Olli Kärkkäinen

mGluR1/5 receptor densities in the brains of alcoholic subjects: A whole-hemisphere autoradiography study

Increased glutamatergic neurotransmission and hyper-excitability during alcoholic withdrawal and abstinence are associated with increased risk for relapse, in addition to compensatory changes in the glutamatergic system during chronic alcohol intake. Type 5 metabotropic glutamate receptor (mGlur5) is abundant in brain regions known to be involved in drug reinforcement, yet very little has been published on mGluR1/5 expression in alcoholics. We evaluated the densities of mGluR1/5 binding in the hippocampus and striatum of post-mortem human brains by using [(3)H]Quisqualic acid as a radioligand in whole hemispheric autoradiography of Cloninger type 1 (n=9) and 2 (n=8) alcoholics and healthy controls (n=10). We observed a 30-40% higher mGluR1/5 binding density in the CA2 area of hippocampus in type 1 alcoholics when compared with either type 2 alcoholics or healthy subjects. Although preliminary, and from a relatively small number of subjects from these diagnostic groups, these results suggest that the mGluR1/5 receptors may be increased in type 1 alcoholics in certain brain areas.

AMPA receptors in post-mortem brains of Cloninger type 1 and 2 alcoholics: A whole-hemisphere autoradiography study

Dysfunction of the brain glutamate system has been associated with alcoholism. Ionotropic glutamatergic alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptors (AMPARs) play an important role in both neurotransmission and post-synaptic plasticity. Alterations in AMPAR densities may also play a role in the neurobiological changes associated with alcoholism. In the present study, [(3)H] AMPA binding density was evaluated in the nucleus accumbens (NAc), frontal cortex, anterior cingulate cortex (ACC), dentate gyrus and hippocampus of Cloninger type 1 (n=9) and 2 (n=8) alcoholics, and compared with non-alcoholic control subjects (n=10) by post-mortem whole-hemisphere autoradiography. The [(3)H] AMPA binding density was significantly higher in the ACC of early onset type 2 alcoholics when compared with controls (p=0.011). There was also a significant negative correlation between [(3)H] AMPA binding and previously published results of dopamine transporter (DAT) density in the ACC in these same brain samples (R=-0.95, p=0.001). Although preliminary, and from a relatively small diagnostic group, the present results help to further explain the pathology of alcohol dependence and impulsive behaviour in type 2 alcoholics.

Increased Metabotropic Glutamate 2/3 Receptor Binding in the Perigenual Anterior Cingulate Cortex of Cloninger Type 2 Alcoholics: A Whole-Hemisphere Autoradiography Study

AIMS Metabotropic glutamate receptors 2 and 3 (mGluR2/3) contribute to control the level of glutamate in the synapse. In rodents, mGluR2/3 agonists attenuate the reinstatement of alcohol-seeking behavior. Linking possible alterations of the mGluR2/3 system to the etiology and type of alcoholism could provide valuable information for the development of novel mGluR2/3 function modulating therapies in addiction treatment. To date, mGluR2/3 binding density has not been studied in human alcoholics. We aimed to investigate the possible differences in mGluR2/3 binding between Cloninger type 1 anxiety-prone and type 2 impulsive alcoholics and controls. METHODS We performed a post-mortem whole-hemisphere autoradiography to study the mGluR2/3 binding density of 9 type 1 alcoholics, 8 type 2 alcoholics and 10 controls. [(3)H]LY341495, a potent group II metabotropic glutamate receptor antagonist, was used as the radio-ligand with l-glutamate as a displacer. RESULTS [(3)H]LY341495 binding density was statistically significantly increased (P = 0.046) in the perigenual anterior cingulate cortex (pACC) of type 2 alcoholics when compared with controls. In other brain areas, no significant difference between the groups was found. CONCLUSION This preliminary study suggests that impulsive type 2 alcoholics might have alterations in the mGluR2/3 function in the pACC, a brain area presumed to be involved in the control of drug-seeking behaviors and self-control.

Lower [3H]Citalopram Binding in Brain Areas Related to Social Cognition in Alcoholics

AIMS In the present study, putative alterations in the serotonin transporter density were evaluated in anterior and posterior insula, posterior cingulate cortex, dorsolateral and dorsomedial prefrontal cortex, hippocampus, parahippocampal gyrus and dorsal raphe nucleus in Cloninger type 1 (n = 9) and type 2 (n = 8) alcoholics and non-alcoholic controls (n = 10). METHODS Human whole-hemisphere autoradiography was used to measure [3H]citalopram binding to serotonin transporters in eight brain areas in all post-mortem brains. RESULTS Significant differences were observed in the mean [3H]citalopram binding between the study groups, with antisocial type 2 alcoholics showing the lowest binding. Differences between the study groups were prominent in the posterior insula and posterior cingulate cortex, where both alcoholic groups had low [3H]citalopram binding, and in the parahippocampal gyrus where only antisocial type 2 alcoholics had low [3H]citalopram binding when compared with non-alcoholic controls. CONCLUSION Although these data are preliminary, and from relatively small diagnostic groups, these results show that alcoholics may have lower serotonergic tone in the brain, thus decreasing social cognition and increasing alcohol-cue reactivity.

[3H]Ifenprodil binding in post-mortem brains of Cloninger type 1 and 2 alcoholics: A whole-hemisphere autoradiography study

The glutamate N-methyl-d-aspartate (NMDA) receptor NR2B subunits are sensitive to ethanol and are found in brain areas related to ethanol addiction, dependence, development of alcohol tolerance, and alcohol withdrawal syndrome. Previous studies indicate that early-onset Cloninger type 2 alcoholics have an intact, responsive, dopaminergic system in the nucleus accumbens (NAC), whereas type 1 alcoholics have dopaminergic defects. NR2B-containing NMDA receptors in the NAC are involved in both non-opioid and opioid receptor-mediated reward. Our aim was to evaluate the putative [(3)H]ifenprodil binding alterations of NR2B receptors in limbic, hippocampal, and cortical brain areas of type 1 alcoholics (n=8), type 2 alcoholics (n=8), and control subjects (n=10) by postmortem whole hemisphere autoradiography. We found significantly different binding levels among these three subject groups, and the main difference was localized in the decreased binding in type 2 alcoholics and controls in the nucleus accumbens. Although preliminary and from relatively small diagnostic groups, these results suggest pathological alterations in the NR2B-mediated reward system of type 2 alcoholics.

Alcohol and substance use are associated with altered metabolome in the first trimester serum samples of pregnant mothers

BACKGROUND Although the effects of alcohol on metabolic processes in the body have been studied widely, there do not appear to be any previous reports clarifying how substance abuse changes metabolic profiles of pregnant women during the first trimester of pregnancy. OBJECTIVE Our aim was to evaluate the effect of substance abuse, especially alcohol use, on the metabolic profile of pregnant women during the first trimester. STUDY DESIGN We applied mass spectrometry based non-targeted metabolite profiling of serum collected during routine visit to the hospital between gestational weeks 9 + 0 to 11 + 6 from controls (n = 55), alcohol users (n = 19), drug users (n = 24) and tobacco smokers (n = 40). RESULTS We observed statistically significantly differences among the study groups in serum levels of glutamate, glutamine, and serotonin (p-values ≤ 0.0001). The serum levels of glutamate were increased in alcohol and drug using mothers when compared to the controls, whereas levels of glutamine were decreased in alcohol and drug using mothers. In addition, serum levels of serotonin were decreased in alcohol using mothers when compared to the controls. CONCLUSION The present study shows that alcohol and drug use were associated with increased glutamate, and decreased glutamine levels, and alcohol use is associated with decreased serotonin levels. This study serves as a proof-of-concept that the metabolite profile of human first trimester serum samples could be used to detect alcohol exposure during pregnancy.

A Non-Targeted LC-MS Profiling Reveals Elevated Levels of Carnitine Precursors and Trimethylated Compounds in the Cord Plasma of Pre-Eclamptic Infants

Preeclampsia (PE) is a complex pregnancy disorder. It is not extensively known how the metabolic alterations of PE women contribute to the metabolism of newborn. We applied liquid chromatography-mass spectrometry (LC-MS) based non-targeted metabolomics to determine whether the metabolic profile of plasma from umbilical cord differs between infants born to PE and non-PE pregnancies in the FINNPEC study. Cord plasma was available from 42 newborns born from PE and 53 from non-PE pregnancies. 133 molecular features differed between PE and non-PE newborns after correction for multiple testing. Decreased levels of 4-pyridoxic acid were observed in the cord plasma samples of PE newborns when compared to non-PE newborns. Compounds representing following areas of metabolism were increased in the cord plasma of PE newborns: urea and creatine metabolism; carnitine biosynthesis and acylcarnitines; putrescine metabolites; tryptophan metabolism and phosphatidylcholines. To our knowledge, this study is the first one to apply LC-MS based metabolomics in cord plasma of PE newborns. We demonstrate that this strategy provides a global picture of the widespread metabolic alterations associated with PE and particularly the elevated levels of carnitine precursors and trimethylated compounds appear to be associated with PE at birth.

Whole grain intake associated molecule 5-aminovaleric acid betaine decreases β-oxidation of fatty acids in mouse cardiomyocytes

Despite epidemiological evidence showing that diets rich in whole grains reduce the risk of chronic life-style related diseases, biological mechanisms for these positive effects are mostly unknown. Increased 5-aminovaleric acid betaine (5-AVAB) levels in plasma and metabolically active tissues such as heart have been associated with consumption of diets rich in whole grains. However, biological effects of 5-AVAB are poorly understood. We evaluated 5-AVAB concentrations in human and mouse heart tissue (3–22 µM and 38–78 µM, respectively) using mass spectrometry. We show that 5-AVAB, at physiological concentration range, dose-dependently inhibits oxygen consumption due to β-oxidation of fatty acids, but does not otherwise compromise mitochondrial respiration, as measured with oxygen consumption rate in cultured mouse primary cardiomyocytes. We also demonstrate that this effect is caused by 5-AVAB induced reduction of cellular L-carnitine. Reduced L-carnitine levels are at least partly mediated by the inhibition of cell membrane carnitine transporter (OCTN2) as evaluated by in silico docking, and by siRNA mediated silencing of OCTN2 in cultured cardiomyocytes. 5-AVAB caused inhibition of β-oxidation of fatty acids is a novel mechanism on how diets rich in whole grains may regulate energy metabolism in the body. Elucidating potentially beneficial effects of 5-AVAB e.g. on cardiac physiology will require further in vivo investigations.

Heart specific PGC-1α deletion identifies metabolome of cardiac restricted metabolic heart failure

Aims Heart failure (HF) is associated with drastic changes in metabolism leading to a cardiac energy deficiency well as maladaptive changes in multiple other tissues. It is still unclear which of these changes originates from cardiomyocyte metabolic remodelling or whether they are induced secondarily by systemic factors. Our aim here was to induce cardiac restricted metabolic changes mimicking those seen in HF and to characterize the associated metabolite changes in the heart, circulation, and peripheral tissues. Methods and results We generated a cardiac specific PGC-1α knockout mice (KO) to specifically induce metabolic dysregulation typically accompanied by HF and performed a non-targeted LC-MS metabolite profiling analysis of heart, plasma, liver, and skeletal muscle to identify metabolites associated with cardiac specific metabolic remodelling. The KO animals developed a progressive cardiomyopathy with cardiac dilatation leading to fatal HF. At 17 weeks of age, when significant remodelling had occurred but before the onset of HF, isolated PGC-1α deficient cardiomyocytes had suppressed glucose and fatty acid oxidation as well as blunted anaerobic metabolism. KO hearts displayed a distinctive metabolite profile with 92 significantly altered molecular features including metabolite changes in energy metabolism, phospholipid metabolism, amino acids, and oxidative stress signalling. Some of the metabolite changes correlated with the specific parameters of cardiac function. We did not observe any significant alterations in the metabolomes of the other measured tissues or in plasma. Conclusions Heart specific PGC-1α KO induces metabolic, functional, and structural abnormalities leading to dilating cardiomyopathy and HF. The metabolic changes were limited to the cardiac tissue indicating that cardiomyocyte metabolic remodelling is not sufficient to evoke the body wide metabolic alterations usually associated with HF.