Characteristics of signalling properties mediated by long-acting insulin analogue glargine and detemir in target cells of insulin

Metabolic and sympathovagal effects of bolus insulin glulisine versus basal insulin glargine therapy in people with type 2 diabetes: A randomized controlled study

AIMS/INTRODUCTION

This study compares the effects of two different insulin regimens - basal versus bolus insulin - on metabolic and cardiovascular autonomic function in Japanese participants with type 2 diabetes.

MATERIALS AND METHODS

Participants were randomly assigned to groups for therapy with insulin glulisine (IGlu) or insulin glargine (IGla). The primary efficacy end-point was glycemic variability, including M-values, mean of glucose levels, and a blood glucose profile of seven time points before and after the intervention. The secondary end-points included pleiotropic effects, including endothelial and cardiac autonomic nerve functions.

RESULTS

Blood glucose levels at all time points significantly decreased in both groups. Post-lunch, post-dinner, and bedtime blood glucose levels were significantly lower in the IGlu group than in the IGla group. Nadir fasting blood glucose levels at the end-point were significantly lower in the IGla group than in the IGlu group. The M-value and mean blood glucose levels were significantly decreased from baseline in both groups, although the former was significantly lower in the IGlu group than in the IGla group. IGla, but not IGlu, was found to elevate 24-h parasympathetic tone, especially during night-time, and it decreased 24-h sympathetic nerve activity, especially at dawn.

CONCLUSIONS

Both IGlu and IGla regimens reduced glucose variability, with IGlu bringing a greater reduction in M-value. IGla, but not IGlu, increased parasympathetic tone during night-time and decreased sympathetic nerve activity at dawn. These findings shed light on the previously unrecognized role of night-time basal insulin supplementation on sympathovagal activity in type 2 diabetes patients.

Intranasal insulin in Alzheimer's dementia or mild cognitive impairment: a systematic review

BACKGROUND AND AIMS

Due to common pathophysiological findings of Alzheimer's disease (AD) with diabetes mellitus (DM), insulin has been suggested as a possible treatment of AD or mild cognitive impairment (MCI). A safe alternative of IV insulin is intranasal (IN) insulin. The aim of this systematic review is to investigate the effects of IN insulin on cognitive function of patients with either AD or MCI.

METHODS

A literature search of the electronic databases Medline, Scopus and CENTRAL was performed to identify RCTs investigating the effect of IN insulin administration on cognitive tasks, in patients with AD or MCI.

RESULTS

Seven studies (293 patients) met our inclusion criteria. Most studies showed that verbal memory and especially story recall was improved after IN insulin administration. Sometimes the effect was restricted for apoe4 (-) patients. Intranasal insulin did not affect other cognitive functions. However, there were some positive results in functional status and daily activity. Data suggested that different insulin types and doses may have different effects on different apoe4 groups. In addition, the effects of treatment on Αβ levels differed from study to study. Finally, IN insulin resulted in minor adverse effects.

CONCLUSIONS

Intranasal insulin improved story recall performance of apoe4 (-) patients with AD or MCI. Other cognitive functions were not affected, but there were some positive results in functional status and daily activity. Since IN insulin is a safe intervention, future studies should be conducted with larger doses and after proper selection of patients and insulin types.

Association between insulin therapy and risk of liver cancer among diabetics: a meta-analysis of epidemiological studies

As the results of the association between insulin therapy and risk of liver cancer among diabetics have been inconsistent in epidemiological studies, we conducted a meta-analysis to quantify this issue. Data of relevant epidemiological studies were collected by searching articles in PubMed, Web of Science, and Embase till 29 June 2017. Random-effects models were employed to combine study-specific risks. Five cohort studies and nine case-control studies were included in our meta-analysis with 285 008 patients with diabetes mellitus and 4329 liver cancer cases. When we compared insulin-use group with noninsulin use group in patients with diabetes mellitus, we observed a statistically significant association between insulin therapy and liver cancer, with an overall relative risk of 1.90 (95% confidence interval: 1.44-2.50, I=76.1%). We did not find heterogeneity between subgroups stratified by study characteristics and adjusted confounders, except for subgroups related to 'follow-up years' of cohort studies. The combined estimate was robust across sensitivity analysis, and no publication bias was detected. Our results indicated that insulin therapy was associated with elevated incidence of liver cancer among diabetics. Given the high prevalence of diabetes, avoiding excess or unnecessary insulin use to control the blood glucose may offer a potential public health benefit in reducing liver cancer risk. Further studies are warranted to investigate the types, doses, and treatment duration of insulin use in large sample size or cohort of diabetic patients.

Different impacts of acylated and non-acylated long-acting insulin analogs on neural functions in vitro and in vivo

AIMS

Centrally administered insulin improves cognitive functions in patients with Alzheimer's disease; however, it remains unknown whether long-acting insulin analogs exert more pronounced effects than insulin. In the present study, we directly compared the effects of insulin and its analogs on neural functions in vitro and in vivo.

METHODS

Cultured rat cerebral cortical neurons were treated with insulin, insulin glargine U100 (Gla), insulin detemir (Det), or insulin degludec (Deg). Moreover, these drugs were intracerebroventricularly administered to mice. Their efficacies were evaluated by biochemical and behavioral analyses.

RESULTS

In cultured neurons, insulin, Gla, and Det increased phosphorylation of Akt and enhanced gene expression of brain-derived neurotrophic factor to a similar extent, although Deg was less effective. The effects of Det and Deg, but not insulin and Gla were suppressed by addition of albumin. When the drug was centrally administered, the increasing effects of insulin on the Akt phosphorylation were comparable to those of Gla but greater than those of Det in hippocampus and cerebral cortex of diabetic db/db and non-diabetic db/m+ mice. Moreover, insulin and Gla enhanced memory functions in Y-maze test and suppressed depression-like behavior in forced swim test in normal mice to a similar extent, and these effects were more potent than those of Det.

CONCLUSIONS

Insulin and Gla have greater impacts on central nervous system than insulin analogs with high albumin sensitivity, such as Det and Deg. These pharmacological profiles should be taken into account for developing an insulin-based therapy to treat Alzheimer's disease.

Long-acting insulin analog detemir displays reduced effects on adipocyte differentiation of human subcutaneous and visceral adipose stem cells

BACKGROUND AND AIMS

Since treatment with insulin detemir results in a lower weight gain compared to human insulin, we investigated whether detemir is associated with lower ability to promote adipogenesis and/or lipogenesis in human adipose stem cells (ASC).

METHODS AND RESULTS

Human ASC isolated from both the subcutaneous and visceral adipose tissues were differentiated for 30 days in the presence of human insulin or insulin detemir. Nile Red and Oil-Red-O staining were used to quantify the rate of ASC conversion to adipocytes and lipid accumulation, respectively. mRNA expression levels of early genes, including Fos and Cebpb, as well as of lipogenic and adipogenic genes, were measured at various phases of differentiation by qRT-PCR. Activation of insulin signaling was assessed by immunoblotting. ASC isolated from subcutaneous and visceral adipose tissue were less differentiated when exposed to insulin detemir compared to human insulin, showing lower rates of adipocyte conversion, reduced triglyceride accumulation, and impaired expression of late-phase adipocyte marker genes, such as Pparg2, Slc2a4, Adipoq, and Cidec. However, no differences in activation of insulin receptor, Akt and Erk and induction of the early genes Fos and Cebpb were observed between insulin detemir and human insulin.

CONCLUSION

Insulin detemir displays reduced induction of the Pparg2 adipocyte master gene and diminished effects on adipocyte differentiation and lipogenesis in human subcutaneous and visceral ASC, in spite of normal activation of proximal insulin signaling reactions. These characteristics of insulin detemir may be of potential relevance to its weight-sparing effects observed in the clinical setting.

Cardiovascular effects of basal insulins

Basal insulin is an important component of treatment for both type 1 and type 2 diabetes. One of the principal aims of treatment in patients with diabetes is the prevention of diabetic complications, including cardiovascular disease. There is some evidence, although controversial, that attainment of good glycemic control reduces long-term cardiovascular risk in both type 1 and type 2 diabetes. The aim of this review is to provide an overview of the potential cardiovascular safety of the different available preparations of basal insulin. Current basal insulin (neutral protamine Hagedorn [NPH], or isophane) and basal insulin analogs (glargine, detemir, and the more recent degludec) differ essentially by various measures of pharmacokinetic and pharmacodynamic effects in the bloodstream, presence and persistence of peak action, and within-subject variability in the glucose-lowering response. The currently available data show that basal insulin analogs have a lower risk of hypoglycemia than NPH human insulin, in both type 1 and type 2 diabetes, then excluding additional harmful effects on the cardiovascular system mediated by activation of the adrenergic system. Given that no biological rationale for a possible difference in cardiovascular effect of basal insulins has been proposed so far, available meta-analyses of publicly disclosed randomized controlled trials do not show any signal of increased risk of major cardiovascular events between the different basal insulin analogs. However, the number of available cardiovascular events in these trials is very small, preventing any clear-cut conclusion. The results of an ongoing clinical trial comparing glargine and degludec with regard to cardiovascular safety will provide definitive evidence.

Classifying the adverse mitogenic mode of action of insulin analogues using a novel mechanism-based genetically engineered human breast cancer cell panel

Insulin analogues are widely used in clinical practice. Modifications on the insulin molecular structure can affect the affinity and activation towards two closely related receptor tyrosine kinases: the insulin receptor (INSR) and the insulin-like growth factor 1 receptor (IGF1R). A switch towards higher IGF1R affinity is likely to emphasize mitogenesis rather than glucose metabolism. Relevant well-validated experimental tools to address the insulin analogue activation of either INSR or IGF1R are missing. We have established a panel of human MCF-7 breast cancer cell lines either ectopically expressing the INSR (A or B isoform) in conjunction with a stable knockdown of the IGF1R or ectopically expressing the IGF1R in conjunction with a stable knockdown of the INSR. In these cell lines, we systematically evaluated the INSR and IGF1R receptor activation and downstream mitogenic signalling of all major clinical relevant insulin analogues in comparison with insulin and IGF1R. While most insulin analogues primarily activated the INSR, the mitogenic activation pattern of glargine was highly similar to IGF1 and insulin AspB10, known to bind IGF1R and induce carcinogenesis. Yet, in a long-term proliferation assay, the proliferative effect of glargine was not much different from regular insulin or other insulin analogues. This was caused by the rapid enzymatic conversion into its two metabolic active metabolites M1 and M2, with reduced mitogenic signalling through the IGF1R. In summary, based on our new cell models, we identified a similar mitogenic potency of insulin glargine and AspB10. However, rapid enzymatic conversion of glargine precludes a sustained activation of the IGF1R signalling pathway.

Insulin therapy and risk of prostate cancer: a systematic review and meta-analysis of observational studies

BACKGROUND

Previous observational studies have shown that insulin therapy may modify the risk of prostate cancer (PCa). However, these studies yielded controversial results. Thus, we performed this meta-analysis to determine whether insulin use was associated with PCa risk in patients with diabetes mellitus (DM).

METHOD

A literature search was carried out in PubMed, EMBASE, and Cochrane Library Central database between January 1966 and January 2013. Fixed-effect and random-effect models were used to estimate pooled relative risks (RR) and corresponding 95% confidence intervals (CIs). Subgroup analyses and sensitivity analyses were also performed.

RESULT

A total of 11 (10 cohorts, and one case-control) studies published between 2007 and 2013 were included in the meta-analysis, representing data for 205,523 male subjects and 7,053 PCa cases. There were five studies investigating the influence of insulin and other glucose-lowering agents on the risk of PCa , and six studies investigating the influence of glargine and non-glargine insulin. Insulin use was not associated with PCa risk when compared with other glucose-lowering agents (RR=0.89, 95% CI, 0.72-1.09). Use of insulin glargine did not contribute to susceptibility to PCa as compared with use of non-glargine insulin (RR=1.26, 95% CI, 0.86-1.84). Sensitivity analysis confirmed the stability of present results, since no individual study affected the pooled result significantly.

CONCLUSIONS

Our results suggest that, there may be no significant association between insulin use and risk of PCa as compared with other glucose-lowering agents in patients with DM, and there was no substantial evidence for increase risk of PCa among insulin glargine users as compared to non-glargine insulin users. Further studies are warranted to validate these conclusions.

Pharmacologic agents for type 2 diabetes therapy and regulation of adipogenesis

The close link between type 2 diabetes and excess body weight highlights the need to consider the effects on weight of different treatments used for correction of hyperglycaemia. Indeed, specific currently available diabetes therapies can cause weight gain, including insulin and its analogues, sulphonylureas, and thiazolidinediones, while others, such as metformin and the GLP-1 receptor agonists, can promote weight loss. Excess body weight in patients with diabetes is largely due to expansion of adipose tissue, and these drugs could interfere with the mechanisms underlying the expansion and differentiation of adipocyte precursors. Almost all anti-diabetes drugs could also potentially affect adipocyte metabolism directly, by modulating lipogenesis, lipolysis, and fat oxidation. This review will examine the available evidence for specific effects of various anti-diabetes drugs on adipose tissue development and function with the ultimate goal of increasing our understanding of how pharmacological agents can modulate energy balance and body fat.

Differences in metabolic and mitogenic signallingof insulin glargine and AspB10 human insulin in rats [corrected]

AIMS/HYPOTHESIS

In vitro, insulin glargine (A21Gly,B31Arg,B32Arg human insulin) has an insulin receptor (IR) profile similar to that of human insulin, but a slightly higher affinity for the IGF-1 receptor (IGF1R). AspB10 human insulin (AspB10), [corrected] the only insulin analogue with proven carcinogenic activity, has a greater affinity for IGF1R and IR, and a prolonged IR occupancy time. The pharmacological and signalling profile of therapeutic and suprapharmacological doses of glargine were analysed in different tissues of rats, and compared with human insulin and AspB10.

METHODS

Male Wistar rats were injected s.c. with human insulin or insulin analogue at doses of 1 to 200 U/kg, and the effects on blood glucose and the phosphorylation status of IR, IGF1R, Akt and extracellular signal-regulated protein kinase 1/2 in muscle, fat, liver and heart samples were investigated.

RESULTS

Glargine, AspB10 and human insulin lowered blood glucose, with the onset of action delayed with glargine. Glargine treatment resulted in phosphorylation levels of IR and Akt that were comparable with those achieved with human insulin, although delayed in time in some tissues. AspB10 treatment resulted in at least twofold higher phosphorylation levels and significantly longer duration of IR and Akt phosphorylation in most tissues. None of the insulin treatments resulted in detectable IGF1R phosphorylation in muscle or heart tissue, whereas intravenous injection of IGF-1 increased IGF1R phosphorylation.

CONCLUSIONS/INTERPRETATION

The IR signalling pattern of AspB10 in vivo is distinctly different from that of human insulin and insulin glargine, and might challenge the notion that activation of IGF1R plays a role in the observed carcinogenic effect of AspB10.

The metabolic and mitogenic properties of basal insulin analogues

CONTEXT

Retrospective, observational studies have reported an association between diabetes treatment with insulin and a higher incidence of cancer.

OBJECTIVE

Overview the literature for in vitro and in vivo studies of the metabolic and mitogenic properties of basal insulin analogues and assess the implications for clinical use.

METHODS

Relevant studies were identified through PubMed and congress abstract database searches; data on metabolic and mitogenic signalling in relation to insulin treatment of diabetes are included in this review.

RESULTS

The balance of evidence shows that although some analogues have demonstrated mitogenic potency in some in vitro studies in cancer cell lines, these findings do not translate to the in vivo setting in animals or to the clinical setting in humans.

CONCLUSIONS

The current consensus is that there is no clinical or in vivo evidence to indicate that any commercially available insulin analogue has carcinogenic effects. Large-scale, prospective clinical and observational studies will further establish any potential link.

Insulin glargine and cancer risk in patients with diabetes: a meta-analysis

AIM

The role of insulin glargine as a risk factor for cancer is controversial in human studies. The aim of this meta-analysis was to evaluate the relationship between insulin glargine and cancer incidence.

METHODS

All observational studies and randomized controlled trials evaluating the relationship of insulin glargine and cancer risk were identified in PubMed, Embase, Web of Science, Cochrane Library and the Chinese Biomedical Medical Literature Database, through March 2012. Odds ratios (ORs) with corresponding 95% confidence interval (CI) were calculated with a random-effects model. Confidence in the estimates of the obtained effects (quality of evidence) was assessed by using the Grading of Recommendations Assessment, Development, and Evaluation approach.

RESULTS

A total of 11 studies including 448,928 study subjects and 19,128 cancer patients were finally identified for the meta-analysis. Insulin glargine use was associated with a lower odds of cancer compared with non-glargine insulin use (OR 0.81, 95% CI 0.68 to 0.98, P = 0.03; very low-quality evidence). Glargine did not increase the odds of breast cancer (OR 0.99, 95% CI 0.68 to 1.46, P = 0.966; very low-quality evidence). Compared with non-glargine insulin, no significant association was found between insulin glargine and prostate cancer, pancreatic cancer and respiratory tract cancer. Insulin glargine use was associated with lower odds of other site-specific cancer.

CONCLUSIONS

Results from the meta-analysis don't support the link between insulin glargine and an increased risk of cancer and the confidence in the estimates of the effects is very low. Further studies are needed to examine the relation between insulin glargine and cancer risk, especially breast cancer.

Effect of insulin analogues on 3t3-l1 adipogenesis and lipolysis

BACKGROUND

Insulin has several biological functions besides glycaemic control. We investigated and compared the effects of six different commercial insulins on adipocyte cell differentiation, the lipolytic activity of differentiated cells, and the expression levels of genes involved in adipogenesis and associated with insulin activity.

MATERIALS AND METHODS

3T3-L1 cells were induced to differentiate with six commercial insulins: glargine, lispro, aspart, detemir, NPH and regular recombinant human insulin (used as control). Cell differentiation, lipolysis and gene expression were measured at day 7 (D7) and day 10 (D10) after induction of differentiation in these cells.

RESULTS

The highest values of cell differentiation and lipolysis were found at D10 for all the insulins used. Preadipocyte differentiation differed at both times depending on the insulin used, with detemir insulin being the least adipogenic. The PPARγ mRNA level varied according to the insulin and was a good genetic marker of adipogenesis at D7. Cells treated with glargine insulin showed the highest lipolysis and HSL expression on both days. Gene expression levels of InsR, SREBP-1c and SCD-1 differed depending on the insulin studied.

CONCLUSIONS

Detemir insulin was the least adipogenic of the insulins tested, whereas treatment with glargine insulin tended to produce the highest lipolysis levels. Under these experimental conditions, the modifications made in commercial insulins to improve glycaemic control also affect adipocyte differentiation, the lipolysis level of differentiated cells, and the expression of different genes that can modify metabolic pathways independently of glucose metabolism.

Differences in bioactivity between human insulin and insulin analogues approved for therapeutic use- compilation of reports from the past 20 years

In order to provide comprehensive information on the differences in bioactivity between human insulin and insulin analogues, published in vitro comparisons of human insulin and the rapid acting analogues insulin lispro (Humalog®), insulin aspart ( NovoRapid®), insulin glulisine (Apidra®), and the slow acting analogues insulin glargine (Lantus®), and insulin detemir (Levemir®) were gathered from the past 20 years (except for receptor binding studies). A total of 50 reports were retrieved, with great heterogeneity among study methodology. However, various differences in bioactivity compared to human insulin were obvious (e.g. differences in effects on metabolism, mitogenesis, apoptosis, intracellular signalling, thrombocyte function, protein degradation). Whether or not these differences have clinical bearings (and among which patient populations) remains to be determined.

Chronic insulin therapy reduces adipose tissue macrophage content in LDL-receptor-deficient mice

AIMS/HYPOTHESIS

Insulin has anti-inflammatory effects in short-term experiments. However, the effects of chronic insulin administration on inflammation are unknown. We hypothesised that chronic insulin administration would beneficially alter adipose tissue inflammation and several circulating inflammatory markers.

METHODS

We administered two forms of long-acting insulin, insulin glargine (A21Gly,B31Arg,B32Arg human insulin) and insulin detemir (B29Lys[ε-tetradecanoyl],desB30 human insulin), to LDL-receptor-deficient mice. After 8 weeks on a diet that causes obesity, hyperglycaemia, adipose tissue macrophage accumulation and atherosclerosis, the mice received subcutaneous glargine, detemir or NaCl (control) for 12 weeks. Serum amyloid A (SAA) and serum amyloid P (SAP), metabolic variables, adipose tissue macrophages and aortic atherosclerosis were evaluated.

RESULTS

Weight gain was equivalent in all groups. The glycated haemoglobin level fell equivalently in both insulin-treated groups. Plasma cholesterol and triacylglycerol levels, and hepatic triacylglycerol level significantly improved in the glargine compared with the detemir or control groups. Levels of mRNA expression for monocyte chemotactic protein-1 and F4/80, a macrophage marker, in adipose tissue were decreased only in the glargine group (p < 0.05). Visceral adipose tissue macrophage content decreased in both insulin groups (p < 0.05), whereas atherosclerosis decreased only in the glargine group. Circulating SAA and SAP did not decrease in either insulin-treated group, but IL-6 levels fell in the glargine-treated mice.

CONCLUSIONS/INTERPRETATION

While chronic insulin administration did not decrease SAA and SAP, administration of glargine but not detemir insulin improved dyslipidaemia, IL-6 levels and atherosclerosis, and both insulins reduced macrophage accumulation in visceral adipose tissue. Thus, chronic insulin therapy has beneficial tissue effects independent of circulating inflammatory markers in this murine model of diet-induced obesity and diabetes.

High dose human insulin and insulin glargine promote T24 bladder cancer cell proliferation via PI3K-independent activation of Akt

BACKGROUND

This study was to investigate the effects of human insulin and insulin glargine on proliferation of T24 human bladder cancer cells and the implication of the PI3K/Akt and MEK/ERK1/2 pathways.

METHODS

After exposure to insulin or glargine at the indicated concentrations for certain time courses, in the absence or presence of inhibitor for MEK (PD98059) or PI3K (LY294002), T24 cell proliferation was evaluated by CCK-8 assay. Phosphorylation of Akt and ERK1/2 was analyzed by Western blot.

RESULTS

Insulin and glargine similarly induced phosphorylation of Akt and slight increases in T24 cell proliferation at 10-100IU/L. LY294002 remarkably reduced T24 cell proliferation in all groups. However, in the presence of LY294002, cell growth was still promoted by insulin and glargine relative to LY294002-treated group. Accordingly, LY294002 profoundly reduced protein levels of pAkt, while insulin and glargine increased pAkt in T24 cells pretreated with LY294002 as compared with cells treated with LY294002 alone. PD98059 reduced pERK while enhanced T24 cell proliferation. Insulin and glargine increased pERK at 15, 30, 60 min, not at 24h.

CONCLUSIONS

High dose human insulin and insulin glargine similarly promoted T24 bladder cancer cell proliferation via PI3K-independent activation of Akt.

Insulin and its analogs: actions via insulin and IGF receptors

Insulin analogs are artificially modified insulin molecules that allow better metabolic controls of diabetes through either more rapid or more prolonged activity. The interaction of insulin analogs with the insulin receptor isoforms (IR-A and IR-B) and with the IGF-I receptor (IGF-IR) is similar but not identical to that of insulin, and therefore, their biological effects do not always reproduce insulin actions in terms of quantity, quality and timing. Studies on in vitro models indicate that short-acting analogs elicit molecular and biological effects that are similar, but not identical, to those of insulin via IR-A, IR-B and IGF-IR. In contrast, long-acting analogs behave in a more different way relative to insulin. Although data are not homogeneous and observations on the more recently introduced detemir are scarce, both glargine and detemir often show a decreased binding to IR and increased binding to IGF-IR. Also, intracellular signaling is different with respect to insulin, with a prevalent activation of the ERK rather than the AKT pathway. Finally, an increased mitogenic response has often been observed with these analogs in a variety of cell models. Of course, in vitro studies do not necessarily reflect what occurs in patients, due to the different metabolism of analogs in vivo and their interaction with components of the extracellular environment. After many years of analog's use, observations in patients indicate that insulin analogs are both effective and safe. Prospective clinical studies, however, may add further useful information on the issue of the insulin analogs' possible differences with respect to native insulin.

Insulin analogues differently activate insulin receptor isoforms and post-receptor signalling

AIMS/HYPOTHESIS

Five insulin analogues, with modified insulin-like molecular structures, are currently approved for treating diabetic patients. They activate cell signalling and biological responses via insulin receptor isoforms (IR-A and IR-B), each having specific characteristics for eliciting cell responses. The molecular and biological effects of these analogues on receptor isoforms in comparison to native insulin are not well defined, and their effects on the IGF1 receptor (IGF1R) are controversial. The characterisation of these effects was the aim of the present study.

METHODS

Short-acting (insulin lispro [B28Lys,B29Pro human insulin], insulin aspart [B28Asp human insulin], insulin glulisine [B3Lys,B29Glu human insulin]) and long-acting (insulin glargine [A21Gly,B31Arg,B32Arg human insulin], insulin detemir [B29Lys(epsilon-tetradecanoyl),desB30 human insulin]) insulin analogues were studied in three engineered cell models (R(-), IGF1R-deprived mouse fibroblasts transfected with either only human IR-A or IR-B or IGF1R). Receptor binding and phosphorylation, AKT and extracellular signal-regulated kinase (ERK) activation, cell proliferation and colony formation were evaluated after exposing the cells to each analogue and were compared with insulin, IGF1 and the carcinogenic analogue B10Asp.

RESULTS

All short-acting insulin analogues produced molecular and biological effects similar but not identical to those of insulin. Relative to insulin, long-acting analogues more strongly activated the ERK pathway via both IR-A and IGF1R as well as increased cell proliferation. At the concentration tested, no analogue (except B10Asp via IR-A) had increased transforming activity.

CONCLUSIONS/INTERPRETATION

Cell models that permit comparisons of the activity of insulin to that of insulin analogues via each receptor individually indicate that only minor differences exist between insulin and short-acting analogues. By contrast, long-acting analogues activate the mitogenic signalling pathway more effectively than insulin and cause increased cell proliferation.

Insulin detemir is a fully efficacious, low affinity agonist at the insulin receptor

AIM

To compare the properties of insulin detemir with human insulin or insulin aspart in various in vitro and in vivo experiments, thereby highlighting the importance of performing dose-response studies when investigating insulin analogues, in this study specifically insulin detemir.

METHODS

Displacement of membrane-associated insulin receptors from human and rat hepatocytes, and from Chinese Hamster Ovary cells over-expressing human insulin receptor (CHO-hIR) at varying albumin concentrations is measured. Lipogenesis in primary rat adipocytes over time and the effects in the simultaneous presence of insulin detemir and human insulin or insulin aspart are assessed. The hyperinsulinaemic euglycaemic clamp technique in rats is used to establish dose-response curves for multiple metabolic endpoints and to investigate the effects of the simultaneous presence of insulin detemir and human insulin.

RESULTS

Both in vitro and in vivo, insulin detemir shows full efficacy and right-shifted parallel dose-response curves compared with human insulin. The potency estimates are different between the in vivo and in vitro conditions and among different in vitro conditions, that is the potency decreases in vitro with increasing albumin concentration. The effects of insulin detemir and human insulin are additive both in vitro and in vivo.

CONCLUSIONS

Insulin detemir is fully efficacious compared with human insulin on all metabolic endpoints measured in vitro and in vivo. The fact that the potency estimates are method-dependent emphasizes the importance of establishing full dose-response relationships when characterizing insulin detemir.

Critical appraisal of the safety and efficacy of insulin detemir in glycemic control and cardiovascular risk management in diabetics

Insulin detemir is an analog of human insulin designed to provide a long duration of basal insulin action. This is achieved by protracted absorption from the injection depot, which results in part from increased self-association of insulin detemir molecules and in part from reversible albumin binding. Subsequent albumin binding in the circulation is thought to buffer changes in the effects at target tissues that could otherwise arise from variability in absorption rate. In consequence, insulin detemir has shown a less variable pharmacodynamic profile than alternative basal insulins; this manifests as more consistent temporal glucose reduction profiles in repeat-clamp studies. In clinical trials, insulin detemir has been characterized by consistent risk reductions in hypoglycemia, as well as reduced weight gain in comparison with other basal insulins. Given some recent associations that have been made in prospective and epidemiologic studies between glucose variability and/or hypoglycemia and increased cardiovascular risk, and the long-known association between excess weight and cardiovascular risk, it is possible that the clinical profile of insulin detemir may carry prognostic value with regard to cardiovascular safety, although this is yet to be substantiated. There have also been some concerns raised recently over the use of insulin analogs and cancer risk, but available clinical data and the receptor interaction profile of insulin detemir suggest no excess in risk in comparison with human insulin therapy. Optimal approaches for the clinical use of insulin detemir have been emerging through an increasing clinical study base, and the analog is becoming established as a potentially valuable therapy option.

An update on the treatment of type 1 and type 2 diabetes mellitus: focus on insulin detemir, a long-acting human insulin analog

Basal insulin analogs are used to minimize unpredictable processes of NPH insulin. Modification of the human insulin molecule results in a slower distribution to peripheral target tissues, a longer duration of action with stable concentrations and thus a lower rate of hypoglycemia. Insulin detemir is a basal insulin analog that provides effective therapeutic options for patients with type 1 and type 2 diabetes. For glycemic control, no significant differences were found in HbA_1c levels compared with NPH and insulin glargine. It is comparable with insulin glargine in significantly reducing rates of all types of hypoglycemia. Clinical studies have demonstrated that detemir is responsible for significantly lower within-subject variability and no or less weight gain than NPH insulin and glargine. Recent pharmacodynamic studies have shown that detemir can be used once daily in many patients with diabetes. Together with patient-friendly injection devices and dose adjustments, it provides a treatment option with the potential to lower the key barriers of adherence to insulin therapy in type 2 diabetes. Recent guidelines for treatment of type 2 diabetes suggest starting intensive therapy of hyperglycemia at an early stage of diabetes and recommend therapeutic options that provide the possibility of reaching HbA_1c goals individually, with a low risk of hypoglycemia or other adverse effects of treatment. The properties of insulin detemir match these requirements.

Spironolactone improves glucose and lipid metabolism by ameliorating hepatic steatosis and inflammation and suppressing enhanced gluconeogenesis induced by high-fat and high-fructose diet

Recent evidence suggests that treatment with mineralocorticoid receptor antagonist suppressed local inflammation in vascular tissues or cardiomyocytes; therefore, we examined the effect of spironolactone on glucose and lipid metabolism in a mouse model with diet-induced diabetes and nonalcoholic fatty liver disease. C57BL/6 mice were fed either the control diet, 60% fat diet with 30% fructose water (HFFD), or HFFD with spironolactone for 8 wk. HFFD mice demonstrated apparent phenotypes of metabolic syndrome, including insulin resistance, hypertension, dyslipidemia, and fatty liver. Although treatment with spironolactone did not affect the increased calorie intake and body weight by HFFD, the increments of epididymal fat weight, blood pressure, serum triglyceride, free fatty acids, leptin, and total cholesterol levels were significantly suppressed. Elevation of blood glucose during glucose and insulin tolerance tests in HFFD mice was significantly lowered by spironolactone. Notably, increased glucose levels during pyruvate tolerance test in HFFD mice were almost completely ameliorated to control levels by the treatment. Staining with hematoxylin-eosin (HE) and Oil-red-O demonstrated marked accumulation of triglycerides in the centrilobular part of the hepatic lobule in HFFD mice, and these accumulations were effectively improved by spironolactone. Concomitantly HFFD feeding markedly up-regulated hepatic mRNA expression of proinflammatory cytokines (TNFalpha, IL-6, and monocyte chemoattractant protein-1), gluconeogenic gene phosphoenolpyruvate carboxykinase, transcription factor carbohydrate response element binding protein, and its downstream lipogenic enzymes, all of which were significantly suppressed by spironolactone. These results indicate that inhibition of mineralocorticoid receptor might be a beneficial therapeutic approach for diet-induced phenotypes of metabolic syndrome and fatty liver.

A robust assay measuring GLUT4 translocation in rat myoblasts overexpressing GLUT4-myc and AS160_v2

Muscle and fat cells translocate GLUT4 (glucose transporter 4) to the plasma membrane when stimulated by insulin. Usually, this event is measured in differentiated adipocytes, myotubes, or cell lines overexpressing tagged GLUT4 by immunostaining. However, measurement of the translocation in differentiated adipocytes or myotubes or GLUT4 overexpressing cell lines is difficult because of high assay variability caused by either the differentiation protocol or low assay sensitivity. We recently reported the identification of a novel splice variant of AS160 (substrate of 160kDa), namely AS160_v2, and showed that its coexpression with GLUT4 in L6 myoblasts increased the insulin-stimulated glucose uptake rate due to an increased amount of GLUT4 on the cell surface. L6 cells, which coexpress myc-tagged GLUT4 and AS160_v2, can be efficiently used to generate an assay useful for identifying compounds that affect cellular responses to insulin. We compared the EC(50) values for radioactive glucose uptake and GLUT4 translocation of different insulins and several small molecules to validate the assay. The use of L6 cells overexpressing AS160_v2 can be considered as a novel tool for the characterization of molecules modulating insulin signaling and GLUT4 translocation, and an image-based assay increases our confidence in the mode of action of the compounds identified.

Oligomers of grape-seed procyanidin extract activate the insulin receptor and key targets of the insulin signaling pathway differently from insulin

Procyanidins are bioactive flavonoid compounds from fruits and vegetables that possess insulinomimetic properties, decreasing hyperglycaemia in streptozotocin-diabetic rats and stimulating glucose uptake in insulin-sensitive cell lines. Here we show that the oligomeric structures of a grape-seed procyanidin extract (GSPE) interact and induce the autophosphorylation of the insulin receptor in order to stimulate the uptake of glucose. However, their activation differs from insulin activation and results in differences in the downstream signaling. Oligomers of GSPE phosphorylate protein kinase B at Thr308 lower than insulin does, according to the lower insulin receptor activation by procyanidins. On the other hand, they phosphorylate Akt at Ser473 to the same extent as insulin. Moreover, we found that procyanidins phosphorylate p44/p42 and p38 MAPKs much more than insulin does. These results provide further insight into the molecular signaling mechanisms used by procyanidins, pointing to Akt and MAPK proteins as key points for GSPE-activated signaling pathways. Moreover, the differences between GSPE and insulin might help us to understand the wide range of biological effects that procyanidins have.