糖尿病為慢性的新陳代謝疾病，病人除了有慢性血糖升高的情況，並且時常伴隨著長期併發症，也比較容易受到感染。糖尿病也被認為是下呼吸道感染的一種獨立危險因子，之前研究顯示，同樣罹患敗血症時，糖尿病人反而比非糖尿病人較不容易進入更嚴重的病程，例如成人呼吸窘迫症。 在特殊感染方面，肺炎克雷伯氏菌特別好發於台灣的糖尿病人，其引起的原發性肺炎，病程進展快速，多數伴隨敗血症症狀，導致了高死亡率。肺臟中常駐的肺泡巨噬細胞，具有吞噬及殺菌能力，並且調節下呼吸道免疫系統的功能，是肺臟中抵抗外來微生物的第一道防線。為了研究糖尿病對於肺泡巨噬細胞功能的影響，本篇實驗先以STZ分別誘發6週齡及30週齡小鼠糖尿病，並持續飼養到第33週齡，使其分別成為慢性及急性糖尿病小鼠後，利用支氣管灌流術分離出小鼠的肺泡巨噬細胞，將肺泡巨噬細胞與標定螢光的小球或大腸桿菌在體外培養2小時後，以流式細胞儀分析肺泡巨噬細胞之吞噬能力。在糖尿病容易遭受肺炎克雷伯氏菌感染之研究方面，本篇實驗從小鼠支氣管注射克雷伯氏菌，造成糖尿病小鼠下呼吸道感染20小時後，取出小鼠的左肺和血漿分別塗抹於培養基上培養18小時，之後計算左肺和血漿中的克雷伯氏菌含量。結果顯示，慢性糖尿病小鼠之肺泡巨噬細胞吞噬能力與正常小鼠相當，而慢性糖尿病小鼠在遭受克雷伯氏菌感染後，其左肺中的克雷伯氏菌含量明顯的較正常小鼠多出 21 倍，但其血漿中的克雷伯氏菌含量與正常小鼠並無差異。至於急性糖尿病小鼠不論在左肺和血漿中克雷伯氏菌含量，均與正常小鼠和慢性糖尿病小鼠沒有差異。本研究顯示台灣糖尿病人對於克雷伯氏菌引起肺炎特殊的易感受性，可能是與糖尿病人肺泡巨噬細胞對於克雷伯氏菌殺菌能力變差有關。經由本篇實驗，可以引導出研究糖尿病下呼吸道免疫機轉的新方向。; Diabetes mellitus is often identified as an independent risk factor for the development of lower respiratory tract infections. Previous studies showed that the diabetic patients with septic shock are susceptible to bacterial lung infections, but less likely to develop severe lung injury, such as ARDS, compared with the nondiabetics. In Taiwan, Klebsiella pneumoniae is a leading pathogen of primary pneumonia with bacteremia in diabetic patients and causes high mortality. Alveolar macrophages (AMs) are a critical component of host defense against lung infections. They not only provide the first-line phagocytic and bactericidal defense against microbial invasion but also modulate the immunity of the lower respiratory tract. To investigate the functions of AMs from diabetic mice, mice were treated with STZ at 6 and 30 wk old, chronic and acute diabetes, respectively, and were kept until 33 wk old for further studies. The phagocytic capacities of AMs from bronchoalveolar lavage were measured by the in-vitro fluorescence-labelled beads or E-coli labeling and subsequent FACScalibur flow cytometer analysis. Furthermore, the chronic and acute diabetic mice were infected with K. pneumoniae by intra-trachea injection. Twenty hr later, the homogenized left lung and the plasma from the infected mice were plated on LB agar and incubated for 18 hr to determine the bacterial count. The results showed that the AMs from chroninc diabetic and control mice had similar phagocytic capacities. The left lung from K. pneumoniae-infected chronic diabetic mice had 21-fold bacteria colonies than that from control mice. However, the bacteria counts from left lung and plasma were similar in the acute and chronic diabetic mice. It is likely that the decrease of the bactericidal ability of AMs contributes to the high susceptibility to K. pneumoniae in diabetic subjects. This study may provide a new approach to the investigation of the immune mechanisms of lower respiratory tract from diabetic animals.
