Kazuo Iwai

Oleuropein supplementation increases urinary noradrenaline and testicular testosterone levels and decreases plasma corticosterone level in rats fed high-protein diet.

The effects of oleuropein, a phenolic compound in extra virgin olive oil, on protein metabolism were investigated by measuring testicular testosterone and plasma corticosterone levels in rats fed diets with different protein levels. In Experiment 1, rats were fed experimental diets with different protein levels (40, 25 and 10 g/100 g casein) with or without 0.1 g/100 g oleuropein. After 28 days of feeding, the testosterone level in the testis was significantly higher and the plasma corticosterone level was significantly lower in rats fed the 40% casein diet with oleuropein than in those fed the same diet without oleuropein. The urinary noradrenaline level, nitrogen balance and hepatic arginase activity were significantly higher in rats fed the 40% casein diet with oleuropein supplementation than in those fed the 40% casein diet without oleuropein supplementation. In Experiment 2, the effects of oleuropein aglycone (a major phenolic compound in extra virgin olive oil and the absorbed form of oleuropein ingested in the gastrointestinal tracts) on the secretion of luteinizing hormone (LH) from the pituitary gland, which regulates testosterone production in the testis, were investigated in anesthetized rats. Plasma LH level increased dose dependently after the administration of oleuropein aglycone (P<.001, r=0.691). These findings suggest that dietary supplementation with 0.1 g/100 g oleuropein alters the levels of hormones associated with protein anabolism by increasing urinary noradrenaline and testicular testosterone levels and decreasing plasma corticosterone level in rats fed a high-protein diet.

Alliin and volatile sulfur-containing compounds in garlic enhance the thermogenesis by increasing norepinephrine secretion in rats

Abstract The effects of alliin and volatile sulfur-containing compounds in garlic on thermogenesis were investigated in rats. Rats were fed high-fat diet with or without a ethanol extracted-garlic powder (EE-garlic) supplemented at 0.8% for 28 days. After feeding, mitochondrial protein content in interscapular brown adipose tissue (IBAT) and plasma norepinephrine secretion were significantly greater in rats given EE-garlic as compared with control rats. The effects of the administrations of EE-garlic and alliin on norepinephrine secretions were evaluated in anesthetized rats. The norepinephrine concentrations of arterial blood were significantly increased by EE-garlic and alliin administration, and these increases were dose dependent. The administration of allylsulfides having a different number of sulfur atoms (diallyldisulfide and diallyltrisulfide) also significantly increased the norepinephrine secretion. The effects of the administration of EE-garlic, alliin, and diallyldisulfide on thermogenesis were examined by the direct measurement of IBAT and rectal temperatures in anesthetized rats. The temperatures were significantly increased by the administration of these compounds, and the effect of diallyldisulfide disappeared in the presence of β-adrenergic blocker. These results suggest that the administration of alliin and volatile sulfur-containing compounds in garlic enhance the thermogenesis by increasing norepinephrine secretion via β-adrenergic action.

Regulation of pyridine nucleotide coenzyme metabolism.

Four NAD biosynthetic pathways are known (Henderson, 1983): (I) Nicotinamide (Nam) → nicotinamide mononucleotide (NMN) →NAD; (II) nicotinic acid (NA) → nicotinic acid mononucleotide (NaMN) → nicotinic acid adenine dinucleotide (NaAD) → NAD; (III) Nam → NA → NaMN → NaAD → NAD; (IV) quinolinic acid (QA) → NaMN → NaAD → NAD.

Oleuropein aglycone enhances UCP1 expression in brown adipose tissue in high-fat-diet-induced obese rats by activating β-adrenergic signaling☆☆☆★

Oleuropein is the pungent principle of raw olives. Oleuropein aglycone (OA) is a major phenolic compound in extra virgin olive oil and the absorbed form of oleuropein. We aimed to determine the mechanism underlying the nutritional effects of oleuropein and OA on interscapular brown adipose tissue (IBAT) in rats with high-fat (HF) diet-induced obesity by examining the agonistic activity of oleuropein and OA toward the transient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1). Four-week-old male Sprague-Dawley rats were fed an HF (palm oil 30% wt:wt) diet alone or with oleuropein (HF-O, 1 g/kg diet) for 28 days. In rats fed HF-O compared to HF, urinary noradrenaline, adrenaline and UCP1 levels in IBAT were significantly higher, whereas plasma leptin levels and the total weight of the abdominal cavity adipose tissue were significantly lower. In anaesthetized 7-week-old male Sprague-Dawley rats, the OA (3.8 mg of intravenous injection)-induced increase in plasma noradrenaline secretion was suppressed by TRPA1 or TRPV1 antagonist and by a β2- or β3-adrenoceptor antagonist. Furthermore, OA-activated rat and human TRPV1s expressed on HEK293 cells at the same level as zingerone (pungent component in ginger). OA also activated humanTRPA1, and its potency was approximately 10-fold stronger than that for TRPV1. These findings suggest that OA is the agonist of both TRPA1 and TRPV1 and that OA enhances UCP1 expression in IBAT with a concomitant decrease in the visceral fat mass of HF-diet-induced obese rats through enhanced noradrenaline secretion via β-adrenergic action following TRPA1 and TRPV1 activation.