NO-1886 (ibrolipim), a lipoprotein lipase activator, increases the expression of uncoupling protein 3 in skeletal muscle and suppresses fat accumulation in high-fat diet-induced obesity in rats

Although the lipoprotein lipase (LPL) activator NO-1886 shows antiobesity effects in high-fat-induced obese animals, the mechanism remains unclear. To clarify the mechanism, we studied the effects of NO-1886 on the expression of uncoupling protein (UCP) 1, UCP2, and UCP3 in rats. NO-1886 was mixed with a high-fat chow to supply a dose of 100 mg/kg to 8-month-old male Sprague-Dawley rats. The animals were fed the high-fat chow for 8 weeks. At the end of the administration period, brown adipose tissue (BAT), mesenteric fat, and soleus muscle were collected and levels of UCP1, UCP2, and UCP3 messenger RNA (mRNA) were determined. NO-1886 suppressed the body weight increase seen in the high-fat control group after the 8-week administration (585 +/- 39 vs 657 +/- 66 g, P < .05). NO-1886 also suppressed fat accumulation in visceral (46.9 +/- 10.4 vs 73.7 +/- 14.5 g, P < .01) and subcutaneous (43.1 +/- 18.1 vs 68.9 +/- 18.8 g, P < .05) tissues and increased the levels of plasma total cholesterol and high-density lipoprotein cholesterol in comparison to the high-fat control group. In contrast, NO-1886 decreased the levels of plasma triglycerides, nonesterified free fatty acid, glucose, and insulin. NO-1886 increased LPL activity in soleus muscle (0.082 +/- 0.013 vs 0.061 +/- 0.016 mumol of free fatty acid per minute per gram of tissue, P < .05). NO-1886 increased the expression of UCP3 mRNA in soleus muscle 3.14-fold (P < .01) compared with the high-fat control group without affecting the levels of UCP3 in mesenteric adipose tissue and BAT. In addition, NO-1886 did not affect the expression of UCP1 and UCP2 in BAT, mesenteric adipose tissue, and soleus muscle. In conclusion, NO-1886 increased the expression of UCP3 mRNA and LPL activity only in skeletal muscle. Therefore, a possible mechanism for NO-1886's antiobesity effects in rats may be the enhancement of LPL activity in skeletal muscle and the accompanying increase in UCP3 expression.     

Effect of the lipoprotein lipase activator NO-1886 on adriamycin-induced nephrotic syndrome in rats

Hyperlipidemia associated with nephrotic syndrome may play a role in the deterioration of renal function. Tsutsumi et al have previously reported that the novel compound NO-1886 increases lipoprotein lipase (LPL) activity, resulting in a reduction of plasma triglycerides and an elevation of high-density lipoprotein (HDL) cholesterol in normal rats. The aim of this study was to ascertain whether NO-1886 suppresses the renal injury by treatment of the hyperlipidemia in an Adriamycin (Kyowa Hakko Kogyo, Tokyo, Japan) induced nephrosis rat model fed a high-protein diet that induced renal dysfunction and tubulointerstitial injury. Administration of Adriamycin caused hyperlipidemia, proteinuria, and edema with ascites in rats in 4 weeks. Furthermore, a combination of Adriamycin and a high-protein diet increased plasma creatinine and blood urea nitrogen (BUN) and decreased plasma albumin. Histologically, in Adriamycin-treated rats, marked interstitial cellular infiltration, tubular lumen dilation, and tubular cast formation in the kidney were observed. NO-1886 decreased plasma triglyceride and increased HDL cholesterol in Adriamycin-induced nephrotic rats. NO-1886 treatment reduced plasma creatinine and BUN levels and increased plasma albumin in Adriamycin-treated rats; it also ameliorated the ascites and proteinuria. Histologically, NO-1886-treated rats showed a quantitatively significant preservation of tubulointerstitial lesions. These data suggest that NO-1886 may have a protective effect against Adriamycin-induced nephrosis with tubulointerstitial nephritis in rats by a modification of the plasma lipid disorder.     

Lipoprotein lipase activator NO-1886 (ibrolipim) accelerates the mRNA expression of fatty acid oxidation-related enzymes in rat liver

The lipoprotein lipase (LPL) activator NO-1886 (ibrolipim) has been shown to have potential benefits for the treatment of obesity in rats. However, the anti-obesity mechanism of NO-1886 has not been clearly understood. To address this, we studied the effects of NO-1886 on the mRNA expression of fatty acid oxidation-related enzymes in rats. The respiratory quotient (RQ) in rats administered a single oral dose of NO-1886 was significantly lower than control rats under both fed and fasted conditions. NO-1886 orally administered to rats for 7 days caused 1.54-fold increase in carnitine palmitoyl transferase II (CPTII) mRNA in the carnitine palmitoyl transferase system. Furthermore, NO-1886 caused a 1.47-fold increase in long-chain acyl-CoA dehydrogenase (LCAD) mRNA, a 1.49-fold increase in acetyl-CoA acyltransferase 2 (ACAA2) mRNA, and a 1.24-fold increase in enoyl-CoA hydratase (ECH) mRNA in rats, all which are liver beta-oxidation enzymes. NO-1886 also increased uncoupling protein-2 (UCP2) mRNA levels in liver by 1.42-fold when compared to the control group. These results suggest that the LPL activator NO-1886 may accelerate the expression of fatty acid oxidation-related enzymes, resulting in a reduction of RQ.     

Lipoprotein lipase activator NO-1886 improves fatty liver caused by high-fat feeding in streptozotocin-induced diabetic rats

NO-1886 is a lipoprotein lipase (LPL) activator. Administration of NO-1886 results in an increase in plasma high-density lipoprotein cholesterol (HDL-C) and a decrease in plasma triglyceride (TG) levels. The aim of this study was to ascertain whether NO-1886 improves fatty liver caused by high-fat feeding in streptozotocin (STZ)-induced diabetic rats. Administration of NO-1886 resulted in increased plasma HDL-C levels and decreased TG levels without affecting total cholesterol and glucose levels in the diabetic rats. NO-1886 dose-dependently decreased liver TG contents and cholesterol contents, resulting in improvement of fatty liver. NO-1886 also reduced plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) that accompany fatty liver. The liver cholesterol contents were inversely correlated with plasma HDL-C levels (r = -0.5862, P <.001) and were positively correlated with plasma TG levels (r = 0.4083, P <.003). The liver TG contents were inversely correlated with plasma HDL-C levels (r = -0.6195, P <.001) and were positively correlated with plasma TG levels (r = 0.5837, P <.001). There was no correlation between plasma cholesterol levels, and cholesterol and TG contents in liver. These results indicate that reducing plasma TG levels and elevating in HDL-C levels may result in improving fatty liver.     

NO-1886 (ibrolipim), a lipoprotein lipase-promoting agent, accelerates the expression of UCP3 messenger RNA and ameliorates obesity in ovariectomized rats

The synthetic compound NO-1886 (ibrolipim, [4-(4-bromo-2-cyano-phenylcarbamoyl)-benzyl]-phosphonic acid diethyl ester, CAS 133208-93-2) is a lipoprotein lipase (LPL)-promoting agent that decreases plasma triglycerides, increases high-density lipoprotein cholesterol levels, and prevents fat accumulation in high fat-fed rats. However, the effect of NO-1886 on body weight, fat accumulation, and energy expenditure in ovariectomized (OVX) rats is not clear. The primary aim of this study was to ascertain whether NO-1886 ameliorated obesity in OVX rats and to examine the effects on fatty acid oxidation-related enzymes. NO-1886 decreased accumulation of visceral fat and suppressed the increase in body weight resulting from the ovariectomy. NO-1886 decreased the respiratory quotient and increased expression of the fatty acid translocase messenger RNA (mRNA) in the liver, soleus muscle, and mesenteric fat. NO-1886 also increased the expression of fatty acid-binding protein mRNA in the liver and soleus muscle and the expression of the uncoupling protein 3 (UCP3) mRNA in the heart, soleus muscle, and mesenteric fat, but not in the brown adipose tissue. Furthermore, NO-1886 did not affect UCP1 and UCP2 in brown adipose tissue. Therefore, amelioration of obesity by NO-1886 in OVX rats is possibly because of an the increased expression of fatty acid oxidation-related enzymes and UCP3, both of which are related to fatty acid transfer and fat use. Our study indicates that the LPL-promoting agent NO-1886 may be potentially beneficial in the treatment of obesity and obesity-linked health problems in postmenopausal women.     

Correlation between lipid and glycogen contents in liver and insulin resistance in high-fat-fed rats treated with the lipoprotein lipase activator NO-1886

Insulin resistance results in accumulation of triglyceride content and reduction of glycogen content in skeletal muscle. However, very few studies have measured lipid content and glycogen content in liver associated with insulin resistance. We studied the relationship between liver lipid content, liver glycogen, and insulin resistance in high-fat-fed rats, which are animal models of insulin resistance. High-fat-fed rats were hyperlipidemic, hyperglycemic, and hyperinsulinemic. Furthermore, the glucose infusion rates (GIR) were lower (normal rats, 10.35 +/- 1.66; high-fat-fed rats, 4.86 +/- 0.93 mg/kg/min; P <.01) and the triglyceride and cholesterol contents in liver were higher in the high-fat-fed rats than in normal rats. On the other hand, the glycogen content in liver was lower than in normal rats. There was an inverse relationship between liver triglyceride content and liver glycogen content. When the lipoprotein lipase (LPL) activator NO-1886 was administered to the high-fat-fed rats at a daily dose of 50 mg/kg body weight for 10 weeks, GIR (9.87 +/- 3.76 mg/kg/min, P <.05 v high-fat-fed control group) improved, causing an improvement of the hyperlipidemia, hyperglycemia, and hyperinsulinemia. Furthermore, NO-1886 decreased triglyceride and cholesterol concentrations and increased glycogen content in liver of the high-fat-fed rats. In this study, we found that insulin resistance caused fatty liver and reduced glycogen content in liver. Administration of the LPL activator NO-1886 improved the insulin resistance, resulting in an improvement in the relationship between triglyceride and glycogen content in liver of high-fat-fed rats.     

A lipoprotein lipase activator,NO-1886 prevents impaired endothelium-dependent relaxation of aorta caused by exercise in aged rats

Exercise decreases plasma total cholesterol and triglycerides, and simultaneously, increases high density lipoprotein (HDL) cholesterol. As a result, exercise is believed to aid in preventing atherosclerosis. However, we do not know whether exercise protects against the development of atherosclerosis in the elderly. The aim of this study was to ascertain whether the lipoprotein lipase activator NO-1886 had an effect on the prevention of atherosclerosis in aged rats which undergo exercise. Exercise for 3 months did not affect plasma lipids but decreased the accumulation of visceral fat in 2-year-old rats (aged rat). Exercise also resulted in an elevation of plasma lipid peroxide (LPO) levels and impaired the endothelium-dependent relaxation of the thoracic aorta caused by acetylcholine in aged rats. On the other hand, NO-1886 decreased plasma triglycerides and increased HDL cholesterol and suppressed the elevation of plasma LPO levels caused by exercise. Furthermore, NO-1886 prevented impaired endothelium-dependent relaxation caused by exercise. In summary, the results of our study indicate that exercise may cause impaired endothelium-dependent relaxation by elevation of LPO in aged rats, and that NO-1886 prevents this impaired endothelium-dependent relaxation of aorta by reducing plasma triglycerides, elevating HDL cholesterol, and suppressing the elevation of plasma LPO caused by exercise.     

Management of primary mixed hyperlipidemia with lovastatin

Many patients with high levels of serum total cholesterol have a concomitant elevation of serum triglyceride levels and thus have mixed hyperlipidemia. In this study, 13 patients with mixed hyperlipidemia were treated with the cholesterol-lowering drug lovastatin to determine its effectiveness. In 9 of these patients, lovastatin therapy used alone was compared with the drug combination of lovastatin and gemfibrozil. In the 13 patients, lovastatin therapy produced a 31% reduction in total cholesterol level and a 32% decrease in triglyceride levels compared with placebo. It lowered very-low-density plus intermediate-density lipoprotein cholesterol levels by 40%, low-density lipoprotein cholesterol levels by 36%, and total apolipoprotein B levels by 28%. Concentrations of high-density lipoprotein cholesterol and apolipoprotein A-I were unchanged, but total cholesterol (and low-density lipoprotein cholesterol)/high-density lipoprotein cholesterol ratios were markedly reduced. Compared with lovastatin alone, lovastatin plus gemfibrozil produced greater decreases in very-low-density plus intermediate-density lipoprotein cholesterol levels and an increase in high-density lipoprotein cholesterol levels, but, in view of the higher risk for severe myopathy with this combination, lovastatin used alone may be adequate therapy for many patients with mixed hyperlipidemia.     

A moderate-fat diet for combined hyperlipidemia and metabolic syndrome

A low-fat diet is recommended for hyperlipidemia. However, low-density lipoprotein (LDL) responses depend on the type of hyperlipidemia (ie, simple hypercholesterolemia or combined hyperlipidemia). In combined hyperlipidemia, which is typical of patients with metabolic syndrome, LDL levels are only one third as responsive to fat and cholesterol as simple hypercholesterolemia. The diminished dietary sensitivity of combined hyperlipidemia is explained by diminished intestinal absorption of cholesterol, a feature of metabolic syndrome. In turn, combined hyperlipidemia is caused by heightened lipid secretion by the liver. A moderate-fat, moderate-carbohydrate diet employing allowable fats has the promise of reducing endogenous lipoprotein production in combined hyperlipidemia. Triglyceride, LDL, and small-dense LDL should be lower, and high-density lipoprotein, apoprotein A-I, and buoyant LDL should be higher. A test of this dietary strategy on lipoproteins and downstream benefits on inflammatory mediators, oxidative stress, and vascular reactivity is now underway.     

NO-1886 Up-regulates Niemann–Pick C1 Protein (NPC1) Expression Through Liver X Receptor α Signaling Pathway in THP-1 Macrophage-Derived Foam Cells

Background  The Niemann–Pick C1 (NPC1) protein regulates the transport of cholesterol from late endosomes/lysosomes to other compartments responsible for maintaining intracellular cholesterol homeostasis. Liver X receptors (LXRs) operate as cholesterol sensors which may protect from cholesterol overload by increasing the amount of free cholesterol in the plasma membrane through inducing NPC1 expression. NO-1886 has been proven to be highly effective at increasing liver X receptor α expression and promoting cellular cholesterol efflux. In this study, the effects of NO-1886 on NPC1 expression were investigated in THP-1 macrophage-derived foam cells. Methods and results  Results showed that NO-1886 markedly increased expression of NPC1 at both mRNA level and protein level in a dose-dependent and time-dependent manner. Cellular cholesterol content was decreased while cholesterol efflux was increased by NO-1886 treatment. In addition, LXR α was also up-regulated by NO-1886 treatment. And LXR α small interfering RNA completely abolished the promotion effect which was induced by NO-1886. Conclusion  These results provide evidence that NO-1886 up-regulates expression of NPC1 through LXR α pathway in THP-1 macrophage- derived foam cells. Xin Ma and Yan-Wei Hu contributed equally to this study.     

Cholesterol absorption and hepatic acyl-coenzyme A:cholesterol acyltransferase activity play major roles in lipemic response to dietary cholesterol and fat in laboratory opossums

Partially inbred lines of laboratory opossums differ considerably in their low-density lipoprotein (LDL) cholesterol responses to dietary cholesterol and fat. Genetic analysis suggested that a single major gene is responsible for the variation in LDL cholesterol on the high cholesterol and high fat (HCHF) diet. We measured cholesterol absorption and acyl-coenzyme A:cholesterol acyltransferase (ACAT) activity in intestine and liver to narrow the search for the major gene. We measured plasma lipoproteins and percent cholesterol absorption by the fecal isotope ratio method in high and low responding lines of opossums on basal and HCHF diets. We also measured lipids in liver and ACAT activity in liver and intestine on the HCHF diet. High and low lines exhibited no differences in percent cholesterol absorption on the basal diet. However, high responding opossums had significantly higher percent cholesterol absorption, hepatic free and esterified cholesterol, and hepatic ACAT activity than low responding opossums on the HCHF diet. Hepatic ACAT activity but not the intestinal ACAT activity was associated with hepatic cholesterol concentration and percent cholesterol absorption. Cholesterol absorption is a major determinant of diet-induced hyperlipidemia in opossums. Hepatic ACAT activity but not the intestinal ACAT may also play a role in diet-induced hyperlipidemia in opossums.     

Measurement of the serum lipoprotein lipase concentration is useful for studying triglyceride metabolism: Comparison with postheparin plasma

The catalytically inactive form of lipoprotein lipase (LPL) is detectable at high levels in serum, although its physiologic role remains unknown. The aim of this study was to elucidate the clinical significance of serum LPL compared with postheparin LPL or the net increment (Δ) of LPL (postheparin − preheparin LPL). We measured the LPL mass before and 15 minutes after the injection of heparin in 164 subjects with hyperlipidemia. LPL mass was measured by a sensitive sandwich enzyme-linked immunosorbent assay (ELISA). Serum LPL was one fifth of the postheparin LPL concentration. There was a weak correlation between the serum LPL and postheparin LPL concentrations (r = .225, P ≤ .005). The Δ LPL concentration was strongly related to the postheparin LPL concentration (r = .965, P ≤ .0001), but not to the preheparin LPL mass, suggesting that the weak correlation between serum LPL and postheparin LPL levels was attributable to contamination of postheparin plasma by pre-existing LPL (preheparin LPL). Both serum and postheparin LPL were significantly lower in diabetic patients and in subjects with high levels of triglyceride or low levels of high-density lipoprotein (HDL). Serum LPL was correlated negatively with triglyceride, remnants, and insulin resistance and was positively correlated with HDL cholesterol and low-density lipoprotein (LDL) size. Postheparin LPL was strongly correlated with HDL cholesterol, but not with other parameters, as was serum LPL. Δ LPL mass did not show a closer association with triglyceride metabolism than postheparin LPL or preheparin LPL. In conclusion, serum LPL measurement is simple and seems to be useful for studying triglyceride metabolism.     

Lipoprotein Lipase Activator NO‐1886

Lipoprotein lipase (LPL) is a rate‐limiting enzyme that hydrolyzes circulating triglyceride‐rich lipoproteins such as very low‐density lipoproteins and chylomicrons. A decrease in LPL activity is associated with an increase in plasma triglycerides (TG) and a decrease in plasma high‐density lipoprotein cholesterol (HDL‐C). The increase in plasma TG and decrease in plasma HDL‐C are risk factors for cardiovascular disease. Tsutsumi et al. hypothesized that elevating LPL activity would cause a reduction of plasma TG and an increase in plasma HDL‐C, resulting in protection against the development of atherosclerosis. To test this hypothesis, Otsuka Pharmaceutical Factory, Inc. synthesized the LPL activator NO‐1886. NO‐1886 increased LPL mRNA and LPL activity in adipose tissue, myocardium and skeletal muscle, resulting in an elevation of postheparin plasma LPL activity and LPL mass in rats. NO‐1886 also decreased plasma TG concentration and caused a concomitant rise in plasma HDL‐C. Long‐term administration of NO‐1886 to rats and rabbits with experimental atherosclerosis inhibited the development of atherosclerotic lesions in coronary arteries and aortas. Multiple regression analysis suggested that the increase in plasma HDL‐C and the decrease in plasma TG protect from atherosclerosis. The atherogenic lipid profile is changed to an antiatherogenic profile by increasing LPL activity, resulting in protection from atherosclerosis. Therefore, the LPL activator NO‐1886 or other possible LPL activating agents are potentially beneficial for the treatment of hyper‐triglyceridemia, hypo‐HDL cholesterolemia, and protection from atherosclerosis.     

Thiazolidinedione- and tumor necrosis factor alpha-induced downregulation of peroxisome proliferator-activated receptor gamma mRNA in differentiated 3T3-L1 adipocytes

Thiazolidinediones (TZDs) are antidiabetic insulin-sensitizing agents that bind to peroxisome proliferator-activated receptor gamma (PPARgamma) and have potent adipogenic effects on 3T3-L1 preadipocytes. In fully differentiated 3T3-L1 adipocytes, TZDs markedly decreased PPARgamma mRNA levels without reducing the expression of genes that are positively regulated by PPARgamma, such as adipocyte lipid-binding protein 2 (aP2) or lipoprotein lipase-(LPL). PPARgamma mRNA levels were also downregulated by tumor necrosis factor alpha (TNFalpha), an antiadipogenic cytokine. We propose that the downregulation of PPARgamma is not the common denominator of the metabolic effects of TZDs and TNFalpha on mature adipocytes.     

应用骨髓移植研究巨噬细胞脂蛋白脂酶对严重高甘油三酯血症小鼠脂代谢的作用

目的 研究骨髓中巨噬细胞来源的脂蛋白脂酶(LPL)对遗传性极高甘油三酯血症小鼠血浆脂蛋白代谢的作用.方法 将8只雌性脂蛋白脂酶基因缺陷(LPL-/-,LK)小鼠随机分为两组,用1 000 rad~(137)Cs照射,6 h后分别尾静脉注射脂蛋白脂酶基因缺陷的雄性小鼠及野生型(WT)雄性小鼠的骨髓.骨髓移植后通过眶静脉采血收集小鼠血浆,监测血浆甘油三酯、胆固醇、血浆脂蛋白脂酶活性等指标的变化,并用快效液相色谱技术检测血浆脂蛋白的分布.结果 移植后第4周,与LPL-/-→LPL-/-骨髓移植组相比,WT→LPL-/-骨髓移植组小鼠血浆甘油三酯水平降低83.2%(P<0.05,n=4),胆固醇水平降低74.4%(P<0.05,n=4).与骨髓移植前相比,WT→LPL-/-骨髓移植组小鼠血浆甘油三酯水平降低86.2%(P<0.05,n=4),胆固醇水平降低78.8%(P<0.01,n=4),脂蛋白脂酶活性增加4.5倍(P<0.05,n=4).LPL-/-→LPL-/-骨髓移植组小鼠血浆甘油三酯、胆固醇水平以及血浆脂蛋白脂酶活性较移植前均无明显改变.结论 骨髓巨噬细胞来源的脂蛋白脂酶对脂代谢具有重要的调节作用,可有效改善遗传性极高甘油三酯血症小鼠的高脂血症.     

泰脂安对老年高脂血症患者C反应蛋白的影响

目的　 研究泰脂安对老年高脂血症患者C反应蛋白 (CRP)的影响。　 方法 　测定 45例老年高脂血症患者应用泰脂安治疗前后血脂、CRP水平的变化。　 结果 　经过 8周泰脂安治疗 ,总胆固醇、LDL、TG及CRP分别下降 2 8 13 % (P <0 0 1)、2 1 92 % (P <0 0 1)、13 3 7% (P <0 0 5 )及 13 75 % (P <0 0 5 ) ,而HDL升高 9 2 5 % (P >0 0 5 )。　 结论 　泰脂安不仅可调脂 ,也可降低CRP水平     

Severe hypercholesterolemia in a double heterozygote for lipoprotein lipase deficiency (LPL(Arita)) and apolipoprotein epsilon4: a report of a family with LPL(Arita)

Although heterozygous lipoprotein lipase (LPL) deficiency is not rare, only part of the phenotypes may have been reported in Japan. Here we describe a Japanese family with LPL(Arita), the most common mutation linked to familial LPL deficiency in Japan, and show for the first time a heterozygote for the mutation who had marked hypercholesterolemia due to increased low-density lipoprotein (LDL) cholesterol. The proband's mother, one of the heterozygotes for LPL(Arita) in the family, had both severe hypercholesterolemia (total cholesterol 306 mg/dl) with an especially increase in LDL-cholesterol and mild hypertriglyceridemia (180 mg/dl). She had normal LDL receptor activity and did not show clear evidence of possible causes of secondary hyperlipidemia. In addition to being heterozygous for LPL deficiency, she was also heterozygous for apo epsilon4. Because the epsilon4 allele is known to be associated with higher LDL-cholesterol, heterozygous apo epsilon4 may be one of causes of her LDL-cholesterol elevation. The other three heterozygotes for LPL(Arita) were moderate drinkers, and all of them had both remarkable hypertriglyceridemia and mild hypercholesterolemia due to increased very-low-density lipoproteins (VLDL). The results suggest that heterozygotes for LPL(Arita) can exhibit various phenotypes of hyperlipidemia, that is, hypertrigliceridemia and/or hypercholesterolemia due to not only increased VLDL but also increased LDL. The phenotypes appear to depend on some other genetic and environmental factors.     

Effect of diet on adipose tissue and skeletal muscle VLDL receptor and LPL: implications for obesity and hyperlipidemia

This study was designed to examine the effect of a high-fat (primarily saturated), refined-carbohydrate (sucrose) diet (HFS), which is known to induce obesity and hyperlipidemia, on adipose tissue and skeletal muscle lipoprotein lipase (LPL) and very-low density lipoprotein receptor (VLDL-R) protein expressions. Female Fischer rats were placed on either a HFS or a low-fat, complex-carbohydrate (LFCC) diet for 22 months beginning at 2 months of age. After 20 months, a subgroup of the HFS rats were switched to the LFCC diet for 2 months (HFS/LFCC). Body weight, feed efficiency, plasma total cholesterol, VLDL-C, low-density lipoprotein cholesterol (LDL-C) and triglyceride (TG) concentrations and LDL-C to high-density lipoprotein cholesterol ratio were all significantly raised by the HFS diet and improved by conversion to the LFCC diet. Adipose tissue heparin-releasable, extractable and total LPL activity expressed per cell were significantly increased in the HFS-fed group. However, LPL protein abundance normalized against total cellular protein was unchanged in the HFS group. This observation is consistent with the presence of adipose tissue hypertrophy. Skeletal muscle LPL protein abundance and heparin-releasable activity were reduced by the HFS diet and improved after switching to the LFCC diet. Both adipose tissue and skeletal muscle VLDL-R protein levels were significantly reduced by the HFS diet and increased after conversion to the LFCC diet. We conclude that an HFS diet induces changes in LPL and VLDL-R in a manner which favors shunting of dietary fat from skeletal muscle to adipose tissue and decreases TG-rich lipoprotein clearance contributing to increased plasma lipids and obesity. Conversion to a LFCC diet can ameliorate the dyslipidemia and tissue changes induced by long-term HFS diet consumption.     

Genetic demonstration of intestinal NPC1L1 as a major determinant of hepatic cholesterol and blood atherogenic lipoprotein levels

Objective: The correlation between intestinal cholesterol absorption values and plasma low-density lipoprotein-cholesterol (LDL-C) levels remains controversial. Niemann-Pick-C1-Like 1 (NPC1L1) is essential for intestinal cholesterol absorption, and is the target of ezetimibe, a cholesterol absorption inhibitor. However, studies with NPC1L1 knockout mice or ezetimibe cannot definitively clarify this correlation because NPC1L1 expression is not restricted to intestine in humans and mice. In this study we sought to genetically address this issue. Methods and results: We developed a mouse model that lacks endogenous (NPC1L1) and LDL receptor (LDLR) (DKO), but transgenically expresses human NPC1L1 in gastrointestinal tract only (DKO/L1^IntOnly mice). Our novel model eliminated potential effects of non-intestinal NPC1L1 on cholesterol homeostasis. We found that human NPC1L1 was localized at the intestinal brush border membrane of DKO/L1^IntOnly mice. Cholesterol feeding induced formation of NPC1L1-positive vesicles beneath this membrane in an ezetimibe-sensitive manner. Compared to DKO mice, DKO/L1^IntOnly mice showed significant increases in cholesterol absorption and blood/hepatic/biliary cholesterol. Increased blood cholesterol was restricted to very low-density lipoprotein (VLDL) and LDL fractions, which was associated with increased secretion and plasma levels of apolipoproteins B100 and B48. Additionally, DKO/L1^IntOnly mice displayed decreased fecal cholesterol excretion and hepatic/intestinal expression of cholesterologenic genes. Ezetimibe treatment virtually reversed all of the transgene-related phenotypes in DKO/L1^IntOnly mice. Conclusion: Our findings from DKO/L1^IntOnly mice clearly demonstrate that NPC1L1-mediated cholesterol absorption is a major determinant of blood levels of apolipoprotein B-containing atherogenic lipoproteins, at least in mice.     

Cholesterol absorption regulates cholesterol metabolism and plasma lipoprotein levels in patients with gut exclusions

The occurrence of cholesterol malabsorption and its role in the regulation of cholesterol metabolism were studied in 30 patients with an earlier gut resection and 9 patients with a jejunoileal bypass for treatment of obesity. Fractional cholesterol absorption varied from 0.1% to 70%, and was lowest in jejunoileal bypass (8.3%) associated with severe fat and moderate bile acid malabsorptions and in 15 patients with a long small-intestinal resection (20.4%) associated with severe bile acid and moderate fat malabsorption. Seven resected patients with normal fecal fat and bile acids and 8 resected patients with malabsorption of only bile acid had normal cholesterol absorption. Low fractional cholesterol absorption was associated with a short length of the remaining proximal small intestine, high dietary intake of plant sterol, and high fecal fat and neutral sterol excretions, but not with bile acid malabsorption. In the whole study population, plasma levels of total, low-density lipoprotein, and high-density lipoprotein cholesterol were positively correlated with fractional cholesterol absorption and the amount of total, dietary, and biliary absorbed cholesterol and were negatively correlated with fecal cholesterol elimination as neutral sterols (less so as bile acids) and cholesterol synthesis. The results emphasize that, in patients with ileal exclusion, plasma levels of low-density lipoprotein and high-density lipoprotein cholesterol are regulated more effectively by cholesterol than by bile acid malabsorption. Moreover, although the fecal loss of bile acids is the main determinant in cholesterol elimination and stimulation of cholesterol synthesis in patients with intestinal exclusions, intestinal cholesterol absorption also contributes noticeably to the regulation of cholesterol synthesis.