Anti-Mullerian Hormone and Macrophage Migration Inhibitory Factor Determine the Reproductive Health of Ladakhi Women Residing at 3,500 m.

Shaw, Snigdha, Himashree Gidugu, Gopinath Bhaumik, Maramreddy Prasanna Kumar Reddy, Usha Panjwani, and Dishari Ghosh. Anti-Mullerian hormone and macrophage migration inhibitory factor determine the reproductive health of Ladakhi women residing at 3,500 m. High Alt Med Biol. 22:317-326, 2021. Background: Reproductive health of Ladakhi high-altitude (HA) native females was investigated for the first time in this study. Available literature suggest that, female reproductive cycle and hormonal profile varies in different HA populations due to heterogeneity. Although these studies illustrate some progress on the role of HA hypoxia, it still leaves scope for evaluation of the remaining mechanisms involved in the maintenance of reproductive health in this contemporary population. Materials and Methods: Menstrual details, phasic variations in circulatory steroid hormones, and gonadotropins along with oxytocin in sea level (SL) and HA (∼3,500 m) native females of India were assessed. Moreover, ovarian reserve marker anti-Mullerian hormone (AMH) and proinflammatory cytokine macrophage migration inhibitory factor (MIF) were measured. Results: A difference in Ladakhi women was registered compared to SL, regarding luteinizing hormone (LH) (2.6 mIU/ml vs. 4.4 mIU/ml, p < 0.05) and progesterone (P) (4.1 ng/ml vs. 9.4 ng/ml, p < 0.05) levels in their luteal phase. Reduced LH might contribute to poor development of the ovarian corpus luteum, subsequently diminish P level. Decreased AMH level in three age groups: 21-30 years (1.4 ng/ml vs. 3.2 ng/ml, p < 0.01), 31-40 years (0.6 ng/ml vs. 2.1 ng/ml, p < 0.01), and >40 years (0.4 ng/ml vs. 1.7 ng/ml, p < 0.01) of Ladakhi women were recorded than their SL counterpart. Elevated oxytocin (83.5 ng/ml vs. 76.3 ng/ml, p < 0.05) and MIF levels (70.2 ng/ml vs. 49.7 ng/ml, p < 0.01) along with low P and AMH levels delineated the reason for recorded early menopause (43.9 years), shorter reproductive span (∼29 years), and history of miscarriage in HA dwellers compared to SL. Conclusion: Therefore, the findings insinuated that the response of the reproductive system to hypoxia in Ladakhi women differs from SL women, and the adaptive response in these women might be in favor of their reproductive health.

Estrogen receptor (ESR1 and ESR2)-mediated activation of eNOS-NO-cGMP pathway facilitates high altitude acclimatization.

Higher levels of circulatory nitric oxide (NO) and NO metabolites reportedly facilitate high altitude acclimatization. But the underlying factors and molecular pathways promoting NO production at high altitude has been poorly characterized. Studying healthy lowlanders at sea level (C, lowlander) and high altitude (3500 m, after day 1, 4 and 7 of ascent), we report higher protein levels of eNOS and eNOSSer1177, higher plasma levels of BH4, NOx (nitrate and nitrites), cGMP and lower levels of endogenous eNOS inhibitor ADMA during healthy high altitude acclimatization. Our qRT-PCR-based gene expression studies identified higher levels of eNOS/NOS3 mRNA along with several other eNOS pathway genes like CALM1, SLC7A1 and DNM2. In addition, we observed higher mRNA levels of estrogen (E2) receptors ERα/ESR1 and ERß/ESR2 at high altitude that transcriptionally activates NOS3. We also observed higher mRNA level of membrane receptor ERBB2 that phosphorylates eNOS at Ser1177 and thus augments NO availability. Evaluating E2 biosynthesis at high altitude, we report higher plasma levels of CYP11A1, CYP19A1, E2, lower levels of testosterone (T) and T/E2 ratio as compared to sea level. Correlation studies revealed moderate positive correlation between E2 and NOx (R = 0.68, p = 0.02) after day 4 and cGMP (R = 0.69, p = 0.02) after day 7 at high altitude. These findings suggest a causative role of E2 and its receptors ESR1 and ESR2 in augmenting eNOS activity and NO availability during healthy high altitude ascent. These results will aid in better understanding of NO production during hypobaric hypoxia and help in designing better high altitude acclimatization protocols.

Alterations of estrous cycle, 3ß hydroxysteroid dehydrogenase activity and progesterone synthesis in female rats after exposure to hypobaric hypoxia.

The underlying mechanism regulating hypoxia induced alteration in female steroid hormones is first time explored in this study. To understand the mechanistic approach, female Sprague- Dawley rats were exposed to acute and chronic hypobaric hypoxia (282 mm-Hg, ~7620 m, 6 hours, 3 and 7 days). Estrous cycle, body weight, plasma progesterone and estradiol levels, morphology, histology and two key steroidogenic enzymes: 3ß hydroxysteroid dehydrogenase (HSD) and 17ß HSD activity of ovary and adrenal gland were studied. A persistent diestrous phase and a significant decrease in body weight were found in chronic hypoxia groups. Histological study suggested degenerative changes in ovarian corpus luteum of 7 days chronic hypobaric hypoxia (7CHH) group and a declined percentage of adrenocortical cells in 3 days chronic hypobaric hypoxia (3CHH) and 7CHH groups. Plasma estradiol level was unaltered, but progesterone level was decreased significantly in all hypoxic groups. Ovarian 3ß HSD activity was decreased significantly with increasing days of hypoxic treatment along with a significantly low adrenal 3ß HSD activity in 7CHH. In conclusion, hypobaric hypoxia causes a state of low circulatory progesterone level in females likely due to the degenerative changes in the female ovarian and adrenal tissues together with low steroidogenic 3ß HSD enzyme activity.

Intermittent normobaric hypoxia facilitates high altitude acclimatization by curtailing hypoxia-induced inflammation and dyslipidemia.

Intermittent hypoxic training (IHT) is a discrete cost-effective method for improving athletic performance and high altitude acclimatization. Unfortunately, IHT protocols widely vary in terms of hypoxia severity, duration, and number of cycles affecting physiological outcomes. In the present study, we evaluated the efficacy of a moderate normobaric IHT protocol (12% FiO2 for 4 h, 4 days) on acclimatization to high altitude (3250 m). Global plasma proteomics studies revealed that IHT elicited acute-phase response proteins like C-reactive protein (CRP), serum amyloid A-1 protein (SAA), and alpha-1-acid glycoprotein 2 (AGP 2) as well as altered levels of several apolipoproteins. On subsequent exposure to high altitude, the IH trained volunteers exhibited significant higher arterial oxygen saturation with concomitant lower incidences of acute mountain sickness (AMS) as compared to controls. Interestingly, IH trained subjects exhibited lower levels of positive acute-phase proteins like C-reactive protein (CRP), serum amyloid A-1 protein (SAA), and fibrinogen (FGA, FGB, and FGG) both after days 4 and 7 of high altitude ascent. High altitude exposure also decreased the levels of HDL, LDL, and associated proteins as well as key enzymes for assembly and maturation of lipoprotein particles like lecithin-cholesterol acyltransferase (LCAT), cholesteryl ester transfer protein (CETP), and phospholipid transfer protein (PLTP). In contrast, IHT curtailed hypoxia-induced alterations of HDL, LDL, Apo-AI, Apo-B, LCAT, CETP, and PLTP. Further validation of results also corroborated attenuation of hypoxia-induced inflammation and dyslipidemia by IHT. These results provide molecular evidences supporting the use of moderate IHT as a potential non-pharmacological strategy for high altitude acclimatization.

Plasma kallikrein-bradykinin pathway promotes circulatory nitric oxide metabolite availability during hypoxia.

Nitric oxide (NO) is an indispensible signalling molecule under hypoxic environment for both ethnic high altitude natives as well as lowland residents at high altitude. Several studies have reported higher levels of NO and bioactive NO products for both high altitude natives as well as healthy high altitude sojourners. But the metabolic pathways regulating the formation of NO and associated metabolites during hypoxia still remain elusive. In the present study, we profiled plasma proteomes of Ladakhi natives (3520 m) and lowland residents (post 1, 4 and 7 days stay) at the same altitude. This has resulted in the identification of 208 hypoxia responsive proteins (p < 0.05) and kininogen-plasma kallikrein-bradykinin as a major pathway regulating eNOS activity during hypoxia. In corroboration, we have also observed significant higher levels of plasma biomarkers for NO production (l-citrulline, nitrite, nitrate) for Ladakhi natives as compared to both lowland individuals healthy high altitude sojourners indicating higher NO availability. Since hypoxia-induced free radicals reduce NO availability, we also measured plasma levels of 8-isoprostanes, protein carbonyls and protein oxidation products in both Ladakhi natives and high altitude sojourners. Interestingly Ladakhi natives had significant lower levels of oxidative stress in comparison to high altitude sojourners but higher than lowland controls. These results suggest that plasma kallikrein-bradykinin-eNOS pathway along with moderate oxidative stress contributes to high altitude adaptation of Ladakhi natives.

Maximum exercise responses of men and women mountaineering trainees on induction to high altitude (4350 m) by trekking.

OBJECTIVE: Maximum aerobic capacity decreases at high altitude. This study was conducted to compare the changes in maximum aerobic capacity in men and women mountaineering trainees on induction to high altitude at 4350 m by trekking. METHODS: Eight men and 8 women mountaineering trainees in a mountaineering course were selected for the study. The initial study was conducted at 2100 m (586 mm Hg) and then during 6 to 7 days of sojourn at 4350 m (435 mm Hg). Maximum oxygen consumption (VO(2max)), maximum heart rate (HR(max)), pulse arterial oxygen saturation (SaO(2)), and maximum ventilation (VE(max)) were measured. RESULTS: VO(2max), HR(max), duration of work (minutes), and SaO(2) saturation decreased significantly (P < .05) with increasing altitude in both sexes. Conversely, VE(max) and ventilatory equivalent (VE/VO(2)) increased significantly (P < .05). Men showed a relatively higher value of maximum exercise variables (total exercise time, exercise intensity, and VO(2)) than women trainees at both altitude locations. The decrement of VO(2max) was 13% in women and 17% in men (P < .05). CONCLUSIONS: The results indicate that the decrement of maximum aerobic capacity at 4350 m was less in women than in men under similar modes of ascent.

Hypoxic ventilatory response changes of men and women 6 to 7 days after climbing from 2100 m to 4350 m altitude and after descent.

To test the hypothesis that the changes in hypoxic ventilatory response (HVR) of men and women mountaineers on induction to HA by trekking is not influenced by gender, isocapnic HVR as DeltaV(E)/DeltaSa(O2) was studied in eight men and eight women mountaineering trainees initially at 2100 m, then during 6 to 7 days of sojourn at 4350 m, and retested again on return to 2100 m. Results indicated that HVR at 2100 m increased significantly at 4350 m in both sexes, and the values reverted to baseline level within 4 to 5 days between leaving high altitude (4350 m) and restudy at 2100 m. No sex differences were observed at 2100- or at 4350-m altitude, indicating that men and women have a similar level of chemosensitive response as measured by HVR during induction to HA.