Introduction Diabetes mellitus is a serious metabolic disorder causing multiple organ damage in human.However, the lipidomic profiles in different organs and their associations are rarely studied in either diabetic patients or animals. ObjectivesTo evaluate and compare the characteristics of lipid species in serum and multiple tissues in a diabetic mouse model. MethodsSemi-quantitative profiling analyses of intact and oxidized lipids were performed in serum and multiple tissues from a diabetic mouse model fed a high fat diet and treated with streptozotocin by using LC/HRMS and MS/MS. The total content of each lipid class, and the tissue-specific lipid species in all tissue samples were determined and compared by multivariate analyses. ResultsThe diabetic mouse model displayed characteristic differences in serum and multiple organs: the brain and heart showed the largest reduction in cardiolipin, while the kidney had the most remarkable alterations in triacylglycerol. Interestingly, the lipidomic differences also existed between different regions of the same organ: triacylglycerol species with shorter fatty acyl chains decreased in renal medulla but increased in cortex; cardiolipin species with highly polyunsaturated fatty acyls decreased only in atrium but not in ventricle.Importantly, diabetes caused an accumulation of lipid hydroperoxides, suggesting that oxidative stress was induced in all organs except for the brain during the development of diabetes. ConclusionThese findings provided novel insight into the organ-specific relationship between diabetes and lipid metabolism, which might be useful for evaluating not only diabetic tissue injury but also the effectiveness of diabetic treatments.

Context: Patients with diabetes are susceptible to heart failure. Defective mitochondria can cause cardiac damage. Mitochondrial autophagy or mitophagy is a quality control mechanism that eliminates dysfunctional mitochondria through lysosome degradation. Mitophagy is essential for maintaining a pool of healthy mitochondria for normal cardiac function. However, the effect of diabetes on the functional status of cardiac mitophagy remains unclear. Objective: To determine and compare cardiac mitophagy flux between diabetic and nondiabetic mice. Methods: Using a novel dual fluorescent mitophagy reporter termed mt-Rosella, we labeled and traced mitochondrial fragments that are sequestered by the autophagosome and delivered to and degraded in the lysosome. Results: Mitophagic activity was reduced in high-glucose–treated cardiomyocytes and in the heart tissue of type 1 diabetic mice. Conclusions: Mitophagy was impaired in the heart of diabetic mice, suggesting that restoring or accelerating mitophagy flux may be a useful strategy to reduce cardiac injury caused by diabetes.

Circularized oligonucleotides, or coligos, were previously found to serve as RNA polymerase III (Pol III) templates in vitro and in human tissue culture cells. Here we randomized the 12-nucleotide larger loop (L-loop) of a well characterized coligo and found unexpectedly that in vitro transcription by FLAG-Pol III was not significantly affected. This observation allowed us to test the variable of coligo L-loop size separately from the variable of its sequence. Transcription efficiency increased with L-loop size from 3 to 12 nucleotides of randomized sequence, and the smallest loop forced initiation to move into the stem region. To test further the need for any specific sequence we compared seven nucleotide L-loops composed of random, abasic and abasic-acyclic nucleotides, and all supported transcription by Pol III. Transcription of a series of coligos containing twelve contiguous randomized nucleotides placed at different locations within the coligo structure provided further evidence that the stem-loop junction structure is important for precise initiation. Nearly the same transcript pattern was formed in vitro by Pol III from yeast and human cells. Overall, these experiments support structure, rather than L-loop sequence, as the major determinant of coligo transcription initiation by Pol III.

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Heart disease and diabetes are among the leading causes of morbidity and mortality. Diabetes can result in diabetic cardiomyopathy, which further increases the risk of heart failure and mortality in diabetic patients. Diabetic cardiac injury has been associated with altered mitochondrial quality control mechanisms including mitophagy, a selective autophagy in which dysfunctional mitochondria are degraded through the lysosome. Lysophagy is the elimination of injured lysosomes by healthy lysosomes which is extremely important for all forms of autophagy. In the present study, we examined the functional status of mitophagy-lysosome system in the diabetic mouse heart. Cardiac mitophagy and lysophagy were determined by using novel dual fluorescent reporter mice, namely, mt-rosella that express mitochondria-targeted RFP-GFP fusion protein and tfgal3 that express RFP-GFP-galectin3, a galactoside-binding lectin. Mice were fed a high fat diet (60%calories by fat) for 1 month and then injected i.p. with streptozotocin (30 mg/kg/d for 3 days). Mice continued on HFD for additional 3 months. Echocardiographic data showed impaired cardiac function in the diabetic mice. Merged confocal images demonstrated that diabetes increased mitophagy flux in the heart as indicated by the red puncta from mt-Rosella and the mitochondrial LC3-II levels with and without lysosomal protease inhibitors pepstatin A and E64d. In addition, diabetes triggered lysosomal injury in the heart as shown by the increased total number of puncta (yellow plus red) from tfgal3 reporter on the merged confocal images. This was associated with accelerated lysophagy flux as shown by the red puncta, suggesting that the injured lysosomes were being actively degraded in the diabetic heart. The increased lysophagy may have contributed to the increased mitophagy flux since the enhanced elimination of injured lysosomes would be expected to help maintain a pool of healthy lysosomes which is essential for the efficient execution of all forms of autophagy. In summary, our results showed an enhanced mitophagy-lysosome system in the diabetic heart which may be an adaptive response that serves to limit diabetic cardiac injury.