Jeffrey C. Hanselman

Inhibition of Sphingomyelin Synthesis Reduces Atherogenesis in Apolipoprotein E–Knockout Mice

Background—In clinical studies, sphingomyelin (SM) plasma levels correlated with the occurrence of coronary heart disease independently of plasma cholesterol levels. We hypothesized that inhibition of SM synthesis would have antiatherogenic effects. To test this hypothesis, apolipoprotein E (apoE)–knockout (KO) mice were treated with myriocin, a potent inhibitor of serine palmitoyltransferase, the rate-limiting enzyme in SM biosynthesis. Methods and Results—Diet-admix treatment of apoE-KO mice with myriocin in Western diet for 12 weeks lowered SM and sphinganine plasma levels. Decreases in sphinganine and SM concentrations were also observed in the liver and aorta of myriocin-treated animals compared with controls. Inhibition of de novo sphingolipid biosynthesis reduced total cholesterol and triglyceride plasma levels. Cholesterol distribution in lipoproteins demonstrated a decrease in &bgr;-VLDL and LDL cholesterol and an increase in HDL cholesterol. Oil red O staining of total aortas demonstrated reduction of atherosclerotic lesion coverage in the myriocin-treated group. Atherosclerotic plaque area was also reduced in the aortic root and brachiocephalic artery. Conclusions—Inhibition of de novo SM biosynthesis in apoE-KO mice lowers plasma cholesterol and triglyceride levels, raises HDL cholesterol, and prevents development of atherosclerotic lesions.

Efficacy and Safety of ETC-1002, a Novel Investigational Low-Density Lipoprotein-Cholesterol–Lowering Therapy for the Treatment of Patients With Hypercholesterolemia and Type 2 Diabetes Mellitus

Objective— 8-Hydroxy-2,2,14,14-tetramethylpentadecanedioic acid (ETC-1002) is a small molecule with a unique mechanism of action shown in nonclinical studies to modulate pathways of cholesterol, fatty acid, and carbohydrate metabolism. In previous phase 2 clinical trials, once daily oral treatment with ETC-1002 significantly reduced low-density lipoprotein-cholesterol in patients with hypercholesterolemia. In this trial, the lipid-lowering efficacy of ETC-1002 was evaluated in patients with type 2 diabetes mellitus and hypercholesterolemia. Additional cardiometabolic biomarkers, including glycemic measures, were also assessed. Approach and Results— A single-center, double-blind, placebo-controlled trial evaluated 60 patients with type 2 diabetes mellitus and elevated low-density lipoprotein-cholesterol. Patients discontinued all diabetes mellitus and lipid-regulating drugs and were randomized to receive ETC-1002 80 mg QD for 2 weeks followed by 120 mg QD for 2 weeks or placebo for 4 weeks. ETC-1002 lowered low-density lipoprotein-cholesterol levels by 43±2.6% (least squares mean±SE), compared with a reduction of 4±2.5% by placebo at day 29 (P<0.0001; primary end point). Non–high-density lipoprotein-cholesterol and total cholesterol were also significantly lowered by ETC-1002 compared with placebo (P<0.0001). High-sensitivity C-reactive protein was reduced by 41% (median) compared with a placebo reduction of 11% (P=0.0011). No clinically meaningful safety findings were observed. Conclusions— ETC-1002 lowered low-density lipoprotein-cholesterol and other lipids and demonstrated improvement in high-sensitivity C-reactive protein in patients with type 2 diabetes mellitus and hypercholesterolemia without worsening glycemic control. ETC-1002 was well tolerated in this population. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT# 01607294.

Discovery of novel hepatoselective HMG-CoA reductase inhibitors for treating hypercholesterolemia: a bench-to-bedside case study on tissue selective drug distribution.

The design of drugs with selective tissue distribution can be an effective strategy for enhancing efficacy and safety, but understanding the translation of preclinical tissue distribution data to the clinic remains an important challenge. As part of a discovery program to identify next generation liver selective HMG-CoA reductase inhibitors we report the identification of (3R,5R)-7-(4-((3-fluorobenzyl)carbamoyl)-5-cyclopropyl-2-(4-fluorophenyl)-1H-imidazol-1-yl)-3,5-dihydroxyheptanoic acid (26) as a candidate for treating hypercholesterlemia. Clinical evaluation of 26 (PF-03491165), as well as the previously reported 2 (PF-03052334), provided an opportunity for a case study comparison of the preclinical and clinical pharmacokinetics as well as pharmacodynamics of tissue targeted HMG-CoA reductase inhibitors.

Atherosclerosis in Octodon degus (degu) as a model for human disease

OBJECTIVE Animal models of atherosclerosis are essential to elucidate disease mechanisms and develop new therapies. Each model features advantages and disadvantages in exemplifying the pathophysiology of human atherosclerosis. Diet-induced development of atherosclerosis in Octodon degus (degu) was examined to demonstrate the potential of the degu as a model of human atherosclerosis. METHODS Degus were fed for 16 weeks with either normal chow or chow containing 0.25% cholesterol and 6% palm oil to induce atherosclerosis. The lipid compositions of plasma lipoproteins and aortas were determined. Locations of aortic lesions were mapped by imaging of fluorescently stained aortic lesions. Lesion morphology in the brachiocephalic artery was detected by histological staining. RESULTS Total plasma cholesterol in chow-fed degus was distributed approximately 60% in HDL, 30% in LDL and less than 10% in VLDL. Cholesterol-fed degus exhibited 4- to 5-fold increases in total plasma cholesterol, principally in the VLDL and LDL fractions. Cholesteryl ester transfer protein activity of similar magnitude to that in human plasma was detected in chow-fed degu plasma. Cholesterol-fed degus developed cholesteryl ester-rich atherosclerotic lesions throughout the aorta. Histological examination of lesions in the brachiocephalic artery showed well-formed, foam cell-rich lesions populated with inflammatory cells. It is also noteworthy that all the degus in this study exhibited hyperglycemia. CONCLUSION These results demonstrate that degus have a human-like lipoprotein metabolism and develop extensive atherosclerosis with cholesterol feeding in the presence of hyperglycemia. These features, combined with the manageable size and handling characteristics, point to the potential of the degu as a useful model for atherosclerosis research.

Hypopigmentation and maternal-zygotic embryonic lethality caused by a hypomorphic mbtps1 mutation in mice.

The site 1 protease, encoded by Mbtps1, mediates the initial cleavage of site 2 protease substrates, including sterol regulatory element binding proteins and CREB/ATF transcription factors. We demonstrate that a hypomorphic mutation of Mbtps1 called woodrat (wrt) caused hypocholesterolemia, as well as progressive hypopigmentation of the coat, that appears to be mechanistically unrelated. Hypopigmentation was rescued by transgenic expression of wild-type Mbtps1, and reciprocal grafting studies showed that normal pigmentation depended upon both cell-intrinsic or paracrine factors, as well as factors that act systemically, both of which are lacking in wrt homozygotes. Mbtps1 exhibited a maternal-zygotic effect characterized by fully penetrant embryonic lethality of maternal-zygotic wrt mutant offspring and partial embryonic lethality (~40%) of zygotic wrt mutant offspring. Mbtps1 is one of two maternal-zygotic effect genes identified in mammals to date. It functions nonredundantly in pigmentation and embryogenesis.

ETC-1002 Reduces Blood Pressure in Hypercholesterolemic Patients with Mildly Elevated Blood Pressure

Methods: Normal human primary hepatocytes (Lonza Walkersville Inc.) were first incubated with palmitic acid (0.5 mM) for 24 h to induce fat accumulation. Cells were then treated with niacin (0-0.5 mM) for 24 h. Cellular fat accumulation and formation of reactive oxygen species (ROS, as an index of oxidative stress) were measured by staining with Nile Red O and DCFDA fluorescence respectively. In-vivo effect of niacin on prevention and regression of hepatic steatosis was assessed in high-fat fed rat model of NAFLD. The histology of liver tissue from animals was examined in paraffin embedded hematoxylin and eosin (H&E) stained sections. Results: Niacin (at 0.25 and 0.5 mM doses) significantly inhibited palmitic acid-induced fat accumulation in hepatocytes by 45-62%. This effect was associated with robust inhibition of diacylglycerol acyltransferase 2 (DGAT2) mRNA expression by niacin. Niacin, in a dose-dependent manner, significantly inhibited ROS production in hepatocytes. In experimental rat model of NAFLD, inclusion of niacin at 0.5% and 1% in the high-fat diet significantly decreased liver fat content, hepatic oxidative products, and prevented hepatic steatosis. Niacin treatment to rats with preexisting hepatic steatosis induced by the high-fat diet significantly regressed steatosis. Conclusion: These novel findings suggest that niacin, through inhibiting hepatocyte fat accumulation and lipid peroxidation products, effectively prevents and causes the regression of hepatic steatosis and NAFLD. Clinical development of niacin formulations and niacin-related compounds for the treatment of NAFLD may offer a very cost-effective opportunity in addressing the unmet need for the development of therapeutic agents for NAFLD and other fatty liver disease. N PBO (95% CI) p-value