Obesity-Associated Neuropathy: Recent Preclinical Studies and Proposed Mechanisms

Hungry for relief: Potential for neurotensin to address comorbid obesity and pain

Chronic pain and obesity frequently occur together. An ideal therapy would alleviate pain without weight gain, and most optimally, could promote weight loss. The neuropeptide neurotensin (Nts) has been separately implicated in reducing weight and pain but could it be a common actionable target for both pain and obesity? Here we review the current knowledge of Nts signaling via its receptors in modulating body weight and pain processing. Evaluating the mechanism by which Nts impacts ingestive behavior, body weight, and analgesia has potential to identify common physiologic mechanisms underlying weight and pain comorbidities, and whether Nts may be common actionable targets for both.

Obesity-related neuropathy: the new epidemic

PURPOSE OF REVIEW

To examine the evidence evaluating the association between obesity and neuropathy as well as potential interventions.

RECENT FINDINGS

Although diabetes has long been associated with neuropathy, additional metabolic syndrome components, including obesity, are increasingly linked to neuropathy development, regardless of glycemic status. Preclinical rodent models as well as clinical studies are shedding light on the mechanisms of obesity-related neuropathy as well as challenges associated with slowing progression. Dietary and surgical weight loss and exercise interventions are promising, but more data is needed.

SUMMARY

High-fat-diet rodent models have shown that obesity-related neuropathy is a product of excess glucose and lipid accumulation leading to inflammation and cell death. Clinical studies consistently demonstrate obesity is independently associated with neuropathy; therefore, likely a causal risk factor. Dietary weight loss improves neuropathy symptoms but not examination scores. Bariatric surgery and exercise are promising interventions, but larger, more rigorous studies are needed. Further research is also needed to determine the utility of weight loss medications and ideal timing for obesity interventions to prevent neuropathy.

Relationship between diabetic peripheral neuropathy and adherence to the Mediterranean diet in patients with type 2 diabetes mellitus: an observational study

PURPOSE

The main study goal is to assess the relationship between adherence to the mediterranean diet (MD) and the presence of diabetic peripheral neuropathy (DPN) in patients with type 2 diabetes mellitus (T2DM).

METHODS

Observational pilot study of 174 patients diagnosed with T2DM. Sociodemographic and anthropometric variables, physical activity, smoking habits, blood biochemical parameters and comorbidities were recorded. The presence of alterations in sensitivity to pressure, pain, thermal and vibration was explored. Good MD adherence was a score  ≥  9 the 14-point MD adherence questionnaire (MEDAS-14).

RESULTS

The study population consisted of 174 patients (61.5% men and 38.5% women), with a mean age of 69.56 ± 8.86 years; 19% of these patients adhered to the MD. The score obtained in the MEDAS-14 was higher in patients who did not present alterations in sensitivity to pressure (p = 0.047) or vibration (p = 0.021). The patients without diabetic peripheral neuropathy were more likely to comply with the MD and had a higher score on the MEDAS-14 (p = 0.047). However, multivariate analysis showed that only altered sensitivity to pressure was associated with adherence to the MD (altered sensitivity OR = 2.9; 95%CI 1.02-8.22; p = 0.045).

CONCLUSIONS

Although the patients with DPN had lower scores on the MEDAS questionnaire and therefore poorer adherence to the mediterranean diet, the only parameter significantly associated with the MD was that of sensitivity to pressure (monofilament test).

Correlates of metabolic syndrome in people with chronic spinal cord injury

PURPOSE

We aimed at identifying clinical risk factors or early markers of metabolic syndrome (MetS) in people with spinal cord injury (SCI) that would facilitate a timely diagnosis and implementation of preventive/therapeutic strategies.

METHODS

One hundred sixty-eight individuals with chronic (> 1 year) SCI underwent clinical and biochemical evaluations. MetS was diagnosed according to modified criteria of the International Diabetes Federation validated in people with SCI. Wilcoxon rank-sum test and χ2 test were used to compare variables between groups with and without MetS. Multiple logistic regression analysis was performed to reveal independent associations with MetS among variables selected by univariate linear regression analyses.

RESULTS

MetS was diagnosed in 56 of 132 men (42.4%) and 17 of 36 women (47.2%). At univariate regression analyses, putative predictors of MetS were an older age, a higher number of comorbidities, a lower insulin-sensitivity, the presence and intensity of pain, a shorter injury duration, a poorer leisure time physical activity (LTPA) and an incomplete motor injury. At the multiple logistic regression analysis, a significant independent association with MetS only persisted for a poorer LTPA in hours/week (OR: 0.880, 95% CI 0.770, 0.990) and more severe pain symptoms as assessed by the numeral rating scale (OR: 1.353, 95% CI 1.085, 1.793).

CONCLUSION

In people with chronic SCI, intense pain symptoms and poor LTPA may indicate a high likelihood of MetS, regardless of age, SCI duration, motor disability degree, insulin-sensitivity and comorbidities.

Comparison of western diet-induced obesity and streptozotocin mouse models: insights into energy balance, somatosensory dysfunction, and cardiac autonomic neuropathy

Metabolic disorders such as obesity and type 2 diabetes (T2D) are increasingly prevalent worldwide, necessitating a deeper comprehension of their underlying mechanisms. However, translating findings from animal research to human patients remains challenging. This study aimed to investigate the long-term effects of Streptozotocin (STZ) on metabolic, cardiac, and somatosensory function in mice fed a Western diet (WD) of high fat, sucrose, and cholesterol with low doses of STZ administration compared to mice fed WD alone. In our research, we thoroughly characterized energy balance and glucose homeostasis, as well as allodynia and cardiac function, all of which have been previously shown to be altered by WD feeding. Notably, our findings revealed that the treatment of WD-fed mice with STZ exacerbated dysfunction in glucose homeostasis via reduced insulin secretion in addition to impaired peripheral insulin signaling. Furthermore, both WD and WD + STZ mice exhibited the same degree of cardiac autonomic neuropathy, such as reduced heart rate variability and decreased protein levels of cardiac autonomic markers. Furthermore, both groups developed the same symptoms of neuropathic pain, accompanied by elevated levels of activating transcription factor 3 (Atf3) in the dorsal root ganglia. These discoveries enhance our understanding of metabolic activity, insulin resistance, neuropathy, and cardiac dysfunction of diet-induced models of obesity and diabetes. The exacerbation of impaired insulin signaling pathways by STZ did not lead to or worsen cardiac and somatosensory dysfunction. Additionally, they offer valuable insights into suitable diet induced translational mouse models, thereby advancing the development of potential interventions for associated conditions.

Severe Cannabis use is Associated with Complications and Prolonged Length of Stay in Bariatric Surgery

PURPOSE

In the United States, recreational and medicinal cannabis use has continually increased in recent years, including in patients undergoing bariatric surgery. However, the effects of cannabis use on morbidity and mortality after bariatric surgery are uncertain, and the literature is limited by a paucity of studies. This study intends to evaluate the effects of cannabis use disorder on outcomes in patients undergoing bariatric surgery.

MATERIALS AND METHODS

The National Inpatient Sample 2016-2019 was queried for patients ≥ 18 years who underwent roux-en-y gastric bypass (RYGB), vertical sleeve gastrectomy (VSG), or adjustable gastric band (AGB) surgery. Cannabis use disorder was identified using ICD-10 coding. Three outcomes were evaluated: medical complications, in-hospital mortality, and length of stay. Logistic regression was used to evaluate effects of cannabis use disorder on medical complications and in-hospital mortality, and linear regression for length of stay. All models controlled for race, age, sex, income, procedure type, and various medical comorbidities.

RESULTS

A total of 713,290 patients were included in this study, with 1,870 (0.26%) having cannabis use disorder. Cannabis use disorder was associated with medical complications (OR: 2.24; 95% CI: 1.31-3.82; P = 0.003) and longer lengths of stay (β: 1.3; SE: 0.297; P < 0.001), but not in-hospital mortality (OR: 3.29; CI: 0.94-11.5); P = 0.062).

CONCLUSIONS

Severe cannabis use was associated with higher risk for complications and extended length of stay. Future investigations are needed to better elucidate the relationship between cannabis use and bariatric surgery, including effects of dosage, chronicity, and method of ingestion.