Cholecystokinin (CCK) Regulation of Pancreatic Acinar Cells: Physiological Actions and Signal Transduction Mechanisms

Discovery of novel glucagon-like peptide 1/cholecystokinin 1 receptor dual agonists

The combined use of gastrointestinal hormones for treating metabolic diseases is gaining increasing attention. The potential of developing novel dual agonists targeting both cholecystokinin 1 (CCK-1) receptor and glucagon-like peptide 1 (GLP-1) receptor to improve the treatment of type 2 diabetes and obesity have not been fully explored. In this investigation, we reported a series of novel GLP-1/CCK-1 receptor co-agonists constructed by linking the C-terminus of a GLP-1 receptor agonist (bullfrog GLP-1) to the N-terminus of a CCK-1 receptor selective agonist NN9056. In comprehensive in vitro assays, these co-agonists exhibited complete agonistic potency on GLP-1 and CCK-1 receptor. Remarkably, 1f displayed superior hypoglycemic and insulinotropic effects when compared to NN9056 and semaglutide. Evaluation in Kunming and diet-induced obesity (DIO) mice unveiled significant acute and enduring hypoglycemic effects of 1f. Administration of 1f to DIO mice resulted in substantial weight loss, normalized lipid metabolism, and enhanced glucose regulation. These preclinical observations strongly advocate for the therapeutic potential CCK-1 and GLP-1 pathways could be harnessed in a single fusion peptide, yielding a promising combination therapy strategy for treating metabolic disorders.

CCK Receptor Inhibition Reduces Pancreatic Tumor Fibrosis and Promotes Nanoparticle Delivery

The poor prognosis for pancreatic ductal adenocarcinoma (PDAC) patients is due in part to the highly fibrotic nature of the tumors that impedes delivery of therapeutics, including nanoparticles (NPs). Our prior studies demonstrated that proglumide, a cholecystokinin receptor (CCKR) antagonist, reduced fibrosis pervading PanIN lesions in mice. Here, we further detail how the reduced fibrosis elicited by proglumide achieves the normalization of the desmoplastic tumor microenvironment (TME) and improves nanoparticle uptake. One week following the orthotopic injection of PDAC cells, mice were randomized to normal or proglumide-treated water for 3-6 weeks. Tumors were analyzed ex vivo for fibrosis, vascularity, stellate cell activation, vascular patency, and nanoparticle distribution. The histological staining and three-dimensional imaging of tumors each indicated a reduction in stromal collagen in proglumide-treated mice. Proglumide treatment increased tumor vascularity and decreased the activation of cancer-associated fibroblasts (CAFs). Additionally, PANC-1 cells with the shRNA-mediated knockdown of the CCK2 receptor showed an even greater reduction in collagen, indicating the CCK2 receptors on tumor cells contribute to the desmoplastic TME. Proglumide-mediated reduction in fibrosis also led to functional changes in the TME as evidenced by the enhanced intra-tumoral distribution of small (<12 nm) Rhodamine-loaded nanoparticles. The documented in vivo, tumor cell-intrinsic anti-fibrotic effects of CCK2R blockade in both an immunocompetent syngeneic murine PDAC model as well as a human PDAC xenograft model demonstrates that CCK2R antagonists, such as proglumide, can improve the delivery of nano-encapsulated therapeutics or imaging agents to pancreatic tumors.

Fetal Hypoglycemia Induced by Placental SLC2A3-RNA Interference Alters Fetal Pancreas Development and Transcriptome at Mid-Gestation

Glucose, the primary energy substrate for fetal oxidative processes and growth, is transferred from maternal to fetal circulation down a concentration gradient by placental facilitative glucose transporters. In sheep, SLC2A1 and SLC2A3 are the primary transporters available in the placental epithelium, with SLC2A3 located on the maternal-facing apical trophoblast membrane and SLC2A1 located on the fetal-facing basolateral trophoblast membrane. We have previously reported that impaired placental SLC2A3 glucose transport resulted in smaller, hypoglycemic fetuses with reduced umbilical artery insulin and glucagon concentrations, in addition to diminished pancreas weights. These findings led us to subject RNA derived from SLC2A3-RNAi (RNA interference) and NTS-RNAi (non-targeting sequence) fetal pancreases to qPCR followed by transcriptomic analysis. We identified a total of 771 differentially expressed genes (DEGs). Upregulated pathways were associated with fat digestion and absorption, particularly fatty acid transport, lipid metabolism, and cholesterol biosynthesis, suggesting a potential switch in energetic substrates due to hypoglycemia. Pathways related to molecular transport and cell signaling in addition to pathways influencing growth and metabolism of the developing pancreas were also impacted. A few genes directly related to gluconeogenesis were also differentially expressed. Our results suggest that fetal hypoglycemia during the first half of gestation impacts fetal pancreas development and function that is not limited to β cell activity.

Neonatal overnutrition, but not neonatal undernutrition, disrupts CCK-induced hypophagia and neuron activation of the nucleus of the solitary tract and paraventricular nucleus of hypothalamus of male Wistar rats

Metabolic programming may be induced by reduction or enhancement of litter size, which lead to neonatal over or undernutrition, respectively. Changes in neonatal nutrition can challenge some regulatory processes in adulthood, such as the hypophagic effect of cholecystokinin (CCK). In order to investigate the effects of nutritional programming on the anorexigenic function of CCK in adulthood, pups were raised in small (SL, 3 pups per dam), normal (NL, 10 pups per dam), or large litters (LL, 16 pups per dam), and on postnatal day 60, male rats were treated with vehicle or CCK (10 µg/Kg) for the evaluation of food intake and c-Fos expression in the area postrema (AP), nucleus of solitary tract (NTS), and paraventricular (PVN), arcuate (ARC), ventromedial (VMH), and dorsomedial (DMH) nuclei of the hypothalamus. Overnourished rats showed increased body weight gain that was inversely correlated with neuronal activation of PaPo, VMH, and DMH neurons, whereas undernourished rats had lower body weight gain, inversely correlated with increased neuronal activation of PaPo only. SL rats showed no anorexigenic response and lower neuron activation in the NTS and PVN induced by CCK. LL exhibited preserved hypophagia and neuron activation in the AP, NTS, and PVN in response to CCK. CCK showed no effect in c-Fos immunoreactivity in the ARC, VMH, and DMH in any litter. These results indicate that anorexigenic actions, associated with neuron activation in the NTS and PVN, induced by CCK were impaired by neonatal overnutrition. However, these responses were not disrupted by neonatal undernutrition. Thus, data suggest that an excess or poor supply of nutrients during lactation display divergent effects on programming CCK satiation signaling in male adult rats.

Cofilin activation in pancreatic acinar cells plays a pivotal convergent role for mediating CCK-stimulated enzyme secretion and growth

Introduction: The actin regulatory protein, cofilin plays a key signaling role in many cells for numerous cellular responses including in proliferation, development, motility, migration, secretion and growth. In the pancreas it is important in islet insulin secretion, growth of pancreatic cancer cells and in pancreatitis. However, there are no studies on its role or activation in pancreatic acinar cells. Methods: To address this question, we studied the ability of CCK to activate cofilin in pancreatic acinar cells, AR42J cells and CCK₁-R transfected Panc-1 cells, the signaling cascades involved and its effect on enzyme secretion and MAPK activation, a key mediator of pancreatic growth. Results: CCK (0.3 and 100 nM), TPA, carbachol, Bombesin, secretin and VIP decreased phospho-cofilin (i.e., activate cofilin) and both phospho-kinetic and inhibitor studies of cofilin, LIM kinase (LIMK) and Slingshot Protein Phosphatase (SSH1) demonstrated these conventional activators of cofilin were not involved. Serine phosphatases inhibitors (calyculin A and okadaic acid), however inhibited CCK/TPA-cofilin activation. Studies of various CCK-activated signaling cascades showed activation of PKC/PKD, Src, PAK4, JNK, ROCK mediated cofilin activation, but not PI3K, p38, or MEK. Furthermore, using both siRNA and cofilin inhibitors, cofilin activation was shown to be essential for CCK-mediated enzyme secretion and MAPK activation. Conclusion: These results support the conclusion that cofilin activation plays a pivotal convergent role for various cell signaling cascades in CCK mediated growth/enzyme secretion in pancreatic acini.

Calcium, mitochondria and the initiation of acute pancreatitis

Acute pancreatitis is characterized by necrosis of its parenchymal cells and influx and activation of inflammatory cells that further promote injury and necrosis. This review is intended to discuss the central role of disorders of calcium metabolism and mitochondrial dysfunction in the mechanism of pancreatitis development. The disorders are placed in context of calcium and mitochondria in physiologic function of the pancreas. Moreover, we discuss potential therapeutics for preventing pathologic calcium signals that injure mitochondria and interventions that promote the removal of injured mitochondria and regenerate new and heathy populations of mitochondria.

Replacing ZnSO4 with Zn-glycine in the diet of goat promotes the pancreatic function of the offspring

Zinc supplementation in the diet of goats affects pancreas development in offspring. However, the impact of maternal inorganic and organic zinc supplementation in offspring is poorly defined. In this study, 14 late-pregnant goats were assigned at random to the zinc sulfate group (ZnSO₄, n = 7) and the zinc-glycine chelate group (Zn-Gly, n = 7), respectively. Serum samples and pancreas tissue were collected from kids whose mothers were fed ZnSO₄ and Zn-Gly at the late pregnancy, respectively. Histologic examination showed no morphologic differences between the 2 groups. Pancreatic zinc content in kids tended to be increased when replacing ZnSO₄ with Zn-Gly. The serum insulin concentration was greater and glucagon less in the Zn-Gly group when compared to the ZnSO₄ group. The activities of lipase and chymotrypsin were enhanced when replacing ZnSO₄ with Zn-Gly. Proteomics results showed that 234 proteins were differentially expressed between the 2 groups, some of which were associated with the secretion of insulin, enzyme activity and signal transduction. The results suggested that supply of dietary Zn-Gly to goats during late pregnancy promoted pancreatic function in offspring compared with dietary ZnSO₄ supplementation. This provides new information about pancreatic function when supplementing different zinc sources in the diets of late pregnant goats.

Triclosan targets miR-144 abnormal expression to induce neurodevelopmental toxicity mediated by activating PKC/MAPK signaling pathway

Although the previous research confirmed that triclosan (TCS) induced an estrogen effect by acting on a novel G-protein coupled estrogen-membrane receptor (GPER), the underlying mechanisms by which downstream pathways induce neurotoxicity remain unclear after TCS activation of GPER. By employing a series of techniques (Illumina miRNA-seq, RT-qPCR, and artificial intervention of miRNA expression), we screened out four important miRNAs, whose target genes were directly/indirectly involved in neurodevelopment and neurobehavior. Especially, the miR-144 up-regulation caused vascular malformation and severely affected hair-cell development and lateral-line-neuromast formation, thereby causing abnormal motor behavior. After microinjecting 1-2-cell embryos, the similar phenotypic malformations as those induced by TCS were observed, including aberrant neuromast, cuticular-plate development and motor behavior. By KEGG pathway enrichment analysis, these target genes were demonstrated to be mainly related to the PKC/MAPK signaling pathway. When a PKC inhibitor was used to suppress the PKC/MAPK pathway, a substantial alleviation of TCS-induced neurotoxicity was observed. Therefore, TCS acts on GPER to activate the downstream PKC/MAPK signaling pathway, further up-regulating miR-144 expression and causing abnormal modulation of these nerve-related genes to trigger neurodevelopmental toxicity. These findings unravel the molecular mechanisms of TCS-induced neurodegenerative diseases, and offer theoretical guidance for TCS-pollution early warning and management.

In Vitro Disease Models of the Endocrine Pancreas

The ethical constraints and shortcomings of animal models, combined with the demand to study disease pathogenesis under controlled conditions, are giving rise to a new field at the interface of tissue engineering and pathophysiology, which focuses on the development of in vitro models of disease. In vitro models are defined as synthetic experimental systems that contain living human cells and mimic tissue- and organ-level physiology in vitro by taking advantage of recent advances in tissue engineering and microfabrication. This review provides an overview of in vitro models and focuses specifically on in vitro disease models of the endocrine pancreas and diabetes. First, we briefly review the anatomy, physiology, and pathophysiology of the human pancreas, with an emphasis on islets of Langerhans and beta cell dysfunction. We then discuss different types of in vitro models and fundamental elements that should be considered when developing an in vitro disease model. Finally, we review the current state and breakthroughs in the field of pancreatic in vitro models and conclude with some challenges that need to be addressed in the future development of in vitro models.

Protective Effects of Sodium Para-aminosalicylic Acid on Manganese-Induced Damage in Rat Pancreas

Sodium p-aminosalicylic acid (PAS-Na) has been previously shown to protect the brain from manganese (Mn)-induced toxicity. However, the efficacy of PAS-Na in protecting other organs from Mn toxicity and the mechanisms associated with this protection have yet to be addressed. Therefore, here, we assessed pancreatic damage in response to Mn treatment and the efficacy of PAS-Na in limiting this effect, along with specific mechanisms that mediate PAS-Na's protection. Mn exposure led to increased blood Mn content in dose- and time-dependent manner. Furthermore, subchronic Mn exposure (20 mg/kg for 8 weeks) led to pancreatic damage in a dose-dependent manner. In addition, the elevated Mn levels increased iron and decreased zinc and magnesium content in the pancreas. These effects were noted even 8 weeks after Mn exposure cessation. Mn exposure also affected the levels of amylase, lipase, and inflammatory factors such as tumor necrosis factor (TNF-α) and interleukin-1 β (IL-1β). PAS-Na significantly inhibited the increase in Mn concentration in both blood and pancreas, restored Mn-induced pancreatic damage, reversed the Mn-induced alterations in metal levels, and restored amylase and lipase concentrations. Taken together, we conclude that in rats, PAS-Na shows pharmacological efficacy in protecting the pancreas from Mn-induced damage.

Experimental Acute Pancreatitis Models: History, Current Status, and Role in Translational Research

Acute pancreatitis is a potentially severe inflammatory disease that may be associated with a substantial morbidity and mortality. Currently there is no specific treatment for the disease, which indicates an ongoing demand for research into its pathogenesis and development of new therapeutic strategies. Due to the unpredictable course of acute pancreatitis and relatively concealed anatomical site in the retro-peritoneum, research on the human pancreas remains challenging. As a result, for over the last 100 years studies on the pathogenesis of this disease have heavily relied on animal models. This review aims to summarize different animal models of acute pancreatitis from the past to present and discuss their main characteristics and applications. It identifies key studies that have enhanced our current understanding of the pathogenesis of acute pancreatitis and highlights the instrumental role of animal models in translational research for developing novel therapies.

Knockout of the Mitochondrial Calcium Uniporter Strongly Suppresses Stimulus-Metabolism Coupling in Pancreatic Acinar Cells but Does Not Reduce Severity of Experimental Acute Pancreatitis

Acute pancreatitis is a frequent disease that lacks specific drug treatment. Unravelling the molecular mechanisms of acute pancreatitis is essential for the development of new therapeutics. Several inducers of acute pancreatitis trigger sustained Ca²⁺ increases in the cytosol and mitochondria of pancreatic acinar cells. The mitochondrial calcium uniporter (MCU) mediates mitochondrial Ca²⁺ uptake that regulates bioenergetics and plays an important role in cell survival, damage and death. Aberrant Ca²⁺ signaling and mitochondrial damage in pancreatic acinar cells have been implicated in the initiation of acute pancreatitis. The primary aim of this study was to assess the involvement of the MCU in experimental acute pancreatitis. We found that pancreatic acinar cells from MCU^-/- mice display dramatically reduced mitochondrial Ca²⁺ uptake. This is consistent with the drastic changes of stimulus-metabolism coupling, manifested by the reduction of mitochondrial NADH/FAD⁺ responses to cholecystokinin and in the decrease of cholecystokinin-stimulated oxygen consumption. However, in three experimental models of acute pancreatitis (induced by caerulein, taurolithocholic acid 3-sulfate or palmitoleic acid plus ethanol), MCU knockout failed to reduce the biochemical and histological changes characterizing the severity of local and systemic damage. A possible explanation of this surprising finding is the redundancy of damaging mechanisms activated by the inducers of acute pancreatitis.

NanoLuc Bioluminescence-Driven Photodynamic Activation of Cholecystokinin 1 Receptor with Genetically-Encoded Protein Photosensitizer MiniSOG

In contrast to reversible activation by agonist, cholecystokinin 1 receptor (CCK1R) is permanently activated by singlet oxygen generated in photodynamic action, with sulphonated aluminium phthalocyanine or genetically encoded mini singlet oxygen generator (miniSOG) as photosensitizer. In these works, a halogen light source was used to power photodynamic action. For possible in vivo application of photodynamic CCK1R physiology, bearing a cumbersome light-delivery device connected to an external light source by experimental animals might interfere with their behavior. Therefore, in the present work, the possibility of bioluminescence-driven miniSOG photodynamic CCK1R activation was examined, as monitored by Fura-2 calcium imaging. In parallel experiments, it was found that, after plasma membrane (PM)-localized expression of miniSOG_PM in AR4-2J cells, light irradiation with blue light-emitting diode (LED) (450 nm, 85 mW·cm^-2, 1.5 min) induced persistent calcium oscillations that were blocked by CCK1R antagonist devazepide 2 nM. NanoLuc was expressed bicistronically with miniSOG_PM via an internal ribosome entry site (IRES) sequence (pminiSOG_PM-IRES-NanoLuc). The resultant miniSOG_PM-IRES-NanoLuc-AR4-2J cells were found to generate strong bioluminescence upon addition of NanoLuc substrate coelenterazine. Strikingly, coelenterazine 5 microM was found to trigger long-lasting calcium oscillations (a hallmark for permanent CCK1R activation) in perifused miniSOG_PM-IRES-NanoLuc-AR4-2J cells. These data indicate that NanoLuc bioluminescence can drive miniSOG_PM photodynamic CCK1R activation, laying the foundation for its future in vivo applications.

Mutation That Promotes Activation of Trypsinogen Increases Severity of Secretagogue-Induced Pancreatitis in Mice

BACKGROUND & AIMS

Mutations in the human serine protease 1 gene (PRSS1), which encodes cationic trypsinogen, can accelerate its autoactivation and cause hereditary or sporadic chronic pancreatitis. Disruption of the locus that encodes cationic trypsinogen in mice (T7) causes loss of expression of the protein, but only partially decreases the severity of secretagogue-induced acute pancreatitis and has no effect on chronic pancreatitis. We investigated whether trypsinogen becomes pathogenic only when its activation is promoted by mutation.

METHODS

We generated mice with knock-in of the p.K24R mutation (called T7K24R mice), which is analogous to human PRSS1 mutation p.K23R. We gave T7K24R and C57BL/6N (control) mice repeated injections of cerulein to induce pancreatitis. Plasma amylase activity, pancreatic edema, and myeloperoxidase content in pancreas and lungs were quantified. We expressed mutant and full-length forms of PRSS1 in Escherichia coli and compared their autoactivation.

RESULTS

The p.K24R mutation increased autoactivation of T7 5-fold. T7K24R mice developed no spontaneous pancreatitis. T7K24R mice given cerulein injections had increased pancreatic activation of trypsinogen and more edema, infiltration of lung and pancreas by inflammatory cells, and plasma amylase activity compared with control mice given cerulein injections. Injection of cerulein for 2 days induced progressive pancreatitis in T7K24R mice, but not in control mice, with typical features of chronic pancreatitis.

CONCLUSIONS

Introduction of a mutation into mice that is analogous to the p.K23R mutation in PRSS1 increases pancreatic activation of trypsinogen during secretagogue-induced pancreatitis. Higher pancreatic activity of trypsin increases the severity of pancreatitis, even though loss of trypsin activity does not prevent pancreatitis in mice.

Group II p21-activated kinase, PAK4, is needed for activation of focal adhesion kinases, MAPK, GSK3, and β-catenin in rat pancreatic acinar cells

PAK4 is the only member of the Group II p21-activated kinases (PAKs) present in rat pancreatic acinar cells and is activated by gastrointestinal hormones/neurotransmitters stimulating PLC/cAMP and by various pancreatic growth factors. However, little is known of the role of PAK4 activation in cellular signaling cascades in pancreatic acinar cells. In the present study, we examined the role of PAK4's participation in five different cholecystokinin-8 (CCK-8)-stimulated signaling pathways (PI3K/Akt, MAPK, focal adhesion kinase, GSK3, and β-catenin), which mediate many of its physiological acinar-cell effects, as well as effects in pathophysiological conditions. To define PAK4's role, the effect of two different PAK4 inhibitors, PF-3758309 and LCH-7749944, was examined under experimental conditions that only inhibited PAK4 activation and not activation of the other pancreatic PAK, Group I PAK2. The inhibitors' effects on activation of these five signaling cascades by both physiological and pathophysiological concentrations of CCK, as well as by 12-O-tetradecanoylphobol-13-acetate (TPA), a PKC-activator, were examined. CCK/TPA activation of focal adhesion kinases(PYK2/p125^FAK) and the accompanying adapter proteins (paxillin/p130^CAS), Mek1/2, and p44/42, but not c-Raf or other MAPKs (JNK/p38), were mediated by PAK4. Activation of PI3K/Akt/p70s6K was independent of PAK4, whereas GSK3 and β-catenin stimulation was PAK4-dependent. These results, coupled with recent studies showing PAK4 is important in pancreatic fluid/electrolyte/enzyme secretion and acinar cell growth, show that PAK4 plays an important role in different cellular signaling cascades, which have been shown to mediate numerous physiological and pathophysiological processes in pancreatic acinar cells.NEW & NOTEWORTHY In pancreatic acinar cells, cholecystokinin (CCK) or 12-O-tetradecanoylphobol-13-acetate (TPA) activation of focal adhesion kinases (p125^FAK,PYK2) and its accompanying adapter proteins, p130CAS/paxillin; Mek1/2, p44/42, GSK3, and β-catenin are mediated by PAK4. PI3K/Akt/p70s6K, c-Raf, JNK, or p38 pathways are independent of PAK4 activation.

NADPH oxidase 1 mediates caerulein-induced pancreatic fibrosis in chronic pancreatitis

Inflammatory disorders of the pancreas are divided into acute (AP) and chronic (CP) forms. Both states of pancreatitis are a result of pro-inflammatory mediators, including reactive oxygen species (ROS). One of the sources of ROS is NADPH oxidase (Nox). The rodent genome encodes Nox1-4, Duox1 and Duox2. Our purpose was to assess the extent to which Nox enzymes contribute to the pathogenesis of both AP and CP using Nox-deficient mice. Using RT-PCR, Nox1 was found in both isolated mouse pancreatic acini and pancreatic stellate cells (PaSCs). Subsequently, mice with genetically deleted Nox1 were further studied and showed that the histo-morphologic characteristics of caerulein-induced CP, but not caerulein-induced AP, was ameliorated in Nox1 KO mice. We also found that the lack of Nox1 impaired caerulein-induced ROS generation in PaSCs. Using Western blotting, we found that AKT mediates the fibrotic effect of Nox1 in a mouse model of CP. We also found a decrease in phospho-ERK and p38MAPK levels in Nox1 KO mice with CP, but not with AP. Both CP-induced TGF-β up-regulation and NF-ĸB activation were impaired in pancreas from Nox1 KO mice. Western blotting indicated increases in proteins involved in fibrosis and acinar-to-ductal metaplasia in WT mice with CP. No change in those proteins were observed in Nox1 KO mice. The lack of Nox1 lowered mRNA levels of CP-induced matrix metalloproteinase MMP-9 and E-cadherin repressor Twist in PaSCs. CONCLUSION: Nox1-derived ROS in PaSCs mediate the fibrotic process of CP by activating the downstream redox-sensitive signaling pathways AKT and NF-ĸB, up-regulating MMP-9 and Twist, and producing α-smooth muscle actin and collagen I and III.

Nonclassical Islet Peptides: Pancreatic and Extrapancreatic Actions

The pancreas has physiologically important endocrine and exocrine functions; secreting enzymes into the small intestine to aid digestion and releasing multiple peptide hormones via the islets of Langerhans to regulate glucose metabolism, respectively. Insulin and glucagon, in combination with ghrelin, pancreatic polypeptide and somatostatin, are the main classical islet peptides critical for the maintenance of blood glucose. However, pancreatic islets also synthesis numerous ‘nonclassical’ peptides that have recently been demonstrated to exert fundamental effects on overall islet function and metabolism. As such, insights into the physiological relevance of these nonclassical peptides have shown impact on glucose metabolism, insulin action, cell survival, weight loss, and energy expenditure. This review will focus on the role of individual nonclassical islet peptides to stimulate pancreatic islet secretions as well as regulate metabolism. In addition, the more recognised actions of these peptides on satiety and energy regulation will also be considered. Furthermore, recent advances in the field of peptide therapeutics and obesity-diabetes have focused on the benefits of simultaneously targeting several hormone receptor signalling cascades. The potential for nonclassical islet hormones within such combinational approaches will also be discussed.