Unraveling the Timing Mechanisms of Animal Feeding Patterns

An investigation spearheaded by Tokyo Metropolitan University, utilizing fruit flies as a model, has illuminated the role of genetic factors in determining daily eating schedules. The gene known as quasimodo (qsm) was revealed to align feeding activities with light and dark cycles. In conditions of constant darkness, genes named clock (clk) and cycle (cyc) continued to govern these cycles, specifically in metabolic tissues. Furthermore, neuronal clocks were pinpointed as crucial elements in aligning eating patterns with daily shifts in light. This research, backed by a variety of institutions and financial grants, augments our knowledge of circadian rhythms in feeding habits and may contribute to future treatments for eating disorders.

The study elucidates the molecular underpinnings that dictate the timing of meals and their alignment with circadian rhythms.

The Tokyo Metropolitan University research team employed fruit flies to investigate the governing principles of daily feeding patterns. They identified the quasimodo (qsm) gene as pivotal in aligning feeding cycles with light and dark phases, although it lost its effectiveness under constant dark conditions. During such conditions, the clk and cyc genes maintained the patterns of eating and fasting.

Additionally, specialized clocks within neurons serve to coordinate these eating and fasting cycles with diurnal variations. Gaining a more nuanced understanding of these molecular controls offers valuable insights into animal and human behaviors.

Adapting to Environmental Stimuli

Members of the animal kingdom generally consume food at consistent times each day. This consistency arises from the necessity to adapt to environmental variables such as light, temperature, food availability, and predator presence, all of which are crucial for survival. It also contributes to efficient metabolism and overall well-being.

The researchers found that while the qsm gene controlled alignment with light and dark phases, neuronal molecular clocks assumed this role in persistent darkness. Meanwhile, the clk and cyc genes regulated the cycles of eating and fasting.

Elucidating the Mechanisms of Feeding Behavior

A myriad of organisms discern their feeding times through circadian rhythms, an almost daily physiological cycle prevalent among a wide range of life forms including animals, plants, bacteria, and algae. This serves as a central timing mechanism, coordinating various rhythmic behaviors. Nonetheless, animals possess other timing systems, referred to as “peripheral clocks,” each governed by distinct biochemical pathways. These can be influenced by external events, such as eating. The specific manner in which these clocks regulate animal feeding is still an area of ongoing research.

Insights from the Fruit Fly Study

The research team, led by Associate Professor Kanae Ando, tackled this question using fruit flies, which serve as a useful model organism reflecting many features of more intricate animals, including humans. Through a technique known as CAFE assay, they measured the precise amounts consumed by individual flies at different intervals, focusing primarily on how these flies adjusted their eating patterns in response to light.

In a light and dark cycle, prior studies had indicated that flies consumed more food during daylight hours, even when mutations in core circadian clock genes were present. The team, however, focused on the quasimodo (qsm) gene, which encodes a light-sensitive protein that modulates the activity of clock neurons. When this gene was inhibited, it was found to significantly alter the daytime feeding patterns of the flies, making it clear that qsm plays a role in synchronizing feeding with light-based rhythms.

The Interplay of Clock Genes and Feeding Cycles

In conditions of continuous darkness, mutations in the primary circadian clock genes resulted in a drastic disturbance in daily eating patterns. Among the four implicated genes—period (per), timeless (tim), cycle (cyc), and clock (clk)—the absence of cyc and clk had a much greater impact. Specifically, these genes were crucial for establishing bimodal feeding patterns, particularly in metabolic tissues. Neuronal molecular clocks were the dominant factors in synchronizing these cycles with diurnal rhythms.

The research team’s findings offer an initial glimpse into how various clocks in different anatomical locations within an organism coordinate feeding and fasting periods, and how these are aligned with day-night cycles. A deeper understanding of these mechanisms holds the potential for new treatments targeting eating disorders.

Acknowledgments

The study was financially supported by the Farber Institute for Neurosciences and Thomas Jefferson University, the National Institutes of Health [R01AG032279-A1], a grant from the Takeda Foundation, and the TMU Strategic Research Fund.

Reference: “Dissecting the daily feeding pattern: Peripheral CLOCK/CYCLE generate the feeding/fasting episodes and neuronal molecular clocks synchronize them” by Akiko Maruko, Koichi M. Iijima and Kanae Ando, published on 7 October 2023 in iScience.
DOI: 10.1016/j.isci.2023.108164

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• Tokyo Metropolitan University Research Programs
• iScience Journal
• National Institutes of Health (NIH) Grants
• Takeda Foundation Grants
• Farber Institute for Neurosciences
• Thomas Jefferson University Research
• Circadian Rhythms: An Overview
• Understanding Eating Disorders
• Model Organisms in Biological Research