Scientists from North Carolina State University found that zebrafish deprived of vitamin D during a critical growth phase were half the size of the others studied and also had significantly more fat reserves. Researchers believe this confirms the need for vitamin D when it comes to development and biological balance.
Researchers divided post-juvenile zebrafish into three groups based on diet. One group was given a diet devoid of vitamin D while the second was given a diet enriched with vitamin D. The control group had a normal diet containing vitamin D.
After four months the fish were measured for growth, bone density, triglyceride, lipid, cholesterol and vitamin D levels. Researchers also looked at metabolic pathways associated with fat production and storage and found the fish deprived of vitamin D were 50 percent smaller and had much greater fat reserves.
"The vitamin D deficient zebrafish exhibited both hypertrophy and hyperplasia—an increase in both the size and number of fat cells," biological sciences professor Seth Kullman said. "They also had higher triglycerides and cholesterol, which are hallmarks of metabolic imbalance that can lead to cardio-metabolic disease. This, combined with the stunted growth, indicates that vitamin D plays an important role in the ability to channel energy into growth versus into fat storage."
The vitamin D-deficient zebrafish were given a diet enriched with vitamin D for six months after the initial testing period to see if the results could be reversed. While the fish did show gains in size and the utilization of fat reserves, they never caught up in size with the other cohorts and also retained residual fat deposits.
"This work shows that vitamin D deficiency can influence metabolic health by disrupting the normal balance between growth and fat accumulation," Kullman says. "Somehow the energy that should be going toward growth is getting shunted into creating fat and lipids, and this occurrence cannot be easily reversed. While we don't yet understand the mechanism, we are beginning to tease that out."
Researchers now plan to explore what impact there might be on the offspring of female zebrafish that are deficient in vitamin D. The goal will be to see if the epigenetic effects are passed to future generations.