Mechanisms of disease: lessons from ethnicity in the role of triglyceride metabolism in ischemic heart disease

Lipid alternations in the plasma of COVID-19 patients with various clinical presentations

Background

COVID-19 is a highly infectious respiratory disease that can manifest in various clinical presentations. Although many studies have reported the lipidomic signature of COVID-19, the molecular changes in asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected individuals remain elusive.

Methods

This study combined a comprehensive lipidomic analysis of 220 plasma samples from 166 subjects: 62 healthy controls, 16 asymptomatic infections, and 88 COVID-19 patients. We quantified 732 lipids separately in this cohort. We performed a difference analysis, validated with machine learning models, and also performed GO and KEGG pathway enrichment analysis using differential lipids from different control groups.

Results

We found 175 differentially expressed lipids associated with SASR-CoV-2 infection, disease severity, and viral persistence in patients with COVID-19. PC (O-20:1/20:1), PC (O-20:1/20:0), and PC (O-18:0/18:1) better distinguished asymptomatic infected individuals from normal individuals. Furthermore, some patients tested positive for SARS-CoV-2 nucleic acid by RT-PCR but did not become negative for a longer period of time (≥60 days, designated here as long-term nucleic acid test positive, LTNP), whereas other patients became negative for viral nucleic acid in a shorter period of time (≤45 days, designated as short-term nucleic acid test positive, STNP). We have found that TG (14:1/14:1/18:2) and FFA (4:0) were differentially expressed in LTNP and STNP.

Conclusion

In summary, the integration of lipid information can help us discover novel biomarkers to identify asymptomatic individuals and further deepen our understanding of the molecular pathogenesis of COVID-19.

Mapping multimorbidity in individuals with schizophrenia and bipolar disorders: evidence from the South London and Maudsley NHS Foundation Trust Biomedical Research Centre (SLAM BRC) case register

OBJECTIVES

The first aim of this study was to design and develop a valid and replicable strategy to extract physical health conditions from clinical notes which are common in mental health services. Then, we examined the prevalence of these conditions in individuals with severe mental illness (SMI) and compared their individual and combined prevalence in individuals with bipolar (BD) and schizophrenia spectrum disorders (SSD).

DESIGN

Observational study.

SETTING

Secondary mental healthcare services from South London PARTICIPANTS: Our maximal sample comprised 17 500 individuals aged 15 years or older who had received a primary or secondary SMI diagnosis (International Classification of Diseases, 10th edition, F20-31) between 2007 and 2018.

MEASURES

We designed and implemented a data extraction strategy for 21 common physical comorbidities using a natural language processing pipeline, MedCAT. Associations were investigated with sex, age at SMI diagnosis, ethnicity and social deprivation for the whole cohort and the BD and SSD subgroups. Linear regression models were used to examine associations with disability measured by the Health of Nations Outcome Scale.

RESULTS

Physical health data were extracted, achieving precision rates (F1) above 0.90 for all conditions. The 10 most prevalent conditions were diabetes, hypertension, asthma, arthritis, epilepsy, cerebrovascular accident, eczema, migraine, ischaemic heart disease and chronic obstructive pulmonary disease. The most prevalent combination in this population included diabetes, hypertension and asthma, regardless of their SMI diagnoses.

CONCLUSIONS

Our data extraction strategy was found to be adequate to extract physical health data from clinical notes, which is essential for future multimorbidity research using text records. We found that around 40% of our cohort had multimorbidity from which 20% had complex multimorbidity (two or more physical conditions besides SMI). Sex, age, ethnicity and social deprivation were found to be key to understand their heterogeneity and their differential contribution to disability levels in this population. These outputs have direct implications for researchers and clinicians.

Maternal plasma cholesterol and duration of pregnancy: A prospective cohort study in Ghana

Low plasma cholesterol may be associated with preterm birth; however, results are mixed and limited primarily to high-income countries. Our objective was to determine whether maternal plasma lipid concentrations are associated with pregnancy duration. We performed a nested cohort (n = 320) study of pregnant Ghanaian women enrolled in a randomized controlled trial. Total cholesterol, high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol, and triglyceride concentrations were analyzed in plasma at ≤20and 36 weeks gestation as continuous variables and also categorized into low, referent, or high (<10th, 10th-90th, >90th percentile). At ≤20 weeks, plasma lipid concentrations were not associated with pregnancy duration. At 36 weeks, total cholesterol and triglyceride concentrations were not associated with pregnancy duration. Higher HDL-C at 36 weeks was associated with a longer pregnancy duration (adjusted β-coefficient ± standard error: 0.05 ± 0.02 days mg^-1 /dL, p = .02); pregnancy duration was 5.9 ± 2.0 (mean ± standard error) days shorter among women with low HDL-C compared with the referent group (10th-90th percentile) (p = .02) and 8.6 ± 2.6 days shorter when compared with the high HDL-C group (p = .003). Pregnancy duration was 4.9 ± 2.1 days longer among women with low low-density lipoprotein cholesterol at 36 weeks gestation when compared with the referent group (p = .051). Our data suggest that low HDL-C in the third trimester of pregnancy is associated with a shorter duration of pregnancy in this study population but do not support the hypothesis that low total cholesterol is associated with a shorter pregnancy duration.

Sociodemographic distribution of non-communicable disease risk factors in rural Uganda: a cross-sectional study

BACKGROUND

Non-communicable diseases (NCDs) are rapidly becoming leading causes of morbidity and mortality in low- and middle-income countries, including those in sub-Saharan Africa. In contrast to high-income countries, the sociodemographic distribution, including socioeconomic inequalities, of NCDs and their risk factors is unclear in sub-Saharan Africa, particularly among rural populations.

METHODS

We undertook a cross-sectional population-based survey of 7809 residents aged 13 years or older in the General Population Cohort in south-western rural Uganda. Information on behavioural, physiological and biochemical risk factors was obtained using standardized methods as recommended by the WHO STEPwise Approach to Surveillance. Socioeconomic status (SES) was determined by principal component analysis including household features, ownership, and occupation and education of the head of household.

RESULTS

SES was found to be associated with NCD risk factors in this rural population. Smoking, alcohol consumption (men only) and low high-density lipoprotein (HDL) cholesterol were more common among those of lower SES. For example, the prevalence of smoking decreased 4-fold from the lowest to the highest SES groups, from 22.0% to 5.7% for men and 2.2% to 0.4% for women, respectively. In contrast, overweight, raised blood pressure, raised HbA1c (women only) and raised cholesterol were more common among those of higher SES. For example, the prevalence of overweight increased 5-fold from 2.1% to 10.1% for men, and 2-fold from 12.0% to 23.4% for women, from the lowest to highest SES groups respectively. However, neither low physical activity nor fruit, vegetable or staples consumption was associated with SES. Furthermore, associations between NCD risk factors and SES were modified by age and sex.

CONCLUSIONS

Within this rural population, NCD risk factors are common and vary both inversely and positively across the SES gradient. A better understanding of the determinants of the sociodemographic distribution of NCDs and their risk factors in rural sub-Saharan African populations will help identify populations at most risk of developing NCDs and help plan interventions to reduce their burden.

The effect of insulin intensification in children and young persons with Type 1 diabetes differs in relation to ethnic group; a prospective observational study

AIMS

We prospectively evaluated the effect of insulin intensification on glycaemic control and lipid levels in children and young persons with Type 1 diabetes in relation to ethnicity.

METHODS

In the first 2 years of a 3-year observation period, as part of routine clinical care, 231 children and young persons (40% white, 28% South Asian, 32% black) from a single clinic were offered intensive insulin therapy. After 2 years, 222 were on intensive therapy and their data were compared between ethnic groups at the end of year 3.

RESULTS

We observed ethnic differences in HbA(1c) levels during the study [study beginning and end: white children and young persons 77 and 70 mmol/mol (9.2 and 8.6%) vs. South Asian 72 and 68 mmol/mol (8.7 and 8.4%) vs. black 83 and 79 mmol/mol (9.7 and 9.4%), P-value for ANCOVA = 0.007]. By study end, South Asians had the lowest HDL cholesterol (2.0 vs. 1.4 vs. 1.6 mmol/l, P-value = 0.03) and highest triglyceride levels (0.9 vs. 1.8 vs. 1.0 mmol/l, P-value = 0.001). In linear mixed modelling, after adjustment for socio-economic deprivation and other covariates: (1) black ethnicity was associated with poorer glycaemic control (P < 0.001) and (2) South Asian ethnicity was associated with higher triglyceride levels (P < 0.001), independent of HbA(1c).

CONCLUSIONS

The effect of insulin intensification on glycaemic control and lipid profile in children and young persons with Type 1 diabetes differs in relation to ethnic group.

Ethnic variation in the activity of lipid desaturases and their relationships with cardiovascular risk factors in control women and an at-risk group with previous gestational diabetes mellitus: a cross-sectional study

BACKGROUND

Lipid desaturase enzymes mediate the metabolism of fatty acids to long chain polyunsaturated fatty acids and their activities are related to metabolic risk factors for Type 2 diabetes (T2DM) and coronary heart disease (CHD). There are marked ethnic differences in risks of CHD and T2DM but little is known about ethnic differences in desaturase activities.

METHODS

Samples from a study of CVD risk in women with previous gestational diabetes were analysed for percentage fatty acids in plasma free fatty acid, triglyceride, cholesterol ester and phospholipid pools for 89 white European, 53 African Caribbean and 56 Asian Indian women. The fatty acid desaturase activities, stearoyl-CoA desaturase (SCD, calculated separately for C16 and C18 fatty acids), delta 6 desaturase (D6D) and delta 5 desaturase (D5D) were estimated from precursor-to-product ratios and their relationships with adiposity, blood pressure, cholesterol, triglycerides, HDL cholesterol and insulin sensitivity explored. Ethnic differences in desaturase activities independent of ethnic variation in risk factor correlates of desaturase activities were then identified.

RESULTS

There was significant ethnic variation in age, BMI, waist circumference, blood pressure, serum triglycerides and HDL cholesterol concentrations and insulin resistance. Desaturase activities showed significant correlations, independent of ethnicity, with BMI, waist circumference, triglycerides and HDL cholesterol. Independent of ethnic variation in BMI, waist circumference, triglycerides and HDL cholesterol, SCD-16 activity, calculated from each of the four lipid pools measured, was 18-35 percent higher in white Europeans than in African Caribbeans or Asian Indians (all p < 0.001). Similar, though less consistent differences were apparent for SCD-18 activity. Also independently of risk factor variation, but specifically when calculated from the cholesterol ester and phospholipid, pools, D6D activity was significantly lower in Asian Indians, and D5D activity higher in African Caribbeans.

CONCLUSIONS

Significant ethnic differences exist in desaturase activities, independently of ethnic variation in other risk factors. These characteristics did not accord with higher risk of T2DM among African Caribbeans and Asian Indians nor with lower risk of CHD among African Caribbeans but did accord with the higher risk of CHD in Asian Indians.

Comparison of various lipid variables as predictors of coronary heart disease in Japanese men and women with type 2 diabetes: subanalysis of the Japan Diabetes Complications Study

OBJECTIVE

To determine the best lipid variable to predict coronary heart disease (CHD) in Japanese patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Eligible Japanese men and women (1,771) aged 40-70 years with type 2 diabetes from 59 institutes nationwide were followed for a planned 8-year period. The performance of eight conventional lipid variables, i.e., total cholesterol (TC), LDL-cholesterol (LDLC), HDL-cholesterol (HDLC), triglycerides (TGs), non-HDLC, TC/HDLC ratio, LDLC/HDLC ratio, and TG/HDLC ratio, as predictors of incident CHD were evaluated by four methods: hazard ratio (HR) per one SD increment by multivariate Cox analysis, χ(2) likelihood ratio test, area under the receiver operating characteristic curve (AUC), and tertile analysis.

RESULTS

Although all variables significantly predicted CHD events in men, non-HDLC (HR per one SD 1.78 [95% CI 1.43-2.21]; AUC 0.726) and TC/HDLC (HR 1.63 [1.36-1.95]; AUC 0.718) had the better predictive performances among the variables, including LDLC. In women, TGs (log-transformed; HR 1.72 [1.21-2.43]; AUC 0.708) were the best predictor according to results of tertile analysis (HR of the top tertile versus the bottom tertile 4.31 [1.53-12.16]). The associations with incident CHD were linear and continuous.

CONCLUSIONS

For Japanese diabetic men, non-HDLC and TC/HDLC were the best predictors, whereas TGs were most predictive for women. These findings, which included prominent sex differences, should be considered among clinical approaches to risk reduction among East Asians with diabetes.

The triglyceride paradox in people of African descent

Even though insulin resistance, cardiovascular disease (CVD), and type 2 diabetes (T2D) are associated with hypertriglyceridemia, blacks with these conditions usually have normal triglyceride (TG) levels. This is often called a lipid paradox. More precisely, it is a "TG paradox." The pathways that lead to hypertriglyceridemia have been intensively explored. Yet, the pathways that allow TG levels to be normal in the presence of insulin resistance have received little attention and this is problematic. Tests designed for the early detection of insulin-resistant conditions often use elevated TG levels as a diagnostic criterion. However, insulin resistance, CVD, and T2D are not usually associated with hypertriglyceridemia in people of African descent; therefore, the widespread use of TG levels to predict these conditions needs re-evaluation. This review focuses on black-white differences in: (1) the lipid profile across North America, Europe, and Africa; (2) the efficacy of TG-based screening tests, specifically the metabolic syndrome and its two abbreviated versions, the hypertriglycerdemic waist and TG/high-density lipoprotein cholesterol (HDL-C) ratio; and (3) the mechanisms that allow TG to be normal even in the presence of insulin resistance. Overall, a broader understanding of how TG physiology varies by race could lead to better diagnostic tests and improved health outcomes.

Genetic variants influencing circulating lipid levels and risk of coronary artery disease

OBJECTIVE

Genetic studies might provide new insights into the biological mechanisms underlying lipid metabolism and risk of CAD. We therefore conducted a genome-wide association study to identify novel genetic determinants of low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides.

METHODS AND RESULTS

We combined genome-wide association data from 8 studies, comprising up to 17 723 participants with information on circulating lipid concentrations. We did independent replication studies in up to 37 774 participants from 8 populations and also in a population of Indian Asian descent. We also assessed the association between single-nucleotide polymorphisms (SNPs) at lipid loci and risk of CAD in up to 9 633 cases and 38 684 controls. We identified 4 novel genetic loci that showed reproducible associations with lipids (probability values, 1.6×10(-8) to 3.1×10(-10)). These include a potentially functional SNP in the SLC39A8 gene for HDL-C, an SNP near the MYLIP/GMPR and PPP1R3B genes for LDL-C, and at the AFF1 gene for triglycerides. SNPs showing strong statistical association with 1 or more lipid traits at the CELSR2, APOB, APOE-C1-C4-C2 cluster, LPL, ZNF259-APOA5-A4-C3-A1 cluster and TRIB1 loci were also associated with CAD risk (probability values, 1.1×10(-3) to 1.2×10(-9)).

CONCLUSIONS

We have identified 4 novel loci associated with circulating lipids. We also show that in addition to those that are largely associated with LDL-C, genetic loci mainly associated with circulating triglycerides and HDL-C are also associated with risk of CAD. These findings potentially provide new insights into the biological mechanisms underlying lipid metabolism and CAD risk.

Hypertension is a major risk factor for future atherosclerotic changes in the Japanese population

Background

Great differences in age-standardized mortality rates by cardiovascular disease exist among countries. We prospectively assessed determinants of future cardiovascular changes in a Japanese cohort.

Methods

In 1996, 1011 men and 1153 women from a Japanese community participated in a study on cardiovascular risk factors at a local health centre. Of these, the 896 subjects who visited the centre both in 1996 and 2001 were selected for the analysis. The presence of cardiovascular changes was defined as the appearance of one or more of the following in five years: positive electrocardiographic findings, intima–media thickness of the carotid artery ≥0.8 mm and retinal vascular changes ≥Keith–Wegener–Barker classification stage I.

Results

Of the 607 subjects who had no history of cardiovascular disease in 1996, 421 showed changes in 2001. Both the age-adjusted and multivariate models showed that the risk of the cardiovascular changes increased as systolic blood pressure (SBP) increased to ≥135 mmHg (multivariate odds ratio = 1.739, 95% confidence interval = 1.076–2.810, P < 0.05) compared with those with an SBP of 110–134 mmHg. When we made the analyses only for laboratory test results by excluding SBP, body mass index, alcohol intake and current smoking from the regression model, high-density lipoprotein cholesterol and fasting plasma glucose were significant variables.

Conclusion

The risk of future cardiovascular changes is significantly greater with higher SBP in the Japanese population.

Triglycerides and coronary heart disease: have recent insights yielded conclusive answers?

PURPOSE OF REVIEW

Despite over 50 years of research, the relevance of triglycerides to coronary heart disease risk remains uncertain.

RECENT FINDINGS

Contrary to prevailing views, recent studies demonstrate that the long-term within-individual variability of triglyceride measurements is similar to that of other lipid fractions. Several prospective studies have reported on associations of circulating triglyceride levels with coronary heart disease risk, but it remains unclear whether observed associations are dependent on levels of conventional risk factors (especially other lipids) or are importantly modified under different circumstances (especially by fasting status). Ongoing large-scale studies should help clarify such outstanding uncertainties and assess whether measurement of triglyceride levels can better identify individuals at increased risk of coronary heart disease than measurement of conventional risk factors alone. Available interventions that lower levels of triglycerides are unable to judge causality as such interventions typically influence levels of several lipid fractions. Study of genetic variants that regulate triglyceride levels may provide an alternative approach to assess causality.

SUMMARY

Although recent studies have progressed our understanding of triglycerides and coronary heart disease, several outstanding uncertainties remain unresolved. Ongoing studies should help clarify these, including whether measurement of triglyceride levels can help improve coronary heart disease risk assessment, and study of genetic variants may help better understand any causal role.

The metabolic syndrome, insulin resistance, and its surrogates in African and white subjects with type 2 diabetes in South Africa

BACKGROUND

Coronary heart disease (CHD) is rare in diabetic Africans in South Africa, unlike diabetic African-Americans, despite moderate levels of conventional risk factors, with absence of the usual male predominance. Because the metabolic syndrome and insulin resistance (IR) are associated with CHD, we have analyzed the prevalence and severity of the metabolic syndrome, and IR, in African and white subjects with type 2 diabetes.

METHODS

A total of 500 African and 254 white diabetic patients were evaluated for features of the metabolic syndrome (International Diabetes Federation [IDF] definition); insulin resistance (homeostasis model assessment-insulin resistance [HOMA-IR]) was calculated in subgroups.

RESULTS

In men, Africans had a lower body mass index (BMI) and smaller waists than white subjects (p < 0.0001); the metabolic syndrome was present in 46.5% and 74.1% of African and white patients respectively (p < 0.0001). In women, frequencies of the metabolic syndrome were similar, but severe metabolic syndrome (4 or 5 criteria) was more frequent in the white group (73.1%) than in the Africans (52.9%) (p = 0.0003). The prevalence of hypertriglyceridemia was lower in African men and women (p < 0.0001) and contributed to their lower prevalence of the metabolic syndrome/severe metabolic syndrome. Compared with the white patients, in African subjects HOMA-IR was 40% lower (p < 0.0001), and correlated with the triglyceride:high-density lipoprotein cholesterol ratio (TG:HDL-C) (r = 0.409, p < 0.0001).

CONCLUSIONS

In diabetic Africans, in comparison with white patients, the lower prevalence of the metabolic syndrome in men and severe metabolic syndrome in women, and lesser insulin resistance, might contribute to their lower risk of CHD; the higher prevalence in women might contribute to the reversal of the male:female ratio. The TG:HDL-C ratio appears to be a valid estimate of insulin resistance in diabetic Africans.

Intrahepatic fat accumulation and alterations in lipoprotein composition in obese adolescents: a perfect proatherogenic state

OBJECTIVE

Among other metabolic consequences, a dyslipidemic profile often accompanies childhood obesity. In adults, type 2 diabetes and hepatic steatosis have been shown to alter lipoprotein subclass distribution and size; however, these alterations have not yet been shown in children or adolescents. Therefore, our objective was to determine the effect of hepatic steatosis on lipoprotein concentration and size in obese adolescents.

RESEARCH DESIGN AND METHODS

Using fast magnetic resonance imaging, we measured intrahepatic fat content in 49 obese adolescents with normal glucose tolerance. The presence or absence of hepatic steatosis was determined by a threshold value for hepatic fat fraction (HFF) of 5.5%; therefore, the cohort was divided into two groups (HFF > or <5.5%). Fasting lipoprotein subclasses were determined using nuclear magnetic resonance spectroscopy.

RESULTS

Overall, the high-HFF group had 88% higher concentrations of large VLDL compared with the low-HFF group (P < 0.001). Likewise, the high-HFF group had significantly higher concentrations of small dense LDL (P < 0.007); however, the low-HFF group had significantly higher concentrations of large HDL (P < 0.001). Stepwise multiple regression analysis revealed that high HFF was the strongest single correlate, accounting for 32.6% of the variance in large VLDL concentrations (P < 0.002).

CONCLUSIONS

The presence of fatty liver was associated with a pronounced dyslipidemic profile characterized by large VLDL, small dense LDL, and decreased large HDL concentrations. This proatherogenic phenotype was strongly related to the intrahepatic lipid content.