Urinary Dopamine Excretion Rate Decreases during Acute Dietary Protein Deprivation and Is Associated with Increased Plasma Pancreatic Polypeptide Concentration

Abstract

Background: Dopamine, a key neurotransmitter in the autonomic nervous system participating in the homeostatic balance between sympathetic and parasympathetic divisions, is involved in food intake regulation. Objective: We investigated whether dopamine is altered by acute fasting or overfeeding diets with varying macronutrient content. Design: Ninety-nine healthy subjects underwent 24-h dietary interventions including eucaloric feeding, fasting, and five different overfeeding diets in a crossover design. Overfeeding diets (200% of eucaloric requirements) included one diet with 3%-protein (low-protein high-fat overfeeding—LPF: 46%-fat), three diets with 20%-protein, and a diet with 30%-protein (44%-fat). Urine was collected for 24 h and urinary dopamine concentration was quantified by high-performance liquid chromatography. Plasma pancreatic polypeptide (PP) concentration, an indirect marker of parasympathetic activity, was measured prior to and after each diet after an overnight fast. Results: During 24-h of fasting, dopamine decreased on average by ~14% compared to eucaloric conditions, whereas PP increased by two-fold (both p < 0.001). Lower dopamine during 24-h fasting correlated with increased PP (r = −0.40, p < 0.001). Similarly, on average urinary dopamine decreased during LPF by 14% (p < 0.001) and lower dopamine correlated with increased PP (r = −0.31, p = 0.01). No changes in dopamine and PP concentrations were observed during other overfeeding diets (all p > 0.05). Conclusions: Dopamine concentrations decrease during short-term fasting and overfeeding with a low-protein diet. As both dietary conditions have in common protein deficit, the correlation between dopamine and PP suggests a compensatory mechanism underlying the shift from sympathetic to parasympathetic drive during dietary protein deprivation.

Ketogenic Diet and Weight Loss: Is There an Effect on Energy Expenditure?

“…The "spendthrift" phenotype is characterized by smaller decreases in EE during fasting and larger increases in EE during overfeeding, whereas the "thrifty" one is an energy-efficient phenotype characterized by a larger decrease in EE during fasting and modest increases in EE during over-feeding [3,4]. Although the mechanisms underlying the metabolic EE response to dietary intervention are not fully elucidated, it has been suggested that changes in body composition [47], hormone levels [55][56][57][58], core body temperature [53] brown adipose tissue activity [59,60], and sympathetic nervous system tone [61][62][63] might play a role in the regulation of the "adaptive metabolic mechanism".…”

Energy Balance and Control of Body Weight: Possible Effects of Meal Timing and Circadian Rhythm Dysregulation

“…The mechanisms involved in the EE responses to dietary intervention in humans have not been fully clarified. It has been hypothesized that body composition [ 30 ], core body temperature [ 55 ], hormones [ 18 , 56 , 57 ], brown adipose tissue [ 58 , 59 ] and sympathetic nervous system tone [ 17 , 57 , 60 , 61 ] might play a role in regulating the metabolic adaption. Recently, it has been proposed that other factors such as the circadian rhythm might play a role in the regulation of the energy balance, through a change in food timing and thermic effect of food, thus influencing body weight regulation [ 62 , 63 ].…”