title: Glomerular cell death and inflammation with high-protein diet and diabetes.
abstract: BACKGROUND
  Overfeeding amino acids (AAs) increases cellular exposure to advanced glycation end-products (AGEs), a mechanism for protein intake to worsen diabetic kidney disease (DKD). This study assessed receptor for AGE (RAGE)-mediated apoptosis and inflammation in glomerular cells exposed to metabolic stressors characteristic of high-protein diets and/or diabetes in vitro with proof-of-concept appraisal in vivo.
  
  
  METHODS
  Mouse podocytes and mesangial cells were cultured under control and metabolic stressor conditions: (i) no addition; (ii) increased AAs (4-6-fold>control); (iii) high glucose (HG, 30.5 mM); (iv) AA/HG combination; (v) AGE-bovine serum albumin (AGE-BSA, 300 µg/mL); (vi) BSA (300 µg/mL). RAGE was inhibited by blocking antibody. Diabetic (streptozotocin) and nondiabetic mice (C57BL/6J) consumed diets with protein calories of 20 or 40% (high) for 20 weeks. People with DKD and controls provided 24-h urine samples.
  
  
  RESULTS
  In podocytes and mesangial cells, apoptosis (caspase 3/7 activity and TUNEL) increased in all metabolic stressor conditions. Both inflammatory mediator expression (real-time reverse transcriptase-polymerase chain reaction: serum amyloid A, caspase-4, inducible nitric oxide synthase, and monocyte chemotactic protein-1) and RAGE (immunostaining) also increased. RAGE inhibition prevented apoptosis and inflammation in podocytes. Among mice fed high protein, podocyte number (WT-1 immunostaining) decreased in the diabetic group, and only these diabetic mice developed albuminuria. Protein intake (urea nitrogen) correlated with AGE excretion (carboxymethyllysine) in people with DKD and controls.
  
  
  CONCLUSIONS
  High-protein diet and/or diabetes-like conditions increased glomerular cell death and inflammation, responses mediated by RAGEs in podocytes. The concept that high-protein diets exacerbate early indicators of DKD is supported by data from mice and people.
authors: Providence Medical Research Center, Providence Sacred Heart Medical Center, Spokane, WA, USA. rick.meek@providence.org
authors: Rick L
authors: RL
authors: Meek
authors: Renee C
authors: RC
authors: LeBoeuf
authors: Sandeep A
authors: SA
authors: Saha
authors: Charles E
authors: CE
authors: Alpers
authors: Kelly L
authors: KL
authors: Hudkins
authors: Sheryl K
authors: SK
authors: Cooney
authors: Robert J
authors: RJ
authors: Anderberg
authors: Katherine R
authors: KR
authors: Tuttle
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D016022:Case-Control Studies; D002478:Cells, Cultured; D003921:Diabetes Mellitus, Experimental / Q000150:complications / Q000473:pathology*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism / Q000473:pathology*; D003928:Diabetic Nephropathies / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D004032:Diet; D004044:Dietary Proteins / Q000494:pharmacology*; D017127:Glycation End Products, Advanced / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007249:Inflammation / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D018836:Inflammation Mediators / Q000378:metabolism; D008297:Male; D050527:Mesangial Cells / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D050199:Podocytes / Q000378:metabolism / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D004044:Dietary Proteins; D017127:Glycation End Products, Advanced; D018836:Inflammation Mediators; D012333:RNA, Messenger; D000067759:Receptor for Advanced Glycation End Products; D011971:Receptors, Immunologic
keywords: apoptosis; high-protein diet; mesangial cells; podocytes; receptor for advanced glycation end-products