Verapamil Prevents Decline of IGF-I in Subjects With Type 1 Diabetes and Promotes β-Cell IGF-I Signaling

Verapamil promotes functional β-cell mass and improves glucose homeostasis in diabetic mice and humans with type 1 diabetes (T1D). Now, our global proteomics analysis of serum from subjects with T1D at baseline and after 1 year of receiving verapamil or placebo revealed IGF-I as a protein with significantly changed abundance over time. IGF-I, which promotes β-cell survival and insulin secretion, decreased during disease progression, and this decline was blunted by verapamil. In addition, we found that verapamil reduces β-cell expression of IGF-binding protein 3 (IGFBP3), whereas IGFBP3 was increased in human islets exposed to T1D-associated cytokines and in diabetic NOD mouse islets. IGFBP3 binds IGF-I and blocks its downstream signaling, which has been associated with increased β-cell apoptosis and impaired glucose homeostasis. Consistent with the downregulation of IGFBP3, we have now discovered that verapamil increases β-cell IGF-I signaling and phosphorylation/activation of the IGF-I receptor (IGF1R). Moreover, we found that thioredoxin-interacting protein (TXNIP), a proapoptotic factor downregulated by verapamil, promotes IGFBP3 expression and inhibits the phosphorylation/activation of IGF1R. Thus, our results reveal IGF-I signaling as yet another previously unappreciated pathway affected by verapamil and TXNIP that may contribute to the beneficial verapamil effects in the context of T1D.

ARTICLE HIGHLIGHTS

Verapamil prevents the decline of IGF-I in subjects with type 1 diabetes (T1D). Verapamil decreases the expression of β-cell IGF-binding protein 3 (IGFBP3), whereas IGFBP3 is increased in human and mouse islets under T1D conditions. Verapamil promotes β-cell IGF-I signaling by increasing phosphorylation of IGF-I receptor and its downstream effector AKT. Thioredoxin-interacting protein (TXNIP) increases IGFBP3 expression and inhibits the phosphorylation/activation of IGF1R in β-cells. Regulation of IGFBP3 and IGF-I signaling by verapamil and TXNIP may contribute to the beneficial verapamil effects in the context of T1D.

An approach for collaborative development of a federated biomedical knowledge graph-based question-answering system: Question-of-the-Month challenges

Knowledge graphs have become a common approach for knowledge representation. Yet, the application of graph methodology is elusive due to the sheer number and complexity of knowledge sources. In addition, semantic incompatibilities hinder efforts to harmonize and integrate across these diverse sources. As part of The Biomedical Translator Consortium, we have developed a knowledge graph-based question-answering system designed to augment human reasoning and accelerate translational scientific discovery: the Translator system. We have applied the Translator system to answer biomedical questions in the context of a broad array of diseases and syndromes, including Fanconi anemia, primary ciliary dyskinesia, multiple sclerosis, and others. A variety of collaborative approaches have been used to research and develop the Translator system. One recent approach involved the establishment of a monthly "Question-of-the-Month (QotM) Challenge" series. Herein, we describe the structure of the QotM Challenge; the six challenges that have been conducted to date on drug-induced liver injury, cannabidiol toxicity, coronavirus infection, diabetes, psoriatic arthritis, and ATP1A3-related phenotypes; the scientific insights that have been gleaned during the challenges; and the technical issues that were identified over the course of the challenges and that can now be addressed to foster further development of the prototype Translator system. We close with a discussion on Large Language Models such as ChatGPT and highlight differences between those models and the Translator system.

What the BTBR/J mouse has taught us about diabetes and diabetic complications

Human and mouse genetics have delivered numerous diabetogenic loci, but it is mainly through the use of animal models that the pathophysiological basis for their contribution to diabetes has been investigated. More than 20 years ago, we serendipidously identified a mouse strain that could serve as a model of obesity-prone type 2 diabetes, the BTBR (Black and Tan Brachyury) mouse (BTBR T+ Itpr3tf/J, 2018) carrying the Lepob mutation. We went on to discover that the BTBR-Lepob mouse is an excellent model of diabetic nephropathy and is now widely used by nephrologists in academia and the pharmaceutical industry. In this review, we describe the motivation for developing this animal model, the many genes identified and the insights about diabetes and diabetes complications derived from >100 studies conducted in this remarkable animal model.

LDB1-mediated transcriptional complexes are sensitive to islet stress

Excess nutrients and proinflammatory cytokines impart stresses on pancreatic islet β-cells that, if unchecked, can lead to cellular dysfunction and/or death. Among these stress-induced effects is loss of key β-cell transcriptional regulator mRNA and protein levels required for β-cell function. Previously, our lab and others reported that LIM-domain complexes comprised the LDB1 transcriptional co-regulator and Islet-1 (ISL1) transcription factor are required for islet β-cell development, maturation, and function. The LDB1:ISL1 complex directly occupies and regulates key β-cell genes, including MafA, Pdx1, and Slc2a2, to maintain β-cell identity and function. Given the importance of LDB1:ISL1 complexes, we hypothesized that LDB1 and/or ISL1 levels, like other transcriptional regulators, are sensitive to β-cell nutrient and cytokine stresses, likely contributing to β-cell (dys)function under various stimuli. We tested this by treating β-cell lines or primary mouse islets with elevating glucose concentrations, palmitate, or a cytokine cocktail of IL-1β, TNFα, and IFNγ. We indeed observed that LDB1 mRNA and/or protein levels were reduced upon palmitate and cytokine (cocktail or singly) incubation. Conversely, acute high glucose treatment of β-cells did not impair LDB1 or ISL1 levels, but increased LDB1:ISL1 interactions. These observations suggest that LDB1:ISL1 complex formation is sensitive to β-cell stresses and that targeting and/or stabilizing this complex may rescue lost β-cell gene expression to preserve cellular function.

Alpha Cell Thioredoxin-interacting Protein Deletion Improves Diabetes-associated Hyperglycemia and Hyperglucagonemia

Thioredoxin-interacting protein (TXNIP) has emerged as a key factor in pancreatic beta cell biology, and its upregulation by glucose and diabetes contributes to the impairment in functional beta cell mass and glucose homeostasis. In addition, beta cell deletion of TXNIP protects against diabetes in different mouse models. However, while TXNIP is ubiquitously expressed, its role in pancreatic alpha cells has remained elusive. We generated an alpha cell TXNIP knockout (aTKO) mouse and assessed the effects on glucose homeostasis. While no significant changes were observed on regular chow, after a 30-week high-fat diet, aTKO animals showed improvement in glucose tolerance and lower blood glucose levels compared to their control littermates. Moreover, in the context of streptozotocin (STZ)-induced diabetes, aTKO mice showed significantly lower blood glucose levels compared to controls. While serum insulin levels were reduced in both control and aTKO mice, STZ-induced diabetes significantly increased glucagon levels in control mice, but this effect was blunted in aTKO mice. Moreover, glucagon secretion from aTKO islets was >2-fold lower than from control islets, while insulin secretion was unchanged in aTKO islets. At the same time, no change in alpha cell or beta cell numbers or mass was observed, and glucagon and insulin expression and content were comparable in isolated islets from aTKO and control mice. Thus together the current studies suggest that downregulation of alpha cell TXNIP is associated with reduced glucagon secretion and that this may contribute to the glucose-lowering effects observed in diabetic aTKO mice.

The effect of distinct dietary interventions on proximal aortic stiffness; the DIRECT-PLUS randomized controlled trial

Background

Proximal aortic stiffness (PAS) reflects arterial aging and is strongly associated with increased cardiovascular risk. Plant-rich, specifically Mediterranean-style, diets are associated with reduced cardiovascular risk. The effect of dietary interventions on PAS remains unclear.

Methods

We randomized participants with abdominal-obesity/dyslipidemia to healthy-dietary-guidelines (HDG), Mediterranean, or green-Mediterranean diets combined with physical activity (PA). Both Mediterranean diets were similarly hypocaloric and included 28g/day walnuts. The green-Mediterranean group also consumed green tea (3–4 cups/day) and a Wolffia-globosa (Mankai) plant green-shake. PAS was estimated based on aortic-arch pulse-wave-velocity using magnetic resonance imaging (MRI) at baseline and after 18-months.

Results

Among 294 participants [age=51±10.6 years, body-mass-index 31.3±4.0 kg/m2, PAS = 6.1±2.7 m/sec, retention rate = 89.8%], 281 had valid PAS measurements. Higher PAS was mostly associated with aging, hypertension, dyslipidemia, diabetes, and increased visceral adiposity (p<0.05 for all). After 18-months of intervention, all diet groups significantly reduced their PAS ([HDG: −4.8% (interquartile-range [IQR]: −22.3 to 8.7); Mediterranean: −7.3%, IQR (−20.8 to 11.9); green-Mediterranean: −14.0%, IQR (−27.0 to 2.4); p<0.05 for within-groups changes).

Green-Mediterranean dieters had significantly greater PAS reduction than HDG dieters (p=0.007), also after controlling for age, sex, baseline-PAS, and Δweight. Further adjustment to baseline dyslipidemia, diabetes, and hypertension also revealed significant differences in PAS reduction between green-Mediterranean and Mediterranean groups (p=0.027). Specifically, greater green tea consumption was associated with greater PAS regression (p=0.04). ΔPAS was significantly associated with improvements in Δlow-density-lipoprotein cholesterol and Δtotal-cholesterol (p<0.05, multivariable models). All lifestyle intervention showed aortic age regression as compared to the expected (1.8±0.14 years vs.: HDG: −2.9±7.5 years; MED: −4.1±7.4 years; green-MED:-4.9±8.0 years; p<0.001).

Conclusions

Higher PAS is strongly related to aging and is associated with traditional cardiovascular risk factors. Lifestyle intervention promotes PAS reduction. Green-Mediterranean diet may be associated with more remarkable aortic rejuvenation.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The Deutsche Forschungsgemeinschaft (DFG, German Research Foundation); the Israel Ministry of Health

Hepatic mTORC2 Signaling Facilitates Acute Glucagon Receptor Enhancement of Insulin-Stimulated Glucose Homeostasis in Mice

Long-term glucagon receptor (GCGR) agonism is associated with hyperglycemia and glucose intolerance, while acute GCGR agonism enhances whole-body insulin sensitivity and hepatic AKTSer473 phosphorylation. These divergent effects establish a critical gap in knowledge surrounding GCGR action. mTOR complex 2 (mTORC2) is composed of seven proteins, including RICTOR, which dictates substrate binding and allows for targeting of AKTSer473. We used a liver-specific Rictor knockout mouse (RictorΔLiver) to investigate whether mTORC2 is necessary for insulin receptor (INSR) and GCGR cross talk. RictorΔLiver mice were characterized by impaired AKT signaling and glucose intolerance. Intriguingly, RictorΔLiver mice were also resistant to GCGR-stimulated hyperglycemia. Consistent with our prior report, GCGR agonism increased glucose infusion rate and suppressed hepatic glucose production during hyperinsulinemic-euglycemic clamp of control animals. However, these benefits to insulin sensitivity were ablated in RictorΔLiver mice. We observed diminished AKTSer473 and GSK3α/βSer21/9 phosphorylation in RictorΔLiver mice, whereas phosphorylation of AKTThr308 was unaltered in livers from clamped mice. These signaling effects were replicated in primary hepatocytes isolated from RictorΔLiver and littermate control mice, confirming cell-autonomous cross talk between GCGR and INSR pathways. In summary, our study reveals the necessity of RICTOR, and thus mTORC2, in GCGR-mediated enhancement of liver and whole-body insulin action.

Deletion of Gdf15 Reduces ER Stress-induced Beta-cell Apoptosis and Diabetes

Endoplasmic reticulum (ER) stress contributes to pancreatic beta-cell apoptosis in diabetes, but the factors involved are still not fully elucidated. Growth differentiation factor 15 (GDF15) is a stress response gene and has been reported to be increased and play an important role in various diseases. However, the role of GDF15 in beta cells in the context of ER stress and diabetes is still unclear. In this study, we have discovered that GDF15 promotes ER stress-induced beta-cell apoptosis and that downregulation of GDF15 has beneficial effects on beta-cell survival in diabetes. Specifically, we found that GDF15 is induced by ER stress in beta cells and human islets, and that the transcription factor C/EBPβ is involved in this process. Interestingly, ER stress-induced apoptosis was significantly reduced in INS-1 cells with Gdf15 knockdown and in isolated Gdf15 knockout mouse islets. In vivo, we found that Gdf15 deletion attenuates streptozotocin-induced diabetes by preserving beta cells and insulin levels. Moreover, deletion of Gdf15 significantly delayed diabetes development in spontaneous ER stress-prone Akita mice. Thus, our findings suggest that GDF15 contributes to ER stress-induced beta-cell apoptosis and that inhibition of GDF15 may represent a novel strategy to promote beta-cell survival and treat diabetes.

Exploratory study reveals far reaching systemic and cellular effects of verapamil treatment in subjects with type 1 diabetes

Currently, no oral medications are available for type 1 diabetes (T1D). While our recent randomized placebo-controlled T1D trial revealed that oral verapamil had short-term beneficial effects, their duration and underlying mechanisms remained elusive. Now, our global T1D serum proteomics analysis identified chromogranin A (CHGA), a T1D-autoantigen, as the top protein altered by verapamil and as a potential therapeutic marker and revealed that verapamil normalizes serum CHGA levels and reverses T1D-induced elevations in circulating proinflammatory T-follicular-helper cell markers. RNA-sequencing further confirmed that verapamil regulates the thioredoxin system and promotes an anti-oxidative, anti-apoptotic and immunomodulatory gene expression profile in human islets. Moreover, continuous use of oral verapamil delayed T1D progression, promoted endogenous beta-cell function and lowered insulin requirements and serum CHGA levels for at least 2 years and these benefits were lost upon discontinuation. Thus, the current studies provide crucial mechanistic and clinical insight into the beneficial effects of verapamil in T1D.

Metabolic determinants of proximal aortic stiffness among healthy people with abdominal obesity

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): (1) the Deutsche Forschungsgemeinschaft; (2) Israel Ministry of Health

Background

Increased proximal aortic stiffness (PAS) is directly associated with cardiovascular risk. Likewise, metabolic syndrome (MS) and abdominal obesity are associated with cardiovascular risk. The direct association between MS determinants and PAS among a healthy population with abdominal obesity remains to be examined.

Purpose

To examine the association between MS determinants and PAS among healthy participants with abdominal obesity.

Methods

We utilized the cross-sectional baseline data of the DIRECT-PLUS study (clinicaltrials.gov NCT03020186), where we recruited healthy participants with abdominal obesity/dyslipidemia. Along with anthropometric measurements and blood tests, all participants underwent magnetic-resonance-imaging from which PAS we assessed by calculating the aortic arch pulse-wave-velocity (from the ascending to the descending aorta). We defined MS according to the NCEP-ATP-III criteria.

Results

Of 282 participants who had a valid PAS estimation [mean-age: 51.0, 88.3% male, mean-body-mass-index: 31.2kg/m2, mean-waist circumference (WC): 109.5cm] 171 (60.9%) had MS. PAS was mainly associated with age (r = 0.735, p < 0.001). PAS was associated with an increased 10-year Framingham Risk Score (β=0.165,p = 0.008 after adjustment for age and gender). Participants with MS had higher PAS than non-MS participants (6.6m/sec vs. 5.4m/sec, p = 0.002 after adjusting for age and gender). PAS increased along with cumulative number of MS criteria (p-of-trend < 0.001). In multivariate models, adjusted for gender, age, and dichotomous-components of the MS, worse PAS remained significantly associated with high-density lipoprotein cholesterol (HDL-c; β=0.-116,p = 0.007) and increased blood-pressure (β=0.165,p < 0.001), but not with fasting-glucose, waist-circumference or plasma-triglycerides (p > 0.05 for all). In models adjusted for age, gender, and continuous determinants of MS, worse PAS remained associated with mean-arterial pressure (β=0.218,p < 0.001) and HDL-c (β=0.-126,p = 0.004).

Conclusions

Among a healthy population with abdominal obesity, reduced HDL-c levels and increased blood pressure might be the more dominant predictors of poor PAS state, out of the MS components.

Human Glucagon Expression Is under the Control of miR-320a

Increased glucagon is a hallmark of diabetes and leads to worsening of the hyperglycemia, but the molecular mechanisms causing it are still unknown. We therefore investigated the possibility that microRNAs might be involved in the regulation of glucagon. Indeed, analysis of the glucagon 3' untranslated region (UTR) revealed potential binding sites for miR-320a, and using luciferase reporter assays we found that miR-320a directly targets the 3' UTRs of human and rodent glucagon. In addition, endogenous glucagon mRNA and protein expression as well as glucagon secretion were reduced in response to miR-320a overexpression, whereas inhibition of miR-320a upregulated glucagon expression. Interestingly, miR-320a expression was decreased by high glucose, and this was associated with an increase in glucagon expression in human islets and mouse αTC1-6 cells. Moreover, miR-320a overexpression completely blunted these effects. Importantly, miR-320a was also significantly downregulated in human islets of subjects with type 2 diabetes and this was accompanied by increased glucagon expression. Thus, our data suggest that glucose-induced downregulation of miR-320a may contribute to the paradoxical increase in glucagon observed in type 2 diabetes and reveal for the first time that glucagon expression is under the control by a microRNA providing novel insight into the abnormal regulation of glucagon in diabetes.

Metformin Use Is Associated With Reduced Mortality in a Diverse Population With COVID-19 and Diabetes

Background

Coronavirus disease-2019 (COVID-19) is a growing pandemic with an increasing death toll that has been linked to various comorbidities as well as racial disparity. However, the specific characteristics of these at-risk populations are still not known and approaches to lower mortality are lacking.

Methods

We conducted a retrospective electronic health record data analysis of 25,326 subjects tested for COVID-19 between 2/25/20 and 6/22/20 at the University of Alabama at Birmingham Hospital, a tertiary health care center in the racially diverse Southern U.S. The primary outcome was mortality in COVID-19-positive subjects and the association with subject characteristics and comorbidities was analyzed using simple and multiple linear logistic regression.

Results

The odds ratio of contracting COVID-19 was disproportionately high in Blacks/African-Americans (OR 2.6; 95% CI 2.19-3.10; p<0.0001) and in subjects with obesity (OR 1.93; 95% CI 1.64-2.28; p<0.0001), hypertension (OR 2.46; 95% CI 2.07-2.93; p<0.0001), and diabetes (OR 2.11; 95% CI 1.78-2.48; p<0.0001). Diabetes was also associated with a dramatic increase in mortality (OR 3.62; 95% CI 2.11-6.2; p<0.0001) and emerged as an independent risk factor in this diverse population even after correcting for age, race, sex, obesity, and hypertension. Interestingly, we found that metformin treatment prior to diagnosis of COVID-19 was independently associated with a significant reduction in mortality in subjects with diabetes and COVID-19 (OR 0.33; 95% CI 0.13-0.84; p=0.0210).

Conclusion

Thus, these results suggest that while diabetes is an independent risk factor for COVID-19-related mortality, this risk is dramatically reduced in subjects taking metformin prior to diagnosis of COVID-19, raising the possibility that metformin may provide a protective approach in this high risk population.

A Small Molecule, UAB126, Reverses Diet-Induced Obesity and its Associated Metabolic Disorders

Targeting retinoid X receptor (RXR) has been proposed as one of the therapeutic strategies to treat individuals with metabolic syndrome, as RXR heterodimerizes with multiple nuclear receptors that regulate genes involved in metabolism. Despite numerous efforts, RXR ligands (rexinoids) have not been approved for clinical trials to treat metabolic syndrome due to the serious side effects such as hypertriglyceridemia and altered thyroid hormone axis. In this study, we demonstrate a novel rexinoid-like small molecule, UAB126, which has positive effects on metabolic syndrome without the known side effects of potent rexinoids. Oral administration of UAB126 ameliorated obesity, insulin resistance, hepatic steatosis, and hyperlipidemia without changes in food intake, physical activity, and thyroid hormone levels. RNA-sequencing analysis revealed that UAB126 regulates the expression of genes in the liver that are modulated by several nuclear receptors, including peroxisome proliferator-activated receptor α and/or liver X receptor in conjunction with RXR. Furthermore, UAB126 not only prevented but also reversed obesity-associated metabolic disorders. The results suggest that optimized modulation of RXR may be a promising strategy to treat metabolic disorders without side effects. Thus, the current study reveals that UAB126 could be an attractive therapy to treat individuals with obesity and its comorbidities.

METFORMIN USE IS ASSOCIATED WITH REDUCED MORTALITY IN A DIVERSE POPULATION WITH COVID-19 AND DIABETES

BACKGROUND

Coronavirus disease-2019 (COVID-19) is a growing pandemic with an increasing death toll that has been linked to various comorbidities as well as racial disparity. However, the specific characteristics of these at-risk populations are still not known and approaches to lower mortality are lacking.

METHODS

We conducted a retrospective electronic health record data analysis of 25,326 subjects tested for COVID-19 between 2/25/20 and 6/22/20 at the University of Alabama at Birmingham Hospital, a tertiary health care center in the racially diverse Southern U.S. The primary outcome was mortality in COVID-19-positive subjects and the association with subject characteristics and comorbidities was analyzed using simple and multiple linear logistic regression.

RESULTS

The odds ratio of contracting COVID-19 was disproportionately high in Blacks/African-Americans (OR 2.6; 95%CI 2.19-3.10; p<0.0001) and in subjects with obesity (OR 1.93; 95%CI 1.64-2.28; p<0.0001), hypertension (OR 2.46; 95%CI 2.07-2.93; p<0.0001), and diabetes (OR 2.11; 95%CI 1.78-2.48; p<0.0001). Diabetes was also associated with a dramatic increase in mortality (OR 3.62; 95%CI 2.11-6.2; p<0.0001) and emerged as an independent risk factor in this diverse population even after correcting for age, race, sex, obesity and hypertension. Interestingly, we found that metformin treatment was independently associated with a significant reduction in mortality in subjects with diabetes and COVID-19 (OR 0.33; 95%CI 0.13-0.84; p=0.0210).

CONCLUSION

Thus, these results suggest that while diabetes is an independent risk factor for COVID-19-related mortality, this risk is dramatically reduced in subjects taking metformin, raising the possibility that metformin may provide a protective approach in this high risk population.

Serum miR-204 is an early biomarker of type 1 diabetes-associated pancreatic beta-cell loss

Pancreatic beta-cell death is a major factor in the pathogenesis of type 1 diabetes (T1D), but straightforward methods to measure beta-cell loss in humans are lacking, underlining the need for novel biomarkers. Using studies in INS-1 cells, human islets, diabetic mice, and serum samples of subjects with T1D at different stages, we have identified serum miR-204 as an early biomarker of T1D-associated beta-cell loss in humans. MiR-204 is a highly enriched microRNA in human beta-cells, and we found that it is released from dying beta-cells and detectable in human serum. We further discovered that serum miR-204 was elevated in children and adults with T1D and in autoantibody-positive at-risk subjects but not in type 2 diabetes or other autoimmune diseases and was inversely correlated with remaining beta-cell function in recent-onset T1D. Thus, serum miR-204 may provide a much needed novel approach to assess early T1D-associated human beta-cell loss even before onset of overt disease.

Diabetes pathogenic mechanisms and potential new therapies based upon a novel target called TXNIP

PURPOSE OF REVIEW

Thioredoxin-interacting protein has emerged as a major factor regulating pancreatic β-cell dysfunction and death, key processes in the pathogenesis of type 1 and type 2 diabetes. Accumulating evidence based on basic, preclinical, and retrospective epidemiological research suggests that TXNIP represents a promising therapeutic target for diabetes. The present review is aimed at providing an update regarding these developments.

RECENT FINDINGS

TXNIP has been shown to be induced by glucose and increased in diabetes and to promote β-cell apoptosis, whereas TXNIP deletion protected against diabetes. More recently, TXNIP inhibition has also been found to promote insulin production and glucagon-like peptide 1 signaling via regulation of a microRNA. β-Cell TXNIP expression itself was found to be regulated by hypoglycemic agents, carbohydrate-response-element-binding protein, and cytosolic calcium or the calcium channel blocker, verapamil. Retrospective studies now further suggest that verapamil use might be associated with a lower incidence of type 2 diabetes in humans.

SUMMARY

TXNIP has emerged as a key factor in the regulation of functional β-cell mass and TXNIP inhibition has shown beneficial effects in a variety of studies. Thus, the inhibition of TXNIP may provide a novel approach to the treatment of diabetes.

miR-204 Controls Glucagon-Like Peptide 1 Receptor Expression and Agonist Function

Glucagon-like peptide 1 receptor (GLP1R) agonists are widely used to treat diabetes. However, their function is dependent on adequate GLP1R expression, which is downregulated in diabetes. GLP1R is highly expressed on pancreatic β-cells, and activation by endogenous incretin or GLP1R agonists increases cAMP generation, which stimulates glucose-induced β-cell insulin secretion and helps maintain glucose homeostasis. We now have discovered that the highly β-cell-enriched microRNA, miR-204, directly targets the 3' UTR of GLP1R and thereby downregulates its expression in the β-cell-derived rat INS-1 cell line and primary mouse and human islets. Furthermore, in vivo deletion of miR-204 promoted islet GLP1R expression and enhanced responsiveness to GLP1R agonists, resulting in improved glucose tolerance, cAMP production, and insulin secretion as well as protection against diabetes. Since we recently identified thioredoxin-interacting protein (TXNIP) as an upstream regulator of miR-204, we also assessed whether in vivo deletion of TXNIP could mimic that of miR-204. Indeed, it also enhanced islet GLP1R expression and GLP1R agonist-induced insulin secretion and glucose tolerance. Thus, the present studies show for the first time that GLP1R is under the control of a microRNA, miR-204, and uncover a previously unappreciated link between TXNIP and incretin action.

Encapsulation of Human Islets Using a Biomimetic Self-Assembled Nanomatrix Gel for Protection against Cellular Inflammatory Responses

The major concern of pancreatic islet transplantation is that the implanted islets are exposed to the immune system of the recipient. To overcome this challenge, the peptide amphiphile (PA) nanomatrix gel was used for immunoisolation of islets through microencapsulation. The PA can self-assemble to form a nanomatrix gel with an extracellular matrix-mimicking, islet nurturing microenvironment and a semipermeable immune barrier. In this study, the islet protective effect of the PA nanomatrix gel was evaluated by coculture of PA-encapsulated human islets with differentiated U937 cells (human monocyte cell-line) for 3 and 7 days. The coculture of the bare islets with the differentiated U937 cells stimulated proinflammatory cytokine (IL-1β and TNF-α) secretion and caused islet death after 7 days, which simulated an early inflammatory response environment after islet transplantation. The PA-encapsulated islets, however, did not stimulate proinflammatory cytokine secretion and maintained islet viability up to 7 days. More insulin-producing β cells were observed when islets were PA-encapsulated than control islets with the differentiated U937 cells for 7 days compared to the bare islets. This result was also confirmed by dithizone staining analysis. Further evaluation of islet functionality was assessed by a glucose-stimulated insulin secretion test. The PA-encapsulated islets showed greater insulin secretion response to glucose stimulation than the bare islets with the differentiated U937 cells after 3 and 7 days. These results demonstrated that islet encapsulation with the PA nanomatrix gel was able to improve islet survival and function in the presence of inflammatory responses, which will increase the success rate of islet engraftment and the efficacy of islet transplantation.

Keeping tabs on fructose

Too much fructose in the diet can worsen metabolic problems via a process that involves thioredoxin-interacting protein.

Islet ChREBP-β is increased in diabetes and controls ChREBP-α and glucose-induced gene expression via a negative feedback loop

Objective

Carbohydrate-response element-binding protein (ChREBP) is the major transcription factor conferring glucose-induced gene expression in pancreatic islets, liver and adipose tissue. Recently, a novel ChREBP isoform, ChREBP-β, was identified in adipose tissue and found to be also expressed in islets and involved in glucose-induced beta cell proliferation. However, the physiological function of this less abundant β-isoform in the islet, and in diabetes, is largely unknown. The aims of the present study, therefore, were to determine how diabetes affects ChREBP-β and elucidate its physiological role in pancreatic beta cells.

Methods

Non-obese diabetic and obese, diabetic ob/ob mice were used as models of T1D and T2D and human islets and the rat INS-1 beta cell line were exposed to low/high glucose and used for ChREBP isoform-specific gain-and-loss-of-function experiments. Changes in ChREBP-β and ChREBP-α were assessed by qRT-PCR, immunoblotting, promoter luciferase, and chromatin immunoprecipitation studies.

Results

Expression of the ChREBP-β isoform was highly induced in diabetes and by glucose, whereas ChREBP-α was downregulated. Interestingly, ChREBP-β gain-of-function experiments further revealed that it was ChREBP-β that downregulated ChREBP-α through a negative feedback loop. On the other hand, ChREBP-β knockdown led to unabated ChREBP-α activity and glucose-induced expression of target genes, suggesting that one of the physiological roles of this novel β-isoform is to help keep glucose-induced and ChREBP-α-mediated gene expression under control.

Conclusions

We have identified a previously unappreciated negative feedback loop by which glucose-induced ChREBP-β downregulates ChREBP-α-signaling providing new insight into the physiological role of islet ChREBP-β and into the regulation of glucose-induced gene expression.

•

ChREBP-β is increased whereas expression of ChREBP-α is decreased in diabetes.

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ChREBP-β downregulates ChREBP-α via a negative feedback loop in islets.

•

ChREBP-β thereby limits excessive glucose-induced ChREBP-α-mediated gene expression.

miR-204 Targets PERK and Regulates UPR Signaling and β-Cell Apoptosis

Endoplasmic reticulum (ER) stress plays an important role in the pathogenesis of diabetes and the associated β-cell apoptosis. Although microRNAs (miRNAs) have been widely studied in various diseases including diabetes, the role of miRNAs in ER stress and β-cell apoptosis has only started to be elucidated. We recently showed that diabetes increases β-cell miR-204 and have now discovered that miR-204 directly targets the 3'untranslated region of protein kinase R-like ER kinase (PERK), 1 of the 3 ER transmembrane sensors and a key factor of the unfolded protein response (UPR). In addition, by using primary human islets, mouse islets, and INS-1 β-cells, we found that miR-204 decreased PERK expression as well as its downstream factors, activating transcription factor 4 and CCAAT enhancer-binding protein homologous protein, whereas it had no effect on the other 2 ER transmembrane sensors, activating transcription factor 6 and inositol-requiring enzyme-1α. Interestingly, we discovered that miR-204 also inhibited PERK signaling in the context of ER stress, and this exacerbated ER stress-induced β-cell apoptosis. This effect could be mimicked by PERK inhibitors supporting the notion that the miR-204-mediated inhibition of PERK and UPR signaling was conferring these detrimental effects on cell survival. Taken together, we have identified PERK as a novel target of miR-204 and show that miR-204 inhibits PERK signaling and increases ER stress-induced cell death, revealing for the first time a link between this miRNA and UPR.

TXNIP regulates myocardial fatty acid oxidation via miR-33a signaling

Myocardial fatty acid β-oxidation is critical for the maintenance of energy homeostasis and contractile function in the heart, but its regulation is still not fully understood. While thioredoxin-interacting protein (TXNIP) has recently been implicated in cardiac metabolism and mitochondrial function, its effects on β-oxidation have remained unexplored. Using a new cardiomyocyte-specific TXNIP knockout mouse and working heart perfusion studies, as well as loss- and gain-of-function experiments in rat H9C2 and human AC16 cardiomyocytes, we discovered that TXNIP deficiency promotes myocardial β-oxidation via signaling through a specific microRNA, miR-33a. TXNIP deficiency leads to increased binding of nuclear factor Y (NFYA) to the sterol regulatory element binding protein 2 (SREBP2) promoter, resulting in transcriptional inhibition of SREBP2 and its intronic miR-33a. This allows for increased translation of the miR-33a target genes and β-oxidation-promoting enzymes, carnitine octanoyl transferase (CROT), carnitine palmitoyl transferase 1 (CPT1), hydroxyacyl-CoA dehydrogenase/3-ketoacyl-CoA thiolase/enoyl-CoA hydratase-β (HADHB), and AMPKα and is associated with an increase in phospho-AMPKα and phosphorylation/inactivation of acetyl-CoA-carboxylase. Thus, we have identified a novel TXNIP-NFYA-SREBP2/miR-33a-AMPKα/CROT/CPT1/HADHB pathway that is conserved in mouse, rat, and human cardiomyocytes and regulates myocardial β-oxidation.

Calcium channel blocker use is associated with lower fasting serum glucose among adults with diabetes from the REGARDS study

BACKGROUND

Ca(2+) channel blockers (CCB) and verapamil in particular prevented β-cell apoptosis and enhanced endogenous insulin levels in recent studies of mouse models of diabetes. Verapamil's effect on serum glucose levels in humans with diabetes is not described.

METHODS

We used data from the REasons for Geographic and Racial Differences in Stroke (REGARDS), a national cohort study of community-dwelling middle-aged and older adults, enrolled between 2003 and 2007 from the continental United States. We examined associations of CCB and verapamil use with fasting serum glucose among 4978 adults with diabetes, controlling for covariates in generalized linear models (GLM).

FINDINGS

The sample included 1484 (29.6%) CCB users, of which 174 (3.4%) were verapamil users. In fully adjusted GLMs, CCB users had 5mg/dL lower serum glucose compared to non-users. Verapamil users had on average 10mg/dL lower serum glucose compared to CCB non-users with substantially greater differences among insulin users: 24mg/dL lower serum glucose among users of insulin in combination with oral agents and 37mg/dL lower among users of insulin alone.

INTERPRETATION

CCB and in particular verapamil use was associated with lower fasting blood glucose levels among REGARDS participants with diabetes.

FUNDING

UO1NS041588 from the National Institute of Neurological Disorders and Stroke, NIH; K24HL111154 and R01HL080477 from the National Heart, Lung, and Blood Institute.

Cytokines Regulate β-Cell Thioredoxin-interacting Protein (TXNIP) via Distinct Mechanisms and Pathways

Thioredoxin-interacting protein (TXNIP) is a key regulator of diabetic β-cell apoptosis and dysfunction, and TXNIP inhibition prevents diabetes in mouse models of type 1 and type 2 diabetes. Although we have previously shown that TXNIP is strongly induced by glucose, any regulation by the proinflammatory cytokines tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), and interferon γ (IFNγ) has remained largely unexplored. Moreover, even though this three-cytokine mixture is widely used to mimic type 1 diabetes in vitro, the mechanisms involved are not fully understood. Interestingly, we have now found that this cytokine mixture increases β-cell TXNIP expression; however, although TNFα had no effect, IL-1β surprisingly down-regulated TXNIP transcription, whereas IFNγ increased TXNIP levels in INS-1 β-cells and primary islets. Human TXNIP promoter analyses and chromatin immunoprecipitation studies revealed that the IL-1β effect was mediated by inhibition of carbohydrate response element binding protein activity. In contrast, IFNγ increased pro-apoptotic TXNIP post-transcriptionally via induction of endoplasmic reticulum stress, activation of inositol-requiring enzyme 1α (IRE1α), and suppression of miR-17, a microRNA that targets and down-regulates TXNIP. In fact, miR-17 knockdown was able to mimic the IFNγ effects on TXNIP, whereas miR-17 overexpression blunted the cytokine effect. Thus, our results demonstrate for the first time that the proinflammatory cytokines TNFα, IL-1β, and IFNγ each have distinct and in part opposing effects on β-cell TXNIP expression. These findings thereby provide new mechanistic insight into the regulation of TXNIP and β-cell biology and reveal novel links between proinflammatory cytokines, carbohydrate response element binding protein-mediated transcription, and microRNA signaling.

The epidemiology of traumatic event exposure worldwide: results from the World Mental Health Survey Consortium

BACKGROUND

Considerable research has documented that exposure to traumatic events has negative effects on physical and mental health. Much less research has examined the predictors of traumatic event exposure. Increased understanding of risk factors for exposure to traumatic events could be of considerable value in targeting preventive interventions and anticipating service needs.

METHOD

General population surveys in 24 countries with a combined sample of 68 894 adult respondents across six continents assessed exposure to 29 traumatic event types. Differences in prevalence were examined with cross-tabulations. Exploratory factor analysis was conducted to determine whether traumatic event types clustered into interpretable factors. Survival analysis was carried out to examine associations of sociodemographic characteristics and prior traumatic events with subsequent exposure.

RESULTS

Over 70% of respondents reported a traumatic event; 30.5% were exposed to four or more. Five types - witnessing death or serious injury, the unexpected death of a loved one, being mugged, being in a life-threatening automobile accident, and experiencing a life-threatening illness or injury - accounted for over half of all exposures. Exposure varied by country, sociodemographics and history of prior traumatic events. Being married was the most consistent protective factor. Exposure to interpersonal violence had the strongest associations with subsequent traumatic events.

CONCLUSIONS

Given the near ubiquity of exposure, limited resources may best be dedicated to those that are more likely to be further exposed such as victims of interpersonal violence. Identifying mechanisms that account for the associations of prior interpersonal violence with subsequent trauma is critical to develop interventions to prevent revictimization.

β-Cell MicroRNAs: Small but Powerful

Noncoding RNA and especially microRNAs (miRs) have emerged as important regulators of key processes in cell biology, including development, differentiation, and survival. Currently, over 2,500 mature miRs have been reported in humans, and considering that each miR has multiple targets, the number of genes and pathways potentially affected is huge. Not surprisingly, many miRs have also been implicated in diabetes, and more recently, some have been discovered to play important roles in the pancreatic islet, including β-cell function, proliferation, and survival. The goal of this Perspective is to offer an overview of this rapidly evolving field and the miRs involved, reveal novel networks of β-cell miR signaling, and provide an outlook of the opportunities and challenges ahead.

MicroRNA-200 is induced by thioredoxin-interacting protein and regulates Zeb1 protein signaling and beta cell apoptosis

Small noncoding microRNAs have emerged as important regulators of cellular processes, but their role in pancreatic beta cells has only started to be elucidated. Loss of pancreatic beta cells is a key factor in the pathogenesis of diabetes, and we have demonstrated that beta cell expression of thioredoxin-interacting protein (TXNIP) is increased in diabetes and causes beta cell apoptosis, whereas TXNIP deficiency is protective against diabetes. Recently, we found that TXNIP also impairs beta cell function by inducing microRNA (miR)-204. Interestingly, using INS-1 beta cells and primary islets, we have now discovered that expression of another microRNA, miR-200, is induced by TXNIP and by diabetes. Furthermore, we found that miR-200 targeted and decreased Zeb1 (zinc finger E-box-binding homeobox 1) and promoted beta cell apoptosis as measured by cleaved caspase-3 levels, Bax/Bcl2 ratio, and TUNEL. In addition, Zeb1 knockdown mimicked the miR-200 effects on beta cell apoptosis, suggesting that Zeb1 plays an important role in mediating miR-200 effects. Moreover, miR-200 increased beta cell expression of the epithelial marker E-cadherin, consistent with inhibition of epithelial-mesenchymal transition, a process thought to be involved in beta cell expansion. Thus, we have identified a novel TXNIP/miR-200/Zeb1/E-cadherin signaling pathway that, for the first time, links miR-200 to beta cell apoptosis and diabetes and also beta cell TXNIP to epithelial-mesenchymal transition. In addition, our results shed new light on the regulation and function of miR-200 in beta cells and show that TXNIP-induced microRNAs control various processes of beta cell biology.

Minireview: Thioredoxin-interacting protein: regulation and function in the pancreatic β-cell

Pancreatic β-cells are responsible for insulin production, and loss of functional β-cell mass is now recognized as a critical step in the pathogenesis of both type 1 and type 2 diabetes. However, the factors controlling the life and death of the pancreatic β-cell have only started to be elucidated. Discovered as the top glucose-induced gene in a human islet microarray study 12 years ago, thioredoxin-interacting protein (TXNIP) has now emerged as such a key player in pancreatic β-cell biology. Since then, β-cell expression of TXNIP has been found to be tightly regulated by multiple factors and to be dramatically increased in diabetic islets. Elevated TXNIP levels induce β-cell apoptosis, whereas TXNIP deficiency protects against type 1 and type 2 diabetes by promoting β-cell survival. TXNIP interacts with and inhibits thioredoxin and thereby controls the cellular redox state, but it also belongs to the α-arrestin family of proteins and regulates a variety of metabolic processes. Most recently, TXNIP has been discovered to control β-cell microRNA expression, β-cell function, and insulin production. In this review, the current state of knowledge regarding regulation and function of TXNIP in the pancreatic β-cell and the implications for drug development are discussed.

Enhanced MIN-6 beta cell survival and function on a nitric oxide-releasing peptide amphiphile nanomatrix

Innovative biomaterial strategies are required to improve islet cell retention, viability, and functionality, and thereby obtain clinically successful outcomes from pancreatic islet cell transplantation. To address this need, we have developed a peptide amphiphile-based nanomatrix that incorporates multifunctional bioactive cues and sustained release of nitric oxide. The goal of this study was to evaluate the effect of this peptide amphiphile nanomatrix on the viability and functionality of MIN-6 islet cells. Additionally, this study provides insight into the role of nitric oxide in islet cell biology, given that conventional nitric oxide donors are unable to release nitric oxide in a controlled, sustained manner, leading to ambiguous results. It was hypothesized that controlled nitric oxide release in synergy with multifunctional bioactive cues would promote islet cell viability and functionality. Nitric oxide-releasing peptide amphiphile nanomatrices within the range of 16.25 μmol to 130 μmol were used to analyze MIN-6 cell behavior. Both 32.5 μmol and 65 μmol peptide amphiphiles showed improved MIN-6 functionality in response to glucose over a 7-day time period, and the elevated functionality was correlated with both PDX-1 and insulin gene expression. Our results demonstrate that nitric oxide has a beneficial effect on MIN-6 cells in a concentration-dependent manner.

Thioredoxin-interacting protein stimulates its own expression via a positive feedback loop

Thioredoxin-interacting protein (TXNIP) has emerged as a key regulator of important cellular processes including redox state, inflammation, and apoptosis and plays a particularly critical role in pancreatic β-cell biology and diabetes development. High glucose and diabetes induce TXNIP expression, whereas inhibition of TXNIP expression or TXNIP deficiency protects against pancreatic β-cell apoptosis and diabetes. We now have discovered that TXNIP stimulates its own expression by promoting dephosphorylation and nuclear translocation of its transcription factor, carbohydrate response element-binding protein (ChREBP), resulting in a positive feedback loop as well as regulation of other ChREBP target genes playing important roles in glucose and lipid metabolism. Considering the detrimental effects of elevated TXNIP in β-cell biology, this novel pathway sheds new light onto the vicious cycle of increased TXNIP, leading to even more TXNIP expression, oxidative stress, inflammation, β-cell apoptosis, and diabetes progression. Moreover, the results demonstrate, for the first time, that TXNIP modulates ChREBP activity and thereby uncover a previously unappreciated link between TXNIP signaling and cell metabolism.

Thioredoxin-interacting protein promotes islet amyloid polypeptide expression through miR-124a and FoxA2

Thioredoxin-interacting protein (TXNIP) is up-regulated by glucose and diabetes and plays a critical role in glucotoxicity, inflammation, and beta-cell apoptosis, whereas we have found that TXNIP deficiency protects against diabetes. Interestingly, human islet amyloid polypeptide (IAPP) is also induced by glucose, aggregates into insoluble amyloid fibrils found in islets of most individuals with type 2 diabetes and promotes inflammation and beta-cell cytotoxicity. However, so far no connection between TXNIP and IAPP signaling had been reported. Using TXNIP gain and loss of function experiments, INS-1 beta-cells and beta-cell-specific Txnip knock-out mice, we now found that TXNIP regulates IAPP expression. Promoter analyses and chromatin-immunoprecipitation assays further demonstrated that TXNIP increases IAPP expression at the transcriptional level, and we discovered that TXNIP-induced FoxA2 (forkhead box A2) transcription factor expression was conferring this effect by promoting FoxA2 enrichment at the proximal FoxA2 site in the IAPP promoter. Moreover, we found that TXNIP down-regulates miR-124a expression, a microRNA known to directly target FoxA2. Indeed, miR-124a overexpression led to decreased FoxA2 expression and IAPP promoter occupancy and to a significant reduction in IAPP mRNA and protein expression and also effectively inhibited TXNIP-induced IAPP expression. Thus, our studies have identified a novel TXNIP/miR-124a/FoxA2/IAPP signaling cascade linking the critical beta-cell signaling pathways of TXNIP and IAPP and thereby provide new mechanistic insight into an important aspect of transcriptional regulation and beta-cell biology.

FOXO1 competes with carbohydrate response element-binding protein (ChREBP) and inhibits thioredoxin-interacting protein (TXNIP) transcription in pancreatic beta cells

Thioredoxin-interacting protein (TXNIP) has emerged as an important factor in pancreatic beta cell biology, and tight regulation of TXNIP levels is necessary for beta cell survival. However, the mechanisms regulating TXNIP expression have only started to be elucidated. The forkhead boxO1 transcription factor (FOXO1) has been reported to up-regulate TXNIP expression in neurons and endothelial cells but to down-regulate TXNIP in liver, and the effects on beta cells have remained unknown. We now have found that FOXO1 binds to the TXNIP promoter in vivo in human islets and INS-1 beta cells and significantly decreases TXNIP expression. TXNIP promoter deletion analyses revealed that an E-box motif conferring carbohydrate response element-binding protein (ChREBP)-mediated, glucose-induced TXNIP expression is necessary and sufficient for this effect, and electromobility shift assays confirmed FOXO1 binding to this site. Moreover, FOXO1 blocked glucose-induced TXNIP expression and reduced glucose-induced ChREBP binding at the TXNIP promoter without affecting ChREBP expression or nuclear localization, suggesting that FOXO1 may compete with ChREBP for binding to the TXNIP promoter. In fact, a FOXO1 DNA-binding mutant (FOXO1-H215R) failed to inhibit TXNIP transcription, and the effects were not restricted to TXNIP as FOXO1 also inhibited transcription of other ChREBP target genes such as liver pyruvate kinase. Together, these results demonstrate that FOXO1 inhibits beta cell TXNIP transcription and suggest that FOXO1 confers this inhibition by interfering with ChREBP DNA binding at target gene promoters. Our findings thereby reveal a novel gene regulatory mechanism and a previously unappreciated cross-talk between FOXO1 and ChREBP, two major metabolic signaling pathways.

Calcium channel blockers act through nuclear factor Y to control transcription of key cardiac genes

First-generation calcium channel blockers such as verapamil are a widely used class of antihypertensive drugs that block L-type calcium channels. We recently discovered that they also reduce cardiac expression of proapoptotic thioredoxin-interacting protein (TXNIP), suggesting that they may have unappreciated transcriptional effects. By use of TXNIP promoter deletion and mutation studies, we found that a CCAAT element was mediating verapamil-induced transcriptional repression and identified nuclear factor Y (NFY) to be the responsible transcription factor as assessed by overexpression/knockdown and luciferase and chromatin immunoprecipitation assays in cardiomyocytes and in vivo in diabetic mice receiving oral verapamil. We further discovered that increased NFY-DNA binding was associated with histone H4 deacetylation and transcriptional repression and mediated by inhibition of calcineurin signaling. It is noteworthy that the transcriptional control conferred by this newly identified verapamil-calcineurin-NFY signaling cascade was not limited to TXNIP, suggesting that it may modulate the expression of other NFY targets. Thus, verapamil induces a calcineurin-NFY signaling pathway that controls cardiac gene transcription and apoptosis and thereby may affect cardiac biology in previously unrecognized ways.

Preventing β-cell loss and diabetes with calcium channel blockers

Although loss of functional β-cell mass is a hallmark of diabetes, no treatment approaches that halt this process are currently available. We recently identified thioredoxin-interacting protein (TXNIP) as an attractive target in this regard. Glucose and diabetes upregulate β-cell TXNIP expression, and TXNIP overexpression induces β-cell apoptosis. In contrast, genetic ablation of TXNIP promotes endogenous β-cell survival and prevents streptozotocin (STZ)- and obesity-induced diabetes. Finding an oral medication that could inhibit β-cell TXNIP expression would therefore represent a major breakthrough. We were surprised to discover that calcium channel blockers inhibited TXNIP expression in INS-1 cells and human islets and that orally administered verapamil reduced TXNIP expression and β-cell apoptosis, enhanced endogenous insulin levels, and rescued mice from STZ-induced diabetes. Verapamil also promoted β-cell survival and improved glucose homeostasis and insulin sensitivity in BTBR ob/ob mice. Our data further suggest that this verapamil-mediated TXNIP repression is conferred by reduction of intracellular calcium, inhibition of calcineurin signaling, and nuclear exclusion and decreased binding of carbohydrate response element-binding protein to the E-box repeat in the TXNIP promoter. Thus, for the first time, we have identified an oral medication that can inhibit proapoptotic β-cell TXNIP expression, enhance β-cell survival and function, and prevent and even improve overt diabetes.

[Implementing mindfulness based therapies as part of the comprehensive treatments in the Beer Sheba Mental Health Center]

In recent years, there has been a growing interest and popularity in mindfulness-based therapies. Theories and practices that, until lately, have been considered esoteric and practiced in private by only a few therapists, are now progressively becoming part of mainstream establishment therapies and are gaining greater interest and recognition. The therapies can be carried out either in an individual or in a group setting and most include formal mindful sitting practice, developing awareness, mindful movement, psycho-education and often include a cognitive component. Furthermore, these therapies are becoming increasingly validated by widespread research pointing to promising results in the treatment of various cLinicaL disorders including anxiety, depression and relapse prevention, personality disorders, attention disorders and psychotic disorders, in both an in-patient and out-patient setting. The aim of this overview is to describe the deveLopment that has taken place in the fast decades within the field of mindfulness-based therapies and to present the most up-to-date research in this area: to show which therapeutic interventions have been proven to be effective; the background of the ideas; and the relevance of these approaches to the mental health system in Israel.

Lack of TXNIP protects against mitochondria-mediated apoptosis but not against fatty acid-induced ER stress-mediated beta-cell death

OBJECTIVE

We have previously shown that lack of thioredoxin-interacting protein (TXNIP) protects against diabetes and glucotoxicity-induced beta-cell apoptosis. Because the role of TXNIP in lipotoxicity is unknown, the goal of the present study was to determine whether TXNIP expression is regulated by fatty acids and whether TXNIP deficiency also protects beta-cells against lipoapoptosis. RESARCH DESIGN AND METHODS: To determine the effects of fatty acids on beta-cell TXNIP expression, INS-1 cells and isolated islets were incubated with/without palmitate and rats underwent cyclic infusions of glucose and/or Intralipid prior to islet isolation and analysis by quantitative real-time RT-PCR and immunoblotting. Using primary wild-type and TXNIP-deficient islets, we then assessed the effects of palmitate on apoptosis (transferase-mediated dUTP nick-end labeling [TUNEL]), mitochondrial death pathway (cytochrome c release), and endoplasmic reticulum (ER) stress (binding protein [BiP], C/EBP homologous protein [CHOP]). Effects of TXNIP deficiency were also tested in the context of staurosporine (mitochondrial damage) or thapsigargin (ER stress).

RESULTS

Glucose elicited a dramatic increase in islet TXNIP expression both in vitro and in vivo, whereas fatty acids had no such effect and, when combined with glucose, even abolished the glucose effect. We also found that TXNIP deficiency does not effectively protect against palmitate or thapsigargin-induced beta-cell apoptosis, but specifically prevents staurosporine- or glucose-induced toxicity.

CONCLUSIONS

Our results demonstrate that unlike glucose, fatty acids do not induce beta-cell expression of proapoptotic TXNIP. They further reveal that TXNIP deficiency specifically inhibits the mitochondrial death pathway underlying beta-cell glucotoxicity, whereas it has very few protective effects against ER stress-mediated lipoapoptosis.

Intracellular shuttling and mitochondrial function of thioredoxin-interacting protein

The thioredoxin-interacting protein TXNIP is a ubiquitously expressed redox protein that promotes apoptosis. Recently, we found that TXNIP deficiency protects against type 1 and 2 diabetes by inhibiting beta cell apoptosis and maintaining pancreatic beta cell mass, indicating that TXNIP plays a key role in beta cell biology. However, very little is known about the intracellular localization and function of TXNIP, and although TXNIP has been thought to be a cytoplasmic protein, our immunohistochemistry studies in beta cells surprisingly revealed a nuclear TXNIP localization, suggesting that TXNIP may shuttle within the cell. Using immunohistochemistry/confocal imaging and cell fractionation/co-immunoprecipitation, we found that, under physiological conditions, TXNIP is localized primarily in the nucleus of pancreatic beta cells, whereas oxidative stress leads to TXNIP shuttling into the mitochondria. In mitochondria, TXNIP binds to and oxidizes Trx2, thereby reducing Trx2 binding to ASK1 and allowing for ASK1 phosphorylation/activation, resulting in induction of the mitochondrial pathway of apoptosis with cytochrome c release and caspase-3 cleavage. TXNIP overexpression and Trx2 (but not cytosolic Trx1) silencing mimic these effects. Thus, we discovered that TXNIP shuttles between subcellular compartments in response to oxidative stress and identified a novel redox-sensitive mitochondrial TXNIP-Trx2-ASK1 signaling cascade.

A painful train of events: increased prevalence of fibromyalgia in survivors of a major train crash

OBJECTIVES

To evaluate the prevalence of fibromyalgia in survivors of a major train crash in southern Israel, three years after the event.

METHODS

Survivors were contacted by mail and telephone. Individuals consenting to participate in the study underwent physical examination, including a tender point count and dolorimetry, as well as extensive evaluation of parameters relating to quality of life, presence of widespread pain, fatigue, physical and social function, posttraumatic symptoms and symptoms related to anxiety, dissociation, depression, somatisation, etc.

RESULTS

Fifteen percent of survivors participating in the study met ACR criteria for the classification of fibromyalgia. Significantly lower rates of physical and emotional functioning were found among survivors with fibromyalgia compared with those not meeting the classification criteria. Survivors with fibromyalgia rated significantly higher on scales of somatisation, obsessive-compulsive ideation, interpersonal sensitivity, depression, anger and hostility, phobic and general anxiety, paranoid ideation and psychoticism. Survivors with fibromyalgia also rated significantly higher on scales of posttraumatic symptoms including intrusion, avoidance and arousal. These individuals also rated significantly higher on the Peritraumatic Dissociative Experiences Questionnaire (PDE-Q) and the Dissociative Experiences Scale (Hebrew version) (DES-H).

CONCLUSION

Fibromyalgia was found to be highly prevalent, three years after a major train crash, among individuals exposed to the combination of physical injury and extreme stress. This finding is in accordance with previous data regarding the association of fibromyalgia with both physical and emotional trauma and calls attention to studying the underlying susceptibility factors which may partake in this association.

Glucose-stimulated expression of Txnip is mediated by carbohydrate response element-binding protein, p300, and histone H4 acetylation in pancreatic beta cells

Recently, we identified Txnip (thioredoxin-interacting protein) as a mediator of glucotoxic beta cell death and discovered that lack of Txnip protects against streptozotocin- and obesity-induced diabetes by preventing beta cell apoptosis and preserving endogenous beta cell mass. Txnip has therefore become an attractive target for diabetes therapy, but although we have found that txnip transcription is highly induced by glucose through a unique carbohydrate response element, the factors controlling this effect have remained unknown. Using transient transfection experiments, we now show that overexpression of the carbohydrate response element-binding protein (ChREBP) transactivates the txnip promoter, whereas ChREBP knockdown by small interfering RNA completely blunts glucose-induced txnip transcription. Moreover, chromatin immunoprecipitation demonstrated that glucose leads to a dose- and time-dependent recruitment of ChREBP to the txnip promoter in vivo in INS-1 beta cells as well as human islets. Furthermore, we found that the co-activator and histone acetyltransferase p300 co-immunoprecipitates with ChREBP and also binds to the txnip promoter in response to glucose. Interestingly, this is associated with specific acetylation of histone H4 and recruitment of RNA polymerase II as measured by chromatin immunoprecipitation. Thus, with this study we have identified ChREBP as the transcription factor that mediates glucose-induced txnip expression in human islets and INS-1 beta cells and have characterized the chromatin modification associated with glucose-induced txnip transcription. In addition, the results reveal for the first time that ChREBP interacts with p300. This may explain how ChREBP induces H4 acetylation and sheds new light on glucose-mediated regulation of chromatin structure and transcription.

Diabetes induces and calcium channel blockers prevent cardiac expression of proapoptotic thioredoxin-interacting protein

Cardiomyocyte apoptosis is a critical process in the pathogenesis of ischemic and diabetic cardiomyopathy, but the mechanisms are not fully understood. Thioredoxin-interacting protein (TXNIP) has recently been shown to have deleterious effects in the cardiovascular system and we therefore investigated whether it may also play a role in diabetes-associated cardiomyocyte apoptosis. In fact, TXNIP expression was increased in H9C2 cardiomyocytes incubated at high glucose, and cardiac expression of TXNIP and cleaved caspase-3 were also elevated in vivo in streptozotocin- and obesity-induced diabetic mice. Together, these findings not only suggest that TXNIP is involved in diabetic cardiomyopathy but also that it may represent a novel therapeutic target. Surprisingly, testing putative TXNIP modulators revealed that calcium channel blockers reduce cardiomyocyte TXNIP transcription and protein levels in a dose-dependent manner. Oral administration of verapamil for 3 wk also reduced cardiac TXNIP expression in mice even in the face of severe diabetes, and these reduced TXNIP levels were associated with decreased apoptosis. To determine whether lack of TXNIP can mimic the verapamil-induced decrease in apoptosis, we used TXNIP-deficient HcB-19 mice, harboring a natural nonsense mutation in the TXNIP gene. Interestingly, we found significantly reduced cleaved caspase-3 levels in HcB-19 hearts, suggesting that TXNIP plays a critical role in cardiac apoptosis and that the verapamil effects were mediated by TXNIP reduction. Thus our results suggest that TXNIP reduction is a powerful target to enhance cardiomyocyte survival and that agents such as calcium channel blockers may be useful in trying to achieve this goal and prevent diabetic cardiomyopathy.

Thioredoxin-interacting protein deficiency induces Akt/Bcl-xL signaling and pancreatic beta-cell mass and protects against diabetes

Pancreatic beta-cell loss through apoptosis represents a key factor in the pathogenesis of diabetes; however, no effective approaches to block this process and preserve endogenous beta-cell mass are currently available. To study the role of thioredoxin-interacting protein (TXNIP), a proapoptotic beta-cell factor we recently identified, we used HcB-19 (TXNIP nonsense mutation) and beta-cell-specific TXNIP knockout (bTKO) mice. Interestingly, HcB-19 mice demonstrate increased adiposity, but have lower blood glucose levels and increased pancreatic beta-cell mass (as assessed by morphometry). Moreover, HcB-19 mice are resistant to streptozotocin-induced diabetes. When intercrossed with obese, insulin-resistant, and diabetic mice, double-mutant BTBRlep(ob/ob)txnip(hcb/hcb) are even more obese, but are protected against diabetes and beta-cell apoptosis, resulting in a 3-fold increase in beta-cell mass. Beta-cell-specific TXNIP deletion also enhanced beta-cell mass (P<0.005) and protected against diabetes, and terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) revealed a approximately 50-fold reduction in beta-cell apoptosis in streptozotocin-treated bTKO mice. We further discovered that TXNIP deficiency induces Akt/Bcl-xL signaling and inhibits mitochondrial beta-cell death, suggesting that these mechanisms may mediate the beta-cell protective effects of TXNIP deficiency. These results suggest that lowering beta-cell TXNIP expression could serve as a novel strategy for the treatment of type 1 and type 2 diabetes by promoting endogenous beta-cell survival.

Thioredoxin-interacting protein: a critical link between glucose toxicity and beta-cell apoptosis

OBJECTIVE

In diabetes, glucose toxicity affects different organ systems, including pancreatic islets where it leads to beta-cell apoptosis, but the mechanisms are not fully understood. Recently, we identified thioredoxin-interacting protein (TXNIP) as a proapoptotic beta-cell factor that is induced by glucose, raising the possibility that TXNIP may play a role in beta-cell glucose toxicity.

RESEARCH DESIGN AND METHODS

To assess the effects of glucose on TXNIP expression and apoptosis and define the role of TXNIP, we used INS-1 beta-cells; primary mouse islets; obese, diabetic BTBR.ob mice; and a unique mouse model of TXNIP deficiency (HcB-19) that harbors a natural nonsense mutation in the TXNIP gene.

RESULTS

Incubation of INS-1 cells at 25 mmol/l glucose for 24 h led to an 18-fold increase in TXNIP protein, as assessed by immunoblotting. This was accompanied by increased apoptosis, as demonstrated by a 12-fold induction of cleaved caspase-3. Overexpression of TXNIP revealed that TXNIP induces the intrinsic mitochondrial pathway of apoptosis. Islets of diabetic BTBR.ob mice also demonstrated increased TXNIP and apoptosis as did isolated wild-type islets incubated at high glucose. In contrast, TXNIP-deficient HcB-19 islets were protected against glucose-induced apoptosis as measured by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and caspase-3, indicating that TXNIP is a required causal link between glucose toxicity and beta-cell death.

CONCLUSIONS

These findings shed new light onto the molecular mechanisms of beta-cell glucose toxicity and apoptosis, demonstrate that TXNIP induction plays a critical role in this vicious cycle, and suggest that inhibition of TXNIP may represent a novel approach to reduce glucotoxic beta-cell loss.

HIV-protease inhibitors induce expression of suppressor of cytokine signaling-1 in insulin-sensitive tissues and promote insulin resistance and type 2 diabetes mellitus

Insulin resistance, hyperglycemia, and type 2 diabetes are among the sequelae of metabolic syndromes that occur in 60-80% of human immunodeficiency virus (HIV)-positive patients treated with HIV-protease inhibitors (PIs). Studies to elucidate the molecular mechanism(s) contributing to these changes, however, have mainly focused on acute, in vitro actions of PIs. Here, we examined the chronic (7 wk) in vivo effects of the PI indinavir (IDV) in male Zucker diabetic fatty (fa/fa) (ZDF) rats. IDV exposure accelerated the diabetic state and dramatically exacerbated hyperglycemia and oral glucose intolerance in the ZDF rats, compared with vehicle-treated ZDF rats. Oligonucleotide gene array analyses revealed upregulation of suppressor of cytokine signaling-1 (SOCS-1) expression in insulin-sensitive tissues of IDV rats. SOCS-1 is a known inducer of insulin resistance and diabetes, and immunoblotting analyses revealed increases in SOCS-1 protein expression in adipose, skeletal muscle, and liver tissues of IDV-administered ZDF rats. This was associated with increases in the upstream regulator TNF-alpha and downstream effector sterol regulatory element-binding protein-1 and a decrease in IRS-2. IDV and other PIs currently in clinical use induced the SOCS-1 signaling cascade also in L6 myotubes and 3T3-L1 adipocytes exposed acutely to PIs under normal culturing conditions and in tissues from Zucker wild-type lean control rats administered PIs for 3 wk, suggesting an effect of these drugs even in the absence of background hyperglycemia/hyperlipidemia. Our findings therefore indicate that induction of the SOCS-1 signaling cascade by PIs could be an important contributing factor in the development of metabolic dysregulation associated with long-term exposures to HIV-PIs.

Exenatide blocks JAK1-STAT1 in pancreatic beta cells

Exenatide (Ex-4) is an antidiabetic drug that acts through the glucagon-like peptide 1 receptor and has recently been approved for the treatment of type 2 diabetes mellitus. Ex-4 also has been shown to affect beta cell gene expression and increase beta cell mass in rodent models of type 1 diabetes mellitus, but the mechanisms are not fully understood. We therefore analyzed the pathways affected by Ex-4 in human islets by using oligonucleotide microarrays and the PathwayStudio software (Ariadne Genomics, Rockville, MD). We identified the JAK1-STAT1 pathway as a novel target of Ex-4 and confirmed the Ex-4-mediated down-regulation of JAK1 and STAT1 by quantitative reverse transcription-polymerase chain reaction in human islets and INS-1 cells. JAK1-STAT1 is the major signaling pathway mediating the interferon gamma effects on beta cell apoptosis in type 1 diabetes mellitus. Thus, these findings suggest that Ex-4 treatment may also be beneficial in type 1 diabetes mellitus, where it may help protect beta cells from cytokine-induced cell death by inhibiting JAK1-STAT1.

Conservative management of implantable cardioverter defibrillator-related endocarditis due to Bacillus spp

Endocarditis is a devastating complication of implantable cardioverter-defibrillator (ICD) therapy. Partial or complete device removal has been advocated for the treatment of this condition although controlled data are lacking. We present a case of ICD-related endocarditis caused by Bacillus spp. that occurred following coronary angiography. To the best of our knowledge, Bacillus spp. has not been previously described in such context. Moreover, conservative treatment with device retention was successful (no recurrence during a 6-year follow-up). Conservative management may be attempted in selected cases of ICD-related endocarditis, especially, those involving low-virulence organisms and rapid response to antibiotic therapy. This case also suggests that coronary angiography may be associated with transient bacteremia and subsequent infection of indwelling cardiac devices.

A cis-element in the 5' untranslated region of the preproinsulin mRNA (ppIGE) is required for glucose regulation of proinsulin translation

Insulin production in pancreatic beta cells is predominantly regulated through glucose control of proinsulin translation. Previously, this was shown to require sequences within the untranslated regions (UTRs) of the preproinsulin (ppI) mRNA. Here, those sequences were found to be sufficient for specific glucose-regulated proinsulin translation. Furthermore, an element 40-48 bp from the 5' end of the ppI mRNA specifically bound a factor present in islets of Langerhans. Glucose-responsive factor binding to this cis-element exhibited temporal and glucose-concentration-dependent patterns that paralleled proinsulin biosynthesis. Mutating this cis-element abolished the ability of ppI mRNA UTRs to confer glucose regulation upon translation. Like the rat 5'UTR, the human ppI 5'UTR conferred glucose regulation of translation. However alternative splicing of the human 5'UTR that disrupts the cis-element abolished glucose-regulated translation. These data indicate that glucose regulation of cis-element/trans-acting factor interaction is a key component of the mechanism by which glucose regulates insulin production.