D-Psicose, a C3 epimer of D-fructose, is known to lower body weight and adipose tissue weight and affect lipid metabolism. The precise mechanism remains unknown. It has been reported that D-psicose has a short half-life and is not metabolized in the body. To determine how D-psicose modifies lipid metabolism, rats were fed diets with or without 3% D-psicose for 4 weeks. Rats were decapitated without fasting every 6 h over a period of 24 h. Changes in serum and liver lipid levels, liver enzyme activity, and gene expression were quantified in experiment 1. Rats fed D-psicose had significantly lower serum insulin and leptin levels. Liver enzyme activities involved in lipogenesis were significantly lowered by the D-psicose diet, whereas gene expression of a transcriptional modulator of fatty acid oxidation was enhanced. In experiment 2, feeding the D-psicose diet gave significantly lower body weight (389 ± 3 vs 426 ± 6 g, p < 0.05) and food intake (23.8 ± 0.2 vs 25.7 ± 0.4 g/day, p < 0.05) compared to the control diet. Rats fed the D-psicose diet gave significantly higher energy expenditure in the light period and fat oxidation in the dark period compared to rats fed the control diet, whereas carbohydrate oxidation was lower. In summary, these results indicate that the D-psicose diet decreases lipogenesis, increases fatty acid oxidation, and enhances 24 h energy expenditure, leading to d-psicose's potential for weight management.

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BACKGROUND: Rare sugars including D-allulose, D-tagatose, and D-sorbose are present in limited quantities in nature; some of these rare sugars are now commercially produced using microbial enzymes. Apart from the anti-obesity and anti-hyperglycaemic activities of D-allulose, effects of these sugars on lipid metabolism have not been investigated. Therefore, we aimed to determine if and how D-tagatose and D-sorbose modulate lipid metabolism in rats. After feeding these rare sugars to rats, parameters on lipid metabolism were determined. RESULTS:No diet-related effects were observed on body weight and food intake. Hepatic lipogenic enzyme activity was lowered by D-allulose and D-sorbose but increased by D-tagatose. Faecal fatty acid excretion was non-significantly decreased by D-allulose, but significantly increased by D-sorbose without affecting faecal steroid excretion. A trend toward reduced adipose tissue weight was observed in groups fed rare sugars. Serum adiponectin levels were decreased by D-sorbose relative to the control. Gene expression of cholesterol metabolism-related liver proteins tended to be down-regulated by D-allulose and D-sorbose but not by D-tagatose. In the small intestine, SR-B1 mRNA expression was suppressed by D-sorbose. CONCLUSION: Lipid metabolism in rats varies with rare sugars. Application of rare sugars to functional foods for healthy body weight maintenance requires further studies. Analysis of gene expression by RT-PCRTo further determine how rare sugars affect lipid metabolism at the molecular level, gene expression of enzymes and proteins involved J Sci Food Agric 2018; 98: 2020-2026

-D-allulose is one of the rare sugars with almost zero calories and several health benefits. Previous studies have reported the safety of D-allulose in normal, overweight/obese, and diabetic humans. However, one study reported significant increases in T-Cho and LDL-C after 12 weeks of D-allulose intake; this report was not a randomized controlled trial and these changes were considered to be due to seasonal variations. We, therefore, conducted a randomized, double-blind, placebo-controlled trial in 90 subjects with high LDL-C levels for 48 weeks to clarify the influence of long-term D-allulose consumption on cholesterol metabolism and efficacy. Subjects were randomly divided into 3 groups: highdose D-allulose (15 g D-allulose/day), low-dose D-allulose (5 g D-allulose/day), and placebo group (0 g D-allulose/day); each subject consumed a daily test beverage for 48 weeks. Clinical examinations were performed every eight weeks, beginning from initial consumption until week 52. No significant increases in T-Cho and LDL-C between test groups were observed, and 48 weeks of D-allulose consumption did not change risk factors for atherosclerotic cardiovascular disease. Furthermore, no clinical problems were recognized for other parameters. Additionally, significant improvements in hepatic enzyme activities, fatty liver score, and glucose metabolism after long-term D-allulose consumption were observed. The results from our study revealed that 1) D-allulose consumption is considered safe for long-term intake up to a year, and 2) D-allulose may be effective for improving hepatic functions and glucose metabolism.