Joshua W. Smith

Lutein and Brain Function

Lutein is one of the most prevalent carotenoids in nature and in the human diet. Together with zeaxanthin, it is highly concentrated as macular pigment in the foveal retina of primates, attenuating blue light exposure, providing protection from photo-oxidation and enhancing visual performance. Recently, interest in lutein has expanded beyond the retina to its possible contributions to brain development and function. Only primates accumulate lutein within the brain, but little is known about its distribution or physiological role. Our team has begun to utilize the rhesus macaque (Macaca mulatta) model to study the uptake and bio-localization of lutein in the brain. Our overall goal has been to assess the association of lutein localization with brain function. In this review, we will first cover the evolution of the non-human primate model for lutein and brain studies, discuss prior association studies of lutein with retina and brain function, and review approaches that can be used to localize brain lutein. We also describe our approach to the biosynthesis of 13C-lutein, which will allow investigation of lutein flux, localization, metabolism and pharmacokinetics. Lastly, we describe potential future research opportunities.

An interaction between carotene-15,15’-monooxygenase expression and consumption of a tomato or lycopene-containing diet impacts serum and testicular testosterone

Lycopene, the red pigment of tomatoes, is hypothesized to reduce prostate cancer risk, a disease strongly dependent upon testosterone. In this study, mice lacking the expression of carotene‐15,15′‐monooxygenase (CMO‐I−/−) or wild‐type mice were fed either a 10% tomato powder (TP), lycopene‐containing (248 nmol/g diet) or their respective control diets for 4 days, after which serum testosterone was measured. A significant diet × genotype interaction (p = 0.02) suggests that the TP reduces serum testosterone concentrations in CMO‐I−/− mice but not in wild‐type mice. Similarly, testicular testosterone was lowered in TP‐fed CMO‐I−/− mice (p = 0.01), suggesting that testosterone synthesis may be inhibited in this group. A similar pattern was also observed for lycopene fed mice. Interestingly, the CMO‐I−/− mice showed a greater expression of the gene encoding the CMO‐II enzyme responsible for eccentric oxidative carotenoid cleavage in the testes. Therefore, we hypothesize that serum testosterone is reduced by lycopene metabolic products of oxidative cleavage by CMO‐II in the testes. Overall, these findings suggest that genetic polymorphisms impacting CMO‐I expression and its interaction with CMO‐II, coupled with variations in dietary lycopene, may modulate testosterone synthesis and serum concentrations. Furthermore, carefully controlled studies with tomato products and lycopene in genetically defined murine models may elucidate important diet × genetic interactions that may impact prostate cancer risk.

13C-lutein is differentially distributed in tissues of an adult female rhesus macaque following a single oral administration: A pilot study

Despite the growing awareness regarding luteins putative roles in eyes and brain, its pharmacokinetics and tissue distribution in primates have been poorly understood. We hypothesized that 13C-lutein will be differentially distributed into tissues of an adult rhesus macaque (Macaca mulatta) 3 days following a single oral dose. After a year of prefeeding a diet supplemented with unlabeled lutein (1 μmol/kg/d), a 19-year-old female was dosed with 1.92 mg of highly enriched 13C-lutein. Tissues of a nondosed, lutein-fed monkey were used as a reference for natural abundance of 13C-lutein. On the third day postdose, plasma and multiple tissues were collected. Lutein was quantified by high-performance liquid chromatography-photodiode array detector, and 13C-lutein tissue enrichment was determined by liquid chromatography quadrupole time-of-flight mass spectrometry. In the tissues of a reference monkey, 12C-lutein with natural abundance of 13C-lutein was detectable. In the dosed monkey, highly enriched 13C-lutein was observed in all analyzed tissues except for the macular and peripheral retina, with the highest concentrations in the liver followed by the adrenal gland and plasma. 13C-lutein accumulated differentially across 6 brain regions. In adipose depots, 13C-lutein was observed, with the highest concentrations in the axillary brown adipose tissues. In summary, we evaluated 13C-lutein tissue distribution in a nonhuman primate following a single dose of isotopically labeled lutein. These results show that tissue distribution 3 days following a dose of lutein varied substantially dependent on tissue type.

Carrot solution culture bioproduction of uniformly labeled 13C-lutein and in vivo dosing in non-human primates:

Lutein is a xanthophyll abundant in nature and most commonly present in the human diet through consumption of leafy green vegetables. With zeaxanthin and meso-zeaxanthin, lutein is a component of the macular pigment of the retina, where it protects against photooxidation and age-related macular degeneration. Recent studies have suggested that lutein may positively impact cognition throughout the lifespan, but outside of the retina, the deposition, metabolism, and function(s) of lutein are poorly understood. Using a novel botanical cell culture system (Daucus carota), the present study aimed to produce a stable isotope lutein tracer for use in future investigations of dietary lutein distribution and metabolism. Carrot cultivars were initiated into liquid solution culture, lutein production conditions optimized, and uniformly labeled 13C-glucose was provided as the sole media carbon source for four serial growth cycles. Lutein yield was 2.58 ± 0.24 µg/g, and mass spectrometry confirmed high enrichment of 13C: 64.9% of lutein was uniformly labeled and 100% of lutein was labeled on at least 37 of 40 possible carbons. Purification of carrot extracts yielded a lutein dose of 1.92 mg with 96.0 ± 0.60% purity. 13C-lutein signals were detectable in hepatic extracts of an adult rhesus macaque monkey (Macaca mulatta) dosed with 13C-lutein, but not in hepatic samples collected from control animals. This novel botanical biofactory approach can be used to produce sufficient quantities of highly enriched and pure 13C-lutein doses for use in tracer studies investigating lutein distribution, metabolism, and function.

Abstract 4327: Dietary tomato reduces castration-resistant prostate cancer progression in TRAMP mice

Epidemiological data support the hypothesis that consumption of diets rich in tomato products are associated with a reduced risk of prostate cancer. Castration-resistant prostate cancer (CRPC) represents the late and lethal phase of human prostate carcinogenesis, and is defined as cancer progression after surgical castration or pharmacologic reduction of serum testosterone through androgen deprivation therapy. Mechanisms involved in the transition to CRPC include cancer cells’ acquired capacity for androgen synthesis or activation of ligand-independent signaling. We have previously shown that dietary tomato can inhibit prostatic androgen signaling and expression of androgen biosynthetic genes, as well as reduce primary cancer incidence in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. Therefore, we examined whether dietary tomato might be an effective inhibitor of CRPC progression in mice. We hypothesized that lifelong dietary intake of tomato, as well as dietary tomato intervention following castration, would reduce tumor burden and growth rate in a mouse model of CRPC. TRAMP mice were fed an AIN-93G diet (CON) for one week and then randomized to the CON diet (n = 28) or a similar diet with 10% w/w lyophilized tomato paste (TP; n = 27) from 4 wks of age until euthanization. A third group, modeling dietary intervention, consumed CON from 4 to 12 wks of age, and the 10% w/w lyophilized tomato paste diet from wk 12 until euthanization (TP-I; n = 25). All animals were castrated at 12 wks of age. Beginning at 10 wks of age, mice were monitored longitudinally with ultrasound for tumor detection, tumor volume estimation, and calculation of tumor growth rate. Serial 2D image slices were used to generate a 3D volume estimate. Mice were euthanized after 5 consecutive tumor scans, or if no tumor had been detected by 30 weeks of age. Tumor growth area under the curve (AUC) was reduced approximately 46% by tomato intervention (TP-I) and 27% by lifelong tomato consumption (TP). At euthanization, TP-I reduced tumor weight by approximately 26%. Additionally, incidence of gross metastases to distant organs (lung, liver, kidney) was strongly inhibited by TP-I, compared to CON (0% and 26%, respectively). TP diet reduced incidence of distant organ gross metastasis to Citation Format: Joshua W. Smith, Joe L. Rowles, Rita J. Miller, Steven K. Clinton, William D. O’Brien, John W. Erdman. Dietary tomato reduces castration-resistant prostate cancer progression in TRAMP mice. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4327.