Article

Amyloid precursor protein expression is upregulated in adipocytes in obesity.

Diabetes and Metabolism Translational Medicine Unit, University of Vermont College of Medicine, Burlington, Vermont, USA.
Obesity (Impact Factor: 4.39). 08/2008; 16(7):1493-500. DOI: 10.1038/oby.2008.267
Source: PubMed

ABSTRACT The aim of this study was to determine whether amyloid precursor protein (APP) is expressed in human adipose tissue, dysregulated in obesity, and related to insulin resistance and inflammation. APP expression was examined by microarray expression profiling of subcutaneous abdominal adipocytes (SAC) and cultured preadipocytes from obese and nonobese subjects. Quantitative real-time PCR (QPCR) was performed to confirm differences in APP expression in SAC and to compare APP expression levels in adipose tissue, adipocytes, and stromal vascular cells (SVCs) from subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) specimens. Adipose tissue samples were also examined by western blot and immunofluorescence confocal microscopy. Microarray studies demonstrated that APP mRNA expression levels were higher in SAC (approximately 2.5-fold) and preadipocytes (approximately 1.4) from obese subjects. Real-time PCR confirmed increased APP expression in SAC in a separate group of obese compared with nonobese subjects (P=0.02). APP expression correlated to in vivo indices of insulin resistance independently of BMI and with the expression of proinflammatory genes, such as monocyte chemoattractant protein-1 (MCP-1) (R=0.62, P=0.004), macrophage inflammatory protein-1alpha (MIP-1alpha) (R=0.60, P=0.005), and interleukin-6 (IL-6) (R=0.71, P=0.0005). Full-length APP protein was detected in adipocytes by western blotting and APP and its cleavage peptides, Abeta40 and Abeta42, were observed in SAT and VAT by immunofluorescence confocal microscopy. In summary, APP is highly expressed in adipose tissue, upregulated in obesity, and expression levels correlate with insulin resistance and adipocyte cytokine expression levels. These data suggest a possible role for APP and/or Abeta in the development of obesity-related insulin resistance and adipose tissue inflammation.

0 Followers
 · 
96 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Adipose tissue inflammation increases with obesity, but adipocyte vs. immune cell contributions are unclear. In the present study, transcriptome analyses were performed on highly-purified subcutaneous adipocytes from lean and obese women, and differentially expressed genes/pathways were determined in both adipocyte and stromal vascular fraction (SVF) samples. Adipocyte but not SVF expression of NOD-like receptor pathway genes, including NLRP3 and PYCARD, which regulate caspase-1-mediated IL-1β secretion, correlated with adiposity phenotypes and adipocyte class II major histocompatibility complex (MHCII) gene expression, but only MHCII remained after adjusting for age and body mass index. IFNγ stimulated adipocyte MHCII, NLRP3 and caspase-1 expression, while adipocyte MHCII-mediated CD4(+) T cell activation, an important factor in adipose inflammation, induced IFNγ-dependent adipocyte IL-1β secretion. These results uncover a dialogue regulated by interactions among T cell IFNγ and adipocyte MHCII and NLRP3 inflammasome activity that appears to initiate and escalate adipose tissue inflammation during obesity.
    Molecular and Cellular Endocrinology 07/2014; 394(1-2). DOI:10.1016/j.mce.2014.06.018 · 4.24 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Antagonists of cannabinoid CB1 receptor (CB1, CNR1) promote weight loss and decrease hyperglycemia in patients with type 2 diabetes. While the endocannabinoid system may modulate islet hormone secretion, the cell-type expressing CB1 receptor in islets has not been fully resolved. In this study, we verified receptor gene expression in rodent islets and cell lines and examined the distribution of CB1 receptor in mouse, rat, and human islets by confocal immunofluorescence (IF) microscopy. IF demonstrated CB1 receptor was present in beta-cell lines, but co-localized solely with somatostatin in the islet delta-cells of Zucker rats, C57BL/6 mice, and humans; no CB1 receptor expression was observed in alpha-, beta-, or pp-cells. Similarly, a rat somatostatinoma cell line, MSL-G2-Tu6, was found to express CB1 receptor. We also found monoacylglycerol lipase (MAGL) to be expressed in delta-cells and fatty acid amide hydrolase (FAAH) to be expressed in alpha-cells. The specific expression of CB1 in delta-cells suggests that the ECS may play a role in modulating islet hormone secretion. As there are some differences between our findings and previous reports, further studies, including detailed physiological studies of the effects of the ECS on islet function, are warranted.
    Biochemical and Biophysical Research Communications 09/2008; 372(4):595-600. DOI:10.1016/j.bbrc.2008.05.077 · 2.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The renin-angiotensin system (RAS) may play a role in dementia pathogenesis because of its effects on vascular and metabolic homeostasis, amyloid metabolism, and learning and memory. The angiotensin-converting enzyme (ACE), a pivotal RAS protein, is encoded for by a gene containing a functional ID variant, which has been related to dementia risk. We examined the relationship between the ACE Insertion Deletion (ACE ID) variant and dementia with consideration for metabolic phenotypes, age and APOEepsilon4 using a population-based, cross-sectional sample of 891 Swedish women and men aged 70-92 years, of whom 61 people were demented. The odds of dementia was two-fold higher among those with ACE II genotype, and ranged from 2.18 to 4.35 among those with dementia onset <or=70 years, an APOEepsilon4 allele, systolic blood pressure <160 mmHg, body mass index <25 kg/m(2), and in women only, waist circumference <or=88 cm and hip circumference <101 cm. Variations among reports on the relationship between the ACE ID polymorphism and dementia may be due to lack of consideration for gene-gene and gene-phenotype associations.
    Neurobiology of aging 10/2008; 31(6):910-6. DOI:10.1016/j.neurobiolaging.2008.07.015 · 4.85 Impact Factor

Preview

Download
0 Downloads