Naked oat combined with a structured dietary intervention affects oxidative stress but not inflammation in diabetic dyslipidemia

Improvement in cardiometabolic risk markers following an oatmeal diet is associated with gut microbiota in mildly hypercholesterolemic individuals

Cardiovascular diseases have been the leading cause of death worldwide for decades. Some animal studies have indicated that oatmeal could improve gut microbiota and cardiometabolic risk markers. However, vivo evidence remained limited, especially in individuals with mild hypercholesterolemia. Our purpose was to explore the beneficial effects of oatmeal on serum lipids, oxidative stress and inflammation levels, and their correlations with gut microbiota and short-chain fatty acids (SCFAs) in mildly hypercholesterolemic individuals. The study was a randomized, single-blind, placebo-controlled trial. A total of 62 qualified participants were randomly divided into control group and oatmeal group with a 45-day follow-up. 16S rDNA and Gas-Chromatography Mass Spectrometry were employed respectively to measure the changes in gut microbiota and SCFAs at the start and the end of the intervention period. Cardiometabolic risk markers were assayed via commercial kits. The results suggested that oatmeal could significantly decrease serum total cholesterol (TC) (-8.59 %, p = 0.013), low density lipoprotein cholesterol (LDL-c) (-12.97 %, p = 0.004) and non-high density lipoprotein cholesterol (non-HDL-c) (-10.98 %, p = 0.040) level. In terms of oxidative stress, oatmeal significantly increased serum total antioxidant capacity (T-AOC) (21.98 %, p < 0.001), superoxide dismutase (SOD) (15.53 %, p = 0.044) levels and decreased concentration of malondialdehyde (MDA) (-19.11 %, p = 0.033) compared with control group. While no significant effect was observed in inflammatory factors. SCFAs results indicated that oatmeal could significantly increase serum acetic acid, propionic acid and valeric acid. The results of 16S rDNA showed that there was a significant difference in the alteration of β-diversity between groups throughout the whole trial. Oatmeal resulted in the increases of Akkermansia, Dialister, Faecalibacterium, Barnesiella, Agathobacter, Lactobacillus and the decrease of Ruminococcaceae-MK4A214-group. Correlation analysis further suggested that the lipids regulation effect of oatmeal may be mainly mediated by Lactobacillus and Dialister, as well as some SCFAs (e.g., acetic acid and propionic acid), while Barnesiella and Akkermansia may play a crucial role in ameliorating oxidative stress level. In conclusion, despite of its small sample size, the present study is the first clinical trial performed in Chinese individuals with mild hypercholesterolemia to explore the effects of oatmeal on serum lipids, oxidative stress, inflammation levels, and gut microbiota. The results demonstrated that oatmeal could induce some beneficial changes in serum lipids, oxidative stress, gut microbiota composition and SCFAs. Correlation analysis further extended our understanding of the role of gut microbiota and SCFAs in improving cardiometabolic risk markers.

Short-chain fatty acids, prebiotics, synbiotics, and systemic inflammation: a systematic review and meta-analysis

BACKGROUND

Prebiotic soluble fibers are fermented by beneficial bacteria in the colon to produce short-chain fatty acids (SCFAs), which are proposed to have systemic anti-inflammatory effects.

OBJECTIVE

This review examines the effect of SCFAs, prebiotics, and pre- and probiotic combinations (synbiotics) on systemic inflammation.

DESIGN

Relevant English language studies from 1947 to May 2017 were identified with the use of online databases. Studies were considered eligible if they examined the effects of SCFAs, prebiotics, or synbiotics; were delivered orally, intravenously, or per rectum; were on biomarkers of systemic inflammation in humans; and performed meta-analysis where possible.

RESULTS

Sixty-eight studies were included. Fourteen of 29 prebiotic studies and 13 of 26 synbiotic studies reported a significant decrease in ≥1 marker of systemic inflammation. Eight studies compared prebiotic and synbiotic supplementation, 2 of which reported a decrease in inflammation with synbiotics only, with 1 reporting a greater anti-inflammatory effect with synbiotics than with prebiotics alone. Meta-analyses indicated that prebiotics reduce C-reactive protein (CRP) [standardized mean difference (SMD): -0.60; 95% CI: -0.98, -0.23], and synbiotics reduce CRP (SMD: -0.40; 95% CI: -0.73, -0.06) and tumor necrosis factor-α (SMD -0.90; 95% CI: -1.50, -0.30).

CONCLUSIONS

There is significant heterogeneity of outcomes in studies examining the effect of prebiotics and synbiotics on systemic inflammation. Approximately 50% of included studies reported a decrease in ≥1 inflammatory biomarker. The inconsistency in reported outcomes may be due to heterogeneity in study design, supplement formulation, dosage, duration, and subject population. Nonetheless, meta-analyses provide evidence to support the systemic anti-inflammatory effects of prebiotic and synbiotic supplementation.

Sustaining Effect of Intensive Nutritional Intervention Combined with Health Education on Dietary Behavior and Plasma Glucose in Type 2 Diabetes Mellitus Patients

Diabetes mellitus is very common in elderly Chinese individuals. Although nutritional intervention can provide a balanced diet, the sustaining effect on at-home dietary behavior and long-term plasma glucose control is not clear. Consequently, we conducted a long-term survey following one month of experiential nutritional intervention combined with health education. Based on the Dietary Guidelines for a Chinese Resident, we found that the food items met the recommended values, the percentages of energy provided from fat, protein, and carbohydrate were more reasonable after one year. The newly formed dietary patterns were “Healthy”, “Monotonous”, “Vegetarian”, “Japanese”, “Low energy”, and “Traditional” diets. The 2h-PG of female participants as well as those favoring the “Japanese diet” decreased above 12 mmol/L. Participants who selected “Japanese” and “Healthy” diets showed an obvious reduction in FPG while the FPG of participants from Group A declined slightly. “Japanese” and “Healthy” diets also obtained the highest DDP scores, and thus can be considered suitable for T2DM treatment in China. The results of the newly formed dietary patterns, “Japanese” and “Healthy” diets, confirmed the profound efficacy of nutritional intervention combined with health education for improving dietary behavior and glycemic control although health education played a more important role. The present study is encouraging with regard to further exploration of comprehensive diabetes care.

GC-TOF-MS-based serum metabolomic investigations of naked oat bran supplementation in high-fat-diet-induced dyslipidemic rats

The present study aimed to explore the metabolic response of oat bran consumption in dyslipidemic rats by a high-throughput metabolomics approach. Four groups of Sprague-Dawley rats were used: N group (normal chow diet), M group (dyslipidemia induced by 4-week high-fat feeding, then normal chow diet), OL group and OH group (dyslipidemia induced, then normal chow diet supplemented with 10.8% or 43.4% naked oat bran). Intervention lasted for 12weeks. Gas chromatography quadrupole time-of-flight mass spectrometry was used to identify serum metabolite profiles. Results confirmed the effects of oat bran on improving lipidemic variables and showed distinct metabolomic profiles associated with diet intervention. A number of endogenous molecules were changed by high-fat diet and normalized following supplementation of naked oat bran. Elevated levels of serum unsaturated fatty acids including arachidonic acid (Log2Fold of change=0.70, P=.02 OH vs. M group), palmitoleic acid (Log2Fold of change=1.24, P=.02 OH vs. M group) and oleic acid (Log2Fold of change=0.66, P=.04 OH vs. M group) were detected after oat bran consumption. Furthermore, consumption of oat bran was also characterized by higher levels of methionine and S-adenosylmethionine. Pathway exploration found that most of the discriminant metabolites were involved in fatty acid biosynthesis, biosynthesis and metabolism of amino acids, microbial metabolism in diverse environments and biosynthesis of plant secondary metabolites. These results point to potential biomarkers and underlying benefit of naked oat bran in the context of diet-induced dyslipidemia and offer some insights into the mechanism exploration.