On 2017 Apr 01, Misha Koksharov commented:

The findings are really interesting! I hope there will be further publications elucidating how Per2 regulates response to food anticipation and fasting.

I have a few questions/comments.

1) To what extent the peak of the 3-OH-butyrate (3HB) at ZT4 (under RF) is just due to fasting? Is there an entrainment contribution to the peak magnitude? For example, the peak level could decrease/increase or stay the same following the entrainment during multiple days under RF.

3HB levels are usually considerably increased in response to fasting. Here it was 16 hour fasting every day. The ~2-fold increase is similar to what was reported for C57BL after 14h fasting (Lin X, 2005). Interestingly, in the recent paper by Chikahisa S, 2014 there was a 4-fold increase after just 6h of fasting but looks like it's specific to their mouse strain (Jcl/IC).

2) Do these results actually mean that mice with liver Per2 KO are unable to increase ketone body synthesis in response to fasting? Or does it just occur later than usual? It seems really interesting if Per2 is important for proper response to fasting.

3) The title says "ketone bodies."

So, have you looked at acetoacetate - the second ketone body? How did it change under AL, RF, fasting? It is known to be increased by fasting as well - similar to 3HB (Chikahisa S, 2014).

Maybe, the release of the relevant amount (or compensation by higher concentration of 3HB) would further improve the rescue.

4) Can the FA in response to 3HB be essentially an example of a conditional training similar to what can be done with visual or sound signals?

It takes 5 days for them to learn to have FA at ZT4. So one can imagine the following situation: (1) 3HB, AcAc levels are increased by 16h fasting every day; (2) mouse brain senses the 3HB levels in the blood and converts them into perceived hunger levels; (3) mice learn after some time that this peak (level of hungriness) corresponds to the long-sought appearance of food;

In this case it would be possible to similarly train them to show FA in response to odors, sounds.

5) Were the metabolites measured only at one specific day or also at the same ZT points several times throughout these 45 days?

6) Fig. S5a

Is there still this weak cycling of 3HB under AL in Per2 KO?

On 2017 Apr 01, Misha Koksharov commented:

The findings are really interesting! I hope there will be further publications elucidating how Per2 regulates response to food anticipation and fasting.

I have a few questions/comments.

1) To what extent the peak of the 3-OH-butyrate (3HB) at ZT4 (under RF) is just due to fasting? Is there an entrainment contribution to the peak magnitude? For example, the peak level could decrease/increase or stay the same following the entrainment during multiple days under RF.

3HB levels are usually considerably increased in response to fasting. Here it was 16 hour fasting every day. The ~2-fold increase is similar to what was reported for C57BL after 14h fasting (Lin X, 2005). Interestingly, in the recent paper by Chikahisa S, 2014 there was a 4-fold increase after just 6h of fasting but looks like it's specific to their mouse strain (Jcl/IC).

2) Do these results actually mean that mice with liver Per2 KO are unable to increase ketone body synthesis in response to fasting? Or does it just occur later than usual? It seems really interesting if Per2 is important for proper response to fasting.

3) The title says "ketone bodies."

So, have you looked at acetoacetate - the second ketone body? How did it change under AL, RF, fasting? It is known to be increased by fasting as well - similar to 3HB (Chikahisa S, 2014).

Maybe, the release of the relevant amount (or compensation by higher concentration of 3HB) would further improve the rescue.

4) Can the FA in response to 3HB be essentially an example of a conditional training similar to what can be done with visual or sound signals?

It takes 5 days for them to learn to have FA at ZT4. So one can imagine the following situation: (1) 3HB, AcAc levels are increased by 16h fasting every day; (2) mouse brain senses the 3HB levels in the blood and converts them into perceived hunger levels; (3) mice learn after some time that this peak (level of hungriness) corresponds to the long-sought appearance of food;

In this case it would be possible to similarly train them to show FA in response to odors, sounds.

5) Were the metabolites measured only at one specific day or also at the same ZT points several times throughout these 45 days?

6) Fig. S5a

Is there still this weak cycling of 3HB under AL in Per2 KO?