In this study the rate of lipolysis (fatty acid and glycerol release into blood) has been quantified in both normal weight and obese volunteers after both 15 and 87 h of fasting. In each study, the basal rate and subsequent response to epinephrine infusion (0.015 microgram X kg-1 X min-1) were determined. The rate of appearance (Ra) of free fatty acids (FFA) and glycerol were quantified by infusion of [1-13C]palmitate and D-5-glycerol, respectively. Substrate flux rates per unit of body fat mass and lean body mass were calculated from total body water measurements using H2(18)O dilution. In normal volunteers, the basal Ra FFA and Ra glycerol rose markedly with 87 h of fasting, whereas the increases were more modest in the obese subjects. However, the rate of mobilization of fat, in relation to the lean body mass, was higher in the obese subjects than in the normal subjects after 15 h of fasting, and the values were similar in both groups after 87 h of fasting. There was an increased lipolytic response to epinephrine after fasting in both groups. This increased sensitivity may have resulted from the enhancement of fatty acid-triglyceride substrate cycling that occurred after fasting.

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Normal subjects, normal-renin hypertensive patients, and low-renin hypertensive patients were evaluated by intravenous saline infusion and with a fludrocortisone acetate (Florinef) protocol to clarify diagnostic criteria for primary aldosteronism that are recommended for the saline infusion protocol. The patients consumed a 200 mEq sodium, 70 mEq potassium diet for 6 days, and on the last 3 days received Florinef 0.5 mg orally twice daily. On Days 3 and 6, urinary aldosterone and tetrahydroaldosterone excretions were determined, and on Days 4 and 7 plasma aldosterone (PA) was determined at 0600 after overnight recumbency and at 0800 after 2 hours of walking. Although the level of normal PA suppression by saline infusion has been commonly defined as 10 ng/dl, a value of 5 ng/dl was originally recommended. In 20 normal subjects and 45 normal-renin hypertensive patients, we found that the PA was almost always suppressed below 5 ng/dl. In 18 of 75 low-renin patients including five with aldosterone-producing adenoma (APA), the PA was never suppressed below 10 ng/dl; thus, these 18 patients had classical primary aldosteronism by generally accepted criteria. The Florinef protocol was performed in eight of these 18 patients and was abnormal in all. An abnormal Florinef protocol was also found in seven of 15 patients studied with PA suppression after saline infusion to between 5 and 10 ng/dl, but in only one of 24 patients studied with PA suppression below 5 ng/dl. Additional studies in the subgroup with abnormal results from the Florinef protocol indicated that none of these patients had evidence of APA, so they had nontumorous primary aldosteronism (NTPA).(ABSTRACT TRUNCATED AT 250 WORDS)

In this study, the rates of lipid mobilization and of lipolysis have been quantified in severely burned children. In all 12 patients studied, the basal rates were determined. In seven patients, the lipolytic responsiveness to an infusion of epinephrine (0.015 micrograms/kg/min) was tested, and in the other five patients, the response to beta-adrenergic blockade (propranolol, 1 mg/kg) was tested. The rate of appearance (Ra) of free fatty acids (FFA) was quantified by means of the infusion of 1-13C-palmitate to determine the rate of lipid mobilization, and Ra glycerol was determined using d5-glycerol to assess the rate of lipolysis more directly. In five patients, body composition was determined after recovery by means of H2(18)O dilution. The basal rate of lipolysis was higher than normal in the burned children. In four of the seven patients infused with epinephrine, there was a pronounced increase in Ra glycerol. In all patients given beta-blockade, Ra glycerol decreased greatly. Changes in Ra FFA corresponded with the changes in Ra glycerol in each case. Total body fat was very low (approximately 2% body weight), reflecting the surgical removal of fat in the process of burn wound excision. From these data it is concluded that lipolytic responsiveness to catecholamines in severely burned children is variable, but not absent, despite chronically elevated levels of catecholamines. The total extent of lipolysis may be limited by the available fat mass in children treated with fascial excision. In such patients, the limitation in the ability to mobilize an adequate amount of FFA to fully meet energy requirements provides an important rationale for the clinical practice of providing nutritional support in hourly boluses, as opposed to infrequent meals, since any period of even a few hours in which nutrients are not being absorbed will result in an energy substrate deficiency and consequent increase in amino acid oxidation.

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