A carnosine analog mitigates metabolic disorders of obesity by reducing carbonyl stress.

Sugar- and lipid-derived aldehydes are reactive carbonyl species (RCS) frequently used as surrogate markers of oxidative stress in obesity. A pathogenic role for RCS in metabolic diseases of obesity remains controversial, however, partly because of their highly diffuse and broad reactivity and the lack of specific RCS-scavenging therapies. Naturally occurring histidine dipeptides (e.g., anserine and carnosine) show RCS reactivity, but their therapeutic potential in humans is limited by serum carnosinases. Here, we present the rational design, characterization, and pharmacological evaluation of carnosinol, i.e., (2S)-2-(3-amino propanoylamino)-3-(1H-imidazol-5-yl)propanol, a derivative of carnosine with high oral bioavailability that is resistant to carnosinases. Carnosinol displayed a suitable ADMET (absorption, distribution, metabolism, excretion, and toxicity) profile and was determined to have the greatest potency and selectivity toward α,ß-unsaturated aldehydes (e.g., 4-hydroxynonenal, HNE, ACR) among all others reported thus far. In rodent models of diet-induced obesity and metabolic syndrome, carnosinol dose-dependently attenuated HNE adduct formation in liver and skeletal muscle, while simultaneously mitigating inflammation, dyslipidemia, insulin resistance, and steatohepatitis. These improvements in metabolic parameters with carnosinol were not due to changes in energy expenditure, physical activity, adiposity, or body weight. Collectively, our findings illustrate a pathogenic role for RCS in obesity-related metabolic disorders and provide validation for a promising new class of carbonyl-scavenging therapeutic compounds rationally derived from carnosine.

D-Carnosine octylester attenuates atherosclerosis and renal disease in ApoE null mice fed a Western diet through reduction of carbonyl stress and inflammation.

BACKGROUND AND PURPOSE: Lipoxidation-derived reactive carbonyl species (RCS) such as 4-hydroxy-2-nonenal (HNE) react with proteins to form advanced lipoxidation end products (ALEs), which have been implicated in both atherosclerosis and renal disease. L-carnosine acts as an endogenous HNE scavenger, but it is rapidly inactivated by carnosinase. This study aimed at assessing the effect of the carnosinase-resistant, D-carnosine, on HNE-induced cellular injury and of its bioavailable prodrug D-carnosine octylester on experimental atherosclerosis and renal disease. EXPERIMENTAL APPROACH: Vascular smooth muscle cells (VSMCs) were exposed to HNE or H2O2 plus D-carnosine. ApoE null mice fed a Western, pro-atherogenic diet were treated with D-carnosine octylester for 12 weeks. KEY RESULTS: In vitro, D-carnosine attenuated the effect of HNE, but not of H2O2, on VSMCs. In vivo, D-carnosine octylester-treated mice showed reduced lesion area and a more stable plaque phenotype compared with untreated animals, with reduced foam cell accumulation, inflammation and apoptosis and increased clearance of apoptotic bodies and collagen deposition, resulting in decreased necrotic core formation. Likewise, renal lesions were attenuated in D-carnosine octylester-treated versus untreated mice, with lower inflammation, apoptosis and fibrosis. This was associated with increased urinary levels of HNE-carnosine adducts and reduced protein carbonylation, circulating and tissue ALEs, expression of receptors for these products, and systemic and tissue oxidative stress. CONCLUSIONS AND IMPLICATIONS: These data indicate RCS quenching with a D-carnosine ester was highly effective in attenuating experimental atherosclerosis and renal disease by reducing carbonyl stress and inflammation and that this may represent a promising therapeutic strategy in humans.

Design, synthesis, ADME properties, and pharmacological activities of ß-alanyl-D-histidine (D-carnosine) prodrugs with improved bioavailability.

ß-Alanyl-D-histidine (D-CAR, the enantiomer of the natural dipeptide carnosine) is a selective and potent sequestering agent of reactive carbonyl species (RCS) that is stable against carnosinase, but is poorly absorbed in the gastrointestinal tract. Herein we report a drug discovery approach aimed at increasing the oral bioavailability of D-CAR. In our study we designed, synthesized, and evaluated a series of novel lipophilic D-CAR prodrugs. The considered prodrugs can be divided into two categories: 1) derivatives with both terminal groups modified, in which the carboxyl terminus is always esterified while the amino terminus is protected by an amidic (N-acetyl derivatives) or a carbamate (ethyloxy or benzyloxy derivatives) function; 2) derivatives with only one terminus modified, which can be alkyl esters as well as amidic or carbamate derivatives. The prodrugs were designed considering their expected lipophilicity and their hydrolysis predicted by docking simulations on the most important human carboxylesterase (hCES1). The stability and metabolic profile of the prodrugs were studied by incubating them with rat and human serum and liver fractions. The octyl ester of D-CAR (compound 13) was chosen as a candidate for further pharmacological studies due to its rapid hydrolysis to the bioactive metabolite in vitro. Pharmacokinetic studies in rats confirmed the in vitro data and demonstrated that the oral bioavailability of D-CAR is increased 2.6-fold if given as an octyl ester relative to D-CAR. Compound 13 was then found to dose-dependently (at daily doses of 3 and 30 mg kg(-1) equivalent of D-CAR) decrease the development of hypertension and dyslipidemia, to restore renal functions of Zucker fa/fa obese rats, and to inhibit the carbonylation process (AGEs and pentosidine) as well as oxidative stress (urinary 8-epi-prostaglandin F2α and nitrotyrosine). A plausible mechanism underlying the protective effects of 13 is RCS sequestration, as evidenced by the significant increase in the level of adduct between CAR and 4-hydroxy-trans-2-nonenal (HNE, the main RCS generated by lipid oxidation) in the urine of treated animals.

Design, synthesis, and evaluation of carnosine derivatives as selective and efficient sequestering agents of cytotoxic reactive carbonyl species.

Carnosine aryl derivatives as sequestering agents of RCS: Reactive carbonyl species (RCS) are cytotoxic mediators representing a novel drug target, as they are presumed to play a pathogenic role in several diseases. Carnosine is a selective RCS-sequestering agent, but is rapidly hydrolyzed by serum carnosinase. Herein we describe the in silico design, synthesis, and evaluation of a set of carnosine aryl derivatives.Reactive carbonyl species (RCS) are important cytotoxic mediators generated by lipid oxidation of polyunsaturated fatty acids (PUFAs) and represent a novel drug target, as they are presumed to play a pathogenic role in several diseases. L-Carnosine (L-CAR, beta-alanyl-L-histidine) is a specific detoxifying agent of RCS, but is rapidly hydrolyzed in human serum by carnosinase, a specific dipeptidase. Herein we describe the in silico design, synthesis, and biological evaluation of carnosine derivatives that are resistant to carnosinase and that have increased quenching efficacy. Stability against carnosinase-mediated turnover was achieved by isomerization of the histidine residue, leading to D-carnosine (D-CAR, beta-alanyl-D-histidine), which maintains the same quenching activity of L-carnosine. A molecular modeling approach was then used to design derivatives characterized by an increased quenching efficacy. The most promising candidates were synthesized, and their stability and quenching activity were evaluated. This study describes a set of aryl derivatives that are characterized by high stability in human plasma and a quenching activity toward 4-hydroxy-trans-2-nonenal (HNE), chosen as a model of RCS, up to threefold greater than D-carnosine.