Praveen Vats

EFFECT OF AN ANTIDIABETIC EXTRACT OF CATHARANTHUS ROSEUS ON ENZYMIC ACTIVITIES IN STREPTOZOTOCIN INDUCED DIABETIC RATS

Hypoglycemic activity was detected in dichloromethane:methanol extract (1:1) of leaves and twigs of Catharanthus roseus (family Apocynaceae), a traditionally used medicinal plant, using streptozotocin (STZ) induced diabetic rat model. Extract at dose 500 mg/kg given orally for 7 and 15 days showed 48.6 and 57.6% hypoglycemic activity, respectively. Prior treatment at the same dose for 30 days provided complete protection against STZ challenge (75 mg/kg/i.p.x1). Enzymic activities of glycogen synthase, glucose 6-phosphate-dehydrogenase, succinate dehydrogenase and malate dehydrogenase were decreased in liver of diabetic animals in comparison to normal and were significantly improved after treatment with extract at dose 500 mg/kg p.o. for 7 days. Results indicate increased metabolization of glucose in treated rats. Increased levels of lipid peroxidation measured as 2-thiobarbituric acid reactive substances (TBARS) indicative of oxidative stress in diabetic rats were also normalized by treatment with the extract.

Ghrelin and leptin levels of sojourners and acclimatized lowlanders at high altitude.

Abstract The circulatory levels of two appetite regulatory hormones i.e. leptin and ghrelin were estimated in sojourners and acclimatized subjects to investigate their possible role in high altitude (HA) induced anorexia. A group of 30 lowlanders who had never visited HA were inducted to a height of 3600m by air and after 48h they were further taken to an altitude of 4300m by road. Blood samples were collected after 48h stay at 3600m and again after 48h and 7 days of stay at 4300m during 0700–0730h. There was a decrease in energy intake (850kcal/day) of sojourners, which resulted in loss of body weight by 2.12kg at HA. At an altitude of 4300m there was a significant increase in leptin over basal levels (54.9%, p <0.001) at 48h that persisted even after 7 days of stay at this altitude. Ghrelin levels of sojourners decreased by more than 30% in comparison to basal values at 48h of ascent to HA. Leptin levels of acclimatized lowlanders were also higher in comparison with control group (acclimatized group 7.6+0.6ng/ml vs. control 5.6+0.5ng/ml, p <0.01, n =50).

Effect of high altitude (7,620 m) exposure on glutathione and related metabolism in rats

Abstract Reduced and oxidised glutathione (GSH and GSSG) contents, and glutathione reductase, and glutathione S-transferase activities were studied in the livers, muscles, and blood/erythrocytes of male Sprague-Dawley rats exposed to intermittent hypoxia (6 h · day−1) at a simulated altitude of 7,620 m for 1, 7, 14, and 21 days. Significant decreases in GSH and increases in GSSG contents were observed in the muscles and blood of hypoxia-exposed rats in comparison to unexposed rats. Significant declines in GSH content by 43% and 45% respectively in muscles and blood were observed in the group exposed for 1 day which tended to recover on subsequent exposure. Glutathione reductase and glutathione S-transferase activities were decreased in the livers and erythrocytes of hypoxia-exposed rats, but were increased significantly in muscle. Lipid peroxidation was also increased in the livers and muscles of exposed rats. The changes were indicative of an increased production of reactive oxygen species and an impairment of drug and xenobiotic metabolism during exposure to high altitude hypoxia.

L-carnitine supplementation attenuates intermittent hypoxia-induced oxidative stress and delays muscle fatigue in rats.

The concept of l‐carnitine (l‐CAR) supplementation to improve muscular performance is based on the role of l‐CAR in regulating aerobic metabolism. l‐CAR has also been found to attenuate free radical‐induced oxidative stress in various pathological conditions. Thus, it was hypothesized that l‐CAR may reduce intermittent hypoxia (IH)‐induced oxidative stress and thereby benefit skeletal muscle performance. Thirty‐six adult male Sprague–Dawley rats were divided into three groups: unexposed control; IH exposed (6 h day−1 for 7 consecutive days), IH exposed with l‐CAR supplementation (100 mg (kg body weight)−1 day−1). Electrical stimulation was used to induce six tetanic muscular contractions in the gastrocnemius muscle after completion of exposure. Percentage mean performed work (PW), time of decay to 50% peak force of contraction (T50), and peak force of contraction (FPeak) were measured during tetanic contractions. Mean frequency (MF) was measured using electromyography between tetanic contractions. Muscle damage was indirectly measured from plasma creatine kinase (CK) and lipid hydroperoxide (LHP) levels. The levels of thiobarbituric acid reactive substances (TBARS), protein carbonyl (PC) and LHP were estimated in the muscle tissue to investigate the efficacy of l‐CAR in attenuating oxidative stress. Significant reduction in TBARS, PC and LHP levels and CK activity in the l‐CAR‐supplemented IH group as compared to the IH placebo group suggests that l‐CAR reduces oxidative damage and thereby delays muscular fatigue, which was evident from MF, T50, PW and FPeak. From these studies, we conclude that l‐CAR delays muscle fatigue by the reducing free radical‐induced oxidative damage of IH exposure.

High altitude induced anorexia: Effect of changes in leptin and oxidative stress levels

Abstract High altitude (HA) exposure usually leads to a significant weight loss in non-acclimatized humans. Anorexia is believed to be the main cause of this body weight loss. Appetite regulatory peptides, i.e. leptin and neuropeptide Y play a key role in food intake and energy homeostasis. Recent studies suggests increased oxidative stress during HA exposure. In present study effect of HA exposure on levels of leptin and NPY was evaluated along with N-acetyl cysteine (NAC) and vitamin E supplementation in relation to food intake and body weight changes. The study was conducted on 30 healthy male volunteers (age 19 – 29 years). Subjects were divided randomly into three groups of 10 each. Group 1 (placebo) supplemented with 400 mg of calcium gluconate, group 2 and 3 were supplemented with 400 mg of NAC and 400 mg vitamin E, respectively per day. The study was conducted at low altitude (320 m, Phase I), at HA 3600 m (Phase II) and at an altitude of 4580 m (Phase III). On HA exposure significant reduction in plasma leptin levels was observed in all the groups on day 2 (Phase II) along with decrease in food intake and reduction in body weight. Statistically significant increase in blood malondialdehyde (MDA) levels was seen in all the groups on HA exposure (Phase II, Day 2), but the maximum increase was in case of placebo group (65.1%) on day 2 (Phase II) in comparison to low altitude values. The decrease in energy intake was almost same in all the groups indicating that antioxidant supplementation did not provide any protection against HA anorexia. From the study, it may be concluded that leptin and oxidative stress possibly are not the key players for HA anorexia.

Changes in cardiovascular functions, lipid profile, and body composition at high altitude in two different ethnic groups.

High altitude (HA) presents inhospitable environmental conditions that adversely affects human physiology and metabolism. Changes in physiological functions are reported during high altitude exposure, but the changes vary with physical state, culture habits, geographical locations, and genetic variation of individual. The present study was carried out to explore the variation in acclimatization pattern of two different ethnic groups in relation to cardiovascular functions, lipid profile and body composition. The study was carried out on 30 human volunteers (20 Indian and 10 Kyrgyz) initially at Bishkek for basal recording and on day 3, 7, 14, and 21 of high altitude (3200 m) induction and again on day 3 of de-induction. On altitude exposure significant decrease in body weight was observed both in Indian (day 14, p<0.001) and Kyrgyz (day 3, p<0.01) subjects. Decreased levels of total body water, extra cellular and intra cellular body water were also observed in both the groups. Significant reduction in body mass index (p<0.01), fat free mass (p<0.01), body cell mass (p<0.01) and body volume (p<0.01) was also observed in Kyrgyz subjects, whereas in Indian subjects the changes were not significant in these variables on high altitude exposure. Diastolic blood pressure and heart rate increased significantly on day 3 (p<0.001 and p<0.01, respectively) of induction in Indian subjects; whereas in Kyrgyz significant increase was observed on day 14 (p<0.05) in both the cases. High density lipoprotein (HDL) cholesterol levels increased significantly on day 7 of HA exposure in both the groups. Results indicate that the Indian and Kyrgyz groups report differently, in relation to changes in cardiovascular functions, lipid profiles, and body composition, when exposed to HA. The difference observed in acclimatization pattern in the two groups may be due to ethnic/genetic variation of two populations.

Glutathione Metabolism Under High-Altitude Stress and Effect of Antioxidant Supplementation

INTRODUCTION Humans have a number of mechanisms for protection against reactive oxygen species, but under stressful conditions these defenses are not completely successful. Glutathione plays an important role in protection against free radicals and reactive oxygen species induced damages. The present study was undertaken to understand the effect of high-altitude (HA) exposure on glutathione metabolism and antioxidant status along with the effects of N-acetyl cysteine (NAC) and vitamin E supplementation in humans. METHODS The study was conducted on 30 healthy male volunteers (age 22.9 +/- 2.6, mean +/- SD) divided into three groups. Group 1 was placebo control and 2 and 3 were supplemented with 400 mg of NAC or vitamin E, respectively, per day. The study was conducted initially at sea level (Phase I, 320 m); then the subjects were taken to high altitude (Phase II, 3600 m) by air. After a week at this altitude, subjects ascended on foot to an altitude of 4580 m (Phase III). RESULTS Significant decreases in reduced glutathione and increases in oxidized glutathione levels were observed on HA exposure. Increase in glutathione peroxidase and glutathione reductase levels were also observed on HA exposure. Lower levels of plasma vitamin C and total antioxidant status were observed during HA exposure. The changes observed were less in the supplemented groups as compared to placebo control. DISCUSSION Results indicate that HA exposure adversely affects glutathione metabolism and antioxidant defense mechanisms and these changes can be ameliorated through supplementation of NAC and vitamin E.

Appetite regulatory peptides in Indian Antarctic expeditioners

Abstract Antarctica presents an inhospitable environment due to extreme low temperature, high wind velocity, low humidity, snowstorms, long polar days and nights, high level of UV radiations, magnetic storms and increased ionisation along with social isolation and sexual deprivation. Acclimatisation to any new condition is associated with certain metabolic changes along with alteration in nutritional requirements. There are reports of increased food intake and gain in body weight during past Indian Antarctic expeditions. Therefore, the present study was undertaken with the aim to assess the changes in appetite regulatory peptides i.e. leptin and neuropeptide Y in relation to energy intake and expenditure of the Antarctic expeditioners. The study was conducted in three phases viz. Phase I at Goa (basal), Phase II 48 h after reaching Antarctica and Phase III after one month of stay at Antarctica. Energy and nutrient intake were analysed from the duplicate plate samples of the expeditioners. Energy expenditure was computed using 24 h activity records for 7 days. Blood samples were collected in each phase for biochemical estimations. After reaching Antarctica, the expeditioners were active and the total energy expenditure (mean ± SEM, n = 10) was found to be 3120 ± 474 kcal/day. The actual energy intake was found to be 3911 ± 310 kcal/day. This indicates that the Antarctic expeditioners had very active life and weight gain during expedition could be due to positive energy balance. After 48 h of stay at Antarctica plasma leptin levels (mean ± SEM, n = 22) decreased from normal basal values 5.66 ( ± 0.59) ng/ml (Phase I) to 4.40 ( ± 0.37) ng/ml (Phase II), even though there was an increase in body fat. Increased level of plasma leptin was observed in Phase III as compared to phase I and II. Concomitantly there was increase in plasma neuropeptide Y levels from 0.303 ( ± 0.004) ng/ml to 1.211 ( ± 0. 27) ng/ml ( p

Hypobaric hypoxia induced arginase expression limits nitric oxide availability and signaling in rodent heart

BACKGROUND This study was aimed to evaluate regulation of cardiac arginase expression during hypobaric hypoxia and subsequent effect on nitric oxide availability and signaling. METHODS Rats were exposed to hypobaric hypoxia (282mmHg for 3h) and ARG1 expression was monitored. The expression levels of eNOS and eNOS(Ser1177) were determined by Western blotting, cGMP levels were measured by ELISA and amino acid concentrations were measured by HPLC analysis. Transcription regulation of arginase was monitored by chromatin immunoprecipitation (ChIP) assay with anti-c-Jun antibody for AP-1 consensus binding site on ARG1 promoter. Arginase activity was inhibited by intra-venous dose of N-(ω)-hydroxy-nor-l-arginine (nor-NOHA) prior to hypoxia exposure and subsequent effect on NO availability and oxidative stress were evaluated. RESULTS Hypobaric hypoxia induced cardiac arginase expression by recruiting c-Jun to AP-1 binding site on ARG1 promoter. This increased expression redirected l-arginine towards arginase and resulted in limited endothelial nitric oxide synthase (eNOS) activity, nitric oxide (NO) availability and cGMP mediated signaling. Inhibition of arginase restored the eNOS activity, promoted cardiac NO availability and ameliorated peroxynitrite formation during hypoxia. CONCLUSIONS Hypoxic induced arginase under transcription control of AP-1 reciprocally regulates eNOS activity and NO availability in the heart. This also results in cardiac oxidative stress. GENERAL SIGNIFICANCE This study provides understanding of hypoxia-mediated transcriptional regulation of arginase expression in the heart and its subsequent effect on eNOS activity, NO availability and signaling as well as cardiac oxidative stress. This information will support the use of arginase inhibitors as therapeutics for pathological hypoxia.

Role of neuropeptide Y and galanin in high altitude induced anorexia in rats.

Anorexia causing weight loss at high altitude (HA) is a major problem. Neuropeptide Y (NPY) and galanin are considered to have appetite regulatory function. The present study was therefore undertaken to investigate the changes in these two peptides at simulated HA and its possible role in anorexia. Male Sprague-Dawley rats (n = 8 in each group) were exposed to simulated HA (7620 m) for 1, 7, 14 and 21 days for 6h a day and to an altitude of 6096 m for 72h to study the effect of intermittent and continuous exposure, respectively. NPY and galanin levels were estimated in different brain parts and plasma of exposed and unexposed control animals. Significant reduction in food intake was observed in rats during both intermittent as well as continuous exposure. In case of 72h continuous exposure severe reduction in food intake was observed (73.2%) with reduction in body mass (∼29.7 g/rat in 48h). Hypothalamic NPY levels were decreased by 54.7, 35.0 and 15.4% in 1, 7, and 14 days, respectively, in case of intermittent exposure to HA. However in case of 72 h HA exposure no significant change in hypothalamic and circulating NPY levels were observed. Plasma galanin levels were decreased in both intermittent and 72h continuous HA exposed rats. Hypothalamic galanin levels were also decreased in 72h exposed rats. The changes in levels of these peptides may be responsible for anorexia at HA.