Insulin resistance in tetraplegia but not in mid-thoracic paraplegia: is the mid-thoracic spinal cord involved in glucose regulation?

The effect of level of injury on diabetes incidence and mortality after spinal cord injury - a longitudinal cohort study

STUDY DESIGN

Retrospective longitudinal cohort study of veterans with SCI.

OBJECTIVES

Spinal cord injury (SCI) is associated with an increased risk of developing diabetes mellitus (DM), likely due to body composition alterations and autonomic nervous system dysfunction. These factors are more pronounced in persons with tetraplegia (TP) versus paraplegia (PP). However, the effect of level of injury (LOI) on DM incidence is largely unknown. Therefore, the objective is to examine the effect of LOI on DM incidence in persons with SCI.

SETTING

South Texas Veterans Health Care System.

METHODS

We obtained electronic record data on age, sex, race/ethnicity, LOI and HbA1c concentration from January 1st 2001 through December 31st 2021. Cox proportional hazard regression analyses were used to assess the association between LOI, DM and all-cause mortality.

RESULTS

Among 728 non-diabetic veterans with SCI (350 TP/ 378 PP, 52 ± 15 years, 690 male/38 female) 243 developed DM, of which 116 with TP and 127 with PP. Despite chronological variations between TP and PP, DM risk over the entire follow-up did not differ between the groups (hazard ratio (HR): 1.06, 95% CI: 0.82-1.38). Mortality was higher in TP versus PP (HR: 1.40, 95% CI: 1.09-1.78). However, developing DM did not increase the risk of death, regardless of LOI (HR: 1.07, 95% CI: 0.83-1.37).

CONCLUSION

Despite chronological variations between both groups, the level of injury had minimal effect on long-term DM development in this cohort of veterans with SCI. Sponsorship NIH (DK105379; MS), RR&D SPiRE (I21RX003724-01A1; MT and SH).

Factors Affecting Metabolic Syndrome in Individuals With Chronic Spinal Cord Injury

Objective

To assess the validity of different anthropometric measures (waist circumference [WC], body mass index [BMI], and percentage body fat) in diagnosing metabolic syndrome (MetS) among individuals with SCI and provides preliminary data for future studies in setting obesity cutoff values for this population.

Methods

This was a single-center retrospective cohort study. Sample information, anthropometric measures, and MetS variables of 157 individuals with chronic SCI were collected from an electronic medical records database.

Results

Increasing age (odds ratio [OR]=1.040, p=0.016) and lower neurological level of injury (OR=1.059, p=0.046) were risk factors for MetS. Male BMI (r=0.380, p<0.001) and male WC (r=0.346, p<0.001) were positively correlated with the number of MetS subfactors. Individuals with non-obese WC, excluding central obesity, were associated with having no MetS subfactors (p=0.005), and individuals with obese WC were associated with one or more subfactors (p=0.005). BMI was associated with MetS diagnosis (area under the curve=0.765, p<0.001), with the calculated cutoff value for BMI being 22.8 kg/m².

Conclusion

This study calls for a stricter BMI cutoff for individuals with SCI in diagnosing MetS and warrants a large population-based study to define central obesity according to sex and ethnicity.

Neurogenic Obesity-Induced Insulin Resistance and Type 2 Diabetes Mellitus in Chronic Spinal Cord Injury

The population with SCI is at a significant risk for both insulin resistance and type 2 diabetes mellitus (T2DM) secondary to neurogenic obesity. The prevalence of insulin resistance and T2DM in persons with SCI suggests that disorders of carbohydrate metabolism are at epidemic proportions within the population. However, the true frequency of such disorders may be underestimated because biomarkers of insulin resistance and T2DM used from the population without SCI remain nonspecific and may in fact fail to identify true cases that would benefit from intervention. Furthermore, diet and exercise have been used to help mitigate neurogenic obesity, but results on disorders of carbohydrate metabolism remain inconsistent, likely because of the various ways carbohydrate metabolism is assessed. The objective of this article is to review current literature on the prevalence and likely mechanisms driving insulin resistance and T2DM in persons with SCI. This article also explores the various assessments and diagnostic criteria used for insulin resistance and T2DM and briefly discusses the effects of exercise and/or diet to mitigate disorders of carbohydrate metabolism brought on by neurogenic obesity.

Exercise and Health-Related Risks of Physical Deconditioning After Spinal Cord Injury

A sedentary lifestyle occurring soon after spinal cord injury (SCI) may be in contrast to a preinjury history of active physical engagement and is thereafter associated with profound physical deconditioning sustained throughout the lifespan. This physical deconditioning contributes in varying degrees to lifelong medical complications, including accelerated cardiovascular disease, insulin resistance, osteopenia, and visceral obesity. Unlike persons without disability for whom exercise is readily available and easily accomplished, exercise options for persons with SCI are more limited. Depending on the level of injury, the metabolic responses to acute exercise may also be less robust than those accompanying exercise in persons without disability, the training benefits more difficult to achieve, and the risks of ill-considered exercise both greater and potentially irreversible. For exercise to ultimately promote benefit and not impose additional impairment, an understanding of exercise opportunities and risks if exercise is undertaken by those with SCI is important. The following monograph will thus address common medical challenges experienced by persons with SCI and typical modes and benefits of voluntary exercise conditioning.

Autonomic dysreflexia after spinal cord injury: Systemic pathophysiology and methods of management

Traumatic spinal cord injury (SCI) has widespread physiological effects beyond the disruption of sensory and motor function, notably the loss of normal autonomic and cardiovascular control. Injury at or above the sixth thoracic spinal cord segment segregates critical spinal sympathetic neurons from supraspinal modulation which can result in a syndrome known as autonomic dysreflexia (AD). AD is defined as episodic hypertension and concomitant baroreflex-mediated bradycardia initiated by unmodulated sympathetic reflexes in the decentralized cord. This condition is often triggered by noxious yet unperceived visceral or somatic stimuli below the injury level and if severe enough can require immediate medical attention. Herein, we review the pathophysiological mechanisms germane to the development of AD, including maladaptive plasticity of neural circuits mediating abnormal sympathetic reflexes and hypersensitization of peripheral vasculature that collectively contribute to abnormal hemodynamics after SCI. Further, we discuss the systemic effects of recurrent AD and pharmacological treatments used to manage such episodes. Contemporary research avenues are then presented to better understand the relative contributions of underlying mechanisms and to elucidate the effects of recurring AD on cardiovascular and immune functions for developing more targeted and effective treatments to attenuate the development of this insidious syndrome following high-level SCI.

Contributors to Metabolic Disease Risk Following Spinal Cord Injury

Spinal cord injury (SCI) induced changes in neurological function have significant impact on the metabolism and subsequent metabolic-related disease risk in injured individuals. This metabolic-related disease risk relationship is differential depending on the anatomic level and severity of the injury, with high level anatomic injuries contributing a greater risk of glucose and lipid dysregulation resulting in type 2 diabetes and cardiovascular disease risk elevation. Although alterations in body composition, particularly excess adiposity and its anatomical distribution in the visceral depot or ectopic location in non-adipose organs, is known to significantly contribute to metabolic disease risk, changes in fat mass and fat-free mass do not fully account for this elevated disease risk in subjects with SCI. There are other negative adaptations in body composition including reductions in skeletal muscle mass and alterations in muscle fiber type, in addition to significant reduction in physical activity, that contribute to a decline in metabolic rate and increased metabolic disease risk following SCI. Recent studies in adult humans suggest cold- and diet-induced thermogenesis through brown adipose tissue metabolism may be important for energy balance and substrate metabolism, and particularly sensitive to sympathetic nervous signaling. Considering the alterations that occur in the autonomic nervous system (SNS) (sympathetic and parasympathetic) following a SCI, significant dysfunction of brown adipose function is expected. This review will highlight metabolic alterations following SCI and integrate findings from brown adipose tissue studies as potential new areas of research to pursue.