Citations

Abstract Circadian clocks regulate numerous physiological processes that vary across the day-night (diurnal) cycle, but whether the circadian clock regulates the adaptive immune response to cancer is mostly unclear. In mouse models of polyposis, and human colorectal cancer patients, we showed that tumor infiltrating Tregs overexpressed b-catenin and RORgt, and secreted IL-17. These Tregs suppressed tumor reactive cytotoxic T cells, and promoted tumor growth. Therefore, we examined how the expression of a dominant negative ClockΔ19 gene affects inflammation and susceptibility to cancer in the APCΔ468 mouse model of hereditary polyposis. ClockΔ19 mutant mice had high expression of RORgt+ and b-catenin+ Tregs. These mice showed a notable expansion of Th17 inflammation in vivo upon injection of aCD3. Functionally these Tregs showed pro-inflammatory properties. In addition to these effects, APCΔ468 ClockΔ19 mice had increased numbers of CD11b+ cell, Ly6C+CXCR1− monocytes, and Ly6C+Ly6G+ myeloid derived suppressor cells (MDSC) as compared with APCΔ468 mice. APCΔ468 ClockΔ19 mice had higher tumor burden in the small intestine and colon than the APCΔ468 mice. Both T-cells and tumors had intense stabilization of nuclear b-catenin and were more aggressive as indicated by abundance of stromal mMCP6+ mast cells (MC), which typically appear at the invasive borders of tumors. Our finding indicating increase in tumor load and worsening inflammation caused by direct ClockΔ19 effects in the epithelium and enhanced TH17 bias in the immune system.

Skeletal muscle insulin resistance contributes to the pathogenesis of type 2 diabetes mellitus. Epidemiological studies have demonstrated that vitamin D deficiency is associated with the presence of type 2 diabetes in humans. To probe the role of the vitamin D receptor (VDR), an intracellular and nuclear protein that mediates the bioactivity of the active vitamin D ligand, 1,25‐dihydroxyvitamin D, in skeletal muscle mediated glucose disposal, we deleted the skeletal muscle VDR in adult mice. We assessed glucose disposal, insulin concentrations and sensitivity, and skeletal muscle gene expression in Vdr knockout and wild‐type Vdr mice. Following the induction of a skeletal muscle‐specific Cre recombinase with tamoxifen in adult male Vdr fl/fl mice, efficient deletion of the Vdr was demonstrated. In skeletal muscle‐specific Vdr knockout mice, basal glucose concentrations were similar to those in wild‐type Vdr mice. In Vdr knockout mice, blood glucose concentrations decreased more rapidly following the administration of intraperitoneal glucose than in control mice expressing wild‐type Vdr (Figure 1A and Figure 1B). The AUC for glucose concentrations in Vdr fl/fl .actin iCre mice treated with tamoxifen was reduced by 20% (p=0.015) compared to the AUC of blood glucose concentrations prior to tamoxifen treatment. Pre‐and post‐treatment AUC’s for blood glucose in Vdr fl/fl .actin iCre mice treated with vehicle and in Vdr fl/fl mice treated with tamoxifen were unchanged (p=0.97,0.23). Plasma insulin concentrations were identical in knockout and wild‐type Vdr mice following a bolus of glucose, demonstrating that deletion of the Vdr in skeletal muscle did not influence the release of insulin in response to glucose (one‐way ANOVA, p=0.45). Insulin sensitivity was similar in Vdr knockout and wild‐type Vdr mice. Gene expression analysis of skeletal muscle mRNA derived from Vdr knockout mice and wild‐type mice demonstrated an increase in the expression of genes associated with oxidative phosphorylation, fatty acid oxidation and adipogenesis pathways that could potentially alter glucose utilization. We conclude that selective deletion of the Vdr in the skeletal muscle of adult mice results in more efficient glucose disposal than in wild‐type Vdr mice; basal and glucose‐stimulated insulin serum concentrations are identical in knock‐out and wild type VDR mice with no changes in insulin sensitivity. The data suggest that modulation of the vitamin‐D endocrine system is unlikely to improve glucose utilization.

Intracellular pH regulation is vital for normal cellular function and is controlled by membrane H + and HCO 3 ‑ transporters. Most pH reporters have green fluorescence (i.e., BCECF, pHlorin) making simultaneous Ca 2+ , Cl ‐ , or other sensing (i.e., green fluorescent sensors) or GFP‐tags impossible. We previously reported a red‐fluorescent pH sensor ( pHire ) with an alkaline‐shifted pKa that increases fluorescence with increasing intracellular pH. pHire was transiently transfect into TM5 cells, but these fibroblast‐like cells did not address continuous expression in epithelial or excitable cells. Our objective was to evaluate pHire responses in multiple cell‐types and show that it can be used for fluorescent multiplexing. We selected pHire‐expressing rat pancreatic β‐cells (INS1 pHire ) and porcine kidney epithelial cells (LLCPK1 pHire ), and then FACS sorted to keep the top 10‐20% fluorescent cells. To test pHire’s usefulness for intact animals, we made transgenic, UAS‐pHire Drosophila , allowing pHire expression in specific tissues via genetic crossing with promoter‐GAL4 lines. By using perfusion chambers, we monitored cellular pHire‐responses to acid‐loading (NH 4 Cl pulse) and CO 2 /HCO 3 ‑ addition. Stable selection of pHire cell lines ensures single cells as well as contiguous cell layers for acid‐base transporter evaluation. Addition of NH 4 Cl quickly alkalinizes all pHire cells. Different acid‐recovery rates were found in individual cells with LLCPK1 pHire cells recovering faster than INS1 pHire cells. CO 2 /HCO 3 ‑ addition acidified both mammalian cell‐types. LLCPK1 pHire cells typically show a Na + dependent recovery (consistent with electrogenic Na + bicarbonate cotransporter, NBCe1, activity) that is absent from INS1 pHire cells. Infection of INS1 pHire cells with a NBCe1A‐GFP AAV allowed clear demonstration of NBCe1 activity. To test pHire’s stability in living animals, we next generated a UAS‐pHire transgenic Drosophila line, allowing pHire expression in specific tissues via genetic crossing with various promoter‐GAL4 lines. We tested renal epithelial (principal cells: Uro‐GAL4, CapaR‐GAL4; stellate cells: c724‐GAL4) and CNS (elav‐GAL4) expression. As observed in mammalian cells, NH 4 Cl acid‐loading showed robust and more uniform non‐HCO 3 ‑ recovery. The pH‐calibration curves for pHire in Drosophila cells were similar those obtained in mammalian cells (pKa>7.4). Thus, pHire characteristics are not changed by continuous expression in whole organisms. This study shows that the pHire sensor can be constitutively expressed into multiple cell lines or whole animals (flies) with an ideal pH range of pH 6 to 9. pHire may also be multiplexed with GFP labels and biosensors to allow real‐time, pH measurements with other ions of interest at a cellular scale. Finally, our data demonstrate that genetically encoded pHire is a reliable and useful tool for studying acid‐base transporters in a variety of cell‐types.

Currently, there is no pharmacological treatment targeting defective tissue repair in chronic disease. Here, we used a transcriptomics-guided drug target discovery strategy using gene signatures of smoking-associated chronic obstructive pulmonary disease (COPD) and from mice chronically exposed to cigarette smoke, identifying druggable targets expressed in alveolar epithelial progenitors, of which we screened the function in lung organoids. We found several drug targets with regenerative potential, of which EP and IP prostanoid receptor ligands had the most profound therapeutic potential in restoring cigarette smoke–induced defects in alveolar epithelial progenitors in vitro and in vivo. Mechanistically, we found, using single-cell RNA sequencing analysis, that circadian clock and cell cycle/apoptosis signaling pathways were differentially expressed in alveolar epithelial progenitor cells in patients with COPD and in a relevant model of COPD, which was prevented by prostaglandin E2 or prostacyclin mimetics. We conclude that specific targeting of EP and IP receptors offers therapeutic potential for injury to repair in COPD.

Time-restricted feeding improves glucose homeostasis through epigenetic control of pancreatic β cell function.

Pancreatic β-cells are responsible for the synthesis and exocytosis of insulin in response to an increase in circulating glucose. Insulin secretion occurs in a pulsatile manner, with oscillatory pulses superimposed on a basal secretion rate. Insulin pulses are a marker of β-cell health, and secretory parameters, such as pulse amplitude, time interval and frequency distribution, are impaired in obesity, aging and type 2 diabetes. In this review, we detail the mechanisms of insulin production and β-cell synchronization that regulate pulsatile insulin secretion, and we discuss the challenges to consider when measuring fast oscillatory secretion in vivo. These include the anatomical difficulties of measuring portal vein insulin noninvasively in humans before the hormone is extracted by the liver and quickly removed from the circulation. Peripheral concentrations of insulin or C-peptide, a peptide cosecreted with insulin, can be used to estimate their secretion profile, but mathematical deconvolution is required. Parametric and nonparametric approaches to the deconvolution problem are evaluated, alongside the assumptions and trade-offs required for their application in the quantification of unknown insulin secretory rates from known peripheral concentrations. Finally, we discuss the therapeutical implication of targeting impaired pulsatile secretion and its diagnostic value as an early indicator of β-cell stress.

Dysregulation of glucose homeostasis in Type 2 diabetes mellitus (T2DM) is attributed to pancreatic β‐cell failure in maintaining adequate glucose‐stimulated insulin secretion (GSIS) to compensate for diminished insulin action. Recent single cell transcriptomics studies of human pancreatic islets have identified Slc4a4 (encoding an electrogenic Na + ‐nHCO 3 − cotransporter, NBCe1) as a gene repressed in healthy non‐diabetic β‐cells, but expressed in human T2DM β‐cells. However the role of Slc4a4 /NBCe1 in pancreatic β‐cell function remains unknown. Thus, in the current study we set out to test the hypothesis that mis‐expression of Slc4a4 in β‐cells contributes to loss of GSIS and impaired glucose homeostasis in T2DM. Subsequently, we first assessed Slc4a4 mRNA expression in isolated human islets (Control vs. T2DM) by qPCR and quantified NBCe1 protein expression by immunofluorescence in autopsy‐derived human pancreas tissue (Control vs. T2DM). We observed a 4‐fold induction in Slc4a4 mRNA expression in T2DM islets compared to non‐diabetic controls ( p =0.004 vs. Control) and significantly increased NBCe1 co‐localization with insulin‐positive β‐cells of T2DM patients compared to controls ( p <0.001 vs. Control). In addition, we also demonstrated that chronic inhibition of NBCe1 activity using the channel specific inhibitor (S0859) significantly enhanced GSIS in islets isolated from T2DM patients (~1.5‐fold increase vs. untreated, p =0.006). To delineate the role NBCe1 plays on β‐cell function in vivo , we generated β‐cell specific knockout ( β‐Slc4a4 −/− ) mice by crossing Slc4a4 fl/fl (G. Shull, UC) and Ins2‐Cre mouse models. We confirmed >50% reduction in Slc4a4 mRNA expression in β‐Slc4a4 −/− islets and complete ablation of NBCe1 protein expression. In order to model the environmental stress that leads to metabolic defects common to T2DM, we exposed β‐Slc4a4 −/− mice and control littermates to either standard chow diet or 60% high fat diet (HFD) for 8 weeks ad libitum . Under chow‐fed conditions, β‐Slc4a4 −/− mice displayed normal glucose tolerance ( p >0.05 vs. β‐Slc4a4 +/+ Chow). Interestingly, β‐Slc4a4 −/− mice exposed to HFD exhibited enhanced glucose tolerance and GSIS ( p <0.05 vs. β‐Slc4a4 +/+ HFD) and thus were protected from development of T2DM phenotype characteristics of HFD treatment. Finally, to understand the mechanism by which Slc4a4 deletion enhanced β‐cell function, we performed RNA‐sequencing on islets isolated from β‐Slc4a4 −/− and β‐Slc4a4 +/+ mice exposed to chow diet or HFD. Notably, gene‐set enrichment analysis of Kyoto Encyclopedia of Genes and Genomes (KEGG) defined biological pathways revealed that Slc4a4 deletion enriched genes associated with the cell cycle ( p <0.001 vs. β‐Slc4a4 +/+ Chow; p <0.001 vs. β‐Slc4a4 +/+ HFD), while suppressing genes associated with apoptosis ( p =0.002 vs. β‐Slc4a4 +/+ Chow; p =0.004 vs. β‐Slc4a4 +/+ HFD) in the presence of both chow diet and HFD. These result suggest that mis‐expression of Slc4a4 plays a novel role in the induction of β‐cell failure in T2DM. Future studies will delineate exact molecular mechanisms underlying NBCe1‐mediated regulation of β‐cell function in health and under conditions of metabolic stress. Support or Funding Information Mayo Clinic Center of Biomedical Discovery This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .

We recently demonstrated that high dietary fat (HFD) consumption results in a dramatic loss of myelinating cells and their progenitors in the adult CNS (Yoon et al., 2016). However, the mechanism(s) by which HFD drives dysmyelination are unknown. Since epidemiological studies indicate that metabolic syndrome is a key risk factor for multiple sclerosis (MS), a better understanding of how HFD contributes to oligodendrocyte loss and the capacity for myelin regeneration has the potential to highlight new treatment targets. In mice fed HFD, we found significant decreases in vertical activity by 4 wk and significant changes in ambulatory and stereotypy movements by 12 wk in the Open Field Test. HFD‐fed mice also spent less time in the center of the field as opposed to the perimeter, indicating an anxious phenotype. Mitochondrial isolated from the spinal cord of mice consuming HFD for 4 wk had significantly higher state 3 and state 4 respiration as determined by high‐resolution respirometry. However, by 12 wk, state 4 mitochondrial respiration was significantly less in the HFD group. Targeted LC‐LC‐mass spectroscopy approaches demonstrated that Citric Acid Cycle intermediates are also depleted in the spinal cord of mice consuming HFD for 12 wk compared to controls. Changes in genes related to mitochondrial morphology, quality control processes, and oxidative stress response were also found. In addition, there were significantly fewer Olig2+ cells and increased signs of lipid peroxidation products (4‐Hydroxynonenal‐immunoreactivity) in the corpus callosum of HFD consuming mice compared to those fed a regular diet. Supporting in vivo findings that oligodendrocytes are reduced in the spinal cord of mice consuming HFD, we observed increased mitochondrial fragmentation and a reduced oxygen consumption rate in oligodendrocyte precursors cultured with palmitic acid. Astrocytes however, significantly increased oxygen consumption following exposure to palmitic acid. Together, these findings suggest that changes in the adult spinal cord in response to HFD consumption creates an environment that is less conducive to neural repair by impacting mitochondria function and morphology and impairing oligodendrocyte function. To determine any impact of HFD on myelin regeneration, studies are ongoing to examine myelin regeneration using a murine model of Cuprizone‐mediated demyelination. Neurobehavioral assessments to date reveal significant interactions between HFD and myelin injury and repair. Understanding the cellular environment in response to dietary factors such as HFD consumption can help to guide care for individuals with MS and other conditions in which myelin loss plays a pathological role and has potential to identify new targets for intervention. This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .