Journal Club
2007年10月11日 8:20-8:50
B棟８階 カンファレンス室
亀田メディカルセンター 糖尿病内分泌内科
Diabetes and Endocrine Department,
Kameda Medical Center
松田 昌文
Matsuda, Masafumi
Figure 1: Search strategy profile
Table 1: Characteristics of trials and participants
RECORD intrim
PROactive
Figure 2: Overall risk for congestive heart failure with (A) TZDs; (B) rosiglitazone;
and (C) pioglitazone
TZDs
Figure 2: Overall risk for congestive heart failure with (A) TZDs; (B) rosiglitazone;
and (C) pioglitazone
rosiglitazone
Figure 2: Overall risk for congestive heart failure with (A) TZDs; (B) rosiglitazone;
and (C) pioglitazone
pioglitazone
Figure 3: Overall risk for cardiovascular death with (A) TZDs; (B) rosiglitazone;
and (C) pioglitazone trials
TZDs
Figure 3: Overall risk for cardiovascular death with (A) TZDs; (B) rosiglitazone;
and (C) pioglitazone trials
rosiglitazone
Figure 3: Overall risk for cardiovascular death with (A) TZDs; (B) rosiglitazone;
and (C) pioglitazone trials
pioglitazone
Figure 4: Comparison of risk of congestive heart failure (A) and cardiovascular
death (B) for rosiglitazone and pioglitazone
Table 2: Congestive heart failure events reported in the thiazolidinedione trials
Table 3: Congestive heart failure and cardiovascular deaths by type of
thiazolidinedione
?
Note
We did not include the smaller trials available
for either rosiglitazone or pioglitazone, since
they might not have had long enough
observation times to accurately measure the
risk for congestive heart failure and
cardiovascular death.
A recent meta-analysis showed that patients
given rosiglitazone had a higher risk of
myocardial infarction than controls; they also
had a higher risk of cardiovascular death,
although this was not significant.
Interpretation
Longer followup and better
characterisation of such patients is
needed to determine the effect of
TZDs on overall cardiovascular
outcome.
1Department
of Medicine, Division of Endocrinology, Beth Israel
Deaconess Medical Center and Harvard Medical School, 99 Brookline
Avenue, Boston, Massachusetts 02215, USA.
2Department of Internal Medicine, Center for Hypothalamic Research, The
University of Texas Southwestern Medical Center, 5323Harry Hines
Boulevard, Dallas, Texas 75390-9077,
USA.
3Division of Neuroscience, Oregon National Primate Research Center,
Oregon Health & Science University, 505 NW185th Avenue, Beaverton,
Oregon 97006, USA.
4State Key Laboratory of Pharmaceutical Biotechnology, School of Life
Sciences, Nanjing University, Nanjing 210093, China.
“Chinese remedmy treats diabetes ???”
Mechanisms for the development
of diabetes mellitus
• Impairment of insulin secretion
• Impairment of insulin sensitivity
Impairment of glucose sensing in the
brain (tasting?)
Thrifty Gene Theory
Abnormality in
the
hypothalamus in
the brain
Brain
Hypothalamus
Abnormality in
the Fat tissue
Obesity
(Energy Storage)
Muscle insulin resistance
+
Delayed & Hyper
insulin secretion
Neel JV: Diabetes mellitus: a ‘thrifty’ genotype rendered detrimental by
“progress”? Am J Hum Genet 14:353–362, 1962
fMRI Response
Matsuda, M. et al Diabetes 48:1801-1806, 1999
Nature 405:1058-1062, 2000
SUR1-Kir6.2 on pancreatic beta cells
Background
Mutant Kir6.2 forms functional KATP
channels that are 250 times less
sensitive to closure by ATP and,
when expressed in pancreatic b-cells,
causes impaired glucose induced
insulin secretion and diabetes.
Journal club Aug 3, 2006
Leptin → Lean : stop appetite, increase energy exp. (increased sympathetic NS)
Insulin → Lean
Increase POMC/CART
decrease NPY/AgRP
IRS
aMSH
MC4Receptors
Hypothesis to be proved
The POMC-mut-Kir6.2 mice expressed the
transgene only in POMC neurons has
impairment in the whole-body response to
a systemic glucose load.
Glucose sensing by POMC neurons
became defective in obese mice on a highfat diet.
Figure 1 | Glucose sensing is lost in POMC-mut-Kir6.2 neurons
a, Structure of the Kir6.2[DN2–30,K185Q]–GFP transgene.
Mice. For generation of POMC-mut-Kir6.2 mice, the mut-Kir6.2 cassette (Kir[D2–30,K185Q]–GFP)7
was inserted into a POMC BAC genomic clone so that the ATG codon replaced that of POMC, as
described previously. POMC-mut-Kir6.2 BAC DNA was prepared using a commercially available
kit (Qiagen) and microinjected into pronuclei of fertilized one-cell-stage embryos of FVB mice
(Jackson Laboratories), resulting in the generation of two POMC-mut-Kir6.2 lines that were
maintained on an FVB inbred background.
POMC-GFP and NPY-GFP mice were generated by insertion of hrGFP into a POMC or NPY BAC,
respectively, as described above.
Ucp2-/- mice were used as described previously. To generate POMC-GFP;Ucp2-/- mice,
heterozygous POMC-GFP transgenic mice were crossed with heterozygous Ucp2-/- mice.
For high fat diet feeding experiments, mice were placed on a high-fat rodent diet (45% kcal from
fat; Research Diets Inc; D12451) at four weeks of age for a total of 20 weeks (or 8 weeks for
electrophysiological studies).
b, Double immunofluorescence staining for GFP (green) and b-endorphin
(yellow) in the arcuate nucleus of POMC-mut-Kir6.2 mice. Arrows indicate
neurons containing both b-endorphin and Kir6.2[DN2–30,K185Q]–GFP.
The carboxy (C)-terminal end of the mutant Kir6.2 contains a green
fluorescent protein (GFP) tag that does not alter the function of the channel
but makes it possible to visualize cells expressing mutant Kir6.2 (mut-Kir6.2).
b-endorphin (a marker for POMC neurons)
c, Loose patch recordings of POMC neurons from wild-type (WT, POMC-GFP) and
POMC-mut-Kir6.2 transgenic mice.
Recordings were made for 5–10 min in aCSF solution containing 5mM glucose.
Once stable activities were observed, the recording chamber was perfused with
aCSF solution containing 3mM glucose for 5–15 min, then switched back to 5mM
glucose for a further 5–10 min. Panels show a representative time course of firing
rate of a glucose-excited wild-type neuron (left) and a glucose-insensitive POMCmut-Kir6.2 neuron (middle). Each bar represents the average firing rate for a 20-s
interval; AP, action potential. The right panel shows the percentage of neurons
activated by 5mM glucose (recordings were obtained from 22 wild-type mice and
12 POMC-mut-Kir6.2 mice, with 2–4 POMC neurons recorded per animal).
OGTT 1g/kg BW
d, aMSH release from hypothalamic slices of wild-type and POMC-mutKir6.2 mice (n=3 hypothalamic slices per data point, ±s.e.m.).
e, Representative glucose tolerance curves from eight-week old male
wild-type and POMC-mut-Kir6.2 littermates (n=8–10 mice per genotype,
±s.e.m.).
Asterisk, P<0.05; two asterisks, P<0.01 compared with wild-type at a given time
point.
Leptin → Lean : stop appetite, increase energy exp. (increased sympathetic NS)
Insulin → Lean
Increase POMC/CART
decrease NPY/AgRP
IRS
aMSH
MC4Receptors
Figure 2 | Glucose-sensing is lost in POMC neurons of mice on a high-fat diet
a, Glucose-induced aMSH release from hypothalamic slices of
wildtype C57BL/6 mice fed chow or a high-fat diet for 20 weeks (mean
± s.e.m.).
b, Bar chart showing the percentage of POMC neurons activated by
5mM glucose in loose-patch recordings from POMC-GFP mice fed
either chow or a high-fat diet (HFD) for eight weeks.
c, In situ hybridization of Ucp2 mRNA in wild-type mice (dark field
photomicrograph of 35S-silvergrains).
VMH, ventromedial hypothalamus; Arc, arcuate nucleus.
d, Double immunohistochemistry and in situ hybridization detecting b-endorphin
protein and Ucp2 mRNA, respectively, in coronal sections from wild-type mice.
Arrows indicate the presence of b-endorphin neurons co-localized with Ucp2
mRNA. 3V, third ventricle.
Ucp2
In pancreatic b-cells, glucose sensing is negatively
controlled by the mitochondrial protein UCP2. UCP2
mediates proton leak across the inner mitochondrial
membrane, decreasing the yield of ATP from glucose.
UCP2 activity is increased in b-cells of animal models
for type 2 diabetes, and various studies have provided
evidence that this increase in UCP2 activity has a role
in the development of b-cell dysfunction.
UCP2 is also expressed in the brain, including in the
arcuate nucleus.
e, f, Relative hypothalamic Ucp2 mRNA expression in wild-type mice on a
high-fat diet (e, n=12; ±s.e.m.) and ob/ob (f, n=6; ±s.e.m.) mice.
Two asterisks, P<0.01; three asterisks, P<0.001 compared to wild type (WT).
Figure 3 | Genipin activates glucose-excited POMC neurons.
Representative time course of firing rates of loose-patch recordings on POMC
neurons from wild-type (WT) (a, b), Ucp2-/- (c), and POMC-mut-Kir6.2 (d) mice.
Recordings were made for 5–10 min in aCSF solution containing 5mM glucose.
Once stable firing rates were observed, the recording chamber was perfused with
aCSF solution containing 3mM glucose for 5–10 min, and then genipin (20 mM)
was added as indicated by the arrow.
a, A glucose-excited POMC neuron activated by genipin, representative of 16 out
of 22 glucose-excited neurons recorded.
b, A glucose-insensitive POMC neuron not activated by genipin, representative of
12 out of 13 glucose-insensitive neurons recorded.
Genipin
We have recently identified a membranepermeant molecule, genipin, which
inhibits UCP2-mediated proton leak.
Geniposide, which is found in the fruit
of Gardenia jasminoides Ellis, in
Tsumura TJ-135 [茵チン蒿湯], used for
liver diseases, is metabolized to
genipin.
“Chinese remedmy treats diabetes”
(BBC news June 6, 2006)
c, A glucose-excited POMCUcp2-/- neuron not activated by genipin,
representative of 11 out of 12 glucose-excited Ucp2-/- neurons recorded.
d, A POMC-mut-Kir6.2 neuron not activated by genipin, representing 13
out of 14 neurons recorded.
e, Bar chart showing the percentage of neurons activated by genipin.
Figure 4 | Acute inhibition or genetic deletion of UCP2 restores or
prevents loss of glucose sensing in POMC neurons as a result of
obesity induced by a high-fat diet.
a, b, aMSH secretion from hypothalamic slices from wild-type (a, WT) and
Ucp2-/- (b) mice in response to glucose, with or without genipin (20 mM).
Data are presented as mean ± s.e.m., n=6 mice for each experimental
condition. Asterisk, P<0.05.
a, b, aMSH secretion from hypothalamic slices from wild-type (a, WT) and
Ucp2-/- (b) mice in response to glucose, with or without genipin (20 mM).
Data are presented as mean ± s.e.m., n=6 mice for each experimental
condition. Asterisk, P<0.05.
Messages
First, we have shown that glucose sensing in POMC neurons
has an important role in controlling systemic glucose
homeostasis.
Second, glucose sensing in these neurons is lost with
obesity linked to a high-fat diet.
Finally, UCP2 is involved in this loss of glucose sensing,
perhaps by decreasing ATP production in POMC neurons.
As POMC neurons represent only a fraction of all glucoseexcited neurons in the brain (which include melaninconcentrating hormone (MCH) neurons in the lateral
hypothalamus, neurons in the ventromedial hypothalamus,
and neurons in the hindbrain), we suggest that UCP2mediated loss of glucose sensing in glucose-excited
neurons could be an important pathogenic component of
type 2 diabetes.