Published Oct 03, 2026 | 7:00 AM ⚊ Updated Oct 03, 2026 | 7:00 AM
Heart tissue from vitamin-D-deficient rats showed more damage to fats and DNA.
Synopsis: Researchers at ICMR-NIN Hyderabad found that prolonged vitamin D deficiency triggered oxidative stress, disrupted antioxidant defences and increased markers of programmed cell death in rat heart tissue. Experiments in cultured rat heart cells also showed vitamin D reduced stress-related damage, highlighting a possible link between vitamin D status and cardiac cellular health.
Thirty rats, weaned at 21 days of age, entered a laboratory at the ICMR-National Institute of Nutrition (NIN) in Hyderabad and were fed one of three diets for the next 20 weeks. One diet contained 2,000 IU of vitamin D per kilogram of food, another contained 200 IU, and the third contained none.
By the end, the rats that received no vitamin D had hearts showing a cascade of cellular stress. Defences that help clear harmful molecules had weakened. Oxidative damage had increased. Stress had built inside heart cells, and signals associated with programmed cell death had switched on.
The institute’s researchers say the findings map, step by step, how vitamin D deficiency may affect the heart at the level of individual cells.
The study, conducted by Athira Anilkumar Sudharma, Shabna Aboo and Ayesha Ismail of the Department of Endocrinology at ICMR-NIN, appeared in the journal Steroids.
The work does not indicate that vitamin D pills would protect human hearts. It shows what prolonged vitamin D deficiency was associated with in rat heart tissue and what happened when the researchers tested it on cultured rat heart cells.
Most people link vitamin D with bones as the body uses it in calcium and bone metabolism.
The authors argue its reach extends further. “Vitamin D is widely recognised for its classical role in calcium homeostasis and bone metabolism. However, emerging research has revealed its broader significance in various non-calcemic tissues, including the cardiovascular system,” they wrote.
Heart cells carry receptors that respond to vitamin D. Earlier research has linked low vitamin D status with cardiovascular problems. The Hyderabad team wanted to understand what might be happening inside heart cells.
The team split the rats into three groups of 10. The diets were designed to produce sufficient, insufficient and deficient vitamin D status.
Blood tests confirmed that the diets produced a clear difference. The rats developed very different vitamin D levels. The average blood level of 25-hydroxyvitamin D, the main marker used to assess vitamin D status, was 58.23 ng/ml in the normal-vitamin-D group. It fell to 21.87 ng/ml in the low-vitamin-D group and 5.81 ng/ml in the vitamin-D-deficient group.
The researchers then studied tissue from the left ventricle, the chamber that pumps blood around the body.
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A protein called Nrf2 helps cells respond to oxidative stress. It switches on genes involved in producing antioxidant defences, which help the cell deal with damaging reactive molecules.
In Vitamin D-deficient rats, the amount of Nrf2 reaching the cell nucleus, where it helps activate protective genes, fell significantly. Researchers also found that MafF and MafK, proteins that work with Nrf2, were reduced. At the same time, Keap1 and Cul3, components of a system involved in Nrf2 breakdown, increased.
The researchers identified this disruption as one of the study’s major findings.
“A major novel finding of this work is the characterisation of the Nrf2 pathway disruption in the VDD heart,” they wrote.
The researchers also found lower levels of several antioxidant genes and proteins controlled by this pathway. Taken together, the findings suggest that vitamin D deficiency disrupted several parts of the heart’s antioxidant defence system.
As antioxidant defences weakened, markers of oxidative damage increased.
Heart tissue from vitamin-D-deficient rats showed more damage to fats and DNA. Glutathione, an antioxidant made by the body, fell, while its oxidised form increased.
Two antioxidant enzymes, glutathione peroxidase and superoxide dismutase, also showed reduced activity in both the low-vitamin-D and deficient groups. Some other changes were not statistically significant.
The researchers also found higher levels of Nox2, an enzyme complex involved in producing reactive oxygen species, in vitamin-D-deficient hearts.
Next, the team studied the endoplasmic reticulum, or ER, a structure inside cells that helps make and process proteins. When proteins become damaged or misfolded and accumulate, the ER can enter a state known as ER stress.
Cells initially respond to ER stress by trying to restore normal function. But prolonged stress can activate pathways associated with programmed cell death.
In vitamin-D-deficient hearts, several ER-stress markers increased. BIP, CHOP and ATF6 proteins were significantly higher than in the normal-vitamin-D group. Markers of autophagy, the cell’s recycling system, also increased.
Dr Ayesha Ismail, the scientist who led the research group, said the findings point to a sequence rather than an isolated cellular change.
“These findings suggest that prolonged oxidative stress associated with inadequate vitamin D may trigger a cascade of cellular responses that can contribute to cardiac cell injury,” Ismail said.
The researchers also reported that vitamin-D-deficient hearts showed increased markers of ER stress, autophagy and apoptosis.
“We further observed increased markers of endoplasmic reticulum (ER) stress, autophagy and apoptosis in vitamin D-deficient hearts,” Ismail said.
“Collectively, the findings establish that vitamin D deficiency creates a cascade of cellular stress responses, beginning with oxidative stress, progressing to ER stress, and autophagy, ultimately leading to enhanced programmed cell death in the cardiac tissue,” the research noted.
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The researchers found higher levels of BAX and BIM, proteins that promote apoptosis, or programmed cell death, in vitamin-D-deficient hearts, as the deficiency caused levels of BCL2, a protein that helps protect cells from apoptosis, to fall.
Caspases, enzymes involved in carrying out programmed cell death, were also more active. These findings provided additional evidence that the cellular stress was accompanied by activation of apoptosis.
The low-vitamin-D group showed some of the same changes, but several findings were weaker and did not reach statistical significance.
The team then moved to cultured rat heart cells. They used H9C2 cardiomyoblasts and exposed them to hydrogen peroxide for four hours to create oxidative stress.
The treatment reduced cell viability, increased caspase-3 activity and raised markers of damage to fats and proteins. It also activated ER stress and autophagy pathways.
The researchers then treated the cells with 1,25-dihydroxyvitamin D3, the active form of vitamin D, before exposing them to hydrogen peroxide.
More cells survived after the vitamin D pretreatment. Markers of oxidative damage fell, antioxidant enzyme activity increased, and markers associated with ER stress, autophagy and apoptosis were reduced.
The authors wrote: “The findings suggest that vitamin D protects the heart from oxidative injury and cell death by antioxidant defence mechanism, upregulating Nrf2/HO-1 signalling while alleviating ER stress.”
This part of the experiment strengthens the proposed mechanism, but it remains a laboratory experiment in rat cells. It does not establish that vitamin D treatment would have the same effect in human heart cells.
Ismail said the study should be understood as an attempt to explain the cellular mechanisms involved rather than as evidence for a vitamin D treatment for cardiovascular disease.
“We are also conducting clinical studies. Our paper is at the mechanistic stage. Individuals should keep a check on their vitamin D levels,” she said.
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The researchers also tested 4-phenylbutyric acid, or 4PBA, a compound that inhibits ER stress. In the oxidative-stress model, 4PBA improved cell viability and reduced markers associated with ER stress and apoptosis.
The researchers found no additional cumulative or synergistic effect when 4PBA and active vitamin D were used together.
They suggested a possible therapeutic role for 4PBA, stating that it “may serve as an adjuvant therapeutic compound along with VD for repression of ERS-associated autophagy and attenuation of adverse cardiovascular outcomes in VDD.”
But that remains a hypothesis from laboratory research. This study did not test 4PBA in vitamin-D-deficient animals or people.
The researchers did not give vitamin D back to deficient rats to determine whether the changes in the heart could be reversed. The experiments were also conducted only in male rats.
“The limitations of this study are not having a VD-deficient group rehabilitated with vitamin D to assess for reversal of the effects in vivo, and experiments were done in male rats only,” they wrote.
That means the study cannot establish whether correcting vitamin D deficiency reverses the cellular changes. It also cannot tell us whether the same process occurs in females or in humans.
The study measured molecular and cellular markers. It did not follow the rats to determine whether these changes eventually produced heart attacks, heart failure or other cardiovascular disease.
Dr Bharati Kulkarni, director, ICMR-NIN, said the findings indicate that adequate vitamin D may help cardiac cells respond to oxidative stress and limit cellular damage.
However, she cautioned against directly extending the findings from the laboratory models to people.
“This study indicates that adequate vitamin D may help cardiac cells cope with oxidative stress and limit stress-related cellular damage. However, since the findings are based on animal and cell models, further investigations in humans are needed,” Kulkarni said.
Her caution mirrors the study’s own limitations. The researchers conclude that their findings highlight the importance of adequate circulating vitamin D for cardiac health, but the evidence comes from preclinical experiments, not a clinical trial showing that vitamin D supplementation prevents cardiovascular disease.
The question matters in India, where a separate report by the Indian Council for Research on International Economic Relations (ICRIER) and the ANVKA Foundation estimates that about one in five Indians may have vitamin D deficiency.
The estimate is based on a review of available evidence rather than a new nationwide blood survey. The report estimates substantial regional variation, ranging from 9.4 per cent in North India to 38.81 per cent in East India. It identifies children, adolescents, pregnant women and older people among groups that may be particularly vulnerable.
The report points to limited sunlight exposure, indoor lifestyles, pollution and dietary factors as contributors. It also highlights the cost of testing and supplementation, while warning that excessive vitamin D intake can itself cause health problems.
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(Edited by Fayisa CA)
