Introduction 
The coronavirus disease (COVID-19), a potentially fatal condition, was discovered towards the end of 2019 (1). It is caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Although WHO declared an end to the COVID global health emergency, the virus has not been completely eradicated, necessitating further research. During the pandemic, the clinical presentation of the disease varied from asymptomatic to catastrophic. In more extreme cases, it led to pneumonia, requiring respiratory support and even death. Apart from respiratory illness, the other causes for mortality include venous thromboembolism, coagulopathy, multi-organ dysfunction and shock (1). Old age, male gender, obesity, cardiovascular diseases, hypertension, and diabetes mellitus were some of the key factors responsible for COVID-19 mortality (2). Even though several studies have elaborated on various pathophysiological aspects of COVID-19, there is not enough data on how the metabolic pathways are affected.
SARS-CoV-2 is an RNA virus with a higher mutation rate and frequency of recombination. In contrast to DNA viruses, RNA viruses control host metabolism through post-transcriptional regulation, to keep up with the replication (3). SARS-CoV-2 requires four major structural proteins namely spike, envelope, membrane, and nucleocapsid to complete the virion assembly and host cell infection (4). 
Lipids, especially cholesterol enriched lipid rafts play a crucial role in activation, incorporation, and cell-to-cell infection spread of SARS-CoV-2 virus (5). The spike protein of SARS-CoV-2 virus binds with the cholesterol of HDL-c and when the scavenger receptor binding protein B1 (SRB1) uptakes HDL-c, it enters the host cell. The cytosolic phospholipase A2 also plays a role in the assembly of SARS-CoV 2 replication organelles (6).
The above examples emphasize the importance of lipids in the life cycle of the virus, leading us to theorize that harnessing the pathways of lipid metabolism for therapeutic intervention might yield prolific results. The most challenging task in any such antiviral agent development is that it requires a profound knowledge of lipid metabolism alteration by SARS COV-2 infection. Hence, the present descriptive study was carried out on COVID-19 patients to observe if there was an association between lipid profile with inflammatory markers, disease severity, and duration of hospital stay. 
Materials & Methods
This retrospective observational study was conducted in a tertiary care hospital in Coimbatore, India, after the approval from the Institutional Human Ethics Committee. The study included subjects admitted between March-2020 and July-2021 with RT-PCR positive COVID-19 tests as per WHO’s interim guidance (7). By convenient sampling, the study involved 320 participants of either gender in whom lipid profile testing was done.
For all subjects, demographic data comprising of age, gender, clinical history including CT score, CO-RADS scores, ICU admission, mechanical ventilation requirement, duration of hospital stay, and mortality were sourced from patients’ medical records. The Laboratory Information System (LIS) was used to obtain lipid profile data including total cholesterol (TC), triglycerides (TGL), high-density lipoprotein cholesterol (HDL-c), and low-density lipoprotein cholesterol (LDL-c). In addition, data of inflammatory markers such as lactate dehydrogenase (LDH), C-reactive protein (CRP), ferritin, procalcitonin (PCT), and interleukin-6 (IL-6) were also obtained. The laboratory parameters were analyzed in Roche Cobas auto-analyzers using dedicated kits and reagents.
Data was analyzed using R software version 4.1.2 and MS Excel. Categorical variables were stated as a frequency table. Mann Whitney U test was applied to compare distributions of lipid profile with indicators of disease severity like ICU admission, mechanical ventilation, and mortality. Spearman’s correlation test analyzed the correlation of CT score, CO-RADS score, duration of hospital stay, and inflammatory markers of COVID-19 with lipid profile. A p-value <0.05 was considered statistically significant.
Results
In the present study, among 320 subjects with age ranging from 18 to 91 years, the mean age was 55.14 ± 14.84 years. Among the study participants, 216 (67.5%) were male and 104 (32.5%) were female with a female-
to-male ratio of 1: 2.08 (Table 1). While 197 (61.56%) subjects needed ICU admission, 26 (8.13%) required mechanical ventilation, and 41 (12.81%) were non-survivor patients (Table 1).
 
Table 1. Descriptive statistics of categorical variables
	
		
			| Variables | Number of Subjects (%) | 
		
			| Age (years) | <20 | 5 (1.5%) | 
		
			| 21-40 | 51 (15.9%) | 
		
			| 41-60 | 139 (43.4%) | 
		
			| 61-80 | 118 (36.8%) | 
		
			| 81-100 | 7 (2.1%) | 
		
			| Mean ± SD (Median)
 | 55.14 ± 14.84 56
 | 
		
			| Gender | Female | 104 (32.5%) | 
		
			| Male | 216 (67.5%) | 
		
			| ICU Admission | No | 123 (38.4%) | 
		
			| Yes | 197 (61.5%) | 
		
			| Mortality | No | 279 (87.1%) | 
		
			| Yes | 41 (12.8%) | 
		
			| Mechanical ventilation | No | 294 (91.8%) | 
		
			| Yes | 26 (8.1%) | 
	
Among the lipid profile parameters, TG showed a significant association among patients requiring ICU admission (p = 0.0359) and mechanical ventilation (p = 0.0085). In case of non-survivor patients, there was a significant difference in distribution of TC (p = 0.0181) and LDL-c (p = 0.0237). Furthermore, a significant association of LDL-c was observed in patients requiring mechanical ventilation (p = 0.0211). There was no significant difference in the distribution of HDL-c among patients who required ICU admission, mechanical ventilation, or non-survivor patients (Table 2). 
 
Table 2. Comparison of lipid profile with ICU admission, mortality and mechanical ventilation
	
		
			| Lipid profile | Variables | 
		
			| ICU admission | Mortality | Mechanical Ventilation | 
		
			| YES | No | p-value | YES | NO | p-value | YES | NO | p-value | 
	
	
		
			| TC mg/dL (Ref: <200)
 Mean ± SD Median
 | 135.05 ± 40.59 130
 | 139.79 ± 36.55 135
 | 0.2345MW | 126.02 ± 49.92 115
 | 138.46 ± 37.09 135
 | 0.0181MW* | 133.12 ± 42.63 128
 | 137.2 ± 38.83 132.5
 | 0.4468MW | 
		
			| HDL-c mg/dL (Ref: 40-60)
 Mean ± SD Median
 | 30.42 ± 9.92 29
 | 32.3 ± 9.03 31
 | 0.118MW | 30.76 ± 13 28
 | 31.2 ± 9.04 30
 | 0.7632MW | 32.38 ± 11.39 32
 | 31.03 ± 9.46 30
 | 0.4989MW | 
		
			| LDL-c mg/dL
 (Ref: <100)
 Mean ± SD Median
 | 81.28 ± 38.08 79
 | 88.25 ± 34.01 84
 | 0.0670MW | 74.2 ± 43.48 63
 | 85.4 ± 35.42 82
 | 0.0237MW* | 69.77 ± 38.07 66
 | 85.22 ± 36.34 82
 | 0.0211MW* | 
		
			| TG mg/dL (Ref: <150)
 Mean ± SD Median
 | 142.25 ± 84.48 120
 | 137.52 ± 129.09 110
 | 0.0359MW* | 142.83 ± 105.54 109
 | 140.08 ± 103.67 117
 | 0.5764MW | 171.62 ± 91.24 152.5
 | 137.68 ± 104.47 112
 | 0.0085MW* | 
	
Abbreviation: MW – Mann Whitney U test, * indicates statistical significance
From the Spearman’s rank correlation, no significant correlation was found between the lipid profile and CO-RADS score. However, there was a significant inverse correlation of TC, HDL-c and LDL-c with CT score and also TC and LDL-c with duration of hospital stay (Table 3). Where the inflammatory markers were considered, a significant inverse correlation of TC, HDL-C and LDL-C with LDH, CRP, ferritin and IL6 was found. However, there was no significant correlation of lipid profile with PCT (Table 4).
 
Table 3. Correlation of lipid profile with CT score, CORADS score, and duration of hospital stay
	
		
			| Lipid profile | CT score | CO-RADS score | Duration of hospital stay | 
		
			| Correlation Coefficient | p-value SP | Correlation Coefficient | p-value SP | Correlation Coefficient | p-value SP | 
		
			| TC | -0.2536 | < 0.001* | -0.1051 | 0.1137 | -0.2102 | < 0.001* | 
		
			| HDL –c | -0.1765 | 0.0138* | -0.0785 | 0.2377 | -0.1011 | 0.071 | 
		
			| LDL-c | -0.3137 | < 0.001* | -0.0934 | 0.1597 | -0.2626 | < 0.001* | 
		
			| TG | 0.0476 | 0.5099 | 0.0546 | 0.4121 | 0.0789 | 0.1591 | 
	
Abbreviation: SP – Spearman’s rank correlation test, * indicates statistical significance
Table 4. Correlation of lipid profile with biochemical markers of COVID-19
	
		
			| Biochemical markers of COVID-19 | Lipid profile | 
		
			| TC | HDL-c | LDL-c | TG | 
		
			| LDH | Correlation Coefficient | -0.1845 | -0.1870 | -0.2403 | 0.0366 | 
		
			| p-value SP | 0.0016* | 0.0014* | < 0.001* | 0.534 | 
		
			| CRP | Correlation Coefficient | -0.2919 | -0.1361 | -0.3654 | -0.0083 | 
		
			| p-value SP | < 0.001* | 0.0318* | < 0.001* | 0.8962 | 
		
			| Ferritin | Correlation Coefficient | -0.1949 | -0.2253 | -0.2911 | 0.0776 | 
		
			| p-value SP | < 0.001* | < 0.001* | < 0.001* | 0.1825 | 
		
			| PCT | Correlation Coefficient | -0.1015 | -0.0568 | -0.155 | 0.0678 | 
		
			| p-value SP | 0.3053 | 0.5668 | 0.1162 | 0.4941 | 
		
			| IL6 | Correlation Coefficient | -0.2703 | -0.1721 | -0.2847 | 0.0252 | 
		
			| p-value SP | < 0.001* | 0.0027* | < 0.001* | 0.6632 | 
	
Abbreviation: SP – Spearman’s rank correlation test, * indicates statistical significance