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PubMed1989

Inositol lipid metabolism in rat hippocampal formation slices: basal metabolism and effects of cholinergic agonists.

Incubation of rat hippocampal formation slices under steady-state conditions with [3H]inositol leads to only three phospholipids becoming labelled: phosphatidylinositol, phosphatidylinositol 4-phosphate, and phosphatidylinositol 4,5-bisphosphate. All three lipids incorporate [32P]Pi into their phosphodiester phosphate group with the polyphosphoinositides also incorporating this tracer into their monoester phosphate groups. As the concentrations of these lipids remain constant during these labelling processes we conclude that the phosphodiester phosphate, the inositol moiety, and the monoester phosphate groups undergo metabolic turnover in hippocampal formation slices incubated in vitro. The rate of incorporation of [3H]inositol into all three inositol phospholipids was stimulated by the addition of methacholine to the medium. Moreover, following steady-state labelling of the inositol lipids with [3H]inositol, methacholine in the presence of 10 mM LiCl caused a transient fall of 13% in the radiochemical concentration of phosphatidylinositol 4,5-bisphosphate after only 30 s stimulation and a fall of 15% in the radiochemical concentration of phosphatidylinositol after 30 min. Concomitantly, there was an approximately stoichiometric rise in the radiochemical concentration of inositol phosphates. Thus, we suggest that methacholine stimulates an inositol phospholipid phosphoinositidase C in rat hippocampal formation slices.

Animals↗
PubMed1988

Between-group differences in basal metabolic rates: an analysis of data collected in Scotland, the Gambia and Thailand.

Basal metabolic rate (BMR; using the Douglas bag method), body weight, and fat-free mass (FFM; using the skinfold method) were measured in 46 Scottish and 47 Gambian women in the non-pregnant non-lactating state and in 91 Scottish, 50 Gambian and 52 Thai women early in pregnancy. There were significant between-country differences in BMR (1) in absolute terms (MJ/d), (2) per kg body weight and (3) per kg FFM. However, these differences probably resulted from differences between the groups in average body weight and body composition. Differences per kg body weight were in part explained by differences in body fat content and the relatively low metabolic rate of adipose tissue. Differences in BMR/kg FFM were largely explained by between-group differences in the mass of the FFM, together with the finding that within each group, the BMR/kg FFM tended to decrease as weight increased. There were no significant differences in BMR between Scottish, Gambian and Thai women of similar FFM. There were, therefore, no apparent effects on BMR due to differences in race, climate, diet or nutritional status. Differences in the composition of the FFM could explain the 15 per cent lower BMR/kg FFM in the heaviest compared to the lightest subjects. This brings into question the widespread practice of using FFM as a metabolic reference standard. In contrast, BMR divided by the square root of FFM was similar in all three countries: for non-pregnant women, in MJ/kg0.5/d (mean and s.d.), Scotland 0.87 (0.07) and The Gambia 0.89 (0.07), and for pregnant women, Scotland 0.86 (0.07), The Gambia 0.87 (0.06) and Thailand 0.87 (0.08), and this may be a useful basis for comparing different groups in future. The accuracy of two equations for predicting BMR was assessed. The equation of FAO/WHO/UNU (1985) accurately predicted, from body weight, the average BMR of Scottish women, but under-estimated the average BMR of Gambian and Thai women by 5-10 per cent. The equation of Garby et al. (1988), which predicts BMR from FFM and fat mass, under-estimated the BMR of Scottish, Gambian and Thai women by 5, 10 and 14 per cent respectively, with the largest error within each group being for subjects with the smallest FFM.

Adipose Tissue↗
PubMed2004

Brief communication: Respiratory function is closely associated with basal metabolic rate in elderly persons.

To investigate the association between respiratory function and basal metabolic rate (BMR), pulmonary function indices and BMR were measured in 251 elderly persons using a spirometer and a body composition analyzer. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were more strongly correlated with BMR (r = 0.48 and r = 0.43, p < 0.01) than with lean body mass (r = 0.36 and r = 0.35, p < 0.01) and waist-to-hip ratio (r = -0.29 and r = -0.32, p < 0.01) in elderly men. FVC and FEV1 in elderly men with BMR > or = 1390 kcal/day averaged 4.05 +/- 0.56 L and 3.19 +/- 0.45 L, which were significantly above the values (3.54 +/- 0.51 L and 2.80 +/- 0.42 L, p < 0.01) in men with BMR < 1390 kcal/ day. Prevalences of the subjects with elevated FVC or FEV1 were significantly higher in the group of men with BMR > or = 1390 kcal/day than in those with BMR < 1390 kcal/day (66.0% and 68.0% vs 28.3% and 33.9%, p < 0.01). No significant differences were observed between the postmenopausal women with BMR > or = 1135 kcal/day and those with BMR < 1135 kcal/day. In summary, respiratory function is more closely associated with BMR in elderly persons, compared to lean body mass, waist-to-hip ratio, or body fat mass, and these associations are stronger in men than in women.

Aged↗
PubMedDate not supplied

Basal metabolic rate in the Yakut (Sakha) of Siberia.

Human indigenous circumpolar populations have elevated basal metabolic rates (BMRs) relative to predicted values; this metabolic elevation has been postulated to be a physiological adaptation to chronic and severe cold stress. The present study examines BMR in the Yakut, an indigenous high-latitude population from the Sakha Republic of Russia to determine (1) whether the Yakut show evidence of an elevated BMR, (2) if the Yakut display evidence of age-related changes in BMR, and (3) whether lifestyle differences influence BMR. BMR was measured during the late summer in 75 women and 50 men (ages 18-56 years) from the Siberian village of Berdygestiakh. Measured BMR (+/- SEM) of the entire sample was significantly elevated (+6.5%) compared to predictions based on body mass (6,623.7 +/- 94.9 vs. 6,218.2 +/- 84.7 kJ/day; P < 0.001). Additionally, measured BMR for the entire sample was significantly higher than predictions based on fat-free mass (+20.8%) and surface area (+8.9%). Males and females both showed significant elevations relative to all three standards. The elevated BMR of the Yakut does not appear to be attributable to extreme levels of protein, since the Yakut consume a mixed diet with a substantial proportion of carbohydrates. No significant age-related changes in BMR were found when controlled for body composition. No significant relationship was found between lifestyle variables and BMR, suggesting the possibility of a genetic or developmental mechanism. This study provides additional evidence of metabolic elevation in indigenous circumpolar groups and has important implications for estimating the nutritional requirements of these populations.

Acclimatization↗
PubMedDate not supplied

The influence of foraging mode and arid adaptation on the basal metabolic rates of burrowing mammals.

Two competing but nonexclusive hypotheses to explain the reduced basal metabolic rate (BMR) of mammals that live and forage underground (fossorial species) are examined by comparing this group with burrowing mammals that forage on the surface (semifossorial species). These hypotheses suggest that the low BMR of fossorial species either compensates for the enormous energetic demands of subterranean foraging (the cost-of-burrowing hypothesis) or prevents overheating in closed burrow systems (the thermal-stress hypothesis). Because phylogentically informed allometric analysis showed that arid burrowing mammals have a significantly lower BMR than mesic ones, fossorial and semifossorial species were compared within these groups. The BMRs of mesic fossorial and semifossorial mammals could not be reliably distinguished, nor could the BMRs of large (>77 g) arid fossorial and semifossorial mammals. This finding favours the thermal-stress hypothesis, because the groups appear to have similar BMRs despite differences in foraging costs. However, in support of the cost-of-burrowing hypothesis, small (<77 g) arid fossorial mammals were found to have a significantly lower BMR than semifossorial mammals of the similar size. Given the high mass-specific metabolic rates of small animals, they are expected to be under severe energy and water stress in arid environments. Under such conditions, the greatly reduced BMR of small fossorial species may compensate for the enormous energetic demands of subterranean foraging.

Acclimatization↗
PubMed1990

Avian basal metabolic rates: their association with body composition and energy expenditure in nature.

Measurements of basal metabolic rate (BMR), body water, fat, and lean dry mass of different organs were obtained in 22 bird species, ranging from 10.8 to 1,253 g body mass. Residuals of BMR (after subtracting BMR allometrically predicted from body mass) were positively correlated with residuals of lean dry heart and kidney mass. Measurements of both BMR and the daily energy expenditure of parent birds (DEEpar) during the period of nestling care as assessed by labeled-water turnover were collected from the literature for 26 altricial bird species. The allometric relationships with body mass in this data set were: log BMR (W) = -1.385 + 0.684 log mass (g) [fraction of variance (r2) = 0.973] and log DEEpar (W) = -0.797 + 0.659 log mass (g) (r2 = 0.967). Residuals of log BMR and log DEEpar were positively correlated with each other. The parallel regressions and correlation of residuals lead to reduced variance in the ratio of BMR/DEEpar (mean 0.301; SD 0.086). We suggest that natural selection has led to an adjustment of the size of organs (such as heart and kidney) involved in sustaining energy metabolism at the DEE maximized during parental care and that size-independent variation in BMR reflects the relative size of this highly metabolically active machinery. These relationships of BMR lead to new interpretations of the decline in mass-specific BMR with increasing body size and decreasing latitude and of the difference in mass-specific BMR between birds and mammals.

Animals↗
PubMed1998

Basal metabolism does not account for high O2 consumption in stunned myocardium.

Myocardial O2 consumption (MVo2) in stunned myocardium is relatively high compared with the reduced ventricular function. The mechanism of this "oxygen paradox" could occur at different levels: basal metabolism, excitation-contraction coupling, and energy production. In one previously reported series on 12 isolated, blood-perfused rabbit hearts, left ventricular systolic and diastolic function in stunned myocardium were significantly decreased compared with control, whereas total MVo2 was not. The MVo2 for the unloaded contraction was overproportionately high for the decreased function in stunned myocardium, and contractile efficiency was clearly deteriorated. To assess whether the basal metabolism specifically is elevated in stunned myocardium, a second series (n = 14) with a similar protocol was performed in this study. Basal MVo2 after KCl arrest (0.5 +/- 0.3 ml.min-1.100 g-1) was significantly lower than that measured after KCl arrest (1.2 +/- 0.5 ml.min-1.100 g-1) in an additional series on nonischemic hearts (n = 8). Our conclusion is that basal MVo2 in stunned myocardium is not elevated. Thus this O2-consuming portion of total MVo2 is not responsible for the inefficiency in stunned myocardium. Instead, a "metabolic stunning" occurs at the level of both excitation-contraction coupling and force development by the contractile apparatus.

Animals↗
PubMed1985

Predicting basal metabolic rate, new standards and review of previous work.

After reviewing the literature on basal metabolism, this paper discusses and reviews recent attempts to predict BMR from age, sex and anthropometric measurements. Criticism is made of the scientific and statistical integrity of a widely used table of standard metabolic rates for weight. The statistical screening of data from the literature of the past 50 years is described and equations computed from these screened data are presented. In these equations, BMR is predicted simply from weight or from weight and height with sex and age taken into account. Information is given on error, and tables estimating error for predictions on new data both for individuals and for means of groups of subjects are included. A table of BMRs for weights from 3 to 84 kg for males and females separately is also included. Cross-validation techniques are used to estimate possible threats to validity from various sources including, for example, different procedures of early workers. It was found that in the data available subjects from developing countries not only were smaller and had lower metabolic rates (as was expected) but also had lower rates per unit body weight than European or North American subjects. It is argued that at an individual level the error of prediction must be high since the global operationalisation of BMR confounds separate effects known to participate in complex relations with sex, age and anthropometric indices. The work reported is aimed at meeting a practical need for equations which are simple to apply. However, it was found that little was gained by the use of more complex equations, although they remain of scientific interest.

Adolescent↗