Statins and vitamin D: a friendly association in pre-dialysis patients

Dietary modulators of statin efficacy in cardiovascular disease and cognition

Cardiovascular disease remains the leading cause of morbidity and mortality in the United States and other developed countries, and is fast growing in developing countries, particularly as life expectancy in all parts of the world increases. Current recommendations for the prevention of cardiovascular disease issued jointly from the American Academy of Cardiology and American Heart Association emphasize that lifestyle modification should be incorporated into any treatment plan, including those on statin drugs. However, there is a dearth of data on the interaction between diet and statins with respect to additive, complementary or antagonistic effects. This review collates the available data on the interaction of statins and dietary patterns, cognition, genetics and individual nutrients, including vitamin D, niacin, omega-3 fatty acids, fiber, phytochemicals (polyphenols and stanols) and alcohol. Of note, although the available data is summarized, the scope is limited, conflicting and disparate. In some cases it is likely there is unrecognized synergism. Virtually no data are available describing the interactions of statins with dietary components or dietary pattern in subgroups of the population, particularly those who may benefit most were positive effects identified. Hence, it is virtually impossible to draw any firm conclusions at this time. Nevertheless, this area is important because were the effects of statins and diet additive or synergistic harnessing the effect could potentially lead to the use of a lower intensity statin or dose.

Statins for renal patients: a fiddler on the roof?

Atherosclerotic cardiovascular disease is the main cause of morbidity and mortality in chronic kidney disease patients. There is a raft of evidence showing that in the general population dyslipidaemia is associated with an increased risk of cardiovascular events, as well as with a greater prevalence of chronic kidney disease. Consequently, the use of statins in the general population with dyslipidaemia is not controversial. Nevertheless, the benefits of statins in patients with chronic kidney disease are more elusive. The authors review the possible effects of statins on the progression of renal disease and cardiovascular events in chronic kidney disease patients.

Hypovitaminosis D and insulin resistance in peritoneal dialysis patients

AIM

An association between hypovitaminosis D and insulin resistance has been highlighted. Effects of vitamin D are not only mediated via the vitamin D receptors by active vitamin D metabolites, but 25(OH)D(3) also acts through VDR-independent pathways directly. It was reported that acute and chronic intravenous 1,25-dihydroxycholecalciferol therapy corrects insulin resistance in dialysis patients. There are no studies in patients on dialysis which evaluated relationship between 25(OH)D levels and insulin resistance. The aim of this study was to evaluate relationship between serum 25 (OH) D levels and insulin resistance in nondiabetic patients on peritoneal dialysis (PD).

MATERIAL METHODS

We studied 53 nondiabetic patients on PD and in 25 age-, gender- and body mass index-matched healthy controls. Insulin resistance was evaluated by the homeostasis model assessment method (HOMA-IR) using fasting glucose and insulin levels. Vitamin D deficiency was defined if 25(OH)D(3) levels are equal to or less to 15 ng/ml.

RESULTS

Mean HOMA-IR index in patients on PD (3.1 ± 3.3) was significantly higher than those of controls (1.7 ± 1.9) (P < 0.05). The mean 25 (OH)D level in PD patients was (21.1 ± 19.0 ng/ml) lower than those of controls (27.5 ± 9.3 ng/ml) (P < 0.05). Twenty-five (47.2%) PD patients had vitamin D deficiency [mean 25(OH)D: 7.2 ± 3.2 ng/ml], and in 28 of them (52.8%) 25 (OH)D levels were more than 15 ng/ml (mean 33.5 ± 18.7 ng/ml). In PD patients with vitamin D deficiency, mean HOMA-IR index (4.2 ± 3.8) was significantly higher than that of PD patients whose 25 (OH)D levels were more than 15 ng/ml (2.2 ± 2.4) (P < 0.05). Twenty-one (84.0%) of PD patients with vitamin D deficiency, and 22 (78.6%) PD patients whose 25 (OH)D levels were more than 15 ng/mL have been receiving active vitamin D compounds for parathyroid hormone (PTH) control (P > 0.05). There was no significant difference between two PD groups according to mean duration of PD, age, gender, PTH, serum calcium, phosphorus, percentage of fat, and body mass index. There was a negative correlation between HOMA-IR index and 25 (OH)D levels in PD patients (r: -0,368, P < 0,05). In multiple regression analyses, the independent predictors of HOMA-IR index were 25(OH)D3 levels, duration of dialysis, and percentage of fat (measured by bioelectrical impedance) in PD patients.

CONCLUSION

Our findings show a negative correlation of 25(OH)D levels with insulin resistance in PD patients. PD patients with hypovitaminosis D are at higher risk of insulin resistance even if they are on treatment with active vitamin D for PTH control. Further studies are required to explore the relation between vitamin D deficiency and insulin resistance in PD patients.