Peripheral polyneuropathy in severely obese patients with metabolic syndrome but without diabetes: Association with low HDL-cholesterol

The Association of Inflammatory Factors With Peripheral Neuropathy: The Study of Women's Health Across the Nation

PURPOSE

Previous work has focused on the role of diabetes in peripheral neuropathy (PN), but PN often occurs before, and independently from, diabetes. This study measures the association of cardiometabolic and inflammatory factor with PN, independent of diabetes.

METHODS

Study of Women's Health Across the Nation participants (n = 1910), ages 60 to 73 (mean 65.6) were assessed for PN by symptom questionnaire and monofilament testing at the 15th follow-up visit (V15). Anthropometric measures and biomarkers were measured at study baseline approximately 20 years prior, and C-reactive protein (CRP) and fibrinogen were measured longitudinally. Log-binomial regression was used to model the association between metabolic syndrome (MetS), obesity (≥35 body mass index), CRP, and fibrinogen with PN, adjusting for sociodemographic and health behavior measures.

RESULTS

Baseline MetS [prevalence ratio (PR) 1.79, 95% CI (1.45, 2.20)], obesity [PR 2.08 (1.65, 2.61)], median CRP [PR 1.32 per log(mg/dL), (1.20, 1.45)], and mean fibrinogen (PR 1.28 per 100 mg/dL, (1.09, 1.50)] were associated with PN symptoms at V15. After excluding participants with baseline diabetes or obesity, MetS [PR 1.59 (1.17, 2.14)] and CRP [PR 1.19 per log(mg/dL), (1.06, 1.35)] remained statistically significantly associated with PN. There was a negative interaction between MetS and obesity, and the association between these conditions and PN was mediated by CRP.

CONCLUSIONS

Cardiometabolic factors and inflammation are significantly associated with PN, independent of diabetes and obesity. CRP mediates the relationship of both obesity and MetS with PN, suggesting an etiological role of inflammation in PN in this sample.

Prevalence of Peripheral Polyneuropathy Before and After Roux-en-Y Gastric Bypass and Sleeve Gastrectomy

PURPOSE

Peripheral polyneuropathy (PPN) can occur in diabetes mellitus (DM), obesity, and after bariatric surgery (BS). We decided to evaluate PPN prevalence before (PreBS-PPN) and after BS (PostBS-PPN) and to look for variables that may be independently associated with both.

METHODS

In this cross-sectional study, we evaluated 1467 participants with obesity and without DM before and 10.4 ± 6.8 months after Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG). The Michigan Neuropathy Screening Instrument and the International Physical Activity Questionnaire were used to define the presence of PPN and the Metabolic Equivalent Task (MET) spent per week, respectively. Using Poisson regression models with a robust estimator, the prevalence of PreBS-PPN and PostBS-PPN was analyzed as dependent variables.

RESULTS

Prevalence of PostBS-PPN (10.5%) was lower than PreBS-PPN (20.4%, p < 0.001), with a prevalence of 12.7% post-RYGB and 8.4% post-SG (p = 0.072). In the univariate analysis, PreBS-PPN was associated with post-menopausal status (PMS), older age, and taller height. In twelve regression models, we found an independent association of PreBS-PPN with older age, PMS, and taller height. PostBS-PPN prevalence was associated with a higher fasting glycemia and stature, and a lower MET on univariate analysis, and with higher fasting glycemia, stature and RYGB in four multivariate regression models.

CONCLUSION

PPN occurs frequently in subjects with obesity without DM and is lower after BS. SG is not likely to be harmful in the development of neuropathy. Studies of PPN incidence and persistence after BS should clarify these factors.

Lipids and peripheral neuropathy

PURPOSE OF REVIEW

Hyperlipidaemia is associated with the development of neuropathy. Indeed, a mechanistic link between altered lipid metabolism and peripheral nerve dysfunction has been demonstrated in a number of experimental and clinical studies. Furthermore, post hoc analyses of clinical trials of cholesterol and triglyceride-lowering pharmacotherapy have shown reduced rates of progression of diabetic neuropathy. Given, there are currently no FDA approved disease-modifying therapies for diabetic neuropathy, modulation of lipids may represent a key therapeutic target for the treatment of diabetic nerve damage. This review summarizes the current evidence base on the role of hyperlipidaemia and lipid lowering therapy on the development and progression of peripheral neuropathy.

RECENT FINDINGS

A body of literature supports a detrimental effect of dyslipidaemia on nerve fibres resulting in somatic and autonomic neuropathy. The case for an important modulating role of hypertriglyceridemia is stronger than for low-density lipoprotein cholesterol (LDL-C) in relation to peripheral neuropathy. This is reflected in the outcomes of clinical trials with the different therapeutic agents targeting hyperlipidaemia reporting beneficial or neutral effects with statins and fibrates. The potential concern with the association between proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor therapy and cognitive decline raised the possibility that extreme LDL-C lowering may result in neurodegeneration. However, studies in murine models and data from small observational studies indicate an association between increased circulating PCSK9 levels and small nerve fibre damage with a protective effect of PCSK9i therapy against small fibre neuropathy. Additionally, weight loss with bariatric surgery leads to an improvement in peripheral neuropathy and regeneration of small nerve fibres measured with corneal confocal microscopy in people with obesity with or without type 2 diabetes. These improvements correlate inversely with changes in triglyceride levels.

SUMMARY

Hyperlipidaemia, particularly hypertriglyceridemia, is associated with the development and progression of neuropathy. Lipid modifying agents may represent a potential therapeutic option for peripheral neuropathy. Post hoc analyses indicate that lipid-lowering therapies may halt the progression of neuropathy or even lead to regeneration of nerve fibres. Well designed randomized controlled trials are needed to establish if intensive targeted lipid lowering therapy as a part of holistic metabolic control leads to nerve fibre regeneration and improvement in neuropathy symptoms.

Early disruption of nerve mitochondrial and myelin lipid homeostasis in obesity-induced diabetes

Diabetic neuropathy is a major complication of diabetes. Current treatment options alleviate pain but do not stop the progression of the disease. At present, there are no approved disease-modifying therapies. Thus, developing more effective therapies remains a major unmet medical need. Seeking to better understand the molecular mechanisms driving peripheral neuropathy, as well as other neurological complications associated with diabetes, we performed spatiotemporal lipidomics, biochemical, ultrastructural, and physiological studies on PNS and CNS tissue from multiple diabetic preclinical models. We unraveled potentially novel molecular fingerprints underlying nerve damage in obesity-induced diabetes, including an early loss of nerve mitochondrial (cardiolipin) and myelin signature (galactosylceramide, sulfatide, and plasmalogen phosphatidylethanolamine) lipids that preceded mitochondrial, myelin, and axonal structural/functional defects; started in the PNS; and progressed to the CNS at advanced diabetic stages. Mechanistically, we provided substantial evidence indicating that these nerve mitochondrial/myelin lipid abnormalities are (surprisingly) not driven by hyperglycemia, dysinsulinemia, or insulin resistance, but rather associate with obesity/hyperlipidemia. Importantly, our findings have major clinical implications as they open the door to novel lipid-based biomarkers to diagnose and distinguish different subtypes of diabetic neuropathy (obese vs. nonobese diabetics), as well as to lipid-lowering therapeutic strategies for treatment of obesity/diabetes-associated neurological complications and for glycemic control.

The emerging role of dyslipidemia in diabetic microvascular complications

PURPOSE OF REVIEW

To summarize recent advancements in our understanding of the impact of dyslipidemia on microvascular complications in type 2 diabetes (T2D), with an emphasis on peripheral neuropathy and nephropathy.

RECENT FINDINGS

Mounting evidence suggests that rigorous glycemic control only mitigates certain microvascular complications in T2D patients. Particularly, well regulated blood glucose levels only marginally improve peripheral neuropathy in the T2D setting. Dyslipidemia, an abnormal lipid profile, is emerging as a key factor in peripheral neuropathy. Furthermore, although glycemic control may prevent or slow nephropathy, recent developments demonstrate that dyslipidemia can also affect kidney outcomes in normoglycemic patients. Transcriptomic, epigenomic, and lipidomic investigations, as well as integrative approaches, are shedding light on potential pathomechanisms. These molecular studies are identifying possible targets for therapeutic intervention. Complementing molecular research, lifestyle interventions are on-going to assess whether dietary choices and/or exercise, weight-loss, or surgical interventions, such as bariatric surgery, can ameliorate peripheral neuropathy and nephropathy in T2D patients.

SUMMARY

Dyslipidemia is an emerging mechanism in microvascular complications in T2D. Elucidating the molecular pathomechanisms may pinpoint potential lipid-centric treatments. Interventional studies of dietary changes, exercise, or weight-loss surgery may also positively impact these highly prevalent and morbid complications.

Polyneuropathy in Severely Obese Women Without Diabetes: Prevalence and Associated Factors

BACKGROUND

Obesity and its complications are prevalent in women and increase with age. Polyneuropathy (PNP) is a complication of obesity and bariatric surgery (BS). In subjects with severe (grades II and III) obesity and without DM who are candidates for BS, the prevalence of PNP and associated conditions are not well characterized. The aim of this study was to evaluate the prevalence of PNP in severely obese (SO) women without DM or common nutritional deficiencies in order to determine factors associated with the presence of PNP.

METHODS

A cross-sectional study was performed on 450 SO women. They were evaluated with the Michigan Neuropathy Screening Instrument, a Sleep Apnea Questionnaire, and the short form of the International Physical Activity Questionnaire. Data on blood pressure, body mass index, waist circumference, serum glucose, glycated hemoglobin, LDL and HDL cholesterol, triglycerides, vitamin B12, and postmenopausal (PM) status were also collected. Patients with DM and other common causes of PNP were excluded. To evaluate which variables were independently associated with PNP (dependent variable), Poisson regression models were used.

RESULTS

The prevalence of PNP was 11.6%. In univariate analysis, PNP was associated with age, PM status, and diagnosis of systemic arterial hypertension (p < 0.001, p < 0.001, and p = 0.016, respectively), and there was a trend toward an association with sleep apnea risk (p = 0.101). In multivariate analysis, PM status (PR = 2.836, 95% CI 1.735-4.636, p = 0.001) and age (PR = 1.0511, 95% CI 1.031-1.071, p = 0.001) were independently associated with PNP diagnosis in two different models.

CONCLUSION

Even prior to BS, PNP is highly prevalent and is associated with PM status and age in SO women without diabetes.