UCP3: An Uncoupling Protein Homologue Expressed Preferentially and Abundantly in Skeletal Muscle and Brown Adipose Tissue

The obesity epidemic is a global issue and shows no signs of abating, while the cause of this epidemic remains unclear. Marketing practices of energy-dense foods and institutionally-driven declines...

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Ten Putative Contributors to the Obesity Epidemic

Human obesity is characterized by profound alterations in the hemodynamic and metabolic states. Whether these alterations involve sympathetic drive is controversial. In 10 young obese subj...

Sympathetic activation in obese normotensive subjects

tant energy source for most body tissues, particularly during periods of food deprivation, but recent evidence suggests that these same molecules subserve a much broader function in whole body fuel homeostasis by virtue of their ability to act as potent signalling entities in a variety of cellular processes. One such auxiliary role of NEFA is to heighten the responsiveness of the pancreatic beta cell to a variety of insulin secretagogues. Importantly, this fatty acid-beta cell interaction, though designed by nature for physiological purposes, can, under certain circumstances, take on a pathophysiological dimension. Some new developments surrounding this Jekyll and Hyde character of fatty acids will be reviewed briefly below.

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Fatty acids, lipotoxicity and insulin secretion.

Background— Muscle sympathetic nerve activity (MSNA) is elevated in obese humans. However, the potential role of abdominal visceral fat as an important adipose tissue depot linking obesity to elevated MSNA has not been explored. Accordingly, we tested the hypothesis that MSNA would be increased in men (age=18 to 40 years, body mass index ≤35 kg/m2) with higher abdominal visceral fat (HAVF; n=13, abdominal visceral fat=118.1±15.8 cm2) compared with their age- (28.7±2.4 versus 25.5±2.0 years, P>0.05), total fat mass-matched (20.6±2.1 versus 20.8±2.4 kg, P>0.05) and abdominal subcutaneous fat-matched (230.6±24.9 versus 261.4±34.8 cm2, P>0.05) peers with lower abdominal visceral fat levels (LAVF; n=13, visceral fat= 73.0±6.0 cm2). Methods and Results— MSNA (microneurography), body composition (dual energy x-ray absorptiometry), and abdominal visceral and subcutaneous fat (computed tomography) were measured in 37 sedentary men across a wide range of adiposity. MSNA was ≈55% higher in men with HAVF compared wit...

Sympathetic neural activation in visceral obesity

The sympathetic nervous system is recognized to play a role in the etiology of animal and possibly human obesity through its impact on energy expenditure and/or food intake. We, therefore, measured fasting muscle sympathetic nerve activity (MSNA) in the peroneal nerve and its relationship with energy expenditure and body composition in 25 relatively lean Pima Indian males (means±SD; 26±6 yr, 82±19 kg, 28±10% body fat) and 19 Caucasian males (29±5 yr, 81±13 kg, 24±9% body fat). 24-h energy expenditure, sleeping metabolic rate, and resting metabolic rate were measured in a respiratory chamber, whereas body composition was estimated by hydrodensitometry. Pima Indians had lowerMSNA than Caucasians (23±6 vs 33±10 bursts/min, P = 0.0007). MSNA was significantly related to percent body fat in Caucasians (r = 0.55,P = 0.01) but not in Pimas. MSNA also correlated with energy expenditure adjusted for fat-free mass, fat mass, and age in Caucasians (r = 0.51, P = 0.03; r = 0.54, P = 0.02; and r = 0.53,P = 0.02 for adjusted 24-h energy expenditure, sleeping metabolic rate, and resting metabolic rate, respectively) but not in Pima Indians. In conclusion, the activity of the sympathetic nervous system is a determinant ofenergy expenditure in Caucasians. Individuals with low restingMSNA may be at risk for body weight gain resulting from a lower metabolic rate. A low resting MSNA and the lack of impact of MSNA on metabolic rate

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A Potential Mechanism Predisposing to Body Weight Gain

Food intake rate has previously been derived from observation of eating behavior in laboratory settings or in public eating establishments. Although it has been suggested that obese individuals eat faster than lean individuals, observations of such an "obese eating style" have yielded mixed results. In the present study, the relationship between ad-libitum food intake rate and obesity was evaluated over 4 days on a metabolic ward in 28 healthy Pima Indian men (Mean +/- SD; 29 +/- 7 y, 100.4 +/- 27.1 kg, 33 +/- 10% body fat) using an automated food selection system containing a large variety of foods. Total energy intake averaged 18829 +/- 3299 kJ/d consisting of 47 +/- 4, 40 +/- 3, and 13 +/- 1 percent of carbohydrate, fat and protein, respectively. The average meal duration was 25 +/- 7 min. Food intake rate was 68 +/- 21 g/min while carbohydrate, fat and protein intake rates were 23 +/- 6, 9 +/- 3 and 6 +/- 2 g/min, respectively. Food intake rate correlated negatively with % body fat (r = -0.61, P < 0.01). Similar relationships were found between the intake rates of carbohydrate, fat and protein and body fatness. Only prospective studies will indicate whether a slow food intake rate may contribute to the etiology of obesity by possibly reducing satiety.

D. Enette Larson

Papers

A Potential Mechanism Predisposing to Body Weight Gain

Do obese eat faster than lean subjects? Food intake studies in Pima Indian men.