Associations of gene polymorphisms and nutrition with calcium homeostasis and bone mineral density : Studies on skeletal nutrigenetics

Heredity explains a major part of the variation in calcium homeostasis and bone strength, and the susceptibility to osteoporosis is polygenetically regulated. Bone phenotype results from the interplay between lifestyle and genes, and several nutritional factors modulate bone health throughout life. Thus, nutrigenetics examining the genetic variation in nutrient intake and homeostatic control is an important research area in the etiology of osteoporosis. Despite continuing progress in the search for candidate genes for osteoporosis, the results thus far have been inconclusive. The main objective of this thesis was to investigate the associations of lactase, vitamin D receptor (VDR), calcium sensing receptor (CaSR) and parathyroid hormone (PTH) gene polymorphisms and lifestyle factors and their interactions with bone health in Finns at varying stages of the skeletal life span. Markers of calcium homeostasis and bone remodelling were measured from blood and urine samples. Bone strength was measured at peripheral and central bone sites. Lifestyle factors were assessed with questionnaires and interviews. Genetic lactase non-persistence (the C/C-13910 genotype) was associated with lower consumption of milk from childhood, predisposing females in particular to inadequate calcium intake. Consumption of low-lactose milk and milk products was shown to decrease the risk for inadequate calcium intake. In young adulthood, bone loss was more common in males than in females. Males with the lactase C/C-13910 genotype may be more susceptible to bone loss than males with the other lactase genotypes, although calcium intake predicts changes in bone mass more than the lactase genotype. The BsmI and FokI polymorphisms of the VDR gene were associated with bone mass in growing adolescents, but the associations weakened with age. In young adults, the A986S polymorphism of the calcium sensing receptor gene was associated with serum ionized calcium concentrations, and the BstBI polymorphism of the parathyroid gene was related to bone strength. The FokI polymorphism and sodium intake showed an interaction effect on urinary calcium excretion. A novel gene-gene interaction between the VDR FokI and PTH BstBI gene polymorphisms was found in the regulation of PTH secretion and urinary calcium excretion. Further research should be carried out with more number of Finns at varying stages of the skeletal life span and more detailed measurements of bone strength. Research should concern mechanisms by which genetic variants affect calcium homeostasis and bone strength, and the role of diet-gene and gene-gene interactions in the pathogenesis of osteoporosis.

Nutrition and bone metabolism : In vivo effects of inorganic phosphate on rats and in vitro effects of bioactive tripeptides on human osteoblasts

Nutrition affects bone health throughout life. To optimize peak bone mass development and maintenance, it is important to pay attention to the dietary factors that enhance and impair bone metabolism. In this study, the in vivo effects of inorganic dietary phosphate and the in vitro effects of bioactive tripeptides, IPP, VPP and LKP were investigated. Dietary phosphate intake is increased through the use of convenience foods and soft drinks rich in phosphate-containing food additives. Our results show that increased dietary phosphate intake hinders mineral deposition in cortical bone and diminishes bone mineral density (BMD) in the aged skeleton in a rodent model (Study I). In the growing skeleton (Study II), increased phosphate intake was observed to reduce bone material and structural properties, leading to diminished bone strength. Studies I and II revealed that a low Ca:P ratio has negative effects on the mature and growing rat skeleton even when calcium intake is sufficient. High dietary protein intake is beneficial for bone health. Protein is essential for bone turnover and matrix formation. In addition, hydrolysis of proteins in the gastrointestinal tract produces short peptides that possess a biological function beyond that of being tissue building blocks. The effects of three bioactive tripeptides, IPP, VPP and LKP, were assessed in short- and long-term in vitro experiments. Short-term treatment (24 h) with tripeptide IPP, VPP or LKP influenced osteoblast gene expression (Study III). IPP in particular, regulates genes associated with cell differentiation, cell growth and cell signal transduction. The upregulation of these genes indicates that IPP enhances osteoblast proliferation and differentiation. Long-term treatment with IPP enhanced osteoblast gene expression in favour of bone formation and increased mineralization (Study IV). The in vivo effects of IPP on osteoblast differentiation might differ since eating frequency drives food consumption, and protein degradation products, such as bioactive peptides, are available periodically, not continuously as in this study. To sum up, Studies I and II raise concern about the appropriate amount of dietary phosphate to support bone health as excess is harmful. Studies III and IV in turn, support findings of the beneficial effects of dietary protein on bone and provide a mechanistic explanation since cell proliferation and osteoblast function were improved by treatment with bioactive tripeptide IPP.

Effects of dairy proteins and calcium on diet-induced obesity in mice

Diet high in dairy products is inversely associated with body mass index, risk of metabolic syndrome and prevalence of type 2 diabetes in several populations. Also a number of intervention studies support the role of increased dairy intake in the prevention and treatment of obesity. Dairy calcium has been suggested to account for the effect of dairy on body weight, but it has been repeatedly shown that the effect of dairy is superior to the effect of supplemental calcium. Dairy proteins are postulated to either enhance the effect of calcium or have an independent effect on body weight, but studies in the area are scarce. The aim of this study was to evaluate the potential of dairy proteins and calcium in the prevention and treatment of diet-induced obesity in C57Bl/6J mice. The effect of dairy proteins and calcium on the liver and adipose tissue was also investigated in order to characterise the potential mechanisms explaining the reduction of risk for metabolic syndrome and type 2 diabetes. A high-calcium diet (1.8%) in combination with dietary whey protein inhibited body weight and fat gain and accelerated body weight and fat loss in high-fat-fed C57Bl/6J mice during long-term studies of 14 to 21 weeks. α-lactalbumin, one of the major whey proteins, was the most effective whey protein fraction showing significantly accelerated weight and fat loss during energy restriction and reduced the amount of visceral fat gain during ad libitum feeding after weight loss. The microarray data suggest sensitisation of insulin signalling in the adipose tissue as a result of a calcium-rich whey protein diet. Lipidomic analysis revealed that weight loss on whey protein-based high-calcium diet was characterised by significant decreases in diabetogenic diacylglycerols and lipotoxic ceramide species. The calcium supplementation led to a small, but statistically significant decrease in fat absorption independent of the protein source of the diet. This augments, but does not fully explain the effects of the studied diets on body weight. A whey protein-containing high-calcium diet had a protective effect against a high-fat diet-induced decline of β3 adrenergic receptor expression in adipose tissue. In addition, a high-calcium diet with whey protein increased the adipose tissue leptin expression which is decreased in this obesity-prone mouse strain. These changes are likely to contribute to the inhibition of weight gain. The potential sensitisation of insulin signalling in adipose tissue together with the less lipotoxic and diabetogenic hepatic lipid profile suggest a novel mechanistic link to explain why increased dairy intake is associated with a lower prevalence of metabolic syndrome and type 2 diabetes in epidemiological studies. Taken together, the intake of a high-calcium diet with dairy proteins has a body weight lowering effect in high-fat-fed C57Bl/6J mice. High-calcium diets containing whey protein prevent weight gain and enhance weight loss, α-lactalbumin being the most effective whey protein fraction. Whey proteins and calcium have also beneficial effects on hepatic lipid profile and adipose tissue gene expression, which suggest a novel mechanistic link to explain the epidemiological findings on dairy intake and metabolic syndrome. The clinical relevance of these findings and the precise mechanisms of action remain an intriguing field of future research.

Defining Adequate Vitamin D Intake : Cross-sectional and Intervention Studies

D-vitamiini ylläpitää normaalia luun kasvua ja uudistumista koko elämän ajan. Suomessa, kuten monissa muissakin länsimaissa, väestön D-vitamiinitilanne on riittämätön – talvisin osalla jopa puutteellinen. Tässä väitöskirjassa on tutkittu, lisääkö D-vitamiini luumassan kertymistä kasvuiässä, ja ylläpitäkö D-vitamiini luuston tasapainoista aineenvaihduntaa aikuisiällä. Nämä vaikutukset saattavat ehkäisi osteoporoosin kehittymistä eri ikäkausina. Väitöskirjatyössä tutkittiin erisuuruisten D-vitamiinilisäysten vaikutuksia kolmessa eri ikäryhmässä, jotka olivat 11-12 -vuotiaat tytöt (N=228), 21-49 -vuotiaat miehet (N=54) ja 65-85 -vuotiaat naiset (N=52). Tutkittavat satunnaistettiin ryhmiin, jotka nauttivat joko lumevalmistetta tai 5-20 µg D3-vitamiinia vitamiinilisänä. Tutkimukset olivat kaksoissokkoutettuja. Tutkimuksen aikana tutkittavilta otettiin paastoveri- ja virtsanäytteitä. Lisäksi he täyttivät tutkimuslomakkeen taustatietojen kartoittamiseksi sekä frekvenssikyselylomakkeen kalsiumin ja D-vitamiinin saannin selvittämiseksi. Tyttöjen luunmineraalitiheys (BMD) mitattiin DXA–laitteella ja miesten volumetrinen luuntiheys pQCT-menetelmällä. Näytteistä määritettiin mm. seerumin 25-hydroksi-D-vitamiinin (=S-25-OHD), lisäkilpirauhashormonin (=S-PTH) ja luun aineenvaihduntaa kuvaavien merkkiaineiden pitoisuuksia. Murrosikäisten tyttöjen poikkileikkaustutkimuksessa S-25-OHD- ja luun muodostusmerkkiaineen pitoisuudet vaihtelivat kuukausien välillä; suurimmat pitoisuudet mitattiin syyskuussa ja pienimmät maaliskuussa, mikä kuvastaa vuodenaikaisvaihtelua. Vastaava vaihtelu havaittiin lannerangan ja reisiluun BMD:ssä. D-vitamiinilisäyksellä oli myönteinen vaikutus tyttöjen luumassan lisääntymiseen. Suurin D-vitamiinilisä (10 µg/vrk) lisäsi luumassaa 17.2% enemmän reisiluussa ja 12.5% enemmän lannerangassa verrattuna lumevalmistetta nauttivien tyttöjen vastaaviin tuloksiin, mutta tulos riippui hoitomyöntyvyydestä. D-vitamiinin vaikutus luustoon välittyi vähentyneen luun hajotuksen kautta. Tutkimustuloksiin perustuen riittävä D-vitamiinin saanti murrosikäisille tytöille on 15 µg/vrk. D-vitamiinilisän vaikutus 65-85 -vuotiaiden naisten S-25-OHD-pitoisuuteen vakioitui kuudessa viikossa annoksen ollessa 5-20 µg/vrk. Näillä D-vitamiiniannoksilla ei saavutettu tavoiteltavaa S-25-OHD-pitoisuutta, joka on 80 nmol/l. Arvioimme, että 60 nmol/l -pitoisuuden, jota esiintyy kesäisin tämän ikäryhmän suomalaisilla, tämän ikäryhmän naiset saavuttaisivat 24 µg:n päivittäisellä D-vitamiinin saannilla. Terveillä miehillä havaittiin vuodenaikaisvaihtelu S-25-OHD- ja S-PTH-pitoisuudessa sekä luun hajotusta kuvaavassa merkkiainepitoisuudessa. Toisaalta vaihtelua ei havaittu radiuksen volumetrisessä luuntiheydessä eikä luun muodostusmerkkiaineen pitoisuudessa. Vuodenaikaisvaihtelu estettiin 17 µg:n päivittäisellä D-vitamiinin saannilla, mutta tämän ei havaittu vaikuttavan radiuksen luuntiheyteen kuusi kuukautta kestävän tutkimuksen aikana. Yhteenvetona todetaan, että D-vitamiinin saanti on edelleenkin riittämätöntä tutkimusten kohderyhmillä. Tämä näkyy S-25-OHD- ja PTH-pitoisuuden sekä luunaineenvaihduntaa kuvaavien merkkiaineiden vuodenaikaisvaihteluna, mikä on haitallista luuston hyvinvoinnille. D-vitamiinin saantia tulisi lisätä, jotta vähintäänkin riittävä D-vitamiinitilanne (S-25-OHD>50 nmol/l) tai mahdollisesti jopa tavoiteltava D-vitaminitilanne (S-25-OHD≥80 nmol/l) saavutettaisiin. Jotta D-vitamiinin saannin lisääminen olisi kaikissa ikäryhmissä mahdollista, on suunniteltava nykyistä enemmän D-vitamiinilla täydennettyjä elintarvikkeita.

Effects of dietary phosphorus and calcium-to-phosphorus ratio on calcium and bone metabolism in healthy 20- to 43-year-old Finnish women

Dietary habits have changed during the past decades towards an increasing consumption of processed foods, which has notably increased not only total dietary phosphorus (P) intake, but also intake of P from phosphate additives. While the intake of calcium (Ca) in many Western countries remains below recommended levels (800 mg/d), the usual daily P intake in a typical Western diet exceeds by 2- to 3-fold the dietary guidelines (600 mg/d). The effects of high P intake in healthy humans have been investigated seldom. In this thesis healthy 20- to 43-year-old women were studied. In the first controlled study (n = 14), we examined the effects of P doses, and in a cross-sectional study (n = 147) the associations of habitual P intakes with Ca and bone metabolism. In this same cross-sectional study, we also investigated whether differences exist between dietary P originating from natural P sources and phosphate additives. The second controlled study (n = 12) investigated whether by increasing the Ca intake, the effects of a high P intake could be reduced. The associations of habitual dietary calcium-to-phosphorus ratios (Ca:P ratio) with Ca and bone metabolism were determined in a cross-sectional study design (n = 147). In the controlled study, the oral intake of P doses (495, 745, 1245 and 1995 mg/d) with a low Ca intake (250 mg/d) increased serum parathyroid hormone (S-PTH) concentration in a dose-dependent manner. In addition, the highest P dose decreased serum ionized calcium (S-iCa) concentration and bone formation and increased bone resorption. In the second controlled study with a dietary P intake of 1850 mg/d, by increasing the Ca intake from 480 mg/d to 1080 mg/d and then to 1680 mg/d, the S-PTH concentration decreased, the S-iCa concentration increased and bone resorption decreased dose-dependently. However, not even the highest Ca intake could counteract the effect of high dietary P on bone formation, as indicated by unchanged bone formation activity. In the cross-sectional studies, a higher habitual dietary P intake (>1650 mg/d) was associated with lower S-iCa and higher S-PTH concentrations. The consumption of phosphate additive-containing foods was associated with a higher S-PTH concentration. Moreover, habitual low dietary Ca:P ratios (≤0.50, molar ratio) were associated with higher S-PTH concentrations and 24-h urinary Ca excretions, suggesting that low dietary Ca:P ratios may interfere with homeostasis of Ca metabolism and increase bone resorption. In summary, excessive dietary P intake in healthy Finnish women seems to be detrimental to Ca and bone metabolism, especially when dietary Ca intake is low. The results indicate that by increasing dietary Ca intake to the recommended level, the negative effects of high P intake could be diminished, but not totally prevented. These findings imply that phosphate additives may be more harmful than natural P. Thus, reduction of an excessively high dietary P intake is also beneficial for healthy individuals.

Effects of oral calcium sensitizers on experimental heart failure

Suun kautta annosteltava kalsiumherkistäjä parantaa sydämen vajaatoimintaan liittyvää pumppausvajetta kokeellisissa sydämen vajaatoimintamalleissa Huolimatta viime vuosikymmenien lääketieteellisestä kehityksestä krooninen sydämen vajaatoiminta on silti edelleen vakava, elämänlaatua voimakkaasti rajoittava sairaus. Kalsiumherkistäjät ovat uusi, sydämen pumppausvoimaa lisäävä lääkeryhmä. Levosimendaani, kotimaista alkuperää oleva kalsiumherkistäjä, on kliinisessä käytössä akuutin vajaatoiminnan hoitoon suonensisäisesti ja lyhytaikaisesti annosteltavana valmisteena. Levosimendaanilla on aktiivinen metaboliitti, OR-1896, jonka oletetaan olevan vuorokauden mittaisen levosimendaani-infuusion jälkeen havaittujen useita päiviä kestävien hyödyllisisten vaikutuksisten takana. Levosimendaanin kroonisen, suun kautta tapahtuvan annostelun vaikutuksista tieto on vähäisempää, mutta sillä näyttää olevan positiivisia vaikutuksia potilaiden raportoimana. FM Marjut Louhelainen on selvittänyt väitöskirjassaan suun kautta annosteltavan levosimendaanin ja sen pitkäkestoisen aktiivisen metaboliitin vaikutuksia kroonisen vajaatoiminnan hoidossa käyttämällä sekä hypertensiivisen sydäntaudin että 2 tyypin diabeteksen komplisoimaan sydäninfarktin kokeellisia malleja. Tutkimuksessa selvitettiin lisäksi vajaatoimintaan johtavia molekyylitason tapahtumia sydänlihaksessa. Tutkimuksessa osoitettiin, että krooninen suun kautta annosteltu hoito sekä kalsiumherkistäjä levosimendaanilla että sen aktiivisella metaboliitilla estää hypertensiiviseen sydämen vajaatoiminnan aikaasaamaa sydämen uudelleenmuovaantumista ja siihen liittyvää kuolleisuutta. Nämä vaikutukset välittyivät vähentyneen sydänlihassoluhypertrofian, solukuolleisuuden ja neurohumaraalisen aktivaation kautta. Levosimendaanin ja OR-1896:n osoitettiin myös parantavan sydämen pumppausfunktiota tyyppi 2 diabeteksen komplisoimassa sydäninfarktissa. Ei-diabeettiseen tilanteeseen verrattuna diabetekseen liittyvä infarktin jälkeinen vajaatoiminnan kehitys oli yhteydessä lisääntyneeseen tulehdukseen, fibroosiin, solukuolemaan, neurohumoraaliseen aktivaatioon ja ennenaikaiseen kudoksen vanhenemiseen. Sekä levosimendaani, että OR-1869 vähensivät tulehduksen, fibroosin ja solukuoleman merkkejä ja vaimensi neurohumoraalista aktivaatiota. OR-1896 myös vähensi solujen vanhenemiseen liittyvien merkkiaineiden ilmentymistä. Väitöskirjassa todettiin, että suun kautta annosteltuna sekä levosimendaani, että sen aktiivinen metaboliitti OR-1896, omaavat terapeuttista potentiaalia sekä hypertensiivisen sydäntaudin hoitoon että sydäninfarktin jälkeisen vajaatoiminnan estoon. FM Marjut Louhelaisen farmakologian alaan kuuluva väitöskirja Effects of oral calcium sensitizers on experimental heart failure tarkastetaan Helsingin yliopiston Lääketieteellisessä tiedekunnassa perjantaina 29.01.2010 klo 12 (Biomedicum Helsinki, luentosali 2, Haartmaninkatu 8, Helsinki). Vastaväittäjänä toimii professori Raimo Tuominen, Helsingin yliopiston Farmasian tiedekunnasta ja kustoksena professori Eero Mervaala Helsingin yliopiston Lääketieteellisestä tiedekunnasta.

Dietary elecrolytes and cyclosporine toxicity. Experimental studies in spontaneuosly hypertensive rats

Cyclosporine-A (CsA) is widely used after organ transplantation to prevent rejection and in the treatment of autoimmune diseases. Hypertension and nephrotoxicity are common side-effects of CsA. Studies in patients on the prevention of the side-effects of CsA are difficult to conduct because the patients often receive a combination of different drugs thus making study of the side-effects of a single drug impossible. A challenge in experimental studies has been the lack of an animal model in which the side-effects concomitantly occur. Epidemiological data show an association between sodium (Na) intake and blood pressure. There is also evidence on low dietary intake of magnesium (Mg) and potassium (K) and high blood pressure. Our study was designed to develop an experimental model to study the side-effects of CsA in spontaneously hypertensive rats (SHR). On high dietary sodium, CsA caused hypertension, left ventricular hypertrophy (LVH), narrowing of the coronary arteries, small myocardial infarctions, and proteinuria, reduced creatinine clearance and histopathological renal injury in SHR. Loss of Mg into the urine caused by CsA resulted in Mg depletion in the tissues. Renal excretion of dopamine was reduced and the renin-angiotensin-aldosterone system was activated. We investigated the effects of dietary Mg and/or K and the calcium antagonist drug, isradipine, on the prevention of CsA toxicity. Dietary supplementation of Mg alone or in combination with K prevented from the deleterious pathophysiological and histopathological changes in the kidneys and the heart. K alone had little effect. Isradipine protected better than Mg from LVH, but the combination of isradipine and Mg was the most effective. Isradipine did not, however, protect against Mg loss. In our animal model, the combination of high dietary Na and treatment with CsA accelerated the development of the cardiovascular and renal changes clinically known as the side-effects of CsA. Dietary supplementation of Mg and K and reduction of Na intake and the calcium antagonist drug isradipine prevent from the deleterious effects of CsA.

Food intake, growth and social interactions of signal crayfish, Pacifastacus leniusculus (Dana)

The knowledge about the optimal rearing conditions, such as water temperature and quality, photoperiod and density, with the understanding of animal nutritional requirements forms the basis of economically stable aquaculture for freshwater crayfish. However, the shift from a natural environment to effective culture conditions induces several changes, not only at the population level, but also at the individual level. The social contacts between conspecifics increase with increasing animal density. The competition for limited resources (e.g. food, shelter, mates) is more severe with the presence of agonistic behaviour and may lead to unequal distribution of these. The objectives of this study were to: 1) study the distribution of a common food resource between communally reared signal crayfish (Pacifastacus leniusculus) and to assign potential feeding hierarchy on the basis of individual food intake measurements, 2) explore the possibilities of size distribution manipulations to affect population dynamics and food intake to improve growth and survival in culture and 3) study the effect of food ration and spatial distribution on food intake and to explore the effect of temperature and food ration on growth and body composition of freshwater crayfish. The feeding ranks between animals were assigned with a new method for individual food intake measurement of communally reared crayfish. This technique has a high feasibility and a great potential to be applied in crayfish aquaculture studies. In this study, signal crayfish showed high size-related variability in food consumption both among individuals within a group (inter-individual) and within individual day-to-day variation (intra-individual). Increased competition for food led to an unequal distribution of this resource and this may be a reason for large growth differences between animals. The consumption was significantly higher when reared individually in comparison with communal housing. These results suggest that communally housed crayfish form a feeding hierarchy and that the animal size is the major factor controlling the position in this hierarchy. The optimisation of the social environment ( social conditions ) was evaluated in this study as a new approach to crayfish aquaculture. The results showed that the absence of conspecifics (individual rearing vs. communal housing) affects growth rate, food intake and the proportion of injured animals, whereas size variation between animals influences the number and duration of agonistic encounters. In addition, animal size had a strong influence on the fighting success of signal crayfish reared in a social milieu with a wide size variation of conspecifics. Larger individuals initiated and won most of the competitions, which suggests size-based social hierarchy of P. leniusculus. This is further supported by the fact that the length and weight gain of smaller animals increased after size grading, maybe because of a better access to the food resource due to diminished social pressure. However, the high dominance index was not based on size under conditions of limited size variation, e.g. those characteristic of restocked natural populations and aquaculture, indicating the important role of behaviour on social hierarchy.

Vitamin E may affect the life expectancy of men, depending on dietary vitamin C intake and smoking

Background: Antioxidants might protect against oxidative stress, which has been suggested as a cause of aging. Methods: The ATBC Study recruited males aged 50-69 years who smoked at least 5 cigarettes per day at the baseline. The current study was restricted to participants who were followed up past the age of 65. Deaths were identified in the National Death Registry (1445 deaths). We constructed Kaplan-Meier survival curves for all participants, and for four subgroups defined by dietary vitamin C intake and level of smoking. We also constructed Cox regression models allowing a different vitamin E effect for low and high age ranges. Results: Among all 10,837 participants, vitamin E had no effect on those who were 65 to 70 years old, but reduced mortality by 24% when participants were 71 or older. Among 2284 men with dietary vitamin C intakes above the median who smoked less than a pack of cigarettes per day, vitamin E extended life-span by two years at the upper limit of the follow-up age span. In this subgroup, the survival curves of vitamin E and no-vitamin E participants diverged at 71 years. In the other three subgroups covering 80% of the participants, vitamin E did not affect mortality. Conclusions: This is the first study to strongly indicate that protection against oxidative stress can increase the life expectancy of some initially healthy population groups. Nevertheless, the lack of effect in 80% of this male cohort shows that vitamin E is no panacea for extending life expectancy.

T-type calcium channel:from physiological function to therapeutical targeting – Exploring neuronal development

Tämän tutkimuksen tarkoitus oli tutkia T-tyypin kalsiumkanavan toimintaa ja sen mahdollista roolia neuronaalisten kantasolujen migraatiossa. T-tyypin kalsiumkanavan tehtävän kehittyneissä aivoissa tiedetään olevan elektroenkefalografisten oskillaatioiden tuottaminen. Nämä taas ovat eräiden fysiologisten ja patofysiologisten tapahtumien säätelyssä avainasemassa. Tällaisia tapahtumia ovat uni, muisti, oppiminen ja epileptiset poissaolokohtaukset. Näiden lisäksi T-tyypin kalsiumkanavalla on myös periferaalisia vaikutuksia, mutta tämä tutkielma keskittyy sen neuronaalisiin toimintoihin. Tämän matalan jännitteen säätelemän kanavan toiminta neurogeneesin aikana on vähemmän tutkittua ja tunnettua kuin sen vaikutukset kehittyneissä aivoissa. T-tyypin kalsiumkanavan tiedetään edistävän kantasolujen proliferaatiota ja erilaistumista neurogeneesiksen aikana, mutta vaikutukset niiden migraatioon ovat vähemmän tunnetut. Tämä tutkimus näyttää T-tyypin kalsiumkanavan todennäköisesti osallistuvan neuronaaliseen migraatioon hiiren alkion subventrikkeli alueelta eristetyillä kanta- tai progeniittorisoluilla tehdyissä kokeissa. Selektiiviset T-tyypin kalsiumkanavan antagonistit, etosuksimidi, nikkeli ja skorpionitoksiini, kurtoxin hidastivat migraatiota erilaistuvissa progeniittorisoluissa. Tämä tutkimus koostuu kirjallisuuskatsauksesta ja kokeellisesta osasta. Tämän tutkimuksen toinen tarkoitus oli esitellä vaihtoehtoinen lähestymistapa invasiiviselle kantasoluterapialle, joka vaatii kantasolujen viljelyä ja siirtämistä ihmiseen. Tämä toinen tapa on endogeenisten kantasolujen eiinvasiivinen stimulointi, jolla ne saadaan migratoitumaan kohdekudokseen, erilaistumaan siellä ja tehtävänsä suoritettuaan lopettamaan jakaantumisen. Non-invasiivinen kantasoluterapia on vasta tiensä alussa, ja tarvitsee farmakologista osaamista kehittyäkseen. Joitain onnistuneita ei-invasiivisia hoitoja on jo tehty selkärangan vaurioiden korjaamisessa. Vastaavanlaisia menetelmiä voitaisiin käyttää myös keskushermoston vaurioiden ja neurodegeneratiivisten sairauksien hoidossa. Näiden menetelmien kehittäminen vaatii endogeenisten kantasoluja inhiboivien ja indusoivien mekanismien tuntemista. Yksi tärkeä kantasolujen erilaistumista stimuloiva tekijä on kalsiumioni. Jänniteherkät kalsiumkanavat osallistuvat kaikkiin neurogeneesiksen eri vaiheisiin. T-tyypin kalsiumkanava, joka ekspressoituu suuressa määrin keskushermoston kehityksen alkuvaiheessa ja vähenee neuronaalisen kehityksen edetessä, saattaa olla oleellisessa asemassa progeniittorisolujen ohjaamisessa.