The alpha-lipoic acid decreases urinary podocalyxin excretion in type 2 diabetics by inhibiting oxidative stress in vivo

Cardiorespiratory Fitness Decreases High-Sensitivity C-Reactive Protein and Improves Parameters of Metabolic Syndrome

AIM

To evaluate the relationship between cardiorespiratory fitness (CRF), expressed as maximal oxygen uptake (ml.kg-1.min-1), metabolic syndrome (MetS), and high-sensitivity C-reactive protein (hs-CRP), a marker of systemic inflammation.

METHODS

The relationship between CRF, MetS, and hs-CRP was examined in a cohort of 173 men and women. CRF was evaluated using a Bruce protocol treadmill test and measured as estimated maximal oxygen uptake (VO2 max). Participants' physical activity status was self-reported. Plasma hs-CRP levels were measured using a standardized immunoassay, and the diagnostic criteria for MetS were based on guidelines established by the International Diabetes Federation (IDF).

RESULTS

An inverse association was observed between hs-CRP levels and estimated VO2 max (p<0.01). Additionally, hs-CRP increased linearly with the number of MetS criteria present (p<0.01), while the estimated VO2 max decreased as the number of MetS criteria increased (p<0.01). Moreover, higher estimated VO2 max correlated with increased self-reported physical activity levels (p<0.01). Notably, participants engaging in two to three hours of exercise per week had hs-CRP levels ≤2.5 mg/L (p=0.018), considered a low-to-moderate risk range.

CONCLUSION

Higher CRF, reflected by an estimated VO2 max, ≥45 ml/kg/min, is associated with lower hs-CRP levels and fewer MetS criteria. Additionally, regular physical activity, corresponding to higher VO2 max, appears to reduce systemic inflammation and ameliorate MetS risk factors. These findings support the mechanisms by which improved CRF and exercise may lower the risk of cardiovascular diseases (CVD) and type 2 diabetes (T2DM).

Effects of Alpha-lipoic Acid Supplementation on Human Diabetic Nephropathy: A Systematic Review and Meta-analysis

BACKGROUND

Diabetic nephropathy (DN) is kidney dysfunction, which occurs due to elevated urine albumin excretion rate and reduced glomerular filtration rate. Studies on animals have shown that alpha-lipoic acid (ALA) supplementation can reduce the development of DN.

OBJECTIVES

We performed a systematic review and meta-analysis to examine the effects of ALA supplementation on biological indices (albumin, creatinine, etc.) indicative of human DN.

METHODS

The search procedure included PubMed Central, Embase, Cochrane Library (trials), and Web of Science (protocol registration: INPLASY202060095).

RESULTS

We found that ALA supplementation decreased 24h urine albumin excretion rate in patients with diabetes (standardized mean difference=-2.27; confidence interval (CI)=(-4.09)-(-0.45); I²=98%; Z=2.44; p=0.01). A subgroup analysis revealed that the results of studies examining only ALA did not differ from those examined ALA in combination with additional medicines (Chisquared= 0.19; p=0.66; I²=0%), while neither ALA nor ALA plus medication had an effect on 24h urine albumin excretion rate (p>0.05). Also, ALA supplementation decreased urine albumin mg/l (mean difference (MD)=-12.95; CI=(-23.88)-(-2.02); I²=44%; Z=2.32; p=0.02) and urine albumin to creatinine ratio (MD=-26.96; CI=(-35.25)-(-18.67); I²=0%; Z=6.37; p<0.01) in patients with diabetes. When the studies examining ALA plus medication were excluded, it was found that ALA supplementation had no effect on urine albumin mg/l (p>0.05) but did significantly decrease urine albumin to creatinine ratio (MD=-25.88, CI=(34.40-(-17.36), I²=0%, Z=5.95, p<0.00001).

CONCLUSION

The available evidence suggests that ALA supplementation does not improve biological indices that reflect DN in humans. Overall, we identified limited evidence, and therefore, the outcomes should be considered with caution.

Effects of valsartan combined with α-lipoic acid on renal function in patients with diabetic nephropathy: a systematic review and meta-analysis

BACKGROUND

Diabetic nephropathy (DN) is one of the most serious microvascular complications of diabetes, valsartan and α-lipoic acid alone or in combination has been used for the treatment of patients with DN. However, some results in these clinical reports were still controversial. The purpose of this study was to evaluate the efficacy of valsartan combined with α-lipoic acid on renal function in patients with DN.

METHODS

We searched the electronic databases including PubMed, Sciencedirect, EMBASE, Cochrane library, Chinese national knowledge infrastructure (CNKI) and Wanfang databases, and the publication deadline was limited to January 2020. Randomized controlled trials (RCTs) evaluating the effects of valsartan combined with α-lipoic acid in DN patients were included. Pooled estimates were conducted using a fixed or random effect model. The outcomes included urinary albumin excretion rate (UAER), and the level of urinary albumin, β₂-microglobulin (β₂-MG), hypersensitive C-reactive protein (hs-CRP) and oxidative stress.

RESULTS

11 studies with 1294 participants were included in this study. The pooled analysis indicated that α-lipoic acid combined with valsartan could remarkably reduce UAER (P < 0.00001, SMD = -1.95, 95%CI = -2.55 to - 1.20; P = 0.03, SMD = -0.85, 95%CI = -1.59 to - 0.1) and the level of urinary albumin (P = 0.001, SMD = -1.48, 95%CI = - 2.38 to - 0.58; P = 0.01, SMD = -1.67, 95%CI = -3.00 to - 0.33), β₂-MG (P < 0.001,SMD = - 2.59, 95%CI = -3.78 to - 1.40; P = 0.03, SMD = -0.48, 95%CI = -0.93 to - 0.04) when compared with valsartan or lipoic acid monotherapy in patients with DN. However, there was no significant difference in the level of hs-CRP among the three therapies (P = 0.06, SMD = -2.80, 95%CI = -5.67 to 0.07; P = 0.10, SMD = -0.42, 95%CI = - 0.92 to 0.08). In addition, α-lipoic acid combined with valsartan markedly increased the level of SOD (P = 0.03, SMD = 1.24, 95%CI = 0.32 to 1.03; P = 0.0002, SMD = 0.68, 95%CI = 0.32 to 1.03) and T-AOC (P < 0.00001, SMD = 0.89, 95%CI = 0.62 to 1.16; P = 0.02, SMD = 0.58, 95%CI = 0.10 to1.07), and reduced the level of MDA(P = 0.0002, SMD = -1.99, 95%CI = -3.02 to - 0.96; P = 0.0001, SMD = -0.69, 95%CI = -1.04 to - 0.34).

CONCLUSIONS

α-lipoic acid combined with valsartan could significantly reduce the level of urinary albumin and oxidative stress, increase antioxidant capacity and alleviate renal function damage in patients with DN, and this will provide a reference for the selection of treatment drugs for DN.

Can antioxidants be effective therapeutics for type 2 diabetes?

The global obesity epidemic and the growing elderly population largely contribute to the increasing incidence of type 2 diabetes. Insulin resistance acts as a critical link between the present obesity pandemic and type 2 diabetes. Naturally occurring reactive oxygen species (ROS) regulate intracellular signaling and are kept in balance by the antioxidant system. However, the imbalance between ROS production and antioxidant capacity causes ROS accumulation and induces oxidative stress. Oxidative stress interrupts insulin-mediated intracellular signaling pathways, as supported by studies involving genetic modification of antioxidant enzymes in experimental rodents. In addition, a close association between oxidative stress and insulin resistance has been reported in numerous human studies. However, the controversial results with the use of antioxidants in type 2 diabetes raise the question of whether oxidative stress plays a critical role in insulin resistance. In this review article, we discuss the relevance of oxidative stress to insulin resistance based on genetically modified animal models and human trials.

Antidiabetic effects of selenium-enriched Bifidobacterium longum DD98 in type 2 diabetes model of mice

Both selenium and probiotics have shown antidiabetic effects in a type 2 diabetes model. The objective of this study is to investigate the alleviating effects of selenium-enriched Bifidobacterium longum DD98 (Se-B. longum DD98) on diabetes in mice and explore the possible underlying mechanism. A type 2 diabetes model was established using a high-fat diet and streptozotocin (STZ) injection in mice. To investigate the beneficial effects of Se-B. longum DD98, diabetic mice were then treated with B. longum DD98, Se-B. longum DD98, or sodium selenite (Na₂SeO₃) for three weeks. The results suggested that all three treatments could reduce the levels of fasting blood glucose (FBG), glycated hemoglobin (HbA1c), insulin and leptin, improve glucose tolerance, regulate lipid metabolism, and protect against the impairment of the liver and pancreas, while Se-B. longum DD98 showed a greater effect on relieving the above mentioned symptoms of type 2 diabetes in mice. Furthermore, this effect was associated with butyrate production and inflammatory response. Se-B. longum DD98 better increased the level of butyrate in feces and decreased the levels of proinflammatory cytokines in the pancreas compared with B. longum DD98 and Na₂SeO₃, leading to ameliorative insulin resistance. Se-B. longum DD98 also improved the glucagon like peptide-1 (GLP-1) level in serum and intestinal cells, which protected the pancreatic β-islet cells from damage induced by type 2 diabetes. These results demonstrated that Na₂SeO₃, B. longum DD98, or Se-B. longum DD98 could alleviate the progression of type 2 diabetes in mice. Se-B. longum DD98 showed greater antidiabetic effects than the other two treatments, and could be considered as a promising candidate for treating type 2 diabetes.

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

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.

Urinary exosomes as a novel biomarker for evaluation of α-lipoic acid's protective effect in early diabetic nephropathy

BACKGROUND

Long-term administration of α-lipoic acid (α-LA) is proved to ameliorate renal impairment. Herein we assessed serum, urinary biomarkers and vascular endothelium function to evaluate its short-period therapeutic effect and identify novel biomarkers for diabetic nephropathy (DN).

METHODS

Sixty-two microalbuminuria-stage DN patients were randomly divided into two groups and received the following treatment for 8 weeks: (1) routine treatment(DM group); (2) routine treatment with 600 mg/d α-lipoic acid intravenously (α-LA group). Another total of 21 patients were recruited for the second-stage study and randomly divided into two groups: normoalbuminuria (UAER <30 mg/24 h) and microalbuminuria (UAER from 30-300 mg/24 h).

RESULTS

With α-LA treatment, urinary albumin excretion rates (UAER), serum creatinine (SCr) and malonaldehyde (MDA) declined significantly, whereas plasma superoxide dismutase (SOD)activity increased and endothelium-dependent flow mediated vasodilation (FMD) flexibility improved dramatically. Furthermore, the improvement of FMD showed positive correlation with the variation in MDA and SOD as well (r values are .516 and .435, P<.01 and P<.05, respectively). In contrast, these markers have no significant difference in the DM group with routine treatment. Notably, the CD63 expressing of exosomes in urine was found higher in the normoalbuminuria patients compared with those in microalbuminuria, parallelly only declined markedly after α-LA administration in normoalbuminuria patients.

CONCLUSION

In summary, we emphasize short-term α-LA could protect the kidney in the early DN against general oxidative stress, particularly the urinary CD63-positive exosome could be a potential sensitive and therapeutic indicator.

Inhibitory effects and mechanism of 25-OH-PPD on glomerular mesangial cell proliferation induced by high glucose

OBJECTIVE

To investigate the protective effects and potential mechanism of the compound 25-OH-PPD (PPD) on the glomerular mesangial cells (GMC) under high glucose condition.

METHODS

The hypertrophic GMC cells were established by DMEM containing glucose and randomly divided into five groups, including the normal control group (Control), the high glucose model group (HG, 25 mmolL(-1)), the PPD low dose group (1μmolL(-1), PPD-L), the PPD middle dose group (5μmolL(-1), PPD -M) and the PPD high dose group (10μmolL(-1), UCN-H). The GMC were incubated for 48h under different treatment factors. Total protein content was determined by Lowry method. The diameter of the single GMC and volume were measured by computer photograph analysis system. The GMC cell viability was analyzed by MTT assay. The level of malondialdehyde (MDA), the content of glutathione (GSH) and superoxide dismutase (SOD) activity were measured by ELISA. [Ca(2+)]і transient was measured by Till image system and by cell-loading Fura-2/AM. The expression of COX-1 and COX-2 were also determined using ELISA method.

RESULTS

The viability of GMC and the total protein content were decreased in HG group, different dosage PPD group could increase these indexes (P<0.05). The level of MDA was increased, the content of GSH and SOD was decreased in HG group, while PPD could reduce the MDA and enhance GSH and SOD (P<0.05). Following treatment with different dosage (PPD-L, PPD-M or PPD-H), the [Ca(2+)]і transient was reduced (P<0.05 or P<0.01). Moreover, the expression of COX-1 was decreased while COX-2 expression was increased in different dosage PPD groups.

CONCLUSION

The protective effects of PPD on GMC from HG-induced hypertrophy may be associated with the inhibition of [Ca(2+)]і transient and decreasing expression of COX-1 via the oxidative-stress injure pathway.

Urinary podocalyxin levels were associated with urinary albumin levels among patients with diabetes

Diabetic nephropathy has dramatically increased worldwide. In this study, we measured urinary podocalyxin in 240 patients with diabetes. The relationship between urinary podocalyxin and clinical parameters and the effects of dipeptidyl peptidase-4 inhibitors (DPP4i) and alpha-glucosidase inhibitor (a-GI) on urinary podocalyxin levels were examined. Urinary podocalyxin levels were significantly higher in patients with microalbuminuria than in those with normoalbuminuria. Urinary podocalyxin levels were also significantly related to albumin-to-creatinine ratio. Neither DPP4i nor α-GI ameliorated the increase in urinary podocalyxin levels. Our results indicated that urinary podocalyxin will be not only an early marker but also a treatment target for DN.