The effect of Glurenorm (gliquidone) on lenses and skin in experimental diabetes

Xenobiotica-metabolizing enzymes in the skin of rat, mouse, pig, guinea pig, man, and in human skin models

Studies on the metabolic fate of medical drugs, skin care products, cosmetics and other chemicals intentionally or accidently applied to the human skin have become increasingly important in order to ascertain pharmacological effectiveness and to avoid toxicities. The use of freshly excised human skin for experimental investigations meets with ethical and practical limitations. Hence information on xenobiotic-metabolizing enzymes (XME) in the experimental systems available for pertinent studies compared with native human skin has become crucial. This review collects available information of which—taken with great caution because of the still very limited data—the most salient points are: in the skin of all animal species and skin-derived in vitro systems considered in this review cytochrome P450 (CYP)-dependent monooxygenase activities (largely responsible for initiating xenobiotica metabolism in the organ which provides most of the xenobiotica metabolism of the mammalian organism, the liver) are very low to undetectable. Quite likely other oxidative enzymes [e.g. flavin monooxygenase, COX (cooxidation by prostaglandin synthase)] will turn out to be much more important for the oxidative xenobiotic metabolism in the skin. Moreover, conjugating enzyme activities such as glutathione transferases and glucuronosyltransferases are much higher than the oxidative CYP activities. Since these conjugating enzymes are predominantly detoxifying, the skin appears to be predominantly protected against CYP-generated reactive metabolites. The following recommendations for the use of experimental animal species or human skin in vitro models may tentatively be derived from the information available to date: for dermal absorption and for skin irritation esterase activity is of special importance which in pig skin, some human cell lines and reconstructed skin models appears reasonably close to native human skin. With respect to genotoxicity and sensitization reactive-metabolite-reducing XME in primary human keratinocytes and several reconstructed human skin models appear reasonably close to human skin. For a more detailed delineation and discussion of the severe limitations see the Conclusions section in the end of this review.

Xenobiotic-metabolizing enzymes in the skin of rat, mouse, pig, guinea pig, man, and in human skin models

The exposure of the skin to medical drugs, skin care products, cosmetics, and other chemicals renders information on xenobiotic-metabolizing enzymes (XME) in the skin highly interesting. Since the use of freshly excised human skin for experimental investigations meets with ethical and practical limitations, information on XME in models comes in the focus including non-human mammalian species and in vitro skin models. This review attempts to summarize the information available in the open scientific literature on XME in the skin of human, rat, mouse, guinea pig, and pig as well as human primary skin cells, human cell lines, and reconstructed human skin models. The most salient outcome is that much more research on cutaneous XME is needed for solid metabolism-dependent efficacy and safety predictions, and the cutaneous metabolism comparisons have to be viewed with caution. Keeping this fully in mind at least with respect to some cutaneous XME, some models may tentatively be considered to approximate reasonable closeness to human skin. For dermal absorption and for skin irritation among many contributing XME, esterase activity is of special importance, which in pig skin, some human cell lines, and reconstructed skin models appears reasonably close to human skin. With respect to genotoxicity and sensitization, activating XME are not yet judgeable, but reactive metabolite-reducing XME in primary human keratinocytes and several reconstructed human skin models appear reasonably close to human skin. For a more detailed delineation and discussion of the severe limitations see the “Overview and Conclusions” section in the end of this review.

Protective effect of vanadyl sulfate on skin injury in streptozotocin-induced diabetic rats

The aim of the present study was to investigate the effect of vanadyl sulfate supplementation on the skin tissues of diabetic and control rats. In this study, 6-6.5 months old male Swiss albino rats were used. The animals were randomly divided into the following four groups: group I, control (nondiabetic intact animals); group II, vanadyl sulfate control; group III, streptozotocin (STZ)-diabetic animals and group IV, STZ-diabetic animals given vanadyl sulfate. The animals were made diabetic by intraperitoneal injection of a single dose of 65 mg/kg STZ in 0.01 M citrate buffer (pH = 4.5). From day 1 to day 60, 100 mg/kg vanadyl sulfate was given daily by gavage technique to one of the control and diabetic groups. Body weights and blood glucose levels were estimated on experimental days 0, 1 and 60. On the 60th day, skin tissue samples were taken, glutathione (GSH), lipid peroxidation (LPO), nonenzymatic glycosylation (NEG) and protein levels, catalase (CAT), superoxide dismutase (SOD) and glutathione-S-transferase (GST) activities were determined. Blood glucose, skin LPO and NEG levels increased, but skin GSH levels and CAT, SOD and GST activities decreased in the STZ group. Treatment with vanadyl sulfate reversed these effects. The present study showed that vanadyl sulfate exerted antioxidant properties and may prevent skin damage caused by diabetes.

Gliquidone decreases urinary protein by promoting tubular reabsorption in diabetic Goto-Kakizaki rats

The efficacy of gliquidone for the treatment of diabetic nephropathy was investigated by implanting micro-osmotic pumps containing gliquidone into the abdominal cavities of Goto-Kakizaki (GK) rats with diabetic nephropathy. Blood glucose, 24 h urinary protein, and 24 h urinary albumin levels were measured weekly. After 4 weeks of gliquidone therapy, pathological changes in the glomerular basement membrane (GBM) were examined using an electron microscope. Real-time PCR, western blotting, and immunohistochemistry were employed to detect glomerular expression of receptors for advanced glycation end products (RAGE) (AGER), protein kinase C β (PKCβ), and protein kinase A (PKA) as well as tubular expression of the albumin reabsorption-associated proteins: megalin and cubilin. Human proximal tubular epithelial cells (HK-2 cells) were used to analyze the effects of gliquidone and advanced glycation end products (AGEs) on the expression of megalin and cubilin and on the absorption of albumin. Gliquidone lowered blood glucose, 24 h urinary protein, and 24 h urinary albumin levels in GK rats with diabetic nephropathy. The level of plasma C-peptide increased markedly and GBM and podocyte lesions improved dramatically after gliquidone treatment. Glomerular expression of RAGE and PKCβ decreased after gliquidone treatment, while PKA expression increased. AGEs markedly suppressed the expression of megalin and cubulin and the absorption of albumin in HK-2 cells in vitro, whereas the expression of megalin and cubilin and the absorption of albumin were all increased in these cells after gliquidone treatment. In conclusion, gliquidone treatment effectively reduced urinary protein in GK rats with diabetic nephropathy by improving glomerular lesions and promoting tubular reabsorption.

Protective Effects of Glurenorm (Gliquidone) Treatment on the Liver Injury of Experimental Diabetes

Oxidative stress plays an important role in chronic complications of diabetes mellitus, and hence the regulation of free radicals is essential in the treatment of diabetes. The aim of the current study is to investigate the effect of glurenorm (10 mg/kg) on liver tissue in experimental diabetes. Diabetes was induced by intraperitoneal injection of 65 mg/kg streptozotocin. Glurenorm was administered to one diabetic and one control group separately, from days 14 to 42. On day 42, cardiac blood samples and liver tissue were taken from each rat. In diabetic rats, blood glucose, serum alkaline phosphatase and serum amino transferase activities, serum uric acid, serum sodium and potassium levels, liver nonenzymatic glycosylation, and lipid peroxidation increased, whereas body weight and liver glutathione levels decreased. The diabetic group given glurenorm blood glucose, serum alkaline phosphatase and aminotransferase activities, serum uric acid, sodium and potassium, liver nonenzymatic glycosylation, and lipid peroxidation levels decreased, and liver glutathione levels increased. As a result of all the biochemical findings obtained, it was concluded that glurenorm has a protective effect on damage of liver of streptozotocin-induced diabetes in rats.

Drug-metabolizing enzymes in the skin of man, rat, and pig

The mammalian skin has long been considered to be poor in drug metabolism. However, many reports clearly show that most drug metabolizing enzymes also occur in the mammalian skin albeit at relatively low specific activities. This review summarizes the current state of knowledge on drug metabolizing enzymes in the skin of human, rat, and pig, the latter, because it is often taken as a model for human skin on grounds of anatomical similarities. However only little is known about drug metabolizing enzymes in pig skin. Interestingly, some cytochromes P450 (CYP) have been observed in the rat skin which are not expressed in the rat liver, such as CYP 2B12 and CYP2D4. As far as investigated most drug metabolizing enzymes occur in the suprabasal (i.e. differentiating) layers of the epidermis, but the rat CYP1A1 rather in the basal layer and human UDP-glucuronosyltransferase rather in the stratum corneum. The pattern of drug metabolizing enzymes and their localization will impact not only the beneficial as well as detrimental properties of drugs for the skin but also dictate whether a drug reaches the blood flow unchanged or as activated or inactivated metabolite(s).

Effects of parsley (Petroselinum crispum) extract versus glibornuride on the liver of streptozotocin-induced diabetic rats

Parsley (Petroselinum crispum) is one of the medicinal herbs used by diabetics in Turkey. The aim of this study is to investigate the effects of parsley (2g/kg) and glibornuride (5mg/kg) on the liver tissue of streptozotocin-induced diabetic rats. Swiss albino rats were divided into six groups: control; control+parsley; control+glibornuride; diabetic; diabetic+parsley; diabetic+glibornuride. Diabetes was induced by intraperitoneal injection of 65 mg/kg streptozotocin (STZ). Parsley extract and glibornuride were given daily to both diabetic and control rats separately, until the end of the experiment, at day 42. The drugs were administered to one diabetic and one control group from days 14 to 42. On day 42, liver tissues were taken from each rat. In STZ-diabetic group, blood glucose levels, serum alkaline phosphatase activity, uric acid, sialic acid, sodium and potassium levels, liver lipid peroxidation (LPO), and non-enzymatic glycosylation (NEG) levels increased, while liver glutathione (GSH) levels and body weight decreased. In the diabetic group given parsley, blood glucose, serum alkaline phosphatase activity, sialic acid, uric acid, potassium and sodium levels, and liver LPO and NEG levels decreased, but GSH levels increased. The diabetic group, given glibornuride, blood glucose, serum alkaline phosphatase activity, serum sialic acid, uric acid, potassium, and liver NEG levels decreased, but liver LPO, GSH, serum sodium levels, and body weight increased. It was concluded that probably, due to its antioxidant property, parsley extract has a protective effect comparable to glibornuride against hepatotoxicity caused by diabetes.

Protective effect of vanadyl sulfate on the pancreas of streptozotocin-induced diabetic rats

The aim of this study is to examine from a biochemical and histological perspective, whether vanadium has a protective effect on the pancreas of diabetic rats. Male, 6-6.5 months old, Swiss albino rats were divided into four groups. Group I: control (intact) animals (n=13). Group II: control rats given vanadyl sulfate (n=5). Group III: streptozotocin-induced diabetic animals (n=11). Group IV: streptozotocin-induced diabetic animals given vanadyl sulfate (n=11). Vanadyl sulfate was given by gavage technique to rats in a dose of 100mg/kg daily for 60 days, after experimental animals were made diabetic. On day 60, the pancreas tissue and blood samples were taken from the animals. In the streptozotocin-induced diabetic group, blood glucose levels significantly increased in contrast to the loss of body weight, but vanadyl sulfate in streptozotocin-diabetic rats reduced blood glucose levels and increased both blood glutathione levels and body weight. Tissue sections were immunostained using an insulin antibody. The control group given vanadyl sulfate was no different from the other intact control group considering the insulin immunoreactivity in B cells. In pancreatic islets of the diabetic group, a decrease in the number of immunoreactive B cells was observed in comparison to the control group. On the other hand, pancreatic islets of the diabetic group given vanadyl sulfate showed a higher number of immunoreactive B cells in comparison to the diabetic group. According to the immunohistochemical and biochemical results obtained, it was concluded that vanadyl sulfate can regenerate B cells of endocrine pancreas in experimental diabetes.

Protective effects of metformin treatment on the liver injury of streptozotocin-diabetic rats

Metformin is a biguanide derivate used as an oral hypoglycaemic drug in diabetics. The aim of this study was to examine the histological and biochemical effects of metformin in streptozotocin (STZ)-treated rats. The animals were rendered diabetic by intraperitoneal injection of 65 mg/kg STZ. Fourteen days later, metformin was given at 25 mg/kg by gavage, daily for 28 days, to STZ-diabetic rats and a control group. In the STZ-diabetic group, some degenerative changes were observed by light microscopic examination. But the degenerative changes were decreased in the STZ-diabetic group given metformin. In the STZ-diabetic group, blood glucose levels, serum alanine and aspartate transaminase (ALT and AST) activities, total lipid levels, and sodium and potassium levels increased, while body weight, serum magnesium levels and liver glutathione (GSH) levels decreased. In the STZ-diabetic group given metformin, blood glucose levels, serum ALT and AST activities, total lipid, and sodium and potassium levels decreased, and liver GSH and serum magnesium levels increased. As a result of all the morphological and biochemical findings obtained, it was concluded that metformin has a protective effect against the hepatotoxicity produced by STZ diabetes.

The morphological and biochemical effects of glibornuride on rat liver in experimental diabetes

Glibornuride is a sulphonylurea derivative used as an oral hypoglycaemic drug in diabetics. The aim of this study was to examine the histological, ultrastructural and biochemical effects of glibornuride in streptozotocin (STZ)-treated rats. The animals were rendered diabetic by intraperitoneal injection of 65 mg/kg STZ. Fourteen days later, glibornuride was given at 5 mg/kg by gavage, daily for 28 days, to one STZ-diabetic and one control group. In the STZ-diabetic group, remarkable degenerative changes were observed. On the other hand, in the STZ-diabetic group given glibornuride, the degenerative changes decreased. In the STZ-diabetic group, blood glucose levels, serum aspartate transaminase activity, and total lipid levels increased, whereas the blood glutathione levels decreased. In contrast, in the STZ-diabetic group given glibornuride blood glucose levels, serum aspartate transaminase activity and total lipid levels decreased and blood glutathione levels increased. Significant changes in total protein levels in the serum were not observed in any group. As a conclusion, we can say that glibornuride has a protective effect against the hepatotoxicity produced by STZ-diabetes.