Inflammation & Allergy-Drug Targets (Discontinued) - Volume 12, Issue 4, 2013

Vitamin D (Vit D) is well known for its traditional role in calcium and bone homeostasis. Sun exposure and diet are essential for Vit D synthesis and intake. However, the association of Vit D deficiency with various diseases has held the attention of clinicians. Of note, Vit D has pleiotropic effects that could be involved in the optimal functioning of many organ systems. Several epidemiologic studies have documented widespread Vit D deficiency worldwide. Vit D deficiency is also frequent in hospitalized patients. Recently, publications have suggested a high prevalence of Vit D deficiency in critically ill patients, which might have a clinical impact in this specific population. However, few studies have specifically investigated the prevalence and risk factors of Vit D deficiency in intensive care units. The available data indicate a Vit D deficiency prevalence of 80% to 100% in critically ill patients. The risk factors associated with Vit D deficiency include variables dependent on demographic characteristics, such as ethnicity, age and sex, lifestyle and diet, medical history and medications, and acute critical illness. Of note, the presence of a systemic inflammatory response and the severity of acute illness may affect the Vit D status. This review presents the current knowledge on the prevalence of Vit D deficiency in the critically ill and the associated risk factors.

Vitamin D deficiency, as measured by a random level of 25-hydroxyvitamin D is very prevalent in critically ill patients admitted to the ICU and is associated with adverse outcomes. Both 25(OH)vitamin D and 1α,25(OH)2D3 are difficult to analyse because of their lipophilic nature, affinity for VDBP and small concentrations. Also, the various tests used to estimate vitamin D levels show significant inter- and intra-assay variability, which significantly affect the veracity of the results obtained and confound their interpretation. The two main types of assays include those that directly estimate vitamin D levels (HPLC, LC-MS/MS) and competitive binding assays (RIA, EIA). The former methods require skilled operators, with prolonged assay times and increased cost, whereas the latter are cheaper and easy to perform, but with decreased accuracy. The direct assays are not affected by lipophilic substances in plasma and heterophile antibodies, but may overestimate vitamin D levels by measuring the 3-epimers. These problems can be eliminated by adequate standardization of the test using SRMs provided by NIST, as well as participating in proficiency schemes like DEQAS. It is therefore important to consider the test employed as well as laboratory quality control, while interpreting vitamin D results. A single random measurement may not be reflective of the vitamin D status in ICU patients because of changes with fluid administration, and intra-day variation in 25-hydroxyvitamin D levels. 1α,25(OH)2D3 may behave differently to 25-hydroxyvitamin D, both in plasma and at tissue level, in inflammatory states. Measurement of tissue 1α,25(OH)2D3 levels may provide the true estimate of vitamin D activity.

The physiological roles of vitamin D in the functioning of the immune and inflammatory systems have been the subject of intense research over the past decade and have stimulated interest in the connections between this steroid hormone and sepsis. While the science directly examining the relationship between sepsis and vitamin D is still emerging, many inferences can be made from current literature from various scientific disciplines looking at the seasonal, geographical and racial patterns of infections and vitamin D deficiency. This review will explore these associations, drawing from the fields of ecology, epidemiology and clinical research and describe the potential causal relationships implicated by the basic sciences.

Acute Lung Injury (ALI) and the more severe form Acute Respiratory Distress Syndrome (ARDS) remain a significant cause of morbidity and mortality in the critically ill patient. It is characterised by a severe inflammatory process resulting in diffuse alveolar damage, influx of neutrophils, macrophages and a protein rich exudate in the alveolar spaces caused by endothelial and epithelial injury. Improvements in outcomes are in part due to restrictive fluid management and protective lung ventilation however successful therapeutic strategies remain elusive with promising therapies failing to translate positively in human studies. The evidence for the role of vitamin D in lung disease is growing - deficiency has been associated with impaired pulmonary function, increased incidence of viral and bacterial infections and inflammatory disease including asthma and COPD. Studies have also reported a high prevalence of vitamin D deficiency in the critically ill and an association with adverse outcomes. Although exact mechanisms are yet to be discerned, vitamin D appears to impact on a variety of inflammatory and structural cells within the lung including macrophages, lymphocytes and epithelial cells. To date there are few directly supportive clinical studies in ALI; this review explores the compelling evidence suggesting arole for vitamin D in ALI and the mechanisms by which it could contribute to pathogenesis.

Vitamin D deficiency is common in critically ill patients and associated with increased mortality, as well as an increased risk of acute kidney injury. The occurrence of acute kidney injury by itself substantially increases critical care mortality. In addition to regulating calcium and phosphorus homeostasis and bone metabolism, vitamin D has pleotropic effects on the immune response. Potential mechanisms of how a deficiency in vitamin D could predispose individuals to increased risk of acute renal failure include dysregulation of the immune system, predisposing patients to sepsis, endothelial dysfunction and prevention of healing of renal ischemia-reperfusion injury. Toll-like receptors, NF-κB and the renin-angiotensin-aldosterone system are mediators of vitamin D effects.

Vitamin D deficiency and its adverse skeletal sequelae are well recognized in the general population. Recent observation of high prevalence of low vitamin D states and their associations with worse clinical outcomes in critically ill populations have sparked interest in the role of supplementation for these patients. High-dose vitamin D efficaciously increases serum levels, but its impact on clinical outcome has not been examined. This article will review results from observational studies on prevalence and outcomes of hypovitaminosis D in critically ill patients, as well as caveats of vitamin D interventional trials. Improved understanding of vitamin D metabolism in critical illness will clarify the therapeutic potential of this pleiotropic hormone and facilitate implementation of cost-effective clinical trials.

Vitamin D deficiency is common in critically ill patients and has been associated with adverse outcomes. Although many interesting observational studies have been published, only four small randomized controlled trials have been conducted in this vulnerable population. Endpoints included bone turnover, inflammatory markers and safety/efficacy issues. However, all of these trials were underpowered to detect clinically relevant endpoints due to their small sample size. Therefore, future studies focusing on morbidity and mortality endpoints are necessary in order to clarify whether vitamin D deficiency is only a surrogate marker for disease severity or whether treatment with sufficiently large doses of vitamin D may improve patient outcome in an intensive care setting.

Diacerein and its active metabolite rhein are promising disease modifying agents for osteoarthritis (OA). Boswellic acid is an active ingredient of Gugglu; a herbal medicine commonly administered in osteoarthritis. Both of them possess excellent anti-inflammatory and anti-arthritic activities. It was thought interesting to conjugate rhein and boswellic acid into a mutual prodrug (DSRB) and evaluate its efficacy on collagenase-induced osteoarthritis in rats wherein the conjugate, rhein, boswellic acid and their physical mixture, were tested based on various parameters. Oral administration of 3.85 mg of rhein, 12.36 mg of boswellic acid and 15.73 mg of DSRB which would release equimolar amounts of rhein and boswellic acid, exhibited significant restoration in rat body weight as compared to the untreated arthritic control group. Increase in knee diameter (mm), due to edema was observed in group injected with collagenase, which reduced significantly with the treatment of conjugate. The hematological parameters (Hb, RBC, WBC and ESR) and biochemical parameters (CRP, SALP, SGOT and SGPT) in the osteoarthritic rats were significantly brought back to normal values on treatment with conjugate. It also showed better anti-ulcer activity than rhein. Further the histopathological studies revealed significant anti-arthritic activity of conjugate when compared with the arthritic control group. In conclusion, the conjugate at the specified dose level of 15.73 mg/kg, p. o. (BID) showed reduction in knee diameter and it could significantly normalize the hematological and biochemical abnormalities in collagenase-induced osteoarthritis in rats. Further the histopathological studies confirmed the additive anti-arthritic effect of DSRB as compared to plain rhein.