Long-Term High Protein Intake Does Not Increase Oxidative Stress in Rats

Abstract

The maximum dietary protein intake that does not cause adverse effects in a healthy population is uncertain. We tested whether a high protein intake enhances oxidative stress. Adult rats were adapted to different casein-based diets containing either an adequate (13.8%; AP), medium (25.7%; MP), or high (51.3%; HP) level of crude protein; a fourth group received a HP diet but no RRR-alpha-tocopherol acetate (HP-toc). After 15 wk of feeding, plasma protein carbonyl concentration, liver lipid peroxide levels [thiobarbituric acid-reacting substances (TBARS)], reduced glutathione (GSH) status and leucine kinetics ([1-(13)C]leucine) were measured. Higher concentrations of protein carbonyls and TBARS were found in rats fed the AP and the HP-toc diets compared with those fed the MP and HP diets (P: < 0.05). GSH concentrations in plasma did not differ but total blood GSH concentrations were significantly (P: < 0.05) lower in rats fed the HP-toc diet compared with those fed the AP, MP and HP diets. Liver GSH concentrations were significantly (P: < 0.01) lower in rats fed the AP diet compared with the other groups. Rates of postabsorptive leucine oxidation (LeuOX) and flux (Q(Leu)) were positively correlated with the dietary protein level (for AP, MP, and HP, respectively: LeuOX, 74.9 +/- 28.5, 109 +/- 35.2, 142.3 +/- 38.4 micromol/(kg. h); Q(Leu), 425 +/- 102, 483 +/- 82, 505 +/- 80 micromol/(kg. h). Only HP-toc resulted in a significantly greater protein breakdown (PB(Leu)) and Q(Leu). No difference was seen in nonoxidative leucine disposal. Long-term intake of high protein diets did not increase variables of oxidative stress, in contrast to our initial hypothesis. An unexpected finding was that adequate protein feeding (AP) may in fact induce oxidative stress.

Effects of Sulla forage (Sulla coronarium L.) on the oxidative status and milk polyphenol content in goats

“…According to those authors, high dietary protein levels can reduce oxidative stress. On the contrary, Petzke et al (2000) observed that long-term intake of high-protein diets did not lead to oxidative stress in adult rats. Celi and Robinson (2010) found that TAC is affected by dietary treatment with yerba mate (Ilex paraguariensis) in dairy calves, most likely because of the high polyphenol content of this herb.…”

Effects of fatty acids on hepatic amino acid catabolism and fibrinogen synthesis in young healthy volunteers

“…13 C]KIC and unlabeled KIC corrected for baseline were used for calibration (41). 13 C enrichment in breath samples was analyzed by IRMS (Breath, Finnigan).…”

Food restriction and refeeding in lambs influence muscle antioxidant status

“…Indeed, it has now clearly been shown that Savary-Auzeloux, Durand, Gruffat, Bauchart and Ortigues-Marty a drastic (a reduction to 60% of the ad libitum food intake level) or a long-lasting (several months) food restriction decreased the carbonyl content in human plasma (Dandona et al, 2001) and in the muscles or in the liver of rodents (Nagai et al, 2000;Pamplona et al, 2002). By contrast, other more specific alterations of the diet composition such as high protein content in the diet of rats (Petzke et al, 2000) or supplementation with eicopentaenoic acid and decosahexaenoic acid (Wander and Du, 2000) in humans had no effect on plasma protein carbonyls. In cattle finished on pasture (rich in polyunsaturated fatty acids) and compared with animals fed high concentrate diets, there was a similar (Mercier et al, 2004) or an increased (SavaryAuzeloux et al, 2001) content in protein carbonyls in some muscles.…”