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Experiments are performed to determine whether tyrosine 1210 contributes to the generation of tyrosine kinase-specific responses and stimulation of DNA synthesis. Tyrosine 1210 in a mutant receptor is replaced by phenylalanine. Results indicate that tyrosine 1210 is not essential for the induction of tyrosine kinase-specific responses, although it is involved in the coupling of the activated of receptor to some downstream targets.

Aim: To determine the effect of the dipeptidyl peptidase‐4 inhibitor linagliptin on postprandial glomerular hyperfiltration compared with the sulphonylurea glimepiride in adults with type 2 diabetes (T2D). Materials and Methods: In this predefined substudy within a randomized, double‐blind, parallel‐group, intervention trial, overweight people with T2D without renal impairment were treated with once‐daily linagliptin 5 mg (N = 10) or glimepiride 1 mg (N = 13) as an add‐on to metformin for 8 weeks. After a standardized liquid protein‐rich meal, the glomerular filtration rate (GFR) and effective renal plasma flow were determined by inulin and para‐aminohippuric acid clearance, respectively, based on timed urine sampling. Intrarenal haemodynamics were estimated using the Gomez equations. Glucoregulatory/vasoactive hormones, urinary pH and fractional excretions (FE) of sodium, potassium and urea were measured. Results: Compared with glimepiride, linagliptin increased the postprandial filtration fraction (FF; mean difference 2.1%‐point; P =.016) and estimated glomerular hydraulic pressure (mean difference 3.0 mmHg; P =.050), and tended to increase GFR (P =.08) and estimated efferent renal arteriolar resistance (RE; P =.08) from baseline to week 8. No differences in FE were noted. Glimepiride reduced HbA1c more than linagliptin (mean difference −0.40%; P =.004), without between‐group differences in time‐averaged postprandial glucose levels. In the linagliptin group, change in FF correlated with change in mean arterial pressure (R = 0.807; P =.009) and time‐averaged mean glucagon (R = 0.782; P =.008), but not with changes in glucose, insulin, intact glucagon‐like peptide‐1, renin or FENa. Change in glucagon was associated with change in RE (R = 0.830; P =.003). Conclusions: In contrast to our hypothesis, compared with glimepiride, linagliptin does not reduce postprandial hyperfiltration, yet appears to increase FF after meal ingestion by increasing blood pressure or RE. [ABSTRACT FROM AUTHOR]

Stimulation of overexpressed receptors for epidermal growth factor and insulin affects mitogenic signaling without influencing the stimulation of p21ras. Initial enhancement of the levels of Ras.GTP is not associated with the magnitude of mitogenic response which is restricted by the large number of autophosphorylated receptors. The magnitude of the initial response of Ras.GTP synthesis is not associated with the inclusion of (3H)thymidine in cells.

Abstract Background In vitro data suggest that changes in myocardial substrate metabolism may contribute to impaired myocardial function in diabetic cardiomyopathy (DCM). The purpose of the present study was to study in a rat model of early DCM, in vivo changes in myocardial substrate metabolism and their association with myocardial function. Methods Zucker diabetic fatty (ZDF) and Zucker lean (ZL) rats underwent echocardiography followed by [11C]palmitate positron emission tomography (PET) under fasting, and [18F]-2-fluoro-2-deoxy-D-glucose PET under hyperinsulinaemic euglycaemic clamp conditions. Isolated cardiomyocytes were used to determine isometric force development. Results PET data showed a 66% decrease in insulin-mediated myocardial glucose utilisation and a 41% increase in fatty acid (FA) oxidation in ZDF vs. ZL rats (both p < 0.05). Echocardiography showed diastolic and systolic dysfunction in ZDF vs. ZL rats, which was paralleled by a significantly decreased maximal force (68%) and maximal rate of force redevelopment (69%) of single cardiomyocytes. Myocardial functional changes were significantly associated with whole-body insulin sensitivity and decreased myocardial glucose utilisation. ZDF hearts showed a 68% decrease in glucose transporter-4 mRNA expression (p < 0.05), a 22% decrease in glucose transporter-4 protein expression (p = 0.10), unchanged levels of pyruvate dehydrogenase kinase-4 protein expression, a 57% decreased phosphorylation of AMP activated protein kinase α1/2 (p < 0.05) and a 2.4-fold increased abundance of the FA transporter CD36 to the sarcolemma (p < 0.01) vs. ZL hearts, which are compatible with changes in substrate metabolism. In ZDF vs. ZL hearts a 2.4-fold reduced insulin-mediated phosphorylation of Akt was found (p < 0.05). Conclusion Using PET and echocardiography, we found increases in myocardial FA oxidation with a concomitant decrease of insulin-mediated myocardial glucose utilisation in early DCM. In addition, the latter was associated with impaired myocardial function. These in vivo data expand previous in vitro findings showing that early alterations in myocardial substrate metabolism contribute to myocardial dysfunction.

Objective: To compare effects of the dipeptidyl peptidase 4 (DPP-4) inhibitor linagliptin with those of a sulfonylurea on renal physiology in metformin-treated patients with type 2 diabetes mellitus (T2DM).Research Design and Methods: In this double-blind randomized trial, 46 overweight T2DM patients without renal impairment received once-daily linagliptin (5 mg) or glimepiride (1 mg) for 8 weeks. Fasting glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were determined by inulin and para-aminohippuric acid clearances. Fractional excretions, urinary damage markers, and circulating DPP-4 substrates (among others, glucagon-like peptide 1 and stromal cell-derived factor-1α [SDF-1α]) were measured.Results: HbA1c reductions were similar with linagliptin (-0.45 ± 0.09%) and glimepiride (-0.65 ± 0.10%) after 8 weeks (P = 0.101). Linagliptin versus glimepiride did not affect GFR, ERPF, estimated intrarenal hemodynamics, or damage markers. Only linagliptin increased fractional excretion (FE) of sodium (FENa) and potassium, without affecting FE of lithium. Linagliptin-induced change in FENa correlated with SDF-1α (R = 0.660) but not with other DPP-4 substrates.Conclusions: Linagliptin does not affect fasting renal hemodynamics compared with glimepiride in T2DM patients. DPP-4 inhibition promotes modest natriuresis, possibly mediated by SDF-1α, likely distal to the macula densa. [ABSTRACT FROM AUTHOR]

The metabolic requirements change during cell proliferation and differentiation. Upon antigen-stimulation, effector T cells switch from adenosine-triphospate (ATP)-production by oxidative phosphorylation in the mitochondria to glycolysis. In the gut it was shown that short chain fatty acids (SCFA), fermentation products of the microbiota in colon, ameliorate inflammatory reactions by supporting the differentiation of regulatory T cells. SCFA are a major energy source, but they are also anabolic metabolites, histone-deacetylase-inhibitors and activators of G protein receptors. Recently, it was reported that a topical application of the SCFA butyrate promotes regulatory T cells in the skin. Here we ask if the SCFA butyrate, propionate and acetate affect the energy metabolism and inflammatory potential of dendritic epidermal T cells (DETC), the innate resident skin γδ T cell population. Using the Seahorse™ technology, we measured glycolysis and oxidative phosphorylation (OXPHOS) in a murine DETC cell line, 7-17, upon TCR-stimulation by CD3/CD28 crosslinking, with or without SCFA addition. TCR engagement resulted in a change of the ratio glycolysis/OXPHOS. A similar metabolic shift has been described for activated CD4 T cells. Addition of 5 mM SCFA, in particular butyrate, antagonized the effect. Stimulated DETC secrete cytokines, e.g. the pro-inflammatory cytokine interferon-gamma (IFNγ), and thereby regulate skin homeostasis. Addition of butyrate and propionate to the cultures at non-toxic concentrations decreased secretion of IFNγ by DETC and increased the expression of the immunoregulatory surface receptor CD69. We hypothesize that SCFA can dampen the inflammatory activity of DETC. [ABSTRACT FROM AUTHOR]

Diversification of cardiac insulin signaling involves the p85[Alpha]/[Beta] subunits of phosphatidylinositol 3-kinase. Am J Physiol Endocrinol Metab 280: E65-E74, 2001.--Ventricular cardiomyocytes and cardiac tissue of lean and genetically obese (fa/fa) Zucker rats were used 1) to study the role of the p85 regulatory subunit isoforms p85[Alpha] and p85[Beta] for insulin signaling through the phosphatidylinositol (PI) 3-kinase pathway, and 2) to elucidate the implications of these mechanisms for cardiac insulin resistance. Western blot analysis of cardiomyocyte lysates revealed expression of p85[Alpha] and p85[Beta] but no detectable amounts of the splice variants of p85[Alpha]. Essentially no p85[Alpha] subunit of PI 3-kinase was found to be associated with insulin receptor substrate (IRS)-1 or IRS-2 in basal and insulin-stimulated (5 min) cardiomyocytes. Instead, insulin produced a twofold increase in p85[Beta] associated with IRS-1, leading to a three- to fourfold increase in p85[Beta]-associated PI 3-kinase activity. This response was significantly reduced in obese animals. Comparable results were obtained in the intact heart after in vivo stimulation. In GLUT-4-containing vesicles, an increased abundance (3.7 [+ or -] 0.7-fold over basal) of p85[Alpha] was observed after insulin stimulation of lean animals, with no significant effect in the obese group. No p85[Beta] could be detected in GLUT-4-containing vesicles. Recruitment of the p110 catalytic subunit of PI 3-kinase and a twofold increase in enzyme activity in GLUT-4-containing vesicles by insulin was observed only in lean rats. We conclude that, in the heart, p85[Alpha] recruits PI 3-kinase activity to GLUT-4 vesicles, whereas p85[Beta] represents the main regulator of IRS-1- and IRS-2-mediated PI 3-kinase activation. Furthermore, multiple defects of PI 3-kinase activation, involving both the p85[Alpha] and the p85[Beta] adaptor subunits, may contribute to cardiac insulin resistance. GLUT-4-containing vesicles; obesity; insulin resistance; cardiac muscle