Minimal changes in environmental temperature result in a significant increase in energy expenditure and changes in the hormonal homeostasis in healthy adults

Abstract

Objective Resting energy expenditure (EE) is a major contributor to the total EE and thus plays an important role in body weight regulation. Adaptive thermogenesis is a major component of EE in rodents, but little is known on the effects of exposure of humans to mild and sustainable reduction in environmental temperature. Design To characterize the dynamic changes in continuously measured resting EE, substrate utilization, and hormonal axes simultaneously in response to mild reduction in environmental temperature, we performed a cross-over intervention. Methods Twenty-five volunteers underwent two 12-h recordings of EE in whole room indirect calorimeters at 24 and 19 °C with simultaneous measurement of spontaneous movements and hormonal axes. Results Exposure to 19 °C resulted in an increase in plasma and urine norepinephrine levels (P<0.0001), and a 5.96% (P<0.001) increase in EE without significant changes in spontaneous physical activity. Exposure to the lower temperature resulted in a significant increase in free fatty acid levels (P<0.01), fasting insulin levels (P<0.05), and a marginal decrease in postprandial glucose levels. A small but significant (P<0.002) increase in serum free thyroxine and urinary free cortisol (P<0.05) was observed at 19 °C. Conclusions Our observations indicate that exposure to 19 °C, a mild and tolerable cold temperature, results in a predictable increase in EE driven by a sustained rise in catecholamine and the activation of counter-regulatory mechanisms.

Cold but not sympathomimetics activates human brown adipose tissue in vivo

“…In addition to glucose, cold exposure had no significant effect on plasma insulin, thyroid hormones, or even epinephrine, demonstrating that there was not a generalized activation of the classic response to stressors (23). The cold-associated increase in C-peptide without changes in glucose reflects a state of relative insulin resistance that may have been caused by elevated norepinephrine, as previously described (24). The elevated lactic acid levels were likely a result of glycolysis and amino acid metabolism in the BAT itself (18,25) and possibly also from subclinical, low-grade muscle contraction.…”

β1-Adrenergic receptor deficiency in ghrelin-expressing cells causes hypoglycemia in susceptible individuals

“…jci.org Volume 126 Number 9 September 2016 in future studies of other important β 1 AR-mediated processes, such as cardiac function, smooth muscle tone, the hypoglycemia counterregulatory response, and adipose tissue physiology. Also, given our findings in calorie-restricted GC-β 1 AR -/-mice, we would predict that other conditions associated with enhanced sympathetic drive, such as psychosocial stress and cold exposure -both of which have been shown to be associated with increased plasma ghrelin levels -may involve robust β 1 AR-dependent ghrelin secretion responses (50,(84)(85)(86)(87) on which the full physiological responses to those conditions may depend. Furthermore, the occurrence of hypoglycemia in calorie-restricted GC-β 1 AR -/-mice and the prevention thereof by ghrelin administration suggest that closer blood glucose monitoring might be prudent in cachectic individuals if beta blocker therapy becomes indicated, just as has already been recommended for children with infantile hemangioma treated with propranolol, for whom we now propose that reduced ghrelin secretion contributes to the beta blocker-associated hypoglycemia.…”

Influence of environmental temperature on risk of gestational diabetes

“…[4][5][6] Based on findings from studies involving animals and humans, the effects of brown adipose tissue activation extend beyond thermogenesis, by influencing whole-body metabolism and possibly overall body weight. [7][8][9][10][11][12][13][14][15][16][17][18] Small intervention trials involving humans have suggested that even mild exposure to ambient cold -such as lowering a thermostat from 24°C to 19°C -can increase activity of brown adipose tissue by 30%-40%, resulting in substantial improvements in insulin sensitivity. [15][16][17][18] In theory, greater insulin sensitivity should improve glucose handling, but whole-population studies evaluating the potential for cold exposure to reduce glucose mishandling are lacking.…”