Lipid-induced insulin resistance affects women less than men and is not accompanied by inflammation or impaired proximal insulin signaling.

OBJECTIVE: We have previously shown that overnight fasted women have higher insulin-stimulated whole body and leg glucose uptake despite a higher intramyocellular triacylglycerol concentration than men. Women also express higher muscle mRNA levels of proteins related to lipid metabolism than men. We therefore hypothesized that women would be less prone to lipid-induced insulin resistance. RESEARCH DESIGN AND METHODS: Insulin sensitivity of whole-body and leg glucose disposal was studied in 16 young well-matched healthy men and women infused with intralipid or saline for 7 h. Muscle biopsies were obtained before and during a euglycemic-hyperinsulinemic clamp (1.42 mU · kg⁻¹ · min⁻¹). RESULTS: Intralipid infusion reduced whole-body glucose infusion rate by 26% in women and 38% in men (P < 0.05), and insulin-stimulated leg glucose uptake was reduced significantly less in women (45%) than men (60%) after intralipid infusion. Hepatic glucose production was decreased during the clamp similarly in women and men irrespective of intralipid infusion. Intralipid did not impair insulin or AMPK signaling in muscle and subcutaneous fat, did not cause accumulation of muscle lipid intermediates, and did not impair insulin-stimulated glycogen synthase activity in muscle or increase plasma concentrations of inflammatory cytokines. In vitro glucose transport in giant sarcolemmal vesicles was not decreased by acute exposure to fatty acids. Leg lactate release was increased and respiratory exchange ratio was decreased by intralipid. CONCLUSIONS: Intralipid infusion causes less insulin resistance of muscle glucose uptake in women than in men. This insulin resistance is not due to decreased canonical insulin signaling, accumulation of lipid intermediates, inflammation, or direct inhibition of GLUT activity. Rather, a higher leg lactate release and lower glucose oxidation with intralipid infusion may suggest a metabolic feedback regulation of glucose metabolism.

Behavioral neurocardiac training in hypertension: a randomized, controlled trial.

It is not established whether behavioral interventions add benefit to pharmacological therapy for hypertension. We hypothesized that behavioral neurocardiac training (BNT) with heart rate variability biofeedback would reduce blood pressure further by modifying vagal heart rate modulation during reactivity and recovery from standardized cognitive tasks ("mental stress"). This randomized, controlled trial enrolled 65 patients with uncomplicated hypertension to BNT or active control (autogenic relaxation), with six 1-hour sessions over 2 months with home practice. Outcomes were analyzed with linear mixed models that adjusted for antihypertensive drugs. BNT reduced daytime and 24-hour systolic blood pressures (-2.4+/-0.9 mm Hg, P=0.009, and -2.1+/-0.9 mm Hg, P=0.03, respectively) and pulse pressures (-1.7+/-0.6 mm Hg, P=0.004, and -1.4+/-0.6 mm Hg, P=0.02, respectively). No effect was observed for controls (P>0.10 for all indices). BNT also increased RR-high-frequency power (0.15 to 0.40 Hz; P=0.01) and RR interval (P<0.001) during cognitive tasks. Among controls, high-frequency power was unchanged (P=0.29), and RR interval decreased (P=0.03). Neither intervention altered spontaneous baroreflex sensitivity (P>0.10). In contrast to relaxation therapy, BNT with heart rate variability biofeedback modestly lowers ambulatory blood pressure during wakefulness, and it augments tonic vagal heart rate modulation. It is unknown whether efficacy of this treatment can be improved with biofeedback of baroreflex gain. BNT, alone or as an adjunct to drug therapy, may represent a promising new intervention for hypertension.

Vitamin E isoform-specific inhibition of the exercise-induced heat shock protein 72 expression in humans.

Increased levels of reactive oxygen and nitrogen species, as seen in response to exercise, challenge the cellular integrity. Important protective adaptive changes include induction of heat shock proteins (HSPs). We hypothesized that supplementation with antioxidant vitamins C (ascorbic acid) and E (tocopherol) would attenuate the exercise-induced increase of HSP72 in the skeletal muscle and in the circulation. Using randomization, we allocated 21 young men into three groups receiving one of the following oral supplementations: RRR-alpha-tocopherol 400 IU/day + ascorbic acid (AA) 500 mg/day (CEalpha), RRR-alpha-tocopherol 290 IU/day + RRR-gamma-tocopherol 130 IU/day + AA 500 mg/day (CEalphagamma), or placebo (Control). After 28 days of supplementation, the subjects performed 3 h of knee extensor exercise at 50% of the maximal power output. HSP72 mRNA and protein content was determined in muscle biopsies obtained from vastus lateralis at rest (0 h), postexercise (3 h), and after a 3-h recovery (6 h). In addition, blood was sampled for measurements of HSP72, alpha-tocopherol, gamma-tocopherol, AA, and 8-iso-prostaglandin-F2alpha (8-PGF2alpha). Postsupplementation, the groups differed with respect to plasma vitamin levels. The marker of lipid peroxidation, 8-iso-PGF2alpha, increased from 0 h to 3 h in all groups, however, markedly less (P < 0.05) in CEalpha. In Control, skeletal muscle HSP72 mRNA content increased 2.5-fold (P < 0.05) and serum HSP72 protein increased 4-fold (P < 0.05) in response to exercise, whereas a significant increase of skeletal muscle HSP72 protein content was not observed (P = 0.07). In CEalpha, skeletal muscle HSP72 mRNA, HSP72 protein, and serum HSP72 were not different from Control in response to exercise. In contrast, the effect of exercise on skeletal muscle HSP72 mRNA and protein, as well as circulating HSP72, was completely blunted in CEalphagamma. The results indicate that gamma-tocopherol comprises a potent inhibitor of the exercise-induced increase of HSP72 in skeletal muscle as well as in the circulation.

Supplementation with vitamins C and E inhibits the release of interleukin-6 from contracting human skeletal muscle.

Contracting human skeletal muscle is a major contributor to the exercise-induced increase of plasma interleukin-6 (IL-6). Although antioxidants have been shown to attenuate the exercise-induced increase of plasma IL-6, it is unknown whether antioxidants inhibit transcription, translation or translocation of IL-6 within contracting human skeletal muscle. Using a single-blind placebo-controlled design with randomization, young healthy men received an oral supplementation with either a combination of ascorbic acid (500 mg day(-1)) and RRR-alpha-tocopherol (400 i.u. day(-1)) (Treatment, n= 7), or placebo (Control, n= 7). After 28 days of supplementation, the subjects performed 3 h of dynamic two-legged knee-extensor exercise at 50% of their individual maximal power output. Muscle biopsies from vastus lateralis were obtained at rest (0 h), immediately post exercise (3 h) and after 3 h of recovery (6 h). Leg blood flow was measured using Doppler ultrasonography. Plasma IL-6 concentration was measured in blood sampled from the femoral artery and vein. The net release of IL-6 was calculated using Fick's principle. Plasma vitamin C and E concentrations were elevated in Treatment compared to Control. Plasma 8-iso-prostaglandin F(2alpha), a marker of lipid peroxidation, increased in response to exercise in Control, but not in Treatment. In both Control and Treatment, skeletal muscle IL-6 mRNA and protein levels increased between 0 and 3 h. In contrast, the net release of IL-6 from the leg, which increased during exercise with a peak at 3.5 h in Control, was completely blunted during exercise in Treatment. The arterial plasma IL-6 concentration from 3 to 4 h, when the arterial IL-6 levels peaked in both groups, was approximately 50% lower in the Treatment group compared to Control (Treatment versus Control: 7.9 pg ml(-1), 95% confidence interval (CI) 6.0-10.7 pg ml(-1), versus 19.7 pg ml(-1), CI 13.8-29.4 pg ml(-1), at 3.5 h, P < 0.05 between groups). Moreover, plasma interleukin-1 receptor antagonist (IL-1ra), C-reactive protein and cortisol levels all increased after the exercise in Control, but not in Treatment. In conclusion, our results show that supplementation with vitamins C and E attenuated the systemic IL-6 response to exercise primarily via inhibition of the IL-6 protein release from the contracting skeletal muscle per se.

Interleukin-6 stimulates lipolysis and fat oxidation in humans.

Although IL-6 is a key modulator of immune function, it also plays a role in regulating substrate metabolism. To determine whether IL-6 affects lipid metabolism, 18 healthy men were infused for 3 h with saline (Con; n = 6) or a high dose (High-rhIL6; n = 6) or a low dose (Low-rhIL6; n = 6) of recombinant human IL-6 (rhIL-6). The IL-6 concentration during Con, Low-rhIL6, and High-rhIL6 was at a steady state after 30 min of infusion at approximately 4, 140, and 320 pg/ml, respectively. Either dose of rhIL-6 was associated with a similar increase in fatty acid (FA) concentration and endogenous FA rate of appearance (R(a)) from 90 min after the start of the infusion. The FA concentration and FA R(a) continued to increase until the cessation of rhIL-6 infusion, reaching levels approximately 50% greater than Con values. The elevated levels reached at the end of rhIL-6 infusion persisted at least 3 h postinfusion. Triacylglycerol concentrations were unchanged during rhIL-6 infusion, whereas whole body fat oxidation increased after the second hour of rhIL-6 infusion. Of note, during Low-rhIL6, the induced elevation in FA concentration and FA R(a) occurred in the absence of any change in adrenaline, insulin, or glucagon, and no adverse side effects were observed. In conclusion, the data identify IL-6 as a potent modulator of fat metabolism in humans, increasing fat oxidation and FA reesterification without causing hypertriacylglyceridemia.

Exercise-induced immunodepression- plasma glutamine is not the link.

The amino acid glutamine is known to be important for the function of some immune cells in vitro. It has been proposed that the decrease in plasma glutamine concentration in relation to catabolic conditions, including prolonged, exhaustive exercise, results in a lack of glutamine for these cells and may be responsible for the transient immunodepression commonly observed after acute, exhaustive exercise. It has been unclear, however, whether the magnitude of the observed decrease in plasma glutamine concentration would be great enough to compromise the function of immune cells. In fact, intracellular glutamine concentration may not be compromised when plasma levels are decreased postexercise. In addition, a number of recent intervention studies with glutamine feeding demonstrate that, although the plasma concentration of glutamine is kept constant during and after acute, strenuous exercise, glutamine supplementation does not abolish the postexercise decrease in in vitro cellular immunity, including low lymphocyte number, impaired lymphocyte proliferation, impaired natural killer and lymphokine-activated killer cell activity, as well as low production rate and concentration of salivary IgA. It is concluded that, although the glutamine hypothesis may explain immunodepression related to other stressful conditions such as trauma and burn, plasma glutamine concentration is not likely to play a mechanistic role in exercise-induced immunodepression.