Inhibition of Fat Absorption as a Mechanism to Treat Obesity

抑制脂肪吸收作为治疗肥胖的机制

• 批准号: 8597918
• 负责人: CHARLES Milton MANSBACH
• 金额: --
• 依托单位: MEMPHIS VA MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-10-01 至 2016-09-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8597918
• 关键词: Abetalipoproteinemia; Address; Adverse effects; Affect; Animals; Binding; Blood Circulation; CD36 gene; Cells; Centers for Disease Control and Prevention (U.S.); Chylomicrons; Colon; Complex; Cytosol; Diarrhea; Diet; Dietary Fats; Effectiveness; Elements; Endoplasmic Reticulum; Enterocytes; Enzymes; Epidemic; Epithelial Cells; Event; FABP1 gene; Fatty Acid-Binding Protein 1; Fatty acid glycerol esters; Female; Gases; Generations; Goals; Golgi Apparatus; Guidelines; Human; In Vitro; Intestines; Laboratories; Lecithin; Lipase; Lipoproteins; Lymph; Measures; Mediating; Membrane; Modeling; Molecular Conformation; Obesity; One-Step dentin bonding system; Output; Pancreas; Pharmacologic Substance; Phosphorylation; Physiological; Population; Process; Proteins; Rattus; Recombinants; Site; Steatorrhea; Surface; Symptoms; Testing; Transport Vesicles; Triglycerides; Triolein; United States; Vesicle; Veterans; Work; absorption; apolipoprotein B-48; design; feeding; inhibitor/antagonist; long chain fatty acid; male; orlistat; prevent; programs; protein complex

DESCRIPTION (provided by applicant): Obesity in the Veteran population has risen to epidemic proportions in the United States. 33% of male Veterans and 37% of female Veterans are obese as classified by CDC guidelines. Studies over many years have tried to address the causes of obesity. While our understanding of this problem has greatly increased, no effective measures have been successful and obesity rates continue to rise. The program proposed here is designed to treat obesity by inhibiting dietary fat absorption at the level of the intestine. Currently, a compound called tetrahydrolipstatin has been developed to inhibit pancreatic lipase, an enzyme required to break down dietary fat prior to its absorption. While this works in reducing fat absorption, its side effects of bloating, gas, nd diarrhea limit its usefulness. The proposed program inhibits fat absorption after the fat is absorbed into the intestine but before it enters the body so that many of the symptoms of the lipase inhibitor are muted. Our plan is to block the absorbed fat at the level of the intestinal absorptive cell. This type of blockade is modeled in a rare human condition called abetalipoproteinemia. In this condition, fat is malabsorbed but the symptoms of this malabsorbtion are lessened by the fact that the intestinal cell holds the fat that is only released into the intestinal lumen and then to the colon when the intestinal cell dies. Each cell lives 2 to4 days. Our laboratory has identified the rate-limiting step in dietary fat absorption in the rat. Tis was found to be at the level of the endoplasmic reticulum (ER). Next we found that the fat exited the ER in a vesicle, the pre-chylomicron transport vesicle (PCTV). We know the proteins that select cargo chylomicrons for inclusion in the vesicle and the protein that initiates this process. Chylomicrons are the lipoprotein by which dietary fat is delivered to the circulation. Our proposal attacks a conundrum in our studies. The liver fatty acid binding protein (FABP1) can, by itself, generate PCTV without the addition of protein phosphorylation supplied by ATP. By contrast, intestinal cell cytosol, which has considerable FABP1, cannot generate PCTV without ATP. Why? We have found in preliminary studies that L-FABP in cytosol is not present as a single protein but is in a protein complex with 3 other proteins, each of which we know. Our first aim is to determine which of the proteins in the complex is phosphorylated during fat absorption and show that blocking this phosphorylation event is effective in preventing FABP1 from attaching to the ER membrane to start the PCTV budding cascade. If we are successful, then we will have identified one step in the process that is subject to pharmaceutical attack. Our second aim is to identify proteins on the ER surface that are phosphorylated by ATP and in so doing increase the binding of L-FABP from the cytosolic protein complex to the ER membrane. Blocking this phosphorylation step may also inhibit PCTV generation. Again, this protein may be open to pharmaceutical attack. Our third aim is to correlate changes in phosphorylation of proteins in the ER or Golgi with changes in chylomicron output into the lymph due to changes in diet or delivery of phosphatidylcholine to the intestine. These changes will also be correlated with PCTV generating activity of the ER. This will give physiological conformation of our in vitro findings.

描述（由申请人提供）： 在美国，退伍军人中的肥胖问题已达到流行病的程度。根据 CDC 指南，33% 的男性退伍军人和 37% 的女性退伍军人患有肥胖症。多年来的研究一直试图解决肥胖的原因。尽管我们对这个问题的认识大大提高，但有效的措施尚未取得成功，肥胖率仍在持续上升。 这里提出的计划旨在通过抑制肠道水平的膳食脂肪吸收来治疗肥胖。目前，一种名为四氢脂抑素的化合物已被开发出来，用于抑制胰脂肪酶，胰脂肪酶是一种在吸收膳食脂肪之前分解膳食脂肪所需的酶。虽然这可以减少脂肪吸收，但其腹胀、胀气和腹泻等副作用限制了其用途。所提出的方案在脂肪被吸收到肠道之后、进入人体之前抑制脂肪吸收，从而减轻脂肪酶抑制剂的许多症状。我们的计划是在肠道吸收细胞水平上阻止脂肪的吸收。这种类型的封锁是在一种称为无β脂蛋白血症的罕见人类疾病中建模的。在这种情况下，脂肪吸收不良，但由于肠细胞保留脂肪，仅释放到肠腔中，然后在肠细胞死亡时释放到结肠，因此减轻了吸收不良的症状。每个细胞可存活 2 至 4 天。 我们的实验室已经确定了大鼠膳食脂肪吸收的限速步骤。发现其位于内质网（ER）水平。接下来，我们发现脂肪在囊泡（前乳糜微粒转运囊泡（PCTV））中离开内质网。我们知道选择货物乳糜微粒包含在囊泡中的蛋白质以及启动该过程的蛋白质。 乳糜微粒是脂蛋白，膳食脂肪通过它输送到循环系统。我们的建议解决了我们研究中的一个难题。肝脏脂肪酸结合蛋白 (FABP1) 本身可以产生 PCTV，无需添加由 ATP 提供的蛋白质磷酸化。相比之下，含有大量 FABP1 的肠细胞胞浆在没有 ATP 的情况下无法产生 PCTV。为什么？ 我们在初步研究中发现，细胞质中的 L-FABP 并不是以单一蛋白质的形式存在，而是与其他 3 种蛋白质形成蛋白质复合物，其中每一种蛋白质都是我们已知的。我们的首要目标是确定复合物中的哪些蛋白质在脂肪吸收过程中被磷酸化，并证明阻断这种磷酸化事件可以有效防止 FABP1 附着到 ER 膜上以启动 PCTV 出芽级联。如果我们成功了，那么我们将确定这一过程中受到药物攻击的一个步骤。 我们的第二个目标是鉴定 ER 表面上被 ATP 磷酸化的蛋白质，从而增加 L-FABP 从胞浆蛋白复合物与 ER 膜的结合。阻断该磷酸化步骤也可能抑制 PCTV 的产生。同样，这种蛋白质可能容易受到药物攻击。 我们的第三个目标是将内质网或高尔基体中蛋白质磷酸化的变化与由于饮食变化或磷脂酰胆碱输送到肠道而导致的乳糜微粒输出到淋巴中的变化联系起来。这些变化也将与 ER 的 PCTV 生成活动相关。这将给出我们体外研究结果的生理构象。