PROP sensitivity affects macronutrient selection

The objective was to study the effect of 6-n-propylthiouracyl (PROP) taster status on macronutrient selection. Thirteen PROP nontasters (PNT) and 23 PROP tasters (PT) were offered three ad libitum lunches in a random order: a high-fat (HF; CHO/P/F: 30/10/60), a high-carbohydrate (HCHO; 80/10/10), and a mixed (MIX) lunch consisting of products of the HF and HCHO lunch. PT compared to PNT ate relatively more fat (47+/-9 vs. 38+/-10%, P<.05) and less carbohydrate (45+/-9 vs. 53+/-10%, P<.05) from the MIX lunch. When dividing PT into supertasters (PST) and medium tasters (PMT), the same relation between PT status and macronutrient selection was observed (P<.05). The energy density of the food consumed was higher for PT than for PNT (P<.05). Protein, food (g) and energy (kJ) intake, appetite, and hedonic value were not different between PT and PNT. At the HCHO as well as HF lunch, no differences with respect to macronutrient selection, food and energy intake, appetite levels, and hedonic value between PT and PNT were observed. However, at the HF lunch, energy density of the food consumed was higher for PT than for PNT, but this effect was not observed during the HCHO lunch. Hunger and satiety scores did not differ between PT and PNT. The hedonic value was higher for the MIX lunch compared to the HCHO and HF lunch for PT as well as for PNT.In conclusion, PT ingest more of the HF foods than of the HCHO foods from a mixed lunch compared to PNT.     

Effect of order of exercise intensity upon cardiorespiratory,metabolic, and perceptual responses during exercise of mixed intensity

Exercise of mixed intensities can be of benefit in many different ways. However, whether physiological interaction exists between exercises of different intensity is questionable. As such, the primary aim of this study was to examine the effect of order of exercise intensity upon cardiorespiratory, metabolic, and perceptual responses during exercise of mixed intensity. Eight males and four females volunteered to serve as subjects for the study. They were informed of the purpose of the experiment and gave their written consent to participate. Each subject completed a peak oxygen uptake (O_2peak) test and two submaximal exercises of mixed intensity on three separate laboratory visits. During each submaximal exercise trial, subjects performed a 15-min (high intensity) exercise at 70%O_2peak that was followed by another 15-min (low intensity) exercise at 50%O_2peak (high/low, H/L), or a 15-min exercise at 50%O_2peak that was followed by another 15-min exercise at 70%O_2peak (low/high, L/H). Oxygen uptake (O₂), respiratory exchange ratio (R), expired ventilation (_E), heart rate (HR) and ratings of perceived exertion (RPE) were measured every 5 min throughout exercise. Energy expenditure and carbohydrate and fat oxidation were calculated from O₂ adjusted for substrate metabolism using R and then accumulated for each phase of exercise intensity as well as for the entire exercise session. O₂ and HR were higher (P<0.05), while R was lower (P<0.05) at the lower intensity in H/L than in L/H. _E and RPE were lower (P<0.05) at the higher intensity in H/L than in L/H. While no differences in caloric expenditure and carbohydrate oxidation between the two trials were observed, fat oxidation was higher (P<0.05) both at the lower intensity and for the entire trial in H/L than in L/H. It appears that during exercise of mixed intensity, placing some periods of moderate intensity exercise prior to a milder one is a more favorable sequence in that it can elicit a greater fat oxidation while being felt less stressful.     

Metabolic Response of the Cerebral Cortex Following Gentle Sleep Deprivation and Modafinil Administration

Study Objectives:

The main energy reserve of the brain is glycogen, which is almost exclusively localized in astrocytes. We previously reported that cerebral expression of certain genes related to glycogen metabolism changed following instrumental sleep deprivation in mice. Here, we extended our investigations to another set of genes related to glycogen and glucose metabolism. We also compared the effect of instrumentally and pharmacologically induced prolonged wakefulness, followed (or not) by 3 hours of sleep recovery, on the expression of genes related to brain energy metabolism.

Design:

Sleep deprivation for 6–7 hours.

Setting:

Animal sleep research laboratory.

Participants:

Adults OF1 mice.

Interventions:

Wakefulness was maintained by “gentle sleep deprivation” method (GSD) or by administration of the wakefulness-promoting drug modafinil (MOD) (200 mg/kg i.p.).

Measurements and Results:

Levels of mRNAs encoding proteins related to energy metabolism were measured by quantitative real-time PCR in the cerebral cortex. The mRNAs encoding protein targeting to glycogen (PTG) and the glial glucose transporter were significantly increased following both procedures used to prolong wakefulness. Glycogenin mRNA levels were increased only after GSD, while neuronal glucose transporter mRNA only after MOD. These effects were reversed after sleep recovery. A significant enhancement of glycogen synthase activity without any changes in glycogen levels was observed in both conditions.

Conclusions:

These results indicate the existence of a metabolic adaptation of astrocytes aimed at maintaining brain energy homeostasis during the sleep-wake cycle.

Citation:

Petit, JM; Tobler I; Kopp C; Morgenthaler F; Borbély AA; Magistretti PJ. Metabolic response of the cerebral cortex following gentle sleep deprivation and modafinil administration. SLEEP 2010;33(7):901–908.     

Behavioural mechanisms affecting energy regulation in mice prone or resistant to diet- induced obesity

We investigated inbred SWR/J and AKR/J mice, two established models for different susceptibility to diet-induced obesity (DIO), to scrutinize the contribution of physical activity and energy assimilation to the etiology of developing obesity. Body mass gain and body composition of mice fed a high-energy (HE) or a low caloric control diet were monitored. In parallel, assimilated energy, locomotor activity and thermoregulatory behaviour were measured. Activity was continuously registered by radio telemetry and, in addition, Open Field (OF) behaviour was used as a quick screening tool for spontaneous activity before and after the feeding trial. Energy assimilation was increased in both strains on HE (AKR/J: + 60.7% and SWR/J: + 42.8%) but only in AKR/J, body mass (+ 8.1%) and fat mass (+ 40.7%) were significantly elevated. As a trend, total home cage activity was increased and was more scattered in SWR/J. Interestingly, HE stimulated OF activity only in SWR/J in the second trial at the end of the feeding experiment. The spatial pattern of OF activity also differed between strains with obese mice avoiding the core area. Under housing conditions, nest building behaviour was more pronounced in AKR/J. To further evaluate OF behaviour as a marker for spontaneous activity an obese mouse line was investigated. Mice lacking the leptin receptor (db/db) showed already before the onset of obesity lowest activity levels in OF.Adjustment of energy intake, higher activity levels and energy consuming thermoregulatory behaviour are mechanisms employed by SWR/J mice to dissipate excess energy as a defence against the onset of obesity. Therefore our results deciphering mechanisms of DIO-sensitivity in mice contribute to the understanding of inter-individual differences in body weight development in an adipogenic environment.     

钉道局部点状固化技术强化椎弓根螺钉固定的生物力学研究

目的探讨钉道局部点状固化技术在体外强化椎弓根螺钉固定的效果。方法选用30个新鲜成年山羊腰椎。每一个椎体一侧椎弓根常规置钉(空白组);另一侧对钉道局部进行点状固化处理后拧入螺钉(实验组)。24h后,随机选取10个椎体行轴向拔出实验,其余20个椎体行周期抗屈实验。结果螺钉最大轴向拔出力(Fmax):空白组(637.60±109.95)N,实验组(816.50±134.88)N;螺钉拔出的能量吸收值:空白组(1.268±0.252)J,实验组(1.631±0.269)J,两组间差异均有统计学意义(P<0.05)。周期抗屈试验中,实验组的螺钉能够耐受更大的负荷或者在同等负荷下所产生的位移较小。结论钉道局部点状固化技术可以显著增加椎弓根螺钉固定的稳定性,为临床解决螺钉松动问题提供了新的研究方向,具有较好的临床应用前景。     

Energy expenditure during cane-assisted gait in patients with knee osteoarthritis

OBJECTIVE: To compare the energy expenditure in patients with unilateral knee osteoarthritis while walking with canes of different lengths. METHODS: A quasi-experimental study (single-group) was carried out on thirty patients with unilateral knee osteoarthritis. An adjustable aluminum cane was used, and three different cane lengths were determined for each subject: C1--length from the floor to the greater trochanter; C2--length from the floor to the distal wrist crease; and C3--length obtained by the formula: height x 0.45 + 0.87 m. Resting and walking heart rates were measured with a Polar hear rate meter. Walking speed was calculated by the time required for the patient to walk 10 m. Gait energy cost was estimated using the physiological cost index, and results were compared. RESULTS: The sample consisted of 25 women and five men (average age of 68 years). Statistically significant differences in physiological cost index measurements were observed between unassisted walking and assisted walking with a cane of any length (p<0.001), as well as between walking with a C2-length cane and unassisted walking, and walking with a C1-length cane and walking with a C3-length cane (p=0.001; p = 0.037; p=0.001; respectively). CONCLUSION: These data demonstrate that small alterations in the length of canes used for weight-bearing ambulation in patients with unilateral knee osteoarthritis increase the energy expenditure measured by the physiological cost index during walking. Further studies are needed for a more precise quantification of the increase in energy expenditure during cane-assisted gait and an assessment of the effectiveness of cane use in relieving pain and improving function in patients with knee osteoarthritis.     

<Superscript>31</Superscript>P magnetic resonance spectroscopy study of the human visual cortex during stimulation in mild hypoxic hypoxia

Effects of mild hypoxic hypoxia on cerebral energy state, as assessed by phosphocreatine (PCr)/γ-ATP and inorganic phosphate (P_i)/(P_i + PCr) ratios and intracellular pH (pH_i) in the human visual cortex, were studied using ³¹P nuclear magnetic resonance spectroscopy (MRS) at 3 T. The working hypothesis that, during compromised O₂ availability obtained by hypoxic hypoxia, both cerebral energy state and pH_i decline due to insufficient O₂ supply for energy metabolism was addressed. Under baseline hypoxic hypoxia, with blood O₂ saturation ranging from 0.95 to 0.83, neither the PCr/γ-ATP and P_i/(P_i + PCr) ratios nor pH_i was affected, thus, showing that cerebral energy metabolism was maintained. Contrary to the formulated hypothesis, visual stimulation during hypoxic hypoxia influenced neither the indicator ratios for energy state nor pH_i in the occipital cortex. Taking these results, together with previous observations showing that cerebral blood flow responses are the same in size both in euoxia and in hypoxia at this depth (Mintun et al. in Proc Natl Acad Sci USA 98:6859–6864, 2001; Tuunanen et al. in J Cereb Blood Flow Metab 26:263–273, 2006a), it is concluded that O₂ delivery to the brain during mild hypoxic hypoxia meets the demand by the energy metabolism both under baseline and stimulated states.     

Elovl6: a new player in fatty acid metabolism and insulin sensitivity

Obesity is a major health problem in industrialized societies often associated with diabetes, insulin resistance, and hepatic steatosis. This review addresses the hypothesis that elongation of long-chain fatty acids family member 6 (Elovl6) has an important role in energy metabolism and insulin sensitivity. Elovl6 is a microsomal enzyme involved in the elongation of saturated and monounsaturated fatty acids with 12, 14, and 16 carbons. Mice with targeted disruption in the gene for Elovl6 (Elovl6 ^−/−) are resistant to diet-induced insulin resistance despite their hepatosteatosis and obesity being similar to that of the wild-type mice. Protection against diet-induced insulin resistance in Elovl6 ^–/– mice is partially due to restoration of hepatic insulin receptor substrate-2 and suppression of hepatic protein kinase C ɛ, resulting in restoration of Akt phosphorylation. We suggest that inhibition of this elongase could be a new therapeutic approach for the treatment of insulin resistance, diabetes, cardiovascular disease, and other metabolic diseases.     

Metabolic abnormalities and hypoleptinemia in α-synuclein A53T mutant mice

Parkinson's disease (PD) patients frequently display loss of body fat mass and increased energy expenditure, and several studies have outlined a relationship between these metabolic abnormalities and disease severity, yet energy metabolism is largely unstudied in mouse models of PD. Here we characterize metabolic and physiologic responses to a high calorie diet (HCD) in mice expressing in neurons a mutant form of human α-synuclein (A53T) that causes dominantly inherited familial forms of the disease. A53T (SNCA) and wild type (WT) littermate mice were placed on a HCD for 12 weeks and evaluated for weight gain, food intake, body fat, blood plasma leptin, hunger, glucose tolerance, and energy expenditure. Results were compared with both SNCA and WT mice on a control diet. Despite consuming similar amounts of food, WT mice gained up to 66% of their original body weight on a HCD, whereas SNCA mice gained only 17%. Further, after 12 weeks on a HCD, magnetic resonance imaging analysis revealed that WT mice had significantly greater total and visceral body fat compared with SNCA mice (p < 0.007). At the age of 24 weeks SNCA mice displayed significantly increased hunger compared with WT (p < 0.03). At the age of 36 weeks, SNCA mice displayed significant hypoleptinemia compared with WT, both on a normal diet and a HCD (p < 0.03). The HCD induced insulin insensitivity in WT, but not SNCA mice, as indicated by an oral glucose tolerance test. Finally, SNCA mice displayed greater energy expenditure compared with WT, as measured in a Comprehensive Laboratory Animal Monitoring System, after 12 weeks on a HCD. Thus, SNCA mice are resistant to HCD-induced obesity and insulin resistance and display reduced body fat, increased hunger, hypoleptinemia and increased energy expenditure. Our findings reveal a profile of metabolic dysfunction in a mouse model of PD that is similar to that of human PD patients, thus providing evidence that α-synuclein pathology is sufficient to drive such metabolic abnormalities and providing an animal model for discovery of the underlying mechanisms and potential therapeutic interventions.     

Mechanical efficiency during repetitive vertical jumping

The purpose of this study was to compare mechanical efficiency between repeated static jumps (SJ), countermovement jumps (CMJ), drop jumps from 75% of maximum CMJ jump height (75DJ) and drop jumps from 125% of maximum CMJ height (125DJ). Subjects included eight jump-trained males. All subjects completed 30 continuous repetitions in the SJ, CMJ, 75DJ, and 125DJ. Oxygen consumption, peak force and center of mass displacement for each repetition during the four jumping patterns were measured. ME was calculated from a combination of force-time curves, displacement-time curves and lactate-corrected oxygen consumption values. In addition, muscle activity was recorded from the vastus medialis, vastus lateralis and biceps femoris using surface electromyography (EMG). 125DJ and 75DJ resulted in significantly (P ≤ 0.05) greater ME in comparison to CMJ and SJ. CMJ resulted in significantly greater ME in comparison to SJ. In addition, braking phase muscle activity was significantly greater in 125DJ and 75DJ in comparison to CMJ. Negative work was significantly different between 125DJ, 75DJ and CMJ (125DJ > 75DJ > CMJ). There was a significant positive correlation (r = 0.68) between ME and negative work performed across 125DJ, 75DJ and CMJ. These findings suggest that stretch-shortening cycle movements, which include a strenuous braking phase combined with simultaneous high muscle activity, increase ME. This may be due to optimal muscle-tendon unit kinetics and usage of stored elastic energy.