Interdepartmental Nutrition Program and Department of Animal Science, North Carolina State University, Raleigh, NC 27695, USA.
J Anim Sci. 2013 May;91(5):2332-42. doi: 10.2527/jas.2012-5694. Epub 2013 Mar 5.
An experiment was conducted to determine the effect of dietary n-3 long chain PUFA on insulin sensitivity in growing steers. Steers (n = 12, initial BW = 336.3 kg, SEM = 7.7) were adapted to a basal diet that was 70% concentrate mix and 30% orchardgrass hay. Steers were fed a daily amount of 0.26 Mcal ME per kg BW (0.75). After 3 wk steers were transitioned to 1 of 2 treatment (Trt) diets (n = 6 per diet) containing added Ca salts of fatty acids at 4% of DM using a source of fat that was enriched in n-3 fatty acids, including eicosapentaenoic acid and docosahexaenoic acid (FOFA), or a source of fat without n-3 fatty acids and a greater percentage of C16:0 and C18:1 (LCFA). Three intravenous (i.v.) glucose tolerance tests (IVGTT) were conducted, 1 during the basal diet, and 2 after transition to treatment diets at time 1 (T1; d 4 Trt) and time 2 (T2; d 39 Trt). Three i.v. insulin challenge tests (IC) were conducted the day after each IVGTT. Measurements on the basal diet were used as covariates. For IVGTT, there was a diet by time interaction (P < 0.05) for glucose area under the response curve (AUC). The AUC50 (mM glucose × 50 min) at T1 was less (P = 0.02) for LCFA (126.2) than FOFA (151.8), AUC50 at T2 tended to be greater (P = 0.07) for LCFA (165.9) than FOFA (146.0). Preinfusion insulin concentration was greater (P < 0.001) before the IVGTT and IC for steers fed LCFA (40.4 and 40.2 µIU/mL) than for steers fed FOFA (23.7 and 27.1 µIU/mL), respectively. Glucose clearance did not differ between treatments. For IC, minimum glucose concentration was greater (P = 0.02) and glucose AUC150 was less (P < 0.01) for steers fed LCFA than for steers fed FOFA. Values for glucose concentration were 1.8 mM and 1.5 mM and for AUC150 (mM glucose × 150 min) were 203.1 and 263.6 for steers fed LCFA and FOFA, respectively. Insulin clearance (fraction/min) was greater (P < 0.01) for steers fed LCFA (0.121) than FOFA (0.101). The insulin AUC60 (µIU/mL × 60 min) postinfusion was less for LCFA (17,674) than FOFA (19,997), and tended to be greater (P = 0.06) at T1 (19,552) than T2 (18,119). Plasma NEFA concentrations at T2 during IVGTT were greater (P < 0.05) in steers fed FOFA than in steers fed LCFA. The results indicated that supplementing with long-chain n-3 PUFA (FOFA) increased insulin sensitivity in growing steers compared with feeding a supplement with greater concentration of SFA (LCFA).
进行了一项实验，以确定饮食中 n-3 长链多不饱和脂肪酸对生长牛胰岛素敏感性的影响。牛（n = 12，初始体重 = 336.3 千克，SEM = 7.7）适应了 70%浓缩饲料混合物和 30%果园草干草的基础饮食。牛每天按 0.26 Mcal ME/kg BW（0.75）的量进食。3 周后，牛过渡到 2 种处理（Trt）饮食中的 1 种（n = 6/饮食），在 DM 中添加 4%的脂肪酸 Ca 盐，使用富含 n-3 脂肪酸的脂肪源，包括二十碳五烯酸和二十二碳六烯酸（FOFA），或不含 n-3 脂肪酸和更高百分比的 C16:0 和 C18:1（LCFA）的脂肪源。进行了 3 次静脉（i.v.）葡萄糖耐量试验（IVGTT），1 次在基础饮食期间，2 次在过渡到处理饮食时（T1；d 4 Trt）和 T2（d 39 Trt）。在每次 IVGTT 后第二天进行了 3 次静脉内胰岛素挑战测试（IC）。基础饮食上的测量值用作协变量。对于 IVGTT，葡萄糖反应曲线下面积（AUC）存在饮食与时间的交互作用（P < 0.05）。T1 时 LCFA（126.2）的 AUC50（mM 葡萄糖×50 分钟）小于 FOFA（151.8）（P = 0.02），T2 时 LCFA（165.9）的 AUC50 趋于大于 FOFA（146.0）（P = 0.07）。静脉内葡萄糖输注前，饲喂 LCFA 的牛（40.4 和 40.2 µIU/mL）的胰岛素浓度高于饲喂 FOFA 的牛（分别为 23.7 和 27.1 µIU/mL）（P < 0.001）。对于 IC，最小葡萄糖浓度对于饲喂 LCFA 的牛（P = 0.02）更高，而饲喂 FOFA 的牛的葡萄糖 AUC150 更低（P < 0.01）。饲喂 LCFA 和 FOFA 的牛的葡萄糖浓度分别为 1.8 mM 和 1.5 mM，AUC150（mM 葡萄糖×150 分钟）分别为 203.1 和 263.6。胰岛素清除率（每分钟分数）对于饲喂 LCFA 的牛（P < 0.01）更高（0.121），而对于 FOFA 的牛（0.101）则较低。静脉内输注后胰岛素 AUC60（µIU/mL×60 分钟）对于 LCFA（17,674）的量小于 FOFA（19,997），并且在 T1（19,552）时趋于大于 T2（18,119）（P = 0.06）。在 IVGTT 期间 T2 时，饲喂 FOFA 的牛的血浆 NEFA 浓度高于饲喂 LCFA 的牛（P < 0.05）。结果表明，与饲喂富含 SFA（LCFA）的补充剂相比，补充长链 n-3 多不饱和脂肪酸（FOFA）可提高生长牛的胰岛素敏感性。
