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Acute stimulation of creatine kinase activity by vitamin D metabolites in the developing cerebellum
I Binderman1, S Harel, Y Earon
1Hard Tissues Laboratory, Ichilov Hospital, Tel Aviv, Israel.
Insights
Vitamin D metabolites are crucial for brain development, influencing creatine kinase activity in rat and rabbit cerebellums. Vitamin D deficiency impairs this activity, highlighting its role in optimal cerebellar growth.
Area of Science:
- Neuroscience
- Developmental Biology
- Endocrinology
Background:
- Vitamin D metabolites are increasingly recognized for their developmental roles.
- The specific activity of creatine kinase (CK) in the brain is a marker of cellular energy metabolism and development.
- Vitamin D's influence on brain CK activity during development is not fully understood.
Purpose of the Study:
- To investigate the impact of vitamin D status on brain creatine kinase activity during postnatal development in rats.
- To determine the differential effects of specific vitamin D metabolites on cerebellar and cerebral CK activity.
- To compare the developmental timing of vitamin D metabolite responsiveness in rat and rabbit cerebellums.
Main Methods:
- Comparison of CK activity in normally fed versus vitamin D-depleted rats.
- Administration of vitamin D metabolites (24R,25-dihydroxyvitamin D3 and 1,25-dihydroxyvitamin D3) to rats and rabbits at different developmental stages.
- Measurement of specific creatine kinase activity in cerebral and cerebellar tissues.
Main Results:
- Vitamin D-depleted rats exhibited reduced postnatal increases in cerebral and cerebellar CK activity compared to normally fed rats.
- The developing cerebellum, but not cerebrum, showed sequential increases in CK activity following vitamin D metabolite injections.
- 24R,25-dihydroxyvitamin D3 stimulated cerebellar CK activity earlier than 1,25-dihydroxyvitamin D3 in both species, with earlier responsiveness observed in rabbits (perinatal developers) compared to rats (postnatal developers).
Conclusions:
- Vitamin D metabolites are essential for normal postnatal development of cerebellar creatine kinase activity.
- The differential timing of responsiveness to vitamin D metabolites in rats and rabbits correlates with their respective brain development patterns.
- These findings suggest that vitamin D metabolites play a critical role in optimizing cerebellar development, potentially by influencing cellular growth rates.
Abstract:
There is increasing evidence that vitamin D metabolites have a developmental function. We have investigated the influence of the vitamin D status on the activity of creatine kinase in the brain. Normally fed rats show an increase in the specific activity of cerebral and cerebellar creatine kinase during postnatal development. Vitamin-D-depleted rats failed to show this normal increase. Developing cerebellum, but not cerebrum, in both vitamin D-depleted rats and in normally fed animals, responded sequentially to a single injection of a vitamin D metabolite by displaying increased creatine kinase specific activity. In 5-25-day-old rats, 24R,25-dihydroxyvitamin D-3 significantly increased creatine kinase specific activity 24 h after injection. In contrast, 1,25-dihydroxyvitamin D-3 stimulated cerebellar creatine kinase activity from 20 days after birth. A similar pattern of sequential responsiveness to vitamin D metabolites, but at an earlier age, was shown in the cerebellum of the rabbit, which is a 'perinatal brain developer' compared to the rat, a 'postnatal brain developer'. Because of the difficulty in obtaining vitamin D-depleted rabbits, studies were carried out in normally fed animals. In these rabbits, 24R,25-dihydroxyvitamin D-3 stimulated cerebellar creatine kinase activity between 6 days before birth and 9 days after birth, while 1,25-dihydroxyvitamin D-3 caused an increase in cerebellar creatine kinase specific activity from 8 days after birth. These developmental differences found in creatine kinase basal activity and responsiveness are correlated with differences in cellular growth rates, both in the rabbit and in the rat, suggesting that vitamin D metabolites may be required for optimal cerebellar development.