Diet‐induced obesity decreases rate‐dependent depression in the Hoffmann’s reflex in adult mice

Abstract

Obesity is associated with balance and motor control deficits. We have recently shown that Group Ia muscle spindle afferents, the sensory arm of the muscle stretch reflex, are less responsive in mice fed a high‐fat diet. Here we test the hypothesis that reflex excitability to sensory information from Group Ia muscle spindle afferents is altered in a mouse model of diet‐induced obesity. We measured the anesthetized Hoffmann’s or H‐reflex, the electrical analog of the muscle stretch reflex. Adult mice of both sexes were fed a control diet (CD; 10% kcal from fat) or a high‐fat diet (HFD; 60% kcal from fat) for 5, 10, or 15 weeks. We used three quantitative measures of H‐reflex excitability: (1) H‐reflex latency; (2) the percentage of motor neurons recruited from electrical stimulation of Group Ia muscle spindle afferents (Hmax/Mmax); and (3) rate‐dependent depression (RDD), the decrease in H‐reflex amplitude to high frequency stimulation (20 stimuli at 5 Hz). A HFD did not significantly alter H latency (P = 0.16) or Hmax/Mmax ratios (P = 0.06), but RDD was significantly lower in HFD compared to CD groups (P < 0.001). Interestingly, HFD males exhibited decreased RDD compared to controls only after 5 and 10 weeks of feeding, but females showed progressive decreases in RDD that were only significant at 10 and 15 weeks on the HFD. These results suggest that high‐fat feeding increases H‐reflex excitability. Future studies are needed to determine whether these changes alter muscle stretch reflex strength and/or balance and to determine the underlying mechanism(s).

Impaired rate-dependent depression of the H-reflex in type-2 diabetes, prediabetes, overweight and obesity: A cross-sectional study

“…[19,20] In contrast, altered RDD was observed in mice fed with a high-fat diet that consequently developed obesity. [21] In line with the evidence in animals, in humans, RDD impairment was reported in individuals with type-1 and type 2 diabetes with painful and non-painful neuropathy. [22,23] Recently, further exploration of optimal RDD parameters has been conducted to study spinal disinhibition in diabetic subpopulations by using stimulation frequencies <3 Hz.…”

“…Previously, it was reported that diet-induced obesity in mice causes impairment of RDD. [ 21 ] Our results represent the first evidence of the loss of RDD in this population and open new questions about the consequences of overweight and obesity on sensory and motor spinal processing.…”

Relationship between the diet and psychiatric diseases such as depression, anxiety and attention-deficit hyperactivity disorder (ADHD)

“…Similar conclusions were made in experiments where depression in offspring appeared on the maternal model of obesity induced by high fat diet [21]. Interestingly, one of the newer studies found that adult mice consuming a high fat diet had a lower percentage of rate dependent depression than the group of adult mice consuming the control diet [22].…”

Evidence of impaired H-reflex and H-reflex rate-dependent depression in diabetes, prediabetes and obesity: a mini-review

“…On the other hand, few studies have evaluated the RDD in conditions of overweight and obesity but their results are interesting. In a preclinical study ( 36 ), male and female mice were fed with a high-fat diet (HFD) and researchers measured the RDD at 5 Hz at weeks 5, 10, and 15, and observed that the HFD male group had impaired RDD at weeks 5 and 10, while the female group had impaired RDD at weeks 10 and 15, compared to the control group. However, in this study, behavioral measures of pain were not assessed to determine if worse scores were related to impaired RDD ( 36 ).…”