Effects of Minocycline on Urine Albumin, Interleukin-6, and Osteoprotegerin in Patients with Diabetic Nephropathy: A Randomized Controlled Pilot Trial

Abstract

Background: We tested minocycline as an anti-proteinuric adjunct to renin-angiotensin-aldosterone system inhibitors (RAASi) in diabetic nephropathy (DN) and measured urinary biomarkers to evaluate minocycline's biological effects.

Design: Prospective, single center, randomized, placebo-controlled, intention-to-treat pilot trial. Inclusion. Type 2 diabetes/DN; Baseline creatinine clearance >30 mL/min; proteinuria ≥1.0 g/day; Age ≥30 years; BP <150/95 mm Hg; intolerant of/at maximum RAASi dose. Protocol. 3-wk screening; Baseline randomization; Urine and blood measures at months 1, 2, 4, and Month 6 study completion. Urine interleukin-6 (IL-6) and osteoprotegerin were measured in a subset. Primary outcome. Natural log of urine protein/creatinine (ln U P:Cr) ratio at Month 6 vs Baseline.

Results: 30 patients completed the study. The 15% decline in U P: Cr in minocycline patients (6 month P:Cr ÷ Baseline P:Cr, 0.85 vs. 0.92) was not significant (p = 0.27). Creatinine clearance did not differ in the 2 groups. Urine IL-6:Cr (p = 0.03) and osteoprotegerin/Cr (p = 0.046) decrements were significant. Minocycline modified the relationship between urine IL-6 and proteinuria, suggesting a protective biological effect.

Conclusions: Although the decline in U P:Cr in minocycline patients was not statistically significant, the significant differences in urine IL-6 and osteoprotegerin suggest that minocycline may confer cytoprotection in patients with DN, providing a rationale for further study.

Trial registration: Clinicaltrials.gov NCT01779089.

Conflict of interest statement

Competing Interests: DaVita Clinical Research provided funding. Meso Scale Discovery performed the urine IL-6 and osteoprotegerin measurements at no cost. This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.

Figures

Fig 1. Enrollment of subjects.

Fig 2. Spaghetti plots of the urine protein: creatinine measurements of each patient in the study over the course of the trial.

Fig 3. Percent change in 24-hour urine protein/creatinine measurements from baseline to 6 months in placebo and minocycline groups.

The edges of the boxes represent the 25% and 75% percentiles, the middle lines represents the median, and the whiskers extend to the minimum and maximum values. The primary outcome, ln (6Month P:Cr/baseline P:Cr), was not significantly different between the groups (p = 0.27).

Fig 4. Spaghetti plots of the urine IL6: creatinine measurements of each patient in the study from baseline to 6 months (end of trial).

Baseline urine values were not available for 3 subjects.

Fig 5. % change in 24-hour urine Il-6: creatinine measurements from baseline to 6 months in placebo and minocycline groups.

The edges of the boxes represent the 25% and 75% percentiles, the middle lines represents the median, and the whiskers extend to the minimum and maximum values. The %change in urine IL-6: creatinine was significantly lower in the minocycline group vs. the placebo group (mean % change -0.13 vs. 0.60, P = 0.03).

Fig 6. Spaghetti plots of the urine osteoprotegerin: Creatinine measurements of each patient in the study from baseline to 6 months (end of trial).

Baseline urine values were not available for 3 subjects.

Fig 7. % change in 24-hour urine osteoprotegerin: creatinine measurements from baseline to 6 months in placebo and minocycline groups.

The edges of the boxes represent the 25% and 75% percentiles, the middle lines represents the median, and the whiskers extend to the minimum and maximum values. The %change in urine osteoprotegerin: creatinine was significantly lower in the minocycline group vs. the placebo group (mean % change -0.09 vs. 0.25, P = 0.046).

Fig 8. Relationship between changes in urine IL-6 and proteinuria in minocycline and placebo patients.

The slope of the regression curve for placebo-treated patients is not different from zero (p> 0.05). The slope of the regression curve for minocycline-treated patients is different from zero (p

Fig 9. Spaghetti plots of the creatinine clearance measurements of each patient in the study over the course of the trial.