Epinephrine sensitivity with respect to metabolic rate and other variables in women.

A test for determination of epinephrine sensitivity has been worked out using six healthy young women. Variables considered were metabolic rate, heart rate, respiratory frequency, blood pressure, blood glucose, plasma insulin, glycerol, free fatty acids, and lactate. After established basal conditions, epinephrine was infused at rates of 0.01, 0.03, and 0.1 microgram X kg fat-free mass-1 X min-1. Most variables responded to epinephrine in a dose-dependent manner. Physiological threshold plasma concentrations of epinephrine ranged from 95 to 250 pg/ml for different variables. Calculated maximal responses ranged from approximately -15% to +900% of basal values and infusion rates giving half-maximal responses from approximately 15 to 190 ng X kg fat-free mass-1 X min-1. On an average, metabolic rate increased by 8, 16, and 29%, respectively, at the three infusion rates, and the maximal metabolic response was calculated to be approximately 35%. The error in determining epinephrine-induced increments in metabolic rate was 7% of the response. As calculated from nonprotein RQ, carbohydrate oxidation increased and lipid oxidation decreased rapidly during the first 10 min of epinephrine infusion. Later, fat oxidation became more important. Results on epinephrine plasma metabolic clearance rate agreed with earlier results in the literature.

Adipose tissue labelling in man, using a structurally-labelled fatty acid as tracer.

Three healthy male subjects had their adipose tissue enriched with a structurally-labelled fatty acid, 13-methyltetradecanoic acid (13-MTD), occurring naturally only in trace amounts. Needle biopsies from femoral, gluteal and abdominal adipose tissue were obtained at several intervals during a 6-week 13-MTD ingestion period and also along an 11-week period following the cessation of the label intake. Fatty acid composition was analysed by gas-liquid chromatography. Using this method, it was possible to show that different adipose tissues had various responsiveness to labelling (with abdominal fat having the highest one) and hence had different turnover rates. Incorporation and particularly disappearance rates were slow, half-lifes for label incorporation ranged from 2 to 12 weeks and that for label mobilization ranged from 4 to 10 months, thus confirming few other published results. The unexpected observation that incorporation of the label did not cease at the end of the 13-MTD feeding period, but did continue for at least a fortnight, might indicate that existence of a buffer pool where fatty acids may be momentarily stored before their definite incorporation into adipose tissue, as suggested in few other studies.

The use of 13-methyltetradecanoic acid as an indicator of adipose tissue turnover.

We show in this paper that 13-methyltetradecanoic acid (13-MTD) can be used as a structually labeled marker for investigating the mobility of fatty acyl chains in adipose tissue in the rat. The presence of an omega-1 methyl group allows easy quantitation by gas liquid chromatography (GLC) and permits an assessment to be made of any oxidation and chain elongation reactions with reincorporation of the label into the adipose tissue, since the iso-acyl chain is well resolved from odd or even-numbered homologous fatty acids with straight chains. The kinetics of uptake and loss of the structural label were different for adipose tissue taken from the various sites which were sampled, namely post abdominal, mesenteric, perirenal, pericardiac and subcutaneous adipose tissue as well as the epidydimal fat pads. We also report preliminary results in man which confirm that the method is applicable to human clinical studies and that 13-MTD kinetics differ for adipose tissue taken from the 3 different subcutaneous sites--waist, arm and thigh.

Site differences in the fatty acid composition of subcutaneous adipose tissue of obese women.

1. Adipose tissue samples were obtained by needle biopsy from three subcutaneous sites (thigh, abdomen and upper arm) in twenty-two obese women. The fatty acid composition was determined using gas-liquid chromatography and the results presented relate to eleven component fatty acids. 2. The fatty acid composition of adipose tissue obtained from the arm and abdomen was remarkably similar, with the exception of the levels of lauric acid. 3. The analyses showed that the majority of the saturated fatty acids were present in smaller proportions whilst the majority of unsaturated fatty acids were present in larger proportions in the thigh than in the two other sites. Highly significant inter-site differences were demonstrated for six of the major fatty acids and also for both the total amounts of saturated and unsaturated fatty acids and their ratios. 4. No marked differences in the fatty acid composition of adipose tissue from obese subjects were revealed during this study when compared with previously reported results obtained from 'normal-weight' subjects.

Role of nutrition in the development of osteomalacia in the elderly.

A dietary survey has been carried out of elderly people with osteomalacia. The commonest type of osteomalacia was that associated with partial gastrectomy. Although a dietary deficiency of vitamin D has been suggested as a cause of the osteomalacia the intake of this substance was not significantly different from that in controls to explain the development of the disease. It was found, however, that patients with osteomalacia went outside much less than controls and given the contribution of sunlight to meeting vitamin D requirements it is suggested that further consideration should be given to this factor in the aetiology of post-gastrectomy osteomalacia.