In people with type 2 diabetes supplements with vitamin D3, or omega-3 fatty acids, has no protective effect on kidney function. These result from of a study, recently published online on JAMA, which excluded any illusions about the clinical effects of these substances, based on their mechanisms of action, which among others potentially involve the renin-angiotensin system, inflammatory processes and the development of renal fibrosis.
Chronic kidney disease in dibetes
Chronic kidney disease is one of the main microvascular complications of diabetes. It is also a condition that sometimes precedes the development of end-stage renal disease. The progression towards this more serious form of nephropathy is characterized by the appearance of micro and macroalbuminuria and is substantially influenced by concomitant conditions, such as hypertension and hyperglycemia.
With the progress achieved in understanding the pathophysiological mechanisms involved in the development of chronic nephropathy, different treatments have been proposed for its prevention and treatment, but sometimes with controversial results.
Animal studies have shown that calcitriol can reduce the activity of the renin-angiotensin system, as well as inflammation in the kidneys and the consequent development of fibrosis. For their part, omega-3 fatty acids showed anti-inflammatory and antithrombotic properties, potentially able to prevent chronic kidney disease.
Vitamin D3 or omega-3 fatty acids to prevent chronic kidney disease
This new study tested whether the intake of vitamin D3 supplements, or omega-3 fatty acids, could prevent the development or progression of chronic kidney disease in patients with type 2 diabetes.
With a randomized, factorial design, the research included over 1,300 subjects, with a mean age of 67.6 years and with a mean baseline eGFR of 85.8 mL/min/1.73 m2. The diagnosis of diabetes was done between 6 and 10 years earlier.
The participants were divided in four treatment groups: vitamin D3 (2000 IU/day) and omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid; 1 g/day), vitamin D3 and placebo, placebo and omega-3 fatty acids or double placebo. The follow-up lasted 5 years.
The main outcome of the study was the change in estimated glomerular filtration rate from baseline visit to follow-up ending.
The results showed similar variations in estimated glomerular filtration rate in the groups treated with the supplements and in those who took placebo. The mean change in estimated glomerular filtration from baseline to year 5 was -12.3 mL / min / 1.73 m2 in patients treated with vitamin D3, -12.2 mL / min / 1.73 m2 in those treated with fatty acids omega-3 and -13.1 mL / min / 1.73 m2 in those who took the placebo.
Of the three secondary endpoints evaluated (time to composite outcome of a reduction of at least 40% eGFR from baseline, renal failure or death; time to a reduction of at least 40% of eGFR from baseline; change in the albumin-creatinine ratio in the urine from baseline to year 5) none showed significant differences related to the treatment.
How to preserve kidney function
Preserving renal function in patients with type 2 diabetes is an important goal. Unfortunately, based on the results of this study, vitamin D3 and omega-3 fatty acids cannot be helpful.
The use of supplements containing these molecules were not able to induce positive changes on the estimated glomerular filtration index, despite a prolonged treatment up to 5 years.
There are many treatments for chronic kidney disease still under evaluation, including the renin-angiotensin blockers, aldosterone antagonists, transforming growth factor beta (TGF-β) inhibitors, analogues of the glucagon-like peptide 1 (GLP-1) and the inhibitors of the sodium-glucose transporter SGLT2. The weapons to fight kidney disease in diabetic patients will not be lacking.
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