Effect of Walker 256 tumor growth on intestinal absorption of leucine, methionine and glucose in newly weaned and mature rats

Abstract

In tumor-bearing rats, most of the serum amino acids are used for synthesis and oxidation processes by the neoplastic tissue. In the present study, the effect of Walker 256 carcinoma growth on the intestinal absorption of leucine, methionine and glucose was investigated in newly weaned and mature rats. Food intake and carcass weight were decreased in newly weaned (NT) and mature (MT) rats bearing Walker 256 tumor in comparison with control animals (NC and MC). The tumor/carcass weight ratio was higher in NT than in MT rats, whereas nitrogen balance was significantly decreased in both as compared to control animals. Glucose absorption was significantly reduced in MT rats (MT = 47.3 ± 4.9 vs MC = 99.8 ± 5.3 nmol min -1 cm -1 , Kruskal-Wallis test, P<0.05) but this fact did not hamper the evolution of cancer. There was a significant increase in methionine absorption in both groups (NT = 4.2 ± 0.3 and MT = 2.0 ± 0.1 vs NC = 3.7 ± 0.1 and MC = 1.2 ± 0.2 nmol min -1 cm -1 , Kruskal-Wallis test, P<0.05), whereas leucine absorption was increased only in young tumor-bearing rats (NT = 8.6 ± 0.2 vs NC = 7.7 ± 0.4 nmol min -1 cm -1 , Kruskal-Wallis test, P<0.05), suggesting that these metabolites are being used for synthesis and oxidation processes by the neoplastic cells, which might ensure their rapid proliferation especially in NT rats.

Effects of leucine supplemented diet on intestinal absorption in tumor bearing pregnant rats

“…Although previous studies have showed that there was a reduction on the ratio gut mass/ protein content in groups which were submitted to tumor implant or food restriction decreasing nutrient intestinal absorption [14], in the present study, this ratio can not be related to leucine absorption in pregnant tumor bearing rats. The decrease in glucose intestinal absorption was due to reduction in the food intake; as glucose absorption is up-regulated and depends on its carrier and the pregnant groups (P and L) were adapted to a non-specific regulation of carriers which can be accompanied by mucosal hyperplasia.…”

“…Increased glucagon levels can lead to anorexia, as well as increased hepatic gluconeogenesis and utilisation of gluconeogenic amino acids at the expense of protein synthesis, leading to a negative energy balance [25]. In a recent study, decrease on food intake was observed in Walker tumor -bearing rats associated to highly decrease in carcass weight [13,14]. …”

“…Experiments studying reciprocal influence between cancer and pregnancy still remain controvertial indicating that, in some cases, pregnancy has a protective mechanism against tumor [12] or that there is an increase in fetal resorption incidence and a decrease in fetal weight [13,14]. …”

Nutritional leucine supplementation attenuates cardiac failure in tumour‐bearing cachectic animals

“…The tumour‐bearing rats received a subcutaneous injection of approximately 2.5 × 10 6 Walker‐256 carcinoma cells in a 0.9% NaCl suspension (0.5 mL) in the right flank . The rats without tumours received a unique injection containing a 0.5 mL NaCl solution (0.9% w/v ) without anaesthesia.…”

Cachexia: a problem of energetic inefficiency

“…A decrease in this parameter represents a decrease in the efficiency of energy intake, one of the key components of the energy balance. In cancer, lipid and carbohydrate alterations in intestinal absorption have been reported in both humans [6] and experimental animals [7,8]. Malabsorption is generally attributed to the consequences of oncologic treatments reducing the gastrointestinal absorption.…”