| 摘要: | 代謝症候群 (Metabolic syndrome)是全球普遍文明病，國人由於飲食西化，攝取過多高油食物及含糖飲料，再加上缺乏運動等因素，發生率逐年增加。本論文研究的目的是以動物模式比較高油飲食或/和糖水的攝食誘發代謝症候群之效果，並探討其可能作用之分子機制。實驗使用C57BL/6J mice及Wistar rats，分別給予30%奶油之高油飼料 (HF; high fat diet + plane water)、30% 蔗糖糖水 (SW; chow diet + sucrose water)或兩種同時給予 (HF + SW; high fat diet + sucrose water )誘發出現代謝症候群症狀，另以接受正常飲食及飲水老鼠（LF; chow diet + plane water）做對照，飼養21週，比較2種變因(高油飲食或糖水)誘發之效果；另外在大鼠飼養第17週時將三組誘導組半數轉為正常飲食（HF/C、HF+SW/C、SW/C），為期四週，期望飲食的轉換可改善代謝症候群的症狀。
在評估代謝症候群症狀方面以體重及腹部脂肪堆積作為肥胖(特別是中央型肥胖)指標；以血糖、血清胰島素、oral glucose tolerance test (OGTT)及insulin tolerance test (ITT)血糖變化評估是否胰島素阻抗；並量測血脂質(Triglyceride; TG及Cholesterol; TC)及血壓。另測量腹部脂肪細胞大小及血液脂肪細胞激素(包括leptin、adiponectin)濃度、肝臟與肌肉內脂質堆積、肝臟脂質代謝相關基因表現及脂肪組織adipocytokines基因表現。在大鼠肝臟並量測負責調控脂質生合成與糖解相關基因的轉錄因子--sterol regulatory element-binding protein (SREBP)-1c與carbohydrate responsive element binding protein（ChREBP）蛋白質在細胞核/細胞質分布。
結果顯示在大鼠方面，三組誘導組體重、體脂堆積及脂肪細胞直徑皆顯著大於LF(P<0.0001)；HF+SW與SW組的血清Leptin顯著高於LF組(P<0.0001)； SW的血清Uric acid顯著高於LF組(P<0.005)；三組誘導組肝臟TG與TC均顯著高於LF (P<0.0001)；HF+SW與SW肌肉內TG顯著高於LF（P<0.05）；SW組的血清TC及SW與HF+SW組的血清TG顯著高於LF組(P<0.0001)；三組誘導組皆呈現高胰島素血症(P<0.05)，SW組禁食血糖顯著高於LF組(P<0.05)；在OGTT與ITT可發現SW組血糖值高於LF（P<0.05）；收縮壓方面HF+SW顯著高於LF（P<0.005），舒張壓方面HF+SW和SW皆顯著高於LF（P<0.05）；SREBP-1c、ChREBP蛋白質nuclear/cytosol比例，SW皆顯著高於LF(P<0.08)；肝臟fatty acid synthase（FAS）mRNA量四組無顯著差異，但SW組有較高趨勢；Glucokinase（GK）mRNA表現量在HF+SW顯著高於其它三組(P<0.08)；脂肪組織中Tumor necrosis factor-α（TNF-α）與resistin mRNA在HF組皆顯著高於LF(P<0.05)。Two-way ANOVA顯示糖水因子對大鼠的體重增加、體脂堆積、肝脂堆積、肌肉內脂質堆積、高Leptin血症、高尿酸血症、血脂、血糖、胰島素及血壓有顯著作用，而高油因子僅對體重增加、體脂堆積、肝脂堆積及禁食血漿胰島素有顯著作用。
誘導組在為期四週飲食轉換後，各指標呈現不等程度改善：HF/C的皮下脂肪、肝臟TC、肝臟GK mRNA量、脂肪組織TNF-α、resistin、Plasminogen activated inhibitor-1（PAI-1）、leptin mRNA量皆顯著性低於HF(P=0.084，<0.05，<0.08，<0.05，<0.05，<0.05，<0.05)，HF+SW/C的皮下脂肪、血清Leptin與TG顯著性低於HF+SW(P=0.0564，<0.05，<0.05)，SW/C的血清TG與肝臟FAS、GK mRNA量顯著性低於SW(P<0.05與<0.05、0.05)。
在小鼠方面，三組誘導組的體重、體脂及血清Leptin顯著高於LF組(P<0.0001)； SW和HF+SW肝中TG含量顯著高於LF(P<0.05)，HF和HF+SW肝中TC含量顯著高於LF (P<0.05)；三組誘導組的血清TC及TG顯著高於LF組(P<0.0001與0.05)，HF與HF+SW呈現高胰島素血症（P<0.05），HF組不但出現高血糖，且OGTT及ITT血糖變化顯著高於它組（P<0.0001，<0.0001，<0.05）；肝臟carnitine palmitoyl CoA transferase 1 mRNA量在HF與HF+SW 顯著高於LF (P<0.0001)，acyl CoA oxidase 與phosphenolpyruvate carboxykinase mRNA量HF顯著高於LF(P<0.05)；脂肪組織中TNF-α、resistin mRNA量在誘導組與對照組雖沒有顯著的差異但有高於對照組的趨勢，Leptin mRNA量在三組誘導組皆顯著高於對照組(P<0.0001)，PAI-1基因表現量在HF與SW顯著高於對照組(P<0.05)；HF的mesoderm specific transcript mRNA量顯著高於LF(P<0.0005)。Two-way ANOVA顯示糖水因子對體重增加、體脂堆積、血脂有顯著上升作用，而高油因子則對體重增加、體脂堆積、肌肉內脂質堆積、高Leptin血症、血脂、血糖及血清胰島素均有顯著作用。總括以上的結果顯示高油或糖水飲食在大、小鼠分別有不同效果，在大鼠糖水誘發代謝症候群效果較佳，而小鼠則是對高油飲食較敏感。而在大鼠中也可看到代謝症候群因飲食的誘發也可因飲食的修正而得到改善。未來若要建立代謝症候群的動物模式應用於健康食品開發，Wistar 大鼠適合以糖水誘發，C57BL/6J小鼠適合以高油飲食誘發。本研究也證實含糖飲料的攝取如同高油食物的確會增加代謝症候群之危險，近年國內杯裝飲料市場大幅成長，消費人口快速增加，其背後潛在的國民健康問題值得注意。
Metabolic syndrome is a global healthy problem with a soaring morbidity. In Taiwan, a dietary patterm change with an increased high fat diet or/and sucrose-sweetened beverage consumption, accompanies with an absence of exercise are considered to be the risk factors of metabolic syndrome. This study was designed to compare the effect of a high fat diet or / and sucrose-containing drinking water on inducing metabolic syndrome and the possible molecular mechanisms involved were also studied. Male C57BL6J mice and Wistar rats were each divided into one control (chow diet; LF) and three inducing groups, including HF, SW and HF+SW, to receive a 30% butter-containing diet, 30% sucrose in drinking water, or both, respectively, After 21 wks, the dietary effects of a high fat diet and the sucrose-containing drinking water were compared among the four groups. For evaluating if it is reversible for diet-induced-metabolic syndrome, half of rats in the three inducing groups were shifted to a control diet（HF/C, HF+SW/C, SW/C）at 17 wks. After 4 wks, the metabolic sequela was compared with HF, HF+SW and SW, respectively.
For assessing metabolic syndrome, body weight and visceral fat accumulation were used as an indicator of obesity, especially for central obesity. Fasting serum glucose and insulin, oral glucose tolerance（OGTT）and insulin tolerance test (ITT) were used as an indicator of insulin resistance. Serum lipid levels including triglyceride and cholesterol and blood pressure were alaso measured. For exploring the possible mechanism for diet-induced metabolic syndrome, adipocyte size in visceral fat, serum levels of adipocytokines （leptin and adiponectin）, lipid accumulation in liver and muscle and the expression levels of genes participating in lipid metabolism in liver and as adipocytokines in adipose tissue were all measured. The nuclear/cytosol distribution of sterol regulatory element-binding protein (SREBP)-1c and carbohydrate responsive element binding protein（ChREBP）proteins were also measured since the two transcription factors play an important role in regulating the lipogenic genes and glycolytic genes expression.
In Wistar rats, results showed the body weight gain, adiposity and the average diameter of adipocyte in three inducing groups were significantly higher than those in the LF group (P<0.0001). The HF+SW and SW groups had a significantly higher serum leptin level than the LF group (P<0.0001). The serum uric acid in SW group was significantly higher than that in the LF group (P<0.005). The TG and TC concentrations in liver of three inducing groups (P<0.0001) and the TG concentration in muscle of the HF+SW and SW groups (P<0.05) were all significantly higher than those in the LF group. As compared with the LF group, the serum TC level in SW group and the serum TG level in SW and HF+SW groups were significantly increased (P<0.0001). Hyperinsulinemia and hyperglycemia were happened in the three inducing groups and in the SW group, respectively. During the 2 hr period of OGTT and ITT, significantly higher serum glucose levels were observed in the SW group as compared with the LF group (P<0.05). The systolic blood pressure in HF+SW group (P<0.005) and the diastolic blood pressure (P<0.05) in HF+SW and SW groups were significantly higher than those in the LF group. The nuclear / cytosol ratios for SREBP-1c and ChREBP in SW group was significantly higher than that in the LF group (P<0.08). For gene expression levels in liver, a higher mRNA level of the fatty acid synthase（FAS) in the SW group was observed, though the difference didn’t reach a statistical significance. The glucokinase（GK） in the HF+SW group was significantly higher than in the other groups (P<0.08). For gene expression levels in adipose tissue, tumor necrosis factor-α（TNF-α）and resistin mRNA levels in the HF group were significantly higher than those in the LF group(P<0.05). Two-way ANOVA showed, the sucrose-containing drinking water has significant effects on body weight gains, adiposity, lipid accumulation in liver and muscle, serum levels of leptin, uric acid, lipids, glucose and insulin. However, the high fat dietary factor only showed significant effects on body weight gains, adiposity, liver lipid accumulation and fasting serum insulin.
After shifting to a control diet for 4wk in inducing groups, most of the unfavorable effects were alleviated with different degrees by this dietary modification. The subcutaneous fat mass, TC concentration in liver, the mRNA levels of GK in liver and TNF-α, resistin, plasminogen activated inhibitor-1（PAI-1） and leptin in adipose tissue were significantly reduced in the HF/C group as compared with the HF group (P=0.084，<0.05，<0.08，<0.05，<0.05，<0.05，<0.05). The subcutaneous fat mass, serum leptin and TG concentrations was significantly reduced in the HF+SW/C group as compared with the HF+SW group (P=0.0564，<0.05，<0.05). The serum level of TG and mRNA levels of FAS and GK in liver was significantly reduced in the SW/C group as compared with the SW group (P<0.05 and <0.05, 0.05).
In C57BL/6J mice, as compared wth the LF group, the body weight gains, adiposity and serum leptin level in three inducing groups were significantly increased (P<0.0001). The liver TG concentration in the SW and HF+SW groups and the TC concentration in HF and HF+SW groups were significantly higher than those in the LF group(P<0.05). The hyperlipidemia (including TC and TG) was observed in the three inducing groups (P<0.0001 and <0.05) and the hyperinsulinemia was observed in the HF and HF+SW groups (P<0.05). The HF group showed not only a hyperglycemia (P<0.0001), but also a significantly higher serum glucose levels during the 2hr period of OGTT and ITT as compared with the other groups（P<0.0001 and <0.05, respectively）. The mRNA levels of the carnitine palmitoyl CoA transferase 1 in liver of the HF and HF+SW groups (P<0.0001) and the acyl CoA oxidase and phosphenolpyruvate carboxykinase in liver of the HF group (P<0.05) were all significantly higher than those in the LF group. In adipose tissue, a higher trend of mRNA level of TNF-α and resistin in the three inducing groups was observed, though the differences didn’t reach a statistically significant level. The mRNA levels of the leptin in the three inducing groups (P<0.0001) and the PAI-1 in the HF and SW groups (P<0.05) were significantly higher than those in the LF group. The mesoderm specific transcript mRNA level in adipose tissue of the HF group was significantly higher than that in the LF group(P<0.0005). Two-way ANOVA showed, the sucrose-containing drinking water has significant effects on body weight gains, adiposity and serum lipids. However, a high fat diet has significant effects on body weight gains, adiposity, lipid accumulation in liver and muscle, serum levels of leptin, lipids, glucose and insulin. From those results, we concluded that a high fat diet and the sucrose-containing drinking water both can induce metabolic syndrome, though with different effects on rats and mice. The Wistar rats are prone to the sucrose water-induced metabolic syndrome, and the C57BL/6J mice are prone to a high fat diet-induced metabolic syndrome. As indicated by the results of dietary shift in rats, the metabolic syndrome induced by dietary factors can be reversed by dietary modulations.
Key Words：Metabolic syndrome、High fat diet、Sucrose-containing water |
