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Objective: There is growing evidence to indicate that somatostatin could be added to the list of natural antiangiogenic factors that exist in the vitreous fluid. In addition, a deficit of intravitreous somatostatin-like immunoreactivity (SLI) has been found in diabetic patients with proliferative diabetic retinopathy (PDR). In the present study, we have determined the main molecular variants of somatostatin (somatostatin-14 and somatostatin-28) in the vitreous fluid and plasma of nondiabetic control subjects and diabetic patients with PDR. In addition, the contribution of cortistatin, a neuropeptide with strong structural similarities to somatostatin, to SLI and its levels in vitreous and plasma in both nondiabetic and diabetic patients has also been measured. RESERCH DESIGN AND METHODS: Plasma and vitreous fluid from 22 diabetic patients with PDR and 22 nondiabetic control subjects were analyzed. Somatostatin-14, somatostatin-28 and cortistatin were measured by radioimmunoassay but separation by high-performance liquid chromatography was required to measure somatostatin-14.Results: The predominant molecular form of somatostatin within the vitreous fluid was somatostatin-28 (fivefold higher than somatostatin-14 in control subjects and threefold higher in patients with PDR). Cortistatin significantly contributed to SLI and its intravitreous levels were higher than those detected in plasma (nondiabetic control subjects: 147 [102-837] vs. 78 [24-32] pg/ml; patients with PDR: 187 [87-998] vs. 62 [24-472] pg/ml; P = 0.01 for both). Intravitreous somatostatin-14 was similar in both subjects with PDR and the control group (P = 0.87). By contrast, somatostatin-28 concentration was lower in patients with PDR than in nondiabetic control subjects (350 +/- 32 vs. 595 +/- 66 pg/ml; P = 0.004).Conclusions: Somatostatin-28 is the main molecular variant in the vitreous fluid. The intravitreous SLI deficit detected in patients with PDR is mainly due to somatostatin-28. Cortistatin is abundant in the vitreous fluid and significantly contributes to SLI. These findings could open up new strategies for PDR treatment. [ABSTRACT FROM AUTHOR]

Objective: Glucagon like peptide-1 (GLP-1) has been suggested as a major factor for the improved glucose tolerance ensuing after Roux-en-Y gastric bypass (RYGBP) surgery. We examined the effect of blocking endogenous GLP-1 action on glucose tolerance in subjects with sustained remission of type 2 diabetes mellitus (T2DM) present before RYGBP., Research Design and Methods: Blood glucose, insulin, C-peptide, glucagon, GLP-1, and glucose-dependent insulinotropic peptide levels were measured after a meal challenge with either exendin-(9-39) (a GLP-1r antagonist) or saline infusion in eight subjects with sustained remission of T2DM after RYGBP and seven healthy controls., Results: Infusion of exendin-(9-39) resulted in marginal deterioration of the 2-h plasma glucose after meal intake in RYGBP subjects [saline 78.4 ± 15.1 mg/dL compared with exendin-(9-39) 116.5 ± 22.3 mg/dL; P < 0.001]. Furthermore, glucose response to meal intake was similarly enlarged in the two study groups [percent change in the area under the curve of glucose exendin-(9-39) infusion versus saline infusion: controls 10.84 ± 8.8% versus RYGBP 9.94 ± 8.4%; P = 0.884]. In the RYGBP group, the blockade of the enlarged GLP-1 response to meal intake resulted in reduced insulin (P = 0.001) and C-peptide (P < 0.001), but no change in glucagon (P = 0.258) responses., Conclusions: The limited deterioration of glucose tolerance on blockade of GLP-1 action in our study suggests the resolution of T2DM after RYGBP may be explained by mechanisms beyond enhancement of GLP-1 action.

Objective: To evaluate through early preclinical atherosclerosis assessment whether repeated episodes of hypoglycemia represent an aggravating factor for macrovascular disease in type 1 diabetes., Research Design and Methods: After sample-size calculation, a case-control study of 25 patients with type 1 diabetes and repeated severe/nonsevere hypoglycemia (H-group) compared with 20 age- and sex-matched type 1 diabetes control subjects (C-group) was designed. Assessment of preclinical atherosclerosis consisted of flow-mediated brachial dilatation (FMD) and carotid and femoral intima-media thickness (IMT) studies. To consider hypoglycemia awareness, two different questionnaires and symptomatic response to an acute induction to hypoglycemia were used. Evaluation of the glycemic profile was obtained from continuous glucose monitoring. Endothelial function/inflammation markers were measured in euglycemia/hypoglycemia. A multivariate linear regression analysis was performed to test whether repeated hypoglycemia was independently associated with atherosclerosis., Results: H-group subjects displayed hypoglycemia unawareness and presented a higher percentage of continuous glucose values and area under the curve <70 mg/dl compared with the C-group (14.2 ± 8.9 vs. 6.3 ± 7.1%, P < 0.02 and 2.4 ± 1.8 vs. 0.6 ± 1.0 mg/dl/day, P < 0.01). The percentage of maximal FMD was lower in the H-group than in the C-group (6.52 ± 2.92 vs. 8.62 ± 3.13%, P < 0.05). A significantly higher IMT was observed at both carotid and femoral sites in the H-group (carotid 0.53 ± 0.09 vs. 0.47 ± 0.08 mm, P < 0.05 and femoral 0.51 ± 0.17 vs. 0.39 ± 0.09 mm, P < 0.05). Baseline inflammation and endothelial function markers were higher in the H-group (leukocytes 7.0 ± 1.8 vs. 5.6 ± 1.4 × 10³/ml, von Willebrand factor 119 ± 29 vs. 93 ± 26%, fibrinogen 2.82 ± 0.64 vs. 2.29 ± 0.44 g/l, and soluble intercellular adhesion molecule-1 408 ± 224 vs. 296 ± 95 ng/ml; P < 0.05 for all)., Conclusions: In addition to the induction of hypoglycemia unawareness and an increased risk for severe hypoglycemia, repeated hypoglycemia could be related to and considered an aggravating factor for preclinical atherosclerosis in type 1 diabetes. The precise mechanisms explaining this association remain to be clarified.

Objective: Adiponectin has been proposed to play important roles in the regulation of energy homeostasis and insulin sensitivity. In experimental studies, adiponectin has also been found to inhibit vascular smooth muscle cell proliferation. Decreased adiponectin levels have been described in patients with coronary artery disease, and circulating adiponectin predicts cardiovascular death in patients with renal failure. Because adiponectin appears to influence both insulin sensitivity and vessel wall physiology, we examined insulin sensitivity and vascular function in relation with circulating adiponectin., Research Design and Methods: We studied brachial artery vascular reactivity (high-resolution external ultrasound) and insulin sensitivity (minimal model) in 68 healthy subjects. Brachial artery vascular reactivity was also determined in 52 patients with altered glucose tolerance: 30 subjects with impaired fasting glucose (IFG) or glucose intolerance (GIT) and 22 patients with type 2 diabetes., Results: Circulating adiponectin concentration was significantly associated with insulin sensitivity (r=0.29, P=0.02) and with fasting serum triglycerides (r=-0.29, P=0.02) in healthy subjects. In the latter, adiponectin levels were positively associated with arterial vasodilation in response to nitroglycerin (endothelium-independent vasodilation [EIVD], r=0.41, P=0.002) but not with flux-induced, endothelium-dependent vasodilation (EDVD) (r=0.007, P=NS). In contrast, EIVD was not significantly associated with adiponectin in subjects with IFG, GIT, or type 2 diabetes (r < or =0.10, P=NS). In a multiple linear regression analysis to predict EIVD in healthy subjects, age (P=0.012), sex (P=0.042), and adiponectin concentration (P=0.045), but not BMI, insulin sensitivity, or fasting triglycerides, contributed to 39% of EIVD variance., Conclusions: Serum adiponectin concentration appears to be significantly associated with vascular function in apparently healthy humans. This association seems to be independent of its link with insulin sensitivity.

Objective: To evaluate the vitreous levels of somatostatin-like immunoreactivity (SLI) in patients with proliferative diabetic retinopathy (PDR)., Research Design and Methods: A total of 14 diabetic patients with PDR, in whom a vitrectomy was performed, were included in the study. Sixteen nondiabetic patients, with other conditions requiring vitrectomy, served as a control group. Both venous blood and vitreous samples were collected at the time of vitreoretinal surgery. Patients in whom intravitreous hemoglobin was detectable were excluded. In addition, a correction for plasma levels of SLI and intravitreal proteins was performed. SLI was measured by radioimmunoassay and vitreous hemoglobin by spectrophotometry., Results: SLI in the vitreous fluid was significantly lower in diabetic patients than in the control group (68 +/- 18.7 vs. 193.6 +/- 30.8 pg/ml, P < 0.01). The vitreous SLI-to-plasma SLI ratio was strikingly higher in nondiabetic subjects than in diabetic patients with PDR (5.3 [1.2-71.1] vs. 0.6 [0.03-4.1], P < 0.01). After correcting for total vitreous protein concentration, SLI (pg/mg of proteins) remained significantly higher in nondiabetic control subjects than in diabetic patients with PDR (186 [51-463] vs. 7.5 [0.8-82], P < 0.0001). Remarkably, intravitreous levels of SLI were higher than those obtained in plasma in nondiabetic control subjects (193.6 +/- 30.8 vs. 43.5 +/- 10.7 pg/ml, P < 0.0001). Finally, a lack of relationship between plasma and vitreous levels of SLI was observed in both diabetic patients with PDR and nondiabetic control subjects., Conclusions: The significantly higher SLI in the vitreous fluid than in plasma detected in nondiabetic control subjects supports the concept that somatostatin plays a relevant role in retinal homeostasis. In addition, the intravitreous deficit of SLI observed in diabetic patients with PDR suggests that it might contribute to the process of retinal neovascularization.