Sarama Saha

Diabetic lipoproteins and adrenal aldosterone synthesis--a possible pathophysiological link?

An increased prevalence of diabetes mellitus (DM) has been reported in patients with primary aldosteronism (PA). DM is associated with abnormal structure and metabolism of circulating lipoproteins, which normally serve as a major source of cholesterol for adrenocortical steroidogenesis. The present study has been designed to investigate the effect of diabetically modified lipoproteins on adrenocortical aldosterone synthesis. Lipoproteins (VLDL, LDL, HDL) isolated from healthy volunteers, were subjected to oxidation or glycoxidation in the presence of sodium hypochlorite (3 mmol/l) or glucose (200 mmol/l), and aldosterone synthesis in human adrenocortical cells (H295R) was examined. Native and glycoxidized VLDL had greatest stimulatory effect on aldosterone production by 15-fold and 14-fold, respectively. At the molecular level, these VLDL produced maximum increases in Cyp11B2 mRNA level up to 17-fold. Experiments with the highly selective scavenger receptor class B type I (SR-BI) inhibitor BLT-1 revealed that cholesterol uptake from native and glycoxidized HDL and VLDL for hormone production is considerably mediated by SR-BI. Western blot analysis of extracellular signal-regulated kinase (ERK 1/2) phosphorylation and experiments with the MEK inhibitor U0126 indicated a specific mechanistic role of the ERK cascade in lipoprotein-mediated steroid hormone release. In summary, diabetic dyslipidemia and modification of circulating lipoproteins may promote adrenocortical aldosterone synthesis.

Impact of the Triglyceride/High-Density Lipoprotein Cholesterol Ratio and the Hypertriglyceremic-Waist Phenotype to Predict the Metabolic Syndrome and Insulin Resistance

Insulin resistance is the underlying mechanism for the metabolic syndrome and associated dyslipidaemia that theoretically implies a practical tool for identifying individuals at risk for cardiovascular disease and type-2-diabetes. Another screening tool is the hypertriglyceremic-waist phenotype (HTW). There is important impact of the ethnic background but a lack of studied European populations for the association of the triglyceride/high-density lipoprotein cholesterol (HDL-C) ratio and insulin resistance. This observational, retrospective study evaluated lipid ratios and the HTW for predicting the metabolic syndrome/insulin resistance in 1932 non-diabetic individuals from Germany in the fasting state and during a glucose tolerance test. The relations of triglyceride/HDL-C, total-cholesterol/HDL-C, and low-density lipoprotein cholesterol/HDL-C with 5 surrogate estimates of insulin resistance/sensitivity and metabolic syndrome were analysed by linear regression analysis and receiver operating characteristics (ROC) in participants with normal (n=1 333) or impaired fasting glucose (n=599), also for the impact of gender. Within the lipid ratios, triglyceride/HDL-C had the strongest associations with insulin resistance/sensitivity markers. In the prediction of metabolic syndrome, diagnostic accuracy was good for triglyceride/HDL-C (area under the ROC curve 0.817) with optimal cut-off points (in mg/dl units) of 2.8 for men (80% sensitivity, 71% specificity) and 1.9 for women (80% sensitivity, 75% specificity) and fair for HTW and HOMA-IR (area under the curve 0.773 and 0.761). These data suggest the triglyceride/HDL-C ratio as a physiologically relevant and practical index for predicting the concomitant presence of metabolic syndrome, insulin resistance and dyslipidaemia for therapeutic and preventive care in apparently healthy European populations.

Circulating Very-Low-Density Lipoprotein from Subjects with Impaired Glucose Tolerance Accelerates Adrenocortical Cortisol and Aldosterone Synthesis

Apart from their role in cardiovascular homeostasis and immunomodulation, aldosterone and cortisol are also implicated in the pathogenesis of insulin resistance and type 2 diabetes mellitus (T2DM). Furthermore, glycoxidative modifications of lipoproteins are increasingly recognized as an etiological factor for increased cardiovascular morbidity and mortality in prediabetic individuals. The causative relationship between in vivo lipoprotein modifications and steroidogenesis in subjects with impaired glucose tolerance (IGT), however, is not well defined. Therefore, we aimed to investigate the impact of in vivo modified lipoproteins on aldosterone and cortisol release from human adrenocortical H295R cells. Following an oral glucose tolerance test, 20 individuals with normal glucose tolerance (NGT) and 20 IGT subjects were randomly selected from the ongoing PRAEDIAS prevention study in our department. Cells were incubated for 24 h with lipoproteins isolated from NGT and IGT individuals and aldosterone and cortisol release was measured in the supernatants. VLDL induced a greater stimulating effect on adrenocortical aldosterone and cortisol release compared to HDL and LDL. Moreover, IGT-VLDL evoked a significantly higher effect (p<0.05) on hormone release than NGT-VLDL. Incubation of cells with in vitro modified lipoproteins and specific pharmacological inhibitors suggests that VLDL presumably recruits ERK1/2 as one of the downstream effectors of Jak-2. In summary, in vivo modified VLDL are able to promote prediabetic hormonal dysregulation by modulating adrenocortical steroidogenesis via Jak-2-ERK dependent pathway.

Modulation of adrenal aldosterone release by oxidative modification of low-density lipoprotein.

BACKGROUND Serum aldosterone is a causative factor for various metabolic and cardiovascular disorders. Low-density lipoprotein (LDL) is a major cholesterol source for aldosterone steroidogenesis; however, the effect of oxidative modification of LDL on aldosterone release is not known. We studied the effect of hypochlorite-oxidized LDL (oxLDL) on adrenal aldosterone secretion. METHODS LDL (native LDL (natLDL)) was obtained from healthy volunteers and oxidatively modified in vitro. NCI-H295R cells were stimulated with natLDL and oxLDL, and the aldosterone release was quantified by radioimmunoassay. Molecular changes were studied with western blot analysis and quantitative RT-PCR analysis. RESULTS NatLDL and oxLDL caused dose-dependent increase in aldosterone release up to threefold. However, the stimulatory effects of modified LDL on aldosterone secretion decreased with increasing degree of LDL oxidation. 24-h incubations with natLDL, mild- and medium-oxidized LDL sensitized the adrenocortical cells to subsequent angiotensin II (Ang II) stimulations by 2.9-, 2.8-, and 2.5-folds, respectively. Heavily oxidized LDL did not sensitize the cells to Ang II stimulations to a similar extent. At the molecular level, the ERK pathway was activated within a minute by both natLDL and oxLDL; however, oxLDL showed a stronger (2.75-fold at 1 and 15 min) and longer (15 min) activation of ERK than natLDL (twofold). CONCLUSIONS This study demonstrates the following: (i) both natLDL and hypochlorite-oxidized LDL utilize ERK pathway to mediate aldosterone release; (ii) mildly oxidized LDL sensitizes the adrenocortical cells to further stimulations by Ang II similar to natLDL that may have a role in pathological processes; (iii) extensive LDL oxidation counteracts adrenocortical aldosterone release.

Crosstalk Between Glycoxidative Modification of Low-Density Lipoprotein, Angiotensin II-Sensitization, and Adrenocortical Aldosterone Release.

Low-density lipoprotein (LDL) is considered to be a risk factor for atherosclerosis. In the presence of hyperglycemia, LDL undergoes glycoxidative modification and this glycoxidized (glycox) LDL promotes atherosclerosis in type 2 diabetic (T2D) individuals. Moreover, because of its cholesterol content, LDL contributes to aldosterone biosynthesis, which is modulated by angiotensin II (AngII) and has been implicated in cardiovascular complications of T2D. However, the molecular mechanism of the crosstalk between glycoxLDL, AngII, and aldosterone has not been explained clearly. Therefore, this study has been aimed to investigate the impact of in vitro modified glycoxLDL on aldosterone release in an AngII-sensitized adrenocortical carcinoma cell line (NCI H295R). Native LDL (natLDL), isolated from healthy volunteers by sequential density gradient ultracentrifugation, was subjected to d-glucose (200 mmol/l), for glycoxidative modification, at 37 °C for 6 days. The AngII-sensitized H295R cells were treated with natLDL and glycoxLDL for 24 h and the supernatant was used for aldosterone measurement. The treated cells were utilized for protein isolation and mRNA quantification. Compared to natLDL, glycoxLDL produced a significantly greater effect on aldosterone release from AngII-sensitized cells. The treatment with specific pharmacological inhibitors suggests that modified LDL recruits ERK1/2 and janus kinase-2 for transcriptional regulation of aldosterone synthase. Moreover, glycoxLDL modulates aldosterone release via cAMP-dependent protein kinase A (PKA) pathway. However, glycoxLDL induces ERK phosphorylation independent of PKA activation and this novel mechanism could be targeted for therapeutic trials. In conclusion, this in vitro study emphasizes a possible causal relationship between LDL glycoxidative modification, AngII-sensitization, and adrenocortical steroid hormone release.

Comparative analysis of diabetes self-management education programs in the European Union Member States

Diabetes self-management education (DSME) is generally considered as an integral part of diabetes care. The availability of different types of self-management in the European Union Member States (EUMS) remains uncertain. The aim of this study is to perform a comparative analysis of existing DSME programs (DSMEP) implemented in EUMS. Unpublished data regarding DSME in the EUMS was assessed with Diabetes Literacy Survey using wiki tool (WT) targeting patients and different stakeholders. An additional literature review (LR) was performed in PubMed to identify published studies regarding DSMEP in the EUMS from 2004 to 2014. A total of 102 DSMEP implemented in EUMS were reported in the WT and 154 programs were identified from the LR. Comparative analysis of the data indicated that a majority of programs are aimed at adults and only a minority at children and elderly. Only a small percentage of the programs utilize information technology for teaching and learning, and only one out of five programs pay attention to depression. The identified DSMEP aimed primarily to empower patients through increasing knowledge and changing attitudes and beliefs towards diabetes. This study provides an overview of the present state-of-the-art on diabetes self-management education programs in the 28 EUMS. To increase participation, existing DSMEP should be made more accessible to the patients as well as tailored to specific patient groups.

State of diabetes self-management education in the European Union Member States and non-EU countries. The Diabetes Literacy project.

Background Diabetes self-management education (DSME) is considered essential for improving the prevention and care of diabetes through empowering patients to increase agency in their own health and care processes. However, existing evidence regarding DSME in the EU Member States (EU MS) is insufficient to develop an EU-wide strategy. Objectives This study presents the state of DSME in the 28 EU MS and contrasts it with 3 non-EU countries with comparable Human Development Index score: Israel, Taiwan, and the USA (ITU). Because type 2 diabetes mellitus (T2DM) disproportionately affects minority and low-income groups, we paid particular attention to health literacy aspects of DSME for vulnerable populations. Methods Data from multiple stakeholders involved in diabetes care were collected from Feb 2014 to Jan 2015 using an online Diabetes Literacy Survey (DLS). Of the 379 respondents (249 from EU MS and 130 from ITU), most were people with diabetes (33% in the EU MS, 15% in ITU) and care providers (47% and 72%). These data were supplemented by an expert survey (ES) administered to 30 key informants. Results Access to DSME varies greatly in the EU MS: an average of 29% (range 21% to 50%) of respondents report DSME programs are tailored for people with limited literacy, educational attainment, and language skills versus 63% in ITU. More than half of adult T2DM patients and children/adolescents participate in DSME in EU MS; in ITU, participation of T1DM patients and older people is lower. Prioritization of DSME (6.1 ± 2.8 out of 10) and the level of satisfaction with the current state of DSME (5.0 ± 2.4 out of 10) in the EU MS were comparable with ITU. Conclusion Variation in availability and organization of DSME in the EU MS presents a clear rationale for developing an EU-wide diabetes strategy to improve treatment and care for people with diabetes.

Assessment of small C-fiber status for screening of oxidative stress in patients at risk of diabetes.

Oxidized LDL (oxLDL), anti-oxLDL antibody (anti-oxLDL) and paraoxonase (PON1) are increasingly being reported to be associated with diabetic atherosclerosis. Oxidative stress could affect also small C-fibers innervating the sweat glands even in prediabetes. Hence it could be hypothesized that sweat dysfunction may be a predictor of oxidative stress status for early detection of diabetes. Ezscan, a new device, has recently been developed to measure the sweat function. Therefore, this study was aimed to determine the relevance of this Ezscan method to identify impairment in oxidative stress parameters. Plasma levels of oxLDL and anti-oxLDL were measured by enzyme immunoassay and ELISA respectively. Small C-fiber status was assessed by measurement of hand and foot sweat function with the help of Ezscan device and subsequent calculation of a risk score. Out of 82 subjects recruited in this study, 38 had impaired glucose tolerance and 6 had newly diagnosed diabetes mellitus. Ezscan risk score was significantly (p=0.004) correlated with oxLDL/anti-oxLDL ratio (0.32). Area under the curve (AUC) of receiver operating characteristics (ROC) analysis for detection of oxLDL/anti-oxLDL ratio (>0.12) was 0.76. For an Ezscan risk score of 50%, the sensitivity and specificity were 68% and 71% respectively. After adjustment for age and BMI, PON1 activity showed significant difference among the 3 risk groups defined by Ezscan risk score. Based on these results it may be concluded that Ezscan could be a useful screening tool in daily practice to assess alterations in oxidative stress parameters in individuals at risk of developing diabetes.

Stimulation of phagocyte adhesion to endothelial cells by modified VLDL and HDL requires scavenger receptor BI

Hyperglycemia- and oxidative stress-induced modification of circulating lipoproteins is being increasingly recognized as an important pathogenetic factor for diabetic cardiovascular damages. This study was designed to investigate the impact of modified very low-density lipoprotein and high-density lipoprotein on phagocyte adhesion to endothelial cells and the involvement of scavenger receptor class B type 1 (SR-BI) in this process. Native lipoproteins were isolated by density gradient ultracentrifugation and in vitro glycoxidative or oxidative modification was performed in the presence of glucose or sodium hypochlorite, respectively. One hour co-incubation experiments with lipoproteins, freshly prepared polymorphonuclear leukocytes (PMN), and venous endothelial cells (HUVEC) were performed in the presence or absence of different scavenger receptors and signal transduction inhibitors. PMN adhesion to HUVEC was quantified fluorimetrically. We demonstrated that oxidized and glycoxidized lipoproteins promote adhesion of PMN to HUVEC from 1.5- to 2.5-fold with oxidized lipoproteins having the greatest effect. Treatment with the highly specific SR-BI inhibitor, BLT-1 produced substantial reduction of lipoprotein-induced adhesion to endothelial cells. Native and modified lipoproteins recruited extracellular signal-regulated kinase (ERK 1/2), p38 mitogen-activated protein kinase, and Janus kinase 2 as downstream signaling pathways for adhesion. From this study, it could be concluded that modification of lipoproteins plays a crucial role in atherosclerotic progression and SR-BI may be considered as a potential therapeutic target for the prevention of diabetic cardiovascular complications.