Metabolism And Health Effects Of Citrus Limonoids in Hypercholesterolemic Humans
Metabolism And Health Effects Of Citrus Limonoids in Hypercholesterolemic Humans
Limonoids are compounds found in citrus juices, seeds and peel. Some research shows that they
 reduce blood cholesterol and also reduce the incidence of several forms of cancer. Although
 these compounds are part of the natural human diet, the dose required to provide health
 benefits and the risks associated with the intake of high doses by humans have not been
 studied. This study will examine metabolism, safety, lipid-lowering and anti-inflammatory
 effects of limonoids. The dose of limonoids in this study is equivalent to that found in six
 8 oz glasses of orange juice per day. The investigators hypothesize that limonin glucoside
 supplementation will reduce total cholesterol, LDL cholesterol, ratio of LDL and HDL
 cholesterol, number of LDL particles, and serum markers of inflammation.
This is a 127-day study with a cross-over design, divided into three metabolic periods (P1,
 P2, and P3). For the first 14 days (P1), all subjects will receive two placebo beverages and
 will be asked to consume one each with breakfast and dinner. Then in metabolic period 2 (P2),
 subjects will be randomly assigned to one of two groups (Group 1 and Group 2). For the next
 56 days, Group 1 will continue to consume two placebo beverages per day, while Group 2 will
 consume two beverages containing limonoids (250 mg/beverage). During the final 56 days (P3),
 the beverages provided to Group 1 will contain limonoids, and beverages provided to Group 2
 will be placebo. Both the placebo and limonoid beverages will be 12-oz buffered, sterile,
 orange flavored, artificially sweetened beverage, containing 60 mg vitamin C, 11 mg
 riboflavin and zero calories. Subjects are instructed that they must drink all the beverage
 provided each day. Beverages will contain a biomarker (riboflavin), and the biomarker is
 assayed in urine samples collected every 2 weeks at the beverage pickup appointments to
 monitor compliance. The subjects will be informed that they are being monitored for
 compliance. Limonin glucoside is obtained from citrus waste materials utilizing
 chromatographic methods that employ food grade approved media and solvents. The final pure
 limonin glucoside is fractionally crystallized from a concentrated water solution of a
 chromatographically purified extract. The crystalline material is separated from the mother
 liquor, dried and subjected to mass spectral and nuclear magnetic resonance assessment. The
 spectral data is compared to data acquired for a pure limonin glucoside standard to establish
 final purity which is better than 95%.

 Blood samples (approximately 70 ml, less than five tablespoons) will be drawn after a 12 hour
 overnight fast on study days 1, 15, 71 and 127 by venipuncture. These blood samples will be
 used to determine serum limonoids, complete blood cell count (CBC), and comprehensive
 chemistry panel (CCP), serum lipids, markers of inflammation, lymphocyte and monocytes
 functions. In addition to the fasting blood draws on days 15 (Group 2) and day 71 (Group 1),
 repeated blood samples (5 ml each time, approximately one teaspoon) will be drawn at 2, 4, 6,
 8, and 24 hr after taking two 12-oz limonoid beverages (total limonoids 500mg) to determine
 the absorption and metabolism of limonoids. The investigators note that the blood samples
 drawn 24-h after the limonoid intake will be on study day 16 for Group 2 and day 72 for Group
 1. The total amount of blood drawn will be less than 500 ml (2 cups) in 127 days. A spot
 urine sample will be collected at the same visit as the fasting blood draws, and every two
 weeks at the beverage pickup appointments. Repeated blood draws at 0, 2, 4, 6, and 8 hr after
 the limonoid supplement will be accompanied by the collection of urine samples. No food will
 be allowed during the 8 hrs; water intake will be monitored and restricted to one liter.
 Subjects will be served two standardized meals during this time, each representing 35% of
 their daily caloric intake, one after the 0 hr blood draw and the other after the 8 hr blood
 draw.

 Subjects will be instructed not to change their diets, exercise or lifestyle during the
 course of the study. They will also be instructed not to consume any citrus fruit/juice
 (orange, grape fruit) throughout the study. Three 24-hour dietary recalls will be collected
 by telephone during the last week of each metabolic period (P1, P2, P3). A standardized diet
 will be served for all three meals for each day prior to the blood draws.
Inclusion Criteria:

 -  Hypercholesterolemic, total blood cholesterol 200-300 mg/dL

 -  BMI 20-35 kg/m2

 -  normal Complete Blood Count

 -  normal serum transaminases, alkaline phosphatase, and creatinine

 -  normal thyroid function

 -  LDL cholesterol > 130 mg/dL

 -  Triglyceride < 300 mg/dL

 -  serum C-Reactive Protein 1.0-25 mg/L

 Exclusion Criteria:

 -  current pregnancy or lactation

 -  smoking

 -  use of alcohol > 1 drink per day (1 oz distilled liquor, 3 oz wine, 12 oz beer)

 -  reported history of cardiovascular disease or chronic inflammatory diseases

 -  current users of oral contraceptives

 -  lipid-lowering, anti-inflammatory, anti-coagulant, or thyroid medications

 -  currently drinking more than 4 glasses per day of orange or grapefruit juice