleotide phosphate oxidase, respectively. RESULTS Although ER stress could be induced by glycolytic intermediates up to and including pyruvate, the SO generation occurred in the presence of glycolytic and mitochondrial metabolites. CONCLUSION Although the mitochondria are the site of signals generated by dextrose to initiate oxidative stress, the dextrose-induced ER stress, unlike SO generation, does not require pyruvate oxidation in the mitochondria.

Effects of antioxidants on glucose-induced oxidative stress and endoplasmic reticulum stress in endothelial cells

AIM Hyperglycemia-induced endothelial cell dysfunction can be the result of increased oxidative stress and concomitant increase in endoplasmic reticulum (ER) stress. To test the extent of coupling between these two stresses, the effect of antioxidant vitamins on glucose-induced oxidative stress and ER stress in endothelial cells were studied. METHODS Human umbilical vein endothelial cells (HUVEC) were treated with physiological (5.5mM) or supra-physiological (27.5mM) dextrose concentrations, and ER stress and oxidative stress were measured. Additional experiments were carried out in HUVEC over-expressing exogenous glucose transporter-1 (Glut-1) and treated with 5.5mM dextrose. RESULTS Supra-physiological dextrose concentrations increased both ER stress and oxidative stress. However, while oxidative stress could be effectively inhibited with alpha-tocopherol and ascorbic acid, these antioxidants had no effect on ER stress. Increasing intracellular glucose levels by exogenous expression of Glut-1 in endothelial cells also increased oxidative stress and ER stress. Whereas the oxidative stress in these cells was reduced with alpha-tocopherol and ascorbic acid and dimethylsulfoxide, the ER stress could not be ameliorated with alpha-tocopherol and ascorbic acid. CONCLUSIONS These results indicate that ER stress can be uncoupled from oxidative stress and antioxidants can ameliorate the latter without altering the ER stress induced by hyperglycemia.

Estrogen-dependent inhibition of dextrose-induced endoplasmic reticulum stress and superoxide generation in endothelial cells.

Increased oxidative stress and endoplasmic reticulum stress (ER stress) have been implicated in atherosclerosis. Estrogens have potent antioxidant activity but their effects on ER stress have not been well studied. Therefore, we studied the effects of estradiol and related sex steroids on dextrose-induced ER stress and superoxide (SO) generation in human umbilical vein endothelial cells (HUVECs). Oxidative stress was measured using hydroethidine fluorescence and MCLA chemiluminescence. ER stress was measured with an ER stress-sensitive secreted alkaline phosphatase (ES-TRAP) assay and by Western blot analysis of the expression of GRP78, JNK1, and phosphorylated JNK1, markers for ER stress. A supraphysiological dextrose concentration (27.5mM) increased ER stress and SO generation compared to treatment with a physiological concentration (5.5mM) of dextrose. In the presence of estradiol or testosterone (T), ER stress and SO generation were significantly reduced. In contrast to T-treated cells, dihydrotestosterone and 5-methyltestosterone were ineffective at alleviating ER stress or SO generation. When HUVECs were treated with T and the aromatase inhibitor 4-hydroxy-4-androstene-3,17-dione, T was no longer effective at suppressing ER stress or inhibiting SO generation. Changes in GRP78 expression and JNK activity in HUVECs support the results obtained in the ES-TRAP assay. These results indicate that dextrose-induced endoplasmic reticulum stress and superoxide generation are reversed by estradiol and testosterone; however, the latter requires aromatase-dependent conversion to estradiol.

Medical Management and Strategies to Prevent Coronary Artery Disease in Patients with Type 2 Diabetes Mellitus

Abstract Coronary artery disease (CAD) in patients with type 2 diabetes mellitus (T2DM) is associated with increased immediate and long–term mortality compared with patients without T2DM. The amplified incidence of CAD stems partly from the aggregation of multiple risk factors, such as obesity, dyslipidemia, and hypertension, which occur in this population. In addition, there appear to be increased forces at play at the molecular and vascular levels in these individuals, which is evidenced by the increased thrombosis and inflammation that is seen in those with diabetic atherosclerosis. Hence, there is a growing need to emphasize early and vigilant risk factor management in patients with T2DM to help reduce their burden of cardiovascular–related mortality. In this article, we review the primary and secondary prevention measures as well as the management of CAD in patients with T2DM.

Role of vitamin D in the onset, progression, and severity of multiple sclerosis.

OBJECTIVE To review and assess the role of vitamin D in the onset, progression, and relapse of multiple sclerosis (MS), based on evidence acquired from the analysis of preclinical, observational, and interventional studies. METHODS All English language literature in MEDLINE (January 1969 through April 2012) was searched for observational and interventional studies on the dosage effect of vitamin D on the onset, progression, and relapse rate of MS. The medical subject heading (MeSH) terms used in the search included Vitamin D and Multiple Sclerosis. Additional publications and abstracts were identified from review articles and from the references cited in the previously found articles. In addition to the experimental studies, only those human studies that specified the population size, doses of vitamin D used, and the resulting effect on MS were considered. RESULTS Vitamin D deficiency is very common among MS patients. Multiple preclinical studies have shown that vitamin D is a potent regulator of inflammation in MS. Most observational studies support an association between high vitamin D levels and a reduced risk of developing MS. However, conflicting results have been reported by observational studies on the correlation between vitamin D and MS severity and by interventional studies using vitamin D as a therapeutic agent for MS. CONCLUSION Vitamin D deficiency in MS patients should be avoided. In addition, the risk of developing MS might be reduced by maintaining optimal vitamin D levels in the healthy population. Larger randomized interventional trials are needed to clarify the therapeutic effect of vitamin D in MS.

The Role of Micronutrients in Managing Diabetes

In Brief With the exceptions of folate for prevention of birth defects and calcium for prevention of bone disease, currently there is no evidence of benefit from vitamin or mineral supplementation in diabetic patients without underlying deficiencies. Given the recent revelations about antioxidant vitamins, it is prudent to refrain from using vitamin E, vitamin C, or vitamin A in excess of the Dietary Reference Intakes.

Inhibition of apolipoprotein A-I gene by the aryl hydrocarbon receptor: a potential mechanism for smoking-associated hypoalphalipoproteinemia.

AIMS Smokers have lower plasma concentrations of high-density lipoprotein (HDL) cholesterol and apolipoprotein A-I (apo A-I) compared with nonsmokers. To determine the molecular basis of this observation, the effect of activation of the aryl hydrocarbon receptor (AhR) on apo A-I gene expression was examined. MAIN METHODS HepG2 cells were treated with AhR receptor agonists benzo(a)pyrene (BaP) and CAY10465, and AhR receptor antagonist CAY10464 and apo A-I protein, mRNA levels and promoter activity were measured. The effect of nicotine on apo A-I protein secretion was also tested. Using a series or apo A-I gene promoter deletion constructs, a xenobiotic response element (XRE) was identified. KEY FINDINGS Treatment of HepG2 cells with the AhR receptor agonists BaP and CAY10465, inhibited apo A-I protein synthesis while nicotine, which does not bind AhR had no effect. Benzo(a)pyrene treatment also suppressed apo A-I mRNA and gene promoter activity. Treatment of HepG2 cells with the AhR receptor antagonist CAY10464 reversed the suppressive effect of BaP on apo A-I gene expression. A putative xenobiotic response element (XRE) was identified between nucleotides -325 and -186 (relative to the transcriptional start site, +1). SIGNIFICANCE These results suggest that the cigarette smoking related environmental contaminant BaP promotes hypoalphalipoproteinemia in part through activation of the hepatic AhR.

Circadian clock desynchronisation and metabolic syndrome

There is emerging evidence in the literature to suggest that disruption of the normal circadian rhythm (sleep–wake cycle signalling) is a potential risk factor to explain the increased incidence of metabolic syndrome. Over the last century, obesity, diabetes and other components of metabolic syndrome have been on the rise. On the other hand, the amount of sleep has decreased from an average of 6–8 h per night. Furthermore, the quality of sleep has declined with more individuals voluntarily decreasing their amount of sleep to work or enjoy leisure activities. Over the last decade, researchers have examined the relationship between disruption in human circadian system and the emergence of symptoms related to metabolic syndrome. Indeed, epidemiological studies suggest a relation between sleep duration and diabetes and obesity. Moreover, experimental animal and human studies suggest such a relation. These studies propose optimum sleep duration of 7–8 h per night to avoid circadian rhythm disruption and suggest that sleep disturbance, whether iatrogenic or disease-related, should be considered as a risk factor for metabolic syndrome, and be addressed. This field is in its infancy and further understanding of specific pathophysiological pathways of circadian desynchronisation will help in developing novel preventive and therapeutic strategies.

The effect of healthcare provider education on diabetes management of hospitalised patients

Background:  The importance of optimising blood glucose (BG) control in hospitalised patients is widely accepted. To determine whether focused education of physicians and nurses would result in measurable changes in glycaemic control, the effect of a diabetes‐focused educational programme on point of care (POC) BG measures was monitored.

25-hydroxyvitamin D levels and acute cellular rejection in liver transplant patients

OBJECTIVE To investigate the association between 25-hydroxyvitamin D [25(OH)D] levels prior to liver transplantation (LT) and the development of acute cellular rejection (ACR) within the first year post LT. METHODS This retrospective study included 275 consecutive LTs performed in 262 patients at Mayo Clinic in Jacksonville, Florida over 13 months. A total of 149 patients met the inclusion criteria. The correlations between 25(OH)D levels and the development, severity, and number of biopsy-proven ACR episodes were assessed. RESULTS The prevalence of 25(OH)D levels <30 ng/mL was 92%. No association was found between pre LT 25(OH)D levels and the diagnosis of ACR (P = .61). Mean ± SD pre LT 25(OH)D levels were 16.1 ± 6.8 ng/mL for 48 subjects with no rejection, 16.1 ± 8.2 ng/mL for those with a mild first episode of ACR (n = 58), and 18.4 ± 12.4 ng/mL for those who experienced a moderate/severe first ACR (n = 39). However, in a subgroup analysis of patients with 25(OH)D levels <30 ng/mL, there was a statistically significant negative correlation (P = .0252) between 25(OH) D level and the ACR rate. CONCLUSION Vitamin D insufficiency and deficiency prior to LT was prevalent in our cohort. There was no statistically significant association between low 25(OH)D levels and the diagnosis or severity of ACR or the number of rejection episodes within the first year post LT. However, there was a negative correlation between 25(OH)D levels below 30 ng/mL and the rate of ACR within 1 year post LT.