Inhibition of Inflammatory Cytokine Expression Prevents High-Fat Diet-Induced Kidney Injury: Role of Lingonberry Supplementation

Abstract

Chronic low-grade inflammation is a major stimulus for progression of chronic kidney disease (CKD) in individuals consuming high-fat diet. Currently, there are limited treatment options for CKD other than controlling the progression rate and its associated complications. Lingonberry (Vaccinium vitis-idaea L.) is rich in anthocyanins with demonstrated anti-inflammatory effect. In the current study, we investigated the potential renal protective effect of lingonberry and its anthocyanin (cyanidin-3-glucoside) in high-fat diet fed obese mice and in human proximal tubular cells. Prolonged consumption of high-fat diets is strongly associated with obesity, abnormal lipid and glucose metabolism. Mice (C57BL/6J) fed a high-fat diet (62% kcal fat) for 12 weeks developed renal injury as indicated by an elevation of blood urea nitrogen (BUN) level as well as an increase in renal kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL) and renin expression. Those mice displayed an activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and increased expression of inflammatory cytokines-monocyte chemoattractant-1 (MCP-1), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) in the kidneys. Mice fed a high-fat diet also had a significant elevation of inflammatory cytokine levels in the plasma. Dietary supplementation of lingonberry for 12 weeks not only attenuated high-fat diet-induced renal inflammatory response but also reduced kidney injury. Such a treatment improved plasma lipid and glucose profiles, reduced plasma inflammatory cytokine levels but did not affect body weight gain induced by high-fat diet feeding. Lingonberry extract or its active component cyanidin-3-glucoside effectively inhibited palmitic acid-induced NF-κB activation and inflammatory cytokine expression in proximal tubular cells. These results suggest that lingonberry supplementation can reduce inflammatory response and prevent chronic kidney injury. Such a renal protective effect by lingonberry and its active component may be mediated, in part, through NF-κB signaling pathway.

Lingonberry Improves Non-Alcoholic Fatty Liver Disease by Reducing Hepatic Lipid Accumulation, Oxidative Stress and Inflammatory Response

“…From the liver tissues that were preserved in RNA later (Thermo Fisher Scientific, Waltham, MA, USA), total RNA was extracted with QIAzol reagent (Qiagen, Hilden, Germany) [ 29 ]. Relative mRNA expression of glutamate–cysteine ligase catalytic subunit ( Gclc ), glutamate–cysteine ligase modifier subunit ( Gclm ), glutathione synthetase ( GS ), sterol regulatory element-binding protein-1c ( SREBP-1c ), acetyl-CoA carboxylase-1 ( ACC-1 ), interleukin-6 ( IL-6 ), monocyte chemoattractant protein-1 ( MCP-1 ), and tumor necrosis factor- α ( TNF-α ) were measured using a StepOne Plus Real-Time qPCR (RT-qPCR) system (Applied Biosystems, Foster City, CA, USA), using previously described protocol [ 29 ]. Total RNA was extracted according to the procedure for the isolation of RNA as described by Chomczynski and Mackey [ 36 ].…”

“…Total proteins were extracted from mouse liver tissues in lysis buffer [20 mM Tris pH 7.4, 150 mM NaCl, 1 mM EGTA, 1 mM EDTA, 2.5 mM sodium pyrophosphate, 1 mM β-glycerophosphate, 1 mM sodium orthovanadate, 2.1 μM leupeptin, 1 mM PMSF, and 1% ( v/v ) Triton X-100] and were separated by electrophoresis in a 10% or 12% SDS-polyacrylamide gel as previously described [ 29 , 38 ]. Following electrophoresis and electrotransfer, the membranes were probed with rabbit anti-Gclc monoclonal antibody (1:1000), rabbit anti-Gclm monoclonal antibody (1:1000), or rabbit anti-GS monoclonal antibody (1:1000), which were purchased from Abcam, Cambridge, UK.…”

“…To ensure equal protein loading, the same membrane was probed with rabbit anti- β -Actin primary antibody (1:5000, Cell Signaling Technology). Nuclear proteins were prepared as previously described [ 29 , 38 ]. Nuclear Nrf2 and SREBP-1c proteins were identified by using rabbit anti-Nrf2 monoclonal antibodies (1:1000, Abcam) and rabbit anti-SREBP-1c monoclonal antibodies (1:1000, Santa Cruz Biotechnology, Inc., Dallas, TX, USA), respectively.…”

“…Paraffin-sectioned livers (5 μm thickness) were stained with hematoxylin and eosin (H&E) to evaluate the morphological changes [ 40 ]. Another set of paraffin-embedded sections were immunostained as previously described [ 29 ], using rat anti-F4/80 antibody (1:100 dilution, MCA497, Bio-Rad), followed by biotinylated goat anti-rat IgG (1:200, Dako, Glostrup, Denmark) and streptavidin-horse radish peroxidase (HRP) conjugate (Zymed Laboratories, Inc., San Francisco, CA, USA). These slides were counterstained with Mayer’s hematoxylin.…”

“…In Quebec, Canada, the Cree of Eeyou Istchee community use lingonberry as a remedy for symptoms of diabetes [ 27 ]. Recent studies including ours have demonstrated that lingonberry anthocyanins have antioxidant, anti-inflammatory, and anti-diabetic properties [ 28 , 29 , 30 ]. A previous study evaluated the metabolic effects of various berries including lingonberry in HFD-fed mice [ 31 ].…”