Continuity of diabetes care among elderly Japanese patients: a medical record review study in a specialized diabetes clinic.

Aims: Continuity of diabetes care is relevant among elderly patients. The aim of this study is to investigate the impact of clinical characteristics on continuing outpatient visits to a specialized diabetes clinic in elderly Japanese patients with diabetes. Methods: We included outpatients with type 2 diabetes aged ≥ 65 years who first visited our clinic from 2006 to 2009. The information of patients' characteristics was obtained through medical record review from the CoDiC database. We have tracked whether the patients continued to visit the clinic until May 31, 2019. A Cox proportional hazards regression model identified variables related to withdrawal. Results: Among 128 patients, 63 patients (49.2%) were withdrawn during the follow-up periods. The average visit duration of withdrawals was 4.6 (range 1, 10) years. The patients who discontinued to visit were older (72.6 vs. 69.5 years old, p = 0.005) compared with those who continued to visit. No significant differences in clinical conditions such as complication of diabetes, Charlson Comorbidity Index and polypharmacy between the first and last visit were observed in each group. Age (≥ 75 years) was significantly associated with withdrawal (hazard ratio 2.72 [95% confidence interval 1.59, 4.63], p < 0.001). Except for age, no significant differences were observed in all variables when adjusted for confounders. Conclusions: Our findings indicated that continuous outpatient visits were difficult in elderly Japanese patients with diabetes. Older age (≥ 75 years) independently affected withdrawal. Future multicenter studies with adequate populations and social and geriatric factors are necessary to confirm our findings.

Hepatic CREB3L3 controls whole-body energy homeostasis and improves obesity and diabetes.

Transcriptional regulation of metabolic genes in the liver is the key to maintaining systemic energy homeostasis during starvation. The membrane-bound transcription factor cAMP-responsive element-binding protein 3-like 3 (CREB3L3) has been reported to be activated during fasting and to regulate triglyceride metabolism. Here, we show that CREB3L3 confers a wide spectrum of metabolic responses to starvation in vivo. Adenoviral and transgenic overexpression of nuclear CREB3L3 induced systemic lipolysis, hepatic ketogenesis, and insulin sensitivity with increased energy expenditure, leading to marked reduction in body weight, plasma lipid levels, and glucose levels. CREB3L3 overexpression activated gene expression levels and plasma levels of antidiabetic hormones, including fibroblast growth factor 21 and IGF-binding protein 2. Amelioration of diabetes by hepatic activation of CREB3L3 was also observed in several types of diabetic obese mice. Nuclear CREB3L3 mutually activates the peroxisome proliferator-activated receptor (PPAR) α promoter in an autoloop fashion and is crucial for the ligand transactivation of PPARα by interacting with its transcriptional regulator, peroxisome proliferator-activated receptor gamma coactivator-1α. CREB3L3 directly and indirectly controls fibroblast growth factor 21 expression and its plasma level, which contributes at least partially to the catabolic effects of CREB3L3 on systemic energy homeostasis in the entire body. Therefore, CREB3L3 is a therapeutic target for obesity and diabetes.

[Granular cell tumor of the neurohypophysis observed with hypoglycemic attack].

Granular cell tumor of the neurohypophysis (GCT) occurs as a solitary, small, nodular tumor and rarely grows to a sufficient size to present symptoms. The authors report a case of a 30-year-old man with GCT presenting with hypoglycemic attack. Hypoglycemic attack could be due to dysfunction of the hypothalamus and one of the important symptoms of GCT.

Elovl6 promotes nonalcoholic steatohepatitis.

UNLABELLED: Nonalcoholic steatohepatitis (NASH) is associated with obesity and type 2 diabetes, and an increased risk for liver cirrhosis and cancer. ELOVL family member 6, elongation of very long chain fatty acids (Elovl6), is a microsomal enzyme that regulates the elongation of C12-16 saturated and monounsaturated fatty acids (FAs). We have shown previously that Elovl6 is a major target for sterol regulatory element binding proteins in the liver and that it plays a critical role in the development of obesity-induced insulin resistance by modifying FA composition. To further investigate the role of Elovl6 in the development of NASH and its underlying mechanism, we used three independent mouse models with loss or gain of function of Elovl6, and human liver samples isolated from patients with NASH. Our results demonstrate that (1) Elovl6 is a critical modulator for atherogenic high-fat diet-induced inflammation, oxidative stress, and fibrosis in the liver; (2) Elovl6 expression is positively correlated with severity of hepatosteatosis and liver injury in NASH patients; and (3) deletion of Elovl6 reduces palmitate-induced activation of the NLR family pyrin domain-containing 3 inflammasome; this could be at least one of the underlying mechanisms by which Elovl6 modulates the progress of NASH. CONCLUSION: Hepatic long-chain fatty acid composition is a novel determinant in NASH development, and Elovl6 could be a potential therapeutic target for the prevention and treatment of NASH.

TFE3 regulates muscle metabolic gene expression, increases glycogen stores, and enhances insulin sensitivity in mice.

The role of transcription factor E3 (TFE3), a bHLH transcription factor, in immunology and cancer has been well characterized. Recently, we reported that TFE3 activates hepatic IRS-2 and hexokinase, participates in insulin signaling, and ameliorates diabetes. However, the effects of TFE3 in other organs are poorly understood. Herein, we examined the effects of TFE3 on skeletal muscle, an important organ involved in glucose metabolism. We generated transgenic mice that selectively express TFE3 in skeletal muscles. These mice exhibit a slight acceleration in growth prior to adulthood as well as a progressive increase in muscle mass. In TFE3 transgenic muscle, glycogen stores were more than twofold than in wild-type mice, and this was associated with an upregulation of genes involved in glucose metabolism, specifically glucose transporter 4, hexokinase II, and glycogen synthase. Consequently, exercise endurance capacity was enhanced in this transgenic model. Furthermore, insulin sensitivity was enhanced in transgenic mice and exhibited better improvement after 4 wk of exercise training, which was associated with increased IRS-2 expression. The effects of TFE3 on glucose metabolism in skeletal muscle were different from that in the liver, although they did, in part, overlap. The potential role of TFE3 in regulating metabolic genes and glucose metabolism within skeletal muscle suggests that it may be used for treating metabolic diseases as well as increasing endurance in sport.

Macrophage Elovl6 deficiency ameliorates foam cell formation and reduces atherosclerosis in low-density lipoprotein receptor-deficient mice.

OBJECTIVE: Elovl6, a long-chain fatty acid elongase, is a rate-limiting enzyme that elongates saturated and monounsaturated fatty acids and has been shown to be related to obesity-induced insulin resistance via modification of fatty acid composition. In this study, we investigated the roles of Elovl6 in foam cell formation in macrophages and atherosclerosis in mice. METHODS AND RESULTS: To investigate the roles of Elovl6 in macrophages in the progression of atherosclerosis, we transplanted bone marrow cells of wild-type or Elovl6(-/-) mice into irradiated LDL-R(-/-) mice that were fed a western diet. Aortic atherosclerotic lesion areas and infiltration of macrophages were significantly smaller in Elovl6(-/-) bone marrow cells-transplanted LDL-R(-/-) mice than in wild-type. Accumulation of esterified cholesterol on exposure to acetylated-LDL was less severe in peritoneal macrophages from Elovl6(-/-) mice than those from wild-type. Cholesterol efflux and expression of cholesterol efflux transporters were increased in Elovl6(-/-) macrophages, although no difference in uptake of acetylated-LDL was found between the two groups. On analysis of fatty acid composition of the esterified cholesterol fraction in macrophages, n-6 polyunsaturated fatty acids were decreased by absence of Elovl6. CONCLUSIONS: These findings suggest that Elovl6 in macrophages may contribute to foam cell formation and progression of atherosclerosis.

Sterol regulatory element-binding protein-1 determines plasma remnant lipoproteins and accelerates atherosclerosis in low-density lipoprotein receptor-deficient mice.

OBJECTIVE: Sterol regulatory element-binding protein-1 (SREBP-1) is nutritionally regulated and is known to be a key transcription factor regulating lipogenic enzymes. The goal of this study was to evaluate the roles of SREBP-1 in dyslipidemia and atherosclerosis. METHODS AND RESULTS: Transgenic mice that overexpress SREBP-1c in the liver and SREBP-1-deficient mice were crossed with low-density lipoprotein receptor (LDLR)-deficient mice, and the plasma lipids and atherosclerosis were analyzed. Hepatic SREBP-1c overexpression in LDLR-deficient mice caused postprandial hypertriglyceridemia, increased very-low-density lipoprotein (VLDL) cholesterol, and decreased high-density lipoprotein cholesterol in plasma, which resulted in accelerated aortic atheroma formation. Conversely, absence of SREBP-1 suppressed Western diet-induced hyperlipidemia in LDLR-deficient mice and ameliorated atherosclerosis. In contrast, bone marrow-specific SREBP-1 deficiency did not alter the development of atherosclerosis. The size of nascent VLDL particles secreted from the liver was increased in SREBP-1c transgenic mice and reduced in SREBP-1-deficient mice, accompanied by upregulation and downregulation of phospholipid transfer protein expression, respectively. CONCLUSIONS: Hepatic SREBP-1c determines plasma triglycerides and remnant cholesterol and contributes to atherosclerosis in hyperlipidemic states. Hepatic SREBP-1c also regulates the size of nascent VLDL particles.

Thunderclap headache without hypertension in a patient with pheochromocytoma.

Pheochromocytoma is a well known, catecholamine-producing tumor characterized by hypertension, headache, hyperglycemia, hypermetabolism, and hyperhydrosis. Approximately 65% of cases of pheochromocytoma were shown to be associated with hypertension. A case of pheochromocytoma that presented with thunderclap headache (TCH) and palpitations is reported. The patient never showed hypertension during the course of the disease. Paroxysmal headache and palpitations led to the identification of the underlying condition, and the final diagnosis was confirmed by histopathological examination of a surgical specimen. Pheochromocytoma should be identified as a less common although important cause of TCH. In addition, due to its lack of utility in identifying this disorder, negative cranial imaging may impede further investigation of extracranial lesions that may be the cause of a patient's headache. According to the International Classification of Headache Disorders (ICHD)-II, headache attributed to pheochromocytoma usually develops concomitantly with an abrupt increase in blood pressure. In our case, however, hypertension was never observed, even when the patient was symptomatic. This is the first report of a case of pheochromocytoma with TCH without hypertension.

Protein kinase Cbeta mediates hepatic induction of sterol-regulatory element binding protein-1c by insulin.

Sterol-regulatory element binding protein-1c (SREBP-1c) is a transcription factor that controls lipogenesis in the liver. Hepatic SREBP-1c is nutritionally regulated, and its sustained activation causes hepatic steatosis and insulin resistance. Although regulation of SREBP-1c is known to occur at the transcriptional level, the precise mechanism by which insulin signaling activates SREBP-1c promoter remains to be elucidated. Here we show that protein kinase C beta (PKCbeta) is a key mediator of insulin-mediated activation of hepatic SREBP-1c and its target lipogenic genes. Activation of SREBP-1c in the liver of refed mice was suppressed by either adenoviral RNAi-mediated knockdown or dietary administration of a specific inhibitor of protein kinase C beta. The effect of PKCbeta inhibition was cancelled in insulin depletion by streptozotocin (STZ) treatment of mice. Promoter analysis indicated that PKCbeta activates SREBP-1c promoter through replacement of Sp3 by Sp1 for binding to the GC box in the sterol regulatory element (SRE) complex, a key cis-element of SREBP-1c promoter. Knockdown of Sp proteins demonstrated that Sp3 and Sp1 play reciprocally negative and positive roles in nutritional regulation of SREBP-1c, respectively. This new understanding of PKCbeta involvement in nutritional regulation of SREBP-1c activation provides a new aspect of PKCbeta inhibition as a potential therapeutic target for diabetic complications.

Cyclin-dependent kinase inhibitor, p21WAF1/CIP1, is involved in adipocyte differentiation and hypertrophy, linking to obesity, and insulin resistance.

Both adipocyte hyperplasia and hypertrophy are determinant factors for adipocyte differentiation during the development of obesity. p21(WAF1/CIP1), a cyclin-dependent kinase inhibitor, is induced during adipocyte differentiation; however, its precise contribution to this process is unknown. Using both in vitro and in vivo systems, we show that p21 is crucial for maintaining adipocyte hypertrophy and obesity-induced insulin resistance. The absence of p21 in 3T3-L1 fibroblasts by RNA-mediated interference knockdown or in embryonic fibroblasts from p21(-/-) mice impaired adipocyte differentiation, resulting in smaller adipocytes. Despite normal adipose tissue mass on a normal diet, p21(-/-) mice fed high energy diets had reduced adipose tissue mass and adipocyte size accompanied by a marked improvement in insulin sensitivity. Knockdown of p21 in enlarged epididymal fat of diet-induced obese mice and also in fully differentiated 3T3-L1 adipocytes caused vigorous apoptosis by activating p53. Thus, p21 is involved in both adipocyte differentiation and in protecting hypertrophied adipocytes against apoptosis. Via both of these mechanisms, p21 promotes adipose tissue expansion during high fat diet feeding, leading to increased downstream pathophysiological consequences such as insulin resistance.

Palmitate impairs and eicosapentaenoate restores insulin secretion through regulation of SREBP-1c in pancreatic islets.

OBJECTIVE: Chronic exposure to fatty acids causes beta-cell failure, often referred to as lipotoxicity. We investigated its mechanisms, focusing on contribution of SREBP-1c, a key transcription factor for lipogenesis. RESEARCH DESIGN AND METHODS: We studied in vitro and in vivo effects of saturated and polyunsaturated acids on insulin secretion, insulin signaling, and expression of genes involved in beta-cell functions. Pancreatic islets isolated from C57BL/6 control and SREBP-1-null mice and adenoviral gene delivery or knockdown systems of related genes were used. RESULTS: Incubation of C57BL/6 islets with palmitate caused inhibition of both glucose- and potassium-stimulated insulin secretion, but addition of eicosapentaenoate (EPA) restored both inhibitions. Concomitantly, palmitate activated and EPA abolished both mRNA and nuclear protein of SREBP-1c, accompanied by reciprocal changes of SREBP-1c target genes such as insulin receptor substrate-2 (IRS-2) and granuphilin. These palmitate-EPA effects on insulin secretion were abolished in SREBP-1-null islets. Suppression of IRS-2/Akt pathway could be a part of the downstream mechanism for the SREBP-1c-mediated insulin secretion defect because adenoviral constitutively active Akt compensated it. Uncoupling protein-2 (UCP-2) also plays a crucial role in the palmitate inhibition of insulin secretion, as confirmed by knockdown experiments, but SREBP-1c contribution to UCP-2 regulation was partial. The palmitate-EPA regulation of insulin secretion was similarly observed in islets from C57BL/6 mice pretreated with dietary manipulations. Furthermore, administration of EPA to diabetic KK-Ay mice ameliorated impairment of insulin secretion in their islets. CONCLUSIONS: SREBP-1c plays a dominant role in palmitate-mediated insulin secretion defect, and EPA prevents it through SREBP-1c inhibition, implicating a therapeutic potential for treating diabetes related to lipotoxicity.

Mouse Elovl-6 promoter is an SREBP target.

Elovl-6, a long fatty acid elongase, contributes to de novo synthesis of fatty acids and regulates hepatic insulin sensitivity. Hepatic regulation of Elovl-6 gene expression in various nutritional conditions suggested that, like other lipogenic enzyme genes, Elovl-6 is a target of SREBP-1, a transcription factor governing fatty acid synthesis. Supportively, adenoviral RNAi knockdown of SREBP-1 in mouse liver suppressed Elovl-6 mRNA and fatty acid synthase levels. Therefore, we analyzed mouse Elovl-6 gene promoter to determine its role as an SREBP-1 target. Luciferase reporter assays of 1.4-kb 5' flanking region of mouse Elovl-6 gene in HepG2 cells demonstrated that nuclear SREBPs activated the Elovl-6 promoter, highlighting two SREBP binding sites: proximal SRE-1 and distal SRE-2. EMSA indicated that SRE-1 had higher affinity than SRE-2 for SREBP. ChIP assays confirmed in vivo binding of hepatic nuclear SREBP-1c protein. These data demonstrated that Elovl-6 is regulated directly and primarily by SREBP-1c.

Involvement of glomerular SREBP-1c in diabetic nephropathy.

The role of glomerular SREBP-1c in diabetic nephropathy was investigated. PEPCK-promoter transgenic mice overexpressing nuclear SREBP-1c exhibited enhancement of proteinuria with mesangial proliferation and matrix accumulation, mimicking diabetic nephropathy, despite the absence of hyperglycemia or hyperlipidemia. Isolated transgenic glomeruli had higher expression of TGFbeta-1, fibronectin, and SPARC in the absence of marked lipid accumulation. Gene expression of P47phox, p67phox, and PU.1 were also activated, accompanying increased 8-OHdG in urine and kidney, demonstrating that glomerular SREBP-1c could directly cause oxidative stress through induced NADPH oxidase. Similar changes were observed in STZ-treated diabetic mice with activation of endogenous SREBP-1c. Finally, diabetic proteinuria and oxidative stress were ameliorated in SREBP-1-null mice. Adenoviral overexpression of active and dominant-negative SREBP-1c caused consistent reciprocal changes in expression of both profibrotic and oxidative stress genes in MES13 mesangial cells. These data suggest that activation of glomerular SREBP-1c could contribute to emergence and/or progression of diabetic nephropathy.

Crucial role of a long-chain fatty acid elongase, Elovl6, in obesity-induced insulin resistance.

Insulin resistance is often associated with obesity and can precipitate type 2 diabetes. To date, most known approaches that improve insulin resistance must be preceded by the amelioration of obesity and hepatosteatosis. Here, we show that this provision is not mandatory; insulin resistance and hyperglycemia are improved by the modification of hepatic fatty acid composition, even in the presence of persistent obesity and hepatosteatosis. Mice deficient for Elovl6, the gene encoding the elongase that catalyzes the conversion of palmitate to stearate, were generated and shown to become obese and develop hepatosteatosis when fed a high-fat diet or mated to leptin-deficient ob/ob mice. However, they showed marked protection from hyperinsulinemia, hyperglycemia and hyperleptinemia. Amelioration of insulin resistance was associated with restoration of hepatic insulin receptor substrate-2 and suppression of hepatic protein kinase C epsilon activity resulting in restoration of Akt phosphorylation. Collectively, these data show that hepatic fatty acid composition is a new determinant for insulin sensitivity that acts independently of cellular energy balance and stress. Inhibition of this elongase could be a new therapeutic approach for ameliorating insulin resistance, diabetes and cardiovascular risks, even in the presence of a continuing state of obesity.

Protein kinase A suppresses sterol regulatory element-binding protein-1C expression via phosphorylation of liver X receptor in the liver.

Sterol regulatory element-binding protein (SREBP)-1c is a transcription factor that controls synthesis of fatty acids and triglycerides in the liver and is highly regulated by nutrition and hormones. In the current studies we show that protein kinase A (PKA), a mediator of glucagon/cAMP, a fasting signaling, suppresses SREBP-1c by modulating the activity of liver X receptor alpha (LXRalpha), a dominant activator of SREBP-1c expression. Activation of PKA repressed LXR-induced SREBP-1c expression both in rat primary hepatocytes and mouse livers. Promoter analyses revealed that the LXRalpha-binding site in the SREBP-1c promoter is responsible for PKA inhibitory effect on SREBP-1c transcription. In vitro and in vivo PKA directly phosphorylated LXRalpha, and the two consensus PKA target sites (195, 196 serines and 290, 291 serines) in its ligand binding/heterodimerization domain were crucial for the inhibition of LXR signaling. PKA phosphorylation of LXRalpha caused impaired DNA binding activity by preventing LXRalpha/RXR dimerization and decreased its transcription activity by inhibiting recruitment of coactivator SCR-1 and enhancing recruitment of corepressor NcoR1. These results indicate that LXRalpha is regulated not only by oxysterol derivatives but also by PKA-mediated phosphorylation, which suggests that nutritional regulation of SREBP-1c and lipogenesis could be regulated at least partially through modulation of LXR.

Granuphilin is activated by SREBP-1c and involved in impaired insulin secretion in diabetic mice.

Granuphilin is a crucial component of the docking machinery of insulin-containing vesicles to the plasma membrane. Here, we show that the granuphilin promoter is a target of SREBP-1c, a transcription factor that controls fatty acid synthesis, and MafA, a beta cell differentiation factor. Potassium-stimulated insulin secretion (KSIS) was suppressed in islets with adenoviral-mediated overexpression of granuphilin and enhanced in islets with knockdown of granuphilin (in which granuphilin had been knocked down). SREBP-1c and granuphilin were activated in islets from beta cell-specific SREBP-1c transgenic mice, as well as in several diabetic mouse models and normal islets treated with palmitate, accompanied by a corresponding reduction in insulin secretion. Knockdown- or knockout-mediated ablation of granuphilin or SREBP-1c restored KSIS in these islets. Collectively, our data provide evidence that activation of the SREBP-1c/granuphilin pathway is a potential mechanism for impaired insulin secretion in diabetes, contributing to beta cell lipotoxicity.

TFE3 transcriptionally activates hepatic IRS-2, participates in insulin signaling and ameliorates diabetes.

Using an expression cloning strategy, we have identified TFE3, a basic helix-loop-helix protein, as a transactivator of metabolic genes that are regulated through an E-box in their promoters. Adenovirus-mediated expression of TFE3 in hepatocytes in culture and in vivo strongly activated expression of IRS-2 and Akt and enhanced phosphorylation of insulin-signaling kinases such as Akt, glycogen synthase kinase 3beta and p70S6 kinase. TFE3 also induced hexokinase II (HK2) and insulin-induced gene 1 (INSIG1). These changes led to metabolic consequences, such as activation of glycogen and protein synthesis, but not lipogenesis, in liver. Collectively, plasma glucose levels were markedly reduced both in normal mice and in different mouse models of diabetes, including streptozotocin-treated, db/db and KK mice. Promoter analyses showed that IRS2, HK2 and INSIG1 are direct targets of TFE3. Activation of insulin signals in both insulin depletion and resistance suggests that TFE3 could be a therapeutic target for diabetes.

Lipid synthetic transcription factor SREBP-1a activates p21WAF1/CIP1, a universal cyclin-dependent kinase inhibitor.

Sterol regulatory element-binding proteins (SREBPs) are membrane-bound transcription factors that regulate lipid synthetic genes. In contrast to SREBP-2, which regulates cellular cholesterol level in normal cells, SREBP-1a is highly expressed in actively growing cells and activates entire programs of genes involved in lipid synthesis such as cholesterol, fatty acids, triglycerides, and phospholipids. Previously, the physiological relevance of this potent activity of SREBP-1a has been thought to regulate the supply of membrane lipids in response to cell growth. Here we show that nuclear SREBP-1a and SREBP-2 bind directly to a novel SREBP binding site in the promoter of the p21(WAF1/CIP1) gene, the major cyclin-dependent kinase inhibitor, and strongly activate its promoter activity. Only the SREBP-1a isoform consistently causes induction of p21 at both the mRNA and protein levels. Colony formation assays and polyploidy of livers from transgenic mice suggest that activation of p21 by SREBP-1a could inhibit cell growth. Activation of endogenous SREBPs in lipid deprivation conditions was associated with induction of p21 mRNA and protein. Expression of p21 was reduced in SREBP-1 null mice. These data suggest a physiological role of SREBP-1a in p21 regulation. Identification of p21 as a new SREBP target might implicate a new paradigm in the link between lipid synthesis and cell growth.

Statins downregulate ATP-binding-cassette transporter A1 gene expression in macrophages.

The ATP-binding-cassette transporter A1 (ABCA1) plays an essential role in cellular cholesterol efflux and helps prevent macrophages from becoming foam cells. The statins are widely used as cholesterol-lowering agents and have other anti-atherogenic actions. We tested the effects of four different statins (fluvastatin, atorvastatin, simvastatin, and lovastatin) on ABCA1 expression in macrophages in vitro. The statins suppressed ABCA1 mRNA expression in RAW246.7 and THP-1 macrophage cell lines and in mouse peritoneal macrophages. The effect was time- and dose-dependent and was abolished by the addition of the post-reductase product, mevalonate. These findings imply that there is a possible modulation of the well-known beneficial effects of the statins on the reverse cholesterol transport pathway.