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 3600 m by air and after 48 h they were further taken to an altitude of 4300 m by road. Blood samples were collected after 48 h stay at 3600 m and again after 48 h and 7 days of stay at 4300 m during 0700-0730 h. There was a decrease in energy intake (850 kcal/day) of sojourners, which resulted in loss of body weight by 2.12 kg at HA. At an altitude of 4300 m there was a significant increase in leptin over basal levels (54.9%, p < 0.001) at 48 h 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 48 h of ascent to HA. Leptin levels of acclimatized lowlanders were also higher in comparison with control group (acclimatized group 7.6 + 0.6 ng/ml vs. control 5.6 + 0.5 ng/ml, p < 0.01, n = 50).

Endocrine and metabolic responses to extreme altitude and physical exercise in climbers

“…An increase in leptin coupled with ghrelin decrease has been described after acute exposure to HA (17,19), but other authors reported that prolonged HA exposure is associated with a reduction of leptin concentrations, likely due to the loss of body mass and the strong hypoxia-related sympathetic activation (18). These studies relied on single leptin and ghrelin measurements while we evaluated mean leptin and ghrelin concentrations over 2 h. Indeed, we found a nonsignificant trend toward decreased leptin levels, but ghrelin levels were completely unchanged despite the significant body weight loss.…”

“…In this context, significant variations in leptin and ghrelin secretion were expected but the data available so far are discrepant. Leptin levels have been reported as either increased (17,19), decreased (18), or unchanged (20), while a trend towards decreased ghrelin levels has been reported at HA (19).…”

“…More recently, the emerging role of leptin and ghrelin in the regulation of energy balance prompted an evaluation of leptin response to HA (17)(18)(19)(20). Subjects exposed to HA lose significant amounts of body mass from fat mass as well as fat-free mass, particularly if involved in physical performance such as climbing (10,11).…”

Adaptation of ghrelin and the GH/IGF axis to high altitude

“…Published data have been somewhat inconsistent reporting an increase (12,37), a decrease (38), or no change (13,39) in leptin after ascent to HA. However, hypoxia has been shown to clearly increase leptin gene expression in adipocyte studies (40).…”

“…Accordingly, an increase in ghrelin levels associated with weight loss during exposure to HA would be expected. However, two studies investigating ghrelin adaptation to HA found a 30% decrease in ghrelin plasma levels in 30 lowlanders 48 h after being taken to 4300 m (12), and unchanged ghrelin levels among nine elite climbers after exposure to very HA respectively (13). Hence, as weight loss is an inevitable consequence from ascent to HA, it may be difficult to discriminate between secondary effects due to weight loss and direct change of endocrine regulation, e.g.…”