Diet-inducing hypercholesterolemia show decreased O-GlcNAcylation of liver proteins through modulation of AMPK

O-GlcNAcylation, a nutritionally driven, post-translational modification of proteins, is gaining importance because of its health implications. Changes in O-GlcNAcylation are observed in various disease conditions. Changes in O-GlcNAcylation by diet that causes hypercholesterolemia are not critically looked into in the liver. To address it, both in vitro and in vivo approaches were employed. Hypercholesterolemia was induced individually by feeding cholesterol (H)/high-fat (HF) diet. Global O-GlcNAcylation levels and modulation of AMPK activation in both preventive and curative approaches were looked into. Diet-induced hypercholesterolemia resulted in decreased O-GlcNAcylation of liver proteins which was associated with decreased O-linked N-acetylglucosaminyltransferase (OGT) and Glutamine fructose-6-phosphate amidotransferase-1 (GFAT1). Activation of AMPK by metformin in preventive mode restored the O-GlcNAcylation levels; however, metformin treatment of HepG2 cells in curative mode restored O-GlcNAcylation levels in HF but failed to in H condition (at 24 h). Further, maternal faulty diet resulted in decreased O-GlcNAcylation in pup liver despite feeding normal diet till adulthood. A faulty diet modulates global O-GlcNAcylation of liver proteins which is accompanied by decreased AMPK activation which could exacerbate metabolic syndromes through fat accumulation in the liver. (AU)

Diet-inducing hypercholesterolemia show decreased O-GlcNAcylation of liver proteins through modulation of AMPK

O-GlcNAcylation, a nutritionally driven, post-translational modification of proteins, is gaining importance because of its health implications. Changes in O-GlcNAcylation are observed in various disease conditions. Changes in O-GlcNAcylation by diet that causes hypercholesterolemia are not critically looked into in the liver. To address it, both in vitro and in vivo approaches were employed. Hypercholesterolemia was induced individually by feeding cholesterol (H)/high-fat (HF) diet. Global O-GlcNAcylation levels and modulation of AMPK activation in both preventive and curative approaches were looked into. Diet-induced hypercholesterolemia resulted in decreased O-GlcNAcylation of liver proteins which was associated with decreased O-linked N-acetylglucosaminyltransferase (OGT) and Glutamine fructose-6-phosphate amidotransferase-1 (GFAT1). Activation of AMPK by metformin in preventive mode restored the O-GlcNAcylation levels; however, metformin treatment of HepG2 cells in curative mode restored O-GlcNAcylation levels in HF but failed to in H condition (at 24 h). Further, maternal faulty diet resulted in decreased O-GlcNAcylation in pup liver despite feeding normal diet till adulthood. A faulty diet modulates global O-GlcNAcylation of liver proteins which is accompanied by decreased AMPK activation which could exacerbate metabolic syndromes through fat accumulation in the liver. (AU)

Diet-inducing hypercholesterolemia show decreased O-GlcNAcylation of liver proteins through modulation of AMPK.

O-GlcNAcylation, a nutritionally driven, post-translational modification of proteins, is gaining importance because of its health implications. Changes in O-GlcNAcylation are observed in various disease conditions. Changes in O-GlcNAcylation by diet that causes hypercholesterolemia are not critically looked into in the liver. To address it, both in vitro and in vivo approaches were employed. Hypercholesterolemia was induced individually by feeding cholesterol (H)/high-fat (HF) diet. Global O-GlcNAcylation levels and modulation of AMPK activation in both preventive and curative approaches were looked into. Diet-induced hypercholesterolemia resulted in decreased O-GlcNAcylation of liver proteins which was associated with decreased O-linked N-acetylglucosaminyltransferase (OGT) and Glutamine fructose-6-phosphate amidotransferase-1 (GFAT1). Activation of AMPK by metformin in preventive mode restored the O-GlcNAcylation levels; however, metformin treatment of HepG2 cells in curative mode restored O-GlcNAcylation levels in HF but failed to in H condition (at 24 h). Further, maternal faulty diet resulted in decreased O-GlcNAcylation in pup liver despite feeding normal diet till adulthood. A faulty diet modulates global O-GlcNAcylation of liver proteins which is accompanied by decreased AMPK activation which could exacerbate metabolic syndromes through fat accumulation in the liver.

Composition and structure elucidation of bovine milk glycosaminoglycans and their anti-adipogenic activity via modulation PPAR-γ and C/EBP-α.

The structure function relation of Glycosaminoglycans from bovine milk (bmGAGs) has not been studied in detail. In the present study bmGAGs was isolated and structurally characterized. Chondroitin sulphate was one of the major GAGs present and had 65% of ΔDi-diSB (GlcA(2S)-GalNAc(4S)), followed by 18% of ΔDi-4S(Δ4,5HexUAα1 â†’ 3GalNAc). Further, bmGAGs exhibited a marked anti-adipogenic effect in 3 T3-L1 cells without affecting cell viability at the concentration used. The triglyceride content treated with bmGAGs was significantly decreased as assessed by Oil-Red O staining. Peroxisome proliferator activated receptor γ (PPAR-γ) and CCAAT/enhancer-binding proteins (C/EBPα) the critical transcription factors in adipogenesis showed significant decrease in both gene and protein levels. Sterol regulatory element-binding protein 1c (SREBP-1c) that promotes the adipocyte differentiation by enhancing the activity of PPAR-γ was inversely affected by bmGAGs and the fatty acid synthase (FAS) expression was modulated. Thus, the present work is among the firsts to demonstrate an anti-adipogenic activity of bmGAGs by modulating the adipogenesis-related marker proteins and hence bmGAGs may be used as a supplement/therapeutic in the management of obesity.

AMPK in microvascular complications of diabetes and the beneficial effects of AMPK activators from plants.

BACKGROUND: Diabetes mellitus is a multifactorial disorder with the risk of micro- and macro-vascular complications. High glucose-induced derangements in metabolic pathways are primarily associated with the initiation and progression of secondary complications namely, diabetic nephropathy, neuropathy, and retinopathy. Adenosine monophosphate-activated protein kinase (AMPK) has emerged as an attractive therapeutic target to treat various metabolic disorders including diabetes mellitus. It is a master metabolic regulator that helps in maintaining cellular energy homeostasis by promoting ATP-generating catabolic pathways and inhibiting ATP-consuming anabolic pathways. Numerous pharmacological and plant-derived bioactive compounds that increase AMP-activated protein kinase activation has shown beneficial effects by mitigating secondary complications namely retinopathy, nephropathy, and neuropathy. PURPOSE: The purpose of this review is to highlight current knowledge on the role of AMPK and its activators from plant origin in diabetic microvascular complications. METHODS: Search engines such as Google Scholar, PubMed, Science Direct and Web of Science are used to extract papers using relevant key words. Papers mainly focusing on the role of AMPK and AMPK activators from plant origin in diabetic nephropathy, retinopathy, and neuropathy was chosen to be highlighted. RESULTS: According to results, decrease in AMPK activation during diabetes play a causative role in the pathogenesis of diabetic microvascular complications. Some of the plant-derived bioactive compounds were beneficial in restoring AMPK activity and ameliorating diabetic microvascular complications. CONCLUSION: AMPK activators from plant origin are beneficial in mitigating diabetic microvascular complications. These pieces of evidence will be helpful in the development of AMPK-centric therapies to mitigate diabetic microvascular complications.

Brain heparan sulphate proteoglycans are altered in developing foetus when exposed to in-utero hyperglycaemia.

In-utero exposure of foetus to hyperglycaemic condition affects the growth and development of the organism. The brain is one of the first organs that start to develop during embryonic period and glycosaminoglycans (GAGs) and proteoglycans (PGs) are one of the key molecules involved in its development. But studies on the effect of hyperglycaemic conditions on brain GAGs/PGs are few and far between. We, therefore, looked into the changes in brain GAGs and PGs at various developmental stages of pre- and post-natal rats from non-diabetic and diabetic mothers as well as in adult rats induced with diabetes using a diabetogenic agent, Streptozotocin. Increased expression of GAGs especially that of heparan sulphate class in various developmental stages were observed in the brain as a result of in-utero hyperglycaemic condition but not in that of adult rats. Changes in disaccharides of heparan sulphate (HS) were observed in various developmental stages. Furthermore, various HSPGs namely, syndecans-1 and -3 and glypican-1 were overexpressed in offspring from diabetic mother. However, in adult diabetic rats, only glypican-1 was overexpressed. The offsprings from diabetic mothers became hyperphagic at the end of 8 weeks after birth which can have implications in the long run. Our results highlight the likely impact of the in-utero exposure of foetus to hyperglycaemic condition on brain GAGs/PGs compared to diabetic adult rats.

Diet-induced hypercholesterolemia imparts structure-function changes to erythrocyte chondroitin sulphate/dermatan sulphate.

Hypercholesterolemia is one of the factors contributing to cardiovascular problems. Erythrocytes are known to contribute its cholesterol to atherosclerotic plaque. Our earlier study showed that erythrocytes overexpress chondroitin sulphate/dermatan sulphate (CS/DS), a linear co-polymer, during diabetes which resulted in increased cytoadherence to extracellular matrix (ECM) components. This study was carried out to determine whether diet-induced hypercholesterolemia had any effect on erythrocyte CS/DS and impacted cytoadherence to ECM components. Unlike in diabetes, diet-induced hypercholesterolemia did not show quantitative changes in erythrocyte CS/DS but showed difference in proportion of un-sulphated and 4-O-sulphated disaccharides. Erythrocytes from hypercholesterolemic rats showed increased adhesion to ECM components which was abrogated to various extents when subjected to chondroitinase ABC digestion. However, isolated CS/DS chains showed a different pattern of binding to ECM components indicating that orientation of CS/DS chains could be playing a role in binding.

Erythrocytes in the combined milieu of high glucose and high cholesterol shows glycosaminoglycan-dependent cytoadherence to extracellular matrix components.

Pathological conditions are bound to affect the molecules on erythrocytes, and accordingly affect their functions. Chondroitin sulphate/dermatan sulphate (CS/DS), one of the classes of molecules found to be expressed in erythrocytes was previously observed by us to be either overexpressed in diabetic condition or undergo structural changes in hypercholesterolemic condition. Both of them had implications on their binding to extracellular matrix components (ECM). In the present work, we have explored the quantitative changes in erythrocyte glycosaminoglycans (GAGs) and their role in erythrocyte binding towards ECM components in the combined milieu of both diabetes and hypercholesterolemia (SFHD). Membrane cholesterol was significantly higher in SFHD group compared to control (SFC) and diabetic groups (SFD). Interestingly, there were no quantitative changes in CS/DS compared to SFC erythrocytes, but showed significantly increased cytoadherence to selected ECM components to various extents. Binding was partly dependent on CS/DS as digesting the chains resulted in relatively decreased cytoadherence. It also showed significantly increased binding to chondroitin sulphate and heparan sulphate. Thus, combined milieu of high glucose and high cholesterol can have more deleterious consequences than either of them independently.

Feeding of banana flower and pseudostem to diabetic rats results in modulation of renal GLUTs, TGFß, PKC and extracellular matrix components.

BACKGROUND AND AIMS: Sustained hyperglycemia as a result of diabetes mellitus results in over-expression of glucose transporters (GLUTs/SGLTs), protein kinase C-α (PKC-α) and transforming growth factor-ß (TGF-ß) in kidney which increases synthesis and accumulation of extracellular matrix (ECM) components leading to diabetic nephropathy. Previous results from our laboratory showed that banana flower (BF) and pseudostem (BS) ameliorated diabetic complications and reduced formation of advanced glycation end-products (AGEs). In this study, attempts were made to delineate the changes observed in GLUTs and ECM components in kidney by feeding BF and BS at the molecular level. METHODS AND RESULTS: Diabetes was induced in male Wistar rats by injecting streptozotocin. Rats were fed with standard AIN-76 diet or diet supplemented with 5% BF or BS. Rats fed with diet supplemented with aminoguanidine (0.05%) were used as a positive control. Effect of BF and BS on expression of GLUTs/SGLTs, PKC and TGF ß in kidney was evaluated by RT-PCR and accumulation of ECM components in kidney was quantitated by ELISA and immunohistochemistry. BF and BS modulated the over-expression of GLUT 1, 2, 5, SGLT 1, 2 and factors such as PKC-α and TGF-ß to various extents. This impinged on the synthesis of ECM components like laminin, fibronectin and type-IV collagen. CONCLUSION: The results suggest that BF and BS reduce the diabetic nephropathy complications which are accompanied by changes at the molecular level.

Progression of early phase diabetic nephropathy in streptozotocin-induced diabetic rats: evaluation of various kidney-related parameters.

Diabetic nephropathy (DN) is one of the serious secondary complications of diabetes, which results in end-stage renal failure. Reports on the progressive nature of early phase DN especially with respect to kidney parameters such as kidney weight, type IV collagen excretion, total kidney and urinary glycosaminoglycans (GAGs) are few. This work was undertaken to determine systematically the progression of early phase DN in relation to various kidney-related parameters for a period of four months. Experimentally-induced diabetic rats were grouped based on fasting blood glucose levels. Various basic and kidney-related parameters such as kidney weight, microalbuminuria, urinary excretion of GAGs and type IV collagen, total kidney GAGs, histopathology, glomerular area and glomerular volume were examined in control and diabetic rats. There was a progressive increase in fasting blood sugar, urine sugar, kidney weight, microalbuminuria, urine glycosaminoglycans, urine type IV collagen, glomerular area and glomerular volume but there was a progressive decrease in kidney glycosaminoglycans. Glomerular sclerotic condition was aggravated with the increase in duration of diabetes from 1 to 4 months. Onset of DN in rats begins subtly after one month of diabetes but gets vitiated and more pronounced at the end of four months.

Erythrocytes express chondroitin sulphate/dermatan sulphate, which undergoes quantitative changes during diabetes and mediate erythrocyte adhesion to extracellular matrix components.

Glycosaminoglycans (GAGs) such as chondroitin sulphate/dermatan sulphate (CS/DS) are complex molecules that are widely expressed on the cell membrane and extracellular matrix (ECM). They play an important role in wide range of biological activities especially during pathological conditions. Diabetes, a metabolic disorder characterized by sustained hyperglycemia, is known to affect GAGs in different tissues and affect erythrocyte adhesion. The present investigation was aimed at exploring the nature of GAGs present in erythrocytes and its role on adhesion of erythrocytes from control and diabetic rats to major extracellular matrix components. GAGs isolated from erythrocytes were demonstrated to be CS/DS and a 2-fold increase was observed in erythrocytes from diabetic rats. Disaccharide composition analysis by HPLC after depolymerization by the enzyme, chondroitinase ABC showed the presence of 4-O sulphated disaccharide units with small amounts of non-sulphated disaccharides, in both control and diabetic erythrocytes. Erythrocytes from diabetic rats, however, showed significantly increased binding to poly-l-ornithine (P-orn), type IV collagen, laminin and fibronectin, which was abrogated on treatment with chondroitinase ABC to various degrees. This study sheds new light on CS/DS in erythrocytes and its likely biological implications in vivo.

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.