Trehalose is a sugar consisting of two molecules of glucose. It is also known as mycose or tremalose. Some bacteria, fungi, plants and invertebrate animals synthesize it as a source of energy, and to survive freezing and lack of water.
Extracting trehalose was once a difficult and costly process, but around 2000, the Hayashibara company (Okayama, Japan) discovered an inexpensive extraction technology from starch. Trehalose has high water retention capabilities, and is used in food, cosmetics and as a drug.
Trehalose is a disaccharide formed by a 1,1-glycosidic bond between two α-glucose units. Two other isomers are not found in nature. It is found in nature as a disaccharide and also as a monomer in some polymers.
Trehalose is a nonreducing sugar formed from two glucose units joined by a 1–1 alpha bond, giving it the name α-D-glucopyranosyl-(1→1)-α-D-glucopyranoside. The bonding makes trehalose very resistant to acid hydrolysis, and therefore is stable in solution at high temperatures, even under acidic conditions. The bonding keeps nonreducing sugars in closed-ring form, such that the aldehyde or ketone end groups do not bind to the lysine or arginine residues of proteins (a process called glycation). Trehalose is less soluble than sucrose, except at high temperatures (>80 °C). Trehalose forms a rhomboid crystal as the dihydrate, and has 90% of the calorific content of sucrose in that form. Anhydrous forms of trehalose readily regain moisture to form the dihydrate. Anhydrous forms of trehalose can show interesting physical properties when heat-treated.
Trehalose aqueous solutions show a concentration-dependent clustering tendency. Owing to their ability to form hydrogen bonds, they self-associate in water to form clusters of various sizes. All-atom molecular dynamics simulations showed that concentration of 1.5–2.2 molar, allow trehalose molecular clusters to percolate and form large, continuous aggregates.
Trehalose directly interacts with nucleic acids, facilitates melting of double stranded DNA and stabilizes single-stranded nucleic acids.
Organisms ranging from bacteria, yeast, fungi, insects, invertebrates, and lower and higher plants have enzymes that can make trehalose.
In nature, trehalose can be found in plants, and microorganisms. In animals, trehalose is prevalent in shrimp, and also in insects, including grasshoppers, locusts, butterflies, and bees, in which trehalose serves as blood-sugar. Trehalose is then broken down into glucose by the catabolic enzyme trehalase for use. Trehalose is also present in the nutrition exchange liquid of hornets and their larvae.
Trehalose is the major carbohydrate energy storage molecule used by insects for flight. One possible reason for this is that the glycosidic linkage of trehalose, when acted upon by an insect trehalase, releases two molecules of glucose, which is required for the rapid energy requirements of flight. This is double the efficiency of glucose release from the storage polymer starch, for which cleavage of one glycosidic linkage releases only one glucose molecule.
In plants, trehalose is seen in sunflower seeds, moonwort, Selaginella plants, and sea algae. Within the fungi, it is prevalent in some mushrooms, such as shiitake (Lentinula edodes), oyster, king oyster, and golden needle.
Even within the plant kingdom, Selaginella (sometimes called the resurrection plant), which grows in desert and mountainous areas, may be cracked and dried out, but will turn green again and revive after rain because of the function of trehalose.
The two prevalent theories as to how trehalose works within the organism in the state of cryptobiosis are the vitrification theory, a state that prevents ice formation, or the water displacement theory, whereby water is replaced by trehalose.
Nutritional and dietary properties
Trehalose is rapidly broken down into glucose by the enzymetrehalase, which is present in the brush border of the intestinal mucosa of omnivores (including humans) and herbivores.:135 It causes less of a spike in blood sugar than glucose. Trehalose has about 45% the sweetness of sucrose at concentrations above 22%, but when the concentration is reduced, its sweetness decreases more quickly than that of sucrose, so that a 2.3% solution tastes 6.5 times less sweet as the equivalent sugar solution.:444
Trehalose has long been known as an autophagy inducer that acts independently of mTOR. In 2017 research was published showing that trehalose induces autophagy by activating TFEB, a protein that acts as a master regulator of the autophagy-lysosome pathway.
In January 2018 research was published showing that some strains of Clostridium difficile found in the human gut microbiome are especially responsive to trehalose; the study found that in the lab and in mice, these strains grew better and produced more toxins when fed trehalose. The authors pointed out a correlation between the timing of the introduction of trehalose into the food supply, and a rise in cases of hospital-acquired C. difficile infections. Suggested that trehalose might be causing the rise in infections. It was not known at that time whether trehalose actually caused the rise in C. difficile infections or affects C. difficile in the human gut.
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