Effects of dietary fat and conjugated linoleic acid on plasma metabolite concentrations and metabolic responses to homeostatic signals in pigs

Sixteen female cross-bred (Large White × Landrace) pigs (initial weight 65 kg) with venous catheters were randomly allocated to four treatment groups in a 2×2 factorial design. The respective factors were dietary fat (25 or 100 g/kg) and dietary conjugated linoleic acid (CLA; 0 or 10 g CLA-55/kg). Pigs were fed every 3 h (close to ad libitum digestible energy intake) for 8 d and were bled frequently. Plasma glucose and non-esterified fatty acid (NEFA) responses to insulin and adrenaline challenges were determined on day 8. Plasma concentrations of NEFA were significantly increased (10·5 and 5·4 % for low- and high-fat diets respectively, P=0·015) throughout the experiment, suggesting that there was a possible increase in fat mobilisation. The increase in lipolysis, an indicator of ß-adrenergic stimulated lipolysis, was also evident in the NEFA response to adrenaline. However, the increase in plasma triacylglycerol (11·0 and 7·1 % for low- and high-fat diets respectively, P=0·008) indicated that CLA could have reduced fat accretion via decreased adipose tissue triacylglycerol synthesis from preformed fatty acids, possibly through reduced lipoprotein lipase activity. Plasma glucose, the primary substrate for de novo lipid synthesis, and plasma insulin levels were unaffected by dietary CLA suggesting that de novo lipid synthesis was largely unaffected (P=0·24 and P=0·30 respectively). In addition, the dietary CLA had no effect upon the ability of insulin to stimulate glucose removal.

The stress and metabolic responses of juvenile Atlantic cod Gadus morhua L. to an acute thermal challenge

Survival, oxygen consumption (M_O2), total plasma cortisol and glucose levels and gill heat-shock protein 70 (hsp70) expression were measured in 10 and 50 g juvenile Atlantic cod Gadus morhua during an acute temperature increase (2° C h⁻¹) to their critical thermal maximum. Ninety three per cent of the fish in both size classes survived to 24° C; however, mortality was 100% within 15 min of reaching this temperature. The M_O2 for both size classes increased significantly with temperature, reaching peak values at 22° C that were c. 2·8-fold those of control (10° C) fish. Resting plasma cortisol and glucose levels were lower in 10 g as compared to 50 g fish. Plasma glucose levels were highly variable in both size classes, and significant increases were only seen at >22° C for the 10 g fish. In contrast, plasma cortisol showed an exponential increase with temperature starting at 16° C in both size classes, and reached maximum levels at 22° C that were 19-fold (10 g fish) and 35-fold (50 g fish) higher than their respective control groups. Both the constitutive (73 kDa) and inducible (72 kDa) isoforms of hsp70 were detected in both size classes using the widely utilized mouse monoclonal antibody. Expression of these isoforms, however, did not change when Atlantic cod were exposed to elevated temperature, and the 72 kDa isoform was not detected using salmonid-specific antibodies. These results indicate that juvenile Atlantic cod are very sensitive to acute increases in water temperature. In addition, they (1) show that M_O2and plasma cortisol, but not plasma glucose or gill hsp 70 levels, are sensitive indicators of thermal stress in Atlantic cod and (2) support previous reports that the upper critical temperature for this species is 16° C.

Hormonal and metabolic responses to repeated cycling sprints under different hypoxic conditions

OBJECTIVE: Sprint exercise and hypoxic stimulus during exercise are potent factors affecting hormonal and metabolic responses. However, the effects of different hypoxic levels on hormonal and metabolic responses during sprint exercise are not known. Here, we examined the effect of different hypoxic conditions on hormonal and metabolic responses during sprint exercise. DESIGN: Seven male subjects participated in three experimental trials: 1) sprint exercise under normoxia (NSE); 2) sprint exercise under moderate normobaric hypoxia (16.4% oxygen) (HSE 16.4); and 3) sprint exercise under severe normobaric hypoxia (13.6% oxygen) (HSE 13.6). The sprint exercise consisted of four 30s all-out cycling bouts with 4-min rest between bouts. Glucose, free fatty acids (FFA), blood lactate, growth hormone (GH), epinephrine (E), norepinephrine (NE), and insulin concentrations in the HSE trials were measured before exposure to hypoxia (pre 1), 15 min after exposure to hypoxia (pre 2), and at 0, 15, 30, 60, 120, and 180 min after the exercise performed in hypoxia. The blood samples in the NSE trial were obtained in normoxia at the same time points as the HSE trials. RESULTS: Circulating levels of glucose, FFA, lactate, GH, E, NE, and insulin significantly increased after all three exercise trials (P < 0.05). The area under the curve (AUC) for GH was significantly higher in the HSE 13.6 trial than in the NSE and HSE 16.4 trials (P < 0.05). A maximal increase in FFA concentration was observed at 180 min after exercise and was not different between trials. CONCLUSION: These findings suggest that severe hypoxia may be an important factor for the enhancement of GH response to all-out sprint exercise.

Physiological response to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups : metabolic rates, energy reserve utilization, and water fluxes

Physiological response to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups: metabolic rates, energy reserve utilization, and water fluxes. Am J Physiol Regul Integr Comp Physiol 297: R1582–R1592, 2009. First published September 23, 2009; doi:10.1152/ajpregu.90857.2008.— Surviving prolonged fasting requires various metabolic adaptations, such as energy and protein sparing, notably when animals are simultaneously engaged in energy-demanding processes such as growth. Due to the intermittent pattern of maternal attendance, subantarctic fur seal pups have to repeatedly endure exceptionally long fasting episodes throughout the 10-mo rearing period while preparing for nutritional independence. Their metabolic responses to natural prolonged fasting (33.4 ± 3.3 days) were investigated at 7 mo of age. Within 4–6 fasting days, pups shifted into a stage of metabolic economy characterized by a minimal rate of body mass loss (0.7%/day) and decreased resting metabolic rate  (5.9 ± 0.1 ml O₂ ·kg^-1·day^-1) that was only 10% above the level predicted for adult terrestrial mammals. Field metabolic rate (289 ± 10 kJ·kg^-1 ·day^-1) and water influx (7.9 ± 0.9 ml·kg^-1 ·day^-1) were also among the lowest reported for any young otariid, suggesting minimized energy allocation to behavioral activity and thermoregulation. Furthermore, lean tissue degradation was dramatically reduced. High initial adiposity (>48%) and predominant reliance on lipid catabolism likely contributed to the exceptional degree of protein sparing attained. Blood chemistry supported these findings and suggested utilization of alternative fuels, such as β-hydroxybutyrate and de novo synthesized glucose from fat-released glycerol. Regardless of sex and body condition, pups tended to adopt a convergent strategy of extreme energy and lean body mass conservation that appears highly adaptive for it allows some tissue growth during the repeated episodes of prolonged fasting they experience throughout their development.

Impact of in vivo fatty acid oxidation blockade on glucose turnover and muscle glucose metabolism during low-dose AICAR infusion

AMPK plays a central role in influencing fuel usage and selection. The aim of this study was to analyze the impact of low-dose AMP analog 5-aminoimidazole-4-carboxamide-1-ß-D-ribosyl monophosphate (ZMP) on whole body glucose turnover and skeletal muscle (SkM) glucose metabolism. Dogs were restudied after prior 48-h fatty acid oxidation (FAOX) blockade by methylpalmoxirate (MP; 5 x 12 hourly 10 mg/kg doses). During the basal equilibrium period (0–150 min), fasting dogs (n = 8) were infused with [3-³H]glucose followed by either 2-h saline or AICAR (1.5–2.0 mg·kg^–1·min^–1) infusions. SkM was biopsied at completion of each study. On a separate day, the same protocol was undertaken after 48-h in vivo FAOX blockade. The AICAR and AICAR + MP studies were repeated in three chronic alloxan-diabetic dogs. AICAR produced a transient fall in plasma glucose and increase in insulin and a small decline in free fatty acid (FFA). Parallel increases in hepatic glucose production (HGP), glucose disappearance (Rd tissue), and glycolytic flux (GF) occurred, whereas metabolic clearance rate of glucose (MCR_g) did not change significantly. Intracellular SkM glucose, glucose 6-phosphate, and glycogen were unchanged. Acetyl-CoA carboxylase (ACC~pSer²²¹) increased by 50%. In the AICAR + MP studies, the metabolic responses were modified: the glucose was lower over 120 min, only minor changes occurred with insulin and FFA, and HGP and Rd tissue responses were markedly attenuated, but MCR_g and GF increased significantly. SkM substrates were unchanged, but ACC~pSer²²¹ rose by 80%. Thus low-dose AICAR leads to increases in HGP and SkM glucose uptake, which are modified by prior FA_ox blockade.

New techniques and issues in assessing walking behavior and its contexts

In the first section of this article, we discuss the metabolic responses to walking by describing the economy of walking during different locomotion velocities. Gender, weight status, and growth effects on metabolic responses to walking are reviewed. In the second section, we examine the use of technology to assess walking patterns and behavior in the community. We use an engineering approach for understanding how to measure objects that move, and these methods are used to assess walking used in transportation. In the third part of the paper, we summarize self-report methods that have been used to assess walking behavior and highlight the strengths and weaknesses of these methods. We illustrate how self-report methods are used to quantify walking behavior in the surveillance systems that are now widely used to ascertain walking prevalence and temporal changes in different populations. In the final section, we discuss ways of measuring the walkability of neighborhoods and the community to understand the influence of the built environment on walking behavior.

Sucrose as an added sweetener in diabetes mellitus

For many years the Diabetes Associations of several countries have recommended the dietary elimination of added sucrose. However, contrary to popular belief, there is no evidence that modest use of added sucrose is detrimental to diabetic control. In this study of 17 non-insulin dependent diabetics, the medium-term metabolic effects of the daily supplementation of a subject's usual diet with either 28 g of sucrose or with saccharin and starch of equivalent sweetener and energy value, were compared over six-week periods. Neither dietary period had any significant effect on fasting concentrations of blood glucose, plasma insulin, GIP or serum triglyceride. The metabolic responses to two different test meals, consisting of a standard breakfast supplemented with either sucrose or saccharin plus starch, did not differ significantly either between test meals or between dietary periods. Similarly neither dietary period had any significant effect on urinary excretion of glucose. Na+ or K+. There was no significant difference in mean blood pressure between dietary periods.

The results of this medium-term study indicate that there are no metabolic contraindications to including a moderate amount of sucrose (up to 28 g e 7 teaspoons) in the diets of patients with non-insulin dependent diabetes mellitus.

Cycling time to failure is better maintained by cold than contrast or thermoneutral lower-body water immersion in normothermia

Purpose
To examine the effects of four commonly used recovery treatments applied between two bouts of intense endurance cycling on the performance of the second bout in normothermia (~21 °C).

Methods
Nine trained men completed two submaximal exhaustive cycling bouts (Ex1 and Ex2: 5 min at ~50 % V˙O2 peak, followed by 5 min at ~60 % V˙O2 peak and then ~80 % V˙O2 peak to failure) separated by 30 min of (a) cold water immersion at 15 °C (C15), (b) contrast water therapy alternating 2.5 min at 8 °C and 2.5 min at 40 °C (CT), (c) thermoneutral water immersion at 34 °C (T34) and (d) cycling at ~40 % V˙O2 peak (AR).

Results
Exercise performance, cardiovascular and metabolic responses during Ex1 were similar among all trials. However, time to failure (~80 % V˙O2 peak bout) during Ex2 was significantly (P < 0.05) longer in C15 (18.0 ± 1.6) than in CT (14.5 ± 1.5), T34 (12.4 ± 1.4) and AR (10.6 ± 1.0); and it was also longer (P < 0.05) in CT than AR. Core temperature and heart rate were significantly (P < 0.05) lower during the initial ~15 min of Ex2 during C15 compared with all other conditions but they reached similar levels at the end of Ex2.

Conclusions
A 30 min period of C15 was more beneficial in maintaining intense submaximal cycling performance than CT, T34 and AR; and CT was also more beneficial than T34 and AR. These effects were not mediated by the effect of water immersion per se, but by the continuous (C15) or intermittent (CT) temperature stimulus (cold) applied throughout the recovery.

Predictors and risks of body fat profiles in young New Zealand European, Māori and Pacific women: study protocol for the women's EXPLORE study.

Body mass index (BMI) (kg/m(2)) is used internationally to assess body mass or adiposity. However, BMI does not discriminate body fat content or distribution and may vary among ethnicities. Many women with normal BMI are considered healthy, but may have an unidentified "hidden fat" profile associated with higher metabolic disease risk. If only BMI is used to indicate healthy body size, it may fail to predict underlying risks of diseases of lifestyle among population subgroups with normal BMI and different adiposity levels or distributions. Higher body fat levels are often attributed to excessive dietary intake and/or inadequate physical activity. These environmental influences regulate genes and proteins that alter energy expenditure/storage. Micro ribonucleic acid (miRNAs) can influence these genes and proteins, are sensitive to diet and exercise and may influence the varied metabolic responses observed between individuals. The study aims are to investigate associations between different body fat profiles and metabolic disease risk; dietary and physical activity patterns as predictors of body fat profiles; and whether these risk factors are associated with the expression of microRNAs related to energy expenditure or fat storage in young New Zealand women. Given the rising prevalence of obesity globally, this research will address a unique gap of knowledge in obesity research.

Breaking up of prolonged sitting over three days sustains, but does not enhance, lowering of postprandial plasma glucose and insulin in overweight and obese adults

To compare the cumulative (3-day) effect of prolonged sitting on metabolic responses during a mixed meal tolerance test (MTT), with sitting that is regularly interrupted with brief bouts of light-intensity walking. Overweight/obese adults (n=19) were recruited for a randomized, 3-day, outpatient, cross-over trial involving: (1) 7-h days of uninterrupted sitting (SIT); and (2) 7-h days of sitting with light-intensity activity breaks [BREAKS; 2-min of treadmill walking (3.2 km/h) every 20 min (total: 17 breaks/day)]. On days 1 and 3, participants underwent a MTT (75 g of carbohydrate, 50 g of fat) and the incremental area under the curve (iAUC) was calculated from hourly blood samples. Generalized estimating equation (GEE) models were adjusted for gender, body mass index (BMI), energy intake, treatment order and pre-prandial values to determine effects of time, condition and time × condition. The glucose iAUC was 1.3 ± 0.5 and 1.5 ± 0.5 mmol·h·l(-1) (mean differences ± S.E.M.) higher in SIT compared with BREAKS on days 1 and 3 respectively (condition effect: P=0.001), with no effect of time (P=0.48) or time × condition (P=0.8). The insulin iAUC was also higher on both days in SIT (day 1: ∆151 ± 73, day 3: ∆91 ± 73 pmol·h·l(-1), P=0.01), with no effect of time (P=0.52) or time × condition (P=0.71). There was no between-treatment difference in triglycerides (triacylglycerols) iAUC. There were significant between-condition effects but no temporal change in metabolic responses to MTT, indicating that breaking up of sitting over 3 days sustains, but does not enhance, the lowering of postprandial glucose and insulin.

Effects of ingesting low glycemic index carbohydrate food for the sahur meal on subjective, metabolic and physiological responses, and endurance performance in Ramadan fasted men

To investigate the effect of low glycemic index (LGI) carbohydrate meal on subjective, metabolic and physiological responses, and endurance performance in the Ramadan fasted state.

Physiological stress responses in the warm-water fish matrinxã (Brycon amazonicus) subjected to a sudden cold shock

The present work evaluated several aspects of the generalized stress response [endocrine (cortisol), metabolic (glucose), hematologic (hematocrit and hemoglobin) and cellular (HSP70)] in the Amazonian warm-water fish matrinxã (Brycon amazonicus ) subjected to an acute cold shock. This species farming has been done in South America, and growth and feed conversion rates have been interesting. However, in subtropical areas of Brazil, where the water temperature can rapidly change, high rates of matrinxã mortality have been associated with abrupt decrease in the water temperature. Thus, we subjected matrinxã to a sudden cold shock by transferring the fish directly to tanks in which the water temperature was 10oC below the initial conditions (cold shock from 28ºC to 18oC). After 1h the fish were returned to the original tanks (28ºC). The handling associated with tank transfer was also imposed on control groups (not exposed to cold shock). While exposure to cold shock did not alter the measured physiological conditions within 1h, fish returned to the ambient condition (water at 28º C) significantly increased plasma cortisol and glucose levels. Exposure to cold shock and return to the warm water did not affect HSP70 levels. The increased plasma cortisol and glucose levels after returning the fish to warm water suggest that matrinxã requires cortisol and glucose for adaptation to increased temperature.

1H-NMR and mass spectrometric characterization of the metabolic response of juvenile Atlantic salmon (Salmo salar) to long-term handling stress

Stressors of various kinds constantly affect fish both in the wild and in culture, examples being acute water temperature and quality changes, predation, handling, and confinement. Known physiological responses of fish to stress such as increases in plasma cortisol and glucose levels, are considered to be adaptive, allowing the animal to cope in the short term. Prolonged exposure to stressors however, has the potential to affect growth, immune function, and survival. Nonetheless, little is known about the mechanisms underlying the long-term stress response. We have investigated the metabolic response of juvenile Atlantic salmon (Salmo salar) to long-term handling stress by analyzing fish plasma via ¹H nuclear magnetic resonance spectroscopy and ultra high performance liquid chromatography–mass spectrometry (UPLC–MS), and comparing results with controls. Analysis of NMR data indicated a difference in the metabolic profiles of control and stressed fish after 1 week of stress with a maximum difference observed after 2 weeks. These differences were associated with stress-induced increases in phosphatidyl choline, lactate, carbohydrates, alanine, valine and trimethylamine-N-oxide, and decreases in low density lipoprotein, very low density lipoprotein, and lipid. UPLC-MS data showed differences at week 2, associated with another set of compounds, tentatively identified on the basis of their mass/charge. Overall the results provided a multi-faceted view of the response of fish to long-term handling stress, indicating that the metabolic disparity between the control and stress groups increased to week 2, but declined by weeks 3 and 4, and revealed several new molecular indicators of long-term stress.

Hormonal responses to extreme fasting in subantarctic fur seal (Arctocephalus tropicalis) pups

Surviving prolonged fasting implies closely regulated alterations in fuel provisioning to meet metabolic requirements, while preserving homeostasis. Little is known, however, of the endocrine regulations governing such metabolic adaptations in naturally fasting free-ranging animals. The hormonal responses to natural prolonged fasting and how they correlate to the metabolic adaptations observed, were investigated in subantarctic fur seal (Arctocephalus tropicalis) pups, which, because of the intermittent pattern of maternal attendance, repeatedly endure exceptionally long fasting episodes throughout their development (1–3 mo). Phase I fasting was characterized by a dramatic decrease in plasma insulin, glucagon, leptin, and total L-thyroxine (T4) associated with reductions in mass-specific resting metabolic rate (RMR), plasma triglycerides, glycerol, and urea-to-creatine ratio, while nonesterified fatty acids (NEFA) and β-OHB increased. In contrast, the metabolic steady-state of phase II fasting reached within 6 days was associated with minimal concentrations of insulin, glucagon, and leptin; unchanged cortisol and triiodothyronine (T3); and moderately increased T4. The early fall in insulin and leptin may mediate the shift to the strategy of energy conservation, protein sparing, and primary reliance on body lipids observed in response to the cessation of feeding. In contrast to the typical mammalian starvation response, nonelevated cortisol and minimal glucagon levels may contribute to body protein preservation and downregulation of catabolic pathways, in general. Furthermore, thyroid hormones may be involved in a process of energy conservation, independent of pups' nutritional state. These original hormonal settings might reflect an adaptation to the otariid repeated fasting pattern and emphasize the crucial importance of a tight physiological control over metabolism to survive extreme energetic constraints.