Repression of hypoxia-inducible factor-1 contributes to increased mitochondrial reactive oxygen species production in diabetes

Background: Excessive production of mitochondrial reactive oxygen species (ROS) is a central mechanism for the development of diabetes complications. Recently, hypoxia has been identified to play an additional pathogenic role in diabetes. In this study, we hypothesized that ROS overproduction was secondary to the impaired responses to hypoxia due to the inhibition of hypoxia-inducible factor-1 (HIF-1) by hyperglycemia. Methods: The ROS levels were analyzed in the blood of healthy subjects and individuals with type 1 diabetes after exposure to hypoxia. The relation between HIF-1, glucose levels, ROS production and its functional consequences were analyzed in renal mIMCD-3 cells and in kidneys of mouse models of diabetes. Results: Exposure to hypoxia increased circulating ROS in subjects with diabetes, but not in subjects without diabetes. High glucose concentrations repressed HIF-1 both in hypoxic cells and in kidneys of animals with diabetes, through a HIF prolyl-hydroxylase (PHD)-dependent mechanism. The impaired HIF-1 signaling contributed to excess production of mitochondrial ROS through increased mitochondrial respiration that was mediated by Pyruvate dehydrogenase kinase 1 (PDK1). The restoration of HIF-1 function attenuated ROS overproduction despite persistent hyperglycemia, and conferred protection against apoptosis and renal injury in diabetes. Conclusions: We conclude that the repression of HIF-1 plays a central role in mitochondrial ROS overproduction in diabetes and is a potential therapeutic target for diabetic complications. These findings are timely since the first PHD inhibitor that can activate HIF-1 has been newly approved for clinical use. Funding: This work was supported by grants from the Swedish Research Council, Stockholm County Research Council, Stockholm Regional Research Foundation, Bert von Kantzows Foundation, Swedish Society of Medicine, Kung Gustaf V:s och Drottning Victorias Frimurarestifelse, Karolinska Institute's Research Foundations, Strategic Research Programme in Diabetes, and Erling-Persson Family Foundation for S-B.C.; grants from the Swedish Research Council and Swedish Heart and Lung Foundation for T.A.S.; and ERC consolidator grant for M.M.Peer reviewe

Diabetes, hypoxia and cardiovascular disease: From molecular mechanism to treatment

publishersversionpublishe

The value of an acute octreotide suppression test in predicting long-term responses to depot somatostatin analogues in patients with active acromegaly.

BACKGROUND: The long-acting depot somatostatin analogues [octreotide LAR (LAR) and lanreotide (LAN)] are among the most effective available medical therapies for acromegaly. However, published data on a biochemical test suitable for predicting the responsiveness to these depot agents are lacking. AIM: To investigate the value of an acute octreotide suppression test (OST) in predicting the responses to treatment with long-acting somatostatin analogues in patients with active acromegaly. PATIENTS AND METHODS: Thirty patients with active acromegaly [mean GH in GH day curve (GHDC) > 5 mU/l] were subjected to an OST [hourly GH measurements for 6 h following 100 microg subcutaneous (s.c.) octreotide]. Subsequently, 14 patients were treated with LAR, 10 with LAN and 6 received both drugs at different times. The final response to treatment was evaluated when the subjects had achieved 'safe' GH levels (mean GH < 5 mU/l) or after receiving the maximal dose of each drug (maximum duration of treatment 6 months). RESULTS: The nadir GH values during the OST were 2.6 +/- 2.5 mU/l (mean +/- SD, range 0.2-8.7) with a percentage fall of 84.8 +/- 15.7% (mean +/- SD, range 26-99%) from the baseline levels (26.2 +/- 31.5 mU/l, mean +/- SD). All the patients except one showed a decrease of greater than 50%. The mean time to achieve the nadir GH value was 3.8 +/- 1.6 h (mean +/- SD, range 1-6). The nadir GH levels showed a positive correlation with both pre-treatment (i.e. before commencing LAN or LAR) GH values during the GHDC (r = 0.63, P < 0.01) and IGF-I levels (r = 0.56, P < 0.05). The nadir GH values during the OST showed a positive correlation with the achieved mean GH levels in patients treated with LAR (r = 0.66, P < 0.01) but not in the ones treated with LAN. The criterion of GH < 5.25 mU/l during the OST had sensitivity 100%, specificity 80%, positive predictive value (PPV) 94% and negative predictive value (NPV) 100% in predicting achievement of 'safe' GH levels in patients treated with LAR. A less optimal prognostic profile was obtained for subjects treated with LAN with the criterion of GH < 6.05 mU/l during the OST providing sensitivity 92%, specificity 67%, PPV 92% and NPV 67%. The above cut-off GH levels had a PPV of only 77% and 60% in predicting normalization of IGF-I on treatment with LAR or LAN, respectively. CONCLUSIONS: The OST is a reliable tool for the selection of patients with active acromegaly who will achieve 'safe' GH levels on therapy with LAR. Its prognostic profile is less optimal for patients treated with LAN. If GH values during the test fall < 5.25 mU/l (in case of LAR treatment) or < 6.05 mU/l (in case of LAN treatment), there is a 92-94% chance of subsequently achieving 'safe' GH levels after up to 6 months treatment with either of these agents

A novel technique for enterotomy closure in stapled laparoscopic intracorporeal anastomosis

Aim: The proximal edge of the enterotomy in a side-to-side anastomosis has been shown to be the site at highest risk of leakage. Several methods have been described to overcome this vulnerability. The technical challenge of intra-corporeal anastomosis (ICA) is to re-create angles between tissues and instruments, similar to those in an open anastomosis. The axis between the suture line and the needle driver is paramount and this angle should be <\ua045\ub0. Method: The crotch stitch of the enterotomy is difficult because of the narrow space between the loops and the depth of the anastomosis. The usual technique is suturing right-handed, \u2018out\u2013in and in\u2013out\u2019, colonic edge first to small bowel. The risk of suture misplacement (e.g. \u2018out\u2013in/out\u2013in\u2019 or \u2018out\u2013out\u2019) is similar to open procedures but laparoscopically the second bite is challenging, due to the straight needle-driver. This may lead to asymmetrical closure of the corner resulting in a slightly larger angle on the bowel side and a potential postoperative leak/fistula. Rotating the small bowel loop to counterbalance this issue, risks tearing of the staple line. The rationale is that starting with a back-handed stitch and taking the small bowel edge first would allow the necessary acute angled bite to be achieved. Subsequently, mounting the needle right-handed for taking the colonic edge also allows achievement of an acute angled bite. Results: Our novel technique, named the \u2018back-handed, left-to-right stitch\u2019 technique, is intended to achieve symmetrical approximation of the ileal and colonic edges during laparoscopy, with an optimal closure of the deepest extremity of the enterotomy. Such a stitch, used in a series of 10 patients, may be useful to avoid leaving an opening within this angle and/or to avoid potential technical pitfalls when closing the deepest apex of the enterotomy. Conclusion: This \u2018back-handed, left-to-right\u2019 stitch described here allows a properly angled closure of the proximal edge of the enterotomy and a safe approximation of the corner of the enterotomy in a side-to-side ICA