A Review of the Role of an Anthocyanin, Cyanidin-3-O-β-glucoside in Obesity-Related Complications

Obesity has become a major health issue worldwide and obese individuals possess higher levels of adipose tissue when compared with healthy individuals. Obesity is highly associated with the development of different chronic diseases, such as diabetes, cardiovascular diseases, hypertension, cancers, etc. Previous studies established that anthocyanin compounds play an important role in attenuating obesity-related consequences. Among various anthocyanin compounds, cyanidin-3-O-β-glucoside (C3G) is the most important component and is widely distributed in various colored edible plant materials, especially berries, cherries, black rice, purple corn, etc. In recent decades, several studies have reported the therapeutical properties of C3G. C3G has various biological properties and health benefits, such as antioxidant, antimicrobial, anti-inflammatory, antidiabetic, anti-obesity, neuroprotective, anticancer, etc. In this review, we summarized the in vitro and in vivo studies in relation to the role of C3G in obesity-related complications. Several mechanistic studies demonstrated that C3G maintains the metabolism of glucose, fatty acids, and lipids by regulating different genes and signaling pathways. It could be concluded that the consumption of C3G protects healthy individuals from obesity-related issues by maintaining body weight and regulating their metabolism and energy balance. This review provides some important signaling pathways/targets of C3G to facilitate the prevention and treatment of obesity, leading to the development of important food supplements.


Introduction
Obesity is one of the most important health problems worldwide with considerable illness and mortality.According to the WHO, more than 2.8 million deaths occur every year due to obesity-related consequences.In 2016, approx.1.9 billion adults were obese [1,2].If secular trends continue, it is estimated that 38% of the world's adult population will be overweight by 2030 and an additional 20% will be obese exclusively in underdeveloped countries [3].Genetic mechanisms, endocrine, appetite disorders, and diabetes-associated diseases are major factors that trigger obesity [4,5].Obesity is a high-risk factor for developing numerous chronic diseases, including diabetes, heart disease, liver disease, and hypertension [6].Lipid and energetic metabolisms comprise a sequence of biosynthetic and oxidative reactions required for the energy supply and differentiation of adipocytes.In these, lipogenesis activates mitochondrial biogenesis, the production of reactive oxygen species, and inflammatory responses that are highly correlated with obesity [5].The major causative factor for obesity is the consumption of more calories accompanied by the accumulation of excessive fat.Although lifestyle changes and improving physical activity are the best strategies for preventing obesity, it can be difficult to continue these activities in the long term [7].Some treatment strategies that can be followed to prevent obesity Plants 2023, 12, 3889 2 of 19 are thermogenesis of brown adipose tissue, genetics and epigenetics, physical exercise, and diet, including foods with bioactive components [8].Therefore, developing a novel effective approach to prevent obesity-related complications is essential for the scientific community [6,7].
Anthocyanins are widely found in colored fruits and vegetables.[4].They are important flavonoid compounds in terms of food as well as medicine due to the availability of numerous structurally different bioactive components [9,10].Anthocyanin components offer potential health-promoting functions due to their strong antioxidant effects [9,11].Anthocyanin components are rich in colored fruits, vegetables, and cereals, including berries, cherries, grapes, black beans, purple cabbage, purple corn, black rice, etc.In addition, anthocyanins are generally treated as colorants in beverages, fruit fillings, and dairy products.Hence, anthocyanins play a significant role in the diet of humans [5,12].Diets supplemented with anthocyanin-rich berries can significantly affect gastrointestinal bacterial communities with respect to obligate anaerobes by decreasing the gastrointestinal luminal oxygen and oxidative stress [13].In particular, cyanidin and its derivatives can exhibit a protective effect on DNA cleavage [14].The administration and consumption of cyanidin glycosides are effective in reducing reactive oxygen species (ROS)-mediated cell and tissue damage [15,16].
In recent times, there has been significant attention in the research of anthocyanin derivatives.Approx.635 different anthocyanin components have been identified in various plants.In particular, pelargonidin, cyanidin, delphinidin, peonidin, petunidin, and malvidin are important aglycones in foods [5].Among them, cyanidin-3-O-β-glucoside (C3G) is an important biologically active component (Figure 1).Numerous studies have confirmed that anthocyanins provide various therapeutic effects, especially C3G, which significantly increases energy expenditure as well as decreases weight gain [10,17].Further, C3G is considered to be the main component in terms of the bioavailability and active form of cyanidin in human tissues [18].C3G markedly reduces lipogenesis, oxidative stress, and inflammation, thereby improving the obesity-mediated dysregulation of metabolism.C3G has the potential to speed up lipolysis and thermogenesis and to reduce body fat accumulation.A study found that a master regulator of energy metabolism, namely peroxisome proliferator-activated receptors (PPARs), is activated by C3G [19].
physical activity are the best strategies for preventing obesity, it can be difficult to cont these activities in the long term [7].Some treatment strategies that can be followed to vent obesity are thermogenesis of brown adipose tissue, genetics and epigenetics, phy exercise, and diet, including foods with bioactive components [8].Therefore, develo a novel effective approach to prevent obesity-related complications is essential for the entific community [6,7].
Anthocyanins are widely found in colored fruits and vegetables.[4].They are portant flavonoid compounds in terms of food as well as medicine due to the availab of numerous structurally different bioactive components [9,10].Anthocyanin compon offer potential health-promoting functions due to their strong antioxidant effects [9 Anthocyanin components are rich in colored fruits, vegetables, and cereals, including ries, cherries, grapes, black beans, purple cabbage, purple corn, black rice, etc.In addi anthocyanins are generally treated as colorants in beverages, fruit fillings, and dairy p ucts.Hence, anthocyanins play a significant role in the diet of humans [5,12].Diets plemented with anthocyanin-rich berries can significantly affect gastrointestinal bact communities with respect to obligate anaerobes by decreasing the gastrointestinal lum oxygen and oxidative stress [13].In particular, cyanidin and its derivatives can exhi protective effect on DNA cleavage [14].The administration and consumption of cyan glycosides are effective in reducing reactive oxygen species (ROS)-mediated cell and sue damage [15,16].
In recent times, there has been significant attention in the research of anthocy derivatives.Approx.635 different anthocyanin components have been identified in ous plants.In particular, pelargonidin, cyanidin, delphinidin, peonidin, petunidin, malvidin are important aglycones in foods [5].Among them, cyanidin-3-O-β-gluco (C3G) is an important biologically active component (Figure 1).Numerous studies confirmed that anthocyanins provide various therapeutic effects, especially C3G, w significantly increases energy expenditure as well as decreases weight gain [10,17].ther, C3G is considered to be the main component in terms of the bioavailability and a form of cyanidin in human tissues [18].C3G markedly reduces lipogenesis, oxida stress, and inflammation, thereby improving the obesity-mediated dysregulation of tabolism.C3G has the potential to speed up lipolysis and thermogenesis and to red body fat accumulation.A study found that a master regulator of energy metabol namely peroxisome proliferator-activated receptors (PPARs), is activated by C3G [19 C3G and its metabolites have better absorption and bioavailability, and their inte tion with gut microbiota may improve their positive health effects.Several studies on have been published in the past decades.However, no detailed review has been publi C3G and its metabolites have better absorption and bioavailability, and their interaction with gut microbiota may improve their positive health effects.Several studies on C3G have been published in the past decades.However, no detailed review has been published Plants 2023, 12, 3889 3 of 19 regarding the role of C3G in obesity-related complications.In this context, the present review aims to discuss the possible therapeutical properties of C3G for preventing and treating obesity based on in vitro and in vivo studies.For this purpose, a literature search was performed in electronic databases using "obesity" as the major term, together with "C3G", and mainly comprised articles in English.This review mainly focused on the role of C3G in obesity with its underlying mechanisms, leading to the development of potent food supplements for preventing obesity-related health issues.

The Occurrence and Color Characteristics of C3G
Anthocyanin content in colored fruits and vegetables varies remarkably, according to different species.In addition, numerous factors influence the level of anthocyanin content, such as the cultivar, geographical location, environmental conditions, cultural practices, harvest time and methods, processing and storage conditions, etc. [20 -22].Berries are a rich source of anthocyanins, including strawberries, blueberries, blackberries, black elderberries, bilberries, blackcurrants, chokeberries, redcurrants, and raspberries [22].In these, the highest anthocyanin content is found in elderberries (1.4 g) and chokeberries (1.8 g) per 100 g of product [23,24].Moreover, purple corn, cherries, plums, pomegranates, eggplant, wine, grapes, and colored vegetables such as black carrots, red cabbage, and purple cauliflower contain appreciable amounts of anthocyanin compounds [24,25].Among the different anthocyanins, C3G is widely found in colorful berries, blue and red fruits, and vegetables.In particular, pomegranates, blackberries, bilberries, elderberries, and mulberries possess a higher bioavailability of C3G.In addition, C3G is commonly found in black rice, black beans, and purple potatoes [26,27].
The color of the anthocyanin pigments usually ranges from pale yellow to blue, but are primarily responsible for the red, purple, and blue colors of different plant organs.In general, C3G is normally found in vegetables and fruits as a red pigment.However, the pH, light, temperature, and structure play a critical role in the color and stability of anthocyanins.At an alkaline pH, anthocyanins are blue pigments, whereas they are red at an acidic pH.However, these pigments are highly unstable and oxidized into dark brown compounds at alkaline conditions due to degradation [28].In their structure, the B-ring and the presence of hydroxyl or methoxyl groups also influence the stability of anthocyanins.Further, the presence of an oxonium ion adjacent to carbon 2, metal ions, temperature, light, and oxygen may also influence the stability of the anthocyanin pigments [22,28].In the flowers and fruits of some plants, the colors may depend on the combined effect of the light absorbance of chlorophylls and anthocyanins [29,30].

The Chemistry of C3G
Anthocyanins are anthocyanidin glycosides (aglycones).They are formed by a flavylium cation backbone that is hydroxylated in different positions to produce diverse anthocyanidins [29].Cyanidin is one of the extensively distributed pigments in plants.In these, C3G is the most characterized anthocyanin in edible plants, followed by delphinidin, pelargonidin, and peonidin glucosides.These aglycones differ according to their B-ring substitution pattern [28].C3G is a monomeric anthocyanin and a water-soluble pigment with a molecular weight of 449.4 g/mol.It is derived from the aglycone cyanidin and is more hydrophilic than cyanidin.C3G consists of an O-glycosylated anthocyanidin with two hydroxyls on the third aromatic ring.In acidic conditions, C3G occurs in the flavylium form.On the other hand, in alkaline conditions, C3G occurs in the carbinol form through the hydration of the flavylium cation or in the quinoidal form through the loss of a proton [31].In plants, C3G is biosynthesized through the flavan-3-ol pathway.Previously, pharmacokinetics studies in humans demonstrated that >20 kinds of C3G metabolites have been identified [32].The main bioactive metabolites of C3G are protocatechuic acid, phloroglucinaldehyde, vanillic acid, and ferulic acid.Furthermore, the stability of C3G is improved when it is acylated with lauric acid, owing to its ester group [33,34].

In Vitro Studies on the Role of C3G in Obesity-Related Complications
The excessive consumption of energy-rich foods and an inactive lifestyle are believed to be the main causes of obesity-related insulin resistance and abnormal glucose metabolism.Scientific studies confirmed that anthocyanins may lower the metabolic risks linked with obesity due to their potent antioxidant and anti-inflammatory properties.The dysfunction of adipocytes is highly correlated with the onset of obesity and insulin resistance.It is believed that obesity and the improvement of insulin sensitivity can be prevented by regulating the secretion of adipocytokine and the expression of adipocyte-specific genes.Table 1 shows the mechanisms of C3G for preventing obesity-related complications under different in vitro conditions.An excessive amount of circulating free fatty acids has been proven to be potentially associated with obesity, insulin resistance, and diabetes.In this context, lipolysis inhibition is the main target for reducing free fatty acids and improving insulin sensitivity.A study reported that C3G effectively suppressed the release of free fatty acids and glycerol from 3T3-L1 adipocytes during hyperglycemia.C3G treatment downregulated the hexosamine biosynthetic pathway by increasing the AMP-activated protein kinase activity, decreasing the glutamine:fructose 6-phosphate aminotransferase activity (GFAT), and reducing the production of cellular UDP-N-acetylglucosamine. Furthermore, C3G downregulated the adipose triglyceride lipase expression by attenuating the forkhead box O1 (FoxO1) transcription factor [45]. C3G efficiently improved insulin resistance in 3T3-L1 adipocytes by upregulating the expression of the glucose transporter type 4 (GLUT4) gene [40].
C3G markedly inhibited basal adipocyte lipolysis in differentiated human fat cells.A mixture of docosahexaenoic acid and C3G reduced the tumor necrosis factor-α (TNF-α) secretion and enhanced insulin-induced lipogenesis [50].Matsukawa et al. [49] demonstrated that C3G treatment differentiated the 3T3-Ll cells into smaller adipocytes by upregulating the gene expressions of PPARγ and C/EBPα, increasing the adiponectin secretion, decreasing the TNF-α secretion, activating insulin signaling, and increasing the glucose uptake.Further, C3G effectively upregulated the expression of PGC-1α, sirtuin-1 (SIRT1), and the uncoupling protein (UCP)-3 genes in C2C12 myotubes.Jia et al. [19] found that C3G effectively enhanced the uptake of glucose in HepG2 cells as well as C2C12 myotubes.Further, C3G stimulated the hepatic fatty acid oxidation rate.The results revealed that C3G upregulated the main regulators of energy metabolism, i.e., PPARs.In rat adipocytes, C3G increased the secretion of adipocytokines, such as adiponectin and leptin.Further, the adipocyte-specific gene expression was upregulated by C3G treatment without PPARγ activation [35].In human adipocytes, C3G or cyanidin treatment significantly upregulated the gene expression of adiponectin as well as downregulated plasminogen activator inhibitor-1 and IL-6.C3G or cyanidin treatment also activated the lipid metabolism-associated genes, such as uncoupling protein2, acyl-CoA oxidase1, and perilipin [36].
One of the promising approaches for treating obesity is to convert white adipocytes into brown-like adipocytes.In 3T3-L1 adipocytes, C3G stimulated phenotypic modifications into white adipocytes, such as higher levels of multilocular lipid droplets and mitochondrial content.In addition, C3G treatment increased the expression of the mitochondrial genes in 3T3-L1.Moreover, C3G improved the differentiation of preadipocytes by activating the CCAAT/enhancer-binding protein β (C/EBPβ) via increasing the level of intracellular cyclic adenosine 3 5 -monophosphate (cAMP) [53].Recently, Han et al. [62] found that Prdm16 bound to the promoter region (−500 to −150 bp) of UCP1 to stimulate its transcription with the presence of C3G in C3H10T12 brown adipose cells, thereby facilitating brown adipose tissue programming.In differentiated palmitate-induced C3H10T1/2 clone8 cells, C3G suppressed the release of adipokines, such as extracellular nicotinamide phosphoribosyltransferase and fibroblast growth factor 21 [54].
In 3T3-L1 adipocytes, a study found that C3G treatment effectively reverted the insulin resistance induced by H 2 O 2 -or TNF-α via the downregulation of the c-Jun N-terminal kinases (JNK) signaling pathway [38].C3G and its metabolite protocatechuic acid improved the uptake of adipocyte glucose and GLUT4 membrane translocation in human omental adipocytes and 3T3-L1 cells.Further, these components markedly increased the nuclear PPARγ activity and the expression of GLUT4 [42].In macrophage-conditioned media-treated adipocytes, C3G and pelargonidin-3-O-glucoside suppressed the activation of the NF-κB and JNK pathways by regulating the phosphorylation of IκBα and JNK, respectively [2].In 3T3-L1 adipocytes, anthocyanins extracted from colored corn blocked the adipocyte differentiation and the accumulation of lipids, and attenuated the transcription of PPAR-γ.In 3T3-L1 cells, black soybean anthocyanins decreased the accumulation of lipids and inhibited the expression of PPARγ [46].Further, anthocyanins improved inflammation induced by TNF-α and insulin resistance in adipocytes by activating insulin signaling and enhanced translocation of GLUT4 [52].
Further, AMPK plays a key role in preventing hepatic lipid metabolism by regulating the downstream acetyl CoA carboxylase and carnitine palmitoyl transferase 1 pathways.A study indicated that C3G regulated hepatic lipid homeostasis through an AMPK-dependent signaling pathway [44].In 3T3-L1 preadipocytes, cyanidin treatment suppressed adipogenesis via the downregulation of gene expressions, such as PPARγ, C/EBPα, adiponectin, and aP2.In addition, intracellular Ca 2+ was increased in the cyanidin-stimulated cells [66].Cyanidin-3-rutinoside (C3R) significantly upregulated the uptake of glucose and the expression of plasma membrane glucose transporter type 4 (GLUT4) by triggering the PI3K/Akt pathways [51].In mesenteric adipose tissue-cultured medium-induced RAW 264.7 cells, cyanidin and C3G markedly inhibited the migration and production of inflammatory chemokines, such as MCP-1 and MRP-2 [37].Zhang et al. [59] investigated the effect of anthocyanin-rich water extracts obtained from 20 different purple corn genotypes on RAW 264.7 macrophages and 3T3-L1 adipocytes.These extracts efficiently decreased the production of the pro-inflammatory mediators, regulated the diabetes-associated key enzymes, and improved insulin sensitivity.In the early phase of adipogenesis, C3G exposure markedly suppressed the expression of (C/EBPβ), PPAR through the transcription factor forkhead box O1 (FoxO1).The authors found that C3G upregulated FoxO1 by enhancing its deacetylation through silent mating type information regulation 2 homolog 1 [47].
In 3T3-L1 adipocytes, a study found that C3G treatment effectively reverted the insulin resistance induced by H2O2or TNF-α via the downregulation of the c-Jun N-terminal kinases (JNK) signaling pathway [38].C3G and its metabolite protocatechuic acid improved the uptake of adipocyte glucose and GLUT4 membrane translocation in human omental adipocytes and 3T3-L1 cells.Further, these components markedly increased the nuclear PPARγ activity and the expression of GLUT4 [42].In macrophage-conditioned media-treated adipocytes, C3G and pelargonidin-3-O-glucoside suppressed the activation of the NF-κB and JNK pathways by regulating the phosphorylation of IκBα and JNK, respectively [2].In 3T3-L1 adipocytes, anthocyanins extracted from colored corn blocked the adipocyte differentiation and the accumulation of lipids, and attenuated the transcription of PPAR-γ.In 3T3-L1 cells, black soybean anthocyanins decreased the accumulation of lipids and inhibited the expression of PPARγ [46].Further, anthocyanins improved inflammation induced by TNF-α and insulin resistance in adipocytes by activating insulin signaling and enhanced translocation of GLUT4 [52].
Further, AMPK plays a key role in preventing hepatic lipid metabolism by regulating the downstream acetyl CoA carboxylase and carnitine palmitoyl transferase 1 pathways.A study indicated that C3G regulated hepatic lipid homeostasis through an AMPK-dependent signaling pathway [44].In 3T3-L1 preadipocytes, cyanidin treatment suppressed adipogenesis via the downregulation of gene expressions, such as PPARγ, C/EBPα, adiponectin, and aP2.In addition, intracellular Ca 2+ was increased in the cyanidin-stimulated cells [66].Cyanidin-3-rutinoside (C3R) significantly upregulated the uptake of glucose and the expression of plasma membrane glucose transporter type 4 (GLUT4) by triggering the PI3K/Akt pathways [51].In mesenteric adipose tissue-cultured medium-induced RAW 264.7 cells, cyanidin and C3G markedly inhibited the migration and production of inflammatory chemokines, such as MCP-1 and MRP-2 [37].Zhang et al. [59] investigated the effect of anthocyanin-rich water extracts obtained from 20 different purple corn genotypes on RAW 264.7 macrophages and 3T3-L1 adipocytes.These extracts efficiently decreased the production of the pro-inflammatory mediators, regulated the diabetes-associated key enzymes, and improved insulin sensitivity.In the early phase of adipogenesis, C3G exposure markedly suppressed the expression of (C/EBPβ), PPAR ɣ , and FAS, and activated the AMPK pathway when compared to late-phase exposure [68].
Saulite et al. [58] investigated the effect of malvidin, cyanidin, and delphinidin against adipose tissue-derived human mesenchymal stem cells.The results revealed that delphinidin suppressed adipogenesis and decreased fatty acid-binding protein 4 (FABP4) and the adiponectin genes.Malvidin stimulated a higher level of calcium accumulation in the cells.Further, the osteocyte-specific gene BMP-2 and Runx-2 expression were upreg-, and FAS, and activated the AMPK pathway when compared to late-phase exposure [68].
Saulite et al. [58] investigated the effect of malvidin, cyanidin, and delphinidin against adipose tissue-derived human mesenchymal stem cells.The results revealed that delphinidin suppressed adipogenesis and decreased fatty acid-binding protein 4 (FABP4) and the adiponectin genes.Malvidin stimulated a higher level of calcium accumulation in the cells.Further, the osteocyte-specific gene BMP-2 and Runx-2 expression were upregulated in addition to the stimulation of BMP-2 secretion by malvidin.According to suitable stimuli, adipocytes can be proliferated and differentiated.The important transcription factor responsible for lipogenesis is the carbohydrate response element-binding protein (ChREBP) chiefly found in lipogenic organs.Pompei et al. [43] found that cyanidin diminished the differentiation by 20% as well as the ChREBP expression in preadipocytes.The authors suggested that cyanidin exhibited an inhibitory activity on adipogenesis by interfering with the extracellular matrix [43].Takahashi et al. [64] reported that C3G showed significant induction in adipocyte differentiation in human amniotic epithelial cells.
Pancreatic lipase is one of the most essential digestive enzymes for metabolism as well as for the absorption of triglycerides to monoglycerides and free fatty acids.In the body, the level of total cholesterol is decreased when inhibiting the lipase enzyme activity [69].In this context, different authors investigated the inhibitory potential of C3G against lipase enzymes.Their studies showed that C3G markedly inhibited the pancreatic lipase activity with IC 50 values of 188.28 µM [57] and 0.268 mg/mL [67].A recent study demonstrated that the development of insulin fibrils was attenuated by anthocyanins, such as cyanidin, C3G, C3R, malvidin, and malvidin-3-glucoside [65].In another study, the results exhibited that C3R effectively inhibited pancreatic lipase (IC 50 at 59.4 µM).Further, C3R showed a considerable reduction in the cholesterol uptake in free cholesterol as well as mixed micelles in addition to the suppression of the NPC1L1 expression in Caco-2 cells [56].Chen et al. [70] found that C3G from Aronia melanocarpa exhibited the strongest inhibitory activity against α-amylase and lipase.However, cyanidin 3-galactoside, cyanidin-3-arabinoside, and cyanidin 3-xyloside did not show any effect on the α-amylase and lipase enzymes.Further, Plants 2023, 12, 3889 9 of 19 Xie et al. [71] suggested that the structures of the B-ring and glycosyl group were mainly associated with the inhibitory potentials of monomeric anthocyanins.

In Vivo Studies on the Role of C3G in Obesity-Related Complications
Similar to the in vitro studies, numerous in vivo studies have been carried out to determine the effect of C3G on obesity-associated mechanisms (Table 2).The C3G-rich purple corn color effectively reduced body weight gain as well as the weights of white and brown adipose tissue in high-fat (HF) diet-induced mice.Further, the purple corn color downregulated the mRNA levels of the enzymes responsible for the synthesis of fatty acid triacylglycerol and reduced the mRNA level of sterol regulatory element-binding protein-1 in white adipose tissue [72].In another study, the dietary intake of anthocyanin upregulated the adiponectin expression in white adipose tissue and suggested that the activation of AMPK was a possible mechanism for these changes [35].It is well known that brown adipose tissue burns energy to generate heat.The previous studies found that C3G can improve the thermogenic ability of brown adipose tissue.Han et al. [62] evaluated the effect of C3G on the UCP1 gene expression in db/db mice induced with a HF, high-fructose diet and found that Prdm16 is directly bound to the promoter region of UCP1.In another study, C3G efficiently regulated the transcription of UCP1 in brown adipose tissue as well as in subcutaneous white adipose tissue by enhancing mitochondrial number and function [17].In the diet-induced obesity mice model, the purple corn cob extract treatment upregulated the M2 markers (ArgI, Fizz1, and TGFβ) and downregulated the inflammatory mediators (TNF-α, IL-6, IL-1β, and COX-2) by suppressing NF-kB signaling [94].Jia et al. [19] reported that the dietary supplementation of C3G upregulated the PPARs in the HF-diet-induced mice.In the KK-Ay mice, C3G significantly enhanced obesity and triglyceride metabolism by partly activating lipoprotein lipase in the plasma and skeletal muscle.The inhibition of lipoprotein lipase (LPL) in adipose tissue following the activation of pAMPK might have been attributed to the inhibition of lipoprotein lipase [41].Guo et al. [76] reported that C3G regulated the signaling pathway, c-Jun N-terminal kinase/foxO1, and its associated inflammatory adipocytokines.Ren-Qiang et al. [78] also reported that C3G diminished obesity-related dyslipidemia and insulin resistance in HF-diet-induced rats by enhancing the level of serum adiponectin.Biswas et al. [83] reported that C3G supplementation in the diet reduced weight gain, and improved food intake and metabolism during obesity.
The combination of peptides and C3G markedly improved the glucose uptake with or without insulin.In addition, this combination suppressed the expression of the angiotensin II receptor, type 1 (AGTR-1), and activated the insulin receptor substrate 1 and GLUT4 expressions [84].In diet-induced obese mice, the mixture of C3G and peptides efficiently decreased systolic as well as diastolic blood pressure.Further, this combination significantly reduced body fat levels and enhanced glucose tolerance [87].In diet-induced obese mice, the combination of C3G and peptides regulated the expression of the genes associated with glucose metabolism [91].The administration of anthocyanins from purple corn remarkably reduced body weight gain, fat mass, total cholesterol, and triglyceride levels in the HFdiet-induced mice.The data demonstrated that the anthocyanin extract suppressed the expression of PPARγ, C/EBPα, and SREBP-1c, subsequently activating the expression of PPARα, PGC1α, PRDM16, and FGF21 [4].Titta et al. [39] demonstrated that the anthocyanin-rich extract from Moro oranges marginally affected the accumulation of fats in C57/Bl6 mice induced with a HF diet.Anthocyanin black carrots fermented with Aspergillus oryzae inhibited lipid and glucose metabolism via the activation of hepatic insulin signaling and the AMPK pathways in OVX rats [48].A study demonstrated that anthocyanins from black rice, black soybeans, and purple corn alleviated oxidative stress and inflammation-related obesity in HF-dietinduced mice by suppressing the expression of TNFα, IL-6, inducible nitric oxide synthase (iNOS), and NF-κB, and increasing the hepatic superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities [82].Blackberries containing 87% of the C3G diet downregulated the expression levels of hepatic NF-κB and cyclooxygenase-2 in ovariectomized rats [75].A C3G-enriched Aronia melanocarpa extract inhibited adipogenesis by downregulating the expressions of the CCAAT/enhancer-binding protein, PPAR, sterol regulatory elementbinding protein-1c, PPARγ coactivator-1, acetyl-CoA carboxylase 1, ATP-citrate lyase, fatty acid synthase, and adipocyte protein 2 [88].The anthocyanin-rich extract from aronia fruit reduced the accumulation of visceral fat and hyperglycemia via the inhibition of pancreatic lipase activity and the adsorption of intestinal lipids [95].In HF-diet-induced rats, C3G isolated from Aronia melanocarpa treatment expressively decreased the levels of TNF-α, IL-6, and IL-1β in the serum.Further, C3G improved HFD-induced obesity by activating AMPK and suppressed HFD-induced inflammation by activating the phosphorylation of STAT3 and suppressing NF-κB p65 in the nucleus [90].
Anthocyanins, such as C3G, C3R, and pelargonidin-3-glucoside, isolated from Chinese mulberry significantly inhibited body weight gain, reduced insulin resistance, lowered the size of adipocytes, and attenuated the accumulation of lipids and the secretion of leptin [77].The supplementation of cyanidin and delphinidin effectively controlled overweight, obesity, and type 2 diabetes by modulating the activity of inflammatory mediators, oxidative stress, and NF-κB/JNK activation [85].Esposito et al. [79] suggested that the gut microbiome and the kind of anthocyanin aglycone moiety could influence the preventive role of anthocyanins in obesity and their associated insulin resistance.The supplementation of cyanidin-and delphinidin-rich extracts also exhibited beneficial effects on unhealthy diets [92].The administration of C3G from Saskatoon berries diminished liver steatosis, insulin resistance, and chronic inflammation in HF and high-sucrose-induced mice [89].
The improvement in the thermogenesis of brown adipose tissue is an efficient strategy for alleviating obesity.A study exhibited that C3G improved the energy expenditure and thermogenesis of brown adipose tissue in mice induced with HF diet obesity.Additionally, C3G upregulated the UCP1 expression as well as other thermogenic genes in inguinal white adipose tissue and brown adipose tissue [86].In db/db mice, C3G treatment restored the endothelium-dependent relaxation of the aorta [47].C3G controlled the adipokine expression in brown adipose tissue in high-fat-cholesterol diet-induced mice [54].A recent study demonstrated that treatment with casein/C3G nanoparticles ameliorated the HFD-induced accumulation of fats and liver oxidative stress in C57BL/6 mice [93].In a recent study, Meleleo et al. [96] demonstrated that anthocyanins, such as cyanidin, C3G quercetin, and quercetin-O-glucoside, interacted with planar lipid membranes and formed conductive units.

Conclusions and Future Perspectives
C3G is an important anthocyanin compound and is widely found in various fruits and vegetables.Previous studies established that C3G supplementation offers numerous health benefits to the consumer.In this review, we discussed the effect of C3G treatment on obesityassociated mechanisms under different in vitro and in vivo models.The mechanisms preventing obesity highly depend on their capacity to control the consumption of food and energy metabolism and improve inflammatory response, insulin resistance, and glucose metabolism.In addition, C3G can effectively inhibit the pancreatic lipase enzyme.A variety of pathways and gene expressions play a crucial role in preventing obesity-related consequences.In particular, AMPK is an important pathway, attributed to the prevention of hepatic lipid metabolism, and PPARs play a key role in energy metabolism.The IRS-1/PI3K/Akt pathway and GLUT4 gene expression are mainly responsible for insulin sensitivity and the NF-κB signaling pathway is for inflammatory response.The published papers clearly showed that C3G could be a potential agent for facilitating the prevention and treatment of obesity-associated complications owing to its multi-targeted activities.Although C3G can effectively attenuate obesity-associated complications, further clinical studies leading to the development of C3G-enriched functional foods are required.

Table 1 .
The effects of cyanidin-3-O-β-glucoside on the obesity-associated mechanisms under in vitro conditions.

Table 2 .
The effect of cyanidin-3-O-β-glucoside on the obesity-associated mechanisms under in vivo conditions.