Intensive insulin therapy prevents the progression of diabetic microvascular complications in Japanese patients with non-insulin-dependent diabetes mellitus: a randomized prospective 6-year study

To examine whether intensive glycemic control could decrease the frequency or severity of diabetic microvascular complications, we performed a prospective study of Japanese patients with non-insulin-dependent diabetes mellitus (NIDDM) treated with multiple insulin injection treatment. A total of 110 patients with NIDDM was randomly assigned to multiple insulin injection treatment group (MIT group) or to conventional insulin injection treatment group (CIT group). Fifty-five NIDDM patients who showed no retinopathy and urinary albumin excretions < 30 mg/24 h at the baseline were evaluated in the primary-prevention cohort, and the other 55 NIDDM patients who showed simple retinopathy and urinary albumin excretions < 300 mg/24 h were evaluated in the secondary-intervention cohort. The appearance and the progression of retinopathy, nephropathy and neuropathy were evaluated every 6 months over a 6-year period. The worsening of complications in this study was defined as an increase of 2 or more steps in the 19 stages of the modified ETDRS interim scale for retinopathy and an increase of one or more steps in 3 stages (normoalbuminuria, microalbuminuria and albuminuria) for nephropathy. The cumulative percentages of the development and the progression in retinopathy after 6 years were 7.7% for the MIT group and 32.0% for the CIT group in the primary-prevention cohort (P = 0.039), and 19.2% for MIT group and 44.0% for CIT group in the secondary-intervention cohort (P = 0.049). The cumulative percentages of the development and the progression in nephropathy after 6 years were 7.7% for the MIT group and 28.0% for the CIT group in the primary-prevention cohort (P = 0.032), and 11.5% and 32.0%, respectively, for the MIT and CIT groups in the secondary-intervention cohort (P = 0.044). In neurological tests after 6 years, MIT group showed significant improvement in the nerve conduction velocities, while the CIT group showed significant deterioration in the median nerve conduction velocities and vibration threshold. Although both postural hypotension and the coefficient of variation of R-R interval tended to improve in the MIT group, they deteriorated in the CIT group. In conclusion, intensive glycemic control by multiple insulin injection therapy can delay the onset and the progression of diabetic retinopathy, nephropathy and neuropathy in Japanese patients with NIDDM. From this study, the glycemic threshold to prevent the onset and the progression of diabetic microangiopathy is indicated as follows; HbA1c < 6.5%, FBG < 110 mg/dl, and 2-h post-prandial blood glucose concentration < 180 mg/dl.

Structure of the insulin receptor substrate IRS-1 defines a unique signal transduction protein

Since the discovery of insulin nearly 70 years ago, there has been no problem more fundamental to diabetes research than understanding how insulin works at the cellular level. Insulin binds to the alpha subunit of the insulin receptor which activates the tyrosine kinase in the beta subunit, but the molecular events linking the receptor kinase to insulin-sensitive enzymes and transport processes are unknown. Our discovery that insulin stimulates tyrosine phosphorylation of a protein of relative molecular mass between 165,000 and 185,000, collectively called pp185, showed that the insulin receptor kinase has specific cellular substrates. The pp185 is a minor cytoplasmic phosphoprotein found in most cells and tissues; its phosphorylation is decreased in cells expressing mutant receptors defective in signalling. We have now cloned IRS-1, which encodes a component of the pp185 band. IRS-1 contains over ten potential tyrosine phosphorylation sites, six of which are in Tyr-Met-X-Met motifs. During insulin stimulation, the IRS-1 protein undergoes tyrosine phosphorylation and binds phosphatidylinositol 3-kinase, suggesting that IRS-1 acts as a multisite 'docking' protein to bind signal-transducing molecules containing Src-homology 2 and Src-homology-3 domains. Thus IRS-1 may link the insulin receptor kinase and enzymes regulating cellular growth and metabolism.

Report of the committee on the classification and diagnostic criteria of diabetes mellitus

CONCEPT OF DIABETES MELLITUS

Diabetes mellitus is a group of diseases associated with various metabolic disorders, the main feature of which is chronic hyperglycemia due to insufficient insulin action. Its pathogenesis involves both genetic and environmental factors. The long-term persistence of metabolic disorders can cause susceptibility to specific complications and also foster arteriosclerosis. Diabetes mellitus is associated with a broad range of clinical presentations, from being asymptomatic to ketoacidosis or coma, depending on the degree of metabolic disorder. CLASSIFICATION TABLES 1 AND 2 AND FIGURE 1: [Table: see text] [Table: see text] Figure 1 A scheme of the relationship between etiology (mechanism) and patho-physiological stages (states) of diabetes mellitus. Arrows pointing right represent worsening of glucose metabolism disorders (including onset of diabetes mellitus). Among the arrow lines, indicates the condition classified as 'diabetes mellitus'. Arrows pointing left represent improvement in the glucose metabolism disorder. The broken lines indicate events of low frequency. For example, in type 2 diabetes mellitus, infection can lead to ketoacidosis and require temporary insulin treatment for survival. Also, once diabetes mellitus has developed, it is treated as diabetes mellitus regardless of improvement in glucose metabolism, therefore, the arrow lines pointing left are filled in black. In such cases, a broken line is used, because complete normalization of glucose metabolism is rare.imageThe classification of glucose metabolism disorders is principally derived from etiology, and includes staging of pathophysiology based on the degree of deficiency of insulin action. These disorders are classified into four groups: (i) type 1 diabetes mellitus; (ii) type 2 diabetes mellitus; (iii) diabetes mellitus due to other specific mechanisms or diseases; and (iv) gestational diabetes mellitus. Type 1 diabetes is characterized by destruction of pancreatic β-cells. Type 2 diabetes is characterized by combinations of decreased insulin secretion and decreased insulin sensitivity (insulin resistance). Glucose metabolism disorders in category (iii) are divided into two subgroups; subgroup A is diabetes in which a genetic abnormality has been identified, and subgroup B is diabetes associated with other pathologic disorders or clinical conditions. The staging of glucose metabolism includes normal, borderline and diabetic stages depending on the degree of hyperglycemia occurring as a result of the lack of insulin action or clinical condition. The diabetic stage is then subdivided into three substages: non-insulin- requiring, insulin-requiring for glycemic control, and insulin-dependent for survival. The two former conditions are called non-insulin-dependent diabetes and the latter is known as insulin-dependent diabetes. In each individual, these stages may vary according to the deterioration or the improvement of the metabolic state, either spontaneously or by treatment. DIAGNOSIS TABLES 3–7 AND FIGURE 2: [Table: see text] [Table: see text] [Table: see text] [Table: see text] [Table: see text] Figure 2 Flow chart outlining steps in the clinical diagnosis of diabetes mellitus. *The value for HbA1c (%) is indicated with 0.4% added to HbA1c (JDS) (%).imageCategories of the State of Glycemia:  Confirmation of chronic hyperglycemia is essential for the diagnosis of diabetes mellitus. When plasma glucose levels are used to determine the categories of glycemia, patients are classified as having a diabetic type if they meet one of the following criteria: (i) fasting plasma glucose level of ≥126 mg/dL (≥7.0 mmol/L); (ii) 2-h value of ≥200 mg/dL (≥11.1 mmol/L) in 75 g oral glucose tolerance test (OGTT); or (iii) casual plasma glucose level of ≥200 mg/dL (≥11.1 mmol/L). Normal type is defined as fasting plasma glucose level of <110 mg/dL (<6.1 mmol/L) and 2-h value of <140 mg/dL (<7.8 mmol/L) in OGTT. Borderline type (neither diabetic nor normal type) is defined as falling between the diabetic and normal values. According to the current revision, in addition to the earlier listed plasma glucose values, hemoglobin A1c (HbA1c) has been given a more prominent position as one of the diagnostic criteria. That is, (iv) HbA1c≥6.5% is now also considered to indicate diabetic type. The value of HbA1c, which is equivalent to the internationally used HbA1c (%) (HbA1c [NGSP]) defined by the NGSP (National Glycohemoglobin Standardization Program), is expressed by adding 0.4% to the HbA1c (JDS) (%) defined by the Japan Diabetes Society (JDS). Subjects with borderline type have a high rate of developing diabetes mellitus, and correspond to the combination of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT) noted by the American Diabetes Association (ADA) and WHO. Although borderline cases show few of the specific complications of diabetes mellitus, the risk of arteriosclerosis is higher than those of normal type. When HbA1c is 6.0-6.4%, suspected diabetes mellitus cannot be excluded, and when HbA1c of 5.6-5.9% is included, it forms a group with a high risk for developing diabetes mellitus in the future, even if they do not have it currently. Clinical Diagnosis: 1 If any of the criteria for diabetic type (i) through to (iv) is observed at the initial examination, the patient is judged to be 'diabetic type'. Re-examination is conducted on another day, and if 'diabetic type' is reconfirmed, diabetes mellitus is diagnosed. However, a diagnosis cannot be made only by the re-examination of HbA1c alone. Moreover, if the plasma glucose values (any of criteria [i], [ii], or [iii]) and the HbA1c (criterion [iv]) in the same blood sample both indicate diabetic type, diabetes mellitus is diagnosed based on the initial examination alone. If HbA1c is used, it is essential that the plasma glucose level (criteria [i], [ii] or [iii]) also indicates diabetic type for a diagnosis of diabetes mellitus. When diabetes mellitus is suspected, HbA1c should be measured at the same time as examination for plasma glucose.2 If the plasma glucose level indicates diabetic type (any of [i], [ii], or [iii]) and either of the following conditions exists, diabetes mellitus can be diagnosed immediately at the initial examination.• The presence of typical symptoms of diabetes mellitus (thirst, polydipsia, polyuria, weight loss)• The presence of definite diabetic retinopathy3 If it can be confirmed that the above conditions 1 or 2 existed in the past, diabetes mellitus can be diagnosed or suspected regardless of the current test results.4 If the diagnosis of diabetes cannot be established by these procedures, the patient is followed up and re-examined after an appropriate interval.5 The physician should assess not only the presence or absence of diabetes, but also its etiology and glycemic stage, and the presence and absence of diabetic complications or associated conditions. Epidemiological Study:  For the purpose of estimating the frequency of diabetes mellitus, 'diabetes mellitus' can be substituted for the determination of 'diabetic type' from a single examination. In this case, HbA1c≥6.5% alone can be defined as 'diabetes mellitus'. Health Screening:  It is important not to misdiagnose diabetes mellitus, and thus clinical information such as family history and obesity should be referred to at the time of screening in addition to an index for plasma glucose level. Gestational Diabetes Mellitus:  There are two hyperglycemic disorders in pregnancy: (i) gestational diabetes mellitus (GDM); and (ii) diabetes mellitus. GDM is diagnosed if one or more of the following criteria is met in a 75 g OGTT during pregnancy: 1 Fasting plasma glucose level of ≥92 mg/dL (5.1 mmol/L)2 1-h value of ≥180 mg/dL (10.0 mmol/L)3 2-h value of ≥153 mg/dL (8.5 mmol/L) However, diabetes mellitus that is diagnosed by the clinical diagnosis of diabetes mellitus defined earlier is excluded from GDM. (J Diabetes Invest, doi: 10.1111/j.2040-1124.2010.00074.x, 2010).

Alternative pathway of insulin signalling in mice with targeted disruption of the IRS-1 gene

The principal substrate for the insulin and insulin-like growth factor-1 (IGF-1) receptors is the cytoplasmic protein insulin-receptor substrate-1 (IRS-1/pp185). After tyrosine phosphorylation at several sites, IRS-1 binds to and activates phosphatidylinositol-3'-OH kinase (PI(3)K) and several other proteins containing SH2 (Src-homology 2) domains. To elucidate the role of IRS-1 in insulin/IGF-1 action, we created IRS-1-deficient mice by targeted gene mutation. These mice had no IRS-1 and showed no evidence of IRS-1 phosphorylation or IRS-1-associated PI(3)K activity. They also had a 50 per cent reduction in intrauterine growth, impaired glucose tolerance, and a decrease in insulin/IGF-1-stimulated glucose uptake in vivo and in vitro. The residual insulin/IGF-1 action correlated with the appearance of a new tyrosine-phosphorylated protein (IRS-2) which binds to PI(3)K, but is slightly larger than and immunologically distinct from IRS-1. Our results provide evidence for IRS-1-dependent and IRS-1-independent pathways of insulin/IGF-1 signalling and for the existence of an alternative substrate of these receptor kinases.

Adiponectin stimulates AMP-activated protein kinase in the hypothalamus and increases food intake

Adiponectin has been shown to stimulate fatty acid oxidation and enhance insulin sensitivity through the activation of AMP-activated protein kinase (AMPK) in the peripheral tissues. The effects of adiponectin in the central nervous system, however, are still poorly understood. Here, we show that adiponectin enhances AMPK activity in the arcuate hypothalamus (ARH) via its receptor AdipoR1 to stimulate food intake; this stimulation of food intake by adiponectin was attenuated by dominant-negative AMPK expression in the ARH. Moreover, adiponectin also decreased energy expenditure. Adiponectin-deficient mice showed decreased AMPK phosphorylation in the ARH, decreased food intake, and increased energy expenditure, exhibiting resistance to high-fat-diet-induced obesity. Serum and cerebrospinal fluid levels of adiponectin and expression of AdipoR1 in the ARH were increased during fasting and decreased after refeeding. We conclude that adiponectin stimulates food intake and decreases energy expenditure during fasting through its effects in the central nervous system.

Nitric oxide-induced apoptosis in pancreatic beta cells is mediated by the endoplasmic reticulum stress pathway

Excessive nitric oxide (NO) production in cytokine-activated beta cells has been implicated in beta cell disruption in type 1 diabetes. beta cells are very vulnerable to NO-induced apoptosis. However, the mechanism underlying this phenomenon is unclear. Low concentrations of NO that lead to apoptosis apparently do not cause severe DNA damage in mouse MIN6 beta cells. CHOP, a C/EBP homologous protein that is induced by endoplasmic reticulum (ER) stress and plays a role in growth arrest and cell death, was induced by a NO donor, S-nitroso-N-acetyl-D,L-penicillamine (SNAP). SNAP increased cytosolic Ca(2+), and only agents depleting ER Ca(2+) induced CHOP expression and led to apoptosis, suggesting that NO depletes ER Ca(2+). Overexpression of calreticulin increased the Ca(2+) content of ER and afforded protection to cells against NO-mediated apoptosis. Furthermore, pancreatic islets from CHOP knockout mice showed resistance to NO. We conclude that NO depletes ER Ca(2+), causes ER stress, and leads to apoptosis. Thus, ER Ca(2+) stores are a new target of NO, and the ER stress pathway is a major mechanism of NO-mediated beta cell apoptosis.

Targeted disruption of the Chop gene delays endoplasmic reticulum stress-mediated diabetes

Overload of pancreatic beta cells in conditions such as hyperglycemia, obesity, and long-term treatment with sulfonylureas leads to beta cell exhaustion and type 2 diabetes. Because beta cell mass declines under these conditions, apparently as a result of apoptosis, we speculated that overload kills beta cells as a result of endoplasmic reticulum (ER) stress. The Akita mouse, which carries a conformation-altering missense mutation (Cys96Tyr) in Insulin 2, likewise exhibits hyperglycemia and a reduced beta cell mass. In the development of diabetes in Akita mice, mRNAs for the ER chaperone Bip and the ER stress-associated apoptosis factor Chop were induced in the pancreas. Overexpression of the mutant insulin in mouse MIN6 beta cells induced Chop expression and led to apoptosis. Targeted disruption of the Chop gene delayed the onset of diabetes in heterozygous Akita mice by 8-10 weeks. We conclude that ER overload in beta cells causes ER stress and leads to apoptosis via Chop induction. Our findings suggest a new therapeutic approach for preventing the onset of diabetes by inhibiting Chop induction or by increasing chaperone capacity in the ER.

AMPK and cell proliferation--AMPK as a therapeutic target for atherosclerosis and cancer

AMPK is a serine/threonine protein kinase, which serves as an energy sensor in all eukaryotic cell types. Published studies indicate that AMPK activation strongly suppresses cell proliferation in non-malignant cells as well as in tumour cells. These actions of AMPK appear to be mediated through multiple mechanisms including regulation of the cell cycle and inhibition of protein synthesis, de novo fatty acid synthesis, specifically the generation of mevalonate as well as other products downstream of mevalonate in the cholesterol synthesis pathway. Cell cycle regulation by AMPK is mediated by up-regulation of the p53-p21 axis as well as regulation of TSC2-mTOR (mammalian target of rapamycin) pathway. The AMPK signalling network contains a number of tumour suppressor genes including LKB1, p53, TSC1 and TSC2, and overcomes growth factor signalling from a variety of stimuli (via growth factors and by abnormal regulation of cellular proto-oncogenes including PI3K, Akt and ERK). These observations suggest that AMPK activation is a logical therapeutic target for diseases rooted in cellular proliferation, including atherosclerosis and cancer. In this review, we discuss about exciting recent advances indicating that AMPK functions as a suppressor of cell proliferation by controlling a variety of cellular events in normal cells as well as in tumour cells.

Endoplasmic reticulum stress-mediated apoptosis in pancreatic beta-cells

Apoptotic cell death in pancreatic beta-cells is involved in the pathogenesis of diabetes. Signals from death receptors and DNA damage have been widely accepted as being triggers of apoptosis in beta-cells. Recent studies indicated that the endoplasmic reticulum (ER) can sense and transduce apoptotic signals. Various genetic and environmental stresses interfere with protein folding in the ER and induce ER stress. In mammals, ER stress transducer proteins IRE1, PERK and ATF6 activate both survival and apoptotic pathways. The former includes transcriptional induction of ER chaperones, translational attenuation, and ER-associated degradation (ERAD) while the latter includes transcriptional induction of CHOP/GADD153, the activation of cJUN NH(2)-terminal kinase, and the activation of caspase-12. A characteristic feature of beta-cells is the highly developed ER apparently due to a heavy engagement in insulin secretion. beta-cells are most susceptible to ER stress. The recent studies reviewed in this article revealed that ER stress-mediated apoptosis in beta-cells plays an important role in the development of diabetes.

Reduced susceptibility to ischemic brain injury and N-methyl-D-aspartate-mediated neurotoxicity in cyclooxygenase-2-deficient mice

Cyclooxygenase-2 (COX-2), a prostanoid-synthesizing enzyme that contributes to the toxicity associated with inflammation, has recently emerged as a promising therapeutic target for several illnesses, ranging from osteoarthritis to Alzheimer's disease. Although COX-2 has also been linked to ischemic stroke, its role in the mechanisms of ischemic brain injury remains controversial. We demonstrate that COX-2-deficient mice have a significant reduction in the brain injury produced by occlusion of the middle cerebral artery. The protection can be attributed to attenuation of glutamate neurotoxicity, a critical factor in the initiation of ischemic brain injury, and to abrogation of the deleterious effects of postischemic inflammation, a process contributing to the secondary progression of the damage. Thus, COX-2 is involved in pathogenic events occurring in both the early and late stages of cerebral ischemia and may be a valuable therapeutic target for treatment of human stroke.

Replacement of lysine residue 1030 in the putative ATP-binding region of the insulin receptor abolishes insulin- and antibody-stimulated glucose uptake and receptor kinase activity

To test whether the tyrosine kinase activity of the insulin receptor is crucial for insulin action, we have constructed mutations of the human insulin receptor at Lys-1030, which is in the presumed ATP-binding region. By using oligonucleotide-directed mutagenesis, this lysine residue was replaced with either methionine, arginine, or alanine. Chinese hamster ovary cells were transfected by mutant cDNAs and the expressed insulin receptors were characterized. We show here that none of these mutants exhibited insulin-activated autophosphorylation and kinase activity in vitro. They also do not mediate insulin- and antibody-stimulated uptake of 2-deoxyglucose. The tyrosine kinase activity is thus required for a key physiological response of insulin.

Impact of mitochondrial ROS production in the pathogenesis of diabetes mellitus and its complications

In this review, the impacts of mitochondrial reactive oxygen species (ROS) on diabetes and its complications are described. In endothelial cells, high-glucose treatment increases mitochondrial ROS and normalization of the ROS production by inhibitors of mitochondrial metabolism, or by overexpression of UCP-1 or MnSOD, prevents glucose-induced activation of PKC, formation of AGE, and accumulation of sorbitol, all of which are believed to be the main molecular mechanisms of diabetic complications. Glomerular hyperfiltration, one of the characteristics of early diabetic nephropathy, may be caused by mitochondrial ROS through activation of COX-2 gene transcription, followed by PGE2 overproduction. In pancreatic beta cells, hyperglycemia also increases mitochondrial ROS, which suppresses the first phase of glucose-induced insulin secretion, at least in part, through the suppression of GAPDH activity. In liver cells, similar to that in hyperglycemia, TNF-alpha increases mitochondrial ROS, which in turn activates apoptosis signal-regulating kinase 1 (ASK1) and c-jun NH2-terminal kinases (JNK), increases serine phosphorylation of IRS-1, and decreases insulin-stimulated tyrosine phosphorylation of IRS-1, leading to insulin resistance. These results suggest the importance of mitochondrial ROS in the pathogenesis of diabetes mellitus and its complications through modification of various cellular events in many tissues, including vessels, kidney, pancreatic beta cells, and liver.

Reactive oxygen species from mitochondria induce cyclooxygenase-2 gene expression in human mesangial cells: potential role in diabetic nephropathy

Hyperglycemia increases the production of reactive oxygen species (ROS) from the mitochondrial electron transport chain in bovine endothelial cells. Because several studies have postulated a role for prostaglandins (PGs) in the glomerular hyperfiltration seen in early diabetes, we evaluated the effect of mitochondrial ROS on expression of the inducible isoform of cyclooxygenase (COX-2) in cultured human mesangial cells (HMCs). We first confirmed that incubation of HMC with 30 mmol/l glucose significantly increased COX-2 mRNA but not COX-1 mRNA, compared with 5.6 mmol/l glucose. Similarly, incubation of HMCs with 30 mmol/l glucose significantly increased mitochondrial membrane potential, intracellular ROS production, COX-2 protein expression, and PGE2 synthesis, and these events were completely suppressed by thenoyltrifluoroacetone or carbonyl cyanide m-chlorophenylhydrazone, inhibitors of mitochondrial metabolism, or by overexpression of uncoupling protein-1 or manganese superoxide dismutase. Furthermore, increased expression of COX-2 mRNA and protein was confirmed in glomeruli of streptozotocin-induced diabetic mice. In addition, hyperglycemia induced activation of the COX-2 gene promoter, which was completely abrogated by mutation of two nuclear factor kappaB (NF-kappaB) binding sites in the promoter region. Our results suggest that hyperglycemia increases mitochondrial ROS production, resulting in NF-kappaB activation, COX-2 mRNA induction, COX-2 protein production, and PGE2 synthesis. This chain of events might contribute to the pathogenesis of diabetic nephropathy.

Semaglutide Added to Basal Insulin in Type 2 Diabetes (SUSTAIN 5): A Randomized, Controlled Trial

CONTEXT

Combination therapy with insulin and glucagon-like peptide-1 receptor agonists (GLP-1RAs) is important for treating type 2 diabetes (T2D). This trial assesses the efficacy and safety of semaglutide, a GLP-1RA, as an add-on to basal insulin.

OBJECTIVE

To demonstrate the superiority of semaglutide vs placebo on glycemic control as an add-on to basal insulin in patients with T2D.

DESIGN

Phase 3a, double-blind, placebo-controlled, 30-week trial.

SETTING

This study included 90 sites in five countries.

PATIENTS

We studied 397 patients with uncontrolled T2D receiving stable therapy with basal insulin with or without metformin.

INTERVENTIONS

Subcutaneous semaglutide 0.5 or 1.0 mg once weekly or volume-matched placebo.

MAIN OUTCOME MEASURES

Primary endpoint was change in glycated Hb (HbA1c) from baseline to week 30. Confirmatory secondary endpoint was change in body weight from baseline to week 30.

RESULTS

At week 30, mean HbA1c reductions [mean baseline value, 8.4% (67.9 mmol/mol)] with semaglutide 0.5 and 1.0 mg were 1.4% (15.8 mmol/mol) and 1.8% (20.2 mmol/mol) vs 0.1% (1.0 mmol/mol) with placebo [estimated treatment difference (ETD) vs placebo, -1.35 (14.8 mmol/mol); 95% CI, -1.61 to -1.10 and ETD, -1.75% (19.2 mmol/mol); 95% CI, -2.01 to -1.50; both P < 0.0001]. Severe or blood glucose-confirmed hypoglycemic episodes were reported in 11 patients (17 events) and 14 patients (25 events) with semaglutide 0.5 and 1.0 mg, respectively, vs seven patients (13 events) with placebo (estimated rate ratio vs placebo, 2.08; 95% CI, 0.67 to 6.51 and estimated rate ratio vs placebo, 2.41; 95% CI, 0.84 to 6.96 for 0.5 and 1.0 mg; both P = nonsignificant). Mean body weight decreased with semaglutide 0.5 and 1.0 mg vs placebo from baseline to end of treatment: 3.7, 6.4, and 1.4 kg (ETD, -2.31; 95% CI, -3.33 to -1.29 and ETD, -5.06; 95% CI, -6.08 to -4.04 kg; both P < 0.0001). Premature treatment discontinuation due to adverse events was higher for semaglutide 0.5 and 1.0 mg vs placebo (4.5%, 6.1%, and 0.8%), mainly due to gastrointestinal disorders.

CONCLUSIONS

Semaglutide, added to basal insulin, significantly reduced HbA1c and body weight in patients with uncontrolled T2D vs placebo.

Mitochondrial reactive oxygen species reduce insulin secretion by pancreatic beta-cells

Pancreatic beta-cells exposed to hyperglycemia produce reactive oxygen species (ROS). Because beta-cells are sensitive to oxidative stress, excessive ROS may cause dysfunction of beta-cells. Here we demonstrate that mitochondrial ROS suppress glucose-induced insulin secretion (GIIS) from beta-cells. Intracellular ROS increased 15min after exposure to high glucose and this effect was blunted by inhibitors of the mitochondrial function. GIIS was also suppressed by H(2)O(2), a chemical substitute for ROS. Interestingly, the first-phase of GIIS could be suppressed by 50 microM H(2)O(2). H(2)O(2) or high glucose suppressed the activity of glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a glycolytic enzyme, and inhibitors of the mitochondrial function abolished the latter effects. Our data suggested that high glucose induced mitochondrial ROS, which suppressed first-phase of GIIS, at least in part, through the suppression of GAPDH activity. We propose that mitochondrial overwork is a potential mechanism causing impaired first-phase of GIIS in the early stages of diabetes mellitus.

Regulation of insulin receptor substrate-1 in liver and muscle of animal models of insulin resistance

Insulin rapidly stimulates tyrosine phosphorylation of a protein of approximately 185 kD in most cell types. This protein, termed insulin receptor substrate-1 (IRS-1), has been implicated in insulin signal transmission based on studies with insulin receptor mutants. In the present study we have examined the levels of IRS-1 and the phosphorylation state of insulin receptor and IRS-1 in liver and muscle after insulin stimulation in vivo in two rat models of insulin resistance, i.e., insulinopenic diabetes and fasting, and a mouse model of non-insulin-dependent diabetes mellitus (ob/ob) by immunoblotting with anti-peptide antibodies to IRS-1 and anti-phosphotyrosine antibodies. As previously described, there was an increase in insulin binding and a parallel increase in insulin-stimulated receptor phosphorylation in muscle of fasting and streptozotocin-induced (STZ) diabetic rats. There was also a modest increase in overall receptor phosphorylation in liver in these two models, but when normalized for the increase in binding, receptor phosphorylation was decreased, in liver and muscle of STZ diabetes and in liver of 72 h fasted rats. In the hyperinsulinemic ob/ob mouse there was a decrease in insulin binding and receptor phosphorylation in both liver and muscle. The tyrosyl phosphorylation of IRS-1 after insulin stimulation reflected an amplification of the receptor phosphorylation in liver and muscle of hypoinsulinemic animals (fasting and STZ diabetes) with a twofold increase, and showed a significant reduction (approximately 50%) in liver and muscle of ob/ob mouse. By contrast, the levels of IRS-1 protein showed a tissue specific regulation with a decreased level in muscle and an increased level in liver in hypoinsulinemic states of insulin resistance, and decreased levels in liver in the hyperinsulinemic ob/ob mouse. These data indicate that: (a) IRS-1 protein levels are differentially regulated in liver and muscle; (b) insulin levels may play a role in this differential regulation of IRS-1; (c) IRS-1 phosphorylation depends more on insulin receptor kinase activity than IRS-1 protein levels; and (d) reduced IRS-1 phosphorylation in liver and muscle may play a role in insulin-resistant states, especially of the ob/ob mice.

Adenosine monophosphate-activated protein kinase suppresses vascular smooth muscle cell proliferation through the inhibition of cell cycle progression

Vascular smooth muscle cell (VSMC) proliferation is a critical event in the development and progression of vascular diseases, including atherosclerosis. We investigated whether the activation of adenosine monophosphate-activated protein kinase (AMPK) could suppress VSMC proliferation and inhibit cell cycle progression. Treatment of human aortic smooth muscle cells (HASMCs) or isolated rabbit aortas with the AMPK activator 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR) induced phosphorylation of AMPK and acetyl Co-A carboxylase. AICAR significantly inhibited HASMC proliferation induced by both platelet-derived growth factor-BB (PDGF-BB) and fetal calf serum (FCS). Treatment with AICAR inhibited the phosphorylation of retinoblastoma gene product (Rb) induced by PDGF-BB or FCS, and increased the expression of cyclin-dependent kinase inhibitor p21(CIP) but not that of p27(KIP). Pharmacological inhibition of AMPK or overexpression of dominant negative-AMPK inhibited both the suppressive effect of AICAR on cell proliferation and the phosphorylation of Rb, suggesting that the effect of AICAR is mediated through the activation of AMPK. Cell cycle analysis in HASMCs showed that AICAR significantly increased cell population in G0/G1-phase and reduced that in S- and G2/M-phase, suggesting AICAR induced cell cycle arrest. AICAR increased both p53 protein and Ser-15 phosphorylated p53 in HASMCs, which were blocked by inhibition of AMPK. In isolated rabbit aortas, AICAR also increased Ser-15 phosphorylation and protein expression of p53 and inhibited Rb phosphorylation induced by FCS. These data suggest for the first time that AMPK suppresses VSMC proliferation via cell cycle regulation by p53 upregulation. Therefore, AMPK activation in VSMCs may be a therapoietic target for the prevention of vascular diseases.

Statins activate peroxisome proliferator-activated receptor gamma through extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase-dependent cyclooxygenase-2 expression in macrophages

Both statins and peroxisome proliferator-activated receptor (PPAR)gamma ligands have been reported to protect against the progression of atherosclerosis. In the present study, we investigated the effects of statins on PPARgamma activation in macrophages. Statins increased PPARgamma activity, which was inhibited by mevalonate, farnesylpyrophosphate, or geranylgeranylpyrophosphate. Furthermore, a farnesyl transferase inhibitor and a geranylgeranyl transferase inhibitor mimicked the effects of statins. Statins inhibited the membrane translocations of Ras, RhoA, Rac, and Cdc42, and overexpression of dominant-negative mutants of RhoA (DN-RhoA) and Cdc42 (DN-Cdc42), but not of Ras or Rac, increased PPARgamma activity. Statins induced extracellular signal-regulated kinase (ERK)1/2 and p38 mitogen-activated protein kinase (MAPK) activation. However, DN-RhoA and DN-Cdc42 activated p38 MAPK, but not ERK1/2. ERK1/2- or p38 MAPK-specific inhibitors abrogated statin-induced PPARgamma activation. Statins induced cyclooxygenase (COX)-2 expression and increased intracellular 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) levels through ERK1/2- and p38 MAPK-dependent pathways, and inhibitors or small interfering RNA of COX-2 inhibited statin-induced PPARgamma activation. Statins also activate PPARalpha via COX-2-dependent increases in 15d-PGJ(2) levels. We further demonstrated that statins inhibited lipopolysaccharide-induced tumor necrosis factor alpha or monocyte chemoattractant protein-1 mRNA expression, and these effects by statins were abrogated by the PPARgamma antagonist T0070907 or by small interfering RNA of PPARgamma or PPARalpha. Statins also induced ATP-binding cassette protein A1 or CD36 mRNA expression, and these effects were suppressed by small interfering RNAs of PPARgamma or PPARalpha. In conclusion, statins induce COX-2-dependent increase in 15d-PGJ(2) level through a RhoA- and Cdc42-dependent p38 MAPK pathway and a RhoA- and Cdc42-independent ERK1/2 pathway, thereby activating PPARgamma. Statins also activate PPARalpha via COX-2-dependent pathway. These effects of statins may explain their antiatherogenic actions.

Efficacy and Safety of Dapagliflozin in Patients With Inadequately Controlled Type 1 Diabetes (the DEPICT-2 Study): 24-Week Results From a Randomized Controlled Trial

OBJECTIVE

This 24-week, double-blinded, phase 3 clinical trial (DEPICT-2; ClinicalTrials.gov, NCT02460978) evaluated efficacy and safety of dapagliflozin as adjunct therapy to adjustable insulin in patients with inadequately controlled type 1 diabetes (HbA_1c 7.5-10.5%).

RESEARCH DESIGN AND METHODS

Patients were randomized 1:1:1 to dapagliflozin 5 mg (n = 271), dapagliflozin 10 mg (n = 270), or placebo (n = 272) plus insulin. Insulin dose was adjusted by investigators according to self-monitored glucose readings, local guidance, and individual circumstances.

RESULTS

Baseline characteristics were balanced between treatment groups. At week 24, dapagliflozin significantly decreased HbA_1c (primary outcome; difference vs. placebo: dapagliflozin 5 mg -0.37% [95% CI -0.49, -0.26], dapagliflozin 10 mg -0.42% [-0.53, -0.30]), total daily insulin dose (-10.78% [-13.73, -7.72] and -11.08% [-14.04, -8.02], respectively), and body weight (-3.21% [-3.96, -2.45] and -3.74% [-4.49, -2.99], respectively) (P < 0.0001 for all). Mean interstitial glucose, amplitude of glucose excursion, and percent of readings within target glycemic range (>70 to ≤180 mg/dL) versus placebo were significantly improved. More patients receiving dapagliflozin achieved a reduction in HbA_1c ≥0.5% without severe hypoglycemia compared with placebo. Adverse events were reported for 72.7%, 67.0%, and 63.2% of patients receiving dapagliflozin 5 mg, dapagliflozin 10 mg, and placebo, respectively. Hypoglycemia, including severe hypoglycemia, was balanced between groups. There were more adjudicated definite diabetic ketoacidosis (DKA) events with dapagliflozin: 2.6%, 2.2%, and 0% for dapagliflozin 5 mg, dapagliflozin 10 mg, and placebo, respectively.

CONCLUSIONS

Dapagliflozin as adjunct therapy to adjustable insulin in patients with type 1 diabetes was well tolerated and improved glycemic control with no increase in hypoglycemia versus placebo but with more DKA events.

4PS/insulin receptor substrate (IRS)-2 is the alternative substrate of the insulin receptor in IRS-1-deficient mice

Insulin receptor substrate-1 (IRS-1) is the major cytoplasmic substrate of the insulin and insulin-like growth factor (IGF)-1 receptors. Transgenic mice lacking IRS-1 are resistant to insulin and IGF-1, but exhibit significant residual insulin action which corresponds to the presence of an alternative high molecular weight substrate in liver and muscle. Recently, Sun et al. (Sun, X.-J., Wang, L.-M., Zhang, Y., Yenush, L. P., Myers, M. G., Jr., Glasheen, E., Lane, W.S., Pierce, J. H., and White, M. F. (1995) Nature 377, 173-177) purified and cloned 4PS, the major substrate of the IL-4 receptor-associated tyrosine kinase in myeloid cells, which has significant structural similarity to IRS-1. To determine if 4PS is the alternative substrate of the insulin receptor in IRS-1-deficient mice, we performed immunoprecipitation, immunoblotting, and phosphatidylinositol (PI) 3-kinase assays using specific antibodies to 4PS. Following insulin stimulation, 4PS is rapidly phosphorylated in liver and muscle, binds to the p85 subunit of PI 3-kinase, and activates the enzyme. Insulin stimulation also results in the association of 4PS with Grb 2 in both liver and muscle. In IRS-1-deficient mice, both the phosphorylation of 4PS and associated PI 3-kinase activity are enhanced, without an increase in protein expression. Immunodepletion of 4PS from liver and muscle homogenates removes most of the phosphotyrosine-associated PI 3-kinase activity in IRS-1-deficient mice. Thus, 4PS is the primary alternative substrate, i.e. IRS-2, which plays a major role in physiologic insulin signal transduction via both PI 3-kinase activation and Grb 2/Sos association. In IRS-1-deficient mice, 4PS/IRS-2 provides signal transduction to these two major pathways of insulin signaling.

Efficacy, Safety, and Tolerability of Oral Semaglutide Versus Placebo Added to Insulin With or Without Metformin in Patients With Type 2 Diabetes: The PIONEER 8 Trial

OBJECTIVE

To investigate the efficacy, safety, and tolerability of oral semaglutide added to insulin with or without metformin.

RESEARCH DESIGN AND METHODS

Patients with type 2 diabetes uncontrolled on insulin with or without metformin were randomized to oral semaglutide 3 mg (N = 184), 7 mg (N = 182), or 14 mg (N = 181) or to placebo (N = 184) in a 52-week, double-blind trial. End points were change from baseline to week 26 in HbA1c (primary) and body weight (confirmatory secondary). Two estimands were defined: treatment policy (effect regardless of trial product discontinuation or rescue medication) and trial product (effect assuming trial product continuation without rescue medication) in randomized patients.

RESULTS

Oral semaglutide was superior to placebo in reducing HbA1c (estimated treatment difference [ETD] -0.5% [95% CI -0.7, -0.3], -0.9% [-1.1, -0.7], and -1.2% [-1.4, -1.0] for 3, 7, and 14 mg, respectively; P < 0.001) and body weight (ETD -0.9 kg [95% CI -1.8, -0.0], -2.0 kg [-3.0, -1.0], and -3.3 kg [-4.2, -2.3]; P = 0.0392 for 3 mg, P ≤ 0.0001 for 7 and 14 mg) at week 26 (treatment policy estimand). Significantly greater dose-dependent HbA1c and body weight reductions versus placebo were achieved with oral semaglutide at weeks 26 and 52 (both estimands). The most frequent adverse event with oral semaglutide was nausea (11.4-23.2% of patients vs. 7.1% with placebo; mostly mild to moderate).

CONCLUSIONS

Oral semaglutide was superior to placebo in reducing HbA1c and body weight when added to insulin with or without metformin in patients with type 2 diabetes. The safety profile was consistent with other glucagon-like peptide 1 receptor agonists.