Introduction

In recent years, interest in companion dog health has been growing, and this has led to a longer lifespan and an increase in the proportion of senior dogs. Old dogs often show fat accumulation, hyperlipidemia, and higher cases of cardiovascular problems because of lower metabolism and hormone changes, so nutritional care is needed (Lee et al., 2025). Blood lipid traits, like total cholesterol (TC), triglycerides (TGs), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C), are important indicators to check health, and they can change much by age or diet factors (Usui et al., 2015; Kim et al., 2018b).

At the same time, many studies have reported that mushrooms contain bioactive compounds with anti-cancer, antioxidant, immune regulation, anti-obesity and anti-hyperlipidemia effects. These effects are mostly from polysaccharides, phenolic compounds, vitamins and minerals (Jang et al., 2015; Youn and Lee, 2021). Shiitake mushroom (Lentinula edodes) is a common edible mushroom, and it contains β-glucan, eritadenine, polyphenol and other bioactive materials that can lower cholesterol, improve antioxidant activity, and enhance immunity (Bisen et al., 2010; Lee et al., 2014; Zhu et al., 2023). Eritadenine especially is known to block cholesterol synthesis in the liver and reduce plasma cholesterol in rodents (Sugiyama et al., 1995). Recent studies also reported that bioactivity of shiitake mushroom can help human health by antioxidant, liver protection, lipid lowering and cardiovascular protection (Camilleri et al., 2025).

Among them, Isulsongi mushroom (Lentinula edodes GNA01) is a new cultivar developed in Korea. It has higher mineral and dietary fiber than normal shiitake, better storage, higher edibility, good flavor and texture (Choi et al., 2016; 2017; Jang et al., 2017). It also shows strong antioxidant activity, so it has high potential as health material (Jang et al., 2015). Previous studies showed extracts from many edible mushrooms could lower blood lipid and improve antioxidant activity in animals fed high-fat and high-cholesterol diets (Jang et al., 2015). Phellinus linteus was also reported to improve serum lipid and increase antioxidant enzyme activity (Song et al., 2010). All these reports suggest edible mushrooms can give positive effect on lipid metabolism.

In recent years, function of mushrooms has been more studied in animal experiments. Medicinal mushroom like Cordyceps sinensis showed antioxidant and anti-lipid effect (Sen et al., 2023). Agaricus bisporus was used as alternative protein source, and when replacing meat, it improved blood lipid profile (Fu et al., 2023). For dogs, a study found that adding shiitake mushroom powder in feed improved palatability and nutritional value (Feng et al., 2020). Although nutritional superiority of Isulsongi mushroom over normal shiitake has been reported, there is no study has yet examined its effect on blood lipid profile in dogs.

Therefore, this study aimed to examine the effect of feeding Isulsongi mushroom to dogs of different ages on blood lipid profile. The purpose was also to consider its potential as a functional material, and to provide base data for age-specific nutrition, functional dog food, and health supplement development.

Materials and Methods

Experimental materials

The mushroom used in this test was Isulsongi (Lentinula edodes GNA01), produced in Jinju, Gyeongsangnam-do, and freeze-dried by Gyeongnam Herbal Cooperative. The freeze-dryer (FDTA-5050, Operon, Korea) worked under chamber pressure of 0.01 - 0.05 mbar, with sublimator and vacuum station attached. The dried mushroom was ground into fine powder using a grinder (PRS-20-1, Kyunghan, Korea) and then given to the dogs.

Experimental design and feeding management

The dogs used in this experiment were Maltese with normal body condition scores (BCSs) and no signs of obesity or disease. A total of ten dogs were divided into two groups according to age: an adult group consisting of five dogs with an average age of 42 months (3 - 4 years) and an average body weight of 2.21 kg, and a senior group consisting of five dogs with an average age of 106 months (8 - 10 years) and an average body weight of 2.81 kg.

The freeze-dried Isulsongi mushroom was given orally once a day at 150 mg·kg^-1 body weight, administered orally after evening feeding, diluted in water, for 9 weeks. The dosage was set by reference to Kusaba et al. (2021). Dogs were fed commercial diet twice a day (morning and evening), about 30 minutes each time, At other times, the dogs were allowed to move freely within the indoor space. To reflect real-life conditions and consider their normal daily patterns, both feed and water were provided ad libitum. The feed was extruded pellet (EP) type from a domestic company (made in Australia), with crude protein over 29.0% and crude fat over 17.0%.

This experiment was approved by the Institutional Animal Care and Use Committee of Daegu University (Approval number: DUIACC-2020-16-0901-003).

Blood collection

Blood was collected four times: before feeding mushroom (week 0), and at 3, 6, and 9 weeks. Sampling was done in the morning before feeding. About 5 mL of blood was taken from the jugular vein using a syringe with 0.3 mL heparin. The blood was kept at room temperature for 30 minutes, then centrifuged (3,500 rpm, 15 min, 4℃) to separate serum. Serum samples were stored frozen at -80℃ until analysis.

Blood analysis

The serum was analyzed for TC, HDL-C, LDL-C, and TGs. Also, atherogenic index (AI) and cardiac risk factor (CRF) were calculated. Commercial kits (Asan Pharm, Korea) were used for all analysis. The formulas were:

where, AI : atherogenic index

TC : total cholesterol

HDL : high-density lipoprotein

CRF : cardiac risk factor

Statistical analysis

Data from the experiment were analyzed using SAS software (SAS, 2023). ANOVA was used, and differences between age groups were tested by t-test. Differences between feeding periods were tested by Duncan’s multiple range test. Statistical significance was judged at 5% level (p < 0.05).

Results

Cholesterol

After feeding Isulsongi mushroom, the serum TC concentration went down in both age groups. At the start (week 0), adult group showed 212.35 mg·dL^-1 and senior group showed 227.41 mg·dL^-1, but as weeks passed, values kept decreasing, and at week 9 they were 180.94 mg·dL^-1 and 188.63 mg·dL^-1. At every time point, the senior group had significantly higher values than adult group (p < 0.05). Especially at week 6 and 9, both groups were significantly lower than those at week 0 (p < 0.05), and the decrease was greater in the senior dogs. This result shows that Isulsongi mushroom can reduce serum TC in dogs effectively, and also age makes difference in response (Table 1).

HDL-C level increased during the feeding period. At week 0, adult group was 69.22 mg·dL^-1 and senior group was 82.89 mg·dL^-1. At week 9, they rose to 90.89 mg·dL^-1 and 98.11 mg·dL^-1. The senior group was higher than adult group in all feeding period (p < 0.05), and in both groups values became significantly higher after week 6 compared to week 0 (p < 0.05). Especially in adult group, HDL level at week 6 and 9 was significantly higher than at week 0 (p < 0.05). These results mean that Isulsongi mushroom feeding can increase HDL-C and give positive influence to lipid metabolism.

LDL-C concentration decreased significantly as the experiment went on (p < 0.05). At week 0, adult group was 126.10 mg·dL^-1 and senior group was 124.80 mg·dL^-1. At week 9, they were 75.43 mg·dL^-1 and 72.24 mg·dL^-1, both significantly lower (p < 0.05). There was no big difference between age groups, but significant decreases were seen at week 3, 6, and 9 compared to week 0 (p < 0.05). These results show that Isulsongi mushroom lowers LDL-C, and the effect becomes clearer with continuous feeding.

Triglyceride

TGs levels also showed an overall decreasing trend during the experiment. In the adult group, it went down from 84.79 mg·dL^-1 at week 0 to 73.11 mg·dL^-1 at week 9. In the senior group, it also dropped from 98.55 to 91.39 mg·dL^-1. At all time points, the senior dogs had higher values than adult dogs (p < 0.05). The adult group showed significant decrease at week 9 compared to week 0 (p < 0.05). On the other hand, in the senior group the decrease was not significant. These results mean that Isulsongi mushroom effect on lowering TGs was more clear in younger dogs (Table 2).

Atherogenic index

The AI decreased significantly as the experiment went on (p < 0.05). In the adult group, it dropped from 2.07 at week 0 to 1.00 at week 9. In the senior group, it went from 1.75 to 0.92 (p < 0.05). Throughout the entire period, the adult group had significantly higher values than the senior group (p < 0.05). In both age groups, significant decrease was already seen after week 3 (p < 0.05). Especially in adult group, AI at week 3, 6, and 9 were all lower than at week 0 (p < 0.05), and the senior group also showed same tendency. These results suggest that Isulsongi mushroom can improve lipid composition and also lower the risk of atherosclerosis (Table 3).

Cardiac risk factor

The CRF also decreased significantly during the experiment. In the adult group, it went down from 3.07 at week 0 to 2.00 at week 9. In the senior group, it dropped from 2.75 to 1.92. Through the whole period, the adult group showed significantly higher values than the senior group (p < 0.05). In both age groups, step by step and significant reduction was confirmed as weeks passed (p < 0.05). In the adult dogs, CRF was already significantly lower after week 3 compared to week 0, and the senior group also showed the same trend of decrease (Table 4).

Discussion

In this study, feeding Isulsongi mushroom (Lentinula edodes GNA01) to dogs for 9 weeks showed improvement in all main indicators related to serum lipid metabolism. TC decreased from 212.35 to 180.94 mg·dL^-1 in the adult group, and from 227.41 to 188.63 mg·dL^-1 in the senior group. These values were a bit higher than the average cholesterol of Maltese dogs in Korea (137.45 mg·dL^-1; Kim et al., 2018a), but they were similar to the mean value (204.7 mg·dL^-1) reported in a large-scale analysis of about 500 dogs in Japan (Usui et al., 2014), and they were inside the healthy dog range (135 - 270 mg·dL^-1) suggested by Costa-Santos et al. (2019). Considering that cholesterol in blood can change widely by breed, age, body size, sex, environment, and diet (Usui et al., 2015), the difference between studies may come from feed or environmental factors. Also, higher cholesterol was seen in the senior dogs through the whole test, which agrees with earlier reports that cholesterol rises with age (Pasquini et al., 2008; Usui et al., 2014).

The decrease of TC in both adult and senior dogs in this study agrees with past studies showing that shiitake and other edible mushroom extracts reduced cholesterol and improved antioxidant activity in rodents fed high-fat and high-cholesterol diets (Kim et al., 2013; Lee et al., 2014). It also agrees with earlier reports that eritadenine in shiitake suppresses cholesterol synthesis in the liver and lowers plasma cholesterol (Sugiyama et al., 1995; Jang et al., 2015).

HDL-C increased significantly, from 69.22 to 90.89 mg·dL^-1 in adults and from 82.89 to 98.11 mg·dL^-1 in seniors. These values were inside the healthy dog HDL range (60 - 140 mg·dL^-1) reported by Costa-Santos et al. (2019), which shows that Isulsongi mushroom can improve lipid metabolism and has anti-atherosclerosis effect. This result matches previous reports that Lentinula edodes extracts improve HDL, antioxidant activity, and vascular function (Jang et al., 2017; Youn and Lee, 2021; Camilleri et al., 2025). In this study, HDL was higher in the senior group than the adult group, which is also consistent with other research that showed HDL tends to rise again in old dogs (Usui et al., 2015).

LDL-C dropped from 126.10 to 75.43 mg·dL^-1 in adults, and from 124.80 to 72.24 mg·dL^-1 in seniors. Unlike the variable patterns reported by Pasquini et al. (2008), this study showed steady decrease, which suggests that Isulsongi mushroom may have consistent effect on LDL-C control. TGs decreased significantly in adults (84.79 to 73.11 mg·dL^-1), but in seniors the decrease (98.55 to 91.39 mg·dL^-1) was not significant. This may be because TGs tend to increase with aging (Usui et al., 2014), and lower metabolism and hormone changes in old dogs limit the effect. However, significant reduction of LDL and TGs in adults is similar to reports that lion’s mane and cauliflower mushroom lowered LDL and TGs and increased antioxidant enzyme activity in rodents (Jang and Yoon, 2017; Im et al., 2021). These effects are thought to come from β-glucan and phenolic compounds commonly contained in mushrooms (Bisen et al., 2010).

Both AI and CRF were improved, which shows that Isulsongi mushroom can help prevent cardiovascular disease. Compared with earlier research that obesity in old dogs raises cardiovascular risk by changing lipid and hormone levels (Kim, 2012), These results suggest that mushroom supplementation has protective effect.

Other animal studies abroad also reported similar outcomes. In rats fed high-fat and high-cholesterol diets, Lentinula edodes and Agaricus bisporus powders reduced TC, LDL-C, and TGs, and lowered liver fat (Handayani et al., 2011; Goyal and Grewal, 2024). Hericium erinaceus and Agaricus brasiliensis also improved blood lipids, suppressed body weight gain, and increased fecal lipid excretion (Jang and Yoon, 2017; Jin and Lee, 2018). The main compounds in shiitake, eritadenine and β-glucan, are known to protect cardiovascular health by blocking cholesterol synthesis, reducing intestinal absorption, and increasing antioxidant activity (Sugiyama et al., 1995; Camilleri et al., 2025). This agrees with the AI and CRF improvements seen in this study.

In this study, feeding Isulsongi mushroom to dogs made TC, LDL, and TGs go down, and HDL go up. In the adult dogs, the improvement in TGs and LDL was more clear, but in the senior dogs, the drop in TGs was not significant. This may be because of lower metabolism and hormone changes with age. AI and CRF also went down in both groups. These results mean that Isulsongi mushroom can be considered as a functional material to help prevent cardiovascular problems in dogs, no matter the age.

Conclusion

In this study, dogs were divided by age and fed Isulsongi mushroom for 9 weeks, and serum indicators related to lipid metabolism were checked. As a result, TC, LDL-C, and TGs decreased significantly, while HDL-C increased. Also, the AI and the CRF were improved, showing that supplementation with Isulsongi mushroom induced positive changes in blood lipid composition.

When compared by age, the senior dogs had higher cholesterol and TGs values than the adult dogs, but the effect of mushroom feeding was seen in both groups. Especially in the adult group, the decrease was more significant, which shows that response in lipid metabolism can be different depending on age.

Therefore, Isulsongi mushroom has potential as a food material that can improve blood lipid metabolism and lower cardiovascular risk in dogs. These findings provide baseline data for age-specific nutrition management and functional feed development. However, this study had limitations due to the small sample size and the use of a single breed, making it difficult to generalize the results. Therefore, further studies involving a larger number of subjects, various breeds, and different conditions are needed.