Tissue-specific and glucose-responsive expression of the pancreatic derived factor (PANDER) promoter

Increased pancreatic-derived factor (PANDER) levels in gestational diabetes mellitus

The aim of the study was to investigate the pancreatic-derived factor (PANDER) levels in healthy pregnant women and in pregnant women with gestational diabetes mellitus (GDM). A total of 50 women consecutively diagnosed with GDM and 30 randomly selected age-matched and gestational-age-matched healthy pregnant women were included in this cross-sectional study. Serum PANDER levels and other variables were analyzed. The age, the gestational age at the time, the blood sample was obtained and the hemoglobin A1c (HbA1c) levels of the GDM and control groups were similar. The body mass index (BMI), fasting blood glucose, insulin, homeostasis model assessment of insulin resistance (HOMA-IR), and serum PANDER levels were significantly higher in the GDM group than the control group. The optimal PANDER cutoff value was 227.2 ng/ml, and the ratios above this value were 100 and 86.6% for sensitivity and specificity, respectively (p=.0001). Serum PANDER levels were higher in women with GDM compared to the control group and were positively correlated with insulin, HOMA-IR, and HbA1c levels. These results suggest that PANDER might be considered a new biomarker for GDM.

Circulating PANDER concentration is associated with increased HbA1c and fasting blood glucose in Type 2 diabetic subjects

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PANcreatic-DERived factor (PANDER) is a novel hormone regulating glucose levels.

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Fasting PANDER levels were measured in T2D and non-T2D matched subjects from U.S.

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Associations between PANDER and other hormones or metabolic parameters were examined.

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PANDER was associated with increased HbA1c and fasting blood glucose in T2D subjects.

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PANDER was not associated with adiponectin, HOMA-β and HOMA-IR.

Aim

PANcreatic-DERived factor (PANDER, FAM3B) is a novel hormone that regulates glucose levels via interaction with both the endocrine pancreas and liver. Prior studies examining PANDER were primarily conducted in murine models or in vitro but little is known regarding the circulating concentration of PANDER in humans, especially with regard to the association of type 2 diabetes (T2D) or overall glycemic regulation. To address this limitation, we performed a cross-sectional analysis of circulating serum PANDER concentration in association with other hormones that serve as either markers of insulin resistance (insulin and adiponectin) or to metabolic parameters of glycemic control such as fasting HbA1c and blood glucose (FBG).

Methods

Fasting serum was obtained from a commercial biorepository from 300 de-identified adult subjects with 150 T2D and non-T2D adult subjects collected from a population within the United States, respectively, matched on gender, age group and race/ethnicity. Concentration of PANDER, insulin and adiponectin were measured for all samples as determined by commercial ELISA. Metadata was provided for each subject including demography, anthropometry, and cigarette and alcohol use. In addition, fasting blood glucose (FBG) and HbA1c were available on T2D subjects.

Results

Multiple linear regression analyses were performed to examine the relationships between circulating log PANDER concentration on HbA1c, fasting glucose, log insulin, log HOMA-β and log HOMA-IR among T2D subjects and for insulin and adiponectin in non-T2D subjects. A significant linear association was identified between PANDER with fasting HbA1c (β 0.832 ± SE 0.22, p = 0.0003) and FBG (β 20.66 ± SE 7.43, p = 0.006) within T2D subjects. However, insulin, HOMA-β, HOMA-IR and adiponectin (p > 0.05) were not found to be linearly associated with PANDER concentration.

Conclusion

Within T2D subjects, PANDER is modestly linearly associated with increased HbA1c and FBG in a US population. In addition, highest circulating PANDER levels were measured in T2D subjects with HbA1c above 9.9. No association was identified with PANDER and insulin resistance or pancreatic β-cell function in T2D subjects.

Pancreatic-derived factor impaired glucagon-like Peptide-1 production from GLUTag enterendorine L-cell line and intestines

PURPOSE

Pancreatic-derived factor (PANDER) is a pancreatic islet-specific cytokine that co-secretes with insulin. However, its biological function remains largely unknown. We have recently shown that the intestine might be its novel target tissue. The aim of this study was to clarify whether PANDER impacts the production of glucagon-like peptide-1 (GLP-1).

METHODS

We treated GLUTag cells from the mouse intestine L cell line with recombinant PANDER protein and hepatic overexpression of PANDER in an obese murine model.

RESULTS

In GLUTag cells, PANDER exposure led to decreased proglucagon gene mRNA expression and GLP-1 secretion without affecting cell viability or caspase-3 activation. Overexpression of PANDER in mice induced glucose intolerance and impaired glucose-stimulated GLP-1 secretion Moreover, PANDER blocked insulin-induced GLP-1 secretion by inhibiting the insulin signalling-Wnt pathway and directly inhibited the cAMP/PKA pathway.

CONCLUSIONS

Our findings indicate that intestinal L cells are responsive to PANDER, and elevated PANDER levels impair GLP-1 production in vitro and in vivo.

Sweet Sixteenth for ChREBP: Established Roles and Future Goals

With the identification of ChREBP in 2001, our interest in understanding the molecular control of carbohydrate sensing has surged. While ChREBP was initially studied as a master regulator of lipogenesis in liver and fat tissue, it is now clear that ChREBP functions as a central metabolic coordinator in a variety of cell types in response to environmental and hormonal signals, with wide implications in health and disease. Celebrating its sweet sixteenth birthday, we review here the current knowledge about the function and regulation of ChREBP throughout usual and less explored tissues, to recapitulate ChREBP's role as a whole-body glucose sensor.

FAM3B mediates high glucose-induced vascular smooth muscle cell proliferation and migration via inhibition of miR-322-5p

The proliferation and migration of vascular smooth muscle cells (VSMCs) play an essential role during the development of cardiovascular diseases (CVDs). While many factors potentially contribute to the abnormal activation of VSMCs, hyperglycemia is generally believed to be a major causative factor. On the other hand, FAM3B (named PANDER for its secretory form) is a uniquely structured protein strongly expressed within and secreted from the endocrine pancreas. FAM3B is co-secreted with insulin from the β-cell upon glucose stimulation and regulates glucose homeostasis. In the present study, we sought to determine the roles of FAM3B in the regulation of VSMC physiology, especially under the hyperglycemic condition. We found that FAM3B expression was induced by hyperglycemia both in vivo and in vitro. FAM3B knockdown inhibited, whereas FAM3B overexpression accelerated VSMC proliferation and migration. At the molecular level, FAM3B inhibited miR-322-5p expression, and enforced expression of miR-322-5p antagonized FAM3B-induced VSMC proliferation and migration, suggesting that FAM3B facilitated VSMC pathological activation via miR-322-5p. Taken together, FAM3B mediates high glucose-induced VSMC proliferation and migration via inhibition of miR-322-5p. Thus, FAM3B may therefore serve as a novel therapeutic target for diabetes-related CVDs.

Elevated circulating level of a cytokine, pancreatic-derived factor, is associated with metabolic syndrome components in a Chinese population

Aims/Introduction

Pancreatic‐derived factor (PANDER) is an important factor involved in obesity, glucose intolerance and abnormal lipid metabolism in animals. Nevertheless, the relationship between PANDER and metabolic syndrome (MetS) in humans has not yet been reported.

Materials and Methods

To determinate the relationship between PANDER and MetS components, 212 individuals aged between 40 and 65 years were recruited. Fasting plasma PANDER and other variables were measured. Correlations of plasma PANDER and other variables were carried out. Plasma PANDER level was compared in participants with no metabolic components and those with any metabolic components, as well as in normal glucose tolerance, impaired glucose tolerance and diabetes mellitus participants.

Results

In all the participants, there were 65 participants in the no metabolic components group and 147 participants in the any metabolic components group. Plasma PANDER level was increased with the number of MetS components (P < 0.05) and correlated with metabolic score (r = 0. 529, P < 0.001). In addition, plasma PANDER significantly correlated with fasting plasma glucose (r = 0.187, P = 0.046), 2‐h plasma glucose (r = 0.195, P = 0.035), homeostasis model assessment of β‐cell function (r = −0.191, P = 0.039), triglyceride (r = 0.305, P = 0.001) and high‐density lipoprotein cholesterol (r = −0.333, P < 0.001). Using multivariable logistic regression analysis, circulating PANDER was associated with an increased risk ratio of impaired glucose tolerance or diabetes mellitus (odds ratio 2.22, 95% confidence interval 1.15–4.42, P = 0.018) after adjustment of the other possible confounders.

Conclusions

Circulating level of PANDER in relation to the accumulation in MetS suggested that persons with elevated levels of PANDER were associated with an increased risk of metabolic syndrome.

Hepatic nutrient and hormonal regulation of the PANcreatic-DERived factor (PANDER) promoter

PANcreatic-DERived factor (PANDER, FAM3B) has been shown to regulate glycemic levels via interactions with both pancreatic islets and the liver. Although PANDER is predominantly expressed from the endocrine pancreas, recent work has provided sufficient evidence that the liver may also be an additional tissue source of PANDER production. At physiological levels, PANDER is capable of disrupting insulin signaling and promoting increased hepatic glucose production. As shown in some animal models, strong expression of PANDER, induced by viral delivery within the liver, induces hepatic steatosis. However, no studies to date have explicitly characterized the transcriptional regulation of PANDER from the liver. Therefore, our investigation elucidated the nutrient and hormonal regulation of the hepatic PANDER promoter. Initial RNA-ligated rapid amplification of cDNA ends identified a novel transcription start site (TSS) approximately 26 bp upstream of the PANDER translational start codon not previously revealed in pancreatic β-cell lines. Western evaluation of various murine tissues demonstrated robust expression in the liver and brain. Promoter analysis identified strong tissue-specific activity of the PANDER promoter in both human and murine liver-derived cell lines. The minimal element responsible for maximal promoter activity within hepatic cell lines was located between -293 and -3 of the identified TSS. PANDER promoter activity was inhibited by both insulin and palmitate, whereas glucose strongly increased expression. The minimal element was responsible for maximal glucose-responsive and basal activity. Co-transfection reporter assays, chromatin-immunoprecipitation (ChIP) and site-directed mutagenesis revealed that the carbohydrate-responsive element binding protein (ChREBP) increased PANDER promoter activity and interacted with the PANDER promoter. E-box 3 was shown to be critical for basal and glucose responsive expression. In summary, in-vitro and in-vivo glucose is a potent stimulator of the PANDER promoter within the liver and this response may be facilitated by ChREBP.

F3MB(PANDER) decreases mice hepatic triglyceride and is associated with decreased DGAT1 expression

OBJECTIVE

Pancreatic-derived factor (PANDER, also named as FAM3B) is secreted by pancreatic α and β cells. Increasing evidence suggests that it may serve a hormonal function related to glycemic and lipid metabolism. In this study, we investigated the effects of PANDER overexpression on hepatic and adipose triglyceride metabolism in high-fat diet-fed male C57BL/6 mice.

METHODS

PANDER overexpression was achieved by tail-vein injection of recombinant Ad-PANDER and Ad-GFP injected mice served as a control. The TG metabolism in both groups were compared.

RESULTS

Adenoviral-mediated overexpression of PANDER did not affect body weight, food consumption, or liver enzymes. The triglyceride (TG) content of both liver and adipose tissue was significantly decreased in Ad-PANDER mice (liver: 6.16±1.89 mg/g vs. control 14.95±2.27 mg/g, P<0.05; adipose: 39.31±1.99 mg/100mg vs. 47.22±2.21 mg/100mg, P<0.05). The free fatty acid (FFA) content of adipose tissue in Ad-PANDER mice was also decreased (1.38±0.18 mg/g vs. 2.77±0.31 mg/g, P<0.01). The investigation of key enzymes of triglyceride hydrolysis and FFA oxidation in liver and adipose tissue showed that p-HSL/HSL was significantly increased and that DGAT1 gene and protein expression were significantly reduced in the liver of PANDER-overexpressing mice. PKA phosphorylation was also significantly increased in the livers of Ad-PANDER mice. No differences in ATGL, CPT1, ACOX1, or DGAT2 expression were observed.

CONCLUSION

Overexpression of PANDER is associated with observable decreases in TG, increases in PKA phosphorylation, and decreased DGAT1 expression, suggesting a possible interrelationship. The mechanisms by which this occurs remain to be elucidated.

Enhanced glucose tolerance in pancreatic-derived factor (PANDER) knockout C57BL/6 mice

Pancreatic-derived factor (PANDER; also known as FAM3B) is a uniquely structured protein strongly expressed within and secreted from the endocrine pancreas. PANDER has been hypothesized to regulate fasting and fed glucose homeostasis, hepatic lipogenesis and insulin signaling, and to serve a potential role in the onset or progression of type 2 diabetes (T2D). Despite having potentially pivotal pleiotropic roles in glycemic regulation and T2D, there has been limited generation of stable animal models for the investigation of PANDER function, and there are no models on well-established genetic murine backgrounds for T2D. Our aim was to generate an enhanced murine model to further elucidate the biological function of PANDER. Therefore, a pure-bred PANDER knockout C57BL/6 (PANKO-C57) model was created and phenotypically characterized with respect to glycemic regulation and hepatic insulin signaling. The PANKO-C57 model exhibited an enhanced metabolic phenotype, particularly with regard to enhanced glucose tolerance. Male PANKO-C57 mice displayed decreased fasting plasma insulin and C-peptide levels, whereas leptin levels were increased as compared with matched C57BL/6J wild-type mice. Despite similar peripheral insulin sensitivity between both groups, hepatic insulin signaling was significantly increased during fasting conditions, as demonstrated by increased phosphorylation of hepatic PKB/Akt and AMPK, along with mature SREBP-1 expression. Insulin stimulation of PANKO-C57 mice resulted in increased hepatic triglyceride and glycogen content as compared with wild-type C57BL/6 mice. In summary, the PANKO-C57 mouse represents a suitable model for the investigation of PANDER in multiple metabolic states and provides an additional tool to elucidate the biological function and potential role in T2D.

FAM3A activates PI3K p110α/Akt signaling to ameliorate hepatic gluconeogenesis and lipogenesis

FAM3A belongs to a novel cytokine-like gene family, and its physiological role remains largely unknown. In our study, we found a marked reduction of FAM3A expression in the livers of db/db and high-fat diet (HFD)-induced diabetic mice. Hepatic overexpression of FAM3A markedly attenuated hyperglycemia, insulin resistance, and fatty liver with increased Akt (pAkt) signaling and repressed gluconeogenesis and lipogenesis in the livers of those mice. In contrast, small interfering RNA (siRNA)-mediated knockdown of hepatic FAM3A resulted in hyperglycemia with reduced pAkt levels and increased gluconeogenesis and lipogenesis in the livers of C57BL/6 mice. In vitro study revealed that FAM3A was mainly localized in the mitochondria, where it increases adenosine triphosphate (ATP) production and secretion in cultured hepatocytes. FAM3A activated Akt through the p110α catalytic subunit of PI3K in an insulin-independent manner. Blockade of P2 ATP receptors or downstream phospholipase C (PLC) and IP3R and removal of medium calcium all significantly reduced FAM3A-induced increase in cytosolic free Ca(2+) levels and attenuated FAM3A-mediated PI3K/Akt activation. Moreover, FAM3A-induced Akt activation was completely abolished by the inhibition of calmodulin (CaM).

CONCLUSION

FAM3A plays crucial roles in the regulation of glucose and lipid metabolism in the liver, where it activates the PI3K-Akt signaling pathway by way of a Ca(2+) /CaM-dependent mechanism. Up-regulating hepatic FAM3A expression may represent an attractive means for the treatment of insulin resistance, type 2 diabetes, and nonalcoholic fatty liver disease (NAFLD).

PANDER transgenic mice display fasting hyperglycemia and hepatic insulin resistance

PANcreatic-DERived factor (PANDER, FAM3B) is a novel protein that is highly expressed within the endocrine pancreas and to a lesser degree in other tissues. Under glucose stimulation, PANDER is co-secreted with insulin from the β-cell. Despite prior creation and characterization of acute hepatic PANDER animal models, the physiologic function remains to be elucidated from pancreas-secreted PANDER. To determine this, in this study, a transgenic mouse exclusively overexpressing PANDER from the endocrine pancreas was generated. PANDER was selectively expressed by the pancreatic-duodenal homeobox-1 (PDX1) promoter. The PANDER transgenic (PANTG) mice were metabolically and proteomically characterized to evaluate effects on glucose homeostasis, insulin sensitivity, and lipid metabolism. Fasting glucose, insulin and C-peptide levels were elevated in the PANTG compared with matched WT mice. Younger PANTG mice also displayed glucose intolerance in the absence of peripheral insulin sensitivity. Hyperinsulinemic-euglycemic clamp studies revealed that hepatic glucose production and insulin resistance were significantly increased in the PANTG with no difference in either glucose infusion rate or rate of disappearance. Fasting glucagon, corticosterones, resistin and leptin levels were also similar between PANTG and WT. Stable isotope labeling of amino acids in cell culture revealed increased gluconeogenic and lipogenic proteomic profiles within the liver of the PANTG with phosphoenol-pyruvate carboxykinase demonstrating a 3.5-fold increase in expression. This was matched with increased hepatic triglyceride content and decreased p-AMPK and p-acetyl coenzyme A carboxylase-1 signaling in the PANTG. Overall, our findings support a role of pancreatic β-cell-secreted PANDER in the regulation of hepatic insulin and lipogenenic signaling with subsequent impact on overall glycemia.

Family with sequence similarity 3 gene family and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) comprises a disease spectrum ranging from simple steatosis (fatty liver) and nonalcoholic steatohepatitis to fibrosis and cirrhosis. NAFLD has become the leading cause of chronic liver diseases as well as liver-related morbidity and mortality worldwide. NAFLD is also associated with increased risk of cardiovascular diseases, hyperlipidemia, and type 2 diabetes. Insulin resistance in adipose tissues and the liver plays crucial roles in the progression of NAFLD. The family with sequence similarity 3 (FAM3) gene family is a cytokine-like gene family with four members designated FAM3A, FAM3B, FAM3C, and FAM3D, respectively. Increasing evidence suggests that the FAM3 gene family members are involved in the pathogenesis of NAFLD. In particular, FAM3B, also called pancreatic-derived factor, is an important regulator of glucose and lipid metabolism. In obesity status, increased expression and secretion of FAM3B in pancreatic islets and liver may induce lipid accumulation in the liver via the induction of hepatic insulin resistance and lipogenesis. FAM3A and FAM3D may also participate in the regulation of lipid and energy metabolism. In this brief review, we discussed the latest findings regarding the role of FAM3 gene family members, in particular FAM3B, in the pathogenesis of NAFLD.

FAM3A is a target gene of peroxisome proliferator-activated receptor gamma

BACKGROUND

To date, the biological function of FAM3A, the first member of FAM3 gene family, remains unknown. We aimed to investigate whether the expression of FAM3A in liver cells is regulated by peroxisome proliferator-activated receptors (PPARs).

METHODS AND RESULTS

The transcriptional activity of human and mouse FAM3A gene promoters was determined by luciferase reporter assay system. PPARγ agonist rosiglitazone induced FAM3A expression in primary cultured mouse hepatocytes and human HepG2 cells. PPARγ antagonism blocked rosiglitazone-induced FAM3A expression, whereas PPARγ overexpression stimulated FAM3A expression in HepG2 cells. In contrast, PPARα agonist fenofibrate or PPARβ agonist GW0742 failed to affect FAM3A expression in HepG2 cells. The transcriptional activities of human and mouse FAM3A promoters were markedly stimulated by PPARγ activation, but not by PPARα and PPARβ activation. Chromatin immunoprecipitation (ChIP) assay revealed a direct binding of PPARγ to the putative peroxisome proliferator response element (PPRE) located at -1258/-1246 in the human FAM3A promoter. Site-directed mutagenesis of this PPRE-like motif abolished PPARγ's stimulatory effect on the transcriptional activity of human FAM3A promoter. In vivo, oral rosiglitazone treatment upregulated FAM3A expression in the livers of C57BL/6 mice and db/db mice. Moreover, upregulation of FAM3A by PPARγ activation was correlated with increased level of phosphorylated Akt (pAkt) in liver cells.

CONCLUSIONS

FAM3A as a novel target gene of PPARγ. Upregulation of FAM3A by PPARγ activation is correlated with increased pAkt level in liver cells.

GENERAL SIGNIFICANCE

Upregulation of FAM3A might contribute to PPARγ's metabolic effects in the liver.

Role of pancreatic-derived factor in type 2 diabetes: evidence from pancreatic β cells and liver

Pancreatic-derived factor (PANDER) is a cytokine-like protein that is highly expressed in pancreatic islets. In vitro, PANDER pretreatment or viral-mediated overexpression promotes apoptosis of islet β cells. Under conditions of insulin resistance, chronic hyperglycemia potently activates PANDER expression and stimulates the cosecretion of insulin and PANDER in β cells. PANDER binds to the liver cell membrane and induces insulin resistance, resulting in increased gluconeogenesis. Recently, PANDER was found to be expressed in rodent and human liver, and its expression is increased in the liver of diabetic mice and rats. Hepatic overexpression of PANDER promotes lipogenesis in the liver and induces insulin resistance in C57BL/6 mice, whereas the inactivation of hepatic PANDER markedly reduces steatosis, insulin resistance, and hyperglycemia in db/db mice. PANDER deficiency protects mice from high-fat-diet-induced hyperglycemia by decreasing gluconeogenesis in the liver. In summary, PANDER plays an important role in the progression of type 2 diabetes by negatively regulating islet β-cell function and insulin sensitivity in the liver.

PANcreatic-DERived factor: novel hormone PANDERing to glucose regulation

PANcreatic-DERived factor (PANDER, FAM3B) is a member of the FAM3 family of cytokine molecules that were initially described in 2002. PANDER expression is primarily localized to the endocrine pancreas and is secreted from both pancreatic α and β-cells. Initial characterization of PANDER revealed a potential role in pancreatic islet apoptosis. However, recent animal models have indicated PANDER functions as a hormone by regulating glucose levels via interaction with both the liver and the endocrine pancreas. An understanding of the function of PANDER can further the insight into the mechanisms of glucose regulation and potentially provide additional therapeutic targets for the treatment of diabetes. This review details the supporting data demonstrating PANDER has a biological function in glycemic regulation.

Pancreatic-derived factor promotes lipogenesis in the mouse liver: role of the Forkhead box 1 signaling pathway

Pancreatic-derived factor (PANDER) is a pancreatic islet-specific cytokine that cosecretes with insulin and is important for β cell function. Here, we show that PANDER is constitutively expressed in hepatocytes, and its expression is significantly increased in steatotic livers of diabetic insulin-resistant db/db mice and mice fed a high-fat diet. Overexpression of PANDER in the livers of C57Bl/6 mice promoted lipogenesis, with increased Forkhead box 1 (FOXO1) expression, whereas small interfering RNA-mediated knockdown of hepatic PANDER significantly attenuated steatosis, with reduced FOXO1 expression in db/db mice. Hepatic PANDER silencing also attenuated insulin resistance and hyperglycemia in db/db mice. In cultured hepatocytes, PANDER overexpression induced lipid deposition, increased FOXO1 expression, and suppressed insulin-stimulated Akt activation and FOXO1 inactivation. Moreover, FOXO1 overexpression increased PANDER expression in cultured hepatocytes and mouse livers.

CONCLUSION

PANDER promotes lipogenesis and compromises insulin signaling in the liver by increasing FOXO1 activity. PANDER may represent a potential therapeutic target for the treatment of fatty liver and insulin resistance.

Liver-specific overexpression of pancreatic-derived factor (PANDER) induces fasting hyperglycemia in mice

The pancreas-derived hormones, insulin and glucagon, are the two main regulators of glucose homeostasis. However, their actions can be modulated by the presence of other circulating factors including cytokines. Pancreatic-derived factor (PANDER) is a novel cytokine-like molecule secreted from the endocrine pancreas, but its biological function is currently unknown. To address this, we employed adenoviral gene delivery to develop a novel murine model of PANDER overexpression, which we used to study PANDER's effect on glucose homeostasis. Although serum metabolites in fed mice were unaffected by PANDER overexpression, fasting glucose, insulin, and corticosterone levels were significantly elevated. Additionally, PANDER-overexpressing mice displayed elevated glucose and insulin levels during a glucose tolerance test, indicating that glucose tolerance was impaired. However, there were no defects in glucose-stimulated insulin secretion or peripheral insulin sensitivity. Elevated transcription of hepatic gluconeogenic genes, PEPCK and G6Pase accompanied the fasting hyperglycemia observed in PANDER-overexpressing animals. Similarly, treatment of primary hepatocytes with PANDER-expressing adenovirus or PANDER-enriched conditioned medium elevated gluconeogenic gene expression and glucose output. PANDER treatment also resulted in higher levels of Ser133-phosphorylated cAMP-response element-binding protein in hepatocytes stimulated with 8-bromo-cAMP and dexamethasone and higher levels of intracellular cAMP upon stimulation with forskolin. In summary, we provide the first report that identifies PANDER as a regulator of hepatic glucose metabolism, where it serves as a novel factor that amplifies hepatic cAMP and cAMP-response element-binding protein signaling to induce gluconeogenic gene expression and glucose output.

Targeted disruption of pancreatic-derived factor (PANDER, FAM3B) impairs pancreatic beta-cell function

OBJECTIVE

Pancreatic-derived factor (PANDER, FAM3B) is a pancreatic islet-specific cytokine-like protein that is secreted from beta-cells upon glucose stimulation. The biological function of PANDER is unknown, and to address this we generated and characterized a PANDER knockout mouse.

RESEARCH DESIGN AND METHODS

To generate the PANDER knockout mouse, the PANDER gene was disrupted and its expression was inhibited by homologous recombination via replacement of the first two exons, secretion signal peptide and transcriptional start site, with the neomycin gene. PANDER(-/-) mice were then phenotyped by a number of in vitro and in vivo tests to evaluate potential effects on glucose regulation, insulin sensitivity, and beta-cell morphology and function.

RESULTS

Glucose tolerance tests demonstrated significantly higher blood glucose levels in PANDER(-/-) versus wild-type male mice. To identify the mechanism of the glucose intolerance, insulin sensitivity and pancreatic beta-cell function were examined. Hyperinsulinemic-euglycemic clamps and insulin tolerance testing showed similar insulin sensitivity for both the PANDER(-/-) and wild-type mice. The in vivo insulin response following intraperitoneal glucose injection surprisingly produced significantly higher insulin levels in the PANDER(-/-) mice, whereas insulin release was blunted with arginine administration. Islet perifusion and calcium imaging studies showed abnormal responses of the PANDER(-/-) islets to glucose stimulation. In contrast, neither islet architecture nor insulin content was impacted by the loss of PANDER. Interestingly, the elevated insulin levels identified in vivo were attributed to decreased hepatic insulin clearance in the PANDER(-/-) islets. Taken together, these results demonstrated decreased pancreatic beta-cell function in the PANDER(-/-) mouse.

CONCLUSIONS

These results support a potential role of PANDER in the pancreatic beta-cell for regulation or facilitation of insulin secretion.

Characterization of the expression, localization, and secretion of PANDER in alpha-cells

The novel islet-specific protein PANcreatic DERived Factor (PANDER; FAM3B) has been extensively characterized with respect to the beta-cell, and these studies suggest a potential function for PANDER in the regulation of glucose homeostasis. Little is known regarding PANDER in pancreatic -cells, which are critically involved in maintaining euglycemia. Here we present the first report elucidating the expression and regulation of PANDER within the alpha-cell. Pander mRNA and protein are detected in alpha-cells, with primary localization to a glucagon-negative granular cytosolic compartment. PANDER secretion from alpha-cells is nutritionally and hormonally regulated by l-arginine and insulin, demonstrating similarities and differences with glucagon. Signaling via the insulin receptor (IR) through the PI3K and Akt/PKB node is required for insulin-stimulated PANDER release. The separate localization of PANDER and glucagon is consistent with their differential regulation, and the effect of insulin suggests a paracrine/endocrine effect on PANDER release. This provides further insight into the potential glucose-regulatory role of PANDER.

Cytokines in the Progression of Pancreatic β-Cell Dysfunction

The dysfunction of pancreatic β-cell and the reduction in β-cell mass are the decisive events in the progression of type 2 diabetes. There is increasing evidence that cytokines play important roles in the procedure of β-cell failure. Cytokines, such as IL-1β, IFN-γ, TNF-α, leptin, resistin, adiponectin, and visfatin, have been shown to diversely regulate pancreatic β-cell function. Recently, islet-derived cytokine PANcreatic DERived factor (PANDER or FAM3B) has also been demonstrated to be a regulator of islet β-cell function. The change in cytokine profile in islet and plasma is associated with pancreatic β-cell dysfunction and apoptosis. In this paper, we summarize and discuss the recent studies on the effects of certain important cytokines on pancreatic β-cell function. The imbalance in deleterious and protective cytokines plays pivotal roles in the development and progression of pancreatic β-cell dysfunction under insulin-resistant conditions.

PANDER binds to the liver cell membrane and inhibits insulin signaling in HepG2 cells

PANDER is a cytokine co-secreted with insulin from islet beta-cells. To date, the physiological function of PANDER remains largely unknown. Here we show that PANDER binds to the liver membrane by (125)I-PANDER saturation and competitive binding assays. In HepG2 cells, pre-treatment with PANDER ranging from 4 pM to 4 nM for 8h resulted in a maximal inhibition of insulin-stimulated activation of insulin receptor and insulin receptor substrate 1 by 52% and 63%, respectively. Moreover, PANDER treatment also reduced insulin-stimulated PI3K and pAkt levels by 55% and 48%, respectively. In summary, we have identified the liver as a novel target for PANDER, and PANDER may be involved in the progression of diabetes by regulating hepatic insulin signaling pathways.

PDX-1 interaction and regulation of the Pancreatic Derived Factor (PANDER, FAM3B) promoter

Pancreatic Derived Factor (PANDER) is a novel cytokine-like protein dominantly expressed within the endocrine pancreas. Our previous study demonstrated that the PANDER promoter was both tissue-specific and glucose-responsive. Surrounding the PANDER transcriptional start site are several putative A- and E-Box elements that may bind to the various pancreatic transcriptional factors of MafA, BETA2/NeuroD, and Pancreatic Duodenal Homeobox-1 (PDX-1). To characterize the transcriptional regulatory factors involved in PANDER gene expression, we performed co-transfection reporter gene analysis and demonstrated upregulation by all three transcription factors, with the greatest individual increase stemming from PDX-1. Potential binding of PDX-1 to A box (TAAT) regions of the PANDER promoter was demonstrated by chromatin immunoprecipitation (ChIP) and further corroborated by electrophoretic mobility shift assay (EMSA). Binding of PDX-1 to the A box regions was inhibited by mutagenized (TAGT) oligonucleotides. Site-directed mutagenesis of the three PDX-1 A box binding motifs revealed that A box sites 2 and 3 in combination were critical for maximal gene expression and deletion resulted in a 82% reduction in promoter activity. Furthermore, deletion of A box sites 2 and 3 completely diminished the glucose-responsiveness of the PANDER promoter. Our findings demonstrate that PANDER is a potential PDX-1 target gene and the A box sites within the promoter region are critical for basal and glucose-stimulated PANDER expression.

Mechanisms of glucose-induced expression of pancreatic-derived factor in pancreatic beta-cells

Pancreatic-derived factor (PANDER) is a cytokine-like peptide highly expressed in pancreatic beta-cells. PANDER was reported to promote apoptosis of pancreatic beta-cells and secrete in response to glucose. Here we explored the effects of glucose on PANDER expression, and the underlying mechanisms in murine pancreatic beta-cell line MIN6 and primary islets. Our results showed that glucose up-regulated PANDER mRNA and protein levels in a time- and dose-dependent manner in MIN6 cells and pancreatic islets. In cells expressing cAMP response element-binding protein (CREB) dominant-negative construct, glucose failed to induce PANDER gene expression and promoter activation. Treatment of the cells with calcium chelator [EGTA, 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl)ester (BAPTA/AM)], the voltage-dependent Ca(2+) channel inhibitor (nifedipine), the protein kinase A (PKA) inhibitor (H89), the protein kinase C (PKC) inhibitor (Go6976), or the MAPK kinase 1/2 inhibitor (PD98059), all significantly inhibited glucose-induced PANDER gene expression and promoter activation. Further studies showed that glucose induced CREB phosphorylation through Ca(2+)-PKA-ERK1/2 and Ca(2+)-PKC pathways. Thus, the Ca(2+)-PKA-ERK1/2-CREB and Ca(2+)-PKC-CREB signaling pathways are involved in glucose-induced PANDER gene expression. Wortmannin (phosphatidylinositol 3-kinase inhibitor), ammonium pyrrolidinedithiocarbamate (nuclear factor-kappaB inhibitor and nonspecific antioxidant), and N-acetylcysteine (antioxidant) were also found to inhibit glucose-induced PANDER promoter activation and gene expression. Because there is no nuclear factor-kappaB binding site in the promoter region of PANDER gene, these results suggest that phosphatidylinositol 3-kinase and reactive oxygen species be involved in glucose-induced PANDER gene expression. In conclusion, glucose induces PANDER gene expression in pancreatic beta-cells through multiple signaling pathways. Because PANDER is expressed by pancreatic beta-cells and in response to glucose in a similar way to those of insulin, PANDER may be involved in glucose homeostasis.

Sp1 and Sp3 control constitutive expression of the human NHE2 promoter by interactions with the proximal promoter and the transcription initiation site

We have previously cloned the human Na+/H+ exchanger NHE2 gene and its promoter region. In the present study, the regulatory elements responsible for the constitutive expression of NHE2 were studied. Transient transfection assays revealed that the -40/+150 promoter region contains the core promoter responsible for the optimal promoter activity. A smaller fragment, -10/+40, containing the TIS (transcription initiation site) showed minimal activity. We identified a palindrome that overlaps the TIS and binds to the transcription factors Sp1 and Sp3. Mutations in the 5' flank of the palindrome abolished the Sp1/Sp3 interaction and reduced promoter activity by approx. 45%. In addition, a conserved GC-box centered at -25 was found to play a critical role in basal promoter activity and also interacted with Sp1 and Sp3. An internal deletion in the GC-box severely reduced the promoter activity. Sp1/Sp3 binding to these elements was established using gel-mobility shift assays, confirmed by chromatin immunoprecipitation and co-transfections in Drosophila SL2 cells. Furthermore, we identified two positive regulatory elements in the DNA region corresponding to the 5'-UTR (5'-untranslated region). The results in the present study indicate that Sp1 and Sp3 are required for constitutive NHE2 expression and that the positive regulatory elements of the 5'-UTR may co-operate with the 5'-flanking region to achieve the optimal promoter activity.

Low concentration of interleukin-1beta induces FLICE-inhibitory protein-mediated beta-cell proliferation in human pancreatic islets

High glucose concentrations have a dual effect on beta-cell turnover, inducing proliferation in the short-term and apoptosis in the long-term. Hyperglycemia leads to beta-cell production of interleuking (IL)-1beta in human pancreatic islets. Fas, a death receptor regulated by IL-1beta, is involved in glucose-induced beta-cell apoptosis. Fas engagement can be switched from death signal to induction of proliferation when the caspase 8 inhibitor, FLICE-inhibitory protein (FLIP), is active. Here, we show that IL-1beta at low concentrations may participate in the mitogenic actions of glucose through the Fas-FLIP pathway. Thus, exposure of human islets to low IL-1beta concentrations (0.01-0.02 ng/ml) stimulated proliferation and decreased apoptosis, whereas increasing amounts of IL-1beta (2-5 ng/ml) had the reverse effects. A similarly bimodal induction of FLIP, pancreatic duodenal homeobox (PDX)-1, and Pax4 mRNA expression, as well as glucose-stimulated insulin secretion, was observed. In contrast, Fas induction by IL-1beta was monophasic. Low IL-1beta also induced the IL-1 receptor antagonist (IL-1Ra), suppression of which by RNA interference abrogated the beneficial effects of low IL-1beta. The Fas antagonistic antibody ZB4 and small interfering RNA to FLIP prevented low IL-1beta-stimulated beta-cell proliferation. Consistent with our in vitro results, IL-1beta knockout mice displayed glucose intolerance along with a decrease in islet Fas, FLIP, Pax4, and PDX-1 transcripts. These findings indicate that low IL-1beta levels positively influence beta-cell function and turnover through the Fas-FLIP pathway and that IL-1Ra production prevents harmful effects of high IL-1beta concentrations.

PANDER-induced cell-death genetic networks in islets reveal central role for caspase-3 and cyclin-dependent kinase inhibitor 1A (p21)

PANcreatic DERived factor is an islet-specific cytokine that promotes apoptosis in primary islets and islet cell lines. To elucidate the genetic mechanisms of PANDER-induced cell death we performed expression profiling using the mouse PancChip version 5.0 in conjunction with Ingenuity Pathway Analysis. Murine islets were treated with PANDER and differentially expressed genes were identified at 48 and 72 h post-treatment. 64 genes were differentially expressed in response to PANDER treatment. 22 genes are associated with cell death. In addition, the genes with the highest fold change were linked with cell death or apoptosis. The most significantly affected gene at 48 h was the downregulated cyclin-dependent kinase inhibitor 1A (CDKN1A or p21). Approximately half of the genes impacted at 72 h were linked to cell death. Cell death differentially expressed genes were confirmed by quantitative RT-PCR. Further analysis identified cell death genetic networks at both time points with 21 of the 22 cell death genes related in various biological pathways. Caspase-3 (CASP3) was biologically linked to CDKN1A in several genetic networks and these two genes were further examined. Elevated cleaved CASP3 levels in PANDER-treated beta-TC3 insulinoma cells were found to abrogate CDKN1A expression. Levels of CDKN1A were not affected in the absence of cleaved CASP3. PANDER-induced downregulation of CDKN1A expression coupled with induced CASP3-activation may serve a central role in islet cell death and offers further insight into the mechanisms of cytokine-induced beta-cell apoptosis.