title: An age-dependent alteration of the respiratory exchange ratio in the db/db mouse.
abstract: The leptin receptor-deficient db/db mouse is a rodent model of type 2 diabetes and obesity. Diabetes in db/db mice shows an age-dependent progression, with early insulin resistance followed by an insulin secretory defect resulting in profound hyperglycemia. However, there is insufficient data on agedependent changes of energy metabolism in db/db mice. We demonstrated an age-dependent decrease in the respiratory exchange ratio (RER), calculated by a ratio of VO2/VCO2, in db/db mice. The RER determined by indirect calorimetry, was 1.03 in db/db mice under 6 weeks of age, which were similar to those in heterozygote (db/+) and wild-type (+/+) mice. However, RER decreased from approximately 0.9 to 0.8 by 10 weeks of age and subsequently returned to approximately 0.9 at 22 weeks of age. The changes in RER were concurrent with the alterations in body weight and blood glucose level. However, other metabolic indicators such as glucose tolerance, changes in body fat mass, and urinary glucose levels, did not change with age. The results suggested that the energy source utilized in db/db mice changed with the age-related progression of diabetes.
authors: Laboratory Animal Resource Center, KRIBB, Cheongju, Korea. ; Laboratory Animal Medicine, College of Veterinary Medicine, Chungbuk National University, Cheongju, Korea.
authors: Hye-Min
authors: HM
authors: Choi
authors: Laboratory Animal Resource Center, KRIBB, Cheongju, Korea.
authors: Hae Rim
authors: HR
authors: Kim
authors: Laboratory Animal Resource Center, KRIBB, Cheongju, Korea.
authors: Eun-Kyoung
authors: EK
authors: Kim
authors: Laboratory Animal Resource Center, KRIBB, Cheongju, Korea.
authors: Yong Sub
authors: YS
authors: Byun
authors: Laboratory Animal Resource Center, KRIBB, Cheongju, Korea.
authors: Young-Suk
authors: YS
authors: Won
authors: Laboratory Animal Resource Center, KRIBB, Cheongju, Korea.
authors: Won-Ki
authors: WK
authors: Yoon
authors: Laboratory Animal Resource Center, KRIBB, Cheongju, Korea.
authors: Hyoung-Chin
authors: HC
authors: Kim
authors: Laboratory Animal Medicine, College of Veterinary Medicine, Chungbuk National University, Cheongju, Korea.
authors: Jong-Goo
authors: JG
authors: Kang
authors: Laboratory Animal Resource Center, KRIBB, Cheongju, Korea.
authors: Ki-Hoan
authors: KH
authors: Nam
keywords: Respiratory exchange ratio; age-dependency; db/db mouse; indirect calorimetry