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Individuals of many species rely on odors to communicate, find breeding partners, locate resources and sense dangers. In vertebrates, odorants are detected by chemosensory receptors of the olfactory system. One class of these receptors, the trace amine-associated receptors (TAARs), was recently suggested to mediate male sexual interest and mate choice. Here we tested this hypothesis in mice by generating a cluster deletion mouse (Taar2-9−/−) lacking all TAARs expressed in the olfactory epithelium, and evaluating transduction pathways from odorants to TAARs, neural activity and behaviors reflecting sexual interest. We found that a urinary volatile amine, isobutylamine (IBA), was a potent ligand for TAAR3 (but not TAAR1, 4, 5, and 6). When males were exposed to IBA, brain regions associated with sexual behaviors were less active in Taar2-9−/− than in wild type males. Accordingly, Taar2-9−/− males spent less time sniffing both the urine of females and pure IBA than wild type males. This is the first demonstration of a comprehensive transduction pathway linking odorants to TAARs and male sexual interest. Interestingly, the concentration of IBA in female urine varied across the estrus cycle with a peak during estrus. This variation in IBA concentration may represent a simple olfactory cue for males to recognize receptive females. Our results are consistent with the hypothesis that IBA and TAARs play an important role in the recognition of breeding partners and mate choice.

Modulating bile acid synthesis has long been considered a good strategy by which to improve cholesterol homeostasis in humans. The farnesoid X receptor (FXR), the key regulator of bile acid synthesis, was, therefore, identified as an interesting target for drug discovery. We compared the effect of four, structurally unrelated, synthetic FXR agonists in two fat-fed rodent species and observed that the three most potent and selective agonists decreased plasma cholesterol in LDL receptor-deficient (Ldlr (-/-)) mice, but none did so in hamsters. Detailed investigation revealed increases in the expression of small heterodimer partner (Shp) in their livers and of intestinal fibroblast growth factor 15 or 19 (Fgf15/19) in mice only. Cyp7a1 expression and fecal bile acid (BA) excretion were strongly reduced in mice and hamsters by all four FXR agonists, whereas bile acid pool sizes were reduced in both species by all but the X-Ceptor compound in hamsters. In Ldlr (-/-) mice, the predominant bile acid changed from cholate to the more hydrophilic β-muricholate due to a strong repression of Cyp8b1 and increase in Cyp3a11 expression. However, FXR agonists caused only minor changes in the expression of Cyp8b1 and in bile acid profiles in hamsters. In summary, FXR agonist-induced decreases in bile acid pool size and lipophilicity and in cholesterol absorption and synthesis could explain the decreased plasma cholesterol in Ldlr (-/-) mice. In hamsters, FXR agonists reduced bile acid pool size to a smaller extent with minor changes in bile acid profile and reductions in sterol absorption, and consequently, plasma cholesterol was unchanged.

Subjects with high HDL-C show elevated plasma markers of cholesterol absorption and reduced markers of cholesterol synthesis. We evaluated the effect of dalcetrapib, a cholesteryl ester transfer protein modulator, on markers of cholesterol homeostasis in healthy subjects.Dalcetrapib was administered daily with or without ezetimibe in a randomized, open-label, crossover study in 22 healthy subjects over three 7-day periods: dalcetrapib 900 mg, ezetimibe 10mg, dalcetrapib 900 mg plus ezetimibe 10mg. Plasma non-cholesterol sterols lathosterol and desmosterol (cholesterol synthesis markers) and campesterol, β-sitosterol and cholestanol (intestinal cholesterol absorption markers) were measured. A hamster model was used to compare the effect of dalcetrapib and torcetrapib with or without ezetimibe on these markers and determine the effect of dalcetrapib on cholesterol absorption.Dalcetrapib increased campesterol, β-sitosterol, and cholestanol by 27% (p = 0.001), 32% (p0.001), and 12% (p = 0.03), respectively, in man (non-cholesterol sterol/cholesterol ratio). Dalcetrapib+ezetimibe reduced campesterol by 11% (p = 0.02); β-sitosterol and cholestanol were unaffected. Lathosterol and desmosterol were unchanged with dalcetrapib, but both increased with ezetimibe alone (56-148%, p0.001) and with dalcetrapib + ezetimibe (32-38%, p0.001). In hamsters, dalcetrapib and torcetrapib increased HDL-C by 49% (p = 0.04) and 72% (p = 0.003), respectively. Unlike torcetrapib, dalcetrapib altered cholesterol homeostasis towards increased markers of cholesterol absorption; cholesterol synthesis markers were unaffected by either treatment. Dalcetrapib did not change plasma (3)H-cholesterol level but increased (3)H-cholesterol in plasma HDL vs non-HDL, after oral dosing of labeled cholesterol.Dalcetrapib specifically increased markers of cholesterol absorption, most likely reflecting nascent HDL lipidation by intestinal ABCA1, without affecting markers of synthesis.

Results: Fifty-eight patients were randomized (39MIPO, 19 PBO) at 26 clinical centers in 6 countries. Forty-five (78%) patients completed the treatment period. Twelve (31%) MIPO and 1 (5%) PBO patient(s) withdrew (8 of the MIPO and the 1 PBO withdrawals were caused by an adverse event [AE]). LDL-C was reduced by 36% from a mean baseline level of 276 mg/dL in the MIPO group vs. an increase of 13% from a BL of 249 mg/dL in the PBO group (p , 0.001). This represents a 101 mg/dL mean reduction of LDL-C in theMIPOgroup. Similarly,MIPOproduced highly significant (P , .001) reductions in other atherogenic lipoproteins, eg, ApoB and Lp(a), there was no change in HDL-C. The most common on-treatment AEs were injection site reactions (90%MIPO, 32% PBO) and flu-like symptoms (46% MIPO, 21% PBO). Six (15%) MIPO patients and no PBO patients had ALT $3!ULN on consecutive measures at least 7 days apart. One MIPO patient had a transient ALT $10! ULN. ALT elevations were not associated with clinically significant increases in bilirubin. Conclusions: MIPO treatment significantly reduced LDL-C and ApoB in patients with severe hypercholesterolemia. The data support the potential utility of MIPO as a pharmacologic option for additional LDL C lowering in patients with heterozygous hypercholesterolemia not adequately controlled under existing LLTs.