Ketone body 3-hydroxybutyrate as a biomarker of aggression.

Human aggression is a complex behaviour, the biological underpinnings of which remain poorly known. To gain insights into aggression biology, we studied relationships with aggression of 11 low-molecular-weight metabolites (amino acids, ketone bodies), processed using 1H nuclear magnetic resonance spectroscopy. We used a discovery sample of young adults and an independent adult replication sample. We studied 725 young adults from a population-based Finnish twin cohort born 1983-1987, with aggression levels rated in adolescence (ages 12, 14, 17) by multiple raters and blood plasma samples at age 22. Linear regression models specified metabolites as the response variable and aggression ratings as predictor variables, and included several potential confounders. All metabolites showed low correlations with aggression, with only one-3-hydroxybutyrate, a ketone body produced during fasting-showing significant (negative) associations with aggression. Effect sizes for different raters were generally similar in magnitude, while teacher-rated (age 12) and self-rated (age 14) aggression were both significant predictors of 3-hydroxybutyrate in multi-rater models. In an independent replication sample of 960 adults from the Netherlands Twin Register, higher aggression (self-rated) was also related to lower levels of 3-hydroxybutyrate. These exploratory epidemiologic results warrant further studies on the role of ketone metabolism in aggression.

Diversity of leisure-time sport activities in adolescence as a predictor of leisure-time physical activity in adulthood.

Because sustained physical activity is important for a healthy life, this paper examined whether a greater diversity of sport activities during adolescence predicts higher levels of leisure-time physical activity (LTPA) in adulthood. From sport activity participation reported by 17-year-old twins, we formed five groups: 1, 2, 3, 4, and 5+ different sport activities. At follow-up in their mid-thirties, twins were divided into four activity classes based on LTPA, including active commuting. Multinomial regression analyses, adjusted for several confounders, were conducted separately for male (N=1288) and female (N=1770) participants. Further, conditional logistic regression analysis included 23 twin pairs discordant for both diversity of sport activities in adolescence and LTPA in adulthood. The diversity of leisure-time sport activities in adolescence had a significant positive association with adulthood LTPA among females. Membership in the most active adult quartile, compared to the least active quartile, was predicted by participation in 2, 3, 4, and 5+ sport activities in adolescence with odds ratios: 1.52 (P=.11), 1.86 (P=.02), 1.29 (P=.39), and 3.12 (P=5.4e-05), respectively. Within-pair analyses, limited by the small sample of twins discordant for both adolescent activities and adult outcomes, did not replicate the association. A greater diversity of leisure-time sport activities in adolescence predicts higher levels of LTPA in adulthood in females, but the causal nature of this association remains unresolved.

The effects of parental education on exercise behavior in childhood and youth: a study in Dutch and Finnish twins.

Twin studies have estimated the relative contribution of genes and the environment to variance in exercise behavior and it is known that parental education positively affects exercise levels. This study investigates the role of parental education as a potential modifier of variance in exercise behavior from age 7 to 18 years. The study is based on large datasets from the Netherlands Twin Register (NTR: N = 24 874 twins; surveys around the ages of 7, 10, 12, 14, 16 and 18 years) and two Finnish twin cohorts (FinnTwin12: N = 4399; 12, 14 and 17 years; FinnTwin16: N = 4648; 16, 17 and 18 years). Regular participation in moderate-to-vigorous exercise activities during leisure time was assessed by survey. Parental education was dichotomized ("both parents with a low education" vs "at least one parent with a high education"). The mean in exercise behavior tended to be higher and the variance tended to be lower in children of high educated parents. Evidence for gene-by-environment interaction was weak. To develop successful interventions that specifically target children of low educated parents, the mechanisms causing the mean and variance differences between the two groups should be better understood.

Probing the biophysical interplay between a viral genome and its capsid.

The interaction between a viral capsid and its genome governs crucial steps in the life cycle of a virus, such as assembly and genome uncoating. Tuning cargo-capsid interactions is also essential for successful design and cargo delivery in engineered viral systems. Here we investigate the interplay between cargo and capsid for the picorna-like Triatoma virus using a combined native mass spectrometry and atomic force microscopy approach. We propose a topology and assembly model in which heterotrimeric pentons that consist of five copies of structural proteins VP1, VP2 and VP3 are the free principal units of assembly. The interpenton contacts are established primarily by VP2. The dual role of the genome is first to stabilize the densely packed virion and, second, on an increase in pH to trigger uncoating by relaxing the stabilizing interactions with the capsid. Uncoating occurs through a labile intermediate state of the virion that reversibly disassembles into pentons with the concomitant release of protein VP4.

Association between habitual dietary intake and lipoprotein subclass profile in healthy young adults.

BACKGROUND AND AIMS: Nutritional epidemiology is increasingly shifting its focus from studying single nutrients to the exploration of the whole diet utilizing dietary pattern analysis. We analyzed associations between habitual diet (including macronutrients, dietary patterns, biomarker of fish intake) and lipoprotein particle subclass profile in young adults. METHODS AND RESULTS: Complete dietary data (food-frequency questionnaire) and lipoprotein subclass profile (via nuclear magnetic resonance spectroscopy) were available for 663 subjects from the population-based FinnTwin12 study (57% women, age: 21-25 y). The serum docosahexaenoic to total fatty acid ratio was used as a biomarker of habitual fish consumption. Factor analysis identified 5 dietary patterns: "Fruit and vegetables", "Meat", "Sweets and desserts", "Junk food" and "Fish". After adjustment for sex, age, body mass index, waist circumference, physical activity, smoking status and alcohol intake, the "Junk food" pattern was positively related to serum triglycerides (r = 0.12, P = 0.002), a shift in the subclass distribution of VLDL toward larger particles (r = 0.12 for VLDL size, P < 0.001) and LDL toward smaller particles (r = -0.15 for LDL size, P < 0.001). In addition, higher scores on this pattern were positively correlated with concentrations of small, dense HDL (r = 0.16, P < 0.001). Habitual fish intake associated negatively with VLDL particle diameter ("Fish" pattern and biomarker) and positively with HDL particle diameter (biomarker). CONCLUSIONS: Our results suggest that in young adults, higher habitual fish consumption is related to favorable subclass distributions of VLDL and HDL, while junk food intake is associated with unfavorable alterations in the distribution of all lipoprotein subclasses independent of adiposity and other lifestyle factors.

Genetic and environmental influences on non-specific neck pain in early adolescence: a classical twin study.

BACKGROUND: Prevalence of neck pain has increased among adolescents. The origins of adult chronic neck pain may lie in late childhood, but for early prevention, more information is needed about its aetiology. We investigated the relative roles of genetic and environmental factors in early adolescent neck pain with a classic twin study. METHODS: Frequency of neck pain was assessed with a validated pain questionnaire in a population-based sample of nearly 1800 pairs of 11-12-year-old Finnish twins. Twin pair similarity for neck pain was quantified by polychoric correlations, and variance components were estimated with biometric structural equation modelling. RESULTS: Prevalence of neck pain reported at least once monthly was 38% and at least once weekly 16%, with no significant differences between gender and zygosity. A greater polychoric correlation in liability to neck pain was found in monozygotic (0.67) than for dizygotic pairs (0.38), suggesting strong genetic influences. Model fitting indicated that 68% (95% confidence interval 62-74) of the variation in liability to neck pain could be attributed to genetic effects, with the remainder attributed to unshared environmental effects. No evidence for sex-specific genetic effects or for sex differences in the magnitude of genetic effects was found. CONCLUSIONS: Genetic and unique environmental factors seem to play the most important roles in liability to neck pain in early adolescence. Future research should be directed to identifying pathways for genetic influences on neck pain and in exploring effectiveness of interventions that target already identified environmental risk factors.

The effect of temperature on di(2-ethylhexyl) phthalate leaching from PVC infusion sets exposed to lipid emulsions.

Poly vinyl chloride (PVC) infusion equipment contains substantial amounts of the plasticiser di(2-ethylhexyl) phthalate (DEHP). We determined the amount of DEHP leached from Mediplus Dual TIVA(®) Infusion sets, into lipid and non-lipid infusates. Two propofol admixtures (Diprivan(®) 1%, Propoven(®) 1%), Intralipid(®) 10% and 0.9% saline were evaluated as infusates. Solutions were infused through TIVA sets at 12 ml.h(-1) for 6 h at 24, 32 and 37 °C. In addition, TIVA sets were filled with 2 ml infusates, sealed and incubated at 24 and 37 °C for 6 h. Di(2-ethylhexyl) phthalate was detected in all lipid infusates after dynamic infusion and static contact, and in 0.9% saline after dynamic infusion at 37 °C. At 32 and 37 °C, the quantity of di(2-ethylhexyl) phthalate leaching into the lipid infusates may exceed the recommended maximum exposure amount set by the European Union for DEHP of 20-48 µg.kg(-1) day(-1) if lipid based infusates are used for sedation or intravenous feeding of infants or neonates.

Whole Genome Methylation Scanning Based on phi29 Polymerase Amplification.

Identifying differences in DNA methylation is critical to understanding how epigenetics influences gene expression during processes such as development. Here, we propose a method that employs a single, methylation-sensitive restriction endonuclease of choice, to produce discrete pools of methylated and unmethylated DNA from the same sample. A pool of restriction fragments representing unmethylated regions of the genome is first obtained by digestion with a methylation-sensitive endonuclease. The restriction-digested DNA is then concatamerized in the presence of stuffer-adaptor DNA, which prevents interference from originally unmethylated DNA by blocking the ends of the restriction fragments. The concatamerized DNA is amplified by phi29 polymerase to remove methylation marks, and again digested with the same endonuclease to produce a pool of DNA fragments representing methylated portions of the genome. The two pools of DNA fragments thus obtained can be analyzed by end-sequencing or hybridization to a genomic array. In this report we detail a proof of concept experiment that demonstrates the feasibility of our method.

Prospective relationships of ADHD symptoms with developing substance use in a population-derived sample.

BACKGROUND: Clinically ascertained reports suggest that boys and girls with attention deficit hyperactivity disorder (ADHD) may differ from each other in their vulnerability to substance use problems. METHOD: A total of 1545 Finnish adolescents were assessed for DSM-IV-based ADHD symptoms by their parents and classroom teachers using standardized rating scales at age 11-12 years. At age 14, substance use disorders and psychiatric co-morbidity were assessed with the Semi-Structured Assessment for the Genetics of Alcoholism, providing DSM-III-R/DSM-IV diagnoses for Axis I disorders. At age 17.5, substance use was assessed by multi-item questionnaire. RESULTS: Although baseline ADHD symptoms were less common among females, they were more predictive of adverse substance use outcomes once conduct disorder and previous substance use were controlled for. Only in females were baseline ADHD symptoms significant predictors of alcohol abuse and dependence and illicit drug use at age 14. At the age of 17.5, parents' reports of inattentiveness and hyperactivity were significant predictors for frequent alcohol use in both sexes, but they were more predictive of frequent alcohol and illicit drug use in girls. Impulsivity in teachers' ratings predicted frequent alcohol use and illicit drug use in boys. Parental reports of inattentiveness in their 11-/12-year-old daughters were a consistent predictor for illicit drug use across adolescence. CONCLUSIONS: Inattentiveness and hyperactivity may be more predictive of alcohol use disorders and maladaptive patterns of alcohol and illicit drug use among girls than boys. The importance of these behavioural symptoms should be assessed further in the community, as they could jeopardize adolescents' successful transitioning into adult roles.

Genetic origins of the association between verbal ability and alcohol dependence symptoms in young adulthood.

BACKGROUND: Cognitive deficits in alcohol dependence (AD) have been observed, poorer verbal ability being among the most consistent findings. Genetic factors influence both cognitive ability and AD, but whether these influences overlap is not known. METHOD: A subset of 602 monozygotic (MZ) and dizygotic (DZ) twins from FinnTwin16, a population-based study of Finnish twins, was used to study the associations of verbal ability with DSM-III-R diagnosis and symptoms of AD, the maximum number of drinks consumed in a 24-h period, and the Rutgers Alcohol Problem Index (RAPI) scores. These twins, most of them selected for within-pair discordance or concordance for their RAPI scores at age 18.5 years, were studied with neuropsychological tests and interviewed with the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) in young adulthood (mean age 26.2 years, range 23-30 years). RESULTS: All alcohol problem measures were associated with lower scores on the Vocabulary subtest of the Wechsler Adult Intelligence Scale - Revised (WAIS-R), a measure of verbal ability. In bivariate genetic models, Vocabulary and the alcohol problem measures had moderate heritabilities (0.54-0.72), and their covariation could be explained by correlated genetic influences (genetic correlations -0.20 to -0.31). CONCLUSIONS: Poorer verbal ability and AD have partly overlapping biological etiology. The genetic and environmental influences on the development of cognitive abilities, alcohol problems and risk factors for AD should be studied further with prospective longitudinal designs.

Tobacco use and reported bruxism in young adults: a nationwide Finnish Twin Cohort Study.

INTRODUCTION: Higher levels of smoking, leading to increased levels of nicotine and dopamine release, may be more strongly related to bruxism, although this relationship has remained unclear. Thus, the aim of the present study was to investigate the possible effect of cumulative tobacco use on bruxism in a large sample of young adults. METHODS: The material of the present study derives from the FinnTwin16, which consists of five birth cohorts born in 1975-1979. A total of 3,124 subjects (mean age 24 years, range 23-27 years) provided data in 2000-2002 on frequency of bruxism and tobacco use. Multinomial logistic regression was used to explore the relationships of frequency of bruxism with smoking and smokeless tobacco use while controlling covariates (alcohol intoxication, alcohol problems [Rutgers Alcohol Problem Index, RAPI], illicit drug use, psychological distress [General Health Questionnaire], and coffee use). RESULTS: Based on subjective response and multivariate analyses, weekly bruxers were more than two times more likely to report heavy smoking than never bruxers (odds ratio [OR] 2.5, 95 % CI 1.8-3.4). The significant association between heavy smoking and bruxism held when the effects of other tobacco use and multiple covariates were controlled. In addition, the use of smokeless tobacco emerged as an independent risk factor for bruxism. DISCUSSION: Given the observed associations with both heavy smoking and smokeless tobacco and a dose-response relationship, the present results support our hypothesis of a link between nicotine intake and bruxism.

The association of homeobox gene expression with stem cell formation and morphogenesis in cultured Medicago truncatula.

Somatic embryogenesis (SE) is induced in vitro in Medicago truncatula 2HA by auxin and cytokinin but rarely in wild type Jemalong. The putative WUSCHEL (MtWUS), CLAVATA3 (MtCLV3) and the WUSCHEL-related homeobox gene WOX5 (MtWOX5) were investigated in M. truncatula (Mt) and identified by the similarity to Arabidopsis WUS, CLV3 and WOX5 in amino acid sequence, phylogeny and in planta and in vitro expression patterns. MtWUS was induced throughout embryogenic cultures by cytokinin after 24-48 h and maximum expression occurred after 1 week, which coincides with the induction of totipotent stem cells. During this period there was no MtCLV3 expression to suppress MtWUS. MtWUS expression, as illustrated by promoter-GUS studies, subsequently localised to the embryo, and there was then the onset of MtCLV3 expression. This suggests that the expression of the putative MtCLV3 coincides with the WUS-CLAVATA feedback loop becoming operational. RNAi studies showed that MtWUS expression is essential for callus and somatic embryo production. Based on the presence of MtWUS promoter binding sites, MtWUS may be required for the induction of MtSERF1, postulated to have a key role in the signalling required for SE induced in 2HA. MtWOX5 expressed in auxin-induced root primordia and root meristems and appears to be involved in pluripotent stem cell induction. The evidence is discussed that the homeobox genes MtWUS and MtWOX5 are "hijacked" for stem cell induction, which is key to somatic embryo and de novo root induction. In relation to SE, a role for WUS in the signalling involved in induction is discussed.

Genetic and environmental effects on body mass index during adolescence: a prospective study among Finnish twins.

OBJECTIVE: To study genetic and environmental factors affecting body mass index (BMI) and BMI phenotypic correlations across adolescence. DESIGN: Prospective, population-based, twin cohort study. PARTICIPANTS AND METHODS: We used twin modeling in 2413 monozygotic and same-sex and opposite-sex dizygotic Finnish twin pairs born in 1983-1987 and assessed using self-report questionnaires at 11-12, 14 and 17 years of age. RESULTS: Heritability of BMI was estimated to be 0.58-0.69 among 11-12- and 14-year-old boys and girls, 0.83 among 17-year-old boys and 0.74 among 17-year-old girls. Common environmental effects shared by siblings were 0.15-0.24 among 11-12- and 14-year-old boys and girls but no longer discernible at 17 years of age. Unique environmental effects were 0.15-0.23. Additive genetic factors explained 90-96% of the BMI phenotypic correlations across adolescence, whereas unique environmental factors explained the rest. Common environment had no effect on BMI phenotypic correlations. CONCLUSIONS: The genetic contribution to BMI is strong during adolescence, and it mainly explains BMI phenotypic correlations across adolescence. Common environmental factors have an effect on BMI during early adolescence, but that effect disappears by late adolescence.

Genetic influences on the difference in variability of height, weight and body mass index between Caucasian and East Asian adolescent twins.

OBJECTIVE: Twin studies are useful for investigating the causes of trait variation between as well as within a population. The goals of the present study were two-fold: First, we aimed to compare the total phenotypic, genetic and environmental variances of height, weight and BMI between Caucasians and East Asians using twins. Secondly, we intended to estimate the extent to which genetic and environmental factors contribute to differences in variability of height, weight and BMI between Caucasians and East Asians. DESIGN: Height and weight data from 3735 Caucasian and 1584 East Asian twin pairs (age: 13-15 years) from Australia, China, Finland, Japan, the Netherlands, South Korea, Taiwan and the United States were used for analyses. Maximum likelihood twin correlations and variance components model-fitting analyses were conducted to fulfill the goals of the present study. RESULTS: The absolute genetic variances for height, weight and BMI were consistently greater in Caucasians than in East Asians with corresponding differences in total variances for all three body measures. In all 80 to 100% of the differences in total variances of height, weight and BMI between the two population groups were associated with genetic differences. CONCLUSION: Height, weight and BMI were more variable in Caucasian than in East Asian adolescents. Genetic variances for these three body measures were also larger in Caucasians than in East Asians. Variance components model-fitting analyses indicated that genetic factors contributed to the difference in variability of height, weight and BMI between the two population groups. Association studies for these body measures should take account of our findings of differences in genetic variances between the two population groups.

Chernobyl exposure as stressor during pregnancy and hormone levels in adolescent offspring.

BACKGROUND: Animal research suggests a programming effect of prenatal stress in the fetal period, resulting in disruptions in behavioural and neuromotor development. Physiological changes that mediate these effects include alterations in the hypothalamic-pituitary-adrenal axis and in testosterone levels. This human study focuses on changes related to these physiological systems after prenatal stress exposure. METHODS: We examined the potential effect of prenatal stress associated with the Chernobyl disaster in an ongoing genetic epidemiological study in Finland. One birth cohort of twins (n = 121 twin pairs) was exposed in utero to maternal stress, and their saliva cortisol and testosterone levels at age 14 were compared with twins (n = 157 twin pairs) born one year later. RESULTS: Cortisol levels in both sexes and testosterone levels among females were significantly elevated after prenatal exposure to maternal stress from the second trimester onwards, compared to reference groups of non-exposed adolescents. Exposure explains 3% of variance (p<0.05) in cortisol levels and 18% of variance in testosterone levels (p<0.001). No significant differences were found for exposure from either first or third trimester onwards. CONCLUSION: Our results suggest that prenatal exposure to maternal stress in the second trimester of pregnancy may have resulted in prenatal programming of physiological systems relating to cortisol and testosterone levels.

Arsenic and heavy metal accumulation by Pteris vittata L. and P. umbrosa R. Br.

This study compared the accumulation of arsenic, copper and chromium by Pteris vittata and Pteris umbrosa grown in a glasshouse in soil from a timber treatment facility. Soil was collected from three locations. Accumulation (as percentage removed) varied between these soils but was not related to soil concentration. P. vittata was more efficient than P. umbrosa, both in accumulating As and metals in the below-ground plant parts and in translocating As to the fronds. Under the experimental conditions, only P. vittata could be effectively used in soil from one location for phytoremediation purposes.

Chernobyl exposure as stressor during pregnancy and behaviour in adolescent offspring.

OBJECTIVE: Research in animals has shown that exposure to stressors during pregnancy is associated with offspring behavioural disorders. We aimed to study the effect of in utero exposure to the Chernobyl disaster in 1986, and maternal anxiety presumably associated with that exposure, on behaviour disorder observed at age 14. METHOD: Exposed (n = 232) and non-exposed Finnish twins (n = 572) were compared. A semi-structured interview was used to assess lifetime symptoms of depression, generalized anxiety disorder, attention deficit hyperactivity disorder, conduct disorder and oppositional defiant disorder symptoms. RESULTS: Adolescents who were exposed from the second trimester in pregnancy onwards, had a 2.32-fold risk (95% CI: 1.13-4.72) of having lifetime depression symptoms, an increased risk of fulfilling DSM-III-R criteria of a major depressive disorder (OR = 2.48, 95% CI: 1.06-5.7), and a 2.01-fold risk (95% CI: 1.14-3.52) of having attention deficit hyperactivity disorder symptoms. CONCLUSION: Perturbations in fetal brain development during the second trimester may be associated with the increased prevalence of depressive and attention deficit hyperactivity disorder symptoms.

Eating styles, overweight and obesity in young adult twins.

OBJECTIVE: To explore the association of eating styles with overweight and obesity in young adults, controlling for identical genetic background in monozygotic twins. DESIGN: Prospective twin cohort study. SETTING: Finland, 1991-2002. SUBJECTS: Two-hundred and thirty-three women and 2060 men from the FinnTwin16 study, aged 16 years at baseline (T1), and ranging from 22 to 27 years at the time of the nutritional assessment (T4). METHODS: Eating styles (Restrictive/overeating, health-conscious, snacking, emotional and externally induced), self-reported at T4, were contrasted with body mass indices (BMIs) at T1 and T4. RESULTS: At T4, obesity (BMI>or=30Kg/m(2)) was significantly cross-sectionally associated with restrictive eating, frequent snacks, eating in the evening, avoiding fatty foods and failure to maintain healthy eating patterns. These associations were independent of BMI at T1. Obese women self-reported more vulnerability to external eating cues and comfort eating than normal-weight women. However, in a multivariable model, only restrictive/overeating and health-conscious eating styles were significant correlates of obesity at T4, independent of gender and BMI at T1. When we controlled for genetic background restricting the analysis to the 39 female and 45 male monozygotic twin pairs discordant for obesity or overweight (BMI>or=25Kg/m(2)), restrictive/overeating eating style was still statistically significantly associated with excess weight. CONCLUSIONS: The eating styles of obese young adults differ from their normal-weight counterparts: restrictive eating, overeating and fewer healthy food choices are associated with obesity. Different eating styles may partially explain weight differences in individuals with identical genetic background.

Breakfast skipping and health-compromising behaviors in adolescents and adults.

OBJECTIVE: To investigate which sociodemographic factors and behaviors are associated with breakfast skipping in adolescents and adults. DESIGN: Five birth cohorts of adolescent twins and their parents received an extensive behavioral and medical self-report questionnaire that also assessed breakfast-eating frequency. SETTING: Finland, 1991-1995. SUBJECTS: A population sample of 16-y-old girls and boys (n=5448) and their parents (n=4660). RESULTS: Parental breakfast eating was the statistically most significant factor associated with adolescent breakfast eating. Smoking, infrequent exercise, a low education level at 16, female sex, frequent alcohol use, behavioral disinhibition, and high body mass index (BMI) were significantly associated with adolescent breakfast skipping. In adults, smoking, infrequent exercise, low education level, male sex, higher BMI, and more frequent alcohol use were associated with breakfast skipping. In the adult sample, older individuals had breakfast more often than younger ones. Both adults and adolescents who frequently skipped breakfast were much more likely to exercise very little compared to those who skipped breakfast infrequently. Breakfast skipping was associated with low family socioeconomic status in adults and adolescent boys, but not in girls. Breakfast skipping clustered moderately with smoking, alcohol use, and sedentary lifestyle in both adults and adolescents. CONCLUSIONS: Breakfast skipping is associated with health-compromising behaviors in adults and adolescents. Individuals and families who skip breakfast may benefit from preventive efforts that also address risk behaviors other than eating patterns. SPONSORSHIP: National Institute of Alcohol Abuse and Alcoholism (AA08315), Academy of Finland (44069), European Union Fifth Framework Program (QLRT-1999-00916), Yrjö Jahnsson Foundation, and Jalmari and Rauha Ahokas Foundation.

Recombinant equine growth hormone administration: effects on synovial fluid biomarkers and cartilage metabolism in horses.

REASONS FOR PERFORMING STUDY: Recombinant equine growth hormone (reGH) has recently been evaluated for effects on body condition and wound healing. It has the potential to influence articular cartilage via stimulation of IGF-1. OBJECTIVES: To investigate effects of administration on synovial joint metabolism. METHODS: Six mature horses were given 20 microg/kg bwt reGH daily for 8 weeks by i.m. injection. Three control horses were injected with sterile water. Serum and synovial fluid samples were collected at 6, 8, 11 and 16 weeks for GH and IGF-1 assays. Articular cartilage harvested at week 16 was evaluated by Western analysis using monoclonal antibodies BC-13, BC-4, 8-A-4 and CH-3. RESULTS: Concentrations of IGF-1 in serum and synovial fluid were significantly elevated (P < 0.05) at 6 and 8 weeks in the reGH group. Glycosaminoglycan concentrations in synovial fluid were significantly less than controls at these time points, suggesting that reGH may modulate proteoglycan metabolism in articular cartilage. In the reGH group, there were not any alterations in synovial fluid content of 3B3(-) epitope or aggrecan metabolite, or in aggrecan or link protein catabolites retained within cartilage, that might be expected with development of osteoarthritis. CONCLUSIONS: Intramuscular administration of reGH may be a more efficient means of delivery of IGF-1 to joints for cartilage resurfacing initiatives. POTENTIAL RELEVANCE: We found no alterations in cartilage metabolism indicative of development of osteoarthritis.