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Horm Metab Res 1987; 19(5): 187-190
DOI: 10.1055/s-2007-1011774
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© Georg Thieme Verlag, Stuttgart · New York

The Regulation of Adipose Tissue Pyruvate Dehydrogenase Activity of Dietary Fiber

J. O. Ogunwole, E. M. Knight1 , J. S. Adkins1 , K. G. Thomaskutty2 , R. H. Pointer2
  • 1Human Nutrition and Food, School of Human Ecology, Howard University, Washington, D.C., U.S.A.
  • 2Department of Biochemistry, College of Medicine, Howard University, Washington, D.C., U.S.A.
  • Department of Biochemistry, College of Medicine and Human Nutrition and Food School of Human Ecology, Howard University, Washington, D.C., U.S.A.
A preliminary report of this work was presented at the 25th Annual Meeting of the American Physiological Society, Lexington, Kentucky. This work is described in a doctoral dissertation submitted to the Graduate School of Arts and Sciences, Howard University Washington, D.C., and was supported in part by NSF grant PRM 8110709.
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1985

1986

Publication Date:
14 March 2008 (online)

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Summary

In vitro studies have established that insulin enhances the oxidation of pyruvate to acetyl CoA by the stimulation of mitochondrial pyruvate dehydrogenase (PDH) activity through plasma membrane binding response (Jarett and Seals 1979;Kiechle, Jarett, Dennis and Kotagal 1980). In the present study adipose tissue PDH activity was utilized as a marker for insulin responsiveness. The metabolic response of this enzyme to exogenous insulin was employed to test the hypothesis that dietary fiber enhances tissue responsiveness to insulin using adipose tissue from male weanling Sprague Dawley rats. Eight groups of rats (n=5 per group) were fed ad libitum various diets containing different levels of cellulose and protein as already reported elsewhere (Ogunwole, Knight, Adkins, Thomaskutty and Pointer 1985). Percent insulin stimulation of PDH from basal activity (PDS) was utilized as an index of insulin responsiveness. Compared to all fiber treated groups, both basal (PDB) and insulin stimulated (PDI) activities were significantly lower (P < 0.05) in the fiber free groups at both low (10%) and high (20%) protein levels. At all fiber levels tested (0, 5,15 and 30%) protein intake resulted in a significant increase in both PDB and PDI. Gradual increase in cellulose intake resulted in a biphasic increase in PDS in both protein groups at the 5% and 30% fiber levels. PDS was higher (P < 0.05) in the 10% protein groups than the 20% protein group at all fiber levels tested. A significant interaction effect of protein and fiber was observed on PDB (P < 0.001) and PDI (P < 0.04) when caloric intake was held constant as a covariate. Higher fiber intake resulted in a decrease in serum insulin (SI). SI showed an inverse relationship with PDS (r = -0.53, P < 0.0001). A significant interaction effect of protein and fiber was observed on SI (P < 0.0001). It is concluded that (i) Diet can modulate insulin responsiveness in growing animals: (ii) The combination of dietary fiber with other nutrients determines its metabolic effect in improving insulin responsiveness via a metabolic response to the membrane receptor binding signal.

Key-Words

Dietary Fiber - Insulin Responsiveness - Pyruvate Dehydrogenase (PDH) - Percent Insulin Stimulation of PDH - Adipose Tissue - Metabolic Response - Glycemic Index