Previous studies have shown that homocysteine (Hcy) is an important intestinal-derived uremic toxin. However, whether Hcy is involved in the epithelial barrier dysfunction observed in uremia remains unclear. This study aimed to investigate the effect of Hcy on intestinal permeability and intestinal barrier structure and function in adenine-induced uremic rats.Sprague-Dawley rats were divided into five groups: normal control (group NC), Hcy (group H), uremia (group U), uremia + Hcy (group UH), and uremia + Hcy + VSL#3 (group UHV). Experimental uremia was induced by intragastric adenine administration, and Hcy was injected subcutaneously. The animal models were assessed for renal function and pathological tissue staining. The pathological changes of intestinal tissue were observed by hematoxylin and eosin staining and electron microscopy. The serum and intestinal tissue levels of Hcy, interleukin (IL)-6, tumor necrosis factor (TNF)-α, superoxide dismutase (SOD), and malondialdehyde (MDA) as well as serum endotoxin and intestinal permeability were assessed. The levels of the tight junction proteins claudin-1, occludin, and zonula occludens-1 (ZO-1) were assessed by western blotting.Blood analyses and renal pathology indicated that experimental uremia was induced successfully. Pathological damage to intestinal structure was most obvious in group UH. Serum and tissue Hcy, serum endotoxin, and intestinal permeability were significantly elevated in group UH. The protein levels of claudin-1, occludin, and ZO-1 were decreased to various degrees in group UH compared with groups NC, H, and U. The serum and tissue levels of IL-6, TNF-α, and MDA were significantly increased, while SOD activity was markedly decreased. Supplementation with the probiotic VSL#3 improved these parameters to various degrees and up-regulated the abundance of tight junction proteins, which indicated a role for Hcy in the increase of intestinal permeability and destruction of the epithelial barrier in uremia.Hcy aggravates the increase of intestinal permeability and destruction of the epithelial barrier by stimulating inflammatory and oxidative damage. Probiotic administration can ameliorate this damage by reducing the levels of Hcy-induced inflammation and oxidation.
Long noncoding RNAs (lncRNAs) are involved in physiological and pathological processes. However, no studies have been conducted on the relationship between lncRNAs and renal aging.First, we evaluated the histopathology of young (3-month-old) and old (24-month-old) C57BL/6J mouse kidneys. Masson trichrome staining and PAS staining showed interstitial collagen deposition and fibrosis, mesangial matrix expansion, a thicker basement membrane and renal interstitial fibrosis in old mouse kidneys. Senescence-associated β-galactosidase (SA-β-gal)-positive areas in the kidneys of old mice were significantly elevated compared to those of young mice. Then, we analyzed the differential expression of lncRNAs and mRNAs in the kidneys of young and old mouse kidneys by RNA-seq analysis. 42 known and 179 novel differentially expressed lncRNAs and 702 differential mRNAs were detected in the mouse kidney. Next, we focused on the differentially expressed mRNAs and lncRNAs by RNA-seq. GO and KEGG analyses were performed based on differentially expressed mRNAs between young and old mouse kidneys. Transregulation based on RIsearch and the correlation coefficient of mRNA-lncRNA were also calculated. The mRNA-lncRNA network was constructed by choosing a Spearman correlation coefficient > 0.9 or <-0.9. GO and KEGG pathway enrichment analyses revealed that differentially expressed mRNAs participated in aging-related pathways. A total of 10 lncRNAs and trans-regulated mRNAs were constructed. Finally, we validated the role of lncRNA Gm43360 by CCK-8, flow cytometry, western blot and SA-β-gal staining. The expression level of Adra1a was positively correlated and Csnk1a1 was negatively correlated with lncRNA Gm43360. The cell counting kit-8 (CCK-8) results showed that lncRNA Gm43360 promoted cell viability. LncRNA Gm43360 increased the percentage of S phase cells and decreased the percentage of G1 phase cells compared with the negative control. LncRNA Gm43360 decreased the expression of p53, p21 and SA-β-gal.LncRNA Gm43360 may play a protective role in kidney aging.
Dyslipidemia plays a critical role in the pathogenesis of metabolic syndrome and diabetes. Evidence has increasingly shown that the ratio of low- to high-density lipoprotein cholesterol (LDL-C/HDL-C) is a novel marker for increased risk of insulin resistance and cardiovascular diseases. However, the correlation between the LDL-C/HDL-C ratio and diabetes risk is rarely reported. This is the first study to investigate the association between the LDL-C/HDL-C ratio and new-onset diabetes in a large community-based cohort.In this retrospective cohort study, a total of 116,661 adults without baseline diabetes were enrolled. Participants were stratified into four groups based on LDL-C/HDL-C ratio quartiles. The outcome of interest was new-onset diabetes.During a median follow-up period of 2.98 years, 2,681 (2.3%) new diabetes cases were recorded. The total cumulative incidence of diabetes progressively increased alongside LDL-C/HDL-C ratio quartiles (0.31, 0.43, 0.68 and 0.88%, respectively, P-value for trend <0.001). After adjusting for potential confounders, using the lowest quartile of the LDL-C/HDL-C ratio as the reference, the risk of diabetes increased with LDL-C/HDL-C ratio quartiles (P-value for trend <0.001); in particular, from the second to fourth quartile, hazard ratios were 1.18 (95% confidence interval 0.87-1.59), 1.42 (95% confidence interval 1.07-1.90) and 1.92 (95% confidence interval 1.43-2.59), respectively. The results were also robust to challenges in multiple sensitivity analyses.Among the Chinese population, elevated LDL-C/HDL-C ratio might be an independent risk factor for new-onset diabetes.
Abstract Kidney aging accelerates the progression of various acute and chronic kidney diseases and can also induce pathological changes in other organs throughout the body. Circular RNAs (circRNAs) have been demonstrated to play a vital role in aging and age-related diseases. However, biological functions and the underlying molecular mechanism of circRNAs in kidney aging remain largely unclear. Uncovering the functions of circRNAs in kidney aging and their underlying regulatory mechanisms may shed new light on the development of novel diagnostic and therapeutic strategies for human aging. Here, we report the important role of circVmn2r1 in the progression of kidney aging. We found that circVmn2r1 was one of the top expressed circRNAs in mouse kidney by RNA sequencing and was significantly upregulated in 24-month-old mouse kidney compared to 3-month-old. More importantly, we demonstrated that overexpression of circVmn2r1 promoted kidney aging in senescence-accelerated mouse prone 8 mice. Cellular assays with mouse kidney tubular epithelium (TCMK-1) cells under both gain-of-function and loss-of-function conditions demonstrated that circVmn2r1 inhibited proliferation and promoted senescence, whereas miR-223-3p counteracted these effects. Mechanistic analysis demonstrated that circVmn2r1 acted as a miR-223-3p sponge to relieve the repressive effect of miR-223-3p on its target NLRP3, which we proved could inhibit proliferation and promote senescence of TCMK-1 cells. Our results indicate that circVmn2r1 promotes kidney aging through acting as a miR-223-3p sponge, consequently upregulating NLRP3 expression, and can be a valuable diagnostic marker and an important therapeutic target for kidney aging.
Circular RNA (circRNA) is a novel type of noncoding RNA expressed in different tissues and species. Up to now, little is known of the function and expression of circRNAs in kidney aging. In this research, we used RNA sequencing to identify 11,929 circRNAs in kidney from 3-, 12-, and 24-month-old mice, of which 12 circRNAs were validated by qPCR. Based on the validated circRNAs and their predicted miRNA-mRNA target pairs, a circRNA-miRNA-mRNA interactions network was conducted. Bioinformatics analysis for all the mRNAs in the ceRNA network showed that the most enriched gene ontology (GO) term and one of the most enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were associated with endoplasmic reticulum (ER). The network also identified circNpas2, which was decreased significantly in mice kidney during aging, as a hub gene. Subsequently, we found that the cell cycle was arrested in G1 phase and the expression of P53 and P16 increased significantly in the circNpas2-knockdown cells. Moreover, knockdown of circNpas2 inhibited expression of ER-related proteins, HSPA5 and ERO1L. Taken together, our findings contribute to a better understanding of the role played by circRNA during kidney aging and provide potential therapeutic targets for the prevention of kidney aging. RESEARCH HIGHLIGHTS: This study is the first to systematically analyze the dysregulated circRNAs and ceRNA network during renal aging. The dysregulated circRNAs during renal aging are most enriched in ER stress-related pathway. CircNpas2 regulates senescence in TCMK-1.
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