Translocation of Viable Gut Microbiota to Mesenteric Adipose Drives Formation of Creeping Fat in Humans.

A mysterious feature of Crohn's disease (CD) is the extra-intestinal manifestation of "creeping fat" (CrF), defined as expansion of mesenteric adipose tissue around the inflamed and fibrotic intestine. In the current study, we explore whether microbial translocation in CD serves as a central cue for CrF development. We discovered a subset of mucosal-associated gut bacteria that consistently translocated and remained viable in CrF in CD ileal surgical resections, and identified Clostridium innocuum as a signature of this consortium with strain variation between mucosal and adipose isolates, suggesting preference for lipid-rich environments. Single-cell RNA sequencing characterized CrF as both pro-fibrotic and pro-adipogenic with a rich milieu of activated immune cells responding to microbial stimuli, which we confirm in gnotobiotic mice colonized with C. innocuum. Ex vivo validation of expression patterns suggests C. innocuum stimulates tissue remodeling via M2 macrophages, leading to an adipose tissue barrier that serves to prevent systemic dissemination of bacteria.

ß-Cell Insulin Secretion Requires the Ubiquitin Ligase COP1.

A variety of signals finely tune insulin secretion by pancreatic ß cells to prevent both hyper-and hypoglycemic states. Here, we show that post-translational regulation of the transcription factors ETV1, ETV4, and ETV5 by the ubiquitin ligase COP1 (also called RFWD2) in ß cells is critical for insulin secretion. Mice lacking COP1 in ß cells developed diabetes due to insulin granule docking defects that were fully rescued by genetic deletion of Etv1, Etv4, and Etv5. Genes regulated by ETV1, ETV4, or ETV5 in the absence of mouse COP1 were enriched in human diabetes-associated genes, suggesting that they also influence human ß-cell pathophysiology. In normal ß cells, ETV4 was stabilized upon membrane depolarization and limited insulin secretion under hyperglycemic conditions. Collectively, our data reveal that ETVs negatively regulate insulin secretion for the maintenance of normoglycemia.

Insulin regulation of hepatic gluconeogenesis through phosphorylation of CREB-binding protein.

Hepatic gluconeogenesis is essential for maintenance of normal blood glucose concentrations and is regulated by opposing stimulatory (cyclic adenosine monophosphate, cAMP) and inhibitory (insulin) signaling pathways. The cAMP signaling pathway leads to phosphorylation of cAMP response element-binding (CREB) protein, resulting in recruitment of the coactivators CREB-binding protein (CBP) and p300 and subsequent activation of gluconeogenesis. Insulin signaling leads to phosphorylation of CBP at serine 436, a residue near its CREB-interacting domain, but it is unknown whether this event modulates cAMP signaling. Here, we show in vitro and in 'knock-in' mice that a mutant CBP (S436A) is aberrantly recruited to CREB protein, resulting in inappropriate activation of gluconeogenesis in the fed state and glucose intolerance resulting from increased hepatic glucose production. We propose that insulin signaling may directly regulate many cAMP signaling pathways at the transcriptional level by controlling CBP recruitment.

Circulating mucosal-associated invariant T cells identify patients responding to anti-PD-1 therapy.

Immune checkpoint inhibitors are used for treating patients with metastatic melanoma. Since the response to treatment is variable, biomarkers are urgently needed to identify patients who may benefit from such therapy. Here, we combine single-cell RNA-sequencing and multiparameter flow cytometry to assess changes in circulating CD8+ T cells in 28 patients with metastatic melanoma starting anti-PD-1 therapy, followed for 6 months: 17 responded to therapy, whilst 11 did not. Proportions of activated and proliferating CD8+ T cells and of mucosal-associated invariant T (MAIT) cells are significantly higher in responders, prior to and throughout therapy duration. MAIT cells from responders express higher level of CXCR4 and produce more granzyme B. In silico analysis support MAIT presence in the tumor microenvironment. Finally, patients with >1.7% of MAIT among peripheral CD8+ population show a better response to treatment. Our results thus suggest that MAIT cells may be considered a biomarker for patients responding to anti-PD-1 therapy.

Benchmarking single-cell RNA-sequencing protocols for cell atlas projects.

Single-cell RNA sequencing (scRNA-seq) is the leading technique for characterizing the transcriptomes of individual cells in a sample. The latest protocols are scalable to thousands of cells and are being used to compile cell atlases of tissues, organs and organisms. However, the protocols differ substantially with respect to their RNA capture efficiency, bias, scale and costs, and their relative advantages for different applications are unclear. In the present study, we generated benchmark datasets to systematically evaluate protocols in terms of their power to comprehensively describe cell types and states. We performed a multicenter study comparing 13 commonly used scRNA-seq and single-nucleus RNA-seq protocols applied to a heterogeneous reference sample resource. Comparative analysis revealed marked differences in protocol performance. The protocols differed in library complexity and their ability to detect cell-type markers, impacting their predictive value and suitability for integration into reference cell atlases. These results provide guidance both for individual researchers and for consortium projects such as the Human Cell Atlas.

The octadecyloxyethyl ester of (S)-9-[3-hydroxy-2-(phosphonomethoxy) propyl]adenine is a potent and selective inhibitor of hepatitis C virus replication in genotype 1A, 1B, and 2A replicons.

The octadecyloxyethyl (ODE) and hexadecyloxypropyl (HDP) esters of (S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine (HPMPA) are potent inhibitors of orthopoxvirus, herpesvirus, human immunodeficiency virus type 1, and hepatitis B virus replication in vitro. HDP and ODE esters of (S)-HPMPA and (R)-HPMPA were evaluated for their activity in hepatitis C virus (HCV) replicon assays using luciferase (1B and 2A replicons) or RNA (1B) quantification. The ODE ester of (S)-HPMPA [ODE-(S)-HPMPA] was the most active compound, with 50% effective concentrations (EC(50)s) in the 0.69 to 1.31 microM range. HDP and ODE esters of (R)-HPMPA were severalfold less active, while (S)-HPMPA and (R)-HPMPA were inactive. In genotype 1A and 1B replicons analyzed by HCV RNA analysis, ODE-(S)-HPMPA was the most active compound, with EC(50)s of 1.8 and 2.1 microM, respectively.

Single-Cell RNA-Sequencing of Peripheral Blood Mononuclear Cells with ddSEQ.

Peripheral blood mononuclear cells (PBMCs) are blood cells that are a critical part of the immune system used to fight off infection. However, due to the complexity of PBMCs, which contain multiple different cell types, studying the function of the individual cell types can be difficult, and often studies rely on bulk measurements. Here, we describe the analysis of PBMCs using single-cell RNA-sequencing in droplets. Data from these studies allow for the identification and quantification of the subpopulation of cells that make up the PBMC sample. In addition, differential gene expression between cell types and samples can be assessed.

Synergy of a hepatitis C virus (HCV) NS4A antagonist in combination with HCV protease and polymerase inhibitors.

Rapid emergence of resistance to monotherapy with virus-specific inhibitors necessitates combination therapy. ACH-806 is a hepatitis C virus NS4A inhibitor with a novel mechanism of action and resistance pathway. This compound was synergistic with NS3 protease inhibitors and NS5B nucleoside and nonnucleoside polymerase inhibitors.

Long-term activation of PKA in ß-cells provides sustained improvement to glucose control, insulin sensitivity and body weight.

Type 2 diabetes is associated with obesity, insulin resistance and ß-cell failure. Therapeutic aims are to reduce adiposity, improve insulin sensitivity and enhance ß-cell function. However, it has been proposed that chronically increasing insulin release leads to ß-cell exhaustion and failure. We previously developed mice to have increased activity of the cAMP-dependent protein kinase (PKA), specifically in ß-cells (ß-caPKA mice). ß-caPKA mice have enhanced acute phase insulin release, which is the primary determinant of the efficacy of glucose clearance. Here these mice were used to determine the sustainability of enhanced insulin secretion, and to characterize peripheral effects of enhanced ß-cell function. Increased PKA activity was induced by tamoxifen administration at 10 weeks of age. Male mice were aged to 12 months of age and female mice to 16 months. Glucose control in both male and female ß-caPKA mice was significantly improved relative to littermate controls with ad libitum feeding, upon refeeding after fasting, and in glucose tolerance tests. In female mice insulin release was both greater and more rapid than in controls. Female mice were more insulin sensitive than controls. Male and female ß-caPKA mice had lower body weights than controls. DEXA analysis of male mice revealed that this was due to reduced adiposity and not due to changes in lean body mass. This study indicates that targeting ß-cells to enhance insulin release is sustainable, maintains insulin sensitivity and reduces body weight. These data identify ß-cell PKA activity as a novel target for obesity therapies.

Dynamic Proteomic Analysis of Pancreatic Mesenchyme Reveals Novel Factors That Enhance Human Embryonic Stem Cell to Pancreatic Cell Differentiation.

Current approaches in human embryonic stem cell (hESC) to pancreatic beta cell differentiation have largely been based on knowledge gained from developmental studies of the epithelial pancreas, while the potential roles of other supporting tissue compartments have not been fully explored. One such tissue is the pancreatic mesenchyme that supports epithelial organogenesis throughout embryogenesis. We hypothesized that detailed characterization of the pancreatic mesenchyme might result in the identification of novel factors not used in current differentiation protocols. Supplementing existing hESC differentiation conditions with such factors might create a more comprehensive simulation of normal development in cell culture. To validate our hypothesis, we took advantage of a novel transgenic mouse model to isolate the pancreatic mesenchyme at distinct embryonic and postnatal stages for subsequent proteomic analysis. Refined sample preparation and analysis conditions across four embryonic and prenatal time points resulted in the identification of 21,498 peptides with high-confidence mapping to 1,502 proteins. Expression analysis of pancreata confirmed the presence of three potentially important factors in cell differentiation: Galectin-1 (LGALS1), Neuroplastin (NPTN), and the Laminin α-2 subunit (LAMA2). Two of the three factors (LGALS1 and LAMA2) increased expression of pancreatic progenitor transcript levels in a published hESC to beta cell differentiation protocol. In addition, LAMA2 partially blocks cell culture induced beta cell dedifferentiation. Summarily, we provide evidence that proteomic analysis of supporting tissues such as the pancreatic mesenchyme allows for the identification of potentially important factors guiding hESC to pancreas differentiation.

PKA Enhances the Acute Insulin Response Leading to the Restoration of Glucose Control.

Diabetes arises from insufficient insulin secretion and failure of the ß-cell mass to persist and expand. These deficits can be treated with ligands to Gs-coupled G-protein-coupled receptors that raise ß-cell cAMP. Here we studied the therapeutic potential of ß-cell cAMP-dependent protein kinase (PKA) activity in restoring glucose control using ß-caPKA mice. PKA activity enhanced the acute insulin response (AIR) to glucose, which is a primary determinant of the efficacy of glucose clearance. Enhanced AIR improved peripheral insulin action, leading to more rapid muscle glucose uptake. In the setting of pre-established glucose intolerance caused by diet-induced insulin resistance or streptozotocin-mediated ß-cell mass depletion, PKA activation enhanced ß-cell secretory function to restore glucose control, primarily through augmentation of the AIR. Enhanced AIR and improved glucose control were maintained through 16 weeks of a high-fat diet and aging to 1 year. Importantly, improved glucose tolerance did not increase the risk for hypoglycemia, nor did it rely upon hyperinsulinemia or ß-cell hyperplasia, although PKA activity was protective for ß-cell mass. These data highlight that improving ß-cell function through the activation of PKA has a large and underappreciated capacity to restore glucose control with minimal risk for adverse side effects.

ß-Cell-specific protein kinase A activation enhances the efficiency of glucose control by increasing acute-phase insulin secretion.

Acute insulin secretion determines the efficiency of glucose clearance. Moreover, impaired acute insulin release is characteristic of reduced glucose control in the prediabetic state. Incretin hormones, which increase ß-cell cAMP, restore acute-phase insulin secretion and improve glucose control. To determine the physiological role of the cAMP-dependent protein kinase (PKA), a mouse model was developed to increase PKA activity specifically in the pancreatic ß-cells. In response to sustained hyperglycemia, PKA activity potentiated both acute and sustained insulin release. In contrast, a glucose bolus enhanced acute-phase insulin secretion alone. Acute-phase insulin secretion was increased 3.5-fold, reducing circulating glucose to 58% of levels in controls. Exendin-4 increased acute-phase insulin release to a similar degree as PKA activation. However, incretins did not augment the effects of PKA on acute-phase insulin secretion, consistent with incretins acting primarily via PKA to potentiate acute-phase insulin secretion. Intracellular calcium signaling was unaffected by PKA activation, suggesting that the effects of PKA on acute-phase insulin secretion are mediated by the phosphorylation of proteins involved in ß-cell exocytosis. Thus, ß-cell PKA activity transduces the cAMP signal to dramatically increase acute-phase insulin secretion, thereby enhancing the efficiency of insulin to control circulating glucose.

3-drug synergistic interactions of small molecular inhibitors of hepatitis C virus replication.

Small molecular inhibitors of hepatitis C virus (HCV) replication provide remarkable potency, but the rapid selection of resistance mutations will require that these agents be used in combination for clinical treatment. Using a model HCV replicon system, we have extended prior in vitro studies of double combinations of candidate small molecular inhibitors to studies evaluating the simultaneous use of 3 agents. This was done in an effort to anticipate conditions that might ultimately be required clinically. We formally demonstrate synergistic antiviral activity with 3-drug combinations in this model, further supporting the concept of clinical investigations of combination therapy for HCV infection.

Synergy of small molecular inhibitors of hepatitis C virus replication directed at multiple viral targets.

Chronic hepatitis C virus (HCV) infection is a significant worldwide health problem with limited therapeutic options. A number of novel, small molecular inhibitors of HCV replication are now entering early clinical trials in humans. Resistance to small molecular inhibitors is likely to be a significant hurdle to their use in patients. A systematic assessment of combinations of interferon and/or novel anti-hepatitis C virus agents from several different mechanistic classes was performed in vitro. Combinations of inhibitors with different mechanisms of action consistently demonstrated more synergy than did compounds with similar mechanisms of action. These results suggest that combinations of inhibitors with different mechanisms of action should be prioritized for assessment in clinical trials for chronic hepatitis C virus infection.

Interplay of Ca2+ and cAMP signaling in the insulin-secreting MIN6 beta-cell line.

Ca2+ and cAMP are important second messengers that regulate multiple cellular processes. Although previous studies have suggested direct interactions between Ca2+ and cAMP signaling pathways, the underlying mechanisms remain unresolved. In particular, direct evidence for Ca2+-regulated cAMP production in living cells is incomplete. Genetically encoded fluorescence resonance energy transfer-based biosensors have made possible real-time imaging of spatial and temporal gradients of intracellular cAMP concentration in single living cells. Here, we used confocal microscopy, fluorescence resonance energy transfer, and insulin-secreting MIN6 cells expressing Epac1-camps, a biosynthetic unimolecular cAMP indicator, to better understand the role of intracellular Ca2+ in cAMP production. We report that depolarization with high external K+, tolbutamide, or glucose caused a rapid increase in cAMP that was dependent on extracellular Ca2+ and inhibited by nitrendipine, a Ca2+ channel blocker, or 2',5'-dideoxyadenosine, a P-site antagonist of transmembrane adenylate cyclases. Stimulation of MIN6 cells with glucose in the presence of tetraethylammonium chloride generated concomitant Ca2+ and cAMP oscillations that were abolished in the absence of extracellular Ca2+ and blocked by 2',5'-dideoxyadenosine or 3-isobutyl-1-methylxanthine, an inhibitor of phosphodiesterase. Simultaneous measurements of Ca2+ and cAMP concentrations with Fura-2 and Epac1-camps, respectively, revealed a close temporal and causal interrelationship between the increases in cytoplasmic Ca2+ and cAMP levels following membrane depolarization. These findings indicate highly coordinated interplay between Ca2+ and cAMP signaling in electrically excitable endocrine cells and suggest that Ca2+-dependent cAMP oscillations are derived from an increase in adenylate cyclase activity and periodic activation and inactivation of cAMP-hydrolyzing phosphodiesterase.

Imaging endoplasmic reticulum calcium with a fluorescent biosensor in transgenic mice.

The use of biosynthetic fluorescent sensors is an important new approach for imaging Ca(2+) in cells. Genetically encoded indicators based on green fluorescent protein, calmodulin, and fluorescence resonance energy transfer (FRET) have been utilized to measure Ca(2+) in nonmammalian transgenic organisms and provide information about the organization and regulation of Ca(2+) signaling events in vivo. However, expression of biosynthetic FRET-based Ca(2+) indicators in transgenic mammals has proven to be problematic. Here, we report transgenic expression of an endoplasmic reticulum (ER) Ca(2+) biosensor in mouse pancreas. We targeted expression of a yellow cameleon3.3er (YC3.3er) transgene with mouse insulin I promoter. YC3.3er protein expression was limited to pancreatic beta-cells within islets of Langerhans and absent in the exocrine pancreas and other tissues. Animals developed and matured normally; sensor expression was unaffected by age. Glucose tolerance in transgenic mice was also unaffected, indicating the transgenic biosensor did not impair endocrine pancreas function. ER Ca(2+) responses after administration of thapsigargin, carbachol, and glucose were measured in individual beta-cells of intact islets using confocal microscopy and confirmed the function of the biosensor. We conclude that controlling transgene transcription with a cell-specific promoter permits transgenic expression of FRET-based Ca(2+) sensors in mammals and that this approach will facilitate real-time optical imaging of signal transduction events in living tissues.