Modulation by geraniol of gene expression involved in lipid metabolism leading to a reduction of serum-cholesterol and triglyceride levels

Protective Effect and Mechanism of Plant-Based Monoterpenoids in Non-alcoholic Fatty Liver Diseases

The protective effect of plant active ingredients against non-alcoholic fatty liver disease (NAFLD) is becoming increasingly prominent, and the terpenoids have always been the main active compounds in Chinese herbal medicine exerting hepatoprotective effects. However, the related pharmacological effects, especially for monoterpenoids or iridoid glycosides, which have obvious effects on improvement of NAFLD, have not been systematically analyzed. The objective of this review is to systematically examine the molecular mechanisms of monoterpenoids in NAFLD. The signaling pathways of peroxisome proliferator-activated receptor, insulin, nuclear factor κB, toll-like receptor, adipocytokine, RAC-α serine/threonine protein kinase, mammalian target of rapamycin, 5'-AMP-activated protein kinase, and autophagy have been proven to mediate this protective effect. We further compared the experimental data from animal models, including the dosage of these monoterpenoids in detail, and demonstrated that they are effective and safe candidate drugs for NAFLD. This review provides a reference for the development of NAFLD drugs as well as a research guideline for the potential uses of plant monoterpenoids.

Cholesterol-Lowering Phytochemicals: Targeting the Mevalonate Pathway for Anticancer Interventions

There are a plethora of cancer causes and the road to fully understanding the carcinogenesis process remains a dream that keeps changing. However, a list of role players that are implicated in the carcinogens process is getting lengthier. Cholesterol is known as bad sterol that is heavily linked with cardiovascular diseases; however, it is also comprehensively associated with carcinogenesis. There is an extensive list of strategies that have been used to lower cholesterol; nevertheless, the need to find better and effective strategies remains vastly important. The role played by cholesterol in the induction of the carcinogenesis process has attracted huge interest in recent years. Phytochemicals can be dubbed as magic tramp cards that humans could exploit for lowering cancer-causing cholesterol. Additionally, the mechanisms that are regulated by phytochemicals can be targeted for anticancer drug development. One of the key role players in cancer development and suppression, Tumour Protein 53 (TP53), is crucial in regulating the biogenesis of cholesterol and is targeted by several phytochemicals. This minireview covers the role of p53 in the mevalonate pathway and how bioactive phytochemicals target the mevalonate pathway and promote p53-dependent anticancer activities.

Association of 3-hydroxy-3-methylglutaryl-coenzyme A reductase gene polymorphism with obesity and lipid metabolism in children and adolescents with autism spectrum disorder

The prevalence of obesity among children and adolescents with autism spectrum disorder (ASD) is higher than that among typically developing children and adolescents. However, very few studies have explored the genetic factors associated with obesity in children and adolescents with ASD. Thus, the aim of this study was to examine the associations between 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) gene polymorphisms and obesity among children and adolescents with ASD. The study participants consisted of 33 children and adolescents with ASD and 271 age- and sex-matched typically developing controls. We compared the metabolic traits (body mass index, blood pressure, triglyceride, high-density lipoprotein, and fasting glucose levels) between the ASD and control group. Furthermore, we assessed the genotypes of rs12654264 in the HMGCR gene within the participants with ASD, and compared metabolic traits among the different allele subgroups. The mean body mass index (BMI) and triglyceride level of the ASD group were significantly higher than those of the control group. Within the ASD group, the triglyceride level of participants with rs12654264-T alleles was significantly higher than that of participants with A-alleles. A pattern of increasing values in the BMI and fasting glucose was also observed in participants with T allele. This is the first study to show that obesity in children and adolescents with ASD is associated with the cholesterol synthesis pathway. Future studies are needed to further clarify the molecular mechanisms by which the HMGCR gene influences metabolic traits.

Natural Products Targeting Liver X Receptors or Farnesoid X Receptor

Nuclear receptors (NRs) are a superfamily of transcription factors induced by ligands and also function as integrators of hormonal and nutritional signals. Among NRs, the liver X receptors (LXRs) and farnesoid X receptor (FXR) have been of significance as targets for the treatment of metabolic syndrome-related diseases. In recent years, natural products targeting LXRs and FXR have received remarkable interests as a valuable source of novel ligands encompassing diverse chemical structures and bioactive properties. This review aims to survey natural products, originating from terrestrial plants and microorganisms, marine organisms, and marine-derived microorganisms, which could influence LXRs and FXR. In the recent two decades (2000-2020), 261 natural products were discovered from natural resources such as LXRs/FXR modulators, 109 agonists and 38 antagonists targeting LXRs, and 72 agonists and 55 antagonists targeting FXR. The docking evaluation of desired natural products targeted LXRs/FXR is finally discussed. This comprehensive overview will provide a reference for future study of novel LXRs and FXR agonists and antagonists to target human diseases, and attract an increasing number of professional scholars majoring in pharmacy and biology with more in-depth discussion.

The Role of Essential Oils and Their Main Compounds in the Management of Cardiovascular Disease Risk Factors

Cardiovascular diseases (CVDs) are a global health burden that greatly impact patient quality of life and account for a huge number of deaths worldwide. Despite current therapies, several side effects have been reported that compromise patient adherence; thus, affecting therapeutic benefits. In this context, plant metabolites, namely volatile extracts and compounds, have emerged as promising therapeutic agents. Indeed, these compounds, in addition to having beneficial bioactivities, are generally more amenable and present less side effects, allowing better patient tolerance. The present review is an updated compilation of the studies carried out in the last 20 years on the beneficial potential of essential oils, and their compounds, against major risk factors of CVDs. Overall, these metabolites show beneficial potential through a direct effect on these risk factors, namely hypertension, dyslipidemia and diabetes, or by acting on related targets, or exerting general cellular protection. In general, monoterpenic compounds are the most studied regarding hypotensive and anti-dyslipidemic/antidiabetic properties, whereas phenylpropanoids are very effective at avoiding platelet aggregation. Despite the number of studies performed, clinical trials are sparse and several aspects related to essential oil’s features, namely volatility and chemical variability, need to be considered in order to guarantee their efficacy in a clinical setting.

Recent Molecular Mechanisms and Beneficial Effects of Phytochemicals and Plant-Based Whole Foods in Reducing LDL-C and Preventing Cardiovascular Disease

Abnormal lipid metabolism leads to the development of hyperlipidemia, a common cause of multiple chronic disorders, including cardiovascular disease (CVD), obesity, diabetes, and cerebrovascular disease. Low-density lipoprotein cholesterol (LDL-C) currently remains the primary target for treatment of hyperlipidemia. Despite the advancement of treatment and prevention of hyperlipidemia, medications used to manage hyperlipidemia are limited to allopathic drugs, which present certain limitations and adverse effects. Increasing evidence indicates that utilization of phytochemicals and plant-based whole foods is an alternative and promising strategy to prevent hyperlipidemia and CVD. The current review focuses on phytochemicals and their pharmacological mode of actions for the regulation of LDL-C and prevention of CVD. The important molecular mechanisms illustrated in detail in this review include elevation of reverse cholesterol transport, inhibition of intestinal cholesterol absorption, acceleration of cholesterol excretion in the liver, and reduction of cholesterol synthesis. Moreover, the beneficial effects of plant-based whole foods, such as fresh fruits, vegetables, dried nuts, flax seeds, whole grains, peas, beans, vegan diets, and dietary fibers in LDL-C reduction and cardiovascular health are summarized. This review concludes that phytochemicals and plant-based whole foods can reduce LDL-C levels and lower the risk for CVD.

Cholesterol-lowering activity of natural mono- and sesquiterpenoid compounds in essential oils: A review and investigation of mechanisms using in silico protein-ligand docking

Mono- and sesquiterpenoids are the main chemical constituents of essential oils. Essential oils and their constituents have received increasing attention for lipid-lowering properties in both cell and animal models. Despite the chemical diversity of essential oil compounds, the effects of many of these compounds on cholesterol metabolism are highly similar. In this report, we review the literature regarding the effects of essential oils and their terpenoid constituents on cholesterol homeostasis, and explore likely mechanisms using protein-ligand docking. We identified 98 experimental and seven clinical studies on essential oils, isolated compounds, and blends; 100 of these described improvements either in blood cholesterol levels or in sterol metabolic pathways. Our review and docking analysis confirmed two likely mechanisms common to many essential oil compounds: (1) direct agonism of peroxisome-proliferator-activated receptors, and (2) direct interaction with sterol-sensing domains, motifs found in key sterol regulatory proteins including sterol regulatory element binding protein cleavage activating protein and HMG-CoA reductase. Notably, these direct interactions lead to decreased transcription and accelerated degradation of HMG-CoA reductase. Our work suggests that terpene derivatives in essential oils have cholesterol-lowering activity and could potentially work synergistically with statins, however, further high quality studies are needed to establish their clinical efficacy.

Protective Effect of Geraniol on Oxidative, Inflammatory and Apoptotic Alterations in Isoproterenol-Induced Cardiotoxicity: Role of the Keap1/Nrf2/HO-1 and PI3K/Akt/mTOR Pathways

Background: Myocardial infarction (MI) is still a major contributor to mortality worldwide, and therefore, searching for new drugs is an urgent priority. Natural products are a renewable source for medicinally and pharmacologically active molecules. The objective of this study was to explore the potential of geraniol, a monoterpene alcohol, to protect against MI. Methods: Five groups of Wister rats were used: a control group; a group treated only with geraniol; a group treated only with isoproterenol, to induce MI; and two groups pretreated with geraniol (100 or 200 mg/kg, respectively) for 14 days and challenged with isoproterenol on the 13th and 14th days. Several parameters were measured including electrocardiogram (ECG), cardiac markers, the expression of Kelch-like ECH-associated protein 1 (Keap1), nuclear factor erythroid 2-related factor 2 (Nrf2), and other downstream antioxidant enzymes, as well as the expression of phosphoinositide 3-kinases (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) and other downstream apoptotic and inflammatory mediators. Results: Geraniol treatment reduced the size of the infarct region, attenuated the levels of cardiac indicators, and diminished myocardial necrosis and immune cell infiltration. Geraniol treatment also activated the Keap1/Nrf2/heme oxygenase-1 (HO-1) pathway, increased antioxidant enzyme activities, modulated the PI3K/Akt/mTOR pathway, and ameliorated myocardial autophagy, inflammation, and apoptosis. Conclusion: Geraniol may possess a protective effect against MI through moderating MI-induced myocardial oxidative stress (glutathione (GSH), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), and Keap1/Nrf2 pathway), inflammation (IL-1β, IL-6, TNF-α, and Nuclear factor-κB (NF-κB)), apoptosis (caspase-3, caspase-9, Bcl2, and Bax), and autophagy (PI3K/Akt/mTOR pathway).

Geraniol attenuates oxidative stress, bioaccumulation, serological and histopathological changes during aluminum chloride-hepatopancreatic toxicity in male Wistar rats

Aluminum chloride (AlCl₃) has different industrial applications including manufacturing paint and water treatment. The present study was designed to evaluate the alleviating effect of geraniol against AlCl₃-induced hepatopancreatic toxicity. To this end, forty male Wistar rats were divided into control (0.9% NaCl, IP), geraniol (100 mg/kg orally), AlCl₃ (70 mg/kg, IP), and AlCl₃ (70 mg/kg, IP) plus geraniol (100 mg/kg orally) groups and then were treated daily for 28 days. Based on the results, serum cholesterol, triglyceride, as well as liver and pancreas enzymes increased significantly (P < 0.05) while the level of insulin significantly decreased in AlCl₃-treated rats compared to the control group (P < 0.05). The presence of geraniol relieved the toxic effects of AlCl₃ as well. On the other hand, the level of malondialdehyde (MDA) increased in the AlCl₃-treated group while the activities of glutathione peroxidase and the total antioxidant activity demonstrated a reduction. However, the MDA level decreased while the antioxidant enzymes increased in co-treated with geraniol group. Histopathological examination revealed that simultaneous treatment with geraniol in AlCl₃ intoxicated rats ameliorate the liver lesions such as necrosis, inflammatory cell infiltration, vacuolar degeneration, along with hyperemia and the cell density of the Langerhans islands. Finally, the results indicated that geraniol attenuated the side effect of AlCl₃-induced hepatopancreatic toxicity.

The Potential of Isoprenoids in Adjuvant Cancer Therapy to Reduce Adverse Effects of Statins

The mevalonate pathway provides sterols for membrane structure and nonsterol intermediates for the post-translational modification and membrane anchorage of growth-related proteins, including the Ras, Rac, and Rho GTPase family. Mevalonate-derived products are also essential for the Hedgehog pathway, steroid hormone signaling, and the nuclear localization of Yes-associated protein and transcriptional co-activator with PDZ-binding motif, all of which playing roles in tumorigenesis and cancer stem cell function. The phosphatidylinositol-4,5-bisphosphate 3-kinase-AKT-mammalian target of rapamycin complex 1 pathway, p53 with gain-of-function mutation, and oncoprotein MYC upregulate the mevalonate pathway, whereas adenosine monophosphate-activated protein kinase and tumor suppressor protein RB are the downregulators. The rate-limiting enzyme, 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR), is under a multivalent regulation. Sterol regulatory element binding protein 2 mediates the sterol-controlled transcriptional downregulation of HMGCR. UbiA prenyltransferase domain-containing protein-1 regulates the ubiquitination and proteasome-mediated degradation of HMGCR, which is accelerated by 24, 25-dihydrolanosterol and the diterpene geranylgeraniol. Statins, competitive inhibitors of HMGCR, deplete cells of mevalonate-derived intermediates and consequently inhibit cell proliferation and induce apoptosis. Clinical application of statins is marred by dose-limiting toxicities and mixed outcomes on cancer risk, survival and mortality, partially resulting from the statin-mediated compensatory upregulation of HMGCR and indiscriminate inhibition of HMGCR in normal and tumor cells. Tumor HMGCR is resistant to the sterol-mediated transcriptional control; consequently, HMGCR is upregulated in cancers derived from adrenal gland, blood and lymph, brain, breast, colon, connective tissue, embryo, esophagus, liver, lung, ovary, pancreas, prostate, skin, and stomach. Nevertheless, tumor HMGCR remains sensitive to isoprenoid-mediated degradation. Isoprenoids including monoterpenes (carvacrol, L-carvone, geraniol, perillyl alcohol), sesquiterpenes (cacalol, farnesol, β-ionone), diterpene (geranylgeranyl acetone), “mixed” isoprenoids (tocotrienols), and their derivatives suppress the growth of tumor cells with little impact on non-malignant cells. In cancer cells derived from breast, colon, liver, mesothelium, prostate, pancreas, and skin, statins and isoprenoids, including tocotrienols, geraniol, limonene, β-ionone and perillyl alcohol, synergistically suppress cell proliferation and associated signaling pathways. A blend of dietary lovastatin and δ-tocotrienol, each at no-effect doses, suppress the growth of implanted murine B16 melanomas in C57BL6 mice. Isoprenoids have potential as adjuvant agents to reduce the toxicities of statins in cancer prevention or therapy.

Medicinal properties of terpenes found in Cannabis sativa and Humulus lupulus

Cannabaceae plants Cannabis sativa L. and Humulus lupulus L. are rich in terpenes - both are typically comprised of terpenes as up to 3-5% of the dry-mass of the female inflorescence. Terpenes of cannabis and hops are typically simple mono- and sesquiterpenes derived from two and three isoprene units, respectively. Some terpenes are relatively well known for their potential in biomedicine and have been used in traditional medicine for centuries, while others are yet to be studied in detail. The current, comprehensive review presents terpenes found in cannabis and hops. Terpenes' medicinal properties are supported by numerous in vitro, animal and clinical trials and show anti-inflammatory, antioxidant, analgesic, anticonvulsive, antidepressant, anxiolytic, anticancer, antitumor, neuroprotective, anti-mutagenic, anti-allergic, antibiotic and anti-diabetic attributes, among others. Because of the very low toxicity, these terpenes are already widely used as food additives and in cosmetic products. Thus, they have been proven safe and well-tolerated.

Citrus reticulata peel oil inhibits non-small cell lung cancer cell proliferation in culture and implanted in nude mice

Mandarin peel oil exerts an antiproliferative effect on in vitro and in vivo human tumour cells without toxicity effects.