Effect of insulin on lipolysis in adipose tissue of rats of different ages

Several authors have not been able to find any antilipolytic effect of insulin in adipose tissue "in vitro". We investigated the possible role of cell size and/or age of donors on this phenomenon. The lipolytic rates (glycerol release per cell) were lower in the small cells of the 4-6 weeks old rats than in the larger cells of the 25-30 weeks old animals; however, the difference disappeared when the data were expressed per unit of cell surface area. Insulin (0.5-50 ng/ml) failed to inhibit both maximally and submaximally noradrenaline stimulated lipolysis in the adipocytes of the young rats, but its antilipolytic action was fully restored by using glucose-free medium. Therefore, at our experimental conditions, a glucose dependent factor, possibly involving the preferential hydrolysis of newly synthetized triglycerides, seems to blunt or to mask the insulin induced inhibition of glycerol release. Relatively higher rates of glucose metabolism and a lower lipolysis in small fat cells might explain the difference in the action of insulin on glycerol release in the adipose tissue of young rats as compared to the older ones.     

Lack of effect of metoclopramide on plasma aldosterone concentrations in young calves

In five 10-day-old Holstein X Friesian male calves, the intravenous injection of the dopamine blocker metoclopramide (1 mg/kg bwt) had no significant effect on plasma aldosterone concentration. Plasma sodium, potassium, cortisol, corticosterone concentrations and plasma renin activity measured in these animals during 120 min following metoclopramide injection were never significantly different from those simultaneously measured in 5 control calves.     

Specific actions of GLP-1 receptor agonists and DPP4 inhibitors for the treatment of pancreatic β-cell impairments in type 2 diabetes

Type 2 diabetes occurs when the β-cells do not secrete enough insulin to counter balance insulin resistance. GLP-1 and GIP are insulinotropic peptides which are thought to benefit to β-cell physiology. On one hand sustained pharmacological levels of GLP-1 are achieved by subcutaneous administration of GLP-1 analogs while transient and lower physiological levels of GLP-1 are attained following DPP4 inhibitor (DPP4i) treatment. On the other hand, DPP4i increase GLP-1 concentration into the portal vein to recruit the gut-to brain-to pancreas axis which is not the case with injected analogs. Hence, these differences between GLP-1 analogs and DPP4i indicate that both strategies could differentially impact β-cell behavior. Here, we summarize the effects of GLP-1 analogs and DPP4i on β-cell physiology. We discuss the possibility that production of signaling molecules, such as cAMP, generated into the β-cells by native GLP-1 or pharmacological GLP-1 analogs may vary and engage different downstream signaling networks. Hence, deciphering which signaling networks are engaged following GLP-1 analogs or DPP4i administration appears to be critical to unveil the contribution of each treatment/strategy to engage β-cell cellular processes.     

Biodiversity responses to land‐use and restoration in a global biodiversity hotspot: Ant communities in Brazilian Cerrado

Given that land‐use change is the main cause of global biodiversity decline, there is widespread interest in adopting land‐use practices that maintain high levels of biodiversity, and in restoring degraded land that previously had high biodiversity value. In this study, we use ant taxonomic and functional diversity to examine the effects of different land uses (agriculture, pastoralism, silviculture and conservation) and restoration practices on Cerrado (Brazilian savanna) biodiversity. We also examine the extent to which ant diversity and composition can be explained by vegetation attributes that apply across the full land management spectrum. We surveyed vegetation attributes and ant communities in five replicate plots of each of 13 land‐use and restoration treatments, including two types of native vegetation as reference sites: cerrado sensu stricto and cerradão. Several land‐use and restoration treatments had comparable plot richness to that of the native reference habitats. Ant species and functional composition varied systematically among land‐use treatments following a gradient from open habitats such as agricultural fields to forested sites. Tree basal area and grass cover were the strongest predictors of ant species richness. Losses in ant diversity were higher in land‐use systems that transform vegetation structure. Among productive systems, therefore, uncleared pastures and old pine plantations had similar species composition to that occurring in cerrado sensu stricto. Restoration techniques currently applied to sites that were previously Cerrado have focused on returning tree cover, and have failed to restore ant communities typical of savanna. To improve restoration outcomes for Cerrado biodiversity, greater attention needs to be paid to the re‐establishment and maintenance of the grass layer, which requires frequent fire. At the broader scale, conservation planning in agricultural landscapes, should recognize the value of land‐use mosaics and the risks of homogenization.     

The effect of obesity management on body image in patients seeking treatment at medical centers

Objective: Body image dissatisfaction is common in treatment‐seeking patients with obesity. We aimed to investigate the effects of obesity management on body image in patients with obesity attending Italian medical centers for weight loss programs. Research Methods and Procedures: A total of 473 obese patients seeking treatment in 13 Italian medical centers (80% females; age, 45.9 ± standard deviation 11.0 years; BMI, 36.8 ± 5.7 kg/m²) were evaluated at baseline and after a 6‐month weight loss treatment. Body uneasiness, psychiatric distress, and binge eating were tested by Body Uneasiness Test (BUT, Part A), Symptom CheckList‐90 (SCL‐90), and Binge Eating Scale (BES), respectively. Results: At 6‐month follow‐up, the percentage weight loss was significantly higher in men (9.0 ± 6.3%) than in women (6.8 ± 7.3%; p = 0.010). Both men and women had a significant improvement in BUT Global Severity Index and in all of the BUT subscales with the exception of the Compulsive Self‐Monitoring subscale. Linear regression analysis selected baseline psychological and behavioral measures (global score of BUT and SCL‐90) and improved psychiatric distress and binge eating as independent predictors of changes in basal body dissatisfaction in females, whereas in males, changes were associated only with baseline BUT‐Global Severity Index score, binge eating, and its treatment‐associated improvement. Pre‐treatment BMI and BMI changes did not enter the regression. Discussion: Obesity treatment, even with a modest degree of weight loss, is associated with a significant improvement of body image, in both females and males. This effect depends mainly on psychological factors, not on the amount of weight loss.     

beta -Arrestin-mediated recruitment of the Src family kinase Yes mediates endothelin-1-stimulated glucose transport

The insulin and the endothelin type A (ETA) receptor both can couple into the heterotrimeric G protein alpha(q/11) (Galpha(q/11)), leading to Galpha(q/11) tyrosine phosphorylation, phosphatidylinositol 3-kinase activation, and subsequent stimulation of glucose transport. In this study, we assessed the potential role of Src kinase in ET-1 signaling to glucose transport in 3T3-L1 adipocytes. Src kinase inhibitor PP2 blocked ET-1-induced Src kinase activity, Galpha(q/11) tyrosine phosphorylation, and glucose transport stimulation. To determine which Src family kinase member was involved, we microinjected anti-c-Src, -c-Fyn, or -c-Yes antibody into these cells and found that only anti-c-Yes antibody blocked GLUT4 translocation (70% decreased). Overexpression or microinjection of a dominant negative mutant (K298M) of Src kinase also inhibited ET-1-induced Galpha(q/11) tyrosine phosphorylation and GLUT4 translocation. In co-immunoprecipitation experiments, we found that beta-arrestin 1 associated with the ETA receptor in an agonist-dependent manner and that beta-arrestin 1 recruited Src kinase to a molecular complex that included the ETA receptor. Microinjection of beta-arrestin 1 antibody inhibited ET-1- but not insulin-stimulated GLUT4 translocation. In conclusion, 1) the Src kinase Yes can induce tyrosine phosphorylation of Galpha(q/11) in response to ET-1 stimulation, and 2) beta-arrestin 1 and Src kinase form a molecular complex with the ETA receptor to mediate ET-1 signaling to Galpha(q/11) with subsequent glucose transport stimulation.     

Miniglucagon (glucagon 19-29), a potent and efficient inhibitor of secretagogue-induced insulin release through a Ca2+ pathway

Using the MIN6 B-cell line, we investigated the hypothesis that miniglucagon, the C-terminal () fragment processed from glucagon and present in pancreatic A cells, modulates insulin release, and we analyzed its cellular mode of action. We show that, at concentrations ranging from 0.01 to 1000 pM, miniglucagon dose-dependently (ID50 = 1 pM) inhibited by 80-100% the insulin release triggered by glucose, glucagon, glucagon-like peptide-1-(7-36) amide (tGLP-1), or glibenclamide, but not that induced by carbachol. Miniglucagon had no significant effects on cellular cAMP levels. The increase in 45Ca2+ uptake induced by depolarizing agents (glucose or extracellular K+), by glucagon, or by the Ca2+channel agonist Bay K-8644 was blocked by miniglucagon at the doses active on insulin release. Electrophysiological experiments indicated that miniglucagon induces membrane hyperpolarization, probably by opening potassium channels, which terminated glucose-induced electrical activity. Pretreatment with pertussis toxin abolished the effects of miniglucagon on insulin release. It is concluded that miniglucagon is a highly potent and efficient inhibitor of insulin release by closing, via hyperpolarization, voltage-dependent Ca2+ channels linked to a pathway involving a pertussis toxin-sensitive G protein.     

Lipopolysaccharide induces apoptosis in adult rat ventricular myocytes via cardiac AT(1) receptors

Lipopolysaccharide (LPS) from gram-negative bacteria circulates in acute, subacute, and chronic conditions. It was hypothesized that LPS directly induces cardiac apoptosis. In adult rat ventricular myocytes (isolated with depyrogenated digestive enzymes to minimize tolerance), LPS (10 ng/ml) decreased the ratio of Bcl-2 to Bax at 12 h; increased caspase-3 activity at 16 h; and increased annexin V, propidium iodide, and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling staining at 24 h. Apoptosis was blocked by the caspase inhibitor benzyloxycarbonyl-valine-alanine-aspartate fluoromethylketone (Z-VAD-fmk), captopril, and angiotensin II type 1 receptor (AT(1)) inhibitor (losartan), but not by inhibitors of AT(2) receptors (PD-123319), tumor necrosis factor-alpha (TNFRII:Fc), or nitric oxide (N(G)-monomethyl-L-arginine). Angiotensin II (100 nmol/l) induced apoptosis similar to LPS without additive effects. LPS in vivo (1 mg/kg iv) increased apoptosis in left ventricular myocytes for 1-3 days, which dissipated after 1-2 wk. Losartan (23 mg. kg(-1). day(-1) in drinking water for 3 days) blocked LPS-induced in vivo apoptosis. In conclusion, low levels of LPS induce cardiac apoptosis in vitro and in vivo by activating AT(1) receptors in myocytes.     

V beta T cell repertoire of CD8+ splenocytes selected on nonpolymorphic MHC class I molecules

In this work, we have studied the role of the MHC class Ib molecules in the selection and maintenance of CD8(+) T splenocytes. We have compared the CD8(+) T cell repertoires of wild-type, H-2K-deficient, H-2D-deficient, or double knockout C57BL/6 mice. We show that the different CD8(+) repertoires, selected either by class Ia and class Ib or by class Ib molecules only, use the various V alpha (AV) and V beta (BV) rearrangements in the same proportion and without biases in the CDR3 size distribution. Furthermore, we have estimated the size of the BV repertoire in the four different strains of mice. Interestingly, we have found that the BV repertoire size is proportional to the overall number of CD8(+) splenocytes. This observation implies that BV diversity is positively correlated with the number of CD8(+) cells, even when the number of CD8(+) splenocytes is dramatically reduced (90% in the double knockout mice).