S-allyl Cysteine Enhances Testosterone Production in Mice and Mouse Testis-Derived I-10 Cells.

Hypogonadism, associated with low levels of testosterone synthesis, has been implicated in several diseases. Recently, the quest for natural alternatives to prevent and treat hypogonadism has gained increasing research interest. To this end, the present study explored the effect of S-allyl cysteine (SAC), a characteristic organosulfur compound in aged-garlic extract, on testosterone production. SAC was administered at 50 mg/kg body weight intraperitoneally into 7-week-old BALB/c male mice in a single-dose experiment. Plasma levels of testosterone and luteinizing hormone (LH) and testis levels of proteins involved in steroidogenesis were measured by enzymatic immunoassay and Western blot, respectively. In addition, mouse testis-derived I-10 cells were also used to investigate the effect of SAC on steroidogenesis. In the animal experiment, SAC significantly elevated testosterone levels in both the plasma and the testis without changing the LH level in plasma and increased phosphorylated protein kinase A (p-PKA) levels. Similar results were also observed in I-10 cells. The findings demonstrating the increasing effect of SAC on p-PKA and mRNA levels of Cyp11a suggest that SAC increases the testosterone level by activating the PKA pathway and could be a potential target for hypogonadism therapeutics.

In vivo and in vitro studies on the absorption characteristics of ß-cryptoxanthin in the intestine.

ß-Cryptoxanthin (ß-CRX) is a carotenoid abundantly present in the Satsuma mandarin (Citrus unshiu Marc.), one of the most popular fruits in Japan, and it is reported to have several health benefits. Although it is thought to have higher bioavailability than other carotenoids, the usual daily intake is small, and a good method to improve its bioavailability is needed. Hence we studied the effect of emulsification on the absorption characteristics of ß-CRX in the intestine. Human trials showed that its serum transfer efficiency was statistically higher in the emulsified formulation than in fresh Satsuma mandarin juice. Caco-2 permeability studies indicated that emulsifiers preferentially accelerate the absorption of the non-esterified form of ß-CRX, suggesting that emulsification is more effective for free ß-CRX. This information might be useful to improve the efficiency of ß-CRX serum transfer, as well as to increase the health benefits of ß-CRX.

Prevention of Adiposity by the Oral Administration of ß-Cryptoxanthin.

ß-Cryptoxanthin (ß-CRX) is a carotenoid found in human blood. It is specifically rich in Satsuma mandarin (Citrus unshiu Marc.) but very little in other fruits or vegetables. Several reports indicate the health promoting benefits of ß-CRX. As we had reported visceral fat reduction on mildly obese male by the oral administration of ß-CRX, a detailed mechanism has not been identified. To identify the mechanism, obese model mouse, TSOD was used in the present study. Oral administration of ß-CRX repressed body weight, abdominal adipose tissue weight, and serum lipid concentrations on TSOD mice. The outstanding observation is the significant repression of adipocyte hypertrophy. DNA microarray analysis strongly indicates that the oral administration of ß-CRX represses the inflammatory cytokine secretion and improves the lipid metabolism and the energy consumption. It also suggests these effects are partly mediated by PPAR-α, not only lipid metabolism and adipocyte differentiation control but possibly internal circadian clock modulation.

Mechanism of visceral fat reduction in Tsumura Suzuki obese, diabetes (TSOD) mice orally administered ß-cryptoxanthin from Satsuma mandarin oranges (Citrus unshiu Marc).

The carotenoid ß-cryptoxanthin (ß-CRX) is abundant in Satsuma mandarins (Citrus unshiu Marc). Several studies have shown a relationship between Satsuma mandarin consumption and a low risk of several diseases, for example, diabetes, gout, and hypertension, suggesting ß-CRX involvement in disease prevention. We investigated the effect of ß-CRX on mildly obese males. ß-CRX administration reduced visceral adipose tissue, body weight, and abdominal circumference. However, the detailed mechanism by which ß-CRX mediates these changes remains unknown. To identify this mechanism, we used an obese model mouse (TSOD). Oral ß-CRX administration repressed body weight, abdominal adipose tissue weight, and serum lipid concentrations in TSOD; these results are identical to previous human trial results. ß-CRX administration significantly repressed adipocyte hypertrophy. Gene expression analysis strongly indicated that ß-CRX can alter cytokine secretion and cell proliferation. These results suggest that ß-CRX derived from Satsuma mandarins can help prevent obesity by repressing hypertrophy of abdominal adipocytes.

ß-cryptoxanthin suppresses the adipogenesis of 3T3-L1 cells via RAR activation.

We recently reported that the oral intake of ß-cryptoxanthin exerted anti-obesity effects by lowering visceral fat levels. In the present study, we characterized the molecular mechanisms underlying the lipid-lowering effects of ß-cryptoxanthin on 3T3-L1 cells. Consistent with our previous findings, ß-cryptoxanthin rapidly reduced the level of intracellular lipids in 3T3-L1 cells as assessed by Oil red O staining. Using an in vitro nuclear receptor binding assay, we demonstrated the ability of ß-cryptoxanthin to bind to and activate members of the retinoic acid receptor (RAR) family. Accordingly, treatment of cells with LE540, an RAR antagonist, abolished the ß-cryptoxanthin-dependent suppression of 3T3-L1 adipogenesis, suggesting that ß-cryptoxanthin mediates its effects on 3T3-L1 cells via RAR activation. In addition, real-time RT-PCR analysis revealed that ß-cryptoxanthin down-regulates mRNA expression of PPARγ, a key regulator of adipocyte differentiation, and that this inhibition was blocked by LE540 treatment. Taken together, these data indicate that RAR activation contributes to the molecular mechanism by which ß-cryptoxanthin prevents obesity.