Comparative trial of N-acetyl-cysteine, taurine, and oxerutin on skin and kidney damage in long-term experimental diabetes

A review of antioxidant N-acetylcysteine in addressing polycystic ovary syndrome

N-acetylcysteine (NAC), a compound known for its cysteine and glutathione precursor properties, has been used in therapeutic applications for many years. Recently, there has been increasing interest in exploring the potential benefits of NAC in addressing polycystic ovary syndrome (PCOS). However, the exact mechanisms underlying NAC's therapeutic and clinical uses remain not fully understood. This review aims to specifically investigate how NAC offers protection against PCOS. This involved an extensive systematic review of the literature, and it made use of PubMed, Embase, and Web of Science databases. By analyzing key findings from over 100 research papers, the potential mechanisms through which NAC produces its effects were explored and summarized. Most studies suggest that NAC, whether used on its own or in combination with other medications, has the potential to counteract oxidative stress, utilize its anti-inflammatory and anti-apoptotic properties, and offer benefits in managing PCOS. Moreover, NAC might have the potential to influence specific signaling pathways in insulin target cells and β cells. Diverse biological effects of NAC indicate its potential usefulness as a supplementary or therapeutic approach for managing PCOS. As a result, additional research is required to explore its potential in addressing PCOS.

Tirzepatide alleviates oxidative stress and inflammation in diabetic nephropathy via IL-17 signaling pathway

Oxidative stress (OS) and inflammation play essential roles in the development of diabetic nephropathy (DN). Tirzepatide (TZP) has a protective effect in diabetes. However, its underlying mechanism in DN remains unclear. DN model mice were induced by intraperitoneal injection of streptozotocin (STZ; 60 mg/kg), followed by administration of different doses of TZP (3 and 10 nmol/kg) via intraperitoneal injection for 8 weeks. The effects of TZP on DN were evaluated by detecting DN-related biochemical indicators, kidney histopathology, apoptosis, OS, and inflammation levels. Additionally, to further reveal the potential mechanism, we investigated the role of TZP in modulating the IL-17 pathway. TZP reduced serum creatinine (sCR), blood urea nitrogen (BUN), and advanced glycosylation end products (AGEs) levels, while simultaneously promoting insulin secretion in diabetic mice. Additionally, TZP attenuated tubular and glomerular injury and reduced renal apoptosis levels. Further studies found that TZP increased the levels of SOD and CAT, and decreased MDA. Meanwhile, TZP also reduced the expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in both mouse serum and kidney homogenates. TZP effectively inhibited the IL-17 pathway, and subsequent intervention with an IL-17 pathway agonist (IL-17A) reversed the suppressive effects of TZP on OS and inflammation. TZP can improve DN by inhibiting OS and inflammation through the suppression of the IL-17 pathway.

Advanced glycation end products and insulin resistance in diabetic nephropathy

Insulin resistance is a central hallmark that connects the metabolic syndrome and diabetes to the resultant formation of advanced glycation end products (AGEs), which further results in the complications of diabetes, including diabetic nephropathy. Several factors play an important role as an inducer to diabetic nephropathy, and AGEs elicit their harmful effects via interacting with the receptor for AGEs Receptor for AGEs, by induction of pro-inflammatory cytokines, oxidative stress, endoplasmic reticulum stress and fibrosis in the kidney tissues leading to the loss of renal function. Insulin resistance results in the activation of other alternate pathways governed by insulin, which results in the hypertrophy of the renal cells and tissue remodeling. Apart from the glucose uptake and disposal, insulin dependent PI3K and Akt also upregulate the expression of endothelial nitric oxide synthase, that results in increasing the bioavailability of nitric oxide in the vascular endothelium, which further results in tissue fibrosis. Considering the global prevalence of diabetic nephropathy, and the impact of protein glycation, various inhibitors and treatment avenues are being developed, to prevent the progression of diabetic complications. In this chapter, we discuss the role of glycation in insulin resistance and further its impact on the kidney.

Role of advanced glycation end products and insulin resistance in diabetic nephropathy

Metabolic syndrome (MetS), i.e. a cluster of physiological and biochemical abnormalities can lead to diabetic nephropathy (DN). Insulin resistance, impaired fasting glucose are the main signs and symptoms of MetS. Excess sugar can induce various substantial structural changes like formation of advanced glycation end products (AGEs). AGEs are formed due to reaction of reducing sugars with amino groups of proteins, lipids and nucleic acids. AGEs when bound to the receptor for advanced glycation end products (RAGE) activate increased production of pro-inflammatory markers like interleukin-6 (IL-6), tumour necrosis factor alpha (TNF-α) along with induction of endoplasmic reticulum (ER) stress. Accumulation of AGEs, enhanced reactive oxygen species (ROS) generation and activation of protein kinase C (PKC), are considered to induce glomerular hypertrophy, podocyte apoptosis, therefore contributing to the development and progression of DN. In this review, we decipher different biochemical and physiological factors that link AGEs and DN.

REDD1 Ablation Attenuates the Development of Renal Complications in Diabetic Mice

Chronic hyperglycemia contributes to development of diabetic kidney disease by promoting glomerular injury. In this study, we evaluated the hypothesis that hyperglycemic conditions promote expression of the stress response protein regulated in development and DNA damage response 1 (REDD1) in the kidney in a manner that contributes to the development of oxidative stress and renal injury. After 16 weeks of streptozotocin-induced diabetes, albuminuria and renal hypertrophy were observed in wild-type (WT) mice coincident with increased renal REDD1 expression. In contrast, diabetic REDD1 knockout (KO) mice did not exhibit impaired renal physiology. Histopathologic examination revealed that glomerular damage including mesangial expansion, matrix deposition, and podocytopenia in the kidneys of diabetic WT mice was reduced or absent in diabetic REDD1 KO mice. In cultured human podocytes, exposure to hyperglycemic conditions enhanced REDD1 expression, increased reactive oxygen species (ROS) levels, and promoted cell death. In both the kidney of diabetic mice and in podocyte cultures exposed to hyperglycemic conditions, REDD1 deletion reduced ROS and prevented podocyte loss. Benefits of REDD1 deletion were recapitulated by pharmacological GSK3β suppression, supporting a role for REDD1-dependent GSK3β activation in diabetes-induced oxidative stress and renal defects. The results support a role for REDD1 in diabetes-induced renal complications.

A systematic review of preclinical studies on the taurine role during diabetic nephropathy: focused on anti-oxidative, anti-inflammation, and anti-apoptotic effects

Diabetic nephropathy is one of the most important and growing diseases globally and the leading cause of cardiovascular mortality in these patients. Taurine is an amino acid that has pleiotropic protective properties on some diseases. This study aimed to investigate the potential role of taurine in the treatment of diabetes-induced nephropathy. To achieve the aim of the present study, a comprehensive systematic search based on PRISMA guidelines has been conducted up to August 2021. A total of 382 articles were found in the electronic databases based on search keywords. After doing the screening, 14 articles were included in the present systematic review. The dated demonstrated elevation of oxidative stress, inflammatory and apoptotic pathways, and changes in other molecules' function plays an essential role in diabetes-induced renal tissue damage. Due to its multiple protective effects, taurine significantly prevented the activation of the pathways mentioned above and altered the function of molecules involved in these pathways, resulting in alleviating diabetic nephropathy. According to the obtained results, it was found that taurine can mitigate diabetes-induced nephropathy, mainly through its anti-oxidant activity, which is an essential factor in activating inflammation and apoptosis pathways.

Nephroprotective Effect of Coenzyme Q10 alone and in Combination with N-acetylcysteine in Diabetic Nephropathy

Aim

Oxidative stress due to chronic hyperglycaemia is a key factor in the development and progression of various microvascular complications including diabetic nephropathy (DN) and associated renal injury. Treatment with antioxidants is one of the strategies to protect the kidney from oxidative tissue damage to improve renal physiology during DN. The investigation, therefore, was designed to assess the nephroprotective effect of coenzyme Q10 (CoQ10) and N-acetylcysteine (NAC), either alone or in combination in streptozotocin (STZ)-nicotinamide (NAD) induced diabetic nephropathy (DN) in rats.

Methods

T2DM induced by STZ (55 mg/kg, i.p.)-NAD (110 mg/kg, i.p.) in Sprague-Dawley rats (220–250 g) was confirmed by the elevated blood glucose level and glycated haemoglobin. DN was assessed by renal function tests. The diabetic rats were treated with CoQ10 (10 mg/kg, p.o.) and/or NAC (300 mg/kg, p.o.) for 8 weeks after confirmation of DN. Oxidative tissue damage due to STZ-NAD was estimated by malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT), reduced glutathione (GSH), myeloperoxidase (MPO) and nitric oxide (NO) in the renal homogenate.

Results

Data showed significant alteration in serum and urinary creatinine, total protein, albumin, serum urea, blood urea nitrogen (BUN) and uric acid in diabetic animals as compared to the control rats. CoQ10 and/or NAC effectively alleviated the disturbances in renal function. Diabetic rats showed increased MDA, decreased SOD and CAT activities and decreased GSH along with a significant increase in MPO activity and nitrite content. Treatment with the aforementioned antioxidants and their combination ameliorated the kidney damage as indicated by the reduced OS with improved renal function.

Conclusion

The investigation suggests that the chronic hyperglycaemia-induced OS leads to the development and progression of DN. The combined treatment with CoQ10 and NAC has shown a remarkable nephroprotective effect suggesting that combined antioxidant therapy with CoQ10 and NAC may be useful in the attenuation of DN.

Randomized controlled open-label study of the effect of vitamin E supplementation on fertility in clomiphene citrate-resistant polycystic ovary syndrome

AIM

To evaluate the effect of vitamin E on ovulation and pregnancy in women with clomiphene citrate (CC)-resistant polycystic ovary syndrome (PCOS).

METHODS

A prospective, randomized, controlled, open label study was conducted on women with CC-resistant PCOS. Patients were randomized, to either control group (n = 30), who received metformin 500 mg thrice daily, in addition to 150 mg/day CC for 5 days starting from day 3 of menstruation for three menstruation cycles, or vitamin E group (n = 30) who received vitamin E 1500 IU/day for the whole study period in addition to metformin and CC with the same previous regimen. The primary outcome was cumulative ovulation rate, while secondary outcomes were pregnancy rate, serum midluteal progesterone, mean follicular diameter, number of dominant follicles and endometrial thickness.

RESULTS

Ovulation was reported in 57 (64.8%) of 88 cycles in the control group and 63 (73.3%) of 86 cycles in the vitamin E group (P = 0.227), while pregnancy was reported in 4 (4.5%) of 88 cycles in the control group and 6 (7%) of 86 cycles in the vitamin E group (P = 0.491).There were nonsignificant differences between groups regarding serum midluteal progesterone, number of dominant follicles and mean follicular diameter. Endometrial thickness was significantly higher in the vitamin E group compared to the control group.

CONCLUSION

The findings of this trial do not support the hypothesis that vitamin E may increase the ovulation and pregnancy rates in women with clomiphene citrate-resistant PCOS.

Arsenic exposure intensifies glycogen nephrosis in diabetic rats

It is known that either arsenic exposure or diabetes can impact renal function. However, it is unclear how these combined factors may influence kidney functions. Therefore, we evaluated morphological, functional, and oxidative parameters in the kidney of diabetic rats exposed to arsenic. Healthy male Wistar rats and streptozotocin-induced diabetic rats were exposed to 0 and 10 mg/L arsenate through drinking water for 40 days. Renal tissue was assessed using morphometry, mitosis and apoptosis markers, mineral proportion, oxidative stress markers, as well as the activity of antioxidant enzymes and membrane-bound adenosine triphosphatases. Arsenate intake altered glucose levels in healthy animals, but it did not reach hyperglycemic conditions. In diabetic animals, arsenate led to a remarkable increase of glycogen nephrosis in distal tubules. In these animals, additionally, the activity of catalase and glutathione S-transferase, besides the proportion of Fe, Cu, and K in renal tissue, was altered. Nevertheless, arsenate did not accumulate in the kidney and did not impact on other parameters previously altered by diabetes, including levels of malondialdehyde, Na, urea, creatinine, and apoptosis and mitosis markers. In conclusion, besides the intensification of glycogen nephrosis, the kidney was able to handle arsenate toxicity at this point, preventing arsenic deposition in the exposed groups and the impairment of renal function.

The Effect of Metformin and Taurine, Alone and in Combination, on the Oxidative Stress Caused by Diabetes in the Rat Brain

This study has compared the effects of metformin (MET) and taurine (TAU), singly and in combination, on the oxidative stress caused by diabetes in the rat brain. For this purpose, male Sprague-Dawley rats, 200-225 g in weight, assigned to groups of 6, were intraperitoneally (i.p.) treated with the diabetogen streptozotocin (STZ, 60 mg/kg, in citrate buffer pH 4.5) on day 1 and, after 14 days, orally (p.o.) with either MET, TAU or MET-TAU (each at 2.4 mM/kg, in water). Control rats received only citrate buffer pH 4.5 (2 mL) or only STZ on day 1 by the i.p. route. All the animals were sacrificed by decapitation on day 57 and their brains collected by the freeze clamp technique. Blood samples were placed in heparinized tubes and used for the assay of the plasma glucose (GLC) and blood insulin (INS) levels. Immediately thereafter, the brains were surgically removed and a portion was used to prepare a homogenate in 0.1 M PBS pH 7.4, which was used for the assay of indices of oxidative stress. Diabetes raised the plasma GLC level (+313%) but lowered that of the blood INS (-76%) compared to corresponding values from nondiabetic rats. In addition it raised the brain malondialdehyde level (+59%) but lowered the reduced/disulfide glutathione ratio (-46%), and activities of catalase (-43%), glutathione peroxidase (-48%), superoxide dismutase (-65%), glutathione reductase (-50%) and glutathione S-transferase (-51%) significantly (all at p < 0.001). Except for the greater decrease in GLC (+90% vs. +22%) and increase in INS (-26% vs. -52%) levels seen in rats receiving MET than in rats receiving TAU, these compounds protected the brain against oxidative stress to significant (p ≤ 0.05%) and rather similar extents. Furthermore, the concurrent administration of MET and TAU to the diabetic rats led to brain values of indices of oxidative stress that were lower than those attained with MET alone, although generally not to a statistically significant degree.

Effects of l-Carnitine on the Follicle-Stimulating Hormone, Luteinizing Hormone, Testosterone, and Testicular Tissue Oxidative Stress Levels in Streptozotocin-Induced Diabetic Rats

The present study was designed to investigate the antioxidant property of l-carnitine (LC) on serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone (TH) and testis oxidative stress in streptozotocin (STZ)-induced diabetic rats. The rats were divided into the following groups: group I, control; group II, LC 100 mg/kg/d; group III, diabetic; and groups IV to VI, diabetic rats treated with 50, 100, and 200 mg/kg/d of LC, respectively. Daily injections were given intraperitoneally for 7 weeks. At the end of experimental period, after sacrificing the rats, FSH, LH, TH, total antioxidant capacity (TAC), malondialdehyde (MDA), glutathione (GSH), catalase (CAT), mitochondrial function (MTT), protein carbonyl (PC), and reactive oxygen species (ROS) levels were measured. STZ caused an elevation of MDA, ROS, and PC (P < .001) with reduction of GSH, CAT, TAC, and MTT (P < .001) in the serum levels. Group VI had significantly increased FSH, LH, and TH levels versus the untreated diabetic group (P < .001). Although groups V and VI significantly decreased MDA (P < .001), PC (P < .01), and ROS (P < .01) compared with the untreated diabetic group; only in group VI, the activity of GSH (P < .001), CAT (P < .01), TAC (P < .001), and MTT (P < .001) significantly increased. The results of the present study suggest that LC decreased diabetes-induced oxidative stress complications and also improved serum level of FSH, LH, and TH by reducing levels of lipid peroxidation and increasing antioxidant enzymes.

Arsenic aggravates oxidative stress causing hepatic alterations and inflammation in diabetic rats

AIMS

Studies have shown that exposure to either environmental toxicants or hyperglycemia causes hepatic injuries. However, it is unclear the extent to which their combined exposure may influence liver functions. Therefore, we aimed to evaluate morphological and functional hepatic parameters in diabetic rats exposed to arsenic.

METHODS

Diabetes was induced in male rats by intraperitoneal streptozotocin injection. While healthy and diabetic animals received saline solution (negative control and diabetes control, respectively), other animals received 10 mg/L sodium arsenate (arsenic control and diabetes + arsenic groups, respectively) for 40 days in drinking water. Liver tissue was subjected to antioxidant enzymes analysis, cytokine assay, arsenic determination, and histopathological evaluation. Functional markers of hepatic damage were analyzed using serum samples.

KEY FINDINGS

Arsenate exposure reduced the antioxidant enzymes activity in healthy rats, and it worsened the reduction of GST in diabetic animals. Consequently, arsenate-exposed animals showed increased malondialdehyde and carbonyl protein levels, being this increase worsened in diabetes + arsenic animals. Arsenate-exposed groups also showed hepatic inflammatory process with high number of mast cells and TNF-α production mainly in diabetes + arsenic animals. Vascular alterations, such as congestion, bleeding, and hemosiderin deposition were intensified in diabetes + arsenic animals, whereas glycogen storage reduced in these animals.

SIGNIFICANCE

We concluded that arsenate exposure was able to intensify morphological and functional damages in liver tissue of diabetic animals.

N-Acetylcysteine as an Adjuvant to Letrozole for Induction of Ovulation in Infertile Patients with Polycystic Ovary Syndrome

Background:

This study was aimed to evaluate the influence of oral N-acetylcysteine (NAC) application as an adjuvant to letrozole on induced ovulation outcomes in patients with polycystic ovary syndrome (PCOS).

Materials and Methods:

This was a placebo-controlled double-blind randomized clinical trial with 130 PCOS patients who were infertile. First, patients were randomly divided into two groups. Patients in Group 1 were administered letrozole 5 mg/d plus NAC 1.2 g/d and patients in Group 2 were administered letrozole plus placebo for 5 days starting at the 3^rd day of the menstruation period. On the 12^th day of the cycle, ultrasound evaluation was performed, and in whom at least one follicle with an 18–20 mm diameter was found, 10,000 unit human chorionic gonadotropin (hCG) was prescribed, and 36 h after hCG injection, timed intercourse was advised. On the 16^th day, after hCG injection, serum β-hCG level was evaluated.

Results:

The number of follicles >18 mm was significantly higher in the letrozole + NAC group (P = 0.007). The ovulation and pregnancy rates were also significantly higher in the letrozole + NAC group (P = 0.045). No adverse side effects and no cases of ovarian hyperstimulation syndrome were observed in NAC group.

Conclusion:

NAC is demonstrated to be a safe and well-tolerated adjuvant to letrozole and can increase the pregnancy rates in PCOS patients.

Eprosartan mesylate loaded bilosomes as potential nano-carriers against diabetic nephropathy in streptozotocin-induced diabetic rats

The objective of the present study was to formulate eprosartan mesylate loaded nano-bilosomes and investigates its potential for controlling streptozotocin induced diabetes nephropathy in Wistar rats. The eprosartan mesylate loaded nano-bilosomes comprising of various ratios of soybean phosphatidylcholine/sodium deoxycholate were prepared by thin film hydration technique. The prepared formulations were evaluated for vesicles size, polydispersity index, zeta potential and entrapment efficiency. Further the optimized formulation was characterized for vesicles morphology, and its efficacy for the management of diabetic nephropathy in Wistar rats. The optimized eprosartan mesylate loaded nano-bilosomes exhibited vesicles size, polydispersity index, zeta potential and entrapment efficiency of 63.88±3.46nm, 0.172±0.026, -30.40±2.75mV and 61.19±0.88% respectively. In vivo activity demonstrated that the prepared eprosartan mesylate loaded nano-bilosomes formulation demonstrated a nephro-protecting outcome as shown by the substantial decrease in serum creatinine, urea, lactate dehydrogenase, total albumin, and malondialdehyde. Additionally, an oral administration of eprosartan mesylate loaded nano-bilosomes decreases the raised expressions of Angiotensin II type 1 receptor, inducible nitric oxide synthase, and transforming growth factor-β1 in Wistar rats. Further, histopathological examination established the nephro-protective effect of prepared formulation. In conclusion, the research work in the paper suggests that the prepared eprosartan mesylate loaded nano-bilosomes could serve as a practical oral formulation for diabetic nephropathy in future therapy and may offer potential benefits in cases with hypertension and renal disease.

Advanced glycation end products mediated cellular and molecular events in the pathology of diabetic nephropathy

Diabetic nephropathy (DN) is a major cause of morbidity and mortality in diabetic patients and a leading cause of end-stage renal disease (ESRD). Degenerative changes such as glomerular hypertrophy, hyperfiltration, widening of basement membranes, tubulointerstitial fibrosis, glomerulosclerosis and podocytopathy manifest in various degrees of proteinuria in DN. One of the key mechanisms implicated in the pathogenesis of DN is non-enzymatic glycation (NEG). NEG is the irreversible attachment of reducing sugars onto free amino groups of proteins by a series of events, which include the formation of Schiff’s base and an Amadori product to yield advanced glycation end products (AGEs). AGE modification of client proteins from the extracellular matrix induces crosslinking, which is often associated with thickening of the basement membrane. AGEs activate several intracellular signaling cascades upon interaction with receptor for AGEs (RAGE), which manifest in aberrant cellular responses such as inflammation, apoptosis and autophagy, whereas other receptors such as AGE-R1, AGE-R3 and scavenger receptors also bind to AGEs and ensue endocytosis and degradation of AGEs. Elevated levels of both serum and tissue AGEs are associated with adverse renal outcome. Increased evidence supports that attenuation of AGE formation and/or inhibition of RAGE activation manifest(s) in improving renal function. This review provides insights of NEG, discusses the cellular and molecular events triggered by AGEs, which manifest in the pathogenesis of DN including renal fibrosis, podocyte epithelial-mesenchymal transition and activation of renin-angiotensin system. Therapies designed to target AGEs, such as inhibitors of AGEs formation and crosslink breakers, are discussed.

Protective and therapeutic effectiveness of taurine in diabetes mellitus: a rationale for antioxidant supplementation

Taurine, 2-amino ethanesulfonic acid, is a conditionally essential β amino acid which is not utilized in protein synthesis. Taurine is one of the most abundant free amino acids in mammals tissues and is one of the three well-known sulfur-containing amino acids; the others are methionine and cysteine which are considered as the precursors for taurine synthesis. Different scientific studies emphasize on the cytoprotective properties of taurine which included antioxidation, antiapoptosis, membrane stabilization, osmoregulation, and neurotransmission. Protective and therapeutic ameliorations of oxidative stress-induced pathologies were also attributed to taurine both in experimental and human models. Data demonstrating the beneficial effectiveness of taurine against type 1 and type 2 diabetes mellitus and their complications are growing and providing a better understanding of the underlying molecular mechanisms. Although the clinical studies are limited compared to the experimental ones, the present updated systematic review of the literature is set up to provide experimental and clinical evidences regarding the effectiveness of taurine in the context of diabetes mellitus and its complications. Gathering these scientific effects of taurine on diabetes mellitus could provide the physicians and specially the endocrinologists with a comprehensive overview on possible trends in the prevention and management of the disease and its complications through antioxidant supplementation.

A flavonoid fraction purified from Rutaceae aurantiae (Daflon(R)) inhibiting AGE formation, reduces urinary albumin clearance and corrects hypoalbuminemia in normotensive and hypertensive diabetic rats

AIM

Advanced glycation endproducts (AGEs) have been shown to contribute to alteration of glomerular permselectivity to proteins in diabetes. Oxidative stress is required for AGE formation. Therefore we studied the effect of an antioxidant micronized purified flavonoid fraction (MPFF, Daflon(R) 500 mg), on urinary albumin clearance in diabetic rats.

METHODS

Hyperglycaemia was induced by streptozotocin 55 mg/kg IM at days 0 and 7 in normotensive Wistar rats (NWR, diabetes duration 5 months) or hypertensive Wistar Kyoto rats (SHR, diabetes duration 2 months). MPFF was administered at 300 mg/kg/day, from day -2 until sacrifice.

RESULTS

After 5 months of diabetes in NWR, MPFF reduced albumin clearance from 729±92 to 392±60 nl/min/kg, p<0.01, and restored albuminemia from 20.4±0.9 to 24.0±1 g/l, p<0.05; albumin fractional clearance was significantly diminished in the flavonoid-treated diabetic rats (0.360±0.037‰ versus 1.335±0.430‰ in the diabetic controls, p<0.001); MPFF did not significantly modify blood glucose and plasma fructosamine levels. After 2 months of diabetes in SHR, MPFF reduced albumin clearance from 243±121 to 101±47 nl/min/kg, p<0.05, and restored albuminemia from 21.1±1.6 to 26.7±2.2 g/l (p<0.05); MPFF also decreased plasma fluorescence characteristic of AGEs (p<0.02). Besides hesperetin, a main metabolite of MPFF recovered in plasma, inhibited in vitro the formation of the crosslinking AGE pentosidine in collagen incubated with high glucose (p<0.001).

CONCLUSION

Our results confirm the role of glycoxidative stress in diabetic nephropathy. MPFF might be useful as complementary treatment for preventing diabetic microangiopathy.

Oxidative stress: A cause and therapeutic target of diabetic complications

Oxidative stress is defined as excessive production of reactive oxygen species (ROS) in the presence of diminished anti‐oxidant substances. Increased oxidative stress could be one of the common pathogenic factors of diabetic complications. However, the mechanisms by which hyperglycemia increases oxidative stress are not fully understood. In this review, we focus on the impact of mitochondrial derived ROS (mtROS) on diabetic complications and suggest potential therapeutic approaches to suppress mtROS. It has been shown that hyperglycemia increases ROS production from mitochondrial electron transport chain and normalizing mitochondrial ROS ameliorates major pathways of hyperglycemic damage, such as activation of polyol pathway, activation of PKC and accumulation of advanced glycation end‐products (AGE). Additionally, in subjects with type 2 diabetes, we found a positive correlation between HbA1c and urinary excretion of 8‐hydroxydeoxyguanosine (8‐OHdG), which reflects mitochondrial oxidative damage, and further reported that 8‐OHdG was elevated in subjects with diabetic micro‐ and macro‐ vascular complications. We recently created vascular endothelial cell‐specific manganese superoxide dismutase (MnSOD) transgenic mice, and clarified that overexpression of MnSOD in endothelium could prevent diabetic retinopathy in vivo. Furthermore, we found that metformin and pioglitazone, both of which have the ability to reduce diabetic vascular complications, could ameliorate hyperglycemia‐induced mtROS production by the induction of PPARγ coactivator‐1α (PGC‐1α) and MnSOD and/or activation of adenosine monophosphate (AMP)‐activated protein kinase (AMPK). We also found that metformin and pioglitazone promote mitochondrial biogenesis through the same AMPK–PGC‐1α pathway. Taking these results, mtROS could be the key initiator of and a therapeutic target for diabetic vascular complications. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00013.x, 2010)

N-acetyl cysteine in clomiphene citrate resistant polycystic ovary syndrome: A review of reported outcomes

Clomiphene citrate (CC) has been the gold-standard drug for ovulation induction in polycystic ovary syndrome (PCOS), but still CC resistance is seen in approximately 15-40% in women with PCOS. N-acetyl cysteine (NAC), a safe and cheap drug available in the market many years ago as mucolytic agent, was found to have a role in infertility management. Recently, some reports discussed the possible beneficial effects of NAC on ovulation. The biological properties of the NAC make this drug a potential candidate for its use in the infertility treatment, especially in the PCOS in inducing or augmenting ovulation. An updated electronic search was performed through PUBMED, MEDLINE, and COCHRANE and focused on peer-reviewed, full text, randomized controlled trials, and observational cohort or case-control studies for role of NAC in CC-resistant PCOS. Thorough search through all the clinical studies showed mixed results. Studies with positive results showed improvement in induction of ovulation as compared to negative studies showing contrary results. More randomized clinical trials are still needed to establish its definitive role in CC-resistant PCOS.

Advanced glycation end products: Key players in skin aging?

Aging is the progressive accumulation of damage to an organism over time leading to disease and death. Aging research has been very intensive in the last years aiming at characterizing the pathophysiology of aging and finding possibilities to fight age-related diseases. Various theories of aging have been proposed. In the last years advanced glycation end products (AGEs) have received particular attention in this context. AGEs are formed in high amounts in diabetes but also in the physiological organism during aging. They have been etiologically implicated in numerous diabetes- and age-related diseases. Strategies inhibiting AGE accumulation and signaling seem to possess a therapeutic potential in these pathologies. However, still little is known on the precise role of AGEs during skin aging. In this review the existing literature on AGEs and skin aging will be reviewed. In addition, existing and potential anti-AGE strategies that may be beneficial on skin aging will be discussed.

An emerging role of glucagon-like peptide-1 in preventing advanced-glycation-end-product-mediated damages in diabetes

Glucagon-like peptide-1 (GLP-1) is a gut hormone produced in the intestinal epithelial endocrine L cells by differential processing of the proglucagon gene. Released in response to the nutrient ingestion, GLP-1 plays an important role in maintaining glucose homeostasis. GLP-1 has been shown to regulate blood glucose levels by stimulating glucose-dependent insulin secretion and inhibiting glucagon secretion, gastric emptying, and food intake. These antidiabetic activities highlight GLP-1 as a potential therapeutic molecule in the clinical management of type 2 diabetes, (a disease characterized by progressive decline of beta-cell function and mass, increased insulin resistance, and final hyperglycemia). Since chronic hyperglycemia contributed to the acceleration of the formation of Advanced Glycation End-Products (AGEs, a heterogeneous group of compounds derived from the nonenzymatic reaction of reducing sugars with free amino groups of proteins implicated in vascular diabetic complications), the administration of GLP-1 might directly counteract diabetes pathophysiological processes (such as pancreatic β-cell dysfunction). This paper outlines evidence on the protective role of GLP-1 in preventing the deleterious effects mediated by AGEs in type 2 diabetes.

Short term supplementation of dietary antioxidants selectively regulates the inflammatory responses during early cutaneous wound healing in diabetic mice

Background

Diabetic foot ulcers are serious complications for diabetic patients, yet the precise mechanism that underlines the treatment of these diabetic complications remains unclear. We hypothesized that dietary antioxidant supplementation with vitamin C, combined either with vitamin E or with vitamin E and NAC, improves delayed wound healing through modulation of blood glucose levels, oxidative stress, and inflammatory response.

Methods

Diabetes was induced by administration of alloxan monohydrate. Mice were divided into 4 groups; CON (non-diabetic control mice fed AIN 93 G purified rodent diet), DM (diabetic mice fed AIN 93 G purified rodent diet), VCE (diabetic mice fed 0.5% vitamin C and 0.5% vitamin E supplemented diet), and Comb (diabetic mice fed 0.5% vitamin C, 0.5% vitamin E, and 2.5% NAC supplemented diet). After 10 days of dietary antioxidant supplementation, cutaneous full-thickness excisional wounds were performed, and the rate of wound closure was examined. TBARS as lipid peroxidation products and vitamin E levels were measured in the liver. Expression levels of oxidative stress and inflammatory response related proteins were measured in the cutaneous wound site.

Results

Dietary antioxidant supplementation improved blood glucose levels and wound closure rate and increased liver vitamin E, but not liver TBARS levels in the diabetic mice as compared to those of the CON. In addition, dietary antioxidant supplementation modulated the expression levels of pIκBα, HO-1, CuZnSOD, iNOS and COX-2 proteins in the diabetic mice.

Conclusions

These findings demonstrated that delayed wound healing is associated with an inflammatory response induced by hyperglycaemia, and suggests that dietary antioxidant supplementation may have beneficial effects on wound healing through selective modulation of blood glucose levels, oxidative stress, and inflammatory response.

Effect of antioxidant N-acetylcysteine on diabetic retinopathy and expression of VEGF and ICAM-1 from retinal blood vessels of diabetic rats

Diabetic retinopathy (DR) is a leading cause of blindness globally and its pathogenesis has still not been completely elucidated. Some studies show a close relation between oxidative stress and DR. This study was aimed to investigate the effects of anti-oxidant in DR and expression of vascular endothelial growth factor (VEGF) and intercellular adhesion molecule-1 (ICAM-1) from retinal blood vessels in diabetic rats. Diabetic rat models were established by intraperitoneal injection of streptozotocin (60 mg/kg) and confirmation of high serum glucose levels in the animals. Antioxidant N-acetylcysteine was given to diabetic rats to elicit antioxidative responses, and rats were sacrificed at 3 and 5 months. Ultrastructures of retinal vascular tissues were observed under transmission electron microscope, and pathology of retinal capillaries was examined using retinal vascular digest preparations. Changes in the expression of VEGF and ICAM-1 were examined by immunofluorescence; and reactive oxygen species contents in the retinas were detected using dichlorofluorescein assay. Compared with normal rats, diabetic rats displayed significant retinopathy both under electronic and light microscopy, accompanied by elevated reactive oxygen species contents in the retinas; N-acetylcysteine treatment alleviated the pathological changes and also decreased reactive oxygen species, most significantly at 5 months. VEGF and ICAM-1 expressions were significantly up-regulated in retinal blood vessels from diabetic rats, and such up-regulation was attenuated by N-acetylcysteine treatment. The expression of both factors returned to basal levels after 5-month treatment with N-acetylcysteine. Long-term N-acetylcysteine treatment exerts protective effects on the diabetic retinas, possibly through its down-regulation of the expression of VEGF and ICAM-1, and reduction of reactive oxygen species content in retinal vascular tissues in diabetic rats.

KIOM-79, an Inhibitor of AGEs-Protein Cross-linking, Prevents Progression of Nephropathy in Zucker Diabetic Fatty Rats

Advanced glycation end products (AGEs) have been implicated in the development of diabetic complications, including diabetic nephropathy. KIOM-79, an 80% ethanolic extract obtained from parched Puerariae Radix, gingered Magnolia Cortex, Glycyrrhiza Radix and Euphorbia Radix, was investigated for its effects on the development of renal disease in Zucker diabetic fatty rats, an animal model of type 2 diabetes. In vitro inhibitory effect of KIOM-79 on AGEs cross-linking was examined by enzyme-linked immunosorbent assay (ELISA). KIOM-79 (50 mg/kg/day) was given to Zucker diabetic fatty rats for 13 weeks. Body and kidney weight, blood glucose, glycated hemoglobin, urinary albumin and creatinine excretions were monitored. Kidney histopathology, collagen accumulation, fibrinogen and transforming growth factor-beta 1 (TGF-β1) expression were also examined. KIOM-79 reduced blood glucose, kidney weight, histologic renal damage and albuminuria in Zucker diabetic fatty rats. KIOM-79 prevented glomerulosclerosis, tubular degeneration, collagen deposition and podocyte apoptosis. In the renal cortex, TGF-β1, fibronectin mRNA and protein were significantly reduced by KIOM-79 treatment. KIOM-79 reduces AGEs accumulation in vivo, AGE-protein cross-linking and protein oxidation. KIOM-79 could be beneficial in preventing the progression of diabetic glomerularsclerosis in type 2 diabetic rats by attenuating AGEs deposition in the glomeruli.

Metformin attenuates streptozotocin-induced diabetic nephropathy in rats through modulation of oxidative stress genes expression

Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion and/or action. One of the most important complications of this metabolic disease is diabetic nephropathy. Hyperglycemia promotes oxidative stress and hence generation of reactive oxygen species (ROS), which is known to play a crucial role in the pathogenesis of diabetic nephropathy. Recent studies have established that metformin, an oral hypoglycemic drug, possesses antioxidant effects. However, whether metformin can protect against diabetic nephropathy has not been reported before. The overall objectives of the present study are to elucidate the potential nephroprotective effect of metformin in a rat diabetic nephropathy model and explore the exact underlying mechanism(s) involved. The effect of metformin on the biochemical changes associated with hyperglycemia induced by streptozotocin was investigated in rat kidney tissues. In addition, energy nucleotides (AMP and ATP), and Acetyl-CoA in the kidney homogenates and mitochondria, and the mRNA expression of oxidative stress and pro-inflammatory mediators were assessed. Our results showed that treatment of normoglycemic rats with metformin caused significant increase in ATP, Acetyl-CoA, and CoA-SH contents in kidney homogenates and mitochondria along with profound decrease in AMP level. On the other hand, treatment of diabetic nephropathy rats with metformin normalized all biochemical changes and the energy status in kidney tissues. At the transcriptional levels, metformin treatment caused significant restoration in diabetic nephropathy-induced oxidative stress mRNA levels, particularly GSTα, NQO1, and CAT genes, whereas inhibited TNF-α and IL-6 pro-inflammatory genes. Our data lend further credence for the contribution of metformin in the nephroprotective effect in addition to its well known hypoglycemic action.

KIOM-79 prevents S100b-induced TGF-beta1 and fibronectin expression in mouse mesangial cells

AIM OF THE STUDY

In this study, we investigated whether KIOM-79 inhibits transforming growth factor-beta 1 (TGF-beta1) and fibronectin expression in mouse mesangial cells cultured under S100b, a specific ligand of the receptor for advanced glycation end products (RAGE).

MATERIALS AND METHODS

Cell counting kit (CCK-8) assay was employed to evaluate the viability of KIOM-79-treated mesangial cells. The effect of KIOM-79 on S100b-induced TGF-beta1 and fibronectin expression was investigated using RT-PCR, ELISA, and Western blot on mesangial cells.

RESULTS

KIOM-79 (up to 50 microg/ml) appeared to have no effect on cell viability. S100b induced an increase in the expression TGF-beta1 and fibronectin. Expression of TGF-beta1 and fibronectin was inhibited significantly by KIOM-79 treatment in mesangial cells. KIOM-79 also inhibited the expression of NF-kB and inactivated p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) 1/2 in mesangial cells. KIOM-79 pretreatment inhibited increased malondialdehyde (a product of lipid peroxidation and a marker for oxidative stress) levels in S100b-induced mesangial cells.

CONCLUSIONS

These data demonstrate that KIOM-79 inhibits expression of TGF-beta1 and fibronectin through inactivation of MAPK/ERK1/2 signaling, reduction in malondiadehyde levels, and inhibition of NF-kB in mesangial cells cultured under diabetic conditions. KIOM-79 could be beneficial for preventing of the development of diabetic complications such as nephropathy.

Glutathione dysregulation and the etiology and progression of human diseases

Glutathione (GSH) plays an important role in a multitude of cellular processes, including cell differentiation, proliferation, and apoptosis, and as a result, disturbances in GSH homeostasis are implicated in the etiology and/or progression of a number of human diseases, including cancer, diseases of aging, cystic fibrosis, and cardiovascular, inflammatory, immune, metabolic, and neurodegenerative diseases. Owing to the pleiotropic effects of GSH on cell functions, it has been quite difficult to define the role of GSH in the onset and/or the expression of human diseases, although significant progress is being made. GSH levels, turnover rates, and/or oxidation state can be compromised by inherited or acquired defects in the enzymes, transporters, signaling molecules, or transcription factors that are involved in its homeostasis, or from exposure to reactive chemicals or metabolic intermediates. GSH deficiency or a decrease in the GSH/glutathione disulfide ratio manifests itself largely through an increased susceptibility to oxidative stress, and the resulting damage is thought to be involved in diseases, such as cancer, Parkinson's disease, and Alzheimer's disease. In addition, imbalances in GSH levels affect immune system function, and are thought to play a role in the aging process. Just as low intracellular GSH levels decrease cellular antioxidant capacity, elevated GSH levels generally increase antioxidant capacity and resistance to oxidative stress, and this is observed in many cancer cells. The higher GSH levels in some tumor cells are also typically associated with higher levels of GSH-related enzymes and transporters. Although neither the mechanism nor the implications of these changes are well defined, the high GSH content makes cancer cells chemoresistant, which is a major factor that limits drug treatment. The present report highlights and integrates the growing connections between imbalances in GSH homeostasis and a multitude of human diseases.

Poorly controlled type 1 diabetes is associated with altered glutathione homeostasis in adolescents: apparent resistance to N-acetylcysteine supplementation

Blood glutathione concentrations represent a measure of protection against oxidative damage. In earlier studies, we observed that, in adolescents with poorly controlled type 1 diabetes mellitus (T1DM), blood glutathione is significantly depleted because of increased rates of glutathione utilization. To determine whether increased availability of cysteine - one of the three constitutive amino acids of glutathione - would attenuate the alterations in glutathione metabolism, ten 16 +/- 1 yr-old adolescents with poorly controlled T1DM [hemoglobin A1c (HbA1c): 9.9 +/- 1.3%] received 5-h infusions of l-[3,3-(2)H(2)] cysteine and d-[6,6-(2)H(2)]glucose on two occasions, 3 wk apart, after a 10-d oral supplementation with (i) N-acetylcysteine (NAC, 30-45 mg/kg/d) or (ii) L-alanine, in randomized order, and with a 3-wk 'washout' interim period. Blood glucose was maintained in the same hyperglycemic range on both infusion study days, using intravenous insulin. Glutathione fractional synthesis rate (FSR) was determined from (2)H(2)-cysteine incorporation into blood glutathione. NAC supplementation failed to raise erythrocyte cysteine concentrations (23 +/- 6 vs. 17 +/- 1 micromol/L, p = 0.853) and did not alter erythrocyte glutathione concentrations (838 +/- 106 vs. 793 +/- 111 micromol/L, p = 0.220) or glutathione FSR (96 +/- 20 vs. 89 +/- 19%/d, p = 0.974). We conclude that in adolescents with poorly controlled T1DM, dietary cysteine supplementation alone cannot correct glutathione status. In the presence of relative insulinopenia, either higher amino acid doses or aggressive insulin therapy may be needed to achieve this goal. This would require further study.

Hypoglycaemic, antioxidative and nephroprotective effects of taurine in alloxan diabetic rabbits

The therapeutic potential of taurine was investigated under diabetic conditions. Alloxan diabetic rabbits were treated daily for three weeks with 1% taurine in drinking water. The following parameters were measured: 1) serum glucose, urea, creatinine and hydroxyl free radical (HFR) levels; 2) blood glutathione redox state; 3) urine albumin concentration; 4) hepatic and renal HFR levels, GSH/GSSG ratios and the activities of catalase, superoxide dismutase and the enzymes of glutathione metabolism; 5) renal NADPH oxidase activity; 6) the rates of renal and hepatic gluconeogenesis. Histological studies of kidneys were also performed. Taurine administration to diabetic rabbits resulted in 30% decrease in serum glucose level and the normalisation of diabetes-elevated rate of renal gluconeogenesis. It also decreased serum urea and creatinine concentrations, attenuated diabetes-evoked decline in GSH/GSSG ratio and abolished hydroxyl free radicals accumulation in serum, liver and kidney cortex. Animals treated with taurine exhibited elevated activities of hepatic gamma-glutamylcysteine syntetase and renal glutathione reductase and catalase. Moreover, taurine treatment evoked the normalisation of diabetes-stimulated activity of renal NADPH oxidase and attenuated both albuminuria and glomerulopathy characteristic of diabetes. In view of these data, it is concluded that: 1) diminished rate of renal gluconeogenesis seems to contribute to hypoglycaemic effect of taurine; 2) taurine-induced increase in the activities of catalase and the enzymes of glutathione metabolism is of importance for antioxidative action of this amino acid and 3) taurine nephroprotective properties might result from diminished renal NADPH oxidase activity. Thus, taurine seems to be beneficial for the therapy of both diabetes and diabetic nephropathy.

A follow-up study of the occurrence and consequences of HbA1c measurements in an unselected cohort of non-pharmacologically treated patients with Type 2 diabetes

OBJECTIVES

To describe the occurrence of HbA1c measurements among non-pharmacologically treated diabetes patients, and to evaluate whether poor blood glucose regulation (HbA1c >8%) prompted intensification of treatment.

METHOD

Data from the National Health Service Registry, the Regional Laboratory Database and the Danish National Hospital Registry were collected from 2002 to 2004 to identify and describe all Type 2 diabetic patients above 40 years of age in a background population of nearly 660,000 citizens in Aarhus County, corresponding to 12% of the total Danish population.

RESULTS

A total of 1989 had at least one HbA1c measurement, whereas 484 (20%) had no HbA1c measurement at all in 2003. Most patients had an HbA1c of less than 8%, and for 820 (41%) HbA1c was less than 6.5%, but for 316 (16%) patients, the first HbA1c measurement in 2003 was above 8%. After 6 months, patients with HbA1c above 8% had a higher probability of initiating pharmacological treatment (M; 0.64; 95% CI 0.58-0.70) (F; 0.68; 95% CI 0.58-0.77) than patients with HbA1c below 8% (M; 0.12; 95% CI 0.10-0.14) (F; 0.11; 95% CI 0.09-0.14).

CONCLUSION

This study indicates that poor blood glucose regulation (HbA1c >8%) prompted a shift from non-pharmacological treatment to pharmacological treatment for most patients. However, a substantial group of patients are either not monitored on a regular basis or, if monitored, their elevated measurements of HbA1c do not prompt initiation of pharmacological treatment.

Increased glomerular cell (podocyte) apoptosis in rats with streptozotocin-induced diabetes mellitus: role in the development of diabetic glomerular disease

AIMS/HYPOTHESIS

Podocyte loss by apoptosis, in addition to favouring progression of established diabetic nephropathy, has been recently indicated as an early phenomenon triggering the initiation of glomerular lesions. This study aimed to assess the rate of glomerular cell death and its relationship with renal functional, structural and molecular changes in rats with experimental diabetes.

METHODS

Male Sprague-Dawley rats with streptozotocin-induced diabetes and coeval non-diabetic control animals were killed at 7 days and at 2, 4 and 6 months for the assessment of apoptosis, renal function, renal structure and the expression of podocyte markers and apoptosis- and cell cycle-related proteins.

RESULTS

Glomerular cell apoptosis was significantly increased in diabetic vs non-diabetic rats at 4 months and to an even greater extent at 6 months, with podocytes accounting for 70% of apoptosing cells. The increase in apoptosis was preceded by increases in proteinuria, albuminuria and mean glomerular and mesangial areas, and by reductions in glomerular cell density and content of synaptopodin and Wilms' tumour protein-1. It coincided with the development of mesangial expansion and glomerular sclerosis, and with the upregulation/activation both of tumour protein p53, which increased progressively throughout the study, and of p21 (also known as cyclin-dependent kinase inhibitor 1A, CIP1 and WAF1), which peaked at 4 months and decreased thereafter.

CONCLUSIONS/INTERPRETATION

Glomerular cell (podocyte) apoptosis is not an early feature in the course of experimental diabetic glomerulopathy, since it is preceded by glomerular hypertrophy, which may decrease glomerular cell density to the point of inducing compensatory podocyte hypertrophy. This is associated with reduced podocyte protein expression (podocytopathy) and proteinuria, and ultimately results in apoptotic cell loss (podocytopenia), driving progression to mesangial expansion and glomerular sclerosis.