Investigating metabolic regulation using targeted neuromodulation

Pulsed magnetic field treatment ameliorates the progression of peripheral neuropathy by modulating the neuronal oxidative stress, apoptosis and angiogenesis in a rat model of experimental diabetes

OBJECTIVE

The present study aimed to investigate the possible anti-neuropathic effects of daily pulsed magnetic field treatments (PMF) in streptozotocin (60 mg/kg) induced 4 weeks diabetic (type-1) wistar rats (6-8 months).

MATERIALS AND METHODS

Body mass, blood glucose and thermal and mechanical sensations were evaluated during the PMF or sham-PMF in diabetic or non-diabetic rats (n = 7/group). After the measurements of motor nerve conduction velocities (MNCV), the levels of several biomarkers for oxidative stress, apoptosis and angiogenesis in spinal cord and sciatic nerve were measured.

RESULTS

PMF for 4 weeks significantly recovered the MCNV (96.9% and 63.9%) and almost fully (100%) restored to the latency and threshold. PMF also significantly suppressed the diabetes induced enhances in biochemical markers of both neuronal tissues.

CONCLUSIONS

Findings suggested that PMF might prevent the development of functional abnormalities in diabetic rats due to its anti-oxidative, anti-apoptotic and anti-angiogenic actions in neuronal tissues.

Introducing stimulogenetics, unraveling pertinent semantic ambiguity, and determining clinical relevance among novel neuromodulation strategies

Deep brain stimulation involving the stereotactic implantation of electrodes in the deeper neural tissue remains one of the most trusted nonpharmacotherapeutic approaches for neuromodulation in the clinical setting. The recent advent of techniques that can modulate the neural structure and/or function at the cellular level has stimulated the exploration of these strategies in managing neurological and psychiatric disorders. Optogenetics, which is widely employed in experimental research, is the prototype of the above techniques. Other methods such as chemogenetics, sonogenetics, and magnetogenetics have also been introduced. Although these strategies possess several noticeable differences, they have an overlapping conceptual framework enabling their classification under a singular hypernym. This article introduces this hypernym, “stimulogenetics” in an attempt to solve the pertinent ambiguity to aid the classification of existing literature. The article also compares the strategies classified under stimulogenetics and concludes that the current literature suggests that nonsurgical approaches such as chemogenetics and sonogenetics are better suited for clinical applications. However, due to the dearth of clinical studies, it is not possible to determine this definitively.

Expression of nano-ferritin in neuronal cells encompassed by minimal Arc promoter system

Genetic engineering for neuronal cell activity labeling and neuronal cell activity modulation are invaluable for elucidating the underlying characteristics of the brain and neurons. In this study, ferritin fusion protein (FFP) was combined with Tet expression construct under a modified immediate-early gene (IEG) Arc/Arg3.1 promoter so-called SARE-ArcMin. This expression system is a neuronal activity-dependent expression module for nano-ferritin, a radio/magnetic wave-sensitive protein well-accepted as a potential recombinant neuronal actuator. The system was characterized in transcriptional and translational levels in human neuroblastoma SH-SY5Y cells. The mRNA and protein expression levels of nano-ferritin were significant in the activated neurons suggesting that the activity dependent expression patterns of the ferritin also acted as a neuronal cell activation indicator. The system sufficed the need for precise neuronal cell activity specific expression and demonstrated a platform that suggested the use of the nano-ferritin for the study of neuronal cells.

Neuromodulation of metabolic functions: from pharmaceuticals to bioelectronics to biocircuits

Neuromodulation of central and peripheral neural circuitry brings together neurobiologists and neural engineers to develop advanced neural interfaces to decode and recapitulate the information encoded in the nervous system. Dysfunctional neuronal networks contribute not only to the pathophysiology of neurological diseases, but also to numerous metabolic disorders. Many regions of the central nervous system (CNS), especially within the hypothalamus, regulate metabolism. Recent evidence has linked obesity and diabetes to hyperactive or dysregulated autonomic nervous system (ANS) activity. Neural regulation of metabolic functions provides access to control pathology through neuromodulation. Metabolism is defined as cellular events that involve catabolic and/or anabolic processes, including control of systemic metabolic functions, as well as cellular signaling pathways, such as cytokine release by immune cells. Therefore, neuromodulation to control metabolic functions can be used to target metabolic diseases, such as diabetes and chronic inflammatory diseases. Better understanding of neurometabolic circuitry will allow for targeted stimulation to modulate metabolic functions. Within the broad category of metabolic functions, cellular signaling, including the production and release of cytokines and other immunological processes, is regulated by both the CNS and ANS. Neural innervations of metabolic (e.g. pancreas) and immunologic (e.g. spleen) organs have been understood for over a century, however, it is only now becoming possible to decode the neuronal information to enable exogenous controls of these systems. Future interventions taking advantage of this progress will enable scientists, engineering and medical doctors to more effectively treat metabolic diseases.

TRPV1 neurons regulate β-cell function in a sex-dependent manner

There is emerging evidence to support an important role for the transient receptor potential vanilloid type 1 (TRPV1) sensory innervation in glucose homeostasis. However, it remains unknown whether the glucoregulatory action of these afferent neurons is sex-biased and whether it is pancreatic β-cell-mediated.

OBJECTIVE

We investigated in male and female mice whether denervation of whole-body or pancreas-projecting TRPV1 sensory neurons regulates adult functional β-cell mass and alters systemic glucose homeostasis.

METHODS

We used a combination of pharmacological and surgical approaches to ablate whole-body or pancreatic TRPV1 sensory neurons and assessed islet β-cell function and mass, aspects of glucose and insulin homeostasis, and energy expenditure.

RESULTS

Capsaicin-induced chemodenervation of whole-body TRPV1 sensory neurons improved glucose clearance and enhanced glucose-stimulated insulin secretion without alterations in β-cell proliferation and mass, systemic insulin sensitivity, body composition, and energy expenditure. Similarly, denervation of intrapancreatic TRPV1 afferents by pancreas intraductal injection of capsaicin or surgical removal of the dorsal root ganglia projecting into the pancreas lowered post-absorptive glucose levels and increased insulin release upon glucose stimulation. The beneficial effects of TRPV1 sensory denervation on glucose tolerance and β-cell function were observed in male but not female mice.

CONCLUSION

Collectively, these findings suggest that TRPV1 neurons regulate glucose homeostasis, at least partly, through direct modulation of glucose-induced insulin secretion and that this regulation operates in a sex-dependent manner.