The PEA15 gene is overexpressed and related to insulin resistance in healthy first-degree relatives of patients with type 2 diabetes

Molecular interactions between a diphenyl scaffold and PED/PEA15: Implications for type II diabetes therapeutics targeting PED/PEA15 - Phospholipase D1 interaction

In a recent study, we have identified BPH03 as a promising scaffold for the development of compounds aimed at modulating the interaction between PED/PEA15 (Phosphoprotein Enriched in Diabetes/Phosphoprotein Enriched in Astrocytes 15) and PLD1 (phospholipase D1), with potential applications in type II diabetes therapy. PED/PEA15 is known to be overexpressed in certain forms of diabetes, where it binds to PLD1, thereby reducing insulin-stimulated glucose transport. The inhibition of this interaction reestablishes basal glucose transport, indicating PED as a potential target of ligands capable to recover glucose tolerance and insulin sensitivity. In this study, we employ computational methods to provide a detailed description of BPH03 interaction with PED, evidencing the presence of a hidden druggable pocket within its PLD1 binding surface. We also elucidate the conformational changes that occur during PED interaction with BPH03. Moreover, we report new NMR data supporting the in-silico findings and indicating that BPH03 disrupts the PED/PLD1 interface displacing PLD1 from its interaction with PED. Our study represents a significant advancement toward the development of potential therapeutics for the treatment of type II diabetes.

Quantitative Proteomics Identifies Novel Nrf2-Mediated Adaptative Signaling Pathways in Skeletal Muscle Following Exercise Training

Exercise training (ExT) improves skeletal muscle health via multiple adaptative pathways. Nrf2 is a principal antioxidant transcription factor responsible for maintaining intracellular redox homeostasis. In this study, we hypothesized that Nrf2 is essential for adaptative responses to ExT and thus beneficial for muscle. Experiments were carried out on male wild type (WT) and iMS-Nrf2flox/flox inducible muscle-specific Nrf2 (KO) mice, which were randomly assigned to serve as sedentary controls (Sed) or underwent 3 weeks of treadmill ExT thus generating four groups: WT-Sed, WT-ExT, KO-Sed, and KO-ExT groups. Mice were examined for exercise performance and in situ tibialis anterior (TA) contractility, followed by mass spectrometry-based proteomics and bioinformatics to identify differentially expressed proteins and signaling pathways. We found that maximal running distance was significantly longer in the WT-ExT group compared to the WT-Sed group, whereas this capacity was impaired in KO-ExT mice. Force generation and fatigue tolerance of the TA were enhanced in WT-ExT, but reduced in KO-ExT, compared to Sed controls. Proteomic analysis further revealed that ExT upregulated 576 proteins in WT but downregulated 207 proteins in KO mice. These proteins represent pathways in redox homeostasis, mitochondrial respiration, and proteomic adaptation of muscle to ExT. In summary, our data suggest a critical role of Nrf2 in the beneficial effects of SkM and adaptation to ExT.

Screening a Molecular Fragment Library to Modulate the PED/PEA15-Phospholipase D1 Interaction in Cellular Lysate Environments

The overexpression of PED/PEA15, the phosphoprotein enriched in diabetes/phosphoprotein enriched in the astrocytes 15 protein (here referred simply to as PED), observed in some forms of type II diabetes, reduces the transport of insulin-stimulated glucose by binding to the phospholipase D1 (PLD1). The inhibition of the PED/PLD1 interaction was shown to restore basal glucose transport, indicating PED as a pharmacological target for the development of drugs capable of improving insulin sensitivity and glucose tolerance. We here report the identification and selection of PED ligands by means of NMR screening of a library of small organic molecules, NMR characterization of the PED/PLD1 interaction in lysates of cells expressing PLD1, and modulation of such interactions using BPH03, the best selected ligand. Overall, we complement the available literature data by providing detailed information on the structural determinants of the PED/PLD1 interaction in a cellular lysate environment and indicate BPH03 as a precious scaffold for the development of novel compounds that are able to modulate such interactions with possible therapeutic applications in type II diabetes.

Steller's sea cow genome suggests this species began going extinct before the arrival of Paleolithic humans

Anthropogenic activity is the top factor directly related to the extinction of several animal species. The last Steller's sea cow (Hydrodamalis gigas) population on the Commander Islands (Russia) was wiped out in the second half of the 18^th century due to sailors and fur traders hunting it for the meat and fat. However, new data suggests that the extinction process of this species began much earlier. Here, we present a nuclear de novo assembled genome of H. gigas with a 25.4× depth coverage. Our results demonstrate that the heterozygosity of the last population of this animal is low and comparable to the last woolly mammoth population that inhabited Wrangel Island 4000 years ago. Besides, as a matter of consideration, our findings also demonstrate that the extinction of this marine mammal starts along the North Pacific coastal line much earlier than the first Paleolithic humans arrived in the Bering sea region.

Validation of mouse phosphoprotein enriched in astrocyte 15 (mPEA15) expressing transgenic pig as a potential model in diabetes translational research

The present study aimed to investigate the characteristics of mPEA15 expressing transgenic pig (TG pig) as a potential model for diabetes. Expression analysis confirmed the ubiquitous expression of mPEA15 in TG pigs at F4. Oral glucose tolerance test results showed that restoration of normal glucose levels was significantly delayed in the TG pigs when compared with that in the wild-type pigs (WT pigs). Primary skeletal muscle cells isolated from TG pigs demonstrated reduced glucose uptake and reduced GLUT4 translocation to the plasma membrane in response to insulin treatment. Combined, these results suggest that mPEA15 expressing pigs has a glucose intolerance and insulin resistance which are known to mediate the pathophysiology of type 2 diabetes mellitus. Thus, mPEA15 transgenic pigs would serve as a promising model for diabetes translational research.

Data-Mining Approach on Transcriptomics and Methylomics Placental Analysis Highlights Genes in Fetal Growth Restriction

Intrauterine Growth Restriction (IUGR) affects 8% of newborns and increases morbidity and mortality for the offspring even during later stages of life. Single omics studies have evidenced epigenetic, genetic, and metabolic alterations in IUGR, but pathogenic mechanisms as a whole are not being fully understood. An in-depth strategy combining methylomics and transcriptomics analyses was performed on 36 placenta samples in a case-control study. Data-mining algorithms were used to combine the analysis of more than 1,200 genes found to be significantly expressed and/or methylated. We used an automated text-mining approach, using the bulk textual gene annotations of the discriminant genes. Machine learning models were then used to explore the phenotypic subgroups (premature birth, birth weight, and head circumference) associated with IUGR. Gene annotation clustering highlighted the alteration of cell signaling and proliferation, cytoskeleton and cellular structures, oxidative stress, protein turnover, muscle development, energy, and lipid metabolism with insulin resistance. Machine learning models showed a high capacity for predicting the sub-phenotypes associated with IUGR, allowing a better description of the IUGR pathophysiology as well as key genes involved.

PEA-15 C-Terminal Tail Allosterically Modulates Death-Effector Domain Conformation and Facilitates Protein-Protein Interactions

Phosphoprotein enriched in astrocytes, 15 kDa (PEA-15) exerts its regulatory roles on several critical cellular pathways through protein–protein interactions depending on its phosphorylation states. It can either inhibit the extracellular signal-regulated kinase (ERK) activities when it is dephosphorylated or block the assembly of death-inducing signaling complex (DISC) and the subsequent activation of apoptotic initiator, caspase-8, when it is phosphorylated. Due to the important roles of PEA-15 in regulating these pathways that lead to opposite cellular outcomes (cell proliferation vs. cell death), we proposed a phosphostasis (phosphorylation homeostasis) model, in which the phosphorylation states of the protein are vigorously controlled and regulated to maintain a delicate balance. The phosphostasis gives rise to the protective cellular functions of PEA-15 to preserve optimum cellular conditions. In this article, using advanced multidimensional nuclear magnetic resonance (NMR) techniques combined with a novel chemical shift (CS)-Rosetta algorithm for de novo protein structural determination, we report a novel conformation of PEA-15 death-effector domain (DED) upon interacting with ERK2. This new conformation is modulated by the irregularly structured C-terminal tail when it first recognizes and binds to ERK2 at the d-peptide recruitment site (DRS) in an allosteric manner, and is facilitated by the rearrangement of the surface electrostatic and hydrogen-bonding interactions on the DED. In this ERK2-bound conformation, three of the six helices (α2, α3, and α4) comprising the DED reorient substantially in comparison to the free-form structure, exposing key residues on the other three helices that directly interact with ERK2 at the DEF-docking site (docking site for ERK, FxF) and the activation loop. Additionally, we provide evidence that the phosphorylation of the C-terminal tail leads to a distinct conformation of DED, allowing efficient interactions with Fas-associated death domain (FADD) protein at the DISC. Our results substantiate the allosteric regulatory roles of the C-terminal tail in modulating DED conformation and facilitating protein–protein interactions of PEA-15.

Interfering PLD1-PED/PEA15 interaction using self-inhibitory peptides: An in silico study to discover novel therapeutic candidates against type 2 diabetes

Diabetes type 2 (T2D) is a very complex disorder with a large number of cases reported worldwide. There are several reported molecular targets which are being used towards drug design. In spite of extensive research efforts, there is no sure shot treatment available. One of the major reasons for this failure or restricted success in T2D research is the identification of a major/breakthrough therapeutic target responsible for the progression of T2D. It has been well documented that one of the major causes mediating the insulin resistance is the interaction of PLD1 with PED/PEA15. Herein, we have performed in silico experiments to investigate the interaction between PLD1 with PED/PEA15. Furthermore, this study has explored pertinent molecular interactions involving the self-derived peptides. The peptides identified in this study are found to be capable of restricting the interaction of these two proteins. Accordingly, the study suggests that the “self-derived peptides” could be used as promising therapeutic candidate(s) against T2D.

Targetting PED/PEA-15 for diabetes treatment

INTRODUCTION

PED/PEA-15 is an ubiquitously expressed protein, involved in the regulation of proliferation and apoptosis. It is commonly overexpressed in Type 2 Diabetes (T2D) and in different T2D-associated comorbidities, including cancer and certain neurodegenerative disorders. Areas covered: In mice, Ped/Pea-15 overexpression impairs glucose tolerance and, in combination with high fat diets, further promotes insulin resistance and T2D. It also controls β-cell mass, altering caspase-3 activation and the expression of pro- and antiapoptotic genes. These changes are mediated by PED/PEA-15-PLD1 binding. Overexpression of PLD1 D4 domain specifically blocks Ped/Pea-15-PLD1 interaction, reverting the effect of Ped/Pea-15 in vivo. D4α, a D4 N-terminal peptide, is able to displace Ped/Pea-15-PLD1 binding, but features greater stability in vivo compared to the entire D4 peptide. Here, we review early mechanistic studies on PED/PEA-15 relevance in apoptosis before focusing on its role in cancer and T2D. Finally, we describe potential therapeutic opportunities for T2D based on PED/PEA-15 targeting. Expert opinion: T2D is a major problem for public health and economy. Thus, the identification of new molecules with pharmacological activity for T2D represents an urgent need. Further studies with D4α will help to identify smaller pharmacologically active peptides and innovative molecules of potential pharmacological interest for T2D treatment.

Comparison between fibroblast wound healing and cell random migration assays in vitro

Cell migration plays a key role in many biological processes, including cancer growth and invasion, embryogenesis, angiogenesis, inflammatory response, and tissue repair. In this work, we compare two well-established experimental approaches for the investigation of cell motility in vitro: the cell random migration (CRM) and the wound healing (WH) assay. In the former, extensive tracking of individual live cells trajectories by time-lapse microscopy and elaborate data processing are used to calculate two intrinsic motility parameters of the cell population under investigation, i.e. the diffusion coefficient and the persistence time. In the WH assay, a scratch is made in a confluent cell monolayer and the closure time of the exposed area is taken as an easy-to-measure, empirical estimate of cell migration. To compare WH and CRM we applied the two assays to investigate the motility of skin fibroblasts isolated from wild type and transgenic mice (TgPED) overexpressing the protein PED/PEA-15, which is highly expressed in patients with type 2 diabetes. Our main result is that the cell motility parameters derived from CRM can be also estimated from a time-resolved analysis of the WH assay, thus showing that the latter is also amenable to a quantitative analysis for the characterization of cell migration. To our knowledge this is the first quantitative comparison of these two widely used techniques.

Parkinson-like phenotype in insulin-resistant PED/PEA-15 transgenic mice

Neurological abnormalities, such as Parkinson-like disorders (PlD), are often co-morbidities of Type 2 Diabetic (T2D) patients, although the epidemiological link between these two disorders remains controversial. The PED/PEA-15 protein represents a possible candidate linking T2D and PD, because it is increased in subjects with T2D and is highly expressed in the brain. To test this hypothesis, we have analyzed the neurological and neurochemical phenotype of transgenic mice overexpressing PED/PEA-15 (tgPED). These mice develop impaired glucose tolerance and insulin resistance, accompanied by neurological features resembling PlD: feet clasping, slow and delayed locomotor movements in different behavioral tests in absence of clear cognitive deficits, ataxia or anxiety. Morphological analysis of the brains showed selective modifications of metabolic activity in the striatal region. In the same region, we have observed 26% decrease of dopamine fibers, confirmed by immunohistochemistry and Western Blot for tyrosine hydroxylase. Moreover, they also showed 48% reduction of dopamine levels in the striatum. Thus the tgPED mice may represent a genetic animal model of neurological disease linked to T2D.

On the Quest of Cellular Functions of PEA-15 and the Therapeutic Opportunities

Phosphoprotein enriched in astrocytes, 15 KDa (PEA-15), a ubiquitously expressed small protein in all mammals, is known for decades for its potent interactions with various protein partners along distinct biological pathways. Most notable interacting partners of PEA-15 include extracellular signal-regulated kinase 1 and 2 (ERK1/2) in the mitogen activated protein kinase (MAPK) pathway, the Fas-associated death domain (FADD) protein involving in the formation of the death-inducing signaling complex (DISC), and the phospholipase D1 (PLD1) affecting the insulin sensitivity. However, the actual cellular functions of PEA-15 are still mysterious, and the question why this protein is expressed in almost all cell and tissue types remains unanswered. Here we synthesize the most recent structural, biological, and clinical studies on PEA-15 with emphases on its anti-apoptotic, anti-proliferative, and anti-inflammative properties, and propose a converged protective role of PEA-15 that maintains the balance of death and survival in different cell types. Under conditions that this delicate balance is unsustainable, PEA-15 may become pathological and lead to various diseases, including cancers and diabetes. Targeting PEA-15 interactions, or the use of PEA-15 protein as therapeutics, may provide a wider window of opportunities to treat these diseases.

Phosphoprotein enriched in astrocytes (PEA)-15: a potential therapeutic target in multiple disease states

Phosphoprotein enriched in astrocytes-15 (PEA-15) is a cytoplasmic protein that sits at an important junction in intracellular signalling and can regulate diverse cellular processes, such as proliferation and apoptosis, dependent upon stimulation. Regulation of these processes occurs by virtue of the unique interaction of PEA-15 with other signalling proteins. PEA-15 acts as a cytoplasmic tether for the mitogen-activated protein kinases, extracellular signal-regulated kinase 1/2 (ERK1/2) preventing nuclear localisation. In order to release ERK1/2, PEA-15 requires to be phosphorylated via several potential pathways. PEA-15 (and its phosphorylation state) therefore regulates many ERK1/2-dependent processes, including proliferation, via regulating ERK1/2 nuclear translocation. In addition, PEA-15 contains a death effector domain (DED) which allows interaction with other DED-containing proteins. PEA-15 can bind the DED-containing apoptotic adaptor molecule, Fas-associated death domain protein (FADD) which is also dependent on the phosphorylation status of PEA-15. PEA-15 binding of FADD can inhibit apoptosis as bound FADD cannot participate in the assembly of apoptotic signalling complexes. Through these protein–protein interactions, PEA-15-regulated cellular effects have now been investigated in a number of disease-related studies. Changes in PEA-15 expression and regulation have been observed in diabetes mellitus, cancer, neurological disorders and the cardiovascular system. These changes have been suggested to contribute to the pathology related to each of these disease states. As such, new therapeutic targets based around PEA-15 and its associated interactions are now being uncovered and could provide novel avenues for treatment strategies in multiple diseases.

Bisphenol-A impairs insulin action and up-regulates inflammatory pathways in human subcutaneous adipocytes and 3T3-L1 cells

Current evidence indicates that chemical pollutants may interfere with the homeostatic control of nutrient metabolism, thereby contributing to the increased prevalence of metabolic disorders. Bisphenol-A (BPA) is a lipophilic compound contained in plastic which is considered a candidate for impairing energy and glucose metabolism. We have investigated the impact of low doses of BPA on adipocyte metabolic functions. Human adipocytes derived from subcutaneous adipose tissue and differentiated 3T3-L1 cells were incubated with BPA, in order to evaluate the effect on glucose utilization, insulin sensitivity and cytokine secretion. Treatment with 1nM BPA significantly inhibited insulin-stimulated glucose utilization, without grossly interfering with adipocyte differentiation. Accordingly, mRNA levels of the adipogenic markers PPARγ and GLUT4 were unchanged upon BPA exposure. BPA treatment also impaired insulin-activated receptor phosphorylation and signaling. Moreover, adipocyte incubation with BPA was accompanied by increased release of IL-6 and IFN-γ, as assessed by multiplex ELISA assays, and by activation of JNK, STAT3 and NFkB pathways. Treatment of the cells with the JNK inhibitor SP600125 almost fully reverted BPA effect on insulin signaling and glucose utilization. In conclusion, low doses of BPA interfere with inflammatory/insulin signaling pathways, leading to impairment of adipose cell function.

Molecular basis of the PED/PEA15 interaction with the C-terminal fragment of phospholipase D1 revealed by NMR spectroscopy

PED/PEA15 is a small protein involved in many protein-protein interactions that modulates the function of a number of key cellular effectors involved in major cell functions, including apoptosis, proliferation and glucose metabolism. In particular, PED/PEA15 interacts with the phospholipase D (PLD) isoforms 1 and 2 increasing protein kinase C-α isoform activity and affects both insulin-stimulated glucose transport and glucose-stimulated insulin secretion. The C-terminal portion (residues 712-1074) of PLD1, named D4, is still able to interact with PED/PEA15. In this study we characterized, by means of NMR spectroscopy, the molecular interaction of PED/PEA15 with D4α, a smaller region of D4, encompassing residues 712-818, shown to have the same affinity for PED/PEA15 and to induce the same effects as D4 in PED/PEA15-overexpressing cells. Chemical shift perturbation (CSP) studies allowed to define D4α binding site of PED/PEA15 and to identify a smaller region likely affected by an allosteric effect. Moreover, ELISA-like experiments showed that three 20-mer overlapping synthetic peptides, covering the 762-801 region of D4α, strongly inhibit PED/PEA15-D4α interaction through their binding to PED/PEA15 with KDs in low micromolar range. Finally, molecular details of the interaction of PED/PEA15 with one of the three peptides have been revealed by CSP and saturation transfer difference (STD) analyses.

Adenoviral gene transfer of PLD1-D4 enhances insulin sensitivity in mice by disrupting phospholipase D1 interaction with PED/PEA-15

Over-expression of phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes (PED/PEA-15) causes insulin resistance by interacting with the D4 domain of phospholipase D1 (PLD1). Indeed, the disruption of this association restores insulin sensitivity in cultured cells over-expressing PED/PEA-15. Whether the displacement of PLD1 from PED/PEA-15 improves insulin sensitivity in vivo has not been explored yet. In this work we show that treatment with a recombinant adenoviral vector containing the human D4 cDNA (Ad-D4) restores normal glucose homeostasis in transgenic mice overexpressing PED/PEA-15 (Tg _ped/pea-15) by improving both insulin sensitivity and secretion. In skeletal muscle of these mice, D4 over-expression inhibited PED/PEA-15-PLD1 interaction, decreased Protein Kinase C alpha activation and restored insulin induced Protein Kinase C zeta activation, leading to amelioration of insulin-dependent glucose uptake. Interestingly, Ad-D4 administration improved insulin sensitivity also in high-fat diet treated obese C57Bl/6 mice. We conclude that PED/PEA-15-PLD1 interaction may represent a novel target for interventions aiming at improving glucose tolerance.

The impact of a family history of type 2 diabetes on insulin secretion and insulin sensitivity in individuals with varying glucose tolerance

INTRODUCTION

This study was performed to investigate the impact of a family history of type 2 diabetes (T2DM) on insulin resistance and beta-cell dysfunction in populations with varying glucose tolerance.

METHODS

Among the total of 142 participants, 73 subjects with no family history of T2DM (FH-) included 42 with normal glucose tolerance (NGT/FH-) and 31 with impaired glucose tolerance (IGT/FH-); and 69 first-degree relatives of patients with T2DM (FH+) included 36 with NGT (NGT/FH+) and 33 with IGT (IGT/FH+). Insulin resistance was evaluated by Insulin Sensitivity Index (ISI) based on the euglycemic hyperinsulinemic clamp. Islet beta-cell function was assessed by disposition index (DI) for the acute insulin response to glucose (AIRg) using intravenous glucose tolerance test. Metabolic data were compared between groups after adjustment for age, sex, body mass index and waist-to-hip ratio.

RESULTS

The NGT/FH+ group showed lower level of ISI (P = 0.023) than the NGT/FH- group, whereas no difference was found in AIRg or DI between these 2 subgroups. In the FH- individuals, both ISI and DI of the IGT/FH- group decreased compared with the NGT/FH- group (both P < 0.05). In the FH+ individuals, no difference was found in ISI between the IGT/FH+ and NGT/FH+ groups, whereas the IGT/FH+ group had a lower level of AIRg and DI than the NGT/FH+ group (both P < 0.0001).

CONCLUSIONS

This study showed that the pathophysiological changes were different between individuals with and without a family history of T2DM during the glucose tolerance aggravation.

Peroxisome proliferator-activated receptor-γ activation enhances insulin-stimulated glucose disposal by reducing ped/pea-15 gene expression in skeletal muscle cells: evidence for involvement of activator protein-1

The gene network responsible for inflammation-induced insulin resistance remains enigmatic. In this study, we show that, in L6 cells, rosiglitazone- as well as pioglitazone-dependent activation of peroxisome proliferator-activated receptor-γ (PPARγ) represses transcription of the ped/pea-15 gene, whose increased activity impairs glucose tolerance in mice and humans. Rosiglitazone enhanced insulin-induced glucose uptake in L6 cells expressing the endogenous ped/pea-15 gene but not in cells expressing ped/pea-15 under the control of an exogenous promoter. The ability of PPARγ to affect ped/pea-15 expression was also lost in cells and in C57BL/6J transgenic mice expressing ped/pea-15 under the control of an exogenous promoter, suggesting that ped/pea-15 repression may contribute to rosiglitazone action on glucose disposal. Indeed, high fat diet mice showed insulin resistance and increased ped/pea-15 levels, although these effects were reduced by rosiglitazone treatment. Both supershift and ChIP assays revealed the presence of the AP-1 component c-JUN at the PED/PEA-15 promoter upon 12-O-tetradecanoylphorbol-13-acetate stimulation of the cells. In these experiments, rosiglitazone treatment reduced c-JUN presence at the PED/PEA-15 promoter. This effect was not associated with a decrease in c-JUN expression. In addition, c-jun silencing in L6 cells lowered ped/pea-15 expression and caused nonresponsiveness to rosiglitazone, although c-jun overexpression enhanced the binding to the ped/pea-15 promoter and blocked the rosiglitazone effect. These results indicate that PPARγ regulates ped/pea-15 transcription by inhibiting c-JUN binding at the ped/pea-15 promoter. Thus, ped/pea-15 is downstream of a major PPARγ-regulated inflammatory network. Repression of ped/pea-15 transcription might contribute to the PPARγ regulation of muscle sensitivity to insulin.

PED/PEA-15 controls fibroblast motility and wound closure by ERK1/2-dependent mechanisms

Cell migration is dependent on the control of signaling events that play significant roles in creating contractile force and in contributing to wound closure. We evaluated wound closure in fibroblasts from mice overexpressing (TgPED) or lacking ped/pea-15 (KO), a gene overexpressed in patients with type 2 diabetes. Cultured skin fibroblasts isolated from TgPED mice showed a significant reduction in the ability to recolonize wounded area during scratch assay, compared to control fibroblasts. This difference was observed both in the absence and in the presence of mytomicin C, an inhibitor of mitosis. In time-lapse experiments, TgPED fibroblasts displayed about twofold lower velocity and diffusion coefficient, as compared to controls. These changes were accompanied by reduced spreading and decreased formation of stress fibers and focal adhesion plaques. At the molecular level, TgPED fibroblasts displayed decreased RhoA activation and increased abundance of phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2). Inhibition of ERK1/2 activity by PD98059 restored RhoA activation, cytoskeleton organization and cell motility, and almost completely rescued wound closure of TgPED fibroblasts. Interestingly, skin fibroblasts isolated from KO mice displayed an increased wound closure ability. In vivo, healing of dorsal wounds was delayed in TgPED and accelerated in KO mice. Thus, PED/PEA-15 may affect fibroblast motility by a mechanism, at least in part, mediated by ERK1/2. J. Cell. Physiol. 227: 2106–2116, 2012. © 2011 Wiley Periodicals, Inc.

Clozapine impairs insulin action by up-regulating Akt phosphorylation and Ped/Pea-15 protein abundance

Clinical and experimental evidence indicates that atypical antipsychotics impair glucose metabolism. We investigated whether clozapine may directly affect insulin action by analyzing insulin signaling in vitro and in vivo. Clozapine reduced insulin-stimulated glucose uptake in PC12 and in L6 cells, representative models of neuron and skeletal muscle, respectively. Consistently, clozapine reduced insulin effect on insulin receptor (IR) by 40% and on IR substrate-1 (IRS1) tyrosine phosphorylation by 60%. Insulin-stimulated Akt phosphorylation was also reduced by about 40%. Moreover, insulin-dependent phosphorylation of protein kinase C-ζ (PKC-ζ) was completely blunted in clozapine-treated cells. Interestingly, clozapine treatment was accompanied by an insulin-independent increase of Akt phosphorylation, with no change of IR, IRS1, and PKC-ζ basal phosphorylation. The cellular abundance of Ped/Pea-15, an Akt substrate and inducer of insulin resistance, was also increased following clozapine exposure, both in the absence and in the presence of cyclohexymide, a protein synthesis inhibitor. Similar as in cellular models, in the caudate-putamen and in the tibialis muscle of clozapine-treated C57/BL/KsJ mice, Akt phosphorylation and Ped/Pea-15 protein levels were increased and PKC-ζ phosphorylation was decreased. Thus, in these experimental models, clozapine deranged Akt function and up-regulated Ped/Pea-15, thereby inhibiting insulin stimulation of PKC-ζ and of glucose uptake.

PED/PEA-15 induces autophagy and mediates TGF-beta1 effect on muscle cell differentiation

TGF-beta1 has been shown to induce autophagy in certain cells but whether and how this action is exerted in muscle and whether this activity relates to TGF-beta1 control of muscle cell differentiation remains unknown. Here, we show that expression of the autophagy-promoting protein phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes (PED/PEA-15) progressively declines during L6 and C2C12 skeletal muscle cell differentiation. PED/PEA-15 underwent rapid induction upon TGF-beta1 exposure of L6 and C2C12 myoblasts, accompanied by impaired differentiation into mature myotubes. TGF-beta1 also induced autophagy in the L6 and C2C12 cells through a PP2A/FoxO1-mediated mechanism. Both the TGF-beta1 effect on differentiation and that on autophagy were blocked by specific PED/PEA-15 ShRNAs. Myoblasts stably overexpressing PED/PEA-15 did not differentiate and showed markedly enhanced autophagy. In these same cells, the autophagy inhibitor 3-methyladenine rescued TGF-beta1 effect on both autophagy and myogenesis, indicating that PED/PEA-15 mediates TGF-beta1 effects in muscle. Muscles from transgenic mice overexpressing PED/PEA-15 featured a significant number of atrophic fibers, accompanied by increased light chain 3 (LC3)II to LC3I ratio and reduced PP2A/FoxO1 phosphorylation. Interestingly, these mice showed significantly impaired locomotor activity compared with their non-transgenic littermates. TGF-beta1 causes transcriptional upregulation of the autophagy-promoting gene PED/PEA-15, which in turn is capable to induce atrophic responses in skeletal muscle in vivo.

Serum 25-Hydroxyvitamin D Levels, phosphoprotein enriched in diabetes gene product (PED/PEA-15) and leptin-to-adiponectin ratio in women with PCOS

Background

Polycystic ovary syndrome (PCOS) is frequently associated with hypovitaminosis D. Vitamin D is endowed with pleiotropic effects, including insulin resistance (IR) and apoptotic pathway. Disruption of the complex mechanism that regulated ovarian apoptosis has been reported in PCOS. Phosphoprotein enriched in diabetes gene product (PED/PEA-15), an anti-apoptotic protein involved in type 2 diabetes mellitus (T2DM), is overexpressed in PCOS women, independently of obesity. Leptin-to-adiponectin ratio (L/A) is a biomarker of IR and low-grade inflammation in PCOS. The aim of the study was to investigate the levels of 25-hydroxy vitamin D (25(OH)D), and L/A, in association with PED/PEA-15 protein abundance, in both lean and overweight/obese (o/o) women with PCOS.

Patients and Methods

PED/PEA-15 protein abundance and circulating levels of 25(OH)D, L/A, sex hormone-binding globulin, and testosterone were evaluated in 90 untreated PCOS patients (25 ± 4 yrs; range 18-34) and 40 healthy controls age and BMI comparable, from the same geographical area. FAI (free androgen index) and the homeostasis model assessment of insulin resistance (HoMA-IR) index were calculated.

Results

In o/o PCOS, 25(OH)D levels were significantly lower, and L/A values were significantly higher than in lean PCOS (p < 0.001), while there were no differences in PED/PEA-15 protein abundance. An inverse correlation was observed between 25(OH)D and BMI, PED/PEA-15 protein abundance, insulin, HoMA-IR, FAI (p < 0.001), and L/A (p < 0.05). At the multivariate analysis, in o/o PCOS L/A, insulin and 25(OH)D were the major determinant of PED/PEA-15 protein abundance (β = 0.45, β = 0.41, and β = -0.25, respectively).

Conclusions

Lower 25(OH)D and higher L/A were associated to PED/PEA-15 protein abundance in PCOS, suggesting their involvement in the ovarian imbalance between pro-and anti-apoptotic mechanisms, with high L/A and insulin and low 25(OH)D levels as the main determinants of PED/PEA-15 protein variability. Further studies, involving also different apoptotic pathways or inflammatory cytokines and granulosa cells are mandatory to better define the possible bidirectional relationships between 25(OH)D, PED/PEA-15 protein abundance, leptin and adiponectin in PCOS pathogenesis.

Phosphoprotein enriched in diabetes gene product (Ped/pea-15) is increased in omental adipose tissue of women with the polycystic ovary syndrome: ex vivo regulation of ped/pea-15 by glucose, insulin and metformin

Polycystic ovary syndrome (PCOS), the commonest endocrine disorder in women, is characterized by an altered steroid milieu and is associated with insulin resistance and type 2 diabetes mellitus (T2DM). Phosphoprotein enriched in diabetes gene product (Ped/pea-15) regulates glucose metabolism and is increased in T2DM. Our novel data indicate that Ped/pea-15 mRNA expression and protein levels are significantly increased in omental adipose tissue (AT) from PCOS women compared to matched controls (p < 0.01); Ped/pea-15 levels in subcutaneous AT were not significantly different. Furthermore, Ped/pea-15 mRNA expression and protein levels were higher in omental compared to subcutaneous AT in PCOS subjects (p < 0.01); however, in control subjects, this was not significant. Glucose was predictive of omental AT Ped/pea-15 mRNA expression (p = 0.045). Importantly, glucose and insulin increased whereas metformin significantly decreased Ped/pea-15 levels in human omental AT explants. Our findings should serve to promote further research on Ped/pea-15 biology.

NMR backbone dynamics studies of human PED/PEA-15 outline protein functional sites

PED/PEA-15 (phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes) is a ubiquitously expressed protein and a key regulator of cell growth and glucose metabolism. PED/PEA-15 mediates both homotypic and heterotypic interactions and is constituted by an N-terminal canonical death effector domain and a C-terminal tail. In the present study, the backbone dynamics of PED/PEA-15 via (15)N R(1) and R(2) and steady-state [(1)H]-(15)N NOE measurements is reported. The dynamic parameters were analyzed using both Lipari-Szabo model-free formalism and a reduced spectral density mapping approach. The results obtained define a polar and charged surface of the death effector domain characterized by internal motions in the micro- to millisecond timescale, which is crucial for the multiple heterotypic functional protein-protein interactions in which PED/PEA-15 is involved. The present study contributes to a better understanding of the molecular basis of the PED/PEA-15 functional interactions and provides a more detailed surface for the design and development of PED/PEA-15 binders.

Residues 762-801 of PLD1 mediate the interaction with PED/PEA15

The interaction of Phospholipase D1 (PLD1) by its C-terminal domain D4 with PED/PEA15 has been indicated as a target for type 2 diabetes. PED/PEA15 is overexpressed in several tissues of individuals affected by type 2 diabetes and its overexpression in intact cells and in transgenic animal models impairs insulin regulation of glucose transport by a mechanism mediated by the interaction with D4 and the consequent increase of protein kinase C-alpha activity. Expression of D4 or administration of a peptide mimicking the PED/PEA15 region involved in this interaction to cells stably overexpressing PED/PEA15 reduces its interaction with PLD1, thereby lowering PKC-alpha activation and restoring normal glucose transport mediated by PKC-zeta. By using D4 deletion mutants, we have restricted the PLD1 region involved in PED/PEA15 interaction to an N-terminal fragment named D4alpha (residues 712-818). This region binds PED/PEA15 with the same efficacy as D4 (K(D) approximately 0.7 microM) and, when transfected in different PED/PEA15-overexpressing cells, it is able to reduce PKC-alpha activity and to restore the sensitivity of PKC-zeta to insulin stimulation, independently of the PI3K/Akt signalling. We also show that the effective disruption of the PED/PEA15-PLD1 interaction can restore the normal ERK1/2 signalling. Finally, using a set of overlapping peptides that cover the D4alpha region, we have further restricted the shortest PED/PEA15-binding site to a segment encompassing residues 762-801, suggesting that a quite limited binding interface mostly contributes to the interaction and can thus be a selective target for the design of effective antagonists.

Preliminary data on effects of metformin on PED/PEA-15 cellular levels in obese women with polycystic ovary syndrome

BACKGROUND

The cellular abundance of the phosphoprotein enriched in diabetes (PED/PEA-15), a 15 kDa protein related to insulin resistance (IR), is increased in women with polycystic ovary syndrome (PCOS).

AIM

To investigate whether metformin (MET) has additive effects on PED/PEA-15 protein levels.

MATERIAL/SUBJECTS AND METHODS

This is an open label, prospective clinical study over 6 months. Ten hyperandrogenic obese PCOS women [age: 24.6+/-1.6 yr; body mass index (BMI): 30.7+/-1.2 kg/m(2)] were treated with MET (1250 mg/day). Ten age- and BMI-matched normo-androgenic women were used as controls. Outcome measures are: PED/PEA-15 protein levels, fasting plasma glucose and insulin (FPI), reciprocal index of homeostasis model assessment of insulin resistance (1/HOMA-IR); quantitative insulin sensitivity check index (QUICKI); wholebody insulin sensitivity index (ISI); SHBG; total testosterone; free androgen index (FAI).

RESULTS

At baseline FPI and PED/PEA- 15 protein levels were higher, while 1/HOMA-IR, QUICKI, and ISI were lower (p<0.001) in MET group than in controls. After treatment, independently of body weight and hyperandrogenism, FPI, and PED/PEA-15 protein levels decreased (p=0.001 and 0.004, respectively), while, 1/HOMA-IR, QUICKI, and ISI increased (p<0.001). PED/PEA-15 protein levels correlated significantly with ISI either before (r=0.636; p=0.048), and after treatment (r=0.758; p=0.011).

CONCLUSIONS

PED/PEA-15 protein levels reduced after a short course of treatment with MET in a group hyperandrogenic obese PCOS women. This effect was independent of body weight and hyperandrogenism, and correlated with ISI, thus adding a further benefit to obese PCOS women.

Effect of physical training on insulin secretion and action in skeletal muscle and adipose tissue of first-degree relatives of type 2 diabetic patients

Physical training affects insulin secretion and action, but there is a paucity of data on the direct effects in skeletal muscle and adipose tissue and on the effect of training in first-degree relatives (FDR) of patients with type 2 diabetes. We studied insulin action at the whole body level and peripherally in skeletal muscle and adipose tissue as well as insulin-secretory capacity in seven FDR and eight control (CON) subjects before and after 12 wk of endurance training. Training improved physical fitness. Insulin-mediated glucose uptake (GU) increased (whole body and leg; P < 0.05) after training in CON but not in FDR, whereas glucose-mediated GU increased (P < 0.05) in both groups. Adipose tissue GU was not affected by training, but it was higher (abdominal, P < 0.05; femoral, P = 0.09) in FDR compared with CON. Training increased skeletal muscle lipolysis (P < 0.05), and it was markedly higher (P < 0.05) in subcutaneous abdominal than in femoral adipose tissue and quadriceps muscle with no difference between FDR and CON. Glucose-stimulated insulin secretion was lower in FDR compared with CON, but no effect of training was seen. Glucagon-like peptide-1 stimulated insulin secretion five- to sevenfold. We conclude that insulin-secretory capacity is lower in FDR than in CON and that there is dissociation between training-induced changes in insulin secretion and insulin-mediated GU. Maximal GU rates are similar between groups and increases with physical training.

Hepatocyte nuclear factor (HNF)-4alpha-driven epigenetic silencing of the human PED gene

AIMS/HYPOTHESIS

Overexpression of PED (also known as PEA15) determines insulin resistance and impaired insulin secretion and may contribute to progression toward type 2 diabetes. Recently, we found that the transcription factor hepatocyte nuclear factor (HNF)-4alpha binds to PED promoter and represses its transcription. However, the molecular details responsible for regulation of PED gene remain unclear.

METHODS

Here we used gain and loss of function approaches to investigate the hypothesis that HNF-4alpha controls chromatin remodelling at the PED promoter in human cell lines.

RESULTS

HNF-4alpha production and binding induce chromatin remodelling at the -250 to 50 region of PED, indicating that remodelling is limited to two nucleosomes located at the proximal promoter. Chromatin immunoprecipitation assays also revealed concomitant HNF-4alpha-induced deacetylation of histone H3 at Lys9 and Lys14, and increased dimethylation of histone H3 at Lys9. The latter was followed by reduction of histone H3 Lys4 dimethylation. HNF-4alpha was also shown to target the histone deacetylase complex associated with silencing mediator of retinoic acid and thyroid hormone receptor, both at the PED promoter, and at GRB14 and USP21 regulatory regions, leading to a reduction of mRNA levels. Moreover, HNF-4alpha silencing and PED overexpression were accompanied by a significant reduction of hepatic glycogen content.

CONCLUSIONS/INTERPRETATION

These results show that HNF-4alpha serves as a scaffold protein for histone deacetylase activities, thereby inhibiting liver expression of genes including PED. Dysregulation of these mechanisms may lead to upregulation of the PED gene in type 2 diabetes.

Overproduction of phosphoprotein enriched in diabetes (PED) induces mesangial expansion and upregulates protein kinase C-beta activity and TGF-beta1 expression

AIMS/HYPOTHESIS

Overproduction of phosphoprotein enriched in diabetes (PED, also known as phosphoprotein enriched in astrocytes-15 [PEA-15]) is a common feature of type 2 diabetes and impairs insulin action in cultured cells and in mice. Nevertheless, the potential role of PED in diabetic complications is still unknown.

METHODS

We studied the effect of PED overproduction and depletion on kidney function in animal and cellular models.

RESULTS

Transgenic mice overexpressing PED (PEDTg) featured age-dependent increases of plasma creatinine levels and urinary volume, accompanied by expansion of the mesangial area, compared with wild-type littermates. Serum and kidney levels of TGF-beta1 were also higher in 6- and 9-month-old PEDTg. Overexpression of PED in human kidney 2 cells significantly increased TGF-beta1 levels, SMAD family members (SMAD)2/3 phosphorylation and fibronectin production. Opposite results were obtained following genetic silencing of PED in human kidney 2 cells by antisense oligonucleotides. Inhibition of phospholipase D and protein kinase C-beta by 2-butanol and LY373196 respectively reduced TGF-beta1, SMAD2/3 phosphorylation and fibronectin production. Moreover, inhibition of TGF-beta1 receptor activity and SMAD2/3 production by SB431542 and antisense oligonucleotides respectively reduced fibronectin secretion by about 50%. TGF-beta1 circulating levels were significantly reduced in Ped knockout mice and positively correlated with PED content in peripheral blood leucocytes of type 2 diabetic patients.

CONCLUSIONS/INTERPRETATION

These data indicate that PED regulates fibronectin production via phospholipase D/protein kinase C-beta and TGF-beta1/SMAD pathways in kidney cells. Raised PED levels may therefore contribute to the abnormal accumulation of extracellular matrix and renal dysfunction in diabetes.

Frontiers: PED/PEA-15, a multifunctional protein controlling cell survival and glucose metabolism

PED/PEA-15 is a 15-kDa ubiquitously expressed protein implicated in a number of fundamental cellular functions, including apoptosis, proliferation, and glucose metabolism. PED/PEA-15 lacks enzymatic function and serves mainly as a molecular adaptor. PED/PEA-15 is an endogenous substrate for protein kinase C (PKC), calcium/calmodulin-dependent protein kinase II (CAM kinase II), and Akt. In particular, PKC phosphorylates PED/PEA-15 at Ser(104) and CAM kinase II or Akt at Ser(116), modifying its stability. Evidence obtained over the past 10 years has indicated that PED/PEA-15 regulates cell survival by interfering with both intrinsic and extrinsic apoptotic pathways. In addition, it may also control cell proliferation by interfering with ERK1/2-mediated pathways. Indeed, PED/PEA-15 has been identified as an ERK1/2 interactor, which modifies its subcellular localization and targeting to a specific subset of substrates. Increased PED/PEA-15 levels may affect tumorigenesis and cancer progression as well as sensitivity to anticancer agents. Moreover, PED/PEA-15 affects astrocyte motility and increases susceptibility to skin carcinogenesis in vivo. PED/PEA-15 expression is regulated at the transcriptional and the posttranslational levels. Increased PED/PEA-15 expression has been identified in individuals with type 2 diabetes early during the natural history of the disease. Evidence generated over the past 10 years indicated that this defect contributes to altering glucose tolerance by impairing insulin action and insulin secretion and might play a role in the development of diabetes-associated neurological disorders. Strategies are being devised to target key signaling events in PED/PEA-15 action aimed at improving glucose tolerance and at facilitating cancer cell death.

Gene expression profile of the bone microenvironment in human fragility fracture bone

Osteoporosis (OP) is a common age-related systemic skeletal disease, with a strong genetic component, characterised by loss of bone mass and strength, which leads to increased bone fragility and susceptibility to fracture. Although some progress has been made in identifying genes that may contribute to OP disease, much of the genetic component of OP has yet to be accounted for. Therefore, to investigate the molecular basis for the changes in bone causally involved in OP and fragility fracture, we have used a microarray approach. We have analysed altered gene expression in human OP fracture bone by comparing mRNA in bone from individuals with fracture of the neck of the proximal femur (OP) with that from age-matched individuals with osteoarthritis (OA), and control (CTL) individuals with no known bone pathology. The OA sample set was included because an inverse association, with respect to bone density, has been reported between OA and the OP individuals. Compugen H19K oligo human microarray slides were used to compare the gene expression profiles of three sets of female samples comprising, 10 OP-CTL, 10 OP-OA, and 10 OA-CTL sample pairs. Using linear models for microarray analysis (Limma), 150 differentially expressed genes in OP bone with t scores >5 were identified. Differential expression of 32 genes in OP bone was confirmed by real time PCR analysis (p<0.01). Many of the genes identified have known or suspected roles in bone metabolism and in some cases have been implicated previously in OP pathogenesis. Three major sets of differentially expressed genes in OP bone were identified with known or suspected roles in either osteoblast maturation (PRRX1, ANXA2, ST14, CTSB, SPARC, FST, LGALS1, SPP1, ADM, and COL4A1), myelomonocytic differentiation and osteoclastogenesis (TREM2, ANXA2, IL10, CD14, CCR1, ADAM9, CCL2, CTGF, and KLF10), or adipogenesis, lipid and/or glucose metabolism (IL10, MARCO, CD14, AEBP1, FST, CCL2, CTGF, SLC14A1, ANGPTL4, ADM, TAZ, PEA15, and DOK4). Altered expression of these genes and others in these groups is consistent with previously suggested underlying molecular mechanisms for OP that include altered osteoblast and osteoclast differentiation and function, and an imbalance between osteoblastogenesis and adipogenesis.

Molecular cloning and characterization of the human PED/PEA-15 gene promoter reveal antagonistic regulation by hepatocyte nuclear factor 4alpha and chicken ovalbumin upstream promoter transcription factor II

Overexpression of the ped/pea-15 gene in mice impairs glucose tolerance and leads to diabetes in conjunction with high fat diet treatment. PED/PEA-15 is also overexpressed in type 2 diabetics as well as in euglycemic offspring from these subjects. The cause(s) of this abnormality remains unclear. In the present work we have cloned and localized the promoter region of the human PED/PEA-15 gene within the first 230 bp of the 5(R)-flanking region. A cis-acting regulatory element located between -320 and -335 bps upstream the PED/PEA-15 gene transcriptional start site (+1) is recognized by both the hepatocyte nuclear factor 4alpha (HNF-4alpha) and the chicken ovalbumin upstream promoter transcription factor II (COUP-TFII), two members of the steroid/thyroid superfamily of transcription factors, both of which are involved in the control of lipid and glucose homeostasis. HNF-4alpha represses PED/PEA-15 expression in HeLa cells, whereas COUP-TFII activates its expression. In hepatocytes, the activation of PED/PEA-15 gene transcription is paralleled by the establishment of a partially dedifferentiated phenotype accompanied by a reduction in mRNA levels encoded by genes normally expressed during liver development. Cotransfection of HeLa cells with a reporter construct containing the PED/PEA-15 response element and various combinations of HNF-4alpha and COUP-TFII expression vectors indicated that COUP-TFII antagonizes the repression of the PED/PEA-15 gene by HNF-4alpha. Thus, at least in part, transcription of the PED/PEA-15 gene in vivo is dependent upon the intracellular balance of these positive and negative regulatory factors. Abnormalities in HNF-4alpha and COUP-TFII balance might have important consequences on glucose tolerance in humans.

Targeting of PED/PEA-15 molecular interaction with phospholipase D1 enhances insulin sensitivity in skeletal muscle cells

Phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes (PED/PEA-15) is overexpressed in several tissues of individuals affected by type 2 diabetes. In intact cells and in transgenic animal models, PED/PEA-15 overexpression impairs insulin regulation of glucose transport, and this is mediated by its interaction with the C-terminal D4 domain of phospholipase D1 (PLD1) and the consequent increase of protein kinase C-alpha activity. Here we show that interfering with the interaction of PED/PEA-15 with PLD1 in L6 skeletal muscle cells overexpressing PED/PEA-15 (L6(PED/PEA-15)) restores insulin sensitivity. Surface plasmon resonance and ELISA-like assays show that PED/PEA-15 binds in vitro the D4 domain with high affinity (K(D) = 0.37 +/- 0.13 mum), and a PED/PEA-15 peptide, spanning residues 1-24, PED-(1-24), is able to compete with the PED/PEA-15-D4 recognition. When loaded into L6(PED/PEA-15) cells and in myocytes derived from PED/PEA-15-overexpressing transgenic mice, PED-(1-24) abrogates the PED/PEA-15-PLD1 interaction and reduces protein kinase C-alpha activity to levels similar to controls. Importantly, the peptide restores insulin-stimulated glucose uptake by approximately 70%. Similar results are obtained by expression of D4 in L6(PED/PEA-15). All these findings suggest that disruption of the PED/PEA-15-PLD1 molecular interaction enhances insulin sensitivity in skeletal muscle cells and indicate that PED/PEA-15 as an important target for type 2 diabetes.

Overexpression of the phosphoprotein enriched in diabetes gene product (Ped/pea-15) in women with polycystic ovary syndrome

OBJECTIVE

To evaluate Ped/pea-15 (phosphoprotein enriched in diabetes) expression in polycystic ovary syndrome (PCOS) women.

DESIGN AND PATIENTS

Thirty PCOS women were studied and compared with other 30 age- and body mass index (BMI)-matched women, considered as the control group. Both patients and controls were divided according to BMI. All subjects underwent endocrine and metabolic investigation and Ped/pea-15 expression was evaluated by western blot analysis. Insulin resistance was assessed by HOMA model and insulin sensitivity index (ISI) composite.

RESULTS

Insulin resistance, evaluated by HOMA-R and ISI composite, was significantly higher in PCOS women and in obese controls than in normal weight controls. Ped/pea-15 expression (%) was higher in PCOS women than in controls (440.4 +/- 220.7 vs. 163.0 +/- 45.5; P < 0.001; range 145.5-987% and 97-281%, respectively), and was positively correlated with insulin, BMI, total testosterone, HOMA index, and family history (P < 0.001). In patients with PCOS univariate analysis of variance showed no effect of BMI variation (P = 0.13) on Ped/pea-15 expression levels. On multiple linear regression analysis, the major determinants of Ped/pea-15 overexpression were family history, insulin, and PCOS status independent of BMI.

CONCLUSION

These preliminary data (1) highlight the overexpression of Ped/pea-15 in PCOS compared to normal controls, independent of obesity; (2) suggest that Ped/pea-15 overexpression might be an early component of the metabolic syndrome in PCOS; and (3) support the hypothesis that Ped/pea-15 represents a possible useful tool to assess the presence of a genetic condition associated with insulin resistance in PCOS.

PED/PEA-15 regulates glucose-induced insulin secretion by restraining potassium channel expression in pancreatic beta-cells

The phosphoprotein enriched in diabetes/phosphoprotein enriched in astrocytes (ped/pea-15) gene is overexpressed in human diabetes and causes this abnormality in mice. Transgenic mice with beta-cell-specific overexpression of ped/pea-15 (beta-tg) exhibited decreased glucose tolerance but were not insulin resistant. However, they showed impaired insulin response to hyperglycemia. Islets from the beta-tg also exhibited little response to glucose. mRNAs encoding the Sur1 and Kir6.2 potassium channel subunits and their upstream regulator Foxa2 were specifically reduced in these islets. Overexpression of PED/PEA-15 inhibited the induction of the atypical protein kinase C (PKC)-zeta by glucose in mouse islets and in beta-cells of the MIN-6 and INS-1 lines. Rescue of PKC-zeta activity elicited recovery of the expression of the Sur1, Kir6.2, and Foxa2 genes and of glucose-induced insulin secretion in PED/PEA-15-overexpressing beta-cells. Islets from ped/pea-15-null mice exhibited a twofold increased activation of PKC-zeta by glucose; increased abundance of the Sur1, Kir6.2, and Foxa2 mRNAs; and enhanced glucose effect on insulin secretion. In conclusion, PED/PEA-15 is an endogenous regulator of glucose-induced insulin secretion, which restrains potassium channel expression in pancreatic beta-cells. Overexpression of PED/PEA-15 dysregulates beta-cell function and is sufficient to impair glucose tolerance in mice.