The impact of Anastrazole and Letrozole on the metabolic profile in an experimental animal model

L-Carnitine alleviates hepatic and renal mitochondrial-dependent apoptotic progression induced by letrozole in female rats through modulation of Nrf-2, Cyt c and CASP-3 signaling

Letrozole (LTZ) is a non-steroidal aromatase inhibitor that is commonly used in breast cancer therapy. It has several side effects that might lead to the drug's cessation and data of LTZ's potential adverse effects on the hepatorenal microenvironment was conflicting. In addition, searching for therapeutic interventions that could modulate its adverse effects will be very beneficial. So, this study aims to determine the impact of LTZ on the hepatorenal microenvironment in cyclic female rats with a proposed regulatory role of L-Carnitine (LC) supplementation giving molecular insights into its possible mechanism of action. LTZ (1 mg/kg using 0.5% carboxy methyl cellulose as a vehicle for 21 consecutive days orally) to assess its impact on hepatorenal microenvironment. After treatment with LC (100 mg/kg orally) for 14 days, hepatorenal redox state (lipid peroxides (MDA), reduced glutathione (GSH) and catalase enzyme (CAT)), as well as relative gene expression of nuclear factor erythroid 2-related factor 2 (Nrf-2), cytochrome-c (Cyt c) and caspase-3 (CASP-3) were evaluated. Histopathological examination and immunohistochemical staining of CASP-3 in both liver and kidney were done. LTZ altered hepatic and renal functions. Relative gene expression of hepatorenal Nrf-2, Cyt c and CASP-3 as well as redox state revealed significant deterioration. Also, the liver and kidney tissues showed several micromorphological changes and intense reaction to CASP-3 upon immunohistochemical staining. It can be concluded that LC alleviates LTZ induced hepatorenal oxidative stress (OS) and mitochondrial-dependent apoptotic progression through modulation of Nrf-2, Cyt c, and CASP-3 signaling in female rats.

Effect of Aromatase Inhibitors on Serum Calprotectin Levels in an Animal Experimental Model: Trial

BACKGROUND/AIM

Utilizing an experimental animal model, we investigated the correlation between aromatase inhibitors (AIs) (anastrozole and letrozole) and Calprotectin levels. AIs have demonstrated superior efficacy when used as adjuvant endocrine therapy or monotherapy for postmenopausal patients with hormone receptor (HR)-positive early-stage breast cancer, although various side effects have been recorded.

MATERIALS AND METHODS

Fifty-five adult female Wistar rats were randomized and assigned into four groups. The control group received no intervention. The other three groups were subjected to ovariectomy, and serum Calprotectin levels were measured at baseline, 2, and 4 months. In addition, glucose, total cholesterol, very low-density lipoprotein- (VLDL-) cholesterol, low-density lipoprotein (LDL-) cholesterol, high-density lipoprotein- (HDL-) cholesterol, and triglyceride levels were measured. Histological analysis of liver tissue was carried out following rats' euthanasia.

RESULTS

Aromatase inhibitors (anastrozole and letrozole) affect calprotectin levels in ovariectomized rats. Calprotectin, a marker of inflammation, was found to be affected by the use of the inhibitors.

CONCLUSION

The potential of hepatotoxicity can be examined by assessing the elevation of inflammation markers such as Calprotectin, which is an indicator that should be strictly taken into consideration when administering aromatase inhibitors as treatment.

Does letrozole treatment have favorable effects on the lipid profile? A systematic review and meta-analysis of randomized clinical trials

As an aromatase inhibitor, letrozole reduces estrogen levels, affecting lipid indices because of the positive role of estrogens in modulating lipoproteins and lipids. Thus, our aim was to meta-analyze data regarding letrozole administration and its effects on the traditional lipid profile. A systematic review and meta-analysis of randomized clinical trials (RCTs) were performed based on the PRISMA guidelines. Web of Science, Scopus, PubMed/Medline, and EMBASE databases were searched until February 11, 2021. From 341 potentially relevant publications, 8 RCTs were selected. All studies used 2.5 mg/d of letrozole. Total cholesterol changed significantly by -6.28 mg/dL (95% CI: -8.73, -3.84, P < 0.001) and HDL-C by -4.40 mg/dL (95% CI: -5.30 to -3.50, p < 0.001) in letrozole group when compared to the control group. Taking into account this comparison between groups, in contrast, LDL-C (WMD: -2.50 mg/dL, 95% CI: -9.94, 4.93, p = 0.510) and triglycerides (WMD: -0.89 mg/dL, 95% CI: -6.87 to 5.07, p = 0.768) did not alter. In conclusion, letrozole administration decreased the concentrations of HDL-C and tocal cholesterol, but not of triglycerides and LDL-C.

A new clinically-relevant rat model of letrozole-induced chronic nociceptive disorders

Among postmenopausal women with estrogen receptor-positive breast cancer, more than 80% receive hormone therapy including aromatase inhibitors (AIs). Half of them develop chronic arthralgia - characterized by symmetric articular pain, carpal tunnel syndrome, morning stiffness, myalgia and a decrease in grip strength - which is associated with treatment discontinuation. Only a few animal studies have linked AI treatment to nociception, and none to arthralgia. Thus, we developed a new chronic AI-induced nociceptive disorder model mimicking clinical symptoms induced by AIs, using subcutaneous letrozole pellets in ovariectomized (OVX) rats. Following plasma letrozole dosage at the end of the experiment (day 73), only rats with at least 90 ng/ml of letrozole were considered significantly exposed to letrozole (OVX + high LTZ group), whereas treated animals with less than 90 ng/ml were pooled in the OVX + low LTZ group. Chronic nociceptive disorder set in rapidly and was maintained for more than 70 days in the OVX + high LTZ group. Furthermore, OVX + high LTZ rats saw no alteration in locomotion, myalgia or experimental anxiety during this period. Bone parameters of the femora were significantly altered in all OVX rats compared to Sham+vehicle pellet. A mechanistic analysis focused on TRPA1, receptor suspected to mediate AI-evoked pain, and showed no modification in its expression in the DRG. This new long-lasting chronic rat model, efficiently reproduces the symptoms of AI-induced nociceptive disorder affecting patients' daily activities and quality-of-life. It should help to study the pathophysiology of this disorder and to promote the development of new therapeutic strategies.