Increase of serum insulin and stable c-peptide concentrations with exhaustive incremental graded exercise during acute hypoxia in sedentary subjects

Abstract

Hypoxia was shown to reduce insulin concentrations at rest and during exercise. However, some studies have also demonstrated increases in the hormone associated with arterial desaturation. This study was conducted in order to decide [1] whether acute alveolar hypoxia increased or decreased the circulating insulin levels, and [2] to elucidate whether interactions of insulin with other hormones were of relevance in this respect. Glucose (GLU), insulin (INS), c-peptide (CP), adrenaline and noradrenaline (CATs), atrial natriuretic peptide (ANP) and cortisol (CORT) as well as the capillary blood gases were determined in 15 healthy fasting male volunteers (age: 26.2 +/- 2.8 years, body mass index: 22.4 +/- 2.7 kg.m-2). On two separate test days the subjects breathed, in random order, either normal air (N) or a gas mixture with reduced oxygen content (H; FIO2: 0.14). Measurements were made at rest as well as during an incremental cycle exercise in a supine position (increments of 6 min and 50 W) at 100 W and 150 W, at volitional exhaustion (N: 227 +/- 36 W; H: 200 +/- 32 W) as well as in the 5th min of recovery. Arterial desaturation was seen throughout on H-day. At rest all hormones and GLU were normal and showed no influence of H. During exercise INS remained constant on N-day, increased on H-day and was significantly higher with H than with N, most pronounced at 150 W and at volitional exhaustion with 20%, respectively. For CP and GLU no significant exercise-induced changes were seen on either test day and no influence of H was detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Endocrine Function

“…Plasma insulin increases after prolonged exposure to high altitude such as in Operation Everest II [ 69 ] and the Sajama expedition [ 70 ], but was found unchanged after a 7-week expedition to Mount Everest [ 18 ]. Serum insulin and C-peptide were found increased in acute hypoxia during intense exercise by sedentary subjects [ 71 ]. Tolerance to glucose decreases with acute hypoxia, suggesting that the decrease in peripheral use of glucose during hypoxic exercise could be an additional factor accounting for hypoxia-induced hyperglycemia [ 72 ].…”

Is Physical Exercise in Hypoxia an Interesting Strategy to Prevent the Development of Type 2 Diabetes? A Narrative Review

“…In healthy sedentary subjects, a single exercise performed in hypoxia increased serum insulin levels during and after exercise, which was not the case when exercise was performed in normoxia. 25 No exercise-induced c-peptide (a short polypeptide released into the bloodstream as a by-product of insulin formation) modifications compared to the resting measurements were seen on either test day. In overweight men, blood glucose and serum insulin concentrations did not differ between normoxic and hypoxic exercise conditions, consisting in three sessions of 30 min within a 7.5-h period, nor between rest and exercise conditions.…”

Nutritional requirement at high-altitude with special emphasises to behaviour of gastro-intestinal tract and hormonal changes

“…The insulin level was found to be elevated in hypoxic condition 53 . Glucagon levels have been reported to be unaltered at HA 54 . Corticosteroids, have a well documented immunosuppressive effect which are released during cold stress, hypothermia, or both 55 .…”