Multimodal Precision Prevention - A New Direction in Alzheimer's Disease

At least 40% of all dementia has been linked to modifiable risk factors suggesting a clear potential for preventative approaches targeting these factors. Despite the recent promising findings from anti-amyloid monoclonal antibodies, a limited proportion of patients are expected to be eligible for these novel AD treatments. Given the heterogeneous nature of AD and the complex multi-level pathological processes leading to dementia (involving, e.g., shared risk factors, interaction of different pathology mechanisms, and their putative synergistic effects on cognition), targeting a single pathology may not be sufficient to halt or significantly impact disease progression. With exponentially increasing numbers of patients world-wide, in parallel to the unprecedented population ageing, new multimodal therapy approaches targeting several modifiable risk factors and disease mechanisms simultaneously are urgently required. Developing the next generation of combination therapies with lifestyle intervention and pharmacological treatments, implementing the right interventions for the right people at the right time, and defining accessible and sustainable strategies worldwide are crucial. Here, we summarize the state-of-the-art multimodal lifestyle-based approaches, especially findings and lessons learned from the FINGER trial, for prevention and risk reduction of cognitive impairment and dementia. We also discuss some emerging underlying biological mechanisms and the current development of precision prevention approaches. We present an example of a novel trial design combining healthy lifestyle changes with a repurposed putative disease-modifying drug and place this study in the context of the World-Wide FINGERS, the first interdisciplinary network of multimodal trials dedicated to the prevention and risk reduction of cognitive impairment and dementia.

Effect of N omega-nitro-L-arginine methyl ester, a nitric oxide synthesis inhibitor, on stress- and morphine-induced prolactin release in male rats

1. The effect of the nitric oxide synthesis inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) was investigated on stress- and morphine-induced prolactin (PRL) secretion in vivo in male rats, by use of a stress-free blood sampling and drug administration method by means of a permanent indwelling catheter in the right jugular vein. 2. Three doses of L-NAME were tested (1, 10 and 30 mg kg-1) and were given intraperitoneally one hour before blood sampling; control rats received saline. After the first blood sample, rats received an initial intravenous injection of morphine (3, 6 or 12 mg kg-1) or were subjected to immobilization stress. In the case of a morphine administration, rats received a second dose of morphine (3, 6 or 6 mg kg-1, respectively) 90 min later, when tolerance had developed, while rats subjected to immobilization stress received 6 mg kg-1 morphine 90 min after onset of stress. 3. L-NAME had no effect on basal plasma PRL concentration. However, it potentiated acute morphine-induced PRL secretion and attenuated the subsequent tolerance in a dose-dependent way. Immobilization stress-induced PRL secretion was inhibited dose-dependently by L-NAME, as was its subsequent tolerance to morphine; however, in this case, in a reversed dose-dependent way. 4. When the highest dose of morphine (12 mg kg-1) was combined with the highest dose of L-NAME pretreatment (30 mg kg-1), all rats showed a dramatic potentiation of the morphine-induced PRL rise compared to controls. Moreover, all of these rats died within 90 min after the administration of morphine. 5. These results show that NO plays a role in the acute opioid action on PRL release during stress as well as in the development of tolerance to the opioid effect, and some possible mechanisms are discussed.

Molecular heterogeneity and glycosylation modulation of rat pituitary prolactin isoforms synthesized and secreted in vitro in postnatal ontogeny, gestation, lactation and weaning

The modulation of both the molecular size heterogeneity and the relative distribution of rat prolactin variants, synthesized and secreted in vitro by rat pituitary cells in the course of postnatal ontogeny and in gestation, lactation and weaning was investigated by SDS-PAGE, immunoblotting, radioimmunological techniques and O-sialoendopeptidase digestion. The outcome of the experiments is as follows: 1) from day 1 of postnatal life 20-, 23-, 26-, 40-44 kDa and oligomeric rat prolactin isoforms were stored and secreted; 2) perinatal life is characterized by a high degree of variability of prolactin size isoforms and their respective repartition in storage and release; in addition to the major variants, transient ones of M, 25-, 28-, 33- and 36 kDa were secreted and/or stored; 3) O-sialoglycoprotease digestion of pituitary cell lysate gave good evidence for 25 kDa prolactin being a glycoform; 4) at 1 month of age 16 kDa rat prolactin appeared and persisted over the whole postnatal span (1 day-->1 year) but only in stored form; 5) the physiology of gestation was essentially characterized by the M(r)-modulation of the glycoform (26 kDa-->26.3 kDa) and the virtual absence of stored 26 kDa rat prolactin at week 1 of pregnancy; 6) in lactation and weaning uncommon multiple banding was observed in secreted oligomeric prolactin; 7) in pregnancy, lactation and weaning the differential distribution of released and stored prolactin isoforms displayed a considerable intra- and intervariability; 8) in the vast array of size isoforms observed in all our experiments monomeric 23 kDa prolactin was always the dominating variant. In conclusion, the molecular size heterogeneity and the differential distribution of secreted and stored rat pituitary prolactin is considerably influenced by age and physiological stimuli. The nature of polymeric prolactin and of the transient variants is presently unclear, and the exact physiological role of molecular heterogeneity modulation is unknown, both in humans and rat, but the patterns of change we observed in definite stages of life, suggest that this phenomenon is important in the maturation of the hypothalamus-pituitary axis and in the metabolic and hormonal changes accompanying gestation.

Modulating effect of the nootropic drug, piracetam on stress- and subsequent morphine-induced prolactin secretion in male rats

1. The effect of the nootropic drug, piracetam on stress- and subsequent morphine-induced prolactin (PRL) secretion was investigated in vivo in male rats, by use of a stress-free blood sampling and drug administration method by means of a permanent indwelling catheter in the right jugular vein. 2. Four doses of piracetam were tested (20, 100, 200 and 400 mg kg-1), being given intraperitoneally 1 h before blood sampling; control rats received saline instead. After a first blood sample, rats were subjected to immobilization stress and received morphine, 6 mg kg-1, 90 min later. 3. Piracetam had no effect on basal plasma PRL concentration. 4. While in the non-piracetam-treated rats, stress produced a significant rise in plasma PRL concentration, in the piracetam-pretreated rats PRL peaks were attenuated, especially in the group given 100 mg kg-1 piracetam, where plasma PRL concentration was not significantly different from basal values. The dose-response relationship showed a U-shaped curve; the smallest dose had a minor inhibitory effect and the highest dose had no further effect on the PRL rise. 5. In unrestrained rats, morphine led to a significant elevation of plasma PRL concentration. After the application of immobilization stress it lost its ability to raise plasma PRL concentration in the control rats, but not in the piracetam-treated rats. This tolerance was overcome by piracetam in a significant manner but with a reversed dose-response curve; i.e. the smaller the dose of piracetam, the higher the subsequent morphine-induced PRL peak. 6. There is no simple explanation for the mechanism by which piracetam induces these contradictory effects. Interference with the excitatory amino acid system, which is also involved in opiate action, is proposed speculatively as a possible mediator of the effects of piracetam.

Secretion of 23 kDa and glycosylated prolactin by rat pituitary cell culture in serum-free media: a comparative morphological, cyto- and immunochemical study

The secretion of 23 kDa prolactin by rat pituitary cells has been thoroughly investigated, but secretion of glycosylated rat prolactin is not currently known. This is mainly due to the lack of an antiserum which is solely specific for glycosylated rat prolactin and therefore we studied the basal secretion of this variant by an indirect method. Rat pituitary cells were cultured in total culture medium and three different serum-free media (DMEM, keratinocyte-serum-free medium, protein-free hybridoma medium) and secretion of 23 kDa and glycosylated rat prolactin was recorded by radioactive techniques and immunoblotting. The pituitary cell quality was monitored by electron microscopy, cell activation-and cell death assessment. In short-range culture (2 days) the pituitary cell quality and behaviour was very good and comparable in total culture medium, DMEM and keratinocyteserum-free medium, i.e. numerous secretory granules, moderate amount of ER, cristae well in place in the mitochondriae. In medium-range culture (8 days) only cells cultured in total culture medium and DMEM presented a parallel behaviour: migration of cells toward each other, marked degranulation, massive array of ER. The inner membrane of the mitochondria was no longer folded into cristae leaving an unoccupied central space. At day 2 of the culture span secretion of 23 kDa rat prolactin was very comparable in all media used; hereafter, secretion of 23 kDa rat prolactin in total culture medium and DMEM assumed the well known pattern of peaking and slowing down, whereas in the other serumfree media it steadily decreased over the culture span. Pertaining to the important novel point of glycosylated rat prolactin secretion, it was low in comparison to the one of 23 kDa rat prolactin and it assumed a near steady pattern in all media used. 26 kDa rat prolactin was identified as the preferentially secreted glycoform, and the 23 kDa isoform as the major secretory product of rat pituitary lactotroph cells.

Identification and localization of 23,000 and glycosylated rat prolactin in subcellular fractions of rat anterior pituitary and purified secretory granules

Rat pituitary homogenates were submitted to differential and density gradient centrifugation. Subcellular fractions as well as the purified secretory granules were examined in electron microscopy, radioimmunological techniques, protease digestion, alkaline treatment and immunoblotting. The global outcome of these experiments was that: 1) the glycosylated rPRL was foremost recorded in the crude secretory granular fraction, also in the microsomal fraction and the cytosol, but virtually not in the plasma membrane fraction; 2) in purified secretory granules glycosylated rPRL appeared as an array of near Mr, such as was formerly obtained by enzymatic deglycosylation; 3) protease digestion and ice-cold alkaline treatment of the secretory granules showed that 23,000 rPRL appears in three different physicochemical states in these organelles: unsequestered within a closed system, membrane-bounded and bound state; 4) likewise treatment of microsomal vesicles showed that 23,000 and glycosylated rPRL are sequestered in these bodies, but apparently 23,000 rPRL appears as both integral membrane-bound and released from the lumen, whereas glycosylated rPRL is chiefly retained as an integral membrane protein. 5) dopamine alters the pattern of glycosylation as well in Mr as in relative percentages of the molecular variants. The systematical occurrence of the array of near Mr glycosylated rPRL is biosynthesized as a pool of proteins with a different degree of glycosylation. On the basis of our data, we speculate that selection of definite molecular variants from this pool could play an important role in the biological function of 23,000 rPRL and that oligosaccharides could perhaps target the glycosylated forms of rPRL to specific sites of action.

Analysis of the receptor specificity of tolerance induction in stress versus opioid-related prolactin secretion in rats

The effects of restraint stress and opiates on prolactin secretion in male rats have been measured. Both induced a short-lived increase in prolactinaemia. Experimental evidence indicates that both opioids and restraint stress bring about their actions by the activation of opioid receptors. When restraint stress was followed by administration of the specific kappa-agonist bremazocine, a second prolactin peak was observed. In contrast, morphine (predominantly a mu-agonist) lost its prolactin-stimulating capacity when given after a period of restraint stress. This indicates cross-tolerance between restraint stress and morphine. Tolerance was overcome when the dose of morphine was doubled, and an increase in prolactin secretion could again be obtained. The cross-tolerance phenomenon argues that a common opioid receptor is involved in morphine- and restraint stress-stimulated prolactin release. In another set of experiments, in which morphine administration replaced restraint stress as a means of inducing tolerance, a second rise in prolactinaemia was seen only with bremazocine and not with a further administration of morphine. This suggests a morphine (mu) receptor-specific development of tolerance. Two consecutive administrations of bremazocine also produced tolerance, in this case for the kappa-receptor. This illustrates the rapid and receptor-specific development of tolerance for the prolactin-releasing capacity of opioid compounds.

The growth hormone secretory response to fentanyl in rat: an involvement of mu type receptors

Fentanyl, a selective mu opioid receptor agonist, administered intravenously, influences growth hormone secretion in conscious male rats. A dose-response study demonstrated that the maximum growth hormone release was obtained with 10 micrograms/kg while higher doses were less or not effective. MR-2266 (6 mg/kg i.v.), a mu and kappa opioid receptor antagonist, and bremazocine (0.1 mg/kg i.v.) a mu opioid receptor antagonist with kappa agonistic properties, both potently inhibited the growth hormone response to fentanyl (10 micrograms/kg i.v.). In contrast, the effect of fentanyl on growth hormone release was not blocked in rats treated with either ICI-154129 (30 mg/kg i.v. or 150 micrograms/kg intracerebroventricularly a selective delta opioid receptor antagonist, or U-50488 (10 mg/kg i.v.), a specific kappa opioid receptor agonist. These results suggest that opioid receptors of the mu type are involved in the fentanyl-induced growth hormone release.