GIANT API: an application programming interface for functional genomics.

GIANT API provides biomedical researchers programmatic access to tissue-specific and global networks in humans and model organisms, and associated tools, which includes functional re-prioritization of existing genome-wide association study (GWAS) data. Using tissue-specific interaction networks, researchers are able to predict relationships between genes specific to a tissue or cell lineage, identify the changing roles of genes across tissues and uncover disease-gene associations. Additionally, GIANT API enables computational tools like NetWAS, which leverages tissue-specific networks for re-prioritization of GWAS results. The web services covered by the API include 144 tissue-specific functional gene networks in human, global functional networks for human and six common model organisms and the NetWAS method. GIANT API conforms to the REST architecture, which makes it stateless, cacheable and highly scalable. It can be used by a diverse range of clients including web browsers, command terminals, programming languages and standalone apps for data analysis and visualization. The API is freely available for use at http://giant-api.princeton.edu.

Acute lung injury and persistent small airway disease in a rabbit model of chlorine inhalation.

Chlorine is a pulmonary toxicant to which humans can be exposed through accidents or intentional releases. Acute effects of chlorine inhalation in humans and animal models have been well characterized, but less is known about persistent effects of acute, high-level chlorine exposures. In particular, animal models that reproduce the long-term effects suggested to occur in humans are lacking. Here, we report the development of a rabbit model in which both acute and persistent effects of chlorine inhalation can be assessed. Male New Zealand White rabbits were exposed to chlorine while the lungs were mechanically ventilated. After chlorine exposure, the rabbits were extubated and were allowed to survive for up to 24h after exposure to 800ppm chlorine for 4min to study acute effects or up to 7days after exposure to 400ppm for 8min to study longer term effects. Acute effects observed 6 or 24h after inhalation of 800ppm chlorine for 4min included hypoxemia, pulmonary edema, airway epithelial injury, inflammation, altered baseline lung mechanics, and airway hyperreactivity to inhaled methacholine. Seven days after recovery from inhalation of 400ppm chlorine for 8min, rabbits exhibited mild hypoxemia, increased area of pressure-volume loops, and airway hyperreactivity. Lung histology 7days after chlorine exposure revealed abnormalities in the small airways, including inflammation and sporadic bronchiolitis obliterans lesions. Immunostaining showed a paucity of club and ciliated cells in the epithelium at these sites. These results suggest that small airway disease may be an important component of persistent respiratory abnormalities that occur following acute chlorine exposure. This non-rodent chlorine exposure model should prove useful for studying persistent effects of acute chlorine exposure and for assessing efficacy of countermeasures for chlorine-induced lung injury.

Diabetic Microvascular Disease and Pulmonary Fibrosis: The Contribution of Platelets and Systemic Inflammation.

Diabetes is strongly associated with systemic inflammation and oxidative stress, but its effect on pulmonary vascular disease and lung function has often been disregarded. Several studies identified restrictive lung disease and fibrotic changes in diabetic patients and in animal models of diabetes. While microvascular dysfunction is a well-known complication of diabetes, the mechanisms leading to diabetes-induced lung injury have largely been disregarded. We described the potential involvement of diabetes-induced platelet-endothelial interactions in perpetuating vascular inflammation and oxidative injury leading to fibrotic changes in the lung. Changes in nitric oxide synthase (NOS) activation and decreased NO bioavailability in the diabetic lung increase platelet activation and vascular injury and may account for platelet hyperreactivity reported in diabetic patients. Additionally, the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway has been reported to mediate pancreatic islet damage, and is implicated in the onset of diabetes, inflammation and vascular injury. Many growth factors and diabetes-induced agonists act via the JAK/STAT pathway. Other studies reported the contribution of the JAK/STAT pathway to the regulation of the pulmonary fibrotic process but the role of this pathway in the development of diabetic lung fibrosis has not been considered. These observations may open new therapeutic perspectives for modulating multiple pathways to mitigate diabetes onset or its pulmonary consequences.

Identification of alkaline-induced thiolyl-chlorogenic acid conjugates with cysteine and glutathione.

Alkaline reactions of chlorogenic acid (CGA) yield undesirable development of brown or green pigments, limiting the utilization of alkalized CGA-rich foods. Thiols such as cysteine and glutathione mitigate pigment formation through several mechanisms, including redox coupling to reduce CGA quinones, and thiol conjugation, which forms colorless thiolyl-CGA compounds that do not readily participate in color-generating reactions. This work provided evidence of the formation of both aromatic and benzylic thiolyl-CGA conjugate species formed with cysteine and glutathione under alkaline conditions in addition to hydroxylated conjugate species hypothesized to arise from reactions with hydroxyl radicals. Formation of these conjugates proceeds more quickly than CGA dimerization and amine addition reactions mitigating pigment development. Differentiation between aromatic and benzylic conjugates is enabled by characteristic fragmentation of CS bonds. Acyl migration and hydrolysis of the quinic acid moiety of thiolyl-CGA conjugates yielded a variety of isomeric species also identified through untargeted LC-MS methods.

A consideration of factors affecting palliative oral appliance effectiveness for obstructive sleep apnea: a scoping review.

STUDY OBJECTIVES: This scoping review allows physicians, researchers, and others interested in obstructive sleep apnea to consider effectiveness of oral appliances (OAs). The intent is to improve understanding of OA effectiveness by considering morphologic interaction in patients with obstructive sleep apnea. METHODS: Morphologic and biomechanical criteria for positional alterations of the mandible assessed success rates of OA appliances. Searches of databases (Medline, PubMed, The Cochrane Library, EBSCO) using terms: OA treatment effectiveness and positive and/or negative outcome predictors. Craniofacial predictors of OAs and obstructive sleep apnea biomechanical factors of anatomical traits associated with OA effectiveness were included. Databases searched radiographic cephalometric imaging for morphology/phenotypes and apnea-hypopnea index responses. Articles were excluded if title or abstract was not relevant or a case report. If the analysis did not report mean or standard deviation for apnea-hypoxia index, it was excluded. No language, age, or sex restrictions were applied. RESULTS: Analysis of 135 articles included in searched literature indicated alterations in musculature and pharyngeal airway structure through OA use. These alterations were individually unpredictable with wide variability 61.81% ± 12.29 (apnea-hypoxia index mean ± standard deviation). Morphologic variations as predictors were typically weak and idiosyncratic. Biomechanical factors and wide variations in the metrics of appliance application were unclear, identifying gaps in knowledge and practice of OAs. CONCLUSIONS: An integrated basis to identify morphologic and biomechanical elements of phenotypic expressions of sleep-disordered breathing in the design and application of OAs is needed. Current knowledge is heterogeneous and shows high variability. Identification of subgroups of patients with obstructive sleep apnea responding to OAs is needed.

Intravital assessment of precapillary pulmonary arterioles of type 1 diabetic mice shows oxidative damage and increased tone in response to NOS inhibition.

Microvascular dilation, important for peripheral tissue glucose distribution, also modulates alveolar perfusion and is inhibited by loss of bioavailable nitric oxide (NO) in diabetes mellitus (DM). We hypothesized that DM-induced oxidative stress decreases bioavailable NO and pulmonary precapillary arteriolar diameter, causing endothelial injury. We examined subpleural pulmonary arterioles after acute NO synthase (NOS) inhibition with NG-nitro-l-arginine methyl ester (l-NAME) in streptozotocin (STZ)- and saline (CTRL)-treated C57BL/6J mice. Microvascular changes were assessed by intravital microscopy in the right lung of anesthetized mice with open chest and ventilated lungs. Arteriolar tone in pulmonary arterioles (27.2-48.7 µm diameter) increased in CTRL mice (18.0 ± 11% constriction, P = 0.034, n = 5) but decreased in STZ mice (13.6 ± 7.5% dilation, P = 0.009, n = 5) after l-NAME. Lung tissue dihydroethidium (DHE) fluorescence (superoxide), inducible NOS expression, and protein nitrosylation (3-nitrotyrosine) increased in STZ mice and correlated with increased glucose levels (103.8 ± 8.8 mg/dL). Fluorescently labeled fibrinogen administration and fibrinogen immunostaining showed fibrinogen adhesion, indicating endothelial injury in STZ mice. In CTRL mice, vasoconstriction to l-NAME was likely due to the loss of bioavailable NO. Vasodilation in STZ mice may be due to decreased formation of a vasoconstrictor or emergence of a vasodilator. These findings provide novel evidence that DM targets the pulmonary microcirculation and that decreased NO bioavailability and increased precapillary arteriolar tone could potentially lead to ventilation-perfusion abnormalities, exacerbating systemic DM complications.NEW & NOTEWORTHY Diabetes pulmonary and microvascular consequences are well recognized but have not been characterized. We assessed lung microvascular changes in a live anesthetized mouse model of type 1 diabetes, using a novel intravital microscopy technique. Our results show new evidence that a diabetes-induced decrease in lung nitric oxide bioavailability underlies oxidative damage, enhanced platelet activation, and endothelial injury causing pulmonary microvascular dysfunction and altered vasoreactivity. These findings could provide novel strategies to prevent or reverse diabetes systemic consequences.

VHL promotes E2 box-dependent E-cadherin transcription by HIF-mediated regulation of SIP1 and snail.

The product of the von Hippel-Lindau gene (VHL) acts as the substrate-recognition component of an E3 ubiquitin ligase complex that ubiquitylates the catalytic alpha subunit of hypoxia-inducible factor (HIF) for oxygen-dependent destruction. Although emerging evidence supports the notion that deregulated accumulation of HIF upon the loss of VHL is crucial for the development of clear-cell renal cell carcinoma (CC-RCC), the molecular events downstream of HIF governing renal oncogenesis remain unclear. Here, we show that the expression of a homophilic adhesion molecule, E-cadherin, a major constituent of epithelial cell junctions whose loss is associated with the progression of epithelial cancers, is significantly down-regulated in primary CC-RCC and CC-RCC cell lines devoid of VHL. Reintroduction of wild-type VHL in CC-RCC (VHL(-/-)) cells markedly reduced the expression of E2 box-dependent E-cadherin-specific transcriptional repressors Snail and SIP1 and concomitantly restored E-cadherin expression. RNA interference-mediated knockdown of HIFalpha in CC-RCC (VHL(-/-)) cells likewise increased E-cadherin expression, while functional hypoxia or expression of VHL mutants incapable of promoting HIFalpha degradation attenuated E-cadherin expression, correlating with the disengagement of RNA polymerase II from the endogenous E-cadherin promoter/gene. These findings reveal a critical HIF-dependent molecular pathway connecting VHL, an established "gatekeeper" of the renal epithelium, with a major epithelial tumor suppressor, E-cadherin.

Fibrinogen induces alterations of endothelial cell tight junction proteins.

We previously showed that an elevated content of fibrinogen (Fg) increased formation of filamentous actin and enhanced endothelial layer permeability. In the present work we tested the hypothesis that Fg binding to endothelial cells (ECs) alters expression of actin-associated endothelial tight junction proteins (TJP). Rat cardiac microvascular ECs were grown in gold plated chambers of an electrical cell-substrate impedance system, 8-well chambered, or in 12-well plates. Confluent ECs were treated with Fg (2 or 4 mg/ml), Fg (4 mg/ml) with mitogen-activated protein kinase (MEK) kinase inhibitors (PD98059 or U0126), Fg (4 mg/ml) with anti-ICAM-1 antibody or BQ788 (endothelin type B receptor blocker), endothelin-1, endothelin-1 with BQ788, or medium alone for 24 h. Fg induced a dose-dependent decrease in EC junction integrity as determined by transendothelial electrical resistance (TEER). Western blot analysis and RT-PCR data showed that the higher dose of Fg decreased the contents of TJPs, occludin, zona occluden-1 (ZO-1), and zona occluden-2 (ZO-2) in ECs. Fg-induced decreases in contents of the TJPs were blocked by PD98059, U0126, or anti-ICAM-1 antibody. While BQ788 inhibited endothelin-1-induced decrease in TEER, it did not affect Fg-induced decrease in TEER. These data suggest that Fg increases EC layer permeability via the MEK kinase signaling pathway by affecting occludin, ZO-1, and ZO-2, TJPs, which are bound to actin filaments. Therefore, increased binding of Fg to its major EC receptor, ICAM-1, during cardiovascular diseases may increase microvascular permeability by altering the content and possibly subcellular localization of endothelial TJPs.

Lung ischemia-reperfusion injury: implications of oxidative stress and platelet-arteriolar wall interactions.

Pulmonary ischemia-reperfusion (IR) injury may result from trauma, atherosclerosis, pulmonary embolism, pulmonary thrombosis and surgical procedures such as cardiopulmonary bypass and lung transplantation. IR injury induces oxidative stress characterized by formation of reactive oxygen (ROS) and reactive nitrogen species (RNS). Nitric oxide (NO) overproduction via inducible nitric oxide synthase (iNOS) is an important component in the pathogenesis of IR. Reaction of NO with ROS forms RNS as secondary reactive products, which cause platelet activation and upregulation of adhesion molecules. This mechanism of injury is particularly important during pulmonary IR with increased iNOS activity in the presence of oxidative stress. Platelet-endothelial interactions may play an important role in causing pulmonary arteriolar vasoconstriction and post-ischemic alveolar hypoperfusion. This review discusses the relationship between ROS, RNS, P-selectin, and platelet-arteriolar wall interactions and proposes a hypothesis for their role in microvascular responses during pulmonary IR.

Impaired control of renal sympathetic nerve activity following neonatal intermittent hypoxia in rats.

Apneas and recurring oxygen desaturations can occur in preterm infants and young children. To investigate long-term effects of neonatal intermittent hypoxia on baroreflex control of sympathetic nerve activity, we studied 5-7-month-old (adult) Sprague-Dawley rats exposed to chronic intermittent hypoxia (CIH, n=9; 8% O2 for 90 s alternating with 90 s 21% O2, 12h/day) for their first 30 postnatal days or controls exposed to normoxia (C, n=9). In adult CIH and C rats, baseline heart rate, mean arterial pressure, and plasma concentration of epinephrine and norepinephrine were similar. Baroreflex sensitivity was evaluated in anesthetized rats by changes in renal sympathetic nerve activity (RSNA) in response to i.v. infusions of phenylephrine (PE,1.5 microg/min/100g) and sodium nitroprusside (SNP, 1.5 microg/min/100g). Acute intermittent hypoxia (AIH, 18 min) induced elevations in RSNA by over 30% of baseline about three times more often in the CIH group than in the C group. After AIH, the gain of the baroreflex sympatho-excitatory response increased by approximately two times in C and did not change in CIH rats. The gain of sympatho-inhibitory responses to SNP at the maximum decrease in MAP was similar in the two groups in normoxia and was not affected by AIH. We conclude that postnatal intermittent hypoxia causes long-lasting impairment in chemoreceptor and baroreceptor control of renal nerve activity.

Adaptive-outward and maladaptive-inward arterial remodeling measured by intravascular ultrasound in hyperhomocysteinemia and diabetes.

BACKGROUND: Coronary artery remodeling implies structural changes in the vessel wall in response to various pathophysiologic conditions. However, the classification of remodeling is unclear. We hypothesized that the adaptive, positive-outward remodeling is a reactive and compensatory response to the stress. The maladaptive negative-inward constrictive remodeling is a passive atherosclerotic condition in which the vessel becomes stiffer. METHODS: Patients with atherosclerotic lesions underwent intravascular ultrasound (IVUS) scans. The size of the vessels distal to and proximal to plaques were analyzed by IVUS. Diabetes was created in mice by an intraperitoneal injection of alloxan (65 mg/kg). To reduce remodeling, mice received ciglitazone, an agonist of peroxisome proliferators activated receptor-gamma (PPARgamma) in drinking water. After 8 weeks, atherosclerotic vessels were analyzed for collagen and elastin. RESULTS: IVUS data suggest an adaptive coronary arterial remodeling was a positive compensatory response to various pathologic stimuli; for example, with the deposition of atherosclerotic plaque, coronary arterial segments enlarged to maintain luminal area. This phenomenon was commonly observed during the initial phases of the development of atherosclerosis. However, negative coronary artery remodeling, or a decrease in vessel area with the formation of atherosclerotic plaque, was maladaptive and was associated with smoking, hypertension, hyperhomocysteinemia, diabetes mellitus, and also after percutaneous coronary interventions (restenosis). In diabetic mice, there was increased collagen and decreased elastin contents; however, treatment with ciglitazone ameliorated the decrease in elastin contents. CONCLUSION: Global enlargement of the coronary vascular tree occurs during pressure and volume overload associated with ventricular hypertrophic states such as athletic conditioning, hypertensive heart disease, and dilated cardiomyopathy. On the other hand, maladaptive coronary arterial remodeling occurs in patients with severe deconditioning, diabetes mellitus, after coronary artery bypass surgery, and in some instances, postintervention.

Arrhythmia and neuronal/endothelial myocyte uncoupling in hyperhomocysteinemia.

Elevated levels of homocysteine (Hcy) known as hyperhomocysteinemia (HHcy) are associated with arrhythmogenesis and sudden cardiac death (SCD). Hcy decreases constitutive neuronal and endothelial nitric oxide (NO), and cardiac diastolic relaxation. Hcy increases the iNOS/NO, peroxynitrite, mitochondrial NADPH oxidase, and suppresses superoxide dismutase (SOD) and redoxins. Hcy activates matrix metalloproteinase (MMP), disrupts connexin-43 and increases collagen/elastin ratio. The disruption of connexin-43 and accumulation of collagen (fibrosis) disrupt the normal pattern of cardiac conduction and attenuate NO transport from endothelium to myocyte (E-M) causing E-M uncoupling, leading to a pro-arrhythmic environment. The goal of this review is to elaborate the mechanism of Hcy-mediated iNOS/NO in E-M uncoupling and SCD. It is known that Hcy creates arrhythmogenic substrates (i.e. increase in collagen/elastin ratio and disruption in connexin-43) and exacerbates heart failure during chronic volume overload. Also, Hcy behaves as an agonist to N-methyl-D-aspartate (NMDA, an excitatory neurotransmitter) receptor-1, and blockade of NMDA-R1 reduces the increase in heart rate-evoked by NMDA-analog and reduces SCD. This review suggest that Hcy increases iNOS/NO, superoxide, metalloproteinase activity, and disrupts connexin-43, exacerbates endothelial-myocyte uncoupling and cardiac failure secondary to inducing NMDA-R1.

Increased pulmonary arteriolar tone associated with lung oxidative stress and nitric oxide in a mouse model of Alzheimer's disease.

Vascular dysfunction and decreased cerebral blood flow are linked to Alzheimer's disease (AD). Loss of endothelial nitric oxide (NO) and oxidative stress in human cerebrovascular endothelium increase expression of amyloid precursor protein (APP) and enhance production of the Aß peptide, suggesting that loss of endothelial NO contributes to AD pathology. We hypothesize that decreased systemic NO bioavailability in AD may also impact lung microcirculation and induce pulmonary endothelial dysfunction. The acute effect of NO synthase (NOS) inhibition on pulmonary arteriolar tone was assessed in a transgenic mouse model (TgAD) of AD (C57BL/6-Tg(Thy1-APPSwDutIowa)BWevn/Mmjax) and age-matched wild-type controls (C57BL/6J). Arteriolar diameters were measured before and after the administration of the NOS inhibitor, L-NAME Lung superoxide formation (DHE) and formation of nitrotyrosine (3-NT) were assessed as indicators of oxidative stress, inducible NOS (iNOS) and tumor necrosis factor alpha (TNF-α) expression as indicators of inflammation. Administration of L-NAME caused either significant pulmonary arteriolar constriction or no change from baseline tone in wild-type (WT) mice, and significant arteriolar dilation in TgAD mice. DHE, 3-NT, TNF-α, and iNOS expression were higher in TgAD lung tissue, compared to WT mice. These data suggest L-NAME could induce increased pulmonary arteriolar tone in WT mice from loss of bioavailable NO In contrast, NOS inhibition with L-NAME had a vasodilator effect in TgAD mice, potentially caused by decreased reactive nitrogen species formation, while significant oxidative stress and inflammation were present. We conclude that AD may increase pulmonary microvascular tone as a result of loss of bioavailable NO and increased oxidative stress. Our findings suggest that AD may have systemic microvascular implications beyond central neural control mechanisms.

Exposure to the Functional Bacterial Amyloid Protein Curli Enhances Alpha-Synuclein Aggregation in Aged Fischer 344 Rats and Caenorhabditis elegans.

Misfolded alpha-synuclein (AS) and other neurodegenerative disorder proteins display prion-like transmission of protein aggregation. Factors responsible for the initiation of AS aggregation are unknown. To evaluate the role of amyloid proteins made by the microbiota we exposed aged rats and transgenic C. elegans to E. coli producing the extracellular bacterial amyloid protein curli. Rats exposed to curli-producing bacteria displayed increased neuronal AS deposition in both gut and brain and enhanced microgliosis and astrogliosis compared to rats exposed to either mutant bacteria unable to synthesize curli, or to vehicle alone. Animals exposed to curli producing bacteria also had more expression of TLR2, IL-6 and TNF in the brain than the other two groups. There were no differences among the rat groups in survival, body weight, inflammation in the mouth, retina, kidneys or gut epithelia, and circulating cytokine levels. AS-expressing C. elegans fed on curli-producing bacteria also had enhanced AS aggregation. These results suggest that bacterial amyloid functions as a trigger to initiate AS aggregation through cross-seeding and also primes responses of the innate immune system.

Homocysteine in microvascular endothelial cell barrier permeability.

Redox stress activates the endothelium and upregulates matrix metalloproteinases (MMPs), which degrade the matrix and lead to blood-endothelial barrier leakage. Interestingly, elevated levels of plasma homocysteine (Hcy) are associated with vascular dementia, seizure, stroke, and Alzheimer disease. Hcy competes with the gamma-aminobutyric acid (GABA)-A/B receptors and behave like an excitatory neurotransmitter. GABA stimulates the inhibitory neurotransmitter GABA-A/B receptor and decreases arterial blood pressure. However, the neural mechanisms of microvascular remodeling in hyperhomocysteinemia are unclear. This review addresses the idea that Hcy induces microvascular permeability by attenuating the GABA-A/B receptors and increasing redox stress, which activates a disintegrin and metalloproteinase that suppresses tissue inhibitors of metalloproteinase. This process causes disruption of the matrix in the blood-brain barrier. Understanding the mechanism of Hcy-mediated changes in permeability of the blood-brain barrier and extracellular matrix that can alter the neuronal environment in cerebral-vascular dementia is of great importance in developing treatments for this disease.

Inhibition of inducible nitric oxide synthase attenuates platelet adhesion in subpleural arterioles caused by lung ischemia-reperfusion in rabbits.

Oxidative stress, induced by lung ischemia-reperfusion, leads to platelet and leukocyte activation and may contribute to decreased alveolar perfusion by platelet adhesion to the arteriolar wall. We investigated the hypothesis that ischemia-reperfusion injury increases inducible nitric oxide synthase (iNOS) activity and subsequent generation of reactive nitrogen species with P-selectin-dependent platelet-endothelial interactions and vasoconstriction during lung reperfusion. Subpleural arterioles, labeled platelets, and leukocytes were examined in anesthetized, open-chest rabbits by intravital fluorescence microscopy. Ischemia was caused by reversible occlusion of the right pulmonary artery for 1 or 2 h (1IR and 2IR groups). During 2 h of reperfusion, postischemic platelet rolling and adhesion were independent from leukocyte-arteriolar wall interactions and correlated with pulmonary arteriolar constriction in proportion to the length of ischemia. In rabbits treated with an iNOS inhibitor (1400W) before occlusion (2IR + 1400W group), platelet-arteriolar wall interactions and vasoconstriction were prevented. iNOS expression and activity in ischemic lung tissue were markedly greater than control and also were proportional to ischemia duration. NOS activity, immunochemically detected P-selectin, and nitrotyrosine expression in ischemic lung tissue from animals subjected to ischemia-reperfusion, as well as the plasma level of soluble P-selectin, were significantly higher than in nonischemic lungs and were inhibited by pretreatment with 1400W. These results show that platelet adhesion and arteriolar constriction during early reperfusion in the ventilated lung can result from increased iNOS activity and is highly correlated with reactive nitrogen species and P-selectin expression.

Hyperhomocysteinemic diabetic cardiomyopathy: oxidative stress, remodeling, and endothelial-myocyte uncoupling.

Accumulation of oxidized-matrix (fibrosis) between the endothelium (the endothelial cells embedded among the myocytes) and cardiomyocytes is a hallmark of diabetes mellitus and causes diastolic impairment. In diabetes mellitus, elevated levels of homocysteine activate matrix metalloproteinase and disconnect the endothelium from myocytes. Extracellular matrix functionally links the endothelium to the cardiomyocyte and is important for their synchronization. However, in diabetes mellitus, a disconnection is caused by activated metalloproteinase, with subsequent accumulation of oxidized matrix between the endothelium and myocyte. This contributes to endothelial-myocyte uncoupling and leads to impaired diastolic relaxation of the heart in diabetes mellitus. Elevated levels of homocysteine in diabetes are attributed to impaired homocysteine metabolism by glucose and insulin and decreased renal clearance. Homocysteine induces oxidative stress and is inversely related to the expression of peroxisome proliferators activated receptor (PPAR). Several lines of evidence suggest that ablation of the matrix metalloproteinase (MMP-9) gene ameliorates the endothelial-myocyte uncoupling in diabetes mellitus. Homocysteine competes for, and decreases the PPARgammaactivity. In diabetes mellitus, endothelial-myocyte uncoupling is associated with matrix metalloproteinase activation and decreased PPARgamma activity. The purpose of this review is to discuss the role of endothelial-myocyte uncoupling in diabetes mellitus and increased levels of homocysteine, causing activation of latent metalloproteinases, decreased levels of thioredoxin and peroxiredoxin, and cardiac tissue inhibitor of metalloproteinase (CIMP) in response to antagonizing PPARgamma.