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Efficacy of black rice extract on obesity in obese postmenopausal women: a 12-week randomized, double-blind, placebo-controlled preliminary clinical trial

Jung, Ah Jin MSc1; Sharma, Anshul PhD2; Lee, Sung-Hyen PhD3; Lee, Sung-Joon PhD4; Kim, Jung-Hwan MD5; Lee, Hae-Jeung PhD1,2

Author Information
doi: 10.1097/GME.0000000000001862

Abstract

Despite many prevention and treatment efforts, the world has seen a significant increase in obesity in the last few decades, causing a tremendous health and economic burden. The World Health Organization (WHO) has stated that the incidence of obesity has surged threefold since 1975 and more than 60% of postmenopausal women have obesity.1 In Korean adults, the prevalence of obesity has risen because of energy imbalances resulting from a Western-style diet and reduced exercise.2 Postmenopausal women are commonly distressed by obesity and fat build-up, with an overall rise in adiposity that can be associated with additional comorbidities, such as osteoporosis, metabolic syndrome, and heart ailments.3 The drop in estrogen levels in menopausal women could be attributed to the reduction in bone mass density and muscle mass as well as a rise in abdominal fat.4 The use of hormone therapy (HT) as the first-line treatment for postmenopausal obesity has decreased because it may be a documented risk factor for coronary artery disease, stroke, breast and ovarian cancer, endometrial hyperplasia, and venous thrombosis.5-7

Recently, many researchers have shifted their focus from synthetic therapeutics to bioactive plant compounds as natural and safe solutions for obesity because such compounds are easily accessible and are inexpensive.8 White rice is typically consumed as a staple food crop by people from both developed and developing countries.9 However, many clinicians have recently begun to investigate pigmented rice because it contains highly bioactive phenolic phytochemicals that confer various health-promoting benefits.10 Black rice (Oryza sativa L.) is one such variety that has recently received widespread attention from scientists. China and other Asian countries account for the major global production of black rice.11 The phenolic compounds in black rice are cultivar-specific, although they primarily consist of anthocyanins.12 Black rice is also a rich source of important amino acids, fibers, and several vitamins.13 A preparative-high-performance liquid chromatography analysis of black rice revealed that among the five monomer anthocyanins, cyanidin-3-glucoside (C3G) was the main monomer, accounting for approximately 95% of anthocyanins.12,14 Indeed, black rice reportedly has the highest anthocyanin content among all other pigmented grains (327.60 mg/100 g).15 This compound is mainly located in the aleuronic layer of the seed.11 The pharmacological properties of black rice and its derivatives include anti-inflammatory,16,17 antioxidant,18,19 antiobesity,20,21 anticancer,22,23 and antidiabetic24 effects. In addition, black rice protects against cardiovascular ailments25 and has a neuroprotective effect against Alzheimer disease.26 Kim et al27 demonstrated that black rice extract (BRE) (Heukmi) inhibited adipogenic differentiation in C3H10T1/2 multipotent stem cells and that BRE had pro-osteogenic and anti-adipogenic effects through Wnt signaling. Specifically, BRE stimulated osteogenic differentiation but inhibited adipogenic differentiation. Eight weeks of BRE supplementation in ovariectomized rats with obesity resulted in decreased fat mass and body weight; it also averted the reduction in bone strength and density normally seen in these rats.28 These studies ascribed such dual effects to Wnt signaling.

In summary, much research attention has recently been directed toward assessing the therapeutic potential of various functional foods for obesity management in postmenopausal women. Given that black rice is an important superfood, the goal of the present study was to ascertain the effect of BRE in postmenopausal women with obesity. To this end, we conducted a 12-week, randomized, double-blind, placebo-controlled clinical trial.

METHODS

Participants

The participants were recruited from Nowon Eulji Medical Center, Seoul, South Korea, to evaluate the efficacy of BRE on body composition in postmenopausal women with obesity. To be eligible for the clinical trial the inclusion criteria were as follows: (1) Women aged between 45 and 69 years, (2) >1 year since the last menstrual period, (3) body mass index (BMI) (weight/height2) ≥25 kg/m2, and (4) women who were not on medication or estrogen therapy related to bone health or obesity for the last 1 year. Before enrollment, all potential participants provided written informed consent and agreed to comply with the study procedures and follow-up. The exclusion criteria were as follows: (1) diseases that can affect bone metabolism, such as thyroid disease, diabetes, kidney disease, and ovarian cancer; (2) current use of hormone therapy; (3) current use of obesity treatment (absorption inhibitors, antidepressants, appetite suppressants, contraceptives, steroids, female hormones); (4) participation in an obesity program or consumption of diet food within the last 3 months; (5) fasting blood glucose ≥ 126 mg/dL, blood glucose ≥ 200 mg/dL, or the use of oral hypoglycemic agents or insulin; (6) history of heart, kidney, liver, thyroid, or cerebrovascular disease; (7) history of gallbladder disease, gastrointestinal disease, gout, or porphyria; (8) history of mental illness, such as depression, schizophrenia, alcoholism, drug addiction, etc.; (9) hypersensitivity to the components contained in the test food; (10) inability to communicate; (11) severe visual or hearing impairment; (12) severe musculoskeletal disorders; (13) history of cancer or treatment for cancer within the last 5 years; (14) asthma and other allergic diseases; (15) history of surgery within the last 1 year; (16) participation in other clinical trials within the last 3 months; (17) inability or impaired ability to read the letter; (18) any other reason for ineligibility that could interfere with the intervention, as determined by the physician. To detect a difference in body fat percentage between groups as 1.2 ± 1.96%, with a significance level of P = 0.05 and a power of 80%, a minimum sample size of 42 was needed in each group.29 A total of 112 participants were screened, 7 of whom were excluded based on the exclusion criteria. The remaining 105 participants were finally enrolled in the study, 17 of whom dropped out. The study had 88 participants, but only 86 of them completed the clinical trial due to the noncompliance of 2 of them. The ethics committee of Nowon Eulji Medical Center IRB (EU 14-07) approved the study protocol. It is registered at the Clinical Research Information Service (CRIS, KCT0005836).

Preparation of black rice extract and placebo

Whole-grain black rice was milled using a milling machine (SAMWOOENG, Seoul, Korea), and the aleurone layer was collected. This layer was then extracted using an industrial extractor (CIP circulation system) by shaking with 50% ethyl alcohol (at 10-times the volume) for 48 hours at 30 to 35°C to obtain an anthocyanin-rich extract. The extract was filtered through micro-filter paper (100 μm). The yield of the final extract was 10%. The extract was concentrated to a 10% solution under reduced pressure (0.1-0.5 atm) and freeze-dried for 3 days in a freeze dryer (Trunas, Chungju, Korea). The extract was finally formulated as hard capsules containing 500 mg of BRE per capsule for the treatment group. The placebo (control group) capsules consisted of maltodextrin and were identical in size, shape, and color to the BRE capsules. Both the BRE and placebo capsules were packed in blister packs, with 10 capsules each pack, in a GMP (good manufacturing practice)-certified facility (ARIBIO, Jecheon, Korea).

For 12 weeks, participants were advised to take two capsules (BRE) a day for a cumulative dosage of 1 g. Based on our previous animal study we found that 90 mg/kg b.w. of BRE extract was the most effective dosage for lowering body fat.30 This was converted to a 1 g/d human equivalent dose (HED) for a 70 kg individual.30,31

Study design

The present study was designed as a 12-week, randomized, double-blind, placebo-controlled clinical trial. Randomization lists were computer generated by investigators who had no contact with participants. Both the participants and investigators were blinded to the treatment allocation until the trial was completed. Prescreening was conducted via a telephone conversation with the participants. After prescreening, the participants were referred to the hospital to provide written consent and to undergo the following diagnostic procedures: questionnaire, physical examination and blood test at screening (-2 weeks). The baseline visit (0-week) was conducted within 2 weeks of the screening visit to examine dual-energy x-ray absorptiometry (DXA), and computed tomography (CT). Participants who satisfied all eligibility criteria were randomly allocated to receive either BRE capsules or placebo capsules. Participants consumed two capsules/d (one capsule each after breakfast and dinner) for 12 weeks; compliance was documented by a trained investigator, who counted the capsules returned by the participants at each visit. At the 4-week and 8-week visits, participants were examined for any adverse effects and signs of vitality. At the same visits, an anthropometric survey and a nutrition survey were performed, and the participants were provided with more BRE or placebo capsules. At the 12-week visit, participants were examined for biomarkers and safety, as in previous visits.

Demographic and anthropometric survey

During the screening visit, the participants provided information regarding their sociodemographic characteristics, such as date of birth, age, family history of disease, exercise, and smoking status. At every visit, the following parameters were measured twice by trained staff, and the average values were recorded: height, weight, body mass index (BMI), upper arm circumference, waist, hip, and thigh circumference, and waist-hip ratio (WHR). During these measurements, the participants wore minimal clothing and no shoes. The participants’ BMI was calculated as their body weight in kg divided by the square of their height in m (kg/m2). The BMI criterion was used in accordance with the WHO guidelines for the Asia-Pacific region: underweight = less than 18.5 kg/m2, normal weight = 18.5 to 22.9 kg/m2, overweight = 23 to 24.9 kg/m2, and obese (≥25 kg/m2). The accorded cutoff for inclusion in the obesity group is over 25 kg/m2.32 Their WHR was calculated as their waist circumference divided by their hip circumference. Body fat mass, body fat percentage, and fat-free mass were measured using bioelectrical impedance analysis (BIA) (InBody 230; INBODY, Seoul, Korea).

DXA and CT

At the 0-week and 12-week visits, DXA and CT were performed to evaluate the effect of obesity. Total and regional body fat (arm, leg, and trunk) were assessed using DXA (Lunar iDXA; GE Healthcare, Chicago, IL). The participants’ subcutaneous and abdominal fat area and the ratio between the two were measured using CT (LightSpeed Ultra 16; GE Healthcare, Chicago, IL, or Discovery CT750 HD; GE Healthcare, Chicago, IL).

Clinical laboratory tests

At the 0-week and 12-week visits, participants’ bloods were collected and examined to check their systemic health status after a 12-hour fast at the Nowon Eulji Medical Center. Alanine aminotransferase, aspartate transaminase, glucose, total cholesterol (TC), triglyceride (TG), free fatty acid, low-density lipoprotein-cholesterol (LDL-c), high-density lipoprotein-cholesterol (HDL-c), total protein, blood urea nitrogen (BUN), tyramine N-feruloyltransferase, albumin, and insulin levels were examined. At the screening and 12-week visits, blood samples were collected in serum separator tubes and centrifuged at 3,000 rpm for 15 minutes to separate the serum. The collected serum was stored frozen at −70°C until analysis. Serum leptin, adiponectin, and malondialdehyde were measured using an enzyme-linked immunosorbent assay, according to the manufacturer's protocol, from Invitrogen (Carlsbad, CA), Invitrogen (Gaithersburg, MD), and BlueGene (Shanghai, China), respectively.

Nutrition survey

Participants were instructed to maintain their usual diet and lifestyle but to refrain from eating anthocyanin-rich foods such as blueberries, grapes, strawberries, eggplant, and red lettuce. Dietary intake was assessed using 24-hour dietary recalls at baseline and at the end of the study under the supervision of a researcher. The participants were instructed to record 3 days (1 weekend day and 2 nonconsecutive weekdays) of food intake in a diet diary each week during the intervention study. To ensure that the dietary records were accurate, the participants were trained using food photographs and plastic models of commercial food to help them estimate portion sizes. Their energy and nutrient intakes were estimated using the CAN PRO 4.0 program (The Korean Nutrition Society, Seoul, Korea). We checked the participants’ food intake pattern using the food frequency questionnaire used in the Korea National Health and Nutrition Survey.

Statistical analysis

The primary efficacy measures related to obesity were body fat and body fat percentages measured using DXA, and abdominal fat measured using CT. The secondary efficacy measures related to obesity were anthropometric measures: weight and BMI as measured using DXA, body fat percentage as measured using BIA, and lipid metabolism. Clinical pathology, blood pressure, and adverse events were assessed as safety measures. Demographic characteristics were gathered in an intention-to-treat (ITT) analysis, which included all randomized participants. The efficacy outcomes were analyzed by using ITT and per-protocol (PP) population who had completed the 12-week treatment and had a compliance rate of over 70% without protocol violations. Safety analyses were carried out in all randomized participants who had taken at least one dose of the study medication. Missing data were replaced using the last observation carried forward analysis. The data were analyzed using SAS version 9.4 software. A paired t test or Wilcoxon rank-sum test was used to determine the efficacy difference between baseline and 12 weeks within the group. The distinction between the BRE and placebo groups was calculated using Student t test. A chi-square test was applied to the baseline characteristics. Repeated measures analysis of variance (RM-ANOVA) was used to confirm the change in efficacy measures over time. Using RM-ANOVA, the efficacy parameters related to obesity were assessed to identify differences between baseline and 12 weeks in both groups. All data are shown as mean ± standard deviation, and P values < 0.05 were considered statistically significant.

RESULTS

The baseline characteristics of participants

Initially, 105 participants were enrolled in the present intervention study. The participants were randomized into treatment or placebo groups: 53 to the BRE group and 52 to the placebo group. Seventeen participants were excluded from the study due to withdrawn consent for personal reasons (n = 12; BRE = 3 and placebo = 9), current use of medication (n = 2; placebo group), and previous or scheduled invasive surgery (n = 3; BRE group) (Fig. 1). The PP analysis provides an estimate of the true efficacy of an intervention, excluding participants who did not complete the 12-week treatment or had a compliance rate < 70%. The average compliance rate of the study participants was 89.8%, and two participants (one from each of the two groups) were omitted from the analysis because their compliance was less than 70%. Thus, a total of 86 participants (PP set) completed the clinical trial.

FIG. 1
FIG. 1:
Flow chart of the black rice extract (BRE) intervention demonstrating enrollment and randomization process.

As shown in Table 1, there were no significant differences between the groups in terms of baseline demographic characteristics, including age, height, weight, BMI, waist circumference, hip circumference, WHR, alcohol use, smoking status, or regular exercise. Based on dietary records, energy and nutrient intakes showed no significant differences between the two groups during the trial period (See Table, Supplemental Digital Content 1, https://links.lww.com/MENO/A817, which presents the daily nutrient intakes of the participants), and there was no significant difference between the groups in terms of physical activity.

TABLE 1 - Demographic characteristics of participants (n = 105)
BRE (n = 53) Placebo (n = 52) P
Age 56.91 ± 5.71 57.32 ± 5.45 0.6 a
Height 156.00 ± 5.51 155.34 ± 4.10 0.5 a
Weight 68.72 ± 9.80 68.32 ± 7.58 0.9 a
BMI 28.10 ± 3.05 28.31 ± 2.80 0.5 a
WC 90.92 ± 7.97 92.07 ± 6.74 0.3 a
HC 101.28 ± 6.14 102.55 ± 5.66 0.4 a
WHR 0.900 ± 0.05 0.900 ± 0.05 0.9 a
Alcohol use (Drinker/non-drinker/ex-drinker) 26/22 30/11 0.8 b
Smoking status (smoker/nonsmoker/ex-smoker) 2/45 0/41 0.3 b
Regular exercise (≥3 d/wk) (Y/N) 15/32 12/29 0.3 b
Values are presented as mean ± SD or percent.BMI, body mass index; BRE, black rice extract; HC, hip circumference; WC, waist circumference; WHR, waist-to-hip ratio.
aCompared between groups: P value by Student t test.
bCompared between groups: P value Chi-square test.

Primary outcomes

With regards to the body composition parameters using DXA and CT, the changes in trunk fat (P = 0.04), total fat (P = 0.04), total body fat percentage (P = 0.04), and trunk body fat (P = 0.04) were significantly different between the two groups (Table 2). However, leg fat and arm fat did not change significantly in either group. There were no significant between-treatment differences in change from baseline total abdominal area (P = 0.7), and subcutaneous fat area (P = 0.3), visceral fat area (P = 0.3), percentage ratio of visceral and total fat (P = 0.2), and percentage ratio of visceral and subcutaneous fat (P = 0.2) (Table 2).

TABLE 2 - Effects of 12-week consumption of BRE on body fat, weight, BMI, and abdominal fat areas
BRE (n = 46) Placebo (n = 40)
0 wk 12 wk Change (12wk-0wk) P a 0 wk 12 wk Change (12wk-0wk) P a P b
DXA measurement
 Trunk fat (kg) 15.03 ± 2.43 14.67 ± 2.44 −0.36 ± 0.62 <0.0001 14.88 ± 1.78 14.74 ± 1.62 −0.13 ± 0.35 0.02 0.04
 Leg fat (kg) 7.53 ± 1.05 7.42 ± 1.01 −0.11 ± 0.31 0.02 7.44 ± 1.06 7.39 ± 1.02 −0.04 ± 0.15 0.06 0.2
 Arm fat (kg) 3.07 ± 0.54 3.05 ± 0.55 −0.02 ± 0 .15 0.3 3.1 ± 0.39 3.11 ± 0.39 0.00 ± 0.09 0.8 0.1
Total fat mass (kg) 26.56 ± 3.53 26.06 ± 3.54 −0.5 ± 1.02 <0.0001 26.35 ± 2.86 26.17 ± 2.65 −0.18 ± 0.52 0.04 0.04
 Total body fat (%) 39.83 ± 2.41 39.73 ± 2.73 −0.15 ± 1.10 0.4 39.61 ± 2.39 39.85 ± 2.45 0.24 ± 0.60 0.01 0.04
 Trunk body fat (%) 43.74 ± 3.36 43.71 ± 3.72 −0.03 ± 1.61 0.9 43.4 ± 2.91 44.02 ± 2.74 0.62 ± 0.92 <0.0001 0.04
 Weight 69.51 ± 9.49 68.68 ± 10.05 −0.83 ± 1.83 0.01 67.8 2 ± 7.23 66.89 ± 6.89 −0.94 ± 1.76 <0.002 0.8
 BMI 28.23 ± 2.87 27.89 ± 2.9 −0.57 ± 0.74 0.01 28.01 ± 2.63 27.61 ± 2.54 −0.28 ± 0.75 <0.002 0.7
CT measurement
 Total Abdominal area (cm2) 35317 ± 9612 34978 ± 8722 −338.53 ± 3635.70 0.8 35086 ± 7924 34470 ± 7157 −616.59 ± 3747.74 0.4 0.7
 Subcutaneous fat area (cm2) 25134 ± 7978 25349 ± 7250 214.47 ± 3087.46 0.4 25606 ± 6523 25177 ± 5842 −429.19 ± 2510.22 0.3 0.3
 Visceral fat area (cm2) 10182 ± 3495 9629 ± 3333 −553.00 ± 1289.86 0.03 9481 ± 3083 9293 ± 3064 −187.41 ± 2287.25 0.5 0.3
 Visceral/total (%) 29.18 ± 7.41 27.63 ± 7.47 −1.55 ± 3.45 0.01 27.23 ± 7.05 27 ± 7.35 −0.23 ± 4.48 0.8 0.2
 Visceral/subcutaneous (%) 42.95 ± 17.46 39.73 ± 15.44 −3.23 ± 7.79 0.01 38.80 ± 14.79 38.5 ± 15.65 −0.30 ± 9.54 0.8 0.2
Values are presented as mean ± SD or percent's.BMI, body mass index; BRE, black rice extract; CT, computed tomography; DXA, dual-energy x-ray absorptiometry.
aCompared within groups: P value by paired t test.
bCompared between groups: P value by RM-ANOVA.

Secondary outcomes

There were no significant between-treatment differences in change from baseline body weight (P = 0.8) and BMI (P = 0.7), measured by DXA. Concerning lipid metabolism, TG levels varied significantly between groups (P = 0.04); otherwise, no significant differences were observed for remaining parameters (Table 3). Body fat percentage, as estimated using BIA, was significantly lower in the BRE group than in the placebo group, with a marginally significant difference between groups (P = 0.05) (See Table, Supplemental Digital Content 2, https://links.lww.com/MENO/A818). There were no significant differences between the placebo and treatment groups regarding anthropometric measures such as weight, BMI, mid-arm circumference, waist circumference, hip circumference, and WHR (See Table, Supplemental Digital Content 2, https://links.lww.com/MENO/A818). Concerning ITT analysis, no significant differences were observed for primary outcomes like body fat, weight, BMI, and abdominal fat regions (See Table, Supplemental Digital Content 3, https://links.lww.com/MENO/A819), as well as secondary outcomes like lipid metabolism, clinical pathology tests, and vital signs (See Tables, Supplemental Digital Content 4, https://links.lww.com/MENO/A820, and Supplemental Digital Content 5, https://links.lww.com/MENO/A821).

TABLE 3 - Effects of 12-wk consumption of BRE on lipid metabolism, leptin, and adiponectin
BRE (n = 46) Placebo (n = 40)
0 wk 12 wk Change (12wk-0wk) P a 0 wk 12 wk Change (12wk-0wk) P a P b
Triglyceride (mg/dL) 139.89 ± 71.16 123 ± 44.19 −16.89 ± 56.27 0.05 110.85 ± 58.35 119.53 ± 63.95 8.68 ± 55.71 0.3 0.04
Free fatty acid (μEg/L) 386.98 ± 181.70 468.35 ± 205.03 81.37 ± 278.89 0.05 422.28 ± 197.13 507.9 ± 223.06 85.63 ± 338.65 0.1 1.0
Total cholesterol (mg/dL) 221.5 ± 37.14 218.85 ± 29.55 −2.65 ± 32.64 0.6 215.08 ± 38.7 219.8 ± 36.39 4.73 ± 27.23 0.3 0.2
LDL (mg/dL) 143.98 ± 31.99 138.13 ± 28.3 −5.85 ± 31.92 0.2 139.23 ± 30.7 140.85 ± 29.9 1.63 ± 25.04 0.7 0.3
HDL (mg/dL) 53.5 ± 9 53.78 ± 9.93 0.28 ± 5.72 0.7 58.4 ± 11.71 56.85 ± 11.34 1.63 ± 25.04 0.2 0.5
MDA (μg/mL) 493.59 ± 217.78 485.37 ± 195.49 −14.22 ± 218.20 0.7 493.11 ± 206.15 491.00 ± 218.11 −2.11 ± 192.40 0.9 0.5
T4 (ng/dL) 1.20 ± 0.16 1.14 ± 0.17 −0.06 ± 0.17 0.02 1.22 ± 0.21 1.14 ± 0.17 −0.08 ± 0.22 0.03 0.6
Leptin (ng/mL) 24.60 ± 11.11 22.09 ± 12.48 0.65 ± 8.44 0.8 18.13 ± 7.77 18.63 ± 7.47 0.97 ± 6.13 0.4 0.9
Adiponectin (ng/mL) 14586 ± 7759 16607 ± 12191 2105.15 ± 9304.91 0.5 12975 ± 7332 15099 ± 10024 2193.74 ± 7152.11 0.2 1.0
Values are presented as mean ± SD.BRE, black rice extract; HDL, high-density lipoprotein; LDL, low-density lipoprotein; MDA, malondialdehyde; T4, thyroxine.
aCompared within groups: P value by paired t test.
bCompared between groups: P value by RM-ANOVA.

Other outcomes

The effect of BRE and placebo on adipokines (leptin and adiponectin) is shown in Table 3. No significant difference was observed in leptin and adiponectin levels between BRE and placebo groups after the 12-week intervention.

Safety

The clinical pathology test results did not show statistically significant differences between BRE and the placebo group (Table 4). Vital signs (systolic blood pressure, diastolic blood pressure, and pulse) did not demonstrate clinically significant changes between the two groups, and levels remained within the normal range. In the BRE group, among the 47 participants, 20 adverse events were reported in 18 participants (38%): 2 cases of dyspepsia, 11 of cold, 1 of flu, 2 of gastritis, 2 of stomachache, and 2 of constipation. Among 41 participants in the placebo group, 26 adverse events were reported in 17 participants (41%): 1 case of feeling hunger after eating, 2 of gastritis, 6 of dyspepsia, 3 of constipation, 9 of cold, 1 of stomachache, 2 of dizziness, 1 of headache, and 1 of insomnia. There was no significant difference in the rate of adverse events between the groups, neither was there any relationship between BRE and these adverse events.

TABLE 4 - Clinical pathology test and vital signs
BRE (n = 47) Placebo (n = 41)
0 wk 12 wk Change (12wk-0wk) P a 0 wk 12 wk Change (12wk-0wk) P a P b
ALT (IU/L) 20.39 ± 9.92 20.50 ± 11.65 0.11 ± 8.70 0.9 22.08 ± 10.55 19.20 ± 7.18 −2.88 ± 9.62 0.04 0.2
AST (IU/L) 21.48 ± 5.10 21.91 ± 6.61 0.43 ± 6.08 0.6 22.68 ± 6.36 22.13 ± 5.28 −0.55 ± 5.89 0.5 0.7
Total protein (g/dL) 7.07 ± 0.36 7.02 ± 0.33 −0.06 ± 0.30 0.2 7.07 ± 0.44 7.09 ± 0.36 0.02 ± 0.34 0.7 0.2
Albumin (g/dL) 4.56 ± 0.19 4.48 ± 0.23 −0.08 ± 0.21 0.009 4.56 ± 0.25 4.54 ± 0.24 −0.02 ± 0.21 0.6 0.1
BUN (mg/dL) 13.57 ± 3.37 14.15 ± 3.97 0.58 ± 3.67 0.4 15.43 ± 3.50 14.29 ± 3.11 −1.14 ± 3.05 0.01 0.2
Glucose (mg/dL) 94.96 ± 10.60 95.74 ± 8.85 1.77 ± 10.15 0.2 95.43 ± 9.08 97.03 ± 7.75 1.60 ± 4.96 0.05 1.0
Insulin (μIU/mL) 6.57 ± 4.76 5.95 ± 4.08 −0.62 ± 3.90 0.2 5.18 ± 2.68 5.48 ± 2.83 0.30 ± 2.42 0.3 0.6
SBP (mmHg) 129.87 ± 13.83 126.00 ± 12.60 −4.11 ± 10.20 0.01 131.14 ± 12.88 125.36 ± 13.37 −9.03 ± 23.51 0.02 0.4
DBP (mmHg) 77.68 ± 8.60 73.76 ± 8.81 −4.09 ± 7.56 <0.001 77.36 ± 7.95 74.83 ± 8.72 −2.7 ± 7.95 0.05 0.4
Pulse (rate/min) 78.80 ± 9.26 76.57 ± 10.79 −2.41 ± 9.74 0.07 76.13 ± 8.03 74.63 ± 8.74 −1.70 ± 7.52 0.2 0.9
Values are presented as mean ± SD.ALT, alanine aminotransferase; AST, aspartate transaminase; BRE, black rice extract; BUN, blood urea nitrogen; DBP, diastolic blood pressure; SBP, systolic blood pressure.
aCompared within groups: P value by paired t test.
bCompared between groups: P value by RM-ANOVA.

DISCUSSION

In our previous in vivo study, it was demonstrated that the extracts of black rice decreased obesity and lipid modulating factors in the estrogen deficiency rat model.30 Thus, in light of previous findings, the aim of this research was to see if a 12-week BRE intervention (500 mg, twice daily) could help obese postmenopausal Korean women lose weight as compared to a placebo. The major findings of this study were the significant differences in trunk fat (kg and %), total fat mass (kg and %), and TG, compared to placebo. Since fat mass is linked to a variety of cardiometabolic comorbidities, it is one of the most important outcomes of weight-loss interventions and a measure of their effectiveness.33 Participants supplementing with BRE observed improved body structure changes by restricting their intake to anthocyanin-rich foods.

A significant decrease in trunk fat and total fat mass was observed after 12 weeks in the treatment group. Interestingly, we also observed this change in the placebo group, which we believe is due to placebo effect. During the present intervention, all participants were instructed to maintain their dietary intake patterns and physical activity routine. We assessed the physical activity of the participants, but there was no significant change between the placebo and treatment groups; thus, the results were not shown. Seasonal variations have been shown to influence nutritional status and body composition.34,35 In fact, the 12-week period of this study may have included other seasons before and after BRE ingestion. Although nutrient intakes were not different between the groups, the placebo group's ingestion of other phytonutrients, such as carotenoids, may have had an antiobesity impact depending on the season.

Germinated black rice has been shown in vivo to ameliorate obesity and improve lipid profile by lowering TG, TC, and LDL-c in serum while increasing HDL-c levels.20 Enhanced expressions of lipolytic enzymes such as hormone-sensitive lipase, adipose TG lipase, and carnitine palmitoyltransferase-1, as well as uncoupling protein 2, while downregulated expressions of lipogenic factors such as peroxisome proliferator-activated receptor gamma, CCAAT enhancer-binding protein alpha/beta (C/EBPα/β), sterol regulatory element-binding protein-1c, fatty acid synthase, and lipoprotein lipase, supported the antiobesity effect of black rice in high-fat diet-induced mice with obesity.20 Likewise, Kim et al demonstrated that black rice (Heukmi) suppressed adipogenesis in mesenchymal (C3H10T1/2) stem cells by downregulating lipogenic factors. The authors correlated this mechanism of regulation with the Wnt signaling pathway because it involved controlled expression of the target genes.27 These findings demonstrate the BRE has some effects on improving obesity.

In our study, there were no significant variations between groups in total abdominal area, subcutaneous fat area, visceral fat area, visceral/total (%) and visceral/subcutaneous (%). Within the BRE intervention group, however, visceral fat region, visceral/total (%), and visceral/subcutaneous (%) showed substantial reductions. Lovejoy et al35 reported that visceral fat rose considerably from 3 to 4 years preceding menopause compared with menopause onset. Furthermore, previous studies have shown that, regardless of the change in body weight, menopause leads to a significant change in visceral fat build-up.36,37 Thus, the nonsignificant differences in this study could be that the participants of the study were obese postmenopausal women, thus the short-term BRE intervention did not reach the optimal degree of significance.

Interestingly, body weight and BMI were decreased in both groups without a significant difference after supplementing BRE for 12 weeks. The plausible reason, why these indicators were not different between BRE and placebo groups, may be that our participants were obese. Second, the small sample size and shorter duration of the study could have limited statistical significance from being attained. A reduction in bone mineral density in postmenopausal women caused an overall bodyweight decline and consequently a mitigation in BMI (weight/height ratio), even when the percentage of fat mass matched with the initial value.38 Indeed, another recent study implied that BMI is not an effective indicator of obesity status in postmenopausal women.39

Obesity is linked to elevated levels of TC, TG, and LDL-c in the blood, as well as low levels of HDL-c.40 Our findings revealed that the BRE intervention had little effect on TC, LDL-c, or HDL-c levels. However, the TG concentration was significantly decreased in the BRE group; thus, black rice intake may improve obesity by reducing body fat accumulation and increasing lipolysis. Several earlier studies have investigated the association between hypertriglyceridemia and body fat mass.41,42 The waist circumference (WC) and waist-to-hip ratio (WHR) are used as indirect measures to estimate visceral fat. In this study, no significant differences were observed between groups for WC and WHR. A randomized clinical (8-wk) trial found that BBT (black soybean testa extracts rich in anthocyanin) treatment showed no significant differences in WC, WHR, TG, and TC in Korean adults with overweight/obesity. BBT, on the other hand, was able to demonstrate a variety of causal results, including improving plasma lipid profiles for reducing abdominal obesity as long as low cholesterol and high fiber diets were sustained. Anthocyanin C3G, the same active ingredient present in black rice, may be responsible for BBT's conditional benefits.43 A meta-analysis of 11 studies has been conducted on obese postmenopausal women to assess the effectiveness of exercise and diet therapy for weight loss and body composition. Dietary interventions are found to be more effective than exercise alone. The study emphasized that the addition of exercise can strengthen the effect of diet therapy on altering body weight and composition.44 Thus, the capacity of BRE to decrease body fat in obese postmenopausal women can be enhanced by including an exercise regimen. As a result, BRE extract can be tested on a significant number of participants for a prolonged period of time to provide a more accurate conclusion about BRE intervention. Furthermore, there is a scarcity of information on nutritional modification trials for weight loss in obese postmenopausal women. Diets that are useful for long-term weight management in obese postmenopausal women should be the subject of future research.

Overall, this preliminary clinical study based on BRE intervention revealed some significant effects on DXA-measured body fat reduction. BRE, on the other hand, showed decreasing trends on other basic indicators with no significant alterations between groups that might be attributed to the short duration of the trial. To the best of our knowledge, no intervention study examining the effects of BRE on postmenopausal women has been published. To fully understand the potential of black rice intervention on obesity, more long-term studies are needed.

Strengths and limitations

The strengths of the present trial include the study design (randomized, placebo-controlled, double-blind intervention) and the measured parameters (anthropometric and biochemical). The limitations of the study include its small sample size and its failure to analyze the intervention in a dose-dependent manner. Another limitation is that our findings do not apply to all postmenopausal women seeking health care for obesity who also have other conditions such as depression, gout, gall bladder disease, and asthma, which were excluded from the study. All these factors could affect the generalizability of the study. Furthermore, because our findings apply to postmenopausal women who are obese, more research is needed to validate these findings in overweight postmenopausal women. All our participants were Korean postmenopausal women; therefore, a study including men, other ethnic populations, and ages is needed to confirm our results. Finally, the short duration of the treatment does not allow for substantial weight loss, which restricts determining the potential long-term effects of BRE. Another drawback of the study is comparisons using multiple statistical approaches. It is common in medical or biomedical science to interpret data using several statistical methodologies in a single paper. In general, the more the hypothesis is evaluated using various statistical methods and more P values are obtained, the more assurance we can have in the results (P values). Taking into account all of the limitations of this preliminary study, further investigation is warranted.

CONCLUSIONS

This was the first randomized, double-blind, placebo-controlled 12-week trial carried out on obese postmenopausal women. BRE intervention ameliorated visceral fat and total fat in obese postmenopausal Korean women, which could be considered as preliminary findings of BRE. Further long-term studies are warranted to investigate the dose-dependent effect; however, BRE supplementation could act as a therapeutic antiobesity functional food in postmenopausal women.

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Keywords:

Anthocyanins; Antiobesity; Body composition; Body fat; Body mass index; Total fat

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Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of The North American Menopause Society.