Diabetes mellitus (DM) is the most prevalent metabolic disorder and continuing to affect a large number of people worldwide. The International Diabetic Federation reported that the prevalence of diabetes is increasing worldwide to epidemic proportions; in 2017, 425 million people were affected by DM and the number is expected to rise to 629 million in 2045 [1
]. DM mainly involves perturbation of metabolic pathways that influence carbohydrate and lipid metabolism; the two major cellular substrates result in the generation of injurious metabolites [2
]. The uncontrolled DM gives rise to microvascular and macrovascular complications affecting structural and functional changes in tissues and may result in organ dysfunction or failure [3
]. The exact underlying molecular mechanisms of the pathogenesis of DM are not fully recognized [4
]. However, the pathogenesis mainly involves beta-cell dysfunction, reduced amount or sensitivity of insulin or insulin resistance (IR) along with oxidative stress, inflammation, mitochondrial dysfunction, and apoptosis [2
Glycemic control is one of the main aims of treatment in the management of DM and to delay the onset and progression of diabetic complications [5
]. Though, the currently available therapeutic strategies are effective but adverse effects, inadequate effectiveness in metabolic and glucoregulatory mechanisms necessitate exploring novel therapeutic and preventive agents for the prevention of diseases related to DM in particularly type 2 diabetes mellitus (T2DM) and IR [5
]. Thus, there is the need for more safer and effective drugs and therapeutic strategies to prevent various short- and long-term risk factors associated with diabetes [7
]. The risk factors, genetic and environmental including obesity, sedentary lifestyle, smoking, alcohol consumption, and diet have been considered to be a major reason of the alarming rise in T2DM worldwide and are the focus of therapeutic targeting to alleviate impaired insulin secretion and IR [9
]. In environmental factors, diets have received interest in the physiological and pharmacological perspective based on the data from epidemiological, preclinical studies and few clinical studies demonstrated that nutraceuticals, functional foods, dietary/food supplements play role in improving postprandial hyperglycemia and adipose tissue metabolism thus modulating glucose and lipid metabolism [11
Mounting evidence indicate that various fruits, vegetables, and whole grains including fermented products, legumes, nuts, green tea, spices, propolis, olive oil, red wine (resveratrol), herbs, and spices are beneficial in T2DM, obesity, and metabolic syndrome due to the presence of non-nutritive secondary metabolites termed as phytochemicals [14
]. The dietary bioactive phytochemicals play significant role in maintaining health and wellness attributed to their potent pharmacological effects that translate to medicinal benefits [19
]. Phytochemicals belong to numerous classes such as polyphenols, terpenoids, flavonoids, alkaloids, sterols, pigments, and unsaturated fatty acids [20
]. Many of the edible plants and phytochemicals are suggested to be useful in T2DM and delay and or prevent complications exerting a pronounced beneficial effect in controlling hyperglycemia due to potent antioxidant and anti-inflammatory effects [14
Among numerous phytochemical classes, specifically, terpenes commonly consumed in plants including edible and medicinal garnered attention because of their potent bioactivities, safety, druggable properties, and potential to target enzymes and receptors that influence glucose and lipid metabolism [18
]. In sesquiterpene compounds, β-caryophyllene (BCP), a bicyclic, non-psychoactive compound of wide natural occurrence in essential oils of many edible plant including spices like clove, cinnamon, thyme, oregano, and black pepper received interest because of its potent pharmacological properties and therapeutic benefits [21
]. BCP naturally occurs in plants with its isomers such as (Z
)-β-BCP also known as isocaryophyllene; a cis
-double bond isomer or α-humulene, also known as α
-caryophyllene, a ring-opened isomer or in a mixture with β
-caryophyllene oxide, an oxidation product of BCP. The cyclobutene ring in the chemical structure of BCP imparts chemical stability and high lipophilicity [23
]. It received approval by European agencies, Flavor, and Extract Manufacturers Association (USFDA), for safe use in foods as additive, preservative, and flavor enhancer. USFDA listed BCP “generally regarded as a safe (GRAS)” for use in food and cosmetics. Since its recognition as a dietary cannabinoid, BCP has received interest for studies to investigate its pharmacological properties and therapeutic potential [22
]. Sharma et al. 2016 have reviewed numerous pharmacological properties of BCP including antioxidant, anti-inflammatory, antimicrobial, chemopreventive, nephroprotective, cardioprotective, neuroprotective, and nephroprotective along with pharmaceutical characteristics [23
Gertsch and colleague for the first time demonstrated a selective and full agonist activity of BCP on cannabinoid type 2 receptors (CB2R), a component of the endocannabinoid system consisting of endocannabinoid ligands that exert their action by binding to two well-characterized cannabinoid receptors type 1 and type 2 (CB1R and CB2R) or endocannabinoid metabolizing enzymes, fatty acid amide hydrolase (FAAH), and monoacylglycerol lipase (MAGL) [22
]. BCP showed binding affinity to the CB2R in nanomolar concentrations and exhibited potent cannabimimetic actions [22
]. BCP does not bind to the centrally expressed CB1 receptors, thus does not exert psychomimetic effects. The activity of CB1 or CB2R can be modulated directly by ligand binding or indirectly by the modulation of the level of endocannabinoids. The role of cannabinoids has been shown to suppress inflammation and oxidative stress, the two-common accompaniment of DM by targeting CB2R [24
Recently, numerous experimental studies revealed that activation of CB2R by agonists have significant pharmacological effects such as anti-inflammatory, immunomodulatory, antioxidant, cardioprotective, hepatoprotective, gastroprotective, neuroprotective, nephroprotective, and atheroprotective and found to be beneficial in controlling hyperglycemia, IR, and dyslipidemia [25
]. In the past few years, significant attention is being focused on the possibility of developing novel drugs that can modulate the endocannabinoid system, in particular, activate CB2R, knowing the adverse psychiatric effects of CB1 receptor modulation and in particular, more emphasis has been given to the CB2R targeting cannabinoids of natural origin over the synthetic ones [24
]. BCP is devoid of psychoactivity, a common feature of many cannabinoids because of the modulation of CB1 receptors. CB2R selectivity and affinity makes BCP a promising candidate for drug development targeting the endocannabinoid system, a relatively new therapeutic target.
BCP is a molecule of special interest with high presence in cannabis as well as the non-cannabis plants including more than 2000 plants and termed as a dietary cannabinoid [22
]. BCP has been suggested to be used as a nutraceutical, functional food, and dietary supplement because of its dietary bioavailability, ample natural occurrence, and multiple therapeutic benefits [23
]. Many formulations such as suspension, PEG formulations, liposomes, wound dressings, hydrogels, and nanoemulsions for topical use, inclusion complexes with cyclodextrins, as well as nanocomposites and nanoparticles have been developed [28
]. These formulations have been shown to overcome the physicochemical issues such as lipophilicity, low stability, and bioavailability that may hinder the pharmaceutical development.
In the past few years, the number of studies demonstrated that BCP possesses a wide range of pharmacological properties including anti-inflammatory and antioxidant and the potential to correct hyperglycemia and improve insulin secretion and sensitivity, thus appearing as a promising molecule for diabetes and its complications [29
]. Given the role of oxidative stress and low-grade chronic inflammation in the pathogenesis of DM [30
], the role of cannabinoid ligands in DM and associated complications have been demonstrated in numerous studies [31
Convincing number of preclinical studies and few clinical studies demonstrated its pharmacological effects and molecular mechanisms, redox and immune-inflammatory axis, and its beneficial effects in low grade chronic inflammatory diseases including DM and its complications [21
]. The current review represents a comprehensive account of preclinical and a few clinical studies concerning the effects of BCP in diabetes and associated diabetic complications. The review also delineates the pharmacological and molecular mechanisms of BCP in diabetes and its complications. The pharmacological effects and mechanisms are summarized in synoptic tables and schemes.
3. β-Caryophyllene in Diabetic Complications
The complications of both T1DM and T2DM constitute retinopathy, nephropathy, neuropathy, cardiomyopathy, and other associated diseases which affect the quality of life and are a main reason for morbidity and mortality [24
]. Diabetic complications arise from hyperglycemia associated with persistent oxidative stress and impairment in multiple metabolic pathways [106
]. Chances of complications are inevitable despite treatment, therefore continued effort for the search of newer agents are ongoing for DM as well as its complications [107
In several diseases involving immune dysregulation including obesity, DM and its complications, the activation of toll-like receptors (TLRs), particularly toll-like receptor 4 (TLR4), among many isoforms showed to garner great therapeutic interest, thus its pharmacological manipulation received interest in recent years [108
]. TLR4 generates an active receptor complex that leads to the initiation of intracellular inflammatory signals and causes the onset and progression of inflammation in diabetic complications. In a very recent study, BCP was found to exert hepatoprotective effects mediating suppression of TLR4/receptor for advanced glycation end-products (RAGE) pathways [109
] and neuroinflammation by attenuating TLR4/NF-κ
B signaling pathway and inhibiting release of pro-inflammatory cytokines production and promotes polarization of M1/M2 phenotypic anti-inflammatory properties [110
Additionally, BCP has been shown to attenuate neuroinflammation and neuron death by mitigating high mobility group box 1 (HMGB1)-TLR4 signaling pathways [111
]. HMGB1 following binding to TLR4 and RAGE results in the induction of inflammatory pathways via activation of NF-kB. TLR4 interfering PGC-1α
enhances oxidative stress, inflammation, and cell death that leads to tissue damage in diabetic complications. The inhibitory effects of BCP on TLR4/RAGE, HMGB1-TLR4, NF-kB, PI3K/Akt, AMPK/CREB, ERK1/2/JNK1/2, SIRT1/PGC-1α, TLR4/NF-kB pathways are suggestive of its pharmacological and molecular mechanism of its potential usefulness in DM and its complications. The molecular targets of BCP are represented in Figure 3
. In addition, BCP was found to significantly improve and augment endogenous antioxidants, scavenge free radicals and inhibit lipid peroxidation in blood and many organ tissues [29
]. Therefore, BCP may have therapeutic potential in DM and its complications by pharmacological targeting of intimately linked oxidative stress-inflammatory cascade.
Neuropathic pain is considered a diabetes consequence and presents a high impact on patient’s quality of life, showing painful thermal, electrical, and sharp sensations [112
]. Diabetic neuropathy is due to neuronal dysfunction, high excitability in the spinal horn, and lowered function of inhibitory neurons. Chronic hyperglycemia activates the polyol pathway and also promotes the release of advanced glycation end products, damaging nerve terminals, evoking pain, and increasing production of substance P and various cytokines such as TNF-α, IL-1β, and IL-6, which have a role in diabetic neuropathy development and permanence [114
]. Aguilar-Ávila, et al. [115
] demonstrated the effect of BCP on neuropathic pain and depressive-like behavior in experimental diabetic mice. BCP given orally to STZ-induced diabetic mice significantly reduced blood glucose levels and enhanced insulin levels. The decrease in blood glucose level is attributed to enhanced insulin secretion by BCP-mediating CB2R agonism. In addition, BCP treatment alleviated the pain associated with diabetic neuropathy. In addition, treatment with BCP significantly reduced substance P and inflammatory cytokines as neuropathic pain was mainly related to substance P and release of IL-6 and IL-1β.
A dietary supplement containing BCP, myrrh, carnosic acid, and PEA evaluated in twenty-five patients with the diagnosis of DM and painful distal symmetric polyneuropathy (PDSPN) showed a reduction of polyneuropathy with enhanced amplitude and reduced pain [116
]. PDSPN is a common complication of DM involving perturbations of metabolic pathways regulating inflammation, microvessel circulation, and axonal degeneration. The formulation was found beneficial in painful diabetic distal symmetric sensory-motor neuropathy in patients with diabetes in an observational clinical study and tolerable with no side effects [116
BCP role in diabetic nephropathy, a major cause of end-stage renal disease in diabetic patients involving structural and functional alteration in podocytes has been demonstrated using an in vitro model of high glucose-induced glomerular mesangial cells [117
]. BCP treatment showed to inhibit cell proliferation, ROS production, and NADPH oxidase (NOX) 2/4 expression along with reduced pro-inflammatory cytokines viz., TNF-α, IL-1β, IL-6, NF-κB activation and increased Nrf2 activation. BCP also attenuated fibronectin (FN) and collagen IV (Col IV) in mesangial cells. The protective effects of BCP in diabetic neuropathy have been attributed to NF-κB and Nrf2 signaling pathway-based anti-inflammatory mechanism [117
]. However, the effects observed in vitro need to be confirmed in the in vivo models of diabetic nephropathy.
Additionally, hyperglycemia a common manifestation in T2DM is also related with a higher risk of developing colorectal cancer evidenced by increased arginine-specific mono-ADP-ribosyltransferase 1 (ART1) levels in colorectal tissues from patients with T2DM compared to non-diabetic patients. The role of BCP on ART1 on glycolysis and energy metabolism has been shown in CT26 cells cultured and exposed to high-glucose conditions and in STZ-induced BALB/c mice transplanted CT26 tumor cell [118
]. BCP treatment reduced the overexpression of ART1 in cells favorably modulated glycolysis and energy metabolism in CT26 cells by regulating the protein kinase B/mammalian target of rapamycin/c-Myc signaling pathway and glycolytic enzymes expression. BCP-induced reduction in the expression levels of ART1 via NF-κB indicates that ART1 is an attractive therapeutic target and BCP may be an attractive molecule for controlling cell proliferation, apoptosis, energy metabolism, tumor growth along with regulating metabolic pathways.
BCP showed potential in ageing and age-related disorders by improving the mean lifespan, reduced feeding behavior, induced dietary restriction like effects, and enhanced longevity-promoting stress resistance ability in Caenorhabditis elegans
]. BCP also attenuated ROS accumulation and levels of intracellular lipofuscin, a marker of aging and age-related cellular damage in Caenorhabditis elegans
. BCP enhanced the expression level of stress and longevity-promoting genes such as daf-16
, and sod-3
, the anti-oxidative enzymes induced in response to oxidative stress. Ageing as well as diabetes also enhances cognitive decline. BCP showed to enhance lifespan, memory performance in young as well as aged mice mediating potent anti-inflammatory properties on pro-inflammatory cytokine [120
]. BCP has been identified as one of the adaptogens constituent in the Kaempferia parviflora
rhizome extracts based on its positive effects on swimming tests of mice [121
Along with ageing, diabetes and obesity are the risk factors for osteoporosis characterized by reduced bone mass through decreased osteoblastic osteogenesis and increased osteoclastic bone resorption. BCP was found to enhance osteoblastic mineralization and suppress adipogenesis and osteoclastogenesis in cultured mouse bone marrow cells [122
]. Obesity and diabetes are also considered to increase the risk of cancer. BCP showed to suppress HFD-stimulated melanoma progression and lymph node metastasis in a high-fat diet (HFD; 60 kcal% fat)-induced melanoma progression in C57BL/6N mice [123
]. Interestingly, BCP reduced the HFD-induced body weight gain, fasting blood glucose, solid tumor growth, metastasis of lymph nodes, proliferation of tumor cells, angiogenesis, and lymphangiogenesis. BCP also suppressed the number of lipid vacuoles and F4/80+ macrophage (MΦ) and macrophage mannose receptor (MMR)+ M2-MΦs in tumor tissues and adipose tissues surrounding the lymph nodes and reduced the CCL19 and CCL21 levels in the lymph node and CCR7 expression in the tumor. BCP also prevented lipid accumulation in the in vitro model of white adipocytes (3T3-L1), migration of monocytes, and secretion of MCP-1 in murine melanoma cells (B16F10), adipocytes and M2-MΦs, angiogenesis and lymphangiogenesis. The inhibition of accumulation of lipids, M2-cells, and CCL19/21-CCR7 axis partly demonstrate the underlying mechanism of BCP in inhibiting HFD-elicited development of melanoma under the conditions of high glucose levels.
In diabetic patients, increased incidence of impaired wound healing severely affects the quality of life leading to prolonged hospitalization and lower limb amputation [124
]. Numerous factors such as age, obesity, malnutrition, and macrovascular and microvascular disease, contribute to wound infection and delayed wound healing in diabetic patients. The onset of hyperglycemia is one of the major reasons affecting cellular response to tissue injury, imbalance of wound healing by PMN leukocytes and fibroblasts, and delayed response to injury and impaired functioning of immune cells in DM. Wound healing involves re-epithelialization mediating growth factors, cytokines, and extracellular matrix components such as collagen, fibronectin, and elastin by keratinocyte, important cell of the epidermis, and proliferation of fibroblasts [124
]. Koyama et al. [125
] found that BCP promoted re-epithelialization and facilitated the healing of cutaneous wounds in mice. Artemisia montana
Pampan essential oil containing BCP has been shown to promote skin regeneration in human keratinocytes and wound healing by increasing phosphorylation of Akt and ERK 1/2 and induced the synthesis of type IV collagen [126
]. In another study, a hydrogel containing nano-emulsified BCP was developed and showed in vitro as well as in vivo wound healing activity [127
BCP alone is an unstable compound as it oxidizes rapidly and is unable to permeate but the nano-emulsion formulation was found to exhibit improved stability for 60 days, superior bio adhesiveness and facilitated skin permeation than BCP alone. The nano-emulsion was found to exert a healing effect in the dorsal wound model by reducing lesions, oxidative stress, and inflammation comparable to a standard cutaneous healing agent (Dersani®
oil). Essential oils of many other plants such as Eugenia dysenterica
DC leaves containing BCP was found to enhance in vitro skin cell migration and promoted angiogenesis with no cytotoxicity [128
]. Similarly, BCP-rich essential oil of black pepper showed anti-proliferative activity by inhibiting Collagen I, Collagen III, and plasminogen activator inhibitor 1, important in inflammation and tissue remodeling for wound healing [129
]. In another study, essential oil of Aspilia africana
(Pers.) C.D. Adams rich in BCP showed wound healing ability by reducing wound bleeding, enhancing wound contraction, increasing concentration of basic fibroblast growth factor and platelet-derived growth factor along with increasing white and red blood cells [130
]. These studies intend that BCP has the potential to be developed for dermatological use specially in wound healing.
The aforementioned studies summarized in Table 3
indicate that BCP might be a potential therapeutic agent for neuropathic pain, nephropathy, cognitive impairment, osteoporosis and delayed wound healing, and colorectal cancer developed in diabetic patients.
4. β-Caryophyllene in Nonalcoholic Fatty Liver Disease (NAFLD)
Hyperlipidemia, particularly hypercholesterolemia, is recognized as a major contributor to the fatty liver diseases, cardiovascular diseases, and carcinogenesis leading to health problems and death around the world [131
]. A diet containing a large amount of fat is linked with higher risk of obesity and hyperlipidemia in preclinical models and humans as it increases levels of cholesterol and triglyceride (TG) in plasma and tissues [132
]. NAFLD is considered as one of the chronic hepatic diseases, characterized by disproportionate accumulation of hepatic lipids in the absence of remarkable ethanol intake. NAFLD was found to range from general steatosis to severe nonalcoholic steatohepatitis (NASH), that may progresses to cirrhosis and hepatic cancer [133
]. There is a direct relationship of steatohepatitis with metabolic syndrome that is identified by abdominal obesity, dyslipidemia, IR with or without hyperglycemia, and hypertension and studies have reported the relation of NASH with metabolic syndrome [134
Sirichaiwetchakoon et al. [136
] reported that Pluchea indica
(L.), popularly known as Indian camphorweed used as a tea and health tonic in Southeast Asia was effective in mitigating hyperglycemia and dyslipidemia induced by high fat diet in mice. It showed to attenuate hyperglycemia and dyslipidemia by correcting altered lipid and hematological profile, restoring liver enzymes and renal function, and improving oral glucose tolerance along with histological salvage of kidney and liver. The benefits of this plant were ascribed to the high content of BCP and advocated to be dietary supplement/nutraceutical for hyperlipidemia, obesity, and T2DM.
Baldissera, et al. [137
] investigated the role of BCP in hypercholesterolemia using a model of hyperlipidemia induced by Triton WR-1339 in rats, as well as its possible effect on hepatic antioxidant enzymes. Hyperlipidemic rats treated with BCP showed decreased total cholesterol, triglycerides, and LDL, similar to the reference drug simvastatin, while HDL levels did not increase following treatment. BCP treatment inhibited the activity of HMG-CoA reductase, as well as suppressed ROS and TBARS levels and improved antioxidant system. The study demonstrates that BCP exerts a hypolipidemic effect through suppression of the hepatic HMG-CoA reductase, like statins class of antihyperlipidemic drugs.
Harb, et al. [138
] have examined the hypolipidemic effects of BCP in hypercholesterolemia induced by high cholesterol and fat diet in male Wistar rats. BCP significantly reduced serum total cholesterol, LDL cholesterol, and the atherogenic index and significantly increased HDL cholesterol level. Moreover, its alleviated liver injury is evidenced by reduced hepatomegaly, macrovesicular steatosis, and the activity of hepatic enzymes. Furthermore, it produced a significant increase in the activity of the antioxidant enzyme superoxide dismutase. BCP significantly suppressed free radical formation, inhibited the activity of hepatic HMG-CoA reductase, and subsequently inhibited endogenous cholesterol synthesis.
In recent years, AMPK activation appears promising as a therapeutic target for the prevention and treatment of obesity, DM, and steatosis [139
]. AMPK, a serine/threonine kinase is involved in a variety of biological activities that maintain energy homeostasis by regulating lipids and glucose in liver [140
]. The active AMPK phosphorylates and inactivates acetyl-CoA carboxylase 1 (ACC1), which is a rate-limiting enzyme in fatty acid synthesis [141
]. In addition, AMPK modulates two critical transcription factors associated with homeostasis of lipids, i.e., sterol regulatory element-binding protein 1c (SREBP-1c), and forkhead box protein O1 (FoxO1). The AMPK-mediated phosphorylation of SREBP-1c precursor inhibits its cleavage, nuclear translocation, and transcriptional activity, results in decreased expression of fatty acid synthase (FAS) [142
]. On the other hand, AMPK directly phosphorylates FoxO1 and then translocated to the nucleus, leading to transcriptional upregulation of adipose triglyceride lipase (ATGL) [143
]. Kamikubo, et al. [144
] evaluated hepatic lipid accumulation inhibitory activity in medicinal foods via involving AMPK using palmitate-overloaded HepG2 cells. The co-incubation of palmitate-exposed HepG2 cells with BCP resulted in a dose-dependent decrease in intracellular lipid content. Moreover, the palmitate-mediated lipid accumulation was significantly alleviated upon BCP pre-incubation. BCP prevented the translocation of SREBP-1c into the nucleus and FoxO1 into the cytoplasm through AMPK signaling, and therefore, induced remarkable downregulation of FAS and upregulation of ATGL, respectively. BCP produced activation of AMPK via CB2R-stimulated Ca2+
signaling pathway. The studies are suggestive of that BCP could be helpful in preventing and ameliorating fatty liver diseases including NAFLD.
Arizuka, et al. [145
] have investigated BCP effects on the methionine- and choline-deficient diet-fed mice model of NASH with cardiometabolic diseases. In steatohepatitis, liver develops histopathological changes along with oxidative stress, inflammation, and fibrosis. In addition to improving liver function and salvaging liver tissues, BCP treatment showed to attenuate hepatic inflammation, oxidative stress, and fibrosis evidenced by reduced expression of cytokines (IL-1β, IL-6 and MCP-1), enhanced antioxidant enzymes (super oxide dismutase 2 and glutathione peroxidase 1) and increased NOX2 (reduced form of nicotinamide adenine dinucleotide phosphate (NADP) oxidase 2), and inhibited fibrotic markers (TGF-β and collagen), respectively.
Recently, BCP structure was utilized as a template for drug discovery [146
]. Following the chemical modifications of BCP, several new bioactive compounds were synthesized which could make an impact in drug discovery targeting the other components of endocannabinoid system including activation of CB2R as well as the inhibition of the enzymes; FAAH, a the major endocannabinoid degrading enzyme and cyclooxygenase-2 (COX-2), an enzyme isoform participates in arachidonic acid metabolism and endocannabinoid signaling [22
]. The anti-inflammatory drugs are well-0known to cause the gastrointestinal adverse effects including dyspepsia and peptic ulcer. However, the gastroprotective properties of BCP are an added advantage in encouraging it for anti-inflammatory properties without the appearance of gastrointestinal issues signaling [147
]. Taken together, these observations point to the direction that BCP exerts its potent anti-inflammatory effect by multimodal mechanisms including the most important COX-2 enzyme, a target for newer anti-inflammatory drugs, coxibs.
The alcoholic extract of clove containing BCP showed to inhibit fatty acid synthase, an enzyme for de novo lipogenesis, inhibited weight gain, abdominal adipose tissue, lowered lipid accumulation in the liver by regulating the content of total triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and epididymal adipose tissue in HFD-induced obesity [148
]. The extract was also found to inhibit the S-phase DNA replication of HepG2 cells and adipocyte differentiation of OP9 cells.
Altogether, these studies indicate that BCP has an antioxidant activity leading to the reduction of ROS, therefore, may be associated with deactivation of HMG-CoA reductase and decreased cholesterol synthesis, leading to hypolipidemia are represented in Figure 4
. Also, BCP activated AMPK signaling via the mediation of the CB2R-dependent Ca2+
signaling pathway leading to the downregulation of FAS and upregulation of ATGL. Additionally, BCP could be a promising therapeutic drug in treating hypercholesterolemia and fatty liver disease.
5. Safety and Toxicity of β-Caryophyllene
BCP is classified as a substance of category five (toxic at doses greater than 2000 mg/kg) in accordance with OECD (Organization for Economic Co-operation and Development) guideline 423 [149
]. BCP administered orally up to 2000 mg/kg did not elicit toxic effects in female Swiss mice [150
] and the LD50
in rats were found greater than 5000 mg/kg [151
]. BCP or its combination with L-arginine supplemented for 14 days at 2000 mg/kg was found non-toxic. Even BCP or the combination after repeated administration of 900 mg/kg did not show mortality [37
]. Also, BCP did not show subchronic toxicity at the dose of 700 mg/kg/day in Wistar rats [151
], and found safe on locomotion and muscle tone with both single and repeated doses in female Swiss mice [150
]. In chronic good laboratory practices-compliant studies, BCP administered for duration of 90 days in Sprague-Dawley rats did not cause mortality or clinical toxicity. At high doses, it reduced body weight, food consumption, and efficiency due to palatability. Neither BCP nor epoxide derivative affected estrus cycle or sperms. Nephropathy and hepatocyte hypertrophy were observed at high doses. No observed adverse effect level (NOAEL) for BCP was found to be 222 mg/kg bw/day and for epoxide derivative was 109 mg/kg/bw/day [152
In rodents, doses ranging from 20 to 300 mg/kg have been used to study pharmacological effects in drugs, xenobiotics or chemical toxicants-induced animal models of the heart [153
], liver [109
], kidney [156
], colon [157
], stomach [147
], and brain [158
] toxicity demonstrate its organoprotective properties and absence of the detrimental effect of these studied doses on organ structure and function [150
]. Moreover, in various studies in female Swiss mice and in Wistar rats, no damage to the gastric mucosa and no changes in organs including brain, heart, liver, lungs, spleen, kidneys, or in hematology were observed [150
]. In addition, Ames test has shown no mutagenicity [147
]. However, bodyweight has reduced by 5% in female Swiss mice, but even if this variation was not significant [150
BCP (20, 200, and 2000 mg/kg) was found antigenotoxic in benzo(a)pyrene-induced toxicity in mice by inhibiting the number of sister-chromatid exchanges and chromosomal aberrations [161
]. The antigenotoxic activity was also shown to be related to its capacity to inhibit molecular oxidation and enhance glutathione-S-transferase (GST) activity. The effects of BCP obtained from curry leaf, a commonly used spice, on P-glycoprotein (P-gp) transport and CYP3A4 metabolism were evaluated in L-MDR1 (LLC-PK1 cells transfected with human MDR1 gene) and Caco-2 (human colon carcinoma) cells and CYP3A4 activity in pooled human liver microsomes [162
]. The IC50
values of BCP on midazolam 1′-hydroxylation in HLM was 1.28 mM. This study indicated the potential of BCP drug interaction with other drugs metabolized by CYP3A4. BCP inhibited CYP3A activities in rats as well as in human hepatic microsomes rat and human hepatic subcellular fractions [163
]. Therefore, BCP may cause drug-drug interaction with concurrently administered drugs. Recently in a placebo-controlled randomized double-blind trial for investigating efficacy in dyspepsia, BCP (126 mg/day) administered orally for eight weeks showed effective and tolerable. BCP being pleiotropic may synergistically provide greater therapeutic efficacy and safety by improving therapeutic outcome and minimizing risks/adverse effects compared to synthetic congeners. It has been found more potent than, probucol, tocopherol [164
] and found synergistic with atorvastatin in reducing hematologic toxicity induced by chemotherapeutic agents [165
]. Based on time tested safety due to dietary consumption and demonstrated efficacy in different animal models of diseases, BCP deserve further preclinical and clinical studies to promote clinical usage and pharmaceutical development. Though, in particular the long-term safety and toxicity of BCP still need to be evaluated.
Overall, the data from preclinical studies demonstrate the underlying mechanisms of BCP particularly in skeletal muscles, adipose tissues, liver, and pancreatic β-cells. The available studies demonstrate that BCP shows the capability to increase insulin secretion, insulin sensitivity, glucose uptake and reduce glucose absorption. In addition, it also reduces the levels of triglycerides and cholesterol, increases fatty acid oxidation and lipid homeostasis along with hypolipidemic effects. Moreover, BCP has insulinotropic effects mediating CB2R- and PPARs-dependent mechanism. BCP is one of the important components of essentials oils of many plants used in diet and traditional medicines for their well-being and health benefits. BCP is unique due to its selective full agonist property on CB2Rs as well as modulating other receptors and enzymes play significant role in glucose and lipid metabolism. However, further studies are required to translate these mechanistic studies into therapeutic benefits in humans.
Based on the health benefits, wide natural occurrence, dietary availability, low toxicity, relatively safe in humans use, and organoprotective properties with a plausible pharmacological affinity, selectivity and potency on different receptors and enzyme and molecular mechanisms targeting signaling pathways involved in glucose and lipid homeostasis, BCP appears to be a promising candidate for use in IR, T2DM, obesity, hyperlipidemia, and diabetic complications. The available literature reveals that BCP can be used as an adjuvant and reduce the doses of the currently used drugs and minimize their adverse effect and synergistically enhance therapeutic effects. Though, in perspective of pharmaceutical and nutraceutical development more pharmacokinetic and regulatory toxicity studies are required to ascertain the safety and efficacy for use in diabetes and associated complications.