Urinary metabolomics signature of animal and plant protein intake and its association with 24-h blood pressure: the African-PREDICT study.

The contrasting relationships of plant and animal protein intake with blood pressure (BP) may be partially attributed to the differential non-protein (e.g., saturated fat and fibre) and amino acid (AA) compositions. This study determined whether animal and plant protein intake were related to differential metabolomic profiles associated with BP. This study included 1008 adults from the African-PREDICT study (aged 20-30 years). Protein intake was determined using 24-h dietary recalls. Twenty-four-hour ambulatory BP was measured. Amino acids and acylcarnitines were analysed in spot urine samples using liquid chromatography-tandem mass spectrometry-based metabolomics. Participants with a low plant, high animal protein intake had higher SBP (by 3 mmHg, p = 0.011) than those with high plant, low animal protein intake (low-risk group). We found that the relationships of plant and animal protein intake with 24-h SBP were partially mediated by BMI and saturated fat intake, which were independently associated with SBP. Protein intake was therefore not related to SBP in multiple regression analysis after adjusting for confounders. In the low-risk group, methionine (Std. ß = -0.217; p = 0.034), glutamic acid (Std. ß = -0.220; p = 0.031), glycine (Std. ß = -0.234; p = 0.025), and proline (Std. ß = -0.266; p = 0.010) were inversely related to SBP, and beta-alanine (Std. ß = -0.277; p = 0.020) to DBP. Ultimately a diet high in animal and low in plant protein intake may contribute to higher BP by means of increased BMI and saturated fat intake. Conversely, higher levels of urinary AAs observed in adults consuming a plant rich diet may contribute to lower BP.

Validation of a short food group questionnaire to determine intakes from healthy and unhealthy food groups in 5-9-year-old South African children.

BACKGROUND: Reliable dietary data for children are necessary to investigate associations with health outcomes. The present study aimed to develop and validate a questionnaire to determine the frequency of intakes of specific healthy and unhealthy food groups in young children. METHODS: Participants were 5-9-year-old South African children (n = 920) from 10 urban schools. Their parents completed a demographic questionnaire and the food intake questionnaire with food pictures. Based on the literature, four healthy food groups (fruits, vegetables, milk, meat/fish/poultry/eggs) and six unhealthy food groups (hot and cold sugar-sweetened beverages, candy, salty snacks, cakes and fast foods) were included, with five different frequency responses. Six experienced nutritionists assessed the face validity and content validity. After pilot testing, construct validity and homogeneity were determined in the participants. Convergent validity was determined using urinary sodium and potassium concentrations as biological intake markers. RESULTS: Nutritionists confirmed face and content validity. Caregivers confirmed understanding of the questionnaire. Three factors explained 50.2% of the variance, with most unhealthy food groups as factor 1, fruits and vegetables as factor 2, and animal source protein and milk groups clustered with sugar-sweetened beverages as factor 3. The frequency of milk group, fruits and vegetables intake correlated negatively, whereas the frequency of salty snacks and fast foods intakes correlated positively with the urinary sodium:potassium ratio. CONCLUSIONS: The healthy and unhealthy food group questionnaire has advantages of low respondent burden, as well as acceptable content and convergent validity in South African children. The questionnaire may be used to investigate associations between food intakes and health outcomes.

Metabolomic Insights on Potassium Excretion, Blood Pressure, and Glucose Homeostasis: The African-PREDICT Study.

BACKGROUND: Low-potassium intake is associated with a higher risk of type 2 diabetes and hypertension. Both conditions occur more frequently in Black populations, who also consume less potassium-rich foods. OBJECTIVES: Using metabolomics to identify dysregulated metabolic pathways associated with low-potassium excretion may procure more accurate entry points for nutritional prevention and intervention for type 2 diabetes and hypertension. METHODS: A total of 440 White and 350 Black adults from the African-PREDICT study (aged 20-30 y) were included. Twenty-four-hour blood pressure (BP) was measured. Potassium, sodium, and fasting glucose concentrations were analyzed in 24-h urine and plasma samples. Liquid chromatography-tandem mass spectrometry-based metabolomics included the analyses of amino acids and acylcarnitines in spot urine samples. RESULTS: Black participants had lower urinary potassium concentrations than Whites (36.6 compared with 51.1 mmol/d; P < 0.001). In White but not Black adults, urinary potassium correlated positively with 2-aminoadipic acid (2-AAA) (r = 0.176), C3-[propionyl]carnitine (r = 0.137), C4-[butyryl]carnitine (r = 0.169) and C5-[isovaleryl]carnitine (r = 0.167) in unadjusted and 2-AAA (r = 0.158) and C4-carnitine (r = 0.160) in adjusted analyses (all P < 0.05 and q < 0.05). Elevated C0-, C3-, and C5-carnitine in turn were positively associated with systolic BP (Black and White groups), diastolic BP (Black group), and glucose (White group) (all P < 0.05). CONCLUSIONS: Racial differences are an important consideration when investigating nutrient-metabolite relationships and the role thereof in cardiovascular disease. Only in White adults did urinary potassium associate with 2-AAA and short-chain acylcarnitines. These metabolites were positively related to BP and fasting plasma glucose concentrations. In White adults, the metabolomic profiles related to potassium excretion may contribute to BP regulation and glucose homeostasis. This trial was registered at clinicaltrials.gov as NCT03292094.

Early evidence for the effectiveness of South Africa's legislation on salt restriction in foods: the African-PREDICT study.

South Africa was among the first countries to adopt mandatory regulation in 2016 to lower the salt content in processed foods, aiming to reduce population salt intake to <5 g/day. To assess the effectiveness of this regulation in 20-30 year-old adults, we determined the change in salt intake over a mean follow-up time of 4.56-years spanning the implementation of the regulation. This observational study included baseline (2013-2016; N = 668; 24.9 ± 3 years; 47.8% black; 40.7% men) and follow-up data (2018-ongoing; N = 311; 25.4 ± 3.05 years; 51.1% black; 43.4% men) for participants of the African-PREDICT study. Salt intake was estimated from 24-h urinary sodium excretion. Median salt intake at baseline (N = 668) was 7.88 g/day (IQR: 5.67). In those followed (N = 311), salt intake reduced from baseline [median (IQR): 7.91 g/day (5.83)] to follow-up [7.26 g/day (5.30)] [unadjusted median: -0.82 g/day]. After adjusting for baseline salt intake to address regression to the mean, the mean salt reduction was -1.2 g/day. The greatest reductions were in men [mean difference: -1.47 g/day], black adults [mean difference: -2.04 g/day], and participants from low [mean difference: -1.89 g/day] or middle [mean difference: -1.84 g/day] socio-economic status groups, adjusting for baseline salt intake. Our preliminary findings suggest that South Africa's salt regulation has been effective in lowering salt intake in young adults by ~1.2 g salt/day. Our study supports the effectiveness of upstream interventions to lower population salt intake, particularly for vulnerable groups who may typically consume more processed foods. It needs to be determined if the legislation has the anticipated population health gains.

Urinary metabolomics, dietary salt intake and blood pressure: the African-PREDICT study.

In Black populations excessive salt intake may exacerbate the genetic predisposition to hypertension and promote the early onset of cardiovascular disease. Ethnic differences in the interaction between sodium intake and the metabolome may play a part in hypertension and cardiovascular disease development. We determined (1) urinary amino acid and acylcarnitine profiles of young Black and White adults according to low, moderate, and high dietary salt intake, and (2) investigated the triad of salt intake, systolic blood pressure (SBP), and the associated metabolomics profile. This study included 447 White and 380 Black adults aged 20-30 years from the African-PREDICT study. Estimated salt intake was determined from 24-hour urinary sodium levels. Urinary amino acids and acylcarnitines were measured using liquid chromatography-tandem mass spectrometry. Black adults exhibited no significant differences in SBP, amino acids, or acylcarnitines across low (<5g/day), moderate (5-10g/day), and high (>10g/day) salt intake. White adults with a high salt intake had elevated SBP compared to those with low or moderate intakes (p < 0.001). Furthermore, gamma-aminobutyric acid (GABA) (q = 0.020), citrulline (q = 0.020), glutamic acid (q = 0.046), serine (q = 0.054) and proline (q = 0.054) were lowest in those with higher salt intake. Only in White and not Black adults did we observe inverse associations of clinic SBP with GABA (Adj. R2 = 0.34; Std. ß = -0.133; p = 0.003), serine (Adj. R2 = 0.33; Std. ß = -0.109; p = 0.014) and proline (Adj. R2 = 0.33; Std. ß = -0.109; p = 0.014). High salt intake in White, but not in black adults, were related to metabolomic changes and may contribute to pathophysiological mechanisms associated with increased BP.

The association between an energy-adjusted dietary inflammatory index and inflammation in rural and urban Black South Africans.

OBJECTIVE: To quantify the inflammatory potential of the diet of rural and urban Black South Africans using an adapted energy-adjusted dietary inflammatory index (AE-DII) and to investigate its relationship with inflammatory and cardio-metabolic disease risk markers. Dietary inflammatory potential has not been investigated in African populations. DESIGN: Cross-sectional investigation. SETTING: Rural and urban sites in the North West province of South Africa. PARTICIPANTS: 1885 randomly selected, apparently healthy Black South Africans older than 30 years. RESULTS: AE-DII scores ranged from -3·71 to +5·08 with a mean of +0·37. AE-DII scores were significantly higher in men (0·47 ± 1·19) than in women (0·32 ± 1·29), and in rural (0·55 ± 1·29) than urban participants (0·21 ± 1·19). Apart from its dietary constituents, AE-DII scores are primarily associated with age, rural-urban status and education. Contrary to the literature, alcohol consumption was positively associated with AE-DII scores. Of the four tested inflammatory and thirteen cardio-metabolic biomarkers, the AE-DII was only significantly negatively associated with albumin and HDL cholesterol, and positively with waist circumference and fasting glucose, upon full adjustment. CONCLUSION: Rural men consumed the most pro-inflammatory diet, and urban women the least pro-inflammatory diet. The diet of the participants was not overtly pro- or anti-inflammatory and was not associated with measured inflammatory markers. The inflammatory potential of alcohol at different levels of intake requires further research. Understanding dietary inflammatory potential in the context of food insecurity, unhealthy lifestyle practices and lack of dietary variety remains limited.

Lifestyle factors associated with the transition from healthy to unhealthy adiposity among black South African adults over 10 years.

BACKGROUND AND AIMS: Obesity is associated with an increasing prevalence of cardiovascular diseases in Africa, but some obese individuals maintain cardiometabolic health. The aims were to track metabolically healthy overweight or obesity (MHO) over 10 years in African adults and to identify factors associated with a transition to metabolically unhealthy overweight or obesity (MUO). METHODS AND RESULTS: The participants were the South African cohort of the international Prospective Urban and Rural Epidemiological study. From the baseline data of 1937 adults, 649 women and 274 men were followed for 10 years. The combined overweight and obesity prevalence of men (19.2%-23.8%, p = .02) and women (58%-64.7%, p < .001), and the prevalence of the metabolic syndrome in all participants (25.4%-40.2%, p < .001) increased significantly. More than a quarter (26.2%) of the women and 10.9% of men were MHO at baseline, 11.4% of women and 5.1% of men maintained MHO over 10 years, while similar proportions (12.3% of women, 4.7% of men) transitioned to MUO. Female sex, age, and total fat intake were positively associated with a transition to MUO over 10 years, while physical activity was negatively associated with the transition. HIV positive participants were more likely to be MHO at follow-up than their HIV negative counterparts. CONCLUSIONS: One in two black adults with BMI ≥25 kg/m2 maintained MHO over 10 years, while a similar proportion transitioned into MUO. Interventions should focus on lower fat intakes and higher physical activity to prevent the transition to MUO.

Nutrient density, but not cost of diet, is associated with anemia and iron deficiency in school-age children in South Africa.

OBJECTIVES: This study aimed to investigate the relationship of nutrient density and diet cost with anemia and iron deficiency (ID) in children. METHODS: Dietary intake data of 5- to 12-y-old children (n = 578) from three independent studies in low-income communities were pooled. Nutrient densities were calculated using the Nutrient Rich Foods index and Nutrient Rich Diet index, with higher scores indicating more nutrient-dense foods and diets. Food prices and food intake data were used to calculate ratios of nutrient density to price for foods and diets. Descriptive and correlation analyses examined associations of nutrient density and diet cost with anemia and ID. RESULTS: Most children (>50%) consumed starchy staples (100%), vegetables that are not vitamin A rich (63.9%), and legumes (58.1%), with mean NRF9.3 scores ranging from 31.9 to 56.3. Cheese, eggs, organ meat, fish, dark-green leafy vegetables, and vitamin A-rich vegetables and fruits had mean NRF9.3 scores ranging from 112.6 to 184.7, but each was consumed by less than a third of the children. Children with anemia or ID had lower NRD9.3 scores than children without (P < 0.001 and P = 0.039, respectively). Diet cost did not differ according to anemia and iron status, but nutrient-density-to-price ratio was lower in children with anemia than without (P = 0.001). CONCLUSIONS: Careful selection of nutrient-dense foods as substitutes for foods with lower nutrient density could make it possible for children to consume a diet richer in specific nutrients and help prevent anemia and ID without affecting diet cost.

Associations of dietary diversity with anaemia and iron status among 5- to 12-year-old schoolchildren in South Africa.

OBJECTIVE: To examine the associations of dietary diversity with anaemia and iron status among primary school-aged children in South Africa. DESIGN: An analysis was conducted with pooled individual data from the baseline surveys from three previously conducted independent intervention studies. Two different dietary diversity scores (DDS) were calculated based on data from 1-day (1-d) and 3-day (3-d) dietary recall periods, respectively. Logistic regression analysis was performed to examine the associations of dietary diversity with anaemia and iron status. SETTING: KwaZulu-Natal and North West provinces, South Africa. PARTICIPANTS: Children (n 578) 5- to 12-year-old. RESULTS: A DDS ≤ 4 was associated with higher odds of being anaemic (1-d P = 0·001; 3-d P = 0·006) and being iron deficient (ID) (3-d P < 0·001). For both recall periods, consumption of 'vegetables and fruits other than vitamin A-rich' and 'animal-source foods (ASF)' was associated with lower odds of being anaemic (both P = 0·002), and 'organ meats' with lower odds of being ID (1-d P = 0·045; 3-d P < 0·001). Consumption of 'meat, chicken and fish' was associated with lower odds of being anaemic (P = 0·045), and 'vegetables and fruits other than vitamin A-rich', 'legumes, nuts and seeds' and 'ASF' with lower odds of being ID for the 3-d recall period only (P = 0·038, P = 0·020 and P = 0·003, respectively). CONCLUSION: In order to improve anaemia and iron status among primary school-aged children, dietary diversification, with emphasis on consumption of vegetables, fruits and ASF (including organ meats), should be promoted.

Associations of linoleic acid with markers of glucose metabolism and liver function in South African adults.

BACKGROUND: The relation between dietary and circulating linoleic acid (18:2 n-6, LA), glucose metabolism and liver function is not yet clear. Associations of dietary and circulating LA with glucose metabolism and liver function markers were investigated. METHODS: Cross-sectional analyses in 633 black South Africans (aged > 30 years, 62% female, 51% urban) without type 2 diabetes at baseline of the Prospective Urban Rural Epidemiology study. A cultural-sensitive 145-item food-frequency questionnaire was used to collect dietary data, including LA (percentage of energy; en%). Blood samples were collected to measure circulating LA (% total fatty acids (FA); plasma phospholipids), plasma glucose, glycosylated hemoglobin (HbA1c), serum gamma-glutamyl transferase (GGT), alanine (ALT) and aspartate aminotransferase (AST). Associations per 1 standard deviation (SD) and in tertiles were analyzed using multivariable regression. RESULTS: Mean (±SD) dietary and circulating LA was 6.8 (±3.1) en% and 16.0 (±3.5) % total FA, respectively. Dietary and circulating LA were not associated with plasma glucose or HbA1c (ß per 1 SD: - 0.005 to 0.010, P > 0.20). Higher dietary LA was generally associated with lower serum liver enzymes levels. One SD higher circulating LA was associated with 22% lower serum GGT (ß (95% confidence interval): - 0.25 (- 0.31, - 0.18), P < 0.001), but only ≤9% lower for ALT and AST. Circulating LA and serum GGT associations differed by alcohol use and locality. CONCLUSION: Dietary and circulating LA were inversely associated with markers of impaired liver function, but not with glucose metabolism. Alcohol use may play a role in the association between LA and liver function. TRIAL REGISTRATION: PURE North-West Province South Africa study described in this manuscript is part of the PURE study. The PURE study is registered in ClinicalTrials.gov (Identifier: NCT03225586; URL).

Nutrient patterns and their relation to anemia and iron status in 5- to 12-y-old children in South Africa.

OBJECTIVE: The aim of this study was to assess nutrient patterns and their relation to anemia and iron status of school children using pooled data from three study populations in South Africa. METHODS: Data from 5- to 12-y-old children (N = 578) from three independent studies conducted in two provinces in South Africa were pooled. Data used in the analysis were dietary intake, hemoglobin, and plasma ferritin concentrations. Nutrient patterns were determined using factor analysis. Logistic regression analysis was performed to determine relationships of nutrient patterns with anemia and iron deficiency. RESULTS: In the pooled group, 13.8% of the children were anemic and 27.7% were iron deficient (ID). More than half of children did not meet the Estimated Average Requirement for various nutrients, including vitamins A, C, B12, folate, and zinc, although only 17.7% of children had an iron intake below the requirements. Median intakes for vitamins A and C were lower for anemic than non-anemic children (P = 0.03 and 0.02, respectively) and for ID versus non-ID children (P = 0.03 and 0.046, respectively). Four nutrient patterns were identified: plant protein, carbohydrate, iron, and B vitamins; animal protein and saturated fat; vitamins A and B12; and calcium and fiber. The vitamin A and B12 nutrient pattern was associated with lower odds of being anemic (odds ratio, 0.63; 95% confidence interval, 0.49-0.91; P = 0.035). CONCLUSION: The present results highlighted the potential role of the combination of dietary vitamin A and B12 in the etiology of nutritional anemia in school-age children in South Africa. Nutrient pattern analysis may improve the understanding of the synergistic role of nutrients related to anemia and may assist in planning intervention strategies.

Dietary intake and breast cancer risk in black South African women: the South African Breast Cancer study.

Incidence rates of breast cancer (BC) are increasing in South Africa. The aim of this study was to investigate the association between dietary intake and BC risk in black South African women. The study population included 396 BC cases and 396 population-based controls matched on age and residence, participating in the South African Breast Cancer study. Diet was assessed using a validated quantified FFQ from which twelve energy-adjusted food groups were formed and analysed. OR were estimated using conditional logistic regressions, adjusted for confounding factors, comparing highest v. lowest median intake. Fresh fruit consumption showed an inverse association with BC risk (OR=0·3, 95 % CI 0·12, 0·80) in premenopausal women, whilst red and organ meat consumption showed an overall inverse association with BC risk (OR=0·6, 95 % CI 0·49, 0·94 and OR=0·6, 95 % CI 0·47, 0·91). Savoury food consumption (sauces, soups and snacks) were positively associated with BC risk in postmenopausal women (OR=2·1, 95 % CI 1·15, 4·07). Oestrogen receptor-positive stratification showed an inverse association with BC risk and consumption of nuts and seeds (OR=0·2, 95 % CI 0·58, 0·86). Based on these results, it is recommended that black South African women follow a diet with more fruit and vegetables together with a decreased consumption of less energy-dense, micronutrient-poor foods such as savoury foods. More research is necessary to investigate the association between BC risk and red and organ meat consumption. Affordable and practical methods regarding these recommendations should be implemented within health intervention strategies.

C679X loss-of-function PCSK9 variant lowers fasting glucose levels in a black South African population: A longitudinal study.

AIMS: To determine the longitudinal association of the loss-of-function (LOF) PCSK9 variants (C679X and A443T), proxies of PCSK9 inhibitor drugs, with LDL-C, fasting glucose and glycated hemoglobin. METHODS: We conducted a five year, longitudinal study, nested within the Prospective Urban and Rural Epidemiology study, among 737 apparently healthy, male and female black South Africans of the North West province. Genotyping of the C679X and A443T PCSK9 variants was achieved using Taqman assays from Applied Biosystems. Generalized estimating equations were used to determine longitudinal association of the A443T and C679X PCSK9 variants with LDL-C, fasting glucose and glycated hemoglobin. RESULTS: C679X and A443T variant carriers were associated with significant reductions in LDL-C of -0.98(-1.29, -0.67) mmol/L; p < 0.001) and -0.39(-0.57, -0.20) mmol/L; p < 0.001) respectively, compared to the non-carriers. Only C679X variant was independently associated with reductions in fasting glucose of -0.37 (-0.61, -0.13) mmol/L; p = 0.002) compared to non-carriers. However, the association of the selected variants with glycated hemoglobin were not significant. C679X and A443T carriers were associated with -0.07 (-0.23, 0.09) %; p = 0.400), 0.05 (-0.13, 0.22) %; p = 0.599) of glycated haemoglobin respectively. CONCLUSION: Our results indicated that carriers of A443T and C679X variants exhibit sustained low LDL-C levels over 5 years and have varied effects on T2D biomarkers compared to non-carriers.

Dietary sodium intake and its relationship to adiposity in young black and white adults: The African-PREDICT study.

Obesity and salt intake are both established factors contributing to cardiovascular disease development. Recently, studies found a controversial positive relationship between dietary salt and obesity. Therefore, the authors investigated whether obesity-related measures are associated with 24-hour urinary sodium in a healthy biethnic population. The study included 761 adults (20-30 years) with complete 24-hour urinary sodium, anthropometry, and bioelectrical impedance measurements. In single regression analyses all obesity-related measures related positively with 24-hour urinary sodium (P ≤ .008). However, with multivariate adjustments for energy intake, accelerometery, age, sex, black and white ethnicity, and other covariates, only body surface area (BSA) remained independently associated with 24-hour urinary sodium (R2  = 0.72, ß = .05, P = .039). To conclude, we found a consistent and robust positive relationship between BSA and estimated salt intake - but not with traditional obesity measures such as body mass index (BMI). Further studies are needed to investigate body surface area and potentially, skin area, in salt handling.

The Sodium Content of Processed Foods in South Africa during the Introduction of Mandatory Sodium Limits.

BACKGROUND: In June 2016, the Republic of South Africa introduced legislation for mandatory limits for the upper sodium content permitted in a wide range of processed foods. We assessed the sodium levels of packaged foods in South Africa during the one-year period leading up to the mandatory implementation date of the legislation. METHODS: Data on the nutritional composition of packaged foods was obtained from nutrition information panels on food labels through both in-store surveys and crowdsourcing by users of the HealthyFood Switch mobile phone app between June 2015 and August 2016. Summary sodium levels were calculated for 15 food categories, including the 13 categories covered by the sodium legislation. The percentage of foods that met the government's 2016 sodium limits was also calculated. RESULTS: 11,065 processed food items were included in the analyses; 1851 of these were subject to the sodium legislation. Overall, 67% of targeted foods had a sodium level at or below the legislated limit. Categories with the lowest percentage of foods that met legislated limits were bread (27%), potato crisps (41%), salt and vinegar flavoured snacks (42%), and raw processed sausages (45%). About half (49%) of targeted foods not meeting the legislated limits were less than 25% above the maximum sodium level. CONCLUSION: Sodium levels in two-thirds of foods covered by the South African sodium legislation were at or below the permitted upper levels at the mandatory implementation date of the legislation and many more were close to the limit. The South African food industry has an excellent opportunity to rapidly meet the legislated requirements.

Nutrient Patterns Associated with Fasting Glucose and Glycated Haemoglobin Levels in a Black South African Population.

Type 2 diabetes (T2D) burden is increasing globally. However, evidence regarding nutrient patterns associated with the biomarkers of T2D is limited. This study set out to determine the nutrient patterns associated with fasting glucose and glycated haemoglobin the biomarkers of T2D. Factor analysis was used to derive nutrient patterns of 2010 participants stratified by urban/rural status and gender. Principal Component Analysis (PCA) was applied to 25 nutrients, computed from the quantified food frequency questionnaires (QFFQ). Three nutrient patterns per stratum, which accounted for 73% of the variation of the selected nutrients, were identified. Multivariate linear regression models adjusted for age, BMI, smoking, physical activity, education attained, alcohol intake, seasonality and total energy intake were computed. Starch, dietary fibre and B vitamins driven nutrient pattern was significantly associated with fasting glucose (ß = -0.236 (-0.458; -0.014); p = 0.037) and glycated haemoglobin levels (ß = -0.175 (-0.303; -0.047); p = 0.007) in rural women. Thiamine, zinc and plant protein driven nutrient pattern was associated with significant reductions in glycated haemoglobin and fasting glucose ((ß = -0.288 (-0.543; -0.033); p = 0.027) and (ß = -0.382 (-0.752; -0.012); p = 0.043), respectively) in rural men. Our results indicate that plant driven nutrient patterns are associated with low fasting glucose and glycated haemoglobin levels.

Candidate gene analysis of the fibrinogen phenotype reveals the importance of polygenic co-regulation.

Fibrinogen and its functional aspects have been linked to cardiovascular disease. There is vast discrepancy between the heritability of fibrinogen concentrations observed in twin studies and the heritability uncovered by genome wide association studies. We postulate that some of the missing heritability might be explained by the pleiotropic and polygenic co-regulation of fibrinogen through multiple targeted genes, apart from the fibrinogen genes themselves. To this end we investigated single nucleotide polymorphisms (SNPs) in genes coding for phenotypes associated with total and γ' fibrinogen concentrations and clot properties. Their individual and accumulative associations with the fibrinogen variables were explored together with possible co-regulatory processes as a result of the gain and loss of transcription factor binding sites (TFBS). Seventy-eight SNPs spanning the APOB, APOE, CBS, CRP, F13A1, FGA, FGB, FGG, LDL-R, MTHFR, MTR, PCSK-9 and SERPINE-1 genes were included in the final analysis. A novel PCSK-9 SNP (rs369066144) was identified in this population, which associated significantly (p=0.04) with clot lysis time (CLT). Apart from SNPs in the fibrinogen (FGA, FGB and FGG) and FXIII (F13A1) genes, the fibrinogen phenotypes were also associated with SNPs in genes playing a role in lipid homeostasis (LDL-R, PCSK-9) together with CBS and CRP polymorphisms (particularly, CRP-rs3093068). The genetic risk scores, presenting accumulative genetic risk, were significantly associated (p≤0.007) with total and γ' fibrinogen concentrations, lag time, slope and CLT, highlighting the importance of a polygenetic approach in determining complex phenotypes. SNPs significantly associated with the fibrinogen phenotypes, resulted in a total of 75 TFBS changes, of which 35 resulted in a loss and 40 in a gain of TFBS. In terms of co-regulation, V$IRF4.02, V$E2FF and V$HIFF were of particular importance. The investigation into TFBS provided valuable insight as to how sequence divergences in seemingly unrelated genes can result in transcriptional co-regulation of the fibrinogen phenotypes. The observed associations between the identified SNPs and the fibrinogen phenotypes therefore do not imply direct effects on cardiovascular disease outcomes, but may prove useful in explaining more of the genetic regulation of the investigated fibrinogen phenotypes.

Predictive utility of a genetic risk score of common variants associated with type 2 diabetes in a black South African population.

AIMS: To determine the predictive utility of polygenic risk scores of common variants associated with type 2 diabetes derived from the European and Asian ethnicities among a black South African population. METHOD: Our study was a case-control study nested within the Prospective Urban and Rural Epidemiological (PURE) study of 178 male and female cases, matched for age and gender with 178 controls. Four types of genetic risk scores (GRS) were developed from 66 selected SNPs. These comprised of beta cell related variants (GRSb), variants which had significant associations with T2D in our study (GRSn), variants from the trans-ethnic meta-analysis (GRStrans) and all the 66 selected SNPs (GRSt). RESULTS: Of the GRS's, only GRSn was associated with increased risk of T2D as indicated by an OR (95CI) of 1.21 (1.02-1.43) p-value=0.015. Stratified analysis of age and BMI, indicated the GRSn to be significantly associated with T2D among the non-obese and participants less than 50years. The area under the ROC of the T2D risk factors only was 0.652 (p value<0.001) and with the addition of GRSn it was 0.665 (p value<0.001). CONCLUSIONS: The GRS of European and Asian derived variants have limited clinical utility in the black South African population. The inclusion of population specific variants in the GRS is pivotal.

Common Variants Associated with Type 2 Diabetes in a Black South African Population of Setswana Descent: African Populations Diverge.

The increasing worldwide prevalence of type 2 diabetes mellitus (T2D) is a serious global health concern. Although T2D has a strong genetic etiology, limited knowledge exists about the common variants associated with it in the black South African population. This study set out to evaluate the association of previously reported common variants in other world populations with T2D susceptibility in a black South African population of Setswana descent. A case-control study design of 178 cases and 178 controls nested in the Prospective Urban Rural Epidemiology (PURE) study was conducted wherein we genotyped for 77 single nucleotide polymorphisms (SNPs). PLINK software was used to evaluate the standard genetic models of disease penetrance for the association of the common variants with impaired glucose tolerance (IGT) while adjusting for age, sex, and body mass index. Only rs1436955 significantly associated with an increase in T2D risk; three other variants, rs831571, rs8050136, and rs7542900, significantly associated with decreased risk of T2D. However, none of the four SNPs had significant associations after correcting for multiple testing (p<0.05). Although further studies are required to confirm these observations, the common variants associated with T2D risk among the Black South Africans of Setswana descent might likely be different than those in the Asian and European populations. This study supports the broader thesis that the genetic background of Africans is diverse and cannot be directly extrapolated using genetic variants from other ethnicities. Therefore there is a need to identify the population-specific variants linked with T2D in Africa.

Common and rare single nucleotide polymorphisms in the LDLR gene are present in a black South African population and associate with low-density lipoprotein cholesterol levels.

The LDL receptor has an essential role in regulating plasma LDL-C levels. Genetic variation in the LDLR gene can be associated with either lower or moderately raised plasma levels of LDL-C, or may cause familial hypercholesterolemia. The prevalence of single-nucleotide polymorphisms (SNPs) in the LDLR in the black South African population is not known and therefore, we aimed to determine the genotypic variation of the LDLR in the study population as well as to define the association of the different genotypes with plasma LDL-C levels. A random selection of 1860 apparently healthy black South African volunteers aged 35-60 years was made in a cross-sectional study. Novel SNPs were identified in a subset of 30 individuals by means of automated sequencing before screening the entire cohort by means of the Illumina VeraCode GoldenGate Genotyping Assay on a BeadXpress Reader system. Twenty-five SNPs were genotyped, two of which were novel. A very rare SNP, rs17249141, in the promoter region was significantly associated with lower levels of LDL-C. Four other SNPs (rs2738447, rs14158, rs2738465 and rs3180023) were significantly associated with increased levels of LDL-C. We can conclude that some of the various SNPs identified do indeed associate with LDL-C levels.