Introduction

Abnormal levels of blood lipid traits in dogs can come from many reasons such as aging, obesity, and breed traits (Kim, 2010; Usui et al., 2015). These problems are known to cause cardiovascular and metabolic diseases. An increase in total cholesterol (TC), triglycerides (TGs), and low-density lipoprotein cholesterol (LDL-C) together with a decrease in high-density lipoprotein cholesterol (HDL-C) can raise the atherogenic index (AI) and cardiac risk factor (CRF), which may ultimately threaten the dog’s health. Korean studies also showed that blood and serum components are different by breed (Kim et al., 2018) and that biochemical parameters change depending on age and body weight (Lee et al., 2025). Another report noted that feeding and housing conditions can alter blood lipid concentrations, suggesting these are also important factors (Na et al., 2014).

What dogs eat also matters for lipid metabolism and for preventing metabolic disorders. Especially, edible and medicinal mushrooms contain many active compounds such as β-glucan, eritadenine, and phenolic substances that have antioxidant, anti-inflammatory, anti-obesity, and anti-hyperlipidemic effects. Extracts of shiitake mushroom (Lentinula edodes) were reported to lower TC, TGs, and LDL-C in hyperlipidemic animals and to suppress HMG-CoA reductase activity (Kim et al., 2013). Feeding fruiting bodies of edible mushrooms also improved lipid levels in rats fed a high-fat, high-cholesterol diet (Kim, 2019).

Many other mushrooms were studied for similar actions. Lion’s mane mushroom (Hericium erinaceus) improved serum lipids and reduced AI in rats (Jang and Yoon, 2017). Agaricus brasiliensis reduced TC, TGs, and LDL-C and increased lipid excretion through feces, showing inhibition of lipid re-absorption (Mori et al., 2008; Jin and Lee, 2018). Phellinus linteus extracts also decreased serum lipids and raised antioxidant enzyme activity (Zhang et al., 2007; Song et al., 2010). Feeding Sparassis latifolia fruiting bodies to hyperlipidemic rats showed both anti-obesity and anti-hyperlipidemic effects (Im et al., 2021). Altogether, such results imply that mushrooms can effectively help lipid metabolism.

The new cultivar, Isulsongi mushroom (Lentinula edodes GNA01), is different from common shiitake. It lacks a cap and stem, and has a large edible portion with good storage stability and palatability (Jang et al., 2015). This mushroom contains more β-carotene, vitamin D, and minerals such as K and Mg (Youn and Lee, 2021), and shows higher total polyphenol content and antioxidant activity than ordinary shiitake (Jang et al., 2017). Antioxidant activity varies with extraction solvent, but even water extracts have strong activity, suggesting potential use as a functional raw material (Jang et al., 2017).

Recently, the pet-food industry has moved from simple nutrient supply toward functional diets for better pet health. Many studies have been reported on functional feed for senior dogs (Lee et al., 2020). However, in Korea, studies on feeding Isulsongi mushroom to dogs are still limited. There has been a report focusing on age-related changes in blood lipid characteristics following Isulsongi mushroom supplementation (Jung and Hwangbo, 2025). Apart from this, studies examining different supplementation levels or feeding periods of Isulsongi mushroom in dogs are scarce.

Therefore, this study aimed to feed dogs with different levels and periods of Isulsongi mushroom powder and to investigate changes in TC, TGs, HDL-C, LDL-C, AI, and CRF, to evaluate the potential of this mushroom as a functional ingredient for companion-animal diets.

Materials and Methods

Experimental materials

The mushroom used in this experiment was Isulsongi mushroom (Lentinula edodes GNA01), produced in Jinju, Gyeongsangnam-do, and freeze-dried by Gyeongnam Herbal Cooperative. A freeze dryer (FDTA-5050, Operon, Korea) was used, with average chamber pressure between 0.01 and 0.05 mbar, and equipped with a sublimator and vacuum station. The dried mushrooms were ground into fine powder using a grinder (PRS-20-1, Kyunghan, Korea) and then fed to the dogs.

Experimental design and feeding management

The experiment was designed by feeding level and feeding period. Dogs were divided into three groups: control (no supplementation, mean body weight 2.5 kg), 0.01% group (100 mg per kg body weight per day, mean 2.5 kg), and 0.02% group (200 mg per kg body weight per day, mean 2.3 kg). A total of 18 Maltese dogs were used, six dogs in each group. Blood was collected four times: before feeding (0 week), and after 3, 6, and 9 weeks of feeding.

Freeze-dried Isulsongi mushroom powder was dissolved in water and given orally once daily after the evening feeding for 9 weeks. The feeding dose was determined based on a previous study (Kusaba et al., 2021). The dogs were fed 80 g of commercial diet twice per day (morning and evening). During the rest of the time, they were kept indoors and allowed to move freely, with free access to water. The feed was an extruded pellet (EP) type product from a domestic company (P Co., Australia origin), containing at least 29.0% crude protein and 17.0% crude fat.

This experiment was approved by the Institutional Animal Care and Use Committee of Daegu University (Approval No.: DUIACC-2020-16-0901-003).

Blood collection

Blood samples were obtained at weeks 0, 3, 6, and 9 following an overnight fast of at least 12 h prior to the morning meal. Blood was drawn from the jugular vein using a 5 mL syringe preloaded with 0.3 mL of heparin as an anticoagulant. After collection, samples were allowed to stand at room temperature for approximately 30 min and were subsequently centrifuged at 3,500 rpm for 15 min at 4℃ to separate the serum fraction. The isolated serum was stored at -80℃ until further analysis.

Serum analysis

Serum concentrations of TC, HDL-C, LDL-C, and TGs were determined. Using the measured cholesterol values, the AI and CRF were calculated. All biochemical analyses were performed with commercially available assay kits (Asan Pharm, Korea). The indices were calculated using the following Eqs. (1) and (2).

where, AI : atherogenic index

TC : total cholesterol

HDL : high-density lipoprotein

CRF : cardiac risk factor

Statistical analysis

The experiment followed a repeated-measures design including two main factors: dietary treatment level (control, 100 mg·kg^-1, and 200 mg·kg^-1) and sampling time (0, 3, 6, and 9 weeks). Individual dogs were considered as repeated experimental units. Statistical evaluation was carried out using a two-way repeated-measures analysis of variance (ANOVA) with SAS software (SAS, 2023). When significant effects were detected, mean comparisons according to feeding level and sampling period were conducted using Duncan’s multiple range test. Statistical significance was accepted at p < 0.05.

Results

Cholesterol

The serum lipid profiles of dogs according to the feeding level and period of Isulsongi mushroom are shown in Table 1.

TC did not show major changes in the control group without mushroom feeding. It was 224.55 mg·dL^-1 at week 0 and 231.78 mg·dL^-1 at week 9. In contrast, TC in the 0.01% group decreased from 219.88 to 184.79 mg·dL^-1, and in the 0.02% group it decreased from 225.40 to 165.81 mg·dL^-1, which was statistically significant (p < 0.05). Comparing between feeding levels at the same week, the control group showed higher values than both treated groups after 3 weeks. At 6 and 9 weeks, the 0.02% group had the lowest TC value, and the difference among groups was clear (p < 0.05). Especially at week 9, the 0.02% group showed the lowest level with 165.81 mg·dL^-1. The interaction effect between feeding level and period was significant (p = 0.002). The cholesterol-lowering effect varied depending on the feeding period.

HDL-C showed distinct differences depending on feeding level. The control group changed little, from 80.72 mg·dL^-1 at week 0 to 75.61 mg·dL^-1 at week 9, showing no significant effect. However, in the 0.01% group HDL-C increased from 76.06 to 94.50 mg·dL^-1, and in the 0.02% group from 82.22 to 104.11 mg·dL^-1, both significant (p < 0.05). When compared at the same week, there was no significant difference among levels at week 0 and week 3, but after week 6, HDL-C in the 0.02% group was higher than in control (p < 0.05). At week 9, not only the 0.02% group but also the 0.01% group had higher HDL-C than the control (p < 0.05). The interaction effect was also significant (p = 0.001). This means that the HDL-increasing effect was not the same at all time points and varied with the feeding period.

LDL-C showed pronounced differences according to feeding level and time. The control group increased slightly from 124.77 to 138.42 mg·dL^-1 at week 9, while the 0.01% group decreased from 125.49 to 73.84 mg·dL^-1, and the 0.02% group decreased sharply from 123.79 to 45.31 mg·dL^-1 (p < 0.05). At each time point, the control group showed the highest LDL-C from week 3, and both 0.01% and 0.02% groups kept lower values (p < 0.05). Especially at week 9, the 0.02% group recorded the lowest LDL-C (45.31 mg·dL^-1), showing significant difference among all groups (p < 0.05). The interaction between them was also significant (p < 0.001). This means that the LDL-lowering effect was not constant and changed with the feeding period.

Triglyceride (TG)

The changes in serum TGs of dogs according to the feeding level and period of Isulsongi mushroom are shown in Table 2.

In the control group without mushroom supplementation, TGs levels slightly decreased from 95.26 mg·dL^-1 at week 0 to 88.74 mg·dL^-1 at week 9, but the change was not statistically significant. The 0.01% group also showed a small decrease, from 91.67 to 82.25 mg·dL^-1. On the other hand, the 0.02% group showed a significant reduction from 96.94 mg·dL^-1 at week 0 to 81.98 mg·dL^-1 at week 9 (p < 0.05), and a statistically significant decrease was observed after week 6.

Across feeding periods (3, 6, and 9 weeks), some differences in mean values were observed among feeding levels (control, 100 mg·kg^-1, 200 mg·kg^-1), but the variations were not statistically significant (p > 0.05).

The interaction effect between feeding level and period was also significant (p = 0.004). This means that the TG-lowering effect was not steady and changed depending on the feeding period.

Atherogenic index (AI)

The serum AI of dogs is shown in Table 3.

AI showed little change in the control group during the experimental period. Both supplemented groups, however, showed a clear decrease over time. In the 0.01% group, AI fell from 1.91 at week 0 to 1.59 at week 3 and further decreased to 1.20 at week 6 and 0.96 at week 9 (p < 0.05). The 0.02% group showed a larger reduction, reaching 0.60 at week 9, and AI values in both supplemented groups were significantly lower than those of the control after week 3 (p < 0.05).

When comparing between feeding levels at the same week, there was no significant difference among groups at week 0. From week 3, however, the 0.01% and 0.02% groups were both lower than the control, and among them, the 0.02% group had the lowest value (p < 0.05).

The interaction effect between the two factors was also significant (p = 0.001). This means that the reduction in AI was not constant and changed with the feeding period.

Cardiac risk factor (CRF)

The CRF of dogs is shown in Table 4.

In the control group without Isulsongi mushroom feeding, CRF started at 2.79 at week 0, then changed slightly to 3.03 at week 3, 2.97 at week 6, and 3.08 at week 9. No notable change was observed during the experimental period.

In the 0.01% group, CRF decreased from 2.91 at week 0 to 2.59 at week 3, and continued to drop to 2.20 at week 6 and 1.96 at week 9, showing a significant reduction (p < 0.05). The 0.02% group also showed a gradual decrease, from 2.75 at week 0 to 2.33, 1.93, and then to the lowest value of 1.60 at week 9 (p < 0.05).

When compared among feeding levels at the same week, there was no significant difference at week 0. However, from week 3, both 0.01% and 0.02% groups had lower CRF values than the control, and the 0.02% group showed the lowest values among all (p < 0.05).

The interaction effect between the two factors was also significant (p = 0.002). This means that the CRF-lowering effect was not steady and changed depending on the feeding period.

Discussion

This study examined the effects of Isulsongi mushroom (Lentinula edodes GNA01) supplementation on blood lipid profiles in dogs. As a result, dogs fed Isulsongi mushroom had lower TC, TGs, and LDL-C than the control group, while HDL-C tended to increase. These findings are generally consistent with previous studies reporting that edible mushrooms have lipid-lowering effects. Earlier animal feeding experiments using shiitake mushroom extracts or edible mushroom fruiting body powders reported significant reductions in TC, TGs, and LDL-C (Kim et al., 2013; Kim, 2019). In addition, several studies showed that Lentinula edodes supplementation improved serum lipid profiles in rats fed a high-cholesterol diet (Alam et al., 2011; Yoon et al., 2011a; Qu et al., 2012), which supports the results of the present study.

The reduction in TGs levels differed according to the supplementation level, and the effect was more apparent in the high-level (0.02%) group. This result suggests that lipid-improving effects may become more evident when a certain supplementation level is reached. Similar trends were reported in studies showing that Hericium erinaceus and Agaricus brasiliensis reduced TGs and LDL-C levels and increased HDL-C in rats fed high-fat and high-cholesterol diets (Jang and Yoon, 2017). In addition, Phellinus linteus extracts were reported to reduce serum lipid levels while enhancing antioxidant activity (Song et al., 2010), which is in line with the present findings. Overseas studies also reported that oyster mushrooms and pink oyster mushrooms reduced TGs levels in hyperlipidemic rodent models (Wasser, 2002; Yoon et al., 2011b). Therefore, the lipid-lowering effects observed in this study may be related to common characteristics of mushrooms rather than to a single specific species.

The increase in HDL-C together with the decrease in LDL-C led to improvements in the AI and CRF. In the present study, the 0.02% supplementation group showed the lowest AI and CRF values at week 9, indicating that Isulsongi mushroom supplementation affected overall lipid status. These results are comparable to previous reports showing that Sparassis latifolia exhibited anti-obesity and hypolipidemic effects in hyperlipidemic rats (Im et al., 2021). Similar findings were also reported for Pleurotus ostreatus, which showed anti-atherosclerotic effects (Cheung, 1996). Based on these results, Isulsongi mushroom may contribute not only to changes in individual lipid parameters but also to overall improvement in lipid profiles.

Recently, Jung and Hwangbo (2025) investigated age-dependent changes in blood lipid characteristics in dogs supplemented with Isulsongi mushroom (Lentinula edodes GNA01). They reported decreases in TC and LDL-C and increases in HDL-C in both adult and aged dogs. Notably, lipid improvements were observed even in aged dogs with relatively high baseline lipid levels. This is consistent with the findings of the present study. However, Jung and Hwangbo (2025) also reported that TGs responses differed depending on age, suggesting that the TGs reduction observed in the present study may vary according to age.

Isulsongi mushroom has been reported to possess higher antioxidant activity than conventional shiitake mushroom (Jang et al., 2015; Youn and Lee, 2021). Bioactive compounds such as β-glucan are known to exhibit immunomodulatory and antioxidant effects (Zhu et al., 2023). The decreases in LDL-C and increases in HDL-C observed in this study may be partly explained by antioxidant properties that suppress LDL oxidation and improve HDL function. Previous studies also reported that mushroom polysaccharides have antioxidant and lipid oxidation-inhibiting effects (Cheung, 1996; Wasser, 2002; Song et al., 2010), which supports this interpretation.

In summary, Isulsongi mushroom supplementation reduced TC, TGs, and LDL-C levels and increased HDL-C levels in dogs, leading to improvements in AI and CRF. These effects were more pronounced in the high-level supplementation group. The present findings suggest that Isulsongi mushroom has potential as a functional ingredient for companion animal diets. However, considering the supplementation period and the limited number of animals in this study, further studies are needed, including different supplementation levels and long-term feeding trials.

Conclusion

Isulsongi mushroom (Lentinula edodes GNA01) supplementation affected serum lipid profiles in dogs. TC and LDL-C were significantly lower in the supplemented groups than in the control group, and HDL-C increased. TGs showed a significant decrease only in the 0.02% group.

As a result, both AI and CRF were decreased, suggesting that Isulsongi mushroom supplementation may help improve cardiovascular health in dogs. Especially at 9 weeks, the 0.02% group showed the lowest TC, TGs, and LDL-C and the highest HDL-C, meaning that the effect became stronger as the feeding level and period increased.

Overall, feeding Isulsongi mushroom to dogs resulted in changes in blood lipid characteristics, together with improvements in AI and CRF. Based on these results, Isulsongi mushroom can be considered as a possible functional feed material for companion animals. However, the present study is limited, and further work will be required. In particular, studies using different feeding levels of Isulsongi mushroom and longer feeding periods should be conducted in the future.