Patients with clinically metabolically healthy obesity are not necessarily healthy subclinically: further support for bariatric surgery in patients without metabolic disease?

Metabolically Healthy Obesity and Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD): Navigating the Controversies in Disease Development and Progression

PURPOSE OF REVIEW

The natural course of metabolic dysfunction-associated steatotic liver disease (MASLD) in the population with metabolically healthy obesity (MHO) has not been adequately explored. In the present narrative review, we summarize the evidence regarding the association between MHO and MASLD prevalence, incidence and progression.

RECENT FINDINGS

Cross-sectional, population-based, cohort studies have shown an increased prevalence of hepatic steatosis and fibrosis in subjects with MHO compared with metabolically healthy non-obese individuals (MHNO). In large-scale longitudinal cohort studies among metabolically healthy subjects, increasing body mass index (BMI) has been found to be independently associated with an increased incidence of MASLD and progressive hepatic fibrosis over a mean follow-up period of 2.2-7.7 years. With regard to advanced MASLD, the prevalence of steatohepatitis and clinically significant liver fibrosis is lower in MHO compared with subjects with metabolically unhealthy obesity (MUO). The presence of MASLD has been proposed as a strong risk factor for metabolic health deterioration in MHO. Furthermore, subjects with MHO and MASLD display an elevated 10-year cardiovascular risk and a three-fold increased risk of incident diabetes compared with MHO without MASLD. MASLD may also predict the failure to convert from MUO to MHO after a weight loss intervention.

Preoperative nonalcoholic steatohepatitis and resolution of metabolic comorbidities after bariatric surgery

BACKGROUND

Most patients undergoing bariatric surgery demonstrate elements of the metabolic syndrome (MetS) and can therefore be diagnosed with metabolically unhealthy obesity (MUO). Nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) as hepatic manifestations of the MetS occur in many patients with obesity, but their leverage on postoperative improvement to Metabolic Health (MH), defined as absence of any metabolic comorbidity, remains unclear.

OBJECTIVES

The aim of this study was to assess the influence of liver health status, operative procedure, and sex on postoperative switch from a MUO to an MH phenotype. Secondary objective was weight loss to MH.

SETTING

University Hospital, Germany.

METHODS

Patients who underwent either Roux-en-Y gastric bypass (RYGB) or sleeve gastrectomy (SG) at our obesity surgery center were included in this retrospective study. Liver biopsy was taken and evaluated for presence of NAFLD/NASH. For diagnosis of MH, blood pressure and laboratory values referring to the MetS were assessed preoperatively and at 3, 6, 12, and 24 months' postoperatively.

RESULTS

One hundred thirty-three patients (73% female) with a mean body mass index of 52.0 kg/m2 and mean age of 43 years were included in this study. A total of 55.6% underwent RYGB and 44.4% underwent SG. NAFLD was found in 51.1% of patients and NASH in 33.8%. All patients were diagnosed MUO at baseline. Postoperatively, 38.3% patients (n = 51) switched to a MH condition. Mean time to MH was 321 days and mean excess body mass index loss to MH was 63.8%. There were no differences regarding liver health status, operative procedure, or sex.

CONCLUSIONS

Bariatric surgery can resolve MUO independent of liver health status, operative procedure, and sex. However, patients should be closely monitored to ensure sustainable long-term outcomes following the switch to the MH condition.

American society for metabolic and bariatric surgery: intra-operative care pathway for minimally invasive Roux-en-Y gastric bypass

BACKGROUND

Clinical care pathways help guide and provide structure to clinicians and providers to improve healthcare delivery and quality. The Quality Improvement and Patient Safety Committee (QIPS) of the American Society for Metabolic and Bariatric Surgery (ASMBS) has previously published care pathways for the performance of laparoscopic sleeve gastrectomy (LSG) and pre-operative care of patients undergoing Roux-en-Y gastric bypass (RYGB).

OBJECTIVE

This current RYGB care pathway was created to address intraoperative care, defined as care occurring on the day of surgery from the preoperative holding area, through the operating room, and into the postanesthesia care unit (PACU).

METHODS

PubMed queries were performed from January 2001 to December 2019 and reviewed according to Level of Evidence regarding specific key questions developed by the committee.

RESULTS

Evidence-based recommendations are made for care of patients undergoing RYGB including the pre-operative holding area, intra-operative management and performance of RYGB, and concurrent procedures.

CONCLUSIONS

This document may provide guidance based on recent evidence to bariatric surgeons and providers for the intra-operative care for minimally invasive RYGB.

Clinical Classification of Obesity and Implications for Metabolic Dysfunction-Associated Fatty Liver Disease and Treatment

Obesity,and metabolic dysfunction-associated fatty liver disease (MAFLD) have reached epidemic proportions globally. Obesity and MAFLD frequently coexist and act synergistically to increase the risk of adverse clinical outcomes (both hepatic and extrahepatic). Type 2 diabetes mellitus (T2DM) is the most important risk factor for rapid progression of steatohepatitis and advanced fibrosis. Conversely, the later stages of MAFLD are associated with an increased risk of T2DM incident. According to the proposed criteria, MAFLD is diagnosed in patients with liver steatosis and in at least one in three: overweight or obese, T2DM, or signs of metabolic dysregulation if they are of normal weight. However, the clinical classification and correlation between obesity and MAFLD is more complex than expected. In addition, treatment for obesity and MAFLD are associated with a reduced risk of T2DM, suggesting that liver-based treatments could reduce the risk of developing T2DM. This review describes the clinical classification of obesity and MAFLD, discusses the clinical features of various types of obesity and MAFLD, emphasizes the role of visceral obesity and insulin resistance (IR) in the development of MAFLD,and summarizes the existing treatments for obesity and MAFLD that reduce the risk of developing T2DM.

Ceramide d18:1/24:1 as a potential biomarker to differentiate obesity subtypes with unfavorable health outcomes

BACKGROUND

The criteria for metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO) remain controversial. This research aimed to identify a potential biomarker to differentiate the subtypes of obesity.

METHODS

The study conducted a lipidomic evaluation of ceramide in the serum of 77 Chinese adults who had undergone hyperinsulinemic-euglycemic clamps. These adults were divided into three groups according to the clinical data: normal weight control group (N = 21), MHO (N = 20), and MUO (N = 36).

RESULTS

The serum Cer d18:1/24:1 level in the MHO group was lower than that in the MUO group. As the Cer d18:1/24:1 level increased, insulin sensitivity decreased, and the unfavorable parameters increased in parallel. Multivariate logistic regression analysis revealed that serum Cer d18:1/24:1 levels were independently correlated with MUO in obesity. Individuals with higher levels of Cer d18:1/24:1 also had an elevated risk of cardiovascular disease. Most ceramide subtype levels increased in obesity compared to normal-weight individuals, but the levels of serum Cer d18:0/18:0 and Cer d18:1/16:0 decreased in obesity.

CONCLUSIONS

The relationships between ceramide subtypes and metabolic profiles might be heterogeneous in populations with different body weights. Cer d18:1/24:1 could be a biomarker that can be used to differentiate MUO from MHO, and to better predict who will develop unfavorable health outcomes among obese individuals.

TRIAL REGISTRATION

The First Affiliated Hospital of Nanjing Medical University's Institutional Review Board authorized this study protocol, and all participants provided written informed consent (2014-SR-003) prior to study entry.

Insulin Resistance Is the Main Characteristic of Metabolically Unhealthy Obesity (MUO) Associated with NASH in Patients Undergoing Bariatric Surgery

(1) Background: Metabolically healthy obesity (MHO) is a concept that applies to obese patients without any elements of metabolic syndrome (metS). In turn, metabolically unhealthy obesity (MUO) defines the presence of elements of metS in obese patients. The components of MUO can be divided into subgroups regarding the elements of inflammation, lipid and glucose metabolism and cardiovascular disease. MUO patients appear to be at greater risk of developing non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) compared to MHO patients. The aim of this study was to evaluate the influence of different MUO components on NAFLD and NASH in patients with morbid obesity undergoing bariatric surgery. (2) Methods: 141 patients undergoing bariatric surgery from September 2015 and October 2021 at RWTH Aachen university hospital (Germany) were included. Patients were evaluated pre-operatively for characteristics of metS and MUO (HbA1c, HOMA, CRP, BMI, fasting glucose, LDL, TG, HDL and the presence of arterial hypertension). Intraoperatively, a liver biopsy was taken from the left liver lobe and evaluated for the presence of NAFLD or NASH. In ordinal regression analyses, different factors were evaluated for their influence on NAFLD and NASH. (3) Results: Mean BMI of the patients was 52.3 kg/m² (36-74.8, SD 8.4). Together, the parameters HbA1c, HOMA, CRP, BMI, fasting glucose, LDL, TG, HDL and the presence of arterial hypertension accounted for a significant amount of variance in the outcome, with a likelihood ratio of χ² (9) = 41.547, p < 0.001, for predicting the presence of NASH. Only HOMA was an independent predictor of NASH (B = 0.102, SE = 0.0373, p = 0.007). Evaluation of steatosis showed a similar trend (likelihood ratio χ² (9) = 40.272, p < 0.001). Independent predictors of steatosis were HbA1c (B = 0.833, SE = 0.343, p = 0.015) and HOMA (B = 0.136, SE = 0.039, p < 0.001). (4) Conclusions: The above-mentioned model, including components of MUO, was significant for diagnosing NASH in patients with morbid obesity undergoing bariatric surgery. Out of the different subitems, HOMA independently predicted the presence of NASH and steatosis, while HbA1c independently predicted steatosis and fibrosis. Taken together, the parameter of glucose metabolism appears to be more accurate for the prediction of NASH than the parameters of lipid metabolism, inflammation or the presence of cardiovascular disease.

Metabolically healthy and unhealthy obesity and the progression of liver fibrosis: A cross-sectional study

BACKGROUND

The development of liver fibrosis is the most important predictor of adverse outcomes in patients with non-alcoholic fatty liver disease (NAFLD). Little is known regarding the risk factors for the progression of NAFLD to liver fibrosis. The present cross-sectional study aimed to examine the association of liver fibrosis with metabolically healthy and unhealthy obesity among patients with NAFLD.

METHODS

The severity of fatty liver was examined using ultrasonography. We used the NAFLD fibrosis score to determine the severity of liver fibrosis. Anthropometric indices, physical activity, and body composition were assessed. Blood samples were collected to determine serum metabolic parameters. Participants without any component of metabolic syndrome and homeostasis model assessment of insulin resistance (HOMA-IR) <2.5 were considered as metabolically healthy. To examine the association of liver fibrosis with metabolically healthy and unhealthy obesity, multivariable-adjusted odds ratios (ORs) were applied.

RESULTS

The current study included a total of 246 patients with NAFLD and low probability of fibrosis. 46.3% of subjects were metabolically healthy and 53.7% were metabolically unhealthy. Among metabolically healthy subjects, multivariable-adjusted ORs (CIs) for worsening of NAFLD fibrosis score comparing body mass indexes (BMIs) 23.0-24.9, 25-29.9, and ≥30 with a BMI=18.5-22.9 kg/m² were 1.28 (1.09-1.56), 1.99 (1.49-2.63), and 3.96 (2.89-4.71), respectively. The corresponding ORs (95% CIs) among metabolically unhealthy subjects were 1.39 (1.32-1.64), 2.27 (1.98-2.49), and 4.11 (3.12-4.93), respectively. Moreover, in both healthy and unhealthy individuals, higher percentages of body fat and waist circumference were significantly associated with worsening of NAFLD fibrosis score.

CONCLUSION

Excess body fat contributes to the progression of liver fibrosis regardless of metabolic health status.

Effectiveness of Bariatric Surgery in Patients with the Metabolically Healthy Obese Phenotype

BACKGROUND

To evaluate the effectiveness and safety of bariatric surgery in metabolically healthy obese (MHO) patients.

METHODS

In this retrospective, observational study, we reviewed the medical records of patients who underwent bariatric surgery at a tertiary care hospital between January 2007 and March 2015. Patients who underwent revisional surgery and patients with type 1 diabetes were excluded from the analysis. MHO patients were defined as those without a previous diagnosis of diabetes or atherogenic dyslipidemia and absence of hypoglycemic treatment or treatment with fibrates.

RESULTS

A total of 188 patients were included (mean age 48.97 ± 10.32 years, 68.6% of women). Sleeve gastrectomy was performed in 121 patients (64%) and a gastric bypass in 67 patients (36%). Prior to surgery, 36 patients (19%) were MHO. In the second- and third-year post-surgery, MHO patients presented a higher percentage of total weight loss (%TWL) (35.16% vs. 30.34%; p = 0.02 and 33.97% vs. 27.78%; p = 0.013 respectively). Multiple regression analysis showed that MHO was associated with a higher weight loss irrespective of age, sex, baseline BMI, and type of surgery. We did not detect any differences in acute complications between patients with and without MHO after bariatric surgery.

CONCLUSIONS

Bariatric surgery in MHO patients in our study was associated with higher weight loss than that in MUHO patients. There were no differences between the two groups in respect to acute complications following surgery.

Prevalence of NASH/NAFLD in people with obesity who are currently classified as metabolically healthy

BACKGROUND

While metabolic health in obesity may confer a protective status, recent studies indicate that nonalcoholic fatty liver disease (NAFLD) or even nonalcoholic steatohepatitis (NASH) may exist in this category of individuals. Although cardiovascular and diabetic risks have been well described, the risk of NAFLD and NASH among this population requires further investigation.

OBJECTIVE

Our goal was to compare the prevalence of steatosis, NAFLD, and NASH between individuals with metabolically healthy obesity (MHO) and individuals with metabolically abnormal obesity (MAO) and to identify preoperative risk factors for these conditions in a prospective cohort with morbid obesity scheduled for bariatric surgery.

SETTINGS

Tertiary referral university hospital in France.

METHODS

The prospective cohort included 837 bariatric patients who also had an intraoperative liver biopsy between 2002 and 2015. Obese individuals fulfilling none of the criteria in the strict definition of metabolic syndrome were considered metabolically healthy. Preoperative blood samples and liver pathology examinations were reviewed. Steatosis, NAFLD, and NASH were carefully identified allowing comparison of prevalence and risk factors between the 2 cohorts.

RESULTS

In total, 149 patients (17.8%) had MHO and the remaining 688 (82.2%) had MAO. The cohort with MHO was significantly younger, had a significantly lower glycosylated hemoglobin, a lower homeostasis model assessment of insulin resistance, and increased C-reactive protein. In individuals with MHO, 44 patients (29.5%) had at least moderate steatosis (>33% macrovesicular steatosis) and 5.4% had NASH. Using logistic regression, waist circumference was positively associated with NASH, whereas body mass index and alanine aminotransferase were significantly associated with severe steatosis (>66%).

CONCLUSION

Our study indicates that obese individuals without metabolic syndrome may develop subclinical liver involvement. Therefore, the occurrence of NAFLD and NASH in this population needs further investigation.

Pathogenesis of non-alcoholic fatty liver disease and implications on cardiovascular outcomes in liver transplantation

Along with the obesity epidemic there has been a major increase in non-alcoholic fatty liver disease (NAFLD) prevalence, paralleling a steady increase in cirrhosis of the liver and hepatocellular cancer (HCC) related to NAFLD. Currently, NAFLD (related HCC and cirrhosis) is the second most common cause for liver transplantation (LT) and it is projected to take the top spot in the next 3-5 years. Patients with NAFLD cirrhosis and HCC have a unique set of comorbidities which potentially increases their risk for cardiovascular disease (CVD) and mortality. However, a review of the published data in NAFLD patients who undergo LT, does not paint a clear picture. While CVD is the most common cause of non-graft related mortality over the long-term, the short and intermediate-term survival post LT in NAFLD cirrhosis appears to be on par with other etiologies when age and comorbidities are factored. The cardiovascular complications are increased in the immediate post-transplant period but there is a shift from ischemic complications to arrhythmias and heart failure (HF). NAFLD recurs in 80-100% patients and occurs de novo in about 50% after LT, potentially impacting their long-term morbidity and mortality. This review summarizes the available data on CVD in NAFLD patients before and after LT, explains what is currently known about the epidemiology and pathogenesis of CVD in NAFLD and posits strategies to improve wait-list and post-transplant survival.

Epidemiology and pathophysiology of the association between NAFLD and metabolically healthy or metabolically unhealthy obesity

The prevalence of nonalcoholic fatty liver disease (NAFLD) is continuing to rise in many countries, paralleling the epidemic of obesity worldwide. In the last years, the concept of metabolically healthy obesity [MHO, generally defined as obesity without metabolic syndrome (MetS)] has raised considerable scientific interest. MHO is a complex phenotype with risks intermediate between metabolically healthy individuals with normal-weight (NWMH) and patients who are obese and metabolically unhealthy (MUO, i.e. obesity with MetS). In this review we aimed to examine the association and pathophysiological link of NAFLD with MHO and MUO. Compared to NWMH individuals, patients with obesity, regardless of the presence of MetS features, are at higher risk of all-cause mortality and cardiovascular events. Moreover, MHO patients have a greater risk of NAFLD development and progression compared to NWMH individuals. However, this risk is generally lower than that of MUO patients, suggesting a stronger adverse effect of coexisting MetS disorders than obesity per se on the severity of NAFLD. Nevertheless, since MHO is a dynamic state (with a significant proportion of MHO subjects progressing to MUO over time) and NAFLD itself may predict the transition from MHO to MUO, we believe that any effort should be made to identify NAFLD in all obese individuals, although they appear to be "metabolically healthy". Future research is needed to better understand the role of NAFLD and other pathogenic factors potentially involved in the transition from MHO to MUO and to elucidate how this transition may affect the presence and severity of NAFLD.

Metabolically Healthy Obesity and Bariatric Surgery

A peculiar category of persons with obesity lacking common metabolic disturbances has been depicted and termed as metabolically healthy obesity (MHO). Yet, although MHO patients are free of obesity-associated complications, they might not be entirely precluded from developing cardio-metabolic disorders. Among patients with morbid obesity (MO) who are referred to bariatric surgery, a subset of metabolically healthy MO (MHMO) has been identified and the question arises if these patients would benefit from surgery in terms of mitigating the peril of cardio-metabolic complications. We revisited the pathophysiological mechanisms that define MHO, the currently available data on the cardio-metabolic risk of these patients and finally we reviewed the benefits of bariatric surgery and the urge to better characterize MHMO before submission to surgery.

Metabolically Healthy versus Unhealthy Morbidly Obese: Chronic Inflammation, Nitro-Oxidative Stress, and Insulin Resistance

Metabolically heathy obesity is characterised by the presence of obesity in the absence of metabolic disturbances. The aim of our study was to analyse pro-inflammatory, nitro-oxidative stress, and insulin-resistance (IR) markers in metabolically healthy morbidly obese (MHMO) with respect to metabolically unhealthy morbidly obese (MUHMO) with metabolic syndrome (MS) and to identify the potential predictors of MS in the MHMO group. Two groups of MHMO and MUHMO with MS were analysed. We evaluated serum high sensitivity C reactive protein (hsCRP), tumor necrosis factor alpha (TNF-α), chemerin, nitrite and nitrate (NOx), total oxidant status (TOS), total antioxidant response (TAR), fasting blood glucose, insulin, and homeostasis model assessment of insulin resistance (HOMA-IR.) MHMO have similar hsCRP and TNF-α values as the MUHMO with MS, while chemerin was significantly lower in MHMO. NOx was higher in MUHMO with MS patients, while no difference regarding TOS and TAR was found between the two groups. HOMA-IR and insulin values were lower in MHMO as compared to the MUHMO with MS group. Insulin, HOMA-IR, and chemerin were identified predictors of MS in MHMO. In conclusion, MHMO and MUHMO display similarities and differences in terms of chronic inflammation, nitro-oxidative stress, and IR. Markers of IR and chemerin are possible predictors of MS in MHMO.