Transcriptional downregulation of sterol metabolism genes in murine liver exposed to acute hypobaric hypoxia.

Ascent to high-altitude results in decreased inspired partial pressure of oxygen because of a decrease in barometric pressure. Altitude acclimatization requires physiological and metabolic changes to improve tolerance to altitude hypoxia. Cellular response to hypoxia results into changes in the profile of gene expression and the present study explored the same in murine model. Liver being the largest metabolic organ, the molecular details of acute hypobaric hypoxia (AHH) induced transcriptional changes in the tissue were investigated. Swiss albino mice were exposed to hypobaric hypoxia ( approximately 426mmHg) in a decompression chamber and cDNA microarray was used to study the transcriptional profile in liver. Notably, by the tenth hour several of the genes involved in sterol metabolism such as SREBF1, INSIG1, HMGCS1, FDFT1, SQLE, and HSD3B4 were downregulated more than 2-fold suggesting that AHH suppresses sterol biosynthesis in the liver. Real-time PCR helped validate the downregulation of SREBF1, HMGCS1, FDFT1, and HSD3B4 genes. However, no significant change was observed in the serum cholesterol levels throughout the AHH exposure. The findings are indicative of transcriptional downregulation of SREBP target genes as a part of acclimatization response to hypoxia. The study highlights the significance of SREBP in the regulation of sterol metabolism under the acute hypoxic response.

Anti-stress and Adaptogenic Activity of l-Arginine Supplementation.

In the present study, oral supplementation of l-arginine in rats was evaluated for its anti-stress and adaptogenic activity using the cold (5 degrees C)-hypoxia (428 mmHg)-restraint (C-H-R) animal model. A dose-dependent study of l-arginine was carried out at doses of 12.5, 25.0, 50.0, 100.0, 200.0 and 500.0 mg/kg body weight, administered orally 30 min prior to C-H-R exposure. The time taken by the rat to attain a rectal temperature of 23 degrees C (T(rec) 23 degrees C) during C-H-R exposure and its recovery to T(rec) 37 degrees C at normal atmospheric pressure and 32 +/- 1 degrees C were used as biomarkers of anti-stress and adaptogenic activity. Biochemical parameters related to lipid peroxidation, anti-oxidants, cell membrane permeability, nitric oxide and stress, with and without administration of the least effective l-arginine dose, were measured in rats on attaining T(rec) 23 degrees C and T(rec) 37 degrees C. The least effective adaptogenic dose of l-arginine was 100.0 mg/kg body weight. The C-H-R exposure of control rats, on attaining T(rec) 23 degrees C, resulted in a significant increase in plasma malondialdehyde (MDA), blood lactate dehydrogenase (LDH) and a decrease in blood catalase (CAT) and plasma testosterone levels. On recovery (T(rec) 37 degrees C) of control rats, there was a further decrease in CAT and plasma testosterone, and an increase in LDH. l-Arginine supplementation resulted in a significant decrease in plasma MDA, an increase in blood superoxide dismutase (SOD), CAT levels maintained at control values and a lower increase in LDH compared with controls (45.3 versus 58.5% and 21.5 versus 105.2%) on attaining T(rec) 23 degrees C during C-H-R exposure and on recovery to T(rec) 37 degrees C. The results suggested that l-arginine possesses potent anti-stress activity during C-H-R exposure and recovery from C-H-R-induced hypothermia.

Association of high-altitude systemic hypertension with the deletion allele-of the angiotensin-converting enzyme (ACE) gene.

People who visit high-altitude areas are exposed to a stressful environment and a good percentage of them suffer from high-altitude-induced diseases, including systemic hypertension. Identification of genetic markers for high-altitude-induced diseases would help to reduce the rate of morbidity/mortality from such diseases. The development of systemic hypertension on exposure to high altitude (3,500 m) for 30 days in otherwise normotensive natives of low-altitudes was investigated. The angiotensin-converting enzyme (ACE) insertion/deletion (I/D) genotypes and renin-angiotensin-aldosterone system were simultaneously studied. In the hypertensives during their stay at high altitude, the ACE D allele frequency was significantly higher than in the normotensives (0.67 versus 0.32 chi(2)(1) = 10.6, P < 0.05). In the normotensives during their stay at high altitude, there was no significant increase in plasma aldosterone levels despite increased plasma renin activity. Results of the present study suggest that environmental changes and pre-existing genetic factors, namely the ACE D allele, might be two of the factors predisposing natives of low altitudes to systemic hypertension, a polygenic disease, at high altitude.

Angiotensin converting enzyme insertion allele in relation to high altitude adaptation.

Angiotensin converting enzyme (ACE) gene I/D polymorphism has been associated with high altitude (HA) disorders as well as physical performance. We, however, envisage that the polymorphism may be associated with adaptation to the hypobaric hypoxia of altitude, thus facilitating physical performance. For this purpose, three unrelated adult male groups, namely (1) the Ladakhis (HLs), who reside at and above a height of 3600 m, (2) lowlanders, who migrated to Ladakh (MLLs), and (3) resident lowlanders (LLs), have been investigated. The HLs had significantly (p & 0.001) greater numbers of the II homozygotes and the ID heterozygotes than the DD homozygotes, the genotype distribution being 0.46, 0.43 and 0.11 for II, ID and DD genotypes respectively. The MLLs comprised 60% II homozygotes, which was higher (p & 0.001) than the HLs (46%). In the LLs, the heterozygotes were greater (p & 0.001) in number than the II and DD homozygotes. The I allele frequency was 0.72 in the MLLs, 0.67 in the HLs and 0.55 in the LLs. Polymorphism study suggested that the II genotype could be associated with altitude adaptation, which might influence physical efficiency.

Effects of a composite Indian herbal preparation on combat effectiveness in low-intensity-conflict operations.

The efficacy of a composite Indian herbal preparation (CIHP) in sustaining the mental performance of soldiers engaged in prolonged low-intensity-conflict operations has been evaluated. For this purpose, a cohort of 56 soldiers acted as volunteers in combat situations. After recording their initial responses to psychological tests such as the d2 test, the trail-making test, the serial addition test, the short-term memory test, and the Institute for Personality and Ability Testing Anxiety Scale, they were randomly given either CIHP or placebo in a double-blind fashion for 8 days while they performed their usual combat duties. The final 3 days of assignments included physically exhausting and life-threatening events. On day 8, they were withdrawn from combat duties and the psychological tests were readministered immediately. After 7 days of rest, the tests were repeated once again. The results indicate comparatively better performance immediately after the mission by the CIHP group. CIHP was effective at sustaining the mental abilities of soldiers in a low-intensity-conflict environment.

Enhanced thermogenesis in rats by a composite Indian herbal preparation-I and its mechanism of action.

OBJECTIVE: A composite Indian herbal preparation-I (CIHP-I) containing ingredients derived from 7 different plants and asphalt was tested for its adaptogenic activity and its mechanism of action was investigated. DESIGN: CIHP-I was tested using the cold-hypoxia-restraint (C-H-R) animal model in which the restrained rats were exposed to 5 degrees C at 428 mm Hg atmospheric pressure. Rectal temperature (Trec) of the rats was continuously monitored during the exposure and the recovery periods. The time for fall of Trec to 23 degrees C and its recovery to 37 degrees C were used as indices of endurance and the adaptogenic activity. Carbohydrate and lipid parameters were investigated to find out the nature of fuel being used during thermogenesis. RESULTS: After 12 weeks of administration of an oral dose of 7.5 mg/kg(-1)/day(-1), CIHP-I was found to possess significant adaptogenic activity. CIHP-I helped improve resistance to C-H-R induced hypothermia (Trec 23 degrees C) in animals by increased mobilization of free fatty acids (FFA) from adipose tissue. Blood glucose and muscle glycogen levels were maintained. CIHP-I treatment restricted the release of creatine phosphokinase (CPK) into the circulation during C-H-R exposure. CONCLUSIONS: The results suggested that CIHP-I is a strong adaptogen. It improved cold resistance during C-H-R exposure and enhanced recovery from hypothermia. The energy-dependent cell membrane permeability was maintained. Stored lipids were mobilised and possibly used for thermogenesis in preference to carbohydrates.

Improved high altitude hypoxic tolerance and amelioration of anorexia and hypophagia in rats on oral glutamate supplementation.

BACKGROUND: The objective of this study is to evaluate the efficacy of oral glutamic acid supplementation in promoting hypoxic tolerance. METHODS: The experiments were conducted in albino rats by exposing them to three levels of hypoxia in a simulated environment for varying periods of time. The parameters studied include: gasping time at 35,000 ft (10,668 m), food and water intake, and heart to body weight (b.w.) ratio at 25,000 ft (7620 m), tolerance to composite stress at 15,000 ft (4572 m) and biodistribution of glutamate (glu). RESULTS: Supplementation of Glu (27 mg x kg(-1) b.w.) as glutamic acid dissolved in normal saline resulted in 4.8 times enhanced hypoxic tolerance (time taken for appearance of first gasp), 23% body weight gain and 24% increase in food consumption over control during hypoxia. When animals were subjected to composite stress of cold, hypoxia and restraint (CHR), the Glu fed animals showed higher resistance to fall in rectal temperature than the control group. Hypoxia significantly enhanced heart to body weight ratio compared with control, and Glu supplementation reduced and brought it down to that of control. CONCLUSION: The study reveals that Glu in optimal doses may be a conditionally essential amino acid resulting in enhanced tolerance to hypoxia and cold.

Enhanced thermogenesis in rats by Panax ginseng, multivitamins and minerals.

Substances which enhance endurance for physical and mental work and increase non-specific resistance to stress during a prolonged stay in physiologically adverse habitats are called 'adaptogens'. Panax ginseng is well known for its anti-stress and adaptogenic properties. In the present study, adaptogenic activity by the intake of a herbo-vitamin-mineral preparation (HVMP) containing P. ginseng and multivitamin-mineral preparation (MVMP) was evaluated using the cold-hypoxia-restrained (C-H-R) animal model. The aim was to determine whether the cold tolerance and recovery from acute hypothermia mediated by P. ginseng was modified by simultaneous intake of additional vitamins and minerals. Results suggest that the adaptogenic effect of HVMP was more or less the sum total of its two components P. ginseng and MVMP. In HVMP, P. ginseng was found to be effective for developing resistance to cooling and MVMP helped in stimulating faster recovery from acute hypothermia.

Phosphoinositides of sheep platelets plasma membranes.

Phospholipid composition of sheep blood platelets and its various plasma membrane fractions have been analyzed. Based on their flotation rates in discontinuous sucrose density gradient centrifugation, three membrane fractions were isolated. 5'-Nucelotidase and alkaline phosphatase were distributed nearly equally in all the three membrane fractions. However these membrane fractions showed differences in the distribution of phosphatidyl ethanolamine, phosphatidyl choline and phosphoinositides. Phosphatidyl ethanolamine was predominant in fraction I (11.05 micrograms PLP/mg protein) while phosphatidyl choline was predominant in fractions II and III (110.10 and 68.30 micrograms PLP/mg protein respectively). Phosphatidyl inositol (Ptd-InsP) was equally distributed in all three membrane fractions. However, both Ptd-InsP and phosphatidyl inositol 4,5-bisphosphate were about 4-fold higher in fraction II (73.55 and 89.89 micrograms PLP/mg protein respectively).

New experimental model for the evaluation of adaptogenic products.

A new animal model for evaluating improvement in physical work performance and endurance in an adverse environment is described. In this model, rats in restraint were exposed to 5 degrees C at 480 mmHg atmospheric pressure. Results were compared to an animal forced to swim in water at 23 degrees C. In both the models, colonic temperature (Tr) of the rats was continually monitored during exposure to adverse environment and during recovery at 32 degrees C and normal atmospheric pressure. The time and pattern for Tr fall to 23 degrees C and its recovery to 37 degrees C were used as measures of endurance. The cold-hypoxia-restraint model was found to provide more precise results compared with the cold-swimming model. Panax ginseng root and Ginkgo biloba leaf extracts were compared for their positive endurance-promoting properties using both models.

Effect of simulated hypoxia (7620 m, 6 h) on hepatic microsomal drug metabolising enzymes activity in rats given ethanol and vitamin A.

The hepatic MFO activity has been studied in rats exposed to acute hypoxia given single dose of ethanol (3 g/kg body weight) alone or along with 10,000 I.U. of vitamin A. The cytochrome P-450 was found to be depressed on ethanol administration in rats. Hypoxic exposure of rats given ethanol with or without vitamin A, however, restored the depressed cytochrome P-450 activity. Cytochrome-c-reductase, on the other hand, was increased on administration of ethanol with or without vitamin A supplementation. Exposure to hypoxia did not have any additional effect on cytochrome c-reductase activity. Aminopyrine-N-demethylase was depressed on ethanol administration. Vitamin A administration further depressed this enzyme. Hypoxic exposure, however, did not restore this enzyme level. Aniline hydroxylase was not affected by ethanol administration, vitamin A supplementation and hypoxic exposure. Thus, mixed function oxidase system appears to be differently affected on ethanol administration, vitamin A supplementation and hypoxic exposure suggesting that these effectors have different loci of interaction in microsomal structure and/or in its micromileau of cofactors.

Interaction of ethanol and acute hypoxia (7620 m) on vitamin A distribution in rat organs.

The effect of a moderate dose of ethanol (3 g/kg body weight) and acute hypoxia (282 mmHg pressure) for 6 h on vitamin A content of rat tissue has been investigated. In addition, to find the effect of ethanol administration and hypoxic exposure on freshly absorbed vitamin A, a tracer dose of 3H-retinyl acetate was administered prior to hypoxic exposure. The results indicate that ethanol and hypoxia interfere in the transfer of vitamin A stored as well as freshly absorbed, from intestine to liver. When ethanol administered rats were exposed to hypoxia, the secretion of vitamin A from liver is also disturbed. The vitamin A metabolism in the tissues like kidney and lung are affected adversely on ethanol administration and/or hypoxic exposure. This could be due to interference in the transfer of vitamin A from intestine to liver and secretion of vitamin A from liver into plasma.

Effect of vitamin A on hepatic microsomal drug metabolising enzymes activity in rats exposed to acute hypoxia.

The hepatic drug metabolising enzymes activity has been studied in rats exposed to acute hypoxia alone or along with supplementation of single dose of 10 000 I.U. Vitamin A. Hypoxic stress reduces the activities of cytochrome P-450, cytochrome c-reductase and aniline hydroxylase. Administration of single dose of 10 000 I.U. of Vitamin A to the rats 12 h before hypoxia reverses the effect of hypoxia on these enzymes. Thus Vitamin A seems to play a protective role in rats exposed to hypoxia on the activity of MFO system.

Effect of restricted potassium intake on its excretion and on physiological responses during heat stress.

The effect of low potassium (K+) intake on its excretion, concentration in sweat and on physiological responses during heat stress was evaluated on eight Indian male soldiers in winter months at Delhi. After a stabilization period of 3 days on each diet, i.e., 85 mEq of K+/d (diet I, normal), 55 mEq of K+/d (diet II), and 45 mEq of K+/d (diet III), the physiological responses and the sodium and potassium concentrations in sweat, plasma, RBC, and urine were measured when the subjects were exposed to heat for 3 h daily in a climatic chamber maintained at 40 degrees C DB and 32 degrees C WB. The subjects worked in the chamber at the rate of 465 W/h for 20 min periods with 40 min rest between each period of exercise. The whole body sweat was collected after the spell of work and was analysed for sodium and potassium levels. Throughout the study the subjects remained on positive sodium balance except on day 4 in diet III. Fluid balance also remained positive while potassium balance was negative in subjects on diet II and diet III. There was no significant change in heart rate, sweat volume, oral temperature, sodium, and potassium concentrations in plasma and RBC during the entire period of the study. Even in the subjects with negative potassium balance there was no change in the sodium and potassium concentrations in sweat during exercise in heat. The only evidence of potassium conservation was a reduced excretion in urine. Out of the eight subjects, in one subject there was a flattening of the 'T' wave in the ECG and reduction in amplitude of the 'T' wave in two more subjects. As there is no reduction in sweat potassium concentration and the urine volume is low, the marginal level of reduced excretion of potassium in urine with a high rate of sweating (7-81) in subjects doing work in the tropics, there is every likelihood of potassium deficiency if a liberal intake is not ensured. In our earlier studies (Malhotra et al. 1976) we found that the concentration of potassium (K+) in sweat is much higher than in plasma even in acclimatised subjects. A large amount of K+ is therefore likely to be lost in sweat during exposure to heat. In that study there was no evidence of a reduction in K+ concentration in the sweat or urine upon repeated exposure of the subjects to heat, indicative of a compensatory mechanism for conservation of K+ losses. However, these earlier studies were done on subjects who were on a normal diet which contained 75-80 mEq of K+ per day. Since a compensatory mechanism may be triggered only when the body K+ becomes dificient and not earlier, as is the case with sodium (Malhotra et al. 1959), we have now investigated the effects of a sequential reduction of reduced dietary K+ on the dermal and urinary losses of K+. The effects of K+ deficiency on the physiological responses to heat have also been studied. The results of these studies are reported here.

Glucose tolerance of lowlanders during prolonged stay at high altitude and among high altitude natives.

The fasting blood sugar level and glucose tolerance were investigated in seven amle lowlanders at sea level, during their stay at an altitude of 4,000 m at intervals of 2 weeks, 10, 15, 20, and 24 months and again on return to sea level during the first week and after 1 month. For comparison, the glucose tolerance of six male Ladakhis (natives of high altitude area) was also determined at altitude. The fasting blood sugar among lowlanders increased to 136.0 plus or minus 4.39 mg per 100 ml during 10 months of stay at altitude followed with a gradual decrease to a value of 76.4 plus or minus 3.8 at the end of 24 months. On return to sea level, the blood glucose showed a tendency to increase. Ladakhis had a lower blood sugar level at altitude (86.4 plus or minus 7.28) as compared with lowlanders at sea level (92.6 plus or minus 2.29). The glucose tolerance curves of lowlanders ran paralell to each other at altitude and at sea level. However, the peak of the glucose tolerance curve shifted towards the left during the 20th and 24th months of stay at altitude and at sea level. However, the peak of the glucose tolerance curve shifted towards the left during the 20th and 24th months of stay at altitude and on return to sea level. The tolerance curve of Ladakhis was similar to that of lowlanders at altitude, but showed a sharper blood sugar decline rate.