Message Number: FHL12185 | New FHL Archives Search
From: Sukie Crandall
Date: 2010-09-08 13:17:23 UTC
Subject: [ferrethealth] Re: ?? for moderator
To: fhl <ferrethealth@yahoogroups.com>

Talk about a timely new study!

=95 K.J. Brothers et al. Rescue of obesity-induced infertility in=20
female mice due to a pituitary-specific knockout of the insulin=20
receptor. Cell Metabolism. Vol. 12, September 8, 2010, p. 295. doi:=20
10.1016/j.cmet.2010.06.010

> Researchers led by Andrew Wolfe of Johns Hopkins University stumbled=20
> upon the discovery


http://www.cell.com/cell-metabolism/abstract/S1550-4131%2810%2900270-6

> Obesity is associated with insulin resistance in metabolic tissues=20
> such as adipose, liver, and muscle, but it is unclear whether=20
> nonclassical target tissues, such as those of the reproductive axis,=20
> are also insulin resistant. To determine if the reproductive axis=20
> maintains insulin sensitivity in obesity in vivo, murine models of=20
> diet-induced obesity (DIO) with and without intact insulin signaling=20
> in pituitary gonadotrophs were created. Diet-induced obese wild-type=20
> female mice (WT DIO) were infertile and experienced a robust=20
> increase in luteinizing hormone (LH) after gonadotropin-releasing=20
> hormone (GnRH) or insulin stimulation. By contrast, both lean and=20
> obese mice with a pituitary-specific knockout of the insulin=20
> receptor (PitIRKO) exhibited reproductive competency, indicating=20
> that insulin signaling in the pituitary is required for the=20
> reproductive impairment seen in DIO and that the gonadotroph=20
> maintainsinsulin sensitivity in a setting of peripheral insulin=20
> resistance.


http://www.sciencenews.org/view/generic/id/63109/title/Study_clarifies_obes=
ity-infertility_link

and notice that NOT all species have LH
behave the same way with obesity so that
is an open question with ferrets for now.

> Being obese has long been linked to infertility in females, but=20
> researchers may have been wrong about how the link was forged...=20
> scientists have thought that the fertility problems were caused by=20
> resistance to the hormone insulin.
>
...
> A new study in mice shows that the pituitary gland, which helps=20
> regulate the release of fertility-associated hormones, remains=20
> sensitive to insulin. But in obese mice, insulin=92s constant=20
> signaling to release the fertility hormones leads to an=20
> overabundance of those hormones, and consequently infertility
>
...
> ...Removing insulin receptors from the pituitary restores fertility=20
> to the obese mice
>
...

[Now HERE below is the part that would be important to know: how high=20
LH levels go in ferrets with obesity. If they go very high then=20
obesity itself might be a risk factor for developing adrenal disease,=20
since chronically high LH levels are the typical cause of adrenal=20
tumors in ferrets. This might make a very interesting and *****novel=20
doctoral project for a veterinary student*****. Many studies on LH=20
levels and weight can be found by using PubMed. BTW, I do NOT know if=20
thin ferrets with sarcopenia -- also sometimes called "thin obesity"=20
if the individual is underweight but still has a good amount of fat=20
due to very poor muscle tone and low muscle amount -- would be wise to=20
include in such a study so only using comparably muscled groupings=20
could make sense to reduce noise.]
> Instead, the team discovered that the pituitary does not lose its=20
> ability to respond to insulin. As insulin levels rise with weight=20
> gain, the pituitary releases ever higher levels of the fertility-
> regulating luteinizing hormone.
>
...
> =93I just didn=92t think that insulin could be such a big role-player, =

> especially in the pituitary,=94 Hausman says. But the evidence=20
> presented in the new study =93is so clear, it=92s so blatant, that I=20
> really have to think more about this.=94
>
> ...but it is not clear whether insulin would have the same effect on=20
> the pituitary in people as it does in mice, says Mark Lawson
>

Sukie (not a vet)

Recommended ferret health links:
http://pets.groups.yahoo.com/group/ferrethealth/
http://ferrethealth.org/archive/
http://www.afip.org/ferrets/index.html
http://www.miamiferret.org/
http://www.ferrethealth.msu.edu/
http://www.ferretcongress.org/
http://www.trifl.org/index.shtml
http://homepage.mac.com/sukie/sukiesferretlinks.html
all ferret topics:
http://listserv.ferretmailinglist.org/archives/ferret-search.html

"All hail the procrastinators for they shall rule the world tomorrow."
(2010, Steve Crandall)










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