Leptin levels in human and rodent: Measurement of plasma leptin and ob RNA in obese and weight-reduced subjects

A new method of total RNA isolation by a single extraction with an acid guanidinium thiocyanate-phenol-chloroform mixture is described. The method provides a pure preparation of undegraded RNA in high yield and can be completed within 4 h. It is particularly useful for processing large numbers of samples and for isolation of RNA from minute quantities of cells or tissue samples.

No current treatment for obesity reliably sustains weight loss, perhaps because compensatory metabolic processes resist the maintenance of the altered body weight. We examined the effects of experimental perturbations of body weight on energy expenditure to determine whether they lead to metabolic changes and whether obese subjects and those who have never been obese respond similarly. We repeatedly measured 24-hour total energy expenditure, resting and nonresting energy expenditure, and the thermic effect of feeding in 18 obese subjects and 23 subjects who had never been obese. The subjects were studied at their usual body weight and after losing 10 to 20 percent of their body weight by underfeeding or gaining 10 percent by overfeeding. Maintenance of a body weight at a level 10 percent or more below the initial weight was associated with a mean (+/- SD) reduction in total energy expenditure of 6 +/- 3 kcal per kilogram of fat-free mass per day in the subjects who had never been obese (P < 0.001) and 8 +/- 5 kcal per kilogram per day in the obese subjects (P < 0.001). Resting energy expenditure and nonresting energy expenditure each decreased 3 to 4 kcal per kilogram of fat-free mass per day in both groups of subjects. Maintenance of body weight at a level 10 percent above the usual weight was associated with an increase in total energy expenditure of 9 +/- 7 kcal per kilogram of fat-free mass per day in the subjects who had never been obese (P < 0.001) and 8 +/- 4 kcal per kilogram per day in the obese subjects (P < 0.001). The thermic effect of feeding and nonresting energy expenditure increased by approximately 1 to 2 and 8 to 9 kcal per kilogram of fat-free mass per day, respectively, after weight gain. These changes in energy expenditure were not related to the degree of adiposity or the sex of the subjects. Maintenance of a reduced or elevated body weight is associated with compensatory changes in energy expenditure, which oppose the maintenance of a body weight that is different from the usual weight. These compensatory changes may account for the poor long-term efficacy of treatments for obesity.

The amount of abdominal visceral adipose tissue measured by computed tomography is a critical correlate of the potentially "atherogenic" metabolic disturbances associated with abdominal obesity. In this study conducted in samples of 81 men and 70 women, data are presented on the anthropometric correlates of abdominal visceral adipose tissue accumulation and related cardiovascular disease risk factors (triglyceride and high-density lipoprotein cholesterol levels, fasting and postglucose insulin and glucose levels). Results indicate that the waist circumference and the abdominal sagittal diameter are better correlates of abdominal visceral adipose tissue accumulation than the commonly used waist-to-hip ratio (WHR). In women, the waist circumference and the abdominal sagittal diameter also appeared more closely related to the metabolic variables than the WHR. When the samples were divided into quintiles of waist circumference, WHR or abdominal sagittal diameter, it was noted that increasing values of waist circumference and abdominal sagittal diameter were more consistently associated with increases in fasting and postglucose insulin levels than increasing values of WHR, especially in women. These findings suggest that the waist circumference or the abdominal sagittal diameter, rather than the WHR, should be used as indexes of abdominal visceral adipose tissue deposition and in the assessment of cardiovascular risk. It is suggested from these data that waist circumference values above approximately 100 cm, or abdominal sagittal diameter values > 25 cm are most likely to be associated with potentially "atherogenic" metabolic disturbances.