Caloric Restriction and Formalin-Induced Inflammation: An Experimental Study in Rat Model

BACKGROUND: Acute and chronic inflammations are difficult to control. Using chemical anti-inflammatory medications along with their complications considerably limit their use. According to Traditional Iranian Medicine (TIM), there is an important relation between inflammation and Imtila (food and blood accumulation in the body); food reduction or its more modern equivalent Caloric Restriction (CR) may act against both Imtila and inflammation. OBJECTIVES: This experimental study aimed to investigate the effect of 30% reduction in daily calorie intake on inflammation in rats. MATERIALS AND METHODS: A total of 18 male rats (Rattus rattus) weighing 220 to 270 g were obtained. Then, the inflammation was induced by injecting formalin in their paws. Next, the rats were randomized by generating random numbers into two equal groups (9 + 9) putting on either normal diet (controls) or a similar diet with 30% reduction of calorie (cases). Paw volume changes were recorded twice per day by one observer in both groups using a standard plethysmometer for 8 consecutive days. Serum C-reactive protein (CRP), Erythrocyte Sedimentation Rate (ESR), complete blood count (erythrocyte, platelet, and white blood cell) and hemoglobin were compared between the groups. RESULTS: Decline of both body weight and paw volume was significantly more prominent in the case than in the control rats within the study period (P < 0.001 and < 0.001, respectively). Paw volume decrease was more prominent after day 3. On day 8, serum CRP-positive (1 or 2 +) rats were more frequent in ad libitum fed group comparing with those received CR (33.3% vs. 11.1%). This difference, however, was insignificant (P = 0.58). At the same time, mean ESR was significantly higher in the control rats comparing with that in the case group (29.00 ± 2.89 h vs. 14.00 ± 1.55 h; P = 0.001). Other serum parameters were not significantly different between the two groups at endpoint. CONCLUSIONS: Rats fed with a 30% calorie-restricted diet in comparison with to ad libitum fed controls for 8 days had significantly more prominent regression of inflammation.