Obesity related pancreatic fat worsens local injury via unsaturated fatty acids

描述（由申请人提供）：急性胰腺炎严重时可能致命，并且发病率不断增加，导致巨大的医疗保健负担和费用。肥胖与严重 AP 相关。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，从而允许治疗窗口期。然而，目前的护理包括保守治疗和并发症治疗。人类严重胰腺坏死伴随着脂肪坏死，这是由游离脂肪酸皂化和脂肪因子升高引起的。这些是该疾病的附带现象还是因果关系尚不清楚。初步数据：为了研究这种与肥胖相关的 AP 恶化，我们检查了对照者和胰腺炎患者尸检的胰腺组织学。我们注意到两组的胰内脂肪 (IPF) 量均随 BMI 的增加而增加。在AP患者中，与对照组相比，脂肪坏死明显增多，并伴有周围腺泡坏死，且随着距脂肪坏死距离的增加而减少。这种脂肪周围腺泡坏死约占总腺泡坏死的一半。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，纤维化阻止脂肪坏死，限制脂肪周围腺泡损伤。为了从机制上理解这一点，我们产生了一种新型的腺泡-脂肪细胞共培养系统。虽然在存在脂肪酶抑制剂奥利司他的情况下，腺泡和脂肪细胞在该培养基中单独或共同发挥正常功能，但省略奥利司他导致几乎完全腺泡坏死，如碘化丙啶摄取、ATP水平下降和LC3-II不增加所证明的。伴随着培养基中脂肪酸和甘油的大量增加，其水平相当于人类严重胰腺坏死的抽吸物中的水平。培养基中的奥利司他防止腺泡死亡和脂肪分解，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。单独而言，严重胰腺坏死患者抽吸物​​中存在的不饱和但不饱和脂肪酸水平增加了腺泡细胞溶质钙，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对腺泡损伤和炎症的相对贡献。我们还建议鉴定导致腺泡损伤的脂肪酶。我们还将比较肥胖与伴有或不伴有纤维化的孤立性 IPF 的相关性，以及肥胖对 AP 严重程度的影响。这些研究可以针对特定的脂肪酶，并根据 IPF 的影像学研究结果，根据严重 AP 的风险对患者进行分层，为这种破坏性疾病开辟新的治疗前沿。 公共卫生相关性：急性胰腺炎具有潜在致命性，严重程度难以预测，发病率不断上升，导致巨大的医疗保健负担和费用（每年 300,000 名患者和 30 亿美元），但没有具体的治疗方法。肥胖与严重 AP 相关。我们的初步数据表明，与肥胖相关的胰内脂肪通过局部脂肪分解（脂解）使 AP 恶化。我们提出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，并根据影像学研究（例如 CT 扫描）中的胰腺内脂肪帮助预测患有严重 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).