Molecular genetics and genetic epidemiology of cardiovascular diseases and diabetes. Introductory remarks: risk factor levels and variability

Isolated systolic hypertension in the young: a position paper endorsed by the European Society of Hypertension

: Whether isolated systolic hypertension in the young (ISHY) implies a worse outcome and needs antihypertensive treatment is still a matter for dispute. ISHY is thought to have different mechanisms than systolic hypertension in the elderly. However, findings from previous studies have provided inconsistent results. From the analysis of the literature, two main lines of research and conceptualization have emerged. Simultaneous assessment of peripheral and central blood pressure led to the identification of a condition called pseudo or spurious hypertension, which was considered an innocent condition. However, an increase in pulse wave velocity has been found by some authors in about 20% of the individuals with ISHY. In addition, obesity and metabolic disturbances have often been documented to be associated with ISHY both in children and young adults. The first aspect to consider whenever evaluating a person with ISHY is the possible presence of white-coat hypertension, which has been frequently found in this condition. In addition, assessment of central blood pressure is useful for identifying ISHY patients whose central blood pressure is normal. ISHY is infrequently mentioned in the guidelines on diagnosis and treatment of hypertension. According to the 2013 European Guidelines on the management of hypertension, people with ISHY should be followed carefully, modifying risk factors by lifestyle changes and avoiding antihypertensive drugs. Only future clinical trials will elucidate if a benefit can be achieved with pharmacological treatment in some subgroups of ISHY patients with associated risk factors and/or high central blood pressure.

Specific advantages of twin registries and biobanks

This chapter briefly reviews the role of twin studies and study designs based on using twins in different settings. In the Nordic countries, twin registers and cohorts have existed already for many decades. These are a unique resource for scientific studies; a major strength being their unselected and representative nature. In the past years, biological samples are also being collected within the studies conducted on the Nordic twins.

Adult hypertension is associated with blood pressure variability in childhood in blacks and whites: the bogalusa heart study

BACKGROUND

Blood pressure (BP) is a variable physiological parameter in health and disease. Increased BP variability over time in adults is associated with severity of end-organ damage and a higher rate of cardiovascular events, even after adjusting for the mean levels. This study tested the hypothesis that childhood BP variability, besides the mean levels, is also predictive of adulthood hypertension.

METHODS

The study cohort consisted of 1,797 subjects (1,091 whites and 706 blacks; age = 21-48 years) enrolled in the Bogalusa Heart Study since childhood. BP variability was depicted as s.d. of 4-8 serial measurements in childhood.

RESULTS

Blacks showed significantly greater childhood systolic BP (SBP) variability than whites. In multivariable logistic regression analyses, adjusting for race, sex, mean childhood age, s.d. of childhood body mass index (BMI), mean childhood BP levels, adulthood age and BMI, adult hypertension was significantly associated with s.d. of childhood SBP (odds ratio (OR) (95% confidence intervals) = 1.28 (1.09, 1.51), P = 0.002) and s.d. of childhood diastolic BP (DBP; 1.36 (1.16, 1.58), P < 0.001). When using adulthood BP levels as continuous dependent variables in linear regression models, adjusting for the same covariates, adulthood SBP and DBP levels were significantly associated with s.d. of childhood SBP (standardized regression coefficient β = 0.086, P < 0.001) and s.d. of childhood DBP (β = 0.105, P < 0.001), respectively.

CONCLUSIONS

Increases in BP variations as well as levels in early life are predictive of adult hypertension, which underscore the childhood origin of the natural history of essential hypertension.

Effects of simvastatin and carnitine versus simvastatin on lipoprotein(a) and apoprotein(a) in type 2 diabetes mellitus

AIM

The aim of the present study was to compare the effects of simvastatin and L-carnitine coadministration versus simvastatin monotherapy on lipid profile, lipoprotein(a) (Lp(a)) and apoprotein(a) (Apo(a)) levels in type II diabetic patients.

PATIENTS/METHODS

In this double-blind, randomized clinical trial, 75 patients were assigned to one of two treatment groups for 4 months. Group A received simvastatin monotherapy; group B received L-carnitine and simvastatin. The following variables were assessed at baseline, after washout and at 1, 2, 3 and 4 months of treatment: body mass index, fasting plasma glucose, glycated hemoglobin, total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, Apolipoprotein A1, Apo B, lipoprotein(a) and apoprotein(a).

RESULTS

At the end of treatment in the carnitine and simvastatin combined group compared with the simvastatin alone group, we observed a significant decrease in glycemia (p < 0.001), triglycerides (p < 0.001), Apo B (p < 0.05), Lp(a) (p < 0.05), apo(a) (p < 0.05), while HDL significantly increased (p < 0.05).

CONCLUSIONS

The coadministration of carnitine and simvastatin resulted in a significant reduction in Lp(a) and apo(a) and may represent a new therapeutic option in reducing plasma Lp(a) levels, LDL cholesterol and Apo B100.

A twin study of C-Reactive Protein compared to other risk factors for coronary heart disease

Coronary heart disease (CHD) tends to cluster in families, and several established risk factors for the disease are to some extent inherited. Inflammation plays a key role in the development of atherosclerosis and CHD. A low-grade inflammation may be detected by highly sensitive C-Reactive Protein (CRP) determination, which is strongly associated to CHD. In order to uncover any role of genetics in low-grade inflammation, we measured CRP in healthy monozygotic twins. The within-pair correlation coefficient of CRP was 0.40, suggesting an important genetic contribution to the control of CRP level. CRP correlated significantly to other CHD risk factors like body mass index (BMI), systolic blood pressure, diastolic blood pressure, plasma fibrinogen, serum high-density lipoprotein cholesterol, plasma homocysteine, and serum triglycerides. Of these variables, BMI was most significantly associated to CRP in a linear multiple regression analysis. We conclude that CRP level (reflecting a low-grade inflammation) exhibits a moderate, but significant degree of heritability. The association between CRP and BMI, which has a larger degree of heritability, could partly explain the heritability of serum CRP level.

Plasma total homocysteine and cysteine in relation to glomerular filtration rate in diabetes mellitus

BACKGROUND

The plasma concentrations of total homocysteine (tHcy) and total cysteine (tCys) are determined by intracellular metabolism and by renal plasma clearance, and we hypothesized that glomerular filtration is a major determinant of plasma tHcy and tCys. We studied the relationships between the glomerular filtration rate (GFR) and plasma tHcy and tCys in populations of diabetic patients with particularly wide ranges of GFR.

METHODS

We measured GFR, urine albumin excretion rate (UAER), plasma tHcy, tCys, methionine, vitamin B12, folate, C-peptide, and routine parameters in 50 insulin-dependent diabetes mellitus (IDDM) and 30 non-insulin-dependent diabetes mellitus (NIDDM) patients. All patients underwent intensive insulin treatment and had a serum creatinine concentration below 115 micromol/liter.

RESULTS

Mean plasma tHcy in diabetic patients (0.1 micromol/liter) was lower than in normal persons (11.1 micromol/liter, P = 0.0014). Mean plasma tCys in diabetic patients (266.1 micromol/liter) was also lower than in normal persons (281.9 micromol/liter, P = 0.0005). Seventy-three percent of the diabetic patients had relative hyperfiltration. Plasma tHcy and tCys were closely and independently associated with GFR, serum folate, and serum B12. However, plasma tHcy was not independently associated with any of the 22 other variables tested, including age, serum creatinine concentration, UAER, total daily insulin dose, and glycemic control.

CONCLUSIONS

Glomerular filtration rate is an independent determinant of plasma tHcy and tCys concentrations, and GFR is rate limiting for renal clearance of both homocysteine and cysteine in diabetic patients without overt nephropathy. Declining GFR explains the age-related increase in plasma tHcy, and hyperfiltration explains the lower than normal mean plasma tHcy and tCys concentrations in populations of diabetic patients.

Variability gene effects of DNA polymorphisms at the apo B, apo A I/C III and apo E loci on serum lipids: the Cardiovascular Risk in Young Finns Study

We studied the influence of selected genetic markers on the intra-individual long-term variability in serum lipid levels. The study cohort consisted of a sub-sample from a large follow-up study of atherosclerosis precursors in children and young adults. A total of 320 subjects had determinations of apo B XbaI RFLP genotypes, 305 subjects had apo AI/CIII SstI RFLP genotype determinations and 1581 subjects had their apo E phenotypes determined. Complete data on serum lipids were available at 3-year intervals over a 6-year follow-up period. The subjects were healthy and aged 3-18 years at baseline. Intra-individual variability was assessed with a nested analysis of variance procedure. Each of the genetic markers studied here significantly affected intra-individual variability of serum lipid levels. No clear sex influence was observed, although the differences in variability tended to be more significant in males. Apo B XbaI genotypes significantly influenced intra-individual variability of total and LDL-cholesterol levels in both sexes. A marked effect of the XbaI genotype was also found on triglyceride variability. In males the standardized intra-individual triglyceride variances were 0.71 and 0.34 in genotypes X1X1 and X2X2, respectively (p < 0.001), with a clear gene dosage effect. The apo AI/CIII genotype had an influence only on the variability of total cholesterol and LDL-cholesterol levels and only in males. The apo E phenotypes were associated with intra-individual variability in total and LDL-cholesterol levels but again, only in males.(ABSTRACT TRUNCATED AT 250 WORDS)