D Deficiency Linked To Heart Failure
From ScienceDaily 9/10 Vitamin D Is a Prognostic Marker in Heart Failure, Study Finds
Survival rates in heart failure patients with reduced levels of vitamin D are
lower than in patients with normal levels. This is the finding of a major study
carried out at University Medical Center, Groningen, Netherlands, according to
a presentation at the European Society of Cardiology's Congress 2010 in
Stockholm. Results also suggest that low levels of vitamin D are associated
with activation of the Renin Angiotensin System (RAS - a pivotal regulatory
system in heart failure) and an altered cytokine profile.
Vitamin D is produced by the skin when it is exposed to the natural Ultra
Violet-B (UV-B) radiation from the sun. Low levels have long been known as the
underlying mechanism of rickets however, in recent years, new studies have
provided novel insight into the multiple vitamin's functions. It has been
proved that most tissues and cells have a vitamin D receptor, and there is
strong evidence that its presence plays a part in reducing the risk factor
profiles of several chronic illnesses, such as common cancers, autoimmune
diseases, kidney diseases, chronic infectious diseases, hypertension and
apparently also heart failure. "By showing that vitamin D is an independent
predictor, we hoped to prove that it is a contributory factor to, rather than
peripheral to, the development and prognosis of heart failure," said Ms.
Licette Liu of the University Medical Center, Groningen. "With this new
information, we then hope to provide better insight into the pathophysiology of
Experiments with mice lacking the vitamin D receptor have shown typical signs of
heart failure, while small-scale clinical studies have shown that low levels
are a consistent factor amongst human heart failure patients. "There are
several potential reasons for low vitamin D levels in heart failure patients,
including the fact that they are often bedridden or house-bound due to their
clinical symptoms" Ms. Liu explains. "This would lead to a serious deficiency,
because 80-90 percent of vitamin D is obtained by UV-B radiation. Another
factor is that the capacity of the skin to produce vitamin D declines with age,
and as heart failure has a high incidence among elderly people, it is not
entirely surprising to measure low levels. Furthermore, severe heart failure is
associated with impaired renal function due to decreased blood supply. This may
be responsible for a reduced synthesis of the active form of vitamin D, since
the final step of conversion takes place in the kidneys. All of these factors
may add to vitamin D deficiency in heart failure patients."
Observations in animal studies suggest that vitamin D is a negative regulator of
the RAS, which is responsible for volume and blood pressure homeostasis and is
a pivotal regulatory system in heart failure. Low levels may activate the RAS,
which in turn may contribute to the development and progression of heart
failure. There is also growing evidence that overproduction of several
pro-inflammatory cytokines (and underproduction of anti-inflammatory cytokines)
plays an important role in heart failure. Several studies have shown that
vitamin D alters the cytokine profile and may therefore contribute to the
inflammatory processes in heart failure.
In the current study, vitamin D concentration was assessed in plasma samples
from 548 heart failure patients, using data supplied by the Coordinating study
evaluating Outcomes of Advising and Counselling in Heart failure (COACH).
Results showed that vitamin D concentration is associated with the prognosis of
heart failure. Patients with lower concentrations had a higher risk of death or
required re-hospitalisation, whereas patients with higher concentrations had
lower survival risks for these endpoints. Further, significant correlations
between vitamin D, and Plasma Renin Activity and C-Reactive Protein were found.
These correlations suggest that the association between vitamin D and the
prognosis in heart failure may be explained by activation of the RAS and an
altered cytokine profile.
This is the first study in a large cohort of patients recruited due to
hospitalisation for heart failure, in which the role of vitamin D has been
determined, along with the roles of plasma renin activity and cytokines.
Previous reports involved smaller study cohorts, and did not determine either
plasma renin activity or cytokines, or they included patients who were referred
routinely for coronary angiography at baseline.
The major limitation of this observational study was that bystander and indirect
effects of variables could not be discounted. Therefore, a prospective
randomised intervention study is necessary to investigate the effect of vitamin
D on the RAS, cytokines profile and, finally, on the prognosis in heart failure
patients. Ms. Liu concludes, "This study provides compelling evidence that a
high vitamin D status is associated with improved survival in heart failure
patients. Until an intervention study has been designed and completed, it seems
that we should advise patients with heart failure to maintain appropriate
vitamin D levels by taking supplements, by eating oily fish or eggs, or simply
by exposure to sunlight."