Vol 3, No 2 (Spring 2017)
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Almost all animals on Earth, whether sedentary sponge, an insect, an elephant or humans, live in a co-evolutionary association with large communities of microbes. The total microorganisms that reside in a particular tissue habitat are termed microbiota (or microflora) and their collective genomes in a microbiota are termed microbiome. The immense size, diversity and rapid growth of microbial populations in various microbiomes provide an enormous opportunity for genetic exploration.
Microbial composition of microbiome is formed by host factors such as genetics and diet, probably early in life. Gut microbiota is able to influence host physiology, development, nutrition, and metabolism; control pathogens, and regulate immune responses in health and disease. It is estimated that human microbiome consists of about 40 to 100 trillion genes. Based on the 16S rRNA gene sequence data, all regions of the human gastrointestinal tract (GIT) contain nutrition-dependent diverse bacterial communities. Environmental factors such as antibiotics could disrupt gut-microbiome interactions, leading to acute or chronic disease in some individuals. Although most current research is focused on bacterial composition, archaea, fungi, and viruses are also included in the host microbiome.
The gastrointestinal tract of healthy humans is colonized by populations of microorganisms ─ gut microbiota that contributes directly to digestion and nutrition by the fermentative degradation of various chemicals contained in foods, for example, polysaccharides in plant cell walls. It is suggested that the combined metabolic activities of microbial and human genome represent a “superorganism”.
Advance in DNA sequencing technologies and bioinformatics is rapidly increasing our knowledge of the number, taxonomic diversity and functional contribution of the gut microbiome that depend on age, diet, medication and antibiotic usage. In addition, GIT microbes contribute to micronutrients and may potentially detoxify toxic substances.
Research interest to understand the nature and functional activity of microbial communities in non-human animals, particularly farm animals, has a long history. However, during the past decade, there has been a rapid growth of research activity on the human microbiome. In contrast to in situ animal studies, most current analyses of the diversity of human and animal model microbiota in the GI tract have been dominated by molecular analyses of fecal bacterial diversity, and it is assumed that it represents microbial composition throughout the GIT. Some animal studies reveal a localized bacterial functional preference for a specific GI region.
With the advancement in molecular technology of rRNA sequencing in identifying culture-independent microbes, there has been a rapid growth of research activity on human microbiome. Moreover, in 2007 the US NIH Microbiome Research Project was initiated with the aim of understanding the human microbial compositions and their genetics, as well as metabolic contribution to normal health and disease. Establishment of other national and international microbiome research collaborations followed. During the past decade, there has been an extensive growth of publications related to human microbiome research. For example, a PubMed search on “human microbiome” in 2007 showed 526 entries, while a recent search produced 7618, a 15-fold growth in 10 years.
Early human microbiome research activity involved identifying microbial compositions of body regions and their role in normal physiology. Current interest includes studying the interactions between host and microbes in health and disease, with some emphasis on the nature of microbial composition during prenatal, neonatal and early life, when the host’s microbiome seems to get established. Although human microbiome projects and potential health benefits may get the most attention, other research projects such as animal, plant and environmental microbiomes are ongoing too. In addition, potential commercial application of microbiome research is also getting significant economic interest in the health industry; examples are microbial replacement for immunological disorders, type-2 diabetes, obesity, cardiovascular disease, and neurological disorders. In addition, research is also ongoing for discovering and developing new applications of microbiome in pharmaceutical and industrial applications
An analysis of gut microbiota has revealed three predominant “enterotypes”, dominated by Bacteroides, Prevotella, and Ruminococcus. Although the basis for this enterotype clustering is unknown, it appears that long-term diet and nutrition play an important role. Thus, it is suggested that a long-term optimal diet is an easiest and simplest way to modulate healthy gut microbiota. Such findings would have practical importance for the development of health interventions that could promote beneficial bacteria and inhibit the growth of bacteria responsible for disease and inflammatory response.
The scientific literature has demonstrated that certain microbes of the gut microbiota act as probiotics that could provide beneficial effects for their host. Identifying nutritive food items that could be included in regular diets to promote the beneficial microbes is of interest to health practitioners and pharmaceutical industries. As mentioned above, the nutrient content of diet plays an important role in the maintenance of and modifying, the resident gut microbiota.
In this issue of the Journal, Alizadeh Sani et al, using an ex-vivo study, showed that Oryzatensin, a rice bioactive peptide, acts as antibacterial and negatively controls the growth of certain colonic bacteria such as Bifidobacteria. This study, in addition to other ongoing research projects as well as organizing mini-symposium on micorbime in Iran, shows that albeit being fragmented, there is active microbiome research in Iranian academic institutions. It is hoped that with the establishment of an Iranian National Microbiome Research Project researchers with common scientific interests will get together to study and benefit from microbiome potentials for improved health and wellbeing.
Objectives: Hypercholesterolemia is a major risk factor associated with coronary heart disease. The medical society recommends the consumption of low-fat and low-cholesterol foods. The current study aimed to explore the effect of different diets with cream or yogurt butter on plasma triglyceride and cholesterol levels in rats.
Methods: Yogurt butter and sweet cream butter were produced and their fatty acid profiles were created using gas chromatography; then, the index of atherogenicity (IA) was calculated for each butter. The rats were divided into three groups, with one group being fed with standard pellets as the control group and the other two with pellets mixed with 10% cream or yogurt butter for 4 weeks. Serum lipid profile was compared between the groups.
Results: In comparison with cream butter and control groups, yogurt butter did not change serum triglycerides. The yogurt butter diet resulted in a lower total cholesterol than the other diets (p = 0.04 for cream butter and p = 0.001 for the control group). The rats fed with the yogurt diet had higher HDL cholesterol. IA decreased (p = 0.0009) and conjugated linoleic acid (p = 0.003) increased significantly in the yogurt butter compared with the cream butter group.
Conclusion: Yogurt butter improved serum lipid profile and fatty acid composition in rats. Further human trials are needed to confirm these results.
Effects of Iranian propolis on glycemic status, inflammatory factors, and liver enzyme levels in type 2 diabetic patients: a randomized, double-blind, placebo-controlled, clinical trial
Objective: Propolis is one of the hive products with a wide clinical usage due to the variety of bioactive components. This clinical trial was conducted to evaluate the effects of propolis supplementation on glycemic status and inflammation.
Methods: In an 8-week randomized, double-blinded, placebo-controlled, clinical trial, patients with type 2 diabetes were randomly assigned to the propolis (n = 31) or control group (n = 31). The first group received propolis capsules (500 mg), 3 times a day. Fasting blood samples were obtained. The liver enzymes, inflammatory markers, and glucose-related indicators were measured at the beginning and the end of the study.
Results: Compared with the control group, the propolis group showed significant changes in fasting plasma glucose (propolis, -19.8 ± 29.16; placebo, 0.7 ± 27.8; p = 0.01), two-hour postprandial glucose (propolis, -27.42 ± 44.5; placebo, -0.95 ± 42.7; p = 0.001), hemoglobin A1c (propolis, -1.07 ± 1.6; placebo, 0.03 ± 1.5; p = 0.041), insulin (propolis, -1.65 ± 4.3; placebo, 0.04 ± 4.02; p = 0.03), HOMA-IR (propolis, -1.08 ± 0.7; placebo, 0.03 ± 0.42; p = .044), TNF-α (propolis, -2.67 ± 4.1; placebo, 0.12 ± 4; p = 0.025), and C-reactive protein (propolis, -2.5 ± 3.01; placebo, -0.67 ± 2.84; p = 0.031). Furthermore, propolis reduced the mean aspartate aminotransferase (AST) (propolis, -1.62 ± 10.4; placebo, 0.13 ± 11.07; p = 0.12) and alanine aminotransferase (ALT) levels (propolis, -0.61 ± 6.47; placebo, 0.12 ± 7.01; p = 0.54), but it was not significant.
Conclusion: Propolis treatment in type 2 diabetic patients had a beneficial effect on the glycemic profile and inflammatory status. However, there was no significant change in the level of AST and ALT enzymes, warranting further research.
Fruit, vegetable, and dietary antioxidant intake and age-related cataract risk: A case-control study
Aim: This study was done to evaluate the relationship between dietary intake of some macronutrients, carotenoids, vitamins C, E, and A, and selenium and the risk of cataract.
Methods: In this case-control study, dietary intakes of 97 cataract patients and 198 controls were assessed using a valid semi-quantitative food frequency questionnaire. Cataract was diagnosed using a slit-lamp examination and defined as any lens opacity in either eye. The associations between cataract incidence and quartiles of macronutrient and micronutrient intakes were investigated using logistic regression models.
Results: After adjusting for the effects of confounding variables, the risk of cataract was significantly low in the highest nutrient intake quartile relative to the lowest quartile for fruits (OR = 0.15; 95% CI = 0.05-0.30) and vegetables (OR= 0.20; 95% CI = 0.08-0.40). We found significant, inverse associations of cataract with high dietary intake of vitamin C (OR = 0.22; 95% CI = 0.09-0.54), alpha-carotene (OR = 0.24; 95% CI = 0.10-0.58), beta-carotene (OR = 0.15; 95% CI = 0.05-0.39), lutein/zeaxanthin (OR = 0.19; 95% CI = 0.08-0.45), and beta-cryptoxanthin (OR = 0.05; 95% CI = 0.01-0.15).
Conclusion: High daily intakes of fruits and vegetables and some dietary antioxidants might be associated with a decrease in cataract risk in Tehran, Iran.
XML | VND.OPENXMLFORMATS-OFFICEDOCUMENT.WORDPROCESSINGML.DOCUMENT | PDF | downloads: 68 | views: 453 | pages: 23-27
Objective: Dietary diversity has been recommended to be effective in achieving an adequate nutrient intake. Few studies have investigated dietary diversity and nutrient intake in Prinzmetal angina patients. This case-control study aimed to assess the association between dietary diversity and Prinzmetal angina incidence.
Method: Energy and nutrient intakes were measured using three day 24-h recall. Dietary diversity was measured by summing the number of food groups consumed over 12 weeks. Independent-samples t test was used to compare quantitative variables between the groups.
Results: The mean score for Prinzmetal angina patients was 3 ± 0.025 groups/day, for controls was 4.5 ± 0.053 groups/day. There was a significant difference in diet diversity score between the groups (p = 0.01). There were significant differences in macro and micronutrient intakes between the groups with the exception of copper (p < 0.05). Intake of vitamin B12 in cases was 0.8 ± 0.02 μg/day and in controls was 1.5 ± 0.01 μg/day. Iron and zinc intakes in cases were lower than in controls.
Conclusion: Increasing dietary diversity in patients with Prinzmetal angina can be an important approach to declining the clinical symptoms of Prinzmetal angina.
Investigating the effects of oryzatensin on gut microbiota growth using a novel quantitative standard curve-fitting method: an ex-vivo study
Objective: Oryzatensin (ORZ) is a refractory, bioactive peptide that is isolated from rice. In the current study, we investigated the effect of ORZ on the growth of gut microbiota.
Methods: Ten apparently healthy subjects were enrolled in the current ex vivo study. Casual stool specimens were obtained from the subjects, then Enterobacteriaceae, Bacilaceae, and probiotic bacterial families were isolated using MAC, MYP, and MRS agars, respectively. The effect of exposure to different concentrations of ORZ (10-4, 10-5, 10-6, and 10-7 mol/L) on the growth of these bacteria was evaluated using the standard curve-fitting method, instead of standard qualitative methods such as MBC and MIC, because of the absence of detectable optical differences among the wells. The bacterial quantity was determined by evaluation of the suspensions turbidity at 492 to 630 nm.
Results: ORZ had an antibacterial effect and negatively controlled the growth of all isolated species compared with the control group. The inhibitory effect of ORZ was most significant at the dose of 10-7 mol/L (not significant at 10-5 and 10-6 mol/L and significant at 10-4 mol/L) for bifidobacteria and 10-4 mol/L for Enterobacteriaceae, Bacilaceae, and lactic acid bacteria.
Conclusion: The findings of the current study reveals that ORZ and possibly rice can reduce intestinal total bacterial count. Moreover, considering the carcinogenic effects of final metabolites of the enteral bacteria, such as free radicals, ORZ and rice may have an antineoplastic effect.
A posteriori dietary patterns are related to C-reactive protein levels: results from a systematic review and meta-analysisXML | VND.OPENXMLFORMATS-OFFICEDOCUMENT.WORDPROCESSINGML.DOCUMENT | MSWORD | MSWORD | MSWORD | MSWORD | PDF | downloads: 43 | views: 294 | pages: 35-48
Objective: Given the small effects of single nutrients, evaluating the relationships between cardiovascular disease risk factors and dietary patterns may be particularly useful. An increasing number of studies in recent years are investigating the association of dietary patterns with C-reactive protein (CRP) levels. This systematic review and meta-analysis examined the association between a posteriori derived dietary patterns and CRP levels in adults.
Methods: PubMed and Scopus were searched for articles published up to March 2015 that examined the association of total diet and CRP levels among adults. Two independent reviewers performed the study selection, quality rating, and data extraction process. Effect sizes of eligible studies were pooled by using random-effects models. Heterogeneity was tested using I2 statistic.
Results: Overall, 16 cross-sectional and 4 case-control studies that used a posteriori approach were considered for the meta-analysis and were eligible for inclusion. The comparison of the highest and lowest categories of healthy/prudent patterns revealed a significant decrease in CRP (mean difference (MD): -0.23; 95% CI: -0.40 to -0.056; p = 0.006) when other lifestyle factors were controlled for, although there was heterogeneity in the studies. Pooled results indicated higher levels of CRP (MD: 0.16; 95% CI: 0.15 to 0.23; p < 0.001) in the highest category of unhealthy/Western pattern compared with those in the lowest category, though there was significant heterogeneity.
Conclusion: The results of the present meta-analysis provide evidence that a healthy/prudent pattern decreases CRP level, while adherence to unhealthy/Western pattern leads to a higher level of CRP in adults.
Objective: We aimed to assess the validity and reproducibility of a short food frequency questionnaire (FFQ) in a pilot study.
Methods: Thirty individuals, age range 35-65 years completed twice the short semi quantitative food item FFQ with six month interval along with two 24 hour dietary recall (24 HR). Food and nutrient intakes were compared using Pearson's and intra-class correlation and Bland-Altman analysis. Also, to assess the internal consistency for the FFQ Cronbach's alpha was measured.
Results: The results showed acceptable internal consistency with Cronbach's alpha 0.67. Pearson's correlation coefficient for reproducibility varied between 0.25 for hot beverages up to 0.72 for dairy products with a mean 0.51 and likewise for ICC, fluctuated between 0.05 for legume up to 0.74 for dairy products with a mean 0.5. The mean ICC and Pearson's correlation coefficient for validity in food groups were 0.39 and 0.47. Also, the validity and reproducibility of questionnaire was assessed for nutrients. The mean Pearson correlation coefficient, ICC were assessed sequentially 0.42 and 0.36 for validity in nutrients and reproducibility in nutrients assessed by Pearson's correlation coefficients 0.59 and ICC 0.62 (P<0.05).
Conclusion: Our results indicated that this questionnaire provides a reasonable measure of macronutrients and micronutrients. However questions which related to consume legumes and protein intake need further investigation and it is recommended that further research with larger population and more 24HR in future.