Plasma free fatty acids in pregnant insulin-independent Natal Indian diabetics

A study was undertaken in Natal Indians to determine the insulin secretory response and the comparative degree of free fatty acidaemia in normal and insulin-independent diabetic pregnant women. The fasting plasma FFA and glucose levels were found to be substantially greater in the diabetic subjects. The pattern of plasma FFA and glucose response to exogenous insulin was similar in both groups. Endogenous insulin produced a similar FFA response, but a markedly obtunded blood sugar response occurred among the diabetics despite adequate plasma insulin levels. The significance of the differential effect of endogenous insulin on FFA and glucose metabolism in pregnant insulin-independent Natal Indian diabetics is discussed.     

Chemokines in proliferative diabetic retinopathy and proliferative vitreoretinopathy

PURPOSE: To determine levels of the chemokines CCL1/I-309, CCL2/MCP-1, CCL3/MIP-1alpha, CCL4/MIP-1beta, CCL7/MCP-3, CCL8/MCP-2, CXCL5/ENA-78, CXCL6/GCP-2, CXCL10/IP-10, and CXCL11/I-TAC in the vitreous humor and serum, from patients with proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and rhegmatogenous retinal detachment with no PVR (RD), and to investigate the expression of MCP-1, CXCL12/SDF-1, and the chemokine receptor CXCR3 in epiretinal membranes. METHODS: Paired vitreous humor and serum samples were obtained from patients undergoing vitrectomy for the treatment of RD (57 specimens), PVR (32 specimens), and PDR (88 specimens). The levels of chemokines were measured by enzyme-linked immunosorbent assays. Eighteen PDR and 5 PVR membranes were studied by immunohistochemical techniques. RESULTS: Of all the chemokines studied, only MCP-1 and IP-10 were detected in vitreous humor samples. MCP-1 levels in vitreous humor samples were significantly higher than in serum samples (p < 0.001). MCP-1 levels were significantly higher in vitreous humor samples from patients with PVR and PDR compared with RD (p = 0.0002). MCP-1 levels in vitreous humor samples from patients with active PDR were significantly higher than in inactive PDR cases (p = 0.0224). IP-10 levels in vitreous humor samples were significantly higher than in serum samples (p = 0.0035). IP-10 levels were significantly higher in vitreous humor samples from patients with PVR and PDR compared with RD (p = 0.0083). The incidence of IP-10 detection in vitreous humor samples was significantly higher in active PDR cases compared with inactive cases (p = 0.0214). There was a significant association between the incidence of IP-10 detection and increased levels of MCP-1 in vitreous humor samples from all patients, and patients with RD and PDR (p < 0.001 for all comparisons). MCP-1, and SDF-1 were localized in myofibroblasts in PVR and PDR membranes and in vascular endothelial cells in PDR membranes. CXCR3 was expressed by vascular endothelial cells in PDR membranes. CONCLUSION: MCP-1, IP-10 and SDF-1 may participate in pathogenesis of PVR and PDR. Myofibroblasts and vascular endothelial cells are the major cell types expressing MCP-1, SDF-1, and CXCR3 in epiretinal membranes.     

Screening of diabetics for retinopathy by ophthalmic opticians.

Diabetes mellitus is a major cause of blindness in England and Wales in those aged between 30 and 64. Photocoagulation can frequently prevent blindness provided the retinopathy is detected at an appropriate stage but unfortunately the benefits are small if the changes are advanced. Early detection of diabetic retinopathy by regular examination is needed. We have shown that ophthalmic opticians have the skill to detect retinal changes at a treatable stage. Out of 844 eye checks, 80 were reported by ophthalmic opticians to justify referral to an ophthalmologist and 20 of these required photocoagulation treatment. Of a sample of 197 patients rechecked by an ophthalmologist reported by ophthalmic opticians not to justify referral, only one needed treatment. With local agreement this system of detecting retinopathy could be easily applied anywhere in the United Kingdom. No extra personnel or facilities are needed.     

Topical application of integrin antagonists inhibits proliferative retinopathy.

The expression of alphav-integrins is highly selective for angiogenic endothelial cells; ligation inhibition by cyclic RGD peptides prevents pathological neovascularization in tumor or retinopathy models to a large extent. We have previously demonstrated that proliferative retinopathy in a mouse model of retinopathy of prematurity (ROP model) can be reduced by more than 70%. To minimize systemic side effects and unwanted interference with responsive angiogenesis, we investigated topical application of cyclic RGD-peptides. In preliminary experiments, we could exclude any inhibiting effects of the carrier solution containing EDTA, Na2S, mannitol, hydroxyethyl starch, and benzalconium chloride on the inhibitory effect of cyclic RGD peptides. Retinal presence of small molecular-mass integrin antagonists after topical application was confirmed using fluorescein-labeled cyclic RGD peptide. Topical application of the peptide to the eye inhibited proliferative retinopathy in a dose-dependent fashion with a maximum of almost 50%. These results suggest that small molecular-mass peptide antagonists of alphav-type integrins are efficient in inhibiting proliferative retinopathy by topical application.     

Factors protective against retinopathy in insulin-dependent diabetics free of retinopathy for 30 years

To investigate which factors might protect against the development of retinopathy 40 insulin-dependent diabetics who had remained free from retinopathy despite diabetes of long duration (mean±1 SD 30±10 years) were compared with 40 patients who had background and 47 who had proliferative retinopathy (mean durations of disease 16±5 and 19±5 years respectively). The three groups had had similar mean ages at onset of diabetes. The mean of all postprandial blood glucose measurements at hospital clinics from diagnosis of diabetes to detection of retinopathy, or to the most recent negative eye examination, was 9·9±2·1 mmol/l (178±38 mg/100 ml) in the group with no retinopathy, 11·8±2·1 mmol/l (213±38 mg/100 ml) in those with background retinopathy, and 12·4±2·1 mmol/l (223±38 mg/100 ml) in those with proliferative retinopathy (p <0·0001). This difference was not reflected in present concentrations of haemoglobin A_1C, probably because glycaemic control had been improved after the development of retinopathy. In the groups with background and proliferative retinopathy there were significant negative correlations between mean blood glucose concentrations and the number of years that had elapsed from diagnosis of diabetes to detection of retinopathy, suggesting that the development of both grades of retinopathy depends on the degree and duration of glycaemic exposure.The patients with no retinopathy had attended clinic more frequently (p <0·025), more of them had required emergency hospital treatment for hypoglycaemia (p <0·0025), and they tended to have had a lower prevalence of hyperglycaemic coma than the other groups. Although mean percentage ideal body weight and diastolic blood pressure were lower in the patients with no retinopathy at the time of study, mean body weight, blood pressure, and the prevalence of smoking in the years before the development of retinopathy had been similar in all groups, suggesting that these did not influence the development of retinopathy.     

Rapid onset of hypoxic vasoconstriction in isolated lungs.

A fast-response O2 analyzer that samples air at low flow rates allows the quasi-instantaneous measurement of O2 concentration change in the airways of isolated blood-perfused rat lungs. This instrument and an oximeter were used to measure the stimulus-response delay time of hypoxic pulmonary vasoconstriction when the lungs were challenged with 10, 5, or 3% O2. The estimate for the shortest delay time between accomplished fall in airway O2 concentration and the onset of hypoxia-induced vasoconstriction was approximately 7 s. We found that the slope of pressure rise, but not the stimulus-response delay time, correlated with the magnitude of hypoxic vasoconstriction. Oscillations in pulmonary arterial pressure were observed when the lungs were challenged with 10% O2 but not when the challenge was 12, 5, or 3%, indicating perhaps that these oscillations were a threshold phenomenon. Established hypoxic vasoconstriction was sensitive to brief changes in airway O2 concentration. Vasodilation occurred when the gas mixture was switched from 3 to 21% O2 for two to five breaths, and vasoconstriction occurred when the gas was changed during a single breath from 5 to 3% O2.     

The therapeutic problem of proliferative diabetic retinopathy: targeting somatostatin receptors.

Clinical management of proliferative diabetic retinopathy has changed very little in the last 5 decades, relying primarily on laser ablation of the retinal vasculature. Several lines of clinical and experimental evidence suggest that somatostatin analogues may be efficacious in inhibiting neovascularization associated with proliferative retinopathy but the mechanism of action for these compounds is unclear. Inhibition of growth hormone secretion and the subsequent suppression of insulin-like growth factor 1 (IGF-1) production by somatostatin has been suggested as the mechanism of action, however, in vitro studies suggest that somatostatin analogues suppress endothelial cell growth through a direct, somatostatin receptor-mediated inhibition of pro-survival signaling pathways. The advent of a new generation of modified peptide and peptidomimetic somatostatin analogues has allowed investigators to more carefully define the receptor subtypes responsible for somatostatin-induced endothelial cell death and may eventually lead to the clinical development of somatostatin analogues that can reduce endothelial cell proliferation, independent of suppression of circulating hormone levels.