Biology subjects

Volcko, K. L.

Publications and source records attributed to Volcko, K. L..

3 recordsLinked to original sources

bioRxiv2024

Rapid fluctuations in histamine associated with intake of nutritive and non-nutritive solutions

The neurotransmitter histamine is involved in control of food intake, yet its dynamics during individual feeding episodes remain unexplored. Therefore, we used the novel genetically-encoded histamine sensor, HisLightG, combined with fiber photometry to measure histamine release in two hypothalamic regions critical for the food-suppressive effects of histamine, the paraventricular nucleus of the hypothalamus (PVH), and the ventromedial hypothalamus (VMH). Male mice were tested under different conditions to assess whether hunger, time of day, or the caloric content of the solution they were given affected histamine fluctuations. We found that histamine levels changed rapidly in response to eating. These histamine fluctuations were influenced by experimental conditions, with slightly smaller responses when the test solution was sucralose (both regions) or during the light cycle (PVH only). Notable regional differences were identified, such that in the PVH histamine rebounded to baseline levels, whereas in the VMH histamine remained lower than baseline for at least 10 seconds after licking ceased. In a separate cohort of male and female mice, enhancing histamine tone via administration of a histamine precursor (L-histidine) reduced the number of licks across multiple sucrose concentrations. Together, these findings indicate that histaminergic activity is modulated rapidly during ingestive episodes, and that understanding these release patterns will give insight into histamines role in appetite suppression.

neuroscience↗

bioRxiv2024

Intermittent protein restriction elevates food intake and plasma ghrelin in male mice

Low-protein diets affect body weight, body composition, food intake, and food preferences in mice. Furthermore, single periods of protein restriction can have lasting effects on these parameters. We sought to examine the effect of multiple, short, bouts of protein restriction, relative to long-term maintenance on either a control (NR) or protein-restricted (PR) diet. We found that male mice experiencing intermittent protein restriction (IPR) were indistinguishable from NR mice in terms of body weight and composition, but had food intake and plasma ghrelin as high as mice on PR diet, even when they were returned to control diet. This was not found in female mice. The results of this experiment highlight the importance of diet history on food intake and ghrelin levels in male mice, and the difference in how PR diet might affect male and female mice.

physiology↗

bioRxiv2022

Protein preference and elevated plasma FGF21 induced by dietary protein restriction is similar in both male and female mice

Animals that are moderately protein restricted respond to this dietary stress by increasing consumption of protein-containing foods. This is true in many species, including rodents. Rodent models of protein restriction have typically relied on only male subjects, and there are plausible reasons why female rodents may respond differently to dietary protein restriction. To address this gap in knowledge, the current experiments examined protein preference after two weeks on a 5% protein diet or 20% protein control diet, in male and female mice. We found that female mice, like male mice, increase consumption of 4% casein (protein) relative to 4% maltodextrin (carbohydrate) when presented with both simultaneously. Interestingly, this increased consumption was due to more bursts in females and more licks per burst in males, indicating possible differences in mechanism by which increased intake is achieved. Stage of the estrous cycle did not affect female responses. Moreover, we measured plasma FGF21 - a hormone induced by protein restriction and necessary for protein preference - in male and female mice. Here, we found no statistical differences between protein-restricted males, females in diestrus, or females in proestrus. In non-restricted mice FGF21 levels were low, but significantly higher in females in proestrus than females in diestrus or males. Overall, these experiments highlight the importance of including female subjects in studies of food choice and macronutrient restriction. Highlights- Protein-restricted male and female mice exhibit protein preference - Estrous cycle stage does not influence protein preference - Estrous cycle stage does not affect plasma FGF21 during protein restriction - Non-restricted females in proestrus have higher FGF21 than those in diestrus or males

neuroscience↗