Metabolic effects of gamma-linolenic acid-alpha-lipoic acid conjugate in streptozotocin diabetic rats.
Data suggesting the involvement of increased oxidative stress in the pathophysiology of diabetes has raised interest in the potential therapeutic benefit of antioxidants. Although beneficial metabolic effects of antioxidant supplementation have been suggested, an antioxidant mode of action, particularly in skeletal muscle, has not been documented. In the present study, we evaluate the metabolic effects of a gamma-linolenic acid-alpha-lipoic acid conjugate (GLA-LA) in streptozotocin-induced diabetic rats, and assess its potential mode of action by comparing its effects with equimolar administration of LA and GLA alone. Ten days of oral supplementation of 20 mg/kg body weight GLA-LA, but not LA or GLA alone, caused a mild reduction in fasting blood glucose concentration as compared with vehicle-treated diabetic rats (375 +/- 11 vs. 416 +/- 16 mg/dl, p = 0.03), with no change in fasting plasma insulin levels. A peripheral insulin-sensitizing effect could be observed with GLA-LA, LA, and GLA treatments, as demonstrated by a significant (p < 0.04) 23%, 13%, and 10% reduction, respectively, in the area under the glucose curve following an intravenous insulin tolerance test. This effect was associated with a 67% and 50% increase in GLUT4 protein content in the membranes of gastrocnemius muscle of GLA-LA and LA-treated animals, respectively; however, no change was observed with GLA treatment alone. Interestingly, both GLA-LA and LA treatments corrected a diabetes-related decrease in the gastrocnemius muscle low-molecular-weight reduced thiols content. These data demonstrate insulin-sensitizing properties of the GLA-LA conjugate by distinct mechanisms attributable to each of its components, which are associated with antioxidant effects.
Department of Clinical Biochemistry, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
M
M
Khamaisi
A
A
Rudich
I
I
Beeri
D
D
Pessler
M
M
Friger
V
V
Gavrilov
H
H
Tritschler
N
N
Bashan
D000818:Animals; D000975:Antioxidants / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D001786:Blood Glucose / Q000032:analysis; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000097:blood / Q000494:pharmacology; D008099:Liver / Q000737:chemistry; D009004:Monosaccharide Transport Proteins / Q000032:analysis; D009124:Muscle Proteins; D018482:Muscle, Skeletal / Q000737:chemistry; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D012313:RNA / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013438:Sulfhydryl Compounds / Q000737:chemistry; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D008063:Thioctic Acid / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*; D017965:gamma-Linolenic Acid / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*
D000975:Antioxidants; D001786:Blood Glucose; D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat; D013438:Sulfhydryl Compounds; D017392:Thiobarbituric Acid Reactive Substances; D012313:RNA; D008063:Thioctic Acid; D017965:gamma-Linolenic Acid