Non-HDL or LDL cholesterol in heterozygous familial hypercholesterolaemia: findings of the Simon Broome Register.

PURPOSE OF REVIEW: The role of non-HDL-C in the identification and management of lipid disorders is not clearly defined, although UK guidelines recommend its wider use in assessing the need for lipid-lowering therapy and as a treatment target. RECENT FINDINGS: We examined the implications of the use of non-HDL-C as opposed to LDL-C in 253 people with hypercholesterolaemia before treatment and 573 after treatment in whom fasting total serum cholesterol, HDL-C and LDL-C had been recorded and the diagnosis of heterozygous familial hypercholesterolemia (heFH) was investigated by genetic testing. The difference and the limits of agreement between non-HDL-C and LDL-C calculated using the Friedewald formula were assessed in those with and without heFH-causing mutations. SUMMARY: There were 147 mutation-positive and 106 mutation-negative pretreatment participants and 395 mutation-positive and 178 mutation-negative patients receiving treatment. The difference between non-HDL-C and LDL-C pretreatment in mutation-positive people (mean LDL-C 7.73 mmol/l) was 0.67 mmol/l (95% CI 0.62-0.73) and posttreatment (mean LDL-C 4.71 mmol/l) was 0.62 mmol/l (95% CI 0.59-0.65) with wide limits of agreement of -0.02 to 1.37 and 0.07-1.18 mmol/l, respectively. Among patients with heterozygous familial hypercholesterolaemia, use of estimated LDL-C derived from non-HDL-C in place of calculated LDL-C may result in diagnostic misclassification and difficulty in assessing the true reduction in LDL-C with treatment, because of the wide inter-individual limits of agreement around the mean difference between non-HDL-C and LDL-C.

Coronary heart disease mortality in severe vs. non-severe familial hypercholesterolaemia in the Simon Broome Register.

BACKGROUND AND AIMS: The International Atherosclerosis Society (IAS) has proposed that patients with "severe" FH (SFH) would warrant early and more aggressive cholesterol-lowering treatment such as with PCSK9 inhibitors. SFH is diagnosed if LDL-cholesterol (LDLC) > 10 mmol/L, or LDLC >8.0 mmol/L plus one high-risk feature, or LDLC >5 mmol/L plus two high-risk features. Here we compare CHD mortality in SFH and non-SFH (NSFH) patients in the UK prospective Simon Broome Register since 1991, when statin use became routine. METHODS: 2929 definite or possible PFH patients (51% women) aged 20-79 years were recruited from 21 UK lipid clinics and followed prospectively between 1992 and 2016. The excess CHD standardised mortality ratio (SMR) compared to the England and Wales population was calculated (with 95% confidence intervals). RESULTS: 1982 (67.7%) patients met the SFH definition. Compared to the non-SFH, significantly (p < 0.001) more SFH patients had diagnosed CHD at baseline (24.6% vs. 17.5%), were current smokers (21.9% vs 10.2%) and had a BMI > 30 kg/m2 (14.9% vs. 7.8%). The SMR for CHD mortality was significantly (p = 0.007) higher for SFH (220 (184-261) (34,134 person years, 129 deaths observed, vs. 59 expected) compared to NSFH of 144 (98-203) (15,432 person years, 32 observed vs. 22 expected). After adjustment for traditional risk factors, the Hazard Ratio for CHD mortality in SFH vs. NSFH was 1.22 (0.80-1.87) p = 0.36, indicating that the excess risk was largely accounted for by these factors. CONCLUSIONS: CHD mortality remains elevated in treated FH, especially for SFH, emphasising the importance of optimal lipid-lowering and management of other risk factors.

Diagnostic scoring for familial hypercholesterolaemia in practice.

PURPOSE OF REVIEW: Diagnostic scoring for familial hypercholesterolaemia (FH) can be used either to screen for possible FH or guide the selection of patients for genetic (DNA) testing. We review the published diagnostic criteria and discuss the options for future development. RECENT FINDINGS: Scoring systems have been developed internationally based on lipid values and various combinations of clinical signs and cardiovascular history. The predictive value varies according to the test population, be it lipid clinic referrals, general population, or relatives of patients with FH. Also, there is increasing recognition of genetic heterogeneity in FH so that criteria are of differing predictive value depending on the genetic variant of FH. SUMMARY: These clinical scoring systems are increasingly used to guide selection of patients for FH genetic testing but no single approach has yet emerged as the system of choice. Further refinement of these scoring tools using more sophisticated calculators are superseding the more manual approaches. These are well suited to web-based tools or smartphone applications.

Integrating provision of specialist lipid services with cascade testing for familial hypercholesterolaemia.

PURPOSE OF REVIEW: To highlight the unmet need for identifying individuals with familial hypercholesterolaemia and exploring the implications that this will have for local and national healthcare services. RECENT FINDINGS: A pathway utilising DNA testing for the diagnosis of familial hypercholesterolaemia, and subsequent cascade testing has been developed in Wales. SUMMARY: Undiagnosed familial hypercholesterolaemia carries a high risk of cardiovascular disease, which is easily preventable with pharmacotherapy, if individuals are appropriately diagnosed, and affected family members identified. The use of DNA testing is cost-effective and allows for efficient cascade testing. This has implications for local services and highlights unmet educational and clinical requirements in clinical lipidology.

Homocysteine and endothelial function in human studies.

The endothelium plays a key role in the pathophysiology of vascular disease. Impaired flow-mediated dilatation (FMD) is a measure of endothelial dysfunction resulting from reduced bioavailability of nitric oxide (NO). Patients with homocystinuria manifest with impaired FMD, but in mild hyperhomocysteinemia, the evidence is conflicting. Oral loading with methionine or homocysteine impairs FMD, but it remains unproven that this effect is mediated directly by homocysteine. In addition, there is no clear consensus as to a mechanisms by which homocysteine would induce endothelial dysfunction. Folate administration lowers plasma homocysteine and enhances FMD. However, the effect of folate only appears to occur at high doses and with a time course that would indicate that it is acting by a mechanism independent of homocysteine lowering. It is possible that folate, in pharmacological doses, may enhance the NO activity by influencing NO-tetrahydrobiopterin interactions. These studies provide some insights and raise intriguing questions concerning the relationship between homocysteine, folate, and endothelial function. However, changes in FMD may not translate into vascular endpoints, and the outcomes of clinical intervention trials with different doses of folic acid are awaited with interest.

Short-term high-dose folic acid does not alter markers of endothelial cell damage in patients with coronary heart disease.

BACKGROUND AND OBJECTIVE: Endothelial dysfunction is an early, pre-clinical manifestation of coronary heart disease and is associated with increased plasma levels of von Willebrand factor (vWF), soluble E-selectin, and thrombomodulin, markers of endothelial cell damage/activation and reduced nitric oxide bioavailability. Homocysteine is associated with an increased risk of cardiovascular disease and mortality. High-dose folic acid treatment lowers plasma homocysteine by 25% and improves nitric oxide bioavailability; however, the effects on other indices of endothelial cell activation/damage has not been examined in patients with coronary heart disease and normal renal function. DESIGN AND METHODS: In a randomised, double-blind, cross-over study in 50 patients with coronary heart disease and normal serum creatinine, folic acid (5 mg/daily) was administered for 6 weeks and blood was analysed for von Willebrand factor, soluble E-selectin, and thrombomodulin. Endothelial nitric oxide bioavailability was assessed by flow-mediated dilatation. RESULTS: Plasma folate levels increased (9.1+/-3.4 vs. 310+/-235 microg/l; p<0.001) and nitric oxide bioavailability improved (47+/-35 vs. 110+/-43 microm; p<0.001) following active treatment. However, markers of endothelial cell injury were not significantly influenced (von Willebrand factor 118+/-33 vs. 119+/-34%; E-selectin 52+/-17 vs. 51+/-16 microg/l; thrombomodulin 3.94+/-1.81 vs. 3.94+/-1.51 microg/l; p=NS comparing post-placebo with post-folate). No correlation was observed between improvement in flow-mediated dilatation and change in endothelial marker proteins. INTERPRETATION AND CONCLUSION: These data suggest that endothelial markers are not useful surrogates of endothelial nitric oxide bioavailability in coronary heart disease and may be a less sensitive marker of endothelial function than nitric oxide.

Folate, homocysteine, endothelial function and cardiovascular disease.

Evidence reported from numerous clinical studies over the past decade has revealed an association between increased plasma total homocysteine (tHcy) concentrations and cardiovascular disease (CVD). In addition, epidemiological studies have identified an inverse association between blood folate concentrations, folate intake and cardiovascular endpoints, that are independent of homocysteine. Folic acid supplementation can lower plasma tHcy concentrations safely and inexpensively. Furthermore, folic acid can reverse endothelial dysfunction observed in patients with CVD. This reversal in endothelial dysfunction with folic acid has been shown to be independent of plasma tHcy lowering, suggesting that folate has pleiotropic effects on the vasculature other than homocysteine lowering. In vitro evidence demonstrates that 5-methyltetrahydrofolate (5MeTHF) the main circulating metabolite of folate, can increase nitric oxide production and can directly scavenge superoxide radicals. The potential beneficial role of folic acid supplements on vascular disease are currently being tested in randomized placebo controlled studies.

Folate bioavailability: UK Food Standards Agency workshop report.

The UK Food Standards Agency convened a group of expert scientists to review current research investigating folate bioavailability. The workshop aimed to overview current research and establish priorities for future research. Discrepancies were observed in the evidence base for folate bioavailability, especially with regard to the relative bioavailability of natural folates compared with folic acid. A substantial body of evidence shows folic acid to have superior bioavailability relative to food folates; however, the exact relative bioavailability still needs to be determined, and in particular with regard to mixed diets. The bioavailability of folate in a mixed diet is probably not a weighted average of that in the various foods consumed; thus the workshop considered that assessment of folate bioavailability of whole diets should be a high priority for future research.

Effect of riboflavin status on the homocysteine-lowering effect of folate in relation to the MTHFR (C677T) genotype.

BACKGROUND: Riboflavin (vitamin B(2)) is the precursor for FAD, the cofactor for methylenetetrahydrofolate reductase (MTHFR). MTHFR catalyzes the formation of 5-methyltetrahydrofolate, which acts as a methyl donor for homocysteine remethylation. Individuals with the MTHFR 677C-->T mutation have increased plasma total homocysteine (tHcy) concentrations, particularly in association with low folate status. It has been proposed that riboflavin may act together with folate to lower plasma tHcy, particularly in individuals with the thermolabile MTHFR T variant. METHODS: We measured B-vitamin status and plasma tHcy in 126 healthy individuals 20-63 years of age (42 CC, 42 CT, and 42 TT MTHFR genotypes) at baseline and after three interventions (4 months): placebo plus natural diet; daily 400 microg folic acid supplement plus natural diet; and increased dietary folate to 400 microg/day. RESULTS: At baseline and after nutritional intervention, lower riboflavin status was associated with increased plasma tHcy concentrations. Plasma tHcy was 2.6 micromol/L higher in the lowest plasma riboflavin quartile compared with the highest (P <0.02) and was 4.2 micromol/L higher in the highest erythrocyte glutathione reductase activation coefficient (EGRAC) quartile compared with the lowest (P <0.001). This effect was not restricted to those with the T allele. Folic acid given as a 400 microg/day supplement appeared to exacerbate a tendency toward riboflavin deficiency, as suggested by an increase in the proportion of individuals with EGRAC > or =1.4 from 52% to 65% after supplementation (P <0.05). CONCLUSIONS: Folate and riboflavin interact to lower plasma tHcy, possibly by maximizing the catalytic activity of MTHFR. The effect may be unrelated to MTHFR genotype.

Methylenetetrahydrofolate reductase 677C-->T genotype modulates homocysteine responses to a folate-rich diet or a low-dose folic acid supplement: a randomized controlled trial.

BACKGROUND: Low folate status and elevated plasma homocysteine are associated with increased risk of neural tube defects and cardiovascular disease. Homocysteine responses to folate may be influenced by genetic variants in folate metabolism. OBJECTIVE: We determined the effect of folate-enhancing dietary interventions on plasma folate and plasma total homocysteine (tHcy) with respect to the methylenetetrahydrofolate reductase 677C-->T genotype. DESIGN: A total of 126 healthy subjects (42 TT, 42 CT, and 42 CC genotypes) completed 3 dietary interventions (4 mo each) in random order: 1) exclusion diet (avoidance of folic acid-fortified foods and ingestion of a placebo daily), 2) folate-rich diet (increased intake of fortified and naturally folate-rich foods to achieve 400 microg folate/d), and 3) supplement (exclusion diet plus a folate supplement of 400 microg/d). RESULTS: Plasma folate was higher (P < or = 0.001) and plasma tHcy lower (P < or = 0.001) after the folate-rich and supplement interventions than after the exclusion diet. Plasma folate was significantly greater after supplementation than after the folate-rich diet, but there was no significant difference in tHcy concentration (P = 0.72). TT homozygotes had higher plasma tHcy (14.5 compared with 8.9 micromol/L, P < or = 0.001) and lower plasma folate (14.8 compared with 19.0 nmol/L, P < or = 0.01) than did subjects with the CC genotype after the exclusion diet. CT heterozygotes had intermediate concentrations. The trend toward higher tHcy in TT homozygotes persisted throughout the study but was less marked with increasing folate intake (TT compared with CC after supplementation, P = 0.097). CONCLUSIONS: A folate-rich diet including folic acid-fortified foods or low-dose supplements effectively increases folate status. TT homozygotes require higher folate intakes than do individuals with the CT or CC genotype to achieve similar tHcy concentrations but are responsive to folate intervention.

Nutritional advice to increase soluble fibre intake does not change plasma folate or homocysteine in men with angina: a randomised controlled trial.

OBJECTIVE: To study the effect of advice to increase dietary soluble fibre, including fruit and vegetables, on plasma folate and homocysteine in men with angina. DESIGN: Data were collected on a subset of subjects from the Diet and Angina Randomised Trial (DART II). In a randomised (2 x 2) factorial design, subjects received advice on either, neither or both interventions to: (1) increase soluble fibre intake to 8.0 g day(-1) (fruit, vegetables and oats); (2) increase oily fish intake to 2 portions week(-1). Those who received soluble fibre advice were compared with those who did not. Subjects were genotyped for C677T variant 5,10-methylenetetrahydrofolate reductase (MTHFR). SETTING/SUBJECTS: Seven hundred and fifty-three male angina patients were recruited from general practice. RESULTS: Plasma homocysteine concentrations were at the upper end of the normal range (median 11.5, 25% 9.4, 75% 14.0 micromol l(-1)). Baseline intake of fruit and vegetables was positively correlated with plasma folate (r(s) = 0.29, P < 0.01). Smokers had lower intakes of fruit and vegetables, lower plasma folate and higher homocysteine (all P < 0.01). Homozygotes for variant MTHFR had higher homocysteine concentrations at low plasma folate (P < 0.01). Reported intakes of fruit and vegetables and estimated dietary folate increased in the intervention group (ca. +75 g day(-1), P < 0.01 and ca. +20 g day(-1), P < 0.05, respectively). However, neither plasma folate (baseline/follow-up 4.5 vs. 4.4 microg l(-1), P = 0.40) nor homocysteine (baseline/follow-up 11.7 vs. 11.7 micromol l(-1), P = 0.31) changed. CONCLUSIONS: Plasma homocysteine, a cardiovascular risk factor, is influenced by MTHFR genotype, plasma folate and smoking status. Dietary advice successfully led to changes in fruit and vegetable intake, but not to changes in plasma folate or homocysteine, possibly because the fruits and vegetables that were chosen were not those richest in folate.

Folic acid improves endothelial function in coronary artery disease via mechanisms largely independent of homocysteine lowering.

BACKGROUND: Homocysteine is a risk factor for coronary artery disease (CAD), although a causal relation remains to be proven. The importance of determining direct causality rests in the fact that plasma homocysteine can be safely and inexpensively reduced by 25% with folic acid. This reduction is maximally achieved by doses of 0.4 mg/d. High-dose folic acid (5 mg/d) improves endothelial function in CAD, although the mechanism is controversial. It has been proposed that improvement occurs through reduction in total (tHcy) or free (non-protein bound) homocysteine (fHcy). We investigated the effects of folic acid on endothelial function before a change in homocysteine in patients with CAD. METHODS AND RESULTS: A randomized, placebo-controlled study of folic acid (5 mg/d) for 6 weeks was undertaken in 33 patients. Endothelial function, assessed by flow-mediated dilatation (FMD), was measured before, at 2 and 4 hours after the first dose of folic acid, and after 6 weeks of treatment. Plasma folate increased markedly by 1 hour (200 compared with 25.8 nmol/L; P<0.001). FMD improved at 2 hours (83 compared with 47 microm; P<0.001) and was largely complete by 4 hours (101 compared with 51 microm; P<0.001). tHcy did not significantly differ acutely (4-hour tHcy, 9.56 compared with 9.79 micromol/L; P=NS). fHcy did not differ at 3 hours but was slightly reduced at 4 hours (1.55 compared with 1.78 micromol/L; P=0.02). FMD improvement did not correlate with reductions in either fHcy or tHcy at any time. CONCLUSIONS: These data suggest that folic acid improves endothelial function in CAD acutely by a mechanism largely independent of homocysteine.

Influence of methylenetetrahydrofolate reductase genotype, exercise and other risk factors on endothelial function in healthy individuals.

Cardiovascular disease has a multifactorial aetiology that is influenced by both genetic and environmental factors. Endothelial dysfunction is a key event in the pathogenesis of vascular disease that occurs before structural vascular changes or clinical symptoms are evident. Conventional risk factors, for example hypertension and diabetes mellitus, are associated with endothelial dysfunction, but the influence of other putative risk factors is not clear. The methylenetetrahydrofolate reductase (MTHFR) C677T genotype, a common polymorphism that induces hyperhomocysteinaemia, has been proposed as being a genetic risk factor for cardiovascular disease. A total of 126 healthy adults recruited by MTHFR C677T genotype (42 of each genotype, i.e. CC, CT and TT) underwent assessment of endothelial function. Brachial artery endothelium-dependent flow-mediated dilatation (FMD) was measured using high-resolution ultrasonic vessel "wall-tracking". Using multiple regression analysis, MTHFR genotype and 21 other subject and subject-lifestyle variables were investigated as potential predictors of endothelial function. FMD was influenced positively by frequency of aerobic exercise and by hormone replacement therapy, and negatively by increases in systolic blood pressure. MTHFR C677T genotype and the associated variation in plasma homocysteine levels did not influence FMD. Additionally, other factors, including plasma cholesterol and self-supplementation with either antioxidant vitamins or cod liver oil, showed no significant relationship with FMD, although these findings are compromised by the narrow range studied for cholesterol and the small number of subjects taking supplements. These observations have implications for risk factor management in the primary prevention of cardiovascular disease in healthy individuals.