Magnetic resonance spectroscopy investigations of brown adipose tissue and isolated brown adipocytes.

Brown adipose tissue and collagenase-isolated brown adipocytes were investigated in rats by means of 1H and 13C nuclear magnetic resonance spectroscopy. After chloroform-methanol extraction of brown adipose tissue, proton and natural abundance 13C spectra of the chloroform fraction showed resonances attributable to triglycerides, and were qualitatively similar to those of the corresponding fraction of white adipose tissue. By means of quantitative analysis of 1H spectra, fatty acid unsaturation and polyunsaturation in triglycerides were found to be lower in brown than white adipose tissue; moreover, unsaturation parameters decreased in triglyceride fatty acids of brown adipose tissue upon norepinephrine administration or cold acclimatization of rats, and were affected by the age of donors. The molar percentage of mono- and polyunsaturated C18 fatty acids in triglycerides was determined from 13C spectra and found to change in the early post-natal period. Isolated, agarose-embedded brown adipocytes from 4-day-old rats showed a number of peaks in the carbohydrate region of 1H spectra that were not present in spectra of white adipocytes and almost disappeared in brown fat cells of older animals. These peaks could be restored by insulin exposure. Natural abundance 13C spectra of isolated brown adipocytes were resolved enough to allow unambiguous assignment of resonances to carbons of fatty acids, glycerol, glucose, ethanolamine, and choline. Calculation of the mono- to polyunsaturated fatty acids ratio in the cells was also performed. Nuclear magnetic resonance spectroscopy is a useful tool for the investigation of brown adipose tissue and adipocytes therefrom

In vivo morphometry and functional morphology of brown adipose tissue by magnetic resonance imaging

Brown adipose tissue (BAT) is the main effector of nonshivering thermogenesis and diet-induced thermogenesis in mammals. Assessment of the magnitude and perturbations of BAT deposits in the intact, living body would be of much relevance for quantitative studies of BAT functions, but such studies have been impossible to date. In this paper it is shown that magnetic resonance imaging (MRI) morphometry can provide the means for accurate, repeated determinations of the volume of BAT deposits in a living animal; moreover, tissue modifications due to acclimation at different ambient temperatures are revealed in vivo by MRI, which correlates with histology and ultrastructure. Furthermore, MRI differentiates areas of BAT responsive to acute adrenergic stimulation, thereby giving information on the thermogenetically active tissue in the intact animal. Therefore, MRI represents a reliable tool for correlative morphological and functional studies of BAT in the living animal

Magnetic resonance spectroscopy investigations of brown adipose tissue and isolated brown adipocytes

Brown adipose tissue and collagenase-isolated brown adipocytes were investigated in rats by means of 1H and 13C nuclear magnetic resonance spectroscopy. After chloroform-methanol extraction of brown adipose tissue, proton and natural abundance 13C spectra of the chloroform fraction showed resonances attributable to triglycerides, and were qualitatively similar to those of the corresponding fraction of white adipose tissue. By means of quantitative analysis of 1H spectra, fatty acid unsaturation and polyunsaturation in triglycerides were found to be lower in brown than white adipose tissue; moreover, unsaturation parameters decreased in triglyceride fatty acids of brown adipose tissue upon norepinephrine administration or cold acclimatization of rats, and were affected by the age of donors. The molar percentage of mono- and polyunsaturated C18 fatty acids in triglycerides was determined from 13C spectra and found to change in the early post-natal period. Isolated, agarose-embedded brown adipocytes from 4-day-old rats showed a number of peaks in the carbohydrate region of 1H spectra that were not present in spectra of white adipocytes and almost disappeared in brown fat cells of older animals. These peaks could be restored by insulin exposure. Natural abundance 13C spectra of isolated brown adipocytes were resolved enough to allow unambiguous assignment of resonances to carbons of fatty acids, glycerol, glucose, ethanolamine, and choline. Calculation of the mono- to polyunsaturated fatty acids ratio in the cells was also performed. Nuclear magnetic resonance spectroscopy is a useful tool for the investigation of brown adipose tissue and adipocytes therefrom

The correlation between magnetic resonance imaging and ultrastructural patterns of brown adipose tissue

The present paper reports on magnetic resonance imaging (MRI) at high spatial resolution of the brown adipose tissue (BAT) in laboratory rodents, in comparison with light and electron microscopy findings. Our aim was to assess whether MRI correlates with the expected ultrastructural differences between newborn and adult BAT. The study was performed on the cervical and the interscapular BAT deposits by means of a nuclear magnetic resonance (NMR)-spectrometer equipped with a high resolution imaging system. Ultrastructural examination of BAT at different ages showed three different patterns of adipocyte ultrastructure in BAT which were associated with different MRI patterns. In BAT, MRI identifies the prevalent type of adipocyte in the tissue providing information consistent with ultrastructural results. Results presented here show that MRI represents a precise and reliable tool to investigate the morphology of tissues in living animals. The safe, non-invasive MRI technique represents a very useful tool in morphological research