Influence of streptozotocin- and alloxan-induced diabetes on the metabolism of glycosaminoglycans

Selected elements of extracellular matrix of the skin in diabetes and insulin resistance

PURPOSE

Reconstruction of the skin extracellular matrix is a physiological phenomenon occurring on a continuous basis. The aim of this study is to evaluate the content of basic enzymes preventing oxidative stress: superoxide dismutase 2 and 3 as well as catalase, the content of hyaluronic acid, and the activity of N-acetyl-β-d-hexosaminidase and β-d-glucuronidase in the skin of rats used as animal models of diabetes and insulin resistance, before and after the treatment.

MATERIALS AND METHODS

The study was conducted on a group of sexually mature male Wistar rats divided into 7 groups of 10 animals. Insulin resistance was induced by feeding the rats with a high-fat diet, and diabetes was induced by a single injection of streptozotocin. Chosen groups of rats were treated with insulin or metformin. After 8 weeks, we excised a fragment of shaved dorsal skin from anesthetized rats in each group.

RESULTS

In the course of diabetes and insulin resistance, an intensified defensive activity of cells against the oxidative stress was observed in the undamaged skin, expressed by an increase in the relative content of superoxide dismutase 2 and 3, catalase and the activity of N-acetyl-β-d-hexosaminidase and β-d-glucuronidase. Diabetes and insulin resistance cause similar skin damage, as there are no differences in the relative contents or specific activities of the examined parameters.

CONCLUSIONS

Insulin and metformin improve the quality of the skin in rats with diabetes and insulin resistance, by restoring the content of hyaluronic acid to the healthy skin level.

Activities of Lysosomal Enzymes in Alloxan-Induced Diabetes in the Mouse

The study investigated a panel of lysosomal enzymes in the liver and kidney tissues in alloxan-induced diabetes in the mouse. The mice were divided into six experimental groups receiving 10% alloxan at a dose of 50 and 75 mg/kg over a period of four, eight, and twelve days; each group was compared with controls receiving 0.9% NaCl. The findings were that diabetes induced by both doses of alloxan was accompanied by significant increases in the lysosomal activities of acid phosphatase and the glycosidases investigated: β-glucuronidase, β-galactosidase, β-glucosidase, and N-acetyl-hexosaminidase. The lysosomal enzyme activity in both liver and kidney cells peaked 12 days after onset of diabetes for most enzymes, at the time when hyperglycemia and hyperinsulinemia already started abating after their peak at 8 days into the course of diabetes. The enzyme activity was in most cases higher with the higher dose of alloxan and thus higher level of glycemia. Lysosomal enzymes degrade glycoconjugates, the molecules that are present in the basement membrane of endothelial cells where they contribute to capillary wall stability. Thus, enhanced activity of these enzymes could presage the progression of diabetic microangiopathy, atherosclerosis, and the development of microvascular complications.

Anti-diabetic activity of different oils through their effect on arylsulfatases

BACKGROUND

Diabetes mellitus (DM) is characterized by the overproduction of the reactive oxygen species which affects the integrity of the lysosomal membrane affecting lysosomal enzymes. The effect of these species is blocked by some natural products as antioxidants. In the current study, groups of normal and streptozotocin (STZ)-induced diabetic rats were treated by Nigella sativa (NS), olive and canola oils and subjected to the study of arylsulfatases as a model of lysosomal enzymes. The aim of the present study is to investigate the effect of STZ-induced diabetes on arylsulfatases in presence and absence of NS, olive and canola oils.

METHODS

Different groups of rats were induced by STZ, treated with different oils and compared to their corresponding control group. All groups were subjected for the assays of blood glucose, insulin, catalase and arylsulfatases. A comparative kinetic study of arylsulfatses was performed to detect the alteration of catalytic characterization.

RESULTS

The results demonstrated that diabetes causes a significant elevation in the level of hepatic arylsulfatase B and a significant reduction of hepatic catalase as an antioxidant enzyme. NS and olive oils returned catalase and arylsulfatase B activities back near to normal by fixing their catalytic properties. Furthermore, the maximum velocity of arylsulfatases A and B was significantly elevated in the induced diabetes, whereas their Km values were significantly changed. The treatment of diabetic rats by NS and olive oils reduced the degree of significance.

CONCLUSION

Diabetes induces significant alterations of the catalytic characters of arylsulfatases and some oils decrease this alteration through an antioxidant-mediated effect.

Effect of spent turmeric on kidney glycoconjugates in streptozotocin-induced diabetic rats

Background

Curcumin known to have number of medicinal use and masked the fiber containing ukonan like active polysaccharide in turmeric and its pharmacological effect will be addressed on diabetic nephropathy particularly the glycoconjugates of extracellular components viz., glycoproteins and glycosaminoglycans - heparan sulfate (HS).

Methods

Male Wistar rats were maintained on AIN-76 diet containing 10% spent turmeric and were grouped into control and STZ induced diabetes SFC/TFC and SFD/TFD, respectively. Diabetic status was monitored using blood and urine, and at the end, harvested kidneys were used to study the amelioration of glycoprotiens (collagen) and HS by enzymatic digestion, spectrophotometric, hydroxyproline and agarose electrophoretic methods.

Results

In the present study spent turmeric (10%) fed diabetic rats showed improved glomerular filtration rate (50%), kidney enlargement (60%) and other glycoconjugate metabolism in kidney. Increased collagen content in diabetic group was observed by hydroxyproline estimation (24%) and periodic acid-Schiff’s (PAS) staining. Furthermore, elevated activities of enzymes involved in the synthesis and degradation of glycosaminoglycans (GAGs) were significantly lowered in spent turmeric fed diabetic group. Improvement in total GAGs (43%) and sulfate content (18%) followed by fractionation of GAGs using specific enzymes led to HS (28%) in the spent turmeric fed diabetic group, when compared to starch fed diabetic group and was further confirmed by electrophoresis of GAG.

Conclusion

These results clearly indicate beneficial role of spent turmeric in controlling glycoconjugates such as glycoproteins and heparan sulfate related kidney complications during diabetes.

Effect of bitter gourd and spent turmeric on glycoconjugate metabolism in streptozotocin-induced diabetic rats

AIM

Changes in glycoconjugate metabolism during the development of diabetic complications and their modulation by feeding bitter gourd and spent turmeric as fiber-rich source.

METHOD

This was studied by measuring the contents of total sugar, uronic acid, amino sugar, and sulfate in the streptozotocin-induced diabetic rats.

RESULTS

Total sugar content decreased in liver, spleen, and brain, while an increase was observed in heart and lungs. Uronic acid content in liver, spleen, and brain decreased, and marginal increase was observed in testis. Amino sugar content decreased in liver, spleen, lungs and heart during diabetes, and augmentation was observed to different extents. Decrease in sulfation of glycoconjugates was observed in liver, spleen, lungs and heart during diabetes and was significantly ameliorated by bitter gourd and spent turmeric, except brain. Protein content decreased in liver, while an increase was observed in brain. The studies clearly showed alteration in glycoconjugate metabolism during diabetes and amelioration to different extents by feeding bitter gourd and spent turmeric.

CONCLUSION

Improvement is due to slow release of glucose by fiber in the gastrointestinal track and short-chain fatty acid production from fiber by colon microbes.

Effect of bitter gourd and spent turmeric on constituents of glycosaminoglycans in different tissues in streptozotocin induced diabetic rats

Diet is now one of the well established means in the management of diabetes. Bitter gourd and spent turmeric at 10% level were tested for their efficacy on glycosaminoglycan metabolism in various tissues viz., liver, spleen, lungs, heart and testis in control, diabetic and treated rats. The glycosaminoglycans (GAGs) were isolated from defatted and dried tissues. The contents of sulfated GAGs decreased in all the tissues and the decrease was more prominent in heart and testis. In the isolated GAGs, contents of total sugar, amino sugar, uronic acid and sulfate were studied. Decrease in total sugar content was maximum in testis. Amino sugar content decreased considerably in testis (38%) and lungs (15%). The content of uronic acid also decreased in testis (33%) besides heart (29%) and liver (25%). Sulfate groups in GAGs perform pivotal functions in many biological events and decrease in sulfate content was significant in heart (40%), testis (37%) and liver (37%). GAGs profile on the cellulose acetate electrophoresis revealed that heparan sulfate (HS), hyaluronic acid (HA) and chondroitin sulfate/dermatan sulfate (CS/DS) were present in liver, spleen and lungs. HS, CS were present in heart, DS/CS was observed in testis. The observed beneficial effects in GAGs metabolism during diabetes may be due to the presence of high amounts of dietary fibres present in bitter gourd and spent turmeric, besides, possible presence of bioactive compounds in one or both of them.

Effect of dietary fibres on constituents of complex carbohydrates in streptozotocin induced diabetic rat tissues

The effect of dietary fibres on constituents of complex carbohydrates in various tissues of streptozotocin induced diabetic rats is presented by analysing different constituents of complex carbohydrates in presence and absence of dietary fibre. Wheat bran was effective in preventing the decrease (14%) in total sugars in spleen and an increase in total sugars in stomach (33%) during diabetes. Decrease in uronic acid content during diabetes in spleen was prevented to the extent of 25% by the presence of wheat bran in the diet. The other parameters which were affected by the presence of wheat bran in the diet during diabetes are amino sugar (brain and stomach), sulphates (liver) and protein (lungs and stomach). Guar gum was effective in preventing the decrease in total sugar content in spleen by 28% and sulphate content in liver by 14% during diabetes. Variation in protein content in lungs was observed in diabetes. The results indicated beneficial role of dietary fibres like wheat bran and guar gum on complex carbohydrates to varying extents in different tissues.

Serum activity of beta-N-acetylglucosaminidase in obese hyperinsulinemic subjects

We have measured serum activity of beta-N-acetylglucosaminidase (NAG, fluorimetric method) in some groups of obese subjects with similar degrees of overweight but with different insulin secretion and glucose tolerance (GT) during OGTT. In the control group (35 normal subjects, mean body weight 102% of ideal body weight, normal GT) NAG was 282 +/- 77 nmol S/h/ml; in group I (11 subjects, body weight 149%, normal GT and insulin levels) NAG was 304 +/- 55; in group II (19 subjects, body weight 142%, normal GT and high insulin levels) NAG was 453 +/- 90 (p less than 0.001 vs group I and controls); in group III (14 subjects, body weight 154%, impaired GT and high insulin levels) NAG was 481 +/- 108 (p less than 0.005 vs group I and controls); in group IV (16 subjects, body weight 153%, diabetic GT and high insulin levels) NAG was 657 +/- 109 (p less than 0.001 vs other groups). Moreover in the whole series NAG levels and insulin areas, but not NAG levels and degree of overweight, were significantly correlated (r=0.46, p less than 0.001). These data show that hyperinsulinism (especially when there is also pathological glucose tolerance) can positively affect NAG levels, probably through altered glycoprotein turnover, of which NAG serum levels are a sensitive indicator.