Role of leptin in the pancreatic β-cell: effects and signaling pathways

Leptin plays an important role in the control of food intake, energy expenditure, metabolism, and body weight. This hormone also has a key function in the regulation of glucose homeostasis. Although leptin acts through central and peripheral mechanisms to modulate glucose metabolism, the pancreatic β-cell of the endocrine pancreas is a critical target of leptin actions. Leptin receptors are present in the β-cell, and their activation directly inhibits insulin secretion from these endocrine cells. The effects of leptin on insulin occur also in the long term, since this hormone inhibits insulin gene expression as well. Additionally, β-cell mass can be affected by leptin through changes in proliferation, apoptosis, or cell size. All these different functions in the β-cell are triggered by leptin as a result of the large diversity of signaling pathways that this hormone is able to activate in the endocrine pancreas. Therefore, leptin can participate in glucose homeostasis owing to different levels of modulation of the pancreatic β-cell population. Furthermore, it has been proposed that alterations in this level of regulation could contribute to the impairment of β-cell function in obesity states. In the present review, we will discuss all these issues with special emphasis on the effects and pathways of leptin signaling in the pancreatic β-cell.     

Positive impact of hepatitis C virus (HCV) treatment on antiretroviral treatment adherence in human immunodeficiency virus-HCV coinfected patients: one more argument for expanded access to HCV treatment for injecting drug users

Aims Treatment for the hepatitis C virus (HCV) may be delayed significantly in human immunodeficiency virus (HIV)/HCV coinfected patients on antiretroviral treatment (ART) for fear that its burden could compromise ART adherence. However, the effect such treatment has on ART adherence in observational settings remains largely unknown. Longitudinal data were used to investigate the relationship between initiating HCV treatment and adherence to ART in HIV/HCV coinfected patients. Design The French national prospective cohort of patients coinfected with HIV and HCV (ANRS‐CO‐13‐HEPAVIH) is a multi‐centre cohort. Setting Seventeen out‐patient hospital services delivering HIV and HCV care in France. Participants HIV/HCV coinfected patients on ART (n = 593 patients, 976 visits). Measurements Self‐administered questionnaires and medical records. A mixed logistic regression model based on generalized estimates equations (GEE) to identify factors associated with non‐adherence to ART. Findings Among the 593 patients, 36% were classified as non‐adherent to ART at the enrolment visit and 12% started HCV treatment during follow‐up. ART adherence was not associated statistically with HCV treatment initiation. The proportion of patients maintaining adherence or becoming adherent to ART for those starting HCV treatment was higher than in the rest of the sample (P = 0.07). After multiple adjustment for known correlates, such as poor housing conditions, binge drinking, recent drug use and depressive symptoms, patients who initiated HCV treatment were less likely to be non‐adherent to ART [odds ratio (95% confidence interval) = 0.41 (0.24–0.71)]. Conclusions Engaging human immunodeficiency virus/hepatitis C virus coinfected individuals in hepatitis C virus treatment is associated with high adherence to antiretroviral treatment. Physicians should prioritize hepatitis C virus treatment as part of a multi‐disciplinary approach.     

Myelin specific cells infiltrate MCAO lesions and exacerbate stroke severity

Although inflammatory responses increase stroke severity, the role of immune cells specific for central nervous system (CNS) antigens remains controversial. Disruption of the blood–brain barrier (BBB) during stroke allows CNS antigens to leak into the peripheral circulation and enhances access of circulating leukocytes to the brain, including those specific for CNS antigens such as myelin oligodendrocyte glycoprotein (MOG) that can induce experimental autoimmune encephalomyelitis (EAE). We here demonstrate for the first time that myelin reactive splenocytes specific for MOG transferred into severe combined immunodeficient (SCID) mice can migrate into the infarct hemisphere of recipients subjected to 60 min middle cerebral artery occlusion (MCAO) and 96 h reperfusion; moreover these cells exacerbate infarct volume and worsen neurological deficits compared to animals transferred with na?ve splenocytes. These findings indicate that autoimmunity in the CNS can exert detrimental injury on brain cells and worsen the damage from ischemic stroke.     

Longitudinal assessment of pigtailed macaque lower genital tract microbiota by pyrosequencing reveals dissimilarity to the genital microbiota of healthy humans

Abstract Vaginal bacterial communities play an important role in human health and have been shown to influence HIV infection. Pigtailed macaques (Macaca nemestrina) are used as an animal model of HIV vaginal infection of women. Since the bacterial microbiota could influence retrovirus infection of pigtailed macaques, the genital microbiota in 10 cycling macaques was determined by pyrosequencing. The microbiota of all macaques was polymicrobial with a median of 13 distinct genera. Strikingly, the genera Sneathia and Fusobacterium, both in the phylum Fusobacteria, accounted for 18.9% and 13.3% of sequences while the next most frequent were Prevotella (5.6%), Porphyromonas (4.1%), Atopobium (3.6%), and Parvimonas (2.6%). Sequences corresponding to Lactobacillus comprised only 2.2% of sequences on average and were essentially all L. amylovorus. Longitudinal sampling of the 10 macaques over an 8-week period, which spanned at least one full ovulatory cycle, showed a generally stable presence of the major types of bacteria with some exceptions. These studies show that the microbiota of the pigtailed macaques is substantially dissimilar to that found in most healthy humans, where the genital microbiota is usually dominated by Lactobacillus sp. The polymicrobial makeup of the macaque bacterial populations, the paucity of lactobacilli, and the specific types of bacteria present suggest that the pigtailed macaque microbiota could influence vaginal retrovirus infection.     

A platelet target for venous thrombosis? P2Y1 deletion or antagonism protects mice from vena cava thrombosis

A role for platelets in the pathogenesis of venous thrombosis was suggested by clinical and preclinical studies. However, examination of the platelet receptor, P2Y1, in this area has been limited. The goal of the current study was to examine effects of P2Y1 deletion, or selective antagonism with MRS2500, in oxidative venous thrombosis in mice. The P2Y12 antagonist, clopidogrel, was included as a reference agent. Anesthetized C57BL/6 or genetically modified mice underwent 3.5 or 5 % FeCl(3)-induced vena cava thrombosis. Pharmacokinetic properties of MRS2500 were defined for dose selection. Platelet aggregation and renal or tail bleeding times (BT) were measured to put antithrombotic effects into perspective. P2Y1 deletion significantly reduced (p < 0.001) venous thrombus weight by 74 % in 3.5 % FeCl(3) injury compared to P2Y1(+/+) littermates. MRS2500 (2 mg/kg, i.v.) significantly decreased (p < 0.001) thrombus weight 64 % in C57BL/6 mice. In the more severe 5 % FeCl(3)-induced injury model, thrombus weight significantly (p < 0.001) decreased 68 % in P2Y1(-/-) mice versus P2Y1(+/+) mice, and MRS2500 (2 mg/kg) was also beneficial (54 % decrease, p < 0.01). Renal BT doubled in P2Y1(-/-) versus P2Y1(+/+) mice, and increased threefold with MRS2500 compared to vehicle. Tail BT was markedly prolonged in P2Y1(-/-) mice (7.9X) and in C57BL/6 mice given MRS2500. The current study demonstrates that P2Y1 deletion or antagonism significantly reduced venous thrombosis in mice, suggesting that P2Y1 receptors play a role in the pathogenesis of venous thrombosis, at least in this species. However as with many antithrombotic agents the benefit comes at the potential price of an increase in provoked bleeding times.     

Anemia as a factor related to the progression of proliferative diabetic retinopathy after photocoagulation

ObjectiveThis study aimed to investigate factors that could be related to the progression of proliferative diabetic retinopathy in patients treated with photocoagulation.MethodsIn this case-control study, a total of 106 patients with diabetic retinopathy participated who were treated with photocoagulation. We analyzed glycaemia, serum cholesterol, triglycerides, hemoglobin, platelet levels, blood pressure measurement, diabetes duration, diabetes and hypertension treatment, sex, and age. The statistical analysis was done with t test, χ² test, odds ratio (OR), and simple linear regression.ResultsWe found statistical significance in blood glucose level (P=.038), cholesterol level (P<.001), and hemoglobin level (P<.001). The simple linear regression was significant with blood glucose level (P<.05) and hemoglobin level (P=.001). Hemoglobin had a significant result: OR=2.432, 95% CI 1.902–3.115; Pearson χ²= 16.812; P<.001.ConclusionsAnemia is an important finding in diabetic patients. Anemia is a relevant factor related to the progression of proliferative diabetic retinopathy, which can be treated with photocoagulation.