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Biomedical subjects

Bente Stallknecht

Publications and source records attributed to Bente Stallknecht.

7 recordsLinked to original sources
PubMed2006

Are blood flow and lipolysis in subcutaneous adipose tissue influenced by contractions in adjacent muscles in humans?

Aerobic exercise increases whole body adipose tissue lipolysis, but is lipolysis higher in subcutaneous adipose tissue (SCAT) adjacent to contracting muscles than in SCAT adjacent to resting muscles? Ten healthy, overnight-fasted males performed one-legged knee extension exercise at 25% of maximal workload (W(max)) for 30 min followed by exercise at 55% W(max) for 120 min with the other leg and finally exercised at 85% W(max) for 30 min with the first leg. Subjects rested for 30 min between exercise periods. Femoral SCAT blood flow was estimated from washout of (133)Xe, and lipolysis was calculated from femoral SCAT interstitial and arterial glycerol concentrations and blood flow. In general, blood flow and lipolysis were higher in femoral SCAT adjacent to contracting than adjacent to resting muscle (time 15-30 min; blood flow: 25% W(max) 6.6 +/- 1.0 vs. 3.9 +/- 0.8 ml x 100 g(-1) x min(-1), P < 0.05; 55% W(max) 7.3 +/- 0.6 vs. 5.0 +/- 0.6 ml x 100 g(-1) x min(-1), P < 0.05; 85% W(max) 6.6 +/- 1.3 vs. 5.9 +/- 0.7 ml x 100 g(-1) x min(-1), P > 0.05; lipolysis: 25% W(max) 102 +/- 19 vs. 55 +/- 14 nmol x 100 g(-1) x min(-1), P = 0.06; 55% W(max) 86 +/- 11 vs. 50 +/- 20 nmol x 100 g(-1) x min(-1), P > 0.05; 85% W(max) 88 +/- 31 vs. -9 +/- 25 nmol x 100 g(-1) x min(-1), P < 0.05). In conclusion, blood flow and lipolysis are generally higher in SCAT adjacent to contracting than adjacent to resting muscle irrespective of exercise intensity. Thus specific exercises can induce "spot lipolysis" in adipose tissue.

Adult↗
PubMed2005

Diet and exercise reduce low-grade inflammation and macrophage infiltration in adipose tissue but not in skeletal muscle in severely obese subjects.

Obesity is associated with low-grade inflammation, insulin resistance, type 2 diabetes, and cardiovascular disease. This study investigated the effect of a 15-wk lifestyle intervention (hypocaloric diet and daily exercise) on inflammatory markers in plasma, adipose tissue (AT), and skeletal muscle (SM) in 27 severely obese subjects (mean body mass index: 45.8 kg/m2). Plasma samples, subcutaneous abdominal AT biopsies, and vastus lateralis SM biopsies were obtained before and after the intervention and analyzed by ELISA and RT-PCR. The intervention reduced body weight (P < 0.001) and increased insulin sensitivity (homeostasis model assessment; P < 0.05). Plasma adiponectin (P < 0.001) increased, and C-reactive protein (P < 0.05), IL-6 (P < 0.01), IL-8 (P < 0.05), and monocyte chemoattractant protein-1 (P < 0.01) decreased. AT inflammation was reduced, determined from an increased mRNA expression of adiponectin (P < 0.001) and a decreased expression of macrophage-specific markers (CD14, CD68), IL-6, IL-8, and tumor necrosis factor-alpha (P < 0.01). After adjusting for macrophage infiltration in AT, only IL-6 mRNA was decreased (P < 0.05). Only very low levels of inflammatory markers were found in SM. The intervention had no effect on adiponectin receptor 1 and 2 mRNA in AT or SM. Thus hypocaloric diet and increased physical activity improved insulin sensitivity and reduced low-grade inflammation. Markers of inflammation were particularly reduced in AT, whereas SM does not contribute to this attenuation of whole body inflammation.

Adiponectin↗
PubMed2005

Effect of intermittent fasting and refeeding on insulin action in healthy men.

Insulin resistance is currently a major health problem. This may be because of a marked decrease in daily physical activity during recent decades combined with constant food abundance. This lifestyle collides with our genome, which was most likely selected in the late Paleolithic era (50,000-10,000 BC) by criteria that favored survival in an environment characterized by fluctuations between periods of feast and famine. The theory of thrifty genes states that these fluctuations are required for optimal metabolic function. We mimicked the fluctuations in eight healthy young men [25.0 +/- 0.1 yr (mean +/- SE); body mass index: 25.7 +/- 0.4 kg/m(2)] by subjecting them to intermittent fasting every second day for 20 h for 15 days. Euglycemic hyperinsulinemic (40 mU.min(-1).m(-2)) clamps were performed before and after the intervention period. Subjects maintained body weight (86.4 +/- 2.3 kg; coefficient of variation: 0.8 +/- 0.1%). Plasma free fatty acid and beta-hydroxybutyrate concentrations were 347 +/- 18 and 0.06 +/- 0.02 mM, respectively, after overnight fast but increased (P < 0.05) to 423 +/- 86 and 0.10 +/- 0.04 mM after 20-h fasting, confirming that the subjects were fasting. Insulin-mediated whole body glucose uptake rates increased from 6.3 +/- 0.6 to 7.3 +/- 0.3 mg.kg(-1).min(-1) (P = 0.03), and insulin-induced inhibition of adipose tissue lipolysis was more prominent after than before the intervention (P = 0.05). After the 20-h fasting periods, plasma adiponectin was increased compared with the basal levels before and after the intervention (5,922 +/- 991 vs. 3,860 +/- 784 ng/ml, P = 0.02). This experiment is the first in humans to show that intermittent fasting increases insulin-mediated glucose uptake rates, and the findings are compatible with the thrifty gene concept.

Adult↗
PubMed2005

No release of interstitial glutamate in experimental human model of muscle pain.

Glutamate may be released from muscle nociceptors and thereby contribute to mechanisms underlying acute and chronic muscle pain. In vivo concentration of glutamate during muscle pain has not previously been studied in either animals or humans. In the present study, we aimed to study the in vivo concentration of glutamate before, during and after acute pain of trapezius muscle in humans using the microdialysis technique. In addition, we examined the nutritive skeletal muscle blood flow and the interstitial concentrations of lactate, glucose, glycerol, pyruvate and urea. Experimental pain and tenderness were induced by intramuscular infusion of a chemical mixture consisting of bradykinin, prostaglandin E(2), histamine and serotonin. One EMG-needle and one microdialysis catheter were inserted into non-dominant and dominant trapezius muscles on a standard anatomical point in 19 healthy subjects. Dialysates were collected at rest, during infusion and 60 and 120 min after stop of infusion. Local tenderness was recorded at baseline and at the end of experiment. Local pain was recorded during infusion. The infusion of chemical mixture was more painful than infusion of placebo (p < 0.05) and resulted in significantly higher local tenderness score than placebo (p = 0.007). There was no difference in change in interstitial concentrations of glutamate, lactate, glucose, glycerol, pyruvate and urea from baseline to infusion and post-infusion periods between chemical mixture and placebo (p > 0.05). Muscle blood flow increased significantly over time in response to infusion of chemical mixture and placebo (p = 0.001). However, we found no difference in changes in muscle blood flow between chemical mixture and placebo (p > 0.05). In conclusion, the present study demonstrates no signs of increased release of glutamate from myofascial nociceptors during and after acute experimentally induced muscle pain and tenderness.

Acute Disease↗
PubMed2003

The effect of graded exercise on IL-6 release and glucose uptake in human skeletal muscle.

In this study, the hypothesis that the release of interleukin (IL)-6 from human muscle is linked to exercise intensity and muscle glucose uptake was investigated. In the overnight fasted state, seven healthy males performed knee extension exercise, kicking with both legs, each at 25 % of maximal power (W(max)) for 45 min (eliciting 23 +/- 1 % of pulmonary maximal oxygen uptake, V(O2,max)) and then simultaneously with one leg at 65 % and the other leg at 85 % W(max) for 35 min (40 +/- 1 % of pulmonary V(O2,max)). Blood was sampled from a femoral artery and both femoral veins, and blood flow was determined by thermodilution. Thigh plasma flow (0.15 +/- 0.01, 1.4 +/- 0.2, 2.0 +/- 0.1 and 2.3 +/- 0.2 l min(-1) thigh(-1) at rest and 25 %, 65 % and 85 % W(max), respectively) and thigh oxygen uptake (0.02 +/- 0.01, 0.27 +/- 0.03, 0.48 +/- 0.04 and 0.55 +/- 0.05 l min(-1) thigh(-1) at rest and 25 %, 65 % and 85 % W(max), respectively) increased with increasing exercise intensity (P < 0.05). Also, thigh IL-6 release (0.4 +/- 0.1, 1.3 +/- 0.5, 1.5 +/- 0.6 and 2.5 +/- 0.7 ng min(-1) thigh(-1) at rest and 25 %, 65 % and 85 % W(max), respectively) and thigh glucose uptake (0.05 +/- 0.01, 0.3 +/- 0.05, 0.75 +/- 0.16, 1.07 +/- 0.15 mmol min(-1) thigh(-1) at rest and 25 %, 65 % and 85 % W(max), respectively) increased with increasing exercise intensity (P < 0.05). During the last 35 min of exercise, arterial catecholamine concentrations were higher (P < 0.05) than at rest and during low-intensity exercise. During exercise, thigh IL-6 release was positively related to both thigh glucose uptake (P < 0.001) and thigh glucose delivery (P < 0.005), but not to thigh glucose extraction. Thigh IL-6 release was also positively related to arterial plasma adrenaline concentration. The pre-exercise muscle glycogen concentration tended to correlate with the arteriovenous IL-6 concentration difference at rest, and the postexercise glycogen concentration was inversely correlated with IL-6 release during the final 35 min of exercise. In conclusion, the study indicates that IL-6 release from human muscle is positively related to exercise intensity, arterial adrenaline concentration and muscle glucose uptake. This supports the hypothesis that IL-6 may be linked to the regulation of glucose homeostasis during exercise. The observation of a relationship between IL-6 release and muscle glycogen store both at rest and after exercise suggests that IL-6 may act as a carbohydrate sensor.

Adult↗
PubMed2002

Gender differences in substrate utilization during submaximal exercise in endurance-trained subjects.

Substrate utilization across the leg during 90 min of bicycle exercise at 58% of peak oxygen uptake (VO(2 peak)) was studied in seven endurance-trained males and seven endurance-trained, eumenorrheic females by applying arteriovenous catheterization, stable isotopes, and muscle biopsies. The female and male groups were matched according to VO(2 peak) per kilogram of lean body mass, physical activity level, and training history of the subjects. All subjects consumed the same diet, well controlled in terms of nutrient composition as well as energy content, for 8 days preceding the experiment, and all females were tested in the midfollicular phase of the menstrual cycle. During exercise, respiratory exchange ratio (RER) and leg respiratory quotient (RQ) were similar in females and males. Myocellular triacylglycerol (TG) degradation was negligible in males but amounted to 12.4 +/- 3.2 mmol/kg dry wt in females and corresponded to 25.0 +/- 6.0 and 5.0 +/- 7.3% of total oxygen uptake in females and males, respectively (P < 0.05). Utilization of plasma fatty acids (12.0 +/- 2.5 and 9.6 +/- 1.5%), blood glucose (13.6 +/- 1.5 and 14.3 +/- 1.5%), and glycogen (48.5 +/- 4.9 and 42.8 +/- 2.1%) were similar in females and males. Thus, in females, measured substrate oxidation accounted for 99% of the leg oxygen uptake, whereas in males 28% of leg oxygen uptake was unaccounted for in terms of measured oxidized lipid substrates. These findings may indicate that males utilized additional lipid sources, presumably very low density lipoprotein-TG or TG located between muscle fibers. On the basis of RER and leg RQ, it is concluded that no gender difference existed in the relative contribution from carbohydrate and lipids to the oxidative metabolism across the leg during submaximal exercise at the same relative workload. However, an effect of gender appears to occur in the utilization of the different lipid sources.

Adult↗