Obesogenic diet and targeted deletion of potassium channel Kv1.3 have differing effects on voluntary exercise in mice

Voluntary exercise is frequently employed as an intervention for obesity. The voltage-gated potassium Kv1.3 is also receiving attention as a therapeutic target for obesity, in addition to potential therapeutic capabilities for neuroinflammatory diseases. To investigate combinatorial effects of these two therapies, we have compared the metabolic status and voluntary exercise behavior of both wildtype mice and a transgenic line of mice that are genetic knockouts for Kv1.3 when provided with a running wheel and maintained on diets of differing fat content and caloric density. We tracked metabolic parameters and wheel running behavior while maintaining the mice on their assigned treatment for 6 months. Wildtype mice maintained on the fatty diet gain a significant amount of bodyweight and adipose tissue and display significantly impaired glucose tolerance, though all these effects were partially reduced with provision of a running wheel. Similarly to previous studies, the Kv1.3-null mice were resistant to obesity, increased adiposity, and impaired glucose tolerance. Both wildtype and Kv1.3-null mice maintained on the fatty diet displayed increased wheel running activity compared to CF-fed mice which was caused primarily by a significant increase in amount of time spent running as opposed to an increase in running velocity. Interestingly, the patterns of running behavior differ between wildtype and Kv1.3-null mice, especially in how their resting periods are distributed through the dark phase. These studies indicate that voluntary exercise combats metabolic maladies and running behavior is modified by both consumption of an obesogenic diet and deletion of the Kv1.3 channel. NEW and NOTEWORTHY Kv1.3-null mice exhibit different running and resting patterns compared to wildtype mice Mice maintained on an obesogenic diet (32% kcal from fat) exhibit increased running distance and increased time spent running compared to mice fed normal rodent chow.

The most promising therapeutic directions for both voluntary exercise and K v 1. 3-9 8 targeted treatments are converging on a subset of human diseases for which both treatments 9 9 might be effective. This is especially true for diseases that have both a metabolic and 1 0 0 autoimmune component. Progress is being made rapidly in both areas of research, but little is 1 0 1 known concerning the potential combinatorial effects of these two therapeutic interventions.  Our investigation is the first to characterize the running phenotype of mice where we 1 0 7 measured the interactions of six-month access to voluntary exercise, diet modification, and 1 0 8 genetic loss of the K v 1.3 channel. We found that both wildtype and K v 1.3-null mice challenged 1 0 9 with a moderately high-fat diet participated in wheel running more often and ran farther than 1 1 0 control-fed mice. We also demonstrated that participation in voluntary exercise, as expected, patterns of resting and running differed across the both the light and dark phases. To investigate the role of the ion channel K v 1.3 on exercise behavior, a transgenic line these two groups were pooled and referred to as wildtype (WT) throughout this manuscript. To compare normal weight gain to the increased weight gain and deposition of adipose weekly. Upon termination, fat pads were excised and weighed by an investigator that was 1 5 8 blind to the genotype and treatment group of the mouse. Endometrial, retroperitoneal, subcutaneous (a subsample of the right side), and mesenteric adipose tissues were collected 1 6 0 and combined. Brown fat was not sampled. Strips (Bayer Healthcare) to determine blood glucose levels at baseline (prior to injection) and 1 6 9 at set timepoints 10, 20, 30, 60, 90, and 120 minutes following the injection. extended into the cage that held the running wheel above the bedding and allowed for rotation.

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A clean wheel was provided weekly and the wheels were lubricated with non-caloric, tasteless, 1-minute bin was the smallest bin size that the software allowed to be exported. concluded that restricting analysis to a 28 day period of only the dark phase is justifiable that were obviously due to a technical error (trapping of bedding or low battery) as opposed to 1 9 0 actual behavioral changes of a mouse.

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Mean running distance was calculated as the daily average of kilometers run per day 1 9 2 across the 28-day sample for each mouse. Active time was calculated as the number of 1-1 9 3 minute bins during which the mouse was participating in wheel running. Running velocity was 1 9 4 reported as the mean wheel rotations per minute for every 1-minute bin during which the mice 1 9 5 was active. Running bursts were defined as consecutive 1-minute bins during which the mouse 1 9 6 was active while rests were defined as consecutive 1-minute bins during which the mouse was 1 9 7 inactive. Latency to run is defined as the mean amount of time after dark onset until a mouse onset until a mouse stopped engaging in wheel running.  the associated plugin ActogramJ {35,36}. Graphs were designed and generated using Origin WT mice fed the CF diet weighed the same regardless of whether they had access to a 2 1 7 running wheel (WT-CF-SED 24-week bodyweight = 27.8 g ± 2.1; WT-CF-RW = 28.0 ± 1.4).

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Wheel running is consistent over time independent of genotype or diet 2 4 8 Following the 3-day acclimation period and barring any technical errors, mice in all 2 4 9 treatment groups that were provided a wheel ran very consistently over the full 120-160 day 2 5 0 running period. Qualitative assessment of double-plotted actograms showed that mice 2 5 1 participate in wheel running in a manner that is entrained to their light/dark cycle with very little weekly and monthly basis, the mice ran consistently ( Figure 4C-D). Both WT and KO mice maintained on the MHF diet ran farther than the two CF-fed 11.91 ± 1.12; F(3,39) = 7.23, p = 0.0006) ( Figure 4A). The WT-MHF and KO-MHF mice ran 2 5 8 slightly faster than the WT-CF and WT-MHF but this did not reach statistical significance 2 5 9 C h e l e t t e e t a l . , P a g e 1 3 length of the running bursts were significantly longer for MHF-fed mice compared to CF-fed 2 8 1 mice for both genotypes (WT-CF-RW = 8.6 ± 1.6 mins per burst, KO-CF-RW = 7.6 ± 0.8, WT-2 8 2 MHF-RW = 11.5 ± 2.0, KO-MHF-RW = 13.5 ± 2.3; F(3,39) = 23.2, p < 0.0001)( Figure 6A+B).

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KO-MHF-RW mice engaged in the fewest rests, significantly less than the CF-fed groups but