Composition and structure of triacylglycerols in brown adipose tissue of rats fed fish oil

A maternal diet of fatty fish reduces body fat of offspring compared with a maternal diet of beef and a post-weaning diet of fish improves insulin sensitivity and lipid profile in adult C57BL/6 male mice

AIM

The maternal diet during pregnancy and lactation may affect the long-term health of the offspring. Our aim was to study how a fish or meat diet perinatal and after weaning affects body composition, insulin sensitivity and the profile of n-3 and n-6 polyunsaturated fatty acids (PUFAs) in breast milk, fat depots, skeletal muscle and liver in male adult mice offspring.

METHODS

During gestation and lactation, C57BL/6 dams were fed a herring- or beef-based diet. Half of the pups in each group changed diets after weaning. In offspring, body composition measured by DEXA, plasma lipid profile and insulin sensitivity measured by euglycemic clamp or QUICKI were monitored to adulthood. Analysis of total FAs by GC-MS were performed in the diet, breast milk and in different tissues.

RESULTS

At 9 week of age, offspring of herring-fed dams had less body fat than offspring of beef-fed dams. Mice fed herring after weaning had increased insulin sensitivity at 15 week of age, reduced total plasma cholesterol and triglyceride levels, and compared with beef-fed mice, larger interscapular brown adipose tissue depots. The FA composition of the maternal diet was mirrored in breast milk, and the herring diet significantly affected the FA profile of different tissues, leading to an increased content of n-3 PUFAs.

CONCLUSION

A herring-based maternal diet reduces body fat in the offspring, but the insulin sensitivity, plasma lipids and amount of brown adipose tissue are affected by the offspring's own diet; the herring diet is more beneficial than the beef diet.

The role of adipose tissue in mediating the beneficial effects of dietary fish oil

Fish oil improves several features of metabolic syndrome (MetS), such as dyslipidemia, insulin resistance and hepatic steatosis. Fish oil may mediate some of its beneficial effects by modulating the storage and/or secretory functions of adipose tissue (AT). The storage of triglycerides in AT is regulated by the availability of free fatty acids and the degree of lipolysis in AT. Fish oil has been shown to reduce lipolysis in several studies, indicating improved triglyceride storage. Importantly, AT secretes a variety of adipokines and fish oil feeding is associated with remarkable changes in the plasma levels of two key adipokines, adiponectin and leptin. Much attention has been focused on the contribution of adiponectin in fish oil-mediated improvements in MetS. However, emerging evidence also indicates a role of leptin in modulating the components of the MetS upon fish oil feeding. In addition to improving the storage and secretory functions of AT, fish oil, and the n-3 fatty acids found in fish oil, has been shown to reduce inflammation in AT. These effects may be in part a result of activation of peroxisome proliferator-activated receptor γ or inhibition of Toll-like receptor 4. Thus, there is compelling evidence that fish oil mediates its beneficial effects on MetS by improving AT storage and secretory functions and by reducing inflammation.

Polyunsaturated fatty acids mapping by (1)H MR-chemical shift imaging

Parametric mapping of polyunsaturated fatty acids (PUFA) distribution in adipose tissues was obtained by (1)H chemical shift imaging (CSI). A matrix of spectra, acquired with a CSI sequence having two spatial and one spectroscopic dimension, was processed with ad hoc algorithms. The protocol was applied to phantoms containing different lipids in which the degree of polyunsaturation was determined by high-resolution nuclear magnetic resonance (NMR). High correlation (R(2) = 0.998) between degrees of polyunsaturation given by our protocol and that measured by high-resolution NMR was found. The thoracic region of rats was also examined. Parametric maps of the polyunsaturation degree were obtained for the brown adipose tissue and the white axillary fat: the first deposit was found more polyunsaturated than the second. Finally, in vivo mapping of the inguinal region of the rat was produced that allowed us to individuate PUFA-rich areas in adipose tissue. This work demonstrates the feasibility of PUFA imaging in vivo.