Diet, genes and disease: implications for nutrition policy

Implementation of Nutrigenetics and Nutrigenomics Research and Training Activities for Developing Precision Nutrition Strategies in Malaysia

Nutritional epidemiological studies show a triple burden of malnutrition with disparate prevalence across the coexisting ethnicities in Malaysia. To tackle malnutrition and related conditions in Malaysia, research in the new and evolving field of nutrigenetics and nutrigenomics is essential. As part of the Gene-Nutrient Interactions (GeNuIne) Collaboration, the Nutrigenetics and Nutrigenomics Research and Training Unit (N2RTU) aims to solve the malnutrition paradox. This review discusses and presents a conceptual framework that shows the pathway to implementing and strengthening precision nutrition strategies in Malaysia. The framework is divided into: (1) Research and (2) Training and Resource Development. The first arm collects data from genetics, genomics, transcriptomics, metabolomics, gut microbiome, and phenotypic and lifestyle factors to conduct nutrigenetic, nutrigenomic, and nutri-epigenetic studies. The second arm is focused on training and resource development to improve the capacity of the stakeholders (academia, healthcare professionals, policymakers, and the food industry) to utilise the findings generated by research in their respective fields. Finally, the N2RTU framework foresees its applications in artificial intelligence and the implementation of precision nutrition through the action of stakeholders.

Guide and Position of the International Society of Nutrigenetics/Nutrigenomics on Personalized Nutrition: Part 2 - Ethics, Challenges and Endeavors of Precision Nutrition

Nutrigenetics considers the influence of individual genetic variation on differences in response to dietary components, nutrient requirements and predisposition to disease. Nutrigenomics involves the study of interactions between the genome and diet, including how nutrients affect the transcription and translation process plus subsequent proteomic and metabolomic changes, and also differences in response to dietary factors based on the individual genetic makeup. Personalized characteristics such as age, gender, physical activity, physiological state and social status, and special conditions such as pregnancy and risk of disease can inform dietary advice that more closely meets individual needs. Precision nutrition has a promising future in treating the individual according to their phenotype and genetic characteristics, aimed at both the treatment and prevention of disease. However, many aspects are still in progress and remain as challenges for the future of nutrition. The integration of the human genotype and microbiome needs to be better understood. Further advances in data interpretation tools are also necessary, so that information obtained through newer tests and technologies can be properly transferred to consumers. Indeed, precision nutrition will integrate genetic data with phenotypical, social, cultural and personal preferences and lifestyles matters to provide a more individual nutrition, but considering public health perspectives, where ethical, legal and policy aspects need to be defined and implemented.

Nutrient intake values for folate during pregnancy and lactation vary widely around the world

Folate is a B-vitamin with particular importance during reproduction due to its role in the synthesis and maintenance of DNA. Folate is well known for its role in preventing neural tube defects (NTDs) during the periconceptional period. There is also an increased need for folate throughout pregnancy to support optimal growth and development of the fetus and blood volume expansion and tissue growth of the mother. During lactation, women are at risk of folate deficiency due to increased demands to accommodate milk folate levels. Nutrient Intake Values (NIVs) for folate have been calculated to take into account additional needs during pregnancy and lactation. However, these values vary widely between countries. For example, the folate requirement that is set to meet the needs of almost all healthy women during pregnancy varies from 300 µg/day in the United Kingdom to 750 µg/day in Mexico. Currently, there is no accepted standardized terminology or framework for establishing NIVs. This article reviews country-specific NIVs for folate during pregnancy and lactation and the basis for setting these reference values.

Ethical issues raised by personalized nutrition based on genetic information

Four principles are taken as basis for the ethical analysis: autonomy, nonmaleficence, beneficence, and justice. Health is understood as a limited aspect of wellbeing. Food is understood as an important aspect of wellbeing, not only an instrument for health. Modern society is characterized by a tendency to identify wellbeing with external rather than subjective circumstances, to identify wellbeing with health, and to create exaggerated health expectations. Based upon this understanding, aspects of personalized nutrition are discussed: genetic testing, counselling, and development of special dietary products. Today the predictive value of genetic tests for personal nutrition is limited, and experimental at best. Recommendations for the future: Personalized nutrition must be based on solid knowledge. Phenotypic analyses should be used when adequate. When a genetic test can have a clear advantage, this should be preferred. Opportunistic screening should only be used when clearly beneficial. Specially trained persons should collect information from genetic tests and carry through councelling on a personal basis. Marketing of genetic tests directly sold to the public should be discouraged. Development of special products for personalized nutrition may be necessary in some cases. However, this may also lead to a medicalization of diet.

Studies of gene variants related to inflammation, oxidative stress, dyslipidemia, and obesity: implications for a nutrigenetic approach

Obesity is currently considered a serious public health issue due to its strong impact on health, economy, and quality of life. It is considered a chronic low-grade inflammation state and is directly involved in the genesis of metabolic disturbances, such as insulin resistance and dyslipidemia, which are well-known risk factors for cardiovascular disease. Furthermore, there is evidence that genetic variation that predisposes to inflammation and metabolic disturbances could interact with environmental factors, such as diet, modulating individual susceptibility to developing these conditions. This paper aims to review the possible interactions between diet and single-nucleotide polymorphisms (SNPs) in genes implicated on the inflammatory response, lipoprotein metabolism, and oxidative status. Therefore, the impact of genetic variants of the peroxisome proliferator-activated receptor-(PPAR-)gamma, tumor necrosis factor-(TNF-)alpha, interleukin (IL)-1, IL-6, apolipoprotein (Apo) A1, Apo A2, Apo A5, Apo E, glutathione peroxidases 1, 2, and 4, and selenoprotein P exposed to variations on diet composition is described.

TYMS, MTHFR, p53 and MDR1 gene polymorphisms in breast cancer patients treated with adjuvant therapy

PURPOSE

The distribution of TSER (TYMS), C677T (MTHFR), Arg72Pro (p53) and C3435T (MDR1) gene polymorphisms was investigated in 80 consecutive breast cancer patients treated with adjuvant chemotherapy.

RESULTS

Observed allelic frequencies were: TSER, (2) 0.55 and (3) 0.45; MTHFR C677T, (C) 0.65 and (T) 0.35; p53 Arg72Pro, (Arg) 0.76 and (Pro) 0.24; MDR1 C3435T, (C) 0.51 and (T) 0.49. MTHFR C677T was found to be a strong predictor of the presence of multifocal tumour (odds ratio, 4.1; 95% CI, 1.1-15.7; P=0.035).

CONCLUSION

Our data indicate that breast cancer patients with the C/C variant may present multifocal tumour most frequently.

Does the MTHFR 677C-->T variant affect the Recommended Dietary Allowance for folate in the US population?

BACKGROUND

The MTHFR 677C-->T variant is associated with reduced enzyme activity, abnormalities of folate metabolism, and potential increase in folate requirement. The effect of this variant on the Recommended Dietary Allowance (RDA) for folate is unclear.

OBJECTIVE

The aim of this study was to assess the effect of the MTHFR 677C-->T polymorphism on the current folate RDA for US adults aged > or =19 y (400 microg/d) by race and ethnicity.

DESIGN

We calculated the projected RDA for folate for each racial and ethnic group according to the methods of the Institute of Medicine. We modeled the projected RDA with different hypothetical effect sizes ranging from 5% to 50%. The RDA value was then weighted according to the US prevalence of the TT (or the combined CT/TT) genotype in each racial and ethnic group.

RESULTS

The projected RDA ranges were based on TT genotype frequencies and on different effect sizes (5-50%) that ranged from 400 to 421 microg/d for non-Hispanic whites, 401-436 microg/d for Mexican Americans, and 400-402 microg/d for non-Hispanic blacks.

CONCLUSIONS

Our findings suggest that the current RDA for folate differs little for non-Hispanic whites, non-Hispanic blacks, and Mexican Americans irrespective of the MTHFR TT genotype, and, from a population perspective, the MTHFR 677C-->T variant does not warrant modifications to the current RDA for dietary folate at this time.

Nutrigenomics and metabolomics will change clinical nutrition and public health practice: insights from studies on dietary requirements for choline

Science is beginning to understand how genetic variation and epigenetic events alter requirements for, and responses to, nutrients (nutrigenomics). At the same time, methods for profiling almost all of the products of metabolism in a single sample of blood or urine are being developed (metabolomics). Relations between diet and nutrigenomic and metabolomic profiles and between those profiles and health have become important components of research that could change clinical practice in nutrition. Most nutrition studies assume that all persons have average dietary requirements, and the studies often do not plan for a large subset of subjects who differ in requirements for a nutrient. Large variances in responses that occur when such a population exists can result in statistical analyses that argue for a null effect. If nutrition studies could better identify responders and differentiate them from nonresponders on the basis of nutrigenomic or metabolomic profiles, the sensitivity to detect differences between groups could be greatly increased, and the resulting dietary recommendations could be appropriately targeted. It is not certain that nutrition will be the clinical specialty primarily responsible for nutrigenomics or metabolomics, because other disciplines currently dominate the development of portions of these fields. However, nutrition scientists' depth of understanding of human metabolism can be used to establish a role in the research and clinical programs that will arise from nutrigenomic and metabolomic profiling. Investments made today in training programs and in research methods could ensure a new foundation for clinical nutrition in the future.

Genotype-by-nutrient interactions assessed in European obese women. A case-only study

BACKGROUND

The development of obesity is influenced by both genetic and environmental risk factors. Whereas changes in the environment appear to be responsible for the increasing prevalence of obesity, genetic factors interacting with environmental factors would contribute to explain obesity onset and severity.

AIM

To explore epidemiologic genotype-by-nutrient interactions in obesity.

METHODS

A total of 42 polymorphisms of 26 candidate genes for obesity were genotyped in 549 adult obese women recruited from eight European centres in a case-only study. The nutritional variables assessed in this study were the dietary fibre intake (grams per day), the ratio of dietary polyunsaturated fat to saturated fat (P:S ratio) and the percentage of energy derived from fat in the diet as calculated from a weighed three-day food record (%E). Under the assumption of genotype-nutrient independence in the population, the odds ratio calculated in a sample of obese women would indicate the existence of genotype-by-nutrient interactions, measured as deviations from the multiplicative effects of the genetic and the nutrient factors separately.

RESULTS

No new but confirmaty evidences for genotype-by-nutrient interactions in obesity were detected in this case-only study. The test of interaction between fibre intake and the -514 C > T polymorphism of the hepatic lipase gene (LIPC) yielded P-values of 0.01 across different statistical models. Likewise, the -11377G > C polymorphism of the adiponectin gene (ADIPOQ) and the -681 C > G polymorphism of the PPARG3 gene might interact with the percentage of energy derived from fat in the diet for the development of obesity (P-values in the range of 0.01-0.05 across different statistical models). The P-values were not adjusted for multiple testing, so these results should be considered with caution.

CONCLUSIONS

Although the use of obese-only samples is theoretically a useful approach to detect interactions, few genotype-by-nutrient interactions have been suggested in obese European women after the analysis of candidate polymorphisms and the selected nutrient variables. The most remarkable multiplicative interaction found in this study refers to the combination of the hepatic lipase gene polymorphism -514 C > T and fibre intake.

Nutrient-gene interaction in ageing and successful ageing. A single nutrient (zinc) and some target genes related to inflammatory/immune response

In this paper, we reviewed data regarding to the pivotal role played by the zinc-gene interaction in affecting some relevant cytokines (IL-6 and TNF-alpha) and heat shock proteins (Hsp70-2) in ageing, successful ageing (nonagenarians) and in some age-related diseases (atherosclerosis and infections). The polymorphisms of the genes codifying these proteins are predictive on one hand in longevity, such as IL-6 -174G/C locus, on the other hand 1267 Hsp70-2A/B or TNF-alpha -308G/A polymorphisms are associated to worsening atherosclerosis or severe infections, respectively, rather than longevity. Taking into account that longevity has a strong genetic component but, at the same time, is affected by life style and environmental factors, the analysis of these polymorphisms in association to some immune parameters (NK cell cytotoxicity) and nutritional factors (zinc) is a useful tool to unravel the role played by these genetic factors in longevity and in the appearance of age-related diseases. Indeed, these polymorphisms are associated with chronic inflammation, low zinc ion bioavailability, depressed innate immune response and high gene expression of metallothioneins, which have a limited zinc release for an optimal innate immune response in ageing. Therefore, the nutrient (zinc)-gene (IL-6, TNF-alpha and Hsp70-2) interaction is pivotal to keep under control the inflammatory/immune response with subsequent longevity, indicating these genes as "robust" for "healthy ageing".

Metabolomics in human nutrition: opportunities and challenges

Metabolomics has been widely adopted in pharmacology and toxicology but is relatively new in human nutrition. The ultimate goal, to understand the effects of exogenous compounds on human metabolic regulation, is similar in all 3 fields. However, the application of metabolomics to nutritional research will be met with unique challenges. Little is known of the extent to which changes in the nutrient content of the human diet elicit changes in metabolic profiles. Moreover, the metabolomic signal from nutrients absorbed from the diet must compete with the myriad of nonnutrient signals that are absorbed, metabolized, and secreted in both urine and saliva. The large-bowel microflora also produces significant metabolic signals that can contribute to and alter the metabolome of biofluids in human nutrition. Notwithstanding these possible confounding effects, every reason exists to be optimistic about the potential of metabolomics for the assessment of various biofluids in nutrition research. This potential lies both in metabolic profiling through the use of pattern-recognition statistics on assigned and unassigned metabolite signals and in the collection of comprehensive data sets of identified metabolites; both objectives have the potential to distinguish between different dietary treatments, which would not have been targeted with conventional techniques. The latter objective sets out a well-recognized challenge to modern biology: the development of libraries of small molecules to aid in metabolite identification. The purpose of the present review was to highlight some early challenges that need to be addressed if metabolomics is to realize its great potential in human nutrition.