抗性淀粉结肠内酵解对大鼠肠道健康的影响

Effects of resistant starch fermentation on physiological changes of colon in rats

目的:探讨不同浓度抗性淀粉(RS),特别在高蛋白饲养模式下,对实验大鼠肠道功能、肠内短链脂肪酸和有害及酵解产物等健康指标的影响. 方法:57只健康♂SD大鼠根据体重随机分成5组,分别给予含有0%,6%和12%RS的基础饲料,或含有6%和12% RS的高蛋白饲料(36%酪蛋白,HP)喂养.实验3 wk进行肠道转运时间(GTT)的观察实验;5 wk连续收集3 d粪便; 7 wk处死大鼠,取盲肠进行形态学和组织学观察,并对盲肠内容物中的短链脂肪酸(SCFA)、氨、酚含量以及肠道pH进行测定. 结果:和0%RS组大鼠相比,12%RS组大鼠GTT明显缩短(601±49 min vs 700±58 min,P<0.001),粪便量、盲肠壁及盲肠内容物质量显著增加(分别为1.04±0.22 g vs 0.37±0.12 g,1.12±0.14 g vs 0.73±0.13 g,P<0.001; 4.78±1.44 g vs 3.00±1.12 g,P=0.004<0.01);盲肠内SCFA增加2-3倍(35.5±11.4μmol/g vs13.9±6.7μmol/g, P=0.003<0.01);粪氨、盲肠内氨及酚浓度下降(0.26±0.13 mg/g vs 0.59±0.15 mg/g.0.35±0.13 mg/g vs 0.63±0.13 mg/g,2.03±0.42 mg/g vs 3.15±0.55 mg/g, P<0.001);盲肠和粪便pH值减低(6.26±0.36 vs 7.46±0.28, 5.67±0.31 vs 7.24±0.31,P<0.001),且粪便pH值显著低于盲肠pH值(P<0.001),提示RS使远端结肠发酵增加. 6%RS组粪氨、盲肠酚及肠道pH值亦有中度下降(P<0.05). 以上各指标与RS摄入量存在明显的剂量反应关系(P<0.01). 和相应等剂量RS组相比,HP+12%RS组大鼠GTT延长(659±47 min,P=0.009<0.01),粪便量减少(0.80±0.29 g,P=0.005<0.01),盲肠内容物SCFA降低(24.6±13.6μmol/g,P=0.043<0.0 5);HP+6RS%组和HP+12RS% 组盲肠内酚浓度增加(分别为3.20±0.49 mg/g,2.71±0.55 mg/g,P<0.001),且肠道pH升高.但随着RS摄入的增加,这一现象有所缓解,HP+12%RS组粪便水分,盲肠SCFA、氨、酚浓度及pH值均与HP+6%组有显著差异(P<0.05).RS和酪蛋白对粪便于质量和盲肠pH值有显著交互作用(P<0.01).组织病理切片未显示实验期间RS喂养大鼠盲肠壁细胞出现异常变化. 结论:RS有助于维持肠道健康相关指标,适量摄取可改善高酪蛋白饮食引起的肠道功能改变,起到酸化肠道,促进肠内有益产物SCFA生成,降低有毒代谢产物酚的作用.

AIM: To evaluate the effects of resistant starch (RS) fermentation on colon health-related indexes, including bowel functions, luminal short-chain fatty acid production and toxic compounds excretion. METHODS: Fifty-seven healthy male SD rats were randomly divided into 5 groups based on body weight, and given basal diets with 0%, 6% and 12% RS, or high-protein diets (36% casein, HP) with 6% or 12% RS, respectively. After fed for 3 wk, gut transit time (GTT) for rats in each group was examined; at 5 wk three day feces samples were collected and their contents were assessed; at 7 wk all rats were killed. The morphological and histo logical characteristics of caecum were observed and the caecal function was evaluated by determination of the weight of caecal wall and caecal digesta, detection of caecal short chain fatty acid (SCFA), ammonia, phenol concentration and pH value. RESULTS: In comparison with those in rats fed with 0% RS diet, shortened GTT was significantly shortened (601± 49 min vs 700±58 min, P<0.001), stool bulk was increased with more moisture (1.04±0.22 g vs 0.37±0.12 g, P <0.001), and weight of caecal wall and caecal digesta was also increased (1.12±0.14 g vs 0.73±0.13 g,P<0.001; 4.78±1.44 g vs 3.00±1.12 g, P= 0.004<0.01) in rats fed with 12% RS diet; the concentration of SCFA in caecum was two- to three-fold enhanced by 12% RS (35.5±11.4 μmol/g vs 13.9±6.7 μmol/g, P =0.003<0.01), while the concentration of ammonia in both feces and caecum and phenol in caecum decreased (0.26±0.13 mg/g 1/50.59± 0.15 mg/g, 0.35±0.13 mg/g vs 0.63±0.13 mg/g, 2.03± 0.42 mg/g vs 3.15±0.55 mg/g, P<0.001, respectively); caecal and fecal pH value dropped significantly (6.26± 0.36 vs 7.46±0.28; 5.67±0.31 vs 7.24±0.31, P<0.001), and the variation of pH in feces was greater than that in caecum (P<0.001), suggesting extended fermentation in distal colon. Rats in 6% RS group had similar but intermediate variances in fecal ammonia, caecal phenol and intestinal pH value (P<0.05). All indexes mentioned above were dose-dependent (P <0.01). For rats fed with HP, GTT was prolonged. Fecal bulk and caecal SCFA level dropped in HP+12% RS group (659 ±47 min, P= 0.009 <0.01; 0.80±0.29 g, P= 0.005<0.01, 24.6±13.6 μmol/g P= 0.043<0.05), compared with 12% RS group. The concentrations of caecal phenol in HP+6% RS and HP+12% RS group were 3.20±0.49 mg/g and 2.71±0.55 mg/g respectively, significantly higher than that in 6% and 12% RS groups (P<0.001); fecal and caecal pH value elevated as well. However, as RS intake increased (12%), these negative changes above were attenuated (P<0.05). There was a significant interaction between RS and casein on fecal dry matter and caecal pH value (P<0.01). Histologi cal observation showed no abnormal changes in caecum tissues of rats fed with RS. CONCLUSION: RS is beneficial to sustain intestinal health related indexes and has potential protective effects on bowel functions. Adequate RS intake could attenuate the negative effects of high casein on colon by improving bowel habit, acidifying intestinal tract, promoting SCFA production and decreasing intestinal inner noxious phenol.