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Glycemic and oxidative status of patients with type 2 diabetes mellitus following oral administration of alpha-lipoic acid: A randomized double-blinded placebo-controlled study


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Despite well-controlled blood glucose levels, diabetic complications still inevitably take place via several mechanisms including excessive generation of free radicals in patients who suffer from diabetes mellitus (DM). A randomized double-blind placebo-controlled clinical trial to investigate the effectiveness of oral supplementation of DL-alpha-lipoic acid (ALA) on glycemic and oxidative status in DM patients was conducted. Thirty eight outpatients with type 2 DM were recruited and randomly assigned to either placebo or treatment in various doses of ALA (300, 600, 900, and 1200 mg/day) for 6 months. Following the treatment, all subjects were evaluated for glucose status and oxidative biomarkers. Results showed that fasting blood glucose, HbA1c trended to decrease in a dose-dependent manner. Increase of urinary PGF2α-Isoprostanes (F2α-IsoP) was noted in placebo but not ALA-treated groups, indicating possible suppressing action of ALA on lipid peroxidation in DM subjects. 8-Hydroxy-2'-deoxyguanosine (8-OHdG) levels, however, were similar in both placebo and ALA groups as well as urinary microalbumin and serum creatinine. Safety evaluation was monitored and treatment was found to be well tolerated despite some minor side effects. Results from this study reflected the benefits of ALA in glucose status with slight efficiency on oxidative stress-related deterioration in DM patients.
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12 Asia Pac J Clin Nutr 2012;21 (1):12-21
Original Article
Glycemic and oxidative status of patients with type 2
diabetes mellitus following oral administration of alpha-
lipoic acid: a randomized double-blinded placebo-
controlled study
Supatra Porasuphatana PhD1, Suthi Suddee MD2, Atinuch Nartnampong MSc3,
Julraht Konsil PhD1, Busakorn Harnwong B.Pharm2, Adichai Santaweesuk BSc3
1Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen 40002, Thailand
2Warinchamrap Hospital, Ubon Ratchathani, Thailand
3Regional Medical Science Center Ubon Ratchathani, Ubon Ratchathani, Thailand
Despite well-controlled blood glucose levels, diabetic complications still inevitably take place via several mecha-
nisms including excessive generation of free radicals in patients who suffer from diabetes mellitus (DM). A ran-
domized double-blind placebo-controlled clinical trial to investigate the effectiveness of oral supplementation of
DL-alpha-lipoic acid (ALA) on glycemic and oxidative status in DM patients was conducted. Thirty eight outpa-
tients with type 2 DM were recruited and randomly assigned to either placebo or treatment in various doses of
ALA (300, 600, 900, and 1200 mg/day) for 6 months. Following the treatment, all subjects were evaluated for
glucose status and oxidative biomarkers. Results showed that fasting blood glucose, HbA1c trended to decrease
in a dose-dependent manner. Increase of urinary PGF2-Isoprostanes (F2-IsoP) was noted in placebo but not
ALA-treated groups, indicating possible suppressing action of ALA on lipid peroxidation in DM subjects. 8-
Hydroxy-2’-deoxyguanosine (8-OHdG) levels, however, were similar in both placebo and ALA groups as well as
urinary microalbumin and serum creatinine. Safety evaluation was monitored and treatment was found to be well
tolerated despite some minor side effects. Results from this study reflected the benefits of ALA in glucose status
with slight efficiency on oxidative stress-related deterioration in DM patients.
Key Words: alpha-lipoic acid (ALA), diabetes, PGF2-Isoprostanes (F2-IsoP), 8-Hydroxy-2’-deoxyguanosine (8-
OHdG), oxidative stress
Diabetes mellitus (DM) is among a leading cause of ill-
nesses for people worldwide. Both type 1 and type 2 DM
are commonly found in Thailand and most patients who
suffer from DM also suffer from diabetic complications
including retinopathy, neuropathy and nephropathy.
Emerging evidences demonstrate oxidative stress by reac-
tive oxygen species (ROS) increase and depletion of cel-
lular antioxidant systems in diabetic patients as a conse-
quence of hyperglycemia. The incidence of oxidative
stress has been closely linked to the occurrence of dia-
betic complications.1,2 Sources of oxidative stress in dia-
betes could originate from several pathways including
glycation reactions, decompartmentatlization of transition
metals, and a shift of the reduced-oxygen status of the
diabetic cells.3 Various reactive species are produced un-
der hyperglycemic conditions, then, play a role in the
pathological alterations. This concept of oxidative stress
is now widely accepted as an important basis in the onset
and progression of diabetes and its complications includ-
ing retinopathy, neuropathy and nephropathy in diabetic
patients.1 Oxidative stress status in diabetes could be
clearly demonstrated by the increase of some specific
biomarkers such as lipid hydroperoxides, DNA adducts
and protein carbonyls.
Experiments supporting the utilization of antioxidants
strongly show their effectiveness in diminishing or pre-
venting damages caused by oxidative stress in diabetes.
Among those, alpha-lipoic acid (thioctic acid, 1,2-
dithiolane-3-pentanoic acid, 1,2-dithiolane-3-valeric; ALA),
a natural occurring potent antioxidant, has been known to
exert beneficial actions against oxidative stress caused by
hyperglycemia. An increase glucose uptake through re-
cruitment of the glucose transporter-4 (GLUT 4) to plasma
membranes, mimicking the action of insulin in stimulat-
ing glucose uptake as well as improvement of glucose
disposal in patients with type 2 diabetes are well evi-
dently described as principal mechanisms of ALA in
Corresponding Author: Dr Supatra Porasuphatana, Faculty of
Pharmaceutical Sciences, Khon Kaen University, Khon Kaen
40002, Thailand
Tel: +66-4336-2089; Fax: +66-4336-2093
Manuscript received 3 November 2010. Initial review com-
pleted 26 July 2011. Revision accepted 5 September 2011.
Alpha lipoic acid in diabetes mellitus 13
diabetes.4-6 Moreover ALA is capable of inducing the
synthesis of endogenous glutathione by reducing the glu-
tathione precursor molecule cycteine to cystine.7 Together
with its reduced form, dihydrolipoic acid, which also ex-
ert powerful antioxidant activity, ALA acts to scavenge
free radicals, regenerate thioredoxin, vitamin C and glu-
tathione which in turn can recycle vitamin E. Due to its
powerful antioxidant properties, ALA is particularly suit-
ed to the prevention and/or treatment of diabetic compli-
cations that arise from an excess oxidative stress.
ALA has been shown to exhibit renoprotective effects
in diabetic rats not only by improving glycemic control
but also its antioxidant activity.8 Clinical studies in hu-
mans also showed improvement in insulin sensitivity in
patients with type 2 DM after oral administration of
ALA,9-11 as well as the attenuation of proteinuria in pa-
tients with type 1 and type 2 DM.12,13 Administration of
ALA has shown improvement in DM patients due to its
antioxidative properties such as improvement in lipid
profile, oxidative pattern, inflammation.14 Whereas a
study in adolescents with type 1 DM reported no change
in clinical measurement including total antioxidant status
and oxidative damage.15 Therefore, the dose-response
effects ALA on oxidative biomarkers as well as glycemic
control in DM patients has still been inconclusive. To
develop better understanding of the preventative and ther-
apeutic potentials of ALA in diabetic complications, this
randomized doubled-blind placebo-controlled study
aimed to determine whether ALA is effective in control-
ling glycemic status and exerting antioxidant action in
patients with type 2 DM by measuring its effect on gly-
cemic control and oxidative biomarkers following a
treatment period of six months.
Volunteer subjects
Thirty eight out-patients with type 2 diabetes mellitus
from the Diabetes Clinic, Warinchamrap Hospital, Thai-
land were enrolled in this randomized, placebo-controlled
trial. Study protocol was approved by the Ethical Review
Committee for Research in Human Subjects, Ministry of
Public Health, Thailand and the Ethics Committee for
Human Research, Khon Kaen University in accordance
with the Declaration of Helsinki and the ICH-GCP. Sub-
jects were informed about the purpose and risks of the
study and informed consents were obtained prior to the
initiation of the study. Inclusion criteria included glyce-
mic status and microalbuminuria (20-200 mg/dL). Exclu-
sion criteria were treatment with antihypertensive agents
and any kind of antioxidants. Subjects were randomly
divided into five groups (n = 7-8 each) to receive either
placebo or different doses of ALA (300, 600, 900 or 1200
mg/day) on a double-blind basis for six months along
with their regular diabetic medications (metformin,
glibenclamide, combined meformin and glibenclamide or
chlorpropamide) and hypoglycemic drugs were periodi-
cally adjusted by physicians. Any drop out was replaced
following the same inclusion and exclusion criteria. All
subjects were asked to maintain their regular life style and
concomitant medication including hypoglycemic medica-
ALA capsules and placebo
Racemic alpha-lipoic acid (ALA) was purchased from
Degussa (Alipure®, Italy). Capsules of 300 mg ALA and
placebo were formulated and manufactured by General
Drugs House Co., Ltd. (Bangkok, Thailand). Specifica-
tions of ALA capsules were tested for assay for active
ingredient, weight variation, and dissolution following
USP26-NF21.16 All products were kept in light protecting
and moisture resistant containers throughout the study
before given to the subjects. Subjects were instructed to
take ALA or placebo capsules 30 minutes before meals
followed by a glassful of water. Subjects’ compliance was
assessed by pill count and medication diary. Doses of
ALA were divided accordingly for the dosages of 600,
900 and 1,200 mg/day. All subjects were inquired to take
ALA or placebo three times per day in order to ensure the
blinding process.
Clinical parameters
Laboratory parameters (fasting blood glucose, microabu-
min, liver enzymes, lipid profiles and hematological pa-
rameters) were analyzed by Vitalab Selectra XL Chemis-
try Analyzer (Vital Scientific NV, Netherlands). Hemo-
globin A1c (HbA1c) was analyzed with automated D-
10TM Hemoglobin Testing System (Bio-Rad Laboratories,
Measurement of oxidative markers
Urinary PGF2-Isoprostanes (F2-IsoP)
Standard 8-iso prostaglandin F2 was obtained from
Cayman and dissolved in DMSO. Determination of F2-
IsoP in this study was carried out using LC-MS/MS as
modified from Liang et al.17 Briefly, all of the urine sam-
ples were aliquoted and stored at -80°C until analysis.
The freshly thawed urines were mixed and centrifuged at
3,500 rpm for 10 min. Three milliliters of urine super-
natant was applied on a C18 solid phase extraction (SPE)
cartridge (Bond Elut C18; 3 CC/500 mg; Variant®, Ha-
bor City, CA, USA) previously conditioned with 5 mL of
ethanol and equilibrated with 5 mL of deionized water.
After washing with 5 ml of water, 5 mL of ethanol:water
(5:95, v/v) and 2 mL of hexane, the cartridge was then
eluted with 4 ml of ethyl acetate. The sample eluent was
evaporated to dryness under a stream of nitrogen gas and
reconstituted in 50 L of acetronitrile:water (20:80, v/v)
before the injection onto a column. The LC-MS/MS anal-
ysis was carried out with an Agilent 1100 LC system con-
sisting of a degasser, a binary pump, an autosampler and
a column heater. The column outlet was coupled to an
Agilent MSD ion Trap XCT mass spectrometer equipped
with electrospray ionization (ESI) source. Data acquisi-
tion and mass spectrometric evaluation was carried out
with Data Analysis software (Bruker). For the chroma-
tographic separation, a Zorbax XDB-C18 column (2.1x50,
3.5m) with an identical guard column (4x10, 5m). Mo-
bile phase consisted of 5 mM ammonium acetate (pH 6.0)
(A) and methanol:acetonitrile (5:95, v/v) (B). The HPLC
separation was carried out with a solvent gradient pro-
gram of 15% to 100% B within 11 min, a linear decrease
from 100-15% B within 1 min. The sample was delivered
at flow rate 200 l/min. A switch valve was used to inject
14 S Porasuphatana, S Suddee, A Nartnampong, J Konsil, B Harnwong and A Santaweesuk
only the components eluted between 7.0-9.0 min into the
mass spectrometer chamber
The following parameters were employed throughout
all MS experiments for ESI with negative ion polarity, the
capillary voltage was set to 4.0 kV, the drying tempera-
ture to 350°C, the nebulizer pressure to 45 psi, and drying
gas flow to 10 L/min. The maximum accumulation time
was 400 msec, the scan speed was ultrascan mode and the
fragmentation time was 40 ms. To determine the product
ions of F2-IsoP, the deprotonated ion ((M-H)-) at m/z 353
was isolated, helium gas introduced into the trap to in-
duce collision with analyte ions and the fragments de-
tected over a scan range of m/z 150-400. The most inten-
sive product ion was m/z 193. Throughout all measure-
ment, F2-IsoP was detected by multiple reaction moni-
toring (MRM). Full method validation was conducted
under the Guideline of Industry Bioanalytical Method
Urinary 8-Hydroxy-2’-deoxyguanosine (8-OHdG)
Urine samples were aliquoted and stored at -80°C until
analysis. The freshly thawed urines were mixed and cen-
trifuged at 3500g for 10 min to precipitate solid matters.
One milliliter of urine supernatant was mixed with 1 mL
of 100 mM KH2PO4 (pH 6.0) and then applied on a Var-
ian’s Bond Elut Certify cartridge previously conditioned
with 10 mL methanol, 5 mL DI water and equilibrated
with 10 mL of 100 mM KH2PO4 (pH 6.0). After washing
with 1 mL of 100 mM hydrochloric acid, the cartridge
was dried for 5 min under full vacuum and eluted with 1
mL of 100 mM KH2PO4 (pH 6.0):NH4OH (8:2). The
sample eluent was evaporated to remove NH4OH under a
stream of nitrogen gas. Samples were then subsequently
injected into the HPLC-ECD system. The separation of 8-
OHdG was carried out on a Phenomenex® C18 column
(4.6150 mm, 4 m) with an identical guard column
(410 mm, 5 m). Mobile phase consisted of 50 mM
KH2PO4 (pH 6.0), 2.5% acetronitrile, 1% methanol (sol-
vent A) and the solvent mixture for wash step contained
50% acetronitrile and 50% methanol (solvent B).
The HPLC system consisted of a binary high pressure
pump (Alltech model 105, USA) and automatic sample
injector (Alltech 570, USA). The electrochemical cell was
equipped with a glassy carbon working electrode operated
at +0.65V versus a Ag׀AgCl reference electrode (Preci-
sion instruments model 105, France). The system was
operated at 10 nA full range detection. Data acquisition
was performed by PeakSimple 3.29 Software.
Safety monitoring
Safety evaluations of all subject volunteers were regularly
monitored by local health staffs and any adverse effects
were immediately reported to the doctors. A grading or
severity scale is provided following the Common Termi-
nology Criteria for Adverse Events v3.0 (CTCAE) which
displays Grade 1 through 5 with unique clinical descrip-
tions of severity.19
Statistical analysis
Values of FBG and HbA1C were expressed as mean ±
SEM whereas those of urinary F2-isoP and 8-OHdG were
expressed as median (95% confident interval (CI)).
Measurements compared between pre- and post-treatment
of two groups (ALA-treated group vs. placebo group)
were performed by using Wilcoxon signed rank test.
Kruskal-Wallis analysis of variance test was used to
compare among placebo and ALA-treated group. Correla-
tion analysis for dose-dependent effect of ALA was per-
formed by using SPSS v.17 (Pearson correlation). A p-
value of less than 0.05 was considered significant.
Subjects’ characteristics
Table 1 showed characteristics of subjects enrolled in the
study (n=38) and divided into five groups (n=7-8 each).
All groups of subjects were found to be comparable in
terms of means of age, period of DM and body weight
despites a heterogeneity of age (44.5±0.88 years) and
period of DM (2.07±0.26 years) in each individual sub-
ject. Thirty three diabetic patients (86.8%) were pre-
scribed hypoglycemic drugs including metformin, gliben-
clamide, both metformin and glibenclamide, and chlor-
propamide whereas five patients (13.2%) were under non-
medication diet control. Number of patients received
medications did not differ significantly in each group. All
patients were diagnosed with mild diabetic nephropathy
based on levels of urinary albumin concentration of their
morning spot urine as microalbuminuria (20-200 mg/L).
Effects on fasting blood glucose and HbA1C levels
Fasting blood glucose (FBG) levels for all DM patients in
this study were 131±4.16 mg/dL, reflecting the hypergly-
cemic status in this group of patients even with the con-
trol of hypoglycemic agents. After six months of treat-
ment, FBG levels in the placebo group were found to be
unchanged, whereas those levels in each ALA groups
reduced during the course of treatment from month 0 to
Table 1. Subjects’ baseline characteristics
Dose (mg/day) Sex
Age (yr)
(mean ± SE)
Period of DM‡
Fasting blood glucose
Hypoglycemic agents
Placebo (n=8) 1/7 42.9 ± 2.52 1.56 ± 0.53 59.9 ± 2.78 122 ± 5.72 4/3/1
300 (n=8) 4/4 42.5 ± 1.12 1.49 ± 0.47 65.1 ± 1.88 141 ± 8.55 3/3/2
600 (n=8) 3/5 45.7 ± 1.68 1.77 ± 0.52 61.4 ± 2.96 136 ± 7.62 2/5/1
900 (n=7) 1/6 44.0 ± 2.00 3.40 ± 0.66 65.6 ± 5.50 130 ± 8.57 5/1/1
1,200 (n=7) 1/6 47.7 ± 2.18 2.33 ± 0.57 66.4 ± 2.35 125 ± 9.83 5/1/1
Total (n=38) 10/28 44.5 ± 0.88 2.07 ± 0.26 63.6 ± 1.43 131 ± 4.16
Results are shown as mean ± SE (Student t-test).
† Number of male and female subjects
‡ Years since first diagnostic of diabetic mellitus
Alpha lipoic acid in diabetes mellitus 15
month 6. Average means of differences between post-
treatment and pre-treatment (average values at month 6
minus values at month 0) from each group were plotted
and shown in Figure 1A. Only placebo group exhibited
the increase of mean FBG at Month 6. Mean different
values of FBG were found to be significantly correlated
(p = 0.004) with ALA doses, confirming dose-dependent
effect of ALA in reducing FBG. When all patients in
ALA groups were pooled and compared to the placebo
treated group, there was a significant difference in the
change of FBG (p<0.05) (Figure 1B).
Similar circumstances were also observed with HbA1C.
Baseline levels in ALA and placebo groups were consid-
erably comparable with wide range of variations. After
treatment with ALA for six months, only mean difference
of HbA1C in the placebo group increased while the val-
ues of all ALA treatment groups were in minus ranges
(less than zero), indicating the reduction of HbA1C fol-
lowing the administration of ALA. Due to the small sam-
ple size and high variations among the subjects, the
changes between pre- and post-treatment in each group
failed to reach a statistical significance. Only when all
patients in the ALA groups were pooled and compared to
the placebo group, was a significant difference in the
change of HbA1C then observed (p<0.05) (Figure 2B).
Significant correlation (p = 0.011) between ALA doses
and HbA1C also confirmed dose-dependent effect of
ALA on glycemic control in DM patients.
Effects on oxidative markers: Urinary F2α-isoP and 8-
By combining the C18 SPE sample preparation and LC-
MS/MS determination of urinary F2α-isoP, we were able
to detect the amount of F2-isoP in the urine samples with
limit of detection as low as 0.2 ng/mL. Method validation
was fully performed in compliance with the guideline as
indicated in Materials and Methods. The measurement of
urinary F2α-isoP in diabetic patients showed comparable
levels in all groups prior to the supplementation of ALA
or placebo. Those levels were also found to be insignifi-
cantly different among male and female subjects. After
six months of the treatment, no significant difference in
Figure 1. Changes of fasting blood glucose (FBG) after the administration of ALA in type 2 DM patients at various doses for six months
compared to placebo. (A) Mean difference of FBG between post-treatment and pre-treatment of ALA (300, 600, 900 and 1,200 mg/d)
groups and placebo group. (Mean ± SEM); significant correlation of ALA doses (p =0.004). (B) FBG levels in type 2 DM patients when
all subjects in ALA groups were ‘pooled’ as ‘ALA-treated’ group and compared to placebo (data were presented as mean ± SEM; signifi-
cant different from placebo group * p<0.05)
16 S Porasuphatana, S Suddee, A Nartnampong, J Konsil, B Harnwong and A Santaweesuk
changes of urinary F2α-isoP was seen with the administra-
tion of either ALA or placebo when compared between
pre- and post-treatment. The levels of urinary F2α-isoP in
all ALA-treated groups, however, increased in the pla-
cebo group (median; 728.32 vs. 1,624.27 pg/mg
creatinine for pre- vs. post-treatment) (Figure 3).
The other oxidative biomarker conducted in this study
was urinary 8-OHdG as determined by HPLC-ECD. Fig-
ure 4 illustrates the levels of 8-OHdG before and after
ALA treatment compared to the placebo group. After six
months, we observed a constant level in median values of
urinary 8-OHdG in the placebo group compared between
month 0 and month 6. Even though there was no signifi-
cant difference in changes of urinary 8-OHdG levels in
the ALA groups following the treatment period, the levels
of 8-OHdG showed slight reductions in median values.
No significant correlation was obtained between both
oxidative biomarkers (urinary F2-isoP and 8-OHdG) and
other parameters (FBG, HbA1C, serum creatinine, uri-
nary creatinine, urinary microalbumin and lipid profiles)
Other clinical parameters
Data on the clinical outcomes of the DM subjects (serum
creatinine, urinary creatinine, microalbumin, lipid profiles)
were not different among the placebo and the ALA-
treated groups when compared after the six-month trial
period. However, liver function enzymes (alanine ami-
notransferase; ALT and aspatate aminotransferase; AST)
slightly but not significantly reduced in the ALA-treated
groups in a dose-dependent manner (data not shown).
Levels of urinary microalbumin were found to be reduced
in all groups, including the placebo group.
Most participants in this study found the intervention to
be well tolerated, despite the fact that some minor adverse
effects were identified and recorded as possible adverse
effects caused by ALA. One patient (2.63%) voluntarily
dropped out from the study due to anorexia, two patients
(5.26%) reported skin rash. Those two adverse events
were categorized as Grade 2 and Grade 1 based on
CTCAE, respectively. Some patients reported bitter taste
in the throat after swallowing ALA capsules.
Figure 2. Changes of hemoglobin A1C (HbA1C) after the administration of ALA in type 2 DM patients at various doses for six months
compared to placebo. (A) Mean difference of HbA1C between post-treatment and pre-treatment of ALA (300, 600, 900 and 1,200 mg/d)
groups and placebo group. (Mean±SEM); significant correlation of ALA doses (p=0.011). (B) HbA1C levels in type 2 DM patients when
all subjects in ALA groups were ‘pooled’ as ‘ALA-treated’ group and compared to placebo (data were presented as mean±SEM; signifi-
cant different from placebo group * p<0.05)
Alpha lipoic acid in diabetes mellitus 17
This randomized double-blind placebo controlled study
demonstrated the effects of oral administration of ALA
ranging from 300 mg/day to 1,200 mg/day for 6 months
in patients with type 2 DM. We examined both glycemic
parameters – fasting blood glucose (FBG), HbA1C – as
well as two reliable oxidative biomarkers – urinary F2-
isoP and 8-OHdG – in type 2 DM patients who constantly
took hypoglycemic drugs or were under diet control.
Hyperglycemia is the most pronounced mechanism in
the pathogenesis of diabetic complications, which has
been evidently linked to the elevation of free radicals and
depletion of antioxidants in diabetic patients. Results
from the administration of antioxidant appear to prove the
pathogenic concept of occurrence of oxidative stress lead-
ing to diabetic complications. Our study showed a de-
creasing trend of blood glucose following the administra-
tion of ALA ranging from dose 300 mg/day to 1,200
mg/day, and only the placebo group exhibited a slight
increase in both FBG and HbA1C after the six-month
period. From the results of this study, we did not achieve
statistical significant in changes of both FBG and HbA1C
when compared between pre- and post-treatment. It is
likely due to a small number of subjects in each group
and high variation of the values. However, results clearly
showed a dose-dependently decline in both glycemic pa-
rameters and only reached significant value when com-
pare between the placebo group with pooled treatment
groups. Similar result was reported by Morcos, et al, in
which, after 18 months of ALA treatment (600 mg/day),16
an increase of HbA1C was seen in the control but not
ALA treated groups. Our study confirmed previous find-
ing with additional information of dose-response effect of
ALA on HbA1c.
Since insulin-resistance in peripheral tissues or im-
paired insulin secretion are associated with pathogenesis
of type 2 DM, the main possible target to normalize gly-
cemia and glucose homeostasis is then to enhance insulin
action through the increase of glucose uptake via glucose
transporter. Metformin, a antidiabetic drug, is one of
Figure 3. Distribution of urinary F2-isoP levels in type 2 DM patients before and after six months of ALA and placebo administration. The
lower and upper edges of the boxes are the 25th and 75th percentile, respectively. The black eclipses and lines within the boxes indicate
means and medians, respectively. The lower and upper bars represent the 10th and 90th percentile. Individual values above the 90th percen-
tile are shown as ( ). The median notches of the boxes are 95% confident interval.
18 S Porasuphatana, S Suddee, A Nartnampong, J Konsil, B Harnwong and A Santaweesuk
those agents found to mainly act to control blood glucose
by increasing glucose transporter 4 (GLUT4) mRNA ex-
pression,20 providing effective mechanism for diabetes
treatment. For ALA, its hypoglycemic action has also
been well documented.8,21,22 It is postulated to be due to
its action to engage the insulin-signaling pathway by en-
hancing muscle GLUT4 protein content,21 as well as in-
creasing GLUT4 translocation to cell membranes which
accelerates glucose uptake into muscle and fat cells.23
Therefore, it is likely that administration of ALA in DM
patients who take metformin can be favorable for blood
glucose controlling via the action through GLUT4.
Besides ALA action through GLUT4, oral administra-
tion of ALA was also reported to increase peripheral insu-
lin sensitivity in DM type 1 patients11 and improve the
impairment of endothelial function caused by hypergly-
cemia.24 Changes of glycemic control by ALA treatment
appear to be a delayed process and not responsive to low
dose of ALA (eg, 300 mg/day). Hahm et al reported un-
changed of blood glucose and HbA1c in DM patients who
received 300 mg/day ALA for 8 weeks.25 In our study, a
slight increase in FBG and HbA1C were obtained from
the placebo group but not in ALA treatment groups, in-
cluding 300 mg/day group, confirming the ability of ALA
to maintain blood glucose levels even at low dose if taken
for a certain period of time.
Urinary F2-isoP, a specific biomarker of lipid peroxida-
tion in human, was determined in this study to indicate
the oxidative stress condition in type 2 DM patients both
before and after ALA treatment with an acceptance of its
reliability for the assessment of in vivo effects of antioxi-
dants as well as a risk marker of diabetes.26 We chose to
measure the levels of urinary F2α-IsoP, instead of plasma
F2α-IsoP, to reflect systemic oxidative stress in the corre-
lation with progressive diabetic nephropathy. This was
due to the reason that increased production of F2α-IsoP in
the body did not lead to an increase in plasma F2α-IsoP
levels because of an increased elimination of this metabo-
lite, and therefore and increased excretion in urine.27
While the levels of urinary F2α-isoP were found to be un-
Figure 4: Distribution of urinary 8-OHdG levels in type 2 DM patients before and after six months of ALA and placebo administration.
The lower and upper edges of the boxes are the 25th and 75th percentile, respectively. The black eclipses and lines within the boxes indi-
cate means and medians, respectively. The lower and upper bars represent the 10th and 90th percentile. Individual values above the 90th
percentile are shown as ( ). The median notches of the boxes are 95% confident interval.
Alpha lipoic acid in diabetes mellitus 19
changed in the ALA groups, the levels in the placebo
group appeared to increase by approximately twofold
(median values), indicating the possible effect of ALA to
suppress the occurrence of lipid peroxidation in type 2
DM. However, the absence of a significant difference
from this data could be presumably due to high variations
of urinary F2α-isoP levels in the participating subjects.
The increased amount of 8-OHdG as a marker of oxi-
dative DNA damage due to hyperglycemic status was
also reported to be elevated in both plasma and tissues of
streptozotocin diabetic rats28 and accepted as a predictive
factor for the progression of diabetic nephropathy.29 Our
preliminary results showed an approximate two-folds
increase in the urinary 8-OHdG in diabetic patients, when
compared to healthy non-diabetic subjects (data not
shown), confirming the enhancement of oxidative damage
to DNA in diabetic patients. However, there were no sig-
nificant differences in urinary 8-OHdG levels in DM pa-
tients who received either ALA or placebo. Similar re-
sults were previously shown in adolescents with type 1
diabetes mellitus in which no significant change in oxida-
tive damage was observed following the supplementation
of ALA for 3 months.30 Despite the extended treatment
period and numerous information on antioxidant action of
ALA, the absence of a potential effect against DNA dam-
age as a result of ALA in this study could be accounted
for limited ability of ALA to cope with continuous pro-
duction of ROS during chronic hyperglycemia in diabetic
Even though allergic skin reactions and possible hypo-
glycemia in diabetic patients with ALA doses over 2,000
mg/day were previously reported,31 we found minor skin
rash (Grade 1, CTCAE) in two patients (5.26%) in which
one patient voluntarily continued until the completion of
the trial and the other patient dropped out. Upon taking
oral antihistamine, the skin rash completely disappeared
within one day. Other complains included loss of appetite
as well as a bitter taste in the throat when swallowing the
capsules. During the course of study, anti-diabetic drug
regimens were accordingly adjusted by physicians and
any hypoglycemic signs were not observed. In this study,
we were unable to demonstrate a positive correlation be-
tween levels of oxidative markers and glycemic status of
the subjects despite the demonstration of the correlation
in other studies.32 Explanation can be achieved via the
fact that the numbers of subjects in each group were quite
small. Due to the short half-life of ALA (t½ ~ 30 min),33
we expected a greater outcome of inhibitory actions of
ALA supplementation against oxidative stress in daily
multiple doses regimens. However, repeated doses of
ALA (two or three times per day when dosages were di-
vided) did not demonstrate this long-lasting achievement.
By conducting a placebo-controlled trial, we were able
to demonstrate a comparison between DM subjects who
received ALA and those who did not (placebo group).
Overall ALA effects in DM patients suggested a clear
dose-response relationship and the highest dosage exam-
ined in this study (1,200 mg/d) was the most preferable
for glycemic control, despite the lack of statistical signifi-
cance for oxidative biomarkers. DM subjects who re-
ceived this dosage were evidently beneficial from ALA
administration during the course of hypoglycemic agents.
In conclusion, this present study demonstrated that oral
treatment of ALA could help improve glycemic status
and iss slightly effective against oxidative stress in Thai
patients with type 2 DM when compared to placebo with
tolerable minor adverse events. The in-trend reduction of
FBG and HbA1C in a dose-dependent manner (ranging
from 300-1,200 mg/day) appeared to reflect advantageous
action of ALA during a regular course of anti-diabetic
drug regimens. Results also provide more constructive
information for the use of ALA as an adjuvant therapy in
type 2 DM patients who constantly take oral hypoglyce-
mic agents. However, more patients may need to be re-
cruited in this study to overcome high variation among
Authors would like to acknowledge financial supports from the
Commission on Higher Education, the Thailand Research Fund
(TRF) (MRG4780213) and Cerebos (Thailand) Co., Ltd. We are
grateful to all volunteer subjects who participated in this study,
to staffs at Warinchamrap Hospital, Ubonratchathani, for their
valuable supports in conducting the clinical research, to Dr.
Sureerat Prachaktham (General Drugs House, Co., Ltd) for pre-
paring ALA and placebo capsules used throughout this study,
and to the Regional Medical Science Center Khon Kaen for
allowing us to access to an LC-MS/MS.
None of the authors (SP, SS, AN, JK, BH and AS) report any
conflict of interest with respect to the current study.
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Alpha lipoic acid in diabetes mellitus 21
Original Article
Glycemic and oxidative status of patients with type 2
diabetes mellitus following oral administration of alpha-
lipoic acid: a randomized double-blinded placebo-
controlled study
Supatra Porasuphatana PhD1, Suthi Suddee MD2, Atinuch Nartnampong MSc3,
Julraht Konsil PhD1, Busakorn Harnwong B.Pharm2, Adichai Santaweesuk BSc3
1Faculty of Pharmaceutical Sciences, Khon Kaen University, Khon Kaen 40002, Thailand
2Warinchamrap Hospital, Ubon Ratchathani, Thailand
3 Regional Medical Science Center Ubon Ratchathani, Ubon Ratchathani, Thailand
補充硫辛酸對於第 2型糖尿病患的血糖和氧化壓力
氧化壓力的影響。從門診招募 38 名第 2型糖尿病患者,隨機分配到安慰劑組或
試驗組(硫辛酸劑量分別為每日 3006009001200 mg)。實驗進行 6個月。
F2-IsoP 濃度在實驗期後升高,服用硫辛酸者則未增加,表示硫辛酸或許有助
於抑制糖尿病患者的脂肪過氧化作用。然而各組尿液中 8-OHdG 及微白蛋白濃
... This rationalizes the insulin sensitizing effects observed when rodent or human type 2 diabetics are fed spirulina [304,305]. It is also reasonable to expect that the downstream impact of oxidants on JNK/IKKβ might be blunted to some degree by Nrf2-inducible enzymes; consistent with this possibility, lipoic acid supplementation has been reported to achieve modest dose-dependent improvements in glycemic control in type 2 diabetics [306]. ...
Full-text available
Oxidative and dicarbonyl stress, driven by excess accumulation of glycolytic intermediates in cells that are highly permeable to glucose in the absence of effective insulin activity, appear to be the chief mediators of the complications of diabetes. The most pathogenically significant dicarbonyl stress reflects spontaneous dephosphorylation of glycolytic triose phosphates, giving rise to highly reactive methylglyoxal. This compound can be converted to harmless lactate by the sequential activity of glyoxalase I and II, employing glutathione as a catalyst. The transcription of glyoxalase I, rate-limiting for this process, is promoted by Nrf2, which can be activated by nutraceutical phase 2 inducers such as lipoic acid and sulforaphane. In cells exposed to hyperglycemia, glycine somehow up-regulates Nrf2 activity. Zinc can likewise promote glyoxalase I transcription, via activation of the metal-responsive transcription factor (MTF) that binds to the glyoxalase promoter. Induction of glyoxalase I and metallothionein may explain the protective impact of zinc in rodent models of diabetic complications. With respect to the contribution of oxidative stress to diabetic complications, promoters of mitophagy and mitochondrial biogenesis, UCP2 inducers, inhibitors of NAPDH oxidase, recouplers of eNOS, glutathione precursors, membrane oxidant scavengers, Nrf2 activators, and correction of diabetic thiamine deficiency should help to quell this.
... This result indicates the effect of ALA in reducing the risk of MetS since hyperglycaemia is the most ascertained mechanism in the pathogenesis of diabetes. In addition, this result is consistent with the previous findings showing a dose-dependent decline in glycaemic parameters in diabetic patients treated with ALA at different daily doses (Porasuphatana S et al., 2012). ...
Full-text available
Background Many of the atypical antipsychotics induce metabolic side effects, limiting their use in clinical practice. Alpha-lipoic acid (ALA) was proposed as a new approach in schizophrenia to improve metabolic effects of atypical antipsychotics. The aim of the study is to evaluate the effect of ALA on metabolic and clinical parameters among schizophrenic subjects. Methods 15 schizophrenic subjects, in stable atypical antipsychotic monotherapy were included in the study. ALA was administrated at the oral daily dose of 600 mg/d in addition to antipsychotic therapy. Metabolic, clinical, and psychopathological parameters were measured at typical antipsychotics. e initial screening, and after 12 weeks. Results ALA produced a statistically significant reduction in QTc (p = 0.012), blood glucose (p = 0.005), AST (p = 0.021), γGT (p = 0.035), CPK (p = 0.005) and prolactinaemia (p = 0.026). In contrast, there was a significant increase in HbA1c (p = 0.026). No effects on body weight and blood lipid levels (triglycerides, total cholesterol, HDL, LDL) emerged. Conclusions ALA treatment appeared to be effective for reducing diabetes risk, liver functionality parameters, hyperprolactinaemia and QTC interval. ALA appears to be safe as adjunctive components in schizophrenia.
... [17] регистрировали снижение уровня глюкозы плазмы натощак и через 2 часа после приёма пищи, инсулинорезистентности у больных СД типа 2 на фоне приёма АЛК в дозе 300 мг в сутки. В другом рандомизированном исследовании у больных СД типа 2 приём АЛК в дозе от 300 до 1200 мг в сутки в течение полугода улучшал гликемический профиль и снижал показатели окислительного стресса [30]. Многоцентровое двойное слепое плацебоконтролируемое исследование NATHAN I (Неврологическая оценка эффекта тиоктовой кислоты при диабетической нейропатии) показало снижение уровня HbA1c [31]. ...
The aim of the article is to evaluate the effectiveness of the thioctic acid preparation in the complex therapy of type 1 diabetes mellitus (T1DM) in children with cardiovascular autonomic neuropathy at the preclinical stage. Materials and methods. A design is a prospective randomized study. A clinical and instrumental examination of 64 children with preclinical stage signs of diabetic cardiovascular autonomic neuropathy (DCAN) was carried out. The cohort was divided into 2 groups: in the main and control groups, glycemic control was normalized by adjusting a dose of insulin therapy; in the main group, the children additionally received thioctic acid at the dose of 600 mg/day for 3 months. To control the effectiveness of the therapy, the technique of laser Doppler flowmetry was used. Results. After the pharmacological intervention, there was an improvement in the disease course, normalization of carbohydrate and lipid metabolism, increased vasomotor mechanisms of the regulation of the tissue blood flow due to an increase in endothelial and neurogenic kinds of activity in combination with a decrease in the intravascular tone and an increase in the effective perfusion in tissues. An increase in the heart rate variability was detected, positive dynamics of cardiovascular tests indicators according to D. Ewing, temporal (pNN50%, SDNN) and spectral indicators (VLF) were diagnosed. Achievement and maintenance of the target values of glycemic control indicators, as well as the absence of glycemic variability, turned out to be clinically significant for reducing the manifestations of neuropathy. The non-invasive technique of laser Doppler flowmetry is informative for the early diagnosis of DCAN in T1DM children. Conclusion. The carried out studies have demonstrated the effectiveness of the lipoic acid use at the dose of 600 mg/day for 3 months in the children with DCAN signs at the preclinical stage. The method of laser Doppler flowmetry for determining indications and monitoring the effectiveness of therapy makes it possible to implement a personalized approach to prescribing preventive treatment in T1DM children.
... Yi et al., 2013), increasing glucose uptake(Jacob, Rett, et al., 1999;Mohammed et al., 2019; Thirunavukkarasu et al., 2004a; Yang et al., 2014) and glucose tolerance (Cummings et al., 2010; Thirunavukkarasu & Anuradha, 2004), enhancing insulin effect on glucose transport activity(Ghelani et al., 2017;Jacob, Streeper, et al., 1996;Kamenova, 2006;M. S. Kim et al., 2004;Peth et al., 2000;Porasuphatana et al., 2012), and reducing fasting blood glucose(Ansar et al., 2011;Atmaca & Akbas, 2017;Morakinyo et al., 2013;E. A. Muellenbach et al., 2008;Thirunavukkarasu et al., 2004a;Thirunavukkarasu & Anuradha, 2004). ...
Metabolic syndrome (MetS) is a multifactorial disease with medical conditions such as hypertension, diabetes, obesity, dyslipidemia, and insulin resistance. Alpha‐lipoic acid (α‐LA) possesses various pharmacological effects, including antidiabetic, antiobesity, hypotensive, and hypolipidemia actions. It exhibits reactive oxygen species scavenger properties against oxidation and age‐related inflammation and refines MetS components. Also, α‐LA activates the 5′ adenosine monophosphate‐activated protein kinase and inhibits the NFκb. It can decrease cholesterol biosynthesis, fatty acid β‐oxidation, and vascular stiffness. α‐LA decreases lipogenesis, cholesterol biosynthesis, low‐density lipoprotein and very low‐density lipoprotein levels, and atherosclerosis. Moreover, α‐LA increases insulin secretion, glucose transport, and insulin sensitivity. These changes occur via PI3K/Akt activation. On the other hand, α‐LA treats central obesity by increasing adiponectin levels and mitochondrial biogenesis and can reduce food intake mainly by SIRT1 stimulation. In this review, the most relevant articles have been discussed to determine the effects of α‐LA on different components of MetS with a special focus on different molecular mechanisms behind these effects. This review exhibits the potential properties of α‐LA in managing MetS; however, high‐quality studies are needed to confirm the clinical efficacy of α‐LA.
... Studies evaluating the effect of alpha-lipoic acid on oxidative stress reduction provide conflicting results. For example, some studies confirm a reduction in oxidative stress markers (MDA, superoxide dismutase SOD, glutathione peroxidase GPx, prostaglandin PGF2α and 8-hydroxy-2 -deoxyguanosine) after oral administration of 300-1200 mg/day in patients with type 2 DM [40,41]. Furthermore, ALA can reduce the formation of advanced glycation end products by decreasing of circulating glucose concentration and then prevent it from reacting with proteins and subsequently decrease the expression of the AGE receptor in the cell membrane [42]. ...
Full-text available
Introduction: One of the most common chronic complications of diabetes mellitus is diabetic neuropathy. The aim of the study was to elucidate the association between selected markers of oxidative stress and markers of vascular stiffness and to contribute to the understanding of the pathophysiological links between oxidative stress and micro- and macrovascular complications of diabetes. Methods: We enrolled patients with type 2 DM (n = 49), with moderate to severe diabetic polyneuropathy of lower extremities, and a control group without microvascular complications (n = 29). The neuropathy group received alpha-lipoic acid infusion therapy. Sampling was performed before and after treatment to determine the level of oxidative markers (advanced glycation end-products—AGEs, glycation products of AOPP proteins, MDA malondialdehyde and oxidized LDL), parameters of metabolic control and parameters of vascular wall stiffness were measured by sphygmomanometry. Results: After the administration of alpha-lipoic acid, we demonstrated a significant reduction in the level of three selected oxidation markers (AOPP: p < 0.001, AGE: p < 0.001, oxLDL: p < 0.05). In contrast, the level of MDA did not change significantly (p = 0.83). Throughout the group, oxLDL was significantly correlated with central BP (SBP and DBP in the aorta, p < 0.05 and <0.01) and with the augmentation index (AiX/75 bpm, p < 0.01). AOPP significantly correlated with systolic BP in the aorta (p < 0.05). We did not find significant associations in the remaining oxidation markers. Conclusion: In our study, we demonstrated a reduction in the level of oxidative markers after alpha-lipoic acid administration and also an association between markers of oxidative damage to lipids and proteins (oxLDL and AOPP) and some parameters of vascular stiffness.
... Compared with animals, the dosages for human were relatively lower.For humans, a safe dose of LA as the health ingredient used in food supplements was recommended as a daily intake of 150-200 mg/d in Denmark [151], through the intakes of 300 to 1800 mg/d to improve symptoms of corresponding diseases had been applied. However, allergic reactions in the skin (e.g., hives and itchiness) and gastrointestinal symptoms (e.g., stomach ache, nausea, and diarrhea) often occurred in long-term applications [152][153][154]. Although there were no reports about the side effects of LA attenuating I/R injury at present and the dosages in present studies were relatively low, it should be considered the potential side effects of LA applying to prevent I/R injury. ...
Full-text available
Ischemia-reperfusion (I/R) injury often occurred in some pathologies and surgeries. I/R injury not only harmed to physiological functions of corresponding organ and tissue but also induced multiple tissue or organ dysfunctions (even these in distant locations). Although the reperfusion of blood attenuated I/R injury to a certain degree, the risk of secondary damages was difficult to be controlled and it even caused failures of these tissues and organs. Lipoic acid (LA), as an endogenous active substance and a functional agent in food, owns better safety and effects in our body (e.g., enhancing antioxidant activity, improving cognition and dementia, controlling weight, and preventing multiple sclerosis, diabetes complication, and cancer). The literature searching was conducted in PubMed, Embase, Cochrane Library, Web of Science, and SCOPUS from inception to 20 May 2021. It had showed that endogenous LA was exhausted in the process of I/R, which further aggravated I/R injury. Thus, supplements with LA timely (especially pretreatments) may be the prospective way to prevent I/R injury. Recently, studies had demonstrated that LA supplements significantly attenuated I/R injuries of many organs, though clinic investigations were short at present. Hence, it was urgent to summarize these progresses about the effects of LA on different I/R organs as well as the potential mechanisms, which would enlighten further investigations and prepare for clinic applications in the future.
Full-text available
Objective: To examine the dose-dependent influence of oral ALA supplementation on cardiometabolic risk factors in type 2 diabetes (T2D) patients. Design: We followed instructions outlined in the Cochrane Handbook for Systematic Reviews of Interventions and the Grading of Recommendations, Assessment, Development, and Evaluation Handbook to conduct our systematic review. The protocol of the study was registered in PROSPERO (CRD42021260587). Method: We searched PubMed, Scopus, and Web of Science to May 2021 for trials of oral ALA supplementation in adults with T2D. The primary outcomes were HbA1c, weight loss, and low-density lipoprotein cholesterol (LDL-C). Secondary outcomes included fasting plasma glucose (FPG), triglyceride, C-reactive protein, and blood pressure. We conducted a random-effects dose-response meta-analysis to calculate the mean difference (MD) and 95%CI for each 500 mg/d oral ALA supplementation. Non-linear dose-response meta-analyses were also conducted. Results: We included 16 trials with 1035 patients. Each 500 mg/d increase in oral ALA supplementation significantly reduced HbA1c, body weight, CRP, FPG, and TG. Dose-response meta-analyses indicated a linear decrement in body weight at ALA supplementation of more than 600 mg/d (mean difference 600 mg/d: -0.30 kg, 95%CI: -0.04, -0.57). A relatively J-shaped effect was seen for HbA1c (mean difference: -0.32%, 95%CI: -0.45, -0.18). Levels of FPG and LDL decreased up to 600 mg/d ALA intake. The point estimates of the certainty of evidence were below minimal clinically important difference thresholds for all outcomes. Conclusion: Despite significant improvements, the effects of oral ALA supplementation on cardiometabolic risk factors in T2D patients were not clinically important.
The antioxidant effect of alpha-lipoic acid (ALA) and its effect in reducing reactive oxygen species has been demonstrated in primary studies. This systematic review and meta-analysis was conducted to evaluate the impact of alpha-lipoic acid (ALA) supplementation on oxidative stress (OS) parameters. We performed a comprehensive search in major electronic databases. A random-effects model was used to pool data and calculated standard mean difference and 95% confidence intervals. Fifteen studies were included in the meta-analyses. The outcomes of this meta-analysis indicated that ALA consumption significantly decreased Malondialdehyde (MDA) levels compare to control group. We found no significant effect of ALA supplementation on other antioxidant enzymes and oxidative stress parameters. Overall, the present meta-analysis indicated that ALA supplementation might lead to an amelioration in lipid peroxidation. It can be recommended that the use of ALA supplementation in < 800 mg/day is a good choice to control lipid peroxidation.
Background Diabetic nephropathy (DN) is a kidney dysfunction, which occurs due to elevated urine albumin excretion rate and reduced glomerular filtration rate. Studies in 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 searching procedure included the databases PubMed Central, Embase, Cochrane Library (trials) and Web of Science, (protocol registration: INPLASY 202060095). Results We found that ALA supplementation decreased urine albumin 24h 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 studies examining only ALA, did not differ from those examined ALA in combination with additional medicines (Chi-squared=0.19; p=0.66; I2=0%), while neither ALA nor ALA plus medication had an effect on urine albumin 24h 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 that examined ALA plus medication were removed, 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.
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R(+)-alpha-lipoic acid is a natural occurring compound that acts as an essential cofactor for certain dehydrogenase complexes. The redox couple alpha-lipoic acid/dihydrolipoic acid possesses potent antioxidant activity. Exogenous racemic alpha-lipoic acid orally administered for the symptomatic treatment of diabetic polyneuropathy is readily and nearly completely absorbed, with a limited absolute bioavailability of about 30% caused by high hepatic extraction. Although the pharmacokinetics of the parent drug have been well characterized in humans, relatively little is known regarding the excretion of alpha-lipoic acid and the pharmacokinetics of any metabolites in humans. In the present study, plasma concentration-time courses, urinary excreted amounts, and pharmacokinetic parameters of alpha-lipoic acid metabolites were evaluated in 9 healthy volunteers after multiple once-daily oral administration of 600 mg racemic alpha-lipoic acid. The primary metabolic pathways of alpha-lipoic acid in man, S-methylation and β-oxidation, were quantitatively confirmed by an HPLC-electrochemical assay newly established prior to the beginning of this study. Major circulating metabolites were the S-methylated β-oxidation products 4,6-bismethylthio-hexanoic acid and 2,4-bismethylthio-butanoic acid, whereas its conjugated forms accounted for the major portion excreted in urine. There was no statistically significant difference in the pharmacokinetic parameters Cmax, AUC, and tmaxbetween day 1 and day 4. Despite the prolonged half-lives of the major metabolites compared to the parent drug, no evidence of accumulation was found. Mean values of 12.4% of the administered dose were recovered in the urine after 24 hours as the sum of alpha-lipoic acid and its metabolites. The results of the present study revealed that urinary excretion of alpha-lipoic acid and five of its main metabolites does not play a significant role in the elimination of alpha-lipoic acid. Therefore, biliary excretion, further electrochemically inactive degradation products, and complete utilization of alpha-lipoic acid as a primary substrate in the endogenous metabolism should be considered.
In 1990 we discovered the formation of prostaglandin F(2)-like compounds, F(2)-isoprostanes (F(2)-IsoPs), in vivo by nonenzymatic free radical-induced peroxidation of arachidonic acid. F(2)-IsoPs are initially formed esterified to phospholipids and then released in free form. There are several favorable attributes that make measurement of F(2)-IsoPs attractive as a reliable indicator of oxidative stress in vivo: (i) F(2)-IsoPs are specific products of lipid peroxidation; (ii) they are stable compounds; (iii) levels are present in detectable quantities in all normal biological fluids and tissues, allowing the definition of a normal range; (iv) their formation increases dramatically in vivo in a number of animal models of oxidant injury; (v) their formation is modulated by antioxidant status; and (vi) their levels are not effected by lipid content of the diet. Measurement of F(2)-IsoPs in plasma can be utilized to assess total endogenous production of F(2)-IsoPs whereas measurement of levels esterified in phospholipids can be used to determine the extent of lipid peroxidation in target sites of interest. Recently, we developed an assay for a urinary metabolite of F(2)-IsoPs, which should provide a valuable noninvasive integrated approach to assess total endogenous production of F(2)-IsoPs in large clinical studies.
A natural cofactor of mitochondrial dehydrogenase complexes and a potent antioxidant, alpha-lipoic acid improves glucose metabolism in people with Type II (non-insulin-dependent) diabetes mellitus and in animal models of diabetes. In this study we investigated the cellular mechanism of action of alpha-lipoic acid in 3T3-L1 adipocytes. We treated 3T3-L1 adipocytes with 2.5 mmol/l R (+) alpha-lipoic acid for 2 to 60 min, followed by assays of: 2-deoxyglucose uptake; glucose transporter 1 and 4 (GLUT1 and GLUT4) subcellular localization; tyrosine phosphorylation of the insulin receptor or of the insulin receptor substrate-1 in cell lysates; association of phosphatidylinositol 3-kinase activity with immunoprecipitates of proteins containing phosphotyrosine or of insulin receptor substrate-1 using a in vitro kinase assay; association of the p85 subunit of phosphatidylinositol 3-kinase with phosphotyrosine proteins or with insulin receptor substrate-1; and in vitro activity of immunoprecipitated Akt1. The effect of R (+) alpha-lipoic acid was also compared with that of S(-) alpha-lipoic acid. Short-term treatment of 3T3-L1 adipocytes with R (+) alpha-lipoic acid rapidly stimulated glucose uptake in a wortmannin-sensitive manner, induced a redistribution of GLUT1 and GLUT4 to the plasma membrane, caused tyrosine phosphorylation of insulin receptor substrate-1 and of the insulin receptor, increased the antiphosphotyrosine-associated and insulin receptor substrate-1 associated phosphatidylinositol 3-kinase activity and stimulated Akt activity. These results indicate that R (+) alpha-lipoic acid directly activates lipid, tyrosine and serine/threonine kinases in target cells, which could lead to the stimulation of glucose uptake induced by this natural cofactor. These properties are unique among all agents currently used to lower glycaemia in animals and humans with diabetes.
Alpha lipoic acid (lipoate [LA]), a cofactor of α-ketodehydrogenase, exhibits unique antioxidant properties. Recent studies suggest a direct effect of LA on glucose metabolism in both human and experimental diabetes. This study examines the possbility that LA positively affects glucose homeostasis in streptozotocin (STZ)-induced diabetic rats by altering skeletal muscle glucose utilization. Blood glucose concentration in STZ-diabetic rats following 10 days of intraperitoneal (IP) injection of LA 30 mg/kg was reduced compared with that in vehicle-treated diabetic rats [495 ± 131 v 641 ± 125 mg/dL in fed state, P = .003, and 189 ± 48 v 341 ± 36 mg/dL after 12-hour fast, P = .001). No effect of LA on plasma insulin was observed. gastroenemius muscle crude membrane GLUT4 protein was elevated both in control and in diabetic rats treated with LA by 1.5- and 2.8-fold, respectively, without significant changes in GLUT4 mRNA levels. Gastroenemius lactic acid was increased in diabetic rats (19.9 ± 5.5 v 10.4 ± 2.8 μmol/g muscle, P < .05 v nondiabetic rats), and was normal in LA-treated diabetic rats (9.1 ± 5.0 μmol/g muscle). Insulin-stimulated 2-deoxyglucose (2 DG) uptake into isolated soleus muscle was reduced in treatment prevented this reduction, resulting in insulin-stimulated glucose uptake comparable to that of nondiabetic animals. These results suggest that daily LA treatment may reduce blood glucose concentrations in STZ-diabetic rats by enhancing muscle GLUT4 protein content and by increasing muscle glucose utilization.
There is a growing evidence that excess generation of highly reactive free radicals, largely due to hyperglycemia, causes oxidative stress, which further exacerbates the development and progression of diabetes and its complications. The purpose of this study was to evaluate the impact of ALA on lipid profile, oxidative pattern and inflammation in patients with controlled non-insulin dependent diabetes mellitus (NIDDM). ALA, 400mg/day was investigated in NIDDM patients over a period of 4 weeks using a randomized, placebo-(PLA)-controlled study with two parallel groups. The marker of oxidative stress was the concentration of reactive oxygen metabolites, evaluated using a commercially available test, called d-ROMs test, and the biological antioxidant potential (BAP); besides, the lipid profile (total cholesterol=TC, high-density lipoprotein-cholesterol = HDL-C; low-density lipoprotein-cholesterol=LDL-C, and triglycerides=TG) and the C-reactive protein (CRP), marker of inflammation were measured at the beginning and at the end of the treatment. A total of 14 patients were randomly assigned to the two groups. ALA was safe and well tolerated in the only oral daily administration. The d-ROMs test (p=0.03) and HDL-C (p=0.04) showed a significant difference between the two groups. BAP (p=0.06) tended to be higher in the treated patients, while LDL-C (p=0.07) presented a moderate decline. There were no significant differences in TC (p=0.65), TG (p=0.78) and CRP (p=0.96) between the ALA and PLA groups. ALA therapy appears to reduce significantly d-ROMs and to improve HDL-C value, especially in men with metabolic syndrome treated with oral hypoglycemic drugs. These findings will be useful in patient selection in future clinical trials with ALA in long term studies.
Diabetes is a common metabolic disorder that is usually accompanied by increased production of reactive oxygen species or by impaired antioxidant defenses. Importantly, oxidative stress is particularly relevant to the risk of cardiovascular disease. Alpha-lipoic acid (LA), a naturally occurring dithiol compound, has long been known as an essential cofactor for mitochondrial bioenergetic enzymes. LA is a very important micronutrient with diverse pharmacologic and antioxidant properties. Pharmacologically, LA improves glycemic control and polyneuropathies associated with diabetes mellitus; it also effectively mitigates toxicities associated with heavy metal poisoning. As an antioxidant, LA directly terminates free radicals, chelates transition metal ions, increases cytosolic glutathione and vitamin C levels, and prevents toxicities associated with their loss. These diverse actions suggest that LA acts by multiple mechanisms both physiologically and pharmacologically. Its biosynthesis decreases as people age and is reduced in people with compromised health, thus suggesting a possible therapeutic role for LA in such cases. Reviewed here is the known efficacy of LA with particular reference to types 1 and 2 diabetes. Particular attention is paid to the potential benefits of LA with respect to glycemic control, improved insulin sensitivity, oxidative stress, and neuropathy in diabetic patients. It appears that the major benefit of LA supplementation is in patients with diabetic neuropathy.
alpha-Lipoic acid, which plays an essential role in mitochondrial dehydrogenase reactions, has recently gained considerable attention as an antioxidant. Lipoate, or its reduced form, dihydrolipoate, reacts with reactive oxygen species such as superoxide radicals, hydroxyl radicals, hypochlorous acid, peroxyl radicals, and singlet oxygen. It also protects membranes by interacting with vitamin C and glutathione, which may in turn recycle vitamin E. In addition to its antioxidant activities, dihydrolipoate may exert prooxidant actions through reduction of iron. alpha-Lipoic acid administration has been shown to be beneficial in a number of oxidative stress models such as ischemia-reperfusion injury, diabetes (both alpha-lipoic acid and dihydrolipoic acid exhibit hydrophobic binding to proteins such as albumin, which can prevent glycation reactions), cataract formation, HIV activation, neurodegeneration, and radiation injury. Furthermore, lipoate can function as a redox regulator of proteins such as myoglobin, prolactin, thioredoxin and NF-kappa B transcription factor. We review the properties of lipoate in terms of (1) reactions with reactive oxygen species; (2) interactions with other antioxidants; (3) beneficial effects in oxidative stress models or clinical conditions.
Thioctic acid (alpha-lipoic acid), a natural cofactor in dehydrogenase complexes, is used in Germany in the treatment of symptoms of diabetic neuropathy. Thioctic acid improves insulin-responsive glucose utilization in rat muscle preparations and during insulin clamp studies performed in diabetic individuals. The aim of this study was to determine the direct effect of thioctic acid on glucose uptake and glucose transporters. In L6 muscle cells and 3T3-L1 adipocytes in culture, glucose uptake was rapidly increased by (R)-thioctic acid. The increment was higher than that elicited by the (S)-isomer or the racemic mixture and was comparable with that caused by insulin. In parallel to insulin action, the stimulation of glucose uptake by thioctic acid was abolished by wortmannin, an inhibitor of phosphatidylinositol 3-kinase, in both cell lines. Thioctic acid provoked an upward shift of the glucose-uptake insulin dose-response curve. The molar content of GLUT1 and GLUT4 transporters was measured in both cell lines. 3T3-L1 adipocytes were shown to have >10 times more glucose transporters but similar ratios of GLUT4:GLUT1 than L6 myotubes. The effect of (R)-thioctic acid on glucose transporters was studied in the L6 myotubes. Its stimulatory effect on glucose uptake was associated with an intracellular redistribution of GLUT1 and GLUT4 glucose transporters, similar to that caused by insulin, with minimal effects on GLUT3 transporters. In conclusion, thioctic acid stimulates basal glucose transport and has a positive effect on insulin-stimulated glucose uptake. The stimulatory effect is dependent on phosphatidylinositol 3-kinase activity and may be explained by a redistribution of glucose transporters. This is evidence that a physiologically relevant compound can stimulate glucose transport via the insulin signaling pathway.
1. Lipoic acid is an example of an existing drug whose therapeutic effect has been related to its antioxidant activity. 2. Antioxidant activity is a relative concept: it depends on the kind of oxidative stress and the kind of oxidizable substrate (e.g., DNA, lipid, protein). 3. In vitro, the final antioxidant activity of lipoic acid is determined by its concentration and by its antioxidant properties. Four antioxidant properties of lipoic acid have been studied: its metal chelating capacity, its ability to scavenge reactive oxygen species (ROS), its ability to regenerate endogenous antioxidants and its ability to repair oxidative damage. 4. Dihydrolipoic acid (DHLA), formed by reduction of lipoic acid, has more antioxidant properties than does lipoic acid. Both DHLA and lipoic acid have metal chelating capacity and scavenge ROS, whereas only DHLA is able to regenerate endogenous antioxidants and to repair oxidative damage. 5. As a metal chelator, lipoic acid was shown to provide antioxidant activity by chelating Fe2+ and CU2+; DHLA can do so by chelating Cd2+. 6. As scavengers of ROS, lipoic acid and DHLA display antioxidant activity in most experiments, whereas, in particular cases, pro oxidant activity has been observed. However, lipoic acid can act as an antioxidant against the pro oxidant activity produced by DHLA. 7. DHLA has the capacity to regenerate the endogenous antioxidants vitamin E, vitamin C and glutathione. 8. DHLA can provide peptide methionine sulfoxide reductase with reducing equivalents. This enhances the repair of oxidatively damaged proteins such as α-1 antiprotease. 9. Through the lipoamide dehydrogenase-dependent reduction of lipoic acid, the cell can draw on its NADH pool for antioxidant activity additionally to its NADPH pool, which is usually consumed during oxidative stress. 10. Within drug-related antioxidant pharmacology, lipoic acid is a model compound that enhances understanding of the mode of action of antioxidants in drug therapy.