Potential Health Benefits of Genetically Modified Rice

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1		Weiqun Wang	--	1860	2023-08-01 15:51:06	\|
2	format correct	Wendy Huang	Meta information modification	1860	2023-08-02 09:46:13	\|

This entry is adapted from the peer-reviewed paper 10.3390/foods12142776

The production of rice, an important cereal crop and staple food for most of the world’s population, faces challenges due to climate change, the increasing global population, and the simultaneous prevalence of hunger and obesity worldwide. These issues could be addressed at least in part by genetically modified rice. Genetically modified rice has been approved by the ISAAA’s GM approval database as safe for human consumption. The aim behind the development of this rice is to improve the crop yield, nutritional value, and food safety of rice grains.

genetically modified rice bioactive components antioxidant activity diabetes anti-inflammatory activity

1. Introduction

Oryza sativa, more commonly known as rice, is an important cereal crop and essential food for most of the world’s population, especially in Asian countries ^[1]^[2]. As shown in Figure 1, rice is the third top grain worldwide in terms of production in 2021/22. The relationship between humans and rice is incredibly old, and it is believed to have been cultivated in China as early as 10,000 years ago ^[3]. Although wild rice is often found in wetlands, there are two types of rice cultivation: dry-land rice and paddy rice. Compared to dry-land crops, paddy-cultivated rice has the advantages of less weeding, less soil runoff, and the ability to be grown in successive crops ^[3]. In addition, it would have a water storage effect as a source of groundwater. Rice, with its historical relationship to people, has significant potential for addressing numerous forthcoming challenges.

While the world population has been growing continually since 1955 (Figure 2), developing and developed countries are facing different types of “malnutrition”. In developing countries, up to 828 million people are experiencing food insecurity and 49 million people are enduring a hunger crisis ^[4]. As a result, malnutrition kills 25,000 people each day ^[4]^[5]. Developed countries also face malnutrition issues, particularly diet-related non-communicable diseases such as heart disease, cancer, stroke, diabetes, and obesity ^[5]. Meanwhile, the world’s climate is rapidly changing. Climate change brings unstable weather, natural disasters, and a disruption to natural resources, all significantly impacting agricultural production. Extremely high temperatures cause depletion of water resources and reduce natural resources, such as habitat and food for beneficial insects (e.g., honeybees) ^[6]. As a result, crop flowering and pollination are inhibited, and weed and pest infestations increase. Droughts cause poor harvests and loss of agricultural land. Heavy rains cause flooding, which removes topsoil and damages crops ^[6]. One study estimates that climate change will make crop production (corn, rice, wheat, and soybeans) more precarious, with production declining by 8% by the 2050s in Africa and South Asia ^[7].

Introduced in 1996, genetically modified (GM) crops have been touted to increase food production by increasing yield per unit area (unit yield) without the destruction of nature by clearing or expanding farmland when compared to non-GM crops ^[8]. Rice has been genetically modified to produce a larger, more nutrient-dense product while increasing herbicide and pesticide resistance, accelerating photosynthesis, and producing essential proteins. The year 2000 marked the approval by the United States of the first two herbicide-resistant GM rice varieties called LLRice60 and LLRice62 ^[9]. Subsequently, GM rice varieties resistant to herbicides, including these and others, received official approval in Canada, Australia, Mexico, and Colombia. Nevertheless, the granting of these approvals did not lead to their commercialization ^[10]. In 2009, it was reported that China had authorized the biosafety of GM rice engineered to resist pests; however, that particular strain was not brought into commercial production ^[11]. Both Canada and the United States granted approval for the cultivation of genetically modified golden rice in 2018. Health Canada and the US Food and Drug Administration affirmed its safety for consumption ^[12]. According to the Qingdao Saline-Alkali Tolerant Rice Research and Development Center, as of 2021, China had successfully cultivated salt-tolerant “seawater” rice on approximately 990,000 acres of land with salt levels of up to 4 g per kilogram ^[13]. As mentioned previously, while GM rice has been developed and accepted in some countries, it has not yet been accepted and commercialized in many others. One possible cause is that GM rice is new, different, and unknown, and people’s uneasiness about side effects may be an obstacle. Political issues are another concern for the commercialization of GM rice. Thus, the prospects for GM rice are expected to flourish, unless it is met by some issues. As GM rice varieties continue to be improved, it is now being grown in the fields of many countries.

The application of new genome-editing breeding technologies has significantly expanded the possibilities for crop improvement in rice. In recent years, various genome-editing techniques, including CRISPR-directed evolution, CRISPR-Cas9, and base editors, have emerged as powerful tools for efficient and precise genome modifications in rice. The suitability of rice as a model system for functional studies, its small genome size, and close syntenic relationships with other cereal crops have further accelerated the development and implementation of novel genome-editing technologies in rice ^[14]. Researchers continue to innovate and refine these technologies specifically tailored for rice, allowing for targeted genetic modifications to improve desired traits ^[15]. By harnessing the power of these emerging technologies, researchers can unlock the full potential of rice as a vital crop, contributing to global food security and sustainable agriculture.

Figure 1. Grain production in 2021/2022 adapted and modified from http://igc.int/en/gmr_summary.aspx ^[16] accessed on 5 July 2023.

Figure 2. Global population growth since 1955 adapted and modified from https://www.unfpa.org/data/world-population-dashboard ^[17] accessed on 9 April 2023.

2. Bioactive Compounds

Rice is rich in nutrients such as carbohydrates, fiber, protein, vitamins, and minerals ^[18] (Table 1). In addition to nutritional components, rice contains bioactive components known as phytochemicals, such as phenolic compounds (e.g., campesterol and caffeic acid), flavonoids (anthocyanin and proanthocyanin), γ-oryzanol, carotenoids (e.g., α-carotene, β-carotene, lycopene, and lutein), phytosterols (e.g., β-sitosterol, stigmasterol, and campesterol), vitamin E isoforms (α-, γ-, δ-tocopherols and tocotrienols), gamma-aminobutyric acid (GABA), phytic acid, coumaric acid, and tricin ^[18]^[19]. These bioactive components have a variety of biological activities, the most significant of which are antioxidant, anticancer, anti-diabetic, and anti-inflammatory ^[19]. The potential health benefits are exhibited in humans as they consume rice as part of their routine daily diet ^[18]. One study conducted in China showed that when compared to wheat preference, rice preference was associated with a lower risk of excessive body fat in men and a lower risk of central obesity in women ^[20].

Table 1. Nutritional composition of brown rice and milled rice ^[21].

Components	Amounts (per 100 g)
Components	Brown Rice	Milled Rice
Carbohydrate (g)	73–87	77–87
Protein (g)	7.1–8.3	6.3–7.1
Fiber (g)	2.9–4.4	0.7–2.7
Fat (g)	1.6–2.8	0.3–0.6
Calcium (mg)	10–50	10–30
Phosphorus (mg)	0.17–0.43	0.08–0.15
Iron (mg)	1.4–5.2	0.3–0.8
Zinc (mg)	1.9–2.8	0.8–2.3
α-tocopherol (mg)	0.8–2.5	0.1–0.3
Phytic acid P (mg)	0.13–2.7	0.02–0.07
Thiamin (mg)	0.4–0.6	0.07–0.17
Riboflavin (mg)	0.04–0.14	0.02–0.06
Niacin (mg)	3.5–6.2	1.3–2.5
Pantothenic acid (mg)	1.4–1.6	0.8–1.3
Vitamin B6 (mg)	0.5–0.7	0.1–0.4
Folate (μg)	16–20	4–9

3. Antioxidant Activity

Antioxidants protect against oxidative damage and help to reduce the risk of chronic diseases such as cancer, cardiovascular disease, and type 2 diabetes ^[22]^[23]^[24]. The vitamin E content found in rice can promote antioxidant activity. Pigmented rice varieties such as black, purple, red, and brown rice contain anthocyanins, the phytochemical responsible for the deep purple and red color in plants like berries and grapes that promote antioxidant activity. Antioxidants like anthocyanins have been associated with a protective factor against some cancers. A study showed a dose-dependent decrease in the size and number of aberrant crypt foci formed and β-catenin expression in rats fed a crude extract of germinated rice ^[25]. Gamma-aminobutyric acid (GABA) is another bioactive compound found in rice. The GABA contents of germinated brown rice were shown to have inhibitory effects on the reproduction of some cancer cells as well as increased stimulation of immune response ^[18]^[26]. GABA is known to improve hypertension, memory impairment, hypo-motivation, and sleep disturbance by suppressing noradrenaline secretion in the periphery, inhibiting excitation of the whole brain through afferent neurotransmission, stimulating cerebral blood flow, increasing oxygen supply, and enhancing the metabolic function of brain cells ^[27]. In a mouse model of type 2 diabetes induced by a high-calorie diet, elevated total and LDL cholesterol levels and decreased adiponectin levels were observed in the blood. To clarify the active ingredient, GABA, which is abundant in the germ extract, was orally administered, and a significant increase in blood adiponectin level was observed with GABA. As mentioned above, inhibitory nerves are likely involved in the GABA mechanism of action. Since the blood adiponectin level generally decreases in humans and mice under stress, the administration of GABA may alleviate stress, resulting in an increase in blood adiponectin level ^[27].

4. Anti-Diabetic Activity

Metabolic improvements associated with germinated brown rice can be helpful in the management of type 2 diabetes. These improvements include better glycemic control, reduced type 1 tissue plasminogen, amelioration of oxidative stress, correction of dyslipidemia, and increased activity of sodium–potassium adenosine triphosphatase and homocysteine thioacetone ^[28]. Using an open-labeled, randomized, cross-over study design, researchers observed that there was a significant decrease in postprandial plasma glucose, hemoglobin A1c (HbA1c), and lactalbumin levels in patients who ate brown rice two times a day when compared with those who ate white rice. (Figure 3) These effects are due to the rich bioactive content such as dietary fiber found in brown rice ^[29].

Figure 3. Levels of HbA1c (mean ± SD) at baseline, 4th, and 12th weeks in individuals with type 2 diabetes following a brown rice-based vegan or conventional diet.

Furthermore, one study reported that a diet composed of GABA-rich germinated brown rice and white rice did not produce significant changes in most metabolic indices in healthy individuals. Using 67 healthy volunteers (71 ± 8 aged), the effects of white rice and germinated brown rice + white rice (1:1, w/w) were determined following consumption for 11–13 months. There was only a significant decrease in HbA1c in the germinated brown rice + white rice group, but no differences were noted in body mass index, blood pressure, serum lipids, and homeostasis model assessment of insulin resistance between the two groups ^[30]. Germination of brown rice is one of the ways to increase the bioactive concentration in order to enhance the functional effect. Although it is not yet clear which bioactive substances are responsible for the functional effects of sprouted brown rice, several bioactive substances may contribute to the observed effects: fiber in the GBR is known to lower blood glucose levels by regulating glucose absorption in the intestine ^[30]. The influence of GABA receptors in pancreatic islets contributes to decreased insulin secretion in type 2 diabetes, and GABA supplementation has been reported to increase insulin secretion. This may explain the reduction in blood glucose levels in diabetes caused by GABA ^[30].

5. Anti-Inflammatory Activity

One study concluded that a brown rice diet may be useful to decrease inflammatory marker levels ^[31]. In that study, overweight or obese women who followed a diet including brown rice had lower diastolic blood pressure and levels of the inflammatory marker hs-CRP compared to those who followed a diet without brown rice ^[31]. Additionally, incorporating brown rice into the diet can be a beneficial strategy for achieving significant weight loss and reducing visceral obesity.

A significant mechanism of immune pathogenesis is inflammation, which is our body’s response to tissue infection, injury, or stress. Some reports have shown that lipophilic phytochemicals, such as γ-oryzanol and vitamin E derivatives contained in pigmented rice germ and bran, may possess anti-inflammatory activity ^[32]. Another study reported that pigmented rice contains large amounts of medium polar or hydrophilic compounds, such as phenolic compounds, anthocyanins, proanthocyanins, and bioflavonoids, which show anti-inflammatory activity in both in vitro and in vivo models ^[33].

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