Effect of acarbose versus sulfonylurea therapy on insulin sensitivity: An insulin clamp study

RETRACTED: Acarbose on insulin resistance after an oral fat load: a double-blind, placebo controlled study

AIM

We evaluated the effects of acarbose on insulin resistance parameters in diabetic patients before and after a standardized oral fat load (OFL).

MATERIALS AND METHODS

Patients were assigned to take acarbose 50 mg three times a day or placebo; after the first month, acarbose was titrated to 100 mg three times a day. We evaluated body mass index, glycemic control, fasting plasma insulin (FPI), post-prandial plasma insulin (PPI), homeostasis model assessment insulin resistance index (HOMA-IR), blood pressure, lipid profile, retinol binding protein-4 (RBP-4), adiponectin (ADN), tumor necrosis factor-α and resistin (r). Furthermore, at the baseline and at the end of the study, all patients underwent an OFL and an euglycemic hyperinsulinemic clamp.

RESULTS

We observed that acarbose was better than placebo in improving glycemic control and HOMA-IR and that it was also more effective in improving lipid profile, RBP-4 and ADN. Regarding FPI, PPI and r, we did not obtain any significant differences between the two groups. During the second OFL, performed after 7 months of therapy with acarbose, we observed a significant decrease of blood glucose, lipid profile and all insulin resistance parameters peaks compared with the OFL administered at baseline with acarbose, but not with placebo.

CONCLUSION

Acarbose was more effective than placebo in improving glycemic and lipid profile and in reducing the post-OFL peaks of the various parameters including the insulin resistance biomarkers.

Combined use of liquid chromatography–nuclear magnetic resonance spectroscopy and liquid chromatography–mass spectrometry for the characterization of an acarbose degradation product

Directly coupled LC-MS and LC-NMR were applied to identify and structurally characterize an acarbose degradation product A in acidic media. A comparative analysis of the stop-flow LC-NMR (1H and TOCSY) and LC-MS data provided evidence that A is structurally related to acarbose, differing from the parent compound in a number of subunits present in the molecule. Spectral analysis revealed that A was the alpha-glucosidase inhibitor amylostatin XG. Complementary information obtained from the two methods led to the structural elucidation of A which was later corroborated by high-resolution NMR spectroscopy of the isolated molecule.

Effect of Herbal Medicines on Cytokine-Induced Cytotoxicity and Major Histocompatibility Complex (MHC) Class II Antigen Expression in Rat Thyroid Cells

The effects of herbal medicines that constitute Gam-du-tang and Gung-gui-tang on cytokine-induced cytotoxicity and thyroid major histocompatibility complex (MHC) class II antigen expression in FRTL rat thyrocytes were investigated. No effect on cell growth was found with interferon (IFN)-gamma. However, tumor necrosis factor (TNF)-alpha was cytotoxic, and this was increased by preincubation with IFN-gamma. Ethanol extract of Glycyrrhizae Radix, black beans, Angelicae Radix, and Cnidii Rhizoma (0.3-15 mg/ml) in both regimens significantly inhibited IFN-gamma and TNF-alpha-mediated cytotoxicity of rat thyroid cells (p<0.05, p<0.01). In addition, IFN-gamma (1-100 U/ml) treatment induced class II antigen expression in up to 60% of FRTL cells, as detected by a murine monoclonal antibody to rat MHC class II antigen (FITC-OX6). Aberrant thyroid cell MHC class II antigen expression induced by IFN-gamma is suppressed by the extract of herbal medicines. These results indicate that herbal medicines inhibit cytokine-induced thyroid cell destruction, therefore, may have therapeutic potential in the treatment of autoimmune thyroid disease.

Effects of a Combination of Traditional Chinese Botanicals (Immune+) on the Secretion of Interleukin-1beta and Interferon-gamma by Peripheral Blood Mononuclear Cells

The use of herbal and other botanical products, including those used extensively in traditional Chinese medicine, has increased dramatically in the last decade. Yet, little scientific research exists concerning their efficacy and safety. We examined the effects of Immune+, a combination of five botanicals frequently used in traditional Chinese medicine, on the production of two cytokines. For this purpose, unstimulated or phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells from healthy volunteers were incubated with different concentrations of Immune+. The secretion of interleukin-1beta (IL-1beta) and interferon-gamma (IFN-gamma) was measured after 72 hours of incubation. At the highest concentration tested (100 micro g/ml), Immune+ significantly increased the secretion of IL-1beta. Importantly, PHA alone had no effect on IL-1beta production, and the combination of PHA with Immune+ resulted in the same increase in IL-1beta production as seen with the botanical extract alone. Immune+ did not have any detectable effect on either unstimulated or PHA-stimulated IFN-gamma synthesis. These in vitro data support the concept that Immune+ may enhance human immune responses.