The effects of acute and chronic exercise on lipocalin-2 in middle-aged and older adults: a randomized control trial.

Acute high-intensity interval exercise (HIIE) produced a significant main effect for time on serum LCN2 levels.

• Circulating serum LCN2 levels increased significantly immediately post-HIIE compared to baseline (P < .001).
• LCN2 levels returned to levels similar to baseline by 60 and 180 min post-HIIE.
• 33 middle-aged and older adults aged 45-84 years participated, with a median BMI of 26.21 kg/m2.
• Blood samples were analyzed at baseline and immediately, 1 h, and 3 h post-HIIE.

Acute HIIE produced a significant main effect for time on insulin, glucose, and HOMA-IR.

• A main effect for time for serum insulin, glucose, and HOMA-IR was detected after acute HIIE (P < .001).
• These metabolic markers were measured at baseline and immediately, 1 h, and 3 h post-HIIE.
• The acute exercise session used was a high-intensity interval exercise protocol.
• Changes in these markers reflect improved insulin sensitivity following acute HIIE.

Four weeks of high-intensity interval training (HIIT) had no significant effect on serum or urinary LCN2 levels.

• Participants were randomized to 4 weeks of HIIT or a control condition.
• Neither serum LCN2 nor urinary LCN2 changed significantly following the 4-week HIIT intervention.
• Urinary LCN2 was assessed pre and post 4 weeks of HIIT.
• The lack of chronic effect suggests LCN2 may not be modifiable by short-duration exercise training in this population.

Four weeks of HIIT improved VO2peak but did not significantly improve physical function.

• VO2peak improved following the 4-week HIIT intervention.
• Physical function did not show a significant improvement after 4 weeks of HIIT.
• The study population consisted of middle-aged and older adults (45-84 years).
• Improvement in VO2peak without corresponding changes in LCN2 or physical function suggests dissociation between cardiorespiratory fitness gains and these outcomes over 4 weeks.

Chronically elevated circulating LCN2 levels are implicated in poor energy regulation, increased cardio-metabolic disease risk, and poor physical function.

• The relationship between LCN2 and these outcomes provided the rationale for investigating whether exercise could modulate LCN2.
• Whether LCN2 is modifiable by exercise was stated as unclear prior to this study.
• The study examined whether exercise-induced changes in LCN2 would relate to glucose regulation, body composition, and physical function.

It remains unclear whether LCN2 is modifiable by chronic exercise training lasting longer than 4 weeks or in people with poor glycaemic control.

• The authors note this as a limitation and area for future investigation.
• The current study only examined a 4-week HIIT intervention.
• Participants had a median BMI of 26.21 kg/m2, which may not represent individuals with poor glycaemic control.
• The authors suggest future studies should examine longer training durations and populations with impaired glucose metabolism.