Abstract
Supplementation with n-3 long-chain (LC) polyunsaturated fatty acids (PUFA) is known to promote thermogenesis via the activation of brown adipose tissue (BAT). Agricultural products that are biofortified with α-linolenic acid (ALA), the precursor of n-3 LC PUFA, have been launched to the market, but their impact on BAT function is unknown. This study aimed to evaluate the effects of ALA-biofortified butter on lipid metabolism and thermogenic functions in the BAT. C57BL/6 mice were fed a high-fat diet containing ALA-biofortified butter (n3Bu, 45% calorie from fat) for ten weeks in comparison with the isocaloric high-fat diets prepared from conventional butter or margarine. The intake of n3Bu significantly reduced the whitening of BAT and increased the thermogenesis in response to acute-cold treatment. Also, n3Bu supplementation is linked with the remodeling of BAT by promoting bioconversion into n-3 LC PUFA, FA elongation and desaturation, and mitochondrial biogenesis. Taken together, our results support that ALA-biofortified butter is a novel source of n-3 PUFA, which potentiates the BAT thermogenic function.
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Key Points
The metabolic improvement by ALA-biofortified butter was associated with augmented bioconversion into n-3 LC PUFA, reduced inflammation in the metabolic tissues (i.e., liver and WAT), and systemic production of anti-inflammatory oxylipins in previous research. This study investigated the impact of ALA-biofortified butter in regulating the BAT thermogenesis. The present work demonstrated that ALA-biofortified butter attenuated HF diet-mediated BAT whitening and inflammation and increased the brown fat specific gene and protein markers and thermogenic activity. In terms of mechanism, the intake of ALA-biofortified butter facilitates cold-mediated lipid remodeling by promoting n-3 LC PUFA conversion, by increasing ELOVL6 and SCD activity and by stimulating mitochondrial biogenesis. The work suggests that ALA-biofortified butter could be an alternative to fish oil in activating brown thermogenesis.
This study thoroughly assessed the metabolic changes in the BAT upon chronic consumption of ALA-enriched butter in comparison with the isocaloric HF feedings prepared from conventional butter or margarine. This study provides a novel insight that ALA-biofortified agricultural-products could be an alternative source of n-3 PUFA other than fish oil. The ALA-enriched butter can recapitulate the enhanced thermogenic energy expenditure, similarly to fish oil supplementation. The thermogenic activation of BAT was associated with the improved biosynthesis of n-3 LC PUFA, FA elongation/desaturation, and mitochondrial biogenesis. By thoroughly evaluating the effectiveness of ALA bio-fortified butter on thermogenesis in comparison with conventional butter and margarine, the study opens a new research avenue for designing health-promoting (or therapeutic) dairy products via manipulation of animal nutrition, metabolism, and presumably ruminal microbiome.