Aerobic exercise in cold weather may affect metabolic diseases and bone‐cartilage formation by increasing CTRP‐3 levels

Abstract

Aerobic exercise is recommended by clinicians in the prevention and treatment of metabolic diseases. The aim of this study is to investigate the effect of aerobic exercise in cold weather on CTRP‐3 levels and its potential implications for metabolic diseases. Twenty‐seven healthy young individuals (age = 22.1 ± 1.7 years, BMI = 22.2 ± 1.3, and n = 27; 13 female and 14 male) voluntarily participated in this study. Participants performed 40 min aerobic running exercise at 0, 12, and 20°C environmental temperatures. Our study demonstrates that 40 min of aerobic exercise at temperatures of 0 and 12°C significantly increased CTRP‐3 levels in athletes, while no significant change was observed at 24°C. The main findings indicated significant differences between pre‐and post‐exercise CTRP‐3 values for 0°C (p = 0.001) and 12°C (p = 0.005) environmental temperature, whereas no significant difference was found at 24°C (p = 0.148). Additionally, two‐way ANOVA revealed that both the temperature (0, 12, and 24°C) and exercise (pre‐ and post‐) affect serum CTRP‐3 levels (p = 0.023). CTRP‐3 elevation from baseline to post‐exercise in the 0°C, 12°C, and 24°C were +23.4%, +10.6%, and +8.1%, respectively. These findings suggest that engaging in aerobic exercise in cold weather conditions may serve as an effective intervention against metabolic disorders, including diabetes and obesity. The significant increases in CTRP‐3 levels following aerobic exercise in cold weather conditions justify the need for further, more extensive studies to assess their potential impact on metabolic diseases, as well as cartilage and bone formation.

Highlights

• Athletes' serum CTRP‐3 levels in 40 min aerobic exercise at 0, 12, and 24°C were evaluated by comparing them with their baselines and healthy controls' values.

• The significant increase in CTRP‐3 levels of 0 and 12⁰C of aerobic exercise suggests that it may influence metabolic diseases and bone‐cartilage production.

1. INTRODUCTION

Regular exercise is recommended in the prevention, treatment, and rehabilitation of obesity, cardiovascular, and metabolic diseases (Kon et al., 2023). Aerobic exercises, such as running and cycling, are both easy to implement and highly effective in glucose and lipid metabolism (Garber et al., 2011). Despite numerous investigations demonstrating the favorable effects of aerobic exercises, such as running and cycling, on glucose and lipid metabolism, the precise mechanisms underlying these effects remain poorly understood (Ruegsegger et al., 2018). Studies have indicated that both exercise and cold exposure may significantly augment the cardiovascular workload. Furthermore, submaximal exercise in cold environments is accompanied by an increase in both energy expenditure and cardiac workload, primarily due to the requirement for nonexercise thermogenic mechanisms to compensate for heat loss and exacerbated by the inherent inefficiency of this form of exercise (Gencoglu et al., 2021; Valtonen et al., 2018).

Adipose tissue is considered as a highly specialized endocrine organ that not only stores excess energy in the form of triglycerides but also synthesizes and secretes numerous bioactive molecules known as adipokines. These adipokines play a crucial role in regulating metabolism and a wide range of physiological functions, including insulin sensitivity, inflammation, and angiogenesis. The complement C1q/tumor necrosis factor‐related protein (CTRP) consists of 15 adipokines that have been shown to play an active role in important metabolic events, such as inflammation, energy metabolism, and insulin secretion (Choi et al., 2013; Schäffler et al., 2012). First discovered in 2001, CTRP‐3 (also called CORS‐26) is an adipokine synthesized by fat cells, effective in energy storage and metabolism. It is also secreted by lung, kidney, spleen, testis, monocytes, and macrophages and to a lesser extent by heart, bone, small intestine, liver, and skeletal muscle. It was determined that CTRP‐3 showed anti‐inflammatory activity by inhibiting the proinflammatory pathway induced by lipopolysaccharides. CTRP‐3, also known as cartducin or cartonectin, has been demonstrated to reduce osteoclastic activity by stimulating the proliferation and differentiation of chondrogenic and osteogenic precursors (Li et al., 2017).

Additionally, studies have indicated that CTRP‐3 levels are reduced in patients with acute coronary syndrome or stable angina pectoris. An inverse relationship has been observed between BMI, insulin, LDL, triglyceride, CRP levels, and CTRP‐3 levels (Li et al., 2017). In the present study, we aimed to assess serum CTRP‐3 levels to investigate the impact of 40 min of aerobic exercise at three different ambient temperatures. We compared the serum CTRP‐3 levels of athletes engaged in aerobic exercise in cold weather conditions with the baseline levels of the athletes and those of healthy controls.

2. MATERIALS AND METHODS

2.1. Study design

This study was conducted to investigate the serum cartonectin (CTRP‐3) responses to aerobic exercise performed under varying environmental temperatures in human subjects. Participants performed 40 min aerobic running exercises at three temperatures (0, 12, and 24°C) after 2–3 days. The study design and research protocol were approved by Ethics Committee of Erzurum Research Training Hospital (Erzurum BEAH KAEK numbered 2021/03–55).

2.2. Participants and ethics

Twenty‐seven healthy young individuals (age = 22.1 ± 1.7 years, BMI = 22.2 ± 1.3, and n = 27; 13 female and 14 male) were included in this study. The inclusion criteria were as follows: individuals aged 18–25 years with no chronic medical conditions requiring regular prescription medication. Subjects with sensitivity to cold, being in a special diet program, were not included. This study was conducted according to the Declaration of Helsinki. All participants were informed about possible risks related to experimental protocols and obtained written informed consent to participate in this study.

2.3. Exercise protocol

After 5 min of warming, subjects were verbally instructed to reach a 70% maximum heart rate (HR_max), and once they reached it, they were asked to keep it for 40 min (Archundia‐Herrera et al., 2017). The intensity of the running was calculated by the formula suggested by Karvonen, Kentala, and Mustala (Karvonen et al., 1957):

$$\text{Target}\text{HRzone}=\left[(\text{HRmax}-\text{HR}\text{resting})\ast \%\text{intensity})+\text{HRresting}\right]$$

HR was followed synchronously with the telemetric HR monitor (S610i, Polar Electro Oy, Kempele, Finland) to control the running speeds during all exercises. Participants were asked to perform the exercises after 3–4 h fasting. Each participant performed the exercises at the same time of the day. All of the exercises were performed at the same humidity (∼40%). Participants were dressed as they wish at 24°C, but they wore three layers of clothing in the 0°C: an inner layer in contact with the skin which does not readily absorb moisture but moves it to other layers (lightweight polyester or polypropylene), a middle layer which provides main insulation (polyester fleece or wool), and an outer layer which maximizes moisture transfer to the environment (Ratamess, 2011).

2.4. Biochemical measurement

After the venous blood taken from the participants before and after exercise was centrifuged at 1000 rpm for 15 min at 4⁰C, the supernatants were collected and stored in eppendorf tubes at −80⁰C until the day of measurement. Serum CTRP‐3 concentrations were measured using a commercially available enzyme‐linked immunosorbent assay kit (Human C1q/TNF‐related Protein3 ELISA kit E3300Hu, BT LAB, China). The levels of CTRP‐3 in the serum were analyzed in a double‐blind fashion.

2.5. Statistical analysis

Data was analyzed using IBM SPSS Statistics (Version 21.0, Armonk, NY). Results were given as mean ± standard deviation. Independent t‐tests compared prestudy CTRP‐3 levels and anthropometric features between genders. A two‐way repeated measures ANOVA examined interactions between time (pre/post‐exercise) and temperature (0, 12, and 24°C). A three‐way ANOVA assessed time, temperature, and gender effects. Sphericity was checked with Mauchly's test. Whenever an assumption was violated, Greenhouse–Geisser correction if epsilon (ε) value was <0.75 and Huynh–Feldt correction if ε was >0.75 were applied on the degree of freedom. A value of p < 0.05 was accepted as statistically significant. Effect sizes for the changes between pre‐ and post‐exercise were calculated using Cohen's d (Cohen, 1988) and classified according to Hopkins (2015). For repeated measures, two‐way analysis of variance (ANOVA) and the effect size was calculated using the partial eta squared coefficient (η _p ²). These computations were systematically conducted and reported utilizing the SPSS 25 statistical software package.

3. RESULTS

Table 1 presents the anthropometric characteristics and CTRP‐3 values of the participants. Height, body mass, and BMI values were significantly higher in men compared to women (p < 0.001 for all). However, there was no significant difference in the CTRP‐3_baseline levels.

TABLE 1.

Comparison of anthropometric characteristics, CTRP‐3 values at the baseline of the participant according to different variables.

	Females	Males	t	p
Age (year)	21.9 ± 2.0	22.4 ± 1.5	−0.732	0.471
Height (cm)	162.5 ± 5.2	175.6 ± 5.1	−6.550	<0.001*
Body Mass (kg)	56.3 ± 4.4	71.5 ± 5.8	−7.614	<0.001*
BMI (kg/m2)	21.2 ± 0.9	23.1 ± 1.1	−4.710	<0.001*
CTRP‐3baseline (ng/ml)	10.9 ± 4.3	13.2 ± 6.0	−1.120	0.274

Note: Data presented as mean ± standard deviation.

Abbreviation: BMI, Body mass index.

*p < 0.05 was accepted as statistically significant.

There was a significant difference between pre‐ and post‐exercise CTRP‐3 values at 0°C (p = 0.001 and d = 0.46) and 12°C (p = 0.005 and d = 0.24) environmental temperature, whereas no significant difference was found at 24°C (p = 0.148 and d = 0.26) [Figure 1]. Two‐way ANOVA revealed that both the temperature (0, 12, and 24°C) and exercise (pre‐ and post‐) affect serum CTRP‐3 levels (F_(2;1) = 4.063, p = 0.023, and η _p ² = 0.14).

FIGURE 1.

Graphical display of CTRP‐3 concentrations pre‐ and post‐exercises of the participants without subgroups. *: significantly different from pre‐exercises value; ‡: significant interaction between temperature (0, 12 and 24°C) and exercise (pre‐ and post‐), n _p ²: partial eta squared.

CTRP‐3 elevation from baseline to post‐exercise in the 0°C, 12°C, and 24°C were +23.4%, +10.6%, and +8.1%, respectively (Figure 2). However, biggest change of amount in the CTRP‐3 levels for both gender was at 0°C (+27.2% for males and +20.6% for females).

FIGURE 2.

Net change from baseline of CTRP‐3 concentrations in the different environmental temperature in the histogram plots (left panel) and in the boxplot (right panel). Box plot explanation: upper horizontal line of box, 75th centile; lower horizontal line, 25th centile; horizontal bar within box, median; upper horizontal bar outside box, 90th centile; lower bar outside box, 10th centile.

There was no significant interaction among the temperature (0, 12, and 24°C), exercise (pre‐ and post‐), and sex (males and females) from the three‐way ANOVA (F_(2;1;1) = 0.175, p = 0.840, and η _p ² = 0.01), but there was a main effect for exercise on the CTRP‐3 concentrations (F₍₁₎ = 11.759, p = 0.002, and η _p ² = 0.32). However, in the pairwise comparisons of sex subgroups between pre‐and post‐exercise (Table 2), CTRP‐3 levels significantly increased at 0°C in females (p = 0.036 and d = 0.54) and males (p = 0.016 and d = 0.40) and 12°C in females (p = 0.038 and d = 0.03) and males (p = 0.030 and d = 0.14), whereas no statistically significant difference was found at the 24°C for CTRP‐3 levels for both females and males (p = 0.337, d = 0.26; p = 0.181, and d = 0.23, respectively).

TABLE 2.

CTRP‐3 concentrations of males and females in the pre‐and post‐exercise at different environmental temperature.

	CTRP‐3 (ng/ml)	Pre‐exercise	Post‐exercise	Net change amount (ng/ml)	Change (%)
0°C	Females	11.0 ± 4.3	14.0 ± 6.5*	3.0 ± 4.6	+27.2%
	Males	13.1 ± 6.0	15.8 ± 7.4*	2.7 ± 3.6	+20.6%
12°C	Females	12.9 ± 5.7	14.8 ± 6.6*	1.9 ± 3.0	+14.7%
	Males	12.5 ± 5.5	13.3 ± 6.0*	0.8 ± 1.3	+6.4%
24°C	Females	12.2 ± 2.8	13.4 ± 6.0	1.3 ± 4.6	+9.8%
	Males	11.5 ± 3.5	12.2 ± 2.6	0.7 ± 1.8	+6.0%

*Significantly different from pre‐exercises value.

4. DISCUSSION

In the present study, the effects of aerobic exercise on CTRP‐3 levels in athletes at different air temperatures were evaluated. Height, body mass, and BMI values were significantly higher in the man compared to woman. No significant baseline CTRP‐3 level difference was observed between female and males. There was a statistically significant rise is detected between pre‐ and post‐exercise values at 0°C and 12°C environmental temperature, whereas no significant difference was found at 24°C. Our literature review revealed a paucity of research examining the impact of aerobic exercise conducted in cold environments on CTRP‐3 levels. In their study with 8 healthy male participants, Kon et al. did not detect a significant change in CTRP‐3 levels after acute high‐intensity all‐out SIT using a bicycle ergometer with 4 min of rest between sets and four 30‐s maximum efforts (Kon et al., 2021). It has been shown that the relationship of CTRP‐3 with energy substrate metabolism and metabolic diseases is related to the 5′ adenosine monophosphate‐activated protein kinase (AMPK) signaling pathway cycling above 60% of VO_2max, which is one of the acute aerobic exercise types, determined that it causes the activation of the AMPK pathway from skeletal muscles in humans (Vickers, 2017). In the study in which 8 healthy exercise habits were given to male volunteers with 30 min of aerobic exercise, the participants were given submaximal aerobic exercise at 75% of the VO_2max in neutral conditions. Serum levels of CTRP‐3 were observed to be significantly elevated at the 60‐min mark post‐exercise in comparison to the baseline levels measured before the exercise. Furthermore, it was ascertained that this increase persisted until the 120th minute mark (Kon et al., 2023). In another study in middle‐aged and older people, aerobic exercise (60%–70% peak oxygen uptake for 45 min, 3 days/wk) every day for 8 weeks significantly increased CTRP‐3 levels, while carotid‐femoral pulse‐wave velocity, abdominal visceral, and whole‐body fat ratio were determined to decrease significantly (Hasegawa et al., 2018). These results show that exercise may induce CTRP‐3 secretion. Zheng et al. suggested that CTRP‐3 had vasodilator effects in mice aortas dose dependent manner (Zheng et al., 2011). In a study comparing 180 obese and essential hypertension patients with 66 healthy control groups, CTRP‐3 levels of the obese and hypertensive group were found to be significantly lower than the normotensive control group (Deng et al., 2015) In their study of 48 obese and 36 normal‐weight prepubertal children, Chen et al. found that serum CTRP‐3 serum levels were lower in obese children than in controls. It has been shown that CTRP‐3 levels in obese children with insulin resistance are significantly lower than in obese children without insulin resistance.

In addition, it was determined that serum CTRP‐3 levels decreased significantly with increasing glucose and insulin levels after a 3‐h oral glucose tolerance test applied to obese children (Chen et al., 2019). In a study conducted in South Korea, 76 obese women were given 45 min of aerobic exercise and 20 min of resistance training exercise 5 days a week for 3 months. At the end of 3 months, cardiometabolic risk factors, such as metabolic syndrome and insulin resistance, and CTRP‐3 levels decreased significantly in women (Choi et al., 2013). Recent studies indicate that CTRP‐3 levels are higher in females than males (Deng et al., 2015; Wolf et al., 2015). The higher levels of CTRP‐3 in females compared to males may be attributed to the greater amount and different distribution of adipose tissue, as well as the influence of sex hormones. On the contrary, in the study of Qu et al., CTRP‐3 levels were found to be higher in men than in women. In this study, it was shown that CTRP‐3 levels were the lowest in both the obese and type 2 diabetic group, while the type 2 diabetic patients were lower than the healthy controls in the obese group (Qu et al., 2015). In our study, however, no significant difference was found in baseline values between men and women. The absence of gender‐based differences in baseline CTRP‐3 levels in our study may be attributed to the inclusion of physically active individuals and athletes without comorbidities affecting CTRP‐3 levels, such as obesity, hyperlipidemia, and diabetes mellitus. In addition, differences in the distribution of adipose tissue related to sexual hormones and gender may be compensated by the high BMI of the men in our study.

CTRP‐3 was highly expressed in osteosarcoma and chondroblastoma cell lines (Akiyama et al., 2009). Detection of CTRP‐3 in developing cartilage and chondrocytes in mouse embryo studies (Maeda et al., 2001, 2006) and suppressing osteoclastic activity, while stimulating osteogenesis and chondrogenesis in vitro studies (Akiyama et al., 2006; Kim et al., 2015; Yokohama‐Tamaki et al., 2011) suggest that CTRP‐3 plays an important role in bone and cartilage development. In our study, aerobic exercise in cold air condition significantly increased CTRP‐3 levels. This increase suggests that CTRP‐3 can be used as a new preventive and therapeutic method against pathologies caused by bone and joint damage by increasing the mitotic activity of CTRP‐3 on bone and killer tissue. Long‐term studies combined with animal studies are needed to clearly demonstrate the inducing effect of aerobic exercise performed in the cold. Peterson et al. found that diet induced obesity decreased CTRP‐3 levels (Peterson et al., 2010). Zhang et al. suggested that the levels of CTRP‐3 decreased significantly in obese children and had negative correlation between the insulin resistance and pancreatic beta cell indicators (Zhang et al., 2019). Choi et al., in a study of 76 Korean obese women, found that 3 months of exercise caused 9% weight loss, while 15% loss in CTRP‐3 levels (Choi et al., 2013). More research is necessary to fully understand the intricate connection between diet, weight management, exercise, and CTRP‐3.

CTRP‐3 has beneficial effects on glucose homeostasis and insulin resistance. CTRP‐3 administration decreased the serum glucose levels for 8 h in rodents. But, it was determined that continuous elevation due to transgenic overexpression did not change glucose values. The increase in serum CTRP‐3 levels during fasting may be attributed to a compensatory mechanism (Peterson et al., 2010), possibly due to the activation of the glucagon pathway and/or inhibition of the insulin pathway. In a study, CTRP‐3 levels were significantly higher in type 2 diabetes mellitus with insulin resistance. This result may be a compensatory mechanism for insulin and leptin resistance (Choi et al., 2012a). CTRP‐3 serum levels were significantly increased in prediabetics (Choi et al., 2012b) and decreased in type 2 diabetes mellitus patients (Deng et al., 2015; Moradi et al., 2019). While oral antidiabetics, such as metformin and GLP‐1 receptor agonist, increased, insulin treatment decreased CTRP‐3 levels (Guo et al., 2020). This suggests that there are different yet undiscovered relationships between CTRP‐3 and insulin. Main findings of the present study suggest that aerobic exercise performed in cold weather may contribute to the regulation of the metabolic system by increasing significantly serum CTRP‐3 levels. In order to clearly demonstrate the metabolic effects of CTRP‐3, further comprehensive studies are required that concurrently assess parameters, such as serum glucose, insulin, and cholesterol levels. To the best of our knowledge, this study is the first and only one to investigate the impact of aerobic exercise at 0 and 12°C on serum CTRP‐3 levels.

4.1. Limitations

This study has several limitations. First, we used a cross‐sectional design with only healthy young volunteers and athletes; therefore, it was not possible to draw generalizable conclusions about causality. Due to the inability of the sedentary control group to perform 40 min of aerobic exercise, only baseline values were measured for this group, preventing the comparison of exercise effects at different temperatures with the control group. It was not feasible to provide neutral conditions for the athletes during cold weather exercise due to ethical concerns, so clothing suitable for cold weather was provided, resulting in direct exposure to cold air only on the face and hands. Additionally, CTRP‐3 levels were only measured in the acute phase after exercise and further evaluation would require measuring levels at 1‐ and 2‐h post‐exercise.

Furthermore, we do not have a data on the tissue from which the CTRP‐3 increase in serum originates and the tissue source of the increased serum CTRP‐3 levels remains unclear. Further, animal studies are required to investigate the main synthesis and secretion sites of CTRP‐3.

5. CONCLUSIONS

As a result, it was shown in our study that 40 min of aerobic exercise at 0 and 12°C significantly increased the CTRP3 levels of the athletes and did not cause a significant change at 24°C.

The findings of this investigation indicate that engaging in aerobic exercise during cold weather conditions could potentially serve as an efficacious intervention for metabolic disorders, such as diabetes mellitus and obesity. Furthermore, it may also exert a significant impact on the promotion of bone and cartilage formation by augmenting CTRP‐3 levels. There is a need for more detailed and comprehensive studies investigating the effects of aerobic exercise at different temperatures on metabolic diseases and bone‐cartilage structure.

AUTHOR CONTRIBUTION

All authors have contributed significantly, and all authors agree with the content of the manuscript.

CONFLICT OF INTEREST STATEMENT

The authors declare no financial support or relationships that may pose a conflict of interest.