Obesity is caused by excessive fat or carbohydrate intake. The improvement of obesity is an important issue, especially in Western societies. Both low-carbohydrate diet (LCD) and low-fat diet (LFD) are used to achieve weight loss in humans. To clarify the mechanisms underlying LCD-induced weight loss, especially in early stage, we compared the gene expression in liver, white adipose tissue (WAT) and brown adipose tissue (BAT) of a very-low carbohydrate diet (VLCD)- and LFD-fed diet-induced obese (DIO) mice.
DIO male ddY mice were divided into high-fat diet (HFD), and isoenergetic VLCD and LFD groups. Pair-feeding was performed in the VLCD and LFD groups. Three weeks later, the body, liver, WAT and BAT were weighed and the serum and hepatic lipids, the mRNA expression levels in each tissue, and energy metabolism were analyzed.
The caloric intake of the VLCD-fed mice was initially reduced but was subsequently restored. The total energy intake was similar in the VLCD- and LFD-fed mice. There was a similar decrease in the BW of the VLCD- and LFD-fed mice. The VLCD-fed mice had elevated levels of serum fibroblast growth factor 21 (FGF21) and ketone bodies, which are known to increase energy expenditure. The browning of WAT was observed to a greater extent in the VLCD-fed mice. Moreover, in the VLCD-fed mice, BAT activation was observed, the weight of the BAT was decreased, and the expression of G-protein-coupled receptor 120, type 2 iodothyronine deiodinase, and FGF21 in BAT was extremely increased. Although the energy expenditure of the VLCD- and LFD-fed mice did not differ, that of the VLCD-fed mice was sometimes higher during the dark cycle. Hepatic TG accumulation was reduced in LFD-fed mice due to their decreased fatty acid uptake but not in the VLCD-fed mice. The pro-inflammatory macrophage ratio was increased in the WAT of VLCD-fed mice.
After 3 weeks, the isoenergetic VLCD- and LFD-fed DIO mice showed similar weight loss. The VLCD-fed mice increased serum concentration of FGF21 and ketone bodies, and marker mRNA levels of browning in WAT, activation in BAT and hepatic lipogenesis.