Obesity comes from excessive body fat accumulation that progresses to severe health impairment [1] . Currently, obesity is considered a pandemic condition and a public health problem associated with increased risk for development of several complications and comorbidities as type 2 diabetes mellitus (DM2), hypertension, and dyslipidemia. In addition, these comorbidities are associated to improved risk of kidney and cardiovascular diseases development [2] . All these functional or metabolic disorders has been stablished as risk factors for Coronavirus disease 2019 and predictors of severity [3, 4] .
It has been known that obesity is implicated in systemic immunomodulatory effects that impair human metabolism and contributes to respiratory viral infection [5] .
Recent publications discus the high prevalence of negative clinical outcomes due COVID-19 infection in obese individuals [6] [7] [8] [9] . This prevalence can be explained by preexisting conditions that impair immune response or amplified pro-inflammatory responses triggered for obesity [8] . Growing evidence strongly suggests an etiological role of inflammation and oxidative stress. In addition, insufficient cellular protection against it also has been ascribed as another contributing factor for intensify inflammation.
Therefore, efficient reduction of oxidative stress through activation of multiple antioxidant defense systems was envisaged as a promising strategy to improve the inflammation and diseases. It is well established that obesity promotes a low-grade chronic systemic inflammation and oxidative stress. However, when COVID-19 is associated to this condition, patients might develop a hyperinflammatory condition and the cytokine storm syndrome, which can lead to organs dysfunctions and failure, and even, death [10, 11] .
The adipose tissue is a dynamic organ responsible not only by the fat storage, but it also exerts an endocrine role, secreting several adipokines that control the organism homeostasis [12, 13] . The adipokines include leptin, adiponectin, and inflammatory cytokines, in a complex network that physiologically regulates appetite, energy expenditure, peripheral insulin sensitivity, redox state, and lipid absorption in non-fat tissues [2] . However, in organisms under positive energetic balance, there is an adipose tissue hypertrophy, which is associated with disturbances in lipid metabolism and alterations in adipokines secretion, installing a pro-inflammatory state and oxidative stress. This adipose tissue dysfunction accelerates the development and progression of obesity-related insulin resistance and chronic diseases [14] .
Efficient therapies or vaccines able to interrupt the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections are still unavailable. In this meantime, the search for alternative therapies to modulate positively the immune response and the COVID-19 progression is urgent [15, 16] . Several mechanisms have been studied around the world to find a strategy to control the virus insidious inflammatory effects. One of these potential mechanisms would be the immune system modulation by down-regulating the inflammatory response and oxidative via the peroxisome proliferator-activated receptor gamma (PPAR-γ). This nuclear receptor is highly expressed in adipose tissue and regulates the expression of several genes involved in adipocyte differentiation, lipid and carbohydrate metabolism, oxidative stress, and inflammation [17] . Considering this, a scientific study written by Ciavarella et al. (2020) , reports that PPAR-γ agonist substances may be candidates for cytokines storm modulation in COVID-19 disease [16] .
Natural compounds as γOz, the main bioactive from rice bran and germ, is a compound with anti-inflammatory and antioxidant activities [18] . Studies have shown that the γOz has a positive action in the treatment of some obesity-related comorbidities and attenuation of proinflammatory cytokines [19] [20] [21] [22] . However, little is known about the γOz action as a possible modulator of PPAR-γ. Thus, since this nuclear factor is synthetized by adipose tissue, the aim of this study was to test the hypothesis that γOz attenuates the cytokine storm by modulating immune system and oxidative in the adipose tissue.
J o u r n a l P r e -p r o o f
All the experiments and procedures were approved by the Animal Ethics Committee of Botucatu Medical School (process nº 1150/2015) and were performed in accordance with the National Institute of Health's Guide for the Care and Use of Laboratory Animals. Male Wistar rats (±187 g) were kept in an environmental controlled room (22 °C ± 3 °C; 12 h light-dark cycle and relative humidity of 60 ± 5%) and randomly divided into 3 experimental groups to receive: control diet (Control, n = 6), high sugar-fat diet (HSF, n = 6), or high sugar-fat diet + γOz (HSF + γOz, n = 6) during 30 weeks. HSF groups also received water + sucrose (25%). The diets and water were ad libitum. The diets used in this study were designed in our laboratory and previously published by our research group [20] . The HSF diet contained soybean meal, sorghum, soybean peel, dextrin, sucrose, fructose, lard, vitamins, and minerals, plus 25% sucrosein drinking water. Control diet contained soybean meal, sorghum, soybean peel, dextrin, soy oil, vitamins, and minerals. The nutrients and nutritional composition of each diet are presented in Table 1 . 
The compound was purchased from Tokyo Chemical Industry Co., Ltd. (Toshima, Kita-ku, Tokyo) (lot.5ZZYLPJ). Due to its nonpolar characteristics, γOz was added to diets to reach 0.5% of final concentration (w/w). This dose was based on the work of Son et al. [22] and on the daily rice consumption of an adult individual in Brazil, according to data from the Family Budget Survey (POF) 2008-2009 [23] .
The nutritional parameters included the following parameters: chow fed, water intake, caloric intake, final body weight, and adiposity index. Caloric intake was determined by multiplying the energy value of each diet (g × Kcal) by the daily food consumption. For the HSF group, caloric intake also considered the calories from water (0.25 × 4 × mL consumed). Body weight was measured weekly. After euthanasia, the fat deposits (visceral (VAT), epididymal (EAT) and retroperitoneal (RAT) were used to calculate the adiposity index (AI) by the following formula: [(VAT + EAT + RAT)/FBW] x100 [21] . insulin (µU/mL))/22.5 [21] .
Systolic blood pressure (SBP) evaluation was assessed in conscious rats by the noninvasive tail-cuff method with a Narco Bio-Systems® electrosphygmomanometer (International Biomedical, Austin, TX, USA). The animals were kept in a wooden box (50 × 40 cm) between 38 and 40°C for 4-5 minutes to stimulate arterial vasodilation [24] .
After this procedure, a cuff with a pneumatic pulse sensor was attached to the tail of each animal. The cuff was inflated to 200mmHg pressure and subsequently deflated. The blood pressure values were recorded on a Gould RS 3200 polygraph (Gould Instrumental
Valley View, Ohio, USA). The average of three pressure readings was recorded for each animal.
Doppler echocardiographic evaluation was performed by a single examiner at the 
Data are presented as means ± standard deviation (SD) or median (interquartile range). Differences among the groups were determined by One-way analysis of variance.
Parametric variables were subjected to the Tukey post-hoc test to compare all the groups.
Non-parametric variables were compared by Kruskal-Wallis post-hoc test. Statistical analyses were performed using Sigma Stat for Windows Version 3.5. (Systat Software, Inc., San Jose, CA, USA). A p <0.05 was considered as statistically significant. Table 1 presents the nutritional, hormonal and cardiometabolic parameters. Both groups that received the HSF diet presented lower chow fed and higher water intake compared to control group with no difference for caloric intake among the groups. The Adipose tissue PPAR-γ gene and protein expression are presented in the figure 5.
It is possible to note that γOz positively modulates both gene and protein expression in the HSF + γOz group. COVID-19, influenza virus has the ability to induce severe disease with remarkable cytokine releasing by inflammatory cells [15, 31] . However, as demonstrated for influenza viruses [32] , the PPAR-γ activation has emerged as treatment for cytokine storm by inducting anti-inflammatory and antioxidant modulation [16] .
PPAR-γ is responsible by controlling several processes, such as adipogenesis, lipolysis, inflammation, oxidative stress, glucose regulation, and lipid metabolism. Thus, any disruption in this receptor function can lead to adipose tissue dysfunction, usually associated with metabolic disorders, as insulin resistance [33] . Confirming the literature, the HSF group presented reduced PPAR-γ expression and insulin resistance and high triglycerides and leptin levels. In opposition, the HSF + γOz group maintained the same PPAR-γ expression as the control group and an attenuation in plasma levels of blood glucose, triglycerides, leptin and decreased final body weight when compared to HSF.
This is an important finding, especially in COVID-19 patients, since the presence of obesity-related comorbidities are associated with negative outcomes [3] .
The literature shows several mechanisms by which γOz can act on glucose metabolism. First, the authors describe that this compound can regulate insulin secretion and hepatic glucose-regulating enzyme activities [22] . Another mechanism described is the improvement in the pancreatic β cells function, mainly through the reduction of endoplasmic reticulum stress, caused by the excess of free fatty acid, glucose and chronic inflammation, leading to the suppression of insulin biosynthesis and resulting apoptosis [34] . In addition to these pathways, we can emphasize that since oxidative stress is considered a key factor in the development of diabetes, the antioxidant action of γOz has also been identified as a glycemic reducer by neutralizing the reactive species. These findings are in agreement with our results, which a decrease in blood glucose, insulin and the HOMA-IR index was observed in HSF + gamma when compared to HSF. About the γOz action on glucose reduction by stimulating PPAR-γ, no studies were performed. This would be very important, since the mechanism of action would be similar to pioglitazone [35] .
Regarding the decrease in plasma triglyceride levels, it is described that γOz increases the elimination of fecal fat by inhibiting intestinal lipase, which impairs the degradation of ingested triglycerides to fatty acid and consequently reduces intestinal absorption, levels of serum triglycerides, and also storage in adipose tissue. Another explanation is that leptin inhibits food intake, stimulates cell energy expenditure, and results in a reduction of the body's fat stores [18] . This behavior was observed in the HSF group, where the reduced PPAR-γ expression was followed by increased insulin resistance, triglycerides and leptin levels. In opposition, the HSF + γOz group was able to sustain the PPAR-γ expression similar to the control group, attenuating the obesityinduced metabolic disorders.
Cardiovascular disease is one of the risk factors for severe COVID-19 disease, and it is well known that obese individuals are more susceptive to develop cardiac dysfunction. This susceptibility is associated to obesity-induced chronic inflammatory condition and oxidative stress [36] . However, our results have showed that γOz was able to protect cardiac remodeling and systolic dysfunction in rats receiving HSF diet. This protective effect can be associated to PPAR-γ modulation in adipose tissue that results in attenuated systemic inflammation and improved RedOx status.
PPAR-γ is involved in adipose tissue inflammatory response, since the upregulation of this nuclear factor inhibits the TNF-α and IL-6 expression, suppresses macrophage infiltration into AT and induces polarization to an anti-inflammatory M2 phenotype [37] . Confirming this finding, the HSF group presented higher levels of MCP-1, IL-6 and TNF-α, whereas the HSF + γOz group was protected against inflammation.
Another explanation to the reduced inflammatory parameters levels is the reduction in malondialdehyde and protein carbonylation, both oxidative stress markers. Alleviate antioxidative pathways is extremely beneficial to prevent or reduce inflammatory conditions. Two nuclear transcription factors closely related to regulation of the redox status are PPAR-γ and the nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Both transcription factors have been shown to be positively modulated by γOz, since these phytochemical enhances body antioxidant capacity by activating antioxidant enzymes [38] and improving obesity-associated inflammatory conditions [21] .
Oxidative stress may affect extra-cellular matrix remodeling, mitochondrial respiration, cell proliferation and stimulate the nuclear factor kappa B (NFκB) to secret cytokines. Moreover, oxidative stress affects cell repair mechanisms and the immune control system, which is one of the main events of the inflammatory response [39] . In the present study, the histological analysis demonstrated that the HSF + γOz group presented hyperplasia while the HSF, hypertrophy. This condition is beneficial to inflammation control and ROS production, since in hyperplasic conditions are observed reduced cellular stress and synthesis of cytokines. PPAR-γ is a crucial regulator of adipocyte differentiation and fat storage as triglycerides. Studies demonstrate that the PPAR-γ is necessary for fat cell differentiation in all adipose depots and contributes to define the maximum threshold of expansion of the adipose tissue [32, 40] . Moreover, in obesity condition, the PPAR-γ expression decreases, which limits the adipose tissue expansion with consequent induction of cytokines production and fibrosis [33] .
In summary, this study showed that γOz attenuates metabolic syndrome, inflammation and oxidative stress in adipose tissue, which may be attributed to PPAR-γ modulation. In addition, risk factors associated to obesity, as cardiac dysfunction, was remarkable reduced in animals feeding γOz. Therefore, modulating these conditions may attenuate the COVID-19 severity in obese patients. Although future clinical studies to verify the γOz ability to activate PPAR-γ in obese patients with COVID-19 are necessary, it is possible to conclude that γOz may be considered as therapeutic adjuvant to avoid/attenuate the systemic cytokine storm in COVID-19.
Funding: São Paulo Research Foundation (FAPESP), grant #2015/10626-0 and #2018/15294-3.
The authors declare no conflict of interest.
Data availability: The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.