Vitamin D receptor-mediated stromal reprogramming suppresses pancreatitis and enhances pancreatic cancer therapy.

The poor clinical outcome in pancreatic ductal adenocarcinoma (PDA) is attributed to intrinsic chemoresistance and a growth-permissive tumor microenvironment. Conversion of quiescent to activated pancreatic stellate cells (PSCs) drives the severe stromal reaction that characterizes PDA. Here, we reveal that the vitamin D receptor (VDR) is expressed in stroma from human pancreatic tumors and that treatment with the VDR ligand calcipotriol markedly reduced markers of inflammation and fibrosis in pancreatitis and human tumor stroma. We show that VDR acts as a master transcriptional regulator of PSCs to reprise the quiescent state, resulting in induced stromal remodeling, increased intratumoral gemcitabine, reduced tumor volume, and a 57% increase in survival compared to chemotherapy alone. This work describes a molecular strategy through which transcriptional reprogramming of tumor stroma enables chemotherapeutic response and suggests vitamin D priming as an adjunct in PDA therapy. PAPERFLICK:

A vitamin D receptor/SMAD genomic circuit gates hepatic fibrotic response.

Liver fibrosis is a reversible wound-healing response involving TGFß1/SMAD activation of hepatic stellate cells (HSCs). It results from excessive deposition of extracellular matrix components and can lead to impairment of liver function. Here, we show that vitamin D receptor (VDR) ligands inhibit HSC activation by TGFß1 and abrogate liver fibrosis, whereas Vdr knockout mice spontaneously develop hepatic fibrosis. Mechanistically, we show that TGFß1 signaling causes a redistribution of genome-wide VDR-binding sites (VDR cistrome) in HSCs and facilitates VDR binding at SMAD3 profibrotic target genes via TGFß1-dependent chromatin remodeling. In the presence of VDR ligands, VDR binding to the coregulated genes reduces SMAD3 occupancy at these sites, inhibiting fibrosis. These results reveal an intersecting VDR/SMAD genomic circuit that regulates hepatic fibrogenesis and define a role for VDR as an endocrine checkpoint to modulate the wound-healing response in liver. Furthermore, the findings suggest VDR ligands as a potential therapy for liver fibrosis.

Vitamin D and Beta Cells in Type 1 Diabetes: A Systematic Review.

The prevalence of type 1 diabetes (T1D) is rising steadily. A potential contributor to the rise is vitamin D. In this systematic review, we examined the literature around vitamin D and T1D. We identified 22 papers examining the role of vitamin D in cultured ß-cell lines, islets, or perfused pancreas, and 28 papers examining vitamin D in humans or human islets. The literature reports strong associations between T1D and low circulating vitamin D. There is also high-level (systematic reviews, meta-analyses) evidence that adequate vitamin D status in early life reduces T1D risk. Several animal studies, particularly in NOD mice, show harm from D-deficiency and benefit in most studies from vitamin D treatment/supplementation. Short-term streptozotocin studies show a ß-cell survival effect with supplementation. Human studies report associations between VDR polymorphisms and T1D risk and ß-cell function, as assessed by C-peptide. In view of those outcomes, the variable results in human trials are generally disappointing. Most studies using 1,25D, the active form of vitamin D were ineffective. Similarly, studies using other forms of vitamin D were predominantly ineffective. However, it is interesting to note that all but one of the studies testing 25D reported benefit. Together, this suggests that maintenance of optimal circulating 25D levels may reduce the risk of T1D and that it may have potential for benefits in delaying the development of absolute or near-absolute C-peptide deficiency. Given the near-complete loss of ß-cells by the time of clinical diagnosis, vitamin D is much less likely to be useful after disease-onset. However, given the very low toxicity of 25D, and the known benefits of preservation of C-peptide positivity for long-term complications risk, we recommend considering daily cholecalciferol supplementation in people with T1D and people at high risk of T1D, especially if they have vitamin D insufficiency.

A fluorescent timer reporter enables sorting of insulin secretory granules by age.

Within the pancreatic ß-cells, insulin secretory granules (SGs) exist in functionally distinct pools, displaying variations in motility as well as docking and fusion capability. Current therapies that increase insulin secretion do not consider the existence of these distinct SG pools. Accordingly, these approaches are effective only for a short period, with a worsening of glycemia associated with continued decline in ß-cell function. Insulin granule age is underappreciated as a determinant for why an insulin granule is selected for secretion and may explain why newly synthesized insulin is preferentially secreted from ß-cells. Here, using a novel fluorescent timer protein, we aimed to investigate the preferential secretion model of insulin secretion and identify how granule aging is affected by variation in the ß-cell environment, such as hyperglycemia. We demonstrate the use of a fluorescent timer construct, syncollin-dsRedE5TIMER, which changes its fluorescence from green to red over 18 h, in both microscopy and fluorescence-assisted organelle-sorting techniques. We confirm that the SG-targeting construct localizes to insulin granules in ß-cells and does not interfere with normal insulin SG behavior. We visualize insulin SG aging behavior in MIN6 and INS1 ß-cell lines and in primary C57BL/6J mouse and nondiabetic human islet cells. Finally, we separated young and old insulin SGs, revealing that preferential secretion of younger granules occurs in glucose-stimulated insulin secretion. We also show that SG population age is modulated by the ß-cell environment in vivo in the db/db mouse islets and ex vivo in C57BL/6J islets exposed to different glucose environments.

First World Consensus Conference on pancreas transplantation: Part II - recommendations.

The First World Consensus Conference on Pancreas Transplantation provided 49 jury deliberations regarding the impact of pancreas transplantation on the treatment of diabetic patients, and 110 experts' recommendations for the practice of pancreas transplantation. The main message from this consensus conference is that both simultaneous pancreas-kidney transplantation (SPK) and pancreas transplantation alone can improve long-term patient survival, and all types of pancreas transplantation dramatically improve the quality of life of recipients. Pancreas transplantation may also improve the course of chronic complications of diabetes, depending on their severity. Therefore, the advantages of pancreas transplantation appear to clearly surpass potential disadvantages. Pancreas after kidney transplantation increases the risk of mortality only in the early period after transplantation, but is associated with improved life expectancy thereafter. Additionally, preemptive SPK, when compared to SPK performed in patients undergoing dialysis, appears to be associated with improved outcomes. Time on dialysis has negative prognostic implications in SPK recipients. Increased long-term survival, improvement in the course of diabetic complications, and amelioration of quality of life justify preferential allocation of kidney grafts to SPK recipients. Audience discussions and live voting are available online at the following URL address: http://mediaeventi.unipi.it/category/1st-world-consensus-conference-of-pancreas-transplantation/246.

Vitamin C improves healing of foot ulcers: a randomised, double-blind, placebo-controlled trial.

Chronic foot ulcers are associated with a high risk of osteomyelitis, poor quality of life, amputations and disability. Few strategies improve their healing, and amputation rates in high-risk foot services are usually over 30 %. We conducted a randomised, inactive-placebo controlled, double-blind trial of 500 mg of slow-release vitamin C in sixteen people with foot ulcers in the Foot Wound Clinic at Westmead Hospital. Nine were randomised to control and seven to vitamin C. When serum vitamin C results become available at 4 weeks, all people with deficiency were offered both vitamin C and glucosamine tablets for the next 4 weeks. Patients without baseline deficiency continued their original assigned treatment. The primary outcome was percentage ulcer healing (reduction in ulcer size) at 8 weeks. Fifty percentage of subjects had baseline vitamin C deficiency, half having undetectable levels. Healing at 8 weeks was significantly better in the vitamin C group (median 100 v. -14 %, P = 0·041). Healing without amputation occurred in all patients in the vitamin C group. In contrast, 44 % of controls had not healed their ulcer at the end of the study period. Vitamin C improved healing of foot ulcers. Further studies are needed to determine whether there is a threshold effect for serum vitamin C above which therapy is ineffective and whether there are better or lesser responding subgroups. Because of its low cost and ease of access and administration, we recommend offering vitamin C therapy to all people who have chronic foot ulcers and potentially suboptimal vitamin C intake. Trial registration number: ACTRN12617001142325.

Differential associations of ferritin and 25-hydroxyvitamin D with fasting glucose and diabetes risk in community dwelling older men.

AIMS: We examined associations of ferritin and 25-hydroxyvitamin D with fasting glucose and prevalent diabetes in older men. METHODS: Cross-sectional analysis of 4153 community-dwelling men aged 70 to 89 years in Western Australia. Plasma ferritin, 25-hydroxyvitamin D, and glucose were assayed. Diabetes was ascertained from self-report, medications, and fasting glucose. RESULTS: There were 577 men with diabetes (13.9%). In the whole cohort, ferritin was associated with fasting glucose (0.051 mmol/L per 1 SD increase in ferritin, P = .006) and 25-hydroxyvitamin D was inversely associated (-0.085 mmol/L per 1 SD, P < .001). Ferritin was not associated with prevalent diabetes (highest vs. lowest quartile; >225 vs <66 µg/L: adjusted odds ratio [OR] 0.97, 95% confidence interval [CI], 0.74-1.27, P = .83). Higher vitamin D was associated with decreased odds of prevalent diabetes (highest vs lowest quartile; >82 nmol/L vs <53 nmol/L: OR = 0.57, 95% CI = 0.43-0.75, P < .001). There was no interaction between ferritin and vitamin D on diabetes risk. CONCLUSIONS: In older men, ferritin is associated with fasting glucose but not prevalent diabetes. Higher 25-hydroxyvitamin D concentrations are independently associated with lower fasting glucose and reduced risk of diabetes. Clinical trials are required to determine whether interventions, which raise vitamin D concentrations, would reduce incidence of diabetes in this expanding demographic group.

The Changing Landscape of Pharmacotherapy for Diabetes Mellitus: A Review of Cardiovascular Outcomes.

The prevention of cardiovascular morbidity and mortality has always been a primary concern in patients with type 2 diabetes. Modern trials of glucose-lowering therapies now assess major adverse cardiac events as an endpoint in addition to the effects on glycaemic control. Whilst the data on the efficacy of intensive glucose lowering on reducing cardiovascular risk are limited, there are now increasing numbers of glucose-lowering therapies that have proven cardiovascular benefit independent of glucose lowering. This review will summarise the available literature on cardiovascular outcomes in relation to metformin, sulphonylureas, di-peptidyl peptidase-4 inhibitors, glucagon-like peptide receptor agonists, sodium-glucose co-transporter 2 inhibitors, thiazolidinediones, acarbose and insulin. In addition, new paradigms in diabetes management and the importance of treatment selection based on considerations including but not limited to glycaemic control will be discussed.

Vitamin D Improves Cardiac Function After Myocardial Infarction Through Modulation of Resident Cardiac Progenitor Cells.

BACKGROUND: Vitamin D has been implicated in the prevention of heart failure. However the underlying mechanism remains unclear. We hypothesised that these effects may be partially mediated by cardiac stem/progenitor cells (CPCs). Therefore, we examined the effects of 1,25-dihydroxyvitamin D3 (1,25D) on cell cycle activity and differentiation of a previously described CPC population called cardiac colony-forming unit fibroblasts (cCFU-Fs). METHODS: cCFU-Fs were isolated from adult male C57Bl/6 mouse hearts using fluorescence-activated cell sorting. The effect of 1,25D on cell proliferation and differentiation were was assessed by colony-forming and fibroblast differentiation assays. Cell cycle was analysed by flow cytometry. Mice with induced myocardial infarction (MI) were treated with 1,25D or vehicle controls and cardiac function assessed by echocardiography. RESULTS: 1,25D dose-dependently increased expression of vitamin D receptor (Vdr) and reduced large colony formation. Addition of 1,25D to cCFU-Fs slowed cell proliferation, promoted cell cycle arrest and decreased expression of pro-fibrotic factors during TGF-ß-induced fibroblast differentiation of cCFU-Fs. After MI, 1,25D-treated mice had less left ventricular wall thinning and significant improvement in left ventricular systolic function compared to vehicle-treated controls. Although no significant changes in myocardial fibrotic area and cardiomyocyte size were noted, treatment with 1,25D significantly inhibited cardiac interstitial cell proliferation after MI. CONCLUSIONS: Vitamin D signalling promotes cardioprotection after myocardial infarction. This may be through modulation of cCFU-F cell cycle. The role of 1,25D and VDR in regulating cardiac stem/progenitor cell function therefore warrants further investigation.

Transplantation sites for human and murine islets.

AIMS/HYPOTHESIS: Beta cell replacement is a potential cure for type 1 diabetes. In humans, islet transplants are currently infused into the liver via the portal vein, although this site has disadvantages. Here, we investigated alternative transplantation sites for human and murine islets in recipient mice, comparing the portal vein with quadriceps muscle and kidney, liver and spleen capsules. METHODS: Murine islets were isolated from C57BL6/J mice and transplanted into syngeneic recipients. Human islets were isolated and transplanted into either severe combined immunodeficiency (SCID) or recombination-activating gene 1 (RAG-1) immunodeficient recipient mice. All recipient mice were 8-12 weeks of age and had been rendered diabetic (defined as blood glucose concentrations ≥20 mmol/l on two consecutive days before transplantation) by alloxan tetrahydrate treatment. Islets were transplanted into five different sites (portal vein, quadriceps muscle, kidney, liver and spleen capsules). Blood glucose concentrations were monitored twice weekly until mice were killed. Dose-response studies were also performed to determine the minimum number of islets required to cure diabetes ('cure' is defined for this study as random fed blood glucose of <15 mmol/l). RESULTS: For transplantation of murine islets into the different sites, the kidney yielded 100% success, followed by muscle (70%), portal vein (60%), spleen capsule (29%) and liver capsule (0%). For human islets, transplantation into the kidney cured diabetes in 75-80% of recipient mice. Transplantation into muscle and portal vein had intermediate success (both 29% at 2000 islet equivalents), while transplantation into liver and spleen capsule failed (0%). With increased islet mass, success rates for muscle grafts improved to 52-56%. CONCLUSIONS/INTERPRETATION: For both human and murine islets, equivalent or superior glucose lowering results were obtained for transplantation into skeletal muscle, compared with the portal vein. Unfortunately, kidney grafts are not feasible in human recipients. Skeletal muscle offers easier access and greater potential for protocol biopsies. This study suggests that human trials of muscle as a transplant site may be warranted.

Transplantation sites for porcine islets.

AIMS/HYPOTHESIS: Xenotransplantation has great potential to provide beta cell replacement and thereby provide a cure for large numbers of people with type 1 diabetes. Crucial to the success of xenotransplantation is establishment of the most viable sites for transplantation. METHODS: We compared porcine islet tissue transplanted into kidney, liver and spleen in pig recipients as assessed by blood glucose levels and IVGTT. RESULTS: Kidney was the superior site for porcine islet tissue transplantation, followed by liver then spleen. This was demonstrated by IVGTTs showing significant difference between the peak glucose levels: 22.8 ± 2.9 mmol/l for kidney compared with 26.8 ± 1.3 mmol/l for spleen and 24.7 ± 1.7 mmol/l for liver. CONCLUSIONS/INTERPRETATION: Kidney grafts are not as feasible in humans and liver results were relatively poorer than spleen. For islet transplantation to be viable and successful in the longer term, there remains a need for future investigation of alternative sites.

Vitamin D in liver disease: Current evidence and potential directions.

Consistent with its multifaceted nature, growing evidence links vitamin D with hepatic disease. In this review, we summarise the roles of vitamin D in different liver pathologies and explore the clinical utility of vitamin D-based treatments in hepatology. We find that the small number of clinical trials coupled with the profound heterogeneity of study protocols limits the strength of evidence needed to ascribe definite clinical value to the hormone in liver disease. Nevertheless, the experimental data is promising and further bench and bedside studies will likely define a clearer role in hepatic therapeutics.

Diabetes Medications and Cardiovascular Outcomes in Type 2 Diabetes.

INTRODUCTION: Patients with type 2 diabetes have an increased risk of developing adverse cardiovascular (CV) outcomes. The evidence relating to the effects of glucose-lowering medications on CV outcomes is of variable quality and there are numerous trials ongoing. RESULTS: In this review, we summarise the available literature on CV outcomes of the following diabetes treatments: metformin, the sulfonylureas, acarbose, glucagon-like peptide 1 (GLP1) receptor agonists, dipeptidyl peptidase-4 inhibitors (DPP4i), sodium-glucose co-transporter 2 inhibitors (SGLT2i), thiazolidinediones (TZDs) and insulin. CONCLUSIONS: Insulin is required if glucose levels are very high. Otherwise, metformin, acarbose, some GLP1 receptor agonists and one SGLT2i appear beneficial for CV outcomes.

Changes in beta cell function occur in prediabetes and early disease in the Lepr (db) mouse model of diabetes.

AIMS/HYPOTHESIS: Type 2 diabetes is a progressive disease that increases morbidity and the risk of premature death. Glucose dysregulation, such as elevated fasting blood glucose, is observed prior to diabetes onset. A decline in beta cell insulin secretion contributes to the later stages of diabetes, but it is not known what, if any, functional beta cell changes occur in prediabetes and early disease. METHODS: The Lepr (db) mouse (age 13-18 weeks) was used as a model of type 2 diabetes and a two-photon granule fusion assay was used to characterise the secretory response of pancreatic beta cells. RESULTS: We identified a prediabetic state in db/db mice where the animals responded normally to a glucose challenge but have elevated fasting blood glucose. Isolated islets from prediabetic animals secreted more and were bigger. Insulin secretion, normalised to insulin content, was similar to wild type but basal insulin secretion was elevated. There was increased glucose-induced granule fusion with a high prevalence of granule-granule fusion. The glucose-induced calcium response was not changed but there was altered expression of the exocytic machinery. db/db animals at the next stage of disease had overt glucose intolerance. Isolated islets from these animals had reduced insulin secretion, reduced glucose-induced granule fusion events and decreased calcium responses to glucose. CONCLUSIONS/INTERPRETATION: Beta cell function is altered in prediabetes and there are further changes in the progression to early disease.

Hypoxia reduces ER-to-Golgi protein trafficking and increases cell death by inhibiting the adaptive unfolded protein response in mouse beta cells.

AIMS/HYPOTHESIS: Hypoxia may contribute to beta cell failure in type 2 diabetes and islet transplantation. The adaptive unfolded protein response (UPR) is required for endoplasmic reticulum (ER) homeostasis. Here we investigated whether or not hypoxia regulates the UPR in beta cells and the role the adaptive UPR plays during hypoxic stress. METHODS: Mouse islets and MIN6 cells were exposed to various oxygen (O2) tensions. DNA-damage inducible transcript 3 (DDIT3), hypoxia-inducible transcription factor (HIF)1α and HSPA5 were knocked down using small interfering (si)RNA; Hspa5 was also overexpressed. db/db mice were used. RESULTS: Hypoxia-response genes were upregulated in vivo in the islets of diabetic, but not prediabetic, db/db mice. In isolated mouse islets and MIN6 cells, O2 deprivation (1-5% vs 20%; 4-24 h) markedly reduced the expression of adaptive UPR genes, including Hspa5, Hsp90b1, Fkbp11 and spliced Xbp1. Coatomer protein complex genes (Copa, Cope, Copg [also known as Copg1], Copz1 and Copz2) and ER-to-Golgi protein trafficking were also reduced, whereas apoptotic genes (Ddit3, Atf3 and Trb3 [also known as Trib3]), c-Jun N-terminal kinase (JNK) phosphorylation and cell death were increased. Inhibition of JNK, but not HIF1α, restored adaptive UPR gene expression and ER-to-Golgi protein trafficking while protecting against apoptotic genes and cell death following hypoxia. DDIT3 knockdown delayed the loss of the adaptive UPR and partially protected against hypoxia-induced cell death. The latter response was prevented by HSPA5 knockdown. Finally, Hspa5 overexpression significantly protected against hypoxia-induced cell death. CONCLUSIONS/INTERPRETATION: Hypoxia inhibits the adaptive UPR in beta cells via JNK and DDIT3 activation, but independently of HIF1α. Downregulation of the adaptive UPR contributes to reduced ER-to-Golgi protein trafficking and increased beta cell death during hypoxic stress.

Subcutaneous fat transplantation alleviates diet-induced glucose intolerance and inflammation in mice.

AIMS/HYPOTHESIS: Adipose tissue (AT) distribution is a major determinant of mortality and morbidity in obesity. In mice, intra-abdominal transplantation of subcutaneous AT (SAT) protects against glucose intolerance and insulin resistance (IR), but the underlying mechanisms are not well understood. METHODS: We investigated changes in adipokines, tissue-specific glucose uptake, gene expression and systemic inflammation in male C57BL6/J mice implanted intra-abdominally with either inguinal SAT or epididymal visceral AT (VAT) and fed a high-fat diet (HFD) for up to 17 weeks. RESULTS: Glucose tolerance was improved in mice receiving SAT after 6 weeks, and this was not attributable to differences in adiposity, tissue-specific glucose uptake, or plasma leptin or adiponectin concentrations. Instead, SAT transplantation prevented HFD-induced hepatic triacylglycerol accumulation and normalised the expression of hepatic gluconeogenic enzymes. Grafted fat displayed a significant increase in glucose uptake and unexpectedly, an induction of skeletal muscle-specific gene expression. Mice receiving subcutaneous fat also displayed a marked reduction in the plasma concentrations of several proinflammatory cytokines (TNF-α, IL-17, IL-12p70, monocyte chemoattractant protein-1 [MCP-1] and macrophage inflammatory protein-1ß [ΜIP-1ß]), compared with sham-operated mice. Plasma IL-17 and MIP-1ß concentrations were reduced from as early as 4 weeks after transplantation, and differences in plasma TNF-α and IL-17 concentrations predicted glucose tolerance and insulinaemia in the entire cohort of mice (n = 40). In contrast, mice receiving visceral fat transplants were glucose intolerant, with increased hepatic triacylglycerol content and elevated plasma IL-6 concentrations. CONCLUSIONS/INTERPRETATION: Intra-abdominal transplantation of subcutaneous fat reverses HFD-induced glucose intolerance, hepatic triacylglycerol accumulation and systemic inflammation in mice.

Higher ferritin levels, but not serum iron or transferrin saturation, are associated with Type 2 diabetes mellitus in adult men and women free of genetic haemochromatosis.

CONTEXT: Iron overload predisposes to diabetes and higher ferritin levels have been associated with diabetes. However, it is unclear whether ferritin reflects differences in iron-related parameters between diabetic and nondiabetic persons. We examined associations of serum ferritin, iron and transferrin saturation with Type 2 diabetes in adults without genetic predisposition to iron overload. DESIGN, PARTICIPANTS AND MEASUREMENTS: Cross-sectional analysis of community-dwelling men and women aged 17-97 years from the Busselton Health Survey, Western Australia. Men and women carrying genotypes associated with haemochromatosis (C282Y/C282Y or C282Y/H63D) were excluded. Serum ferritin, iron and transferrin saturation were assayed. RESULTS: There were 1834 men (122 with diabetes, 6·6%) and 2351 women (141 with diabetes, 6%). In men, higher serum ferritin was associated with diabetes after adjusting for age, smoking, alcohol, cardiovascular history, body mass index (BMI), waist, blood pressure, lipids, C-reactive protein (CRP), adiponectin, alanine transaminase (ALT) and gamma-glutamyl transpeptidase (GGT) [odds ratio (OR): 1·29 per 1 unit increase log ferritin, 95% confidence interval (CI) = 1·01-1·65, P = 0·043]. In women, higher serum ferritin was associated with diabetes [fully adjusted OR: 1·31 per 1 unit increase log ferritin, 95% CI = 1·04-1·63, P = 0·020; 1·84 for tertile (T) 3 vs T1, 95% CI = 1·09-3·11]. Neither iron levels nor transferrin saturation were associated with diabetes risk in men or women. Higher ferritin was not associated with insulin resistance in nondiabetic adults. CONCLUSIONS: In adults, higher ferritin levels are independently associated with prevalent diabetes while iron and transferrin saturation are not. Ferritin is a robust biomarker for diabetes risk, but further investigation is needed to clarify whether this relationship is mediated via iron metabolism.

Vitamin D Receptor Ablation and Vitamin D Deficiency Result in Reduced Grip Strength, Altered Muscle Fibers, and Increased Myostatin in Mice.

Vitamin D deficiency is associated with muscle weakness, pain, and atrophy. Serum vitamin D predicts muscle strength and age-related muscle changes. However, precise mechanisms by which vitamin D affects skeletal muscle are unclear. To address this question, this study characterizes the muscle phenotype and gene expression of mice with deletion of vitamin D receptor (VDRKO) or diet-induced vitamin D deficiency. VDRKO and vitamin D-deficient mice had significantly weaker grip strength than their controls. Weakness progressed with age and duration of vitamin D deficiency, respectively. Histological assessment showed that VDRKO mice had muscle fibers that were significantly smaller in size and displayed hyper-nuclearity. Real-time PCR also indicated muscle developmental changes in VDRKO mice with dysregulation of myogenic regulatory factors (MRFs) and increased myostatin in quadriceps muscle (>2-fold). Vitamin D-deficient mice also showed increases in myostatin and the atrophy marker E3-ubiqutin ligase MuRF1. As a potential explanation for grip strength weakness, both groups of mice had down-regulation of genes encoding calcium-handling and sarco-endoplasmic reticulum calcium transport ATPase (Serca) channels. This is the first report of reduced strength, morphological, and gene expression changes in VDRKO and vitamin D-deficient mice where confounding by calcium, magnesium, and phosphate have been excluded by direct testing. Although suggested in earlier in vitro work, this study is the first to report an in vivo association between vitamin D, myostatin, and the regulation of muscle mass. These findings support a direct role for vitamin D in muscle function and corroborate earlier work on the presence of VDR in this tissue.

Reduction of ARNT in myeloid cells causes immune suppression and delayed wound healing.

Aryl hydrocarbon receptor nuclear translocator (ARNT) is a transcription factor that binds to partners to mediate responses to environmental signals. To investigate its role in the innate immune system, floxed ARNT mice were bred with lysozyme M-Cre recombinase animals to generate lysozyme M-ARNT (LAR) mice with reduced ARNT expression. Myeloid cells of LAR mice had altered mRNA expression and delayed wound healing. Interestingly, when the animals were rendered diabetic, the difference in wound healing between the LAR mice and their littermate controls was no longer present, suggesting that decreased myeloid cell ARNT function may be an important factor in impaired wound healing in diabetes. Deferoxamine (DFO) improves wound healing by increasing hypoxia-inducible factors, which require ARNT for function. DFO was not effective in wounds of LAR mice, again suggesting that myeloid cells are important for normal wound healing and for the full benefit of DFO. These findings suggest that myeloid ARNT is important for immune function and wound healing. Increasing ARNT and, more specifically, myeloid ARNT may be a therapeutic strategy to improve wound healing.