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Renal Lipotoxicity-Associated Inflammation and Insulin Resistance Affects Actin Cytoskeleton Organization in Podocytes.

Martínez-García C, Izquierdo-Lahuerta A, Vivas Y, Velasco I, Yeo TK, Chen S, Medina-Gomez G - PLoS ONE (2015)

Bottom Line: Our results show that treatment of podocytes with palmitic acid produced intracellular accumulation of lipid droplets and abnormal glucose and lipid metabolism.We found specific rearrangements of the actin cytoskeleton and slit diaphragm proteins (Nephrin, P-Cadherin, Vimentin) associated with this insulin resistance in palmitic-treated podocytes.We conclude that lipotoxicity accelerates glomerular disease through lipid accumulation and inflammation.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Ciencias Básicas de la Salud, Área de Bioquímica y Genética Molecular. Universidad Rey Juan Carlos, Avda. de Atenas s/n, Alcorcón, Madrid, Spain.

ABSTRACT
In the last few decades a change in lifestyle has led to an alarming increase in the prevalence of obesity and obesity-associated complications. Obese patients are at increased risk of developing hypertension, heart disease, insulin resistance (IR), dyslipidemia, type 2 diabetes and renal disease. The excess calories are stored as triglycerides in adipose tissue, but also may accumulate ectopically in other organs, including the kidney, which contributes to the damage through a toxic process named lipotoxicity. Recently, the evidence suggests that renal lipid accumulation leads to glomerular damage and, more specifically, produces dysfunction in podocytes, key cells that compose and maintain the glomerular filtration barrier. Our aim was to analyze the early mechanisms underlying the development of renal disease associated with the process of lipotoxicity in podocytes. Our results show that treatment of podocytes with palmitic acid produced intracellular accumulation of lipid droplets and abnormal glucose and lipid metabolism. This was accompanied by the development of inflammation, oxidative stress and endoplasmic reticulum stress and insulin resistance. We found specific rearrangements of the actin cytoskeleton and slit diaphragm proteins (Nephrin, P-Cadherin, Vimentin) associated with this insulin resistance in palmitic-treated podocytes. We conclude that lipotoxicity accelerates glomerular disease through lipid accumulation and inflammation. Moreover, saturated fatty acids specifically promote insulin resistance by disturbing the cytoarchitecture of podocytes. These data suggest that renal lipid metabolism and cytoskeleton rearrangements may serve as a target for specific therapies aimed at slowing the progression of podocyte failure during metabolic syndrome.

No MeSH data available.


Related in: MedlinePlus

Changes in cytoskeleton and slit-diaphragm related to PA treatment.(A) Representative immunofluorescence micrographs of phalloidin (red) and paxillin (green) staining. White arrows indicate locations of actin filaments (anti-phalloidin) or focal adhesions (anti-paxillin). Original magnification: 200×. (B) mRNA levels of cytoskeleton and slit-diaphragm related genes such as: Vimentin, Collagen3A4 (Col3A4), Fibronectin (FN), P-Cadherin (P–Cad), cluster of differentiation-2 associated protein (CD2AP), Nephrin (Nphs1), Vascular endothelial growth factor (VEGF), and Osteopontin (OPN) in podocytes treated 24 h with vehicle, 100, 500 or 750 μM of PA. Data is expressed as mean ± SEM and normalized with GeNorm; *** p<0.001 PA vs. Veh.; ** p<0.01 PA vs. Veh.; * p<0.05 PA vs. Veh.
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pone.0142291.g005: Changes in cytoskeleton and slit-diaphragm related to PA treatment.(A) Representative immunofluorescence micrographs of phalloidin (red) and paxillin (green) staining. White arrows indicate locations of actin filaments (anti-phalloidin) or focal adhesions (anti-paxillin). Original magnification: 200×. (B) mRNA levels of cytoskeleton and slit-diaphragm related genes such as: Vimentin, Collagen3A4 (Col3A4), Fibronectin (FN), P-Cadherin (P–Cad), cluster of differentiation-2 associated protein (CD2AP), Nephrin (Nphs1), Vascular endothelial growth factor (VEGF), and Osteopontin (OPN) in podocytes treated 24 h with vehicle, 100, 500 or 750 μM of PA. Data is expressed as mean ± SEM and normalized with GeNorm; *** p<0.001 PA vs. Veh.; ** p<0.01 PA vs. Veh.; * p<0.05 PA vs. Veh.

Mentions: To assess the cytoskeletal structure and its role in the development of insulin resistance in podocytes treated with PA, we performed immunofluorescence (IF) wherein the different components of the cytoskeleton were labelled (Fig 5A). Phalloidin toxin (red colour) was used to label the actin cytoskeleton. As shown in the figure, the actin filaments of podocytes treated with vehicle were arranged radially along the entire cell. However, the actin filaments in the 500 μM PA-treated podocytes were reorganized from the radial area to the peripheral zone. A cytoskeleton breakdown was observed in the 750 μM PA-treated podocytes consistent with the higher level of apoptosis observed. The inadequate polymerization of cytoskeletal actin filaments causes the stress fiber formation and fiber termination in focal adhesion proteins. To visualize this process we performed an anti-paxillin IF (green colour) to label the focal adhesions (Fig 5A). Podocytes treated with 500 or 750 μM of PA showed a larger increase in focal adhesions and stress fiber labelling than in the vehicle-treated podocytes.


Renal Lipotoxicity-Associated Inflammation and Insulin Resistance Affects Actin Cytoskeleton Organization in Podocytes.

Martínez-García C, Izquierdo-Lahuerta A, Vivas Y, Velasco I, Yeo TK, Chen S, Medina-Gomez G - PLoS ONE (2015)

Changes in cytoskeleton and slit-diaphragm related to PA treatment.(A) Representative immunofluorescence micrographs of phalloidin (red) and paxillin (green) staining. White arrows indicate locations of actin filaments (anti-phalloidin) or focal adhesions (anti-paxillin). Original magnification: 200×. (B) mRNA levels of cytoskeleton and slit-diaphragm related genes such as: Vimentin, Collagen3A4 (Col3A4), Fibronectin (FN), P-Cadherin (P–Cad), cluster of differentiation-2 associated protein (CD2AP), Nephrin (Nphs1), Vascular endothelial growth factor (VEGF), and Osteopontin (OPN) in podocytes treated 24 h with vehicle, 100, 500 or 750 μM of PA. Data is expressed as mean ± SEM and normalized with GeNorm; *** p<0.001 PA vs. Veh.; ** p<0.01 PA vs. Veh.; * p<0.05 PA vs. Veh.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4636358&req=5

pone.0142291.g005: Changes in cytoskeleton and slit-diaphragm related to PA treatment.(A) Representative immunofluorescence micrographs of phalloidin (red) and paxillin (green) staining. White arrows indicate locations of actin filaments (anti-phalloidin) or focal adhesions (anti-paxillin). Original magnification: 200×. (B) mRNA levels of cytoskeleton and slit-diaphragm related genes such as: Vimentin, Collagen3A4 (Col3A4), Fibronectin (FN), P-Cadherin (P–Cad), cluster of differentiation-2 associated protein (CD2AP), Nephrin (Nphs1), Vascular endothelial growth factor (VEGF), and Osteopontin (OPN) in podocytes treated 24 h with vehicle, 100, 500 or 750 μM of PA. Data is expressed as mean ± SEM and normalized with GeNorm; *** p<0.001 PA vs. Veh.; ** p<0.01 PA vs. Veh.; * p<0.05 PA vs. Veh.
Mentions: To assess the cytoskeletal structure and its role in the development of insulin resistance in podocytes treated with PA, we performed immunofluorescence (IF) wherein the different components of the cytoskeleton were labelled (Fig 5A). Phalloidin toxin (red colour) was used to label the actin cytoskeleton. As shown in the figure, the actin filaments of podocytes treated with vehicle were arranged radially along the entire cell. However, the actin filaments in the 500 μM PA-treated podocytes were reorganized from the radial area to the peripheral zone. A cytoskeleton breakdown was observed in the 750 μM PA-treated podocytes consistent with the higher level of apoptosis observed. The inadequate polymerization of cytoskeletal actin filaments causes the stress fiber formation and fiber termination in focal adhesion proteins. To visualize this process we performed an anti-paxillin IF (green colour) to label the focal adhesions (Fig 5A). Podocytes treated with 500 or 750 μM of PA showed a larger increase in focal adhesions and stress fiber labelling than in the vehicle-treated podocytes.

Bottom Line: Our results show that treatment of podocytes with palmitic acid produced intracellular accumulation of lipid droplets and abnormal glucose and lipid metabolism.We found specific rearrangements of the actin cytoskeleton and slit diaphragm proteins (Nephrin, P-Cadherin, Vimentin) associated with this insulin resistance in palmitic-treated podocytes.We conclude that lipotoxicity accelerates glomerular disease through lipid accumulation and inflammation.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Ciencias Básicas de la Salud, Área de Bioquímica y Genética Molecular. Universidad Rey Juan Carlos, Avda. de Atenas s/n, Alcorcón, Madrid, Spain.

ABSTRACT
In the last few decades a change in lifestyle has led to an alarming increase in the prevalence of obesity and obesity-associated complications. Obese patients are at increased risk of developing hypertension, heart disease, insulin resistance (IR), dyslipidemia, type 2 diabetes and renal disease. The excess calories are stored as triglycerides in adipose tissue, but also may accumulate ectopically in other organs, including the kidney, which contributes to the damage through a toxic process named lipotoxicity. Recently, the evidence suggests that renal lipid accumulation leads to glomerular damage and, more specifically, produces dysfunction in podocytes, key cells that compose and maintain the glomerular filtration barrier. Our aim was to analyze the early mechanisms underlying the development of renal disease associated with the process of lipotoxicity in podocytes. Our results show that treatment of podocytes with palmitic acid produced intracellular accumulation of lipid droplets and abnormal glucose and lipid metabolism. This was accompanied by the development of inflammation, oxidative stress and endoplasmic reticulum stress and insulin resistance. We found specific rearrangements of the actin cytoskeleton and slit diaphragm proteins (Nephrin, P-Cadherin, Vimentin) associated with this insulin resistance in palmitic-treated podocytes. We conclude that lipotoxicity accelerates glomerular disease through lipid accumulation and inflammation. Moreover, saturated fatty acids specifically promote insulin resistance by disturbing the cytoarchitecture of podocytes. These data suggest that renal lipid metabolism and cytoskeleton rearrangements may serve as a target for specific therapies aimed at slowing the progression of podocyte failure during metabolic syndrome.

No MeSH data available.


Related in: MedlinePlus