**3.2 Curcumin**

Curcumin is the yellow-colored hydrophobic polyphenol that is available in extracts of turmeric roots belongs to the family of Zingiberaceae with genus

### **Figure 3.**

*Dietary components involved in the mechanism involved in brown adipogenesis, mitochondrial biogenesis, and energy expenditure. (a) Activation of SIRT1 either directly and/or indirectly through AMPK results in deacetylation and interaction of key transcription factors that induce brown and beige adipogenesis as PPAR α/γ and PRDM16. It was also found that PPAR/PRDM16 complex was able to bind and activate PGC1α, another co-factor expressed in brown and beige adipocytes that trigger the transcription of multiple genes engaged in thermogenesis and mitochondrial biogenesis. Likewise, AMPK may also directly magnify PGC1α activity by phosphorylation, which ultimately increases mitochondrial biogenesis. (b) The activation of TRPM8 in brown adipocytes increases the expression of thermogenic genes through the Ca2 + dependent PKA signaling pathway. (c) Due to the triggering of TRPV1 receptors in the gastrointestinal tract, and stimulation of the vagal afferent pathways, neurons within the ventromedial hypothalamus get activated. This leads to the induction of a cold-independent adrenergic response that intervenes brown adipogenesis. The adrenergic stimulation in brown adipocytes may also be promoted by decreasing the deterioration of (d) cAMP and (e) norepinephrine via direct inhibition of PDEs and COMT activity, respectively. Here, TRPM8-transient receptor potential cation channel melastatin 8, UCP1- uncoupling protein 1, TRPV1-transient receptor potential vanilloid 1, SNA- sympathetic nerve activity, AMPK- adenosine monophosphate-activated protein kinase, SIRT1- sirtuin-1, PGC-1α-peroxisome proliferator-activated receptor gamma coactivator 1-alpha, COMT- catechol-O-methyl-transferase, cAMP-cyclic adenosine monophosphate, PDEs- phosphodiesterases, PUFAs-polyunsaturated fatty acids, Ac-acetyl group, PPARα/γ peroxisome proliferatoractivated receptor alpha/gamma, PKA- protein kinase A, PRDM16- PR-domain containing 16. (+) – stimulation, (−)- inhibition, increase. The figure was modified from the following research paper by El Hadi et al., 2019. The images used in drawing the figure were extracted from the following links as described below: 1. DNA- https:// images.freeimg.net/thumbs/dna-2316536\_1280.png, 2. Brain- https://timvandevall.com/wp-content/uploads/ human-brain-parts-1.jpg, 3. Gastrointestinal tract- https://spng.subpng.com/20180425/fre/kisspng-gastrointestinaltract-human-digestive-system-diag-abdominal-5ae0b2080064a3.8564190715246750800016.jpg.*

*Mechanism and Impact of Food Components in Burning Calories from White-to-Brown Adipose… DOI: http://dx.doi.org/10.5772/intechopen.104616*

Curcuma of the plant. It has numerous therapeutic potentials like anti-obesity, anti-diabetic, antioxidant, and anti-inflammatory; used as a spice in cooking generally in India. Akbari et al., 2019 stated that supplementation of curcumin decreases body mass index (BMI), percent body fat, leptin and increases adiponectin level in obese humans [9]. Earlier studies also reported that curcumin induces browning in WAT via adenosine monophosphate-activated protein kinase (AMPK) activation and inhibition of preadipocyte differentiation by downregulating the peroxisome proliferator-activated receptor gamma (PPAR γ) and CCCAAT/Enhancer Binding Protein α (C/EBP α) [5, 10–12].

### **3.3 Resveratrol**

Resveratrol is a natural polyphenol that is mostly found in grapes (Vitaceae family with genus Vitis), blueberries (Ericaceae family with genus Vaccinium), cranberries (Ericaceae family with genus Vaccinium), red and white wines, peanuts (Fabaceae family with genus Arachis), cocoa and dark chocolates (Malvaceae family with genus Theobroma). It is well known that resveratrol plays numerous vital roles in the human body like anti-inflammatory as well as maintaining glucose metabolism and insulin sensitivity which are relevant to obesity [13]. It also possesses anti-lipolytic, cardioprotective, neuroprotective, and anti-cancerous effects [13]. Earlier studies revealed that resveratrol exerts thermogenic effects and contributes to increased respiration [14]. Another clinical study stated that resveratrol is considered a natural activator of the sirtuins family [15]. AMPK activation by resveratrol can stimulate mitochondrial biogenesis through SIRT1 [14]. Additionally, it also activates the deacetylation of PGC-1α, a regulator of energy metabolism that leads to ATP production by modulating mitochondrial function [13].

### **3.4 Menthol**

Menthol is also called mint camphor that is produced from the plant peppermint (family Lamiaceae with genus Mentha) or maybe extracted synthetically. Menthol possesses various biological properties like anti-inflammatory, anti-bacterial, antipruritic, antitussive, and analgesic properties [6, 16]. Since menthol induces cooling sensation by activating the TRPM8 receptor, a Ca2 + − permeable non-selective channel that detects cold stimuli in the thermosensory system [6, 17, 18]. Several clinical studies also reported that menthol stimulates transient receptor potential cation channel melastatin 8 (TRPM8) expression on the white and brown adipocytes.

### **3.5 Capsaicin and Capsinoids**

Capsaicin and capsinoids are the compounds that are generally found in red peppers belong to the family of Solanaceae with genus capsicum of the plant. Several studies reported that capsaicin and capsinoids have various properties like antiobesity, anti-diabetic and anti-inflammatory. Earlier studies reported that capsaicin and capsinoids played a pivotal role in fat oxidation and EE [19]. Yoneshiro et al., 2013 reported that supplementation of capsinoids over 6 weeks decreases body weight in humans [20]. Despite the above, it was also reported that exposure of cold cumulative with ingestion of capsinoids results in activation of brown and beige adipose tissues [5, 20]. This activation happens as a result of activation of the transient receptor potential cation channel subfamily V member 1 (TRPV1) in the gastrointestinal tract

which sends signals to the central nervous system (CNS) leading to 2-AR signaling activation in adipose tissue [5, 21]. It was also stated in earlier studies that capsaicin triggers browning of WAT by stimulating the expression of SIRT1, UCP1, bone morphogenetic protein 8B (BMP8B), and PPAR γ, PGC-1 α in white adipocytes.

### **3.6 Green tea**

Green tea is considered a widely consumed beverage all over the world. It is extracted from fresh leaves of a green tea plant named Camellia sinensis belongs to the family of Theaceae. It contains huge amounts of polyphenols, mainly tea catechins like epicatechin, epicatechin gallate, and epigallocatechin that possesses properties like antioxidants, hypocholesterolemic, antihypertensive, and anticarcinogenic [14]. Various clinical studies also enumerated that consumption of green tea helps in weight management by modifying fat metabolism and calories expenditure. Earlier studies also reported that green tea contains a substantial amount of caffeine; which is known for its thermogenic properties [6, 22]. Dulloo et al., 1999 in human studies, also stated that green tea enhances fat oxidation and energy expenditure [23]. Nevertheless, catechins and caffeine may synergically mediate adrenergic-induced BAT thermogenesis by acting at different checkpoints of the norepinephrine-cyclic adenosine monophosphate (cAMP) axis. It was recommended that green tea catechins may promote sympathetic nerve activity (SNA) by decreasing the degradation of norepinephrine through direct inhibition of catechol-O-methyl-transferase (COMT) [6]. Furthermore, it was also reported that caffeine may synergically prolong the effects of norepinephrine by direct inhibition of phosphodiesterases (PDEs) activity [6, 23, 24].
