Pharmacotherapy and evolution Hofbauer, Karl G.; Huppertz, Christine
Trends in Ecology & Evolution,
07/2002, Letnik:
17, Številka:
7
Book Review, Journal Article
Recenzirano
The therapeutic effects of a drug are the result of its action on a specific molecular target combined with the counterregulatory responses of the organism that aim to restore the affected parameters ...to previous values. The regulatory systems that control the steady state have evolved under natural selection, but because natural selection is a slow process and cannot foresee future developments, these systems are not always adjusted optimally to current conditions. Their activation can therefore reduce or prevent the desired effects of a drug and can even produce adverse effects. Recent examples from the treatment of obesity and arterial hypertension provide new insight to the contribution of such ancient counterregulatory responses to the therapeutic effects of modern pharmacotherapy. This widens the scope of the rapidly growing field of evolutionary medicine, because it demonstrates that evolutionary principles apply not only to the pathogenesis of human diseases, but also to their treatment.
The treatment of obesity and arterial hypertension provides new insight about the contribution of ancient counterregulatory responses to modern pharmacotherapy and demonstrates that evolutionary principles apply to the treatment of human diseases.
A polymerase chain reaction-based cloning approach was employed in order to identify ADP-ribosylation factors (ARF) in murine
3T3-L1 cells and to study their expression before and after ...differentiation of cells to the adipocyte-like phenotype. Partial
sequences comprising the effector domains of ARF were amplified with degenerate primers and cloned. Five of these sequences
were identified as murine homologues of known human ADP-ribosylation factors (ARF 1, 2, 4, 5, and 6). In addition, partial
sequences of two previously unknown isoforms were found, and complete cDNA clones were isolated from a rat fat cell library
and were sequenced. Both sequences harbor a putative myristoylation site in position 2, the known consensus sequences presumably
involved in GTP binding and hydrolysis, and lack cysteine residues in the C terminus. Their amino acid sequences share a 56
and 41% identity, respectively, with human ARF 1. Based on a comparison with the known ARF isoforms, the first clone appears
to represent the mammalian homologue of a known sequence from Drosophila (dARL 1, 79% identity) and was therefore designated
rARL 1. The second clone resembled none of the known ARF-like proteins and was designated rARL 4. mRNA of ARL 4 was undetectable
in the fibroblasts but abundant in the adipocyte-like phenotype, its expression starting on day 6 of the differentiation.
In contrast, ARF 1, 2, and 5 were unaltered by differentiation of the 3T3-L1 cells; mRNA levels of ARF 6, and also of ARL
1 and ARF 4, were reduced after differentiation. It is suggested that the function of ARL 4 is related to the adipocyte-like
phenotype of 3T3-L1 cells.
The PPP1R3 gene encoding the G-subunit of protein phosphatase-1 has three polymorphisms in linkage disequilibrium in the Pima Indians: an mRNA-destabilizing element in the 3′-untranslated region ...(ARE1/ARE2 alleles), Arg883Ser, and Asp905Tyr substitutions. The ARE2 allele, Arg883, and Asp905 variants are associated with insulin resistance and higher prevalence of type 2 diabetes in the Pima Indians. The ARE2 allele is associated with lower PPP1R3 transcript and protein levels in muscle tissue. Here we determined the functional contribution of the amino acid substitutions independent of the ARE alleles to insulin-stimulated glycogen synthesis by adenoviral-mediated gene expression in L6 myotubes. Similar overexpression levels of the G-subunit variants increased glycogen synthase fractional activity in the presence (∼1.5-fold) of insulin compared to control myotubes transduced with adenovirus encoding β-galactosidase. The glycogen synthesis rate of myotubes overexpressing the G-subunit variants also increased by ∼1.7-fold over the control with and without insulin. However, these measures were not significantly different among the variants. This study does not support a role for Arg883 and Asp905 variants independent of the ARE2 allele in the impaired insulin-stimulated glycogen synthesis in the muscle of Pima Indians.
The role of the actin cytoskeleton and/or GTPases of the Rho/Rac-family in glucose transport regulation was investigated in 3T3-L1 cells with clostridial toxins which depolymerize actin by ...inactivation of Rho/Rac (Clostridium difficile toxin B and Clostiridium sordellii lethal toxin (LT)) or by direct ADP-ribosylation (Clostridium botulinum C2 toxin). Toxin B and C2 reduced insulin-stimulated, but not basal, 2-deoxyglucose (2-DOG) uptake rates in 3T3-L1 fibroblasts. In parallel, the toxins produced morphological alterations of the cells reflecting disruption of the actin cytoskeleton. Both toxins reduced the maximum response to insulin but failed to alter the half-maximally stimulating concentrations of insulin. In 3T3-L1 adipocytes, the lethal toxin reduced the effect of insulin on 2-DOG uptake, whereas toxin B and C2 failed to affect glucose transport or cell morphology. When cells were exposed to the toxins after treatment with insulin, both toxin B and the lethal toxin, in contrast to the phosphatidylinositol (PI) 3-kinase inhibitor wortmannin, failed to reduce the 2-DOG uptake rates. Thus, both translocation to the plasma membrane and internalization of glucose transporters were inhibited by the toxins, whereas the PI 3-kinase inhibitor selectively affects translocation. The data suggest that the effects of the clostridial toxins on trafficking of glucose transporters are mediated by the depolymerization of the actin cytoskeleton and are an indirect consequence of Rho or Rac inactivation. It is suggested that pathways signalling through Rac or Rho may play a modulatory role in glucose transport regulation through their effects on the actin network.
The abundance and the subcellular distribution of GTP‐binding proteins was studied in membrane fractions (plasma membranes and low‐density microsomes) from 3T3‐L1 cells before and after ...differentiation to the insulin‐sensitive phenotype. After differentiation, the abundance of αi (α subunit of GTP‐binding protein Gi), αi (α subunit of GTP‐binding protein Gi), and of a 47‐kDa αs, (α subunit of GTP‐binding protein Gs) as detected by immunoblotting with specific antisera was reduced by 10–50% when normalized per membrane protein. In contrast, a 43‐kDa αs was increased about threefold after differentiation. Furthermore, cholera‐toxin‐catalyzed ADP‐ribosylation of both 43‐kDa and 47‐kDa αs was disproportionately increased ninefold and threefold, respectively, possibly reflecting the increased production of an ADP‐ribosylation factor in the differentiated cells. The small GTP‐binding protein Ha‐ras was reduced by 50%, whereas rab1 and other small GTP‐binding proteins tentatively identified as rab‐isoforms (ras‐homologous gene products from brain) were increased by 100% and 70%, respectively. Since the total protein content of 3T3‐L1 cells was increased threefold after differentiation, the observed increase of the 43‐kDa αs, rab1 and of the other rab isoforms was eightfold, sixfold and fivefold, respectively, when normalized/cell count. With the exception of the rab isoforms, all GTP‐binding proteins were predominantly, if not exclusively, located in the plasma membrane; comparable amounts of the rab isoforms were found in plasma membranes and low‐density microsomes. Insulin induced the characteristic redistribution of glucose transporters GLUT4 from low‐density microsomes to the plasma membranes, but failed to alter the subcellular distribution of any of the GTP‐binding proteins investigated. These data suggest that the increase in the abundance of the 43‐kDa αs subunit and of several rab isoforms might be related to specific functions of the adipocyte‐like phenotype, but that none of the investigated guanine‐nucleotide‐binding regulatory (G)‐proteins appears to be tightly associated with the GLUT4.
OBJECTIVE:To assess the utility of serum neurofilament for diagnosis and monitoring of primary progressive aphasia (PPA) variants.
METHODS:We investigated neurofilament light chain (NF-L) levels in ...blood of 99 patients with PPA (40 with nonfluent variant PPA nfvPPA, 38 with semantic variant PPA svPPA, 21 with logopenic variant PPA lvPPA) and compared diagnostic performance with that reached by CSF NF-L, phosphorylated neurofilament heavy chain (pNF-H), β-amyloid (Aβ1-42), tau, and phosphorylated tau. The longitudinal change of blood NF-L levels was measured and analyzed for correlation with functional decline and brain atrophy.
RESULTS:Serum NF-L is increased in PPA compared to controls and discriminates between nfvPPA/svPPA and lvPPA with 81% sensitivity and 67% specificity (cutoff 31 pg/mL). CSF NF-L, pNF-H, tau, phosphorylated tau, and Aβ1-42 achieved similar performance, and pNF-H was the only marker for discrimination of nfvPPA from svPPA/lvPPA. In most patients with nfvPPA and svPPA, but not lvPPA, serum NF-L increased within follow-up. The increase correlated with functional decline and progression of atrophy of the left frontal lobe of all patients with PPAs and the right middle frontal gyrus of patients with nfvPPA and svPPA.
CONCLUSIONS:Blood level of NF-L can aid the differential diagnosis of PPA variants, especially in combination with CSF pNF-H. Because serum NF-L correlates with functional decline and atrophy in the disease course, it qualifies as an objective disease status marker. Extended follow-up studies with cases of known neuropathology are imperative.
CLASSIFICATION OF EVIDENCE:This study provides Class I evidence that in patients with PPA, blood levels of NF-L can distinguish the logopenic variant from the nonfluent/agrammatic and semantic variants.
OBJECTIVETo determine the association of serum neurofilament light chain (NfL) with functional deterioration and brain atrophy during follow-up of patients with behavioral variant frontotemporal ...dementia (bvFTD).
METHODSBlood NfL levels from 74 patients with bvFTD, 26 with Alzheimer disease (AD), 17 with mild cognitive impairment (MCI), and 15 healthy controls (Con) at baseline and follow-up were determined and analyzed for the diagnostic potential in relation to functional assessment (Clinical Dementia Rating Scale Sum of Boxes CDR-SOB, frontotemporal lobar degeneration–related CDR-SOB, Mini-Mental State Examination MMSE) and brain volumetry.
RESULTSAt baseline, serum NfL level correlated with CSF NfL (bvFTD r = 0.706, p < 0.0001; AD/MCI r = 0.666, p = 0.0003). Highest serum levels were observed in bvFTD (p <0 0.0001 vs Con and MCI, p = 0.0078 vs AD, respectively). Discrimination of bvFTD from Con/MCI/AD was possible with 91%/74%/74% sensitivity and 79%/74%/58% specificity. At follow-up, serum NfL increased in bvFTD and AD (p = 0.0039 and p = 0.0006, respectively). At baseline and follow-up, NfL correlated with functional scores of patients with bvFTD (e.g., CDR-SOB baseline r = 0.4157, p = 0.0006; follow-up r = 0.5629, p < 0.0001) and with atrophy in the gray and white matter of many brain regions including frontal and subcortical areas (e.g., frontal lober = −0.5857, p < 0.0001; 95% confidence interval −0.7415 to −0.3701). For patients with AD/MCI, NfL correlated with the functional performance as well (e.g., CDR-SOB baseline r = 0.6624, p < 0.0001; follow-up r = 0.5659, p = 0.0003) but not with regional brain volumes.
CONCLUSIONSAs serum NfL correlates with functional impairment and brain atrophy in bvFTD at different disease stages, we propose it as marker of disease severity, paving the way for its future use as outcome measure for clinical trials.
CLASSIFICATION OF EVIDENCEThis study provides Class III evidence that for patients with cognitive problems, serum NfL concentration discriminates bvFTD from other forms of dementia.
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