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，大约有一半没有意识到自己患有这种疾病。糖尿病神经病变是一种常见的继发性并发症，在超过50%的患者中存在，但只有13%的患者意识到这些症状。一种更敏感的非侵入性筛查试验将有助于神经病的诊断。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变特征表明，感觉神经受累的最早形态迹象发生在感觉神经的最远端。这些是属于C类伤害性感受器的表皮神经纤维(ENF)。在一些患者中，ENF严重枯竭，即使在仅深50微米的表皮下神经丛轻度变薄的情况下也是如此。我们推测，检测到ENF的开始变性将是糖尿病神经病变的最早诊断形态学标志，而ENF的再生将是神经病变逆转的第一个迹象。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ENF，这些患者有轻微或没有神经病变，以及已知神经病变患者的无症状近端皮肤区域。最近，已经有几项治疗糖尿病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受益所需的灵敏度。我们相信，皮肤活检和皮肤起泡方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的ENF再生来确定糖尿病受试者重新支配表皮的能力，在这两组患者中，条件有利于再生。第一类是糖尿病神经病变患者，他们将受到一个小的标准化水泡伤口的影响，众所周知，在正常受试者中，这种伤口可以迅速愈合和重新神经支配。第二类是胰腺移植功能正常的患者，他们随后血糖正常，因此不再患有糖尿病。最后，本项目将使用皮肤活检和皮肤水泡的方法来确定神经生长因子(NGF)是否可以促进上述水泡创面中表皮神经纤维的侧枝萌发和再生。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可能是最有潜力促进ENF再生的，因为它对作为ENF来源的背根神经节神经元具有特异性。如果NGF可以促进皮肤伤口的神经再支配，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.