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- Title
The Effect of Aging on Postabsorptive Gluconeogenesis Is Sex Specific.
- Authors
Morais, José A.; Chevalier, Stéphanie; Gougeon, Réjeanne; Malloy, Craig R.; Burgess, Shawn C.
- Abstract
We have shown that aging is associated with insulin resistance of protein concurrent with that of glucose and that the increased contribution of gluconeogenesis via phosphoenol pyruvate (GNG[sub PEP]) to glucose production with obesity is related to increased postabsorptive whole-body leucine Ra (protein breakdown) and insulin resistance. We tested whether GNG[sub PEP] is increased with aging. The % contributions of glycogen, glycerol and GNG[sub PEP] to endogenous glucose production (EGP) were measured at 17-h of fasting using the oral deutered water method and ²H nuclear magnetic resonance spectroscopy of plasma glucose in 22 young (Y; 12 M: 27 y, 23 ± 1 kg/m²; 10 W: 25 y, 21 ± 1 kg/m²) and 19 elderly (E; 9 M: 70 y, 26 ± 1 kg/m²; 10 W: 70 y, 23 ± 1 kg/m²) nondiabetic subjects. Whole-body protein and glucose kinetics were assessed with [sup 13]C-leucine and ³H-glucose, respectively. When adjusted for fat-free mass, Insulin Sensitivity Index (ISI) was lower only in EM vs YM (P = 0.043) but total EGP and fasting leucine Ra were not different between groups. GNG[sup PEP] contributed more in EM compared with YM (48 ± 4 vs 39 ± 3%, P = 0.038) whereas it contributed less in EW compared with YW (37 ± 5 vs 47 ± 3%, P = 0.039). Conversely, the contribution of glycogen was less in EM compared with YM (37 ± 5 vs 52 ± 3%, P= 0.012) whereas no difference was seen for that of glycerol. GNG[sup PEP] flux (%GNG x EGP) correlated with protein breakdown, synthesis and plasma glucose (all, R = 0.348 - 0.453, P < 0.03). Thus the sex specific effect of aging on the contribution of GNG[sup PEP] to EGP is associated with insulin resistance of glucose and is also related to protein turnover.
- Publication
Diabetes, 2007, Vol 56, pA368
- ISSN
0012-1797
- Publication type
Academic Journal