Combination therapy of flaxseed and hesperidin enhances the effectiveness of lifestyle modification in cardiovascular risk control in prediabetes: a randomized controlled trial

Type 2 diabetes mellitus (T2DM) and prediabetes (PD) are nowadays serious health problems all over the world and are usually accompanied with other metabolic disorders such as obesity, nonalcoholic fatty liver disease and cardiovascular diseases, mainly due to insulin resistance [1].

The prevalence of people with prediabetes in the world is reported to be more than 25%, all of whom are at risk for diabetes and its complications [2]. In addition to preclinical impaired glucose regulation, changes in insulin production, secretion from the pancreatic β-cells and its function in skeletal muscle, adipose tissue and liver are some of the prominent hallmarks of pre-diabetes and T2DM [3]. Lifestyle modifications (LSM) including increasing exercise and optimizing dietary composition have been proposed as a therapeutic and preventive strategy for PD [4]. However, it has been shown that even though lifestyle modification strategies are adapted, many people with pre-diabetes will progress to T2DM [5].

Flaxseed and hesperidin may improve cardiovascular health due to their numerous attributes [6, 7]. Hesperidin and flaxseed have emerged as promising phyto-therapeutic agents, which may exert potential benefits on health mainly through improving the antioxidant status [8], and providing adequate fiber and omega-3 [9‐11], respectively. The therapeutic effects of these two compounds on metabolic dysregulation in PD can be attributed to their powerful biological properties on improving glucose homeostasis and insulin resistance [12‐15].

Recently, several studies have shown anti-diabetic [15, 16] and anti-inflammatory [17] properties of hesperidin and flaxseed. Intake of omega-3 fatty acids and fiber, both of which are compounds of flaxseed, can contribute to reducing the risk of metabolic abnormalities [9, 18, 19]. Beneficial effects of flaxseed on lowering plasma glucose in patients with diabetes as well as metabolic syndrome have been reported [20‐22]. Similar effects have been obtained with the consumption of flax lignan [21]. Although hesperidin exerts many health benefits [23], its effects on blood glucose have been inconsistent in various studies, as in four studies [24‐27], no effect was detected and in one study [28], blood sugar was reduced.

Although the beneficial effects of flaxseed and hesperidin on cardiometabolic risk factors have been shown previously, no study has evaluated the effects of their combinations on pre-diabetic patients. Considering lack of data on such combination therapies in patients with PD, we aimed to investigate whether patients following LSM program along with supplementing with 30 g milled brown flaxseed and one g hesperidin per day, would have better metabolic parameters compared with those who just follow the LSM program.

A total of 80 patients completed the initial screening, of which 32 were excluded due to a lack of interest and failure to meet the entrance criteria. Finally, 48 patients received the allocated intervention. All patients completed a 12-week follow-up program, with an overall intervention adherence rate of 100%. Flow diagram of the study is presented in Fig. 1.

As shown in Table 1, there was no significant difference between two groups with regard to baseline characteristics including anthropometric measurements, blood pressure and serum biochemistry tests. There were 25 men (52%), and 23 women (48%) among all participants. The mean age of participants was 44.5 ± 10.7 and 46.7 ± 11.5 in intervention and control group, respectively. No significant differences among the distributions of sex and age between two groups were observed.

Furthermore, data on diet indicated no significant differences in total energy, macronutrients or micronutrients intake between groups. Although the results of the paired t-test revealed a significant decrease in energy intake and macronutrients, except for protein, throughout the study in both groups; but this difference between the two groups was not significant.

A paired t-test was used to compare the changes in each group during the 12-week intervention period. All of the measurements in flax-hes group were significantly improved, except for HDL-C and hs-CRP. In control group, in addition to these two factors, systolic blood pressure and serum triglyceride, AIP and non-HDL/HDL ratio did not show significant changes (Table 2).

The difference of changes between two groups during the interventions were analyzed using ANCOVA adjusted for baseline value of the outcome, age, sex and mean changes in BMI, MET and energy intake.

Mean changes of metabolic characteristics of participants from baseline are presented in Table 2. Anthropometric data comparison between the two groups showed a significantly more reduction in weight in intervention group compared to placebo group (P = 0.048). With regard to waist circumference, although in the intervention group, WC reduction was about twice that of the control group (− 6.75 cm vs − 3.57 cm), but this difference was not statistically significant (P = 0.306).

Comparison of blood pressure changes throughout the study between the two groups indicated a greater reduction in blood pressure in the intervention group, although this difference was significant only for systolic blood pressure (P = 0.049). Regarding the glucose homeostasis factors, only significant differences were observed in the values of FBS and QUICKI (P = 0.007, and P = 0.023, respectively). Also, we found approximately near to the significant level differences in HOM-IR (P = 0.055). However, the changes in insulin levels were fairly similar in both groups (Table 2).

Based on the results presented in Table 2, the reduction in TG and LDL was significantly more in flax-hes group than the control group after 12 weeks of intervention (P = 0.020, and P = 0.016, respectively).. Although HDL levels increased within both groups, there was no significant difference between the two groups. Improving atherogenicity indices in the intervention group was significantly superior to the control group (P = 0.039). Coadministration of flaxseed and hesperidin could significantly reduce AIP, LDL/HDL ratio and non-HDL/HDL ratio over a 12-week period. While in the control group, only LDL/HDL ratio reduction was significant.

We found that including daily intake of 30 g of whole flaxseed and one gram of hesperidin can modulate cardiometabolic risk factors in patients with prediabetes. The combination of hesperidin, as a flavonoid, and flaxseed, as a functional food, can exhibit a great potency in preventing and controlling cardiometabolic abnormalities through their combined anti-inflammatory and anti-oxidant properties as well as high fiber content. Reducing the risk of cardiometabolic complications has been stem from increasing insulin sensitivity, improving dyslipidemia and lowering blood pressure succeeding consumption of flaxseed and hesperidin.

In the present study, although the concentration of HDL did not change, a decline in the concentration of triglyceride and LDL was observed in response to hes-flax supplementation. These findings are consistent with preceding studies. Administration of 500 mg of purified hesperidin to patients with hypertriglyceridemia markedly reduced serum triglyceride levels over a 24-week period [35], while 800 mg of hesperidin failed to affect plasma HDL-cholesterol after 4 weeks [36]. Though in another study, oral administration of 500 mg hesperidin for 3 weeks resulted in a significant increase in HDL, while failed to reduce triglyceride levels [37]. One of the proposed mechanisms of the hesperidin effects on lipid profile modulation is through increasing the transcription of the peroxisome proliferator-activated receptor alpha (PPAR-α) gene [38]. In order to achieve significant clinical outcomes, flavonoids should be sufficiently consumed. Moreover, the patient population and length of study are other imperative determinants. In fact, lipid-lowering effects of purified hesperidin should be interpreted with caution as this may not be achievable with usual dietary intake [38].

On the other hand, flaxseed has beneficial effects on lipid profile and atherogenicity, which are due to its components specially fiber and omega-3 fatty acids. A recent clinical trial revealed that adding 10 g flaxseed pre-mixed in cookies twice a day to the usual diet significantly ameliorated the serum levels of cholesterol, LDL-C and cholesterol/HDL ratio in patients with T2DM. Their results indicate that the benefits of flaxseed in weight reduction, lipid profile control and glucose homeostasis is superior to those of psyllium [39]. Also, it was reported in a study conducted in diabetic patients that daily consumption of flaxseed enriched yogurt (containing 30-g flaxseed), although could not alter serum LDL-C and HDL-C, decreased serum triglycerides and total cholesterol significantly [40]. Moreover, high content of flaxseed lignan can reduce triglyceride levels through suppressing the sterol regulatory element-binding proteins (SREBP) mRNA [41]. It has been revealed that the hypocholesterolemic effect of flaxseed is more pronounced than wheat in hypercholesterolemic adults, though it led to a slight decrease in HDL-C concentration [42]. What seems to have arisen from this study is that fiber alone cannot fully account for all the positive effects of flaxseed in improving the lipid profile. At least part of these beneficial effects is due to omega-3 fatty acids, which has been mentioned in previous studies [43, 44]. However, the findings of some studies are inconsistent with these results [45], possibly because the dose or duration of the intervention was insufficient. Since it has been reported that at least consumption of 30 grams flaxseed is required to convert alpha linolenic acid (ALA) to eicosapantanoic acid (EPA) in young, healthy adults [46]. Thus, it seems that the synergistic effects of flaxssed and hesperidin reduced TG and LDL in our study.

One of the most remarkable findings of the present study was the improvement of glycemic parameters, including fasting plasma glucose, insulin, HOMA-IR and QUICKI after 12 weeks treatment with combination of hesperidin and flaxseed, which is in line with the findings of most previous studies [24, 47, 48]. Although no study has evaluated the effects of combination of these supplements, there are several studies that have shown the beneficial effects of each of them alone on glycemic homeostasis.

A study by Cunnane et al. reported the hypoglycemic effects of both whole flaxseed and isolated flaxseed fiber [22]. Improvements in either HOMA-IR or QUICKI following flaxseed consumption was described for the first time in 2013 [42]. The prominent point of these studies is that flaxseed supplementation can only affect glycemic parameters in interventions duration of at least 12 weeks. The study conducted by Barre and colleagues [21] is in line with this finding, in which 3 months supplementation of flaxseed lignan in patients with type 2 diabetes led to plasma glucose reduction. This was also confirmed in another study in which flaxseed consumption in patients with metabolic syndrome could result in blood glucose control and insulin resistance decline after 12 weeks [20]. Also, a recently published meta-analysis in this area also indicated this, but with this difference that only whole flaxseed, but not flaxseed oil and lignan extract, has significant effects on controlling glycemic parameters [49]. A possible explanation for the necessity of long-term intervention (≥ 12 weeks) is that improving glucose control and insulin sensitivity require an increase in EPA and Docosahexaenoic acid (DHA) concentrations [50, 51] and ALA conversion to these two fatty acids is time-consuming [52]. Also, the function of the gut microflora is enhanced gradually by flaxseed fiber consumption, which in turn led to improved blood glucose control and insulin function [53, 54]. As well, the higher initial concentration of plasma glucose (> 100 mg/dL), the more pronounced changes can be achieved via the flaxseed supplement [49].

On the other hand, according to the Nurses’ Health Studies (NHS) I and II, higher urinary excretion of hesperetin is associated with a lower middle- and long-term risk of type 2 diabetes (OR: 0.68) [55]. Improving insulin sensitivity and reducing insulin resistance has been stated repeatedly after treatment with hesperidin [24, 37, 56]. Increased skeletal muscle glucose uptake has been shown following the positive regulation of insulin signaling by hesperidin. That is why intake of orange juice containing hesperidin following a high-fat and high-carbohydrate meal, prevents increases in the expression of suppressor of cytokine signaling-3, a negative modulator of insulin signaling [57]. Thus, combination of hesperidin and flaxseed had synergistic effects on reduction of blood glucose in our study.

Our results demonstrated that patients supplementing with the combination of flaxseed and hesperidin experienced lowered systolic blood pressure after 12 weeks. The anti-hypertensive effect of flaxseed and hesperidin has been shown in previous studies. In the same way, a study conducted in 2015 found that higher urinary polyphenol excretion was allied with lower systolic and diastolic blood pressure, which was attributed to nitric oxide production [58, 59]. A meta-analysis of the effects of flaxseed on blood pressure showed that supplementation of various products of the flaxseed can exert beneficial effects on systolic and diastolic blood pressure control [60]. This study stated that flaxseed can cause a decrease of 2.85/2.39 mmHg in blood pressure. Since patients with prediabetes are at high risk for cardiovascular disease, this finding is very valuable. Similarly, Heart Outcome Evaluation study proposed that a 3.3/1.4 mmHg reduction in blood pressure is associated with a 22% decline of relative risk of cardiovascular mortality [61].

It is supposed that flaxseed lignan can possess an inhibitory action on angiotensin-converting enzyme (ACE) which results in blood pressure reduction [62]. Also, ALA in flaxseed suppresses the soluble epoxide hydrolase activity, which reduces blood pressure through inhibiting the production of inflammatory oxylipins and following vasoconstriction, inflammation and hypertension [63]. Although the blood pressure lowering effects of flaxseed have been attributed to fiber and ALA, the exact mechanisms involved in this effect are still not fully understood. Although bioavailability of ALA in whole flaxseed is lower than that of flaxseed oil, whole grain flaxseed has the advantage of providing all bioactive components and fiber with well tolerability [64, 65]. Although in our study, combination of flaxseed and hesperidin reduced more than previous studies that used them individually [66, 67], we did not find a significant difference between two groups in DBP. This might be due to receiving the lifestyle modification in control group, which caused a significant decrease in DBP of them.

Undeniably, obesity and overweight as well as central obesity are important risk factors for cardiometabolic diseases [68]. Our study showed significant reduction in weight and waist circumference after 12 weeks supplementation with the combination of flaxseed and hesperidin, although the difference of WC was not significant between two groups, compared to baseline. Studies regarding the effect of hesperidin on anthropometric measures are limited. Supplementation with citrus juice containing vitamin C and hesperidin have no significant effect on weight and WC [56]. Therefore, it appears that the weight loss observed in present study is possibly due to the flaxseed, which is in line with previous studies [42, 69]. Recent review and meta-analysis study also confirms the positive effects of flaxseed on weight loss, especially if the intervention durations of ≥ 12 weeks [70].

ALA can exert its anti-obesity effects via subsequent converting into long chain poly unsaturated fatty acids in the body [71‐73]. Furthermore, flaxseed lignans under the gut microflora produced enterolactone, the main component of mammalian lignans, which has been negatively correlated with obesity [74, 75].

The present study has several strengths; to the best of our knowledge, it is the first interventional study investigating the effect of flaxseed and hesperidin combination as an adjunct to lifestyle modification for the cardiovascular control in prediabetes. Although the exact clinical implication of these findings is yet undefined, it could be proposed as a preventive strategy. It needs further studies to explore full potential of flaxseed and hesperidin and confirm these findings.

In conclusion, incorporating 30 g of brown flaxseed and one-gram hesperidin into a healthy diet along with increasing physical activity seems reasonable and valuable to reduce risk of cardiometabolic abnormalities through ameliorating insulin resistance, lowering blood pressure, improving glycemic control, modifying lipid profile, and reduction of inflammation [11, 76, 77].