Interactions of dietary fat intake and the hepatic lipase -480C-->T polymorphism in determining hepatic lipase activity: the Hoorn Study

Obesity-Associated Dyslipidemia Is Moderated by Habitual Intake of Marine-Derived n-3 Polyunsaturated Fatty Acids in Yup'ik Alaska Native People: A Cross-Sectional Mediation-Moderation Analysis

BACKGROUND

Obesity leads to insulin resistance, altered lipoprotein metabolism, dyslipidemia, and cardiovascular disease. The relationship between long-term intake of n-3 polyunsaturated fatty acids (n-3 PUFAs) and prevention of cardiometabolic disease remains unresolved.

OBJECTIVES

The aim of this study was to explore direct and indirect pathways between adiposity and dyslipidemia, and the degree to which n-3 PUFAs moderate adiposity-induced dyslipidemia in a population with highly variable n-3 PUFA intake from marine foods.

METHODS

In total, 571 Yup'ik Alaska Native adults (18-87 y) were enrolled in this cross-sectional study. The red blood cell (RBC) nitrogen isotope ratio (15N/14N, or NIR) was used as a validated objective measure of n-3 PUFA intake. EPA and DHA were measured in RBCs. Insulin sensitivity and resistance were estimated by the HOMA2 method. Mediation analysis was conducted to evaluate the contribution of the indirect causal path between adiposity and dyslipidemia mediated through insulin resistance. Moderation analysis was used to assess the influence of dietary n-3 PUFAs on the direct and indirect paths between adiposity and dyslipidemia. Outcomes of primary interest included plasma total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), non-HDL-C, and triglycerides (TG).

RESULTS

In this Yup'ik study population, we found that up to 21.6% of the total effects of adiposity on plasma TG, HDL-C, and non-HDL-C are mediated through measures of insulin resistance or sensitivity. Moreover, RBC DHA and EPA moderated the positive association between waist circumference (WC) and TC or non-HDL-C, whereas only DHA moderated the positive association between WC and TG. However, the indirect path between WC and plasma lipids was not significantly moderated by dietary n-3 PUFAs.

CONCLUSIONS

Intake of n-3 PUFAs may independently reduce dyslipidemia through the direct path resulting from excess adiposity in Yup'ik adults. NIR moderation effects suggest that additional nutrients contained in n-3 PUFA-rich foods may also reduce dyslipidemia.

Mimicking Gene-Environment Interaction of Higher Altitude Dwellers by Intermittent Hypoxia Training: COVID-19 Preventive Strategies

Cyclooxygenase 2 (COX2) inhibitors have been demonstrated to protect against hypoxia pathogenesis in several investigations. It has also been utilized as an adjuvant therapy in the treatment of COVID-19. COX inhibitors, which have previously been shown to be effective in treating previous viral and malarial infections are strong candidates for improving the COVID-19 therapeutic doctrine. However, another COX inhibitor, ibuprofen, is linked to an increase in the angiotensin-converting enzyme 2 (ACE2), which could increase virus susceptibility. Hence, inhibiting COX2 via therapeutics might not always be protective and we need to investigate the downstream molecules that may be involved in hypoxia environment adaptation. Research has discovered that people who are accustomed to reduced oxygen levels at altitude may be protected against the harmful effects of COVID-19. It is important to highlight that the study's conclusions only applied to those who regularly lived at high altitudes; they did not apply to those who occasionally moved to higher altitudes but still lived at lower altitudes. COVID-19 appears to be more dangerous to individuals residing at lower altitudes. The downstream molecules in the (COX2) pathway have been shown to adapt in high-altitude dwellers, which may partially explain why these individuals have a lower prevalence of COVID-19 infection. More research is needed, however, to directly address COX2 expression in people living at higher altitudes. It is possible to mimic the gene-environment interaction of higher altitude people by intermittent hypoxia training. COX-2 adaptation resulting from hypoxic exposure at altitude or intermittent hypoxia exercise training (IHT) seems to have an important therapeutic function. Swimming, a type of IHT, was found to lower COX-2 protein production, a pro-inflammatory milieu transcription factor, while increasing the anti-inflammatory microenvironment. Furthermore, Intermittent Hypoxia Preconditioning (IHP) has been demonstrated in numerous clinical investigations to enhance patients' cardiopulmonary function, raise cardiorespiratory fitness, and increase tissues' and organs' tolerance to ischemia. Biochemical activities of IHP have also been reported as a feasible application strategy for IHP for the rehabilitation of COVID-19 patients. In this paper, we aim to highlight some of the most relevant shared genes implicated with COVID-19 pathogenesis and hypoxia. We hypothesize that COVID-19 pathogenesis and hypoxia share a similar mechanism that affects apoptosis, proliferation, the immune system, and metabolism. We also highlight the necessity of studying individuals who live at higher altitudes to emulate their gene-environment interactions and compare the findings with IHT. Finally, we propose COX2 as an upstream target for testing the effectiveness of IHT in preventing or minimizing the effects of COVID-19 and other oxygen-related pathological conditions in the future.

The cross-sectional study of hepatic lipase SNPs and plasma lipid levels

By the combination of meta-analysis, the data of the 1,000 Genomes Project Phase 3, and the promoter sequence of hepatic lipase (LIPC), we performed the cross-sectional study to explore the associations of four variants (rs1077835; rs1077834; rs1800588 [C-514T], and rs2070895 [G-250A]) in LIPC promoter with plasma lipid levels. Our results indicate that the first and the next three of the four SNPs are, respectively, reported to be associated with the decreased and increased HDL-c level. Meta-analysis of 87 studies with 101,988 participants indicates that HDL-c level in rs1800588 (C-514T) (pooled mean difference = 0.03, 95%CI (0.03, 0.04), p < .001) and rs2070895 (G-250A) (pooled mean difference = 0.07, 95%CI (0.05, 0.09), p < .001) is higher in allele T or A carriers. Similarly, LDL-c, TC, TG, and BMI levels are generally increased in T or A alleles carriers. We failed to conduct the meta-analysis of rs1077835 and rs1077834 due to the limited previous reports. Data from the 1,000 Genomes indicate that the allele frequencies of the four SNPs in total or subpopulations are almost equal to each other. The paired value r 2 and D' of the four SNPs are larger than 0.8, which indicate the linkage disequilibrium of the four variants. The analysis of LIPC promoter indicate that C-514T and G-250A are, respectively, located in transcriptional factor binding sites of USF1and Pbx1b, which may partly explain the effect of the two SNPs on the decreased LIPC activity in the alleles carriers and the corresponding increased plasma lipids hydrolyzed by LIPC. These results may help us to better understand the different effects of the four SNPs on the plasma lipid levels among subpopulations and offer clues for future clinical treatment of dyslipidemia-related diseases.

Dietary Fat Intake Modifies the Effect of a Common Variant in the LIPC Gene on Changes in Serum Lipid Concentrations during a Long-Term Weight-Loss Intervention Trial

BACKGROUND

Hepatic lipase (HL) plays a pivotal role in the metabolism of HDL and LDL. Recent genome-wide association studies have identified common variants in the HL gene (LIPC) associated with HDL cholesterol.

OBJECTIVE

We tested the effect of a common variant in LIPC on changes in blood lipids in response to weight-loss diets in the Preventing Overweight Using Novel Dietary Strategies Trial.

METHODS

We genotyped LIPC rs2070895 in 743 overweight or obese adults aged 30-70 y (61% women) who were assigned to high-fat (40% energy) or low-fat (20% energy) diets for 2 y. We measured serum concentrations of total cholesterol (TC), triglycerides, LDL cholesterol, and HDL cholesterol at baseline and 2 y of intervention.

RESULTS

At 2 y of intervention, dietary fat modified effects of the variant on changes in serum TC, LDL cholesterol, and HDL cholesterol (P-interaction: 0.0008, 0.004, and 0.03, respectively). In the low-fat group, as compared to the G allele, the A allele tended to be related to the decrease in TC and LDL cholesterol concentrations [TC (β ± SE): -5.5 ± 3.0, P = 0.07; LDL cholesterol: -4.8 ± 2.5, P = 0.06] and a lower increase in HDL cholesterol concentrations (β ± SE: -1.37 ± 0.69, P = 0.048), whereas an opposite effect in the high-fat diet group was evident [TC (β ± SE): 7.3 ± 2.7, P = 0.008; LDL cholesterol: 4.1 ± 2.3, P = 0.07], and there was no genetic effect on changes in HDL cholesterol concentrations (P = 0.54).

CONCLUSION

Dietary fat intake modifies the effect of a common variant in LIPC on changes in serum lipids during a long-term weight-loss intervention in overweight or obese adults. This trial was registered at clinicaltrials.gov as NCT00072995.

A high carbohydrate diet induces the beneficial effect of the CC genotype of hepatic lipase C-514T polymorphism on the apoB100/apoAI ratio only in young Chinese males

Both diet and genetic background have profound effects on plasma lipid profiles. It was hypothesized that a high carbohydrate (high-CHO) diet could affect the ratios of serum lipids and apolipoproteins (apo) differently in subjects with different genotypes of the C-514T hepatic lipase rs1800588 polymorphism. Fifty-six healthy university students were given a stabilization diet of 54.1% carbohydrate for 7 days, followed with a high-CHO diet of 70.1% carbohydrate for 6 days. Body composition, serum lipids, apolipoproteins and the hepatic lipase C-514T rs1800588 polymorphism were analyzed. The ratios of serum lipids and apolipoproteins were calculated afterwards. At baseline, females have significantly lower waist circumference (WC) (CC genotype: p = 0.049; T carriers: p = 0.015) and waist-to-hip ratio (WHR) (CC genotype: p = 0.019; T carriers: p = 0.000) than males. When compared with those before the high-CHO diet, the body mass index (BMI) (p = 0.043) and WC (p = 0.048) were significantly decreased in the male T carriers, the TG/HDL-C ratios were significantly increased in females (CC genotype: p = 0.047; T carriers: p = 0.003). The TC/HDL-C ratios were significantly decreased in males (CC genotype: p = 0.000; T carriers: p = 0.003). And the LDL-C/HDL-C ratios were significantly decreased in all subjects (males with the CC genotype: p = 0.001; male T carriers: p = 0.000; females with the CC genotype: p = 0.018; female T carriers: p = 0.006). However, the apoB100/apoAI ratio was only significantly decreased in male CC genotype after the high-CHO diet (p = 0.005).

Gender differences in cardiac remodeling and clinical outcomes in chronic stable angina pectoris (from the ACTION Trial)

Our objective was to determine the gender differences in the relation between the echocardiographic parameters of cardiac remodeling and clinical outcomes in patients with chronic stable angina. The baseline ejection fraction (EF), end-diastolic volume, and end-systolic volume were assessed in 7,016 patients in the study "A Coronary disease Trial Investigating Outcomes with Nifedipine gastrointestinal therapeutic system" (ACTION). All-cause and cardiac mortality and incident heart failure were determined after a median of 5.0 years. Cox proportional hazard models were fit to determine the effect of gender on the relation between the echocardiographic parameters and clinical outcomes (interaction p <0.10). The association between the EF and mortality differed significantly between men and women, with women demonstrating a marked increase in risk as the EF decreased, compared to men (interaction p = 0.03, adjusted p = 0.07). Also, a significant interaction by gender was seen for the association between the end-systolic volume and the risk of heart failure (interaction p = 0.01, adjusted p = 0.05). In conclusion, the relation between EF and mortality differed according to gender in patients with chronic coronary disease, with women having a greater risk of adverse outcomes as the EF decreased. Similar findings were observed with the end-systolic and end-diastolic volumes and the risk of heart failure. These findings may reflect inherent gender-based differences in ischemic heart disease and cardiac remodeling and might help to identify women at high risk.

Vitamin D and mortality in older men and women

OBJECTIVE

Vitamin D deficiency is common among the elderly and may contribute to cardiovascular disease. The aim of our study was to elucidate whether low serum levels of 25-hydroxyvitamin D [25(OH)D] are associated with an increased risk of all-cause and cardiovascular mortality.

DESIGN AND PATIENTS

The Hoorn Study is a prospective population-based study among older men and women.

MEASUREMENTS

Fasting serum 25(OH)D was determined in 614 study participants at the follow-up visit in 2000-2001, the baseline for the present analysis. To account for sex differences and seasonal variations of 25(OH)D levels we formed sex-specific quartiles, which were calculated from the 25(OH)D values of each season.

RESULTS

After a mean follow-up period of 6.2 years, 51 study participants died including 20 deaths due to cardiovascular causes. Unadjusted Cox proportional hazard ratios (HRs; with 95% confidence intervals) for all-cause and cardiovascular mortality in the first when compared with the upper three 25(OH)D quartiles were 2.24 (1.28-3.92; P = 0.005) and 4.78 (1.95-11.69; P = 0.001), respectively. After adjustment for age, sex, diabetes mellitus, smoking status, arterial hypertension, high-density lipoprotein-cholesterol, glomerular filtration rate and waist-to-hip ratio, the HRs remained significant for all-cause [1.97 (1.08-3.58; P = 0.027)] and for cardiovascular mortality [5.38 (2.02-14.34; P = 0.001)].

CONCLUSIONS

Low 25(OH)D levels are associated with all-cause mortality and even more pronounced with cardiovascular mortality, but it remains unclear whether vitamin D deficiency is a cause or a consequence of a poor health status. Therefore, intervention studies are warranted to evaluate whether vitamin D supplementation reduces mortality and cardiovascular diseases.

The G-250A polymorphism in the hepatic lipase gene promoter is associated with changes in hepatic lipase activity and LDL cholesterol: The KANWU Study

BACKGROUND AND AIMS

Hepatic lipase (HL) catalyzes the hydrolysis of triglycerides and phospholipids from lipoproteins, and promotes the hepatic uptake of lipoproteins. A common G-250A polymorphism in the promoter of the hepatic lipase gene (LIPC) has been described. The aim was to study the effects of the G-250A polymorphism on HL activity, serum lipid profile and insulin sensitivity.

METHODS AND RESULTS

Altogether 151 healthy subjects (age 49+/-8 years, BMI 26.5+/-3.0kg/m(2)) were randomly assigned for 3 months to an isoenergetic diet containing either a high proportion of saturated fatty acids (SFA diet) or monounsaturated fatty acids (MUFA diet). Within groups there was a second random assignment to supplements with fish oil (3.6g n-3 FA/day) or placebo. At baseline, the A-250A genotype was associated with high serum LDL cholesterol concentration (P=0.030 among three genotypes). On the MUFA diet carriers of the A-250A genotype presented a greater decrease in LDL cholesterol concentration than subjects with other genotypes (P=0.007 among three genotypes). The rare -250A allele was related to low HL activity (P<0.001 among three genotypes). The diet did not affect the levels of HL activity among the genotypes.

CONCLUSION

The A-250A genotype of the LIPC gene was associated with high LDL cholesterol concentration, but the MUFA-enriched diet reduced serum LDL cholesterol concentration especially in subjects with the A-250A genotype.

Complexity of type 2 diabetes mellitus data sets emerging from nutrigenomic research: a case for dimensionality reduction?

Nutrigenomics promises personalized nutrition and an improvement in preventing, delaying, and reducing the symptoms of chronic diseases such as diabetes. Nutritional genomics is the study of how foods affect the expression of genetic information in an individual and how an individual's genetic makeup affects the metabolism and response to nutrients and other bioactive components in food. The path to those promises has significant challenges, from experimental designs that include analysis of genetic heterogeneity to the complexities of food and environmental factors. One of the more significant complications in developing the knowledge base and potential applications is how to analyze high-dimensional datasets of genetic, nutrient, metabolomic (clinical), and other variables influencing health and disease processes. Type 2 diabetes mellitus (T2DM) is used as an illustration of the challenges in studying complex phenotypes with nutrigenomics concepts and approaches.

Gene-lifestyle interaction on risk of type 2 diabetes

The descriptive epidemiology of type 2 diabetes suggests that gene-lifestyle interactions are critical to the development of the condition. However, unravelling the molecular detail of these interactions is a complex task. The existing literature is based on small intervention studies or cross-sectional observational quantitative trait studies. Our systematic review of the literature identified some evidence of interactions, most notably for a common variant in the PPAR-gamma gene which appears to interact with the nature of dietary fat intake. Other interactions have been reported for adrenoceptors, uncoupling proteins, fatty acid binding proteins, apolipoproteins and lipoprotein lipase. There are, to date, no reports based on the ideal study design which is a case-control study nested within a cohort. To limit the likelihood of false discovery, such studies would need to be large and the search for interaction should be restricted to a priori biologically driven hypotheses. Additional study designs that examine differential response to lifestyle change or test interaction in the context of quantitative trait studies would complement the nested case-control approach, but the emphasis here should be on precision of measurement of both phenotype and lifestyle behaviour.

Application of nutrigenomic concepts to Type 2 diabetes mellitus

The genetic makeup that individuals inherit from their ancestors is responsible for variation in responses to food and susceptibility to chronic diseases such as Type 2 diabetes mellitus (T2DM). Common variations in gene sequences, such as single nucleotide polymorphisms, produce differences in complex traits such as height or weight potential, food metabolism, food-gene interactions, and disease susceptibilities. Nutritional genomics, or nutrigenomics, is the study of how foods affect the expression of genetic information in an individual and how an individual's genetic makeup affects the metabolism and response to nutrients and other bioactive components in food. Since both diet and genes alter one's health and susceptibility to disease, identifying genes that are regulated by diet and that cause or contribute to chronic diseases could result in the development of diagnostic tools, individualized intervention, and eventually strategies for maintaining health. Translating this research through clinical studies promises contributions to the development of personalized medicine that includes nutritional as well as drug interventions. Reviewed here are the key nutrigenomic concepts that help explain aspects of the development and complexity of T2DM.

Genes, environment and the value of prospective cohort studies

Case-control studies have many advantages for identifying disease-related genes, but are limited in their ability to detect gene-environment interactions. The prospective cohort design provides a valuable complement to case-control studies. Although it has disadvantages in duration and cost, it has important strengths in characterizing exposures and risk factors before disease onset, which reduces important biases that are common in case-control studies. This and other strengths of prospective cohort studies make them invaluable for understanding gene-environment interactions in complex human disease.

The human obesity gene map: the 2005 update

This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTL) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2005, 176 human obesity cases due to single-gene mutations in 11 different genes have been reported, 50 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 244 genes that, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 408. The number of human obesity QTLs derived from genome scans continues to grow, and we now have 253 QTLs for obesity-related phenotypes from 61 genome-wide scans. A total of 52 genomic regions harbor QTLs supported by two or more studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably, with 426 findings of positive associations with 127 candidate genes. A promising observation is that 22 genes are each supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. The electronic version of the map with links to useful publications and relevant sites can be found at http://obesitygene.pbrc.edu.