Diet restriction alone improves glucose tolerance and insulin sensitivity than its coadministration with krill or fish oil in a rabbit model of castration‐induced obesity

Abstract

This study investigated the effect of 50% diet restriction and its coadministration with krill oil (KO) or fish oil (FO) on glucose tolerance and insulin sensitivity in a rabbit model of obesity. Castrated male rabbits were 50% restricted fed and supplemented with KO or FO (600 mg omega‐3 polyunsaturated fatty acids/daily) for 2 months. Simultaneously, two control groups were used: castrated, full‐diet‐fed and castrated, 50% restricted fed rabbits without additives restricted group (RG). The energy‐restricted diet decreased final body weight in castrated male rabbits and improved most insulin sensitivity and β‐cell function indexes. Combining the same diet and KO or FO, further reduced fasting blood glucose levels. However, this feed regime significantly accelerated insulin secretion and reduced gene expression of insulin receptor substrate‐1, pyruvate kinase and 3‐hydroxy‐3‐methylglutaryl‐CoA synthase 2. This was manifested by reduced dynamic insulin sensitivity, assessment homoeostasis‐β‐cell function indices and increased glucose elimination rate to levels comparable to or above the obese animals. Aspartate and alanine aminotransferases enzyme activities were raised more than those in the obese group. Surprisingly, KO and FO administration downregulated acetyl‐coenzyme A oxidase and carnitine palmitoyltransferase 2 messenger RNA gene expression compared to the RG. In conclusion, we can assume that a better effect on insulin sensitivity and glucose tolerance was observed in the diet restriction alone than in the coadministration of KO or FO when animals are exposed to highly obesity predisposing factors. These effects could be at least in part ascribed to the modified gene expression levels of some critical enzymes and factors involved in liver glucose metabolism and β‐oxidation.

Evaluation of Fasting and Probiotics in Reducing Postweaning Stress in Rabbits: Study of their Effects on Biochemical and Gene expression Patterns

“…On the other hand, Rajman et al [ 40 ] found a decrease in plasma glucose with a short (24 h) period of food restriction in chickens. Similarly, Jamshed et al [ 41 ] and Grigorova et al [ 42 ] observed that a slight restriction (50 g feed/head/day) reduced blood glucose during the feed restriction period.…”

Differential effects of fish-oil and cocoa-butter based high-fat/high-sucrose diets on endocrine pancreas morphology and function in mice

“…The Cocoa-HFDS group had higher fasting blood glucose concentrations than the Fish-HFDS group, which raises the possibility of a disturbance of glucose metabolism in the Cocoa-HFDS group. It was shown previously by several studies that the presence of fish oil in the high-sucrose diet affects the fasting glucose concentration, albeit within the normal range, in comparison to other groups that had only a high-sucrose diet alone or with a different source of fat (e.g., corn oil, lard, argan oil, and krill oil) (1,2,8,14,22,25). In our study, compared to normal (chow) diet and regular HFD, the mice fed with Fish-HFDS had similar fasting blood glucose concentrations as the mice fed with chow diet and had lower fasting blood glucose concentrations than the mice fed with regular HFD.…”

“…Therefore, the fish oil as a source of fat in a high-sucrose high-fat diet effectively increased these hormones in mice. However, the previous studies on rats ( 25 ) and rabbits ( 22 ) fed a high-sucrose diet showed that insulin concentration was either not affected ( 25 ) or decreased ( 22 ) by fish oil supplementation. We speculate that different feeding regimens used in these dietary investigations, including ours, may be the source of differences in results regarding the circulatory insulin levels.…”

“…High-sucrose diets are known to increase body weight ( 2 , 6 , 10 ); however, when supplemented with fish oil, using different models, animals either gained ( 8 , 19 , 20 ), lost ( 21 , 22 ), or showed no change ( 2 , 10 , 14 , 15 , 23 – 25 ) in their body weight. Here, we show that fish oil fat source in high fat/high sucrose diet does not, in fact, increase the body weight when compared to a high-fat diet based on cocoa butter as fat source.…”