A high-fat diet aggravates tubulointerstitial but not glomerular lesions in obese Zucker rats.
BACKGROUND
Despite a large body of evidence that manipulation of dietary fat alters glomerular lesions, reports regarding the effects of dietary fat on tubulointerstitial lesions are limited. Obese Zucker rats (OZR) spontaneously develop glomerular and tubulointerstitial lesions in association with hyperlipidemia. We sought to elucidate the effects of dietary fat on glomerular and tubulointerstitial lesions in OZR versus lean Zucker rats (LZR) and to assess the involvement of macrophages in the development of these lesions.


METHODS
We fed LZR and OZR either a low- (1%) or high-fat (20%) diet. After 30 weeks of the specified diet, the creatinine clearance (Ccr) and renal histology as well as plasma lipid concentrations were examined. For morphological evaluation, glomerular sclerosis (GSI) and tubulointerstitial indices (TII) were each determined by a point-counting method. Infiltrating macrophages were stained immunohistochemically using an avidin-biotin complex technique.


RESULTS
The high-fat diet increased the plasma low-density lipoprotein concentration in OZR. Both low- and high-fat OZR groups had higher GSI and TII than LZR receiving either diet. The high-fat diet aggravated TII but not GSI or Ccr in OZR; conversely, high fat intake worsened GSI and Ccr but not TII in LZR. Tubulointerstitial macrophages were most prominent in the high-fat OZR group, followed by the low-fat OZR group. Glomerular macrophages were similar in number in all groups.


CONCLUSIONS
The manipulation of dietary fat has diverse effects on the kidney. A high-fat diet aggravated macrophage-mediated tubulointerstitial lesions in OZR, whereas in LZR, the diet induced glomerulosclerosis.
Kagawa Nutrition Junior College, Tokyo, Japan.
S
S
Matsuda
T
T
Arai
K
K
Iwata
M
M
Oka
M
M
Nagase
D000419:Albuminuria / Q000652:urine; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004041:Dietary Fats / Q000008:administration & dosage*; D002149:Energy Intake / Q000187:drug effects; D007678:Kidney Glomerulus / Q000187:drug effects* / Q000473:pathology; D007684:Kidney Tubules / Q000187:drug effects* / Q000473:pathology; D008077:Lipoproteins, LDL / Q000097:blood / Q000187:drug effects; D008264:Macrophages / Q000473:pathology; D008297:Male; D009765:Obesity / Q000503:physiopathology*; D011506:Proteins / Q000187:drug effects / Q000378:metabolism; D011507:Proteinuria / Q000652:urine; D051381:Rats; D011924:Rats, Zucker; D017392:Thiobarbituric Acid Reactive Substances / Q000378:metabolism
D004041:Dietary Fats; D008077:Lipoproteins, LDL; D011506:Proteins; D017392:Thiobarbituric Acid Reactive Substances