Influence of Ramadan fasting on enzymes in small intestine and liver of rats
The digestion and absorption of food components are major functions of the intestinal mucosa. Fasting dramatically alters these functions.
Ramadan fasting in man results in increased serum lipids, uric acid, urea, and a decrease in blood glucose, lactate and pyruvate, indicating alterations in metabolic activities. The changes in urine volume, osmolarity, total solutes and ions (Sodium and Potassium) and urea produce no adverse health effects on renal function. Basal metabolism slows down, whereas body fat is utilized efficiently during Ramadan fasting. HDL cholesterol increases whereas LDL cholesterol decreases with Ramadan fasting. Owing to different dietary habits and physical activities, both a gain and a loss, and sometimes no change, in body weight have been reported after Ramadan fasting.
The influence of Fasting on enzymes of carbohydrate metabolism and brush border membrane (BBM) in rat intestine and liver was determined. The activities of enzymes involved in glucose oxidation (eg. Lactate dehydrogenase, isocitrate dehydrogenase, succinate dehydrogenase, malate dehydrogenase) and its production (eg. Fructose 1,6-biphosphatase, glucose-6-phosphatase) markedly increased in mucosal and liver homogenates in Ramadan fasting compared with controlled rats. However, the enzymes of the BBM involved in the terminal digestion and/or absorption of nutrients decreased in intestine but increased in liver.
The results support that Ramadan Fasting results in specific intestinal and liver metabolic adaptations. Indeed, the activities of enzymes belonging to various metabolic pathways, for example glycolysis, the tricarboxylic acid cycle and gluconeogenesis, profoundly increased in both the intestine and liver with Ramadan fasting.
At the end of 30 days, body weight in rats was slightly but insignificantly lower in Ramadan Fasting rats compared to control rats. The loss of body weight in human subjects has been attributed to either dehydration or loss of body fat during the course of fasting. The lowering of serum glucose, cholesterol and LDH activity in rats is in partial agreement with the reported decrease in blood glucose, lactate and pyruvate in people after Ramadan fasting.
The enzymes involved in glucose degradation and production were significantly enhanced in both the mucosa and the liver. Anaerobic glycolysis, compared with oxidative metabolism, has been shown to be the major source of energy in the rat intestine. Oxidative metabolism in addition to glycolysis becomes involved in increased energy production during prolonged intermittent Ramadan Type Fasting. Increased fatty acid oxidation may result in enhanced activities of enzymes in the tricarboxylic acid cycle.
Fasting is known to produce extensive morphological as well as biochemical changes in the small intestine and liver; these include decreased mucosal weight, a reduction in the number and length of microvilli and hence a lowering of the total surface area of the villi and microvilli. Refeeding, in contrast, causes a reversal of these effects. Furthermore, the activities of certain enzymes involved in carbohydrate metabolism decrease after fasting and are restored upon refeeding. In contrast, gluconeogenesis is known to increase with fasting and decrease upon refeeding. A rapid degradation of various proteins and enzymes has also been reported by fasting, whereas refeeding results in increased protein/enzyme synthesis.
Conclusion: Ramadan Fasting in rats results in specific adaptive changes in the metabolic activities of both the intestine and the liver. The increased activities of enzymes involved in the degradation as well as the production of glucose suggest that Ramadan fasting enhances nutrition and energy metabolism.
