2011 ADA Posters 1261-2041.indd - Diabetes

expression. These fi ndings suggest that TLR4 in Kupffer cells mediates the
progression from simple steatosis to infl ammation, partly by inducing the
production of ROS, thereby leading to the activation of XBP-1.
Supported by: Hong Kong Research Grant Council (HKU 5/CRF/08 and HKU
2/07C)
& 1656-P
Liver-Specifi c Deletion of JAK2 Leads to Profound Fatty Liver but
Suppression of Infl ammation and Protection Against Systemic Insulin
Resistance
RUBÉN GARCÍA, SALLY YU SHI, DIANA CHOI, ROBIN E. DUNCAN, SHUN YAN LU,
STEPHANIE A. SCHROER, ERICA P. CAI, CHRISTINE TANG, ADRIA GIACCA, MARK
NAPLES, MARK J. DEKKER, KAY-UWE WAGNER, KHOSROW ADELI, RICHARD P.
BAZINET, MINNA WOO, Toronto, ON, Canada, Omaha, NE
Non-alcoholic fatty liver disease (NAFLD) is considered to be the hepatic
manifestation of the metabolic syndrome, a well-recognized precursor for
many chronic diseases including type 2 diabetes, cardiovascular diseases
and some cancers. NAFLD is a disease spectrum hypothesized to be
induced by a two-step process: the fi rst hit, steatosis, sensitizes the liver
to the infl ammatory damage induced by a second pathogenic insult, which
promotes steatohepatitis. The exact pathogenesis of NAFLD, however, is
not well understood. The Janus kinase-signal transducers and activators of
transcription (JAK-STAT) pathway is involved in both infl ammatory signalling
and in lipid homeostasis in the liver and may contribute to the pathogenesis
of NAFLD. To investigate the role of hepatic JAK2, an essential player in
the JAK-STAT pathway, we generated mice with deletion of jak2 specifi cally
in hepatocytes (L-JAK2 KO) using the cre-loxP system. L-JAK2 KO mice
developed spontaneous hepatosteatosis early in life, similar to liverspecifi
c growth hormone receptor- and STAT5-defi cient mice. However, in
contrast to these mice, L-JAK2 KO mice did not develop systemic insulin
resistance or glucose intolerance. Interestingly, the fatty acid composition
of liver triglycerides showed, in addition to increased palmitate, a persistent
predominance of the less toxic oleate, which was accompanied by reduced
hepatic infl ammation in L-JAK2 KO mice. Even when challenged with a
prolonged high fat diet, these mice were completely protected against
systemic infl ammation and insulin resistance, resulting in improved glucose
tolerance. Together, our fi ndings indicate a critical and unique role of hepatic
jak2 in the regulation of fatty acid metabolism and infl ammation, leading
to a complete halt in NAFLD progression and development of systemic
insulin resistance in mice lacking JAK2 in hepatocytes. Targeting the JAK-
STAT pathway may therefore provide a novel therapeutic strategy for the
treatment of type 2 diabetes.
Supported by: CIHR; Ibercaja Foundation (Spain); BBDC-Novo Nordisk Studentship
& 1657-P
Liver-Specifi c Ablation of PPARγ Reduces Hepatic Mitochondrial
β-Oxidation and Lipid Accumulation, but Aggravates High Fat Diet-
Induced Insulin Resistance
ANISHA A. GUPTE, LAURIE J. MINZE, JESSICA R. WILES, MARTINEZ JESSICA,
ALAN R. COLLINS, CHRISTOPHER J. LYON, WILLA A. HSUEH, Houston, TX
Fatty liver is thought to contribute to insulin resistance and diabetes.
Although peroxisome proliferator-activated receptor-γ (PPARγ) activation
can increase de novo lipogenesis in the liver during high fat diet (HFD), we
found that activation increases β-oxidation, improves liver mitochondrial
function and decreases liver fat accumulation (Gupte A, et al, Hepatology,
2010). However, very little is known about the role of liver-PPARγ and its
effects, if any, upon liver metabolism. We thus generated mice with liverspecifi
c PPARγ knockout (L-PPARγKO), and found that L-PPARγKO mice
fed obesogenic HFD for 3 months had 50% the liver fat of wild type (WT)
littermates. However, L-PPARγKO had elevated fasting insulin vs. WT mice
and impaired insulin sensitivity when assayed by insulin tolerance test,
but no differences in plasma triglycerides, phospholipids or free fatty acid
levels. Insulin-stimulated Akt phosphorylation was suppressed in liver, fat
and skeletal muscle of WT mice on HFD vs. chow, but was increased in liver,
unchanged in fat, and reduced in skeletal muscle of HFD-fed L-PPARγKO mice
vs. WT mice. Thus, L-PPARγKO mice have skeletal muscle insulin resistance,
but decreased liver fat and improved liver insulin sensitivity. Mitochondrial
function analyses revealed signifi cant suppression of β-oxidation in the
livers of L-PPARγKO mice, but there was reduced expression of lipogenic
genes (e.g. fatty acid synthase) corresponding with reduced hepatic fat
accumulation, suggesting that liver-PPARγ directly regulates hepatic lipid
synthesis and metabolism. Surprisingly, the PPARγ agonist rosiglitazone
restored β-oxidation in L-PPARγKO mice on HFD to that seen in WT mice.
These data suggest: 1) liver PPARγ directly regulates hepatic lipid synthesis
ADA-Funded Research
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INTEGRATED CATEGORY PHYSIOLOGY—LIVER
A451
and mitochondrial β-oxidation of fatty acids, 2) PPARγ effects outside the
liver also impact hepatic β-oxidation, and 3) liver PPARγ may exert signifi cant
effects upon skeletal muscle insulin sensitivity, even in the absence of
liver fat. We conclude that liver PPARγ may have important therapeutic
implications for liver complications found in obesity and diabetes.
& 1658-P
Rat Krueppel-Like Factor 10 (Klf-10) Gene Expression Is Regulated
by the Carbohydrate Response Element Binding Protein ChREBP in
Primary Rat Hepatocytes
KATSUMI IIZUKA, YUKIO HORIKAWA, REIKO TOMITA, TETSUYA SUWA, JUN
TAKEDA, Gifu, Japan
We previously reported that the carbohydrate response element binding
protein ChREBP plays an important role in the regulation of glucose and lipid
metabolism by regulating hepatic glycolytic and lipogenic gene expression.
We then established a mouse model infected by an adenovirus expressing
dominant active ChREBP (daChREBP). Using the DNA microarray technique,
we identifi ed the Krueppel-like factor 10 (Klf-10) as a candidate for one of
the ChREBP target genes. Recently, Klf-10 has been identifi ed as a circadian
transcriptional regulator that links the molecular clock to energy metabolism
in the liver. Here we investigate whether ChREBP directly regulates Klf-10
gene expression in rat primary hepatocytes and the pancreatic beta cell
line INS-1E. Klf-10 mRNA is ubiquitously expressed and highly expressed
in muscles and the liver. The hepatic Klf-10 mRNA in ob/ob mice is about
2-fold higher than that in C57BL/6 mice. In rat primary hepatocytes and
INS-1E cells, glucose stimulation and overexpression of daChREBP induces
klf-10 mRNA in a dose-dependent manner. Consistent with these fi ndings,
overexpression of dominant negative Mlx inhibits glucose induction of liver
type pyruvate kinase (Lpk) and fatty acid synthase (Fasn) mRNA. A deletion
study of pGL3 vector with rat KLF-10 promoter and a CHIP assay against anti-
ChREBP antibody demonstrated that the carbohydrate response element
(ChoRE) is located between -200 and -100 bp in the rat Klf-10 gene promoter.
In addition, adenoviral overexpression of Klf-10 partly inhibits glucose
induction of ChREBP target genes (Lpk and Fasn) in primary hepatocytes. In
conclusion, these fi ndings suggest that ChREBP directly regulates Klf-10 gene
expression at the transcription level and that Klf-10 also weakly contributes
to regulating ChREBP transactivities. Crosstalk between ChREBP and Klf-10
is involved in the regulation of the lipogenic pathway.
& 1659-P
Role of Sdf2l1, a Novel ER Stress-Related Protein, in the Regulation
of Hepatic Insulin Sensitivity
TAKAYOSHI SASAKO, KOHJIRO UEKI, MITSURU OHSUGI, NAOTO KUBOTA,
KAZUYUKI TOBE, TAKASHI KADOWAKI, Tokyo, Japan, Toyama, Japan
Dys-regulation of dynamic metabolic changes in liver during the transition
between fasting and feeding leads to metabolic disorders. To further
elucidate these changes, we compared global gene expressions in livers
of B6J mice in 24h-fasted and 6h-refed states by microarray analysis.
Interestingly several ER stress-related genes were up-regulated by
refeeding. Among them, we focused on Sdf2l1, a component of chaperone
complexes, showing the second largest increase of all the genes. Indeed
hepatic expression of ER stress markers as well as Sdf2l1 was elevated
prominently and transiently by refeeding in B6J mice. In order to explore the
role of Sdf2l1 in response to ER stress, we performed promoter assay and
ChIP assay, revealing that Sdf2l1 was regulated by Xbp1 and ATF6, despite
absence of conventional ERSE in the promoter region. Since ER stress is
thought to be a pivotal regulator of hepatic insulin sensitivity, to assess the
role of Sdf2l1 in this context, we knocked down hepatic Sdf2l1 expression
by adenovirus-mediated RNA interference. Knocking down of Sdf2l1 in B6J
mice resulted in greater elevation of ER stress markers after refeeding, while
it impaired glucose tolerance, attenuated insulin signaling after refeeding,
and increased triglyceride contents. These prompted us to hypothesize that
dys-regulation of Sdf2l1 might contribute to insulin resistance in obesity.
Indeed in livers of db/db mice, a model of obesity and diabetes, Sdf2l1 was
down-regulated, accompanied by decreased binding of Xbp1, but not ATF6,
with the promoter region. By contrast, adenovirus-mediated restoration of
Sdf2l1 in livers of db/db mice improved glucose tolerance, insulin signaling
after refeeding, and fatty liver. These data suggest that feeding induces ER
stress in liver even under the physiological condition, while Sdf2l1 regulated
by Xbp1 and ATF6 may switch off the ER stress response, maintaining
hepatic insulin sensitivity after feeding. On the other hand, suppression of
hepatic Sdf2l1 expression in obesity may contribute to the development of
systemic insulin resistance, providing the possibility of Sdf2l1 to be a novel
therapeutic target of obesity-induced diabetes.
For author disclosure information, see page 785.
Integrated Physiology/
Obesity
POSTERS