Obesity related pancreatic fat worsens local injury via unsaturated fatty acids

描述(由申请人提供)：急性胰腺炎在严重时具有潜在的致命性，并且发病率正在增加，导致巨大的医疗负担和成本。肥胖与严重的急性胰腺炎有关。第一周后AP的死亡率是由严重的胰腺坏死及其相关并发症造成的，允许一个治疗窗口期。然而，目前的护理包括对其并发症的保守治疗和治疗。在人类中，严重的胰腺坏死与脂肪坏死一起发生，这是由于游离脂肪酸的皂化和脂肪因子的升高造成的。目前尚不清楚这些是该病的一种附带现象还是因果关系。初步数据：为了研究这种肥胖相关的AP恶化，我们从对照组和胰腺炎患者的尸检中检查了胰腺组织学。我们注意到两组BMI患者的胰腺内脂肪(IPF)量均有增加。AP组脂肪坏死较对照组明显增多，并伴有周围腺泡坏死，且随着距离脂肪坏死距离的增加而减少。脂肪周围的腺泡坏死约占整个腺泡坏死的一半。相比之下，慢性胰腺炎患者的IPF似乎与BMI无关，并伴有纤维化，后者将脂肪坏死隔开，限制了脂肪周围腺泡的损害。为了从机制上理解这一点，我们建立了一种新的腺泡-脂肪细胞共培养系统。在脂肪酶抑制剂奥利司他的存在下，腺泡细胞和脂肪细胞在这种介质中单独和一起都能正常工作，而奥利司他的缺失会导致近乎完全的腺泡坏死，表现为摄取碘化丙啶，ATP水平下降，没有LC3-II增加。伴随而来的是培养液中脂肪酸和甘油的大幅增加，其水平相当于人类严重胰腺坏死的吸出物中的水平。介质中的奥利司他阻止腺泡死亡和脂解，并恢复重新纯化的腺泡对类似于对照腺泡的刺激的反应性。单独来看，严重胰腺坏死患者吸液中存在的不饱和但不饱和脂肪酸水平增加了腺泡细胞内钙，并导致细胞色素C渗漏和细胞死亡。因此，我们假设肥胖相关的胰腺内脂肪通过局部脂肪分解产生的不饱和脂肪酸加重胰腺损伤。我们建议研究脂肪酸和脂肪因子在腺泡损伤和炎症中的相对作用。此外，我们还建议确定导致腺泡损伤的脂肪酶(S)。我们还将比较肥胖与单纯性IPF伴和不伴纤维化的相关性，以了解其对AP严重性的影响。这些研究可以针对特定的脂肪酶(S)，并根据IPF的影像研究结果，根据严重AP的风险对患者进行分层，从而开辟这种毁灭性疾病的新治疗前沿。 与公共卫生相关：急性胰腺炎具有潜在的致命性、不可预测的严重性，发病率不断增加，导致巨大的医疗负担和费用(每年30万名患者和30亿美元)，但没有具体的治疗方法。肥胖与严重的急性胰腺炎有关。我们的初步数据显示，肥胖相关的胰腺内脂肪通过局部脂肪分解(脂肪分解)加重AP。我们建议的研究可以通过预防脂肪分解来帮助治疗这种毁灭性的疾病，并帮助根据胰腺内脂肪的成像研究(例如CT扫描)预测有严重AP风险的患者。

DESCRIPTION (provided by applicant): Acute Pancreatitis is potentially lethal when severe and is increasing in incidence, resulting in significant health care burden and costs. Obesity is associated with severe AP. Mortality from AP after the first week results from severe pancreatic necrosis and its associated complications, allowing a therapeutic window period. However, care currently consists of conservative management and treatment of its complications. Severe pancreatic necrosis in humans occurs with fat necrosis, which results from the saponification of free fatty acids along with elevated adipokines. Whether these are an epiphenomenon or causal in the disease is unknown. PRELIMINARY DATA: To study this obesity-associated exacerbation of AP, we examined pancreas histology from autopsies of controls and patients with pancreatitis. We noted an increase in the amount of intrapancreatic fat (IPF) with BMI in both groups. In AP patients, there was significantly more fat necrosis compared with controls, which was accompanied by surrounding acinar necrosis, which decreased with increasing distance from the fat necrosis. This peri-fat acinar necrosis contributed to about half of the total acinar necrosis. In contrast, IPF in patients with chronic pancreatitis seemed unrelated to BMI, was accompanied by fibrosis, which walled off fat necrosis, limiting peri-fat acinar damage. To understand this mechanistically, we generated a novel acinar-adipocyte co-culture system. While acini and adipocytes functioned normally in this medium both individually and together in the presence of the lipase inhibitor orlistat, omission of orlistat resulted in near total acinar necrosis, as evidenced by propidium iodide uptake, drop in ATP levels, and absence of LC3-II increase. This was accompanied by a large increase in fatty acids and glycerol in the medium, with levels equivalent to those in aspirates from severe pancreatic necrosis in humans. Orlistat in the medium prevented acinar death and lipolysis and restored responsiveness of repurified acini to stimuli similar to control acini. Individually, unsaturated but not saturated fatty acids at levels present in aspirates from patients with severe pancreatic necrosis increased acinar cytosolic calcium and caused cytochrome C leakage and cell death. We therefore hypothesize that obesity-associated intrapancreatic fat worsens pancreatic injury via unsaturated fatty acids generated from local lipolysis. We propose to study the relative contribution of fatty acids and adipokines to acinar injury and inflammation. We additionally propose to identify the lipase(s) responsible for acinar injury. We will also compare the relevance of obesity to isolated IPF with and without fibrosis with regard to its impact on the severity of AP. These studies could open a new therapeutic frontier for this devastating disease by targeting specific lipases(s) and by stratifying patients according to risk of severe AP based on findings of IPF on imaging studies. PUBLIC HEALTH RELEVANCE: Acute Pancreatitis is potentially lethal, unpredictably severe, increasing in incidence, resulting in significant health care burden and costs (300,000 patients and $3 billion annually), but has no specific treatment. Obesity is associated with severe AP. Our preliminary data show that obesity-associated intrapancreatic fat worsens AP via local fat breakdown (lipolysis). Our proposed studies could help treat this devastating disease by preventing lipolysis and help predict patients at risk of severe AP based on intrapancreatic fat on imaging studies (e.g. CT scan).