The Effect of 600 mg Alpha-lipoic Acid Supplementation on Oxidative Stress, Inflammation, and RAGE in Older Adults with Type 2 Diabetes Mellitus

Abstract

Alpha-lipoic acid (ALA) has been used as a dietary supplement at different doses in patients with diabetes mellitus type 2 (T2DM) due to its antioxidant, anti-inflammatory, and hypoglycemic effects. However, the reports on the effects of ALA are controversial. For this reason, the purpose of the present study was to determine the effect of 600 mg/day of ALA on the markers of oxidative stress (OxS) and inflammation and RAGE in older adults with T2DM. A quasiexperimental study was carried out with a sample of 135 sedentary subjects (98 women and 37 men) with a mean age of 64 ± 1 years, who all had T2DM. The sample was divided into three groups: (i) experimental group (EG) with 50 subjects, (ii) placebo group (PG) with 50 subjects, and control group (CG) with 35 subjects. We obtained the following measurements in all subjects (pre- and posttreatment): glycosylated hemoglobin (HbA1c), receptor for advanced glycation end products (RAGE), 8-isoprostane, superoxide dismutase (SOD), glutathione peroxidase (GPx), total antioxidant status (TAS), and inflammatory (CRP, TNF-α, IL-6, IL-8, and IL-10) markers. Regarding the effect of ALA on HbA1c, a decrease was observed in the EG (baseline 8.9 ± 0.2 vs. posttreatment 8.6 ± 0.3) and the PG (baseline 8.8 ± 0.2 vs. posttreatment 8.4 ± 0.3) compared to the CG (baseline 8.8 ± 0.3 vs. six months 9.1 ± 0.3) although the difference was not statistically significant (p < 0.05). There was a statistically significant decrease (p < 0.05) in the blood concentration of 8-isoprostane in the EG and PG with respect to the CG (EG: baseline 100 ± 3 vs. posttreatment 57 ± 3, PG: baseline 106 ± 7 vs. posttreatment 77 ± 5, and CG: baseline 94 ± 10 vs. six months 107 ± 11 pg/mL). Likewise, a statistically significant decrease (p < 0.05) in the concentration of the RAGE was found in the EG (baseline 1636 ± 88 vs. posttreatment 1144 ± 68) and the PG (baseline 1506 ± 97 vs. posttreatment 1016 ± 82) compared to CG (baseline 1407 ± 112 vs. six months 1506 ± 128). A statistically significant decrease was also observed in all markers of inflammation and in the activity of SOD and GPx in the CG with respect to the EG and PG. Our findings suggest that the administration of ALA at a dose of 600 mg/day for six months has a similar effect to that of placebo on oxidative stress, inflammation, and RAGE in older adults with T2DM. Therefore, higher doses of ALA should be tried to have this effect. This trial is registered with trial registration number ISRCTN13159380.

Figure 1

Outline of the study.

Figure 2

Plasma concentration of alpha-lipoic acid (ALA) before and after treatment in the study groups. A significant increase in the concentration of ALA was observed in the experimental group (before 0.222 ± 0.03 vs. after 3.503 ± 0.2μg/mL) compared to the placebo (before 0.2 ± 0.02 vs. after 0.179 ± 0.03μg/mL) and control groups (before 0.202 ± 0.04 vs. after 0.197 ± 0.03μg/mL). The values represent mean + standard error. Repeated measure analysis of variance. p < 0.01.