Deletion of skeletal muscle Akt1/2 causes osteosarcopenia and reduces lifespan in mice.

Aging is considered to be accelerated by insulin signaling in lower organisms, but it remained unclear whether this could hold true for mammals. Here we show that mice with skeletal muscle-specific double knockout of Akt1/2, key downstream molecules of insulin signaling, serve as a model of premature sarcopenia with insulin resistance. The knockout mice exhibit a progressive reduction in skeletal muscle mass, impairment of motor function and systemic insulin sensitivity. They also show osteopenia, and reduced lifespan largely due to death from debilitation on normal chow and death from tumor on high-fat diet. These phenotypes are almost reversed by additional knocking out of Foxo1/4, but only partially by additional knocking out of Tsc2 to activate the mTOR pathway. Overall, our data suggest that, unlike in lower organisms, suppression of Akt activity in skeletal muscle of mammals associated with insulin resistance and aging could accelerate osteosarcopenia and consequently reduce lifespan.

Effect of a Multifactorial Intervention on Fracture in Patients With Type 2 Diabetes: Subanalysis of the J-DOIT3 Study.

AIMS: To evaluate the effects of an intensified multifactorial intervention and patient characteristics on the incidence of fractures comorbid with type 2 diabetes. METHODS: Fracture events were identified and analyzed among adverse events reported in the J-DOIT3 study, a multicenter, open-label, randomized, parallel-group trial that was conducted in Japan, in which patients with type 2 diabetes were randomly assigned to receive conventional therapy for glucose, blood pressure, and lipids (targets: HbA1c < 6.9%, blood pressure <130/80 mm Hg, LDL-cholesterol <120mg/dL) or intensive therapy (HbA1c < 6.2%, blood pressure <120/75 mm Hg, LDL-cholesterol <80mg/dL) (ClinicalTrials.gov registration no. NCT00300976). RESULTS: The cumulative incidence of fractures did not differ between those receiving conventional therapy and those receiving intensive therapy (hazard ratio (HR) 1.15; 95% CI, 0.91-1.47; P = 0.241). Among the potential risk factors, only history of smoking at baseline was significantly associated with the incidence of fractures in men (HR 1.96; 95% CI, 1.04-3.07; P = 0.038). In contrast, the incidence of fractures in women was associated with the FRAX score [%/10 years] at baseline (HR 1.04; 95% CI, 1.02-1.07; P < 0.001) and administration of pioglitazone at 1 year after randomization (HR 1.59; 95% CI, 1.06-2.38; P = 0.025). CONCLUSIONS: Intensified multifactorial intervention may be implemented without increasing the fracture risk in patients with type 2 diabetes. The fracture risk is elevated in those with a history of smoking in men, whereas it is predicted by the FRAX score and is independently elevated with administration of pioglitazone in women.

Multifactorial intervention has a significant effect on diabetic kidney disease in patients with type 2 diabetes.

To evaluate the effect of multifactorial intervention on the onset and progression of diabetic kidney disease in the patients with type 2 diabetes, we analyzed the effects of intensified multifactorial intervention by step-wise intensification of medications and life-style modifications (intensive therapy treatment targets; HbA1c under 6.2%, blood pressure under 120/75 mmHg, low-density lipoprotein cholesterol under 80 mg/dL) comparing with the guideline-based standard care (conventional therapy treatment targets: HbA1c under 6.9%, blood pressure under 130/80 mmHg, low-density lipoprotein cholesterol under 120 mg/dL) on diabetic kidney disease. A total of 2540 eligible patients in the Japan Diabetes Optimal Integrated Treatment for three major risk factors of cardiovascular diseases (J-DOIT3) cohort were randomly assigned to intensive therapy (1269) and conventional therapy (1271) and treated for a median of 8.5 years. The prespecified kidney outcome measure was a composite of progression from normoalbuminuria to microalbuminuria or progression from normoalbuminuria to macroalbuminuria or progression from microalbuminuria to macroalbuminuria, serum creatinine levels elevated by two-fold or more compared to baseline, or kidney failure. Primary analysis was carried out on the intention-to-treat population. Changes in the estimated glomerular filtration rate and albuminuria were also analyzed. A total of 438 kidney events occurred (181 in the intensive therapy group and 257 in the conventional therapy group). Intensive therapy was associated with a significant 32% reduction in kidney events compared to conventional therapy and was associated with a change in HbA1c at one year from study initiation. Thus, prespecified analysis shows that intensified multifactorial intervention significantly reduced the onset and progression of diabetic kidney disease compared to currently recommended care.

Insulin- and Lipopolysaccharide-Mediated Signaling in Adipose Tissue Macrophages Regulates Postprandial Glycemia through Akt-mTOR Activation.

The physiological role of immune cells in the regulation of postprandial glucose metabolism has not been fully elucidated. We have found that adipose tissue macrophages produce interleukin-10 (IL-10) upon feeding, which suppresses hepatic glucose production in cooperation with insulin. Both elevated insulin and gut-microbiome-derived lipopolysaccharide in response to feeding are required for IL-10 production via the Akt/mammalian target of rapamycin (mTOR) pathway. Indeed, myeloid-specific knockout of the insulin receptor or bone marrow transplantation of mutant TLR4 marrow cells results in increased expression of gluconeogenic genes and impaired glucose tolerance. Furthermore, myeloid-specific Akt1 and Akt2 knockout results in similar phenotypes that are rescued by additional knockout of TSC2, an inhibitor of mTOR. In obesity, IL-10 production is impaired due to insulin resistance in macrophages, whereas adenovirus-mediated expression of IL-10 ameliorates postprandial hyperglycemia. Thus, the orchestrated response of the endogenous hormone and gut environment to feeding is a key regulator of postprandial glycemia.

Hepatic Sdf2l1 controls feeding-induced ER stress and regulates metabolism.

Dynamic metabolic changes occur in the liver during the transition between fasting and feeding. Here we show that transient ER stress responses in the liver following feeding terminated by Sdf2l1 are essential for normal glucose and lipid homeostasis. Sdf2l1 regulates ERAD through interaction with a trafficking protein, TMED10. Suppression of Sdf2l1 expression in the liver results in insulin resistance and increases triglyceride content with sustained ER stress. In obese and diabetic mice, Sdf2l1 is downregulated due to decreased levels of nuclear XBP-1s, whereas restoration of Sdf2l1 expression ameliorates glucose intolerance and fatty liver with decreased ER stress. In diabetic patients, insufficient induction of Sdf2l1 correlates with progression of insulin resistance and steatohepatitis. Therefore, failure to build an ER stress response in the liver may be a causal factor in obesity-related diabetes and nonalcoholic steatohepatitis, for which Sdf2l1 could serve as a therapeutic target and sensitive biomarker.

The RNA Methyltransferase Complex of WTAP, METTL3, and METTL14 Regulates Mitotic Clonal Expansion in Adipogenesis.

Adipocyte differentiation is regulated by various mechanisms, of which mitotic clonal expansion (MCE) is a key step. Although this process is known to be regulated by cell cycle modulators, the precise mechanism remains unclear. N6-Methyladenosine (m6A) posttranscriptional RNA modification, whose methylation and demethylation are performed by respective enzyme molecules, has recently been suggested to be involved in the regulation of adipogenesis. Here, we show that an RNA N6-adenosine methyltransferase complex consisting of Wilms' tumor 1-associating protein (WTAP), methyltransferase like 3 (METTL3), and METTL14 positively controls adipogenesis by promoting cell cycle transition in MCE during adipogenesis. WTAP, coupled with METTL3 and METTL14, is increased and distributed in nucleus by the induction of adipogenesis dependently on RNA in vitro Knockdown of each of these three proteins leads to cell cycle arrest and impaired adipogenesis associated with suppression of cyclin A2 upregulation during MCE, whose knockdown also impairs adipogenesis. Consistent with this, Wtap heterozygous knockout mice are protected from diet-induced obesity with smaller size and number of adipocytes, leading to improved insulin sensitivity. These data provide a mechanism for adipogenesis through the WTAP-METTL3-METTL14 complex and a potential strategy for treatment of obesity and associated disorders.

Effect of an intensified multifactorial intervention on cardiovascular outcomes and mortality in type 2 diabetes (J-DOIT3): an open-label, randomised controlled trial.

BACKGROUND: Limited evidence suggests that multifactorial interventions for control of glucose, blood pressure, and lipids reduce macrovascular complications and mortality in patients with type 2 diabetes. However, safe and effective treatment targets for these risk factors have not been determined for such interventions. METHODS: In this multicentre, open-label, randomised, parallel-group trial, undertaken at 81 clinical sites in Japan, we randomly assigned (1:1) patients with type 2 diabetes aged 45-69 years with hypertension, dyslipidaemia, or both, and an HbA1c of 6·9% (52·0 mmol/mol) or higher, to receive conventional therapy for glucose, blood pressure, and lipid control (targets: HbA1c <6·9% [52·0 mmol/mol], blood pressure <130/80 mm Hg, LDL cholesterol <120 mg/dL [or 100 mg/dL in patients with a history of coronary artery disease]) or intensive therapy (HbA1c <6·2% [44·3 mmol/mol], blood pressure <120/75 mm Hg, LDL cholesterol <80 mg/dL [or 70 mg/dL in patients with a history of coronary artery disease]). Randomisation was done using a computer-generated, dynamic balancing method, stratified by sex, age, HbA1c, and history of cardiovascular disease. Neither patients nor investigators were masked to group assignment. The primary outcome was occurrence of any of a composite of myocardial infarction, stroke, revascularisation (coronary artery bypass surgery, percutaneous transluminal coronary angioplasty, carotid endarterectomy, percutaneous transluminal cerebral angioplasty, and carotid artery stenting), and all-cause mortality. The primary analysis was done in the intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT00300976. FINDINGS: Between June 16, 2006, and March 31, 2009, 2542 eligible patients were randomly assigned to intensive therapy or conventional therapy (1271 in each group) and followed up for a median of 8·5 years (IQR 7·3-9·0). Two patients in the intensive therapy group were found to be ineligible after randomisation and were excluded from the analyses. During the intervention period, mean HbA1c, systolic blood pressure, diastolic blood pressure, and LDL cholesterol concentrations were significantly lower in the intensive therapy group than in the conventional therapy group (6·8% [51·0 mmol/mol] vs 7·2% [55·2 mmol/mol]; 123 mm Hg vs 129 mm Hg; 71 mm Hg vs 74 mm Hg; and 85 mg/dL vs 104 mg/dL, respectively; all p<0·0001). The primary outcome occurred in 109 patients in the intensive therapy group and in 133 patients in the conventional therapy group (hazard ratio [HR] 0·81, 95% CI 0·63-1·04; p=0·094). In a post-hoc breakdown of the composite outcome, frequencies of all-cause mortality (HR 1·01, 95% CI 0·68-1·51; p=0·95) and coronary events (myocardial infarction, coronary artery bypass surgery, and percutaneous transluminal coronary angioplasty; HR 0·86, 0·58-1·27; p=0·44) did not differ between groups, but cerebrovascular events (stroke, carotid endarterectomy, percutaneous transluminal cerebral angioplasty, and carotid artery stenting) were significantly less frequent in the intensive therapy group (HR 0·42, 0·24-0·74; p=0·002). Apart from non-severe hypoglycaemia (521 [41%] patients in the intensive therapy group vs 283 [22%] in the conventional therapy group, p<0·0001) and oedema (193 [15%] vs 129 [10%], p=0·0001), the frequencies of major adverse events did not differ between groups. INTERPRETATION: Our results do not fully support the efficacy of further intensified multifactorial intervention compared with current standard care for the prevention of a composite of coronary events, cerebrovascular events, and all-cause mortality. Nevertheless, our findings suggest a potential benefit of an intensified intervention for the prevention of cerebrovascular events in patients with type 2 diabetes. FUNDING: Ministry of Health, Labour and Welfare of Japan, Asahi Kasei Pharma, Astellas Pharma, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Daiichi Sankyo, Eli Lilly, GlaxoSmithKline, Kissei Pharmaceutical, Kowa Pharmaceutical, Mitsubishi Tanabe Pharma, Mochida Pharmaceutical, MSD, Novartis Pharma, Novo Nordisk, Ono Pharmaceutical, Pfizer, Sanwa Kagaku Kenkyusho, Shionogi, Sumitomo Dainippon Pharma, Taisho Toyama Pharmaceutical, and Takeda.

CD206+ M2-like macrophages regulate systemic glucose metabolism by inhibiting proliferation of adipocyte progenitors.

Adipose tissue resident macrophages have important roles in the maintenance of tissue homeostasis and regulate insulin sensitivity for example by secreting pro-inflammatory or anti-inflammatory cytokines. Here, we show that M2-like macrophages in adipose tissue regulate systemic glucose homeostasis by inhibiting adipocyte progenitor proliferation via the CD206/TGFß signaling pathway. We show that adipose tissue CD206+ cells are primarily M2-like macrophages, and ablation of CD206+ M2-like macrophages improves systemic insulin sensitivity, which was associated with an increased number of smaller adipocytes. Mice genetically engineered to have reduced numbers of CD206+ M2-like macrophages show a down-regulation of TGFß signaling in adipose tissue, together with up-regulated proliferation and differentiation of adipocyte progenitors. Our findings indicate that CD206+ M2-like macrophages in adipose tissues create a microenvironment that inhibits growth and differentiation of adipocyte progenitors and, thereby, control adiposity and systemic insulin sensitivity.Adipose tissue contains macrophages that can influence both local and systemic metabolism via the secretion of cytokines. Here, Nawaz et al. report that M2-like macrophages, present in adipose tissue, create a microenvironment that inhibits proliferation of adipocyte progenitors due to the secretion of TGF-ß1.

Design of and rationale for the Japan Diabetes Optimal Integrated Treatment study for 3 major risk factors of cardiovascular diseases (J-DOIT3): a multicenter, open-label, randomized, parallel-group trial.

OBJECTIVE: Multifactorial intervention including the management of levels of blood glucose (BG), blood pressure (BP), and lipids has been suggested to decrease cardiovascular disease (CVD) risk. However, the target ideal and feasible levels for these individual parameters have not been fully evaluated. In this study, we examine the hypothesis that stricter control compared with the current targets in the Japanese guideline for BG, BP, and lipids could efficiently and safely reduce CVD risk. RESEARCH DESIGN AND METHODS: We screened patients with type 2 diabetes and hypertension and/or dyslipidemia among 81 hospitals in Japan and allocated them into 2 groups: the intensive therapy group (ITG) and the conventional therapy group (CTG). For the 2 respective groups, the target for glycated hemoglobin (HbA1c) is <6.2% (44 mmol/mol) and <6.9% (52 mmol/mol), for BP it is <120/75 mm Hg and <130/80 mm Hg, and for low-density lipoprotein cholesterol it is <80 mg/dL (<70 mg/dL in the presence of CVD history) and <120 mg/dL (<100 mg/dL in the presence of CVD history). The primary end point is the occurrence of CVD events or death by any cause. These patients are scheduled for stepwise intensifications of medication for BG, BP, and lipid control in the ITG, until the number of primary end point events reaches 250. RESULTS: We recruited 2542 patients and randomly allocated 1271 into the ITG and 1271 into the CTG between June 2006 and March 2009. The mean HbA1c was 8.0% (64 mmol/mol) and the mean duration of diabetes was 8.3 years. CONCLUSIONS: This randomized controlled study will test the hypothesis that strict multifactorial intervention therapy is effective for the prevention of CVDs in patients with type 2 diabetes who are at high CVD risk. TRIAL REGISTRATION NUMBER: NCT00300976.

Case of acrodermatitis continua of Hallopeau following psoriasis with atypical clinical presentation.

We present a 63-year-old Japanese woman who had clinically unique symmetrical skin rashes on her lower face, inframammary area, back and extremities, with some pustules on the cheeks. Skin biopsy specimens showed typical findings of psoriasis, and Psoriasis Area and Severity Index score was 5.9. After the skin lesions were treated successfully with vitamin D3 ointment, pustules developed on the tips of the fingers and toes, with paronychial and subungual involvement. The pathology of the nail matrix was consistent with pustular psoriasis, and the patient was diagnosed with acrodermatitis continua of Hallopeau (ACH) following psoriasis with an unusual clinical presentation. ACH was well controlled with a low dose of cyclosporin. Our patient is a rare case chronologically affected by two diseases in the same category. We confirmed that ACH is a variant of pustular psoriasis, and believe that the patient could provide another clue to determining the entity of ACH.

Adiponectin enhances insulin sensitivity by increasing hepatic IRS-2 expression via a macrophage-derived IL-6-dependent pathway.

Insulin resistance is often associated with impeded insulin signaling due either to decreased concentrations or functional modifications of crucial signaling molecules including insulin receptor substrates (IRS) in the liver. Many actions of adiponectin, a well-recognized antidiabetic adipokine, are currently attributed to the activation of two critical molecules downstream of AdipoR1 and R2: AMP-activated kinase (AMPK) and peroxisome proliferator-activated receptor α (PPARα). However, the direct effects of adiponectin on insulin signaling molecules remain poorly understood. We show here that adiponectin upregulates IRS-2 through activation of signal transducer and activator of transcription-3 (STAT3). Surprisingly, this activation is associated with IL-6 production from macrophages induced by adiponectin through NFκB activation independent of its authentic receptors, AdipoR1 and AdipoR2. These data have unraveled an insulin-sensitizing action initiated by adiponectin leading to upregulation of hepatic IRS-2 via an IL-6 dependent pathway through a still unidentified adiponectin receptor.

Blockade of class IB phosphoinositide-3 kinase ameliorates obesity-induced inflammation and insulin resistance.

Obesity and insulin resistance, the key features of metabolic syndrome, are closely associated with a state of chronic, low-grade inflammation characterized by abnormal macrophage infiltration into adipose tissues. Although it has been reported that chemokines promote leukocyte migration by activating class IB phosphoinositide-3 kinase (PI3Kγ) in inflammatory states, little is known about the role of PI3Kγ in obesity-induced macrophage infiltration into tissues, systemic inflammation, and the development of insulin resistance. In the present study, we used murine models of both diet-induced and genetically induced obesity to examine the role of PI3Kγ in the accumulation of tissue macrophages and the development of obesity-induced insulin resistance. Mice lacking p110γ (Pik3cg(-/-)), the catalytic subunit of PI3Kγ, exhibited improved systemic insulin sensitivity with enhanced insulin signaling in the tissues of obese animals. In adipose tissues and livers of obese Pik3cg(-/-) mice, the numbers of infiltrated proinflammatory macrophages were markedly reduced, leading to suppression of inflammatory reactions in these tissues. Furthermore, bone marrow-specific deletion and pharmacological blockade of PI3Kγ also ameliorated obesity-induced macrophage infiltration and insulin resistance. These data suggest that PI3Kγ plays a crucial role in the development of both obesity-induced inflammation and systemic insulin resistance and that PI3Kγ can be a therapeutic target for type 2 diabetes.

Class IA phosphatidylinositol 3-kinase in pancreatic ß cells controls insulin secretion by multiple mechanisms.

Type 2 diabetes is characterized by insulin resistance and pancreatic ß cell dysfunction, the latter possibly caused by a defect in insulin signaling in ß cells. Inhibition of class IA phosphatidylinositol 3-kinase (PI3K), using a mouse model lacking the pik3r1 gene specifically in ß cells and the pik3r2 gene systemically (ßDKO mouse), results in glucose intolerance and reduced insulin secretion in response to glucose. ß cells of ßDKO mice had defective exocytosis machinery due to decreased expression of soluble N-ethylmaleimide attachment protein receptor (SNARE) complex proteins and loss of cell-cell synchronization in terms of Ca(2+) influx. These defects were normalized by expression of a constitutively active form of Akt in the islets of ßDKO mice, preserving insulin secretion in response to glucose. The class IA PI3K pathway in ß cells in vivo is important in the regulation of insulin secretion and may be a therapeutic target for type 2 diabetes.

[Japan Diabetes Outcome Intervention Trial 3 (Japan Diabetes Optimal Integrated Treatment Study for 3 major risk factors of cardiovascular diseases: J-DOIT3)].

J-DOIT3 was designed to examine whether intensive therapy in which the targets of HbA1c (JDS 5.8%), blood pressure(BP) (120/75mmHg) and LDL cholesterol (80 mg/ dL) are extremely aggressive compared to the those adopted by the guidelines, would efficiently suppress diabetic macrovascular complications (DMC). Although previous studies failed to significantly decrease the risk of DMC by the intensive therapy for hyperglycemia presumably due to the marked increases in severe hypoglycemic events and body weight, the patients in the intensive therapy group in J-DOIT3 have shown well-controlled blood glucose as well as BP and LDL with a very few severe hypoglycemic episodes. Thus, J-DOIT3 is expected to provide the first evidence that tight glycemic control as well as BP and LDL can efficiently and safely suppress DMC.

Decreased insulin secretion and accumulation of triglyceride in beta cells overexpressing a dominant-negative form of AMP-activated protein kinase.

Adenosine 5' -monophosphate-activated protein kinase (AMPK) has been implicated in the regulation of energy metabolism, although its role in the pancreatic beta cells remains unclear. In the present, we have overexpressed a dominant negative form of AMPKalpha1 subunit (Asp57Ala) tagged with c-myc epitope (AMPKalpha1-DN) in INS-1D cells with an adenoviral vector. After 48 h of adenoviral infection, overexpression of AMPKalpha1-DN in INS-1D cells was confirmed by Western blot analysis with anti-c-myc antibody. Phosphorylation of the Thr172 in AMPKalpha1/alpha2 subunit was progressively decreased in parallel with increasing number of adenoviral titers. Glucose-stimulated insulin secretion in response to 30 mmol/L glucose was decreased in INS-1D cells overexpressing AMPKalpha1-DN as compared to control cells infected with adeno- LacZ vector. Neither cellular insulin content nor insulin mRNA level was changed between the two groups. Phosphorylation of acetyl-CoA carboxylase (ACC), a down-stream substrate of AMPK, was decreased, indicating that ACC activity was increased, due to the decreased AMPK activity. In fact, intracellular triglyceride content was increased as compared to control cells. The beta-oxidation of palmitate was decreased at 30 mmol/L glucose. Insulin secretion in response to potassium chloride or glibenclamide was also decreased as compared to control cells. In conclusion, suppression of AMPK activity in beta-cells inhibited insulin secretion in response to glucose, potassium chloride or glibenclamide without altering insulin content. Accumulation of triglyceride subsequent to the activation of ACC by suppression of AMPK activity, was suggested to be, at least in part, responsible for the impaired insulin secretion through so-called lipotoxicity mechanism.

Adiponectin suppresses hepatic SREBP1c expression in an AdipoR1/LKB1/AMPK dependent pathway.

Adiponectin, one of the insulin-sensitizing adipokines, has been shown to activate fatty acid oxidation in liver and skeletal muscle, thus maintaining insulin sensitivity. However, the precise roles of adiponectin in fatty acid synthesis are poorly understood. Here we show that adiponectin administration acutely suppresses expression of sterol regulatory element-binding protein (SREBP) 1c, the master regulator which controls and upregulates the enzymes involved in fatty acid synthesis, in the liver of +Lepr(db)/+Lepr(db) (db/db) mouse as well as in cultured hepatocytes. We also show that adiponectin suppresses SREBP1c by AdipoR1, one of the functional receptors for adiponetin, and furthermore that suppressing either AMP-activated protein kinase (AMPK) via its upstream kinase LKB1 deletion cancels the negative effect of adiponectin on SREBP1c expression. These data show that adiponectin suppresses SREBP1c through the AdipoR1/LKB1/AMPK pathway, and suggest a possible role for adiponectin in the regulation of hepatic fatty acid synthesis.

Role of uncoupling protein-2 up-regulation and triglyceride accumulation in impaired glucose-stimulated insulin secretion in a beta-cell lipotoxicity model overexpressing sterol regulatory element-binding protein-1c.

Triglyceride (TG) accumulation in pancreatic beta-cells is thought to be associated with impaired insulin secretory response to glucose (lipotoxicity). To better understand the mechanism of the impaired insulin secretory response to glucose in beta-cell lipotoxicity, we overexpressed a constitutively active form of the sterol regulatory element-binding protein- 1c (SREBP-1c), a master transcriptional factor of lipogenesis, in INS-1 cells with an adenoviral vector. This treatment was associated with strong activation of transcription of the genes involved in fatty acid biosynthesis, increased cellular TG content, severely blunted glucose-stimulated insulin secretion, and enhanced expression of the uncoupling protein-2 (UCP-2), which supposedly dissipates the mitochondrial electrochemical potential. To decrease the up-regulated UCP-2 expression, small interfering RNA for UCP-2 was used. Introduction of the small interfering RNA increased the ATP/ADP ratio and partially rescued the glucose-stimulated insulin secretion in the cells overexpressing SREBP-1c, but did not affect the cellular TG content. Next, the effect of the AMP-activated protein kinase (AMPK) agonist, 5-amino-4-imidazolecarboxamide riboside, was examined in the lipotoxicity model. Exposure of the cells with lipotoxicity to 5-amino-4-imidazolecarboxamide riboside increased free fatty acid oxidation, partially reversed the TG accumulation, phosphorylated AMPK and acetyl-coenzyme A carboxylase, and improved the impaired glucose-stimulated insulin secretion. These results suggest that UCP-2 down-regulation and AMPK activation could be candidate targets for releasing beta-cells from lipotoxicity.