Diabetes and zinc dyshomeostasis: Can zinc supplementation mitigate diabetic complications?

Zinc present in the islet cells of the pancreas is crucial for the synthesis, storage, and secretion of insulin. The excretion of large amounts of zinc from the body is reported in diabetic situations. Zinc depletion and increased oxidative stress have a major impact on the pathogenesis of diabetic complications. It would be most relevant to ascertain if intervention with supplemental zinc compensating for its depletion would beneficially mitigate hyperglycemia and the attendant metabolic abnormalities, and secondary complications in diabetes. An exhaustive literature search on this issue indicates: (1) Concurrent hypozincemia and decreased tissue zinc stores in diabetes as a result of its increased urinary excretion and/or decreased intestinal absorption, (2) Several recent experimental studies have documented that supplemental zinc has a potential hypoglycemic effect in the diabetic situation, and also beneficially modulate the attendant metabolic abnormalities and compromised antioxidant status, and (3) Supplemental zinc also alleviates renal lesions, cataract and the risk of cardiovascular disease accompanying diabetes mellitus, and help restore gastrointestinal health in experimental diabetes. These studies have also attempted to identify the precise mechanisms responsible for zinc-mediated beneficial effects in diabetic situation. The evidence discussed in this review highlights that supplemental zinc may significantly contribute to its clinical application in the management of diabetic hyperglycemia and related metabolic abnormalities, and in the alleviation of secondary complications resulting from diabetic oxidative stress.

Anti-cholelithogenic potential of dietary spices and their bioactives.

Dietary hypocholesterolemic spices-curcumin (active compound of turmeric (Curcuma longa)) and capsaicin (active compound of red pepper (Capsicum annuum)), the active principles of spices-turmeric (Curcuma longa) and red pepper (Capsicum annuum), fenugreek (Trigonella foenum-graecum) seeds, garlic (Allium sativum), and onion (Allium cepa) are documented to have anti-cholelithogenic property in animal model. These spices prevent the induction of cholesterol gallstones by lithogenic high cholesterol diet and also regress the pre-established cholesterol gallstones, by virtue of their hypolipidemic potential. The antilithogenic influence of these spices is primarily attributable to their hypocholesterolemic effect. Increased cholesterol saturation index, cholesterol:phospholipid ratio and cholesterol:bile acid ratio in the bile caused by the lithogenic diet was countered by these spices. The antilithogenicity of these hypocholesterolemic spices was considered to be due also to their influence on biliary proteins that have pro-nucleating activity and anti-nucleating activity. Investigations on the involvement of biliary proteins in cholesterol crystal nucleation revealed that in an in vitro bile model, low molecular weight biliary proteins of the lithogenic diet fed animals have a pro-nucleating activity. On the contrary, low molecular weight biliary proteins of the animals fed hypocholesterolemic spices along with lithogenic diet showed a potent anti-nucleating activity.

Attenuation of oxidative stress and cardioprotective effects of zinc supplementation in experimental diabetic rats.

Oxidative stress plays a major role in the pathogenesis of diabetes mellitus, which further exacerbates damage of cardiac, hepatic and other tissues. We have recently reported that Zn supplementation beneficially modulates hyperglycaemia and hypoinsulinaemia, with attendant reduction of associated metabolic abnormalities in diabetic rats. The present study assessed the potential of Zn supplementation in modulating oxidative stress and cardioprotective effects in diabetic rats. Diabetes was induced in Wistar rats with streptozotocin, and groups of diabetic rats were treated with 5- and 10-fold dietary Zn interventions (0·19 and 0·38 g Zn/kg diet) for 6 weeks. The markers of oxidative stress, antioxidant enzyme activities and concentrations of antioxidant molecules, lipid profile, and expressions of fibrosis and pro-apoptotic factors in the cardiac tissue were particularly assessed. Supplemental Zn showed significant attenuation of diabetes-induced oxidative stress in terms of altered antioxidant enzyme activities and increased the concentrations of antioxidant molecules. Hypercholesterolaemia and hyperlipidaemia were also significantly countered by Zn supplementation. Along with attenuated oxidative stress, Zn supplementation also showed significant cardioprotective effects by altering the mRNA expressions of fibrosis and pro-apoptotic factors (by >50 %). The expression of lipid oxidative marker 4-hydroxy-2-nonenal (4-HNE) protein in cardiac tissue of diabetic animals was rectified (68 %) by Zn supplementation. Elevated cardiac and hepatic markers in circulation and pathological abnormalities in cardiac and hepatic tissue architecture of diabetic animals were ameliorated by dietary Zn intervention. The present study indicates that Zn supplementation can attenuate diabetes-induced oxidative stress in circulation as well as in cardiac and hepatic tissues.

Bioaccessibility of polyphenols from selected cereal grains and legumes as influenced by food acidulants.

BACKGROUND: Polyphenols in food are valued for their health-beneficial influences. Food acidulants lime juice and amchur used in Indian cookery were evaluated for their influence on polyphenol bioaccessibility from food grains. RESULTS: Lime juice increased bioaccessible flavonoids by 25% in roasted finger millet, while there was no change in total bioaccessible polyphenols in pressure-cooked, open-pan-boiled and roasted finger millet in the presence of food acidulants. Addition of amchur to pressure-cooked and microwave-heated pearl millet increased bioaccessible flavonoids by 30 and 53% respectively, while lime juice increased them by 46% in pressure-cooked pearl millet. Increased bioaccessibility of specific phenolic acids from finger millet and pearl millet was observed upon addition of these food acidulants. The presence of either lime juice or amchur increased bioaccessible flavonoids from both legumes studied. Addition of lime juice and amchur, however, exerted a negative effect on the bioaccessibility of several phenolic compounds from food grains in native state and under certain processing conditions. CONCLUSION: Thus food acidulants lime juice and amchur had a significant influence on the bioaccessibility of health-beneficial phenolic compounds from food grains. Use of food acidulants in food preparations could be a strategy to enhance the bioavailability of polyphenols, especially flavonoids from grains. © 2016 Society of Chemical Industry.

Anti-hypercholesterolemic influence of the spice cardamom (Elettaria cardamomum) in experimental rats.

BACKGROUND: Cardamom (Elettaria cardamomum) is an aromatic seed spice grown extensively in India and used as a flavoring in sweets. In this study, the anti-hypercholesterolemic effect of cardamom was evaluated in Wistar rats by inducing hypercholesterolemia with a high-cholesterol diet for 8 weeks. Dietary interventions were made with (a) cardamom powder (50 g kg-1 ), (b) cardamom oil (3 g kg-1 , equivalent to 50 g kg-1 cardamom) and (c) de-oiled cardamom powder (50 g kg-1 ). RESULTS: A significant reduction in blood total cholesterol (31%) and low-density lipoprotein cholesterol (44%) was observed by oral administration of cardamom oil in hypercholesterolemic rats, accompanied by a marked decrease in serum triglycerides by 42%. The cholesterol content of cardiac muscle was beneficially lowered by 39% with administration of cardamom oil in hypercholesterolemic rats. Liver triglycerides were reduced by 33%. Incorporation of cardamom oil/powder in the diet did not alter feed consumption by rats. Compromised activities of hepatic antioxidant enzymes in the hypercholesterolemic situation were generally countered by dietary cardamom. Treatment with de-oiled cardamom as well as cardamom oil countered the diminished activity of catalase in hypercholesterolemic animals. Cardamom also enhanced the activity of heart superoxide dismutase in the hypercholesterolemic situation. The concentration of ascorbic acid in serum was significantly increased by dietary cardamom or its fractions in the hypercholesterolemic situation. CONCLUSION: This animal study has established the potential of cardamom oil in restoring the alteration in lipid homeostasis in conditions of hypercholesterolemia. The significant reduction in atherogenicity index by dietary intervention with cardamom powder and cardamom oil indicates the potential cardioprotective effect of cardamom. © 2016 Society of Chemical Industry.

Biological Activities of Red Pepper (Capsicum annuum) and Its Pungent Principle Capsaicin: A Review.

Capsaicin, the pungent alkaloid of red pepper (Capsicum annuum) has been extensively studied for its biological effects which are of pharmacological relevance. These include: cardio protective influence, antilithogenic effect, antiinflammatory, and analgesia, thermogenic influence, and beneficial effects on gastrointestinal system. Therefore, capsaicinoids may have the potential clinical value for pain relief, cancer prevention and weight loss. It has been shown that capsaicinoids are potential agonists of capsaicin receptor (TRPV1). They could exert the effects not only through the receptor-dependent pathway but also through the receptor-independent one. The involvement of neuropeptide Substance P, serotonin, and somatostatin in the pharmacological actions of capsaicin has been extensively investigated. Topical application of capsaicin is proved to alleviate pain in arthritis, postoperative neuralgia, diabetic neuropathy, psoriasis, etc. Toxicological studies on capsaicin administered by different routes are documented. Capsaicin inhibits acid secretion, stimulates alkali and mucus secretion and particularly gastric mucosal blood flow which helps in prevention and healing of gastric ulcers. Antioxidant and antiinflammatory properties of capsaicin are established in a number of studies. Chemopreventive potential of capsaicin is evidenced in cell line studies. The health beneficial hypocholesterolemic influence of capsaicin besides being cardio protective has other implications, viz., prevention of cholesterol gallstones and protection of the structural integrity of erythrocytes under conditions of hypercholesterolemia. Beneficial influences of capsaicin on gastrointestinal system include digestive stimulant action and modulation of intestinal ultrastructure so as to enhance permeability to micronutrients.

Bioavailability of Micronutrients from Plant Foods: An Update.

Deficiencies of iron, zinc, iodine and vitamin A are widespread in the developing countries, poor bioavailability of these micronutrients from plant-based foods being the major reason for their wide prevalence. Diets predominantly vegetarian are composed of components that enhance as well as inhibit mineral bioavailability, the latter being predominant. However, prudent cooking practices and use of ideal combinations of food components can significantly improve micronutrient bioavailability. Household processing such as heat treatment, sprouting, fermentation and malting have been evidenced to enhance the bioavailability of iron and ß-carotene from plant foods. Food acidulants amchur and lime are also shown to enhance the bioavailability of not only iron and zinc, but also of ß-carotene. Recently indentified newer enhancers of micronutrient bioaccessibility include sulphur compound-rich Allium spices-onion and garlic, which also possess antioxidant properties, ß-carotene-rich vegetables-carrot and amaranth, and pungent spices-pepper (both red and black) as well as ginger. Information on the beneficial effect of these dietary compounds on micronutrient bioaccessibility is novel. These food components evidenced to improve the bioavailability of micronutrients are common ingredients of Indian culinary, and probably of other tropical countries. Fruits such as mango and papaya, when consumed in combination with milk, provide significantly higher amounts of bioavailable ß-carotene. Awareness of the beneficial influence of these common dietary ingredients on the bioavailability of micronutrients would help in devising dietary strategies to improve the bioavailability of these vital nutrients.

Zinc supplementation alleviates hyperglycemia and associated metabolic abnormalities in streptozotocin-induced diabetic rats.

The cause and effect relationship between diabetes and zinc is complex and unclear. This animal study has examined the potential of zinc supplementation in beneficial modulating hyperglycemia, insulin secretion, and metabolic abnormalities associated with diabetes. The study was conducted in streptozotocin-induced diabetic rats. Groups of hyperglycemic rats were subjected to dietary interventions for 6 weeks with zinc supplementation (5 times and 10 times the normal level). Supplemental-zinc-fed diabetic groups showed significant control on hyperglycemia and hypoinsulinemia. There was a significant reduction in protein glycosylation, glucosuria, and urinary excretion of proteins and urea in diabetic animals maintained on a zinc-supplemented diet. Diabetic rats showed significantly higher plasma albumin and lower plasma urea and creatinine levels upon zinc supplementation. Significant alterations in insulin sensitivity indices HOMA-IR, HOMA-B, and QUICKI were also indicated by zinc supplementation. The pathological abnormalities in pancreatic islets of diabetic animals were significantly alleviated by dietary zinc intervention. This study provides the first evidence that zinc supplementation can partially ameliorate the severity of diabetic hyperglycemia and associated metabolic abnormalities, hypoinsulinemia, insulin resistance, and altered pancreatic morphology. Thus, zinc supplementation may offer a significant potential for clinical application in managing diabetic hyperglycemia and related metabolic complications.

Potentiation of anti-cholelithogenic influence of dietary tender cluster beans (Cyamopsis tetragonoloba) by garlic (Allium sativum) in experimental mice.

BACKGROUND & OBJECTIVES: Dietary fibre-rich tender cluster beans (Cyamopsis tetragonoloba; CB) are known to exert beneficial cholesterol lowering influence. We examined the influence of a combination of dietary tender CB and garlic (Allium sativum) in reducing the cholesterol gallstone formation in mice. METHODS: Cholesterol gallstones were induced in Swiss mice by feeding a high-cholesterol diet (HCD) for 10 wk. Dietary interventions were made with 10 per cent CB and 1 per cent garlic included individually or together along with HCD. A total of 100 mice were divided into five groups of 20 mice each. RESULTS: Dietary CB, garlic and CB+garlic reduced the formation of cholesterol gallstones by 44, 25 and 56 per cent, respectively, lowered cholesterol by 23-48, 16-24, and 24-58 in bile, serum, and liver, respectively. Cholesterol saturation index in bile and cholesterol: phospholipid ratio in circulation and hepatic tissue were significantly lowered by these dietary interventions, with highest beneficial effect from CB+garlic. Activities of hepatic cholesterol metabolizing enzymes were modulated by CB, garlic and CB+garlic. Elevation in lipid peroxides caused by HCD was also countered by these dietary interventions, the combination producing the highest effect. INTERPRETATION & CONCLUSIONS: The results showed that the prevention of experimentally induced formation of cholesterol gallstones by dietary CB and garlic was due to decreased biliary cholesterol secretion and increased cholesterol saturation index. In addition of anti-lithogenic effect, dietary CB and garlic in combination had a beneficial antioxidant effect.

Potentiation of antioxidant effect of dietary tender cluster beans (Cyamopsis tetragonoloba) by garlic (Allium sativum) in high-cholesterol-fed rats.

The antioxidant role of tender cluster beans (Cyamopsis tetragonoloba, CB), a rich source of soluble fibre, was investigated in a hypercholesterolemia-induced oxidative stress situation in rats. In the context of dietary garlic (Allium sativa) potentiating the hypocholesterolemic influence of CB, we also examined if dietary garlic enhances the antioxidant potential of CB. Groups of Wistar rats were rendered hypercholesterolemic by feeding them a 0.5% cholesterol diet for 8 weeks. Dietary interventions were made by inclusion of 15% tender CB powder or 1% garlic powder or their combination in a high-cholesterol diet. Concentrations of antioxidant molecules and activities of antioxidant enzymes in blood and liver were examined. Dietary CB displayed an antioxidant influence in terms of elevating ascorbic acid and glutathione concentrations and stimulating the activities of antioxidant enzymes both in blood and liver. The antioxidant effect of dietary CB was generally potentiated by co-administration of garlic. Thus, consumption of tender CB and garlic together could form a strategy for improving the body's antioxidant status.

Beneficial influence of fungal metabolite nigerloxin on diabetes-induced oxidative stress in experimental rats.

Oxidative stress plays a key role in the progression of diabetes and its complications. In this study, the beneficial influence of the fungal metabolite nigerloxin, a new aldose reductase inhibitor and a free-radical scavenger, was investigated on oxidative stress in streptozotocin-induced diabetic rats. Groups of diabetic rats were orally administered nigerloxin for 30 days at a dose of 25 and 100 mg·(kg body mass)(-1)·day(-1). Diabetic rats showed significantly increased lipid peroxide levels in blood and liver, which was accompanied by lowered concentrations of antioxidant molecules and activities of antioxidant enzymes in blood and liver. Administration of nigerloxin for 30 days at a daily dose of 100 mg∙(kg body mass)(-1) to diabetic rats significantly decreased plasma and liver lipid peroxides, elevated the nonenzymatic antioxidants ascorbic acid, reduced glutathione, and total thiols, and elevated the activities of antioxidant enzymes in blood and liver. Nigerloxin showed a tendency to counter lipid abnormalities in diabetic animals, while fasting glucose and body mass were unaffected by nigerloxin treatment. Thus, this animal study has indicated the beneficial influence of nigerloxin on oxidative stress associated with diabetes that may have an implication in delaying or ameliorating the secondary complications.

Beneficial influence of fungal metabolite nigerloxin on eye lens abnormalities in experimental diabetes.

Osmotic and oxidative stress have been implicated in the pathogenesis of diabetic cataract. Nigerloxin, a fungal metabolite, has been shown to possess aldose reductase inhibitory and free radical scavenging potential, in vitro. In the present study, the beneficial influence of nigerloxin was investigated on diabetes-induced alteration in the eye lens of rats treated with streptozotocin. Groups of diabetic rats were administered nigerloxin orally (100 mg·(kg body mass)(-1)·day(-1)) for 30 days. The activity of lens polyol pathway enzymes (aldose reductase and sorbitol dehydrogenase), lipid peroxides, and advanced glycation end products (AGEs) were increased in the diabetic animals. Levels of glutathione as well as the activity of antioxidant enzymes (superoxide dismutase, glutathione-S-transferase, and glutathione peroxidase) were decreased in the eye lens of the diabetic animals. The administration of nigerloxin significantly decreased levels of lipid peroxides and AGEs in the lens of the diabetic rats. Increase in the activity of aldose reductase and sorbitol dehydrogenase in the lens was countered by nigerloxin treatment. The activity of glutathione and antioxidant enzyme in the lens was significantly elevated in nigerloxin-treated diabetic rats. Examination of the treated rats' eyes indicated that nigerloxin delayed cataractogenesis in the diabetic rats. The results suggest the beneficial countering of polyol pathway enzymes and potentiation of the antioxidant defense system by nigerloxin in diabetic animals, implicating its potential in ameliorating cataracts in diabetics.

Assessment of zinc deficiency and effect of dietary carrot, amchur and onion on zinc status during repletion in zinc-deficient rats.

BACKGROUND: Food acidulants, ß-carotene-rich vegetables and sulfur compound-rich Allium spices are known to improve zinc bioaccessibility from food grains. This animal study evaluated the positive influence of these promoters of zinc bioaccessibility on zinc status during zinc repletion in Wistar rats previously rendered zinc-deficient by feeding a zinc-deficient semi-synthetic diet for 4 weeks. Groups of these zinc-deficient animals were subsequently maintained on a zinc-containing grain-based diet for 2 weeks. Various experimental diets consisted of the grain-based diet supplemented with (1) carrot, (2) onion, (3) amchur, (4) carrot + amchur and (5) onion + amchur. RESULTS: Zinc deficiency was confirmed by lower zinc concentration in tissues and bones and lower activity of zinc-containing enzymes. Zinc concentration was 10-15% lower in serum, liver and kidney of zinc-deficient rats. Bone weight in zinc-deficient rats was 20% lower than that in normal rats. Activities of zinc-containing enzymes (hepatic superoxide dismutase and alcohol dehydrogenase and serum alkaline phosphatase) were lower in the zinc-deficient group. Animals fed diets supplemented with these promoters of zinc bioaccessibility showed better zinc status in tissues and bones compared with those repleted with the control stock diet. CONCLUSION: This animal study supports the claim of promoters of zinc bioaccessibility for improving zinc status, which may find practical application.

Fat digestion and absorption in spice-pretreated rats.

BACKGROUND: A few common spices are known to stimulate secretion of bile with higher amount of bile acids which play a major role in digestion and absorption of dietary lipids. It would be appropriate to verify if these spices enable efficient digestion and absorption during high-fat intake. In this context, dietary ginger (0.05%), piperine (0.02%), capsaicin (0.015%), and curcumin (0.5%) were examined for their influence on bile secretion, digestive enzymes of pancreas and absorption of dietary fat in high-fat (30%) fed Wistar rats for 8 weeks. RESULTS: These spices enhanced the activity of pancreatic lipase, amylase, trypsin and chymotrypsin by 22-57%, 32-51%, 63-81% and 12-38%, respectively. Dietary intake of spices along with high-fat enhanced fat absorption. These dietary spices increased bile secretion with higher bile acid content. Stimulation of lipid mobilisation from adipose tissue was suggested by the decrease in perirenal adipose tissue weight by dietary capsaicin and piperine. This was also accompanied by prevention of the accumulation of triglyceride in liver and serum in high-fat fed rats. Activities of key lipogenic enzymes in liver were reduced which was accompanied by an increased activity of hormone-sensitive lipase. CONCLUSION: Thus, dietary ginger and other spice compounds enhance fat digestion and absorption in high-fat fed situation through enhanced secretion of bile salts and a stimulation of the activity pancreatic lipase. At the same time, the energy expenditure is facilitated by these spices to prevent the accumulation of absorbed fat.

Dietary fenugreek and onion attenuate cholesterol gallstone formation in lithogenic diet-fed mice.

An animal study was conducted to evaluate the antilithogenic effect of a combination of dietary fenugreek seeds and onion. Lithogenic conditions were induced in mice by feeding them a high (0.5%) cholesterol diet (HCD) for 10 weeks. Fenugreek (12%) and onion (2%) were included individually and in combination in this HCD. Fenugreek, onion and their combination reduced the incidence of cholesterol gallstones by 75%, 27% and 76%, respectively, with attendant reduction in total cholesterol content by 38-42%, 50-72% and 61-80% in serum, liver and bile respectively. Consequently, the cholesterol/phospholipid ratio was reduced significantly in serum, liver and bile. The cholesterol saturation index of bile was reduced from 4.14 to 1.38 by the combination of fenugreek and onion and to 2.33 by onion alone. The phospholipid and bile acid contents of the bile were also increased. Changes in the hepatic enzyme activities (3-hydroxy-3-methylglutaryl Coenzyme A reductase, cholesterol-7α-hydroxylase and cholesterol-27-hydroxylase) induced by HCD were countered by fenugreek, onion and their combination. Hepatic lipid peroxides were reduced by 19-22% and 39-45% with fenugreek, onion and their combination included in the diet along with the HCD. Increased accumulation of fat in the liver and inflammation of the gallbladder membrane produced by HCD were reduced by fenugreek, onion and their combination. The antilithogenic influence was highest with fenugreek alone, and the presence of onion along with it did not further increase this effect. There was also no additive effect of the two spices in the recovery of antioxidant molecules or in the antioxidant enzyme activities.

Influence of dietary spices on the in vivo absorption of ingested ß-carotene in experimental rats.

Animal studies were conducted to evaluate the influence of dietary spice compounds, piperine, capsaicin and ginger, on the absorption of orally administered ß-carotene and its conversion to vitamin A. In rats maintained on these spice-containing diets for 8 weeks, concentrations of ß-carotene and retinol were determined in the serum, liver and intestine 4 h after a single oral administration of ß-carotene. ß-Carotene concentration was significantly increased in the serum, liver and intestine of piperine- and ginger-fed rats, suggesting improved absorption of ß-carotene. However, retinol concentration was not significantly changed in these animals, suggesting that the bioconversion of ß-carotene to vitamin A was not similarly influenced. Between the two enzymes involved in the bioconversion of ß-carotene to vitamin A, the activity of intestinal and hepatic ß-carotene 15,15'-dioxygenase was either unaffected or lowered by these spice treatments. The activity of intestinal and hepatic retinal reductase was unaffected by the dietary spices. Activities of these two enzymes involved in the bioconversion of ß-carotene to retinal were inhibited by the test spices in vitro, thus corroborating with the in vivo observation. Although the bioconversion of ß-carotene was not promoted, increased absorption and tissue levels of ß-carotene by the dietary spices may contribute to a higher antioxidant protection.

Promoting influence of combinations of amchur, ß-carotene-rich vegetables and Allium spices on the bioaccessibility of zinc and iron from food grains.

Deficiencies of iron and zinc among the population dependent on plant foods necessitate strategies to maximize their bioavailability. In this context, specific combinations of promoters of iron and zinc bioaccessibility-namely, amchur (0.75 g/10 g), ß-carotene-rich vegetables (2.5 g/10 g) and Allium spices (1.5 g/10 g)-were evaluated for a possible additive/synergistic effect on the bioaccessibility of iron and zinc from food grains. The positive influence on the bioaccessibility of iron was additive in the case of combinations of amchur-carrot, amchur-garlic, onion-carrot, and onion-amaranth in a few specific grains. Positive influence on the bioaccessibility of iron was even synergistic for combinations of amchur-onion and amchur-garlic in a few grains. The influence of amchur-garlic and amchur-onion was additive while the combination of amchur-amaranth and amchur-garlic produced a synergistic-promoting influence on zinc bioaccessibility in a few instances. This observation would be useful in evolving dietary strategies to maximize the bioavailability of minerals from grains.

Influence of combinations of promoter and inhibitor on the bioaccessibility of iron and zinc from food grains.

Inherent phytic acid and tannins interfere with bioavailability of iron and zinc from plant-based foods. Food acidulants, ß-carotene-rich vegetables and Allium spices are understood to promote mineral bioaccessibility (an estimate of bioavailability using in vitro method) from food grains. In this study, we have verified whether these promoters would counter negative effects of phytate and tannin on bioaccessibility of iron and zinc from grains. Combinations of promoters - amchur, carrot and onion with phytic acid and tannin exogenously added individually were examined for their influence on iron and zinc bioaccessibility from the food grain. Effect of these promoters was generally dominant in the presence of phytic acid or tannic acid. The negative effect of the inhibitor was not only annulled, but also the positive influence of the promoter was fully retained. This information helps to evolve diet-based strategy to maximize mineral bioavailability and prevent deficiency situations prevalent in population dependent on plant foods.

Beneficial influence of dietary spices on the ultrastructure and fluidity of the intestinal brush border in rats.

The beneficial influence of three common spices was examined in experimental rats on: (i) the membrane fluidity of intestinal brush-border membranes (BBM), (ii) the activity of intestinal membrane-bound enzymes, and (iii) ultrastructural alterations in the intestinal epithelium. Groups of male Wistar rats were maintained on dietary black pepper (0.5 %), red pepper (3.0 %), ginger (0.05 %) and spice bioactive compounds piperine (0.02 %) and capsaicin (0.01 %) for 8 weeks. A membrane fluidity study using an apolar fluorescent probe showed increased BBM fluidity in all the spice-fed animals. This was corroborated by a decreased cholesterol:phospholipid ratio in the jejunal and ileal regions of the intestine. These dietary spices stimulated the activities of BBM enzymes (glycyl-glycine dipeptidase, leucine amino peptidase and gamma-glutamyl transpeptidase) in the jejunal mucosa, suggesting a modulation in membrane dynamics due to the apolar spice bioactive compounds interacting with surrounding lipids and hydrophobic portions in the protein vicinity, which may decrease the tendency of membrane lipids to act as steric constraints to enzyme proteins and thus modify enzyme conformation. Scanning electronic microscopy of the intestinal villi in these spice treatments revealed alterations in the ultrastructure, especially an increase in microvilli length and perimeter which would mean a beneficial increase in the absorptive surface of the small intestine, providing for an increased bioavailability of micronutrients. Thus, dietary spices (black pepper, red pepper and ginger) were evidenced to induce alterations in BBM fluidity and passive permeability property, associated with the induction of an increased microvilli length and perimeter, resulting in an increased absorptive surface of the small intestine.

Beneficial effect of xylo-oligosaccharides and fructo-oligosaccharides in streptozotocin-induced diabetic rats.

The beneficial influences of xylo-oligosaccharides (XOS) obtained from alkali-pretreated corncob and fructo-oligosaccharides (FOS) obtained from cane sugar were evaluated in experimental diabetes. These oligosaccharides were supplemented at 10 % (w/w) in the basal diet of streptozotocin-induced diabetic Wistar rats, while the control rats were fed with a basal diet for a period of 6 weeks. Both the oligosaccharides exerted favourable influences in diabetic rats by significantly improving body weight and reducing hyperglycaemia and cholesterol. The characteristic diabetic complications such as severe glucosuria, proteinuria and advanced glycation end products in renal tissue, diabetic nephropathy, and blood creatinine and urea concentrations were notably reduced. Besides, these oligosaccharide supplementations significantly increased the activity of antioxidant enzymes - catalase and glutathione reductase - in the blood of diabetic rats. Supplementation of XOS and FOS resulted in a significant increase in the bifidobacteria and lactobacilli population in the caecum. The present study indicates that XOS and FOS have an ameliorating influence on metabolic abnormalities associated with diabetes, besides conferring an optimal milieu of lactobacilli and bifidobacteria, thus suggesting their potential health benefit in diabetics.