Comparison of the effects of food versus protein restriction on selected nutritional and inflammatory markers in rats

Abstract

We previously demonstrated that feeding a 2% protein AIN-76 diet ad libitum for 14 days resulted in substantial clinical and biochemical changes including weight loss, hypoglycemia, hypoalbuminemia, higher levels of plasma cytokines, oxidative stress in the liver, and activation of inflammatory signaling to interleukin (IL)-6, as compared with a 20% protein diet. In the present study, 54 rats were randomly given a standard rat chow diet ad libitum, or a 25% or 50% reduction of this intake for 14 days. The results showed that weight gain was less in the 25% food-restricted group and halted in the 50% group as compared with the control group. Unlike protein restriction, neither level of food restriction altered plasma levels of albumin and glucose, the hepatic protein abundance of signal transducers and activators of transcriptions and of mitogen-activated protein kinases, or the hepatic contents of total glutathione and malondialdehyde. The intracellular signaling in response to IL-6 stimulation was also well maintained. However, both levels of food restriction elevated IL-1 and corticosterone in plasma, did not alter ghrelin, and decreased plasma levels of free fatty acids. Because these latter 3 markers were not examined previously, 20 rats were fed an AIN-76 diet, either with 20% or 2% protein, ad libitum for 14 days. The 2% protein diet significantly decreased plasma levels of free fatty acids and increased ghrelin and corticosterone as compared with the 20% protein diet. Thus, food restriction, where all essential nutrients are reduced in proportion, is a physiologic stress that, while limiting growth, does not activate or impair the systemic inflammatory response, whereas a very low protein diet with little change in energy intake has a substantial impact on systemic inflammation, body composition, and growth.

Effects of caloric restriction on oxidative stress parameters

“…Similar to our results, Chacón and co-workers reported increased plasma corticosterone level in rats after 4 weeks receiving 66% of recommended caloric needs (Chacón et al 2005). Increased plasma corticosterone level was also reported in rats whose food intake during 14 days was reduced for 25% and 50%, comparing to control group (Ling and Bistrian 2009).…”

Insufficient Protein Intake Is Associated With Increased Mortality in 630 Patients With Cirrhosis Awaiting Liver Transplantation

“…In both animal and human studies, a protein‐restricted diet impairs both cell‐mediated and humoral immunity 31 , 32 . Moreover, dietary protein restriction produces a pro‐inflammatory state (increase in IL‐1, IL‐6, and TNF‐α) that is interestingly not seen with caloric restriction alone 33 . As protein intake is a potentially modifiable prognostic factor, these findings support the performance of prospective randomized trials in the area.…”

Impaired ghrelin signaling is associated with gastrointestinal dysmotility in rats with gastroesophageal reflux disease

“…However, the pair-fed sham-operated rats that were controlled in order that they would consume the same amount of food as that consumed by GERD rats showed plasma ghrelin levels similar to those in shamoperated rats. It has been reported that plasma ghrelin levels in rats with food intake restricted by 25% and 50% that were measured 15 days after the initiation of restriction did not differ from rats with ad libitum food intake (27). Therefore, it has been suggested that the increased plasma ghrelin levels in GERD rats may have not resulted solely from reduced food intake.…”