Circadian clock organize a wide array of metabolic functions in a coherent daily schedule and ensure synchrony of this schedule with environmental rhythms. Daily rhythmicity of lipid metabolism has been described in rodents and ruminants. We examined daily level variations of serum lipids (NEFA, triglycerides, phospholipids, total cholesterol and total lipids) in healthy dogs, particularly focusing on their temporal relationship to lighting and fasting cycles. While serum NEFA levels did not change across the day, we showed daily variations in levels of total lipids, total cholesterol, phospholipids, and triglycerides in dogs maintained under 12L:12D cycles and fed a single meal in the day. Interestingly, only the rhythmic pattern of triglycerides respond to a shift of the 12L:12D cycle suggesting a cardinal role of a light-entrained circadian oscillator in its generation. To investigate whether temporal variations in serum lipids depend to physiological post-prandial changes, we measured lipid levels in fasted dogs. Rhythms of total lipids, total cholesterol, phospholipids, and triglycerides vanished when dogs were food deprived indicating that these rhythms are driven by the digestive process. The serum NEFA pattern in fasted dogs had a different trend: levels were significantly high during fasting than after food intake. The increase of NEFA concentrations during fasting may reflect the adipose tissue NEFA mobilization mediated by the decrease in insulin with its lypolitic effects. To know the existence of daily lipid rhythmicity is a fundamental necessity to understand the metabolism of the dog, an animal model frequently used for research in metabolic pathophysiology.
Daily rhythms of serum lipids in dogs: influence of lighting and fasting cycles
BERTOLUCCI, CristianoPrimo
;
2008
Abstract
Circadian clock organize a wide array of metabolic functions in a coherent daily schedule and ensure synchrony of this schedule with environmental rhythms. Daily rhythmicity of lipid metabolism has been described in rodents and ruminants. We examined daily level variations of serum lipids (NEFA, triglycerides, phospholipids, total cholesterol and total lipids) in healthy dogs, particularly focusing on their temporal relationship to lighting and fasting cycles. While serum NEFA levels did not change across the day, we showed daily variations in levels of total lipids, total cholesterol, phospholipids, and triglycerides in dogs maintained under 12L:12D cycles and fed a single meal in the day. Interestingly, only the rhythmic pattern of triglycerides respond to a shift of the 12L:12D cycle suggesting a cardinal role of a light-entrained circadian oscillator in its generation. To investigate whether temporal variations in serum lipids depend to physiological post-prandial changes, we measured lipid levels in fasted dogs. Rhythms of total lipids, total cholesterol, phospholipids, and triglycerides vanished when dogs were food deprived indicating that these rhythms are driven by the digestive process. The serum NEFA pattern in fasted dogs had a different trend: levels were significantly high during fasting than after food intake. The increase of NEFA concentrations during fasting may reflect the adipose tissue NEFA mobilization mediated by the decrease in insulin with its lypolitic effects. To know the existence of daily lipid rhythmicity is a fundamental necessity to understand the metabolism of the dog, an animal model frequently used for research in metabolic pathophysiology.File | Dimensione | Formato | |
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