Dietary Mannoheptulose Does Not Significantly Alter Daily Energy Expenditure in Adult Labrador Retrievers

Abstract

Mannoheptulose (MH), a sugar found in avocados that inhibits glycolysis in vitro, has been preliminarily investigated as a novel food ingredient for dogs. This study aimed to determine the effects of dietary MH, delivered as an extract of un-ripened avocado, on energy expenditure (EE) in healthy adult Labrador Retriever dogs (total of 12 dogs, 26.99 ± 0.634 kg, 4.9 ± 0.2 y). The study was a double-blind, cross-over with each dog receiving both dietary treatments, control (CON) and MH (400 mg/kg of diet; 6 mg/kg BW), in random order. Resting and post-prandial (10 h) EE and respiratory quotient (RQ) were determined by indirect calorimetry (d 42). The following day, body composition was assessed using dual X-ray absorptiometry. Continuous activity monitoring was conducted using an Atical® accelerometer (d 43-47). A vastus lateralis muscle biopsy was obtained prior to the morning meal (d 49) and 4 h after consumption of their meal (d 56) to determine the protein content and phosphorylation of 5' adenosine monophosphate-activated protein kinase (AMPK). Diet did not affect body weight, resting EE or skeletal muscle AMPK phosphorylation. Dogs fed MH had significantly lower post-prandial RQ (p = 0.02) and ratio of fat to lean body mass (p = 0.02). Physical activity during light time periods (but not dark) was lower in dogs fed MH (p < 0.05) during weekends, but not on weekdays. These results suggest that MH affects energy balance of adult dogs, but that these effects are not dose dependent and not due to physical activity.

Fig 1. Weekly body weights (kg).

Dogs were randomized to dietary treatment order, a MH containing diet (MH, 400 mg/kg) followed by control diet (CON) (■) (n = 6) or CON followed by MH (□) (n = 6), with a 3 wk dietary washout between periods.

Fig 2. The ratio of phosphorylated to total AMPK (pAMPK/total) protein abundance in vastus lateralis muscle of adult Labrador Retrievers.

Fasting muscle samples were taken prior to the dog’s morning meal (18 h since last meal). Fed muscle samples were taken 4 h after the dogs consumed their full daily ration of test diet, either control or mannoheptulose (400 mg/kg). Data are means with pooled standard errors. ¹ N = 9; ² N = 9; ³ N = 7; ⁴ N = 10