The Finnish genetic heritage in 2022 – from diagnosis to translational research

Isolated populations have been valuable for the discovery of rare monogenic diseases and their causative genetic variants. Finnish disease heritage (FDH) is an example of a group of hereditary monogenic disorders caused by single major, usually autosomal-recessive, variants enriched in the population due to several past genetic drift events. Interestingly, distinct subpopulations have remained in Finland and have maintained their unique genetic repertoire. Thus, FDH diseases have persisted, facilitating vigorous research on the underlying molecular mechanisms and development of treatment options. This Review summarizes the current status of FDH, including the most recently discovered FDH disorders, and introduces a set of other recently identified diseases that share common features with the traditional FDH diseases. The Review also discusses a new era for population-based studies, which combine various forms of big data to identify novel genotype–phenotype associations behind more complex conditions, as exemplified here by the FinnGen project. In addition to the pathogenic variants with an unequivocal causative role in the disease phenotype, several risk alleles that correlate with certain phenotypic features have been identified among the Finns, further emphasizing the broad value of studying genetically isolated populations.

A multi-layer functional genomic analysis to understand noncoding genetic variation in lipids

A major challenge of genome-wide association studies (GWASs) is to translate phenotypic associations into biological insights. Here, we integrate a large GWAS on blood lipids involving 1.6 million individuals from five ancestries with a wide array of functional genomic datasets to discover regulatory mechanisms underlying lipid associations. We first prioritize lipid-associated genes with expression quantitative trait locus (eQTL) colocalizations and then add chromatin interaction data to narrow the search for functional genes. Polygenic enrichment analysis across 697 annotations from a host of tissues and cell types confirms the central role of the liver in lipid levels and highlights the selective enrichment of adipose-specific chromatin marks in high-density lipoprotein cholesterol and triglycerides. Overlapping transcription factor (TF) binding sites with lipid-associated loci identifies TFs relevant in lipid biology. In addition, we present an integrative framework to prioritize causal variants at GWAS loci, producing a comprehensive list of candidate causal genes and variants with multiple layers of functional evidence. We highlight two of the prioritized genes, CREBRF and RRBP1, which show convergent evidence across functional datasets supporting their roles in lipid biology.

Dietary Intervention in Infancy and Cognitive Function in Young Adulthood: The Special Turku Coronary Risk Factor Intervention Project

OBJECTIVE

Consumption of saturated fatty acids (SAFAs), polyunsaturated fatty acids (PUFAs), cholesterol, and fiber have been linked with cognitive function in adults. We evaluated these associations from childhood by leveraging data from the Special Turku Coronary Risk Factor Intervention Project (STRIP).

STUDY DESIGN

STRIP recruited children aged 5 months and randomly assigned them into intervention/control groups. The intervention introduced a heart-healthy diet, characterized mainly by low consumption of SAFAs and cholesterol, through counseling at least biannually between age 7 months and 20 years. Diet was assessed repeatedly using food diaries. Six years after the end of the intervention phase, at age 26 years, the participants were invited to the first postintervention follow-up, which included cognitive testing that covered learning and memory, verbal memory, short-term working memory, reaction time, information processing, and cognitive flexibility and inhibitory control. We studied the associations of the STRIP intervention and the consumptions of SAFAs, PUFAs, cholesterol, and fiber within these cognitive domains.

RESULTS

Participants in the STRIP intervention group had better cognitive flexibility and inhibitory control and were better able to manage conflicting information and ignore task-irrelevant information (0.18 SD higher in the intervention group, adjusted for sex and socioeconomic status). No associations were observed with the dietary components studied.

CONCLUSIONS

The infancy-onset STRIP intervention, which promoted a heart-healthy diet, was favorably associated with cognitive flexibility and inhibitory control at age 26 years. No associations were found for the intervention targets studied, indicating that these specific dietary components did not underlie the observed effect of the intervention.

An Infancy-Onset 20-Year Dietary Counselling Intervention and Gut Microbiota Composition in Adulthood

The randomized controlled Special Turku Coronary Risk Factor Intervention Project (STRIP) has completed a 20-year infancy-onset dietary counselling intervention to reduce exposure to atherosclerotic cardiovascular disease risk factors via promotion of a heart-healthy diet. The counselling on, e.g., low intake of saturated fat and cholesterol and promotion of fruit, vegetable, and whole-grain consumption has affected the dietary characteristics of the intervention participants. By leveraging this unique cohort, we further investigated whether this long-term dietary intervention affected the gut microbiota bacterial profile six years after the intervention ceased. Our sub-study comprised 357 individuals aged 26 years (intervention n = 174, control n = 183), whose gut microbiota were profiled using 16S rRNA amplicon sequencing. We observed no differences in microbiota profiles between the intervention and control groups. However, out of the 77 detected microbial genera, the Veillonella genus was more abundant in the intervention group compared to the controls (log2 fold-change 1.58, p < 0.001) after adjusting for multiple comparison. In addition, an association between the study group and overall gut microbiota profile was found only in males. The subtle differences in gut microbiota abundances observed in this unique intervention setting suggest that long-term dietary counselling reflecting dietary guidelines may be associated with alterations in gut microbiota.

Comparison of glucose metabolism and anthropometry in women with previous gestational diabetes treated with metformin vs. insulin: 9-year follow-up of two randomized trials

INTRODUCTION

The main aim was to study whether the long-term incidences of type 2 diabetes, pre-diabetes and metabolic syndrome differed between women who were treated with metformin or insulin for gestational diabetes.

MATERIAL AND METHODS

This 9-year follow-up study of two open-label randomized trials compares metformin and insulin treatments of gestational diabetes. In all, 165 women, 88 previously treated with insulin and 77 treated with metformin in the index pregnancy, were included in the analyses. An oral glucose tolerance test was performed, and measures of anthropometry, glucose metabolism, serum lipids and inflammatory markers were compared between the treatment groups. Disorders of glucose metabolism (pre-diabetes and type 2 diabetes) at the 9-year follow-up was the primary outcome of this study. This study was registered at ClinicalTrials.gov: NCT02417090.

RESULTS

The incidences of pre-diabetes and type 2 diabetes (40.3% vs. 46.6%, odds ratio [OR] 0.77, 95% CI 0.40-1.50, p = 0.51), type 2 diabetes (14.3% vs. 15.9%, OR 0.88, 95% CI 0.34-2.26, p = 0.94), pre-diabetes (26.0% vs. 30.7%, OR 0.79, 95% CI 0.38-1.65, p = 0.62), and metabolic syndrome (45.9% vs. 55.2%, OR 0.69, 95% CI 0.35-1.35, p = 0.31) were comparable between the metformin and insulin groups. Moreover, there were no evident differences in the individual measures of anthropometry, glucose metabolism including HOMA-insulin resistance, serum lipids or inflammatory markers between the two treatment groups.

CONCLUSIONS

Treatment of gestational diabetes with metformin vs. insulin during pregnancy is unlikely to have diverging long-term effects on maternal anthropometry, glucose metabolism or serum lipids. From this perspective, both treatments may be considered in gestational diabetes.

Weight gain in infancy and markers of cardiometabolic health in young adulthood

Aim

We studied whether repeatedly measured weight gain from birth up to age 2 years associated with cardiometabolic health in young adulthood.

Methods

Using the data collected in the longitudinal Special Turku Coronary Risk Factor Intervention Project, we investigated in 454 healthy subjects how early weight gain in six age intervals (birth to 7 months, 7–13 months, 13–18 months, 18–24 months, and birth to 13 and 24 months) associated with measures of cardiometabolic health at age 20 years. Linear regression analyses were controlled for (1) child's sex, intervention/control group, gestational age, baseline weight and change in length for each interval, and (2) parents’ education, mother's weight before pregnancy, height and weight gain during pregnancy, and father's body mass index at the 7‐month visit.

Results

Weight gain after the first year of life associated directly, when adjusted for traits of the child and parents, with systolic blood pressure, waist circumference and body mass index at age 20 years. In the fully adjusted analyses, weight gain from birth to 1 year and to 2 years of age associated inversely with insulin and insulin resistance. We found no association between early growth and diastolic blood pressure or serum lipids.

Conclusion

Early weight gain during first 2 years of life may predict later markers of cardiometabolic health.

Metformin versus insulin therapy for gestational diabetes: Effects on offspring anthropometrics and metabolism at the age of 9 years: A follow-up study of two open-label, randomized controlled trials

AIMS

To compare anthropometrics, and lipid and glucose metabolism in the 9-year-old offspring of mothers treated with metformin or insulin for gestational diabetes mellitus (GDM).

MATERIALS AND METHODS

This was a Finnish two-centre, 9-year follow-up study of two open-label, randomized controlled trials comparing the effects observed in the offspring of mothers who received metformin and insulin treatment for GDM. Measurements included anthropometrics, blood pressure, lipoproteins, and oral glucose tolerance tests. This study was registered with ClinicalTrials.gov, number NCT02417090.

RESULTS

At the age of 9 years 172 children (55% of the original study cohort, 82 from the metformin and 90 from the insulin group) participated in the study. No differences were found between the 9-year-old offspring groups in anthropometric variables, including body mass index and waist-to-height ratio. The offspring in the metformin group had higher high-density lipoprotein (HDL) cholesterol concentrations (1.72 vs. 1.54 mmol/L; P = 0.039) but lower low-density lipoprotein cholesterol (2.39 vs. 2.58 mmol/L; P = 0.046) and apolipoprotein B concentrations (0.63 vs. 0.67 g/L; P = 0.043) than the offspring in the insulin group. The difference in HDL cholesterol concentration was found to be significant only in boys (P = 0.003). The 2-hour glucose value in the oral glucose tolerance test was 0.6-mmol/L lower in boys from the metformin group than in those from the insulin group (P = 0.015).

CONCLUSIONS

Metformin treatment for GDM is associated with similar offspring growth and glucose metabolism but a more favourable lipid profile at the age of 9 years as compared to insulin treatment.

Childhood exposure to parental smoking and life-course overweight and central obesity

OBJECTIVE

To evaluate the association between childhood parental smoking exposure and the risk of overweight/obesity from childhood to adulthood.

METHODS

This study leverages the data from two longitudinal population based cohort studies, the Cardiovascular Risk in Young Finns Study between years 1980-2011/2012 (YFS; N = 2,303; baseline age 3-18 years) and the Special Turku Coronary Risk Factor Intervention Project between years 1989-2009/2010 (STRIP; N = 632; baseline age 7 months). Weight, height and waist circumference were measured from childhood to adulthood. Overweight/obesity was defined as body mass index ≥25 kg/m2 in adults and using the Cole criteria in children. Central obesity was defined as waist circumference > 100/90 cm in men/women and as a waist-to-height ratio > 0.50 in children. Statistical analyses were adjusted for age, sex, socioeconomic status, smoking, birth weight, parental ages, diet and physical activity.

RESULTS

Childhood parental smoking exposure was associated with increased risk for life-course overweight/obesity (YFS: RR1.13, 95%CI 1.02-1.24; STRIP: RR1.57, 95%CI 1.10-2.26) and central obesity (YFS: RR1.18, 95%CI 1.01-1.38; STRIP: RR1.45, 95%CI 0.98-2.15).

CONCLUSIONS

Childhood exposure to parental smoking is associated with increased risk of overweight/obesity over the life-course. KEY MESSAGES Exposure to parental smoking in childhood was associated with increased risk of overweight/obesity, central obesity and adiposity measured by skinfold thickness from childhood to adulthood.

Birth weight for gestational age and later cardiovascular health: a comparison between longitudinal Finnish and indigenous Australian cohorts

INTRODUCTION

Small or large birth weight for gestational age has been linked with later cardiovascular disease risk. However, cardiovascular risk markers from childhood to adulthood according to birth weight in diverse longitudinal settings globally have not been extensively studied.

OBJECTIVES

To examine the relationship between birth weight and cardiovascular risk profile from childhood until young adulthood in two geographically and socioeconomically distinct cohorts.

METHODS

Data were derived from two longitudinal birth cohort studies; one from southern Finland (Special Turku Coronary Risk Factor Intervention Project, STRIP) and one from northern Australia comprising Indigenous Australians (Aboriginal Birth Cohort, ABC). The sample included 747 Finnish participants and 541 Indigenous Australians with data on birth weight, gestational age and cardiovascular risk factors (body mass index [BMI]), waist-to-height ratio [WHtR], lipid profile, blood pressure) collected at ages 11, 18 and 25 or 26 years. Carotid intima-media thickness (cIMT) was assessed at age 18 or 19 years. Participants were categorised according to birth weight for gestational age (small [SGA], appropriate [AGA] or large [LGA]). Associations between birth weight category and cardiovascular risk markers were studied using a repeated measures ANOVA.

RESULTS

Higher birth weight category was associated with higher BMI later in life in both cohorts (p=.003 for STRIP and p<.0001 for ABC). In the ABC, higher birth weight category was also associated with higher WHtR (p=.004). In the ABC, SGA participants had lower systolic and diastolic blood pressure than AGA participants (p=.028 for systolic, p=.027 for diastolic) and lower systolic blood pressure than LGA participants (p=.046) at age 25. In the STRIP cohort, SGA participants had lower cIMT than LGA participants (p=.024).

CONCLUSIONS

Birth weight can predict future cardiovascular risk profile in diverse populations. Thus, it needs to be included in targeted public health interventions for tackling the obesity pandemic and improving cardiovascular health worldwide.Key messagesThe strongest association between birth weight and later cardiovascular risk profile was manifested as differences in body mass index in two culturally and geographically distinct cohorts.Foetal growth is a determinant for later cardiovascular health in diverse populations, indicating a need to focus on maternal and foetal health to improve cardiovascular health worldwide.

The power of genetic diversity in genome-wide association studies of lipids

Increased blood lipid levels are heritable risk factors of cardiovascular disease with varied prevalence worldwide owing to different dietary patterns and medication use1. Despite advances in prevention and treatment, in particular through reducing low-density lipoprotein cholesterol levels2, heart disease remains the leading cause of death worldwide3. Genome-wideassociation studies (GWAS) of blood lipid levels have led to important biological and clinical insights, as well as new drug targets, for cardiovascular disease. However, most previous GWAS4-23 have been conducted in European ancestry populations and may have missed genetic variants that contribute to lipid-level variation in other ancestry groups. These include differences in allele frequencies, effect sizes and linkage-disequilibrium patterns24. Here we conduct a multi-ancestry, genome-wide genetic discovery meta-analysis of lipid levels in approximately 1.65 million individuals, including 350,000 of non-European ancestries. We quantify the gain in studying non-European ancestries and provide evidence to support the expansion of recruitment of additional ancestries, even with relatively small sample sizes. We find that increasing diversity rather than studying additional individuals of European ancestry results in substantial improvements in fine-mapping functional variants and portability of polygenic prediction (evaluated in approximately 295,000 individuals from 7 ancestry groupings). Modest gains in the number of discovered loci and ancestry-specific variants were also achieved. As GWAS expand emphasis beyond the identification of genes and fundamental biology towards the use of genetic variants for preventive and precision medicine25, we anticipate that increased diversity of participants will lead to more accurate and equitable26 application of polygenic scores in clinical practice.

Achievement of the Targets of the 20-Year Infancy-Onset Dietary Intervention-Association with Metabolic Profile from Childhood to Adulthood

The Special Turku Coronary Risk Factor Intervention Project (STRIP) is a prospective infancy-onset randomized dietary intervention trial targeting dietary fat quality and cholesterol intake, and favoring consumption of vegetables, fruit, and whole-grains. Diet (food records) and circulating metabolites were studied at six time points between the ages of 9-19 years (n = 549-338). Dietary targets for this study were defined as (1) the ratio of saturated fat (SAFA) to monounsaturated and polyunsaturated fatty acids (MUFA + PUFA) < 1:2, (2) intake of SAFA < 10% of total energy intake, (3) fiber intake ≥ 80th age-specific percentile, and (4) sucrose intake ≤ 20th age-specific percentile. Metabolic biomarkers were quantified by high-throughput nuclear magnetic resonance metabolomics. Better adherence to the dietary targets, regardless of study group allocation, was assoiated with higher serum proportion of PUFAs, lower serum proportion of SAFAs, and a higher degree of unsaturation of fatty acids. Achieving ≥ 1 dietary target resulted in higher low-density lipoprotein (LDL) particle size, lower circulating LDL subclass lipid concentrations, and lower circulating lipid concentrations in medium and small high-density lipoprotein subclasses compared to meeting 0 targets. Attaining more dietary targets (≥2) was associated with a tendency to lower lipid concentrations of intermediate-density lipoprotein and very low-density lipoprotein subclasses. Thus, adherence to dietary targets is favorably associated with multiple circulating fatty acids and lipoprotein subclass lipid concentrations, indicative of better cardio-metabolic health.

Effects of Randomized Controlled Infancy-Onset Dietary Intervention on Leukocyte Telomere Length-The Special Turku Coronary Risk Factor Intervention Project (STRIP)

Reduced telomere length (TL) is a biological marker of aging. A high inter-individual variation in TL exists already in childhood, which is partly explained by genetics, but also by lifestyle factors. We examined the influence of a 20-year dietary/lifestyle intervention on TL attrition from childhood to early adulthood. The study comprised participants of the longitudinal randomized Special Turku Coronary Risk Factor Intervention Project (STRIP) conducted between 1990 and 2011. Healthy 7-month-old children were randomized to the intervention group (n = 540) receiving dietary counseling mainly focused on dietary fat quality and to the control group (n = 522). Leukocyte TL was measured using the Southern blot method from whole blood samples collected twice: at a mean age of 7.5 and 19.8 years (n = 232; intervention n = 108, control n = 124). Yearly TL attrition rate was calculated. The participants of the intervention group had slower yearly TL attrition rate compared to the controls (intervention: mean = −7.5 bp/year, SD = 24.4 vs. control: mean = −15.0 bp/year, SD = 30.3; age, sex and baseline TL adjusted β = 0.007, SE = 0.004, p = 0.040). The result became stronger after additional adjustments for dietary fat quality and fiber intake, serum lipid and insulin concentrations, systolic blood pressure, physical activity and smoking (β = 0.013, SE = 0.005, p = 0.009). A long-term intervention focused mainly on dietary fat quality may affect the yearly TL attrition rate in healthy children/adolescents.

Novel loci for childhood body mass index and shared heritability with adult cardiometabolic traits

The genetic background of childhood body mass index (BMI), and the extent to which the well-known associations of childhood BMI with adult diseases are explained by shared genetic factors, are largely unknown. We performed a genome-wide association study meta-analysis of BMI in 61,111 children aged between 2 and 10 years. Twenty-five independent loci reached genome-wide significance in the combined discovery and replication analyses. Two of these, located near NEDD4L and SLC45A3, have not previously been reported in relation to either childhood or adult BMI. Positive genetic correlations of childhood BMI with birth weight and adult BMI, waist-to-hip ratio, diastolic blood pressure and type 2 diabetes were detected (Rg ranging from 0.11 to 0.76, P-values <0.002). A negative genetic correlation of childhood BMI with age at menarche was observed. Our results suggest that the biological processes underlying childhood BMI largely, but not completely, overlap with those underlying adult BMI. The well-known observational associations of BMI in childhood with cardio-metabolic diseases in adulthood may reflect partial genetic overlap, but in light of previous evidence, it is also likely that they are explained through phenotypic continuity of BMI from childhood into adulthood.

Attainment of Targets of the 20-Year Infancy-Onset Dietary Intervention and Blood Pressure Across Childhood and Young Adulthood: The Special Turku Coronary Risk Factor Intervention Project (STRIP)

We examined whether success in achieving the key targets of an infancy-onset 20-year dietary intervention was associated with blood pressure (BP) from infancy to young adulthood. In the prospective randomized STRIP (Special Turku Coronary Risk Factor Intervention Project; n=877 children), dietary counseling was provided biannually based on the Nordic Nutrition Recommendations primarily to improve the quality of dietary fat in children's diets and secondarily to promote intake of vegetables, fruits, and whole grains. Dietary data and BP were accrued annually from the age of 13 months to 20 years. The dietary targets for fat quality were defined as the ratio of saturated fatty acids to monounsaturated and polyunsaturated fatty acids <1:2 and intake of saturated fatty acids <10 E%, dietary fiber intake in the top age-specific quintile, and dietary sucrose intake as being in the lowest age-specific quintile. Attaining a higher number of the dietary targets was associated with lower systolic BP (mean [SE] systolic BP, 107.3 [0.3], 107.6 [0.3], 106.8 [0.3], and 106.7 [0.5] mm Hg in participants meeting 0, 1, 2, and 3 to 4 targets, respectively; P=0.03) and diastolic BP (mean [SE] diastolic BP, 60.4 [0.2], 60.5 [0.2], 59.9 [0.2], and 59.9 [0.3] mm Hg; P=0.02). When the lowest age-specific quintile of dietary cholesterol was added as an additional target, the association with systolic BP remained significant (P=0.047), but the association with diastolic BP attenuated (P=0.13). Achieving the key targets of an infancy-onset 20-year dietary intervention, reflecting dietary guidelines, was favorably albeit modestly associated with systolic and diastolic BP from infancy to young adulthood. Registration- URL: https://www.clinicaltrials.gov; Unique identifier: NCT00223600.

Temperament profiles are associated with dietary behavior from childhood to adulthood

BACKGROUND AND OBJECTIVES

Temperament may be associated with eating behaviors over the lifespan. This study examined the association of toddlerhood temperament with dietary behavior and dietary intervention outcomes across 18 years.

METHODS

The study comprised 660 children (52% boys) from The Special Turku Intervention Project (STRIP), which is a longitudinal randomized controlled trial from the age of 7 months until the age of 20 years (1990-2010). Temperament was assessed using Carey temperament scales when the participants were 2 years of age. Latent profile analysis yielded three temperament groups, which were called negative/low regulation (19% of the children), neutral/average regulation (52%) and positive/high regulation (28%). Dietary behavior was examined from 2 to 20 years of age using food records, which were converted into a diet score (mean = 15.7, SD 4.6). Mixed random-intercept growth curve analysis was the main analytic method.

RESULTS

Dietary behavior showed a significant quadratic U-shaped curve over time (B for quadratic association = 0.39, P<.001; B for linear association = 0.09, P = 0.58). Children in the negative/low regulation temperament group had a lower diet score (less healthy diet) across the 18 years compared to children in the neutral/average or in the positive/high regulation group. Temperament was not associated with the rate of change in diet over time. Temperament did not have any interactive effects with the intervention (F [2, 627], P = 0.72).

CONCLUSION

Children with a temperament profile characterized by high negative mood, high irregularity and high intensity in emotion expression constitute a risk group for less healthy eating over the lifespan.

Changes in body composition by age and obesity status in preschool-aged children: the STEPS study

BACKGROUND/OBJECTIVES

Obesity in early childhood is associated with increased risk of chronic diseases, but studies of body composition at preschool ages are sparse. Therefore, we examined differences in body composition by sex and obesity status in Finnish preschool-aged children and within-individual changes in body composition in normal and overweight children.

SUBJECT/METHODS

Body composition was measured using segmental multifrequency bioimpedance analysis (BIA) in 476 children and in 781 children at age 3 and 5 years, respectively. Of those, 308 had repeated BIA measurements at both ages. BMI-SDS was used for classification of normal weight and overweight children.

RESULTS

Sex difference in the amount of lean mass (LM) was already seen at 3 years of age (boys 11.7 kg, girls 11.3 kg; p < 0.001). At 5 years of age, boys had lower fat mass (FM; 3.6 kg vs. 3.9 kg, p < 0.001), lower percent fat mass (%FM; 17.2% vs. 19.1%; p < 0.001), and higher LM (16.0 kg vs. 15.2 kg; p < 0.001) than girls. Overweight children had higher values in FM, %FM, and LM compared with normal weight peers at both ages. Among normal weight children, the increase of LM by age was associated with only minor changes in FM, whereas children who were or became overweight both LM and FM was substantially increased between 3 and 5 years of age.

CONCLUSIONS

BIA-assessed body composition differs by sex and obesity status already at age of 3 years. For children who are or become overweight at very young age, the patterns for the changes in LM and FM by age are different than for normal weight children.

Mendelian randomization analysis does not support causal associations of birth weight with hypertension risk and blood pressure in adulthood

Epidemiology studies suggested that low birthweight was associated with a higher risk of hypertension in later life. However, little is known about the causality of such associations. In our study, we evaluated the causal association of low birthweight with adulthood hypertension following a standard analytic protocol using the study-level data of 183,433 participants from 60 studies (CHARGE-BIG consortium), as well as that with blood pressure using publicly available summary-level genome-wide association data from EGG consortium of 153,781 participants, ICBP consortium and UK Biobank cohort together of 757,601 participants. We used seven SNPs as the instrumental variable in the study-level analysis and 47 SNPs in the summary-level analysis. In the study-level analyses, decreased birthweight was associated with a higher risk of hypertension in adults (the odds ratio per 1 standard deviation (SD) lower birthweight, 1.22; 95% CI 1.16 to 1.28), while no association was found between genetically instrumented birthweight and hypertension risk (instrumental odds ratio for causal effect per 1 SD lower birthweight, 0.97; 95% CI 0.68 to 1.41). Such results were consistent with that from the summary-level analyses, where the genetically determined low birthweight was not associated with blood pressure measurements either. One SD lower genetically determined birthweight was not associated with systolic blood pressure (β = - 0.76, 95% CI - 2.45 to 1.08 mmHg), 0.06 mmHg lower diastolic blood pressure (β = - 0.06, 95% CI - 0.93 to 0.87 mmHg), or pulse pressure (β = - 0.65, 95% CI - 1.38 to 0.69 mmHg, all p > 0.05). Our findings suggest that the inverse association of birthweight with hypertension risk from observational studies was not supported by large Mendelian randomization analyses.

Dietary Fats and Atherosclerosis From Childhood to Adulthood

BACKGROUND

The association of dietary fat distribution with markers of subclinical atherosclerosis during early life is unknown. We examined whether success in achieving the main target of an infancy-onset dietary intervention based on the distribution of dietary fat was associated with aortic and carotid intima-media thickness (IMT) and distensibility from childhood to young adulthood.

METHODS

In the prospective randomized controlled Special Turku Coronary Risk Factor Intervention Project trial, personalized dietary counseling was given biannually to healthy children from infancy to young adulthood. The counseling was based on Nordic Nutrition Recommendations, with the main aim of improving the distribution of dietary fat in children's diets. IMT and distensibility of the abdominal aorta and common carotid artery were measured repeatedly at ages 11 (n = 439), 13 (n = 499), 15 (n = 506), 17 (n = 477), and 19 years (n = 429). The targeted distribution of dietary fat was defined as a ratio of saturated fatty acids to monounsaturated and polyunsaturated fatty acids of <1:2 and as an intake of saturated fatty acids of <10% of energy intake. Participants who met ≥1 of these 2 criteria were defined to achieve the main intervention target.

RESULTS

Individuals who achieved the main intervention target had lower aortic IMT (age- and sex-adjusted mean difference 10.4 µm; 95% confidence interval: 0.3 to 20.5 µm) and better aortic distensibility (0.13% per 10 mm Hg; 95% confidence interval: 0.00% to 0.26% per10 mm Hg) compared with their peers who did not meet the target.

CONCLUSIONS

Achieving the main target of an infancy-onset dietary intervention, reflecting dietary guidelines, was favorably associated with aortic IMT and distensibility during the early life course. These data support the recommendation of favoring unsaturated fat to enhance arterial health.

Age-Specific Estimates and Comparisons of Youth Tri-Ponderal Mass Index and Body Mass Index in Predicting Adult Obesity-Related Outcomes

OBJECTIVES

To estimate and compare tri-ponderal mass index (TMI) and body mass index (BMI) at each age from childhood to young adulthood in the prediction of adulthood obesity-related outcomes.

STUDY DESIGN

Participants of this observational study (n = 432) were from a 20-year infancy-onset randomized atherosclerosis prevention trial. BMI and TMI were calculated using weight and height measured annually from participants between ages 2 and 20 years. Outcomes were aortic intima-media thickness (at the age of 15, 17, or 19 years), impaired fasting glucose and elevated insulin levels, homeostasis model assessment of insulin resistance index, serum lipids, and hypertension at the age of 20 years. Poisson regressions, Pearson correlation, logistic regression, and area under the curve (AUC) were used to estimate and/or compare associations and predictive utilities between BMI and TMI with all outcomes.

RESULTS

The associations and predictive utilities of BMI and TMI with all outcomes were stronger at older ages. BMI had significantly stronger correlations than TMI with insulin (at age 16 years), systolic blood pressure (age 5-20 years), and triglycerides (age 18 years). BMI had significantly greater predictive utilities than TMI for insulin resistance (at age 14-16 years; difference in AUC = 0.018-0.024), elevated insulin levels (age 14-16 years; difference in AUC = 0.018 and 0.025), and hypertension (age 16 to 20 years; difference in AUC = 0.017-0.022) but they were similar for other outcomes.

CONCLUSIONS

TMI is not superior to BMI at any ages from childhood to young adulthood in the prediction of obesity-related outcomes in young adulthood.

Association of Birth Weight With Type 2 Diabetes and Glycemic Traits: A Mendelian Randomization Study

IMPORTANCE

Observational studies have shown associations of birth weight with type 2 diabetes (T2D) and glycemic traits, but it remains unclear whether these associations represent causal associations.

OBJECTIVE

To test the association of birth weight with T2D and glycemic traits using a mendelian randomization analysis.

DESIGN, SETTING, AND PARTICIPANTS

This mendelian randomization study used a genetic risk score for birth weight that was constructed with 7 genome-wide significant single-nucleotide polymorphisms. The associations of this score with birth weight and T2D were tested in a mendelian randomization analysis using study-level data. The association of birth weight with T2D was tested using both study-level data (7 single-nucleotide polymorphisms were used as an instrumental variable) and summary-level data from the consortia (43 single-nucleotide polymorphisms were used as an instrumental variable). Data from 180 056 participants from 49 studies were included.

MAIN OUTCOMES AND MEASURES

Type 2 diabetes and glycemic traits.

RESULTS

This mendelian randomization analysis included 49 studies with 41 155 patients with T2D and 80 008 control participants from study-level data and 34 840 patients with T2D and 114 981 control participants from summary-level data. Study-level data showed that a 1-SD decrease in birth weight due to the genetic risk score was associated with higher risk of T2D among all participants (odds ratio [OR], 2.10; 95% CI, 1.69-2.61; P = 4.03 × 10-5), among European participants (OR, 1.96; 95% CI, 1.42-2.71; P = .04), and among East Asian participants (OR, 1.39; 95% CI, 1.18-1.62; P = .04). Similar results were observed from summary-level analyses. In addition, each 1-SD lower birth weight was associated with 0.189 SD higher fasting glucose concentration (β = 0.189; SE = 0.060; P = .002), but not with fasting insulin, 2-hour glucose, or hemoglobin A1c concentration.

CONCLUSIONS AND RELEVANCE

In this study, a genetic predisposition to lower birth weight was associated with increased risk of T2D and higher fasting glucose concentration, suggesting genetic effects on retarded fetal growth and increased diabetes risk that either are independent of each other or operate through alterations of integrated biological mechanisms.

Maternal and fetal genetic effects on birth weight and their relevance to cardio-metabolic risk factors

Birth weight variation is influenced by fetal and maternal genetic and non-genetic factors, and has been reproducibly associated with future cardio-metabolic health outcomes. In expanded genome-wide association analyses of own birth weight (n = 321,223) and offspring birth weight (n = 230,069 mothers), we identified 190 independent association signals (129 of which are novel). We used structural equation modeling to decompose the contributions of direct fetal and indirect maternal genetic effects, then applied Mendelian randomization to illuminate causal pathways. For example, both indirect maternal and direct fetal genetic effects drive the observational relationship between lower birth weight and higher later blood pressure: maternal blood pressure-raising alleles reduce offspring birth weight, but only direct fetal effects of these alleles, once inherited, increase later offspring blood pressure. Using maternal birth weight-lowering genotypes to proxy for an adverse intrauterine environment provided no evidence that it causally raises offspring blood pressure, indicating that the inverse birth weight-blood pressure association is attributable to genetic effects, and not to intrauterine programming.

Low-saturated-fat and low-cholesterol diet does not alter pubertal development and hormonal status in adolescents

Aim

The aim was to assess the influence of dietary counselling on the pubertal development and hormonal status in healthy adolescents.

Methods

We used a subcohort of 193 healthy boys (52%) and girls (48%) from the Special Turku Coronary Risk Factor Intervention Project. Participants were recruited by nurses at the well‐baby clinics in Turku Finland in 1990–1992 and randomised into intervention and control groups. Intervention children received low‐saturated fat and low‐cholesterol dietary counselling initiated at seven months of age. Participants were examined once a year with Tanner staging, anthropometric measurements and serial reproductive hormones from 10 to 19 years of age. In girls, postmenarcheal hormones were not analysed.

Results

Pubertal hormones in boys or girls did not differ between the intervention and control groups. However, we observed slight differences in pubertal progression by Tanner staging and in anthropometric parameters. The intervention boys progressed faster to G4 (p = 0.008), G5 (p = 0.008) and P5 (p = 0.03). The intervention boys were taller than control boys (p = 0.04), while weight and body mass index did not differ.

Conclusion

Dietary intervention did not affect pubertal hormonal status. This finding supports the safety of implemented counselling in respect to puberty.

Success in Achieving the Targets of the 20-Year Infancy-Onset Dietary Intervention: Association With Insulin Sensitivity and Serum Lipids

OBJECTIVE

We examined whether success in achieving the key targets of an infancy-onset 20-year dietary intervention associated with insulin sensitivity and serum lipids from early childhood to young adulthood.

RESEARCH DESIGN AND METHODS

The sample comprised 941 children participating in the prospective, randomized Special Turku Coronary Risk Factor Intervention Project (STRIP). Dietary counseling was given biannually based on the Nordic Nutrition Recommendations with the main aim to improve the quality of dietary fat in children's diets and the secondary aim to promote intake of vegetables, fruits, and whole-grain products. Food records and serum lipid profile were studied annually from 1 to 20 years of age, and HOMA of insulin resistance (HOMA-IR) was assessed between 7 and 20 years of age. Meeting the intervention targets for quality of dietary fat was defined as the ratio of saturated fatty acids (SAFA) to monounsaturated and polyunsaturated fatty acids (MUFA + PUFA) <1:2 and intake of SAFA <10% of total energy intake (E%). Meeting the target for intake of whole-grain products, fruits, and vegetables was indicated by a fiber intake ≥3 g/MJ.

RESULTS

Participants in the intervention group had a higher probability of meeting the targets of SAFA/(PUFA + MUFA) <1:2 (risk ratio [RR] 3.91 [95% CI 3.33-4.61]), intake of SAFA <10 E% (RR 3.33 [95% CI 2.99-3.96]), and intake of fiber >3 g/MJ (RR 1.37 [95% CI 1.04-1.80]). Participants who achieved more targets had lower HOMA-IR, lower concentrations of fasting serum glucose, insulin, LDL cholesterol, and non-HDL cholesterol, and a lower ratio of apolipoprotein (Apo) B/ApoA1 (P values all ≤0.003).

CONCLUSIONS

Achieving the key targets of an infancy-onset 20-year dietary intervention was associated with better insulin sensitivity and serum lipid profile throughout the early life course.