Effects of chronic hyperinsulinemia in insulin-resistant patients

Light and Shadow of Na-Glucose Cotransporter 2 Inhibitors in the Treatment of Diabetes Mellitus: Points for Improvement Based on Our Clinical Experience

We analyzed the effect of Na-glucose cotransporter 2 inhibitors (SGLT2-I) in diabetic patients visiting our hospital. The study included 236 patients treated with SGLT2-I alone or with codiabetic drugs for at least two years. We analyzed overtime changes in glycosylated hemoglobin A1c (HbA1c) in the patients by repeated analyses of variance (ANOVA) and evaluated the therapeutic effect. HbA1c levels decreased significantly in the first six months after treatment. Afterward, they leveled off and increased slightly over the next two years. Six months after treatment, the mean (SD) of HbA1c was 8.19 (1.46) %; the mean difference dropped by 0.91%, and HbA1c in mild DM2 did not drop by below 8.0%. Overall, there was only a slight improvement. We performed multivariate logistic regression analysis using a model with or without improvement as the objective variable and several explanatory variables. Na and Hct were significant factors. They increased considerably over six months and then leveled off. eGFR significantly reduced in the hyperfiltration group six months after treatment. The annual decline rate in eGFR was also faster, even in the nonhyperfiltration group than in the healthy subjects, which may be a characteristic of renal clearance in SGLT2-I treatment. In conclusion, SGLT2-I is an excellent antidiabetic, nephroprotective agent to eliminate hyperfiltration, but unfortunately, SGLT2-I alone does not have enough power to reduce blood glucose levels. SGLT2-I, with insulin or insulin secretagogues, enhances insulin resistance, induces hyperinsulinemia, and exacerbates type 2 DM. In contrast, SGLT2-I, with noninsulin antidiabetic agents and a low-carbohydrate diet, may bring better results.

Type 2 diabetes and cardiovascular disease: Have all risk factors the same strength?

Diabetes mellitus is a chronic condition that occurs when the body cannot produce enough or effectively use of insulin. Compared with individuals without diabetes, patients with type 2 diabetes mellitus have a considerably higher risk of cardiovascular morbidity and mortality, and are disproportionately affected by cardiovascular disease. Most of this excess risk is it associated with an augmented prevalence of well-known risk factors such as hypertension, dyslipidaemia and obesity in these patients. However the improved cardiovascular disease in type 2 diabetes mellitus patients can not be attributed solely to the higher prevalence of traditional risk factors. Therefore other non-traditional risk factors may be important in people with type 2 diabetes mellitus. Cardiovascular disease is increased in type 2 diabetes mellitus subjects due to a complex combination of various traditional and non-traditional risk factors that have an important role to play in the beginning and the evolution of atherosclerosis over its long natural history from endothelial function to clinical events. Many of these risk factors could be common history for both diabetes mellitus and cardiovascular disease, reinforcing the postulate that both disorders come independently from “common soil”. The objective of this review is to highlight the weight of traditional and non-traditional risk factors for cardiovascular disease in the setting of type 2 diabetes mellitus and discuss their position in the pathogenesis of the excess cardiovascular disease mortality and morbidity in these patients.

Effect of insulin glargine and n-3FA on carotid intima-media thickness in people with dysglycemia at high risk for cardiovascular events: the glucose reduction and atherosclerosis continuing evaluation study (ORIGIN-GRACE)

OBJECTIVE

To evaluate the effects of insulin glargine and n-3 polyunsaturated fatty acid (n-3FA) supplements on carotid intima-media thickness (CIMT).

RESEARCH DESIGN AND METHODS

We enrolled 1,184 people with cardiovascular (CV) disease and/or CV risk factors plus impaired fasting glucose, impaired glucose tolerance, or early type 2 diabetes in a randomized multicenter 2 × 2 factorial design trial. Participants received open-label insulin glargine (targeting fasting glucose levels ≤ 5.3 mmol/L [95 mg/dL]) or standard glycemic care and double-blind therapy with a 1-g capsule of n-3FA or placebo. The primary trial outcome was the annualized rate of change in maximum CIMT for the common carotid, bifurcation, and internal carotid artery segments. Secondary outcomes were the annualized rates of change in maximum CIMT for the common carotid and the common carotid plus bifurcation, respectively. Baseline followed by annual ultrasounds were obtained during a median follow-up of 4.9 years.

RESULTS

Compared with standard care, insulin glargine reduced the primary CIMT outcome, but the difference was not statistically significant (difference = 0.0030 ± 0.0021 mm/year; P = 0.145) and significantly reduced the secondary CIMT outcomes (differences of 0.0033 ± 0.0017 mm/year [P = 0.049] and 0.0045 ± 0.0021 mm/year [P = 0.032], respectively). There were no differences in the primary and secondary outcomes between the n-3FA supplement and placebo groups.

CONCLUSIONS

In people with CV disease and/or CV risk factors and dysglycemia, insulin glargine used to target normoglycemia modestly reduced CIMT progression, whereas daily supplementation with n-3FA had no effect on CIMT progression.

Risk factors for pancreatic ductal adenocarcinoma specifically stimulate pancreatic duct glands in mice

Diabetes mellitus type 2 and chronic pancreatitis are regarded as risk factors for pancreatic cancer. Pancreatic duct glands (PDGs) were recently described as a new compartment of the major duct in humans and mice. To evaluate the influence of diabetes and chronic pancreatitis on PDGs, cerulein was injected i.p., repetitively over 10 weeks, in mice exhibiting obesity and a type 2 diabetes-like syndrome (B6.V-Lep(ob/ob)) and in lean littermates. By using 5-bromo-2'-deoxyuridine (BrdU), a label-retaining cell population was characterized in PDGs. Cerulein administration led to more BrdU(+) cells in PDGs of obese mice compared with lean mice. The observed increase was specific to PDGs, because BrdU incorporation in cells of the pancreatic duct was not increased. In addition, the expression of distinct tumor markers in PDGs was characterized by Muc5ac, S100P, regenerating islet-derived 3β, 14-3-3 σ, and prostate stem cell antigen immunochemistry. Type 2 diabetes-like syndrome, accompanied by chronic pancreatitis, enhanced nuclear localization of S100P. Both risk factors for pancreatic cancer also induced the production of Muc5ac and the nuclear localization of S100P [corrected]. These results demonstrate that diabetes and chronic pancreatitis jointly enhance BrdU incorporation and production of pancreatic cancer-specific proteins in PDGs. The observed alterations suggest that pancreatic tumors might originate from the newly discovered histomorphological structures, called PDGs, which could represent a target for future anticancer therapies.

A control engineering approach to understanding the TGF-β paradox in cancer

TGF-β, a key cytokine that regulates diverse cellular processes, including proliferation and apoptosis, appears to function paradoxically as a tumour suppressor in normal cells, and as a tumour promoter in cancer cells, but the mechanisms underlying such contradictory roles remain unknown. In particular, given that this cytokine is primarily a tumour suppressor, the conundrum of the unusually high level of TGF-β observed in the primary cancer tissue and blood samples of cancer patients with the worst prognosis, remains unresolved. To provide a quantitative explanation of these paradoxical observations, we present, from a control theory perspective, a mechanistic model of TGF-β-driven regulation of cell homeostasis. Analysis of the overall system model yields quantitative insight into how cell population is regulated, enabling us to propose a plausible explanation for the paradox: with the tumour suppressor role of TGF-β unchanged from normal to cancer cells, we demonstrate that the observed increased level of TGF-β is an effect of cancer cell phenotypic progression (specifically, acquired TGF-β resistance), not the cause. We are thus able to explain precisely why the clinically observed correlation between elevated TGF-β levels and poor prognosis is in fact consistent with TGF-β's original (and unchanged) role as a tumour suppressor.

Reducing cardiovascular disease risk in patients with type 2 diabetes and concomitant macrovascular disease: can insulin be too much of a good thing?

Despite improvement of microvascular outcomes as a consequence of optimal glucose control in patients with type 2 diabetes, prevention of macrovascular complications is still a major challenge. Of interest, large-scale intervention studies (Action to Control Cardiovascular Risk in Diabetes, Action in Diabetes and Vascular Disease-Preterax and Diamicron Modified Release Controlled Evaluation and Veterans Affairs Diabetes Trial) comparing standard therapy versus more intensive glucose-lowering therapy failed to report beneficial impacts on macrovascular outcomes. Consequently, it is currently under debate whether the high doses of exogenous insulin that were administered in these trials to achieve strict target glucose levels could be responsible for these unexpected outcomes. Additionally, a potential role for plasma insulin levels in predicting macrovascular outcomes has emerged in patients with or without type 2 diabetes. These observations, combined with evidence from in vitro and animal experiments, suggest that insulin might have intrinsic atherogenic effects. In this review, we summarize clinical trials, population-based studies as well as data emerging from basic science experiments that point towards the hypothesis that the administration of high insulin doses might not be beneficial in patients with type 2 diabetes and established macrovascular disease.

Diabetes and risk of tumors: oncologic considerations

Type 2 diabetes mellitus and malignant tumors are frequent diseases worldwide. The incidence of these two diseases is growing continuously and causes serious health care problem. Population based epidemiologic studies show that the coexistence of type 2 diabetes and malignant tumors is more frequent than expected by the age-corrected incidence and prevalence of each disease. Epidemiologic studies and meta-analyses show that type 2 diabetes increases the risk and tumor specific mortality of certain cancers. The overlapping risk factors of the diseases suggest a relationship between type 2 diabetes and malignant tumors, with a significant role of obesity as a major risk factor. In the pathophysiology of type 2 diabetes there are several biological processes, which may explain the higher cancer risk in type 2 diabetes. In vitro experiments, and in vivo animal studies show that the mitotic effect of hyperinsulinemia plays an important role in the relationship of cancer and type 2 diabetes mellitus. Recent studies show that the different treatment modalities, antidiabetic drugs and their combinations used for the treatment of type 2 diabetes can modify cancer risk. The majority of the data show that metformin therapy decreases, while insulin secretagog drugs slightly increase the risk of certain types of cancers in type 2 diabetes. Metformin can decrease cell proliferation and induce apoptosis in certain cancer cell lines. Endogenous and exogenous (therapy induced) hyperinsulinemia may be mitogenic and may increase the risk of cancer in type 2 diabetes. Human studies showed that the analogue insulin glargin increases the risk of certain cancers. As a result of conceptual weaknesses in study design, data collection, and statistical methods the results of these studies are questionable. According to present knowledge, obtaining and maintaining optimal metabolic target values with the appropriate choice of treatment modality is the aim of treatment in type 2 diabetes. Presently, study results showing elevated mitogenic potential with some antidiabetic treatment modalities are not taken into account, when considering the choice of antidiabetic treatment in type 2 diabetic patients. In the care of patients with increased cancer risk, oncologic considerations should be taken into account. Well designed, prospective, clinical studies would be necessary to demonstrate the possible correlation between treatment modalities of type 2 diabetes and change of cancer risk in type 2 diabetes mellitus. Orv. Hetil., 2011, 152, 1144–1155.

The association between C-reactive protein levels and insulin therapy in obese vs nonobese veterans with type 2 diabetes mellitus

The authors studied the association between insulin use and C-reactive protein (CRP) levels in obese (body mass index > or = 30 kg/m(2)) and nonobese (body mass index <30 kg/m(2)) patients with type 2 diabetes at the Providence Veterans Affairs Medical Center. There were 64 nonobese participants (insulin use and average daily dose, 23.4% and 7.0+/-18.2 units at baseline and 27.1% and 9.3+/-21.0 units at follow-up, respectively) and 106 obese participants (insulin use and daily dose, 39.6% and 28.2+/-47.3 units at baseline and 43.0% and 28.7+/-47.7 units at follow-up, respectively). Both use and daily dose of insulin were modeled with CRP levels of participants upon discharge from an intensive cardiac risk management clinic and at a 1-year follow-up visit using a linear mixed effects model for repeated measures. There was a significant direct association between log CRP and both insulin use and daily dose for nonobese participants (beta=0.3, P=.03 and beta=0.01, P=.02, respectively) but not for obese participants (P=.8 and P=.5, respectively). Due to the association between insulin therapy and CRP in nonobese patients, these results may aid clinicians in deciding on the initiation of insulin therapy for nonobese diabetic patients when noninsulin alternatives are available.

Mechanism of the mitogenic influence of hyperinsulinemia

Either endogenous or exogenous hyperinsulinemia in the setting of insulin resistance promotes phosphorylation and activation of farnesyltransferase, a ubiquitous enzyme that farnesylates Ras protein. Increased availability of farnesylated Ras at the plasma membrane enhances mitogenic responsiveness of cells to various growth factors, thus contributing to progression of cancer and atherosclerosis. This effect is specific to insulin, but is not related to the type of insulin used. Stimulatory effect of hyperinsulinemia on farnesyltransferase in the presence of insulin resistance represents one potential mechanism responsible for mitogenicity and atherogenicity of insulin.

Weight change, blood pressure, lipids and glycemic control among patients with type 2 diabetes

BACKGROUND/AIM

Although weight loss in patients with type 2 diabetes is very important, available data on the effects of long-term weight change on blood pressure (BP), lipids and glycemic control in these patients are limited. The aim of this study was to assess the long-term impact of weight change on BP, plasma lipids and glycemic control among patients with type 2 diabetes receiving routine care.

METHODS

During the mean [standard deviation (SD)] follow-up period of 9.2 (3.4; range 2-15) years, 7,712 patients with type 2 diabetes were examined to determine changes in weight, BP, plasma lipids and glycemic control using a linear mixed-effects model for repeated measures. The mean (SD) age of participants was 51.3 (10.5) years with a mean (SD) duration of diabetes of 6.3 (6.3) years at initial registration.

RESULTS

The change in fasting plasma glucose and glycosylated hemoglobin (HbA(1c)) from baseline to the last follow-up examination was significantly more favorable in those patients who gained weight during follow-up than in those who lost weight or whose weight remained stable. Systolic and diastolic BP and lipids also rose more significantly in the group with weight gain.

CONCLUSIONS

Although this population of type 2 diabetes in Iran had negligible weight change over mean 9.2 years, this weight gain was associated with an increase in BP and plasma lipids, but also an improvement in glycemic control.

Insulin resistance: pathophysiology and rationale for treatment

After binding to its receptor and activating the β-subunit, insulin is faced with two divergent pathways: one is phosphatidylinositol 3-kinase (PI 3-K) dependent, while another is dependent upon activation of mitogen-activated protein kinase (MAP-K). The former is absolutely necessary for mediating most metabolic and antiapoptotic effects; the latter is linked to nonmetabolic, proliferative and mitogenic effects. In obese patients, especially with type 2 diabetes mellitus (DM2), only the PI 3-K, but not the MAP-K, is resistant to insulin stimulation: hence insulin resistance is better defined as metabolic insulin resistance. The resulting 'compensatory hyperinsulinemia' is an unsuccessful attempt to overcome the inhibition of the metabolic pathway at the price of unopposed stimulation of the MAP-K pathway, and the administration of exogenous insulin might worsen the metabolic dysfunction. As the preferential activation of the MAP-K pathway in insulin-resistant patients has atherogenic and mitogenic properties, this leads to atherosclerosis and cancer. Metformin may carry out direct protective action on human β cells, inasmuch as it improves both primary and secondary endpoints through selective inhibition of fatty acyl oxidation.

Mitogenic action of insulin: friend, foe or 'frenemy'?

Either endogenous or exogenous hyperinsulinaemia in the setting of insulin resistance promotes phosphorylation and activation of farnesyltransferase, a ubiquitous enzyme that farnesylates Ras proteins. Increased availability of farnesylated Ras at the plasma membrane enhances mitogenic responsiveness of cells to various growth factors, thus contributing to progression of cancer and atherosclerosis. This effect is specific to insulin, but is not related to the type of insulin used. The stimulatory effect of hyperinsulinaemia on farnesyltransferase in the presence of insulin resistance represents one potential mechanism responsible for mitogenicity and atherogenicity of insulin.

Quantitative modeling and analysis of the transforming growth factor beta signaling pathway

Transforming growth factor beta (TGF-beta) signaling, which regulates multiple cellular processes including proliferation, apoptosis, and differentiation, plays an important but incompletely understood role in normal and cancerous tissues. For instance, although TGF-beta functions as a tumor suppressor in the premalignant stages of tumorigenesis, paradoxically, it also seems to act as a tumor promoter in advanced cancer leading to metastasis. The mechanisms by which TGF-beta elicits such diverse responses during cancer progression are still not entirely clear. As a first step toward understanding TGF-beta signaling quantitatively, we have developed a comprehensive, dynamic model of the canonical TGF-beta pathway via Smad transcription factors. By describing how an extracellular signal of the TGF-beta ligand is sensed by receptors and transmitted into the nucleus through intracellular Smad proteins, the model provides quantitative insight into how TGF-beta-induced responses are modulated and regulated. Subsequent model analysis shows that mechanisms associated with Smad activation by ligand-activated receptor, nuclear complex formation among Smad proteins, and inactivation of ligand-activated Smad (e.g., degradation, dephosphorylation) may be critical for regulating TGF-beta-targeted functional responses. The model was also used to predict dynamic characteristics of the Smad-mediated pathway in abnormal cells, from which we generated four testable hypotheses regarding potential mechanisms by which TGF-beta's tumor-suppressive roles may appear to morph into tumor-promotion during cancer progression.

Type 2 diabetes and metabolic syndrome as conditions leading to malignant tumors

Az utóbbi években egyre több bizonyíték szólt a metabolikus szindróma és a 2-es típusú diabetes mellitus karcinogén hatásáról. A bizonyítékok között első helyen az epidemiológiai észlelések állnak. A különböző tumorfajták és a metabolikus szindróma, illetve a 2-es típusú diabetes mellitus között nemek, rasszok és földrajzi elterjedtség szerint eltérő mértékben mutatható ki kauzális összefüggés. A lehetséges közös patomechanizmusok az elhízáskor a zsírszövetben excesszíven termelődő adipokinek, a tartós és postprandialis hyperglykaemia, a hyperinsulinismus és az inzulinrezisztencia, egyéb növekedési faktorok, mint a proinzulin, inzulinszerű növekedési faktor-1, reaktív oxigén-szabadgyökök, angiogenezis, inflammáció és gyulladásos citokinek sejtproliferatív hatásai. Kiderült, hogy a peroxiszómaproliferátor aktiválta receptoroknak és az őket szabályozó ubiquitin proteaszómarendszernek is meghatározó szerepe van a sejtproliferáció befolyásolásában. Ezek a mechanizmusok metabolikus szindrómában mind atherosclerosis, mind karcinogenezis irányában kockázati tényezőként szerepelnek. Ez a felismerés új utat nyithat mindkét kórkép megelőzése és kezelése szempontjából.