Betaine

What is Betaine?

Betaine is an osmolyte derived from Rice bran and sugarcane and is a byproduct of beet processing. It is non-toxic, highly water-soluble, and chemically stable. It is also found in our body as it serves multiple essential functions in the liver, kidney, and skin. Structurally, it is a zwitterion (has both negative and positive charge) and can hold water. At pH 1 it cationic, gradually switches to a zwitterion at pH of 3.2 and at pH of 5.5, it mainly exists as a zwitterion where it functions as a buffer as well. It is mostly used as a humectant and anti-irritant in skincare, but its skin benefits go beyond just these two. Its benefits are as follows:

• Hydration
• Barrier Repair
• Anti-irritant (especially against surfactant damage)
• Anti-inflammatory
• Indirect antioxidant
• Anti-hyperpigmentation
• Anti-aging

How does it hydrate the skin?

Osmolytes like Betaine are usually found in plants that can withstand extreme drought. They do this through molecules like Betaine as it can hold water and resist dehydration of cells.

If you look at the structure of Betaine, you’ll see that it kind of looks like a helicopter. The mobility of the three methyl groups around the C-N axis and their mobile arrangement due to steric hindrance pushes the water attached to the hydration sphere of Betaine. The polar molecule of Betaine (COOH) attracts water, then the oscillating fan at the other end blows it away. Why is this important? This unique ability of betaine results in it having a high Huggin’s constant. Huggin’s constant is the interaction factor accounting for the easy exchange of water molecules. This means that Betaine does not immobilize water molecules as many humectants like glycerin does, which allows water for the living cells to be completely available. It attracts water, but because of the “fan-like” release, Betaine releases water to the environment when required, making it a true water carrier.^[2]

Betaine is tested to have a higher water-binding capacity than glycerin. 5% of Betaine showed significant hydration compared to control as measured by corneometer. ^[3] 4% Betaine solution increased hydration value and decreased macrorugosity (wrinkle depth) of the skin, and it was shown to be not statistically different from 4% glycerin. ^[4]

 How does it help in Barrier Repair?

One of the components of the barrier is the Tight Junction (TJ) in the Stratum Granulosum. The Tight junctions are multi-protein complexes composed of transmembrane proteins such as the Claudin family, Occludin and Cytoplasmic proteins such as ZO-1. TJs prevent the leakage of molecules and ions in the epidermis, forming that almost impenetrable seal. They have a direct role in forming the moisture barrier. In fact, Claudin-1 knockout mice (Mice with deleted Claudin-1 gene) die 24 hours after birth.

UVB irradiation increases the penetration of biotinylated markers through TJs, suggesting an impairment in the TJ function. Immunostaining revealed that TJ proteins were delocalized from the cell membrane to the cytoplasm of cells. Exposure to H2O2 showed the same results with Claudin-1 proteins. The Radical Oxygen Species (ROS) from UV exposure are directly responsible for the moisture barrier’s impairment through delocalization of the TJ proteins. During the disruption of the TJs by oxidative stress, Occludin phosphorylation was increased, leading to the dissociation of Occludin-ZO complexes in the intercellular junction. In short, UVB causes the TJs to not stick to each other anymore, leading to barrier impairment.

Incubation with Organic Osmolytes (OOs) like Betaine, Taurine and Myoinositol showed that cells are partially protected from ROS damage. They did not decrease ROS production, but they protected the cells from shrinking upon UV exposure. TJs’ gene expression was not affected by incubation with OOs, but the TJ protein levels were increased. This suggests that OOs protect the TJ proteins on a post-translational level. A number of studies have revealed that OOs like Betaine protect TJs via their ability to protect the native conformation of proteins by interacting with their peptide backbone to stabilize proteins and force proteins in their native conformation. You’ll see later that OOs’ ability to stabilize protein comes in handy in other things such as anti-irritation.^[5]

We know that skin cells originate from the stratum basale and mature and die towards the stratum corneum. As they migrate towards the cell’s outer parts, they flatten and lose their organelles and nucleus. But where does this waste go? The answer is Autophagy.

Autophagy (self-eating) is a mechanism that mediates lysosomal delivery and degradation of protein aggregates, damaged organelles and intracellular microorganisms. This means that the skin cells eat itself up when it differentiates in the skin. How is this good? Over time, skin cells accumulate damage through various factors such as ROS damage through UVB irradiation. Zombie cells or senescent cells are aged/damaged cells that stopped multiplying into younger cells. They also secrete various inflammatory factors that cause further damage to nearby cells and prevent collagen repair, leading to the appearance of wrinkles. Autophagy’s role is to eliminate these aged cells and damaged organelles to make way for younger ones. Unfortunately, in the presence of pro-oxidants, the process of Autophagy cannot degrade protein aggregates in damaged cells and organisms. This is one of the major causes of aging. Skincare science has shifted from adding back things to the skin to removing thing i.e. Senescent cells. 

Incubation with Betaine upregulated Autophagy and decreased senescent cells in the skin. How does it do this? It’s a bit complicated, so brace yourself for a bit of Biochemistry.

Autophagy is regulated through the AMPK-LKB1 energy pathway. AMPK is regulated through upstream kinases like LKB1, which is a tumor suppressor. Upon activation of AMPK, it binds to ULK1, which triggers Autophagy. On the other hand, the mTOR pathway is responsible for negatively regulating Autophagy to prevent the cell from eating themselves. If we trigger AMPK-LKB1 while inhibiting mTOR, we can induce Autophagy to get rid of senescent cells. By the way, other factors like Genistein, Resveratrol, Metformin or even Exercise can also activate the AMPK pathway; that is why exercise can keep you young. This is where Betaine comes in. Incubation of cells with B activated the AMPK-LKB1 energy pathway while inhibiting mTOR. (Some studies argue that Betaine’s Autophagy isn’t mTOR mediated) This resulted in the activation of Autophagy, leading to decreased Senescent cells compared to control. B is shown to be a novel regulator of Autophagy as it may induce epidermal turnover and improve barrier abnormality of the aged epidermis. Clinically, this translated to an increased epidermal thickness in skin equivalent under B treatment. More studies need to be done in order to properly assess the direct and indirect effects of B on barrier repair.^[6][7]

How does it mitigate irritation?

Betaine is mainly known for its anti-irritation properties. Adding 3-5% of B to mixed-surfactant solutions reduced red blood cells’ damage and decreased their zein number (aggressiveness towards proteins). In addition, a progressive decrease of SLES-induced skin irritation is detected by a human-patch test when the amount of B is increased.^[2:1] A progressive decrease of SLES-induced skin irritation is detected by the human patch test when the amount of betaine increases.^[8] Another study with 21 subjects did 24-hour patch occlusion with SLS, CAPB alone or together, with B alongside two controls with water and one unoccluded one. The results show that irritation was decreased with the addition of Betaine.^[9] Interestingly, another study showed the same results in soap irritation, but increasing B’s concentration from 1% to 10% did not yield a significant increase in anti-irritation property.^[10] Since Betaine is able to protect protein against denaturation, as discussed above, it also serves to protect corneocytes from surfactant damage due to degradation. For this reason, Betaine and other Organic Osmolytes are termed Chemical Chaperones as they cozy up to proteins and prevent their damage. In contrast to other osmolytes, B reduces water’s ability to solvate proteins, thus stabilizing their native protein structure. Betaine is also one of the important methyl donors in the body, which protects cells from detergents’ attacks. This methyl donation mechanism will be discussed in detail below.

How does it fight inflammation?

When our cells encounter damage, some of the vital processes are affected. One of these processes is protein folding in the Endoplasmic Reticulum (ER). Accumulation of misfolded or unfolded proteins in the ER leads to ER stress, which is undesirable because it leads to apoptosis (programmed cell death. Your cell basically commits suicide because of stress. Betaine was shown to inhibit ER stress in cells indirectly. It does this by inhibiting several key molecules in the apoptosis pathway, including Homocysteine, GRP78, CHOP, ATF-3 and Caspase-3. Aside from the anti-apoptotic effect, B inhibits inflammation by inhibiting the NF-kB signaling pathway, one of the major controls of inflammatory response. It does this by inhibiting IKK, MAPK and HDAC3, which initiate activation of NF-kB. B can also reduce the mRNA and protein expressions of high-mobility group box 1, which is a positive regulator of TLR-4 activation. It is also able to inhibit the NLRP3 inflammasome activation. All of these factors lead to the attenuation of inflammatory response.^[11]

How does it work as an antioxidant?

One of the results of UV radiation is cell shrinkage due to the opening of K+ channels due to the generation of hydroperoxides and hydrogen peroxide. It was shown that NHK cells uptake more osmolytes like Betaine upon exposure to UVR. In addition, there was a 3-fold upregulation of BGT-1 mRNA expression at six and 24-hour post-exposure. BGT-1 is responsible for the uptake of Betaine inside the cell. Ultimately, B was able to resist cell shrinkage after UVR exposure.^[12] The same scenario happens in hyperosmotic conditions where B increases cytoplasmic volume and free water content of cells to prevent shrinkage. It was also able to inhibit various hyperosmotic-induced apoptosis-related proteins.^[11:1]

Betaine’s ability to inhibit oxidative stress is through an indirect method. It can’t decrease ROS production, but it is able to decrease the damage resulting from it. Together with Methionine and choline, Betaine are the most crucial methyl group donors present in the diet. The enzyme Betaine-homocysteine methyltransferase (BHMT) catalyzes the addition of a methyl group from Betaine to Homocysteine to form Methionine. Betaine now becomes Dimethylglycine, which is possibly degraded into sarcosine and ultimately Glycine. As mentioned above, Homocysteine is one of the key molecules in the apoptotic pathway. As Betaine detoxifies Homocysteine to Methionine, Methionine levels are correlated with the increase in B. Methionine plays an important role in inhibiting oxidative stress via chelation as well as GSH synthesis. Although Homocysteine also plays a role in GSH synthesis, too much of it can lead to oxidative stress and apoptosis. In addition to its indirect effect, B can inhibit Nitric Oxide Synthase 2 expression. However, the primary antioxidant mechanism of Betaine is through amelioration of Sulfur Amino Acid Metabolism.^[11:2]

How does it improve pigmentation?

Korean Rice Bran is currently one of the popular Asian ingredients for hyperpigmentation. Fourteen compounds were isolated from Korean Rice Bran extract, which were then investigated for their hypopigmentary activity. Among the 14, Betaine was surprisingly the most active ingredient in Korean Rice Bran. It inhibited mushroom tyrosinase activity by 34% together with cellular Tyrosinase by 22% compared to arbutin at only 10%. B also reduced melanin content by 22%.

Its main anti-melanogenic activity roots from its inhibitory action on Microphthalmia-Associated Transcription Factor (MITF), which is the gene responsible for the expression of Tyrosinase mRNA and other melanogenesis enzymes. B reduced the concentration of cAMP, leading to the inhibition of PKA. Reduced PKA means that CREB would not stimulate MITF promoter activity. In addition, B activates AKT-GSK3B and ERK, which have inhibitory activity on MITF. These three events work together to prevent the activation of MITF, leading to less Tyrosinase formed.^[11:3]

A clinical study done on 22 subjects showed a significant increase in luminance after 56 days.^[13] This was the only clinical study done on the brightening activity of Betaine. Because of its charge, it doesn’t reach sufficient concentration in the epidermis’ deeper parts. Even if it has excellent MITF inhibitory ability, it would not be useful if we can’t deliver it properly to the deeper parts. However, there might be a potential for Betaine with the help of penetration enhancers. Various intrusive methods can potentially deliver it since it has low irritation potential and inherent anti-irritation and anti-inflammatory properties.

How does it help in anti-aging?

Betaine’s potential effect in anti-aging is not yet convincing, although it has potential. In-vitro results show that oral supplementation of mice reduces UVB-induced wrinkle formation. B inhibited the UVB-induced expression of mitogen-activated protein kinase (MAPK), ERK, and MMP-9. MMP-9 is a 92-kDa gelatinase that degrades collagen IV. Expression of MMP-9 in the epidermis leads to apoptosis, photoaging, and inflammation by stimulating the expression of inflammatory cytokines, including TNF-a and IL-1B. B’s inhibition of the MAPK/ERK pathway led to the inhibition of MMP-9, which accounts for the inhibition of epidermal thickening in mice and protection of collagen. It was shown to reduce wrinkle formation and collagen fiber damage.^[14]

How well this translates to topical products is still a debate. Like its anti-melanogenic property, its low penetration limits B’s anti-aging property. More studies need to be performed in order to say that it actually has anti-aging effects.

Does it penetrate?

Betaine has low penetration in Franz chamber with freshly isolated human epidermis. ^[1] Because of its charge, it readily associates with proteins in the epidermis, and this prevents it from penetrating further. However, for its primary function on hydration, anti-irritancy and barrier repair, it doesn’t need to reach the dermo-epidermal junction as it just needs to reach the stratum granulosum to have effects.

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