The effect of nitric oxide donor sodium nitroprusside on glucose uptake in human primary skeletal muscle cells

Nitric oxide (NO) has been implicated as an important signaling molecule in the insulin-independent, contraction-mediated glucose uptake pathway and may represent a novel strategy for blood glucose control in patients with type 2 diabetes (T2DM). The current study sought to determine whether the NO donor, sodium nitroprusside (SNP) increases glucose uptake in primary human skeletal muscle cells (HSkMC) derived from both healthy individuals and patients with T2DM. Vastus lateralis muscle cell cultures were derived from seven males with T2DM (aged 54 &plusmn; 2 years, BMI 31.7 &plusmn; 1.2 kg/m2, fasting plasma glucose 9.52 &plusmn; 0.80 mmol/L) and eight healthy individuals (aged 46 &plusmn; 2 years, BMI 27.1 &plusmn; 1.5 kg/m2, fasting plasma glucose 4.69 &plusmn; 0.12 mmol/L). Cultures were treated with both therapeutic (0.2 and 2 &mu;M) and supratherapeutic (3, 10 and 30 mM) concentrations of SNP. An additional NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP) was also examined at a concentration of 50 &mu;M. Glucose uptake was significantly increased following both 30 and 60 min incubations with the supratherapeutic SNP treatments (P = 0.03) but not the therapeutic SNP doses (P = 0.60) or SNAP (P = 0.54). There was no difference in the response between the healthy and T2DM cell lines with any treatment or dose. The current study demonstrates that glucose uptake is elevated by supratherapeutic, but not therapeutic doses of SNP in human primary skeletal muscle cells derived from both healthy volunteers and patients with T2D. These data confirm that nitric oxide donors have potential therapeutic utility to increase glucose uptake in humans, but that SNP only achieves this in supratherapeutic doses. Further study to delineate mechanisms and the therapeutic window is warranted.<br /

Frequent interruptions of sedentary time modulates contraction- and insulin-stimulated glucose uptake pathways in muscle:Ancillary analysis from randomized clinical trials

Epidemiological studies have observed associations between frequent interruptions of sitting time with physical activity bouts and beneficial metabolic outcomes, even in individuals who regularly exercise. Frequent interruptions to prolonged sitting reduce postprandial plasma glucose. Here we studied potential skeletal muscle mechanisms accounting for this improved control of glycemia in overweight adults under conditions of one day uninterrupted sitting and sitting interrupted with light-intensity or moderate-intensity walking every 20-min (n = 8); and, after three days of either uninterrupted sitting or light-intensity walking interruptions (n = 5). Contraction- and insulin-mediated glucose uptake signaling pathways as well as changes in oxidative phosphorylation proteins were examined. We showed that 1) both interventions reduce postprandial glucose concentration, 2) acute interruptions to sitting over one day stimulate the contraction-mediated glucose uptake pathway, 3) both acute interruptions to sitting with moderate-intensity activity over one day and light-intensity activity over three days induce a transition to modulation of the insulin-signaling pathway, in association with increased capacity for glucose transport. Only the moderate-intensity interruptions resulted in greater capacity for glycogen synthesis and likely for ATP production. These observations contribute to a mechanistic explanation of improved postprandial glucose metabolism with regular interruptions to sitting time, a promising preventive strategy for metabolic diseases

Effects of high-density lipoprotein elevation with cholesteryl ester transfer protein inhibition on insulin secretion

RATIONALE:: High-density lipoprotein cholesterol elevation via cholesteryl ester transfer protein (CETP) inhibition represents a novel therapy for atherosclerosis, which also may have relevance for type 2 diabetes mellitus. OBJECTIVE:: The current study assessed the effects of a CETP inhibitor on postprandial insulin, ex vivo insulin secretion, and cholesterol efflux from pancreatic β-cells. METHODS AND RESULTS:: Healthy participants received a daily dose of CETP inhibitor (n=10) or placebo (n=15) for 14 days in a randomized double-blind study. Insulin secretion and cholesterol efflux from MIN6N8 β-cells were determined after incubation with treated plasma. CETP inhibition increased plasma high-density lipoprotein cholesterol, apolipoprotein AI, and postprandial insulin. MIN6N8 β-cells incubated with plasma from CETP inhibitor-treated individuals (compared with placebo) exhibited an increase in both glucose-stimulated insulin secretion and cholesterol efflux over the 14-day treatment period. CONCLUSIONS:: CETP inhibition increased postprandial insulin and promoted ex vivo β-cell glucose-stimulated insulin secretion, potentially via enhanced β-cell cholesterol efflux

Basal and insulin-stimulated glucose uptake in cultured skeletal myotubes.

<p>Conditioned media (2% in final media volume) from <b>(a,</b> basal state; <b>b</b> insulin-stimulated<b>)</b> primary human and <b>(c,</b> basal state; <b>d</b> insulin-stimulated<b>)</b> THP-1 macrophages treated with vehicle (PBS), 75 µg/ml acLDL/10 µg/ml Sandoz compound with or without 50 µg/ml HDL for 18 hours was placed on human primary skeletal myotubes for 24 hours. Cells were treated with insulin (100 nM) or vehicle for 30 minutes before glucose uptake was measured. n = 6/group; data are presented as mean ± SEM; *indicates significantly different from Con and acLDL+HDL, P<0.05.</p

Myotube Akt phosphorylation, human primary macrophage cholesterol content and THP-1 macrophage JNK phosphorylation. (a)

<p>Phosphorylation of Akt at Serine-473 in human primary skeletal myotubes treated as for <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0056601#pone-0056601-g001" target="_blank">Figure 1</a>, n = 6/group. <b>(b)</b> Total intracellular cholesterol (free cholesterol and cholesteryl esters) in human primary macrophages after treatment with vehicle (PBS) or 75 µg/ml acLDL/10 µg/ml Sandoz with or without 50 µg/ml HDL for 18 hours, n = 6/group. <b>(c)</b> Phosphorylation of JNK in THP-1 macrophages treated with vehicle or 75 µg/ml acLDL/10 µg/ml Sandoz with or without 50 µg/ml HDL for 1, 2 and 4 hours. n = 9/group; data are presented as mean ± SEM; *indicates significantly different from Con at the corresponding time point, P<0.05.</p

Fold-change in UCP1 protein content post-differentiation compared with pre-differentiation (n = 4, L; Lean, O; Obese; *P<0.05 vs pre-differentiation, † P<0.05 vs Obese post-differentiation, pre-differentiation normalized to 1.0).

<p>Fold-change in UCP1 protein content post-differentiation compared with pre-differentiation (n = 4, L; Lean, O; Obese; *P<0.05 vs pre-differentiation, † P<0.05 vs Obese post-differentiation, pre-differentiation normalized to 1.0).</p