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Home: Papers of the Week
Annotation


Jonsson T, Atwal JK, Steinberg S, Snædal J, Jonsson PV, Bjornsson S, Stefansson H, Sulem P, Gudbjartsson D, Maloney J, Hoyte K, Gustafson A, Liu Y, Lu Y, Bhangale T, Graham RR, Huttenlocher J, Bjornsdottir G, Andreassen OA, Jönsson EG, Palotie A, Behrens TW, Magnusson OT, Kong A, Thorsteinsdottir U, Watts RJ, Stefansson K. A mutation in APP protects against Alzheimer's disease and age-related cognitive decline. Nature. 2012 Aug 2;488(7409):96-9. PubMed Abstract

  
Comments on Paper and Primary News
  Primary News: Protective APP Mutation Found—Supports Amyloid Hypothesis

Comment by:  Eric M. Reiman, ARF Advisor
Submitted 13 July 2012  |  Permalink Posted 13 July 2012

This elegant and important study finds an association between a rare APP variant and a lower risk of AD, and it provides strong evidence to suggest that the protective effects of this variant may be attributable to reductions in BACE1-mediated APP cleavage. This study provides additional support for the amyloid hypothesis and the potential role of BACE1 inhibitors in the preclinical treatment of AD. It also illustrates the potential value of whole-genome sequencing studies, when used in conjunction with relevant basic scientific research, to advance the understanding of AD and the discovery of promising investigational treatments.

This study only adds to the interest that my Alzheimer's Prevention Initiative (API) colleagues, other researchers, and I have in the possibility of evaluating suitable BACE1 inhibitors (and related agents) in persons at increased risk of developing AD, and our interest in learning more about safety, tolerability, and certain other effects in clinically affected patients. We see particular value in the possibility of evaluating anti-amyloid...  Read more


  Primary News: Protective APP Mutation Found—Supports Amyloid Hypothesis

Comment by:  Luciano D'Adamio
Submitted 15 July 2012  |  Permalink Posted 18 July 2012

I agree with the comments underlying the importance of this paper, which supports the pathogenic role of APP processing by BACE in sporadic AD. As noted in many comments, these findings also suggest that inhibition of BACE processing of APP will be a beneficial therapeutic approach for both familial and sporadic AD. Perhaps, this treatment may also improve performance in elderly with no obvious cognitive deficiency. BACE1 inhibitors may, however, have toxic effects related to the important biological functions of BACE processing of other substrates. Therefore, as noted by Dr. Tanzi, "inhibitors might need to be selective for APP in order to be safe enough for such long-term use." Interestingly, a molecule with these features has been recently described—MoBA, Modulator of Β-processing of APP (Tamayev et al., 2012), and may represent a leading compound to develop drugs that interfere with BACE1 processing of APP without inhibiting the proteolytic activity of BACE1 on the other substrates.

However, contrary to what is said by many, I do not think that the finding validates or...  Read more


  Primary News: Protective APP Mutation Found—Supports Amyloid Hypothesis

Comment by:  Michael Castello, Salvador Soriano, Matthew Zabel
Submitted 16 July 2012  |  Permalink Posted 18 July 2012

New APP Mutation Does Not Advance the Amyloid Hypothesis Debate
In response to the question, Does β amyloid accumulation drive Alzheimer’s disease?, the answer is “most likely no,” and the new data presented by Jonsson et al. does not change that answer.

That the amyloid hypothesis inadequately accounts for the current data has been known for some time. It lacks a theoretical foundation from which the physiological generation of Aβ can be understood, and therapeutic approaches based on its premises have all failed. Furthermore, there is no significant correlation between Aβ accumulation and cognitive deterioration in either humans or in mouse models, and Aβ-containing senile plaques have been found in the brains of approximately 30 percent of individuals with no signs of dementia (Crystal et al., 1988; Price et al., 2009).

This does not necessarily indicate that Aβ is not a key factor in AD. The weakness of the amyloid hypothesis is not that it links Aβ and AD, but rather that it places Aβ as the key pathogenic trigger of the disease and, accordingly, ought...  Read more


  Primary News: Protective APP Mutation Found—Supports Amyloid Hypothesis

Comment by:  Jens Pahnke
Submitted 17 July 2012  |  Permalink Posted 18 July 2012

This is a nice finding by Jonsson et al., and adds more evidence to the idea published in 2009 by an Italian group that changes to this amino acid position in APP can prevent or facilitate aggregation of human Aβ.

It seems that amino acids at position 2 of hAβ with larger side chains than alanine may prevent aggregation. Di Fede showed that a transition, A2V, in Aβ was protective in heterozygotes, whereas homozygotic individuals had a higher risk in the studied family tree.

They also presented aggregation profiles of pure and mixed Aβ species that nicely supported the aggregation idea. Thus, the question remains whether it is indeed a BACE-related mechanism or just an aggregation problem of these Aβ species due to stereology. In our hands, cerebral injection and chronic infusion of A2V Aβ1-6 peptides reduced plaque formation in mice. That could be exploited as a treatment option (unpublished data).

As we know, mouse Aβ is different in three amino acids at the N-terminal, and these differences completely prevent plaque formation and fibril generation in mice.

References:
Di Fede G, Catania M, Morbin M, Rossi G, Suardi S, Mazzoleni G, Merlin M, Giovagnoli AR, Prioni S, Erbetta A, Falcone C, Gobbi M, Colombo L, Bastone A, Beeg M, Manzoni C, Francescucci B, Spagnoli A, Cantù L, Del Favero E, Levy E, Salmona M, Tagliavini F. A recessive mutation in the APP gene with dominant-negative effect on amyloidogenesis. Science. 2009 Mar 13;323(5920):1473-7. Abstract

Giaccone G, Morbin M, Moda F, Botta M, Mazzoleni G, Uggetti A, Catania M, Moro ML, Redaelli V, Spagnoli A, Rossi RS, Salmona M, Di Fede G, Tagliavini F. Neuropathology of the recessive A673V APP mutation: Alzheimer disease with distinctive features. Acta Neuropathol. 2010 Dec;120(6):803-12. Abstract

View all comments by Jens Pahnke


  Primary News: Protective APP Mutation Found—Supports Amyloid Hypothesis

Comment by:  Sanjay W. Pimplikar
Submitted 18 July 2012  |  Permalink Posted 24 July 2012

This study provides elegant genetic evidence that reducing the BACE processing of APP protects against late-onset AD. The finding complements the long-standing observations that increased BACE processing (APPswe mutation or elevated BACE levels [1]) enhances the risk for AD.

What gets ignored in ensuing discussions, however, is the fact that BACE processing of APP generates not only Aβ peptides, but also β-CTFs and AICD peptides (studies from three groups show that BACE processing enhances AICD generation and signaling [2-4]). Since both β-CTF and AICD cause AD-like pathological features in vivo in mouse models (5,6), the present study is consistent with, but cannot be claimed to support, the amyloid hypothesis (the causal role of Aβ in AD).

Nonetheless, this study is important because it identifies a unique human population (A673T carriers) that can be used to further validate neuroimaging (PIB imaging) and CSF biomarkers. Indeed, it will be very informative to see whether biomarker changes in this population appear at the same time as in the non-carriers or are...  Read more

Comments on Related News
  Related News: Wave of New BACE Inhibitors Heading to Phase 2

Comment by:  Michael Castello, Salvador Soriano, Matthew Zabel
Submitted 31 July 2012  |  Permalink Posted 3 August 2012

What could possibly go wrong with the use of BACE inhibitors for the prevention or treatment of AD?

The latest flurry of results from pharmaceutical companies showing that BACE inhibitors reduce the levels of amyloid-β in the brain has led to a renewed wave of optimism that this approach may lead to an effective treatment for AD, possibly even a cure. This optimism has been amplified by the recent report of a mutation in the APP gene, A673T, that reduces BACE activity and protects against AD (Jonsson et al., 2012).

We have recently suggested that there is a plausible explanation for the effect of the APP A673T mutation on AD rates that goes beyond the conventional wisdom of “less Aβ protects, more Aβ harms” involving a fine-tuning effect on Aβ levels by the A673T mutation that improves the adaptive response of APP to AD-causing brain stress (Castello and Soriano, 2012). In other words, there is likely a range of Aβ that optimizes the adaptive response of APP to brain stress, and the A673T mutation helps to maintain Aβ levels within that range.

It is very unlikely...  Read more


  Related News: Wave of New BACE Inhibitors Heading to Phase 2

Comment by:  Trent Nichols
Submitted 20 August 2012  |  Permalink Posted 21 August 2012

BACE1 inhibition is an important potential theurapeutic arm of the β amyloid clearance phenomenon in Alzheimer's which needs to be realized clinically.

However, another BACE1 inhibitor, minocycline, which is also neuroprotective and is already an approved therapeutic agent, is now undergoing trials in cognitively normal individuals and patients with mild cognitive impairment (MCI) or Alzheimer's disease (AD) at Huntington Medical Research Institute. Patients and controls will undergo clinical screening, neuropsychological tests, blood and urine analyses, quantitative magnetic resonance imaging (MRI), and 1H and 13C magnetic resonance spectroscopy (MRS). Each individual will receive minocycline oral administration for four weeks initially, after which MRI, MRS, and neuropsych results will be recorded. If no adverse side effects occur, subjects will continue minocycline administration for an additional five months.

A study by Ferretti demonstrated recently that minocycline corrects early, pre-plaque neuroinflammation and inhibits BACE1 in a transgenic model of Alzheimer's...  Read more

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