Low-protein diet improves blood and urinary glucose levels and renal manifestations of diabetes in C57BLKS-db/db mice.
OBJECTIVE
Dietary protein content is related clinically to the development of diabetic nephropathy. Here, we investigated how dietary protein content (12-24 % energy) within the range used by humans affected renal manifestations including the expressions of genes involved in the renin-angiotensin (RA) system in control and diabetic mice. Moreover, we examined the effects of dietary protein content on HbA1c and urinary glucose.


METHODS
Control (CT) and leptin receptor-deficient obese (db) mice, 5 weeks old, were fed the diets below. Under ad libitum conditions, mice were fed 12, 18, and 24 % energy from protein (L-, M-, and H-diets) for 8 weeks. Under pair-feeding conditions, db mice were supplied H-diet (db-Hp) to the equivalent energy to that consumed by db-L mice. Renal manifestations and values related to glucose and insulin were examined biochemically and pathologically.


RESULTS
Under ad libitum conditions, db mice consumed food and water dose dependently of the dietary protein content, although they were consumed similarly by CT mice. CT-L mice showed lower urinary albumin and kidney weight, in association with lower mRNA levels of angiotensinogen and renin, than CT-H mice. Under pair-feeding conditions, db-L mice showed a lower ratio of kidney/body weight, HbA1(C), and urinary glucose, and a higher β-cell distribution rate in the pancreas than db-Hp mice.


CONCLUSIONS
Low-protein intake in the range used by humans may relieve renal manifestations through the suppressed expression of genes in the renal RA system of CT mice. On the other hand, in db mice, low-protein intake improved hyperglycemia and the renal manifestations of diabetes.
Department of Life and Environmental Science, Kagoshima Prefectural College, Kagoshima, Japan.
Emi
E
Arimura
Masahisa
M
Horiuchi
Hiroaki
H
Kawaguchi
Noriaki
N
Miyoshi
Kohji
K
Aoyama
Toru
T
Takeuchi
D000419:Albuminuria / Q000178:diet therapy; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D003921:Diabetes Mellitus, Experimental / Q000097:blood / Q000178:diet therapy*; D003928:Diabetic Nephropathies / Q000097:blood / Q000178:diet therapy; D018753:Diet, Protein-Restricted; D004044:Dietary Proteins / Q000008:administration & dosage / Q000097:blood; D005215:Fasting; D006442:Glycated Hemoglobin / Q000032:analysis / Q000378:metabolism; D006030:Glycosuria, Renal / Q000178:diet therapy*; D006943:Hyperglycemia / Q000097:blood / Q000178:diet therapy; D007328:Insulin / Q000097:blood; D007668:Kidney / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D009765:Obesity / Q000097:blood / Q000178:diet therapy; D010179:Pancreas / Q000378:metabolism; D012084:Renin-Angiotensin System
D001786:Blood Glucose; D004044:Dietary Proteins; D006442:Glycated Hemoglobin; D007328:Insulin