Obesity promotes adipose tissue inflammation and leads to impaired local but also systemic immune cell homeostasis. This chronic low-grade inflammation plays a significant role in the development of obesity-associated secondary diseases such as metabolic associated fatty liver disease or cancer. The spleen as the central organ of immune cell regulation is anatomically directly connected to the visceral adipose tissue and the liver via the portal vein circulation. However, the inter-organ crosstalk and linkage between obesity-induced systemic, hepatic and splenic immune cell dysregulation is not clearly outlined. In this study blood, spleen, and liver immune cells of non-obese wildtype vs. leptin deficient obese BTBR mice were isolated and analyzed in terms of leukocyte composition by flow cytometry. Significant differences between circulating, spleen- and liver-resident immune cell distribution revealed, that obesity-induced hepatic and systemic immune cell dysregulation is distinct from splenic immune cell reprogramming. Fatty liver inflammation was associated with splenic myeloid derived suppressor cell (MDSC) and natural killer T cell (NKT) enrichment whereas loss of hepatic T and B cells was not reflected by the splenic lymphocyte landscape. Correlation analysis confirmed a selective strong positive correlation between spleen and liver MDSC and NKT cell distribution indicating that the spleen-liver axis modulates obesity-induced immune dysregulation in a cell-specific manner. Similar results were observed in a diet-induced obesity mouse model. These data provide novel insights into the role of the spleen-liver axis in obesity-induced inflammation and foster the understanding of obesity-associated complications such as fatty liver disease and cancer.

Introduction Allograft rejection is still an important complication after kidney transplantation. Currently, monitoring of these patients mostly relies on the measurement of serum creatinine and clinical evaluation. The gold standard for diagnosing allograft rejection, i.e. performing a renal biopsy is invasive and expensive. So far no adequate biomarkers are available for routine use. Objectives We aimed to develop a urine metabolite constellation that is characteristic for acute renal allograft rejection. Methods NMR-Spectroscopy was applied to a training cohort of transplant recipients with and without acute rejection. Results We obtained a metabolite constellation of four metabolites that shows promising performance to detect renal allograft rejection in the cohorts used (AUC of 0.72 and 0.74, respectively). Conclusion A metabolite constellation was defined with the potential for further development of an in-vitro diagnostic test that can support physicians in their clinical assessment of a kidney transplant patient.

The hypoxia-inducible factor 1α (Hif1α) represents the master transcription factor coordinating cellular responses to oxygen depletion. With hundreds of target genes it plays a key role in numerous bio-medical conditions as well as neoplastic and non-cancerous diseases, which in turn requires a strict regulation. Long non-coding RNAs have the potential to virtually control every step of gene expression. We aimed to investigate the expression and role of HIF1A antisense lncRNAs HIF1A-AS1, AS2, and AS3 under hyperglycemic, hypoxic, or both conditions in three non-cancerous human renal cell types: HK-2 cells, primary RPTECs, and mesangial cells. We observed that HIF1A-AS2 and AS3 expression was upregulated under oxygen deprivation. Furthermore, knockdown (KD) of HIF1A-AS3 resulted in a significant reduction of HIF1A-AS2 and even more important of Hif1α in HK-2 cells but not mesangial cells. While KD of HIF1A also had a diminishing effect on HIF1A-AS2 and AS3 RNA levels, KD of HIF1A-AS2 only affected HIF1A-AS3 but not HIF1A. Treating HK-2 cells with Actinomycin D revealed a high HIF1A-AS3 RNA stability. In conclusion, our data reveal a cell-type specific effect of HIF1A-AS3 on HIF1A RNA and protein expression which might allow the development of a cell-type specific HIF1A antagonist based on lncRNAs.

The prevalence of type 2 diabetes mellitus (T2DM) and by association diabetic nephropathy (DN) will continuously increase in the next decades. Nevertheless, the underlying molecular mechanisms are largely unknown and studies on the role of new actors like long non-coding RNAs (lncRNAs) barely exist. In the present study, the inherently insulin-resistant mouse strain “black and tan, brachyuric” (BTBR) served as T2DM model. While wild-type mice do not exhibit pathological changes, leptin-deficient diabetic animals develop a severe T2DM accompanied by a DN, which closely resembles the human phenotype. We analyzed the glomerular expression of lncRNAs from wild-type and diabetic BTBR mice (four, eight, 16, and 24 weeks) applying the “GeneChip Mouse Whole Transcriptome 1.0 ST” array. This microarray covered more lncRNA gene loci than any other array before. Over the observed time, our data revealed differential expression patterns of 1746 lncRNAs, which markedly differed from mRNAs. We identified protein-coding and non-coding genes, that were not only co-located but also co-expressed, indicating a potentially cis-acting function of these lncRNAs. In vitro-experiments strongly suggested a cell-specific expression of these lncRNA-mRNA-pairs. Additionally, protein-coding genes, being associated with significantly regulated lncRNAs, were enriched in various biological processes and pathways, that were strongly linked to diabetes.

Mesangial cells (MCs), substantial cells for architecture and function of the glomerular tuft, take a key role in progression of diabetic kidney disease (DKD). Despite long standing researches and the need for novel therapies, the underlying regulatory mechanisms in MCs are elusive. This applies in particular to long non-coding RNAs (lncRNA) but also microRNAs (miRNAs). In this study, we investigated the expression of nuclear paraspeckle assembly transcript 1 (NEAT1), a highly conserved lncRNA, in several diabetes in-vitro models using human MCs. These cells were treated with high glucose, TGFβ, TNAα, thapsigargin, or tunicamycin. We analyzed the implication of NEAT1 silencing on mesangial cell migration, proliferation, and cell size as well as on mRNA and miRNA expression. Here, the miRNA hsa-miR-339-5p was not only identified as a potential interaction partner for NEAT1 but also for several coding genes. Furthermore, overexpression of hsa-miR-339-5p leads to a MC phenotype comparable to a NEAT1 knockdown. In-silico analyses also underline a relevant role of NEAT1 and hsa-miR-339-5p in mesangial physiology, especially in the context of DKD.

Due to organ shortage and rising life expectancy the age of organ donors and recipients is increasing. Reliable biomarkers of organ quality that predict successful long-term transplantation outcomes are poorly defined. The aim of this study was the identification of age-related markers of kidney function that might accurately reflect donor organ quality. Histomorphometric, biochemical and molecular parameters were measured in young (3-month-old) and old (24-month-old) male Sprague Dawley rats. In addition to conventional methods, we used urine metabolomics by NMR spectroscopy and gene expression analysis by quantitative RT-PCR to identify markers of ageing relevant to allograft survival. Beside known markers of kidney ageing like albuminuria, changes in the concentration of urine metabolites such as trimethylamine-N-oxide, trigonelline, 2-oxoglutarate, citrate, hippurate, glutamine, acetoacetate, valine and 1-methyl-histidine were identified in association with ageing. In addition, expression of several genes of the toll-like receptor (TLR) pathway, known for their implication in inflammaging, were upregulated in the kidneys of old rats. This study led to the identification of age-related markers of biological allograft age potentially relevant for allograft survival in the future. Among those, urine metabolites and markers of immunity and inflammation, which are highly relevant to immunosuppression in transplant recipients, are promising and deserve further investigation in humans.