MO019MATERNAL UNDERNUTRITION AMELIORATES CYST GROWTH IN ADPKD MODEL MICE*
Authors: Yoshikawa Junpei , Saori Nishio , Hattanda Fumihiko , Nakazawa Daigo , Atsumi Tatsuya 
Published: May 2021

Abstract

Background and Aims
Autosomal dominant polycystic kidney disease (ADPKD) is characterized by the progressive development of kidney and liver cysts. The major factors predicting disease progression in ADPKD are total kidney volume, genotype, age, sex. Recently, several studies have suggested that dietary intervention might be a potential treatment to prevent ADPKD progression. On the other hand, it has been reported that low-birth weight infants because of maternal global nutrient restriction are at increased risk for hypertension, type 2 diabetes, and metabolic syndrome and chronic kidney disease. However, little has been reported on relationship between maternal undernutrition and cyst formation in ADPKD. Therefore the purpose of this study is to clarify whether maternal undernutrition is associated with progression in ADPKD.

Method
We used Pkd1 conditional knockout mice (Pkd1flox/flox･Mx1-Cre mice). The offspring of dams given food ad libitum (control(CON)) and those subjected to nutrient restriction throughout pregnancy (food restriction (FR)) were examined. In FR, nutrient-restricted mothers were given about half amount of food by control mice during pregnancy. After delivery, food for children was given ad libitum. Mice were injected with polyinosinic-polycytidylic acid for 6 consecutive days from postnatal day 5 (P5) to P10 to inactivate Pkd1. We analyzed the phenotype of cystic kidneys by kidney/body weight ratio (2KW/BW), and cystic index (CI) which was defined as the percentage of areas occupied by cysts at P20, 35, 56. We carried out a series of analyses by kidney/body weight ratio, liver /body weight ratio or cystic index (CI) which was defined as the percentage of areas occupied by cysts. Elastica-Masson staining was performed for analyzing tissue fibrosis. The fibrotic index (FI) was expressed as the (fibrotic area/ total non-cystic area) ×100 (%). For evaluation of glomerular hypertrophy, glomerular area was measured in PAS-stained kidney sections using Image J software. The assay of renal function was performed by using UN-ML kit. We also performed western blotting of signaling pathway of proliferation by using whole kidneys. Data are shown as mean ± SEM. Two-tailed Student’s t-test was performed for comparing two groups.

Results
Food restriction of pregnant dams reduced birth weight. (FR 1.26±0.16 g vs CON 1.55±0.11g). However, FR showed rapid gain weight. There was no significant difference after P20. There were no difference between two groups in 2KW/BW, serum blood urea nitrogen (BUN) levels, CI of kidney and liver until P35. At P56, 2KW/BW was significantly greater in FR (4.59±0.52%) than in CON mice (2.91±0.98%; p＜0.01). CI of both kidney and liver was significantly higher in FR than in CON (Kidney : FR58.1±2.04% vs CON46.3±3.04%; p＜0.05) (Liver : FR11.1±1.41% vs CON 4.89±0.61%; p＜0.001). BUN levels elevated in FR (FR 58.1±5.76mg/dL vs CON 46.3±5.11mg/dL; p＜0.05) .FR showed glomerular sclerosis with PAS staining. Mean Glomerular volume was significantly increased in FR compared with CON (P35: FR 5625±419μm2 vs CON 3255±433μm2; p＜0.001, P56: FR 5780±1195μm2 vs CON 3756±266μm2; p＜0.001) . FR group showed significantly greater fibrosis in kidney (P35: FI 15.3±2.04% vs CON 11.1±1.41%; p＜0.01,P56: FI 42.1±3.2% vs CON 30.8±3.89%; p＜0.001). In western blotting analysis, MAPK pathway and mTOR pathway were suppressed in FR compared with CON at P20. In contrast, MAPK pathway and mTOR pathway were upregulated in FR compared with CON at P56.

Conclusion
Maternal undernutrition accelerates disease progression via kidney fibrosis, MAPK and mTOR pathway.