13th balkan biochemical biophysical days & meeting on metabolic disorders’ programme & abstracts

NEUROENDOCRINE SYSTEM AND OBESITY

Energy expendıture and inhibition of appetite are increased by Hypotalamic stimulii.

The hormon LEPTIN which is produced in the fat tissue binds to its own spesific receptors in the Hypothalamus and causes the inhibition of appetite and the energy loosing.One the other hand a negativ feed back system operates between Cortisol

Leptin and Insulin.Insulin and Cortisol stimulate the production and the secretion of Leptin.In turn Leptin inhibits the secretion of Insulin.

NPY is another Hypothalamic neuropeptide which stimulates the appetite and promotes the energy expenditure in contraste to LEPTIN.NPY stimulates the Hypothalamico-Hypopyseal axis,causes the increase of ACTH and Cortisol.In turn NPY production is inhibited by ACTH and LEPTİN whose production and secretion is stimulated by Cortisol.On the other hand NPY stimulates the secretion of Insulin, and eventually the production of LEPTIN.LEPTIN inhibits the secretion of NPY.

Apart from these, two groups of neuropeptideswhich are called OREXIGENIC and ANOREXIGENIC take place in the Hypothalamus.LEPTIN inhibits the OREXIGENICS and stimulates the others.

Besides the Hypothalamic peptides, intestinal peptides play roles in the control of appetite.OREXINES and COLESYSTOKININ are the intestinal substances which can be found olso in the brain,enhances and supress feeling of hunger respectively.

The transfer of Phenylalanine into the CSF promotes the production and secretion of SEROTONIN which inhibits the appetite and especially CARBOHYDRATE CRAVING.INSULIN which is secreted as a result of carbohydrate consumption promotes the transfer of Phenylalanin into the brain tissue.

Candeğer Yılmaz

ESKANDARI H. G.

Disorders of lipid metabolism will be discussed in two major categories. One of them is composed of frequently seen lipoprotein disorders in clinical biochemistry laboratories. Different disorders of lipoprotein metabolism are triggered by apolipoproteins, enzymes, and lipoprotein receptors, some clinically characterized by hyperlipoproteinemia. These disorders can be classified under seven titles according to Frederickson and WHO. Hypolipoproteinemias which are not seen as frequent as hyperlipoproteinemias are also types of lipoprotein metabolism disorders. Routine tests such as total cholesterol, triglyceride, HDL cholesterol, LDL cholesterol, lipoprotein (a), apo AI, and apo B, and spesific tests such as HDL subfractions, lipoprotein (a) isoforms, apo E polymorphism, apo B-3500-apo CII-apo CIII mutations, and hepatic lipase-lipoprotein lipase, lechitine cholesterol acyl transferase activities are being used to determine the etiopathogenesis of lipoprotein metabolism disorders.

The second category of the lipid metabolism disorders is composed of mitochondrial fatty acid oxidation defects. These disorders are caused by a group of enzyme deficiencies and transport defects, and clinically characterized by hypoglycemic-hypoketotic coma, induced by fasting. In acute phase of these disorders, serum electrolytes, glucose, ammonia, transaminase levels are routine screening tests, while carnitine-acylcarnitine levels, and acylcarnitine profiles, urinary organic acid analyses by GC-MS, measurements of enzyme activities, and mutation analyses are required in determining the etiology. With its significant incidence detected in these patients, and similar frequency as phenylketonuria in North Europe, MCAD deficiency is thought to be included in newborn screening programs. It is advised to check acylcarnitine levels, especially octanoylcarnitine by tandom-MS, in blood samples taken for screening of phenylketonuria and neonatal hypothyroidism.

LECTURE 5

H. Asuman ÖZKARA

The glycosphingolipidoses are a set of diseases that are caused by defects in the lysosomal degradation of glycolipids derived from the plasma membrane. Catabolism of these lipids contains enzymes and activator proteins.

Over the past decade, biochemical and molecular genetic studies of sphingolipidoses have expanded our understanding of underlying metabolic principles of these diseases and their genes. A new lysosomal digestion model was developed and mechanisms of glycosphingolipids hydrolysis within the lysosome was understood. The discovery of sphingolipid activator proteins was an important factor in this process. By investigating the molecular basis of the diseases, basic principles of storage disease pathology begin to understood and several mechanisms were described in the pathogenesis. However, our understanding of pathogenesis in these diseases is incomplete. The generation of mouse models and sphingolipid research on cell signaling will help to investigate the pathophysiology and have facilitated the development of new and promising therapeutic strategies for these diseases, most of which are not treatable at present. Currently few options exist for therapy. One of these is enzyme replacement therapy (ERT) that has been a highly effective therapy in type 1 Gaucher disease and more recently has been undertaken in Fabry disease. ERT is not beneficial to the neuronopathic form of glycosphingolipidoses. Gene therapy holds considerable promise for this family of diseases and evaluation in mouse models is a major way forward in evaluating different gene delivery systems and evaluating efficacy. Small-molecule drugs have recently emerged as candidate therapeutics for juvenile and adult forms of glycosphingolipidoses. The approach is to use inhibitors of glycosphingolipid biosynthesis and thereby reduce the number of glycosphingolipid molecules the cells degrade. These drugs have been evaluated multiple mouse models of glycosphingolipidoses, including those with brain involvement. In all cases efficacy has been demonstrated.

It is interesting to reflect that diseases that glycolipid catabolism helped unravel the basic biochemistry of glycolipids and this knowledge, in turn, has led to new therapies for these diseases. The science has therefore gone full circle from disease to basic biochemistry to disease therapy.

APOE AND PON 55/192 POLYMORPHISM AND EFFECTS ON PON ACTIVITY AND LIPIDS IN NIDDM

Bedia AĞACHAN¹, Hulya YILMAZ¹, Zeynep KARAALI², Turgay İSBİR<sup>1

1</sup>University of Istanbul, Institute of Experimental Medical Research, Department of Molecular Medicine, Istanbul, Turkey; ²Haseki State Hospital, Department of Internal Medicine, Istanbul, Turkey

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Objective: Paraoxonase (PON1) and Apolipoprotein E (ApoE) have emerged as independent risk factor for cardiovascular disease. As there are no existing data for the Turkish population, we investigated the relationship between apolipoprotein E and PON 55 / 192 polymorphisms and furthermore to assess the effect of apoE polymorphisms on lipid levels in 157 non-insulin dependent diabetes mellitus (NIDDM) individuals and 116 non-diabetic controls in Turkish subjects.

Methods and Results: Apolipoprotein E and PON1 genotypes were identified by PCR amplification and subsequent restriction endonuclease digestion. Apo E 4+ genotype frequencies significantly higher in NIDDM groups (²:4,122 p:0,042) than controls. We found an associations between the 4 allele and increased total cholesterol and LDL­cholesterol in the diabetes group, the 2 allele and increased triglyceride levels in NIDDM group (P<0.01). In our sample, we showed that the two PON1 polymorphisms were associated with PON1 activity, which increased in the order of the AA < AB < BB genotype in the PON1 192 polymorphism and MM < ML < LL genotype in the PON1 55 polymorphism.

Discussion: We found an positive association between PON55 MM, PON192 AA haplotypes and Apo 4 alleles. Thus we assumed that presence of Apo 4 allele, subjects with low PON activity (M or A) allele carriers might be a risk factor for NIIDDM.

P2

MTHFR C677T MUTATION HAS AN IMPORTANT EFFECT ON HYPERHOMOCYSTEINEMIA AND LVH IN NIDDM

Elevated plasma concentrations of homocysteine (Hcy) as a risk factor of coronary artery disease (CAD), essential hypertension and diabetic target organ damage. Methylenetetrahydrofolatereductase (MTHFR) gene C677T polymorphism is associated with hyperhomocysteinemia. This study was designed to investigate an association of MTHFR C677T polymorphism with homocysteine levels and diabetic complications in the Turkish population.

Our study was carried out in 249 patients with type II diabetes mellitus (T2DM) (102 men, 147 women) and 214 healthy volunteers as controls (91 men, 123 women). Serum Hcy levels were measured in the fasting state by immunological assay. MTHFR C677T genotypes were determined by PCR, RFLP techniques.

No differences were observed in the distribution of MTHFR genotypes or allele frequencies in cases versus controls. In the T2DM and control groups, The homozygous mutant genotype (T/T) had the highest homocysteine levels compared to wild (C/C) and heterozygous mutant (C/T) genotypes (p<0,001). We found high prevalence of left ventricul hypertrophy in T2DM who had hyperhomocysteinuria (p=0,29, X2=1,10, Odds ratio:2,40, 95% CI: 0,38-15,14). Patients with TT genotype showed a higher prevalence of left venticular hypertrophy (LVH) compared to patients with CC and CT genotypes (p=0,28, X2=1,15, Odds ratio:2,62, 95% CI: 0,43-15,81).

The MTHFR C677T mutation had a significant effect on the plasma homocysteine level in Turkish T2DM patients and healthy controls. Neither hyperhomocysteinemia nor MTHFR C677T mutation found significant effects on complications associated to T2DM. However, MTHFR TT genotypes and hyperhomocysteinemia were observed to related to LVH risk in T2DM patients.

P3

YEAST GROWTH STIMULATION AND SUPRESSION OF ARGINAZA AND ENZYMES OF PROLINE BIOSYNTHESIS WITH THE HELP OF HERBAL EXTRACTS

A.Kh. AGADJANYAN, S.V.CHUBARYAN, L.R.TUMANYAN, A.A.AgGADJANYAN, A.A.NIKOYAN, A.V.MANUKYAN