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A series of cycloalkyl-substituted oxo-alkanedicarboxylic acids have been prepared by the TosMIC methodology departing from haloalkyl-substituted cycloalkylcarboxylic esters. cyclopropyl derivatives showed IC50 activity in the 0.3–1.0 μM range on the de novo incorporation of radiolabeled acetate into lipids in primary cultures of rat hepatocytes, and they showed lipid-regulating properties when tested in vivo in female obese Zucker fatty rats.

We have identified a novel omega-hydroxy-alkanedicarboxylic acid, ESP 55016, that favorably alters serum lipid variables in obese female Zucker (fa/fa) rats. ESP 55016 reduced serum non-HDL-cholesterol (non-HDL-C), triglyceride, and nonesterified fatty acid levels while increasing serum HDL-C and beta-hydroxybutyrate levels in a dose-dependent manner. ESP 55016 reduced fasting serum insulin and glucose levels while also suppressing weight gain. In primary rat hepatocytes, ESP 55016 increased the oxidation of [(14)C]palmitate in a dose- and carnitine palmitoyl transferase-I (CPT-I)-dependent manner. Furthermore, in primary rat hepatocytes and in vivo, ESP 55016 inhibited fatty acid and sterol synthesis. The "dual inhibitor" activity of ESP 55016 was unlikely attributable to the activation of the AMP-activated protein kinase (AMPK) pathway because AMPK and acetyl-CoA carboxylase (ACC) phosphorylation states as well as ACC activity were not altered by ESP 55016. Further studies indicated the conversion of ESP 55016 to a CoA derivative in vivo. ESP 55016-CoA markedly inhibited the activity of partially purified ACC. The activity of partially purified HMG-CoA reductase was not altered by the xenobiotic-CoA. These data suggest that ESP 55016-CoA favorably alters lipid metabolism in a model of diabetic dyslipidemia in part by initially inhibiting fatty acid and sterol synthesis plus enhancing the oxidation of fatty acids through the ACC/malonyl-CoA/CPT-I regulatory axis.

To induce atherogenesis in mice, a high fat (HF) diet is supplemented with cholic acid (CA), which increases apoB-containing particles and lower apoA-I-containing particles. HF diet without CA increases levels of both HDL and LDL, suggesting that CA may be responsible for the elevation of LDL and lowering of HDL. The mechanism of dietary CA-induced lowering of apoA-I-containing particles has recently been reported. In this study, we examined the mechanism of CA- and HF-induced elevation of apoB-containing lipoproteins in mice. Mice were fed the following four diets: control chow (C), high fat high cholesterol, (HF), control and 0.5% cholate (CA), and HF + CA. Dietary CA increased the plasma levels of apoB-containing particles by ∼2-fold when compared to control; VLDL levels increased 2-fold, and LDL levels increased 1.3-fold. On HF diet, VLDL increased by 1.4-fold, and LDL by 2-fold, suggesting that CA and HF-induced increases of apoB-containing particles occurred by different mechanisms. We investigated the potential mechanisms regulating plasma levels of apoB in CA- and HF-fed mice. Although hepatic apoB mRNA levels did not change on CA diet, apoB-100 mRNA increased relative to B-48 as a result of decreased editing of apoB mRNA. Measurements of hepatic LDL receptor mRNA suggested that CA diet down-regulated LDL receptor mRNA, possibly by increasing the levels of hepatic cholesterol. Since plasma and hepatic vitamin E levels did not show significant changes on CA-containing diets, it suggests that dietary CA did not act by increasing the absorption of dietary fat. Hepatic lipase, known to modulate plasma levels of apoB-containing particles, did not show changes in CA- or HF-fed mice. Taken together, these results suggest that dietary CA increased apoB-containing particles both in chow-fed and fat-fed mice by enhancing the relative production of apoB-100, and also by reducing LDL receptor-mediated clearance of apoB-containing particles. Thus, dietary cholate modulates plasma levels of apoB primarily by posttranscriptional mechanisms. © 2001 Elsevier Science Ltd. All rights reserved.

In the current studies we describe the effects of PD 72953 and related compounds on lipoprotein levels in chowfed male rats. After 2 weeks, 10 mg/kg of PD 72953 daily was as effective as 100 mg/kg gemfibrozil for elevating HDL-cholesterol. At 100 mg/kg, PD 72953 further elevated HDL-cholesterol to 232% of control levels, and was associated with increased HDL size and plasma apoE (169% of control), despite no change in hepatic apoE mRNA. ApoA-I rose transiently (at 1 week), but by 2 weeks only apoE remained elevated. PD 72953 dose-dependently reduced plasma apoB, VLDL-cholesterol, LDL-cholesterol, and triglyceride. Hepatic apoC-III mRNA reduction parallelled triglyceride lowering. After 1 week, 30 and 100 mg/kg per day PD 72953 reduced plasma apoC-III levels by 30 and 34%, and triglycerides by 60 and 83%, respectively. PD 72953 treatment had no effect on triglyceride production rates; however,125I-labeled VLDL apoB disappearance was enhanced. We compared PD 72953 to a structurally similary diacid, PD 69405, that also reduced VLDL and LDL, but had no effect on HDL elevation. Compared to PD 72953, PD 69405 further accelerated 125I-labeled VLDL apoB disappearance, decreased triglyceride production, and elevated the ratio of post-heparin hepatic to lipoprotein lipase activity. Whole animal studies, transient transfection studies in HepG2 cells, and chimeric receptor studies in kidney 293 cells suggest that PD 72953 is a ligand for the peroxisomal proliferation activated receptor alpha (PPARα), and PPARγ. Overall, PD 72953 may act through a peroxisomal proliferation activated receptor and result in plasma triglycerides and apoB-containing lipoprotein reduction, while also raising HDL cholesterol. Reduced apoC-III may allow triglyceride-rich remnants to more efficiently bind and present substrate to peripheral tissue lipoprotein lipase, and therefore allow enhanced shedding of remnant phospholipid surface for HDL production.—Bisgaier, C. L., A. D. Essenburg, B. C. Barnett, B. J. Auerbach, S. Haubenwallner, T. L, A. D. White, P. Creger, M. E. Pape, T. J. Rea, and R. S. Newton. A novel compound that elevates high density lipoprotein and activates the peroxisome proliferator activated receptor. J. Lipid Res. 1998. 39: 17–30.

A series of long (11-15) hydrocarbon chain diols and diacids with various central functional groups and terminal gem-dimethyl or -methyl/aryl substituents was synthesized and evaluated in both in vivo and in vitro assays for its potential to favorably alter lipid disorders including metabolic syndrome. Compounds were assessed for their effects on the de novo incorporation of radiolabeled acetate into lipids in primary cultures of rat hepatocytes, as well as for their effects on lipid and glycemic variables in obese female Zucker fatty rats, Crl:(ZUC)-faBR. The most active compounds were hydroxyl-substituted symmetrical diacids and diols with a 13-atom chain and terminal gem-dimethyl substituents. Furthermore, biological activity was enhanced by central substitution with O, C=O, S, S=O compared to the methylene analogues and was diminished for compounds with central functional groups such as carbamate, ester, urea, acetylmethylene, and hydroxymethylene.

Poly(A)+ RNA from lactating rat mammary glands was size-fractionated to enrich the relative amount of acetyl-CoA carboxylase mRNA. The enriched mRNA was used to generate a lambda gt11 cDNA library. Initial screening with polyclonal antiserum to acetyl-CoA carboxylase produced three positive clones. Western blot analysis revealed that two clones, lambda DH3 and lambda KH18, synthesized 165,000-dalton proteins that were recognized by antibodies to acetyl-CoA carboxylase and beta-galactosidase, indicating that acetyl-CoA carboxylase/beta-galactosidase fusion proteins were produced. Competition experiments with purified acetyl-CoA carboxylase further demonstrated that the fusion proteins contained acetyl-CoA carboxylase protein segments. Antibodies which are specific to the fusion proteins were isolated. These antibodies cross-reacted only with acetyl-CoA carboxylase in a preparation of partially purified acetyl-CoA carboxylase. In addition, the antibodies immunoprecipitated enzyme activity from a crude liver homogenate. Northern blot analysis of total RNA revealed two RNA species: one 10 kilobases and the other 3.0 kilobases. The levels of these RNA species increased when starved animals were fed a fat-free diet, indicating that they are coordinately regulated.

Tumor necrosis factor (TNF) is secreted by macrophages in response to various stimuli and blocks lipid accumulation during the conversion of preadipocytes to adipocytes in culture. In the present report, we investigate the effect of recombinant TNF on the expression of acetyl-coenzyme-A (CoA) carboxylase, the rate-limiting enzyme for long-chain fatty acid biosynthesis. We used a preadipocyte cell line, 30A-5, derived from 10T1/2 mouse fibroblasts after treatment with 5-azacytidine. Treatment of the preadipocyte cell line with dexamethasone and insulin triggers the conversion of these cells to mature adipocytes as evidenced by the accumulation of lipid. The mRNA and enzyme levels of acetyl-CoA carboxylase as well as the enzyme activity increase markedly during the conversion process. TNF prevents the conversion of preadipocytes to adipocytes with a concomitant inhibition in the accumulation of acetyl-CoA carboxylase mRNA and decrease in enzyme activity. This observed reduction in acetyl-CoA carboxylase mRNA levels is reversible upon removal of TNF. Acetyl-CoA carboxylase mRNA levels and enzyme activity also decrease when fully differentiated adipocytes are exposed to TNF but to a much lesser extent. These results suggest that TNF affects de novo lipid synthesis in part by altering the mRNA levels of acetyl-CoA carboxylase.

We measured acetyl-CoA carboxylase mRNA levels in various tissues of the rat under different nutritional and hormonal states using a cDNA probe. We surveyed physiological conditions which are known to alter carboxylase activity, and thus fatty acid synthesis, to determine whether changes in the levels of carboxylase mRNA are involved. The present studies include the effects of fasting and refeeding, diabetes and insulin, and lactation on carboxylase mRNA levels. Northern blot analysis of liver RNA revealed that fasting followed by refeeding animals a fat-free (high carbohydrate) diet dramatically increased the amount of carboxylase mRNA compared to the fasted condition. These changes in the level of mRNA correspond to changes in the activity and amount of acetyl-CoA carboxylase. Acetyl-CoA carboxylase mRNA levels in epididymal fat tissue decreased upon fasting and increased to virtually normal levels after 72 h of refeeding, closely resembling the liver response. The amount of acetyl-CoA carboxylase mRNA decreased markedly in epididymal fat tissue of diabetic rats as compared to nondiabetic animals. However, 6 h after injection of insulin the mRNA level returned to that of the nondiabetic animals. Gestation and lactation also affected the levels of carboxylase mRNA in both liver and mammary gland. Maximum induction in both tissues occurred 5 days postpartum. These studies suggest that these diverse physiological conditions affect fatty acid synthesis in part by altering acetyl-CoA carboxylase gene expression.

Poly(A)+ RNA from lactating rat mammary glands was fractionated according to size by isokinetic sucrose gradient centrifugation to obtain a fraction enriched for acetyl-CoA carboxylase. In vitro translation of this RNA preparation yielded apparent full-length acetyl-CoA carboxylase with a molecular weight of 260,000. The synthesized protein was identified as acetyl-CoA carboxylase by specific immunoprecipitation. Tests with antiserum to fatty acid synthetase, revealed that the fractions containing acetyl-CoA carboxylase mRNA also contained mRNA for fatty acid synthetase; both of these mRNAs were approximately 10 kb. Fatty acid synthetase with a molecular weight of 250,000 was synthesized. Using an in vitro rabbit reticulocyte lysate translation system, we have shown that the amount of translatable acetyl-CoA carboxylase mRNA increases during lactation. On the fifth day postpartum the level of translatable acetyl-CoA carboxylase mRNA increased to a peak level seven times that on the day of parturition.