Faculty Bibliography

Macrophages accumulate prominently in the visceral adipose tissue (VAT) of obese humans and high fat diet (HFD) fed mice, and this is linked to insulin resistance and type II diabetes. While the mechanisms regulating macrophage recruitment in obesity have been delineated, the signals directing macrophage persistence in VAT are poorly understood. We previously showed that the neuroimmune guidance cue netrin-1 is expressed in the VAT of obese mice and humans, where it promotes macrophage accumulation. To better understand the source of netrin-1 and its effects on adipose tissue macrophage (ATM) fate and function in obesity, we generated mice with myeloid-specific deletion of netrin-1 (Ntn1^fl/flLysMCre^+/-; Ntn1^Δmac). Interestingly, Ntn1^Δmac mice showed a modest decrease in HFD-induced adiposity and adipocyte size, in the absence of changes in food intake or leptin, that was accompanied by an increase in markers of adipocyte beiging (Prdm16, UCP-1). Using single cell RNA-seq, combined with conventional histological and flow cytometry techniques, we show that myeloid-specific deletion of netrin-1 caused a 50% attrition of ATMs in HFD-fed mice, particularly of the resident macrophage subset, and altered the phenotype of residual ATMs to enhance lipid handling. Pseudotime analysis of single cell transcriptomes showed that in the absence of netrin-1, macrophages in the obese VAT underwent a phenotypic switch with the majority of ATMs activating a program of genes specialized in lipid handling, including fatty acid uptake and intracellular transport, lipid droplet formation and lipolysis, and regulation of lipid localization. Furthermore, Ntn1^Δmac macrophages had reduced expression of genes involved in arachidonic acid metabolism, and targeted LCMS/MS metabololipidomics analysis revealed decreases in proinflammatory eicosanoids (5-HETE, 6-trans LTB₄, TXB₂, PGD₂) in the obese VAT. Collectively, our data show that targeted deletion of netrin-1 in macrophages reprograms the ATM phenotype in obesity, leading to reduced adipose inflammation, and improved lipid handling and metabolic function.

Diaphanous 1 (DIAPH1), a member of the formin family, binds to the cytoplasmic domain of the receptor for advanced glycation end products (RAGE) and is required for RAGE signal transduction. Experiments employing genetic over-expression or deletion of Ager (the gene encoding RAGE) or its pharmacological antagonism, implicate RAGE in the pathogenesis of diabetes-associated nephropathy. We hypothesized that DIAPH1 contributes to pathological and functional derangements in the kidneys of diabetic mice. Here, we show that DIAPH1 is expressed in the human and murine diabetic kidney, at least in part in the tubulointerstitium and glomerular epithelial cells, or podocytes. To test the premise that DIAPH1 is linked to diabetes-associated derangements in the kidney, we rendered male mice globally devoid of Diaph1 or wild-type controls (C57BL/6 background), diabetic with streptozotocin. Control mice received equal volumes of citrate buffer. After six months of hyperglycemia, diabetic mice devoid of Diaph1 displayed significantly reduced mesangial sclerosis, podocyte effacement, glomerular basement thickening, and urine albumin/creatinine ratio, compared to diabetic mice expressing Diaph1. Analysis of whole kidney cortex revealed that deletion of Diaph1 in diabetic mice significantly reduced expression of genes linked to fibrosis and inflammation. In glomerular isolates, expression of two genes linked to podocyte stress, Gas1 and Cd36, was significantly attenuated in diabetic mice devoid of Diaph1 vs. controls, in parallel with significantly higher levels of Nes mRNA, a podocyte marker. Collectively, these data implicate DIAPH1 in the pathogenesis of diabetes-associated nephropathy and suggest that RAGE/DIAPH1 is a logical target for therapeutic intervention in this disorder.

PURPOSE/OBJECTIVE:integrins in a mouse hindlimb ischemia model of peripheral artery disease. PROCEDURES/METHODS:, VEGFR-1, VEGFR-2, as well as certain cell lineage markers. RESULTS:with endothelial cell marker FVIII, but not with CD31. Immunostaining for VEGFR-1 and VEGFR-2 additionally co-localized with lineage markers for endothelial progenitor cell and monocytes/macrophages, with a more diverse pattern of co-localization for VEGFR-2. CONCLUSION/CONCLUSIONS:Tc]scV may be due to the presence of VEGF receptors on additional cell types.

PURPOSE/OBJECTIVE:The soluble receptor for advanced glycation end-products (sRAGE) and endogenous secretory RAGE (esRAGE) have been considered as biomarkers of several chronic diseases. However, the temporal reliability of their concentrations in the circulation is yet to be demonstrated. We evaluated whether a single measurement of serum sRAGE and esRAGE could serve as an estimate for usual serum levels in epidemiologic studies. METHODS:Serum sRAGE and esRAGE were measured using ELISAs in three yearly samples from 36 participants in the New York University Women's Health Study. The intraclass correlation coefficient (ICC) was used to evaluate temporal reliability. RESULTS:-transformed data. CONCLUSION/CONCLUSIONS:Our results indicate that a single measurement of serum sRAGE and esRAGE is a sufficiently reliable measure of their usual levels that can be used in epidemiologic studies.

Islet amyloid formation contributes to β-cell death and dysfunction in type-2 diabetes and to the failure of islet transplants. Amylin (Islet amyloid polypeptide, IAPP), a normally soluble 37 residue polypeptide hormone produced in the pancreatic β-cells, is responsible for amyloid formation in type-2 diabetes. The peptide is deficient in type-1 diabetes. Amylin normally plays an adaptive role in metabolism and the development of non-toxic, non-amyloidogenic, bioactive variants of human amylin are of interest for use as adjuncts to insulin therapy. Naturally occurring non-amyloidogenic variants are of interest for xenobiotic transplantation and because they can provide clues towards understanding the amyloidogenicity of human amylin. The sequence of amylin is well conserved among species, but sequence differences strongly correlate with in vitro amyloidogenicity and with islet amyloid formation in vivo. Bovine amylin differs from the human peptide at ten positions and is one of the most divergent among known amylin sequences. We show that bovine amylin oligomerizes, but is not toxic to cultured β-cells and is considerably less amyloidogenic than the human polypeptide and is only a low potency agonist at human amylin-responsive receptors. The bovine sequence contains several non-conservative substitutions relative to human amylin including His to Pro, Ser to Pro and Asn to Lys replacements. The effect of these substitutions is analyzed in the context of wild type human amylin; the results provide insight into their role in receptor activation, the mode of assembly of human amylin and into the design of soluble amylin analogs.

Cigarette smoking alters the oral microbiome; however, the effect of alternative tobacco products remains unclear. Middle Eastern tobacco products like dokha and shisha, are becoming globally widespread. We tested for the first time in a Middle Eastern population the hypothesis that different tobacco products impact the oral microbiome. The oral microbiome of 330 subjects from the United Arab Emirates Healthy Future Study was assessed by amplifying the bacterial 16S rRNA gene from mouthwash samples. Tobacco consumption was assessed using a structured questionnaire and further validated by urine cotinine levels. Oral microbiome overall structure and specific taxon abundances were compared, using PERMANOVA and DESeq analyses respectively. Our results show that overall microbial composition differs between smokers and nonsmokers (p = 0.0001). Use of cigarettes (p = 0.001) and dokha (p = 0.042) were associated with overall microbiome structure, while shisha use was not (p = 0.62). The abundance of multiple genera were significantly altered (enriched/depleted) in cigarette smokers; however, only Actinobacillus, Porphyromonas, Lautropia and Bifidobacterium abundances were significantly changed in dokha users whereas no genera were significantly altered in shisha smokers. For the first time, we show that smoking dokha is associated to oral microbiome dysbiosis, suggesting that it could have similar effects as smoking cigarettes on oral health.

Proteotoxicity plays a key role in many devastating human disorders, including Alzheimer's, Huntington's and Parkinson's diseases; type 2 diabetes; systemic amyloidosis; and cardiac dysfunction, to name a few. The cellular mechanisms of proteotoxicity in these disorders have been the focus of considerable research, but their role in prevalent and morbid disorders, such as diabetes, is less appreciated. There is a large body of literature on the impact of glucotoxicity and lipotoxicity on insulin-producing pancreatic β-cells, and there is increasing recognition that proteotoxicty plays a key role. Pancreatic islet amyloidosis by the hormone IAPP, the production of advanced glycation endproducts, and insulin misprocessing into cytotoxic aggregates are all sources of β-cell proteotoxicity in diabetes. Advanced glycation endproducts, produced by the reaction of reducing sugars with proteins and lipids are ligands for the receptor for advanced glycation endproducts (RAGE), as are the toxic pre-fibrillar aggregates of IAPP produced during amyloid formation. The mechanisms of amyloid formation by IAPP in vivo or in vitro are not well understood, and the cellular mechanisms of IAPP-induced β-cell death are not fully defined. Here, we review recent findings that illuminate the factors and mechanisms involved in β-cell proteotoxicity in diabetes. Together, these new insights have far-reaching implications for the establishment of unifying mechanisms by which pathological amyloidoses imbue their injurious effects in vivo.