THE ADVANTAGES OF PLANT DERIVED 1, 25 (OH)2 D3 GLYCOSIDE OVER OTHER METABOLITES OF VITAMIN D

Introduction: –

Vitamin D is a fat-soluble vitamin critical for maintaining calcium and phosphorus balance, promoting proper bone development and eggshell integrity, supporting muscle function and modulating the immune system of animals and birds. Vitamin D is absorbed from the digestive tract and requires the presence of bile salts for absorption (Braun, 1986).Cholecalciferol (Vitamin D3), occurring in animals and Ergocalciferol (Vitamin D2), occurring in plants are the two main natural sources of Vitamin D.

Compared to cholecalciferol (Vitamin D₃), its metabolites 25 (OH) D3, 1- α -(OH) D3 and 1, 25 (OH)2 D3 are more effective because all the cholecalciferol entering the system is not converted into active metabolites. Active metabolites may directly reach the target tissue by bypassing hydroxylation in liver and kidney or both, hence have more efficacy than Vitamin D₃ (Goodgame et al., 2011).

Supplementing Vitamin D metabolites in addition to cholecalciferol ensures that animals receive the active or near-active forms of Vitamin D, enhancing their ability to regulate calcium and phosphorus metabolism efficiently. This is particularly important in fast-growing species like poultry and livestock, which have high nutrient demands.

1,25(OH)₂D₃ is the biologically active form of Vitamin D. It is beneficial as it bypasses the need for metabolic conversion, making it a preferred choice for supplementation. Plants in the Solanaceae family contain 1,25(OH)₂D₃ as an active compound, and in these plants, 1,25(OH)₂D₃ is found in glycosidic form.

Glycoside form of 1,25(OH)₂D₃ :-

1,25-dihydroxy Vitamin D3 Glycosides (1,25(OH)₂D₃-gly) are the active compounds in plants responsible for their Vitamin D-like activity. In addition to these 1,25(OH)₂D₃-gly, plants also contain free 1,25(OH)₂D₃, along with 25-hydroxycholecalciferol, 7-dehydrocholesterol and cholecalciferol (EFSA, 2015, Jäpelt, & Jakobsen 2013). The glycosylation pattern of 1,25(OH)₂D₃ includes a distribution of 1 to 12 hexose units per aglycone, with mono-, di-, and tri-glycosides being identified (Bachmann et al., 2013). This glycosylation forms a protective structure that serves as a natural slow-release source of 1,25(OH)₂D₃ and creates the high storage and processing stability of the active molecule (Klis, 2024).

Benefits of 1,25(OH)₂D₃-gly over other metabolites of Vitamin D

1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃-gly) is the biologically active form of Vitamin D, and it offers several advantages over other Vitamin D metabolites like 25-hydroxyvitamin D₃ (25(OH)D₃) and 1-alpha-hydroxyvitamin D₃ (1α(OH)D₃) due to its direct physiological roles and bypass of metabolic conversion. Here is a detailed comparison:

1. Bypasses Metabolic Activation in Liver and Kidneys

• Studies (Christakos et al., 2016; Soares et al., 1976; Stevens & Blair, 1987) have shown that animals or birds with chronic kidney disease, liver dysfunction, or advanced age, the hydroxylation of 25(OH)D₃ into 1,25(OH)₂D₃ is impaired. This hydroxylation is crucial for intestinal calcium absorption, and its disruption negatively affects calcium and phosphorus homeostasis, bone quality, eggshell formation and immunity against infection.
• The ability of glycosidic 1,25(OH)₂D₃ to bypass these steps ensures sufficient active Vitamin D levels for physiological functions.

2. Metabolism:

• Gly-1,25(OH)₂D₃ exhibits delayed absorption and elimination due to the slow and sustained de-glycosylation, resulting in an extended half-life (T½) of approximately 30 hours (EFSA, 2015).
• In contrast, 1α-hydroxyvitamin D₃ (1α(OH)D₃) is metabolized in the liver to form 1,25(OH)₂D₃, which has a significantly shorter half-life, ranging from 6 to 8 hours (Garcia et al, 2013).
• Sustained activity of Gly-1,25(OH)₂D₃ enhances calcium metabolism, leading to improved calcium absorption and strengthening immune function.

3. Shelf life and stability:

• Available data show that the content of Gly-1,25(OH)₂D₃ remains stable even after extended storage periods of 12, 36, and 66 months and different conditions (4–8 °C, at 20–26 °C or at 37 °C), with no significant reduction in its potency (EFSA, 2015).
• This long-term stability offers a major commercial advantage compared to other synthetic forms such as 25(OH)D₃ and 1α(OH)D₃.

Particulars	Metabolites of Vitamin D
	Plant origin 1,25(OH)₂D₃	25(OH) D3	1α(OH)D₃
Principal molecule	Gly- 1,25(OH)₂D₃	25(OH) D3	1α(OH)D₃
Origin	Natural	Synthetic/Fermented	Synthetic
Shelf life	24 Month	06-24 Month	18 Month

4. Safety profile and reduced risk of toxicity

• 1,25(OH)₂D₃-gly exhibit water solubility, which influences their absorption and metabolism in the body. Unlike fat-soluble vitamins, which can be stored in fatty tissues. This mechanism helps to prevent the accumulation of potentially toxic levels of Vitamin D in the body, thereby reducing the risk of hypervitaminosis D and associated complications such as hypercalcemia.
• Thus, 1,25(OH)₂D₃-gly offers a safer profile compared to its fat-soluble counterparts, ensuring that adequate levels can be maintained without the risk of overaccumulation.
• Free 1,25(OH)₂D₃ is rapidly degraded once its physiological role is fulfilled, ensuring tight regulation and minimizing the risk of prolonged activity, which might otherwise result in adverse effects such as calcium dysregulation.

5. Improved Immune Function

• Gly-1,25(OH)₂D₃ has a direct immunomodulatory role as it enhances the innate immune responses by inducing antimicrobial peptides, such as cathelicidins and defensins, which are critical for fighting infections.
• 1,25(OH)₂D₃ modulates the activity of T cells and dendritic cells, promoting a balanced immune response and preventing excessive inflammation (Nunes et al., 2020).
• Carlberg and Haq (2020) reviewed the effects of 1,25(OH)₂D₃ on immune system modulation, highlighting its role in reducing the risk of autoimmune disorders and enhancing pathogen defense.

6. Effect on Calcium and Phosphorus Homeostasis

• 1,25(OH)2D3 is the dominant hormonal player in regulating calcium metabolism. In conjunction with parathyroid hormone, and calcitonin it enhances the absorption of calcium and phosphorus in the intestines, which is essential for maintaining proper bone density and mineralization, eggshell formation, regulating muscle contraction, and nerve transmission.
• It directly influences calcium homeostasis by binding to the Vitamin D receptor (VDR) in intestinal epithelial cells, upregulating the expression of calcium transport proteins, such as calbindin (Lihua et al., 2022).
• Adequate levels of 1,25(OH)₂D₃ are vital for maintaining bone density and preventing fractures (Schwartz & Lizaola, 2014). Edwards and Hardy, 1989 indicated that supplementation of 1,25 (OH)₂ D₃ significant decrease in the occurrence of tibial dyschondroplasia (TD) and an increase in overall bone ash compared to 25-(OH) D₃. 1,25(OH)₂D₃ directly increases the synthesis of calcium-binding proteins in the intestines, facilitating more efficient mineral uptake to prevent such conditions (Dusso et al., 2005).
• Chennaiah et al. (2004) found that supplementation with 1,25(OH)₂D₃ resulted in significantly higher specific gravity in the eggs and improved egg production (McCoy, 2009) compared to those receiving only 25(OH)D₃ or 1α(OH)D₃.

7- Phytase and 1,25-(OH)₂D₃

• Recent studies have elucidated the synergistic relationship between phytase and 1,25-(OH)₂D₃ in enhancing phosphorus and calcium utilization in poultry.
• For instance, a study by Geng et al. (2021) found that the combination of phytase and 1,25-(OH)₂D₃ significantly improved phosphorus retention and bone mineralization in broiler chickens, reducing the need for supplemental inorganic phosphorus in diets.
• Jiang et al. (2022) demonstrated that supplementing diets with phytase and 1,25-(OH)₂D₃ led to significant improvements in growth performance, and reductions in phosphorus excretion in broilers. Their findings indicate that this synergistic approach not only enhances nutrient utilization but also supports skeletal integrity and overall health in poultry.
• The study highlighted that this combination maximizes the bioavailability of phosphorus from plant-based feed ingredients, which often contain phytate-bound phosphorus that is not readily absorbable.

Conclusion

• In conclusion, glycosylated 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃-gly) offers significant advantages over traditional Vitamin D metabolites, such as 25-hydroxyvitamin D₃ (25(OH)D₃) and 1-alpha-hydroxyvitamin D₃ (1α(OH)D₃).
• Its unique property of bypassing metabolic activation in the liver and kidneys along with slow and sustained release facilitates better bioavailability, making it beneficial for animals. This direct availability enhances intestinal calcium and phosphorus absorption, critical for maintaining bone health eggshell strength and overall mineral homeostasis.
• The extended half-life and stability of 1,25(OH)₂D₃-gly contribute to sustained physiological effects, optimizing its role in calcium metabolism and immune function while minimizing the risk of toxicity associated with excess Vitamin D.

The synergistic interaction between 1,25(OH)₂D₃-gly and phytase further improves the bioavailability of phosphorus from feed, promoting enhanced growth performance, bone mineralization, eggshell strength, and overall health in poultry.