Dietary Mannoheptulose Increases Fasting Serum Glucagon Like Peptide-1 and Post-Prandial Serum Ghrelin Concentrations in Adult Beagle Dogs

Different Diet Energy Levels Alter Body Condition, Glucolipid Metabolism, Fecal Microbiota and Metabolites in Adult Beagle Dogs

Diet energy is a key component of pet food, but it is usually ignored during pet food development and pet owners also have limited knowledge of its importance. This study aimed to explore the effect of diet energy on the body condition, glucolipid metabolism, fecal microbiota and metabolites of adult beagles and analyze the relation between diet and host and gut microbiota. Eighteen healthy adult neutered male beagles were selected and randomly divided into three groups. Diets were formulated with three metabolizable energy (ME) levels: the low-energy (Le) group consumed a diet of 13.88 MJ/kg ME; the medium-energy (Me) group consumed a diet of 15.04 MJ/kg ME; and the high-energy (He) group consumed a diet of 17.05 MJ/kg ME. Moreover, the protein content of all these three diets was 29%. The experiment lasted 10 weeks, with a two-week acclimation period and an eight-week test phase. Body weight, body condition score (BCS), muscle condition score (MCS) and body fat index (BFI) decreased in the Le group, and the changes in these factors in the Le group were significantly higher than in the other groups (p < 0.05). The serum glucose and lipid levels of the Le and He groups changed over time (p < 0.05), but those of the Me group were stable (p > 0.05). The fecal pH of the Le and He groups decreased at the end of the trial (p < 0.05) and we found that the profiles of short-chain fatty acids (SCFAs) and bile acids (BAs) changed greatly, especially secondary BAs (p < 0.05). As SCFAs and secondary BAs are metabolites of the gut microbiota, the fecal microbiota was also measured. Fecal 16S rRNA gene sequencing found that the Me group had higher α-diversity indices (p < 0.05). The Me group had notably higher levels of gut probiotics, such as Faecalibacterium prausnitzii, Bacteroides plebeius and Blautia producta (p < 0.05). The diet-host-fecal microbiota interactions were determined by network analysis, and fecal metabolites may help to determine the best physical condition of dogs, assisting pet food development. Overall, feeding dogs low- or high-energy diets was harmful for glucostasis and promoted the relative abundance of pathogenic bacteria in the gut, while a medium-energy diet maintained an ideal body condition. We concluded that dogs that are fed a low-energy diet for an extended period may become lean and lose muscle mass, but diets with low energy levels and 29% protein may not supply enough protein for dogs losing weight.

An Avocado Extract Enriched in Mannoheptulose Prevents the Negative Effects of a High-Fat Diet in Mice

Beginning at 16 weeks of age and continuing for 44 weeks, male C57BL/6J were fed either a control (CON) diet; a high-fat (HF) diet (60% unsaturated); or the HF diet containing an extract of unripe avocados (AvX) enriched in the 7-carbon sugar mannoheptulose (MH), designed to act as a glycolytic inhibitor (HF + MH). Compared to the CON diet, mice on the HF diet exhibited higher body weights; body fat; blood lipids; and leptin with reduced adiponectin levels, insulin sensitivity, VO2max, and falls from a rotarod. Mice on the HF + MH diet were completely protected against these changes in the absence of significant diet effects on food intake. Compared to the CON diet, oxidative stress was also increased by the HF diet indicated by higher levels of total reactive oxygen species, superoxide, and peroxynitrite measured in liver samples by electron paramagnetic resonance spectroscopy, whereas the HF + MH diet attenuated these changes. Compared to the CON, the HF diet increased signaling in the mechanistic target of the rapamycin (mTOR) pathway, and the addition of the MH-enriched AvX to this diet attenuated these changes. Beyond generating further interest in the health benefits of avocados, these results draw further new attention to the effects of this rare sugar, MH, as a botanical intervention for preventing obesity.

Characterization and Mechanisms of Action of Avocado Extract Enriched in Mannoheptulose as a Candidate Calorie Restriction Mimetic

Increased consumer interest in the avocado (Persea americana or Persea gratissima) has been attributed to established health benefits of this fruit associated with a wide range of ingredients. In search of effective calorie restriction mimetics (CRM), we present herein a consideration of possible health benefits of the rare sugar, mannoheptulose (MH), which acts as an intracellular glycolytic inhibitor and presents the highest concentration of this inhibitor in unripe avocados. A method for producing an extract of unripe avocado (AvX) to enrich concentrations of MH is described. Experiments using myocyte cultures demonstrated a pattern of CRM-like responses when treated with AvX. In vivo experiments confirmed that orally consumed AvX is bioavailable in both mice and dogs, as observed in urine and blood samples. Additional experiments in both these species demonstrated CRM-like improvements in glucose and insulin responses. In sum, the MH-enriched AvX exhibits promise as a CRM.

Glycolytic inhibition: an effective strategy for developing calorie restriction mimetics

Calorie restriction mimetics encompass a growing research field directed toward developing treatments that mimic the anti-aging effects of long-term calorie restriction without requiring a change in eating habits. A wide range of approaches have been identified that include (1) intestinal inhibitors of fat and carbohydrate metabolism; (2) inhibitors of intracellular glycolysis; (3) stimulators of the AMPK pathway; (4) sirtuin activators; (5) inhibitors of the mTOR pathway, and (6) polyamines. Several biotech companies have been formed to pursue several of these strategies. The objective of this review is to describe the approaches directed toward glycolytic inhibition. This upstream strategy is considered an effective means to invoke a wide range of anti-aging mechanisms induced by CR. Anti-cancer and anti-obesity effects are important considerations in early development efforts. Although many dozens of candidates could be discussed, the compounds selected to be reviewed are the following: 2-deoxyglucose, 3-bromopyruvate, chrysin, genistein, astragalin, resveratrol, glucosamine, mannoheptulose, and D-allulose. Some candidates have been investigated extensively with both positive and negative results, while others are only beginning to be studied.

Avocado Intake, and Longitudinal Weight and Body Mass Index Changes in an Adult Cohort

Avocados contain nutrients and bioactive compounds that may help reduce the risk of becoming overweight/obese. We prospectively examined the effect of habitual avocado intake on changes in weight and body mass index (BMI). In the Adventist Health Study (AHS-2), a longitudinal cohort (~55,407; mean age ~56 years; U.S. and Canada), avocado intake (standard serving size 32 g/day) was assessed by a food frequency questionnaire (FFQ). Self-reported height and weight were collected at baseline. Self-reported follow-up weight was collected with follow-up questionnaires between four and 11 years after baseline. Using the generalized least squares (GLS) approach, we analyzed repeated measures of weight in relation to avocado intake. Marginal logistic regression analyses were used to calculate the odds of becoming overweight/obese, comparing low (>0 to <32 g/day) and high (≥32 g/day) avocado intake to non-consumers (reference). Avocado consumers who were normal weight at baseline, gained significantly less weight than non-consumers. The odds (OR (95% CI)) of becoming overweight/obese between baseline and follow-up was 0.93 (0.85, 1.01), and 0.85 (0.60, 1.19) for low and high avocado consumers, respectively. Habitual consumption of avocados may reduce adult weight gain, but odds of overweight/obesity are attenuated by differences in initial BMI values.

Dietary mannoheptulose does not alter glucose or lipid metabolism in adult Labrador Retrievers

Mannoheptulose (MH), a glycolytic inhibitor, has been preliminarily investigated as a novel functional food ingredient for dogs. This study aimed to determine the effects of dietary MH, delivered as an extract of un-ripened avocados, on fatty acid and glucose kinetics in healthy adult Labrador Retriever dogs (n = 12 dogs). The study was a double-blindcrossover with each dog receiving both dietary treatments, control (CON) and MH (400 mg/kg of diet), in random order. Glucose and glycerol plasma turnover (Ra) and oxidation (Ox) were measured in fasting and in response to repeated meal feeding ("fed") with stable isotope tracers (U-¹³ C-glucose, 1,1,2,3,3-D₅ -glycerol) and indirect calorimetry. Palmitate Ra and Ox were examined during repeated meal feeding only using an oral bolus of U-¹³ C-K₂ -palmitate and indirect calorimetry. MH had no discernible effect on fasting glucose Ra (677, 722 SEM 36 μmol/min, CON, MH) or Ox (107, 109 μmol/min, CON, MH SEM 10 μmol/min) or fed glucose Ra (2913, 3626 SEM 644 μmol/min, CON, MH) or Ox (951, 936 SEM 174 μmol/min, CON, MH). Glycerol Ra, an index of the rate of lipolysis, was not different between dietary treatments (Fast 162, 113 SEM 35 μmol/min CON, MH; Fed 172, 135 SEM 21 μmol/min, CON, MH). Similarly, palmitate oxidation was not impacted by MH feeding (1966, 2276 SEM 79 μmol/min, CON, MH). Together, these findings do not support MH as a novel functional food ingredient at least at the dietary dose tested.