Effects of Swimming at Different Water Temperatures on Muscle and Adipose Tissue Adaptation in Diet-Induced Obese Mice.

Swimming at 25°C and 32°C significantly reduced body weight and epididymal fat pad (EFP) weight in diet-induced obese mice.

• Obese mice were subjected to swimming at three water temperatures: 15°C, 25°C, or 32°C.
• Body weight and EFP weight reductions were significant in the 25°C and 32°C groups but not the 15°C group.
• High-fat diet-induced obesity was used as the experimental model prior to swimming interventions.
• Changes in tissue weight were assessed alongside metabolic profiles and grip strength.

Cold-water swimming at 15°C enhanced endurance performance compared to other temperature groups.

• Exhaustive swimming performance was used as a measure of endurance capacity.
• The 15°C group showed enhanced endurance performance while not producing the same body weight or fat reduction seen at 25°C and 32°C.
• FNDC5 protein expression in muscle was most pronounced in the 15°C group.
• Cold water swimming appeared to drive adaptations distinct from those observed at moderate or warm temperatures.

All swimming groups showed increased oxidative (Type I) muscle fibers, with histological analysis confirming muscle fiber composition changes.

• Histological analyses of gastrocnemius muscles were performed to assess muscle fiber composition.
• Type I (oxidative) fiber increases were observed across all swimming temperature groups (15°C, 25°C, and 32°C).
• Grip strength improvements were significant in the 25°C and 32°C groups.
• Muscle fiber composition was assessed alongside adipose tissue remodeling markers.

Adipocyte size was reduced most prominently in the 25°C swimming group, accompanied by elevated Pgc-1α expression in epididymal fat pads.

• Histological analysis of epididymal fat pads revealed reduced adipocyte size in the 25°C group.
• Gene expression analysis measured Ucp1, Pgc-1α, Prdm16, and Cidea in EFP.
• Elevated Pgc-1α expression in EFP was 'particularly prominent at 25°C.'
• Adipose tissue remodeling markers suggest browning-related adaptations were temperature-dependent.

The SIRT1-PGC-1α-FNDC5 pathway in muscle showed temperature-dependent activation, with FNDC5 most pronounced at 15°C.

• Western blot analyses were used to assess the SIRT1-PGC-1α-FNDC5 pathway in gastrocnemius muscle.
• FNDC5 protein expression in muscle was most pronounced in the 15°C cold-water swimming group.
• The SIRT1-PGC-1α-FNDC5 pathway is associated with irisin signaling and muscle-adipose tissue crosstalk.
• Temperature-dependent differences in this pathway suggest distinct molecular mechanisms underlie adaptations at each water temperature.

Swimming at 25°C and 32°C improved metabolic profiles in diet-induced obese mice.

• Key metabolic parameters were assessed across all swimming temperature groups.
• Significant metabolic improvements were observed in the 25°C and 32°C groups but were less prominent in the 15°C group.
• Metabolic benefits included improvements alongside reductions in body weight and EFP weight.
• The study used a high-fat diet-induced obesity mouse model to establish metabolic dysfunction prior to intervention.

Water temperature during swimming produces distinct temperature-dependent metabolic and muscular adaptations in obese mice.

• Three experimental water temperatures (15°C, 25°C, 32°C) produced qualitatively different physiological outcomes.
• Moderate and warm temperatures favored fat reduction, metabolic improvement, and grip strength, while cold temperature favored endurance.
• Gene expression patterns (Ucp1, Pgc-1α, Prdm16, Cidea) and protein expression differed across temperature groups.
• The authors conclude that 'distinct temperature-dependent metabolic and muscular adaptations' occur during swimming in obese mice.