The development of insulin resistance with aging is well documented. In addition, an estimated 22 million individuals in this country develop non-insulin-dependent diabetes mellitus as an adult-onset disease. Diabetes has been well established as a major risk factor for the development of atherosclerosis and recently, attention has focused on the importance of insulin resistance. Hyperglycemia is also thought to play a role in changes in proteins associated with the aging process. Thus, it is obvious that an understanding of the mechanisms involved in insulin resistance and overt diabetes, as well as ways of reversing or preventing them is important for the health and economy of our nation.
The aim of this proposal is to investigate the mechanisms responsible for the insulin resistance associated with aging by studying the glucose transport system in skeletal muscle the major target tissue for insulin action. In addition, we will investigate the roles that diet and exercise play in the development and reversal of aging associated insulin resistance. To accomplish these aims, glucose tolerance tests will be performed on Fisher 344 rats ages 2, 3, 12, 24, and 30 months to establish exactly when significant insulin resistance develops in our experimental model. We will then pick one young and one old aged, insulin-resistant group to study the glucose transport system in skeletal muscle. Sarcolemmal vesicles will be isolated from hind-limb muscles to study a) insulin binding b) tyrosine kinase phosphorylation activity of the insulin receptor c) specific D-glucose transport kinetics and d) the number and affinity of glucose transport units. In addition, we will quantitate the microsomal fraction of glucose transporters to assess a possible change in the cytoplasmic pool of transporters. Following these initial studies, we will investigate the effects of acute exercise, exercise training, a high-fat, sucrose diet and caloric restriction on the glucose transport system in aging rats to assess their roles in modulating insulin resistance.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
5R01AG007592-05
Application #
3118749
Study Section
Metabolism Study Section (MET)
Project Start
1989-01-01
Project End
1994-03-31
Budget Start
1993-01-01
Budget End
1994-03-31
Support Year
5
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of California Los Angeles
Department
Type
Schools of Arts and Sciences
DUNS #
119132785
City
Los Angeles
State
CA
Country
United States
Zip Code
90095
Youngren, J F; Paik, J; Barnard, R J (2001) Impaired insulin-receptor autophosphorylation is an early defect in fat-fed, insulin-resistant rats. J Appl Physiol 91:2240-7
Roberts, C K; Barnard, R J; Jasman, A et al. (1999) Acute exercise increases nitric oxide synthase activity in skeletal muscle. Am J Physiol 277:E390-4
Berger, J J; Barnard, R J (1999) Effect of diet on fat cell size and hormone-sensitive lipase activity. J Appl Physiol 87:227-32
Barnard, R J; Roberts, C K; Varon, S M et al. (1998) Diet-induced insulin resistance precedes other aspects of the metabolic syndrome. J Appl Physiol 84:1311-5
Roberts, C K; Barnard, R J; Scheck, S H et al. (1997) Exercise-stimulated glucose transport in skeletal muscle is nitric oxide dependent. Am J Physiol 273:E220-5
Youngren, J F; Barnard, R J (1995) Effects of acute and chronic exercise on skeletal muscle glucose transport in aged rats. J Appl Physiol 78:1750-6
Zernicke, R F; Salem, G J; Barnard, R J et al. (1995) Long-term, high-fat-sucrose diet alters rat femoral neck and vertebral morphology, bone mineral content, and mechanical properties. Bone 16:25-31
Barnard, R J; Faria, D J; Menges, J E et al. (1993) Effects of a high-fat, sucrose diet on serum insulin and related atherosclerotic risk factors in rats. Atherosclerosis 100:229-36
Barnard, R J; Youngren, J F (1992) Regulation of glucose transport in skeletal muscle. FASEB J 6:3238-44
Barnard, R J; Lawani, L O; Martin, D A et al. (1992) Effects of maturation and aging on the skeletal muscle glucose transport system. Am J Physiol 262:E619-26

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