That's not nandi's statement,although he's not a fan of ALA either.
It's not true that there's a huge difference between racemate and R+ in insulin resistant subjects in their effect on muscle glucose transport, plasma insulin, etc.... here's a comparison:
Differential effects of lipoic acid stereoisomers on glucose metabolism in insulin-resistant skeletal muscle
RYAN S. STREEPER, ERIK J. HENRIKSEN, STEPHAN JACOB, JASON Y. HOKAMA, DONOVAN L. FOGT, AND HANS J. TRITSCHLER
Streeper, Ryan S., Erik J. Henriksen, Stephan Jacob, Jason Y. Hokama, Donovan L. Fogt, and Hans J.
Tritschler. Differential effects of lipoic acid stereoisomers on glucose metabolism in insulin-resistant skeletal muscle. Am.
J. Physiol. 273 (Endocrinol. Metab. 36): El&j--E191, 1997. The racemic mixture of the antioxidant a-lipoic acid (ALA)
enhances insulin-stimulated glucose metabolism in insulin resistant humans and animals. We determined the individual
effects of the pure R-(+) and S-(-) enantiomers of ALA on glucose metabolism in skeletal muscle of an animal model of
insulin resistance, hyperinsulinemia, and dyslipidemia: the obese Zucker (falfa) rat. Obese rats were treated intraperito-
neally acutely (100 mg/kg body wt for 1 h) or chronically [IO days with 30 mg/kg of R-( +)-ALA or 50 mg/kg of S-(-)-ALA].
Glucose transport [2-deoxyglucose (2-DG) uptake], glycogen synthesis, and glucose oxidation were determined in the
epitrochlearis muscles in the absence or presence of insulin (13.3 nM).Acutely, R-(+)-ALA increased insulin-mediated
2-DG uptake by 64% (P < 0.05), whereas S-(-)-ALA had no significant effect. Although chronic R-(+)-ALA treatment
significantly reduced plasma insulin (17%) and free fatty acids (FFA; 35%) relative to vehicle-treated obese animals,
S-(-)-ALA treatment further increased insulin (15%) and had no effect on FFA. Insulin-stimulated 2-DG uptake was in-
creased by 65% by chronic R-(+)-ALA treatment whereas S-(-)-ALA administration resulted in only a 29% improve-
ment. Chronic R-(+)-ALA treatment elicited a 26% increase in insulin-stimulated glycogen synthesis and a 33% enhance-
ment of insulin-stimulated glucose oxidation.
The antioxidant alpha-lipoic acid enhances insulin-stimulated glucose metabolism in insulin-resistant rat skeletal muscle
S Jacob, RS Streeper, DL Fogt, JY Hokama, HJ Tritschler, GJ Dietze and EJ Henriksen
Department of Physiology, University of Arizona College of Medicine, Tucson, USA.
Insulin resistance of muscle glucose metabolism is a hallmark of NIDDM. The obese Zucker (fa/fa) rat--an animal model of muscle insulin resistance--was used to test whether acute (100 mg/kg body wt for 1 h) and chronic (5-100 mg/kg for 10 days) parenteral treatments with a racemic mixture of the antioxidant alpha-lipoic acid (ALA) could improve glucose metabolism in insulin-resistant skeletal muscle. Glucose transport activity (assessed by net 2-deoxyglucose [2-DG] uptake), net glycogen synthesis, and glucose oxidation were determined in the isolated epitrochlearis muscles in the absence or presence of insulin (13.3 nmol/l). Severe insulin resistance of 2-DG uptake, glycogen synthesis, and glucose oxidation was observed in muscle from the vehicle-treated obese rats compared with muscle from vehicle-treated lean (Fa/-) rats. Acute and chronic treatments (30 mg.kg-1.day-1, a maximally effective dose) with ALA significantly (P < 0.05) improved insulin-mediated 2-DG uptake in epitrochlearis muscles from the obese rats by 62 and 64%, respectively. Chronic ALA treatment increased both insulin-stimulated glucose oxidation (33%) and glycogen synthesis (38%) and was associated with a significantly greater (21%) in vivo muscle glycogen concentration. These adaptive responses after chronic ALA administration were also associated with significantly lower (15-17%) plasma levels of insulin and free fatty acids. No significant effects on glucose transporter (GLUT4) protein level or on the activities of hexokinase and citrate synthase were observed. Collectively, these findings indicate that parenteral administration of the antioxidant ALA significantly enhances the capacity of the insulin-stimulatable glucose transport system and of both oxidative and nonoxidative pathways of glucose metabolism in insulin-resistant rat skeletal muscle.
So, both have similar effects, it's not true that S- inhibits R+, that racemic increases plasma insulin, etc. so as I said I don't see any reason to stack them.
When I made a comment about its effect on insulin sensitive subjects, I was referring to:
J Appl Physiol 92: 50-58, 2002; 10.1152/japplphysiol.000617.2001
Effects of exercise training and antioxidant R-ALA on glucose transport in insulin-sensitive rat skeletal muscle
In which no effect was noticed... I did see a study in which it enhanced glucose uptake (in insulin sensitive muscle) in vitro.
