The effect of voluntary fasting and dehydration on posterior ocular structures

Purpose: Islamic Ramadan is the month of fasting, in which intake of food and drink is restricted from sunrise until sunset. The objective of the present study was to find out the effects of religious fasting on posterior ocular structures.

Materials and methods: In this prospective study, 34 eyes of 34 healthy volunteers with a mean age of 34.09?±?7.20?years were enrolled. Volunteers with any systemic disorder and eyes with pathology or previous surgery were excluded. One week before Ramadan (non-fasting period) and during Ramadan (fasting period) at the same hours (at 08:00 and 16:00?h), choroidal, macular, and retinal nerve fibre layer (RNFL) thicknesses were measured by spectral domain optical coherence tomography. Results were compared using paired sample t-test, and a p value <0.05 was accepted as statistically significant.

Results: The comparison of 16:00-h measurements significantly revealed lower values during fasting period when compared non-fasting period for choroidal thickness (non-fasting and fasting, respectively; subfoveal: 299.26?±?41.3 and 280.03?±?38.75 p?p?p?=?0.001) and paracentral macular thickness (superior: p?=?0.002, inferior: p?=?0.010, temporal: p?=?0.013, and nasal: p?=?0.016). By contrast, no significant differences were found in the central macular thickness between the fasting and non-fasting periods (p?=?0.735). Also, no statistically significant difference was noted for RNFL thickness at the different periods and time points.

Conclusion: Our results reveal that Islamic religious fasting is associated with statistically significant alterations in choroidal and paracentral macular thickness in healthy volunteers. However, more detailed investigations should be designed to evaluate whether fasting has a pivotal influence on pathological conditions.     

GCK-MODY diabetes as a protein misfolding disease: The mutation R275C promotes protein misfolding,self-association and cellular degradation

GCK-MODY, dominantly inherited mild hyperglycemia, is associated with more than 600 mutations in the glucokinase gene. Different molecular mechanisms have been shown to explain GCK-MODY. Here, we report a Pakistani family harboring the glucokinase mutation c.823C > T (p.R275C). The recombinant and in cellulo expressed mutant pancreatic enzyme revealed slightly increased enzyme activity (k_cat) and normal affinity for α-D-glucose, and resistance to limited proteolysis by trypsin comparable with wild-type. When stably expressed in HEK293 cells and MIN6 β-cells (at different levels), the mutant protein appeared misfolded and unstable with a propensity to form dimers and aggregates. Its degradation rate was increased, involving the lysosomal and proteasomal quality control systems. On mutation, a hydrogen bond between the R275 side-chain and the carbonyl oxygen of D267 is broken, destabilizing the F260-L271 loop structure and the protein. This promotes the formation of dimers/aggregates and suggests that an increased cellular degradation is the molecular mechanism by which R275C causes GCK-MODY.     

雷公藤甲素对高糖刺激足细胞转分化的影响

目的 探讨雷公藤甲素（TP）对高糖刺激的足细胞转分化的影响及可能机制.方法 将体外培养的小鼠永生化足细胞分为正常组（加入D-葡萄糖5.5 mmol/L）、高糖组（加入D-葡萄糖30 mmol/L）、TP低剂量组（加入D-葡萄糖30mmol/L＋ TP 3 ng/mL）、TP高剂量组（加入D-葡萄糖30 mmol/L＋ TP 10 ng/mL）及甘露醇组（加入D-葡萄糖5.5 mmol/L＋甘露醇24.5 mmol/L）,采用荧光定量PCR法和Western blot法分别检测各组足细胞Smad3、Smad7、Ssynaptopodin、Ddesmin mRNA及蛋白的表达量.结果 TP低剂量组、TP高剂量组Smad3、Desmin mRNA及蛋白表达均低于高糖组（P＜0.05）,Smad7、Synaptopodin mRNA及蛋白表达均高于高糖组（P＜0.05）.结论 TP可抑制高糖刺激引起的足细胞转分化,其机制可能为在转录水平和蛋白水平调节足细胞Smad3、Smad7表达异常.     

空腹血糖受损并糖耐量受损患者血管内皮功能及代谢功能观察

目的：观察空腹血糖受损并糖耐量受损（ IFG＋IGT）患者血管内皮功能及代谢功能情况。方法选择IFG＋IGT者72例（ E组）,其中非肥胖30例（ E1组）,肥胖42例（ E2组）;另选择糖耐量正常的健康人群142例（ N组）,其中非肥胖75例（ N1组）、肥胖67例（ N2组）。做口服葡萄糖耐量试验及胰岛素释放试验检测血糖、免疫活性胰岛素,同时检测空腹血脂、游离脂肪酸、脂联素。采用免疫比浊法检测超敏C反应蛋白（ hs-CRP）,RIA法检测血清内皮素（ SET）。留取晨尿,采用未抽提法测定内皮素（ UET）,散射比浊法检测尿微量白蛋白（ MUA）。观察血压和腰围。彩超测定肱动脉休息时、加压及服用硝酸甘油后的内径变化,计算内皮依赖性血管舒张功能（ EDD）及内皮非依赖性血管舒张功能（ EID）指标（ΔD％、ΔD1％）。结果校正性别、年龄后,E和N组比较、E2与N2组比较及E1与N1组比较,MUA、hs-CRP、UET、SET、ΔD％、ΔD1％差异有统计学意义（P均＜0．05）;N2与N1组比较hs-CRP、UET和SET差异有统计学意义（P均＜0．05）;E2与E1组比较MUA、hs-CRP、UET和SET差异有统计学意义（P均＜0．05）。结论 IFG＋IGT患者大血管和微血管内皮功能均出现异常,尤以肥胖者为著;患者的代谢功能亦出现异常,主要表现为高血压、高血糖、脂代谢紊乱、胰岛素抵抗及胰岛分泌功能下降。     

Ceramides are associated with inflammatory processes in human mediastinal adipose tissue

Background and AimCeramides are poorly characterized in human adipose tissue. The aim of this study was to investigate concentrations of different ceramide species in human subcutaneous and visceral adipose tissue depots and to determine associations between ceramides and global gene expression profiles.Methods and ResultsConcentrations of six ceramide species were determined in plasma and in subcutaneous and mediastinal adipose tissue from 10 overweight subjects (BMI 29.4 ± 4.9 kg/m²). In the adipose tissue biopsies gene expression arrays were performed and relationships between ceramides and gene expression analyzed. Immunostaining of the two adipose tissue depots was performed in an independent group of 10 patients. Mediastinal adipose tissue contained significantly higher concentrations (p < 0.05) of all six ceramide species than the subcutaneous depot. Of the six ceramides in plasma, concentrations of only two (Cer d18:1/18:0 and Cer d18:1/22:0) correlated significantly (p < 0.05) with the corresponding species in mediastinal adipose tissue, but there were no significant correlations between ceramides in plasma and subcutaneous adipose tissue. Multivariate analysis identified significant correlations between the total ceramide concentration and global gene expression within mediastinal, but not subcutaneous adipose tissue, according to cross-validation. Gene ontology analysis of genes related to ceramides in the mediastinal depot revealed that genes positively correlated with ceramides were associated mainly with immune and inflammatory categories, while genes negatively correlated with ceramides were associated mainly with lipid and carbohydrate metabolism.ConclusionsCeramides in human mediastinal adipose tissue may be involved in inflammation and lipid and carbohydrate metabolism.     

Prevalence and progression of carbohydrate disorders in patients with pheochromocytoma/paraganglioma: retrospective single-center study

BackgroundCarbohydrate disorders are the most frequent metabolic disorders, affecting a significant proportion of patients with pheochromocytoma.ObjectiveA retrospective study assessed the prevalence and progression of carbohydrate disorders in 204 patients (92 men, 112 women) with histologically proven pheochromocytoma diagnosed in a single specialized tertiary center during a 40-year period (1978–2017). One hundred were followed-up after tumor removal.ResultsCarbohydrate disorders were diagnosed in 49.5% of cases: 30.4% with diabetes and, 19.1% prediabetes. Subjects with carbohydrate disorders had significantly greater age at diagnosis and higher 24-hour urine metanephrine and normetanephrine concentrations than those with normal glucose tolerance. One-third of patients with diabetes achieved good glycemic control under oral treatment (54% on metformin monotherapy). One-third of patients overall required preoperative insulin treatment. Postoperative follow-up (100 patients; 5-year mean duration) showed reduced prevalence of diabetes (13% vs. 33%; P = 0.0007) and prediabetes (12% vs. 24%; P = 0.027). Almost 60% of subjects initially diagnosed with carbohydrate disorders recovered normal glucose tolerance after surgery; these subjects had significantly higher preoperative urine metanephrine/normetanephrine levels than those with persistent diabetes/prediabetes. Correlation analysis revealed a moderate negative relationship between urine metanephrine/normetanephrine concentration and the outcome of the carbohydrate disorders (Spearmen's Rho = − 0.507; P = 0.013). There was no significant difference according to pre- or postoperative prevalence of obesity (15% vs. 16%; P = 0.845) or dyslipidemia (46% vs. 39%; P = 0.316).ConclusionsCarbohydrate disorders affect approximately 50% of pheochromocytoma patients; 30% develop overt diabetes, which may be the only clinical manifestation in some rare cases. Pheochromocytoma-related diabetes is more likely to affect patients with predominant adrenaline secretion. It is often easy to control and usually requires oral antidiabetic treatment. Reversibility of carbohydrate disorders depend on severity, preoperative metanephrine level, age and weight.