METHODS TO DIAGNOSE AND EVALUATE THERAPY FOR DIABETES

美国糖尿病协会（1998）估计大约有1600万美国人患有糖尿病。在这些人中，大约有一半人不知道自己患有这种疾病。糖尿病性神经病变是一种常见的继发性并发症，超过50%的患者存在这种并发症，但只有13%的患者意识到症状。更灵敏的非侵入性筛选试验将有助于神经病变的诊断。这将允许在不可逆转的变化发生之前更早地开始严格控制血糖。糖尿病神经病变的远端退行性特征表明，感觉受累的最早形态学征象发生在感觉神经的最远端。这些是表皮神经纤维（ENFs）是C类伤害感受器。在一些患者中，ENFs严重耗损，即使存在表皮下神经丛轻度变薄，深度仅为50微米。我们假设ENFs开始变性的检测将是糖尿病神经病变的最早诊断形态学征象，ENFs再生将是神经病变逆转的第一个征象。我们将尝试建立新的早期诊断方法，通过量化短期无症状糖尿病患者皮肤活检和皮肤水泡中的ENFs，这些患者只有很少或没有神经病变，以及已知神经病变患者的无症状近端皮肤区域。最近有几项治疗糖尿病性神经病变的临床试验。然而，目前的诊断测试不具备评估患者获益所需的敏感性。我们相信皮肤活检和皮肤起泡法可以填补这一空白。我们将首先通过研究两个特定患者组ENF再生来确定糖尿病患者表皮神经再生的能力，这两组患者的条件有利于再生的发生。第一类是患有糖尿病神经病变的患者，他们将受到一个小的标准化水疱伤口，这种伤口在正常受试者中可以迅速愈合和神经再生。第二种是胰腺移植功能正常的患者，随后血糖正常，因此不再是糖尿病患者。最后，本项目将采用皮肤活检和皮肤水疱法来确定神经生长因子（NGF）是否可以促进上述水疱伤口表皮神经纤维的侧支发芽和再生。在进入糖尿病神经病变临床治疗试验的神经营养因子中，NGF可能最有潜力促进ENF再生，因为它对ENF的起源细胞背根神经节神经元具有特异性。如果神经生长因子能增强皮肤创面的再神经支配，这些方法可能有助于评估临床治疗试验的结果。

The American Diabetes Association (1998) estimates that about 16 million Americans have diabetes. Of these, about one-half are unaware that they have the disease. Diabetic neuropathy is a common secondary complication that is present in over 50 percent of patients but only 13 percent are aware of symptoms. Diagnosis of neuropathy would be facilitated by a more sensitive non- invasive screening test. This would allow earlier onset of tight control of blood glucose, before irreversible changes occur. The distal degenerative characteristic of diabetic neuropathy suggests that the earliest morphological signs of sensory involvement occur in the most distal segment of sensory nerves. These are the epidermal nerve fibers (ENFs) which are class C nociceptors. In some patients there is severe depletion of ENFs, even in the presence of mild thinning of the subepidermal plexus, just 50 mum deeper. We hypothesize that detection of beginning degeneration of ENFs will be the earliest diagnostic morphological sign of diabetic neuropathy and that regeneration of ENFs will be the first sign of reversal of neuropathy. We will attempt to establish new methods for early diagnosis by quantifying ENFs in skin biopsies and skin blisters of asymptomatic patients with diabetes of short duration who have minimal or no neuropathy and in non symptomatic proximal skin areas of patients with known neuropathy. Recently there have been several clinical trials for treatment of diabetic neuropathy. However, the current diagnostic tests do not have the sensitivity required to evaluate patient benefit. We believe that the skin biopsy and skin blister methods can fill this void. We will first determine the ability of diabetic subjects to reinnervate epidermis by studying ENF regeneration in two specific patient groups in which conditions are favorable for regeneration to occur. The first are patients with diabetic neuropathy who will be subjected to a small standardized blister wound that is known to heal and reinnervate rapidly in normal subjects. The second are patients who have a functioning pancreas transplant who are subsequently euglycemic and are therefore no longer diabetic. Lastly, this project will use skin biopsy and skin blister methods to determine if nerve growth factor (NGF) can enhance collateral sprouting and regeneration of epidermal nerve fibers in the above blister wound. Of the neurotrophins entered into clinical therapeutic trials for diabetic neuropathy, NGF may have the most potential to enhance ENF regeneration because of its specificity for dorsal root ganglia neurons which are the cells of origin of ENFs. If NGF can enhance reinnervation in the skin wound these methods may be useful to evaluate the results of clinical therapeutic trials.